JPH05150574A - Electrophotographic device - Google Patents

Abstract

(57) [Abstract] [Purpose] When forming an image while avoiding the seam 6 of the photoconductor 3, the intermediate transfer member home position 2 and the photoconductor may be different due to the difference between the peripheral length of the photoconductor 3 and the peripheral length of the intermediate transfer member 1. The phase difference at home position 4 changes. When the width of change exceeds one round (return to origin), one idle cycle for the process is required, and the printing speed decreases. SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic apparatus in which the home position return width is significantly reduced and printing speed is hardly reduced. [Arrangement] One position detection mark is provided on the photosensitive member, and a plurality of position detection marks are provided on the intermediate transfer member. One of the intermediate transfer member marks is selected based on the detection timing of the photosensitive member mark and the intermediate transfer member mark. The time difference between the selection and the detection of the selected mark and the photoconductor mark is measured, the selected mark position of the intermediate transfer member is set as a reference position, and the image forming timing is determined based on this reference position and the time difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus for obtaining a high quality recorded image.

[0002]

2. Description of the Related Art Conventionally, printers of various principles have been proposed as output terminals for personal computers, workstations, etc. In particular, a laser beam printer (hereinafter LBP) using an electrophotographic process and laser technology has a recording speed. It is highly advantageous in terms of printing quality and is rapidly becoming popular.

On the other hand, there is an increasing demand for full-color LBP in the market, but in the case of full-color LBP, it is necessary to stack toners of three primary colors of printing, cyan, magenta, yellow, and black, so that a specific image carrier is required. Each color image must be formed on top of it in the correct position. Generally, for this alignment, a method is used in which a reference mark is provided on an image carrier on which images are overlapped and the image forming process of each color is started when the mark is detected.

The conventional electrophotographic apparatus will be described below. An electrophotographic apparatus capable of outputting a color image, in particular, a latent image formed by a laser beam or the like on a photoconductor is developed by a developing device for each color. A so-called intermediate transfer body system in which each color image formed on these photoconductors is temporarily overlapped and held on the intermediate transfer body and the composite image on the intermediate transfer body is collectively transferred to a sheet will be described.

FIG. 15 is a diagram showing an intermediate transfer member used in a conventional electrophotographic apparatus. In FIG. 15, 1 is an intermediate transfer member, and 2 is an intermediate transfer member position detection mark. The intermediate transfer body 1 is a loop belt made of a conductive resin or the like and seamless in terms of its structure and electrical characteristics. In order to improve the position detection accuracy of the intermediate transfer body in the rotational direction, a transmission type optical sensor is often used as the detection means, and the intermediate transfer body position detection mark 2 is generally a slit.

FIG. 16 is a diagram showing the periphery of a photosensitive member used in a conventional electrophotographic apparatus. In FIG. 16, 3 is a photoconductor, 4 is a photoconductor position detection mark, 5 is a photoconductor position detection sensor, 6 is a photoconductor seam, 7 is an image forming area head, 8 is an exposure position, and 9 is a photoconductor position detection mark 4. To the photoconductor seam 6. Further, d1 is the rotation direction of the photoconductor 3.

The photosensitive member 3 in which a photosensitive layer such as an organic photoconductor (OPC) is applied in a thin film on the outer peripheral surface of a belt base material in a closed loop shape is rotated by a driving source (not shown) in a rotating direction d1.
Driven to. The photoconductor 3 is provided with one photoconductor position detection mark 4, and the photoconductor position detection sensor 5 can detect the position of the photoconductor 3. The photoconductor 3 has a seam in the manufacturing process, and the part of the photoconductor seam 6 is an area in which an image cannot be formed. Therefore, during the image forming operation, it is necessary to always avoid the photoconductor seam 6 to form an image. For example, the image formation may be started immediately after the photoconductor seam 6 passes the exposure position 8 in the rotation direction d1. Good. More specifically, the exposure may be started when the photoconductor seam 6 reaches the position of the photoconductor position detection sensor 5. The position at this time is the top 7 of the image forming area. At the exposure position 8, the photoreceptor 3 is actually irradiated with an exposure light beam to form a latent image. At the time when the photoconductor position detection sensor 5 detects the photoconductor position detection mark 4, since the image forming area head 7 has not reached the exposure position 8, the photoconductor position detection sensor 5 detects the photoconductor position detection mark 4 during exposure. It is necessary to delay the detection by a specific time and then start. If exposure is started when the photoconductor seam 6 reaches the position of the photoconductor position detection sensor 5, the photoconductor seam 6 can be reliably avoided at the exposure position 8. Since the distance from the photoconductor position detection mark 4 to the photoconductor seam 6 is known, the photoconductor position detection mark 4 is detected by the photoconductor position detection sensor 5 by dividing the distance 9 by the driving speed of the photoconductor 3. After that, the time to be delayed before the start of exposure can be calculated. Hereinafter, this time will be referred to as a delay time Td.

The peripheral length of the intermediate transfer member 1 and the peripheral length of the photosensitive member 3 are nominally designed to be equal, but since the error does not become zero, there is always a difference in peripheral length. Intermediate transfer member 1 and photoconductor 3
Are driven by the same drive source at the same reduction ratio,
Due to this difference in peripheral length, one cycle of the intermediate transfer member 1 and the photosensitive member 3 is slightly different. For example, it is assumed that a certain point on the intermediate transfer member 1 and the photosensitive member 3 are currently in contact with each other. However, when the intermediate transfer member 1 makes one full turn, the photosensitive member 3 either does not completely go around one turn or slightly makes an extra turn. The difference between the cycles of the intermediate transfer member 1 and the photosensitive member 3 will be hereinafter referred to as a phase difference.

When forming a color image, it is necessary to accurately superpose images of a plurality of colors (black, cyan, magenta and yellow). In the intermediate transfer body method described so far, the monochromatic images of the respective colors developed on the photoconductor 3 are superimposed on the intermediate transfer body 1 to finally obtain a full-color image. In the intermediate transfer body method, since the above-mentioned phase difference exists, the position information from the photoconductor 3 cannot be used as the image forming reference. Because photoconductor 3
When a specific position (for example, the photosensitive member position detection mark 4) is set as an image forming reference position and an image is formed at an image forming timing based on the image forming reference position, monochromatic images of respective colors are formed on the photosensitive member 3 at exactly the same position. However, since there is a difference in peripheral length, they do not overlap at the same place on the intermediate transfer member 1. Therefore, at the image forming timing, it is necessary to form an image based on the position information of the image carrier on which the images of the respective colors are superposed, in this example, the intermediate transfer member 1. In this case, the monochromatic images of the respective colors on the photoconductor 3 are formed at different positions.

An LBP which forms a color image by applying an electrophotographic process technique selectively irradiates a light beam corresponding to each color onto a photosensitive member having a photosensitive layer to form an image, and forms a plurality of predetermined color components. A plurality of electrostatic latent images corresponding to the respective components of the characteristics are developed with respective predetermined toners, and the monochromatic toner images are superposed on the intermediate transfer member to form a color image on one recording sheet. The method of doing is adopted.

Next, the overall structure of a conventional electrophotographic apparatus will be described with reference to FIG. FIG. 17 is a diagram showing the structure of a conventional electrophotographic apparatus. The image is developed in the order of black, cyan, magenta, and yellow.

When an image forming command is issued from the outside, the photosensitive member 3 is driven in the driving direction d1, and the intermediate transfer member 1 is driven in the driving direction d2.
Are driven by the same drive source (not shown),
The reduction ratio is set so that the peripheral speeds of the two become the same constant speed. Further, the intermediate transfer member 1 has an image forming area set in advance by an intermediate transfer member position detection sensor 25 that detects the intermediate transfer member position detection mark 2 for determining the reference position.

In this state, first, a high voltage of about -4000 V to -5000 V is applied to the charging wire in the charger 13 connected to the high voltage power source to cause corona discharge, and the surface of the photoconductor 3 is uniformly -700 V. Charge to a certain degree. Next, when an exposure light beam 19 of a laser beam corresponding to a predetermined black (K) of a plurality of color components is radiated on the surface of the photoconductor 3 which is uniformly charged, the photoconductor 3 is radiated. The electric charge disappears in the portion and an electrostatic latent image is formed. The timing of the latent image formation start at this time is determined by a signal from the intermediate transfer member position detection sensor 25 that detects the intermediate transfer member position detection mark 2 of the intermediate transfer member 1. On the other hand, black developing device 15K
Detects the intermediate transfer member position detection mark 2 with the intermediate transfer member position detection sensor 25, and after a predetermined time elapses, the separation / contact cam 2
It is pushed in the driving direction d3 by the rotation of 0K and comes into contact with the photoconductor 3. On the other hand, immediately before contact, a negative potential of about -300 V is applied to the developing sleeve 37K having toner on the surface. If a negative charge is given to the toner in advance, the toner adheres only to the portion (electrostatic latent image portion) on the photoconductor 3 where the exposure light beam is irradiated and the charge is lost, and the development is performed by the so-called negative-positive process. After the development, the black developing device 15K is moved from the contact position with the photoconductor 3 to the separation position by the 180 ° rotation of the separation cam 20K. The toner image formed on the photoconductor 3 by the black developing device 15K is transferred onto the intermediate transfer body 1 by the intermediate transfer roller 24 which is arranged in contact with the photoconductor 3 for each color.
It is transferred by applying a high voltage of +800 V to. The residual toner not transferred from the photoconductor 3 to the intermediate transfer body 1 is removed by the photoconductor cleaning device 17,
Furthermore, the charge on the photoconductor 3 from which the residual toner has been scraped off by the static eliminator 18 is removed.

Next, when the color of cyan (C) is selected, the separation cam 20C rotates, and this time, the developing device 15C is pushed in the direction d3 of the photoconductor 3 and brought into contact with the photoconductor 3 to bring the cyan (C) color. Start development. In the case of a copying machine or printer using four colors, the above developing operation is sequentially repeated four times, and toner images of four colors (black, cyan, magenta and yellow) are superposed on the intermediate transfer body 1 to form a composite image. In the composite image formed in this way, the paper transfer roller 33, which has been separated so far, comes into contact with the intermediate transfer body 1, a high voltage of about +1000 V is applied to the paper transfer roller 33, and pressure is applied from the recording paper cassette 27. It is collectively transferred to the recording paper 28 sent along the paper carrying path 30. Subsequently, the recording paper 28 on which the toner image is transferred is sent to the fixing device 34, where it is fixed by the heat of the heat roller 35 and the nip pressure of the pressure roller 36, and is output as a color image. The residual toner on the intermediate transfer body 1 which is not completely transferred onto the recording paper 28 by the paper transfer roller 33 is removed by the intermediate transfer body cleaning device 26. The intermediate transfer member cleaning device 26 is at a position apart from the intermediate transfer member 1 until a combined image is obtained once, and a combined image is obtained and the combined image is transferred onto the recording paper 28 by the paper transfer roller 33. The post-contact state is reached and the residual toner is removed.

With the above operation, recording of one image is completed, and a color recorded image is obtained. As described above, the intermediate transfer body 1 and the photoconductor 3 are designed to have the same circumference, but in reality, it is impossible to obtain the same circumference because of the tolerance. For this reason, the intermediate transfer member 1 and the photosensitive member 3 generate a phase difference due to the difference in peripheral length while rotating. Next, the phase difference compensating method in the conventional electrophotographic apparatus will be described with reference to FIGS.

FIG. 18 is a timing chart showing the phase difference compensating method in the conventional electrophotographic apparatus, and shows the case where the peripheral length of the photosensitive member 3 is shorter than the peripheral length of the intermediate transfer member 1. Further, FIG. 19 is a timing chart showing a phase difference compensation method in the electrophotographic apparatus of the conventional example.
The case where the perimeter of is longer than the perimeter of the intermediate transfer body 1 is illustrated.

In these drawings, reference numeral 38 denotes an intermediate transfer member home position signal indicating that the intermediate transfer member position detection mark 2 has been detected by the intermediate transfer member position detection sensor 25, which is a CPU (central processing unit (not shown)). Z)) constantly monitors the intermediate transfer member home position signal 38, and
N (mark found) and OFF (mark not found) can be evaluated. Reference numeral 39 denotes a photoconductor home position signal indicating that the photoconductor position detection mark 4 has been detected by the photoconductor position detection sensor 5. The CPU constantly monitors the photoconductor home position signal 39 to turn it on (mark found) and off. (Mark not found) can be evaluated. In FIG. 18, since the peripheral length of the photoconductor is shorter than that of the intermediate transfer body, it is shown that the cycle of the photoconductor home position signal 39 is shorter than that of the intermediate transfer body home position signal 38. In FIG. Since the peripheral length of the photosensitive member is longer than that of the intermediate transfer member, the cycle of the photosensitive member home position signal 39 is longer than that of the intermediate transfer member home position signal 38.
Reference numeral 40 denotes a time from when the intermediate transfer member home position signal 38 is turned on to when the photosensitive member home position signal 39 is turned on, which is a phase difference time between the intermediate transfer member 1 and the photosensitive member 3. The phase difference time at each rotation is δt1, δt2
It is expressed as. Reference numeral 41 denotes a print command generated from inside the electrophotographic apparatus (a controller of the electrophotographic apparatus or the like) or outside (for example, a host computer).
Upon receiving 1, the electrophotographic apparatus starts image formation. Four
Reference numeral 2 indicates a period for checking the presence / absence of a print command. Reference numeral 43 is a flag indicating that printing is in progress. Reference numeral 44 indicates a trigger signal for the electrophotographic apparatus to start an image forming operation. Reference numeral 45 is an image signal, and the exposure light beam 19 is emitted during the period when the image signal is ON. 46 and 47 are timings for setting a delay time and the like, which will be described later, in the electrophotographic apparatus.

Details of the phase difference compensation operation of the conventional electrophotographic apparatus will be described below. Upon receiving the print command 41, the electrophotographic apparatus rotates various motors and the like required for image formation. In this state, the intermediate transfer member position detection mark 2 is detected. Intermediate transfer member position detection mark 2 of the intermediate transfer member 1
If is detected, the CPU (central processing unit (not shown)) starts the timer and waits until the photoconductor position detection mark 4 of the photoconductor 3 is detected.

The time from the detection of the intermediate transfer member position detection mark 2 by the intermediate transfer member position detection sensor 25 to the detection of the photosensitive member position detection mark 4 by the photosensitive member position detection sensor 5 is the phase difference time 40. Is. Phase difference time 4
When 0 is obtained, the print command 41 is checked again (the print command check 42 means that the print command is checked during the ON period). If the print command 41 is ON, the in-print flag 43 is printed. Turn on. The print start trigger 44 is a signal obtained by performing waveform shaping or the like on the intermediate transfer member home position signal 38, and is a reference signal for hardware and software to start an image forming operation.

All the operations of the electrophotographic apparatus are started by the print start trigger 44. This is because if the intermediate transfer member position detection mark 2 of the intermediate transfer member 1 which is a medium for superimposing color images is used as a reference for image formation, a single color image of each color cannot be superimposed at the same position on the intermediate transfer member 1. is there.

On the other hand, the phase difference time 40 is the time from the detection of the intermediate transfer member position detection mark 2 to the detection of the photosensitive member position detection mark 4. The intermediate transfer member position detection sensor 25 detects the intermediate transfer member. It is intended to predict how long time has passed since the position detection mark 2 was detected before the photoconductor position detection mark 4 can be detected at the position of the photoconductor position detection sensor 5.

Further, as described above, there is a delay time Td after the photoconductor position detection mark 5 is detected by the photoconductor position detection sensor 5 until the photoconductor seam 6 reaches the position of the photoconductor position detection sensor 5. ..

Therefore, the intermediate transfer member position detection sensor 25 detects the intermediate transfer member position detection mark 2 and sets it as the print start trigger 44, and after receiving the print start trigger 44, the phase difference time (for example, δt1). ) After the time delay of 40 + Td is caused, if the exposure and the operation of each actuator are started in response to the image signal 45, it is theoretically possible to always avoid the photoconductor seam 6 to form an image. .. Hereinafter, the phase difference time + Td will be referred to as the total delay time. The total delay time is set to the timing when the photoconductor home position signal 39 is detected, that is, the timing 46 immediately before the first black printing is started. Specifically, the total delay time is converted into the number of rasters of the electrophotographic apparatus and set in a counter (not shown) activated by the print start trigger 44. The electrophotographic apparatus decrements the counter for each raster of the exposure optical system 14, and starts irradiation of the effective exposure light beam 19 when the counting is completed. Further, the electrophotographic apparatus has a timer by software, and by setting the total delay time in this timer, the overall operation of the process can be offset. It goes without saying that the countdown of this timer is also started by the print start trigger 44.

When forming a color image, the set value of the phase difference time 40 should not be changed for each print start trigger 44 of each color. When the intermediate transfer body 1 and the photoconductor 3 are rotating relative to each other, the phase difference time 40 always changes,
If the time from the print start trigger 44 to the image forming operation is not fixed during the formation of one image, the monochromatic images of the respective colors on the intermediate transfer body 1 do not overlap accurately.

In the case of continuous printing, the next total delay time (Td + in FIG. 17) is detected at the time when the photoconductor home position signal 39 is detected after the printing of the final color is started, that is, at timing 47.
δt5) will be set.

As the image formation progresses in this way, as the intermediate transfer member 1 and the photosensitive member 3 rotate, the peripheral length difference between them is different, so that the phase difference between the home position detections gradually changes. Here, the case where the phase difference exceeds one revolution and becomes 0 during the continuous printing, or the state where the phase difference is 0 is about one revolution will be described in detail. Hereinafter, this phenomenon will be referred to as “origin return” for simplicity.

FIG. 18 is a diagram showing a phase difference compensating method for a conventional electrophotographic apparatus in the case where the peripheral length of the photosensitive member 3 is shorter than the peripheral length of the intermediate transfer member 1. First, in the photoconductor home position signal 39 of FIG. 18, the phase difference is returned to the origin between δt2 and δt3. That is, two home position signals are detected almost simultaneously at δt2, and δt3 of the next lap is detected.
Causes a delay of almost one lap. The total delay time (Td + δt5) for the second sheet is set at the time when the photoconductor home position signal 39 is detected after the printing reference for the final color (first sheet yellow printing reference) is input, that is, at timing 47. At this time, the total delay time exceeds the time required to drive the intermediate transfer member 1 and the photosensitive member 3 one round. Therefore, even if the print start trigger 44 for the second black sheet is generated, the image signal 45 is output with a delay of one round or more. Therefore, the output timing of the second black image signal 45 is B
The position is indicated by k-2.

Next, FIG. 19 is a view showing a phase difference compensating method for a conventional electrophotographic apparatus in the case where the peripheral length of the photosensitive member 3 is longer than the peripheral length of the intermediate transfer member 1. In the photoconductor home position signal 39 in FIG. 19, the phase difference is returned to the origin between δt3 and δt4. That is, the two home position signals are detected at δt3 with a time difference of about one round, and at the next round, δt4, the two home positions are detected almost at the same time. The total delay time (Td + δt4) for the second sheet is set at the time when the photoconductor home position signal 39 is detected after the printing reference for the final color (first sheet yellow printing reference) is input, that is, at timing 47. At this time, since the total delay time is very short, the image signals 45 overlap when performing continuous printing. That is, as shown at the bottom of FIG. 19, the first yellow print (Y-1) and the second black print (Bk-2) overlap in timing. In this way, the peripheral length of the photoconductor 3 is equal to that of the intermediate transfer member 1.
If the phase difference between the intermediate transfer member home position signal 38 and the photosensitive member home position signal 39 returns to the origin, the print start trigger 4
It is necessary to devise so that the hardware does not accept 4.

[0029]

However, the electrophotographic apparatus described as the conventional example has the following problems to be solved.

Since the peripheral length of the intermediate transfer member 1 and the peripheral length of the photosensitive member 3 cannot be made completely the same, as described above, avoid returning the home position to the origin with the rotation of the intermediate transfer member 1 and the photosensitive member 3. I can't. It is necessary to devise that the hardware does not accept the print start trigger 44 when the home position origin return occurs. Even if the hardware does not accept the print start trigger 44, for example, when continuous printing of several sheets is performed, if the home position return to the home position occurs in the middle of the continuous printing, the intermediate transfer member 1 and the photoconductor In No. 3, since one idle rotation period is required, the printing speed is reduced.

This also affects the printing speed of the first print. If the phase difference between the intermediate transfer member home position signal 38 and the photosensitive member home position signal 39 is large, the delay time of about one rotation is reflected as it is in the first print speed as compared with the case where the phase difference is 0. ..

Even if the intermediate transfer body 1 and the photoconductor 3 having completely the same circumferential length can be produced by some means, these members are consumable items, and the first print is always performed at the time of replacement. It is necessary to adjust to the highest speed, there is a problem in maintainability, and considering the secular change of the mechanism etc., it may be considered that it is almost impossible to always maintain the same circumference.

That is, in the configuration of the conventional example, the joint 6 of the photoconductor 3 is
When trying to form an image while avoiding this, an idling period for one rotation of the intermediate transfer member and the photosensitive member is required every time the phase difference between the photosensitive member home position and the intermediate transfer member home position returns to the origin, and the printing speed increases. It deteriorates extremely.

The present invention solves the above-mentioned conventional problems by significantly reducing the home return width of the home position.
It is an object of the present invention to provide an electrophotographic apparatus in which the printing speed hardly decreases.

[0035]

In order to achieve this object, an electrophotographic apparatus of the present invention is provided with one photosensitive member position detection mark on a photosensitive member and a plurality of intermediate transfer member position detection marks on an intermediate transfer member. Is provided.

Further, in the state where the photoconductor and the intermediate transfer member are rotated, a plurality of position detections performed on the intermediate transfer member based on the detection timing of the position detection mark of the photoconductor and the position detection mark of the intermediate transfer member. There is a means for selecting one of the use marks, the selected mark position is used as an image formation reference position, and the image formation timing is determined based on this reference position.

Further, the above selection operation is performed during image formation, but when a plurality of colors are overlapped to obtain a color image, the image formation timing of each color is determined based on one image formation reference position.

The image forming reference position is the position detecting mark position of the intermediate transfer member, which is detected immediately before the position detecting mark of the photosensitive member is detected.

[0039]

With this structure, the origin return width of the phase difference generated by rotating the intermediate transfer member and the photosensitive member can be reduced to such an extent that it does not cause a problem. Therefore, it is possible to prevent a decrease in printing speed during continuous printing and first printing.

[0040]

EXAMPLE 1 An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an intermediate transfer member of an electrophotographic apparatus according to an embodiment of the present invention. In the conventional example, only one intermediate transfer member position detection mark is provided on the intermediate transfer member, whereas in the first embodiment, a plurality of intermediate transfer member position detection marks are arranged around the intermediate transfer member position detection mark. In the following explanation, the peripheral length of the intermediate transfer member is set to 400 mm for simplification.
It is assumed that the individual intermediate transfer member position detection marks are evenly arranged at the end of the intermediate transfer member at intervals of 50 mm. Further, the process speed (= driving speed of the intermediate transfer member) is set to 100 mm / sec.

Since the structure other than the intermediate transfer member is the same as that of the conventional example including the structure around the photosensitive member, the drawings for explaining the operation also use FIG. 16 and FIG. Descriptions and operations will be omitted.

Now, as described in the conventional example, the intermediate transfer member 1
And the photoconductor 3 are designed to have the same circumference,
In reality, it is impossible to obtain completely the same circumference because of the tolerance. For this reason, the intermediate transfer member 1 and the photosensitive member 3 generate a phase difference due to the difference in peripheral length while rotating. Next, the phase difference compensating method in the electrophotographic apparatus of the embodiment will be described with reference to FIGS. 2, 3, 4, 5, 5, and 7.

FIG. 2 is a timing chart showing a phase difference compensating method for an electrophotographic apparatus in one embodiment of the present invention, showing a case where the peripheral length of the photosensitive member is shorter than the peripheral length of the intermediate transfer member, and FIG. FIG. 6 is a timing chart showing a phase difference compensation method for an electrophotographic apparatus in one embodiment of the present invention, showing a case where the peripheral length of a photosensitive member is longer than the peripheral length of an intermediate transfer member.

In FIGS. 2 and 3, reference numeral 38 denotes an intermediate transfer member position detecting mark 2 and 38 denotes an intermediate transfer member position detecting sensor 25.
CPU (central processing unit (not shown))
Always monitors the intermediate transfer member home position signal 38,
It is possible to evaluate ON (mark found) and OFF (mark not found). Reference numeral 39 denotes a photoconductor home position signal indicating that the photoconductor position detection mark 4 has been detected by the photoconductor position detection sensor 5. The CPU constantly monitors the photoconductor home position signal 39 to turn it on (mark found) and off.
(Mark not found) can be evaluated. 40 is the time from the intermediate transfer member home position signal 38 that was turned on immediately before the photosensitive member home position signal 39 changed to ON to the photosensitive member home position signal 39, which is the phase difference time between the intermediate transfer member 1 and the photosensitive member 3. is there. The phase difference time at each rotation is δt
1 and expressed as δt2. Reference numeral 41 denotes a print command generated from inside the electrophotographic apparatus (a controller of the electrophotographic apparatus) or outside (for example, a host computer),
Upon receiving the print command 41, the electrophotographic apparatus starts image formation. Reference numeral 42 indicates a period for checking the presence / absence of a print command. Reference numeral 43 is a flag indicating that printing is in progress. Reference numeral 45 is an image signal, and the exposure light beam 19 is emitted during the period when the image signal is ON.

Reference numeral 48 denotes a print start trigger, and the software masks the signal to the hardware to select one of the plurality of intermediate transfer member position detection marks 2. The print start trigger 48 is a signal obtained by performing waveform shaping on the intermediate transfer member home position signal 38, and is a reference signal for image forming operation start for hardware and software. That is, not only the image forming timing is instructed to the hardware, but also the external interrupt signal is generated to the software. Reference numeral 49 is a first print flag, which is interrupted by software when interrupted when the first sheet black print start trigger 48 is received immediately after the first sheet print is started in the process of forming an image by the electrophotographic apparatus. To be done. The electrophotographic apparatus of the embodiment changes the content of the processing according to the logic of the printing flag 43 and the first print flag 49. 5
0 is the intermediate transfer member home position count value, which is a numerical value recognized only by software. The software constantly counts the home position count value 50 of the intermediate transfer member, and executes processing according to the value. 51 is the process A. In process A, the masking for the hardware and software interrupts is released, the print start trigger 48 is enabled, and the exposure delay time and process delay time based on the phase difference between the intermediate transfer body 1 and the photoconductor 3 are set. 52 is a process B. Process B
Masks for hardware and software interrupts. Only the process B is executed in the software interrupt process. Therefore, the process B is not described in the flowchart of the home position manager described later. 53 is a process C. Process C unmasks the hardware and software interrupts.

The operation of the electrophotographic apparatus which operates according to the above timing chart will be described in detail with reference to FIGS. 4, 5, 6 and 7. 4 to 7 are flowcharts of software of the electrophotographic apparatus in one embodiment of the present invention, and this software will be referred to as a home position manager hereinafter.

FIG. 4 is a flowchart of the software of the electrophotographic apparatus in one embodiment of the present invention, showing the initialization part of the home position manager. The home position manager constantly monitors the rotations of the drive motors (shared) for the intermediate transfer member 1 and the photosensitive member 3 (step 1). If the motor is off, continue to initialize all variables and external conditions for home position manager. Specifically, the hardware is masked so that the print start trigger 48 does not act, and software interrupts are prohibited (step 2). The photoconductor home position signal 39 is actually latched by the flip-flop, but this latch is cleared (step 3).
Further, the intermediate transfer member home position signal 38 is actually latched by the flip-flop, but this latch is cleared (step 4). The first print flag 49 is turned on (step 5). T, which is a variable for monitoring the cycle of the intermediate transfer member home position signal 38
OMCNT and OPCCNT which is a variable for monitoring the cycle of the photoconductor home position signal 39 are both cleared to "0" (step 6). The intermediate transfer member home position count value 50 is initialized to "7" (step 7). The home position count value correction request flag is initialized to OFF. That is, in the initial stage, it is specified that the phase difference of each home position does not return to the origin (step 8). Finally, a 10 ms pause (step 9) is performed.

After the above processing, the process jumps again to step 1. The home position manager repeats the above steps until the intermediate transfer member and the photoconductor driving motor start rotating. This is the end of the description of FIG.

Next, the continuation will be described with reference to FIG. FIG. 5 is a flowchart of the software of the electrophotographic apparatus according to the embodiment of the present invention, and is a diagram showing a portion related to the detection of the intermediate transfer member home position signal of the home position manager.

At the time of P2, the drive sources for the intermediate transfer member and the photosensitive member have started to rotate. First, the state of the intermediate transfer member home position signal 38 is evaluated. The intermediate transfer member home position signal is actually latched by hardware, and ON / OFF of the signal after latching is evaluated (step 10). If not detected, jump to P3. When the intermediate transfer member home position signal 38 is detected, the latch output of the intermediate transfer member home position signal 38 is first cleared (step 11). The variable TOMCNT for monitoring the cycle of the intermediate transfer member home position signal 38 is checked (step 12). TOMCNT is counted up in a timer interrupt routine (not shown) of 1 ms apart from the home position manager,
The home position manager is responsible for evaluating the TOMCNT value and clearing the value. If TOMCNT is 5
If 00 exceeds 10% (drive speed of intermediate transfer body is 100 mm / sec, home position of intermediate transfer body is 50 mm)
Cycle and TOMCNT are counted in 1ms units. Therefore, ideally, TOMCNT is provided between each home position of the intermediate transfer member.
Will count 500) and jump to E2. E2 is an error handling routine. If TOMCNT is within the specified value, TOMCNT is cleared (step 1
3). The home position count value 50 of the intermediate transfer member is evaluated (step 14). At the time of initialization, the intermediate transfer member home position count value 50 is initialized to "7". Therefore, when the intermediate transfer member home position signal 38 is first detected, the evaluation is "No." The transfer member home position count value 50 is cleared to "0" (step 15), and the process jumps to P3. If the intermediate transfer member home position count value 50 is smaller than "7", the intermediate transfer member home position count value 50 is incremented (step 16).

Intermediate transfer member home position count value =
It is evaluated whether it is "4" (step 17). Here, the case where the intermediate transfer member home position count value ≠ 4 will be described. Because the value of the intermediate transfer member home position count value 50 is first evaluated in step 17,
This is because it is not "4". Therefore, in step 17, "N
o. Is evaluated. Next, it is evaluated whether the intermediate transfer member home position count value is "1" (step 18).
If the evaluation in step 18 is "No.", the process immediately jumps to P3. This means that the home position manager does not perform any processing except when the intermediate transfer member home position count value 50 is "4" or "1". Figure 2
Further, according to FIG. 3, it is described that the process B is performed when the home position count value of the intermediate transfer member is “2”. Actually, the process B is not processed by the home position manager,
When an interrupt occurs in the CPU by the print start trigger 48, it is performed by the interrupt processing program.

Intermediate transfer member home position count value =
In the case of "1", the first print flag 49 is evaluated (step 19). First print flag 49
When is ON, the evaluation is "No.", and then the printing flag 43 is evaluated (step 20). If the printing flag 43 is OFF, the process immediately jumps to P3. This situation corresponds to the timing 54 in FIGS. 2 and 3. That is, before the print command check 42 is performed,
This is an area where the print start trigger 48 should be invalidated. When it is evaluated as “No.” in step 20, the process A
Is performed (step 21). In process A, the masking for the hardware and software interrupts is released, the print start trigger 48 is enabled, and the exposure delay time and process delay time based on the phase difference between the intermediate transfer body 1 and the photoconductor 3 are set.
This situation corresponds to the timing 55 in FIGS. 2 and 3. That is, the print start trigger 48 for the first color of the first sheet is validated.

If "Yes." Is evaluated in step 19, the printing flag 43 is evaluated (step 22). When it is evaluated as "Yes." In step 22, processing A (step 21) is performed. This situation corresponds to the timing 56 in FIGS.
That is, the printing start trigger 4 for the first color of the second sheet during continuous printing
Enable 8. When it is evaluated as "No." in step 22, processing C is performed (step 23). Process C unmasks the hardware and software interrupts. This situation corresponds to the timing 57 in FIGS. That is, the print start triggers 48 other than the first color during image formation are enabled. After the end of the process C, the process jumps to P3.

Here, the description of FIG. 5 will be interrupted and the description of FIG. 6 will be continued. After jumping to P3 in FIG. 5, P3 in FIG.
Processing shifts to. FIG. 6 is a flowchart of the software of the electrophotographic apparatus according to the embodiment of the present invention, and is a diagram showing a portion related to detection of the photoconductor home position signal of the home position manager.

The photoconductor home position signal 39, which evaluates the photoconductor home position signal 39, is latched by the hardware, and the home position manager
The latched signal is evaluated (step 24). If the evaluation result is "No.", the variable OPCCNT for monitoring the cycle of the photoconductor home position signal 39 is incremented (counted up) (step 25). Since the processing cycle of the home position manager is set to 10 ms, the variable OPCCNT is incremented by 1 every 10 ms (step 26). Well step 2
4 is "Yes.", The latch of the photoconductor home position signal 39 is cleared (step 2).
7). Further, since the photoconductor 3 has the photoconductor seam 6, it is necessary to separate the photoconductor cleaning device 17 at a specific timing. Photoconductor home position signal 3
The separation process of the photoconductor cleaning device 17 is started every time 9 is detected (step 28). It is checked whether OPCCNT is within the specified value (step 29). Since the photoconductor 3 is nominally designed to have the same circumference as that of the intermediate transfer body 1, if the photoconductor 3 is driven by the same drive source at the same speed reduction ratio, it makes one rotation in about 4 seconds. OPCCNT count-up is 10 ms
Therefore, OPCCNT ideally counts 400 per one rotation of the photoconductor 3. Here, an allowable width of about 10% is provided, and if OPCCNT is 440 or more, it is determined that an error has occurred and the process jumps to the error processing routine E3. If the evaluation in step 29 is “Yes.”, OPCC
Clear NT with 0 (step 30).

Next, the first print flag 49 is evaluated (step 31). First print flag 49
Is ON (the evaluation in step 31 is "No."), the printing flag 43 is evaluated (step 32). If the evaluation result is "Yes.", The intermediate transfer member home position count value 50 is cleared to "0" (step 3).
3). This situation is the timing 58 in FIGS.
Equivalent to. At this time, the intermediate transfer member home position count value 50 is forcibly cleared to "0".
That is, before the print command check 42 is performed, the intermediate transfer member home position count value 50 is cleared to "0" every time the photosensitive member home position signal 39 is detected. In this way, the intermediate transfer member home position signal 38 detected immediately before detecting the photosensitive member home position signal 39 is defined as the intermediate transfer member home position count value = “0”. The value (= 0) of the intermediate transfer member home position count value 50 that has been forcibly cleared is stored in a variable on the software as the main home value (step 34). On the other hand, when it is evaluated as “Yes.” In step 31,
Alternatively, if "No." is evaluated in step 32, the current intermediate transfer member home position count value is stored as a main home value in a variable on software (step 34). This situation includes all of the first print command check 42 onward in FIGS. 2 and 3. That is, during image formation, each time the photosensitive member home position signal 39 is detected, the intermediate transfer member home position count value 50 at that time is set as the main home value. As a result, the phase difference between the intermediate transfer body 1 and the photoconductor 3 increases during image formation,
It can be detected that the main home value deviates. For example, FIG. 2 shows a case where the circumference of the photoconductor 3 is shorter than the circumference of the intermediate transfer body 1. Intermediate transfer member 1 between δt4 and δt5
The phase difference between the photosensitive member 3 and the photoconductor 3 returns to the origin (at δt4, two home positions were detected almost simultaneously, but at δt5, there is a phase difference of one home position of the intermediate transfer member). When the home return occurs, the main home value is "7", and the home return is correctly detected. Further, FIG. 3 shows a case where the circumference of the photoconductor 3 is longer than the circumference of the intermediate transfer body 1. The phase difference between the intermediate transfer body 1 and the photoconductor 3 is returned to the origin between δt2 and δt3. (At δt2, there is a phase difference of one home position of the intermediate transfer body.
At δt3, two home positions are detected almost at the same time), but the main home value after the home position return becomes “1”, and the home position return is correctly detected in this case as well. Summarizing the above-mentioned phenomenon of origin return, when the circumference of the photoconductor 3 is shorter than the circumference of the intermediate transfer body 1, when the origin return occurs, the main home value is changed from "0" to "7".
When the circumference of the photoconductor 3 is longer than the circumference of the intermediate transfer body 1, the main home value is “0” when the origin return occurs.
Changes to "1".

Now, the intermediate transfer member home position signal 38
The variable TOMCNT for monitoring the cycle of is the step 1 in FIG.
3 is cleared every time the intermediate transfer member home position signal 38 is detected, and the count-up of TOMCNT is performed by a timer interrupt every 1 ms.
As described above. That is, the count up of TOMCNT is performed by other than the home position manager, and if the value of TOMCNT is referred to when the photoconductor home position signal 39 is detected, TOMCNT is the intermediate transfer immediately before the photoconductor home position signal 39 is detected. The time difference from the body home position signal 38 to the detection of the current photosensitive body home position signal 39 is shown. This time difference is stored as the variable δt (step 35). This δt is set as the process delay time in step 21, and the number of rasters is further converted,
It is set as the exposure delay time.

Next, the main home value is evaluated (step 36). When the main home value = “0”, the home position return has not occurred, so it is determined that it is not necessary to change the home position, and the process proceeds to step 26 and returns to P1. If the home return has occurred, it is evaluated as "No." in step 36, and the home position count value correction request flag is turned on.
(Step 37). This is the end of the description of FIG.

Next, the description returns to FIG. 5 again. Figure 5 here
The case where it is determined in step 17 that the intermediate transfer member home position count value = “4” will be described in detail.

First, the first print flag 49 is evaluated (step 38). If the evaluation result is ON, the process immediately jumps to P3. If the evaluation result is OFF,
Further, the printing flag 43 is evaluated (step 39).
If the evaluation result is OFF, the process immediately jumps to P3. Next, the home position count value correction request flag is evaluated (step 40). If the evaluation result is OFF, the process immediately jumps to P3. Now, the evaluation results of step 38, step 39, and step 40 have the following meanings. By checking the first print flag 49 and the in-print flag 43 in steps 38 and 39, specific processing is performed only when the final color image is being formed and the intermediate transfer member home position count value = “4”. The algorithm is as follows. This part plays an important role in the home position manager. Further, in step 40, the home position count value correction request flag is determined, and only when the origin return occurs in the home positions of the intermediate transfer body 1 and the photoconductor 3, step 40 is executed.
It is possible to proceed to the subsequent processing.

First, the home position count value correction request flag is turned off (step 41). Next, it is evaluated whether or not the main home value is "1" (step 42). Step 42 is a process performed when the circumference of the photoconductor 3 is longer than the circumference of the intermediate transfer body 1. If the main home value = “1” in step 42, the intermediate transfer member home position count value 50 is counted down by “1”.
That is, the intermediate transfer member home position count value is decremented (counted down) from "4" to "3" at the timing 59 in FIG. 3 (step 4).
3). Further, in FIG. 3, if the intermediate transfer member home position signal 38 is subsequently detected, the intermediate transfer member home position count value 50 is incremented from "3" to "4".

On the other hand, the evaluation in step 42 is "N
o. If it is, it is evaluated whether or not the main home value is "7" (step 44). If the evaluation result of step 44 is "No.", the main home value is neither "1" nor "7", and it means that two or more origin returns have occurred during one image forming period. I mean. In this embodiment, the intermediary transfer member position detection marks 2 are evenly arranged.
Since the interval is set to mm, one image formation (ie 4
During the rotation, the phase difference of 50 mm or more increases, and it is determined that there is some abnormality in the drive system, the periphery of the intermediate transfer member, and the periphery of the photosensitive member, and the process jumps to the error processing routine E1.

Now, step 44 is a process performed when the peripheral length of the photoconductor 3 is shorter than the peripheral length of the intermediate transfer member 1. If the main home value = “7” in step 44,
The intermediate transfer member home position count value is incremented by "1". That is, the intermediate transfer member home position count value is set to "4" →
It is incremented (counted up) to "5" (step 45). Further, in FIG. 2, if the intermediate transfer member home position signal 38 is subsequently detected, the intermediate transfer member home position count value 50 is “5” → “6”.
It is counted up to.

As described above, when the main home value takes a value other than "0", the intermediate transfer member home position count value is corrected at a specific timing 59.

Next, the meaning of the home position count value correction will be described below. In the algorithm based on the flow described above, the intermediate transfer member home position signal 38 immediately before detecting the photosensitive member home position signal 39 is used as the main home. Further, the main home is controlled so as to be always "0" at the time of starting the formation of one image. That is, the image forming standard on the software is always the time when the numerical value described in the intermediate transfer member home position count value 50 in FIGS. 2 to 3 is “0”. In an actual operation, a phase difference in home position detection occurs due to a difference between the circumferential length of the intermediate transfer body 1 and the circumferential length of the photoconductor 3, so that the main home is not "0" at a certain point. If this is left as it is and image formation is always continued using the same intermediate transfer member home position, the image forming area of the photoconductor 3 gradually shifts, and finally the photoconductor joint 6 is formed.
The image area extends over. The home position count value correction according to the present embodiment accurately detects the home position origin return due to the expansion of the phase difference between the intermediate transfer member 1 and the photosensitive member 3, and detects it immediately before detecting the photosensitive member home position signal 39. Intermediate transfer member home position signal 38
The intermediate transfer body home position count value 50 that has been incremented in step 1 is corrected so that the intermediate transfer body home position count value is always "0", and the hardware and software are adjusted according to the intermediate transfer body home position count value. Controls the mask for interrupt processing. As a result, even if the origin return occurs due to the expansion of the phase difference, the timing of the image signal 45 never exceeds one revolution of the intermediate transfer member 1 and the photosensitive member 3, and the printing speed can always be kept high. it can.

This is the end of the description of FIG. There is a constant Td in the total delay time described in the conventional example. However, in the first embodiment, it is not necessary to directly consider Td. The reason will be described in detail below. For example, in FIG. 2, the intermediate transfer member home position count value 5
0 is assigned a number from "0" to "7" in terms of software management. If the concept of Td does not exist, the print start trigger 48 may be enabled when the intermediate transfer member home position count value 50 is "0".
The system in which the concept of Td does not exist is a system in which the photoconductor seam 6 can be surely avoided by outputting the image signal 45 and starting the exposure when the photoconductor home position signal 39 is detected. ..

However, in reality, since the photoconductor position detection mark 4 and the photoconductor seam 6 are not at the same place, a delay of Td is provided after the photoconductor home position signal 39 is detected, and exposure is started after that. Body seam 6 cannot be avoided. However, if the distance 9 from the photoconductor position detection mark 4 to the photoconductor seam 6 is a multiple of the interval (= 50 mm) between the intermediate transfer member position detection marks 2, the home position manager performs, for example, mask release processing. All you have to do is change the position.

In the embodiment, the distance 9 from the photoconductor position detection mark 4 to the photoconductor seam 6 is set to 100 mm, which is exactly a multiple of the interval between the intermediate transfer member position detection marks 2. Therefore, in a system in which the concept of Td does not exist, the print start trigger 48 is enabled when the home position count value of the intermediate transfer body is "0". However, in the embodiment, the home position count value of the intermediate transfer body = "2 (100 mm / 50 mm = 2) ”, the print start trigger 48 is activated to compensate for the delay of Td.

Next, FIG. 7 will be described. FIG. 7 is a flowchart of the software of the electrophotographic apparatus according to the embodiment of the present invention, and is a diagram showing an error processing routine of the home position manager.

E1 is an error in the home position count value correction when the main home value is neither "1" nor "7". This is a case where there is an abnormality in the drive system, the periphery of the intermediate transfer body, and the periphery of the photoconductor, and a "drive error" is displayed to stop all the operations of the electrophotographic apparatus.

E2 is TOMCNT in step 12
It occurs when the TOMCNT value exceeds the specified value when the value is checked. This indicates that the detection cycle of the mark for detecting the position of the intermediate transfer member is abnormal, displays "intermediate transfer member home detection error", and stops all operations of the electrophotographic apparatus.

E3 is OPCCNT in step 29.
Occurs when the OPCCNT value exceeds the specified value when the value is checked. This indicates that the detection cycle of the photoconductor position detection mark is abnormal, displays "photoconductor home detection error", and stops all operations of the electrophotographic apparatus.

This is the end of the description of FIG. (Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 8 is a diagram showing an intermediate transfer member of an electrophotographic apparatus according to the second embodiment of the present invention. In the first embodiment, the number of intermediate transfer body position detection marks is eight, whereas in the second embodiment, the number of intermediate transfer body position detection marks is increased to twenty. The reason why the number N of the intermediate transfer member position detection marks is 20 in the second embodiment is as follows.

Lm is the circumference of the photoconductor, Lp is the maximum image area length, δl is the difference between the circumference of the photoconductor and the circumference of the intermediate transfer member, and n.
The number of cycles required to form one color image, D
When T is the distance between the photoconductor home position and the seam, N is the minimum integer that satisfies the following formula (1) N> Lm / (Lm-Lp-2 * δl * n) (1). Then, when N is further substituted into the following equation (2), M = DT / (Lm / N) (2) M is selected as a condition.

For example, when the maximum image area Lp is a legal size (355.6 mm) and one color image is formed by developing four times as in the first embodiment, Lm = 400 mm Lp = 355.6 mm n = 4 If δl = 2.5 mm, then N> 17 from the equation (1). Further, if DT = 100 mm, the value of N that makes M in equation (2) an integer is N = 4, 8, 12, 16, 20, 24, .. Therefore, the minimum N satisfying N> 17 is Twenty.

The mechanical structure of the second embodiment other than the intermediate transfer member is the same as the mechanical structure of the first embodiment. Therefore, the image forming operation of the electrophotographic apparatus is the same as that of the first embodiment. A description of image creation will be omitted. The difference from the first embodiment is the phase difference compensation method, and this point will be described.

FIG. 9 is a timing chart showing a phase difference compensating method for the electrophotographic apparatus in the second embodiment, showing a case where the photoconductor has a shorter cycle than that of the intermediate transfer body.
FIG. 4 is a diagram showing a case where the circumference of the photoconductor is longer than that of the intermediate transfer body. Since these drawings correspond to FIGS. 2 and 3 of the first embodiment, respectively, there are many overlapping portions. The differences between FIGS. 2 and 3 are the following 1) and 2). 1) The frequency of the intermediate transfer member home position signal is higher than that in FIG. This is because N = 8 in the first embodiment, whereas N = 20 in the second embodiment. Correspondingly, the value of the main home value and the value of the intermediate transfer member home position count value are also different. 2) The phase difference time δt is omitted. The other description of FIGS. 9 and 10 is omitted to avoid duplication. Next, the operation of the electrophotographic apparatus that operates according to the above timing chart will be described with reference to FIGS. 11, 12, and 13. Note that FIG. 11 is a diagram corresponding to FIG. 4 of the first embodiment, and the only difference is that the value of the intermediate transfer member home position count value in step 7 is changed from 7 to 19, so description thereof is omitted. To do.

Next, the continuation will be described with reference to FIG. Figure 1
FIG. 2 is a flowchart of software of the electrophotographic apparatus in the second embodiment of the present invention, showing a portion related to detection of the intermediate transfer member home position signal of the home position manager.

At the time of P2, the drive sources for the intermediate transfer member and the photosensitive member have started to rotate. First, the state of the intermediate transfer member home position signal 38 is evaluated. The intermediate transfer member home position signal is actually latched by hardware, and ON / OFF of the signal after latching is evaluated (step 10). If not detected, jump to P3. When the intermediate transfer member home position signal 38 is detected, the latch output of the intermediate transfer member home position signal 38 is first cleared (step 11). The variable TOMCNT for monitoring the cycle of the intermediate transfer member home position signal 38 is checked (step 12). TOMCNT is counted up in a timer interrupt routine (not shown) of 1 ms apart from the home position manager,
The home position manager is responsible for evaluating the TOMCNT value and clearing the value. If TOMCNT is 2
If 00 exceeds 10% (drive speed of intermediate transfer body is 100 mm / sec, home position of intermediate transfer body is 20 mm)
Cycle and TOMCNT are counted in 1ms units. Therefore, ideally, TOMCNT is provided between each home position of the intermediate transfer member.
Will count 200) and jump to E2. E2 is an error handling routine. If TOMCNT is within the specified value, TOMCNT is cleared (step 1
3). The home position count value 50 of the intermediate transfer member is evaluated (step 14). At initialization, the intermediate transfer member home position count value 50 is initialized to "19",
When the intermediate transfer member home position signal 38 is first detected, the evaluation is "No.", the intermediate transfer member home position count value 50 is cleared to "0" (step 15), and the process jumps to P3. If the intermediate transfer member home position count value 50 is smaller than "19", the intermediate transfer member home position count value 50 is incremented (step 16).

Intermediate transfer member home position count value = “1”
It is evaluated whether it is "0" (step 17). Here, the case where the intermediate transfer member home position count value ≠ 10 will be described. Because the value of the intermediate transfer member home position count value 50 is first evaluated in step 17,
This is because it is not "10". Therefore, in step 17, "No." is evaluated. Next, it is evaluated whether or not the intermediate transfer member home position count value = “4” (step 1
8). If the evaluation in step 18 is "NO.", The process immediately jumps to P3. This means that the home position manager does not perform any processing except when the intermediate transfer member home position count value 50 is "10" or "4". 2 and 3, it is described that the process B is performed when the home position count value of the intermediate transfer member is "5". Actually, the process B is not executed by the home position manager, and is executed by the interrupt processing program when the print start trigger 48 causes an interrupt to the CPU.

Intermediate transfer member home position count value =
In the case of "4", the printing flag 43 is evaluated (step 19). If the printing flag 43 is OFF, the process immediately jumps to P3. This situation corresponds to the timing 53 in FIGS. 9 and 10. That is, print command check 4
Before 2 is performed, this is an area in which the print start trigger 48 should be invalidated. If the printing flag 43 is ON in step 19, processing A is performed (step 20). This situation corresponds to the timing 54 in FIGS. 9 and 10.

Process A releases the mask for the hardware and software interrupts and enables the print start trigger 48.

Here, the explanation of FIG.
Will be explained. After jumping to P3 in FIG.
The processing shifts to P3 of 3. FIG. 13 is a flowchart of the software of the electrophotographic apparatus according to the second embodiment of the present invention, and is a diagram showing a portion related to detection of the photoconductor home position signal of the home position manager.

The photoconductor home position signal 39 which evaluates the photoconductor home position signal 39 is latched by the hardware, and the home position manager
The latched signal is evaluated (step 21). If the evaluation result is "No.", the variable OPCCNT for monitoring the cycle of the photoconductor home position signal 39 is incremented (counted up) (step 22). Since the processing cycle of the home position manager is set to 10 ms, the variable OPCCNT is incremented by 1 every 10 ms (step 23). Well step 2
When the evaluation in 1 is "Yes.", The latch of the photoconductor home position signal 39 is cleared (step 2).
4). Further, since the photoconductor 3 has the photoconductor seam 6, it is necessary to separate the photoconductor cleaning device 17 at a specific timing. Photoconductor home position signal 3
The separation process of the photoconductor cleaning device 17 is started every time 9 is detected (step 25). It is checked whether OPCCNT is within the specified value (step 26). Since the photoconductor 3 is nominally designed to have the same circumference as that of the intermediate transfer body 1, if the photoconductor 3 is driven by the same drive source at the same speed reduction ratio, it makes one rotation in about 4 seconds. OPCCNT count-up is 10 ms
Therefore, OPCCNT ideally counts 400 per one rotation of the photoconductor 3. Here, an allowable width of about 10% is provided, and if OPCCNT is 440 or more, it is determined that an error has occurred and the process jumps to the error processing routine E3. If the evaluation in step 26 is “Yes.”, Then OPCC
Clear NT to 0 (step 27).

Next, the first print flag 49 is evaluated (step 28). First print flag 49
Is ON (the evaluation in step 28 is "No."), the printing flag 43 is evaluated (step 29). If the evaluation result is "Yes.", The intermediate transfer member home position count value 50 is cleared to "0" (step 3).
0). This situation is timing 5 in FIGS. 9 and 10.
Equivalent to 5. At this time, the intermediate transfer member home position count value 50 is forcibly cleared to "0". That is, before the print command check 42 is performed, the intermediate transfer member home position count value 50 is cleared to "0" every time the photosensitive member home position signal 39 is detected. In this way, the intermediate transfer member home position signal 38 detected immediately before detecting the photosensitive member home position signal 39 is defined as the intermediate transfer member home position count value = “0”.
The value (= 0) of the intermediate transfer member home position count value 50 that has been forcibly cleared is stored in a variable on the software as the main home value (step 31).
On the other hand, if "Yes." Is evaluated in step 28, or if "No." is evaluated in step 29, the current intermediate transfer member home position count value is stored as a main home value in a variable on software. (Step 31). This situation includes all of the first and subsequent print command checks 42 in FIGS. 9 and 10. That is, during image formation, the photoconductor home position signal 3
Each time 9 is detected, the intermediate transfer member home position count value 50 at that time is set as the main home value. As a result, it is possible to detect that the phase difference between the intermediate transfer member 1 and the photosensitive member 3 is increased during image formation and the main home value is shifted.
For example, FIG. 9 shows a case where the circumference of the photoconductor 3 is shorter than the circumference of the intermediate transfer body 1. It shows that the main home value changed from “0” to “19” on the way and the phase difference returned to the origin.

FIG. 10 shows a case where the peripheral length of the photosensitive member 3 is longer than the peripheral length of the intermediate transfer member 1. It shows that the main home value changed from "0" to "1" on the way and the phase difference returned to the origin. Summarizing the above-described phenomenon of origin return, when the circumference of the photoconductor 3 is shorter than the circumference of the intermediate transfer body 1, the main home value changes from "0" to "19" when the origin return occurs. When the perimeter of is longer than the perimeter of the intermediate transfer body 1, the main home value changes from “0” to “1” when the origin return occurs.

Next, the main home value is evaluated (step 32). When the main home value = “0”, the origin return has not occurred, so it is determined that the home position need not be changed, and the process proceeds to step 23 and returns to P1. If the return to origin has occurred, it is evaluated as "No." in step 32, and the home position count value correction request flag is turned on.
(Step 33). This is the end of the description of FIG.

Next, the description returns to FIG. 12 again. Here, the case where it is determined in step 17 in FIG. 12 that the intermediate transfer member home position count value = “10” will be described in detail.

First, the first print flag 49 is evaluated (step 34). If the evaluation result is ON, the process immediately jumps to P3. If the evaluation result is OFF,
Further, the printing flag 43 is evaluated (step 35).
If the evaluation result is OFF, the process immediately jumps to P3. Next, the home position count value correction request flag is evaluated (step 36). If the evaluation result is OFF, the process immediately jumps to P3. The evaluation results of step 34, step 35, and step 36 have the following meanings. By checking the first print flag 49 and the in-print flag 43 in steps 34 and 35, specific processing is performed only when the final color image is being formed and the intermediate transfer member home position count value = “10”. The algorithm is as follows. This part plays an important role in the home position manager. Further, in step 36, the home position count value correction request flag is determined, and only when the home return of the home positions of the intermediate transfer body 1 and the photoconductor 3 occurs, step 36 is performed.
It is possible to proceed to the subsequent processing.

First, the home position count value correction request flag is turned off (step 37). Next, it is evaluated whether or not the main home value is "1" (step 38). Step 38 is a process performed when the circumference of the photoconductor 3 is longer than the circumference of the intermediate transfer body 1. If the main home value = “1” in step 38, the intermediate transfer member home position count value 50 is counted down by “1”.
That is, the intermediate transfer member home position count value is decremented (counted down) from "10" to "9" at the timing 56 in FIG. 10 (step 39). Further, in FIG. 10, if the intermediate transfer member home position signal 38 is detected thereafter, the intermediate transfer member home position count value 50 is incremented from "9" to "10".

On the other hand, the evaluation in step 38 is "N
o. If it is, it is evaluated whether or not the main home value is "19" (step 40). If the evaluation result of step 40 is "No.", the main home value is "1".
However, this is not "19", which means that two or more origin returns occurred during one image forming period. In this embodiment, the intermediate transfer member position detection marks 2 are evenly set at intervals of 20 mm, so that the phase difference of 20 mm or more is enlarged during one image formation (that is, four rotations). , The drive system, the periphery of the intermediate transfer member and the periphery of the photosensitive member are determined to be abnormal, and an error processing routine E
Jump to 1.

Step 41 is a process performed when the peripheral length of the photoconductor 3 is shorter than the peripheral length of the intermediate transfer member 1. If the main home value = “19” in step 40, the intermediate transfer member home position count value is incremented by “1”. That is, the intermediate transfer member home position count value is set to "1" at the timing 56 in FIG.
It is incremented (counted up) from "0" to "11" (step 41). Further in FIG.
If the intermediate transfer member home position signal 38 is detected thereafter, the intermediate transfer member home position count value 50 becomes "1.
The count is incremented from 1 ”to“ 12 ”.

As described above, when the main home value takes a value other than "0", the intermediate transfer member home position count value is corrected at a specific timing 56.

Next, the meaning of the home position count value correction will be described below. In the algorithm based on the flow described above, the intermediate transfer member home position signal 38 immediately before detecting the photosensitive member home position signal 39 is used as the main home. Further, the main home is controlled so as to be always "0" at the time of starting the formation of one image. That is, the image forming standard on the software is always the time when the numerical value described in the intermediate transfer member home position count value 50 in FIGS. 9 to 10 is “0”. In an actual operation, a phase difference in home position detection occurs due to a difference between the circumferential length of the intermediate transfer body 1 and the circumferential length of the photoconductor 3, so that the main home is not "0" at a certain point.
If this is left as it is, and image formation is always continued using the same intermediate transfer member home position, the image forming region of the photoconductor 3 gradually shifts, and finally the image region extends to the photoconductor seam 6. I will get out. The home position count value correction according to the present embodiment accurately detects the home position origin return due to the expansion of the phase difference between the intermediate transfer member 1 and the photosensitive member 3, and detects it immediately before detecting the photosensitive member home position signal 39. Intermediate transfer member home position signal 3
The intermediate transfer body home position count value itself, which is counted up in step 8, is corrected so that the intermediate transfer body home position count value 50 is always "0". Controls the mask for software interrupt processing. As a result, even if the origin return occurs due to the expansion of the phase difference, the timing of the image signal 45 never exceeds one revolution of the intermediate transfer member 1 and the photosensitive member 3, and the printing speed can always be kept high. it can.

This is the end of the description of FIG. There is a constant Td in the total delay time described in the conventional example. However, in the second embodiment, it is not necessary to directly consider Td as in the first embodiment. The reason for this has been described in the first embodiment, and will be omitted.

Further, in the second embodiment, the phase difference time δt shown in the conventional example and the first embodiment does not appear. Since the strict definition of the phase difference time is the time difference from the detection of the intermediate transfer member home position signal 37 to the detection of the photoconductor home position signal 38, the phase difference time naturally exists also in this embodiment. .. However, the intermediate transfer member position detection mark 2
If the number N is selected based on the above equations (1) and (2), it is not necessary to bother to obtain the phase difference time and set it each time the photoconductor home position signal 38 is detected.

The formula (1) will be described here. 14
Represents the positional relationship between the image area and the photoconductor.
In FIG. 14, points P and U are the seams of the photoconductor, and therefore the length Lm of PU is the circumference of the photoconductor. The photoconductor is assumed to move from left to right in FIG. The photoconductor position detection mark is located at point M to the right of point P. When the photoconductor position detection mark passes the photoconductor detection sensor, a photoconductor home position signal is output. As described with reference to FIG. 9 or FIG. 10, the print start is started when a predetermined number of intermediate transfer body home position signals are counted from the time when the photoconductor home position signal is output. At this time, the distance between the photosensitive member position detection mark M and the printing start point changes depending on the timing of the intermediate transfer member home position signal and the photosensitive member home position signal, but the maximum change width is the intermediate transfer member home position. It is a distance corresponding to the signal interval. This distance is a value obtained by dividing the circumference of the intermediate transfer body by the number N of the intermediate transfer body position detection marks. Since the peripheral length of the intermediate transfer member and the peripheral length of the photosensitive member are originally made substantially equal to each other, the above distance is Lm.
It is represented by / N. That is, when the print start point is the Q point, the point at which the print is started later than the above timing is the R point. The image area on the photoconductor is determined by using the Q point or the R point as a reference point, and the image area moves on the photoconductor due to the peripheral length difference δl between the photoconductor and the intermediate transfer body as described above. As described with reference to FIGS. 9 and 10, the movement direction is the direction of arrow A in FIG. 14A and the direction of arrow B in FIG. 14B. The movement distance is δl per rotation.
When the number of rotations of the photoconductor for one color image is n, then δl × n. Therefore, when the image region is most advanced on the photoconductor (when it is moved to the right), the point P is the point P to the right by δl × n from the point Q. Further, when the image area is most retracted on the photoconductor (when it moves to the left), the point U becomes the left U point by δl × n from the T point. Therefore, when the size of the image area is Lp, the peripheral length Lm of the photoconductor must satisfy the following expression (3).

Lm> Lp + Lm / N + 2 × δl × n (3) By solving the equation (3) for N, the equation (1) is obtained.

That is, when N is selected so as to satisfy the expression (1), the image area does not overlap the photoconductor joint without considering the phase difference time δt.

Further, as described in the first embodiment of the present invention, in the present invention, unlike the conventional example, the delay time Td (after the photoconductor position detection sensor detects the photoconductor position detection mark, the photoconductor seam is Instead of using the time to reach the position of the photosensitive member position detection sensor), the intermediate transfer member home position signal is counted. For this purpose, when the distance between the position of the photoconductor position detection mark and the photoconductor seam is DT, the value M of M = DT / (Lm / N) (2) must be an integer.

It suffices that the value of N satisfies the above equations (1) and (2). However, since the amount of computer software increases as the value of N increases, the above equations (1) and (2) are satisfied. It is best to choose the smallest value that

[0104]

As described above, according to the present invention, one photosensitive member position detection mark is provided on the photosensitive member, a plurality of intermediate transfer member position detection marks are provided on the intermediate transfer member, and the photosensitive member and the intermediate transfer member are provided. A means for selecting one of a plurality of position detection marks provided on the intermediate transfer member based on the detection timing of the position detection mark of the photosensitive member and the position detection mark of the intermediate transfer member in a rotated state; , A means for measuring the time difference between the detection of the selected mark on the intermediate transfer member and the position detection mark on the photosensitive member, and the selected mark position on the intermediate transfer member as the image forming reference position. Since the image formation timing is determined based on the time difference between the intermediate transfer body and the photoconductor, the phase difference due to the rotation of the intermediate transfer body and the photosensitive body, which have different circumferential length differences, causes the home position return width even if the home position home return occurs. The minimum The timing of pressing and forming an image never exceeds the circumference of the intermediate transfer member or the photosensitive member, so the printing speed can always be kept high while forming the image while avoiding the seams of the photosensitive member. High and extremely useful.

[Brief description of drawings]

FIG. 1 is a diagram showing an intermediate transfer member of an electrophotographic apparatus according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing a phase difference compensating method for an electrophotographic apparatus according to the first embodiment of the present invention, showing a case where the peripheral length of a photosensitive member is shorter than the peripheral length of an intermediate transfer member.

FIG. 3 is a timing chart showing a phase difference compensating method for the electrophotographic apparatus according to the first embodiment of the present invention, showing a case where the peripheral length of the photosensitive member is longer than that of the intermediate transfer member.

FIG. 4 is a flowchart of the software of the electrophotographic apparatus according to the first embodiment of the present invention, showing the initialization portion of the home position manager.

FIG. 5 is a flowchart of software of the electrophotographic apparatus according to the first exemplary embodiment of the present invention, showing a portion related to detection of an intermediate transfer member home position signal of a home position manager.

FIG. 6 is a flowchart of software of the electrophotographic apparatus according to the first exemplary embodiment of the present invention, showing a portion related to detection of a photoconductor home position signal of a home position manager.

FIG. 7 is a flowchart of software of the electrophotographic apparatus in the first embodiment of the present invention, showing an error processing routine of the home position manager.

FIG. 8 is a diagram showing an intermediate transfer member of an electrophotographic apparatus according to a second embodiment of the present invention.

FIG. 9 is a timing chart showing a phase difference compensating method for an electrophotographic apparatus according to a second embodiment of the present invention, showing a case where the peripheral length of a photosensitive member is shorter than the peripheral length of an intermediate transfer member.

FIG. 10 is a timing chart showing a phase difference compensating method for an electrophotographic apparatus according to a second embodiment of the present invention, showing a case where the peripheral length of a photosensitive member is longer than that of an intermediate transfer member.

FIG. 11 is a flowchart of the software of the electrophotographic apparatus according to the second embodiment of the present invention, showing the initialization portion of the home position manager.

FIG. 12 is a flowchart of software of the electrophotographic apparatus according to the second embodiment of the present invention, showing a portion related to detection of an intermediate transfer member home position signal of a home position manager.

FIG. 13 is a flowchart of the software of the electrophotographic apparatus according to the second embodiment of the present invention, showing a part relating to detection of a photoconductor home position signal of a home position manager.

FIG. 14 is a formula (1) for determining the number N of intermediate transfer member position detection marks of the electrophotographic apparatus in the second embodiment of the present invention,
Explanatory drawing for explaining (2)

FIG. 15 is a diagram showing an intermediate transfer member used in a conventional electrophotographic apparatus.

FIG. 16 is a diagram showing the periphery of a photoconductor used in a conventional electrophotographic apparatus.

FIG. 17 is a diagram showing a configuration of a conventional electrophotographic apparatus.

FIG. 18 shows a phase difference compensation method for an electrophotographic apparatus of a conventional example,
The figure which shows about the case where the circumference of the photoconductor is shorter than the circumference of the intermediate transfer body.

FIG. 19 shows a phase difference compensating method for a conventional electrophotographic apparatus,
FIG. 3 is a diagram showing a case where the circumference of the photoconductor is longer than that of the intermediate transfer body

[Explanation of symbols]

 1 intermediate transfer body 2 intermediate transfer body position detection mark 3 photoconductor 4 photoconductor position detection mark 5 photoconductor position detection sensor 6 photoconductor seam 7 image forming area top 8 exposure position 9 from photoconductor position detection mark to photoconductor seam Distance 25 Intermediate transfer member position detection sensor 38 Intermediate transfer member home position signal 39 Photosensitive member home position signal 40 Phase difference time 41 Print command

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location G03G 15/16 21/00 118 (72) Inventor Yuzo Kawano 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Sangyo Co., Ltd. (72) Inventor Makoto Ueoka 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. An endless belt or drum-shaped photosensitive member having a photosensitive layer on its surface, a photosensitive member position detecting means for detecting a position of the photosensitive member in a rotating direction, and a latent image by scanning on the photosensitive member. Image forming means for forming a latent image, developing means of a plurality of colors for developing the latent image, an intermediate transfer body for temporarily holding the visualized image on the photoconductor, and rotation of the intermediate transfer body. An electrophotographic apparatus having an intermediate transfer member position detecting means for detecting a position in a direction, wherein the photosensitive member is provided with one position detecting mark, and the intermediate transfer member is provided with a plurality of position detecting marks. 2. A photosensitive member and an intermediate transfer member are rotated,
A means for selecting one of a plurality of position detection marks provided on the intermediate transfer member based on the detection timing of the position detection mark of the photosensitive member and the detection timing of the position detection mark of the intermediate transfer member is provided. The electrophotographic apparatus according to claim 1, wherein the selected mark position is used as an image formation reference position, and the image formation timing is determined based on this reference position. 3. A photosensitive member and an intermediate transfer member are rotated,
Means for selecting one from a plurality of position detection marks provided on the intermediate transfer member based on the detection timing of the position detection mark of the photosensitive member and the detection timing of the position detection mark of the intermediate transfer member, A means for measuring the time difference between the detection of the selected mark and the position detection mark of the photoconductor, and the selected mark position as an image formation reference position, and based on this reference position and the time difference The electrophotographic apparatus according to claim 1, wherein the image forming timing is determined. 4. The number of cycles required to form one color image, wherein the difference between the peripheral length of the photosensitive member and the peripheral length of the intermediate transfer member is .delta.l, the peripheral length of the photosensitive member is Lm, the maximum image area length is Lp. The electrophotographic apparatus according to claim 1, wherein the number N of home positions of the intermediate transfer member satisfies N> Lm / (Lm-Lp-2 * [delta] l * n), where n is n. 5. A position detection mark applied to a photoconductor, wherein a signal generated each time a plurality of position detection marks provided on an intermediate transfer member passes through an intermediate transfer member position detection sensor is used as an intermediate transfer member home position signal. Of the intermediate transfer body home position signal and the photo conductor home position signal detected immediately before the photo conductor home position signal is detected. A time interval is defined as a phase difference time, and a change in the relative position between the photoconductor and the intermediate transfer member is detected by detecting a change in the sign of the phase difference time. The electrophotographic apparatus according to claim 1, further comprising means for recognizing that the interval has been exceeded. 6. The intermediate transfer member home position signal is set to 0 according to the order of generation of the intermediate transfer member home position signal.
Is stored as the intermediate transfer body home position count value, and the intermediate transfer body home position count value is stored as the main home value each time the photoconductor home position signal is generated. The electrophotographic apparatus according to claim 4, wherein a sign change of a phase difference time between the position signal and the photoconductor home position signal is detected. 7. An interrupt means for increasing / decreasing the intermediate transfer member home position count value based on the value of the main home value when a sign change of the phase difference time between the intermediate transfer member home position signal and the photosensitive member home position signal is detected. The electrophotographic apparatus according to claim 5, further comprising: