JPH0980862A - Image forming device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To prevent the residual toner to be cleaned from remaining on the photosensitive member or the intermediate transfer member in the case of defective conveyance of the recording material such as non-feeding and double feeding, and to improve image quality and maintainability. Try. SOLUTION: The distance between the first developing device and the primary transfer means on the latent image carrier path is l1, the distance between the primary transfer means and the secondary transfer means on the intermediate transfer body path is l2, and the secondary transfer is performed. The distance between the recording medium detection unit and the recording medium detection unit on the recording medium conveyance path is l3,
Perimeter of the intermediate transfer member is L, maximum allowable recording material length is lm
Let ax be L> lmax-l1-l2 + l3,
Further, when the recording material detecting unit detects the recording material at the predetermined time tSE, the process proceeds to the non-feed processing sequence, and the subsequent development and primary transfer are not performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image using an electrophotographic process, such as a printer or a copying machine, and more particularly to an electrophotographic image forming apparatus using an intermediate transfer member.

[0002]

2. Description of the Related Art Image forming apparatuses using a color electrophotographic process are classified into several types according to a method of superposing images of respective colors. Of these, the toner image formed on the photoconductor is transferred to the intermediate transfer body for each color, the colors are overlaid, and after the color image is completed on the intermediate transfer body, it is collectively transferred to the recording material (intermediate transfer method) Has advantages such as high flexibility in setting the recording material conveyance path, good compatibility with paper types, and high image quality.

By the way, in an image forming apparatus such as a printer or a copying machine, the recording material does not reach the secondary transfer portion due to a failure in picking up from a container for accommodating the recording material (referred to as non-feeding). When two sheets of paper are overlapped and dragged while being conveyed (called double feeding), a conveyance failure of the recording material often occurs. In that case, it is necessary to detect it, interrupt the image forming operation, and shift to the operation of resetting to the initial state. In the color electrophotographic process of the intermediate transfer method, if the next image forming job is already started and a toner image is already formed on the photoconductor or the intermediate transfer member when the conveyance failure of the recording material is detected, For the next image forming operation, the toner image formed on the photoconductor or the intermediate transfer body must be directly cleaned. In the case of a normal cleaning operation, it is sufficient to clean a small amount of toner (transfer residual toner) remaining without being transferred in the primary transfer or the secondary transfer, so that sufficient cleaning can be performed and the amount of waste toner stored is small. . However, as described above, when the toner image itself is cleaned, the toner amount is remarkably large as compared with the normal amount, and therefore a cleaning residue may occur, which may cause scumming in the next image. Further, assuming that the toner image itself is frequently cleaned as described above, the amount of waste toner to be stored increases, the size of the waste toner container increases, and the size of the apparatus itself increases, or the waste toner container is replaced. It is necessary to set a shorter period, which deteriorates maintainability.

Therefore, in Japanese Unexamined Patent Publication No. 5-289440, when a paper feed error is detected, the operation is stopped after the image formation on the intermediate transfer member is finished, and a return signal is input. It is disclosed that the image is directly transferred to a recording material and output.

[0005]

However, in the above-mentioned conventional example, the toner image is left on the intermediate transfer member for an indefinite time, the characteristics such as the charge amount are changed, and the transfer to the recording material is not performed thereafter. It may not work well. Further, as a result of a paper feed error, there is a problem that the operator touches the toner on the intermediate transfer member and stains his / her hand when trying to perform the jam clearance operation.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. (1) A latent image carrier and a latent image on the latent image carrier are toner images. Developing means for developing a plurality of colors, an intermediate transfer body that carries the toner image transferred from the latent image carrier, and a primary device that transfers the toner image from the latent image carrier to the intermediate transfer body. Transfer means, secondary transfer means for transferring the toner image from the intermediate transfer body to a recording material, and the second transfer means for transferring the toner image to the recording material.
In an image forming apparatus, which is provided with the recording material detection means on the upstream side of the next transfer means, forms a multicolor image by collectively transferring the toner images of a plurality of colors onto the intermediate transfer body and then collectively transferring the recording material onto the recording material. , The distance between the developing means and the primary transfer means on the latent image carrier path is l1, the distance between the primary transfer means and the secondary transfer means on the intermediate transfer body path is l2, the secondary L> lmax + l1 + l2-l3 where L3 is the distance between the transfer means and the recording material detection means on the recording material conveyance path, L is the circumferential length of the intermediate transfer member, and lmax is the maximum allowable recording material length. More preferably, when a plurality of image forming operations are continuously performed, the time at which the developing unit starts the developing operation for the nth image forming operation is tD, and n−
The time when the trailing edge of the recording material of the maximum length passes the recording material detecting means for the first image forming operation is tE,
The recording material conveyance start time from the state in which the recording material is accommodated for the n-th image forming operation is set to tF, and the recording material front end serves as the recording material detection means from the state in which the recording material is accommodated. Δt is the time required for the transportation to reach
When F is set, the recording material conveyance start time tF is set such that the time after ΔtF has elapsed from tF is after tE and before tD, and after the time when ΔtF has elapsed from tF, And a predetermined time tSF before tD
In the case where the recording material detecting means detects the absence of the recording material, it has a means for prohibiting the developing operation after that time.
(2) Latent image carrier, developing means for a plurality of colors that visualize the latent image on the latent image carrier as a toner image, and the toner image transferred from the latent image carrier to be carried. Intermediate transfer body, primary transfer means for transferring the toner image from the latent image carrier to the intermediate transfer body, secondary transfer means for transferring the toner image from the intermediate transfer body to a recording material, and the recording material. A recording material detection unit is provided on the upstream side of the secondary transfer unit in the transporting path of the multi-color image by superimposing toner images of a plurality of colors on the intermediate transfer member and then collectively transferring the images onto the recording material. In the image forming apparatus for forming a sheet, the distance between the primary transfer unit and the secondary transfer unit on the intermediate transfer member path is set to l.
2. If the distance between the secondary transfer means and the recording material detecting means on the recording material conveying path is l3, the peripheral length of the intermediate transfer member is L, and the maximum allowable recording material length is lmax, L> lmax + l2-l3, and more preferably, the time at which the primary transfer unit starts the primary transfer operation for the nth image forming operation is tT when a plurality of image forming operations are continuously performed. , N−1th image forming operation, the time when the trailing edge of the recording material of the maximum length passes the recording material detecting means is t.
E, the recording material conveyance start time from the state where the recording material is accommodated for the n-th image forming operation is tF, and the recording material front end is the recording material when the recording material is accommodated. Assuming that the time required for the conveyance to reach the detection means is ΔtF, the time when ΔtF has elapsed from tF is after tE and before tT.
The conveyance start time tF of the recording material is determined, and from tF to ΔtF
When the recording material detection unit detects the absence of the recording material at a predetermined time tSF that is after the elapsed time and before tT, the recording material detection unit has a unit that prohibits the primary transfer operation after that time. , Is characterized.

[0007]

1 is a schematic sectional view of a color printer which is an embodiment of an image forming apparatus of the present invention. The charging roller 2 charges the photoconductor 1, which is a latent image carrier, to a uniform predetermined potential (for example, −700 V). The laser beam from the exposure device 3 that performs image exposure by performing laser scanning is guided to the photoconductor 1 by the folding mirrors 31 and 32, and the surface potential of the portion irradiated with the beam is, for example, −10.
An electrostatic latent image is formed by the attenuation to about 0V. Next, in the one-component pressure contact developing type developing device 4 which can be separated from and contacted with the photoconductor 1, the yellow developing device 41 is brought into contact with the other developing devices and the other developing devices are separated from each other, and the negative polarity is obtained by the action of the electric field of the power source not shown. Reversal development of yellow toner
Visualized above. The visualized yellow toner is transferred to the primary transfer roller by applying a bias having a polarity opposite to that of the toner to the primary transfer roller on the intermediate transfer body 51 whose resistance value is set to an appropriate value. The untransferred toner on the photoconductor 1 is collected by a photoconductor cleaner 6 that contacts a blade to clean the toner. The same operation is performed on the intermediate transfer member 5.
By repeating the process for the magenta developing device 42, the cyan developing device 43, and the black developing device 44 at the position of 1 and the light emission timing of the exposure device 3, the toners of the respective colors are superposed on the intermediate transfer member 51 to form a full-color image. To be done. During this time, the secondary transfer roller 56 and the intermediate transfer member cleaner 52 are in the separated state. On the other hand, after the recording material 9 is conveyed from the paper feed cassette 82 to the registration roller 85 by the pickup roller 84, the recording material 9 is formed by the secondary transfer roller 56 and the drive roller 55 in synchronization with the full-color image on the intermediate transfer body 51. Is transported to the secondary transfer unit. In the secondary transfer portion, the secondary transfer roller 56 contacts the intermediate transfer member 51 to form a nip portion in synchronization with the recording material 9, and a bias is applied by a power source (not shown) to record a full-color toner image. It is transferred to the material 9. At this time, the cleaner 52 of the intermediate transfer body 51 contacts the intermediate transfer body 51, and the transfer residual toner after the secondary transfer passes through the tension roller 54 and is collected by the intermediate transfer body cleaner 52. The recording material 9 is fixed by the fixing device 7 after the full color image is transferred, and is discharged to the outside of the device.

Several methods are conceivable as an operation procedure for continuously forming a plurality of color images in this intermediate transfer method. The number of output sheets per hour is the largest because there is no wasteful operation.
This is a system in which the primary transfer of each color from the photoconductor to the intermediate transfer member 51 is repeated without interruption at the secondary transfer portion, and at the same time, the secondary transfer onto the recording material 9 is performed at the secondary transfer portion. For example, the primary transfer operation is continuously repeated in the order of yellow, magenta, cyan, black, yellow, magenta, cyan, and black, and the area where the primary transfer of black is performed is performed on the recording material 9 simultaneously with the primary transfer operation. Secondary transfer is also performed. By doing so, the color image can be output once every four rotations of the intermediate transfer member 51. As a method of not performing such a continuous operation, after all the primary transfer of each color from the photoconductor 1 to the intermediate transfer body 51 is performed, the intermediate transfer body 51 is rotated again to perform the secondary transfer to the recording material 9. There is also a method of doing so, but at that time, the color image is output once every five rotations of the intermediate transfer member 51.

FIG. 2 shows the n-1st sheet and the nth sheet in the case of the continuous multiple image forming method in which the color image is output once by four rotations of the intermediate transfer member 51 in the image forming apparatus of FIG. 3 is a timing chart of the main processes showing the operation of the first half of FIG. The exposure, development, and primary transfer operations are performed corresponding to the image portion with a time lag due to the different positions on the photoconductor 1. Further, the secondary transfer operates corresponding to the image portion with a time lag due to the different position on the intermediate transfer body 51. The intermediate transfer member 51 is continuously rotated at a constant speed to continuously perform primary transfer of yellow (Y in the drawing), magenta (M in the drawing), cyan (C in the drawing), and black (K in the drawing) colors in order. The second transfer is performed once for every four rotations of the intermediate transfer member 51.
Times take place. In this way, high speed color image formation is achieved.

As described above, in an image forming apparatus such as a printer or a copying machine, the recording material 9 such as paper or film is often not properly conveyed. In particular, when a plurality of recording materials 9 are picked up from the paper feed cassette 82 that previously stores the recording materials 9 and are simultaneously conveyed to the recording material conveying path 8 (double feeding).
In many cases, the recording material 9 is not picked up and conveyed to the recording material conveyance path 8 (non-delivery).

When the recording materials 9 are fed in a double-fed manner without any overlap, no problem in operation timing occurs, but in many cases, the leading edge is often displaced to some extent.
A sensor for detecting the presence / absence of the recording material 9, such as the recording material detection sensor 81, detects the presence / absence of the recording material 9 at a predetermined timing, and determines whether or not the recording material 9 is conveyed normally based on the information. To be done. When the leading edge of the recording material 9 is misaligned and is double-fed, the length of the recording material 9 is longer than expected, and the recording material detection sensor provided on the recording material conveying path 8 is provided. Reference numeral 81 detects the presence of the recording material 9 at the timing when the recording material 9 has not already passed and is present, and it is determined that the conveyance is defective.

As described above, whether or not the recording material 9 is detected by the recording material detection sensor 81 immediately after the recording material 9 is fed to the position of the recording material detection sensor 81.
The double feeding is determined by whether or not the recording material detection sensor 81 detects the recording material 9 at a timing immediately after the length of the recording material 9 which has been assumed in advance passes through the recording material detection sensor 81.

By the way, when performing a continuous plural-sheet image forming operation, when double feeding is detected in the (n-1) th image forming operation, or when non-feeding is detected in the nth image forming operation, n-1
Since the second image forming operation is normal, it is desirable to output the image as it is. On the other hand, if the nth image forming operation has already been performed when non-feeding or double feeding is detected, for example, the developing operation has already been performed and the toner image has already been formed on the photoconductor 1. In this case, the toner image must be cleaned with the photoconductor cleaner 6 and then image formation must be performed again. Further, when the toner image is partially transferred onto the intermediate transfer body 51, the toner image must be once cleaned by the intermediate transfer body cleaner 52 and then the image formation must be started again. The problems it causes are as described in the description of the prior art.

According to the present invention, when the recording material 9 is not properly conveyed, the image forming operation is appropriately interrupted before the n-th developing operation or the primary transfer operation is started. Or intermediate transfer body cleaner 52
The conditions and sequence processes to be satisfied by the path lengths of the respective parts are disclosed so that no inconvenience occurs. First, the conditions that each path length must satisfy will be described.

FIG. 3 is a schematic diagram for explaining the image carrying path length in the image forming apparatus of FIG. On the photoconductor 1, the distance from the point P1 to the point P2 at which the development (the first color developing device that develops first among the developing devices for each color, the yellow developing device in the case of the sequence of FIG. 2) is performed is l1, The distance from the point P2 for performing the primary transfer to the point P3 for performing the secondary transfer on the intermediate transfer body 51 is 12 and from the point P3 for performing the secondary transfer on the recording material conveyance path 8 to the point P4 for detecting the recording material. Let the distance be l3. The recording material detection sensor 81 outputs an ON signal while the recording material 9 is passing over the point P4, and outputs an OFF signal at other times. Therefore, at the predetermined leading edge detection timing, it is determined that the recording material detection sensor 81 is normal when the recording material detection sensor 81 is ON, and is not sent when the recording material detection sensor 81 is OFF. If the recording material detection sensor 81 is OFF at the predetermined trailing edge detection timing, it is normal.
If it is N, it is judged as a double feed.

Here, if the time at which the multifeed is judged in the n-1th image forming operation is earlier than the developing operation or the primary transfer operation in the nth image forming operation, the nth developing operation or the primary transfer operation is performed. Prior to starting the operation, the image forming operation may be interrupted and the toner image to be cleaned need not be formed. In a normal image forming apparatus, several kinds of recording material 9 lengths are allowed, but since the trailing edge detection timing of the recording material having the maximum length is the latest, recording of the maximum allowable length is performed. If the above condition is satisfied for the material 9, it is satisfied in all cases. Of the lengths of the recording material 9 assumed in advance for determining the conveyance failure of the recording material 9, the maximum length allowed by the image forming apparatus is defined as the maximum recording material length lmax.

The conditions under which the image formation can be interrupted without entering the next developing operation after detecting the double feed when the path length is as shown in FIG. 3 will be described with reference to the timing chart of FIG. The timing chart of FIG. 4 shows whether or not each of the points P1, P2, and P3 of development, primary transfer, and secondary transfer is performing an image forming operation, and the recording material 9 is passing at the position P4 of the recording material detection sensor 81. Indicates whether or not. Strictly speaking, since the margins are provided at the leading end and the trailing end of the recording material 9, the lengths of the image forming portion and the recording material 9 are different, but they are not essential to the present invention and are ignored. That is, the image is formed over the entire length of the recording material. In the timing chart of FIG. 4, the timing delay time t1 between the developing portion and the primary transfer portion is
This is due to the path difference l1 on the photoconductor 1, and when the process speed is v, t1 = 11 / v. The delay time t2 between the primary transfer portion and the secondary transfer portion is due to the path difference 12 on the intermediate transfer member 51, and is t2 = 12 / v. Two
The delay time difference t4 between the next transfer portion and the recording material conveyance detection sensor 81 is due to the path difference l3 on the paper conveyance path 8.
3 = 13 / v. The cycle T of the image forming operation for each color is
It is determined by the circumferential length L of the intermediate transfer member 5, and T = L / v. Further, the time tmax during which the recording material 9 having the maximum allowable length passes through the recording material conveyance detection sensor 81 is tmax.
= 1max / v.

In the timing chart of FIG. 4, the start timing tD of the developing operation for the first color in the nth image forming operation is used as a reference. 1 in the nth image forming operation
The timing when the primary transfer of the color is started is tD + t1. Then, the timing at which the primary transfer of the n−1th final color is started can be traced back by one round of the intermediate transfer member 51 from the timing at which the primary transfer of the nth first color is started, so tD + t1−T is there. Further, the timing at which the secondary transfer operation in the (n-1) th image forming operation is started is when t2 has elapsed from the timing at which the primary transfer operation of the final color of the (n-1) th image forming operation was started. Therefore, tD + t1-T + t2. The leading edge of the recording material 9 in the (n-1) th image forming operation is the recording material detection sensor 8
The timing of passing 1 may be traced back by t3 from the timing when the secondary transfer of the n-1th image forming operation is started, and is tD + t1-T + t2-t3. Since the maximum time during which the recording material 9 can be present on the recording material detection sensor 81 is tmax, the time tmax has elapsed from the timing when the leading edge of the recording material 9 passed the recording material detection sensor 81 the last time, that is, the maximum allowable value. Timing tE at which the trailing edge of the length of the recording material 9 passes the recording material detection sensor 81
After that, the recording material 9 is detected, and if a signal indicating that the recording material 9 is present is output at that time, it is determined that the multi-feeding has occurred. From the history thus far, tE can be written as tE = tD + t1-T + t2-t3 + tmax. Of course, the timing tSE for detecting the rear edge is
It must be after the timing tE described above. This t
If SE is earlier than the timing tD when the developing operation is started, the developing operation can be canceled in advance. In order for such timing tSE to exist, tE <tD, that is, t1-T + t2-t3 + tmax> 0. When this condition is represented by the path length, L> lmax + l1-l2 + l3. At this time, as described above, the trailing edge detection may be performed at the timing of tE <tSE <tD, and if the recording material 9 is present, the next developing operation may not be performed.

Next, the non-transmission in the n-th image forming operation is
Detected before starting the th 1st color development operation,
A method of performing processing for appropriately suspending the image forming operation will be described. That is, the n-th recording material 9 is picked up without waiting for the completion of the (n-1) th image forming operation, the recording material detection sensor 81 is previously conveyed, and the recording material detection sensor 81 is stopped there. It can be realized by That is, the pickup of the n-th recording material 9 is started as soon as possible, and it is attempted to know in advance whether or not the recording material 9 has not been sent. However, when the leading edge detection timing of the nth recording material 9 is earlier than the trailing edge detection timing of the n−1th recording material 9, the recording material 9 always exists on the recording material detection sensor 81. As a result, the timing for determining that the trailing edge of the recording material 9 in the n-1th image forming operation has normally passed is lost.

Therefore, in order to be able to perform the process of stopping the image forming operation before developing the toner image of the nth image forming operation on the photoconductor 1, it is necessary to detect the trailing edge of the n-1th image forming operation. It is understood that the leading edge of the n-th recording material 9 must be detected after the recording is performed and before the development operation of the first color of the n-th image forming operation is started. In order to have such a timing for detecting the leading edge, first, n−
It is necessary that the timing for detecting the trailing edge of the recording material 9 in the first image forming operation is earlier than the timing for starting the developing operation for the first color in the nth image forming operation. This is the same as the condition for interrupting the image forming operation before the start of development in the case of double feeding, so that L> lmax + l1-l2 + l3.

Further, after the trailing edge of the (n-1) th image forming operation is detected and before the development operation for the first color of the nth image forming operation is started, the recording material 9 of the nth recording material 9 is recorded. It is necessary to start the pickup operation of the recording material 9 so that the leading edge can be detected. Here, the time required for the conveyance from the state where the recording material 9 is accommodated to the arrival of the leading edge of the recording material 9 at the recording material detection sensor 81 is ΔtF, and the conveyance start from the state where the recording material 9 is accommodated ( Pickup start) When the timing is tF, the timing at which the leading edge of the recording material 9 reaches the recording material detection sensor 81 is tF + Δt.
F. Therefore, the timing for starting the developing operation for the first color of the n-th image forming operation is set to tD, and the trailing edge of the recording material 9 of the maximum length allowed above is the recording material detection sensor 81.
When the condition for starting the pick-up operation of the recording material 9 is expressed by using the time tE that passes through, it is sufficient if tF + ΔtF is after tE and before tD.

The timing tSF at which the leading edge is detected may be after the leading edge of the recording material 9 reaches the recording material detection sensor 81 and before the first color developing operation of the nth image forming operation is started. , TSF may be after tF + ΔtF and before tD. The leading edge is detected at such timing, and if the recording material 9 is detected, it is regarded as normal, and if it is not detected, it is determined that the recording material 9 is not sent. When it is determined that the image has not been sent, the developing operation of the nth image forming operation may be prohibited.

In order to prevent the developing operation, the developing rollers 41, 42, 43 and 44 are separated from the photoconductor 1 in the case of contact developing such as the pressure developing method as shown in the embodiment of FIG. Just go. In the case of non-contact development such as the jumping development method, a bias having a polarity that does not transfer toner may be applied.

Although the above-mentioned path length l1 has been described as the length from the position where the developing device for performing the image forming operation for the first color develops to the primary transfer position, as shown in FIG. When the developing position differs depending on the developing device, if the developing position farthest from the primary transfer position to the upstream side in the rotational direction of the photoconductor 1 is set as l1, which developing device is set to the first color. However, the above condition is satisfied, and the degree of freedom of the operation sequence is increased, which is more desirable.

FIG. 6 is a schematic view of a so-called rotary developing system in which a plurality of developing devices are selected by rotating. As represented by the rotary developing method, when the developing positions of a plurality of developing devices can be regarded as the same,
The length of the primary transfer position from that position may be set to l1.

Next, conditions for appropriately interrupting the image forming operation before starting the n-th primary transfer operation will be described. The basic method is the same as the method for obtaining the conditions for appropriately interrupting the image forming operation before starting the developing operation.

First, when the path length is as shown in FIG. 3, the condition under which the image formation can be interrupted without entering the n-th primary transfer operation after detecting the double feeding will be described with reference to the timing chart of FIG. . 1 of the first color in the nth image forming operation
The start timing tT of the next transfer operation is used as a reference. n-1
The timing when the primary transfer of the th final color is started is n
Since it is sufficient to trace back one cycle of the intermediate transfer body 51 from the timing when the primary transfer of the first color is started, tT
-T. Further, the timing at which the secondary transfer operation in the (n-1) th image forming operation is started is when t2 has elapsed from the timing at which the primary transfer operation of the final color of the (n-1) th image forming operation was started. Therefore, it is tT-T + t2. The timing when the leading edge of the recording material 9 passes the recording material detection sensor 81 in the (n-1) th image forming operation is n
It is sufficient to go back t3 from the timing when the secondary transfer of the -1st image forming operation is started, and tT-T + t2-t
It is 3. Since the maximum time that the recording material 9 can exist on the recording material detection sensor 81 is tmax, the recording material is recorded after the time tE when tmax has elapsed from the timing when the leading edge of the recording material 9 passed the recording material detection sensor 81 last time. 9 is detected, and if a signal indicating that the recording material 9 is present is output at that time, it is determined that the multi-feed has occurred. From the process so far, it can be written that tE = tT-T + t2-t3 + tmax. Of course, the timing tSE for detecting the rear edge is
It must be after the timing tE described above. This t
If SE is earlier than the timing tT when the primary transfer operation is started, the primary transfer operation can be canceled in advance. In order that such timing tSE can exist, tE <tT, that is, -T + t2-t3 + tmax> 0. When this condition is expressed by a path length, L> lmax + l2-l3. At this time, as described above, the trailing edge detection may be performed at the timing of tE <tSE <tT, and the next primary transfer operation may not be performed if the recording material 9 exists.

Regarding the process of detecting the non-delivery in the nth image forming operation before the nth first color primary transfer operation and canceling it, the nth first color developing operation is also performed. This is similar to the method of detecting and processing before starting. The timing of the developing operation under the above conditions may be replaced with the timing of the primary transfer operation. Therefore, the condition that the path length must satisfy is L> lmax + l2-l3, and the condition that the operation timing must satisfy is the recording material 9
Δt is a time required for the conveyance from the state where the recording material 9 is accommodated until the leading end of the recording material 9 reaches the recording material detection sensor 81.
F, the conveyance start (pickup start) timing from the state where the recording material 9 is accommodated is tF, and the timing when the primary transfer operation of the first color of the nth image forming operation is started is tF.
Assuming that T is the timing tSF at which the leading edge is detected, tF
+ ΔtF is after tE, before tT, and tSF is tF +
It may be after tF and before tT. The leading edge is detected at such timing, and if the recording material 9 is detected, it is regarded as normal, and if it is not detected, it is determined that the recording material 9 is not sent. When it is determined that the image has not been sent, 1 of the nth image forming operation is performed.
The next transfer operation may be prohibited.

In order to prevent the primary transfer, it is only necessary to apply a bias of a polarity that does not transfer the toner, or to separate the intermediate transfer member 51 from the photosensitive member 1.

(Embodiment 1) Table 1 shows a concrete embodiment corresponding to claims 1 and 2, which satisfies the condition of the path length, the condition of the recording material detection timing, and the condition of the recording material conveyance start.

[0031]

[Table 1]

At this time, from the time tE when the trailing edge of the recording material of the maximum length in the n-1th image formation passes the recording material detection sensor, the developing operation start time tD of the first color in the nth image formation. Until (L-lmax-l1-l2 +
It can be calculated by 13) / v, which is 0.2 seconds. Therefore, from the earliest time, the time tE at which the trailing edge of the maximum length recording material passes the recording material detection sensor, the time tSE at which the trailing edge detection is performed, and the time tF + ΔtF when the leading edge of the recording material reaches the recording material detection sensor. , The time tSF at which the leading edge is detected and the developing operation start time tD. This satisfies the condition that non-feeding and double feeding can be detected before the start of the developing operation described above.

FIG. 7 is a flow chart showing the operation sequence of the first embodiment. In the first embodiment, double feeding and non-feeding are detected before development of the next image formation, and the subsequent development operation and the subsequent steps are interrupted. What is shown in the flowchart is a part of control of a series of image forming operations based on the signal of the recording material detection sensor 81. Start and stop of normal exposure, development, primary transfer operation, secondary transfer operation, etc. are controlled by a timer set separately. First, the pickup operation of the recording material 9 which is the base point of the sequence is performed. When the time counted by the timer reaches tSF, which is before the developing operation start time tD, the recording material detection sensor 81 detects the presence or absence of the recording material 9, and if the recording material 9 does not exist, the non-delivery process is performed. Transfer to the sequence. In the non-feeding processing sequence, the developing operation and the primary transfer operation are not started, and the secondary transfer and fixing operations that are currently in progress are continued to continue.
Is discharged. Therefore, the image forming operation is restarted when an opening / closing signal of a jam releasing cover (not shown) or a restart signal from the operation panel or the like is input. If the recording material 9 is present,
The developing operation for the first color starts in accordance with the timing signal from the timer, and thereafter, each process repeats the start and stop, and images of four colors are superposed on the intermediate transfer body 51. Further, when the timing counted by the timer reaches tSE, the recording material conveyance sensor 81 detects the presence or absence of the recording material 9, and if the recording material 9 exists, the multi-feed processing sequence is entered. Similarly to the non-feeding process sequence, the double-feeding process sequence also continues the secondary transfer and fixing operations currently in progress, and discharges the recording material 9. If the recording material 9 does not exist, the operation is continued normally, the number of sheets is increased, and the operation is repeated until the desired number of sheets is reached.

(Embodiment 2) Next, Table 2 shows the second embodiment of the conditions of the path length, the condition of the recording material detection timing, and the recording material conveyance start, which correspond to claims 3 and 4.

[0035]

[Table 2]

At this time, from the time tE when the trailing edge of the recording material having the maximum length in the (n-1) th image formation passes the recording material detection sensor, the primary transfer operation of the first color in the nth image formation is started. The time until time tT is (L-1max-1 2 + l
3) / v can be calculated and it takes 0.2 seconds. Therefore, from the earliest time, the time tE at which the trailing edge of the maximum length recording material passes the recording material detection sensor, the time tSE at which the trailing edge detection is performed, and the time tF + ΔtF when the leading edge of the recording material reaches the recording material detection sensor. , The time tSF at which the leading edge is detected and the primary transfer operation start time tT. This satisfies the condition that non-feeding and double feeding can be detected before the start of the primary transfer operation described above.

The flowchart of FIG. 8 is a flowchart showing the operation sequence of the second embodiment. Example 2 is
Non-feeding and double feeding are detected before the primary transfer for the next image formation, and the next 1
This is a process of interrupting the subsequent transfer operation. The difference from FIG. 7 is that the next developing operation has already started when non-feeding or double feeding is detected, and the toner image is transferred to the intermediate transfer body 51 by performing processing such that primary transfer is not performed. I try not to. Other processes are the same as those in FIG. 7.

Photoreceptor 1 of Examples 1 and 2 described above
In the image forming apparatus satisfying the relationships among the upper path length, the path length on the intermediate transfer member 51, and the path length on the recording material conveying path 8, detection of non-feeding and double feeding at the above-described timing, and subsequent processing It was confirmed that by performing the above, the opportunity to clean the toner image to be originally transferred onto the recording material 9 can be almost eliminated.

[0039]

As described above, according to the present invention,
In the invention of claim 1, the distance between the developing means and the primary transfer means on the latent image carrier path is l1, and the distance between the primary transfer means and the secondary transfer means on the intermediate transfer body path is l.
2, assuming that the distance between the secondary transfer means and the recording material detection means on the recording material conveyance path is l3, the circumferential length of the intermediate transfer member is L, and the maximum allowable recording material length is lmax, L> lmax + l1 + l2-l3 Therefore, in the continuous image forming operation for a plurality of sheets,
Even if the recording material is double-fed, the toner image to be cleaned is not formed on the photoconductor 1, and the cleaning residue of the photoconductor cleaner does not occur, so that the next image is not stained. It is possible to realize a high quality intermediate transfer type image forming apparatus. Also, the amount of waste toner to be stored is small, and the waste toner container for the photoconductor becomes smaller, or
It is possible to set a longer replacement period for the waste toner container for the photoconductor, and it is possible to reduce the size of the apparatus and improve maintainability.

Further, in the invention according to claim 2,
When a plurality of image forming operations are continuously performed, the time when the developing unit starts the developing operation for the nth image forming operation is set to tD, and the maximum length for the (n-1) th image forming operation is set. The time when the trailing edge of the recording material passes the recording material detecting means is tE, and the recording material conveyance start time from the state where the recording material is accommodated for the n-th image forming operation is tF, and the recording material is ΔtF is the time required for the conveyance from the housed state until the leading edge of the recording material reaches the recording material detection means.
Then, the conveyance start time tF of the recording material is determined so that the time after ΔtF has elapsed from tF is after tE and before tD, and after the time when ΔtF has elapsed from tF, and When the recording material detection unit detects the absence of the recording material at a predetermined time tSF, which is before tD, even if the recording material is not fed, it has a unit for prohibiting the developing operation after that time. Since the toner image to be cleaned is not formed on the photoconductor 1, the above effect becomes remarkable.

According to the third aspect of the invention, since L> lmax-l2 + l3, in the plural-sheet continuous image forming operation,
Even if the recording material is double-fed, the toner image to be cleaned is not formed on the intermediate transfer member, and the cleaning residue of the intermediate transfer member cleaner does not occur, so that the next image is not stained. It is possible to realize a high quality intermediate transfer type image forming apparatus. Also, the amount of waste toner to be stored is small, and the waste toner container for the intermediate transfer body becomes smaller,
Alternatively, it is possible to set the replacement time of the waste toner container for the intermediate transfer member to be long, and it is possible to realize the downsizing of the apparatus and the improvement of maintainability.

Further, in the invention according to claim 4,
When a plurality of image forming operations are continuously performed, the time at which the primary transfer unit starts the primary transfer operation for the nth image forming operation is set to tT, and for the (n-1) th image forming operation. The time when the trailing edge of the recording material of the maximum length passes the recording material detecting means is tE, and the recording material transport start time from the state where the recording material is accommodated for the nth image forming operation is tF.
And the time required for conveyance from the state where the recording material is accommodated until the leading end of the recording material reaches the recording material detecting means is Δt.
Assuming that F, the recording material conveyance start time tF is set such that the time when ΔtF has elapsed from tF is after tE and before tT, and after the time when ΔtF has elapsed from tF, And a predetermined time tSF that is before tT
When the recording material detection means detects the absence of the recording material, it has a means for prohibiting the primary transfer operation after that time, so that even if the recording material is not fed, the intermediate transfer is performed. Since the toner image to be cleaned is not formed on the body 1, the above effect becomes remarkable.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment in which the present invention is applied to a printer device.

FIG. 2 is a timing chart of an embodiment in which the present invention is applied to a printer device.

FIG. 3 is a schematic diagram of a path length for explaining the conditions of the present invention.

FIG. 4 is a timing chart for explaining the conditions of the present invention.

FIG. 5 is a schematic diagram of a path length for explaining the conditions of the present invention.

FIG. 6 is a schematic diagram of a path length for explaining the conditions of the present invention.

FIG. 7 is a flowchart showing an operation sequence of the first embodiment of the present invention.

FIG. 8 is a flowchart showing an operation sequence of the second embodiment of the present invention.

[Explanation of symbols]

 1 Photosensitive Body 2 Charging Roller 3 Exposure Device 4 Developing Device 5 Transfer Device 51 Intermediate Transfer Body 52 Intermediate Transfer Body Cleaner 53 Primary Transfer Roller 56 Secondary Transfer Roller 6 Photosensitive Body Cleaner 7 Fixing Device 8 Recording Material Conveying Path 81 Recording Material Detection Sensor 82 Recording material storage tray 84 Pickup roller 9 Recording material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuro Osawa 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Co., Ltd. (72) Inventor Akira Kubota 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Within the corporation

Claims (4)

[Claims] 1. A latent image carrier, a developing means of a plurality of colors for developing the latent image on the latent image carrier as a toner image, and the toner image transferred from the latent image carrier. An intermediate transfer member that carries the toner image, a primary transfer unit that transfers the toner image from the latent image carrier to the intermediate transfer member, a secondary transfer unit that transfers the toner image from the intermediate transfer member to a recording material, and The recording material detecting means is provided on the upstream side of the secondary transfer means in the recording material conveying path, and the toner images of a plurality of colors are superposed on the intermediate transfer body and then collectively transferred to the recording material. In an image forming apparatus for forming a color image, the distance on the latent image carrier path between the developing means and the primary transfer means is 11, and on the intermediate transfer body path between the primary transfer means and the secondary transfer means. At a distance of 12 between the secondary transfer means and the recording material detection means. The distance in the serial recording material conveyance on the path l
3. The image forming apparatus, wherein L> lmax + l1 + l2-l3, where L is the peripheral length of the intermediate transfer member and lmax is the maximum permissible recording material length. 2. When a plurality of image forming operations are continuously performed, the time when the developing unit starts the developing operation for the nth image forming operation is set to tD, and the n-1th image forming operation is performed. On the other hand, the time when the trailing edge of the recording material of the maximum length passes the recording material detecting means is tE, and the recording material conveyance is started from the state where the recording material is accommodated for the nth image forming operation. Assuming that the time is tF, and the time required for conveyance from the state where the recording material is accommodated until the leading end of the recording material reaches the recording material detecting means is ΔtF, then tF
From the time tD after tE and tD
The recording material conveyance start time tF is set as before, and the recording material detection unit detects the recording material at a predetermined time tSF after the time when ΔtF has elapsed from tF and before tD. 2. When the absence is detected, a means for prohibiting the developing operation after that time is provided.
The image forming apparatus as described in the above. 3. A latent image carrier, a developing device of a plurality of colors for developing the latent image on the latent image carrier as a toner image, and the toner image transferred from the latent image carrier. An intermediate transfer member that carries the toner image, a primary transfer unit that transfers the toner image from the latent image carrier to the intermediate transfer member, a secondary transfer unit that transfers the toner image from the intermediate transfer member to a recording material, and The recording material detecting means is provided on the upstream side of the secondary transfer means in the recording material conveying path, and the toner images of a plurality of colors are superposed on the intermediate transfer body and then collectively transferred to the recording material. In an image forming apparatus for forming a color image, the distance between the primary transfer means and the secondary transfer means on the intermediate transfer body path is 12, and the recording material conveyance path between the secondary transfer means and the recording material detection means. The distance above is l3, and the perimeter of the intermediate transfer member is L. An image forming apparatus, wherein L> lmax + l2-l3, where lmax is the maximum recording material length. 4. When a plurality of image forming operations are continuously performed, the time at which the primary transfer means starts the primary transfer operation for the nth image forming operation is defined as tT, and the (n-1) th image forming operation is started. The time at which the trailing edge of the recording material of the maximum length passes the recording material detecting means with respect to the image forming operation is tE, and the recording material from the state where the recording material is accommodated with respect to the nth image forming operation. Assuming that the recording material conveyance start time is tF and the time required for the recording material to be conveyed from the state where the recording material is accommodated until the leading edge of the recording material reaches the recording material detection means is ΔtF, the time when ΔtF has elapsed from tF is , After tE,
The recording material conveyance start time tF is set so as to be before tT, and the recording material detection unit performs recording at a predetermined time tSF that is after the time when ΔtF has elapsed from tF and before tT. 4. The image forming apparatus according to claim 3, further comprising means for prohibiting the primary transfer operation after that time when the absence of the material is detected.