JPH04149479A - image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an image forming apparatus.

[Conventional technology]

As an example of a conventional image forming apparatus, a laser beam modulated according to recorded information is irradiated onto a photosensitive drum, an electrostatic latent image on the photosensitive drum is developed by an electrophotographic process, and an image is transferred onto transfer paper. It has multiple recording devices for transcription,
In a color image forming apparatus that sequentially conveys a transfer sheet to each recording device using a conveyor belt and transfers each color image in a superimposed manner, each photosensitive ram may be affected by mechanical installation errors between each photosensitive ram, y-path length errors of each laser beam, optical path changes, etc. An electrostatic latent image is formed on the photosensitive drum and developed on the recording paper on the transfer belt, thereby eliminating the registration of each color image. For this reason, conventionally, a registration correction pattern image formed on each photosensitive drum or ε transfer belt is read with a CCD sensor, etc., and the registration deviation on the photosensitive drum corresponding to each color is detected, and the image to be recorded is detected. By electrically correcting the signal and driving, for example, a reflecting mirror provided in the optical path of the laser beam, changes in optical path length or optical path changes are corrected.

[Problem that the invention is trying to solve]

However, in the above conventional example, when the conveyor belt driving roller and the driven roller are attached, the roller positions are not completely parallel but have an inclination, so as the transfer belt rotates, the transfer belt shifts in the direction perpendicular to the belt rotation direction. It will move out of the specified position. Therefore, in order to prevent this, a means for detecting the heald position is provided, and based on this output result, the direction in which the belt is shifted is determined, and the inclination of the transfer belt drive roller or driven roller is controlled to control the shift of the conveyor belt. was. However, a CCD sensor or the like reads the registration correction pattern image formed on the conveyor belt in a certain offset direction of the transfer belt, detects the registration deviation of each color, and electrically corrects the image signal to be recorded. Even if the registration of each color is matched, due to the conveyor belt bias control,
In the opposite biasing direction, there is a drawback that the main scanning direction registration of each color image becomes inconsistent due to the movement in the direction perpendicular to the rotational direction of the conveyor belt (main scanning direction of the recorded image).

That is, since the control of the offset of the conveyor belt and the control based on the result of recording the registration correction pattern are each performed separately and independently, there is a problem that it is difficult to form a good image due to the mismatch between the control states.

This problem occurs not only in the image forming apparatus that forms images using the electrophotographic process described above, but also in image forming apparatuses that use other recording methods, such as inkjet recording methods.

It is an object of the present invention to provide an image forming apparatus that solves the problems related to the present invention.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides an image forming apparatus that sequentially transports a transfer material to each recording station using a transport belt and transfers images of each color in a superimposed manner. It is characterized by comprising a correction means for forming a pattern image for registration correction and correcting the registration/con deviation according to the reading result of reading the formed pattern image and the state detected by the detection means. .

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram of four recording devices and a transfer belt showing an embodiment of the present invention.

Magenta (M a ), cyan (Cy), yellow (Y
e) Black (Bk) photosensitive drums 2.3.4.5 are rotationally driven by drum motors 11, 12, 13.14, respectively, and are uniformly charged by a charging unit (not shown). Ma, Cy, Ye, Bk photosensitive drums 2,3°4.
5 is a laser beam 11 and A2 optically modulated by a video signal.
．． A3. A4 is exposed to light, and each electrostatic latent image is formed on the drum and developed by a developing unit (not shown) to form a developed image.

Next, the developed image formed on the drum is fed from a paper feeding unit (not shown), and transferred at a predetermined timing onto the copy paper electrostatically attracted to the transfer belt l. The paper is transported in the direction of the middle arrow, fixed via the fixing unit, and then ejected.

Next, reading of the registration correction pattern image will be explained. Each photosensitive drum 2, 3.4. The pattern images visualized on the transfer belt 5 are each transferred onto the transfer belt 1 at the timing shown in FIG. 4 and conveyed in the direction of the arrow in the figure. The pattern image that has been conveyed is illuminated by the illumination lamp 6.
．． 7, a condensing lens 8, and a reflecting mirror 9, which are sequentially read by a CCD sensor IO.

FIG. 2 shows a block diagram of the image pattern reading and registration correction circuit. Pattern images of each color formed on the front and back sides of the transfer belt 1 as shown in FIG. 5 are read by CCD sensors 10a and 10b. Original oscillation clock l from the registration controller 20 50
7. f 508 is the CCD driver 18. 19, and is necessary for driving the CCD sensor 10a and Job, and is locked (transfer pulse, reset pulse, shift pulse, etc.)
41' 501. f 502 is generated and CCD1Oa
.

10b. The pattern image signal read by the CCD 10a and Job is sent to the CCD driver 18. 19
Processing such as amplification, DC regeneration, and A/D conversion is performed by
Digital signal 41! 505. 1 506 to the registration controller 20. Each color pattern image signal received by the registration controller 20 is temporarily stored in memory, and under CPU control, the amount of registration deviation is calculated based on the pattern image of a certain color, and the electric current of each color scan and sub-scan is calculated. A pulse motor 23. which sends target image writing timing setting data 1509 to the system controller 21 and drives and controls a reflection mirror provided in the optical path for correcting changes in the optical path length and changes in the optical path of the recording laser beam. 2
4. 25. 26 pulse data 1511 is supplied to the mirror motor driver 22. Mirror motor driver 2
2, each negative reflection mirror drive pulse motor 23, 24 . 25. 26 to supply a current signal to the pulse motor 23. 24. 25.
26 is driven to control the reflecting mirror. These registration corrections are executed by being supplied to the registration controller 20 by an activation signal 1510 from the system controller 21.

FIG. 3 shows a block diagram of the registration correction image pattern forming circuit of this embodiment. The H enable signal 1516 is generated by the main scanning enable signal generation circuit 27 using a beam detect (BD) signal 1528 obtained by scanning outside the image recording area with a laser beam as a synchronization signal in the main scanning direction, and the H enable signal 1516 is generated by the main scanning enable signal generation circuit 27. The V enable signal 1517 is generated from the output timing signal (r TOP) 1529 by the sub-scanning enable signal generating circuit 28 . H, V enable signal j1! 516. f
An address signal f 531 is generated by the address counter 29 based on the signal f 517, and is supplied as a readout signal to the pattern RAM 30 in which the pattern image for registration correction is stored. The pattern image signal 1518 read out from the pattern RAM is then supplied to the selector 32. The other input of the selector 32 is the output signal I! of the batch register 31! 519 is connected, but this is because when a carbon black type toner is used as the Bk toner, the pattern image cannot be read in a reflective optical system because the carbon black absorbs light. Other colors (M a , CV ) that reflect light there.

In order to form a solid pattern (batch) using any of the toners (Ye in this embodiment) and form a registration correction pattern image thereon, the pattern image signal I! 518 and batch signal 1519 by the selector 32. The switching signal of this selector 32 is the CPU's data bus I! 530 uses the output signal p526 from register 35.

In this embodiment, only Ye input is switched to the selector 32 and outputted to f520. In the next selector 33, whether to write the normal image (VIDEO) A 521 or the pattern image 1520 is determined by the data bus 153 of the CPU.
0 selectively outputs the output signal 1527 from the register 35 as a switching signal to the laser driver 38 via the γRAM 34 and the gate 37, and optically modulates the laser beam from the laser diode 39 according to the input image signal 1525. is output.

FIG. 6 shows a flowchart of the registration correction mode of this embodiment, and the registration correction mode will be explained in conjunction with FIG.

First, it is determined by the belt position sensor 40 whether the transfer belt (I) is cutting the belt position sensor 40 or not. (1
) When the belt position sensor 40 is turned off (belt position sensor ON), the output signal 1532 becomes logic "H",
The transfer belt bias control circuit 41 drives the transfer belt swing motor 17 clockwise by a predetermined amount 2) to control the inclination of the transfer belt driven roller 16. Next, the photoreceptor 2 is processed by the registration correction pattern image forming circuit shown in FIG.
．． 3. Write the pattern image to 4.5 (3)
, the pattern image of each color transferred onto the transfer belt l and conveyed sequentially to the pattern image reading position is read by the pattern image reading circuit shown in FIG. 2 (4), and the main scanning direction timing correction data Di of each color is read by the registration correction circuit. Compute and calculate (M, C,, Y, K) (
5). In step (2), the transfer belt 1 shifts in the direction away from the belt position sensor 40, but next, it is determined whether it has completely separated from the belt position sensor 40 (6), and if it has separated (belt position sensor 0FF),
The rotation of the transfer belt 1 is stopped (7). Main scanning direction timing correction data DI (M.

Main scanning direction timing correction data D2 (
M, C, Y, K) have already been obtained.8
), in this case, since it has not yet been obtained, the transfer belt swing motor 17 is driven counterclockwise by a predetermined amount by the transfer belt bias control circuit 41 (9), and the transfer belt driven roller 1 is
6. Perform tilt control. Next, the registration correction pattern image forming circuit shown in FIG.
5 (10), each color pattern image is transferred onto the transfer belt L and is sequentially conveyed to the pattern image reading position, and the pattern image reading circuit shown in FIG. 2 reads the pattern image (11) for registration. The correction circuit calculates main scanning direction timing correction data D2 (M, C, Y, K) for each color (12).

In step (9), the transfer belt 1 moves toward the belt position sensor 40. Next, it is determined whether or not the belt position sensor 40 is cut (13). If the belt position sensor 40 is cut (belt position sensor ON), the transfer belt 1 1 is stopped (14). Main scanning direction timing correction data DI
It is determined whether (M, CSY, K) have already been obtained (15), and since they have been obtained in step (5), the registration correction mode is ended (16).

As described above, the main scanning direction timing correction data DI (M, C, Y, K) and D2 (
M, C, Y, K) are obtained.

FIG. 7 shows a flowchart of the normal image copy mode. Determine whether the copy key has been pressed (1), and if it has been pressed (copy key ON), determine whether the transfer belt 1 is cutting off the belt position sensor 40 (2)
. If it is off (belt position sensor ON), set the main scanning timing correction data DJ (M, C, Y, K) 3) and set the image writing timing in the main scanning direction.

Next, the transfer belt shifting control circuit 41 drives the transfer belt swing motor 17 clockwise by a predetermined amount (4), and if the transfer belt 1 has not cut off the belt position sensor 40 in step (2), position sensor 0FF)
, main scanning timing correction data D2 (MXC, Y, K
) to set the image writing timing in the main scanning direction. Next, the transfer belt oscillation motor 17 is driven counterclockwise by a predetermined amount by the transfer belt shifting control circuit 41 (11). Next, the transfer belt 1 is rotated 5) to feed the copy paper from the paper feed unit 6), and the copy paper is electrostatically attracted to the transfer belt 1 at a predetermined timing. M, C, Y,
An image is written on the photosensitive drum 2.3.4.5, the electrostatic latent image is developed by a developing unit, and the developed image is transferred to the copy paper on the transfer belt (7). Next, the fixing unit fixes the image 8), and the copy sheet on which the fixing has been completed is ejected 9), and the copy sequence ends and returns to the initial state.

[Other Embodiments] In the description of the first embodiment of the present invention, the belt position sensor 40 has been described as a non-contact type sensor, for example, an optical reflection type sensor, but depending on the material of the transfer belt 1, it may be a light transmission type sensor, a light transmission type sensor, or a light transmission type sensor. The position of the transfer belt 1 cannot be detected with a light absorption type. In this case, the direction in which the transfer belt is shifted is determined by detecting the transfer belt position using a contact type mechanical sensor.

As described above, according to this embodiment, when the transfer belt is rotated, the deviation direction detection means detects the deviation direction of the transfer belt, and the deviation control of the transfer belt is performed based on the result of the transfer belt deviation direction detection means. A transfer belt offset control means, a pattern image forming means for forming a registration correction pattern image for each color on the transfer belt, and a pattern image reading means for reading the pattern image formed on the transfer belt for each color. and a registration correction means for correcting the registration deviation of each color based on the reading result of the pattern image reading means. By performing registration correction for each color, it is possible to eliminate image color shift in the main scanning direction with respect to the direction in which the transfer belt is offset.

In addition, in this embodiment, belt deviation control was performed according to the detected belt deviation direction, but such control was not performed and each negative side laser beam was modulated according to the detected belt deviation direction. Registration correction may be performed by controlling only the readout timing of the image signal.

Furthermore, rather than detecting the direction in which the conveyor belt is shifted, it may be possible to simply determine whether or not the belt is in the correct position.

Furthermore, the present invention is applicable not only to image forming apparatuses using an electrophotographic process but also to other recording apparatuses, such as inkjet recording apparatuses.

Further, the present invention is particularly effective in a recording apparatus that superimposes color images while conveying a recording material with a belt.

〔Effect of the invention〕

As explained above, according to the present invention, the state of the conveyor belt,
Since the registration correction is performed based on the result of reading the formed registration correction pattern, highly accurate lens alignment is possible.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a recording device and transfer belt showing an embodiment of the present invention, Fig. 2 is a block diagram of an image pattern reading and registration correction circuit, and Fig. 3 is an image pattern and patch forming circuit for each color. 4 is an image pattern and patch writing timing chart, FIG. 5 is a diagram showing the image pattern and patches on the transfer belt, FIG. 6 is a flowchart 1 of the registration correction mode, and FIG. 7 is a flowchart of the registration correction mode. 3 is a flowchart of normal image copy mode. 1... Transfer belt 2... Ma photosensitive drum 3... Cy photosensitive drum 4... Ye photosensitive drum 5... Bk photosensitive drum 10a, 1ob/-ccD sensor 17... Transfer belt swing motor 20... Registration controller 21...
System controller 22...Reflection mirror motor driver 30...Image pattern RAM 38...Laser driver 39...Laser diode 40...Belt position sensor 41...Transfer belt deviation control circuit

Claims (3)

[Claims] (1) In an image forming apparatus that sequentially transports a transfer material to each recording station by a transport belt and transfers images of each color in a superimposed manner, a detection means for detecting the uneven state of the transport belt and a pattern image for registration correction for each color are formed. An image forming apparatus comprising: a correction means for correcting a registration shift according to a reading result of a formed pattern image and a state detected by the detection means. (2) The image forming apparatus according to claim 1, wherein the correction of the registration deviation is performed by varying the electrical write timing setting of the recorded image in the main scanning direction. (3) A deviation direction detection means for detecting the deviation direction of the conveyor belt, based on the result of the conveyor belt deviation direction detection means,
Belt offset control means for controlling the offset of the conveyor belt, pattern image forming means for forming a registration correction pattern image for each color, pattern image reading means for reading the formed pattern image for each color,
Image formation characterized by comprising a registration correction means configured to perform registration correction for each color according to the reading result of the pattern image reading means and the direction of deviation of the conveyor belt controlled by the belt deviation control means. Device.