JPH01142679A - 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 such as an electrophotographic apparatus, a laser beam printer, a printing apparatus, etc., and particularly relates to an image forming apparatus such as an electrophotographic apparatus, a laser beam printer, a printing apparatus, etc. The present invention relates to a forming device.

[Conventional technology]

Conventionally, so-called image forming apparatuses include a plurality of image forming sections, each image forming section forms images of different colors, and these images are sequentially superimposed on the same transfer material and transferred continuously at high speed. Various color image forming apparatuses have been proposed.

This type of device has an optical scanning means (scanner, etc.) serving as an image forming section and a photoreceptor serving as an image bearing member, and when transferring an image from this image forming section to a transfer material, the transfer material is used to form an image. In many cases, a belt is used as a conveyance means for conveying the image to the image forming section, or as an intermediate transfer material (once the image formed on the image forming section is transferred and held, and then transferred to a transfer paper serving as a transfer material).

However, in this type of belt, the belt conveyance speed fluctuates due to changes in the torque or friction applied to the belt, and when the image is transferred from each image forming section (image forming station) to a single sheet of transfer material, Transfer misalignment occurs between the two. This causes serious problems such as color bleeding and hue changes, especially in color images.

For this reason, in the past, belt drive was controlled to suppress speed fluctuations due to load fluctuations and always drive at a stable speed. Some belts are equipped with a detection member that detects the conveyance speed, and are configured to feedback control the speed of the drive device so as to maintain the belt speed constant.

However, the image forming timing (top margin, left margin) of each image forming station is off! Image positional deviation also occurs when there is a change in the positional relationship between the two conveying belt devices and the image forming station or between the image forming stations.

FIG. 10 is a schematic diagram illustrating the types of image misalignment in an image forming apparatus having a plurality of image carriers, and (a) shows misalignment (top margin misalignment) in the transport direction (six directions in the figure) of the transfer material S. ), (b) shows the positional deviation (left margin deviation) in the main scanning direction (direction B in the figure) perpendicular to the transport direction, (e) shows the scanning line tilt deviation, and (d)
indicates the magnification error shift.

As can be seen from this figure, for example, the top margin shift or left margin shift shown in FIG. 10 (a) or (b) occurs due to the image writing timing shift at each image forming station. Furthermore, the scanning line inclination shift shown in FIG. 10(C) occurs due to angular shift due to replacement of the image carrier, etc. Furthermore, the magnification error shift shown in FIG. 10(d) This occurs due to a deviation in the optical path length of the optical scanning means in the image forming section.

Therefore, by adjusting the image writing timing regarding the top margin deviation or left margin deviation, and by moving the optical scanning means or the image carrier with respect to the conveyance direction of the conveyance body regarding the scanning line inclination error, Furthermore, regarding magnification errors, the above-mentioned positional deviation factors that occur individually at each image forming station can be eliminated by moving the optical scanning means or image carrier in the vertical direction with respect to the direction of the conveyor. It is corrected all at once.

[Problem that the invention seeks to solve]

Now, the rotational drive control of the conveyor belt is automatically processed during the execution of a normal image sequence, but electrical adjustment of the image forming timing and mechanical position adjustment of the image forming unit require some specialized technology. This is difficult for general users to carry out, and is generally limited to the time of assembly and adjustment of the device before shipping the product, or the time of adjustment by a service person.

However, when an abnormality occurs in the device during an image sequence, for example, when a paper jam occurs, it is necessary to remove the transfer paper to facilitate clearing the paper jam, that is, to secure space for removing the jammed transfer paper. Some models are equipped with a mechanism that temporarily retracts the conveyor belt system from its normal position, and such a jam release process inevitably causes a situation in which the conveyor belt cannot return to its normal position. This may lead to the above-mentioned image position shift, causing a serious problem of deteriorating image quality.

In addition, due to maintenance by service personnel, for example, when replacing the belt drive unit of the image forming section, etc.
The position may be slightly misaligned from the factory assembled position, and it may not be possible to set it in the perfect position without wobbling, which may result in the image position shift as described above.

Furthermore, in addition to such abnormalities, the position of the belt conveyance drive system may deviate from its normal position due to sudden shocks applied from the outside, and this also causes the image misalignment as described above. .

Even if this type of positional deviation correction is left to the user's maintenance, as is clear from the above reasons, there is no guarantee that the correction will be made with high precision, and there is a strong possibility that the image quality will be further degraded.

This invention was made to solve the above problems, and detects the retracted/approached state of the conveying body that conveys the transfer paper to each image carrier at each image forming station.
By controlling the start of the image position deviation detection operation, it is possible to detect image position deviations caused by movement of the transfer paper transport system in order to avoid troubles that occur during the image sequence at each image forming station. An object of the present invention is to provide an image forming apparatus that can automatically correct the image with high accuracy.

[Means for solving problems]

The image forming apparatus according to the present invention has the following features:
A system comprising: a state change detecting means for detecting the moving state of a conveyance body approaching; and a mark detection control means for controlling the start of detection of each registration mark image by the detecting means based on the output state of the state change detecting means. It is.

[Function] In the present invention, when the state detection means detects that the conveyance body has moved away from/approached from the surrounding area where each image carrier is disposed, the mark detection control means causes the detection means to detect each registration mark image. start.

[Embodiment 1] FIG. 1 is a perspective view illustrating the configuration of a four-drum full-power single-type image forming apparatus showing an embodiment of the present invention.
C, IM, IY, and IBK are photosensitive drums, and are cyan, magenta, and yellow, respectively.

An optical scanning system 3C, 3 is provided for each image forming station equipped with black developer (toner).
Light emitted from M, 3Y, and 38K forms electrostatic latent images corresponding to each color on each photosensitive drum IC, IM, IY, and IBK. 4 is a conveyor belt serving as a conveyor, and each photosensitive drum IC.

Registration marks 11 and 12 for each color formed with IM, IY, and IBK are transferred. Registration mark 11.12
are transferred in parallel on a straight line orthogonal to the conveyance direction of the conveyor belt 4.

Note that the optical scanning systems 3C, 3M, 3Y, and 3BK can be moved in a predetermined direction by an actuator mechanism described later.

Reference numeral 5.6 denotes a mark detector composed of a charge-coupled device such as a CCD, and the mark detector 5 receives reflected light from the lamp 7 that has been exposed to the conveyor belt 4 via a condenser lens 9. , image data of a registration mark 11 (each registration mark 11 is composed of, for example, four medium-sized mark images (transferred at each image forming station)) detected in synchronization with a detection timing signal output from the controller 13. is output to the controller 13, and the mark detector 6 receives the reflected light of the light exposed on the conveyor belt 4 from the lamp 7 via the condenser lens 10, and in synchronization with the detection timing signal output from the controller 13. The image data of the detected registration marks 12 (each registration mark 12 is composed of, for example, four medium-sized mark images (transferred at each image forming station)) is output to the controller 13.

A cleaner member 8 collects toner images corresponding to the registration marks 11 and 12 transferred to the conveyor belt 4. 1
Reference numeral 4 denotes a microswitch serving as a state change detection means of the present invention, and the conveyor belt unit (consisting of the conveyor belt 4 and conveyor rollers 2a to 20, etc.) is moved in the direction B in the figure by operating a release lever (not shown). It is placed in a predetermined position to turn on when the lock is activated and turn off when the release lever is properly locked. This on/off signal is output to the controller 13.

In addition to the above-mentioned microswitch 14, the state change detection means may be composed of a photosensor, a piezoelectric element, or the like.

The controller 13 also serves as mark detection control means of the present invention, and when an on/off signal is output from the microswitch 14, it monitors the on/off status and controls the operation of the release lever. When the transport system is locked in a predetermined position, the registration mark 11
．． 12 is transferred to the conveyor belt 4, and the registration mark image data of each image station outputted from the mark detectors 5 and 6 is compared with the registration mark image data stored in advance. 5. Uniquely detected mark detection timing and sequential mark detectors (sometimes referred to as stations).
According to the difference between the detection timing of the registration mark image data of each subsequent image station output from 6,
Each photosensitive drum IC, IM, 1Y, IBK of the light beam emitted from each optical scanning system 3C, 3M, 3Y, 38K
optical path length, scanning length, scanning direction (photosensitive drum IC,
By adjusting the drive of actuators (described later) provided at each image station (with respect to the axial directions of IM, IY, and IBK), positional deviations at all image stations are adjusted.

FIG. 2 is a perspective view illustrating the arrangement of the optical scanning system shown in FIG. 1, and the same components as in FIG. 1 are given the same reference numerals. Note that the same configuration as this is provided for each image station.

In this figure, 20 is an fθ lens, and a laser light source 22
A polygon mirror 21 that is fired from and rotates at a constant speed.
A laser beam (light beam) L that is directed horizontally by is focused on, for example, a photosensitive drum 1C at a constant speed. 23 is an optical box which integrally accommodates the above-mentioned 20 to 22. Note that the laser beam L emitted from the laser light source 22 is emitted from the opening 23a via the FE lens 20.

Reference numeral 24 indicates a mounting hole, and the optical box 23 is slidably inserted into the mounting hole 24. The mounting shaft 24 is positioned by a shaft (not shown). 25 is a linear step actuator (actuator) composed of, for example, a stepping motor;
The optical box 23 is moved up and down six times in the direction of arrow al+82 in the figure in accordance with the step amount output from the controller 13 to correct the optical path length and adjust the magnification error.

26 is a linear step actuator (actuator) composed of, for example, a stepping motor, which moves the optical box 23 according to the step amount output from the controller 13.
is rotated in the direction of arrow b (b+, b2) around the rotation axis °C.

The linear step actuators 25 and 26 move the output shaft of a stepping motor linearly, and have a trapezoidal screw structure inside the motor roller and the output shaft, and are mainly used for heads such as floppy disks. It is suitable for those normally used for sending. Note that the linear step actuator 25.
In place of 26, a lead screw (with a thread cut on the shaft) fixed to the shaft of a normal stepping motor can be used, and a movable member with a thread formed to correspond to the lead screw described above can be used to function in the same way. It is possible to do so. Specifically, the screw formed on the lead screw is 4P0.
5 (nominal diameter 4 mm, pitch 0.5 mm), and when the step angle of the stepping motor is 48 steps/one revolution, the advance amount SS of the output section is 5S = 0.5/48 = 1
0.42μm/step, and this IC1,42μm
/The optical box 23 can be driven and controlled by one step-by-step feed.

Next, the driving operation of the actuators 25 and 26 shown in FIG. 2 will be explained with reference to FIGS. 3(a) to 3(C).

FIGS. 3(a) to 3(C) are schematic diagrams illustrating image shift on the image carrier, and S indicates a transfer material, and this transfer material S is conveyed in the direction of arrow A (the conveyance direction of the conveyor belt 4). be done.

Here, by driving the actuator 25 in the a1 direction, which is the emission direction of the light beam L from the scanning optical device, the optical box 23 is moved approximately in parallel in the a direction, and the photosensitive drum 1
Shorten the optical path length up to C and move the actuator 25 to a2.
By driving in the direction, the optical path length can be adjusted to be long.

By adjusting the optical path length in this way, the length of the scanning line of the light beam L having a predetermined spread angle on the photosensitive drum 1C can be adjusted to, for example, m as shown in FIG. 3(a). (solid line)
can be varied from m+ (broken line).

Further, when the actuator 26 is driven in the b1 direction or in the b2 direction, the optical box 23 is rotated about the rotation axis 1 as shown in FIG. 3(b).

Scanning line m in (c). is the scanning line m2. The slope can be varied as shown in m3 (broken line).

In this way, the optical box 23 is arranged in the optical beam path from the scanning optical device to the photosensitive drum 1C, and the optical path length or the optical beam scanning inclination is adjusted by adjusting the position of the optical box 23 with the actuator 25 or 26. Each can be adjusted independently. That is, the optical box 23
By moving the light beam L in the direction a, the light beam L
By moving the optical box 23 in the b direction, it is possible to correct the imaging angle on the photosensitive drum 1C without changing the optical path length of the light beam L. .

In this embodiment, the optical box 23 and the actuator mechanism for adjusting the position of the optical box 23 are installed on the photosensitive drums 1C, IM, and IY, which serve as image carriers of each image forming means, in a four-drum full-color printer. , IBK, and individually correct the magnification error, top margin, and left margin based on the inclination of the scanning line and the difference in optical path length.
It is configured to remove color misregistration between the toners of each color that are sequentially transferred onto the transfer material S.

Hereinafter, the reading operation of the registration marks 11 and 12 for color misregistration detection and the color misregistration correction feedback control operation executed based on this reading will be sequentially explained with reference to FIG.

FIG. 4 is a control block diagram illustrating the internal configuration of the controller 13 shown in FIG. 1, and the same components as in FIG. 1 are given the same reference numerals.

In this figure, 31a is an amplifier that amplifies the mark image signal output from the mark detector 5. A binarization circuit 32a converts the analog signal output from the amplifier 31a into digital data and outputs image data CCD2P to the exclusive logic gate 35b and the counter 42.

32b is a binarization circuit that converts the analog signal output from the amplifier 31b into digital data, which is the image data C.
CDIP is output to exclusive logic gate (EXI) 35a and counter 39.

33 is a clock generator, which generates one main scanning period signal CD
H3YNC is generated, and this one main scanning period signal CDHS
It outputs YNC as a reading synchronization signal for the mark detector 5.6, and outputs VSYNC counters 37C and 37M.
, 37Y, and 378 are output to the human clock CLK.

34 is a first counter circuit, which receives one main scanning period signal CDH3.
Image data CCDI for the registration mark 12 detected by the mark detector 6 at the YNC sending timing ■
P is obtained, and one main scanning period signal CDH is generated in synchronization with a start signal 5TARTI which is an exclusive OR output of this image data CCDIP and one main scanning period signal CDH5YNC.
Start counting 5YNC, 1 main scanning period signal CDH
Image data CCD for the registration mark 11 detected by the mark detector 5 at the SYNC sending timing ■
Counting of one main scanning period signal CDH3YNC is completed in synchronization with stop signal 5TOP2 which is an exclusive OR output of 2P and one main scanning period signal CDHSYNC.

The count data counted from the start to the end of the count is obtained as the scanning line inclination amount N, and this scanning line inclination amount N is stored in the subsequent stage 1 ROM 35 (a control value for moving the actuator 26 in a designated direction). ) is output as a selection signal.

Note that the first counter circuit 34 is enabled based on a station select signal output from a CPU (not shown). 36 is a selector circuit, and each control value ADC, ADM, ADY, ADBK read from the first ROM is outputted to the actuator 26 that drives the optical box 23 of each image station.

37C is a VSYNC counter, which is synchronized with the registration mark write signal that is output at the timing when the cyan registration mark (the first image of registration marks 11 and 12) is written at the first image station! The main scanning period signal CDH5YNC starts counting, and the mark detector 6
The exclusive OR gate 35a is synchronized with the image data CCD 1 that is output when the register mark 12 is detected.
When the start signal 5TARTI is outputted from the start signal 5TARTI, the count of one main scanning period signal CDH5YNC is finished, and the count value, that is, the difference amount C1 is transferred to the third ROM 38 in the subsequent stage () - a control value for correcting the margin. is stored in advance) as a selection signal. The third ROM 3 outputs a delay signal DELAYC for correcting the top margin to the actuator 26 of the first image station.

Similarly, VSYNC counters 37M and 37Y.

1 main scanning period signal CDH3YNC which is also manually input to 378
difference amounts Ml, Yl for counting and correcting the top margin of each image station.

BKI is output as a selection signal to the subsequent third ROM 38 (in which control values for correcting the top margin are stored in advance), and a delay signal DELAY is output from the third ROM 3B to the actuator 26 of each image station.
M, DELAYY, and DELAY BK are output, respectively.

39 is a second counter circuit, which receives one main scanning period signal CDH5.
Start counting XICLOCK manually in synchronization with YNC, and when mark detector 6 detects registration mark 12 and outputs image data CCDIP, XICL
The OCK count ends and the count value becomes 1. is output to the subsequent comparator 40. The comparator 40 compares the preset center value t0 and the count value t1 counted by the second counter circuit 39, and calculates the difference Δ1.
．． is output to the second ROM 41 as a selection signal. 2nd R
Optimal control values A1 to A4 for driving the actuators 25 of the first to fourth image stations are output to the OM 41 according to the difference Δt1, respectively.

42 is a third counter circuit, which receives one main scanning period signal CDHS.
YNC1, m synchronizes and starts counting XICLOCK manually, and when the mark detector 5 detects the registration mark 11 and the image data CCD2P is output, the XI
The CLOCK count ends and the count value t2 is output to the comparator 43 at the subsequent stage.

The comparator 43 outputs a preset center value 0 and a count value t2 counted by the third counter circuit 42.
and outputs the difference Δt2 to the second ROM 41 as a selection signal. The second ROM 41 stores the actuators 2 of the first to fourth image stations according to the difference Δt2.
Optimum delay control values (left margin control output values) DCI, DMI, DYI, and DBKI for driving 6 are output, respectively, or the vertical synchronization signal output timing that determines the image writing timing is adjusted according to the difference Δt2.

Note that the mark detectors 5 and 6 are positioned so as to start reading in the main scanning direction from a reference 1.2 shown in FIG.

Next, the operation shown in FIG. 4 will be explained with reference to FIGS. 5 and 6.

FIG. 5 is a diagram for explaining the reading operation of the registration marks 11 and 12 by the mark detectors 5 and 6 shown in FIG. 4, and the same parts as in FIG. 1 are given the same reference numerals.

In this figure, IA indicates the normal write output and IB
Indicates off-state write output. 3A is mark reading data, which corresponds to the binary output for the regular write output IA.

3B is mark reading data, deviation status write output IB
This corresponds to the binarized output for .

FIG. 6 is a timing chart explaining the operation of FIG. 4, and the same parts as in FIG. 4 are given the same reference numerals.

First, the output operations of the mark detectors 5 and 6 in response to the occurrence of magnification errors and left margin errors will be explained.

When registration marks 11 and 12 are written at regular timing, mark detectors 5 and 6 output X in synchronization with one main scanning period signal CDHSYNC. Although the mark reading data 3A is obtained during the time, if its position shifts on the mark detector 5 side as shown in FIG.
The mark reading data 3B is output during time to (to = Xo) in synchronization with HSYNC, but on the mark detector 5 side, mark read data 3B is output during time t2 (t2<t+) in synchronization with one main scanning period signal CDHSYNC. Therefore, the image magnification becomes smaller than that of the mark reading data 3A. For this reason, the left margin and reference position are 2A to 2A.
It will shift to B.

The magnification error and left margin shift amount detection operations will be described below.

The mark detectors 5 and 6 receive one main scanning period signal C outputted from the clock generator 33 at sending timings ■ to ■.
The registration marks 11.12 conveyed in synchronization with DHSYNC (Fig. 4) are read, and the image data CCDIP and CCD2P shown in Fig. 6 are sequentially output. Since the registration marks 11 and 12 have not been read, no image signal is output. Then, at the sending timing ■, the detection signal for the registration mark 12 detected by the mark detector 6 is binarized at time 11 (equal to 70 shown in FIG. 5) from the 1 main scanning period signal CDH5YNC. image data CCDIP is obtained. Then, at the sending timing (3), image data CCD2P is obtained by binarizing the detection signal for the registration mark 11 detected by the mark detector 5 at time t2 from the one main scanning period signal CDHSYNC. However, time t2 is the same as t above.

shorter than time.

In this way, when the image data CCDIP and CCD2P are obtained from the binarization circuits 32a and 32b, the second counter circuit 39. The counting process by the third counter circuit 42 is started as described above, and the count value 1. ,12
is sent to comparators 40.43. Therefore, the comparator 40 manually inputs the count value 1. and a preset center value t0, and outputs the difference Δt1 (content O) to the second ROM 41 as a selection signal, and the comparator 43 compares the input count value t2 and the preset center value 1o. The difference Δt2 (content -1) is outputted to the second ROM 41 as a selection signal.

As a result, the optimal movement control values (control values A1 to A4) for driving the actuator 25 of each image station are output from the table in which the magnification movement amount and left margin movement amount are set, which are stored in advance in the second ROM 41. At the same time, the delay control values DC1, DMI, DYI, and DBKI, which are the movement amount of the left margin, are set to the second RO.
They are sequentially output in accordance with the station select signals manually input to the selection boat S of M41.

Therefore, by this correction, the magnification error and left margin deviation are corrected by moving them to their normal positions.

Next, the correction process for the amount of scanning line inclination will be explained.

Similarly to the above, the binarization circuit 32b reads the registration mark 12 from the mark detector 6 in synchronization with the 1 main scanning period signal CDHSYNC sent out at the sending timing ■.
When the image data CCDIP is obtained, the exclusive OR gate 35a at the subsequent stage erases the one main scanning period signal CDHSYNC, which is one manual input, and generates the start signal 5TARTI, and this start signal 5TAR
T1 is the 5TART signal terminal of the first counter circuit 34 and the VSYNC counters 37C, 37M.

37Y and 378 are input to the human clock CLK. In response to this, the first counter circuit 34 starts counting one main scanning period signal CDH3YNC.

Next, at sending timing (3), the mark detector 5 reads the registration mark 11 and outputs image data C0D2P from the binarization circuit 32a. Next, a stop signal 5T is sent from the exclusive OR gate (EX2) 35b at the subsequent stage.
By inputting OP2 to the 5TOPi4 children of the first counter circuit 34, the counting process of one main scanning period signal CDHSYNC is stopped, the count number counted up to that point, that is, the scanning line slope amount N is obtained, and this scanning line The amount of inclination N is output as a selection signal to the first ROM 35 at the subsequent stage (in which a control value for moving the actuator 26 in a specified direction is stored). The actuator 26 positions the optical box 23 at an appropriate position in accordance with this control value. By similarly performing this operation for magenta, yellow, and black registration marks, the selector circuit 36
Each control value ADC, ADM, ADY, ADBK is output to the actuator 26 of each image forming station according to the station select signal inputted to each optical box 2.
3 is positioned at an appropriate position, and the amount of scanning line inclination is corrected.

Next, a top margin shift correction process will be described.

Top margin correction control for cyan is performed on photosensitive drum 1C.
When registration marks 11 and 12 are started to be written, that is, the C registration mark write signal reaches VSYNC counter 3.
It starts from the time it is sent to the 5TART terminal of 7C,
After this C registration mark write signal is sent to the 5TART terminal of the VSYNC counter 37C, when the mark detector 6 detects the first mark of the registration mark 12, the image data C0DI is output from the binarization circuit 32b.
1 counted by the VSYNC counter 37C while the start signal 5 TARTI is output in response to P.
The value of the main scanning period signal CDH3YNC, that is, the difference amount C
1 to the third ROM38. Accordingly, the third
Delay signal DELAYC that becomes the top margin correction value (difference value compared with the value output when register marks are written at a predetermined position) stored in advance in the ROM 38
The top margin correction is executed by outputting the signal to the actuator 26 of the first image forming station or by adjusting the vertical synchronization signal output timing specified for each image forming station. This completes the top margin correction of the cyan image forming station.

Station select signal 3 to which this correction process is input
By executing the process for each of the magenta, yellow, and black image forming stations according to Step 5, the top margins of each image forming station are all adjusted to preset regular positions.

In addition, each VSYNC counter 37C, 37M.

At 37Y and 378, the counting operation is terminated by a start signal 5TARTI based on the image data CCDIP outputted from the registration mark images of each image forming station sequentially detected by the mark detector 6, but the registration marks are continuously detected. In order to detect an image, it is necessary to monitor it accurately so that the counting operation does not end with image data CCDIP at an unnecessary position. Also,
When the detection of the registration marks 11.12 by the mark detector 5.6 is completed, the registration mark image transferred to the conveyor belt 4 is cleaned by the cleaner member 8 in preparation for writing the next registration mark.

Next, the mark detection timing will be explained.

In normal cases, the conveyor belt 4 or the photosensitive drums IC, I
By controlling the speeds of M, IY, and IBK, it is possible to calculate and maintain an image without transfer misalignment, so there is no need to perform mark detection @processing after initial adjustment. If an abnormality such as a paper jam occurs around the unit, the user operates a release lever (not shown) according to the instructions in the manual to evacuate the transport drive system in direction B shown in Figure 1. Execute the release process. As a result, Micro Sun Tsuchi 1
4 is turned on and notifies the controller 13 that the evacuation operation has been executed. Note that the operation for retracting the conveyance drive system in the direction B shown in FIG. 1 is not limited to the upper jam release process, but also occurs when the photosensitive drum, transfer unit, etc. are removed and replaced.

Then, when the jammed paper as described above is released and approaches the image carrier by the release lever, the microswitch 14 is turned off. At this time, as described above, the transport drive system including the transport belt 4 is often slightly deviated from the normal position.

Image position shift detection processing that detects image position shift by transferring the above-mentioned registration mark images 11 and 12 onto the conveyor belt 4 in a non-dangerous state, for example, waiting for the body cover to return to its normal position. Start.

This allows image position deviations that occur at unexpected timing to be detected and automatically corrects the image position deviations before the start of a normal image sequence, so that clear color images can always be formed even after paper jam recovery. As a result, image position deviation correction will not be executed after the power is turned on unless the transport drive system retreats/approaches. There is no need for time, the time required to form one image can be reduced, and throughput can be improved. Note that when the above-mentioned conveyance drive system is evacuated, the power is cut off from the viewpoint of user protection. For this reason, even if the restored power is supplied, the temperature of the heat fixing roller necessary for image formation increases (for example, 18°C).

C) There is a waiting time for it to rise. Therefore,
If you use this waiting time to perform the above image position deviation detection and image position deviation correction processing, the image position deviation correction can be completed before the temperature of the fixing unit reaches the specified temperature, and the image position deviation can be corrected. It is no longer necessary to add a specific sequence for correction, and the first print after restoration can be output without any change from the conventional print sequence.

Next, the registration mark image detection processing operation according to the present invention will be explained with reference to FIG.

FIG. 7 is a flowchart illustrating an example of a registration mark image detection processing procedure according to the present invention. In addition, (1
) to (9) indicate each step.

First, when the power is turned on (1), the controller 13 initializes each part. Next, the above-mentioned registration marks 11 and 12 are transferred onto the conveyor belt 4 (2).

Next, the mark detector 5.6 detects the registration mark 1 corresponding to each image forming station transferred onto the conveyor belt 4.
1. Wait until 12 is detected 3), and if detected, judge whether a positional deviation has occurred 4). If No, proceed to step (6) and onward; if YES, start the above-mentioned positional deviation correction. Do (5).

Next, it is determined whether the microswitch 14 is turned on or off (6), and if YES, the process returns to step (2), and after the main body cover etc. are closed, the above-mentioned image position shift detection and associated image position shift correction are performed. Start.

On the other hand, if the determination in step (6) is No, the system waits for the print command for image formation to be manually input 7);
Once activated, allow the image sequence to begin and resume the normal image sequence (8).

Next, determine whether the power is off or not 9), YES
If so, the process ends; if NO, the process returns to step (6).

On the other hand, in the above embodiment, the present invention is applied to a case where four photosensitive drums IC, 1M, IY, and IBK serving as image carriers are arranged in parallel as shown in FIG. However, this invention can be applied as long as the number of image carriers is two or more.

Furthermore, in the above embodiment, a case has been described in which the mark detector 5.6 detects the registration marks 11° 12 formed at each image forming station through the condensing lens 9.10. It may be a contact type detection element that reads the registration mark 11.12 without going through the optical lens 9.10, or it may be an area sensor if the resolution is sufficient.

A detection element such as a phototransistor array may also be used.

Further, in the above embodiment, the case where the top margin and the left margin are adjusted by the image writing timing has been described, but the photosensitive drum 1C.

The positions of IM, IY, and IBK can be corrected by mechanical minute displacement, and the positions of photosensitive drums IC, IM, and IY can be corrected by mechanically minute displacement.

The correction may be made by changing the rotational speed of the IBK or the driving speed of the conveyor belt 4.

In the above embodiment, the case where the registration marks 11 and 12 are transferred to the conveyor belt 4 was explained, but since a conveyor can function as a mark transfer material, for example, a transfer sheet placed on the conveyor belt 4 and conveyed However, if this transfer paper is test fed during mark transfer, the cleaner member 8 of the transfer belt 4 can be omitted. In addition, when using transfer paper as the transfer material S for the registration marks 11.12, compared to the case where the registration marks 11.12 are transferred to the transparent conveyor belt 4 and read, since the background is white, it is difficult to read the registration marks 11.12 from other than the mark position. Since the scattered light becomes stronger, the read signal level becomes lower than when transferred to the conveyor belts 1 to 4, so it is necessary to adjust the threshold level in the detection circuit 15.

Further, the present invention can be easily applied to a model that employs an intermediate transfer material. That is, each photosensitive drum IC
, IM, IY, and IBK, the registration mark images (corresponding to each image forming station) are sequentially transferred to the intermediate transfer belt, and these are read by the mark detector 5.6 described above, thereby detecting each image forming station. Needless to say, it is possible to detect image position shifts.

Note that in the above embodiment, there is no particular mention of the start timing of image position deviation and associated image position deviation correction processing, but for example, when the image sequence is not being executed, such as when the ohm is up or just before stopping, If the above-mentioned correction processing is performed, there is no need to provide a special waiting time required for the correction processing, the speed of the image forming processing can be further improved, and the throughput of high-quality color images can be increased.

Further, in the above embodiment, the endless conveyor belt 4 is wound around the conveyor rollers 2a to 2C, and transfer paper is electrostatically attracted to the surface of the endless conveyor belt 4, thereby transferring multiple images formed at each image forming station. In the above, the case where the present invention is implemented has been described, but even if the drive of the conveyor belt 4 is controlled to stabilize the conveyance speed, the conveyor belt 4 may meander, elongate, shrink, or
Transfer misalignment may occur due to instability of the adsorption force, and this may not be completely detected and corrected by the above-mentioned image position misalignment detection.

Therefore, as shown in Fig. 8, as a conveyor for transfer paper,
A case in which the present invention is applied to an image forming apparatus employing a transfer drum will be described below.

FIG. 8 is a sectional view illustrating an example of an image forming apparatus illustrating another embodiment of the present invention, in which reference numeral 51 is a transfer drum serving as a conveying member, and a photosensitive drum 52C that is exposed to light is placed around the transfer drum 51. , 52M.

52Y and 528K are arranged as shown in the figure, and the images written by the scanning optical devices 53C, 53M, 53y, and 53BK are sequentially multiple-transferred onto the transfer paper P wound around the transfer drum 51 by a gripper, which will be described later. 5
Reference numeral 4 denotes a paper feed cassette, which feeds the transfer paper P to the position of registration rollers 57 via a conveyance guide 56 by rotation of a paper feed roller 55 . 58: A mark detector detects a registration mark transferred onto the film belt 51b (see FIG. 9) adhered to the cylindrical drum 51a constituting the transfer drum 51. A separating claw 59 separates the transfer paper P wound around the transfer drum 51 from the transfer drum 51.

A cleaning roller 60 collects toner remaining on the film belt 51b. A fixing device 61 fixes the toner image on the separated transfer paper P to the transfer paper P.

Note that the transfer drum 51. Photosensitive drums 52C, 52M.

Although the transfer drums 52Y and 528 are rotated by drive systems (not shown), even if the drive systems are independent drives, the transfer drums 51. A type that drives the photosensitive drums 52C, 52M, 52Y, and 52BK may also be used.

The transfer belt 51 is configured to be movable from the position shown by a solid line to the position shown by a broken line for maintenance and inspection by a cam or the like (not shown), and the position information is reported to a controller (not shown).

As described above, when the power of the apparatus is turned on, registration mark formation and detection 1 image position deviation correction are executed during warm-up. When the transfer drum 51 moves to the position indicated by the broken line due to the occurrence of an abnormality or maintenance, for example, the controller is notified of this fact. , the above-mentioned registration mark formation.

Detection 1 image position deviation correction is executed as follows.

That is, when a registration mark formation command is manually issued from the controller, the photosensitive drums 52C, 52M, 52Y, 5
The registration marks 1 shown in FIG.
Marks similar to 1.12 are formed and sequentially transferred onto the film belt 5ib of the transfer drum 51. The transferred four-color registration marks are sequentially detected by the mark detector on the 5th day, and the amount of deviation between each mark is calculated by the controller.
Depending on the amount of deviation, the image forming timing of each image forming station and the scanning optical devices 53C, 53M, 53Y are determined.
.

The position at 538 is slightly moved by an actuator (not shown) in the directions E and F, as shown in FIG. 8, for example, to correct the image position deviation specific to each image forming station.

On the other hand, after the image reading is completed, the registration marks of each color sequentially transferred onto the film belt 51b are collected by the cleaning roller 60 to prevent toner from adhering to the back side of the transfer paper P that is transported for the next image formation. do.

In this way, by executing the image position shift detection correction along with the movement of the transfer drum 51, the meandering inherent to the conveyor belt 4 can be reduced compared to an image forming apparatus that employs the conveyor belt 4.
Since it is not affected by expansion, contraction, etc., it can be used regardless of whether it is during a normal image sequence or after the retraction operation of the transfer drum 51.
High-quality color images can always be formed during the entire image forming process.

In the image forming apparatus having the transfer drum 51 as described above, it is necessary to synchronize the timing of the feeding transfer paper P and the grippers GPI to GP3 (see FIG. 9) on the cylindrical drum 51a. Although the throughput is lower than the type in which the transfer paper S is transported by the transport belt 4 shown in FIG.
3 firmly holds the transfer paper, compared to electrostatic adsorption methods, the transfer paper transport characteristics are less affected by paper quality and environmental changes, for example, and transfer misalignment is kept to a minimum, and high-quality color images can be formed. produce an effect. Note that the effects of the present invention are not inhibited by electrostatic adsorption.

[Effects of the Invention] As explained above, the present invention provides a method for retracting/retracting from each image carrier.
a state change detection means for detecting a state change that detects the movement state of a conveyance body that is approaching; and a mark detection control means for controlling the start of detection of each registration mark image by the detection means based on the output state of the state change detection means. Even if the conveying body moves away from or approaches each image carrier at an unexpected timing, such as due to maintenance 1 paper jam being cleared, the conveying body can always be positioned at the correct position. At the same time, the image position shift detection process for positioning and the associated image position shift correction process can be completed within the normal image sequence waiting time, so high-quality images can always be maintained without sacrificing the high-speed image forming process. It has excellent effects such as being able to form color images.

[Brief explanation of the drawing]

FIG. 1 is a perspective view illustrating the configuration of a four-drum full-power single-type image forming apparatus showing an embodiment of the present invention, and FIG. 2 is an arrangement of the scanning mirror and optical scanning system shown in FIG. 1. 3(a) to 3(C) are schematic diagrams illustrating the image shift of the image carrier; FIG. 4 is a perspective view illustrating the configuration; FIG. 4 illustrates the internal configuration of the troller shown in FIG. 1; control block diagram,
5 is a diagram for explaining the registration mark reading operation by the mark detector shown in FIG. 4, FIG. 6 is a timing chart for explaining the operation in FIG. 4, and FIG. 7 is a diagram for explaining the operation of reading the registration marks by the mark detector shown in FIG. - A flowchart illustrating an example of a mark image detection processing procedure, FIG. 8 is a perspective view of a main part illustrating an example of an image forming apparatus illustrating another embodiment of the present invention, and FIG. FIG. 10 is a perspective view illustrating the structure of a transfer drum, and FIG. 10 is a schematic diagram illustrating types of image position shift in an image forming apparatus having a plurality of image carriers. In the figure, IC, IM, IY, IBK are photosensitive drums, 3C,
3M, 3Y, 38 are optical scanning systems, 4 is a conveyor belt, 5
．． 6 is a mark detector, 11.2 is a registration mark, 13
is a controller, and 14 is a microswitch. Figure 3 (a) (b) (C) Figure 1 Figure 5 1+ (=to) 3B-yo1: 111 Figure 7 = f! + Profit share - N right - 1 Ino h No. 10 (a) (C) (b)

Claims (4)

[Claims] (1) a plurality of image carriers arranged at predetermined intervals;
and a detection means for detecting each registration mark image formed on each image carrier and sequentially transferred to a conveying body, and in which the conveying body can be moved a predetermined amount away from/approaching each image bearing body, a state change detection means for detecting a movement state of the conveyance body moving away from/approaching each of the image carriers;
An image forming apparatus comprising: mark detection control means for controlling the start of detection of each of the registration mark images by the detection means based on the output state of the state change detection means. (2) The image forming apparatus according to claim (1), wherein the conveyance member is constituted by a conveyance belt that conveys the transfer material. (3) The image forming apparatus according to claim (2), wherein the conveyor belt is suspended by a plurality of rollers. (4) The image forming apparatus according to claim (1), wherein the conveyance member is constituted by a transfer drum that rotationally holds the transfer material.