JP2006195275A - Image forming apparatus and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine the circumferential rotational operating state of an intermediate transfer body, on the basis of history information of a circumferential length value of the intermediate transfer body, and to control image forming operation, on the basis of the determination result. <P>SOLUTION: The image forming operation is controlled, by measuring the circumferential length value of the intermediate transfer body, on the basis of a reference position in the intermediate transfer body, storing the circumferential length value as the history information, and determining the circumferential rotational operation state of the intermediate transfer body on the basis of the history information. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a multi-function machine, and a printer that forms an image on recording paper by an electrophotographic method, and an image forming control method. The present invention relates to an image forming apparatus and an image formation control method for forming an image by performing a secondary transfer of a toner image on an intermediate transfer member onto a recording sheet after the primary transfer.

  Conventionally, after a toner image formed on a photosensitive member is temporarily transferred to an intermediate transfer member, the toner image is secondarily transferred onto a recording medium such as recording paper or an OHP sheet, and the toner image on the recording material is transferred. 2. Description of the Related Art Image forming apparatuses such as copiers, multifunction machines, and printers that perform image formation by an “electrophotographic method” that obtains a toner image by fixing a toner are known. In addition, drum-like or belt-like intermediate transfer members used for transfer have been put into practical use, but the transfer method using a belt-like intermediate transfer member is a space-related aspect when installed in an image forming apparatus. In view of the fact that the image forming apparatus is desired to be reduced in size, it is a transfer system that attracts attention today.

  In addition, in an image forming apparatus that performs transfer using the above-described intermediate transfer belt method, it is difficult to form a toner image on a photoreceptor when a full color image is obtained. , Cyan and magenta, or four color toner images with black added, are sequentially transferred from the photoreceptor in sequence, and the full-color toner images superimposed on the intermediate transfer belt are collectively transferred to the recording material. A full color image is obtained.

  When obtaining good image quality with a full-color image obtained by the above-described process, if the positions where the three-color or four-color toner images are superimposed are slightly shifted, the color of the obtained image is Since the color of the original image formed on the medium is completely different from that of the original image, it is necessary to accurately align the multicolor toner images superimposed on the intermediate transfer belt.

  Therefore, a reference mark serving as a reference for image formation timing is provided at a predetermined position on the intermediate transfer belt, and the reference mark is detected by an optical sensor or the like provided at a predetermined position on the conveyance path. By starting the image forming process at a predetermined timing, it is possible to primarily transfer and superimpose a multicolor toner image at a certain position on the intermediate transfer belt. In addition, improved techniques for more accurately aligning multicolor toner images have been proposed (see, for example, Patent Documents 1 and 2).

  However, if image formation is continued by the above-described method, there is a possibility that an image defect may occur due to deterioration of the intermediate transfer belt. That is, according to the above-described method, the toner image is always superimposed on a certain area on the intermediate transfer belt, so that the state of the conductive agent in the intermediate transfer belt changes with time, and the toner image on the intermediate transfer belt is changed. A phenomenon occurs in which the resistance value of the region where the layers are overlapped decreases. Then, there is a difference in primary transfer property and secondary transfer property between the region where the resistance value is reduced and the other region, and a large halftone image is formed between the region where the resistance value is reduced and the other region. At this time, image defects such as white spots may be conspicuous.

  To solve such a problem, a plurality of reference marks are provided on the intermediate transfer belt, and one of the plurality of reference marks is detected by a photosensor, and then the photosensitive member is exposed at a predetermined timing. A technique has been proposed in which the timing is controlled to accurately align the multicolor toner images and the toner images are primarily transferred to different positions on the intermediate transfer belt (see, for example, Patent Document 3).

  In the timing control of the image forming process using the plurality of reference marks described above, it is necessary to perform control while identifying the identification display by a sensor by attaching an identification display for specifying the plurality of reference marks to the reference mark. That is, for example, when a yellow toner image is transferred to the intermediate transfer belt with reference to a reference mark a provided at a predetermined position on the intermediate transfer belt, the next toner image is superimposed, for example, a cyan toner image is transferred to the intermediate transfer belt. Also when transferring, it is necessary to transfer with reference mark a as a reference, and color misregistration occurs with reference to another reference mark b.

  However, it may be difficult to identify the identification mark attached to the reference mark on the intermediate transfer belt rotating in synchronization with the image forming speed on the recording material. In particular, it has recently been required to increase the image forming speed, and it is becoming difficult to accurately read the identification display of the intermediate transfer belt that rotates at high speed. Alternatively, in such a case, a high-performance sensor that can accurately read the identification display is required, which is disadvantageous in cost. Further, when the surface of the intermediate transfer belt is cleaned with a cleaning blade, the identification display may disappear. In these cases, proper timing control cannot be performed, and color misregistration may occur.

  Further, in the above-described timing control of the image forming process using the plurality of reference marks, the image formation is started by detecting the first reference mark after the preparation of the first color image (preparation of toner image) is completed. At least the wait time from image formation preparation to detection of the first reference mark is added as a full color FCOT (first copy time).

Therefore, recently, as a method of actively reducing the wait time, the circumference, which is the length in the circumferential direction (rotation direction) of the intermediate transfer drum, is detected in advance and stored in a RAM or the like to prepare for image formation. A method of generating an image formation start signal at an arbitrary timing in accordance with a program after completion of the process is being studied. In this method, an image formation start signal for the first color is generated at an arbitrary timing, and the intermediate transfer drum makes one turn based on the peripheral length and the peripheral speed (circulation speed) detected in advance. By generating an image formation start signal for the next color when it reaches, the wait time until the first reference mark is detected is eliminated, and a full-color FCOT can be achieved compared to a method of starting image formation based on the reference mark. There is an advantage that it becomes faster (see, for example, Patent Document 4).
JP-A-7-92763 JP-A-7-281536 JP-A-8-146698 Japanese Patent Laid-Open No. 10-20614

  However, in the above-described conventional technology, the detected circumference is detected during the circumference detection period due to a load fluctuation caused by a mechanical shock when the cleaning blade is brought into contact with or separated from the intermediate transfer member or due to environmental changes over time. A slight difference in circumference occurs in the value. As a result, image formation timing is generated in the sub-scanning direction (paper feeding direction) of image formation based on the detected circumference, and the four color toner images are superimposed on the intermediate transfer member. Sometimes, for example, an alignment error of about 1 main scan (1 line) or less than 1 main scan (1 line) occurs, and a registration error called “color misregistration” or the like, that is, an image misalignment occurs. There was a problem that.

  In addition, when the peripheral length value of the intermediate transfer member fluctuates in comparison with the previously detected peripheral length value, it cannot be determined as an error, or a deviation occurs in the detection result of one round, within an appropriate range. There was also a problem that the circumference value could not be updated.

  Furthermore, there has been a problem that the replacement of the intermediate transfer member cannot be detected to reset the peripheral length value or its history, and the color misregistration is deteriorated at the time of replacement. Further, there was no simple treatment method for inputting an initial circumference value at the time of replacement.

  The present invention has been made to solve the above-described problems, and determines a state of a circular operation of an intermediate transfer member based on a peripheral length value of the intermediate transfer member, and controls an image forming operation based on the determination result. With the goal.

  In the present invention, an image formed on an image bearing member is subjected to primary transfer to an intermediate transfer member that is driven in a circular manner, and then the image transferred to the intermediate transfer member is secondarily transferred to a recording material to form an image. In the forming apparatus, a reference position detection unit that detects a reference position in the intermediate transfer member, a measurement unit that measures a peripheral value of the intermediate transfer member based on the reference position, and a circumference measured by the measurement unit Storage means for storing a value, determination means for determining the circumferential operation state of the intermediate transfer body based on the circumference value, and control means for controlling an image forming operation based on the circumference operation state. Features.

  In the present invention, an image formed on an image carrier is primarily transferred to an intermediate transfer member that is driven around, and then the image transferred to the intermediate transfer member is secondarily transferred to a recording material to form an image. A control method for an image forming apparatus to perform, a reference position detecting step for detecting a reference position in the intermediate transfer member, a measuring step for measuring a circumference value of the intermediate transfer member based on the reference position, and the measurement A storage step for storing the circumference value measured in the step, a determination step for determining the circumference operation state of the intermediate transfer member based on the circumference value, and an image forming operation based on the circumference operation state. And a control step.

  According to the present invention, it is possible to determine the rotating operation state of the intermediate transfer member based on the peripheral length value of the intermediate transfer member, and to control the image forming operation based on the determination result.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing the internal structure of the image forming apparatus according to the present embodiment. The image forming apparatus shown in FIG. 1 is configured as a copying machine, for example, and includes a laser unit 6; a polyhedral mirror (polygon mirror) 7; a scanner motor 8; a scanner unit 1 having a beam detection signal (BD signal) generation circuit 200; Photosensitive drum 3, intermediate transfer belt 4, circumferential length detection sensor 5, development rotary 10 having developer units 10a to 10d for each color, secondary transfer roller 11, environmental sensor 13, cleaning blades 14 and 15, fixing device 16, recording A recording material 17 such as paper, a paper feed cassette 18, a manual feed tray 19, a discharge port 20, and the like are provided.

  Note that a configuration relating to a document reading mechanism that reads an image from a document to be copied and a description thereof are omitted.

  The following description focuses on control related to color matching in the sub-scanning direction for each color of yellow (Y), magenta (M), cyan (C), and black (Bk) in the image forming process. First, the configuration of each part of the image forming apparatus will be described. In the scanner unit 1, a laser unit (hereinafter referred to as "laser") 6 is based on an image signal sent from an image forming part 27 shown in FIG. A modulated laser beam is emitted. A polyhedral mirror (polygon mirror) 7 that is rotationally driven by the scanner motor 8 deflects the laser light emitted from the laser 6 to scan the photosensitive drum 3, and forms an electrostatic latent image on the photosensitive drum 3. It is a rotating polygon mirror for forming. When the beam detection signal (BD signal) generation circuit 200 detects the laser beam deflected by the polygon mirror 7 in the main scanning direction, it outputs a BD signal to the image forming unit 27.

  On the other hand, the development rotary 10 converts the electrostatic latent image formed on the photosensitive drum 3 into developer units 10a, 10b, and 10c for each color of yellow (Y), magenta (M), cyan (C), and black (Bk). Develop with 10d. The photosensitive drum 3 primarily transfers the developer on the photosensitive drum 3 developed by the developing rotary 10 to the intermediate transfer belt 4. The secondary transfer roller 11 abuts on the intermediate transfer belt 4 and secondarily transfers the developer on the intermediate transfer belt 4 to a recording medium such as a recording sheet fed from the paper feed cassette 18 or the manual feed tray 19.

  The circumferential length detection sensor 5 detects the circumferential length, which is the length in the circumferential direction (rotation direction) of the intermediate transfer belt 4, and is disposed inside the unit of the intermediate transfer belt 4. In the present embodiment, for example, an optical reflection type sensor is used as the circumference detection sensor 5. As shown in FIG. 1, the intermediate transfer belt 4 is wound around the outer periphery of a plurality of rollers and is circulated through each roller. A reference mark 12 is arranged on the back surface of the intermediate transfer belt 4. It is installed. In the present embodiment, the reference mark 12 is made of a seal made of a material having a high reflectance. That is, the reference mark 12 disposed on the back surface of the intermediate transfer belt 4 is irradiated with light from a light source (not shown) such as an LED, and the circumference detection sensor 5 detects the reflected light. Yes.

  The photosensitive drum 3 is rotationally driven in the clockwise direction in FIG. 1, and the intermediate transfer belt 4 is rotationally driven in the counterclockwise direction in FIG. 1 contrary to the photosensitive drum 3, and each is not shown at the same constant speed. It is rotationally driven by a drive mechanism.

  The environmental sensor 13 detects temperature and humidity, and the amount of water around the intermediate transfer belt 4 is calculated based on the detection result of the environmental sensor 13. The control using the environment sensor 13 will be described in more detail in a second embodiment to be described later.

  The cleaning blade 14 is always in contact with the photosensitive drum 3 and performs cleaning by scraping off residual toner on the surface of the photosensitive drum 3. The cleaning blade 15 can be separated from and contacted with the intermediate transfer belt 4, and cleaning is performed by scraping residual toner on the surface of the intermediate transfer belt 4 at the time of contact.

  The fixing device 16 performs a fixing operation for fixing the toner image transferred onto the recording paper 17 by heating and pressing. The sheet feeding cassette 18 stores a plurality of recording sheets 17, and the recording sheet 17 fed out from the sheet feeding cassette 18 is fed to the secondary transfer position on the intermediate transfer belt 4. The manual feed tray 19 is used when manually feeding the recording paper 17. The recording paper 17 inserted in the manual feed tray 19 is fed to the secondary transfer position on the intermediate transfer belt 4. Then, the recording paper 17 on which image formation (copying) has been completed is discharged to the discharge port 20.

  Next, the operation of each part of the image forming apparatus will be described. First, image formation of yellow (Y) data is performed. That is, when a user instructs the start of an image forming job from an operation unit (not shown) of the image forming apparatus, an image forming preparation initialization operation is performed, and an electrical START signal generated based on a predetermined program is generated. As a trigger, a top (TOP *) signal generation counter (not shown) in which a target value is set for each color in the top signal generator 22 shown in FIG. 4 is activated. When the value of the yellow (Y) TOP signal generation counter of the first color reaches the target value, a yellow (Y) top signal is generated, and the write timing of the laser 6 in the scanner unit 1 is received in response to the top signal. And a laser beam is emitted from the laser 6, whereby a yellow (Y) data latent image is written on the photosensitive drum 3.

  Subsequently, the photosensitive drum 3 is rotated by a driving mechanism (not shown), and the photosensitive drum 3 is exposed to the yellow (Y) developer unit 10a in the developing rotary 10 by the yellow (Y) developer. The latent image above is visualized. Further, the photosensitive drum 3 is rotated by this drive mechanism, and the primary transfer of the yellow (Y) developer on the photosensitive drum 3 is performed on the intermediate transfer belt 4 at a position where the photosensitive drum 3 contacts the intermediate transfer belt 4. Is called. Here, the development rotary 10 rotates about 90 degrees to prepare for the development of the next magenta (M).

  Next, in the image formation of magenta (M) data, the top signal generated during the image formation of yellow (Y) data is used as a trigger, and each color in the top signal generation unit 22 shown in FIG. A top signal generation counter (not shown) in which a target value is set every time is started. When the value of the top signal generation counter of the second color magenta (M) reaches the target value, a top signal of magenta (M) is generated, and the write timing of the laser 6 in the scanner unit 1 is received in response to the top signal. Then, a laser beam is emitted from the laser 6. As a result, the laser beam is emitted from the laser 6 at the same writing start timing for yellow (Y) and the rotation position of the intermediate transfer belt 4, so that the magenta (M) data latent on the photosensitive drum 3. An image is written.

  Subsequently, the photosensitive drum 3 is rotated by the driving mechanism described above, and the latent image on the photosensitive drum 3 is developed by the magenta (M) developer at the same rotational position of the intermediate transfer belt 4 as that of yellow (Y). Is visualized. Further, the photosensitive drum 3 is rotated by the driving mechanism, and the magenta (M) developer on the photosensitive drum 3 is transferred onto the intermediate transfer belt 4 at the same rotation position of the intermediate transfer drum 4 as that of yellow (Y). Primary transfer is performed.

  Subsequently, cyan (C) and black (BK) are also controlled by the image forming process similar to the above-described yellow (Y) and magenta (M), and yellow (Y) and magenta ( M), cyan (C), and black (Bk) four color developers are overlaid, and then the recording paper 17 is fed from the paper feed cassette 18 or the manual feed tray 19 at a predetermined position to the intermediate transfer belt 4. The secondary transfer roller 11 is brought into contact. As a result, the developer on the intermediate transfer belt 4 is secondarily transferred to the recording paper 17 by the secondary transfer roller 11. Here, the secondary transfer roller 11 that has been in contact with the intermediate transfer belt 4 is separated when all the developer is transferred onto the recording paper 17. Then, the developer on the recording paper 17 is fixed by the fixing device 16, and the recording paper 17 on which image formation is completed is discharged to the discharge port 20.

  Next, the cleaning operation of the intermediate transfer belt 4 by the cleaning blade 15 described later will be described. In order to perform cleaning of the intermediate transfer belt 4 as a pre-process for forming the four colors as described above, the cleaning blade 15 is brought into contact with the intermediate transfer belt 4 before developing yellow (Y) as the first color. . The cleaning blade 15 in contact with the intermediate transfer belt 4 is separated from the intermediate transfer belt 4 before the leading edge of the first color yellow (Y) developer transferred to the intermediate transfer belt 4 reaches the position of the cleaning blade 15. Then, the cleaning pretreatment is terminated. Further, as described above, when the four color developers are superimposed and the developer is secondarily transferred to the recording paper 17, the cleaning blade 15 is again used to scrape off the developer remaining on the intermediate transfer belt 4. When all the developer is scraped off, it is separated from the intermediate transfer belt 4 and the post-cleaning process ends.

  Note that the target value set for each of the yellow (Y), magenta (M), cyan (C), and black (Bk) colors described above is the circumferential length disposed inside the unit of the intermediate transfer belt 4. This is determined based on the detection result of the circumference of the intermediate transfer belt 4 by the detection sensor 5.

  Next, a method for detecting the reference mark 12 arranged on the back surface of the intermediate transfer belt 4 by the circumference detection sensor 5 and measuring the circumference of the intermediate transfer belt 4 to set the above-described target value will be described in detail. To do.

  FIG. 2 is a diagram illustrating a configuration example of a measurement circuit that measures the circumference of the intermediate transfer belt 4. As shown in FIG. 2, the measurement circuit includes an oscillator 301, a frequency divider 302, a circumference detection counter 307 having a counter unit 303 and a circumference register unit 304, and the circumference detection sensor 5 shown in FIG. And a CPU 306.

  First, the oscillator 301 generates a primary clock (original clock). The frequency divider 302 generates a reference clock for the circumference detection counter 307 based on the primary clock input from the oscillator 301. The CPU 306 is connected to the circumference detection counter 307 and controls each unit shown in FIG. The counter unit 303 performs a counting operation described later. The circumference register 304 stores the count value obtained by the counter 303.

  Next, the operation of this measurement circuit will be described. The primary clock generated by the oscillator 301 is input to the frequency divider 302, and the frequency divider 302 generates a reference clock for the circumference detection counter 307. The circumference detection counter 307 is connected to the CPU 306, and the CPU 306 can always read the count value of the counter unit 303 loaded in the circumference length register 304 of the circumference detection counter 307 via the bus. The enable signal of the counter unit 303 of the circumference detection counter 307 is generated.

  The counter 303 of the circumference detection counter 307 starts counting the reference clock using the enable signal of the CPU 306 and the detection signal of the circumference detection sensor 5 as triggers, and the next detection signal is input from the circumference detection sensor 5. Then, the count value at that time is loaded into the circumference register unit 304, the count value is cleared, and the re-counting is repeated. That is, the counter unit 303 measures the time from the first detection signal obtained from the circumference detection sensor 5 to the second detection signal obtained along with the rotation of the intermediate transfer belt 4.

  Next, an actual target value setting sequence set for each color of yellow (Y), magenta (M), cyan (C), and black (Bk) in the image forming apparatus having the above-described configuration will be described.

  First, a mechanical shock (for example, the contact / separation of the cleaning blade 15 and the secondary transfer roller 11 with respect to the intermediate transfer belt 4 when the image is formed on the intermediate transfer belt 4 during the initialization operation when the power of the image forming apparatus is turned on). At a timing at which no accompanying shock or the like occurs, a circumference detection sequence for detecting the circumference of the intermediate transfer belt 4 using the circumference detection sensor 5 and the circumference detection counter 307 is performed.

  FIG. 3 is a diagram for explaining the operation of the circumference detection counter 307 in the circumference detection sequence. When the circumference detection sensor 5 detects the reference mark 12 on the back surface of the intermediate transfer belt 4 as the intermediate transfer belt 4 rotates, the circumference detection sensor 5 sends a detection signal to the counter 303 of the circumference detection counter 307. (HP signal) is output. Accordingly, the counter unit 303 counts the reference clock input to the counter unit 303 from the rising edge of the detection signal. When the intermediate transfer belt 4 further circulates, the circumference detection sensor 5 detects the reference mark 12 again, and until the counter 303 of the circumference detection counter 307 inputs the above-described detection signal (HP signal). The number of reference clocks is counted, and the count value at that time is loaded into the circumference register 304 in the circumference detection counter 307.

  The peripheral value of the intermediate transfer belt 4 can be measured by the resolution unit of the reference clock of the peripheral length detection counter 307 by the count value obtained as described above. The one-round time of the intermediate transfer belt 4 can be managed by the peripheral movement speed of the intermediate transfer belt 4 at the time of image (speed at which the circular operation is performed).

  However, in actuality, as described later, a mechanical shock to the intermediate transfer belt 4 at the time of image formation (for example, a shock caused by contact / separation of the cleaning blade 15 or the secondary transfer roller 11 with respect to the intermediate transfer belt 4) The one-round time of the intermediate transfer belt 4 is different from the one-round time calculated by the above measurement, and has a value having a certain offset.

  Therefore, the target value of each color input to the TOP signal generation counter (top signal generation unit 22) for each color at the time of image formation is set by adding the respective offset values.

  For example, the offset value is calculated by rotating the intermediate transfer belt 4 at the time of shipment from the factory, and applying the contact / separation of the cleaning blade 15 and the secondary transfer roller 11 for each rotation during one rotation. A difference Δ from the case where the contact / separation of the blade 15 and the secondary transfer roller 11 is not given is calculated as an offset value, and a method of storing in the apparatus or a predetermined value is initially set as an offset value, and an image forming operation is performed. At this time, the CPU 306 starts the operation of the circumferential length detection counter 307 at a timing when the cleaning blade 15 and the secondary transfer roller 11 do not contact / separate, and the circumferential length of the intermediate transfer belt 4 is measured. Similarly, the CPU 306 makes a circumference detection counter 307 at the timing at which the 11 contacts / separates. Operation to start to measure the circumference of the intermediate transfer belt 4 the difference Δ between the measured value of the former is calculated as an offset value, be reflected in the initial setting setting value, there is a method of storing the device.

  Furthermore, the target value of the top signal generation counter (top signal generation unit 22) can be set independently for four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). Further, it is possible to set independently for the A side corresponding to the odd number of recording sheets to be attached to the intermediate transfer belt 4 and for the B side corresponding to the even number of recording sheets to be attached to the intermediate transfer belt 4. It is.

  By the way, even if the position of the top of each color of yellow (Y), magenta (M), cyan (C), and black (Bk) (the image destination that is the leading edge of the image formation timing) is accurately synchronized, intermediate transfer is performed. A top signal (TOP *) indicating writing of each color in the sub-scanning direction obtained by rotation of the belt 4 and a beam detection signal (BD signal) indicating writing of each color in the main scanning direction obtained by rotation of the scanner motor 8. If synchronization is not achieved, the writing position of each color in the sub-scanning direction may cause a phase difference between the top signal of each color and the BD signal, that is, a shift of one line in the maximum sub-scanning direction.

  This can be solved if the time (cycle) in which the intermediate transfer belt 4 makes one round is exactly an integral multiple of the cycle of the BD signal. However, in general, it is difficult to set the cycle of the intermediate transfer belt 4 to an integral multiple of the cycle of the BD signal because it imposes restrictions on the design of the image forming apparatus.

  Therefore, in the present embodiment, using a known technique that is already known, a target signal serving as a reference corresponding to the position of the polygon mirror 7 on the scanner motor 8 is recreated every time the intermediate transfer belt 4 makes one revolution, By simply controlling the rotation of the scanner motor 8 by applying phase control to the target signal, the color misregistration of each color of yellow (Y), magenta (M), cyan (C), and black (Bk) is completely eliminated. The present invention provides a multicolor (full color) image forming apparatus that can be eliminated.

  FIG. 4 is a block diagram showing an example of the configuration of the scanner motor control system. As shown in FIG. 4, the scanner motor control system of the image forming apparatus includes a laser 6, a scanner motor 8 having a scanner motor driving circuit 8-1 and a scanner motor body (SM) 8-2, a CPU 21, and a top signal generator 22. , Timer 23, ROM 24, oscillator 25, laser control unit 26, image forming unit (image forming control circuit) 27, drum motor control unit 28, scanner motor control circuit 29, oscillator 30, beam detection signal (BD signal) generating circuit 200 Have In FIG. 4, the same components as those in FIG.

  The CPU 21 controls the entire image forming apparatus based on a program stored in the ROM 24. The CPU 21 controls the CPU 306, the circumference detection counter 307, the environment sensor 13, and the like described above, and is shown in a flowchart described later. Execute the process. The CPU 21 has a memory (not shown) (a work area of the CPU 21) inside the CPU 21 or in another place. The ROM 24 is a memory that stores a series of controls of the CPU 21 as a program procedure. The drum motor control unit 28 controls the rotation / stop of the intermediate transfer belt 4 and the photosensitive drum 3. The top signal generation unit 22 starts the timer 23 based on the above-described predetermined number of steps of one turn of the intermediate transfer belt 4 and one cycle time, and electrically generates a top signal (TOP) for each color during actual image formation. *) Is created.

  It is also useful to store the circumference value and its history when the circumference detection sequence mode is executed in a predetermined area of a memory (not shown) (work area of the CPU 21). For example, history information such as the number of executions of the circumference detection sequence and the execution date and time may be stored in a memory (not shown) (work area of the CPU 21).

Here, in order to simplify the description, a simple address and data will be described as an example. As described below, the execution history may be stored in a memory (not shown).
[Address 1000] Data: Execution count once, execution date and time 2003/12/26 08: 00
[Address 1001] Data: Execution count 2 times, execution date and time 2003/12/26 09:00:00
[Address 1002] Data: 3 executions, execution date and time 2003/12/26 13:00
[Address 1003] Data: Execution frequency 4 times, execution date and time 2003/12/27 08:00:00
[Address 1004] Data: 5 executions, latest execution date 2003/12/27 09:00:00
As a result, the date and time of execution of the latest circumference detection sequence and the cumulative number of executions become clear.

The print sequence execution history may also be stored in a memory (not shown) (a work area of the CPU 21). For example, the print sequence execution history may be stored in a memory (not shown) as follows.
[Address 2000] Data: Print execution count once, execution date and time 2003/12/26 08:10
[Address 2001] Data: Print execution count 2 times, execution date and time 2003/12/26 09:10
[Address 2002] Data: Print execution count 3 times, execution date and time 2003/12/26 13:10
[Address 2003] Data: Print execution count 4 times, execution date and time 2003/12/27 08:10
[Address 2004] Data: Print execution count 5 times, Latest execution date 2003/12/27 09:10
As a result, the latest machine state and the machine history can be stored by comparing the history of the printing operation as the image forming operation and the history of executing the circumference detection sequence.

  The oscillator 25 generates a clock that serves as a reference time for the operation of the CPU 21. The timer 23 divides the clock generated by the oscillator 25 and serves as a basis for time measurement and the like. In this case, if a one-chip CPU is generally used in a part of the configuration shown in FIG. 4, the CPU 21, the top signal generation unit 22, the timer 23, the ROM 24, and the drum motor control unit 28 can be accommodated in one chip. Therefore, the image forming apparatus can be further reduced in size and cost.

  The scanner motor 8 is provided with the polygon mirror 7 shown in FIG. 1, and includes a scanner motor drive circuit 8-1, a scanner motor body (SM) 8-2, and a scanner motor control / drive circuit shown in FIG. The rotation / stop is performed by the control of the scanner motor control circuit 29 under the instruction of the CPU 21.

  The beam detection signal (BD signal) generation circuit 200 detects the laser beam deflected by the polygon mirror 7 as the polygon mirror 7 rotates, and becomes a start reference signal in the main scanning direction (synchronization signal in the main scanning direction). A beam detection signal (BD signal) is generated. With respect to the beam detection signal (BD signal), when a six-sided polyhedral mirror is used as the polygon mirror 7, six beam detection signals (BD signals) are issued for one rotation of the scanner motor 8.

  The oscillator 30 generates a reference clock for operating the image forming unit (image forming control circuit) 27. The image forming unit (image forming control circuit) 27 includes a sub-scanning control circuit and a main scanning control circuit. The image forming unit (image forming control circuit) 27 generates a timing for forming video data by communicating with a controller (not shown) and generates a top signal (TOP). *) The sub-scan and main scan are synchronized based on the beam detection signal (BD signal) and a laser emission signal corresponding to the video signal is generated.

  The laser control unit 26 controls driving of the laser 6 in synchronization with each color in the sub-scanning direction according to a print command from the CPU 21 and a top signal (TOP *) from the top signal creation unit 22. The laser 6 receives a signal from the laser control unit 26 and writes latent image data on the photosensitive drum 3 by an actual laser beam.

  The scanner motor control circuit 29 includes a control circuit that operates to generate a target BD signal as a target immediately after the electrical top signal (TOP *) is generated and eliminate the phase difference from the actual BD signal. ing.

  FIG. 5 is a diagram showing a detailed configuration of the scanner motor control circuit 29 shown in FIG. As shown in FIG. 5, the scanner motor control circuit 29 includes a counter 31, a phase comparison circuit 34, and a charge pump circuit 35. In FIG. 5, 22 is the top signal generator shown in FIG. 4, 32 is a BD signal in the scanner motor control circuit 29, and 33 is a target BD signal in the scanner motor control circuit 29. 5, the same components as those in FIG. 4 are denoted by the same reference numerals.

  The counter 31 in the scanner motor control circuit 29 generates a target BD signal 33 as a target. The scanner motor control circuit 29 has a configuration in which the counter 31 for generating the target BD signal is reset and the target BD signal is regenerated, particularly immediately after detecting the output (TOP *) of the top signal generator 22.

  The phase comparison circuit 34 compares the phase of the target BD signal 33 generated by the counter 31 with the phase of the actual BD signal 32 detected by the beam detection signal (BD signal) generation circuit 200, and a LAG signal, which will be described later, The LEAD signal is output. The charge pump circuit 35 receives the output signal of the phase comparison circuit 34 and converts the phase difference between the two signals into a control voltage. Here, since the phase difference time is proportionally operated as the control amount as it is, the charge pump circuit 35 has a constant voltage and the control voltage of “+” / “−” according to the “advance” / “lag” of the phase difference. generate.

  FIG. 6 is a diagram showing a detailed configuration of the scanner motor control / drive circuit in the scanner motor 8 shown in FIG. As shown in FIG. 6, the scanner motor 8 includes a scanner motor driving circuit 8-1, a scanner motor main body (SM) 8-2, a frequency divider 41, a speed discriminator 42, a resistor 43, an integrator 44, an integration filter. 45, a control amplifier 46, and a resistor 48. Reference numeral 25 shown in FIG. 6 denotes the oscillator shown in FIG. In FIG. 6, the same components as those in FIG. 4 are denoted by the same reference numerals.

  The scanner motor control / drive circuit is composed of a frequency divider 41 to a resistor 48. The scanner motor control / drive circuit controls the scanner motor body (SM) 8-2 using a control signal from the scanner motor control circuit 29 shown in FIG. A control circuit to be driven. The frequency divider 41 divides the reference clock of the oscillator 25 by a predetermined frequency dividing ratio, and generates a frequency that becomes the reference speed of the scanner motor main body 8-1. The speed discriminator 42 is a BD signal 32 for detecting the rotational speed of the polygon mirror 7 (see FIG. 1) attached to the scanner motor 8 and a frequency divider 41 that generates a frequency that becomes the reference speed of the polygon mirror 7. And the speed of the polygon mirror 7 is determined based on the comparison result.

  The integrator 44 receives a control signal output from the scanner motor control circuit 29 via the resistor 48 and a control signal output from the speed discriminator 42 via the resistor 43, and is an integration filter composed of a resistor and a capacitor. It operates as an integrator having a predetermined gain and frequency characteristics determined from 45 and the resistor 43. The control amplifier 46 receives the signal from the integrator 44 and amplifies it to a predetermined gain so as to drive the scanner motor main body 8-2. The scanner motor drive circuit 8-1 includes a transistor and the like, and drives the scanner motor main body 8-2.

  Next, the control operation of the scanner motor 8 will be described. When the rotation control of the scanner motor 8 is performed by the scanner motor control / drive circuit configured as described above, the speed discriminator 42 monitors the BD signal 32 to determine whether the scanner motor 8 is at a predetermined speed. By a feedback control loop that generates an output signal to increase the speed when the scanner motor 8 does not reach the predetermined speed and to decrease the speed when the scanner motor 8 exceeds the predetermined speed. Rotation control is performed.

  However, in this feedback control loop, there is no control based on the phase difference between the above-mentioned BD signal and the output signal of the frequency divider 41 at the frequency that becomes the reference speed. The motor 8 is controlled slightly deviating from a predetermined speed.

  In order to faithfully control the scanner motor 8 at a predetermined target speed, the output of the phase difference between the target BD signal 33 and the actual BD signal 32 obtained by the scanner motor control circuit 29 shown in FIG. It is necessary to perform a PLL (Phase Locked Loop) speed control by injecting into the integrator 44 in parallel with the resistor 43 via 48.

  Here, the gain of the PLL control loop may be considerably lower than the gain of the speed discriminator 42, and the resistor 48 may be set to, for example, 10 times or more compared to the resistor 43. This is because if the gain of the PLL control is high, the followability to the target phase is improved, but the pull-in of the PLL to the locked state is deteriorated.

  By injecting the PLL control of the phase difference between the target BD signal 33 and the actual BD signal 32, the rotation of the scanner motor 8 can be controlled at a speed at which the actual BD signal 32 is generated in the cycle of the target BD signal 33. It becomes possible.

  Next, the PLL control operation of the image forming apparatus will be described in detail with reference to the timing chart shown in FIG.

  In FIG. 7, ENABLE * is a signal indicating a print area / non-print area (non-latent image forming section in the sub-scanning direction of the photosensitive drum 3), and “High” sections 701 and 702 in the figure indicate print areas. The other areas indicate non-printing areas. TOP * is a TOP signal, which is generated by the top signal generator 22 as a synchronization signal for starting printing in the sub-scanning direction. REFBD * is a target BD signal and is generated by the counter 31 of the scanner motor control circuit 29. BD * is an actual BD signal, which is generated by the beam detection signal (BD signal) generation circuit 200 as a synchronization signal for starting printing in the main scanning direction. LAG * is a LAG signal, which indicates a delay of the phase of the actual BD signal (BD *) with respect to the target BD signal (REFBD *), and is output by the phase comparison circuit 34 of the scanner motor control circuit 29.

  LEAD * is a LEAD signal, indicating the phase advance of the actual BD signal (BD *) with respect to the target BD signal (REFBD *), and is output by the phase comparison circuit 34 of the scanner motor control circuit 29.

  The LEAD signal (LEAD *) becomes “Low” only when the phase of the actual BD signal (BD *) is delayed from the phase of the target BD signal (REFBD *). The LEAD signal (LEAD *) becomes “Low” only when the phase of the actual BD signal (BD *) is ahead of the phase of the target BD signal (REFBD *).

  CPUMP is a combined signal of the LAG signal (LAG *) and the LEAD signal (LEAD *) output from the phase difference comparison circuit 34 of the scanner motor control circuit 29, and is generated by the charge pump circuit 35 of the scanner motor control circuit 29. The Is indicates a current actually output to the scanner motor 8.

  Next, the PLL control operation by the scanner motor control / drive circuit (frequency divider 41 to resistor 48) in the scanner motor 8 shown in FIG. 6 will be described.

  Before the top signal (TOP *) is generated by the top signal generator 22, the scanner motor 8 performs the phase of the target BD signal (REFBD *) and the actual BD signal (BD *) by speed discriminator control and PLL control. The PLL speed is controlled so that

  After that, when the top signal (TOP *) is generated, the counter 31 of the scanner motor control circuit 29 that creates the target BD signal (REFBD *) is immediately cleared at the falling edge of the top signal (TOP *), The counter 31 performs a counting operation from the beginning to recreate a new target BD signal (REFBD *). The actual BD signal (BD *) continues to be output in the same cycle because the speed of the scanner motor 8 cannot be changed rapidly. The phase comparison circuit 34 of the scanner motor control circuit 29 sets the LAG signal (LAG *) to “Low” only when the phase of the actual BD signal (BD *) is delayed from the phase of the target BD signal (REFBD *). Only when the phase of the actual BD signal (BD *) is ahead of the phase of the target BD signal (REFBD *), the LEAD signal (LEAD *) is set to “Low” and output.

  That is, the output from the phase comparison circuit 34 of the scanner motor control circuit 29 is the LAG signal (LAG *) when the phase of the actual BD signal (BD *) is delayed from the phase of the target BD signal (REFBD *). Is “Low”, the LEAD signal (LEAD *) remains “High”, and the phase of the actual BD signal (BD *) is ahead of the phase of the target BD signal (REFBD *), the LEAD signal ( LEAD *) is “Low”, and the LAG signal (LAG *) remains “High”.

  The charge pump circuit 35 of the scanner motor control circuit 29 synthesizes the LAG signal (LAG *) indicating phase lag and the LEAD signal (LEAD *) indicating phase advance to generate a CPUMP signal. Here, when the phase is delayed, the charge pump circuit 35 of the scanner motor control circuit 29 needs to accelerate the scanner motor 8 and outputs a voltage of “+”, and when the phase is advanced. Since the scanner motor 8 needs to be decelerated, it is configured to output a voltage of “−”.

  As a result of such a control signal being injected into the scanner motor control / drive circuit in the scanner motor 8 shown in FIG. 6 as a signal relating to PLL control, the speed of the scanner motor 8 is slightly lower than the conventional speed. Accelerating control is injected, the phase delay gradually decreases, and control is continued when equilibrium is maintained. That is, the phase of the actual BD signal (BD *) is synchronized with the target BD signal (REFBD *), and the speed difference is completely zero. The phase difference is the speed discriminator in the scanner motor 8 described above. It cancels out the speed deviation at 42 and settles down to maintain equilibrium.

  If printing starts at the time when the actual BD signal (BD *) reaches the time when the phase of the target BD signal (REFBD *) is balanced, the printing position of each color (printing start position in the sub-scanning direction) will match exactly. Can be made.

  Further, since the scanner motor control circuit 29 operates so that the actual BD signal (BD *) is kept in phase with the target BD signal (REFBD *) even during the printing operation, the actual BD signal is kept until the printing operation is completed. The scanner motor 8 can be controlled by synchronizing (BD *) with the target BD signal (REFBD *).

  As described above, even in an image forming apparatus in which the time for one rotation of the intermediate transfer belt 4 is not set to an integral multiple of the BD cycle, the main scanning synchronization signal (BD signal) and the sub-scanning synchronization signal (top signal) Can be matched in phase.

  Next, operations and effects unique to the present invention in the image forming apparatus having the above-described configuration will be described in detail.

  FIG. 8 is a diagram showing a sequence relating to generation of a top signal (TOP *) in color printing. The intermediate transfer belt 4 used in the present embodiment has one circumference, and, for example, two sheets of A4 size recording paper are pasted (processing for simultaneously forming images corresponding to two recording sheets on the intermediate transfer belt 4). FIG. 8 shows a sequence at the time of color image formation by sticking two sheets on a small size recording paper such as A4.

  Note that counters for each color including a yellow A surface (YA) counter and a yellow B surface (YB) counter described below are provided in the top signal generating unit 22.

  First, using an electrical START signal generated based on a predetermined program as a trigger, the yellow A side (YA) counter and the yellow B side (YB) counter start counting simultaneously. Here, the A side (odd-numbered surface of the recording paper) is the first half of the circumference of the intermediate transfer belt 4, and the B-side (even-numbered surface of the recording paper) is the intermediate transfer belt. 4 is the latter half part of one round. As shown in FIG. 8, when the predetermined count time (TYA, TYB) is reached, the top signal (TOP *) VYA * signal and VYB * signal corresponding to the A side and B side of yellow (Y) are respectively displayed. In response to these signals, the writing timing of the laser 6 in the scanner unit 1 is taken, and the laser 6 emits laser light. Thereby, the latent image writing of yellow (Y) data on the photosensitive drum 3 is performed.

  Next, when the yellow (Y) VYA * signal and VYB * signal are used as triggers, when the predetermined count time (TMA, TMB) corresponding to one round time of the intermediate transfer belt 4 is reached, the A side of magenta (M), A VMA * signal and a VMB * signal, which are top signals (TOP *) corresponding to the B side, are respectively generated, and upon receiving these signals, the writing timing of the laser 6 in the scanner unit 1 is taken, and the laser 6 emits the laser beam. Exit. Thereby, the latent image writing of the magenta (M) data on the photosensitive drum 3 is performed.

  Subsequently, cyan (C) and black (Bk) are also controlled in the same manner as yellow (Y) and magenta (M) described above, and the latent data of cyan (C) and black (Bk) on the photosensitive drum 3 is controlled. Image writing is performed.

  When four color developers are superimposed on the intermediate transfer belt 4, the registration roller ON counter counted by the VKA * signal and the VKB * signal, which is the black (Bk) top signal (TOP *), is used for registration. Signals (RA, RB) are sequentially generated, a recording material such as recording paper 17 is fed from the paper feed cassette 18 or the manual feed tray 19, and the secondary transfer roller 11 is brought into contact with the intermediate transfer belt 4. The four color developers are secondarily transferred to the recording paper 17.

  FIG. 9 is a diagram showing a circuit configuration of a video data request signal generation counter corresponding to each color (yellow, magenta, cyan, black). In FIG. 9, as described above, the START signal is input to the yellow (Y) counters A and B for the first color, and the top color generated from the counter for the previous color is supplied to the counters for the next and subsequent colors. The sequence of the first embodiment is made possible by adopting a daisy chain structure in which a signal is used as an activation trigger.

  Next, it occurs at the time of actual image formation in the image forming apparatus based on the configuration of the image forming apparatus shown in FIGS. 1, 2, and 4 to 6 and the top signal generation sequence in the color printing shown in FIG. A sequence in consideration of mechanical shock (for example, mechanical shock generated when the cleaning blade 15 is separated when forming a toner image on the intermediate transfer belt 4) will be described.

  FIG. 10 is a diagram showing a sequence obtained by extracting the sequence shown in FIG. 8 and adding the timing of the mechanical shock to the intermediate transfer belt 4 and the actual image destination timing corresponding thereto. As shown in FIG. 10, during the actual image formation in the image forming apparatus, the cleaning blade 15 that has been in contact with the intermediate transfer belt 4 for cleaning as a pre-process for performing the above-described four-color image formation is yellow ( Y) Separated from the intermediate transfer belt 4 in the second half of the B-side image forming timing, and contacts the intermediate transfer belt 4 in the second half of the black (Bk) B-side image forming timing as a post-cleaning process. In addition, as described above, the secondary transfer roller 11 also has a timing (black (Bk) A surface image forming timing shown in FIG. 10) at which the four color developing materials superimposed on the intermediate transfer belt 4 are transferred to the recording paper. It contacts the intermediate transfer belt 4 in the latter half.

  Actually, the contact / separation operation of the cleaning blade 15 with respect to the intermediate transfer belt 4 acts in a direction in which the load torque of the intermediate transfer belt 4 decreases, and the intermediate transfer belt 4 rotates instantaneously and rotates (intermediate transfer belt). Operation in the circumferential direction). Conversely, when the cleaning blade 15 is separated from the intermediate transfer belt 4 and brought into contact with the intermediate transfer belt 4, the load torque of the intermediate transfer belt 4 increases, and the intermediate transfer belt 4 rotates and rotates around instantaneously. When the secondary transfer roller 11 comes into contact with the intermediate transfer belt 4, it also acts in a direction in which the load torque of the intermediate transfer belt 4 increases, and similarly, the intermediate transfer belt 4 rotates instantaneously and rotates. To do.

  Therefore, the peripheral movement of the intermediate transfer belt 4 varies due to the driving of the mechanical load (the cleaning blade 15 and the secondary transfer roller 11) described above, and as a result, the actual image destination timing is changed as shown in FIG. In this sequence, the actual image destination timing of each color is the top signal (TOP * in this embodiment) of each color generated by the top signal (TOP *) generation counter for each color regardless of the load fluctuation as described above. As shown in FIG. 10, there is a shift of ΔL from the actual image destination timing, and in the four-color image forming operation, the accumulation of such a shift for each color is a full-color image forming apparatus. Color misregistration in the image formation result.

  Specifically, as shown in FIG. 10, when the cleaning blade 15 is separated from the intermediate transfer belt 4, one round time in the region of yellow (Y) → magenta (M) on the intermediate transfer belt 4 is the A side. , B side is shortened by ΔLy−c, and the contact time of the secondary transfer roller 11 with respect to the intermediate transfer belt 4 causes one round time of the cyan (C) → black (Bk) region on the intermediate transfer belt 4 to be ΔLc−. shortened by k.

  The actual color misregistration amount due to this time variation amount is about 50 μm-100 μm (in this embodiment, the contact operation of the cleaning blade 15 and the separation operation of the secondary transfer roller have a small influence, so that they are illustrated and described. Is omitted).

  However, the generation timing of the shock caused by the separation of the cleaning blade 15 from the intermediate transfer belt 4 and the shock caused by the contact of the secondary transfer roller 11 with the intermediate transfer belt 4 as described above is not changed in the image forming sequence. There is also a tendency for actual fluctuations in the movement of the intermediate transfer belt 4 due to a shock.

  FIGS. 11 to 14 are flowcharts showing processing for setting a target value in the top signal (TOP *) generation counter for yellow, magenta, cyan, and black.

  First, as shown in FIG. 11, with respect to the yellow (Y) counter, the time from the START signal to the top signal of yellow (Y) is constant regardless of the circumference of the intermediate transfer belt 4, and therefore a predetermined counter Values are set for the A side and B side of the intermediate transfer belt 4 (YS1).

  Next, as shown in FIG. 12, the magenta (M) counter determines whether or not it is after the circumference detection mode for detecting the circumference of the intermediate transfer belt 4 (MS1). Note that after the circumference detection mode is after the circumference measurement of the intermediate transfer belt 4 is completed, and actually measured by the circumference register 304 in the circumference detection counter 307 shown in FIG. This is after the actual circumference value has been stored. The circumference detection mode may be measured, for example, at the time of pre-rotation when the apparatus is turned on, when the environment changes after a predetermined time after the circumference detection mode is implemented.

  If it is determined that the peripheral length detection mode has been set, the peripheral length of the intermediate transfer belt 4 measured by the peripheral length detection sensor 5 is read from the peripheral length register 304 of the peripheral length detection counter 307, and the RAM (see FIG. (Not shown) (MS2).

  Next, counter values TMA and TMB corresponding to one round time of the intermediate transfer belt 4 are calculated based on the circumference of the intermediate transfer belt 4 stored in the RAM of the CPU 306 and a predetermined image forming speed (MS3). Next, the offset amount Mcl-off of the circumferential movement variation time of the intermediate transfer belt 4 corresponding to the separation shock of the cleaning blade 15 with respect to the intermediate transfer belt 4 is added to TMA and TMB, respectively, and the target value TMA of the magenta (M) counter ', TMB' is set for A side and B side respectively (MS4).

  Next, as shown in FIG. 13, for the cyan (C) counter, it is determined whether or not it is after the circumference detection mode for detecting the circumference of the intermediate transfer belt 4 (CS1). If it is determined that the peripheral length detection mode has been set, the peripheral length of the intermediate transfer belt 4 measured by the peripheral length detection sensor 5 is read from the peripheral length register 304 of the peripheral length detection counter 307, and the RAM (see FIG. (CS2).

  Next, counter values TCA and TCB corresponding to one round time of the intermediate transfer belt 4 are calculated from the circumference of the intermediate transfer belt 4 stored in the RAM of the CPU 306 and a predetermined image forming speed, and magenta (M) → In the image forming process between cyan (C), since there is no assumed mechanical shock, target values TCA and TCB of the cyan (C) counter are set for the A side and B side, respectively (CS3).

  Finally, as shown in FIG. 14, it is determined whether or not the black (Bk) counter is after the circumference detection mode for detecting the circumference of the intermediate transfer belt 4 (KS1). If it is determined that the circumference detection mode has been set, the circumference measured by the circumference detection sensor 5 is read from the circumference register 304 of the circumference detection counter 307 and stored in a RAM (not shown) of the CPU 306. (KS2).

  Next, counter values TKA and TKB corresponding to one round time of the intermediate transfer belt 4 are calculated based on the circumferential length of the intermediate transfer belt 4 stored in the RAM of the CPU 306 and a predetermined image forming speed. Since there is no assumed mechanical shock for the A plane, the target value TKA of the counter is set for the A plane (KS4).

  On the other hand, for the B side, an offset amount Kcl-on of the circumferential movement variation time of the intermediate transfer belt 4 corresponding to the contact shock of the secondary transfer roller 11 with respect to the intermediate transfer belt 4 is added to TKB, and black (Bk) The counter target value TKB ′ is set for the B side (KS5).

  As described above, by setting the target value, the cleaning blade 15 separation operation with respect to the intermediate transfer belt 4 and the secondary transfer roller contact operation with respect to the intermediate transfer belt 4 that occur in the image forming sequence shown in FIG. The top signal (TOP *) of each color can be generated almost in synchronization with the image destination timing, and a good image can be output without causing a large color shift in the image forming apparatus.

  It is also useful to store the result of circumference detection by executing the circumference detection sequence as a history in a predetermined area of a memory (not shown) (work area of the CPU 21).

  For example, the circumference detection history information such as the circumference value of the circumference detection result and the execution date / time may be stored in a memory (not shown) (work area of the CPU 21).

  Here, a simple address and data will be described as an example.

  For example, when the diameter Dr of the photosensitive drum is 62 mm and the circumference of the intermediate transfer belt (ITB) is made three times the outer circumference of the photosensitive drum, the outer circumference L of the photosensitive drum is 194.77874 mm (= 3.1415927 × 62).

  If the resolution of one line is 600 dpi (dot / inch), the distance Pt of one line pitch is 42.3333 μm (= 25.4 / 600 = 0.0423333 mm).

  When the outer circumference L of the photosensitive drum is converted into the number of lines, the number of photosensitive drum lines is 4601.076 lines (L / Pt = 194.77874 / 0.0423333) in 600 dpi conversion.

  When the ITB circumference Lb is converted into the number of lines, the ITB circumference Lb is three times the outer circumference L of the photosensitive drum. Therefore, in 600 dpi conversion, the number of ITB circumference Lb is 13803.228 lines (Lb / Pt = 3L / Pt = 3 × 4601.076).

  Therefore, if circumference detection can be detected with an accuracy of 1/100 of 1 line (600dpi), 1 line pitch is 1/100 of 42.3333μm, so it has a detection resolution of about 0.42μm. become.

  At this time, for example, when the circumference Lb of the ITB in the calculation result is handled as the number of lines, the value of Lb / Pt is used so that the result of the circumference detection does not need to treat the decimal point as a numerical value of less than one line. A value obtained by multiplying 1000 by 1000 will be described as an example.

  First, the ideal circumference value is LBPT = 1000 × Lb / Pt = 13803228 line (1000 times of 600dpi) when Lb / Pt = 13803.228 line (600dpi) is defined as LBPT. It becomes.

[Definition of circumference value that is not an error]
It is assumed that a deviation from a reference value for detecting the circumference of one or more lines is an error in circumference value. Here, if the ITB circumference in the image forming apparatus is an ideal value, the normal circumference value range is 13802228 <LBPT <13804228.

  For example, it can be regarded as normal when the circumference value (1000 times converted in 600 dpi) and LBPT = 13803200 (1000 times in 600 dpi) = 13803.200 mm. A good image quality printout without color misregistration images can be obtained.

[Definition of circumference value near error limit value]
Even if the above-mentioned LBPT is within the range of 13802228 <LBPT <13804228, for example, if a circumference deviation of 1/4 line or more occurs, the 1/4 line is set to execute the circumference detection again. If there is a discrepancy between the ideal value of 250 or more and the detected circumference value multiplied by 1000 because it is 0.25 lines, the circumference value may be updated to the latest detected circumference value to improve color misregistration. Useful.

  For example, it can be regarded as normal when the circumference value is 1000 times converted to 600 dpi and the LBPT is 13803200 (1000 times 600 dpi converted) = 13803.200 mm.

  For example, when the LBPT is deviated by 1/4 line from the ideal value, 250 is added to the ideal value LBPT = 13803228, and LBPT = 13803478 is obtained. At this time, LBPT = 13803478 <13804228 (= value at the time of error), which is not an error state.

  Therefore, the latest circumference value (for example, 13803468) is measured by starting the circumference detection sequence operation, and is set as the latest circumference value LBPT1. That is, by updating the latest circumference value LBPT1 to the latest circumference value and determining the image forming timing based on the latest circumference value LBPT1, the image quality of the color misregistration image can be improved. Further, instead of updating the latest circumference value LBPT1, the circumference value in such a case may be stored in advance and this value may be used.

Error condition definition
It is assumed that a deviation from a reference value for detecting the circumference of one or more lines is an error in circumference value. Here, assuming that the ITB circumference in the image forming apparatus is an ideal value, if 13802228 ≧ LBPT or LBPT ≧ 13804228, it is defined as a circumference detection error.

  For example, if the circumference value (1000 times converted to 600 dpi) is 13803200 (1000 times 600 dpi equivalent) = 13803.200 mm, it can be considered normal, but the detected circumference value is 13810000 (1000 times 600 dpi equivalent). ) = 13810.000mm, etc., it is a significant difference in circumference value, and is judged as an error.

  For example, an error display announcement screen may be displayed on an operation unit (not shown) by the CPU to prohibit the operation of the machine.

  Then, for example, the circumference value LBPT at the time of execution of the latest circumference sequence and the execution date and time are stored in a memory (not shown).

[Example when normal]
The circumference value and its execution history may be stored as follows.
[Address 3000] Data: Circumference value 13803218, Execution date 2003/12/26 08:00:00
[Address 3001] Data: Circumference value 13803000, Execution date 2003/12/26 09: 00
[Address 3002] Data: Circumference value 13803111, Execution date 2003/12/26 13:00
[Address 3003] Data: Circumference value 13803222, Execution date 2003/12/27 08:00:00
[Address 3004] Data: Circumference value 13803221, Latest execution date 2003/12/27 09:00:00
[Example when an error occurs]
The circumference value and its execution history may be stored as follows.
[Address 3000] Data: Circumference value 13803218, Execution date 2003/12/26 08:00:00
[Address 3001] Data: Circumference value 13810000, Execution date 2003/12/26 09: 00
(At this time, the circumference value is 13810000, which is an error.)
[Address 3002] Data: Circumference value 13803111, Execution date 2003/12/26 13:00
[Address 3003] Data: Circumference value 13803222, Execution date 2003/12/27 08:00:00
[Address 3004] Data: Circumference value 13803221, Latest execution date 2003/12/27 09:00:00
[Normal example: Deviation of about 1/4 line]
The circumference value and its execution history may be stored as follows.
[Address 3000] Data: Circumference value 13803218, Execution date 2003/12/26 08:00:00
[Address 3001] Data: Circumference value 13803000, Execution date 2003/12/26 09: 00
[Address 3002] Data: Circumference value 13803111, Execution date 2003/12/26 13:00
[Address 3003] Data: Circumference value 13803200, Execution date 2003/12/27 08:00:00
[Address 3004] Data: Circumference value 13803468, Latest execution date 2003/12/27 09:00:00
(Updated to the latest value LBPT1 = 13803468 after the circumference detection is executed, and image formation is performed).

  As described above, according to the first embodiment, the load (cleaning blade 15, secondary transfer roller 11, etc.) on the intermediate transfer belt 4 for performing the primary transfer in the image forming process is separated and contacted. The rotation time of the intermediate transfer belt 4 varies depending on the mechanical load, and the rotation time of the intermediate transfer belt 4 varies from color to color. In the conventional color superposition process, the colors of the first color and the second and subsequent colors are different. It is possible to improve the problem that the deviation occurs. In addition, by storing a history of circumference values, circumference detection can be performed with an appropriate margin, and erroneous error determination can be prevented. Further, when an abnormality occurs, an error can be appropriately set, and both a printing operation with appropriate quality and accurate error processing can be achieved.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described in detail with reference to the drawings. The structure of the image forming apparatus (FIG. 1), the configuration of the circumference detection counter (FIG. 2), the configuration of the scanner motor control system (FIG. 4), the detailed configuration of the scanner motor control circuit (FIG. 5), the scanner motor control The detailed configuration of the drive circuit (FIG. 6) and the like are the same as in the first embodiment, and description thereof is omitted.

  A feature of the second embodiment is that the environment sensor 13 is provided around the intermediate transfer belt 4 (for example, on the outer peripheral side) so that the humidity and temperature can be monitored and the amount of water around the intermediate transfer belt 4 can be calculated. It is the point which arranged.

  That is, the environmental sensor 13 detects humidity and temperature, and the CPU 301 (FIG. 2) calculates the amount of water around the intermediate transfer belt 4 based on the detection result of the environmental sensor 13.

  FIG. 15 is a diagram illustrating a sequence for generating a top signal (TOP *) in color printing. Note that the intermediate transfer belt 4 used in the second embodiment has one circumference as in the first embodiment, and can, for example, adhere two sheets of A4 size recording paper. FIG. 15 shows a sequence at the time of color image formation by sticking two sheets on a small size recording paper such as A4.

  First, each of the A-side and B-side generated based on the program is triggered by a separate electrical START signal, and the yellow A-side (YA) counter and the yellow B-side (YB) counter start counting. . As shown in FIG. 15, when a predetermined count time (TYA, TYB) is reached, the VYA * signal and VYB * signal, which are the top signals (TOP *) corresponding to the A side and B side of yellow (Y), are displayed. Respectively generated, receiving these signals, the writing timing of the laser 6 in the scanner unit 1 is taken, and the laser 6 emits laser light. Thereby, the latent image writing of yellow (Y) data on the photosensitive drum 3 is performed.

  Next, when the yellow (Y) VYA * signal and VYB * signal are used as triggers, when the predetermined count time (TMA, TMB) corresponding to one round time of the intermediate transfer belt 4 is reached, magenta (M) A VMA * signal and a VMB * signal, which are top signals (TOP *) corresponding to the A side and the B side, are respectively generated. Upon receiving these signals, the writing timing of the laser 6 in the scanner unit 1 is taken. A laser beam is emitted. Thereby, the latent image writing of the magenta (M) data on the photosensitive drum 3 is performed.

  Subsequently, cyan (C) and black (Bk) are controlled in the same manner as yellow (Y) and magenta (M), and latent image writing of cyan (C) and black (Bk) data on the photosensitive drum 3 is performed. Is done.

  When the four color developers are superimposed on the intermediate transfer belt 4, the registration roller is turned on by the counter for turning on the registration roller, which is counted based on the VKA * signal and the VKB * signal as the top signal (TOP *) of black (Bk). Signals (RA, RB) are sequentially generated, a recording material such as recording paper 17 is fed from the paper feed cassette 18 or the manual feed tray 19, and the secondary transfer roller 11 is brought into contact with the intermediate transfer belt 4. The four color developers are secondarily transferred to the recording paper 17.

  FIG. 16 is a diagram illustrating a circuit configuration of a top signal generation counter corresponding to each color (yellow, magenta, cyan, black). In the second embodiment, ENABLE_A and ENABLE_B gates are provided in front of the yellow (Y) counters A and B of the first color as compared with the circuit configuration in the first embodiment. By performing the off operation, a START signal is input to each of the A side and B side, and the video data request signal generated by the previous color counter is used as a start trigger for the counter for the next and subsequent colors. By adopting such a daisy chain configuration, the sequence of the second embodiment is made possible.

  In the second embodiment, in addition to the mechanical shocks described above, it is possible to correct even a change in the peripheral length of the intermediate transfer belt 4 caused by an environmental difference that occurs when an image is formed and output on a large number of recording sheets. When the moisture level calculated using the environmental sensor 13 exceeds a predetermined level, the circumference value of the intermediate transfer belt 4 measured in the circumference detection mode for detecting the circumference of the intermediate transfer belt 4 can be changed. It is said.

  By reflecting this in the target value of the top signal (TOP *) generation counter for each color, a change in the amount of water around the intermediate transfer belt 4 over time during execution of an image forming job for forming an image on recording paper. It is possible to cope with a change in the circumferential length of the intermediate transfer belt 4 and a change in the environment during execution of the image forming job.

  It should be noted that when the image forming apparatus is actually started up from room temperature due to a long-time image forming job, the temperature rises by about 30 ° C., and the humidity also changes accordingly. Actually, the peripheral length difference of the intermediate transfer belt 4 (which uses a polyimide material in the present embodiment) differs by about several μm.

  17 to 20 show target values set by adding an offset value by mechanical shock for each color to the top signal (TOP *) generation counter for each color performed in the first embodiment, and subsequent continuous copying operations. It is a flowchart which shows the process in time.

  First, as shown in FIG. 17, for the yellow (Y) counter, the time from the START signal to the top signal of yellow (Y) is constant regardless of the circumference of the intermediate transfer belt 4, so Counter values are set for the A side and the B side, respectively (YS1).

  Next, as shown in FIG. 18, for the magenta (M) counter, every time a predetermined number of sheets (number of copies of recording paper) has elapsed since the start of the continuous copying operation (MS1), the temperature and humidity detected by the environment sensor 13 are set. Based on this, the amount of water around the intermediate transfer belt 4 is calculated (MS2). Further, the difference between the calculated water content around the intermediate transfer belt 4 and the water content when the peripheral length of the intermediate transfer belt 4 is detected is compared (MS3). Here, when a difference value greater than or equal to a predetermined amount occurs between the moisture amounts of the two, the counter offset value Thum due to the environmental change calculated according to the circumferential offset value Lhum of the intermediate transfer belt 4 according to the moisture amount difference is set. The value is added to the magenta counter values TMA and TMB that have already been set. The target values TMA ″ and TMB ″ of the counters thus corrected for the environment are newly set for the A side and the B side, respectively (MS4).

  19 and 20, for cyan (C) and black (Bk), similarly to the magenta (M) counter target value, the counter offset value Thum due to environmental change is used for the A plane and the B plane, respectively. (MC1 to MC4 shown in FIG. 19, MK1 to MK4 shown in FIG. 20).

  Accordingly, in the second embodiment, not only the mechanical shock amount correction for the intermediate transfer belt 4 as in the first embodiment but also the circumferential length of the intermediate transfer belt 4 due to environmental changes over time during continuous copying. Responding to deviations in the image destination timing due to changes, the top signal (TOP *) of each color can be generated in accordance with the actual image destination timing with higher accuracy than in the first embodiment. A good image can be output without causing color misregistration.

  As described above, according to the second embodiment, due to separation and contact of each load (cleaning blade 15, secondary transfer roller, etc.) with respect to the intermediate transfer belt 4 for performing primary transfer in the image forming process. Since the rotation time of the intermediate transfer belt 4 is different for each color due to a mechanical load fluctuation that can make a difference in the rotation speed of the intermediate transfer belt 4, the first color and the second and subsequent colors in the conventional color superposition process. This can improve the problem of color misregistration.

  Furthermore, color misregistration due to a change in the peripheral length of the intermediate transfer belt 4 due to an environmental change with time during continuous copying can be improved.

  In the second example, a target value is set by adding an offset value by a mechanical shock for each color to the top signal (TOP *) generation counter for each color performed in the first embodiment. The processing at the time of the continuous copying operation is shown, but the target value is set by adding the offset value by the mechanical shock for each color to the top signal (TOP *) generation counter of each color performed in the first embodiment. 18 may be omitted, and if there is an environmental change, it may be detected by MS2 in FIG. 8 and processed in subsequent steps.

[Normal example: Deviation of about 1/4 line]
As described below, the circumference value and its execution history may be stored. For such misalignment, the circumference difference due to the thermal expansion of the housing of the main body or the ITB drive roller due to the temperature is caused. Arise.
[Address 3000] Data: Circumference value 13803218, Execution date 2003/12/26 08:00:00
[Address 3001] Data: Circumference value 13803000, Execution date 2003/12/26 09: 00
[Address 3002] Data: Circumference value 13803111, Execution date 2003/12/26 13:00
[Address 3003] Data: Circumference value 13803200, Execution date 2003/12/27 08:00:00
[Address 3004] Data: Circumference value 13803468, Latest execution date 2003/12/27 09:00:00
(Updated to the latest value LBPT1 = 13803468 after the circumference detection is executed, and image formation is performed)
In this way, the latest circumference value is measured by starting the circumference detection sequence operation, and the latest circumference value LBPT1 is updated to the latest circumference value by setting the latest circumference value LBPT1, By determining the image formation timing based on the latest circumference value LBPT1, the image quality of the color misregistration image can be improved.

  According to the embodiment described above, the problem of color misregistration due to the occurrence of mechanical load fluctuations in the color superimposing process is improved, and further, the intermediate transfer member is changed due to environmental changes over time during continuous copying. Color shift due to circumference change is also improved.

  In addition, circumference detection can be performed with an appropriate margin, erroneous error determination can be prevented, and an error can be appropriately set when an abnormality occurs, and there is an effect that both a printing operation with appropriate quality and accurate error processing can be achieved.

  Further, when the circumference detection result in the circumferential movement of the intermediate transfer belt is an abnormal value, the circumference detection operation can be appropriately performed by setting an error state. And when the circumference detection result is near the limit of the normal range, the initial circumference value stored in advance is used, so that there is a margin for error judgment in circumference detection and an appropriate The amount of deviation in the range becomes acceptable.

  When the amount of deviation is not problematic in terms of image quality, it is possible to prevent the occurrence of a false detection error that erroneously results in an error.

  Instead of using the detected circumference value, for example, the previously detected circumference value can be used instead, and image formation using the current detection result is possible due to various factors such as detection error. When it is not optimal, it becomes possible to use the circumference value detected last time.

  For example, the circumference detection timing can be detected only when the reference member or reference mark of the intermediate transfer belt passes the vicinity of the detection means. Since the forming operation can be performed, when there is no problem in image quality such as color misregistration, the waiting time of the machine is eliminated, and the productivity and the first copy time can be shortened.

  Color misregistration can be prevented and machine downtime can be shortened with a simple and low-cost configuration without an image misregistration detection means such as an expensive registration detection sensor.

  Even when the circumference detection result fluctuates due to changes in temperature and humidity, an image can be formed by circumference detection with an appropriate margin, so that an inadvertent error and machine down can be prevented.

[Other Embodiments]
The present invention is not limited to the configurations of the first and second embodiments, and any configuration can be used as long as the functions shown in the claims or the functions of the configurations of the embodiments can be achieved. Even so, it is applicable.

  For example, in the first and second embodiments, when a switch or a sensor detects whether or not an intermediate transfer member or an intermediate transfer unit including the intermediate transfer member has been replaced, and detects the replacement, It may be controlled to reset the history of the circumference value described, measure the circumference of the latest intermediate transfer member, and store the data and history information thereof.

  As a result, it is possible to improve the image quality without deteriorating color misregistration during replacement of the intermediate transfer member or the intermediate transfer unit.

  Further, at the time of belt replacement, the circumference value may be set to a predetermined initial value from the operation unit or an external host computer.

  Thereby, exchange time can be shortened and the service at the time of exchange can be improved.

  In the first and second embodiments, the case where an intermediate transfer belt is used as an intermediate transfer member provided in the image forming apparatus is taken as an example, but the present invention is not limited to this, and the intermediate transfer member is not limited thereto. The present invention is also applicable when an intermediate transfer drum is used.

  In the first and second embodiments, the case where two sheets of A4 size recording paper are pasted in one circumference of the intermediate transfer belt of the image forming apparatus has been described as an example. However, the present invention is limited to this. However, the size of the recording paper and the number of images attached (formed) corresponding to the recording paper on the intermediate transfer belt can be arbitrarily set within the scope not departing from the gist of the present invention.

  Furthermore, in the first and second embodiments, the case of a copying machine as an example of an image forming apparatus has been described as an example. However, the present invention is not limited to this, and can be applied to a printer and a multifunction machine in addition to the copying machine. Is possible.

  Another object of the present invention is to supply a recording medium recording software program codes for realizing the functions of the embodiment to a system or apparatus, and the system or apparatus computer (or CPU, MPU, etc.) records the recording medium on the recording medium. It is also achieved by reading and executing the programmed program code.

  In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention.

  As a recording medium for supplying the program code, for example, a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, a DVD- RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM, or the like can be used.

  Further, by executing the program code read by the computer, not only the functions of the embodiment are realized, but also an OS (operating system) running on the computer based on the instruction of the program code is actually A case where part or all of the processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

  Further, after the program code read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes the case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

1 is a schematic diagram showing an internal structure of an image forming apparatus in the present embodiment. FIG. 3 is a diagram illustrating a configuration example of a measurement circuit that measures the circumferential length of an intermediate transfer belt. It is a figure for demonstrating operation | movement of the counter 307 for circumference detection in a circumference detection sequence. It is a block diagram which shows an example of a structure of a scanner motor control system. FIG. 5 is a diagram showing a detailed configuration of a scanner motor control circuit 29 shown in FIG. FIG. 5 is a diagram showing a detailed configuration of a scanner motor control / drive circuit in the scanner motor 8 shown in FIG. 4. FIG. 4 is a diagram illustrating a timing chart in PLL control of the image forming apparatus. FIG. 6 is a diagram illustrating a sequence relating to generation of a top signal (TOP *) in color printing of the image forming apparatus. It is a figure which shows the circuit structure of the video data request signal generation counter corresponding to each color (yellow, magenta, cyan, black). FIG. 9 is a diagram showing a sequence obtained by extracting the sequence shown in FIG. 8 and adding the timing of mechanical shock to the intermediate transfer belt 4 and the actual image destination timing corresponding thereto. It is a flowchart which shows the process which sets a target value to the top signal (TOP *) production | generation counter about yellow. It is a flowchart which shows the process which sets a target value to the top signal (TOP *) production | generation counter about magenta. It is a flowchart which shows the process which sets a target value to the top signal (TOP *) production | generation counter about cyan. It is a flowchart which shows the process which sets target value to the top signal (TOP *) production | generation counter about black. FIG. 5 is a diagram illustrating a sequence for generating a top signal (TOP *) in color printing of the image forming apparatus. It is a figure which shows the circuit structure of the top signal production | generation counter corresponding to each color (yellow, magenta, cyan, black). It is a flowchart which shows the process which sets target value to the top signal (TOP *) production | generation counter about yellow in 2nd Embodiment. It is a flowchart which shows the process which sets target value to the top signal (TOP *) production | generation counter about magenta in 2nd Embodiment. It is a flowchart which shows the process which sets target value to the top signal (TOP *) production | generation counter about cyan in 2nd Embodiment. It is a flowchart which shows the process which sets target value to the top signal (TOP *) production | generation counter about black in 2nd Embodiment.

Claims (8)

In an image forming apparatus for performing image formation by first transferring an image formed on an image bearing member to an intermediate transfer member that is driven in a circle and then secondarily transferring the image transferred to the intermediate transfer member to a recording material.
A reference position detecting means for detecting a reference position in the intermediate transfer member;
Measuring means for measuring a peripheral value of the intermediate transfer member based on the reference position;
Storage means for storing the circumference value measured by the measurement means;
Determination means for determining a circular operation state of the intermediate transfer member based on the peripheral length value;
An image forming apparatus comprising: control means for controlling an image forming operation based on the rotating operation state.   The image forming apparatus according to claim 1, wherein the control unit adjusts an image forming timing in an image forming operation for superimposing a plurality of color images.   The image forming apparatus according to claim 1, wherein the storage unit stores the circumference value measured by the measurement unit as history information.   When the measured circumference value exceeds the first limit value, the determination unit determines that a predetermined deviation or more has occurred in the rotation operation of the intermediate transfer member, and is in a first rotation operation state. This is stored in the storage means, and the control means uses a predetermined circumference value stored in advance in the storage means or a circumference value updated from the circumference value instead of the measured circumference value. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled to perform image formation.   When the measured circumference value exceeds a second limit value, the determination unit determines that an abnormal shift has occurred in the rotation operation of the intermediate transfer member, and determines that the second rotation state is set. The image forming apparatus according to claim 1, wherein the image forming apparatus is stored in a storage unit.   When the intermediate transfer member is replaced, the measurement unit measures a circumference value of the exchanged intermediate transfer member, and stores the measured circumference value in the storage unit. Item 2. The image forming apparatus according to Item 1.   The image forming apparatus according to claim 1, wherein when the intermediate transfer member is replaced, a predetermined circumference value can be input as an initial value. Control of an image forming apparatus that forms an image by first transferring an image formed on an image bearing member to an intermediate transfer member that is driven in a circle and then secondarily transferring the image transferred to the intermediate transfer member to a recording material A method,
A reference position detecting step for detecting a reference position in the intermediate transfer member;
A measurement step of measuring a circumference value of the intermediate transfer member based on the reference position;
A storage step of storing the circumference value measured in the measurement step;
A determination step of determining a circular operation state of the intermediate transfer member based on the peripheral length value;
And a control step of controlling an image forming operation based on the rotating operation state.

Images