JP2013029630A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that performs belt skew correction control by properly using edge profile data regardless of belt conveyance speed.SOLUTION: The image forming device 1 includes an edge sensor 60 for detecting a position of an intermediate transfer belt 31 in a direction orthogonal to the conveyance direction of the intermediate transfer belt 31, and a ROM 101 for storing edge profile data P that is shape data for one turn of the edge of the intermediate transfer belt 31. The CPU 100 executes skew control by controlling inclination of a steering roller 32 on the basis of the edge data E as a result detected by the edge sensor 60 and the edge profile data P. The CPU 100 also sets a detection period of the edge sensor 60 according to a change in conveyance speed of the intermediate transfer belt 31.

Description

  The present invention relates to an image forming apparatus that forms a toner image on a recording sheet through steps of charging, exposure, development, and transfer by an electrophotographic method.

  Conventional image forming apparatuses are provided with various types of belts such as an intermediate transfer belt, a fixing belt, and a recording paper conveyance belt.

  These belts are driven to rotate by being suspended by a plurality of rollers. During the belt rotation process, the belt moves toward one end or the other end in the width direction (hereinafter referred to as meandering). Tend to. Due to the meandering of the belt, the belt may fall off from the roller that is suspending the belt, or the end of the belt may be damaged.

  Therefore, it has an edge sensor that detects the position of the edge (end) in the width direction of the belt, and controls the tilting operation of the steering roller that supports the belt based on the detection result of the edge sensor at regular time intervals. There is one that corrects the meandering of the belt (for example, see Patent Document 1). This edge sensor has a contactor that contacts one end of the belt and a displacement sensor that detects a positional variation of the contactor, and continuously detects meandering of the belt.

  In addition, in order to perform highly accurate meandering correction without being affected by the edge shape of the belt, there is one in which edge shape data for one round of the belt is stored in advance in a memory as edge profile data (for example, Patent Documents). 2). By using this edge profile data, the belt meandering correction is performed with high accuracy by canceling the position variation of the belt edge based on the shape of the belt edge.

Japanese Patent Laid-Open No. 11-295948 JP 2010-145655 A (paragraphs 0046 to 0049)

  However, in the invention described in Patent Document 2, in order to match the position of the edge profile data with respect to the belt home position and the detection position of the edge sensor, the belt speed is set to a predetermined target speed. I have to detect the edge of

  As shown in FIG. 10, when the belt speed = the target speed, the position of the edge profile data and the detection position of the edge sensor can be matched, but when the belt speed <the target speed, the position of the edge profile data and the edge The detection position of the sensor shifts. This is because when the belt speed is smaller than the target speed, if the belt edge position is detected at a constant time interval, the belt moving distance after the predetermined time becomes shorter than when the belt speed is equal to the target speed. Because. Similarly, when the belt speed> the target speed, the position of the edge profile data on the basis of the belt home position is shifted from the detection position of the edge sensor.

  Therefore, if meandering correction control using edge profile data is performed when the belt speed is not equal to the target speed, belt position fluctuations based on the shape of the belt edge cannot be cancelled. If an image is to be formed in this state, high-accuracy meandering correction cannot be performed, so that a color-shifted image is generated due to a shift in image transfer position for each color.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of appropriately performing belt meandering correction control using edge profile data regardless of the belt conveyance speed.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an image carrier on which a toner image is formed, a belt used for transferring the toner image formed on the image carrier to a recording paper, A steering roller for rotatably supporting the belt; an inclining means for inclining an axis of the steering roller; a detecting means for detecting the position of the belt in a direction orthogonal to the belt conveying direction; and an end of the belt By controlling the tilt of the steering roller by the tilting means based on the storage means for storing the edge profile data which is the shape data for one round of the part, the detection result of the detecting means and the edge profile data, Control means for executing meandering control, wherein the control means detects the detection means in response to a change in the belt conveyance speed. And sets the cycle.

  According to the present invention, meandering correction control of a belt using edge profile data can be appropriately performed regardless of the belt conveyance speed.

1 is a schematic sectional view of an image forming apparatus. It is a figure which shows schematic structure for demonstrating the meandering correction | amendment control of an intermediate transfer belt. FIG. 6 is a diagram illustrating an example of non-uniformity of an end portion of an intermediate transfer belt. 2 is a control block diagram of the image forming apparatus. FIG. It is a figure explaining the correction process of the detection period of an edge sensor in 1st Embodiment. It is a flowchart which shows the correction process of the detection period of an edge sensor in 1st Embodiment. It is a flowchart explaining meandering correction control. It is a figure which shows the switching timing of the detection period of an edge sensor in 2nd Embodiment. It is a flowchart which shows the correction process of the detection period of an edge sensor in 2nd Embodiment. It is a figure for demonstrating the subject of this invention.

(First embodiment)
FIG. 1 is a schematic sectional view of the image forming apparatus.

  The image forming apparatus 1 of the present embodiment is a color electrophotographic apparatus in which a plurality of image forming units are arranged in parallel and an intermediate transfer method is adopted. The image forming apparatus 1 includes a recorded image signal output unit 1R and an image output unit 1P. The image output unit 1P includes four image forming units 10 (10a, 10b, 10c, 10d) arranged side by side, a paper feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, and a control unit 70. . Further, each unit will be described in detail.

  The image forming units 10a to 10d have the same configuration. In each of the image forming units 10a to 10d, cylindrical electrophotographic photosensitive members, that is, photosensitive drums 11a to 11d (image bearing members) are rotatably supported. It is rotationally driven in the direction of the arrow. The primary chargers 12a to 12d, the exposure systems 13a to 13d, the mirrors 16a to 16d, the developing devices 14a to 14d, and the cleaning devices 15a to 15d are arranged in the rotation direction facing the outer peripheral surfaces of the photosensitive drums 11a to 11d. Yes.

  In the primary chargers 12a to 12d, charges of a uniform charge amount are given to the surfaces of the photosensitive drums 11a to 11d. Next, the exposure systems 13a to 13d expose the photosensitive drums 11a to 11d on the photosensitive drums 11a to 11d via the mirrors 16a to 16d, which are modulated according to the recording image signal from the recording image signal output unit 1R. To form an electrostatic latent image there.

  Further, the developer of four colors such as yellow, cyan, magenta, and black (hereinafter referred to as “toner”) is visualized by the developing devices 14a to 14d accommodated therein. The visualized toner image is transferred to the intermediate transfer belt 31 constituting the intermediate transfer unit 30 by the primary transfer rollers 35a to 35d. The cleaning devices 15 a to 15 d clean the drum surface by scraping off toner remaining on the photosensitive drums 11 a to 11 d without being transferred to the intermediate transfer belt 31.

  The secondary transfer roller 36 transfers the toner image on the intermediate transfer belt 31 to the recording paper P. The cleaning device 50 cleans the surface of the intermediate transfer belt 31. The cleaning device 50 includes a cleaning blade for removing toner on the intermediate transfer belt 31 and a waste toner box for storing waste toner.

  The paper feed unit 20 includes cassettes 21 a and 21 b, pickup rollers 22 a, 22 b and 26, a pair of paper feed rollers 23, a paper feed guide 24, registration rollers 25 a and 25 b, and a manual feed tray 27. The recording paper P stored in the cassettes 21a, 21b and the manual feed tray 27 is sent out by the pickup rollers 22a, 22b, 26. The fed recording paper P is conveyed to the registration rollers 25a and 25b by the paper feed roller pair 23. The registration rollers 25a and 25b send the recording paper P to the secondary transfer roller 36 in accordance with the image formation timing of each image forming unit.

  The fixing unit 40 includes a fixing roller having a heat source such as a halogen heater therein, and a pressure roller that pressurizes the roller (this roller may also have a heat source).

Next, the operation of the image forming apparatus 1 configured as described above will be described.
When an image forming operation start signal is issued, first, the recording paper P is sent out one by one from the cassette 21a by the pickup roller 22a. Then, the recording paper P is guided between the paper feed guides 24 by the paper feed roller pair 23 and conveyed to the registration rollers 25a and 25b. At that time, the registration rollers 25a and 25b are stopped, and the leading edge of the recording paper P hits the nip portion. Thereafter, the registration rollers 25a and 25b start to rotate in accordance with the timing at which the image forming unit starts to form an image. The rotation timing is set so that the recording paper P and the toner image primarily transferred from the image forming unit onto the intermediate transfer belt 31 coincide with each other in the secondary transfer roller 36.

  On the other hand, in the image forming unit, when an image forming operation start signal is issued, the toner image formed on the photosensitive drum 11d by the process described above is transferred to the intermediate transfer belt 31 by the primary transfer roller 35d to which a high voltage is applied. Is done. The transferred toner image is conveyed to the next primary transfer roller 35c. In this case, image formation is performed with a delay by the time during which the toner image is conveyed between the image forming units, and the next toner image is transferred with the position aligned on the previous image. The same process is repeated thereafter, and finally the four color toner images are transferred onto the intermediate transfer belt 31.

  Thereafter, when the recording paper P enters the secondary transfer roller 36 and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passage timing of the recording paper P. As a result, the four color toner images formed on the intermediate transfer belt 31 are transferred onto the surface of the recording paper P. Thereafter, the recording paper P is guided to the fixing unit 40. The fixing unit 40 fixes the toner image on the surface of the recording paper P by applying heat and pressure to the recording paper P. Thereafter, the recording paper P is discharged out of the apparatus.

FIG. 2 is a diagram showing a schematic configuration for explaining meandering correction control of the intermediate transfer belt.
The intermediate transfer belt 31 is rotatably supported by a driving roller 33, a steering roller 32, and a secondary transfer counter roller 34. A primary transfer plane is formed between the drive roller 33 and the steering roller 32. The drive roller 33 is configured to coat the surface of the metal roller with rubber having a thickness of several millimeters to prevent slippage with the belt in order to transmit the drive to the intermediate transfer belt 31.

  The steering roller 32 rotates following the rotation of the intermediate transfer belt 31. One shaft of the steering roller 32 is fixed, and a steering arm 64 is connected to the other shaft. The control unit 70 controls the driving of the steering motor 63 and rotates the cam 62. When the cam 62 rotates, the steering arm 64 rotates about the shaft 65. In other words, the tilt of the steering roller 32 can be controlled by the control unit 70 controlling the rotational position of the cam 62.

  An edge sensor 60 is disposed between the steering roller 32 and the photosensitive drum 11a. The edge sensor 60 detects the position of the end of the intermediate transfer belt 31 and outputs an output signal (edge data) corresponding to the meandering of the intermediate transfer belt 31. The edge sensor 60 is an optical sensor that detects the amount of light according to the position of the flag member that contacts the end of the intermediate transfer belt 31. However, if the edge sensor 60 can detect the position of the end of the intermediate transfer belt 31, such as a line sensor. It is not limited to these.

  Since the end (edge) in the width direction of the intermediate transfer belt 31 is cut in the manufacturing process so as to have a desired width, the end of the intermediate transfer belt 31 detected by the edge sensor 60 is not uniform. The end positions are non-uniform within about 100 μm.

FIG. 3 is a diagram illustrating an example of non-uniformity at the end of the intermediate transfer belt.
As described above, the end of the intermediate transfer belt 31 in the width direction (the direction orthogonal to the conveyance direction of the intermediate transfer belt 31) is uneven. As shown in FIG. 3 (a), some are uneven unevenly over the entire circumference of the belt and as shown in FIG. 3 (b), they are uneven with a short period and no regularity. Further, when the intermediate transfer belt 31 is cut by the cutter while rotating the intermediate transfer belt 31 in the manufacturing process of the intermediate transfer belt 31, the cut surface is cut between the cutting start position and the cutting end position after one turn as shown in FIG. A level difference occurs without matching. Such edge unevenness is included in the edge data E detected by the edge sensor 60 as an error.

  In order to solve this problem, the edge profile data P, which is shape data for one round of the end of the intermediate transfer belt 31, is measured in advance and held in the ROM 101, and the edge data that is the detection result of the edge sensor 60 is stored. Control is performed to eliminate the error due to edge unevenness from E.

  At this time, an HP mark 37 indicating the home position of the intermediate transfer belt 31 and a belt HP sensor 61 for detecting the HP mark 37 are used. The HP mark 37 is affixed to the back surface of the intermediate transfer belt 31 and serves as a reference position for associating the edge profile data P with the position in the width direction of the intermediate transfer belt 31. The belt HP sensor 61 is a reflective optical sensor for detecting the HP mark 37.

  In order to indirectly measure the conveyance speed of the intermediate transfer belt 31, a code wheel 38 and an encoder sensor 39 are attached to the shaft of the drive roller 33. The code wheel 38 has 20 black marks printed at equal intervals in one turn. This is configured to be detected by an encoder sensor 39 which is a transmissive optical sensor.

FIG. 4 is a control block diagram of the image forming apparatus.
The control unit 70 includes a CPU 100, a ROM 101, and a RAM 102. The CPU 100 is a control circuit that controls the entire image forming apparatus 1. The ROM 101 stores a control program for controlling various processes executed by the image forming apparatus 1. The RAM 102 is a system work memory for the CPU 100 to operate, and also functions as an image memory for temporarily storing image data. The operation unit 67 includes a touch panel display and receives an operation instruction from the user.

  The belt drive motor 66 is a motor for driving the drive roller 33 that rotates the intermediate transfer belt 31. The CPU 100 controls the rotational speed of the intermediate transfer belt 31 by controlling the current that flows to the belt drive motor 66.

  Detection signals of the edge sensor 60 and the belt HP sensor 61 are transmitted to the CPU 100, converted from an analog signal to a digital signal by an AD conversion circuit built in the CPU 100, and processed by the CPU 100. The CPU 100 calculates steering data S for controlling the steering motor 63 based on the edge data E output from the edge sensor 60 and the edge profile data P stored in the ROM 101.

  The CPU 100 controls the inclination of the steering roller 32 by rotating the cam 62 by controlling the current flowing to the steering motor 63 based on the steering data S. Details of this point will be described later with reference to the flowchart of FIG.

  The encoder sensor 39 transmits a signal that detects the print mark of the code wheel 38 to the CPU 100. The detection signal of the encoder sensor 39 is a digital pulse signal whose cycle changes with the rotational speed of the drive roller 33. The CPU 100 indirectly detects the speed of the intermediate transfer belt 31 by counting the period of the digital pulse signal from the encoder sensor 39 and detecting the rotational speed of the drive roller 33.

  Next, detection timing control of the end position of the intermediate transfer belt 31 will be described. This control is a control for changing the detection cycle of the edge sensor 60 based on the detection signal of the encoder sensor 39.

FIG. 5 is a diagram for explaining correction processing of the detection cycle of the edge sensor in the first embodiment.
The upper waveform shows the fluctuation in the rotational speed of the code wheel 38. As described above, since the code wheel 38 has 20 black marks printed at equal intervals in one turn, 20 pulse signals are generated from the encoder sensor 39 when the drive roller 33 makes one turn. The CPU 100 measures the time intervals T1, T2,..., T20 of each pulse signal using a timer. In addition, the CPU 100 calculates the average value AveT of the time intervals of the respective pulse signals using Expression (1).
AveT = (T1 + T2 + T3... + T20) / 20 (1)

  The measured T1 to T20 and the calculated average value AveT are stored in the RAM 102. The reason why the average value AveT is calculated is to cancel the rotational fluctuation component accompanying the shaft eccentricity of the drive roller 33 or the code wheel 38. If the rotational speed of the intermediate transfer belt 31 matches the target speed, AveT = Tg.

Next, the CPU 100 calculates a difference ΔT between the target value Tg and the average value AveT of the actually measured values based on the formula (2). The rotational speed of the drive roller 33 is shifted by the amount of ΔT calculated here. The target value Tg is a value set in advance as a target value for the time interval of the pulse signal.
ΔT = Tg−AveT (2)

Next, the CPU 100 calculates the detection cycle of the edge sensor 60 based on the formula (3). Here, the detection cycle of the edge sensor 60 when the average value AveT is equal to the target value Tg is Tsns, and the corrected detection cycle is Tsns ′. As indicated by this equation, the detection cycle of the edge sensor 60 is corrected according to the ratio of the deviation amount (difference) ΔT with respect to the target value Tg.
Tsns ′ = Tsns (1−ΔT / Tg) (3)

FIG. 6 is a flowchart showing a correction process of the detection cycle of the edge sensor in the first embodiment.
A program for executing this flowchart is stored in the ROM 101 and is executed by being read by the CPU 100. The process according to this flowchart is executed when the meander control is started by driving the intermediate transfer belt 31 such as when a job start instruction is given.

  First, the CPU 100 controls the belt drive motor 66 to start driving the intermediate transfer belt 31 (S600). Then, the CPU 100 starts meandering control of the intermediate transfer belt 31 (S601). Here, the CPU 100 executes meandering control shown in FIG. 7 described later in parallel.

  Next, the CPU 100 measures the time intervals T1, T2,..., T20 of each pulse signal generated from the encoder sensor 39 using a timer (S603). The measured values of T1, T2,..., T20 are stored in the RAM 102. Then, the CPU 100 calculates the average value AveT of the time intervals of the respective pulse signals based on the above-described equation (1) (S604).

  Next, the CPU 100 calculates a difference ΔT between the target value Tg and the average value AveT of the actually measured values based on the above-described equation (2) (S605). Thereafter, the CPU 100 sets the detection cycle Tsns ′ of the edge sensor 60 based on the above-described equation (3) (S606). Based on the detection cycle Tsns' calculated here, end detection of the intermediate transfer belt 31 in meandering control is performed.

  Next, the CPU 100 determines whether to end the meandering control, for example, when ending the job (S607). If it is determined not to end the meandering control, the process returns to step S603 described above. If it is determined that the meandering control is to be terminated, the CPU 100 stops the meandering control by stopping the driving of the steering motor 63 (S608), and stops the driving of the intermediate transfer belt 31 by stopping the belt driving motor 66. (S609).

FIG. 7 is a flowchart for explaining meandering correction control.
A program for executing this flowchart is stored in the ROM 101 and is executed by being read by the CPU 100. As described above, execution of this flowchart is started in step S601.

  First, the CPU 100 determines whether or not a belt HP signal is input from the belt HP sensor 61 (S701). The belt HP signal is output when the belt HP sensor 61 detects the HP mark 37. When the belt HP signal is input, the CPU 100 initializes the address X to 1 (S702). On the other hand, when the belt HP signal is not input, the address X is not initialized.

  Then, the CPU 100 acquires edge data EX corresponding to the address X from the edge sensor 60 (S703). In addition, the CPU 100 acquires edge profile data PX corresponding to the address X from the ROM 101 (S704).

  Based on the edge data EX and edge profile data PX obtained here, the CPU 100 calculates steering data SX (S705). Specifically, the CPU 100 obtains the displacement HX of the intermediate transfer belt 31 by a calculation formula of HX = PX−EX and then obtains the steering data SX by a calculation formula of SX = α · HX. α is a preset coefficient.

  Then, the CPU 100 drives the steering motor 63 based on the calculated steering data SX (S706). In response to this, the steering motor 63 is controlled, the steering arm 64 moves in the direction in which the displacement H of the intermediate transfer belt 31 becomes 0, and the steering roller 32 tilts.

  Thereafter, the CPU 100 determines whether or not to stop meandering correction control in step S608 described above (S707). When the meandering correction control is not stopped, the CPU 100 adds 1 to the address X (S708).

  Then, the CPU 100 waits until the detection cycle Tsns ′ calculated in step S606 described above elapses from the previous detection of edge data (S709). This is because edge data is sampled every detection cycle Tsns'. After the elapse of the detection cycle Tsns ′, the process returns to step S701 described above. On the other hand, when stopping the meandering correction control in step S707, the CPU 100 ends this control flow.

  As described above, according to the present embodiment, the detection cycle Tsns ′ is corrected in accordance with the conveyance speed of the intermediate transfer belt 31, so that the edge profile data is appropriately obtained regardless of the conveyance speed of the intermediate transfer belt 31. The meandering correction control used can be performed.

(Second Embodiment)
In the second embodiment, only the parts different from the first embodiment will be described, and the description of the same configuration and control contents as in the first embodiment will be omitted. In the first embodiment, the rotation speed of the driving roller 33 is detected using the encoder sensor 39, and the detection cycle of the belt end position is corrected according to the detected rotation speed. On the other hand, in the second embodiment, the encoder sensor 39 is not used, and control for switching the detection cycle of the edge sensor 60 in a stepwise manner according to the elapsed time from the start of conveyance of the intermediate transfer belt 31 is executed. The

  Hereinafter, switching control of the detection cycle of the edge sensor 60 in the present embodiment will be described. The CPU 100 has a function of measuring the elapsed time from the start of conveyance of the intermediate transfer belt 31 with a timer and switching the detection cycle in four stages according to the measured elapsed time. Four different detection periods are stored in the RAM 102 in advance.

FIG. 8 is a diagram illustrating the switching timing of the detection cycle of the edge sensor in the second embodiment.
As time passes after the conveyance and meandering control of the intermediate transfer belt 31 is started, the conveyance speed of the intermediate transfer belt 31 increases to the target speed V as shown in FIG. When the elapsed time is t1, the speed is V1, when the elapsed time is t2, the speed is V2, and when the elapsed time is t3, the target speed V is reached.

  Further, as shown in FIG. 8B, the end position of the intermediate transfer belt 31 is detected at a cycle of Tv1 until the elapsed time from the start of conveyance and meandering control of the intermediate transfer belt 31 to t1. To do. The period from t1 to t2 is switched to the Tv2 period, the period from t2 to t3 is switched to the Tv3 period, and the period after t3 is switched to the Tv period.

  The elapsed times t1, t2, and t3 and the detection periods Tv1, Tv2, and Tv3 are determined in advance based on the degree of speed increase until the conveyance speed of the intermediate transfer belt 31 reaches the target speed. The detection cycle Tv is a numerical value obtained by equally dividing the time required for the intermediate transfer belt 31 to make one revolution when the conveyance speed of the intermediate transfer belt 31 is operating at the target speed V. In the present embodiment, the time required for the intermediate transfer belt 31 to make one revolution at the target speed V is 3 sec, and is divided into 30 to have a Tv = 100 msec cycle.

  In this embodiment, t1 = 1 sec, t2 = 2 sec, and t3 = 3 sec are set. Further, Tv1 = 400 msec, Tv2 = 300 msec, and Tv3 = 200 msec are set.

FIG. 9 is a flowchart illustrating correction processing for the detection cycle of the edge sensor according to the second embodiment.
A program for executing this flowchart is stored in the ROM 101 and is executed by being read by the CPU 100. The process according to this flowchart is executed when the meander control is started by driving the intermediate transfer belt 31 such as when a job start instruction is given.

  First, the CPU 100 controls the belt drive motor 66 to start driving the intermediate transfer belt 31 (S900). Then, the CPU 100 starts meandering control of the intermediate transfer belt 31 (S901). Here, the CPU 100 executes the meandering control shown in FIG. 7 in parallel.

  Next, the CPU 100 sets the detection cycle of the edge sensor 60 to Tv1 (400 msec) (S902). Thereafter, the CPU 100 waits until the elapsed time t1 (1 sec) has elapsed since the start of the driving of the intermediate transfer belt 31 (S903).

  Next, the CPU 100 sets the detection cycle of the edge sensor 60 to Tv2 (300 msec) (S904). Thereafter, the CPU 100 waits until an elapsed time t2 (2 sec) has elapsed since the start of driving of the intermediate transfer belt 31 (S905).

  Next, the CPU 100 sets the detection cycle of the edge sensor 60 to Tv3 (200 msec) (S906). Thereafter, the CPU 100 waits until an elapsed time t3 (3 sec) has elapsed since the start of driving of the intermediate transfer belt 31 (S907).

  Next, the CPU 100 sets the detection cycle of the edge sensor 60 to Tv (100 msec) (S908). At this time, since the conveyance speed of the intermediate transfer belt 31 has reached the target speed, the subsequent detection cycle remains Tv.

  Next, the CPU 100 waits until the meandering control is finished, for example, when the job is finished (S909). If it is determined that the meandering control is to be terminated, the CPU 100 stops the meandering control by stopping the driving of the steering motor 63 (S910), and stops the driving of the intermediate transfer belt 31 by stopping the belt driving motor 66. (S911).

  Note that the detection cycles Tv, Tv1, Tv2, and Tv3 of the edge sensor 60 set in the flowchart of FIG. 9 are used as the detection cycle Tsns ′ in step S709 of FIG.

  A difference in effect between the first embodiment and the second embodiment will be briefly described. In the first embodiment, since the end position detection cycle is controlled according to the conveyance speed of the intermediate transfer belt 31, not only when the conveyance of the intermediate transfer belt 31 is started but also the sudden speed of the intermediate transfer belt 31. It is possible to cope with fluctuations.

  On the other hand, the second embodiment cannot be applied to sudden belt speed fluctuations of the intermediate transfer belt 31, but can also be applied to an apparatus that does not include the encoder sensor 39 that detects the rotational speed of the drive roller 33. .

  In this embodiment, the meandering control of the intermediate transfer belt 31 has been described as an example, but the meandering control of the present invention may be performed on other belts. For example, the present invention may be applied to a conveyance belt that conveys a recording sheet so that toner images on a plurality of photosensitive drums are directly transferred to the recording sheet without using an intermediate transfer belt.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Photosensitive drum (image carrier)
31 Intermediate transfer belt (belt)
32 Steering roller 39 Encoder sensor (speed detection means)
60 Edge sensor (detection means)
61 HP sensor 62 Cam (tilting means)
63 Steering motor 100 CPU (control means)
102 RAM (storage means)

Claims (4)

An image carrier on which a toner image is formed;
A belt used for transferring a toner image formed on the image carrier to a recording paper;
A steering roller that rotatably supports the belt;
Tilting means for tilting the shaft of the steering roller;
Detection means for detecting the position of the belt in a direction perpendicular to the belt conveyance direction;
Storage means for storing edge profile data which is shape data for one round of the end of the belt;
Control means for executing meandering control by controlling the inclination of the steering roller by the inclination means based on the detection result of the detection means and the edge profile data;
The image forming apparatus according to claim 1, wherein the control unit sets a detection cycle of the detection unit in accordance with a change in a conveyance speed of the belt. A speed detecting means for detecting the conveying speed of the belt;
The image forming apparatus according to claim 1, wherein the control unit sets a detection cycle of the detection unit based on a conveyance speed of the belt detected by the speed detection unit. It further has a measuring means for measuring the elapsed time from the start of conveyance of the belt,
The image forming apparatus according to claim 1, wherein the control unit sets a detection cycle of the detection unit to be shorter as the elapsed time measured by the measurement unit becomes longer.   The belt is one of an intermediate transfer belt to which a toner image is transferred from the image carrier and a conveyance belt that conveys the recording paper so that the toner image is directly transferred from the image carrier to the recording paper. The image forming apparatus according to claim 1.

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