JPH1124498A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device accurately controlling the traveling speed of an image carrier belt without making the size of a device large and increasing a cost. SOLUTION: This image forming device forms an image by making an endless intermediate transfer belt 18 travel by rotating a driving roll 20 by means of a driving motor 29. In this case, the image forming device is provided with a home sensor 23 detecting a mark formed on the intermediate transfer belt 18, and a control part 31 obtaining the traveling speed information of the belt 18 from the detection timing of the mark by the sensor 23 and also arithmetically calculating the belt traveling controlled variable based on the traveling speed information, and controlling the driving condition of the motor 29 based on the calculated result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by running an endless image carrier belt.

[0002]

2. Description of the Related Art Generally, an image forming apparatus such as a copying machine or a printer includes an intermediate transfer belt for secondary-transferring a toner image primary-transferred from a photosensitive drum to a sheet, and a transfer position of the photosensitive drum. An image carrier belt such as a paper transport belt for transporting a sheet to a sheet is known. In this type of image forming apparatus, an endless image carrier belt is supported by a plurality of rolls, and one of the rolls is driven to rotate as a drive roll, so that the image carrier belt runs.

When the image carrier belt is run by the rotation of the driving roll as described above, when a certain load is applied to the image carrier belt, the running speed of the image carrier belt is reduced due to a load change accompanying the load. Change.
At this time, if a constant load is constantly applied to the image carrier belt, the belt traveling speed is also maintained at a constant level, but for example, a belt cleaner is used to remove residual toner on the intermediate transfer belt during the belt traveling. Contact
Due to the load fluctuation accompanying this, the belt running speed greatly changes, and this causes the occurrence of color misregistration.

More specifically, by running the intermediate transfer belt over a plurality of rounds, toner images of respective colors are transferred from a single photosensitive drum onto the intermediate transfer belt in a superimposed manner.
In the case of a so-called multi-pass type image forming apparatus, the cleaning is started while the final color toner image is being transferred to the intermediate transfer belt. The transfer position of the color toner image gradually shifts. As a result, the final color toner image does not accurately overlap with the other color toner images,
As a result, color misregistration occurs and image quality deteriorates.

Therefore, conventionally, an encoding roll, which is a combination of a roll that rotates in conjunction with the running operation of the intermediate transfer belt and an encoder that detects the rotation speed of the roll, is incorporated in a belt traveling system, and the encoding roll uses the encoding roll. One that detects the traveling speed and controls the speed is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-24296.
No. 2, JP-A-63-12568, JP-A-63
It is described in, for example, JP-A-300248.

[0006]

However, in the technique described in the above-mentioned conventional publication, a mechanical mechanism for detecting the traveling speed of the intermediate transfer belt becomes large, and the use of an encoder increases the apparatus cost. There was a problem that it would. In addition, since the detection data has an error due to the eccentricity of the roll itself, there is also a problem that the traveling speed of the intermediate transfer belt cannot be properly controlled.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to control the traveling speed of an image carrier belt accurately without increasing the size and cost of the apparatus. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and comprises an image forming apparatus having an endless image carrier belt and a belt driving means for running the image carrier belt. In the apparatus, a traveling speed information of the image carrier belt is acquired from a sensor for detecting a mark formed on the image carrier belt and a mark detection timing by the sensor, and belt traveling control is performed based on the traveling speed information. And a control means for calculating the amount and controlling the driving conditions of the belt driving means based on the calculation result.

In the image forming apparatus having the above structure, when the belt is driven by the belt driving means, the mark formed on the belt is detected by the sensor. At this time, since the detection timing of the mark by the sensor corresponds to the traveling speed of the image carrier belt, the control means acquires the traveling speed information of the image carrier belt from the above detection timing, and further acquires the traveling speed information. The driving condition of the belt driving means is controlled by calculating the belt control amount based on the above. With this, when the running speed of the image carrier belt fluctuates, the driving conditions of the belt driving unit are changed according to the fluctuation, so that the running speed of the image carrier belt is kept at a constant level. It is possible to hold.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, the configuration and operation of an image forming apparatus to which the present invention is applied are shown in FIG.
This will be described with reference to FIG. The illustrated image forming apparatus mainly includes an image input unit 1 that scans a document and outputs an image signal.
And an image output unit 2 for forming an image on a sheet based on the image signal.

An image input unit 1 includes a lamp 4 for irradiating a document (not shown) placed on an upper surface of a transparent document table 3 with light;
Mirrors 5 and 6 for reflecting light from the original, a lens 7 for converging the light reflected from the mirrors 5 and 6, and a charge-coupled device (CCD: Ch) for receiving the light converged by the lens 7
arge coupled device) 8, and the light received by the charge coupled device 8 is color-separated into R (red), G (green), and B (blue) signals to optically read an original image. I have.

The image output unit 2 separates the R, G, and B signals supplied from the image input unit 1 into yellow (Y), magenta (M), cyan (C), and black (K), and retains them. It has an image processing unit (not shown) and an image writing unit 9 for writing an image with a laser beam based on the image data processed by the image processing unit. The image writing unit 9 includes a polygon mirror (rotating polygon mirror) 10 for deflecting a laser beam modulated based on the image data,
A drive motor 11 for rotating the polygon mirror 10
And an SOS sensor 1 disposed on the optical path of the laser beam
And 2. The SOS sensor 12 detects the start of scanning in each cycle in the main scanning direction based on the transmission of the laser beam and outputs a scanning start (SOS) signal.

The laser beam transmitted through the SOS sensor 12 is reflected by a reflection mirror 13 and irradiates the outer peripheral surface of a photosensitive drum 14, and is main-scanned in the axial direction of the drum. By repeating this main scanning at a constant cycle, the first to fourth colors are formed on the outer peripheral surface of the photosensitive drum 14.
The electrostatic latent images up to the color are sequentially written. In FIG. 1, reference numeral 15 denotes a charger for uniformly charging the outer peripheral surface of the photosensitive drum 14 before writing the above-described electrostatic latent image, and reference numeral 16 denotes a residual toner on the photosensitive drum 14. It is a drum cleaner to remove.

When an electrostatic latent image of an arbitrary color is written on the photosensitive drum 14, development is immediately performed by a rotary developing device 17. The developing unit 17 includes yellow, magenta, cyan, and black developing sleeves 17a to 17a.
and supplies a toner of a color corresponding to the electrostatic latent image written by the image writing unit 9 to the photosensitive drum 14. And the toner image thus formed is
The primary transfer is performed on an intermediate transfer belt (image carrier belt) 18 which is always in contact with the outer peripheral surface of the photoconductor drum 14. By repeating this primary transfer, the toner images of the first to fourth colors (yellow → magenta → cyan → black) are sequentially transferred onto the intermediate transfer belt 18 so as to form a color toner image. . Reference numeral 19 denotes a transfer corotron that charges the intermediate transfer belt 1 to a charge having a polarity opposite to that of the toner.

On the other hand, the intermediate transfer belt 18 is supported in a loop by a drive roll 20 and a pair of support rolls 21 and 22. The drive roll 20 is driven to rotate in the direction of the arrow in the figure. Also,
As shown in FIG. 2, a mark 18 a having a different reflectance from the surface of the belt is formed on the surface of the intermediate transfer belt 18. On the other hand, a home sensor 23 is disposed between the drive roll 20 and the support roll 22 so as to face the intermediate transfer belt 18. This home sensor 23
A belt reference signal is output when the mark 18a formed on the intermediate transfer belt 18 is detected. The position at which the belt reference signal is output is the reference position (home position) of the intermediate transfer belt 18.

A belt cleaner 24 for removing residual toner on the intermediate transfer belt 18 is disposed near the drive roll 20. This belt cleaner 24
Is provided so as to be able to contact and separate from the intermediate transfer belt 18. Further, a secondary transfer roll 25 is disposed near the support roll 22. This secondary transfer roll 25 is
The toner image of each color is firstly transferred onto the intermediate transfer belt 18 and then pressed against the support roll 22, so that the paper is supplied to the pressed portion.

That is, the sheets stacked on the sheet feed tray 26 are taken out one by one by a sheet feed roll 27 and supplied to the press-contact portion (nip position) between the support roll 22 and the secondary transfer roll 25 described above. . At that time, the paper is charged to a polarity opposite to that of the toner by a charger (not shown). As a result, the color toner image on the intermediate transfer belt 18 is secondarily transferred to the sheet at the roll pressing portion. At this time, the residual toner remaining on the intermediate transfer belt 18 without being transferred to the sheet is removed by the belt cleaner 24. On the other hand, the sheet on which the color toner image has been transferred is sent to the fixing device 28, where the toner image is fixed, and then discharged outside the apparatus.

FIG. 3 is a functional block diagram showing a control configuration of the image forming apparatus of the present embodiment. In FIG. 3, a drive motor 29 rotates a drive roll 20 for running the belt, and the drive motor 29 is configured to rotate in accordance with a drive signal from a motor control unit 30. On the other hand, the control unit 31 acquires travel speed information of the intermediate transfer belt 18 from the detection timing of the mark 18a by the home sensor 23, calculates a belt travel control amount based on the travel speed information, and calculates the calculation result. Based on this, the driving condition of the driving motor 29 by the motor control unit 30 is controlled. The control unit 31 is supplied with a belt reference signal from the home sensor 23 and a cleaner ON signal from the cleaner control unit 32.

The cleaner controller 32 turns on the belt cleaner 24 at a predetermined timing, thereby bringing the belt cleaner 24 into contact with the intermediate transfer belt 18. At this time, the cleaner controller 32 sends the cleaner to the controller 31. An ON signal is output. Further, a control signal for controlling the driving conditions of the drive motor 29 is given from the control unit 31 to the motor control unit 30. In accordance with the control signal, the motor control unit 30
Is driven.

FIG. 4 shows the relationship between the belt running speed and the image transfer position during image formation. The upper part of the figure shows the change over time of the belt running speed, and the lower part shows the change over time of the image transfer position. First, when the toner images of each color are primary-transferred from the photosensitive drum 14 to the intermediate transfer belt 18, while the toner images of the first to third colors are being primary-transferred, the belt cleaner 24 is moved by the intermediate transfer. It is held in a state separated from the belt 18. Therefore, the intermediate transfer belt 18
Travels at a predetermined reference level, whereby the toner images of the first to third colors are also transferred to specified positions.

On the other hand, the toner image of the fourth color (final color) is
When the next transfer is performed, the belt cleaner 24
Is in the ON state, and comes into contact with the intermediate transfer belt 18. As a result, the driving load of the intermediate transfer belt 18 fluctuates (increases) during the primary transfer of the fourth color toner image.
I do. Then, the running speed of the intermediate transfer belt 18 decreases by a predetermined level (here, ΔV) from the ON timing of the belt cleaner 24, and accordingly, the image transfer position of the fourth color (primary transfer position). Gradually deviates from the prescribed positions (the image forming positions of the first to third colors).

When the final color toner image deviates from the prescribed position, it appears as a color deviation of the image on the paper. Therefore, the control unit 31 prevents the occurrence of color misregistration by a processing procedure as shown in FIG. First, in the first (n = 0) image forming process after the power of the apparatus is turned on, the timer incorporated in the control unit 31 is reset (step S1). Next, it is determined whether the first belt reference signal (1st reference) has been output from the home sensor 23 (step S2), and a timer is started at the time of output (step S2).
3).

Next, it is determined whether or not the second belt reference signal (2nd reference)) has been output from the home sensor 23 (step S4).
The required time TR _n1 of the lap is acquired (step S5).
Thereafter, each time the home sensor 23 outputs the third and fourth belt reference signals (3rd reference and 4th reference) from the home sensor 23, the required time TR _{n2 for the} second lap of the belt, and further, the third lap of the belt The required time TR _n3 is acquired in order (steps S6 to S9).

Subsequently, it is determined whether a cleaner ON signal has been output from the cleaner controller 32 (step S1).
0). Then, when the cleaner ON signal is output, the process proceeds to step S11, where it is determined whether or not this is the first routine (n = 0?). At this point, since the image forming process is the first image forming process, the process proceeds to step S13, and it is determined whether or not the fifth belt reference signal (5th reference) has been output. The fifth when the belt reference signal is output to get the required time TM _n belt 4 round (step S14), and stops the timer at that time (step S15).

Here, the intermediate transfer belt 18 is actually
Image area for transferring the image and non-image area adjacent to it
The image area is set side by side in the belt circumferential direction.
Normally, the belt reference signal is output from the home sensor 23.
Thereafter, the image on the intermediate transfer belt 18 is removed at a predetermined timing.
It is controlled so that the rear top position reaches the primary transfer position.
Have been. However, for the sake of clarity here,
, A belt reference signal is output from the home sensor 23
At the same time as the image area of the intermediate transfer belt 18
Is to reach the primary transfer position. so
Then, the toner images of the first to fourth colors are intermediately transferred.
When the primary transfer is performed on the photo belt 18, one round of each belt
Required time TR_n1, TR_n2, TR_n3, TM _nAnd each color
FIG. 6 shows the relationship between the image areas of the ner image.

As described above, the required time T for four rotations of the belt is
When R _n1 , TR _n2 , TR _n3 , and TM _n (running speed information) are obtained, the control unit 3 uses these measurement data.
In step 1, a predetermined calculation process is performed (step S16). Hereinafter, an example of a specific calculation process will be described.

First, using the required times TR _n1 , TR _n2 and TR _n3 from the first to third rounds, the required time TR _n for one round of the belt therebetween is determined by the following equation (1). . TR _n = (TR _n1 + TR _n2 + TR _n3 ) / 3 (1)

[0028] Here, in a state where a load by the belt cleaner 24 is not applied to the intermediate transfer belt 18 (steady state), although the time required TR _n corresponding to one rotation of the belt is determined by the averaging process, which Besides, for example, the first
Required time TR _n1 , TR _n2 , TR _n3 from the lap to the third lap
And measure only one of them.
It may be adopted as _n . However, even when the load from the belt cleaner 24 is not applied, the required time T for one rotation of the belt from the first rotation to the third rotation.
Since slight variations occur in R _n1 , TR _n2 , and TR _n3 , it is preferable to use the averaged data as TR _n as in the above equation (1).

Here, as shown in FIG. 7, the length (perimeter) of the intermediate transfer belt 18 is L, and the belt traveling distance after the belt cleaner 24 is turned on in the fourth rotation of the belt is Ls. Then, the value of L is determined from the belt design value, and the value of Ls is determined by the O of the belt cleaner 24.
From N timings, it can be given to the control unit 31 as known information in advance.

In such a case, the time from the output of the belt reference signal (4th reference) to the occurrence of a load change due to the cleaner ON in the fourth rotation of the belt is “TR”.
_n (L−L _S ) / L ”. Since the required time for the fourth round of the belt is TM _n (acquired in step S14), the required travel time during the travel distance L _S is“ TM _n -TR
_n (L−L _S ) / L ”. Accordingly, the belt traveling speed at the traveling distance L _S is“ L _S / ΔTM _n −TR ”.
_n (L−L _S ) / L｝ ″.

[0031] Here, if the "V _{re f"} a belt running speed of the criteria set in the control unit 31, the deviation amount from the reference speed due to the load variation, and therefore the speed decrease is, "V _ref -L _{S / {TM n -TR n (L} -L S) /
L｝ ”, and this speed decrease corresponds to ΔV in FIG. 4. Therefore, in order to correct this speed decrease ΔV, an apparent reference belt running speed (V
since it is sufficient to correct the belt running control amount so that the speed decrease in _ref) ([Delta] V) is plus, in the first image forming process V _ref = V _n as a belt running control amount V
_{n + 1 is obtained} by the following equation (2). _{V n + 1 = 2V n -L} S / {TM n -TR n (L-L S) / L} ... (2) By the way, since the first image forming process has a n = 0, this case belt control quantity V _{n + 1} is calculated to become "V _1".

When the first (when n = 0) image forming process is completed in this way, in the next image forming process (when n = 1), the belt is rotated one round by the same processing as in steps S1 to S9. Traveling time T from the first lap to the third lap
R _n1 , TR _n2 , TR _n3 are obtained, and thereafter, step S1
When the cleaner ON signal is output from the cleaner control unit 32 at 0, the process proceeds from step S11 to step S12.

In step S12, the drive conditions of the drive motor 29 are changed based on the belt travel control amount V _n (n = 1) calculated in the preceding image forming process. Specifically, the control signal corresponding to the belt running control amount V _n at that time is given to the motor control unit 30, thereby is accelerated by the ratio rotational speed of the predetermined starting from the cleaner ON timing of the drive motor 29. As a result, the actual belt traveling speed is maintained at the reference level even if a load change due to the cleaner ON occurs.

Thereafter, from step S12 to step S1
Then, it is determined whether the belt reference signal (5th reference) is output from the home sensor 23 as described above. Then, when the belt reference signal is output to get the belt 4 lap drive elapsed time TM _n, stops the timer (step S14, S15). At this time, the travel time required TM _n of 4 lap belt from the first lap belt 3
The required travel time TR _n1 , TR _n2 , TR _n3 up to the lap is a value close to the required time. The reason is that even if there is a load change due to the cleaner ON during the fourth rotation of the belt, as described above, the drive condition of the drive motor 29 is changed in step S12 so that the actual belt traveling speed becomes the specified level. Because it is.

Subsequently, in the calculation processing of step S16,
The belt traveling control is performed according to the above-described equations (1) to (6).
Quantity V_{n + 1}(N = 1) is obtained. However, this image formation
In the process, the belt travel control determined in the previous image forming process
Quantity V₁Becomes the reference level, and the belt runs at n = 1
Control amount V_{n + 1}That is, V _TwoWill be newly calculated
You. From this, for example, the traveling time required for the fourth lap of the belt
TM_nAnd the average travel time TR from the first lap to the third lap_n
If there is a slight difference between
Adopted in the next image formation (when n = 2)
Belt travel control amount V_nWill be slightly modified
You.

As described above, in the image forming apparatus of this embodiment, the mark 18 formed on the intermediate transfer belt 18
a is detected by the home sensor 23, a belt travel control amount is calculated based on the detection result, and the cleaner is turned on.
When the load fluctuation occurs due to the above, the driving condition of the driving motor 29 is changed based on the above-described belt control amount at the load application timing, and the running speed of the intermediate transfer belt 18 is controlled to the reference level. Image shift (color shift) due to load fluctuation can be effectively prevented without employing an expensive encoding roll system as in the related art. Further, if the running speed of the intermediate transfer belt 18 decreases due to a load change due to the cleaner ON, a delay occurs in the arrival timing of the image on the secondary transfer roll 25, so that the image transfer position on the paper is shifted from a predetermined position. However, as in the present embodiment, the drive motor 29
By changing the driving conditions described above, it is possible to prevent displacement of the entire image at the secondary transfer position.

Further, since the traveling speed information of the intermediate transfer belt 18 is obtained using the detection signal of the home sensor 23 which is an essential component in the existing image forming apparatus,
There is no need to incorporate a dedicated mechanical mechanism as a belt traveling speed detection system. In addition to this change, the belt control amount V _n employed in cleaner ON timing. Thus finely corrected in the repetition of the image formation processing, for example by an intermediate transfer size of the belt 18, such as a greenhouse of the environment even when changes or aging to case of, with a constantly correct belt control quantity V _n can change the driving condition of the drive motor 29.

In the first image forming process (when n = 0), the driving conditions of the driving motor 29 are not changed at the cleaner ON timing. Image shift will occur. Therefore, it is preferable that the first image forming process is performed at the time of warm-up when the apparatus power is turned on.

When the drive conditions of the drive motor 29 are changed at the cleaner ON timing (load application timing), as shown in FIG. 8, the belt travel control amount in the control unit 31 is corrected from the reference level _Vref by a correction value. changing a time to V _n is, disturbance of locally image by overshoot when the speed change is also a concern to occur. In order to solve such a concern, it is effective as a control mode of the control unit 31 to change the driving condition of the driving motor 29 so that the traveling speed of the intermediate transfer belt 18 gradually changes starting from the load application timing. Means.

Specifically, for example, as shown in FIG.
Change of belt running speed is started at load application timing.
Time from end to T_PAnd this T_Ptime
, The increase in the travel control amount of the intermediate transfer belt 18 (V
_n-V_ref) Is divided into m times (m = 4 in the figure)
Put on. This gives T_PDuring the time, the intermediate transfer
The travel control amount of the default 18 is 1 / mT _PAt the time pitch of 1 /
m (V_n-V_ref)
The belt running speed is set at T from the load application timing._PTime
It gradually (gradually) increases in between. The result
As a result, the occurrence of overshoot due to speed changes is prevented.
It becomes possible.

However, when such a control mode is adopted, the travel control amount of the intermediate transfer belt 18 is set to the target value (V _n ).
In this case, the actual belt running speed is lower than the specified speed until the image speed reaches the predetermined speed, so that a positional shift of the image due to the speed delay remains. As the countermeasure, between times T _P to the end of the similarly by changing the belt running speed by the load application timing is started, the increase in the running control amount of the intermediate transfer belt 18 (V _n -V _ref ) Is added a plurality of times to m, and after the travel control amount reaches the target speed (V _n ), in order to complement the speed delay up to that time, for example, as shown in FIG. after plus the speed control amount by the time pitch of _P by _{1 / m (V n -V ref} ), 1 time the pitch of _{1 / mT P / m (V} n -V
_ref ), the speed control amount is decreased by 1 to return to the target value. That is, within the time of T _P + T _P , the speed delay in the first half of the T _P time is offset by the surplus of the control amount in the second half of the T _P time. As a result, T _P + T _P
After the time, it is possible to form an image at a regular position without causing a shift in the image forming position due to the speed delay.

In the above embodiment, one mark 18a is formed on the intermediate transfer belt 18, and the belt travel control amount is calculated from the detection timing of the mark 18a by the home sensor 23. Such an image forming apparatus is not limited to this.

For example, as shown in FIG. 11, a large number of marks 18a, 18a,.
And the marks 18a, 18a,
.. May be detected by the home sensor 23 to calculate the belt travel control amount. In this case, when the intermediate transfer belt 18 travels, a short time from when an arbitrary mark 18a is detected by the home sensor 23 to when an adjacent mark 18a is detected by the home sensor 23 is, for example, a high-speed clock. The belt running speed information is obtained by performing the measurement one after another by using the above-described method. The marks 18a, 18 on the intermediate transfer belt 18
a,... may be formed in advance at the belt manufacturing stage, or may be formed by transferring a toner image without a change in load. As a result, the speed decrease at the time of load change can be obtained in the same manner as in the above-described embodiment. Therefore, at the cleaner ON timing, the drive condition of the drive motor 29 is changed by adding the speed decrease to the load change. Of the image can be prevented from being misaligned.

In addition to the above, for example, a cleaner ON
The measurement time between each mark obtained before the load change due to the cleaner is averaged and set as a reference value, and the difference between the measurement time between the marks obtained from the time when the load change due to the cleaner ON occurs and the above reference value is calculated. The running speed of the intermediate transfer belt 18 can also be controlled to a specified level by changing the driving conditions of the driving motor 29 in real time by known feedback control (for example, proportional integral differentiation (PID) control).

In the above-described embodiment, image formation is performed in which toner images of each color are transferred from the photosensitive drum 14 to the intermediate transfer belt 18 and the resulting color toner images are transferred from the intermediate transfer belt 18 to paper. Although an example of application to the apparatus has been described, the present invention is not limited to this, and for example, an image forming apparatus including a sheet conveyance belt for conveying a sheet to an image transfer position by a photosensitive drum as an image carrier belt, The present invention can be similarly applied to a so-called tandem type image forming apparatus having a body drum and an image writing unit.

[0046]

As described above, according to the image forming apparatus of the present invention, the mark formed on the image carrier belt is detected by the sensor, and the traveling speed information of the image carrier belt is obtained from the detection timing. Since the configuration is adopted in which the driving conditions of the belt driving unit are obtained by the control unit, the belt traveling speed during image formation can be accurately controlled without employing an expensive encoding roll system as in the related art. Can be. As a result, it is possible to prevent a color shift of an image due to a load change and obtain a high-quality color image without increasing the size and cost of the apparatus.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a configuration example of an image reading apparatus to which the present invention is applied.

FIG. 2 is a perspective view of an intermediate transfer belt.

FIG. 3 is a functional block diagram illustrating a control configuration of the image forming apparatus according to the embodiment.

FIG. 4 is a diagram illustrating a relationship between a belt traveling speed and an image transfer position.

FIG. 5 is a flowchart showing a processing procedure by a control unit.

FIG. 6 is a diagram illustrating a relationship between a required time for one rotation of a belt and an image area of a toner image of each color.

FIG. 7 is a diagram for explaining an arithmetic processing form of a belt travel control amount.

FIG. 8 is a diagram illustrating a first modification of driving conditions.

FIG. 9 is a diagram illustrating a second modification of the driving conditions.

FIG. 10 is a diagram showing a third modification of the driving conditions.

FIG. 11 is a diagram illustrating another mark detection method.

[Explanation of symbols]

Reference numeral 18: intermediate transfer belt (image carrier belt), 18a: mark, 20: drive roll, 23: home sensor, 24:
Belt cleaner 29 drive motor 31 control unit (control means) 32 cleaner control unit

Continued on the front page (72) Inventor Tsutomu Udaka 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Works

Claims (4)

[Claims] 1. An image forming apparatus comprising: an endless image carrier belt; and belt driving means for running the image carrier belt, wherein: a sensor for detecting a mark formed on the image carrier belt; The traveling speed information of the image carrier belt is acquired from the detection timing of the mark by the sensor, the belt traveling control amount is calculated based on the traveling speed information, and the driving of the belt driving unit is performed based on the calculation result. An image forming apparatus, comprising: control means for controlling conditions. 2. The image forming apparatus according to claim 2, wherein when a load is applied to the image carrier belt at a predetermined timing, the control unit changes a driving condition of the belt driving unit at the load application timing. 2. The image forming apparatus according to 1. 3. The control unit changes drive conditions of the belt driving unit such that a running speed of the image carrier belt gradually changes at a timing when a load is applied to the image carrier belt. The image forming apparatus according to claim 2, wherein: 4. The apparatus according to claim 1, wherein the control unit changes a driving condition of the belt driving unit so as to complement a speed delay until the traveling speed of the image carrier belt reaches a predetermined belt traveling speed. The image forming apparatus according to claim 3.