JP2018036452A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing the positional deviation of an image formed on a recording medium, even when the image is intermittently formed.SOLUTION: An image forming apparatus 1 includes an image forming part 3, a detection part 10, and a control part 8. The image forming part 3 includes an intermediate transfer belt 41 and a driving roller 41a. The detection part 10 includes a first detection part 11 and a second detection part 12. The first detection part 11 outputs a first signal indicating the temperature of the vicinity of the driving roller 41a. The second detection part 12 outputs a second signal indicating the temperature of an environment where the image forming apparatus 1 is installed. The control part 8 determines whether or not the operation of the driving roller 41a is an intermittent operation in a predetermined time on the basis of the first signal. When the operation of the driving roller 41a is the intermittent operation, the control part 8 adjusts the rotational speed of the driving roller 41a, so that the rotational speed of the intermediate transfer belt 41 becomes constant according to the first signal and the second signal.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus.

  The image forming apparatus described in Patent Literature 1 includes an image forming unit, a fixing unit, and a detection unit. The image forming unit forms a toner image on the recording medium. The image forming unit includes a transfer belt, a driving roller, and a driven roller. The transfer belt is stretched between the driving roller and the driven roller. The transfer belt is rotated by the rotation of the drive roller. The fixing unit fixes the toner image on the recording medium. The fixing unit includes a heating roller and a pressure roller. The heating roller melts the toner of the toner image. The heating roller has a heat source. A detection part detects the temperature of the vicinity of a drive roller. In the case of a contact type that contacts the driving roller, the detection unit deteriorates with time due to sliding with the driving roller.

  For example, the driving roller of the image forming unit expands by heat generated by a heat source. The rotation speed of the transfer belt increases due to the expansion of the driving roller. As a result, the toner image transferred to the recording medium is displaced. In the image forming apparatus described in Patent Document 1, the rotation speed of the drive roller is adjusted based on the temperature in the vicinity of the drive roller detected by the detection unit so that the rotation speed of the transfer belt is constant.

Japanese Patent Laid-Open No. 2005-91948

  However, in the image forming apparatus described in Patent Document 1, the temperature in the vicinity of the drive roller is set as the temperature of the drive roller. The drive roller contacts the transfer belt. For this reason, the temperature of the driving roller changes due to heat exchange with the transfer belt. In the transfer belt, the temperature of the portion near the heat source is maintained high by the heat source within a predetermined time after the image is formed, and the temperature of the portion far from the heat source is decreased by the outside air. Therefore, when the image is intermittently formed, the temperature of the driving roller decreases as the transfer belt rotates. As a result, the temperature detected by the detection unit is different from the temperature of the drive roller. The detection unit detects the temperature of air raised by the heat source when the image is intermittently formed. That is, it is difficult to adjust the rotation speed of the driving roller based on the temperature in the vicinity of the driving roller so that the rotation speed of the transfer belt is constant. When an image is formed intermittently, the image formed on the recording medium may be displaced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of preventing the displacement of an image formed on a recording medium even when an image is intermittently formed. There is.

  An image forming apparatus according to the present invention includes an image forming unit, a detection unit, and a control unit. The image forming unit forms an image on a recording medium. The detection unit detects a temperature. The control unit controls the image forming unit. The image forming unit includes a transfer belt and a driving roller. The transfer belt transfers the image to the recording medium. The drive roller drives the transfer belt. The detection unit includes a first detection unit and a second detection unit. The first detection unit outputs a first signal indicating a temperature in the vicinity of the driving roller. The second detection unit outputs a second signal indicating a temperature of an environment where the image forming apparatus is installed. The controller determines whether the operation of the drive roller is an intermittent operation within a predetermined time based on the first signal. When the operation of the driving roller is the intermittent operation, the control unit is configured so that the rotation speed of the transfer belt is constant according to the first signal and the second signal. Adjust the rotation speed of the drive roller.

  According to the image forming apparatus of the present invention, it is possible to prevent the positional deviation of the image formed on the recording medium even when the image is intermittently formed.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the image formation part of FIG. It is a graph which shows the relationship between the temperature of a drive roller, and elapsed time. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus in FIG. 1. It is a flowchart which shows the correction control by the control part of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 1 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment is a multifunction machine. The image forming apparatus 1 may be a copy, a printer, or a facsimile. The multi-function peripheral has, for example, at least two functions among a copy function, a printer function, and a facsimile function. Further, the image forming apparatus 1 of the present embodiment is a tandem method capable of forming a color image.

  The image forming apparatus 1 includes a storage unit 2, an image forming unit 3, a fixing unit 5, a discharge tray 6, a control unit 8, a storage unit 9, and a detection unit 10.

  The storage unit 2 includes a paper feed cassette 21. The paper feed cassette 21 is detachable from the lower part of the image forming apparatus 1. The paper feed cassette 21 can store a plurality of sheets S. Note that the storage unit 2 of the present embodiment further includes a manual feed tray. A plurality of sheets S can be placed on the manual feed tray.

  In FIG. 1, the side in which the paper feed cassette 21 is detached from the image forming apparatus 1 is defined as the front side, and the front-rear direction is defined. Further, the left-hand side is defined as the left side toward the front of the image forming apparatus 1, and the left-right direction is defined. Further, the front-rear direction and the direction orthogonal to the left-right direction are defined as the up-down direction.

  The paper S is an example of the recording medium of the present invention. The paper S is, for example, plain paper, copy paper, recycled paper, thin paper, thick paper, glossy paper, or OHP (Overhead Projector) paper. The paper S is transported from the storage unit 2 to the discharge tray 6 along the paper transport path L.

  The control unit 8 controls the image forming unit 3 and the fixing unit 5. The control unit 8 is constituted by, for example, a CPU (Central Processing Unit).

  The storage unit 9 includes a semiconductor memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM stores, for example, various computer programs executed by the control unit 8. The RAM stores, for example, image data of an image formed on the paper S.

  The image forming unit 3 is disposed on the downstream side of the storage unit 2 in the paper transport path L. The image forming unit 3 forms a toner image on the paper S. The image forming unit 3 includes image forming units 30y, 30c, 30m, and 30k, and a transfer unit 4.

  The transfer unit 4 includes an intermediate transfer belt 41, a driving roller 41a, a driven roller 41b, and a secondary transfer roller 42. The intermediate transfer belt 41 is endless. The intermediate transfer belt 41 is stretched between the driving roller 41a and the driven roller 41b. The intermediate transfer belt 41 is rotated by a driving roller 41a.

  Each of the image forming units 30y, 30c, 30m, and 30k corresponds to any one of yellow, cyan, magenta, and black toner colors. Next, the image forming unit 30y corresponding to the yellow toner color will be described. The image forming units 30c, 30m, and 30k corresponding to the cyan, magenta, and black toner colors are configured in the same manner as the image forming unit 30y that corresponds to the yellow toner color, and thus description thereof is omitted here. .

  The image forming unit 30y includes a photosensitive drum 31y, a charging unit 32y, an exposure unit 33y, a developing unit 34y, a toner supply unit 35y, and a primary transfer roller 36y. The photosensitive drum 31y has a photosensitive layer. The photosensitive layer is formed on the surface of the photosensitive drum 31y.

  The charging unit 32y charges the surface of the photosensitive drum 31y to a predetermined potential. The exposure unit 33y irradiates the surface of the charged photosensitive drum 31y with laser light to form an electrostatic latent image. The electrostatic latent image is formed based on the image data. The toner supply unit 35y supplies toner to the developing unit 34y. The developing unit 34y develops the electrostatic latent image formed on the surface of the photosensitive drum 31y as a toner image.

  The primary transfer roller 36y transfers the toner image on the surface of the photosensitive drum 31y to the surface of the intermediate transfer belt 41. The primary transfer roller 36 y presses the photosensitive drum 31 y via the intermediate transfer belt 41. A primary transfer voltage is applied to the surface of the primary transfer roller 36y. Therefore, when the toner image on the photosensitive drum 31y is pressed against the intermediate transfer belt 41, the toner image is transferred to the intermediate transfer belt 41 by the electrostatic attraction of the primary transfer roller 36y.

  The image forming units 30y, 30c, 30m, and 30k superimpose the toner images of the respective colors on the surface of the intermediate transfer belt 41. As a result, a color toner image is formed on the surface of the intermediate transfer belt 41. The color toner image is conveyed to the secondary transfer roller 42 by the rotation of the intermediate transfer belt 41.

  The secondary transfer roller 42 transfers the color toner image of the intermediate transfer belt 41 to the paper S. The secondary transfer roller 42 presses the drive roller 41 a via the intermediate transfer belt 41. The secondary transfer roller 42 forms a secondary transfer nip with the driving roller 41 a via the intermediate transfer belt 41. A secondary transfer voltage is applied to the secondary transfer roller 42. Therefore, the color toner image is transferred to the sheet S by matching the timing when the color toner image on the intermediate transfer belt 41 passes through the secondary transfer nip and the timing when the sheet S passes through the secondary transfer nip. The

  The fixing unit 5 fixes the toner image transferred to the paper S. The fixing unit 5 includes a fixing roller 51 and a pressure roller 52. The fixing roller 51 includes a heat source 51 a that heats the paper S. The fixing roller 51 and the pressure roller 52 are in pressure contact with each other. When the sheet S on which the toner image is transferred passes between the fixing roller 51 and the pressure roller 52, the toner image is fixed on the sheet S by heating by the fixing roller 51. The sheet S on which the toner image is fixed is discharged to the discharge tray 6 along the sheet conveyance path L.

  The detection unit 10 includes a first detection unit 11, a second detection unit 12, and a third detection unit 13. The first detection unit 11, the second detection unit 12, and the third detection unit 13 can detect the temperature of the object to be detected. In the present embodiment, the object to be detected is air. The 1st detection part 11, the 2nd detection part 12, and the 3rd detection part 13 are thermistors whose resistance changes with respect to the change of temperature, for example. The thermistor is cheaper than, for example, a non-contact type temperature sensor, and the manufacturing cost of the image forming apparatus 1 can be reduced. The non-contact type temperature sensor is, for example, thermography capable of detecting the temperature of an object to be detected at a remote position.

  The first detection unit 11 is disposed in the vicinity of the drive roller 41 a of the transfer unit 4. The first detection unit 11 detects the temperature in the vicinity of the drive roller 41a. The first detection unit 11 of the present embodiment is disposed inside the rotation path of the intermediate transfer belt 41. The first detection unit 11 outputs a first signal indicating the temperature near the drive roller 41 a to the control unit 8. In addition, the 1st detection part 11 does not contact the drive roller 41a. Therefore, the first detection unit 11 is prevented from deterioration over time such as wear due to sliding with the drive roller 41a, as compared with the contact type detection unit.

  The second detection unit 12 is disposed at a position that is not easily affected by the heat generated by the image forming apparatus 1. The second detection unit 12 of this embodiment is arranged in the storage unit 2. Specifically, the second detection unit 12 is disposed on the rear side of the paper feed cassette 21 and on the lower side of the paper transport path L. The second detection unit 12 detects the temperature of the outside air that indicates the temperature of the environment in which the image forming apparatus 1 is installed. The second detection unit 12 outputs a second signal indicating the temperature of the outside air to the control unit 8.

  The third detection unit 13 is disposed in the vicinity of the heat source 51 a of the fixing unit 5. Specifically, the third detection unit 13 is disposed on the front side of the fixing roller 51 having the heat source 51a. The third detector 13 detects the temperature of the heat generated by the heat source 51a. The third detection unit 13 outputs a third signal indicating the temperature of heat generated by the heat source 51 a to the control unit 8.

  With reference to FIG. 2 and FIG. 3, the mechanism by which the rotational speed of the intermediate transfer belt 41 decreases when an image is intermittently formed will be described. Here, the case where the image is intermittently formed is a case where the image is formed again after a predetermined time elapses after the image is formed. The predetermined time is, for example, a time until the temperature of the intermediate transfer belt 41 becomes substantially uniform. The case where the image is intermittently formed specifically refers to a case where the image formation is resumed within a predetermined time after the image formation is interrupted by JAM processing or the like.

  FIG. 2 is a diagram illustrating the image forming unit 3. The image forming unit 3 in FIG. 2 omits the exposure units 33y, 33c, 33m, and 33k and the toner supply units 35y, 35c, 35m, and 35k shown in FIG. In FIG. 2, the rotation direction D of the intermediate transfer belt 41, the rotation direction Da of the drive roller 41a, the rotation direction Db of the driven roller 41b, and the rotation direction Dc of the secondary transfer roller 42 are shown.

  The intermediate transfer belt 41 is rotated in the rotation direction D by the drive roller 41a when an image is formed on the paper S. The intermediate transfer belt 41 contacts the outer surface of the drive roller 41a. Therefore, the rotation speed of the intermediate transfer belt 41 is proportional to the rotation speed of the drive roller 41a and the outer diameter of the drive roller 41a. As a result, the rotational speed of the intermediate transfer belt 41 also changes as the outer diameter of the drive roller 41a changes.

  When the rotational speed of the intermediate transfer belt 41 changes, the toner image transferred to the paper S is displaced. Specifically, when the rotation speed changes, the intermediate transfer belt 41 causes the toner image forming surface to reach the image forming units 30y, 30c, 30m, and 30k at a timing different from a predetermined timing. As a result, the color of the image formed on the paper S is shifted. In addition, the intermediate transfer belt 41 causes the toner image to reach the secondary transfer roller 42 at a timing different from a predetermined timing when the rotation speed changes. Therefore, the image formed on the paper S is displaced. For example, when the rotation speed of the intermediate transfer belt 41 decreases, the toner image is displaced to the rear end side of the paper S. Conversely, when the rotational speed of the intermediate transfer belt 41 increases, the toner image is displaced to the front end side of the paper S.

  The drive roller 41a expands due to heat. Therefore, the outer diameter of the driving roller 41a changes according to the temperature of the driving roller 41a. For example, during the initial operation of the image forming apparatus 1, the temperature of the driving roller 41 a sequentially increases due to the heat generated by the heat source 51 a of the fixing unit 5 described with reference to FIG. 1.

  FIG. 3 is a graph showing the relationship between the temperature T of the drive roller 41a and the elapsed time t when images are intermittently formed. In FIG. 3, the vertical axis indicates the temperature T of the drive roller 41a, and the horizontal axis indicates the elapsed time t. When the images are continuously formed, the temperature of the drive roller 41a is increased by the heat source 51a at the elapsed time t1. Therefore, the rotation speed of the intermediate transfer belt 41 increases at the elapsed time t1. Further, the temperature of the driving roller 41a is decreased by the outside air at the elapsed time t2 after the images are continuously formed.

  The temperature of the driving roller 41a is lowered by the intermediate transfer belt 41 at the elapsed time t3 when an image is intermittently formed. Specifically, the temperature of the intermediate transfer belt 41 is lowered by the outside air after the images are continuously formed. In the intermediate transfer belt 41, the temperature on the side far from the heat source 51a decreases more quickly. The drive roller 41 a contacts the low temperature portion of the intermediate transfer belt 41 by the rotation of the intermediate transfer belt 41 when the image is intermittently formed. Therefore, the temperature of the driving roller 41 a is lowered by heat exchange with the intermediate transfer belt 41. Therefore, the rotational speed of the intermediate transfer belt 41 decreases at the elapsed time t3 when images are formed intermittently.

  Further, after the temperature of the driving roller 41a is lowered by the intermediate transfer belt 41, the temperature is raised by the heat generated by the heat source 51a at the elapsed time t4. Therefore, the rotation speed of the intermediate transfer belt 41 increases at the elapsed time t4. Note that when the image is intermittently formed, the driving roller 41a decreases in temperature at the elapsed time t3 not by heat exchange via air by outside air but by heat exchange by contact with the intermediate transfer belt 41. Therefore, the speed at which the temperature of the drive roller 41a decreases at the elapsed time t3 is faster than the speed at which the temperature of the drive roller 41a decreases at the elapsed time t2. Further, at the elapsed time t3, the heat generated by the heat source 51a increases, whereas the temperature of the drive roller 41a decreases. Therefore, it is difficult to detect the temperature of the drive roller 41a by the first detection unit 11 as in the past at the elapsed time t3.

  The configuration of the control unit 8 will be described with reference to FIG. FIG. 4 is a block diagram illustrating a configuration of the image forming apparatus 1. The control unit 8 functions as a determination unit 81, an adjustment unit 82, and an extraction unit 83 by executing a computer program stored in advance in the storage unit 9.

  The storage unit 9 further stores a plurality of correction values. The correction value is selected by the control unit 8 when adjusting the rotation speed of the drive roller 41a. The correction value is set in advance based on the change in the temperature of the intermediate transfer belt 41 and the temperature of the driving roller 41a over time after the image is formed. Specifically, the correction value is set by detecting a change in the rotational speed of the intermediate transfer belt 41 by, for example, experiments. In the experiment, for example, the time until the next image is formed after the image is formed and the temperature of the environment in which the image forming apparatus 1 is installed are appropriately changed.

  The determination unit 81 determines whether the operation of the drive roller 41a is an intermittent operation based on the first signal input from the first detection unit 11 when an image is formed on the paper S. Specifically, the determination unit 81 of the present embodiment compares the first signal with a threshold when an operation signal for forming an image is input, and drives when the temperature indicated by the first signal is equal to or higher than the threshold. It is determined that the operation of the roller 41a is an intermittent operation. On the other hand, the determination unit 81 determines that the operation of the drive roller 41a is not an intermittent operation when the temperature indicated by the first signal is less than the threshold value.

  Further, when the determination unit 81 determines that the operation of the driving roller 41a is an intermittent operation, refer to FIG. 3 based on the first signal and the third signal input from the third detection unit 13. The length of the elapsed time t3 described above is determined. The determination unit 81 determines the length of the elapsed time t3 with reference to a table indicating the relationship between the temperature in the vicinity of the drive roller 41a and the temperature in the vicinity of the heat source 51a that is stored in advance in the storage unit 9.

  The extraction unit 83 selects a correction value from the storage unit 9 based on the second signal input from the second detection unit 12 when the determination unit 81 determines that the operation is intermittent. Specifically, the extraction unit 83 of the present embodiment calculates a change in the temperature of the intermediate transfer belt 41 based on the temperature indicated by the second signal and the temperature indicated by the third signal input from the third detection unit 13. . The extraction unit 83 selects a correction value from the storage unit 9 based on the elapsed time calculated by the determination unit 81 and the temperature change of the intermediate transfer belt 41.

  The adjustment unit 82 adjusts the rotation speed of the drive roller 41a based on the correction value selected by the extraction unit 83. Based on the correction value, the adjustment unit 82 adjusts the rotational speed of the drive roller 41a so that the rotational speed of the intermediate transfer belt 41 is constant. Further, the adjustment unit 82 adjusts the rotation speed of the drive roller 41a based on the first signal so that the rotation speed of the intermediate transfer belt 41 becomes constant after the elapsed time t3 has elapsed.

  The adjustment unit 82 determines that the rotation speed of the intermediate transfer belt 41 is constant based on the first signal input from the first detection unit 11 when the determination unit 81 determines that the operation is not intermittent. Thus, the rotational speed of the drive roller 41a is adjusted.

  As described with reference to FIGS. 1 to 4, according to the image forming apparatus 1 of the present embodiment, the temperature in the vicinity of the driving roller 41 a and the outside air temperature even when an image is intermittently formed. And the rotational speed of the drive roller 41a is adjusted based on the temperature in the vicinity of the heat source 51a. As a result, even when an image is intermittently formed, the rotational speed of the drive roller 41a can be adjusted so that the rotational speed of the intermediate transfer belt 41 is constant.

  With reference to FIG. 5, the correction control of the control unit 8 according to the present embodiment will be described. FIG. 5 is a flowchart showing the correction control of the control unit 8.

  As shown in FIG. 5, in step S10, an operation signal indicating the start of image formation is input. The operation signal is input through a communication network, for example. When an operation signal is input in step S10, the determination unit 81 compares the temperature indicated by the first signal with a threshold value in step S20.

  In step S20, when the temperature indicated by the first signal is equal to or higher than the threshold value (Yes in step S20), the determination unit 81 determines the length of the elapsed time t3 in step S30. When the length of the elapsed time t3 is determined in step S30, the extraction unit 83 calculates a change in the temperature of the intermediate transfer belt 41 in step S40. When the temperature change of the intermediate transfer belt 41 is calculated in step S40, the extraction unit 83 selects a correction value from the storage unit 9 in step S50. When a correction value is selected in step S50, in step S60, the adjustment unit 82 adjusts the rotation speed of the drive roller 41a based on the correction value. When the rotation speed of the drive roller 41a is adjusted in step S60, the adjustment unit 82 determines whether or not the elapsed time t3 has elapsed in step S70. When it is determined in step S70 that the elapsed time t3 has passed (Yes in step S70), in step S80, the control unit 8 causes the adjustment unit 82 to adjust the driving roller 41a based on the temperature indicated by the first signal. The rotation speed is adjusted and the correction control is finished.

  In step S20, when the temperature indicated by the first signal is less than the threshold (No in step S20), in step S80, the adjusting unit 82 adjusts the rotation speed of the drive roller 41a based on the temperature indicated by the first signal. Then, the correction control is finished. If it is determined in step S70 that the elapsed time t3 has not elapsed (No in step S70), the process returns to step S60, and the adjustment unit 82 adjusts the rotation speed of the drive roller 41a based on the correction value. .

  The image forming apparatus 1 according to the embodiment of the present invention has been described above with reference to FIGS. However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof.

  For example, in the embodiment of the present invention, the temperature near the heat source 51a is detected by the third detection unit 13 and the third signal is output to the control unit 8, but the present invention is not limited to this. As the temperature near the heat source 51a indicated by the third signal, a temperature stored in advance in the storage unit 9 may be used. As a result, the third detector 13 that detects the temperature in the vicinity of the heat source 51a can be reduced, and the cost of the image forming apparatus 1 can be reduced.

  In order to facilitate understanding, the drawings schematically show each component mainly, and the thickness, length, etc. of each component shown in the drawings are different from the actual for convenience of drawing. . In addition, the material, shape, dimensions, and the like of each component shown in the above embodiment are merely examples, and are not particularly limited, and various changes can be made without departing from the effects of the present invention. is there.

  The present invention relates to an image forming apparatus, and is useful for an image forming apparatus that transfers an image onto a recording medium using an intermediate transfer belt.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image forming part 8 Control part 10 Detection part 11 First detection part 12 Second detection part 41 Intermediate transfer belt 41a Drive roller S Paper

Claims (4)

An image forming unit for forming an image on a recording medium;
A detection unit for detecting the temperature;
An image forming apparatus comprising: a control unit that controls the image forming unit;
The image forming unit includes a transfer belt that transfers the image to the recording medium, and a driving roller that drives the transfer belt,
The detection unit outputs a first signal indicating a temperature in the vicinity of the drive roller, and a second detection unit outputs a second signal indicating the temperature of the environment in which the image forming apparatus is installed. Have
The control unit determines whether the operation of the driving roller is an intermittent operation within a predetermined time based on the first signal,
When the operation of the driving roller is the intermittent operation, the control unit is configured so that the rotation speed of the transfer belt is constant according to the first signal and the second signal. An image forming apparatus that adjusts the rotational speed of a driving roller. A storage unit for storing a plurality of correction values;
The control unit selects the correction value according to the first signal and the second signal,
The image forming apparatus according to claim 1, wherein the control unit adjusts a rotation speed of the drive roller based on the selected correction value. A fixing unit for fixing the image on the recording medium;
The fixing unit has a heat source,
The detection unit further includes a third detection unit that outputs a third signal indicating a temperature of heat generated by the heat source,
The control unit determines an operation of the driving roller based on the first signal and the third signal,
The image forming apparatus according to claim 1, wherein the control unit adjusts a rotation speed of the driving roller in accordance with the first signal, the second signal, and the third signal.   The said control part adjusts the rotational speed of the said driving roller according to a said 1st signal, when the operation | movement of the said driving roller is not the said intermittent operation | movement. The image forming apparatus described in the item.

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