JP2009048088A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress vibration caused in a carrying member in addition to deposition of contamination on an image carrier. <P>SOLUTION: The image forming apparatus includes four photoreceptor drums 52 and an intermediate transfer belt 15 disposed in contact with each photoreceptor drum 52. Each photoreceptor drum 52 and the intermediate transfer belt 14 are rotated at a drum circumferential velocity VD and at a belt circumferential velocity VB slightly higher than the drum circumferential velocity VD, respectively. The belt load torque required for driving of the intermediate transfer belt 14 is measured while changing the circumferential velocity difference between the drum circumferential velocity VD and the belt circumferential velocity VB at a time when no image forming operation is performed, and a predetermined circumferential velocity difference to be actually used in image forming operation is determined from a range in which the belt load torque is increased in response to an increase in circumferential velocity difference. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a recording medium.

  As an image forming apparatus such as a printer or a copying machine, for example, an image formed on an image carrier such as a photosensitive drum is sequentially primary-transferred onto a conveying member such as an intermediate transfer belt, and then primary-transferred onto the conveying member. 2. Description of the Related Art An image is secondarily transferred to a recording medium such as paper. Here, Patent Document 1 discloses a technique of driving while making a difference in peripheral speed between the image carrier and the conveying member in order to remove foreign matters such as discharge products attached to the image carrier. .

JP 2004-93864 A

By the way, from the viewpoint of removing foreign matter on the image holding member, it is preferable to set a large peripheral speed difference between the image holding member and the conveying member in the image forming apparatus. On the other hand, if the difference in the peripheral speed between the image holding member and the conveying member is excessively large, the conveying member is vibrated, and an image transferred from the image holding member to the conveying member is striped. There was a thing.
An object of the present invention is to suppress adhesion of foreign matter to an image carrier and to suppress vibration generated in a conveying member.

  According to the first aspect of the present invention, an image holding body that holds an image, and an image transferred from the image holding body or a recording material on which the image is transferred from the image holding body are conveyed in contact with the image holding body. A conveying member that drives the image holding member and the conveying member with a predetermined peripheral speed difference, and the image holding member as the peripheral speed difference between the image holding member and the conveying member increases. Alternatively, the image forming apparatus includes a setting unit that sets the predetermined peripheral speed difference within a range in which a load torque required for driving the conveyance member increases.

  According to a second aspect of the present invention, the setting means drives the image holding body and the conveying member at a plurality of peripheral speed differences by the driving means, and the image holding body or the conveying member at a plurality of the peripheral speed differences. 2. The image forming apparatus according to claim 1, wherein the load torque is measured, and the range is determined based on a relationship between a plurality of the peripheral speed differences and the plurality of measured load torques. is there.

According to a third aspect of the present invention, an image holding body that holds an image, and an image transferred from the image holding body or a recording material on which the image is transferred from the image holding body are conveyed in contact with the image holding body. The conveying member, the driving means for driving the image holding member and the conveying member with a predetermined peripheral speed difference, and the difference in the peripheral speed difference between the image holding member and the conveying member. An image forming apparatus comprising: a measuring unit that measures a load torque applied to the image carrier or the conveying member; and a determining unit that determines the predetermined peripheral speed difference based on the load torque measured by the measuring unit. is there.
According to a fourth aspect of the present invention, the measurement means replaces the load torque with a drive current value supplied to a drive motor of the image holding body or the conveying member, or rotation of the image holding body or the conveying member. The image forming apparatus according to claim 3, wherein the period is measured.

According to the first aspect of the present invention, compared to the case where the predetermined peripheral speed difference is determined without using the relationship between the peripheral speed difference and the load torque, the adhesion of foreign matter to the image carrier is suppressed. It is possible to further suppress vibration generated in the transport member.
According to the second aspect of the present invention, it is possible to easily grasp the range in which the load torque increases as the peripheral speed difference increases as compared with the case where the present configuration is not provided.
According to the third aspect of the present invention, compared to the case where the predetermined peripheral speed difference is determined without using the relationship between the peripheral speed difference and the load torque, the adhesion of foreign matter to the image carrier is suppressed. It is possible to further suppress vibration generated in the transport member.
According to the fourth aspect of the present invention, the configuration of the measuring means can be simplified as compared with the case of directly measuring the load torque.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
<Embodiment 1>
FIG. 1 shows the overall configuration of an image forming apparatus 10 to which the exemplary embodiment is applied. The image forming apparatus 10 includes a main body 12, and a belt unit 15 including an intermediate transfer belt 14 and, for example, four image forming units 16Y, 16M, 16C, and 16K are provided in the main body 12. . In the present embodiment, the plurality of image forming units 16Y, 16M, 16C, and 16K are arranged obliquely from the upper right direction to the lower left direction in the drawing. The image forming unit 16Y forms a yellow toner image, the image forming unit 16M forms a magenta toner image, the image forming unit 16C forms a cyan toner image, and the image forming unit 16K forms a black toner image. Each color toner image is transferred to the intermediate transfer belt 14.

  A sheet feeding device 18 is provided at the lower part of the main body 12. The sheet supply device 18 includes, for example, a sheet stacking unit 20 on which sheets made of plain paper, OHP sheets, and the like are stacked, a take-out roll 22 that takes out the sheets stacked on the sheet stacking unit 20, and a feed roll 24 that sends out the sheets while rolling them. And a retard roll 26. The sheet stacking unit 20 is detachably provided on the main body 12 so that the sheet stacking unit 20 can be pulled out to the front side in the figure, for example.

  Near one end of the main body 12 (near the left end in the figure), a sheet supply path 28 is provided along a substantially vertical direction. Around the sheet supply path 28, a transport roll 29, a resist roll 30, a secondary transfer roll 32, a fixing device 34 and a discharge roll 36 are provided along the sheet supply path 28. The registration roll 30 temporarily stops the sheet sent to the sheet supply path 28 and sends it to the secondary transfer roll 32 side at a timing. The fixing device 34 includes a heating roll 34a and a pressure roll 34b. The toner image is fixed to the sheet by applying heat and pressure to the sheet passing between the heating roll 34a and the pressure roll 34b. .

  A paper discharge accommodating portion 38 is provided on the upper portion of the main body 12. The sheet on which the toner image is fixed is discharged to the paper discharge container 38 by the discharge roll 36 described above, and is stacked on the paper discharge container 38. Accordingly, the sheets sent from the sheet stacking unit 20 are sequentially discharged to the paper discharge storage unit 38 through a C-shaped path.

  Further, four toner bottles 40Y, 40M, 40C, and 40K that store the developer are provided on the other end side (right side in the drawing) of the main body 12. The toner bottle 40Y contains yellow toner, the toner bottle 40M contains magenta toner, the toner bottle 40C contains cyan toner, and the toner bottle 40K contains black toner. The toner bottle 40Y is supplied to the image forming unit 16Y, the toner bottle 40M is supplied to the image forming unit 16M, the toner bottle 40C is supplied to the image forming unit 16C, and the toner bottle 40K is supplied to the image forming unit 16K by supply pipes or the like. Corresponding color toners are supplied via (not shown). These four toner bottles 40Y, 40M, 40C, and 40K are detachably attached to the main body 12 so that they can be pulled out to the front side in the figure, for example.

  Each of the image forming units 16Y, 16M, 16C, and 16K includes an image forming unit 48 that is disposed to face one surface (outer peripheral surface) of the intermediate transfer belt 14. Each image forming unit 48 can be attached to and detached from the main body 12. For example, the image forming unit 48 can be pulled out to the front side in the figure after being moved downward in the figure with respect to the intermediate transfer belt 14, for example.

  The intermediate transfer belt 14 as an example of a conveying member is stretched around a first roll 41, a second roll 42, and a third roll 43, and is supported so as to rotate in the arrow direction in the figure. In addition, in the portion from the third roll 43 to the first roll 41, an image (toner image) formed by the plurality of image forming portions 16Y, 16M, 16C, and 16K is transferred to the intermediate transfer belt 14. The transfer surface 45 is formed. The transfer surface 45 is formed obliquely from the upper right to the lower left in the figure with respect to the horizontal direction.

  The first roll 41 is driven by a belt drive motor, which will be described later, and functions as a drive roll that rotates the intermediate transfer belt 14 in the direction of the arrow in the figure. Further, the second roll 42 is used as a backup roll disposed opposite to the secondary transfer roll 32 with the intermediate transfer belt 14 interposed therebetween. On the other hand, a spring 46 is connected to the third roll 43. The spring 46 applies a force in which the third roll 43 moves away from the first roll 41 and the second roll 42 and applies a predetermined tension to the intermediate transfer belt 14. That is, the third roll 43 functions as a tension roll.

  Four primary transfer rolls 50 are attached to the inner side of the intermediate transfer belt 14 so as to face the image forming units 48 of the image forming units 16Y, 16M, 16C, and 16K. These four primary transfer rolls 50 are disposed in contact with the intermediate transfer belt 14 and rotate as the intermediate transfer belt 14 moves.

  A belt cleaner 44 for cleaning the intermediate transfer belt 14 is disposed at a position on the upper end side of the intermediate transfer belt 14 and facing the third roll 43 with the intermediate transfer belt 14 interposed therebetween. Therefore, the third roll 43 also functions as an opposing roll for the belt cleaner 44.

Here, the intermediate transfer belt 14, the first roll 41, the second roll 42, the third roll 43, the four primary transfer rolls 50, and the belt cleaner 44 are integrated as the belt unit 15 described above. The belt unit 15 is detachable from the main body 12 and can be pulled out to the front side in the figure.
The secondary transfer roll 32 is also unitized as a secondary transfer unit 33. The secondary transfer unit 33 can be attached to and detached from the main body 12, and can be pulled out to the front side in the figure.

  FIG. 2 is a diagram for explaining the image forming unit 48 constituting each of the image forming units 16Y, 16M, 16C, and 16K. The image forming units 16Y, 16M, 16C, and 16K have the same configuration of the image forming unit 48, although the color of the developer used is different. The image forming unit 48 includes a photosensitive drum 52 having a photosensitive layer (not shown), a charging device 54 made of, for example, a roll for charging the photosensitive drum 52, and an LED (Light Emitting Diode), for example. An exposure device 56 for forming a latent image thereon, a developing device 58 for developing the latent image on the photosensitive drum 52 formed by the exposure device 56 with toner, and the toner remaining on the photosensitive drum 52 after transfer A drum cleaner 60 for cleaning. In the present embodiment, each photosensitive drum 52 is used as an example of an image carrier.

  The image forming unit 48 is configured by combining a detachable photosensitive unit 62 and a developing unit 64. In the photoconductor unit 62, the photoconductor drum 52, the charging device 54, the exposure device 56, and the drum cleaner 60 are accommodated in the first housing 66. On the other hand, in the developing unit 64, the developing device 58 is accommodated in the second housing 68. The first housing 66 and the second housing 68 are detachably coupled to form the image forming unit 48.

  In addition, bearings 53 that rotatably support the photosensitive drum 52 are mounted at both ends in the longitudinal direction of the photosensitive drum 52. A part of the bearing 53 is exposed from the first casing 66 and the second casing 68 together with a part of the photosensitive drum 52.

  The developing device 58 employs a two-component developing system using a two-component developer containing toner and carrier as a developer. The developing device 58 includes, for example, a first auger 70 and a second auger 72 that are arranged in parallel in the horizontal direction, and a developing roll 74 that is arranged obliquely above the second auger 72. The first auger 70 and the second auger 72 are agitated and conveyed and supplied to the developing roll 74. In the developing roll 74, a magnetic brush is formed by a carrier, the toner attached to the carrier is conveyed by the magnetic brush, and the electrostatic latent image on the photosensitive drum 52 is developed by the toner.

  The drum cleaner 60 includes, for example, a toner scraping unit 76 formed of a blade, and a collecting unit 78 that collects the toner scraped off by the toner scraping unit 76.

In the image forming apparatus 10 configured as described above, the surface of the photosensitive drum 52 is uniformly charged by the charging device 54 in each of the image forming units 16Y, 16M, 16C, and 16K, and the photosensitive drum is uniformly charged. A latent image is written on the surface 52 by the exposure device 56. Next, the latent image is developed by the developing device 58 to form a toner image on the surface of the photosensitive drum 52, and the toner image is primarily transferred to the intermediate transfer belt 14 by the primary transfer roll 50. As a result, the toner images formed by the image forming units 16Y, 16M, 16C, and 16K are superimposed on the intermediate transfer belt 14 by primary transfer.
The toner image superimposed on the surface of the intermediate transfer belt 14 is secondarily transferred to a sheet by a secondary transfer roll 32, and the toner image secondarily transferred to the sheet is fixed by a fixing device 34. Then, the sheet on which the toner image has been fixed is discharged to a paper discharge container 38 via a discharge roll 36.

FIG. 3 is a diagram showing a drive system of each photosensitive drum 52 and intermediate transfer belt 14 in the image forming apparatus 10 shown in FIG.
In the present embodiment, the intermediate transfer belt 14 is composed of an endless belt made of polyimide resin. Moreover, the 1st roll 41 and the 3rd roll 43 are comprised by metal rolls, such as aluminum and stainless steel, for example, and the 2nd roll 42 is comprised by the rubber roll which forms a rubber layer in a metal shaft. Further, the secondary transfer roll 32 is configured by forming a foamed rubber layer on the outer periphery of the metal shaft.

A drum driving motor 81 is connected to the four photosensitive drums 52 via a drum driving gear train 82. The drum driving motor 81 rotates and drives each photosensitive drum 52 at the drum peripheral speed VD. On the other hand, a belt drive motor 83 is connected to the first roll 41 that spans the intermediate transfer belt 14 via a belt drive gear train 84. The belt drive motor 83 rotates the intermediate transfer belt 14 at the belt peripheral speed VB. In the present embodiment, the drum drive motor 81 and the belt drive motor 83 are constituted by a brushless DC motor in which the drive current and the generated torque are proportional. The drum drive gear train 82 and the belt drive gear train 84 are each configured by meshing a plurality of gears. In this embodiment, the drum drive motor 81 and the belt drive motor 83 are used as an example of a drive unit.
The drum drive motor 81 and the belt drive motor 83 are controlled by a drive control unit 90 as an example of setting means or determination means.

Here, the relationship between the drum peripheral speed VD of the photosensitive drum 52 and the belt peripheral speed VB of the intermediate transfer belt 14 will be described.
FIG. 4 is a diagram showing the relationship between the peripheral speed difference between the drum peripheral speed VD and the belt peripheral speed VB and a problem that occurs according to the peripheral speed difference.
In the image forming apparatus 10 according to the present exemplary embodiment, the photosensitive drum 52 is charged by the charging device 54. When charging is performed, a discharge product generated by the charging device 54 adheres to the photosensitive drum 52. When discharge products accumulate on the photosensitive drum 52, the transfer performance from the photosensitive drum 52 to the intermediate transfer belt 14 is degraded. In the following description, the phenomenon that discharge products adhere to the photosensitive drum 52 is referred to as filming. Therefore, the discharge product is removed from the photosensitive drum 52 by creating a circumferential speed difference between the drum circumferential speed VD and the belt circumferential speed VB and rubbing the surface of the photosensitive drum 52 using the intermediate transfer belt 14. It is possible. As shown in FIG. 4, when the drum peripheral speed VD and the belt peripheral speed VB are substantially the same, a transfer failure due to filming occurs. On the other hand, for example, when the belt peripheral speed VB is made higher than the drum peripheral speed VD to some extent (when the intermediate transfer belt 14 is fast), transfer defects due to filming hardly occur. Conversely, when the drum peripheral speed VD is made higher than the belt peripheral speed VB to some extent (when the photosensitive drum 52 is fast), transfer defects due to filming are less likely to occur.
Therefore, it can be seen that it is preferable to increase the peripheral speed difference between the drum peripheral speed VD and the belt peripheral speed VB from the viewpoint of removing the discharge products adhering to the photosensitive drum 52, that is, avoiding filming.

  On the other hand, if the difference in the peripheral speed between the drum peripheral speed VD and the belt peripheral speed VB is too large, the intermediate transfer belt 14 or the photosensitive drum 52 or both of the intermediate transfer belt 14 and the photosensitive drum 52 are subjected to fluctuations in rotational speed. As a result of the vibration, the image density of the toner image formed on the photosensitive drum 52 and the toner image transferred to the intermediate transfer belt 14 varies periodically along the moving direction of the intermediate transfer belt 14. Defects will occur. In the following description, an image quality defect caused by rotational fluctuation and vibration of the intermediate transfer belt 14 and the photosensitive drum 52 is referred to as banding.

  From the above, it can be seen that the peripheral speed difference between the drum peripheral speed VD and the belt peripheral speed VB is preferably as large as possible within a range where transfer defects due to filming and image quality defects due to banding do not occur. FIG. 4 shows a region where both of these can be satisfied as a compatible region.

Next, factors that cause banding will be described.
FIG. 5A is a diagram showing the relationship between the peripheral speed difference between the photosensitive drum 52 and the intermediate transfer belt 14 and the uneven speed of the intermediate transfer belt 14 generated at that time. Here, the speed unevenness of the intermediate transfer belt 14 corresponds to the level of banding. In the example shown in FIG. 5A, the speed unevenness of the intermediate transfer belt 14 is substantially constant at a low level until the peripheral speed difference reaches 2%. On the other hand, when the peripheral speed difference exceeds 2%, the level of the uneven speed of the intermediate transfer belt 14 is rapidly increased. That is, in this example, banding occurs when the peripheral speed difference exceeds 2%.

FIG. 5B illustrates a load as an example of a driving load applied to the belt driving motor 83 that drives the intermediate transfer belt 14 at that time, and the difference in the peripheral speed between the photosensitive drum 52 and the intermediate transfer belt 14. It is a figure which shows the relationship with a torque, ie, belt load torque. In the example shown in FIG. 5B, the load torque increases in proportion to the circumferential speed difference until the circumferential speed difference reaches 2%. On the other hand, when the peripheral speed difference exceeds 2%, the load torque applied to the intermediate transfer belt 14 becomes substantially constant at a high level regardless of the peripheral speed difference.
Therefore, from FIGS. 5 (a) and 5 (b), banding does not occur in a region with a small peripheral speed difference where the load torque increases as the peripheral speed difference increases, whereas the peripheral speed difference increases. It can also be seen that banding occurs in the region where the peripheral speed difference is large where the load torque does not increase.

  FIG. 6 shows a transfer function of the drive system of the intermediate transfer belt 14 shown in FIG. Here, FIG. 6A shows the transfer function when the peripheral speed difference between the drum peripheral speed VD and the belt peripheral speed VB is set in a range where banding does not occur (for example, about 1% in the example shown in FIG. 5). Show. On the other hand, FIG. 6B shows a transfer function when the peripheral speed difference between the drum peripheral speed VD and the belt peripheral speed VB is set in a range where banding occurs (for example, about 5% in the example shown in FIG. 5). Yes. 6 (a) and 6 (b), the horizontal axis represents frequency and the vertical axis represents magnification.

Here, when FIG. 6A is compared with FIG. 6B, the peak on the amplification side exists in the vicinity of 50 Hz in FIG. 6B, whereas in FIG. It can be seen that there is no major peak but rather the attenuation side.
In the present embodiment, the photosensitive drum 52 is driven via a drum drive gear train 82, and the intermediate transfer belt 14 is driven via a belt drive gear train 84. At this time, in the drum drive gear train 82 and the belt drive gear train 84, a predetermined meshing frequency is generated as the gear meshes, but when the peripheral speed difference is small, as is apparent from FIG. Since the vibration in the vicinity of 50 Hz is attenuated, the intermediate transfer belt 14 is less likely to vibrate even if a gear meshing frequency exists in the vicinity of 50 Hz. On the other hand, when the peripheral speed difference is large, as is apparent from FIG. 6B, the vibration in the vicinity of 50 Hz is amplified, so that the intermediate transfer belt 14 is likely to vibrate, resulting in banding. It tends to occur.

However, the profile of the transfer function of the drive system of the intermediate transfer belt 14 depends on the change of each component over time and the environment in which the image forming apparatus 10 is placed even if the peripheral speed difference is always constant. change. Further, the state of the interface where the photosensitive drum 52 and the intermediate transfer belt 14 are in contact also changes depending on the time or environment.
Therefore, in this embodiment, the relationship between the peripheral speed difference between the photosensitive drum 52 and the intermediate transfer belt 14 at the timing when the image forming operation is not performed, and the belt load torque required for driving the intermediate transfer belt 14 at that time. The peripheral speed difference used in the image forming operation, that is, a predetermined peripheral speed difference is determined based on the result of the investigation.

  FIG. 7 is a block diagram of the drive control unit 90 shown in FIG. The CPU 91 of the drive control unit 90 executes processing while appropriately exchanging data with the RAM 93 according to a program stored in the ROM 92. Further, the drive control unit 90 receives a power-on signal from the power switch 101 of the image forming apparatus 10 via the input / output interface 94, and from the environment sensor 102 provided in the image forming apparatus 10 to the inside of the image forming apparatus 10. Temperature and humidity signals are input respectively. Further, a belt load torque signal generated by the belt drive motor 83 is also input to the drive control unit 90 from a torque meter 103 as an example of a measuring unit attached to the belt drive motor 83 shown in FIG. On the other hand, the drive controller 90 outputs drive signals to the drum drive motor 81 and the belt drive motor 83 via the input / output interface 94, respectively.

  FIG. 8 is a flowchart for explaining processing for determining a peripheral speed difference used in the image forming operation. This process is executed, for example, when the power switch 101 is turned on and the image forming apparatus 10 starts to move, or when the temperature or humidity detected by the environmental sensor 102 is greatly changed from the previous state, for example.

First, the drive control unit 90 sets the drum peripheral speed VD of each photosensitive drum 52 to the reference peripheral speed V0 (step 101) and sets n = 1 (step 102). Here, the reference peripheral speed V0 is the peripheral speed of the photosensitive drum 52 used in the actual image forming operation.
Next, the drive control unit 90 sets the n-th belt peripheral speed VB of the intermediate transfer belt 14 to V (n) = V0 + α × n (step 103). Here, the coefficient α is set to a magnitude of, for example, about 0.1 to 1.0% with respect to the reference circumferential speed V0. Therefore, for example, the first belt circumferential speed V (1) is set to be higher by 0.1% to 1% than the reference circumferential speed V0.

  Then, the drive control unit 90 outputs a drive signal to the drum drive motor 81 so that the drum peripheral speed VD becomes the reference peripheral speed V0, and the belt peripheral speed VB to the belt drive motor 83 is the nth belt. A drive signal is output so that the peripheral speed V (n). The drum drive motor 81 starts to rotate in response to the drive signal, and rotates the photosensitive drums 52 through the drum drive gear train 82 so as to have the reference peripheral speed V0. On the other hand, the belt drive motor 83 starts to rotate in response to the drive signal so that the intermediate transfer belt 14 reaches the nth belt peripheral speed V (n) via the belt drive gear train 84 and the first roll 41. Rotate to

  Subsequently, the drive control unit 90 acquires the torque of the belt drive motor 83 measured by the torque meter 103, that is, the n-th belt load torque T (n) (step 104). Next, the drive control unit 90 calculates the difference between the acquired nth belt load torque T (n) and the previously acquired n−1th belt load torque T (n−1). It is determined whether the difference is smaller than a predetermined threshold value TX (step 105). If the belt load torque difference is equal to or greater than the threshold TX, the drive control unit 90 resets n to n + 1 (step 106), returns to step 103, and continues the process. On the other hand, when the difference in the belt load torque is less than the threshold value TX in step 105, the drive control unit 90 performs the (n−1) th when the n−1th belt load torque T (n−1) is generated. The belt peripheral speed V (n−1) is determined as the belt peripheral speed VB used in the image forming operation (step 107), and a series of processing is completed.

  In the actual image forming operation, each photosensitive drum 52 is driven at the drum peripheral speed VD = reference peripheral speed V0, and the intermediate transfer belt 14 is driven at the belt peripheral speed VB determined in step 107. The difference between the peripheral speeds at this time is within the compatible range shown in FIG. 4 and is close to the upper limit value on the side where the peripheral speed difference is large.

  In this embodiment, the peripheral speed difference is set based on the measurement result of the belt load torque in the belt drive motor 83 that drives the intermediate transfer belt 14, but the drum drive that drives each photosensitive drum 52 is used. The peripheral speed difference may be set based on the measurement result of the drum load torque in the motor 81.

<Embodiment 2>
FIG. 9 shows a block diagram of the drive control unit 90 in the present embodiment. The basic configuration of the drive control unit 90 is basically the same as that described in the first embodiment, but an ammeter 104 as an example of a measuring unit is connected instead of the torque meter 103. This ammeter 104 measures the value of the current flowing through the belt drive motor 83. As described in the first embodiment, the belt drive motor 83 is configured by a brushless DC motor, and the magnitude of the drive current value flowing through the belt drive motor 83 and the magnitude of the generated belt load torque have a proportional relationship. is doing. Therefore, the magnitude of the drive current value can be a substitute characteristic of the belt load torque in the first embodiment.

  FIG. 10 is a flowchart for explaining processing for determining a peripheral speed difference used in the image forming operation. Note that this processing is the same as in the first embodiment, for example, when the power switch 101 is turned on and the image forming apparatus 10 starts to move, or for example, the temperature and humidity detected by the environment sensor 102 change greatly from the previous state. Executed when.

The drive controller 90 first sets the drum peripheral speed VD of each photosensitive drum 52 to the reference peripheral speed V0 (step 201), and sets n = 1 (step 202).
Next, the drive controller 90 sets the n-th belt peripheral speed VB of the intermediate transfer belt 14 to V (n) = V0 + α × n (step 203).

  Then, the drive control unit 90 outputs a drive signal to the drum drive motor 81 so that the drum peripheral speed VD becomes the reference peripheral speed V0, and the belt peripheral speed VB to the belt drive motor 83 is the nth belt. A drive signal is output so that the peripheral speed V (n). The drum drive motor 81 starts to rotate in response to the drive signal, and rotates the photosensitive drums 52 through the drum drive gear train 82 so as to have the reference peripheral speed V0. On the other hand, the belt drive motor 83 starts to rotate in response to the drive signal so that the intermediate transfer belt 14 reaches the nth belt peripheral speed V (n) via the belt drive gear train 84 and the first roll 41. Rotate to

  Subsequently, the drive control unit 90 acquires the drive current value of the belt drive motor 83 measured by the ammeter 104, that is, the n-th belt drive current value I (n) (step 204). Next, the drive control unit 90 calculates the difference between the acquired nth belt drive current value I (n) and the previously acquired n−1th belt drive current value I (n−1), It is determined whether or not the obtained difference is smaller than a predetermined threshold value IX (step 205). If the belt drive current value difference is equal to or greater than the threshold IX, the drive control unit 90 resets n to n + 1 (step 206), returns to step 203, and continues the process. On the other hand, if the difference in the belt drive current value is less than the threshold value IX in step 205, the drive control unit 90 performs the (n−1) th when the n−1th drive current value I (n−1) is generated. The belt peripheral speed V (n-1) is determined as the belt peripheral speed VB used in the image forming operation (step 207), and a series of processing is completed.

  In the actual image forming operation, each photosensitive drum 52 is driven at the drum peripheral speed VD = reference peripheral speed V0, and the intermediate transfer belt 14 is driven at the belt peripheral speed VB determined in step 207. The peripheral speed difference at this time is within the compatible range shown in FIG. 4 as in the first embodiment, and is close to the upper limit value on the side where the peripheral speed difference is large.

<Embodiment 3>
FIG. 11 shows a block diagram of the drive control unit 90 in the present embodiment. The basic configuration of the drive control unit 90 is basically the same as that described in the first embodiment, but a mark detection sensor 105 as an example of a measuring unit is connected instead of the torque meter 103. This mark detection sensor 105, for example, in FIG. 3, is disposed inside the intermediate transfer belt 14 so as to face the intermediate transfer belt 14. Further, a mark is formed at a specific location inside the intermediate transfer belt 14, and the mark detection sensor 105 reads the mark formed on the intermediate transfer belt 14. Accordingly, the period from when the mark is detected by the mark detection sensor 105 until the next mark is detected is the rotation cycle of the intermediate transfer belt 14. The rotation cycle of the intermediate transfer belt 14 is a range in which the belt load torque of the intermediate transfer belt 14 increases as the peripheral speed difference increases, in other words, the interaction between each photosensitive drum 52 and the intermediate transfer belt 14. While rotating while rotating, it increases as the peripheral speed difference increases. On the other hand, the rotation cycle of the intermediate transfer belt 14 is a range in which the belt load torque of the intermediate transfer belt 14 becomes substantially constant at a high level regardless of an increase in the peripheral speed difference, in other words, each photosensitive drum 52 and the intermediate transfer belt. While each of them independently rotates without interacting with 14, it becomes substantially constant at a high level regardless of an increase in the peripheral speed difference. Therefore, the rotation cycle of the intermediate transfer belt 14 can be a substitute characteristic of the belt load torque in the first embodiment.

  FIG. 12 is a flowchart for explaining processing for determining the peripheral speed difference used in the image forming operation. Note that this processing is the same as in the first embodiment, for example, when the power switch 101 is turned on and the image forming apparatus 10 starts to move, or for example, the temperature and humidity detected by the environment sensor 102 change greatly from the previous state. Executed when.

The drive controller 90 first sets the drum peripheral speed VD of each photosensitive drum 52 to the reference peripheral speed V0 (step 301), and sets n = 1 (step 302).
Next, the drive controller 90 sets the n-th belt peripheral speed VB of the intermediate transfer belt 14 to V (n) = V0 + α × n (step 303).

  Then, the drive control unit 90 outputs a drive signal to the drum drive motor 81 so that the drum peripheral speed VD becomes the reference peripheral speed V0, and the belt peripheral speed VB to the belt drive motor 83 is the nth belt. A drive signal is output so that the peripheral speed V (n). The drum drive motor 81 starts to rotate in response to the drive signal, and rotates the photosensitive drums 52 through the drum drive gear train 82 so as to have the reference peripheral speed V0. On the other hand, the belt drive motor 83 starts to rotate in response to the drive signal so that the intermediate transfer belt 14 reaches the nth belt peripheral speed V (n) via the belt drive gear train 84 and the first roll 41. Rotate to

  Subsequently, the drive control unit 90 calculates the detection period of the mark on the intermediate transfer belt 14 by the mark detection sensor 105, that is, the nth belt rotation period P (n) (step 304). Next, the drive control unit 90 calculates the difference between the acquired nth belt rotation period P (n) and the n−1th belt rotation period P (n−1) calculated before that. It is determined whether the difference is smaller than a predetermined threshold PX (step 305). If the belt rotation cycle difference is equal to or greater than the threshold value PX, the drive control unit 90 resets n to n + 1 (step 306), returns to step 303, and continues the processing. On the other hand, if the difference in the belt rotation period is less than the threshold value PX in step 305, the drive control unit 90 determines that the (n−1) th belt circumferential speed at the (n−1) th rotation period P (n−1). V (n-1) is determined as the belt peripheral speed VB used in the image forming operation (step 307), and a series of processing is completed.

  In the actual image forming operation, each photosensitive drum 52 is driven at the drum peripheral speed VD = reference peripheral speed V0, and the intermediate transfer belt 14 is driven at the belt peripheral speed VB determined in step 307. The difference between the peripheral speeds at this time is within the compatible range shown in FIG. 4 and is close to the upper limit value on the side where the peripheral speed difference is large.

In the first to third embodiments, the toner image formed on each photosensitive drum 52 is primarily transferred onto the intermediate transfer belt 14, and then the toner image on the intermediate transfer belt 14 is secondarily transferred to a sheet. Although the forming apparatus has been described, the image forming apparatus to which the present invention is applicable is not limited to this. In other words, the present invention is applied to an image forming apparatus that employs a system in which a conveyance belt is disposed opposite to each photosensitive drum 52 and a toner image formed on each photosensitive drum 52 is sequentially transferred onto a sheet conveyed by the conveyance belt. May be.
In the first to third embodiments, the belt peripheral speed VB is set higher than the drum peripheral speed VD. However, as is apparent from the relationship shown in FIG. 4, for example, the drum peripheral speed VD is changed to the belt peripheral speed VB. You may set faster than.

1 is a diagram illustrating an overall configuration of an image forming apparatus to which an embodiment is applied. It is a figure for demonstrating the image formation unit which comprises an image formation part. FIG. 3 is a diagram illustrating a driving system for each photosensitive drum and an intermediate transfer belt. It is a figure which shows the relationship between the peripheral speed difference of a drum peripheral speed and a belt peripheral speed, and the malfunction generate | occur | produced according to a peripheral speed difference. (A) is a diagram showing the relationship between the circumferential speed difference between the photosensitive drum and the intermediate transfer belt and the uneven speed of the intermediate transfer belt that occurs at that time, and (b) is a diagram showing the relationship between the photosensitive drum and the intermediate transfer belt. FIG. 7 is a diagram illustrating a relationship between a peripheral speed difference from a belt and a belt load torque applied to a belt driving motor that drives an intermediate transfer belt at that time. (A), (b) is a figure which shows the transfer function of the drive system of an intermediate transfer belt. 2 is a block diagram of a drive control unit in Embodiment 1. FIG. 4 is a flowchart for illustrating a peripheral speed difference determination process in the first embodiment. 6 is a block diagram of a drive control unit in Embodiment 2. FIG. 12 is a flowchart for illustrating a peripheral speed difference determination process in the second embodiment. FIG. 10 is a block diagram of a drive control unit in a third embodiment. 10 is a flowchart for illustrating a peripheral speed difference determination process in the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 14 ... Intermediate transfer belt, 16Y, 16M, 16C, 16K ... Image forming part, 41 ... First roll, 42 ... Second roll, 43 ... Third roll, 50 ... Primary transfer roll, 52 ... Photosensitive drum, 54 ... charging device, 56 ... exposure device, 58 ... developing device, 60 ... drum cleaner, 81 ... drum drive motor, 82 ... drum drive gear train, 83 ... belt drive motor, 84 ... belt drive gear train, DESCRIPTION OF SYMBOLS 90 ... Drive control part, 101 ... Power switch, 102 ... Environmental sensor, 103 ... Torque meter, 104 ... Ammeter, 105 ... Mark detection sensor

Claims (4)

An image carrier for holding an image;
A conveying member that is disposed in contact with the image carrier and conveys an image transferred from the image carrier or a recording material onto which the image is transferred from the image carrier;
Drive means for driving the image carrier and the transport member with a predetermined peripheral speed difference;
Setting means for setting the predetermined circumferential speed difference within a range in which a load torque required to drive the image holding body or the transport member increases with an increase in the peripheral speed difference between the image carrier and the transport member; An image forming apparatus including: The setting means includes
Driving the image carrier and the conveying member at a plurality of peripheral speed differences by the driving means;
Measuring the load torque applied to the image carrier or the conveying member at a plurality of the peripheral speed differences,
The image forming apparatus according to claim 1, wherein the range is determined based on a relationship between a plurality of peripheral speed differences and a plurality of measured load torques. An image carrier for holding an image;
A conveying member that is disposed in contact with the image carrier and conveys an image transferred from the image carrier or a recording material onto which the image is transferred from the image carrier;
Drive means for driving the image carrier and the transport member with a predetermined peripheral speed difference;
Measuring means for measuring a load torque applied to the image holding member or the conveying member while varying the size of the peripheral speed difference between the image holding member and the conveying member;
An image forming apparatus including: a determining unit configured to determine the predetermined peripheral speed difference based on the load torque measured by the measuring unit;   The measuring means measures, instead of the load torque, a drive current value supplied to a drive motor of the image carrier or the transport member, or a rotation period of the image carrier or the transport member. The image forming apparatus according to claim 3.

Images