JP7468104B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming device.

Patent document 1 discloses a process for controlling the drive motor taking into consideration the static friction coefficient between the first and second rotating bodies, the contact pressure between the first and second rotating bodies, the load torque of the second rotating body, and the drive torque of the second drive motor.

JP 2013-76948 A

2. Description of the Related Art In an image forming apparatus, an image held by an image holder is sometimes transferred onto a recording material by using a transfer member, thereby forming an image on the recording material.
Here, if the transfer member is not driven in an appropriate state, for example, if the rotation speed of the transfer member is too high or too low, the image formed on the recording material will stretch or shrink, resulting in a deterioration in the quality of the formed image.
An object of the present invention is to enable the driving of a transfer member used for transferring an image to be performed under more appropriate conditions, compared to a case in which it is not possible to set the driving conditions of a driving means for driving the transfer member.

The invention described in claim 1 includes an image carrier that is rotatably provided and that holds an image to be transferred to a recording material, carrier drive means for driving and rotating the image carrier, a transfer member that is rotatably provided and used to transfer the image on the image carrier to the recording material, transfer member drive means for driving and rotating the transfer member, an application means for applying a voltage between the image carrier and the transfer member, and a processor, wherein the processor obtains drive information that is information related to the drive of at least one of the carrier drive means and the transfer member drive means, and calculates a voltage when the application means is applying a voltage to between the image carrier and the transfer member. The image forming apparatus sets driving conditions for the transfer member driving means based on first driving information, which is the driving information, and second driving information, which is the driving information for a second state in which no voltage is applied by the application means or a voltage smaller than the applied voltage in the first state is applied, and when an image on the image carrier is transferred to a recording material, the transfer member is disposed at a predetermined location, and the transfer member is disposed at a location retreated from the image carrier relative to the predetermined location in each of the first state and the second state .
The invention described in claim 2 is the image forming apparatus described in claim 1 , wherein the transfer member disposed at the retreated position is disposed in a state of contact with the image carrier.
The invention described in claim 3 is an image forming apparatus described in claim 1, in which when the image on the image holder is transferred to a recording material, a voltage of a predetermined value is applied between the image holder and the transfer member, and the value of the voltage applied when the application means is in the first state is greater than the predetermined value.
The invention described in claim 4 is an image forming apparatus described in any of claims 1 to 3, wherein the processor sets the driving conditions of the transfer member driving means so that the difference between the value specified by the first driving information and the value specified by the second driving information is small.
The invention described in claim 5 is an image forming apparatus described in any one of claims 1 to 4, wherein the processor drives the transfer member driving means under each of a plurality of mutually different conditions, acquires the second driving information for each of the conditions, acquires a plurality of the second driving information, and sets the driving conditions of the transfer member driving means based on the conditions when second driving information having a predetermined relationship with the first driving information is acquired from the plurality of acquired second driving information.
The invention described in claim 6 is an image forming apparatus described in claim 5 , wherein the processor sets the driving conditions of the transfer member driving means based on the conditions when second driving information is obtained, among the multiple acquired second driving information, whose difference from a value specified by the first driving information falls within a predetermined range.
The invention described in claim 7 is an image forming apparatus described in any of claims 1 to 6, wherein the processor drives the transfer member driving means under each of a plurality of mutually different conditions, acquires the first driving information for each of the conditions, acquires a plurality of the first driving information, and sets the driving conditions of the transfer member driving means based on the conditions when first driving information having a predetermined relationship with the second driving information is acquired from the plurality of acquired first driving information.
The invention described in claim 8 is an image forming apparatus described in claim 7 , wherein the processor sets the driving conditions of the transfer member driving means based on the conditions when first driving information is obtained, among the multiple acquired first driving information, whose difference from a value specified by the second driving information falls within a predetermined range.
The invention described in claim 9 is an image forming apparatus described in claim 7, wherein the processor changes the conditions in sequence when driving the transfer member driving means under each of the multiple conditions which are different from each other, and the conditions are changed in sequence while maintaining the first state in which voltage is applied between the image carrier and the transfer member.
The invention described in claim 10 is an image forming apparatus described in any of claims 1 to 9 , wherein the processor outputs information regarding a malfunction of the image forming apparatus when a value specified by the set driving conditions exceeds a predetermined value.

According to the invention of claim 1, it is possible to drive the transfer member under more appropriate conditions compared to a case where it is not possible to set the driving conditions of the driving means that drives the transfer member used to transfer the image, and it is easier to create a difference between the value specified by the first driving information and the value specified by the second driving information compared to a case where the transfer member is positioned at the location where the transfer member is positioned when the image on the image carrier is transferred to the recording material.
According to the invention of claim 2 , when a voltage is applied between the image holder and the transfer member, the transfer member arranged in the retracted location can be pressed more firmly against the image holder, compared to when the transfer member is arranged at a distance from the image holder.
According to the invention of claim 3 , when the application means is in the first state, it is possible to press the transfer member against the image carrier more strongly than when the voltage value applied by the application means in the first state is the same as the voltage value applied when the image on the image carrier is transferred to the recording material.
According to the invention of claim 4 , the difference between the peripheral speed of the image carrier and the peripheral speed of the transfer member can be reduced compared to a case in which the difference between the value specified by the first driving information and the value specified by the second driving information does not become smaller.
According to the invention of claim 5 , it becomes possible to set driving conditions that can reduce the difference between the circumferential speed of the image carrier and the circumferential speed of the transfer member, compared to when the driving conditions of the transfer member driving means are set based on the conditions when the second driving information identified without taking into account the first driving information was obtained from among the multiple acquired second driving information.
According to the invention of claim 6 , the difference between the circumferential speed of the image carrier and the circumferential speed of the transfer member can be made smaller than when the driving conditions of the transfer member driving means are set based on the conditions when the second driving information is obtained, among the multiple acquired second driving information, whose difference from the value specified by the first driving information does not fall within a predetermined range.
According to the invention of claim 7 , it becomes possible to set driving conditions that can reduce the difference between the circumferential speed of the image carrier and the circumferential speed of the transfer member, compared to when the driving conditions of the transfer member driving means are set based on the conditions under which the first driving information identified without taking into account the second driving information was obtained from among multiple acquired first driving information.
According to the invention of claim 8 , the difference between the circumferential speed of the image carrier and the circumferential speed of the transfer member can be made smaller than when the driving conditions of the transfer member driving means are set based on the conditions when the first driving information is obtained, among the multiple acquired first driving information, whose difference from the value specified by the second driving information does not fall within a predetermined range.
According to the ninth aspect of the present invention, the driving conditions of the transfer member driving means can be set in a shorter time than in the case where the application of voltage is temporarily stopped every time the conditions are changed.
According to the tenth aspect of the present invention, information regarding a malfunction of the image forming apparatus can be output.

FIG. 1 illustrates an image forming apparatus. FIG. 2 is a diagram showing functional units realized by a control device. 1A and 1B are diagrams illustrating an example of processing performed in an image forming apparatus. 13 is a diagram showing information on the number of rotations when the PWM value is changed in a first state in which a voltage is applied between the intermediate transfer belt and the secondary transfer roll. FIG. 11 is a flowchart showing a process flow. 11A and 11B are diagrams illustrating another example of the process performed in the image forming apparatus. 11A and 11B are diagrams illustrating another example of the process performed in the image forming apparatus. FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device. FIG. 2 is a diagram showing the state of an intermediate transfer belt, a secondary transfer roll, etc.;

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing an image forming apparatus 1 according to an embodiment of the present invention.
The image forming apparatus 1 of this embodiment includes an image forming section 10 , a paper transport section 20 , an image reading section 30 , and a control device 40 .

The image forming section 10 includes a plurality of image forming units 11 ( 11 Y, 11 M, 11 C, and 11 K), an intermediate transfer belt 12 , a secondary transfer section 13 , a fixing device 14 , and a cooler 15 .
In this embodiment, the image forming units 11 are provided as four image forming units 11Y, 11M, 11C, and 11K corresponding to four colors, Y (yellow), M (magenta), C (cyan), and K (black).

The four image forming units 11 are arranged side by side in the moving direction of the intermediate transfer belt 12. Each of the image forming units 11 has a photosensitive drum 111, a charging device 112, an exposure device 113, and a developing device 114, and forms an image formed from toner on the intermediate transfer belt 12 using an electrophotographic method.
In addition, in this embodiment, the image forming unit 11 forms images of the respective colors of Y, M, C, and K. Then, in this embodiment, these formed images are transferred to the intermediate transfer belt 12. As a result, images of the respective colors of Y, M, C, and K are formed on the intermediate transfer belt 12.

The photoconductor drum 111 rotates in the direction of arrow A in the figure at a predetermined speed.
The surface of the photoconductor drum 111 is charged by the charging device 112. Furthermore, the exposure device 113 irradiates the charged surface of the photoconductor drum 111 with light.
As a result, an electrostatic latent image corresponding to the image to be formed is formed on the outer circumferential surface of the photoconductor drum 111 .

Thereafter, the developing device 114 develops the photoconductor drum 111 and forms an image on the photoconductor drum 111. More specifically, the developing device 114 deposits a developer onto the surface of the photoconductor drum 111 on which the electrostatic latent image has been formed, and forms an image on the surface of the photoconductor drum 111.
In each of the image forming units 11Y, 11M, 11C, and 11K, yellow, magenta, cyan, and black images are formed on the surface of the photoconductor drum 111.

The images formed on the photoconductor drums 111 are transferred (primary transfer) onto the intermediate transfer belt 12 in the primary transfer section 115 .
As a result, a color image made up of a plurality of colors is formed on the intermediate transfer belt 12. In other words, the intermediate transfer belt 12 temporarily holds the color image.

The intermediate transfer belt 12 , which is an example of an image carrier, is supported by a plurality of roll-shaped members 122 .
Furthermore, in this embodiment, a belt driving mechanism 200 that drives and rotates the intermediate transfer belt 12 is provided.
The belt driving mechanism 200, which is an example of a holder driving means, controls the driving of the intermediate transfer belt 12 so that the intermediate transfer belt 12 rotates at a predetermined constant speed.
In addition, the belt driving mechanism 200 controls the driving of the intermediate transfer belt 12 so that the intermediate transfer belt 12 rotates at a predetermined speed based on the output from a sensor or the like that detects the rotation speed of the intermediate transfer belt 12.

In this embodiment, the belt driving mechanism 200 includes a belt motor MB and a driving roll 121 that is arranged in contact with the inner circumferential surface of the intermediate transfer belt 12 and rotated by the belt motor MB. The belt driving mechanism 200 also includes a transmission unit (not shown) that is configured with gears or the like and transmits a driving force from the belt motor MB to the driving roll 121.
The intermediate transfer belt 12 circulates in the direction of the arrow B. In other words, the intermediate transfer belt 12 is rotated in the counterclockwise direction by the belt driving mechanism 200.

The image formed on the intermediate transfer belt 12 moves to the secondary transfer unit 13 along with the movement of the intermediate transfer belt 12. Then, the image that has moved to the secondary transfer unit 13 is transferred by the secondary transfer unit 13 onto paper P, which is an example of a recording material, that has been transported by the paper transport unit 20.
The secondary transfer unit 13 is provided with a secondary transfer roll 134 that is in contact with the outer circumferential surface of the intermediate transfer belt 12 and is used to transfer the image on the intermediate transfer belt 12 to the paper P.
Furthermore, the secondary transfer section 13 is provided with a backup roll 132 that is disposed inside the intermediate transfer belt 12 and serves as a counter electrode for the secondary transfer roll 134 .

The backup roll 132 is disposed on the opposite side of the intermediate transfer belt 12 from the side on which the secondary transfer roll 134 is disposed.
Furthermore, in this embodiment, a secondary transfer roll 134 as an example of a transfer member is pressed against the backup roll 132 via the intermediate transfer belt 12 .

Furthermore, in this embodiment, an application device 250 is provided as an example of an application unit that applies a voltage between the intermediate transfer belt 12 and the secondary transfer roll 134 .
In this embodiment, the image on the intermediate transfer belt 12 is transferred to the paper P passing between the intermediate transfer belt 12 and the secondary transfer roll 134 by the voltage applied by the voltage application device 250 .
Furthermore, in this embodiment, a cleaning blade 180 is provided as a cleaning member that is pressed against the secondary transfer roll 134 and cleans the secondary transfer roll 134 .

The secondary transfer roll 134 is provided so as to be movable toward and away from the intermediate transfer belt 12. Furthermore, the secondary transfer roll 134 is rotatable.
Furthermore, in this embodiment, a roll driving mechanism 300 is provided as an example of a transfer member driving means. The roll driving mechanism 300 drives the secondary transfer roll 134 to rotate.

The roll driving mechanism 300 is provided with a roll motor MR and a transmission unit (not shown) that is configured with gears and the like and transmits the driving force from the roll motor MR to the secondary transfer roll 134 .
In this embodiment, the rotation of the roll motor MR is controlled by a PWM (Pulse Width Modulation) control method.

Furthermore, in this embodiment, there is provided an advancing/retreating mechanism 280 that moves the secondary transfer roll 134 and the roll driving mechanism 300 forward and backward relative to the intermediate transfer belt 12. This advancing/retreating mechanism 280 is not particularly limited and is configured by a known mechanism.
Furthermore, in this embodiment, a belt cleaner 124 that cleans the outer circumferential surface of the intermediate transfer belt 12 after secondary transfer is provided downstream of the secondary transfer unit 13 in the moving direction of the intermediate transfer belt 12 .

The paper transport section 20 is provided with a paper storage section 21 in which a plurality of sheets of paper P are stored in a stacked state, and a delivery roll 22 that delivers the paper P stored in the paper storage section 21 .
The paper transport section 20 is also provided with a transport roll 23 that transports the paper P sent out by the feed roll 22, and a guide member 24 that guides the paper P transported by the transport roll 23 to the secondary transfer section 13.
Furthermore, the paper transport section 20 is provided with a transport belt 25 that transports the paper P after the secondary transfer to the fixing device 14, and a guide member 26 that guides the paper P after the fixing to the cooler 15.

The fixing unit 14 is disposed downstream of the secondary transfer unit 13 in the transport direction of the paper P. The fixing unit 14 includes a fixing roll 141 having a heat source (not shown) and a pressure roll 142 pressed against the fixing roll 141.
The paper P that has passed through the secondary transfer unit 13 passes between the fixing roll 141 and the pressure roll 142. As a result, the paper P is pressurized and heated, and the image on the paper P is fixed to the paper P.
In this embodiment, a cooler 15 is provided downstream of the fixing unit 14. The cooler 15 cools the paper P conveyed from the fixing unit 14.

The image reading unit 30 reads the image formed on the paper P.
Specifically, the image reading unit 30 reads the image transferred to the paper P by the secondary transfer unit 13. The image reading unit 30 is provided with a light source that emits light to the paper P, an image sensor that receives the light reflected from the paper P, and an imaging lens that guides the light reflected from the paper P to the image sensor.

FIG. 8 is a diagram illustrating an example of a hardware configuration of the control device 40. As shown in FIG.
The control device 40 has a CPU (= Central Processing Unit) 911 as an example of a processor, a ROM (= Read Only Memory) 912 in which basic software, a BIOS (= Basic Input Output System), etc. are stored, and a RAM (= Random Access Memory) 913 used as a work area. The control device 40 is a so-called computer.
In this embodiment, the CPU 911 executes programs stored in the ROM 912 or the like to perform various processes, which will be described later.

Here, the program executed by CPU 911 can be provided to image forming apparatus 1 in a state where it is stored on a computer-readable recording medium such as a magnetic recording medium (magnetic tape, magnetic disk, etc.), an optical recording medium (optical disk, etc.), a magneto-optical recording medium, or a semiconductor memory.
Furthermore, the program executed by the CPU 911 may be provided to the image forming apparatus 1 using a communication means such as the Internet.

In this embodiment, the term "processor" refers to a processor in a broad sense, and includes general-purpose processors (e.g., CPU: Central Processing Unit, etc.) and dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).
In addition, the operations of the processor may not only be performed by one processor, but may be performed by multiple processors in physically separate locations working together. The order of the operations of the processor is not limited to the order described in this embodiment, and may be changed.

FIG. 2 is a diagram showing functional units realized by the control device 40. As shown in FIG.
In this embodiment, the CPU 911 executes a program stored in the ROM 912, a HDD (Hard Disk Drive) (not shown), etc., to realize each of the functional units, namely, the driving information acquisition unit 41, the driving condition setting unit 42, and the output unit 43.

The driving information acquisition unit 41 , which is an example of a driving information acquisition means, acquires driving information, which is information related to the driving of at least one of the belt driving mechanism 200 and the roll driving mechanism 300 .
The drive condition setting unit 42 , which is an example of a setting unit, sets the drive conditions of the roll drive mechanism 300 .
The output unit 43 , which is an example of an output unit, outputs information related to a malfunction of the image forming apparatus 1 .

In this embodiment, a CPU 911 (an example of a processor) executes a program stored in a ROM 912 or a HDD to realize the processing described below.
In other words, in this embodiment, the CPU 911, as an example of a processor, executes a program stored in the ROM 912 or the HDD to realize each functional unit shown in FIG. 2, and each functional unit realizes the processing described below.

In the image forming apparatus 1 (see FIG. 1) of this embodiment, the image held by the intermediate transfer belt 12 is transferred onto the paper P using the secondary transfer roll 134, thereby forming the image on the paper P.
Here, if the rotation speed of the secondary transfer roll 134 is too fast or too slow, the paper P positioned between the intermediate transfer belt 12 and the secondary transfer roll 134 is affected by the secondary transfer roll 134, resulting in a deterioration in the quality of the image on the paper P.

Specifically, if the rotation speed of the secondary transfer roll 134 is too low, the movement speed of the paper P relative to the intermediate transfer belt 12 in the secondary transfer section 13 will decrease, which may cause the image formed on the paper P to shrink.
Furthermore, if the rotation speed of the secondary transfer roll 134 is too high, the moving speed of the paper P relative to the intermediate transfer belt 12 in the secondary transfer section 13 increases, which may cause the image formed on the paper P to be elongated.
Therefore, in this embodiment, the process described below is performed to set the driving conditions (PWM value of the roll motor MR) of the roll driving mechanism 300. This makes it difficult for problems caused by the secondary transfer roll 134 to occur.

3A and 3B are diagrams illustrating an example of processing performed by the image forming apparatus 1 of this embodiment.
In the processing of this embodiment, when in a first state in which voltage is being applied by the application device 250 (see Figure 3 (A)), the drive information acquisition unit 41 (see Figure 2) obtains first drive information, which is information about the drive of the roll drive mechanism 300.
In addition, in a second state in which no voltage is applied by the application device 250 (see Figure 3 (B)), the drive information acquisition unit 41 obtains second drive information, which is information about the drive of the roll drive mechanism 300.

In addition, in each of the first and second states, the secondary transfer roll 134 is arranged in a so-called half-nip state, as shown in (B) of Figure 9 (a diagram showing the state of the intermediate transfer belt 12, the secondary transfer roll 134, etc.).
In other words, in each of the first and second states, the secondary transfer roll 134 is disposed in a state retreated from the intermediate transfer belt 12 further than in the full nip state shown in FIG. 9A.

In this embodiment, when an image on the intermediate transfer belt 12 is transferred to paper P, as shown in Figure 9 (A), the secondary transfer roll 134 is placed at a predetermined position and is pressed firmly against the intermediate transfer belt 12.
The state in which the secondary transfer roll 134 is pressed strongly against the intermediate transfer belt 12 in this manner is called a full nip state.

In contrast, in each of the first and second states, as shown in FIG. 9(B), the secondary transfer roll 134 is positioned at a location further away from the intermediate transfer belt 12 than the above-mentioned predetermined position.
More specifically, in each of the first and second states, the retraction mechanism 280 retracts the secondary transfer roll 134 from the intermediate transfer belt 12, creating a half-nip state in which the contact pressure between the intermediate transfer belt 12 and the secondary transfer roll 134 is small.

In the half nip state, the secondary transfer roll 134 is disposed in a state of contact with the intermediate transfer belt 12. In other words, compared to the full nip state, the secondary transfer roll 134 that has been retracted from the intermediate transfer belt 12 is disposed in a state of contact with the intermediate transfer belt 12.
In the present embodiment, in each of the first state and the second state, as described above, the secondary transfer roll 134 is disposed at a position retracted from the intermediate transfer belt 12. In the present embodiment, even when the secondary transfer roll 134 is disposed at a position retracted from the intermediate transfer belt 12, the secondary transfer roll 134 is disposed in a state of contact with the intermediate transfer belt 12.

In this embodiment, the value of the voltage applied by the voltage application device 250 in the first state is greater than the value of the voltage applied by the voltage application device 250 during transfer.
More specifically, in this embodiment, when an image on the intermediate transfer belt 12 is transferred to the paper P, a voltage of a predetermined value is applied between the intermediate transfer belt 12 and the secondary transfer roll 134. In this embodiment, the value of the voltage applied by the voltage application device 250 in the first state is greater than this predetermined value.

The processing performed by the control device 40 will now be described in further detail.
In this embodiment, as shown in FIGS. 3A and 3B, the first driving information and the second driving information are obtained.
When the first drive information and the second drive information are obtained, the drive condition setting unit 42 (see Figure 2) sets new drive conditions (PWM values) for the roll drive mechanism 300 based on the first drive information and the second drive information.
That is, the drive condition setting unit 42 (see Figure 2) sets new drive conditions (PWM values) for the roll drive mechanism 300 based on the first drive information obtained in a first state in which voltage is being applied by the application device 250 and the second drive information obtained in a second state in which voltage is not being applied by the application device 250.

To explain more specifically, in this embodiment, first, when in the first state shown in Figure 3 (A), the drive information acquisition unit 41 acquires information about the rotation speed of the roll drive mechanism 300 (rotation speed information) as an example of first drive information regarding the drive of the roll drive mechanism 300.
More specifically, the drive information acquisition unit 41 acquires information from the encoder and a signal from the roll motor MR, etc., and acquires information about the rotation speed of the rotating part of the roll drive mechanism 300 that rotates in conjunction with the secondary transfer roll 134.
In addition, the drive information acquisition unit 41 acquires information on the number of rotations of the roll drive mechanism 300 when the secondary transfer roll 134 rotates following the intermediate transfer belt 12 .

Next, in this process, the application of voltage by the application device 250 is stopped, and a second state (see FIG. 3B ) is entered in which no voltage is applied by the application device 250. In this second state, the contact pressure between the intermediate transfer belt 12 and the secondary transfer roll 134 is smaller than the contact pressure in the first state.
Then, in the second state (state where no voltage is applied), the drive information acquisition unit 41 acquires information (second drive information) about the rotation speed of the roll drive mechanism 300 while sequentially changing the PWM value (drive condition) of the roll motor MR.
In the second state, i.e., when the contact pressure between the intermediate transfer belt 12 and the secondary transfer roll 134 is small, the mutual influence between the secondary transfer roll 134 and the intermediate transfer belt 12 is small, and the secondary transfer roll 134 rotates independently without being influenced by the intermediate transfer belt 12.

Here, in this embodiment, the second driving information is acquired every time the PWM value (driving condition) changes, and ultimately, a plurality of pieces of second driving information are acquired.
In this embodiment, the PWM value and the second drive information obtained at this PWM value are stored in a storage device such as an HDD in a state where they are associated with each other.

Next, in this embodiment, the drive condition setting unit 42 sets the drive conditions of the roll drive mechanism 300 based on the first drive information (rotation speed information) obtained in the first state and the multiple pieces of second drive information (rotation speed information) obtained in the second state.
Specifically, in this example, the drive condition setting unit 42 sets the PWM value of the roll motor MR based on the first drive information and a plurality of pieces of second drive information.

More specifically, first, the drive condition setting unit 42 identifies, from the multiple obtained second drive information (rotation speed information), the second drive information (rotation speed information) that is closest to the first drive information (rotation speed information).
Then, the drive condition setting unit 42 acquires the drive condition (PWM value) when the specified second drive information is obtained. In other words, the drive condition setting unit 42 acquires the drive condition (PWM value) stored in the storage device in association with the specified second drive information.
Then, the drive condition setting unit 42 sets the final PWM value (drive condition) based on the acquired PWM value.

In this embodiment, the drive information acquisition unit 41 acquires information (first drive information) about the rotation speed of the roll drive mechanism 300 in the above-mentioned first state in which there is no slippage between the intermediate transfer belt 12 and the secondary transfer roll 134 and the secondary transfer roll 134 rotates in conjunction with the intermediate transfer belt 12.
In this embodiment, in the first state, the secondary transfer roll 134 is pressed against the intermediate transfer belt 12 by the electrostatic attraction force acting between the intermediate transfer belt 12 and the secondary transfer roll 134 .
In this case, slippage does not occur between the intermediate transfer belt 12 and the secondary transfer roll 134, and in this embodiment, the output of the belt motor MB (see Figure 1) is greater than the output of the roll motor MR, so that the secondary transfer roll 134 rotates in conjunction with the intermediate transfer belt 12.
In the first state, information on the rotation speed of the roll driving mechanism 300 when no slippage is occurring is obtained.

Furthermore, in a second state in which no voltage is applied by the application device 250, the drive information acquisition unit 41 drives the roll drive mechanism 300 under each of a plurality of mutually different conditions, acquires second drive information for each of the conditions, and acquires a plurality of second drive information.
In other words, in a second state in which the secondary transfer roll 134 does not follow the intermediate transfer belt 12, the roll driving mechanism 300 is driven with each of a plurality of different PWM values. Then, second driving information is obtained for each PWM value, and a plurality of pieces of second driving information are obtained.

In this way, the drive information acquisition unit 41 acquires, for each PWM value, the second drive information which is information about the rotation speed of the roll drive mechanism 300. In this way, the drive information acquisition unit 41 acquires a plurality of pieces of second drive information.
As described above, each of the multiple pieces of second drive information (rotation speed information) is stored in the storage device in association with the PWM value that was set when the second drive information was obtained.

Next, the drive condition setting unit 42 identifies second drive information (rotation speed information) that has a predetermined relationship with the first drive information (rotation speed information) from among the multiple acquired second drive information (from among the second drive information stored in the storage device).
More specifically, the drive condition setting unit 42 identifies, from among a plurality of second drive information (rotation speed information), second drive information whose difference from the value (rotation speed information) identified by the first drive information falls within a predetermined range.

Then, the drive condition setting unit 42 acquires the drive condition of the roll drive mechanism 300 when the specified second drive information is obtained. Specifically, the drive condition setting unit 42 acquires the PWM value stored in the storage device in association with the specified second drive information.
Then, the drive condition setting unit 42 sets the final drive condition (PWM value) of the roll drive mechanism 300 based on the acquired PWM value.

By the above process, the difference between the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 is reduced, and problems caused by this difference are less likely to occur. Specifically, the image formed on the paper P is prevented from shrinking or stretching.
In addition, by performing the above process, the secondary transfer roll 134 is prevented from rotating late relative to the intermediate transfer belt 12 , and the secondary transfer roll 134 is prevented from rotating relatively faster than the intermediate transfer belt 12 .

In other words, when the above processing is performed, new drive conditions for the roll drive mechanism 300 are set so that the difference between the value specified by the first drive information (rotation speed information) and the value specified by the second drive information (rotation speed information) is reduced.
In addition, even if a difference exists between the value identified by the first drive information (rotation speed information) and the value identified by the second drive information (rotation speed information) before the above processing is performed, this difference becomes smaller by performing the above processing.
This reduces the difference between the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134, making it difficult for problems to occur due to this difference.

In other words, before the above processing is performed, the fact that there is a difference between the value specified by the first driving information (rotation speed information) and the value specified by the second driving information (rotation speed information) means that the circumferential speed of the intermediate transfer belt 12 and the circumferential speed of the secondary transfer roll 134 are different.
When the processing of this embodiment is performed, the difference between the value specified by the first driving information (rotation speed information) and the value specified by the second driving information (rotation speed information) becomes smaller, and the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 become closer.

Here, in order to reduce the contact pressure between the secondary transfer roll 134 and the intermediate transfer belt 12 as in the second state described above, for example, it is possible to completely separate the secondary transfer roll 134 from the intermediate transfer belt 12.
In this case, however, when switching between the first state and the second state, it becomes necessary to move the secondary transfer roll 134 forward and backward with respect to the intermediate transfer belt 12, and this forward and backward movement may cause problems.
For example, the impact caused by the advancement and retreat of the device may cause toner to fly around, components to be easily damaged, the alignment between components may deviate from the original state, and processing may take longer.

In contrast, in this embodiment, there is no need to move the secondary transfer roll 134 back and forth to switch between the first state and the second state.
In other words, in this embodiment, switching between the first state and the second state is performed not by moving the secondary transfer roll 134 forward or backward, but by switching between application and non-application of a voltage.
As a result, in this case, the above-mentioned problems caused by the forward and backward movement of the secondary transfer roll 134 are less likely to occur.

In the above, the case where the voltage application by the application device 250 is stopped in the second state has been described.
However, the second state is not limited to this. In the second state, a voltage smaller than that in the first state may be applied.
Even when a voltage is applied in the second state, if the value is smaller than the voltage applied in the first state, the contact pressure between the intermediate transfer belt 12 and the secondary transfer roll 134 will be smaller than in the first state.

Here, the process for acquiring the first drive information (rotation speed information) will be described in detail.
In this embodiment, when obtaining the first driving information (rotation speed information) (see FIG. 3A), the driving conditions of the roll driving mechanism 300 are changed (the PWM value is changed) in a first state in which a voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134.
Then, information on the number of rotations of the roll driving mechanism 300 is obtained under each of a plurality of driving conditions having mutually different driving conditions (PWM values).

In this embodiment, the above-mentioned single piece of first drive information (rotation speed information) is obtained based on the multiple pieces of rotation speed information obtained.
In addition, in this embodiment, the first driving information is obtained based on the multiple pieces of rotation speed information obtained under the condition that the secondary transfer roll 134 rotates in association with the intermediate transfer belt 12 .

FIG. 4 is a diagram showing rotation speed information (rotation speed information for the roll drive mechanism 300) when the PWM value is changed in the first state in which a voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134.
In this embodiment, if the PWM value is set too large in the first state, slippage occurs between the intermediate transfer belt 12 and the secondary transfer roll 134, and the rotation speed of the roll driving mechanism 300 increases, as shown by reference symbol 4A in FIG.
Furthermore, in the first state, if the PWM value is set too small, slippage also occurs between the intermediate transfer belt 12 and the secondary transfer roll 134, and the rotation speed of the roll driving mechanism 300 decreases, as shown by reference symbol 4B.

Here, if the first drive information is acquired after setting the PWM value to a single fixed value rather than changing the PWM value as in this embodiment (for example, if the first drive information is acquired for a single fixed PWM value as indicated by reference symbol 4C), there is a risk that the rotation speed information of the value indicated by reference symbol 4D will be acquired as the first drive information.
In other words, in this case, the rotation speed information in a state where slippage occurs between the intermediate transfer belt 12 and the secondary transfer roll 134 is acquired as the first drive information.

For this reason, in this embodiment, as described above, the PWM value is changed to obtain multiple pieces of rotation speed information. Then, in this embodiment, the first drive information, which is the rotation speed information under conditions where no slippage is occurring, is obtained from among the multiple pieces of rotation speed information.

More specifically, in the example shown in FIG. 4, the number of rotations at a point indicated by reference symbol 4E is acquired as the first drive information.
In addition, in this embodiment, when the PWM value and the rotation speed information are plotted, a horizontal portion indicated by reference symbol 4F is generated, and the rotation speed information corresponding to this horizontal portion is acquired as the first drive information.

More specifically, when acquiring the first drive information, the rotation speed information that appears frequently is identified from the multiple pieces of rotation speed information obtained, and the first drive information is determined based on this rotation speed information that appears frequently.
In addition, when no slippage occurs, the frequency of occurrence of the rotation speed information increases within a specific range indicated by the reference symbol 4G.
In other words, when the frequency distribution of the rotation speed information is grasped as shown by reference symbol 4H, when no slippage is occurring, the frequency of the rotation speed information becomes large within a specific range as shown by reference symbol 4G.

In this embodiment, the first drive information is determined based on the rotation speed information that appears frequently.
More specifically, for example, a range in which the frequency (occurrence frequency) of rotation speed information is high is identified, and the average of a plurality of rotation speed information (rotation speeds) included in this range is determined as the first drive information.
It should be noted that the method for determining the first drive information is not limited to this, and for example, an average of all the rotation speed information may be determined as the first drive information.

In this embodiment, as described above, when the first drive information is acquired, the PWM value is changed. In other words, in this embodiment, when the first drive information is acquired, the rotation speed of the secondary transfer roll 134 is changed.
Here, when changing the rotation speed of the secondary transfer roll 134, there are two possible modes: driving the secondary transfer roll 134 so that the rotation speed gradually increases, and driving the secondary transfer roll 134 so that the rotation speed gradually decreases.
Of these two aspects, the more preferred aspect is to drive the secondary transfer roll 134 so that the rotation speed gradually increases.

In a mode in which the secondary transfer roll 134 is driven so that the rotation speed gradually decreases, the rotation speed is changed from a high rotation speed state to a low rotation speed state.
In this case, in the initial stage of changing the rotation speed, a driving force is applied from the secondary transfer roll 134 having a higher rotation speed to the intermediate transfer belt 12 , and the rotation speed of the intermediate transfer belt 12 may be increased by the secondary transfer roll 134 .

In this case, the rotation speed of the intermediate transfer belt 12 may exceed a predetermined allowable value, and the intermediate transfer belt 12 may be stopped by a stopping mechanism provided in the image forming apparatus 1 .
On the other hand, in a mode in which the secondary transfer roll 134 is driven so that the rotation speed gradually increases, the driving of the secondary transfer roll 134 starts from a state in which the rotation speed is low.
In this case, the intermediate transfer belt 12 is less likely to stop compared to when the driving of the secondary transfer roll 134 is started from a situation where the rotation speed is high.

In this embodiment, when acquiring the first driving information, the driving information acquisition unit 41 rotates the secondary transfer roll 134 under each of a plurality of driving conditions in which the rotation speed of the secondary transfer roll 134 differs from one another.
At this time, it is preferable to rotate the secondary transfer roll 134 so that the rotation speed of the secondary transfer roll 134 gradually increases.

In other words, in this embodiment, one piece of first drive information is obtained based on multiple pieces of rotation speed information, but when obtaining this multiple pieces of rotation speed information, it is preferable to drive the roll drive mechanism 300 so that the rotation speed of the secondary transfer roll 134 gradually increases, as described above.

Furthermore, in this embodiment, the driving information acquisition unit 41 gradually increases the PWM value in order to gradually increase the rotation speed of the secondary transfer roll 134 .
At this time, every time the PWM value is changed to another larger PWM value, the drive information acquisition unit 41 calculates and obtains the increase rate of the rotation speed of the secondary transfer roll 134. In other words, every time the PWM value is changed to another larger PWM value, the drive information acquisition unit 41 calculates and obtains the amount of change in the rotation speed of the secondary transfer roll 134.

When the amount of change exceeds a predetermined threshold value, the drive information acquisition unit 41 stops increasing the PWM value.
Then, the driving information acquisition unit 41 drives the roll driving mechanism 300 so that the rotation speed of the secondary transfer roll 134 gradually decreases thereafter.
Specifically, the driving information acquisition unit 41 gradually decreases the PWM value so that the rotation speed of the secondary transfer roll 134 gradually decreases.

Here, for example, when the PWM value is changed from the PWM value indicated by symbol 4K in Figure 4 to the PWM value indicated by symbol 4C, the rotation speed of the roll drive mechanism 300 increases rapidly, and the amount of change in the rotation speed of the roll drive mechanism 300 exceeds a predetermined threshold value.
In this case, the driving information acquisition unit 41 thereafter decreases the PWM value, and gradually decreases the rotation speed of the roll driving mechanism 300 .

Here, for example, if the PWM value is increased starting from the point indicated by the reference symbol 4K, the above-mentioned horizontal portion will hardly occur.
In contrast, if the PWM value is decreased halfway through as described above, it becomes possible to obtain rotation speed information even in the region indicated by reference symbol 4M. In addition, if the PWM value is decreased halfway through, it becomes possible to obtain a longer horizontal portion.

In addition, when changing the rotation speed of the secondary transfer roll 134, as described above, there is also a mode in which the secondary transfer roll 134 is initially driven so that the rotation speed gradually decreases.
In this case as well, the amount of change in the number of rotations of the roll driving mechanism 300 is calculated each time the PWM value is changed to a smaller PWM value.

When the amount of change exceeds a predetermined threshold, the drive information acquisition unit 41 stops decreasing the PWM value.
More specifically, if the PWM value is set to a smaller value, slippage may occur between the intermediate transfer belt 12 and the secondary transfer roll 134, causing the rotation speed of the roll drive mechanism 300 to decrease suddenly, resulting in a large amount of change.
In this case, the drive information acquisition unit 41 drives the roll drive mechanism 300 so that the rotation speed of the secondary transfer roll 134 gradually increases thereafter.

In this embodiment, when the first driving information is acquired, the PWM value is changed in sequence while maintaining the first state in which a voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134.
In addition, in this embodiment, when the first driving information is acquired, the driving conditions of the roll driving mechanism 300 are changed in sequence while maintaining the first state in which voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134.

In addition, in this embodiment, when driving the roll driving mechanism 300 under each of a plurality of mutually different conditions (when acquiring the first driving information), the driving information acquisition unit 41 sequentially changes the conditions.
At this time, in this embodiment, the first state in which a voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134 is maintained, and the conditions are changed in sequence.

Here, the change in conditions may be performed in such a manner that the application of voltage by the application device 250 is temporarily stopped, the conditions are changed, and then the application of voltage by the application device 250 is resumed.
In this case, the processing takes time. In contrast, in the present embodiment, when the conditions of the roll driving mechanism 300 are changed while the first state is maintained, the processing takes less time.

Furthermore, in this embodiment, if the value finally set as the driving condition by the driving condition setting unit 42 exceeds a predetermined specific value, the output unit 43 outputs information related to a malfunction of the image forming apparatus 1 .
Here, when the value set by the drive condition setting unit 42 is large and exceeds a predetermined specific value, it is assumed that, for example, the cleaning blade 180 (see FIG. 1) is turned over, and the load acting on the roll drive mechanism 300 is large. In other words, it is assumed that a malfunction has occurred in a part of the image forming apparatus 1.

Therefore, in this embodiment, if the value set by the driving condition setting unit 42 exceeds a predetermined specific value, it is determined that a malfunction has occurred in the device, and the output unit 43 outputs information regarding the malfunction of the image forming device 1.
This notifies the user of the occurrence of the malfunction. The information output from the output unit 43 may be displayed on an information display unit (not shown) provided in the image forming apparatus 1, or may be transmitted to the user by e-mail or the like.

FIG. 5 is a flowchart showing the flow of the above-described process.
In this embodiment, as described above, first, in the first state, the PWM value is changed and multiple pieces of rotation speed information are obtained (step S101).
Then, based on the plurality of pieces of rotation speed information, first driving information is obtained, which is rotation speed information under a condition where no slippage occurs between the intermediate transfer belt 12 and the secondary transfer roll 134 (step S102).
In this embodiment, the PWM value is changed in this way, but a single predetermined PWM value may be prepared and the first drive information may be acquired using this single PWM value. In other words, the single drive information obtained at this single PWM value may be acquired as the first drive information.

Next, the voltage application by the voltage application device 250 is stopped, and the state is changed from the first state to the second state (step S103). Then, in this second state, the PWM value is changed in sequence, and multiple pieces of second drive information are obtained (step S104).
Next, from among the plurality of second drive information, second drive information that satisfies a predetermined relationship with the first drive information is identified (step S105), and the PWM value when this second drive information is obtained is identified (the PWM value associated with the second drive information is identified) (step S106).

Next, based on the identified PWM value, the final PWM value is determined (step S107).
In this embodiment, when determining the final PWM value, a predetermined correction process is performed on the PWM value specified in step S106, and the PWM value after the correction process is set as the final PWM value.
More specifically, in this embodiment, correction processing is performed based on environmental information such as temperature and humidity and information such as the type of paper P being transported, and the PWM value after correction processing is set as the final PWM value.

Here, in this embodiment, for example, when the paper P is thick paper, the PWM value correction process is performed so that the PWM value is increased.
For example, if the paper P is thick paper, it may be difficult to transport the paper P, which may cause the image on the paper P to shrink. In contrast, as described above, if the PWM value correction process is performed so as to increase the PWM value, the paper P is more easily transported downstream, which suppresses the image from shrinking. The PWM value specified in step S106 may itself be determined as the final PWM value.

Here, in the above description, the first drive information is acquired first, and then the second drive information is acquired. However, the present invention is not limited to this, and the second drive information may be acquired first, and then the first drive information may be acquired.
As another processing mode, for example, the PWM value may not be changed, and the first drive information and the second drive information may be acquired under one PWM value, and the final PWM value may be set based on the first drive information and the second drive information.
In an aspect in which the first drive information and the second drive information are acquired under one PWM value, if the second drive information is smaller than the first drive information, the PWM value is increased, and if the second drive information is larger than the first drive information, the PWM value is decreased.

6A and 6B are diagrams illustrating another example of the process performed by the image forming apparatus 1. In FIG.
In this process, the drive information acquisition unit 41 acquires the current value of the belt motor MB provided in the belt drive mechanism 200 (the current value of the current supplied to the belt motor MB) as the first drive information and the second drive information.
In other words, in this process, information on the load acting on the intermediate transfer belt 12 from the secondary transfer roll 134 is acquired as the first driving information and the second driving information.

More specifically, in this processing example, the drive information acquisition unit 41 first drives the roll drive mechanism 300 under each of a plurality of different conditions in a first state (voltage applied state) as shown in Figure 6 (A), and acquires the first drive information (current value of the belt motor MB) for each of the conditions.
As a result, the drive information acquisition unit 41 acquires a plurality of pieces of first drive information.

More specifically, in a first state, the drive information acquisition unit 41 drives the roll motor MR with each of a plurality of different PWM values, and acquires first drive information (current value of the belt motor MB) for each of the different PWM values.
As a result, the driving information acquisition unit 41 acquires a plurality of pieces of first driving information (current values of the belt motor MB).

In this embodiment, when the PWM value is small, the secondary transfer roll 134 applies a load to the intermediate transfer belt 12, and the first driving information (current value of the belt motor MB) becomes large.
On the other hand, when the PWM value is large, a driving force is supplied from the secondary transfer roll 134 to the intermediate transfer belt 12, and the first driving information (current value of the belt motor MB) becomes small.

Furthermore, the drive information acquisition unit 41 stops the application of voltage by the application device 250, and acquires second drive information which is drive information in the second state, as shown in FIG. 6(B).
More specifically, after the application of voltage by the voltage application device 250 is stopped, the drive information acquisition unit 41 acquires a current value from the belt motor MB, and acquires this current value as the second drive information.

Then, the drive condition setting unit 42 sets the drive conditions (PWM values) of the roll drive mechanism 300 based on the acquired multiple pieces of first drive information (current values) and second drive information (current values).
More specifically, the drive condition setting unit 42 identifies, from among the multiple acquired first drive information (current values), the first drive information (current value) that has a predetermined relationship with the second drive information (current value).

More specifically, the drive condition setting unit 42 identifies, from among the multiple acquired first drive information (current values), a first drive information whose difference from the value (current value) identified by the second drive information falls within a predetermined range.
Then, the drive condition setting unit 42 specifies the drive condition (PWM value) of the roll drive mechanism 300 when this specified first drive information (current value) is obtained.

In other words, the drive condition setting unit 42 identifies the drive condition (PWM value) of the roll drive mechanism 300 that is stored in the storage device in association with the identified first drive information (current value).
Then, the drive condition setting unit 42 sets the final drive conditions (PWM values) of the roll drive mechanism 300 based on the identified drive conditions, in the same manner as described above.

Here, when the circumferential speed of the intermediate transfer belt 12 and the circumferential speed of the secondary transfer roll 134 are equal, the current value of the belt motor MB does not change between a first state in which voltage is applied by the application device 250 and a second state in which voltage is not applied by the application device 250.
Conversely, when the current value of the belt motor MB is different between the first state and the second state, the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 are different.

In this process, the difference between the current value of the belt motor MB obtained in the first state and the current value of the belt motor MB obtained in the second state becomes smaller, and the difference between the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 becomes smaller.
In addition, even if there is a difference between the value specified by the first driving information (current value) and the value specified by the second driving information (current value) before performing this processing, this difference will be reduced by performing this processing.

In this process, the case where the current value of the belt motor MB is acquired as the first drive information and the second drive information (as information related to the load acting on the intermediate transfer belt 12) has been described as an example.
However, the information regarding the load acting on the intermediate transfer belt 12 is not limited to this, and for example, the driving torque of the belt driving mechanism 200 may be measured and information on this driving torque may be obtained as the first driving information and the second driving information.
In this case, too, by reducing the difference between the driving torque obtained as the first driving information and the driving torque obtained as the second driving information, the difference between the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 is reduced.

In this process, as in the above, when the multiple pieces of first driving information are acquired, the multiple pieces of first driving information are acquired while maintaining the first state in which a voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134.
In other words, while the first state in which a voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134 is maintained, the condition (PWM value) is changed in sequence.
In this embodiment, when driving the roll driving mechanism 300 under each of a plurality of mutually different conditions, the conditions are changed in sequence, and when changing the conditions, the first state is maintained while the conditions are changed in sequence.

Also, as described above, when changing the rotation speed of the secondary transfer roll 134 in the first state, it is preferable to drive the roll drive mechanism 300 so that the rotation speed of the secondary transfer roll 134 gradually increases.

Also, as described above, if the change in current value when the rotation speed of the secondary transfer roll 134 is increased to another rotation speed exceeds a predetermined threshold value, it is preferable to drive the roll driving mechanism 300 so that the rotation speed of the secondary transfer roll 134 gradually decreases thereafter.
In addition, if the rotation speed of the secondary transfer roll 134 is increased and becomes excessive, slippage occurs between the intermediate transfer belt 12 and the secondary transfer roll 134, the load acting on the intermediate transfer belt 12 decreases rapidly, and the current value decreases significantly.
In this case, it is preferable to drive the roll driving mechanism 300 thereafter so that the rotation speed of the secondary transfer roll 134 gradually decreases.

Also, as described above, when changing the rotation speed of the secondary transfer roll 134, the secondary transfer roll 134 may first be driven so that the rotation speed gradually decreases. In this case, too, the amount of change in the current value is calculated each time the PWM value is changed to a smaller PWM value.
In this case, if the change in the current value when the rotation speed of the secondary transfer roll 134 is reduced to another rotation speed exceeds a predetermined threshold value, the roll drive mechanism 300 is driven thereafter so that the rotation speed of the secondary transfer roll 134 gradually increases.

When the rotation speed of the secondary transfer roll 134 is reduced, slippage occurs between the intermediate transfer belt 12 and the secondary transfer roll 134, the load acting on the intermediate transfer belt 12 decreases rapidly, and the current value decreases significantly.
In this case, thereafter, the roll driving mechanism 300 is driven so that the rotation speed of the secondary transfer roll 134 gradually increases.
Furthermore, similarly to the above, when the value set as the driving condition by the driving condition setting unit 42 exceeds a predetermined specific value, it is preferable to output information regarding a malfunction of the image forming apparatus 1 .

Also, similarly to the above, the PWM value may not be changed, and the first drive information (current value) and the second drive information (current value) may be obtained under one PWM value.
Then, a new PWM value may be set based on the first drive information and the second drive information obtained under this one PWM value.

In a mode in which first drive information and second drive information are acquired under one PWM value, if the first drive information (current value) is greater than the second drive information (current value), the PWM value is increased. Also, if the first drive information is smaller than the second drive information, the PWM value is decreased.

7A and 7B are diagrams illustrating another example of the process performed by the image forming apparatus 1 of the present embodiment.
In this process, the drive information acquisition unit 41 acquires, as the first drive information and the second drive information, the drive torque of the roll drive mechanism 300. In other words, in this process, information on the load acting on the roll drive mechanism 300 is acquired.

Specifically, in this process, the drive information acquisition unit 41 drives the roll drive mechanism 300 under a plurality of different conditions in the first state (voltage applied state) shown in Fig. 7A, and acquires the first drive information (drive torque) for each condition. In this way, the drive information acquisition unit 41 acquires a plurality of pieces of first drive information.
In other words, the drive information acquisition unit 41 drives the roll drive mechanism 300 with each of a plurality of different PWM values, acquires the first drive information (drive torque) for each PWM value, and obtains a plurality of pieces of first drive information.

In this embodiment, when the PWM value is increased, a load is applied from the intermediate transfer belt 12 to the roll driving mechanism 300 as a reaction, and the driving torque increases.
On the other hand, when the PWM value is decreased, the driving force from the intermediate transfer belt 12 that is rotated at a constant speed is supplied to the roll driving mechanism 300, and the driving torque is reduced.

Furthermore, in this process, the drive information acquisition unit 41 stops the application of voltage by the application device 250, and sets the state to the second state as shown in FIG. 7(B).
Then, in this second state, the driving information acquisition unit 41 acquires the driving torque in the roll driving mechanism 300 as second driving information.

When obtaining the second drive information, the PWM value may or may not be changed.
In the second state in which the voltage application by the voltage application device 250 is stopped, the load acting on the roll driving mechanism 300 is constant and does not change. In other words, in the second state in which the voltage application by the voltage application device 250 is stopped, the roll driving mechanism 300 is in an idling state, and the load acting on the roll driving mechanism 300 is constant.
Therefore, whether the PWM value is changed or not, the driving torque in the roll driving mechanism 300 (the driving torque obtained as the second driving information) remains constant (does not change).

Thereafter, in this embodiment, the drive condition setting unit 42 sets new drive conditions (PWM values) for the roll drive mechanism 300 based on the multiple acquired first drive information (drive torque) and second drive information (drive torque).
Specifically, the drive condition setting unit 42 identifies, from among the multiple acquired first drive information, a piece of first drive information that has a predetermined relationship with the second drive information.

Specifically, the driving condition setting unit 42 identifies, from among the multiple acquired first driving information (driving torque), the first driving information (driving torque) whose difference from the value (driving torque) identified by the second driving information falls within a predetermined range.
Then, the drive condition setting unit 42 specifies the drive conditions (PWM values) when the specified first drive information is obtained, and sets new drive conditions (PWM values) for the roll drive mechanism 300 based on the specified drive conditions (PWM values).

Here, when the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 are equal, the driving torque of the roll driving mechanism 300 does not change between a first state in which voltage is applied by the application device 250 and a second state in which voltage is not applied by the application device 250.
For this reason, when the driving torque is different between the first state and the second state, it can be said that the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 are different.

In this process, the difference between the driving torque obtained in the first state and the driving torque obtained in the second state becomes smaller, and the difference between the peripheral speed of the intermediate transfer belt 12 and the peripheral speed of the secondary transfer roll 134 becomes smaller.
In other words, even if a difference exists between the value specified by the first driving information (driving torque) and the value specified by the second driving information (driving torque) before performing this processing, this difference will be reduced by performing this processing.

In this process, similarly to the above, when the multiple pieces of first driving information (driving torque) are acquired, the multiple pieces of first driving information are acquired while maintaining the first state in which voltage is applied by the application device 250.
In other words, while the first state in which a voltage is applied between the intermediate transfer belt 12 and the secondary transfer roll 134 is maintained, the conditions are changed in sequence.
In this embodiment, when driving the roll driving mechanism 300 under each of a plurality of mutually different conditions, the conditions are changed in sequence, and when changing the conditions, the first state is maintained while the conditions are changed in sequence.

Also, as described above, when changing the rotation speed of the secondary transfer roll 134 (when changing the PWM value) in the first state, it is preferable to drive the roll drive mechanism 300 so that the rotation speed of the secondary transfer roll 134 gradually increases.

Also, as described above, if the change in drive torque when the rotation speed of the secondary transfer roll 134 is increased to another rotation speed exceeds a threshold value, it is preferable to drive the roll drive mechanism 300 thereafter so that the rotation speed of the secondary transfer roll 134 gradually decreases.
If the rotation speed of the secondary transfer roll 134 is increased and becomes excessively high, slippage occurs between the intermediate transfer belt 12 and the secondary transfer roll 134, the load acting on the secondary transfer roll 134 decreases rapidly, and the drive torque decreases significantly.
In this case, thereafter, the roll driving mechanism 300 is driven so that the rotation speed of the secondary transfer roll 134 gradually decreases.

In addition, when changing the rotation speed of the secondary transfer roll 134, the secondary transfer roll 134 may first be driven so that the rotation speed gradually decreases. In this case, too, the change in the drive torque is calculated each time the PWM value is changed to a smaller PWM value.
In this case too, if the change in drive torque when the rotation speed of the secondary transfer roll 134 is reduced to another rotation speed exceeds a predetermined threshold value, the roll drive mechanism 300 is driven thereafter so that the rotation speed of the secondary transfer roll 134 gradually increases.

When the rotation speed of the secondary transfer roll 134 is reduced, slippage occurs between the intermediate transfer belt 12 and the secondary transfer roll 134, the load acting on the secondary transfer roll 134 increases, and the drive torque increases.
In addition, since the driving force is no longer supplied from the intermediate transfer belt 12 to the secondary transfer roll 134, the driving torque increases.

In this case, thereafter, the roll driving mechanism 300 is driven so that the rotation speed of the secondary transfer roll 134 gradually increases.
Furthermore, similarly to the above, when the value (PWM value) set as the driving condition by the driving condition setting unit 42 exceeds a specific value, it is preferable to output information regarding a malfunction of the image forming apparatus 1 .

Also, similarly to the above, the PWM value may not be changed, and the first drive information (drive torque) and the second drive information (drive torque) may be obtained under one PWM value.
Then, a new PWM value may be set based on the first drive information and the second drive information.

In a mode in which the first drive information and the second drive information are acquired under one PWM value, if the first drive information (drive torque) is greater than the second drive information (drive torque), the PWM value is decreased, and if the first drive information (drive torque) is smaller than the second drive information (drive torque), the PWM value is increased.
In addition, in this process, a case has been described in which the driving torque is acquired as the first driving information and the second driving information, but in addition to this, for example, the current value of the roll motor MR may be acquired as the first driving information and the second driving information.

(others)
In the above, a case where the PWM value of the roll motor MR is set in setting the drive conditions of the roll drive mechanism 300 has been described as an example.
Incidentally, the setting of the drive conditions of the roll drive mechanism 300 is not limited to the setting of the PWM value, and other elements may be set as long as the rotation speed of the secondary transfer roll 134 can be changed.
For example, if the roll driving mechanism 300 has a mechanism (mechanism such as a brake) for reducing the number of rotations of the secondary transfer roll 134, settings for this mechanism may be performed.

In the above, the process in the image forming apparatus 1 provided with the intermediate transfer belt 12 has been described, but this is merely an example.
In addition, the above-described processes can also be performed in an image forming apparatus that does not have an intermediate transfer belt 12 and has a photosensitive drum as an image carrier and a transfer member arranged opposite the photosensitive drum.

In the above description, when the rotation speed information of the roll driving mechanism 300 is acquired as the first driving information (see FIG. 3A), the PWM value is changed to acquire the first driving information. In this case, the first driving information can be acquired with high accuracy.
However, this is not limited to this (changing the PWM value is not essential), and if the conditions (PWM value) under which no slippage occurs are known in advance, the first drive information may be acquired under these known conditions (one specific PWM value).

When obtaining the driving torque in the roll driving mechanism 300 as the second driving information (see FIG. 7B), the PWM value may or may not be changed as described above.
When the drive torque (second drive information) is acquired without changing the PWM value, a specific PWM value is used, such as the center value of the PWM values acquired in advance during design. When the drive torque (second drive information) is acquired by changing the PWM value, the second drive information can be acquired more accurately.

1...image forming device, 12...intermediate transfer belt, 41...driving information acquisition unit, 42...driving condition setting unit, 134...secondary transfer roll, 200...belt driving mechanism, 300...roll driving mechanism

Claims (10)

an image carrier that is rotatably provided and that carries an image to be transferred to a recording material;
a holder driving means for rotating the image holder;
a transfer member that is rotatably provided and is used for transferring the image on the image carrier to a recording material;
a transfer member driving means for driving the transfer member to rotate;
an application means for applying a voltage between the image carrier and the transfer member;
A processor;
Equipped with
The processor,
obtaining driving information which is information regarding driving of at least one of the holder driving means and the transfer member driving means;
setting a driving condition for the transfer member driving means based on first driving information, which is the driving information in a first state in which a voltage is applied by the application means, and second driving information, which is the driving information in a second state in which the application means is not applying a voltage or is applying an applied voltage that is smaller than the applied voltage in the first state ;
An image forming apparatus ,
When the image on the image carrier is transferred to a recording material, the transfer member is disposed at a predetermined location,
the transfer member is disposed at a position retreated from the image carrier relative to the predetermined position when in each of the first state and the second state;
Image forming device . 2. The image forming apparatus according to claim 1 , wherein the transfer member disposed at the retreated position is disposed in a state of contact with the image carrier. When the image on the image carrier is transferred to the recording material, a voltage of a predetermined value is applied between the image carrier and the transfer member,
2. The image forming apparatus according to claim 1 , wherein a value of the voltage applied by said applying means when said applying means is in said first state is greater than said predetermined value. The processor,
4. An image forming apparatus according to claim 1, wherein a driving condition of the transfer member driving means is set so that a difference between a value specified by the first driving information and a value specified by the second driving information is small. The processor,
driving the transfer member driving means under each of a plurality of conditions different from each other, and acquiring the second driving information for each of the conditions, thereby acquiring a plurality of pieces of the second driving information;
5. An image forming apparatus according to claim 1, wherein the driving conditions of the transfer member driving means are set based on the conditions when second driving information having a predetermined relationship with the first driving information is obtained from among the multiple acquired second driving information. The processor,
The image forming apparatus according to claim 5, wherein the driving conditions of the transfer member driving means are set based on the conditions when second driving information is obtained, among the multiple acquired second driving information, whose difference from a value specified by the first driving information falls within a predetermined range. The processor,
driving the transfer member driving means under each of a plurality of conditions different from each other, and acquiring the first driving information for each of the conditions, thereby acquiring a plurality of pieces of the first driving information;
7. An image forming apparatus according to claim 1, wherein the driving conditions of the transfer member driving means are set based on the conditions when first driving information having a predetermined relationship with the second driving information is obtained from among the multiple acquired first driving information. The processor,
8. The image forming apparatus according to claim 7, wherein the driving conditions of the transfer member driving means are set based on the conditions when first driving information is obtained, among the multiple acquired first driving information, whose difference from a value specified by the second driving information falls within a predetermined range. The processor,
When driving the transfer member driving means under each of the plurality of conditions different from each other, the conditions are changed in sequence;
8. The image forming apparatus according to claim 7 , wherein the conditions are changed in sequence while maintaining the first state in which a voltage is applied between the image carrier and the transfer member. The processor,
10. The image forming apparatus according to claim 1 , wherein when a value specified by the set driving condition exceeds a predetermined value, information relating to a failure of the image forming apparatus is output.

Images