Image formation device

Abstract

To suppress a variation in transfer positions where images are transferred to a transfer medium.SOLUTION: An image formation device comprises: an annular transfer belt on an outer peripheral surface of which an image formed on a forming body is transferred; a drive roll around which the transfer belt is wound so as to rotate the transfer belt; a transfer body that transfers the image to a recording medium from the transfer belt in a transfer area between itself and the transfer belt while conveying the recording medium; a drive mechanism that rotates and drives the transfer body; a holding part that holds the recording medium and integrally moves with rotational movement of the transfer body to make the recording medium pass through the transfer area; and a speed adjustment mechanism that adjusts the rotational speed of the transfer body driven by the drive mechanism in a cycle unit, the speed adjustment mechanism performing switching between a first adjustment pattern and a second adjustment pattern different from the first adjustment pattern in a cycle unit, and synchronizing the switch timing with a holding start timing when the holding part starts holding the recording medium.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses a transfer device having a belt-shaped image carrier that carries an image, a drive roller that moves the image carrier carrying the image while wrapping it around, a first tension roller that wraps the image carrier moved by the drive roller and applies tension to the image carrier, a first elastic support part that has a first elastic member that generates the tension and supports one side of the rotation shaft of the first tension roller, a second elastic support part that has a second elastic member that generates the tension and supports the other side of the rotation shaft of the first tension roller, a backup roller that wraps the image carrier wrapped around the tension roller, a transfer roller that has a recess on its peripheral surface and comes into contact with the image carrier wrapped around the backup roller to form a transfer nip, and a second tension roller that wraps the image carrier wrapped around the backup roller and applies tension to the image carrier. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-220812 A Summary of the Invention [Problem to be solved by the invention]

[0004] As an image forming device, an image forming apparatus that includes a circular transfer belt on whose outer surface an image formed on a forming body is transferred, a drive roll around which the transfer belt is wound and which rotates the transfer belt, a transfer body that transfers the image from the transfer belt to the recording medium in a transfer area between the transfer belt and the recording medium while transporting the recording medium, a drive mechanism that drives and rotates the transfer body, a holding section that holds the recording medium and moves integrally with the rotational movement of the transfer body to pass the recording medium through the transfer area, and a speed adjustment mechanism that adjusts the rotation speed of the transfer body by the drive mechanism in units of one revolution of the transfer body, and the speed adjustment mechanism switches between a first adjustment pattern and a second adjustment pattern having a speed profile different from that of the first adjustment pattern in units of one revolution of the transfer body.

[0005] In this image forming device, when the speed adjustment mechanism switches between the first adjustment pattern and the second adjustment pattern regardless of the timing at which the holding section starts holding the recording medium, the holding position at which the holding section holds the recording medium varies, and as a result, the transfer position at which the image is transferred to the recording medium may vary.

[0006] The present disclosure aims to suppress variation in the transfer position at which an image is transferred to a recording medium, compared to a case in which a speed adjustment mechanism switches between a first adjustment pattern and a second adjustment pattern, regardless of the holding start timing at which the holding portion starts holding the recording medium. [Means for solving the problem]

[0007] A first aspect includes a circular transfer belt on whose outer peripheral surface an image formed on a forming body is transferred, a drive roll around which the transfer belt is wound and which rotates the transfer belt, a transfer body that transfers the image from the transfer belt to the recording medium in a transfer area between the transfer belt and the recording medium while transporting the recording medium, a drive mechanism that drives and rotates the transfer body, a holding section that holds the recording medium and moves integrally with the rotational movement of the transfer body to pass the recording medium through the transfer area, and a speed adjustment mechanism that adjusts the rotation speed of the transfer body by the drive mechanism in units of one revolution of the transfer body, the speed adjustment mechanism switching between a first adjustment pattern and a second adjustment pattern different from the first adjustment pattern in units of one revolution of the transfer body, and synchronizing the switching timing with the holding start timing at which the holding section starts holding the recording medium.

[0008] A second aspect of the present invention is a recording medium transfer device according to the first aspect, comprising a rotating body that rotates in synchronization with the rotation of the transfer body, a detection unit that detects a predetermined rotational position of the rotating body, and a sending unit that sends out a recording medium toward the holding unit based on the detection timing at which the detection unit detects the rotational position, wherein the holding unit holds the recording medium sent out from the sending unit and moves integrally with the rotational movement of the transfer body to pass the recording medium through the transfer area, and the speed adjustment mechanism synchronizes the switching timing with the detection timing.

[0009] In a third aspect, in the first aspect, the first adjustment pattern is a pattern that adjusts the rotational speed of the transfer body during a revolution that includes a state in which the transfer body is not transporting the recording medium, and the second adjustment pattern is a pattern that adjusts the rotational speed of the transfer body during a revolution that includes a state in which the transfer body is transporting the recording medium.

[0010] In a fourth aspect, in the third aspect, the transfer body has a recess on its outer surface capable of accommodating the holding portion, and the second adjustment pattern is such that the average value of the rotational speed of the transfer body when a portion of the transfer body other than the recess passes through the transfer area is different from the average value in the first adjustment pattern.

[0011] In a fifth aspect, in the first aspect, the speed adjustment mechanism is capable of changing the speed profile while maintaining the average value of the rotational speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern during the rotation of the transfer belt.

[0012] In a sixth aspect, in the fifth aspect, when the speed adjustment mechanism changes the speed profile while maintaining the average value of the rotational speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern during the rotation of the transfer belt, the holding section holds the recording medium at the same holding start timing as before the change.

[0013] In a seventh aspect, in the fifth aspect, when the speed adjustment mechanism changes the speed profile while maintaining the average value of the rotational speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern during the rotation of the transfer belt, the sending section sends out the recording medium at the same sending timing as before the change. Effect of the Invention

[0014] According to the configuration of the first aspect, regardless of the holding start timing at which the holding portion starts holding the recording medium, variation in the transfer position at which the image is transferred to the recording medium is suppressed compared to when the speed adjustment mechanism switches between the first adjustment pattern and the second adjustment pattern.

[0015] According to the configuration of the second aspect, regardless of the detection timing at which the detection unit detects the rotational position, variation in the transfer position at which the image is transferred to the recording medium is suppressed compared to when the speed adjustment mechanism switches between the first adjustment pattern and the second adjustment pattern.

[0016] According to the configuration of the third aspect, compared to when the first adjustment pattern and the second adjustment pattern are patterns that adjust the rotational speed of the transfer body during a revolution that includes a state in which the transfer body is transporting the recording medium, it is possible to adjust the rotational speed of the transfer body to an appropriate rotational speed when the transfer body is transporting the recording medium and to an appropriate rotational speed when the transfer body is not transporting the recording medium.

[0017] According to the configuration of the fourth aspect, it is possible to reduce the torque fluctuation of the drive roll compared to when the average value of the rotational speed of the transfer body in the second adjustment pattern when parts other than the recesses of the transfer body pass through the transfer area is the same as the average value in the first adjustment pattern.

[0018] According to the configuration of the fifth aspect, the rotation speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern can be changed in response to the torque fluctuation of the drive roll while the transfer belt is rotating.

[0019] According to the configuration of the sixth aspect, it is not necessary to control the holding start timing of the holding unit.

[0020] According to the configuration of the seventh aspect, it becomes unnecessary to control the sending timing of the sending section. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing a configuration around a transfer cylinder according to the embodiment. [Diagram 3] FIG. 2 is a perspective view showing a configuration around a fixing cylinder according to the embodiment. [Figure 4] FIG. 2 is a perspective view showing the configuration of a pair of sprockets according to the embodiment of the present invention. [Diagram 5] FIG. 2 is a perspective view showing a gripper according to the embodiment. [Figure 6] 2 is a block diagram showing a hardware configuration of a control device according to the embodiment. FIG. [Figure 7]FIG. 2 is a block diagram showing an example of a functional configuration of a control device according to the present embodiment. [Figure 8] 5A and 5B are diagrams illustrating a first adjustment pattern and a second adjustment pattern according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. <Image forming apparatus 10> First, a description will be given of the configuration of an image forming apparatus 10 according to this embodiment. Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 10 according to this embodiment.

[0023] In addition, the arrow UP shown in the figure indicates the top of the device (vertically upward), and the arrow DO indicates the bottom of the device (vertically downward). In addition, the arrow LH shown in the figure indicates the left side of the device, and the arrow RH indicates the right side of the device. In addition, the arrow FR shown in the figure indicates the front of the device, and the arrow RR indicates the rear of the device. These directions are determined for the convenience of explanation, and the device configuration is not limited to these directions. In addition, the word "device" may be omitted in each direction of the device. That is, for example, "above the device" may be simply indicated as "upper". In addition, the front-rear direction corresponds to the axial direction of the sprocket 75 described later, and may also be referred to as the lateral direction or horizontal direction. In addition, the up-down direction, the left-right direction, and the front-rear direction are directions that intersect with each other (specifically, directions that are perpendicular to each other).

[0024] In addition, the symbol "x" inside a "circle" in the figure means an arrow pointing from the front to the back of the page. In addition, the symbol "·" inside a "circle" in the figure means an arrow pointing from the back to the front of the page.

[0025] 1 is an electrophotographic image forming apparatus that forms a toner image (an example of an image) on a recording medium P. Specifically, the image forming apparatus 10 includes a medium storage section 12, a sending section 13, an image forming section 14, a transport mechanism 16, a first rotational position sensor 91, a second rotational position sensor 92, and a control device 40. Below, each section of the image forming apparatus 10 (the medium storage section 12, the sending section 13, the image forming section 14, the transport mechanism 16, the first rotational position sensor 91, the second rotational position sensor 92, and the control device 40) will be described.

[0026] <Medium storage section 12> The medium container 12 is a component that contains the recording medium P in the image forming apparatus 10. The recording medium P contained in the medium container 12 is sent out to the transport mechanism 16 by the sending section 13.

[0027] For example, paper is used as the recording medium P. Note that the recording medium P is not limited to paper and may be, for example, a film or the like, as long as it is a medium on which an image can be formed.

[0028] <Transmission section 13> The sending unit 13 is a component that sends out the recording medium P accommodated in the medium accommodation unit 12. Specifically, the sending unit 13 has a sending member 13A that sends out the recording medium P toward a gripper 24 (described later) of the transport mechanism 16 at a predetermined sending timing.

[0029] The delivery member 13A is configured, for example, with a transport roll (so-called registration roll) that transports the recording medium P delivered from the medium container 12 at a predetermined delivery timing.

[0030] <Image forming unit 14> 1 is a component that forms an image on a recording medium P. Specifically, the image forming unit 14 includes a toner image forming unit 30, a transfer device 60, and a fixing device 15, as shown in FIG.

[0031] <Toner image forming unit 30> The toner image forming unit 30 shown in Fig. 1 is a component that forms a toner image. A plurality of toner image forming units 30 are provided so as to form a toner image for each color. In this embodiment, toner image forming units 30 for a total of four colors, yellow (Y), magenta (M), cyan (C), and black (K), are provided. (Y), (M), (C), and (K) shown in Fig. 1 indicate components corresponding to the above-mentioned respective colors.

[0032] In addition, since the toner image forming units 30 of each color are configured in the same manner except for the toner used, in FIG. 1, the respective parts of the toner image forming unit 30(M) are denoted by reference numerals as a representative of the toner image forming units 30 of each color.

[0033] Specifically, each color toner image forming unit 30 has a photoconductor 32 that rotates in one direction (for example, counterclockwise in FIG. 1). Each color toner image forming unit 30 also has a charger 31, an exposure device 36, and a developing device 38. The photoconductor 32 is an example of a forming body. The exposure device 36 is an example of a writing unit.

[0034] In the toner image forming section 30 for each color, the charger 31 charges the photoconductor 32 (charging step). Furthermore, the exposure device 36 exposes the photoconductor 32 charged by the charger 31 to light, forming an electrostatic latent image on the photoconductor 32 (exposure step). Specifically, the exposure device 36 exposes the photoconductor 32 to light at a predetermined writing timing, thereby writing an electrostatic latent image on the photoconductor 32. Furthermore, the development device 38 develops the electrostatic latent image formed on the photoconductor 32 by the exposure device 36 to form a toner image (developing step).

[0035] In this manner, a toner image is formed by developing the electrostatic latent image on the photoconductor 32. The electrostatic latent image is an example of a latent image, and the toner image is an example of an image.

[0036] In this embodiment, when forming a toner image in a total of four colors, namely yellow (Y), magenta (M), cyan (C), and black (K), the processes of charging, exposure, development, and the primary transfer described below are carried out in the order of toner image forming unit 30(Y), toner image forming unit 30(M), toner image forming unit 30(C), and toner image forming unit 30(K).

[0037] <Transfer device 60> The transfer device 60 shown in Fig. 1 is a device that transfers the toner images formed in the toner image forming units 30 of each color onto a recording medium P. Specifically, the transfer device 60 performs primary transfer of the toner images of the photoconductors 32 of each color onto a transfer belt 62 serving as an intermediate transfer body, and performs secondary transfer of the superposed toner images onto the recording medium P. As shown in Fig. 1, the transfer device 60 includes an annular transfer belt 62, a plurality of primary transfer rolls 35, and a transfer cylinder 70. The transfer cylinder 70 is an example of a transfer body.

[0038] The primary transfer roll 35 is provided for each toner image forming unit 30, and is a roll that transfers the toner image of the photoconductor 32 of each color to the transfer belt 62 in a primary transfer region T1 between the photoconductor 32 and the primary transfer roll 35. In this embodiment, a primary transfer electric field is applied between the primary transfer roll 35 and the photoconductor 32, so that the toner image formed on the photoconductor 32 is transferred to the transfer belt 62 in the primary transfer region T1.

[0039] The toner image is transferred from the photoconductor 32 of each color to the outer peripheral surface of the transfer belt 62. As shown in Fig. 1, the transfer belt 62 is endless and is wound around a plurality of rolls 64 including a driving roll 64D and an opposing roll 65 so as to assume a substantially inverted triangular posture when viewed from the front. The driving roll 64D is rotated by a driving unit 67 constituted by a driving motor and the like, thereby rotating the transfer belt 62 in the direction of arrow A.

[0040] The transfer cylinder 70 has a function of transferring the toner image transferred to the transfer belt 62 onto a recording medium P. As shown in Figures 1 and 2, this transfer cylinder 70 (specifically, a cylinder main body 72 described below) has a recess 71 formed on an outer circumferential surface 70A, and rotates in a rotation direction B (the direction of arrow B). The recess 71 is elongated along the axial direction of the transfer cylinder 70, and has a depth along the radial direction of the transfer cylinder 70.

[0041] 1, the transfer cylinder 70 is disposed diagonally downward to the left of the transfer belt 62 so as to face the transfer belt 62. Furthermore, the transfer cylinder 70 contacts the transfer belt 62 in the range of the outer peripheral surface 70A from the upstream end to the downstream end of the recess 71 in the rotation direction, and is not in contact with the transfer belt 62 at the recess 71.

[0042] 2, the transfer cylinder 70 is provided with a pair of sprockets 75 on both axial ends. Specifically, the transfer cylinder 70 is configured to have a substantially cylindrical cylinder main body 72 and a pair of sprockets 75 provided on both axial ends of the cylinder main body 72. The pair of sprockets 75 are arranged coaxially on the cylinder main body 72.

[0043] In the transfer device 60, a drive mechanism 79 (see FIG. 1) composed of a drive motor and the like drives and rotates the transfer cylinder 70. In the transfer cylinder 70, the cylinder main body 72 is driven to rotate by the drive mechanism 79 and rotates in a rotational direction B, so that the cylinder main body 72 and the pair of sprockets 75 rotate integrally in the rotational direction B.

[0044] In this embodiment, the transfer belt 62 and the transfer cylinder 70 (specifically, the cylinder main body 72) convey the recording medium P conveyed by the conveying mechanism 16 (specifically, the gripper 24 described below) by rotating while sandwiching the recording medium P in the secondary transfer region T2. ​​Then, the transfer cylinder 70 transfers the toner image transferred to the transfer belt 62 to the recording medium P in the secondary transfer region T2 by applying a secondary transfer electric field between the opposing roll 65 and the transfer cylinder 70. In this way, the transfer cylinder 70 transfers the toner image from the transfer belt 62 to the recording medium P in the secondary transfer region T2 between the transfer cylinder 70 and the transfer belt 62 while conveying the recording medium P.

[0045] <Fixing device 15> 1 is a device that fixes a toner image transferred to a recording medium P by a transfer cylinder 70 to the recording medium P. Specifically, as shown in FIGS. 1 and 3, the fixing device 15 has a fixing cylinder 50 and a heating roll 52.

[0046] Fixing cylinder 50 (specifically, cylinder main body 53 described below) has recess 51 formed on its outer circumferential surface, and rotates in rotation direction E (arrow E direction). Recess 51 is elongated along the axial direction of fixing cylinder 50, and has a depth along the radial direction of fixing cylinder 50.

[0047] As shown in Fig. 3, fixing cylinder 50 is provided with a pair of sprockets 55 on both axial ends. Specifically, fixing cylinder 50 is configured to have a substantially cylindrical cylinder main body 53 and sprockets 55 provided on both axial ends of cylinder main body 53. The pair of sprockets 55 are arranged coaxially on cylinder main body 53. In fixing cylinder 50, cylinder main body 53 is rotated by a drive unit (not shown) and rotates in rotation direction E, so that cylinder main body 53 and the pair of sprockets 55 rotate together in rotation direction E.

[0048] The heating roll 52 is disposed above the fixing cylinder 50. The heating roll 52 has a heat source 52A (see FIG. 1) such as a halogen lamp inside the roll. Furthermore, the heating roll 52 rotates in a rotation direction F (arrow F direction) which is opposite to the rotation direction E.

[0049] In the fixing device 15, the heating roll 52 and the fixing cylinder 50 rotate while sandwiching the recording medium P conveyed by the conveying mechanism 16 (specifically, the gripper 24 described below) at the fixing position NP, thereby conveying the recording medium P. The heating roll 52 heats the recording medium P, and the heating roll 52 and the fixing cylinder 50 pressurize the recording medium P, thereby fixing the toner image transferred to the recording medium P to the recording medium P.

[0050] <Transport mechanism 16> The transport mechanism 16 shown in Fig. 1 is a mechanism that transports the recording medium P. As shown in Fig. 1 and Fig. 4, the transport mechanism 16 has a pair of sprockets 27, a pair of chains 22, and a gripper 24. The gripper 24 is an example of a holding portion.

[0051] In FIG. 1, one of the pair of chains 22 and one of the pair of sprockets 27 are shown, and the chains 22, the sprockets 27, and the gripper 24 are shown in a simplified manner.

[0052] The pair of sprockets 27 is an example of a rotating body, and is disposed below the pair of sprockets 75 and the pair of sprockets 55 and to the right of the pair of sprockets 55 (i.e., on the side of the pair of sprockets 75). As shown in Fig. 4, the pair of sprockets 27 are disposed with a gap between them in the front-rear direction.

[0053] The pair of chains 22 is formed in a ring shape as shown in FIG. 1. The pair of chains 22 is arranged at an interval in the front-rear direction as shown in FIG. 4. Each of the pair of chains 22 is wound around each of the pair of sprockets 75 provided at both axial ends of the transfer cylinder 70, each of the pair of sprockets 55 provided at both axial ends of the fixing cylinder 50, and each of the pair of sprockets 27. The transfer cylinder 70 is rotated in the rotation direction B, and the fixing cylinder 50 is rotated in the rotation direction E, so that the chain 22 rotates in the rotation direction (arrow C direction). In this way, the chain 22 functions as a rotation part that rotates in the rotation direction C. The transfer cylinder 70 and the fixing cylinder 50 are rotated synchronously, and the pair of sprockets 27 rotate following the rotation of the chain 22. Therefore, in this embodiment, the pair of chains 22, the pair of sprockets 27, the transfer cylinder 70, and the fixing cylinder 50 rotate integrally.

[0054] 4, mounting members 23 having grippers 24 attached thereto are hung in the front-rear direction between the pair of chains 22. A plurality of mounting members 23 are fixed to the pair of chains 22 at predetermined intervals along the circulating direction C of the chains 22.

[0055] As shown in Fig. 4, a plurality of grippers 24 are attached to the mounting member 23 at predetermined intervals along the front-rear direction. The grippers 24 function as a holder that holds the leading end of the recording medium P. Specifically, as shown in Fig. 5, the gripper 24 has a claw 24A and a claw base 24B. The gripper 24 is configured to hold the recording medium P by pinching the leading end of the recording medium P between the claw 24A and the claw base 24B. For example, the gripper 24 has the claw 24A pressed against the claw base 24B by a spring or the like, and the claw 24A is opened and closed relative to the claw base 24B by the action of a cam or the like.

[0056] In the transport mechanism 16, the leading end of the recording medium P sent from the medium storage unit 12 by the sending unit 13 is held by the gripper 24 as shown in Fig. 5. In this embodiment, the gripper 24 starts holding the recording medium P at a predetermined holding start position (for example, the position indicated by the symbol SP in Fig. 1).

[0057] Here, in the transport mechanism 16, for example, the circumferential length of the chain 22 is a natural number multiple of the circumferential length of the sprocket 27. Furthermore, the attachment members 23 (i.e., the grippers 24) are attached to the chain 22 at intervals corresponding to the circumferential length of the sprocket 27. As a result, every time the sprocket 27 rotates once, the multiple grippers 24 reach the holding start positions in sequence and start holding the recording medium P at the holding start positions.

[0058] Furthermore, in the transport mechanism 16, the gripper 24 holding the leading end of the recording medium P moves integrally with the rotational movement of the transfer cylinder 70 as the chain 22 rotates in the circumferential direction C to transport the recording medium P and pass through the secondary transfer region T2. ​​Then, in the secondary transfer region T2, the transfer cylinder 70 secondarily transfers the toner images of each color that have been primarily transferred and superimposed on the transfer belt 62 in the primary transfer region T1 to the recording medium P in the secondary transfer region T2.

[0059] Furthermore, as the chain 22 rotates in the rotation direction C, the gripper 24 holding the leading end of the recording medium P conveys the recording medium P and passes through the fixing position NP. Then, in the fixing device 15, at the fixing position NP, the heating roll 52 sandwiches the recording medium P between the fixing cylinder 50 and the recording medium P, and the image on the recording medium P is fixed to the recording medium.

[0060] When passing through the secondary transfer region T2, the gripper 24 is accommodated together with the mounting member 23 in a recess 71 formed on the outer circumferential surface of the transfer cylinder 70, thereby avoiding contact with the transfer belt 62. When passing through the fixing position NP, the gripper 24 is accommodated together with the mounting member 23 in a recess 51 formed on the outer circumferential surface of the fixing cylinder 50, thereby avoiding contact with the heating roll 52.

[0061] In addition, a pair of sprockets 75 provided on both axial ends of the transfer cylinder 70 and a pair of sprockets 55 provided on both axial ends of the fixing cylinder 50 can be understood as components of the conveying mechanism 16.

[0062] <First rotational position sensor 91> 4 is an example of a detection unit, and is a component that detects a predetermined rotational position (hereinafter referred to as a first reference rotational position) of sprocket 27. That is, first rotational position sensor 91 detects that rotating sprocket 27 has reached the first reference rotational position (in other words, a predetermined rotation angle).

[0063] As the first rotational position sensor 91, for example, a photosensor that detects the passage of an actuator 91A attached to the rotary shaft 29 of the sprocket 27 can be used (see FIG. 4).

[0064] Here, in this embodiment, the timing at which each of the grippers 24 reaches the holding start position each time the sprocket 27 rotates once is synchronized with the timing at which the grippers 24 reach the holding start position (in other words, the holding start timing at which the grippers 24 start holding the recording medium P) and the timing at which the sprocket 27 reaches the first reference rotational position (i.e., the timing at which the first reference rotational position is detected by the first rotational position sensor 91).

[0065] Furthermore, the detection timing of the first rotational position sensor 91 serves as a reference for the sending timing of the sending unit 13. In this embodiment, as described later, the sending unit 13 sends out the recording medium P toward the gripper 24 based on the detection timing at which the first rotational position sensor 91 detects the first reference rotational position. As a result, the recording medium P reaches the holding start position in accordance with the timing at which the gripper 24 reaches the holding start position (in other words, the timing at which the gripper 24 starts holding the recording medium P).

[0066] The detection information (i.e., a detection signal) of the first rotational position sensor 91 detecting the reference rotational position is transmitted to the control device 40. One rotation of the sprocket 27 is the period from when the first rotational position sensor 91 detects the first reference rotational position to when it detects the first reference rotational position again.

[0067] <Second rotational position sensor 92> 2 is a component that detects a predetermined rotational position (hereinafter referred to as a second reference rotational position) of the transfer cylinder 70. That is, the second rotational position sensor 92 detects that the rotating transfer cylinder 70 has reached the second reference rotational position (in other words, a predetermined rotation angle).

[0068] As the second rotational position sensor 92, for example, a photosensor that detects the passage of an actuator 92A attached to the rotation shaft 73 of the transfer cylinder 70 can be used (see FIG. 2).

[0069] Here, in this embodiment, the second reference rotational position detected by the second rotational position sensor 92 coincides with the position at which secondary transfer is started (hereinafter referred to as the secondary transfer start position) onto the recording medium P which is placed on the outer peripheral surface 70A of the transfer cylinder 70 and transported by the transport mechanism 16 (specifically, the gripper 24).

[0070] Therefore, the detection timing at which the second rotational position sensor 92 detects the second reference rotational position is synchronized with the secondary transfer start timing at which secondary transfer is started onto the recording medium P that is placed on the outer circumferential surface 70A of the transfer cylinder 70 and transported by the transport mechanism 16 (specifically, the gripper 24). The secondary transfer start timing can also be said to be the timing at which the recording medium P (specifically, the leading edge of the transfer area on the recording medium P) reaches the secondary transfer start position. This secondary transfer start timing is an example of the transfer start timing.

[0071] Specifically, the secondary transfer start position is a position where the leading end (downstream end in the transport direction) of the image area of ​​the recording medium P arranged on the outer circumferential surface 70A of the transfer cylinder 70 starts to be introduced into the secondary transfer region T2. ​​For example, the secondary transfer start position is a position where the rotation direction upstream end 71X (see FIG. 2) of the recess 71 of the transfer cylinder 70 starts to be introduced into the secondary transfer region T2 (position facing the opposing roll 65).

[0072] Furthermore, the detection timing of the second rotational position sensor 92 serves as a reference for the writing timing of the exposure device 36. In this embodiment, as described later, the exposure device 36 writes an electrostatic latent image on the photoconductor 32 based on the detection timing at which the second rotational position sensor 92 detects the second reference rotational position.

[0073] The detection information (i.e., a detection signal) of the second rotational position sensor 92 detecting the reference rotational position is transmitted to the control device 40. One rotation of the transfer cylinder 70 is the period from when the second rotational position sensor 92 detects the second reference rotational position to when it detects the second reference rotational position again.

[0074] <Control device 40> The control device 40 is an example of a speed adjustment mechanism, and includes a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a storage 44, and a communication interface (I / F) 45, as shown in Fig. 6. Each component is connected to each other so as to be able to communicate with each other via a bus 49. The CPU 41 (specifically, a speed adjustment unit 82 described later) may be understood as an example of the speed adjustment mechanism.

[0075] The CPU 41 is a central processing unit that executes various programs and controls each part. The ROM 42 stores various programs including a control program and various data. The RAM 43 temporarily stores programs or data as a working area. The storage 44 is composed of a storage medium such as an HDD (Hard Disk Drive), an SSD (Solid State Drive) or a flash memory, and stores various programs including an operating system and various data. The control program may be stored in the storage 44.

[0076] The communication interface 45 is an interface for communicating with other components such as the image forming unit 14 including the exposure device 36, the sending unit 13, the first rotational position sensor 91, the second rotational position sensor 92, the driving unit 67, and the driving mechanism 79. The communication interface 45 communicates with the other components by using communication means such as wired, wireless, the Internet, and an intranet.

[0077] In the control device 40, the CPU 41 reads various programs including the control program from the ROM 42 or the storage 44, and executes the programs using the RAM 43 as a working area. The CPU 41 executes the control programs to control the operation of each part of the image forming apparatus 10. The following describes the functional configuration realized by the cooperation of the CPU 41 as a hardware resource and the information processing program as a software resource. Figure 7 is a block diagram showing an example of the functional configuration of the control device 40 according to this embodiment.

[0078] The control device 40 may be configured as a speed adjusting device specialized for adjusting the rotation speed of the transfer cylinder 70 .

[0079] In the control device 40, the CPU 41 executes a control program to function as an acquisition unit 80, a drive control unit 81, a speed adjustment unit 82, a transmission control unit 83, and an exposure control unit 84, as shown in FIG.

[0080] The acquiring unit 80 acquires detection information (i.e., a detection signal) indicating that the first rotational position sensor 91 has detected the first reference rotational position from the first rotational position sensor 91. The acquiring unit 80 also acquires detection information (i.e., a detection signal) indicating that the second rotational position sensor 92 has detected the second reference rotational position from the second rotational position sensor 92.

[0081] The sending control unit 83 controls the sending unit 13 to send out the recording medium P toward the gripper 24 (i.e., the holding start position) based on the detection timing at which the first rotational position sensor 91 detects the first reference rotational position so that the recording medium P reaches the holding start position at the timing when the gripper 24 reaches the holding start position (in other words, the timing when the gripper 24 starts holding the recording medium P).

[0082] The sending speed (conveying speed) by the sending unit 13 and the path length from the sending unit 13 to the holding start position may be set so that the timing at which the gripper 24 reaches the holding start position (in other words, the timing at which the gripper 24 starts holding the recording medium P) and the timing at which the recording medium P reaches the holding start position are synchronized by the sending unit 13 sending out the recording medium P at the timing detected by the first rotational position sensor 91. In this case, the sending control unit 83 controls the sending unit 13 to send out the recording medium P at the timing detected by the first rotational position sensor 91.

[0083] The exposure control unit 84 controls the exposure device 36 to write an electrostatic latent image on the photoconductor 32 based on the detection timing at which the second rotational position sensor 92 detects the second reference rotational position so that the timing at which the toner image transferred from the photoconductor 32 to the transfer belt 62 reaches the secondary transfer start position is synchronized with the secondary transfer start timing (specifically, the timing at which the recording medium P reaches the secondary transfer start position).

[0084] The exposure device 36 to be controlled is the exposure device 36 in the toner image forming unit (e.g., the toner image forming unit 30(Y) located on the most upstream side) where the exposure device 36 operates first among the multiple toner image forming units 30 (e.g., toner image forming units 30(Y), 30(M), 30(C), 30(K)). In this embodiment, after the exposure device 36 whose writing timing is controlled starts writing in the toner image forming unit, the exposure devices 36 start writing sequentially in the other toner image forming units. Then, after the development process is performed in each of the toner image forming units, the toner image is transferred to the transfer belt 62.

[0085] The drive control unit 81 is a functional unit that controls the drive of the drive unit 67 that rotates the drive roll 64D. The drive control unit 81 generates, for example, a pulse signal and controls the drive of the drive unit 67 by the pulse signal. Note that, for example, a servo motor or a stepping motor is used as the drive unit 67.

[0086] The speed adjustment unit 82 is a functional unit that adjusts the speed of the transfer cylinder 70 by controlling the driving of the drive mechanism 79 that rotates the transfer cylinder 70. The speed adjustment unit 82 generates, for example, a pulse signal and controls the driving of the drive mechanism 79 by the pulse signal. Specifically, for example, a servo motor or a stepping motor is used as the drive mechanism 79.

[0087] The speed adjustment unit 82 adjusts the rotation speed of the transfer cylinder 70 driven by the drive mechanism 79 for each revolution of the transfer cylinder 70. Specifically, the speed adjustment unit 82 switches between a first adjustment pattern 101 (see FIG. 8) and a second adjustment pattern 102 (see FIG. 8) having a speed profile different from that of the first adjustment pattern 101 for each revolution of the transfer cylinder 70.

[0088] Here, the load (rotational resistance) acting on the transfer belt 62 can change depending on whether the transfer cylinder 70 and the transfer belt 62 are in contact with each other, and whether the transfer cylinder 70 is transporting the recording medium P while in contact with the transfer belt 62 (in other words, whether the recording medium P passes through the secondary transfer region T2 or not). In this embodiment, the fluctuation (i.e., variation) of the rotational torque in the drive roll 64D is suppressed by switching between a first adjustment pattern 101 (see FIG. 8) and a second adjustment pattern 102 (see FIG. 8) set as follows, in units of one revolution of the transfer cylinder 70.

[0089] The first adjustment pattern 101 is a pattern for adjusting the rotation speed of the transfer cylinder 70 during a revolution that includes a state in which the transfer cylinder 70 is not transporting the recording medium P. The second adjustment pattern 102 is a pattern for adjusting the rotation speed of the transfer cylinder 70 during a revolution that includes a state in which the transfer cylinder 70 is transporting the recording medium P.

[0090] The time for the first adjustment pattern 101 and the second adjustment pattern 102 coincides with the time for the transfer cylinder 70 to rotate once, and the average value of the rotation speed for the first adjustment pattern 101 and the average value of the rotation speed for the second adjustment pattern 102 coincide.

[0091] In this embodiment, in the second adjustment pattern 102, the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portions 71 passes through the secondary transfer region T2 is different from the average value in the first adjustment pattern 101. Specifically, as an example, in the second adjustment pattern 102, the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portions 71 passes through the secondary transfer region T2 is higher than the average value in the first adjustment pattern 101.

[0092] In addition, in this embodiment, as an example, the second adjustment pattern 102 has a lower average rotation speed of the transfer cylinder 70 when the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 than the average value in the first adjustment pattern 101.

[0093] Also, in the first adjustment pattern 101, as an example, the average rotational speed of the transfer cylinder 70 when the recess 71 of the transfer cylinder 70 passes through the secondary transfer region T2 is higher than the average rotational speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recess 71 passes through the secondary transfer region T2.

[0094] The adjustment pattern is switched depending on the transport status of the recording medium P by the transport mechanism 16, for example, by executing one of the first adjustment pattern 101 and the second adjustment pattern 102 once or multiple times and then switching to the other.

[0095] <Actions of the First Adjustment Pattern 101 and the Second Adjustment Pattern 102> In this embodiment, as described above, the first adjustment pattern 101 is a pattern that adjusts the rotational speed of the transfer cylinder 70 during a revolution that includes a state in which the transfer cylinder 70 is not transporting the recording medium P, and the second adjustment pattern 102 is a pattern that adjusts the rotational speed of the transfer cylinder 70 during a revolution that includes a state in which the transfer cylinder 70 is transporting the recording medium P.

[0096] Therefore, compared to the case where the first adjustment pattern 101 and the second adjustment pattern 102 are patterns that adjust the rotational speed of the transfer cylinder 70 during a rotation that includes a state in which the transfer cylinder 70 is transporting the recording medium P, it is possible to adjust the rotational speed of the transfer cylinder 70 to an appropriate rotational speed when the transfer cylinder 70 is transporting the recording medium P, and to an appropriate rotational speed when the transfer cylinder 70 is not transporting the recording medium P.

[0097] Furthermore, in this embodiment, the second adjustment pattern 102 has a higher average rotation speed of the transfer cylinder 70 when the portion other than the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 than the average value in the first adjustment pattern 101.

[0098] Here, when the recording medium P passes through the secondary transfer region T2, the load on the transfer belt 62 may be larger than when the recording medium P does not pass through the secondary transfer region T2. ​​In this case, by increasing the average value in the second adjustment pattern 102, the load on the transfer belt 62 is reduced.

[0099] Therefore, it is possible to reduce the torque fluctuation of the drive roll 64D compared to when the average value of the rotational speed of the transfer cylinder 70 in the second adjustment pattern 102 when parts of the transfer cylinder 70 other than the recessed parts 71 pass through the secondary transfer region T2 is the same as the average value in the first adjustment pattern 101.

[0100] In this embodiment, the second adjustment pattern 102 has a lower average rotation speed of the transfer cylinder 70 when the recessed portions 71 of the transfer cylinder 70 pass through the secondary transfer region T2 than the average rotation speed of the first adjustment pattern 101.

[0101] As described above, in this embodiment, the second adjustment pattern 102 is configured so that the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portion 71 passes through the secondary transfer region T2 is higher than the average value in the first adjustment pattern 101. Therefore, compared to a case where the average value of the rotation speed of the transfer cylinder 70 when the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 in the second adjustment pattern 102 is the same as the average value in the first adjustment pattern 101, the difference between the overall average value of the rotation speed of the transfer cylinder 70 in the first adjustment pattern 101 and the overall average value of the rotation speed of the transfer body in the second adjustment pattern 102 becomes smaller. In other words, it is possible to make the overall average value of the rotation speed of the transfer cylinder 70 in the first adjustment pattern 101 coincide with the overall average value of the rotation speed of the transfer body in the second adjustment pattern 102.

[0102] <Synchronization with Switching Timing in Speed ​​Adjustment Unit 82> Speed ​​adjustment unit 82 synchronizes the timing of switching between first adjustment pattern 101 and second adjustment pattern 102 (hereinafter referred to as switching timing) with the detection timing at which second rotational position sensor 92 detects the second reference rotational position. This detection timing is synchronized with the transfer start timing at which transfer cylinder 70 starts transferring the toner image transferred to transfer belt 62 to recording medium P. Therefore, speed adjustment unit 82 synchronizes the switching timing with the transfer start timing at which transfer cylinder 70 starts transferring the toner image transferred to transfer belt 62 to recording medium P.

[0103] Moreover, the speed adjustment unit 82 synchronizes the switching timing with the detection timing at which the first rotational position sensor 91 detects the first reference rotational position. The detection timing is synchronized with the arrival timing of the gripper 24 at the holding start position (in other words, the holding start timing of the recording medium P in the gripper 24). Therefore, the speed adjustment unit 82 synchronizes the switching timing with the holding start timing at which the gripper 24 starts holding the recording medium P.

[0104] <Synchronization with the switching timing in the speed adjustment unit 82> In this embodiment, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment pattern 101 and the second adjustment pattern 102 with the holding start timing at which the gripper 24 starts holding the recording medium P.

[0105] Here, in a case where the speed adjustment unit 82 switches between the first adjustment pattern 101 and the second adjustment pattern 102 regardless of the timing at which the gripper 24 starts holding the recording medium P (hereinafter referred to as form A), the speed profiles of the first adjustment pattern 101 and the second adjustment pattern 102 are different, so that the holding position at which the gripper 24 holds the recording medium P may vary, and the gripping margin (i.e., the margin on the leading edge side of the recording medium P) may change. As a result, the transfer position at which the image is transferred to the recording medium P may vary.

[0106] In contrast, in this embodiment, as described above, the speed adjustment unit 82 synchronizes the switching timing for switching between the first adjustment pattern 101 and the second adjustment pattern 102 with the holding start timing at which the gripper 24 starts holding the recording medium P, so that even when the adjustment pattern is switched between the first adjustment pattern 101 and the second adjustment pattern 102, the holding position at which the gripper 24 holds the recording medium P is suppressed from varying compared to form A. As a result, the transfer position at which the image is transferred to the recording medium P is suppressed from varying.

[0107] Furthermore, in this embodiment, the speed adjustment unit 82 synchronizes the switching timing for switching between the first adjustment pattern 101 and the second adjustment pattern 102 with the detection timing for the first rotational position sensor 91 to detect the first reference rotational position.

[0108] Here, the sending unit 13 sends out the recording medium P towards the gripper 24 (specifically, the holding start position) based on the detection timing, and in a case where the speed adjustment unit 82 switches between the first adjustment pattern 101 and the second adjustment pattern 102 regardless of the detection timing (hereinafter referred to as form B), the speed profiles of the first adjustment pattern 101 and the second adjustment pattern 102 are different, so that the holding position where the gripper 24 holds the recording medium P varies, and the gripping margin (i.e., the margin on the leading edge side of the recording medium P) may change. As a result, the position where the image is transferred to the recording medium P may vary.

[0109] In contrast, in this embodiment, as described above, the speed adjustment unit 82 synchronizes the switching timing for switching between the first adjustment pattern 101 and the second adjustment pattern 102 with the detection timing for the first rotational position sensor 91 to detect the first reference rotational position, so that even when the adjustment pattern is switched between the first adjustment pattern 101 and the second adjustment pattern 102, the holding position at which the gripper 24 holds the recording medium P is suppressed from varying compared to form B. As a result, the transfer position at which the image is transferred to the recording medium P is suppressed from varying.

[0110] Furthermore, in this embodiment, the switching timing at which the speed adjustment unit 82 switches between the first adjustment pattern 101 and the second adjustment pattern 102 is synchronized with the detection timing at which the second rotational position sensor 92 detects the second reference rotational position.

[0111] Here, in the case where the speed adjustment unit 82 switches between the first adjustment pattern 101 and the second adjustment pattern 102 regardless of the detection timing (hereinafter referred to as form C), since the speed profiles of the first adjustment pattern 101 and the second adjustment pattern 102 are different, the writing timing at which the exposure device 36 starts writing may vary, and the transfer position at which the image is transferred to the recording medium P may vary.

[0112] In contrast, in this embodiment, as described above, the speed adjustment unit 82 synchronizes the switching timing for switching between the first adjustment pattern 101 and the second adjustment pattern 102 with the detection timing at which the second rotational position sensor 92 detects the second reference rotational position. Therefore, even when the adjustment pattern is switched between the first adjustment pattern 101 and the second adjustment pattern 102, the variation in the writing timing is suppressed compared to form C, and the variation in the transfer position at which the image is transferred to the recording medium P is suppressed.

[0113] In addition, in this embodiment, the speed adjustment unit 82 synchronizes the switching timing for switching between the first adjustment pattern 101 and the second adjustment pattern 102 with the secondary transfer start timing at which the transfer cylinder 70 starts transferring the toner image transferred to the transfer belt 62 onto the recording medium P.

[0114] Here, when the speed adjustment unit 82 switches between the first adjustment pattern 101 and the second adjustment pattern 102 regardless of the transfer start timing (hereinafter referred to as form D), the speed profiles of the first adjustment pattern 101 and the second adjustment pattern 102 are different, so the transfer start timing may vary and the transfer position at which the image is transferred to the recording medium P may vary.

[0115] In contrast, in this embodiment, as described above, the speed adjustment unit 82 synchronizes the switching timing for switching between the first adjustment pattern 101 and the second adjustment pattern 102 with the transfer start timing at which the transfer cylinder 70 starts transferring the toner image transferred to the transfer belt 62 to the recording medium P. Therefore, even when the adjustment pattern is switched between the first adjustment pattern 101 and the second adjustment pattern 102, the variation in the transfer start timing is suppressed compared to form D, and variation in the transfer position at which the image is transferred to the recording medium P is suppressed.

[0116] <Changing the profile in the speed adjustment unit 82> Furthermore, while the transfer belt 62 is rotating, the speed adjustment unit 82 is capable of changing the speed profile while maintaining the average value of the rotational speed of the transfer cylinder 70 in each of the first adjustment pattern 101 and the second adjustment pattern 102, as shown by the dotted line in Figure 8.

[0117] When the speed adjustment unit 82 changes the speed profile while maintaining the average value of the rotation speed of the transfer cylinder 70 in each of the first adjustment pattern 101 and the second adjustment pattern 102 during rotation of the transfer belt 62 (hereinafter referred to as when profile change X1 is performed), the exposure control unit 84 controls the exposure device 36 to write an electrostatic latent image on the photoconductor 32 at the same write timing as before the change. As a result, even when profile change X1 is performed, the exposure device 36 writes an electrostatic latent image on the photoconductor 32 at the same write timing as before the change.

[0118] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the transfer cylinder 70 starts transferring the toner image transferred onto the transfer belt 62 onto the recording medium P at the same start timing as before the change.

[0119] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the gripper 24 holds the recording medium P at the same holding start timing as before the change.

[0120] In addition, in this embodiment, when the speed adjustment unit 82 changes the profile to X1, the sending control unit 83 controls the sending unit 13 to send out the recording medium P at the same sending timing as before the change. As a result, even when the profile change X1 is made, the sending unit 13 sends out the recording medium P at the same sending timing as before the change.

[0121] <Effect of changing profile in speed adjustment unit 82> In this embodiment, as described above, the speed adjustment unit 82 is capable of changing the speed profile while maintaining the average value of the rotational speed of the transfer cylinder 70 in each of the first adjustment pattern 101 and the second adjustment pattern 102 while the transfer belt 62 is rotating, as shown by the dotted line in Figure 8.

[0122] This makes it possible to change the rotation speed of the transfer cylinder 70 at each of the first adjustment pattern 101 and the second rotational position sensor 92 in response to torque fluctuations of the drive roll 64D while the transfer belt 62 is rotating.

[0123] Here, in this embodiment, the switching timing for switching between the first adjustment pattern 101 and the second adjustment pattern 102 is synchronized with various timings (the detection timing in the first rotational position sensor 91 and the second rotational position sensor 92, the holding start timing, and the secondary transfer start timing). Therefore, even if the speed profile is changed in each of the first adjustment pattern 101 and the second adjustment pattern 102, variations in various timings are unlikely to occur, and variations in the transfer position at which the image is transferred to the recording medium P are suppressed.

[0124] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the exposure device 36 writes an electrostatic latent image on the photoconductor 32 at the same writing timing as before the change. Therefore, it is not necessary to control the writing timing of the exposure device 36.

[0125] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the transfer cylinder 70 starts transferring the toner image transferred onto the transfer belt 62 onto the recording medium P at the same secondary transfer start timing as before the change. Therefore, it is not necessary to control the secondary transfer start timing of the transfer cylinder 70.

[0126] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the gripper 24 holds the recording medium P at the same holding start timing as before the change. Therefore, it is not necessary to control the holding start timing of the gripper 24.

[0127] In addition, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the sending unit 13 sends out the recording medium P at the same sending timing as before the change. Therefore, it is not necessary to control the sending timing of the sending unit 13.

[0128] <Modification> In the present embodiment, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment pattern 101 and the second adjustment pattern 102 with the detection timing at which the second rotational position sensor 92 detects the second reference rotational position, but this is not limited to this. For example, the speed adjustment unit 82 may be configured to switch between the first adjustment pattern 101 and the second adjustment pattern 102 regardless of the detection timing.

[0129] In addition, in this embodiment, the switching timing at which the speed adjustment unit 82 switches between the first adjustment pattern 101 and the second adjustment pattern 102 is synchronized with the secondary transfer start timing at which the transfer cylinder 70 starts transferring the toner image transferred to the transfer belt 62 onto the recording medium P, but this is not limited to this. For example, the speed adjustment unit 82 may be configured to switch between the first adjustment pattern 101 and the second adjustment pattern 102 regardless of the transfer start timing.

[0130] In the present embodiment, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment pattern 101 and the second adjustment pattern 102 with the detection timing at which the first rotational position sensor 91 detects the first reference rotational position, but this is not limited to this. For example, the speed adjustment unit 82 may be configured to switch between the first adjustment pattern 101 and the second adjustment pattern 102 regardless of the detection timing.

[0131] In addition, in this embodiment, the first adjustment pattern 101 is a pattern for adjusting the rotation speed of the transfer cylinder 70 during a revolution that includes a state in which the transfer cylinder 70 is not transporting the recording medium P, and the second adjustment pattern 102 is a pattern for adjusting the rotation speed of the transfer cylinder 70 during a revolution that includes a state in which the transfer cylinder 70 is transporting the recording medium P, but this is not limited to this. For example, the first adjustment pattern 101 and the second adjustment pattern 102 may be patterns for adjusting the rotation speed of the transfer cylinder 70 during a revolution that includes a state in which the transfer cylinder 70 is transporting the recording medium P, and the first adjustment pattern 101 and the second adjustment pattern 102 can be adjustment patterns configured with any speed profile.

[0132] In the present embodiment, the second adjustment pattern 102 has a higher average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portion 71 passes through the secondary transfer region T2 than the average value in the first adjustment pattern 101, but this is not limited thereto. For example, the second adjustment pattern 102 may have a configuration in which the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portion 71 passes through the secondary transfer region T2 is the same as the average value in the first adjustment pattern 101. For example, the second adjustment pattern 102 may have a configuration in which the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portion 71 passes through the secondary transfer region T2 is lower than the average value in the first adjustment pattern 101. Here, when the recording medium P passes through the secondary transfer region T2, the load on the transfer belt 62 may be smaller than when the recording medium P does not pass through the secondary transfer region T2. ​​In this case, the load on the transfer belt 62 is reduced by lowering the average value in the second adjustment pattern 102. Therefore, it is possible to reduce the torque fluctuation of the drive roll 64D compared to when the average value of the rotational speed of the transfer cylinder 70 in the second adjustment pattern 102 when parts of the transfer cylinder 70 other than the recessed parts 71 pass through the secondary transfer region T2 is the same as the average value in the first adjustment pattern 101.

[0133] In the present embodiment, the second adjustment pattern 102 has an average value of the rotation speed of the transfer cylinder 70 when the recesses 71 of the transfer cylinder 70 pass through the secondary transfer region T2 that is lower than the average value in the first adjustment pattern 101, but this is not limited to the above. For example, the second adjustment pattern 102 may have an average value of the rotation speed of the transfer cylinder 70 when the recesses 71 of the transfer cylinder 70 pass through the secondary transfer region T2 that is the same as the average value in the first adjustment pattern 101. For example, the second adjustment pattern 102 may have an average value of the rotation speed of the transfer cylinder 70 when the recesses 71 of the transfer cylinder 70 pass through the secondary transfer region T2 that is higher than the average value in the first adjustment pattern 101.

[0134] In addition, in the first adjustment pattern 101, as an example, the average value of the rotation speed of the transfer cylinder 70 when the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 is set to be higher than the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portion 71 passes through the secondary transfer region T2, but this is not limited to the above. For example, in the first adjustment pattern 101, the average value of the rotation speed of the transfer cylinder 70 when the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 may be configured to be the same as the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2. ​​In addition, in the first adjustment pattern 101, for example, the average value of the rotation speed of the transfer cylinder 70 when the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 may be configured to be lower than the average value of the rotation speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the recessed portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2.

[0135] In the present embodiment, the speed profile can be changed while maintaining the average value of the rotation speed of the transfer cylinder 70 in each of the first adjustment pattern 101 and the second adjustment pattern 102 during rotation of the transfer belt 62, but this is not limited to the above. The speed profile in each of the first adjustment pattern 101 and the second adjustment pattern 102 may be configured to be always maintained (i.e., cannot be changed).

[0136] In the present embodiment, when the profile change X1 is performed, the exposure device 36 is configured to write an electrostatic latent image onto the photoconductor 32 at the same writing timing as before the change, but this is not limiting. For example, when the profile change X1 is performed, the exposure device 36 may be configured to write an electrostatic latent image onto the photoconductor 32 at a writing timing different from that before the change.

[0137] In addition, in this embodiment, when profile change X1 is performed, transfer cylinder 70 is configured to start transferring the toner image transferred to transfer belt 62 to recording medium P at the same start timing as before the change, but this is not limited to the above. For example, when profile change X1 is performed, transfer cylinder 70 may be configured to start transferring the toner image transferred to transfer belt 62 to recording medium P at a start timing different from that before the change.

[0138] In the present embodiment, when the profile change X1 is performed, the gripper 24 is configured to hold the recording medium P at the same holding start timing as before the change, but this is not limited to the above. For example, when the profile change X1 is performed, the gripper 24 may be configured to hold the recording medium P at a holding start timing different from before the change.

[0139] In the present embodiment, when the profile change X1 is made, the sending unit 13 is configured to send out the recording medium P at the same sending timing as before the change, but this is not limited to the above. For example, when the profile change X1 is made, the sending unit 13 may be configured to send out the recording medium P at a sending timing different from that before the change.

[0140] The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements are possible without departing from the spirit and scope of the present invention. For example, the above-described modified examples may be combined in combination as appropriate.

[0141] In addition, in the above embodiment, the processor refers to a processor in a broad sense, and includes a general-purpose processor (e.g., the aforementioned CPU, etc.) and a dedicated processor (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0142] In addition, the operations of the processor in the above embodiment may be performed not only by one processor but also by multiple processors located at physically separate locations working together. The order of the operations of the processor is not limited to the order described in the above embodiment, and may be changed as appropriate.

[0143] <Additional Notes> (((1))) a circular transfer belt on whose outer circumferential surface an image formed on the forming body is transferred; a drive roll around which the transfer belt is wound and which rotates the transfer belt; a transfer body that transfers the image from the transfer belt to the recording medium in a transfer region between the transfer body and the recording medium while conveying the recording medium; A drive mechanism that rotates the transfer body; a holding section that holds the recording medium and moves together with the rotational movement of the transfer body to pass the recording medium through the transfer area; a speed adjustment mechanism that adjusts a rotation speed of the transfer body by the drive mechanism in units of one revolution of the transfer body, the speed adjustment mechanism switching between a first adjustment pattern and a second adjustment pattern different from the first adjustment pattern in units of one revolution of the transfer body, and synchronizing the switching timing with a holding start timing at which the holding unit starts holding the recording medium; An image forming apparatus comprising:

[0144] (((2))) a rotating body that rotates in synchronization with the rotation of the transfer body; A detection unit that detects a predetermined rotation position of the rotating body; a sending unit that sends out the recording medium toward the holding unit based on a detection timing at which the detection unit detects the rotation position; Equipped with The holding portion is a recording medium conveying unit that conveys the recording medium from the conveying unit to the recording medium conveying unit; The speed adjustment mechanism includes: The switching timing is synchronized with the detection timing. The image forming apparatus according to (((1))).

[0145] (((3))) The first adjustment pattern is a pattern for adjusting the rotation speed of the transfer body during a revolution including a state in which the transfer body is not conveying the recording medium, The second adjustment pattern is A pattern for adjusting the rotation speed of the transfer body during a revolution including a state in which the transfer body is transporting the recording medium. The image forming apparatus according to any one of claims 1 to 4,

[0146] (((4))) the transfer body has a recess in its outer circumferential surface capable of accommodating the holding portion, The second adjustment pattern is The average value of the rotation speed of the transfer body when a portion other than the recessed portion of the transfer body passes through the transfer region is different from the average value in the first adjustment pattern. The image forming apparatus according to (((3))).

[0147] (((5))) The speed adjustment mechanism includes: During rotation of the transfer belt, In each of the first adjustment pattern and the second adjustment pattern, a speed profile can be changed while maintaining an average value of the rotation speed of the transfer body. The image forming apparatus according to any one of (((1))) to (((5))).

[0148] (((6))) The holding portion is When the speed adjustment mechanism changes the speed profile while maintaining the average value of the rotation speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern during rotation of the transfer belt, The recording medium is retained at the same retention start timing as before the change. The image forming apparatus according to (((5))).

[0149] (((7))) The sending unit is When the speed adjustment mechanism changes the speed profile while maintaining the average value of the rotation speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern during rotation of the transfer belt, The recording medium is sent out at the same sending timing as before the change. The image forming apparatus according to (((5))) or (((6))).

[0150] According to the configuration (((1))), regardless of the timing at which the holding portion starts holding the recording medium, variation in the transfer position at which the image is transferred to the recording medium is suppressed compared to the case where the speed adjustment mechanism switches between the first adjustment pattern and the second adjustment pattern.

[0151] According to the configuration (((2))), regardless of the detection timing at which the detection unit detects the rotational position, variation in the transfer position at which the image is transferred to the recording medium is suppressed compared to the case where the speed adjustment mechanism switches between the first adjustment pattern and the second adjustment pattern.

[0152] According to the configuration (((3))), compared to the case where the first adjustment pattern and the second adjustment pattern are patterns that adjust the rotational speed of the transfer body during a revolution that includes a state in which the transfer body is transporting the recording medium, it is possible to adjust the rotational speed of the transfer body to an appropriate rotational speed when the transfer body is transporting the recording medium and to an appropriate rotational speed when the transfer body is not transporting the recording medium.

[0153] According to the configuration (((4))), the average value of the rotational speed of the transfer body when parts other than the recesses of the transfer body pass through the transfer area in the second adjustment pattern is the same as the average value in the first adjustment pattern, and thus the torque fluctuation of the drive roll is reduced compared to the case where the average value in the first adjustment pattern is the same as the average value in the second adjustment pattern.

[0154] According to the configuration of (((5))), the rotation speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern can be changed in response to the torque fluctuation of the drive roll while the transfer belt is rotating.

[0155] According to the configuration (((6))), it is not necessary to control the holding start timing of the holding unit.

[0156] According to the configuration (((7))), it is not necessary to control the sending timing of the sending unit. [Explanation of symbols]

[0157] 10 Image forming device 12 Media storage section 13 Transmission section 13A Delivery member 14 Image forming section 15 Fixing device 16 Conveyor mechanism 22 Chain 23 Mounting material 24 Gripper (an example of a holding part) 27 Sprocket (an example of a rotating body) 30 Toner image forming unit 31 Charger 32 Photoconductor (an example of a forming body) 35 Primary transfer roll 36 Exposure equipment 38 Developing device 40 Control device (an example of a speed adjustment mechanism) 50 Fixed torso 51 Recess 52 Heating roll 55 Sprocket 60 Transcription device 62 Transfer belt 64 rolls 64D Driving Roll 65 Opposing Roll 67 Drive unit 70 Transfer cylinder (an example of a transfer body) 71 Recess 75 sprocket 79 Drive Mechanism 80 Acquisition Department 81 Drive control unit 82 Speed ​​adjustment section 83 Transmission control section 84 Exposure control section 91 First rotational position sensor (an example of a detection unit) 92 Second Rotational Position Sensor 101 First Adjustment Pattern 102 Second Adjustment Pattern P Recording medium

Claims

1. a circular transfer belt on whose outer circumferential surface an image formed on the forming body is transferred; a drive roll around which the transfer belt is wound and which rotates the transfer belt; a transfer body that transfers the image from the transfer belt to the recording medium in a transfer region between the transfer body and the recording medium while conveying the recording medium; A drive mechanism that rotates the transfer body; a holding section that holds the recording medium and moves together with the rotational movement of the transfer body to pass the recording medium through the transfer area; a speed adjustment mechanism that adjusts a rotation speed of the transfer body by the drive mechanism in units of one revolution of the transfer body, the speed adjustment mechanism switching between a first adjustment pattern and a second adjustment pattern different from the first adjustment pattern in units of one revolution of the transfer body, and synchronizing the switching timing with a holding start timing at which the holding unit starts holding the recording medium; An image forming apparatus comprising:

2. a rotating body that rotates in synchronization with the rotation of the transfer body; A detection unit that detects a predetermined rotation position of the rotating body; a sending unit that sends out the recording medium toward the holding unit based on a detection timing at which the detection unit detects the rotation position; Equipped with The holding portion is a recording medium conveying unit that conveys the recording medium from the conveying unit to the recording medium conveying unit; The speed adjustment mechanism includes: The switching timing is synchronized with the detection timing. The image forming apparatus according to claim 1 .

3. The first adjustment pattern is a pattern for adjusting the rotation speed of the transfer body during a revolution including a state in which the transfer body is not conveying the recording medium, The second adjustment pattern is A pattern for adjusting the rotation speed of the transfer body during a revolution including a state in which the transfer body is transporting the recording medium. The image forming apparatus according to claim 1 .

4. the transfer body has a recess in its outer circumferential surface capable of accommodating the holding portion, The second adjustment pattern is The average value of the rotation speed of the transfer body when a portion other than the recessed portion of the transfer body passes through the transfer region is different from the average value in the first adjustment pattern. The image forming apparatus according to claim 3 .

5. The speed adjustment mechanism includes: During rotation of the transfer belt, In each of the first adjustment pattern and the second adjustment pattern, a speed profile can be changed while maintaining an average value of the rotation speed of the transfer body. The image forming apparatus according to claim 1 .

6. The holding portion is When the speed adjustment mechanism changes the speed profile while maintaining the average value of the rotation speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern during rotation of the transfer belt, The recording medium is retained at the same retention start timing as before the change. The image forming apparatus according to claim 5 .

7. The sending unit is When the speed adjustment mechanism changes the speed profile while maintaining the average value of the rotation speed of the transfer body in each of the first adjustment pattern and the second adjustment pattern during rotation of the transfer belt, The recording medium is sent out at the same sending timing as before the change.

6. The image forming apparatus according to claim 5, which is dependent on claim 2.

Images