Image forming apparatus

Abstract

An image forming apparatus includes: an endless transfer belt that transfers an image formed on a forming body to an outer peripheral surface; a drive roller on which the transfer belt is wound and which surrounds the transfer belt; a transfer body that transfers the image from the transfer belt to a recording medium in a transfer region between the transfer body and the transfer belt while conveying the recording medium; a drive mechanism that rotationally drives the transfer body; a holding unit that holds the recording medium and moves integrally with the rotational movement of the transfer body to pass the recording medium through the transfer region; and a speed adjustment mechanism that adjusts the rotational speed of the transfer body by the drive mechanism in units of one circle of the transfer body, and that switches between a first adjustment mode and a second adjustment mode different from the first adjustment mode in units of one circle of the transfer body, the switching timing is synchronized with a holding start timing at which the holding unit starts to hold the recording medium.

Description

Technical Field

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

[0002] Patent document 1 discloses a transfer device, characterized in that it comprises: a belt-shaped image carrier that carries an image; a driving roller that winds up the image carrier that carries the image and moves it; a first tension roller that winds up the image carrier moved by the driving roller and applies tension to the image carrier; a first elastic supporting portion that has a first elastic component that generates the tension and supports one rotating shaft of the first tension roller; a second elastic supporting portion that has a second elastic component that generates the tension and supports the other rotating shaft of the first tension roller; a supporting roller that winds up the image carrier wound around the tension roller; a transfer roller that has a concave portion on its circumferential surface and abuts against the image carrier wound around the supporting roller to form a transfer nip portion; and a second tension roller that winds up the image carrier wound around the supporting roller and applies tension to the image carrier.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-220812

[0004] As an image forming device, the following image forming device can be considered, which comprises: an endless transfer belt that transfers the image formed on the forming body to the outer peripheral surface; a drive roller around which the transfer belt is wound and causes the transfer belt to circulate; 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 transfer body while conveying the recording medium; a drive mechanism that rotationally drives the transfer body; a holding portion 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 rotational speed of the transfer body based on the drive mechanism in units of one turn of the transfer body, and switches to a first adjustment mode and a second adjustment mode with a speed distribution different from that of the first adjustment mode in units of one turn of the transfer body.

[0005] In this image forming device, when the speed adjustment mechanism switches between the first adjustment mode and the second adjustment mode regardless of the timing at which the holding portion starts holding the recording medium, the holding position of the recording medium held by the holding portion may deviate, and as a result, the transfer position of the image onto the recording medium may sometimes deviate. Summary of the Invention

[0006] The present invention aims to suppress the occurrence of deviation in the transfer position of an image onto a recording medium, compared to a case where the first adjustment mode and the second adjustment mode are switched regardless of the timing at which the speed adjustment mechanism and the holding portion start holding the recording medium.

[0007] The first method comprises: an endless transfer belt that transfers the image formed on the forming body to the outer peripheral surface; a driving roller around which the transfer belt is wound and causes the transfer belt to circulate; 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 transfer body while conveying the recording medium; a driving mechanism that rotationally drives the transfer body; a holding portion 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 rotational speed of the transfer body based on the driving mechanism in units of one turn of the transfer body, and switches to a first adjustment mode and a second adjustment mode different from the first adjustment mode in units of one turn of the transfer body, and synchronizes the switching timing with the holding start timing of the holding portion starting to hold the recording medium.

[0008] According to the first method, in the second method, it comprises: a rotating body that rotates synchronously with the rotation of the transfer body; a detection unit that detects a predetermined rotation position of the rotating body; and a delivery unit that delivers the recording medium to the holding unit based on the detection timing of the rotation position detected by the detection unit, the holding unit holds the recording medium delivered from the delivery unit, and moves integrally with the rotational movement of the transfer body to make the recording medium pass through the transfer area, and the speed adjustment mechanism synchronizes the switching timing with the detection timing.

[0009] According to the first method or the second method, in the third method, the first adjustment mode is a mode for adjusting the rotation speed of the transfer body in a loop including a state in which the transfer body does not convey the recording medium, and the second adjustment mode is a mode for adjusting the rotation speed of the transfer body in a loop including a state in which the transfer body conveys the recording medium.

[0010] According to the third method, in the fourth method, the transfer body has a recessed portion on its outer peripheral surface that can accommodate the retaining portion, and in the second adjustment mode, the average value of the rotational speed of the transfer body when the part of the transfer body other than the recessed portion passes through the transfer area is different from the average value in the first adjustment mode.

[0011] According to any one of the first to fourth aspects, in the fifth aspect, the speed adjustment mechanism can change the speed distribution while maintaining the average value of the rotation speed of the transfer body in each of the first adjustment mode and the second adjustment mode during the rotation of the transfer belt.

[0012] According to the 5th method, in the 6th method, when the speed adjustment mechanism changes the speed distribution while maintaining the average value of the rotation speed of the transfer body in the first adjustment mode and the second adjustment mode during the circulation process of the transfer belt, the holding portion holds the recording medium with the same holding start timing as before the change.

[0013] According to the 5th or 6th method, in the 7th method, when the speed adjustment mechanism changes the speed distribution while maintaining the average value of the rotation speed of the transfer body in the first adjustment mode and the second adjustment mode during the circulation process of the transfer belt, the delivery portion delivers the recording medium at the same delivery timing as before the change.

[0014] Effects of the Invention

[0015] According to the configuration of the first aspect, compared to the case where the first adjustment mode and the second adjustment mode are switched regardless of the timing at which the speed adjustment mechanism and the holding portion start holding the recording medium, it is possible to suppress deviations in the transfer position of the image onto the recording medium.

[0016] According to the configuration of the second aspect, compared to the case where the first adjustment mode and the second adjustment mode are switched regardless of the detection timing of the rotational position by the speed adjustment mechanism and the detection unit, it is possible to suppress deviation in the transfer position of the image onto the recording medium.

[0017] According to the structure of the third method, compared with the first adjustment mode and the second adjustment mode, which are modes for adjusting the rotation speed of the transfer body in a circle including a state in which the transfer body transports the recording medium, the rotation speed of the transfer body can be adjusted to an appropriate rotation speed in a state in which the transfer body transports the recording medium and an appropriate rotation speed in a state in which the transfer body does not transport the recording medium.

[0018] According to the fourth aspect, the torque fluctuation of the driving roller can be reduced compared to the case where the average value of the rotational speed of the transfer body when the portion of the transfer body excluding the recessed portion passes through the transfer area in the second adjustment mode is the same as that in the first adjustment mode.

[0019] According to the configuration of the fifth aspect, the rotational speed of the transfer body in each of the first adjustment mode and the second adjustment mode can be changed according to the torque fluctuation of the drive roller during the rotation of the transfer belt.

[0020] According to the configuration of the sixth aspect, it is unnecessary to control the holding start timing of the holding unit.

[0021] According to the configuration of the seventh aspect, it is unnecessary to control the delivery timing of the delivery unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0023] Figure 1 is a schematic diagram showing an image forming apparatus according to this embodiment;

[0024] Figure 2 is a perspective view showing the structure of the periphery of the transfer cylinder according to the present embodiment;

[0025] Figure 3 is a perspective view showing the structure of the fixing cylinder and its surroundings according to the present embodiment;

[0026] Figure 4 is a perspective view showing the structure of a pair of sprockets and their surroundings according to the present embodiment;

[0027] Figure 5 is a perspective view showing a clamper according to the present embodiment;

[0028] Figure 6 is a block diagram showing the hardware configuration of the control device according to the present embodiment;

[0029] Figure 7 is a block diagram showing an example of the functional configuration of the control device according to the present embodiment;

[0030] Figure 8 It is a diagram showing the first adjustment mode and the second adjustment mode according to the present embodiment.

[0031] Explanation of symbols

[0032] 10-Image forming device, 12-Media storage unit, 13-Feeding unit, 13A-Feeding member, 14-Image forming unit, 15-Fixing device, 16-Conveying mechanism, 22-Chain, 23-Mounting member, 24-Gripper (an example of a holding unit), 27-Sprocket (an example of a rotating body), 30-Toner image forming unit, 31-Charger, 32-Photoreceptor (an example of a forming body), 35-Primary transfer roller, 36-Exposure device, 38-Developing device, 40-Control device (an example of a speed adjustment mechanism), 50-Fixing cylinder, 51-Concave portion, 5 2-heating roller, 55-sprocket, 60-transfer device, 62-transfer belt, 64-roller, 64D-drive roller, 65-opposing roller, 67-drive unit, 70-transfer cylinder (an example of a transfer body), 71-recessed portion, 75-sprocket, 79-drive mechanism, 80-acquisition unit, 81-drive control unit, 82-speed adjustment unit, 83-feed control unit, 84-exposure control unit, 91-first rotation position sensor (an example of a detection unit), 92-second rotation position sensor, 101-first adjustment mode, 102-second adjustment mode, P-recording medium. DETAILED DESCRIPTION

[0033] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

[0034] <Image Forming Apparatus 10 >

[0035] First, the configuration of the image forming apparatus 10 according to this embodiment will be described. Figure 1 It is a schematic diagram showing the structure of the image forming apparatus 10 according to this embodiment.

[0036] In addition, the arrow UP shown in the figure indicates the top of the device (vertically above), and the arrow DO indicates the bottom of the device (vertically below). Furthermore, 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. Furthermore, 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 directions specified for the convenience of explanation, so the device structure is not limited to these directions. In addition, for each direction of the device, the term "device" is sometimes omitted. That is, for example, sometimes "the top of the device" is simply shown as "the top". Furthermore, the front-to-back direction is equivalent to the axial direction of the sprocket 75 described later, and can also be called a lateral or horizontal direction. Furthermore, the up-down direction, the left-right direction, and the front-to-back direction are directions that intersect with each other (specifically, orthogonal directions).

[0037] In addition, the symbol "X" written in "○" in the figure represents an arrow pointing from the front side to the back side of the paper. In addition, the symbol "·" written in "○" in the figure represents an arrow pointing from the back side to the front side of the paper.

[0038] Figure 1 The image forming apparatus 10 shown 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 unit 12, a delivery unit 13, an image forming unit 14, a transport mechanism 16, a first rotational position sensor 91, a second rotational position sensor 92, and a control device 40. The following describes each component of the image forming apparatus 10 (the medium storage unit 12, the delivery unit 13, the image forming unit 14, the transport mechanism 16, the first rotational position sensor 91, the second rotational position sensor 92, and the control device 40).

[0039] <Media storage unit 12>

[0040] The medium storage unit 12 is a component of the image forming apparatus 10 that stores the recording medium P. The recording medium P stored in the medium storage unit 12 is fed to the transport mechanism 16 by the feed unit 13 .

[0041] For example, paper is used as the recording medium P. The recording medium P is not limited to paper, and may be, for example, a film, as long as an image can be formed thereon.

[0042] <Sending part 13>

[0043] The delivery unit 13 delivers the recording medium P accommodated in the medium accommodating unit 12. Specifically, the delivery unit 13 includes a delivery member 13A that delivers the recording medium P to a gripper 24 of the transport mechanism 16, which will be described later, at a preset delivery timing.

[0044] The delivery member 13A is constituted by, for example, a delivery roller (so-called registration roller) and the like, and the delivery roller delivers the recording medium P delivered from the medium storage unit 12 at a predetermined delivery timing.

[0045] <Image Forming Unit 14>

[0046] Figure 1 The image forming unit 14 shown is a component that forms an image on the recording medium P. Specifically, Figure 1 As shown, the image forming section 14 includes a toner image forming section 30 , a transfer device 60 , and a fixing device 15 .

[0047] <Toner Image Forming Unit 30 >

[0048] Figure 1 The toner image forming unit 30 shown is a component that forms a toner image. Multiple toner image forming units 30 are provided to form toner images for each color. In this embodiment, toner image forming units 30 for four colors, namely yellow (Y), magenta (M), cyan (C), and black (K), are provided. Figure 1 The shown (Y), (M), (C), and (K) represent components corresponding to the above-mentioned colors.

[0049] The toner image forming units 30 of each color have the same structure except for the toner used. Therefore, the toner image forming units 30 of each color are used as representatives. Figure 1 Components of the toner image forming section 30 (M) are denoted by reference numerals.

[0050] Specifically, the toner image forming section 30 of each color has a toner image forming section 30 extending in one direction (for example, Figure 1 The photoreceptor 32 rotates (counterclockwise in the image). Furthermore, the toner image forming unit 30 for each color includes a charger 31, an exposure device 36, and a developing device 38. The photoreceptor 32 is an example of a forming unit. The exposure device 36 is an example of a writing unit.

[0051] In the toner image forming unit 30 for each color, the charger 31 charges the photoreceptor 32 (charging step). The exposure device 36 then exposes the photoreceptor 32 charged by the charger 31 to form an electrostatic latent image on the photoreceptor 32 (exposure step). Specifically, the exposure device 36 exposes the photoreceptor 32 at a preset writing timing, thereby writing the electrostatic latent image onto the photoreceptor 32. The developing device 38 then develops the electrostatic latent image formed on the photoreceptor 32 by the exposure device 36 to form a toner image (development step).

[0052] In this manner, the electrostatic latent image is developed to form a toner image on the photoreceptor 32. The electrostatic latent image is an example of a latent image, and the toner image is an example of an image.

[0053] In this embodiment, when a toner image is formed using four colors, namely yellow (Y), magenta (M), cyan (C), and black (K), the processes of charging, exposure, development, and the primary transfer described later are performed in the order of the toner image forming section 30 (Y), the toner image forming section 30 (M), the toner image forming section 30 (C), and the toner image forming section 30 (K).

[0054] <Transfer device 60>

[0055] Figure 1 The transfer device 60 shown in the figure is a device that transfers the toner images formed by the toner image forming unit 30 of each color to the recording medium P. Specifically, the transfer device 60 transfers the toner images of the photoreceptors 32 of each color to the transfer belt 62 as an intermediate transfer body, and then transfers the superimposed toner images to the recording medium P. Figure 1 As shown, the transfer device 60 includes an endless transfer belt 62, a plurality of primary transfer rollers 35, and a transfer cylinder 70. The transfer cylinder 70 is an example of a transfer member.

[0056] The primary transfer roller 35 is provided in each toner image forming section 30 and is a roller that transfers the toner image of each color of the photoreceptor 32 onto the transfer belt 62 in the primary transfer region T1 between the photoreceptor 32 and the primary transfer roller 35. In the present embodiment, a primary transfer electric field is applied between the primary transfer roller 35 and the photoreceptor 32, so that the toner image formed on the photoreceptor 32 is transferred onto the transfer belt 62 in the primary transfer region T1.

[0057] The toner image is transferred from the photoconductor 32 of each color to the outer peripheral surface of the transfer belt 62. Figure 1As shown, the transfer belt 62 is annular and is wound around a plurality of rollers 64 including a drive roller 64D and an opposing roller 65 in a substantially inverted triangle shape when viewed from the front. The drive roller 64D is rotated by a drive unit 67 such as a drive motor, thereby causing the transfer belt 62 to revolve in the direction of arrow A.

[0058] The transfer drum 70 has a function of transferring the toner image transferred onto the transfer belt 62 onto the recording medium P. Figure 1 and Figure 2 As shown, the transfer cylinder 70 (specifically, the cylinder body 72 described later) has a recess 71 formed on its outer peripheral surface 70A and rotates in the rotation direction B (arrow B direction). The recess 71 is formed long in the axial direction of the transfer cylinder 70 and has a depth along the radial direction of the transfer cylinder 70.

[0059] like Figure 1 As shown, the transfer cylinder 70 is disposed opposite the transfer belt 62 and obliquely to the lower left side of the transfer belt 62. The transfer cylinder 70 is in contact with the transfer belt 62 over the outer peripheral surface 70A from the upstream end to the downstream end in the rotational direction of the recessed portion 71, and is not in contact with the transfer belt 62 in the recessed portion 71.

[0060] like Figure 2 As shown, the transfer cylinder 70 is provided with a pair of sprockets 75 at both ends in the axial direction. Specifically, the transfer cylinder 70 is configured to include a substantially cylindrical cylinder body 72 and a pair of sprockets 75 provided at both ends in the axial direction relative to the cylinder body 72. The pair of sprockets 75 are arranged coaxially with the cylinder body 72.

[0061] In the transfer device 60, a drive mechanism 79 (see Figure 1 ) The transfer cylinder 70 is rotationally driven. In the transfer cylinder 70, the cylinder body 72 is rotationally driven by the drive mechanism 79 and rotates in the rotation direction B. As a result, the cylinder body 72 and the pair of sprockets 75 rotate in the rotation direction B integrally.

[0062] In this embodiment, the transfer belt 62 and the transfer drum 70 (specifically, the drum body 72) rotate while sandwiching the recording medium P being conveyed by the conveying mechanism 16 (specifically, the clamper 24 described below) in the secondary transfer region T2, thereby conveying the recording medium P. Furthermore, by applying a secondary transfer electric field between the opposing roller 65 and the transfer drum 70, the transfer drum 70 transfers the toner image transferred to the transfer belt 62 onto the recording medium P in the secondary transfer region T2. ​​In this manner, while the transfer drum 70 conveys the recording medium P, it transfers the toner image from the transfer belt 62 to the recording medium P in the secondary transfer region T2 between the transfer drum 70 and the transfer belt 62.

[0063] <Fixing device 15>

[0064] Figure 1 The fixing device 15 shown is a device that fixes the toner image transferred to the recording medium P by the transfer cylinder 70 on the recording medium P. Specifically, Figure 1 and Figure 3 As shown, the fixing device 15 includes a fixing drum 50 and a heating roller 52 .

[0065] The fixing cylinder 50 (specifically, the cylinder body 53 described later) has a recess 51 formed on its outer peripheral surface and rotates in the rotation direction E (arrow E direction). The recess 51 is formed to be long in the axial direction of the fixing cylinder 50 and has a depth along the radial direction of the fixing cylinder 50 .

[0066] like Figure 3 As shown, the fixing cylinder 50 is provided with a pair of sprockets 55 at both axial ends. Specifically, the fixing cylinder 50 is configured to include a substantially cylindrical cylinder body 53 and sprockets 55 provided at both axial ends relative to the cylinder body 53. The pair of sprockets 55 are coaxially arranged with the cylinder body 53. Furthermore, in the fixing cylinder 50, as the cylinder body 53 is driven by a driving unit (not shown) to rotate in the rotation direction E, the cylinder body 53 and the pair of sprockets 55 rotate integrally in the rotation direction E.

[0067] The heating roller 52 is arranged on the upper side relative to the fixing cylinder 50. The heating roller 52 has a heat source 52A such as a halogen lamp inside the roller (see FIG. Figure 1 ). Furthermore, the heating roller 52 rotates in a direction opposite to the rotation direction E, that is, in a rotation direction F (direction of arrow F).

[0068] In the fixing device 15, the heat roller 52 and the fixing cylinder 50 rotate while sandwiching the recording medium P conveyed by the conveying mechanism 16 (specifically, the clamper 24 described later) at the fixing position NP, thereby conveying the recording medium P. The heat roller 52 heats the recording medium P, and the heat roller 52 and the fixing cylinder 50 apply pressure to the recording medium P, thereby fixing the toner image transferred to the recording medium P onto the recording medium P.

[0069] <Transmission mechanism 16>

[0070] Figure 1 The transport mechanism 16 shown is a mechanism for transporting the recording medium P. Figure 1 and Figure 4 As shown, the conveying mechanism 16 includes a pair of sprockets 27, a pair of chains 22, and a clamper 24. The clamper 24 is an example of a holding portion.

[0071] In addition, Figure 1 1 shows one of the pair of chains 22 and one of the pair of sprockets 27 , and the chain 22 , the sprocket 27 and the clamp 24 are shown in a simplified manner.

[0072] 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 on the right side relative to the pair of sprockets 55 (ie, on the side of the pair of sprockets 75). Figure 4 As shown, the pair of sprockets 27 are arranged at intervals in the front-rear direction.

[0073] like Figure 1 As shown, a pair of chains 22 are formed into a ring shape. Figure 4 As shown, the pair of chains 22 are arranged at intervals in the front-to-back direction. The pair of chains 22 are respectively wound around each of a pair of sprockets 75 provided on both axial ends of the transfer cylinder 70, each of a pair of sprockets 55 provided on both axial ends of the fixing cylinder 50, and each of a pair of sprockets 27. Furthermore, the transfer cylinder 70 is driven to rotate in the rotation direction B, and the fixing cylinder 50 is driven to rotate in the rotation direction E, whereby the chain 22 is wound around in the winding direction (direction of arrow C). In this way, the chain 22 functions as a winding portion that is wound around in the winding direction C. In addition, the transfer cylinder 70 and the fixing cylinder 50 are driven to rotate synchronously, and the pair of sprockets 27 rotates as the chain 22 is wound around. Therefore, in this embodiment, the pair of chains 22, the pair of sprockets 27, the transfer cylinder 70, and the fixing cylinder 50 rotate as a whole.

[0074] like Figure 4 As shown, the mounting member 23 having the clamp 24 mounted thereon spans the pair of chains 22 in the front-rear direction. The plurality of mounting members 23 are fixed to the pair of chains 22 at predetermined intervals along the circling direction C of the chains 22.

[0075] like Figure 4 As shown in FIG. 1 , a plurality of clamps 24 are mounted on the mounting member 23 at predetermined intervals along the front-back direction. The clamps 24 function as a holding portion for holding the front end portion of the recording medium P. Specifically, as shown in FIG. Figure 5 As shown, the clamper 24 includes a claw 24A and a claw frame 24B. The clamper 24 is configured to hold the recording medium P by clamping the leading end of the recording medium P between the claw 24A and the claw frame 24B. Furthermore, in the clamper 24, for example, the claw 24A is pressed against the claw frame 24B by a spring or the like, and the claw 24A opens and closes relative to the claw frame 24B by a cam or the like.

[0076] In the transmission mechanism 16, as Figure 5 As shown, the front end of the recording medium P fed out from the medium storage unit 12 by the feeding unit 13 is held by the clamper 24. In this embodiment, the clamper 24 is at a predetermined holding start position (for example, Figure 1 The recording medium P is maintained starting from the position indicated by the symbol SP in FIG.

[0077] Here, in the transport mechanism 16, the circumference of the chain 22 is set to, for example, a natural multiple of the circumference of the sprocket 27. Furthermore, the mounting members 23 (i.e., the clampers 24) are mounted on the chain 22 at intervals corresponding to, for example, the circumference of the sprocket 27. Thus, each time the sprocket 27 rotates once, the plurality of clampers 24 sequentially reach the holding start position and begin holding the recording medium P at the holding start position.

[0078] Furthermore, in the transport mechanism 16, the gripper 24 holding the leading end of the recording medium P is rotated in the rotation direction C by the chain 22, and moves integrally with the rotation of the transfer drum 70, thereby transporting the recording medium P and passing through the secondary transfer area T2. In the secondary transfer area T2, the transfer drum 70 secondary transfers the toner images of each color, which were primarily transferred onto the transfer belt 62 in the primary transfer area T1, onto the recording medium P in the secondary transfer area T2.

[0079] The chain 22 is then wound in the winding direction C, and the gripper 24 holding the leading end of the recording medium P conveys the recording medium P and passes through the fixing position NP. Furthermore, in the fixing device 15, the recording medium P is clamped by the heating roller 52 and the fixing cylinder 50 at the fixing position NP, and the image on the recording medium P is fixed to the recording medium.

[0080] Furthermore, when the gripper 24 passes through the secondary transfer area T2, it is accommodated together with the mounting member 23 in a recessed portion 71 formed on the outer peripheral surface of the transfer cylinder 70, thereby avoiding contact with the transfer belt 62. Furthermore, when the gripper 24 passes through the fixing position NP, it is accommodated together with the mounting member 23 in a recessed portion 51 formed on the outer peripheral surface of the fixing cylinder 50, thereby avoiding contact with the heating roller 52.

[0081] Furthermore, the pair of sprockets 75 provided at both ends of the transfer cylinder 70 in the axial direction and the pair of sprockets 55 provided at both ends of the fixing cylinder 50 in the axial direction can be understood as components of the conveying mechanism 16 .

[0082] <First Rotational Position Sensor 91>

[0083] Figure 4 The first rotational position sensor 91 shown 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 the sprocket 27. Specifically, the first rotational position sensor 91 detects when the rotating sprocket 27 has reached the first reference rotational position (in other words, a predetermined rotational angle).

[0084] As the first rotation position sensor 91, for example, a photosensor (see FIG. 1 ) that detects the passage of an actuator 91A attached to the rotation shaft 29 of the sprocket 27 can be used. Figure 4 ).

[0085] Here, in this embodiment, the arrival timing of each clamp 24 reaching the holding start position whenever the sprocket 27 rotates one circle (in other words, the holding start timing at which the clamp 24 starts to hold the recording medium P) is synchronized with the timing at which the sprocket 27 reaches the first reference rotation position (i.e., the timing at which the first rotation position sensor 91 detects the first reference rotation position).

[0086] Furthermore, the detection timing of the first rotational position sensor 91 serves as a reference for the delivery timing of the delivery unit 13. In this embodiment, as will be described later, the delivery unit 13 delivers the recording medium P to the clamper 24 based on the detection timing of the first reference rotational position by the first rotational position sensor 91. Thus, the recording medium P reaches the holding start position in synchronization with the timing at which the clamper 24 reaches the holding start position (in other words, the holding start timing of the recording medium P in the clamper 24).

[0087] Detection information (ie, detection signal) of the reference rotational position detected by the first rotational position sensor 91 is transmitted to the control device 40. 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 is one rotation of the sprocket 27.

[0088] <Second Rotational Position Sensor 92>

[0089] Figure 2 The second rotational position sensor 92 shown is a component that detects a predetermined rotational position (hereinafter referred to as a second reference rotational position) of the transfer cylinder 70. Specifically, the second rotational position sensor 92 detects when the rotating transfer cylinder 70 has reached the second reference rotational position (in other words, a predetermined rotational angle).

[0090] As the second rotation position sensor 92, for example, a photosensor (see FIG. 1 ) that detects the passage of an actuator 92A attached to the rotation shaft 73 of the transfer cylinder 70 can be used. Figure 2 ).

[0091] Here, in this embodiment, the second reference rotation position detected by the second rotation position sensor 92 coincides with the position at which the secondary transfer of the recording medium P transported by the transport mechanism 16 (specifically, the clamp 24) in a state of being arranged on the outer peripheral surface 70A of the transfer cylinder 70 is started (hereinafter referred to as the secondary transfer start position).

[0092] Therefore, the 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 of the recording medium P, which is being transported by the transport mechanism 16 (specifically, the gripper 24) while being disposed on the outer peripheral surface 70A of the transfer cylinder 70, begins. The secondary transfer start timing can also be referred to as the timing at which the recording medium P (specifically, the leading end of the transfer area in the recording medium P) reaches the secondary transfer start position. This secondary transfer start timing is an example of transfer start timing.

[0093] Specifically, the secondary transfer start position is the position where the front end (downstream end in the conveying direction) of the image area of ​​the recording medium P disposed on the outer peripheral surface 70A of the transfer cylinder 70 begins to be introduced into the secondary transfer area T2. For example, the secondary transfer start position is the upstream end 71X in the rotation direction of the concave portion 71 of the transfer cylinder 70 (refer to Figure 2 ) starts to be introduced into the position of the secondary transfer area T2 (the position facing the opposing roller 65).

[0094] 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 will be described later, the exposure device 36 writes the electrostatic latent image on the photoreceptor 32 based on the detection timing when the second rotational position sensor 92 detects the second reference rotational position.

[0095] Detection information (i.e., detection signal) of the reference rotational position detected by the second rotational position sensor 92 is transmitted to the control device 40. 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 is one rotation of the transfer cylinder 70.

[0096] <Control device 40>

[0097] The control device 40 is an example of a speed adjustment mechanism. Figure 6 As shown, the system includes a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a storage device 44, and a communication interface (I / F) 45. Furthermore, each component is connected to each other via a bus 49 so as to be communicable with each other. Furthermore, the CPU 41 (specifically, the speed adjustment unit 82 described later) can also be understood as an example of a speed adjustment mechanism.

[0098] The CPU 41 is a central processing unit that executes various programs and controls various components. The ROM 42 stores various programs, including control programs, and various data. The RAM 43 serves as a work area for temporary storage of programs and data. The storage device 44 is composed of a storage medium such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or flash memory, and stores various programs, including the operating system, and various data. The control program may also be stored in the storage device 44.

[0099] The communication interface 45 is an interface for communicating with other components, including the image forming unit 14 of the exposure device 36, the delivery unit 13, the first rotational position sensor 91, the second rotational position sensor 92, the drive unit 67, and the drive mechanism 79. The communication interface 45 communicates with the other components using a communication method such as wired, wireless, the Internet, or an intranet.

[0100] In the control device 40, the CPU 41 reads various programs, including the control program, from the ROM 42 or storage device 44 and executes the programs using the RAM 43 as a work area. Furthermore, the CPU 41 controls the operation of each component of the image forming apparatus 10 by executing the control programs. The following describes the functional configuration achieved through the collaboration of the CPU 41 as a hardware resource and the information processing program as a software resource. Figure 7 This is a block diagram showing an example of the functional configuration of the control device 40 according to the present embodiment.

[0101] In addition, the control device 40 may be configured as a speed adjustment device specifically for adjusting the rotation speed of the transfer cylinder 70 .

[0102] In the control device 40, the CPU 41 executes the control program, such as Figure 7 As shown, it functions as an acquisition section 80 , a drive control section 81 , a speed adjustment section 82 , a delivery control section 83 , and an exposure control section 84 .

[0103] The acquisition unit 80 acquires detection information (i.e., a detection signal) from the first rotational position sensor 91 indicating that the first rotational position sensor 91 has detected the first reference rotational position. Furthermore, the acquisition unit 80 acquires detection information (i.e., a detection signal) from the second rotational position sensor 92 indicating that the second rotational position sensor 92 has detected the second reference rotational position.

[0104] The delivery control unit 83 controls the delivery unit 13 to deliver the recording medium P to the clamp 24 (i.e., the holding start position) based on the detection timing of the first reference rotation position detected by the first rotation position sensor 91, so that the recording medium P reaches the holding start position at the timing when the clamp 24 reaches the holding start position (in other words, the holding start timing of the recording medium P in the clamp 24).

[0105] Alternatively, the delivery speed (conveying speed) of the delivery unit 13 and the path length from the delivery unit 13 to the holding start position may be set so that the recording medium P is delivered by the delivery unit 13 at the detection timing of the first rotational position sensor 91, and the timing at which the gripper 24 reaches the holding start position (in other words, the timing at which the recording medium P in the gripper 24 starts to be held) is synchronized with the timing at which the recording medium P reaches the holding start position. In this case, the delivery control unit 83 controls the delivery unit 13 to deliver the recording medium P at the detection timing of the first rotational position sensor 91.

[0106] The exposure control unit 84 controls the exposure device 36 to write the electrostatic latent image onto the photosensitive body 32 based on the detection timing of the second reference rotation position detected by the second rotation position sensor 92, so that the timing at which the toner image transferred from the photosensitive body 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).

[0107] 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)) that is initially activated among the multiple toner image forming units 30 (e.g., the toner image forming unit 30(M), 30(C), and 30(K)). In this embodiment, after the exposure device 36 with controlled writing timing has written in this toner image forming unit, the exposure devices 36 in the other toner image forming units sequentially write. Furthermore, after the development process is performed in each toner image forming unit, the toner image is transferred to the transfer belt 62.

[0108] The drive control unit 81 is a functional unit that controls the driving of the drive unit 67 that rotationally drives the drive roller 64D. For example, the drive control unit 81 generates a pulse signal and controls the driving of the drive unit 67 based on the pulse signal. A servo motor or a stepping motor is used as the drive unit 67, for example.

[0109] The speed adjustment unit 82 is a functional unit that adjusts the speed of the transfer cylinder 70 by controlling the driving mechanism 79 that rotationally drives the transfer cylinder 70. For example, the speed adjustment unit 82 generates a pulse signal and controls the driving mechanism 79 based on the pulse signal. Specifically, a servo motor or a stepping motor is used as the driving mechanism 79.

[0110] The speed adjustment unit 82 adjusts the rotation speed of the transfer cylinder 70 by the drive mechanism 79 in units of one rotation of the transfer cylinder 70. Specifically, the speed adjustment unit 82 switches to the first adjustment mode 101 (see FIG. 1 ) in units of one rotation of the transfer cylinder 70. Figure 8 ) and a second adjustment mode 102 (reference Figure 8 ).

[0111] Here, the load (rotational resistance) acting on the transfer belt 62 changes depending on whether the transfer drum 70 is in contact with the transfer belt 62 and whether the transfer drum 70 is conveying the recording medium P while the transfer drum 70 is in contact with the transfer belt 62 (in other words, whether the recording medium P passes through the secondary transfer area T2). In this embodiment, the first adjustment mode 101 (see FIG. 1 ) set as follows is switched to each rotation of the transfer drum 70. Figure 8 ) and the second adjustment mode 102 (reference Figure 8 ) to suppress the variation (ie, deviation) of the rotational torque in the driving roller 64D.

[0112] The first adjustment mode 101 is a mode for adjusting the rotation speed of the transfer cylinder 70 in a loop including a state where the transfer cylinder 70 does not convey the recording medium P. The second adjustment mode 102 is a mode for adjusting the rotation speed of the transfer cylinder 70 in a loop including a state where the transfer cylinder 70 conveys the recording medium P.

[0113] The time of the first adjustment mode 101 and the second adjustment mode 102 coincides with the time it takes for the transfer drum 70 to make one rotation, and the average value of the rotation speed in the first adjustment mode 101 coincides with the average value of the rotation speed in the second adjustment mode 102 .

[0114] In the present embodiment, the average value of the rotational speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 excluding the recessed portion 71 passes through the secondary transfer region T2 in the second adjustment pattern 102 is different from the average value in the first adjustment pattern 101. Specifically, as an example, the average value of the rotational speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 excluding the recessed portion 71 passes through the secondary transfer region T2 in the second adjustment pattern 102 is higher than the average value in the first adjustment pattern 101.

[0115] Furthermore, in this embodiment, as an example, the average value of the rotational speed of the transfer drum 70 when the concave portion 71 of the transfer drum 70 passes through the secondary transfer region T2 in the second adjustment mode 102 is lower than that in the first adjustment mode 101 .

[0116] Furthermore, in the first adjustment mode 101, as an example, the average value of the rotational speed of the transfer cylinder 70 when the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer area T2 is higher than the average value of the rotational speed of the transfer cylinder 70 when the portion other than the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer area T2.

[0117] The adjustment mode is switched according to the transport status of the recording medium P by the transport mechanism 16 , for example, by switching to the other mode after executing one of the first adjustment mode 101 and the second adjustment mode 102 once or more.

[0118] <Functions of the First Adjustment Mode 101 and the Second Adjustment Mode 102>

[0119] In this embodiment, as described above, the first adjustment mode 101 is a mode for adjusting the rotation speed of the transfer cylinder 70 in a loop including a state in which the transfer cylinder 70 does not transport the recording medium P, and the second adjustment mode 102 is a mode for adjusting the rotation speed of the transfer cylinder 70 in a loop including a state in which the transfer cylinder 70 transports the recording medium P.

[0120] Therefore, compared with the first adjustment mode 101 and the second adjustment mode 102, which are modes for adjusting the rotation speed of the transfer cylinder 70 in a circle including a state in which the transfer cylinder 70 transports the recording medium P, the rotation speed of the transfer cylinder 70 can be adjusted to an appropriate rotation speed in a state in which the transfer cylinder 70 transports the recording medium P and an appropriate rotation speed in a state in which the transfer cylinder 70 does not transport the recording medium P.

[0121] Furthermore, in this embodiment, the average value of the rotational speed of the transfer drum 70 when the portion of the transfer drum 70 excluding the recessed portions 71 passes through the secondary transfer region T2 in the second adjustment mode 102 is higher than that in the first adjustment mode 101 .

[0122] Here, when the recording medium P passes through the secondary transfer area T2, the load on the transfer belt 62 may be greater than when the recording medium P does not pass through the secondary transfer area T2. In this case, by increasing the average value in the second adjustment mode 102, the load on the transfer belt 62 is reduced.

[0123] Therefore, compared with the case where the average value of the rotation speed of the transfer drum 70 when the portion of the transfer drum 70 excluding the recessed portion 71 passes through the secondary transfer area T2 in the second adjustment pattern 102 is the same as that in the first adjustment pattern 101 , the torque fluctuation of the drive roller 64D can be reduced.

[0124] Furthermore, in this embodiment, the average value of the rotational speed of the transfer drum 70 when the concave portion 71 of the transfer drum 70 passes through the secondary transfer region T2 in the second adjustment mode 102 is lower than that in the first adjustment mode 101 .

[0125] As described above, in this embodiment, the average value of the transfer cylinder 70's rotational speed when the portion of the transfer cylinder 70 excluding the recessed portions 71 passes through the secondary transfer area T2 in the second adjustment pattern 102 is set higher than the average value in the first adjustment pattern 101. Therefore, compared to a case where the average value of the transfer cylinder 70's rotational speed when the recessed portions 71 of the transfer cylinder 70 pass through the secondary transfer area 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 transfer cylinder 70's rotational speed in the first adjustment pattern 101 and the overall average value of the transfer cylinder 70's rotational speed in the second adjustment pattern 102 is smaller. In other words, the overall average value of the transfer cylinder 70's rotational speed in the first adjustment pattern 101 and the overall average value of the transfer cylinder 70's rotational speed in the second adjustment pattern 102 can be made equal.

[0126] <Synchronization with Switching Timing in Speed ​​Adjustment Unit 82>

[0127] The speed adjustment unit 82 synchronizes the timing for switching between the first adjustment mode 101 and the second adjustment mode 102 (hereinafter referred to as the switching timing) with the timing at which the second rotational position sensor 92 detects the second reference rotational position. This detection timing is synchronized with the transfer start timing at which the transfer drum 70 starts transferring the toner image transferred onto the transfer belt 62 onto the recording medium P. Therefore, the speed adjustment unit 82 synchronizes this switching timing with the transfer start timing at which the transfer drum 70 starts transferring the toner image transferred onto the transfer belt 62 onto the recording medium P.

[0128] Furthermore, the speed adjustment unit 82 synchronizes this switching timing with the detection timing of the first reference rotational position by the first rotational position sensor 91. This detection timing is synchronized with the timing when the clamper 24 reaches the holding start position (in other words, the timing when the clamper 24 starts holding the recording medium P). Therefore, the speed adjustment unit 82 synchronizes this switching timing with the timing when the clamper 24 starts holding the recording medium P.

[0129] <Effect of Synchronization with Switching Timing in Speed ​​Adjustment Unit 82>

[0130] In the present embodiment, the speed adjustment section 82 synchronizes the switching timing between the first adjustment mode 101 and the second adjustment mode 102 with the holding start timing at which the clamper 24 starts holding the recording medium P.

[0131] Here, when the speed adjustment unit 82 switches between the first adjustment mode 101 and the second adjustment mode 102 regardless of the timing at which the clamper 24 starts holding the recording medium P (hereinafter referred to as mode A), the speed profiles of the first adjustment mode 101 and the second adjustment mode 102 differ, and thus the holding position of the recording medium P by the clamper 24 may deviate, thereby changing the clamping margin (i.e., the margin at the leading end of the recording medium P). As a result, the transfer position of the image onto the recording medium P may deviate.

[0132] In contrast, in this embodiment, as described above, the speed adjustment unit 82 synchronizes the timing of switching between the first adjustment mode 101 and the second adjustment mode 102 with the timing at which the clamper 24 starts holding the recording medium P. Therefore, even when the adjustment mode is switched between the first adjustment mode 101 and the second adjustment mode 102, the position at which the clamper 24 holds the recording medium P is less likely to deviate from the position at which the clamper 24 holds the recording medium P, compared to method A. As a result, the position at which the image is transferred to the recording medium P is less likely to deviate from the position at which the image is transferred.

[0133] Furthermore, in the present embodiment, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment mode 101 and the second adjustment mode 102 with the detection timing of the first reference rotational position by the first rotational position sensor 91 .

[0134] Here, the delivery unit 13 delivers the recording medium P to the clamper 24 (specifically, the holding start position) based on this detection timing. When the speed adjustment unit 82 switches between the first adjustment mode 101 and the second adjustment mode 102 regardless of this detection timing (hereinafter referred to as mode B), the speed profiles of the first adjustment mode 101 and the second adjustment mode 102 differ, and thus the holding position of the recording medium P by the clamper 24 may deviate, thereby changing the clamping margin (i.e., the margin on the leading end of the recording medium P). As a result, the position at which the image is transferred onto the recording medium P may deviate.

[0135] In contrast, in this embodiment, as described above, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment mode 101 and the second adjustment mode 102 with the detection timing of the first reference rotational position by the first rotational position sensor 91. Therefore, even when the adjustment mode is switched between the first adjustment mode 101 and the second adjustment mode 102, the position at which the clamper 24 holds the recording medium P is less likely to deviate from the position at which the clamper 24 holds the recording medium P, compared to method B. As a result, the position at which the image is transferred to the recording medium P is less likely to deviate from the position at which the image is transferred.

[0136] Furthermore, in the present embodiment, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment mode 101 and the second adjustment mode 102 with the detection timing of the second reference rotational position by the second rotational position sensor 92 .

[0137] Here, when the speed adjustment unit 82 switches between the first adjustment mode 101 and the second adjustment mode 102 regardless of the detection timing (hereinafter referred to as method C), since the speed distribution of the first adjustment mode 101 and the second adjustment mode 102 are different, the writing timing of the exposure device 36 sometimes deviates, thereby causing a deviation in the transfer position of the image transferred to the recording medium P.

[0138] In contrast, in this embodiment, as described above, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment mode 101 and the second adjustment mode 102 with the detection timing of the second reference rotation position by the second rotation position sensor 92. Therefore, even when the adjustment mode is switched between the first adjustment mode 101 and the second adjustment mode 102, the deviation in the writing timing is suppressed compared to method C, thereby suppressing the deviation in the transfer position of the image transferred to the recording medium P.

[0139] Furthermore, in this embodiment, the speed adjustment section 82 synchronizes the switching timing between the first adjustment mode 101 and the second adjustment mode 102 with the secondary transfer start timing when the transfer drum 70 starts transferring the toner image transferred onto the transfer belt 62 onto the recording medium P.

[0140] Here, when the speed adjustment unit 82 switches between the first adjustment mode 101 and the second adjustment mode 102 regardless of the transfer start timing (hereinafter referred to as method D), since the speed distribution of the first adjustment mode 101 and the second adjustment mode 102 are different, the transfer start timing sometimes deviates, thereby causing a deviation in the transfer position where the image is transferred to the recording medium P.

[0141] In contrast, in the present embodiment, as described above, the speed adjustment unit 82 synchronizes the switching timing between the first adjustment mode 101 and the second adjustment mode 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 mode is switched between the first adjustment mode 101 and the second adjustment mode 102, the deviation in the transfer start timing is suppressed compared to method D, thereby suppressing the deviation in the transfer position of the image transferred to the recording medium P.

[0142] <Change of Distribution in Speed ​​Adjustment Unit 82>

[0143] Furthermore, during the rotation of the transfer belt 62, the speed adjustment unit 82 is in the first adjustment mode 101 and the second adjustment mode 102, as shown in FIG. Figure 8 As shown by the two-dot chain line, the speed distribution can be changed while maintaining the average value of the rotation speed of the transfer drum 70 .

[0144] When the speed adjustment section 82 changes the speed profile while maintaining the average value of the rotational speed of the transfer drum 70 in each of the first adjustment mode 101 and the second adjustment mode 102 during the revolving process of the transfer belt 62 (hereinafter referred to as a case where the profile change X1 is performed), the exposure control section 84 controls the exposure device 36 to write the electrostatic latent image onto the photoreceptor 32 at the same writing timing as before the change. Thus, even when the profile change X1 is performed, the exposure device 36 writes the electrostatic latent image onto the photoreceptor 32 at the same writing timing as before the change.

[0145] Furthermore, in this embodiment, when the speed adjustment section 82 performs the distribution change X1 , the transfer drum 70 starts transferring the toner image transferred to the transfer belt 62 to the recording medium P at the same start timing as before the change.

[0146] Furthermore, in the present embodiment, when the speed adjustment unit 82 performs the distribution change X1, the clamper 24 holds the recording medium P at the same holding start timing as before the change.

[0147] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the feed control unit 83 controls the feed unit 13 to feed the recording medium P at the same feed timing as before the change. Thus, even when the profile change X1 is performed, the feed unit 13 feeds the recording medium P at the same feed timing as before the change.

[0148] <Effect of Change in Distribution in Speed ​​Adjustment Unit 82>

[0149] In this embodiment, as described above, the speed adjustment unit 82 is in the first adjustment mode 101 and the second adjustment mode 102 during the circulation of the transfer belt 62. Figure 8 As shown by the two-dot chain line, the speed distribution can be changed while maintaining the average value of the rotation speed of the transfer drum 70 .

[0150] Thus, the rotation speed of the transfer drum 70 in each of the first adjustment mode 101 and the second adjustment mode 102 can be changed according to the torque fluctuation of the drive roller 64D during the rotation of the transfer belt 62 .

[0151] Here, in this embodiment, since the switching timing of switching the first adjustment mode 101 and the second adjustment mode 102 is synchronized with various timings (detection timing, hold start timing, and secondary transfer start timing in the first rotation position sensor 91 and the second rotation position sensor 92), even if the speed distribution is changed in the first adjustment mode 101 and the second adjustment mode 102, it is not easy to produce various timing deviations, thereby suppressing the deviation of the transfer position of the image transferred to the recording medium P.

[0152] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the exposure device 36 writes the electrostatic latent image on the photoreceptor 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.

[0153] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the profile change X1, the transfer drum 70 starts transferring the toner image transferred to 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 drum 70.

[0154] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the distribution change X1, the clamper 24 holds the recording medium P at the same hold start timing as before the change. Therefore, it is not necessary to control the hold start timing of the clamper 24.

[0155] Furthermore, in this embodiment, when the speed adjustment unit 82 performs the distribution change X1, the delivery unit 13 delivers the recording medium P at the same delivery timing as before the change. Therefore, it is not necessary to control the delivery timing of the delivery unit 13.

[0156] Modifications

[0157] In this embodiment, the speed adjustment unit 82 synchronizes the timing of switching between the first adjustment mode 101 and the second adjustment mode 102 with the timing of detecting the second reference rotational position by the second rotational position sensor 92. However, the present invention is not limited to this. For example, the speed adjustment unit 82 may be configured to switch between the first adjustment mode 101 and the second adjustment mode 102 independently of the detection timing.

[0158] Furthermore, in this embodiment, the speed adjustment unit 82 synchronizes the timing of switching between the first adjustment mode 101 and the second adjustment mode 102 with the timing at which the transfer drum 70 starts secondary transfer of the toner image transferred onto the transfer belt 62 onto the recording medium P. However, the present invention is not limited thereto. For example, the speed adjustment unit 82 may be configured to switch between the first adjustment mode 101 and the second adjustment mode 102 independently of the transfer start timing.

[0159] Furthermore, in this embodiment, the speed adjustment unit 82 synchronizes the timing of switching between the first adjustment mode 101 and the second adjustment mode 102 with the timing of detecting the first reference rotational position by the first rotational position sensor 91. However, this is not limiting. For example, the speed adjustment unit 82 may be configured to switch between the first adjustment mode 101 and the second adjustment mode 102 independently of the detection timing.

[0160] Furthermore, in this embodiment, the first adjustment pattern 101 is a mode for adjusting the rotational speed of the transfer cylinder 70 during a loop including a state in which the transfer cylinder 70 is not conveying the recording medium P, and the second adjustment pattern 102 is a mode for adjusting the rotational speed of the transfer cylinder 70 during a loop including a state in which the transfer cylinder 70 is conveying the recording medium P. However, the present invention is not limited thereto. For example, the first adjustment pattern 101 and the second adjustment pattern 102 may be modes for adjusting the rotational speed of the transfer cylinder 70 during a loop including a state in which the transfer cylinder 70 is conveying the recording medium P. The first adjustment pattern 101 and the second adjustment pattern 102 may also be any adjustment pattern consisting of a speed distribution.

[0161] Furthermore, in this embodiment, the average value of the transfer drum 70's rotational speed when the portion of the transfer drum 70 excluding the recessed portions 71 passes through the secondary transfer area T2 in the second adjustment pattern 102 is set to be higher than the average value in the first adjustment pattern 101, but this is not limiting. For example, the average value of the transfer drum 70's rotational speed when the portion of the transfer drum 70 excluding the recessed portions 71 passes through the secondary transfer area T2 in the second adjustment pattern 102 may be the same as the average value in the first adjustment pattern 101. Furthermore, for example, the average value of the transfer drum 70's rotational speed when the portion of the transfer drum 70 excluding the recessed portions 71 passes through the secondary transfer area T2 in the second adjustment pattern 102 may be lower than the average value in the first adjustment pattern 101. Here, when the recording medium P passes through the secondary transfer area T2, the load on the transfer belt 62 may be reduced compared to when the recording medium P does not pass through the secondary transfer area T2. In this case, the load on the transfer belt 62 is reduced by reducing the average value in the second adjustment pattern 102. Therefore, compared with the case where the average value of the rotational speed of the transfer drum 70 when the portion of the transfer drum 70 excluding the recessed portion 71 passes through the secondary transfer area T2 in the second adjustment pattern 102 is the same as the average value in the first adjustment pattern 101, the torque fluctuation of the drive roller 64D can be reduced.

[0162] Furthermore, in this embodiment, the average value of the rotational speed of the transfer cylinder 70 when the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer area T2 in the second adjustment pattern 102 is set to be lower than the average value in the first adjustment pattern 101, but this is not limiting. For example, the average value of the rotational speed of the transfer cylinder 70 when the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer area T2 in the second adjustment pattern 102 may be the same as the average value in the first adjustment pattern 101. Furthermore, for example, the average value of the rotational speed of the transfer cylinder 70 when the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer area T2 in the second adjustment pattern 102 may be set to be higher than the average value in the first adjustment pattern 101.

[0163] Furthermore, in the first adjustment mode 101, as an example, the average rotational speed of the transfer cylinder 70 when the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 is set to be higher than the average rotational speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the concave portion 71 passes through the secondary transfer region T2, but the present invention is not limited thereto. For example, in the first adjustment mode 101, the average rotational speed of the transfer cylinder 70 when the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 may be the same as the average rotational speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the concave portion 71 passes through the secondary transfer region T2. ​​Furthermore, in the first adjustment mode 101, the average rotational speed of the transfer cylinder 70 when the concave portion 71 of the transfer cylinder 70 passes through the secondary transfer region T2 may be set to be lower than the average rotational speed of the transfer cylinder 70 when the portion of the transfer cylinder 70 other than the concave portion 71 passes through the secondary transfer region T2.

[0164] Furthermore, in this embodiment, the speed distribution can be changed while maintaining the average value of the rotational speed of the transfer drum 70 in each of the first adjustment mode 101 and the second adjustment mode 102 during the revolving process of the transfer belt 62. However, the present invention is not limited to this. Alternatively, a configuration may be employed in which the speed distribution in each of the first adjustment mode 101 and the second adjustment mode 102 is always maintained (i.e., a configuration in which the speed distribution cannot be changed).

[0165] Furthermore, in this embodiment, when the distribution change X1 is performed, the exposure device 36 is configured to write the electrostatic latent image onto the photoreceptor 32 at the same writing timing as before the change. However, the present invention is not limited to this. For example, when the distribution change X1 is performed, the exposure device 36 may be configured to write the electrostatic latent image onto the photoreceptor 32 at a writing timing different from that before the change.

[0166] Furthermore, in this embodiment, when the distribution change X1 is performed, the transfer drum 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. However, the present invention is not limited to this. For example, when the distribution change X1 is performed, the transfer drum 70 may start transferring the toner image transferred onto the transfer belt 62 onto the recording medium P at a different start timing than before the change.

[0167] Furthermore, in this embodiment, when the distribution change X1 is performed, the clamper 24 is configured to hold the recording medium P at the same hold start timing as before the change. However, the present invention is not limited to this. For example, when the distribution change X1 is performed, the clamper 24 may be configured to hold the recording medium P at a different hold start timing than before the change.

[0168] Furthermore, in this embodiment, when the distribution change X1 is performed, the delivery unit 13 is configured to deliver the recording medium P at the same delivery timing as before the change. However, this is not limiting. For example, when the distribution change X1 is performed, the delivery unit 13 may be configured to deliver the recording medium P at a different delivery timing than before the change.

[0169] The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made without departing from the spirit of the present invention. For example, the above-described modified examples can be appropriately combined in multiple configurations.

[0170] Furthermore, in the above-mentioned embodiment, the processor refers to a processor in a broad sense, including general-purpose processors (for example, the aforementioned CPU, etc.), special-purpose processors (for example, GPU: Graphics Processing Unit (image processor), ASIC: Application Specific Integrated Circuit (application-specific integrated circuit), FPGA: Field Programmable Gate Array (field programmable gate array), programmable logic devices, etc.).

[0171] Furthermore, the operations of the processors in the above embodiments may be performed not only by a single processor but also by a plurality of processors located in physically separate locations working together. Furthermore, the order of the operations of the processors is not limited to that described in the above embodiments and may be modified as appropriate.

[0172] <Note> (1)

[0174] An image forming apparatus comprising:

[0175] An endless transfer belt transfers the image formed on the forming body to the outer peripheral surface;

[0176] a driving roller, wound with the transfer belt and causing the transfer belt to revolve;

[0177] a transfer body for transferring the image from the transfer belt to the recording medium in a transfer area between the transfer belt and the recording medium while the recording medium is being conveyed;

[0178] a driving mechanism for rotating and driving the transfer body;

[0179] a holding portion that holds the recording medium and moves integrally with the rotation of the transfer body to allow the recording medium to pass through the transfer area; and

[0180] A speed adjustment mechanism adjusts the rotational speed of the transfer body based on the driving mechanism in units of one revolution of the transfer body, and switches between a first adjustment mode and a second adjustment mode different from the first adjustment mode in units of one revolution of the transfer body, and synchronizes the switching timing with the holding start timing of the holding portion starting to hold the recording medium. (2)

[0182] The image forming apparatus according to (1), comprising:

[0183] a rotating body that rotates synchronously with the rotation of the transfer body;

[0184] a detection unit for detecting a preset rotational position of the rotating body; and

[0185] a delivery unit that delivers the recording medium to the holding unit based on a detection timing at which the detection unit detects the rotational position,

[0186] The holding portion holds the recording medium fed from the feeding portion and moves integrally with the rotation of the transfer body to allow the recording medium to pass through the transfer area.

[0187] The speed adjustment mechanism synchronizes the switching timing with the detection timing. (3)

[0189] The image forming apparatus according to (1) or (2), wherein

[0190] The first adjustment mode is a mode for adjusting the rotation speed of the transfer body in a rotation including a state in which the transfer body does not convey the recording medium.

[0191] The second adjustment mode is a mode for adjusting the rotation speed of the transfer body in a loop including a state in which the transfer body conveys the recording medium. (4)

[0193] The image forming apparatus according to (3), wherein

[0194] The transfer body has a recessed portion on its outer peripheral surface that can accommodate the holding portion.

[0195] In the second adjustment mode, an average value of the rotational speed of the transfer body when a portion of the transfer body other than the concave portion passes through the transfer region is different from the average value in the first adjustment mode. (5)

[0197] The image forming apparatus according to any one of (1) to (4), wherein

[0198] The speed adjustment mechanism can change the speed distribution while maintaining the average value of the rotational speed of the transfer body in each of the first adjustment mode and the second adjustment mode during the rotation of the transfer belt. (6)

[0200] The image forming apparatus according to (5), wherein

[0201] When the speed adjustment mechanism changes the speed distribution while maintaining the average value of the rotation speed of the transfer body in the first adjustment mode and the second adjustment mode during the rotation of the transfer belt, the holding portion holds the recording medium with the same holding start timing as before the change. (7)

[0203] The image forming apparatus according to (5) or (6), wherein

[0204] When the speed adjustment mechanism changes the speed distribution while maintaining the average value of the rotation speed of the transfer body in the first adjustment mode and the second adjustment mode during the rotation of the transfer belt, the delivery portion delivers the recording medium at the same delivery timing as before the change.

[0205] According to the configuration of (1), compared with the case where the first adjustment mode and the second adjustment mode are switched regardless of the timing at which the speed adjustment mechanism and the holding portion start holding the recording medium, it is possible to suppress deviations in the transfer position of the image onto the recording medium.

[0206] According to the configuration (2), compared to the case where the first adjustment mode and the second adjustment mode are switched regardless of the detection timing of the rotational position by the speed adjustment mechanism and the detection unit, it is possible to suppress the deviation of the transfer position of the image onto the recording medium.

[0207] According to the structure of (3), compared with the first adjustment mode and the second adjustment mode, which are modes for adjusting the rotation speed of the transfer body in a circle including a state in which the transfer body transports the recording medium, the rotation speed of the transfer body can be adjusted to an appropriate rotation speed in a state in which the transfer body transports the recording medium and an appropriate rotation speed in a state in which the transfer body does not transport the recording medium.

[0208] According to the configuration of (4), the torque fluctuation of the driving roller can be reduced compared to the case where the average value of the rotational speed of the transfer body when the portion of the transfer body other than the concave portion passes through the transfer area in the second adjustment mode is the same as the average value in the first adjustment mode.

[0209] According to the configuration of (5), the rotational speed of the transfer body in each of the first adjustment mode and the second adjustment mode can be changed according to the torque fluctuation of the drive roller during the rotation of the transfer belt.

[0210] According to the configuration of (6), it is not necessary to control the holding start timing of the holding unit.

[0211] According to the configuration of (7), there is no need to control the delivery timing of the delivery section.

[0212] The above-described embodiments of the present invention are provided for the purpose of illustration and explanation. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed embodiments. It is obvious that various modifications and variations are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily explain the principles of the present invention and its application. Thus, other technical personnel in this field can understand the present invention through various modifications optimized for specific uses of the assumed various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. An image forming device comprising: The endless transfer belt transfers the image formed on the forming body to the outer peripheral surface; a driving roller, which is wound with the transfer belt and causes the transfer belt to revolve; a transfer body, which transfers the image from the transfer belt to the recording medium in a transfer area between the transfer belt and the recording medium while conveying the recording medium; A driving mechanism, which rotationally drives the transfer body; a holding portion that holds the recording medium and moves integrally with the rotational movement of the transfer body to allow the recording medium to pass through the transfer area; and A speed adjustment mechanism adjusts the rotation speed of the transfer body based on the driving mechanism in units of one revolution of the transfer body, and switches between a first adjustment mode and a second adjustment mode different from the first adjustment mode in units of one revolution of the transfer body, and synchronizes the switching timing with the holding start timing of the holding portion starting to hold the recording medium.

2. The image forming apparatus according to claim 1, comprising: a rotating body that rotates synchronously with the rotation of the transfer body; a detection unit, which detects a preset rotation position of the rotating body; and a delivery unit that delivers the recording medium to the holding unit based on a detection timing when the detection unit detects the rotational position, The holding portion holds the recording medium fed out from the feeding portion and moves integrally with the rotational movement of the transfer body to allow the recording medium to pass through the transfer area. The speed adjustment mechanism synchronizes the switching timing with the detection timing.

3. The image forming apparatus according to claim 1 or 2, wherein: The first adjustment mode is a mode for adjusting the rotation speed of the transfer body in a rotation including a state in which the transfer body does not convey the recording medium. The second adjustment mode is a mode for adjusting the rotation speed of the transfer body in a loop including a state in which the transfer body conveys the recording medium.

4. The image forming apparatus according to claim 3, wherein: The transfer body has a concave portion on its outer peripheral surface that can accommodate the holding portion. In the second adjustment mode, an average value of the rotation speed of the transfer body when a portion of the transfer body other than the concave portion passes through the transfer region is different from the average value in the first adjustment mode.

5. The image forming apparatus according to any one of claims 1 to 4, wherein: The speed adjustment mechanism can change the speed distribution while maintaining the average value of the rotation speed of the transfer body in each of the first adjustment mode and the second adjustment mode during the rotation of the transfer belt.

6. The image forming apparatus according to claim 5, wherein: When the speed adjustment mechanism changes the speed distribution while maintaining the average value of the rotation speed of the transfer body in the first adjustment mode and the second adjustment mode during the rotation of the transfer belt, the holding unit holds the recording medium at the same holding start timing as before the change.

7. The image forming apparatus according to claim 5 or 6, wherein: When the speed adjustment mechanism changes the speed distribution while maintaining the average value of the rotation speed of the transfer body in the first adjustment mode and the second adjustment mode during the rotation of the transfer belt, the delivery section delivers the recording medium at the same delivery timing as before the change.

Images