Image forming device

Abstract

To provide an image forming device capable of suppressing the disturbance of an image transferred to a recording medium, in comparison with a case of performing drive control of a transfer roller without taking account of a conveyance position of the recording medium.SOLUTION: An image forming device comprises: an annular transfer belt where an image is transferred to an outer peripheral surface thereof; a driving roller for moving the transfer belt wound therearound; a transfer roller which forms a transfer area between the transfer belt and itself and transfers an image onto a recording medium when the recording medium passes through the transfer area; a drive mechanism for rotating the transfer roller; and a speed adjustment mechanism for adjusting a rotational speed of the transfer roller by the drive mechanism in cycle units of the transfer roller and switching and executing between a first adjustment pattern for adjusting the rotational speed of the transfer roller in a cycle including a state where the transfer roller conveys the recording medium and a second adjustment pattern for adjusting the rotational speed of the transfer roller in a pattern different from the first adjustment pattern.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The following Patent Document 1 discloses an image forming device having a belt-shaped image carrier and a transfer roller having a cylindrical circumferential surface with a cutout, in which speed fluctuations of the intermediate transfer belt that occur at the secondary transfer position due to the rotation of the secondary transfer roller are absorbed by two tension rollers, thereby suppressing the impact on image formation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-220812 Summary of the Invention [Problem to be solved by the invention]

[0004] In an image forming apparatus, the load generated between the transfer belt and the transfer roller may differ depending on whether the recording medium being conveyed to the transfer roller passes through a transfer area where an image is transferred to the recording medium or not. In relation to this, the image transferred to the recording medium may be distorted depending on whether the recording medium is in the transfer area.

[0005] The present disclosure aims to provide an image forming device that suppresses distortion of the image transferred to the recording medium compared to when the transfer roller is driven and controlled without taking into account whether the transfer roller is transporting the recording medium or not. [Means for solving the problem]

[0006] In order to achieve the above object, an image forming apparatus according to a first aspect of the present disclosure includes a circular transfer belt on whose outer surface an image is transferred, a drive roller that wraps around and moves the transfer belt, a transfer roller that forms a transfer area between the transfer belt and the drive roller and transfers an image onto the recording medium when the recording medium passes through the transfer area, a drive mechanism that rotates the transfer roller, and a speed adjustment mechanism that adjusts the rotation speed of the transfer roller by the drive mechanism in units of the cycle of the transfer roller, the speed adjustment mechanism switching between a first adjustment pattern that adjusts the rotation speed of the transfer roller in a cycle that includes a state in which the transfer roller is transporting the recording medium, and a second adjustment pattern that adjusts the rotation speed of the transfer roller in a pattern different from the first adjustment pattern.

[0007] An image forming apparatus according to a second aspect of the present disclosure is the image forming apparatus according to the first aspect of the present disclosure, further comprising a holding member that holds the recording medium and passes it through the transfer area, wherein the transfer roller has a recess on its circumferential surface that can accommodate the holding member, and the speed adjustment mechanism adjusts, on a periodic basis, the rotational speed of the transfer roller when the recessed portion passes through the transfer area to be faster than the average value when the average value of the rotational speed of the transfer roller when the part other than the recessed portion of the transfer roller passes through the transfer area is slower than a specific value, and adjusts the rotational speed of the transfer roller when the recessed portion passes through the transfer area to be slower than the average value when the average value of the rotational speed of the transfer roller when the part other than the recessed portion of the transfer roller passes through the transfer area is faster than the specific value.

[0008] An image forming apparatus according to a third aspect of the present disclosure is the image forming apparatus according to the second aspect of the present disclosure, wherein the first adjustment pattern and the second adjustment pattern adjust the average value of the rotational speed of the transfer roller in units of one cycle, and the speed adjustment mechanism adjusts the rotational speed of the transfer roller so that the average value of the rotational speed of the transfer roller in one cycle in the first adjustment pattern matches the average value of the rotational speed of the transfer roller in one cycle in the second adjustment pattern.

[0009] An image forming apparatus according to a fourth aspect of the present disclosure is an image forming apparatus according to any one of the first to third aspects of the present disclosure, further comprising a torque detection unit that detects torque fluctuations of the drive roller, and the rotation speed of the transfer roller in the first adjustment pattern and the second adjustment pattern is set based on the detection results of the torque detection unit.

[0010] An image forming apparatus according to a fifth aspect of the present disclosure is an image forming apparatus according to any one of the first to third aspects of the present disclosure, further comprising a drive source that rotates the drive roller and a current value detection unit that detects the current value supplied to the drive source, and the rotation speed of the transfer roller in the first adjustment pattern and the second adjustment pattern is set based on the detection result of the current value detection unit.

[0011] An image forming apparatus according to a sixth aspect of the present disclosure is an image forming apparatus according to any one of the first to fifth aspects of the present disclosure, further comprising a belt speed measuring unit that measures the moving speed of the transfer belt, and the rotation speed of the transfer roller in the first adjustment pattern and the second adjustment pattern is set based on the measurement results of the belt speed measuring unit.

[0012] An image forming apparatus according to a seventh aspect of the present disclosure is an image forming apparatus according to any one of the first to sixth aspects of the present disclosure, wherein the speed adjustment mechanism continuously changes the information contained in the first adjustment pattern and the second adjustment pattern to be executed based on at least one of torque fluctuations of the drive roller, the current value supplied to the drive source that rotates the drive roller, and the movement speed of the transfer belt.

[0013] An image forming apparatus according to an eighth aspect of the present disclosure is an image forming apparatus according to any one of the first to seventh aspects of the present disclosure, further comprising a plurality of storage sections capable of storing different recording media, each of the first and second adjustment patterns including a plurality of adjustment patterns corresponding to the plurality of storage sections, and the speed adjustment mechanism executes, as the first and second adjustment patterns, one adjustment pattern among the plurality of adjustment patterns corresponding to the storage section in which the recording medium to be transported to the transfer area was stored. [Effects of the Invention]

[0014] According to the image forming apparatus of the first aspect of the present disclosure, distortion of the image transferred to the recording medium is suppressed compared to when the transfer roller is driven and controlled without taking into account whether the transfer roller is transporting the recording medium or not.

[0015] According to the image forming apparatus of the second aspect of the present disclosure, torque fluctuations due to speed changes of the transfer roller can be suppressed from being transmitted to the transfer belt and drive roller, compared to when the rotation speed of the transfer roller is changed at the timing when parts other than the recessed portion pass through the transfer area.

[0016] According to the image forming apparatus according to the third aspect of the present disclosure, the rotation speed of the transfer roller when the recessed portion passes through the transfer area can be used as an adjustment amount for the average rotation speed of the transfer roller in one cycle.

[0017] According to the image forming apparatus according to the fourth aspect of the present disclosure, each adjustment pattern can be set based on the torque detection result of the drive roller.

[0018] According to the image forming apparatus according to the fifth aspect of the present disclosure, each adjustment pattern can be set based on the value of the current supplied to the drive source that drives the drive roller.

[0019] According to the image forming apparatus according to the sixth aspect of the present disclosure, each adjustment pattern can be set based on the measurement result of the belt speed measurement unit.

[0020] According to the image forming device according to the seventh aspect of the present disclosure, the information included in the adjustment pattern is continuously changed while the image forming device is in operation.

[0021] According to the image forming apparatus according to the eighth aspect of the present disclosure, a different control pattern is executed for each recording medium. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic explanatory diagram illustrating an example of an image forming apparatus according to a first embodiment of the present disclosure. [Figure 2] 2 is an enlarged perspective view showing a part of a secondary transfer body of the image forming apparatus shown in FIG. 1. FIG. [Figure 3] 3 is an enlarged perspective view showing a gripper portion of the secondary transfer body shown in FIG. 2. FIG. [Figure 4] 2 is a functional block diagram illustrating an example of a control device of the image forming apparatus shown in FIG. 1. FIG. [Figure 5] 2 is an explanatory diagram of the operation of the transfer area portion of the image forming apparatus shown in FIG. 1. FIG. [Figure 6] 2 is an explanatory diagram of the operation of the transfer area portion of the image forming apparatus shown in FIG. 1. FIG. [Figure 7] 7A and 7B are diagrams showing an example of the results of adjustment using a speed adjustment mechanism in the image forming apparatus shown in FIG. 1, where FIG. 7A shows the change in torque value of the drive roller before adjustment using the speed adjustment mechanism, FIG. 7B shows the change in the speed adjustment amount of the transfer cylinder after adjustment using the speed adjustment mechanism, and FIG. 7C shows the change in torque value of the drive roller after adjustment using the speed adjustment mechanism. [Figure 8] 8A and 8B are diagrams showing another example of the results of adjustment using the speed adjustment mechanism in the image forming apparatus shown in FIG. 1, where FIG. 8A shows the change in the speed adjustment amount of the transfer cylinder after adjustment using the speed adjustment mechanism, and FIG. 8B shows the change in the torque value of the drive roller after adjustment using the speed adjustment mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, each embodiment for carrying out the present disclosure will be described with reference to the drawings. Note that the scope necessary for the explanation to achieve the object of the present disclosure will be schematically shown below, and the scope necessary for explaining the relevant parts of the present disclosure will be mainly explained, and the parts for which explanation is omitted will be considered to be publicly known technologies.

[0024] First Embodiment FIG. 1 is a schematic explanatory diagram showing an example of an image forming apparatus according to a first embodiment of the present disclosure. As shown in FIG. 1, image forming apparatus 10 according to this embodiment may be a so-called electrophotographic image forming apparatus that transfers a desired image (toner image) onto a recording medium P made of, for example, paper. This image forming apparatus 10 may include an image forming unit 12, a conveying unit 14, and a control device 16. Note that FIG. 1 is a front view of the main parts of image forming apparatus 10, and the following description will be given assuming that the width direction is the X direction, the depth direction is the Y direction, and the height direction is the Z direction. Furthermore, the various components included in FIG. 1 are shown in simplified form.

[0025] The image forming unit 12 may be a unit for forming a toner image (one example of an image) on the recording medium P. In order to form the toner image on the recording medium P, the image forming unit 12 may include a toner image forming unit 20 and a transfer device 30.

[0026] A plurality of toner image forming units 20 may be arranged along the conveyance direction (also referred to as the rotation direction) RD1 of the intermediate transfer belt 31 to form toner images of each color on the outer peripheral surface of the intermediate transfer belt 31 included in the transfer device 30 described below. In this embodiment, four toner image forming units 20, each of which corresponds to yellow (Y), magenta (M), cyan (C), and black (K), are arranged in this order from the upstream side of the conveyance direction of the intermediate transfer belt 31. Note that (Y), (M), (C), and (K) in FIG. 1 indicate components corresponding to the respective colors. In the following description, when it is necessary to distinguish between yellow (Y), magenta (M), cyan (C), and black (K), (Y), (M), (C), and (K) are added after the reference numerals of the respective components. When it is not necessary to distinguish between the respective colors, (Y), (M), (C), and (K) may be omitted. Furthermore, since the toner image forming units 20 of each color can have the same configuration except for the type of toner, only the configuration of the toner image forming unit 20(Y) will be described below as a representative of the toner image forming units 20 of each color. In addition, in Figure 1, only the components of this toner image forming unit 20(Y) are labeled with reference numerals, and the components of the other toner image forming units are omitted. Incidentally, of the toner image forming units 20, the toner image forming units 20(Y) and 20(M) and the toner image forming units 20(C) and 20(K) are positioned differently relative to the intermediate transfer belt 31, so there are slight differences in the layout of each unit, but the components are the same.

[0027] 1, the toner image forming unit 20(Y) can include a photosensitive drum 22 that rotates in one direction (counterclockwise in FIG. 1). Around the photosensitive drum 22, a charger 23, an exposure device 24, a developing device 25, and a removal device 26 are arranged in this order.

[0028] An example of the primary transfer process onto the intermediate transfer belt 31 using the photosensitive drum 22 is as follows. First, the photosensitive drum 22 is charged by the charger 23. Next, the photosensitive drum 22 charged by the charger 23 is exposed to light by the exposure device 24, forming an electrostatic latent image on the photosensitive drum 22. Once the electrostatic latent image is formed, the developing device 25 develops the electrostatic latent image to form a toner image. The toner image formed on the photosensitive drum 22 is then transferred (primary transfer) to the intermediate transfer belt 31 as a yellow image. Finally, the removal device 26 removes toner remaining on the surface of the photosensitive drum 22 after transfer to the intermediate transfer belt 31. The toner image forming unit 20(Y) performs the above-described process at specific timing, thereby transferring a yellow toner image onto the intermediate transfer belt 31.

[0029] The transfer device 30 may be a device for transferring toner images formed by the plurality of toner image forming units 20 onto a recording medium P. Specifically, the transfer device 30 includes a circular intermediate transfer belt (an example of a transfer belt) 31, a drive roller 32 around which the intermediate transfer belt 31 is wound and which moves the intermediate transfer belt 31 in a rotation direction RD1 (clockwise in FIG. 1 ), a plurality of support rollers 33 around which the intermediate transfer belt 31 is wound to support the intermediate transfer belt 31 in a profile (posture) along a desired path, a steering roller 34 for suppressing meandering or deviation of the intermediate transfer belt 31, one or more tension rollers 35 for applying tension to the intermediate transfer belt 31, a primary transfer roller 36 that brings the intermediate transfer belt 31 into contact with the photosensitive drums 22 of each color to perform primary transfer of an image, and a secondary transfer roller 37 that forms a transfer area TA of the intermediate transfer belt 31 between the primary transfer roller 36 and a transfer cylinder 50 (described later) and performs secondary transfer of the image formed on the intermediate transfer belt 31 onto a recording medium P passing through the transfer area TA. Known specific configurations can be adopted for the multiple types of rollers described above, but for example, their axial lengths may be slightly longer than the width of the intermediate transfer belt 31, and their diameters may be adjusted appropriately depending on the application. The multiple types of rollers described above may be arranged so that their axial directions extend along the depth direction (Y direction) of the image forming apparatus 10. Furthermore, of the multiple rollers described above, all rollers other than the drive roller 32 may be configured as driven rollers that are not connected to a drive source such as a motor.

[0030] The intermediate transfer belt 31 may be configured as a circular belt-like member, more specifically, an endless belt, onto whose outer peripheral surface an image is transferred. The intermediate transfer belt 31 may be disposed so that its width extends in the depth direction (Y direction) of the image forming apparatus 10. The intermediate transfer belt 31 may be brought into contact with the photosensitive drums 22 of the toner image forming units 20 of each color by a primary transfer roller 36, thereby transferring the toner images sequentially (primary transfer). In addition, the transferred toner images may be transferred (secondary transfer) onto the surface of the recording medium P passing through a transfer area TA by a secondary transfer roller 37, which brings the intermediate transfer belt 31 into contact with a transfer cylinder 50 (described later) to form a transfer area TA.

[0031] The drive roller 32 has a rotation shaft connected to a drive roller motor 32M (see FIG. 4) as an example of a drive source, and rotates by receiving a driving force from the drive roller motor 32M, thereby moving the intermediate transfer belt 31 wound around the drive roller 32 in a rotation direction RD1. The rotation shaft of the drive roller 32 is preferably connected to the drive roller motor 32M via a well-known reducer. The drive roller 32 according to this embodiment is disposed downstream of the transfer area TA and upstream of the toner image forming unit 20(Y) in the transport direction of the intermediate transfer belt 31, in contact with the inner circumferential surface of the intermediate transfer belt 31.

[0032] The conveying unit 14 may perform a series of conveyances, moving the recording medium P to an image transfer position, transferring the image onto the recording medium P, and discharging the recording medium P with the transferred image outside the image forming apparatus 10. The conveying unit 14 may include a conveying path 40 along which the recording medium P is conveyed, a storage unit 41 that stores one or more recording media P before image formation, a secondary transfer body 42 that transfers the image onto the recording medium P, a fixing device 43 that fixes the image on the recording medium P after the image has been transferred, and a recording medium detection sensor 44 that is provided at a position adjacent to the storage unit 41 on the conveying path 40 and detects the position of the recording medium P by detecting the passage of the recording medium P.

[0033] The conveying path 40 starts from the storage section 41, passes through the transfer area TA, and then passes between a pair of rollers that constitute the fixing device 43, thereby enabling the recording medium P with the printed image to be discharged onto a discharge tray (not shown) provided in the image forming apparatus 10. A plurality of conveying rollers (not shown) may be arranged along the conveying path 40. Also, while FIG. 1 shows only one tray as the storage section 41, there may be a plurality of storage sections 41. In an image forming apparatus 1 having a plurality of storage sections 41, the recording media P stored in each storage section 41 may be different in size, material, thickness, etc.

[0034] 2 is an enlarged perspective view showing a portion of the secondary transfer body of the image forming apparatus according to the first embodiment of the present disclosure. As shown in FIGS. 1 and 2, the secondary transfer body 42 is disposed on the conveying path 40 between the storage unit 41 and the fixing device 43, and may convey the recording medium P to the transfer area TA and transfer an image formed on the intermediate transfer belt 31 onto the surface of the recording medium P. The secondary transfer body 42 may include a transfer cylinder 50 as an example of a transfer roller, a pair of sprockets 51, a pair of chains 52, and a gripper 53.

[0035] The transfer cylinder 50 is an example of a transfer roller that forms a transfer area TA between itself and the intermediate transfer belt 31 and transfers an image formed on the surface of the intermediate transfer belt 31 to the surface of the recording medium P when the recording medium P passes through the transfer area TA. The transfer area TA formed by the transfer cylinder 50 refers to the area where the recording medium P is sandwiched between the surface of the intermediate transfer belt 31, the back side of which is supported by the secondary transfer roller 37, and the surface of the transfer cylinder 50 (this area is also referred to as a nip area). The secondary transfer roller 37, which supports the intermediate transfer belt 31 so that it contacts the transfer cylinder 50, may be positionally adjustable toward or away from the transfer cylinder 50. Changing the position of the secondary transfer roller 37 mainly changes the length of the transfer area TA in the rotation direction RD1. Note that, although the transfer roller is exemplified in this embodiment as the transfer cylinder 50, the transfer roller is not limited thereto and may be any roller that brings the recording medium P into contact with the intermediate transfer belt 31 to perform secondary transfer. In this regard, the image forming apparatus of the present disclosure does not necessarily have to have other specific components of the secondary transfer body 42, such as the gripper 53 and the recess 50A, which will be described later.

[0036] The transfer cylinder 50 is fixed to a rotating shaft 54. The rotating shaft 54 ​​is connected to a transfer cylinder motor 50M (see FIG. 4), which is an example of a drive mechanism. The rotating shaft 54 ​​receives driving force from the transfer cylinder motor 50M and rotates in one direction (hereinafter also referred to as the "rotation direction") RD2, causing a pair of chains 52 to revolve via a pair of sprockets 51. When a recording medium P is sandwiched between the gripper 53, the recording medium P is transported to the transfer area TA as the pair of chains 52 revolve. The rotating shaft 54 ​​of the transfer cylinder 50 is preferably connected to the transfer cylinder motor 50M via a well-known reducer. While the present embodiment illustrates a configuration in which the transfer cylinder motor 50M is connected to the rotating shaft 54, the connection position of the transfer cylinder motor 50M can be changed as long as its functionality is maintained. Specifically, the rotating shaft 54 ​​can be connected to a pair of sprockets 51 that rotate in conjunction with the transfer cylinder 50 via a pair of chains 52.

[0037] A pair of transfer cylinder side sprockets 55 may be attached to both axial ends of the transfer cylinder 50. As shown in Fig. 2, the pair of transfer cylinder side sprockets 55 are arranged to sandwich the transfer cylinder 50 therebetween and can be configured to rotate together with the transfer cylinder 50 by being fixed to a rotation shaft 54. The outer diameter of the pair of transfer cylinder side sprockets 55 may be smaller than the outer diameter of the transfer cylinder 50. A pair of chains 52 is wound around the pair of transfer cylinder side sprockets 55, respectively.

[0038] The transfer cylinder 50 may be formed of a base material 50B and a surface layer 50C replaceably wrapped around the outer periphery of the base material 50B. The base material 50B may be made of a metal material such as stainless steel, and the surface layer 50C may be made of a resin material such as urethane rubber, ethylene-propylene rubber (EPM), silicone rubber, fluororubber (FKM), or epichlorohydrin / butadiene rubber. The circumferential length of the transfer cylinder 50 that can be employed in this embodiment may be substantially equal to the length along the conveyance direction of the maximum paper size of the recording medium P that can be used in the image forming apparatus 10. Alternatively, a length shorter or longer than the length along the conveyance direction of the recording medium P of this maximum paper size may be employed. Furthermore, a recess 50A is formed on the outer periphery of the transfer cylinder 50, extending along the axial direction of the transfer cylinder 50, capable of accommodating a gripper 53. While the transfer cylinder 50 according to this embodiment has only one recess, two or more recesses may be formed at intervals.

[0039] The pair of sprockets 51 may have a pair of chains 52 wound around them, similar to the pair of transfer cylinder side sprockets 55 connected to the transfer cylinder 50, and may support the pair of chains 52 in a specific position together with the pair of transfer cylinder side sprockets 55. The pair of sprockets 51 are disposed on the side closer to the fixing device 43 (in the -X direction in FIG. 1) with respect to the transfer cylinder 50. The pair of sprockets 51 may also be supported by the main body (not shown) of the image forming apparatus 10 so as to be coaxially rotatable together.

[0040] As shown in FIG. 1, the pair of chains 52 may be formed in an annular shape and wound around a pair of sprockets 51 and a pair of transfer cylinder sprockets 55. As shown in FIG. 2, the pair of chains 52 may be spaced apart in the depth direction of the image forming apparatus 10 (the Y direction in FIGS. 1 and 2). The pair of chains 52 is exemplified as being configured to rotate in the same direction (counterclockwise in FIG. 1) when the transfer cylinder 50 receives power from the transfer cylinder motor 50M and rotates in the same direction RD2. Note that the winding angle should be at least 90 degrees or more to facilitate the conveyance of the recording medium P along the surface of the transfer cylinder 50. Furthermore, as shown in FIG. 2, mounting members 56, to which grippers 53 are attached, are stretched across the pair of chains 52 in the depth direction of the image forming apparatus 10. One or more mounting members 56 are fixed to the pair of chains 52 at predetermined intervals along the direction of rotation of the chains 52.

[0041] FIG. 3 is a further enlarged perspective view of the gripper portion of the secondary transfer body shown in FIG. 2. As shown in FIGS. 2 and 3, a plurality of grippers 53 (two in FIG. 1) may be attached to mounting members 56 at predetermined intervals along the depth direction of image forming apparatus 10. In other words, grippers 53 may be attached to chains 52 via mounting members 56. Gripper 53 is an example of a holding member that has the function of holding the front end of recording medium P in the transport direction. Specifically, as shown in FIG. 3, gripper 53 has claw 53A and claw base 53B. Gripper 53 can hold recording medium P by pinching the front end of recording medium P between claw 53A and claw base 53B. Gripper 53 holds the front end of recording medium P outside the image area, which is the area of ​​recording medium P where a toner image is transferred. The gripper 53 may be configured to hold the recording medium P by, for example, pressing the claws 53A against the claw base 53B with a spring or the like, and opening and closing the claws 53A relative to the claw base 53B with the action of a cam or the like.

[0042] The above-described series of components allows the transport unit 14 to perform the following transport operation. Specifically, the recording medium P is first sent from the storage unit 41 onto the transport path 40 by transport rollers (not shown). When the recording medium P reaches the portion of the transport path 40 where the secondary transfer body 42 is located, the leading edge of the recording medium P is held by the gripper 53. The gripper 53, holding the leading edge of the recording medium P, moves further along the transport path 40 as the chain 52 rotates, and the gripper 53 is housed in the recess 50A of the transfer cylinder 50. The gripper 53 housed in the recess 50A further transports the recording medium P as the transfer cylinder 50 rotates, and the recording medium P passes through the transfer area TA while still held by the gripper 54. After passing through the transfer area TA, the recording medium P is transported to the fixing device 43, where the transferred toner image is fixed. The recording medium P with the fixed toner image is then discharged to an output tray (not shown) provided in an appropriate position in the image forming apparatus 10.

[0043] The control device 16 may function as a controller for controlling a series of operations in the image forming apparatus 10. The control device 16 may be configured, for example, by a well-known computer. Here, the well-known computer may include at least a volatile or non-volatile memory (e.g., a random access memory (RAM) or a hard disk drive (HDD)) and a processor such as a central processing unit (CPU). In this regard, the various operations of the control device 16 described below may be provided in the form of a program stored in memory or in the form of a non-transitory computer-readable medium on which the program is stored.

[0044] Fig. 4 is a functional block diagram showing an example of the control device shown in Fig. 1. Of the various functions of the control device 16, Fig. 4 shows only the functions related to speed control of the image forming unit 12 and the conveying unit 14, and omits the description of the configuration for realizing the other functions. As shown in Fig. 4, the control device 16 can include a first drive control unit 60 that operates the drive roller motor 32M, a second drive control unit 70 that operates the transfer cylinder motor 50M, and a speed adjustment mechanism 80 that adjusts the rotation speed of the transfer cylinder motor 50M.

[0045] The first drive control unit 60 can be configured with a driver that outputs a drive signal to the drive roller motor 32M based on the received control pulse signal. The drive roller motor 32M, which operates based on the drive signal from the first drive control unit 60, can be a motor capable of measuring load torque and controlling its speed with high precision, such as an AC servo motor or a stepping motor. The drive roller motor 32M, which receives the drive signal from the first drive control unit 60, can operate in a speed control mode that rotates the drive roller 32 at a specific target rotation speed, and rotates the intermediate transfer belt 31 along the rotation direction RD1.

[0046] The second drive control unit 70 can be configured as a driver that outputs a drive signal to the transfer cylinder motor 50M based on the received control pulse signal. The transfer cylinder motor 50M, which operates based on the drive signal from the second drive control unit 70, can be a motor capable of measuring load torque and controlling its speed with high precision, such as an AC servo motor or a stepping motor. Upon receiving the drive signal from the second drive control unit 70, the transfer cylinder motor 50M rotates the rotation shaft 54 ​​at a specific rotation speed, rotating the transfer cylinder 50 in the rotation direction RD2. The second drive control unit 70 and the transfer cylinder motor 50M are an example of a drive mechanism.

[0047] In the image forming apparatus 10 according to the present embodiment, as described above, the intermediate transfer belt 31 moves in the rotation direction RD1 as a result of the rotation of the drive roller 32 by the drive roller motor 32M, and the transfer cylinder 50 rotates by the transfer cylinder motor 50M. The moving intermediate transfer belt 31 and the rotating transfer cylinder 50 come into direct or indirect contact with each other in the transfer area TA. Therefore, the speed of the rotation of the intermediate transfer belt 31 is affected not only by the rotation speed of the drive roller 32 but also by the rotation speed of the transfer cylinder 50. Specifically, for example, when the rotation speed of the drive roller 32 is slower than the rotation speed of the transfer cylinder 50, at least a portion of the torque of the transfer cylinder 50 acts via the transfer area TA in a direction that increases the rotation speed of the intermediate transfer belt 31 (i.e., acts as an accelerator). Conversely, when the rotation speed of the drive roller 32 is faster than the rotation speed of the transfer cylinder 50, at least a portion of the torque of the transfer cylinder 50 acts via the transfer area TA in a direction that decreases the rotation speed of the intermediate transfer belt 31 (i.e., acts as a brake). The load from the transfer cylinder 50, which is generated by the difference in speed between the rotational speed of the intermediate transfer belt 31 and the rotational speed of the transfer cylinder 50, can cause fluctuations in the rotational speed of the intermediate transfer belt 31 and expansion and contraction of the intermediate transfer belt 31. Such unexpected fluctuations in the rotational speed and expansion and contraction of the intermediate transfer belt 31 can cause banding (streaks or uneven image density extending in a direction intersecting the transport direction of the intermediate transfer belt 31) and deviations in color registration (positioning of images of each color).

[0048] In addition, the torque value of the drive roller motor 32M required to rotate the intermediate transfer belt 31 at a specific speed varies depending on the operating state of the image forming apparatus 10. Specifically, the torque value required of the drive roller motor 32M differs depending on whether the recording medium P is passing through the transfer area TA or not. This is presumably caused by at least one of the following: a change in the amount of penetration of at least one of the secondary transfer roller 37 and the transfer cylinder 50 due to the passage of the recording medium P; a change in frictional force resulting from the change in the object that the intermediate transfer belt 31 contacts in the transfer area TA from the transfer cylinder 50 to the recording medium P (or from the recording medium P to the transfer cylinder 50); and an electrostatic attraction force generated between the secondary transfer roller 37 and the transfer cylinder 50 due to the transfer bias current applied to the secondary transfer roller 37 to transfer the toner image onto the recording medium P.

[0049] In the image forming apparatus 10 according to the present embodiment, taking the above points into consideration, a speed adjustment mechanism 80 is employed to eliminate the speed difference between the rotational speed of the intermediate transfer belt 31 and the rotational speed of the transfer cylinder 50.

[0050] The speed adjustment mechanism 80 adjusts the rotation speed of the transfer cylinder 50 by selectively using two different adjustment patterns (described later) based on the transport position of the recording medium P. The rotation speed of the transfer cylinder 50 adjusted by the speed adjustment mechanism 80 can function to eliminate the speed difference between the rotation speed of the intermediate transfer belt 31 and the rotation speed of the transfer cylinder 50. As shown in FIG. 4, the speed adjustment mechanism 80 may include at least a medium position prediction unit 81, a reference position detection unit 82, an adjustment pattern selection unit 83, and a control data storage unit 84.

[0051] The medium position prediction unit 81 may predict the position of the recording medium P being transported on the transport path 40. In particular, an example of this medium position prediction unit 81 is one that predicts the timing when the transfer cylinder 50 will start transporting the recording medium P and the timing when the transfer cylinder 50 will finish transporting the recording medium P, thereby predicting the timing when the transfer cylinder 50 will be in a state of transporting the recording medium P. The medium position prediction unit 81 may be connected to the recording medium detection sensor 44. Furthermore, the medium position prediction unit 81 can predict the position of the recording medium P being transported on the transport path 40 with high accuracy by taking into consideration the rotation speed of the pair of chains 52, the operation instructions acquired by the control device 16, specifically whether double-sided printing is being performed, etc., in addition to the detection result of the recording medium detection sensor 44.

[0052] The reference position detection unit 82 may determine the period of the transfer cylinder 50 by detecting a specific reference position on the transfer cylinder 50. For example, a photosensor (see FIG. 2) that detects the passage of an actuator attached to the rotation shaft 54 ​​can be used as this reference position detection unit 82. The specific reference position described above is not particularly limited, but in this embodiment, for ease of understanding, the position immediately before the recess is provisionally defined as the reference position RP (see FIG. 1, etc.), and the period from when the reference position RP passes through the transfer area TA until when it reaches the transfer area TA again is provisionally defined as one revolution of the transfer cylinder 50.

[0053] The adjustment pattern selection unit 83 may select an adjustment pattern to be used for controlling the transfer cylinder 50 based on the position of the recording medium P predicted by the medium position prediction unit 81, more specifically, based on whether the position is being transported by the transfer cylinder 50. This adjustment pattern selection may be performed on a periodic basis detected by the reference position detection unit 82. Here, selecting and applying an adjustment pattern on a "periodic basis" means that the adjustment pattern is selected and applied once per rotation of the transfer cylinder 50 or once per two or more specific rotations. The adjustment pattern selection unit 83 also generates a control pulse signal based on the selected adjustment pattern and transmits the generated control pulse signal to the second drive control unit 70, and may use a mechanism generally known as an electronic cam.

[0054] The control data storage unit 84 can be configured as a recording medium capable of storing various data necessary for the speed adjustment mechanism 80 to adjust the rotation speed of the transfer cylinder 50. This control data storage unit 84 may store control data corresponding to at least a first adjustment pattern and a second adjustment pattern. Here, the "adjustment pattern" refers to control information for rotating the transfer cylinder 50, and is called "cam data" in the case of an electronic cam.

[0055] The first adjustment pattern is an adjustment pattern that includes control information (hereinafter also referred to as "adjustment pattern data") for adjusting the rotation speed of the transfer cylinder 50 during a cycle that includes at least a state in which the transfer cylinder 50 is transporting the recording medium P. The control information that constitutes the first adjustment pattern may be determined in advance through experiments or the like. The rotation speed in the first adjustment pattern may be set to operate at a constant speed value during a specific cycle, or may be set to change the speed value at a specific timing during the cycle.

[0056] The second adjustment pattern is an adjustment pattern that includes control information for adjusting the rotation speed of transfer cylinder 50 in a pattern different from the first adjustment pattern. This second adjustment pattern may be applied mainly to adjusting the rotation speed in a cycle that does not include a state in which transfer cylinder 50 is transporting recording medium P. Here, examples of cycles that do not include a state in which transfer cylinder 50 is transporting recording medium P include a cycle that corresponds to a timing when only the primary transfer operation is being performed by image forming unit 12, and a cycle that corresponds to a timing of image quality adjustment performed while intermediate transfer belt 31 is moving.

[0057] 5 and 6 are explanatory diagrams of the operation of the transfer area portion of the image forming apparatus shown in FIG. 1. Note that FIGS. 5 and 6 show enlarged views of the portion corresponding to the transfer area TA. Below, one method of speed adjustment using the speed adjustment mechanism 80 including the above-described configuration will be described with reference to FIGS. 5 and 6. Note that in the following description, an example is given in which the adjustment pattern selection unit 83 can change the adjustment pattern for the rotation speed of the transfer cylinder 50 every cycle, in other words, every time the reference position RP passes through the transfer area TA. Also, an example is given in which the length of the recording medium P onto which the image is transferred in the transport direction is shorter than the circumferential length of the transfer cylinder 50 (see FIG. 6).

[0058] First, the image forming apparatus 10 is powered on, and the image transfer operation to the recording medium P is initiated, for example, by an operator operating a user interface (e.g., a touch panel or buttons) (not shown) of the image forming apparatus 10, or by receiving an operational instruction transmitted via a network from a client computer or the like. In the image forming apparatus 10, the toner image forming units 20 for each color start forming an image, and the primary transfer operation of the image for each color onto the intermediate transfer belt 31 is initiated. The rotation operation of the transfer cylinder 50 may be initiated in synchronization with or prior to the start of the primary transfer operation (see FIGS. 5A and 5B). This rotation operation of the transfer cylinder 50 may be initiated by the adjustment pattern selector 83 selecting a second adjustment pattern and transmitting a control pulse signal adjusted based on the second adjustment pattern to the second drive controller 70.

[0059] Next, when the recording medium P starts to be conveyed out of the storage unit 41 and the recording medium detection sensor 44 detects the passage of the recording medium P, the medium position prediction unit 81 selects a first adjustment pattern after a specific waiting time has elapsed and generates a control pulse signal adjusted based on the first adjustment pattern (or transitions to control using the first cam data). The control pulse signal generated here is sent to the second drive control unit 70 so that adjustment of the rotation speed of the transfer cylinder 50 based on the first adjustment pattern is started at a timing before the transfer cylinder 50 starts transferring to the recording medium P, for example, at a timing when the cycle of the transfer cylinder 50 including the timing when the transfer cylinder 50 starts transporting the recording medium P is reached (see FIG. 5(C)).

[0060] The recording medium P is transported to the transfer cylinder 50, whose rotation speed has been adjusted using the first adjustment pattern, and passes through the transfer area TA (see FIGS. 6A and 6B), whereby the image formed on the intermediate transfer belt 31 is transferred onto the surface of the recording medium P. Even after the recording medium P has passed through the transfer area TA, the rotation speed of the transfer cylinder 50 continues to be adjusted using the first adjustment pattern until the reference position RP passes through the transfer area TA again.

[0061] In order to identify the adjustment pattern for the rotational speed of the transfer cylinder 50 in the cycle after the reference position RP of the transfer cylinder 50 reaches the transfer area TA again, the adjustment pattern selection unit 83 selects an adjustment pattern based on whether or not the transfer cylinder 50 has started transporting a new recording medium P, based on the output of the medium position prediction unit 81. Specifically, if the next cycle includes the timing to start transporting the new recording medium P, the adjustment pattern selection unit 83 continues adjusting the rotational speed based on the first adjustment pattern, and if the next cycle does not include the timing to start transporting the new recording medium P, the adjustment pattern selection unit 83 generates a control pulse signal or the like to change to adjustment of the rotational speed based on the second adjustment pattern (or transitions to control using the second cam data).

[0062] As described above, the speed adjustment mechanism 80 according to this embodiment operates the transfer cylinder 50 at a rotational speed adjusted based on the first adjustment pattern during a cycle that includes a state in which the transfer cylinder 50 is transporting the recording medium P, and operates the transfer cylinder 50 at a rotational speed adjusted based on the second adjustment pattern during other cycles. This allows the adjustment pattern for the rotational speed of the transfer cylinder 50 to be changed depending on whether the recording medium P is passing through the transfer area TA or not, without requiring any operation by an operator. Therefore, it is possible to prepare a first adjustment pattern that corresponds to the optimal rotational speed of the transfer cylinder 50 when the recording medium P is passing through the transfer area TA. This also reduces distortion of the image transferred to the recording medium P compared to when the transfer cylinder 50 is driven and controlled without considering whether the recording medium P is being transported.

[0063] Optionally, in addition to the above components, the speed adjustment mechanism 80 may include a torque detection unit 85 that detects the torque of the drive roller 32, in other words, the torque of the drive roller motor 32M. This torque detection unit 85 may be capable of detecting the torque value of the drive roller motor 32M directly from the drive roller motor 32M or via a servo amplifier (not shown) that is provided separately from the drive roller motor 32M. The torque value detected by this torque detection unit 85 may be used to create the above-mentioned first and second adjustment pattern data.

[0064] In this embodiment, the drive roller motor 32M operates in a speed control mode in which the drive roller 32 rotates at a specific target rotation speed. Therefore, a strong correlation is recognized between the current value supplied to the drive roller motor 32M and the torque value of the drive roller motor 32M. Therefore, as another option, the speed adjustment mechanism 80 can employ, in addition to the above-described components, a current value detection unit (not shown) that detects the current value supplied to the drive roller motor 32M. The current value detected by this current value detection unit can also be used to generate the above-described first and second adjustment pattern data, similar to the torque value detected by the torque detection unit 85. This current value detection unit can be employed instead of or in addition to the torque detection unit 85.

[0065] As another option, the speed adjustment mechanism 80 may include, in addition to the above-described components, a belt speed measurement unit 86 capable of measuring the rotational speed of the intermediate transfer belt 31. This belt speed measurement unit 86 may be connected to a speed sensor 87 provided on, for example, one of the support rollers 33 supporting the intermediate transfer belt 31, specifically, on the support roller 33A (see FIG. 1 ) disposed downstream in the rotation direction RD1 of the intermediate transfer belt 31 from the position where the black (K) toner image forming unit 20(K) is disposed. Note that the installation position of the speed sensor 87 is not limited thereto, and it may be any other position as long as it is capable of measuring the speed of the intermediate transfer belt 31. The rotational speed of the intermediate transfer belt 31 measured by this belt speed measurement unit 86 may be used to generate the above-described first and second adjustment pattern data, similar to the torque value detected by the torque detection unit 85 and the current value detected by the current value detection unit.

[0066] In the first embodiment described above, the control information constituting the first and second adjustment patterns is configured with predetermined arbitrary values. However, the present disclosure is not limited to this. Specifically, for example, at least one of the torque detection unit 85, current value detection unit, and belt speed measurement unit 86 described above may be employed, and the control information contained in each adjustment pattern may be continuously changed to an appropriate value by utilizing the detection or measurement results (i.e., at least one of the torque fluctuation of the drive roller 32, the current value supplied to the drive roller motor 32M, and the movement speed of the intermediate transfer belt 31). In other words, the control information including various parameters constituting each adjustment pattern may be updated to appropriate information during operation of the image forming apparatus 10. This enables optimal adjustment results to be continuously obtained by applying each adjustment pattern. It is also possible to address differences in the optimal adjustment pattern that arise due to, for example, individual differences in the surface layer 50C of the transfer cylinder 50, differences in the operating environment of the image forming apparatus 10, the type of recording medium P used, and the like. Furthermore, the frequency of maintenance required for changing (fine-tuning) the control information contained in the adjustment pattern may be reduced.

[0067] In the embodiment described above, the speed adjustment mechanism 80 changes the rotation speed of the transfer cylinder 50 by switching between two different adjustment patterns. Changing the rotation speed of the transfer cylinder 50, even by a small amount (e.g., about 0.1%), can affect the rotation speed of the intermediate transfer belt 31 or the rotation speed of the drive roller 32 (as an accelerator or brake). Therefore, the first and second adjustment patterns selected by the speed adjustment mechanism 80 according to this embodiment are preferably set so that the timing for changing the rotation speed is when the recessed portion 50A passes through the transfer area TA. When the recessed portion 50A passes through the transfer area TA, the transfer cylinder 50 and the intermediate transfer belt 31 are not in contact with each other, which minimizes the effect on the speed of the intermediate transfer belt 31.

[0068] Furthermore, in the above-described embodiment, the rotation speed of the transfer cylinder 50 is adjusted to eliminate the speed difference between the rotation speed of the intermediate transfer belt 31 and the rotation speed of the transfer cylinder 50. Specifically, the rotation speed is changed in cycles by switching between two different adjustment patterns. If the rotation speed differs in cycles, the timing at which the recessed portion 50A passes through the transfer area TA, in other words, the timing at which the conveyed recording medium P begins to pass through the transfer area TA, will not be constant. To suppress such timing discrepancies, the speed adjustment mechanism 80 adjusts the rotational speed of the transfer cylinder 50 when the recessed portion 50A passes through the transfer area TA to be relatively slower if the torque value of the drive roller motor 32M when the part of the transfer cylinder 50 other than the recessed portion 50A passes through the transfer area TA is higher than the torque value when it passes through the recessed portion 50A, since increasing the speed of the transfer cylinder 50 when it passes through the transfer area TA will reduce the torque; and if the torque value of the drive roller motor 32M when the part of the transfer cylinder 50 other than the recessed portion 50A passes through the transfer area TA is lower than the torque value when it passes through the recessed portion 50A, since decreasing the speed of the transfer cylinder 50 when it passes through the transfer area TA will increase the torque, it is preferable to adjust the rotational speed of the transfer cylinder 50 when the recessed portion 50A passes through the transfer area TA to be relatively faster.

[0069] Additionally, in the image forming apparatus 10, the timing of forming images on the intermediate transfer belt 31, in other words, the interval (pitch) between images formed on the intermediate transfer belt 31, is adjusted to coincide with the timing at which the recording medium P passes through the transfer area TA. Therefore, if the timing at which the recording medium P starts passing through the transfer area TA is not constant, it becomes necessary to adjust the operation timing of the toner image forming units 20 for each color to coincide with the timing at which the recording medium P currently passes through the transfer area TA. Therefore, in the speed adjustment mechanism 80 according to the present embodiment, taking the above points into consideration, it is preferable to make the average value of the rotation speed of the transfer cylinder 50 in one cycle consistent regardless of whether the first or second adjustment pattern is applied.

[0070] FIG. 7 shows an example of the results of adjustment using the speed adjustment mechanism in the image forming apparatus shown in FIG. 1 . FIG. 7(A) shows the change in torque value of the drive roller before adjustment using the speed adjustment mechanism. FIG. 7(B) shows the change in the speed adjustment amount of the transfer cylinder after adjustment using the speed adjustment mechanism. FIG. 7(C) shows the change in torque value of the drive roller after adjustment using the speed adjustment mechanism. In FIGS. 7(A) and 7(C), the horizontal axis represents time and the vertical axis represents the change in torque value of the drive roller motor 32M. On the other hand, FIG. 7(B) shows the change in rotational speed of the transfer cylinder 50 over two cycles, from a state where the second adjustment pattern is applied to a state where the first adjustment pattern is applied. Here, the rotational speed of the transfer cylinder 50 is adjusted to a specific average speed so that the average torque value of the drive roller motor 32M when the recessed portion 50A passes through the transfer area TA is approximately equal to the average torque value of the drive roller motor 32M when the portion other than the recessed portion 50A passes through the transfer area TA. If the torque value of the drive roller motor 32M without adjusting the rotational speed of the transfer cylinder is as shown in FIG. 7A, the speed adjustment mechanism 80 adjusts the rotational speed of the transfer cylinder 50 to adjust the torque change of the drive roller motor 32M per cycle to the value shown in FIG. 7C, which is approximately equal. In this case, it is preferable to adjust the torque change of the drive roller motor 32M per cycle by using a speed adjustment value such as that shown in FIG. 7B. While FIG. 7C shows torque values ​​on the vertical axis, the rotational speed of the intermediate transfer belt 31 may be used instead of torque values. In other words, the rotation speed of the transfer cylinder 50 may be adjusted by the speed adjusting mechanism 80 so that the rotation speed of the intermediate transfer belt 31 in each cycle is substantially constant.

[0071] When matching the average rotation speed of the transfer cylinder 50 over one cycle, the controller 100 determines whether the average speed at which the portions of the transfer cylinder 50 other than the recessed portions 50A pass through the transfer area TA matches a specific preset value. If the average speed at which the portions other than the recessed portions 50A pass through the transfer area TA is slower than the specific value, the controller 100 sets the control information for the applied adjustment pattern to increase the speed at which the recessed portions 50A pass through the transfer area TA so that the average speed over one cycle matches the specific value. Conversely, if the average speed at which the portions other than the recessed portions 50A pass through the transfer area TA is faster than the specific value, the controller 100 sets the control information for the applied adjustment pattern to decrease the speed at which the recessed portions 50A pass through the transfer area TA (see, for example, the change in the speed adjustment value over one cycle when the second adjustment pattern is applied in Figure 7(B)) so that the average speed over one cycle matches the specific value. Furthermore, if the average value of the rotation speed of the transfer cylinder 50 in one cycle matches a specific value, the control information of the applied adjustment pattern can be set so that the speed at which the recessed portion 50A passes through the transfer area TA matches the speed at which parts other than the recessed portion 50A pass through the transfer area TA (see, for example, the speed change in one cycle when the first adjustment pattern is applied in FIG. 7). Furthermore, if the timing for changing the rotation speed of the transfer cylinder 50 is when the recessed portion 50A is passing through the transfer area TA, as shown in FIG. 7(B), the speed change of the transfer cylinder 50 will not affect the intermediate transfer belt 31.

[0072] As described above, by varying the speed at which the recessed portions 50A pass through the transfer area TA, the average rotation speed of the transfer cylinder 50 when the first and second adjustment patterns are applied can be made to match a specific value, thereby making it possible to keep constant the intervals between images formed on the intermediate transfer belt 31. This eliminates the need to check the timing at which the recording medium P passes through the transfer area TA. This also makes it easier to apply various image quality adjustments when forming images on the intermediate transfer belt 31.

[0073] FIG. 8 shows another example of the results of adjustment using the speed adjustment mechanism in the image forming apparatus shown in FIG. 1 . FIG. 8(A) shows the change in the speed adjustment amount of the transfer cylinder after adjustment using the speed adjustment mechanism, and FIG. 8(B) shows the change in the torque value of the drive roller after adjustment using the speed adjustment mechanism. In FIGS. 8(A) and 8(B), the vertical and horizontal axes correspond to FIGS. 7(B) and 7(C) described above. While the rotational speed control shown in FIG. 7 illustrates a case in which the rotational speed is constant when the portion other than the recessed portion 50A passes through the transfer area TA, the present disclosure is not limited to this. Specifically, as shown in FIG. 8(A), the rotational speed when the portion other than the recessed portion 50A passes through the transfer area TA may be continuously varied. However, even when the rotational speed when the portion other than the recessed portion 50A passes through the transfer area TA is continuously varied, the average rotational speed of the transfer cylinder 50 during one cycle is controlled to match a specific value, similar to the average speed values ​​in other cycles. 8A, the rotation speed of the recessed portion 50A of the transfer cylinder 50 when it passes through the transfer area TA can be adjusted so that the total area of ​​the region A1 or A2 surrounded by the line showing the change in rotation speed when the portion of the transfer cylinder 50 other than the recessed portion 50A passes through the transfer area TA and the line showing the zero value of the speed adjustment amount is the same as the area of ​​the region B1 or B2 surrounded by the line showing the change in rotation speed when the portion of the transfer cylinder 50 other than the recessed portion 50A passes through the transfer area TA and the line showing the zero value of the speed adjustment amount. This makes it possible to maintain a constant interval between images formed on the intermediate transfer belt 31 even if the rotation speed when the portion of the transfer cylinder 50 other than the recessed portion 50A passes through the transfer area TA is not constant.

[0074] As a modification, if the image forming apparatus 10 according to the present embodiment has multiple storage compartments 41 housing different recording media P, the first and second control patterns executed by the speed adjustment mechanism 80 may include multiple adjustment patterns set corresponding to the multiple storage compartments 41. In this manner, multiple adjustment patterns are prepared in advance for each of the multiple storage compartments 41, i.e., for each recording medium P to be used. By selecting and executing an adjustment pattern corresponding to the storage compartment 41 housing the recording medium P transported along the transport path 40 as the first and second adjustment patterns, it becomes possible to change the optimal rotation speed adjustment amount even when the optimal rotation speed adjustment amount varies depending on, for example, the transfer current setting value for each recording medium P. To select one adjustment pattern from the multiple adjustment patterns, it is preferable to set a correspondence relationship between the multiple adjustment patterns and some of the setting parameters for each storage compartment. In this way, by switching the adjustment pattern depending on the recording medium P passing through the transfer area TA, it becomes possible to suppress distortion of the image transferred to each recording medium P even in an image forming device that selectively uses recording media P of different types (specifically, size, material, thickness, etc.).

[0075] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the present disclosure, all of which are included in the technical concept of the present disclosure. [Explanation of symbols]

[0076] 10 Image forming device 12 Image forming unit 14 Conveying section 16 Control device 20 Toner image forming unit 30 Transcription device 31 Intermediate transfer belt (an example of a transfer belt) 32 Drive roller 32M Drive roller motor (example of drive source) 40 Transport Route 42 Secondary transfer body 50 Transfer cylinder (an example of a transfer roller) 50A recess 50M Transfer cylinder motor (an example of a drive mechanism) 53 Gripper (an example of a holding member) 60 First drive control section 70 Second drive control section 80 Speed ​​adjustment mechanism 81 Media position prediction unit 82 Reference position detection unit 83 Adjustment pattern selection section 84 Data storage unit 87 Speed ​​Sensor P Recording medium TA transcription region RP reference position RD1 (Intermediate transfer belt) rotation direction RD2 (transfer cylinder) rotation direction

Claims

1. an annular transfer belt on whose outer circumferential surface an image is transferred; a drive roller that moves the transfer belt while wrapping it around; a transfer roller that forms a transfer area between itself and the transfer belt and transfers an image onto the recording medium when the recording medium passes through the transfer area; a drive mechanism for rotating the transfer roller; a speed adjustment mechanism that adjusts the rotation speed of the transfer roller driven by the drive mechanism in units of a cycle of the transfer roller, the speed adjustment mechanism switching between a first adjustment pattern that adjusts the rotation speed of the transfer roller in a cycle that includes a state in which the transfer roller is transporting the recording medium, and a second adjustment pattern that adjusts the rotation speed of the transfer roller in a pattern different from the first adjustment pattern in a cycle that does not include a state in which the transfer roller is transporting the recording medium; a holding member that holds the recording medium and passes it through the transfer area, the transfer roller has a recess on its circumferential surface that can accommodate the holding member, The speed adjustment mechanism periodically adjusts the rotational speed of the transfer roller when the portion other than the recessed portion of the transfer roller passes through the transfer area and the rotational speed of the transfer roller when the recessed portion passes through the transfer area so that, when an average value of the rotational speed of the transfer roller when the portion other than the recessed portion of the transfer roller passes through the transfer area is slower than a specific value, the rotational speed of the transfer roller when the recessed portion passes through the transfer area is faster than the specific value, and so that, when an average value of the rotational speed of the transfer roller when the portion other than the recessed portion of the transfer roller passes through the transfer area is faster than the specific value, the rotational speed of the transfer roller when the recessed portion passes through the transfer area is slower than the average value. Image forming device.

2. the first adjustment pattern and the second adjustment pattern adjust an average value of the rotation speed of the transfer roller in units of one cycle, the speed adjustment mechanism adjusts the rotation speed of the transfer roller so that an average value of the rotation speed of the transfer roller in one cycle in the first adjustment pattern matches an average value of the rotation speed of the transfer roller in one cycle in the second adjustment pattern. The image forming apparatus according to claim 1 .

3. An annular transfer belt on whose outer peripheral surface an image is transferred; a drive roller that moves the transfer belt while wrapping it around; a transfer roller that forms a transfer area between itself and the transfer belt and transfers an image onto the recording medium when the recording medium passes through the transfer area; a drive mechanism for rotating the transfer roller; a speed adjustment mechanism that adjusts the rotation speed of the transfer roller driven by the drive mechanism in units of a cycle of the transfer roller, the speed adjustment mechanism switching between a first adjustment pattern that adjusts the rotation speed of the transfer roller in a cycle that includes a state in which the transfer roller is transporting the recording medium, and a second adjustment pattern that adjusts the rotation speed of the transfer roller in a pattern different from the first adjustment pattern in a cycle that does not include a state in which the transfer roller is transporting the recording medium; a torque detection unit that detects torque fluctuations of the drive roller, the rotation speed of the transfer roller in the first adjustment pattern and the second adjustment pattern is set based on the detection result of the torque detection unit; Image forming device.

4. An annular transfer belt on whose outer peripheral surface an image is transferred; a drive roller that moves the transfer belt while wrapping it around; a transfer roller that forms a transfer area between itself and the transfer belt and transfers an image onto the recording medium when the recording medium passes through the transfer area; a drive mechanism for rotating the transfer roller; a speed adjustment mechanism that adjusts the rotation speed of the transfer roller driven by the drive mechanism in units of a cycle of the transfer roller, the speed adjustment mechanism switching between a first adjustment pattern that adjusts the rotation speed of the transfer roller in a cycle that includes a state in which the transfer roller is transporting the recording medium, and a second adjustment pattern that adjusts the rotation speed of the transfer roller in a pattern different from the first adjustment pattern in a cycle that does not include a state in which the transfer roller is transporting the recording medium; a drive source that rotates the drive roller; a current value detection unit that detects a current value supplied to the drive source, the rotation speed of the transfer roller in the first adjustment pattern and the second adjustment pattern is set based on the detection result of the current value detection unit; Image forming device.

5. An annular transfer belt on whose outer peripheral surface an image is transferred; a drive roller that moves the transfer belt while wrapping it around; a transfer roller that forms a transfer area between itself and the transfer belt and transfers an image onto the recording medium when the recording medium passes through the transfer area; a drive mechanism for rotating the transfer roller; a speed adjustment mechanism that adjusts the rotation speed of the transfer roller driven by the drive mechanism in units of a cycle of the transfer roller, the speed adjustment mechanism switching between a first adjustment pattern that adjusts the rotation speed of the transfer roller in a cycle that includes a state in which the transfer roller is transporting the recording medium, and a second adjustment pattern that adjusts the rotation speed of the transfer roller in a pattern different from the first adjustment pattern in a cycle that does not include a state in which the transfer roller is transporting the recording medium; a belt speed measuring unit that measures the moving speed of the transfer belt, the rotation speed of the transfer roller in the first adjustment pattern and the second adjustment pattern is set based on the measurement result of the belt speed measurement unit; Image forming device.

6. An annular transfer belt on whose outer peripheral surface an image is transferred; a drive roller that moves the transfer belt while wrapping it around; a transfer roller that forms a transfer area between itself and the transfer belt and transfers an image onto the recording medium when the recording medium passes through the transfer area; a drive mechanism for rotating the transfer roller; a speed adjustment mechanism that adjusts the rotation speed of the transfer roller driven by the drive mechanism in units of a cycle of the transfer roller, the speed adjustment mechanism switching between a first adjustment pattern that adjusts the rotation speed of the transfer roller in a cycle that includes a state in which the transfer roller is transporting the recording medium, and a second adjustment pattern that adjusts the rotation speed of the transfer roller in a pattern different from the first adjustment pattern in a cycle that does not include a state in which the transfer roller is transporting the recording medium; the speed adjustment mechanism continuously changes information included in the first adjustment pattern and the second adjustment pattern to be executed based on at least one of a torque fluctuation of the drive roller, a current value supplied to a drive source that rotates the drive roller, and a moving speed of the transfer belt. Image forming device.

7. An annular transfer belt on whose outer peripheral surface an image is transferred; a drive roller that moves the transfer belt while wrapping it around; a transfer roller that forms a transfer area between itself and the transfer belt and transfers an image onto the recording medium when the recording medium passes through the transfer area; a drive mechanism for rotating the transfer roller; a speed adjustment mechanism that adjusts the rotation speed of the transfer roller driven by the drive mechanism in units of a cycle of the transfer roller, the speed adjustment mechanism switching between a first adjustment pattern that adjusts the rotation speed of the transfer roller in a cycle that includes a state in which the transfer roller is transporting the recording medium, and a second adjustment pattern that adjusts the rotation speed of the transfer roller in a pattern different from the first adjustment pattern in a cycle that does not include a state in which the transfer roller is transporting the recording medium; a plurality of storage units capable of storing different recording media; each of the first and second adjustment patterns includes a plurality of adjustment patterns corresponding to the plurality of storage portions; the speed adjustment mechanism executes, as the first and second adjustment patterns, one adjustment pattern among the plurality of adjustment patterns that corresponds to the accommodation unit in which the recording medium to be transported to the transfer area was accommodated. Image forming device.

Images