Image forming apparatus and program

Abstract

This suppresses the effects of belt movement caused by resist correction. [Solution] An image forming apparatus 100 that forms an image on a recording medium P by multiple processes, comprising: a media oscillation mechanism 34 that oscillates the recording medium along the media width direction CD; a media detection unit SE2 that detects the position of the edge of the recording medium in the media width direction; belt correction mechanisms 62, 55 that correct the position of belts 6, 53 that execute one of the image forming processes in the media width direction; belt detection units 63, 56 that detect the position of the edge of the belt in the media width direction; and a control device 11 that performs a first correction control that causes the media oscillation mechanism to correct the position of the edge of the recording medium based on the detection of the media detection unit, and a second correction control that causes the belt correction mechanism to correct the position of the edge of the belt based on the detection of the belt detection unit, wherein the control device performs a correction to the second correction control when the recording medium spans both the media oscillation mechanism and the belt during the first correction control.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and a program.

Background Art

[0002] In an image forming apparatus, a sheet-like recording medium on which image formation is performed may be shifted in a direction crossing the conveyance direction of the recording medium due to various factors. In such a state where the recording medium is shifted, there is a problem that the image formation position on the recording medium is shifted from the original proper position.

[0003] Conventionally, a shifted recording medium has been corrected by sandwiching it with a registration roller and swinging it in the medium width direction (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In an image forming apparatus that forms an image on a recording medium through a plurality of image forming processes, a belt that contacts the recording medium is used in a part of the process. In that case, registration correction (hereinafter referred to as registration correction) by a registration roller may be performed while the recording medium is in contact with the belt. As a result, the belt may be pulled by the paper and move, which may affect the quality of image formation.

[0006] An object of the present invention is to suppress the influence of the movement of the belt due to registration correction.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides An image forming apparatus that forms an image on a recording medium by multiple processes, A media oscillating mechanism that oscillates the recording medium along the media width direction intersecting the transport direction of the recording medium, A media detection unit that detects the position of the edge of the recording medium in the media width direction, A belt correction mechanism that corrects the position of a belt in the media width direction of a belt that is in contact with the recording medium and performs any of the processes, A belt detection unit that detects the position of the end of the belt in the media width direction, The control device includes a first correction control that causes the media oscillation mechanism to correct the position of the end of the recording medium based on the detection of the media detection unit, and a second correction control that causes the belt correction mechanism to correct the position of the end of the belt based on the detection of the belt detection unit. The control device performs a correction to the second straightening control when the first straightening control is performed with the recording medium spanning both the medium oscillation mechanism and the belt.

[0008] Furthermore, another invention is a program, A computer in an image forming apparatus comprising: a media oscillating mechanism that oscillates the recording medium along the media width direction intersecting the transport direction of the recording medium; a media detection unit that detects the position of the end of the recording medium in the media width direction; a belt correction mechanism that corrects the position of a belt in the media width direction of a belt that contacts the recording medium and performs one of the processes of forming an image on the recording medium; and a belt detection unit that detects the position of the end of the belt in the media width direction, A function to perform first correction control, which causes the media oscillation mechanism to correct the position of the edge of the recording medium based on the detection of the media detection unit, A function to perform a second correction control that causes the belt correction mechanism to correct the position of the end of the belt based on the detection of the belt detection unit, The recording medium is provided with a function to correct the second straightening control when the first straightening control is performed across both the medium oscillation mechanism and the belt. [Advantages of the Invention]

[0009] According to the present invention, it becomes possible to suppress the influence of the movement of the belt due to resist correction. [Brief Description of the Drawings]

[0010] [Figure 1] It is a configuration diagram schematically showing the image forming apparatus according to the present embodiment. [Figure 2] It is a perspective view of the intermediate transfer belt stretched and supported in the apparatus as seen from the downstream side in the medium conveyance direction. [Figure 3] It is a rear view of the upper part of the intermediate transfer belt as seen from the back side in the drawing plane of FIG. 1. [Figure 4] It is a perspective view of the upper part of the intermediate transfer belt as seen from the downstream side in the medium conveyance direction. [Figure 5] It is an explanatory diagram showing the rocking process of the paper by the resist roller. [Figure 6] It is a perspective view showing the configuration of the heating side arranged above the fixing device. [Figure 7] It is a perspective view of the same configuration as FIG. 6 as seen from a different direction. [Figure 8] It is a perspective view of the same configuration as FIG. 6 as seen from a further different direction. [Figure 9] It is a block diagram schematically showing the configuration of the control system of the image forming apparatus of FIG. 1. [Figure 10] It is a flowchart of the operation control executed by the control unit for each part of the image forming apparatus when the recording medium is conveyed. [Modes for Carrying Out the Invention]

[0011] Hereinafter, the present embodiment will be described in detail based on the drawings. However, the scope of the invention is not limited to the illustrated examples.

[0012] [Overview of Each Component of the Image Forming Apparatus] First, the configuration of the image forming apparatus 100 in the present embodiment will be described. FIG. 1 is a configuration diagram schematically showing an image forming apparatus 100 according to the present embodiment. This image forming apparatus 100 is an electrophotographic image forming apparatus 100 such as a copying machine, for example. The image forming apparatus 100 is of a tandem type that forms a color image by arranging a plurality of photoreceptors facing a single intermediate transfer belt in the vertical direction. However, as an embodiment, color and tandem type are just examples, and other image forming apparatuses may be exemplified. The recording medium P on which the image forming apparatus 100 forms an image is not limited to various recording papers such as plain paper. The recording medium P includes all sheet-like recording media on which image formation is possible, such as cut paper, continuous paper, long paper, OHP sheets, and the like.

[0013] The image forming apparatus 100 includes an original document reading device SC, an image forming unit 10, a fixing device 50, an image reading unit 35, a medium conveyance unit 20, and a control unit 11. The image forming apparatus 100 houses these in a single housing.

[0014] [Original document reading device] The original document reading device SC scans and exposes the image of the original document with the optical system of the scanning exposure device, reads the reflected light with a line image sensor, and obtains an image signal. This image signal is input to the control unit 11 as image data after being subjected to processes such as A / D conversion, shading correction, and compression. Note that the image data input to the control unit 11 is not limited to that read by the original document reading device SC. The image data may be, for example, received from a personal computer or another image forming apparatus through the communication unit 13.

[0015] [Image forming unit] The image forming unit 10 includes four sets of image forming units 10Y, 10M, 10C, 10K, an intermediate transfer belt 6, a secondary transfer roller 9 and the like. The image forming units 10Y, 10M, 10C, 10K are image forming units for each color of Y, M, C, K. The "Y" included in the reference numeral indicates that it is related to the formation of images of each color of yellow, "M" indicates magenta, "C" indicates cyan, and "K" indicates black.

[0016] The image forming unit 10Y includes a photosensitive drum 1Y and surrounding it a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y. The image forming unit 10M includes a photosensitive drum 1M and surrounding it a charging unit 2M, an optical writing unit 3M, a developing device 4M, and a drum cleaner 5M. The image forming unit 10C includes a photosensitive drum 1C and surrounding it a charging unit 2C, an optical writing unit 3C, a developing device 4C, and a drum cleaner 5C. The image forming unit 10K includes a photosensitive drum 1K and surrounding it a charging unit 2K, an optical writing unit 3K, a developing device 4K, and a drum cleaner 5K.

[0017] The photoreceptor drums 1Y to 1K are uniformly charged on their surfaces by the charging units 2Y to 2K. Furthermore, scanning exposure by the light writing units 3Y to 3K forms a latent image on the photoreceptor drums 1Y to 1K. Then, the developing units 4Y to 4K develop the latent image on the photoreceptor drums 1Y to 1K by developing it with toner. As a result, toner images of predetermined colors corresponding to yellow, magenta, cyan, and black are formed on the photoreceptor drums 1Y to 1K. The toner images formed on the photoreceptor drums 1Y to 1K are sequentially transferred to the intermediate transfer belt 6 by the primary transfer rollers 7Y, 7M, 7C, and 7K.

[0018] The intermediate transfer belt 6 is a belt that carries the toner image and performs the intermediate transfer process, which involves secondary transfer to the recording medium P. The toner image, consisting of each color, transferred onto the intermediate transfer belt 6 is transferred to the recording medium P by the secondary transfer roller 9. This secondary transfer roller 9 is a pressure-contacting member that forms a nip portion (hereinafter referred to as the "transfer nip portion") by being positioned in pressure contact with the intermediate transfer belt 6.

[0019] [Image forming section: Around the intermediate transfer belt] Figure 2 is a perspective view of the intermediate transfer belt 6, which is tensioned and supported within the device, as seen from the downstream side in the media transport direction FD. Figure 3 is a rear view of the upper part of the intermediate transfer belt 6, as seen from the far side of the page in Figure 1. Figure 4 is a perspective view of the upper part of the intermediate transfer belt 6 as seen from the downstream side in the media transport direction FD. The media transport direction FD is the sub-scanning direction, which is parallel to the transport direction when the recording medium P is transported by the media transport unit 20 in the correct orientation. In the following description, the direction parallel to the recording medium P and intersecting the media transport direction FD is referred to as the media width direction CD. More specifically, the media width direction CD is exemplified as the direction perpendicular to the media transport direction FD. The correct orientation is the direction in which one side edge of the media width direction CD of the recording medium P is parallel to the transport direction planned for the media transport unit 20. The various components of the image forming apparatus 100 may be described using the media transport direction FD and the media width direction CD.

[0020] The intermediate transfer belt 6 consists of an endless annular belt with a polyimide base material and a release coating applied to its surface. Some or all of the rollers on which the intermediate transfer belt 6 is stretched may be configured to be rotationally driven by a motor. The upper side of the intermediate transfer belt 6 is stretched in a V-shape by three rollers, and the lower side is stretched by two rollers. The number of rollers supporting the intermediate transfer belt 6 is just one example and can be increased or decreased within a range of two or more. One of the lower rollers forms a nip with the aforementioned secondary transfer roller 9, and transfers the toner image from the intermediate transfer belt 6 to the recording medium P. The roller at the top of the three upper rollers is the steering roller 61. The five rollers, including the steering roller 61, are, in principle, oriented so that their axis of rotation is parallel to the media width direction CD.

[0021] Furthermore, the steering roller 61 can have its rotation axis tilted by the first steering mechanism 62, which acts as a belt correction mechanism. By tilting its rotation axis, the steering roller 61 can correct the position CD of the intermediate transfer belt 6 in the media width direction.

[0022] As shown in Figure 3, the first steering mechanism 62 is driven by a steering motor 621 and can rotate the outer peripheral cam 622 to any angle via a reduction mechanism. The steering roller 61 has one end in the media width direction CD that is rotatably supported by a lever member 623 that extends in the vertical direction. Furthermore, the outer peripheral cam 622 has a shape in which its outer diameter increases or decreases along the circumferential direction. The outer circumference of this outer peripheral cam 622 abuts against the lower side end of the lever member 623 on the downstream side in the media transport direction FD. Therefore, when the outer peripheral cam 622 rotates, the upper end of the lever member 623 swings, and the rotation axis of the steering roller 61 tilts.

[0023] When the rotation axis of the steering roller 61 tilts, the intermediate transfer belt 6 moves in one of the directions of the media width CD, depending on the direction of the tilt. Therefore, if the intermediate transfer belt 6 becomes misaligned in one of the directions of the media width CD, the misalignment can be corrected by moving it in the opposite direction.

[0024] The amount of deviation of the media width CD of the intermediate transfer belt 6 can be detected by the first deviation detection device 63, which acts as a belt detection unit. The first deviation detection device 63 detects the position of one end of the media width direction CD in the media width direction CD at the upper part of the intermediate transfer belt 6. As shown in Figure 4, the first misalignment detection device 63 includes a detection arm 631, a swinging arm 632, a first sensor 633, a second sensor 634, and a support plate 635. The detection arm 631 is rotatably supported on the support plate 635. The rotatable end of the detection arm 631 abuts against one end of the intermediate transfer belt 6 in the medium width direction CD. Furthermore, a weak spring pressure is applied to the detection arm 631 by a spring 636 to maintain contact with the intermediate transfer belt 6.

[0025] The oscillating arm 632 is connected to the detection arm 631 so as to rotate integrally with it. The detection arm 631 is provided with a plate-shaped detectable portion 631a that is detected by the first sensor 633. The oscillating arm 632 is provided with a plate-shaped detectable portion 632a that is detected by the second sensor 634.

[0026] The first and second sensors 633 and 634 each have a detection element that performs optical detection of the respective detected parts 631a and 632a. Each detection element may detect the presence or absence of the detected parts 631a and 632a within its detection range. Alternatively, each detection element may detect the position and amount of movement of the detected parts 631a and 632a in a predetermined direction, similar to a line sensor. In the former case, each detection element can determine whether the position of the intermediate transfer belt 6 in the media width direction CD is appropriate based on the combination of patterns of the presence or absence of the detected parts 631a and 632a. For example, one combination pattern indicates that the intermediate transfer belt 6 is in the correct position in the media width direction CD. Another pattern indicates that the intermediate transfer belt 6 is off-center to one side in the media width direction CD. Yet another pattern indicates that the intermediate transfer belt 6 is off-center to the other side in the media width direction CD. Furthermore, in the latter case, the deviation of the intermediate transfer belt 6 from its proper position in the media width direction CD can be detected from the detected amount of the detected parts 631a and 632a. This makes it possible to detect whether the position of the intermediate transfer belt 6 in the media width direction CD is correct, and to what extent it is deviated to one side or the other.

[0027] The control unit 11, acting as a control device, performs a second corrective control on the first steering mechanism 62 based on the detection by the first deviation detection device 63. The second corrective control performed by the control unit 11 on the first steering mechanism 62 will be described separately later.

[0028] [Media Transport Section] The media transport unit 20 transports the recording medium P according to the transport path of the recording medium P. The recording medium P is housed in the supply tray 21, and the recording medium P is taken in by the supply roller 22a of the supply unit 22 and sent to the transport path. Alternatively, the recording medium P is supplied from outside the image forming apparatus 100 through an external supply port and sent to the transport path. For example, a recording medium P made of long paper is supplied to the image forming apparatus 100 via an external supply port.

[0029] In the above transport path, multiple transport means for transporting the recording medium P are provided upstream of the transfer nip portion of the secondary transfer roller 9. Each transport means consists of a pair of pressed rollers. Each transport means transports the recording medium P by the rotational drive of at least one roller via a drive mechanism mainly consisting of an electric motor. Furthermore, the pair of rollers constituting each transport means are configured to be able to switch between a pressed state and a separated state.

[0030] Intermediate transport rollers 23-25, loop rollers 26, and registration rollers 27 are provided along the transport path of the recording medium P from the upstream to the downstream side. These transport means may consist of pairs of rollers, belts, or a combination of belts and rollers.

[0031] [Media transport section: Register roller] The recording medium P supplied to the transport path is sequentially transported by a plurality of intermediate transport rollers 23-25 ​​and a loop roller 26 located from the upstream to the downstream side. The leading edge of the recording medium P then abuts against a registration roller 27 that is in a stopped state. Furthermore, the loop roller 26 continues to rotate for a predetermined time. This forms a loop on the recording medium P. This loop formation corrects the curvature of the leading edge of the recording medium P. In other words, the tilt of the recording medium P is skew-corrected. That is, the leading edge of the recording medium P becomes parallel to the nip portion of the registration roller 27, which is parallel to the CD in the media width direction, and the curvature is corrected.

[0032] Next, the register roller 27 starts rotating at a predetermined timing in synchronization with the toner image carried by the intermediate transfer belt 6. At this time, the intermediate transport rollers 23-25 ​​and the loop roller 26 are switched from a pressed state to a separated state. That is, when the intermediate transport rollers 23-25 ​​and the loop roller 26 are separated, the recording medium P is transported by the register roller 27 alone. The register roller 27 transports the recording medium P to the intermediate transfer belt 6, which acts as the image carrier, and to the transfer nip portion of the secondary transfer roller 9, which acts as the transfer section. At this time, the register roller 27 acts as an oscillating roller, performing the oscillating process described later while transporting the recording medium P.

[0033] Figure 5 is an explanatory diagram illustrating the oscillation process of the recording medium P by the register roller 27. The register roller 27 is configured to oscillate in the media width direction CD. In addition to the register motor 271 that performs rotational drive, a media oscillation mechanism 34 driven by a motor is connected to the register roller 27. The register roller 27 is driven by the media oscillation mechanism 34 and can move in the media width direction CD starting from a predetermined home position.

[0034] The register roller 27 moves along the media width direction CD in accordance with the passage period of the recording medium P as it passes through it. This allows the transported recording medium P to move along the media width direction CD (oscillation process). Hereinafter, the movement of the recording medium P along the media width direction CD by the register roller 27 will be referred to as "oscillation of the recording medium P". As a result, the registration roller 27 adjusts the transport position of the recording medium P in the media width direction CD to align with the position of the toner image being transferred. Here, the position that the side edge of the recording medium P should pass through in the media width direction CD is called the target position Tp. This target position Tp is the position where the positional relationship between the recording medium P and the toner image is expected to be optimal when the side edge of the recording medium P passes through it. For example, it is the position where the center of the recording medium P in the width direction coincides with the center of the toner image in the width direction. The registration roller 27 is subject to the first correction control described later. This causes the registration roller 27 to adjust the transport position of the recording medium P in the media width direction CD so that the side edge of the recording medium P is at the target position Tp. The position of the toner image where the positional relationship between the recording medium P and the toner image is optimal is called the optimal image position.

[0035] The transport path is equipped with a resist sensor SE1 and a position detection sensor SE2. The control unit 11 controls the operation of the resist roller 27 based on the detection by the sensor SE1. In the transport path, a resist sensor SE1 is positioned between the resist roller 27 and the loop roller 26. The resist sensor SE1 detects the arrival of the leading edge of the recording medium P at a predetermined distance before the resist roller 27. The detection result of the resist sensor SE1 is used to determine the rotation start timing of the resist roller 27.

[0036] In the transport path, a position detection sensor SE2 is provided as a media detection unit downstream of the register roller 27 in the media transport direction FD. The position detection sensor SE2 is a detection unit that detects the position of the media width direction CD at the side edge of the recording medium P. The position detection sensor SE2 is, for example, a linear image sensor in which multiple light-receiving elements are arranged linearly along the media width direction CD. The detection result of this position detection sensor SE2 is output to the control unit 11 and used for determining the oscillation control information of the register roller 27 in the oscillation process. Furthermore, the operation of the media oscillation mechanism 34 is controlled based on this determination.

[0037] The control unit 11 performs a first correction control that causes the media oscillation mechanism 34 to correct the position of the edge of the recording medium P based on the detection by the position detection sensor SE2. The first corrective control performed by the control unit 11 on the media oscillation mechanism 34 will be described separately later.

[0038] [Media transport unit: Media sensor] A media sensor 33, which serves as a media detection unit, is provided on the transport path between the intermediate transport roller 24 and the intermediate transport roller 25. The media sensor 33 detects the physical properties of the recording medium P. The media sensor 33 includes a thickness sensor, a moisture content sensor, a basis weight sensor, and a stiffness sensor. The thickness sensor detects the thickness of the recording medium P. The moisture content sensor detects the moisture content of the recording medium P. The basis weight sensor detects the basis weight of the recording medium P. The stiffness sensor detects the stiffness of the recording medium P.

[0039] [Fusing device] Figure 6 is a perspective view showing the configuration of the heating side located above the fixing device 50, and Figure 7 is a perspective view of the same configuration as Figure 6 from a different direction. Figure 8 is a perspective view of the same configuration as Figure 6 from yet another different direction. The fixing device 50 is a device that performs a fixing process on the recording medium P onto which the toner image has been transferred, that is, on the recording medium P that has been fed out from the transfer nip section. The fixing device 50 includes, for example, first and second heating rollers 51 and 52, a fixing belt 53, a pressure roller 54, a second steering mechanism 55, and a second misalignment detection device 56.

[0040] The first and second heating rollers 51 and 52 are positioned above the transport path of the recording medium P, with their rotation axes generally parallel to the media width direction CD. The first heating roller 51 has a built-in heater, which is the heating source, and is located above the second heating roller 52. A fixing belt 53 is stretched between the first heating roller 51 and the second heating roller 52 in a taut state. The second heating roller 52 forms a nip section with the pressure roller 54 via the fixing belt 53, and fixes the recording medium P that passes through the nip section. The pressure roller 54 is positioned so as to be in contact with the second heating roller 52 via the fixing belt 53, with its rotation axis parallel to the media width direction CD. Any of the rollers 51, 52, or 54 may be used, but this example illustrates a configuration in which the pressure roller 54 is rotationally driven by a motor. The fixing belt 53 is a belt that performs the process of fixing the toner image onto the recording medium P. The fixing belt 53 consists of an endless annular belt with a polyimide base material and a release coating applied to its surface. The fixing device 50 fixes the toner image onto the recording medium P through the action of pressurization and heating during the transport process of the recording medium P.

[0041] Furthermore, the second steering mechanism 55 can tilt its rotation axis relative to the first heating roller 51. By tilting its rotation axis, the first heating roller 51 can correct the position of the fixing belt 53 in the media width direction CD. As shown in Figure 7, the second steering mechanism 55 uses a steering motor 551 as a drive source and can rotate the outer peripheral cam 552 to any angle via a reduction mechanism. When the outer peripheral cam 552 rotates, one end of the first heating roller 51 in the media width direction CD tilts in a predetermined direction. When the rotation axis of the first heating roller 51 tilts, the fixing belt 53 moves in one of the directions of the media width CD, depending on the direction of the tilt. Therefore, if the fixing belt 53 becomes misaligned in one of the directions of the media width CD, the misalignment can be corrected by moving it in the opposite direction.

[0042] The amount of deviation of the media width CD of the fixing belt 53 can be detected by the second deviation detection device 56, which acts as a belt detection unit. As shown in Figure 8, the second bias detection device 56 detects the position of one end of the media width direction CD in the media width direction CD at the upper part of the fixing belt 53. The second misalignment detection device 56 includes a detection arm 561, a first sensor 563, a second sensor 564, a third sensor 565, and a support plate 566. The detection arm 561 is rotatably supported on the support plate 566. The detection arm 561 has a round bar-shaped detection piece 562 that abuts against one end of the intermediate transfer belt 6 in the medium width direction CD. The detection arm 561 is also subjected to a weak spring pressure by a spring (not shown) to maintain contact with the fixing belt 53.

[0043] The detection arm 561 is provided with plate-shaped detectable parts 561a to 561c that are detected by the first to third sensors 563 to 565. The first to third sensors 563 to 565 each have a detection element that performs optical detection on their respective detected parts 561a to 561c. Each detection element may detect the presence or absence of the detected parts 561a to 561c within its detection range. Alternatively, each detection element may detect the position and amount of movement of the detected parts 561a to 561c in a predetermined direction, similar to a line sensor. In the former case, each detection element detects a combination of patterns of the presence or absence of the detected parts 561a to 561c. Based on the individual patterns detected, it is possible to determine whether the position of the fixing belt 53 in the media width direction CD is appropriate. For example, one combination pattern indicates that the fixing belt 53 is located within the appropriate range in the media width direction CD. Another pattern indicates that the fixing belt 53 is off-center to one side in the media width direction CD. Yet another pattern indicates that the fixing belt 53 is off-center to the other side in the media width direction CD. In the latter case, the position of the fixing belt 53 in the media width direction CD can be detected from the detected amount of the detected parts 561a to 561c. This makes it possible to detect whether the position of the fixing belt 53 in the media width direction CD is within the appropriate range, and to what extent there is a bias to one side or the other.

[0044] The control unit 11 performs a second corrective control on the second steering mechanism 55 based on the detection by the second deviation detection device 56. The second corrective control performed by the control unit 11 on the second steering mechanism 55 will be described separately later.

[0045] [Image reading section] The image reading unit (ICCU) 35 is configured to include, for example, a linear image sensor (e.g., a CCD line sensor), an optical system, a light source, etc. The image reading unit 35 reads the recording medium P on which the toner image has been transferred and outputs the obtained read image to the control unit 11. In this embodiment, the image reading unit 35 is capable of measuring the color of the toner image on the recording medium P. However, the image reading unit 35 is not particularly limited as long as it can recognize at least the area of ​​the recording medium P and the area of ​​the toner image. Also, in this embodiment, the image reading unit 35 is positioned downstream of the fuser 50 and before the transport path is switched by the switching gate 30. However, the image reading unit 35 may be positioned downstream of the secondary transfer roller 9 and capable of reading both sides of the recording medium P. The recording medium P may be positioned so that one side at a time can be read. Furthermore, the image reading unit 35 may be placed downstream of the image forming apparatus 100 as an optional device.

[0046] The recording medium P, which has been fixed by the fixing device 50, is read by the image reading unit 35. The recording medium P is then discharged by the discharge roller 28 to the discharge tray 29 attached to the outer side of the housing. If image formation is also performed on the back side of the recording medium P, the recording medium P, after image formation on the paper surface has been completed, is read by the image reading unit 35. The recording medium P is then transported by the switching gate 30 to the inversion roller 31 located below. The inversion roller 31 grips the rear end of the transported recording medium P, then reverses the recording medium P by moving it in the opposite direction and sends it to the resupply transport path. The recording medium P sent to this resupply transport path is transported to the register roller 27 by multiple resupply transport means. Furthermore, the recording medium P is returned to the transfer nip section via the register roller 27. The discharge roller 28, switching gate 30, inversion roller 31, and resupply transport means also constitute the media transport unit 20 described above.

[0047] [Control system for image forming apparatus] Figure 9 is a schematic block diagram showing the configuration of the control system of the image forming apparatus 100 according to this embodiment. The control unit 11 is connected to the storage unit 12, communication unit 13, operation unit 14, document reader SC, image forming unit 10, media transport unit 20, and fixing unit 50. Furthermore, the control unit 11 is connected to the image reading unit 35, resist sensor SE1, position detection sensor SE2, environment sensor SE3, and media sensor 33. The control unit 11 is composed of a CPU, RAM, etc.

[0048] The CPU of the control unit 11 reads the system program and various processing programs stored in the memory unit 12 and loads them into RAM. Furthermore, the control unit 11 centrally controls the operation of each part of the image forming apparatus 100 according to the loaded programs. For example, when the control unit 11 receives an image formation job execution command from the operation unit 14, it executes the image formation job. Specifically, the control unit 11 controls the formation of a toner image on the recording medium P based on the image data input by the document reader SC and the communication unit 13. Furthermore, the first correction control, the second correction control, and the correction processing for the second correction control, which will be described later, are all based on processing programs stored in the memory unit 12. These controls and processes are realized by the CPU of the control unit 11 executing each processing program.

[0049] The storage unit 12 is composed of non-volatile semiconductor memory, an HDD (Hard Disk Drive), etc. The storage unit 12 stores various programs executed by the control unit 11, as well as parameters and data necessary for each unit.

[0050] The communication unit 13 is equipped with various interfaces for connecting to external devices. These interfaces include NIC (Network Interface Card), MODEM (Modulator-DEModulator), USB (Universal Serial Bus), etc.

[0051] The operation unit 14 outputs various information set by the user to the control unit 11. For example, the operation unit 14 can be a touch panel that allows input operations to be performed according to the information displayed on the display. Through the operation unit 14, the user can set image formation settings. These settings include image density, magnification, whether or not to print on both sides, and the transport conditions for the recording medium P. Furthermore, the transport conditions for the recording medium P include the transport speed of the recording medium P, the type of recording medium P (e.g., size, paper quality, etc.), and the supply tray to be used. The size of the recording medium P includes both the size of the FD in the media transport direction and the size of the CD in the media width direction. This image formation setting information is stored in the storage unit 12. Furthermore, the thickness, moisture content, basis weight, and stiffness of the recording medium P detected by the aforementioned media sensor 33 are also stored in the storage unit 12 as transport conditions for the recording medium P. The media sensor 33 performs detections periodically. Therefore, the setting information for the thickness, moisture content, basis weight, and stiffness of the recording medium P in the storage unit 12 is updated sequentially.

[0052] Furthermore, the user can input job execution commands and operation instructions in adjustment mode through the operation unit 14. The control unit 11 can also control the operation unit 14 and display various messages to the user through the operation unit 14.

[0053] The environmental sensor SE3 is configured to include, for example, a temperature sensor and a humidity sensor, and detects the temperature and humidity inside the housing of the image forming apparatus 100, and outputs the detection results to the control unit 11.

[0054] [Control performed by the control unit: First corrective control for the media oscillation mechanism] The control unit 11 performs a first correction control (media correction control) on the media oscillating mechanism 34 to correct any misalignment of the CD in the media width direction during transport of the recording medium P. When the control unit 11 detects an imbalance in the media width direction CD relative to the target position Tp of the recording medium P, it controls the media oscillation mechanism 34 to correct the imbalance. The imbalance in the media width direction CD relative to the target position Tp of the recording medium P is detected by the position detection sensor SE2.

[0055] From this point forward, for the sake of clarity, one side of the CD's width direction may be referred to as the "left" and the other as the "right." The control unit 11 periodically monitors the output of the position detection sensor SE2 while the register roller 27 is being driven. This allows the control unit 11 to acquire bias information indicating the magnitude of the bias of the recording medium P relative to the target position Tp. The bias information includes a numerical value indicating the magnitude of the bias and a direction indicating whether the bias is left or right.

[0056] When the control unit 11 acquires the bias information, it determines the oscillation speed of the media oscillation mechanism 34 according to the magnitude of the bias. The oscillation speed of the media oscillation mechanism 34 is the speed at which the resist roller 27 moves along the media width direction CD by the media oscillation mechanism 34. At this time, the control unit 11 determines the direction of the oscillation speed of the media oscillation mechanism 34 to be in the opposite direction based on the direction of the bias included in the bias information. For example, if the bias of the recording medium P is to the left, the register roller 27 is oscillated to the right, and if the bias of the recording medium P is to the right, the register roller 27 is oscillated to the left.

[0057] The control unit 11 determines the oscillation speed of the media oscillation mechanism 34 using table data that defines the correlation between the magnitude of the bias and the oscillation speed of the media oscillation mechanism 34. Alternatively, the control unit 11 may calculate the oscillation speed of the media oscillation mechanism 34 from the magnitude of the bias using a predetermined calculation. Furthermore, the oscillation speed of the media oscillation mechanism 34 should be increased or decreased in accordance with the transport speed of the recording medium P. Accordingly, the control unit 11 reads the set value of the transport speed of the recording medium P from the transport conditions of the recording medium P in the storage unit 12. Then, it multiplies the oscillation speed of the media oscillation mechanism 34, which is determined from the magnitude of the bias, by a coefficient correlated with the transport speed of the recording medium P, to determine the final oscillation speed. Alternatively, a numerical value correlated with the transport speed of the recording medium P may be added to or subtracted from the oscillation speed of the media oscillation mechanism 34, which is determined from the magnitude of the bias.

[0058] The control unit 11 drives the motor at the final determined oscillation speed and direction of the media oscillation mechanism 34, causing the register roller 27 to oscillate in one direction in the media width direction CD. As mentioned above, the control unit 11 periodically reads the position detection sensor SE2, and each time, it performs the first corrective control on the media oscillation mechanism 34.

[0059] [Control performed by the control unit: Second corrective control for the steering mechanism of the intermediate transfer belt] The control unit 11 performs a second straightening control (belt straightening control) of the first steering mechanism 62 to correct any deviation of the media width CD during transport of the intermediate transfer belt 6. When the control unit 11 detects an imbalance in the media width direction CD relative to the correct position of the intermediate transfer belt 6, it controls the first steering mechanism 62 to correct the imbalance. The imbalance in the media width direction CD relative to the correct position of the intermediate transfer belt 6 is detected by the first imbalance detection device 63.

[0060] The control unit 11 periodically monitors the output of the first deviation detection device 63 while the intermediate transfer belt 6 is being transported. The control unit 11 then acquires deviation information, including the magnitude and direction of the deviation relative to the proper position of the intermediate transfer belt 6.

[0061] The control unit 11 determines the corrective movement speed and direction of the intermediate transfer belt 6 according to the magnitude and direction of the deviation of the intermediate transfer belt 6 included in the deviation information. The control unit 11 may also use table data that defines the correlation between the magnitude of the deviation of the intermediate transfer belt 6 and the corrective movement speed of the intermediate transfer belt 6. Furthermore, the corrective movement speed of the intermediate transfer belt 6 in the media width direction of the CD should be increased or decreased to follow the transport speed of the recording medium P. Accordingly, the control unit 11 reads the set value of the transport speed of the recording medium P from the transport conditions of the recording medium P in the storage unit 12. Then, it multiplies the corrective movement speed of the intermediate transfer belt 6 by a coefficient correlated with the transport speed of the recording medium P to determine the final corrective movement speed. Alternatively, a numerical value correlated with the transport speed of the recording medium P may be added to or subtracted from the corrective movement speed of the intermediate transfer belt 6, which is determined from the magnitude of the deviation.

[0062] The straightening movement speed and direction of the intermediate transfer belt 6 are correlated with the tilt angle of the rotation axis of the steering roller 61. Furthermore, the tilt angle of the rotation axis of the steering roller 61 is correlated with the axis angle of the steering motor 621. Therefore, the control unit 11 may use table data that defines the correlation between the straightening movement speed of the intermediate transfer belt 6 and the axis angle of the steering motor 621. Therefore, when the control unit 11 obtains the magnitude and direction of the deviation of the intermediate transfer belt 6, it drives the steering motor 621 to the corresponding axial angle.

[0063] The control unit 11 periodically reads the first deviation detection device 63, and each time, executes a second corrective control for the first steering mechanism 62.

[0064] [Control performed by the control unit: Second corrective control for the steering mechanism of the fixing belt] The control unit 11 performs a second straightening control (belt straightening control) of the second steering mechanism 55, which corrects any deviation of the media width CD when the fixing belt 53 is being transported. When the control unit 11 detects an imbalance in the media width direction CD relative to the proper position of the fixing belt 53, it controls the second steering mechanism 55 to correct the imbalance. The imbalance in the media width direction CD relative to the proper position of the fixing belt 53 is detected by the second imbalance detection device 56.

[0065] The control unit 11 periodically monitors the output of the second deviation detection device 56 while the fixing belt 53 is being transported. The control unit 11 then acquires deviation information, including the magnitude and direction of the deviation relative to the proper position of the fixing belt 53.

[0066] The control unit 11 determines the corrective movement speed and direction of the fixing belt 53 according to the magnitude and direction of the misalignment of the fixing belt 53 included in the misalignment information. The control unit 11 may also use table data that defines the correlation between the magnitude of the misalignment of the fixing belt 53 and the corrective movement speed of the fixing belt 53. Furthermore, the straightening movement speed of the fixing belt 53 in the media width direction of the CD should be increased or decreased to follow the transport speed of the recording medium P. Accordingly, the control unit 11 reads the set value of the transport speed of the recording medium P from the transport conditions of the recording medium P in the storage unit 12. Then, it multiplies the straightening movement speed of the fixing belt 53 by a coefficient correlated with the transport speed of the recording medium P to determine the final straightening movement speed. Alternatively, a numerical value correlated with the transport speed of the recording medium P may be added to or subtracted from the straightening movement speed of the fixing belt 53, which is determined from the magnitude of the deviation.

[0067] The straightening movement speed and direction of the fixing belt 53 are correlated with the tilt angle of the rotation axis of the first heating roller 51. Furthermore, the tilt angle of the rotation axis of the first heating roller 51 is correlated with the axis angle of the steering motor 551. Therefore, the control unit 11 may use table data that defines the correlation between the straightening movement speed of the fixing belt 53 and the axis angle of the steering motor 551. Therefore, once the control unit 11 obtains the magnitude and direction of the offset of the fixing belt 53, it drives the steering motor 551 to the corresponding axis angle.

[0068] The control unit 11 periodically reads the second deviation detection device 56, and each time, executes a second corrective control for the second steering mechanism 55.

[0069] [Control performed by the control unit: Correction processing for the second corrective control] As the recording medium P passes through the register roller 27, it may reach the intermediate transfer belt 6 or the fixing belt 53 and straddle the space between them. If the first straightening control is performed on the recording medium P in this state, the intermediate transfer belt 6 or the fixing belt 53 may move in the same direction as the oscillation of the recording medium P. Therefore, if the above-mentioned overlap occurs, it is necessary to correct the corrective movement speed of the intermediate transfer belt 6 or the fixing belt 53 by the second corrective control.

[0070] First, the control unit 11 determines whether the resist roller 27 is straddling the intermediate transfer belt 6 or the fixing belt 53. The transport distance from the resist roller 27 to the nip portion of the intermediate transfer belt 6 or the fixing belt 53 is design information and a known value. Hereinafter, the transport distance from the resist roller 27 to the nip portion of the intermediate transfer belt 6 or the fixing belt 53 will be referred to as the "belt-to-belt distance". The size of the recording medium P in the medium transport direction (hereinafter referred to as "medium transport length") can be obtained from the transport conditions of the recording medium P in the storage unit 12. The control unit 11 determines that a straddling condition occurs when the media feed length is greater than the distance between belts. Furthermore, the control unit 11 can determine whether or not a straddling state is currently occurring based on the elapsed time since the start of driving the register roller 27. When the straddling state occurs, the control unit 11 performs a correction process on the corrective movement speed of the intermediate transfer belt 6 or the fixing belt 53 by the second corrective control.

[0071] Next, we will explain the content of the correction process for the correction movement speed by the second correction control. Here, we will use the case of the intermediate transfer belt 6 as an example. The control unit 11 periodically repeats the correction process while the straddling state is occurring. The control unit 11 determines the correction speed while the straddling state is occurring and performs a correction on the correction movement speed determined by the second correction control. The control unit 11 first determines a reference value for the correction speed. This reference value for the correction speed is determined based on the oscillation speed of the media oscillation mechanism 34 determined in the first correction control. As a general rule, the direction of the correction speed is opposite to the direction of the oscillation speed of the media oscillation mechanism 34. Hereinafter, the oscillation speed of the media oscillation mechanism 34 determined by the first correction control will be referred to as "oscillation speed A". Furthermore, the reference value of the correction speed relative to the correction movement speed by the second correction control will be referred to as "correction speed B".

[0072] The control unit 11 calculates the correction speed B by multiplying the oscillation speed A by a predetermined coefficient k1 (0 <k1<1)。 B=k1·A Note that this is just one example; instead of multiplying the oscillation speed A by a coefficient k1, one could also add or subtract a predetermined value, or both could be used to obtain the corrected speed B.

[0073] For example, when the recording medium P is oscillated to the left by the register roller 27, the belt 6 is corrected for a rightward movement component. In this case, if the second straightening control sets a rightward straightening movement speed for the belt 6, the correction is made to increase the rightward movement component. Conversely, if the second straightening control sets a leftward straightening movement speed for the belt 6, the correction is made to decrease the rightward movement component. On the other hand, when the recording medium P swings to the right by the resist roller 27, the situation is reversed. Note that the value of the correction speed B may be greater than the correction movement speed of the belt 6 determined by the second correction control. In that case, the belt 6 moves in the direction opposite to the correction movement speed determined by the second correction control.

[0074] Next, the control unit 11 further corrects the correction speed B serving as a reference value based on a predetermined parameter. The predetermined parameter in this case is the "size in the conveyance direction FD", "size in the medium width direction CD", and "stiffness" of the recording medium P included in the conveyance conditions of the recording medium P. As described above, the "size in the conveyance direction FD" of the recording medium P is abbreviated as the "medium feed length". Also, the "size in the medium width direction CD" of the recording medium P is abbreviated as the "medium width".

[0075] As the medium feed length increases, the influence of the movement of the belt 6 pulled by the recording medium P swinging by the resist roller 27 is reduced. Therefore, the control unit 11 performs a correction in which the correction speed B is reduced according to the medium feed length. Specifically, the correction is performed with a value obtained by multiplying the medium feed length by a predetermined coefficient k2 (0 < k2). In the following formula, "L" represents the medium feed length, and "B1" represents the corrected correction speed. B1 = B - k2·L = k1·A - k2·L

[0076] As the medium width increases, the influence of the movement of the belt 6 pulled by the recording medium P swinging by the resist roller 27 increases. Therefore, the control unit 11 performs a correction in which the correction speed B is increased according to the medium width. Specifically, the correction is performed with a value obtained by multiplying the medium width by a predetermined coefficient k3 (0 < k3). In the following formula, "W" represents the medium width, and "B2" represents the corrected correction speed. B2 = B1 + k3·W = k1·A - k2·L + k3·W

[0077] As the stiffness increases, the influence of the movement of the belt 6 pulled by the recording medium P swinging by the resist roller 27 increases. Therefore, the control unit 11 makes a correction such that the correction speed B increases according to the medium width. Specifically, the correction is made with a value obtained by multiplying the stiffness by a predetermined coefficient k4 (0 < k4). In the following equation, "G" represents the stiffness and "B3" represents the corrected correction speed. B3 = B2 + k4·G = k1·A - k2·L + k3·W + k4·G

[0078] Note that, although an example in which the correction of each parameter with respect to the correction speed B is performed by multiplying and adding / subtracting a predetermined coefficient to the numerical value of the parameter has been shown, it is not limited thereto. For example, a coefficient may be determined for each numerical value of each parameter, and the correction may be made by multiplying the correction speed B by the coefficient corresponding to the numerical value of each parameter. Also, it is preferable to make a correction for each parameter with respect to the correction speed B, but it is not necessarily required. Alternatively, the correction of each parameter with respect to the correction speed B may be made for any one or two of the medium feed length, medium width, and stiffness of the recording medium P.

[0079] Furthermore, it is preferable to consider the conveyance speed of the recording medium P for the correction speed B. In this regard, the correction speed B is obtained by multiplying the rocking speed A by the coefficient k1, and the rocking speed A is a value considering the conveyance speed of the recording medium P. Therefore, the correction speed B is a value considering the conveyance speed of the recording medium P.

[0080] Also, it is preferable to consider the rocking direction of the recording medium P and the offset direction of the belt 6 for the correction speed B. In order to reduce the influence of the rocking direction of the recording medium P, the correction speed B is, in principle, corrected in the opposite direction to the rocking direction. Furthermore, with respect to the correction speed B, the correction values by each parameter are also increased or decreased in consideration of each direction. Therefore, the corrected values B1, B2, B3 of the correction speed B are values considering the rocking direction of the recording medium P.

[0081] Furthermore, when considering the direction of belt 6's misalignment, the direction in which belt 6 is corrected and the direction in which the correction speed B acts on belt 6 should be considered to coincide. As mentioned above, the direction in which the correction speed B acts on belt 6 is opposite to the direction in which the resist roller 27 oscillates. If the direction in which the belt 6 is straightened coincides with the direction in which the correction speed B acts on the belt 6, an adjustment to increase the correction speed B may be made. Conversely, if the direction in which the belt 6 is straightened and the direction in which the correction speed B acts on the belt 6 are opposite, an adjustment to decrease the correction speed B may be made.

[0082] Furthermore, the control unit 11 also performs a correction process for the straightening movement speed of the fixing belt 53 using the second straightening control, in the same way as in the case of the intermediate transfer belt 6. However, the fixing belt 53 is located further away from the resist roller 27 than the intermediate transfer belt 6, with the intermediate transfer belt 6 interposed between them. Therefore, the effect of resist oscillation on the fixing belt 53 is smaller than that on the intermediate transfer belt 6. Accordingly, taking this into consideration, the coefficients k1 to k4 used to determine the correction speed B and correction values ​​B1, B2, B3 are smaller than those of the intermediate transfer belt 6.

[0083] [Operation control during transport of recording media] The operation control performed by the CPU of the control unit 11 on each part of the image forming apparatus 100 during the transport of the recording medium P will be explained based on the flowchart in Figure 10.

[0084] The control unit 11 detects the physical properties of the recording medium P when the media transport unit 20 starts transporting the recording medium P and it passes through the media sensor 33 (S1). The thickness, moisture content, basis weight, and stiffness of the recording medium P detected by the media sensor 33 are stored in the storage unit 12 as transport conditions for the recording medium P.

[0085] When the leading edge of the recording medium P is detected by the position detection sensor SE2 (S3), the control unit 11 reads image formation setting information from the storage unit 12 (S5). As a result, the control unit 11 acquires the transport conditions of the recording medium P, such as the transport speed of the recording medium P, the size of the direction FD and direction CD of the recording medium P, the basis weight, and the stiffness.

[0086] Furthermore, the control unit 11 starts transporting the recording medium P by the register roller 27 by driving the register motor 271 (S7). Then, the control unit 11 abuts the leading edge of the recording medium P against the nip portion of the register roller 27 to form a loop, separating it from the intermediate transport rollers 23-25. Furthermore, the control unit 11 starts detecting the bias of the recording medium P in the media width direction CD using the position detection sensor SE2. Once bias of the recording medium P is detected, the control unit 11 determines the oscillation speed and direction of the recording medium P by the media oscillation mechanism 34. This drives the media oscillation mechanism 34 to oscillate the recording medium P along the media width direction CD (S9).

[0087] Next, the control unit 11 determines whether or not a condition occurs where the register roller 27 of the recording medium P and the intermediate transfer belt 6 are straddling each other (S11). If a straddle condition occurs, the control unit 11 performs a second straightening control and its correction process on the intermediate transfer belt 6 (S13). Specifically, the control unit 11 determines the corrective movement speed and direction of the intermediate transfer belt 6 based on the output of the first deviation detection device 63. Furthermore, the control unit 11 calculates a correction speed B based on the oscillation speed of the recording medium P, the medium feed length of the recording medium P, the medium width, and the stiffness. Then, the control unit 11 drives the steering motor 621 with the corrective movement speed corrected by the correction speed B. This makes it possible to correct the position of the intermediate transfer belt 6 in the medium width direction CD while suppressing the influence of being pulled by the recording medium P. Then, the control unit 11 proceeds to step S17.

[0088] On the other hand, if no overlapping condition occurs, the control unit 11 executes a second straightening control on the intermediate transfer belt 6 and does not perform any correction processing (S15). Specifically, the control unit 11 determines the corrective movement speed and direction of the intermediate transfer belt 6 based on the output of the first misalignment detection device 63. Then, the control unit 11 drives the steering motor 621 at this corrective movement speed. Then, the control unit 11 proceeds to step S17.

[0089] In step S17, the control unit 11 determines whether the end of the recording medium P has passed the register roller 27 (S17). If the process has not been completed, the control unit 11 returns to step S9 and executes the processes in steps S9 to S17 again.

[0090] In the above operation description, the processing of steps S9 to S17 was explained for the intermediate transfer belt 6. However, the control unit 11 also performs the processing of steps S9 to S17 for the fixing belt 53 in parallel with this.

[0091] Then, when it is determined in step S17 that the recording medium P has passed the register roller 27, the control unit 11 stops the register roller 27 (S19). Furthermore, the control unit 11 determines whether or not the end of the recording medium P has passed the nip portion of the intermediate transfer belt 6 (S21). If it has not passed, the control unit 11 returns to step S15. The control unit 11 executes the processes of steps S15 to S19 again and performs the second straightening control of the intermediate transfer belt 6. Furthermore, the control unit 11 also performs the processing in steps S15 to S19 on the fixing belt 53 until the recording medium P passes over its nip portion. Then, after passing through the nip sections of the intermediate transfer belt 6 and the fixing belt 53, the control unit 11 discharges the recording medium P into the discharge tray 29 (S23). Then, the transport operation ends.

[0092] In the above example of operation control during transport, a correction process for the second correction control was given while the recording medium P was straddling the other side, but this is not the only example. For example, the occurrence of a straddle state of the recording medium P may be known in advance from the length of the recording medium P. In this case, the correction process of the second straightening control may be started before the recording medium P reaches belts 6, 53. In this case, the correction process of the second straightening control can be started at any timing between the recording medium P reaching belt 6 or 53 from register roller 27. Furthermore, it is preferable that the execution of the early start of the correction process of the second correction control described above be configurable, for example, from the operation unit 14. In this case, it is preferable that the setting of whether or not to execute the early start is stored in the storage unit 12 as a transport condition for the recording medium P. In this case, it is preferable to include setting information that specifies the early start timing of the correction process of the second correction control.

[0093] [Technical Effects of Embodiments of the Invention] In the image forming apparatus 100 described above, the control unit 11 performs a correction to the second correction control when the first correction control is performed when an overlap occurs on the recording medium P. Therefore, the image forming apparatus 100 reduces the effect of resist fluctuations on the belt 6 or 53. Furthermore, it is possible to maintain the belt 6 or 53 in a more appropriate position, perform image forming well, and improve image quality.

[0094] The control unit 11 corrects the second straightening control based on the oscillation speed of the recording medium P by the media oscillation mechanism 34. Therefore, the straightening movement speed of the belts 6 and 53 is corrected according to the oscillation speed of the recording medium P, and the effect of resist oscillation can be reduced more effectively.

[0095] The control unit 11 makes corrections to the second straightening control based on the transport conditions of the recording medium P. Various transport conditions increase or decrease the influence of the oscillation speed of the recording medium P on the straightening movement speed of the belts 6 and 53. Therefore, the control unit 11 can suppress the influence of the transport conditions of the recording medium P and more effectively reduce the influence of resist oscillation on the belts 6 and 53.

[0096] The control unit 11 obtains the transport conditions for the recording medium P from the image formation setting information. The image formation setting information is stored in the storage unit 12. Therefore, by referring to the storage unit 12, the control unit 11 can more effectively reduce the effect of resist oscillation on the belts 6 and 53. Furthermore, there is no need to obtain or pre-enter the transport conditions for the recording medium P from an external source.

[0097] The control unit 11 obtains the transport conditions for the recording medium P from the media sensor 33, which detects the recording medium P being transported. Therefore, there is no need to obtain the transport conditions for the recording medium P from an external source or input them in advance.

[0098] The control unit 11 determines the amount of correction for the second straightening control based on the oscillation speed of the recording medium P by the media oscillation mechanism 34 and the size of the recording medium P. This allows for more appropriate correction to be made to the straightening movement speed of the belts 6 and 53, which fluctuates as a result, and the effect of resist oscillation can be reduced more effectively.

[0099] The control unit 11 determines the amount of correction for the second straightening control based on the oscillation speed of the recording medium P by the media oscillation mechanism 34 and the stiffness of the recording medium P. This allows for more appropriate correction to be made to the straightening movement speed of the belts 6 and 53, which fluctuates as a result, and the effect of resist oscillation can be reduced more effectively.

[0100] The control unit 11 determines the amount of correction for the second straightening control based on the oscillation speed of the recording medium P by the media oscillation mechanism 34 and the transport speed of the recording medium P. This allows for more appropriate correction to be made to the straightening movement speed of the belts 6 and 53, which fluctuates as a result, and the effect of resist oscillation can be reduced more effectively.

[0101] The control unit 11 determines the amount of correction for the second straightening control by considering the direction of oscillation of the recording medium P by the medium oscillation mechanism 34 and the direction of deviation of the belts 6 and 53. Therefore, the straightening movement speed of the belts 6 and 53 can be corrected without excess or deficiency for any combination of these directions. In other words, the image forming apparatus 100 can more effectively reduce the effects of resist oscillation.

[0102] The control unit 11 can also start correcting the second straightening control before the recording medium P reaches belts 6,53 if it is predicted that the recording medium P will be straddling the belts. Therefore, if the effect of resist fluctuations on belt 6 or 53 is significant, it becomes possible to address this early and effectively reduce its impact.

[0103] The control unit 11 can also perform corrections to the second straightening control while the recording medium P is passing through belts 6 and 53. Therefore, it becomes possible to effectively reduce the impact of resist fluctuations on belt 6 or 53 that occur in real time by performing corrections.

[0104] Since the belt subject to correction of the corrective movement speed is the intermediate transfer belt 6, it is possible to optimize the corrective movement speed of a good intermediate transfer belt 6. This allows for proper transfer during image formation and improves image quality.

[0105] Since the belt subject to correction of the corrective movement speed is the fixing belt 53, it is possible to optimize the corrective movement speed of a good fixing belt 53. This allows for proper fixing during image formation and improves image quality.

[0106] Since the fixing belt 53 is supported by two axes, it is susceptible to the effects of resist oscillation. In response to this, the control unit 11 performs a correction to the second straightening control, making it possible to quickly reduce the effects of resist oscillation.

[0107] Since the intermediate transfer belt 6 is supported by three or more axes, the effects of resist oscillation can be reduced, but it is difficult to move the belt 6. In response to this, the control unit 11 performs a correction to the second straightening control, making it possible to return the belt 6, which has moved due to resist oscillation, to the correct position.

[0108] Since belts 6 and 53 use polyimide as their base material, they have high mechanical strength and excellent heat resistance. Therefore, good transfer to the intermediate transfer belt 6 and good fixing by the fixing belt 53 are possible, which improves image quality.

[0109] [others] The embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments described above. For example, in the embodiments, a component integrally formed from a single member may be replaced with a component divided into multiple members that are connected or fixed to each other. Also, a component formed by connecting multiple members may be replaced with a component integrally formed from a single member. Furthermore, details shown in the embodiments can be modified as appropriate without departing from the spirit of the invention.

[0110] Furthermore, while the above description discloses examples using non-volatile memory, hard disks, etc., as computer-readable media for the program according to the present invention, the invention is not limited to these examples. Portable recording media such as CD-ROMs can also be used as other computer-readable media. In addition, carrier waves can be used as a medium for providing the program data according to the present invention via a communication line.

[0111] Furthermore, the detailed configuration and operation of the image forming apparatus can also be modified as appropriate without departing from the spirit of the present invention. [Explanation of Symbols]

[0112] 6. Intermediate transfer belt 61 Steering Roller 62. First steering mechanism (belt correction mechanism) 621 Steering motor 63. First deviation detection device (belt detection unit) 633 First Sensor 634 Second Sensor 7Y,7M,7C,7K Primary transfer roller 9. Secondary transfer roller 10 Image forming unit 11 Control Unit (Control Device) 12 Storage section 20 Media transport section 27 Resist Roller 271 Resist Motor 33. Media Sensor (Media Detection Unit) 34. Media Oscillating Mechanism 35 Image reading unit 50 Fixing device 51 First heating roller 51, 52 Second heating roller 53 Fixing belt 54 Pressure rollers 55. Second steering mechanism (belt correction mechanism) 551 Steering motor 56 Second deviation detection device (belt detection unit) 563-565 First-Third Sensors 100 Image forming apparatus CD media width direction FD media transport direction P recording medium SE1 Resistance Sensor SE2 Position detection sensor (media detection unit) SE3 Environmental Sensor Tp target position

Claims

1. An image forming apparatus that forms an image on a recording medium by multiple processes, A media oscillating mechanism that oscillates the recording medium along the media width direction intersecting the transport direction of the recording medium, A media detection unit that detects the position of the edge of the recording medium in the media width direction, A belt correction mechanism for correcting the position of a belt in the media width direction for performing one of the processes of image formation on the recording medium, A belt detection unit that detects the position of the end of the belt in the media width direction, The control device includes a first correction control that causes the media oscillation mechanism to correct the position of the end of the recording medium based on the detection of the media detection unit, and a second correction control that causes the belt correction mechanism to correct the position of the end of the belt based on the detection of the belt detection unit. The control device is an image forming apparatus that performs corrections to the second straightening control when the first straightening control is performed with the recording medium spanning both the medium oscillation mechanism and the belt.

2. The image forming apparatus according to claim 1, wherein the control device performs a correction to the second correction control based on the oscillation speed of the recording medium by the medium oscillation mechanism.

3. The image forming apparatus according to claim 2, wherein the control device performs a correction to the second correction control based on the transport conditions of the recording medium.

4. The image forming apparatus according to claim 3, wherein the transport conditions for the recording medium are obtained from the image forming setting information.

5. The image forming apparatus according to claim 3, wherein the transport conditions for the recording medium are obtained from a media detection unit that performs detection on the transported recording medium.

6. The image forming apparatus according to claim 3, wherein the control device determines the amount of correction for the second correction control based on the oscillation speed of the recording medium by the media oscillation mechanism and the size of the recording medium included in the transport conditions for the recording medium.

7. The image forming apparatus according to claim 3, wherein the control device determines the correction amount for the second correction control based on the oscillation speed of the recording medium by the media oscillation mechanism and the stiffness of the recording medium included in the transport conditions for the recording medium.

8. The image forming apparatus according to claim 3, wherein the control device determines a correction amount for the second correction control based on the oscillation speed of the recording medium by the media oscillation mechanism and the transport speed of the recording medium included in the transport conditions for the recording medium.

9. The image forming apparatus according to claim 3, wherein the control device determines the correction amount for the second straightening control by considering the direction of oscillation of the recording medium by the medium oscillation mechanism and the direction of deviation of the belt.

10. The image forming apparatus according to claim 1, wherein the control device is expected to perform the first straightening control on the recording medium as it spans both the medium oscillation mechanism and the belt, and the control device starts correcting the second straightening control before the recording medium reaches the belt.

11. The image forming apparatus according to claim 1, wherein the control device performs a correction to the second straightening control while the recording medium is passing through the belt.

12. The image forming apparatus according to claim 1, wherein the belt is a transfer belt for performing the transfer process.

13. The image forming apparatus according to claim 1, wherein the belt is a fixing belt that performs the fixing process.

14. The image forming apparatus according to claim 1, wherein the belt is supported by two axes.

15. The image forming apparatus according to claim 1, wherein the belt is supported by three or more axes.

16. The image forming apparatus according to claim 1, wherein the belt has a base material of polyimide.

17. A computer in an image forming apparatus comprising: a media oscillating mechanism that oscillates the recording medium along the media width direction intersecting the transport direction of the recording medium; a media detection unit that detects the position of the end of the recording medium in the media width direction; a belt correction mechanism that corrects the position of a belt in the media width direction that performs one of the processes of forming an image on the recording medium; and a belt detection unit that detects the position of the end of the belt in the media width direction, A function to perform first correction control, which causes the media oscillation mechanism to correct the position of the edge of the recording medium based on the detection of the media detection unit, A function to perform a second correction control that causes the belt correction mechanism to correct the position of the end of the belt based on the detection of the belt detection unit, A program that provides a function to correct the second straightening control when the first straightening control is performed on the recording medium across both the medium oscillation mechanism and the belt.

Images