Image forming apparatus

Abstract

To increase opportunities to perform steering control.SOLUTION: An image forming apparatus includes: an endless belt stretched around a plurality of rollers; a tiltable steering roller around which the belt is stretched; a measurement section that outputs a measured value corresponding to a position of the belt in a width direction intersecting a rotation direction; a processing section that estimates the position of the belt on the basis of the measured value output from the measurement section and performs steering control to correct the position of the belt by tilting the steering roller such that the belt is positioned within a predetermined region in the width direction; and a non-volatile storage section that stores the position of the belt estimated by the processing section. The processing section estimates the current position of the belt on the basis of the position of the belt stored in the storage section, in a case where the measured value output from the measurement section exceeds a threshold indicating the outside of the predetermined region when the power supply is turned on.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus having an endless belt that rotates while being stretched over a plurality of rollers. [Background technology]

[0002] In recent years, image forming devices have been known that include an endless belt that rotates while being tensioned around multiple rollers, and examples of such endless belts include an intermediate transfer belt, a fixing belt, etc. In such image forming devices, a technology is known (Patent Document 1) that performs steering control to correct the movement of the belt in the width direction by measuring the position of the belt in the width direction, which intersects with the direction of rotation, using a sensor, and tilting the tension roller in the axial direction according to the measured position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-96276 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the power is turned off after the belt has moved widthwise outside the predetermined range where the measurement value output from the sensor changes, the measurement value output from the sensor will not change even if the power is turned on. Therefore, it is not possible to determine which side in the widthwise direction the belt has moved from the measurement value output from the sensor, and it is not possible to perform steering control (retry control) to return the belt to the predetermined range where the measurement value output from the sensor changes. [Means for solving the problem]

[0005] A typical configuration of the present invention includes an endless belt stretched over a plurality of rollers, a tiltable steering roller stretching the belt, a measurement unit that outputs a measurement value according to the position of the belt in a width direction that intersects with the rotation direction of the belt, a processing unit that estimates the position of the belt based on the measurement value output from the measurement unit and performs steering control to tilt the steering roller to correct the position of the belt so that the belt is positioned within a predetermined region in the width direction, and a non-volatile memory unit that stores the position of the belt estimated by the processing unit, wherein when the power is turned on, if the measurement value output from the measurement unit exceeds a threshold value indicating outside the predetermined region, the processing unit estimates the current position of the belt based on the position of the belt stored in the memory unit. [Effects of the Invention]

[0006] According to the present invention, when the measurement value output from the measurement unit exceeds the threshold value, the current belt position can be estimated based on the belt position stored in the memory unit, thereby increasing the opportunities to perform steering control to correct the belt position in the width direction. [Brief explanation of the drawings]

[0007] [Figure 1] Image forming system configuration diagram [Figure 2] Image forming system block diagram [Figure 3] Cross-sectional view of an image forming system [Figure 4] Belt unit configuration diagram [Figure 5] Diagram showing the configuration of the belt position sensor [Figure 6] Diagram showing the relationship between sensor output and belt position [Figure 7] Flowchart of the process for determining belt position based on sensor measurements [Figure 8] Flowchart of belt position estimation process [Figure 9] Steering control flowchart [Figure 10] (a)(b)(c) Diagram of the display showing a yori-kiri error DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions, and are not intended to limit the scope of the present invention to those alone.

[0009] <Hardware configuration of image forming system> 1 is an overall diagram of the hardware configuration of an image forming system. The image forming system includes an image forming apparatus 101 and a print controller 102. The image forming apparatus 101 and the print controller 102 are communicably connected via an internal LAN 105 and a video cable 106.

[0010] When the print controller 102 receives a print instruction from a print job registration PC (not shown), it performs data analysis and rasterization processing, issues a print instruction to the image forming device 101 via the internal LAN 105, and transmits image data via the video cable 106.

[0011] The image forming device 101 can be connected to devices with multiple different functions, and is configured to be able to connect devices that not only form images, but also have a paper feeding function for holding large stacks of paper for mass printing, a stacking function for stacking large amounts of printed materials, and post-processing functions such as binding.

[0012] The image forming apparatus 101 shown in FIG. 1 exemplifies a configuration in which a paper feeder 109, a printer 107, and a large-capacity stacker 108, each having a plurality of different functions, are connected.

[0013] The paper feeder 109 holds stacks of paper in two trays and supplies paper in response to instructions from the printing device 107. As will be described later, of the two trays, the upper tray is the first tray and the lower tray is the second tray.

[0014] The printing device 107 forms an image on paper conveyed from a paper feeder 109. The printing device 107 performs printing by feeding paper from a tray specified in a print instruction received from the print controller 102. In this embodiment, an image is formed using an electrophotographic method, but other printing methods such as an inkjet method or an offset printing method may also be used.

[0015] The large-capacity stacker 108 is a stacker capable of stacking and loading paper sheets, and receives paper sheets transported from the printing device 107 and loads the paper sheets onto a built-in loading tray.

[0016] The image forming system described in FIG. 1 is configured such that the print controller 102 is connected separately from the image forming device 101, but the present invention is not limited to such a configuration, and for example, the print controller 102 may be incorporated into the image forming device 101.

[0017] <Block structure of image formation system> 2 is a block diagram showing the configuration of an image forming system. 2 is a block diagram showing the system configuration of an image forming apparatus 101 and a print controller 102. The image forming apparatus 101 further includes a printing apparatus 107, a paper feeder 109, and a large-capacity stacker 108.

[0018] The control block 210 (hereinafter referred to as the print controller control block 210) represents the system configuration of the print controller 102. The print controller control block 210 is composed of a CPU 211, memory 212, HDD 213, keyboard 214, display 215, LAN I / F 216, LAN I / F 217, and video I / F 218. Each element of the print controller control block 210 is connected via a system bus 219.

[0019] The CPU 211 comprehensively executes processes such as receiving print instructions from a print job registration PC (not shown), RIP processing, and sending print data to the image forming apparatus 101 based on programs and data stored in the HDD 213. The memory 212 stores programs and data required for the CPU 211 to perform various processes and operates as a work area. The HDD 213 stores programs and data required for operations such as print processing. The keyboard 214 is a device for inputting operation instructions for the print controller 102. The display 215 displays information such as the application executed by the print controller 102 using video signals of still images and moving images.

[0020] The LAN I / F 216 is connected to an external LAN (not shown), and communication such as receiving print instructions from a print job registration PC (not shown) is carried out via this.

[0021] The LAN I / F 217 is connected to the internal LAN 105, and communication such as sending a print instruction to the image forming apparatus 101 is performed via this.

[0022] The video I / F 218 is connected to the video cable 106, and communication such as transmission of image data to the image forming apparatus 101 is performed via this.

[0023] The control block 220 (hereinafter referred to as the printing device control block 220) represents the control block of the printing device 107. The printing device control block 220 is composed of a CPU 221, memory 222, HDD 223, operation unit 224, display 225, LAN I / F 226, communication I / F 227, and video I / F 228. The printing device 107 further comprises an image forming unit 229 and a fixing unit 230. Each of the components is connected via a system bus 232.

[0024] The CPU 221 controls image processing and the printing device 107 based on programs and the like stored in the HDD 223. The memory 222 stores data such as programs and image data required for the CPU 221 to perform various processes, and operates as a work area. The HDD 223 is a storage device that stores device control programs and non-volatile data used for control. The operation unit 224 accepts various setting inputs and operation instructions from the user. The display 225 is a display unit. The display 225 displays setting information for the image forming device 101, the processing status of print instructions, and information about errors that have occurred in the image forming device 101.

[0025] The CPU 221 is a processing unit that estimates the position of the intermediate transfer belt 318 in the width direction, which intersects with the rotation direction, based on measurements output from a belt position sensor (measurement unit) 401 (described later). The CPU 221 performs steering control to tilt the steering roller 402 to correct the position of the intermediate transfer belt 318 so that the intermediate transfer belt 318 is positioned within a predetermined area in the width direction. The HDD 223 is a non-volatile storage unit that stores the position of the intermediate transfer belt 318 estimated by the CPU 221. The non-volatile storage unit is a storage unit that can retain stored information even when power is not supplied.

[0026] The LAN I / F 226 is connected to the internal LAN 105, and communication such as receiving print instructions from the print controller 102 is performed via this. The communication I / F 227 is connected to communication cables 233 and 234, and communication such as control information for transferring paper between the paper feeder 109 and the large-capacity stacker 108 is performed via this.

[0027] The video I / F 228 is connected to the video cable 106, and communication such as receiving image data sent from the print controller 102 is carried out via this.

[0028] The image forming unit 229 forms a toner image on a photosensitive drum by electrophotography and transfers the formed toner image onto paper transported from the paper feeder 109. The fixing unit 230 is a device that melts and fixes the toner image on the paper to the paper using heat and pressure.

[0029] Control block 270 (hereinafter referred to as paper feeder control block 270) represents the control block of paper feeder 109. It is composed of a communication I / F 271, a CPU 272, memory 273, ROM 274, a first tray control unit 275, and a second tray control unit 276, and each of these components is connected via a system bus 277.

[0030] The communication I / F 271 is connected to the printing device 107 via a communication cable 234, and communicates control information necessary for paper transfer. The CPU 272 controls paper supply based on a control program stored in the ROM 274.

[0031] The memory 273 temporarily stores programs and data that are executed or referenced by the CPU 272, and operates as a work area.

[0032] The ROM 274 is a non-volatile storage device that stores control programs and data for the device, and is configured as a flash memory in this embodiment.

[0033] Based on instructions from the CPU 272, the first tray control unit 275 separates the paper from the first tray and controls the transport.

[0034] Based on instructions from the CPU 272, the second tray control unit 276 separates the paper from the second tray and controls the transport.

[0035] The control block 240 (hereinafter referred to as the large-capacity stacker control block 240) represents the control block of the large-capacity stacker 108. The large-capacity stacker control block 240 is composed of a communication I / F 241, a CPU 242, a memory 243, a ROM 244, and a paper discharge control unit 245, and each of these components is connected via a system bus 246.

[0036] The communication I / F 241 is connected to the printing device 107 via a communication cable 233, and communicates control information necessary for paper transfer. The CPU 242 controls the loading of paper in accordance with a control program stored in the ROM 244.

[0037] The memory 243 temporarily stores programs and data that are executed or referenced by the CPU 242, and operates as a work area.

[0038] The ROM 244 is a non-volatile storage device that stores control programs and data for the device, and is configured as a flash memory in this embodiment.

[0039] The paper discharge control unit 245 controls the transport of the transported paper to the stack tray 331 or the paper discharge tray 335 based on instructions from the CPU 242 .

[0040] In the above description, the print controller 102 and the image forming apparatus 101 are connected via an internal LAN 105 and a video cable 106, but any configuration is possible as long as the data required for printing can be sent and received, and for example, a connection configuration using only a video cable is also acceptable.

[0041] Furthermore, although the printing device control block 220 and the paper feeder control block 270 are connected by a dedicated communication cable 234, they may have a different configuration, for example, the paper feeder control block 270 may be connected to the internal LAN 105.

[0042] Furthermore, the printer control block 220 and the large-capacity stacker control block 240 are connected by a dedicated communication cable 233, but a different configuration may also be used, for example, the large-capacity stacker control block 240 may be connected to the internal LAN 105.

[0043] Furthermore, the memory 212, memory 222, memory 243, and memory 273 each use a storage device such as an SRAM or DRAM that stores data and programs, but are not limited to these.

[0044] Furthermore, the HDD 213, HDD 223, ROM 244, and ROM 274 are not limited to the configurations of this embodiment, and other nonvolatile storage units may be used.

[0045] <Basic image formation operations of the image forming device> 3 is a cross-sectional view of the image forming apparatus 101. The basic image forming operation of the image forming apparatus will be described with reference to FIG.

[0046] The paper feeder 109 is composed of a first tray 301, a second tray 304, a transport path 307, and a transport path 308. The first tray 301 and the second tray 304 can hold 2,500 sheets of various types of paper. The paper feeder 109 separates the topmost sheet of paper stored in a tray specified by the printing device 107 and transports it to the transport path 307. The first tray 301 is composed of a lifter 302 and a sheet separator 303. The second tray 304 is composed of a lifter 305 and a sheet separator 306. When operating in a configuration in which multiple paper feeders 109 are connected, the transport path 308 receives paper from a paper feeder that is further upstream.

[0047] The image forming apparatus 101 has an automatic tray switching function that automatically switches the tray used for paper feeding during continuous printing, which has the effect of reducing downtime. In the automatic tray switching function, the process of determining the tray to switch to is performed by the printing apparatus 107.

[0048] The printing device 107 forms an image to be printed on a sheet. A transport path 313 transports paper from transport path 307 of the paper feeder 109. Development stations 314-317 form toner images using yellow (Y), magenta (M), cyan (C), and black (K) color toners, respectively, to form electrophotographic color images. The toner images formed here are primarily transferred onto an intermediate transfer belt 318 that rotates clockwise, and then secondarily transferred to a sheet transported from sheet transport path 313 at secondary transfer position 319. A display 225 displays information about the printing status and settings of the image forming device 101. An operation unit 224 accepts an operation to switch the paper feed mode of the paper feeder 109. A fixing unit 321 fixes the toner image to the sheet. The fixing unit 321 includes a pressure roller and a heating roller, and fixes the toner image on the sheet as it passes between these rollers. After passing through the fixing unit 321, the sheet is transported via sheet transport path 322 to transport path 325. Depending on the type of sheet, the sheet that has passed through the fixing unit 321 may require further fusing and pressing for fixing. In this case, after passing through the fixing unit 321, the sheet is transported to the second fixing unit 323 using the upper sheet transport path. After being transported to the second fixing unit 323, the sheet is subjected to additional fusing and pressing, and then transported to transport path 325 via sheet transport path 324. If the image formation mode is double-sided, the sheet is transported to sheet inversion path 326. After being inverted by sheet inversion path 326, the sheet is transported to double-sided transport path 327, where the image on the second side is transferred at secondary transfer position 319.

[0049] In this embodiment, the image forming apparatus 101 can form images on A4 size plain paper sheets with a productivity of 100 ppm (page per minute).

[0050] The large-capacity stacker 108 is capable of stacking a large number of sheets. The large-capacity stacker 108 has a stack tray 331 and a transport tray 332 as trays for stacking sheets. Sheets that have passed through the printing device 107 are transported to the large-capacity stacker 108 via a sheet transport path 333. The sheets are stacked on the stack tray 331 via a sheet transport path 334 from the sheet transport path 333. The large-capacity stacker 108 also has a paper output tray 335. The paper output tray 335 is used to output sheets on which sample printing has been performed by the printing device 107, adjustment sheets, etc. When a sheet is to be output to the paper output tray 335, the sheet is transported from the sheet transport path 333 to the paper output tray 335 via a sheet transport path 336. When a sheet is to be transported to a post-processing device (not shown) downstream of the large-capacity stacker 108, the sheet is transported to the post-processing device via a sheet transport path 337. The inverting unit 338 is used to invert the sheet. This reversing unit 338 is used when stacking sheets on the stack tray 331. When stacking on the stack tray 331, the sheets are reversed once by the reversing unit 338 so that the orientation of the input sheets is the same as the orientation of the sheets at the time of output. When conveying the sheets to the discharge tray 335 or to a subsequent post-processing device, the sheets are discharged as is without being flipped when stacked, and therefore the reversing operation by the reversing unit 338 is not performed.

[0051] <Belt unit configuration diagram> 4 is a diagram showing the configuration of a belt unit 400 having an intermediate transfer belt 318. The configuration of the belt unit 400 will be described with reference to FIG.

[0052] The belt unit 400 is composed of an intermediate transfer belt 318, which is an endless belt, a plurality of rollers that stretch the intermediate transfer belt 318, and a belt position sensor 401, which is a measurement unit. The plurality of rollers include a steering roller 402 and a drive roller 403.

[0053] The steering roller 402 is supported so as to be tiltable and stretch the intermediate transfer belt 318. Here, the steering roller 402 is configured so as to be able to oscillate (rotate, tilt) in a direction 402F or a direction 402R opposite to the direction 403F, with a fulcrum 402S as the origin. The steering roller 402 is connected to a motor (not shown) via a cam (not shown) or the like, and is steered in the direction 402F or the direction 402R based on the operation of the motor.

[0054] The configuration for tilting the steering roller 402 is not limited to the above-described configuration, and other configurations may be used.

[0055] The drive roller 403 stretches the intermediate transfer belt 318 and rotates the intermediate transfer belt 318. The drive roller 403 is connected to a motor (not shown) via a gear (not shown), and rotates the intermediate transfer belt 318 based on the operation of the motor.

[0056] By operating the steering roller 402 in direction 402F or direction 402R while the intermediate transfer belt 318 is being rotated, it is possible to correct the position of the intermediate transfer belt 318 in the width direction, which intersects with the rotation direction. Specifically, by operating the steering roller 402 in direction 402F around fulcrum 402S while the intermediate transfer belt 318 is being rotated, it is possible to move the position of the intermediate transfer belt 318 to the front side in the width direction. Conversely, by operating the steering roller 402 in direction 402R around fulcrum 402S, it is possible to move the position of the intermediate transfer belt 318 to the rear side in the width direction.

[0057] The steering roller 402 is operated based on the belt position measured by the belt position sensor 401. The motor (not shown) that operates the steering roller 402 and the belt position sensor 401 are connected to the image forming unit 229 shown in FIG. 2 and are configured to be accessible from the CPU 221.

[0058] Although the belt unit 400 includes the belt position sensor 401 in this example, the present invention is not limited to this. The belt position sensor 401 may be provided separately from the belt unit 400.

[0059] <Diagram showing the configuration and output of the belt position sensor> 5 is a diagram showing the configuration and output of the belt position sensor 401. The belt position sensor 401 will be described with reference to FIG.

[0060] The belt position sensor 401 is a measurement unit that outputs a measurement value according to the position in the width direction that intersects with the rotation direction of the intermediate transfer belt 318. Here, the belt position sensor 401 is composed of a light receiving element 501, a light receiving element 502, a light emitting element 503, and a following member 504.

[0061] Light receiving element 501 and light receiving element 502 are photodiodes or phototransistors, and output a voltage corresponding to the intensity of received light. Light receiving element 501 outputs a voltage corresponding to the intensity of received light as output A1. Light receiving element 502 outputs a voltage corresponding to the intensity of received light as output A2.

[0062] The light emitting element 503 is an LED, and is disposed at a position facing the light receiving elements 501 and 502 so that the emitted light is incident on the light receiving elements 501 and 502 .

[0063] The follower member 504 includes a light-shielding member 504F. The follower member 504 is configured to abut against one end 318R of the intermediate transfer belt 318 in the width direction by the biasing force of a spring (not shown) or the like, and to be able to move parallel to the front-rear direction along the axis 504A. Here, the front-rear direction along the axis 504A corresponds to the axial direction of the rotation center of the drive roller 403, and also corresponds to the width direction perpendicular to the rotation direction of the intermediate transfer belt 318. Therefore, the follower member 504 can move in the front-rear direction along the axis 504A, following the movement of the intermediate transfer belt 318 in the width direction.

[0064] Furthermore, the light blocking member 504F is disposed between the two light receiving elements 501 and 502 and the light emitting element 503, which are arranged side by side in the width direction, and can block light emitted from the light emitting element 503 toward the light receiving elements 501 and 502. Therefore, the light blocking member 504F follows the position of the intermediate transfer belt 318 in the front-rear direction, and an amount of light corresponding to the position of the light blocking member 504F is incident on the light receiving elements 501 and 502, thereby obtaining outputs A1 and A2 corresponding to the position in the width direction of the intermediate transfer belt 318.

[0065] Although the belt position sensor 401 has been illustrated here as having two light receiving elements 501 and 502, a light emitting element 503, and a following member 504, the present invention is not limited to this. The belt position sensor 401 may have any other configuration as long as it is a measurement unit that outputs a measurement value corresponding to the position of the intermediate transfer belt 318 in the width direction.

[0066] <Relationship between belt position sensor output and belt position> FIG. 6 is a diagram showing the relationship between the "sensor output" of the belt position sensor, the "output of the belt position determination process based on the sensor measurement," and the "hardware area."

[0067] "Sensor output" indicates the measurement value output from the belt position sensor 401 in the front-to-back direction (width direction) of the intermediate transfer belt 318. Output A1 indicates the measurement value output from the light receiving element 501, and output A2 indicates the measurement value output from the light receiving element 502.

[0068] The "areas on the hardware" are classifications of "Rh1," "Rh2," "Rh3," and "Rh4" based on the actual positions of the intermediate transfer belt 318. In the width direction of the intermediate transfer belt 318, "Rh1" indicates the front-side shifted area, "Rh2" indicates the front-side normal area, "Rh3" indicates the rear-side normal area, and "Rh4" indicates the rear-side shifted area.

[0069] When tilting the steering roller 402 to correct the position of the intermediate transfer belt 318, steering control is performed so that the intermediate transfer belt 318 is positioned within a predetermined region, and the aforementioned normal regions "Rh2" and "Rh3" correspond to the predetermined regions at that time. Of these, the normal region "Rs2" is a region on one side of the predetermined region divided into multiple regions in the width direction. The normal region "Rs3" is a region on the other side of the predetermined region divided into multiple regions in the width direction.

[0070] In addition, the steering control described below is performed so that the intermediate transfer belt 318 is positioned in the normal area of ​​"Rh2" or "Rh3", and if it deviates into "Rh1" or "Rh4", it is treated as an error and the image forming device is stopped.

[0071] The "output of the belt position determination process based on sensor measurement" is the position of the intermediate transfer belt 318 determined from the outputs A1 and A2 output from the belt position sensor 401. The positions of the intermediate transfer belt 318 determined from the outputs A1 and A2 are classified into "Rs1," "Rs2," and "Rs3."

[0072] Here, the point where the output A1 of the light receiving element 501 and the output A2 of the light receiving element 502 become the same is designated as c1. At the position shown in FIG. 5 where the light blocking member 504F blocks the light receiving elements 501 and 502, the output A1 of the light receiving element 501 and the output A2 of the light receiving element 502 become the same. On the other hand, at the front position where the light blocking member 504F does not block the light receiving elements 501 and 502, the point where the output A1 of the light receiving element 501 and the output A2 of the light receiving element 502 both reach the threshold Vth is designated as c2. Furthermore, at the rear position where the light blocking member 504F does not block the light receiving elements 501 and 502, the point where the output A1 of the light receiving element 501 and the output A2 of the light receiving element 502 both reach the threshold Vth is designated as c3.

[0073] "Rs2" indicates the region (normal region on the front side) where the light blocking member 504F moves from the position shown in FIG. 5 toward the front side and the outputs A1 and A2 change from being equal to the threshold value Vth. "Rs2" is the region from point c1 to point c2 shown in FIG. 6, where the outputs A1 and A2 change as shown in FIG. 6. The sensor output "Rs2" indicates that the actual position of the intermediate transfer belt 318 is "Rh2."

[0074] "Rs3" indicates the region (hereinafter referred to as the normal region on the rear side) where the light blocking member 504F moves from the position shown in FIG. 5 toward the rear side, and where the outputs A1 and A2 change from being the same to both reaching the threshold value Vth. "Rs3" is the region from point c1 to point c3 shown in FIG. 6, where the outputs A1 and A2 change as shown in FIG. 6. The sensor output "Rs3" indicates that the actual position of the intermediate transfer belt 318 is "Rh3."

[0075] "Rs1" indicates the region where the light-blocking member 504F moves to a rearward or forward position where it does not block light from the light receiving elements 501 and 502, and both the output A1 and the output A2 exceed the threshold Vth (hereinafter referred to as the "close-in region"). "Rs1" is the frontward region beyond point c2 shown in FIG. 6, or the rearward region beyond point c3, and both the output A1 and the output A2 become the same output and exceed the threshold Vth. The sensor output "Rs1" indicates that the actual position of the intermediate transfer belt 318 is "Rh1 or Rh4." In other words, the sensor output "Rs1" cannot determine whether the actual position of the intermediate transfer belt 318 is in the frontward-side close-in region beyond point c2 shown in FIG. 6, or in the rearward-side close-in region beyond point c3. This is because the output of the belt position sensor 401 is the same for "Rh1" and "Rh4."

[0076] <Flowchart of Belt Position Determination Process Based on Sensor Measurement> 7 is a flowchart of a process for determining the current belt position based on the outputs A1 and A2 of the belt position sensor 401. The process in FIG. 7 is a subroutine called from the "belt position estimation process" in step S803 in FIG.

[0077] In step S701, the CPU 221 acquires the outputs A1 and A2 of the belt position sensor 401. The outputs A1 and A2 are measurement values ​​output from the belt position sensor 401, the output A1 is the output of the light receiving element 501, and the output A2 is the output of the light receiving element 502.

[0078] In step S702, it is determined whether the conditions "A1>Vth" are satisfied, that is, the output A1 is an output that exceeds the threshold Vth, and "A2>Vth" are satisfied, that is, the output A2 is an output that exceeds the threshold Vth.

[0079] In step S702, if the acquired outputs A1 and A2 satisfy the condition "A1>Vth and A2>Vth" (Yes in S702), proceed to step S703. In step S703, it is determined that the current belt position is "Rs1". Then, the process ends.

[0080] On the other hand, in step S702, if the acquired outputs A1 and A2 do not satisfy the condition "A1>Vth and A2>Vth" (No in S702), the process proceeds to step S704.

[0081] In step S704, it is determined whether the condition "A1>A2" is satisfied, that is, the output A1 is greater than the output A2.

[0082] In step S704, if the output A1 and the output A2 satisfy the condition "A1>A2" (Yes in S704), the process proceeds to step S705. In step S705, it is determined that the current belt position is "Rs2." Then, the process ends.

[0083] On the other hand, if the output A1 and the output A2 do not satisfy the condition "A1>A2" in step S704 (No in S704), the process proceeds to step S706. In step S705, it is determined that the current belt position is "Rs3". Then, the process ends.

[0084] In this way, this process determines the current belt position according to the output of the belt position sensor 401. The possible results based on the measurement values ​​(outputs A1 and A2) output from the belt position sensor 401 are "Rs1," "Rs2," and "Rs3," and there is no ability to distinguish between front and rear yori-kiri.

[0085] <Belt position estimation process flowchart> Fig. 8 is a flowchart of a process for estimating the belt position by adding the "previous belt position estimation (non-volatile)" stored in the non-volatile storage unit, HDD 223, to the result of the "belt position determination process based on sensor measurement" in Fig. 7. The process in Fig. 8 is a subroutine called from step S903 "steering control" in Fig. 9.

[0086] This process uses the variable "previous belt position estimate (non-volatile)." This is stored in the HDD 223, which is a non-volatile area, and is not erased when the power is turned off and on. The possible values ​​for the variable "previous belt position estimate (non-volatile)" are "Rh1," "Rh2," "Rh3," "Rh4," or "Rh1 or Rh4."

[0087] In step S801, a branch is made depending on whether or not it is the first execution since startup. If it is the first execution (Yes in S801), the process proceeds to step S802, and if it is not the first execution (No in S802), the process proceeds to step S803.

[0088] In step S802, variables are initialized. "Undefined" is assigned to both "Previous belt position" and "Current belt position." Note that both of these variables can take the values ​​"Undefined," "Rs1," "Rs2," and "Rs3." Then, the process proceeds to step S803.

[0089] It should be noted that the values ​​of "previous belt position" and "current belt position" are stored in a volatile memory such as memory 222. For example, the value of "current belt position" is periodically updated. In this case, the updated value becomes the "current belt position," and the "current belt position" immediately before the update becomes the "previous belt position." Volatile memory is memory that cannot retain stored information unless power is supplied.

[0090] In step S803, the "belt position determination process based on sensor measurement" described with reference to FIG. 7 is executed.

[0091] In step S804, the result of the determination obtained in step S803 is substituted into the variable "current belt position."

[0092] In step S805, branching is performed according to the variable "current belt position." If the "current belt position" is "Rs1" (Rs1 in S805), the process proceeds to step S806.

[0093] On the other hand, if the "current belt position" is not "Rs1" but "Rs2" in step S805 (Rs2 in S805), the process proceeds to step S815, where it is estimated that the current belt position is "Rh2", and the process then proceeds to step S817.

[0094] If the "current belt position" is not "Rs1" or "Rs2" but "Rs3" in step S805 (Rs3 in S805), the process proceeds to step S816, where it is estimated that the current belt position is "Rh3", and then the process proceeds to step S817.

[0095] In step S806, branching is performed according to the variable "previous belt position." If the "previous belt position" is "undefined" (undefined in S806), the process proceeds to step S810.

[0096] On the other hand, if the "previous belt position" is not "undefined" but "Rs2" in step S806 (Rs2 in S806), the process proceeds to step S807, where the current belt position is estimated to be "Rh1." That is, the CPU 221 estimates that the current belt position is "Rh1," which is on one side (the front side) in the width direction outside the predetermined area (normal area). The process then proceeds to step S817.

[0097] Also, if the "previous belt position" is not "indefinite" or "Rs2" but "Rs3" in step S806 (Rs3 in S806), the process proceeds to step S808, where the current belt position is estimated to be "Rh4." That is, the CPU 221 estimates that the current belt position is "Rh4," which is on the other side (rear side) in the width direction outside the predetermined area (normal area). The process then proceeds to step S817.

[0098] Also, if in step S806 the "previous belt position" is not "undefined," "Rs2," or "Rs3," but "Rs1" (Rs1 in S806), the process proceeds to step S809, where the current belt position is estimated to be "Rh1 or Rh4." The process then proceeds to step S817. Here, the estimation result of "Rh1 or Rh4" means that the belt is positioned in the shift area, but it is not possible to distinguish whether it is on the front side or the back side.

[0099] In step S810, a branch is made according to the variable "previous belt position estimation (non-volatile)." That is, if the "previous belt position" is "undefined," a branch is made according to the "previous belt position estimation (non-volatile)" stored in the HDD 223, which is a non-volatile area.

[0100] As mentioned above, the variable "previous belt position estimation (non-volatile)" can take any of the values ​​"Rh1," "Rh2," "Rh3," "Rh4," and "Rh1 or Rh4." If "previous belt position estimation (non-volatile)" is "Rh1 or Rh4," the current belt position is estimated to be "Rh1 or Rh4" as is, although this is not shown in the figures after step S810.

[0101] If the "previous belt position estimation (non-volatile)" is "Rh1" in step S810 (Rh1 in S810), the process proceeds to step S811, where the current belt position is estimated to be "Rh1." That is, the CPU 221 estimates that the current belt position is "Rh1," which is on one side (the front side) in the width direction outside the predetermined area (normal area). The process then proceeds to step S817.

[0102] If the "previous belt position estimate (non-volatile)" is not "Rh1" but "Rh4" (Rh4 in S810) in step S810, the process proceeds to step S812, where the current belt position is estimated to be "Rh4." That is, the CPU 221 estimates that the current belt position is "Rh4," which is on the other side (rear side) in the width direction outside the predetermined area (normal area). The process then proceeds to step S817.

[0103] If the "previous belt position estimate (non-volatile)" is not "Rh1" or "Rh4" but "Rh2" (Rh2 in S810), proceed to step S813, where the current belt position is estimated to be "Rh1 or Rh4," and then proceed to step S817.

[0104] If the "previous belt position estimate (non-volatile)" is not "Rh1," "Rh4," or "Rh2," but "Rh3" (Rh3 in S810), proceed to step S814, where the current belt position is estimated to be "Rh1 or Rh4," and then proceed to step S817.

[0105] In step S817, the value of "current belt position" is substituted for the variable "previous belt position." Then, the process proceeds to step S818.

[0106] In step S818, the estimation result of the belt position is recorded in the nonvolatile area of ​​the HDD 223. That is, the CPU 221 stores the value of the "current belt position" which is the estimation result of the belt position as a variable "previous belt position estimation (nonvolatile)" in the nonvolatile area of ​​the HDD 223. Then, the process ends.

[0107] In this way, the belt position estimation result (variable "previous belt position estimation (non-volatile)") is recorded in the non-volatile area of ​​HDD223, and when the power is turned on and the belt position is at the close-in position, the close-in position can be identified by making an estimation based on this variable.

[0108] Therefore, in the "steering control" described in FIG. 9, steering control (retry control) can be performed even for a lean-to-center steering when the power is turned on, and opportunities for performing steering control can be increased.

[0109] <Steering control flowchart> 9 shows a process for steering the intermediate transfer belt 318 based on the result of the "belt position estimation process." This process includes a steering control (hereinafter also referred to as "retry control") that returns from a short-term bias.

[0110] Furthermore, this process also stops the driving of the intermediate transfer belt 318 and displays an error message on the display 225 if it is estimated that the belt position is in the biased region.

[0111] This process is executed periodically while the intermediate transfer belt 318 is being driven, for example, every time the belt travels a predetermined distance (50 cm).

[0112] In step S901, a branch is made depending on whether or not the execution is the first time since startup. If it is the first time (Yes in S901), the process proceeds to step S902, and if it is not the first time (No in S902), the process proceeds to step S903.

[0113] In step S902, variables are initialized. 0 is assigned to the variable "number of retries." Note that the variable "number of retries" can take an integer value equal to or greater than 0. Then, the process proceeds to step S903.

[0114] In step S903, the "belt position estimation process" described with reference to FIG. 8 is performed.

[0115] In step S904, a branch is made based on the result of the "belt position estimation process" in step S903.

[0116] In step S904, if the current belt position is estimated to be "Rh2" or "Rh3" (Yes in S904), the process proceeds to step S905.

[0117] On the other hand, in step S904, if the current belt position is not estimated to be "Rh2" or "Rh3" (No in S904), the process proceeds to step S906, where further conditional branching is performed. Here, the "current belt position" can take on values ​​of "Rh1," "Rh4," and "Rh1 or Rh4." Of these, "Rh1" and "Rh4" indicate a situation where the "current belt position" is in the shift-toward area and the near side or the far side has been distinguished, while "Rh1 or Rh4" indicates a situation where the "current belt position" is in the shift-toward area but the near side or the far side has not been distinguished.

[0118] In step S906, if the current belt position is not estimated to be "Rh1 or Rh4" (No in S906), the process proceeds to step S907. In other words, if the current belt position is not estimated to be "Rh1 or Rh4", the current belt position is estimated to be either "Rh1" or "Rh4". If the current belt position is estimated to be either "Rh1" or "Rh4", the "current belt position" is in the shifted position area and the front or rear side is identified, so there is room to operate the steering roller 402 to return the belt to the normal area.

[0119] In step S907, a branch is performed according to a condition. If the variable "number of retries" is smaller than the allowable number N, the process proceeds to step S908. The allowable number N is 1, for example.

[0120] In step S908, the variable "number of retries" is incremented by 1. Then, the process proceeds to step S905.

[0121] In step S905, the steering roller 402 is operated to steer the intermediate transfer belt 318. More specifically, if the intermediate transfer belt 318 is estimated to be on the front side ("Rh1" or "Rh2"), the steering roller 402 is operated in direction 402R to correct the widthwise position of the intermediate transfer belt 318. Conversely, if the intermediate transfer belt 318 is estimated to be on the rear side ("Rh3" or "Rh4"), the steering roller 402 is operated in direction 402F to correct the widthwise position of the intermediate transfer belt 318. Then, this process ends.

[0122] On the other hand, if the current belt position is estimated to be "Rh1 or Rh4" in step S906 (Yes in S906), the process proceeds to step S909. This is because the current belt position is in the shift-over area, but the front or back side cannot be distinguished, and it is impossible to return the belt to the normal area by operating the steering roller 402.

[0123] Also, in step S907, if the variable "retry count" is greater than the allowable count N (Yes in S907), the process proceeds to step S909.

[0124] In step S909, an error has been detected, and the belt is stopped. Specifically, the drive of the intermediate transfer belt 318 is stopped, and a message indicating that a bias error has occurred is displayed on the display 225, which is a display unit. Then, this process ends.

[0125] The error detection state means that the current belt position is in the shift area "Rh1 or Rh4" but the front side or the back side cannot be distinguished. In this state, the CPU 221 stops driving the intermediate transfer belt 318 and displays an error message (see FIG. 10(c)) on the display 225, which is a display unit.

[0126] Furthermore, even if the current belt position is in the pull-out area but the front side or the back side cannot be distinguished and the belt position is not stored in the HDD 223, which is a storage unit, the CPU 221 displays an error message on the display 225.

[0127] <Display including error message> 10(a), 10(b), and 10(c) are diagrams showing error messages displayed on the display 225. When step S909 in FIG. 9 is executed, a display 1001 including an error message 1002 is displayed on the display 225.

[0128] 10A shows a display 1001 including an error message 1002 indicating that the intermediate transfer belt 318 has shifted to the front side in the width direction. This display appears when the estimated belt position in FIG. 9 is "Rh1" and the number of retries is greater than the allowable number N.

[0129] 10B shows a display 1001 including an error message 1002 indicating that the intermediate transfer belt 318 has shifted all the way to the rear in the width direction. This display appears when the estimated belt position in FIG. 9 is "Rh4" and the number of retries is greater than the allowable number N.

[0130] 10C shows a display 1001 that indicates that the intermediate transfer belt 318 has shifted to the width direction, but includes an error message 1002 that indicates that the front side or the back side in the width direction cannot be determined. This display appears when the estimated belt position in FIG. 9 is "Rh1 or Rh4."

[0131] According to this embodiment, when the outputs A1 and A2, which are measurement values ​​output from the belt position sensor 401, exceed the threshold value Vth, it is possible to estimate to which side in the width direction the belt has moved, based on the previous belt position stored in the HDD 223. This increases the opportunities to perform steering control to correct the belt position in the width direction.

[0132] In the above-described embodiment, the intermediate transfer belt 318 is used as an example of an endless belt member, and the present invention is applied to an image forming apparatus that transfers toner images carried on the intermediate transfer belt to paper (recording material) all at once. However, the present invention is not limited to this. For example, the endless belt member may be a conveyor belt that conveys paper and is stretched over multiple rollers. The same effect can be achieved by applying the present invention to an image forming apparatus equipped with such a conveyor belt. Alternatively, the endless belt member may be a fixing belt that fixes an image on paper and is stretched over multiple rollers. The same effect can be achieved by applying the present invention to an image forming apparatus equipped with a fixing device having such a fixing belt.

[0133] In the above-described embodiment, the electrophotographic method is used as the recording method, but the present invention is not limited to this, and other recording methods such as an inkjet method may also be used. [Explanation of symbols]

[0134] 101 ...Image forming device 220 ... Printer control block 221 ...CPU (processing unit) 222...Memory 223...HDD (storage unit) 224...Operation unit 225 ... Display (display unit) 318...Intermediate transfer belt (belt) 400...Belt unit 401 ... Belt position sensor (measurement unit) 402 ... Steering roller 402S... Fulcrum 403 ... Drive roller 501, 502 ... Light receiving element 503 ...light-emitting element 504 ...Following member 504A…Axis line 504F...Light blocking material 1001…display 1002 ...Error message

Claims

1. an endless belt stretched over a plurality of rollers; a tiltable steering roller around which the belt is stretched; a measuring unit that outputs a measurement value according to a position in a width direction that intersects with a rotation direction of the belt; a processing unit that estimates a position of the belt based on the measurement value output from the measurement unit, and performs steering control to tilt the steering roller to correct the position of the belt so that the belt is positioned within a predetermined area in the width direction; a non-volatile storage unit that stores the position of the belt estimated by the processing unit; Equipped with The image forming apparatus is characterized in that, when the power is turned on, if the measurement value output from the measurement unit exceeds a threshold value indicating outside the specified area, the processing unit estimates the current position of the belt based on the position of the belt stored in the memory unit.

2. When the belt position stored in the memory unit is a position on one side in the width direction outside the predetermined area, the processing unit estimates that the current belt position is a position on one side in the width direction outside the predetermined area based on the measurement value exceeding the threshold value, When the position of the belt stored in the memory unit is a position on the other side in the width direction outside the predetermined area, the processing unit estimates that the current position of the belt is a position on the other side in the width direction outside the predetermined area based on the measurement value exceeding the threshold value, 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. the processing unit performs the steering control when it estimates that the current belt position is outside the predetermined region and on one side in the width direction; the processing unit performs the steering control when it estimates that the current belt position is outside the predetermined region and on the other side in the width direction.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. A display unit is provided, 2. The image forming apparatus according to claim 1, wherein when the power is turned on, if the measurement value output from the measurement unit exceeds the threshold value and the position of the belt is not stored in the memory unit, the processing unit displays an error message on the display unit.

5. 2. The image forming apparatus according to claim 1, wherein, when the measurement value output from the measurement unit exceeds a threshold value indicating the outside of the predetermined area, the processing unit estimates the current position of the belt based on the position of the belt before it moved outside the predetermined area.

6. If the position of the belt before moving outside the predetermined area is in one of the areas on one side in the width direction obtained by dividing the predetermined area in the width direction, the processing unit estimates, based on the measurement value exceeding the threshold, that the current position of the belt is a position on one side in the width direction outside the predetermined area, 6. The image forming apparatus according to claim 5, wherein, when the position of the belt before moving outside the specified area is in the other side of the widthwise area obtained by dividing the specified area into multiple sections in the widthwise direction, the processing unit estimates that the current position of the belt is the other side of the widthwise position outside the specified area based on the measurement value that exceeds the threshold value.

7. 2. The image forming apparatus according to claim 1, wherein the processing unit stores the estimated belt position in the storage unit.

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