Belt conveying apparatus and image forming apparatus
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- CANON KK
- Filing Date
- 2025-01-22
- Publication Date
- 2026-08-03
Smart Images
Figure 2026125385000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a belt conveyance device used in an image forming apparatus such as a copying machine, a printer device, a facsimile device, or a multi-functional device having a plurality of these functions using an electrophotographic method or an inkjet recording method, and an image forming apparatus equipped with the belt conveyance device.
Background Art
[0002] Conventionally, in an image forming apparatus using an electrophotographic method or an inkjet recording method, a belt conveyance device including an endless belt stretched over a plurality of tension rollers has been used. The belt is used as a conveyance body that carries and conveys a toner image or an ink image, or carries and conveys a recording material on which an image is formed.
[0003] Examples of the conveyance body that carries and conveys the toner image include an intermediate transfer belt that carries and conveys the toner image transferred from the photoreceptor to the recording material. Examples of the conveyance body that carries and conveys the recording material on which an image is formed include a conveyance belt that carries and conveys the recording material onto which the image has been transferred from the photoreceptor, and a fixing belt that sandwiches and conveys the recording material in a fixing device in order to fix the unfixed image onto the recording material.
[0004] Generally, there is a problem that "drift (snaking)" occurs in a belt that is stretched over a plurality of tension rollers and rotationally driven. Belt drift refers to a phenomenon in which when the belt is rotationally driven, the conveyance position of the belt in the width direction (direction substantially orthogonal to the conveyance direction) of the belt moves toward one end side. If the belt drifts too much, the belt end may contact other members, etc., and there is a risk that the belt or other contacted members may be damaged.
[0005] Therefore, belt drift control is performed to correct the belt drift by causing a sensor unit to detect the width direction position of the belt end and tilting one of the plurality of rollers that stretch the belt based on the output of this sensor unit.
[0006] Patent Document 1 describes a sensor unit for detecting the widthwise position of the belt end, which has a light-emitting unit and two light-receiving units. The sensor detects the belt's position based on the output signals of the two light-receiving units, which change according to the belt's position. While the belt is in the normal position, it performs PI control, which is a stable feedback control using the deviation between the target position and the current position. When the belt begins to move outside the normal position, it performs pull-in control, which corrects it with a constant control amount regardless of the deviation. Furthermore, when the belt has moved completely out of position, it is determined that the belt has reached its limit and the rotation of the belt is stopped. [Prior art documents] [Patent Documents]
[0007] [Patent Document 1] Japanese Patent Publication No. 2012-234063 [Overview of the project] [Problems that the invention aims to solve]
[0008] In this type of belt control, there is a risk that the belt may interfere with surrounding components during the process of detecting a belt slippage error and stopping the belt's rotation, potentially damaging the expensive belt or surrounding components. To avoid this, it is necessary to detect belt slippage errors as quickly as possible.
[0009] In conventional control methods, the voltage levels of the output signals from two light-receiving units were compared with predetermined thresholds to determine the switching between PI control and pull-in control, as well as belt shifting errors. In other words, the threshold for switching between PI control and pull-in control and the threshold for determining belt shifting errors were set to the same value. Therefore, in order to determine belt shifting errors more quickly, it was necessary to lower the threshold level for determining a shifting error. However, doing so also lowered the threshold level for switching the belt control method from PI control to pull-in control, resulting in a shorter period during which stable PI control could be performed.
[0010] The present invention has been made in view of the above circumstances, and aims to provide a belt conveying device that can quickly determine belt misalignment errors while ensuring a stable control period in belt misalignment control, thereby reducing the risk of damage to expensive belts and surrounding parts due to interference between the belt and surrounding components, and an image forming apparatus equipped with the belt conveying device. [Means for solving the problem]
[0011] To achieve the above objective, the present invention provides an endless belt stretched between a plurality of support members, a steering roller for stretching the belt, a position detection means for detecting the position of the end of the running belt in the width direction, and a correction means for correcting the meandering of the belt in the width direction by changing the steering angle of the steering roller based on the detection result of the position detection means, the correction means for executing a first control and a second control different from the first control, and a determination means for determining a close-out error when the detection result of the position detection means exceeds a first threshold, wherein the correction means executes the first control when the detection result of the position detection means is within a range of a second threshold different from the first threshold from a reference position, and executes the second control when it exceeds the second threshold. [Effects of the Invention]
[0012] According to the present invention, it is possible to provide a belt conveying device that can quickly determine belt cutting errors while ensuring a stable control period in belt grabbing control, thereby reducing the risk of damage to expensive belts and surrounding parts due to interference between the belt and surrounding components, and an image forming apparatus equipped with the belt conveying device. [Brief explanation of the drawing]
[0013] [Figure 1] This is a schematic front cross-sectional view of a full-color image forming apparatus according to the first embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of a fixing device according to one embodiment of the present invention. [Figure 3]It is a perspective view showing the overall configuration of the sensor unit according to the first embodiment of the present invention. [Figure 4] It is a cross-sectional view of the sensor of the sensor unit according to the first embodiment of the present invention as viewed from below in FIG. 3. [Figure 5] It is an enlarged view of the light-receiving portion of the sensor according to the first embodiment of the present invention. [Figure 6] It is a graph showing the relationship between the position of the end portion in the belt width direction of the fixing belt and the voltage output of the light-receiving portion according to the first embodiment of the present invention. [Figure 7] It is a truth table according to the first embodiment of the present invention. [Figure 8] It is a flowchart showing the processing performed by the CPU in the control unit of FIG. 1 according to the first embodiment of the present invention. [Figure 9] It is a graph showing the relationship between the position of the end portion in the belt width direction of the fixing belt and the voltage output of the light-receiving portion according to the second embodiment of the present invention. [Figure 10] It is a truth table according to the second embodiment of the present invention. [Figure 11] It is a flowchart showing the processing performed by the CPU in the control unit of FIG. 1 according to the second embodiment of the present invention. [Figure 12] It is an overall configuration diagram of a fixing device according to the third embodiment of the present invention.
Mode for Carrying Out the Invention
[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the components described in the following embodiments are merely examples, and various conditions such as the configuration, function, dimensions, materials, shapes, relative arrangements, etc. of the device to which the present invention is applied can be appropriately modified or changed without departing from the gist of the present invention, and the present invention is not limited to the following embodiments.
[0015] 〔First Embodiment〕 FIG. 1 is a schematic front cross-sectional view of a full-color image forming apparatus according to the first embodiment of the present invention.
[0016] In FIG. 1, the image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd as image forming means provided corresponding to four colors of yellow, magenta, cyan, and black. In the present embodiment, the image forming units Pa, Pb, Pc, and Pd are arranged in a tandem type along the rotation direction of an intermediate transfer belt 204 described later. The image forming apparatus 1 forms a toner image (image) on a recording material according to an image signal from an image reading unit (document reading apparatus) 2 connected to the image forming apparatus main body 3 or a host device such as a personal computer communicably connected to the image forming apparatus main body 3. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.
[0017] The image forming apparatus 1 includes an image reading unit 2 and an image forming apparatus main body 3. The image reading unit 2 reads a document placed on a document table glass 21, and the light irradiated from a light source 22 is reflected by the document and imaged on a CCD sensor 24 via an optical system member 23 such as a lens. Such an optical system unit scans in the direction of the arrow to convert the document into an electrical signal data series for each line. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus main body 3, and image processing is performed by a control unit 30 in accordance with each image forming unit described later. Further, the control unit 30 also receives an external input from an external host device such as a print server as an image signal.
[0018] The image forming apparatus main body 3 includes a plurality of image forming units Pa, Pb, Pc, and Pd, and in each image forming unit, image formation is performed based on the above-described image signal. That is, the image signal is converted into a laser beam PWM (pulse width modulation control) by the control unit 30. A polygon scanner �1 as an exposure device scans a laser beam according to the image signal. Then, the photosensitive drums 200a to 200d as image carriers of the respective image forming units Pa to Pd are irradiated with the laser beam.
[0019] Pa is the yellow (Y) image forming unit, Pb is the magenta (M) image forming unit, Pc is the cyan (C) image forming unit, and Pd is the black (Bk) image forming unit, each forming an image of the corresponding color. Since the configurations of the image forming units Pa to Pd are almost identical, the details of the Y image forming unit Pa will be explained below, and the explanations of the other image forming units will be omitted by assigning the same number and the designation b to d to the corresponding configuration.
[0020] In the image forming section Pa, a toner image is formed on the surface of the photosensitive drum 200a based on the image signal, as described below.
[0021] The charging roller 201a, acting as a primary charger, charges the surface of the photosensitive drum 200a to a predetermined potential, preparing it for electrostatic latent image formation. An electrostatic latent image is formed on the surface of the photosensitive drum 200a, which has been charged to the predetermined potential, by a laser beam from the polygon scanner 31. The developer 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. The primary transfer roller 203a discharges from the back of the intermediate transfer belt 204, applying a primary transfer bias with the opposite polarity to the toner, and transfers the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After the transfer, the surface of the photosensitive drum 200a is cleaned by the cleaner 207a.
[0022] Furthermore, the toner image on the intermediate transfer belt 204 is transported to the next image forming section, and the toner images of each color formed in the respective image forming sections are transferred sequentially in the order of Y, M, C, and Bk, forming a four-color image on its surface. The toner image that has passed through the Bk image forming section Pd, which is the furthest downstream in the rotational direction of the intermediate transfer belt 204, is transported to a secondary transfer section consisting of a pair of secondary transfer rollers 205 and 206. In the secondary transfer section, a secondary transfer electric field with the opposite polarity to the toner image on the intermediate transfer belt 204 is applied, thereby secondary transferring the toner image on the intermediate transfer belt 204 to the recording material.
[0023] The recording material is housed in a cassette 9. The recording material fed from the cassette 9 is transported to a registration unit 208, which consists of a pair of registration rollers, and waits there. Subsequently, the timing of the registration unit 208 is controlled to align the position of the toner image on the intermediate transfer belt 204 with the position of the recording material, and the recording material is transported to the secondary transfer unit.
[0024] The recording material onto which the toner image has been transferred in the secondary transfer unit is transported to the fuser unit 8, where it is heated and pressurized to fix the toner image onto the recording material. The recording material that has passed through the fuser unit 8 is discharged to the discharge tray 7. When image formation is performed on both sides of the recording material, once the transfer and fixing of the toner image to the first side (front) of the recording material is complete, the front and back sides of the recording material are reversed via the inversion transport unit 10, and the toner image is transferred and fixed to the second side (back) of the recording material, which is then loaded onto the discharge tray 7.
[0025] The control unit 30 controls the entire image forming apparatus 1 as described above. Furthermore, the control unit 30 can perform various settings based on inputs from the operation unit 4 and display unit 5 of the image forming apparatus 1. The operation unit 4 and display unit 5 are provided in the image forming apparatus 1 and include, for example, a touch panel or buttons that can be operated by touch.
[0026] Such a control unit 30 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU controls each part while reading programs corresponding to control procedures stored in ROM. The RAM stores working data and input data, and the CPU performs control by referring to the data stored in RAM based on the aforementioned programs, etc.
[0027] Next, the fixing device 8 to which the belt conveying device of this embodiment is applied will be described using Figure 2. Figure 2 is a configuration diagram of the fixing device 8 of Figure 1.
[0028] In Figure 2, the fixing device 8 of this embodiment can be broadly divided into a belt unit 300 and a pressure roller 330.
[0029] The pressure roller 330, as a rotating body, has its rotation axis supported by the frame 385 of the fixing device 8, and is rotated via gears by a drive source (not shown). The pressure roller 330 is designed to press against the outer surface of the fixing belt 310 of the belt unit 300, thereby applying pressure to the fixing belt 310. In other words, the pressure roller 330 is movable between a pressurized position, where it contacts and applies pressure to the fixing belt 310, and a non-pressurized position, where it is separated from the fixing belt 310 and does not apply pressure. To enable the pressure roller 330 to move between the pressurized and non-pressurized positions, it is supported by a pressure lever 333, which is pivotally supported by the rotation axis 332 and oscillated by a pressure motor (not shown).
[0030] Furthermore, in this embodiment, a halogen heater 331 is placed inside the pressure roller 330, and the temperature of the pressure roller 330 can be adjusted using this halogen heater 331.
[0031] As the pressure roller 330, for example, one may have an elastic layer made of silicone rubber, fluororubber, or fluororesin on the outer circumference of a metal rotating shaft (core), or one may have a release layer made of fluororesin such as PTFE, PFA, or FEP on the outer circumference of the elastic layer. In this embodiment, a pressure roller 330 is used that has an elastic layer made of silicone rubber with a thickness of "300 μm" and a release layer made of PFA with a thickness of "30 μm".
[0032] The belt unit 300, as a belt conveying device, includes a fixed belt 310 which is an endless (cylindrical) belt, a heating roller 340, a steering roller 350, a pressing member 380, a sensor unit 390, and a steering mechanism 400. In this embodiment, the fixed belt 310 is stretched by a plurality of support members, which are the heating roller 340 as a first roller, the steering roller 350 as a second roller, and the pressing member 380.
[0033] As the fixing belt 310, a resin belt made of resin, for example, which has an elastic layer with high thermal conductivity and low heat capacity, or a composite layer structure belt with a metal belt such as stainless steel (SUS) as the base layer and an elastic layer, a release layer, etc. on its outer circumference may be used.
[0034] In this embodiment, a fixing belt 310 was used, having a base layer made of SUS, an elastic layer made of silicone rubber with a thickness of approximately 250 μm, and a release layer made of PFA tubing with a thickness of 30 μm. The release layer is preferably a sheet or coating layer with high release properties, and for example, fluororesins such as PFA or PTFE can be used. Alternatively, a heat-resistant sheet-like material such as polyester, polyethylene terephthalate, or polyimideamide may be used as the base layer, with a conductive layer laminated on top of it, and a surface release layer further laminated on top of that.
[0035] The heating roller 340 is, for example, a stainless steel pipe with a thickness of 1 mm, and a halogen heater 341 is disposed inside it. The heating roller 340 is rotationally driven by a drive motor M1 via gears, and the fixing belt 310 rotates in accordance with the rotation of the heating roller 340. As the heating roller 340 is heated by the halogen heater 341, the temperature of the fixing belt 310 rises via the heating roller 340. The temperature of the fixing belt 310 is adjusted to a predetermined target temperature, for example, depending on the type of recording material to be image-formed, based on the detection result of a temperature sensor 370 such as a thermistor sensor.
[0036] The steering roller 350 presses the anchoring belt 310 from the inside outwards in order to tension the anchoring belt 310 with a predetermined tension. To do this, the steering roller 350 is biased by the spring 351. In this way, the steering roller 350 has the function of applying a predetermined tension to the anchoring belt 310.
[0037] Furthermore, in this embodiment, the steering roller 350 controls the meandering of the fixing belt 310 in the belt width direction (the direction intersecting the conveying direction of the recording material) by turning the steering angle with its central part or one end in the direction of its rotation axis as the pivot point. In other words, the steering roller 350 also has the function of adjusting the alignment of the fixing belt 310.
[0038] To control the alignment of the anchoring belt 310, a sensor unit 390 is provided as a position detection means for detecting the displacement position in the belt width direction, which is the end position of the anchoring belt 310 in the belt width direction. In response to the output of this sensor unit 390, a steering motor in the steering mechanism 400, which is a correction means for correcting the meandering of the belt, changes the steering angle of the steering roller 350. Details of the structure and characteristics of this sensor unit 390 for detecting the end position of the belt will be described later.
[0039] The pressing member 380 has a stay 360 and a pressure pad 320. The stay 360 is a rigid metal member, such as stainless steel, that extends in the width direction of the fixing belt 310 and supports the pressure pad 320 so that it can be attached on the pressure roller 330 side. In this embodiment, the pressure pad 320 supported by the stay 360 contacts the inner circumferential surface of the fixing belt 310 and presses the fixing belt 310 from the inner circumferential surface side toward the fixing nip portion N. As a result, in cooperation with the heating roller 340, the fixing nip portion N for gripping, transporting, pressurizing, and heating the recording material on which the toner image has been formed is more reliably formed. Furthermore, by supporting the pressure pad 320 on the highly rigid stay 360, the deflection generated in the pressure pad 320 by the pressure from the pressure roller 330 is reduced, so that a uniform nip width can be obtained in the direction of the rotation axis of the pressure roller 330.
[0040] Furthermore, it is preferable to interpose a lubricant, such as a lubricating sheet containing silicone oil or silicone oil itself, between the pressure pad 320 and the fixing belt 310 so that the fixing belt 310 and the pressure pad 320 can slide smoothly against each other.
[0041] The pressure pad 320 is a resin component formed to extend in a width direction intersecting the rotational direction of the fixing belt 310 along the stay 360. Such a pressure pad 320 is formed from a material with good insulating and heat-resistant properties, such as phenolic resin, polyimide resin, polyamide resin, polyamide-imide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, or LCP resin.
[0042] In Figure 2, the fixing device 8 is shown as a combination of an endless belt-shaped fixing belt 310 and a roller-shaped pressure roller 330, but it is not limited to this. For example, an endless belt-shaped pressure belt may be used instead of the pressure roller 330. In this case, the endless belt-shaped fixing belt 310 may be combined with the pressure belt as is, or a roller-shaped fixing roller may be combined instead of the fixing belt 310. That is, the fixing device 8 may be configured to form the fixing nip portion N with a roller and a belt, or it may be configured to form the fixing nip portion N with a pair of belts.
[0043] Generally, when an endless belt, such as a fixing belt 310, is supported and rotated by multiple rollers, a meandering phenomenon can occur where the rotating endless belt moves in the belt width direction (a direction approximately perpendicular to the conveying direction of the endless belt). This can be caused by shape errors in the rollers supporting the endless belt or the endless belt itself, such as variations in the surface shape of the rollers or the precision of the endless belt in the width and circumferential directions, or by misalignment of the rollers' positions. In the case of the fixing device 8 shown in Figure 2, if the fixing belt 310 bends, it may come into contact with other parts and be damaged, such as by tearing. Therefore, in the case of the fixing device 8 shown in Figure 2, it is necessary to suppress the meandering phenomenon of the fixing belt 310.
[0044] One of the representative technologies for correcting the meandering of an endless belt, such as the anchor belt 310, is the steering method. In the steering method, one of the multiple rollers supporting the endless belt is used as a steering roller 350 and is oscillated to move the endless belt in the width direction, thereby suppressing (correcting) the meandering phenomenon of the endless belt. Compared to methods that physically restrain and correct the meandering of the endless belt using ribs or guides, this steering method applies less force to the endless belt, resulting in the advantage of high reliability and a long lifespan.
[0045] Next, the configuration of the sensor unit 390, which detects the end position of the fixing belt 310 in the belt width direction, will be explained using Figure 3. Figure 3 is a perspective view showing the overall configuration of the sensor unit 390.
[0046] In Figure 3, the sensor unit 390 of this embodiment includes a contact portion 391 that abuts against the end of the fixing belt 310 in the belt width direction, an arm member 392, a light-shielding portion 393, a support shaft portion 394, and a sensor 395. In this configuration, when the fixing belt 310 moves, the contact portion 391 and the light-shielding portion 393 are displaced around the support shaft portion 394.
[0047] An optical sensor is used as the detection means, sensor 395. Figure 4 is a cross-sectional view of sensor 395 as seen from below in Figure 3. As shown in Figure 4, the structure of sensor 395 includes a light-emitting part 396 and a light-receiving part 397. A light-shielding part 393 is positioned between the light-emitting part 396 and the light-receiving part 397.
[0048] Figure 5 is an enlarged view of the light-receiving unit 397. In Figure 5, the light-receiving unit 397 is divided into two light-receiving units PD1 and PD2, which serve as multiple detection light-receiving areas. When the light-shielding unit 393 rotates, the area where light from the opposing light-emitting unit 369 is blocked changes, causing a change in the amount of light received by the light-receiving units PD1 and PD2. Since the light-receiving units PD1 and PD2 each output a voltage corresponding to the amount of light received, the output voltage of the sensor 395 changes when the amount of light received changes.
[0049] Figure 6 is a graph showing the relationship between the voltage outputs VPD1 and VPD2 of the light receiving units PD1 and PD2, respectively, according to the end position in the belt width direction of the fixing belt 310. In Figure 6, the horizontal axis of the upper graph represents the end position in the belt width direction of the fixing belt 310, and the vertical axis represents the output voltages of VPD1 and VPD2, respectively. Output voltage VPD1 is shown as a solid line, and output voltage VPD2 is shown as a dashed line. The lower graph in Figure 6 shows the differential calculation VPD1-VPD2 of output voltages VPD1 and VPD2 on the vertical axis.
[0050] In Figure 6, the end position 0 in the belt width direction of the fixing belt 310 is the reference position. In Figure 5, the area shielded by the light shielding portion 393 is the same for the light receiving portions PD1 and PD2, and the output voltage is VPD1 = VPD2. The result of the differential calculation VPD1 - VPD2 is 0.
[0051] In the graph in Figure 6, the horizontal axis, which represents the end position of the fixing belt in the belt width direction, being in the + direction means that in Figure 3 the fixing belt is moved from the reference position in the + direction (forward), and in Figure 5 the light-shielding part 393 is displaced in the + direction. As the light-shielding part moves in the + direction, the amount of light received by the light-receiving part and PD2 decreases, and the amount of light received by the light-receiving part PD1 increases. Since the output voltages VPD1 and VPD2 change according to the amount of light received, the output voltage VPD1 of the light-receiving part PD1 increases, and the output voltage VPD2 of the light-receiving part PD2 decreases.
[0052] In the graph in Figure 6, the horizontal axis, which represents the end position of the fixing belt in the belt width direction, being in the - direction means that in Figure 3 the fixing belt is moved in the - direction (inward) from the reference position, and in Figure 5 the light-shielding part 393 is displaced in the - direction. When the light-shielding part 393 moves in the - direction, the amount of light received by the light-receiving part PD1 decreases, and the amount of light received by the light-receiving part PD2 increases. Since the output voltages VPD1 and VPD2 change according to the amount of light received, the output voltage VPD1 of the light-receiving part PD1 decreases, and the output voltage VPD2 of the light-receiving part PD2 increases.
[0053] In the graph of FIG. 6, the threshold value for determining the skew error as the first threshold value is Vth_err (<Vth_cnt), the threshold value for switching between PI control and pull-in control as the second threshold value is Vth_cnt, and the voltage at which the output voltages VPD1 and VPD2 of the light receiving parts PD1 and PD2 cross each other (the magnitudes of the output voltages VPD1 and VPD2 are interchanged) is Vcrss. Since we want to widely use the region where VPD1 - VPD2 changes linearly as PI control, it is desirable to set Vth_cnt to as large a value as possible. Therefore, only the case where Vth_cnt is greater than Vcrss is considered. Note that in this embodiment, the threshold value Vth_err for determining an error is greater than Vcrss.
[0054] Next, the switching of control and the skew error determination will be described with reference to the truth tables of FIGS. 6 and 7. In this embodiment, since Vth_cnt is used for switching the control method and Vth_err is used for independently determining the skew error, the unused parts in the truth table of FIG. 7 are indicated as "-".
[0055] In the region A where the fixing belt 310 is deeper than the position X1, Vth_err < VPD1 and Vth_err < VPD2, resulting in a belt skew error. A skew error is a state where the risk of the belt's skew becoming larger than a predetermined position and the end of the belt interfering with a member other than the belt increases, and the device enters a state of stopping due to the skew error before interference causes damage to the belt.
[0056] In the region B where the fixing belt 310 is in the range of X1 to X2, Vth_cnt < VPD1 and VPD2 < Vth_cnt, and pull-in control is performed. Pull-in control is a control method that corrects (modifies) with a constant control amount regardless of the deviation when the belt starts to skew. It has the characteristics that the skew correction force is strong but the control is rougher than PI control and it is more likely to meander.
[0057] In the region C where the fixing belt 310 is within the range of X2 to X3, VPD1 < Vth_cnt and VPD2 < Vth_cnt, and PI control is performed. PI control is a stable control method performed when the fixing belt 310 is near the normal position which is a predetermined section. It performs feedback control to correct the deviation of the belt by determining the gain using the proportional relationship from the deviation between the target position and the current position. In this region, the differential operation result VPD1 - VPD2 has a linearly increasing characteristic with a rising right shoulder. In the deviation control operation, the operation is performed using the result of VPD1 - VPD2.
[0058] In the region D where the fixing belt 310 is within the range of X3 to X4, VPD1 < Vth_cnt and Vth_cnt < VPD2, and pull-in control is performed.
[0059] In the region E where the fixing belt 310 is on the front side of the position X4, Vth_err < VPD1 and Vth_err < VPD2, resulting in a belt deviation error.
[0060] Next, the deviation control process will be described according to the flowchart of FIG. 8. FIG. 8 is a flowchart showing the process performed by the CPU in the control unit 30 of FIG. 1 when the conveyance of the fixing belt 310 is started.
[0061] When the conveyance of the fixing belt 310 is started, the output voltages VPD1 and VPD2 of the sensor unit 390 that detects the widthwise end positions of the fixing belt 310 are acquired by being converted from analog voltages to digital values via the AD port of the CPU at step S101.
[0062] Next, at step S102, as a determination means for determining the deviation error, the deviation error is determined at step S102. The output voltages VPD1 and VPD2 of the sensor unit 390 acquired at step S101 are compared with a threshold value Vth_err (hereinafter referred to as the deviation threshold) for determining whether the fixing belt 310 has deviated. If both of the output voltages VPD1 and VPD2 are not greater than Vth_err, it is not determined as a deviation error, and the process proceeds to the process of step S103.
[0063] In step S102, if both the output voltages VPD1 and VPD2 of the sensor unit 390 are greater than the belt shifting threshold Vth_err, a belt shifting error is determined, the drive motor M1 is stopped, the transport of the fixing belt 310 is stopped, and the belt shifting control process ends. If it is determined in step S102 that the belt has not shifted completely, the process proceeds to the control method switching process in step S103.
[0064] In step S103, the output voltages VPD1 and VPD2 of the sensor unit 390 acquired in step S101 are compared with a threshold Vth_cnt (hereafter, the control switching threshold) used to determine the switching between PI control and pull-in control. If both output voltages VPD1 and VPD2 are smaller than the control switching threshold Vth_cnt, the process proceeds to step S105. In step S105, the steering motor of the steering mechanism 400 is driven so that the tilt amount of the steering roller 350 is stable under PI control.
[0065] In step S103, if either the output voltage VPD1 or VPD2 of the sensor unit 390 is greater than the control switching threshold Vth_cnt, the process proceeds to step S106, where the steering motor of the steering mechanism 400 is driven to achieve the amount of tilt of the steering roller 350 due to the retraction control.
[0066] In step S107, it is checked whether belt conveying is continuing. If it is continuing, the process returns to step S101. If belt conveying has stopped, the steering control process ends.
[0067] As described above, control switching and collision error detection are performed independently, allowing for faster collision error detection.
[0068] [Second Embodiment] Next, a second embodiment of the present invention will be described.
[0069] In the first embodiment, the example was such that the threshold value for determining the belt-overlapping error was larger than Vcrss at which the output voltages VPD1 and VPD2 of the light-receiving unit cross each other. In this embodiment, the threshold value for determining the belt-overlapping error is smaller than Vcrss at which the output voltages VPD1 and VPD2 of the light-receiving unit cross each other (Vth_err < Vcrss < Vth_cnt).
[0070] Note that since the basic configuration and operation of this embodiment are the same as those of the first embodiment, those are incorporated herein and the description thereof is omitted.
[0071] FIG. 9 is a graph showing the relationship between the voltage outputs of VPD1 and VPD2 according to the position of the end portion in the belt width direction of the fixing belt in this embodiment. In FIG. 9, the horizontal axis of the upper graph is the position of the end portion in the belt width direction of the fixing belt 310, and the vertical axis is the output voltage of each of the outputs VPD1 and VPD2. The output voltage VPD1 is indicated by a solid line, and the output voltage VPD2 is indicated by a broken line. The lower graph in FIG. 9 is a graph representing the differential operation VPD1 - VPD2 of the output voltages VPD1 and VPD2 on the vertical axis.
[0072] Next, the control switching and error determination will be described using FIG. 9 and the truth table of FIG. 10. The italicized portions in the truth table of FIG. 10 are the portions used for determination. Also, the notation X in the table means that the condition is satisfied in either state. In this embodiment, since Vth_err < Vcrss, if an attempt is made to determine the belt-overlapping error only by the belt-overlapping threshold value Vth_err as in the first embodiment (Vth_err < VPD1 and Vth_err < VPD2), the regions X2’ to X3 ’ where PI control is desired also satisfy this condition, and it will be determined as a belt-overlapping error. Therefore, both the belt-overlapping threshold value Vth_err and the control switching threshold value Vth_cnt are used for the determination of the belt-overlapping error.
[0073] In the region A where the fixing belt 310 is deeper than the position X1, Vth_cnt < VPD1 and Vth_err < VPD2, resulting in a belt-overlapping error.
[0074] In the region B where the fixing belt 310 is in the range of X1 to X2, when Vth_cnt < VPD1 and VPD2 < Vth_err, pull-in control is performed.
[0075] In the region C where the fixing belt 310 is in the range of X2 to X3, when VPD1 < Vth_cnt and VPD2 < Vth_cnt, PI control is performed.
[0076] In the region D where the fixing belt 310 is in the range of X3 to X4, when VPD1 < Vth_err and Vth_cnt < VPD2, pull-in control is performed.
[0077] In the region E where the fixing belt 310 is on the front side of the X4 position, when Vth_err < VPD1 and Vth_cnt < VPD2, a belt gathering error occurs.
[0078] Next, the following describes the processing of the gathering control according to the flowchart of FIG. 11. FIG. 11 is a flowchart showing the processing performed by the CPU in the control unit 30 in FIG. 1 when the conveyance of the fixing belt 310 is started.
[0079] When the conveyance of the fixing belt 310 is started, the output voltages VPD1 and VPD2 of the sensor unit 390 that detects the widthwise position of the fixing belt 310 are obtained by converting from an analog voltage to a digital value via the AD port of the CPU.
[0080] Next, in step S202, it is determined whether to switch to PI control. The output voltages VPD1 and VPD2 of the sensor unit 390 obtained in step S201 are compared with the control switching threshold value Vth_cnt. If both the output voltages VPD1 and VPD2 are smaller than the threshold value Vth_cnt, the process proceeds to the processing of step S203. In step S203, the steering motor of the steering mechanism 400 is driven so that the tilting amount of the steering roller 350 is obtained by stable PI control.
[0081] If the conditions for the above PI control are not satisfied in step S202, the process proceeds to step S204. In step S204, if the output voltage VPD1 is greater than the threshold value Vth_cnt and the output voltage VPD2 is less than the threshold value Vth_err, or if the output voltage VPD1 is less than the threshold value Vth_err and the output voltage VPD2 is greater than the threshold value Vth_cnt, satisfying the conditions for pull-in control, the process proceeds to the processing of step S205, and the steering motor of the steering mechanism 400 is driven so as to obtain the tilting amount of the steering roller 350 by pull-in control.
[0082] If the conditions for the above pull-in control are not satisfied in step S204, it is determined as a centering error in step S206, the drive motor M1 is stopped to stop the conveyance of the fixing belt 310, and the processing of the centering control ends. <Since the basic configuration and operation of this embodiment are the same as those of the first embodiment, we will use those descriptions as a reference and omit further explanation.
[0088] Figure 12 is an overall configuration diagram of the fixing device in an inkjet recording device, including the upper fixing belt system 500 and the lower fixing belt system 600. The inkjet recording device forms an inkjet image on the recording material and fixes it by drying the moisture in the inkjet. The upper fixing belt system 500 and the lower fixing belt system 600 are fixing systems in which the image-formed recording material is transported between the upper belt 510 and the lower belt 610, which are heated endless belts, respectively, and the image is fixed to the recording material.
[0089] In Figure 12, the upper belt 510 and the lower belt 610 are rotated by their respective drive motors (not shown), and the recording material S is transported in the direction of the arrows. In an inkjet recording device, ink is applied to the upper surface that nip with the upper belt 510, so heaters 520, 530, and 540 are provided on the upper belt 510 side to dissolve the ink. In addition, heaters 620 and 630 are provided on the lower belt 610 side to heat the recording material itself to which the ink is applied. By long-nipping and heating the recording material S with both the upper belt 510 and the lower belt 610, the ink applied to the recording material S penetrates into the recording material, achieving high print quality.
[0090] The upper anchoring belt system 500 consists of heaters 520, 530, 540, temperature sensors 550, 560, 570, and a temperature sensor 580 that controls the temperature of the upper belt 510.
[0091] Heaters 520, 530, and 540 are covered with reflectors and heat the upper belt 510 directly below them.
[0092] Temperature sensors 550, 560, and 570 are safety sensors that detect the temperature of the belt area heated by heaters 520, 530, and 540 on the upper belt 510, and detect whether the temperature exceeds 150°C. This 150°C temperature is set to prevent deformation of the upper belt and is determined according to the material of the upper belt; therefore, it does not prevent other temperatures from being set depending on the material of the upper belt.
[0093] The temperature sensor 580 is a sensor that detects the temperature of the upper belt 510 and adjusts the temperatures of the heaters 520, 530, and 540. The temperature sensor 580, which adjusts the temperature of the upper belt 510, is located downstream of the upper belt 510 from the heaters 520, 530, and 540, and adjusts the temperature of the upper belt 510 to 100°C to achieve high print quality. This 100°C temperature is the temperature at which the ink fixes to the recording material, and since it is a temperature determined according to the ink material, it does not prevent other temperatures from being set depending on the ink material.
[0094] In this case, if heaters 520, 530, and 540 malfunction, it takes time for the temperature sensor 580, which regulates the temperature of heaters 520, 530, and 540, to stop the malfunction. Therefore, when heaters 520, 530, and 540 malfunction, the temperature sensors 550, 560, and 570 detect the temperature directly below the heaters, allowing the malfunction of heaters 520, 530, and 540 to be stopped immediately.
[0095] By providing these two types of sensors, even when a long nip configuration is adopted, the temperature of the upper belt 510 can be precisely adjusted to a predetermined temperature, and even if the heaters 520, 530, and 540 malfunction, the heaters 520, 530, and 540 can be stopped without deforming the belt.
[0096] A sensor unit 390 for detecting the end position of the upper belt 510 in the belt width direction is provided at the front end position of the upper belt 510 in the belt width direction, in order to control the meandering of the upper belt 510 by the steering mechanism 400.
[0097] The lower fixing belt system 600 consists of heaters 620 and 630, temperature sensors 640 and 650 that detect the surface temperature of the rollers heated by heaters 620 and 630, and a temperature sensor 660 that detects the temperature of the lower belt 610.
[0098] The heaters 620 and 630 are configured to be placed inside the rollers, and they heat the belt via the rollers.
[0099] Temperature sensors 640 and 650 are safety temperature sensors that detect the surface temperature of the rollers of heaters 620 and 630 and stop heaters 620 and 630 when the temperature exceeds 150°C. This 150°C temperature is set to prevent deformation of the lower belt 610 and is determined according to the material of the lower belt 610; therefore, it does not prevent other temperatures from being set depending on the material of the lower belt.
[0100] The temperature sensor 660 is a temperature control sensor that regulates the temperature of the lower belt 610. The temperature of the lower belt 610 is adjusted by controlling the heaters 620 and 630 according to the temperature of the temperature sensor 660.
[0101] A sensor unit 390 for detecting the end position of the lower belt 610 in the belt width direction is provided at the far end position of the lower belt 610 in the belt width direction, in order to control the meandering of the lower belt 610 by the steering mechanism 400.
[0102] Although the above embodiments have described the control of the fixing belt's trajectory, the present invention can be similarly applied to the control of the intermediate transfer belt or the recording material conveying belt's trajectory.
[0103] Furthermore, although the above embodiments described an optical sensor with two light-receiving units as the sensor 395, it is possible to similarly stabilize the control by comparing multiple output voltages with multiple thresholds even if the light-receiving units are three or more optical sensors or PSD (position detection element) sensors. [Explanation of Symbols]
[0104] 1…Image forming apparatus 2…Image reading unit 3…Image forming apparatus main unit 8… Fixing device 30…Control Unit 204...Intermediate transfer belt 300... Belt unit 310... Fixing belt 330... Compression roller 340...Heating roller 350... Steering roller 380... Pressing member 390...Sensor unit 395...Sensor 400... Steering mechanism 500... Upper anchoring belt system 510... Upper belt 600... Lower anchoring belt system 610... Lower belt M1…Drive motor Pa, Pb, Pc, Pd...Image forming section
Claims
1. An endless belt stretched between multiple support members, A steering roller that tensions the aforementioned belt, A position detection means for detecting the position of the end of the belt in the width direction as it travels, A correction means for correcting the meandering of the belt in the width direction by changing the steering angle of the steering roller based on the detection result of the position detection means, the correction means for performing a first control and a second control different from the first control, A determination means for determining a close-out error when the detection result from the position detection means exceeds a first threshold, It has, The correction means executes the first control when the detection result from the position detection means is within a range of a second threshold different from the first threshold from the reference position, and executes the second control when it exceeds the second threshold. A belt conveying device characterized by the following features.
2. The belt conveying device according to claim 1, characterized in that the distance between the reference position and the first threshold is greater than the distance between the reference position and the second threshold.
3. The belt conveying device according to claim 1, characterized in that the first control is a feedback control corresponding to the deviation of the belt's displacement in the belt width direction, and the second control is a control with a stronger corrective force than the first control.
4. The belt conveying device according to claim 1, characterized in that the first control is a feedback control corresponding to the deviation of the belt's displacement in the belt width direction, and the second control is a control that corrects with a constant control amount having a stronger corrective force than the first control.
5. The belt conveying device according to claim 1, characterized in that the position detection means has a plurality of output signals that change in accordance with the displacement of the belt in the belt width direction.
6. The belt conveying device according to claim 1, characterized in that the position detection means has multiple output signals output from multiple detection light receiving regions that change in accordance with the displacement of the belt in the belt width direction.
7. The belt conveying device according to claim 1, characterized in that when the determination means determines the belt misalignment error, the belt stops moving.
8. The belt conveying device according to claim 1, characterized in that the belt is a fixing belt of a fixing device for fixing an image onto a recording material.
9. The belt conveying device according to claim 1, characterized in that the belt is an intermediate transfer belt for transferring an image onto a recording material.
10. Image forming means for forming an image, A belt conveying device according to any one of claims 1 to 9, An image forming apparatus characterized by having the following features.