Fixing device, image forming apparatus, and abnormality detection method

Abstract

To provide a fixing device, an image forming apparatus, and an abnormality detection method capable of detecting an abnormality of a stepping motor without providing an additional sensor.SOLUTION: A fixing device comprises: a heating unit 42 which is provided in contact with an inner peripheral surface of a fixing belt, and heats the fixing belt via a contact portion with the fixing belt; a stepping motor 47 which rotates a pressure roller for rotating the fixing belt in a driven manner; a temperature sensor 54 which is used for drive control of the heating unit 42; a drive processing unit 61 which drives the heating unit 42 when driving of the stepping motor 47 is started; and a detection processing unit 62 which detects an abnormality of the stepping motor 47 on the basis of the transition in the detection temperature of the temperature sensor 54 from a start of driving of the heating unit 42 by the drive processing unit 61.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fixing device, an image forming apparatus, and an abnormality detection method. [Background technology]

[0002] An electrophotographic image forming apparatus includes a fixing device that fixes a toner image transferred onto a sheet to the sheet. For example, the fixing device includes a fixing belt, a heater, a pressure roller, a stepping motor, and a temperature sensor (see, for example, Patent Document 1). The fixing belt is used to fix the toner image. The heater is provided in contact with the inner circumferential surface of the fixing belt and heats the fixing belt via the contact portion with the fixing belt. The pressure roller is provided opposite the heater across the fixing belt and rotates the fixing belt. The stepping motor rotates the pressure roller. The temperature sensor is used to control the drive of the heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-65383 Summary of the Invention [Problem to be solved by the invention]

[0004] In the image forming apparatus, the stepping motor may lose synchronization, causing the pressure roller and the fixing belt to stop rotating. If the heater is driven in a state where the pressure roller and the fixing belt have stopped rotating, the heater may overheat, causing problems such as a breakdown of the heater.

[0005] In response to this, a configuration may be considered in which a sensor is provided to detect an abnormality in the stepping motor, and the operation of the image forming apparatus is stopped when the sensor detects an abnormality in the stepping motor. However, this configuration requires the provision of an additional sensor to detect the abnormality in the stepping motor.

[0006] An object of the present invention is to provide a fixing device, an image forming apparatus, and an abnormality detection method that are capable of detecting an abnormality in a stepping motor without providing an additional sensor. [Means for solving the problem]

[0007] A fixing device according to one aspect of the present invention includes a fixing belt, a heater, a pressure roller, a stepping motor, a temperature sensor, a drive processing unit, and a detection processing unit. The fixing belt fixes a toner image transferred onto a sheet onto the sheet. The heater is provided in contact with the inner circumferential surface of the fixing belt and heats the fixing belt via a contact portion with the fixing belt. The pressure roller is provided opposite the heater across the fixing belt and rotates the fixing belt. The stepping motor rotates the pressure roller. The temperature sensor is used to control the drive of the heater. The drive processing unit drives the heater when the drive of the stepping motor is started. The detection processing unit detects an abnormality in the stepping motor based on a change in the temperature detected by the temperature sensor from when the drive processing unit starts driving the heater.

[0008] An image forming apparatus according to another aspect of the present invention includes the fixing device described above, and forms an image on the sheet using the fixing device.

[0009] According to another aspect of the present invention, there is provided an abnormality detection method for a fixing device including: a fixing belt that fixes a toner image transferred onto a sheet onto the sheet; a heater that is disposed in contact with the inner circumferential surface of the fixing belt and heats the fixing belt via a contact portion with the fixing belt; a pressure roller that is disposed opposite the heater across the fixing belt and drives the fixing belt; a stepping motor that rotates the pressure roller; and a temperature sensor used to control the driving of the heater. The abnormality detection method includes a driving step and a detection step. In the driving step, the heater is driven when driving of the stepping motor is started. In the detection step, an abnormality in the stepping motor is detected based on a change in the temperature detected by the temperature sensor from the time when driving of the heater is started in the driving step. [Effects of the Invention]

[0010] According to the present invention, it is possible to detect an abnormality in the stepping motor of the fixing device without providing an additional sensor. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the system configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing the configuration of the fixing device of the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the configuration of the heating unit of the image forming apparatus according to the embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart showing an example of an abnormality detection process executed in the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0013] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Here, Figure 1 is a cross-sectional view showing the configuration of the image forming apparatus 100.

[0014] For ease of explanation, the vertical direction in the installation state where image forming apparatus 100 is usable (the state shown in FIG. 1) is defined as the up-down direction D1. Also, the front-to-back direction D2 is defined with the left side of image forming apparatus 100 shown in FIG. 1 as the front (front face). Also, the left-to-right direction D3 is defined with the front face of image forming apparatus 100 in the installation state as the reference point.

[0015] Image forming apparatus 100 is a printer having a print function that forms an image based on image data. Note that the present invention can be applied to fax machines, copy machines, multifunction machines, and the like that form images using an electrophotographic method.

[0016] 1 and 2, the image forming apparatus 100 includes an image forming unit 1, a sheet conveying unit 2, an operation and display unit 3, a storage unit 4, and a control unit 5. The image forming unit 1, the sheet conveying unit 2, the storage unit 4, and the control unit 5 are housed in a housing 101 (see FIG. 1) of the image forming apparatus 100. The housing 101 is formed in a substantially rectangular parallelepiped shape. The operation and display unit 3 and a sheet receiving unit 102 (see FIG. 1) onto which sheets on which images have been formed by the image forming apparatus 100 are discharged are formed on the top of the housing 101.

[0017] The operation display unit 3 is a user interface of the image forming apparatus 100. The operation display unit 3 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit 5, and an operation unit such as operation keys or a touch panel that inputs various information to the control unit 5 in response to user operations.

[0018] The storage unit 4 is a non-volatile storage device, such as a flash memory.

[0019] The control unit 5 performs overall control of the image forming apparatus 100. As shown in FIG. 2, the control unit 5 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various types of arithmetic processing. The ROM 12 is a non-volatile storage device that pre-stores information such as control programs for causing the CPU 11 to execute various processes. The RAM 13 is a volatile or non-volatile storage device used as a temporary storage memory (work area) for the various processes executed by the CPU 11. In the control unit 5, the CPU 11 executes various control programs pre-stored in the ROM 12. In this way, the control unit 5 performs overall control of the image forming apparatus 100. The control unit 5 may be configured with an electronic circuit such as an integrated circuit (ASIC). The control unit 5 may also be a control unit provided separately from a main control unit that performs overall control of the image forming apparatus 100.

[0020] The image forming unit 1 is capable of forming an image on a sheet by electrophotography based on image data input from an external information processing device such as a personal computer. As shown in Fig. 1, the image forming unit 1 includes a photosensitive drum 21, a charging device 22, an optical scanning device 23, a developing device 24, a transfer roller 25, a cleaning device 26, and a fixing device 27.

[0021] The photosensitive drum 21 is rotatably supported by the housing 101. The photosensitive drum 21 receives a rotational driving force transmitted from a motor (not shown) and rotates in the direction of the arrow shown in FIG.

[0022] The charging device 22 charges the surface of the photosensitive drum 21 .

[0023] The optical scanning device 23 irradiates the surface of the photosensitive drum 21, which has been charged by the charging device 22, with light based on image data. An electrostatic latent image is formed on the surface of the photosensitive drum 21 by the optical scanning device 23.

[0024] The developing device 24 uses a developer containing toner to develop the electrostatic latent image formed on the surface of the photosensitive drum 21. A toner image is formed on the surface of the photosensitive drum 21 by the developing device 24.

[0025] The transfer roller 25 transfers the toner image formed on the surface of the photosensitive drum 21 onto the sheet being conveyed by the sheet conveying section 2 toward the fixing device 27 .

[0026] The cleaning device 26 cleans the surface of the photosensitive drum 21 after the toner image has been transferred by the transfer roller 25 .

[0027] The fixing device 27 heats the sheet onto which the toner image has been transferred, thereby fixing the toner image to the sheet.

[0028] The sheet conveying unit 2 conveys a sheet on which an image is formed by the image forming unit 1. As shown in Fig. 1, the sheet conveying unit 2 includes a paper feed cassette 31, a sheet conveying path 32, a paper feed unit 33, a pair of registration rollers 34, and a pair of paper discharge rollers 35.

[0029] The paper feed cassette 31 stores sheets on which images are formed by the image forming unit 1. As shown in FIG. 1, the paper feed cassette 31 is provided at the bottom of the housing 101. For example, the paper feed cassette 31 stores sheet materials such as paper, coated paper, postcards, envelopes, and transparencies. The paper feed cassette 31 has a lift plate that lifts up the multiple sheets stored therein.

[0030] The sheet transport path 32 is a passageway along which a sheet travels from the paper feed cassette 31 to the sheet receiving section 102 via the transfer roller 25 and the fixing device 27. The sheet transport path 32 is provided with a plurality of roller pairs, including a registration roller pair 34 and a paper discharge roller pair 35. In the sheet transport path 32, a sheet discharged from the paper feed cassette 31 is transported by the plurality of roller pairs in a transport direction D4 (see FIG. 1 ) toward the sheet receiving section 102. The sheet transport path 32 is formed by a pair of transport guide members provided inside the housing 101.

[0031] The paper feed unit 33 feeds sheets stored in the paper feed cassette 31 one by one to the sheet transport path 32. The paper feed unit 33 includes a pickup roller, a paper feed roller, and a retard roller. The pickup roller rotates while contacting the upper surface of the topmost sheet among the multiple sheets lifted by the lift plate of the paper feed cassette 31, thereby feeding the sheet to the paper feed roller. The paper feed roller rotates while contacting the upper surface of the sheet fed by the pickup roller, thereby feeding the sheet to the sheet transport path 32. The retard roller is biased from below the paper feed roller toward the paper feed roller. When multiple overlapping sheets are fed by the pickup roller, the retard roller separates the sheets other than the topmost sheet from the overlapping multiple sheets.

[0032] The pair of resist rollers 34 transports the sheet to the transfer position in accordance with the timing at which the toner image formed on the surface of the photosensitive drum 21 is transported to the transfer position by the transfer roller 25 by the rotation of the photosensitive drum 21.

[0033] The pair of paper discharge rollers 35 discharges the sheet on which the toner image has been fixed by the fixing device 27 to the sheet receiving section 102 .

[0034] [Configuration of fixing device 27] Next, the configuration of the fixing device 27 will be described with reference to Figures 2 to 4. Figure 3 is a cross-sectional view showing the configuration of the fixing device 27. Figure 4 is a cross-sectional view showing the configuration of the heating section .

[0035] 3, the fixing device 27 includes a fixing belt 41, a heating section 42, a support section 43, a pressing member 44, and a pressure roller 45. The fixing device 27 also includes a stepping motor 47 shown in FIG.

[0036] The fixing belt 41 is heated to a predetermined fixing temperature by the heating unit 42. The fixing belt 41 contacts a sheet in a heated state, thereby fixing the toner image transferred to the sheet to the sheet. As shown in FIG. 3, the fixing belt 41 is endless. The fixing belt 41 is flexible. The fixing belt 41 includes a base layer, an elastic layer disposed on the outer peripheral surface of the base layer, and a release layer disposed on the outer peripheral surface of the elastic layer. The base layer is formed of a metal material such as stainless steel or a nickel alloy. The elastic layer is formed of a material such as silicone rubber. The release layer is formed of a fluorine-based resin material such as PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin). The fixing belt 41 is elongated along the left-right direction D3. The size of the fixing belt 41 in the left-right direction D3 is determined according to the maximum size of a sheet on which an image can be formed by the image forming apparatus 100.

[0037] The pressure roller 45 is provided at a position where it can come into contact with the outer peripheral surface 41A (see FIG. 3) of the fixing belt 41. Specifically, as shown in FIG. 3, the pressure roller 45 is provided below the fixing belt 41. The pressure roller 45 is elongated along the left-right direction D3. The pressure roller 45 includes a shaft portion 45A and an elastic layer 45B. The shaft portion 45A is formed in a cylindrical shape from a metal material. The elastic layer 45B is formed on the outer periphery of the shaft portion 45A from an elastic material. The shaft portion 45A is rotatably supported by a pair of side plates provided inside the housing 101. The pressure roller 45 receives a rotational driving force supplied from a motor (not shown) and rotates in a rotational direction D5 (see FIG. 3).

[0038] The heating unit 42 heats the fixing belt 41. As shown in FIG. 3, the heating unit 42 is provided inside the inner circumferential surface 41B (see FIG. 3) of the fixing belt 41, facing the pressure roller 45 with the fixing belt 41 in between. The heating unit 42 is elongated in the left-right direction D3 and extends across both outer sides of the fixing belt 41 in the left-right direction D3. The heating unit 42 is provided in contact with the inner circumferential surface 41B of the fixing belt 41, and heats the fixing belt 41 via the contact portion with the fixing belt 41. The heating unit 42 is an example of a heater of the present invention.

[0039] As shown in FIG. 4, the heating unit 42 includes a substrate 51, a resistance heating element 52, a protective layer 53, and a temperature sensor 54.

[0040] The substrate 51 is a flat member that is long in the left-right direction D3. The substrate 51 is made of a material that has excellent heat resistance, electrical insulation, and low heat capacity. For example, the substrate 51 is made of ceramic such as alumina. The size of the substrate 51 in the left-right direction D3 is larger than that of the fixing belt 41. The substrate 51 is disposed so as to extend on both outer sides of the fixing belt 41 in the left-right direction D3. Therefore, both end portions of the substrate 51 in the left-right direction D3 protrude outward from the fixing belt 41 in the left-right direction D3.

[0041] 3 and 4, the lower surface of substrate 51 faces inner circumferential surface 41B of fixing belt 41. As shown in FIG. 4, resistance heating element 52 is disposed on the lower surface of substrate 51. Furthermore, the area of the lower surface of substrate 51 facing inner circumferential surface 41B of fixing belt 41 is covered with protective layer 53 (see FIG. 4). Protective layer 53 is made of an electrically insulating material such as glass.

[0042] As shown in Figures 3 and 4, the upper surface of the substrate 51 faces the bottom surface of the recess 43A of the support portion 43. As shown in Figure 4, a temperature sensor 54 is disposed on the upper surface of the substrate 51. The temperature sensor 54 is used to control the driving of the heating portion 42. The temperature sensor 54 detects the temperature of the heating portion 42 and outputs an electrical signal corresponding to the detected temperature. The electrical signal output from the temperature sensor 54 is input to the control portion 5. The control portion 5 controls the driving of the heating portion 42 based on the electrical signal input from the temperature sensor 54. Specifically, the control portion 5 controls the driving of the heating portion 42 so that the temperature detected by the temperature sensor 54 becomes a specific temperature based on the fixing temperature.

[0043] The resistance heating element 52 generates heat in response to power supply. The resistance heating element 52 is formed in a strip shape that is elongated in the left-right direction D3 and has a predetermined thickness in a direction perpendicular to the lower surface of the substrate 51. The size of the resistance heating element 52 in the left-right direction D3 is smaller than that of the fixing belt 41. The resistance heating element 52 is disposed inside the opposing region on the lower surface of the substrate 51.

[0044] The support portion 43 supports the heating portion 42. As shown in FIG. 3, the support portion 43 is provided inside the inner circumferential surface 41B of the fixing belt 41. The support portion 43 is elongated in the left-right direction D3 and extends across both outer sides of the fixing belt 41 in the left-right direction D3. A recess 43A corresponding to the shape of the heating portion 42 is formed in the bottom of the support portion 43. The heating portion 42 is fitted into the recess 43A.

[0045] The pressing member 44 presses the support portion 43 toward the pressure roller 45. As shown in FIG. 3 , the pressing member 44 is provided inside the inner circumferential surface 41B of the fixing belt 41, facing the pressure roller 45 with the support portion 43 interposed therebetween. The pressing member 44 is elongated in the left-right direction D3 and extends across both outer sides of the fixing belt 41 in the left-right direction D3. Both ends of the pressing member 44 in the left-right direction D3 are urged toward the pressure roller 45 by urging members (not shown). As a result, the pressing member 44 presses the support portion 43 toward the pressure roller 45. As the support portion 43 is pressed toward the pressure roller 45, the heating unit 42 supported by the support portion 43 is pressed toward the pressure roller 45.

[0046] Heating unit 42 is pressed toward pressure roller 45 by pressing member 44, and is thereby brought into pressure contact with inner circumferential surface 41B of fixing belt 41. As a result, a fixing nip portion 46 is formed between fixing belt 41 and pressure roller 45, where a toner image transferred to a sheet is fixed to the sheet. In this specification, the area where fixing belt 41 and pressure roller 45 contact each other is defined as fixing nip portion 46. Note that a lubricant such as fluorine grease is applied between heating unit 42 and inner circumferential surface 41B of fixing belt 41.

[0047] Fixing belt 41 is sandwiched between heating unit 42 and pressure roller 45. When pressure roller 45 rotates in rotation direction D5, fixing belt 41 rotates along belt rotation direction D6 (see FIG. 3) following the rotation of pressure roller 45.

[0048] The support portion 43 includes a pair of guide portions 43B that contact the inner circumferential surface 41B of the fixing belt 41 to guide the running of the fixing belt 41. The pair of guide portions 43B are provided at both ends of the support portion 43 in the front-rear direction D2. The pair of guide portions 43B guide the fixing belt 41 to run along a predetermined running path.

[0049] The stepping motor 47 rotates the pressure roller 45 .

[0050] The pressure roller 45 may be biased toward the heating unit 42. In this case, the pressing member 44 does not have to be biased by the biasing member.

[0051] Incidentally, in the image forming apparatus 100, the stepping motor 47 may lose synchronization, causing the pressure roller 45 and the fixing belt 41 to stop rotating. If the heating unit 42 is driven in a state in which the pressure roller 45 and the fixing belt 41 have stopped rotating, the temperature of the heating unit 42 may rise excessively, causing problems such as a breakdown of the heating unit 42.

[0052] In response to this, a configuration may be considered in which a sensor is provided to detect an abnormality in stepping motor 47, and the operation of image forming apparatus 100 is stopped when the sensor detects an abnormality in stepping motor 47. However, in this configuration, it is necessary to additionally provide the sensor to detect the abnormality in stepping motor 47.

[0053] In contrast to this, in the image forming apparatus 100 according to the embodiment of the present invention, as will be described below, it is possible to detect an abnormality in the stepping motor 47 without providing an additional sensor.

[0054] [Configuration of control unit 5] The configuration of the control unit 5 will be described below with reference to FIG.

[0055] As shown in FIG. 2, the control unit 5 includes a drive processing unit 61, a detection processing unit 62, and a stop processing unit 63.

[0056] Specifically, an abnormality detection program for causing CPU 11 to function as each of the above-mentioned processing units is stored in advance in ROM 12 of control unit 5. CPU 11 executes the abnormality detection program stored in ROM 12 to function as drive processing unit 61, detection processing unit 62, and stop processing unit 63. An apparatus including fixing device 27 and control unit 5 is an example of the fixing device of the present invention.

[0057] The anomaly detection program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and stored in the storage unit 4. Some or all of the processing units included in the control unit 5 may be configured with electronic circuits. The anomaly detection program may also be a program for causing multiple processors to function as the processing units included in the control unit 5.

[0058] The drive processing unit 61 drives the heating unit 42 when the driving of the stepping motor 47 starts.

[0059] For example, the drive processing unit 61 simultaneously drives the stepping motor 47 and the heating unit 42. The drive processing unit 61 may drive the heating unit 42 before the stepping motor 47 starts to be driven or before or after the stepping motor 47 starts to be driven.

[0060] The detection processing unit 62 detects an abnormality in the stepping motor 47 based on the transition of the temperature detected by the temperature sensor 54 from the time when the drive processing unit 61 starts driving the heating unit 42 .

[0061] For example, the detection processing unit 62 detects an abnormality in the stepping motor 47 based on the change in the temperature detected by the temperature sensor 54 during the detection period from when the drive processing unit 61 starts driving the heating unit 42 until a predetermined time has elapsed.

[0062] For example, if the increase in the temperature detected by the temperature sensor 54 during the detection period exceeds a predetermined threshold, the detection processing unit 62 determines that there is an abnormality in the stepping motor 47. Note that abnormalities in the stepping motor 47 include loss of synchronization of the stepping motor 47 and a malfunction of the stepping motor 47.

[0063] For example, the threshold value is set based on the results of an experiment in which an abnormal-free stepping motor 47 is used to investigate the amount of increase in the temperature detected by the temperature sensor 54 during the detection period. The control unit 5 may also execute a setting process for setting the threshold value in response to a predetermined user operation on the operation / display unit 3. The setting process is a process in which the stepping motor 47 and the heating unit 42 are simultaneously driven, the amount of increase in the temperature detected by the temperature sensor 54 during the detection period is obtained, and the threshold value is set based on the obtained amount of increase in the detected temperature.

[0064] It is preferable that the length of the detection period be as short as possible within a range that allows for distinguishing between the rate of increase in the temperature detected by the temperature sensor 54 when the stepping motor 47 is normal and the rate of increase in the temperature detected by the temperature sensor 54 when the stepping motor 47 is abnormal.

[0065] After the detection period ends, the drive processing unit 61 stops driving the heating unit 42. This makes it possible to avoid unnecessary driving of the heating unit 42. Note that the drive processing unit 61 may continue driving the heating unit 42 even after the detection period ends.

[0066] When the detection processing unit 62 detects an abnormality in the stepping motor 47, the stop processing unit 63 stops the operation of the image forming apparatus 100.

[0067] [Anomaly detection processing] 5, an example of the procedure of the abnormality detection process executed by the control unit 5 in the image forming apparatus 100 will be described, along with the abnormality detection method of the present invention. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 5. The abnormality detection process is executed when the operating state of the image forming apparatus 100 transitions from a stopped state in which image formation is not possible to a standby state in which image formation is possible.

[0068] <Step S11> First, in step S11, the control unit 5 starts driving the stepping motor 47.

[0069] <Step S12> In step S12, the control unit 5 starts driving the heating unit 42. The process of step S12 is an example of a driving step of the present invention, and is executed by the drive processing unit 61 of the control unit 5.

[0070] <Step S13> In step S13, the control unit 5 acquires the temperature detected by the temperature sensor .

[0071] <Step S14> In step S14, the control unit 5 determines whether or not the detection period has ended.

[0072] Here, if the control unit 5 determines that the detection period has ended (Yes in step S14), it shifts the process to step S15. On the other hand, if the detection period has not ended (No in step S14), the control unit 5 shifts the process to step S13. As a result, the temperature detected by the temperature sensor 54 is periodically acquired during the detection period. Note that the control unit 5 may acquire the temperature detected by the temperature sensor 54 only at the beginning and end of the detection period.

[0073] <Step S15> In step S15, the control unit 5 stops driving the heating unit .

[0074] <Step S16> In step S16, the control unit 5 executes a detection process to detect an abnormality in the stepping motor 47 based on the transition of the detected temperature by the temperature sensor 54 during the detection period. The process of step S16 is an example of a detection step of the present invention, and is executed by the detection processing unit 62 of the control unit 5.

[0075] Specifically, the control unit 5 determines that the stepping motor 47 is abnormal if the increase in the detected temperature of the temperature sensor 54 during the detection period, calculated based on the detected temperature obtained by the processing of step S13, exceeds the threshold value.

[0076] <Step S17> In step S17, the control unit 5 branches the process depending on the result of the detection process executed in step S16. Specifically, if an abnormality in the stepping motor 47 is detected in the detection process (Yes in step S17), the control unit 5 shifts the process to step S18. On the other hand, if an abnormality in the stepping motor 47 is not detected in the detection process (No in step S17), the control unit 5 ends the abnormality detection process. In this case, the control unit 5 waits for input of an instruction to execute image formation process while rotating the stepping motor 47 at a predetermined speed.

[0077] <Step S18> In step S18, the control unit 5 stops the operation of the image forming apparatus 100. The process of step S18 is executed by the stop processing unit 63 of the control unit 5.

[0078] Specifically, the control unit 5 stops driving the stepping motor 47. In addition, the control unit 5 stops driving the image forming unit 1 and the sheet conveying unit 2, which have been started to be driven in response to the transition from the stopped state to the standby state.

[0079] <Step S19> In step S19, the control unit 5 notifies the user that an abnormality has been detected in the stepping motor 47. For example, the control unit 5 causes the operation display unit 3 to display a message indicating that an abnormality has been detected in the stepping motor 47.

[0080] Each time the process of step S13 is executed during the detection period, the control unit 5 may calculate the amount of increase in temperature detected by the temperature sensor 54 since the previous execution of step S13, and immediately detect an abnormality in the stepping motor 47 if the calculated amount of increase exceeds a predetermined specific amount. In other words, the control unit 5 may detect an abnormality in the stepping motor 47 before the end of the detection period. In this case, the control unit 5 may determine that the stepping motor 47 is not abnormal (is normal) if no abnormality in the stepping motor 47 is detected by the end of the detection period.

[0081] In this way, in image forming apparatus 100, heating unit 42 is driven when stepping motor 47 starts to be driven. Then, an abnormality in stepping motor 47 is detected based on the change in the temperature detected by temperature sensor 54 from the time when heating unit 42 starts to be driven. This makes it possible to detect an abnormality in stepping motor 47 using temperature sensor 54 used to control the drive of heating unit 42, i.e., the existing sensor. Therefore, it is possible to detect an abnormality in stepping motor 47 without providing an additional sensor.

[0082] Note that image forming apparatus 100 may include a temperature sensor that detects the temperature of fixing belt 41 instead of temperature sensor 54. For example, image forming apparatus 100 may include a first temperature sensor that detects the temperature of a first region of fixing belt 41 that forms fixing nip 46. In this case, detection processing unit 62 may detect an abnormality in stepping motor 47 if the increase in temperature detected by the first temperature sensor during the detection period exceeds a predetermined value. Image forming apparatus 100 may also include a second temperature sensor that detects the temperature of a second region of fixing belt 41 that is different from the first region. In this case, detection processing unit 62 may detect an abnormality in stepping motor 47 if the increase in temperature detected by the second temperature sensor during the detection period is less than a predetermined value.

[0083] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0084] <Appendix 1> a fixing device comprising: a fixing belt that fixes a toner image transferred onto a sheet onto the sheet; a heater that is arranged in contact with the inner surface of the fixing belt and heats the fixing belt via a contact portion with the fixing belt; a pressure roller that is arranged opposite the heater across the fixing belt and rotates the fixing belt; a stepping motor that rotates the pressure roller; a temperature sensor used to control the drive of the heater; a drive processing unit that drives the heater when the drive of the stepping motor is started; and a detection processing unit that detects an abnormality in the stepping motor based on the change in the temperature detected by the temperature sensor from the time the drive processing unit starts to drive the heater.

[0085] <Appendix 2> 2. The fixing device according to claim 1, wherein the temperature sensor detects the temperature of the heater.

[0086] <Appendix 3> 2. The fixing device according to claim 1, wherein the temperature sensor detects the temperature of the fixing belt.

[0087] <Appendix 4> The fixing device according to any one of appendices 1 to 3, wherein the detection processing unit detects an abnormality in the stepping motor based on a change in the detected temperature of the temperature sensor during a detection period from when the drive processing unit starts driving the heater until a predetermined time has elapsed, and the drive processing unit stops driving the heater after the detection period ends.

[0088] <Appendix 5> An image forming apparatus comprising the fixing device according to any one of appendices 1 to 4, and forming an image on the sheet using the fixing device.

[0089] <Appendix 6> 6. The image forming apparatus according to claim 5, further comprising a stop processing unit that stops operation of the image forming apparatus when an abnormality in the stepping motor is detected by the detection processing unit.

[0090] <Appendix 7> An abnormality detection method to be performed in a fixing device including a fixing belt that fixes a toner image transferred onto a sheet onto the sheet, a heater that is arranged in contact with the inner surface of the fixing belt and heats the fixing belt via a contact portion with the fixing belt, a pressure roller that is arranged opposite the heater across the fixing belt and rotates the fixing belt in a driven manner, a stepping motor that rotates the pressure roller, and a temperature sensor used to control the drive of the heater, the abnormality detection method including: a driving step that drives the heater when drive of the stepping motor is started; and a detection step that detects an abnormality in the stepping motor based on the change in the temperature detected by the temperature sensor from the time drive of the heater begins by the driving step. [Explanation of symbols]

[0091] 1 Image forming unit 2 Sheet transport section 3 Operation display section 4 Storage section 5. Control section 21 Photosensitive drum 22 Charging device 23 Optical scanning device 24 Developing device 25 Transfer roller 26 Cleaning device 27 Fixing device 41 Fixing belt 42 Heating section 43 Support part 44 Pressing member 45 Pressure Roller 46 Fixing nip 47 Stepping motor 52 Resistive heating element 54 Temperature Sensor 61 Drive processing unit 62 Detection processing section 63 Stop processing unit 100 Image forming device

Claims

1. a fixing belt for fixing the toner image transferred onto the sheet; a heater provided in contact with an inner circumferential surface of the fixing belt, the heater heating the fixing belt through a contact portion with the fixing belt; a pressure roller that is disposed opposite the heater across the fixing belt and that rotates the fixing belt; a stepping motor that rotates the pressure roller; a temperature sensor used to control the heater; a drive processing unit that drives the heater when driving of the stepping motor is started; a detection processing unit that detects an abnormality in the stepping motor based on a change in the temperature detected by the temperature sensor from when the drive processing unit starts driving the heater; A fixing device comprising:

2. The temperature sensor detects the temperature of the heater. The fixing device according to claim 1 .

3. The temperature sensor detects the temperature of the fixing belt. The fixing device according to claim 1 .

4. the detection processing unit detects an abnormality in the stepping motor based on a transition of the detected temperature of the temperature sensor during a detection period from when the drive processing unit starts driving the heater until a predetermined time has elapsed; the drive processing unit stops driving the heater after the detection period ends. The fixing device according to claim 1 .

5. A fixing device according to any one of claims 1 to 4, forming an image on the sheet using the fixing device; Image forming device.

6. a stop processing unit that stops operation of the device when an abnormality in the stepping motor is detected by the detection processing unit; The image forming apparatus according to claim 5 .

7. An abnormality detection method executed in a fixing device including: a fixing belt that fixes a toner image transferred onto a sheet onto the sheet; a heater that is provided in contact with an inner circumferential surface of the fixing belt and heats the fixing belt via a contact portion with the fixing belt; a pressure roller that is provided opposite the heater across the fixing belt and rotates the fixing belt; a stepping motor that rotates the pressure roller; and a temperature sensor that is used to control the drive of the heater, a driving step of driving the heater when driving of the stepping motor is started; a detecting step of detecting an abnormality in the stepping motor based on a transition of the temperature detected by the temperature sensor from the start of driving of the heater in the driving step; An anomaly detection method comprising:

Images