Image forming apparatus, method for abnormality determination, and program

Abstract

To reduce service call opportunities due to abnormality of a temperature detection sensor.SOLUTION: An image forming apparatus 1 includes: a heating unit 41 for fixing an image formed on a sheet 9 to the sheet 9; and a temperature detection sensor 50 for detecting the surface temperature of the heating unit 41. The image forming apparatus 1 further includes an abnormality determination unit 64 for determining abnormality of the temperature detection sensor 50 on the basis of the detected temperature by the temperature detection sensor 50. The abnormality determination unit 64 determines, on the basis of the detected temperature of the temperature detection sensor 50, whether one of a first abnormal state and a second abnormal state different from the first abnormal state has occurred in the temperature detection sensor 50.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, an abnormality determination method, and a program, and more particularly to a technique for detecting an abnormality in a temperature detection sensor provided in a fixing device of an image forming apparatus. [Background technology]

[0002] Electrophotographic image forming devices such as printers and MFPs (Multifunction Peripherals) are equipped with a fixing device that fixes an image formed on a sheet such as printing paper to the sheet. The fixing device has a heating section equipped with a heating roller. The fixing device heats the heating section to a predetermined temperature, thereby applying heat and pressure to the sheet on which the image has been formed, thereby fixing the image to the sheet.

[0003] Such a fixing device is equipped with a temperature detection sensor that detects the surface temperature of the heating unit, and controls the heating unit to a predetermined temperature based on the temperature detected by the temperature detection sensor. If the temperature detected by the temperature detection sensor is inaccurate, the fixing device will not be able to control the heating unit to an appropriate temperature. Therefore, any abnormality in the temperature detection sensor should be detected early.

[0004] Conventionally, an image forming apparatus has been proposed that includes an environmental temperature sensor that detects the environmental temperature in addition to a temperature detection sensor that detects the surface temperature of the heating unit (for example, Patent Document 1). Before heating the heating unit, this image forming apparatus acquires the temperature detected by the temperature detection sensor and the temperature detected by the environmental temperature sensor. Then, the image forming apparatus determines whether an abnormality has occurred in the temperature detection sensor based on the difference between the temperature detected by the temperature detection sensor and the temperature detected by the environmental temperature sensor.

[0005] Also proposed in the past is an image forming apparatus that detects an abnormality in a temperature detection sensor based on the power supplied to the heating unit after heating of the heating unit has started (for example, Patent Document 2). This image forming apparatus acquires the temperature detected by the temperature detection sensor after heating of the heating unit has started, and then acquires the temperature detected by the temperature detection sensor after a predetermined time has passed. The image forming apparatus then determines whether an abnormality has occurred in the temperature detection sensor based on the temperature rise value after the predetermined time has passed and the power supplied to the heating unit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-137055 [Patent Document 2] Japanese Patent Application Publication No. 2018-137054 Summary of the Invention [Problem to be solved by the invention]

[0007] The temperature detection sensor's temperature detection becomes inaccurate when foreign matter adheres to the sensor's detection surface. Examples of foreign matter that can adhere to the sensor's detection surface include paper dust and toner. When paper dust or toner adheres to the detection surface, the sensitivity of the temperature detection sensor decreases. As a result, the temperature detection sensor is unable to detect the temperature accurately. In this case, the problem cannot be resolved unless the temperature detection sensor or the fixing device is replaced. Therefore, a service technician is called and the temperature detection sensor or the fixing device is replaced.

[0008] Condensation can also be a foreign object that adheres to the sensor's detection surface. For example, this occurs when moisture contained in a sheet evaporates during heating, and the evaporated water condenses on the detection surface. When condensation forms on the detection surface, the sensitivity of the temperature detection sensor decreases. As a result, the temperature detection sensor is unable to detect the temperature accurately. However, condensation on the detection surface is a temporary anomaly and disappears from the detection surface after a certain period of time has passed. Therefore, if the anomaly is due to condensation, there is no need to replace the temperature detection sensor or the fixing device.

[0009] The conventional image forming apparatus described above cannot distinguish between the two abnormal states, which results in a problem that even when the abnormality is due to condensation, a service technician is called, increasing the number of times a service technician is dispatched.

[0010] The present invention has been made to solve the above-mentioned problems of the prior art. That is, an object of the present invention is to provide an image forming apparatus, an abnormality discrimination method, and a program that can reduce the need for service personnel by discriminating between the above two abnormal states. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the invention of claim 1 is an image forming apparatus characterized by comprising: a heating unit that fixes an image formed on a sheet to the sheet; a temperature detection sensor that detects the surface temperature of the heating unit; and an abnormality determination unit that determines whether a first abnormal state of the temperature detection sensor or a second abnormal state different from the first abnormal state has occurred based on the temperature detected by the temperature detection sensor.

[0012] The invention of claim 2 is characterized in that, in the image forming apparatus of claim 1, the abnormality determination unit determines whether the abnormality state is the first abnormality state or the second abnormality state based on the amount of change in the temperature detected by the temperature detection sensor.

[0013] The invention of claim 3 is characterized in that, in the image forming apparatus of claim 1 or 2, the temperature detection sensor is provided below the heating section and is positioned facing upward with its detection surface, which detects the surface temperature of the heating section, facing the surface of the heating section.

[0014] The invention of claim 4 is characterized in that, in the image forming apparatus of claim 3, the first abnormal state is a state in which paper dust or toner adheres to the detection surface of the temperature detection sensor, and the second abnormal state is a state in which condensation has formed on the detection surface of the temperature detection sensor.

[0015] The invention of claim 5 is characterized in that, in the image forming apparatus of claim 2, the abnormality determination unit calculates the amount of change in the temperature detected by the temperature detection sensor when the temperature detected by the temperature detection sensor drops below a predetermined value while control is being performed to heat the heating unit to a predetermined target temperature.

[0016] The invention of claim 6 is characterized in that, in the image forming apparatus of claim 2 or 5, the abnormality determination unit determines that the first abnormal state exists when the amount of change is greater than a first threshold value or when the amount of change is smaller than a second threshold value that is smaller than the first threshold value, and determines that the second abnormal state exists when the amount of change is greater than or equal to the second threshold value and less than or equal to the first threshold value.

[0017] The invention of claim 7 is characterized in that, in the image forming apparatus of claim 1, the abnormality determination unit notifies that the temperature detection sensor needs to be replaced when it determines that the temperature detection sensor is in the first abnormal state.

[0018] The invention of claim 8 is an image forming apparatus of claim 1, further comprising a job control unit that controls job execution, and when the abnormality determination unit determines that the temperature detection sensor is in the second abnormal state, it stops the job execution by the job control unit and transitions to a standby state.

[0019] The invention of claim 9 is characterized in that, in the image forming apparatus of claim 8, the abnormality determination unit notifies the transition to the standby state when it determines that the temperature detection sensor is in the second abnormal state.

[0020] The invention of claim 10 is characterized in that, in the image forming apparatus of claim 8 or 9, the abnormality determination unit cancels the standby state after the temperature detection sensor returns to a normal state from the second abnormal state.

[0021] The invention of claim 11 is characterized in that, in the image forming apparatus of claim 8 or 9, the abnormality determination unit continues the operation of heating the heating unit at a predetermined power when transitioning to the standby state, and cancels the standby state when a predetermined time has elapsed after transitioning to the standby state.

[0022] The invention of claim 12 is characterized in that, in the image forming apparatus of claim 7 or 9, it further comprises a display unit that displays various information to the user, and the abnormality determination unit notifies the user by displaying a notification screen on the display unit.

[0023] The invention of claim 13 is characterized in that, in the image forming apparatus of claim 7 or 9, it further comprises a communication unit that communicates with an external device, and the abnormality determination unit notifies the external device via the communication unit.

[0024] The invention of claim 14 is an image forming apparatus according to claim 1, 2, 8, or 9, further comprising a sheet storage section for storing sheets on which images are to be formed, and a dehumidifying heater for heating and dehumidifying the sheets stored in the sheet storage section, wherein the abnormality determination section is configured to drive the dehumidifying heater when the temperature detection sensor determines that the second abnormal state has occurred.

[0025] The invention according to claim 15 is the image forming apparatus according to claim 1, characterized in that the temperature detection sensor is a thermal sensor or a quantum sensor.

[0026] The invention of claim 16 is an abnormality detection method for detecting an abnormality in the temperature detection sensor in an image forming device equipped with a heating section that fixes an image formed on a sheet to the sheet and a temperature detection sensor that detects the surface temperature of the heating section, characterized in that it is determined whether either a first abnormal state of the temperature detection sensor or a second abnormal state different from the first abnormal state has occurred based on the temperature detected by the temperature detection sensor.

[0027] The invention of claim 17 is a program executed in an image forming device having a heating section that fixes an image formed on a sheet to the sheet and a temperature detection sensor that detects the surface temperature of the heating section, characterized in that the program causes the image forming device to execute a process that determines whether either a first abnormal state of the temperature detection sensor or a second abnormal state different from the first abnormal state has occurred based on the temperature detected by the temperature detection sensor. [Effects of the Invention]

[0028] According to the present invention, it is possible to determine whether the temperature detection sensor is in a first abnormal state or a second abnormal state based on the temperature detected by the temperature detection sensor, thereby reducing the number of times a service technician needs to be dispatched. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a diagram illustrating a conceptual configuration of an image forming apparatus. [Figure 2] FIG. 2 is a cross-sectional view showing an example of the configuration of a fixing device. [Figure 3] 10A and 10B are diagrams illustrating how toner and paper dust adhere to the detection surface of a temperature detection sensor. [Figure 4]FIG. 10 is a diagram showing a change in detected temperature when the detection surface of the temperature detection sensor is normal. [Figure 5] 10A and 10B are diagrams illustrating changes in detected temperature when a foreign object adheres to the detection surface of the temperature detection sensor. [Figure 6] FIG. 2 is a block diagram showing an example of the configuration of a control unit. [Figure 7] FIG. 10 is a diagram illustrating the relationship between a first threshold value and a second threshold value. [Figure 8] 10 is a flowchart illustrating an example of a processing procedure performed by an abnormality determination unit. [Figure 9] FIG. 10 is a diagram showing an example of a notification screen displayed when a first abnormal state occurs. [Figure 10] FIG. 10 is a diagram showing an example of a notification screen displayed when a second abnormal state occurs. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Elements common to the embodiments described below are designated by the same reference numerals, and redundant description thereof will be omitted.

[0031] FIG. 1 is a diagram illustrating a conceptual configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 shown in FIG. 1 is a printer capable of forming color images using a tandem system. The image forming apparatus 1 has a sheet storage unit 8 that stores multiple sheets 9, such as printing paper, and feeds the sheets one by one. The image forming apparatus 1 forms a color or monochrome image on the sheets 9 fed from the sheet storage unit 8. The image forming apparatus 1 then discharges the sheets 9 with the images formed thereon through a discharge port 5 provided at the top of the apparatus main body 1a and stacks them on a paper output tray 6. The image forming apparatus 1 includes a conveying unit 2, an image forming unit 3, and a fixing unit 4 inside the apparatus main body 1a. The conveying unit 2 conveys the sheets 9. The image forming unit 3 transfers and forms an image on the sheets 9 conveyed by the conveying unit 2. The fixing unit 4 applies heat and pressure to the sheets 9 with the transferred image, thereby fixing the image to the sheets 9. The image forming apparatus 1 forms an image on a sheet 9 by synchronously operating the conveying unit 2, the image forming unit 3, and the fixing device 4. The image forming apparatus 1 also includes a control unit 7 inside the apparatus main body 1a. The control unit 7 controls the operation of each unit, such as the conveying unit 2, the image forming unit 3, and the fixing device 4.

[0032] The conveying section 2 includes a sheet storage section 8 , a pickup roller 10 , a conveying roller 12 , a conveying path 13 , a timing roller 14 , and a secondary transfer roller 15 .

[0033] The sheet storage unit 8 is a tray-shaped container that stores sheets 9 such as printing paper. Various types of sheets 9 can be stored in the sheet storage unit 8, including thin paper, thick paper, plain paper, recycled paper, coated paper, and transparency film. While FIG. 1 shows a case in which the image forming apparatus 1 has one sheet storage unit 8, this is not limiting. For example, the image forming apparatus 1 may have multiple sheet storage units 8.

[0034] A pickup roller 10 and a transport roller 12 are provided near the sheet storage unit 8. The pickup roller 10 and the transport roller 12 are rollers for sending out sheets 9 stored in the sheet storage unit 8 to a transport path 13. The pickup roller 10 comes into contact with the uppermost sheet 9 stored in the sheet storage unit 8 and sends out the uppermost sheet 9 toward the transport roller 12. The transport roller 12 includes a feed roller 12a and a separation roller 12b, and has the function of feeding only the uppermost sheet 9 to the downstream transport path 13 when multiple sheets 9 are sent out by the pickup roller 10.

[0035] The sheet 9 sent into the conveying path 13 is then sent by timing rollers 14 toward secondary transfer rollers 15, where an image is transferred. The conveying path 13 is a path for conveying the sheet 9 in the direction of arrow F2 when the image forming apparatus 1 forms an image on the sheet 9. For example, the conveying unit 2 temporarily stops conveying the sheet 9 when the leading edge of the sheet 9 reaches the timing rollers 14. The conveying unit 2 then drives the timing rollers 14 in synchronization with the timing at which the toner image formed on the intermediate transfer belt 33 in the image forming unit 3 reaches the position of the secondary transfer roller 15, thereby conveying the sheet 9 to the position of the secondary transfer roller 15. As a result, the toner image (image) is transferred onto the surface of the sheet 9 as it passes the position of the secondary transfer roller 15. The sheet 9 is then guided to the fixing device 4, where the toner image is fixed, including heating and pressing.

[0036] A dehumidifying heater 18 is provided near the sheet storage unit 8. The dehumidifying heater 18 is a heater that is driven by the control unit 7. For example, the dehumidifying heater 18 is driven when it is determined that the moisture content of the sheets 9 is high, and heats the sheets 9 stored in the sheet storage unit 8 to reduce the moisture content of the sheets 9.

[0037] The image forming unit 3 forms toner images of four colors: Y (yellow), M (magenta), C (cyan), and K (black). The image forming unit 3 simultaneously transfers the four color toner images onto the sheet 9 when the sheet 9 conveyed by the conveying unit 2 passes the position of the secondary transfer roller 15. The image forming unit 3 includes a plurality of toner bottles 19 (19Y, 19M, 19C, 19K) corresponding to each of the four colors. The image forming unit 3 also includes a plurality of image forming units 20 (20Y, 20M, 20C, 20K) corresponding to each color. The image forming unit 3 also includes a plurality of exposure units 25 (25Y, 25M, 25C, 25K) corresponding to each color. The image forming unit 3 also includes a transfer unit 30.

[0038] The transfer unit 30 is an integrally assembled unit that includes an intermediate transfer belt 33 and multiple primary transfer rollers 34 (34Y, 34M, 34C, and 34K). The intermediate transfer belt 33 is an endless belt that is stretched over a pair of rollers 31 and 32 that are spaced a predetermined distance apart. The primary transfer rollers 34 (34Y, 34M, 34C, and 34K) are positioned inside the intermediate transfer belt 33 so as to face the image forming units 20.

[0039] Of the pair of rollers 31, 32, one roller 31 is a drive roller that is mounted on a drive shaft provided inside the device main body 1a and rotates. When the drive shaft of roller 31 is driven to rotate, intermediate transfer belt 33 circulates in the direction of arrow F1. The other roller 32 is mounted on a driven shaft provided inside the device main body 1a. Roller 32 is driven to rotate in accordance with the circulating movement of intermediate transfer belt 33. This pair of rollers 31, 32 are installed at positions separated by a predetermined distance inside the device main body 1a, with a certain tension applied to the intermediate transfer belt 33. By being mounted on the drive shaft, roller 31 is installed in a position facing secondary transfer roller 15. Roller 31 applies a pressing force to intermediate transfer belt 33 with intermediate transfer belt 33 sandwiched between roller 31 and secondary transfer roller 15. The roller 31 sandwiches and presses the sheet 9 transported by the transport unit 2 between the intermediate transfer belt 33 and the secondary transfer roller 15, thereby secondary transferring the toner image formed on the surface of the intermediate transfer belt 33 onto the sheet 9.

[0040] Image forming units 20Y, 20M, 20C, and 20K corresponding to each color are provided below transfer unit 30. Exposure sections 25Y, 25M, 25C, and 25K corresponding to each color are provided below each image forming unit 20Y, 20M, 20C, and 20K. Toner bottles 19Y, 19M, 19C, and 19K are disposed above transfer unit 30 and supply developer containing toner of each color to each image forming unit 20Y, 20M, 20C, and 20K.

[0041] The image forming units 20Y, 20M, 20C, and 20K have the same configuration and differ only in the color of the toner they use. That is, each of the image forming units 20Y, 20M, 20C, and 20K includes an image carrier 21 configured as a photosensitive drum. Each of the image forming units 20Y, 20M, 20C, and 20K also includes a charging unit 22, a developing device 23, and a cleaning blade 24, which are arranged around the image carrier 21. Note that, hereinafter, when there is no need to distinguish between the image forming units 20Y, 20M, 20C, and 20K, they will be collectively referred to as image forming units 20.

[0042] The image carrier 21 has a photosensitive layer on its drum surface. The image carrier 21 rotates clockwise while in contact with the intermediate transfer belt 33 to which transfer pressure is applied by the primary transfer roller 34 of the transfer unit 30, for example. A cleaning blade 24, a charging unit 22, and a developing unit 23 are arranged around the image carrier 21 along the rotation direction. The charging unit 22 includes a charging roller that contacts the surface of the image carrier 21 and charges the surface of the image carrier 21 to a predetermined charge. The exposure unit 25 exposes the photosensitive layer charged by the charging unit 22 based on image data, thereby forming an electrostatic latent image on the surface of the image carrier 21. The developing unit 23 is filled with a developer containing toner and carrier. The developing unit 23 supplies the developer to the surface of the image carrier 21 and develops the electrostatic latent image with toner, thereby forming a toner image on the surface of the image carrier 21. The toner image formed on the image carrier 21 is primarily transferred to the intermediate transfer belt 33 at a position where it comes into contact with the intermediate transfer belt 33. A bias voltage having a polarity opposite to that of the charged toner image formed on the surface of the image carrier 21 is applied to the primary transfer roller 34. The toner image formed on the surface of the image carrier 21 is primarily transferred to the intermediate transfer belt 33 by the electrostatic force.

[0043] Each image forming unit 20Y, 20M, 20C, and 20K cooperates with its respective primary transfer rollers 34Y, 34M, 34C, and 34K to perform primary transfer while sequentially superimposing toner images of each color onto the intermediate transfer belt 33, which circulates in the direction of arrow F1. Therefore, when the intermediate transfer belt 33 passes the position of the most downstream image forming unit 20K, a color image in which four color toner images are superimposed is formed on the surface of the intermediate transfer belt 33. When a monochrome image is formed on the sheet 9, the image forming units 20Y, 20M, and 20C do not operate, and only the image forming unit 20K corresponding to K (black) operates, forming a monochrome image using only K toner on the intermediate transfer belt 33.

[0044] When the toner image formed on the intermediate transfer belt 33 passes a position facing the secondary transfer roller 15, it comes into contact with the sheet 9 fed by the conveying unit 2 and is secondarily transferred onto the surface of the sheet 9. That is, when the toner image primarily transferred onto the intermediate transfer belt 33 comes into contact with the sheet 9, the secondary transfer roller 15 applies a bias voltage of opposite polarity to that of the charged toner, thereby secondarily transferring the toner image onto the sheet 9.

[0045] The sheet 9 onto which the toner image has been transferred at the position of the secondary transfer roller 15 is then conveyed to the fixing device 4. The fixing device 4 applies heat and pressure to the sheet 9 onto which the toner image has been transferred. The fixing device 4 has a fixing member 40 for fixing the toner image to the sheet 9. The fixing member 40 has a heating section 41 and a pressure section 42. The heating section 41 and the pressure section 42 abut against each other to form a nip section, and the sheet 9 is subjected to heat and pressure by passing through the nip section.

[0046] Fig. 2 is a cross-sectional view showing an example of the configuration of the fixing device 4. As shown in Fig. 2, a path 13a through which the sheet 9 passes is formed in the fixing device 4. This path 13a is connected to the conveying path 13 of the sheet 9 conveyed by the conveying unit 2. The heating unit 41 and the pressure unit 42 are disposed at positions facing each other with the path 13a in between.

[0047] The heating unit 41 includes a heating roller 43, a pad unit 45, and a fixing belt 46. The pad unit 45 is disposed opposite the pressure unit 42. The heating roller 43 includes a heater 44 as an internal heat source. The fixing belt 46 is an endless belt that is stretched across the pad unit 45 and the heating roller 43. The heating unit 41 rotates the heating roller 43 in the R1 direction, thereby circulating the fixing belt 46 in the F3 direction. The heater 44 is configured, for example, as a halogen lamp and heats the heating roller 43 by generating heat when turned on. The heater 44 heats the heating roller 43 from inside, thereby raising the surface of the heating roller 43 to a predetermined temperature. The heating of the heating roller 43 by the heater 44 also heats the fixing belt 46. The fixing belt 46, heated to the predetermined temperature, circulates in the F3 direction, thereby applying a heat treatment to the sheet 9 passing through the path 13a.

[0048] The pressure unit 42 includes a pressure roller 47 disposed opposite the heating unit 41. The pressure roller 47 contacts the fixing belt 46 at a position opposite the pad unit 45, forming a nip that sandwiches the sheet 9. When the sheet 9 passes through the nip, the pressure roller 47 applies a predetermined pressing force to the sheet 9, thereby applying pressure.

[0049] The image formed on the sheet 9 is fixed by heating and pressing processes performed by the heating unit 41 and the pressing unit 42. Guide members 48 and 49 are provided above the heating unit 41 and the pressing unit 42 to guide the leading edge of the sheet 9 to the downstream conveying path 13. The sheet 9 passes between the guide members 48 and 49 and is guided to the downstream conveying path 13.

[0050] A separation claw 49a is provided at the bottom of the guide member 49. The separation claw 49a extends from the bottom of the guide member 49 to a position near the surface of the pressure roller 47. The separation claw 49a is used to separate the leading edge of the sheet 9 from the surface of the pressure roller 47. Note that a separation claw having a similar function may also be provided at the bottom of the guide member 48.

[0051] The fixing device 4 also includes a temperature detection sensor 50 located near the heating unit 41. The temperature detection sensor 50 is a sensor that detects the surface temperature of the heating unit 41 without contact and is configured as a thermal sensor or a quantum sensor. The temperature detection sensor 50 has a detection surface 51 that detects temperature. The temperature detection sensor 50 is located with its detection surface 51 facing the heating unit 41, thereby detecting the surface temperature of the heating unit 41. The surface temperature of the heating unit 41 is detected by the temperature detection sensor 50, and the surface temperature of the heating unit 41 is controlled to a predetermined temperature. In other words, the control unit 7 controls the surface temperature of the heating unit 41 to be the predetermined temperature based on the temperature detected by the temperature detection sensor 50.

[0052] If the temperature detection sensor 50 is located above the heating unit 41, the temperature detected by the temperature detection sensor 50 will be affected by convection heat from the heating unit 41. When affected by convection heat, the temperature detected by the temperature detection sensor 50 will be higher than the actual surface temperature of the heating unit 41. To prevent such an effect from convection heat, the temperature detection sensor 50 is preferably installed below the heating unit 41, as shown in FIG. 2.

[0053] However, if the temperature detection sensor 50 is provided below the heating unit 41, the detection surface 51 is positioned facing upward so as to face the surface of the heating unit 41. As a result, as a job such as a print job is executed in the image forming apparatus 1, toner and paper dust may adhere to and accumulate on the detection surface of the temperature detection sensor 50.

[0054] FIG. 3 illustrates how toner and paper dust adhere to the detection surface 51 of the temperature detection sensor 50. When the image forming apparatus 1 executes a job, the sheet 9 onto which the toner 35 has been transferred passes between the heating unit 41 and the pressure unit 42, as shown in FIG. 3(a). At this time, the toner 35 transferred to the sheet 9 may peel off from the sheet 9 and adhere to the fixing belt 46. The toner 36 adhering to the fixing belt 46 circulates along with the fixing belt 46 in the direction F3. As the fixing belt 46 rotates along the outer circumferential surface of the heating roller 43, the toner 36 moves to a predetermined position on the outer circumferential surface of the heating roller 43, where it separates from the fixing belt 46 and falls. At this time, the toner 36 may fall onto the detection surface 51 of the temperature detection sensor 50 and accumulate.

[0055] 3(a), as the sheet 9 passes between the heating unit 41 and the pressure unit 42, paper dust 37 may fly off the sheet 9. The paper dust 37 floats in the internal space of the fixing device 4 and eventually falls. Such paper dust 37 gradually accumulates on the detection surface 51 of the temperature detection sensor 50.

[0056] 3(b) shows a state in which foreign matter 38 is attached to the detection surface 51 of the temperature detection sensor 50. When foreign matter 38 is attached to the detection surface 51 as shown in FIG. 3(b), the sensitivity of the temperature detection sensor 50 decreases, and the surface temperature of the heating unit 41 cannot be detected accurately. Specifically, as the amount of foreign matter 38 attached to the detection surface 51 increases, the temperature detected by the temperature detection sensor 50 becomes lower than the actual surface temperature of the heating unit 41. In this case, the control unit 7 will no longer be able to appropriately control the surface temperature of the heating unit 41.

[0057] For example, the toner 36 that peels off from the sheet 9 may not be in the form of particles but may be in the form of clumps. If such clumps of toner 36 adhere to the detection surface 51 of the temperature detection sensor 50, the sensitivity of the temperature detection sensor 50 will drop sharply. Such a sudden drop in sensitivity can occur during job execution.

[0058] Meanwhile, paper dust 37 and particulate toner gradually accumulate on the detection surface 51 of the temperature detection sensor 50. In this case, the sensitivity of the temperature detection sensor 50 decreases gradually. When the amount of accumulated paper dust 37 and the like is small, the impact of foreign matter 38 is small. Therefore, the control unit 7 can appropriately control the surface temperature of the heating unit 41 based on the temperature detected by the temperature detection sensor 50. However, if the image forming apparatus 1 is used for a long period of time and the amount of foreign matter 38 adhering to the detection surface 51 exceeds a predetermined amount, the control unit 7 will no longer be able to appropriately control the surface temperature of the heating unit 41.

[0059] Therefore, if toner 36 or paper dust 37 adheres to the detection surface 51 of the temperature detection sensor 50 as foreign matter 38 and the sensitivity of the temperature detection sensor 50 drops below a predetermined level, it is necessary to replace the temperature detection sensor 50 or the fixing device 4. In other words, if an abnormality occurs in the detected temperature of the temperature detection sensor 50 due to the adhesion of toner 36 or paper dust 37, the abnormality becomes a first abnormal state that requires replacement of the temperature detection sensor 50 or the fixing device 4.

[0060] Condensation may occur on the detection surface 51 of the temperature detection sensor 50. For example, if the image forming apparatus 1 is installed in a high-humidity environment, moisture may penetrate the sheet 9 stored in the sheet storage unit 8. When such a sheet 9 passes through the fixing device 4, the moisture in the sheet 9 evaporates due to heating by the heating unit 41. This may cause high humidity in the internal space of the fixing device 4, resulting in condensation on the detection surface 51 of the temperature detection sensor 50. For example, when the image forming apparatus 1 executes a job in which images are continuously formed on multiple sheets 9, the condensation on the detection surface 51 gradually worsens. The condensation on the detection surface 51 also becomes foreign matter 38 as shown in FIG. 3B. Therefore, even if condensation occurs on the detection surface 51, the sensitivity of the temperature detection sensor 50 also decreases. The decrease in sensitivity due to condensation gradually progresses during the execution of the job.

[0061] However, the condensation on the detection surface 51 will disappear naturally. When the condensation on the detection surface 51 disappears, the sensitivity of the temperature detection sensor 50 will return to normal. Therefore, even if condensation adheres to the detection surface 51 and the sensitivity of the temperature detection sensor 50 drops below the predetermined sensitivity, there is no need to replace the temperature detection sensor 50 or the fixing device 4. In other words, if condensation adheres to the detection surface 51 and an abnormality occurs in the detected temperature of the temperature detection sensor 50, the abnormality will become a second abnormal state that will be resolved over time.

[0062] FIG. 4 shows the change in the detected temperature when the detection surface 51 of the temperature detection sensor 50 is normal. After a job starts to be executed in the image forming apparatus 1, the fixing device 4 starts driving the heater 44 at time t1 to heat the surface of the heating unit 41 to a predetermined temperature Tt. The temperature detected by the temperature detection sensor 50 starts to rise from time t1 and reaches the predetermined temperature Tt at time t2. When the control unit 7 detects that the temperature detected by the temperature detection sensor 50 has reached the predetermined temperature Tt, it controls the heater 44 thereafter to maintain the predetermined temperature Tt until the job is completed. If there is no abnormality in the temperature detected by the temperature detection sensor 50, the control unit 7 can maintain the surface temperature of the heating unit 41 at the predetermined temperature Tt. The predetermined temperature Tt is preset depending on the size and type of the sheet 9.

[0063] 5 is a diagram showing changes in the detected temperature when a foreign substance 38 adheres to the detection surface 51 of the temperature detection sensor 50. As described above, after execution of a job is started in the image forming apparatus 1, the fixing device 4 starts driving the heater 44 at time t1 to heat the surface of the heating unit 41 to a predetermined temperature Tt. The temperature detected by the temperature detection sensor 50 starts to rise from time t1 and reaches the predetermined temperature Tt at time t2. When the control unit 7 detects that the temperature detected by the temperature detection sensor 50 has reached the predetermined temperature Tt, it controls the heater 44 thereafter to maintain the predetermined temperature Tt until execution of the job is completed.

[0064] Thereafter, at time t3, when foreign matter 38 adheres to detection surface 51, the temperature detected by temperature detection sensor 50 drops. If the temperature detected by temperature detection sensor 50 drops below predetermined temperature Te even though heater 44 is driven with a constant power, control unit 7 detects that an abnormality has occurred in temperature detection sensor 50.

[0065] For example, if a clump of toner 36 adheres to the detection surface 51 during job execution, the temperature detected by the temperature detection sensor 50 will appear as a change C1 shown in Figure 5. The clump of toner 36 will rapidly reduce the sensitivity of the temperature detection sensor 50. As a result, the amount of change ΔT in the change C1 per unit time Δt will increase.

[0066] Furthermore, if condensation occurs on the detection surface 51 during the execution of a job, the temperature detected by the temperature detection sensor 50 will appear as a change C2 shown in Fig. 5. Condensation on the detection surface 51 progresses gradually during the execution of the job. Therefore, the amount of change ΔT of the change C2 per unit time Δt is smaller than the amount of change ΔT of the change C1.

[0067] Furthermore, when paper dust 37 or particulate toner gradually accumulates on detection surface 51, the temperature detected by temperature detection sensor 50 appears as change C3 shown in Figure 5. When paper dust 37 or particulate toner accumulates on detection surface 51, the decrease in sensitivity of temperature detection sensor 50 is the most gradual. Therefore, the change ΔT of change C3 per unit time Δt is even smaller than the change ΔT of change C2.

[0068] When an abnormality occurs in the temperature detected by the temperature detection sensor 50, the control unit 7 of this embodiment determines whether the abnormality is a first abnormal state or a second abnormal state based on the amount of change ΔT in the detected temperature. An example of the detailed configuration of the control unit 7 will be described below.

[0069] FIG. 6 is a block diagram showing an example configuration of the control unit 7. The control unit 7 includes a processor 60 and a storage unit 61. The processor 60 is a hardware processor configured with a CPU (Central Processing Unit) or the like. The storage unit 61 is a non-volatile storage device configured with a hard disk drive (HDD), a solid state drive (SSD), or the like. The storage unit 61 stores a program 62, a first threshold value TH1, and a second threshold value TH2. The program 62 is a computer-readable program executed by the processor 60. The first threshold value TH1 and the second threshold value TH2 are threshold values ​​that are set in advance to determine whether the abnormal state of the temperature detection sensor 50 is a first abnormal state or a second abnormal state.

[0070] The control unit 7 controls the operations of the conveying unit 2, the image forming unit 3, and the fixing device 4. In addition, the control unit 7 is connected to an operation panel 70 and a communication unit 73.

[0071] The operation panel 70 is a user interface when a user uses the image forming apparatus 1. The operation panel 70 includes a display unit 71 that displays various information, and an operation unit 72 that accepts user operations. The display unit 71 is configured, for example, by a color liquid crystal display. The operation unit 72 is configured by touch keys, push button keys, etc.

[0072] The communication unit 73 connects the image forming apparatus 1 to a network such as a LAN (Local Area Network) and communicates with external devices via the network. For example, the control unit 7 receives jobs such as print jobs sent from external devices via the communication unit 73. The external devices include server devices at service centers that provide maintenance services for the image forming apparatus 1. Therefore, the control unit 7 can notify the server devices at the service centers of various types of information via the communication unit 73.

[0073] The processor 60 reads and executes the program 62 from the storage unit 61. As a result, the processor 60 functions as a job control unit 63 and an abnormality determination unit 64.

[0074] The job control unit 63 controls the execution of jobs in the image forming apparatus 1. The job control unit 63 drives the conveying unit 2, the image forming unit 3, and the fixing device 4, and controls the operation of forming an image on a sheet 9. At this time, the job control unit 63 drives the heater 44 of the heating unit 41 based on the temperature detected by the temperature detection sensor 50, and controls the surface temperature of the heating unit 41 to a predetermined temperature Tt. When driving the heater 44, the job control unit 63 also limits, for example, the power supplied to the heater 44 to within a predetermined range. This allows the job control unit 63 to prevent the heating unit 41 from being heated to an abnormally high temperature.

[0075] 6, the fixing device 4 is provided with a detection circuit 53 connected to the temperature detection sensor 50. The detection circuit 53 amplifies the analog signal output from the temperature detection sensor 50 and converts the amplified analog signal into a digital signal. This digital signal is the temperature detected by the temperature detection sensor 50. The control unit 7 obtains the temperature detected by the temperature detection sensor 50 based on the digital signal output from the detection circuit 53.

[0076] The abnormality determination unit 64 monitors the temperature detected by the temperature detection sensor 50 while the job control unit 63 is executing a job, and determines whether an abnormality has occurred in the temperature detection sensor 50. For example, when the temperature detected by the temperature detection sensor 50 drops to a predetermined temperature Te, the abnormality determination unit 64 detects that an abnormality has occurred in the temperature detection sensor 50.

[0077] When an abnormality in the temperature detection sensor 50 is detected, the abnormality determination unit 64 calculates the amount of change ΔT in the temperature detected by the temperature detection sensor 50. That is, the abnormality determination unit 64 calculates the amount of change ΔT in the detected temperature per unit time Δt. The abnormality determination unit 64 reads out a first threshold value TH1 and a second threshold value TH2 from the memory unit 61. The abnormality determination unit 64 compares the calculated amount of change ΔT with the first threshold value TH1 and the second threshold value TH2, and determines whether the abnormal state of the temperature detection sensor 50 is a first abnormal state or a second abnormal state.

[0078] 7 is a diagram showing the first threshold value TH1 and the second threshold value TH2. As shown in FIG. 7, the first threshold value TH1 is a value greater than the second threshold value TH2. The first threshold value TH1 is a threshold value for distinguishing between a first abnormal state in which clumps of toner 36 have adhered to the detection surface 51 of the temperature detection sensor 50 and a second abnormal state in which condensation has adhered to the detection surface 51. The second threshold value TH2 is a threshold value for distinguishing between the second abnormal state in which condensation has adhered to the detection surface 51 and the first abnormal state in which paper dust 37 or particulate toner has accumulated on the detection surface 51.

[0079] 7, when the amount of change ΔT in the detected temperature is greater than the first threshold value TH1, the abnormality determination unit 64 determines that a first abnormal state has occurred, in which clumps of toner 36 have adhered to the detection surface 51. When the amount of change ΔT in the detected temperature is smaller than the second threshold value TH2, the abnormality determination unit 64 determines that a first abnormal state has occurred, in which paper dust 37 or the like has adhered to the detection surface 51. In other words, when the amount of change ΔT in the detected temperature is greater than the first threshold value TH1 or when the amount of change ΔT in the detected temperature is smaller than the second threshold value TH2, the abnormality determination unit 64 determines that a first abnormal state has occurred.

[0080] Furthermore, as shown in FIG. 7, when the change ΔT in the detected temperature is greater than or equal to the second threshold value TH2 and less than or equal to the first threshold value TH1, the abnormality determination unit 64 determines that a second abnormal state has occurred in which condensation has adhered to the detection surface 51.

[0081] If the temperature detection sensor 50 determines that the first abnormal state is present during job execution, the abnormality determination unit 64 commands the job control unit 63 to forcibly terminate execution of the job. This causes the fixing device 4 to terminate the heating operation of the heating unit 41. By forcibly terminating execution of the job when the first abnormal state is present, it is possible to prevent poor fixing of the image formed on the sheet 9.

[0082] Furthermore, if it is determined that the temperature detection sensor 50 is in the second abnormal state during job execution, the abnormality determination unit 64 commands the job control unit 63 to temporarily suspend execution of the job. Then, the abnormality determination unit 64 transitions the image forming apparatus 1 to a standby state. In this case, the standby state continues until the second abnormal state is resolved.

[0083] When the image forming apparatus 1 is in standby mode, the abnormality determination unit 64 continues the operation of heating the heating unit 41 of the fixing device 4 at a predetermined power. In this case, the predetermined power is lower than the power required to maintain the heating unit 41 at a predetermined temperature Tt. In other words, the abnormality determination unit 64 continues the operation of heating the heating unit 41 at a lower power than during normal control, thereby maintaining the interior of the fixing device 4 at a relatively high temperature. This shortens the time it takes for the condensation on the detection surface 51 to disappear, allowing the image forming apparatus 1 to return to standby mode more quickly.

[0084] Furthermore, when the abnormality determination unit 64 determines that the temperature detection sensor 50 is in the second abnormal state, it drives the dehumidifying heater 18. This reduces the amount of moisture contained in the sheets 9 stored in the sheet storage unit 8. Therefore, when the sheets 9 fed from the sheet storage unit 8 are subjected to the fixing process in the fixing device 4 after returning from the standby state, the amount of moisture evaporating from the sheets 9 can be reduced. Therefore, it is possible to prevent the temperature detection sensor 50 from entering the second abnormal state again after returning from the standby state.

[0085] The abnormality determination unit 64 includes a notification unit 65. The notification unit 65 functions when the abnormality determination unit 64 detects an abnormality in the temperature detection sensor 50. When it is determined that the abnormal state of the temperature detection sensor 50 is the first abnormal state, the notification unit 65 notifies that the temperature detection sensor 50 is in the first abnormal state. When it is determined that the abnormal state of the temperature detection sensor 50 is the second abnormal state, the notification unit 65 notifies that the temperature detection sensor 50 is in the second abnormal state. The notifications by the notification unit 65 include notifications to the user of the image forming apparatus 1 and notifications to the server device at the service center.

[0086] When the first abnormal state is detected, the notification unit 65 notifies the user of the image forming apparatus 1 that the temperature detection sensor 50 or the fixing device 4 needs to be replaced. For example, the notification unit 65 notifies the user by displaying a notification screen on the display unit 71 of the operation panel 70. The notification unit 65 also notifies the server device at the service center via the communication unit 73 that the temperature detection sensor 50 or the fixing device 4 needs to be replaced. Upon receiving the notification from the abnormality determination unit 64, the server device requests a service technician located near the location where the image forming apparatus 1 is installed to replace the temperature detection sensor 50 or the fixing device 4.

[0087] Furthermore, if a second abnormal state is detected, the notification unit 65 notifies the user of the image forming apparatus 1 that job execution will be temporarily suspended and the apparatus will enter a standby state. At this time, the notification unit 65 may also notify the server device at the service center via the communication unit 73 that the apparatus will enter a standby state. By notifying the server device that the image forming apparatus 1 will enter a standby state, an operator can respond appropriately even if the service center receives an inquiry from a user. In other words, the operator can inform the user that the apparatus will return from the standby state once the condensation on the temperature detection sensor 50 disappears.

[0088] 8 is a flowchart showing an example of a processing procedure by the abnormality determination unit 64. This processing is performed by the processor 60 executing the program 62. The abnormality determination unit 64 repeatedly executes the processing based on the flowchart shown in FIG. 8. When the abnormality determination unit 64 starts this processing, it determines whether or not a job is being executed by the job control unit 63 (step S10). If a job is not being executed (NO in step S10), the fixing device 4 is not operating, and therefore the processing by the abnormality determination unit 64 ends.

[0089] If a job is being executed (YES in step S10), the abnormality determination unit 64 determines whether an abnormality in the temperature detected by the temperature detection sensor 50 has been detected (step S11). For example, if the temperature detected by the temperature detection sensor 50 drops to a predetermined temperature Te, the abnormality determination unit 64 determines that the detected temperature is abnormal. If it is determined that the detected temperature is not abnormal (NO in step S11), the processing by the abnormality determination unit 64 ends.

[0090] If it is determined that the detected temperature is abnormal (YES in step S11), the abnormality determination unit 64 calculates a change amount ΔT in the detected temperature (step S12). For example, the abnormality determination unit 64 measures the temperature detected by the temperature detection sensor 50 for a predetermined time, and obtains the change amount ΔT by calculating the difference between the detected temperature at the start and end of the measurement. Next, the abnormality determination unit 64 determines whether the change amount ΔT is greater than a first threshold value TH1 or less than a second threshold value TH2 (step S13).

[0091] If the amount of change ΔT is greater than the first threshold value TH1 or less than the second threshold value TH2 (YES in step S13), the abnormality determination unit 64 determines that the abnormal state of the temperature detection sensor 50 is the first abnormal state (step S14). In this case, the abnormality determination unit 64 forcibly terminates the execution of the job (step S15). Then, the abnormality determination unit 64 executes notification processing by the notification unit 65 (step S16).

[0092] 9 is displayed on the display unit 71 of the operation panel 70. This notification screen G1 displays a message 81 indicating that the temperature detection sensor 50 is in the first abnormal state, and a message 82 indicating that the fixing device 4 or the temperature detection sensor 50 needs to be replaced. By checking the notification screen G1 displayed on the display unit 71, the user can understand that replacement work by a service technician is required.

[0093] In step S16, the notification unit 65 notifies the server device at the service center that it is necessary to replace the fixing device 4 or the temperature detection sensor 50. In response, the server device requests a service technician to replace the fixing device 4 or the temperature detection sensor 50.

[0094] On the other hand, if the change amount ΔT in the detected temperature is equal to or greater than the second threshold value TH2 and equal to or less than the first threshold value TH1 (NO in step S13), the abnormality determination unit 64 determines that the abnormal state of the temperature detection sensor 50 is the second abnormal state (step S17). In this case, the abnormality determination unit 64 temporarily suspends the execution of the job (step S18). Then, the abnormality determination unit 64 executes a notification process by the notification unit 65 (step S19).

[0095] In the notification process of step S19, a notification screen G2 such as that shown in FIG. 10 is displayed on the display unit 71 of the operation panel 70. This notification screen G2 displays a message 83 indicating that the temperature detection sensor 50 is in the second abnormal state and a message 84 indicating that the image forming apparatus 1 will transition to a standby state. By checking the notification screen G2 displayed on the display unit 71, the user can understand that replacement by a service technician is not necessary and that the image forming apparatus 1 will automatically return to normal once the condensation is resolved. By displaying the notification screen G2 shown in FIG. 10, the notification unit 65 can reduce the number of times a service technician is called in. At this time, the notification unit 65 may notify the server device of the service center that the image forming apparatus 1 will transition to a standby state.

[0096] After performing the notification process, the abnormality determination unit 64 transitions the image forming apparatus 1 to a standby state (step S20). At this time, the abnormality determination unit 64 continues the heating operation of the heating unit 41 of the fixing device 4. This allows the condensation on the detection surface 51 of the temperature detection sensor 50 to be quickly eliminated.

[0097] Furthermore, the abnormality determination unit 64 drives the dehumidifying heater 18 provided near the sheet storage unit 8 (step S21). This reduces the amount of moisture contained in the sheets 9 stored in the sheet storage unit 8, and prevents the temperature detection sensor 50 from entering the second abnormal state again after the job is restarted.

[0098] Thereafter, the abnormality determination unit 64 determines whether the second abnormal state has been resolved and the image forming apparatus 1 has returned to a normal state (step S22). The abnormality determination unit 64 then continues the standby state until the image forming apparatus 1 returns to a normal state. For example, the abnormality determination unit 64 determines that the image forming apparatus 1 has returned to a normal state when a predetermined time has elapsed since the image forming apparatus 1 entered the standby state. When the abnormality determination unit 64 determines that the image forming apparatus 1 has returned to a normal state (YES in step S22), the image forming apparatus 1 resumes the execution of the job that was paused (step S23). In other words, if the temperature detection sensor 50 is in the second abnormal state, the image forming apparatus 1 automatically returns to a normal state once the second abnormal state is resolved. Therefore, the image forming apparatus 1 of this embodiment has the advantage of reducing the need for a service technician and reducing downtime.

[0099] As described above, the image forming apparatus 1 of this embodiment includes a heating unit 41 that fixes an image formed on a sheet 9 to the sheet 9, and a temperature detection sensor 50 that detects the surface temperature of the heating unit 41. When heating the heating unit 41, the image forming apparatus 1 controls the surface temperature of the heating unit 41 to a predetermined temperature based on the temperature detected by the temperature detection sensor 50. In this configuration, the abnormality determination unit 64 monitors the temperature detected by the temperature detection sensor 50. The abnormality determination unit 64 then determines whether an abnormality has occurred in the temperature detection sensor 50 based on the temperature detected by the temperature detection sensor 50. If the abnormality determination unit 64 determines that an abnormality has occurred in the temperature detection sensor 50, the abnormality determination unit 64 determines whether the abnormality in the temperature detection sensor 50 is a first abnormal state or a second abnormal state based on the detected temperature.

[0100] As described above, the first abnormal state is an abnormality that requires replacement of the temperature detection sensor 50 or the fixing device 4. Therefore, to resolve the first abnormal state, a service technician must visit the installation location of the image forming apparatus 1 and perform the replacement work. In contrast, the second abnormal state is an abnormality that returns to a normal state when the condensation disappears. Therefore, in the case of the second abnormal state, a service technician does not need to visit the installation location of the image forming apparatus 1. Therefore, when the temperature detection sensor 50 is abnormal, the image forming apparatus 1 can reduce the number of times a service technician needs to visit by determining whether the abnormality is the first abnormal state or the second abnormal state.

[0101] Although a preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible.

[0102] For example, in the above embodiment, the image forming apparatus 1 is a color machine capable of forming a color image on the sheet 9. However, the image forming apparatus 1 to which the present invention is applicable is not limited to a color machine. For example, the image forming apparatus 1 may be a monochrome machine capable of forming only a monochrome image on the sheet 9.

[0103] Furthermore, the program 62 executed by the processor 60 of the control unit 7 described in the above embodiment is not limited to being pre-installed in the image forming apparatus 1. In other words, the program 62 executed by the processor 60 of the control unit 7 may be a program that can be traded on its own. In this case, the program 62 may be provided online via a network such as the Internet, or may be provided in a state recorded on a computer-readable recording medium such as a USB memory. [Explanation of symbols]

[0104] 1. Image forming device 4 Fixing device 7 Control Unit 8 Seat storage area 9 sheets 18 Dehumidifying heater 41 Heating section 43 Heating roller 50 Temperature detection sensor 51 Detection surface 60 processors 62 Programs 63 Job control section 64 Abnormality determination unit 65 Notification Department 70 Operation Panel 71 Display section 73 Communications Department TH1 First threshold TH2 Second threshold

Claims

1. a heating section for fixing an image formed on a sheet to the sheet; a temperature detection sensor for detecting a surface temperature of the heating unit; an abnormality determination unit that determines whether or not a first abnormal state of the temperature detection sensor or a second abnormal state different from the first abnormal state has occurred, based on the temperature detected by the temperature detection sensor; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the abnormality determination unit determines whether the abnormality is the first abnormal state or the second abnormal state based on a change in the temperature detected by the temperature detection sensor.

3. 3. The image forming apparatus according to claim 1, wherein the temperature detection sensor is provided below the heating unit and is positioned facing upward with its detection surface, which detects the surface temperature of the heating unit, facing the surface of the heating unit.

4. the first abnormal state is a state in which paper dust or toner adheres to a detection surface of the temperature detection sensor, 4. The image forming apparatus according to claim 3, wherein the second abnormal state is a state in which condensation occurs on the detection surface of the temperature detection sensor.

5. The image forming apparatus according to claim 2, characterized in that the abnormality determination unit calculates the amount of change in the temperature detected by the temperature detection sensor when the temperature detected by the temperature detection sensor drops below a predetermined value while control is being performed to heat the heating unit to a predetermined target temperature.

6. The image forming apparatus according to claim 2 or 5, characterized in that the abnormality determination unit determines that the first abnormal state exists when the amount of change is greater than a first threshold value or when the amount of change is smaller than a second threshold value that is smaller than the first threshold value, and determines that the second abnormal state exists when the amount of change is greater than or equal to the second threshold value and less than or equal to the first threshold value.

7. 2. The image forming apparatus according to claim 1, wherein the abnormality determination unit notifies the user that the temperature detection sensor needs to be replaced when it determines that the temperature detection sensor is in the first abnormal state.

8. a job control unit that controls the execution of jobs; Further provided with 2. The image forming apparatus according to claim 1, wherein the abnormality determination unit, when determining that the temperature detection sensor is in the second abnormal state, stops the execution of the job by the job control unit and transitions to a standby state.

9. 9. The image forming apparatus according to claim 8, wherein the abnormality determination unit notifies the image forming apparatus of a transition to the standby state when the temperature detection sensor determines that the temperature detection sensor is in the second abnormal state.

10. 10. The image forming apparatus according to claim 8, wherein the abnormality determination unit cancels the standby state after the temperature detection sensor has returned to a normal state from the second abnormal state.

11. The image forming apparatus according to claim 8 or 9, characterized in that the abnormality determination unit continues the operation of heating the heating unit at a predetermined power when transitioning to the standby state, and cancels the standby state when a predetermined time has elapsed after transitioning to the standby state.

12. A display unit that displays various information to the user; Further provided with 10. The image forming apparatus according to claim 7, wherein the abnormality determination unit notifies the user by displaying a notification screen on the display unit.

13. a communication unit for communicating with an external device; Further provided with 10. The image forming apparatus according to claim 7, wherein the abnormality determination unit notifies the external device via the communication unit.

14. a sheet storage section that stores sheets on which images are to be formed; a dehumidifying heater that heats and dehumidifies the sheets stored in the sheet storage section; Further provided with 10. The image forming apparatus according to claim 1, wherein the abnormality determination unit drives the dehumidifying heater when the temperature detection sensor determines that the temperature detection sensor is in the second abnormal state.

15. 2. The image forming apparatus according to claim 1, wherein the temperature detection sensor is a thermal sensor or a quantum sensor.

16. a heating section for fixing an image formed on a sheet to the sheet; a temperature detection sensor for detecting a surface temperature of the heating unit; An abnormality detection method for determining an abnormality in the temperature detection sensor in an image forming apparatus comprising: An abnormality detection method characterized by determining whether a first abnormal state of the temperature detection sensor or a second abnormal state different from the first abnormal state has occurred based on the temperature detected by the temperature detection sensor.

17. a heating section for fixing an image formed on a sheet to the sheet; a temperature detection sensor for detecting a surface temperature of the heating unit; A program executed in an image forming apparatus comprising: a process of determining whether or not a first abnormal state of the temperature detection sensor or a second abnormal state different from the first abnormal state has occurred, based on the temperature detected by the temperature detection sensor; A program characterized by executing the following.

Images