Fixing apparatus and image forming apparatus

Abstract

To provide a fixing device and the like that, when a measured value of a non-contact temperature sensor does not match a predicted value, can specify if the detection performance of the non-contact temperature sensor is reduced.SOLUTION: A fixing device comprises: a fixing member that is heated by a heat source; a pressure member that forms a nip part with the fixing member; a first temperature sensor that measures the temperature of the fixing member in a non-contact manner; and a second temperature sensor that measures the temperature of the pressure member, and the fixing device can execute a sequence to heat the fixing member with the heat source. The fixing device executes a first sequence during calibration to correct an output value from the first temperature sensor, and during the execution of the first sequence, the first temperature sensor measures the temperature of the fixing member, and the second temperature sensor measures the temperature of the pressure member.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a fixing device and an image forming apparatus.

Background Art

[0002] In a conventional image forming apparatus, in order to control the temperature of a fixing member heated by a heat source, it is known to measure the temperature of the fixing member by a non-contact temperature sensor such as a thermopile. For example, when the lens of the non-contact temperature sensor is contaminated by toner scattering in the image forming apparatus, the detection performance of the non-contact temperature sensor deteriorates, and the measured temperature of the fixing member becomes lower than the actual temperature. In this case, if temperature control is performed according to the measured temperature of the non-contact temperature sensor, the fixing member may be overheated compared to the temperature control corresponding to the actual temperature, resulting in problems such as smoking and ignition.

[0003] Techniques for correcting the detection error and output value of a non-contact temperature sensor are known. For example, in Patent Document 1, the detected temperature of a temperature sensor that measures the temperature of a fixing member non-contact is corrected using the average value of the detected temperatures during a sequence operation performed in advance and the average value of the detected temperatures during the sequence operation in calibration. In Patent Document 2, a contact type temperature sensor that contacts a fixing roller and a non-contact type temperature sensor that does not contact the fixing roller are provided, and the non-contact type temperature sensor measures the same area of the fixing roller as the measurement area of the contact type temperature sensor. The measurement result of the non-contact type temperature sensor is corrected according to the difference between the measurement temperature of the non-contact type temperature sensor and the measurement temperature of the contact type temperature sensor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] In image forming apparatuses, it is known that a pressure member, such as a pressure roller, is pressed against a fixing member to form a nip at the contact point. In such a configuration, a portion of the thermal energy supplied to the fixing member during heating is transferred to the pressure member via the nip. As the hardness of the pressure member decreases with the progression of the image forming apparatus's product life, the width of the nip increases, making it easier for thermal energy to transfer from the fixing member to the pressure member.

[0006] For example, in the method described in Patent Document 1, the reference temperature of the fixing member detected during a pre-executed sequence operation is set to "150°C," and the measured temperature of the fixing member detected during the sequence operation in calibration is set to "145°C." In this case, the reason why the measured temperature is "5°C" lower than the reference temperature is thought to be a decrease in the detection performance of the non-contact temperature sensor and an increase in the width of the nip portion, which caused heat to transfer to the pressurizing member.

[0007] If the former is the cause, the actual temperature of the fixing member is the same as the reference temperature, "150°C". In this case, if the output value of the temperature sensor is corrected to be "5°C" higher than the measured temperature, the output value of the temperature sensor will match the actual temperature of the fixing member, and the heating temperature of the fixing member can be accurately controlled based on this output value. On the other hand, if the latter is the cause, the actual temperature of the fixing member will be "145°C", which is lower than the reference temperature. In this case, if the output value of the temperature sensor is corrected to be "5°C" higher than the measured temperature, the output value of the temperature sensor will not match the actual temperature of the fixing member, and the heating temperature of the fixing member cannot be accurately controlled.

[0008] Both Patent Documents 1 and 2 correct the temperature sensor based on the measured temperature of the fixing member, and do not take into account the thermal energy transferred from the fixing member to the pressure roller. Therefore, even if the actual temperature measured by the non-contact temperature sensor does not match the reference temperature due to the passage of the product life, the above-mentioned correction may still be performed, which could make it impossible to accurately control the heating temperature of the fixing member.

[0009] In view of the above-mentioned problems, this disclosure aims to provide a fixing device, etc., that can identify whether the detection performance of a non-contact temperature sensor has deteriorated when the measured value of the non-contact temperature sensor does not match the expected value. [Means for solving the problem]

[0010] To solve the above-mentioned problems, the fixing apparatus according to the present disclosure comprises a fixing member heated by a heat source, a pressurizing member that forms a nip portion between itself and the fixing member, a first temperature sensor that measures the temperature of the fixing member in a non-contact manner, and a second temperature sensor that measures the temperature of the pressurizing member, and is capable of executing a sequence of heating the fixing member with the heat source, wherein the first sequence is executed during calibration to correct the output value of the first temperature sensor, the first temperature sensor measures the temperature of the fixing member and the second temperature sensor measures the temperature of the pressurizing member during the execution of the first sequence.

[0011] The image forming apparatus according to this disclosure comprises a fixing device and a control unit, wherein the control unit corrects the output value of the first temperature sensor based on a first comparison result obtained by comparing the measurement value of the first temperature sensor in the first sequence with the measurement value of the first temperature sensor in a previously executed second sequence, and a second comparison result obtained by comparing the measurement value of the second temperature sensor in the first sequence with the measurement value of the second temperature sensor in the second sequence. [Brief explanation of the drawing]

[0012] [Figure 1]It is a cross-sectional view showing a schematic configuration of an image forming apparatus. [Figure 2] It is a schematic configuration diagram of a fixing device. [Figure 3] It is a graph showing temperature changes during a sequence. [Figure 4] It is a diagram showing the configuration of a predicted temperature table according to the first embodiment. [Figure 5] It is a flowchart of calibration processing according to the first embodiment. [Figure 6A] It is a graph showing temperature changes during a sequence in a sensor degradation state. [Figure 6B] It is a graph showing temperature changes during a sequence in a nip change state. [Figure 6C] It is a graph showing temperature changes of a fixing belt in each state. [Figure 7A] It is a diagram showing the data configuration of a predicted temperature table according to the second embodiment. [Figure 7B] It is a specific example of a predicted temperature table according to the second embodiment. [Figure 8] It is a flowchart of calibration processing according to the second embodiment. [Figure 9A] It is a diagram showing the data configuration of a predicted temperature table according to the third embodiment. [Figure 9B] It is a specific example of a predicted temperature table according to the third embodiment. [Figure 10] It is a flowchart of calibration processing according to the third embodiment. [Figure 11] It is a specific example of interpolating a predicted temperature table according to the third embodiment.

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Regarding the drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicate explanations are omitted.

[0014] <First Embodiment> The overall configuration of the image forming apparatus 1 will be described. FIG. 1 is a cross-sectional view showing the schematic configuration of the image forming apparatus 1. In the following description, the front side and the back side of the paper surface in FIG. 1 are defined as the front side and the back side of the image forming apparatus 1, respectively. The upper side, the lower side, the left side, and the right side of FIG. 1 are defined as the upper side, the lower side, the left side, and the right side of the image forming apparatus 1, respectively.

[0015] The image forming apparatus 1 is a multifunction peripheral (MFP) having functions such as a copying function, a printer function, a scanner function, and a facsimile function. It transmits the image of the document read by the image reading unit 18 to the outside, and forms an image of the read document image or the image received from the outside on a sheet in color or monochrome.

[0016] The image forming apparatus 1 includes an apparatus main body 11 including an image forming unit 12 and the like, and an image reading unit 18 disposed above it. A document feeder (ADF) 17 that is supported so as to be openable and closable is provided above the image reading unit 18. In the document feeder 17, the document placement table 19 of the image reading unit 18 can be opened to place a document by hand. Further, the document feeder 17 automatically conveys the placed document. The image reading unit 18 reads the placed document or the document conveyed from the document feeder 17 to generate image data.

[0017] The apparatus main body 11 is provided with a control unit 100 including a CPU, a memory, and the like, and an image forming unit 12 and the like. The control unit 100 is a controller for controlling the entire image forming apparatus 1, and realizes various functions by reading and executing various programs stored in the memory. The control unit 100 may be a MCU (Micro Control Unit) or a MPU (Micro Processor Unit), or may be an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or other circuits having an arithmetic function.

[0018] The image forming unit 12 includes an exposure unit 13, a developing unit 20, a photoreceptor unit 30, an intermediate transfer belt unit 40, a transfer roller 14, and a fixing device 50, etc. It forms an image on paper transported from the paper feed tray 15 or the manual feed tray 90, and discharges the image-formed paper to the output tray 16. Image data used to form an image on the paper includes image data read by the image reading unit 18 or image data transmitted from an external computer. The two units, the developing unit 20 and the photoreceptor unit 30, are integrated and separable from each other to form a process cartridge 10.

[0019] The image data handled by the image forming apparatus 1 corresponds to a color image using four colors: black (K), cyan (C), magenta (M), and yellow (Y). Therefore, the apparatus body 11 is equipped with four process cartridges 10 to form four different latent images corresponding to each color, and these constitute four image stations. The four process cartridges 10 are arranged in a single horizontal row along the direction of travel on the surface of the intermediate transfer belt 41.

[0020] The exposure unit 13 is configured as a laser scanning unit (LSU) equipped with a laser emitter and a reflective mirror, and forms an electrostatic latent image on the surface of the charged photoreceptor drum 31 corresponding to the image data by exposing the surface of the photoreceptor drum 31.

[0021] The photoreceptor unit 30 includes a photoreceptor drum 31, a charger 32, and a cleaner unit 33, etc. The photoreceptor drum 31 is an electrostatic latent image carrier in which a photosensitive layer is formed on the surface of a conductive cylindrical substrate, and is rotatable around an axis by a drive mechanism (not shown). The charger 32 charges the surface of the photoreceptor drum 31 to a predetermined potential. The cleaner unit 33 includes a cleaning blade, etc., and after the transfer of the toner image to the intermediate transfer belt 41, removes and recovers the toner remaining on the surface of the photoreceptor drum 31.

[0022] The developing unit 20 visualizes the electrostatic latent image formed on the surface of the photoreceptor drum 31 using four-color (YMCK) toner (forming a toner image), and includes a developing roller 21 and a transport member 22 for supplying toner to the photoreceptor drum 31. The developing roller 21 is positioned close to the photoreceptor drum 31 so as to follow its contour and is rotatable around its axis. The developing housing 23 of the developing unit 20 contains a developer containing toner and a carrier, and the toner is supplied to the photoreceptor drum 31 via the developing roller 21.

[0023] The intermediate transfer belt unit 40 comprises an intermediate transfer belt 41, a drive roller 42, a driven roller 43, and an intermediate transfer roller 44, and is positioned above the photoreceptor drum 31. The intermediate transfer belt 41 is provided to contact each photoreceptor drum 31, and by using the intermediate transfer roller 44 to sequentially transfer the toner images of each color formed on each photoreceptor drum 31 onto the intermediate transfer belt 41, a multi-color toner image is formed on the intermediate transfer belt 41. A transfer roller 14 is positioned near the drive roller 42, and as the paper passes through the nip area between the intermediate transfer belt 41 and the transfer roller 14 of the secondary transfer section, the toner image formed on the intermediate transfer belt 41 is transferred to the paper. Above the transfer roller 14, a fixing device 50 is positioned to heat-fix the toner image transferred to the paper, but details will be described later.

[0024] The main body of the device 11 is provided with a first paper transport path 501 for sending paper from the paper feed tray 15 or manual feed tray 90 to the output tray 16 via the registration roller 56, transfer roller 14, and fuser 50. Furthermore, when performing double-sided printing, a second paper transport path 502 is provided to return the paper, after single-sided printing is complete and it has passed through the fuser 50, to the first paper transport path 501 upstream of the transfer roller 14 in the paper transport direction. The first paper transport path 501 and the second paper transport path 502 are appropriately equipped with multiple transport rollers 57 to provide auxiliary propulsion to the paper.

[0025] The fixing device 50 will now be described. Figure 2 is a schematic diagram of the fixing device 50. The fixing device 50 includes a fixing belt 51, a pressure roller 52, a heating roller 53, a heat source 54, a nip forming member 55, a first temperature sensor 110, a second temperature sensor 120, etc. The fixing belt 51 is a fixing member that is heated by the heat source 54. The pressure roller 52 is a pressure member that forms a nip portion N between itself and the fixing member.

[0026] The fixing belt 51 is an endless belt provided within the fixing device 50. The base material of the fixing belt 51 can be a metal belt such as nickel or stainless steel, or a resin material such as polyimide, polyamide, or fluororesin. The heating roller 53 is positioned inside the fixing belt 51 and is a roller that can rotate integrally with the fixing belt 51. The heat source 54 is a heating unit located inside the heating roller 53. In this example, the heat source 54 is a halogen heater lamp, but an electromagnetic induction heating method may be used, or a resistance heating element or carbon heater may be used.

[0027] The nip-forming member 55 abuts against the inside of the fixing belt 51. In this example, the nip-forming member 55 is a fixing pad positioned between the inner circumferential surface of the fixing belt 51 and the outer circumferential surface of the heating roller 53. To ensure its rigidity, the nip-forming member 55 is made of heat-resistant resin or metal.

[0028] The pressure roller 52 is a metal roller with a silicone rubber layer on its outer circumference. The pressure roller 52 is located on the opposite side from the heating roller 53 when viewed from the nip forming member 55, and faces the nip forming member 55 across the fixing belt 51. The nip portion N is formed between the nip forming member 55, which abuts the inside of the fixing belt 51, and the pressure roller 52. The pressure roller 52 is pressed against the fixing belt 51 by an elastic body (e.g., a spring) not shown. As a result, the outer surfaces of the pressure roller 52 and the fixing belt 51 are elastically deformed, and the nip width H, which is the width of the nip portion N, becomes a predetermined size.

[0029] The fixing device 50 is capable of executing a sequence of heating the fixing member using a heat source 54. Specifically, the heating roller 53 is heated by the heat source 54, thereby transferring thermal energy from the heating roller 53 to the fixing belt 51, and heating the fixing belt 51 to a predetermined fixing temperature. The heating roller 53 is rotated counterclockwise in a front view by a drive source (not shown), causing the fixing belt 51 to rotate counterclockwise as well. The pressure roller 52 is rotated clockwise in a front view by a drive source (not shown).

[0030] As a result, in the fixing device 50, the paper onto which the toner image has been transferred by the intermediate transfer belt 41 is transported upward so as to pass through the nip section N. At this time, in the nip section N, the toner image transferred to the paper is melted, mixed, and pressed by the heated fixing belt 51, and fixed to the paper.

[0031] The first temperature sensor 110 measures the temperature of the fixing member non-contact. In this example, the first temperature sensor 110 is a thermopile that is positioned at a distance from the fixing belt 51 toward the outer circumference and capable of measuring the temperature of the outer surface of the fixing belt 51 non-contact. By using this non-contact type first temperature sensor 110, the temperature can be measured without damaging the outer surface of the fixing belt 51. The first temperature sensor 110 may measure the temperature of the fixing belt 51 using a method other than a thermopile, as long as it can measure the temperature of the fixing belt 51 non-contact.

[0032] The second temperature sensor 120 measures the temperature of the pressurizing member. In this example, the second temperature sensor 120 is a thermistor that is provided near the pressurizing roller 52 and can measure the temperature by contacting the outer surface of the pressurizing roller 52. Such a contact-type second temperature sensor 120 is less prone to deterioration in detection performance compared to a non-contact type temperature sensor, and can accurately measure the temperature of the pressurizing roller 52. The second temperature sensor 120 may also be a non-contact type temperature sensor, as long as it can accurately measure the temperature of the pressurizing roller 52.

[0033] One aspect of the sequence performed by the fixing device 50 will be described. Figure 3 is a graph showing the temperature change during the sequence. In the graph of Figure 3, the X axis represents time (seconds). The Y axis represents the temperature (°C) of the fixing belt 51 and the pressure roller 52, and the ON (lit) or OFF (off) state of the heat source 54. "Lamp" indicates the transition between the lit and off states of the heat source 54. "Belt (predicted)" shows the temperature transition of the fixing belt 51 detected by the first temperature sensor 110. "Pressure R (predicted)" shows the temperature transition of the pressure roller 52 detected by the second temperature sensor 120.

[0034] In the example shown in Figure 3, one sequence is executed for 30 seconds, during which the fixing belt 51 and pressure roller 52 are rotated, and the fixing belt 51 is heated by the heat source 54. During the initial heating period immediately after the start of the sequence, the heat source 54 is continuously lit for a predetermined time (9 seconds in Figure 3), and the fixing belt 51 rapidly rises to the fixing temperature. After the initial heating period has elapsed, the heat source 54 is repeatedly turned on and off, and the fixing belt 51 is intermittently heated by the heat source 54. As a result, the temperature of the fixing belt 51 fluctuates up and down within the allowable range of the fixing temperature.

[0035] On the other hand, since the fixing belt 51 and the pressure roller 52 are in contact at the nip portion N, some of the thermal energy supplied from the heat source 54 to the fixing belt 51 during the sequence is transferred to the pressure roller 52 via the nip portion N. As the sequence progresses, the temperature of the pressure roller 52 also rises.

[0036] The manufacturer or designer pre-executes the above sequence using the fixing device 50 before the product life begins (i.e., before product shipment). In this sequence, the temperature change of the fixing belt 51 is detected by the first temperature sensor 110, and the temperature change of the pressure roller 52 is detected by the second temperature sensor 120. Based on these temperature changes, the predicted temperatures of the fixing belt 51 and the pressure roller 52 in one sequence are calculated. As an example, the average value of the temperature change of the fixing belt 51 in one sequence is calculated as the predicted temperature of the fixing belt 51. The average value of the temperature change of the pressure roller 52 in one sequence is calculated as the predicted temperature of the pressure roller 52.

[0037] The predicted temperature table 400, created based on these calculation results, is pre-stored in the memory of the control unit 100. Figure 4 shows the configuration of the predicted temperature table 400 according to the first embodiment. The predicted temperature table 400 has the predicted temperatures calculated as described above set in correspondence with the sensor type and the object to be measured. The example in Figure 4 shows that when one sequence is executed in a normal state fixing device 50, the predicted temperature of the fixing belt 51 detected by the first temperature sensor 110 is "150°C", and the predicted temperature of the pressure roller 52 detected by the second temperature sensor 120 is "100°C". Note that a normal state fixing device 50 is one in which there is no lens contamination or change in nip width H, and there are no measurement errors compared to before product shipment.

[0038] The calibration process performed in the image forming apparatus 1 of the first embodiment will now be described. Figure 5 is a flowchart of the calibration process according to the first embodiment. For example, the user inputs a calibration execution instruction to correct the output value of the first temperature sensor 110 on the patch panel of the image forming apparatus 1. Upon receiving this execution instruction, the control unit 100 starts the calibration process shown in Figure 5 based on a program stored in memory. The control unit 100 may also automatically execute the calibration process when a predetermined time has elapsed or when a predetermined number of printing operations have been performed.

[0039] In S501, the control unit 100 executes a sequence to heat the fixing belt 51 with the heat source 54. In this example, the control unit 100 controls the fixing device 50, etc., to execute the same sequence as in Figure 3. In S503, while this sequence is being executed, the control unit 100 detects the temperature change of the fixing belt 51 with the first temperature sensor 110 and the temperature change of the pressure roller 52 with the second temperature sensor 120.

[0040] In this manner, the fixing device 50 executes a first sequence during calibration to correct the output value of the first temperature sensor 110. During the execution of this sequence, the first temperature sensor 110 measures the temperature of the fixing belt 51, which is the fixing member, and the second temperature sensor 120 measures the temperature of the pressure roller 52, which is the pressure member. The first sequence is the sequence executed in S501.

[0041] Then, as will be explained below, the control unit 100 corrects the output value of the first temperature sensor 110 based on a first comparison result obtained by comparing the measurement value of the first temperature sensor 110 in the first sequence with the measurement value of the first temperature sensor 110 in a previously executed second sequence, and a second comparison result obtained by comparing the measurement value of the second temperature sensor 120 in the first sequence with the measurement value of the second temperature sensor 120 in the second sequence. The second sequence is a sequence executed to create a predicted temperature table 400.

[0042] In the following explanation, the measurements from the first temperature sensor 110 and the second temperature sensor 120 in the first sequence are the actual temperatures of the fixing belt 51 and the pressure roller 52 in the sequence S501. The measurements from the first temperature sensor 110 and the second temperature sensor 120 in the second sequence are the predicted temperatures of the fixing belt 51 and the pressure roller 52 based on a previously executed sequence. The first comparison result is the comparison result of S505, which will be described later. The second comparison result is the comparison result of S509, which will be described later.

[0043] In S505, the control unit 100 compares the measured temperature of the pressure roller 52 with the predicted temperature. Specifically, based on the temperature changes of the pressure roller 52 detected in S503, the control unit 100 calculates the measured temperature of the pressure roller 52 using the same calculation method as the predicted temperature described above. In this example, the average value of the temperature changes of the pressure roller 52 detected in S503 is calculated as the measured temperature of the pressure roller 52. The control unit 100 compares the calculated measured temperature with the predicted temperature of the pressure roller 52 set in the predicted temperature table 400.

[0044] In S507, the control unit 100 determines whether there is a difference in the comparison results from S505. For example, if the difference between the measured temperature and the predicted temperature of the pressure roller 52 is less than a threshold (e.g., 1°C), the control unit 100 determines that there is no difference in the comparison results. In this case, the control unit 100 assumes that the nip width H has not changed since the product was shipped and then performs the following processing.

[0045] In S509, the control unit 100 compares the measured temperature of the fixing belt 51 with the predicted temperature. Specifically, based on the temperature changes of the fixing belt 51 detected in S503, the control unit 100 calculates the measured temperature of the fixing belt 51 using the same calculation method as the predicted temperature described above. In this example, the average value of the temperature changes of the fixing belt 51 detected in S503 is calculated as the measured temperature of the fixing belt 51. The control unit 100 compares the calculated measured temperature with the predicted temperature of the fixing belt 51 set in the predicted temperature table 400.

[0046] In S511, the control unit 100 determines whether there is a difference in the comparison results from S509. For example, the control unit 100 determines that there is a difference in the comparison results if the difference between the measured temperature and the predicted temperature of the fixing belt 51 is greater than or equal to a threshold (e.g., 1°C). In this case, the cause of the discrepancy between the measured temperature and the predicted temperature of the fixing belt 51 is considered to be the deterioration of the detection performance of the first temperature sensor 110 due to lens contamination or the like.

[0047] Therefore, in S513, the control unit 100 performs a correction of the first temperature sensor 110. For example, the control unit 100 adds a correction value to the output value of the first temperature sensor 110, which corresponds to the difference between the measured temperature and the predicted temperature of the fixing belt 51, so that the output value of the first temperature sensor 110 matches the temperature trend in a normal state (see Figure 3). From this point onward, the temperature obtained by adding the above correction value to the measured temperature of the fixing belt 51 is output as the output value of the first temperature sensor 110. After the execution of S513, or if it is determined in S511 that there is no difference in the comparison result, the control unit 100 terminates the calibration process.

[0048] On the other hand, in this embodiment, if the control unit 100 determines, based on the second comparison result, that the difference between the measurement value of the second temperature sensor 120 in the first sequence and the measurement value of the second temperature sensor 120 in the second sequence is greater than or equal to the threshold, it does not correct the output value of the first temperature sensor 110.

[0049] Specifically, in S507, if the difference between the measured temperature and the predicted temperature of the pressure roller 52 is greater than or equal to a threshold (e.g., 1°C), the control unit 100 determines that there is a difference in the comparison result and considers that the nip width H has changed since the product was shipped. In this case, if the output value of the first temperature sensor 110 is corrected in S513, the output value of the first temperature sensor 110 may not match the actual temperature of the fixing belt 51. Therefore, the control unit 100 terminates the calibration process without correcting the output value of the first temperature sensor 110.

[0050] The specific details of the calibration process described above will now be explained. Figure 6A is a graph showing the temperature change during the sequence in a sensor degradation state. When the lens of the first temperature sensor 110 becomes contaminated, for example, the fixing device 50 enters a sensor degradation state in which the detection performance of the first temperature sensor 110 deteriorates. When the calibration process is performed in the fixing device 50 in the sensor degradation state, the same sequence as in Figure 3 is executed in S501, and the temperature transition shown in Figure 6A is detected in S503. In the graph of Figure 6A, "Belt (Detection 1)" shows the temperature transition of the fixing belt 51, and "Pressure R (Detection 1)" shows the temperature transition of the pressure roller 52.

[0051] As shown in Figure 6A, in a fixing device 50 with a degraded sensor, if the nip width H has not changed since the product was shipped, the actual temperature of the fixing belt 51 and the pressure roller 52 is the same as in a normal state. Therefore, the measured temperature of the pressure roller 52 measured by the second temperature sensor 120 changes in the same way as in a normal state (see Figure 3). Consequently, in S507, it is determined that the measured temperature of the pressure roller 52 is no different from the predicted temperature of the pressure roller 52 in the predicted temperature table 400.

[0052] On the other hand, in the fixing device 50 with a degraded sensor, the detection performance of the first temperature sensor 110 is degraded, so the actual temperature of the fixing belt 51 measured by the first temperature sensor 110 remains lower than when it is in a normal state (see Figure 3). In this case, in S511, it is determined that the actual temperature of the fixing belt 51 is different from the predicted temperature of the fixing belt 51 in the predicted temperature table 400. Therefore, in S513, the output value of the first temperature sensor 110 is corrected based on the difference between the actual temperature and the predicted temperature of the fixing belt 51.

[0053] Figure 6B is a graph showing the temperature change during the sequence in the nip change state. For example, as the hardness of the pressure roller 52 decreases with the passage of product life, the nip width H increases from the time of product shipment. On the other hand, as the elastic force of the elastic body pressing the pressure roller 52 decreases with the passage of product life, the nip width H decreases from the time of product shipment. In these cases, the fixing device 50 enters a nip change state in which the heat transfer from the fixing belt 51 to the pressure roller 52 changes due to the increase or decrease in the nip width H.

[0054] When calibration processing is performed in the fixing device 50 in the nip change state, the same sequence as in Figure 3 is executed in S501, and the temperature change shown in Figure 6B is detected in S503. In the graph of Figure 6B, "Belt (Detection 2)" shows the temperature change of the fixing belt 51, and "Pressure R (Detection 2)" shows the temperature change of the pressure roller 52.

[0055] As shown in Figure 6B, in the fixing device 50 under nip change conditions, for example, if the nip width H increases from the time of product shipment, the amount of heat transferred from the fixing belt 51 to the pressure roller 52 increases. In this case, compared to the normal state, the actual temperature of the fixing belt 51 decreases, and the actual temperature of the pressure roller 52 increases. Therefore, the measured temperature of the pressure roller 52 measured by the second temperature sensor 120 remains higher than in the normal state (see Figure 3). Consequently, in S507, it is determined that the measured temperature of the pressure roller 52 differs from the predicted temperature, and the output value of the first temperature sensor 110 is not corrected.

[0056] In the fixing device 50 under nip change conditions, the detection performance of the first temperature sensor 110 does not deteriorate, but as described above, thermal energy is transferred to the pressure roller 52, causing the actual temperature of the fixing belt 51 to be lower than in the normal state. Therefore, the measured temperature of the fixing belt 51 measured by the first temperature sensor 110 remains lower than in the normal state (see Figure 3).

[0057] Thus, in the fixing device 50 of this embodiment, if the measured value of the first temperature sensor 110, which is a non-contact type temperature sensor, does not match the predicted value, it is possible to identify whether the detection performance of the first temperature sensor 110 has deteriorated. Figure 6C is a graph showing the temperature change of the fixing belt 51 in each state. In the graph of Figure 6C, the "belt (predicted)" in the normal state shown in Figure 3, the "belt (detected 1)" in the sensor deterioration state shown in Figure 6A, and the "belt (detected 2)" in the nip change state shown in Figure 6B are shown simultaneously.

[0058] As mentioned above, when the fixing device 50 is in a sensor degradation state, the actual temperature of the fixing belt 51 is the same as when it is in a normal state. However, because the detection performance of the first temperature sensor 110 is degraded, the measured temperature of the fixing belt 51 detected by the first temperature sensor 110 is lower than the actual temperature of the fixing belt 51. Therefore, in the calibration process, the output value of the first temperature sensor 110 is corrected to approximate the actual temperature of the fixing belt 51. This makes it possible to accurately control the heating temperature of the fixing belt 51 based on the output value of the first temperature sensor 110.

[0059] On the other hand, when the fixing device 50 is in a nip change state, the actual temperature of the fixing belt 51 is lower than in the normal state. Since the detection performance of the first temperature sensor 110 has not deteriorated, the measured temperature of the fixing belt 51 detected by the first temperature sensor 110 is the same as the actual temperature of the fixing belt 51. In the example in Figure 6C, the measured temperature of the fixing belt 51 in the nip change state is lower than the measured temperature in the normal state, and higher than the measured temperature in the sensor deterioration state.

[0060] Therefore, the calibration process does not correct the output value of the first temperature sensor 110, which has not deteriorated in detection performance. This prevents the output value of the first temperature sensor 110 from being inconsistent with the actual temperature of the fixing belt 51, and thus allows for accurate control of the heating temperature of the fixing belt 51 based on the output value of the first temperature sensor 110.

[0061] <Second Embodiment> The second embodiment of this disclosure differs from the first embodiment in the details of the calibration process. Figure 7A is a diagram showing the data structure of the predicted temperature table 700 according to the second embodiment. Figure 7B is a specific example of the predicted temperature table 700 according to the second embodiment. In the second embodiment, the predicted temperature table 700 is pre-stored in the memory of the control unit 100 instead of the predicted temperature table 400 (see Figure 4) described above.

[0062] The predicted temperature table 700 has the predicted temperatures for the fixing belt 51 and pressure roller 52 set in correspondence with the nip width H. Figure 7A illustrates the data setting rules for the predicted temperature table 700. In this example, the nip width H of the fixing device 50 in a normal state, "10 mm", is used as the reference value (Def.) for the nip width H. The actual measured temperatures of the fixing belt 51 and pressure roller 52 when the above sequence is executed on this fixing device 50 are used as the reference values ​​(Def.) for the predicted temperatures of the fixing belt 51 and pressure roller 52.

[0063] In the example of the predicted temperature table 700, each predicted temperature corresponding to the nip width H is set as follows: When the nip width H increases by "1 mm" from the reference value, the predicted temperature of the fixing belt 51 is the reference value minus "8°C", and the predicted temperature of the pressure roller 52 is the reference value plus "4°C". When the nip width H decreases by "1 mm" from the reference value, the predicted temperature of the fixing belt 51 is the reference value plus "10°C", and the predicted temperature of the pressure roller 52 is the reference value minus "5°C".

[0064] The manufacturer or designer executes the above sequence (see Figure 3) in the fixing device 50 under normal conditions, measures the temperatures of the fixing belt 51 and pressure roller 52 during the sequence, and implements the predicted temperature table 700 based on the measurement results. In the example in Figure 7B, the measured temperature of the fixing belt 51, "150°C," is set as the reference value for the predicted temperature of the fixing belt 51, and the measured temperature of the pressure roller 52, "100°C," is set as the reference value for the predicted temperature of the pressure roller 52. Based on these reference values, the predicted temperatures for each case when the nip width H increases by "1 mm" from the reference value, and the predicted temperatures for each case when the nip width H decreases by "1 mm" from the reference value are set.

[0065] The calibration process performed in the image forming apparatus 1 of the second embodiment will now be described. Figure 8 is a flowchart of the calibration process according to the second embodiment. First, the control unit 100 executes S501 to S505 in the same manner as in the first embodiment. Then, as will be described below, the control unit 100 identifies the nip width H, which is the formation width of the nip portion N, based on the second comparison result, and corrects the output value of the first temperature sensor 110 based on the first comparison result and the nip width H.

[0066] In S801, the control unit 100 determines the nip width H based on the temperature change of the pressure roller 52 detected in S503. For example, the control unit 100 calculates the average value of the temperature change of the pressure roller 52 as the actual measured temperature of the pressure roller 52 during the sequence. The control unit 100 refers to the predicted temperature table 700 to determine the predicted temperature corresponding to the actual measured temperature of the pressure roller 52, and further determines the nip width H corresponding to this predicted temperature.

[0067] In S803, the control unit 100 refers to the predicted temperature table 700 and determines the predicted temperature of the fixing belt 51 corresponding to the nip width H determined in S801. In S509, the control unit 100 compares the measured temperature of the fixing belt 51 with the predicted temperature, similar to the first embodiment. However, the control unit 100 compares the measured temperature of the fixing belt 51 with the predicted temperature determined in S803. The subsequent processing is the same as in the first embodiment.

[0068] For example, if the measured temperature of the pressure roller 52 based on the temperature detection in S503 is "104°C", then in S801, the nip width H "Def. +1mm" (i.e., 11mm) corresponding to the predicted temperature "104°C" is identified by referring to the predicted temperature table 700 in Figure 7B. In this case, the fixing device 50 is considered to be in a nip change state. In S803, the predicted temperature of the fixing belt 51 corresponding to this nip width H is identified as "142°C" by referring to the predicted temperature table 700 in Figure 7B. In S509, the measured temperature of the fixing belt 51 based on the temperature detection in S503 is compared with this predicted temperature "142°C".

[0069] In this case, if the measured temperature of the fixing belt 51 is the same as the predicted temperature of "142°C", the detection performance of the first temperature sensor 110 is considered not to have deteriorated, and no correction is performed on the first temperature sensor 110. On the other hand, if the measured temperature of the fixing belt 51 is different from the predicted temperature, the detection performance of the first temperature sensor 110 is considered to have deteriorated. In this case, for example, if the measured temperature of the fixing belt 51 is "140°C", the output value of the first temperature sensor 110 is corrected in S513 to be "2°C" higher.

[0070] If the predicted temperature in the predicted temperature table 700 does not match the measured temperature of the pressure roller 52, the control unit 100 may identify the predicted temperature in the predicted temperature table 700 that most closely matches the measured temperature. Alternatively, the control unit 100 may interpolate the predicted temperature table 700. For example, in S801 and S803, the control unit 100 may obtain the nip width and predicted temperature corresponding to the measured temperature of the pressure roller 52 by linearly approximating the data in the predicted temperature table 700.

[0071] As described above, in the second embodiment, the current nip width H is determined based on the measured temperature of the pressure roller 52. If the measured temperature of the fixing belt 51 differs from the predicted temperature corresponding to the current nip width H, the fixing device 50 is considered to be in a sensor degradation state. In S513, the output value of the first temperature sensor 110 is corrected to approximate the actual temperature of the fixing belt 51 based on the predicted temperature of the fixing belt 51 corresponding to the current nip width H. Therefore, even when the nip width H changes as described above, the heating temperature of the fixing belt 51 can be accurately controlled based on the output value of the first temperature sensor 110.

[0072] <Third Embodiment> The third embodiment of this disclosure differs from the first and second embodiments in the details of the calibration process. Figure 9A is a diagram showing the data structure of the predicted temperature table 900 according to the third embodiment. Figure 9B is a specific example of the predicted temperature table 900 according to the third embodiment. In the third embodiment, the predicted temperature table 900 is pre-stored in the memory of the control unit 100 instead of the aforementioned predicted temperature tables 400 and 900.

[0073] The predicted temperature table 900 contains the predicted temperatures for the fixing belt 51 and the pressure roller 52, corresponding to the input voltage and nip width H. Figure 9A illustrates the data setting rules for the predicted temperature table 900. In this example, multiple input voltage patterns for the fixing device 50 are defined. For each of these input voltages, the nip width H and the predicted temperature are defined.

[0074] In the example of the predicted temperature table 900, each predicted temperature corresponding to the input voltage and nip width H is set as follows. When the input voltage to the fuser 50 is "100V", the correspondence between the nip width H and each predicted temperature is the same as in the predicted temperature table 700 (see Figure 7A). On the other hand, in the predicted temperature table 900, the higher the input voltage to the fuser 50, the higher the predicted temperature corresponding to each nip width H, and the lower the input voltage to the fuser 50, the lower the predicted temperature corresponding to each nip width H.

[0075] In the example shown in Figure 9A, when the input voltage to the fuser 50 is "110V", the predicted temperature corresponding to each nip width H is the value obtained by multiplying the predicted temperature when the input voltage is "100V" by "1.03". When the input voltage to the fuser 50 is "90V", the predicted temperature corresponding to each nip width H is the value obtained by multiplying the predicted temperature when the input voltage is "100V" by "0.95".

[0076] The manufacturer or designer executes the above sequence (see Figure 3) in a normal fixing device 50 under the condition that the input voltage is "100V". The temperatures of the fixing belt 51 and pressure roller 52 are measured during this sequence, and a predicted temperature table 900 is implemented based on the measurement results. In the example of Figure 9B, the reference value for the nip width H is set to "10mm", the reference value for the predicted temperature of the fixing belt 51 is set to "150℃", and the reference value for the predicted temperature of the pressure roller 52 is set to "100℃". Based on these reference values, the correspondence between the nip width H and each predicted temperature at other input voltages is also set.

[0077] The calibration process performed in the image forming apparatus 1 of the third embodiment will now be described. Figure 10 is a flowchart of the calibration process according to the third embodiment. First, the control unit 100 executes S501 to S505 in the same manner as in the first embodiment. Then, as will be described below, the control unit 100 identifies the input voltage to the fixing device 50 in the first sequence, identifies the nip width H which is the formation width of the nip portion N based on the second comparison result, and corrects the output value of the first temperature sensor 110 based on the first comparison result, the nip width H, and the input voltage.

[0078] In S1001, the control unit 100 detects the input voltage to the fixing device 50 in the sequence of S501. In this example, S1001 is executed between S503 and S505, but it is sufficient that it is executed at least after S501. In S1003, the control unit 100 determines the nip width H based on the input voltage detected in S1001 and the temperature change of the pressure roller 52 detected in S503. For example, the control unit 100 calculates the average value of the temperature change of the pressure roller 52 as the measured temperature of the pressure roller 52 in the sequence. The control unit 100 refers to the data corresponding to the detected input voltage in the predicted temperature table 900 to determine the predicted temperature corresponding to the measured temperature of the pressure roller 52, and further determines the nip width H corresponding to this predicted temperature.

[0079] In S1005, the control unit 100 refers to the predicted temperature table 900 and determines the predicted temperature of the fixing belt 51 corresponding to the nip width H determined in S1003. In S509, the control unit 100 compares the measured temperature of the fixing belt 51 with the predicted temperature, similar to the first embodiment. However, the control unit 100 compares the measured temperature of the fixing belt 51 with the predicted temperature determined in S1005. The subsequent processing is the same as in the first embodiment.

[0080] For example, in a fixing device 50 with an input voltage of "110V", if the measured temperature of the pressure roller 52 based on the temperature detection in S503 is "107℃", then in S1003, the nip width H "Def. +1mm" (i.e., 11mm) corresponding to the predicted temperature "107℃" is identified by referring to the predicted temperature table 900 in Figure 9B. In this case, the fixing device 50 is considered to be in a nip change state. In S1005, the predicted temperature of the fixing belt 51 "146℃" corresponding to the input voltage "110V" and the nip width H "Def. +1mm" is identified by referring to the predicted temperature table 900 in Figure 9B. In S509, the measured temperature of the fixing belt 51 based on the temperature detection in S503 is compared with this predicted temperature "146℃".

[0081] In this case, if the measured temperature of the fixing belt 51 is the same as the predicted temperature of "146°C", the detection performance of the first temperature sensor 110 is considered not to have deteriorated, and no correction is performed on the first temperature sensor 110. On the other hand, if the measured temperature of the fixing belt 51 is different from the predicted temperature, the detection performance of the first temperature sensor 110 is considered to have deteriorated. In this case, for example, if the measured temperature of the fixing belt 51 is "141°C", the output value of the first temperature sensor 110 is corrected in S513 to be "5°C" higher.

[0082] If the same voltage value as the input voltage to the fixing device 50 is not set in the predicted temperature table 900, or if the same predicted temperature as the measured temperature of the pressure roller 52 is not set in the predicted temperature table 900, the control unit 100 may identify the predicted temperature that most closely approximates the measured temperature from among the predicted temperatures set in the predicted temperature table 900. Alternatively, the control unit 100 may interpolate the predicted temperature table 900. Figure 11 shows a specific example of an interpolated predicted temperature table 900 according to the third embodiment.

[0083] For example, let's assume that the input voltage to the fixing device 50 is "106V", the measured temperature of the pressure roller 52 is "101℃", and the measured temperature of the fixing belt 51 is "150℃". In this case, the control unit 100 generates the predicted temperature table 900 for an input voltage of "106V" shown in Figure 11 by interpolating the data corresponding to the input voltage "100V" and the data corresponding to the input voltage "110V" from the predicted temperature table 900 using linear approximation.

[0084] The fixing device 50 executes the processes from S505 onward based on the predicted temperature table 900 shown in Figure 11. In this example, the measured temperature of the pressure roller 52, "101°C," is between "97°C" and "102°C," which are two predicted temperatures for the pressure roller 52 set in the predicted temperature table 900. Therefore, assuming that the same predicted temperature as the measured temperature of the pressure roller 52 is set in the predicted temperature table 900, the predicted temperature of the fixing belt 51 corresponding to this predicted temperature is calculated by linear approximation as follows. (163-153) / (97-102)*(101-102)+153=155

[0085] In this case, in S511, it is determined that there is a difference between the measured temperature of the fixing belt 51, which is "150°C", and the predicted temperature of the fixing belt 51, which is "155°C". Since the detection performance of the first temperature sensor 110 is considered to have deteriorated, in S513 the output value of the first temperature sensor 110 is corrected to be "5°C" higher.

[0086] As described above, in the third embodiment, the current nip width H is determined based on the input voltage to the fixing device 50 and the measured temperature of the pressure roller 52. If the measured temperature of the fixing belt 51 differs from the predicted temperature corresponding to the current nip width H, the fixing device 50 is considered to be in a sensor degradation state. In S513, the output value of the first temperature sensor 110 is corrected to approximate the actual temperature of the fixing belt 51 based on the input voltage to the fixing device 50 and the predicted temperature of the fixing belt 51 corresponding to the current nip width H. Therefore, even when the input voltage and nip width H are changing as described above, the heating temperature of the fixing belt 51 can be accurately controlled based on the output value of the first temperature sensor 110.

[0087] <Remarks> This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0088] For example, in the fixing device 50 of the above embodiment, the fixing member is a fixing belt 51, the pressurizing member is a pressurizing roller 52, and a nip portion N is formed using a nip forming member 55. Alternatively, the fixing member may be a roller instead of a belt. The pressurizing member may be a different member from the roller (for example, a non-rotating body). The fixing device 50 may also be configured such that the nip portion N is formed between the fixing member and the pressurizing member without the nip forming member 55.

[0089] In the above embodiment, the measured values ​​(hereinafter referred to as "actual values") of the first temperature sensor 110 and the second temperature sensor 120 in the first sequence are exemplified by the actual temperatures of the fixing belt 51 and the pressure roller 52 in the sequence S501. The measured values ​​(hereinafter referred to as "predicted values") of the first temperature sensor 110 and the second temperature sensor 120 in the second sequence are exemplified by the predicted temperatures of the fixing belt 51 and the pressure roller 52 based on a previously executed sequence. These actual and predicted values ​​are not limited to the average values ​​of the temperature changes of the fixing belt 51 and the pressure roller 52, but may also be the maximum value, median value, standard value, etc., of the temperature changes.

[0090] Furthermore, the measured and predicted values ​​mentioned above may be average values ​​based on the temperature changes over a predetermined period within the sequence, or they may represent the slope or curve of the temperature changes over that predetermined period. For example, during the initial heating period immediately after the start of the sequence (the period from 0 to 9 seconds in the sequence shown in Figure 3), the heat source 54 remains lit, causing the fixing belt 51 and pressure roller 52 to rise rapidly and stably, making it easy to see the characteristics of the temperature changes. Therefore, the predetermined period mentioned above may be the initial heating period within the sequence.

[0091] As shown in Figure 3, if a sequence includes periods of illumination and deactivation of the heat source 54, the temperature changes will follow an upward curve during the illumination period and a downward curve during the deactivation period. In this case, the predetermined period may be either the illumination period or the deactivation period within the sequence. Also, if a sequence includes illumination periods with different duty cycles for the heat source 54, the predetermined period may be the illumination period with a 100% duty cycle, or the illumination period with a reduced duty cycle. Furthermore, if a sequence includes periods of rotation and stopping of the fixing belt 51, the predetermined period may be either the rotation period or the stopping period within the sequence. [Explanation of Symbols]

[0092] 1. Image forming apparatus 50 Fixing device 51 Fixing belt 52 Pressure rollers 54 Heat source 55 Nip forming member 100 Control Unit 110 First temperature sensor 120 Second temperature sensor

Claims

1. comprising a fixing device and a control unit, The fixing device is A fixing member heated by a heat source, A pressurizing member that forms a nip portion between itself and the fixing member, A first temperature sensor for non-contact measurement of the temperature of the fixing member, A second temperature sensor for measuring the temperature of the pressurizing member, A fixing device comprising, capable of executing a sequence of heating the fixing member with the heat source, During calibration to correct the output value of the first temperature sensor, the first sequence is executed as the sequence, and during the execution of the first sequence, the first temperature sensor measures the temperature of the fixing member and the second temperature sensor measures the temperature of the pressurizing member. The control unit corrects the output value of the first temperature sensor based on a first comparison result obtained by comparing the measurement value of the first temperature sensor in the first sequence with the measurement value of the first temperature sensor in a second sequence which is a previously executed sequence, and a second comparison result obtained by comparing the measurement value of the second temperature sensor in the first sequence with the measurement value of the second temperature sensor in the second sequence. Image forming apparatus.

2. If the control unit determines, based on the second comparison result, that the difference between the measurement value of the second temperature sensor in the first sequence and the measurement value of the second temperature sensor in the second sequence is greater than or equal to a threshold, it will not correct the output value of the first temperature sensor. The image forming apparatus according to claim 1.

3. The control unit, Based on the second comparison result, the nip width, which is the width of the nip portion, is determined. Based on the first comparison result and the nip width, the output value of the first temperature sensor is corrected. The image forming apparatus according to claim 1.

4. The control unit, Identify the input voltage to the fixing device in the first sequence, Based on the second comparison result, the nip width, which is the width of the nip portion, is determined. Based on the first comparison result, the nip width, and the input voltage, the output value of the first temperature sensor is corrected. The image forming apparatus according to claim 1.

5. The fixing member is a fixing belt, The aforementioned pressurizing member is a pressurizing roller, The nip portion is formed between the nip-forming member that abuts the inside of the fixing belt and the pressure roller. The image forming apparatus according to claim 1.

6. The first temperature sensor is a non-contact thermopile, The second temperature sensor is a contact-type thermistor. The image forming apparatus according to claim 1.

Images