Image forming device

Abstract

To accurately predict the remaining amount state of lubricant.SOLUTION: An image heating device comprises a cylindrical film, a roller 15 in contact with an outer peripheral surface of the film, and a nip forming member provided in an internal space of the film and forming a nip part with the roller 15 with the film therebetween. Lubricant is applied between the film and the nip forming member. The image heating device sandwiches and conveys a recording medium at the nip part. The image heating device further comprises a torque detection unit that acquires, as torque information being the torque of the roller 15 or a physical quantity correlated to the torque of the roller 15, first torque information of the roller 15 when the roller 15 rotates at a first rotation speed and second torque information of the roller 15 when the roller 15 rotates at a second rotation speed faster than the first rotation speed, and a control unit that gives a notification of information on the remaining amount of lubricant interposed between the film and the nip forming member based on the first torque information and the second torque information.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an image heating device such as a fixing device mounted in an electrophotographic image forming apparatus such as a copying machine or a printer, or a gloss imparting device that improves the glossiness of an image by reheating a fixed toner image on a recording material, and also to an image forming apparatus equipped with an image heating device. [Background technology]

[0002] Conventionally, image heating devices mounted on image forming devices such as copiers and laser beam printers include a device that includes a cylindrical fixing film, a heater that contacts the inner surface of the fixing film, and a pressure roller that forms a nip portion together with the heater via the fixing film. In such image heating devices, the toner image on the recording material is heated and fixed by supplying heat from the heater, which is a heat source, to the recording material via the fixing film.

[0003] In an image heating device as described above, when the fixing film rotates, the inner surface of the fixing film always slides against a nip forming member such as a heater. Patent Document 1 discloses a configuration in which a lubricant such as fluorine-based grease or silicone oil is applied to the surface of a ceramic heater, which is a nip forming member, in order to ensure the sliding property between the fixing film and the nip forming member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-27619 Summary of the Invention [Problem to be solved by the invention]

[0005] In an image heating device configured to have a lubricant interposed between the inner surface of the fixing film and the nip forming member, the amount of lubricant decreases as the image heating device is used repeatedly. When the lubricant runs out, the sliding properties between the inner surface of the fixing film and the nip forming member deteriorate, and abnormal noise occurs due to stick-slip, in which the fixing film rotates and stops repeatedly. Therefore, the image heating device requires maintenance or replacement before the lubricant runs out.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an image heating apparatus that is capable of accurately predicting the remaining amount of lubricant between the fixing film and the nip forming member. [Means for solving the problem]

[0007] In order to achieve the above object, an image forming apparatus according to the present invention comprises: an image forming section for forming an image on a recording material; an image heating device including a cylindrical film, a roller that contacts an outer peripheral surface of the film, and a nip forming member that is provided in an internal space of the film and forms a nip portion with the roller via the film, and fixes an image formed on a recording material to the recording material; a motor that is driven by a current flowing through a coil, the motor being a drive source that drives the roller to rotate and drives the image forming unit; a lubricant is applied between the film and the nip forming member, and a recording medium is nipped and conveyed at the nip portion, the nip forming member includes a heater that heats the film and is controlled to a predetermined temperature; Torque of the roller About As the torque information, first torque information of the roller when the roller rotates at a first rotation speed and second torque information of the roller when the roller rotates at a second rotation speed slower than the first rotation speed are obtained. By measuring the current value flowing through the coil of the motor, A torque detector for acquiring the torque; When a change amount of the difference between the first torque information and the second torque information becomes equal to or less than a predetermined value, it is determined that the lubricant is depleted, and a user is notified of the end of life of the image heating apparatus. A control unit.、 The torque detection unit obtains the first torque information and the second torque information in a state in which the heaters are controlled to be at the same temperature. It is characterized by the above. Effect of the Invention

[0008] According to the image forming apparatus of the present invention, it is possible to provide an image heating device that is capable of accurately predicting the remaining amount of lubricant between the fixing film and the nip forming member. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment. [Diagram 2] 1 is a schematic cross-sectional view of an image heating apparatus according to a first embodiment. [Diagram 3] 11 is a graph showing the relationship between the torque and the rotation speed of the pressure roller in a fluid lubricated state. [Figure 4] 1 is a graph showing the relationship between the torque and the rotation speed of a pressure roller in a boundary lubrication state. [Diagram 5] FIG. 2 is a schematic configuration diagram of a fixing motor according to the first embodiment. [Figure 6] FIG. 2 is a control circuit diagram of a fixing motor according to the first embodiment. [Figure 7] 4 is a graph showing the relationship between the coil current and the driving torque of the fixing motor. [Figure 8] 5 is a graph showing a transition of driving torque during driving torque measurement control. [Figure 9] 11 is a graph showing the relationship between the number of sheets passed and a driving torque difference TΔ. [Figure 10] FIG. 11 is a schematic cross-sectional view of a radiation heating type image heating apparatus according to a modified example. [Figure 11] FIG. 13 is a schematic cross-sectional view of an electromagnetic induction heating type image heating apparatus according to a modified example. [Figure 12] 10 is a graph showing a transition curve of a driving torque difference TΔ according to a second embodiment. [Figure 13] FIG. 11 is a schematic cross-sectional view of an image forming apparatus according to a third embodiment. [Figure 14]13 is a graph showing the relationship between the number of passed sheets and the torque difference MΔ according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the mode for carrying out the present invention will be described based on the examples with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments should be appropriately changed depending on the configuration and various conditions of the device to which the invention is applied. In other words, the scope of the present invention is not limited to the following embodiments.

[0011] <First Example> (1) Configuration of Image Forming Apparatus 1 The configuration of an image forming apparatus 1 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view of the image forming apparatus 1. The image forming apparatus 1 is a laser printer that forms an image on a sheet-like recording medium P by using an electrophotographic method.

[0012] The image forming apparatus 1 includes a photosensitive drum 19 as an image carrier, a charging roller 16 as a charging means, a developing roller 17 as a developing means, and a cleaning unit including a cleaning blade 18 as a cleaning means. These members are configured as a process cartridge 10 so as to be detachable from the main body of the image forming apparatus 1. Image forming apparatus 1 includes a paper feed cassette 21, a pickup roller 22, a paper feed roller 23, a pair of registration rollers 24, and a transfer roller 12 as a transfer member. Image forming apparatus 1 further includes an image heating device (fixing device) 13, a pair of fixing discharge rollers 25, a pair of main body discharge rollers 26, a control unit 40, a fixing motor 20 as a drive means for image heating device 13, and a main motor 50 as a drive means for the other members.

[0013] The photosensitive drum 19 is driven to rotate in the clockwise direction in FIG. 1 at a predetermined peripheral speed (process speed). The charging roller 16 uniformly charges the peripheral surface of the photosensitive drum 19 to a predetermined polarity and potential. The charged surface of the charged photosensitive drum 19 is scanned and exposed to laser light emitted from the laser scanner 11. The laser scanner 11, which serves as an image exposure means, receives image information from an external device such as an image scanner or computer (not shown) and outputs laser light that is on / off modulated in response to a time-series electric digital pixel signal of the image information. This scanning exposure removes electric charges from the exposed light portion of the peripheral surface of the photosensitive drum 19, and an electrostatic latent image corresponding to the target image information is formed on the peripheral surface of the photosensitive drum 19.

[0014] The developing roller 17 carries a developer (toner) on its surface and supplies the toner to the peripheral surface of the photoconductor drum 19, thereby sequentially developing the electrostatic latent image formed on the peripheral surface of the photoconductor drum 19 into a toner image. Laser printers generally use a reversal development method in which toner is applied to exposed light areas of the electrostatic latent image for development.

[0015] The paper feed cassette 21 is detachably attached to the image forming apparatus 1, and stacks and stores sheet-like recording media P. The recording media P in the paper feed cassette 21 are transported to the paper feed roller 23 by the pickup roller 22 based on a paper feed start signal, and are separated and fed one by one into the main body of the image forming apparatus 1 by the paper feed roller 23. The recording media P fed into the image forming apparatus 1 by the paper feed roller 23 passes through a conveying path 30 and is conveyed to the pair of registration rollers 24. The recording media P conveyed to the pair of registration rollers 24 is introduced by the pair of registration rollers 24 through a conveying path 31 into the transfer nip T of the image forming section formed by the photosensitive drum 19 and the transfer roller 12.

[0016] The recording medium P introduced into the transfer nip T is sandwiched and transported in the transfer nip T, during which a predetermined transfer voltage controlled by a transfer voltage application power source (not shown) is applied to the transfer roller 12. By applying a transfer voltage of opposite polarity to the toner to the transfer roller 12, the toner image formed on the circumferential surface of the photosensitive drum 19 is electrostatically transferred to the surface of the recording medium P. The recording medium P with the transferred toner image is transported from the transfer nip T through a transport path 32 and introduced into the image heating device 13.

[0017] The image heating device 13 includes a fixing film 14 and a pressure roller 15. The recording medium P introduced into the image heating device 13 is sandwiched and transported in a fixing nip F formed by the fixing film 14 and the pressure roller 15. During this time, the recording medium P is heated by the fixing film 14, which is controlled to a predetermined temperature (fixing temperature), and the toner image on the recording medium P is fixed to the recording medium P. The recording medium P, on which the toner image has been fixed by the image heating device 13, is discharged from the image heating device 13 by a pair of fixing discharge rollers 25 that discharge the recording medium P, and is transported along a transport path 33. The recording medium P is then discharged from the image forming device 1 to a paper discharge tray 27 by a pair of main body paper discharge rollers 26 provided at the end of the transport path 33, and image formation is completed.

[0018] In the case of double-sided printing, the recording medium P is sent to the pair of main body paper discharge rollers 26, and then the pair of main body paper discharge rollers 26 rotate in the reverse direction at a predetermined timing, so that the recording medium P is pulled back into the image forming apparatus 1. The pulled back recording medium P is transported along the double-sided transport path 34, and an image is formed on the second side.

[0019] After the toner image is transferred to the recording medium P, the peripheral surface of the photosensitive drum 19 is cleaned of residual toner and paper dust by a cleaning blade 18, and is then charged again for use in the next image formation.

[0020] By repeating the above operations, continuous image formation can be performed. The image forming apparatus 1 of this embodiment has a first speed mode and a second speed mode that are selected according to the image forming operation. In the first speed mode, it is possible to print 40 black and white images per minute on A4 size [210 mm x 297 mm] paper at a process speed of 240 mm / sec. In the second speed mode, it is possible to print 20 black and white images per minute on A4 size paper at a process speed of 120 mm / sec. The first speed mode also allows printing of 20 black and white images per minute on paper with a basis weight of 75 g / m2. 2 The above-mentioned plain paper mode uses the optimized fixing temperature for plain paper, and the grammage mode uses 75 g / m 2 The thin paper mode is optimized for thin paper of less than 100 mm and performs fixing at a lower fixing temperature than in the normal paper mode.

[0021] (2) Configuration of image heating device 13 A detailed configuration of image heating device 13 according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic cross-sectional view showing image heating device 13 of this embodiment. Image heating device 13 includes fixing film 14, a pressure roller 15 that contacts the outer peripheral surface of fixing film 14, and a heater 60 as a heating body provided in the internal space of fixing film 14.

[0022] The fixing film 14 is a highly heat-resistant member having a multi-layer structure formed in a cylindrical shape, and has a base layer made of a heat-resistant resin such as polyimide having a thickness of 100 μm or less, and a release layer coated with a fluororesin having excellent release properties such as PFA, which corresponds to the surface layer of the fixing film 14.

[0023] The pressure roller 15 has a core metal made of iron, aluminum or the like, and an elastic layer made of a highly heat-resistant rubber material such as silicone rubber.

[0024] The heater 60 is a ceramic heater in which a heating element made of silver paste or the like is applied to a ceramic substrate such as alumina as a base material by screen printing or the like, and a glass coating is formed thereon as an insulating protective layer. The glass coating of the heater 60 comes into contact with the inner surface of the fixing film 14.

[0025] Grease G as a lubricant is applied in advance onto the glass coat of the heater 60. Good sliding properties are ensured by the presence of the grease G between the inner surface of the fixing film 14 and the glass coat of the heater 60. As the grease G, for example, grease made by thickening perfluoropolyether base oil with fluororesin can be used.

[0026] The heater 60 is held by a heater holding member 61. Furthermore, the heater holding member 61 holding the heater 60 is held by a metal stay member 63. A pressure mechanism (not shown) applies pressure to the pressure roller 15, and the pressure roller 15 is pressed toward the heater 60 through the fixing film 14, thereby forming a fixing nip F. That is, the heater 60 not only heats the fixing film 14 as a heating element, but also forms the fixing nip F (nip portion) together with the pressure roller 15 as a nip forming member.

[0027] The core of the pressure roller 15 is connected to the fixing motor 20 by a coupling gear or the like, and the fixing film 14 is rotated as the pressure roller 15 is rotated by the fixing motor 20. The recording medium P is sandwiched and conveyed while being heated in the fixing nip F, whereby the unfixed toner image Tn on the recording medium P is fixed.

[0028] A thermistor 62 serving as a temperature detection element is in contact with the heater 60. Based on the detection result of the thermistor 62, the control unit 40 controls the power supply to the heater 60 so that the temperature detected by the thermistor 62 becomes the desired target temperature. The control unit 40 performs image formation and fixing operations under image formation conditions and at a fixing temperature according to the print mode set by the user.

[0029] (3) Reduction of lubricant and occurrence of stick-slip As described above, in image heating device 13, grease G is present between fixing film 14 and heater 60, but the amount of intervening grease G decreases as image heating device 13 is used repeatedly. Then, the contact state between fixing film 14 and heater 60 changes depending on the amount of intervening grease G.

[0030] The grease G interposed between the fixing film 14 and the heater 60 is present between the inner surface of the fixing film 14 and the surface of the heater 60 with a sufficient oil film thickness in the initial state when the image heating device 13 is first used (fluid lubrication state). On the other hand, when the image heating device 13 is used repeatedly, the interposed grease G is reduced, and the oil film thickness of the grease G becomes smaller. When the reduction in the grease G progresses and the oil film thickness of the grease G becomes smaller, a mixture of a portion where the inner surface of the fixing film 14 and the surface of the heater 60 directly contact and slide, and a portion where the inner surface of the fixing film 14 and the surface of the heater 60 contact with the grease G interposed therebetween is formed (mixed lubrication state). Furthermore, when the image heating device 13 is used repeatedly from the mixed lubrication state, the reduction in the grease G progresses, and the interposed grease G is almost depleted, and the oil film thickness becomes almost zero. Then, a state where the inner surface of the fixing film 14 and the surface of the heater 60 directly contact and slide is formed (boundary lubrication state).

[0031] When the grease G is almost depleted and the fixing film 14 and the heater 60 are in a boundary lubrication state, the sliding property between the inner surface of the fixing film 14 and the surface of the heater 60 deteriorates, and the fixing film 14 rotates and stops repeatedly, causing stick-slip. When stick-slip occurs, it may be accompanied by abnormal noise. For this reason, it is desirable for the image forming apparatus to be configured to be able to notify the user, etc. that the grease G is about to run out and that the image heating device 13 is about to reach the end of its life, before stick-slip occurs. The image heating device 13 that is about to run out of grease G can be made continuously usable again by replacement work of replacing the film unit including the heater 60 to which grease G has been applied, or maintenance work of reapplying grease G to the heater 60.

[0032] Since it is generally not practical to directly measure the remaining amount of grease G, it is conceivable that the life of the image heating device 13 is managed, for example, by the number of sheets of recording medium P passed through the image heating device 13. If it is possible to notify a user or the like that the grease G is about to run out before the number of sheets of recording medium P passed reaches the number of sheets that is considered to cause the grease G to run out, maintenance of the image heating device 13 can be performed at an appropriate timing before stick-slip occurs. However, the degree of reduction in the grease G varies depending on the usage conditions and usage environment of the image heating device 13. For example, the higher the usage temperature in the image heating device 13, the greater the reduction in the amount of grease G. Therefore, when comparing the above-mentioned case where printing is performed only in the plain paper mode with the case where printing is performed using both the thin paper mode and the plain paper mode, the reduction in the grease G is faster when printing is performed only in the plain paper mode, which has a higher usage temperature. Therefore, in a configuration having multiple printing modes such as image forming apparatus 1, when managing the lifespan of image heating device 13 by the number of recording media P, the lifespan of recording media P must be set on the assumption that image heating device 13 will be used under the most stringent conditions.

[0033] In the image forming apparatus 1, when the life of the image heating device 13 is managed by the number of sheets of recording medium P that have passed, the number of sheets of recording medium P that have passed when the grease G runs out when only the plain paper mode is continuously used as the strictest condition is set as the life number. However, in this case, when the plain paper mode and the thin paper mode are used in combination, the image heating device 13 may reach the end of its life even though there is still enough grease G remaining and the image heating device 13 is still in a usable state. Therefore, in a method of managing the lifespan of image heating device 13 by the number of sheets of recording medium P that have passed through, control unit 40 cannot notify of the lifespan of image heating device 13 at the appropriate timing, depending on the usage conditions of image heating device 13. In other words, for appropriate lifespan management of image heating device 13, it is necessary to be able to predict the remaining amount of grease G in accordance with each usage condition, even if the usage conditions of image heating device 13 change.

[0034] (4) Relationship between the driving torque and the rotation speed of the pressure roller 15 according to the remaining amount of grease G In order to predict when grease G is about to run out in image heating device 13, the inventors of the present application have focused on the fact that the relationship between the drive torque and rotation speed of pressure roller 15 changes depending on the remaining amount of grease G. To explain a method of predicting the remaining amount of grease G according to a first embodiment, first the relationship between the drive torque and rotation speed of pressure roller 15 will be explained.

[0035] FIG. 3 is a graph showing the relationship between the rotation speed and the drive torque of the pressure roller 15 when the fixing film 14 and the heater 60 are in a fluid lubrication state. In the graph of FIG. 3, the vertical axis is the drive torque of the pressure roller 15, and the horizontal axis is the rotation speed of the pressure roller 15. When the image heating device 13 starts to be used, grease G is interposed between the inner surface of the fixing film 14 and the surface of the heater 60 with a sufficient oil film thickness. In the case of a fluid lubrication state in which a lubricant with a sufficient oil film thickness exists between the members, the internal friction of the lubricant is dominant, and it is known that the greater the relative speed between the members, the greater the friction coefficient. That is, the faster the rotation speed of the fixing film 14, the greater the friction coefficient between the fixing film 14 and the heater 60. Here, the fixing film 14 rotates following the pressure roller 15. Therefore, the faster the rotation speed of the pressure roller 15, the greater the friction force between the fixing film 14 and the heater 60, and therefore the greater the drive torque of the pressure roller 15. As a result, as shown in FIG. 3, the driving torque of the pressure roller 15 increases substantially in proportion to the rotation speed of the pressure roller 15.

[0036] FIG. 4 is a graph showing the relationship between the rotation speed and the drive torque of the pressure roller 15 when the grease G has decreased and the fixing film 14 and the heater 60 are in a boundary lubrication state. In the graph of FIG. 4, the vertical axis is the drive torque of the pressure roller 15, and the horizontal axis is the rotation speed of the pressure roller 15. When the image heating device 13 is used repeatedly and the grease G is in a state where it is about to run out, the inner surface of the fixing film 14 and the surface of the heater 60 directly contact each other in most parts between the fixing film 14 and the heater 60. In this case, since there is almost no grease G between the members and the friction between the members is dominant, the absolute value of the friction coefficient becomes large, but the sensitivity of the friction coefficient to the relative speed between the members becomes small. As a result, as shown in FIG. 4, the slope of the linear approximation of the relationship between the rotation speed of the pressure roller 15 and the drive torque of the pressure roller 15 becomes small. In other words, when the remaining amount of the grease G is small, the amount of fluctuation of the pressure roller 15 when the rotation speed of the pressure roller 15 fluctuates becomes small. That is, in image heating device 13, the relationship between the rotation speed and drive torque of pressure roller 15 changes depending on the remaining amount of grease G.

[0037] (5) Structure of the fixing motor 20 and detection of the driving torque of the fixing motor 20 Next, a method for detecting the driving torque of the pressure roller 15 in the first embodiment will be described. The pressure roller 15 is driven to rotate by the fixing motor 20, which is a brushless motor. The image forming apparatus 1 is provided with a mechanism for detecting the current (coil current) passed through the coil of the fixing motor 20 when the fixing motor 20 is driven.

[0038] The structure of the fixing motor 20, which is a drive source for driving the pressure roller 15, will be described with reference to Fig. 5. Fig. 5 is a schematic diagram of the fixing motor 20. The fixing motor 20 is made up of a 6-slot stator 240 and a 4-pole rotor 241. The stator 240 includes two U-phase coils 235, two V-phase coils 236, and two W-phase coils 237. The rotor 2 The coils 235, 236, and 237 are each connected to an inverter output 233, which will be described later.

[0039] Next, the motor control unit 220 configured with a circuit for driving the fixing motor 20 and the drive current detection mechanism will be described with reference to Fig. 6. Fig. 6 is a control circuit diagram of the fixing motor 20. The motor control unit 220 includes an arithmetic processing unit using a microcomputer 221. The microcomputer 221 includes a communication port 222, an AD converter 229, a counter 223, a non-volatile memory 224, a reference clock generation unit 225, a PWM port 227, and a current value calculation unit 228.

[0040] The reference clock generating unit 225 generates a reference clock based on the output of a crystal oscillator 226 provided in the motor control unit 220. The counter 223 performs a counting operation based on the reference clock generated by the reference clock generating unit 225, and measures the period of the input pulse based on the count value, generates a PWM signal, and so on. The PWM port 227 has six terminals and outputs PWM signals of three high-side signals (UH, VH, WH) and three low-side signals (UL, VL, WL). The motor control unit 220 has a three-phase inverter 231 composed of three high-side and three low-side switching elements. For example, a transistor or an FET can be used as the switching element. Each switching element is connected to the PWM port 227 via a gate driver 232, and can be controlled to be ON / OFF by the PWM signal output from the PWM port 227. Note that each switching element is turned ON when the PWM signal is H and turned OFF when the PWM signal is L.

[0041] An inverter output (U, V, W phase output) 233 of the inverter 231 is connected to coils 235, 236, 237 of the fixing motor 20, and can control the coil current flowing through each of the coils 235, 236, 237. The coil current flowing through each of the coils 235, 236, 237 is detected by a current detection unit. The current detection unit is composed of a current sensor 230, an amplifier unit 234, an AD converter 229, and a current value calculation unit 228.

[0042] The current flowing through the coils 235, 236, and 237 is first converted to a voltage by the current sensor 230. The voltage is amplified and an offset voltage is applied to the amplifier unit 234, and then input to the AD converter 229 of the microcomputer 221. For example, if the current sensor 230 outputs a voltage of 0.01 V per 1 A, the amplification factor of the amplifier unit 234 is 10 times, and the applied offset voltage is 1.6 V, the output voltage of the amplifier unit 234 when a current of -10 A to +10 A flows is 0.6 to 2.6 V. The AD converter 229 outputs a voltage of, for example, 0 to 3 V as an AD value of 0 to 4095. Therefore, the AD value when a current of -10 A to +10 A flows is approximately 819 to 3549. The positive and negative of the current is defined as + when the current flows from the three-phase inverter 231 to the fixing motor 20.

[0043] The current value calculation unit 228 performs a predetermined operation on the AD converted data (hereinafter, referred to as the AD value) to calculate the current value. That is, the offset value is subtracted from the AD value, and the current value is obtained by multiplying the offset value by a predetermined coefficient. In the above case, the offset value is the AD value with an offset voltage of 1.6V, so that the offset value is approximately 2184, and the coefficient is approximately 0.00733. When calculating the offset value, the AD value when no coil current flows is read, stored, and used. The predetermined coefficient is stored in the non-volatile memory 224 as a standard coefficient in advance. The microcomputer 221 controls the three-phase inverter 231 via the gate driver 232, so that current flows through the coils 235, 236, and 237 of the fixing motor 20. The microcomputer 221 detects the coil current using the current sensor 230, the amplifier unit 234, and the AD converter 229, and calculates the rotor position and speed of the fixing motor 20 from the detected coil current. With the above-described configuration, the microcomputer 221 can control the rotation of the fixing motor 20.

[0044] FIG. 7 is a graph showing the relationship between the torque of the fixing motor 20 and the coil current driving the fixing motor 20 (TI characteristic). In the graph of FIG. 7, the vertical axis is the coil current of the fixing motor 20, and the horizontal axis is the torque of the fixing motor 20. As shown in FIG. 7, the torque of the fixing motor 20 and the coil current are almost proportional, so that the torque of the fixing motor 20 can be calculated from the coil current of the fixing motor 20. In the first embodiment, a conversion formula obtained from the measurement result of the TI characteristic of the fixing motor 20 is stored in advance in the non-volatile memory 224 of the control unit 40, so that the torque of the fixing motor 20 can be converted from the detected coil current. In the image heating device 13, the fixing motor 20 and the core metal of the pressure roller 15 are connected by a coupling gear or the like, and the torque of the fixing motor 20 and the driving torque of the pressure roller 15 have the same value. Therefore, the motor control unit 220 as a torque detection unit can obtain the driving torque of the pressure roller 15 from the coil current and torque of the fixing motor 20, which are physical quantities correlated with the driving torque of the pressure roller 15. In this way, in image heating device 13, the drive torque of pressure roller 15 can be detected by utilizing the coil current and torque of fixing motor 20.

[0045] (6) Prediction of remaining amount of grease G Next, it will be described how to predict the remaining amount of grease G in image heating device 13. In a first embodiment, the remaining amount of grease G is predicted from the difference in the driving torque of each of pressure rollers 15 when pressure rollers 15 operate at different rotation speeds.

[0046] After the fixing operation of recording medium P in image heating device 13 is completed, and before stopping the rotational drive of pressure roller 15, control unit 40 continues the rotational drive of pressure roller 15 in a state in which recording medium P is not conveyed to image heating device 13, thereby performing drive torque measurement control. Figure 8 is a graph showing the transition of the drive torque of pressure roller 15 when drive torque measurement control is performed. In the graph of Figure 8, the vertical axis represents the drive torque of pressure roller 15, and the horizontal axis represents time.

[0047] In the driving torque measurement control, first, as the first driving torque measurement control, the image heating device 13 is driven for 5 seconds at a target temperature of 180° C. of the fixing nip F and a first rotation speed of 240 mm / sec of the pressure roller 15. The average value Ta of the driving torque of the pressure roller 15 at this time is calculated as the first torque information (first torque). After that, as the second rotation torque measurement control, the image heating device 13 is driven for 5 seconds at a target temperature of 180° C. of the fixing nip F and a second rotation speed of 120 mm / sec of the pressure roller 15. The average value Tb of the driving torque of the pressure roller 15 at this time is calculated as the second torque information (second torque). Since the second rotation speed is set to be slower than the first rotation speed, the average value Tb is smaller than the average value Ta. Then, after the second rotation torque measurement control is completed, the driving of the image heating device 13 is stopped, and the image heating device 13 prepares for the next printing operation.

[0048] When the average values ​​Ta and Tb of the driving torque of the pressure roller 15 are obtained, the control unit 40 calculates the driving torque difference TΔ=Ta-Tb. In the first embodiment, the above-mentioned driving torque measurement control is performed every 5,000 sheets of paper passed, and the driving torque difference TΔ is calculated. FIG. 9 is a graph showing the relationship between the number of sheets of the recording medium P passed and the driving torque difference TΔ. In the graph of FIG. 9, the vertical axis represents the driving torque difference TΔ, the horizontal axis represents the number of sheets passed, and the driving torque difference TΔ is plotted every 5,000 sheets of paper passed.

[0049] As explained in section (4), in a fluid lubrication state where grease G is present between the inner surface of the fixing film 14 and the surface of the heater 60 with a sufficient oil film thickness, the driving torque difference TΔ is larger than in a boundary lubrication state. This is because, as shown in FIG. 3, the slope of the graph of the driving torque and rotation speed of the pressure roller 15 is large. On the other hand, when the image heating device 13 is used repeatedly and the amount of grease G decreases, the driving torque difference TΔ becomes smaller. This is because, as shown in FIG. 4, as the amount of grease G decreases, the slope of the graph of the driving torque and rotation speed of the pressure roller 15 becomes smaller. In other words, as the amount of grease G decreases, the driving torque difference TΔ becomes smaller. Therefore, the remaining amount of grease G can be predicted from the driving torque difference TΔ.

[0050] In the first embodiment, when the driving torque difference TΔ≦0.2 kgf·cm, the control unit 40 determines that the grease G is about to run out and that stick-slip is about to occur, and notifies the user of the end of its life. As a notification method, various methods can be adopted, such as displaying a message indicating that the image heating device 13 has reached the end of its life on a control panel (not shown) provided in the image forming apparatus 1. Note that the threshold value of the driving torque difference TΔ for determining that the grease G is about to run out is not limited to the above-mentioned value, and can be changed according to the configuration and use conditions of the image heating device. Furthermore, notification of the remaining amount information of the grease G is not limited to the timing when the grease G is about to run out, and may be performed multiple times at different timings to notify the user of the worn-out state of the image heating device 13.

[0051] In other words, image heating apparatus 13 acquires a first torque of pressure roller 15 when pressure roller 15 rotates at a first rotation speed, and a second torque of pressure roller 15 when pressure roller 15 rotates at a second rotation speed slower than the first rotation speed. Then, image heating apparatus 13 does not notify information about grease G when the amount of fluctuation between the first torque and the second torque is the first amount of fluctuation, and notifies information about grease G when the amount of fluctuation is a second amount of fluctuation less than the first amount of fluctuation. In this embodiment, the first amount of fluctuation is a value that exceeds the threshold value, and the second amount of fluctuation is a value equal to or less than the threshold value.

[0052] (7) Verification test of life prediction accuracy of image heating device 13 Next, a test performed to verify the accuracy of life prediction of image heating device 13 by the above-mentioned method for predicting the remaining amount of grease G using image heating device 13 of the first embodiment will be described. In the verification test, image heating device 13 repeatedly heated and transported recording medium P until the end of the life of image heating device 13 was notified, and the number of sheets passed at which the end of the life of image heating device 13 was notified was obtained as a result. Furthermore, even after the end of the life of image heating device 13 was notified, image heating device 13 repeatedly heated and transported recording medium P, and the number of sheets passed at which stick-slip occurred was also obtained as a result. Furthermore, in order to confirm whether the remaining amount state of grease G can be predicted appropriately in accordance with the usage conditions of image heating device 13, three types of usage conditions were used in the verification test.

[0053] In the verification test condition 1, all printing is performed in the plain paper mode. Specifically, all printing is performed with the pressure roller 15 rotation speed of 240 mm / sec, the target temperature of 200° C., and the basis weight of 80 g / m 2 As described above, the target temperature is set higher in the plain paper mode than in the thin paper mode, so condition 1 is the condition in which the grease G is reduced the fastest among the three conditions.

[0054] In the verification test condition 2, all printing is performed in the thin paper mode. Specifically, all printing is performed with the rotation speed of the pressure roller 15 at 240 mm / sec, the target temperature at 170° C., and the basis weight at 60 g / m 2 The test was performed using a recording material of Condition 2. Condition 2 was the condition in which the reduction in grease G was the slowest among the three conditions.

[0055] In the verification test condition 3, printing is performed by switching between the plain paper mode and the thin paper mode every 100 sheets. In other words, the above-mentioned conditions 1 and 2 are alternately repeated.

[0056] Furthermore, in the verification test, as a comparative example, the lifespan of image heating device 13 was managed based on the number of sheets passed, and a test was also conducted on a configuration in which the lifespan of image heating device 13 was notified. The device configuration of the comparative example was the same as that of the first embodiment, except for the method of managing the lifespan of image heating device 13. In the comparative example, image heating device 13 was used continuously under condition 1, in which the amount of reduction in grease G was the largest. With this in mind, the device is designed to notify users of the end of its life when the number of sheets passed through reaches 150,000.

[0057] Table 1 shows the results of a verification test of the life prediction accuracy of image heating device 13. Table 1 shows the number of passed sheets when life notification was given and the number of passed sheets when stick-slip occurred under each condition in the first embodiment and the comparative example.

[0058] [Table 1]

[0059] Under condition 1, in both the configurations of the first embodiment and the comparative example, the number of passed sheets when life was notified was 150,000 sheets, and the number of passed sheets when stick-slip occurred was 155,000 sheets. In other words, the number of passed sheets when life was notified and the number of passed sheets when stick-slip occurred are close values, and in both configurations, the life of image heating device 13 can be notified at the appropriate timing with respect to the actual timing of stick-slip occurrence.

[0060] On the other hand, in condition 2, in the configuration of the comparative example, the number of sheets passed when the life was notified was 150,000 sheets, and the number of sheets passed when stick-slip occurred was 255,600 sheets, and there was a large difference between the respective numbers of sheets passed. In other words, in the comparative example, the life of image heating apparatus 13 is notified at a timing significantly earlier than the timing when stick-slip actually occurs. In contrast, in the configuration of the first embodiment, the number of sheets passed when the life was notified was 250,000 sheets, and the number of sheets passed when stick-slip occurred was 255,600 sheets, and the respective numbers of sheets passed were close to each other. In other words, in the first embodiment, even in condition 2, which is a different usage condition from condition 1, the life of image heating apparatus 13 can be notified at an appropriate timing with respect to the timing when stick-slip actually occurs.

[0061] Under condition 3, in the configuration of the comparative example, the number of sheets passed when life was notified was 150,000 sheets, and the number of sheets passed when stick-slip occurred was 185,300 sheets. Also, in the first embodiment, the number of sheets passed when life was notified was 180,000 sheets, and the number of sheets passed when stick-slip occurred was 185,300 sheets. That is, in the first embodiment, even under condition 3, the life of image heating device 13 can be notified at the appropriate timing.

[0062] The results of the verification test showed that, with the configuration of the first embodiment, even if the conditions of use of image heating device 13 change, it is possible to detect when grease G is about to run out, and to notify the user of the end of life of image heating device 13 at the appropriate time.

[0063] As described above, according to the present invention, it is possible to highly accurately predict the remaining amount of grease G interposed between fixing film 14 and heater 60 based on the driving torque difference TΔ of pressure roller 15 at different rotation speeds. Furthermore, it is possible to notify the end of life of image heating device 13 at an appropriate timing before stick-slip occurs.

[0064] The application of the present invention is not limited to the above-mentioned configuration, and various modifications are possible within the scope of the invention embodied in the above-mentioned embodiment. For example, in the first embodiment, the drive torque measurement control is performed every predetermined number of sheets (every 5,000 sheets), but the period and timing for performing the drive torque measurement control can be appropriately changed.

[0065] Furthermore, in the above embodiment, the drive torque is controlled during the period from the end of the fixing operation of recording medium P to the stop of the rotational drive of pressure roller 15, but it may be controlled during other periods when recording medium P is not transported to image heating device 13. For example, the drive torque measurement control may be performed during the period from the start of the rotational drive of pressure roller 15 to the start of the fixing operation of recording medium P. Alternatively, the drive torque measurement control may be performed during the period from the end of the fixing operation of recording medium P and the stop of the rotational drive of pressure roller 15 to the start of the rotational drive of pressure roller 15 for the next fixing operation.

[0066] In addition, the timing of performing the drive torque measurement control may be optimized by, for example, increasing the frequency of performing the rotation torque measurement control as the number of sheets that can be used increases, and decreasing the frequency when the number of sheets that can be used decreases. Furthermore, for example, when it is determined that the usage rate of the plain paper mode is high, the frequency of the rotation torque measurement control may be increased, and when it is determined that the usage rate of the thin paper mode is high, the frequency may be decreased.

[0067] Furthermore, in predicting the remaining amount of grease G, the driving conditions of image heating device 13 in driving torque measurement control are not limited to the above-mentioned conditions, and it is sufficient if the driving torque of pressure roller 15 can be measured at different rotational speeds under the same target temperature.

[0068] In the first embodiment, the driving torque difference TΔ is used to predict the remaining amount of grease G, but the application of the present invention is not limited to this. For example, the remaining amount of grease G may be predicted based on the value of Ta / Tb, which is the ratio of the average value Ta of the driving torque at the first rotation speed to the average value Tb of the driving torque at the second rotation speed. Alternatively, the remaining amount of grease G may be predicted based on the value obtained by calculating the slope when the relationship between the rotation speed and the driving torque of the pressure roller 15 is linearly approximated, that is, (Ta-Tb) / (first rotation speed-second rotation speed).

[0069] In the first embodiment, a brushless motor is used for the fixing motor 20, and the driving torque of the pressure roller 15 is calculated from the driving current value, but the remaining amount of grease G may be predicted based on the current value before being converted into driving torque. In other words, it is also possible to use a physical quantity correlated with the driving torque of the pressure roller for predicting the remaining amount of grease G without calculating the driving torque of the pressure roller. In addition, when calculating the driving torque of the pressure roller 15, a mechanism capable of directly measuring the driving torque of the pressure roller 15 may be provided, instead of calculating it from the current of the fixing motor 20.

[0070] In the above embodiment, the present invention is applied to an image heating device that heats the film with a ceramic heater, but the application of the present invention is not limited to this. For example, the present invention may be applied to a radiation-type film heating type image heating device that uses a halogen heater or the like. FIG. 10 is a schematic cross-sectional view showing a radiation heating type image heating device 113, which is a modified example to which the present invention can be applied. The image heating device 113 includes a halogen heater 81 as a heating body in the internal space of the fixing film 14, and a sliding plate 83 that forms a fixing nip F with the pressure roller 15 via the fixing film 14. The image heating device 113 further includes a guide member 85 that supports the sliding plate 83 and guides the rotation of the fixing film 14, and a metal stay member 87 that holds the guide member 85. The sliding plate 83 as a nip forming member can be formed of, for example, an aluminum plate. In addition, a groove is provided between the inner peripheral surface of the fixing film 14 and the sliding plate 83. Reese G is involved.

[0071] The guide member 85 has an opening 85a that opens between the halogen heater 81 and the sliding plate 83, and the radiant heat of the halogen heater 81 is radiated to the sliding plate 83 through the opening 85a, and the fixing film 14 is heated via the sliding plate 83. In addition, the metal stay member 87 has an opening 87a that is located on the opposite side of the opening 85a with respect to the halogen heater 81, and the radiant heat of the halogen heater 81 is directly transmitted to the inner circumferential surface of the fixing film 14 through the opening 87a.

[0072] The present invention may also be applied to an image heating device of a film heating type using induction heating with a heating member formed of a magnetic core or an excitation coil. FIG. 11 is a schematic cross-sectional view showing an image heating device 213 of an electromagnetic induction heating type as a modified example to which the present invention can be applied. The image heating device 213 includes a magnetic core 91 and an excitation coil 93 as heating bodies, a guide member 95 that forms a fixing nip F with the pressure roller 15, and a metal stay member 97 that holds the guide member 95 in the internal space of the fixing film 14. The guide member 95 also has a function of guiding the rotation of the fixing film 14, and is held by the metal stay member 97. The guide member 95 as a nip forming member can be formed of, for example, a heat-resistant resin. Grease G is interposed between the inner circumferential surface of the fixing film 14 and the guide member 95.

[0073] The magnetic core 91 is inserted into the internal space of the fixing film 14, and has an excitation coil 93 wound around the magnetic core 91 in a spiral shape. The magnetic core 91 has a role of inducing magnetic field lines (magnetic flux) generated by the excitation coil 93 into the heat generating layer of the fixing film 14, and forming a path (magnetic path) of the magnetic field lines. The magnetic core 91 is formed of a ferromagnetic material with high magnetic permeability, such as sintered ferrite or ferrite resin. The excitation coil 93 is formed of a copper wire (single conductor) with a diameter of 1 to 2 mm covered with heat-resistant polyamideimide, for example. The excitation coil 93 is wound around the magnetic core 91 in a direction intersecting the axial direction of the fixing film 14. Therefore, when a high-frequency current is applied to the excitation coil 93, an alternating magnetic field is generated in a direction parallel to the axial direction, and an induced current flows in the heat generating layer of the fixing film 14, causing the fixing film 14 to heat up. In other words, the present invention is applicable to an image heating device that includes a fixing film to be heated, and a nip forming member that contacts the inner surface of the fixing film and forms a nip portion with a pressure roller via the fixing film, and in which a lubricant is interposed between the fixing film and the nip forming member.

[0074] In the above embodiment, the pressure roller 15 is driven by the fixing motor 20, and the fixing film 14 is rotated in accordance with the rotation of the pressure roller 15. However, the fixing film 14 may be directly rotated by a drive source. For example, the fixing film may be rotated by holding both ends of the fixing film in the direction of the axis of rotation with rotatable cap members or the like.

[0075] <Second Example> Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in that the number of sheets of recording medium P that will pass through image heating device 13 until the end of its life is predicted in advance before grease G is about to run out and image heating device 13 reaches the end of its life. In the following explanation, only the characteristic parts of the second embodiment will be explained, and explanations of the basic configurations of image forming apparatus 1 and image heating device 13 similar to those of the first embodiment will be omitted.

[0076] In the first embodiment, when the driving torque difference TΔ of pressure roller 15 when rotating at different speeds becomes equal to or less than a predetermined value, specifically when the driving torque difference TΔ≦0.2 kgf cm, it is determined that image heating device 13 has reached the end of its life and a notification is given. In the second embodiment, the timing when image heating device 13 will reach the end of its life is predicted from the progress of the driving torque difference TΔ, and the user is able to know in advance the number of sheets remaining until image heating device 13 reaches the end of its life.

[0077] Fig. 12 is a graph showing the transition of the driving torque difference TΔ when the driving torque measurement control is performed every 5,000 sheets of paper as in the first embodiment, and the driving torque difference TΔ=Ta-Tb. The graph in Fig. 12 has the driving torque difference TΔ on the vertical axis and the number of sheets of paper on the horizontal axis, and the driving torque difference TΔ is plotted for every 5,000 sheets of paper up to the number of sheets of paper 100,000.

[0078] In the second embodiment, the control unit 40 generates a TΔ transition curve, which is an approximation curve (regression curve), for example, by the least squares method from the transition of the drive torque difference TΔ up to the number of passed sheets being 100,000. Then, the control unit 40 predicts and calculates the number of sheets to reach the end of life Ppre, which is the number of sheets to be passed when the drive torque difference TΔ=0.2 kgf·cm, from the obtained TΔ transition curve. By predicting and calculating the number of sheets to reach the end of life Ppre in advance in this manner, the control unit 40 can display, for example, the difference between the predicted number of sheets to reach the end of life Ppre and the current number of sheets to be passed as the remaining number of sheets that can be passed until the end of the life of the image heating device 13, on a control panel or the like. With this configuration, the user can know in advance the timing for replacement or maintenance of the image heating device 13.

[0079] It should be noted that the TΔ transition curve need not be generated just once, but may be generated each time the drive torque measurement control is performed and the value of the drive torque difference TΔ is updated. By generating a TΔ transition curve based on more drive torque differences TΔ, the prediction accuracy of the number of sheets to reach the end of life Ppre is improved. It should be noted that the threshold value of the drive torque difference TΔ for determining that the image heating apparatus is about to run out is not limited to the above-mentioned value, and can be changed according to the configuration and use conditions of the image heating apparatus.

[0080] <Third Example> Next, a third embodiment of the present invention will be described. The third embodiment differs from the first embodiment in that the motor that drives image heating device 13 also drives devices other than the image heating device. In the following explanation, only the characteristic parts of the third embodiment will be explained, and explanations of the basic configurations of image forming device 1 and image heating device 13 similar to those of the first embodiment will be omitted.

[0081] 13 is a schematic cross-sectional view of an image forming apparatus 1 in the third embodiment. All members that were driven by the fixing motor 20 and the main motor 50 in the first embodiment are driven only by the motor 70 in the third embodiment.

[0082] In the third embodiment, the motor 70 drives all the members, so the torque of the motor 70 includes torques other than the driving torque of the pressure roller 15 of the image heating device 13. Specifically, the torque includes the rotation torque of the photosensitive drum 19, the rotation torque of the recording material conveying system such as the pickup roller 22, the paper feed roller 23, and the pair of registration rollers 24. In such a case, the torque of the motor 70 and the driving torque of the pressure roller 15 do not match, so the absolute value of the driving torque of the pressure roller 15 cannot be calculated. Therefore, the third embodiment is configured to calculate the torque difference MΔ as the difference in the torque of the motor 70 when the pressure roller 15 is rotated at different rotation speeds. Then, the remaining amount state of the grease G interposed between the fixing film 14 and the heater 60 is predicted from the transition of the torque difference MΔ.

[0083] In the third embodiment, similarly to the first embodiment, after image heating device 13 performs the fixing process on recording medium P, the driving of motor 70 is continued in a state in which recording medium P is not being transported into image forming apparatus 1, and torque measurement control is performed. For example, as a first torque measurement control, image heating device 13 is driven for 5 seconds at a target temperature of fixing nip F of 180° C. and a first rotation speed of 240 mm / sec. The average value Ma of the torque of motor 70 at this time is calculated as first torque information. Thereafter, as a second torque measurement control, image heating device 13 is driven for 5 seconds at a target temperature of fixing nip F of 180° C. and a second rotation speed of 120 mm / sec. The average value Mb of the torque of motor 70 at this time is calculated as second torque information. Then, after the second torque measurement control ends, driving of image heating device 13 is stopped, and image heating device 13 prepares for the next printing operation.

[0084] When the control unit 40 obtains the average values ​​Ma and Mb of the driving torque of the motor 70, it calculates the torque difference MΔ=Ma-Mb. Such torque measurement control is performed, for example, every 5,000 sheets of paper passed, and the torque difference MΔ is calculated, thereby obtaining the transition of the torque difference MΔ. FIG. 14 is a graph showing the transition of the torque difference MΔ with the torque difference MΔ on the vertical axis and the number of sheets passed on the horizontal axis. As shown in FIG. 14, once a certain number of sheets is passed, the graph remains almost flat even if the number of sheets passed increases, and the torque difference MΔ is an almost constant value. The reason for this will be explained below.

[0085] As described above, the motor 70 is a driving source for driving the pressure roller 15 and other members. Therefore, the torque difference MΔ of the motor 70 is the sum of the driving torque difference TΔ of the pressure roller 15 and the driving torque difference SΔ of the other members, and has a relationship of MΔ=TΔ+SΔ. Here, the driving torque difference TΔ of the pressure roller 15 changes according to the reduction of the grease G interposed in the fixing film 14 as described in the first embodiment. Therefore, the driving torque difference TΔ decreases according to the increase in the number of sheets passed. On the other hand, in the transport roller that transports the photosensitive drum 19 and the recording medium P, the main factor generating the driving torque is not the influence of a lubricant such as grease G, but the direct sliding between the members and the friction with the bearings. In particular, the driving torque of the transport roller, which is dominated by the influence of friction with the bearings, does not change almost depending on the rotation speed because the friction coefficient does not depend on the rotation speed. In other words, the driving torque difference SΔ due to the transport roller is almost 0. On the other hand, the dominant factor in the rotation torque of the photosensitive drum 19 is the friction between the cleaning blade 18 and the photosensitive drum 19. Because the cleaning blade 18 is made of a viscoelastic material, the friction between the cleaning blade 18 and the photosensitive drum 19 tends to increase as the rotation speed increases (SΔ>0). However, the frictional force between the cleaning blade 18 and the photosensitive drum 19 is determined by the physical properties of the material and the contact pressure, and changes very little even when the image forming apparatus 1 is used repeatedly. Therefore, the driving torque difference SΔ attributable to the photosensitive drum 19 is an approximately constant value regardless of the durability state of the material.

[0086] That is, while the driving torque difference TΔ of the pressure roller 15 decreases as the number of sheets of paper increases, the driving torque difference SΔ of rollers other than the pressure roller 15 hardly changes. Then, when the grease G of the image heating device 13 runs out, the driving torque difference TΔ of the pressure roller 15 also stops decreasing. That is, the torque difference MΔ of the motor 70 initially decreases as the number of sheets of the recording medium P increases, but as the number of sheets of paper increases further, it becomes an almost constant value and transitions as shown in FIG. 14. In other words, in the MΔ transition curve, at the point when the decrease in the torque difference MΔ stops, the driving torque difference TΔ of the pressure roller 15 does not change, and the grease G interposed between the inner surface of the fixing film 14 and the surface of the heater 60 is in a state immediately before being depleted.

[0087] For this reason, the third embodiment is configured to calculate the value of the torque difference MΔ every 1,000 sheets of paper, and predict the remaining amount state of grease G from the amount of change in the torque difference MΔ. Specifically, when the amount of change between the value of the torque difference MΔa calculated in the torque measurement control and the value of the torque difference MΔb calculated in the torque measurement control performed next becomes 0.2 kgf·cm or less, it is determined that grease G is about to run out. Then, when control unit 40 determines that grease G is about to run out and that stick-slip is about to occur, it notifies the user, etc. of the life of image heating device 13. Note that the threshold value of the amount of change in the torque difference MΔ for determining that grease G is about to run out is not limited to the above-mentioned value, and can be changed according to the configuration and usage conditions of the image heating device.

[0088] As described above, according to the present invention, a dedicated mode for driving image heating device 13 as in the third embodiment is used. Even in a configuration in which there is no motor and the entire image forming apparatus 1 is driven by a single motor, it is possible to accurately predict the remaining amount of grease G interposed between the fixing film 14 and the heater 60. Furthermore, it is possible to notify the end of life of the image heating device 13 at an appropriate timing before stick-slip occurs.

[0089] The disclosure of this embodiment includes the following configurations (and methods). (Configuration 1) A cylindrical film; A roller that contacts an outer peripheral surface of the film; a nip forming member provided in an internal space of the film and forming a nip portion with the roller via the film; a lubricant is applied between the film and the nip forming member, and a recording medium is nipped and conveyed at the nip portion, a torque detection unit that acquires, as torque information that is a torque of the roller or a physical quantity correlated with the torque of the roller, first torque information of the roller when the roller rotates at a first rotation speed and second torque information of the roller when the roller rotates at a second rotation speed that is slower than the first rotation speed; a control unit that notifies information about a remaining amount of the lubricant interposed between the film and the nip forming member based on the first torque information and the second torque information; An image heating apparatus further comprising: (Configuration 2) 2. The image heating apparatus according to configuration 1, wherein the torque detection section acquires the torque information every time a predetermined number of sheets of the recording medium are passed through. (Configuration 3) The image heating apparatus described in configuration 1 or 2, characterized in that when the difference between the first torque information and the second torque information becomes equal to or less than a predetermined value, the control unit reports, as the remaining amount information, that the lubricant interposed between the film and the nip forming member is about to run out. (Configuration 4) The image heating apparatus described in configuration 1 or 2, characterized in that when a ratio of the first torque information to the second torque information becomes equal to or less than a predetermined value, the control unit reports, as the remaining amount information, that the lubricant interposed between the film and the nip forming member is about to run out. (Configuration 5) The image heating apparatus described in configuration 2, characterized in that the control unit acquires a difference between the first torque information and the second torque information for each of the specified number of sheets passed, predicts a change in the difference, and notifies the remaining number of sheets that can be passed until the lubricant is depleted. (Configuration 6) The image heating apparatus described in configuration 1 or 2, characterized in that when a difference between a first difference amount between the first torque information and the second torque information at a first number of sheets passed and a second difference amount between the first torque information and the second torque information at a second number of sheets passed that is greater than the first number of sheets passed becomes less than a predetermined value, the control unit reports, as the remaining amount information, that the lubricant interposed between the film and the nip forming member is about to run out. (Configuration 7) The image heating apparatus described in any one of configurations 1 to 6, characterized in that the control unit rotates the roller at the first rotation speed or the second rotation speed when a recording medium is not nipped and transported in the nip portion, and during that time, the torque detection unit acquires the first torque information or the second torque information. (Configuration 8) The control unit is The period from the end of the fixing operation of the recording medium to the stop of the rotational drive of the roller, or A period from when the roller starts to rotate until when the fixing operation of the recording medium starts, or The image heating apparatus of configuration 7, characterized in that the roller is rotated at the first rotation speed or the second rotation speed during any period from after a fixing operation of a recording medium is completed and the rotational driving of the roller is stopped to when the rotational driving of the roller is started for the next fixing operation. (Configuration 9) a motor driven by a current flowing through a coil to rotate the roller; 10. The image heating apparatus according to any one of configurations 1 to 9, wherein the torque detection section acquires the torque of the motor as the physical quantity correlated with the torque of the roller. (Configuration 10) a motor driven by a current flowing through a coil to rotate the roller; 2. The image heating apparatus according to configuration 1, wherein the torque detection section obtains a magnitude of a current flowing through the coil as the physical quantity correlated with the torque of the roller. (Configuration 11) 11. An image heating apparatus according to any one of configurations 1 to 10, wherein the nip forming member is a heater that heats the film. (Configuration 12) 11. An image heating apparatus according to any one of configurations 1 to 10, further comprising a halogen heater that heats the film. (Configuration 13) 13. An image heating apparatus according to configuration 12, wherein the nip forming member is a sliding plate. (Configuration 14) 11. An image heating apparatus according to any one of configurations 1 to 10, further comprising a heating member that is constituted by a magnetic core and an exciting coil, and that heats the film. (Configuration 15) 15. An image heating apparatus according to configuration 14, wherein the nip forming member is a guide member that guides the rotation of the film. (Configuration 16) A cylindrical film; A roller that contacts an outer peripheral surface of the film; a nip forming member provided in an internal space of the film and forming a nip portion with the roller via the film; a lubricant is applied between the film and the nip forming member, and a recording medium is nipped and conveyed at the nip portion, an image heating apparatus comprising: an image heating device, the image heating device comprising: an image heating device that, when a variation amount between a first torque of the roller when the roller rotates at a first rotation speed and a second torque of the roller when the roller rotates at a second rotation speed slower than the first rotation speed, does not notify information about the lubricant when the variation amount is a first variation amount; and, when the variation amount is a second variation amount smaller than the first variation amount, notifies information about the lubricant. (Configuration 17) 17. The image heating apparatus according to configuration 16, further comprising a control unit that acquires the first torque and the second torque and calculates the amount of fluctuation. (Configuration 18) The present invention is characterized in that the control unit further includes a control unit that acquires first torque information, which is a physical quantity correlated with the first torque, and second torque information, which is a physical quantity correlated with the second torque, and calculates a variation between the first torque information and the second torque information. Image heating device. (Configuration 19) a motor driven by a current flowing through a coil to rotate the roller; 19. An image heating apparatus according to any one of configurations 16 to 18, wherein the first torque and the second torque are obtained from a current flowing through the coil. (Configuration 20) 20. An image heating apparatus according to any one of configurations 16 to 19, wherein the nip forming member is a heater that heats the film. (Configuration 21) 20. An image heating apparatus according to any one of Configurations 16 to 19, further comprising a halogen heater that heats the film. (Configuration 22) 22. An image heating apparatus according to configuration 21, wherein the nip forming member is a sliding plate. (Configuration 23) 20. An image heating apparatus according to any one of Configurations 16 to 19, further comprising a heating member that is constituted by a magnetic core and an exciting coil, and that heats the film. (Configuration 24) 24. An image heating apparatus according to configuration 23, wherein the nip forming member is a guide member that guides the rotation of the film. (Configuration 25) an image forming section for forming an image on a recording material; An image heating device according to any one of configurations 1 to 24, which fixes an image formed on a recording material to the recording material; An image forming apparatus comprising: [Explanation of symbols]

[0090] 13: image heating device, 14: fixing film (film), 15: pressure roller (roller), 40: control section, 60: heater (nip forming member), F: fixing nip (nip section), G: grease (lubricant), P: recording material

Claims

1. an image forming section for forming an image on a recording material; an image heating device including a cylindrical film, a roller that contacts an outer peripheral surface of the film, and a nip forming member that is provided in an internal space of the film and forms a nip portion with the roller via the film, and fixes an image formed on a recording material to the recording material; a motor that is driven by a current flowing through a coil, the motor being a drive source that drives the roller to rotate and drives the image forming unit; a lubricant is applied between the film and the nip forming member, and a recording medium is nipped and conveyed at the nip portion, the nip forming member includes a heater that heats the film and is controlled to a predetermined temperature; a torque detection unit that acquires, as torque information related to the torque of the roller, first torque information of the roller when the roller rotates at a first rotation speed and second torque information of the roller when the roller rotates at a second rotation speed slower than the first rotation speed, by measuring a current value flowing through the coil of the motor; a control unit that determines that the lubricant is depleted when a change amount of a difference between the first torque information and the second torque information becomes equal to or less than a predetermined value, and notifies a user of the end of life of the image heating apparatus, The image forming apparatus according to claim 1, wherein the torque detection unit obtains the first torque information and the second torque information in a state in which the heaters are controlled to have the same temperature.

2. 2. The image forming apparatus according to claim 1, wherein the torque detection unit obtains the torque information every time a certain number of sheets of the recording medium are passed through.

3. The image forming apparatus according to claim 2, characterized in that the control unit acquires the difference between the first torque information and the second torque information for each fixed number of sheets passed, predicts the change in the difference, and notifies the user of the remaining number of sheets that can be passed until the lubricant is depleted.

4. The control unit controls the roller when the recording medium is not being nipped and conveyed in the nip portion. 2 . The image forming apparatus according to claim 1 , wherein the image forming apparatus is rotated at the first rotation speed or the second rotation speed, and the torque detection unit acquires the first torque information or the second torque information during the rotation.

5. The control unit is The period from the end of the fixing operation of the recording medium to the stop of the rotational drive of the roller, or A period from when the roller starts to rotate until when the fixing operation of the recording medium starts, or 5. The image forming apparatus according to claim 4, wherein the roller is rotated at the first rotation speed or the second rotation speed during any period from after the fixing operation of the recording medium is completed and the rotational drive of the roller is stopped to before the rotational drive of the roller is started for the next fixing operation.

6. 2. The image forming apparatus according to claim 1, wherein the nip forming member is a heater that heats the film.

7. 2. The image forming apparatus according to claim 1, further comprising a halogen heater for heating the film.

8. 8. The image forming apparatus according to claim 7, wherein the nip forming member is a sliding plate.

9. 2. The image forming apparatus according to claim 1, further comprising a heating member that is constituted by a magnetic core and an exciting coil and that heats the film.

10. 10. The image forming apparatus according to claim 9, wherein the nip forming member is a guide member that guides the rotation of the film.

Images