Image heating device and imaging device

Abstract

The present invention provides an image heating device and an imaging device. An image heating device includes: a film in contact with a recording material; a heater unit configured to contact the inner surface of the film, the heater unit including a heater and a heater support member supporting the heater, wherein the heater is fixed to the heater support member; a pressure roller, which forms a clamping portion with the heater unit under the intervention of the film, the clamping portion is used to clamp and convey the recording material; a pressing member, which presses the heater toward the pressure roller without the intervention of the heater support member; a pressure adjustment mechanism for adjusting the pressure in the clamping portion; and a control unit that controls the pressure adjustment mechanism, wherein the control unit adjusts the pressure according to the temperature detected by the temperature detection member that detects the temperature of the heater.

Description

Technical Field

[0001] The present invention relates to an image heating device used in an image forming apparatus such as a copying machine or a laser beam printer. Background Art

[0002] An image forming apparatus (e.g., an electrophotographic system type copier or a laser beam printer) includes a transfer device for transferring a toner image onto a recording material and an image heating device (hereinafter referred to as a fixing device) for heating and pressurizing the toner image to fix it on the recording material. The image forming apparatus causes interruption of recording material conveyance due to some error, which is called a paper jam. Japanese Patent Application Publication No. H07-129018 discloses a technology in which a recording material detection unit for detecting whether a recording material remains on a fixing device and a pressure release mechanism for releasing the pressure of the fixing device are provided to allow the pressure of the fixing device to be automatically released when a paper jam is detected, thereby facilitating the removal of the jammed recording material from the fixing device.

[0003] A technology is also disclosed in which, when the power of the image forming apparatus is turned off or during transition to a sleep mode in which the image forming apparatus is not used for a period of time, pressurization of the fixing device is automatically released to prevent deterioration such as deformation of the fixing member due to prolonged pressurization.

[0004] Suggested examples of heating methods for fixing devices include: a heating roller method using a fixing roller in the form of a cylindrical body containing a halogen heater or the like, and a pressure roller; and a film heating method as a heating method capable of achieving power saving for the fixing device. Examples of fixing devices using the film heating method include a fixing device in which a sliding clamping portion (hereinafter referred to as an inner surface clamping portion) is formed by a low heat capacity tubular belt (hereinafter referred to as a film) mainly made of a heat-resistant resin or metal, a heating body (hereinafter referred to as a heater) made of ceramics or the like that comes in sliding contact with the inner surface of the cylindrical belt, and a heating body support (hereinafter referred to as a heater support or a heater holder), and a pressure contact clamping portion (hereinafter referred to as a fixing clamping portion) is formed by pressurizing with a pressure member under the intervention of the film.

[0005] This fixing device is configured such that: the heater is attached to the heater holder, and pressing members (such as a thermistor for detecting the temperature of the heater, a thermal switch as a safety element, and a connector for supplying power to the heater) are inserted through holes provided in the surface of the heater support seat of the heater holder to press the heater. These pressing members are supported in press contact with the heater, and a force acts in a direction to separate the heater from the heater holder.

[0006] When the pressure of the fixing device is automatically released in the imaging device and the heater is pulled away from the heater holder by pressing from the above-mentioned pressing member in a state such as when a paper jam is detected, when the power is turned off, and during the transition to the sleep mode, the supporting state of the pressing member changes. This may cause the working conditions of the temperature detection and safety element made by the thermistor to be unstable, or cause the edge of the heater to contact the inner surface of the film and damage the inner surface of the film. Japanese Patent Application Publication No. 2016-12077 discloses a structure that suppresses the separation of the heater caused by the above-mentioned pressing member by inserting an adhesive at a predetermined space between the heater and the heater holder to support the heater.

[0007] Typical examples of the above adhesive include an adhesive of a silicone rubber system having elasticity for absorbing stress due to the difference in thermal expansion coefficient between the heater and the heater holder and for withstanding a high temperature of 200° C. or more.

[0008] Unfortunately, silicone rubber-based adhesives generally have a property in which, as the temperature rises above normal temperature, the adhesive itself softens, which can easily cause scratches. When the pressurization of the fixing device is automatically released as described above, the adhesive tends to stretch in the direction in which the heater is separated from the heater holder due to the pressure of the pressing member. In particular, high temperature conditions (such as when a paper jam is detected) cause the adhesive to stretch to a greater extent, so that a large load is applied to the interface (bonding interface) between the heater or heater holder and the adhesive through the elastic restoring force of the adhesive. When such a load is repeatedly applied, the bonding strength in the bonding interface gradually decreases, so that adhesive peeling easily occurs. This will make the number of repetitions of pressure release (such as the number of paper jams or the number of power off times) a rate limiting value for the life of the fixing device.

[0009] In recent years, from the viewpoint of saving energy used by the imaging device, it has become standard to control the transition to sleep mode immediately after the print job is completed. This leads to an increase in the frequency of releasing the pressurization of the fixing device under high temperature conditions, thus increasing the impact on the life of the fixing device.

[0010] An object of the present invention is to provide a technique capable of reducing the influence of pressure release on the life of an image heating device by improving the pressure release control of the image heating device to prevent the adhesive strength between a heater and a heater holder from being reduced. Summary of the invention

[0011] In order to achieve the above object, the image heating device of the present invention comprises the following:

[0012] a film formed into a tubular shape and configured to rotate in contact with a recording material;

[0013] a heater unit configured to contact the inner surface of the film, the heater unit comprising a heater and a heater support configured to support the heater in a longitudinal direction of the heater, wherein the heater is fixed to the heater support by an adhesive;

[0014] a temperature detection member configured to detect a temperature of the heater;

[0015] a pressure roller configured to contact the outer surface of the film and to form a nip portion with the heater unit under the intervention of the film, the nip portion being used to nip and convey the recording material;

[0016] a pressurizing spring configured to pressurize the heater toward the pressurizing roller under the intervention of a heater support member for forming a nip portion;

[0017] a pressing member configured to press the heater toward the pressure roller without the intervention of the heater support;

[0018] a pressure regulating mechanism configured to regulate the pressure of the pressurizing spring; and

[0019] a control unit configured to control the pressure regulating mechanism;

[0020] The control unit causes the pressure adjustment mechanism to adjust the pressure according to the temperature detected by the temperature detection member.

[0021] In order to achieve the above object, the imaging device of the present invention comprises the following:

[0022] an image forming section configured to form an image on a recording material; and

[0023] a fixing unit configured to fix the image formed on the recording material on the recording material,

[0024] Here, the fixing unit is the image heating device of the present invention.

[0025] The present invention can reduce the influence of the pressurization release on the life of the image heating device by preventing the adhesive strength between the heater and the heater support from decreasing.

[0026] Other features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. The various embodiments of the present invention described below may be implemented individually or in combination with a plurality of embodiments. Similarly, the features of the various different embodiments may also be combined when necessary or when it is beneficial to combine the elements or features from the various embodiments into a single embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a cross-sectional view of the imaging device 100;

[0028] Figure 2 is a cross-sectional view of the fixing device 200;

[0029] Figure 3A 3B and 3C are explanatory diagrams showing the bonding structure between the heater 210 and the heater holder 220 in Example 1;

[0030] Figure 4 shows the temperature characteristics of the interfacial bonding strength of the adhesive 280;

[0031] Figure 5A and Figure 5B The mechanism of the temperature characteristics of the interfacial peeling force of the adhesive 280 is shown;

[0032] Figure 6 is a control flow chart for releasing the pressure when a jam of the recording material P is detected;

[0033] Figure 7 is a control flow chart for pressure release when the printer power is turned off;

[0034] Figure 8 is a control flow chart for pressure release when transitioning to sleep mode;

[0035] Fig. 9 is a control flow chart of pressure release in Example 2; and

[0036] Fig.10 This is a control flow chart for pressure release in Example 3. DETAILED DESCRIPTION

[0037] Hereinafter, a description of an embodiment (example) of the present invention will be given with reference to the accompanying drawings. However, the size, material, shape, relative arrangement, etc. of the constituent elements described in the embodiment may be appropriately changed according to the configuration of the device to which the present invention is applied, various conditions, etc. Therefore, the size, material, shape, relative arrangement, etc. of the constituent elements described in the embodiment are not intended to limit the scope of the present invention to the following embodiments.

[0038] Example 1

[0039] Figure 1 1 is a cross-sectional view of a laser printer (image forming apparatus) 100 using an electrophotographic recording technique. Examples of image forming apparatuses to which the present invention is applicable include copiers and printers using an electrophotographic system and an electrostatic recording system. Then, the case described here is that the present invention is applied to a laser printer that forms an image on a recording material P using an electrophotographic system.

[0040] The video controller 120 receives and processes image information and print instructions sent from an external device such as a personal computer. The control section 113 is connected to the video controller 120, and controls each unit constituting the imaging device in response to an instruction from the video controller 120. When the video controller 120 receives a print instruction from an external device, imaging is performed by the following actions.

[0041] When a print signal is generated, the scanning unit 21 emits a laser beam modulated according to the image information, and then scans the photoreceptor 19 electrostatically charged to a predetermined polarity by the electrostatic charging roller 16. This causes an electrostatic latent image to be formed on the photoreceptor 19. The developing device 17 supplies toner to the electrostatic latent image to form a toner image corresponding to the image information on the photoreceptor 19. Then, the recording material (recording paper) P stacked in the paper feed cassette (paper feed section) 11 is fed sheet by sheet by the pickup roller 12 and conveyed toward the stop roller 14 by the roller 13. In synchronization with the moment when the toner image on the photoreceptor 19 reaches the transfer position defined by the photoreceptor 19 and the transfer roller 20, the recording material P is further conveyed from the stop roller 14 to the transfer position. In the process of the recording material P passing through the transfer position, the toner image on the photoreceptor 19 is transferred to each sheet of the recording material P. Then, the recording material P is heated by the fixing device (image heating device) 200 as a fixing section (image heating section), and the toner image is heated and fixed on each recording material P. Each recording material P carrying the fixed toner image is discharged into a tray at the upper part of the laser printer 100 by rollers 26 and 27. A cleaner for cleaning the photoreceptor 19 is marked as 18. Electric power is supplied to the fixing device 200 from a control circuit 40 connected to a commercial AC power supply 41. The photoreceptor 19, the electrostatic charging roller 16, the scanning unit 21, the developing device 17, and the transfer roller 20 as described above constitute an image forming section for forming an unfixed image on each recording material P. A cartridge as a replaceable unit is marked as 15.

[0042] Figure 22 is a cross-sectional view of the fixing device 200. The fixing device 200 includes a thin-walled heater 210 as a heating body, a heater holder 220 as a heating body supporting member (heater support), and a tubular film 230, which travels and moves as a moving body while in sliding contact with the heater 210. The fixing device 200 also includes: a thermistor 250 as a temperature detection member for detecting the temperature of the heater 210; and a pressure roller 290 as a pressure member, which forms a fixing nip N as a pressure contact nip for clamping each recording material P with the heater 210 under the intervention of the film 230 at a predetermined pressure, and the fixing nip N is formed between the outer surface of the film 230 and the pressure roller 290. The fixing device 200 also includes a pressure mechanism 300 as a pressure adjustment mechanism, which can apply or release the pressure for forming the fixing nip N.

[0043] The film 230 may include a substrate made of a heat-resistant resin (such as polyimide) or a metal (such as stainless steel), on which an elastic layer made of heat-resistant rubber or the like and a release layer made of a heat-resistant resin may be provided. The pressure roller 290 includes a core metal 291 made of a material such as iron or aluminum and an elastic layer 292 made of a material such as silicone rubber. The pressure roller 290 rotates in the direction of the arrow by receiving power from the motor M1. The heater 210 is mainly made of ceramic (such as alumina) or metal (such as stainless steel (SUS)), and is provided with a resistive heating element that generates heat when power is supplied. The heater 210 is supported by a heater holder 220 made of a heat-resistant resin (such as a liquid crystal polymer) by using an adhesive described later.

[0044] The heater 210 has an opposite surface opposite to the sliding contact surface with which the film 230 is in sliding contact, such as Figure 3AThe pressing member of thermistor 250 and safety element 260 shown in FIG. 3C is arranged to contact the opposite surface, so as to press the heater 210 in the direction of peeling the heater 210 from the heater holder 220. Thermistor 250 is a temperature detection member for detecting the temperature of the heater 210 and feeding back the temperature to control the temperature. The present embodiment adopts a unit member formed in the following manner: a resistance element whose resistance varies with temperature is supported on a heat-resistant member (such as ceramic paper) and insulated and protected by a pressure-resistant member (such as polyimide film). Thermistor 250 is arranged to contact the heater 210 by the pressure of thermistor pressure spring 250a held by the pressing member holder 270. Safety element 260 is a protection element, such as a thermal switch or a temperature fuse, which operates in an abnormally high temperature state to cut off the power supplied to the heater 210, thereby preventing the temperature of the heater 210 from excessively rising. The safety element 260 is arranged to be in contact with the heater 210 by the pressure of the safety element pressing spring 260 a held by the pressing member holder 270 .

[0045] The heater holder 220 has an opposite surface opposite to the surface supporting the heater, and the pressing bracket 240 is a thick-walled member formed of a rigid member (such as metal), and the pressing bracket 240 is arranged to contact the opposite surface, thereby forming a fixing nip N by applying pressure to the pressing roller 290.

[0046] The pressure mechanism 300 includes a fixing frame 201, a pressure spring 202, a pressure plate 203, and a pressure release cam 204. The pressure mechanism 300 applies the pressure of the pressure spring 202 held by the fixing frame 201 to both ends of the longitudinal direction of the pressure bracket 240 as the second pressure member by the pressure plate 203. When the pressure is transmitted toward the pressure roller 290 through the contact area with the heater holder 220, the fixing nip N is formed. This embodiment allows the heater 210, the heater holder 220, the pressure bracket 240, etc. to constitute the heater unit 222 that contacts the inner surface of the film 230.

[0047] Then, the pressure release cam 204 is arranged to contact the pressure plate 203, and the command to release the pressure of the fixing device 200 causes the pressure release cam 204 to rotate a predetermined amount using the power from the motor M2 to lift the pressure plate 203, thereby releasing the pressure forming the fixing nip N. The operation flow of releasing the pressure of the fixing device 200 will be described in detail later. The pressure release in this embodiment includes not only not generating pressure, but also reducing the pressure required to heat and fix the toner image on the recording material P to a degree that allows paper jam processing and deformation of the fixing member.

[0048] Figure 3A3C are explanatory diagrams showing the bonding structure between the heater 210 and the heater holder 220 .

[0049] Figure 3A 2 is a plan view of the heater 210 viewed from the fixing nip N side. The heater 210 includes a substrate 211 on which a resistance heating element layer 212 that generates heat by energizing is formed, an electrode 213 for energizing the resistance heating element layer 212, and a protective layer 214 that insulates and protects the resistance heating element layer 212. Although in the present embodiment, the surface provided with the resistance heating element 212 is configured to slide on the film 230 and the opposite surface is configured to be bonded to the heater holder 220, the surface provided with the resistance heating element 212 may be configured to be bonded to the heater holder 220.

[0050] 3B is a plan view of the heater supporting surface of the heater holder 220 viewed from the fixing nip N side, and FIG. 3C is a cross-sectional view of the heater 210 and the heater holder 220 bonded to each other by the adhesive 280, taken along line X-X in FIG. 3B.

[0051] The heater holder 220 has a heater support surface in which respective through holes are opened at predetermined longitudinal positions, and thermistors 250, 251, and 252 and the safety element 260 are arranged to pass through the corresponding through holes to contact the heater 210. In the present embodiment, each of the thermistor and the safety element has a pressure of 5N each.

[0052] Adhesive points 281 are provided in the longitudinal direction of the heater holder 220 across the corresponding thermistors 250, 251 and 252 and across the safety element 260, so that the heater 210 and the heater holder 220 are bonded to each other using the adhesive 280 of the silicone rubber system. In this embodiment, the adhesive points 281 in the heater holder 220 all have an uneven surface profile to increase the bonding area. In addition, the surface profile can be flat, or, for example, the surface can be sandblasted.

[0053] For the adhesive 280 in this embodiment, the adhesive KE-3417 of a one-component and condensation reaction (moisture curing) silicone rubber system available from Shin-Etsu Chemical Co., Ltd. is used. In addition, the adhesive 280 may be a two-component and addition reaction (heat curing) adhesive, or may be an adhesive of a rubber system having heat resistance of 200°C or more. In addition, a primer may be used alone to enhance the bonding strength. Each bonding point 281 has a coating range of 5 mm in diameter, and the coating amount of the adhesive 280 is 10 mg.

[0054] Next, the temperature characteristics of the adhesive strength of the adhesive 280 obtained by the inventors through previous investigations will be described. In this embodiment, the adhesive strength represents the interfacial peeling force between the adhesive 280 and the heater holder 220, or the interfacial peeling force between the adhesive 280 and the heater 210, but does not represent the fracture strength of the adhesive itself.

[0055] The present inventors conducted a previous investigation as described below to measure the bonding strength of each bonding point.

[0056] The assembly for evaluation is formed as follows: a portion of the heater holder 220 is cut out, the portion including one bonding point and two open through holes spanning the one bonding point in the longitudinal direction; and a portion cut out from the heater 210 having a length similar to that of the portion cut out from the heater holder is bonded to the portion cut out from the heater holder under the above conditions, but the thermistor and the safety element are not assembled. The exposed surface of the heater of the assembly for evaluation is placed on a hot plate adjustable from room temperature to 230°C, and the heater is pressed against the hot plate via two through holes using a heater pressing tool. After the heater temperature is sufficiently increased, the assembly is pulled in a direction to separate the heater 210 from the heater holder 220 using a dynamometer. Then, the peak value of the tensile strength at the time of peeling of the bonding interface is defined as the interface peeling force or simply the bonding strength.

[0057] Figure 4 The trend of hot plate temperature with respect to interfacial peel force obtained using the above-mentioned components for evaluation is shown. Figure 4 As shown, the interfacial peeling force decreases from room temperature to high temperature, and in this embodiment, the interfacial peeling force at 230° C. is less than half of the interfacial peeling force at room temperature, so it is found that as the temperature increases, a smaller force can be used to peel the interface.

[0058] Figure 5A and Figure 5B The mechanism of the temperature characteristics of the interfacial peeling force as described above is shown. When a predetermined tensile strength or, for example, a 5N force for separating the heater 210 from the heater holder 220 is applied to the component for evaluation, Figure 5A shows a schematic state of the adhesive 280 at room temperature, Figure 5B A schematic state of adhesive 280 at 230° C. is shown.

[0059] Compare Figure 5A and Figure 5B, when the heater 210 and the heater holder 220 are pulled with equal force, it is found that the elongation of the adhesive in the tensile direction is different (hollow arrow). This is due to the typical characteristics of the adhesive of the silicone rubber system, in which the adhesive softens as the temperature rises from room temperature and is therefore easy to stretch. However, the rubber itself does not soften and deteriorate, so that the hardness and elongation of the rubber return to the original value when the temperature returns to room temperature.

[0060] When the adhesive is pulled, the adhesive has a cross-sectional shape that narrows in the middle like a hand drum. At this time, the adhesive 280 tends to recover to its original state using elastic restoring force, so the large stress ( Figure 5A and Figure 5B ) is applied to the bonding interface between the adhesive 280 and the heater 210 or the heater holder 220, particularly to the edge portion of the bonding surface.

[0061] Then, at temperatures above Figure 5A Room temperature Figure 5B The shrinkage is greater because Figure 5B The elongation of the adhesive is greater than Figure 5A This is due to the elongation of the adhesive in the bonding interface. This also leads to an increase in the above-mentioned stress applied to the edge of the bonding interface. Therefore, the following temperature characteristics are shown: as the temperature increases, Figure 4 Raised, the bonding interface can be peeled off with less force,

[0062] Next, the control of the fixing device 200 in this embodiment will be described. In this embodiment, the film surface temperature required for fixing the toner image to the recording material P is 180° C. The thermistor 250 in the paper passing portion is adjusted to 200° C. to 230° C. according to the heating level of the fixing device 200, so that the desired film temperature can be obtained. Then, the adhesive 280 is exposed to a temperature close to the temperature of the thermistor near a corresponding one of the bonding points.

[0063] Here, the fixing device 200 or the laser printer 100 mounted with the fixing device 200 includes a recording material jam detection unit (not shown), and thus can detect whether the recording material P remains in the fixing device 200 when a jam is detected.

[0064] The fixing device 200 or the laser printer 100 equipped with the fixing device 200 further includes a power switch (not shown) as a power switch component for controlling the start and stop of the device, so that the power of the device can be turned on and off by switching the power switch.

[0065] In addition, the fixing device 200 or the laser printer 100 equipped with the fixing device 200 has a normal power mode for fixing a toner image on a recording material P and a sleep mode as a power saving mode with less power consumption. When the device is not used for a predetermined time during the normal power mode, the device will transition to the sleep mode. When a print signal is received during the sleep mode, the device returns to the normal power mode.

[0066] In the following case, the laser printer 100 mounted with the fixing device 200 performs the pressure releasing operation of the fixing device 200 .

[0067] (1) When the laser printer 100 detects a paper jam, the recording material P remains in the fixing device 200 .

[0068] (2) The power of the laser printer 100 is turned off.

[0069] (3) The laser printer 100 shifts to the sleep mode.

[0070] Then, the operation of applying pressure to the fixing device 200 is performed in the following condition.

[0071] (4) The recording material P remaining in the fixing device 200 is removed.

[0072] (5) Turn on the power of the laser printer 100.

[0073] (6) The laser printer 100 returns from the sleep mode.

[0074] Figures 6 to 8 The control flowcharts of the pressure release of the fixing device 200 in this embodiment are shown respectively. Hereinafter, the operation will be described with reference to each flowchart.

[0075] Figure 6 The operation when the laser printer 100 detects a jam of the recording material P is shown. When the laser printer 100 detects a jam (S603) during the printing operation (S602), the laser printer 100 stops the printing operation (S604) to stop the electric heating of the heater 210. Next, the detection unit (not shown) detects whether the recording material P remains in the fixing device 200 (S605). When the recording material P remains, the flow processing waits until the temperature detected by each thermistor 250, 251 and 252 is lower than a predetermined threshold value or lower than 175° C. in this embodiment (S606), and then the pressure of the fixing device 200 is released (S607). When no recording material P remains in S605, it is not necessary to release the pressure of the fixing device 200. In this embodiment, after spending a maximum of two seconds of waiting time in S606, the pressure of the fixing device 200 is released, and then the jammed recording material P can be removed.

[0076] Figure 7 1 shows the operation when the power of the laser printer 100 is turned off. When a signal to turn off the power of the printer is sent by a power off operation of the main body (e.g., pressing the power button of the laser printer 100) (S702), the flow processing waits until the temperature detected by each of the thermistors 250, 251, and 252 is lower than a predetermined threshold value or lower than 175° C. in the present embodiment (S703), and then the pressure of the fixing device 200 is released (S704). After the flow processing progresses through another power off operation (S705), all operations of the laser printer 100 are stopped. Except just after the printing job is completed, the temperature of each thermistor is sufficiently reduced to be lower than the threshold value, so that the pressure release operation is immediately started in response to the signal to turn off the power.

[0077] Figure 8 1 shows the operation when the laser printer 100 is shifted to the sleep mode. When a signal to shift to the sleep mode is sent, for example, when the laser printer 100 does not receive a print signal within a predetermined time (S802), the flow processing will wait until the temperature detected by each thermistor 250, 251 and 252 is lower than a predetermined threshold value or lower than 175°C in the present embodiment (S803), and then release the pressure of the fixing device 200 (S804). After the flow processing progresses through another operation to shift to the sleep mode (S805), the laser printer 100 shifts to the sleep mode. Except just after the print job is completed, the temperature of each thermistor is sufficiently reduced to below the threshold value so that the pressure release operation is immediately started in response to the signal to shift to the sleep mode.

[0078] When the control flow of the present invention is not used, for example, when a paper jam is detected, in addition to Figure 6 In addition to S606 in, the pressure of the fixing device 200 is released according to the control process. However, depending on the situation, the pressurization will be released at the thermistor temperature of 230°C. As mentioned above, the interfacial peeling force of the adhesive 280 decreases under high temperature conditions. This results in a reduction in the margin between the force of separating the heater 210 from the heater holder 220 using the pressure of the thermistor (250, 251, 252) and the safety element 260 when the pressurization is released and the interfacial peeling force of the adhesive 280. When this depressurization is repeated, the interfacial peeling force will further deteriorate. This requires limiting the number of times the pressurization of the fixing device 200 is released, and therefore this limitation is a rate limit on the life of the fixing device 200.

[0079] As described above, when a paper jam is detected in the image forming apparatus, when the printer power is turned off, and during transition to the sleep mode, the pressure of the fixing device is released while monitoring the temperature transition of the fixing device. This makes it possible to ensure a margin for peeling of the adhesive interface between the heater and the heater holder, thereby reducing the influence on the life of the fixing device due to the release of the pressure.

[0080] The temperature threshold for pressure release should be appropriately adjusted according to the interfacial peeling force suitable for the fixing device structure. Specifically, the temperature threshold is preferably set to a value that can ensure the margin of the interfacial peeling force of the adhesive according to the physical properties of the adhesive, the shape of the bonding point, the bonding range, the arrangement and pressure of the pressing member, etc.

[0081] In this embodiment, the temperature threshold for pressure release is set by using the temperature detected by the thermistor arranged in contact with the heater. In addition, even when the pressure release is controlled by predicting the adhesive temperature using a device for detecting the temperature of the heater holder, the film, and the pressure roller, the effect of the present invention can be obtained.

[0082] The present embodiment is described above by taking the case where the thermistor and the safety element are arranged on the back side of the heater (the heater surface opposite to the heater surface near the fixing nip) as the pressing member as an example. In addition, even in the example where the electrode that generates heat by energization is arranged on the back side of the heater and the contact member for supplying power to the electrode is arranged as the pressing member, the effect of the present invention can be obtained.

[0083] Example 2

[0084] Embodiment 1 is described above by taking as an example a method of controlling the release of pressure of the fixing device 200, in which the pressure release operation is performed when the temperature of the thermistor decreases below a predetermined temperature threshold. Embodiment 2 is described by taking as an example a case in which the temperature threshold for pressure release is changed according to the number of repetitions of pressure release performed when a paper jam is detected, when the printer power is turned off, or during transition to a sleep mode. The configurations of the laser printer and the fixing device in this embodiment are similar to those in Embodiment 1, and therefore a detailed description is omitted.

[0085] Fig. 9is a control flow chart of the present embodiment. The temperature threshold for causing the fixing device 200 to perform a pressure release operation is designated as Ta (initial value is 200°C). When a paper jam is detected, when the printer power is turned off, or during transition to sleep mode (S903), a pressure release operation sequence is performed as in Embodiment 1, wherein a pressure release operation is performed when the temperature detected by each thermistor (250, 251, and 252) is lower than a temperature threshold Ta (S904). Then, the number of pressure releases C is counted (S905), and the temperature threshold Ta is set to a temperature corresponding to the count C according to Table 1 (S906). Table 1 is set so that as the number of pressure releases increases, the pressure release operation is performed at a lower temperature. When the number of pressure releases reaches the count upper limit Cmax (S907), a life warning of the fixing device 200 is notified (S908). In the present embodiment, Cmax is set to 15,000 counts. By assuming that the number of pressure releases per day is 10 times and the number of printer operating days per month is 20 days, Cmax in the present embodiment is set to the number of times counted after 6 years or more have passed in a normal office environment.

[0086]

Table 1

[0087] Pressure release times C Temperature threshold Ta C＜5000 200℃ 5000≤C＜10000 190℃ 10000≤C＜15000 180℃ 15000≤C 175℃

[0088] Executing control as in this embodiment allows a margin for adhesive interface peeling to be left while the number of repetitions of pressure release is small, so that the pressure release operation can be performed in a shorter time. Then, as the number of repetitions of pressure release increases, the margin for adhesive interface peeling can be ensured by changing the temperature threshold.

[0089] Example 3

[0090] Embodiment 3 is described taking as an example a case where the temperature threshold for the pressure release operation is changed according to the thermal history of the fixing device 200. The configurations of the laser printer and the fixing device in this embodiment are similar to those in Embodiment 1, so detailed description is omitted.

[0091] Fig.10is a control flow chart of the present embodiment. The temperature threshold value for causing the fixing device 200 to perform a pressure release operation is designated as Ta (initial value is 200°C). During the printing operation (S1003), the cumulative number of sheets Cp of the recording material P is counted (S1004), and it is determined whether pressure release is required (S1005), for example, when a paper jam is detected, when the printer power is turned off, or during transition to a sleep mode. When it is determined to be required, the temperature threshold value Ta is set to a temperature corresponding to the cumulative number of sheets Cp according to Table 2 (S1006), and then the pressure release operation sequence as in Embodiment 1 is performed (S1007). Table 2 is set so that as the cumulative number of sheets Cp of the recording material P increases, the pressure release operation is performed at a lower temperature. When the cumulative number of sheets reaches the upper limit Cpmax (S1008), a life warning of the fixing device 200 is notified (S1009). In the present embodiment, Cpmax is set to 150,000 sheets.

[0092]

Table 2

[0093] The number of sheets passed through the system Cp Temperature threshold Ta Cp<50000 200℃ 50000≤Cp<100000 190℃ 100000≤Cp<150000 180℃ 150000≤Cp 175℃

[0094] Controlling as in this embodiment allows a margin for adhesive interface peeling to be made while the number of recording material P passes is small or the fixing device has a small thermal history and the adhesive has a small thermal degradation, so that the pressure release operation can be performed at an early timing. Then, as the number of cumulative sheet passes increases and the thermal degradation of the adhesive due to the thermal history of the fixing device progresses, a margin for adhesive interface peeling during the life of the fixing device can be ensured by changing the temperature threshold.

[0095] The present embodiment has been described above by taking the example of changing the temperature threshold value Ta according to the cumulative number of sheets of recording material P that have passed through. Alternatively, the same effect can be obtained by changing the temperature threshold value by appropriately estimating the cumulative estimated heat storage amount of the fixing device according to the thermal history, for example, using the history of the cumulative operating time of the fixing device, the heating temperature, and the heating time.

[0096] Although Embodiments 1 to 3 have been described, any variation is possible within the technical concept of the present invention. Although in the above-mentioned embodiments, the thermistor, the safety element, and the contact member are exemplified as a pressing member pressed against the heater surface opposite to the heater surface facing the inner surface of the film, the present invention is not limited thereto. In addition, various preset temperatures as predetermined thresholds may be appropriately set to temperatures different from the above-mentioned temperatures, respectively, according to the device configuration.

[0097] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures and functions.

Claims

1. An image heating device for heating an image formed on a recording material, the image heating device comprising: a film formed into a tubular shape and configured to rotate in contact with a recording material; a heater unit configured to contact the inner surface of the film, the heater unit comprising a heater and a heater support configured to support the heater in a longitudinal direction of the heater, wherein the heater is fixed to the heater support by an adhesive; a temperature detection member configured to detect a temperature of the heater; a pressure roller configured to contact the outer surface of the film and to form a nip portion with the heater unit under the intervention of the film, the nip portion being used to nip and convey the recording material; a pressurizing spring configured to pressurize the heater toward the pressurizing roller under the intervention of a heater support member for forming a nip portion; a pressing member configured to press the heater toward the pressure roller without the intervention of the heater support; a pressure adjustment mechanism configured to adjust the pressure of the pressurized spring; and a control unit configured to control the pressure regulating mechanism; Wherein, in at least one of the following situations, the control unit controls the pressure regulating mechanism to start operating to release or reduce the pressure according to the temperature detected by the temperature detecting member: When the recording material jams; When the power of the image heating device is turned off; When the image heating unit enters sleep mode.

2. The image heating device according to claim 1, in, The pressing member is a part of the temperature detecting member.

3. The image heating device according to claim 1, Also included is a safety element configured to prevent the heater from overheating; in, The pressing member is part of the safety element.

4. The image heating device according to claim 1, in, The pressing member is a contact member configured to supply power to the heater.

5. The image heating device according to claim 1, further comprising: a paper jam detection unit configured to detect a paper jam of the recording material, Here, when the jam detection unit detects a jam and the temperature detected by the temperature detection member is lower than a predetermined threshold, the control unit causes the pressure adjustment mechanism to release or reduce the pressure.

6. The image heating device according to claim 1, further comprising: A power switch member configured to switch the image heating device on and off; When the power switch member stops the image heating device and the temperature detected by the temperature detection member is lower than a predetermined threshold, the control unit causes the pressure adjustment mechanism to release or reduce the pressure.

7. The image heating device according to claim 1 or 2, in, The image heating device has a normal power mode for heating an image and a power saving mode that consumes less power than the normal power mode, and When the image heating device changes from the normal power mode to the power saving mode and the temperature detected by the temperature detection member is lower than a predetermined threshold, the control section causes the pressure adjustment mechanism to release or reduce the pressure.

8. The image heating device according to claim 5 or 6, in, The control section is configured to change the threshold value according to the number of times the pressure regulating mechanism has previously released or reduced the pressure.

9. The image heating device according to claim 5 or 6, in, The control section is configured to change the threshold value according to the thermal history of the image heating device.

10. The image heating device according to claim 9, in, The thermal history is the cumulative amount of recorded material that passes through the nip.

11. The image heating device according to claim 9, in, The thermal history is the accumulated operating time of the image heating device.

12. The image heating device according to claim 9, in, The thermal history is the cumulative estimated heat storage of the image heating device.

13. An imaging device, comprising: an image forming section configured to form an image on a recording material; and a fixing unit configured to fix the image formed on the recording material on the recording material, Here, the fixing unit is the image heating device according to claim 1 or 2.

Images