JP2018081163A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device that can reduce the occurrence of damage to a fixing member caused by an excessive increase in temperature.SOLUTION: A fixing device 20 comprises: a fixing member 30 including a surface part 50 and a support part 40 that rotatably supports the surface part 50; a pressure member 60 that is in pressure contact with the surface part 50 of the fixing member 30 to form a nip part N with the surface part 50; a heat source 70 that heats the surface part 50 of the fixing member 30; and an excessive temperature increase prevention system 80 that includes a temperature detection part 81 and stops energization to the heat source 70 when a predetermined temperature condition is established. The support part 40 of the fixing member 30 is formed of a specific material that starts phase transition involving endothermic reaction from a first solid phase to a second solid phase at a temperature higher than a target fixing temperature to be set and lower than a heatproof temperature of the surface part 50.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device for fixing a toner image on the surface of the recording medium by passing the recording medium having the toner image formed on the surface through the nip portion and applying heat and pressure to the toner image, and such fixing. The present invention relates to an image forming apparatus including the apparatus.

  In the image forming apparatus, the fixing device (fixing member) is heated to a predetermined temperature or higher in order to fix the toner image on the surface of the recording medium. By reducing the heat capacity of the fixing device, the heating rate of the fixing device is increased. High-speed printing can be realized to improve user convenience, and the energy consumption of the fixing device can be reduced.

  Usually, the fixing device is provided with a temperature detection sensor, and the surface temperature of the fixing member is detected by the temperature detection sensor. Based on the detection result, the surface of the fixing member is set to a predetermined target fixing temperature by turning on / off the heat source or increasing / decreasing the amount of heating by the heat source. The target fixing temperature is a temperature set in advance so that the toner can be more appropriately fixed according to the type of toner used, the type of recording medium, and the like, and is an index for controlling the output of the heat source. .

  The fixing device disclosed in Japanese Patent Application Laid-Open No. 61-093474 (Patent Document 1) includes a heat fixing roller, and a latent heat storage material is disposed inside the heat fixing roller. The heat supplied from the heat source is temporarily stored in the latent heat storage material, and then transmitted to the surface of the heat fixing roller. This publication states that according to this configuration, the heat radiation from the surface of the heat-fixing roller and the fluctuation of the surface temperature of the heat-fixing roller due to the on / off of the heat source can be reduced.

JP-A 61-093474

  In a fixing device, when a mechanical or electrical malfunction occurs, an excessive temperature rise may occur in the fixing member. In order to prevent such an excessive temperature increase, an excessive temperature rise prevention system (hard protection) Also called). For example, when it is detected that an excessive temperature rise has occurred in the fixing member based on the detection result of the temperature detection sensor, energization to the heat source is stopped. Here, a certain amount of time is required to detect that an excessive temperature increase has occurred in the fixing member by the excessive temperature increase prevention system.

  As described above, if the temperature raising speed of the fixing member is improved, high-speed printing can be realized to improve the convenience for the user, and the energy consumption of the fixing device can be reduced. However, when the temperature rise rate of the fixing member is improved, the fixing member is damaged due to the excessive temperature rise before the over temperature prevention system detects that the fixing member is overheated. It can happen. Ideally, the overheating prevention system should be activated immediately after the overheating occurs to stop energization of the heat source, but it has not been easy to achieve this with conventional technology. .

  The present invention has been created in view of the above-described circumstances, and a fixing device capable of suppressing the occurrence of damage due to excessive temperature rise in a fixing member, and an image including such a fixing device. An object is to provide a forming apparatus.

  The fixing device according to the present invention includes a fixing member including a surface portion and a support portion that rotatably supports the surface portion, and a nip portion between the surface portion by pressing against the surface portion of the fixing member. Including a pressure member that forms a surface, a heat source that heats the surface portion of the fixing member, and a temperature detection unit, and when a predetermined temperature condition is satisfied, energization to the heat source is stopped An endothermic reaction from the first solid phase to the second solid phase at a temperature higher than a set target fixing temperature and lower than a heat-resistant temperature of the surface portion. It consists of a specific material that initiates a phase transition with

  Preferably, in the fixing device, the surface portion of the fixing member is constituted by a belt having an endless shape, and the support portion of the fixing member is disposed so as to contact an inner peripheral surface of the belt, and the belt A first support member that forms the nip portion by pressing the pressure member through the belt, and an inner peripheral surface of the belt, and the belt is cooperated with the first support member. A first support member or the second support member made of the specific material, and the heat source is disposed on the inner peripheral surface side of the belt, By heating the second support member, the surface portion of the belt is indirectly heated through the second support member, and the temperature detection unit is configured to move the second support member out of the outer peripheral surface of the belt. Of the above belt in contact It is arranged to face the outer peripheral surface portion corresponding to the peripheral surface portion, detects the temperature of the outer peripheral surface portion of the belt, and the over temperature rise prevention system detects that the detection result of the temperature detecting portion is a predetermined detection temperature. When the above temperature condition is satisfied, energization to the heat source is stopped.

  Preferably, in the fixing device, the surface portion of the fixing member is constituted by a belt having an endless shape, and the support portion of the fixing member is disposed so as to contact an inner peripheral surface of the belt, and the belt A first support member that forms the nip portion by pressing the pressure member through the belt, and an inner peripheral surface of the belt, and the belt is cooperated with the first support member. A first support member or the second support member made of the specific material, and the heat source is disposed on the inner peripheral surface side of the belt, By heating the second support member, the surface portion of the belt is indirectly heated through the second support member, and the temperature detection unit is configured to move the second support member out of the outer peripheral surface of the belt. Of the above belt in contact It is arranged so as to face the outer peripheral surface portion corresponding to the peripheral surface portion, detects the temperature of the outer peripheral surface portion of the belt, and the overheat prevention system is arranged to face the outer peripheral surface of the belt. When the temperature condition that the temperature of the overtemperature rise prevention device reaches a predetermined operating temperature is satisfied, the energization to the heat source is stopped.

  Preferably, in the fixing device, the surface portion of the fixing member is configured by a belt having an endless shape, and the support portion of the fixing member is disposed so as to contact an inner peripheral surface of the belt. A support member, and a second support member that is disposed so as to contact the inner peripheral surface of the belt and that stretches the belt in cooperation with the first support member, the first support member or The second support member is made of the specific material, the heat source is disposed so as to contact a part of the inner peripheral surface of the belt and the second support member, and the temperature detection unit The temperature condition that is disposed so as to contact the second support member, detects the temperature of the second support member, and the over-temperature prevention system has a detection result of the temperature detection unit equal to or higher than a predetermined detection temperature. If the The stops.

  Preferably, in the fixing device, the surface portion of the fixing member is configured by a belt having an endless shape, and the support portion of the fixing member is disposed so as to contact an inner peripheral surface of the belt. A support member, and a second support member that is disposed so as to contact the inner peripheral surface of the belt and that stretches the belt in cooperation with the first support member, the first support member or The second support member is made of the specific material, the heat source is disposed so as to contact a part of the inner peripheral surface of the belt and the second support member, and the temperature detection unit An overheat prevention device, arranged to contact the second support member, detects the temperature of the second support member, and the overheat prevention system is arranged to contact the second support member. And the temperature of the overheat prevention device is predetermined. The power supply to the heat source is stopped when the temperature condition is satisfied that reaches the operating temperature.

  Preferably, in the fixing device, the surface portion of the fixing member is constituted by a belt having an endless shape, and the support portion of the fixing member is disposed so as to contact an inner peripheral surface of the belt, and the belt A first support member that forms the nip portion by pressing the pressure member through the belt, and an inner peripheral surface of the belt, and the belt is cooperated with the first support member. A second support member that stretches the belt, wherein the first support member or the second support member is made of the specific material, and the heat source is disposed to face the outer peripheral surface of the belt. The second support member is heated in a non-contact manner, and the belt is indirectly heated through the second support member, and the temperature detection unit is configured to support the second support on the outer peripheral surface of the belt. The parts are in contact The belt is disposed so as to face the outer peripheral surface portion corresponding to the inner peripheral surface portion of the belt, detects the temperature of the outer peripheral surface portion of the belt, and the overheat prevention system detects the detection result of the temperature detection unit. When the temperature condition that the temperature is equal to or higher than a predetermined detection temperature is satisfied, the energization to the heat source is stopped.

  Preferably, in the fixing device, the surface portion of the fixing member is constituted by a belt having an endless shape, and the support portion of the fixing member is disposed so as to contact an inner peripheral surface of the belt, and the belt A first support member that forms the nip portion by pressing the pressure member through the belt, and an inner peripheral surface of the belt, and the belt is cooperated with the first support member. A second support member that stretches the belt, wherein the first support member or the second support member is made of the specific material, and the heat source is disposed to face the outer peripheral surface of the belt. The second support member is heated in a non-contact manner, and the belt is indirectly heated through the second support member, and the temperature detection unit is configured to support the second support on the outer peripheral surface of the belt. The parts are in contact The belt is disposed so as to face the outer peripheral surface portion corresponding to the inner peripheral surface portion of the belt, detects the temperature of the outer peripheral surface portion of the belt, and the excessive temperature rise prevention system faces the outer peripheral surface of the belt. When the temperature condition that the temperature of the over-temperature rise prevention device reaches a predetermined operating temperature is satisfied, the energization to the heat source is stopped.

  Preferably, in the fixing device, the second support member forms the nip portion by pressing the pressure member via the belt.

  Preferably, in the fixing device, the temperature of the specific material when the specific material starts the phase transition is the predetermined detection temperature when the overheating prevention system stops energizing the heat source. Higher than.

  Preferably, in the fixing device, the temperature of the specific material when the specific material starts the phase transition is the predetermined operating temperature when the overheating prevention system stops energizing the heat source. Higher than.

  In the fixing device, the specific material is preferably composed of a vanadium-based composite oxide.

  An image forming apparatus according to the present invention includes the above-described fixing device according to the present invention.

  According to the above configuration, even when the excessive temperature rise prevention system is not operating, the temperature rise rate of the fixing member is lowered or the temperature of the fixing member is lowered due to the endothermic action of the specific material. The fixing member can be prevented from being damaged due to excessive temperature rise.

1 is a schematic diagram showing an image forming apparatus 100 according to Embodiment 1. FIG. FIG. 2 is a diagram schematically illustrating a fixing device 20 according to the first embodiment. FIG. 6 is a diagram for explaining the operation and effect of the fixing device 20 in the first embodiment, and shows a general overheat prevention operation performed by the overheat prevention system 80; FIG. 6 is a diagram for explaining the operation and effect of the fixing device 20 according to the first embodiment, and before the excessive temperature rise prevention system 80 detects that an excessive temperature rise has occurred in the fixing member 30, the fixing member 30. This shows that the temperature reaches the heat resistant temperature of the fixing member 30. FIG. 5 is a diagram for explaining the operational effect of the fixing device 20 according to the first embodiment, and a specific material before the excessive temperature increase prevention system 80 detects that an excessive temperature increase has occurred in the fixing member 30. This shows a state in which the temperature of the fixing member 30 is lowered by the endothermic action. FIG. 6 is a diagram for explaining the operational effect of the fixing device 20 in the modification of the first embodiment, before the excessive temperature increase prevention system 80 detects that the excessive temperature increase has occurred in the fixing member 30; A state in which the temperature of the fixing member 30 is lowered due to the endothermic action of a specific material is shown. FIG. 6 is a diagram schematically illustrating a fixing device 20A according to a second embodiment. FIG. 10 schematically shows a fixing device 20B according to Embodiment 3. FIG. 10 schematically illustrates a fixing device 20C according to a fourth embodiment. FIG. 10 schematically illustrates a fixing device 20D according to a fifth embodiment. FIG. 10 schematically illustrates a fixing device 20E according to a sixth embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

[Embodiment 1]
(Image forming apparatus 100)
FIG. 1 is a diagram schematically illustrating the overall configuration of an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 includes image forming units 10Y, 10M, 10C, and 10K, a paper feed cassette 11, an intermediate transfer belt 18, a secondary transfer roller 19, and a fixing device 20. Each of the image forming units 10Y, 10M, 10C, and 10K includes a photoreceptor 12, a charging device 13, an exposure device 14, a developing device 15, a primary transfer roller 16, and a cleaner 17.

  The intermediate transfer belt 18 rotates (circulates) along the direction of arrow A. The image forming units 10Y, 10M, 10C, and 10K form toner images having colors of yellow, magenta, cyan, and black on the surface of the intermediate transfer belt 18, respectively. The toner images of the respective colors are superimposed on the surface of the intermediate transfer belt 18. Thereafter, the toner image on the intermediate transfer belt 18 is conveyed to a position (secondary transfer portion) between the intermediate transfer belt 18 and the secondary transfer roller 19.

  The paper feed cassette 11 contains a plurality of recording media S. The recording medium S is conveyed to the secondary transfer unit. The toner image carried on the surface of the intermediate transfer belt 18 is transferred onto the surface of the recording medium S at the secondary transfer portion. The toner image transferred onto the surface of the recording medium S is fixed on the surface of the recording medium S by the fixing device 20. Thereafter, the recording medium S is discharged onto a paper discharge tray. The image forming process by the image forming apparatus 100 is as described above.

(Fixing device 20)
FIG. 2 is a diagram schematically showing the fixing device 20 according to the first embodiment. The fixing device 20 includes a fixing member 30, a pressure roller 60 (pressure member), a heat source 70, and an excessive temperature rise prevention system 80.

  The fixing member 30 includes a support portion 40 and a belt 50 (surface portion). The support unit 40 includes a first support member 41 and a second support member 42. The belt 50 has an endless shape. The belt 50 is wound around the first support member 41 and the second support member 42 and is rotatably supported by the first support member 41 and the second support member 42.

  The first support member 41 of the present embodiment has a pressing member 41A and a base member 41B. The pressing member 41 </ b> A has a substantially U-shaped cross-sectional shape, and the base member 41 </ b> B supports the pressing member 41 </ b> A from the side opposite to the position of the pressure roller 60. The pressing member 41 </ b> A is disposed so as to contact the inner peripheral surface of the belt 50, and presses the pressure roller 60 via the belt 50.

  The pressure roller 60 presses the belt 50 of the fixing member 30 to form a nip portion N between the pressure roller 60 and the belt 50. The pressure roller 60 is rotated at a predetermined rotation speed by a motor (not shown). The belt 50 travels (circulates) following the rotation of the pressure roller 60. The second support member 42 has a half-divided cylindrical shape, is disposed so as to contact the inner peripheral surface of the belt 50, and stretches the belt 50 in cooperation with the first support member 41.

  The heat source 70 is disposed on the inner peripheral surface side of the belt 50. The heat source 70 of the present embodiment is disposed inside the curved shape of the second support member 42. The heat source 70 is composed of, for example, a halogen heater lamp. The heat source 70 indirectly heats the belt 50 (the surface portion of the fixing member 30) via the second support member 42 by heating the second support member 42.

  The recording medium S (FIG. 1) onto which the toner image has been transferred is conveyed to the nip portion N of the fixing device 20 with the surface onto which the toner image has been transferred facing the belt 50 side. When the recording medium S passes through the nip portion N, the toner image formed on the surface of the recording medium S is heated and pressurized by the belt 50. As a result, the toner image is fixed on the surface of the recording medium S.

  The excessive temperature rise prevention system 80 includes a temperature detection sensor 81 (temperature detection unit), and stops energization from the outside to the heat source 70 when a predetermined temperature condition is satisfied. The overheat prevention system 80 of the present embodiment includes a temperature detection sensor 81 and an overheat prevention device 82.

  The temperature detection sensor 81 is composed of, for example, a thermistor. The temperature detection sensor 81 is disposed so as to face the outer peripheral surface portion corresponding to the inner peripheral surface portion of the belt 50 with which the second support member 42 is in contact with the outer peripheral surface of the belt 50. Detect the surface temperature.

  Based on the detection result of the temperature detection sensor 81, the surface of the belt 50 (the surface portion of the fixing member 30) is set to a predetermined target fixing temperature by turning on and off the heat source 70 and increasing / decreasing the amount of heating by the heat source 70. Can be set. In addition to such temperature control operation, the excessive temperature rise prevention system 80 stops energization of the heat source 70 when the temperature condition that the detection result of the temperature detection sensor 81 is equal to or higher than a predetermined detection temperature is satisfied. The temperature of the belt 50 is prevented from exceeding the heat resistance temperature of the belt 50.

  The over-temperature rise prevention device 82 is composed of, for example, a thermostat and has a function as a so-called temperature fuse. The overheat prevention device 82 is also disposed so as to face the outer peripheral surface portion of the outer peripheral surface of the belt 50 corresponding to the inner peripheral surface portion of the belt 50 with which the second support member 42 is in contact. The overheat prevention device 82 is electrically connected to the heat source 70 in series, for example. The overheat prevention system 80 stops energization of the heat source 70 when the temperature condition that the temperature of the overheat prevention device 82 reaches a predetermined operating temperature is satisfied, and the temperature of the belt 50 is changed to the belt 50. To prevent exceeding the heat-resistant temperature.

  Here, the support portion 40 of the fixing member 30 is a first solid phase at a temperature (phase transition temperature) higher than the set target fixing temperature and lower than the heat resistance temperature of the surface portion (belt 50) of the fixing member 30. It consists of a specific material that initiates a phase transition with an endothermic reaction from the first to the second solid phase. The target fixing temperature is a temperature (for example, 130 ° C. or higher and 200 ° C. or lower) set in advance so that the toner can be more appropriately fixed according to the type of toner to be used, the type of the recording medium S, or the like. This is an index for controlling 70 outputs.

  The heat resistance temperature of the surface portion (belt 50) of the fixing member 30 (for example, 250 ° C. or more and 300 ° C. or less, or 400 ° C. or more and 500 ° C. or less) is that the surface portion (belt 50) of the fixing member 30 is affected by heat. The temperature at which the irreversible change may occur in the surface portion (belt 50) of the fixing member 30 such as breakage or deformation. The phase transition temperature of the specific material is set to a value higher than 200 ° C. and lower than 250 ° C., for example. The pressing member 41A and / or the second supporting member 42 of the first supporting member 41 is made of such a specific material.

  The specific material is composed of a so-called solid-solid phase transition material, and changes in phase from the first solid phase (solid phase α) having a different crystal structure to the second solid phase (solid phase β) as the temperature rises. To do. During phase change, certain materials absorb certain energy as latent heat. A specific material having such characteristics can be easily used as a member constituting the second support member 42 and / or the pressing member 41A.

  When an excessive temperature rise occurs in the belt 50, the temperature of the specific material arranged so as to come into contact with the belt 50 is similarly increased. When a specific material undergoes a phase transition from the first solid phase to the second solid phase, an endothermic action occurs in the specific material. The phase transition temperature of the specific material is set higher than the target fixing temperature set by the fixing device 20 and lower than the heat resistant temperature of the belt 50. When an excessive temperature increase occurs in the belt 50 or when an excessive temperature increase is occurring in the belt 50, a specific material absorbs heat from the belt 50, thereby reducing the temperature increase rate of the belt 50, The temperature of 50 can be lowered.

  As the specific material having the above characteristics, for example, a vanadium-based composite oxide or a titanium-based composite oxide can be used. In the titanium-based composite oxide, energy is accumulated when the material undergoes a phase transition from the first solid phase to the second solid phase, but energy is released to the material and returned from the second solid phase to the first solid phase. In order to do this, it is necessary to apply pressure to the material. On the other hand, in the vanadium-based composite oxide, energy is accumulated when the material undergoes a phase transition from the first solid phase to the second solid phase, but the first solid phase is changed from the second solid phase by lowering the temperature of the material. The phase transition to the phase and the stored energy can be released.

(Function and effect)
Referring to FIG. 3, in fixing device 20, overheating may occur in fixing member 30 (here, belt 50) in the event of some mechanical or electrical malfunction. In order to prevent the temperature, an excessive temperature rise prevention system 80 (also referred to as a hard protect) is used. FIG. 3 shows a general overheat prevention operation performed by the overheat prevention system 80.

  For example, it is assumed that the image forming apparatus 100 is operated and heating of the fixing member 30 is started at time 0 (FIG. 3). The temperature of the fixing member 30 (the temperature of the belt 50) increases as time passes. Although the temperature detection sensor 81 of the excessive temperature rise prevention system 80 detects the temperature of the fixing member 30, it is difficult to detect the temperature of the fixing member 30 in real time, and the temperature detection sensor 81 determines the actual temperature of the fixing member 30. A certain time difference (time lag) occurs before detection. When the heat capacity of the fixing member 30 is large and the heating rate of the fixing member 30 is slow, this time difference is small.

  At time T0, the temperature of the fixing member 30 reaches the target fixing temperature TA. When some mechanical or electrical malfunction occurs in a part of the fixing device 20, the heating by the heat source 70 is not stopped, and the temperature of the fixing member 30 continues to rise beyond the target fixing temperature TA. . At time T1, the temperature detected by the temperature detection sensor 81 reaches the operation start temperature TB of the excessive temperature rise prevention system 80. At time T1, based on the detection result of the temperature detection sensor 81, it is detected that an excessive temperature rise has occurred in the fixing member 30, and energization to the heat source 70 is stopped.

  At time T1, the temperature of the fixing member 30 has already reached the temperature TC. The temperature TC is higher than the target fixing temperature TA, but is lower than the heat resistance temperature TD of the fixing member 30. After the excessive temperature rise prevention system 80 is activated at time T1 and energization of the heat source 70 is stopped, the temperature of the fixing member 30 takes a maximum value at time T2 (this maximum value is also the heat resistant temperature of the fixing member 30). After that, since the temperature of the fixing member 30 starts to decrease, the fixing member 30 is not damaged.

  In the example shown in FIG. 3, for convenience of explanation, the temperature of the fixing member 30 (the temperature of the belt 50) and the value detected by the temperature detection sensor 81 are described so as to change or change on the same scale. The temperature of the member 30 and the value detected by the temperature detection sensor 81 may be different scales. That is, the meaning that the above time difference (time lag) occurs means that an excessive temperature rise has occurred in the fixing member 30 based on the detection result of the temperature detection sensor 81 and the energization to the heat source 70 is stopped. This means that there is a certain time difference between the timing and the timing at which the temperature of the fixing member 30 rises and reaches a specific value (a heat resistant temperature or a temperature in the vicinity thereof). The same applies to the case of the overheat prevention device 82 described below.

  The overheat prevention system 80 of this embodiment includes not only the temperature detection sensor 81 but also an overtemperature prevention device 82. Similarly to the case of the temperature detection sensor 81, for example, at the time T1, the temperature of the overtemperature rise prevention device 82 is changed to the operating temperature of the overtemperature rise prevention device 82 (overtemperature rise prevention). The operating start temperature TB) of the system 80 is reached. At time T1, the temperature of the fixing member 30 has already reached the temperature TC. At time T1, the temperature of the fixing member 30 starts to decrease as the overheat prevention system 80 (temperature overheat prevention device 82) is activated and the energization of the heat source 70 is stopped. No damage will occur.

  Referring to FIG. 4, as described at the beginning, when the temperature increase rate of fixing member 30 (here, belt 50) is improved, high-speed printing is realized to improve the convenience of the user, It is possible to reduce energy consumption. However, when the rate of temperature increase of the fixing member 30 (belt 50) is improved, an excessive temperature increase occurs in the fixing member 30 (in other words, the temperature of the fixing member 30 increases and the heat resistance of the fixing member 30 increases). Before the overheating prevention system 80 detects that the temperature has reached the temperature, or that the temperature of the fixing member 30 has risen to reach a temperature near the heat-resistant temperature of the fixing member 30). The temperature of the fixing member 30 may reach the heat resistance temperature of the fixing member 30 and damage due to excessive temperature rise may occur.

  For example, it is assumed that the image forming apparatus 100 is operated and heating of the fixing member 30 is started at time 0 (FIG. 4). The temperature of the fixing member 30 increases as time passes. At time T0, the temperature of the fixing member 30 reaches the target fixing temperature TA. When some mechanical or electrical malfunction occurs in a part of the fixing device 20, the heating by the heat source 70 is not stopped, and the temperature of the fixing member 30 continues to rise beyond the target fixing temperature TA. .

  At time T1, the temperature detected by the temperature detection sensor 81 reaches the operation start temperature TB of the excessive temperature rise prevention system 80. At time T1, based on the detection result of the temperature detection sensor 81, it is detected that an excessive temperature rise has occurred in the fixing member 30, and energization to the heat source 70 is stopped. In the example shown in FIG. 4, the heat capacity of the fixing member 30 is small and the heating rate of the fixing member 30 is faster than in the example shown in FIG. 3. At time T1, the temperature of the fixing member 30 has already reached the temperature TC. The temperature TC is higher than the heat resistant temperature TD of the fixing member 30. There is a possibility that the surface portion (belt 50) of the fixing member 30 is damaged (for example, irreversible change).

  Referring to FIG. 5, in the present embodiment, support portion 40 of fixing member 30 is a temperature that is higher than the set target fixing temperature and lower than the heat resistance temperature of the surface portion (belt 50) of fixing member 30. Thus, it is composed of a specific material that initiates a phase transition accompanied by an endothermic reaction from the first solid phase to the second solid phase. The pressing member 41A and / or the second supporting member 42 of the first supporting member 41 is made of such a specific material.

  Assume that the image forming apparatus 100 is operated and heating of the fixing member 30 is started at time 0 (FIG. 5). The temperature of the fixing member 30 increases as time passes. At time T0, the temperature of the fixing member 30 (the temperature of the belt 50) reaches the target fixing temperature TA. When some mechanical or electrical malfunction occurs in a part of the fixing device 20, the heating by the heat source 70 is not stopped, and the temperature of the fixing member 30 continues to rise beyond the target fixing temperature TA. .

  At time T1, the temperature of the support portion 40 (the pressing member 41A and / or the second support member 42) of the fixing member 30 reaches the phase transition temperature TE. In FIG. 5, for convenience of explanation, the temperature of the fixing member 30 (the temperature of the belt 50) and the temperature of the support portion 40 of the fixing member 30 are displayed as the same value. When a specific material constituting the support portion 40 of the fixing member 30 undergoes a phase transition from the first solid phase to the second solid phase, an endothermic action occurs in the specific material.

  At the time T1, that is, when an excessive temperature rise occurs in the fixing member 30 (belt 50), or when an excessive temperature increase is occurring in the fixing member 30, the detected temperature of the excessive temperature rise prevention system 80 is detected. Although TF is lower than the operation start temperature TB, when a specific material absorbs heat from the fixing member 30, the temperature increase rate of the fixing member 30 decreases or the temperature of the fixing member 30 decreases.

  In the case of the example shown in FIG. 4, since neither the pressing member 41A of the first support member 41 nor the second support member 42 is made of the specific material as described above, the temperature of the fixing member 30 is a dotted line. It continues to rise as shown in LN (FIG. 5). In the case of the present embodiment, due to the endothermic action of a specific material, as shown by the solid line in FIG. 5, the heating rate of the fixing member 30 is decreased or the temperature of the fixing member 30 is decreased.

  At the time T2, the temperature of the fixing member 30 detected by the temperature detection sensor 81 reaches the operation start temperature TB of the excessive temperature rise prevention system 80. At time T2, based on the detection result of the temperature detection sensor 81, it is detected that an excessive temperature rise has occurred in the fixing member 30, and energization to the heat source 70 is stopped.

  In the example shown in FIG. 5, the heat capacity of the fixing member 30 is smaller and the heating rate of the fixing member 30 is faster than in the example shown in FIG. 3, but the temperature of the fixing member 30 is heat resistant at time T2. The temperature TD has not been reached. There is almost no possibility that the surface portion (belt 50) of the fixing member 30 is damaged (for example, irreversible change). Therefore, according to the fixing device 20 of the present embodiment, it is possible to prevent the fixing member 30 (here, the belt 50) from being damaged due to excessive temperature rise.

(Modification)
In the above-described embodiment, the overheat prevention system 80 uses both the temperature detection sensor 81 and the overheat prevention device 82. It may be configured such that the temperature detection sensor 81 operates primarily and the temperature overheat prevention device 82 operates secondarily, or vice versa. As the excessive temperature rise prevention system 80, only one of the temperature detection sensor 81 and the excessive temperature rise prevention device 82 may be used.

  In the above-described embodiment, the temperature of the specific material (phase transition temperature TE shown in FIG. 5) when the specific material starts the phase transition is detected by the excessive temperature rise prevention system 80 by the temperature detection sensor 81. Is set to be higher than a predetermined detected temperature (operation start temperature TB of the excessive temperature rise prevention system 80 shown in FIG. 5) when the power supply to the heat source 70 is stopped based on the above.

  As shown in FIG. 6, contrary to the above case, the temperature of the specific material when the specific material starts the phase transition (phase transition temperature TE shown in FIG. Is set to be lower than a predetermined detection temperature (operation start temperature TB of the excessive temperature rise prevention system 80 shown in FIG. 6) when the power supply to the heat source 70 is stopped based on the detection result of the temperature detection sensor 81. It does not matter.

  In the above-described embodiment, the temperature of the specific material (phase transition temperature TE shown in FIG. 5) when the specific material starts the phase transition is determined by the overtemperature prevention system 80 using the overtemperature prevention device 82. Is set so as to be higher than a predetermined operating temperature (operation start temperature TB of the excessive temperature rise prevention system 80 shown in FIG. 5) when the power supply to the heat source 70 is stopped by the operation of.

  As shown in FIG. 6, contrary to the above case, the temperature of the specific material when the specific material starts the phase transition (phase transition temperature TE shown in FIG. Is set to be lower than a predetermined operating temperature (operation start temperature TB of the excessive temperature rise prevention system 80 shown in FIG. 6) when the energization to the heat source 70 is stopped by the operation of the temperature excess temperature rise prevention device 82. It does not matter.

[Embodiment 2]
FIG. 7 is a diagram schematically illustrating a fixing device 20A according to the second embodiment. The first embodiment and the second embodiment are different in the following points.

  In the fixing device 20A according to the second embodiment, the first support member 41 is formed of a cylindrical member. Also in the present embodiment, the pressing member 41A and / or the second support member 42 of the first support member 41 is made of the specific material as described above, so that the same action as in the above-described first embodiment is achieved. And can get the effect.

[Embodiment 3]
FIG. 8 is a diagram schematically illustrating the fixing device 20B according to the third embodiment. The first embodiment and the third embodiment are different in the following points.

  The support portion 40 in the third embodiment is disposed so as to contact the inner peripheral surface of the belt 50 and the first support member 41 disposed so as to contact the inner peripheral surface of the belt 50. And a second support member 42 that stretches the belt 50 in cooperation with each other. The pressing member 41A and / or the second supporting member 42 of the first supporting member 41 is made of a specific material as described above. The heat source 70 has a planar (plate-like) shape, and is arranged so as to contact a part of the inner peripheral surface of the belt 50 and the second support member 42.

  The temperature detection sensor 81 is disposed on the inner peripheral surface side of the belt 50 so as to contact the second support member 42 and detects the temperature of the second support member 42. The excessive temperature rise prevention system 80 stops energization to the heat source 70 when the temperature condition that the detection result of the temperature detection sensor 81 is equal to or higher than a predetermined detection temperature is satisfied. Also with this configuration, the same operations and effects as those of the first embodiment can be obtained.

  The overtemperature prevention device 82 is disposed so as to contact the second support member 42 on the inner peripheral surface side of the belt 50. The overheat prevention system 80 stops energization of the heat source 70 when the temperature condition that the temperature of the overheat prevention device 82 reaches a predetermined operating temperature is satisfied. Also with this configuration, the same operations and effects as those of the first embodiment can be obtained.

  In the present embodiment, the temperature detection sensor 81 and the overtemperature rise prevention device 82 are in contact with the second support member 42. When the second support member 42 is made of a specific material as described above, the operation timing (response speed) of the overheat prevention system 80 based on the temperature detection sensor 81 and the overheat prevention device 82 is implemented. Compared to the case of Form 1, it can be accelerated.

  Also in the present embodiment, the excessive temperature rise prevention system 80 uses both the temperature detection sensor 81 and the excessive temperature rise prevention device 82. It may be configured such that the temperature detection sensor 81 operates primarily and the temperature overheat prevention device 82 operates secondarily, or vice versa. As the excessive temperature rise prevention system 80, only one of the temperature detection sensor 81 and the excessive temperature rise prevention device 82 may be used.

[Embodiment 4]
FIG. 9 is a diagram schematically illustrating a fixing device 20C according to the fourth embodiment. The third embodiment and the fourth embodiment are different in the following points.

  In the case of the above-described third embodiment (FIG. 8), the first support member 41 presses the pressure roller 60 via the belt 50 to form the nip portion N. In the present embodiment, the second support member 42 presses the pressure roller 60 via the belt 50 to form the nip portion N. Also in the present embodiment, the pressing member 41A and / or the second support member 42 of the first support member 41 is made of the specific material as described above, so that the same action as in the above-described first embodiment is achieved. And can get the effect.

[Embodiment 5]
FIG. 10 is a diagram schematically illustrating a fixing device 20D according to the fifth embodiment. The first embodiment and the fifth embodiment are different in the following points.

  In the present embodiment, the heat source 70 is disposed so as to face the outer peripheral surface of the belt 50. The heat source 70 heats the second support member 42 in a non-contact manner using, for example, the principle of induction heating, and indirectly heats the belt 50 via the second support member 42. Also in the present embodiment, the pressing member 41A and / or the second support member 42 of the first support member 41 is made of the specific material as described above, so that the same action as in the above-described first embodiment is achieved. And can get the effect.

[Embodiment 6]
FIG. 11 is a diagram schematically illustrating the fixing device 20E according to the sixth embodiment. The first embodiment and the sixth embodiment are different in the following points.

  In the present embodiment, the fixing member 30 includes a support portion 40 and an elastic layer 50A (surface portion). The support part 40 is comprised from the cylindrical member. The elastic layer 50 </ b> A is formed on the surface layer of the support portion 40 and is rotatably supported by the support portion 40. Also in the present embodiment, the support portion 40 is made of the specific material as described above, so that the same operations and effects as those of the first embodiment can be obtained.

  Although the embodiment has been described above, the above disclosure is illustrative in all respects and is not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention relates to a fixing device for fixing a toner image on the surface of the recording medium by passing the recording medium having the toner image formed on the surface through the nip portion and applying heat and pressure to the toner image, and such fixing. The present invention can be used for an image forming apparatus including the apparatus.

  10C, 10K, 10M, 10Y Image forming unit, 11 paper feed cassette, 12 photoconductor, 13 charging device, 14 exposure device, 15 developing device, 16 primary transfer roller, 17 cleaner, 18 intermediate transfer belt, 19 secondary transfer Roller, 20, 20A, 20B, 20C, 20D, 20E Fixing device, 30 fixing member, 40 support portion, 41 first support member, 41A pressing member, 41B base member, 42 second support member, 50 belt (surface portion) , 50A elastic layer (surface portion), 60 pressure roller (pressure member), 70 heat source, 80 excessive temperature rise prevention system, 81 temperature detection sensor, 82 excessive temperature rise prevention device, 100 image forming apparatus, N nip portion, S Recording medium.

Claims (12)

A fixing member including a surface portion and a support portion that rotatably supports the surface portion;
A pressure member that forms a nip portion with the surface portion by pressing against the surface portion of the fixing member;
A heat source for heating the surface portion of the fixing member;
An over-temperature rise prevention system that includes a temperature detection unit and stops energization to the heat source when a predetermined temperature condition is established,
The supporting portion of the fixing member undergoes a phase transition accompanied by an endothermic reaction from the first solid phase to the second solid phase at a temperature higher than a set target fixing temperature and lower than the heat resistant temperature of the surface portion. Composed of specific materials to start with,
Fixing device. The surface portion of the fixing member is composed of a belt having an endless shape,
The support portion of the fixing member is
A first support member disposed so as to contact the inner peripheral surface of the belt and forming the nip portion by pressing the pressure member via the belt;
A second support member disposed so as to contact the inner peripheral surface of the belt and extending the belt in cooperation with the first support member;
The first support member or the second support member is made of the specific material,
The heat source is disposed on the inner peripheral surface side of the belt, and indirectly heats the surface portion of the belt through the second support member by heating the second support member.
The temperature detection unit is disposed so as to face an outer peripheral surface portion corresponding to an inner peripheral surface portion of the belt with which the second support member is in contact with the outer peripheral surface of the belt. Detect the surface temperature,
The excessive temperature rise prevention system stops energization to the heat source when the temperature condition that the detection result of the temperature detection unit is equal to or higher than a predetermined detection temperature is satisfied,
The fixing device according to claim 1. The surface portion of the fixing member is composed of a belt having an endless shape,
The support portion of the fixing member is
A first support member disposed so as to contact the inner peripheral surface of the belt and forming the nip portion by pressing the pressure member via the belt;
A second support member disposed so as to contact the inner peripheral surface of the belt and extending the belt in cooperation with the first support member;
The first support member or the second support member is made of the specific material,
The heat source is disposed on the inner peripheral surface side of the belt, and indirectly heats the surface portion of the belt through the second support member by heating the second support member.
The temperature detection unit is disposed so as to face an outer peripheral surface portion corresponding to an inner peripheral surface portion of the belt with which the second support member is in contact with the outer peripheral surface of the belt. Detect the surface temperature,
The overheat prevention system has an overheat prevention device disposed so as to face the outer peripheral surface of the belt, and the temperature of the overheat prevention device reaches a predetermined operating temperature. Stop energization of the heat source when the temperature condition is satisfied,
The fixing device according to claim 1. The surface portion of the fixing member is composed of a belt having an endless shape,
The support portion of the fixing member is
A first support member arranged to contact the inner peripheral surface of the belt;
A second support member disposed so as to contact the inner peripheral surface of the belt and extending the belt in cooperation with the first support member;
The first support member or the second support member is made of the specific material,
The heat source is disposed so as to contact a part of the inner peripheral surface of the belt and the second support member,
The temperature detector is disposed so as to contact the second support member, detects the temperature of the second support member,
The excessive temperature rise prevention system stops energization to the heat source when the temperature condition that the detection result of the temperature detection unit is equal to or higher than a predetermined detection temperature is satisfied,
The fixing device according to claim 1. The surface portion of the fixing member is composed of a belt having an endless shape,
The support portion of the fixing member is
A first support member arranged to contact the inner peripheral surface of the belt;
A second support member disposed so as to contact the inner peripheral surface of the belt and extending the belt in cooperation with the first support member;
The first support member or the second support member is made of the specific material,
The heat source is disposed so as to contact a part of the inner peripheral surface of the belt and the second support member,
The temperature detector is disposed so as to contact the second support member, detects the temperature of the second support member,
The overheat prevention system includes an overheat prevention device disposed so as to contact the second support member, and the temperature of the overheat prevention device reaches a predetermined operating temperature. Stop energization of the heat source when the temperature condition is satisfied,
The fixing device according to claim 1. The surface portion of the fixing member is composed of a belt having an endless shape,
The support portion of the fixing member is
A first support member disposed so as to contact the inner peripheral surface of the belt and forming the nip portion by pressing the pressure member via the belt;
A second support member disposed so as to contact the inner peripheral surface of the belt and extending the belt in cooperation with the first support member;
The first support member or the second support member is made of the specific material,
The heat source is disposed so as to face the outer peripheral surface of the belt, heats the second support member in a non-contact manner, and indirectly heats the belt through the second support member,
The temperature detection unit is disposed so as to face an outer peripheral surface portion corresponding to an inner peripheral surface portion of the belt with which the second support member is in contact with the outer peripheral surface of the belt. Detect the surface temperature,
The excessive temperature rise prevention system stops energization to the heat source when the temperature condition that the detection result of the temperature detection unit is equal to or higher than a predetermined detection temperature is satisfied,
The fixing device according to claim 1. The surface portion of the fixing member is composed of a belt having an endless shape,
The support portion of the fixing member is
A first support member disposed so as to contact the inner peripheral surface of the belt and forming the nip portion by pressing the pressure member via the belt;
A second support member disposed so as to contact the inner peripheral surface of the belt and extending the belt in cooperation with the first support member;
The first support member or the second support member is made of the specific material,
The heat source is disposed so as to face the outer peripheral surface of the belt, heats the second support member in a non-contact manner, and indirectly heats the belt through the second support member,
The temperature detection unit is disposed so as to face an outer peripheral surface portion corresponding to an inner peripheral surface portion of the belt with which the second support member is in contact with the outer peripheral surface of the belt. Detect the surface temperature,
The overheat prevention system has an overheat prevention device disposed so as to face the outer peripheral surface of the belt, and the temperature of the overheat prevention device reaches a predetermined operating temperature. Stop energization of the heat source when the temperature condition is satisfied,
The fixing device according to claim 1. The second support member forms the nip portion by pressing the pressure member via the belt.
The fixing device according to claim 4 or 5. The temperature of the specific material when the specific material starts the phase transition is higher than the predetermined detection temperature when the overheating prevention system stops energization of the heat source,
The fixing device according to claim 2. The temperature of the specific material when the specific material starts the phase transition is higher than the predetermined operating temperature when the overheating prevention system stops energizing the heat source,
The fixing device according to any one of claims 3, 5, and 7. The specific material is composed of a vanadium-based composite oxide.
The fixing device according to claim 1. The fixing device according to claim 1 is provided.
Image forming apparatus.

Images