Image heating apparatus

Abstract: An image heating apparatus includes a heater (6) provided with a heat generating element (5) generating heat upon electric energization to a base; a supporting member (3) for supporting the heater (6); a back-up member (2) press-contacted to the heater; wherein an image on a recording material (P) is heated by heat from the heater; wherein at least such a portion of the supporting member as supports the heater is of thermoplastic material.

Description: The present invention relates to an image heating apparatus usable with an image forming apparatus such as a copying machine or printer, and more particularly to an image heating device wherein a heating element per se is broken at the time of an abnormal temperature rise of the heating element. A film heating type heating device has been proposed by the assignee of this application in Japanese Laid Open Patent Application No. SHO-63-313182, Japanese Laid Open Patent Application No. HEI-1-263679 Japanese Laid Open Patent Application No. HEI-2-157878, Japanese Laid Open Patent Application No. HEI-4-44075-44083 , EP-A-0 604 976 or the like. In that heating device, a heating element having a heat generating element generating heat upon energization thereto is supported on a supporting member, and the heating element and an elastic pressing roller as a pressing member are pressed to each other with a heat resistive film material (or sheet material) therebetween to form a heating nip. Between the pressing roller and the heat resistive film material, a member to be heated is introduced and is fed through the nip together with the heat resistive film material by which thermal energy of the heating element is applied to the member to be heated through the heat resistive film material in the heating nip. This type is advantageous in that the used heating element has a low thermal capacity with a high temperature rise speed (quick start feature) and can concentratedly apply the heat. The heating device is usable as an image heating device for the image fixing in an image forming apparatus such as a copying machine or printer, more particularly as a heating device for heat-fixing, into a permanent fixed image, an unfixed toner image formed and carried on a recording material (transfer material photosensitive paper electrostatic recording paper or the like) through an image formation process (transfer type or direct type) such as electrophotographic process, electrostatic recording process, or magnetic recording. As an example of a heating element having a low thermal capacity with high temperature rise speed, there is a so-called ceramic heater having a high thermal conductivity ceramic substrate of heat-resistivity and insulative property, and a heat generating resistor printed or sintered thereon. The electric power is supplied to the heat generating resistor to generate heat. The electric power supply to the heat generating resistor is controlled so as to maintain a predetermined temperature, 160 - 180 °C in an image heat-fixing device, by a temperature control system including a temperature sensing element (thermister or the like) for detecting the temperature of the heater. As a safety measure, a safety element such as a temperature fuse is connected in series with the heat generating resistor in the electric energy supply system therefor, and is contacted to the back side of the heater similarly to a thermistor. Upon breakdown of the temperature sensing element such as a thermistor in the temperature control system, or the electric power control system such as AC driver or TRIAC in the electric energy supply system for the A/D converter, control means (CPU) or the heat generating resistor, electric power may be supplied to the heat generating resistor of the heater without control. If this occurs, the heater temperature may continuously rise (runaway of the heater). As a safety measure in consideration of the failure or disorder of the safety element such as the fuse, means is provided to spontaneously let the heater crack so as to result in a disconnection of the AC line (the heat generating resistor per se and the electroconductive path connected therewith). More particularly, the heater is provided with a weakened portion in the form of an opening or scribed groove to cause thermal stress in the heater to be concentrated on the weakened portion upon the over-heat state due to the runaway so as to stop the runaway by letting the heater cracking occur which leads to disconnection of the AC line. In this case, the way of cracking or the cracking position of the heater is important. For example, a way of cracking or cracking position which does not result in the disconnection of the AC line, which does not break the insulation between the AC line and the DC line (thermister and electroconductive path therefor formed on the heater), or which only the DC line is disconnected, cannot stop the runaway of the heater. The heater weakened portion is provided so as to assure the stop of the heater runaway. However, when the weakened portion is formed in the heater as above, the yield decreases in the manufacturing process of the heater per se since the heater is relatively easily broken at the weakened portion. Accordingly, it is a principal object of the present invention to provide an image heating device wherein thermal damage of the device is prevented by break or rupture of the heater during use without decreasing the yield of the heater in manufacture. The image heating apparatus of the present invention is of the kind disclosed in European Patent Application EP-A-0372479, comprising: a heater including an elongate base, and a heat generating element, on said base, for generating heat upon electric energization; a supporting member having a supporting surface portion of a thermoplastics material for supporting said heater; a pressing member urged toward said supporting member with said heater therebetween, whereby a recording material carrying an image can be passed between said heater and said pressing member so that the image can be heated. According to the present invention, the aforesaid image heating apparatus is characterised in that: a non-thermoplastic member is provided in said supporting surface portion of said supporting member, and said non-thermoplastic member has a length shorter than that of said heat generating element and is provided within the length of said heat generating element. These and other features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, wherein: Figure 1 is a schematic illustration of an example of an image forming apparatus; Figure 2 is an enlarged cross-sectional view of a major part of an image heat-fixing device using a film type heating device; Figure 3 is a longitudinal section of the same device; Figure 4, (a) is a partly broken plan view of a heater (ceramic heater), and (b) is a back side view; Figure 5 is an exploded perspective view of a heater and a heater supporting member; Figure 6 is an exploded perspective view of a modified heater supporting member and a heater; Figure 7 is a longitudinal sectional view of a major part of an image heating device; Figure 8 is an exploded perspective view of the heater and heater supporting member of the preferred embodiment; Figure 9 shows a relation between the heater and the heater supporting member end portion of the preferred embodiment; and Figure 10, (a), (b) and (c), show structures of alternative film type heating devices. Referring to the accompanying drawings, first and second background examples will be described preceding the description of the preferred embodiment of this invention. Background Example 1 (Figure 1 - Figure 5) (1) Example of Image Forming Apparatus Figure 1 shows example of an image forming apparatus in which the image heating apparatus of the present invention may be used. The image forming apparatus of this example is a laser beam printer using an image transfer type electrophotographic process. Designated by 13 is an electrophotographic photosensitive member of a rotatable drum type as an image bearing member, and is rotated at a predetermined peripheral speed (process speed) in the clockwise direction indicated by the arrow. The photosensitive member 13 of this example is an OPC photosensitive member having a diameter of 30 mm, and is rotated at 25 mm/sec. Designated by 14 is a contact type charging roller as a primary charging means contacted to the photosensitive member 13. The charging roller 14 is supplied with a predetermined charging bias voltage from a charging bias voltage source, so that the peripheral surface of the rotatable photosensitive member 13 is uniformly charged (primary charging). In this example, it is charged to -650 V. The charged surface of the rotatable photosensitive member is subjected to a scanning exposure by a laser beam emitted from a laser diode 15 of a laser scanner with modulation in accordance with image information signal representative of the intended image (image exposure) L, so that an electrostatic latent image is formed on the surface of the rotatable photosensitive member 13. Then, the electrostatic latent image is developed into a toner image by a developing device 16. In this example, the developing device is a reverse jumping development type using a magnetic single component toner. On the other hand, a transfer material P as a recording material is fed sheet by sheet into the device from a sheet feeding tray by driving a sheet feeding roller 17, and is introduced into a nip between a transfer roller 18 and the photosensitive member 13 at a predetermined timing, and the toner image on the surface of the photosensitive member is continuously transferred onto the introduced transfer material surface. The transfer roller 18 is supplied with a predetermined transfer bias from an unshown transfer bias voltage source. The transfer material P having passed through the transfer portion, is separated from the surface of the rotatable photosensitive member 13, and is introduced into a heat-fixing device A so that the unfixed toner image is fixed, and then, the transfer material is discharged. The surface of the photosensitive member 13 after the separation of the transfer material, is cleaned by a cleaning blade of urethane rubber contacted to the surface of the photosensitive member 13 in a cleaning device 19 so that residual matter such as untransferred toner is removed to be prepared for repeated image forming operation. (2) Heat-fixing Device A The heat-fixing device A of this example is of a film heating type using a heat resistive film material (heat resistive sleeve) in the form of an endless belt type. Figure 2 is an enlarged cross-sectional view of a major part; Figure 3 is a longitudinal sectional view of the major part; Figure 4, (a) shows the front side of a heater, (b) shows the back side; Figure 5 is an exploded perspective view of the heater showing separately the heating element and the heater supporting member. Designated by 6 is a heater. The heater of this example is an elongated flat plate-like ceramic heater extending in a direction perpendicular to the transporting direction of the transfer material as a member to be heated introduced into the device. It is a low thermal capacity heater which rapidly increases the temperature upon energization to the heat generating resistor 5, which will be described hereinafter. Designated by 3 is an elongated heater supporting member as a heating element supporting member, and the heater 6 is embedded in a counterbore 22 having the form of a recess extended in the longitudinal direction in the bottom surface of the heater supporting member 3 with the heater at the outside. The heater 6 may be bonded to the counterbore 22 of the heater supporting member 3 or may be simply fitted. The heater supporting member 3 is of a thermoplastic resin material, for example, a liquid crystal polymer, PPS or the like, which has a heat-resistivity of not less than 200 °C and is plasticized at a temperature not less than 250 °C. The configuration is maintained by a reinforcing plate 20 of channel-like shape cross-section on the upper surface side (the side opposite from the heater support side) of the heater supporting member 3. The assembly of the heater 6, supporting member 3 and reinforcing plate 20, is fixed on an unshown supporting member with the heater 6 facing down. Designated by 11 and 12 are a driving roller and a tension roller disposed in parallel with the assembly of the heater 6, the supporting member 3 and the reinforcing plate 20. Designated by 1 is a heat resistive film material (fixing film) in the form of an endless belt, and stretched around the heater 6, driving roller 11 and the tension roller 12. The fixing film 1 may be a monolayer film of PTFE, PFA or the like or a complex layer film comprising a base film of polyimide, polyamide-imide, PEEK, PES PPS or the like and a parting layer of PTFE, PFA, FEP or the like. It has a total thickness 100 µm, preferably, 20 - 40 µm and has a heat-resistivity, parting property, strength and durability. Designated by 2 is a pressing roller as a pressing member having a heat resistive elastic layer with high parting property such as silicone rubber. It is press-contacted, with a predetermined urging force against the elastic layer, to the lower surface of the heater 6 with the fixing film 1 therebetween, thus forming a heating nip portion N of a predetermined width (fixing nip). By rotation of the driving roller 11, the fixing film 1 is rotated in the clockwise direction indicated by the arrow, at least during the image fixing operation, at a predetermined peripheral speed (the same as the feeding speed of the transfer material P introduced into the device A) while sliding on the bottom surface of the heater in close contact with the bottom surface of the heater 6. The pressing roller 2 is driven by the rotation of the fixing film 1. In the state that the fixing film 1 is rotated and that the heater 6 is controlled at a predetermined temperature by the electric power supply to the heat generating resistor 5 of the heater 6, the transfer material P is introduced between the fixing film 1 of the fixing nip N and the pressing roller 2, so that the transfer material P is passed through the fixing nip N while the transfer material P is kept in close contact with the fixing film 1. In the fixing nip passing process, thermal energy is applied to the transfer material P through the fixing film 1 from the heater 6, so that the unfixed toner image T on the transfer material P is heated, fused and fixed. The transfer material P is separated from the fixing film 1 after passing the fixing nip, and is discharged. The film heating type is advantageous in that a very low thermal capacity heater 6 is usable so that the time required for reaching the predetermined heating temperature can be significantly reduced. In addition, it is easy to increase the temperature to a high temperature from the normal running temperature, and therefore, there is no need of stand-by temperature control when the device is in the stand-by state. Referring to Figure 4, the constituent elements of the ceramic heater 6 will be described. The heater substrate is a ceramic substrate 30 such as alumina having a low thermal capacity, high heat conduction property, electric insulation property, and in the form of an elongated flat plate-like and having a length of 270 mm, width of 7 mm and a thickness of 0.635 mm. The heat generating resistor 5 having a resistance value of 34&O& in this example and of Ag/Pa or the like pattern-printed or sintered into a thin stripe longitudinally extended on a substantially central portion of a width of one of the surfaces of the heater substrate 30 (front side). First and second electric energy supply electrode patterns 32,33 of Ag or the like, are electrically connected with the opposite end portions of the heat generating resistor 5 by pattern printing and sintering on the surface of the heater substrate. A surface protection layer 31 of the heater of heat resistive glass or the like is provided on the surface of the heater substrate to cover the heat generating resistor 5 except for the electrode pattern 32 and 33 portions. A thermistor 4 as a temperature sensing element is provided by pattern printing and sintering or bonding on a proper position on the other side (back side) of the heater substrate 30. Two electroconductive path patterns 36 and 37 and third and fourth electrode patterns 38 and 39 are provided by pattern printing and sintering on the heater substrate, as signal supplying leads connected with thermistor 4. A temperature fuse 21 is provided on a proper part of the back side of the heater substrate by press-contacting with heat resistive adhesive material, as safety element. The AC line is constituted by the heat generating resistor 5, and the first and second electrode patterns 32, 33 in the heater 6. The DC line is constituted by thermistor 4, electroconductive path patterns 36, 37 and third and fourth electrode patterns 38, 39 in the heater 6. The first and and second electrode patterns 32, 33 in AC line are connected with electric energy supply contacts 34, 35 (Figures 3, 4) of unshown electric energy supply connector at the heater opposite end portions. The third and fourth electrode patterns 38, 39 of the DC line are connected with the A/D converter of the control system. Across the first and and second electrode patterns 32, 33 of the AC line, the electric power is supplied by the electric energy supply contacts 34, 35 from the AC voltage source S through the AC driver 9, so that the heat generating resistor 5 generates heat over the total length thereof, and thus quickly raises the temperature. The rising temperature of the heater 6 is detected by thermistor 4, and the sensed heater temperature information is supplied to the control means (CPU) 8 through the A/D converter 7 from the third and fourth electrode patterns 38, 39 of the DC line. The A/D converter 7 digitalizes the output of thermistor 4 and then the digitalized signal is supplied to the control means 8. The control means 8 controls the AC driver 9 including a TRIAC or the like on the basis of the input supplied thereto to control the energization electric power to the heat generating resistor 5 in the AC line, so that the surface temperature of the heater 6 is maintained at a predetermined heating temperature (fixing temperature). The target heater temperature of this example is 165 °C. For the electric power supply control of the heat generating resistor 5, use is made of phase control, wave number control or the like. For example, in the wave number control, 14 waves of the AC input voltage are used as a basic unit, and the input electric energy is changed by changing the number of the waves of 14 waves to be supplied to the heat generating resistor 5. The ratio of ON/OFF is represented by a duty ratio and can be controlled in the range of 0 - 100 %. (Heater Runaway) The temperature fuse 21 as the safety element, has an operation temperature of 183 °C in this example, and is serially connected between the electric energy supply contact 34 for the first electrode pattern 32 of the heat generating resistor 5 and the AC driver 9, and contacted to the back side of the heater substrate 30. Designated by 40 (Figure 3) is a heater receiving hole of the heater supporting member 3. The temperature fuse 21 does not operate as long as the heater 6 is controlled at the predetermined target temperature, which is not more than the operation temperature of the temperature fuse 21. Even if the temperature of the heater 6 rises significantly by overshooting the target temperature upon starting, the temperature of the fuse does not rise to the operating temperature because thermal capacity of the temperature fuse 21 is relatively large, and therefore, the electric power supply to the heat generating resistor 5 of the heater 6 is not shut off. When the heater 6 runs away, the temperature fuse 21 operates when the operation temperature of 183 °C is reached, to shut off the electric power supply to the heat generating resistor 5, thus prohibiting any problem. Although the heater supporting member 3 is of thermoplastic resin material, it has a heat-resistivity of not less than 200 °C, and is plasticized at not less than 250 °C, so that the heat resistive range thereof is sufficiently higher than the target temperature of the heater 6 and the operation temperature of temperature fuse 21 so as to stably keep the function of the heater supporting member 3 without thermal deformation. When the temperature fuse 21 is failed at the time of heater runaway, so that the temperature fuse 21 is inoperable or is very slow in response, the heater 6 temperature continues to rise beyond the operation temperature of the temperature fuse 21 (overheating) without operation of the temperature fuse 21. In this case, however, when the heater 6 temperature reaches 250 °C which is the plasticization temperature of the heater supporting member 3, at least heater supporting surface (mounting surface) of the heater supporting member 3 is plasticized and fused by the heat of the over-heated heater 6. Here, referring to Figure 3, a is a length range where the pressing roller 2 is press-contacted to the heater 6 with the fixing film 1 therebetween; b is a width of the fixing film 1; and c is a length of the heater 6, wherein a<b<c is satisfied. Therefore, the heater 6 is pushed by the pressing roller 2 in the range 'a' corresponding to the roller length. The length of the heater 6 is longer than the heater urging length range a provided by the pressing roller 2, and the opposite end portions of the heat generating resistor 5 of the heater 6 extend outwardly of the heater urging length range a provided by the pressing roller 2. When the temperature of the heater 6 rises to not less than 250 °C under the heater 6 runaway condition and under the failure of the temperature fuse 21, the length range of the heater supporting member 3 corresponding to the heater urging length range a, inter alia, the neighborhood of the supporting surface for the heater, is plasticized and fused by the heat and the pressure with the result of the deformation due to the heat and pressure so that the heater mounting seat sinks. On the other hand, the heater supporting member portion other than the range a, does not deform because of the lack of the pressure or heat generation or because of the insufficient temperature, and therefore, a deviation or step occurs relative to the range a. Then, a stress in the direction perpendicular to the surface of the heater 6 occurs at a position Z (a position substantially corresponding to each of the end portions of the pressing roller 2) corresponding to each of the ends of the range a. This is effective to disconnect the heat generating resistor 5 in the AC line to stop the electric power supply to the heat generating resistor 5, thus preventing the heater temperature from rising to as high as 400 °C. Thus, in this example, the heater cracking can assuredly occur at a predetermined position Z upon the overheating beyond the operation temperature of the temperature fuse 21 so that the overheating can be safely prevented without the necessity for the provision of the weakened portion at a predetermined position. Therefore, the decrease in the yield when the heater is provided with a weakened portion for predetermining the heater cracking position, can be avoided. The entirety of the heater supporting member 3 may be of a thermoplastic resin material to provide the required thermal deformation property, or this thermal deformation property may be provided only for the heater supporting surface portion (heater mounting seat). Background Example 2 (Figures 6, 7) In this example, the heater supporting member 3 is provided with an inside counterbore 23 by providing an additional recess in the counterbore 22 for the heater, as shown in Figure 6. With this structure, when the heater runs away with the result of overheating as in the foregoing, the neighborhood of the heater supporting surface of the heater supporting member 3 is plasticized and fused by the heat and pressure. In this case, the plasticized and fused portion deforms into the inside of the counterbore 23 so that the heater mounting seat can further sink. If the inside counterbore 23 does not extend to the longitudinal end portion of the counterbore 22 for mounting the heater, namely, if the counterbore 22 is provided only inside the heater 6 in the longitudinal direction, the stress perpendicular to the surface of the heater 6 is concentrated to the ends 23a, 23b of the inside counterbore 23. Thus, the heater is broken at the positions 23a, 23b (Z). By aligning the ends 23a and 23b of the hole 23 with the ends of the heater urging length range a provided by the pressing roller 2, the heater 6 is more easily broken at positions 23a, 23b when the heater runaway runs away. As shown in Figure 7, by aligning the ends of the inside counterbore 23 of the heater supporting member 3 with the end surfaces of the pressing roller 2, the stress by the pressing force of the pressing roller 2 and the stress due to the difference in the heat conduction to the heater supporting member 3 are concentrated , thus promoting cracking of the heater 6. Preferred Embodiment In this example, a non-fusible member (not plasticized by heat) is provided in the heater supporting surface portion of thermoplastic heater supporting member 3, in the structure of Background Examples 1 or 2. When the heater 6 temperature continues to rise without operation of the safety fuse 21 at the time of the heater 6 running away, the heater supporting surface (the mounting seat of the heater) of the heater supporting member 3 is plasticized and fused, as has been described hereinbefore, and therefore, it sinks. But, it does not sink at the non-fused member portion, and therefore, the forces are applied to the both sides of the heater with the non-fused member portion functioning as a fulcrum, so that the breakage or rupture occurs at the fulcrum portion. Figure 8 shows this example, wherein a non-fusible portion material 24 is placed in the inside counterbore 23 in the structure of embodiment 2 having the inside counterbore 23. When the heater 6 length is 270 mm, and the width thereof is 7 mm, it is preferable that the non-fused member 24 has a contact width relative to the heater 6 not more than 1 mm, or it is further preferable that the contacting end is in the form of an edge. This is because the edge configuration is effective to concentrate the pressure more, thus further assuring the cracking of the heater 6. The contact position relative to the heater 6 suffices if it is between a position 30 mm away from the heater end portion and the centre portion thereof. If it is too close to the end, the heater is supported at two positions since the heater supporting member does not fuse at the end portions of the heater 6. In this case, the heater is not easily cracked. Such a non-fused member 24 may be of a material having a heat-resistivity and not having thermoplastic property, such as thermosetting polyimide, polyamide-imide, polyamide, phenolic resin, ceramic or the like, preferably. Particularly, it preferably is of electrically insulative material to prevent electric conduction after the heater 6 cracks. It further preferably has a larger thermal-expansion than the heater supporting member 3. Under the normal state, the non-fused member 24 is contacted to the heater 6 or disposed with a clearance not more than 0.1 mm therefrom. When the heater supporting member 3 starts to fuse, the heater 6 is pushed by the pressing roller 2 at the both sides with the non-fused member 24 functioning as a fulcrum in the counterbore 22. By this, the heater 6 breaks at the position of the non-fused member 24. Figure 10, (a), (b), and (c), show other examples of heating devices of film heating type, to which the present invention is applicable. In (a), an endless belt type heat resistive film 1 is stretched and extended around two members, namely, a driving roller 11 and a heater 6 supported on a heater supporting member 3, and is moved by the driving roller 11. In (b), a cylindrical heat resistive film 1 is loosely extended around a heater supporting member 3 which also functions as a film guide, and the film 1 is press-contacted to the heater 6 by the pressing roller 2. By rotating the pressing roller 2, the film 1 is rotated while the inner surface of the film 1 is in sliding contact with the heater 6 surface (pressing roller driving type). In (c), heat resistive film 1 is a non-endless film rolled around a feeding shaft 41, and is fed to the take-up shaft through the heater 6 at a predetermined speed. The heating device of the present invention is applicable not only to the image heat-fixing device A in the foregoing embodiments, but also to an apparatus for heating a recording material carrying an image to improve the surface finish, to an apparatus for temporarily fixing an image, to a drying or laminating apparatus applying heat to a fed sheet-like material. The present invention is applicable to a device or the like wherein a heating element supported on a heater supporting member is directly contacted to a member to be heated. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the scope of the following claims.

Claims: An image heating apparatus, comprising: a heater (6) including an elongate base (30), and a heat generating element (5), on said base, for generating heat upon electric energization; a supporting member (3) having a supporting surface portion of a thermoplastics material for supporting said heater; a pressing member (2) urged toward said supporting member with said heater therebetween, whereby a recording material (P) carrying an image (T) can be passed between said heater (6) and said pressing member (2) so that the image (T) can be heated; characterised in that : a non-thermoplastic member (24) is provided in said supporting surface portion of said supporting member (3), and said non-thermoplastic member (24) has a length shorter than that of said heat generating element (5) and is provided within the length of said heat generating element. An apparatus according to claim 1, wherein said heater (6) has respective electrodes (32,33) for electric energization located at respective longitudinal end portions of said heat generating element (5). An apparatus according to claim 1, wherein said pressing member (2) extends to each side of said non-thermoplastic member (24) in the longitudinal direction of said base (30). An apparatus according to claim 1, wherein said heater (6) extends in the longitudinal direction of said base (30). An apparatus according to claim 1, wherein the base (30) is a ceramic substrate. An apparatus according to claim 1, wherein said thermoplastics material is composed of a thermoplastics resin material. An apparatus according to claim 6, wherein said thermoplastics resin material is a liquid crystal polymer or a polyphenylene sulphide (PPS) material. An apparatus according to claim 1, wherein said supporting member (3) is entirely composed of a thermoplastics material. An apparatus according to claim 1, wherein said thermoplastics material is a material that is plasticized at a temperature of not less than 250°C. An apparatus according to claim 1, wherein said supporting surface portion is provided with a recess (23) which is recessed away from said heater (6). An apparatus according to claim 10, wherein said recess (23) is provided within the length of said heater (6). An apparatus according to claim 11, wherein the respective positions of the end walls (23a,23b) of said recess (23) correspond to the positions of the respective ends of said pressing member (2) in the longitudinal direction of said base (30). An apparatus according to claim 1 wherein said non-thermoplastic member (24) is composed of thermosetting resin material. An apparatus according to claim 1, wherein said non-thermoplastic member (24) has a thermal expansion coefficient larger than that of the supporting surface portion of the supporting member (3). An apparatus according to claim 1, wherein a film (1) is provided between said heater (6) and said pressing member (2) and is arranged so that one side of said film (1) is in sliding contact relative to said heater (6), and the opposite side of said film is movable in contact with a recording material (P) carrying an image (T). An apparatus according to claim 15 wherein said heat generating element (5) is operable to generate sufficient heat to fix an image (T) on a recording material movable together with, and in contact with, the opposite side of said film (1). An apparatus according to claim 1, wherein said pressing member (2) is a pressing roller. An image heating apparatus according to any preceding claim wherein said heater (6) includes, on that side of said base (30) opposite to said heat generating element (5), a temperature sensing element (4). An image heating apparatus according to any preceding claim wherein said heater (6) includes, on that side of said base (30) opposite to said heat generating element (5), a temperature fuse (21), which has a fusing temperature that is calculated to be between the normal operational temperature of said heater (6) and the plasticization temperature of said thermoplastic material.

Inventors: MUKATAKA OSAMU, OGAWA KENICHI, OHTSUKA YASUMASA, TAKANO MANABU, TOMOYUKI YOHJI, WATANABE YASUNARI, YANO HIDEYUKI, YOSHIOKA MAHITO, MUKATAKA, OSAMU, OGAWA, KENICHI, OHTSUKA, YASUMASA, TAKANO, MANABU, TOMOYUKI, YOHJI, WATANABE, YASUNARI, YANO, HIDEYUKI, YOSHIOKA, MAHITO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1996
Main classification: G03G15
IPC codes: G03G15, H05B3