JP2017120334A - Heat conduction sheet member, image heating device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conduction sheet member that has high strength and high thermal conductivity and has heat conduction anisotropy, and provide an image heating device and an image forming apparatus that can efficiently reduce a temperature rise of a non-paper feed part.SOLUTION: The present heat conduction sheet member is a heat conduction sheet member used for an image heating device that heats a toner image formed on a recording material, and has a lamination structure including a first sheet layer having heat conduction anisotropy and a second sheet layer having higher tensile strength than that of the first sheet layer, where the first sheet layer is exposed on one face. In an image heating device that heats a toner image formed on a recording material by conveying, while holding, the recording material at a nip part formed by a self-heating, flexible cylindrical heating member and a pressure member, a surface of the heat conduction sheet member on the opposite side of the first sheet layer is in slidable contact with a non-paper feed area that is a local temperature rising area of the cylindrical heating member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat conductive sheet member used as a countermeasure for raising the temperature of a non-sheet passing portion of a film heating type or heating belt type image heating apparatus, and an image heating apparatus and an image forming apparatus using the same.

2. Description of the Related Art Conventionally, as an image heating apparatus using a heat conductive sheet member as a countermeasure for raising the temperature of a non-sheet passing portion, for example, those described in Patent Document 1 and Patent Document 2 are known.
An image heating apparatus described in Patent Document 1 includes a flexible rotatable heating film, a heating member that slidably contacts an inner peripheral surface of the heating film, a heating member support member that supports the heating member, And a pressure member that forms a nip portion by pressure contact with the heating member via a heating film.
In the case of such a film heating type image heating apparatus, due to the temperature difference between the paper passing portion and the non-paper passing portion in the temperature increase in the non-sheet passing portion, thermal stress is applied to the heater constituting the heating member, and the heater substrate is cracked, Use as a heater may become impossible.
Therefore, in Patent Document 1, a single-layer graphite sheet (heat conduction anisotropic sheet) having a high thermal conductivity in the longitudinal direction is interposed between the contact surfaces of the heating member and the heating member support member. Through this graphite sheet, the heat of the non-sheet passing portion, which has been locally heated, is conducted to the relatively low temperature sheet passing region, and the temperature is made uniform to alleviate the local temperature rise of the heating member. It was.

On the other hand, the image heating apparatus described in Patent Document 2 includes a flexible endless belt, a radiant heating element that heats the endless belt, and a support member (belt guide) that slidably contacts the inner peripheral surface of the endless belt. And a pressure member that forms a nip portion by pressure contact with the support member via a fixing belt.
Inside this endless belt, a sheet member having a high thermal conductivity is provided such that the front surface is in contact with the inner peripheral surface of the endless belt and the back surface is in contact with the support, thereby reducing a significant temperature increase in the non-sheet passing region. It was like that.
The thermally conductive sheet member has a three-layer configuration of a glass fiber sheet, a polyimide sheet, and a graphite sheet (thermally conductive anisotropic sheet) provided between the glass fiber sheet and the polyimide sheet. A glass fiber sheet comprises the front surface of the sheet | seat member which contact | connects the inner peripheral surface of a belt, and hold | maintains a lubrication agent with glass fiber. On the other hand, the polyimide sheet constitutes the back surface of the sheet member in contact with the support member, and is a low friction sheet.

JP 2003-317898 A Japanese Patent No. 4774769 JP 2011-145656 A JP 2011-248098 A

However, since the single-layer graphite sheet as in Patent Document 1 is very brittle and tearable, there is a risk that the graphite sheet may be damaged due to friction and thermal stress in the thermal expansion difference between the heater and the heating member support member. is there. In particular, when the primary current is not controlled and the heater overheats at the time of failure of a triac or relay used in the power supply circuit, the difference in thermal expansion becomes large, and the stress acting on the graphite sheet becomes excessive.
On the other hand, although the sheet member as shown in Patent Document 2 uses a graphite sheet with high thermal conductivity, both surfaces thereof are covered with a glass fiber sheet and a polyimide sheet, and a thermal barrier is provided. It has become. For this reason, there is a problem that the heat transmitted to the graphite sheet cannot be efficiently transmitted to the heat radiating member or the heat equalizing member.
In particular, when the endless belt of Patent Document 2 is a heat generating belt that generates heat from the fixing belt itself as shown in Patent Documents 3 and 4, the non-sheet passing portion temperature rises constantly. That is, since the heat generating belt generates heat uniformly in the longitudinal direction, even when a recording material having the maximum width that can be passed is passed, the non-sheet passing portion temperature rise occurs in the region outside the maximum width, and the end The calorific value of the part increases, and soaking and heat dissipation performance is insufficient. On the other hand, when the thickness of the sheet member is increased, the heat is taken as much as that, so that the startup time of the apparatus is increased and the productivity is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a heat conductive sheet member having high heat conductivity anisotropy and high strength, and non-paper passing. An object of the present invention is to provide an image heating apparatus and an image forming apparatus that can efficiently reduce the temperature rise in the area.

In order to achieve the above object, a heat conductive sheet member of the present invention is a heat conductive sheet member used in an image heating apparatus for heating a toner image formed on a recording material, and at least a heat conductive anisotropy. The first sheet layer is exposed on one surface in a laminated structure including a first sheet layer having a second sheet layer having a tensile strength stronger than that of the first sheet layer. It is characterized by that.
Further, the image heating apparatus according to the present invention is formed on a recording material by sandwiching and conveying the recording material at a nip portion formed by a flexible, cylindrical heating member that self-heats and a pressure member. In an image heating device for heating a toner image,
The surface opposite to the first sheet layer of the heat conductive sheet member according to the invention is slidably in contact with the non-sheet passing portion region which is a local temperature rising region of the cylindrical heating member. It is characterized by.
Another invention of the image heating apparatus includes a flexible cylindrical rotating body, a heating member that slidably contacts the inner periphery of the cylindrical rotating body, a support member that supports the heating member, and a cylindrical shape. In an image heating apparatus having a pressure member that is pressed against a heating member via a rotating body to form a nip portion,
The heat conductive sheet member according to the invention is sandwiched between the heating member and the support member, and the surface of the heat conductive sheet member opposite to the first sheet layer is in contact with the heating member, and the first sheet layer Is in contact with the support member.
Furthermore, an image forming apparatus of the present invention includes an image forming unit that forms a toner image on a recording material, and the image heating device according to the invention that heats the toner image formed by the image forming unit.

  According to the present invention, it is possible to realize a sheet member having high thermal conductivity anisotropy and high thermal conductivity. Further, it is possible to realize an image heating apparatus and an image forming apparatus that can efficiently reduce the temperature rise of the non-sheet passing portion.

(A) is principal part sectional drawing which shows typically the fixing device of Embodiment 1, (B) is a principal part front view of (A). FIG. 2A is a schematic configuration diagram of an image forming apparatus according to a first embodiment, and FIG. 2B is a schematic diagram of a control unit in FIG. (A) is a perspective view explaining the holding method of the heat conductive sheet of Embodiment 1, (B) is a schematic block diagram of a heat conductive sheet, (C) is explanatory drawing of the heat flow of a fixing film and a heat conductive sheet. FIG. 3 is a longitudinal temperature distribution diagram of a fixing film in a comparative experiment of Embodiment 1. FIG. 4 is a cross-sectional view of a main part of a fixing device according to a second embodiment. (A) And (B) is the perspective view and top view of the heat conductive sheet member of Embodiment 2, and an aluminum plate. FIG. 6 is a longitudinal temperature distribution diagram of a fixing film in a comparative experiment of Embodiment 2. FIG. 9 is a cross-sectional view schematically showing a main part of a fixing device according to a third embodiment.

The best mode for carrying out the present invention will be exemplarily described in detail below based on the embodiments with reference to the drawings.
[Embodiment 1]
(Schematic configuration of image forming apparatus)
FIG. 2A is a schematic diagram illustrating a configuration example of an image forming apparatus to which the image heating apparatus according to the first embodiment of the present invention is applied. FIG. 2B is a schematic diagram of a control unit of the image forming apparatus in FIG.
The image forming apparatus 100 is a laser beam printer, and includes an image forming unit that forms a toner image on a recording material by an electrophotographic method, and a fixing device 110 as an image heating device that heats and fixes the toner image formed on the recording material. I have.
That is, reference numeral 101 denotes a photosensitive drum as an image carrier, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined process speed (peripheral speed). The photosensitive drum 101 is uniformly charged to a predetermined polarity and potential by the charging roller 102 during its rotation.
On the other hand, the printer controller 301 develops the pixel signal corresponding to the digital pixel signal input from the host computer 311, and the engine control unit 302 drives each component described later.
Reference numeral 103 denotes a laser beam scanner as image exposure means, which outputs laser light S that is on / off modulated with respect to the above-described pixel signals, and scan-exposes the charged surface of the photosensitive drum 101. By this scanning exposure, the charge of the exposed bright portion on the surface of the photosensitive drum 101 is removed, and an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 101.

A developing device 104 supplies developer (toner) to the surface of the photosensitive drum 101 from the developing roller 104a, and the electrostatic latent image on the surface of the photosensitive drum 101 is sequentially developed as a toner image which is a transferable image. Is done.
Reference numeral 105 denotes a paper feed cassette on which the recording material P is loaded and stored. The paper feed roller 106 is driven based on the paper feed start signal, and the recording material P in the paper feed cassette 105 is separated and fed one by one. Then, the toner is introduced at a predetermined timing into a transfer portion 108T that is a contact nip portion with the transfer roller 108 that is rotated by contact with the photosensitive drum 101 via the registration roller pair 107. That is, the conveyance of the recording material P is controlled by the registration roller pair 107 so that the leading edge of the toner image on the photosensitive drum 101 and the leading edge of the recording material P reach the transfer portion 108T at the same time.

Thereafter, the recording material P is nipped and conveyed at the transfer portion 108T, and during that time, a transfer voltage (transfer bias) controlled by the energization control unit 304 is applied to the transfer roller 108 from a transfer bias application power source (not shown). A transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 108, and the toner image on the surface side of the photosensitive drum 101 is electrostatically transferred onto the surface of the recording material P at the transfer portion 108T. The recording material P after the transfer is separated from the surface of the photosensitive drum 101, passes through the conveyance guide 109, and is introduced into a fixing device 110 as an image heating device.
The fixing device 110 receives a thermal fixing process for the toner image. On the other hand, the surface of the photosensitive drum 101 after the transfer of the toner image to the recording material P is cleaned by the cleaning device 111 after removal of transfer residual toner, paper dust, and the like, and is repeatedly used for image formation. The recording material P that has passed through the fixing device 110 is discharged from the paper discharge port 112 onto the paper discharge tray 113.

(Configuration of fixing device)
1A is a cross-sectional side view of the main part of the fixing device 110 of this example, and FIG. 1B is a front model view of the main part. In the present embodiment, the fixing device 110 is an energization heat generation type device.
That is, the recording material is nipped and conveyed between the fixing film 1 which is a flexible and cylindrical heating member and a pressure roller 8 as a pressure member, and the recording material is thereby conveyed. The toner image formed in this is heat-fixed.
Inside the fixing film 1 that is a cylindrical heating member, a film guide 6 as a support member that supports the surface on the nip portion side of the inner periphery of the film that is the inner periphery of the cylindrical heating member, and the film guide 6 are pressed. A pressure stay 7 is provided. The pressure stay 7 presses the film guide 6 toward the pressure roller 8.
Further, a heat conductive sheet member 2 to be described later is disposed inside the fixing film 1, and the second sheet layer 22 of the heat conductive sheet member 2 is slidably in contact with the inner peripheral surface of the fixing film 1.

  The fixing film 1 is a cylindrical rotating body having a composite structure of a heat generating layer 1a as a base layer, an elastic layer 1b laminated on the outer surface, and a release layer 1c laminated on the outer surface. In the heat generating layer 1a, the carbon nanomaterial and the filamentous metal fine particles are substantially uniformly dispersed in a matrix resin made of polyimide. By applying an alternating current to the heat generating layer 1a through flange members 12a and 12b as electrode members, current is applied in a direction perpendicular to the rotation direction of the fixing film 1, and the heat generating layer 1a generates heat. This heat is transmitted to the elastic layer 1b and the release layer 1c, the entire fixing film 1 is heated, and the recording material P passed through the nip portion N is heated to fix the toner image T. The heat generating layer 1a has a diameter of 10 to 50 mm and a thickness of about 30 to 200 μm, for example.

The pressure roller 8 includes a cored bar 8a and a heat-resistant elastic material layer 8b such as silicone rubber, fluororubber, or fluororesin that is formed and coated in a roller shape concentrically around the cored bar 8a. A release layer 8c is provided on the surface layer. Both ends of the cored bar 8a are rotatably supported through conductive bearings between chassis side metal plates (not shown) of the apparatus.
The film guide 6 is a long body having a U-shaped cross section, a guide main body 61 corresponding to the area of the nip portion N, and a downstream guide portion provided on the downstream side and the upstream side in the rotation direction of the fixing film 1 of the guide main body portion 61. 62 and an upstream guide portion 63. The surface of the guide main body 61 on the nip N side is an arc surface, and the back surface opposite to the nip is a flat surface.
The pressure stay 8 is a long member having a U-shaped cross section, and is fitted between the upstream guide portion 42 and the downstream guide portion 43 of the heater holder 4 with the open side facing downward, and both leg portions 81 and 82 are formed. It is in contact with the guide main body 61.
The pressurizing stay 7 is a long member having an inverted U-shaped cross section that opens downward, and both end portions protrude in the longitudinal direction toward the chassis from the fixing film 1 and the film guide 6. Pressure springs 17a and 17b (see FIG. 1B) are provided between both ends of the pressure stay 7 and spring receiving members 18a and 18b on the apparatus chassis side (see FIG. 1B), respectively. The pressing force is applied by shrinking the. In the fixing device 110 of the present embodiment, a pressing force with a total pressure of about 100 to 300 N is applied. As a result, the lower surface of the film guide 6 made of the heat-resistant resin PPS and the like and the upper surface of the pressure roller 8 are pressed through the pressure stay 7 with the fixing film 1 serving as a heating member interposed therebetween, and have a predetermined width. A nip portion N is formed.

During the operation of the fixing device 110, the driving gear G of the pressure roller 8 receives the driving force from the driving source M, and is rotationally driven in the counterclockwise direction indicated by the arrow at a predetermined process speed. In the present embodiment, the rotation speed of the pressure roller 8 is set so that the conveyance speed of the recording material P is 240 mm / sec. Along with the rotational driving of the pressure roller 8, a clockwise rotational force indicated by an arrow acts on the fixing film 1 by a frictional force acting between the pressure roller 8 and the fixing film 1 in the nip portion N. The flange members 12a and 12b are externally fitted to the left and right ends of the film guide 6,
The left and right positions are fixed by the restricting members 13a and 13b and are rotatably attached. When the fixing film 1 rotates, it receives the end of the fixing film 1 and plays a role of regulating the movement of the film guide 6 of the fixing film 1 that is offset.
As materials of the flange members 12a and 12b, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, fluorine resin (PFA, PTFE, FEP, etc.), LCP (Liquid Crystal Polymer): liquid crystal Polymer) resin, a material having good heat resistance such as a mixed resin thereof is preferable. The flange members 12a and 12b also function as electrode members for supplying power to a heat generating layer 1a described later. A conductive material such as Ag is applied to the surface in contact with the fixing film 1 to fix the alternating current. It also plays the role of conducting to the film.
Further, the temperature detection of the fixing device 110 is performed by temperature measuring elements 9, 10, 11 such as a non-contact type thermistor (see FIGS. 2A and 2B). The temperature measuring elements 9, 10, 11 are arranged at the longitudinal center and opposite positions of the fixing film 1 on the side where the recording material P is conveyed to the fixing device 110.
The fixing temperature control unit 303 (see FIG. 2B) controls the energization control unit 304 (see FIG. 2B) based on the temperature detected by the temperature measuring element 9 at the longitudinal center of the fixing film 1. Thereby, the fixing film 1 is energized, and the surface temperature is maintained and adjusted to a predetermined target temperature.

(Arrangement configuration of heat conductive sheet member 2)
In the internal space of the fixing film 1, the flexible heat conductive sheet member 2 is disposed so as to be slidably in contact with a non-sheet passing portion area that is a local temperature rising area of the fixing film 1. Yes.
The heat conductive sheet member 2 has a laminated structure including a first sheet layer 21 having heat conduction anisotropy and a second sheet layer 22 having a tensile strength stronger than that of the first sheet layer 21. The first sheet layer 21 is exposed on one surface. A second sheet layer 22 located on the surface opposite to the first sheet layer 21 is slidably in contact with the fixing film 1, and is larger than the maximum sheet passing width of the recording material P of the fixing film 1. Is also in contact with the non-sheet passing region on the outside in the longitudinal direction. That is, the local temperature rise is reduced by contacting a non-sheet passing region which is a local temperature rise region of the fixing film 1 as a heating member.
The non-sheet-passing region is present at both ends in the longitudinal direction of the fixing film 1, and the heat conductive sheet member 2 is provided at two locations corresponding to both ends in the longitudinal direction of the cylindrical heating member. In the figure, the reference numerals of the two heat conductive sheet members 2 are distinguished from 2a and 2b. However, since they have the same configuration, the following explanation will be made assuming that the reference numeral is 2 unless otherwise required. .
In the fixing device 110 of the present embodiment, as shown in FIG. 1B, a film having a longitudinal width Lf of 234 mm is used as the fixing film 1, and the maximum width Lp of the transportable recording material P is 216 mm. is there. Correspondingly, the longitudinal length Ws of the heat conductive sheet member 2 is 7 mm.
The heat conductive sheet member 2 is elastic and has a belt-like configuration extending in the rotation direction of the fixing film 1. The heat conductive sheet member 2 is fixed to the film guide 6 as a support member and rotates along the inner periphery of the fixing film 1 from the fixed portion. It extends in the shape of a strip downstream in the direction. The portion along the inner periphery of the fixing film 1 is elastically deformed following the inner peripheral shape of the cylindrical heating member, and the surface on the second sheet layer 22 side has a reaction force on the inner peripheral surface of the fixing film 1. Are in sliding contact. In this example, one end of the heat conductive sheet member 2 is fixed to the surface on the back side with respect to the nip portion N of the guide main body 61 of the film guide 6, and the other end rotates along the inner peripheral surface of the fixing film 1. It extends in the downstream direction.

FIG. 3A is a perspective view for explaining a method of holding the heat conductive sheet member 2.
The film guide 6 and the pressure stay 7 are provided with notches 6 a and 7 a so as to avoid the portion where the heat conductive sheet member 2 is provided so that the heat conductive sheet member 2 can be inscribed in the fixing film 1. Yes. The notch 6 a of the film guide 6 is provided in the downstream guide portion 62, and the depth of the notch 6 a is notched to the same height as the back surface of the guide main body portion 61.
In the heat conductive sheet member 2, the fixed portion 2A, which is a portion fixed to the guide main body 61, has a flat plate shape, and almost the entire width of the guide main body 61 (recording material) except for the legs on the upstream side of the pressure stay 7. In the conveying direction) and in contact with the back surface of the guide body 61. The fixing portion 2A is fixed to the boss 3 protruding from the surface opposite to the nip forming side of the guide main body 61 with a push nut. In the fixed portion 2 </ b> A, the surface on the second sheet layer 22 side is a contact surface with the guide main body 61. Further, the first sheet layer 21 of the fixed portion 2A is exposed to the internal space of the fixing film, in this example, the space between the pressure stay and the film guide 6, and functions as a heat radiating surface.
On the other hand, the notch 7a provided in the leg portion on the downstream side of the pressure stay 7 is such that the thickness of the heat conductive sheet member 2 does not interfere. From the notch 7a of the pressure stay 7 and the notch 6a of the downstream guide portion 62, the free portion 2A of the heat conductive sheet member 2 is elastically deformed along the inner peripheral surface of the fixing film 1 to form the second sheet. The surface on the layer 22 side is in contact with the fixing film 1 over almost the entire length and extends downstream in the rotational direction. The contact length in the rotational direction is long, and in the illustrated example, the free end extends to the vicinity of the upper end of the film in the drawing. The first sheet layer 21 of the free portion 2B is exposed to the internal space of the fixing film 1 and functions as a heat radiating surface.
The free part 2B of the heat conductive sheet member 2 is arranged so as to be in contact with 0.4 N along the inner surface of the fixing film 1, for example. From the standpoint of springiness and high thermal conductivity, the total thickness of the sheet is 60 μm, and heat uniformity is ensured while stably contacting over a wide range of the inner surface of the fixing film 1.

(Detailed configuration of the heat conductive sheet member 2)
Next, the detailed structure of the heat conductive sheet member 2 is demonstrated.
As shown in FIG. 3B, the heat conductive sheet member 2 of the present embodiment is laminated on one surface of the first sheet layer 21 containing graphite having heat conduction anisotropy and the first sheet layer 21. And a second sheet layer 22 made of a different material. The second sheet layer 22 has a higher tensile strength than the first sheet layer 21, and the surface on the second sheet layer side is a non-sheet-passing region that is a local temperature rising region of the fixing film 1 that is a heating member. Touching the area.
The second sheet layer 22 that is in contact with the fixing film 1 that is a rotary heating member at a high temperature has heat resistance and less friction with the fixing film 1, so that heat can be efficiently transferred to the first sheet layer 21. In addition, it is desirable that the thermal conductivity is high (high λ). Further, it is desirable that the tensile strength is strong against a stress generated by a process of removing the remaining recording material when a paper jam occurs.
In the present embodiment, the second sheet layer 22 is a composite material containing a binder of PI, PTFE particles, and a metal silicon filler with polyimide (PI) as a base material, and is used by coating the graphite layer 22 to a thickness of 20 μm. In addition, a composite material of polyamideimide (PAI), polyetheretherketone (PEEK), PES, polyfinylene sulfide (PPS), and the like, and these resins and ceramics, metal, glass, or the like may be used.
The first sheet layer 21 is in close contact with the second sheet layer 22 described above, and has a feature that the thermal conductivity in the surface direction is very high. It plays the role of soaking. In addition, the surface of the first sheet layer 21 opposite to the second sheet layer 22 is changed in surface property, so that when the heat conductive sheet member 22 is used alone, heat dissipation can be improved, It is also possible to dissipate heat by connecting to a large member.
The graphite sheet used as the first sheet layer 21 in this embodiment is a trade name “Graphinity” manufactured by Kaneka Co., Ltd. having a heat resistant temperature of 500 ° C. and a thickness of 40 microns. The thermal conductivity in the plane direction and the thickness direction is as shown in (Table 1), which is lower in density than other high thermal conductivity metals such as aluminum and copper, and the thermal conductivity in the plane direction is 300 times that in the thickness direction. It is high and has excellent heat uniformity in the surface direction.

However, the tensile strength is low compared to other materials, and it is fragile in a configuration in which it is rubbed for a long time while being in contact with the inner surface of a fixing film that is rotated and heated at a high temperature like the fixing device of the present embodiment. There is a risk of tearing before life.
Therefore, as described above, the second sheet layer 22 made of polyimide having a tensile strength of about 9 times that of the graphite sheet is provided on one side of the first sheet layer 21 having a thickness of 40 μm, and the surface thereof is slidable. Let Further, the back surface of the first sheet layer 21 opposite to the second sheet layer 22 is provided with unevenness with a 400th sandpaper so that the surface area is increased to obtain heat dissipation.
The first sheet layer 21 need not be limited to a graphite sheet, and may be, for example, a composite sheet layer containing graphite in which a graphite is dispersed in a metal. Furthermore, the sheet layer is not limited to griffite, and may be any sheet layer having thermal conductivity anisotropy that has a high thermal conductivity in the plane direction with respect to the thickness direction and excellent thermal uniformity in the plane direction. .
Further, in the present embodiment, the heat conductive sheet member 2 having a two-layer structure has been described. However, a multilayer structure having the first sheet layer 21 and the second sheet layer 22 has a multilayer structure of three or more layers. May be. In the case of three or more layers, the first sheet layer 21 may be configured to be exposed on one surface of the heat conductive sheet member 2, and the second sheet layer 22 is formed on the other surface of the heat conductive sheet member 2. The structure which exposes may be sufficient and may be arrange | positioned at the intermediate | middle layer. For example, in addition to the high-strength second sheet layer 22, a sheet layer made of a material having excellent slidability is laminated and exposed on the surface opposite to the first sheet layer 21 of the heat conductive sheet member 2. Also good.

(Operation of Embodiment 1)
FIG. 3C schematically shows the heat flow at the contact portion between the heat conductive sheet member 2 and the fixing film 1.
The figure shows a case where a portion H in the longitudinal direction of the fixing film 1 is locally hotter than other portions. In this embodiment, in addition to the heat flow A in the longitudinal direction of the fixing film 1, the heat from the fixing film 1 to the heat conductive sheet member 2 in the portion of the fixing film 1 that is in contact with the heat conductive sheet member 2. The flow of Furthermore, a heat flow B that flows in the longitudinal direction of the heat conductive sheet member 2 and returns to the fixing film 1 again, and further a heat flow C that radiates heat from the back side of the heat conductive sheet member 2 is generated. By this action, soaking and temperature rise of the non-sheet passing portion of the fixing film 1 are suppressed.

(Experimental result)
Next, a comparative experiment between a conventional fixing device in which the heat conductive sheet member 2 is not provided in the non-sheet passing portion and the fixing device of this embodiment will be described.
In the comparative experiment, LETTER size paper having a longitudinal width of 216 mm was used, and the longitudinal temperature distribution during passing of the fixing film 1 was measured with a thermo viewer at the timing when the non-sheet passing portion temperature was saturated.
FIG. 4 shows the measured temperature distribution, and Table 2 shows the maximum temperature reached at the center and the non-sheet passing portion at that time. Compared with the conventional example, it can be seen that the temperature distribution in the non-sheet-passing area is broad and soaking in the longitudinal direction. As a result, the maximum temperature reached could be reduced by 10 ° C.

また、単層のグラファイトシートと本実施形態の熱伝導シート部材２をそれぞれ具備した定着装置での、耐久試験結果を（表３）に示す。（表３）の数値は、グラファイトシートが初期性能を保ち、破断せずに使用できた時間である。単層のグラファイトシートが５０時間で破断してしまったのに対し、本実施形態の熱伝導シート部材２では、２５０時間でも継続使用することができた。

Further, (Table 3) shows the durability test results for the fixing devices each including the single-layer graphite sheet and the heat conductive sheet member 2 of the present embodiment. The numerical values in (Table 3) are times when the graphite sheet maintained initial performance and could be used without breaking. While the single-layer graphite sheet broke in 50 hours, the heat conductive sheet member 2 of the present embodiment could be used continuously even for 250 hours.

As described above, durability is improved compared to single-layer graphite sheets in cases where heat-generating members that generate mechanical or thermal stress are in sliding contact and require soaking or heat dissipation. can do. In addition, since the graphite surface on the back surface is not provided with a thermal barrier, it was possible to efficiently transfer the heat taken away to the heat radiating member and the heat equalizing member.
In this embodiment, the heat generating layer 1a is directly rubbed and soaked by a sheet member having a leaf spring shape from the inner surface of the fixing film 1, but is pressed from the release layer side of the outer surface of the fixing film 1. It does not matter as a configuration to hit. In addition, the fixing device in which the fixing film generates heat when energized has been described, but an induction heating type fixing device may be used.

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described. Since the basic configuration is the same as that of the first embodiment, in the following description, the same components are denoted by the same reference numerals, detailed description thereof is omitted, and only different portions are described.
FIG. 5 is a schematic cross-sectional view of the fixing device according to the second embodiment, and FIGS. 6A and 6B are perspective views of the heat conductive sheet member 2 and the soaking plate 4.
In the second embodiment, the first sheet layer 21 of the heat conductive sheet member 2 of the first embodiment is fixed in close contact with a heat equalizing plate (heat conductive member) 4 from which another heat equalizing effect is obtained. . Thereby, it is set as the structure which makes the reduction effect of non-sheet-passing part temperature rise larger and lasting.
The soaking plate 4 is disposed over the entire length of the fixing film 1 in the guide body 61 of the film guide 6 in contact with the inner surface of the fixing film 1 in the nip N. In the illustrated example, the soaking plate 4 is separated in the height direction by a predetermined dimension at the nip portion N so that the first printout time is not delayed. In addition, the heat insulating structure is configured such that the longitudinal temperature distribution is not affected when the fixing device is started up.
As the soaking plate 4, an aluminum plate having a length in the short direction of 6 mm, a thickness of 1 mm, and a length in the longitudinal direction of 234 mm is used, and is separated from the nip portion N by about 2.0 mm. The soaking plate is not limited to an aluminum plate as long as it has a high thermal conductivity.
Fixing portions 2 </ b> A located in the middle of the heat conductive sheet member 2 are fixed to both ends of the soaking plate 4. The free portion 2B extends from the fixed portion 2A to both the downstream side in the rotational direction and the upstream side in the rotational direction of the fixing film 1, and is in contact with the fixing film 1 in a wider range than in the first embodiment.
In the fixed portion 2A, in the thickness direction of the nip portion N, the first sheet layer 21 and the soaking plate 4 are brought into close contact with each other by a pressing force from the film guide 6. The heat equalizing plate 4 and the heat conductive sheet member 2 are fixed, for example, by providing a concave portion to which the heat equalizing plate 4 is mounted on the surface of the guide main body 66 opposite to the nip portion N. It may be fixed to the guide main body 6 or may be fixed by pressing the lid with the pressure stay 7.
As a result, the heat generated at the non-sheet passing portions located at both ends of the fixing film 1 is transferred from the heat conductive sheet member 2 to the heat equalizing plate 4 so that the recording material is conveyed again in the longitudinal nip. It can be returned to part N.
In the present embodiment, in FIG. 6B, the surface of the first sheet layer 21 is roughened in order to improve the heat dissipation performance, as in the first embodiment, in the region that does not contact the hatched heat equalizing plate 4. doing. On the contrary, the region that is in close contact with the soaking plate 4 was subjected to a mirror surface treatment so that the contact thermal resistance was reduced.

[Features of Embodiment 2]
Generally, the temperature for melting and fixing the toner image on the recording material P needs to be increased as the conveyance speed of the recording material P increases. That is, in the nip portion N between the fixing film 1 and the pressure roller 8, the amount of heat applied per unit time is reduced. Therefore, when the process speed is high, the temperature of the fixing film is increased to provide the same amount of heat in a short time. Must. As a result, as the image forming apparatus is capable of high-speed sheet passing, the temperature difference between the non-sheet passing part and the temperature of the sheet passing part becomes larger, and the temperature rise of the non-sheet passing part becomes more remarkable.
As in the first embodiment, LETTER size paper was used, and the temperature distribution of the fixing film 1 at the timing when the non-sheet passing portion temperature was saturated was compared.
As a result, in the fixing device of Embodiment 1 that does not have the soaking plate 4, as shown in (Table 4), the fixing property is improved when the recording material conveyance speed is 300 mm / s, compared to 240 mm / s. The temperature at the center of the paper passing portion, which was continuously satisfactory, increased by 20 ° C., the maximum temperature reached at the non-paper passing portion reached 245 ° C., and exceeded the heat resistance temperature of the silicone rubber of the fixing film 1.

実施形態１の構成における、搬送速度違いによる定着フィルム温度

Fixing film temperature due to difference in conveyance speed in the configuration of Embodiment 1

(Comparative example)
The results of comparison experiments between the fixing device of the first embodiment and the fixing device of the present embodiment under the condition that the conveyance speed of the recording material P is 300 mm / s are shown below.
As in the first embodiment, LETTER size paper was used, and the longitudinal temperature distribution during passing of the fixing film 1 at the timing when the non-sheet passing portion temperature was saturated was measured with a thermo viewer and compared. FIG. 7 shows the measured temperature distribution, and Table 5 shows the maximum temperature reached at the center and the non-sheet passing portion at that time. Compared with the configuration of the first exemplary embodiment, even when the recording material conveyance speed is increased, the temperature distribution in the non-sheet passing portion region becomes broad, so that heat can be uniformly distributed in the longitudinal direction. The temperature could be reduced.

As described above, the second embodiment has been described with respect to the heat conductive sheet member 2 that can suppress the non-sheet-passing temperature rise even when the conveyance speed of the recording material P is high.
In the second embodiment, the heat soaked in the heat conductive sheet 2 is transferred to the heat equalizing plate 4 in the film guide 6, but the present invention is not limited to this configuration. For example, when the heat equalizing plate 4 cannot be inserted due to the size restriction of the fixing device, the heat transfer sheet 7 may be configured to conduct heat, and the heat dissipation effect of the heat conductive sheet member 2 alone is insufficient. However, what is necessary is just the structure which heat-transfers to another member with big heat capacity so that a soaking | uniform-heating effect can be improved and maintained.
In each of the above embodiments, the heat conduction sheet member 2 having a leaf spring shape is slidably contacted directly from the inner surface of the fixing film 1 to the heat generating layer 1a. It may be configured to be pressed from the layer 1c side. Further, the fixing device in which the fixing film 1 generates heat when energized has been described, but an induction heating type fixing device may be used. Furthermore, for example, as in Patent Document 2, a flexible endless belt, a radiant heating element that heats the endless belt, a support member (belt guide) that slidably contacts the inner peripheral surface of the endless belt, The present invention can also be applied to a fixing device including a pressing member that presses and contacts a supporting member via a fixing belt to form a nip portion.

[Other Embodiments]
In each of the above-described embodiments, the image heating apparatus in which the fixing film self-heats has been described. However, for example, as in Patent Document 3, a fixing apparatus using a known ceramic heater as a heating element is also effective.
That is, as shown in FIG. 8, a tubular film 20 that is a flexible tubular rotating body, a heating plate 202 as a heating member that slidably contacts the inner periphery of the tubular film 201, and a heating plate And a support member 203 that supports 202. And a pressure roller 8 as a pressure member that is pressed against the heating plate 202 through the tubular film 201 to form the nip portion N, and the recording material P is nipped and conveyed between the nip portions N. The toner image is heated and fixed.
The heat conductive sheet member 2 is sandwiched between the heating plate 202 and the support member 203, the surface of the heat conductive sheet member 2 on the second sheet layer 22 side is in contact with the heating plate 202, and the first side on the opposite side. The surface on the sheet layer 21 side is in contact with the support member 203.
Due to the temperature difference between the sheet passing portion and the non-sheet passing portion when the non-sheet passing portion temperature rises, the heating plate 202 may be subjected to thermal stress on the heater, and in some cases, the substrate may be cracked and cannot be used as a heater. There is. For such a problem, conventionally, the heat conductive sheet member 2 of the present invention is used for a configuration in which a single layer graphite sheet is installed between the heating plate 202 and the back of the supporting member 203 and the supporting member. Thus, it is possible to protect the first sheet layer 21 from friction and thermal stress in the thermal expansion of the heater of the heating plate 202.
In addition, the heat conduction sheet member 2 is used for cracking of the heater at the time of thermal runaway in which the heater is overheated when the primary current is input to the heater without being controlled when a triac or relay used in the power supply circuit fails. Is also effective. That is, when a thermal runaway occurs, the thermo switch or the like is activated to cut off the power supply, but during that time, excessive thermal stress is applied to the heater substrate of the heating plate 202 or the holder holding the heater is melted. There is a risk that the substrate will break due to mechanical stress due to the above. In the meantime, although it is rubbed due to the difference in thermal expansion with the heat conductive sheet member 2 of the present invention, since the second sheet layer 22 is in contact, damage to the heat conductive sheet member 2 itself can be prevented. Moreover, since heat is dissipated by the heat conductive sheet member 2, damage to the heater can be prevented as much as possible. As described above, the heat conductive sheet member 2 of the present invention can be applied to various types of image heating apparatuses that heat the toner image formed on the recording material.

  In each of the above embodiments, the image heating device of the present invention is applied to a fixing device that fixes an unfixed toner image formed on a recording material by heating and pressing, but is not limited to a fixing device. Absent. For example, the present invention can be applied as a device for giving gloss to a toner image fixed on a recording material.

1 Fixing film (cylindrical heating member: self-heating)
2 heat conductive sheet member 21 1st sheet layer (layer which has heat conduction anisotropy)
22 Second sheet layer 4 Heat equalizing plate 6 Film guide (supporting member)
8 Pressure roller (Pressure member)
201 Cylindrical film (cylindrical rotating body)
202 Heating plate (heating member)
203 Support member Lf Longitudinal width Lp Maximum width N Nip portion P Recording material T Toner image

Claims (13)

A heat conductive sheet member used in an image heating apparatus for heating a toner image formed on a recording material,
At least a first sheet layer having thermal conductivity anisotropy, and a second sheet layer having a tensile strength stronger than the first sheet layer,
The heat conductive sheet member, wherein the first sheet layer is exposed on one surface.   2. The heat conductive sheet according to claim 1, wherein the sheet layer exposed on the surface opposite to the surface on which the first sheet layer of the heat conductive sheet member is exposed has lower friction than the first sheet layer. Element.   The heat conductive sheet member according to claim 1 or 2, wherein the first sheet layer is a sheet layer containing graphite.   The heat conductive sheet member according to any one of claims 1 to 3, wherein the heat conductive sheet member has a two-layer structure of the first sheet layer and the second sheet layer. In an image heating apparatus that heats a toner image formed on a recording material by sandwiching and conveying the recording material at a nip formed by a flexible and cylindrical heating member that is self-heating and a pressure member,
The surface on the opposite side to the first sheet layer of the heat conductive sheet member according to any one of claims 1 to 4, in a non-sheet passing portion region that is a local temperature rising region of the cylindrical heating member. An image heating apparatus characterized by being configured to contact slidably.   6. The image heating apparatus according to claim 5, wherein the first sheet layer of the heat conductive sheet member is exposed in the cylindrical heating member. Inside the cylindrical heating member, a support member that supports the surface on the nip portion side of the inner periphery of the cylindrical heating member is provided,
The heat conductive sheet member has a belt-like configuration extending in the rotation direction of the cylindrical heating member, is fixed to the support member, and extends from the fixed portion to at least one of the upstream side and the downstream side in the rotation direction of the cylindrical heating member. 7. The cylindrical heating member according to claim 5 or 6, wherein the cylindrical heating member is elastically deformed following the inner peripheral shape of the cylindrical heating member, and is in sliding contact with a reaction force on the inner peripheral surface of the cylindrical heating member. Image heating device.   The image heating apparatus according to claim 7, wherein one end of the heat conductive sheet member is fixed to the support member and the other end extends downstream in the rotation direction along the inner peripheral surface of the cylindrical heating member.   The image heating apparatus according to claim 5, wherein the heat conductive sheet member is fixed to the support member via a heat conductive member in contact with the first sheet layer.   The image heating apparatus according to claim 9, wherein the heat conducting member extends in a longitudinal direction of the cylindrical heating member.   The non-sheet passing portion region is provided at both ends in the longitudinal direction of the cylindrical heating member, the heat conductive sheet member is provided on the inner periphery of both ends in the longitudinal direction of the cylindrical heating member, and both ends of the heat conductive member The image heating apparatus according to claim 7, wherein the image heating apparatus is configured to contact the first sheet layer of the conductive sheet member. A flexible cylindrical rotating body, a heating member that is slidably in contact with the inner periphery of the cylindrical rotating body, a support member that supports the heating member, and a heating member that is pressed through the cylindrical rotating body A pressure member that forms a nip portion,
The heat conductive sheet member according to any one of claims 1 to 4 is sandwiched between the heating member and the support member, and the first sheet layer of the heat conductive sheet member is in contact with the heating member and is opposite thereto. An image heating apparatus, wherein a side surface is in contact with a support member.   An image forming apparatus comprising the image heating apparatus according to claim 5.

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