JP2003131504A - Heating fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure roller 6 which suppresses the over temperature rise of non-paper-feeding part 6b in the case of performing continuous paper-feeding of a small size of paper for a long time by means of effective heat transfer, prevents the occurrence of distortion of a fixing film 2 and, thereby, prevents defective fixation, defective paper-feeding and breakage of device, etc. SOLUTION: In this fixing device of a film heating type, the pressure roller 6 is pressed with contact with a heater 3 via the fixing film 2, the formed fixed nip part is allowed to hold and convey a recording material P and a toner image T is fixed on the recording material P by heating and pressing. Therein, further, the pressure roller 6 is constituted in such a manner that a heat-resistant elastic under layer 10 is formed on a core bar 7 which is a rotation shaft, thereupon, a high thermal conductivity intermediate layer 9 and heat-resistant elastic upper layer 11 are successively formed on the paper feeding part 6a, in the non-paper-feeding part 6b, the high thermal conductivity intermediate layer 9 which is thicker than that in the paper-feeding part 6a is formed and, further over the whole region, a releasing surface layer 8 is formed. Therein, coefficient of thermal conductivity of the high thermal conductivity intermediate layer 9 is higher than that of the other layer and high thermal conductivity silicone rubber, metallic thin film and the like are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device in an image forming apparatus using an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, as a heat fixing device, for example,
There is an image heating and fixing device in an image forming apparatus such as a copying machine, a printer and a facsimile which uses electrophotography. In this method, a toner image formed by using a toner such as a heat-meltable resin in the image forming process means is heated and fixed on a recording material as a permanently fixed image.

A heat fixing device used in a copying machine or the like will be described below as an example of the heat fixing device.

An example of the heat fixing device is Japanese Patent Laid-Open No. 63-
As described in JP-A-313182 and JP-A-2-157878, there has been proposed a film heating device (tensionless heating device) using a heating member having a rapid temperature rise and a thin heat-resistant film.

An example of the film heating device is shown in FIG.

In FIG. 8, 102 is a fixing film as a film, 103 is a heater as a heating member, and the heater 103 is a heating element 10 which generates heat when energized.
4 and a good thermal conductive substrate 105. The temperature of the heater 103 is controlled by controlling the energization of the heating element 104 by the CPU 110 so that the temperature detected by the thermistor 109 becomes constant. 101 is a heater 10
It is a horizontally long stay that holds 3 insulatively. Reference numeral 106 denotes a pressure roller as a pressure member that also functions as a drive roller that drives the fixing film 102, and includes a core metal 1 made of iron, stainless steel, or the like.
07, a releasable surface layer 108 made of a rubber elastic body having a good releasability such as silicone rubber is formed. Then, the recording material P is conveyed and passed through a fixing nip portion formed between the heater 103 and the pressure roller 106, so that the toner image T is heated and pressed to be fixed on the recording material P. ing.

In such a film heating type fixing device, the heat of the heater 103 is applied to the fixing film 1 having a low heat capacity.
Since heat can be directly transmitted to the recording material P via 02 and the heat capacity of the heater 103 is significantly smaller than that of the conventional heat roller system, the wait time can be shortened and so-called quick start can be performed.

Further, since the quick start is possible, preheating during the non-printing operation is not necessary, and it is possible to achieve a comprehensive power saving.

[0009]

However, in the above-mentioned conventional example, when a paper of a size smaller than the longitudinal width of the heating element is continuously fed as a recording material for a long time, film twist occurs in the fixing film, which causes fixing failure. In some cases, the pressurizing member or the fixing film may be thermally deteriorated to shorten the service life of the component itself, or in the worst case, the device may be damaged.

As a solution to this problem, a method of providing a plurality of heating patterns of a heater and energizing only that area in accordance with the paper size is conceivable, but the apparatus and control method become complicated, leading to an increase in cost. There is a drawback that.

Further, there is a method of lowering the temperature of the non-sheet passing portion by increasing the heat conductivity in the longitudinal direction of the pressure member to improve the flow of heat from the non-sheet passing portion to the paper passing portion. 7-363
No. 03, JP-A-10-115991, and the like.

An object of the invention according to the present application is to suppress the excessive temperature rise of a non-sheet passing portion when continuous feeding of a paper having a size smaller than the longitudinal width of a heat generating element is continued for a long time, thereby preventing the fixing film from being twisted or twisted. It is an object of the present invention to provide a heat fixing device that avoids heat deterioration of members and prevents fixing defects, paper passing defects, device damage, and the like.

[0013]

The first constitution of the heat fixing device according to the present invention is such that a recording material is integrated with the film at a fixing nip portion formed by a pressure member being pressed against the heating member via a film. In a heating and fixing device in which a developer is fixed on a recording material by being heated and pressed after being conveyed and passed through, the pressure member causes heat conduction to an area where the recording material is not sandwiched depending on the size of the recording material from other areas. It has parts with a high rate.

A second structure of the heat fixing device according to the present invention is the same as the first structure, wherein the pressure member comprises a heat-resistant elastic lower layer having heat resistance and elasticity on a core metal as a rotating shaft. A roller member in which a high thermal conductivity intermediate layer having high thermal conductivity, a heat resistant elastic upper layer having heat resistance and elasticity, and a releasable surface layer having releasability are sequentially formed,
The high thermal conductivity intermediate layer has a higher thermal conductivity than the heat resistant elastic upper layer, the heat resistant elastic lower layer, and the releasable surface layer, and the longitudinal width of the heat resistant elastic upper layer in the rotation axis direction is the high thermal conductivity. It is shorter than the longitudinal width of the intermediate layer in the rotation axis direction.

A third structure of the heat fixing device according to the present invention is the same as the second structure, wherein the heat-resistant elastic lower layer has a thermal conductivity of 0.6 × 10 ⁻³ cal / cm · sec · ° C. or less, The thermal conductivity of the high thermal conductivity intermediate layer is 1.0 × 10 ⁻³
cal / cm · sec · ° C. or higher, and the thermal conductivity of the heat resistant elastic upper layer is 0.6 × 10 ⁻³ cal / cm · sec · ° C. or lower.

In a fourth constitution of the heat fixing device according to the present invention, in the above second or third constitution, the layer thickness of the high thermal conductive intermediate layer in a region not covered by the heat resistant elastic upper layer is the heat resistance. It is thicker than the layer thickness of the high thermal conductivity intermediate layer in the region covered with the elastic top layer.

A fifth constitution of the heat fixing device according to the present invention is the constitution of any one of the second to fourth constitutions, wherein silicone rubber is used as the heat resistant elastic upper layer.

In a sixth structure of the heat fixing device according to the present invention, in any one of the second to fifth structures, a silicone rubber having a high heat conductivity is used as the high heat conductivity intermediate layer.

A seventh constitution of the heat fixing device according to the present invention is the constitution of any one of the second to fifth constitutions, wherein the high thermal conductive intermediate layer is made of silicone rubber in which particles having good thermal conductivity are dispersed. To use.

An eighth structure of the heat fixing device according to the present invention is the one of the second to fifth structures, wherein a metal thin film is used as the high thermal conductive intermediate layer.

A ninth constitution of the heat fixing device according to the present invention is the constitution of any one of the second to eighth constitutions, wherein silicone rubber is used as the heat resistant elastic lower layer.

In a tenth constitution of the heat fixing device according to the present invention, in any one of the second to eighth constitutions, the heat-resistant elastic lower layer is a rubber layer.

The eleventh constitution of the heat fixing device according to the present invention is the constitution of any one of the second to eighth constitutions, wherein the heat-resistant elastic lower layer is a sponge layer.

According to the above construction, the high thermal conductive intermediate layer having a specific thermal conductivity is provided just inside the releasable surface layer of the pressing member, and is specified as the upper layer of the high thermal conductive intermediate layer. By providing the heat-resistant elastic upper layer having the thermal conductivity of 1, the heat transfer property of the pressing member in the longitudinal direction is improved to reduce the excessive temperature rise of the non-sheet passing portion, and the heat resistance of the pressing member is further improved. The thermal conductivity of the elastic elastic lower layer is specified to suppress the transfer of heat to the inside of the pressure member, and the amount of heat transfer in the longitudinal direction of the pressure member is further increased to prevent overheating of the non-sheet passing area. It can be suppressed more effectively. Moreover, since the temperature of the recording material is efficiently raised, the power consumption required for controlling the fixing temperature of the heating member can be suppressed.

Further, according to the above structure, in the high thermal conductive intermediate layer, the layer thickness of the high thermal conductive intermediate layer in a region longer than the longitudinal width of the heat resistant elastic upper layer is set to the lower layer of the heat resistant elastic upper layer. By making the layer thickness higher than that of the high thermal conductive intermediate layer, it is possible to more effectively transfer the heat due to the excessive temperature rise of the non-sheet passing portion to the pressure member, and the heat transfer in the longitudinal direction of the pressure member By reducing the excessive temperature rise of the non-sheet passing portion and by further specifying the thermal conductivity of the heat-resistant elastic lower layer of the pressure member to suppress the transfer of heat into the pressure member, the longitudinal direction of the pressure member. It is possible to more effectively suppress the excessive temperature rise of the non-sheet passing portion by further increasing the amount of heat transfer. Moreover, since the temperature of the recording material is efficiently raised, the power consumption required for controlling the fixing temperature of the heating member can be suppressed.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the embodiments, but the present invention is not limited to these embodiments.

(First Embodiment) A fixing device using a tensionless film heating system will be described below as an example of the heat fixing device according to the first embodiment with reference to the drawings. In addition, the same code | symbol is described in the member common to each figure.

FIG. 1 is a schematic sectional view showing the structure of the fixing device according to the first embodiment.

In FIG. 1, reference numeral 1 denotes a resin horizontally long stay, which serves as an inner surface guide member of a fixing film 2 which will be described later.

Reference numeral 2 denotes an endless film-shaped fixing film (film) having heat resistance, and a laterally long stay 1 including a heating body 3 as a heating member is circumscribed. The inner peripheral length of the fixing film 2 is longer than the outer peripheral length of the horizontal stay 1 including the heating body 3 by, for example, about 3 mm. Therefore, the peripheral length of the fixing film 2 is larger than that of the horizontal stay 1 including the heating body 3. Circulates loosely.

As the fixing film 2, in order to reduce its heat capacity and improve quick start property,
The total thickness of the fixing film 2 is 100 μm or less,
PTFE, P with heat resistance, releasability, strength, durability, etc.
A single layer film such as FA or FEP, or a full-layer film such as polyimide, polyamide imide, PEEK, PES, PPS or the like whose outer peripheral surface is coated with PTFE, PFA, FEP or the like can be used. In the first embodiment, a film 2 having a total thickness of 60 μm obtained by coating a polyimide film of 50 μm with PTFE 10 μm was used.

A heating element 3 is provided along the substantially central portion of the substrate made of alumina or the like as a heating element 4 such as Ag / P.
About 10μ in thickness of electrical resistance material such as d (silver palladium)
m and a width of 1 to 3 mm are formed by coating by screen printing or the like, and a protective layer 5 is coated with glass, a fluororesin or the like. The heating body thermistor 12 is provided on the surface of the heating body 3 opposite to the fixing film 2, and the temperature of the heating body 3 is controlled by the temperature detected by the heating body thermistor 12.

Reference numeral 6 denotes a pressure roller (pressure member) as a rotating body for driving the fixing film 2, and the fixing film 2 is sandwiched between the heating body 3 and the heating body 3 to form a fixing nip portion.
Further, as shown in FIG. 4, the core metal 7 of the pressure roller 6 is held by a heating device frame 17 via bearings 15 and 16, and a driving gear to which a driving force from a driving motor (not shown) is transmitted. It is configured to rotate by 14.

FIG. 2 (a) is a schematic perspective view showing the structure of the pressure roller 6, and FIGS. 2 (b) and 2 (c) are respectively (a).
FIG. 3 is a schematic sectional view taken along lines A and B in FIG.

In the first embodiment, the pressure roller 6
As shown in FIG. 2, a heat-resistant elastic lower layer 10 has a length of 317 mm, a thickness of about 4 mm, and a thermal conductivity of 7 on a core metal 7 having an outer diameter of 17 mm connected to the drive gear 14 at its longitudinal end. those coated with silicone rubber layer of ^{0.5 × 10 -3 cal / cm ·} sec · ℃, thermal conductivity ^{1.2 × 10 -3 cal / cm ·} sec · ℃ high thermal as high heat conducting intermediate layer 9 A conductive silicone rubber layer (magnesium oxide-dispersed silicone rubber) is coated to a thickness of 200 μm. The heat resistance elastic upper layer 11 has a thermal conductivity of 0.5.
Silicone rubber of × 10 ⁻³ cal / cm · sec · ° C. was laminated to a width of 120 mm located 60 mm to the left and right from the center of the pressure roller 6 in the longitudinal direction to a thickness of 200 μm. Then, a pressure roller having a structure in which a modified PFA tube was adhered as a releasable surface layer 8 by 50 μm on the entire surface area was used.

As the high thermal conductivity intermediate layer 9, a high thermal conductivity silicone rubber (magnesium oxide dispersed silicone rubber) having a thermal conductivity of 1.2 × 10 ⁻³ cal / cm · sec · ° C. is used. May be configured. Here, the higher the thermal conductivity of the high thermal conductivity intermediate layer 9 and the thicker the thickness thereof, the more effective the heat radiation from the end portion is. However, in order to increase the thermal conductivity, the silicone rubber has a good heat resistance. It is preferable to disperse conductive particles (alumina, aluminum nitride, quartz, etc.). On the other hand, although the thermal conductivity of silicone rubber increases with the addition of fillers such as particles, the hardness of the silicone rubber itself also increases, which may make it difficult to obtain a nip width as a heating device, which may lead to a decrease in fixing ability. is there. Therefore, the hardness and thickness of the high thermal conductivity intermediate layer 9 are preferably designed so that the pressure roller 6 has a hardness of 30 ° (JIS-A) or less at the maximum.

The heat resistant elastic upper layer 11 is made of silicone rubber having a thermal conductivity of 0.5 × 10 ⁻³ cal / cm · sec · ° C., but a thermal conductivity of 0.6 × 10 ⁻³ cal /
Any material can be used as long as it is not more than cm · sec · ° C. In order to obtain a proper nip width and secure sufficient fixing property, silicone rubber is preferably used.

As the releasable surface layer 8, a commonly used fluororubber latex can be used. Alternatively, a PFA tube or a modified PFA tube laminated with a primer without shrinkage may be used.

By using the fixing device using the pressure roller 6 configured as described above, the temperature rise in the non-paper passing portion 6b and the paper passing portion 6a of the pressure roller 6 is measured, and the fixing film 2 is twisted. The experiment was performed.

In FIG. 5, the temperature of the heating element 3 is controlled to 195 ° C. under the environment of temperature 7.5 ° C. and humidity 50%, and the pressure roller 6 is pressed.
Envelope (width 105 mm, length 241) as the recording material P which is said to have a large temperature rise in the non-sheet passing portion 6 b with respect to the sheet passing portion 6 a.
(mm) is continuously fed at a process speed of 30 π mm / sec, the results of measuring the temperatures of the paper passing portion 6a and the non-paper passing portion 6b of the pressure roller 6 are shown.

The measurement at this time was performed by pressing a thermocouple under the pressure roller 6 with a pad. The measurement points are set such that the point of the sheet passing portion 6a is the center of the pressure roller 6 in the longitudinal direction and the point of the non-sheet passing portion 6b is 100 mm from the center of the pressure roller 6 in the longitudinal direction.

As can be seen from FIG. 5, when 60 envelopes are continuously fed, the temperature difference ΔT between the paper passing portion 6a and the non-paper passing portion 6b.
Is ΔT = 60 deg. Further, the fixing film 2 is not twisted.

As described above, according to the first embodiment, the temperature rise of the non-sheet passing portion 6b is reduced. This is the pressure roller 6
Since the heat-resistant elastic upper layer 11 is formed on the high thermal conductive intermediate layer 9 in the paper passing portion 6a, compared to the non-paper passing portion 6b in which the heat resistant elastic layer 11 is not formed, The thermal conductivity of 6a becomes very small, and as a result, the non-sheet passing portion 6b
The amount of heat transfer is increased. The heat of the high thermal conductive intermediate layer 9 of the non-paper passing portion 6b is dispersed by the heat radiating action in the end direction and the movement of the heat to the high thermal conductive intermediate layer 9 of the paper passing portion 6a, The temperature rise of the non-sheet passing portion 6b is moderated.

(Second Embodiment) Next, a second embodiment according to the present invention will be described with reference to FIG. It should be noted that the same reference numerals are given to the members common to the above figures.

FIG. 3 is a sectional view of the pressure roller 6 according to the second embodiment in the axial direction.

In FIG. 3, on the core metal 7 of the pressure roller 6, as the heat resistant elastic lower layer 10, instead of the silicone rubber used in the first embodiment, a silicone rubber having a length of 317 mm and a thickness of about 4 mm is used. Sponge layer (The thermal conductivity of the silicone rubber raw material is 0.5 × 10 ^-3 cal / cm · se
c. C.). The high thermal conductivity intermediate layer 9 has a thermal conductivity of 0.56c instead of the high thermal conductivity silicone rubber.
Using a metal thin film of aluminum of al / cm · sec · ° C, a film thickness of about 5 μm is formed over the entire area, and plus 5 μm is formed in the area outside 60 mm to the left and right of the longitudinal center of the pressure roller 6. The film thickness is set to about 10 μm, and the thickness of the high thermal conductive intermediate layer 9 at the end portion in the longitudinal direction of the pressure roller 6 is increased.

Except for the above, the pressure roller 6 has the same structure as that of the first embodiment.

Application of the metal thin film layer to the high thermal conductivity intermediate layer 9 has a thermal conductivity of 1.0 × 10 ⁻³ cal / cm.
-Any metal can be used as long as it is sec / ° C or higher, but aluminum is preferably used from the viewpoint of easy availability. In addition, metals with higher thermal conductivity (gold, silver, copper,
It is more preferable to use iron or the like). To form the metal thin film layer, a metal foil tube is used to bond each layer with a primer, or instead of covering the metal foil tube, the metal thin film layer is formed by vapor deposition on the surface of the elastic layer. Good. The thickness of the metal thin film layer is preferably 10 μm or less in order to obtain the nip width for ensuring sufficient fixing property.

Further, the high thermal conductive intermediate layer 9 has a thickness of the high thermal conductive intermediate layer 9 in a region longer than the longitudinal width of the heat resistant elastic upper layer 11 and a high thermal conductive intermediate layer under the heat resistant elastic upper layer 11. Even when the layer 9 is thicker than the layer 9, the pressure at the end in the longitudinal direction is increased due to the arrangement of the pressure spring (not shown) that is pressing the pressure roller 6, so that the nip width can be secured.

By using a sponge having a higher heat insulating property for the heat-resistant elastic lower layer 10, a more energy-saving structure with less heat leak into the pressure roller 6 can be realized.

As the heat-resistant elastic lower layer 10, an elastic body such as silicone rubber, or a sponge-like material of the elastic body is preferably used. Particularly when a metal thin film layer is used as the high thermal conductivity intermediate layer 9, by using a sponge-like elastic body, the influence on the hardness of the pressure roller 6 can be reduced and a sufficient nip width can be obtained. . At this time, the thermal conductivity of the elastic layer is 0.5 × 10.
It may be ^-3 cal / cm · sec · ° C or less, but a smaller one suppresses diffusion of heat into the pressure roller,
This can contribute to prevention of excessive temperature rise of the non-sheet passing portion 6b in small size paper.

Using the pressure roller 6 having the above structure, an experiment was conducted on the temperature rise of the pressure roller 6 and the twist of the fixing film 2 under the same conditions as the experiment performed in the first embodiment.
The result is shown in FIG.

As can be seen from FIG. 6, the temperature difference ΔT between the paper-passing portion 6a and the non-paper-passing portion 6b of the pressure roller 6 in the continuous passage of 60 envelopes is ΔT = 45 deg. Did not occur. More ΔT than in the first embodiment
Was small and the temperature rise of the non-sheet passing portion 6b was suppressed. This is because the heat-resistant elastic lower layer 10 uses a sponge having a high heat insulating property, so that heat leak into the pressure roller 6 is reduced, and a metal thin film is used for the high thermal conductive intermediate layer 9, and This is because the thickness of the high thermal conductive layer 9 at the end portion is made thicker than the thickness of the high thermal conductive intermediate layer 9 of the paper passing portion 6a, so that the heat conducting effect of the non-paper passing portion 6b becomes larger.

(Comparative Example 1) Next, the first embodiment described above will be described.
In place of the pressure roller 6 used in the above, a pressure roller 6 having a similar structure except for the high thermal conductive intermediate layer 9 immediately inside the releasable surface layer 8 and the heat resistant elastic upper layer 11 of the paper passing portion 6a is used. The non-sheet passing portion 6b of the pressure roller 6 is used as in the first embodiment.
Also, the temperature rise of the paper passing portion 6a and the twist of the fixing film 2 were tested. The results are shown in FIG. 7.

In FIG. 7, the number of continuous sheets to be passed through the envelope is 40.
The temperature of the non-sheet passing portion 6b exceeds 280 ° C. in one sheet, and if the sheet passing is continued as it is, the fixing film 2 may be damaged and the heating element 3 may be cracked, so the measurement was stopped during the sheet passing. From this result, it is understood that it is necessary to provide the pressure roller 6 with a heat radiation means.

[0056]

As described above, according to the present invention,
In a heating and fixing device for conveying a recording material integrally with the film to a fixing nip portion formed by pressing a heating member through a film via a film, and fixing the developer on the recording material by heating and pressing. , By increasing the thermal conductivity of the pressure member in the region where the pressure member and the heating member are in direct contact when nipping and transporting a smaller recording material, the temperature distribution of the pressure member is made uniform, and the pressure member and the heating member are heated. It is possible to avoid excessive temperature rise of the member.

Further, according to the present invention, the pressing member comprises:
By sequentially forming a heat-resistant elastic lower layer, a high heat-conductive intermediate layer, a heat-resistant elastic upper layer, and a releasable surface layer on the core metal of the rotating shaft, heat is dispersed and heat-resistant in the high heat-conductive intermediate layer. The elastic elastic lower layer further increases the amount of heat transfer in the high thermal conductivity intermediate layer, and can make the temperature distribution of the pressing member uniform. Further, at this time, the heat-resistant elastic upper layer is formed only in the region of the pressure member where the smaller recording material is sandwiched and conveyed, that is, in the central portion in the longitudinal direction, so that heat conduction from the recording material to the pressure member is reduced. You can As a result, it is possible to avoid excessive temperature rise of the pressure member and the heating member.

Further, according to the present invention, the layer thickness of the high thermal conductive intermediate layer is made thicker in a region not covered by the heat resistant elastic upper layer, so that the heat of a region of the pressing member which does not sandwich a recording material smaller than that of the pressure member is sandwiched. The conductivity can be increased and the temperature of the pressing member can be made more uniform.

According to the present invention, the heat-resistant elastic upper layer is made of silicone rubber, so that a proper nip width is formed between the pressure member and the heating member to ensure sufficient fixing property. You can

According to the present invention, the high thermal conductive intermediate layer is made of silicone rubber having high thermal conductivity or silicone rubber in which particles having good thermal conductivity are dispersed.
The thermal conductivity can be improved. Furthermore, by using a metal thin film as the high thermal conductivity intermediate layer, higher thermal conductivity can be obtained.

Further, according to the present invention, the heat-resistant elastic lower layer is made of a silicone rubber layer, so that heat from the heating member is prevented from leaking to the pressure member, and the temperature of the pressure member is further reduced. It is possible to effectively make it uniform and save power. Further, the heat resistant elastic lower layer is made of a sponge layer instead of the silicone rubber layer, so that the effect is further improved.

As a result, in the heat fixing device according to the present invention, the temperature distribution in the longitudinal direction of the heating member can be made uniform and the excessive heating of the heating member and the pressing member can be avoided.
It is possible to prevent improper fixing, paper passing, damage to the device, etc.
Since heat energy is efficiently applied to the recording material, power saving can be achieved. Furthermore, when the present invention is applied to a film heating type heat fixing device, the device can be comfortably used because the occurrence of twist of the fixing film is suppressed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a configuration of a fixing device according to a first embodiment of the present invention.

FIG. 2A is a schematic perspective view of a pressure roller included in the fixing device according to the first embodiment of the present invention, and FIG.
6A is a sectional configuration diagram in A, and FIG. 7C is a sectional configuration diagram in B in FIG.

FIG. 3 is an axial cross-sectional configuration diagram of a pressure roller included in the fixing device according to the second embodiment of the present invention.

FIG. 4 is a schematic front view of a pressure roller included in the fixing device according to the first embodiment of the present invention.

FIG. 5 is a graph showing a change in temperature depending on the number of sheets passed through a non-sheet passing portion and a sheet passing portion of the pressure roller included in the fixing device according to the first exemplary embodiment of the present invention.

FIG. 6 is a graph showing changes in temperature depending on the number of sheets of paper passing through a non-sheet passing portion and a sheet passing portion of a pressure roller included in the fixing device according to the second embodiment of the present invention.

FIG. 7 is a graph showing a change in temperature depending on the number of sheets passed through a non-sheet passing portion and a sheet passing portion of a pressure roller provided in a fixing device according to Comparative Example 1 of the present invention.

FIG. 8 is a schematic sectional view showing the structure of a conventional heat fixing device.

[Explanation of symbols]

1 Horizontally long stay 2 Fixing film 3 Heating element 4 Heating element 5 Protective layer 6 Pressure roller 6a Paper passing portion 6b Non-passing portion 7 Core metal 8 Releasable surface layer 9 High thermal conductive intermediate layer 10 Heat resistant elastic lower layer 11 Heat resistance Elastic upper layer 12 heating thermistor 14 drive gears 15 and 16 bearing 17 heating device frame P recording material T toner image 101 landscape stay 102 fixing film 103 heating heater 104 heating element 105 good heat conductive substrate 106 pressure roller 107 core metal 108 Releasable surface layer 109 Thermistor 110 CPU

Claims (11)

[Claims] 1. A recording material is conveyed integrally with the film to a fixing nip portion formed by a pressure member being pressed against the heating member via a film, and the developer is fixed on the recording material by heating and pressing. In the heat fixing device, the pressing member is provided in an area where the recording material is not sandwiched depending on the size of the recording material.
A heat-fixing device having a portion having a higher thermal conductivity than other regions. 2. The pressure member has a heat-resistant elastic lower layer having heat resistance and elasticity, a high heat conductive intermediate layer having high heat conductivity, and heat resistance and elasticity on a core metal as a rotating shaft. A heat-resistant elastic upper layer and a releasable surface layer having releasability, which is a roller member sequentially formed, wherein the high thermal conductivity intermediate layer is the heat-resistant elastic upper layer, the heat-resistant elastic lower layer,
And a thermal conductivity higher than that of the releasable surface layer, and a longitudinal width of the heat-resistant elastic upper layer in a rotation axis direction is shorter than a longitudinal width of the high thermal conductivity intermediate layer in a rotation axis direction.
The heat fixing device described. 3. The thermal conductivity of the heat resistant elastic lower layer is 0.6.
× 10 ⁻³ cal / cm · sec · ° C. or less, the thermal conductivity of the high thermal conductivity intermediate layer is 1.0 × 10 ⁻³ cal / cm · s.
ec · ° C or higher, the thermal conductivity of the heat-resistant elastic upper layer is 0.6.
The heating and fixing device according to claim 2, wherein the heat fixing device has a temperature of x10 ^-3 cal / cm · sec · ° C or less. 4. The layer thickness of the high thermal conductive intermediate layer in the region not covered by the heat resistant elastic upper layer is thicker than the layer thickness of the high thermal conductive intermediate layer in the region covered by the heat resistant elastic upper layer. The heat fixing device according to claim 2 or 3. 5. The heat fixing device according to claim 2, wherein silicone rubber is used as the heat resistant elastic upper layer. 6. The heat fixing device according to claim 2, wherein a silicone rubber having a high heat conductivity is used as the high heat conductivity intermediate layer. 7. The heat fixing device according to claim 2, wherein a silicone rubber in which particles having good heat conductivity are dispersed is used as the high heat conductivity intermediate layer. 8. The heat fixing device according to claim 2, wherein a metal thin film is used as the high thermal conductivity intermediate layer. 9. The heat fixing device according to claim 2, wherein silicone rubber is used as the heat resistant elastic lower layer. 10. The heat fixing device according to claim 2, wherein the heat resistant elastic lower layer is a rubber layer. 11. The heat fixing device according to claim 2, wherein the heat resistant elastic lower layer is a sponge layer.