JP2001075392A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent warming-up time from getting longer, productivity from getting low and energy efficiency from lowering by restraining the heat loss of an endless belt in a fixing device what is called a belt nip type fixing device. SOLUTION: This fixing device is equipped with a fixing member 1 equipped with a heating source 1a and rotatably disposed, the endless belt 2 rotating in a state where it is arranged to press-contact with the member 1 and interposing a recording medium K carrying an unfixed toner image T between the member 1 and the belt 2, a pressure imparting member 3 provided to abut on the belt 2 inside the belt 2 and pressing the belt 2 toward the member 1 side, and a holding member 4 disposed inside the belt 2 and holding the member 3. Then, a heat insulating layer 5 is provided on the outer peripheral surface of the member 4 opposed to the inner surface of the belt 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used to heat and pressure-fix an unfixed image in an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a fixing member such as a heating roll. The present invention relates to an improvement of a so-called belt nip type fixing device in which an endless belt is disposed in pressure contact with a recording medium, and a recording medium is passed through a contact nip area formed between the fixing member and the endless belt.

[0002]

2. Description of the Related Art Conventionally, as a belt nip type fixing device of this type, for example, a rotatable heating roll having a heating source, an endless belt pressed against the heating roll and rolling with the heating roll, and an endless belt And a pressure pad which is disposed inside the endless belt and presses the endless belt against a heating roll and forms a contact nip area between the endless belt and the heating roll. 10
-228196). In this type of fixing device, an unfixed toner image on the recording medium is heated and pressed and fixed by inserting the recording medium into a contact nip area between the heating roll and the endless belt. .

[0003]

By the way, in such a belt nip type fixing device, the endless belt is heated by a heating roll when passing through the contact nip area, and after passing through the contact nip area, its front and back surfaces are heated. The process of being cooled by the heat radiation from the heater and heated again when passing through the contact nip region is repeated. Therefore, the endless belt always removes heat from the heating roll when it enters the contact nip area, thereby causing a decrease in the temperature of the heating roll, so that the time required for initial heating and reheating of the heating roll is reduced. As long as it has to be secured, the warm-up time will be prolonged and productivity will decrease,
There was a technical problem in that energy efficiency was reduced due to the need to secure a large amount of heating power.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and it is intended to reduce the heat loss of the endless belt to prolong the warming-up time, reduce the productivity, and reduce the energy efficiency. An object of the present invention is to provide a fixing device of a belt nip type capable of preventing a reduction.

[0005]

That is, according to the present invention, as shown in FIG. 1, a fixing member 1 having a heating source 1a and rotatably disposed, and a pressure member disposed in pressure contact with the fixing member 1 are provided. An endless belt 2 that rotates and holds a recording medium K carrying an unfixed toner image T between the fixing member 1 and an endless belt 2 provided inside the endless belt 2 so as to contact the endless belt 2; A pressure applying member 3 for pressing the endless belt 2 toward the fixing member 1 side, and a holding member 4 disposed inside the endless belt 2 for holding the pressure applying member 3
And a heat insulating layer 5 is provided on the outer peripheral surface of the holding member 4 facing the inner surface of the endless belt 2.

In such technical means, if the fixing member 1 is rotatably disposed, the fixing member 1 has a roll shape.
A belt or the like may be selected as appropriate. The heating source 1a provided in the fixing member 1 may be of a type built in the fixing member 1 as shown in FIG. 1 or of a type for externally heating the fixing member 1. .

Further, the endless belt 2 may be supported in a non-stretched state as shown in FIG. 1, or may be supported by being stretched over a plurality of rolls. You may. Here, in a mode in which the endless belt 2 is stretched and supported, it is preferable to provide a heat insulating layer, which will be described later, also on the outer peripheral surface of, for example, a roll member on which the endless belt 2 is stretched.

The pressure applying member 3 is provided with the fixing member 1.
The material may be appropriately selected as long as the material presses the endless belt 2 toward the surface, but from the viewpoint of preventing thermal deterioration, it is preferable that the material has heat resistance.

Further, the holding member 4 may be any member that is provided inside the endless belt 2 and has a function of holding the pressure applying member 3.

The heat insulating layer 5 may be appropriately selected as long as it has a function of preventing the heat radiated from the inner surface of the endless belt 2 from being taken away by the holding member 4. From the viewpoint of ensuring heat resistance performance, a foam is preferable, and from the viewpoint of ensuring good heat resistance performance and mechanical properties, a heat-resistant resin is preferable. From such a viewpoint, the heat insulating layer 5 is preferably made of a foam containing any of polyethylene terephthalate, urea resin, and melamine resin.

Also, from the viewpoint of preventing normal rotation of the endless belt 2 from being hindered by contact between the endless belt 2 and the heat insulating layer 5, the heat insulating layer 5 faces the inner surface of the endless belt 2. It is preferable to provide a low friction layer 6 on the part side surface, and it is particularly preferable to set a friction coefficient between the inner surface of the endless belt 2 and the low friction layer 6 to 0.5 or less. Here, as for the low friction layer 6, when the heat insulation layer 5 itself is made of a material having low friction properties, the heat insulation layer 5 may also serve as the low friction layer 6, Even if the heat insulating layer 5 is made of a material having a high friction property, if the surface of the heat insulating layer 5 can be processed with a low friction property, the processed layer is formed of the low friction layer 6.
You may make it comprise as. Further, it goes without saying that the low friction layer 6 may be formed separately from the heat insulating layer 5.

Further, from the viewpoint of minimizing the heat released from the outer peripheral surface of the fixing member 1 or the outer peripheral surface of the endless belt 2, at least one of the fixing member 1 and the endless belt 2 is used. One of them is preferably housed in a heat-insulating housing having a heat-insulating layer around the periphery and having an opening near the contact portion between the fixing member 1 and the endless belt 2.

Next, the operation of the above technical means will be described. In FIG. 1, the fixing member 1 is heated by a heating source 1 a, while the endless belt 2 is pressed toward the fixing member 1 by a pressure applying member 3. Then, the fixing member 1 and the endless belt 2 rotate, and the recording medium K carrying the unfixed toner image T is sandwiched and fixed between them. Here, the endless belt 2 that has passed through the portion facing the fixing member 1 moves in a state close to the outer peripheral surface of the holding member 4, but moves on the outer peripheral surface of the holding member 4 that faces the inner surface of the endless belt 2. Since the heat insulating layer 5 is formed, the situation in which the heat accumulated in the endless belt 2 is taken away by the holding member 4 and the temperature of the endless belt 2 is reduced is avoided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 is a schematic configuration diagram illustrating a fixing device according to a first embodiment of the present invention. In FIG. 1, a fixing device according to the present embodiment includes a heating roller 10 as a fixing member rotatably disposed, and an endless belt-shaped fixing roller which is in pressure contact with the heating roller 10 and rotates with the heating roller 10. And a fixing belt 20. In the present embodiment, the heating roll 10 is provided with a heat-resistant release resin layer 12 such as a tetrafluoroethylene resin having a thickness of 10 to 80 μm on the outer peripheral surface of an iron hollow roll core 11 having a thickness of 350 μm. Has a built-in halogen lamp 13 as a heating source. The material of the hollow roll core 11 is not limited to iron, but may be aluminum, stainless steel,
It may be copper or the like. Further, for the purpose of increasing the nip width or improving the image quality, the thickness between the hollow roll core 11 and the heat-resistant release resin layer 12 is 0.1 to 3 mm.
A heat-resistant and high-thermal-conductivity rubber layer of a certain degree may be provided. A temperature sensor (not shown) such as a thermistor and a thermocouple is disposed on the outer peripheral surface of the heating roll 10, and the detection signal is guided to a known control means (not shown), and The temperature of the outer peripheral surface of the halogen lamp 1
3, the unfixed toner image T on the sheet P
Is always uniformly melted.

On the other hand, the fixing belt 20 has a diameter of 35 mm,
80 μm thick polyimide film with a thickness of 10
One coated with μm ethylene tetrafluoride is used. Note that, as a base material of the fixing belt 20, a metal thin film such as nickel electroforming can be used.

In the present embodiment, the fixing belt 20 does not have a tension roll or the like, but has a heat-resistant rubber-based material such as silicone rubber or fluorine rubber inside the fixing belt 20 facing the heating roll 10. The first pressure pad 21 made of is arranged and supported. Then, the fixing belt 20 is pressed toward the heating roll 10 by the first pressure pad 21 to form a contact nip region n therebetween, and the unfixed toner image T is carried in the contact nip region n. By passing the sheet P, the unfixed toner image T is heated and pressed and fixed.

The first pressure pad 21 is inserted into a second pressure pad 22 having a substantially concave cross section. In the present embodiment, the second pressure pad 22
Is formed of a resin-based material such as polycarbonate having heat resistance, and the protruding portion 22 a protruding toward the fixing belt 20 downstream of the first pressure pad 21 presses the fixing belt 20, thereby making the contact. The paper P that has passed through the nip area n is peeled off without sticking to the heating roll 10.

Here, in the present embodiment, the first pressing pad 21 is provided with a glass on the side facing the fixing belt 20 for the purpose of suppressing abrasion due to sliding with the fixing belt 20 and driving torque. A heat resistant low coefficient of friction film (not shown) in which fibers are impregnated with ethylene tetrafluoride is attached. On the other hand, the protrusion 22 of the second pressure pad 22
Such a heat resistant low friction coefficient film is not attached to a. This is because the coefficient of friction between the resin-made second pressure pad 22 and the fixing belt 20 is relatively low at about 0.4, and the heat-resistant low-friction film layer is located between the protrusion 22a and the fixing belt 20. Is provided, the nip shape of the contact nip region n is not stable, and it is difficult to apply local distortion, and as a result, it is difficult to separate the paper P.

The second pressure pad 22 and the first pressure pad 21 fitted in the second pressure pad 22 are supported by a pad support member 23 disposed inside the fixing belt 20. It has become. The pad support member 23 is configured such that both ends thereof are supported by the fixing device main body, and is made of a material having a relatively large heat capacity such as iron, aluminum, and stainless steel in order to secure its rigidity. In the present embodiment, aluminum is adopted from the viewpoint of weight reduction and rust prevention, its volume is 1.1 × 10 ⁻⁴ m ³ , and its volume heat capacity is about 280 J /
Km ³ .

In the present embodiment, the heat conduction of 3.5 × 10 ⁻² W / m ° C. or less at a thickness of 2 mm is provided on the outer peripheral surface of the pad support member 23, that is, on the side facing the inner surface of the fixing belt 20. Low thermal conductivity polypropylene foam (P
FB: made of Sekisui Plastics Co., Ltd.)
Are arranged. Further, on the outer periphery of the heat insulating layer 24,
A heat-resistant low-friction coefficient film made of glass fiber impregnated with ethylene tetrafluoride (FGF-400 manufactured by Chuko Kasei Kogyo Co., Ltd.) in order to suppress wear due to sliding with the fixing belt 20 and driving torque.
-4) is provided.

Next, the fixing process of the fixing device according to the present embodiment will be described. When the paper P carrying the unfixed toner image T passes through the contact nip area n, the unfixed toner image T is formed by the heat from the heating roll 10 by the halogen lamp 13 and the pressure received from the contact nip area n. The image is fixed on the sheet P. At this time, in the contact nip region n, the fixing belt 20 is also heated by the heat from the heating roll 10. Then, the fixing belt 2 having passed through the contact nip area n
0 continues the rotation and reaches the contact nip area n again. During this time, the heat accumulated inside the fixing belt 20 is released from the front and back surfaces, but in the present embodiment, the pad support member 23 disposed on the inner surface side of the fixing belt 20 is used in the present embodiment.
Since the heat insulating layer 24 is formed on the outer peripheral surface of the fixing belt 20, the heat accumulated inside the fixing belt 20 is taken by the pad supporting member 23 made of aluminum and having a large heat capacity, and the temperature of the fixing belt 20 is remarkably lowered. The situation will be avoided. Therefore, the amount of heat for reheating the fixing belt 20 that has reached the contact nip region n again can be reduced, so that the time required for warming up and the productivity are not reduced, and the power required for reheating is also reduced. You will need less. In the present embodiment, the first pressure pad 21 and the second pressure pad 22 are used as pressure applying members.
Are used in combination, but the present invention is not limited to this, and it goes without saying that one kind of pressure pad may be used.

Embodiment 2 The present embodiment is almost the same as Embodiment 1, except that the surface layer of the heat insulating layer 24 is also used as a low friction layer as shown in FIG. is there. Note that among the components of the fixing device according to the present embodiment, the same components as those of the fixing device according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof will be given here. Omitted. In the present embodiment, the heat insulating layer 24 is made of polyethylene terephthalate foam (Cellpet: manufactured by Sekisui Plastics Co., Ltd.). In the heat insulating layer 24, a portion on the pad support member 23 side is formed of a normal foamed layer 24a, but a portion (surface layer) on the fixing belt 20 side is a so-called foamed surface which is not exposed. It is configured to be covered with the skin layer 24b. This is obtained in order to smooth the portion that comes into contact with the mold when the foam is cast into the mold and molded.

In this embodiment, as in the first embodiment, it is possible to avoid a situation in which the heat of the fixing belt 20 is taken away by the pad supporting member 23. Also,
Unlike Embodiment 1, there is no need to provide a low friction layer separately from the heat insulating layer 24, so that the number of parts and the cost can be reduced.

The present inventor uses a fixing device according to the first and second embodiments and a fixing device according to a comparative example in which the heat insulating layer is not provided on the pad support member 23, and
Investigations were made on the rate of temperature rise during the initial heating of the heating roll 10 and the amount of temperature drop during the execution of the fixing process. This survey was conducted as follows. First, 600 W was supplied as input power to the halogen lamp 13 to start up from room temperature, and the heating roll 10 was heated while rotating the heating roll 10 and the fixing belt 20. Here heating roll 1
The set temperature of 0 was 150 ° C. And heating roll 1
When 0 reached the set temperature, 100 sheets of P paper manufactured by Fuji Xerox Co., Ltd. (JIS A4 size) were fed sideways and continuously. The evaluation was performed by measuring the temperature transition of the heating roll 10.

FIG. 4 shows the results. In the fixing devices according to the first and second embodiments, the rise time until the set temperature was reached was 30 seconds and 32 seconds, respectively, whereas in the comparative example without the heat insulating layer, it was 40 seconds. Was. On the other hand, in the fixing devices according to the first and second embodiments, the amount of temperature drop due to continuous insertion of the paper P is also 1 at maximum.
Since the temperature was 3 ° C. and 15 ° C., it was 25 ° C. in the comparative example without the heat insulating layer. From these results, it is understood that the provision of the heat insulating layer 24 on the pad support member 23 prevents heat from flowing from the fixing belt 20 to the pad support member 23.

Further, the present inventor investigated the most suitable material for the heat insulating layer 24 using the fixing device according to the second embodiment, and also examined the difference due to the presence or absence of the skin layer 24b. In this study,
Polyethylene terephthalate foam, polypropylene foam, urea resin foam, styrene foam, silicone sponge, and melamine sponge were selected as materials for forming the heat insulating layer 24. As for each material, those having and not having the skin layer 24b were prepared. Then, using the fixing device described in Embodiment 2, the set temperature of the heating roll 10 is set to 180 ° C., and the rotation speed of the heating roll 10 and the fixing belt 20 is set to 100 mm /.
s, and idle for 150 hours (this is equivalent to fixing 200,000 sheets by JIS standard A4 size transverse feed), the fluctuation of the thickness of the fixing belt 20 (abrasion amount) and after the test. Of the heat insulating layer 24 (level of damage and abrasion) was evaluated. In this study, the reason why the idle running time is set to 150 hours is that the reliability of functional components such as a belt is generally required to withstand the use of 100,000 sheets, and the reliability is guaranteed. This is because, in order to ensure the reliability, a guarantee of 200,000 sheets is doubled.

FIG. 5 shows the results. In the figure, the coefficient of friction of each material with the belt, that is, the skin layer 2
4B, the coefficient of friction between the skin layer 24b and the fixing belt 20 is shown. For the material without the skin layer 24b, the coefficient of friction between the foam layer 24a and the fixing belt 20 is also shown. ing. According to this, it was found that regardless of the presence or absence of the skin layer 24b, the styrene foam and the polypropylene foam were deformed (shrinked) by the heat received from the heating roll 10, and were not suitable for practical use. Here, the deformation amount was large for the styrene foam and small for the polypropylene foam. Regarding the silicone sponge, it was confirmed that the silicone sponge was broken immediately after the test irrespective of the presence or absence of the skin layer 24b, which proved to be unsuitable for practical use.

On the other hand, regarding the polyethylene terephthalate foam, urea resin and melamine resin, the skin layer 2
Relatively good results were obtained regardless of the presence or absence of 4b.
However, when the difference due to the presence or absence of the skin layer 24b is confirmed for each material, when there is no skin layer 24b, there is no problem at first, but when it is assumed that the material will be used for a long time,
Since fine powder of the heat insulating layer 24 is generated due to abrasion and abrasion of the fixing belt 20, the skin layer 24b
Has been found to be more suitable. Further, with respect to the melamine sponge, it was confirmed that good results were obtained when the skin layer 24b was provided, and that when the skin layer was not provided, the melamine sponge was broken immediately after the test and was not suitable for practical use. The materials selected in this study have good performance as the heat insulating layer 24 shown in the first embodiment, that is, the heat insulating layer 24 in a mode in which the low friction layer 25 is formed of a material different from the heat insulating layer 24. It is.

The thickness of the fixing belt 20 is 80 μm in consideration of the formability of the contact nip area n.
The degree is the limit, and if it is 70 μm or less, a problem occurs in mechanical strength. Therefore, the allowable thickness reduction due to wear is 1
It is considered to be about 0 μm. Here, referring to FIG. 5, the coefficient of friction between the fixing belt 20 and the heat insulating layer 24 (foam layer 24a or skin layer 24b) and the fixing belt 20
It can be seen that there is a correlation with the amount of wear. Accordingly, in order to suppress the amount of abrasion of the fixing belt 20, the friction coefficient between the fixing belt 20 and the heat insulating layer 24 (foam layer 24a or skin layer 24b) is 0.8 or less, preferably 0.5 or less. It can be seen that it should be set to.

Embodiment 3 This embodiment is almost the same as Embodiment 2, except that the heating roll 10 and the fixing belt 20 are housed in a heat insulating housing, respectively, as shown in FIG. Further, heat radiation from these is prevented. Note that among the components of the fixing device according to the present embodiment, Embodiment 2
The fixing device according to the second embodiment is similar to the fixing device according to the second embodiment.
The same reference numerals are used and the detailed description is omitted here.

In the present embodiment, the heating roll 10
Are housed in a heat insulating housing 40 that opens downward. In the present embodiment, the heat insulating housing 40 is 3.5 × 10 ⁻² W at an average thickness of 4 mm.
The base layer 43 made of a low thermal conductivity polypropylene foam (PFB: manufactured by Sekisui Plastics Co., Ltd.) having a thermal conductivity of not more than / m ° C. and a heat resistant temperature of 220 ° C. adhered inside the base layer 43 A heat-resistant layer 44 made of polyethylene terephthalate foam having a thickness of 2 mm (Celpet: manufactured by Sekisui Chemical Co., Ltd.), and a thickness of 15 μm adhered inside the heat-resistant layer 44 and facing the heating roll 10.
And a highly reflective layer 45 made of a highly smooth aluminum layer. In the present embodiment, the base layer 43 and the heat-resistant layer 4
4 and the high-reflection layer 45 are in close contact with each other, so that heat conduction and heat radiation from the high-reflection layer 45 can be significantly reduced, and the reflection efficiency can be improved. I have. If the thickness of the high-reflection layer 45 is set to 5 to 20 μm, the heat capacity of the high-reflection layer 45 itself becomes small, so that the heat reflection efficiency becomes very good.

In the heat insulating housing 40, a heating roll 10 is provided at an end 40a on the upstream side of the contact nip region n.
And a sealing film 41 extending toward the axial direction of the heating roll 10 is provided so as to contact the heating roll 10. On the other hand, a sealing film 42 extending toward the heating roll 10 and extending in the axial direction of the heating roll 10 also contacts the heating roll 10 at an end 40b on the downstream side of the contact nip region n in the heat insulating housing 40. It is arranged as follows. This seal film 4
2 is a heating roll 1 for feeding the paper P passing through the contact nip area n.
It also plays a role as a peeling member for ensuring separation from zero. And these sealing films 41
And 42 are formed by coating a polyimide film having a thickness of 75 μm with a fluororesin having a thickness of 10 μm. In the present embodiment, the heat insulating housing 40
In addition, the sealing films 41 and 42 form a heat-insulating air layer 46 on the outer peripheral surface of the heating roll 10 that is shielded from the outside air.

On the other hand, the fixing belt 20 is housed in a heat insulating housing 50 that opens upward. The heat insulation housing 50 has the same configuration as the heat insulation housing 40 described above, and has a seal film 51 attached to an end 50a of the heat insulation housing 50 on the upstream side of the contact nip region n and the downstream side of the contact nip region n. The seal film 52 attached to the side end 50b also has the same configuration as the seal films 41 and 42 described above. In this embodiment, the heat insulating housing 50 and the sealing films 51 and 52 allow the heat insulating air layer 53 on the outer peripheral surface of the fixing belt 20 to be shielded from the outside air.
Is formed.

In the present embodiment, similarly to the second embodiment, it is possible to avoid a situation in which the heat of the fixing belt 20 is taken away by the pad supporting member 23. Since the heat insulating air layers 46 and 53 are formed around the fixing belt 20 and are isolated from the outside air, the heat retaining effect of the heating roll 10 and the fixing belt 20 is further enhanced.

The inventor of the present invention has a fixing device in which the heat insulating housings 40 and 50 of the third embodiment are provided in the fixing device of the first embodiment (hereinafter referred to as a fixing device A) and a fixing device of the second embodiment. A fixing device in which the heat insulating housings 40 and 50 according to the third embodiment are disposed in the fixing device (hereinafter referred to as a fixing device B), a fixing device according to the first embodiment (hereinafter referred to as a fixing device C), Using the fixing device according to the embodiment 2 (hereinafter, referred to as a fixing device D) and the fixing device having no heat insulating layer 24 used in the above-described comparative embodiment (hereinafter, referred to as a fixing device E), the discharge at the time of initial heating is performed. A survey was conducted on the amount of heat. This survey was conducted as follows. First, 500 W is supplied as input power to the halogen lamp 13 to start it up, and the heating roll 10 and the fixing belt 20 are turned off by one.
It is rotated at 50 mm / s, and from the time when the set temperature (150 ° C.) is reached, the minimum electric power that can maintain the set temperature of 150 ° C. is supplied while adjusting with SLIDAC (registered trademark), and every 20 minutes until 20 minutes have passed. The heat release was measured, the input power value was read as the heat release, and the average was used for evaluation.

FIG. 7 shows the results. According to this, the fixing device C (Embodiment 1) is better than the fixing device E (Comparative embodiment).
Further, it is confirmed that the heat radiation amount of the fixing device D (Embodiment 2) is small, and the heat radiation amount of the fixing device A and the fixing device B (both Embodiment 3) is smaller than those of the fixing device C and the fixing device D. . Thus, it is understood that the power supply during the initial heating can be reduced by using the fixing device described in the first to third embodiments. This is particularly effective when a small number of copies are required, such as in a small-sized image forming apparatus.

[0037]

As described above, according to the present invention,
In a so-called belt nip type fixing device, the heat loss of the endless belt is suppressed by providing a heat insulating layer on the outer peripheral surface of the holding member facing the inner surface of the endless belt, so that the warming-up time is lengthened and productivity is increased. , And a decrease in energy efficiency can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of a fixing device according to the present invention.

FIG. 2 is an explanatory diagram illustrating an outline of a fixing device according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating an outline of a fixing device according to a second embodiment.

FIG. 4 is a graph showing a temperature rise rate during initial heating and a temperature drop amount during execution of a fixing process.

FIG. 5 is a table showing a result of a survey on materials constituting a heat insulating layer.

FIG. 6 is an explanatory diagram illustrating an outline of a fixing device according to a third embodiment.

FIG. 7 is a table showing a heat radiation amount at the time of initial heating.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixing member, 1a ... Heat source, 2 ... Endless belt, 3 ... Pressure applying member, 4 ... Holding member, 5 ... Heat insulation layer, 6 ... Low friction layer, T ... Unfixed toner image, K ... Recording medium, 10 ... Heating roll, 13 ... Halogen lamp, 20 ... Fixing belt, 21
... First press pad, 22 ... Second press pad, 23 ... Pad support member, 24 ... Heat insulation layer, 24a ... Foam layer, 24b ...
Skin layer, 25: low friction layer, 40, 50: heat insulating housing, 41, 42, 51, 52: seal film, 46,
53 ... Insulated air layer

Claims (5)

[Claims] A fixing member provided with a heating source and rotatably disposed; and a recording medium rotatably disposed in pressure contact with the fixing member and carrying an unfixed toner image between the fixing member and the fixing member. An endless belt to be clamped; a pressure applying member provided inside the endless belt so as to contact the endless belt, and pressing the endless belt toward the fixing member side; and a pressure applying member disposed inside the endless belt. And a holding member for holding the pressure applying member, wherein a heat insulating layer is provided on an outer peripheral surface of the holding member facing an inner surface of the endless belt. 2. The fixing device according to claim 1, wherein the heat-insulating layer is made of a foam containing any of polyethylene terephthalate, urea resin, and melamine resin. 3. The fixing device according to claim 1, wherein a low friction layer is provided on a surface of the heat insulating layer facing the inner surface of the endless belt. 4. The fixing device according to claim 3, wherein a coefficient of friction between the inner surface of the endless belt and the low friction layer is set to 0.5 or less. 5. The fixing device according to claim 1, wherein at least one of the fixing member and the endless belt has a heat insulating layer around the fixing member and the vicinity of a contact portion between the fixing member and the endless belt. A fixing device, wherein the fixing device is housed in an open heat-insulating housing.