JPH11265127A - Belt type thermal fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix an unfixed toner image to an image supporting body by heating with an appropriate heating value and good response in accordance with changes in a preheat state which affects the fixation of an image, to easily obtain a fixed image in a constant and stable state, without remarkably complicating its structure and without making the device large in size, in the case of preheating the unfixed toner image and the image supporting body for holding the unfixed toner image prior to the image fixation, as for a thermal fixing device for heat-fixing the unfixed toner image to the image supporting body with the unfixed toner image held. SOLUTION: An endless fixing belt 1 for heating is stretched to be laid between a fixing roller 2 and a heating roller 3, and a pressure roller 4 is brought into press contact with the fixing belt part on the fixing roller 2 so as to form a press-contact nip part for fixing a toner image to an image supporting body. Besides, a guide plate 5 for the image supporting body is arranged opposite to the fixing belt 1, and fixing conditions such as a fixation speed, temperature of the fixing belt 1, fixation pressure by the pressure roller 4 and an interval between start signals for paper-passing, etc., are changed in accordance with the temperature of the guide plate 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt-type heat fixing device for heating and fixing an unfixed toner image on an image support holding an unfixed toner image in an image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art Generally, a heat roller system is used in a heat fixing device in an image forming apparatus such as a copying machine or a printer. In the heat-fixing device of the heat roller type, at least one of the fixing rollers is a heating roller, and a pair of fixing rollers pressed against each other is used, and the fixing roller pair passes through the image support holding the unfixed toner image in a press-contact nip portion thereof. Then, the image is heated and fixed on the image support. The fixing roller pair usually includes a heating roller and a pressure roller pressed against the heating roller.

However, the following problems have been pointed out with respect to such a heat roller type heat fixing device.
That is, conditions affecting the image fixing performance of the fixing roller pair, in other words, the type (material, thickness, etc.) of the image support, the amount of toner adhered on the image support, the environmental temperature and humidity around the fixing device, the fixing There is a problem that the fixing state of an image fluctuates due to a fluctuating factor such as the temperature of a pressure roller having no heat source in the roller pair.

For example, in an electrophotographic full-color image forming apparatus, a multi-toner image formed of cyan, magenta, yellow, and black toners formed on an image support is fixed to the image support. When fixing a multi-toner image, a larger amount of heat is required than when fixing is performed on an image support. At this time, assuming that the fixing temperature (heating roller temperature) in the fixing device is the same, even if the monochrome toner image can be fixed without any trouble, the multi-toner image may have a fixing failure due to insufficient heat, or the toner with the fixing failure may be defective. Transfer to the fixing roller may occur.

For this reason, a heat fixing device used in a full-color image forming apparatus uses a large-diameter heating roller to increase the fixing time and increases a nip portion width (image support conveyance) in comparison with a monochrome heat fixing device having the same fixing speed. (The length of the nip portion in the direction), and an elastic material such as rubber (a typical example is silicone rubber) is applied to the surface of the roller in order to melt the toner on the image support without unnecessary crushing at the nip portion. In order to ensure the releasability of the elastic material, a release agent such as oil (a typical example is silicone oil) is applied.

However, in such a heat fixing device, the diameter of the heat roller becomes large and a complicated oil application mechanism is required. Therefore, the heat fixing device becomes large in size and the oil application mechanism becomes complicated. The device configuration becomes complicated. In this regard, for example, Japanese Patent Application Laid-Open No. Hei 6-318001 discloses that an endless belt is wound around a fixing roller and a heating roller upstream of the fixing roller in the image support transport direction, and a pressure roller is wound around the fixing roller via the belt. Press
A belt type in which a guide member for guiding the image support to a nip portion between the pressure roller and the upper belt portion of the fixing roller is provided opposite to the endless belt, and thus a preheating passage is formed between the belt and the guide member. He teaches fixing devices.

According to the heat fixing apparatus having such a preheating means, for example, when a multi-toner image composed of toners of respective colors formed on an image support in a color image formation is heat-fixed to the image support, By using the preheating means, the heat energy given at the fixing roller nip portion can be reduced accordingly. Therefore, if there is no such preheating means, the fixing roller diameter is increased and the nip portion width is increased to increase the toner nip. The required heat amount must be obtained by increasing the fixing time under a fixing temperature that does not cause over-melting of the fixing roller. Thermal energy given at the roller nip can be reduced to prevent over-melting of the toner and prevent transfer of over-melted toner to the fixing roller The coating amount of oil such as release agents may be applied to the fixing roller even corner in trace amounts, simplify release agent application mechanism, can be miniaturized, simplified thereof by the fixing device,
Compactness can be achieved.

Japanese Patent Publication No. 58-48902 discloses an endless heating and fixing device provided with a preheating means, wherein an image support having an unfixed toner image supported by two rollers is supported and conveyed from the back side thereof. A fixing nip is formed by winding the belt and pressing the fixing roller to the roller on the downstream side in the image support conveying direction via the endless belt, and further forming a fixing nip portion, and the lower surface of an area of the endless belt supporting the image support. Teaches a belt-type heat-fixing device in which a sheet heating element is installed.

[0009]

However, in such a heating and fixing device that performs preheating using a belt,
The thermal energy supplied to the image support in the preheating area is the temperature of the belt, the temperature of the roller around which the belt is wound without a heat source, the temperature and humidity environment around the fixing device, and only one image support. It varies depending on whether the sheet is passed or a plurality of image supports are successively passed.

For example, in the belt-type heat fixing apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 6-318001, the preheating is carried out by the radiant heat from the belt and the heat transfer effect from the guide member heated by the belt, and the image support is held by the belt. Since this is achieved by supplying heat to the unfixed toner image, the guide facing the belt depends on the rotation speed of the belt (accordingly, the fixing speed), the number of image supports passing through the preheating area, the time interval, and the like. The temperature of the member changes, and consequently, the preheating state of the image support and the unfixed toner image held thereon changes, which causes a difference in the heating state of the toner, and a difference in image quality such as crushing and gloss of the fixed image. Becomes remarkable. Further, the toner adheres to and contaminates a belt or the like due to overmelting or insufficient fixation of the toner, and further, there is a problem that the adhered toner adheres to the image support again.

In the fixing device taught by Japanese Patent Publication No. 58-48902, the temperature of the belt changes depending on the rotation speed of the belt (accordingly, the fixing speed), the number of image supports passing through the preheating area, the time interval, and the like. In addition to the problem described above, in order to set the temperature of the surface of the image support holding the toner image to a predetermined temperature, it is necessary to set the belt supporting the image support from the back side above the fixing roller temperature, Moreover, the efficiency of heat supply to the toner surface side is poor (in other words, the response to the heat change required on the toner surface side is poor), and a large amount of electric power is required to obtain a good image fixing property, and the fixing speed is low. At higher speeds, more power is required, so that there is a problem that it is difficult to cope with high speeds.

Accordingly, the present invention provides a heat fixing device for heat-fixing an unfixed toner image to an image support holding the unfixed toner image, and preheating the unfixed toner image and the image support holding the image support prior to image fixing. A belt-type heat fixing device capable of heating and fixing an unfixed toner image to an image support with an appropriate amount of heat in response to a change in a preheating state that affects the image fixing property with good responsiveness. An object of the present invention is to provide a belt-type heat-fixing device that can obtain a stable fixed image and that can easily obtain a fixed and stable fixed image without significantly increasing the structure and complexity.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is a belt-type heat-fixing apparatus for heating and fixing an unfixed toner image on an image support holding the image, and at least one of the belt-type heat-fixing apparatuses comprises a heating roller. And two rollers having one of them as a fixing roller, an endless fixing belt wound around the two rollers, and a pressure roller pressed against the fixing roller with the fixing belt therebetween. A press-contact nip portion for fixing the toner image to the image support by passing the image support holding the unfixed toner image between the fixing belt and the fixing belt portion on the fixing roller. The pressure roller and the roller around which the fixing belt is wound, the image support is guided from a region facing one of the rollers to the fixing roller toward the pressure contact nip portion. An internal member, a temperature detection sensor for detecting a temperature of the guide member, and a fixing condition changing device that can change a fixing condition of the toner image to the image support based on a temperature detected by the temperature detection sensor. The present invention provides a belt-type heat fixing device characterized by the following.

The fixing belt has heat resistance to withstand the heat applied. It is desirable that the surface of the fixing belt is formed of a heat-resistant, elastically deformable material. It is still more desirable that the material is formed of a material having releasability from the toner. It is assumed that the fixing roller and the pressure roller can withstand applied heat. At least one of these rollers is desirably formed of an elastically deformable material having heat resistance.

The belt-type heat fixing device of the present invention can be used by mounting it on an image forming apparatus such as an electrophotographic system. In the belt-type heat fixing device of the present invention, of the rollers around which the endless fixing belt for heating is wound, the heating roller is heated to heat the belt, and the heat from the belt approaches the belt. Also, the guide member, the pressure roller, and the like that are in contact with or are heated.

The unfixed toner image formed on the image support is supported and guided by a guide member together with the image support, and is conveyed to a nip portion between the belt portion on the fixing roller and the pressure roller, and at the same time. On the guide member, it is preheated by the radiant heat from the fixing belt installed opposite thereto and the heat from the guide member, then enters the press-contact nip portion, and passes therethrough, whereby the unfixed toner image is transferred to the image support. Be established.

When the toner image is fixed, the temperature of the guide member is detected by the temperature detection sensor in order to detect a change in the preheating state on the guide member which affects the image fixing property. On the basis of this, one or more of the fixing conditions are changed by the fixing condition changing device, whereby the preheating state is optimized, and a fixed and stable good fixed image is obtained.

The following are examples of the fixing condition varying device. It is to be noted that a fixing condition varying device combining the following devices can also be adopted. A device that controls the fixing speed. A device for controlling the temperature of the fixing belt. A device for controlling a pressure contact force between the pressure roller and the fixing belt portion on the fixing roller, in other words, a fixing pressure contact force. An apparatus for controlling a passage time interval between the image supports in a case where a plurality of image supports are sequentially and sequentially passed through the press-contact nip portion.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view showing a configuration of an example of a belt-type heat fixing device according to the present invention, and FIG. 2 is a schematic perspective view. This fixing device is mounted and used in an image forming apparatus, and includes a fixing belt 1, a fixing roller 2, a heating roller 3, a pressure roller 4, a guide plate 5, and a release agent applying device 6.

The fixing belt 1 is wound around a fixing roller 2 and a heating roller 3. The belt 1 can be rotated counterclockwise in the figure by the fixing roller 2 being driven to rotate by a driving unit D1 including a main motor of the image forming apparatus and a transmission mechanism for transmitting the power to the fixing roller. In any case, the start and stop of the operation of the fixing roller 1 by the driving unit D1,
Speed adjustment and the like are performed based on an instruction from a control device CONT mainly composed of a computer that controls the operation of the entire image forming apparatus.

The heating roller 3 is disposed upstream of the fixing roller 2 in the image support conveying direction α. The fixing device includes a fixing device frame (not shown), and the fixing roller 1 is rotatably supported at a fixed position of the frame. The heating roller 3 is rotatably supported by a pair of bearings 31 at a roller shaft portion as shown in FIG. 2, and the pair of bearings is supported by a frame (not shown) so as to be able to approach and separate from the fixing roller 1. Have been. Each bearing 31 is constantly elastically pushed in a direction away from the fixing roller 1 by a spring 32, thereby applying a predetermined tension to the belt 1.

The heating roller 3 has a built-in heater H,
A temperature detection sensor (here, a thermistor TH1) for controlling the temperature of the heating roller and thus controlling the temperature of the fixing belt is in contact with the belt portion on the heating roller. The thermistor TH1 is connected to the control device CONT, and the control device controls the power supply section E to the heater H based on the temperature information input from the thermistor TH1, and can control the heating roller temperature and, consequently, the belt temperature to a predetermined temperature.

The pressure roller 4 is arranged at a position facing the fixing roller 1, and the roller shaft is supported by a pair of bearings 41. Each bearing 41 is mounted on the fixing device frame (not shown) so as to be able to move up and down, and is pushed upward by a spring 42. As a result, the pressure roller 4 is pressed against the fixing roller 2 via the belt 1, and forms a pressure contact nip portion N for image fixing between the belt portion on the fixing roller and the pressure roller 4. I have. The pressure roller 4 rotates following the rotation of the belt 1.

The spring 42 is supported by a spring supporting member 43, and the spring supporting member can be moved up and down by a driving unit D2. By raising the spring supporting member 43 by the driving unit D2, the pressing force of the pressing roller 3 against the belt 1 in the pressing nip N can be increased to increase the fixing pressure bonding force, and the spring supporting member 43 can be lowered. Can reduce the fixing pressure bonding force. The adjustment of the fixing pressure is performed by the driving unit D2 based on an instruction from the control unit CONT.

The guide plate 5 is provided below the belt 1 so that the image support can be guided from the area facing the heating roller toward the pressure nip N. The guide plate 5 is also attached to the fixing device frame. A thermistor TH2 is attached to the lower surface of the guide plate 5 as a temperature detection sensor for detecting the temperature of the guide plate, and guide plate temperature information detected by the thermistor is input to the control unit CONT.

The release agent application device 6 applies silicone oil, which is a release agent here, to the belt 1, and includes an oil application roller 61 and an oil supply member 62 for supplying oil to the roller. The oil application roller 61 is disposed at a position upstream of the heating roller 3 and downstream of the fixing roller 2 in the rotation direction of the belt 1, and is in contact with the fixing belt 1. The oil supply member 62 is brought into contact with the oil application roller 61, but is held by a holder (not shown) and is detachable from the fixing device. The silicone oil, which is a release agent, is once transferred from the oil supply member 62 to the oil application roller 61, and further applied to the fixing belt 1 from the oil application roller 61.

The control unit CONT also outputs a paper feed start signal for starting the supply of the image support from the image support supply unit in the image forming apparatus. Next, the material of each member will be described. The fixing belt 1 is an endless belt made of nickel and has a thickness of 40 μm, and its surface is covered with a heat-resistant release layer (here, a silicone rubber layer) having a thickness of 150 μm. I have.

The fixing roller 2 is obtained by covering a core metal with a silicone sponge having heat resistance and elasticity. The surface layer of the pressure roller 4 is formed of silicone rubber, and the relationship between the roller surface hardness and the pressure roller 4 (the pressure roller 4 ≧ the fixing roller 2) is determined.
Thus, the cross-sectional shape of the nip portion N obtained by pressing against the fixing roller 2 becomes convex toward the fixing roller 2. This facilitates separation of the image support from the fixing belt 1.

The heating roller 3 is made of an aluminum pipe, and is subjected to an alumite treatment to prevent abrasion.
The oil application roller 61 is formed by coating a core metal with silicone rubber having a good affinity for silicone oil as a release agent, and the silicone oil is uniformly applied from the oil supply member 62. The surface of the silicone rubber of the oil application roller 61 is made rougher than the surface of the fixing belt 1 in order to adhere dirt from the fixing belt 1 (the surface roughness of the fixing belt, the center line average roughness Ra 0.1, the surface of the oil application roller). (Roughness center line average roughness Ra 0.5), which tends to deteriorate the releasability. Instead of such a difference in surface roughness, a silicone rubber material having lower releasability than the fixing belt 1 may be used for the surface.

As shown in FIG. 1, the oil application roller 61 is disposed inside a tangent line connecting the surface of the fixing roller 2 and the surface of the heating roller 3. Oil application roller 61
In order to remove dirt from the fixing belt 1 and supply oil from the application roller 61 efficiently.

The oil supply member 62 is formed by winding a heat-resistant paper impregnated with silicone oil on the surface of a cored bar, and providing a synthetic leather layer on the surface for regulating the amount of silicone oil applied. Although silicone rubber is used for the heat-resistant release layer of the fixing belt 1 in the above configuration, a heat-resistant release layer made of, for example, ethylene tetrafluoride resin may be used instead. In the belt-type heat fixing device described above, the belt 1 is heated by heating the heating roller 2 under the heat generated by the power supply to the heater H of the heating roller 2, and the belt 1 is heated by the heat from the belt 1. The guide member 5 and the pressure roller 4 approaching or in contact with are also heated.

The unfixed toner image 8 (see FIG. 2) formed on the image support 7 such as a paper sheet or a sheet for an overhead projector is supported and guided by the guide plate 5 together with the image support 7 and is fixed on the fixing roller 2. Is transported to the mutual pressing nip N between the belt portion and the pressing roller 4, and
The unfixed toner image is preheated on the guide plate 5 by the radiant heat from the fixing belt 1 installed opposite to the guide plate 5 and the heat from the guide plate 5, whereby the unfixed toner image is softened to some extent and subsequently enters the press contact nip N. Then, the unfixed toner image 8 is finally fixed to the image support 7 by passing therethrough.

In fixing the toner image, the temperature of the guide plate 5 is detected by the thermistor TH2 to detect a change in the preheating state on the guide plate 5 which affects the image fixing property, and is input to the control unit CONT. You. Control device C
The ONT controls the fixing speed, in other words, the conveyance speed of the image support in the image forming apparatus, in other words, the rotation speed of the main motor, based on the change of the preheating state according to the temperature of the guide plate. .

That is, as shown in a flow chart of a part of the operation of the control device CONT in FIG. 3, the control device reads the temperature of the guide plate 5 based on the temperature information from the thermistor TH2. It is determined whether or not the fixing speed is low (step S11).
c is set (step S21). 70 above 50 ° C
If the temperature is lower than ° C, the fixing speed is set to 70 mm / sec (steps S31 and S41). 9 above 70 ° C
If the temperature is lower than 0 ° C., the fixing speed is set to 80 mm / sec (steps S51 and S61). If the temperature is 90 ° C. or higher, the fixing speed is set to 90 mm / sec (step S71). Thereafter, the process returns to an appropriate step in a main routine or the like of the operation of the control device.

As described above, when the temperature of the guide plate 5 is low, the fixing speed is decreased, and when the temperature of the guide plate 5 is high, the fixing speed is increased. In addition, an appropriate amount of heat required for fixing an image is given to an image support holding the same, so that a fixed and stable fixed image can be obtained. Although a fixed and stable fixed image can be obtained as described above, since a configuration is not adopted in which a heater for controlling the temperature of the guide plate 5 is separately provided on the guide plate, the fixing is performed as a whole. A fixed and stable fixed image can be easily obtained without significantly complicating or increasing the size of the device structure.

In the above example, the fixing speed, which is one of the fixing conditions, is changed according to the temperature of the guide plate 5.
The ONT can also fix and stabilize the fixed image by changing the fixing conditions as follows. (1) The temperature of the fixing roller 1 is controlled by controlling the temperature of the heating roller 3 according to the temperature of the guide plate 5 by controlling the operation of the heater H. The control unit CONT is configured to control the fixing belt temperature in this manner.

In this case, as shown in FIG.
The ONT reads the temperature of the guide plate 5 based on the temperature information from the thermistor TH2, determines whether or not the temperature T is lower than 50 ° C. (step S12), and when it is lower, sets the temperature of the belt 1 to 185 ° C. (Step S22). 50 ° C
When the temperature is lower than 70 ° C., the belt temperature is set to 180 °
C is set (steps S32 and S42). When the temperature is 70 ° C. or higher and lower than 90 ° C., the belt temperature is set to 175 ° C.
(Steps S52 and S62). If it is 90 ° C. or higher, the belt temperature is set to 170 ° C. (step S72). Thereafter, the process returns to an appropriate step in a main routine or the like of the operation of the control device.

As described above, when the temperature of the guide plate 5 is low, the temperature of the fixing belt 1 is set high, and when the temperature of the guide plate 5 is high, the temperature of the fixing belt 1 is set low. In the fixing device as a whole, the unfixed toner image and the image support holding the unfixed toner image are given an appropriate amount of heat required for fixing the image, whereby a fixed and stable fixed image can be obtained.

Although a fixed and stable fixed image can be obtained as described above, the structure of the fixing device is not significantly complicated and large. (2) The pressing force of the pressing roller 4 against the belt portion on the fixing roller, that is, the pressing nip portion N in accordance with the temperature of the guide plate 5
Is controlled by the fixing pressure bonding force. The control unit CONT is configured to control the driving unit D2 according to the temperature of the guide plate so that the fixing pressure can be adjusted.

In this case, as shown in the flowchart of FIG. 5, the control device CONT reads the temperature of the guide plate 5 based on the temperature information from the thermistor TH2, and the temperature T becomes 50 °.
C is determined (step S13), and if it is lower, the fixing pressure is set to 20 kgf (step S2).
3). When the temperature is equal to or higher than 50 ° C. and lower than 70 ° C., the fixing pressure is set to 17 kgf (steps S33 and S4).
3). When the temperature is 70 ° C. or higher and lower than 90 ° C., the fixing pressure is set to 14 kgf (steps S53 and S6).
3). If the temperature is 90 ° C. or higher, the fixing pressure is set to 11 kgf (step S73). Thereafter, the process returns to an appropriate step in a main routine or the like of the operation of the control device.

As described above, when the temperature of the guide plate 5 is low, the fixing pressure is set high, and when the temperature of the guide plate 5 is high, the fixing pressure is set low. Then, an appropriate amount of heat required for fixing the image is given to the unfixed toner image and the image support holding the unfixed toner image as a whole of the fixing device, whereby a fixed and stable fixed image can be obtained.

Although a fixed and stable fixed image can be obtained as described above, the structure of the fixing device is not significantly complicated and large. (3) The time interval (sheet passing time interval) for passing the image support in the press-contact nip portion N is controlled according to the temperature of the guide plate 5. This is effective when, for example, a plurality of image supports are sequentially and continuously passed through the fixing device, and the temperature of the guide plate 5 gradually decreases due to the heat taken by the image supports. Here, the control unit CONT is configured so as to adjust the interval of the sheet passing start signal for determining the start of supply of each image support from the image support supply unit in the image forming apparatus according to the temperature of the guide plate.

In this case, as shown in the flowchart of FIG. 6, the control device CONT reads the temperature of the guide plate 5 based on the temperature information from the thermistor TH2, and the temperature T becomes 50 °.
It is determined whether it is lower than C (step S14). If it is lower than C, the sheet passing start signal interval is set to 10 seconds (step S24). If the temperature is equal to or higher than 50 ° C. and lower than 70 ° C., the sheet passing start signal interval is set to 7.5 seconds (steps S34 and S44). 90 ° C above 70 ° C
If it is lower, the paper passing start signal interval is set to 6 seconds (steps S54 and S64). If the temperature is equal to or higher than 90 ° C., the sheet passing start signal interval is set to 5 seconds. Thereafter, the process returns to an appropriate step in a main routine or the like of the operation of the control device.

As described above, when the temperature of the guide plate 5 is low, the interval between the sheet passing start signals is lengthened to wait for the temperature of the guide plate 5 to rise. When the temperature of the guide plate 5 is high, the interval between the sheet passing start signals is increased. By reducing the temperature of the guide plate 5 by shortening it, the unfixed toner image and the image support holding the unfixed toner image are given an appropriate amount of heat required for fixing the image, as a whole.
Thereby, a fixed and stable fixed image can be obtained.

Although a fixed and stable fixed image can be obtained as described above, the structure of the fixing device is not significantly complicated and large. It should be noted that two or more of the methods shown in FIGS. 3 to 6 can be used in combination.

[0046]

According to the present invention, the unfixed toner image and the image support holding the image are fixed to the image support holding the unfixed toner image before the image is fixed. A belt-type heat-fixing device capable of preheating, capable of heat-fixing an unfixed toner image to an image support with an appropriate amount of heat in response to a change in a preheating state that affects image fixability with a good response. A fixed and stable fixed image can be obtained.
It is possible to provide a belt-type heat-fixing device capable of easily obtaining a fixed and stable fixed image without increasing the size.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an example of a belt-type heat fixing device according to the present invention.

FIG. 2 is a schematic perspective view of the heat fixing device shown in FIG.

FIG. 3 is a flowchart showing a fixing condition changing operation in the control device.

FIG. 4 is a flowchart showing another example of the fixing condition changing operation in the control device.

FIG. 5 is a flowchart showing still another example of the fixing condition changing operation in the control device.

FIG. 6 is a flowchart showing still another example of the fixing condition changing operation in the control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing belt 2 Fixing roller D1 Driving part of fixing roller 3 Heating roller 31 Bearing 32 Spring H Heater TH1 Thermistor 4 Pressure roller 41 Bearing 42 Spring 43 Spring support D2 Spring support driving part 5 Guide plate TH2 Thermistor 6 Release type Coating device N Pressure nip CONT control device

Claims (5)

[Claims] 1. A belt-type heat fixing device for heating and fixing an unfixed toner image on an image support holding the image, wherein at least one of the belts is a heating roller and at least one is a fixing roller. And an endless fixing belt wound around the two rollers; and a pressing roller pressed against the fixing roller with the fixing belt in between, and a fixing belt portion on the fixing roller. A pressure roller that forms a pressing nip portion for fixing the toner image to the image support by passing the image support holding an unfixed toner image; and a roller around which the fixing belt is wound. A guide member that guides the image support from an area facing the other one of the rollers to the fixing roller toward the press-contact nip portion; and a temperature that detects a temperature of the guide member. And detection sensor, the temperature detected based sensor according to the detected temperature belt type heat fixing device, characterized in that a fixing condition changing device that fixing condition possible changes to the image support in the toner image. 2. A belt-type heat fixing device according to claim 1, wherein said fixing condition changing device is a device for controlling a fixing speed. 3. The belt-type heat fixing device according to claim 1, wherein the fixing condition changing device is a device for controlling a temperature of the fixing belt. 4. A belt-type heat fixing device according to claim 1, wherein said fixing condition changing device is a device for controlling a pressure contact force between said pressure roller and said fixing belt portion on said fixing roller. 5. The apparatus according to claim 1, wherein the fixing condition changing device controls a passage time interval between the image supports when a plurality of image supports are successively passed through the press-contact nip portion. Belt type heat fixing device.