JPH09244465A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress overheating in a paper nonpassing region, to prevent the damage of a shaft end part and to secure fixability in a paper passing region by providing a heater in which the quantity of heat supplied to the passing region is set larger than that to the nonpassing region, in a smallest- sized transfer paper, in a heating roller. SOLUTION: When small-sized transfer papers 5 consecutively pass through, the temp. t1 of the heating roller in a paper passing part is measured by a temperature detector 7 and further, the temp. t2 of the heating roller in a paper nonpassing part is measured by another temperature detector. When the temp. t1 in the paper passing part becomes lower than a specified fixable lowest temp. t0, a lamp heater 103 generates heat, to raise only the temp. t1 in the paper passing part. On the other hand, at the time of fixing a transfer paper whose passing region is extended over a nearly whole roller, the energization of the heater 103 is stopped and a heater 2 generates the heat. From the result of this operation, even if the small-sized transfer papers consecutively pass through, the rising of the temp. in the paper nonpassing area of the end part of the roller is suppressed and the damage caused by the overheating of the shaft end part can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic process such as a copying machine, a facsimile, a printer.

[0002]

2. Description of the Related Art Conventionally, as a fixing device in an electrophotographic process, a heat roller fixing device which applies pressure and heat to unfixed toner on a transfer paper at the same time is generally used.

1 and 2 show the structure of a conventional heat roller fixing device. FIG. 3 shows the temperature distribution of the heating roller surface when small size paper such as a postcard is continuously passed.

As shown in FIG. 1, the heat roller fixing device includes a halogen lamp 2 as a heat source and a cylindrical heating roller 1.
And a pressure roller 3 made of a rubber member that is in pressure contact with the heating roller, and a temperature detector 7 that is in contact with the surface of the heating roller and is installed in the transfer paper passage area at the substantially central portion in the roller axial direction.
Hereinafter, the fixing principle of the conventional configuration will be described. The radiant heat generated from the halogen run 2 heats the inner surface of the heating roller 1, and the heat conduction in the member of the heating roller 1 raises the temperature of the outer surface of the heating roller 1. Heated roller 1
And the pressure roller 3 are rotating in contact with each other, and heat and pressure are simultaneously applied to the toner 4 by passing the transfer paper 5 having the unfixed toner 4 on the contact portion.

As a result, the toner 4 is softened and is subjected to a pressure at the same time, and the softened toner spreads and penetrates into the paper fibers of the transfer paper. Furthermore, after passing through the contact portion between the heating roller 1 and the pressure roller 3, the heat of the toner and the transfer paper escapes to the surroundings and cools down, so that the toner is fixed while permeating the paper fiber. As a result, the toner is fixed on the transfer paper.

Here, as shown in FIG. 2, in the heat roller fixing device which has been generally used in the past, the transfer paper 5 is irrespective of the size of the transfer paper, and the transfer paper 5 is at the same portion in the substantially central portion in the axial direction of the heating roller. 8 is configured to pass through.

[0007]

When a small-sized transfer paper 5 such as a postcard is continuously fixed to the heat roller fixing device having the above-mentioned structure, the transfer paper 5 passes through the same portion 8 near the center in the roller axial direction. . In the transfer paper passage area 8, that is, in the vicinity of the center of the roller axis, heat is taken from the heating roller 1 to the transfer paper 5, so that the temperature of the heating roller decreases, while in the non-paper passage area 9, that is, near the end of the roller shaft. Since the heating roller comes into contact with the rubber pressure roller 3 having a high heat insulating property, the temperature drop is small.

As a result, when a small size paper such as a postcard is continuously passed through the same portion of the heating roller central portion, as shown in 10a of FIG. 3, the shaft end portion is more than the sheet feeding area of the heating roller central portion. The temperature of the non-sheet passing area in the vicinity increases, and a temperature difference occurs in the roller longitudinal direction.

Moreover, the temperature difference increases with an increase in the number of continuously fed sheets. Therefore, if the small size paper such as a postcard is continuously fixed as it is, the temperature of the heating roller in the sheet passing region becomes lower than the minimum temperature at which fixing is possible, and fixing failure occurs.

Conventionally, in order to prevent such fixing failure, a temperature detector is installed in the heating roller 1 substantially at the center in the axial direction, and when the surface temperature of the heating roller in the paper passing area falls below the fixing possible temperature, the inside of the heating roller is fixed. The heating roller 1 is heated by the halogen lamp 2 and is controlled so as to keep the roller outer surface temperature constant at 180 to 200 degrees as shown in FIG. However, in general, halogen lamps 2
Since the illuminance distribution is set so as to uniformly heat the roller in the axial direction of the roller, if the temperature near the center of the roller having the temperature detector is heated to an appropriate temperature (180 to 200 degrees), the temperature in FIG. As shown in, the shaft end temperature is 23
The temperature rises from 0 to 240 degrees, and the resin member near the shaft end is damaged by heat.

Conventionally, these problems have been dealt with by improving the heat resistance of the end resin member or by blocking the heat transfer to the end member, but the use of these heat resistant members and heat insulating members leads to an increase in cost. Was there.

In view of the above problems, an object of the present invention is to prevent overheating in the non-sheet passing area of the shaft end of the fixing device and prevent damage to the shaft end even when a small size transfer paper is continuously fixed. With
An object of the present invention is to provide an image forming apparatus having a fixing device capable of ensuring the fixing property in the paper passing portion.

[0013]

In order to solve the above-mentioned problems, an image forming apparatus of the present invention comprises a cylindrical heating roller which contains a heating element and is heated by the heating element, and a pressing roller which presses against the heating roller. In an image forming apparatus that causes a transfer paper carrying an unfixed toner image to pass through a pressure contact portion with a pressure roller to fix the toner image on the transfer paper, the heating roller is of the smallest size among the transfer papers. The image forming apparatus is characterized by having a heating element in which the amount of heat supplied to the passage region is set to be larger than the amount of heat supply to the non-passage region.

Further, according to the present invention, the heating element is two lamp heating elements, one of which is set so that the illuminance in the passage area of the minimum size transfer paper is larger than that in the non-passage area. In the image forming apparatus having a fixing device, the illuminance in the non-passage area of the minimum size transfer paper is set to be larger than the illuminance in the paper passage area.

Further, the present invention includes a lamp heating element,
A transfer paper carrying an unfixed toner image is passed through a pressure contact portion between a cylindrical heating roller heated by the lamp heating element and a pressure roller in pressure contact with the heating roller to transfer the toner image to the transfer paper. In the image forming apparatus for fixing,
Temperature detecting means 1 for detecting the temperature of the surface of the heating roller in the passage area of the transfer paper, and temperature detecting means 2 for detecting the temperature of the surface of the heating roller in the area outside the passage area of the transfer paper.
The image forming apparatus is characterized in that the transfer paper passage area in the longitudinal direction of the heating roller is changed in accordance with the temperature detected by the first temperature detecting means or the temperature detected by the second temperature detecting means.

Further, the present invention is an image forming apparatus characterized in that, when a small size transfer paper is continuously fixed, a plurality of papers are simultaneously passed in the longitudinal direction of the fixing device and the fixing is performed at the same time.

Further, according to the present invention, there is provided a temperature detecting means 1 for detecting the temperature of the surface of the heating roller which is the minimum pass area of the transfer paper, and a surface of the heating roller which is outside the transfer paper passage area. A fixing device characterized by having a temperature detecting means 2 for detecting a temperature, and changing a transfer paper conveyance timing in accordance with a temperature detected by the first temperature detecting means or a temperature detected by the second temperature detecting means. An image forming apparatus having a.

Further, according to the present invention, a transfer paper carrying an unfixed toner image is passed through a pressure contact portion between a heating roller having a heat source and a pressure roller pressed against the heating roller to fix the toner image on the transfer paper. In an image forming apparatus having a heat fixing device, temperature detecting means means for detecting a temperature of a surface of the heating roller other than a passing region of the transfer paper of the smallest size, and a surface of the heating roller which is the surface of the heating roller. An image forming apparatus having a fixing device, characterized in that it has a cooling means for cooling an outer portion of the transfer paper passage area, and operates the cooling means according to the temperature detected by the temperature detecting means.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 4 to 17.

(Specific Embodiment 1) FIGS. 4, 5 and 6 show a first embodiment of the image forming apparatus of the present invention.

In FIG. 4, 1 is a heating roller, 2 is a lamp heat source for uniformly heating the heating roller, 3 is a pressure roller, 4 is unfixed toner, 5 is small size transfer paper such as postcard, and 6 is fixing. The generated toner, 7 is a heating roller surface temperature detector in the transfer paper passage area, and the lamp heating element 2 is shown in FIG.
130b, the illuminance distribution is substantially uniform in the roller axis direction. The above is the same structure as the conventional heat fixing device. Further, in the present invention, the heating roller surface temperature detector 102 in the non-passage area of the transfer paper and the lamp heating element 103 having a uniform illuminance distribution as shown by 130a in FIG. Is different from the conventional configuration.

The operation of this embodiment will be described below with reference to FIGS. 4, 5 and 6. When the small-sized transfer paper 5 is continuously passed, the temperature detector 7 causes the temperature t of the heating roller at the paper passing portion to pass.
1 is measured. Further, the temperature detector 102 measures the heating roller temperature t2 in the non-sheet passing portion. Then, when the paper passing temperature t1 becomes lower than a certain minimum fixable minimum temperature t0, the lamp heating element 103 that heats only the paper passing area is caused to generate heat, and only the paper passing temperature t1 is increased.

It should be noted that a few sheets of the small-sized transfer paper 5 are heated by the heating element 2 after the paper starts to be fed, and the temperature t2 other than the non-paper feed area is reached.
However, the power supply to the heating element 2 is stopped at the stage when the threshold value t3 for ensuring the heat resistance of the shaft end member is exceeded, and the heating element 103 is stopped.
You may start energizing to.

On the other hand, at the time of fixing a transfer sheet of a size other than a small size, in which the sheet passing area covers almost the entire roller, the heating element 103 is de-energized and the heating element 2 is caused to generate heat.

As a result of the above operation, even when the small size transfer paper is continuously passed, the rise of the temperature of the non-sheet passing area of the roller end is suppressed, and the damage and the fixing failure due to the overheating of the shaft end are prevented. It is possible to secure stable fixing.

Further, according to the present invention, both the heat sources 2 and 102 generate heat during the warm-up time, which is the time until printing is possible after the power is turned on, so that the warm-up time can be shortened. .

The heating element 2 and the heating element 103 may be planar heating elements other than the lamp heating element.

(Specific Embodiment 2) FIGS. 7, 8 and 9 show a second embodiment of the image forming apparatus of the present invention.

In FIGS. 7 and 8, 1 is a heating roller, 3 is a pressure roller, 4 is unfixed toner, 5 is a small size transfer paper such as a postcard, 6 is fixed toner, and 7 is a transfer paper passage area. This is a heating roller surface temperature detector, and small size paper such as postcards passes through the same location near the center of the roller. The above is the same structure as the conventional heat fixing device.

The present invention further comprises a heating roller surface temperature detector 102 in the non-passage area of the transfer paper, and lamp heating elements 104 and 105 for heating the heating roller.

Conventionally, the lamp heating element has formed a substantially uniform illuminance distribution in the longitudinal direction of the roller, but in the present invention, as shown by 106 in FIG. 9, the heating element 104 is closer to the end of the roller shaft. Also, the lamp illuminance near the roller central portion is high, and on the other hand, as shown by 107 in FIG. 9, the lamp illuminance is set higher near the roller shaft end portion than in the roller central portion. Is different from the first embodiment and the conventional configuration.

The operation of this embodiment will be described below with reference to FIGS. 7, 8 and 9. When passing a transfer paper other than a small size paper such as a postcard, the lamp heating elements 104 and 105 both generate heat to heat the entire heating roller substantially uniformly.

On the other hand, when the small-sized transfer paper 5 is continuously fed, or when the roller shaft end temperature t2 measured by the temperature detector 102 exceeds a certain threshold temperature t3, A lamp heating element 10 such as 107 in FIG. 9 in which the illuminance is increased in the transfer paper passage area at the center of the roller.
Only 4 is made to generate heat, and only the transfer paper passage area at the center of the roller is heated.

As a result, it is possible to prevent overheating in the vicinity of the roller end portion, which is the non-sheet passing portion, and to perform stable fixing without causing defective fixing.

Moreover, since the non-sheet passing portion is not heated when the small size sheet is passed, an energy saving effect can be obtained.

The heating element 104 and the heating element 105 may be planar heating elements other than the lamp heating element.

(Specific Embodiment 3) FIG. 10 shows the third embodiment of the image forming apparatus of the present invention.

In FIG. 10, 1 is a heating roller, 2 is a lamp heating element, 15, 16 and 17 are small-sized transfer papers such as postcards, and 7 is a heating roller surface temperature detector near the center of the heating roller. The above is the same structure as the conventional heat fixing device. Further, in the present invention, the heating roller surface temperature detector 102 near the end portion of the heating roller shaft and the controller 10 for controlling the paper passing path by the temperature data of both temperature detectors.
9. It differs from the conventional configuration in that it has transport mechanisms 110a, 110b, 110c that transport the paper to the sheet passing position in response to the output signal of the controller 109. The transport mechanism of this embodiment is the controller 1
Roller 110c that rotates according to the 09 signal and roller 1
It is composed of a belt 110b that converts the rotation of 10c into a linear motion in the axial direction of the heating roller, and a transport table 110a that adsorbs the transfer paper and moves integrally with the belt 110b.

The operation of this embodiment will be described below with reference to FIG. The temperature detector 7 measures the heating roller temperature t1 near the center of the heating roller. On the other hand, the temperature detector 102
Thus, the heating roller temperature t2 at the end of the heating roller shaft is obtained. Then, the paper passing portion temperature t1 is a certain temperature (about 2
The lamp heating element 2 generates heat so as to be maintained at 00 degrees), and heats the entire heating roller.

First, when the small-sized transfer paper 155 is continuously passed through the central portion of the heating roller, the temperature near the central portion is lowered as described above. Then, the temperature t1 detected by the paper passing portion temperature detector 7 becomes equal to or lower than the lower limit fixing temperature t0, or the temperature t2 near the shaft end detected by the non-paper passing portion temperature detector 102 rises, When the temperature reaches the threshold temperature t3 or above, which causes damage to the shaft end member, the transfer paper passage area is changed from the roller center to the position 16 or 17 from the roller shaft end.

The change of the paper passing position is performed by the temperature detectors 7 and 1
The controller 109 selects the optimum position for fixing based on the temperature data of 02 and the roller 1 based on the output signal.
10c rotates, and the belt 110b causes the rotation of the roller 110c to move linearly in the axial direction of the heating roller.
By moving 10a, it is moved to a predetermined position in the heating roller axial direction.

As described above, according to the present invention, stable fixing can be performed while keeping the heating roller temperature uniform in the axial direction.

The route may be changed to a predetermined paper passing position by setting it at a predetermined passing position when the paper is fed from the paper feeding box, or by setting a route between the transfer process and the fixing device. It may be changed.

The heating element 2 may be a sheet heating element other than the lamp heating element. (Specific Embodiment 4) FIGS. 11 and 12 show a fourth embodiment of the image forming apparatus of the present invention.

In FIG. 11, reference numerals 18, 19 and 20 denote small-sized transfer sheets such as postcards, 21 denotes a paper feeding cassette, 2
Reference numeral 4 is a transport mechanism for transporting the paper into the copying machine.

Further, according to the present invention, partitions 22 and 23 are provided in the paper feed cassette so that a plurality of small size papers can be arranged in parallel and stored, and further, a paper feed mechanism 24 capable of simultaneously feeding a plurality of transfer papers. Is provided.

Conventionally, only one type of paper is stored in the paper feed cassette, and is not stored in parallel as in the present invention.

In FIG. 12, 1 is a heating roller, 2 is a lamp heating element, 4 is unfixed toner, 5 is a small size transfer paper such as a postcard, and 7 is a heating roller surface temperature detector near the center of the heating roller. . The above is the same structure as the conventional heat fixing device. The present invention further differs from the conventional configuration in that the heating roller surface temperature detector 102 near the end of the heating roller shaft is provided.

The operation of this embodiment will be described below with reference to FIGS. When a continuous copy command for small size paper such as a postcard is received, a plurality of sheets are simultaneously fed into the copying machine by the transport mechanism 24 from the sheet feeding cassette 21 in which transfer sheets are arranged as shown in FIG. The development and transfer processes are performed simultaneously in the longitudinal direction of the photoconductor and the fixing device. And FIG.
In the fixing process as shown in 2, the paper is fixed in the longitudinal direction of the heating roller 1 at the same time.

As a result, the heat is uniformly absorbed in the paper in the longitudinal direction of the heating roller. Therefore, even if the paper is continuously passed for a long time, the entire heating roller is uniformly heated as in the conventional case. Also, the heating roller surface temperature has a uniform temperature distribution without a temperature difference between the paper passing area and the non-paper passing area, and it is possible to prevent the shaft end member from being damaged due to the temperature rise.

Further, according to the present invention, it is possible to print a plurality of sheets at a time, so that a large amount of printouts can be made in a shorter time than in the past.

The heating element 2 may be a planar heating element other than the lamp heating element. (Fifth Embodiment) FIGS. 13, 14 and 15 show a fifth embodiment of the image forming apparatus of the present invention.

In FIG. 13, 1 is a heating roller, 2 and 1
6 is a lamp heating element, 3 is a pressure roller, 4 is unfixed toner, 5 is a small size transfer paper such as a postcard, 6 is fixed toner, 7 is a heating roller surface temperature detector in the transfer paper passage area, Is. Further, the small-sized transfer paper passes through the same position in the substantially central portion of the roller. The above is the same configuration as the conventional one.

The present invention is different from the prior art in that, in the prior art, ON / OFF of the lamp heating element and the sheet passing timing were controlled only by the output of the temperature detector 7 at the center of the roller. It has a temperature detector 102 in the non-passage area of the transfer paper at the end of the roller, and a controller 110 that controls the energization of the lamp 2 and the roller drive. Depending on the temperatures of both the temperature detector 7 and the temperature detector 102, The point is that the timing of energization of the lamp heating element 2 and the timing of sheet passing are controlled.

The operation of this embodiment will be described below with reference to FIG. FIG. 15 shows changes in the roller surface temperature during continuous fixing of small size paper. In FIG. 15, 120 is a non-sheet passing position temperature measured by the temperature detector 102, and 121 is a change in the sheet passing position temperature measured by the temperature detector 7.

When a small size transfer sheet such as a postcard is continuously fed, the heating roller temperature in the sheet passing area at the center of the roller is as shown in FIG.
No. 3 121, while the shaft end temperature rises 120. When the roller end temperature t2 becomes higher than the threshold temperature t3 determined from the heat resistant temperature of the member, or the roller center temperature t1 becomes lower than the fixable temperature t0,
From controller 110 to charging, developing, transferring,
Stop each fixing process. As a result, since heat is not radiated from the roller surface to the paper, the temperature difference between the roller central portion and the roller end portion becomes small, and the roller temperature can be made uniform. Then, the lamp is turned on / off as required, and the roller center temperature t1 and the shaft end temperature t2 are 180 to 2
When the proper fixing temperature of about 00 degrees is reached, the charging, developing, transferring, and fixing processes are restarted from the paper feeding.

By repeating this operation, it is possible to realize a fixing device which does not cause a problem of overheating of the shaft end portion and a fixing defect at a low cost without largely changing the structure of the conventional fixing device.

The heating element 2 may be a planar heating element other than the lamp heating element. (Concrete Embodiment 6) FIGS. 16 and 17 show a sixth embodiment of the image forming apparatus of the present invention.

In FIG. 16, 1 is a heating roller, 2 is a lamp heating element, 3 is a pressure roller, 4 is unfixed toner, 5 is small size transfer paper such as postcard, 6 is fixed toner, and 7 is fixed toner.
Is a heating roller surface temperature detector in the transfer paper passage area.
The above is the same as the conventional fixing device configuration. Further, in the present invention, the heating roller surface temperature detector 10 in the non-passage area of the transfer paper is used.
2. It differs from the conventional configuration in that it is provided with a controller 114 for operating the heating roller surface cooling means 112, 113 and the cooling means. The cooling means of this embodiment does not contact the heating roller 1 and is disposed in the vicinity of the duct 112.
And a fan 113 for supplying air into the duct, and the air is blown onto the surface of the heating roller 1 to cool it.

The operation of this embodiment will be described below with reference to FIGS. When the small-sized transfer paper 5 is continuously fed, the temperature detector 7 causes the temperature t1 of the heating roller at the paper feeding portion.
Is measured. Further, the temperature detector 102 measures the heating roller temperature t2 in the non-sheet passing portion. When the temperature t1 of the sheet passing portion becomes lower than a certain minimum feasible fixing temperature t0, the lamp heating element 2 generates heat and heats the entire heating roller. As a result, the sheet passing temperature t1 increases and
The non-sheet passing temperature t2 also rises. When the temperature t2 becomes equal to or higher than a preset threshold value t3, the controller 114 gives an operation signal to the fan as the cooling means, and the fan 113
As a result, air is sent from the outside of the fixing device into the duct, and the air is blown onto the surface of the non-sheet passing area of the heating roller. As a result, the temperature of the non-sheet passing portion is lowered, and overheating of the shaft end portion can be prevented.

Further, the temperature t2 of the non-sheet passing portion is lowered and becomes lower than the temperature t1 of the sheet passing portion, or when the sheet feeding is completed, the controller 114 issues a cooling operation stop signal and the fan is stopped.

Instead of blowing air to the heating roller, a fan may suck in warm air near the surface of the heating roller in the non-sheet passing area.

In addition to air cooling, the cooling effect can be similarly obtained by bringing a high thermal conductor such as Al into contact with the vicinity of the shaft end.

The heating element 2 may be a planar heating element other than the lamp heating element.

[0065]

As described above, according to the present invention, even when a small size transfer paper is continuously fixed, the temperature difference between the paper passing area and the paper non-passing area of the heating roller can be reduced, and the non-paper passing portion can be reduced. It is possible to suppress an increase in temperature. As a result, it is possible to prevent the resin member at the end portion of the heating roller from being damaged due to overheating and to always perform reliable fixing.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a fixing device having a conventional structure.

FIG. 2 is a plan view of an operation state of a fixing device having a conventional configuration.

FIG. 3 is a roller temperature distribution diagram during continuous fixing of small-size paper in a conventional fixing device.

FIG. 4 is a sectional view of the first embodiment of the present invention in an operating state.

FIG. 5 is a plan view showing an operation state of the first embodiment of the present invention.

FIG. 6 is a diagram showing the illuminance distribution of the lamp heating element according to the first embodiment of the present invention.

FIG. 7 is a sectional view of a second embodiment of the present invention in an operating state.

FIG. 8 is a plan view of the second embodiment of the present invention in an operating state.

FIG. 9 is a diagram showing an illuminance distribution of a lamp heating element according to a second embodiment of the present invention.

FIG. 10 is a plan view showing the operation of the third embodiment of the present invention.

FIG. 11 is a plan view showing a paper feed mechanism of a fourth embodiment of the present invention.

FIG. 12 is a plan view showing a fixing device according to a fourth embodiment of the invention.

FIG. 13 is an operation sectional view of the fifth embodiment of the present invention.

FIG. 14 is an operational plan view of the fifth embodiment of the present invention.

FIG. 15 is a roller surface temperature change diagram in the fifth embodiment.

FIG. 16 is an operation sectional view in the sixth embodiment.

FIG. 17 is an operation plan view of the sixth embodiment.

[Explanation of symbols]

1 heating roller 2 lamp heating element 3 pressure roller 4 unfixed toner 5 small size transfer paper such as postcard 6 fixed toner 7 temperature detector in paper passing area 8 small paper passing area 9 small paper non-passing area 10a , 10b Roller surface temperature distribution during continuous fixing of small size paper 15,16,17,18,19,20 Small size transfer paper 21 Paper feed cassette 22 of the fourth embodiment 22,23 Partition plate 24 Paper feeder 102 Non-paper feed Area temperature detector 103 Lamp heating element 104 of the first embodiment 104, 105 Lamp heating element of the second embodiment 106 Illuminance distribution of the lamp heating element 104 107 Illuminance distribution of the lamp heating element 109, 111 Controller 110a Carrier 110b Through Paper position setting belt 110c Paper passing position setting roller 112 Duct 113 Fan 114 Fan control controller 120 Temperature Roller temperature of the shaft end portion of the small size paper non-passing position measured by the output device 121 121 Roller temperature of the small size paper passing position measured by the temperature detector 7a Illuminance distribution of the lamp heating element 103 b Lamp heating element 2 illuminance distribution

Claims (6)

[Claims] 1. A transfer paper carrying an unfixed toner image is passed through a pressure contact portion between a cylindrical heating roller which is heated by the heat generating element and a pressure roller which pressure contacts the heating roller. In the image forming apparatus for fixing the toner image on the transfer paper, the heating roller sets the heat supply amount of the smallest size transfer paper to the passage area larger than the heat supply amount to the non-passage area. An image forming apparatus having a heat generating element. 2. The heating roller contains two lamp heating elements, one of which has a illuminance in the pass area of the minimum size transfer paper set to be larger than that in the non-pass area, and another lamp. 2. The image forming apparatus according to claim 1, further comprising a fixing device, wherein the illuminance in the non-passage area of the minimum size transfer paper is set to be larger than the illuminance in the paper passage area. 3. A transfer paper containing a lamp heating element and carrying an unfixed toner image at a pressure contact portion between a cylindrical heating roller heated by the lamp heating element and a pressure roller in pressure contact with the heating roller. In an image forming apparatus for passing the toner image onto the transfer sheet to fix the toner image, the temperature detecting means 1 for detecting the temperature of the passage area of the transfer sheet and the surface of the heating roller. Temperature detecting means 2 for detecting the temperature of the outer portion of the passage area of the transfer paper, and according to the temperature detected by the first temperature detecting means or the temperature detected by the second temperature detecting means,
An image forming apparatus, wherein the transfer paper passage area in the longitudinal direction of the heating roller is changed. 4. When continuously fixing small size transfer paper, a plurality of papers are simultaneously passed in the longitudinal direction of the fixing roller,
An image forming apparatus characterized by fixing at the same time. 5. A temperature detecting means 1 for detecting a temperature in a pass area of a transfer sheet of a minimum size on the surface of the heating roller, and a roller shaft on a surface of the heat roller outside the pass area of the transfer sheet. It has a temperature detection means 2 for detecting the edge temperature, and changes the transfer paper conveyance timing in accordance with the temperature detected by the first temperature detection means or the temperature detected by the second temperature detection means. Image forming apparatus having a fixing device for fixing. 6. A thermal fixing device for fixing the toner image on the transfer paper by passing a transfer paper carrying an unfixed toner image through a pressure contact portion between a heating roller having a heat source and a pressure roller pressed against the heating roller. In the image forming apparatus having: a temperature detecting means for detecting the temperature of the surface of the heating roller other than the pass region of the smallest size transfer paper, and the surface of the heating roller for the transfer paper. An image forming apparatus having a fixing device, which has a cooling means for cooling an outer portion of the passage area, and operates the cooling means according to the temperature detected by the temperature detecting means.