JPH06194994A - Fixing device - Google Patents

Abstract

PURPOSE:To precisely measure the surface temperature of a heat roller without dissipating the heat thereof to outside and to accurately control the temperature by disposing a temperature detection element in a holding container provided with an aperture. CONSTITUTION:A thermistor 14 is held and fixed by a thermistor holder 15 whose one part is formed with a screw hole. Besides, the holder 15 is fixed and supported by an L-shaped slider 16. The slider 16 is disposed in a thermistor cover 19 while being pressed by a thermistor adjustment spring 18 consisting of a compression spring so that the holder 15 is moved only in the radial direction of the heat roller 8. By turning a thermistor adjustment screw 17, a distance between the slider 16 and the roller 8 can be adjusted. Besides, a roller 20 guaranteeing the distance between the cover 19 and the roller 8 is disposed between them. Thus, heat generated from the roller 8 is insulated without being released from the inside of the holder and transmitted to the thermistor 14 by convection or radiated heat transmission.

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 in an image forming apparatus such as a copying machine, and more particularly to a fixing device for fixing a toner image on a recording material as a permanent image.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image recording apparatus,
An electrostatic latent image is formed on an image carrier, a toner image is formed by development, the toner image is transferred onto a recording material, and then the toner image is fixed on the recording material to form an image. To fix the toner image adhering to the recording material, see FIG.
A heat roller fixing device as shown in (1) is often used.
In this heat roller fixing device, a toner image is attached between a heat roller 8 that rotates by incorporating a heat source such as an infrared lamp and a pressure roller 9 that presses and rotates in cooperation with the heat roller 8. The material is nipped and conveyed to perform fixing. When fixing with the heat roller fixing device, the temperature of the heat roller is kept in a certain range called control temperature, and the thermistor is provided in contact with the heat roller 8. It was controlled by the temperature sensor 50.

However, when the temperature sensor 50 is brought into contact with the heat roller 8 to detect the temperature, the hardened toner adheres to the temperature sensor 50, and the heat roller 8 portion in contact with the temperature sensor 50 is scratched and fixed. There is a problem that performance deteriorates.

In order to avoid this problem, as shown in FIG. 10, a fixing device for detecting a temperature by providing a non-contact temperature sensor 51 slightly apart from the surface of the heat roller is known as a fixing device.
Many proposals such as Japanese Patent No. 9973 have been proposed.

[0005]

However, in the conventional example as described in JP-A-4-9973, since the temperature sensor 50 is arranged away from the heat roller 8, the wind flowing in the roller rotating direction is generated. Flowed between the heat roller 8 and the temperature sensor 51, and the actual roller surface temperature could not be accurately measured due to the influence. Further, the wind flowing in the roller circumferential direction is blown against the temperature sensor 51 and the member holding the temperature sensor 51, and the heat of the temperature sensor 51 is released, so that the temperature measured when the roller temperature rises and when the temperature falls. There was a difference. That is, there is a drawback that the hysteresis of the measured temperature is large. Further, when fixing with the heat roller 8, the toner adhering on the recording material and the paper powder of the recording material scatter, which causes the temperature sensor 51.
Toner or paper dust scattered from another unit of the image forming apparatus such as a copying machine enters the fixing unit and adheres to the temperature sensor 51. Therefore, the temperature sensor 51 cannot accurately measure the surface temperature of the heat roller 8.

When the temperature of the heat roller is detected to be higher than the actual temperature due to the above measurement error, the temperature control means tries to correct the temperature of the heat roller 8 within the control temperature range. The surface temperature of the roller was lowered, resulting in poor fixing. Further, due to poor fixing, the heat roller 8 may be soiled with toner, and the toner may be offset on the image. On the contrary, if it is detected that the temperature is lower than the actual heat roller temperature, the heat roller surface temperature will be raised, but if small size paper is continuously fed while the surface temperature is high, the heat roller area that does not come into contact with the paper The surface temperature of the sheet was abnormally raised, and so-called non-sheet passing portion temperature rise was occurring. Further, there is a problem in that the high temperature offset and the heat-resistant allowable range of parts such as the heat insulating bush and the bearing and the gear supporting the heat roller are exceeded and the parts are damaged.

Further, as a result of experiments, it was found that in the conventional apparatus shown in FIG. 10, the tolerance of the distance d between the temperature sensor 51 and the heat roller 8 needs to be ± 0.1 mm.
This is because the surface temperature of the heat roller 8 deviates by ± 5 ° C. or more when the distance d deviates by ± 0.1 mm or more, which causes the above-mentioned poor fixing property, high temperature offset, and rotational support of the heat roller 8. This is because various problems such as melting of the bearing that is being used will occur.

However, in the configuration of the apparatus shown in FIG. 10, the distance d between the temperature sensor 51 and the heat roller 8 is equal to the temperature sensor 51, the parts 52 supporting the temperature sensor 51,
It is very difficult to keep the tolerance of d within ± 0.1 mm because all of the tolerances of the components such as 53 and the components holding the heat roller 8 have an influence. In order to avoid this problem, a fixing device as shown in FIG. 18 has been proposed in which the position of the temperature sensor 51 is adjustable and the distance d is set to an appropriate distance.

According to this fixing device, the temperature sensor 51
The sensor adjusting plate 52 attached to the sensor can be adjusted by rotating the sensor adjusting screw 54. When the position of the temperature sensor 51 is determined, the fixing screw 55 is tightened to fix the position of the temperature sensor 51. Reference numeral 56 is a sensor adjustment spring that is a compression coil spring that facilitates adjustment of the temperature sensor 51.

However, in the fixing device shown in FIG. 18, since the adjusting process is added at the final stage of the manufacturing process of the fixing device, there is a problem that the assembling time and the assembling cost increase accordingly. Also, in consideration of the safety of the worker who assembles, the adjustment was made when the heat roller 8 was cooled,
When the heat roller 8 is heated and expanded to increase the roller diameter, the distance d between the heat roller 8 and the temperature sensor 51 is different from that during cooling.

Further, since the heat roller 8 rubs against the paper, the Teflon layer which is the surface layer of the heat roller 8 is reduced, and as a result, the outer diameter of the heat roller 8 is reduced. This is larger than the above, causing an error in the temperature detected by the temperature sensor 51.

Further, since the distance d is adjusted at rest, when the heat roller 8 is driven, it is affected by the dimensional tolerance of the fixing side plate holding the heat roller 8 and the resulting rotation of the heat roller 8 is one revolution. The eccentricity of the hit causes an error in the distance d.

Further, when replacing the heat roller 8, it is necessary to remove the thermistor close to the roller, which requires a serviceman to readjust it, which deteriorates serviceability and may cause erroneous adjustment. There was also.

A first object of the present invention is to solve the above-mentioned problems and prevent the escape of heat and the adhesion of toner and the like even when the temperature sensor is provided in a non-contact manner with the heat roller, thereby ensuring an accurate temperature. It is to provide a fixing device that can be controlled.

A second object of the present invention is to solve the above-mentioned problems and to expand the heat roller, wear the surface layer, and hold the heat roller even when the temperature sensor is provided in a non-contact manner with the heat roller. It is an object of the present invention to provide a fixing device that does not cause an error in the gap with respect to the heat roller due to the dimension crossing, improves the workability at the time of exchanging the heat roller, and can reliably secure the gap even after the work.

[0016]

According to the present invention, the above object is to detect a temperature of the heat roller, a heat roller having a built-in heat source, a pressure roller that comes into pressure contact with the heat roller and rotates in cooperation with the heat roller. A fixing device including a temperature detecting element arranged in a non-contact position in proximity to the heat roller for controlling the temperature of the heat source based on the temperature detected by the temperature detecting element. The temperature detecting element is arranged movably in a radial direction of the heat roller in a holding container having an opening at a portion facing the heat roller. This is achieved by attaching a member that holds the gap of the holding container.

[0017]

According to the present invention, since the temperature detecting element is arranged in the holding container having an opening at the portion facing the heat roller, the heat generated from the surface of the heat roller escapes from the inside of the holding container. It is thermally insulated without incident, and is transferred to the temperature detection element by convective heat transfer and radiant heat transfer. Further, the holding container protects the temperature detecting element from paper dust and scattered toner. further,
The temperature sensing element is adjustably arranged to maintain an appropriate gap with the heat roller. Therefore, according to the present invention,
Accurate temperature control is performed. Further, since the gap holding member attached to the holding container maintains the predetermined gap between the holding container and the heat roller, the surface layer of the heat roller is not damaged.

Further, since the gap between the heat roller and the holding container can be easily secured by the gap holding member, the gap between the heat roller and the temperature detecting element is determined by determining the relative position of the temperature detecting element with respect to the holding container. Is ensured at a predetermined value. Therefore, for example, after positioning the temperature detecting element by using the adjusting jig, it is only necessary to attach the holding container to the fixing device so that the gap holding member and the heat roller come into contact with each other. The gap is set to a predetermined value.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 5 is a front view showing the entire image forming apparatus according to the first embodiment of the present invention.

In the apparatus shown in FIG. 5, the primary charger 2
The exposure device 3 performs exposure on the uniformly charged photoconductor 1, and the potential on the photoconductor 1 is attenuated to form a latent image. This latent image is developed by the developing device 4, and then transferred onto the recording material P by the transfer separation charger 5. The recording material P is supplied to the transfer portion at a transfer timing by a paper feeding device. The developer T remaining on the photoconductor 1 is removed by the cleaning device 6.

The recording material P to which the unfixed developer image is transferred as described above is sent to the pressure contact position between the heat roller 8 and the pressure roller 9 by the paper conveying device 7 and the paper guide 10. A heater 13 is provided inside the heat roller 8, and the temperature of the heat roller 8 is controlled to be a constant temperature based on the temperature detected by the temperature detector 11.
Further, the heat roller 8 is connected to a rotation driving device so as to be rotatable in a predetermined direction, and the recording material is formed in a pressure contact portion formed between the heat roller 8 and a pressure roller 9 which is rotated by being driven by the heat roller 8. The unfixed developer image on the recording material P is fixed on the recording material P by sandwiching P and conveying it while heating and pressing.

Therefore, the developer which cannot be fixed at that time adheres to the heat roller 8, but is removed by the cleaning device C arranged so as to contact the heat roller 8. On the other hand, the recording material P that has passed between the heat roller 8 and the pressure roller 9 is separated from the roller by the separation claw 12 and is discharged to the outside by the paper discharge roller pair 40.

The temperature detecting device 11 in the apparatus of this embodiment as described above has the heat roller 8 as shown in FIG. 1 or 2.
It is arranged in the vicinity and its cross section is as shown in FIG. Further, as shown in FIG. 4 viewed from the direction of arrow A shown in FIG. 3, a thermistor 14 is attached inside the temperature detecting device 11. The thermistor 14 is a non-contact thermistor having good responsiveness (hereinafter referred to as the thermistor), and is provided at a distance of, for example, 1 mm ± 0.1 mm from the surface of the heat roller 8, and detects the surface temperature of the heat roller 8.

The temperature detected by the thermistor 14 is fed back to the control section of the image forming apparatus main body by a well-known technique, and the control section controls the temperature of the heater 13 according to the temperature data. The thermistor 14 may be a thermocouple or infrared temperature sensor having good response.

As shown in FIGS. 3 and 4, the thermistor 14 is held and fixed by a thermistor holder 15 having a screw hole in a part thereof, and the thermistor holder 1
5 is fixed and supported by an L-shaped slider 16. The slider 16 is a thermistor holder 15
Is arranged in the thermistor cover 19 while being biased by a thermistor adjusting spring 18 composed of a compression spring so that the roller moves only in the radial direction of the heat roller 8. By rotating the thermistor adjusting screw 17, The distance is adjustable. The thermistor holder 15 is made of a material having a low heat capacity, and a ceramic material such as alumina is preferable. The slider 16 is made of a heat-resistant material having a low heat capacity, and for example, a resin material such as PPS is preferable. Further, the thermistor cover 19 is formed of a heat-resistant heat insulating material, and a material such as PPS, econol, PI or the like is preferable.

A roller 20 is provided on the outer wall of the thermistor cover 19 for ensuring the distance between the thermistor 14 and the heat roller 8 and for ensuring the distance between the thermistor cover 19 and the heat roller 8. It is preferable that the material of the roller 20 is excellent in slidability, heat resistance, and wear resistance, does not change in outer diameter due to temperature change, and has a small expansion coefficient. Further, the surface of the roller 20 is preferably such that toner is hard to adhere thereto. For example, a PPS surface with a fluorine coating or a PI surface with a fluorine coating is preferable. The cross-sectional shape of the roller 20 is A shown in FIG.
The shape of B is preferable to the shape of. This is because the contact part needs to be as small as possible in order to prevent heat dissipation in the detection part.

The roller 20 is made of a heat-resistant resin (for example, P
The roller holder 21 made of PS) is thermally caulked by its rotating shaft. As shown in FIG. 4, the rollers 20 are attached to the roller holder 21 at three points, and the rollers 20 are in contact with the heat roller 8 at three points and are driven to rotate. By supporting at three points, the gap between the thermistor cover 19 and the heat roller 8 can be made uniform without deviation. In addition, the roller holder 21 and the thermistor cover 19 are fixed screws 22
The distance B between the heat roller contact portion of the roller 20 and the thermistor cover 19 shown in FIG. 3 is adjusted to be minimized. The shape of the thermistor cover 19 facing the heat roller 8 at a predetermined distance B by the roller 20 is a linear shape in the longitudinal direction of the heat roller 8 and an encircling shape along the circumference of the heat roller in the circumferential direction. There is. As a result, the heat generated from the surface of the heat roller 8 is insulated without escaping from the inside of the holder, and is transferred to the thermistor 14 by convective heat transfer and radiant heat transfer.

Also, on the side surface of the thermistor cover 19, 4
There is a boss 23 at a place, and a part of the thermistor stay 24 made of heat-resistant / heat-insulating resin is fitted into the boss 23 to fit the thermistor cover 19 to the heat roller 8.
It is configured to slide in the direction of the rotation axis.

Further, by providing a thermistor spring 25 between the thermistor stay 24 and the roller holder 21, the roller 20 is biased and brought into contact with the heat roller 8 and is driven to rotate. The pressing force of the thermistor spring needs to be sufficient because the roller 20 is driven to rotate on the heat roller 8. However, if the applied pressure is too large, the amount of surface wear of the heat roller 8 becomes large, so it must be minimized.

The thermistor stay 24 is fixed with screws 27 to the thermistor guide 26 fixed between the fixing side plates.

Further, it is desirable that the contact position of the roller 20 with the heat roller 8 does not coincide with the position of the separation claw 12.
This is because if the positions are matched, the distance between the heat roller 8 and the thermistor 14 becomes shorter when the fixing roller is scraped off by the separating claw for some reason, and the thermistor 14 makes a false detection higher than the actual roller surface temperature. This is because the fixing property is deteriorated because the temperature is controlled to be lowered.

The distance between the thermistor 14 and the heat roller 8 is
According to the experiment by the present inventor, it is necessary to set the distance to 1 ± 0.1 mm. This is because if the distance d deviates by ± 0.1 mm or more, the surface temperature of the heat roller 8 deviates by ± 5 ° C. or more, which results in poor fixing, high-temperature offset, and melting of the bearing that rotatably supports the heat roller 8. This is because various problems occur.

When the temperature detecting device 11 is assembled, the adjustment is performed by using a measuring jig such as a laser length measuring machine and a thermistor adjusting screw 17 with an exclusive jig having an adjusting roller having the same shape as the heat roller 8. While adjusting, the distance d between the heat roller 8 and the thermistor 14 with respect to the adjusting roller having the same shape is set to 1 m.
Adjust to m ± 0.1, and fix the slider 16 to the thermistor cover 19 with the fixing screw 28. At this time, the distance B between the heat roller 8 and the thermistor cover 19 is adjusted using a measuring machine such as a laser length measuring machine by the method described above.

At the time of assembling the fixing unit, it is only necessary to attach the adjusted temperature detecting device 11. Also,
The roller 20 wears after the endurance, and the non-contact thermistor 14
When the end of the service life of the
Collect 1. The temperature detecting device 11 can be reused if it is collected in a remanufacturing factory, the non-contact thermistor 14 and the roller 20 are exchanged, and readjustment is carried out by the above adjustment dedicated jig.

One of the features of the present invention is the thermistor cover 1
The shape of the heat roller 8 is 9
And has a shape surrounding the thermistor 14. As a result, the heat generated from the surface of the heat roller 8 is insulated without escaping from the inside of the holder, and is transferred to the thermistor 14 by convective heat transfer and radiant heat transfer. Further, the layer of oil applied from the fixing web C to the heat roller 8 is evened by the thermistor cover 19 as shown in FIG. This allows
It is possible to prevent the oil layer from being too thick or non-uniform, and to measure the surface temperature of the heat roller 8 with high accuracy without causing unevenness in heat dissipation of the heat roller 8.

The thermistor cover 19 is used in this embodiment.
The distance between the thermistor cover 19 and the heat roller 8 was adjusted by moving the roller holder 21 by using the roller holder 21 supporting the roller 20 as a separate member.
The thermistor cover 19 may directly support the rollers and the distance may not be adjusted.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 7 is a cross-sectional view of the temperature detecting device 11 according to the second embodiment, and FIG. 8 is a view on arrow A of FIG.

While the shape of the thermistor cover 19 of the first embodiment is a square tubular whole surface surrounding shape, the thermistor cover 19 of the present embodiment has a cylindrical shape on the inside and a square shape on the outside. It has a double structure. Heat roller 8
The heat generated from the thermistor 14 is transferred to the thermistor 14 by convective heat transfer and radiant heat transfer by infrared rays.
Is arranged in the center of the cylindrical portion 29 of the thermistor cover, the radiant heat can be concentrated on the thermistor 14 and the heat transfer efficiency can be improved. Also, the thermistor cover 19
It is possible to improve the reflection efficiency of the radiant heat transfer by subjecting the inner surface of the cylindrical portion 29 of the above to a metal plating treatment.

Since the air layer 30 is provided between the double-structured thermistor covers, it is difficult for heat to escape to the outside from the cylindrical wall of the thermistor cover, and there is a heat insulating effect.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. In addition, Example 1
The same parts as in FIG.

The apparatus of this embodiment is used in an image forming apparatus as shown in FIG. 15, but the configuration of the image forming apparatus is the same as that of the apparatus shown in FIG. 5 except for the configuration of the fixing device. The description will be omitted, and the temperature detection device 11 will be mainly described below.

The temperature detecting device 11 in this embodiment is also arranged in the vicinity of the heat roller 8 as shown in FIGS. 11 to 13, and is shown in FIG. 14 viewed from the direction of arrow D in FIGS. 13 and 13. As shown, the same non-contact thermistor 14 as that of the first embodiment is provided.

As shown in FIG. 14, the non-contact thermistor 14 is fixed to a slider 121 made of a heat-resistant material with a screw hole partially cut. The slider 12
1 is a thermistor adjusting spring 125 composed of a compression coil spring.
It is held by the support portion 122 of the thermistor holder 118 while being urged to move, the movement of the heat roller 8 in the longitudinal direction is restricted, and the movement of the heat roller in the radial direction can be adjusted by the thermistor adjusting screw 123. After the adjustment, as shown in FIGS. 11, 12, and 14, the fixing screw 124
The position is fixed with.

The non-contact thermistor 14 is surrounded by the thermistor holder 1 except for the side facing the heat roller 8.
It is surrounded by eighteen surrounding parts 126. This prevents the wind from hitting the non-contact thermistor 14, enhances the heat insulating effect, and prevents the scattered toner from adhering to the non-contact thermistor 14.

The thermistor holder 118 is a thermistor holder made of a heat-resistant material (for example, PPS) that can move in the direction of arrow C, and a roller 117 is attached as shown in FIGS. 11 to 13. The roller 11
Reference numeral 7 is a roller that is in contact with and driven by the heat roller 8 to maintain and guarantee the distance from the non-contact thermistor 14 to the surface of the heat roller 8. The material of the roller 117 is slidability, heat resistance,
Has excellent wear resistance, the outer diameter does not change due to temperature changes,
Those having a small expansion coefficient are preferable. Further, it is preferable that the surface of the roller 17 is such that toner hardly adheres thereto. For example, P
Fluorine coating on the surface of PS or PI
It is better to have a fluorine coating on the surface. The cross-sectional shape of the roller 117 is the same as that of the roller 2 described in the first embodiment.
Similar to 0, the shape of B is preferable to the shape of A shown in FIG. This is because the contact portion needs to be as small as possible in order to prevent heat dissipation in the detection portion.

On the other hand, the opposite side of the roller 117 mounting portion of the thermistor holder 118 is fitted with a thermistor stay 120 made of heat-resistant plastic such as PPS and is urged by a thermistor spring 119. The thermistor spring 119 causes the roller 117 to contact the heat roller 8 at a predetermined pressure. The pressing force of the spring needs to be sufficient because the roller 117 is driven to rotate on the heat roller 8. However, if the applied pressure is too large, the amount of wear on the surface of the heat roller 8 increases, so it must be minimized. The point of action of pressurization should be as close as possible to the roller 117. When the point of action of pressurization is in the center of the thermistor holder 118, the thermistor holder 118
This is because the bending of the non-contact thermistor 14 causes the detection position of the non-contact thermistor 14 to shift.

In the apparatus of this embodiment as described above, the distance from the detection surface of the non-contact thermistor 14 to the surface of the heat roller 8 must be maintained at 1 mm ± 0.1 mm for the reason described above. However, the thermistor holder 11
8 and the play of the roller 117, the parts precision of the non-contact thermistor 14, the thermistor holder 118, and the mounting precision, this precision is considerably difficult. Therefore, in this embodiment, the position of the non-contact thermistor 14 can be easily adjusted by adopting the above-mentioned configuration.

At the time of adjustment, the thermistor adjusting screw 123 is rotated to adjust the non-contact thermistor 14, and when the position is determined, the slider 121 is fixed with the fixing screw 124. The adjustment is performed when the temperature detection device 11 is assembled by the heat roller 8
The distance between the non-contact thermistor 14 and the heat roller 8 having the same shape using a measuring machine such as a laser length measuring machine with an adjustment jig having the same shape as the adjustment roller. It is only necessary to adjust d to 1 mm ± 0.1 and attach the adjusted temperature detecting device 11 when assembling the fixing unit. Further, when the roller 117 wears after the endurance or when the life of the non-contact thermistor 14 is reached, the service person collects the temperature detecting device 11. The temperature detectors 11 are collected in the recycling factory, and the non-contact thermistor 14 and the roller 11
It can be reused by replacing 7 and readjusting it with the adjustment jig.

Further, it is desirable that the longitudinal position of the heat roller 8 of the roller 17 does not coincide with the position of the separating claw 12.
This is because, if the positions are matched, when the fixing roller is scraped off by the separating claw for some reason, the distance d between the heat roller 8 and the non-contact thermistor becomes large, and the fixing property deteriorates. <Embodiment 4> Next, Embodiment 4 of the present invention will be described with reference to FIGS.
It will be described based on 7. The same parts as those in the third embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 16 shows the fourth embodiment
17 is a sectional view of a fixing device including the temperature detecting device 11 of FIG.
FIG. 6 is a perspective view of a temperature detection device 11 of Example 2.

In the third embodiment, the rollers 117 are brought into contact with and rotated at two places on the same peripheral surface of the heat roller 8, whereas in the present embodiment, the roller 117 is rotated on the same peripheral surface of the heat roller 8. The rollers 17 are abutted on both outer sides of the thermistor 14 without abutting the rollers. As a unique effect of this configuration, the roller 117
It is possible to reduce the heat dissipation on the same peripheral surface of the heat roller 8 which is in contact with, and it is possible to prevent a decrease in the surface temperature of the heat roller 8 corresponding to the contact portion of the roller 117, that is, deterioration of the fixing property. Further, since two rollers do not abut on the same place, good results can be obtained against roller wear.

[0052]

As described above, according to the present invention,
Since the temperature detecting element is arranged in the holding container having the opening, the surface temperature of the heat roller can be accurately measured without letting the temperature of the heat roller surface escape to the outside of the surrounding area. Further, due to this heat insulating effect, the surface temperature of the heat roller can be measured accurately even when the temperature of the heat roller rises or falls. Further, it is possible to prevent the scattered toner and paper powder at the time of fixing, and the toner and paper powder scattered from another unit from adhering to the temperature sensor, so that the surface temperature of the heat roller can be accurately measured. In addition, the thickness unevenness of the oil layer applied to the heat roller can be made uniform, and the surface temperature of the heat roller can be accurately measured. Therefore, it is possible to prevent the fixing failure, the offset, the temperature rise in the non-sheet passing portion, and the destruction of the heat insulating bush, the bearing, the gear, etc. supporting the heat roller.

Further, since the holding container is provided with the gap holding member and the gap holding member is brought into contact with the heat roller, when the positioning of the temperature detecting element with respect to the holding container is completed by the adjusting jig, the assembly can be performed at the time of assembly. It is possible to reduce the assembling time and the assembling cost without the need for the adjusting step. Since the position adjustment and assembly of the temperature detection element can be performed independently, if a heat roller is used as the adjustment jig while the fixing device is operating, the assembly can be performed even when the assembly is performed when the roller is cooled. The surface temperature of the heat roller can be accurately detected by ensuring the distance between the heat roller and the temperature detecting element. Furthermore, even if the diameter of the heat roller becomes smaller after it has been durable, the relative position of the temperature detection element to the holding container does not change, so the distance between the heat roller and the temperature sensor is guaranteed, and the surface temperature of the heat roller can be detected accurately. it can. Further, when replacing the heat roller or the temperature sensor, it is not necessary to adjust the distance between the heat roller and the temperature sensor, and serviceability can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a temperature detection device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a fixing device provided with the temperature detection device of FIG.

3 is a cross-sectional view of the temperature detection device of FIG.

FIG. 4 is a view on arrow A in FIG.

5 is a cross-sectional view of an image forming apparatus including the temperature detection device of FIG.

6 is a cross-sectional view showing the shape of a gap maintaining member of the temperature detecting device of FIG.

FIG. 7 is a sectional view showing a temperature detecting device according to a second embodiment of the present invention.

8 is a view on arrow A in FIG. 7. FIG.

FIG. 9 is a cross-sectional view showing a conventional example of a heat roller fixing device.

FIG. 10 is a sectional view showing another conventional example of a heat roller fixing device.

FIG. 11 is a cross-sectional view of a fixing device including a temperature detecting device according to a third embodiment of the invention.

FIG. 12 is a perspective view of a temperature detecting device according to a third embodiment of the present invention.

FIG. 13 is a sectional view of a temperature detecting device according to a third embodiment of the present invention.

14 is a view on arrow D of FIG. 3. FIG.

FIG. 15 is a cross-sectional view of an image forming apparatus including the apparatus of FIG.

FIG. 16 is a cross-sectional view of a fixing device including a temperature detection device according to a fourth exemplary embodiment of the present invention.

FIG. 17 is a perspective view of a temperature detecting device according to a fourth embodiment of the present invention.

FIG. 18 is a sectional view of a conventional fixing device.

[Explanation of symbols]

 8 Heat Roller 9 Pressure Roller 13 Heat Source 14 Temperature Detection Element (Non-contact Thermistor) 19 Holding Container (Thermistor Cover) 20 Gap Holding Member (Roller) 117 Rotating Member (Roller)

Claims (6)

[Claims] 1. A heat roller having a built-in heat source, a pressure roller that comes into pressure contact with the heat roller and rotates in cooperation with the heat roller, and a non-contact position close to the heat roller to detect the temperature of the heat roller. In a fixing device provided with a temperature detecting element provided and means for performing temperature adjustment control of the heat source based on the temperature detected by the temperature detecting element, the temperature detecting element is a portion facing the heat roller. It is arranged so as to be movable in the radial direction of the heat roller in a holding container having an opening, and a member for holding a gap between the heat roller and the holding container is attached to the holding container. Fixing device characterized by. 2. The fixing device according to claim 1, wherein a front edge portion of the holding container facing the heat roller has an arc shape along a circumferential direction of the heat roller. 3. The fixing device according to claim 1, wherein the holding container is provided with adjusting means for adjusting a gap between the temperature detecting element and the heat roller. 4. The member for holding the gap between the heat roller and the holding container is a rotating member that abuts on the heat roller and rotates in cooperation therewith, and is attached to at least two positions of the holding container. The fixing device according to claim 1 or claim 3. 5. The fixing device according to claim 4, wherein the rotating member is arranged so as to sandwich the temperature detecting element, and the disposing positions are different positions in the circumferential direction of the heat roller. 6. The fixing device according to claim 4, wherein the rotating member is arranged so as to sandwich the temperature detecting element, and the disposing positions are different positions in the generatrix direction of the heat roller.