JP2001228738A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device in which adhesion of a lump of offset toner turning back from a thermistor to the image surface or non-image surface is prevented. SOLUTION: In the fixing device in which a halogen heater 16 is disposed inside at least one of a pair of fixing and pressure rollers 14 and 15 oppositely pressure-contacted, and the thermistor 25 as a heat detecting means for controling on-off of the halogen heater 16 is disposed to the outside, a cleaning roller (roller member) 26 of alumina material is partially disposed at the same position as the thermistor 25 with respect to the longitudinal direction of the fixing roller 14 (or pressure roller 15) where the thermistor 25 is disposed. Even if a lump of toner deposited on the tape surface of the thermistor 24 turns back to the fixing roller 14 and the pressure roller 15, the toner which turned back adheres to the surface of the cleaning roller 26 of alumina material having a releasing property inferior to the releasing property of the surfaces of the fixing roller 14 and the pressure roller 15, and does not return to the fixing roller 14 and the pressure roller 15. As a result, the adhesion of toner to the image surface or the non-image surface is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a fixing device employing a heating system has a halogen heater inside a fixing roller having a silicon rubber layer formed around a hollow aluminum core and a release layer formed on the surface thereof. And heat the fuser roller,
A one-sided heating roller fixing system is generally adopted in which a sponge roller is brought into pressure contact with the fixing roller so that the unfixed paper is held between the rollers and a toner image is fixed on the unfixed paper.

FIG. 10 is a cross-sectional view showing a schematic structure of a fixing device employing a one-sided heating roller fixing method. In the figure, reference numeral 1 denotes a fixing roller, and the fixing roller 1 is provided on the outer periphery of a hollow Fe material. It is configured by forming a release layer such as a PFA tube. A halogen heater 3 is disposed inside the fixing roller 1, and the fixing roller 1 is rotatably supported by a fixing frame 4.

A pressure roller 2 is formed by forming a thick heat-resistant sponge layer around a solid shaft. The pressure roller 2 is pressed against the fixing roller 1 via a bearing 5 by an urging means 6. ing. Reference numeral 7 denotes an entrance guide for guiding the unfixed paper P to a holding portion (hereinafter, referred to as a nip) formed by the fixing roller 1 and the pressure roller 2, and reference numeral 8 denotes a discharge rotatably supported by a discharge lower guide 9. The paper rollers 10 are paper discharge rollers supported by the paper discharge upper guide 11 and pressed against the paper discharge roller 8 by urging means (not shown).

Reference numeral 12 denotes a thermistor serving as a temperature control means. The thermistor 12 controls ON / OFF of the halogen heater 3 so as to maintain the outer peripheral surface temperature of the fixing roller 1 in a range of 160.degree. . Reference numeral 13 denotes a thermoswitch serving as a safety valve, which cuts off the power supply to the halogen heater 3 when the outer peripheral surface of the fixing roller 1 is abnormally heated.

In the above configuration, the unfixed paper P sent through a developing means, a transferring means and a conveying means (not shown) is used.
Is guided between the fixing roller 1 and the pressure roller 2 by being guided by the entrance guide 7, and after the toner image is fixed,
The sheet is sandwiched between the sheet discharging roller 8 and the sheet discharging roller 10 and is transferred to a sheet discharging / transporting unit (not shown). The fixing roller 1 and the paper discharge roller 8 are driven to rotate in the directions of arrows A and B, respectively, by the cooperation of a driving unit (not shown).

[0007]

In recent years, as an image forming apparatus such as a printer or a copying machine, there has been an increasing demand for a color / monochrome dual-use machine capable of obtaining a color image rather than a monochrome single machine. In order to obtain a color image, at least three primary colors of cyan, magenta and yellow are superimposed and developed. However, in order to obtain an image of only black characters, black is formed by superimposing three colors. Because of the loss of throughput time, it is common to have four cyan, magenta, yellow and black toner cartridges as a result.

In the color image forming apparatus, the outer layers of the fixing roller and the pressure roller are formed of a rubber layer so as to increase the nip width in order to emphasize the fixing property of the color image.

However, since the physical properties of the cyan, magenta, and yellow toners and the black toner are different, the linear pressure is insufficient in the black toner layer, a slight toner offset occurs on the fixing roller, and At the same time, the toner accumulates on the abutting surface of the thermistor, and as a result, a trouble occurs in which the toner mass returned to the fixing roller or the pressure roller adheres to the image surface or the non-image surface.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a fixing device capable of preventing a mass of offset toner returning from a thermistor from adhering to an image surface or a non-image surface. To provide.

[0011]

In order to achieve the above object, according to the present invention, a heater is arranged inside at least one of a pair of fixing and pressure rollers which are pressed against each other, and the heater is arranged outside the heater. In a fixing device including a thermistor serving as a heat detecting unit for controlling ON / OFF of a heater, a roller made of an alumina material is provided at the same position as the thermistor in the longitudinal direction of the fixing roller or the pressure roller in which the thermistor is disposed. The member is partially arranged.

According to a second aspect of the present invention, in the first aspect of the invention, the width of the roller member is set to be larger than the contact width of the thermistor with respect to the fixing or pressure roller.

According to a third aspect of the present invention, in the first aspect of the present invention, the roller member comprises a cylindrical portion made of alumina material and a shaft portion made of a sliding mold material.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the roller member is provided with a polyimide film material which is in contact with a longitudinal direction thereof.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the width of the film material is set to be larger than the longitudinal width of the roller member in contact with the fixing or pressure roller. And

According to a sixth aspect of the present invention, in the first aspect of the invention, the roller member is provided on the periphery of the fixing and pressing roller at a position downstream of the holding portion of the fixing and pressing roller pair in the roller rotation direction. It is characterized by being arranged upstream of the thermistor in the roller rotation direction.

Therefore, according to the present invention, even if a lump of toner deposited on the tape surface of the thermistor returns to the fixing roller and the pressure roller during rotation of the fixing roller and the pressure roller, the toner that has returned has a large effect. The toner does not adhere to the surface of the roller member made of alumina, which is inferior to the surface of the fixing roller and the pressure roller, and does not return to the fixing roller and the pressure roller. Adhesion is prevented.

[0018]

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

<First Embodiment> FIG. 1 is a main sectional view showing a schematic structure of a fixing device according to a first embodiment of the present invention.
The illustrated fixing device employs a two-sided heating roller system.

In FIG. 1, reference numeral 14 denotes a fixing roller.
This is formed by forming a silicone rubber layer around a hollow alumina material and wrapping the periphery with a PFA tube,
It is rotatably supported by the fixing frame 17. Reference numeral 15 denotes a pressure roller, which is formed by forming a silicon rubber layer around a hollow alumina material like the fixing roller 14 and wrapping the periphery with a PFA tube, and rotatably supported by a pressure frame 18. ing. Here, the pressure frame 18 is pivotally supported by the fixing frame 17, and is in pressure contact with the fixing roller 14 by the urging means 19. Note that a halogen heater 16 is disposed inside each of the fixing roller 14 and the pressure roller 15.

Reference numeral 20 denotes an entrance guide for guiding unfixed paper to a fixing nip formed by the fixing roller 14 and the pressure roller 15, reference numeral 21 denotes a paper discharge roller rotatably supported by a paper discharge lower guide 22, 23 is a paper discharge roller supported by the paper discharge upper guide 24 and pressed against the paper discharge roller 21; 25 is a thermistor for controlling the temperature of the fixing roller 14 and the pressure roller 15 so as to maintain the surface temperature at about 180 ° C; Reference numeral 26 denotes an alumina cleaning roller. Here, the cleaning roller 26 is rotatably supported by a bearing 27 at the same position as the thermistor 25 in the longitudinal direction of the fixing roller 14, and is fixed by a cleaner holder 29 via a coil spring 28 as an urging means. The fixing roller 14 is fixed to the stay 30 and pressed against the fixing roller 14. The width of the cleaning roller 26 is set to be larger than the tape width of the thermistor 25.

FIG. 2 shows a configuration around the cleaning roller 26.

Next, the structure around the pressure roller 15 will be described with reference to FIG.

FIG. 3 is a perspective view showing the structure around the pressure roller 15. The pressure roller 15 is rotatably supported at both ends by a pressure frame 18 by bearings 31.
A halogen heater 16 is disposed inside.

In FIG. 3, reference numeral 32 denotes the fixing roller 14.
And a thermoswitch for cutting off the current supply to the halogen heater 16 when the surface of the pressure roller 15 is abnormally heated. The thermo-switch 31 is supported by a thermo-switch holder 33, and the thermo-switch holder 33 is supported by a thermo-switch stay 34, which is fixed at both ends to the bearing 31, and the thermistor 25 is supported by the thermo-switch stay 34. Have been.

Further, the cleaning roller 26 is fixed to the thermoswitch stay 34 while being held by the cleaner holder 29 at the same position as the thermistor 25 in the longitudinal direction of the pressure roller 15, and is pressed against the pressure roller 15. Has been abutted.

By employing the above configuration, the lump of toner deposited on the tape surface of the thermistor 25 returns to the fixing roller 14 and the pressure roller 15 while the fixing roller 14 and the pressure roller 15 are rotating. However, since the returned toner does not adhere to the surface of the cleaning roller 26 made of an alumina material, which is less releasable than the surfaces of the fixing roller 14 and the pressure roller 15, and does not return to the fixing roller 14 and the pressure roller 15, This prevents the toner from adhering to an image surface or a non-image surface.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS.

The present embodiment is characterized in that the cleaning roller in the first embodiment is divided into a cylindrical roller portion made of alumina material and a sliding shaft portion made of a mold material. Since the portion can be directly fixed to the leaf spring as the urging means, the configuration can be simplified.

FIG. 4 is an exploded perspective view showing the structure around the cleaning roller 35. The cleaning roller 35 is made of a hollow alumina material, and the cleaning roller 35 has a sliding shaft 36 of a mold material disposed therein. In this state, it is rotatably supported by the bearing 37 a of the leaf spring 37. Note that the width of the cleaning roller 35 is
Is set to be larger than the tape width.

FIG. 5 is a main sectional view of the fixing device according to the present embodiment. As shown in FIG.
Is fixed to the upper fixing stay 30 by screwing, and the cleaning roller 35 is brought into contact with the fixing roller 14. In FIG. 5, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

FIG. 6 is a perspective view showing the structure around the pressure roller 15, and as shown in FIG.
Is fixed to the pressing frame 18 by screwing, and the cleaning roller 35 is brought into contact with the pressing roller 15.

The other configuration is the same as that of the first embodiment, and a description thereof will be omitted.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG.

The present embodiment is characterized in that a polyimide film material is brought into contact with the surface of the alumina cleaning roller in the first and second embodiments. The toner accumulated on the sheet can be scraped off positively, so that it is possible to prevent the toner from being re-offset to the fixing roller and the pressure roller due to the collapse of the toner layer.

FIG. 7 is a perspective view of the cleaning roller 35. In FIG. 7, reference numeral 38 denotes a scraper made of a polyimide film. One end of the scraper 38 is adhesively fixed to a leaf spring 37, and the other end is a cleaning roller. 35 is in contact with the surface. In addition, the scraper 38
Is set to be larger than the width of the cleaning roller 35.

The other configuration is the same as that of the second embodiment, and the description thereof is omitted.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIGS.

In this embodiment, the cleaning roller of the alumina material according to the first to third embodiments is arranged on the periphery of the fixing and pressing roller downstream of the holding portion (nip portion) of the fixing and pressing roller pair in the roller rotation direction. And the roller is arranged upstream of the thermistor in the roller rotation direction. With such a configuration, the offset generated when the unfixed paper passes through the holding portion of the fixing and pressure roller pair. Since the toner can be cleaned immediately before the thermistor position, it is possible to prevent the offset toner from adhering to the tape of the thermistor.

FIG. 8 is a main sectional view of the fixing device according to the present embodiment. As shown in FIG.
Is fixed to the paper discharge stay 40 by screwing, and the cleaning roller 35 is in contact with the fixing roller 14.

FIG. 9 is a perspective view showing the structure around the pressure roller 15. As shown in FIG. 9, a leaf spring 41 which supports the clearing roller 35 is fixed to the pressure frame 18 by screwing. , Cleaning roller 35
Are brought into contact with the pressure roller 15.

The other configuration is the same as that of the first embodiment, and the description thereof is omitted.

[0043]

As is apparent from the above description, according to the present invention, a heater is disposed inside at least one of the pair of fixing and pressure rollers which are pressed against each other, and ON / OFF of the heater is disposed outside the heater. In a fixing device in which a thermistor serving as a heat detecting unit for controlling OFF is disposed, a roller member made of an alumina material is partially disposed at the same position as the thermistor in the longitudinal direction of the fixing roller or the pressure roller in which the thermistor is disposed. Because of this arrangement, it is possible to prevent the mass of the offset toner returning from the thermistor from adhering to the image surface or the non-image surface.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view showing a configuration around a cleaning roller of the fixing device according to the first embodiment of the present invention.

FIG. 3 is a perspective view illustrating a configuration around a pressure roller of the fixing device according to the first exemplary embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a configuration around a cleaning roller of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a main cross-sectional view illustrating a schematic configuration of a fixing device according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a configuration around a pressure roller of a fixing device according to a second embodiment of the present invention.

FIG. 7 is a perspective view of a cleaning roller portion of a fixing device according to a third embodiment of the present invention.

FIG. 8 is a main sectional view showing a schematic configuration of a fixing device according to a fourth embodiment of the present invention.

FIG. 9 is a perspective view showing a configuration around a pressure roller of a fixing device according to a fourth embodiment of the present invention.

FIG. 10 is a main cross-sectional view illustrating a schematic configuration of a conventional fixing device.

[Explanation of symbols]

 Reference Signs List 14 fixing roller 15 pressure roller 16 halogen heater (heater) 25 thermistor 26 cleaning roller (roller member) 35 cleaning roller (roller member: cylindrical portion) 36 sliding shaft (shaft portion) 38 scraper (film material)

Claims (6)

[Claims] 1. A heater is disposed inside at least one of a pair of fixing and pressure rollers which are pressed against each other, and a thermistor serving as heat detecting means for controlling ON / OFF of the heater is disposed outside the heater. In the fixing device, a roller member made of an alumina material is partially disposed at the same position as the thermistor in the longitudinal direction of the fixing roller or the pressure roller in which the thermistor is disposed. 2. The fixing device according to claim 1, wherein a width of the roller member is set to be larger than a contact width of the thermistor to a fixing or pressure roller. 3. The fixing device according to claim 1, wherein said roller member comprises a cylindrical portion made of alumina material and a shaft portion made of a sliding mold material. 4. The fixing device according to claim 1, wherein the roller member includes a polyimide film material that is in contact with a longitudinal direction of the roller member. 5. The fixing device according to claim 1, wherein the width of the film material is set to be larger than the width of the roller member in the longitudinal direction in contact with the fixing or pressure roller. 6. The fixing device according to claim 1, wherein the roller member is disposed on the periphery of the fixing and pressure roller at a position downstream of the holding portion of the fixing and pressure roller pair in the roller rotation direction and at a position upstream of the thermistor in the roller rotation direction. The fixing device according to claim 1, wherein: