JP2001075394A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop the power feed to a fixing roller when an insulating layer of the fixing roller is simultaneously destroyed at several points and to improve safety by providing the outer surface of the fixing roller near the inner side at both ends of the exothermic part of the resistance heating layer of the fixing roller with temperature controllers. SOLUTION: The fixing roller 1 has a substrate made of a thin metal consisting of a thin pipe of Al or Fe and is constituted by laminating an electrical insulating layer consisting of a resin film of polyimide, etc., and the resistance heat generating layer consisting of a SUS-base metal on its inner side and forming a release layer consisting of 'Teflon (R)', etc., having a release property and heat resistance ion the outer side of the substrate. The outside surfaces of the roller near S1 and S2 (50 mm) on the inner side at both ends of the exothermic part 18 of the resistance heat generating layer of the fixing roller 1 are provided with the temperature controllers 22-1, 2, by which the abnormal heat generation of the fixing roller 1 may be prevented even if the electrical insulating layer of the fixing roller 1 is simultaneously damaged at >=2 points.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In general, a fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile or the like rotates a heated fixing roller while transferring toner between the rotating fixing roller and a pressure roller. Is inserted into the printing paper, the toner is heated and melted, and the toner is fused on the printing paper.In recent years, environmental regulations and awareness of environmental protection have increased. 2. Description of the Related Art Power consumption is reduced by interrupting energization of a heater and energizing only when necessary.

In such an energy-saving fixing device, the surface temperature of the fixing roller must immediately reach the set temperature during operation. In order to satisfy this requirement, in a system in which a halogen lamp is used from the inside of a metal base, the thickness is reduced to 1 mm or less in order to reduce the heat capacity of the fixing roller. As another means, there is a direct heating type fixing roller having a heat generating layer. By changing from heating by radiation of the halogen lamp to heat conduction by the heat generating layer, the thermal efficiency is improved and the rise time can be reduced by about 20 to 30%. In this case as well, a further rapid temperature increase is achieved by combining with a technique for thinning the substrate.

[0004]

In such a fixing roller having a heat generating layer, when the insulating layer of the fixing roller is broken at several places at the same time, the power supply portions are located at both ends of the fixing roller. Between the destruction portions, the heating element does not flow, but the resistance flows through the fixing roller base that is smaller than the heating element, and only the heating elements at both ends of the fixing roller are heated. Since the apparatus is installed at the center of the fixing roller, it cannot cope with such a situation, and there is a problem that the temperature of the end of the fixing roller sharply rises, which may cause a fire or the like.

[0005] Therefore, the problem of the present invention is to solve the above-mentioned problems of the conventional fixing device. When the insulating layer of the fixing roller is broken at several places at the same time, the power supply to the fixing roller is stopped. Another object of the present invention is to provide a fixing device that can further improve safety.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a fixing roller which is driven to rotate, and a temperature control device which contacts the fixing roller and controls the temperature of the fixing roller. And an over-temperature prevention device for controlling runaway of the temperature of the fixing roller. The invention according to claim 1, wherein the fixing roller comprises a hollow cylindrical metal base, and a peripheral layer formed on the metal base. And a temperature control device provided on the outer surface of the roller near the inside of both ends of the heat generating portion of the resistance heat generating layer of the fixing roller.

According to a second aspect of the present invention, the fixing roller has a hollow cylindrical metal base, an electrical insulating layer and a resistance heating layer sequentially laminated on the peripheral surface of the fixing base, and a fixing device for preventing excessive temperature rise. Are provided on the outer surface of the roller near the inside of both ends of the heat generating portion of the resistance heat generating layer of the fixing roller.

[0008] The invention according to claim 3 is the invention according to claim 1 or 2.
Wherein the mounting position of the temperature control device or the excessive temperature rise prevention device is located inside both ends of the heat generating portion of the resistance heat generating layer of the fixing roller and outside the paper passing width. is there.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first embodiment of the present invention shown in FIGS. 1 and 2, a pressure roller 2 is pressed against a fixing roller 1 with a constant pressing force by a spring (not shown). Is mounted on the fixing side plate 5 via the heat insulating bush 3 and the bearing 4, and the gear 6 engages with a drive source (not shown) to perform a rotational drive.

The fixing roller 1 has a thin metal base 7 made of a thin pipe made of Al or Fe.
It is about 0.2 to 0.8 mm. Inside it has a volume resistivity of 10 ¹³ Ω−
An electrical insulating layer 8 made of a resin film of polyimide or the like having a thickness of not less than 100 cm and a resistance heating layer 9 made of a SUS-based metal is laminated on the outside of the base 7. Thus, a release layer 11 is formed.

At both ends of the resistance heating layer 9, a disk-shaped power receiving electrode 12 for supplying electricity to the resistance heating layer 9 is provided, and the power supply electrode 14 is fixed by leaf springs 13-1 and 13-2 indicated by a bracket 15. It is pressed by the load of. Power receiving electrode
12 is provided with an air hole for releasing the expanding air inside the fixing roller 1 at the time of heating. In addition, power is supplied to the resistance heating layer 9 through the power supply unit 17 while the power supply electrode 14 and the power reception electrode 12 slide, and the heat generation unit 18 is heated.

By forming the power receiving electrode 12 in a disk shape, the sliding portion can be positioned at the center of rotation, the relative speed of the sliding portion can be reduced, and the sliding friction can be reduced. The fixing roller 1 includes a bracket 21-1 attached to the top plate 19 and provided so as to contact the fixing roller 1.
Temperature control device 22- such as a thermistor held by 2
The temperature is controlled by 1 and 2. Also temperature control device
When 22-1 and 22-2 malfunction, the overheating prevention device 23 such as a thermostat for preventing the temperature runaway
The fixing roller 1 is fixed by a bracket 24 attached to the fixing roller 19.
Is held in contact with the

The control circuit for the above-described components will be described. 31 is a power supply, 32 is an input circuit, and 33 is a C
PU and 34 indicate drives, these are connected in series, and both ends of the power supply 31 are connected to one end of the overheat prevention device 23 and one end of the drive 34 by wires 36 and 37, respectively, to prevent overheating. The other end of the device 23 is connected to one leaf spring 13-1 by a wire 38, the other end of the drive 34 is connected to the other leaf spring 13-2 by a wire 39, and both ends of the input circuit 32 are wires. 41 and 42 are connected to both temperature control devices 22-1 and 22-2.

In such a case, a current is supplied from the power source 31 to the resistance heating layer 9 of the fixing roller 1 in the same manner as in a normal case,
This heat causes the fixing roller 1 to be heated to fix the toner image on the transfer paper.
The temperature is controlled by 22-1 and 22-2, and the overheating is prevented by the overheating prevention device 23. However, since this is conventionally known, the description is omitted.

During the fixing operation as described above, the electric insulating layer 8 of the fixing roller 1 has two or more points, for example, a damaged part.
In the case of simultaneous failure at 26 and 27, the current flowing through the resistance heating layer 9 flows through the thin base material having a small resistance between the damaged portions 26 and 27. Therefore, current flows through the resistance heating layer 9 only outside the damaged portions 26 and 27, and heat is generated. This is because, regardless of where the electrical insulating layer 8 is damaged in the fixing roller 1, power is supplied to the resistance heating layer 9 from the power receiving electrode 12 provided on the fixing roller 1 via the power supply section 17, and the heating section 18 is heated. Is heated, so that S1 and S2 near the inside of both ends 20 of the heat generating portion 18 are always heated.

Accordingly, the temperature control devices 22-1 and 22-2 are attached to the outer surfaces of the rollers S1 and S2 (50 mm) near the insides of both ends 28 of the heat generating portion 18 of the resistance heat generating layer 9 of the fixing roller 1.
By providing -1-2, even if two or more points of the electrical insulating layer 8 of the fixing roller 1 are simultaneously damaged, abnormal heat generation of the fixing roller 1 can be prevented, and the safety of the fixing device is improved. be able to.

FIG. 4 shows a second embodiment of the present invention. In the second embodiment, the same parts as those in the first embodiment will be referred to by the same numerals, and description thereof will be omitted, and different parts will be mainly described. The fixing roller 1 is fixed by a bracket 21 attached to a top plate 19.
The temperature is controlled by a temperature control device 22 such as a thermistor provided and held in contact with the fixing roller 1.

When the temperature control device 22 malfunctions, the overheating prevention devices 23-1 and 23-2 for preventing runaway of the temperature are fixed by the brackets 24-1 and 24-2 which are also mounted on the top plate 19. Is held in contact with the

If the electrical insulating layer 8 of the fixing roller 1 is damaged at two or more points, for example, at the damaged points 26 and 27 at the same time as described above, the current flowing through the resistance heating layer 9 is changed to the damaged points 26 and 27.
Flows through a thin-walled substrate having low resistance. Therefore, current flows through the resistance heating layer 9 only outside the damaged portions 26 and 27, and heat is generated.

This is because, regardless of the location of the fixing roller 1 where the electrical insulating layer 8 is damaged, the resistance heating layer 9 is supplied with electricity from the power receiving electrode 12 provided on the fixing roller 1 via the power supply unit 17, Since the heating portion 18 is heated, the regions S1 and S2 between the vicinity of the inside of both ends 20 of the heating portion 18 and the damaged portions 26 and 27 of the electrical insulating layer 8 are necessarily heated.

Accordingly, the overheat prevention devices 23-1 and 23-2 are mounted on the outer surfaces of the rollers S1 and S2 (50 mm) near the inside of both ends 20 of the heat generating portion 18 of the resistance heating layer 9 of the fixing roller 1 on the outer surface. By providing 23-1 and 23-2, even if two or more points of the electric insulating layer 8 of the fixing roller 1 are damaged at the same time, abnormal heat generation of the fixing roller 1 can be prevented, and the safety of the fixing device is improved. Can be done.

Further, the mounting position of the over-temperature preventing devices 23-1 and 23-2 is set to a region S3 inside the both ends 20 of the heat generating portion 18 of the resistance heat generating layer 9 of the fixing roller 1 and outside the width of the paper passing 35. , S
4, the overheat prevention device 23-
Even if the release layer 11 of the fixing roller 1 is damaged due to the contact abrasion of the fixing rollers 1 and 2, an offset image is not generated on the transfer paper, so that the replacement time of the fixing roller 1 can be extended and the running cost can be reduced. be able to.

[0023]

As described above, the present invention is directed to a fixing roller which is driven to rotate, a temperature control device which contacts the fixing roller and controls the temperature of the fixing roller, In a fixing device having an overheating prevention device to be controlled, the invention according to claim 1 is characterized in that the fixing roller has a hollow cylindrical metal base, an electric insulating layer sequentially layered on the peripheral surface thereof, and a resistance heating. And the temperature control device is provided on the outer surface of the roller near the inside of both ends of the heat generating portion of the resistance heat generating layer of the fixing roller. It is possible to prevent abnormal heat generation of the roller, and it is possible to improve the safety of the fixing device.

According to a second aspect of the present invention, the fixing roller has a hollow cylindrical metal base, an electric insulating layer and a resistance heating layer sequentially laminated on the peripheral surface thereof, Is provided on the outer surface of the roller near the inside of both ends of the heat generating portion of the resistance heat generating layer of the fixing roller. Therefore, even if two or more electric insulating layers of the fixing roller are simultaneously damaged, abnormal heat generation of the fixing roller can be prevented. And the safety of the fixing device can be improved.

According to the third aspect of the present invention, the mounting position of the temperature control device or the excessive temperature rise prevention device is located inside both ends of the heating portion of the resistance heating layer of the fixing roller and outside the paper passing width. Even if the release layer of the fixing roller is damaged due to contact abrasion of the excessive rise prevention device, the offset image does not occur on the transfer paper, so that the replacement time of the fixing roller can be extended and the running cost can be reduced. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a partially longitudinal front view of a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional side view of the fixing roller according to the first embodiment.

FIG. 3 is a front view of the resistance heating layer according to the first embodiment.

FIG. 4 is a partially longitudinal front view of a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fixing roller 2 pressure roller 3 heat-insulating bush 4 bearing 5 fixing side plate 6 gear 7 base 8 electric insulating layer 9 resistance heating layer 11 release layer 12 power receiving electrode 13 leaf spring 14 power supply electrode 17 power supply part 18 heat generation part 19 top plate 20 End 21; 21-1, bracket 22; 22-1, temperature control device 23; 23-1, temperature overheat prevention device 24; 24-1, bracket 26 damaged part 27 damaged part 31 power supply 32 input Circuit 33 CPU 34 Drive 35 Paper feed

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jun Yura 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2H033 AA32 AA42 BA32 BA37 BB19 BB21

Claims (3)

[Claims] 1. A fixing device comprising: a fixing roller that is driven to rotate; a temperature control device that abuts on the fixing roller to control the temperature of the fixing roller; and a temperature rise prevention device that controls runaway of the temperature of the fixing roller. In the apparatus, the fixing roller has a hollow cylindrical metal base, an electrical insulating layer and a resistance heating layer sequentially laminated on the peripheral surface thereof, and a temperature control device is provided for the heating section of the resistance heating layer of the fixing roller. A fixing device, wherein the fixing device is provided on the outer surface of a roller near the inside of both ends. 2. A fixing device comprising: a fixing roller that is driven to rotate; a temperature controller that controls the temperature of the fixing roller in contact with the fixing roller; and an overheating prevention device that controls a temperature runaway of the fixing roller. In the apparatus, the fixing roller has a hollow cylindrical metal base, an electrical insulating layer and a resistance heating layer sequentially laminated on the peripheral surface thereof, and an overheating prevention device is used to heat the resistance heating layer of the fixing roller. A fixing device provided on the outer surface of the roller near the inside of both ends of the roller. 3. The fixing device according to claim 1, wherein the temperature control device or the excessive temperature rise prevention device is mounted at a position inside both ends of the heat generating portion of the resistance heat generating layer of the fixing roller and outside the sheet passing width. Or the fixing device according to 2.