JP2959203B2 - Toner fixing device using positive temperature coefficient thermistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner fixing device using a PTC thermistor as a heat source.

[0002]

2. Description of the Related Art Conventionally, in a dry-type copying machine or the like,
As a fixing device for heating and fixing the toner transferred to the PPC paper, as shown in FIG. 3, which consist of heat radiation roller 2 and the pressing roller 3 with a built-in heat source 1 is well known. As the heat source 1, a halogen lamp, a nichrome wire, a sheathed heater, or the like is used. When the PPC paper S passes between the rollers 2 and 3, the unfixed toner T is heated by the roller 2 heated by heat radiation from the heat source 1. It is heated and fixed.

However, a heat source such as a halogen lamp or a nichrome wire has a complicated voltage control mechanism for maintaining a fixed fixing temperature and is difficult to control itself. In particular, since a large power supply capacity is required, a power supply device is large. This causes a problem such as abnormal heating.

Therefore, it has been proposed to use a PTC thermistor having a safe self-temperature control function as a heat source. As shown in FIG. 4 , the PTC thermistor element 6 and the power supply terminal 7 are sandwiched and held in a heat dissipation roller 5 by fins 8 made of an elastic material. However, this heating device has a problem that the power supply mechanism is complicated in order to cope with the rotation of the heat radiating roller 5.

In order to solve the above problems, a fixing device of a type in which a heat radiating portion is fixed and a heat-resistant film is rotated around the fixing portion has been studied. However, as shown in FIG. 5 , the positive temperature coefficient thermistor element 9 is set to the width W of the maximum size PPC paper.
Need to be juxtaposed. In order to heat the entire paper width at the same temperature, all the positive temperature coefficient thermistor elements 9 need to be planar-polished to the same thickness, and at present, their manufacture is extremely difficult and expensive. .

Accordingly, an object of the present invention is to provide a simple configuration,
It is to provide a toner constant wearing location to dissipate quickly and efficiently constant temperature in the length direction uniform.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method in which a PP is provided between a roller and a radiating head.
C paper is transported and toner is fixed on PPC paper.
A fixing unit, wherein the heat radiating head has a fixing unit
And a circulation passage for the working fluid is integrally formed.
And the radiating head has a self-temperature control function.
And a positive temperature coefficient thermistor having the following.

The heat radiation head is fixed at a fixed position, and heat radiation from the positive temperature coefficient thermistor uniformly and quickly heats the heat radiation head by a working fluid flowing through the circulation passage, for example, Freon, Fluorinert, oil or the like. The PPC paper to which the toner has been transferred passes through the top of the heat dissipation head, and at this time, the toner is heated and fixed. The top of the radiating head is coated with a heat-resistant and smooth resin such as Teflon or a heat-resistant resin film such as polyimide amide at the same speed as the PPC paper transport speed to ensure smooth passage of the PPC paper. Is preferably moved (rotated).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a toner fixing device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a fixing device 10 according to a first embodiment of the present invention.
It has .

The heat generating unit 20 is composed of a heat radiating head 21 having good thermal conductivity and a positive temperature coefficient thermistor element 23. The radiating head 21 is made of aluminum, copper, or an alloy thereof having good thermal conductivity, and a circulation passage 22 for a working fluid is formed in a longitudinal direction (a direction orthogonal to the paper passing direction A of the PPC paper S). Is a fixing unit 21a, and a storage chamber 21b is formed in a lower part. The radiation head 21 having such a shape can be easily manufactured by extrusion molding. The positive temperature coefficient thermistor element 23 is placed in a storage chamber 21b of the heat radiation head 21 via an insulating plate 25 having good thermal conductivity in a state where a power supply terminal 24 is in contact with electrodes (not shown) provided on the front and back surfaces. It is housed and held by the insulating cover 26.

A working fluid, for example,
It is filled with Freon, Florinert, water, oil, etc., and the working fluid circulates by utilizing the gravitational field. To circulate the working fluid, the end of the circulation passage 22 is connected by a header pipe (not shown), and is sealed by vacuum brazing. For the circulation of the working fluid, the passage 22 needs at least an evaporator, a heat insulator, and a condenser, and the PTC thermistor 23 is attached to the evaporator.

The heat-generating unit 20 having the above structure is covered with a stainless steel cooling structure material 15 except for the fixing portion 21a. A polyimideamide heat-resistant resin film 16 is provided around the cooling structure material 15 in the direction of arrow B. It is provided so as to be rotatable. The resin film 16 is for preventing the PPC paper S from abrading the fixing portion 21a.

Further, a pressure roller 11 is provided directly above the fixing portion 21a of the heat radiation head 21 via a resin film 16 so as to be rotatable in the direction of arrow C. The surface of the pressure roller 11 is coated with a material such as Teflon which prevents toner from adhering.

In the above configuration, when a current is supplied, the PTC thermistor element 23 generates heat in accordance with the amount of current,
The heat is conducted to the heat radiating head 21 via the insulating plate 25. Part of the heat directly heats the fixing unit 21a, and most of the heat heats the fixing unit 21a in a state of being uniformly diffused in the longitudinal direction via the working fluid circulating in the passage 22.

The PPC paper S on which the toner T has been transferred is shown in FIG.
The sheet is conveyed in the direction of arrow A from the middle left, and is fed into the fixing device 10. The resin film 16 and the pressure roller 11 are PPC
The PPC paper S is rotated in the directions of arrows B and C at the same speed as the transport speed of the paper S.
1 and pass through the fixing unit 21a. At this time, the toner T is heated via the resin film 16 and P
The image is fixed on the PC paper S. P passing through the fixing unit 21a
The heat dissipation of the PC paper S is immediately promoted via the cooling structure material 15, and the fixing of the toner T is stabilized.

In the above-described embodiment, the heat radiation of the positive temperature coefficient thermistor element 23 is carried out through the radiating head 2 through the circulating working fluid.
Since the heat is transmitted to the first fixing unit 21a, heat can be uniformly and quickly transmitted in the width direction of the PPC sheet S, and the start-up time when the power is turned on can be shortened. In particular, since the heat radiating head 21 is formed as an integrally molded product, the heat transfer efficiency is good, the response to a load change is quick, and the heat generating unit 20 itself can be made compact. In addition, since the heating unit 20 is of a fixed type, the mechanism for supplying power to the PTC thermistor 23 can be simplified. Further, since the positive temperature coefficient thermistor 23 is built in the heat radiating head 21 at a distance from the fixing unit 21a, there is no possibility that dust or dust (including conductive material) adheres, and the progress of deterioration is slowed.

According to the experiment, the length of the heat radiation head 21 is set to 3
When the thickness was set to 00 mm, the temperature variation at each point in the length direction in the fixing unit 21a could be controlled to about 1 to 2 ° C. The heating temperature of the positive temperature coefficient thermistor 23 is set to 80 ° C.
In this case, the fixing section 21a showed stable temperature characteristics at about 76 ° C. On the other hand, when the temperature of the fixing unit 21a was measured after removing the hydraulic fluid, the temperature rose only about 35 to 40 ° C.

FIG. 2 shows a fixing device according to a second embodiment of the present invention.
The heat-dissipating head 31 has an inverted U-shape and has a large number of working fluid circulation passages 32 formed along the curved direction. The positive characteristic thermistor element 33 is sandwiched between the power supply terminals 34 from the left and right, and is attached to the heat radiation head 31 via an insulating plate 35.

The heating unit 30 having the above configuration is incorporated in the fixing device in the same form as that of the first embodiment, and the operation and effect are the same as those of the first embodiment.

The toner fixing device according to the present invention is not limited to the above embodiments, but can be variously modified within the scope of the invention. For example, the heat radiating head 21,3 1
Not need to be a single piece, or may be assembled stampings. On the other hand, the fixing units 21a and 31a
In order to prevent abrasion due to PPC paper, a Teflon resin having excellent heat resistance and abrasion resistance may be coated instead of the resin film 16.

[0021]

As is apparent from the above description, according to the present invention, the radiating head is provided with the circulation passage for circulating the working fluid, and the PTC thermistor having the self-temperature control function is attached. Heat is uniformly and quickly transmitted to the entire radiating head via the working fluid,
Highly responsive and can be controlled at a constant temperature, ideal for fixing toner
It is possible to obtain the Do not equipment. Also, a working fluid circulation passage
Is formed integrally with the heat radiating head,
, And efficient heat transfer becomes possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment der belt toner fixing device of the present invention.

FIG. 2 shows a toner fixing device according to a second embodiment of the present invention;
Sectional drawing of the heating unit formed .

FIG. 3 is a cross-sectional view of a toner fixing device having a heat generating unit .
The figure shows the prior art.

FIG. 4 shows a heat dissipation roller using a positive temperature coefficient thermistor as a heat source.
The cross-sectional view shown shows the prior art.

FIG. 5 shows a positive characteristic circuit used in a fixed heat radiation head .
FIG. 1 shows a perspective view of a mister, prior art.

[Description of Reference Numerals] 10 ... toner fixing device 20, 3 0 ... heating unit 21,3 1 ... radiating head 21a, 31 a ... fixing portion 22,3 2 ... working fluid circulation passage 23, 3 3 ... thermistor element

Claims (1)

(57) [Claims] 1. A PPC sheet between a roller and a heat radiating head.
Is transported and the toner is fixed to fix the toner on PPC paper.
A radiating head having a fixing portion at a top portion and a working flow
A circulating passage for the body is integrally formed, and the heat radiation head has a positive characteristic sensor having a self-temperature control function.
Fixing device using a positive temperature coefficient thermistor,
Place.