JPH09197876A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device where defective fixing is prevented by making fixing temperature by a heating roller uniform,. and the mold-released layer of a surface is prevented form being damaged by preventing the rising of temperature at an end part in the case of continuously passing small-sized transfer paper, and a center part and the end part are separately controlled, and only a part of a fixing roller in a circumfernetial direction is heated though a range to be heated is small and the defective fixing is prevented by preventing temperature drop at the end part for the case of continuously passing large-sized transfer paper. SOLUTION: The unfixed image formed on transfer material is fixed on the transfer material by the heating and pressing of a pair of rotatable rollers 2 having the heating roller 1. Then, the outside and inside surfaces of the heating roller 1 composed of metallic material are coated with insulating material 3 and 4, and a resistant heat generating layer 4 and a heat-resistant mold released layer 4 arranged on the outside surface of the resistant heat generating layer 4 are formed on the outside surface of the heating roller 1 and the resistant heat generating layer 7 is formed at inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device such as a copying machine, a fax machine or a printer.

[0002]

2. Description of the Related Art A typical fixing device of this type as shown in FIG. 9 has a fixing roller 51 in which a fixing heater is installed in contact with the transfer surface side of a transfer material.
And a pressure roller 52 that pressurizes the surface of the fixing roller 51, and heats a transfer material carrying an unfixed image, which is formed by a toner made of a heat-meltable resin or the like by these rollers 51, 52. By applying pressure, the image is fixed on the transfer material. Reference numeral 53 is a coating felt, 54 is a pressure cam for pressing the pressure roller 52, and 55 is a fixing claw.
By the way, in such a fixing device, (1) the heating efficiency of the fixing roller 51 is poor when heated by the fixing heater, and (2)
There is a problem that the temperature of the end portion of the fixing roller 51 drops at the time of rising, and (3) wasteful power consumption is consumed.

In order to solve such a problem, there has been proposed one disclosed in JP-A-5-35137, and the fixing roller 51 is as shown in FIG. , A roller body 61 made of a metal material, and an insulating layer 62 and a resistance heating layer 6 on the outer surface thereof.
3. Has a heat-resistant release layer 64, and the resistance heating layer 63 is the roller body 61.
It has a resistance heating element 65 that is exposed on the surface at one end, extends from this end to the other end, then folds back, and returns to the one end again.
A power supply means 66 for supplying power to the resistance heating element 65 is provided. Then, the resistance heating element 65 is arranged so that the amount of heat generation increases from the center of the roller body 61 to both ends thereof.
Is set to prevent the temperature of the end portion of the fixing roller 51 from dropping at the time of start-up, and to heat only the pressure contact portion between the fixing roller 51 and the pressure roller 52 and the resistance heating element 65 near the upstream side thereof. The purpose is to prevent useless power consumption.

[0004]

The fixing roller 51 is
With the above-mentioned configuration, the problems of the conventional fixing device as described above can be solved, but (4) the resistance heating element 65 should not come into contact with each other. , An insulating layer 62 must be provided between them to isolate them, so that the fixing temperature becomes uneven between the pitches where the resistance heating element 65 is absent, causing fixing failure, and (5) transfer of a small size. When the paper is continuously fed, the heat of the central portion is removed by the transfer paper and the temperature of the same portion is decreased, while the temperature of the end portion is increased and the release layer on the surface is damaged, and (6)
Since the resistance heating layer 63 is a single layer and the central part and the end part cannot be controlled separately, when only a part of the fixing roller 51 in the circumferential direction is heated, the heating range is small, When continuously passing the sheets of size, there is a problem that a large amount of heat is dissipated at the end portion, so that a temperature drop occurs and fixing failure occurs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional ones, to prevent the fixing temperature of the heat roller from becoming uniform, and to prevent fixing failure. In the above, the temperature of the end portion is prevented from rising, the release layer on the surface is not damaged, and the central portion and the end portion can be controlled separately, and the circle of the fixing roller can be controlled. Only heating part of the circumference,
It is an object of the present invention to provide a fixing device in which a heating range is at least prevented from causing a temperature drop at the end portion during continuous large-size paper feeding, and does not cause fixing failure.

[0006]

In order to achieve the above-mentioned object, the present invention according to claim 1 provides an unfixed image formed by a toner on a transfer material by pressing them together. In a fixing device that fixes onto a transfer material by heating and pressing a pair of rotatable rollers, at least one of which is a heat roller that generates heat, the heat roller is made of a metal material, and its inner and outer surfaces are formed of insulating layers. The roller body has a covered roller body, a resistance heating layer is formed on the outer surface of the roller body, and a heat-resistant release layer is formed on the outer surface of the resistance heating layer. Is formed, which allows the power feeding parts to be installed in parallel, and shortens the length of the heat roller.

According to the second aspect of the present invention, the pattern of the resistance heating elements of the resistance heating layer formed on the inner and outer surfaces of the roller body is the same, and the inner resistance is provided between the outer resistance heating elements. It is characterized in that the heating element is arranged so that the other resistance heating layer is positioned between the one resistance heating layer, and heat is generated from almost the entire surface to make the temperature of the heat roller uniform. To do.

According to a third aspect of the present invention, the roller body between the resistance heating layers formed on the inner and outer sides is made of a material such as glass or ceramic having an insulating property and a small specific heat. As a result, it is not necessary to provide a resin-made insulating layer on the roller body, the thermal conductivity is better than that of the resin-made insulating layer, and the specific heat is small, so the rise time is shortened.

According to a fourth aspect of the present invention, the pattern of the resistance heating element of the resistance heating layer formed on the inner and outer surfaces of the roller body is changed so that two patterns are formed on the outer center portion and the end portion of the roller body.
A plurality of temperature detecting means are provided, and a power feeding means for separately supplying power to the resistance heating elements inside and outside the roller body is provided, and the resistance heating elements inside and outside the roller body are separately controlled by the temperature detecting means. This is to prevent the temperature drop at the edge at the rising edge and the temperature rise at the edge at the continuous feeding of small size transfer paper.

The invention according to claim 5 is characterized in that a heat insulating layer made of an insulating material having a low thermoelectric coefficient is provided further inside the resistance heating layer formed inside, and heat radiation into the air is performed. It can prevent and improve the heat efficiency,
The insulation prevents accidents such as short circuits.

According to a sixth aspect of the present invention, the unfixed images formed by the toner made of a heat-meltable resin or the like on the transfer material are in contact with each other and at least one of them is a heat roller which is a heat roller and is rotatable. In a fixing device for fixing on a transfer material by heating and pressurizing a pair of rollers, a pattern of two or more resistance heating elements of a resistance heating layer formed on the surface of the roller body of the heat roller is changed, Two or more temperature detecting means are provided at the outer central portion and the end portion of the roller body, and power feeding means for separately supplying power to the resistance heating elements is provided, and each resistance heating element is separately controlled by the temperature detecting means. The toner is fixed by this,
Prevents defective coloring and uneven coloring.

According to a seventh aspect of the present invention, among the resistance heating elements provided over the entire circumference of the heat roller, only the resistance heating elements respectively disposed near the pressure contact position between the heat rollers and the upstream side in the rotation direction. The present invention is characterized in that it selectively generates heat, and prevents a temperature drop at the end of a large size continuous sheet even if the heating range is small.

[0013]

Embodiments of the present invention will be described with reference to the drawings. In each embodiment, the same parts are designated by the same reference numerals, and the description thereof will be omitted. The different parts will be mainly described.

In the first embodiment shown in FIGS.
Is a heat roller, and this heat roller 1 is made of Al, N
The roller body 2 is made of a metal material having i or Fe as a main material, the outer surface of the roller body 2 is covered with a first insulating layer 3, and the outer surface of the first insulating layer 3 is covered with a first insulating layer 3. A heat-resistant release layer 5 covered with the resistance heating layer 4 and the outer surface of the first resistance heating layer 4 made of fluororesin or the like.
It is covered with. The inner surface of the roller body 2 is covered with the second insulating layer 6, and the inner surface of the second insulating layer 6 is covered with the second resistance heating layer 7.

A first resistance heating element 8 and a second resistance heating element 9 are provided on the first resistance heating layer 4 and the second resistance heating layer 7, respectively. The first resistance heating element 8 is the same as the second resistance heating element 9 and is composed of a plurality of resistance heating elements arranged in parallel with each other in the axial direction of the roller body 2 at predetermined intervals in the circumferential direction. The second resistance heating elements 9 are arranged in a pattern so that the second resistance heating elements 9 are circumferentially shifted in phase so as to be located between the first resistance heating elements 8.

Power supply brushes are provided on the outer and inner peripheral sides of both ends of the roller body 2.
11 and 12 are arranged, the power feeding brush 11 is in sliding contact with both side electrode portions 13 of the first resistance heating layer 4, and the power feeding brush 12 is in sliding contact with both side electrode portions 14 of the second resistance heating layer 7. Power supply to the two-resistance heating layers 4 and 7 can be controlled separately. 16 indicates a central thermistor.

The second embodiment shown in FIG. 3 is a roller body 2
Is made of a material having heat insulating glass such as glass, enamel or ceramic having an insulating property and a small specific heat, and the first and second resistance heating layers 4 and 7 having different patterns are formed on the outer and inner sides thereof. The heat-resistant release layer 5 and the insulating layer 6 are formed on the outer and inner sides thereof.

The fourth embodiment shown in FIG. 4 is a modification of the third embodiment, in which the structure of the first resistance heating layer 4 is different, and the first resistance heating element 8 in this first resistance heating layer 4 is The central heating element portion 17 is inside the first resistance heating layer 4, and the heating element portions at both ends thereof are exposed to the outside to form the electrode portion 13.

The fifth embodiment shown in FIG. 5 is a modification of the fourth embodiment, in which the central heating element part 17 of the first resistance heating element 8 in the first resistance heating layer 4 is the left and right heating element parts 17. -1,2
, Which are connected by conductors 18.

The sixth embodiment shown in FIGS. 6 to 8 has a roller main body 22 constructed in the same manner as in the above-mentioned respective embodiments, and the outer surface of the roller main body 22 has a central resistance heating portion 23 and end resistance heating. The central resistance heating element 23 is covered with a portion 24, and further covered with an insulating layer 26.
Are embedded to expose the electrode portions 28 and 29 on the surface of the insulating layer 26. End resistance heating elements 31 and 32 are embedded in both ends of the end resistance heating section 24, and the electrode sections 33 and 34 are formed into insulating layers.
Exposed on the surface of 26. Further, in this embodiment, the patterns of the central resistance heating element 27 and the end resistance heating elements 31, 32 are out of phase in the circumferential direction, but they may be at the same position.

Power supply brushes 3 are provided on the outer peripheral sides of both ends of the roller body 22.
6, 37, 38, 39 are arranged, the power feeding brushes 36, 37 are in sliding contact with the electrode portions 28, 29 of the central resistance heating element 27, and the power feeding brushes 38, 39.
Is in sliding contact with the electrode portions 33 and 34 of the end resistance heating elements 31 and 32, and the power supply to the first and second resistance heating layers 4 and 7 can be separately controlled by the control means (not shown). 41 is a central thermistor and 42 is an end thermistor. The power supply brushes 36, 37 are brought into sliding contact with the electrode portions 28, 29 of the central resistance heating element 27, so that the heat roller 20
And the pressure contact position of the pressure roller 21 and its upstream vicinity, that is, in the circumferential direction of the heat roller 20 as shown in FIG.
Only the heating resistor in the area A, which is about 1/4, generates heat.

When a transfer sheet is passed through the fixing device having the sixth embodiment, the temperature of the end portion of the heat roller 20 rises when a small-sized transfer sheet is passed. The end thermistor 42 detects this, and the control means adjusts the voltage applied to the end resistance heating elements 31, 32 of the end resistance heating section 24, so that the temperature of the end resistance heating elements 31, 32 rises. Prevent. Further, when the heat roller 20 rises, the temperature of the end portion of the heat roller 20 is lower than that of the central portion. The end thermistor 42 detects this, adjusts the voltage applied to the end resistance heating elements 31 and 32 of the end resistance heating section 24, and raises the temperature of the end resistance heating elements 31 and 32. To prevent poor fixing.

[0023]

The present invention is as described above. According to the invention of claim 1, in the fixing device, the heat roller is made of a metal material, and the inner and outer surfaces of the roller body are covered with an insulating layer. This roller body has a resistance heating layer formed on the outer surface thereof, a heat-resistant release layer disposed on the outer surface of the resistance heating layer, and a resistance heating layer formed on the inner side of the roller body. Since the resistance heating layer is formed on the inner and outer surfaces of the roller body, the power feeding parts can be installed in parallel, the length of the heat roller can be shortened, and the materials used can be saved. In addition to being able to reduce the cost, there is an effect that processing and assembling are easy.

According to a second aspect of the present invention, the pattern of the resistance heating elements of the resistance heating layer formed on the inner and outer surfaces of the roller body is the same, and the inner resistance is provided between the outer resistance heating elements. Since the heating element is arranged so as to be positioned, there is an effect that the temperature of the heat roller can be made uniform and the occurrence of fixing failure can be prevented.

According to the third aspect of the present invention, the roller main body between the resistance heating layers formed on the inner and outer sides is made of a material such as glass or ceramic having an insulating property and a small specific heat. It is not necessary to provide an insulating layer made of resin on the roller body, the thermal conductivity is better than that of the insulating layer made of resin, and the specific heat is small, so that the rise time can be shortened. .

According to a fourth aspect of the present invention, the pattern of the resistance heating element of the resistance heating layer formed on the inner and outer surfaces of the roller body is changed so that the center portion and the end portion of the roller body have two patterns.
Since more than one temperature detecting means is provided, and further, power feeding means for separately feeding power to the resistance heating elements inside and outside the roller body are provided, the resistance heating elements inside and outside the roller body are separately controlled by the temperature detection means, There is an effect that it is possible to prevent the temperature drop at the end portion at the time of rising and the temperature rise at the end portion at the time of continuous feeding of small-sized transfer paper.

According to the fifth aspect of the present invention, since a heat insulating layer made of an insulating material having a low thermoelectric coefficient is provided further inside the resistance heating layer formed inside, heat dissipation to the air is prevented,
The thermal efficiency can be improved, and the insulation can prevent an accident such as a short circuit.

According to a sixth aspect of the present invention, in the fixing device, the pattern of two or more resistance heating elements of the resistance heating layer formed on the surface of the roller body is changed, and the outer central portion of the roller body is formed. Two or more temperature detecting means are provided at the end portion, and a power feeding means for separately supplying power to each resistance heating element is provided, and each resistance heating element is separately controlled by the temperature detecting means, so that toner fixing and color development are performed. This has an effect of preventing the occurrence of defects and uneven coloring.

According to the invention described in claim 7, among the resistance heating elements provided over the entire circumference of the heat roller, only the resistance heating elements respectively disposed near the pressure contact position between the heat rollers and upstream in the rotational direction. Since the sheet is selectively heated, there is an effect that it is possible to prevent a temperature drop at the end portion when a large-sized continuous sheet is passed even if the heating range is small.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a first embodiment of the present invention.

FIG. 2 is a central longitudinal side view of the same.

FIG. 3 is a side view of a central longitudinal section of a second embodiment of the present invention.

FIG. 4 is a developed plan view of the third embodiment of the present invention.

FIG. 5 is a developed plan view of a fourth embodiment of the present invention.

FIG. 6 is a perspective view of a fifth embodiment of the present invention.

FIG. 7 is a vertical sectional front view of the same.

FIG. 8 is an explanatory diagram of a contact portion between the power feeding brush and the electrode portion of the above.

FIG. 9 is a front view of a conventional fixing device of the same type as the present invention.

FIG. 10 is a partially cutaway perspective view of the above heat roller.

[Explanation of symbols]

 1 Heat Roller 2 Roller Body 3 First Insulating Layer 4 First Resistance Heating Layer 5 Heat Resistant Release Layer 6 Second Insulation Layer 7 Second Resistance Heating Layer 8 First Resistance Heating Element 9 Second Resistance Heating Element 11 Power Supply Brush 12 Power Supply Brush 13 Electrode part 14 Electrode part 16 Central thermistor 17 Central heating element part 18 Conductor 20 Heat roller 21 Pressure roller 22 Roller body 23 Central resistance heating part 24 Edge resistance heating part 26 Insulation layer 27 Central resistance heating element 28 Electrode part 29 Electrode 31 End resistance heating element 32 End resistance heating element 33 Electrode section 34 Electrode section 36 Feed brush 37 Feed brush 38 Feed brush 39 Feed brush 41 Central thermistor 42 End thermistor

Claims (7)

[Claims] 1. An unfixed image formed by a toner made of a heat-meltable resin or the like on a transfer material is heated by a pair of rotatable rollers which are heat rollers in which at least one of them is heated by pressing them against each other. In the fixing device for fixing the unfixed image on the transfer material by pressure, the heat roller is made of a metal material and has a roller body whose inner and outer surfaces are covered with an insulating layer, and the roller body has an outer surface. A fixing device comprising a resistance heating layer formed on a surface thereof, a heat-resistant release layer disposed on an outer surface of the resistance heating layer, and a resistance heating layer formed inside a roller body. 2. The pattern of the resistance heating elements of the resistance heating layer formed on the inner and outer surfaces of the roller body is the same, and the inner resistance heating element is positioned between the outer resistance heating elements. The fixing device according to claim 1, wherein the fixing device is arranged. 3. The roller body between the resistance heating layers formed on the inner and outer sides is made of a material having a small specific heat and having an insulating property such as glass or ceramics. The fixing device described. 4. The pattern of the resistance heating element of the resistance heating layer formed on the inner and outer surfaces of the roller body is changed, and two or more temperature detecting means are provided at the outer center portion and the end portion of the roller body. 4. The resistance heating elements inside and outside the roller body are separately provided with power feeding means, and the resistance heating elements inside and outside the roller body are separately controlled by the temperature detecting means. The fixing device according to any one of claims. 5. The fixing device according to claim 1, further comprising a heat insulating layer made of an insulating material having a low thermoelectric coefficient, further inside the resistance heating layer formed inside. . 6. An unfixed image formed by a toner made of a heat-fusible resin or the like on a transfer material is heated by a pair of rotatable rollers which are heat rollers in which at least one of them is heated by being pressed against each other. In a fixing device for fixing an unfixed image on a transfer material by pressure, a pattern of two or more resistance heating elements of a resistance heating layer formed on the surface of the roller body of the heat roller is changed to change the pattern of the roller body. The present invention is characterized in that two or more temperature detecting means are provided at an outer central portion and an end portion, and further, power feeding means for separately feeding power to each resistance heating element is provided, and each resistance heating element is separately controlled by the temperature detecting means. And fixing device. 7. Among the resistance heating elements provided over the entire circumference of the heat roller, only the resistance heating elements respectively disposed near the pressure contact position between the heat rollers and upstream in the rotation direction are selectively caused to generate heat. The fixing device according to claim 6, wherein: