JPH11282300A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent high voltage and high current from creeping to a secondary circuit from a primary side by providing an insulating means having specified withstand voltage between the surface of a fixing roller and a thermistor element. SOLUTION: This device is provided with an insulating plate 601 being an insulating means satisfying >=1500 V withstand voltage between the surface of the fixing roller 100A and the thermistor element 603 of a thermistor 600, and a discharging brush 700 being a discharging means grounding the conductive mold-released layer 104 on the surface of the fixing roller 100A or a pressure roller 200. As for the fixing roller 100A; a thin metallic base substance 101 is set as base substance and a 1st electric insulating layer 102 and a resistance heating layer 103 are successively laminated on the outer surface of the base substance 101. The surface temperature of the fixing roller 100A is detected by the thermistor 600, and the supply power to the resistance heating layer 103 of the fixing roller 100A is controlled based on an output signal from the thermistor 600 by a temperature controller 623 so that the surface temperature of the fixing roller 100A may be the specified temperature.

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 electrophotographic copying machine, a printer, a facsimile, and the like, and more particularly to a fixing device having a uniform temperature distribution and capable of saving power. .

[0002]

2. Description of the Related Art Generally, in an electrophotographic copying machine, a printer, a facsimile, and the like, a fixing device in which a pressure roller is pressed against a fixing roller is used. In this fixing device, while rotating the heated fixing roller, the printing paper on which the toner is transferred is layered between the rotating fixing roller and the pressing roller, and the toner is heated and melted and fused on the printing paper. Is what you do.

[0003] Due to recent environmental regulations and increasing awareness of environmental protection, it has been practiced to reduce the power consumption of various electrophotographic apparatuses by shutting off the power to the fixing heater when not in use and supplying power only when necessary. Have been done.

In such an energy-saving electrophotographic apparatus,
During printing, the surface temperature of the fixing roller must immediately reach the set temperature. In order to satisfy this requirement, in a method of performing a halogen lamp from the inside of the 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 copying 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.

However, when the surface heating roller is controlled by a conventional control system, the insulating layer formed on the outer surface or the inner surface of the surface heating roller is broken, and the power supply line to the heating roller and the signal line of the thermistor are changed. If contact occurs, the temporary high-voltage / high-current sneak into the secondary circuit, causing a dangerous state.

To solve the problem, Japanese Patent Application Laid-Open Nos. 9-114314 and 9-1278 disclose a fixing device for preventing a high voltage and a high current from flowing into a secondary circuit from a temporary side.
No. 14 is known.

Japanese Patent Application Laid-Open No. Hei 9-114314 discloses a fixing device provided with an intermediate member for maintaining a distance between a temperature detecting means and the surface of a fixing roller at a predetermined insulating distance or more.

In the fixing device disclosed in Japanese Patent Application Laid-Open No. 9-127814, the surface of the resistance heating layer is formed to a thickness of 0.4 mm or less.
It is coated with a heat-resistant electrical insulating layer having a withstand voltage of 3000 [V] or more, and the temperature detecting surface of the thermistor TM is also 0.4 mm thick.
mm or less and covered with a heat-resistant electric insulating layer having a withstand voltage of 3000 [V] or more, and a thermistor T interposed between the two electric recording insulating layers.
The point at which M is brought into contact with the resistance heating layer is shown.

In these fixing devices, when the fixing roller is in an electrically floating state, it is possible to prevent high voltage and high current from flowing into the secondary circuit from the temporary side by the insulating plate.

[0010]

However, when the fixing roller is electrically floated, the fuse may not be cut off depending on the state of destruction. For example, if there are several breaks, the leakage may occur from the heat-generating portion of the surface heat-fixing roller to the fixing roller core, and the current may return to the heat-generating portion again from another break. Since the fuse is not cut off, current may continue to flow.

In view of the above, the present invention can prevent high voltage and high current from flowing into the secondary circuit from the temporary side, and can reliably cut off the fuse and stop supply of current when a leak occurs. An object of the present invention is to provide a fixing device that can perform the fixing.

[0012]

According to a first aspect of the present invention, there is provided a fixing device comprising: a fixing roller which is driven to rotate; and a pressure roller which is in contact with the fixing roller at a predetermined pressure and is rotatable. A fixing device for inserting a transfer paper having the toner transferred between the two rotating rollers, heating and melting the toner to fuse the toner on the transfer paper, wherein the fixing roller includes a hollow cylindrical metal base; An electric insulating layer satisfying a withstand voltage of 1500 V or more and a resistance heating layer heating a fixing roller are laminated on the outer surface or the inner surface of the hollow cylindrical metal substrate, and the outer surface of the fixing roller and the pressure roller is electrically conductive. Provided with a release layer having heat resistance and release properties, a thermistor that contacts the fixing roller and detects the temperature of the fixing roller, and a temperature control device that performs temperature control according to the output of the thermistor. ing In wearing device, voltage resistance between the fixing roller surface and the thermistor of the thermistor element 1
It is characterized in that an insulating means that satisfies 500 V or more is provided, and a charge removing means that grounds a surface release layer of the fixing roller or the pressure roller is provided.

With this configuration, even if the insulating layer formed on the outer surface or the inner surface of the fixing roller is broken and the power supply line to the heating roller and the signal line of the thermistor come into contact with each other, the thermistor element and Insulating means provided between the fixing roller and the fixing roller can prevent high voltage and high current from flowing into the secondary circuit from the primary side, and provide a static elimination means for grounding the release layer in the direction of the fixing roller. Thereby, a high voltage and a high current from the fixing roller can be dropped to the ground.

According to a second aspect of the present invention, in the fixing device according to the first aspect, at least a contact side of the insulating unit with the fixing roller is formed of a heat-resistant film having a releasing property and an insulating property. It is characterized by being coated.

In this configuration, since the heat-resistant film is made of a material having heat resistance, release property and insulating property, the insulating effect can be further improved and the safety can be improved.

According to a third aspect of the present invention, in the fixing device of the first aspect, the insulating means has a volume resistance of at least 10 ¹⁴ Ωcm at room temperature, a thermal conductivity of at least 150 W / m · K, and a density of 2. 9 to 3.5 g / cm ³ , specific heat 0.7 to
It is characterized by being formed using a high thermal conductivity material having a characteristic of 0.8 J / g ° C.

In this configuration, the insulation means has a volume resistance of at least 10 ¹⁴ Ωcm, a thermal conductivity of at least 150 W / m · K, a density of 2.9 to 3.5 g / cm ³ , and a specific heat of 0.7 to 0.8 J / cm ² .
Since a high thermal conductivity material having a characteristic of g ° C. is used, the temperature of the fixing roller can be controlled without substantially deteriorating the thermal response to the thermistor element.

According to a fourth aspect of the present invention, in the fixing device of the first aspect, the insulating means has a volume resistance of 10 ¹⁴ Ωcm or more at room temperature and a thermal conductivity of 75 to 150 W / m · cm.
K, density 2.0 g / cm ³ or less, the specific heat 0.7~0.8J
/ G ° C., characterized in that it is made of a low density, low specific heat material.

In this configuration, the insulation means has a volume resistance of 10 ¹⁴ Ωcm or more, a thermal conductivity of 75 to 150 W / m · K,
Since a low density material having a density of 2.0 g / cm ³ or less and a specific heat of 0.7 J / g ° C. is used, this low density material has a lower thermal conductivity than the above high thermal conductive material, but has a lower density and thus has a lower heat capacity. , The thermal responsiveness substantially equal to that of the high thermal conductive material can be obtained, and the cost can be reduced.

According to a fifth aspect of the present invention, in the fixing device according to the first aspect, the thickness of the insulating means is set to 0.1.
4 to 0.6 mm.

In this configuration, by setting the thickness of the insulating means between the thermistor element and the surface of the fixing roller to 0.4 to 0.6 mm, the pressure resistance can be satisfied and the heat capacity can be reduced. Responsiveness is hardly degraded, and the fixability can be stabilized.

The fixing device according to a sixth aspect of the present invention is the fixing device according to the fifth aspect, wherein an insulation distance between the thermocouple element of the thermistor and a contact portion on the surface of the fixing roller is 2.5.
It is characterized by a length of up to 15 mm.

In this configuration, the insulation distance between the thermistor element and the contact portion on the surface of the fixing roller is 2.5 to 15 mm.
By satisfying the pressure resistance, the insulation distance can be shortened and the size of the insulation means can be reduced and the heat capacity can be reduced as compared with the conventional case. Stability can be achieved.

According to a seventh aspect of the present invention, in the fixing device according to the fifth or sixth aspect, the insulating means is provided with a fixing portion for fixing a thermocouple element of a thermistor. Features.

In this configuration, since the fixing means for fixing the thermocouple element of the thermistor is provided in the insulating means, the insulation distance between the thermocouple element and the contact part on the surface of the fixing roller is ensured. Therefore, the tolerance of the insulation distance can be reduced, and the insulation distance can be shortened, the size of the insulation means can be reduced, and the heat capacity can be reduced. Without fixing, the fixing property can be stabilized.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a main part showing a fixing device according to a first embodiment of the present invention. As shown in FIG. 1, the fixing device of the first embodiment includes a fixing roller 100A that is driven to rotate, and a pressure roller 200 that is in contact with the fixing roller 100A with a predetermined pressure and is rotatable. A fixing device in which a transfer paper having toner transferred thereto is inserted between a pressure roller 200 and the toner is heated and melted to fuse the toner onto the transfer paper. The fixing roller 100A is a thin metal substrate that is a hollow cylindrical metal substrate. 101, an outer surface of a thin metal substrate 101, a first and an electrically insulating layers 102 and 105 satisfying a withstand voltage of 1500 V or more, and a resistance heating layer 103 for heating a fixing roller between these layers;
Conductive release layers 104 and 201 having conductivity, heat resistance and release properties are provided on the outer surfaces of the fixing roller 100A and the pressure roller 200, respectively, and contact the fixing roller 100A to detect the temperature of the fixing roller 100A. Performing thermistor 60
0 and a temperature control device 623 that performs temperature control according to the output of the thermistor 600.
An insulating plate 601 is provided between the surface of the fixing roller 100A and the thermistor element 603 of the thermistor 600. The insulating plate 601 satisfies the withstand voltage of 1500 V or more, and the conductive release of the surface of the fixing roller 100A or the pressure roller 200 is performed. It is characterized in that a static elimination brush 700 which is a static elimination means for grounding the layers 104 and 201 is provided.

In this fixing device, the pressing roller 200 is pressed against the fixing roller 100A with a constant pressing force by a biasing means such as a spring (not shown).

The fixing roller 100A is attached to the fixing side plates 400a and 400b through insulating bushes 401a and 401b having insulation properties and metal bearings 402a and 402b. Further, the gear 403 engages with a drive source (not shown) to rotate the fixing roller 100A.

The fixing roller 100A is based on a thin metal base 101 made of a thin pipe of Al or Fe, and has a thickness of about 0.2 to 0.8 mm. On the outer surface of the thin metal substrate 101, a first electrically insulating layer 10 made of a material such as a polyimide film or ceramic is provided.
2 and a resistance heating layer 103 made of a metal such as SUS or silver and glass powder are sequentially laminated. Further, a second electric insulating layer 105 made of the same material as the first electric insulating layer 102 is laminated on the outside of the resistance heating layer 103, and the outermost conductive insulating material such as Teflon, which has conductivity, heat resistance and mold release properties. A mold layer 104 is formed. Power receiving electrodes 50 for supplying current to the resistance heating layer 103 are provided at both ends of the resistance heating layer 103.
0a, b are provided, and the power supply electrodes 501a, b are pressed against the power receiving electrodes 500a, 500b by a constant load by the leaf springs 502a, 502b. Electric power is supplied to the resistance heating layer 103 while the power supply electrodes 501a and 501b and the power receiving electrodes 500a and 500b slide.

The conductive release layer 1 of the fixing roller 100A
A static elimination brush 700 is in contact with the surface of 04 and is electrically dropped to ground. As shown by a two-dot chain line in FIG. 2, the charge removing brush 700 may be in contact with the conductive release layer 201 of the pressure roller 200.

Further, a thermistor 600 utilizing the fact that the resistance is a function of temperature is provided on the surface of the fixing roller 100A.
And the thermistor 600 fixes the fixing roller 1
00A is detected, and the temperature of the fixing roller 1 is determined based on the output signal of the thermistor 600 by a temperature controller described later.
The power supplied to the resistance heating layer 103 of 00 A is supplied to the fixing roller 1.
The surface temperature of 00A is controlled to be a predetermined temperature.

FIG. 2 is a diagram showing the details of the structure of the thermistor 600. The thermistor element 603 is supported by a support 602 made of a heat-resistant elastic material such as silicone sponge, and is provided on the fixing roller 100A side of the support 602 by insulating means having heat resistance and insulation so as to contact the surface of the thermistor element 603. An insulating plate 601 is provided. The support 602, the thermistor element 603, and the insulating plate 601 are integrally contacted with the fixing roller 100A by a leaf spring 605 made of a spring material.

The insulating plate 601 has a volume resistance of 10 ¹⁴ Ω at room temperature.
cm or more, thermal conductivity of 150 W / m · K or more, density 2.9
It is made of a high thermal conductivity material such as AlN (aluminum nitride) having characteristics of up to 3.5 g / cm ³ and specific heat of 0.7 to 0.8 J / g ° C. Therefore, thermistor element 6
Fixing roller 1 with almost no thermal response to 03
The temperature of 00A can be controlled.

The insulating plate 601 has a volume resistance of 10 ¹⁴ Ω.
low-density material such as BN (boron nitride) having the characteristics of not less than 75 cm, not more than 75-150 W / m · K, not more than 2.0 g / cm ^{3, and not} more than 0.7-0.8 J / g ° C. specific heat. May be used. This low-density material has a lower thermal conductivity than a high-thermal-conductivity material such as AlN (aluminum nitride), but has a small density and therefore a small heat capacity, so that it has approximately the same thermal response as the high-thermal-conductivity material. And the cost can be reduced.

The insulating plate 601 has a withstand voltage of 1500 V.
Is satisfied, the thickness t of the insulating plate 601 between the thermistor element 603 and the surface of the fixing roller needs to be 0.4 mm or more. However, if the thickness is too large, the heat capacity of the insulating plate 601 increases, and the response speed of the thermistor element 603 decreases. Therefore, in order to increase the response speed, it is desirable to reduce the thickness as much as possible. Therefore, it is considered optimal to set the thickness t of the insulating plate 601 between the thermistor element 603 and the surface of the fixing roller 100A to 0.4 to 0.6 mm.

As described above, the thickness t of the insulating plate 601 between the thermistor element 603 and the surface of the fixing roller 100A is set to 0.
By setting the thickness to 4 to 0.6 mm, the pressure resistance can be satisfied and the heat capacity can be reduced. Therefore, the responsiveness of the thermistor element 603 is hardly deteriorated, and the fixing property can be stabilized.

It has been experimentally confirmed that the insulation distance 1 between the thermistor element 603 and the contact portion of the surface of the fixing roller 100A must be 2.5 mm or more in order to satisfy the withstand voltage of 1500 V. . In order to prevent the response speed of the thermistor element 603 from decreasing, the insulating plate 60 is used.
1 must be as small as possible. Therefore, it is considered optimal to set the insulation distance 1 between the thermistor element 603 and the contact portion of the surface of the fixing roller 100A at 2.5 to 15 mm.

As described above, by setting the insulation distance 1 between the thermistor element 603 and the abutting portion on the surface of the fixing roller 100A to 2.5 to 15 mm, the pressure resistance is satisfied and the insulation distance 1 Is shortened, the size of the insulating plate 601 is reduced, and the heat capacity can be reduced. Therefore, the response of the thermistor element 603 is hardly deteriorated, and the fixing property can be stabilized.

In order to secure the insulation distance l, the thermistor element 60 is placed on the side of the insulating plate 601 opposite to the fixing roller.
A fixing portion 601a for fixing the position of No. 3 is provided.

As described above, by providing the fixing portion 601a for fixing the position of the thermistor element 603 on the opposite side of the insulating plate 601 from the fixing roller, the gap between the thermistor element 603 and the contact portion on the surface of the fixing roller 100A is provided. Since the insulation distance l can be ensured, the tolerance of the insulation distance l can be reduced, and the insulation distance l can be shortened to reduce the size of the insulating plate and reduce the heat capacity. The responsiveness of the thermistor element hardly deteriorates, and the fixing property can be stabilized.

Further, a thermistor element 603 and a support 60 are provided by a thermistor film 604 which is a heat-resistant film.
2. The outside of the insulating plate 601 and the leaf spring 605 are integrally coated.

Since the thermistor film 604 is made of a material having heat resistance, release property, insulating property and smoothness such as polyimide and Teflon, the thermistor element 603, the support 602 and the insulating plate 601 are integrated. By coating, the insulating effect can be further improved, and the safety can be improved. Further, even if the thermistor 600 slides with the fixing roller 100A, the thermistor film 6
Because of the interposition of 04, wear is small and adhesion of toner and the like can be prevented. In addition, the support 602 may be omitted from the above configuration, and the thermistor element 603 may be provided directly on the leaf spring 605.

FIG. 3 is a sectional view showing a main part of a fixing device according to a second embodiment of the present invention. As shown in FIG. 3, similarly to the fixing device of the first embodiment, the fixing device of the second embodiment includes a fixing roller 100B that is driven to rotate, and a rotatable pressing roller that is brought into contact with the fixing roller 100B with a predetermined pressure. A fixing device including a pressure roller 200, wherein the transfer paper having the toner transferred thereto is inserted between the fixing roller 100 </ b> B and the pressure roller 200, and the toner is heated and melted and fused on the transfer paper; Has a thin metal substrate 101. Further, a conductive release layer 104 having conductivity, heat resistance and release properties is provided on the outer surface of the thin metal substrate 101, and an electric insulating layer 102 satisfying a withstand voltage of 1500 V or more is provided on the inner surface of the thin metal substrate 101. And a resistance heating layer 103 for heating the fixing roller are sequentially laminated, and a conductive release layer 201 having conductivity, heat resistance and releasability is provided on the outer surface of the pressure roller 200, and is brought into contact with the fixing roller 100B. The fixing device includes a thermistor 600 for detecting the temperature of the fixing roller 100B and a temperature control device 623 for controlling the temperature in accordance with the output of the thermistor 600. Between the fixing roller 100B and the pressure roller 200 is provided. Sexual release layer 104 or 201
, A static elimination brush 700 for grounding is provided.

In this fixing device, the pressing roller 200 is pressed against the fixing roller 100B by a spring (not shown) with a constant pressing force. The fixing roller 100B includes insulating bushes 401a and 401b having insulating properties, and a metal bearing 402.
a, b are attached to the fixing side plates 400a, 400b. Further, the gear 403 engages with a drive source (not shown) to perform rotational driving. The fixing roller 100B is made of Al or Fe
The base is a thin-walled metal base 101 made of a thin pipe having a thickness of about 0.2 to 0.8 mm. An electric insulating layer 102 made of a material such as a polyimide film or a ceramic
A metal such as US or silver and a resistance heating layer 103 made of glass powder or the like are sequentially laminated. Further, a conductive release layer 104 such as Teflon having heat resistance and release properties is formed on the outer surface of the thin metal substrate. Resistance heating layer 10
3 are provided at both ends with disk-shaped power receiving electrodes 500a and 500b for supplying electricity to the resistance heating layer 103, and leaf springs 502a and
The power supply electrodes 501a and 501b are pressed with a constant load by b. The power supply electrode 50 is connected to the resistance heating layer 103.
Electric power is supplied to the power receiving electrodes 500a and 500a while sliding. By forming the power receiving electrode in a disk shape, the sliding portion can be positioned at the center of rotation, and the relative speed of the sliding portion can be reduced to reduce sliding friction. Further, instead of making the power receiving electrode into a disk shape, it may be an electrode having a longitudinal shape including a diameter, or may be an electrode having a longitudinal shape including a radius. It is only necessary that a part be arranged.

As in the fixing device of the first embodiment, the static elimination brush 700 is in contact with the fixing roller 100B and is electrically grounded. FIG.
As shown by the two-dot chain line, the pressure roller 200 may be in contact with the conductive release layer 201.

In the fixing device of the second embodiment, the structure of the thermistor 600 is the same as that of the first embodiment.

FIG. 5 is a circuit diagram including the temperature control device 623 used in the first and second embodiments.

In FIG. 5, the fixing rollers 100A, 100
The thermistor element 603 abutting on the fixing roller 100B via the insulating plate 601 is a fixing roller 100A, which is a surface heat roller.
The resistance value changes according to the temperature of 100B, and the detection potential Vr is divided by the thermistor element 603 and the resistor R1.
Get. The detected potential Vr is input to the temperature control device 623, and the temperature control device 623 outputs an output signal for controlling energization to the surface heat roller to the TRC (triac) 616 through the photocoupler 624 in accordance with the input signal. It is configured as follows.

When the fixing rollers 100A and 100B, which are the surface heating rollers, are controlled by such a control system, the insulating layers 102 and 105 formed on the outer or inner surfaces of the fixing rollers 100A and 100B are broken, and the fixing rollers 100A and 100B are broken. ,
If the power supply line to the 100B and the thermistor signal system line come into contact with each other, there is a possibility that a high voltage and a high current on the primary side flow into the secondary side circuit.

At this time, an insulating plate 601 provided between the thermistor element 603 and the fixing rollers 100A and 100B prevents high voltage and high current from flowing from the primary side to the secondary side circuit, and furthermore, fixes the fixing roller 100A. , 100
B (or the pressure roller 200) on the surface of the neutralizing brush 700
Is brought into contact with the fixing rollers 100A and 100B.
By lowering the higher voltage and higher current to the ground, the fuse 615 can be surely cut off and the supply of the current from the power supply 610 can be stopped.

Further, the charge removing brush 700 also prevents the toner from adhering to the surfaces of the fixing rollers 100A and 100B and the pressure roller 200 due to static electricity, and can improve the image quality by reducing the electrostatic offset.

In the above embodiment, the metal bearing 40
Although 2a and 2b are used, an insulating resin bearing may be used instead of the metal bearings 402a and 402b.

Although the case where the insulating plate is used as the insulating means has been described, the shape may be other than the plate shape.

Further, the case where the charge removing brush is used as the charge removing means has been described, but other means may be used as long as the surface release layer of the fixing roller or the pressure roller can be grounded.

The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention.

[0056]

As is apparent from the above description, according to the fixing device of the first aspect, there is provided a fixing roller which is driven to rotate, and a pressure roller which is in contact with the fixing roller at a predetermined pressure and is rotatable. A fixing device for inserting a transfer paper having the toner transferred between the two rotating rollers, heating and melting the toner and fusing the toner on the transfer paper, wherein the fixing roller includes a hollow cylindrical metal substrate, An electrical insulating layer satisfying a withstand voltage of 1500 V or more and a resistance heating layer for heating a fixing roller are laminated on the outer surface or inner surface of the cylindrical metal substrate, and the outer surface of the fixing roller and the pressing roller has conductivity and heat resistance. A release layer having a releasability and a releasability, comprising a thermistor that contacts the fixing roller to detect the temperature of the fixing roller, and a temperature control device that performs temperature control according to the output of the thermistor. Fixing equipment In, voltage resistance 1500V between the fixing roller surface and the thermistor of the thermistor element
In addition to providing insulating means that satisfies the above and providing static elimination means for grounding the surface release layer of the fixing roller or pressure roller, the secondary circuit is provided by the insulating means provided between the thermistor element and the fixing roller. High voltage and high current from the primary side of the fixing roller can be prevented, and by providing a static eliminator for grounding the release layer on the side of the fixing roller, high voltage and high current from the fixing roller can be grounded. Can be dropped.

According to a second aspect of the present invention, there is provided a fixing device according to the first aspect, wherein at least a contacting side of the insulating unit with the fixing roller has a releasing property and an insulating property. Since the heat-resistant film is made of a material having heat resistance, release property and insulating property, the insulating effect can be further improved and safety can be improved.

According to the fixing device of the third aspect, in the fixing device of the first aspect, the insulating means has a volume resistance of 10 ¹⁴ Ωcm or more at room temperature and a thermal conductivity of 150 W / m · cm.
K or more, density 2.9 to 3.5 g / cm ³ , specific heat 0.7
Since it is made of a high thermal conductivity material having a characteristic of about 0.8 J / g ° C., the temperature of the fixing roller can be controlled without substantially deteriorating the thermal response to the thermistor element.

According to the fixing device of the fourth aspect, in the fixing device of the first aspect, the insulating means has a volume resistance of at least 10 ¹⁴ Ωcm at room temperature and a thermal conductivity of 75 to 150 W.
/ M · K, density 2.0g / cm ³ or less, specific heat 0.7 ~
The low-density material has a lower thermal conductivity than the above-described high-thermal-conductivity material because of its low-density, low-specific-heat material having a characteristic of 0.8 J / g ° C. Thus, it is possible to obtain substantially the same thermal responsiveness as that of the high heat conductive material and to reduce the cost.

According to the fixing device of the fifth aspect, in the fixing device of the first aspect, since the thickness of the insulating means is 0.4 to 0.6 mm, the insulating means satisfies pressure resistance. The heat capacity can be reduced, the responsiveness of the thermistor element hardly deteriorates, and the fixing property can be stabilized.

According to the fixing device of the sixth aspect, in the fixing device of the fifth aspect, the insulation distance between the thermocouple element of the thermistor and the contact portion on the surface of the fixing roller is:
Since the length is 2.5 to 15 mm, the pressure resistance is satisfied, the insulation distance is shorter than before, the size of the insulating means is reduced, the heat capacity can be reduced, and the responsiveness of the thermistor element is improved. The fixability can be stabilized with almost no deterioration.

According to the fixing device of the seventh aspect, in the fixing device of the fifth or sixth aspect, the insulating means is provided with a fixing portion for fixing a thermocouple element of a thermistor. Therefore, the insulation distance between the thermocouple element and the abutting portion on the surface of the fixing roller can be secured, the tolerance of the insulation distance can be reduced, and the insulation distance can be reduced to reduce the size of the insulation means. Since the heat capacity can be reduced by reducing the size, the responsiveness of the thermocouple element hardly deteriorates,
Fixability can be stabilized.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating details of a configuration of a thermistor used in the fixing device according to the first embodiment.

FIG. 3 is a sectional view of a main part showing a fixing device according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating details of a configuration of a thermistor used in a fixing device according to a second embodiment.

FIG. 5 is a circuit diagram including a temperature control device used in the first and second embodiments.

[Explanation of symbols]

 100A Fixing Roller 100B Fixing Roller 101 Thin Metal Substrate 102 First Electrical Insulating Layer 103 Resistance Heating Layer 104 Release Layer 105 Second Electrical Insulating Layer 200 Pressure Roller 201 Conductive Release Layer 601 Insulating Plate 601a Fixed Section 604 Thermistor Film ( Heat-resistant film) 605 Leaf spring 623 Temperature control device 700 Static elimination brush t Thickness of insulating plate l Insulation distance

Claims (7)

[Claims] An image forming apparatus comprising: a fixing roller that is driven to rotate; and a rotatable pressure roller that abuts on the fixing roller at a predetermined pressure and that is rotatable. A transfer sheet on which toner is transferred is inserted between the two rotating rollers. A fixing device, wherein the fixing roller includes a hollow cylindrical metal substrate, and an outer surface or an inner surface of the hollow cylindrical metal substrate has a withstand voltage of 1500 V or more. An electric insulating layer to be heated and a resistance heating layer for heating the fixing roller are laminated, and a release layer having conductivity, heat resistance and release properties is provided on the outer surfaces of the fixing roller and the pressure roller, and the fixing roller is provided on the fixing roller. A fixing device comprising: a thermistor that abuts on the fixing roller to detect the temperature of the fixing roller; and a temperature control device that performs temperature control according to the output of the thermistor. With an insulating means for satisfying the above voltage resistance 1500V between the child, the fixing apparatus characterized in that a discharging means for grounding the release layer of the fixing roller or the pressure roller. 2. The fixing device according to claim 1, wherein at least a contact side of the insulating unit with the fixing roller is covered with a heat-resistant film having a releasing property and an insulating property. 3. The method according to claim 1, wherein the insulating means has a volume resistance of 10 ¹⁴ at room temperature.
Ωcm or more, thermal conductivity of 150 W / m · K or more, density 2.
9-3.5 g / cm ³ , specific heat 0.7-0.8 J / g ° C
2. The fixing device according to claim 1, wherein the fixing device is formed using a high thermal conductivity material having the following characteristics. 4. The insulating means has a volume resistance of 10 ¹⁴ at room temperature.
Ωcm or more, thermal conductivity of 75 to 150 W / m · K, density of 2.0 g / cm ³ or less, specific heat of 0.7 to 0.8 J / g ° C. The fixing device according to claim 1, wherein: 5. The insulating means has a thickness of 0.4 to 0.6.
The fixing device according to claim 1, wherein 6. An insulation distance between a thermocouple element of the thermistor and a contact portion on a surface of a fixing roller is 2.5 to 15 mm.
The fixing device according to claim 5, wherein the fixing device has a length. 7. The fixing device according to claim 5, wherein the insulating unit includes a fixing portion for fixing a thermocouple element of a thermistor.