JP2002260506A - Excessive temperature rise preventing device, heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal switch type excessive temperature rise preventing device (thermoprotector, thermoswitch) with improved high speed response, operation stability, reliability, etc. SOLUTION: In the device, a part of the constituting part such as a moving pin 6b, a pin guide 6c and a thermoswitch housing 6d that are in contact with a thermal part 6a of the excessive temperature rise preventing device 6 is constituted from resin or base material where glass fiber is added to resin and particles 90 with lower thermal conductivity than the base material is dispersed inside the base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an apparatus for preventing excessive temperature rise,
The present invention relates to a heating device as an image heating unit and an unfixed image heating and fixing unit provided with the excessive temperature rise prevention device, and an image forming apparatus provided with the heating device.

[0002]

2. Description of the Related Art Conventionally, for example, a heating device for a recording material for heating and fixing an image in an image forming apparatus such as a copying machine or a laser beam printer includes a heating roller maintained at a predetermined temperature and an elastic roller. 2. Description of the Related Art A heat roller system in which a recording material as a material to be heated is heated while being nipped and conveyed by a pressure roller which is in pressure contact with the heating roller via a body layer.

Recently, instead of such a method, a heating member (heater) is fixedly supported on a stay (support), and a heat-resistant film (fixing film) conveyed while being pressed against the heating member; A pressurizing body (pressurizing roller) for bringing the recording material as the material to be heated into close contact with the heating body via the film,
An image heating / fixing device (a film heating type) in which an unfixed image formed and carried on the recording material surface is heated and fixed to the recording material surface by applying heat of the heating body to the recording material via the film. Heating device) has been devised.

[0004] In these heating devices, an overheating prevention device (thermal protector) is usually provided as a safety device at the time of runaway of the heating device, and when the temperature becomes abnormally high, the thermal protector operates. Thus, a configuration is adopted in which the heat generation path is hardly shut off.

[0005] Examples of the thermal protector include a temperature fuse and a thermoswitch. Of these, thermoswitches are heat-sensitive switches that use a heat-reversing bimetal, etc., and because of their characteristics, even if power is once cut off, the switch can be released by cooling, so that the heating device can be reused after a runaway. Heating devices incorporating the thermoswitch have been widely put to practical use.

FIGS. 10 and 11 are schematic sectional views showing the configuration around a thermoswitch in a conventional heating apparatus when a thermoreversing bimetal switch type thermoswitch 6 is used. FIG. 10 shows a state before the heat generation path is cut off, and FIG. 11 shows a state after the heat generation path is cut off.

Reference numeral 3 denotes a heating element. The heating element 3 of this example is a so-called ceramic heater having a ceramic substrate 31, a resistance heating element 32 provided on the front surface side of the substrate, a heat-resistant overcoat layer 33, and the like as basic components.

The thermoswitch 6 is held by a thermoswitch holder 7, and a heat-sensitive portion 6 a on the side opposite to the holder 7 side.
Is brought into contact with the back surface of the heating element 3, and the pressure spring 8 is contracted between the holder 9 and the spring receiving member 9 a, and the heat-sensitive portion 6 a of the thermoswitch 6 is heated by the tension force of the pressure spring 8. It is kept pressed against the back.

The temperature of the heating element 3 is rapidly increased by heating the resistance heating element 32 and is controlled to a predetermined temperature by a temperature control circuit. When a failure occurs in the energization / temperature control system of the heating element 3 and energization to the resistance heating element 32 is continued without control, so that the heating element 3 is overheated, that is, in a so-called thermal runaway state, the thermal protector 6 operates. In addition, the configuration is such that the heat generation path of the heating element 3 is cut off in a hardware manner, that is, the power supply to the heating element 3 is cut off.

The main components of this type of thermoswitch 6 are a heat inversion type bimetal 6a as a heat-sensitive member for sensing the heat of the heating section, and a fixed contact plate 6e as an electric contact connected to the heating element 3. And movable contact plate 6f, and movable pin 6 as an energization interrupting means for interrupting energization by pushing up movable contact plate 6f when bimetal 6a is inverted.
b, a pin guide 6c for supporting the movable pin, and a housing 6d for accommodating these components.

Normally, the heat reversal type bimetal 6a is
The movable pin 6b is convex with respect to the heating element 3 as shown in FIG.
Is held in the lowered position, the movable contact plate 6f is in electrical contact with the fixed contact plate 6e, and a current can be supplied from the current supply system to the resistance heating element 32 of the heating element 3.

When the heating body 3 is overheated due to the thermal runaway and the heat reversible bimetal 6a, which is a heat sensitive member, is heated to a predetermined temperature or higher, the heat reversing bimetal 6a is transferred to the heating body 3 as shown in FIG. On the other hand, the concave bending reversal operation is performed, and the movable pin 6b is pushed up accordingly, the movable contact plate 6f is separated from the fixed contact plate 6e, and the heat generation path of the heating element 3 is cut off in a hardware manner (heating element 3). To the power supply).

Of the components of the thermoswitch 6, the members constituting the movable pin 6b, the pin guide 6c, and the housing 6d are made of a material having heat resistance higher than the thermoswitch operating temperature, mechanical strength and dimensional accuracy. Is needed. As materials satisfying these required characteristics, for example, ceramic members such as alumina, PPS, LC
High heat-resistant resin members in which glass fibers are mixed with a resin such as P have been used.

[0014]

However, for example, in a film heating type heating device, the heat of the members constituting the movable pin 6b, the pin guide 6c, the housing 6d, etc. of the thermoswitch 6, which is an overheating prevention device, is considered. When the conductivity is high, the escape of heat (heat leak) from the bimetal 6a, which is a heat-sensitive member, increases, so that when the heating device (heating body) runs out of heat, the temperature of the bimetal 6 is lower than the temperature of the thermoswitch 6 on the heating body side. The part temperature will be very low.
As a result, it took 10 to several tens of seconds from immediately after the runaway of the heating device to the activation of the thermo switch.

Therefore, in the present invention, an overheating prevention device such as the above-mentioned thermoswitch, a heating device as an image heating means and an unfixed image heating and fixing means provided with the overheating prevention device, and the heating device are provided. The purpose of the present invention is to reduce the thermal conductivity of the components of the excessive temperature rise prevention device to prevent heat leak, and to achieve high-speed response and stable operation of the excessive temperature rise prevention device.

[0016]

According to the present invention, there is provided an overheating prevention device, a heating device, and an image forming apparatus having the following constitutions.

(1) A heat-sensitive switch type that has a heat-sensitive member that changes its state when the temperature rises to a predetermined temperature or higher due to the heat of the heat- ing member, and that performs a switching operation to cut off the power supply to the heating member when the state of the heat-sensitive member changes. In the excessive temperature rise prevention device, a part of components including a housing of the device is formed of a resin or a base material in which glass fiber is blended with the resin, and heat conduction in the base material is higher than that of the base material. An overheating prevention device characterized by dispersing particles having a low rate.

(2) In the apparatus for preventing excessive temperature rise according to the above (1), the heat-sensitive member is a heat inversion type bimetal,
An overheating prevention device characterized by comprising a power supply cutoff means for cutting off power supply to a heating element when the bimetal is thermally inverted, a support for the power supply cutoff means, and a device housing as main components.

(3) In the excessive temperature rise prevention device according to (2), the base material of any one of the power supply cut-off means, the power supply cut-off means support, and the apparatus housing is provided with the base material. An excessive temperature rise prevention device characterized by dispersing particles having a lower thermal conductivity than a base material.

(4) The apparatus for preventing excessive temperature rise according to (1), (2) or (3), wherein the particles dispersed in the substrate are hollow. Thermal protection device.

(5) In the apparatus for preventing excessive heating according to the above (1), (2) or (3), the particles dispersed in the base material are hollow spheres. Thermal protection device.

(6) The overheating prevention device according to (4) or (5), wherein the outer shell of the hollow body or the hollow sphere is formed of resin. .

(7) The overheating prevention device according to (4) or (5), wherein the outer shell of the hollow body or the hollow sphere is formed of an inorganic compound. apparatus.

(8) In the overheating prevention device according to (4), (5) or (7), the outer shell of the hollow body or the hollow sphere is formed of glass. Temperature rise prevention device.

(9) A heating apparatus having a heating element for heating a material to be heated by generating heat by energization, and comprising an overheating prevention device for cutting off energization to the heating element when the heating element overheats. The overheating prevention device has a heat-sensitive member that changes its state when the temperature rises to a predetermined temperature or higher due to the heat of the heating member, and performs a switch operation to cut off the power supply to the heating member when the state of the heat-sensitive member changes. A device of the heat-sensitive switch type for preventing the overheating of the heating body by heating, wherein a part of the components including the housing of the overheating preventing device is made of resin or a base material in which glass fiber is mixed with resin. A heating device, wherein particles having a lower thermal conductivity than the substrate are dispersed in the substrate.

(10) A pair of heating and pressurizing rotating bodies including a heating body which generates heat by energization are heated by sandwiching and conveying the material to be heated at a press contact portion formed by pressurizing the heating body. In a heating device provided with an overheating prevention device that cuts off current supply to the heating body when the temperature rises, the overheating prevention device includes a heat-sensitive member that changes state when the temperature rises to a predetermined temperature or more due to the heat of the heating body. A heat-sensitive switch-type device that has a switch operation of interrupting energization of the heating element by a change in state of the heat-sensitive member to prevent overheating of the heating element, and includes a housing of the overheating prevention device. A part of the components is made of a resin or a base material in which glass fiber is blended with the resin, and particles having a lower thermal conductivity than the base material are dispersed in the base material. apparatus.

(11) A heating element, a film that slides in contact with the heating element, and a pressurizing member that brings a material to be heated into close contact with the heating element via the film, wherein the heating element and the heating element The film and the material to be heated are nipped and conveyed together in a nip formed by a pressure member to heat the material to be heated and to shut off the current supply to the heating element when the temperature of the heating element rises excessively. In a heating device provided with a temperature prevention device, the excessive temperature rise prevention device has a heat-sensitive member that changes its state when the temperature rises to a predetermined temperature or higher due to the heat of the heating member, and the state of the heat-sensitive member changes to the heating member. This is a heat-sensitive switch type device that performs a switch operation to cut off the current supply to prevent overheating of the heating element. A part of the component including the housing of the overheating prevention device is made of resin or glass fiber. Composed of a base material And has a heating device, characterized in that said than substrate by dispersing low particle thermal conductivity in the substrate.

(12) The above (9), (10) or (1)
1) The heating device according to 1), wherein the heat-sensitive member of the excessive temperature rise prevention device is a heat reversing type bimetal, and a current interrupting unit that cuts off current to the heating element when the bimetal is thermally inverted, and a support of the current interrupting unit. A heating device comprising a body and a device housing as main components.

(13) In the heating device according to the above (12), the base of any one of the power supply cutoff means, the power supply cutoff means support, and the device housing of the excessive temperature rise prevention device. A heating device, wherein particles having a lower thermal conductivity than the base material are dispersed therein.

(14) In the heating device according to any one of (9) to (13), the particles dispersed in the base material of the excessive temperature rise prevention device are hollow. Characteristic heating device.

(15) In the heating device according to any one of (9) to (13), the particles dispersed in the base material of the excessive temperature rise prevention device are hollow spheres. Characteristic heating device.

(16) The heating device according to (14) or (15), wherein the outer shell of the hollow body or the hollow sphere is formed of a resin.

(17) The heating device according to (14) or (15), wherein the outer shell of the hollow body or the hollow sphere is formed of an inorganic compound.

(18) The above (14), (15) or (1)
The heating device according to 7), wherein the outer shell of the hollow body or the hollow sphere is formed of glass.

(19) In an image forming apparatus having an image forming means for forming an image on a recording material and an image heating means for heating the image on the recording material, (9) to (9) are used as the image heating means. An image forming apparatus comprising the heating device according to any one of 18).

(20) In an image forming apparatus having an image forming means for forming an unfixed image on a recording material and a fixing means for heating the unfixed image and fixing it on the recording material, An image forming apparatus comprising the heating device according to any one of (9) to (18).

<Operation> More specifically, a part of components such as a movable pin, a pin guide, and a thermoswitch housing, which are in contact with the heat-sensitive portion of the overheat prevention device, is made of resin or resin mixed with glass fiber. It is composed of a base material, in which particles having a lower thermal conductivity than the base material are dispersed.

By using the overheating prevention device, the thermal heating device, and the image forming apparatus having the above-described structures, the thermal conductivity of the components of the overheating prevention device can be reduced, and the heat leakage from the heat-sensitive portion can be reduced. , The temperature difference between the temperature of the heat-sensing part side and the temperature of the heat-sensing part during runaway of the heating device can be reduced, and high-speed response and stable operation of the overheating prevention device can be achieved. . As a result, the safety and reusability of the heating device can be improved.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> A first embodiment of the present invention will be described below with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 1 shows a main part of a laser beam printer as an image forming apparatus in this embodiment.

Reference numeral 101 denotes an organic photosensitive drum as an image carrier, which is rotated at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow. Reference numeral 102 denotes a transfer roller, and the organic photosensitive drum 101
And a transfer nip portion is formed by contacting with a predetermined pressing force. Reference numeral 103 denotes a fixing device (fixing device).

The rotating organic photosensitive drum 101 is uniformly charged with a negative charge by a charging device (not shown), and an image corresponding to the exposure is obtained by laser beam scanning exposure of the charged surface with a laser exposure device (not shown). An electrostatic latent image of the information is formed. Next, in a developing device (not shown), the charged toner adheres to the electrostatic latent image on the organic photosensitive drum 101, and the electrostatic latent image becomes a visible image as a toner image. Thus, the image is transferred onto paper P as a recording material (transfer material).

The recording material P is separated and fed one by one from a paper feed cassette 104 by a paper feed roller 105, and a paper path 106,
At a predetermined control timing, the organic photosensitive drum 101 is fed to the transfer nip portion, which is a pressure contact portion between the organic photosensitive drum 101 and the transfer roller 102, via the registration roller 107, and the organic photosensitive drum 101 is nipped and conveyed during the transfer nip portion. The toner image is transferred to the recording material P from the side.

The paper P to which the toner image has been transferred after passing through the transfer nip is separated from the surface of the organic photosensitive drum 101, introduced into the fixing device 103, subjected to the heat fixing process of the toner image, and subjected to image forming (printing). , Copy).

(2) Fixing Device 103 FIG. 2 is a schematic cross-sectional view of the fixing device 103. The fixing device 103 of this embodiment is a so-called tensionless type film heating type heating device disclosed in JP-A-4-44075-44083 and JP-A-4-20498-0204498.

In this apparatus, an endless belt or a cylindrical heat-resistant film is used, and at least a part of the peripheral length of the film is always tension-free (in a state where tension is not applied). This device is driven by a rotational driving force.

1 is a support (stay) also serving as a film guide member, 2 is an endless heat-resistant film, and 3 is a heater (heater). A heating element 3 is fixedly supported on the lower surface side of the stay 1, and the film 2 is loosely fitted to the stay 1 including the heating element 3. Reference numeral 9 denotes a U-shaped sheet metal which is inserted into the inside of the stay 1 and has a downward U-shaped cross section.

Reference numeral 4 denotes an elastic pressure roller as a pressure roller, which is disposed so as to be rotatably supported by a bearing member (not shown). The assembly of the stay 1, the film 2, the heating element 3, and the sheet metal 9 is arranged above the pressure roller 4 in parallel with the pressure roller 4 with the heating element 3 facing downward. The urging means urges the pressing roller 4 downward against the elasticity of the pressure roller 4 or presses the pressing roller 4 upward against the elasticity of the pressing roller 4 by the urging means shown in the figure. The pressing is performed by pressing the heating element 3 and the pressing roller 4 with the film 2 interposed therebetween to form a pressing nip portion N having a predetermined width.

In the present embodiment, the inner peripheral length of the endless heat-resistant film 2 and the outer peripheral length of the stay 1 including the heating element 3 are made larger by about 3 mm for the film 2. Therefore, the film 2 is externally fitted with a margin in the circumference.

The pressure roller 4 is rotationally driven at a predetermined peripheral speed in a clockwise direction indicated by an arrow by a drive system (not shown). Following the rotation of the pressure roller 4, the film 2 rotates counterclockwise while the inner surface of the film 2 is in close contact with the lower surface of the heating body 3 at the press-contact nip portion N.

The film 2 has a film thickness of 100 to reduce the heat capacity and improve the quick start property.
μm or less, preferably 60 μm or less 20 μm or more heat-resistant single-layer film such as PTFE, PFA, FEP,
Or polyimide, polyamide imide, PEEK, PE
PTFE, PF on the outer peripheral surface of film such as S, PPS
A, FEP or the like coated composite layer film can be used. In this embodiment, a polyimide film having a thickness of about 50 μm and having an outer peripheral surface coated with PTFE was used.

FIG. 3 is a partially cutaway plan view of the heating element 3 in this embodiment. Heating body 3 is heat-resistant film 2
Alternatively, an elongated heat-resistant / insulating / good-heat-conductive substrate 31 having a longitudinal direction perpendicular to the conveying direction A (FIG. 2) of the recording material P as a material to be heated, and a short surface side of the substrate 31 A resistance heating element 32 formed at the center in the hand direction along the length of the substrate, a heat-resistant overcoat layer 33 protecting the surface of the heating element on which the resistance heating element 32 is formed, and a resistance heating element 3
2 is a plate-like heating element having a low heat capacity as a whole, comprising power supply electrodes 21 and 22 at the longitudinal ends and a temperature detecting element 5 such as a thermistor provided on the back side of the substrate.

As shown in FIG. 2, the heating element 3 exposes the surface on which the resistance heating element 32 is formed and is exposed downward to the lower surface of the rigid and heat-resistant stay 1 (heat-resistant temperature of 350 ° C.). It is fixed and disposed.

The heater substrate 31 is made of a material such as alumina or aluminum nitride. In this embodiment, an alumina substrate having a thickness of 1 mm, a width of 7 mm, and a length of 270 mm is used. The resistance heating element 32 is, for example, Ag / Pd
(Silver palladium), RuO2, Ta2N or the like is formed by applying an electric resistance material such as screen printing or the like in a linear or narrow band shape. In this embodiment, Ag / Pd is screen-printed to a thickness of about 10 μm. It was formed by coating to a width of 1 mm. As the power supply electrodes 21 and 22, a screen printing pattern layer of Ag / Pd was used. Overcoat layer 33
Used a heat-resistant glass layer having a thickness of about 50 μm.

The heating element 3 is supplied with electric power to the power supply electrodes 21 and 22 at the longitudinal ends of the resistance heating element 32 so that the resistance heating element 3
2 generates heat over the entire length thereof, thereby increasing the temperature. The temperature rise is detected by the temperature detecting element 5, and the output of the temperature detecting element 5 is changed to A /
D-converted and taken into the CPU 24 (FIG. 2), and based on the information, the triac 25 controls the AC voltage of the AC power supply 26 that energizes the resistance heating element 32 by phase control, wave number control, and the like to control the temperature of the heating element 3. Is made. That is, when the temperature detected by the temperature detecting element 5 is lower than a predetermined set temperature, the heating element 3
By controlling the energization so that the temperature rises when the temperature is higher than the set temperature, the temperature of the heating element 3 is adjusted to a constant value during fixing.

The pressure roller 4 is a pressure roller as a film outer surface contact driving means for forming a pressure contact nip portion N with the film 2 sandwiched between the heating member 3 and the film 2 and rotating the film 2 as described above. is there. The film driving roller and pressure roller 4 includes a cored bar 4a, an elastic layer 4b made of silicone rubber or the like, and an outermost release layer 4c. The rotational force acts on the film 2 by the frictional force at the pressure contact nip N between the roller and the outer surface of the film due to the rotational drive of the pressure roller 4. In this embodiment, the pressure roller 4 used had a heat-resistant temperature of 230 ° C.

In a state where the temperature of the heating element 3 rises to a predetermined value and the rotational peripheral speed of the film 2 is stabilized by the rotation of the pressure roller 4, the heating element 3 and the pressure roller The recording material P to be fixed as an image to be heated is introduced from the image forming portion (transfer portion) between the film 2 of the press contact nip portion N formed by the pressure roller 4 and the pressure roller 4 and is together with the film 2. The heat of the heating element 3 is applied to the recording material P via the film 2 by nipping and transporting the pressure contact nip portion N, and the unfixed visible image (toner image) T on the recording material P is heated to the surface of the recording material P. It will be established. The recording material P that has passed through the pressure nip N is separated from the surface of the film 2 and conveyed.

(3) Overheating preventing device As shown in FIG. 4, a thermoswitch 6 as an overheating preventing device (thermal protector) is provided at a predetermined position on the surface of the heating element 3 facing the film 2 side. Are in contact with a suitable pressing force via the thermoswitch holder 7. That is, the thermoswitch 6 is held by the thermoswitch holder 7, the heat-sensitive portion on the side opposite to the holder 9 is brought into contact with the back surface of the heating element 3, and a pressure spring is provided between the holder 9 and the spring receiving member 9 a. The thermo-switch 6 is kept in a state in which the thermo-sensitive portion of the thermo-switch 6 is pressed against the back surface of the heating element by the tension force of the pressure spring 8.

Grease (not shown) for transmitting the heat of the heating element 3 to the thermoswitch 6 is applied between them.

The thermoswitch 6 in this embodiment is basically the same as the thermoswitch 6 shown in FIGS. 10 and 11, and includes a heat inversion type bimetal 6a on the heating body 3 side and a movable pin 6b as heat sensitive members. , A pin guide 6c, a housing 6d, a fixed contact plate 6e, a movable contact plate 6f, and the like. The rated operating temperature of the thermoswitch 6 in the present embodiment is 250 ° C., and when the bimetal portion 6a reaches the predetermined temperature, the thermoswitch reverses its heat and pushes up the movable contact plate 6f via the movable pin 6b to thereby make electrical contacts. Open. Thus, the power supply to the heating element 3 connected in series with the contact plates 6e and 6f is cut off.

In the film heating type fixing device 103 described above, when the thermal conductivity of the movable pin 6b, the pin guide 6c, and the housing 6d among the components constituting the thermoswitch 6 is high, the movable pin 6b is removed from the bimetal 6a. Therefore, the temperature of the bimetal portion 6a cannot sufficiently reflect the temperature of the heater 3 side, and the temperature difference becomes extremely large when the fixing device 103 runs away. As a result, the fixing device 1
In the runaway of 03, 10 before the thermo switch 6 is activated
It takes more than a few seconds.

Therefore, in the present embodiment, particles (low heat conductive filler) having a lower thermal conductivity than the base material constituting the thermoswitch 6 are dispersed in the components of the thermoswitch 6, and the heat of the components of the thermoswitch 6 is reduced. The conductivity has been reduced.

The movable pin 6b, the pin guide 6c, and the housing 6d are generally made of a high heat resistant resin such as PPS, LCP, polyimide, polyamide imide, or ceramic such as alumina. In this embodiment, a base material (material) in which glass fiber is mixed with PPS is used. The purpose of blending this glass fiber is to improve the heat resistance, mechanical strength, and dimensional accuracy of PPS. Particles having lower thermal conductivity than the composite material of PPS and glass fiber are dispersed in 6b, 6c, and 6d, respectively.

In this embodiment, hollow microspheres 90 whose outer shell (shaded portion) 90a shown in FIG. 8 is a thermoplastic synthetic resin are used as the low heat conductive filler. As thermoplastic synthetic resins, polyolefin resins, polyvinyl compounds,
Polymethacrylate ester and the like can be used. In this example, a resin made of a vinylidene chloride copolymer having a particle size of 10 to 20 μm and a specific gravity of 1.1 and having an outer shell (Matsumoto Yushi Seiyaku Co., Ltd., product name: Matsumoto Microsphere, model number:
F-20) was used. Since the resin microspheres 90 are filled with air, the thermal conductivity is sufficiently lower than the thermal conductivity of the composite material of PPS and glass fiber.

The following is a comparison between the case where the resin microspheres 90 are dispersed in the constituent members of the thermoswitch 6 and the case where they are not dispersed.

Conventional Example 1) In the case where dispersion is not performed (comparative example), movable pin 6b, pin guide 6c, housing 6d
A thermoswitch in which all members are composed of “PPS: 70 parts by weight + glass fiber: 30 parts by weight”.

Example 2) In the case of dispersing, as shown in FIG. 4, the member of the movable pin 6b is composed of "PPS: 70 parts by weight + glass fiber: 25 parts by weight + resin microsphere 90: 5 parts by weight". The members of the pin guide 6c and the housing 6d are the same as those in 1) "PPS: 70 parts by weight + glass fiber:
Thermoswitch consisting of "30 parts by weight".

Embodiment 3) As shown in FIG. 5, the pin guide 6c
Is composed of “PPS: 70 parts by weight + glass fiber: 25 parts by weight + resin microspheres 90: 5 parts by weight”, and the members of the movable pin 6 b and the housing 6 d are the same as those in 1), “PPS: 70 parts by weight”. Part + glass fiber: 3
Thermo switch consisting of "0 parts by weight".

Embodiment 4) As shown in FIG.
Is composed of “PPS: 70 parts by weight + glass fiber: 25 parts by weight + resin microspheres 90: 5 parts by weight”, and the members of the movable pin 6 b and the pin guide 6 c are the same as those in 1) “PPS: 70”. Parts by weight + glass fiber: 3
Thermo switch consisting of "0 parts by weight".

Embodiment 5) As shown in FIG.
A thermoswitch in which all members of the pin guide 6c and the housing 6d are composed of “PPS: 70 parts by weight + glass fiber: 25 parts by weight + resin microsphere 90: 5 parts by weight”.

As described above, the five types of thermoswitches of the conventional example 1), the embodiment 2), the embodiment 3), the embodiment 4) and the embodiment 5) are incorporated in the fixing device 103 of the present embodiment, respectively. The runaway was forcibly performed in a state in which the thermoswitch 6 was not driven, and the time until the thermoswitch 6 was activated, the temperature of the heating element 3 when the thermoswitch 6 was activated, and whether or not the stay 1 and the pressure roller 4 were melted were compared. In this comparison, everything except the thermoswitch 6 was performed under the same conditions. Table 1 shows the results.

[0072]

[Table 1]

First, in Examples 2) to 5), the temperature of the heating element 3 at the time of operation of the thermoswitch 6 is reduced and the melting level of the stay 1 and the pressure roller 4 is improved as compared with the conventional example 1). You can see that

Embodiments 2), 3) and 4)
According to the comparison, when the movable pin 6b in contact with the bimetal 6a is made of a low heat conductive member, the temperature of the heating body 3 is lowest in the embodiment 2), and the stay 1 and the pressure roller 4 do not melt. You can see that.

Then, the movable pin 6b, the pin guide 6c,
In the case of Embodiment 5) in which all the members of the housing 6d are made of low heat conductive members, the temperature of the heater 3 is further reduced.

In general, the thermal conductivity of glass fiber is higher than that of resin such as PPS. To simply lower the thermal conductivity of the entire thermoswitch 6, the amount of PPS of the constituent members is increased and the amount of glass fiber is reduced. Good to reduce.

However, as described above, if the amount of glass fiber is excessively reduced, heat resistance, mechanical strength, and dimensional accuracy are reduced, and the amount of PPS is increased since PPS is generally more expensive than glass. This increases the cost of the thermoswitch 6 as a whole.

In the end, in order to achieve both heat resistance, mechanical strength, dimensional accuracy, etc., which are characteristics required for the movable pin 6b, the pin guide 6c, and the housing 6d, and low heat conduction, and to realize further low cost. It is most effective to disperse the resin microspheres 90 with the composition as in this embodiment.

In the above embodiment, a thermoplastic synthetic resin is used as the outer shell 90a of the resin microspheres 90. However, a thermosetting synthetic resin such as a phenol-based, epoxy-based, or urea-based resin may be used. This is an effective means from the viewpoint of the heat resistance of the resin microspheres 90.

As described above, in this embodiment, by dispersing the resin microspheres 90 in the constituent members of the thermoswitch 6, the thermal conductivity of the entire thermoswitch 6 can be reduced. Can be reduced, and the temperature difference between the temperature of the bimetal portion 6a and the temperature of the heating element 3 can be reduced. As a result, even when the fixing device 103 runs away,
, The reliability of the fixing device 103 in terms of safety can be improved.

<Second Embodiment> In this embodiment, a hollow glass balloon is used as the low thermal conductive filler described in the first embodiment.

The other configurations of the thermoswitch 6, which is an excessive temperature rise prevention device, the fixing device 103, which is a heating device, and the image forming apparatus are the same as those of the first embodiment.

The movable pin 6b, the pin guide 6c, and the housing 6d among the constituent members of the thermoswitch 6 are made of a material in which PPS is mixed with glass fiber, similarly to the first embodiment. Balloons 91 are dispersed.

As shown in FIG. 9, the glass balloon 91 has an outer shell 91a made of glass and filled with air. The glass balloon 91 (manufactured by Sumitomo 3M Ltd., product name: Glass Bubbles, model number: S60) used in this example has an average particle diameter of 100 μm, a specific gravity of 0.6, and a strength of the components 6b, 6c, and 6d of the thermoswitch 6. In order to prevent the glass balloon 91 from breaking at the time of molding, a resin having a residual ratio of 90% (vol%) when a pressure of 10,000 psi was applied was used. Since the glass balloon 91 is filled with air, its thermal conductivity is sufficiently lower than the thermal conductivity of the composite material of PPS and glass fiber.

A comparison between the case where the glass balloon 91 is dispersed in the constituent members of the thermoswitch 6 and the case where it is not dispersed will be described below.

As a case where the dispersion is not performed, the thermoswitch of the conventional example 1) (comparative example) described in the first embodiment will be described.

Embodiment 6) In the case of dispersing, all members of the movable pin 6b, the pin guide 6c, and the housing 6d are "PPS: 70 parts by weight + glass fiber: 25 parts by weight + glass balloon 91: 5 parts by weight" Thermo switch composed of.

Embodiment 7): Movable pin 6b, pin guide 6
c, A thermoswitch in which all members of the housing 6d are composed of "PPS: 80 parts by weight + glass fiber: 10 parts by weight + glass balloon 91:10 parts by weight".

As described above, three types of thermoswitches are incorporated in the fixing device 103 of the present example, and the thermoswitch is forcibly runaway without driving the fixing device 103. Time until 6 is activated,
The temperature on the side of the heating element 3 at the time of operation and the presence or absence of melting of the stay 1 and the pressure roller 4 were compared. The comparison conditions are the same as in the first embodiment. Table 2 shows the results.

[0090]

[Table 2]

By comparing conventional example 1) and embodiment 6), P
When the weight of the PS is the same and the glass fibers are reduced and the glass balloon 91 is dispersed (the configuration of the present embodiment), the temperature difference between the temperature of the bimetal portion 6a of the thermoswitch 6 and the temperature of the heating element 3 side is greatly reduced. It can be seen that the stay 1 and the pressure roller 4 can be prevented from melting when the thermoswitch 6 is operated.

The operation of the thermoswitch 6 immediately after the runaway compared with the embodiment 5) (in which the resin microspheres 90 described in the first embodiment are dispersed) having the same composition ratio in the embodiment 6). The time is short, and the temperature on the heating body 3 side is low.

This is considered to be mainly due to the fact that the glass balloon 91 has better heat resistance and strength than the resin microspheres 90, and has a high residual ratio during molding of the thermoswitch. Further, in another embodiment of the present embodiment, in which the weight part of the glass balloon 91 is increased to 10, the embodiment 7) further reduces the operating time of the thermoswitch 6, thereby reducing the temperature of the heating element 3 side.

As described above, simply increasing the PPS and decreasing the glass fiber will reduce the thermal conductivity, but will increase the cost of the entire thermoswitch. When the glass balloon 91 is dispersed, the specific gravity of the glass balloon 91 is small and the residual ratio at the time of molding the thermoswitch components 6b, 6c, 6d is high, so that the weight of the thermoswitch 6 can be reduced. The amount of PPS used per unit can be reduced.

In addition, since the glass balloon 91 is not so expensive, the cost of the entire thermoswitch can be reduced as compared with the case where the glass fiber is simply reduced.

In addition, heat resistance, mechanical strength, and dimensional accuracy due to the reduction in glass fiber are reduced by the resin microspheres 9.
In the case where the glass balloon 91 was dispersed, the value was smaller than that in the case where 0 was dispersed.

That is, the thermoswitch constituent members 6b, 6
By dispersing the glass balloon 91 in c and 6d, it is possible to shorten the operation time of the thermoswitch and prevent damage to the fixing parts at low cost, and it is possible to provide a heating device having high safety and high reusability.

In the above embodiment, the glass balloon 91 is used as the low thermal conductive filler. However, it is also possible to use an inorganic balloon such as an aminosilicate having high heat resistance, and the same effect as in the above embodiment can be obtained. can get.

<Others> In the above embodiment, an example is shown in which a thermo-inverting bimetal-type thermoswitch is used as the thermal protector. However, the present invention is not limited to this, and a shape-memory alloy switch type or the like may be used as long as it has temperature deformability.

2. In the above embodiment, an example was described in which a heating element was used in which a heating element was provided on the surface of the substrate (the surface on the side of the material to be heated). A configuration using a backside heating type heating element provided with a heating element on the surface opposite to the heating material) may be used.

3. In the above-described embodiment, an example in which a so-called ceramic heater is used as the heating body has been described. However, the invention is not limited thereto, and an electromagnetic induction heating-type heating body that generates heat by applying a magnetic force to a conductive member may be used.

4. In the above-described embodiment, an example in which a so-called film heating method is used as a heating method has been described. However, the present invention is not limited to this, and a heating device using various heating methods such as a so-called heat roller method using a halogen heater may be used. good.

[0103]

As described above, according to the present invention, among the components of the thermal protector, the heat conductivity of the components other than the heat-sensitive member is reduced to prevent heat leak from the heat-sensitive portion,
It is possible to shorten the operation time of the thermal protector and prevent damage to the fixing parts at low cost, and it is highly safe and reusable.
An overheating prevention device, a heating device, and an image forming device can be provided.

[Brief description of the drawings]

FIG. 1 is a main part diagram of a laser beam printer as an image forming apparatus in an embodiment.

FIG. 2 is a schematic configuration diagram of a film heating type image heating fixing device (heating device) in an embodiment.

FIG. 3 is a partially cutaway model plan view of a heating body in an embodiment.

FIG. 4 is a structural model diagram of a thermoswitch (Example 2)

FIG. 5 is a structural model diagram of a thermoswitch (Example 3)

FIG. 6 is a schematic diagram of a configuration of a thermoswitch (Example 4).

FIG. 7 is a schematic diagram of a configuration of a thermoswitch (Example 5).

FIG. 8 is a schematic cross-sectional model view of a hollow microsphere made of resin in the first embodiment.

FIG. 9 is a schematic sectional view of a glass balloon according to a second embodiment.

FIG. 10 is a schematic cross-sectional model diagram of a thermo switch of a conventional example (before heat generation path is cut off).

FIG. 11 is a schematic cross-sectional view of a conventional thermoswitch (after the heat generation path is cut off).

[Explanation of symbols]

 Reference Signs List 6 thermo switch 6a heat reversing bimetal part (thermosensitive member) 6b movable pin 6c pin guide 6d housing 90 hollow microsphere made of resin 90a outer shell of hollow microsphere (thermoplastic synthetic resin) 91 glass balloon 91a: Outer shell of glass balloon (glass)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 3/00 310 H05B 3/00 310G 335 335 F-term (Reference) 2H033 AA23 AA42 BA05 BA31 BA34 BB01 BE03 CA06 CA07 CA27 CA34 3K058 AA12 AA42 AA73 BA18 CA72 CA91 DA01 GA06 5G041 AA02 AA08 BB11 DA01 DA11 DB01 DC12 5H323 AA36 BB03 BB04 BB17 CA08 CB03 DA01 DA10 DB24 FF01 GG23 KK05 MM02 TT06 TT19 TT19 TT19

Claims (20)

[Claims] 1. A heat-sensitive switch type having a heat-sensitive member that changes its state when the temperature thereof rises to a predetermined temperature or higher due to the heat of a heating element, and that performs a switch operation of interrupting energization to the heating element when the heat-sensitive member changes state. In the excessive temperature rise prevention device, a part of the component including the housing of the device is formed of a resin or a base material in which glass fiber is blended with the resin, and the heat conductivity in the base material is higher than that of the base material. Overheat prevention device characterized by dispersing particles with low temperature. 2. The overheating prevention device according to claim 1, wherein the heat-sensitive member is a heat-reversal type bimetal, and a current-cutoff unit that cuts off current to a heating element when the bimetal is thermally inverted, and the power-cutoff. An apparatus for preventing excessive temperature rise, comprising a support for the means and a device housing as main components. 3. The excessive temperature rise prevention device according to claim 2, wherein the base material is included in the base material of any one of the power supply cutoff means, the power supply cutoff means support, and the device housing. An apparatus for preventing excessive temperature rise, wherein particles having lower thermal conductivity are dispersed. 4. The overheating prevention device according to claim 1, wherein the particles dispersed in the base material are hollow. 5. The overheating prevention device according to claim 1, wherein the particles dispersed in the base material are hollow spheres. 6. The overheating prevention device according to claim 4, wherein an outer shell of the hollow body or the hollow sphere is formed of a resin. 7. The overheating prevention device according to claim 4, wherein the outer shell of the hollow body or the hollow sphere is formed of an inorganic compound. 8. The overheating prevention device according to claim 4, wherein the outer shell of the hollow body or the hollow sphere is formed of glass. 9. A heating apparatus, comprising: a heating element that generates heat when energized to heat a material to be heated, and an overheating prevention device that shuts off energization to the heating element when the heating element overheats. The excessive temperature rise prevention device has a heat-sensitive member that changes state when the temperature rises to a predetermined temperature or higher due to the heat of the heating body, and performs a switch operation to cut off the power supply to the heating body by changing the state of the heat-sensitive member. A device of a heat-sensitive switch type for preventing an excessive temperature rise of a heating element, wherein a part of components including a housing of the excessive temperature rise prevention device is made of a resin or a base material in which a glass fiber is mixed with a resin. A heating device, wherein particles having a lower thermal conductivity than the substrate are dispersed in the substrate. 10. Heating is performed by sandwiching and transporting a material to be heated by a press-contact portion formed by pressurizing a pair of heating and pressurizing rotating bodies including a heating body that generates heat when energized, thereby causing the heating body to overheat. A heating device provided with an overheating prevention device that cuts off current supply to the heating element when the temperature is high, wherein the overheating prevention device has a heat-sensitive member that changes state when the temperature of the heating object is increased to a predetermined temperature or more by heat. A heat-sensitive switch-type device that performs a switch operation to cut off the power supply to the heating element when the state of the heat-sensitive member changes, thereby preventing overheating of the heating element, and includes a housing of the overheating prevention device. A heating device, wherein a part of the component is constituted by a resin or a base material in which glass fiber is mixed with the resin, and particles having a lower thermal conductivity than the base material are dispersed in the base material. . 11. A heating member, a film that slides in contact with the heating member, and a pressure member that brings a material to be heated into close contact with the heating member via the film. The film and the material to be heated are sandwiched and conveyed together in the nip portion formed by the member, thereby heating the material to be heated and shutting off the power supply to the heating element when the temperature of the heating element is excessively increased. In a heating device provided with a prevention device, the excessive temperature rise prevention device has a heat-sensitive member that changes state when the temperature rises to a predetermined temperature or higher due to heat of the heating member, and the state of the heat-sensitive member changes the state of the heating member. This is a heat-sensitive switch type device that performs a switch operation to cut off the power supply to prevent overheating of the heating element. A part of a component including a housing of the overheating prevention device is made of resin or glass fiber in resin. Composed of blended base materials Ri, the heating device being characterized in that said than substrate by dispersing low particle thermal conductivity in the substrate. 12. The heating device according to claim 9, 10 or 11, wherein the heat-sensitive member of the excessive temperature rise prevention device is a heat reversal type bimetal, and the power is cut off when the bimetal is thermally reversed. A heating device comprising a shutoff means, a support for the power cutoff means, and an apparatus housing as main components. 13. The heating device according to claim 12, wherein the base of any one of the power supply cutoff means, the power supply cutoff means support, and the device housing of the excessive temperature rise prevention device is provided. A heating device in which particles having a lower thermal conductivity than the base material are dispersed. 14. The heating device according to claim 9, wherein the particles dispersed in the base material of the excessive temperature rise prevention device are hollow bodies. apparatus. 15. The heating device according to claim 9, wherein the particles dispersed in the base material of the excessive temperature rise prevention device are hollow spheres. apparatus. 16. The heating device according to claim 14, wherein an outer shell of the hollow body or the hollow sphere is formed of a resin. 17. The heating device according to claim 14, wherein an outer shell of the hollow body or the hollow sphere is formed of an inorganic compound. 18. The heating apparatus according to claim 14, wherein the outer shell of the hollow body or the hollow sphere is formed of glass. 19. An image forming apparatus comprising: an image forming unit for forming an image on a recording material; and an image heating unit for heating the image on the recording material, wherein the image heating unit is used as the image heating unit. An image forming apparatus comprising the heating device according to claim 1. 20. An image forming apparatus comprising: an image forming unit that forms an unfixed image on a recording material; and a fixing unit that heats the unfixed image and fixes the unfixed image on the recording material. Item 19. An image forming apparatus comprising the heating device according to any one of Items 9 to 18.