JP2002260825A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device which makes a temperature detecting element surely touch a heater, and reduces the internal stress generated in the heater. SOLUTION: The heating device has a temperature detecting means mounted to a hole part 9a formed to a heater holder 9 holding a heater 8 of a film type fixing device. For the heating device comprising a temperature detecting element 1 touching the heater and detecting temperature, a temperature detecting element holding member 4 holding the temperature detecting element 1 through a heat resistant elastic body 2, and a heat resistant protection sheet 3 held by the temperature detecting element holding member covering the temperature detecting element 1 and the heat resistant elastic body 2, at least one end part of the heat resistant elastic body 2 is made to expose from the heat resistant protection sheet 3, and a heat insulation material is arranged between the elastic body 2 and the hole part 9a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention fixes an unfixed toner image used in an image forming apparatus using an electrophotographic process, such as a copying machine, a laser printer, and a facsimile, on a recording medium such as a sheet by heating and pressing. And an image forming apparatus.

[0002]

2. Description of the Related Art A conventional image forming apparatus using electrophotography is configured, for example, as shown in FIG. In FIG.
201 is a photosensitive drum, 202 is a charging roller, 203 is a laser exposure device, 204 is a reflection mirror, 205 is a developing sleeve, 206 is toner, 207 is a toner container, 208 is a transfer roller, P is a sheet as a recording medium, 210 Is the cleaning blade, 2
11 is a waste toner container, 212 is a fixing device, 213 is a paper cassette, 214 is a paper feed roller, 215 is a separation pad, and 216 is a high voltage power supply.

Next, an outline of the operation of the image forming apparatus will be described.
The photosensitive drum 201 rotates in the direction of the arrow, and is uniformly charged by the charging roller 202 supplied with power from the high-voltage power supply 216.
The laser light emitted from the laser exposure device 203 is reflected by the reflection mirror 204 and then applied to the photosensitive drum 201 to form an electrostatic latent image on the photosensitive drum 201. Toner container 207
Is filled with toner 206, and the developing sleeve 205
With the rotation of, after an appropriate amount of toner receives an appropriate charge,
It is supplied onto the photosensitive drum 201.

[0004] The toner 206 on the developing sleeve 205 adheres to the electrostatic latent image on the photosensitive drum 201, and the latent image is developed and visualized as a toner image. The paper feed roller 214 feeds the sheets P one by one from the paper cassette 213 at appropriate timing.

[0005] The separation pad 215 is disposed in contact with the paper feed roller 214, and its surface friction coefficient, ground contact angle, and shape are adjusted so that only one recording medium is fed per paper feed. . The visualized toner image on the photosensitive drum 201 is transferred onto the sheet P by the transfer roller 208. The transfer residual toner remaining on the photosensitive drum 201 without being transferred is stored in the waste toner container 211 by the cleaning blade 210, and the photosensitive drum 201 whose surface has been cleaned repeatedly enters the next image forming process.

[0006] The sheet P on which the toner image is placed is heated and pressed by the fixing device 212, and the toner image is permanently fixed on the sheet P.

Next, an outline of the fixing unit 212 will be described.
FIG. 6 is a schematic diagram of the fixing device 212 in the longitudinal direction, and FIG. 7 is a cross-sectional view taken along line AA of FIG. FIG. 8 is a schematic longitudinal view of the thermistor portion.

As shown in Japanese Patent Application Laid-Open No. 63-31382, the fixing device 212 is a heater in which a pattern of a resistance heating element is provided on a ceramic substrate to form a heating element, and the heater is used to generate heat. A film heating method is used in which a sheet carrying an unfixed toner image is heated via a film.

Reference numeral 108 denotes a heater, on which a resistance heating element 108a is formed on a ceramic substrate, and a glass layer 108b is coated thereon as a protective layer. The resistance heating element 108a is supplied with power by a power source (not shown) and generates heat. The thermistor 117 is in contact with the back surface of the heater 108, and detects the temperature of the heater 108.

The thermistor 117 includes a temperature detecting element 101, a heat-resistant elastic body 102 for elastically holding the temperature detecting element 101, a thermistor frame supporting the temperature detecting element 101 and the elastic body 102 and having a positioning shape with respect to the heater holder 109. 104
And a thermistor metal 105 integrally formed with the thermistor frame 104 and electrically connected to the temperature detecting element 101, and the thermistor metal 105 covering the temperature detecting element 101 and the elastic body 102.
And a heat-resistant protective sheet 103 positioned at the bottom.

The temperature detecting element 101 is a thermistor frame 1
The grooves provided in the 04 allow the elastic body 102 to move up and down by the amount of expansion and contraction. The thermistor 117 is positioned by the heater holder 109 and has a pair of thermistor holding springs 1.
06 urges the heater 108. 107 is a thermistor holding spring support member. The power supply amount is controlled by a CPU (not shown) so that the temperature of the thermistor 117 becomes constant.

The heater holder 109 supports the heater 108,
It is formed of a heat-resistant resin such as PPS or liquid crystal polymer, and also has a role as a guide member for promoting smooth rotation of the fixing film 111.

A heater clip 114 and a heater connector 112 for supplying electricity to the heater include a heater 108 and a heater holder.
Hold the end of 109. The fixing film 111 is a cylindrical heat-resistant film having a three-layer structure. The innermost layer is a base layer, which is responsible for mechanical properties such as torsional strength and smoothness of the fixing film 111, and is made of a resin such as polyimide.

The next layer is a conductive primer layer, in which conductive particles such as carbon black are dispersed.
The conductive primer layer also serves as an adhesive for bonding the third layer and the base layer. The outermost layer is a top layer and is designed to have an optimum resistance value and film thickness so as not to cause various image defects. 110 is a fixing stay made of metal such as iron and aluminum. The fixing stay 110 plays a role of suppressing deformation of the heater holder 109 due to creep and increasing rigidity of the heater holder 109. Numerals 113 are flanges mounted on both ends of the fixing stay 110, respectively.

The fixing film 111 externally fitted to the heater 108, the heater holder 109, and the fixing stay 110 is located between the flanges 113 at both ends in the axial direction and is restricted in the longitudinal direction. The above assembly is a film unit.

Reference numeral 119 denotes a pressure roller. The pressure roller 119 covers a metal core 119a made of aluminum, cast iron, or the like with a rubber 119b having heat resistance such as silicon rubber. The surface layer of the rubber 119b of the pressure roller is PFA, PTF which has release properties from toner.
Fluorine resin coating such as E and FEP is provided. Both ends of the pressure roller 119 are rotatably supported between side plates of a heating device (not shown). The film unit is opposed to the upper side of the pressure roller 119 so that the heater 108 faces downward.
The fixing nip N is formed by pressing the pressing member 13 downward by the pressing spring 116.

The pressure roller core metal 119a of the pressure roller 119 is rotationally driven by the pressure roller gear 115, and
Numeral 11 rotates following the fixing nip N. The sheet P carrying the toner is conveyed by the transfer roller 208 and the photosensitive drum 201, and is guided to the fixing nip N by the fixing entrance guide 118. The toner T on the sheet P is pressed and heated on the recording medium P at the fixing nip N, and the toner T
Is softened and adheres to the sheet P to be permanently fixed. In such a film heating type fixing device, a heating element having a low heat capacity can be used.
Shortening of the wait time (quick start) becomes possible. Further, by enabling quick start, preheating during non-printing operation is not required, and power saving can be achieved comprehensively.

[0018]

However, the conventional heating apparatus has the following problems.

In the conventional thermistor 117, the protective sheet 103 has a shape that completely covers the temperature detecting element 101 and the elastic body 102.

Therefore, in order for the temperature detecting element 101 to reliably contact the heater 108 via the protective sheet 103, in order to prevent the protective sheet 103 from interfering with the hole 109a of the heater holder 109 and climbing up, FIG. As shown in the figure, it is necessary to ensure a sufficient gap G3 between the protection sheet 103 and the heater holder 109.

On the other hand, when the gap G3 becomes large, when the heater 108 generates heat, there are a portion where the member (the heater holder 109 and the protection sheet 103) is in contact with the upper surface side of the heater 108 and a portion where there is no member (the gap G3). A temperature difference occurs, and a difference in internal stress applied to the inside of the heater 108 increases, which may cause the heater 108 to be damaged.

An object of the present invention is to ensure that the temperature detecting element 101 abuts on the heater 108 and reduce the difference in internal stress applied to the heater 108 in the heating apparatus having the above-described film unit.

[0023]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional heating apparatus.
The invention has a heating element having a heating section on one surface extending in a direction perpendicular to the transport direction of the medium to be heated, a heating element holding member that holds the heating element with the heating section being the transported medium to be heated, Temperature detecting means mounted on a hole formed in the heating element holding member and exposing the other side of the heating element,
The temperature detecting means includes a temperature detecting element for detecting a temperature in contact with the heating element, a temperature detecting element holding member for holding the temperature detecting element via a heat-resistant elastic body, the temperature detecting element and the heat resistant element. A heat-resistant protective sheet that covers the elastic body, wherein at least one end of the heat-resistant elastic body is exposed from the heat-resistant protective sheet.

A second invention is characterized in that a heat insulating layer is formed between the heat-resistant elastic body and the periphery of an opening provided in the heating element holding member.

In a third aspect based on the second aspect, the heat-insulating layer includes at least one slope portion formed around the opening of the hole that spreads away from the heating element, And a portion having a size larger than a hole of the heating body holding member formed on the body.

According to a fourth aspect of the present invention, in the third aspect, the portion of the heat-resistant elastic body having a size larger than the hole of the heating-member holding member is heated as the distance from the heating body increases. Is formed on a slope extending in the longitudinal direction.

In a fifth aspect based on the third aspect, the portion of the heat-resistant elastic body having a size larger than the hole of the heating-member holding member is set so that the portion of the heating-element holding member becomes farther away from the heating-element side. Are formed in a step-shaped portion extending in the longitudinal direction.

According to a sixth aspect, in the fifth aspect, the heat-resistant elastic body is constituted by a combination of at least two or more heat-resistant elastic parts having different longitudinal dimensions of the heating element. Features.

According to a seventh aspect of the present invention, in any one of the above-mentioned inventions, a pressurized contact is made between the cylindrical sheet provided on the heating element and the heating element holding member via the cylindrical sheet. And a pressurizing member that performs the operation.

According to an eighth aspect of the present invention, there is provided the heating device according to the seventh aspect, wherein a recording medium carrying an unfixed toner image is passed between the pressurizing member and the cylindrical sheet. And fixing the unfixed toner image to the recording medium by applying heat and pressure.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 shows a temperature detecting means attached to a heating device according to Embodiment 1 of the present invention. Other than the temperature detecting means, that is, the thermistor, is the same as the conventional image forming apparatus.

The thermistor for detecting the temperature of the heater 8 is as follows:
A temperature detecting element 1, a heat-resistant elastic body 2 elastically holding the temperature detecting element 1, a thermistor frame 4 supporting the temperature detecting element 1 and the elastic body 2 and having a positioning shape with respect to the heater holder 9, and a thermistor frame 4. It is composed of a thermistor metal 5 integrally formed and electrically connected to the temperature detecting element 1, and a heat-resistant protective sheet 3 which covers the temperature detecting element 1 and the elastic body 2 and is positioned on the thermistor metal 5.

The temperature detecting element 1 can be moved up and down by an amount of expansion and contraction of the elastic body 2 by a groove provided in the thermistor frame 4. The thermistor is positioned by the heater holder 9, and is urged by the thermistor pressing spring 6 to the heater 8. Reference numeral 7 denotes a thermistor holding spring support member. The amount of power supplied is controlled by the CPU so that the temperature of the thermistor becomes constant.

In order for the temperature detecting element 1 to reliably contact the heater 8 via the protective sheet 3, it is necessary to prevent the protective sheet 3 from interfering with the hole 9a of the heater holder 9 and getting on.

Therefore, the protection sheet 3 and the heater holder 9 are taken into account in consideration of the component tolerance and the assembly tolerance of the protection sheet 3.
Is sufficiently secured.

On the other hand, even if the elastic body 2 and the heater holder 9 interfere with each other, the end of the elastic body 2 can absorb the interference due to the elasticity of the elastic body 2.
1 is sufficiently smaller than the gap G2.

Therefore, the positional relationship between the elastic body 2 and the protective sheet 3 is such that the elastic body 2 is exposed from the protective sheet 3.

As described above, in the first embodiment, the following effects are obtained by exposing the elastic body 2 constituting the thermistor from the protective sheet.

First, the protection sheet 3 and the heater holder 9
Since the gap G2 with the hole 9a can be sufficiently ensured, the temperature detecting element 1 reliably contacts the heater 8, and the reliability of the detected temperature is improved.

Second, the hole 2a of the elastic body 2 and the heater holder 9
Can be minimized by utilizing the elasticity of the elastic body 2. Therefore, when the heater 8 generates heat, a member (heater holder 9,
The temperature change of the heater 8 is reduced between the portion where the protective sheet 2) is provided and the portion where the protective sheet 2 is not provided (gap G1), and the difference in internal stress applied to the heater 8 is reduced, so that a highly reliable heating device can be provided. I can do it.

(Embodiment 2) FIG. 2 shows a temperature detecting means attached to a heating device according to Embodiment 2. Embodiment 2 is the same as Embodiment 1 except for the elastic body 2 provided in the thermistor.

In the second embodiment, the structure of the first embodiment, that is, “the elastic body 2 forming the thermistor is replaced with the protective sheet 3
From the heater holder 9
The portion facing the heater in the longitudinal direction at a has an inclined surface 9b inclined toward the hole 9a and a shape in which the inclined end of the inclined surface 9b is continuous with the flat surface 9c.

In the elastic body 2, overhanging portions 2a projecting toward the inclined surface 9b are formed on both sides in the longitudinal direction of the heater. Therefore, the size of the elastic body 2 in the heater longitudinal direction is formed larger than the hole 9 a of the heater holder 9.

In the present embodiment, when the heater 8 generates heat, the elastic body 2 and the heater holder 9 overlap in the vertical direction.
Is formed.

Therefore, the temperature change of the heater 8 is reduced more than the configuration shown in the first embodiment, and the internal stress difference applied to the inside of the heater 8 is reduced.

In the second embodiment, the end of the elastic body 2 has a stepped shape. However, as shown in FIG.
Slope portion 2 which becomes wider in the longitudinal direction of the heater (as it goes upward in the figure)
b may be provided, and the hole 9a of the heater holder 9 may be provided with inclined surfaces 9d at both ends in the longitudinal direction of the heater. Larger than.

As described above, in the configuration of the second embodiment, when the heater 8 generates heat, the elastic member 2 and the hole 9a of the heater holder 9 are heated.
Are formed at the portions where
(Heater holder 9, protective sheet)
2) The temperature change of the heater 8 in the portion where there is and the portion where there is no (gap G1) is reduced more than the embodiment shown in Embodiment 1, and the heater 8
Since the internal stress difference applied to the inside becomes small, it is possible to provide a heating device having excellent reliability.

(Embodiment 3) FIG. 4 shows a temperature detecting means attached to a heating device according to Embodiment 3. Except for the elastic body 2 provided in the thermistor, it is the same as the first and second embodiments.

In the structure of the second embodiment, a step-like shape is provided such that the end of the elastic body 2 is separated from the heater 9 and becomes wider, and the size of the elastic body 2 in the heater longitudinal direction is larger than the hole 9a of the heater holder 9. are doing. that time,
In order to form the elastic body 2 in a stepped shape, it is necessary to perform secondary processing such as cutting on the elastic body 2, so that there is a problem that the cost increases.

Therefore, in the third embodiment, the second elastic body 2b having a shorter length in the heater longitudinal direction than the first elastic body 2a is provided below the first elastic body 2a which is longer in the heater longitudinal direction.
Are overlapped with each other to obtain the same step shape at the end of the elastic body 2 as in the first embodiment.

As described above, in the form of the third embodiment, the elastic body 2 having the stepped end face of the first embodiment is formed by overlapping the elastic bodies 2a and 2b each formed of two rectangular parallelepipeds. Therefore, it is not necessary to perform secondary processing of the elastic body 2.

Therefore, in addition to the effects shown in the first embodiment, an inexpensive heating device can be provided to the user.

[0053]

As described above, according to the first aspect of the present invention, by exposing the elastic body from the protective sheet, the gap between the protective sheet and the hole of the heating element holding member can be sufficiently secured. The gap between the elastic body and the hole of the heating element holding member is
It is possible to minimize using the elasticity of the elastic body.
Therefore, of course, the reliability of the detected temperature is improved,
It is possible to provide a highly reliable heating device in which the temperature change of the heating element during heat generation is reduced and the difference in internal stress applied to the heating element is reduced.

According to the invention according to claims 2 to 5 of the present application,
In addition to the effects of the invention described above, for example, at both ends of the elastic body,
By providing a step-shaped portion or a slope portion that becomes wider apart from the heating element, and by making the side of the elastic body opposite to the heating element larger than the hole of the heating element holding member, when the heating element generates heat, A heat insulating layer is formed at the portion where the holes of the heating element holding member overlap.

Therefore, it is possible to provide a highly reliable heating device in which the change in temperature of the heating element is further reduced, and the difference in internal stress applied to the heating element is further reduced.

According to the invention of claim 6 of the present application, since the elastic body is formed by overlapping two elastic bodies, it is not necessary to perform secondary processing on the elastic body. Therefore, it is possible to provide an inexpensive heating device that has a small difference in internal stress applied to the heating body and has excellent reliability to the user.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a thermistor of a heating device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a thermistor of a heating device according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram of a thermistor of the heating device according to the second embodiment of the present invention.

FIG. 4 is a schematic diagram of a thermistor of a heating device according to a third embodiment of the present invention.

FIG. 5 is a schematic diagram of an image forming apparatus.

FIG. 6 is a schematic longitudinal view of a conventional heating device.

FIG. 7 is a sectional view taken along line AA of FIG. 6;

FIG. 8 is a schematic diagram of the thermistor of FIG. 6;

[Explanation of symbols]

 1. Temperature sensing element 2. Elastic body 3. Protective sheet 4. Thermistor frame 5. Thermistor metal 6. Thermistor presser spring 7. Thermistor presser spring support member 8. Heater 9. Heater holder 10. Fixing stay

Claims (8)

[Claims] A heating element having a heating section on one surface extending in a direction perpendicular to the transport direction of the medium to be heated; a heating element holding member configured to hold the heating element with the heating section being a transport side of the medium to be heated; Temperature detecting means mounted on a hole formed in the heating element holding member and exposing the other side of the heating element, wherein the temperature detection means detects a temperature in contact with the heating element. A heating device comprising: an element, a temperature detection element holding member that holds the temperature detection element via a heat-resistant elastic body, and a heat-resistant protection sheet that covers the temperature detection element and the heat-resistant elastic body. A heating device, wherein at least one end of the heat-resistant elastic body is exposed from the heat-resistant protective sheet. 2. The heating apparatus according to claim 1, wherein a heat insulating layer is formed between the heat-resistant elastic body and a periphery of an opening provided in the heating element holding member. 3. The heat-insulating layer includes at least one slope formed around the opening of the hole that spreads away from the heating element side, and the heating element holding member formed on the heat-resistant elastic body. The heating device according to claim 2, wherein the heating device includes a portion having a size larger than the hole. 4. A portion having a size larger than a hole portion of the heating element holding member formed in the heat resistant elastic body is formed on a slope portion which spreads in a longitudinal direction of the heating element as being away from the heating element side. The heating device according to claim 3, wherein: 5. A portion having a size larger than a hole of the heating element holding member formed in the heat-resistant elastic body is formed as a step-shaped portion which spreads in a longitudinal direction of the heating element as being away from the heating element side. The heating device according to claim 3, wherein: 6. The heat-resistant elastic body is constituted by a combination of at least two heat-resistant elastic parts having different longitudinal dimensions of the heating element.
A heating device according to claim 1. 7. A heating device comprising: a tubular sheet provided on the heating element and the heating element holding member; and a pressing member for bringing the heating element into pressure contact with the heating element via the cylindrical sheet. The heating device according to claim 1. 8. An unfixed toner image having the heating device according to claim 7, wherein a recording medium carrying an unfixed toner image is passed between the pressurizing member and the tubular sheet. An image forming apparatus comprising: fixing an image to the recording medium by applying heat and pressure.