JPH11194635A - Heating roller for fixing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating roller excellent in safety without igniting foaming resin material being a pressing member even when a heating element causes local overheat. SOLUTION: This heating roller 1 is constituted so that a hollow cylindrical aluminum roller main body 3 is used as base material, an adhesion preventing layer 8 is formed on the outer peripheral surface of the main body 3, three layers of a 1st heat-resisting insulating layer 5, a heating layer 7 and a 2nd heat-resistant insulating layer 9 in order from an outer periphery side are formed on the inner peripheral surface of the main body 3, and film material consisting of the three layers is put and held between a conductive elastic body 6 arranged inside the film material and the main body 3. The elastic body 6 is a leaf spring obtained by forming a stainless steel, aluminum or copper thin plate to be cylindrical, and it is excellent in heat conductivity, has small heat capacity because it is thin in thickness and is excellent in heat saturation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device provided in an image forming apparatus such as a printer or a copying machine for fixing a recording material adhered onto a recording medium by heating and melting or softening the recording material. Heating roller (hereinafter,
Simply referred to as “heating roller”).

[0002]

2. Description of the Related Art In a conventional image forming apparatus, for example, an electrophotographic printer or copier, a heating roller of a fixing device provided for fixing toner as a recording material onto paper as a recording medium is made of aluminum or aluminum. 2. Description of the Related Art In many cases, a halogen lamp is arranged inside a hollow cylindrical roller formed of stainless steel, and the entire roller is heated to a constant temperature by radiant heat generated by light emission of the halogen lamp.

However, such a heating roller has a low thermal efficiency because the halogen lamp is disposed at the center of the heating roller and is not in close contact with the roller surface. However, there is a problem that it takes a long time to reach a predetermined temperature suitable for fixing the image.

Under these circumstances, for example, Japanese Patent Application Laid-Open No. Hei 9-1386
As disclosed in Japanese Patent Application Laid-Open No. 2005-179423 and Japanese Patent Application Laid-Open No. 9-179423, there has been proposed a heating roller in which a resistance heating element layer is provided on the inner peripheral surface of a heating roller, and the resistance heating element layer is used as a heat source. Specifically, as shown in FIG. 7A, the heating roller includes a metal pipe 101 and a metal pipe 1.
Heat-resistant insulating layer 1 having a heating element disposed on the inner peripheral surface
02 and a pressure contact body 103a mounted on the inner surface of the heat-resistant insulating layer.
2 is pressed and fixed in the inner peripheral direction of the metal pipe 101. The heat-resistant insulating layer 102 is formed by fixing a heating element on the surface of a film material such as polyimide.
The heating element is directly pressed by a pressure contact body 103 formed of a foamed resin material such as a silicone resin. Pressing body 10
Reference numeral 3 is formed of a hollow cylindrical or solid cylindrical foamed rubber body or a curable foamed resin material. For this reason, the close contact between the heat-resistant insulating layer 102 and the inner peripheral surface of the metal pipe 101 is achieved by the internal pressure of the foamed rubber body or the foamed resin material, and the heat of the heating element is transmitted well to the metal pipe. .

[0005]

However, since the foamed resin material has a foaming gap, if the pressing force is insufficient at a portion not in contact with the heating element, local overheating of the heating element may occur. . In addition, silicone resin or the like used as the foamed resin member has poor heat conductivity, and thus has a poor function of dispersing local heat generated from the heating element. As a result, the foamed resin material is thermally broken, and in the worst case, it may cause ignition.

That is, the heat resistance of polyimide or the like used as the heat-resistant insulating layer is about 500 ° C. while the insulation and mechanical strength are guaranteed, whereas the heat resistance of the silicone sponge or the like used as the foamed resin material is about 500 ° C. Is 350
Since the temperature is as low as 360 ° C., when the resistance heating element causes abnormal overheating, the silicone sponge quickly breaks down heat. When the silicone sponge undergoes thermal destruction, the molecular structure of the silicone sponge changes and its elasticity is reduced, so that the heat-resistant resin layer 102 on which the heating element is formed cannot be adhered to the inner peripheral surface of the metal pipe 101. If the heat-resistant resin layer 102 and the metal pipe 101 do not adhere to each other, the heat of the heating element becomes difficult to be transmitted to the metal pipe 101, and the heat is not radiated. Breakdown occurs between the metal heating element and the metal pipe, causing current to leak and causing ignition. These series of phenomena occur instantaneously once the thermal destruction of the silicone sponge occurs. in this case,
It is conceivable to detect overheating of the roller by an overheating temperature sensor or the like.However, thermal destruction of the silicone sponge due to local overheating occurs instantaneously. In order to detect the surface temperature, it is necessary to prepare a large number of overheat temperature sensors, and there is a problem that it is technically and costly.

[0007] It is an object of the present invention to provide a heating roller excellent in safety which prevents a pressing member from being thermally broken even when a heating element causes local overheating and does not cause ignition. .

[0008]

SUMMARY OF THE INVENTION In view of the above problems, a heating roller according to a first aspect of the present invention includes a hollow cylindrical roller body and a first roller disposed on an inner surface of the roller body. A heat-resistant insulating layer, a resistance heating element disposed on the inner surface of the first heat-resistant insulating layer, a second heat-resistant insulating layer disposed on the inner surface of the resistance heating element, and an inner surface of the second heat-resistant insulating layer And a conductive elastic body that presses the second heat-resistant insulating layer in the inner circumferential direction of the roller body, wherein the first heat-resistant insulating layer and the resistance heating element are formed by the elastic force of the conductive elastic body. And the second heat-resistant insulating layer is fixed to the roller body.

In the above heating roller, the resistance heating element is
For example, a foil film made of stainless steel, copper, or the like is formed in a predetermined pattern. Then, the roller body is heated by the heated resistance heating element so that the surface temperature thereof has a predetermined temperature distribution.

A first heat-resistant insulating layer is provided outside the resistance heating element in order to ensure insulation between the heating roller and the metal roller body. The first heat-resistant insulating layer is a layer composed of one or a plurality of insulating resin films or the like, and the above-described resistance heating element is disposed on the inner surface of the insulating resin film forming the innermost layer. .

Further, a second or a plurality of insulating resin films or the like formed inside the resistance heating element are provided.
A conductive elastic body is provided via a heat-resistant insulating layer. The conductive elastic body is a thin-plate cylindrical elastic body that presses and fixes the layer disposed on the outer side thereof in the direction of the inner peripheral surface of the roller body by its elastic force. Therefore, it has excellent thermal conductivity and small heat capacity, so that it has good temperature saturation. That is, even if the resistance heating element disposed outside has a locally high temperature, the heat generated there is dispersed and saturated throughout the conductive elastic body. For this reason, temperature unevenness due to local heat generation does not occur, and partial abnormal overheating of the heating roller can be effectively prevented. Since the second heat-resistant insulating layer is disposed between the conductive elastic body and the resistance heating element, insulation is ensured, and no short circuit or the like occurs.

A heating roller according to a second aspect of the present invention is characterized in that the conductive elastic body is formed of metal. That is, the conductive elastic body is configured as a leaf spring in which a thin plate of stainless steel, aluminum, copper, or the like is formed in a cylindrical shape. Since the metal has sufficient elasticity and is a good conductor of heat, the effect as the conductive elastic body can be remarkably exhibited.

The heat roller according to claim 3 of the present application is characterized in that the heat conductivity of the conductive elastic body is higher than the heat conductivity of the second heat-resistant insulating layer. Generally, the material used as the heat-resistant insulating layer has poor thermal conductivity, so that heat tends to stagnate locally, and the temperature may rise abnormally at that portion. Since the conductive elastic body has excellent heat conductivity, a part of the conductive elastic body receives local heat and can uniformly disperse the heat throughout the conductive elastic body. When this heat is saturated in the conductive elastic body, the dispersed heat is transmitted to the heat-resistant insulating layer again. Therefore, temperature unevenness does not occur over the entire roller body. As a result, it is possible to effectively prevent thermal breakdown and further dielectric breakdown of the heat-resistant insulating layer and the like.

According to a fourth aspect of the present invention, in the heating roller, the heat resistance of the conductive elastic body is higher than the heat resistance of the second heat insulating layer. Since the conductive elastic body has excellent thermal conductivity, it is necessary that the conductive elastic body itself does not have a risk of ignition or the like, and the heat resistance is ensured, so that the safety is further improved. A heated roller can be provided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings in order to further clarify the embodiments of the present invention. FIG. 1 is a schematic cross-sectional view of a printer as an image forming apparatus configured using the heating roller according to the present embodiment,
FIG. 2 is a side cross-sectional view of a fixing device configured using the heating roller, FIG. 3 is a front cross-sectional view of the fixing device, and FIG.
FIG. 3 shows a cross-sectional view of the heating roller.

As shown in FIG. 1, a laser printer P according to this embodiment has a fixing device 10, an image forming mechanism 20, a paper supply mechanism 30, a paper discharge mechanism 60 and the like housed in a housing 70. Have been. After the fixing device 10 forms an image made of toner (hereinafter, referred to as a toner image) on paper as a recording medium in the image forming mechanism 20,
The paper is heated while being transported downstream in the paper transport direction,
The toner is fused or softened on the paper to fix the toner image on the paper.

As is well known, the image forming mechanism 20 includes:
It performs an electrophotographic image forming process, and includes a drum type electrophotographic photosensitive member, a charger, an exposure device, a developing device, a transfer device, a static eliminator, and the like. When forming a toner image on paper,
A charge is given to the surface of the drum type electrophotographic photosensitive member,
The electrostatic latent image is formed by projecting light from a laser light source on the surface, the electrostatic latent image is developed with toner, and an image composed of the toner is transported from the upstream side to the downstream side in the paper transport direction. Is performed.

A paper supply mechanism 30 is provided upstream of the image forming mechanism 20 in the paper transport direction. The paper supply mechanism 30 includes a paper cassette unit 4 in which paper is stacked and stored.
0, or the paper is taken in from one of the manual paper feed units 50 that can supply the paper one by one, and the paper is sandwiched between rotating rollers while moving to the image forming mechanism 20 side downstream in the paper transport direction. Transport. Further, a sheet discharging mechanism 60 is disposed downstream of the fixing device 10 in the sheet conveying direction. The paper discharge mechanism 60 conveys the paper on which the toner image has been fixed in the fixing device 10 to a tray on the upper part of the main body.

Next, the fixing device 10 will be described in detail. As shown in FIG. 2, the fixing device 10 includes a heating roller 1 and a pressure roller 2 paired with the heating roller. As will be described in detail later, the heating roller 1 is formed by fixing a heating element on the inner peripheral surface side of a cylindrical body made of aluminum. The pressure roller 2 is formed by providing heat-resistant silicone rubber around a metal shaft.

The heating roller 1 and the pressure roller 2 are arranged in parallel with their outer peripheral surfaces in contact with each other. The pressure roller 2 is rotatably supported by a movable bearing 14, and the movable bearing 14 is urged by a spring 16. As a result, the pressure roller 2 is in pressure contact with the heating roller 1.

In the vicinity of the heating roller 1 and the pressure roller 2, paper guides 12, 13 are provided. The paper guide 13 is a member that guides the paper S transported from the image forming mechanism 20 on the upstream side in the paper transport direction to the pressure contact surfaces of the heating roller 1 and the pressure roller 2. The sheet guide 12 is a member that guides the sheet S, which is sandwiched between the pressure contact surfaces of the heating roller 1 and the pressure roller 2 and is sent with the rotation of both rollers, to the sheet discharge mechanism 60 further downstream in the sheet conveying direction. It is.

Further, a cover 15 provided with a paper guide 17 is disposed above the heating roller 1 in order to prevent the sheet S from coming into contact with the heated heating roller 1 again. An overheat temperature sensor 26 is mounted on the cover 15. The overheating temperature sensor 26 is disposed to face the outer peripheral surface of the heating roller 1 and, when an abnormal overheating of the heating roller 1 occurs due to a runaway of the control device or the like, detects the abnormal overheating and shuts off the power supply circuit. . Overheat temperature sensor 2
Specifically, a thermal fuse or a thermostat can be used as 6. The fixing device 10 is provided with a temperature sensor (not shown) for detecting the surface temperature of the heating roller 1 separately from the overheating temperature sensor 26. The temperature sensor constantly monitors the surface temperature of the heating roller 1. Then, control is performed so that an appropriate temperature is maintained.

The heating roller 1 configured as described above
As shown in FIG. 3, the bearing 4 fixed to the body frame
1 and 41 rotatably supported. A driving gear 25 is mounted on one end of the heating roller 1, and a driving force from a motor (not shown) is transmitted to the driving gear 25 to rotate the heating roller 1. The drive gear 25 is formed by processing PPS (polyphenylene sulfide resin) having excellent heat resistance, and the bearing 41 is formed by molding a composite resin material in which carbon is dispersed as a conductive filler in PPS serving as a matrix. It is processed and has heat resistance and conductivity that do not soften up to about 250 ° C. to 260 ° C. As a result, the heating roller 1
As long as is used under normal temperature conditions (about 200 ° C.), the bearing 41 and the drive gear 25 do not deform. The heating roller 1 is electrically connected to grounded metal parts and the like via the bearings 41, 41, thereby preventing the heating roller 1 from being charged.

Further, sliding contact mechanisms 75, 75 are formed at both ends of the heating roller 1. The sliding contact mechanism 75 includes a rotating electrode member 71 fixed to the heating roller 1 and rotating integrally with the heating roller 1, and a stationary electrode member 72 fixed to the main body frame and in contact with the rotating electrode member 71. The rotating electrode member 71 is electrically connected to a current-carrying terminal of a sheet-like heating element, which will be described later, fixed to the inner peripheral surface side of the heating roller 1. Further, the stationary electrode member 72 is in pressure contact with the rotating electrode member 71 with elastic deformation. As a result, the two electrode members slide while maintaining the contact even when the heating roller 1 rotates, and can maintain a state in which both are electrically connected. In addition, electric power is supplied to the heating element through the sliding contact mechanisms 75, 75. As shown in FIG. 4, the heating roller 1 itself has a hollow cylindrical aluminum roller body 3.
An anti-adhesion layer 8 is formed on the outer peripheral surface of the roller body 3 using the base material as a base material, and the first heat-resistant insulating layer 5, the heat-generating layer 7, and the second heat-resistant insulating layer 9 Three layers are formed, and the film material constituting the three layers is sandwiched and held between the inner peripheral surface of the roller main body 3 by the conductive elastic body 6 disposed inside the film material.

The adhesion preventing layer 8 is provided to prevent the toner on the recording medium from adhering to the surface of the heating roller 1 during the fixing process. It is formed by coating a fluororesin-based material with excellent properties and separation properties, and its thickness is about 10-30 μm.
m.

First heat resistant insulating layer 5 and second heat resistant insulating layer 9
Are made of one or a plurality of polyimide resin film materials, and have excellent heat resistance and insulation properties. In order to prevent an unexpected short circuit or an electric shock accident, the heating layer 7 is sandwiched from both sides to electrically isolate the heating layer 7 from the roller body 3, the conductive elastic body 6, and other members.

The conductive elastic body 6 is formed by forming a thin plate of stainless steel, aluminum, copper, or the like into a cylindrical shape. The conductive elastic body 6 is excellent in conductivity, has good heat conductivity, and has a small thickness, and therefore has heat capacity. Small and excellent in heat saturation. The conductive elastic body 6 is a cylindrical body having an outer diameter slightly larger than the diameter formed by the inner peripheral surface of the second heat-resistant insulating layer 9 provided on the outer periphery thereof. 6 (a) shows a conductive elastic body 6a. When inserting into the roller main body 3, it is inserted in a state where the outer diameter is contracted by cooling. The inserted conductive elastic body 36 expands in the direction in which the outer diameter returns to its original state as the temperature rises, and presses the first heat-resistant insulating layer 5, the heat-generating layer 7, and the second heat-resistant insulating layer 9 to remove them. It is in a state of being sandwiched between the roller body 3. That is, the conductive elastic body 6 has a leaf spring functioning as a pressing body using its own deformation energy.

The heating layer 7 is constituted by a sheet-like heating element 57 shown in FIG. This sheet-like heating element 5
7 is an insulating substrate 5 made of a polyimide resin film
1 is a flexible sheet on which a resistance heating element 55 made of a stainless steel foil film is adhered. When the heating element 1 is disposed in the heating roller 1, the resistance heating element 55
It is arranged in the direction in contact with. The insulating substrate 5
1 forms a part of the first heat-resistant insulating layer 5 (see FIG. 4), that is, the innermost layer of the first heat-resistant insulating layer 5.

The resistance heating element 55 includes a pattern section 55a functioning as a heating element, a first current-carrying terminal section 55b and a second current-carrying terminal section 55c connected to both ends of the pattern section 55a, respectively. Then, when a current flows between the two energizing terminal portions 55b and 55c, the pattern portion 55a
Has a structure that generates heat. Such a resistance heating element 5
The pattern portion 55a of No. 5 can be formed by forming a stainless steel foil film on the insulating base material 51 and performing an etching process on the stainless steel.

The temperature distribution of the calorific value of the resistance heating element 55 is adjusted by the shape, cross-sectional area, etc. of the pattern in the pattern section 55a. That is, by utilizing the fact that the calorific value is large in the region with a small cross-sectional area and small in the region with a large cross-sectional area, the calorific value is adjusted so that the temperature distribution on the outer peripheral surface of the heating roller 1 becomes uniform. doing. In the present embodiment, the cross-sectional area of the pattern is
The heating roller 1 is heated as it approaches the both ends of the heating roller 1 from the pattern A to the pattern D shown in FIG. This is because both ends of the heating roller 1 have a larger amount of heat radiation than the central portion, and if the heat generation amount is the same over the entirety, the surface temperature tends to be lower near the both ends than at the central portion. is there.

As described above, the heating roller in this embodiment uses a conductive leaf spring as the conductive elastic body 6, so that the layer disposed outside the heating roller can be easily formed on the inner peripheral surface of the roller body 3. It can be pressed and fixed in the direction. Further, since the above-mentioned leaf spring is made of a thin plate having good conductivity, it has excellent heat conductivity. Furthermore, the surface of the conductive elastic body 6
Since it is smoother and has no gaps as compared with the foam, it is possible to uniformly press the layer disposed outside the foam.

Accordingly, there is little possibility that local overheating of the resistance heating element 55 occurs due to the uneven pressing force. Nevertheless, for some reason, even if the temperature of the resistance heating element 55 disposed outside thereof is locally increased, and the second heat-resistant insulating layer 9 disposed inside the resistance heating element 55 is locally heated, However, the heat generated there is received by a part of the conductive elastic body 6 disposed further inside, and is uniformly dispersed and saturated throughout the conductive elastic body 6. For this reason, the temperature unevenness due to the local heat generation does not occur on the heating roller 1 itself, and the outer surface of the heating roller 1 can maintain a stable heating state. Further, the conductive elastic body 6 is not thermally broken, and the film material used as the first heat-resistant insulating layer 5 disposed outside the resistance heating element 55 is broken, and current leaks due to dielectric breakdown. Not even.
Since the second heat-resistant insulating layer 9 is disposed between the conductive elastic body 6 and the resistance heating element 55, insulation is ensured, and no short circuit occurs.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various embodiments can be adopted without departing from the gist of the present invention. For example, in this embodiment, a laser printer is used as the image forming apparatus, but a copying machine or a facsimile may be used. Further, the image forming method is not limited to the electrophotographic method using a toner, but may be a hot melt ink jet method using a heat-meltable ink.
Although the material of the roller body 3 of the heating roller 1 is aluminum, this material may be a conductor or a non-conductor.
Any material having good thermal conductivity may be used.

In the above embodiment, the conductive elastic body 6 used was a cylindrical body as shown in FIG. 6A. However, as shown in FIG. A shape with a notch may be used. in this case,
The outer diameter of the cylindrical body is slightly larger than the diameter formed by the inner peripheral surface of the second heat-resistant insulating layer 9. When the conductive elastic body 6 is inserted into the roller main body 3, the pressing is released after the cutting is performed in a direction in which the notch is closed and the outer diameter is reduced. Then, the inserted conductive elastic body 36 expands in a direction in which the outer diameter returns to its original state, and presses the first heat-resistant insulating layer 5, the heat-generating layer 7, and the second heat-resistant insulating layer 9, and the roller body 3 It is in a state of being sandwiched between.

Further, the conductive elastic body 6 is formed as shown in FIG.
As shown in the above, a shape in which a spiral gap is formed on the circumference of the cylindrical body may be used. The outer diameter of this cylindrical body is the second
The diameter is slightly larger than the diameter formed by the inner peripheral surface of the heat-resistant insulating layer 9. When the conductive elastic body 6 is inserted into the inside of the roller body 3, the conductive elastic body 9 is twisted in the outer peripheral direction so that the outer diameter is reduced and then the torsional force is released. Then, the inserted conductive elastic body 36 expands in a direction in which its outer diameter returns to its original state, and presses the first heat-resistant insulating layer 5, the heat-generating layer 7, and the second heat-resistant insulating layer 9, and the roller body 3 It is in a state of being sandwiched between.

The conductive elastic body 6 shown in FIGS. 6B and 6C is preferably configured so that no gap is formed in the cut when the conductive elastic body 6 is mounted inside the roller body 3. . Further, a thin plate made of a shape memory alloy may be used as the conductive elastic body 6 and may be inserted into the roller body 3 in a rolled state. The inserted conductive elastic body tries to return to the original shape inside the rotor body,
This returning force is the force pressing the outer layer.

Further, as a matter of course, a rectangular thin plate may be simply rounded and inserted into the roller body 3 as the conductive elastic body 6. However, it is preferable that the length of the thin plate is longer than the length of the inner circumference of the roller body 3 in order to ensure a uniform pressing force on the layer disposed on the outside.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a laser printer having a heating roller as an embodiment.

FIG. 2 is an enlarged sectional view of a fixing device using a heating roller according to the embodiment.

FIG. 3 is a view taken in the direction of arrows AA in FIG. 2;

FIG. 4 is a sectional view of a heating roller according to the embodiment (BB in FIG. 3);
FIG.

FIG. 5 is an explanatory diagram of a heating element sheet of the heating roller according to the embodiment.

FIG. 6 is an explanatory diagram of a conductive elastic body of the heating roller according to the embodiment.

FIG. 7 is an explanatory view schematically showing a conventional heating roller.

[Explanation of symbols]

1 ... heating roller, 2 ... pressure roller, 3
... Roller body, 5 ... First heat-resistant insulating layer, 6 ...
· Conductive elastic body · · · · · · · heat generating layer · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Resistance heating element,
55a: Pattern part, P: Laser printer

Claims (4)

[Claims] A roller body having a hollow cylindrical shape; a first heat-resistant insulating layer disposed on an inner surface of the roller body; a resistance heating element disposed on an inner surface of the first heat-resistant insulating layer; A second heat-resistant insulating layer disposed on an inner surface of the heating element; and a conductive elastic body mounted on the inner surface of the second heat-resistant insulating layer and pressing the second heat-resistant insulating layer in an inner circumferential direction of the roller body. Wherein the first heat-resistant insulating layer, the resistance heating element, and the second heat-resistant insulating layer are fixed to the roller body by the elastic force of the conductive elastic body. Heating roller. 2. The fixing heating roller according to claim 1, wherein said conductive elastic body is formed of metal. 3. The thermal conductivity of the conductive elastic body is equal to the second conductivity.
The fixing heat roller according to claim 1, wherein the heat roller has a thermal conductivity larger than a heat conductivity of the heat-resistant insulating layer. 4. The fixing heat roller according to claim 1, wherein the heat resistance of the conductive elastic body is higher than the heat resistance of the second heat insulating layer.