JP2003122147A - Thermal fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a pressurizing mechanism for pressurizing a heating body to a pressure roller through a film in a film heating type fixing device. SOLUTION: Both ends of the pressure roller 6 are attached to between a pair of pressure roller supporting members 7 provided at both ends of a metallic stay 4, and resin regulation members 5 provided at both ends of the metallic stay 4 of a heating body holding member 3 are arranged above the roller 6 further, then the positioning projection 5b of the member 5 is fit in the hole of a pressurizing plate 8 capable of rocking in the up-and-down direction with a fulcrum at its one end, and a compression spring 9 is arranged between the other end of the plate 8 and the member 7. By making pressurizing force act on the pressurizing part 5a of the member 5 by the lever action of the plate 8 and turning a lever 10, the plate 8 is moved upward against the spring force of the spring 9, and the pressurizing force acting on the pressurizing part 5a of the member 5 is decreased.

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 of an image forming apparatus such as a copying machine, a laser printer, a facsimile, etc., which uses an electrophotographic process.

[0002]

2. Description of the Related Art An image forming apparatus using a conventional electrophotographic process is constructed, for example, as shown in FIG.

In FIG. 4, 201 is a photosensitive drum and 202
Is a charging roller, 203 is a laser exposure device, 204 is a reflection mirror, 205 is a developing sleeve, 206 is toner, and 2
Reference numeral 07 is a toner container, 208 is a transfer roller, 209 is paper as a recording medium, 210 is a cleaning blade, and 2 is a cleaning blade.
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.

The photosensitive drum 201 rotates in the direction of the arrow,
It is uniformly charged by the charging device 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 irradiated on the photosensitive drum 201, and an electrostatic latent image is formed on the photosensitive drum 201.

A toner container 207 is filled with toner 206, and an appropriate amount of toner 206 is appropriately charged with the rotation of the developing sleeve 205 and then supplied onto the photosensitive drum 201. 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 recording medium one by one from the paper cassette 213 at a timing. Separation pad 215
Is arranged in contact with the paper feed roller 214, and the friction coefficient, the ground contact angle, and the shape of the surface thereof are adjusted so that only one recording medium is fed for each paper feed.

The visualized toner image on the photosensitive drum 201 is transferred onto a recording medium by a 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. The recording medium 209 on which the toner image is placed is heated and pressed by the fixing device 212 so that the toner image is permanently fixed on the paper.

Conventionally, as the fixing device 212, Japanese Patent Laid-Open No. 63-63
As disclosed in Japanese Laid-Open Patent Publication No. 313182, there is a film heating method in which a heating element pattern is provided on a ceramic base material to form a heating element, and the heating element is heated to heat an object to be heated through a thin film. It is used.

However, in such a film heating system, a large biasing force is generated in the endless belt-shaped film. As a countermeasure against this, a method of suspending and driving the endless film disclosed in JP-A-04-44057 and JP-A-04-44077 with a margin to reduce the film deviation force and drive torque is practically used. Has been converted.

An example of a sectional view of such a film fixing device is shown in FIG. In FIG. 5, reference numeral 2 is a heating element, and a heating element 2a is formed on a ceramic base material, and a glass layer 2b is coated thereon as a protective layer. A thermistor 107 is mounted on the back surface of the heating element 2 to detect the temperature of the heating element 2. The heating element section is powered by a power source (not shown) to generate heat. The triac is driven by the CPU so that the temperature of the thermistor 107 is constant and the amount of power supply is controlled.

The heat resistant film 1 is a tubular heat resistant film having a three-layer structure. The innermost layer is a base layer, which is a layer responsible for mechanical properties such as twist strength and smoothness of the heat-resistant film 1, and polyimide, polyamide-imide, PEEK,
It is made of resin such as PES and PPS. The next layer is a conductive primer layer, which is a conductive layer in which conductive particles such as carbon black are dispersed, and plays a role of an adhesive for joining the third layer and the base layer. The outermost layer is the top layer and is designed to have the optimum resistance value and film thickness so as not to cause various image defects.

Reference numeral 3 denotes a heating member holding member, which supports the heating member 2 and is formed of a heat-resistant resin such as PPS or liquid crystal polymer, and also functions as a guide member for promoting smooth rotation of the heat-resistant film 1. . A metal stay 4 is made of metal such as iron and aluminum. The metal stay 4 suppresses the deformation of the heating element support member 3 due to creep and plays a role of increasing the rigidity of the heating element support member 3. Reference numeral 6 denotes a pressure roller, which covers a cored bar 6a made of aluminum, cast iron or the like with a heat-resistant elastic body 6b such as silicon rubber. The surface layer of the pressure roller 6 has a releasing property with respect to the toner PFA, P
A fluororesin coating such as TFE or FEP is provided.

The pressure roller 6 is pressed against the heating body 2 with the heat-resistant film 1 sandwiched therebetween, and the pressure contact portion forms a fixing nip portion N. The core metal 6a of the pressure roller 6 is driven to rotate,
The heat resistant film 1 is driven to rotate in the fixing nip portion N. The recording material P carrying the toner T is conveyed by a transfer roller (not shown) and a photosensitive drum, and is guided to the fixing nip portion N by the fixing entrance guide 105. The toner T on the recording material P is pressed and heated on the recording material P at the fixing nip portion N, and the toner resin is softened and adheres to the recording material P to be permanently fixed.

In such a film heating type fixing device, since a heater having a low heat capacity can be used as the heating element 2, the weight time can be shortened (quick start) as compared with the conventional heat roller type. Become. In addition, since quick start is possible, preheating during non-printing operation is not required, and overall power saving can be achieved.

FIGS. 6A and 6B are views of a pressing portion of a conventional heat fixing device, FIG. 6A being a perspective view and FIG. 6B being a side view. In FIG. 6, 1 is a heat resistant film, 2 is a heating body, 3 is a heating body holding member, 4 is a metal stay, 15 is a resin member, 15a is a pressing portion, 6 is a pressing roller, 17 is a pressing roller supporting member, 1
8 is a pressure plate, 18a is a positioning hole, 29 is a compression spring, 2
Reference numeral 0 is a pressure releasing means, and 21 is a spring pressing member.

As shown in FIG. 6, the pressing plate 18 presses the pressing portion 15a of the resin member 15 by the compression spring 29, so that the heating element 2 is pressed through the metal stay 4 and the heating element holding member 13. The roller 6 can be pressed against the roller 6.

Further, as shown in FIG. 7, the user can rotate the pressure releasing means 20 in the direction A in the figure to raise and support the pressure plate 18 in the direction B in the figure. This is because when the recording paper jams in the heat fixing device and the device stops, the user reduces the pressing force of the compression spring 29 to release the pressure contact between the heat resistant film 1 and the pressure roller 6 and jam the recording paper. Is a consideration to make it easier to process. At this time, until the heat resistant film 1 and the pressure roller 6 are completely separated from each other, the pressure plate 18
The jammed recording paper is, of course, the easiest to process if the temperature is raised.
Even if it is in the range of contacting, the jammed recording paper can be easily processed if the applied pressure is reduced.

The spring pressing member 21 has a function of pressing the upper end of the compression spring 29, but if the function is satisfied, the spring pressing member 21 may be integrally formed from the pressure roller supporting member 17. However, the pressure roller support member 17
When the resin member 15 is integrally formed with the pressure roller support member 17, it becomes difficult to incorporate the resin member 15 from the direction C in FIG. Therefore, when assembling the compression spring 29, there is a problem regarding workability such that the compression spring 29 must be inserted from the side while being compressed. Therefore, the spring pressing member 21 is provided as a separate component.

[0018]

However, the conventional heat-fixing device has the following problems.

The first problem is that the compression spring 29 has a large spring force. It is common to apply a total pressure of 10 kg or more, and it is inevitable that the thermal efficiency will have to be improved more and more in the future in view of market demands for higher speed printing and improved fixability of laser printers in the future. Further, the pressing force tends to increase. As described above, the larger spring load exceeds 5 kg on each side, which is a cause of problems such as large load variations and free length variations during spring fabrication, large measurement variations during quality control, and poor workability during assembly. It was.

The second problem is that the pressing force varies due to the dimensional variation of the spring pressing member 21. Since the spring pressing member 21 is a sheet metal part that is bent several times as shown in the figure, the manufacturing variation of the F dimension in FIG. 6 is large. This dimensional change causes a change in the attachment length of the spring and is directly connected to a change in the pressing force, which is a factor that causes the fixing property of the heat fixing device to vary.

The third problem is that the presence of the spring pressing member 21 makes the device large and complicated. As described above, the spring retainer member 21 bears a load exceeding 5 kg, and therefore needs to have a highly rigid structure. Therefore, there are problems that the parts become large, the manufacturing cost is high, and the fixing means also needs rigidity.

The present invention solves the above-mentioned problems of the prior art. By providing the pressure roller support member with a function equivalent to that of the conventional spring pressing member without impairing the workability during assembly, the spring pressing member is provided. By abolishing the members and reducing the load on the spring that bears the pressure, a high-quality heat fixing device with less variation in the pressure is realized.

[0023]

In order to solve the above-mentioned problems, the present invention holds a heat resistant film, a heating body composed of at least an insulating substrate and a resistance heating body, and the heating body and the film. A heating body holding member, a metal stay provided on the opposite side of the heating body holding surface of the heating body holding member, a regulation surface provided at both ends of the metal stay and regulating the width direction of the film, and pressure. A regulating member made of resin having a portion and a positioning protrusion, a pressure roller for bringing the film into pressure contact with the heating body, and for driving the film while sliding the film on the surface of the heating body; A pressure roller support member that supports both end portions and a positioning hole that supports the pressure member of the regulation member so as to be able to press and that the positioning protrusion fits are formed, and one end portion of the roller support member is formed. And is arranged between the pressure plate that is swingably engaged in the vertical direction and the other end of the pressure plate and the roller support member, and applies a pressure force to the regulation member via the pressure plate. , Spring means for pressing the heating body against the pressure roller while sandwiching the film, and resisting the spring force of the spring means in a direction to reduce the force for pressing the pressing portion of the regulating member by the pressing plate. Pressure release means capable of moving the pressure plate.

According to the above structure, a pair of left and right regulating members provided on both ends of the metal stay for regulating the width direction of the heat-resistant film, a pressing portion, and a pair of left and right regulating members having positioning protrusions are formed.
A pressing member supported by a pressing member of the restricting member, and a pair of left and right pressing plates having positioning holes for the restricting member are provided,
In order to make the pressure plate act as a "lever", the spring means is provided at a point different from the pressure portion of the regulation member, so the load of the spring means can be reduced and at the same time workability is not impaired, which is essential in the conventional example. The existing spring retainer can be eliminated.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below. In the description of the embodiments of the present invention, the entire construction and the printing operation from the paper feeding to the image formation, fixing, and paper ejection have been performed conventionally. Since it is substantially the same as the example, the description thereof is omitted, and only the pressing unit of the fixing heating device, which is a feature of the present invention, will be described.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
3A and 3B are views showing a pressing portion of the heat fixing device in the embodiment, wherein FIG.

In FIG. 1, 1 is a heat-resistant film, 2 is a heating element having a heating element and a conductive pattern on at least one surface of a substrate made of ceramic, and 3 is the heating element 2 and the heat-resistant film 1. The heating element holding members 4, 4 are metal stays provided on the opposite side of the heating element holding member 3 from the mounting surface of the heating elements 2, and 5 are provided at both ends of the metallic stays 4 to regulate the width direction of the heat resistant film 1. It is a pair of left and right resin regulation members on which a regulation surface, a pressurizing portion 5a and a positioning protrusion 5b are formed.

Reference numeral 6 denotes a pressure roller provided so as to convey the recording paper in one direction by sandwiching the heat resistant film 1 and the recording paper against the heating body 2 and rotating them in one direction. A pressure roller support member 8 for supporting both ends of the pressure roller 6 is supported so as to be able to press the pressure portion 5a of the regulation member 5, and a positioning hole 8 for the regulation member 5 is provided.
A pair of left and right pressure plates having a formed therein has one end acting on the pressure plate 8 and the other end locked to a spring pressing portion 7a which is a bent portion of the pressure roller support member 7 to form the pressure plate 8. The compression springs 10 provided on the left and right so as to urge the pressurizing portion 5a of the regulating member 5 are arranged in the direction in which the pressure plate 8 reduces the force for urging the pressurizing portion 5a of the regulating member 5. The lever is a pressure releasing means that can move the pressure plate 8 against the spring force of the spring means 9, and the compression spring 9 is arranged corresponding to the acting portion of the lever 10.

As shown in FIG. 1, a "lever" in which the pressing plate 8 is a fulcrum at a point A, a point B is a force point, and a point C is an action point is shown in FIG.
As a result, the pressing force of the compression spring 9 is multiplied by E / D and acts on the pressing portion 5a of the regulating member 5, so that the heating member 2 presses the heating member 2 through the metal stay 4 and the heating member holding member 3. It is configured so that it can be pressed against 6.

Further, as shown in FIG. 2, when the user rotates the lever 10 as the pressure releasing means in the direction A in the drawing, the user can easily carry out the post-processing of the jamming as in the conventional example. Is.

By utilizing the pressure plate 8 as a "lever", the load of the compression spring 9 can be adjusted to the lever ratio (D: shown in the figure) even if the pressure applied to the pressure portion 5a is constant.
It becomes possible to reduce by the ratio of E).

Further, unlike the conventional example, it is not necessary to provide the compression spring 9 directly above the regulating member 5, so that the regulating member 5 can be assembled from above as in the present embodiment.
The function of pressing the upper end of the compression spring 9 can be formed in the pressure roller support member 7. As a result, since the spring holding member is eliminated, the device can be simplified.

Since the load of the compression spring 9 is reduced at the ratio of the lever ratio, the work of inserting the compression spring 9 from the side while compressing the compression spring 9 becomes very easy and at the same time,
It is not necessary to excessively strengthen the rigidity of the pressure roller support member 7 around the spring pressing portion 7a.

The pressure plate 8 is positioned with respect to the pressure portion 5a of the regulation member 5 by the positioning hole 8a of the pressure plate 8 and the positioning protrusion 5b of the regulation member 5 because of the lever ratio dimension. This is a consideration for improving accuracy, and the lever ratio does not vary due to the effect of this positioning, and the pressing force at the pressurizing portion 5a can be stabilized.

Further, in the conventional example, the mounting length of the spring is determined by the pressure plate 8, the pressure roller holding member 7, and the spring pressing member, whereas in the present embodiment, the pressure plate 8 and the pressure roller holding member are held. The member F alone determines the illustrated F dimension, which is the attachment length of the spring. As described above, since the spring retainer member is a component having a relatively large dimensional variation, the structure of the present embodiment using the pressure plate 8 that is a component that does not bend and has a relatively small dimensional variation can be achieved by the conventional method. Compared with the example, it is possible to greatly improve the dimensional accuracy of the mounting length of the spring, which is an advantage that is directly connected to the stability of the pressing force.

As described above, according to the structure of the present embodiment, the pressing roller supporting member 7 is provided with a function corresponding to that of the conventional spring pressing member without impairing the workability during assembly. It is possible to eliminate the members, reduce the load of the spring that bears the pressing force, and realize a high-quality heat fixing device with less variation in the pressing force.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
3A and 3B are diagrams of a pressure unit of the heat fixing device in the embodiment, FIG. 6A is a perspective view, and FIG.

In FIG. 3, 1 is a heat-resistant film, 2 is a heating element, 3 is a heating element holding member, 4 is a metal stay, 5 is a resin member, 5a is a pressing portion, 5b is a positioning protrusion, and 6 is a pressing roller. , 7 is a pressure roller support member, 7a is a spring pressing portion, 8 is a pressure plate, 8a is a positioning hole, 19 is a compression spring,
Reference numeral 10 denotes a pressure releasing means, which has the same configuration as that of the first embodiment except that two compression springs 19 are arranged side by side.

In the heat fixing device of the present embodiment, since the compression spring 19 is provided not at the position directly above the pressure roller 6 but at a shifted position, the degree of freedom in space is increased, and a plurality of compression springs 19 are provided. The arrangement is easier than in the conventional example. Therefore, by arranging two compression springs 19 side by side as in the present embodiment, the load per spring can be further reduced or dispersed, and the assembling property can be further improved, as compared with the conventional example. You can Further, by using a plurality of the same compression springs 19, it is possible to further reduce the variation in the pressing force, and to realize a heating and fixing device in which the pressing force is more stable as compared with the first embodiment.

[0040]

As described above, according to the present invention, the restriction surfaces provided on both ends of the metal stay for restricting the width direction of the heat-resistant film, the pressurizing portion, and the pair of left and right restricting members having the positioning projections are formed. , A pair of left and right pressure plates that are supported so as to be able to press the pressure member of the restriction member and that have positioning holes for the restriction member, and the pressure member of the restriction member so that the pressure plate acts as a "lever". Since the spring means is provided at a different point from the above, the load of the spring means can be reduced, and at the same time, the spring pressing member, which is essential in the conventional example, can be eliminated without impairing workability. Moreover, the load of the spring means can be reduced / distributed with a simple structure without impairing workability, and a heat fixing device with stable pressing force can be realized, and the effect of the invention is great.

[Brief description of drawings]

1A and 1B are views showing the periphery of a pressure unit of a heat fixing device according to a first embodiment of the present invention, in which FIG. 1A is a perspective view and FIG.
Is a side view

FIG. 2 is a side view of a state in which a pressure releasing unit of a pressure unit of the heat fixing device according to the first embodiment of the present invention is rotated.

3A and 3B are views showing the periphery of a pressing portion of a heat fixing device according to a second embodiment of the present invention, FIG. 3A being a perspective view and FIG.
Is a side view

FIG. 4 is a sectional view of a conventional image forming apparatus.

FIG. 5 is a sectional view of a conventional heat fixing device.

6A and 6B are views showing the periphery of a pressing portion of a conventional heat fixing device, in which FIG. 6A is a perspective view and FIG. 6B is a side view.

FIG. 7 is a side view of a state in which a pressure releasing unit of a pressure unit of a conventional heat fixing device is rotated.

[Explanation of symbols]

1 ... Heat resistant film 2 ... Heating body 3 ... Heating body holding member 4 ... Metal stay 5 ... Resin member 5a ... Pressurized part 5b ... positioning protrusion 6 ... Pressure roller 7 ... Pressure roller support member 7a ... Spring pressing part 8 ... Pressure plate 8a ... Positioning hole 9, 19 ... Compression spring 10 ... Pressure releasing means

Claims (3)

[Claims] 1. A heat-resistant film, a heating body composed of at least an insulating substrate and a resistance heating body, a heating body holding member for holding the heating body and the film, and a heating body mounting surface of the heating body holding member. A metal stay provided on the opposite side of the metal stay, and a resin regulation member provided at both end portions of the metal stay and having a regulation surface for regulating the width direction of the film, a pressurizing portion, and a positioning protrusion, A pressure roller for bringing the film into pressure contact with a heating body, and driving the film while sliding the film on the surface of the heating body; a pressure roller support member for supporting both ends of the pressure roller; A pressing plate that supports a pressing portion so that it can be pressed, and a positioning hole into which the positioning protrusion fits, and one end of which is engaged with the roller supporting member in a vertically swingable manner; A spring that is arranged between the other end of the plate and the roller support member, applies a pressing force to the regulating member via the pressure plate, and presses the heating body against the pressure roller while sandwiching the film. Means and pressure releasing means capable of moving the pressure plate against the spring force of the spring means in a direction to reduce the force of the pressure plate pressing the pressure portion of the regulating member. Characteristic heating and fixing device. 2. The total number of the spring means is N (left and right) (N ×
2. The heat fixing device according to claim 1, wherein the heat fixing device comprises two identical compression springs. 3. The heating fixing device according to claim 1, further comprising: a pressure nip portion between the heating body and the pressure roller, which is in pressure contact with the film, between the film and the pressure roller. A recording medium on which a toner image has been transferred by an image forming means is introduced, and the toner image is fixed to the recording medium by moving the recording medium along with the film through the pressure contact nip portion. apparatus.