JPH0844225A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent the increase of torque, jamming and the damage of a film caused by a failure in rotation by stabilizing the traveling rotation of the film, in a fixing device using an endless fixing film. CONSTITUTION:The fixing device forming an image in an electrophotographic process and fixing toner on a recording material by pressure and heat is provided with a heating body 1, a holding member 2 holding it, an endless belt-like fixing film 3 heated by the heating body 1, a pressurizing member 4 pressurizing the film 3 and the recording material against the heating body 1, to form a nip 5 and holding/carrying the fixing film 3 and the recording material, a guiding member 6 guiding the fixing film 3 to make its traveling free and further, a reinforcing member 10 between the guiding member 6 and the holding member 2 of the heating body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to a fixing device which is used in an image forming apparatus such as a facsimile and heats and fixes an unfixed image on a recording material.

[0002]

2. Description of the Related Art A fixing device of this type is known as shown in FIG. In FIG. 6 showing a sectional view of this fixing device, a ceramic heater 1 which is a heating element is housed in a concave portion of a heater holder 2 which is a holding member, and the ceramic heater 1 is thermoset on the surface of the concave portion of the heater holder 2. It is adhered by an adhesive.

In FIG. 6, reference numeral 3 is an endless film made of PI polyimide which is heated by the ceramic heater 1 and has a thickness of about 60 μm.

The film 3 is pressed by a pressure roller 4 to form a nip 5.

When the pressure roller 4 rotates in the direction of the arrow shown in the figure, the film 3 is guided along the arc-shaped guide stay 6 which is a guide member of the film and smoothly rotates.

When recording is performed, the recording material is guided to the nip 5 from the direction of the entrance guide 7 shown in the figure and the toner is fixed through the film 3 by the ceramic heater 1.

After fixing, the sheet is conveyed along a sheet discharge guide indicated by reference numeral 8 in the figure, and discharged by a sheet discharge roller 9 to the outside of the apparatus.

In this conventional apparatus, the heater holder 2 and the guide stay 6 are made of liquid crystal polymer in consideration of heat resistance, heat insulation to the nip 5, and slidability.

[0009]

However, in the above-mentioned conventional apparatus, due to the pressurization and creep, and the warp of the heater holder 2 and the guide stay 6, etc.
It was difficult to stabilize the guide shape (see FIG. 7) during film transport with high accuracy.

When the film 3 as described above is conveyed,
First, the film 3 and the guide portion (heater,
The clearance between the heater holder and the guide stay), that is, the difference in circumferential length, has a great effect.

For example, as shown in FIG. 8, when there is not much difference between the peripheral length of the film and the peripheral length of the guide portion and the film 3 is almost in tension, even if the pressure roller 4 is rotated, the film 3 has a degree of freedom. Since it does not exist and it rubs strongly against the guide stay 6, it becomes difficult to rotate. On the contrary, when there is too much clearance with respect to the film length as shown in FIG. 9, the rigidity of the film itself becomes low, and as shown in FIG. 10, buckling occurs at the film end.

Further, for example, when the guide portion changes with time as shown in FIG. 11 due to deformation and creep due to pressurization, the amount of the nip becomes uneven in the longitudinal direction, causing uneven fixing and paper wrinkles. .

The first object of the present application is to solve the above-mentioned problems, to stabilize the running rotation of the film, to prevent torque increase due to poor rotation, to prevent jamming, and to prevent damage to the film. This is to prevent fixing defects and paper wrinkles due to deformation and creep.

A second object of the present application is to improve the shape accuracy of the guide portion.

Further, a third object of the present application is to save space and cost, and to reduce uneven temperature distribution.
The purpose is to further stabilize the guide shape.

A fourth object of the present application is to reduce the influence of warpage (bimetal phenomenon) due to the difference in the coefficient of thermal expansion and to stabilize the guide shape in the above structure.

[0017]

According to the present invention, the first object is to form an image by an electrophotographic process,
In a fixing device for fixing toner on a recording material by pressure and heat, a heating body and a holding member for holding the heating body, an endless belt-shaped fixing film heated by the heating body, the fixing film and the recording The pressure member presses the material toward the heating element to form a nip, and has a pressing member that nip and conveys the fixing film and the recording material, and a guide member that guides the fixing film so that the fixing film can travel freely. This is achieved by the first invention, which comprises having a reinforcing member between the holding members of the body.

The second object is achieved by the guide member being positioned in at least one direction by the reinforcing member.

Further, the third object is achieved by the reinforcing member being a metal plate.

Further, a fourth object is that the guide member has at least two or more fixing portions, and the fixing is carried out with either the heating member holding member or the reinforcing member, whichever has the closest coefficient of thermal expansion. Achieved by

[0021]

In the first invention according to the present application, the reinforcing member is provided between the guide member and the heating member holding member, so that the reinforcing member reduces deformation and creep even in a pressurized or heated state. , The guide shape is kept constant.

According to the second aspect of the invention, the guide member is positioned in at least one direction by the reinforcing member, and the guide member is corrected in a manner following the reinforcing member, and is less affected by pressure deformation, warpage, creep and the like. Become.

According to the third aspect of the invention, the reinforcing member is a metal plate, which is thin and space-saving, so that a highly effective reinforcing member can be obtained at low cost. Furthermore, since it is a metal, the heat distribution is kept uniform in the longitudinal direction, and variations in the guide shape due to variations in temperature are suppressed.

Further, according to the fourth invention, the guide member has at least two or more fixing portions, and the fixing is performed by either the heating member holding member or the reinforcing member, whichever has the closest thermal expansion coefficient. The birefringence of the bimetal (hereinafter referred to as "bimetal phenomenon") is suppressed by the difference in the coefficient of thermal expansion during heating, and the shape accuracy and dimensions of the guide portion are stabilized.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a vertical sectional view of an apparatus according to the first embodiment of the present invention. In this embodiment, the heater holder 2 which is a heating member holding member and the guide stay 6 which is a guiding member for guiding the fixing film 3 are provided.
The reinforcing member 10 is arranged between the two. The reinforcing member 10
Is a metal plate made of iron and has a plate thickness of about 2 mm.

In FIG. 2, a ceramic heater 1 which is a heating body is attached to a heater holder 2 which is a holding member in a concave portion of the heater holder 2 with a thermosetting adhesive.

Further, in the case of this embodiment, the heater holder 2 is positioned by the reinforcing member 10 at three bosses 15 in the longitudinal direction. The reason why there are three bosses is that the boss 15 is fitted into the holes 16 and 17 of the reinforcing member 10 to correct the warp in the longitudinal direction of the heater holder 2 shown in FIG.

Further, in FIG. 2, the holes of the heater stay 10 which is a reinforcing member with respect to the bosses 15 at the above-mentioned three positions are round holes at the central position, and the holes are completely fitted to the boss 15. The two holes 16 at both ends have a long hole shape having a clearance in the longitudinal direction. This is when heated
This is to prevent the bimetal phenomenon from occurring due to the difference in the coefficient of thermal expansion between the heater holder 2 and the reinforcing member 10 and causing the heater holder to deform and warp.

Further, the heater holder 2 and the heater stay 1
After the above boss fitting, 0 is press-fitted from above so that the tooth 19 is hard to be bossed by the toothed snap ring 14 as shown in FIG. 3, and there is some play in the vertical direction (reference numeral 2 in the figure).
It is stopped with 0). This is also to prevent the heater holder 2 and the heater stay 10 from being completely fixed with screws or the like to prevent deformation and warpage due to the bimetal phenomenon as described above.

In this structure, even if some rattling occurs in the vertical direction (20) by stopping with the toothed snap ring, the pressure is applied from below by the pressure roller 4 and the heater stay 10 is pressed against the heater stay 10. Since the surface is straightened, there is no problem in shape accuracy.

Next, the state where the guide stay 6 is attached will be described. FIG. 4 shows a state in which the guide stay 6 is screwed to the heater stay 10, which is a reinforcing member, with a screw 13. The fixing portion of the screw is fixed by the two bosses shown in FIG. The reason why the fixing is two places is that the warp of the guide stay 6 does not cause variations in the guide shape of the film, as shown in FIG. This is because the guide stay 6 is corrected to the shape of the heater stay 10 by forming the receiving portion 11 and screwing it to prevent warping and deformation due to creep.

Further, in this embodiment, both the heater holder 2 and the guide stay 6 are injection molded from liquid crystal polymer, and both have the same coefficient of thermal expansion. Therefore, even during heating, warpage and deformation due to the bimetal phenomenon are less likely to occur.

Next, the operation of the apparatus of this embodiment having the above structure will be described.

First, the heater stay 10 is provided between the heater holder 2 and the guide stay 6, and both the heater holder 2 and the guide stay 6 are straightened into the heater stay 10. As a result, warp deformation at the time of pressurization and change over time due to creep are prevented, and uneven fixing and paper wrinkles are eliminated.
Also, the guide shape of the film is always kept constant, and buckling and damage of the film are prevented.

Further, since the guide stay 6 is abutted against the heater stay 10 and a positioning portion 11 is provided as a receiving portion, even if the guide stay 6 is warped and deformed to some extent, the guide stay 6 abuts on the positioning portion 11 and the guide size is stable. Buckling of the film is prevented. Generally, the heater holder 2 side is pressed by the pressing roller 4, so that the heater stay 10
However, when the pressure is small, a positioning abutting portion may be similarly provided.

Further, the heater stay 1 which is a reinforcing member
No. 0 is made of sheet metal, and it is possible to obtain a large strength in a space-saving manner, and since the metal has high thermal conductivity, temperature unevenness during heating is reduced, the guide shape deviation due to thermal expansion is corrected, and the guide shape is Stabilize.

Further, as described above, the heater holder 2 and the guide stay 6 made of the same material are fixed by screws, the bimetal phenomenon is suppressed, the guide shape is stabilized, and the buckling and damage of the film are prevented. It

(Second Embodiment) In the first embodiment,
I am using a sheet metal bent in a U shape as a reinforcing member,
It may be plastic, ceramics, metal pipes, rods, etc. that contain glass and have improved rigidity. The material may be stainless steel or aluminum instead of iron. That is, any material may be used as long as it is not deformed by pressure or creeps.

In the first embodiment, the reinforcing plate is completely inserted into the heater holder 2 and the guide stay 6. However, if the reinforcing plate is shaped like the reinforcing plate, a part of the reinforcing plate is formed. It may be exposed.

(Third Embodiment) In the first embodiment, the guide stay 6 is fixed to the heater holder 2 with screws, but the guide stay 6 is fixed to the heater stay 10.
You may stop directly at.

Further, in the first embodiment, the screws are also stopped at two points, but depending on the degree of warpage, three or four or more points may be provided, and the warp direction of the guide stay 6 is set to one direction. If it can be limited, it may be located at one central position. Also, the positioning portions 11 of the guide stay 6 with respect to the heater stay 10 are three places in the first embodiment, but depending on the direction of the warp, it may be two places at both ends or four or more places. Just decide.

Further, when the degree of warpage is small and the guide accuracy is not so required, the positioning by abutting is not necessarily required.

[0044]

As described above, the first aspect of the present application
According to the invention, by providing the reinforcing member between the heating member holding member and the guide member, it is possible to prevent the change of the guide shape and the creep at the time of pressurization, and the unevenness of fixing, paper wrinkles, and film due to defective guiding of the film. Buckling and damage can be prevented.

According to the second aspect of the present invention, in the above fixing device, the guide member is abutted and positioned on the reinforcing member, whereby the warp deformation of the guide stay can be corrected and the precision of the guide shape of the film is improved. The film can be prevented from buckling and breaking.

Further, according to the third aspect of the invention, in the fixing device, the reinforcing member is formed of a sheet metal, so that high strength can be obtained in a small space, and the temperature distribution in the longitudinal direction can be obtained by heat conduction. It becomes uniform, and the transport of the film is stable.

Further, according to the fourth aspect of the invention, in the fixing device, the guide stay is fixed to either the heating member holding member or the reinforcing member, whichever has a smaller coefficient of thermal expansion, so that the guide stay is deformed by the bimetal phenomenon. Can be prevented, and buckling and damage due to poor transport of the film can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment device of the present invention.

FIG. 2 is a perspective view showing attachment of a heater stay of the apparatus shown in FIG.

FIG. 3 is a diagram showing a fixed state of a toothed snap ring in the apparatus of FIG. 1;

FIG. 4 is a view showing a mounting state of a guide stay in the apparatus shown in FIG.

5 is a cross-sectional view showing a mounting state of a guide stay in the apparatus shown in FIG.

FIG. 6 is a cross-sectional view of a conventional device.

FIG. 7 is a view showing a modification of the guide stay in the apparatus shown in FIG.

8 is a diagram showing a clearance between a film and a guide in the apparatus shown in FIG.

9 is a diagram showing a clearance between a film and a guide in the apparatus shown in FIG.

FIG. 10 is a diagram showing film end buckling in the apparatus of FIG. 6;

11 is a diagram showing creep deformation due to a pressing force in the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating body (ceramic heater) 2 Holding member (heater holder) 3 Fixing film 4 Pressurizing member (pressurizing roller) 5 Nip 6 Guide member (guide stay) 10 Reinforcing member (heater stay)

Claims (4)

[Claims] 1. In a fixing device for forming an image by an electrophotographic process and fixing toner on a recording material by pressure and heat, a heating member, a holding member for holding the heating member, and heating by the heating member. An endless belt-shaped fixing film, a pressing member that presses the fixing film and the recording material toward a heating body to form a nip, and a fixing member that sandwiches and conveys the fixing film and the recording material, and the fixing film can run freely. A fixing device comprising: a guide member for guiding, and a reinforcing member between the guide member and the holding member of the heating body. 2. The fixing device according to claim 1, wherein the guide member is positioned in at least one direction by a reinforcing member. 3. The fixing device according to claim 1, wherein the reinforcing member is a metal plate. 4. The guide member has at least two fixing portions, and the fixing is performed by either the heating body holding member or the reinforcing member, whichever has the closest thermal expansion coefficient.
The fixing device according to claim 3.