JP2003098877A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of the pressing member as well as control the rise in the temperature of an area for not to letting paper through in a heating member and the pressing member, by installing an evenly thermalizing member in a fixing device of induction heating system. SOLUTION: A fixing device 40 is provided with a heating roller 10 induced and heated and a pressure roller 20 forming a fixing nip N by compressing it. An evenly thermalizing roller 25, that has high thermal conductivity is compressed on the pressure roller 20, so as to control the rise in the temperature of the area to not the paper pass through in the heating roller 10 and the pressure roller 20. Both edges of the even heating roller 25 are made longer, to stick out of the pressure roller 20 for preventing both edges 25a of the even heating roller 25 from scratching the surface of a covered layer of the pressure roller 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating type fixing device and an electrophotographic image forming apparatus including the fixing device.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, the surface of a photosensitive member, such as a photosensitive drum, is charged to a predetermined potential, and an image is exposed on the surface to form an electrostatic latent image. The image is developed with a developer (toner) by a developing means to be visualized as a toner image, and the obtained toner image is transferred to a recording material such as paper conveyed to a photosensitive drum, thus forming the toner image. Send the carried recording material to the fixing device,
Therefore, the unfixed toner image on the recording material is fixed to obtain a print image on the recording material.

As shown in FIG. 6, the fixing device 40 includes a heating roller (fixing roller) 42 as a heating member having a heating source inside and a pressurizing member which presses the heating roller 42 to form a fixing nip N. The heating roller 42 is rotationally driven by a drive source (not shown), and the pressing roller 46 is rotated by being driven by the heating roller 42. The heating roller 42 and the pressure roller 46 heat and pressurize the recording material P while sandwiching and conveying the recording material P at the fixing nip N to melt and fix the toner image on the recording material P.

Conventionally, a halogen lamp has been used as a heating source of the heating roller 42, but in recent years, in order to save energy, an induction heating system using an induction coil is adopted as a highly energy efficient heating source. Is being attempted.

In the case of the induction heating system, the induction coil 4 is provided inside.
Ferromagnetic metals such as iron and nickel are used for the cored bar 44 of the heating roller 42 on which the 3 is arranged, but these metals have poor heat conduction as compared with aluminum alloys generally used as conventional cored bars. The heat transfer in the axial direction of the heating roller 42 is poor.

For this reason, when a small-sized recording material having a small width is passed through the fixing nip N, the sheet passing portion of the heating roller 42, which is in contact with the recording material and is deprived of heat, is different from both end portions which are not in contact with the recording material. The temperature rises remarkably in the non-sheet passing area, and the heating roller 4
There is a temperature difference between both ends and the center of No.2. Further, also in the pressure roller 46 to which the heat of the heating roller 42 is transferred, the temperature rises in the non-sheet passing portions at both ends, and a temperature difference occurs between the both ends and the central portion of the pressure roller 46.

As described above, the heating roller 42 and the pressure roller 4
When a large-sized recording material having a large width is passed through the fixing nip in the state where there is a temperature difference in 6 in the axial direction, unevenness in image fixing occurs in the toner image on the recording material due to temperature unevenness in the roller axial direction.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 9-127811, in order to prevent the temperature difference between the heating roller and the pressure roller in the axial direction, a high heat conductive temperature-uniforming member such as an aluminum roller is used as the pressure roller. It is considered to arrange by pressure contact.

This publication discloses the case of a fixing device in which the heating source of the heating roller is a Halongen lamp. Even in the fixing device of the induction heating type, as shown in FIG.
If such a heat equalizing roller 48 having high thermal conductivity is installed in pressure contact with the pressure roller 46, heat from both ends of the pressure roller 46 can be transferred to the central portion of the pressure roller 46 via the heat equalizing roller 48. Therefore, it is possible to suppress the temperature rise in the non-sheet passing portion at both ends of the pressure roller 46 and reduce the temperature difference in the axial direction of the pressure roller 46 (the direction orthogonal to the sheet passing direction). Further, the heat amount at both ends of the heating roller 42 taken by the pressure roller 46 is increased to suppress the temperature rise in the non-sheet passing portions at both ends of the heating roller 42, and the axial direction of the heating roller 42 (perpendicular to the sheet passing direction). The difference in temperature (direction) can be reduced.

[0010]

However, as shown in FIG. 7, both ends of the heat equalizing roller 48 have the pressure roller 4.
If the length is set so as to come into contact with 6, the soaking roller 4
Since the edges 48a at both ends are pressed against the pressure roller 46, the surface of the soft coating layer such as silicone rubber or fluororesin coated on the pressure roller 46 is damaged and the durability of the pressure roller 46 is impaired. There was a problem that

An object of the present invention is to suppress the temperature rise of the non-sheet passing portion of the heating member and the pressure member by the heat equalizing member and to improve the durability of the pressure member, Another object of the present invention is to provide an image forming apparatus including the fixing device.

[0012]

In order to solve the above problems, the invention according to claim 1 is a heating member which is induction-heated, and a pressing member which presses against the heating member to form a fixing nip. A heating member, which is in pressure contact with the pressure member to uniformly heat the pressure member, and by rotating the heating member, the pressure member and the temperature uniforming member, Heating and pressurizing the inserted recording material,
In a fixing device for fixing the toner image on the recording material,
It is characterized in that the heat equalizing member is made longer so that the left and right end portions of the heat equalizing member project to the left and right than the left and right end portions of the pressing member.

According to the first aspect of the present invention, the soaking member is made long so that the left and right end portions of the soaking member project leftward and rightward from the left and right end portions of the pressing member. The edges of both ends of the member are not pressed against the pressure member, the surface of the soft coating layer coated on the pressure member is not damaged, and the durability of the pressure member can be improved. Of course, the heat of both ends of the pressure member is carried to the central portion of the pressure member via the temperature equalizing member to suppress the temperature rise of the non-sheet passing portion of the both ends of the pressure member, and to pass the sheet of the pressure member. It is possible to reduce the temperature difference in the direction orthogonal to the direction, and to increase the amount of heat at both ends of the heating member that is deprived by the pressure member to suppress the temperature rise of the non-sheet passing portion at both ends of the heating member and to prevent the passage of the heating member. The temperature difference in the direction orthogonal to the paper direction can be reduced.

According to a second aspect of the present invention, there is provided a heating member which is induction-heated, a pressing member which presses against the heating member to form a fixing nip, and the pressing member which presses against the pressing member. A uniformizing member for uniformly heating, and by rotating the heating member, the pressing member and the uniformizing member, the recording material inserted into the fixing nip is heated and pressed to perform the recording. In a fixing device for fixing a toner image on a material, the heat equalizing member is arranged so as to be shorter than the pressure member and located in the range between the left and right ends of the pressure member, It is characterized in that the left and right edges of the member are rounded.

According to the second aspect of the present invention, the soaking member is arranged so as to be shorter than the pressing member and located in the range between the left and right ends of the pressing member. Since the edges at the left and right ends are rounded, the edges at the left and right ends of the heat equalizing member are not pressed against the pressure member even if the temperature equalizing portion is pressed against the pressure member. Since the surface of the soft coating layer covered with the above is not damaged, it is possible to obtain the operational effects such as improving the durability of the pressing member as in the case of the first aspect of the invention.

According to a third aspect of the invention, there is provided an image forming apparatus including the fixing device according to the first or second aspect.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic view showing an embodiment of an image forming apparatus of the present invention. The image forming apparatus includes a photosensitive drum 30.
The surface of No. 0 is charged to a predetermined potential by the charger 32, and the image is exposed by the exposing means 34 to form an electrostatic latent image on the surface of the photosensitive drum 30, and the latent image is developed by the developing device 36 with a developer (toner). ) Is used to visualize the toner image as a toner image, and the obtained toner image is transferred to the recording material P such as paper conveyed to the photosensitive drum 30 by the transfer means 38. After the transfer, the photosensitive drum 30 is subjected to the next image formation after removing the transfer residual toner remaining on the surface thereof by the cleaner 39. On the other hand, the recording material P carrying the toner image as described above is
It is sent from the photosensitive drum 30 to the fixing device 40, where the unfixed toner image on the recording material P is fixed, and a print image is obtained on the recording material P. In this embodiment, the fixing device 40 is of the induction heating type, and the pressure roller 2 of the fixing device 40 is used.
A soaking roller 25 is installed in pressure contact with zero. The present embodiment is characterized in that the length of the heat equalizing roller 25 is controlled.

In the present embodiment, the fixing device 40 is
As shown in FIG. 2, a heating roller (heating roller) 10 as a heating member and a pressure roller 20 as a pressure member are provided, and a soaking roller 25 is installed on the pressure roller 20. . The heating roller 10 has a coating layer 14 around the core metal 12 and an induction coil 13 inside the core metal 12. The coating layer 14 has an elastic layer and a surface release layer. The coating layer 14 does not include the elastic layer and may be only the release layer. In this example, the induction coil 13 is formed on the cylindrical support 13a by extending the coil wire in the coil axis direction while turning the coil wire at both ends in the roller axis direction in a hairpin shape.

An alternating current of, for example, several tens of kHz is supplied to the induction coil 13 from an alternating current power source (not shown). As a result, a magnetic field (magnetic flux) is generated in the induction coil 13 and acts on the cored bar 12 to induce an eddy current in the cored bar 12.
2 heats up. The heat generated by the cored bar 12 is transferred to the coating layer 14, and the heating roller 10 is heated in this manner.

The temperature of the coil 13 is detected by a temperature sensor 15 arranged in contact with the support 13a. The temperature of the heating roller 10 is detected by a temperature sensor 16 such as a thermistor placed in contact with the surface of the heating roller 10. Based on the detection result of the surface temperature of the heating roller 10,
The heating roller 10 is maintained at a predetermined fixing temperature by controlling ON / OFF of the alternating current passing through the coil 13.

As shown in FIG. 3, the heating roller 10 has both ends rotatably supported by bearings 17, and is connected to a drive source (not shown) through a gear 18 provided outside one of the bearings 17. There is. The heating roller 10 is rotated in the direction of the arrow by being driven by the driving source.

The pressure roller 20 is provided with a soft coating layer made of silicone rubber, fluororesin or the like around a core metal (not shown). The pressure roller 20 is rotatably supported by bearings 22 having a rotating shaft 21 protruding from both ends. The pressure roller 20 is pressed against the heating roller 10 with a predetermined pressure by an urging means (not shown), and is driven to rotate in the direction of the arrow as the heating roller 10 rotates.

A fixing nip N is formed between the heating roller 10 and the pressure roller 20 by pressing the pressure roller 20 against the heating roller 10. By rotating the heating roller 10 and the pressure roller 20, the recording material P inserted in the fixing nip N is nipped and conveyed, and the recording material P is heated and pressed during the conveyance, and the recording material P is recorded. The upper toner image is fused and fixed.

The heat equalizing roller 25 is on the side opposite to the heating roller 10 with respect to the pressure roller 20, that is, the pressure roller 20 in this example.
The rotating shaft 26, which is arranged on the lower side along the roller axis direction and projects from both ends of the heat equalizing roller 25,
It is rotatably supported by 7. The soaking roller 25 is
The pressure roller 2 is pressed at a predetermined pressure by an urging means (not shown).
The pressure roller 20 is pressed against 0 and is rotated by the rotation of the pressure roller 20 during fixing. The heat equalizing roller 25 is a roller having high heat conductivity such as aluminum.

As described above, the core metal 12 of the induction heating type heating roller 10 is made of a ferromagnetic metal such as iron or nickel and has poor heat conduction, so that heat is transferred in the axial direction of the heating roller 10. Is bad. Therefore, when a small-sized recording material having a small width is passed through the fixing nip N, the heating roller 10
In contrast to the paper-passing portion that comes into contact with the recording material and loses heat, the temperature significantly rises at the non-paper-passing portions at both ends that do not contact the recording material,
A temperature difference occurs between both ends and the center of the heating roller 10.
Moreover, even in the pressure roller 20 to which the heat of the heating roller 10 is transferred
The temperature rises at the non-sheet passing portions at both ends, and a temperature difference occurs between the both ends and the central portion of the pressure roller 20.

Therefore, the soaking roller 2 having high thermal conductivity
If the pressure roller 5 is installed in pressure contact with the pressure roller 20, the heat from both ends of the pressure roller 20 is transferred to the central portion of the pressure roller 20 via the heat equalizing roller 25, and the paper is not passed through both ends of the pressure roller 20. It is possible to suppress the temperature rise in each part and reduce the temperature difference in the axial direction of the pressure roller 20 (the direction orthogonal to the sheet passing direction). Further, the amount of heat at both ends of the heating roller 10 robbed by the pressure roller 20 is increased to suppress the temperature rise in the non-sheet passing portion at both ends of the heating roller 10, and the axial direction of the heating roller 10 (orthogonal to the sheet passing direction). It is possible to reduce the temperature difference (in the direction).

However, the edges 2 at both ends of the heat equalizing roller 25
When 5a is pressed against the pressure roller 20, the pressure roller 20
The surface of the soft coating layer such as silicone rubber or fluororesin coated on the surface is damaged, and the durability of the pressure roller 20 is impaired.

Therefore, in the present embodiment, the heat equalizing roller 25 is made longer than the pressure roller 20, and the heat equalizing roller 2 is
The left and right ends of the pressure roller 5 are arranged to project right and left from the left and right ends of the pressure roller 20. The protrusion lengths of the left and right ends of the heat equalizing roller 25 are the same. Therefore, the soaking roller 1
Even when 5 is pressed against the pressure roller 20, the soaking roller 25
The edges 25a at both ends are not pressed against the pressure roller 20, and the surface of the soft coating layer coated on the pressure roller 20 is not damaged, and the durability of the pressure roller 20 can be improved. . Of course, heating roller 1
0, the temperature rise of the non-sheet passing portion at both ends of the pressure roller 20 can be suppressed, and the temperature difference between the pressure roller 10 and the pressure roller 20 in the axial direction can be reduced. As a result, in the image forming apparatus of the present embodiment, it is possible to obtain a good image without uneven fixing.

[Second Embodiment] FIG. 4 is a sectional view showing a fixing device according to still another embodiment of the present invention, and FIG. 5 is a front view of the fixing device. 4 to 5, the same reference numerals as those shown in FIGS. 2 to 3 denote the same members. The configuration of the image forming apparatus itself is the same as that shown in the first embodiment.

In the present embodiment, the fixing device 40 is
It is different from the first embodiment in that the structure of the heat equalizing roller 25 is different from that of the first embodiment. The induction coil 13 of the heating roller 10 is formed in a so-called spring type in which a coil wire is wound around a support 13a in the circumferential direction.
A winding type coil of a coil wire similar to that in the first embodiment may be used.

In the present embodiment, the heat equalizing roller 2 is used.
5 is shorter than the pressure roller 20 as shown in FIG.
In addition, the edges 25a at both ends are rounded. The heat equalizing roller 25 is arranged so as to be located at the center of the range between the left and right ends of the pressure roller 20. The edges 25a at both ends of the heat equalizing roller 25 are rounded so that the edges 25a are in smooth contact with the surface of the pressure roller 20. Therefore, even if both ends of the heat equalizing roller 25 are brought into pressure contact with the pressure roller 20, the edges 25a at both ends are not brought into pressure contact with the pressure roller 20.
It is possible to improve the durability of the pressure roller 20 without damaging the surface of the soft coating layer coated with 0. Of course, the pressure roller 2 and the heating roller 10 are prevented from increasing in temperature at the non-sheet passing portions at both ends thereof, and the pressure roller 2
0, the temperature difference in the axial direction of the heating roller 10 can be reduced, and the image forming apparatus can obtain a good image without fixing unevenness.

In each of the above embodiments, the fixing device uses the roller-shaped heating roller as the heating member, but instead of the induction heating heating roller,
A fixing device using a flexible heating belt (fixing belt) having a metal layer that generates heat by induction heating may be used. The same effect can be obtained by installing a heat equalizing member such as a heat equalizing roller in pressure contact with the pressure roller pressed against the heating belt, and by using the same heat equalizing member as in the embodiment. You can Further, although the image forming apparatus has shown the case of forming a monochrome image such as black and white, it can also be applied to an image forming apparatus which forms a multi-color image of a plurality of colors or a full color image. It is possible to obtain various effects.

[0034]

As described above, according to the present invention,
By placing the heat equalizing member in pressure contact with the fixing device, it is possible to suppress the temperature rise of the non-sheet passing portion of the heating member and the pressure member of the fixing device, and improve the durability of the pressure member. A good image without uneven fixing can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a fixing device installed in the image forming apparatus of FIG.

FIG. 3 is a front view of the fixing device of FIG.

FIG. 4 is a cross-sectional view showing a fixing device according to another embodiment of the present invention.

FIG. 5 is a front view of the fixing device of FIG.

FIG. 6 is a cross-sectional view showing a conventional fixing device.

7 is a front view showing a state where a heat equalizing roller is installed in the fixing device of FIG.

[Explanation of symbols]

10 heating roller 12 core metal 13 induction coil 14 coating layer 20 pressure roller 25 soaking roller 25a edge 30 photosensitive drum 36 Developer 38 transfer means P recording material

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[Procedure amendment]

[Submission date] September 26, 2001 (2001.9.2)
6)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

In order to solve the above problems, the invention according to claim 1 is a heating member which is induction-heated, and a pressing member which presses against the heating member to form a fixing nip. A heating member, which is in pressure contact with the pressure member to uniformly heat the pressure member, and by rotating the heating member, the pressure member and the temperature uniforming member, Heating and pressurizing the inserted recording material,
In a fixing device for fixing the toner image on the recording material,
It is characterized in that the heat equalizing member is made longer so that both longitudinal end portions of the heat equalizing member project in the longitudinal direction than both longitudinal end portions of the pressing member.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

According to the first aspect of the invention, the soaking member, the longitudinal both ends in the longitudinal direction is the pressure member of soaking member
Since long to protrude from the opposite ends in the longitudinal direction, without edges at both ends of the temperature control member is pressed against the pressure member, scratch the surface of the soft coating layer is coated on the pressure member As a result, the durability of the pressure member can be improved. Of course, the heat of both ends of the pressure member is carried to the central portion of the pressure member via the temperature equalizing member to suppress the temperature rise of the non-sheet passing portion of the both ends of the pressure member, and to pass the sheet of the pressure member. It is possible to reduce the temperature difference in the direction orthogonal to the direction, and to increase the amount of heat at both ends of the heating member that is deprived by the pressure member to suppress the temperature rise of the non-sheet passing portion at both ends of the heating member and to prevent the passage of the heating member. The temperature difference in the direction orthogonal to the paper direction can be reduced.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

According to a second aspect of the present invention, there is provided a heating member which is induction-heated, a pressing member which presses against the heating member to form a fixing nip, and the pressing member which presses against the pressing member. A uniformizing member for uniformly heating, and by rotating the heating member, the pressing member and the uniformizing member, the recording material inserted into the fixing nip is heated and pressed to perform the recording. In a fixing device for fixing a toner image on a material, the soaking member is arranged so as to be shorter than the pressing member and located in a range between both ends in the longitudinal direction of the pressing member. It is characterized in that edges of both ends of the chemical conversion member in the longitudinal direction are rounded.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

According to the second aspect of the present invention, the heat equalizing member is arranged so as to be shorter than the pressing member and located in a range between both ends in the longitudinal direction of the pressing member, Length of soaking material
Since the edges at both ends in the hand direction are rounded, even if the heat equalizing portion is pressed against the pressure member, the edges at both longitudinal ends of the heat equalizing member are not pressed against the pressure member. Since the surface of the soft coating layer coated on the pressure member is not damaged, it is possible to obtain operational effects such as improvement of durability of the pressure member as in the case of the first aspect of the invention.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

Therefore, in the present embodiment, the heat equalizing roller 25 is made longer than the pressure roller 20, and the heat equalizing roller 2 is
5, both end portions in the longitudinal direction (left and right in FIG. 3) of the pressure roller 20.
It was made to project to the left and right from both ends in the longitudinal direction (left and right in FIG. 3) . The protrusion lengths of the left and right ends of the heat equalizing roller 25 are the same. Therefore, even if the temperature-uniforming roller 15 is pressed against the pressure roller 20, the edges 25a at both ends of the temperature-uniforming roller 25 are not pressed against the pressure roller 20, and the pressure roller 20 is covered with a soft material. The surface of the coating layer is not damaged, and the durability of the pressure roller 20 can be improved. Of course, it is possible to suppress the temperature rise in the non-sheet passing portions at both ends of the heating roller 10 and the pressure roller 20 and reduce the temperature difference between the pressure roller 10 and the pressure roller 20 in the axial direction. As a result, in the image forming apparatus of the present embodiment,
A good image without uneven fixing can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miho Toyoda             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             Inside the company F term (reference) 2H033 AA03 BB00 BB18 BB29 BB37                       BE06 CA07 CA45                 3K059 AB00 AD05 AD25 CD55

Claims (3)

[Claims] 1. A heating member that is induction-heated, a pressure member that presses against the heating member to form a fixing nip, and a pressure member that presses against the pressure member to heat the pressure member uniformly. A heat equalizing member, and by rotating the heating member, the pressure member, and the heat equalizing member, the recording material inserted into the fixing nip is heated and pressed to form a toner image on the recording material. In the fixing device for fixing, the heat equalizing member is elongated so that the left and right end portions of the heat equalizing member protrude leftward and rightward from the left and right end portions of the pressure member. 2. A heating member that is induction-heated, a pressure member that is in pressure contact with the heating member to form a fixing nip, and a pressure member that is in pressure contact with the pressure member to uniformly heat the pressure member. A heat equalizing member, and by rotating the heating member, the pressure member, and the heat equalizing member, the recording material inserted into the fixing nip is heated and pressed to form a toner image on the recording material. In the fixing device for fixing, the heat equalizing member is arranged so as to be shorter than the pressure member and located in the range between the left and right ends of the pressure member, and the edges of the left and right ends of the heat equalizing member are fixed. A fixing device characterized by having roundness. 3. An image forming apparatus comprising the fixing device according to claim 1.