JP3846255B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in an image forming apparatus having a heating and pressing type fixing device provided with a heating roller incorporating an electromagnetic induction heating coil, a pressure roller, and an endless fixing belt.
[0002]
[Prior art]
Up to now, a heating method using electromagnetic induction heating has been proposed as a heat supply source in a fixing device of an image forming apparatus. In addition, a fixing device has been proposed in which the fixing belt is used to lengthen the nip time, and the pressure roller is released from pressure bonding to shorten the warm-up time.
[0003]
[Problems to be solved by the invention]
However, in such a system, since the pressure roller of the fixing device is released or the pressure is activated during warm-up and during image formation, the transport path of the endless fixing belt is in each case. It fluctuates and interference between the electromagnetic induction heating coil and the heating roller occurs. To avoid this, the gap distance between the electromagnetic induction heating coil and the heating roller cannot be reduced and is considerably separated. Therefore, the heat generation efficiency has been reduced.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus having a heating and pressing type fixing device with high heat generation efficiency, which eliminates the disadvantages of the prior art.
[0005]
[Means for Solving the Problems]
This object is achieved by any one of the following technical means (1) to (4) .
[0006]
(1) In an image forming apparatus having a heat and pressure type fixing device, the heat and pressure type fixing device comprises:
An electromagnetic induction heating coil ;
A heating roller made of a ferromagnetic roller;
A first pressure roller ;
And endless fixing belt that is wound between the pressure roller and the heating row La of the first,
A second pressure roller pressed against the first pressure roller via the fixing belt; and the second pressure roller pressed against or released from the first pressure roller. and a pressure connecting unit,
The heating roller is applied with a biasing force in a direction in which tension is applied to the fixing belt,
Wherein with the operation for releasing compression or crimping pressure detachable unit, together with the fixing belt route condition is changed, the heating roller is a rotating center position movable,
The image forming apparatus, wherein the heating roller and the electromagnetic induction heating coil are supported concentrically by the same movable support member, and the electromagnetic induction heating coil is movable concentrically with the heating roller .
(2) The image forming apparatus according to (1), wherein the electromagnetic induction heating coil is built in the ferromagnetic roller .
(3) the support shaft constituting the fixed shaft of the bearing which constitutes the rotation axis of the heating roller and the electromagnetic induction heating coil, characterized in that it is retained concentrically movable movable support member (1 Or the image forming apparatus according to (2).
(4) The contact start point of the second pressure roller and the contact start point of the first pressure roller are at different phase angle positions with respect to the fixing belt (1). The image forming apparatus according to any one of to (3).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The description in this column does not limit the technical scope of the claims or the meaning of terms. In addition, the following assertive description in the embodiment of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention.
[0009]
FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the image forming apparatus of the present invention.
[0010]
This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless transfer belt unit 7, a sheet feeding and conveying means, and a heating and pressing type. And a fixing device 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.
[0011]
An image forming unit 10Y that forms a yellow image includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a primary transfer unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A primary transfer roller 5Y and a cleaning means 6Y are provided. An image forming unit 10M that forms a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller 5C as a primary transfer unit. It has cleaning means 6C. The image forming unit 10K that forms a black image includes a drum-shaped photoreceptor 1K as a first image carrier, a charging unit 2K, an exposure unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit. 6K.
[0012]
The endless transfer belt unit 7 is wound by a plurality of rollers 71, 72, 73, 74, and 76, and is endless transfer as a semiconductive endless belt-like second image carrier that is rotatably supported. A belt 70 is provided.
[0013]
Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating endless transfer belt 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K, and the combined color. An image is formed. A sheet P as a transfer material, which is a recording medium housed in the sheet cassette 20 (hereinafter referred to as a sheet P) is fed by a sheet feeding means 21 and a plurality of intermediate rollers 22A, 22B, 22C, 22D. Then, after passing through the registration roller 23, it is conveyed to the secondary transfer means 5A, and the color images are collectively transferred onto the paper P. The paper P on which the color image has been transferred is fixed by the heat and pressure type fixing device 24, sandwiched between the paper discharge rollers 25, and placed on a paper discharge tray 26 outside the apparatus.
[0014]
On the other hand, after the color image is transferred to the paper P by the secondary transfer means 5A, the residual toner is removed by the cleaning means 6A from the endless transfer belt 70 from which the paper P is separated by curvature.
[0015]
During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rollers 5Y, 5M, and 5C are pressed against the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.
[0016]
The secondary transfer unit 5A comes into pressure contact with the endless transfer belt 70 only when the sheet P passes through the secondary transfer unit 5A and secondary transfer is performed.
[0017]
In this way, a toner image is formed on the photosensitive member by charging, exposure, and development, and each color is superimposed on the transfer belt, transferred onto a sheet as a transfer material, and pressed by a heat and pressure type fixing device.・ Fix by heating. After the toner image is transferred to the sheet, the photosensitive member and the transfer belt enter the next image forming cycle after cleaning the toner remaining in the cleaning device.
[0018]
Next, an embodiment of the heat and pressure type fixing device 24 incorporated in the image forming apparatus of the present invention will be described with reference to the schematic diagram of FIG. 2 and the partial sectional view of FIG.
[0019]
The electromagnetic induction heating coil 243 is moved concentrically in conjunction with the heating roller 241 that moves as the second pressure roller 247 is pressed or released with respect to the first pressure roller 245 at the fixed position. . Therefore, as an embodiment, the heating roller 241 and the electromagnetic induction heating coil 243 mounted on the support shaft 243A are supported through concentric bearings 242A and a fixed member 24B of the same movable support member 24A. The fixing member 24B supports the support shaft 243A of the electromagnetic induction heating coil 243 concentrically without rotating.
[0020]
The heating roller 241 is composed of a ferromagnetic roller 242 having a spiral electromagnetic induction heating coil 243 built therein. The heating and pressing type fixing device 24 includes a heating roller 241 whose rotational center position is movable, the heating roller 241, An endless fixing belt 246 wound with a tension applied between the first pressure rollers 245 having a rotation shaft at a fixed position and having an elastic layer on the surface, a sheet P carrying an unfixed image, and endless And a second pressure roller 247 that presses and presses the fixing belt 246 in the shape of the first pressure roller 245. The second pressure roller 247 also has an elastic layer.
[0021]
The second pressure roller 247 installed outside the endless fixing belt 246 has a predetermined image formation for shortening the warm-up time and for avoiding permanent deformation of the roller elastic layer due to pressure during non-operation. Is not supported by the endless fixing belt 246 so that the pressure can be released from the endless fixing belt 246, and the endless fixing belt 246 is supported so that the pressure can be released. Through a fixing belt 246 and a sheet P as a transfer material, the pressure is pressed against a first pressure roller 245 installed in an endless fixing belt 246 with its position fixed. At this time, in order to lengthen the contact time between the endless fixing belt 246 and the paper P, the contact point between the second pressure roller 247 outside the endless fixing belt 246 and the endless fixing belt 246, and the inside The first pressure roller 245 and the contact start point of the endless fixing belt 246 are at different phase angle positions, between the two points, and the endless portion of the portion held by the second pressure roller 247 The fixing belt 246 and the paper P are kept in a close contact state and a pressurized state, and a sufficient amount of nip and necessary heat are ensured to maintain a stable fixing state.
[0022]
Then, the length of y shown in the schematic diagram of FIG. 2 changes due to the attachment / detachment of the contact between the endless fixing belt 246 and the second pressure roller 247 outside the end, and the path state of the endless fixing belt 246 is changed. Changes. Along with this, the center position of the ferromagnetic roller 242 in the heating roller 241 changes by the length of x, but the electromagnetic induction heating coil 243 in the heating roller 241 changes its position concentrically, so the mutual position changes. In addition, interference between the ferromagnetic roller 242 of the heating roller 241 and the electromagnetic induction heating coil 243 and non-uniform heating can be avoided and heat generation efficiency can be kept large.
[0023]
As described above, the heating roller 241 rotates integrally with the ferromagnetic roller 242 and the built-in electromagnetic induction heating coil 243 is non-rotatably installed at the center, but the fixing member for the support shaft 243A is provided. since the 24B is provided on the movable support member 24A to the rotary bearing 242A and concentric of the ferromagnetic roller 242, together with the uniform heat generation is enabled, an electromagnetic induction heating coil 243 of the ferromagnetic roller 24 2 a gap distance Since it can be made small, high heat generation efficiency is also possible.
[0024]
Although not shown, the second pressure roller is urged by a spring provided in the holder of the bearing. When the urging is released such as when warming up, the holder as a member that supports the spring is moved to the second pressure roller. Pressure release means is provided for releasing pressure by a solenoid, a cam, or the like that moves away from one pressure roller 245, or by applying pressure by removing the restriction of moving away from the pressure roller 245 by a solenoid, a cam, or the like.
[0025]
Further, the heating roller 241 is supported with the electromagnetic induction heating coil 243 incorporated in the movable support member 24A, the the movable supporting member 24A shown are not provided with a spring mechanism, the tension in endless fixing belt 246 An urging force is applied in the direction of application, and the movable support member 24A can be moved each time the second pressure roller 247 is attached / detached by the operation of the pressure attaching / detaching means.
[0026]
In the above embodiment, the coil formed in a spiral shape around the central axis of the heating roller 241 is taken as an example, but a line perpendicular to the central axis of the heating roller 241 as shown in the plan view of FIG. This is also effective for an electromagnetic induction heating coil 243V which is a so-called vertical coil in which an elliptical shape having a major axis parallel to the central axis of the heating roller 241 is formed in a spiral shape.
In the above embodiment, the electromagnetic induction heating coil 243 is incorporated in the heating roller 241. However, although not shown, the electromagnetic induction heating coil 243 has an outer periphery of the heating roller 241. A similar effect can be obtained with a system arranged outside the surface.
[0027]
【The invention's effect】
By adopting the configuration of the present invention, uniform heat generation is possible, and the gap distance between the electromagnetic induction heating coil and the heating roller can be reduced, so that high heating efficiency is also possible. In addition, the elastic layer of the pressure roller is less likely to be damaged during standby or when stopped for a long time, and the standby time itself can be shortened to improve image forming efficiency.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus of the present invention.
FIG. 2 is a schematic diagram of a heat and pressure type fixing device used in the present invention.
FIG. 3 is a partial cross-sectional view showing a state in which an electromagnetic induction heating coil is mounted on a heating and pressing type fixing device used in the present invention.
FIG. 4 is a plan view showing another shape of the electromagnetic induction heating coil of the heating and pressing type fixing device used in the present invention.
[Explanation of symbols]
1Y, 1M, 1C, 1K Photoconductors 2Y, 2M, 2C, 2K Charging means 3Y, 3M, 3C, 3K Exposure means 4Y, 4M, 4C, 4K Developing means 5A Secondary transfer means 5Y, 5M, 5C, 5K Primary transfer Rollers 6A, 6Y, 6M, 6C, 6K Cleaning means 7 Endless transfer belt units 10Y, 10M, 10C, 10K Image forming unit 24 Heating and pressing type fixing device 24A Support member 24B Fixing member 241 Heating roller 242 Ferromagnetic roller 242A Bearing 243 Electromagnetic induction heating coil 243A Support shaft 245 First pressure roller 246 Endless fixing belt 247 Second pressure roller

Claims (4)

In the image forming apparatus having a heating and pressing type fixing device, the heating and pressing type fixing device includes:
An electromagnetic induction heating coil ;
A heating roller made of a ferromagnetic roller;
A first pressure roller ;
And endless fixing belt that is wound between the pressure roller and the heating row La of the first,
A second pressure roller pressed against the first pressure roller via the fixing belt; and the second pressure roller pressed against or released from the first pressure roller. and a pressure connecting unit,
The heating roller is applied with a biasing force in a direction in which tension is applied to the fixing belt,
Wherein with the operation for releasing compression or crimping pressure detachable unit, together with the fixing belt route condition is changed, the heating roller is a rotating center position movable,
The image forming apparatus, wherein the heating roller and the electromagnetic induction heating coil are supported concentrically by the same movable support member, and the electromagnetic induction heating coil is movable concentrically with the heating roller . The image forming apparatus according to claim 1, wherein the electromagnetic induction heating coil is built in the ferromagnetic roller . According to claim 1 or 2 wherein the support shaft constituting the fixed shaft of the bearing which constitutes the rotation axis of the heating roller and the electromagnetic induction heating coil, characterized in that it is retained concentrically movable movable support member The image forming apparatus described in 1. 4. The contact start point of the second pressure roller and the contact start point of the first pressure roller with respect to the fixing belt are at different phase angle positions. The image forming apparatus according to claim 1.

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