JPH06102784A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To accomplish a compact thin shape electrophotographic device by arranging a position for pressing a backup roller to a heat generating body within an area surrounded by common tangent lines of a driving pulley and a tension pulley. CONSTITUTION:As to the electrophotographic device provided with a means for fixing a toner image formed by a recording part on a paper through a heat-resistant belt 22, the position for pressing the backup roller 21 to the heat generating body 23 is arranged within the area surrounded by the common tangent lines A and B of the driving pulley 27 and the tension pulley 28, or arranged within the area which is formed by the heat-resistant belt 22 in a stretched state. Thus, such a constitution that the backup roller 21 is pushed into the area surrounded by two common tangent lines A and B of the driving pulley 27 and the tension pulley 28 can be obtained, so that a thermal fixing device 20 can be made thinner. And by installing the thermal fixing device 20 having such the constitution, the electrophotographic device for a printer and a copying machine, etc., can be made thinner and also made compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus having means for transferring heat of a heating element through a heat resistant belt to fix a toner image formed in a recording section on a sheet.

[0002]

2. Description of the Related Art As described in JP-A-3-89378, a conventional apparatus shares a heating roller portion with a driving roller (driving pulley) and a driven roller (tensioning pulley). It was arranged outside the area surrounded by tangents.

[0003]

The above-mentioned prior art has a problem that the fixing device is enlarged, and it is difficult to reduce the size, cost and thickness of the electrophotographic apparatus such as a printer and a copying machine.

An object of the present invention is to solve the above problems and to provide an electrophotographic apparatus having a small and thin fixing device.

[0005]

In order to achieve the above object, according to the present invention, a drive pulley, an endless heat-resistant belt that is rotated by the drive pulley, and an endless heat-resistant belt are arranged inside. A heat fixing device including a heating element and a backup roller for urging the heating element through a heat resistant belt; and a developing device for visualizing image information on a recording medium conveyed to the heat fixing device, In an electrophotographic apparatus including a transport system for transporting a recording medium, the endless heat-resistant belt is rotated by a drive pulley and a tension pulley that applies tension to the heat-resistant belt.

Further, the position where the backup roller is biased to the heating element is located within the area sandwiched by the two shared tangent lines of the drive pulley and the tension pulley, or is located inside the heat-resistant belt. The heat-resistant belt is arranged in the region formed in a stretched state by the driving pulley and the tension pulley.

Further, a tension pulley for applying tension to the heat resistant belt is supported by a member which can freely rotate, and a spring force acts on the swingable member to apply tension to the heat resistant belt. I did it. The spring force may be applied by a leaf spring.

A drive pulley, an endless heat-resistant belt which is rotated by the drive pulley, a heating element disposed inside the endless heat-resistant belt, and a biasing force applied to the heating element via a heat-resistant belt. A heat fixing device provided with a convex rib on at least one end in the width direction inside the heat-resistant belt, and a developing device for visualizing image information on a recording medium conveyed to the heat fixing device. In a electrophotographic apparatus having a transport system for transporting a recording medium, the position for biasing the backup roller to the heating element is determined by a drive pulley and a tension pulley arranged inside the heat resistant belt. The heat-resistant belt may be arranged in an area where it is stretched, and the tension pulley may have a taper formed at the end of the heat-resistant belt on the side where the convex ribs are provided.

[0009]

With the structure in which the endless heat-resistant belt is rotated by the drive pulley and the tension pulley, the heat-resistant belt portion can be formed in a flat shape, and the heat fixing device can be made thin.

Further, the position at which the backup roller is biased to the heating element is within the region sandwiched by the two shared tangents of the drive pulley and the tension pulley, or the drive pulley and the tension pulley. By arranging the heat-resistant belt in the area where the heat-resistant belt is attached, the backup roller can be pushed into the area, and the heat fixing device can be made thinner.

By providing the heat fixing device having the above structure,
It is possible to make an electrophotographic apparatus such as a printer or a copying machine thin and small.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

An electrophotographic apparatus adopting an embodiment of the present invention is shown in FIG.

The sheets 2 accumulated in the hopper 1 are separated one by one and fed to the conveying path 3. On the other hand, the electrostatic latent image on the photosensitive drum 4 is formed by the laser optical system 11 and visualized by the developing device 5 to become a toner image. Photosensitive drum 4
The upper toner image is transferred onto the sheet 2 by the transfer belt 6 and is conveyed to the fixing device 20. In the fixing device 20, the toner image on the paper 2 is heated by the heat generating member 23 via the heat resistant belt 22.
It is sandwiched between the sheet 2 and the backup roller 21, which is a heat-resistant elastic roller, and is fixed to the sheet 2.
After that, the paper 2 is conveyed to the discharge roller 7, and the stacker 8
Is discharged to. On the other hand, the toner remaining on the photosensitive drum 4
The image is cleaned by the cleaner 9.

FIG. 2 shows an enlarged cross-sectional view of the fixing device 20 which is the main part of FIG.

The heat-resistant belt 22 in which the surface of the ultra-thin belt 25 made of Ni as a base material is coated with Teflon resin 26 is
It is rotated between the reel 27 and the tension pulley 28. The drive pulley 27 is driven by the motor 10. The tension pulley 28 is pulled by the spring 31 to apply tension to the belt 22. The backup roller 21 covered with rubber, which is an elastic body, is rotatably installed on the side plate 29 of the fixing device so as to be movable up and down, urged by the coil spring 30, and fixed to the heating element 23 via the heat resistant belt 22. Press with the required load. The pressing force of the roller 21 can be adjusted by moving the spring force adjustment table 37. The heating element 23 is supported by the holder 24, and is further fixed to the side plate 29 by the step 34. The surface of the backup roller 21 is covered with heat-resistant silicone rubber which is an elastic body, so that the toner image can be pressed against the paper 2 with a uniform pressure. The toner image adhered on the sheet 2 is surrounded by the shared tangents A and B of the drive pulley 27 and the tension pulley 28 shown in FIG. In the pressing portion of, the heat and pressure transmitted from the heat generating body 23 via the heat resistant belt 22 fixes the paper 2 introduced along the guide plate 32.

The belt 22 is provided with convex guides 33 on both sides and engages with the inclined portion 28 'of the tension pulley 28 to maintain the parallelism between the drive pulley 27 and the tension pulley 28. Be done.

Further, the backup roller 21 and the heating element 2
The contact portion with 3 is the drive pulley 27 and the tension pulley 2
8 is provided inside the belt inscribed therein.

Further, the backup roller 21 and the heating element 2
The contact portion with 3 is provided in the area surrounded by the heat resistant belt.

The essential parts of one embodiment of the present invention will be described in more detail with reference to FIGS.

The drive pulley 27 includes side plates 29 and 2 of the fixing device.
9'is rotatably supported, and a transmission force is transmitted from a drive force transmission system provided at the end of the drive pulley 27 to rotate. The driving force transmission system is rotated by receiving the driving force from a motor not shown here. The rotation direction is the direction indicated by the arrow in the figure. The tension pulley 28 has springs 31 and 31 '.
Gives tension.

Cylinder length lt of tension pulley 28
Are convex guides 33, 3 provided at both ends of the heat resistant belt 22.
It is shorter than the distance lc between 3 '. The length of the drive pulley 27 is shorter than the distance lc between the convex guides 33 and 33 ′ provided at both ends of the heat resistant belt 22, and the heat resistant belt 22 is offset to one side so that the convex guides 33 and 33 ′ are Tension pulley 2
The drive pulley 27 is supported at a position where it does not come into contact with the end portions of the drive pulley 27 even when the convex guides 33, 33 'are in contact with the inclined portion 28' of FIG. There is. The tension pulley 28 is a tension roller 35,
35 'is positioned with respect to the side plates 29, 29'.

The length and arrangement of the heating element 23 are the same as the length and arrangement of the drive pulley 27.

Tension pulley 28, drive pulley 27,
The length and arrangement of the heating element 23 are for consideration so as not to hinder the running of the convex guides 33 provided at both ends of the heat resistant belt 22. Therefore, the driving pulley 27 and the convex guides 33, 3 of the heating element 23 are provided so as not to hinder the running of the convex guides 33, 33 'provided at both ends of the heat resistant belt 22.
The same effect can be obtained with the configuration in which the traveling portion 3 ′ is deleted.

Next, the heat generating member 23 is inserted through the heat resistant belt 22.
The situation where the backup roller 21 comes into contact with the toner image and the toner image is fixed on the sheet 2 will be described with reference to FIG.

In the heat-resisting belt 22 having no seams, the tension pulley 28, the heating element 23, the holder 24 for holding the heating element 23, and the holder 3 for supporting the holder 24.
4 and drive pulley 27 are internal. The heating element 23 and the holder 24 are fixed to the stay 34, and the stay 34 is fixed to the side plate 2.
9 is fixed and positioned. The heat resistant belt 22 is rotated by a drive pulley 27 not shown in FIG. The heat resistant belt 22 and the heating element 23 slide in a solid lubricating state while being pressed by the backup roller 21. The sheet 2 having the toner image is carried between the heat-resistant belt 22 and the backup roller 21. On the surface of the backup roller 21,
It is covered with heat-resistant silicone rubber that is an elastic body,
The toner image can be pressed against the sheet 2 with a uniform pressure.

The toner image on the sheet 2 receives compression pressure from the backup roller 21 via the sheet 2 and from the heating element 23 via the heat resistant belt 22. Further, the toner image on the sheet 2 is heated from the heating element 23 at a temperature corresponding to the toner on the sheet 2 of 150 ° C. or higher.

The step 34 has sufficient rigidity against the pressing force of the backup roller 21. Further, when the backup roller 21 having a convex crown shape whose central portion has a diameter larger than the diameters of both end portions is used for the purpose of correcting the bending of the backup roller 21 due to the pressing force, the fixing is uniform in the axial direction. Performance is obtained.

The pressing force of the backup roller 21 is, for example, the coil springs 30 and 30 'by the backup roller bearing 3
Obtained by pushing up 6, 36 '. The backup roller bearings 36 and 36 'are attached to the side plates 29 and 29' so as to be vertically movable. The pressing force can be adjusted by adjusting the positions of the spring force adjustment bases 37 and 37 '. Next, a biasing prevention mechanism for the heat resistant belt will be described.

At both shaft ends of the tension pulley 28, an inclination of θ = 10 ° to 30 ° determined by experiments is provided. Under the condition of θ ≦ 10 °, tension pulley 2 during assembly
8 and the drive pulley 27 are required to have high parallelism.
The deviation prevention effect can be achieved under the condition of θ ≧ 30 °,
The heat-resistant belt 22 has poor stability in the direction of the rotation axis and is frequently moved in the direction perpendicular to the rotation axis.
It will disturb the image.

At both ends of the heat-resistant belt 22, heat-resistant convex guides 3 made of, for example, silicone resin bonded in a rib shape.
3, 33 'are provided.

When the heat resistant belt 22 is biased in the R direction, the convex guides 33 and 33 'adhered to both end portions of the heat resistant belt 22 come into contact with the inclined portion of the tension pulley 28 so that the tension guides are tensioned. L between drive 28 and drive pulley 27
The axial distance on the side is reduced, and the heat resistant belt 22 is biased in the L direction. By repeating this operation, the position of the heat resistant belt 22 is maintained.

Tension pulley 2 when the fixing device 20 is assembled
If the error in the parallelism between the drive pulley 27 and the drive pulley 27 exceeds the offset prevention effect of the convex guide 33 provided on the tension pulley 28, the heat resistant belt 22 cannot be prevented from being offset. Therefore, the shape in the height direction of the convex guide 33 provided on the tension pulley 28 depends on the accuracy of the fixing device 20.

By making the parallelism between the tension pulley 28 and the drive pulley 27 of the fixing device 20 so that the heat-resistant belt 22 is offset in one direction, the tension pulley 28 is formed.
Since the convex guide 33 provided on the side of the convex guide 33 is provided only on the side where the convex guide 33 comes into contact with the inclined portion of the tension pulley 28 due to the deviation, the deviation can be prevented.

FIG. 5 shows an example of an offset prevention structure in which the convex guide 33 is provided only on one end of the fixing device.

Even if the heat-resistant belt 22 shifts in one direction and the convex guide 33 abuts on the inclined portion of the tension pulley 28 and rides up, the rotation speed of the heat-resistant belt 22 by the drive pulley 27 does not change. . The length of the drive pulley 27 is such that the convex guide 33 and the drive pulley 27 do not interfere with each other so that the heat resistant belt 22 can always be rotated by the drive pulley 27 with the same radius of gyration. Alternatively, it is because the shapes of both shaft ends are determined.

By the way, in the contact portion between the backup roller 21 and the heating element 23, which is set inside the drive pulley 27 and the tension pulley 28, which are surrounded by the common tangents A and B, the heat-resistant belt is used. , Heating element 2 via heat-resistant belt 22
The toner is fixed on the sheet 2 by the heat and pressure transmitted from the sheet 3. The contact portion between the backup roller 21 and the heating element 23 shown in FIGS. 1, 2, 3, 4, and 5 is a drive pulley 27 and a tension pulley 28 via an endless drive belt 22.
The structure arranged on the tangent line B of FIG.

According to one embodiment of the present invention, the position where the backup roller is biased to the heating element via the heat resistant belt between the drive pulley and the tension pulley is set to the drive pulley and the tension pulley. Since the fixing device is arranged in a region sandwiched by two shared tangents, the fixing device can be made small and thin, and thus an electrophotographic device such as a printer and a copying machine can be realized in a small and thin shape.

According to one embodiment of the present invention, a convex rib is provided on at least one end of the inner surface of the heat resistant belt, and a drive pulley for rotating the heat resistant belt and a tension pulley for applying tension to the heat resistant belt are provided. It is supported by a member that can freely rotate, and the heat-resistant belt shifts to one side and the convex rib rides on the inclined part at the end of the tension pulley, changing the parallelism of the tension pulley to the drive pulley. Since it is intended to prevent the heat-resistant belt from being biased, it is possible to prevent the heat-resistant belt from being biased by detecting the bias of the heat-resistant belt and changing the pulley alignment based on the detected amount as in the conventional case. It is possible to realize the prevention of the belt deviation at a low cost, as compared with the configuration in which the configuration is performed.

However, even in the structure in which the contact portion between the backup roller 21 and the heating element 23 is arranged on the tangent line B between the drive pulley 27 and the tension pulley 28, the mesh is shown as shown in FIG. In many cases, the area C that becomes a dead space becomes a dead space.

Another embodiment of the present invention will be described with reference to FIGS. 7, 8 and 9.

The toner image attached on the sheet 2 is surrounded by the shared tangent lines A and B of the drive pulley 27 and the tension pulley 28 shown in FIG.
At the contact portion between the heat generating member 23 and the heat generating member 23, heat and pressure transmitted from the heat generating member 23 through the heat resistant belt 22 cause the paper 2
Is fixed in. As a result, the area C shown by the mesh in FIG.
The dead space is eliminated and further thinning can be realized.

The drive pulley 27 is rotatably supported by the side plate 29 of the fixing device, and the drive force is transmitted from the drive force transmission gear 20 provided at the end of the drive pulley 27 to rotate. The driving force transmission gear 59 is rotated by the driving force transmission system transmitting the driving force from a motor (not shown). The rotation direction is the direction indicated by the arrow in the figure.

The side plates 29, 29 'of the fixing device are the columns A5.
7. Positioned by the column B58.

By applying a rotational force to the link B51 by the leaf spring 52 with the rotary shafts 50 and 50 'as the center of rotation, the tension pulley 28 rotatably supported by the link B51 tensions the heat resistant belt 22. To act. The leaf spring 52 is fixed to the pedestal 53 with a set screw 55,
Is fixed to the side plates 29, 29 'of the fixing device by fixing screws 54.

The holder is surrounded by the heat resistant belt 22.
The heating element 23 supported by 24 is arranged. Holder-24
Is fixed to the side plates 29, 29 'of the fixing device with fixing screws 56, 56' via the stage 34. The holder 24 has sufficient rigidity against the pressing force of the backup roller 21. The spring 40 applies a rotating force to the link about the rotating shaft 43 as a center of rotation, thereby providing a backup backup.
Tension is applied to the reel 21. The other end of the spring 40 has a spring stopper 4
It is fixed at 1. In addition, backup roll by pressing force
In order to correct the deflection of the roller 21, a backup roller 2 having a convex crown shape whose central portion has a diameter larger than those of both ends.
When set to 1, uniform fixing performance can be obtained in the axial direction.

Heat is generated via the heat-resistant belt 22 at the contact portion between the backup roller 21 and the heating element 23 which is set inside the shared tangent lines A and B of the drive pulley 27 and the tension pulley 28. The heat and the pressure transmitted from the body 23 fix the paper 2 to the paper 2.

According to another embodiment of the present invention, the position where the backup roller is urged to the heating element via the heat resistant belt between the drive pulley and the tension pulley is set to the drive pulley and the tension. Since the fixing device can be made smaller and thinner because it is arranged further inside the area sandwiched by the two shared tangents of the pulley, the electrophotographic device such as a printer or a copying machine can be made smaller and thinner. realizable.

[0049]

According to the present invention, by arranging the position where the backup roller is biased to the heating element in the area surrounded by the shared tangent line of the drive pulley and the tension pulley, a small and thin electronic device is provided. A photographic device becomes feasible.

[Brief description of drawings]

FIG. 1 is a partial sectional perspective view of an embodiment in which the present invention is applied to a laser printer.

FIG. 2 is a schematic configuration diagram of a main part of FIG.

FIG. 3 is a perspective view of a heat-resistant belt rotating mechanism according to the present invention.

4 is a cross-sectional view taken along the line DD 'of FIG.

FIG. 5 is a cross-sectional configuration diagram of another example of a fixing device used in the electrophotographic apparatus of the present invention.

FIG. 6 is an explanatory view of thinning according to the present invention.

FIG. 7 is a sectional view of another embodiment of the fixing device used in the electrophotographic apparatus of the present invention.

FIG. 8 is a perspective view of another embodiment of the fixing device used in the electrophotographic apparatus of the present invention.

FIG. 9 is a perspective sectional view of another embodiment of the fixing device used in the electrophotographic apparatus of the present invention.

[Explanation of symbols]

1 ... Hopper, 2 ... Paper, 3 ... Conveyance path, 4 ... Photosensitive drum,
5 ... Developing device, 6 ... Transfer belt, 7 ... Eject roller, 8 ... Stacker, 9 ... Cleaner, 10 ... Motor, 11 ... Laser optical system, 20 ... Fixing device, 21 ... Backup roll -La, 22
... Heat-resistant belt, 23 ... Heating element, 24 ... Holder, 25 ...
Ultra-thin belt, 26 ... Teflon resin, 27 ... Drive pulley,
28 ... Tension pulley, 29 ... Side plate, 30 ... Coil spring, 31 ... Extension spring, 32 ... Guide guide, 33 ... Convex guide, 34 ... Steer, 35 ... Tension roller bearing, 36 ... Backup roll Ra bearing, 37 ... Spring force adjustment base, 40 ... Link spring, 41 ... Spring stop, 42 ... Link A, 43 ... Rotating shaft A, 44 ... Backup roller bearing,
50 ... Rotation axis B, 51 ... Link B, 52 ... Leaf spring, 53
... Pedestal, 54 ... Fixing screw, 55 ... Set screw, 56 ... Stay
Fixing screw 57 ... Strut A, 58 ... Strut B, 59 ... Driving force transmission gear.

Claims (6)

[Claims] 1. A drive pulley, an endless heat-resistant belt that is rotated by the drive pulley, a heating element disposed inside the endless heat-resistant belt, and the heat-resistant belt via the heat-generating belt. An electrophotographic apparatus including a thermal fixing device including a backup roller that biases the thermal fixing device, a developing device that visualizes image information on a recording medium conveyed to the thermal fixing device, and a conveying system that conveys the recording medium. In the apparatus, the endless heat-resistant belt is rotated by a drive pulley and a tension pulley that applies tension to the heat-resistant belt. 2. The electrophotographic apparatus according to claim 1,
An electrophotographic apparatus, wherein a position for urging a backup roller against the heating element is arranged in a region sandwiched by two shared tangent lines of the drive pulley and the tension pulley. 3. The electrophotographic apparatus according to claim 1, wherein:
The position where the backup roller is urged to the heating element is arranged in the region formed by the drive pulley and the tension pulley arranged inside the heat-resistant belt in a state where the heat-resistant belt is stretched. An electrophotographic device characterized in that 4. The electrophotographic apparatus according to claim 1, wherein a tension pulley for imparting tension to the heat resistant belt is supported by a member which can be freely rotated, and which can be rocked. An electrophotographic apparatus, wherein a spring force is applied to various members to apply tension to the heat resistant belt. 5. The electrophotographic apparatus according to claim 4, wherein a spring force acting on the swingable member is applied by a leaf spring. 6. A drive pulley, an endless heat-resistant belt that is rotated by the drive pulley, a heating element disposed inside the endless heat-resistant belt, and the heat-resistant belt via the heat-generating belt. And a backup roller for urging the heat-resistant belt, and a thermal fixing device provided with a convex rib on at least one end in the width direction inside the heat-resistant belt, and image information is visualized on a recording medium conveyed to the thermal fixing device. In the electrophotographic apparatus comprising a developing device for carrying a recording medium and a carrying system for carrying a recording medium, a position where the backup roller is biased to the heating element is located inside the heat resistant belt. And the tension pulley, the heat-resistant belt is arranged in an area where the heat-resistant belt is adhered, and the tension pulley has a taper formed at the end portion of the heat-resistant belt on the side where the convex ribs are provided. Electrophotography characterized by being a thing Location.