JP3016850B2 - Electrophotographic device fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic method (transfer of an image formed on a photoreceptor to a recording medium such as paper or an envelope) using a laser, such as a printer, a copying machine, and a facsimile. Recording method)
Thus, the present invention can be applied to an electrophotographic apparatus that performs recording on a recording medium. More specifically, the present invention relates to a fixing device for fixing an image transferred on a recording medium in such an electrophotographic apparatus.

2. Description of the Related Art Conventionally, as shown in FIG. 7, for example, as shown in FIG. 7, a pressing roller is pressed against a fixing roller 2 having a built-in heater 1 by a pressing means 3 so that both rollers 2 and 4 are fixed. There has been a configuration in which a transfer image on the sheet P is rotated through the sheet P conveyed after the image transfer between the rollers 2 and 4 and transferred.

However, in a fixing device using these two rollers 2.4, for example, when a recording medium such as an envelope formed by stacking a plurality of sheets of paper is passed between the rollers 2.4, the two rollers 2.4 are formed. There has been a problem that the front and back are misaligned based on the curvature difference in the fixing nip portion 5 and wrinkles are generated, so that poor fixing is likely to occur.

For this reason, some other conventional fixing devices include, for example, the sixth fixing device.
As shown in the drawing, an endless belt 9 is stretched between a driving roller 6, a driven roller 7, and a tension roller 8, the belt 9 is pressed against the fixing roller 2, and the fixing roller 2 and the belt 9 are driven to fix the belt. There is a configuration in which a transferred image is satisfactorily fixed without causing wrinkles on the recording medium P through the recording medium P after image transfer between the roller 2 and the belt 9.

When the recording medium P is jammed between the fixing roller 2 and the belt 9, the fixing roller 2 and the belt 9 are reversely driven to return the recording medium to the medium entry side (right side in FIG. 6) and jam. Remove the recording medium. However, this belt 9
Since a plurality of belt rollers 6, 7, 8 are used at the time of reverse driving, the frictional load between the roller shafts and the bearings increases, and the fixing roller 2 and the belt 9 record. Because of slippage with the medium P, it is difficult to manually and easily return the jammed recording medium P to its entry side.

Therefore, conventionally, in the above-mentioned belt-type fixing device,
Although illustration is omitted in order to facilitate the jam processing, (a)
(B) a belt and a roller for the belt are formed as one belt unit;
In some cases, the fixing roller is removably configured to be detachable, and in the other case, the jammed paper is returned by manually rotating the fixing roller in the reverse direction without manual operation.

Problems to be Solved by the Invention However, the above-mentioned conventional belt-type fixing device (a)
Of (b) and (c), in (a), there is a possibility that a part of the belt may fall off the roller or be offset in the roller axis direction by loosening the belt. (B) requires extra space for removing the belt unit. (C) has a problem that the structure becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem and to enable a jam processing to be easily performed from a medium entry side.

Means for Solving the Problems Therefore, the present invention according to claim 1 is, for example, as shown in the following illustrated embodiment, a belt roller 38.
An endless belt 44 is stretched between 39 and 40 or belt rollers 58 and 59, and the belt 44 is pressed against the fixing roller 30, and a recording medium such as paper 17 is passed between the fixing roller 30 and the belt 44. In the fixing device 23/23 'of the electrophotographic apparatus for fixing the transfer image on the recording medium, the belt roller 38/39 or 58/59 is moved to the retracted position to move the belt 44 with respect to the fixing roller 30. A configuration in which the cam mechanisms 33 and 50 for releasing the pressing are provided, and the post-movement belt roller does not become smaller than the sum of the inter-axis distances of the adjacent belt rollers before moving to the retracted position. It is characterized by becoming.

Further, the present invention described in claim 2 is, for example, as described in the following embodiments, the fixing devices 23.2 according to claim 1
3 'is characterized in that the cam mechanisms 33 and 50 are provided only on one end side of the belt rollers 38 and 39 or 58 and 59.

Further, the present invention described in claim 3 is, for example, as shown in the following embodiment shown in FIG. 1 and FIG.
In the fixing device 23, the belt rollers 38 and 39
A biasing mechanism 45 for biasing the belt 44 to apply a substantially constant tension to the belt 44 before and after the belt rollers 38, 39 and 40 are moved to the retracted position.

Further, according to a fourth aspect of the present invention, in the fixing device 23 according to the first aspect, the cam mechanism 33 is connected to the belt for the belt as shown in the following embodiments shown in FIGS. It is characterized by comprising a sector gear 34 having a cam portion such as a cam groove 34a / 34b engaged with the roller shafts 38a / 39a of the rollers 38/39 and rotatable by an external operation.

Further, according to the present invention described in claim 5, according to the embodiment shown in FIGS. 3 and 4, in the fixing device 23 'according to claim 1, the belt rollers 58 An inner cam that presses against the fixing roller 30 with an urging member such as a compression coil sling 62 or 63 and releases the pressing by an external operation against the urging member.
The cam mechanism 50 is constituted by a cam such as 52.

According to the present invention, when the recording medium is jammed between the fixing roller 30 and the belt 44, the cam mechanisms 33 and 50 are operated to operate the belt rollers 38, 39, 58 and 59.
Is moved to the retracted position, and the belt 44 with respect to the fixing roller 30 is moved.
Is released, and the belt 44 is stretched between the belt rollers.

Further, according to the present invention, at the time of the above-described jam clearance, the cam mechanisms 33 and 50 are operated only at one end side of the belt rollers 38, 39, 58 and 59 to operate the belt rollers 38 and 39.
Move 58 and 59 to the retracted position and release the pressing of the belt 44 against the fixing roller 30.

Further, according to the present invention, the belt rollers 38, 39, and 40 are constantly urged by operating the urging mechanism 45 to apply a substantially constant tension to the belt 44.

Furthermore, according to the present invention, the sector gear 34 is rotated by an external operation at the time of the above-described jam processing,
The belt rollers 38 and 39 are moved to the retracted positions via the cam portions, and the pressing of the belt 44 against the fixing roller 30 is released.

Further, according to the present invention, at the time of the above-described jam processing, the cam is operated by an external operation to move the belt rollers 58 and 59 to the retracted position against the urging member, and the fixing roller is moved. The pressing of the belt 44 against 30 is released.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 5 shows an overall schematic configuration of an internal mechanism of a laser printer having a fixing device according to the present invention. What is indicated by reference numeral 10 in the figure is the apparatus main body. A belt-shaped photoconductor 11 is provided in the center of the apparatus main body 10. And the photoconductor
Around the reference numeral 11, a charging charger 12, a laser optical system 13, a developing device 14, a transfer charger 15, and a cleaning device 16 are arranged in the rotation direction (clockwise direction in the drawing). This device body
On the right side in FIG. 10, a paper feed tray 18 for storing paper 17 is removably loaded. A paper feed unit having a paper feed roller 19, a paper guide plate 20, etc.
21 is provided. On the other hand, a conveyance guide 22, a fixing device 23 according to the present invention, and the like are arranged side by side on the side opposite to the sheet feeding section 21 with the transfer charger 15 therebetween. Also, the device body 10
On the upper side of the figure, a paper receiving tray 24 for receiving the paper 17 to be discharged is provided.

When recording by an electrophotographic process using the laser printer, the paper feed roller 19 is driven to feed out the paper 17 from the paper feed tray. Then, the sheet is guided and conveyed by the paper guide plate 20, and the leading end of the sheet 17 is detected by a registration sensor (not shown). Then, the leading end of the sheet 17 is abutted against the registration rollers 25.

On the other hand, the surface of the photoreceptor 11 is sequentially and uniformly charged by the charging charger 12 while rotating clockwise in the figure, and the next laser optical system 13 irradiates a laser beam to form an electrostatic latent image on the surface. When the electrostatic latent image is formed and subsequently passes through the developing device 14, the electrostatic latent image is sequentially visualized with toner. Then, the sheet 17 that has been in contact with the above-described registration roller 25 is sent out toward the photoconductor 11 in synchronization with the timing of the image. Then, the image on the photoconductor 11 is transferred to the sheet 17 by the transfer charger 15. After the image is transferred, the residual toner remaining on the photoconductor 11 is scraped off by the cleaning device 16, and the surface of the photoconductor 11 is cleaned by the cleaning device 16.

On the other hand, the paper 17 is sent to the fixing device 23 by the conveyance guide 22, and the transferred image is thermally fixed by the fixing device 23. After the fixing, the paper 17 is discharged from the apparatus main body 10 and sequentially stacked on the paper discharge receiver 24.

By the way, specifically, the fixing device 23 according to the present invention includes:
For example, the configuration is as shown in FIG. Reference numeral 30 in the figure
Denotes a fixing roller. The fixing roller 30 is made of a metal pipe and has a heater 31 built in the center. Although not shown in the figure, both ends are connected to a drive motor via a gear train, and both ends are respectively rotatable clockwise as shown by an arrow in the figure.
32 (one side plate is not shown). Three guide holes 32a, 32b, and 32 are provided in the side plates 32 below the fixing roller 30.
c is provided. Among them, the left and right guide holes 32a and 32b near the fixing roller 30 are formed by long holes so as to form a C shape, and the other guide holes 32c are formed by long holes provided longer toward the center axis of the fixing roller 30. Do it. Further, on both side plates 32, cam mechanisms 33 are provided at both ends of the fixing roller 30. The cam mechanism 33 is constituted by using a sector gear 34 supported on both side plates 32 so as to be rotatable about the axis of the fixing roller 30. The sector gear 34 is provided in a meandering manner as shown in FIG.
It has two cam grooves 34a and 34b (cam parts). And
The gear 37 meshes with the gear 37 of the external operation dial 36 via the intermediate gear 35, and the external operation dial 36 can be turned by a turning operation thereof. Further, between the side plates 32, below the fixing roller 30,
Over three belt rollers 38, 39, 40. Among them, a belt roller 38 disposed near the fixing roller 30 and on the left side in the drawing.
Is a driving roller, and the roller shaft 38a of the driving roller passes through the guide hole 32a and engages with the cam groove 34a via the bearing 41. On the other hand, the belt roller 39 on the right side is a driven roller, and the roller shaft 39a of the driven roller passes through the guide hole 32b and engages with the cam groove 34b via the bearing 42. The other belt roller 40 is a tension roller, and its roller shaft 40a is engaged with the guide hole 32c via a bearing 43.
Then, an endless and wide belt 44 is stretched between these belt rollers 38, 39, and 40. Also, belt rollers
A biasing mechanism 45 is provided below 40. The biasing mechanism 45 includes a pin 46 provided on the side plate 32, and a tension spring 47 that hooks one end of the pin 46 and locks the other end of the bearing 43, and uses the tension spring 47 to rotate the belt roller 40. It is always urged in the direction indicated by the arrow in the figure. Then, a certain tension is applied to the belt 44, and the bearing 41 of the belt roller 38 abuts against the opening edge of the guide hole 32a on the urging mechanism 45 side to hold the belt roller 38, and the bearing of the belt roller 39
The belt roller 39 is held by contacting the cam groove 34b with the opening edge of the cam groove 34b on the urging mechanism 45 side. The belt 44 is pressed against the fixing roller 30 between the belt rollers 38 and 39.

Meanwhile, in the normal case where the transfer image is fixed by the above-described fixing device 23, the transferred paper 17 is passed between the fixing roller 30 and the belt 44 driven in the direction indicated by the arrow in FIG.
The transferred image is fixed by heat and pressure. If the paper 17 is jammed between the fixing roller 30 and the belt 44 during the image fixing, the driving of the driving motor is stopped, and then the external operation dial 36 is rotated clockwise in FIG.
34 is rotated clockwise as indicated by arrow A. Then, the bearings 41 and 42 of the belt rollers 38 and 39 are respectively fitted to the cam grooves 34a and 3a.
4b While pressing down on the upper opening edge, as shown in FIG.
The guide hole 32 is moved to a retracted position where the roller is retracted from the outer periphery of the fixing roller 30.
Guide rollers a and 32b move the belt rollers 38 and 39.

Then, the pressing of the belt 44 against the fixing roller 30 is released. Then, the jammed sheet 17 is removed from the sheet entry side on the right side in the drawing, and the jam processing is performed. After this jam processing, as shown in FIG. 2, the external operation dial 36 is rotated counterclockwise in the figure to rotate the sector gear 34 counterclockwise as shown by the arrow B. Then, while pushing up the bearings 41 and 42 of the belt rollers 38 and 39 at the lower opening edges of the cam grooves 34a and 34b, the guide holes 32a and 32b return to the original proximity position close to the outer periphery of the fixing roller 30. Guide to belt roller
Move 38/39. Then, again fix the belt 44 to the fixing roller
Press on 30.

By the way, in the above-described embodiment, only the belt 44 is pressed against the fixing roller 30. However, in the present invention, for example, as shown in the following other embodiment,
The belt rollers may also be configured to be pressed against the fixing roller 30 with the belt 44 spanned therebetween. In the other embodiment, as shown in FIG. 3, two guide holes 32a and 3a are provided.
2b is provided on both side plates 32 (not shown) in a C-shape. Then, cam mechanisms 50 are provided on the side plates at both ends of the fixing roller 30. The cam mechanism 50 has a mounting plate 51 rotatably supported on both side plates, and an inner cam (cam) 52 and an outer cam 52 on the mounting plate 51 so as to be integrally rotatable about the axis of the fixing roller 30 together therewith. 53 is provided. The inner cam 52 has a pair of cam concave surfaces on the lower peripheral edge in the drawing.
54a and 55a and cam convex surfaces 54b and 55b are formed. On the other hand, the outer cam 53 has a pair of cam convex surfaces 56a on the inner cam 52 side.
57a and cam concave surfaces 56b and 57b are formed. Although not shown, the cam mechanism 50 is configured to be externally operable. Further, between the side plates, two belt rollers 58 and 59 are extended below the fixing roller 30. The belt rollers 58 and 59 respectively support roller shafts 58a and 59a as bearings 60.
-Engage with the guide holes 32a and 32b via 61. Then, the endless and wide belt 44 is stretched between the belt rollers 58 and 59. Thus, each of the bearings 60 and 61 of the belt rollers 58 and 59 is connected to a compression coil spring (biasing member) 62 and 63.
To press the belt rollers 58 and 59 against the fixing roller 30. Compression coil spring
62 and 63 are housed in the guide holes 32a and 32b, respectively, and one end is attached to pins 64a and 64a provided at one end of the support levers 64 and 65, and the other end is pressed against the bearings 60 and 61. Support lever
The reference numerals 64 and 65 are attached to the side plates so as to be rotatable around pins 64b and 65b provided at the other ends, respectively, and the pins 64a and 65a are pressed against the cam convex surfaces 56a and 57a by compression coil springs 62 and 63 and stopped.

In the normal case where the transfer image is fixed by the fixing device 23 'in the above-described other embodiment, the transferred paper 17 is passed between the fixing roller 30 and the belt 44 which are driven in the direction indicated by an arrow in FIG. The transferred image on 17 is fixed by heat and pressure. If the paper 17 is jammed between the fixing roller 30 and the belt 44 during the image fixing, the driving of the driving motor is stopped, and then the inner cam 52 and the outer cam 53 are externally operated to indicate the clock indicated by the arrow C. Rotate in the direction. Then, while pushing down the bearings 60 and 61 of the belt rollers 58 and 59 with the concave cam surfaces 54a and 55a against the compression coil springs 62 and 63, as shown in FIG. And the guide holes 32a and 32b guide and move the cam convex surfaces 54b and 5b.
Ride on 5b. Then, the pressing of the belt 44 against the fixing roller 30 is released. At this time, support lever 64
65 is pushed by compression coil springs 62 and 63 and pins 64a and 6
While guiding 5a from the cam convex surfaces 56a / 57a to the cam concave surfaces 56b / 57b, it rotates counterclockwise in the figure to rotate the belt rollers 58/57.
Follow the movement to the 59 evacuation position. As a result, the compression coil springs 62 and 63 can be
This prevents the load when the cams 52 and 53 rotate from increasing, and also prevents the spring characteristics of the compression coil springs 62 and 63 from changing. In addition, the belt roller 58
59, the distance between the shafts after retreat shown in FIG. 4 becomes larger than that before retreat shown in FIG.
44 prevents the belt rollers 58 and 59 from loosening between the belt rollers 58 and 59 to prevent a part of the rollers from dropping or offset. Then, after the pressing of the belt 44 is released, the jammed sheet 17 is taken out from the sheet entry side on the right side in FIG. After this jam processing, the cams 52 and 53 are rotated counterclockwise in the drawing by an external operation. Then, this time, the bearings 60
While being pushed up by the compression coil springs 62 and 63, respectively, the guide 61 is guided by the guide holes 32a and 32b to the original proximity position close to the outer periphery of the fixing roller 30, and moves. Then, the belt rollers 58 and 59 are again pressed against the fixing roller 30 with the belt 44 interposed therebetween.

By the way, in each of the illustrated embodiments described above, the cam mechanism is provided at both ends of the belt rollers 38 and 39 or the belt rollers 58 and 59, but the cam mechanism is provided only at one end and one cam is provided. The belt roller may be moved by a mechanism. This simplifies the structure by reducing parts.

In the present invention, for example, the sector gear 34 described above is used.
The sector gear 34 can also serve as a bearing for the fixing roller 30 by forming a cylindrical protrusion in the cylindrical protrusion and rotatably inserting the roller shaft of the fixing roller 30 into the cylindrical protrusion.

Therefore, according to the first aspect of the present invention, since the belt roller is moved to the retracted position by the cam mechanism to release the pressing of the belt, the jam easily occurs from the medium entry side. The belt can be processed, and the total distance between the shafts after the retraction of the belt roller is not smaller than that before the retraction, so that it is possible to prevent the belt from partly dropping or offset. it can.

According to the second aspect of the present invention, since the cam mechanism is provided only on one end side of the belt roller, the number of components can be reduced by that amount and the structure can be simplified.

According to the third aspect of the present invention, the biasing mechanism applies a substantially constant tension to the belt before and after the belt roller moves to the retracted position. It is possible to prevent a part of the belt from dropping or offset after the evacuation.

Furthermore, according to the present invention, the cam mechanism is constituted by a sector gear, so that easy jam clearance from the medium entry side can be realized.

According to the fifth aspect of the present invention, the cam mechanism is constituted by a cam that releases the pressing against the urging member that presses the belt roller against the fixing roller. Easy jam processing can be realized.

[Brief description of the drawings]

FIG. 1 is a structural view showing a main part of a fixing device according to an embodiment of the present invention, FIG. 2 is a state explanatory diagram showing a state of the fixing device at the time of jam processing, and FIG. FIG. 4 is a structural view showing a main part of a fixing device according to an embodiment, FIG. 4 is a state explanatory diagram showing a state of the fixing device during jam processing, and FIG. FIG. FIG. 6 is a schematic configuration diagram showing a conventional fixing device for pressing a belt against a fixing roller, and FIG. 7 is a schematic configuration diagram showing a conventional fixing device for pressing a pressure roller against a fixing roller. 17 ... paper (recording medium), 23/23 '... fixer, 30 ...
Fixing roller, 33/50 ... Cam mechanism, 34 ... Sector gear,
34a ・ 34b …… Cam groove (cam part), 38 ・ 39 ・ 40 ・ 58 ・ 59…
… Belt roller, 38a ・ 39a… Roller shaft, 44… Belt, 45… Biasing mechanism, 52… Inner cam (cam), 62 · 63
... Compression coil spring (biasing member).

Claims (5)

(57) [Claims] 1. An electrophotographic apparatus in which an endless belt is stretched between belt rollers, the belt is pressed against a fixing roller, and a transfer image on the recording medium is fixed between the fixing roller and the belt through a recording medium. In the fixing device, a cam mechanism for moving the belt roller to the retracted position to release the pressing of the belt against the fixing roller is provided, and each of the cams before moving the belt roller to the retracted position is provided. A fixing device for an electrophotographic apparatus, wherein the fixing device after the movement does not become smaller than the total distance between the shafts of adjacent belt rollers. 2. The fixing device of an electrophotographic apparatus according to claim 1, wherein said cam mechanism is provided only on one end side of said belt roller. A biasing mechanism for biasing the belt roller and applying a substantially constant tension to the belt before and after moving the belt roller to a retracted position;
A fixing device for the electrophotographic apparatus according to claim 1. 4. The electrophotographic apparatus according to claim 1, wherein said cam mechanism comprises a sector gear having a cam portion engaged with a roller shaft of said belt roller and rotatable by an external operation. Fixing unit. 5. A cam mechanism comprising a cam which presses the belt roller against the fixing roller with an urging member and releases the pressing by an external operation against the urging member. A fixing device for the electrophotographic apparatus according to claim 1.