JPH0675488A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a belt system fixing device where heating temperature is low, and which is compact, advantageous in terms of cost and excellent in fixing performance. CONSTITUTION:This fixing device 18 is constituted of a housing 18a, an upper roller 20 incorporating a heater for heating 20a, an advacing roller 21 provided on the upstream side of the roller 20 in the carrying direction of a transfer material 40, an ejecting roller 22 provided on the downstream side of the roller 20, an endless belt 23 wound round the respective rollers 20, 21 and 22, and a lower roller 24 press-contacting with the roller 20 by interposing the belt 23 between them. The roller 21 is provided obliquely right below the roller 20, and an angle formed by a center line linking the rollers 21 and 20 and a center line linking the rollers 20 and 22 is set to an almost right angles. Therefore, a large lap amount alpha that the roller 24 and the belt 23 are mutually overlapped is formed on the peripheral surface of the roller 24 and the surface of the belt 23. Since the transfer material 40 is heated for a comparatively long time in virtue of the lap amount alpha, the heating temperature is set low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device having a belt provided in a color image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art Generally, in a color image forming apparatus such as a copying machine or a printer using electrophotography, a fixing means using a belt is effective as one means for obtaining gloss of an image to be recorded. A device has been proposed. This belt fixing device is composed of, for example, an upper roller having a heat source and an ejecting roller provided on the downstream side of the upper roller in the transfer material conveying direction, and an endless belt wound around the lower roller to press the upper roller against the upper roller. The transfer material on which the toner image has been transferred is heated in the process of passing between the belt surface and the lower roller, so that an image having a required gloss is fixed.

[0003]

However, the conventional belt-type fixing device requires a relatively large space in the transfer material conveying direction, and in addition, for example, each of reverse sheet discharge, automatic double-sided printing device (hereinafter referred to as ADU) and the like. In order to change the transport direction of the transfer material with respect to the apparatus, a dedicated guide member or roller is provided after passing through the fixing. It is well known that preheating the transfer material and the toner in heat fixing contributes to the improvement of the fixing property, but the lower roller that presses against the belt surface conventionally contacts with the belt surface close to the tangent line. Since the contact area between them is small, the heating time to the transfer material is short, and the heating effect is poor, a relatively large capacity heat source is used, and in addition to the above, there is a serious disadvantage in space and cost. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a fixing device that is compact and has an advantageous cost and that lowers a heating temperature and has high thermal efficiency.

[0004]

[Means for Solving the Problems]
It is achieved by any one of b, c and d.

(A) An upper roller having a heat source, an entrance roller provided on the upstream side of the upper roller in the transfer material conveying direction to serve as an entrance guide for the transfer material, and a transfer material discharge guide provided on the downstream side of the upper roller. A fixing device of an image forming apparatus, comprising: a discharge roller, which is a roller, an endless belt wound around each of the rollers, and a lower roller that presses the upper roller with the belt sandwiched between the lower roller surface and the lower roller surface. A fixing device, wherein the fixing device is configured such that the belt surface and the belt surface are overlapped with each other and pressed against each other.

(B) The fixing device according to item (a), wherein the overlap amount at which the lower roller surface and the belt surface overlap is set in the range of 45 ° to 90 ° at the central angle of the lower roller.

(C) A fixing device characterized in that the lower roller has a heat source in the item (a).

(D) A fixing device characterized in that the entrance roller has a heat source in the item (a).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is a side sectional view showing a schematic structure of a fixing device of FIG. 1, a side sectional view showing a structure of a color image forming apparatus of FIG. 2 and each roller of the fixing device of FIG. Description will be given with reference to a perspective view showing a method of adjusting parallelism and a side sectional view of a fixing device showing a method of switching the conveyance path in FIG. However, the present invention is not limited to this embodiment.

In FIG. 2, reference numeral 1 denotes a flexible photosensitive belt which is a belt-shaped image forming body. The photosensitive belt 1 is stretched between rotating rollers 2 and 3 and drives the rotating roller 2. Is conveyed in the clockwise direction indicated by the arrow.

Reference numeral 4 denotes a support member, that is, a guide member, fixed to the main body of the apparatus so as to be inscribed in the photosensitive belt 1. The photosensitive belt 1 is tensioned by a mechanical action of the tension roller 5 upward. The inner peripheral surface is rubbed against the guide member 4.

Therefore, the photoconductor on the outer peripheral surface of the photoconductor belt 1 is always kept in a constant relation position with respect to the surface of the guide member 4 even during conveyance, so that a stable image forming surface can be formed.

6 is a scorotron charger as a charging means, and 7
Is a laser writing system unit as an image exposing means, 8 to 11
Is a plurality of developing means, that is, developing devices, each containing a developer of a specific color, and these image forming means are arranged to face the outer peripheral surface of the photosensitive belt 1 with the guide member 4 on the back side. It

Each of the developing devices 8, 9, 10, 11 is housed in a detachable developing device housing case C, and its horizontal position is regulated, and a plurality of springs are further sandwiched on its bottom surface. Due to the repulsive action of S, it is urged upward, that is, toward the photosensitive belt 1.

The developing units 8, 9, 10, and 11 respectively contain, for example, yellow, magenta, cyan, and black developing agents, respectively, and developing sleeves 8A, 9A, which keep a predetermined gap from the photosensitive belt 1. Equipped with 10A and 11A, it has a function to visualize the latent image on the photosensitive belt 1 by a non-contact developing method. Unlike the contact development, this non-contact development has an advantage that it does not hinder the movement of the photosensitive belt.

A transfer device 12 and a cleaning device 13 are a blade 13A of the cleaning device 13 and a toner conveying roller 13
B is kept at a position apart from the surface of the photosensitive belt 1 during image formation and is pressed against the surface of the photosensitive belt 1 only as shown in the figure during cleaning after image transfer.

The paper feed cassette 14 for accommodating the transfer material 40 is set so as to be attached to the bottom surface of the image forming apparatus 30. 15
Is a first paper feed roller that feeds the transfer material 40 in the paper feed cassette 14 to a standby position before the second paper feed roller 17. Reference numeral 17 is suitable for temporarily stopping the transfer material 40 fed by the first paper feed roller 15 at the standby position and thereafter aligning the visible image front end of the photoconductor 1 and the transfer material 40 front end at the transfer position. The second paper feed roller re-feeds paper toward the transfer position at a timing. 16 is the transfer material fed by the first paper feed roller 15.
Reference numeral 16A is a guide plate for guiding 40 to the position of the second paper feed roller 17, and 16A is a guide plate for guiding the transfer material 40 after transfer to the fixing device 18. Reference numeral 18 denotes a belt type fixing device described later.

A color image forming process by the color image forming apparatus 30 is performed as follows.

First, the formation of a multicolor image according to this embodiment is performed according to the following image forming system. That is, the data obtained by the color image data input unit in which the image sensor scans the original image is processed by the image data processing unit to create image data, which is once stored in the image memory. Next, the image memory is taken out at the time of recording and is inputted to a color image forming apparatus 30 which is a recording unit, for example, shown in the embodiment of FIG.

That is, the color signal output from the image reading device separate from the printer is the laser writing system unit 7.
Input to the laser writing system unit 7, a laser beam generated by a semiconductor laser (not shown) is rotationally scanned by a polygon mirror 7B rotated by a drive motor 7A, passes through an fθ lens 7C, and a mirror 7D. The optical path is bent by 7E, and a bright line is formed on the peripheral surface of the photoreceptor belt 1 to which electric charges have been previously applied by the charger 6 as a charging means.

On the other hand, when the scanning is started, the beam is detected by the index sensor, the modulation of the beam by the first color signal is started, and the modulated beam scans the peripheral surface of the photosensitive belt 1. Therefore, a latent image corresponding to the first color is formed on the peripheral surface of the photosensitive belt 1 by the main scanning by the laser beam and the sub-scanning by the conveyance of the photosensitive belt 1. This latent image is developed by the developing device 8 in which yellow (Y) toner (visual medium) is loaded in the developing means to form a toner image on the drum surface. The obtained toner image is separated from the peripheral surface of the photosensitive belt 1 while being held on the drum surface, which is a cleaning device 13 as a cleaning unit.
And the next copy cycle begins.

That is, the photosensitive belt 1 is recharged by the charger 6, and then the second belt output from the signal processing section is output.
Is input to the writing system unit 7, and writing is performed on the drum surface in the same manner as in the case of the first color signal described above to form a latent image. The latent image is developed by the developing device 9 loaded with magenta (M) toner as the second color.

This magenta (M) toner image is formed in the presence of the previously formed yellow (Y) toner image.

Reference numeral 10 denotes a developing device having cyan (C) toner, which forms a cyan (C) toner image on the drum surface based on a control signal generated by a signal processing section.

Further, reference numeral 11 denotes a developing device having black toner, which is formed by superposing a black toner image on the belt surface by the same process. A DC or further AC bias is applied to each sleeve of each of these developing devices 8, 9, 10 and 11 to perform jumping development by a two-component developer which is a developing means, and a photoreceptor whose base is grounded. The belt 1 is developed in a non-contact manner. As the development, non-contact development using a one-component developer can also be used.

The color toner image thus formed on the peripheral surface of the photosensitive belt 1 is transferred by the transfer device 12 to the transfer material 40 sent from the paper feed cassette 14 through the paper feed guide 16.

That is, the transfer material 40 stored in the paper feed cassette 14 is carried out by the rotation of the paper feed roller 15 so that the uppermost one sheet is carried out obliquely upward to the left and then stands by before the second paper feed roller 17. To do. Then, the sheet is fed to the transfer device 12 by the second sheet feeding roller 17 at the same timing as the image formation on the photosensitive belt 1.

The transfer material 40, which has been subjected to image transfer and charge removal, is reliably separated from the photosensitive belt 1 which suddenly changes its direction along the rotating roller 2 and is directed upward, and passes through the guide plate 16A to fix the toner of the present invention. The image is fused by the device 18 and then discharged onto the tray 19.

On the other hand, the photosensitive belt 1 which has finished the transfer to the transfer material 40 is further conveyed to remove the residual toner in the cleaning device 13 in which the blade 13A and the toner conveying roller 13B are brought into pressure contact with each other, and the termination is completed. Then, the blade 13A is separated again, and a little later, the toner conveying roller 13B smoothes the toner accumulated on the photosensitive belt 1 corresponding to the tip of the blade 13A, and then the toner conveying roller 13B is separated to form a new image. Enter the process.

The fixing device 18 according to the present invention is constructed as follows.

As shown in FIG. 1, the fixing device 18 includes a casing 18a, an upper roller 20 having a heater 20a built in the central portion thereof, and a predetermined interval on the upstream side of the upper roller 20 in the conveying direction of the lower right transfer material 40. And a discharge roller 22 provided at a downstream side of the upper roller 20 in the conveying direction of the left transfer material 40, and an entrance roller 21 with the upper roller 20 in the middle. An endless belt (hereinafter simply referred to as a belt) 23 wound around each of the discharge rollers 22 and a lower roller 24 sandwiching the belt 23 and pressingly contacting the upper roller with a predetermined pressing force.

The rollers 20, 21, 22 are rotatably supported on both side surfaces of the housing 18. As shown in the figure, the line connecting the centers of the upper roller 20 and the entrance roller 21 and the upper roller
An advancing roller 21 is provided facing the lower roller 24 on the right side of the lower lower roller 24, which is bent at an angle formed by the line connecting the centers of the discharge roller 22 and the discharge roller 22 to a substantially right angle. Therefore, when the lower roller 24 presses against the upper roller 20 with the belt 23 sandwiched between them, the belt 23 becomes in a tension state and the peripheral surface of the lower roller 24 and the surface of the belt 23 are in close contact with each other and the overlap amount α is overlapped. Is formed.

This lapping amount α is determined by the upper roller as described above.
Entry roller 21 and ejection roller provided on both sides of 20
22 and 22 are formed in proportion to the angle at which they are arranged. The overlap amount α where the lower roller 24 surface and the belt 23 surface are in intimate contact and overlap with each other is set in the range of 45 ° to 90 ° at the central angle of the lower roller 24, and is preferably set to about 80 ° as shown in the figure. .
As shown in FIG. 1, the guide plate 16 is provided on the lower surface of the housing 18a.
An entrance 18b for the transfer material 40 is provided facing A, and a discharge opening 18c located substantially at a right angle to the entrance 18b is provided on the left side surface of the housing 18a.

After the transfer, the transfer material 40 is transferred to the guide plate 16
The wrap amount α formed by the circumferential surface of the lower roller 24 and the surface of the belt 23, which is conveyed along the left side surface of the belt 23 which is conveyed from the entrance 18b into the fixing device 18 via A and is wound around the entrance roller 21. The toner image having a predetermined gloss is fixed by passing through the above portion while being converted by the upper roller 20 while being changed in direction at a substantially right angle. Then, the transfer material 40 on which the image is fixed is conveyed while being in close contact with the belt 23 wound around the discharge roller 22, separated from the belt 23 by the paper discharge roller 22, and discharged to the paper discharge tray 19 of the image forming apparatus 30. To be done. Reference numeral 25 is a guide plate provided so that the transfer material 40 is smoothly discharged onto the discharge tray 19. In this way, a relatively large overlap amount α is formed between the peripheral surface of the lower roller 24 and the surface of the belt 23, so that the heating time for the transfer material 40 can be extended and the transfer material 40 to be fixed can be efficiently and stably stabilized. Heating is performed.
Therefore, the heater 20a having a smaller capacity than that of the conventional heater is used, which is extremely advantageous in terms of space and cost, and further, the warm-up time can be shortened and stable fixing can be obtained.

Although not shown, in the present invention, a heater is provided in the entrance roller 21 to preheat the unfixed toner on the surface of the transfer material 40 to further improve the fixing property. Further, since the lower roller 24 is also provided with a heater to preheat the transfer material 40, more efficient and stable fixing is performed. The heaters provided on the entrance roller 21 and the lower roller 24 may be provided on both rollers or the fixing device 18
It may be separately provided to either one of the rollers depending on the characteristics of the above. The fixing device 18 having the above-described structure has the following advantages by adding the following functions.
That is, if the ingress roller 21, the upper roller 20, the discharge roller 24, and the lower roller that are axially supported on both sides of the housing 18 are not accurately parallel to each other, a piece of the belt 23 is fixed when the transfer material 40 is fixed. This causes deviation and causes wrinkles and jams on the transfer material 40 during the fixing process. Therefore, as shown in FIG. 3, for example, one of the ingress rollers 21 is rotatably supported by a known eccentric bearing (not shown), and in order to obtain parallelism with the discharge roller 22 in assembling, the eccentric bearing vertically or vertically is used. Finely adjust to the left and right to absorb errors in component processing so that mutual parallelism is achieved. Therefore, the entrance roller 21 can also be used as a displacement roller for controlling the skew of the belt. This parallelism adjustment may be performed not only by the displacement of the entrance roller 21 but also by the discharge roller 22.

Further, depending on the specifications of the image forming apparatus 30, for example, when the transfer material 40 discharged after the fixing is reversed and discharged or is conveyed to the ADU apparatus, a conveying path for changing the direction is inevitably necessary. . Therefore, as shown in FIG. 4, when it is desired to convey the sheet upward for reverse sheet discharge, the sheet discharge roller 21, the belt 23, and the guide plate 25 are slightly displaced upward as indicated by the arrow by utilizing the flexibility of the belt 23. Transfer material ejected upwards
The tip end of 40 is directionally changed upward along an upper curved surface 18d formed above the left side surface of the housing 18a facing the paper ejection roller 22, and is conveyed to a predetermined reverse paper ejection conveyance path. Further, when it is desired to convey the image to the ADU device provided below the image forming apparatus 30, the discharge roller 22, the belt 23, and the guide plate 25 are slightly rotated downward as shown by the arrow, and the tip of the transfer material 40 discharged downward is The direction is changed downward along a lower curved surface 18e formed on the lower side of the left side surface of the housing 18a facing the discharge roller 22, and is conveyed to a conveyance path of a predetermined ADU device. Therefore, it is possible to easily switch between the upper and lower curved surfaces 18d and 18e by simply rotating the discharge roller 22 and the guide plate 25 up and down, which is extremely advantageous in terms of space and cost. . The rotation of the discharge roller 22 including the belt and the guide plate 25 may be performed by a method of using an eccentric cam that engages with the support shaft of the discharge roller 22 or a method of interlocking with the operation of a plunger by a solenoid. A known technique is used for the operation method, and the switching and timing of the operation are controlled by a CPU (not shown) incorporated in the image forming apparatus 30.

[0037]

As described above, according to the present invention, with respect to the upper roller having the heater, the entrance roller serving as the entrance guide of the transfer material and the discharge roller serving as the discharge guide are provided on both sides of the upper roller at substantially right angles. Since the lower roller is pressed against the rollers by sandwiching the endless belt wound around each roller, the peripheral surface of the lower roller and the belt surface are overlapped with each other to form a relatively large amount of wrap, which increases the heating time for the transfer material. In addition, since the heating can be performed with extremely high thermal efficiency, the capacity of the heater can be reduced, which is extremely advantageous in terms of space and cost. Also, by providing a heater on the entrance roller and the lower roller, effective preheating of the toner and the transfer material is performed, so that extremely stable fixing is performed and a beautiful color image having a required gloss is fixed. became. Further, after the fixing, the direction of the transfer material can be easily changed, and the parallelism of each roller at the time of assembly can be easily adjusted, so that the belt can be stably fixed without being biased. .

[Brief description of drawings]

FIG. 1 is a side sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a configuration of a color image forming apparatus including a fixing device according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a method of adjusting parallelism of each roller of the fixing device according to the exemplary embodiment of the present invention.

FIG. 4 is a side sectional view of a fixing device showing a method of switching a conveyance path according to an embodiment of the present invention.

[Explanation of symbols]

 1 photoconductor belt 18 fixing device 18a housing 18b entrance 18c discharge port 20 upper roller 20a heating heater 21 entry roller 22 discharge roller 23 endless belt 24 lower roller 30 color image forming device 40 transfer material α wrap amount

Claims (4)

[Claims] 1. An upper roller having a heat source, an entrance roller provided upstream of the upper roller in the transfer material conveying direction and serving as an entrance guide for the transfer material, and a transfer material discharge guide provided downstream of the upper roller. A discharge roller, an endless belt wound around each of the rollers, and a lower roller that presses the upper roller with the belt sandwiched between the lower roller and the lower roller surface. A fixing device having a structure in which the surfaces and the surfaces are pressed against each other with an overlapping amount. 2. The fixing device according to claim 1, wherein the overlap amount at which the lower roller surface and the belt surface are overlapped with each other is set in a range of 45 ° to 90 ° at a central angle of the lower roller. 3. The fixing device according to claim 1, wherein the lower roller has a heat source. 4. The fixing device according to claim 1, wherein the entrance roller has a heat source.