JPH09230723A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a fixing belt by transmitting rotation to one of the fixing belt and a moving roller or one of the moving roller and a fixed roller, in accordance with a state. SOLUTION: A pressure roller (moving roller) 24 is constituted of a metallic roller 26 or a roller having a rubber layer 28 on the outer periphery of the metallic roller 26 and switched to a first state of press-contact with the belt part, a supporting roller 14 and a heating roller 16 and a second state away from the fixing belt 12 by a switching mechanism. Then, in the first state where an arm is turned to bring the pressure roller 24 into press-contact with the fixing belt 12, a drive transmission gear is engaged with the gear of the heating roller 16. On the other hand, in the second state where the arm is reversely turned to separate the pressure roller 24 from the fixing belt 12 and bring the pressure roller 24 into press-contact with a heating roller 30, the drive transmission gear is engaged with the drive transmission gear of the heating roller 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed developer to a sheet such as a sheet by fixing the unfixed developer in an electrophotographic copying machine or printer.

[0002]

2. Description of the Related Art As the above fixing device, a roller type fixing device and a belt type fixing device are known. A roller type fixing device generally includes a heating roller having a heat source and a pressure roller that comes into pressure contact with the heating roller, and the developer is melted and fixed on the sheet at the contact portion between these two rollers. On the other hand, a belt type fixing device is equipped with a belt supported by a plurality of rollers, a pressure roller in pressure contact with the outer peripheral surface of the belt, and a heat source for heating the belt. At the contact portion, the developer is melted and fixed on the sheet.

[0003]

However, although the roller type fixing device is excellent in durability, it cannot be applied to the developer because the contact length between the heating roller and the pressure roller cannot be made sufficiently long. There is a limit to the amount of heat that can be generated, and it is not suitable for an image forming apparatus that forms a full-color image by stacking a plurality of developers. On the other hand, the belt type fixing device has an advantage that a sufficient amount of heat can be given to the developer because the contact length between the fixing belt and the pressure roller can be made sufficiently long, but the belt durability is improved. Considering it, it is not suitable for continuous use for a long time.

[0004]

Therefore, in the present invention, one fixing device is provided with a roller type fixing function and a belt type fixing function, and these are selectively used as necessary. Specifically, (a) an endless fixing belt, (b) a plurality of rollers that support the fixing belt from the inside thereof, and (c) a first heating unit that heats the fixing belt in the fixing device. And (d) moving roller, (e)
The first moving roller is brought into contact with the outer peripheral surface of the fixing belt.
Switching means for switching between the above state and the second state in which the fixing belt does not come into contact with the outer peripheral surface of the fixing belt, (f) the fixed roller that comes into contact with the moving roller in the second state, and (g) the moving roller and the fixed roller. A second heating means for heating at least one of the above, and (h) in the first state, the sheet is supplied to the contact portion between the fixing belt and the moving roller, and in the second state, Is a sheet supply means for supplying a sheet to the contact portion between the moving roller and the fixed roller,
(I) In the first state, the rotation is transmitted to at least one of the fixing belt and the moving roller, and in the second state, the rotation is transmitted to at least one of the moving roller and the fixed roller. And a driving means for driving.

[0005]

The above-mentioned fixing device operates as follows. That is, when the belt type fixing function is required, the moving roller is set to the first state by the switching means and is brought into pressure contact with the fixing belt. Further, when set to the first state, the rotation is transmitted to the fixing belt, the moving roller, or both by the driving unit, the fixing belt and the moving roller rotate in a predetermined direction, and the fixing belt moves to the first position. It is heated by the heating means. Then, the sheet having the unfixed developer is supplied to the contact portion between the fixing belt and the moving roller by the sheet supply means, and the unfixed developer is heated and melted by the fixing belt and fixed on the sheet.

On the other hand, when a roller type fixing function is required, the moving roller is set to the second state by the switching means and is brought into pressure contact with the fixed roller. Further, the drive is transmitted to the moving roller or the fixed roller or both by the driving means, the moving roller and the fixed roller rotate in a predetermined direction, and the moving roller and the fixed roller or both of them move to the second heating means. Is heated by. Then, the sheet having the unfixed developer is supplied to the contact portion between the moving roller and the fixed roller by the sheet supply means, and the unfixed developer is heated and melted by the heated roller to be fixed on the sheet.

As described above, in the fixing device of the present invention, the belt type fixing function and the roller type fixing function can be arbitrarily selected. Therefore, for example, in the case of forming a full-color image in which a plurality of developers are stacked, the belt type fixing function is selected so that the developer in the lowermost layer can be sufficiently heated and fixed on the sheet. When the roller type fixing function is applicable (for example, when a single color image is created), the roller type fixing function is switched to, and the fixing belt is stopped. Therefore, the life of the fixing belt is extended.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an outline of a fixing device 10 according to the present invention. In this fixing device 10,
The endless fixing belt 12 is formed by applying a fluororesin or a silicone resin to the outer periphery of a base layer made of a resin thin film such as a polyimide resin or a metal thin film such as nickel electroforming, and a fixing device main body (not shown). It is supported by two rollers, that is, a support roller 14 and a heating roller 16, which are rotatably and parallel to each other. The heating roller 16 is the heater 1
8 is built in, and this heater 18 is connected to a power source 22 via a switch 20. The pressure roller (moving roller) 24 is composed of a metal roller 26 made of aluminum or the like or a roller having a rubber layer 28 having a thickness of about 0.5 mm or less on the outer periphery of the metal roller 26, and includes a supporting roller 14 and a heating roller 16. It is arranged in parallel with the support roller 14 and the like so as to face the belt portion extending between the first and second portions, and is in a first state in which the support roller 14 and the heating roller 16 are pressed into contact with the belt portion and the belt portion by the switching mechanism described later. (Displayed by a solid line) and a second state (displayed by a dotted line) separated from the fixing belt 12 can be switched. The heating roller (fixed roller) 30 has a rubber layer 3 having a thickness of about 1.0 mm or less on the outer circumference of a metal roller 32 made of aluminum or the like.
4 is provided in the fixing device main body in parallel with the support roller 14 and the like so as to come into contact with the pressure roller 24 set in the second state. Further, the heating roller 30 has a heater 36 built therein, and the heater 36 is connected to the power source 22 via a switch 38.

The first contact portion (nip portion 40) between the fixing belt 12 and the pressure roller 24 set to the first state, or the heating roller 30 and the pressure roller 2 set to the second state.
The transport mechanism that feeds the sheet to the contact portion (nip portion 42) with the sheet 4 is a first passage 44 that transports the sheet on which the developer is transferred in the transfer portion (not shown) toward the fixing device 10, and Two branch paths 46 and 48 branched from the first path 44 are provided, one branch path 46 extends toward the nip portion 40, and the other branch path 48 extends toward the nip portion 4.
It extends toward 2. Further, a switching lever 50 for allocating the sheet passing through the passage 44 to the branch passages 46 or 48 is provided at the start ends of the branch passages 46 and 48. The switching lever 50 is moved by the switching mechanism of the pressure roller 24 to the solid line position. And can be switched to the dotted line position.

The switching mechanism 52, as shown in FIG.
The fixing device main body includes a pair of rotatably provided arms 54. These arms 54 are rotatably supported by a shaft 56 arranged in parallel with the support roller 14, and support the pressure roller 24 in parallel with the support roller 14. The arm 54 is also connected to the solenoid 58, and the arm 54 operates based on the drive of the solenoid 58 to switch the pressure roller 24 between the first and second states. Further, the arm 54 is connected to the lever 50 by a gear mechanism or the like not shown, and the pressure roller 24
Is set to the first position, the lever 50 is set to the solid line position. Conversely, when the pressure roller 24 is set to the second position, the lever 50 is set to the dotted line position.

The drive connection mechanism 60 of the fixing device 10 will be described. As shown in FIGS. 2 to 4, a drive gear 62 is rotatably provided on a shaft 56 supporting the arm 54, and the drive gear 62 is connected to a motor 64. A drive transmission gear 66 is rotatably provided on the arm 54, and the drive transmission gear 66 meshes with the drive gear 62. On the other hand, a gear 70 is provided on the shaft 68 of the heating roller 16 supporting the fixing belt 12. On the other hand, the shaft 72 of the heating roller 30 is provided with a gear 74, and this gear 74 meshes with another drive transmission gear 76. Then, in the first state where the arm 54 is rotated to press the pressure roller 24 against the fixing belt 12, the drive transmission gear 66 is used.
Meshes with the gear 70 of the heating roller 16 (see FIG. 3),
On the other hand, in the second state in which the arm 54 is rotated in the opposite direction so that the pressure roller 24 is separated from the fixing belt 12 and pressed against the heating roller 30, the drive transmission gear 66 meshes with the drive transmission gear 76 of the heating roller 30. (See Figure 4).

The operation of the fixing device 10 will be described with reference to FIG. 1 and others. The fixing device 10 has a control device 78.
When information of an image to be created from a main controller (not shown) of the image forming apparatus is input to the controller 78, the controller 78 operates the solenoid 58 and the like based on the information. Switch control. Now, it is assumed that the information that the image to be created is a full-color image in which a plurality of colors are superimposed is input to the control device 78. At this time, if the pressure roller 24 is in the second state, the solenoid 58 is driven to rotate the arm 54, press the pressure roller 24 against the fixing belt 12, and move the lever 50 from the dotted line position to the solid line position. Switch to. In the drive coupling mechanism 60, the arm 5
The drive transmission gear 66 meshes with the gear 70 based on the rotation of No. 4 (see FIG. 3). Then, the control device 78 uses the switch 3
8 is turned off and switch 20 is turned on to turn on heater 1.
8 is energized to heat the fixing belt 12 in contact with it via the heating roller 16. Then, the motor 64 is driven to rotate the heating roller 16 in the direction of arrow 80. As a result, the fixing belt 12 rotates in the direction of arrow 82 and the support roller 14 rotates in the direction of arrow 84. Further, the pressure roller 24 rotates in the direction of arrow 86. Therefore, when the sheet having the unfixed developer enters the nip portion 40 through the passage 44 and the branch passage 46, the unfixed developer is melted by the heat of the fixing belt 12 and fixed on the sheet. Since the length of the nip portion 40 between the fixing belt 12 and the pressure roller 24 is comparatively long, the developer passing through the nip portion 40 is sufficiently heated and melted to the lowest layer. To do.

When the fixing device 10 is in the above-mentioned state, it is assumed that information that the image to be created next is a monochromatic image is input to the control device 78. In this case, the control device drives the solenoid 58 to rotate the arm 54 to move the pressure roller 2
4 is separated from the fixing belt 12 and pressed against the heating roller 30, and the lever 50 is moved from the solid line position to the dotted line position. In the drive coupling mechanism 60, the drive transmission gear 66 meshes with the gear 76 based on the rotation of the arm 54 (see FIG. 4). Then, the controller 78 turns off the switch 20 and turns on the switch 38 to energize the heater 36,
The heating roller 30 is heated. Then, the motor 64 is driven to rotate the heating roller 30 in the direction of arrow 88. Also,
When the pressure roller 24 comes into contact with the heating roller 30, the arrow 9
The rotation direction is switched to the 0 direction. Therefore, when the sheet having the unfixed developer enters the nip portion 42 via the passage 44 and the branch passage 48, the unfixed developer is melted by the heat of the heating roller 30 and fixed on the sheet. Here, the nip portion 42 between the pressure roller 24 and the heating roller 30.
Is shorter than the length of the nip portion 42 between the fixing belt 12 and the pressure roller 24, but since there is only one layer of developer on the sheet, the developer is sufficiently melted and fixed on the sheet. .

In the above embodiment, the pressure roller 24 is supported by the pair of arms 54, and by operating the arms 54, the pressure roller 24 can be switched between the first and second states. The mechanism for switching the position of the pressure roller 24 is not limited to this. Also, lever 5
0 may be switched to two positions by a single drive source.

Although the fixing belt 12 is heated by the heater 18 built in the heating roller 16, it may be heated by another heater provided inside or outside the fixing belt 12 or both. Similarly, the heating roller 30 may also be heated by another heater provided around the heating roller 30.

Further, in the first state, the heat generated by the heater 18 built in the heating roller 16 melts the toner,
In the second state, the toner is melted by the heat generated from the heater 36 incorporated in the heating roller 30, but a heater for heating the pressure roller 24 is provided, and the heater or the heater 18 is provided in the first state. Alternatively, the toner may be heated by heat of both of them, or in the second state, the toner may be heated by heat of the heater, the heater 36, or both of them.

Further, the drive transmission to each roller is not limited to that in the above embodiment, for example, the pressure roller 24 is connected to a motor, and the rotation thereof is fixed belt 12 or heating roller 3.
It may be transmitted to 0.

In the above embodiment, the roller 24 is in pressure contact with the rollers 14 and 16 in the first state, but it may be so arranged that it is in pressure contact with only the belt portion.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a fixing device according to the present invention and a control circuit diagram thereof.

FIG. 2 is a diagram showing a switching mechanism that moves a pressure roller.

FIG. 3 is a diagram showing a drive connection mechanism when a pressure roller is pressed against a fixing belt.

FIG. 4 is a diagram showing a drive connection mechanism when a pressure roller is pressed against a heating roller.

[Explanation of symbols]

10 ... Fixing device, 12 ... Fixing belt, 14 ... Support roller, 16 ... Heating roller, 18 ... Heater, 20, 38 ... Switch, 22 ... Power supply, 24 ... Pressure roller, 30 ... Heating roller, 36 ... Heater, 50 ... lever, 52 ... switching mechanism,
54 ... Arm, 58 ... Solenoid, 62 ... Motor, 78
…Control device.

Claims (1)

[Claims] 1. A fixing device for heating an unfixed developer to fix it on a sheet, comprising: (a) an endless fixing belt;
(B) a plurality of rollers that support the fixing belt from the inside, (c) a first heating unit that heats the fixing belt, (d) a moving roller, and (e) a moving roller,
Switching means for switching between a first state in which the outer peripheral surface of the fixing belt is in contact with a second state in which the outer peripheral surface of the fixing belt is not in contact, and (f) a fixed roller in contact with the moving roller in the second state. , (G) second heating means for heating at least one of the moving roller and the fixed roller, and (h) supplying the sheet to the contact portion between the fixing belt and the moving roller in the first state. In the second state, a sheet feeding unit that feeds a sheet to the contact portion between the moving roller and the fixed roller; and (i) in the first state, at least one of the fixing belt and the moving roller. The rotation is transmitted to one of them, and in the second state, the moving roller,
A fixing device provided with a driving unit that transmits rotation to at least one of the fixed rollers.