JP2001005330A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device, in which the inertia force applied at the starting time of printing is reduced by rotating a pressure roller and a guide roller so that their outer peripheral speeds become equal to or higher than printing speed, the start of printing. SOLUTION: This fixing device is provided with an auxiliary roller 28, which is brought into contact with the pressure roller 15 in the state of being separated from a heating roller 14 and a drive source 29 for causing the auxiliary roller to rotate and drive. Thus, since the inertia force of the pressure roller 15 and the guide roller at the starting time of the printing is reduced, the necessary torque of the drive source, such as a motor driving the heating roller, is restrained to a minimum, and also since the inertia force of the guide roller does not exceed the generating tension of a paper feeding roller, paper becomes easy to peel off from the heating roller by the paper feeding roller, and as a result, paper is not wound on the heating roller 14, so that the cause of defective printing is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium comprising a heating roller having a heat source such as a heater therein, and a pressure roller provided so as to be able to press against the heating roller.
The present invention relates to a fixing device for fixing a toner image formed on a recording material to the recording material, and more particularly to a fixing device for stabilizing the conveyance of the recording material at the start of printing.

[0002]

2. Description of the Related Art In a printing apparatus, a recording material (paper) on which a toner image is formed (electrostatically transferred) is sent to a fixing device by a transport device such as a tractor or a transport roller. In the fixing device, the paper on which the toner image is formed is heated and pressurized by being nipped and conveyed by a heating roller and a pressure roller to fix the toner image on the paper.

FIG. 3 shows an example of a fixing device of a conventional continuous paper electrophotographic printing apparatus. FIG. 3 shows a state where the pressure roller 15 and the guide roller 27 are separated from the heating roller 14 (at the time of non-printing). At the time of printing, the pressure roller 15 is in pressure contact with the heating roller 14, and the guide roller 27 is also in pressure contact with or close to the heating roller 14.

[0004] A preheating plate 13 preheats the recording paper 7 from the back surface. The heating roller 14 has a heater lamp 25 such as a halogen heater inside. The surface is covered with a material having good releasability such as silicon rubber or fluororesin. ON / OF of power supply
F etc. are performed, the surface temperature is kept at a constant temperature,
It can be rotated in the direction of the arrow by a drive source such as a motor. The pressure roller 15 has a surface covered with an elastic body such as silicon rubber or the like, and is incorporated in a mechanism capable of pressing against the heating roller 14 with a certain load during printing.
The pressure roller 15 presses the sheet 7 against the heating roller 14, and the rotation of the heating roller 14 causes the pressure roller 15 to be driven to rotate. The guide roller 27 moves to a position where the sheet 7 is wound around the heating roller 14 during printing. Next, the paper feed roller 16 disposed downstream of the guide roller 27 is a mechanism that can pull the paper 7 with a certain tension.

[0005] The toner formed on the paper 7 by electrostatic transfer is preheated by passing over the preheating plate 13, and is passed between the pressure roller 15, which is in pressure contact with the heating roller 14, and is nipped and conveyed to be heated. Pressurized, and the guide roller 27
As a result, the sheet is wound around the heating roller 14 to maintain the heated state, and is fixed on the sheet 7. Next, the sheet 7 is separated from the heating roller 14 by the sheet feed roller 16 and discharged from the fixing device 12.

[0006]

In the above-mentioned conventional construction, the driving source such as the motor for driving the heating roller also rotates the pressure roller, so that the torque applied at the start of printing becomes excessive, and the driving force is required more than necessary. And Furthermore, if the inertial force of the guide roller, which rotates only due to the frictional force with the paper, exceeds the tension generated by the paper feed roller,
The paper feed roller cannot separate the paper from the heating roller. As a result, the paper is wrapped around the heating roller (roller wrap), causing a printing failure.

Accordingly, an object of the present invention is to fix the outer peripheral speed of the pressure roller and the guide roller until the printing speed is equal to or higher than the printing speed by the start of printing to reduce the inertial force applied at the start of printing. It is to provide a device.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to nip and convey a recording material between a heating roller having a heat source such as a heater therein and a pressure roller provided so as to be able to press against the heating roller. In a fixing device that fixes a toner image formed on a recording material to a recording material, an auxiliary roller that contacts a pressure roller that is separated from the heating roller, and a driving source that rotationally drives the auxiliary roller are provided. Achieved by providing.

[0009]

An embodiment of the present invention will be described below in detail with reference to the drawings. First, an overall configuration of a laser beam printer using an electrophotographic method to which the present invention is applied will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a laser beam printer, and the photosensitive drum 21 starts rotating in the direction of an arrow based on a printing operation start signal from a controller 22 thereof. The photosensitive drum 21 rotates at a speed corresponding to the printing speed of the laser beam printer 1, and continues to rotate until the printing operation ends. When the photosensitive drum 21 starts rotating, a high voltage is applied to the corona charger 2, and the surface of the photosensitive drum 21 is uniformly charged with, for example, a positive charge.

The rotary polygon mirror 3 is a laser beam printer 1
As soon as the power is turned on, the motor starts rotating, and the constant-speed rotation is maintained with high accuracy while the power is turned on. A laser beam output from a light source 4 composed of a semiconductor laser, a light emitting diode, or the like is reflected by the rotating polygon mirror 3 and irradiated while scanning the photosensitive drum 21 through the fθ lens 5.

When the character data or graphic data converted into the dot image is sent from the controller 22 to the laser beam printer 1 as an on / off signal of the laser beam, the portion where the laser beam is irradiated on the surface of the photosensitive drum 21 and the irradiation are performed. And a so-called electrostatic latent image is formed. When the photosensitive drum area holding the electrostatic latent image reaches a position facing the developing device 6, toner is supplied to the electrostatic latent image, and a portion on the photosensitive drum 21 where the charge on the photosensitive drum 21 has disappeared due to the irradiation of the laser beam. For example, the toner charged to a positive charge is attracted by static electricity,
A toner image is formed thereon.

The continuous paper 7 stored in the paper hopper 11 is rotated by the paper transport tractor 8 in synchronization with the timing at which the toner image of the print data formed on the photosensitive drum 21 reaches the transfer position. And transfer device 1
It is transported between 0.

The toner image formed on the photosensitive drum 21 is sucked onto the sheet 7 by the action of the transfer unit 10 which applies a charge of the opposite polarity to the toner image on the back side of the sheet 7.

In this manner, the sheet 7 set in the sheet hopper 11 is transferred to the sheet transport tractor 8 and the transfer unit 1.
0, the sheet is conveyed to the fixing device 12 via the sheet conveying tractor 9 and the buffer plate 24. The sheet 7 arriving at the fixing device 12 is preheated by a preheater 13 and then heated and pressed by a nip formed by a pair of fixing rollers including a heating roller 14 having a heater lamp 25 and a pressure roller 15. The toner image is nipped and conveyed, and the toner image is fused and fixed on the sheet 7.

The paper 7 sent out by the heating roller 14 and the pressure roller 15 is sent out to the stacker table 19 side by the paper sending out roller 16 and
The swinging fins 17 are alternately folded along the perforations by the swinging operation of the swing fins 17, and the folding state is adjusted by the rotating paddle 18.
Stacked on top of 9. The area that has passed the transfer position of the photosensitive drum 21 is cleaned by the cleaning device 20, and is prepared for the next printing operation.

In FIG. 1, reference numeral 23 denotes a display screen for displaying information based on the state of the laser beam printer 1 during a printing operation. Further, the above-described buffer plate 24 is provided between the paper transport tractor 9 and the fixing rollers 14,1.
This is to absorb the slack or tension generated in the sheet 7 when the sheet conveyance speed difference occurs between the sheets 5.
Reference numeral 26 denotes a web member provided so as to be in contact with the surface of the heating roller 14 and to be able to be wound, and is used for cleaning the surface of the heating roller 14 and applying a release agent to the surface of the heating roller 14. Things.

Next, FIG. 2 shows a detailed configuration of the fixing device according to the present invention. In the printing stop state, the pressure roller 15 moves to a position having a certain gap from the heating roller 14.
The auxiliary roller 28 is disposed at a position where the auxiliary roller 28 comes into contact with the pressure roller 15 after the movement, and the auxiliary roller 28 can be rotated by driving a motor 29. The rotation of the auxiliary roller 28 is transmitted to the pressure roller 15 and the motor 29 Is transmitted to the pressure roller 15 finally. Similarly, when printing is stopped, the guide roller 27 also moves from the position where the paper 7 is wound around the heating roller 14 to a position where it comes into contact with the auxiliary roller 28. The driving force of the motor 29 is transmitted to the guide roller 27 after the movement as the rotational force of the guide roller 27. Therefore, if the motor 29 is driven and the auxiliary roller 28 is rotated before printing is started, the pressure roller 15 and the guide roller 27 can be rotated according to the rotation speed of the motor 29.

[0018]

According to the present invention, since the inertial force of the pressure roller and the guide roller at the start of printing can be reduced, the required torque of a drive source such as a motor for driving the heating roller can be minimized. In addition, since the inertial force of the guide roller does not exceed the tension generated by the paper feed roller, the paper feed roller can easily separate the paper from the heating roller, and as a result, the paper is heated by the heating roller. And the occurrence of printing defects can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a laser beam printer.

FIG. 2 is a schematic configuration diagram of a fixing device of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional fixing device.

[Explanation of symbols]

7 recording material, 13 preheating plate, 14 heating roller, 15
Pressure roller, 16 paper feed roller, 27 ... guide roller, 28 ... auxiliary roller, 29 ... motor.

Claims (2)

[Claims] An image forming apparatus includes: a heating roller having a heat source such as a heater therein; and a pressure roller provided so as to be able to press against the heating roller. In a fixing device for fixing a recording material to a recording material,
A fixing device comprising: an auxiliary roller that comes into contact with a pressure roller that is separated from the heating roller; and a driving source that rotates the auxiliary roller. 2. A recording method in which the recording material is wound around the surface of the heating roller by a predetermined length when the heating roller and the pressure roller are in a pressure contact state downstream of the pressure roller in the recording material conveyance direction. A guide roller provided to guide a material, and to be separated to a predetermined position together with the pressure roller when the heating roller and the pressure roller are separated from each other, the pressure roller and the guide being separated from the heating roller The fixing device according to claim 1, wherein the auxiliary roller is provided at a position where the auxiliary roller can contact the roller.