JP2000250351A - Heat roller fixing device for electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely peel the leading end of a paper from a fixing roller, besides, to prevent a fixing roller surface and a toner image on a printing paper from being scratched by providing a cutout groove formed on the fixing surface of a heat roller and a peeling pawl equipped with an air path, inserting the leading end of the peeling pawl in the position of the cutout groove with rotation and supplying a compressed air through the air path of the peeling pawl at the printing paper leading end position. SOLUTION: The printing paper 6 is carried until the leading end of the printing paper 6 is detected by a printing paper leading end detecting part 5, and then, held until the leading end part 71 of the cutout groove of the heat roller reaches a prescribed position. While the printing paper 6 is fed toward the heat roller 1, the peeling pawl 10 is moved with rotation so that the leading end part 101 may get into the cutout groove 7 at the point of time when the leading end part 71 of the cutout groove 7 comes close to the pawl 10. The device is controlled so that the peeling pawl 10 may get into the cutout groove 7 of the heat roller 1 in accordance with the feeding of the printing paper 6. The compressed air is jetted 13 from the leading end part 101 of the peeling pawl 10 toward the leading end part 61 of the printing paper 6 in this state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing paper peeling mechanism of a heat roller fixing device used in an electrophotographic apparatus such as an electrophotographic copying machine and an electrophotographic printer.

[0002]

2. Description of the Related Art In an electrophotographic copying machine or a printing machine, a fixing device is incorporated in order to permanently fix toner transferred to a printing paper on the printing paper. In most cases, the fixing device fixes the toner by heat melting. Therefore, a heat roller fixing device having a relatively small device size is often used in consideration of thermal efficiency and fixing speed.
This heat roller fixing device removes printing paper to which toner
The sheet is nipped by a book roller, and heat and pressure are applied to the sheet and the toner at the nip portion of the roller to melt the toner and to permeate the melted toner into the sheet.

[0003] Further, in principle, the heat roller fixing device must separate the toner and the paper from the roller after the toner is fixed on the paper, and the surface of the roller has good releasability such as rubber or Teflon resin. It is necessary to coat the material to improve the releasability of the toner.

[0004] There are two types of heat roller fixing devices, one which heats with two rollers (both surfaces heated) and the other which heats only with one roller. In both cases, at least one of the rollers has a nip forming layer ( In many cases, a release layer (which also serves to protect the nip forming layer) for improving the releasability of the toner is provided on the roller surface having a heat-resistant rubber) and in contact with the toner. For heating the roller, a halogen lamp is generally installed in the hollow portion of the roller as a heater.

FIG. 3 shows an example of a structure (cross-sectional view) of a general heat roller fixing device (one-side heating). In the figure, 2 is a halogen lamp as a heat source, 30 is a peeling layer of a heat roller, 31 is a heat roller body (metal cylinder), 32 is a nip forming layer (heat-resistant rubber), and 33 is a pressing roller body (metal). Cylinder).

Unfixed toner image 34 transferred to printing paper 6
Is fed to a nip portion 8 formed by applying a load to two rollers of a heat roller fixing device. After being heated and pressurized for a predetermined time, the nip portion is separated from the heat roller and discharged from the nip portion. Is done. Here, if the printing paper discharged from the nip portion is to be peeled from the fixing roller, the printing paper adheres to the surface of the fixing roller due to the viscosity of the toner melted by heat. Therefore, it is necessary to peel off the printing paper from the fixing roller by some mechanical force.

[0007]

In a fixing device in which the printing speed is low and the diameter of the fixing roller is relatively small, the viscosity of the toner is reduced due to the elasticity of the printing paper or the like. By applying a release agent (silicone oil) to the surface of the fixing roller, the printing paper can be released from the fixing roller without a mechanical release mechanism. However, as the printing speed increases, the diameter of the fixing roller needs to be increased, and the influence of the viscosity of the toner becomes relatively large because, for example, the time for peeling the printing paper becomes short. Would. as a result,
Without a mechanical peeling mechanism, it is difficult to peel the printing paper from the fixing roller.

In this case, a mechanical peeling mechanism is usually provided by gripping (pushing) the leading end of the printing paper with the peeling claw 10 shown in FIG. 3, and the leading end of the peeling claw is brought into contact with the fixing roller. The higher the printing speed, the higher the degree of damage to the release layer on the surface of the fixing roller. This also means that the degree of occurrence of scratches due to the peeling nails increases with respect to the toner image on the printing paper surface.

Although the heat roller fixing device is relatively small in size, has high thermal efficiency, and has the property of easily coping with high-speed printing, there are some problems in actually manufacturing a high-speed heat roller for a large-sized printing press. There were challenges. One of the problems is the peeling of the printing paper from the fixing roller. The peeling of the printing paper becomes more difficult as the fixing roller becomes larger and as the printing speed becomes higher.

An object of the present invention is to provide a heat roller fixing device suitable for a large-size, high-speed electrophotographic copying machine or printing machine in consideration of the conventional problems of such a heat roller fixing device. .

[0011]

SUMMARY OF THE INVENTION In order to solve such a problem, the present invention provides a printing paper leading edge detecting means for detecting a leading edge of a printing paper being conveyed in a heat roller fixing section of an electrophotographic apparatus. Rotation angle detection means for detecting the rotation angle of the heat roller fixing device, a plurality of cutout grooves carved on the heat roller fixing surface that rotates corresponding to the leading edge of the printing paper, and a peeling claw having an air passage therein, Peeling claw rotation control means for rotatingly inserting the leading end of the peeling claw back and forth in accordance with the position of the notch groove, and squeezing from the air passage inside the peeling claw corresponding to the detected leading end position of the printing paper. Compressed air supply means for supplying air.

With the above-described structure, the mechanical peeling ability is sufficiently maintained even for high-speed printing, and the possibility that the peeling claw comes into contact with the surface of the fixing roller or the toner image on the printing paper is greatly reduced. In addition, with these improvements,
Even if the heat roller is enlarged to cope with high-speed printing, and the speed at which the printing paper is separated from the surface of the fixing roller is increased, the printing paper can be reliably separated from the fixing roller. Furthermore, when the leading end of the printing paper approaches the leading end of the peeling claw, compressed air is blown to peel off the leading end of the printing paper. It has become possible to greatly improve the deterioration of the image quality due to the nails damaging the toner image on the printing paper.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Outline of Configuration> FIGS. 1 and 2 show configuration diagrams according to an optimal embodiment of the present invention. In both figures, the embodiment of the single-sided heating type heat roller fixing device illustrated in FIG. 3 is shown, and the components related to the present invention are mainly shown.

FIG. 2 is a perspective view schematically showing how the plurality of notches 7 and the peeling claws 10 according to the present invention are arranged on the side surface of the heat roller. For ease of illustration, the peeling claw 10 is shown intentionally separated from the side surface of the heat roller (a more accurate arrangement of the peeling claw 10 is shown in FIG. 1). In addition, reference numeral 20 in the drawing denotes a peeling claw rotation control unit, which has a function of controlling the rotating shaft 11 in response to the movement of the cut groove 7 due to the rotation of the heat roller 1. Further, reference numeral 21 denotes a compressed air supply unit, which corresponds to the positional relationship between the leading end of the printing paper (61 in FIG. 1) to be described later and the peeling claw 10, and pressurized air through an air passage formed inside the peeling claw 10. Supply. The compressed air supply hose for that is shown at 12.

The cross section along the broken line 16 in FIG.
FIG. 1 shows a cross-sectional structural view to which the print paper leading edge detection unit 5 is added. In the figure, reference numeral 1 denotes a cylindrical heat roller, and 2 denotes a halogen lamp as a heat source. The heat roller 1 rotates in the direction of an arrow 15 and its rotation angle is controlled by an encoder
, And these constitute a heat roller rotation angle detection unit. Further, a plurality of cutout grooves 7 having a depth indicated by concentric circles 9 are formed in the heat roller 1, and peeling claws 10 are provided corresponding to the positions. Peeling nail 10
Is reciprocatingly rotated in the direction of arrow 14 by the rotating shaft 11, and a passage (air passage) for compressed air supplied from a compressed air supply hose 12 is formed inside the peeling claw 10.
The compressed air is emitted in the direction of arrow 13 in response to the movement of the leading end 61 of the printing paper 6.

<Description of Detailed Operation> Hereinafter, based on FIG.
The detailed operation of the embodiment according to the present invention will be described.

The printing paper to which the toner image has been transferred is printed by a printing paper leading edge detecting unit 5 by a transporting device (not shown).
Is transported until the leading end 61 of the heating roller is detected, and waits until the leading end 71 of the cut groove of the heat roller comes to a predetermined position. This position is detected by the rotary encoder 3 detecting a preset rotation angle, and in response to this, the printing paper transport device feeds the printing paper 6 to the heat roller 1.

While the printing paper 6 is fed toward the heat roller 1, the peeling claw 10 retreats to a position where the leading end 101 does not contact the side surface of the heat roller 1 in a positional relationship away from the cut groove 7. When the leading end portion 71 of the cutout groove 7 approaches, the tip end portion 101 is rotationally moved to a position where it enters the inside of the cutout groove 7. This rotational movement is performed by the peeling claw rotation control unit 20 via the rotating shaft 11 under the control of the peeling claw rotation control unit 20 in FIG. 2 in synchronization with the rotation of the heat roller 1.

The transported printing paper 6 is sandwiched by the nip portion 8 of the heat roller 1, and the toner image is fixed on the printing paper 6 by heat and pressure. FIG. 1 shows the state just at this point. That is, immediately after the leading end portion 61 of the printing paper 6 passes through the nip portion 8, the printing paper 6 is conveyed so that the other end 72 of the cutout groove 7 provided on the heat roller 1 comes, and at the same time, as shown in FIG. The peeling claw rotation control unit 20 controls the peeling claw 10 so as to enter the cut groove 7 of the heat roller 1 so as to be in the state.

Next, in this state, the tip 10 of the peeling claw 10
Compressed air is emitted in the direction of arrow 13 from 1 toward the leading end 61 of the printing paper 6. The compressed air is supplied from the compressed air supply hose 12 extending from the compressed air supply unit 21 to the other end of the peeling claw 10, and passes through an air path formed inside the peeling claw 10, and the distal end of the peeling claw 10. 101 are supplied.

When the compressed air is fired, the leading end 61 of the printing paper 6 which has been heated and pressed at the nip portion 8 and is in close contact with the surface of the heat roller 1 is peeled off by the air pressure, and the timing is just raised. Thus, the rotational position of the peeling claw 10 is controlled so as to be gripped (ridden) by the tip portion 101 of the peeling claw 10. Thus, the leading end portion 101 of the peeling claw 10 is separated from the roller by the leading end portion 101 of the peeling claw 10 without forming a scratch on the surface of the heat roller 1 or the image forming surface of the printing paper. Will be done. Thereafter, the peeling claw 10 is gradually rotated outward in accordance with the rotation of the heat roller 1, and the peeling claw 10 is controlled so as to gradually come out of the notch 7. 6 is peeled downward from the peeling nail 10.

With the above mechanism, even in a large-sized, high-speed heat roller fixing device, even if the paper peeling speed increases, the leading edge of the paper can be reliably peeled off from the fixing roller, and the surface of the fixing roller or the printing paper can be removed. The possibility of damaging the toner image above can be greatly reduced.

Further, the pinching of the leading end of the sheet over the groove of the fixing roller is performed by a sensor for detecting the leading end of the sheet, an encoder provided on the fixing roller, and a sheet conveying device which controls the sheet conveying speed based on these signals. Can be ensured.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a peeling mechanism of a heat roller fixing device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a perspective configuration of a heat roller fixing device according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a cross-sectional configuration of a general heat roller fixing device (single-sided heating type).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat roller 2 Halogen lamp for heating 3 Rotary encoder 4 Encoder drive gear 5 Printing paper leading end detection part 6 Printing paper 7 Cut groove 8 Nip part 9 Concentric circle indicating depth of cut groove 10 Peeling claw 11 Peeling claw rotating shaft 12 Squeezing Air supply hose 13 Arrow indicating the direction in which compressed air is emitted 14 Arrow indicating the direction of rotation of the peeling claw tip 15 Arrow indicating the direction of rotation of the heat roller 16 Cut surface in FIG. 1 20 Stripping claw rotation control unit 21 Compressed air supply unit 30 Release layer of heat roller 31 Heat roller main body (metal cylinder) 32 Nip forming layer (heat-resistant rubber) 33 Press-contact-side roller main body (metal cylinder) 34 Unfixed toner image 35 Fixed toner image 61 Leading edge of printing paper 71 One end of cut groove 72 The other end of the cut groove 101 The tip of the peeling claw

Claims (1)

[Claims] In a heat roller fixing section of an electrophotographic apparatus,
Printing paper leading edge detecting means for detecting the leading edge of the printing paper being conveyed, rotation angle detecting means for detecting the rotating angle of the heat roller fixing device, and engraving on the heat roller fixing surface which rotates corresponding to the printing paper leading edge position. A plurality of cut grooves, a peeling claw having an air passage therein, a peeling claw rotation control means for rotatingly inserting a tip of the peeling claw back and forth corresponding to the position of the cut groove, and the detected printing. A heat roller fixing device, comprising: compressed air supply means for supplying compressed air from an air passage inside the peeling claw corresponding to the leading end position of the paper.