JPH07225527A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain a fixing device which surely prevents the generation of wrinkles on a transfer material after a fixing process and further, never causes the jamming of a paper sheet by providing a freely rotatable press roll for guiding the transfer material in the vicinity of a peeling pawl peeling the transfer material from a heating roller. CONSTITUTION:The fixing device is the one of a model that the heating roller 1 and a pressure roller 2 or a belt press-contacting therewith are provided and the transfer material P carrying a toner image passes through therebetween to fix the toner image on the transfer material P. The freely rotatable press roll 7 for guiding the transfer material P is provided in the vicinity of the peeling pawl 6 for peeling the transfer material P from the heating roller 1. By such a constitution, the transfer material P after the fixing process is peeled from the periphery of the heating roller 1 by the peeling pawl 6, smoothly guided into a guiding path by the freely rotatable press roll 7 provided in a guiding path entrance and fed to a pair of ejecting roller 5 to be ejected without being curved.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, as a means for fixing a toner image after transfer, a transfer material is supplied between a heating roller and a pressure roller (or belt) to fix the toner image. There is a roller type fixing device.

In general, as a roller type fixing device, as shown in FIG. 4, a heating roller 1 and a pressure roller 2 are arranged in a pressure contact state, and a discharge roller for discharging a transfer material P such as paper to the outside of the machine. The pair 5 is provided downstream of the guide path 51 for the transfer material P. The pair of fixing rollers 1 and 2 and the pair of discharging rollers 5 are provided with an upper guide 30 and a lower guide 40 for guiding the transfer material P, and are peeled off so as to project from the upper guide 30. A claw 60 is provided. Peeling claw 60
The front end 60a of the sheet is in contact with the peripheral surface of the heating roller 1, and after the fixing process, the transfer material P adhering to the peripheral surface of the heating roller 1 is peeled off to prevent the transfer material P from being wound around the heating roller 1. .

In such a conventional apparatus, as shown in FIG. 5, the transfer material P separated by the separation claw 60 is sent to the paper discharge roller pair 5 and discharged while being largely curved. As a result, there is a problem that the transfer material P after paper discharge has wrinkles.

In order to solve this, for example, the actual Kaihei 3-
In Japanese Patent Publication No. 29873, there is proposed a structure in which a rib that largely projects on the guide path side of the upper guide is provided to narrow the gap between the guide paths to eliminate the above-mentioned curvature and prevent wrinkles from occurring.

[0006]

However, in the above-mentioned prior art, it is difficult to set the size of the rib, that is, the gap between the guide paths, and if the gap between the guide paths is too large,
In the case where the effect of preventing the above-described curving is small, and when the effect is narrow, the toner is still soft due to heat, so that the upper guide plate causes an image “slip”. There is a risk of paper jam due to the resistance of the transfer material and the upper guide plate.

The present invention has been made in view of the above problems, and reliably prevents wrinkles from being generated on the transfer material P after the fixing step.
Moreover, it is an object to provide a fixing device that does not cause a paper jam in a simple form.

[0008]

In order to solve the above-mentioned problems, a fixing device according to the present invention comprises a heating roller and a pressure roller or belt in pressure contact with the heating roller, and a transfer material carrying a toner image between them. In a fixing device of a type in which a toner image is passed and fixed on a transfer material, a rotatable pressing roller for guiding the transfer material is provided near a separation claw for separating the transfer material from a heating roller. It is characterized by

Further, in particular, the fixing device has upper and lower guides that define guide paths for guiding the transfer material separated from the heating roller to the discharge roller, and the lower end of the pressing roller is The roller is arranged so as to project toward the guide path at the entrance of the guide path, and the roller is provided coaxially with the support shaft of the peeling claw.

[0010]

In this structure, the transfer material P that has undergone the fixing process is peeled off from the peripheral surface of the heating roller 1 by the peeling claw 6 and smoothly rotated by the rotatable pressing roller 7 provided at the entrance of the guide path. The paper is guided in the guide path and is sent to the paper discharge roller pair 5 without being curved as in the prior art and is discharged thereby.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a fixing device according to the present invention. Reference numeral 1 is a heating roller that rotates in the direction indicated by arrow A, and has a hollow cylindrical body made of a metal having good thermal conductivity such as aluminum, on the outer surface of which polytetrafluoroethylene or trade name Teflon or silicone rubber is provided. In some cases, a release agent such as silicone oil is applied on top of it. A rod-shaped heater 11 is fixed inside the heating roller 1 independently of the rotation of the heating roller 1, and is turned on / off by an appropriate temperature controller to keep the temperature of the heating roller within a predetermined temperature range. Is urged by. Further, the pressure roller 2 has a layer 22 made of a heat-resistant material having appropriate elasticity such as silicon rubber on the outer peripheral surface of the hollow aluminum roller 21, and is pressed against the heating roller by the urging means shown in the drawing. It is energized and driven by frictional contact with the heating roller 1.

On the paper discharge side of the fixing device, there are provided a peeling claw 6, a pressing roller 7, and an upper guide 3 and a lower guide 4 for guiding the transfer material P toward the paper discharge roller pair 5. The peeling claw 6 is configured such that the tip end thereof is brought into pressure contact with the outer surface of the heating roller 1 with a predetermined pressing force by means of a spring 8 (FIG. 2) or the like, and the transfer material P attached to the heating roller 1 is peeled off. It is designed to be peeled off by being guided by the tip of the. A plurality of peeling claws 6 are arranged at appropriate intervals in the axial direction of the support shaft 50 that pivotally mounts them.

As shown in FIG. 2, a plurality of pressing rollers 7 are rotated between the peeling pawls 6 and 6 coaxially with the peeling pawls 6, that is, along the axial direction of the heating roller 1 at appropriate intervals. It is provided freely. By providing the pressing roller coaxially with the peeling claw 6, the number of parts and the space can be reduced, which is particularly preferable, but the pressing roller can be provided at an appropriate position in the vicinity of the peeling claw. Pressing roller 7
Is preferably a disk shape having a narrow peripheral edge of about 0.5 to 2 mm, and the pressing roller 7 has such a narrow width.
"Slip" of the image due to contact between the periphery of the sheet and the surface of the transfer material P
Etc. can be prevented. The pressing roller 7 may have a disc shape or a spur shape in which a plurality of protrusions are formed in a saw shape on its peripheral surface.

As shown in the figure, the lower end of the pressing roller 7 projects below the upper guide 3 at the entrance of the guide path 51, that is, toward the guide path 51 side, and guides the peeled transfer material to the guide path. Since the transfer material is smoothly guided to the guide path 51 by the function of the rotatable pressing roller 7, the gap between the upper guide 3 and the lower guide 4 defining the guide path 51 can be reduced, It is possible to prevent the transfer material from being curved as in the technique. Transfer material P guided in this way
Is discharged to the outside of the machine by the pair of discharge rollers 5. The pressing roller 7 is preferably made of a material having excellent thermoplasticity, heat resistance, wear resistance, and mechanical strength, and for example, polyacetal resin can be used. Reference numeral 9 denotes a rib-shaped projection formed on the upper guide 3.

As shown in FIG. 3, the same effect can be obtained by using the pressure roller 2 instead of the endless belt 10.

[0016]

With the above-described structure, the fixing device according to the present invention, unlike the structure of the conventional example as shown in FIG. Since it is provided on the same axis as the peeling claw, the number of parts can be small and it is inexpensive.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment according to the present invention.

FIG. 2 is a view of the pressing roller, the peeling claw, and the upper guide as viewed from above.

FIG. 3 is a side view showing another embodiment according to the present invention.

FIG. 4 is a diagram showing a conventional example of a fixing device.

FIG. 5 is a diagram illustrating a problem of the fixing device in FIG.

[Explanation of symbols]

 1 Heating Roller 2 Pressure Roller 3 Upper Guide 4 Lower Guide 5 Paper Ejecting Roller Pair 6 Peeling Claw 7 Pressing Roller 10 Endless Belt

Claims (3)

[Claims] 1. A fixing device comprising a heating roller and a pressure roller or a belt in pressure contact with the heating roller, wherein a transfer material carrying a toner image is passed between them to fix the toner image on the transfer material. A fixing device characterized in that a rotatable pressing roller for guiding the transfer material is provided in the vicinity of a peeling claw for peeling the transfer material from the heating roller. 2. An upper side guide and a lower side guide that define a guide path for guiding the transfer material separated from the heating roller to the discharge roller, and the lower end of the pressing roller is on the guide path side at the entrance of the guide path. The fixing device according to claim 1, wherein the fixing device protrudes to the outside. 3. The fixing device according to claim 1, wherein the pressing roller is provided coaxially with a support shaft of the peeling claw.