JPH0452678A - Fixing device of image forming device - Google Patents

Abstract

PURPOSE:To make a pressure lever short and to enable the fall incorporation of the fixing device by interposing a link member when the press-contacting force between a pressure roller and a heat roller is released through the pressure lever by opening an upper frame. CONSTITUTION:When the upper frame 2 is opened, a projection 17 provided to a bracket 4 presses up the other end 18b of the link member 18, which rotates clockwise around a shaft 19, so that one end 18a rotates the pressure lever 13 anticlockwise around a shaft 15 through the bent part 13a of the pressure lever 13 against a pressure spring 14. Namely, the lever 13 is pressed down, and the pressure roller 12 leaves the heat roller 11 to release fixing pressure. Further, the other end 18b of the member 18 is only positioned above the projection 17, so the fixing device 10 can be fallen from above and then incorporated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device in an image forming apparatus such as a copying machine, a laser printer, or a laser facsimile.

It is already known that the fixing device described above has a heat roller and a pressure roller paired with the heat roller, and the pressure roller is urged by a pressure spring and is pressed against the heat roller by a pressure lever. It is being

FIG. 3 is a schematic diagram of a conventional laser printer equipped with a fixing device of the type described above.

In FIG. 3, the printer main body 1 is divided into a lower frame 2 and an upper frame 3, and the upper frame 3 is connected to the lower frame via a rotation shaft 5 near the tip of a bracket 4 integrally provided therein. It is attached so that it can be opened and closed.

The upper frame 3 is provided with a laser unit 6 and the like therein, and further removably supports an image forming unit 7 at its lower part. On the other hand, the lower frame 2 includes a paper feed section 8, a transfer charge 9. A fixing device 10 and the like are respectively provided.

The fixing device [10 has a fixing roller pair consisting of a heat roller 11 and a pressure roller 12, and the pressure roller 12 is movable in the direction toward and away from the heat roller 11.
It is supported by the side plate of 0.

The pressure roller 12 is urged by a pressure spring 14 and pressed against the heat roller 11 by a pressure lever 13, and a predetermined fixing pressure is applied thereto.

The pressure lever 13 has one end rotatably attached to the side plate via a shaft 15, and the other end extends to the tip of the bracket 4. The pressurizing lever 13 is moved to the shaft 15 by the pressurizing spring 14 which is locked in its intermediate region.
A clockwise rotational force is applied around , and the pressure roller 12 is held at a position where it comes into pressure contact with the heat roller.

On the other hand, an operating pin 16 is installed in the bracket 4,
When the upper frame 3 is opened, the pressure lever 13 is rotated counterclockwise about the shaft 15 as shown in FIG. 4, and the pressure roller 12 is separated from the heat roller 11 by its own weight.

In the fixing device 10 which is configured so that the pressure is released, the pressure release means is the pressure lever 1.
3 and the pin 16 of the bracket 4. However, this makes the pressure lever 13 long, which causes not only poor balance but also the problem that the pressure lever protrudes too much during packaging. Furthermore, when assembling the fixing device, the pressure lever 13
must be worked without getting it under the operating pin 16,
There was a problem in that it took time and effort to assemble.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device which solves the above-mentioned conventional problems, allows the pressure lever to be shortened, and also greatly improves the ease of assembly.

for The structure of the present invention that achieves the above object is as follows.

A fixing device for an image forming apparatus in which an upper frame of the apparatus main body can be opened and closed with respect to a lower frame, and includes a heat roller, a pressure roller paired with the heat roller, and a pressure roller that is biased by a pressing means to push up the pressure roller. In the fixing device, the fixing device includes a pressure lever that presses against the heat roller, and a pressure release mechanism that lowers the pressure lever by opening the upper frame and releases the pressure force of the pressure roller against the heat roller. a release mechanism between the upper frame and the pressure lever;
A fixing device characterized in that a link member swingably supported by a side plate of the fixing device is interposed.

According to the above structure, the link member is interposed between the upper frame and the pressure lever, so that the pressure lever can be shortened and the fixing device can be assembled by dropping it.

Nu J1 Bonito Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an enlarged view of the main parts showing the upper frame 3 in a closed state, and the same members as in FIG. 3 are given the same reference numerals. In this fixing device 1o, the pressure lever 13 biased by the pressure spring 14 touches the bearing part of the pressure roller 12 and lifts the pressure roller 12, so that a predetermined fixing pressure between the heat roller 11 and the pressure roller 12 is applied. It is given. However, the pressure release mechanism is composed of a pressure lever 13, a projection 17 provided on the bracket 4, and a link member 18.

The link member 18 is swingably attached to a side plate 20 of the fixing device via a shaft 19. This link member 18
One end 18a of the link member 18 is located on the bent piece 13a formed on the pressure lever 13, and the other end 18b of the link member 18 is located on the protrusion 17. When the upper frame 2 is closed, both ends 18a and 18b of the link member 18
Either one of them is lightly touching the bent piece 13a or the protrusion 17, or both are stationary and spaced apart as shown in the figure.6 Note that the reference numeral 21 indicates a heater built into the heat roller 11, and 22 23 is a separation claw, and 23 is a guide plate.

In the fixing device configured as above, when the upper frame 2 is opened,
As shown in FIG. 2, the protrusion 17 provided on the bracket 4 pushes up the other end 18b of the link member 18, and the link member 1
8 is rotated clockwise around the shaft 19. Due to this rotation, one end 18a of the link member 18 is moved to the pressure lever 1.
The pressure lever 13 is rotated counterclockwise about the shaft 15 through the bent portion 13a of the pressure lever 13 against the action of the pressure spring 14. That is, the pressure lever 13 is pushed down, thereby separating the pressure roller 12 from the heat roller 11 and releasing the fixing pressure.

Furthermore, when the upper frame 2 is closed, the protrusion 17 separates from the link member 18 and returns to its original position, and the pressure lever 13 also presses the pressure roller 12 against the heat roller 11 by the bias of the pressure spring 14. The state returns to the state shown in FIG.

Thus, since the fixing device 1o of the present invention has the link member 18 interposed in the pressure release mechanism, the pressure lever 13 can be shortened. Furthermore, since the other end 18b of the link member 18 only needs to be positioned above the protrusion 17, the fixing device 1o can be assembled by dropping it from above. Furthermore, in this embodiment, the other end 18b side of the link member 18 is inclined slightly upward.

Therefore, when the upper frame 2 is opened, the amount by which the pressure lever 13 is lowered can be made smaller than the amount by which the protrusion 17 moves. With this configuration, when the upper frame 1 is opened, the pressure roller 12 can be set in a state slightly lowered from the heat roller 11. If the rollers are separated more than necessary, force will be applied to the protrusion 17 side, and the parts However, this problem can be solved.

Effects According to the above structure, the present invention has a simple structure in which a link member is interposed between the upper frame and the pressure lever, so that the pressure lever can be shortened and the fixing device can be assembled by dropping it. .

[Brief explanation of the drawing]

Figure 1 is an enlarged view of the main parts with the upper frame closed, Figure 2 is an enlarged view of the upper frame shown in Figure 1 when it is open, and Figure 3 is an enlarged view of the main parts when the upper frame is open.
The figure is a schematic diagram of a laser printer equipped with a conventional fixing device, and FIG. 4 is a schematic diagram of the upper frame of FIG. 3 when it is opened. 2 ・ 3 ・ 4 ・ 10 ・ 11 ・ 12 ・ 13 ・ 14 ・ 17 ・ 18 ・ Upper frame, lower frame, bracket, fixing device, heat roller, pressure roller, pressure lever, pressure spring, protrusion, link Element

Claims (1)

[Scope of Claims] A fixing device for an image forming apparatus in which an upper frame of an apparatus main body can be opened and closed with respect to a lower frame, the fixing device comprising: a heat roller, a pressure roller paired with the heat roller, and a pressing means; It has a pressure lever that pushes up the pressure roller to press it against the heat roller, and a pressure release mechanism that lowers the pressure lever when the upper frame is opened and releases the pressure roller from pressing against the heat roller. The fixing device, wherein the pressure release mechanism has a link member swingably supported by a side plate of the fixing device interposed between the upper frame and the pressure lever.