JPH08190291A - Paper sheet guiding device in fixing device - Google Patents

Abstract

PURPOSE: To prevent an image disturbance and the image wear by a trailing end bounce of a paper sheet at the time of passing a fixing device in a simple constitution and with an inexpensive device. CONSTITUTION: On the down stream side of the fixing device 7, an outlet roll device 12 is disposed which is capable of moving one hand of roll 14 in the direction away from or nearer to corresponding to the other hand of roll 13, and energizing it by the spring force in the direction to be butted. On the upstream side of the fixing device 7, the paper sheet guide plate 19 for guiding the paper sheet from a transfer unit to the fixing device 7 is provided so as to be movable up and down. This device is constituted that the paper sheet guide plate 19 and a supporting shaft of the roll 14 making the outlet roll device 12 movable, are connected so as to become a posture for guiding the paper sheet toward a little above a nip part of the fixing device 7, when the movable roll 14 is held in a state of rotary contact with the other roll 13, and so as to come down in a portion corresponding to a gap size, when the paper sheet is allowed to pass in-between the both roller 13 and 14, and in the state that one side of the roll is distanced from the other side of roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an electrophotographic copying machine or printer to heat and fix a toner image transferred from a photoconductor onto a sheet by a transfer device. The present invention relates to a paper guide device for guiding the paper from the transfer device to a fixing device.

[0002]

2. Description of the Related Art This type of paper guide device can change the guide position according to the kind of paper, and prevents paper wrinkles, vibrations, and image distortion especially when a strong paper such as an envelope is used. As a conventional paper guide device, a device disclosed in Japanese Patent Laid-Open No. 4-1112 is known.

In this conventional paper guide device, the position of the paper guide plate for guiding the paper to the nip portion formed by the heating roll and the pressure roll of the fixing device can be changed according to the type of the paper. In addition, a solenoid is used to change the position of the paper guide plate, and the change in the type of paper is detected by the detection switch.

[0004]

In the above-mentioned conventional paper guide device, since the switch for detecting the kind of the paper and the drive device such as the solenoid for changing the position of the paper guide plate are used, the whole device becomes complicated. There was a problem that it was expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a driving means such as a solenoid for operating the paper guide plate and a detection means for detecting the type of paper are unnecessary, and the structure is simple. Another object of the present invention is to provide a sheet guide device in a fixing device of a copying machine which can be obtained at low cost.

[0006]

In order to achieve the above object, the paper guide device in the fixing device of the copying machine according to the present invention is located upstream of the fixing device of the electrophotographic copying machine or printer. In the paper guide device for guiding the paper after the toner image transfer to the fixing device, one roll 13 is movable toward and away from the one roll 13 on the downstream side of the fixing device 7. An exit roll device 12 that is biased by a spring in a direction is provided, and a paper guide plate 19 that guides the paper 6 from the transfer device 4 to the fixing device 7 is provided on the upstream side of the fixing device 7 so as to be movable up and down. In the state where the movable roll 14 is in rolling contact with the other roll 13 between the paper guide plate 19 and the support shaft of the movable roll 14 of the exit roll device 12, the paper 6 is fixed to the fixing device 7 Slightly above the nip part of With the paper 6 passing between the two rolls 13 and 14 and one roll separated from the other roll, they are connected so as to move downward by an amount corresponding to the distance. Has become.

[0007]

[Operation] Both rolls 13 and 14 of the exit roll device 12
If there is no sheet 6 between them, the sheet 6 guided by the sheet guide plate 19 is guided slightly upward from the nip portion of the fixing device 7, and a wrinkle may occur regardless of the type of the sheet 6. Instead, it is guided to the fixing device 7.

Then, the sheet 6 passes through the fixing device 7 and is applied to the exit roll device 12, and one of the rolls 14
When the sheet is moved in the direction away from the other roll 13 by the thickness of the sheet 6, the sheet guide plate 19 is moved downward in conjunction with this. This movement amount is proportional to the thickness of the above-mentioned paper 6, and the thicker it is, the larger the movement amount of the paper guide plate 19 becomes.
In the case of thick paper, the guide direction of the paper guide plate 19 is slightly downward from the nip portion of the fixing device 7.

[0009]

EXAMPLES Examples of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an example of an electrophotographic copying machine to which the paper guiding apparatus according to the present invention is applied. In this copying machine, an image input device 1 inputs an original image to a photoconductor 2. The latent image formed by being input to the photoconductor 2 is developed into a toner image by the developing device 3, and then transferred to the paper 6 fed by the paper feeding device 5 by the transfer device 4. Then, the image is fixed by the fixing device 7 and discharged. The transport 8 is provided upstream of the fixing device 7.
Paper guide device 9 for guiding the paper 6 from the paper to the fixing device 7
Is prepared.

The paper guide device 9 is as shown in FIG. In FIG. 2, 10 and 11 are a heating roll and a pressure roll that constitute the fixing device 7. The fixed roll 13 and the urging roll 14 of the exit roll device 12 are arranged in rolling contact with each other on the downstream side of the fixing device 7 composed of both rolls 10 and 11, and the fixed roll 13 is on the lower side. A drive unit (not shown) is connected to the fixed roll 13. The shaft 15 of the biasing roll 14 is supported at one end of a lever 17 pivotally supported by a fulcrum 16 located between the biasing roll 14 and the fixing device 7. The shaft 15 of the biasing roll 14 is biased toward the fixed roll 13 side (lower side) by a spring 18.

The levers 17 are arranged on both sides of the paper path, and the other ends of both levers 17 extend to the upstream side of the fixing device 7. The guide plate 19 is fixed. This paper guide plate 19
Is a state in which the biasing roll 14 of the exit roll device 12 is in contact with the fixed roll 13, and the downstream end A
However, from the nip part of both rolls 10 and 11 of the fixing device 7,
The sheet 6 from the transport 8 is guided slightly upward, for example, about 0.4 mm. As a result, even if the paper 6 has a normal thickness or is thinner than the normal paper, the paper is guided to the fixing device 7 without causing wrinkles.

A distance AB between the downstream end A of the sheet guide plate 19 and the fulcrum B of the lever 17, and a distance BC between the fulcrum B of the lever 17 and the nip C of the exit roll device 12.
The relationship of the turning radii is approximately AB: BC = 5: 1.

In the above-mentioned structure, in the copying operation by the copying machine, the paper 6 on which the toner image is transferred by the transfer device 4 is transferred.
Is guided to the sheet guide device 9 through the transport 8 and sent to the fixing device 7. At this time, the paper 6 is guided by the paper guiding device 9 and both rolls 10 and 11 of the fixing device 7 are guided.
Since it is guided slightly upward from the nip part of, it is guided to the nip part of the fixing device 7 without causing paper wrinkles,
And it passes and is fixed.

When the sheet 6 that has passed through the fixing device 7 enters the nip portion of the exit roll device 12, the urging roll 14 of the exit roll device 12 is separated from the fixed roll 13 by the thickness of the paper 6 and moves upward. Move to. As a result, the paper guide plate 19 connected to the biasing roll 14 via the lever 17 is interlocked and moved downward.

At this time, when the thickness of the paper 6 is 0.1 mm, the paper guide plate 19 has a thickness of 0. 5
It moves downward by mm and goes down slightly below the nip part. Therefore, the trailing portion of the sheet 6 guided by the sheet guide plate 19 is linearly fed to the nip portion of the fixing device 7,
Paper trailing edge does not occur.

[0016]

As described above, the present invention operates the sheet guide plate which has been conventionally used to prevent the image disturbance and the image rubbing caused by the trailing edge of the sheet when passing through the fixing device 7, which has been a problem in the past. This can be prevented without using a driving unit such as a solenoid or a detecting unit for detecting the type of the sheet, and the structure is simple and can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing an example of an electrophotographic copying machine to which the present invention is applied.

FIG. 2 is a partially cutaway side view showing a main part of an embodiment of the present invention.

FIG. 3 is a plan view showing a main part of an embodiment of the present invention.

[Explanation of symbols]

1 ... Image input device, 2 ... Photosensitive member, 3 ... Developing device, 4 ... Transfer device, 5 ... Paper feeding device, 6 ... Paper, 7 ... Fixing device, 8 ... Transport, 9 ... Paper guiding device, 10 ... Heating Roll, 1
DESCRIPTION OF SYMBOLS 1 ... Pressure roll, 12 ... Exit roll device, 13 ... Fixed roll, 14 ... Energizing roll, 15 ... Shaft, 16 ... Support point, 17
... Lever, 18 ... Spring, 19 ... Paper guide plate.

Claims (1)

[Claims] 1. A paper guide device which is located upstream of a fixing device of an electrophotographic copying machine or printer and which guides a paper after a toner image is transferred to the fixing device.
One roll 13 to the other roll 1 downstream
4 is provided with an exit roll device 12 that is movable in the contacting / separating direction and is biased by a spring in the contacting direction. Further, on the upstream side of the fixing device 7, the paper 6 from the transfer device 4 is transferred to the fixing device 7. A paper guide plate 19 for guiding is provided so as to be movable up and down, and the paper guide plate 19 and the spindle of the movable roll 14 of the exit roll device 12 are connected to the other roll 13 by the movable roll 14. In the state of rolling contact, the paper 6 is in a posture of being guided slightly upward from the nip portion of the fixing device 7, the paper 6 passes between both rolls 13 and 14, and one roll is separated from the other roll. Then, the paper guide device in the fixing device is characterized in that the paper guide device is connected so as to move downward by an amount corresponding to the distance.