JPH0619349A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a situation that the vicinity of the exit of a fixing device is filled with air containing much moisture by providing many through holes in a diameter direction on a roller shaft. CONSTITUTION:A fixing roller 31 incorporating a heat source and a pressure roller 32 pressed on the roller 31 are housed in the fixing device 20. A pair of post-fixing rollers 34 and 35 and one end of post-fixing guide 36 are provided in the vicinity of the exit of the fixing device 20. Many through holes 41... are formed in the diameter direction on the roller shaft 39 of one roller 34 of the rollers 34 and 35. When a sheet S on which an image has been transferred is allowed to pass between the rollers 31 and 32 so that the image on the sheet S may be fixed by applying heat and pressure, the moisture in the sheet is vapored by heating and the vapor is allowed to pass through the through holes 41... and diffused from the vicinity of the exit of the fixing device 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an image forming apparatus that records on a sheet by printing, transferring, copying, printing, etc., such as a copying machine and a printing machine.

[0002]

2. Description of the Related Art In a laser printer, for example, a fixing roller containing a heat source and a pressure roller pressed against the fixing roller are housed in a fixing device, and a pair of fixing devices are provided near the outlet of the fixing device. There is a configuration in which a rear roller and a post-fixing guide are provided. Then, the sheet after the image transfer is passed between the fixing roller and the pressure roller, where heat and pressure are applied to fix the transferred image on the sheet, and the sheet is sent out by the roller after fixing and guided by the guide after fixing. And then discharged it to the outside.

[0003]

However, in the conventional laser printer, since the post-fixing roller and the post-fixing guide are located near the exit of the fixing device, the water in the sheet is evaporated by being heated during the fixing. Also, there is a problem that the water vapor is difficult to diffuse and such water vapor is likely to be trapped near the exit of the fixing device. Then, when the steam that has collected is cooled, for example, water droplets adhere to the guide after fixing, and the water droplets adhere to the sheet.

Therefore, an object of the present invention is to prevent air containing a large amount of water from being collected near the outlet of the fixing device.

[0005]

Therefore, what is stated in claim 1 is, for example, as shown in the following illustrated embodiment,
In the image forming apparatus, the sheet S after the image transfer is put in the fixing device 20, heat is applied by the fixing device 20 to fix the transferred image on the sheet S, and then the rollers 34 and 35 are sent after fixing.
A plurality of radial through holes 41 ... Are formed in the roller shaft 39 of the post-fixing roller 34.

According to a second aspect of the present invention, for example, as shown in the following illustrated embodiment, in the image forming apparatus of the first aspect, the roller shaft 39 of the post-fixing roller 34 is hollow, It is characterized in that the hygroscopic agent 45 is housed in the hollow.

[0007]

In the invention described in claim 1, the fixing device 2
When heat is applied at 0 to fix the transfer image on the sheet S,
Water vapor generated by evaporation from the sheet S passes through the through hole 41 ....
Through the vicinity of the exit of the fixing device 20.

According to the second aspect of the invention, the water vapor is absorbed by the hygroscopic agent 45 through the through holes 41, ...
Spread from near the exit.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows an overall schematic configuration of an internal mechanism of a laser printer which is an embodiment of the present invention.

Reference numeral 10 in the drawing is a main body of the apparatus. A drum-shaped photosensitive member 11 that rotates clockwise in the drawing is provided in the center of the apparatus main body 10. Around the photoconductor 11, a charging device 12, an optical writing device 13, a developing device 14, a transfer device 15, and a cleaning device 16 are arranged in this order in the rotation direction.

On the other hand, on the right side of the apparatus main body 10 in the drawing, the paper feed cassettes 17 containing the sheets S are detachably attached in two upper and lower stages. A registration roller pair 18 is arranged on the right side of the transfer device 15. On the other hand, on the side opposite to the registration roller 18 with the transfer device 15 interposed therebetween,
The transport device 19 and the fixing device 20 are arranged side by side in this order.

Therefore, in the illustrated laser printer, either one of the paper feed rollers 22 and 22 is appropriately selected and driven, and the sheets S are sequentially fed out from the paper feed cassette 17,
Stop it by hitting the registrar roller 18.

On the other hand, the surface of the photosensitive member 11 is sequentially charged by the charger 12 while rotating in the clockwise direction in the figure, and laser light is emitted by the next optical writer 13 to electrostatically latent the surface. An image is formed, and subsequently, when the toner passes through the position of the developing device 14, toner is attached to make the electrostatic latent image successively visible. Then, the registration roller 18 is driven in synchronism with the image to send the sheet S toward the photoconductor 11. Then, the visible image on the photoconductor 11 is transferred onto the surface of the sheet S by the transfer device 15. After the transfer, the surface of the photoconductor 11 is cleaned by the cleaning device 16, while the sheet S is sent to the fixing device 20 by the conveying device 19, and the transferred image is fixed by the fixing device 20. Then, the sheet is discharged to the discharged sheet stack section 26 through the sheet discharge path 25.

By the way, the above-mentioned fixing device 20 is provided with a cover 30, which is covered with the fixing roller 31 and the pressure roller 32 inside. The fixing roller 3
As shown in FIG. 1, 1 has a heater 33 built-in, a fixing gear at one end of a roller shaft (not shown), and meshes with a drive gear train (not shown). On the other hand, the pressure roller 32 is biased by a biasing spring (not shown) and pressed against the fixing roller 31. A pair of post-fixing rollers 34 and 35 are rotatably provided near the outlet on the left side of the fixing device 20 in the drawing, and one end of a post-fixing guide 36 is provided.

In the fixing device 20 described above, however, at the time of image fixing, the driving force of the driving motor is transmitted through the driving gear train to rotate the fixing roller 31, and the pressure roller 32 is driven to rotate. Then, the sheet S after the image transfer is passed between the rollers 31 and 32, and heat and pressure are applied to the sheet S to fix the transferred image on the sheet S. After that, after fixing rollers 34 and 35
The sheet S after the image is fixed is fed out by the guide, and is guided by the fixing guide 36 to pass through the sheet discharge path 25 and the discharge stack unit 2
Discharge to 6.

In the present invention, as shown in detail in FIGS. 1 and 2, one of the pair of post-fixing rollers 34 and 35 is a post-fixing roller 34, which is a shaft of a roller shaft 39. Attach a plurality of rollers 40 at a predetermined interval in the direction,
A large number of radial through holes 41 are formed in the roller shaft 39 between the rollers 40. In the figure, reference numeral 42 is a roller of the roller 35 after fixing, and reference numeral 43 is its roller axis.

When the image is fixed, the moisture in the sheet S which is heated and evaporated is diffused from the vicinity of the outlet of the fixing device 20 through the through holes 41.

In the above embodiment, the roller 3 after fixing is used.
.. is formed in the roller shaft 39 of No. 4 in the radial direction. However, after fixing the roller shaft 3 of the roller 34
9 not only has radial through holes 41 ...
As shown in FIG. 3, the roller shaft 39 may be hollow and the hygroscopic agent 45 may be housed in the hollow. As a result, the water vapor diffuses from the vicinity of the outlet of the fixing device 20 through the through holes 41, ... And is absorbed by the absorbent 45.

[0019]

As described above, according to the present invention, when heat is applied by the fixing device to fix the transferred image on the sheet,
Moisture evaporates from the sheet and diffuses from the vicinity of the fixing device outlet through the through hole, so air with a large amount of moisture is not trapped near the fixing device outlet, water droplets can be suppressed, and water droplets adhere to the sheet It is possible to prevent the malfunction.

According to the second aspect of the present invention, moisture is evaporated from the sheet, diffused from the vicinity of the outlet of the fixing device through the through hole, and absorbed by the hygroscopic agent, so that more moisture is removed and water droplets are removed. The generation can be further suppressed.

[Brief description of drawings]

FIG. 1 is a schematic diagram around a fixing device in a laser printer according to an embodiment of the present invention.

FIG. 2 is a perspective view of a part of a roller after fixing.

FIG. 3 is a partial cross-sectional view of another example of the roller after fixing.

FIG. 4 is a schematic configuration diagram of an entire internal mechanism of the laser printer.

[Explanation of symbols]

 20 Fixing device 34/35 Roller after fixing 39 Roller shaft 41 Through hole 45 Absorbent S sheet

Claims (2)

[Claims] 1. An image forming apparatus in which a sheet after image transfer is placed in a fixing device, heat is applied by the fixing device to fix the transferred image on the sheet, and then the image is sent out by a roller after fixing. An image forming apparatus in which a large number of radial through holes are formed in a roller shaft of a roller. 2. The image forming apparatus according to claim 1, wherein the roller shaft of the roller after fixing is hollow, and a hygroscopic agent is stored in the hollow.