JP2002268521A - Electrophotographic image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic image formation device for which the temperature rise of a photosensitive body drum and a cleaning means is reduced. SOLUTION: This electrophotographic image formation device is provided with the photosensitive body drum 1 for forming toner images, a transfer charger 9 for transferring the toner images formed on the photosensitive body drum 1 to a sheet, a cleaner 20 for cleaning toner remaining on the photosensitive body drum 1 after the toner images are transferred to the sheet, a fixing device 50 for heating and fixing the toner images transferred to the sheet and a carrying belt 40 for carrying the sheet from a toner image transfer part by the transfer charger 9 to the fixing device 50. The cleaner 20 is arranged above the carrying belt 40, a heat insulation wall 103 is provided between the cleaner 20 and the carrying belt 40 and an air flow is formed between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, such as a copying machine or a printer, provided with a sheet reversing double-side unit used for forming an image on both sides of a sheet.

[0002]

2. Description of the Related Art A conventional electrophotographic image forming apparatus provided with a sheet reversing double-sided unit (hereinafter referred to as a double-sided unit) performs the following operations when forming images on both sides of a sheet (transfer paper). Had been

First, when image formation is started, sheets are fed from a sheet storage unit such as a paper feed cassette. It is transported to an image forming section provided with a photosensitive drum, where an image (toner image) is transferred to one side. Next, the toner image is heat-fixed to the sheet by passing through a fixing device including a pair of rollers heated to a high temperature, and then the sheet is conveyed to a duplex unit.

In recent years, in order to increase productivity of double-sided image formation, a sheet-through type is widely used for a double-sided unit.

After the sheet conveyed to the double-sided unit is switched back, the sheet passes through the unit, and is conveyed again to the image forming unit by a plurality of pairs of conveying means such as rollers. At this time, the sheet is turned upside down, and an image is formed on a surface on which no image is formed yet. After that, the toner image on the surface is heat-fixed again, and is discharged to a discharge tray outside the apparatus.

[0006]

When a double-sided image is formed using such an image forming apparatus, the sheet passing through the double-sided unit after the image is formed on one side is heated to a high temperature after the image is formed. Therefore, the sheet passes through the duplex unit in a high temperature state.

Therefore, when the sheet is re-fed and conveyed to the photosensitive drum immediately after passing through the duplex unit, the sheet is still in a high temperature state.

As a result, for example, the photosensitive drum is heated and the temperature of the surface of the photosensitive drum rises. Then, cleaning of the residual toner remaining on the surface of the photosensitive drum after the image transfer by the cleaner becomes insufficient, and there is a possibility that cleaning failure may be caused. Further, there is a problem that the waste toner adheres to the waste toner discharging screw in the cleaner and the conveying performance of the screw is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrophotographic image forming apparatus capable of reducing the temperature rise of a photosensitive drum and a cleaning unit.

[0010]

A typical configuration according to the present invention for achieving the above object is to provide an electrophotographic photosensitive member for forming a toner image and a toner image formed on the electrophotographic photosensitive member on a sheet. A transfer unit for transferring, a cleaning unit for cleaning toner remaining on the electrophotographic photosensitive member after transferring the toner image to the sheet, a fixing unit for heating and fixing the toner image transferred to the sheet, and the transfer Conveying means for conveying a sheet from the toner image transfer unit to the fixing means by means, wherein the cleaning means is disposed above the conveying means, and a wall is provided between the cleaning means and the conveying means, An airflow is formed between the two.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an electrophotographic image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic side view of a main part of an image forming apparatus. The process of forming an image on both sides of a sheet will be described below with reference to FIG. For simplicity, a description will be given of double-sided image formation on two sheets.

{Overall Configuration} 1 is a photosensitive drum rotating at a constant speed in the direction of arrow A in the figure. The photosensitive drum has a cylindrical shape extending in the direction perpendicular to the plane of FIG. 1, and the surface photosensitive layer is uniformly charged by the charger 2.

Reference numeral 3 denotes a laser scanner for modulating an image signal input to the image forming apparatus to turn on / off a laser beam. A laser beam 4 emitted from a laser light source (not shown) in the laser scanner is scanned in a direction perpendicular to the plane of FIG. 1 by a polygon mirror 5 also located in the laser scanner. The laser beam reflected by the folding mirror 6 is projected on the charged surface to form an electrostatic latent image on the surface of the photosensitive drum 1.

When the latent image reaches the developing site where the developing device 7 is located with further rotation of the photosensitive drum 1, the latent image is developed by toner supplied from the sleeve 8 of the developing device to the latent image. The image is formed into a toner image. When the photosensitive drum 1 further rotates, the toner image reaches a transfer site where the photosensitive drum 1 and a transfer charger 9 as a transfer unit face each other.

On the other hand, the first sheet is picked up from the sheet cassette 10 by the pickup roller 11. The sheet reaches a registration roller pair 15 via a known sheet separation mechanism 12 and a plurality of conveyance roller pairs 13 and 14.

Next, the same sheet is supplied to the transfer portion from the registration roller pair 15 at the same time as the toner image, and a transfer bias is applied to a transfer charger.
The toner image on the photosensitive drum side is transferred to the sheet.

At the time of transfer, a small amount of untransferred toner remaining on the photosensitive drum without transferring to the sheet advances as it is, reaches the position of the cleaner 20 as the cleaning means, and is removed by the cleaning blade 21. Further, the residual charge is erased by the pre-exposure lamp 22, and the photosensitive drum 1 is ready for the next image forming step.

The transfer residual toner removed by the cleaning blade 21 falls into the cleaner container 23 and accumulates in the lowermost portion of the container. Further, at the same position, a toner discharging screw 24 for discharging the untransferred toner to the outside of the cleaner container 23 is arranged, and the configuration is such that the untransferred toner is conveyed. In FIG. 1, a screw 24 for discharging toner is used.
Is configured to convey the transfer residual toner from the near side to the far side.

On the other hand, after the transfer is completed, a separation current is applied to the sheet from a separation charger 30, and the sheet is separated from the photosensitive drum 1, and is fixed by a conveying belt 40 constituting a sheet conveying means as a fixing means. The toner image is conveyed to the device 50 and fixed on the first side of the first sheet.

After that, the sheet is flapper shown in FIG.
Due to the arrangement of 60, it is transported to the arrow B side in the figure, and the roller pair 61
To enter the reverse path 62. The reversing path 62 includes a pair of reversing rollers 63 capable of normal and reverse rotation. When the sensor 64 detects the end of the sheet entering the reversing path, the rotation direction is reversed and the sheet is switched back.

The switched back sheet is subsequently conveyed to the duplex unit 70 shown in FIG. Duplex unit
Within 70, in order to secure productivity when forming double-sided images,
The sheet is conveyed at a high speed approximately twice as fast as the process speed, and stands by at a position 71 where refeeding is possible.

As described above, while the first sheet arrives at the re-feedable position from the image formation, the second sheet is fed from the sheet feeding cassette 10 and is similar to the first sheet. In the image forming process.

The first sheet waiting at the re-feedable position in the duplex unit 70 can be separated from the second sheet in order to maximize the productivity of the image forming apparatus. The sheet is re-supplied to the registration roller in a state where the sheet is kept as small as possible. At this time, needless to say, the first sheet has the second surface on the photosensitive drum side.

After the above-described toner image forming process is performed on the second surface of the first sheet, the first sheet is separated from the photosensitive drum 1 and is conveyed to the fixing device 50 by the conveying belt 40. The toner image is also fixed and fixed on the second side.

Subsequently, a toner image is sequentially formed on the second surface of the second sheet.

On the other hand, the sheet that has passed through the fixing device is shown in FIG.
Is transported to the arrow C side in the figure and discharged to a tray 80 outside the apparatus.

{Adiabatic Configuration} In the fixing device, the heat roller 51 in the fixing device 50 is heated to a little less than 200 degrees in order to thermally fix the toner image on the sheet. Therefore, particularly when images are formed on both sides of the sheet, the sheet is heated to fix the toner image on the first side, the sheet in the high temperature state is re-fed, and arrives at the image transfer portion again. In particular, when performing double-sided image formation continuously for a long time, the heated sheet frequently arrives at the image processing section including the photosensitive drum 1.

That is, the photosensitive drum 1 and the cleaner
20 gradually accumulates heat radiated by the sheet near the photosensitive drum. As a result, the temperature rise of each part due to the heat has a great effect on the image quality and the performance of discharging the waste toner in the cleaner.

FIG. 4 is an explanatory view in which the vicinity of the cleaner of the present embodiment is enlarged. The cleaner container 23 integrally supports the bearing portion 101, and the bearing portion 101 has a shaft 1 perpendicular to the plane of FIG.
02 penetrates. Reference numeral 103 denotes a heat insulating wall for insulating the cleaner container 23 from the high-temperature sheet 105 passing over the conveyor belt 104 below the cleaner. This heat insulating wall 103 is attached to a cleaner container 23 as a housing of the cleaning means. That is, the heat insulating wall 103 has a U-shaped groove 106, and the U-shaped groove 106 is fitted to the shaft 102. A holding plate 107 is arranged above the shaft 102. The pressing plate 107 straddles the U-shaped groove 106 and has a configuration in which the heat insulating wall 103 is suspended with respect to the shaft 102 at hooks 108 and 109 on both sides of the U-shaped groove. Also this holding plate 1
07 is fixed to the heat insulating wall with screws 110.

On the other hand, a leaf spring 111 is integrated with the pressing plate 107 by a fixing method such as caulking. Since the leaf spring 111 abuts on the cleaner container 23 at the point a in FIG. 4, the pressing plate 107 or the heat insulating wall 103 generates a rotational force around the shaft 102 in the counterclockwise direction of FIG. Given. In addition, a convex portion 103a is formed at the rotating end of the heat insulating wall 103,
When rotated by the bias of the leaf spring 111, the projection 103
Since a contacts the cleaner container 23 in the part b of FIG. 4, the heat insulating wall 103 is positioned with respect to the cleaner container 23.

Reference numeral 112 denotes an air guide for guiding an air flow generated by a fan (not shown) to the cleaner container 23 side. The shape of the air guide 112 is arranged at a position where air flows between the cleaner container 23 and the heat insulating wall 103 as shown by an arrow D in FIG.

By adopting such a configuration, at the time of double-sided image formation, the cleaner container 23 is reliably insulated from the heat emitted from the heated sheet 105 and the air flowing into the vicinity of the cleaner container 23 is efficiently removed. It can be sprayed on the cleaner container 23. Therefore, it is effective to prevent the temperature rise in the case where the aggregation of the waste toner due to the temperature rise, for example, around the waste toner discharge screw in the cleaner container 23, significantly affects the waste toner discharge performance of the screw.

[Second Embodiment] The second embodiment shown in FIG. 5 is a further development of the first embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals.

FIG. 5 shows a fixing device 50 and a cleaner.
An air duct 152 is provided between the air duct 20. Further, an intake fan 153 is arranged on the front side of the apparatus, and air flows in the longitudinal direction of the apparatus from an intake port 154 of the air duct 152. This air flows in the longitudinal direction, flows into the vertical duct 155, and is discharged from the air duct discharge port 156 as shown by an arrow E in FIG. The air thus discharged is further guided to the cleaner container 23 by the guide member 157.

Under the cleaner container 23, a heat insulating wall 103 is provided.
Is disposed so as to be directly suspended with respect to the cleaner container 23.

Also in this embodiment, the cleaner container 23
The shape of the guide member 157 is determined so that the air guided by the guide member 157 flows between the space and the heat insulating wall 103.

The transfer charger 170 and the separation charger 171 used in this embodiment are corotron type chargers, and ozone generated when the transfer charger 170 and the separation charger 171 discharge. Is provided immediately below the transfer charger 170 and the separation charger 171.

Then, the cleaner container 23 and the heat insulating wall 10
If an air flow configuration (arrow E in FIG. 5) is used in which the air passing between the air suction device 3 and the suction fan 3 is sucked by the suction fan 172,
The temperature rise immediately below the cleaner container 23 can be suppressed more efficiently, and the photosensitive drum 1 after the sheet separation can be cooled.

Also, the photosensitive drum 1
By applying air to the sheet immediately after being separated from
There are advantages such as the use of the air flow as an aid for sheet separation.

[Other Embodiments] In the above-described embodiment, an example was described in which the heat insulating wall 103 is directly suspended from the cleaner container 23. However, the heat insulating wall insulates the heat from the sheet to the cleaner container. And, if the purpose of efficiently blowing the air flowing into the vicinity of the cleaner container to the same container is achieved, a configuration independent of the cleaner container,
For example, it may be supported by the apparatus main body.

[0042]

As described above, according to the present invention, when an image is formed on both sides of a sheet, even if the sheet heated by the fixing means is re-fed to the image processing section,
It is possible to reliably insulate the cleaner container from the high-temperature sheet. For this reason, it is possible to prevent the cleaning performance from being deteriorated and the deterioration of the conveying performance of the screw due to the waste toner adhering to the screw for discharging the waste toner in the cleaner. Therefore, double-sided image formation with high productivity can be continuously performed.

[Brief description of the drawings]

FIG. 1 is a schematic side view illustrating a main part of an image forming apparatus.

FIG. 2 is an explanatory diagram of sheet conveyance to a duplex unit.

FIG. 3 is an explanatory diagram of sheet discharge after completion of double-sided recording.

FIG. 4 is an explanatory diagram in which the vicinity of a cleaner of the present embodiment is enlarged.

FIG. 5 is an explanatory diagram of a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum 2 ... Charger 3 ... Laser scanner 4 ... Laser beam 5 ... Polygon mirror 6 ... Folding mirror 7 ... Developer 8 ... Sleeve 9 ... Transfer charger 10 ... Paper feed cassette 11 ... Pickup roller 12 ... Sheet separation mechanism 13, 14: transport roller pair 15: registration roller pair 20: cleaner 21: cleaning blade 22: pre-exposure lamp 23: cleaner container 24: toner discharge screw 30: separation charger 40: transport belt 50: fixing device 51: heat Roller 60 ... Flapper 61 ... Roller pair 62 ... Reversing path 63 ... Reversing roller pair 64 ... Sensor 70 ... Double-sided unit 71 ... Position 80 ... Tray 101 ... Bearing part 102 ... Shaft 103 ... Heat insulating wall 103a ... Convex part 104 ... Transport belt 105 … Sheet 106… U-shaped groove 107… Holding plate 108,109… Hook 110… Screw 111… Leaf spring 112… Air guide 152… Air duct 153… Intake fan 154… Inlet 155… Vertical duct 156… Air duct outlet 157… Guide member 170… Transfer charger 171… Separation charger 172… Suction fan

Claims (3)

[Claims] An electrophotographic photoreceptor for forming a toner image; a transfer unit for transferring a toner image formed on the electrophotographic photoreceptor to a sheet; Cleaning means for cleaning residual toner; fixing means for heating and fixing the toner image transferred to the sheet; and conveying means for conveying the sheet from the toner image transfer section by the transfer means to the fixing means. Placing the cleaning means above the transport means;
A wall is provided between the cleaning unit and the transport unit,
An electrophotographic image forming apparatus, wherein an air flow is formed between the two. 2. An electrophotographic image forming apparatus according to claim 1, wherein said wall is supported by a housing of said cleaning means. 3. The transfer means is constituted by a corotron-type charger, a suction fan is provided below the charger, and air passing between the wall and the cleaning means is sucked by the suction fan. The electrophotographic image forming apparatus according to claim 1, wherein: