JPH0362074A - Paper transport type electrophotographic device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is applicable to printers, facsimile machines, etc. using lasers.
The present invention can be applied to electrophotographic devices such as copying machines that record on paper using an electrophotographic process. In particular, the present invention relates to an on-paper transport type electrophotographic apparatus that transports a paper through the upper side of a photoreceptor drum and performs recording by transferring an image on the photoreceptor drum to the lower surface of the paper.

Traditionally, in this type of electrophotographic apparatus, the paper is guided by upper and lower pre-transfer guides, and is further guided by the entrance guide section of the transfer charger to be guided between the transfer charger and the photoreceptor drum. Ta.

In order to obtain a good image, it is necessary to bring the paper into close contact with the photoreceptor drum as much as possible, so in order to press the paper onto the photoreceptor drum, the entrance guide of the transfer charger is positioned at the top of the photoreceptor drum. The lower end position of the was set quite low, and the exit position of the upper pre-transfer guide was also set quite low. Also.

Accordingly, the position of the transfer charge wire that is passed over the photoreceptor drum is also set as close to the paper feed side as possible from a vertical line passing through the center of the photoreceptor drum.

As a result, the paper conveyance path bends significantly, impeding the smooth conveyance of the paper, adding great stress to the paper, and causing problems when the trailing edge of the paper leaves the pre-transfer upper guide and when the transfer charger There is a problem in that when the paper leaves the entrance guide section, it jumps up, causing a transfer failure at the trailing edge of the paper.

In addition, at the conventional transfer charge wire spanning position,
There has been a problem in that the transfer quality of toner images deteriorates in high temperatures and high humidity.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve such conventional problems in an electrophotographic apparatus of paper transport type, smooth paper transport to eliminate stress on the paper, prevent transfer omissions, and improve temperature control. The objective is to obtain good images regardless of changes in temperature and humidity.

Means to solve the problem Therefore 1M requirement 1. In the above-paper conveyance type electrophotographic apparatus according to the present invention described in , for example, as shown in the illustrated embodiment below, the paper 17 guided by the pre-transfer upper and lower guides 33b and 37 is further transferred to the inlet guide section 3 of the transfer charger 34.
6a and guided between the transfer charger 34 and the photoreceptor drum 11, and the image on the photoreceptor drum 11 is generated by electric discharge from the transfer wire and the yarn wire stretched over the photoreceptor drum 11 in the axial direction. is transferred to the paper 17.
In an on-paper transport type electrophotographic apparatus that performs recording, the lower end position Q of the entrance guide portion 36a is lowered by 0 to 1.5 am with respect to the apex position P of the photosensitive drum 11, and the transfer charge wire 38 is lowered by 0 to 1.5 am. It is characterized in that the spanning position is set at a position of 5 to 7 III m from the vertical line 2 passing through the center of the photosensitive drum 11 toward the sheet feeding side.

Also, claim 2. In the above-paper transport type electrophotographic apparatus according to the present invention described in 1, for example, as shown in the illustrated embodiment below, the paper 1 is guided by pre-transfer upper and lower guides 33b and 37.
7, and the entrance guide portion 36a of the transfer charger 34.
guide the transfer charger 34 and the photosensitive drum 11.
An on-paper conveyance type in which the image on the photosensitive drum 11 is transferred and recorded on the paper 17 by electric discharge from a transfer charge wire that is guided between the photosensitive drums 11 and stretched in the axial direction of the photosensitive drums 11. In the electrophotographic apparatus, the entrance guide portion 3 is
6a lower end position f21. Q is lowered by 0 to 1°5 rm, and the exit position O of the pre-transfer upper guide 33b is set at a position of ±21 m with respect to the lower end position Q, and the extending position of the transfer charge wire 38 is set to the position of the photoreceptor. It is characterized by being set at a position of 5 to 7 circles from a vertical line passing through the center of the drum 1 toward the paper feed side.

Operation Then, the paper 17 guided by the pre-transfer upper and lower guides 33b and 37 is guided by the entrance guide section 36a and guided between the transfer charger 34 and the photosensitive drum 11, and the paper 17 is guided by the entrance guide section 3.
While pressing lightly with 6a.

The paper 17 is brought into close contact with the photosensitive drum 1 by its own weight.

Gei-J Rainbow-Bao The present invention will be described in detail below with reference to one drawing.

FIG. 3 is a laser printer which is an embodiment of the present invention, and shows the overall schematic structure of its internal mechanism.

The reference numeral 10 in the figure is the main body of the apparatus. Inside the apparatus main body 10, there is provided a photosensitive drum 1 in the center.

A charger 12, a developing device 13, a transfer/separation charger 4, and a cleaning device 15 are arranged around the photosensitive drum king 1 in this order in the rotation direction (counterclockwise in the figure). A laser writing device 16 is provided below the developing device 13. On the other hand, two paper feed cassettes 18 for storing paper 17 are attached to the right side of the apparatus main body 10 in the figure. A paper feed unit 20 having a paper feed roller 19 is provided at the mounting portion of each paper feed cassette 18 . The paper feed section 20 and the paper feed path 21 communicate with each other, and the developing device 1
3, a pair of registration rollers 22 is arranged.

On the other hand, a conveyor 23 and a fixing device 24 are arranged in this order on the opposite side of the registration roller pair 22 across the transfer/separation charger 14 described above.

A pair of paper ejection rollers 25 is provided on the left side of the fixing device 24 in the figure, and a paper ejection receiver 26 is further provided on the left side thereof, protruding from the apparatus main body IO.

When forming an image using this laser printer, the paper feed roller 19 is driven to feed the paper 17 from the paper feed cassette 18 in the direction of arrow A in the figure. and,
It passes through two paper feed paths and abuts its tip against a pair of registration rollers 22. On the other hand, while rotating counterclockwise in the figure, the surface of the photosensitive drum 11 is first uniformly charged with a charger 12, and then a laser beam is irradiated with a laser writer 6 to electrostatically charge the surface. A latent image is formed, and then the electrostatic latent image is sequentially visualized using toner in a developing device 13. Then, in synchronization with the image, the above-mentioned paper 17 which had been in contact with the pair of registration rollers 22 is guided onto the photosensitive drum 1. When the paper passes over the photoreceptor drum 11, the transfer/separation charger 14 transfers and records the image formed on the surface of the photoreceptor drum 1 to the lower surface of the paper 17, and then the photoreceptor drum 11 The paper 17 that is in close contact with the paper 17 is electrostatically separated. And photosensitive drum 1
The surface of 1 is cleaned with a cleaning device 15.

The residual toner on the photosensitive drum 11 is removed.

On the other hand, the paper 17 is sent to a fixing device 24 by a conveyor 23, and the transferred image is fixed by the fixing device 24. Thereafter, the sheets 17 are ejected and sent out in the direction of arrow B in the figure by the pair of rollers 25, and the sheets 17 on which recording has been completed are sequentially stacked on the eject tray 26.

Incidentally, in the laser printer shown in FIG. 3, the apparatus main body 10 is separated by the paper conveyance path, and the cover main body 3 is attached to a base main body 30 so as to be openable and closable about a shaft 31.
It consists of 2. The lower surface of the cover body 32 is covered with a guide cover 33. As shown in FIG. 2, the guide cover 33 has an elongated charger storage recess 33a facing the photosensitive drum 11, and a pre-transfer upper guide 33.
A roller storage recess 33c is formed by sandwiching the rollers b. and,
The transfer/separation charge roller 4 described above is housed in the charger housing recess 33a, and the upper registration roller 22a is housed in the roller housing recess 33c. The upper registration roller 22a is connected to the lower registration roller 22 in the base body 30.
Press it against b.

As shown in FIG. 2, the transfer/separation charger 14 includes a transfer charger 34 that transfers the image on the photoreceptor drum 11 onto the paper 17, and a separation charger that removes electricity from the paper 17 after transfer and separates it from the photoreceptor drum king 1. It consists of 35. The transfer charger 34 has an entrance guide portion 36a in its casing 36 that guides the paper 17. On the other hand, a plate-shaped lower pre-transfer guide 37 installed within the base body 30 is opposed to the upper pre-transfer guide 33b. Further, the transfer charger 34 is disposed in its casing 36 surrounding a transfer charge wire 38, and the transfer charge wire 38 is stretched parallel to the axis of the photosensitive drum 11. Then, the paper 17 sent out at the right timing by the pair of registration rollers 22a and 22b is guided by the upper and lower pre-transfer guides 33b and 37, and further the paper 17 is guided by the entrance guide section 3.
6a to guide the transfer charger 34 and photosensitive drum 11.
It will surely lead you between. Then, the image on the photosensitive drum 11 is transferred and recorded onto the paper 17 by the discharge of the transfer charge wire 38.

Now, as shown in FIG. 1, the apex position of the photoreceptor drum AE is P, the lower end position of the entrance guide part 36a is Q, the exit position of the pre-transfer upper guide 33b is ○, and the transfer charge wire 3.
Let S be the crossing position of 8.

Then, the lower end position BQ is set a lower than the apex position P, and the exit position [0 is set at the position b with respect to the lower end position Q. Furthermore, the transfer charge wire 38 is moved from a perpendicular line Ω passing through the center of the photosensitive drum 11 to C on the sheet feeding side.
Set to the position. Then, in this invention, a is set to 0 to
1.5mm, b is ±2 degrees, and C is 5 to 7-.

Then, the paper 17 guided by the pre-transfer upper and lower guides 33b and 37 is guided by the entrance guide part 36a of the casing 36 and guided between the transfer charger 34 and the photosensitive drum 11, and is lightly pushed by the entrance guide part 36a. , the paper 17 is brought into close contact with the photosensitive drum 11 by its own weight.

In the above embodiment, a part of the guide cover 33 forms the pre-transfer upper guide 33b. However, as shown in FIG. 4, a plate-shaped pre-transfer upper guide 39 is provided independently from the guide cover 33, and its exit position O is located at a position b relative to the lower end position Q of the entrance guide portion 36a. , i.e. ±
It may be set at a position of 2 mm. Portions in FIG. 4 that correspond to those in FIG. 1 are given the same reference numerals.

Therefore, according to the present invention, in a paper conveyance type electrophotographic apparatus, the apex position of the photosensitive drum and the lower end position of the inlet guide portion of the transfer charger, and the lower end position and the pre-transfer upper guide By minimizing the height difference between the exit position and the exit position, and by moving the transfer charge wire as close as possible to the vertical line passing through the center of the photoreceptor drum, the bending of the paper transport path is minimized and paper transport is improved. It can be smooth. At the same time, this minimizes the bounce of the trailing edge of the paper, presses it lightly with the entrance guide of the transfer charger, and brings the paper into close contact with the photosensitive drum by its own weight, thereby preventing transfer failure. Even under high temperature and high humidity conditions, a good transferred image can be obtained without deteriorating the transferred image quality of the toner image.

[Brief explanation of drawings]

Figure 1 is a partially enlarged view of Figure 2, and Figure 2 is a transcription of Figure 3.
FIG. 3 is an enlarged view of the separate charger and its surrounding parts, and is a general schematic diagram of the internal mechanism of a laser printer according to an embodiment of the present invention. FIG. 4 is an enlarged view of a transfer/separation charger and its surroundings showing another embodiment of the present invention. 11......Photoreceptor drum, 17...
...Paper, 33b...Top guide before transfer, 34...Transfer charger, 36a.
......Entrance guide section, 37...
・Lower guide before transfer, 38...Transfer charge wire, 39...Upper guide before transfer, P
・・・・・・・・・Vertex position of photoreceptor drum, Q...
...Lower end position of the entrance guide part, O...
...Pre-transfer upper guide exit position, S...
・Latching position of transfer charge wire, Q...
...The vertical line of the photoreceptor drum.

Claims (1)

[Claims] 1. The paper guided by the pre-transfer upper and lower guides is further guided by the inlet guide section of the transfer charger and guided between the transfer charger and the photoreceptor drum, and the paper is placed on the photoreceptor drum. In an on-paper conveyance type electrophotographic apparatus that transfers an image on the photoreceptor drum and records it on the paper by electric discharge from a transfer charge wire stretched in the axial direction, with respect to the apex position of the photoreceptor drum. The lower end position of the entrance guide portion is lowered by 0 to 1.5 mm, and the transfer charge wire is set at a position 5 to 7 mm from a vertical line passing through the center of the photoreceptor drum toward the paper feed side. This is a paper transport type electrophotographic device. 2. Before transfer, the paper guided by the upper and lower guides was further guided by the inlet guide section of the transfer charger, guided between the transfer charger and the photosensitive drum, and stretched over the photosensitive drum in the axial direction. In an on-paper conveyance type electrophotographic apparatus that transfers an image on the photoreceptor drum and records on the paper by discharge from a transfer charge wire, the lower end of the entrance guide portion is located relative to the apex position of the photoreceptor drum. The position is lowered by 0 to 1.5 mm, and set at a position ±2 mm from the exit position of the upper pre-transfer guide with respect to its lower end position, and the crossing position of the transfer charge wire passes through the center of the photoreceptor drum. From the vertical line to the paper feed side 5~
An electrophotographic device that transports on paper and is set at a position of 7 mm.