JPH02201465A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress the wasting of toner by providing a controlling means, which restricts and controls the area electrified of a photosensitive drum, driven so that paper is positioned on the photosensitive drum responding to the size of the detected paper. CONSTITUTION:Each paper feeding cassette 131 and 132 have their cassette sizes detected by cassette size detecting switches 601 and 602. Electrification controlling members 40a and 40b are provided responding to the image carrier (photosensitive drum) 10. The electrification controlling members 40a and 40b are constituted of members with electro conductivity obtained by dispersing electro conductive particles, such as carbon black, and reciprocate against the center of the transferring material (paper). Then, to control the electrified area of the photosensitive drum 10, the area to be electrified of the photosensitive drum 10 by the electrifier 11, which electrifies the photosensitive drum 10, is controlled by driving the member with electro conductivity on the photosensitive body surface. Thus the toner consumption can be cut down.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to an image forming apparatus, and particularly to an image forming apparatus that controls the charged area of an image carrier.

(Prior Art) Conventionally, among image forming apparatuses, for example, the process of an electronic copying machine has been described in Japanese Utility Model Publication No. 59-37795 and Japanese Patent Application Laid-Open No. 1983-1999.
No. 59277.

In the former two, after the surface of the photosensitive drum is charged by a charger, it is exposed to light reflected from the original document to form a latent image. After the latent image is formed, toner is attached to the latent image by a developing device and developed, and then the image is transferred to a transfer material (paper) and discharged to a paper discharge tray. In the above process, since the photoreceptor drum is uniformly charged by the charger, toner from the developing device is deposited on areas of the photoreceptor drum other than the paper to be transferred, resulting in wasted toner.

(Problems to be Solved by the Invention) In conventional devices, since the surface of the photoreceptor drum is uniformly charged by the charger, toner remains attached to the area of the photoreceptor drum other than the latent image on the paper. Transfer the image. Toner attached to areas of the photoreceptor drum other than the latent image is not used for transferring the latent image, and is therefore wasted, which may result in waste of toner.

The present invention has been made in view of the above, and an object of the invention is to provide an image forming apparatus that suppresses wastage of toner by charging an image bearing member in accordance with the size of paper. .

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a detection means for detecting the size of a transfer material to which an image formed on an image carrier is transferred, and a charging device installed opposite to the image carrier for charging the image carrier; and a member for regulating the area of the image carrier to be charged by the charging device; The object of the present invention is to include a control means for regulating and controlling the charged area of the image carrier by driving the member to be positioned on the surface of the image carrier in accordance with the size of the material.

(Function) In the image forming apparatus having the above configuration, the image carrier (
The size of the transfer material to which the image formed on the photoreceptor drum is to be transferred is detected. Controlling the charging area of the image carrier by driving a conductive member toward the image carrier surface by a charging means that charges the image carrier in accordance with the size of the transfer material. Therefore, toner consumption can be reduced.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows an image forming apparatus of the present invention, such as an electronic copying machine. That is, 1 is a main body of a copying machine, and a document table (transparent glass) 2 is fixed to the upper surface of the main body 1 to support a document.

The original placed on the document table 2 is exposed and scanned by an optical system consisting of an exposure lamp 4 and mirrors 5, 6, and 7 reciprocating along the lower surface of the document table 2 in the direction of arrow a. It is now possible to do so.

In this case, mirror 6.7 moves at half the speed of mirror 5 so as to maintain the optical path length. The light reflected from the original by the scanning of the optical system, that is, the light reflected from the original by the light irradiation of the exposure lamp 4, is reflected by the mirror 5, 6, 7, passes through the variable magnification lens block 8, and is further reflected by the mirror 5.6.7. 9 and guided to the photoreceptor drum 10,
An image of the original is formed on the surface of the photosensitive drum 10.

The photosensitive drum 10 rotates in the direction indicated by the arrow in the drawing, and first, the surface thereof is charged by a charging device 11, and then an electrostatic latent image is formed on the surface by slit exposure of the image. This electrostatic latent image is made visible by applying toner by the developing device 12. The developing device 12 is detachably attached to the main body 1 of the copying machine. Further, code information (not shown) indicating the color of the stored toner is provided on the side surface of the developing device 12, and when the developing device 12 is inserted into the copying machine main body 1, the copying machine main body 1
This code information is read by a sensor (not shown) on the side, and the color of the toner can be determined.

On the other hand, the paper (transfer material) is delivered from the selected upper paper feed cassette 1311 or lower paper feed cassette 132 to the feed roller 14. 142 and roller pair 15+, the sheets are taken out one by one and guided to registration roller pair 17,
The registration roller pair 17 guides the image to the transfer section.

Here, the paper feed cassettes 131 and 132 are the main body 1
It is removably provided at the lower right end of the screen, and either one can be selected on the operation panel described later. Each of the paper feed cassettes 131 and 132 also has a cassette size detection switch 60. 602
The cassette size is detected by This cassette size detection switch 60. 602 is
It is composed of a switch 51, which will be described later, having a plurality of microswitches that are turned on and off in accordance with the insertion of cassettes containing paper of different sizes. Further, a manual feed guide 13g is provided on the upper surface of the paper feed cassette 131, and the paper P manually inserted through the manual feed guide 13a is fed from the paper feed cassette 131 by the roller pair 151. The paper P is conveyed in the same way as the paper P.

On the other hand, the paper P sent to the transfer section comes into close contact with the surface of the photoreceptor drum 10 at the transfer charger 18.
The toner image on the photosensitive drum 10 is transferred by the action of the charger 18 . The transferred paper P is electrostatically peeled off from the photoreceptor drum 10 by the action of a peeling charger 19 and conveyed by a conveyor belt 20, and then transferred to a fixing roller 21 as a fixing device provided at the end of the conveyor belt 20. The transferred image is fixed by passing through this area. After fixing, the paper P is discharged to a tray 25 outside the main body 1.

Further, after the transfer, the residual toner on the surface of the photosensitive drum 10 is removed by the cleaner unit 26, and the residual image is erased by the static elimination lamp 27, so that the photosensitive drum 10 returns to its initial state. Note that 29 is a cooling fan for preventing the temperature inside the main body 1 from rising.

FIG. 2 is a diagram showing the arrangement around the photosensitive drum 10. As shown in FIG. A charger 1 for charging is provided around the photoreceptor drum 10.
1, developing device 12, transfer charger 18, peeling charger 1
9, a cleaner unit 26 and a static elimination lamp 27 are provided. A charging device 11 is provided near the top of the photosensitive drum 10 in the figure, and the surface of the drum 10 is charged.

Exposure light from a document is incident adjacent to the charger 11 for charging, and an electrostatic latent image is formed on the drum 10.

Further, at the lower right side in the direction of the exposure arrow, a developing device 12 is provided that supplies toner charged to the opposite polarity to the surface potential of the drum 10 to the surface of the photoreceptor drum 10 to form a toner image. ing.

In the lower part of the figure, in order to transfer the toner image formed on the photoreceptor drum 10 onto the paper P, the toner having a polarity opposite to that of the toner forming the toner image is applied (a voltage is applied), and the transfer is charged. A transfer charger 18 is provided adjacent to the transfer charger 18 in order to separate the paper P from the photoreceptor drum 10.
In order to neutralize the paper P, a peeling charger 19 is provided to which an AC voltage is applied to discharge the paper P. A peeling error sensor 38 is provided on the upper left side of the peeling charger 19 in the figure to detect a peeling error when the paper P is wrapped around the photoreceptor drum 10. An AC charger 39 is provided that comes into contact with the peeling error sensor 38 and suppresses the residual toner potential remaining on the photoreceptor drum 10 . Further, a cleaner unit 26 for removing residual toner attached to the photosensitive drum 10 is provided above the AC charger 39 in the drawing. The cleaning unit 26 is rotatably supported at the upper part of the casing that surrounds the photoreceptor drum 10 and has an elastic blade 35 that is pressed in the direction of the drum IO, and the toner wiped off by the blade 35 is transferred to the blade 35. It consists of a scraping plate 36 that prevents the toner from accumulating, and a screw 37 that is located near the mounting base of the scraping plate 36 and collects the wiped toner. A neutralizing lamp 27 is provided adjacent to the cleaner unit 26 for erasing an afterimage on the surface of the drum 10. FIG. 3 is a configuration diagram showing a charge control member installed facing the photoreceptor drum 10. As shown in FIG. Charge control members 40a and 40b are installed facing the photoreceptor drum 10. The charge control members 40a and 40b are members that are made conductive by dispersing conductive fine particles such as carbon black, and reciprocate with respect to the center of the paper P. Further, the charge control members 40a and 40b prevent the photoreceptor drum 10 from being charged by the charge from the charger.

At the right end of the charge control member 40b in the drawing, there is provided a columnar pinion 42 that has a sawtooth rack 41 and meshes with the sawtooth of the rack 41. The pinion 42 is connected to a pulse motor 43 via a shaft, and rotates in conjunction with the rotational drive of the pulse motor 43. The pulse motor 43 is rotated in response to a pulse signal from a control section 50, which will be described later. As the pinion 42 rotates in the forward and reverse directions, the charge control members 4a and 40b move towards and away from each other with respect to the paper. That is, when the paper size is small, for example, 85 plate, the charge control members 40a and 40b move closer to each other with respect to the paper.

On the other hand, when the paper size is large, for example, A3 size, the charge control members 40a and 40b move away from each other with respect to the paper. For example, the charge control member 40a
, 40b is the width W, and when the width of the paper is determined to be W by a switch described later, the rack 41 is moved by the rotational drive of the pulse motor 43 in response to a drive signal from the control unit 50 described later, and the charging control members 40a, 40b are moved. The width of is the paper width W
controlled in the same way.

FIG. 4 is a control block diagram of the image forming apparatus of the present invention.

The image forming apparatus includes a control section 50. switch 51, cassette selection key 52. It has a copy button 53.

The control unit 50 is equipped with a microcomputer,
It controls the entire device. The switch 51 is provided in the cassette size detection sensor 601602 and detects the size of the paper P stored in the cassette based on the number of claw members of the cassette.

The cassette selection key 52 and the copy button 53 are provided on an operation panel (not shown), and the cassette selection key 52 is
For example, when A4 size paper P is selected, a corresponding key is pressed and a detection signal is output to the control section 50. The copy button 53 is a key that indicates the start of a copying operation.

The image forming apparatus also includes a driver 54 and the pulse motor 43 described above. The driver 54 responds to the drive signal input from the control unit 50, for example, A4.
In the case of a plate of paper, 100 pulses are output to the pulse motor 43, and in the case of 85 plates, 120 pulses are output to the pulse motor 43 to control the rotation of the pulse motor 43.

Next, the operation of this embodiment will be explained.

First, the staff turns on one main switch to turn on the power to the copying machine main body 1. When the main switch is turned on, the control section 50 specifies the paper feed cassettes 131 and 132 using the cassette selection key 52 for selecting the size of paper P input from an operation panel (not shown). Next, when the copy button 53 on the operation panel is pressed, the control section 50 activates the cassette size detection switch 601.
．． A detection signal from switch 51 602 detects the size of paper P stored in a paper feed cassette set in the main body of the apparatus. Here, for example, when the A4 size is selected from the cassette selection key 52, the control section 50 outputs a drive signal to the driver 54 in response to a detection signal from the switch 51. The driver 54 outputs a pulse signal, for example, 100 pulses, to the pulse motor 43 in response to a manually inputted drive signal. The pulse motor 43 rotates and drives the pinion 42 in response to an input pulse signal.
is driven to move the charge control members 40a and 40b to the size of paper, for example, A4 size. Charge control members 60a, 6
After the movement of 0b, an area corresponding to an A4 size plate is charged on the surface of the photosensitive drum 10 by the charging device 11. The charged photosensitive drum 10 is exposed to light to form a latent image, and then toner is attached by the developing device 12, and the image is transferred onto the paper P by development.

Here, the amount of toner attached to the photoreceptor drum 10 from the developing device 12 is controlled by the charge control member 40a.

In order to correspond to the paper size controlled by 40b,
It is possible to prevent toner from adhering to areas other than the paper as in the conventional case.

As described above, the present invention can be implemented with various modifications within the scope of the invention.

〔Effect of the invention〕

As explained above, according to the present invention, the charged area of the image carrier is controlled by driving the members arranged opposite to the image carrier according to the size of the transfer material. Toner waste can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is a main part view of the side sectional view shown in FIG. 1, and FIG.
This figure shows a charge control member, and FIG. 4 shows a control according to the present invention. 1... Copying machine body 10... Photoreceptor 11... Charger 12... Developing device 131... Upper cassette throat 132... Lower cassettes 40a, 40b... Charge control member 41. ... Rack 42 ... Pinion 43 ... Pulse motor 60, . 602...Cassette 50...Control unit 51...Switched size detection switch

Claims (1)

[Scope of Claims] A detection means for detecting the size of a transfer material to which an image formed on an image carrier is transferred, and a charging means installed opposite to the image carrier to charge the image carrier. and a member for regulating the area of the image bearing member charged by the charging means, the member is configured to control the image bearing member in accordance with the size of the transferred material detected by the detection means. An image forming apparatus characterized by having a control means for regulating and controlling the charged area of the image carrier by driving the image carrier to be positioned above the body surface.