JPH0443378A - Printing device - Google Patents

Abstract

PURPOSE:To eliminate the deformation of a developing roller or a photosensitive body and to decrease toner consumption by switching the developing roller to a non-contact state with an electrostatic latent image carrier while the developing roller is rotated in a state where the electrostatic latent image carrier is rotated after finishing a developing action. CONSTITUTION:After finishing the developing action, that is, in the case a printing action is finished perfectly, a cam 15 is rotated by 90 deg. in a direction shown by an arrow (e') to release pressing force for a developer container 8. Therefore, the container 8 is moved by a spring 17 in a direction shown by an arrow (d') and the developing roller 4 separates from the photosensitive body 1. While separating and contacting actions are performed, the photosensitive body 1 is always electrostatically charged and a bias voltage is always impressed on the developing roller and the photosensitive body 1 and the developing roller 4 are always rotated, so that useless toner which does not contribute to printing does not adhere to the photosensitive body 1. Thus, the deformation of the developing roller 4 or the photosensitive body 1 is eliminated and the toner consumption is decreased.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electrophotographic one-component developing device in which development is carried out by bringing a developing roller carrying a developer on its surface into contact with an electrostatic latent image carrier. Adopted. It relates to printing devices such as copying machines, printers, and facsimile machines.

(Prior art) Conventionally, when developing by bringing a developing roller into contact with an electrostatic latent image carrier, (1) a relatively high-rigid metal or plastic developing member is placed on a belt and an elastic electrostatic latent image carrier; There are two types of devices: (2) a device that brings an elastic developing roller into contact with an electrostatic latent image carrier made of a relatively rigid base material such as metal or plastic.

FIG. 6 is a side view of a conventional printing device.
is supported by the main unit so as to be rotatable in the direction of the arrow a.

2 is a charger that uniformly charges the surface of the photoreceptor to a constant potential; 3
4 is an elastic developing roller made of conductive silicone rubber or conductive urethane rubber, 13 is a transfer paper guide member, and 14 is on the photoreceptor 1. This is a transfer device that transfers the toner image onto transfer paper.

The developing roller 4 is rotatably supported in the developing container 8 in the direction of the arrow.
Component toner 7 (hereinafter abbreviated as toner) is stored. Reference numeral 5 indicates a toner replenishment roller which is disposed in parallel with the developing roller 4 and is rotatably supported in the direction of arrow C; 10 is a power source connected between the photoreceptor 1 and the developing roller 4; and 18 is a developing roller that is applied with a predetermined pressing force by a spring 19. This is the blade that comes into contact with 4.

Toner 7 supplied to the developing roller 4 by the toner supply roller 5
is conveyed as the developing roller 4 rotates in the direction of arrow a, and is thinned to a constant thickness and triboelectrically charged by the blade 18.

Thereafter, the thinned and simultaneously charged toner layer contacts the surface of the photoreceptor 1, and due to the electric field of the developing bias voltage applied by the power source 10 and the electrostatic latent image potential of the photoreceptor 1, t. selectively moves toward photoreceptor 1 and
An electrostatic latent image is developed. At this time, the developing roller 4 and the photoreceptor 1 are pressed against each other with a predetermined pressure.

The developed toner image on the photoreceptor 1 is transferred by a transfer device 14 to a transfer paper conveyed along a transfer paper guide member 13, and fixed by a fixing device (not shown) to complete printing.

In the above-mentioned conventional printing device, the developing roller 4 is not brought into contact with or separated from the photoreceptor 1, and the constituent materials of the photoreceptor 1 and the developing roller 4 are selected to have a small permanent deformation, or the electrostatic latent image carrier is Techniques were used to minimize the contact pressure of the developing roller.

(Problems to be Solved by the Invention) However, the conventional configuration has the following problems.

1) Even if the above conventional photoreceptor (electrostatic latent image carrier) and developing roller are made of materials with low permanent deformation, the photoreceptor and the developing roller are left in contact for a long time when not in operation, causing the belt to deteriorate. Alternatively, the photoreceptor made of an elastic material or the developing roller may be deformed. As a result, if the photoconductor is deformed, uneven charging may occur due to changes in the distance from the charger, uneven development may occur due to changes in the contact state with the developing roller,
Transfer unevenness caused by variations in the contact state with the transfer paper, and cleaning unevenness caused by variations in the contact state with the cleaning member used to clean residual toner on the photoreceptor after transfer, may cause image fluctuations due to the rotation period of the photoreceptor. Causes unevenness.

2) If the developing roller is deformed, the contact state between the developing roller and the toner thinning blade that forms a thin toner layer on the developing roller changes, making it impossible to form a uniform thin toner layer on the developing roller surface, resulting in poor development. becomes non-uniform, resulting in image unevenness in the rotation period of the developing roller.

3) If the contact pressure between the photoreceptor and the developing roller is set to a level that is low enough to prevent permanent deformation of the components of the photoreceptor and the developing roller, the contact state will be uneven, resulting in uneven development and uneven development. It becomes an image.

4) Even when the photoreceptor is not rotating, the developing roller and the photoreceptor are always in contact with each other, and toner adheres to the surface of the photoreceptor at the contact portion and is consumed as invalid toner that does not contribute to printing.

5) After stopping the photoreceptor and developing roller after the development operation is completed,
When separating the developing roller from the photoreceptor, it is impossible for the photoreceptor and the developing roller to stop without slipping at all.
As shown in FIG. 6, the thin toner layer on the developing roller is scraped together, causing the developing roller to come into direct contact with the photoreceptor without intervening the toner layer. For this reason, if the developing roller is made of a material that easily contaminates the photoreceptor, such as silicone rubber, the photoreceptor will be contaminated, resulting in problems in image quality as described above.

6) After the photoreceptor and developing roller stop after the development operation is completed,
When the developing roller is separated from the photoreceptor, the potential of the photoreceptor is lowered due to dark decay and light leakage from the outside, and even if a bias voltage is applied to the developing roller, toner adheres to the photoreceptor and becomes invalid toner. It will be consumed as.

Therefore, it is an object of the present invention to provide a printing device that does not cause deformation of the developing roller or photoreceptor and consumes less toner.

(Means for Solving the Problems) Therefore, the present invention provides an electrostatic latent image carrier that is charged and imagewise exposed to form an electrostatic latent image, and an electrostatic latent image carrier that carries a developer on its surface and that forms an electrostatic latent image. A developing roller that performs development in contact with the image carrier, a developing roller support means that can switch the developing roller to a state of contact or non-contact with the electrostatic latent image carrier, and before the start of the developing operation. After the electrostatic latent image carrier rotates, the developing roller is rotated and brought into contact with the electrostatic latent image, and after the development operation is completed, the developing roller is rotated while the electrostatic latent image carrier is rotating. The developing roller state switching means is configured to switch the state of the developing roller to a non-contact state with respect to the electrostatic latent image carrier while rotating.

(Function) With the above configuration, the printing device is capable of eliminating image unevenness without causing partial permanent distortion of the photoreceptor or the developing roller by bringing the developing roller into contact with the photoreceptor only during printing operation. The purpose is to provide.

(Example) Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side view showing a part of the printing device, and in FIG. 1, 1 is a photoreceptor, 2 is a charger, 3 is an image exposure means, 4 is a developing roller, 5 is a toner supply roller, 7 is toner, 8 is a developer container, 10 is a power source, 13 is a transfer paper guide member, 14 is a transfer device, 18 is a blade, 19 is a spring,
Since these components are the same as those of the conventional device shown in FIG. 6, the same parts are given the same reference numerals and redundant explanation will be omitted.

9, the developer container 8 is moved to the support member 11 in the direction of arrow d so that the developer roller 4 approaches and separates from the photoreceptor 1.

d' is a roller supported movably in the force direction, and the developer container 8, roller 9, and support member 11 constitute a developer roller support means.

Reference numeral 15 denotes a cam that changes the state of the developing roller. This cam 15 is rotationally driven by a rotation angle control device 16 such as a clutch or a stepping motor, so that the developing roller 4
The developer container 8 is configured to be pressed against the restoring spring 17 so as to come into pressure contact with the developer container 8 . Here, the cam 15, the rotation angle control device 16, and the restoring spring 17 constitute a developing roller state switching means.

This device has the above-mentioned configuration, and its operation will be explained next.

Now, from the state shown in FIG. 2 where the developing roller 4 is separated from the photoreceptor l, the rotation angle control device 16 moves the cam 15 in the direction of the arrow e.
The cam 15 presses and moves the developing container 8 in the direction of the arrow d, resulting in the state shown in FIG. 1 in which the developing roller 4 is in pressure contact with the photoreceptor 1.

In the state shown in FIG. 1, the developing operation is started, and the toner 7 is sent to the toner supply roller 5 by the rotation of the agitator 6 in the direction of arrow F, and further by the rotation of the toner supply roller 5 in the direction of arrow C. The image is sent to the developing roller 4.

The toner 7 supplied to the developing roller 4 is conveyed as the developing roller 4 rotates in the direction of the arrow, and is thinned to a constant thickness by a blade 18 that is pressed against the developing roller 4 by a spring 19 with a predetermined pressing force. Frictionally charged.

Thereafter, the thinned and simultaneously charged toner layer contacts the surface of the photoreceptor 1, and due to the electric field between the developing bias voltage applied by the power source 10 and the electrostatic latent image potential of the photoreceptor 1, the toner layer is It selectively moves toward the photoreceptor 1, and the electrostatic latent image on the photoreceptor 1 is developed.

The developed toner image on the photoreceptor 1 is indicated by the arrow 12 shown in the figure.
The image is transferred by the transfer device 14 onto the transfer paper conveyed from the direction along the transfer paper guide member 13, and is fixed by a fixing device (not shown) to complete printing.

After the development operation is completed, that is, the printing operation is completely completed, and the printer is in standby mode or the printer is turned off,
As shown in FIG. 3, the cam 15 is rotated 90 degrees in the direction of arrow e' opposite to that shown in FIG. 2 to release the pressing force against the developer container 8.

As a result, the developing container is moved by the spring 17 in the direction of the arrow d' opposite to that described above, resulting in the state shown in FIG. 4, and the developing roller 4 is separated from the photoreceptor 1.

The movement of the developer container 8 toward and away from the developer container 8 is performed according to the control timing shown in FIG. In addition, since the photoreceptor 1 and the developing roller 4 are constantly rotating, wasteful toner that does not contribute to printing does not adhere to the photoreceptor.

In addition, if the developing roller is made of a material such as silicone rubber that would contaminate the photoreceptor, it will not come into contact with the photoreceptor for a long period of time, and there will be no space between the developing roller and the photoreceptor while the developing roller and the photoreceptor are rotating. Since the toner layer is always present, contamination of the photoreceptor is reduced.

In the above embodiments, the photoreceptor is drum-shaped, but the same applies even if the photoreceptor is belt-shaped. Further, in the above embodiments, a photoreceptor having a photoconductive layer on the surface was used as an electrostatic latent image carrier, but an insulating material can also produce the same effects as in the above embodiments.

(Effects of the Invention) As explained above, the present invention provides an electrostatic latent image carrier that is charged and imagewise exposed to form an electrostatic latent image, and an electrostatic latent image carrier that carries a developer on its surface. a developing roller that performs development in contact with the electrostatic latent image bearing member; a developing roller supporting means capable of switching the developing roller between a contact state and a non-contact state with respect to the electrostatic latent image carrier; After the electrostatic latent image carrier rotates, the developing roller is rotated and brought into contact with the electrostatic latent image, and after the development operation is completed, the developing roller is rotated while the electrostatic latent image carrier is rotating. Since the developing roller state switching means is configured to switch the state of the developing roller to a non-contact state with respect to the electrostatic latent image carrier while the electrostatic latent image bearing member is in contact with the electrostatic latent image carrier, deformation of the developing roller or the photoreceptor can be eliminated and toner consumption can be reduced. Furthermore, it is possible to use materials that easily contaminate the latent image carrier as the developing roller.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is a sectional view showing a developing device during a developing operation, and Fig. 2 is an operation of bringing the developing roller into contact with a photoreceptor before the developing operation in the developing device. 3 is a sectional view showing the operation of separating the developing roller from the photoreceptor after the development operation is completed in the developing device, and FIG. 4 is a sectional view showing the state in which the printing operation is completed in the developing device. 5 is a timing chart showing control timing. FIG. 6 is a cross-sectional view showing a conventional developing device in which the photoreceptor and the developing roller are stopped while in contact. 1... Electrostatic latent image carrier, 4... Developing roller, 8.9.11... Developing roller support means, 15°1
6.17 . . . Developing roller state switching means. Applicant Matsushita Electric Industrial Co., Ltd. Representative Patent Attorney Shigetaka Awano and 1 other person 0 ψ \, (In <D \ 0 ψ

Claims (1)

[Scope of Claims] An electrostatic latent image carrier that is charged and imagewise exposed to form an electrostatic latent image, and a developer that is carried on the surface and is brought into contact with the electrostatic latent image carrier to perform development. a developing roller; a developing roller support means capable of switching the developing roller to a contact state or a non-contact state with respect to the electrostatic latent image carrier; and a means for rotating the electrostatic latent image carrier before starting a developing operation. After the development operation, the developing roller is rotated while the electrostatic latent image carrier is brought into contact with the electrostatic latent image, and after the development operation is completed, the electrostatic latent image carrier is rotated while the developing roller is rotated. 1. A printing device comprising a developing roller state switching means for switching a developing roller state to a non-contact state.