JPS5898761A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the abnormal discharge, by actuating a developer supporting means when a mobile latent image supporting means moves and a latent image to be developed passes a developing part and holding the developer at such potential state in which the developer does not come off from a fiber brush while the developer supporting means is at pause. CONSTITUTION:A changeover switch 14 is connected to a contact 14' as soon as a roller 9 starts its rotations immediately before a latent image to be developed reaches a developing part D and after a photoreceptor 1 starts its rotations and a latent image forming means 3 starts its operation and at a time point when the latent image to be developed reaches the part D. Then the voltage supplied from an alternating bias power supply 13 is applied to a developing roller 7. The roller 9 is grounded electrically at a time point when the photoreceptor 1 keeps its rotations and the latent image to be developed has passed through the part D. As a result, the abnormal discharge is prevented to prevent the scattering the toner from a fiber brush 8. Thus the uneven coating is avoided for the toner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device, and more particularly to a developing device.
The present invention relates to a developing device in which a one-component developer is supplied to a fiber brush, the fiber brush coated with the developer is placed in contact with or close to a latent image support, and the developer supporting means 3Jtm is provided.

- A developing device using a component developer, especially a non-magnetic one-component developer, in which the developer is conveyed to a latent image support (electrophotographic photoreceptor, etc.) by a developing roller having a fiber brush surface on the base roller. Devices configured to supply the same are known. If an alternating bias voltage is applied to this developing roller to form an alternating electric field between the roller and the latent image support, the brush fibers will vibrate due to this electric field, improving the friction between the brush fibers and the developer and developing the image. By increasing the triboelectric charge of the agent and loosening the developer particles so as to separate them from the brush, the developer density can be increased, the gradation is good, and sharp images can be obtained. However, in this case, when an alternating electric field is applied while the latent image support and the image lifting roller are stationary, the 3A developer is abnormally detached from the brush, and the developer is scattered to the side near the developing section where the electric field is weaker. . This is thought to be because the alternating electric field of the brush causes the developer support to vibrate even when it is stationary. For this reason, the scattered developer accumulates on the developing roller, which has been uniformly coated with developer, before development, resulting in surface unevenness. If development is performed in such a coating state, an image will be uneven. Further, when the developer is removed from the brush due to the above-mentioned scattering, an abnormal discharge phenomenon occurs between the brush and the support, especially when the resistance of the brush is low.

Further, it is not preferable to apply the violet developer removed by the above-mentioned scattering to the brush in a uniform manner in a predetermined amount of noise because it adds a load to the supply application system.

As mentioned above, there are many troubles caused by applying an alternating electric field while the developer support is stationary.

An object of the present invention is to provide a developing device that solves the above-mentioned disadvantages.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram of an embodiment of the present invention. In the figure, reference numeral 1 is provided on the circumferential surface of a drum-shaped conductive support 20 which is rotated in the direction of the arrow by an electrophotographic photoreceptor. Photoreceptor 1 rotates as it rotates.

Well-known electrostatic ffI image forming means 5 comprising a light-emitting device or the like.
, an electrostatically deposited image to be developed is formed.

This latent image is developed by a developing device 4, which will be described later, using a one-component developer that is a non-magnetic insulating toner. The toner image thus obtained is transferred onto a transfer paper by a well-known transfer means 5 comprising a transfer charger, a paper conveyance device, etc. The toner image transferred to the transfer paper is fixed to the paper by a well-known fixing device (not shown), while the surface of the photoreceptor after the transfer is cleaned by a well-known cleaning means 6 comprising a toner removing device or the like.

The developing device 4 has a developing roller 9 that rotates in the stamp direction. The developing roller 9 is constructed by providing short fiber pushers 8 on the surface of the roller 7, which is formed by providing a layer of conductive elastic material such as a conductive sponge on the surface needle or core roller of the metal roller 7.

In the illustrated embodiment, the average thickness is 1 denier and the average length is 0.8
A brush 8 obtained by electrostatically flocking am nylon yarn onto the surface of the conductive roller 7 is used. In the illustrated example, the minimum gap between the surface of the roller 7 and the surface of the photoreceptor 10 without the brush 8 is set to 0.911 un, so the brush 8 is substantially not in contact with the photoreceptor 1. (However, it is normal for some brush fibers to have an average length of 0.8 mm and some fibers exceeding 0.9 mm, so some fibers may come into contact with the photoreceptor.) The brush 8 may be brought into substantial contact with the photoreceptor 1, but in this case the roller 9. Photoreceptor 1
An alternating electric field is formed between the rollers 9 and 5, and the brush fibers become distorted when the roller 9 stops rotating.

Reference numeral 10 denotes a hopper that supplies a one-component insulating non-magnetic developer (hereinafter also referred to as toner) 11 to the brush 8;
The toner supplied to the brush 8 from the toner is regulated by the application brush 12 which is in contact with the east brush 8, and is uniformly applied to the bottom brush 8. During this application, the toner is between the brush 8.12,
Due to friction, it is charged to the opposite polarity to the dark potential of the latent image.

A power supply 15 applies a developing bias voltage to the developing roller 7. As the power supply 13, an alternating voltage source or a voltage source in which a direct current voltage is superimposed on an alternating voltage is used. For example, while the dark area is +600 V and the bright area is +50 V, the developing roller 2 is supplied with 1800 Vpp, 800 Hz A,
A developing bias in which a DC voltage of +250 V is superimposed on the C voltage is applied to the roller 9 to develop the latent image.

On the other hand, the conductive support 2 of the photoreceptor 1 is electrically grounded. In this way, an alternating electric field is formed between the photoreceptor 1 and the developing roller 9, which causes the fibers of the brush 8 to vibrate in the developing section, and toner is ejected from the brush 8.

When the direction of the alternating electric field is such that the toner is urged toward the photoreceptor, the toner flies through the gap between the brush and the photoreceptor and reaches the photoreceptor 1. When the direction of the alternating electric field is reversed, the toner that was in the bright potential area of the photoconductor 1 flies through the gap and returns to the brush 8, but the toner that was in the bright potential area of the photoconductor 1 is electrostatically transferred to the dark potential area of the photoconductor 1. The adsorbed toner continues to adhere and does not return to the brush 8, but leaves the developing section.

Reference numeral 14 designates a changeover switch which is used to switch the rotation of the roller 9 after the photoconductor 1 starts rotating and the rotation forming means 6 starts operating, just before the latent image to be developed reaches the developing section DK, or slightly later than that. When the latent image to be developed reaches the developing section DKX, the contact 14' is connected, and the voltage from the alternating bias power supply 16 is applied to the developing roller 7, and the photoreceptor 1 continues to rotate until the latent image to be developed reaches the developing part DKX. When the development is completed, that is, when the image has passed through the development section, the roller 9 stops rotating and at the same time the contact 1 is opened.
4" to electrically ground the roller 9.

When roller 9 is electrically grounded, no toner is dissipated from brush 8.

Figure 2 shows the sequence related to a misfire. When the main switch is turned on, the photoconductor 1 rotates, a preparatory rotation is performed to equalize the sensitivity of the photoconductor, and then the photoconductor enters a standby state. stops rotating. Next, in response to a copy-on command, the photoreceptor 1 performs a pre-rotation to equalize the potential state and sensitivity around the entire circumference, and then i! to form a latent image. l
I-image exposure is started. In the following steps, the developing roller 9 starts rotating a little before the latent image formed by the non-lighting reaches m'GIImDK, and then a developing bias is applied until the latent image completes passing 48 copies. Continue applying for
When the image leaves the image 48, the rotation of the roller 9 is stopped and the switch 14 is switched to the contact 14''.

The photoreceptor 1 continues to rotate, the image on the photoreceptor is transferred to the transfer paper, and the photoreceptor 1 undergoes post-rotation for a period of time to make the photoreceptor uniform, and enters a standby state.

In addition, in FIG. 2, the application period of the developing bias is 3jts.
Although it is set within the rotation period of the roller, it can also be set at 1 ilJ or outside the rotation period of the roller as long as the above-mentioned abnormal scattering of toner does not occur by gradually applying bias.

As described above, according to the present invention, it is possible to provide a developing device having a structure in which uneven coating due to abnormal flying of developer is eliminated and load is not placed on the supply coating system.

[Brief explanation of the drawing]

FIG. 1 is a decoy for explaining one embodiment of the present invention, and FIG. 2 is an explanatory diagram of an operation sequence. 1 is an electrophotographic photosensitive member, 8 is a brush, 9 is a developing roller,
16 is an alternating power supply, and 14 is a changeover switch.

Claims (1)

[Scope of Claims] A developing device that develops the latent image by applying an alternating electric field between a movable developer support means having a fiber brush for conveying the developer and a movable latent image support means. When the supporting means moves and the latent image to be developed passes through the developing section, the developer supporting means is moved and the alternating electric field is applied. fJL111! to a potential state that does not leave from. A developing device characterized by holding agent supporting means.