JPH0440199Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a recording device such as an electrophotographic copying device, and particularly to a discharge device such as a charger or a transfer device using corona discharge.

[Prior art]

A discharge device used in a recording device, such as a charger or a transfer device, applies a high voltage to a discharge wire to generate a corona discharge, a charger applies a uniform charge to the photosensitive surface, and a transfer device creates a toner image on a transfer paper. is transcribed. For this reason, it is necessary to connect a high-voltage power source to the discharge line provided in the charger, transfer device, etc.

Conventionally, this high-voltage power source has been divided into two types: one is a discharge device that uses two separate power supplies to supply the charger and the transfer device, and the other is a discharge device that uses a single high-voltage power source for both the charger and the transfer device. exists. For example, when two high-voltage power supplies are used, a high-voltage power supply 3 dedicated to the charger 2 is used for the charger 2, which is desired to uniformly charge the surface of the photoreceptor 1, as shown in FIG. The transfer device 4 is equipped with a high-voltage power supply 5 exclusively for the transfer device.
is used. Therefore, the image forming process of a recording device using such a conventional discharge device requires a high-voltage power source 3.
A charger 2 to which a high voltage is applied applies a uniform charge to the photoreceptor 1, and the photoreceptor 1 is charged by blank exposure 6, image exposure 7, and development by a developer 8.
The toner image formed is transferred to a transfer paper by a transfer device 4 to which high voltage from a high voltage power source 5 is applied, and then residual toner is removed by a cleaner 9 and an eraser 10
The charge is removed by

On the other hand, when a single high-voltage power source is commonly used for the charger and the transfer device, the same output of the high-voltage power source is supplied to the charger and the transfer device.

[Problems with conventional technology]

In the conventional discharge device as described above, connecting multiple high-voltage power supplies to each discharge device individually increases the cost of the recording device itself because the high-voltage power source is expensive, and also limits the miniaturization of the recording device. will be given. On the other hand, in a usage method where a single high-voltage power supply is simply shared between a charger and a transfer device,
Since multiple outputs are obtained from one high-voltage power supply, charging timing a and transfer timing b should normally be controlled differently as shown in Figure 3, but charging and transfer are controlled differently as shown in Figure 3c. They have no choice but to do it at the same time. In this case, high voltage is applied to the charger 2 or the transfer device 4 at unnecessary times during the copying process, charging unnecessary portions of the photoreceptor 1 and consuming unnecessary toner.

[Purpose of invention]

The present invention has been devised in view of the above-mentioned drawbacks of the conventional methods, and the high-voltage power supply for each discharge device is shared, and each discharge device is
The object of the present invention is to provide a discharge device that allows the ON and OFF timings to be set individually.

[Key points of the idea]

According to the present invention, the above object includes a plurality of dischargers disposed facing different parts of the peripheral surface of the electrostatic latent image carrier and to which the same output from the DC high voltage power supply is always commonly supplied. At least one of the dischargers includes a discharge wire, a shield member surrounding a part of the periphery of the discharge wire, a grid member electrically connected to the shield member, and a potential of the shield member and the grid member set to a predetermined potential. or switching means for switching to the ground potential, and the switching means sets the grid member to the ground potential, thereby prohibiting the action of the discharger on the electrostatic latent image carrier, and disabling the plurality of discharges. This is achieved by providing a discharge device that selectively operates electric appliances.

[Example of idea]

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

In this embodiment, the discharge device of the present invention is applied to a charging device and a transfer device placed near a photoreceptor drum, and Fig. 1 shows a part of a recording device using this charging device and transfer device. A configuration diagram is shown. In the figure, a charger 12, a developing device 13, a transfer device 14, and a cleaner 15 are provided near the photosensitive surface 11a of the photosensitive drum 11, and the photosensitive drum 11 is provided with a conductive base member and a surface of the base member. The base member is grounded. In addition, the charger 12 is a corona discharge wire 12.
a, a shield plate 12b, and a grid 12c, the discharge wire 12a is connected to the high voltage output of a constant current high voltage power source 16, the shield member 12b and the grid 12c are electrically connected, and grounded via a constant voltage element 17. and is grounded via a switch 18 connected in parallel to the constant voltage element 17. Further, the transfer device 14 includes a corona discharge wire 14a and a shield plate 14b.
is connected to the high voltage output of the same high voltage power supply 16 to which the corona discharge wire 12a of the charger 12 described above is connected, and the shield 14b is grounded. Furthermore, the ground terminal of the high voltage power supply 16 is grounded.

To briefly explain the operation of the recording apparatus configured as described above, first, a uniform charge is applied to the photosensitive surface 11a of the photosensitive drum 11 rotating in the direction of the arrow 19 by the corona discharge wire 12a of the charger 12. Give. Photosensitive surface 11a uniformly charged
When the light reaches the exposure section, the reflected light of the light irradiated onto the document (not shown) is exposed 20 to the photosensitive surface 11a through a lens (not shown), forming an electrostatic latent image of the document on the photosensitive surface 11a.

Further, when the electrostatic latent image formed on the photosensitive surface 11a reaches the developing section, the electrostatic latent image formed on the photosensitive surface 11a is transferred to the developing device 13 by the developing device 13.
3 is visualized to form a toner image. This toner image is transferred to a transfer paper that is conveyed to the transfer section by a mechanism (not shown) by a corona discharge of the corona discharge wire 14a to which a high voltage is applied to the transfer device 14, and the transfer paper is conveyed. After the toner image is thermally fixed by the fixing device, it is carried out of the machine. On the other hand, the toner that has not been completely transferred by the transfer device 4 remains as residual toner on the photosensitive surface 11a. Various charges are applied.

The relationship between the corona discharge in the charger 12 and the transfer device 14 of the present invention used in the recording apparatus having the above configuration and recording process and the high voltage power supply 16 will be described below.

First, when the charger 12 and the transfer device 14 are used at the same time, for example at the start of an image forming process, the switch 18 is in an open state, and a voltage is output from the high voltage power supply 16 according to the operation signal of the recording device. A high voltage is applied between the discharge wire 12a and ground. At this time, the corona current of the charging device 12 flows to the photosensitive drum 11, the shield plate 12b, and the grid 12c. A predetermined voltage is generated in the constant voltage element 17 by the corona current flowing toward the shield plate 12b and the grid 12c, and the potential of the grid 12c becomes equal to the voltage generated in the constant voltage element 17. As a result, corona discharge toward the photoreceptor drum 11 is controlled, and the photoreceptor drum 11 is charged to a voltage specified by the constant voltage element 17.

On the other hand, corona discharge is also performed on the transfer device 14, and the discharge current flows to the photosensitive drum and the transfer shield 14b.

Next, when stopping only the operation of the charger 12,
For example, at the end of the charging process, that is, when the position of the photosensitive surface 11a corresponding to the area without or between the transfer sheets (not shown) approaches the charger 12,
Switch 18 is closed. At this time, since it is grounded to the shield plate 12b and grid 12c,
Most of the corona current of the charging device 12 flows to the shield plate 12b and the grid 12c, and no current flows to the photosensitive surface 11a side. This state is the same as when only the charging device 12 is turned off. Therefore, the portion of the photoreceptor 11 that does not correspond to the transfer paper (not shown) is not charged. Therefore, unlike the conventional case, unnecessary charging is not performed, and toner consumption in the developing device 13 can be avoided.

Although the above embodiment describes an example in which the corona discharge action of the charger 12 is substantially stopped, the present invention is not limited to this, and by using the same configuration for other dischargers, a single high voltage Even in a discharge device in which a plurality of dischargers are operated by a power source, each discharger can be turned on and off at individual timings.

Furthermore, when the common high-voltage power supply 16 is used for both charging and transfer as in the past, the on and off timings for charging and transfer are common, and the charges formed on the photosensitive surface 1a between the transfer sheets are reduced. Blank exposure is necessary for erasing, but in the present invention, unnecessary charging is not performed, so blank exposure is not necessary.

[Effect of idea]

As explained in detail above, according to the present invention, by using a single high-voltage power source to supply power to, for example, a charger and a transfer device, it is possible to reduce the cost of the device, and also to reduce the need for unnecessary parts on the photosensitive surface. Since no static electricity is applied, waste of toner can be prevented. Further, blank exposure for eliminating the potential of the photoreceptor in the portion corresponding to the space between the transfer sheets becomes unnecessary.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a recording device including the discharge device of the present invention, Fig. 2 is a block diagram of a conventional recording device, and Fig. 3 is a time chart showing the output timing of a high-voltage power source used in a conventional discharge device. It is a diagram. 11... Photosensitive drum, 12... Charger, 12
a, 14a...corona discharge wire, 12b, 14b...
...shield plate, 12c...grid, 14...transfer device, 16...high voltage power supply, 17...constant voltage element,
18...Switch.

Claims (1)

[Scope of utility model registration request] It includes a plurality of dischargers arranged facing different parts of the peripheral surface of the electrostatic latent image carrier and to which the same output from the DC high voltage power supply is always commonly supplied, and at least one of the dischargers is connected to a discharge wire. , a shield member surrounding a part of the periphery of the discharge wire, a grid member electrically connected to the shield member, and a switching means for switching the potentials of the shield member and the grid member to a predetermined potential or a ground potential. and the plurality of dischargers are selectively operated by setting the grid member to a ground potential by the switching means, thereby prohibiting the discharger from acting on the electrostatic latent image carrier. A discharge device that uses