JPH0746929Y2 - Transfer device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus that forms an image using an electrophotographic process, and more particularly to a transfer apparatus that transfers a toner image on an image carrier to a sheet.

[Prior Art] An image forming apparatus that forms an image using an electrophotographic process such as an electrophotographic copying machine and various printers includes a charger, an exposure unit, and a developer on the peripheral surface of an image carrier (for example, a photosensitive drum). ,
An image forming member such as a transfer device and a charge eliminating brush is provided, and the electrostatic latent image formed by the charging device and the exposure means is developed by the developing device (toner image formation), and this toner image is transferred onto the sheet by the transfer device. ing. Further, the paper on which the toner image is transferred by the transfer device is sent to a fixing device for fixing the toner image on the paper while contacting the static elimination brush.

FIG. 3 is a configuration diagram of the transfer device 7 including the transfer device and a circuit for supplying a high voltage to the transfer device (however, the photosensitive drum 1 is also shown in the drawing). As shown in the figure, a predetermined high voltage is applied from the high voltage circuit 3 to the transfer device 2, and the output current is controlled by the constant current control circuit 4 so that a constant high voltage is applied to the transfer device 2. There is. The transfer device 2 is composed of a corona discharge line 2a and a shield case 2b, and the corona discharge line 2a is moved to the photosensitive drum 1 by applying the above-mentioned high voltage.
A corona discharge is performed to transfer the toner image onto a sheet (not shown) conveyed between the photoconductor drum 1 and the transfer device 2. The static elimination brush 5 has one end grounded and a brush portion 5a formed at the other end. Then, the brush portion 5a comes into contact with the back surface of the conveyed paper to remove the charge on the paper.

[Problems of conventional technology]

In the conventional transfer device as described above, the shield case 2b prevents the corona discharge current from the corona discharge line 2a from leaking to the outside.However, due to the conditions of the installation position of the electrophotographic copying machine, etc. (High temperature, high humidity, low temperature, low humidity) changes, the resistance value of the atmosphere changes, and the corona discharge current is affected accordingly. Particularly, when the humidity is high, the corona discharge current from the corona discharge wire 2a leaks to the brush portion 5a and flows to the ground via the static elimination brush 5. This leak current flows into the high-voltage circuit 3 via the static elimination brush 5 → constant current control circuit 4 as shown in the path 6, and the constant current control circuit 4 carries out current control including this leak current, so that the photoconductor drum 1 is reached. It reduces the corona discharge current that should flow. For this reason, the transfer of the toner image onto the paper becomes insufficient, and good transfer cannot be performed.

[Purpose of device]

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a transfer device capable of performing excellent transfer without being affected by environmental conditions.

[Key points of device]

In order to achieve the above-mentioned object, the present invention provides a toner formed on the surface of an image bearing layer by outputting a corona discharge current by facing the image bearing body in which an image bearing layer is laminated on a grounded conductive substrate. A corona discharge electrode for transferring an image to a transfer sheet that is conveyed, a shield member provided to surround the corona discharge electrode except for a portion which is grounded and faces the image carrier, and the corona discharge. Immediately after transfer by the corona discharge electrode, a high-voltage generating circuit and a constant current control circuit that are arranged in series between the electrode and the ground in order to apply a voltage to the corona discharge electrode, and are provided with a predetermined gap from the image carrier. And a charge removing member for removing charge on the transfer material, the charge removing member is electrically connected to a connection portion of the high-voltage generating circuit and the constant current control circuit, and a diode is connected from the connection portion. A circuit for grounding via a magnetic field is provided, and of the trona discharge current output from the corona discharge electrode, a feedback current returning from the conductive base of the image carrier via ground and the shield member via ground. And a feedback current to be fed back to the high-voltage generating circuit through the constant-current control circuit, and a leak current of the corona discharge current flowing to the static elimination member is returned to the high-voltage generating circuit without passing through the constant-current control circuit. At the same time, the discharging current flowing from the transfer material to the discharging member is made to flow to the ground via the diode.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic configuration diagram of a liquid crystal printer using the transfer device of one embodiment. In FIG. 1, the liquid crystal printer 8 includes a photosensitive drum 9, a charging device 10, a print head 11, a developing device 12, a transfer device 13, which are sequentially arranged near the peripheral surface of the photosensitive drum 9.
It is composed of a static eliminating brush 14 and a cleaner 15. Charger 10
Is an apparatus that applies an initial charging voltage to the photosensitive surface of the photosensitive drum 9 that rotates in the direction of arrow A, and the print head 11 is an apparatus that exposes the photosensitive surface based on image data. Developer 12
Is a device for converting the electrostatic latent image formed on the photosensitive surface by the above-mentioned exposure into a toner image (visualization), and the transfer device 13 is a device for transferring the toner image onto the sheet P. The static elimination brush 14 is
The cleaner 15 is a device for removing charges on the paper P, and the cleaner 15 is a device for removing toner remaining on the photosensitive surface. The sheet P is transported in the direction of arrow B by a sheet transport mechanism (not shown). The above-mentioned transfer device 13 is a transfer device together with the high-voltage circuit unit 16.
Make up 17

FIG. 1 is a diagram showing a detailed configuration of the above-mentioned transfer device 17 (however, the photosensitive drum 9 is also shown). As shown in the figure, the transfer device 13 is composed of a corona discharge wire 13a stretched in the direction perpendicular to the paper surface of the figure and a shield case 13b extending similarly to the direction perpendicular to the paper surface. High voltage circuit section 16
Is composed of a high voltage circuit 18, a constant current control circuit 19, and a diode 20 connected between a connection point C between the circuits 18 and 19 and the ground. A backflow prevention diode 21 is also connected to the output of the constant current control circuit 19.

In the transfer device 17 thus configured, when the paper P is conveyed between the photoconductor drum 9 and the transfer device 13, a predetermined high voltage is output from the high voltage circuit 18 to the corona discharge line 13a, and the output current at this time is Constant output current controlled by constant current control circuit 19
i _a . The corona discharge line 13a outputs a corona discharge current to the photosensitive surface via the paper P, and at this time, the corona discharge current i _b output from the corona discharge line 13a transfers the toner image on the photosensitive surface to the paper P. The corona discharge current i _b thus output to the photoconductor drum 9 flows into the ground of the photoconductor drum 9. In addition, a part of the corona discharge current (corona discharge current i _c ) output from the corona discharge line 13a is part of the shield case 13b.
Through to the ground. Furthermore, a part of the corona discharge current flows into the charge removal brush 14 via the brush portion 14a as a high-humidity leak current i _d . The above-mentioned corona discharge currents i _b and i _c are respectively input to the constant current control circuit 19 via the ground, and the constant current control circuit 19 compares them with a predetermined current value (regular predetermined current i _a to the corona discharge line 13). Then, the control current based on the comparison value is applied to the high voltage circuit 18
Output to. On the other hand, the leakage current i _d is the arrow D shown in FIG.
Input to the high voltage circuit 18 through the above-mentioned connection point C as shown in FIG. The leakage current i _d does not flow to the high voltage circuit 18 via the circuit of the diode 20 → ground → constant current control circuit 19 because the ground portion is actually formed by many mechanical parts. This is because the leak current i _d flows through the shortest circuit (arrow D) that is connected. Therefore, the leak current i _d is not input to the constant current control circuit 19, and the constant current control circuit 19 is not affected by the leak current i _d . Therefore,
An output current i _a of _a constant value can always be supplied to the corona discharge line 13a, and a constant corona discharge current can be output to the photosensitive surface.

On the other hand, when the brush portion 14a comes into contact with the paper P to remove the electric charge on the paper P, the static elimination brush 14 has a static elimination current i _e at this time.
Flows into the ground through the diode 20 as shown by the dotted line in FIG. 1 and removes the charges on the paper P.

As described above, in this embodiment, the corona discharge current (leakage current i _d ) leaking from the corona discharge line 13a to the static elimination brush 14 is directly fed back to the high voltage circuit 18 without passing through the constant current control circuit 19 even in high humidity. Thus, the constant current control circuit 19 can accurately perform the constant current control.

Although the transfer device is applied to the liquid crystal printer 8 in this embodiment, it is needless to say that the transfer device is not limited to the liquid crystal printer.

[Effect of device]

As described in detail above, according to the present invention, a constant corona discharge current can be supplied to an image carrier such as a photoconductor drum even at high humidity, and a good toner image transfer can be realized.

Further, the present invention can be easily constructed by simply connecting the diode to a predetermined circuit.

[Brief description of drawings]

FIG. 1 is a block diagram of a transfer device of one embodiment, FIG. 2 is a block diagram of a liquid crystal printer to which the transfer device of one embodiment is applied, and FIG. 3 is a block diagram of a conventional transfer device. 13 …… Transfer device, 13a …… Corona discharge wire, 13b …… Shield case, 17 …… Transfer device, 18 …… High voltage circuit, 19 …… Constant current control circuit, 20 …… Diode.

Claims (1)

[Scope of utility model registration request] 1. A transfer method in which a toner image formed on the surface of an image bearing layer is conveyed by outputting a corona discharge current by facing an image bearing body having an image bearing layer laminated on a grounded conductive substrate. A corona discharge electrode to be transferred to paper, a shield member provided to surround the corona discharge electrode except for a portion which is grounded and faces the image carrier, and between the corona discharge electrode and the ground in order. A high voltage generating circuit and a constant current control circuit which are arranged in series and apply a voltage to the corona discharge electrode, and a charge on the transfer material immediately after transfer by the corona discharge electrode, which is provided with a predetermined gap from the image carrier. In a transfer device provided with a charge removing member for removing charge, the charge removing member is electrically connected to a connection portion of the high-voltage generating circuit and the constant current control circuit, and grounded via a diode from the connection portion. A circuit is provided, and among the corona discharge currents output from the corona discharge electrode, a feedback current returning from the conductive base of the image carrier through the ground and a feedback current returning from the shield member through the ground. Is fed back to the high voltage generation circuit through the constant current control circuit, and the leak current of the corona discharge current flowing to the static elimination member is fed back to the high voltage generation circuit without passing through the constant current control circuit, and at the same time, the transfer material. 2. A transfer device, characterized in that a static elimination current flowing from the static elimination member to the static elimination member is caused to flow to the ground via the diode.