JPH0572878A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To provide a small, lightweight and inexpensive electrophotographic device which prevents, by means of a simple constitution, the movement of nonmagnetic one-component toner from a developing roller to a photosensitive body at the time of initializing the device and is free from the waste of toner and the stain of a transfer device and a sheet feeder. CONSTITUTION:The toner 3 is prevented from moving from the developing roller 1 to the photosensitive body 2 by applying a developing bias 16 of the opposite polarity to that of the electrified toner 3 to the developing roller 1 at the time of initializing the device. Oversupply of the toner 3 is suppressed by applying a developing bias 17 of the same polarity as that of the electrified toner 3 after the prescribed lapse of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus for developing an electrostatic latent image by using a non-magnetic one-component developer, and more particularly to an electrophotographic apparatus such as an electrophotographic copying apparatus, a printer and a facsimile.

[0002]

2. Description of the Related Art Conventionally, a contact developing method in an electrophotographic apparatus, that is, a method of developing an electrostatic latent image by bringing a developing roller, a web or the like into contact with a photosensitive member carrying an electrostatic latent image, is disclosed in USP 2,895. , 847 or USP
3, 152, 012 and the like are already known. By the way, in the case of the contact developing method using a non-magnetic one-component toner as a developer, there is a problem that the toner is transferred to the photoconductor even during non-developing, which causes waste of the toner, unlike the magnetic brush developing method.

In order to solve such a problem, Japanese Unexamined Patent Publication No.
Proposals such as No. 2-194272 have been made. The configuration will be described below.

FIG. 3 is a schematic configuration diagram of a conventional developing device. Reference numeral 1 is a conductive developing roller which is pressed against the photosensitive member 2 to rotate, and 4 is contacted with the developing roller 1 so that toner is formed on the surface of the roller 1. Is an electrically conductive elastic roller provided in the opening of the casing 5 for replenishing the toner. An agitator 6 prevents the toner in the casing 5 from blocking and conveys the toner to the elastic roller 4. The controller 7 is configured so that the contact pieces 8 and 9 can be switched and connected to the contact points 8a, 8b, 9a and 9b provided between the developing roller 1, the elastic roller 4 and the grounded conductor. A bias voltage can be applied to the developing roller 1 and the elastic roller 4 in order to change the attraction force of each toner at the time of development and at the time of non-development via a control device 7 connected to a power source 10.

In the above configuration, for example, when developing with a toner having a negative charging polarity, the control device 7 controls the relay control circuit 1 for switching the contact between non-developing and developing.
1 is applied to the developing roller 1 at the time of non-developing with a bias voltage of, for example, 0 V having a small toner attraction force, and the elastic roller 4 is applied with a bias voltage of, for example, +300 V having a large toner attraction force, so that the toner to the developing roller 4 is not charged. It is designed to prevent supply. Further, at the time of development, a bias voltage having a large toner attraction force of, for example, +300 V is applied to the developing roller 1, and a bias voltage of 0 V having a small toner attraction force is applied to the elastic roller 4 to replenish the developing roller 1 with toner. There is.

[0006]

However, in the above-described conventional configuration, when a part or all of the photoconductor contacting the developing roller is not charged, such as immediately after the power is turned on to the apparatus or after the jam processing, it is already possible. The toner replenished to the developing roller moves to the uncharged portion of the photoconductor.
That is, in the above configuration, the toner supply to the developing roller can be prevented only during non-developing, and the transfer of the toner already supplied to the developing roller to the photosensitive member cannot be prevented. Not only that, when it is judged that the toner is not being developed, a bias is applied to the developing roller so that the toner attracting force is small, so that the transfer of the toner to the photoconductor is promoted, which not only wastes the toner. Since the toner transferred to the photoconductor stains the transfer device and the paper feeding device, a complicated mechanism is required for cleaning them, and the device becomes large.

Therefore, the present invention solves the above-mentioned problems, and a developing device for developing an electrostatic latent image by bringing a developing roller into contact with a photosensitive member at an appropriate pressure and effectively using a non-magnetic one-component developer. It is an object of the present invention to provide an electrophotographic apparatus having the above.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a developing means for bringing a developing roller into contact with a photoconductor to develop an electrostatic latent image using a non-magnetic one-component developer, First bias means for applying a voltage having the same polarity as that of the magnetic one-component developer to the developing means, second bias means for applying a voltage having a polarity opposite to that of the first bias means to the developing means, and There is provided switching means for activating the second bias means during the initialization operation performed after power-on or after the jam processing, and activating the first bias means after a lapse of a predetermined time.

[0009]

According to the present invention, due to the above-described structure, a bias having a polarity opposite to that of the toner is applied to the developing roller even when the photoconductor has an uncharged portion at the time of the initialization operation performed immediately after the power supply to the electrophotographic apparatus or after the jam processing. Therefore, the toner can be prevented from being attracted to the developing roller and being transferred to the photoconductor.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart of the electrophotographic apparatus according to an embodiment of the present invention, and 2 is a photosensitive member holding an electrostatic latent image. The developing roller 1 is provided in contact with this, and rotates in the direction of arrow T. The developing roller 1 is made of an elastic material such as silicon rubber or polyurethane rubber having conductivity of 10 ³ to 10 ⁹ Ωcm by adding carbon. The volume resistance value of the casing 5 is 1
The non-magnetic one-component toner 3 of 0 ¹⁴ Ω · cm to 10 ¹⁶ Ω · cm is stored, and the agitator 6 prevents the toner 3 in the toner hopper 5a from blocking and conveys the toner to the elastic roller 4 for supplying toner. There is. The elastic roller 4 is made of a sponge such as urethane foam resin, and adheres the toner 3 onto the developing roller 1 at the contact portion with the developing roller 1.
Further, it rotates in the direction of the arrow while having a relative speed difference with the developing roller 1 so as to scrape off the residual toner on the developing roller 1 after the development is completed. A toner layer thickness regulating member 13 forms a uniform thin layer of the toner 3 on the developing roller 1,
In addition, in order to be charged, a material separated from the toner 3 in the triboelectric charging order is selected, and a resin material such as silicon rubber, Teflon rubber, polyimide rubber, polyester rubber or the like is a main component. The toner 3 supplied to the developing roller 1 by the elastic roller 4 regulates the amount of toner on the developing roller 1 by the toner layer thickness regulating member 13 and charges the toner 3 to the same polarity as the electrostatic latent image. Around the photoconductor 2, a charging device 12 that charges the surface of the photoconductor 2 to about -500 V, an exposure unit that irradiates a laser beam 14 according to image information by an exposure device (not shown), and the developing roller 1 is a developing bias. It is in contact with the first developing bias applying device 16 or the second developing bias applying device 17 via the switching device 15 via the rotating shaft. 18 is a transfer roller, 10 ⁶
It is a sponge roller with a hardness of about 30 degrees from Ω · cm to 10 ¹⁰ Ω · cm. The toner 3 on the photoconductor 2 is transferred onto the transfer paper 19 by the transfer roller 18 by pressure and electrostatic force. Here, the normal printing mode, that is, the printing operation performed when the electrophotographic apparatus main body (not shown) is powered on and the initialization operation is already completed will be described. When the main body of the electrophotographic apparatus receives a print command, the photoconductor 2 rotates in the direction of arrow S for printing, and the surface of the photoconductor 2 is evenly moved to −50 by the charging device 12.
It is charged to 0V. When it reaches the exposed portion, it is exposed according to the image information, and the surface potential of the exposed portion of the photoconductor 2 is about -50.
It becomes about V, and an electrostatic latent image is formed. After that, the electrostatic latent image on the photoconductor 2 reaches the developing device, but in this state,
The developing bias switching device 15 enables the first developing bias applying device 16, and the developing roller 1 has a bias voltage of −200 V, which is the charging polarity and the conducting polarity of the toner 3, as a bias voltage.
DC voltage is being applied. The toner 3 moves from the developing roller 1 to the exposed portion of the photosensitive member 2 due to the potential difference between the developing roller 1 and the exposed portion of the photosensitive member 2, and the electrostatic latent image on the photosensitive member 2 is developed. Next, the toner image on the photoconductor 2 is transferred onto the transfer paper 19 by the transfer roller 18. Then, after this, the transfer paper 19 is discharged to the outside of the main body through a fixing device (not shown), the printing process of the first sheet is completed, and the printing of the second sheet is started. However, about 10% of the toner 3 at the time of development still remains on the photoconductor 2 after the completion of the transfer in the printing process of the first sheet, but the residual toner 3 is removed by the cleaner 20. It is scraped off from No. 2 and collected in the discharged toner box 21. By the way, considering the case where the photoconductor 2 is exposed to external light before power is turned on to the electrophotographic apparatus or due to jam processing or the like, it is possible that part or all of the photoconductor 2 is not charged. There is. Here, the initialization operation performed after the power supply to the electrophotographic apparatus is turned on or after the jam processing is performed will be described. When the main body of the electrophotographic apparatus is powered on, the initialization operation is executed. Therefore, first, the photoconductor 2 is rotated in the direction of arrow S and the charging device 12 is driven to charge the photoconductor 2. However, due to the above reasons, the A portion of the photoconductor 2 may not be charged unlike the normal printing state. When the photoconductor 2 contacts the developing roller 1 in a non-charged state, the toner 3 is transferred from the developing roller 1 to the photoconductor 2. Therefore, at the time of initialization, the developing bias switching device 15 first activates the second developing bias applying device 17, and the developing roller 1 is applied with a DC voltage of +200 V having a reverse polarity to the charging polarity of the toner 3 as a bias voltage. Has been done. Therefore, the toner 3 is attracted to the developing roller 1 and does not move to the photoconductor 2. Further, even if unnecessary toner 3 is present on the portion A of the photoconductor 2 due to jam processing or maintenance, the toner is attracted to the developing roller 1, the photoconductor 2 is cleaned, and the transfer roller 18 is not contaminated. When the photoconductor 2 rotates about 1/3 to 1/2 after a predetermined time has passed since the start of the initialization operation, the photoconductor 2 contacting the developing roller 1 is already uniformly at -500V.
Is charged. Here, the developing bias switching device 1
Reference numeral 5 performs a developing bias switching operation, enables the first developing bias applying device 16, and applies a DC voltage of -200 V to the developing roller 1 as a bias voltage. This is because by applying a first developing bias having a toner repulsive force to the developing roller 1, the toner 3 excessively supplied to the developing roller 1 is scraped by the elastic roller 4 while the second bias applying device 17 is effective. This is for returning the toner 3 on the developing roller 1 to an amount suitable for developing. When the photoconductor 2 further makes one revolution from about 1/2 to 1, the apparatus completes the initialization operation and enters the print command standby state. After that, when the electrophotographic apparatus main body receives a print command, printing is performed in the normal printing state as described above. When a jam occurs during printing, the electrophotographic device interrupts the printing operation. When the user properly performs the jam processing, the electrophotographic apparatus executes the initialization operation as described above, and when the initialization is completed, the electrophotographic apparatus enters the normal print state or the print command standby state.

[0012]

As described above, according to the present invention, even if the photoconductor has an uncharged portion at the time of the initialization operation performed immediately after the electrophotographic apparatus is powered on or after the jam processing,
Since the bias having the polarity opposite to that of the toner is applied to the developing roller, it is possible to prevent the toner from being attracted to the developing roller and being transferred to the photoconductor. Therefore, waste of toner can be prevented, and the capacity of the toner hopper of the developing device and the capacity of the toner discharge box of the cleaner can be reduced. Since the developing bias is switched to the same polarity as the toner after a predetermined time, there is no problem that the toner is excessively supplied to the developing roller during the printing operation. Further, even if there is unnecessary toner on the photoconductor after the jam processing or the like, the toner is attracted to the developing roller, so that the transfer device and the paper feeding device are not contaminated by the toner. In particular, in a contact-type transfer device using a transfer roller or the like, the transfer roller is free from stains and the cause of stains on the back of the paper is eliminated.
Not only the printing quality is improved, but also it is not necessary to provide a complicated mechanism such as a separating / contacting mechanism of the transfer roller with respect to the photosensitive member or a cleaning mechanism. Therefore, it is possible to reduce the size and weight of the apparatus and to provide an inexpensive electrophotographic apparatus.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a timing chart of the electrophotographic apparatus in one embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional developing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 developing roller 2 photoconductor 3 one-component toner 4 elastic roller 5 casing 6 agitator 7 controller 8 contact piece 8a contact point 8b contact point 9 contact piece 9a contact point 9b contact point 10 power supply 11 relay control circuit 12 charging device 13 toner layer thickness regulating member 14 Laser light 15 Development bias switching device 16 First development bias application device 17 Second development bias application device 18 Transfer roller 19 Transfer paper 20 Cleaner 21 Exhaust toner box

Claims (1)

[Claims] 1. A photoconductor, an electrostatic latent image forming means for forming an electrostatic latent image on the photoconductor, and a developing roller in contact with the photoconductor, and an electrostatic latent image is formed using a non-magnetic one-component developer. Developing means for developing the latent image; first bias means for applying a voltage having the same polarity as that of the non-magnetic one-component developer to the developing means;
Second bias means for applying a voltage having a polarity opposite to that of the bias means to the developing means, and a voltage is applied to the developing means by the second bias means at the time of initialization of the apparatus, and after a lapse of a predetermined time, the An electrophotographic apparatus comprising: a switching unit that applies a voltage to the developing unit by a first bias unit.