JPH0274975A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain the electrophotographic device in which one piece of electrifier required for a transfer drum is enough by providing the transfer drum provided with a dielectric layer on the surface of a metallic roll, and the corona electrifier which is placed in the vicinity of a transfer paper peeling position of said transfer drum and driven selectively by a unipolar power source. CONSTITUTION:In a transfer drum 16, a dielectric layer 19 consisting of, for instance, a dielectric film is laminated and attached to the surface of a metallic roll 17 through a dielectric rubber layer 18. An electrifier 20 is placed in the vicinity of a peeling position for transfer paper 11, and driven selectively by a unipolar power source 21. In such a way, the electrifier 20 required for the transfer drum 16 is only one piece provided in the vicinity of the peeling position for the transfer paper 11, and as to a power source for driving the electrifier, as well, one piece of unipolar power source 21 is enough, the structure becomes simpler than a conventional one, a control system can also be simplified, and the whole device can be miniaturized. In such a way, an electrophotographic device in which one piece of electrifier required for the transfer drum is enough can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrophotographic apparatus, and more particularly, to an improvement in a portion for transferring a toner image onto a transfer paper.

(Prior Art) A type of electrophotographic apparatus is configured to develop an electrostatic latent image formed on a photosensitive drum by attaching toner to it, and then transfer this toner image onto transfer paper wrapped around a transfer drum. There is something.

FIG. 2 is a configuration explanatory diagram showing an example of such a conventional device. In FIG. 2, 1 is a photosensitive drum, and 2 is a charger that charges the photosensitive drum 1 to a positive polarity. 3 is a semiconductor laser that is driven on and off in accordance with a recording signal to selectively form an electrostatic latent image on the photosensitive drum 1;
Its output beam is a polygon mirror 4. The light is incident on the positively charged surface of the photosensitive drum 1 through an optical system consisting of an fθ lens 5 and a mirror 6. A developing device 7 applies toner to the electrostatic latent image formed on the surface of the photosensitive drum 1 to develop the image. 8 is a transfer drum composed of a mesh screen made of an insulator, and a paper feed roll 9
A transfer paper 11 is then wound around the pressure roller 10 . 12 is a charger that charges the transfer drum 8 to electrostatically attract the transfer paper 11 to the transfer drum 8; 13 is a photosensitive member of the transfer drum 8 that is used to transfer the toner image formed on the photosensitive drum 1 onto the transfer paper 11; A charger 15 is arranged inside the drum 1 to face the drum 1, and a charger 15 is a transfer drum near the peeling part to neutralize and eliminate the charge on the transfer drum 8 in order to peel the transfer paper 11 electrostatically attracted to the transfer drum 8. This is a charger placed inside the 8. A fixing device 15 fixes the toner image transferred to the transfer paper 11. 16 is a cleaner for removing residual toner adhering to the photosensitive drum 1; 17;
is an eraser that uniformly irradiates the entire surface of the photosensitive drum 1 to neutralize and remove the electrical charge, thereby setting the photosensitive drum 1 to an initial state.

With this configuration, a toner image obtained by developing an electrostatic latent image formed on the photosensitive drum 11 is transferred and fixed onto the transfer paper 11.

(Problems to be Solved by the Invention) However, according to such a conventional configuration, the transfer drum 8
One charger 12 must be provided outside the transfer drum 8, and two chargers 13 and 14 must be provided inside the transfer drum 8, making it difficult to downsize the device. In addition, multiple power supply circuits are required to drive these chargers individually.
Their control also becomes complicated.

The present invention has focused on this point, and an object thereof is to provide an electrophotographic apparatus in which only one charger is required for the transfer drum.

(Means for Solving the Problems) The electrophotographic apparatus of the present invention develops an electrostatic latent image formed on a photosensitive drum by attaching toner to it, and transfers this toner image onto a transfer paper wrapped around a transfer drum. An electrophotographic apparatus configured to perform transfer includes a transfer drum having a dielectric layer provided on the surface of a metal roll, and a transfer drum located near the transfer paper peeling position of the transfer drum and selectively driven by a unipolar power source. It is characterized by being equipped with a corona charger.

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

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, and the same parts as in FIG. 2 are given the same reference numerals. In FIG. 1, 16 is a transfer drum, and a dielectric layer 19 made of, for example, a dielectric film is laminated and adhered to the surface of a metal roll 17 with a dielectric rubber layer 18 interposed therebetween. Reference numeral 20 denotes a charger, which is arranged near the peeling position of the transfer paper 11. 21 is a unipolar power source that selectively drives the charger 20.

The operation of the device configured in this way will be explained.

The metal roll 17 of the transfer drum 16 is grounded, and the wire of the charger 20 is driven with a negative high voltage output from the unipolar power source 21 while the transfer drum 16 is rotated. As a result, the dielectric layer 19 is charged to a negative potential by the corona ions. Dielectric layer 19 is -16
When charged to a surface potential of 00 to -2000V, charger 2
Turn off the power to 1. In this state, when the transfer paper 11 is sent out so as to be pressed against the transfer drum 16 via the paper feed roller 9° and the pressure roller 10, the transfer paper 11 is electrostatically attracted to the transfer drum 16 and wound around it. The surface potential of the transfer paper 11 wound around the transfer drum 16 in this manner is approximately 11ooov, which is sufficient to transfer a 1 to toner image.

In synchronization with the winding of the transfer paper 11 around the transfer drum 16, an electrostatic latent image is formed on the photosensitive drum 1 and the electrostatic latent image is developed with toner. Then, the transfer paper 11 is aligned, and the toner image is transferred to the transfer paper 11 at the contact portion between the photosensitive drum 1 and the transfer drum 16.

- When reverse transfer is performed, the surface potential of the transfer paper 11 is neutralized by the glass charge of the toner and the positive charge of the photosensitive drum 1 and lowers. In the case of color development, it is necessary to repeat development and transfer three times, so when the transfer paper 11 comes to the position of the charger 20, the charger 20 is energized to replenish the transfer paper 11 with negative charge. For this kind of charge replenishment,
The voltage or current is made smaller than the initial charging value.

If the charger 20 is driven under the same conditions as the initial charging, the potential difference between the transfer paper 11 and the dielectric layer 19 will disappear, and the charges on both the transfer paper 11 and the dielectric layer 19 will repel each other, and the transfer paper 11 will be transferred. It peels off from drum J-6.

To separate the transfer paper 11 from the transfer drum 16 after the transfer is completed, the charger 20 is initialized for a short period of time (for example, about 0.5 seconds) when the leading edge of the transfer paper 11 is not at the position of the charger 20. Drive under the same conditions as for charging. As a result, the leading edge of the transfer paper 11 is peeled off from the transfer drum 16 and lifted up, and is sent to the fixing device 15.

According to such a configuration, the only charger required for the transfer drum 16 is the one installed near the peeling position of the transfer paper 11, and the power source for driving the charger only needs to be a unipolar power supply, which is different from the conventional one. The structure is simpler than that, the control system can be simplified, and the entire device can be made smaller.

In the above embodiment, the conductive rubber layer 18 is interposed between the dielectric layer 19 and the metal roll 17 to impart elasticity to the surface of the transfer drum 16. As a result, the photosensitive drum 1
The contact area between the transfer drum 16 and the transfer drum 16 is wider than that in the case of mutual contact between rigid bodies, and a stable transfer operation can be obtained, but it may be omitted depending on the application.

Further, the dielectric layer is not limited to a film, but may be coated with a dielectric material, or may be formed by surface treatment.

Furthermore, the present invention is not limited to monochrome developing apparatuses as shown in the embodiments, but is also effective to multicolor developing electrophotographic apparatuses.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize an electrophotographic apparatus in which only one charger is required for the transfer drum, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention, and FIG. 2 is a configuration explanatory diagram showing an example of a conventional device. 1... Photosensitive drum, 16... Transfer drum, I7...
- Metal roll, 19... dielectric layer, 20... charger, unipolar power supply.

Claims (1)

[Scope of Claims] An electrophotographic apparatus configured to apply toner to an electrostatic latent image formed on a photosensitive drum to develop it, and to transfer this toner image to transfer paper wrapped around a transfer drum, An electronic device comprising: a transfer drum having a dielectric layer provided on the surface of a metal roll; and a corona charger disposed near the transfer paper peeling position of the transfer drum and selectively driven by a unipolar power source. Photographic equipment.