JP2003149945A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device with a catch roll that recovers carrier sticking to the surface of a photoreceptor used in an electrophotographic device, wherein the catch roll is in inexpensive and prevents developer from sticking to and accumulating on the vicinity of the outside of the outer sleeve of a shaft. SOLUTION: The developing device has the catch roll shaft in which at least one end is made of a non-magnetic material and a portion that is in contact with a magnet within the sleeve is made of a magnetic material and thus the nonmagnetic material and the magnetic material are combined and integrated.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electrophotographic apparatus such as a copying machine and a laser beam printer. 2. Description of the Related Art A developing device using a two-component developer composed of a toner and a carrier, which is a magnetic powder, used in a conventional electrophotographic apparatus will be described. In the catch roll for collecting the carrier adhered to the photoreceptor surface together with the toner during the development, the magnet fixed inside the rotatable outer sleeve has a square cross section in the axial direction of the outer sleeve. . The shaft that holds the magnet and acts as a positioning for the magnet has a flat portion, and the flat portion and one surface of the magnet are fixed in contact with each other, so that the magnet is securely held and positioned. In addition, a magnet is located in the majority of the axial direction of the shaft, and a flat part is required to make contact with the magnet at that part. A square shaft having an axial cross section, which does not require machining of a flat portion and is inexpensive, is used as compared with a round shaft having a structure having a round axial cross section. Further, as a material of the square shaft, it is common to use a magnetic material such as a SUM material which is easy to purchase and inexpensive. [0003] However, in the above-described catch roll using the conventional magnetic shaft, a magnet forms a magnetic circuit in the axial direction of the magnetic shaft, and a magnetic field extends to the shaft end. Further, the developer containing the carrier of the magnetic powder that has come around may adhere and deposit on the end of the shaft outside the sleeve. In addition, the portion of the shaft end located outside the sleeve is located near the axial end of the photoreceptor, and the end surface of the photoreceptor is a portion in which the raw tube inside the photoreceptor on which the photosensitive layer is not applied is exposed. When the bias voltage is applied to the catch roll, the ears of the developer accumulated outside the sleeve of the shaft and the base tube on the end surface of the photoreceptor are exposed. There is a problem that the contact occurs and the bias voltage is short-circuited. The problem of the conventional developing device will be described with reference to FIG. In FIG. 2, the shaft 7c of the catch roll 7 attached to the developing device 1 is a magnetic material, and the shaft 7c
When magnetized, the developer 5 containing the wrapped magnetic powder may be deposited around the periphery of the shaft 7c located outside the sleeve 7b. The photosensitive member 4 whose surface is close to the catch roll 7 has a photosensitive layer 4b and a tubular portion 4c at both ends.
And the portion of the shaft portion 7c located outside the sleeve 7b is in the vicinity, so that the accumulated developer 5 can come into contact with the tube portion 4c. Thus, the developer 5
When the element 4c comes into contact with the element 4c, the bias voltage applied to the shaft 7c is short-circuited via the accumulated developer 5 to the element 4c grounded by a conductor. Further, if a non-magnetic material is used for the shaft so that a magnetic circuit is not formed to the end of the shaft, it is difficult to satisfy the accuracy required for the non-magnetic material. A shaft made of a body material is expensive. Also, when a relatively inexpensive round shaft made of a non-magnetic material such as stainless steel is used, a portion of the shaft for fixing the magnet may be expensive. Also,
It was also found that when a non-magnetic shaft was used, the magnetic circuit in the radial direction of the shaft was affected and did not meet the specifications. An object of the present invention is to solve the above-mentioned problems and to provide a developing device having an inexpensive catch roll. [0007] At least one end of the shaft of the catch roll is made of a non-magnetic material, and a portion in contact with a magnet inside the sleeve is made of a magnetic and inexpensive square shaft. By forming the shaft into which the magnetic material and the magnetic material are combined, a catch roll that is inexpensive and does not cause a problem that the developer adheres to a portion located outside the outer peripheral sleeve of the shaft can be obtained. Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic diagram showing the structure of the developing device according to the present invention. In FIG. 3, a developing roll 2 of a developing device 1 includes a magnet roll 2a fixed inside and a rotatable developing sleeve 2b on the outer peripheral portion, and is attracted onto the developing sleeve 2b on the outer peripheral portion of the developing roll 2. The developer 5 including the toner and the carrier is rotated by the rotation of the developing sleeve 2b, is conveyed to a position facing the photoconductor 4, and reaches the developing area. In this developing region, the surface of the photoconductor 4 is rubbed by the developer 5 so that the electrostatic latent image carried on the surface of the photoconductor 4 is developed. When the electrostatic latent image on the photosensitive member 4 is developed in the developing area, a small amount of the carrier 6 in the developer 5 may adhere to the surface of the photosensitive member. The carrier 6 attached to the surface of the photoconductor 4 is guided to a position facing the catch roll 7 by the rotation of the photoconductor 4. The catch roll 7 has a magnet 7a fixed inside and a rotatable sleeve 7b on the outer periphery. The carrier 6 attached to the surface of the photoreceptor 4 is moved by the magnetic force of the N pole of the magnet roll 7a and the sleeve. It is attracted by the bias voltage applied to 7b. Adsorbed carrier 6
Is guided to a position where the scraper 3 is in contact with the sleeve 7b by the rotation of the sleeve 7b of the catch roll 7,
The carrier 6 on the sleeve 7b is scraped off by the scraper 3 and returned to the inside of the developing device 1. FIG. 1 is a schematic view showing the vicinity of a catch roll of a developing device according to an embodiment of the present invention. In FIG.
The shaft 7c of the catch roll 7 is a magnetic shaft 7c.
c ′ and the non-magnetic material shaft 7c ″ are press-fitted into one body. Since the portion of the shaft 7c located outside the sleeve 7b is the non-magnetic material shaft 7c ″, it is not magnetized and the developer 5 is not magnetized. Is not deposited. According to the present invention, it is possible to provide a developing device provided with a catch roll which is inexpensive and does not adhere the developer to a portion located outside the outer peripheral sleeve of the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a catch roll according to an embodiment of the present invention. FIG. 2 is a schematic view of a catch roll in a conventional developing device. FIG. 3 is a schematic view of a developing device according to an embodiment of the present invention. [Description of Signs] 1 ... Developing device, 2 ... Developing roll, 3 ... Scraper, 4 ...
Photoconductor, 5: developer, 6: carrier, 7: catch roll.

Continuation of front page    (72) Inventor Yoshitaka Fujinuma             1060 Takeda, Hitachinaka City, Ibaraki Prefecture Hitachi             Machine Co., Ltd. (72) Inventor Kenji Nakamura             1060 Takeda, Hitachinaka City, Ibaraki Prefecture Hitachi             Machine Co., Ltd. F-term (reference) 2H031 AC38 AD13 AE00 BA04 BA09

Claims (1)

Claims: 1. A toner comprising: a rotatable outer peripheral sleeve for collecting a carrier attached to a surface of a photoreceptor; a magnet located inside the outer peripheral sleeve; and a catch roll having a shaft for holding the magnet. A developing device for an electrophotographic apparatus that develops an electrostatic latent image formed on the surface of a photoreceptor using a two-component developer composed of a magnetic material and a non-magnetic material. And a non-magnetic part provided at least at one end of the shaft.