JPS6279482A - Developing device - Google Patents

Abstract

PURPOSE:to uniform the height of bristles of a magnetic brush and to obtain an image of high quality which has uniform density over the entire image plane by uniforming magnetic flux density on the surface of a sleeve in the axial direction of a developing roller. CONSTITUTION:The developing roller consists of the sleeve 1 made of a nonmagnetic body and a magnet roller 2 which has many magnetic poles internally and the sleeve 1 and roller 2 are rotated coaxially. Both end parts of the roller 2 are tapered so that magnetic pole surfaces of magnets are separated from the sleeve 1. Consequently, the magnetic pole surfaces of the magnets are separated from the surface of the sleeve 1 more and more toward both end parts to uniform the magnetic flux density on the surface of the sleeve 1 in the axial direction of the roller 2 within the range of the internal magnets. Thus, the magnetic brush 3 is formed of a developer having uniform height in the axial direction.

Description

[Detailed Description of the Invention] [Summary] By forming both ends of the magnet roller of the image retouching device into a tapered shape, the magnetic flux density is made uniform, the image density is made uniform, and the image quality is improved. Realize.

[Industrial application field]

The present invention relates to a magnetic brush developing device for an electrostatic recording device or an electrophotographic recording device, and more particularly to a developing device that can perform development under uniform conditions over the entire recording screen and obtain high-quality images.

[Conventional technology]

A magnetic brush developing device for an electrophotographic recording device holds developer on the surface of a non-magnetic sleeve containing a magnet, forms a magnetic brush, and brings it into contact with or near a photoreceptor on which a latent image has been written. Then, perform development. The depth at which the magnetic brush tip contacts the photoreceptor, or the distance between the tip and the photoreceptor, is closely related to the image density.This contact depth or the distance between the tip and the photoreceptor is not uniform. As a result, the density of the recorded image becomes non-uniform. In the conventional developing device Jt, as shown in FIG. 4, the shape of the magnet roller 2 included in the image forming roller is such that the magnetic pole surface is parallel to the surface of the sleeve l, and the magnetic flux density of the developing roller in one direction is
As shown in FIG. 5, both ends are larger than the center.

[Problem that the invention seeks to solve]

When a magnetic brush is formed on the sleeve of the developing roller, the height of the ears of the magnetic brush is higher at both ends in the axial direction of the developing roller than at the center due to the difference in magnetic flux density. For this reason, in conventional developing devices, the depth at which the tip of the magnetic brush contacts the photoreceptor in the axial direction of the developing roller, or the distance between the tip and the surface of the photoreceptor, is not uniform, resulting in uneven image density. There were drawbacks.

[Means for solving problems]

The present invention provides a developing device that can obtain uniform image density over the entire recording screen by making the magnetic flux density uniform in the axial direction of the developing roller on the sleeve surface of the developing roller and making the height of the ears of the magnetic brush uniform. The purpose is to provide.

[Effect]

In the present invention, the magnetic pole surfaces of the magnets included in the developing roller are inclined at both ends of the developing roller in the axial direction so as to be separated from the sleeve surface, so that the magnetic flux density on the sleeve surface is uniform ξζ along the axial direction. It is.

〔Example〕

FIG. 1 shows an embodiment of a developing device according to the present invention.
FIG. 3 is a diagram showing the structure of the developing roller. The developing roller is
It is composed of a sleeve l made of a non-magnetic material and a magnet roller 2 having multiple magnetic poles inside the sleeve l, both of which can rotate coaxially. The magnet roller 2 has a tapered shape at both ends. This tapered shape aims to make the magnetic flux density uniform.

FIG. 2 shows a cross section V of the developing roller. Since the magnet roller 2 is tapered at both ends, the magnetic pole face of the magnet becomes farther away from the surface of the sleeve l as it goes toward both ends. By making the Madai Totroller 2 into such a shape,
The magnetic flux density on the surface of the sleeve 1 is as shown in Fig. 3.
In the axial direction of the developing roller, the magnetic brush is uniform over the range where the magnets are present inside, and therefore, it is possible to form a magnetic brush having a uniform height in the axial direction.

In the above example, a developing device was described in which the developer is transported by rotating a magnet roller inside the developing roller, but the magnet in the sleeve is fixed and only the sleeve is rotated to transport the developer. Regarding the developing device,
A similar effect can be obtained if the magnet is tapered at both ends. Further, in this case, it is not necessary to tapered both ends of all the plurality of magnets in the sleeve, and at least the magnets at the position facing the photoreceptor and where development is performed may have this shape.

〔Effect of the invention〕

According to the present invention, the height of the ears of the magnetic brush can be made uniform by making the magnetic flux density uniform on the sleeve surface by the axial heating of the developing roller, so that it is uniform over the entire screen. This has the effect that a high-quality image with a high density can be obtained.

[Brief explanation of drawings]

1 and 2 are diagrams showing the structure of the developing roller of the apparatus of the present invention, FIG. 3 is an explanatory diagram of an embodiment of the present invention, FIG. 4 is a sectional view of a conventional developing roller, and FIG. FIG. 3 is an axial magnetic flux density distribution diagram on the sleeve surface of a conventional developing roller. In the figure, l is the sleeve, 2 is the magnet roller, and 3 is the sleeve.
is a magnetic brush using developer. , / 綽關远黑°1. 11k, Keihaku 5θ Moon Plate 9J Fig. 2, iii+1ntffilJf country @ 3 m

Claims (1)

[Claims] A developing device that performs development by holding developer on the surface of a sleeve containing a magnetic roller, characterized in that both ends of the magnetic roller in the axial direction are tapered away from the sleeve surface. .