JPS59145507A - Magnet-roll for dry development - Google Patents

Abstract

PURPOSE:To obtain a magnet-roll which has a magnetizing wave-form by which an efficient development property can be obtained and whose weight can be reduced by a method wherein a sectional shape of a part of a circumference of a permanent magnet is a circular arc coaxial with a non-magnetic sleeve and poles are provided to the circular arc part and the plane part of the circumference of the permanent magnet. CONSTITUTION:A semi-cylindrical permanent magnet 1 is used as a permanent magnet member and fitted to a shaft 2. One pole (N-pole) is provided to a circular arc part of a circumference of the permanent magnet 1 and one pole (S- pole) is provided to each of the plane parts 4 and 4' of the circumference. With a pole arrangement like this, a magnetized state expressed by broken lines is obtained. As the flux in the magnet flows from the N-pole of the circular arc part to the S-poles of the plane parts 4 and 4', a large flow of flux whose expanse is more than the angle theta (in the Figure, theta=180 deg.) between the plane parts 4 and 4' can be formed. In this example, the angle is 180 deg. because a semi-cylindrical magnet is applied as the permanent magnet 1, but the angle can be determined optionally by changing the shape of the permanent magnet 1 corresponding to the construction of a developing equipment and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing magnet roll used as a magnetic brush forming means in a magnetic brush developing device.

In a magnetic brush developing device, the magnetic developer is a two-component developer, which is a mixture of a ferromagnetic carrier such as iron powder or two-light powder, and a toner powder containing a colorant or the like in a binder resin. Component-based magnetic toners are used. The magnetic developer is attracted onto a magnet roll having a permanent magnet member consisting of a cylindrical non-magnetic sleeve and a permanent magnet having a plurality of magnetic poles fixed to the shaft, and the non-magnetic sleeve and the permanent magnet member is conveyed to the development area by the relative rotation of. At least in the development area, the magnetic developer forms a magnetic brush, and the magnetic brush rubs the surface of the image carrier to visualize the electrostatic latent image formed on the surface.

As the above-mentioned magnet roll, those having various structures are known.

First, a permanent magnet member made by fixing an anisotropic block magnet obtained by molding hard turite powder in a magnetic field and then connecting it around a shaft (for example,
(Refer to Publication No. 8) is known, but one assembly man-hour is a lot. There are problems such as low-temperature demagnetization.

Next, there is also known a Macnet roll (see, for example, Japanese Patent Publication No. 55-6907), which uses a permanent magnet member in which a cylindrical permanent magnet made of hard ferrite is fixed to a shaft. As shown in Fig. 1, this magnet roll is made by fixing a cylindrical two-light magnet 1a to a shaft 2 having an outer diameter slightly smaller than its inner diameter with an adhesive (not shown) or the like, and then adjusting the outer peripheral surface to a predetermined dimension. After grinding, the outer circumferential surface is magnetized to become a permanent magnet.

A surface member 3 was formed, and the permanent magnet member 3 was held inside a cylindrical nonmagnetic sleeve (not shown).

In a magnetic brush development system using a two-component developer, a permanent magnet member is generally fixed so that one magnetic pole faces the surface of the image carrier, and only the nonmagnetic sleeve is rotated. Therefore, it is necessary to scrape off the developer after development and uniformly stir and mix it, so the two-light magnet 1a is magnetized asymmetrically (6 poles in the figure) as shown in FIG.
・Ru.

In FIG. 1, broken lines represent the flow of magnetic flux lines inside the magnet. Therefore, half of the cylindrical two-light magnet 1α remains unmagnetized and is not used, resulting in wasted magnet material.
There was also the problem of weight.

Therefore, as shown in Fig. 2, a semi-cylindrical two-light magnet 1b obtained by cutting a cylinder or molding it into a semi-cylindrical shape and sintering it is fixed to the shaft 2 to form a permanent magnet member. It is also possible to do so. However, according to this permanent magnet member, when the outer circumferential surface of the magnet is magnetized with six poles similar to that shown in Fig. 1, the flow of magnetic flux lines inside the magnet becomes as shown by the broken line in the figure, and the N pole The S poles on both sides are arranged within an angular range inside the angle between the flat surface groove and 6 on the outer peripheral surface of the two-light magnet 1h. Therefore, even if magnetization is performed according to the same specifications as in FIG. 1, the distribution of magnetic flux density will be different, and the magnetic flux will have a small radius, making it impossible to form an effective magnetic brush.

On the other hand, in order to obtain the same magnetic flux density distribution as in Fig. 1,
As shown in FIG. 6, it is conceivable to use a ferrite magnet 1C with a cross-sectional path C" shape in which the magnet part is enlarged.
This is disadvantageous compared to the one shown in FIG. 2 in terms of the amount of magnet material used and the closure of the magnet mold.

An object of the present invention is to solve the problems of the prior art described above and to provide a magnet roll for dry development that can achieve effective magnetic pole arrangement and weight reduction.

The magnet roll for dry development of the present invention includes a permanent magnet member formed by fixing a permanent magnet having a plurality of magnetic poles to a shaft;
A magnet roll for dry development having a cylindrical non-magnetic sleeve concentrically and rotatably arranged surrounding the permanent magnet member.

The permanent magnet is characterized in that a part of its outer peripheral surface has a cross-sectional shape forming an arc concentric with the non-magnetic sleeve, and magnetic poles are provided on the arc portion and the flat portion of the outer peripheral surface of the permanent magnet. There is.

Below, details of the present invention will be explained with reference to the drawings.

FIG. 4 is a sectional view showing an example of a permanent magnet member used in the Macnet roll of the present invention.

1 In Figure 4, 1 is a permanent magnet, 2 is a shaft, 4
4' indicates a flat portion of the outer peripheral surface of the permanent magnet.

Note that the two-dot chain line in the figure indicates the nonmagnetic sleeve.

The permanent magnet member shown in FIG. 4 is the same as that shown in FIG. The magnet has one magnetic pole (N pole) on the arcuate part of the outer peripheral surface of the permanent magnet 1, and one magnetic pole (S pole) on the flat parts 4 and 4' of the outer peripheral surface (
It also differs from the one in Figure 2 in some respects. With such a magnetic pole arrangement, a magnetization state as shown by the broken line in the figure can be obtained. In other words, if we look at the flow of magnetic flux from the N pole to the 5 poles inside the magnet, the flat part is 4° 4' from the N pole in the arcuate part.
Since the direction is toward the S pole at , the angle θ(
In the figure, a large flow of magnetic flux greater than θ=18o° can be formed.

In the above embodiment, since a semi-cylindrical permanent magnet 1 was used, the angle θ is j 8 D' and 1. C.

Of course, the above angle can be arbitrarily set by changing the shape of the permanent magnet 1 depending on the structure of the developing device.

Furthermore, as the material of the permanent magnet 1, the aforementioned two-light magnet (which may be isotropic or anisotropic) can of course be used. In addition, flexible magnets (for example, U.S. Pat. No. 5,455.276,
JP-A-57-150407, JP-A-57-L64
77i, etc.) may be used; in this case, it is more advantageous than ferrite magnets in terms of weight reduction.

Next, specific examples of the present invention will be shown.

A cylindrical barium 7=light magnet with an outer diameter of 29 mm and an inner diameter of 10 mm is magnetized as shown in Figure 1 so that the angle θ1 between the NS poles is 90 degrees, and the magnet is After fixing it in place, it was assembled into an aluminum alloy sleeve with an outer diameter of 31 mm 9' and an inner diameter of 60 mm. When the magnetic flux density on the sleeve was set to a constant value, the magnetic flux density distribution shown by the solid line in FIG. 5 was obtained.

In addition, after the above-mentioned cylindrical two-light magnet was divided into two along the plane containing the axis, magnetized as shown in Fig. 2 -fvt]<, and assembled into a sleeve in the same manner as above - the magnetic flux density on the sleeve When the distribution was set to 1, the result was shown by the dashed dotted line in FIG. j tr, that is, the angle θ2 between the NS poles
is about 70'', which is about 20° smaller than in the above case, and it was not possible to obtain the same magnetization waveform and the same developing performance as when using a single cylindrical two-light magnet.

On the other hand, the above-mentioned cylindrical two-light magnet was divided into two on a plane including the axis, magnetized as shown in Fig. 4, and then assembled into a sleeve in the same manner as above, and then magnetic flux density distribution on the sleeve. When measured, the results shown by the broken line in FIG. 5 were obtained. '1'', that is, the magnetization waveform in this case is approximately the same as the magnetization waveform when a cylindrical 7=nyrite stone is used, and the same is true in a mounting test conducted by incorporating it into a developing device.

The developing performance was obtained.

In addition, when the length of the magnet is 260 pieces, the weight of the magnet roll using the above-mentioned cylindrical ferrite magnet (however, the shaft is made of stainless steel) is about 12:9,
The weight of a magnet roll containing a semi-cylindrical two-light magnet is approximately 0.7 Ff, and can be reduced in weight by approximately O5.

As described above, according to the present invention, a magnet roll for dry development can be obtained which has a magnetization waveform that provides effective development performance and which can also achieve weight reduction.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views showing examples of permanent magnet members used in conventional magnet rolls. FIG. 4 is a sectional view showing an example of a permanent magnet member used in the magnet roll of the present invention, and FIG. 5 is a view showing magnetic flux density distributions on the sleeve of permanent magnets of various shapes. 1: Permanent magnet, 2I axis, 4, 4', flat part.

Claims (1)

[Scope of Claims] 1. A permanent magnet member including a permanent magnet having a plurality of magnetic poles fixed to a shaft, and a cylindrical member that surrounds the permanent magnet member and is rotatably arranged in the same shape. In the magnet roll for dry development having a non-magnetic sleeve, the permanent magnet has a cross-sectional shape in which a part of the outer peripheral surface thereof forms an arc concentric with the non-magnetic sleeve, and a flat surface with the arc portion of the outer peripheral surface of the permanent magnet. A magnet roll for dry-type development characterized by having a magnetic pole provided in each part.
2. A magnet roll for dry development according to claim 1, characterized in that a flexible magnet in which light powder is bound with a high molecular weight polymer is used.