JPS58100405A - Magnetic roller - Google Patents

Abstract

PURPOSE:To provide magnetic rollers having sufficiently large surface magnetic flux density of magnetic poles and superior in the action of moving magnetic particles in the axial direction by providing the spiral magnetic poles on the outer peripheral surface of a cylindrical body. CONSTITUTION:A magnetic pole piece 1 is a magnetic substance for the permanent magnet and has a form similar to one of equidivided cylinder which is sector-shaped in section and elongated in the axial direction. Plural magnetic pole pieces are combined to form a cylindrical body 2 and spiral magnetic poles are deposited on the outer peripheral surface of the cylindrical body, thereby to constitute a magnetic roller as shown in the figure. In this way, N poles and S poles are alternately formed on the outer peripheral surface of the cylindrical body 2 in a spiral shape. The bottom figure is a graph which shows the result when the surface magnetic flux density is measured along the spiral magnetic poles of the magnetic roller. The difference (y) between the maximum and minimum portions serves to accelerate the lateral movement of the magnetic particles when applied to magnetic brushes or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic roller for forming a magnetic brush or the like in an electrophotographic developing device.

Generally, in an electrophotographic developing device, a non-magnetic sleeve is provided concentrically around the outer periphery of a magnetic roller, and a magnetic brush that attracts magnetic toner particles is placed on the outer periphery of the sleeve, facing a rotating developing drum. In this case, if there is no function to move the magnetic toner particles in the axial direction of the magnetic brush, if the same image is developed continuously, the toner density distribution will be uneven, resulting in an uneven distribution of toner density. This may cause images not to be obtained.

In view of the above-mentioned points, the present invention aims to provide a magnetic roller which has a sufficiently large surface magnetic flux density of its magnetic poles and is excellent in the action of moving magnetic particles in the axial direction.Hereinafter, the present invention will be described. Examples of the magnetic roller according to the present invention will be described according to the drawings.

FIG. 1 shows an example of a magnetic pole piece 1 used in an embodiment of the present invention. This pole piece IFi is made of a magnetic material for permanent magnets, and its cross section is fan-shaped by equally dividing a cylinder. It has an elongated shape. Here, the magnetic pole piece 1 has anisotropy and is configured so that the magnetic flux is concentrated at the middle part of the outer periphery of the fan-shaped cross section, that is, near the dotted line a. A cylindrical body 2 is created by combining a plurality of such magnetic pole pieces l, and by magnetizing spiral magnetic poles on the outer peripheral surface of this cylindrical body, a magnetic field as shown in FIGS. 2 and 3 is generated. The roller is configured. As a result, N poles and S poles are alternately formed in a spiral shape on the outer peripheral surface of the cylindrical body 2, as shown in the developed view of FIG. Therefore, the number of magnetic poles is equal to the number of spirals. Here, since the point 11a extending in the axial direction of the outer peripheral surface of the cylindrical body 2 is the part where the magnetic pole is strongest due to the anisotropy imparted to the magnetic pole piece 1, the N pole formed in a spiral shape, At the intersection X between the S pole and the dotted line a, the S pole or the N pole appears most strongly.

Figure 5 is a graph of the surface magnetic flux density measured along the spiral magnetic poles of the magnetic roller.The reason why the surface magnetic flux density is wavy is because the cylindrical body 2 has multipolar anisotropy on the outer periphery. This is because they are doing so. In other words, the magnetic pole is strongest at the part X where the spiral magnetic pole intersects the point l1la parallel to the axial direction where the magnetic pole is strongly generated due to the anisotropy of the magnetic pole piece 1, and the magnetic pole is the weakest at the middle part of the part X. So,
The difference y between the strongest part and the weakest part of the magnetic pole acts to promote the lateral movement of the magnetic particles when used in a magnetic brush school. That is, it is considered that the difference y acts equivalent to imparting vibration to the magnetic particles.

As for the material of the magnetic pole piece 1, it is possible to use a plastic magnet made by mixing ferrite powder with plastic and molding it, a rubber magnet made by mixing 7-pole powder and rubber, or a sintered ferrite magnet. . In addition, it is possible to perform spiral magnetization.

FIG. 6 shows another embodiment of the invention. In this diagram,
A non-magnetic spacer 3 is interposed between each magnetic pole piece 1,
In this way, magnetic poles are provided in a spiral shape on the outer peripheral surface of the cylindrical body 4 in which the magnetic pole pieces 1 and the nonmagnetic spacers 3 are arranged alternately.

FIG. 7 shows a surface magnetic flux density of 11[!] along the spiral magnetic pole of the magnetic roller shown in FIG. The variation in surface magnetic flux density in this case is considerably larger due to the provision of the non-magnetic spacer 3, and the difference 2 between the strongest and weakest parts of the magnetic pole is greater than the difference y in the 5th - Mokana Sho is getting bigger. This difference also acts to promote the lateral movement of magnetic particles when used in a magnetic brush, etc. Furthermore, the size of difference 2 can be changed by adjusting the width of the non-magnetic spacer 30, etc. . Furthermore, even if an isotropic material is used as the magnetic pole piece 1, the surface magnetic flux density can be made to wave as shown in Fig. '7.
According to the present invention, by providing a spiral magnetic pole on the outer circumferential surface of a cylindrical body composed of magnetic pole pieces having a fan-shaped cross section, the surface magnetic flux density of the magnetic pole is sufficiently large, and the magnetic particles are moved in the axial direction. You can get an excellent magnetic roll.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a magnetic pole piece used in an embodiment of the present invention, FIG. 2 is a sectional view showing an embodiment of a magnetic roller according to the present invention, FIG. 3 is a perspective view thereof, and FIG. Developed diagram, No. 5
The figure is a graph showing the surface magnetic flux density along the spiral magnetic pole, Figure 6 is a cross-sectional view showing another embodiment of the present invention, and Figure 7 is a graph showing the surface magnetic flux density along the spiral magnetic pole.
The figure is a graph showing the surface magnetic flux density along a spiral magnetic pole. 1... Magnetic pole piece, 2, 4... Cylindrical body, 3... Nonmagnetic spacer. Patent applicant Tokyo Denki Kagaku Kogyo Co., Ltd. Representative Patent attorney Takashi Murai Figure 1 Figure 4 Figure 5

Claims (3)

[Claims] (1) A magnetic roller characterized in that a spiral magnetic pole is provided on the outer peripheral surface of a cylindrical body made up of a combination of magnetic pole pieces having a fan-shaped cross section. (2) The magnetic roller according to claim 1, wherein the magnetic pole piece has anisotropy such that magnetic flux is concentrated at the middle part of the outer periphery of the fan-shaped cross section. (3) A magnetic solar device in which the cylindrical body has a non-magnetic spacer between each magnetic pole piece.