JPH03150808A - Permanent magnet roller - Google Patents

Abstract

PURPOSE:To provide a rotatable, multipole-magnetized permanent magnet roller with high surface flux density, requiring no cylindrical nonmagnetic sleeve for transporting developer, by specifying the magnet thickness and the ratio of the peripheral pole width to the magnet thickness. CONSTITUTION:Cylindrical permanent magnet 1 is fixed to a shaft 4 with a spacer 5 fixed in contact with the periphery of a cylindrical soft magnetic material 2. The ratio W/t of the peripheral pole width W to the magnet thickness (t) is 1-3, and (t) is 0.5-2mm. The thickness of the permanent magnet is preferably more than 0.5 as for easy shaping, and less than 2mm for the product cost. The ratio W/t is preferably 1 to 3. Within this range, effective multipole magnetization is possible on the periphery of a radial anisotropic magnet. Further, imperfect magnetization is reduced with the magnet thickness less than 1 when the peripheral pole width is 1. In this manner, multipole magnetization and high surface flux density are achieved. It is thus possible to provide a rotatable permanent magnet which requires no cylindrical nonmagnetic sleeve for transporting developer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a permanent magnet roller used in a magnetic brush developing device.

[Prior art] Conventional magnetic brush developing device g1 (-component magnetic brush and
The permanent magnet roller used in the two-component magnetic brush is
As is known, a rotatable non-magnetic cylindrical developer transport sleeve has a cylindrical magnetic roller magnetized with a plurality of magnetic poles inside it, and the surface of the developer transport sleeve is moved according to the magnetic field generated by the magnetic roller. The device conveys the developer, and the magnetic roller is coated with sintered ferrite or wood JJ.
An i-coupled ferrite permanent magnet was used.

[Problems to be Solved by the Invention] However, in the conventional method as described above, a rotatable non-magnetic cylindrical developer conveying sleeve is used, and the surface of the sleeve cannot be machined with high precision to make it smooth. In addition, cylindrical permanent magnets were placed on the inner surface of the sleeve at extreme intervals and rotated, requiring high processing accuracy.

For the cylindrical permanent magnet, a ferrite permanent magnet with a low magnetic energy product is used.In the tree-11rI bonded permanent magnet, which is easy to achieve dimensional accuracy during processing, the binder is a thermosetting resin such as epoxy, Alternatively, by mixing and molding a thermoplastic resin such as nylon, the content of ferrite permanent magnet powder in the resin mixture decreases, and it is possible to add magnetic anisotropy to the structure and increase the surface magnetic flux. However, because the magnetic properties were generally low, the magnetic flux sometimes did not reach the set value even if the thickness of the magnet was increased.

Sintered ferrite permanent magnets, also known as ceramic magnets, have higher magnetic properties than resin-bonded ferrite permanent magnets because the binder resin is not mixed.
Since it is heat-treated and sintered at high temperature after forming, when magnetic anisotropy is added to obtain high surface magnetic flux, the shrinkage rate during sintering varies depending on the direction of the anisotropy, making it prone to cracking, making mass production difficult. .

As described above, since ferrite permanent magnets have low magnetic properties, attempts are made to increase the wall thickness to obtain high surface magnetic flux, and it has not been possible to significantly increase the number of outer circumferential magnetized poles.

Therefore, the present invention is intended to solve these problems, and its purpose is to achieve multipolar magnetization and obtain a high surface magnetic flux density by using a thin permanent magnet with high magnetic performance. It is an object of the present invention to provide a permanent magnet roller which is capable of rotating and does not require a rotatable non-magnetic cylindrical developer conveying sleeve.

[Measures 12 for Solving the Problems] The permanent magnet roller of the present invention holds the developer on the permanent magnet roller by a magnetic field generated in a cylindrical permanent magnet roller magnetized with a plurality of magnetic poles, and In the permanent magnet roller of the developing device that rotates to convey the developer, the outer circumference-magnetic pole width W and the permanent magnet wall thickness t are W/l=1.
3, and the permanent magnet wall thickness t is 0.5 to 2.

Further, in the permanent magnet roller of the present invention, the cylindrical permanent magnet is made of samarium, cobalt, which are generally called rare earth permanent magnets, and permanent magnet powder containing the respective elements as main components (in detail, as an example, 5trrCos or 51
12 (Coo, asFeo, osMno, o4Cro
, oz) +7) containing samarium and cobalt) and a resin as a binder.

[Function] According to the above configuration of the present invention, by using a thin permanent magnet with high magnetic performance, multipolar magnetization can be achieved, high surface magnetic flux density can be obtained, and a rotatable non-magnetic cylindrical magnet can be formed. A permanent magnet roller that does not require a developer conveying sleeve can be created.

Table 1 shows the thickness of the permanent magnet and the width of one magnetic pole.

The thickness of the permanent magnet was set to 0.5 mm or more in view of formability, and 2 mm in view of the cost of the permanent magnet raw material.

In addition, normally, the range in which outer circumference multi-pole magnetization of a radial anisotropic permanent magnet can be performed efficiently is when the outer circumference-pole width W is 1.
When the magnet wall thickness t is set to 1 or less, incompletely magnetized portions are reduced, so w/l was set to be 1 to 3.

Table-1 Magnet wall thickness and magnetic pole width Permanent magnet wall thickness t=0.5~2 degrees Relationship with temporary pole width W　w/l=1~3 [Example] The present invention will be explained in detail below with reference to Examples.

FIG. 1 shows a cross-sectional view of the permanent magnet roller of the present invention viewed from the axial direction.

In FIG. 1, a cylindrical permanent magnet 1 is closely fixed to the outer periphery of a cylindrical soft magnetic material 2 and is fixed to a shaft 4 by a spacer 5.

The cylindrical permanent magnet 1 has samarium and cobalt as its main components.
o, o2a) After melting and casting a 2-17 Sm-Co rare earth permanent magnet alloy generally represented by the composition formula 8.37, heat treatment is performed to improve and stabilize the magnetic properties,
This ingot was pulverized, and 2% by weight of epoxy resin as a binder was mixed with rare earth permanent magnet powder whose particle size was adjusted and used as a raw material.

For molding, an extrusion molding machine that is basically the same as the extrusion molding method used for extruding vinyl chloride vibrators, etc. is used, and a radial magnetic field extrusion molding machine is used that has an additional device for applying a magnetic field to add radial anisotropy. φ20X inner diameter φ1
A ring-shaped radially anisotropic permanent magnet No. 7 is extruded and molded, and a cylindrical soft magnetic material 2 processed by a6ffi, which is a vibrator whose main component is iron containing low carbon and has an outer diameter of 17 mm and an inner diameter of 15 mm, is closely attached to the inner surface of the magnet. Fixed with agent and length 2
After cutting in 20III11, the epoxy resin was heated and solidified.

Furthermore, even if a thermoplastic resin such as nylon 12 or nylon 6 is used as a binder, it can be molded in the same way by extruding it while heating, but in that case, the permanent magnet powder is
If it is not 0 to 70 vol%, the fluidity will be poor and molding will be difficult, but it can be assimilated only by cooling.

In this example, after molding the cylindrical permanent magnet, it was closely fixed to the cylindrical soft magnetic material t[, but it is also possible to insert mold it inside the permanent magnet during extrusion molding.

The outer circumferential surface of the cylindrical permanent magnet 1 was multi-poled equally into 20 poles with 10 poles each of N and S%i using a magnetizing device and a magnetizing yoke.

Because the permanent magnet has radial anisotropy, it is magnetized from the outer circumferential surface,
In addition, a magnetic circuit is assembled that returns to the outer circumferential surface of the permanent magnet via the soft magnetic material that is in close contact with the inner circumferential surface, and a high surface magnetic flux can be obtained.

Further, the cylindrical permanent magnet 1 and the cylindrical soft magnetic material 2, which were molded, bonded, and magnetized as described above, were fixed to a shaft 4 via a spacer 5 to form a permanent magnet roll.

The surface magnetic flux density of the permanent magnet roller of the present invention was measured using a commercially available Gauss meter and a Hall probe.

The shaft 4 of the permanent magnet roller was rotated to turn the cylindrical permanent magnet 1, and the output was read using a Gauss meter from a Hall probe that was in contact with the surface of the permanent magnet 1, and was further recorded using an oscilloscope with a memory function.

The magnetization waveform is very similar to a regular sine wave, the maximum value is 1550.1530 Gauss for both N and S poles, the minimum value is 1260.1240 Gauss for N and S poles, and the average N pole is 1.
420, and the S pole was 1400 Gauss. As a comparative example, a permanent magnet roller of the same size made of a ferrite permanent magnet according to the prior art was measured.

It has the structure shown in the sectional view of FIG. 2, and uses a sintered type ferrite permanent magnet which has higher magnetic properties than the resin bonded type.

The cylindrical permanent magnet 6 is a sintered ferrite permanent magnet, and has a shaft 4 fixed in its center, and a non-magnetic cylindrical sleeve 3 on the outside that freely rotates relative to the cylindrical permanent magnet 6. .

The dimensions are the same as in the example: permanent magnet outer diameter φ20, length 22
0 mm, but since the permanent magnet is thick and does not exhibit radial anisotropy, an isotropic sintered ferrite permanent magnet was used.

The surface magnetic flux density was measured in the same manner as in this example.

The magnetization waveform is a regular sine wave with a maximum value of 820.830 Gauss for both N and S poles, a minimum value of 690.705 Gauss for N and S poles, and an average N pole of 785 Gauss.
, S pole was 790 Gauss.

In this embodiment, an example of the combination of the permanent magnet wall thickness t and the one magnetic pole width W is described, but w/l=1 to 3 and t=0.5 to
Similar high surface magnetic flux can be obtained within the range of 2++++s.

[Effects of the Invention] As described above, according to the permanent magnet roller of the present invention,
In a permanent magnet roller of a developing device that holds the developer on the permanent magnet roller by a magnetic field generated in a cylindrical permanent magnet roller magnetized with a plurality of magnetic poles, and rotates and conveys the developer, the outer periphery is - The magnetic pole width W and the permanent magnet wall thickness t are W/l=1 to 3, and the permanent magnet wall thickness t
is 0°5 to 2 mm, and is made of a mixture of permanent magnet powder containing samarium and cobalt, both of which are called rare earth permanent magnets as main components, and resin as a binder. , a permanent magnet that can be multi-pole magnetized by using a thin permanent magnet (with high magnetic performance), can obtain high surface magnetic flux density, and does not require a rotatable non-magnetic cylindrical developer conveying sleeve. This has the effect of being able to provide rolls.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the permanent magnet roller of the present invention. FIG. 2 is a sectional view of a permanent magnet roller according to the prior art. ■...Cylindrical permanent magnet 2...Cylindrical soft magnetic material 4...
Shaft 5...Spacer 6...One or more cylindrical permanent magnets

Claims (2)

[Claims] (1) A permanent magnet roller of a developing device that holds the developer on the permanent magnet roller by a magnetic field generated in a cylindrical permanent magnet roller magnetized with a plurality of magnetic poles, and rotates to convey the developer. A permanent magnet roller characterized in that the outer periphery-magnetic pole width W and the permanent magnet wall thickness t are W/t=1 to 3, and the permanent magnet wall thickness t is 0.5 to 2 mm. (2) A claim characterized in that the cylindrical permanent magnet is made of a mixture of permanent magnet powder containing samarium and cobalt, which are generally called rare earth permanent magnets, and a resin serving as a binder. Permanent magnet roller according to item (1).