JPH07319283A - Magnet roll - Google Patents

Abstract

PURPOSE:To make bonding strength high and to drastically reduce production cost by providing a shaft part made of thermoplastic resin and piercing a cylindrical permanent magnet part. CONSTITUTION:This magnet roll is provided with the cylindrical permanent magnet part 2 having plural magnetic poles on its surface and the shaft 3 made of the thermoplastic resin and piercing the magnet part 2; and the shaft 3' is provided with a supporting part brought into contact with the inner peripheral surface of the magnet part 2 and a pivotally supporting part extended from the supporting part in an axial direction. In the magnet roll 1, the shaft 3 inserted through the magnet part 2 is formed of the thermoplastic resin, so that it is assembled by small man-hour by injecting the thermoplastic resin in the cavity of a metallic mold in which the magnet part 2 is inserted. By providing a locking part brought into contact with the end face of the magnet part 2 in the shaft 3, the shaft 3 is surely prevented from coming off from the magnet part 2 or from being turned. The shaft 3 and the magnet part 2 are firmly integrated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roll used as a conveying means for a magnetic developer in an electrophotographic device, an electrostatic recording device or the like.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus, a magnet roll with a sleeve used as a developing roll or a cleaning roll has a structure as shown in FIG. In FIG. 3, reference numeral 1 denotes a magnet roll, which has a cylindrical permanent magnet 2 having a plurality of magnetic poles (not shown) on its surface, and a shaft 30 coaxially fixed to its center. Flange 4, 5 on both ends of the shaft
Is rotatably fitted through the bearings 6, 6 and the flange 4,
A sleeve 7 formed in a hollow cylindrical shape is fitted into the sleeve 5. The flanges 4 and 5 and the sleeve 7 are formed of a non-magnetic material such as aluminum alloy or stainless steel. According to the developing roll 8 configured as described above, the magnet roll 1 and the sleeve 7 are attracted to the outer peripheral surface of the sleeve by relative rotation (for example, the magnet roll is fixed and the sleeve 7 is rotated). A magnetic developer (for example, a one-component magnetic toner or a two-component developer composed of a toner and a magnetic carrier) is conveyed to the developing area, and the latent image is visualized. The above magnet roll 1
Is, for example, a shaft 3 in a hollow hole of a cylindrical permanent magnet portion (isotropic ferrite magnet) 2 obtained by press-molding hard ferrite powder (for example, rubber pressing method) and then sintering.
It is prepared by inserting 0 into the cylindrical permanent magnet portion 2 through an adhesive agent, fixing the both to each other with an adhesive, processing the outer peripheral surface of the cylindrical permanent magnet portion 2 to a predetermined size, and magnetizing the outer peripheral surface to a multi-pole magnet. (See, for example, Japanese Patent Publication No. 55-6907). The magnet roll using the above-mentioned isotropic ferrite magnet can adjust the strength and arrangement of the magnetic pole in a wide range by changing the yoke shape of the magnetizing device, the winding method or the magnetizing current. There are advantages that the magnetic waveform has a high degree of freedom and that a very uniform magnetic field can be formed in the longitudinal direction.
In addition, the metal shaft is bonded and fixed despite the magnet having extremely high rigidity.

[0003]

When the magnet roll is produced by the above method, the work of adhering the shaft to the hollow hole of the cylindrical permanent magnet portion is complicated, and the number of manufacturing and assembling steps is large. There is. That is, when a shaft having an adhesive applied on the surface is inserted into the hollow hole of the permanent magnet portion, the adhesive may stick out, so that it is necessary to remove and clean the excess adhesive. Further, since a heat-curable adhesive is used as the adhesive from the viewpoint of adhesive strength, a work of heating the adhesive is added. Since the hollow hole of the permanent magnet part and the shaft are in a loose state, it is necessary to completely fill the gap between them with the adhesive, but the gap is not always filled uniformly with the adhesive, and the bonding There is a problem of insufficient strength or variation. Further, as shown in FIG. 3, both ends of the shaft 30 have end portions 31a, 31 having a diameter smaller than that of the middle portion.
Since it is necessary to secure the fitting with the bearing 6 and to form the contact surface, it is necessary to perform the turning processing and the grinding processing of the end portion. For this reason, since the manufacturing cost of the shaft 30 is increased, a large number of man-hours are required for manufacturing the magnet roll, and the manufacturing cost is increased.

Therefore, an object of the present invention is to solve the problems existing in the above-mentioned prior art, and to have a large bonding strength,
An object of the present invention is to provide a magnet roll that can significantly reduce the manufacturing cost.

[0005]

To achieve the above object, in the present invention, a cylindrical permanent magnet portion having a plurality of magnetic poles on its surface and a thermoplastic resin penetrating the cylindrical permanent magnet portion are used. And a shaft portion that is in contact with the inner circumferential surface of the permanent magnet portion, and a shaft support portion that extends in the axial direction from the support portion. In the present invention, it is preferable that the support portion has locking portions that are in close contact with both end surfaces of the permanent magnet portion. Further, in the present invention, it is preferable that the hollow section of the cylindrical permanent magnet section has a non-circular cross section (for example, a polygonal shape).

[0006]

In the magnet roll of the present invention, the shaft that is inserted into the cylindrical permanent magnet portion is made of thermoplastic resin. Therefore, for example, the thermoplastic resin is injected into the cavity of the mold in which the cylindrical permanent magnet is inserted. Can be assembled with less man-hours. Further, by providing the shaft portion with a locking portion that is in close contact with the end surface of the permanent magnet, it is possible to more reliably prevent the shaft from slipping out of the cylindrical permanent magnet or rotating the shaft, so that the shaft and the cylindrical permanent magnet are separated from each other. Can be firmly integrated.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an example of a magnet roll of the present invention. In FIG. 1, 1 is a magnet roll, which has a cylindrical permanent magnet portion 2 and a shaft portion 3 fixed thereto. The cylindrical permanent magnet part 2 is made of, for example, hard ferrite powder (MO.nFe ₂ O ₃ (M: Ba, Sr, Pb 1
Seed or more, n = 5 to 6), if necessary, an organic binder (methyl cellulose, carbothyl cellulose, etc.) is added (preferably 2% by weight or less), and after kneading with a kneader, granulated and dried raw materials are used. Created. That is, this raw material powder is filled in a cylindrical molding die having a core rod in the center and formed of an elastically deformable material such as rubber, and a working fluid such as oil or water is supplied from around the molding die. Pressurize to form a cylindrical molded body, and press the molded body 110
Sintering is performed at a temperature of 0 to 1300 ° C., both ends of the obtained sintered body are cut, and after being processed to a predetermined length, grinding processing (for example, centerless processing) is performed to obtain a magnet material having a predetermined size. The magnet material is prepared by preparing a slurry (solid content 60 to 90% by weight) containing the ferrite powder, a mixed medium (water or polyvinyl alcohol, etc.) and the organic binder, and extruding the slurry to a predetermined length. It may be produced by cutting, drying, sintering and processing. According to this extrusion molding, an isotropic ferrite magnet can be obtained as a whole,
Since the molding is performed by sliding on the inner peripheral surface of the mold in the process of extrusion molding, the ferrite particles on the surface of the molded body are mechanically oriented in the axial direction, and some anisotropy (extrusion anisotropic Sex) may be given.

Next, the magnet material is set in a mold (not shown), and a molding cavity (a hollow portion of the magnet material and both ends thereof) is formed.
The shaft portion 3 is molded by injecting a melted material of a thermoplastic resin. The molding conditions in this case may be selected depending on the type of resin. For example, the mold temperature is 60 to 130 ° C., the resin temperature is 200 to 320 ° C., and the injection pressure is 400 to 2000 k.
g / cm ^2, injection speed may be selected in the range of 1~150g / s. After cooling and solidifying the thermoplastic resin, the shaft magnet is taken out of the mold, and then the outer peripheral surface is subjected to multi-pole magnetization, whereby the cylindrical permanent magnet portion 2 and the shaft portion 3 made of the thermoplastic resin are integrally formed. A combined magnet roll is obtained. Here, the shaft portion 3 is a cylindrical permanent magnet 2
Since both ends of the supporting portion 3a that supports the inner peripheral surface of the permanent magnet 2 have the locking portions 3b and 3b that contact the magnet end surface, the thermoplastic resin contracts during the cooling and solidification, and the inner peripheral surface of the permanent magnet 2 and the supporting portion Even if there is a gap between the outer peripheral surface of 3a and the permanent magnet 2
And the shaft portion 3 are firmly fixed. For example, the locking portion 3
If b is omitted, there is a possibility that the shaft portion 3 may come out of the permanent magnet 2. The shaft portion 3 has a shaft support portion 3C extending in the axial direction from the end portion of the locking portion 3b,
This shaft support is in sliding contact with the bearing (see FIG. 3). In addition,
If the contact fixing of the permanent magnet and the resin is practically sufficient, the locking portion can be omitted when the fixing torque in use is, for example, 10 kgf · cm or less.

As the above-mentioned thermoplastic resin, a known resin may be used, but one having a large rigidity "having an elastic modulus of 1.1 x
10 ² kg / cm ² or more (more preferably 2.4 × 10 ²
kg / cm ² or more) ”is preferable. Examples of such a resin include polypropylene, polystyrene, polyacetal and the like.

In the present invention, the cross section of the hollow portion of the cylindrical permanent magnet portion 2 is preferably non-circular "for example, polygonal (hexagonal, octagonal, etc.)" as shown in FIG. By forming the hollow portion in such a shape, it is possible to prevent the fixing strength from being reduced due to the shrinkage of the thermoplastic resin described above (a circumferential rotation can be prevented).

Next, the results of comparison with the conventional one will be shown for specific examples. Ba ferrite powder (average particle size 1.0 μm)
By using a rubber press method to form a cylindrical molded body,
Sintered at 1200 ° C and processed to have an outer diameter of about 18 mm and an inner diameter of about 1
A cylindrical isotropic ferrite magnet (YBM-3 made by Hitachi Metals) having a length of 0 mm and a length of 210 mm was prepared. A nylon adhesive (Aaron Mighty FS-1175PF manufactured by Toagosei Co., Ltd.) is applied to the large diameter portion of a SUS304 shaft (large diameter portion outer diameter 8 mm, small diameter portion outer diameter 6 mm), and then applied to the hollow portion of the ferrite magnet. It was inserted and heated at 180 ° C. for 10 minutes to prepare a magnet with a shaft, and the surface was subjected to 8-pole symmetrical magnetization to obtain a magnet roll (magnetic flux density 750 G on a non-magnetic sleeve having an outer diameter of 20 mm). The bonding strength (circumferential direction) of the magnet and shaft of this magnet roll is 160 kg.
It was cmf.

On the other hand, in the present invention, the above-mentioned ferrite magnet is set in a mold, and polyacetal resin (Delrin 500) is injected (injection temperature 200 ° C., injection pressure 2000 kg / cm ² , injection speed 50 g / s, mold temperature 100 ° C), cooling and solidifying (water cooling, 100
C), the magnet roll shown in FIG. 1 (locking part: outer diameter (d
₁ ) 14.5 mm, thickness (t) 4.25 mm, shaft support:
An outer diameter (d ₂ ) of 6 mm) was created. With this magnet roll, the bonding strength between the magnet and shaft (circumferential direction)
Was 85 kgf · cm, which was a sufficiently large value for practical use.

Although both of the above magnet rolls have the same joining strength, it was confirmed that the manufacturing cost of the present invention can be reduced by about 60% as compared with the conventional one. This is because in the conventional one, machining of the end portions 31a and 31b of the shaft 30 and the bonding of the shaft and the magnet are necessary, whereas in the present invention,
This is because the shaft can be molded and the magnet and the shaft can be joined at the same time as shown in FIG.

[0014]

Since the present invention has the structure and operation as described above, it is possible to obtain a magnet roll having a high fixing strength between the shaft and the magnet and at a low cost.

[Brief description of drawings]

FIG. 1 is a partially omitted vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the present invention.

FIG. 3 is a partially omitted vertical sectional view showing an example of a conventional magnet roll.

[Explanation of symbols]

 1 Magnet roll 2 Cylindrical permanent magnet part 3 Shaft

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[Procedure amendment]

[Submission date] June 6, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an example of a magnet roll of the present invention. In FIG. 1, 1 is a magnet roll, which has a cylindrical permanent magnet portion 2 and a shaft portion 3 fixed thereto. The cylindrical permanent magnet part 2 is made of, for example, hard ferrite powder {(MO · nFe ₂ O ₃ (M: Ba, Sr, one or more kinds of Pb, n = 5 to 6)}, if necessary, an organic binder (methyl cellulose, carboxyl). Cellulose or the like) is added (preferably 2% by weight or less), and the mixture is kneaded with a kneader and then granulated and dried to make a raw material, that is, this raw material powder has a core rod in the center and a rubber. And the like are filled in a cylindrical molding die formed of an elastically deformable material, and a working fluid such as oil or water is pressed from around the molding die to create a cylindrical molding body.
Sintering is performed at a temperature of 00 to 1300 ° C., both ends of the obtained sintered body are cut, and after being processed to a predetermined length, grinding processing (for example, centerless processing) is performed to obtain a magnet material having a predetermined size. The magnet material is prepared by preparing a slurry (solid content 60 to 90% by weight) containing the ferrite powder, a mixed medium (water or polyvinyl alcohol, etc.) and the organic binder, and extruding the slurry to a predetermined length. It may be produced by cutting, drying, sintering and processing. According to this extrusion molding, an isotropic ferrite magnet can be obtained as a whole, but since the molding is performed by sliding on the inner peripheral surface of the mold in the process of extrusion molding, the ferrite particles on the surface portion of the molded body can be obtained. May be mechanically oriented in the axial direction to give some anisotropy (extrusion anisotropy).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Next, the results of comparison with the conventional one will be shown for specific examples. Ba ferrite powder (average particle size 1.0 μm)
By using a rubber press method to form a cylindrical molded body,
Sintered at 1200 ° C and processed to have an outer diameter of about 18 mm and an inner diameter of about 1
A cylindrical isotropic ferrite magnet (YBM-3 made by Hitachi Metals) having a length of 0 mm and a length of 210 mm was prepared. A nylon adhesive (Aaron Mighty FS-1175PF manufactured by Toagosei Co., Ltd.) is applied to the large diameter portion of a SUS304 shaft (large diameter portion outer diameter 8 mm, small diameter portion outer diameter 6 mm), and then applied to the hollow portion of the ferrite magnet. It was inserted and heated at 180 ° C. for 10 minutes to prepare a magnet with a shaft, and the surface was subjected to 8-pole symmetrical magnetization to obtain a magnet roll (magnetic flux density 750 G on a non-magnetic sleeve having an outer diameter of 20 mm). The joint strength (circumferential direction) between the magnet and the shaft of this magnet roll is 160 kgf.
・ It was cm.

Claims (3)

[Claims] 1. A cylindrical permanent magnet portion having a plurality of magnetic poles on a surface thereof, and a shaft portion made of a thermoplastic resin penetrating the cylindrical permanent magnet portion, the shaft portion of the permanent magnet portion. A magnet roll having a support portion that is in close contact with the inner peripheral surface and a shaft support portion that extends axially from the support portion. 2. The magnet roll according to claim 1, wherein the support portion has locking portions that are in close contact with both end surfaces of the permanent magnet portion. 3. The magnet roll according to claim 1, wherein the inner peripheral surface of the cylindrical permanent magnet portion is formed to have a non-circular cross section.