JPH0869170A - Magnet roll and its production - Google Patents

Abstract

PURPOSE: To provide a magnet roll which can be produced at a low cost and can maintain magnetic characteristics and strength even when the roll has a small diameter, and to provide its production method. CONSTITUTION: This magnet roll is produced by fixing a supporting shaft to a permanent magnet member 1 produced by sintering a powder magnetic material into a hollow cylindrical body. In this roll, a shaft member 11 comprising a material which can cause plastic deformation and having a supporting shaft at one end and an inserting part 13 where plural projections are formed on the other end. This axial member is engaged under pressure with at least one end of the permanent magnet member 1 in such a manner that the shaft member 11 is fixed to the permanent member 11 by plastic deformation of the projections.

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 developing roll or a cleaning roll in electrophotography, electrostatic recording and the like, and a method for producing the magnet roll. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in electrophotography, electrostatic recording, etc., a magnet roll used as a developing roll or a cleaning roll is most commonly of a structure as shown in FIG. In FIG. 5, reference numeral 1 denotes a permanent magnet member, which is formed into a hollow cylindrical shape by a powder sintered permanent magnet material such as hard ferrite or a mixed material of a ferromagnetic powder material and a binder, and has a shaft at the center. 2 is fixed coaxially.

A plurality of magnetic poles (not shown) extending in the axial direction are provided on the outer peripheral surface of the permanent magnet member 1, and these are arranged at equal or unequal intervals in the circumferential direction.
Next, a flat plate-shaped flange 3 and a shaft-equipped flange 4 are rotatably mounted on both ends 2a and 2b of the shaft 2 via bearings 5 and 5, and are attached to the outer circumferences of the flat-plate-shaped flange 3 and the shaft-equipped flange 4. Is fitted with a sleeve 6 formed in a hollow cylindrical shape.

The plate-like flange 3, the shaft-equipped flange 4 and the sleeve 6 are made of a non-magnetic material such as aluminum alloy or stainless steel. 7
Is a seal member and is fitted between the flat plate-shaped flange 3 and the end portion 2 a of the shaft 2. Further, the permanent magnet member 1 often has a diameter of 10 to 60 mm and a length of 200 to 350 mm.

With the above configuration, the relative rotation between the permanent magnet member 1 and the sleeve 6 (for example, the permanent magnet member 1 is fixed and the sleeve 6 is rotated by the flange 4 with the shaft) causes the outer peripheral surface of the sleeve 6 to be rotated. The magnetic developer is adsorbed to form a magnetic brush and a predetermined developing operation or the like is performed, or an excess magnetic developer after transfer from the surface of the photoconductor is adsorbed and a predetermined cleaning operation is performed.

It should be noted that the flat flange 3 in FIG. 5 has a hollow cylindrical projecting portion 3a provided at the center thereof as shown in FIG. 6, and the sealing member 7 (see FIG. 5) is omitted, and the projecting portion is formed. It may be used for driving the sleeve 6 or supporting the sleeve 6 via the portion 3a.

[0007]

When forming the permanent magnet member 1 having the above-mentioned structure, first, in the case of using a powder sintered magnet material such as hard ferrite, for example, an appropriate amount of polyvinyl alcohol (P) is added to barium ferrite particles.
VA) is added and kneaded with a double-arm kneader, and then granulated and dried raw material powder is prepared. Next, this raw material powder is filled into a bag of a thin film made of rubber or plastic, which has a core rod in the center, and is placed in a liquid such as oil, glycerin, or water, and liquid pressure is applied. Pressure molding (hydrostatic pressure molding or rubber pressing) is performed from the surroundings and firing is performed to mold a hollow cylindrical material.

A shaft (see reference numeral 2 in FIG. 5) separately prepared is fixed in the hollow hole of the above material with an adhesive, and then subjected to predetermined processing to provide a plurality of magnetic poles extending in the axial direction on the outer peripheral surface. Of.

However, when the above means is used, the work of molding the raw material from the raw material powder is relatively complicated, and the work of fixing the shaft to the hollow hole of the raw material is also complicated, and the number of manufacturing and assembling steps is increased. However, there is a problem in that the manufacturing cost rises due to the large size. Especially, since the hollow hole of the material and the shaft are in a loose state, it is necessary to completely fill the gap between them with the adhesive. Therefore, when the material and the shaft are combined, excess adhesive is removed and cleaned. There is a need to. Further, there is a drawback that heating is required to cure the adhesive.

On the other hand, a means for molding the permanent magnet member 1 by a so-called bonded magnet containing a mixture of ferrite particles and a thermoplastic resin material as a main component is also commonly used. In this case, a mold for injection molding is used, the shaft 2 is previously inserted in a predetermined portion of the molding space, the thermoplastic resin material is heated and melted, and is injected and filled into the molding space, followed by cooling. It can be taken out after solidification. In addition, in order to improve the magnetic characteristics, a magnetic field forming means for providing anisotropy by providing a magnetic field generating means in the injection molding die is commonly used.

The permanent magnet member manufactured by the anisotropic bonded magnet as described above has advantages of relatively small manufacturing steps and light weight, but on the other hand, the injection molding die becomes complicated. At the same time, when the number of magnetic poles is large, there may occur a situation where molding in a magnetic field is impossible. In particular, if the permanent magnet member has a small diameter of, for example, 20 mm or less, the magnetic field generating means may come close to or come into contact with each other, and it may be substantially impossible to manufacture an injection molding die. Therefore, there is a problem that the degree of freedom of the magnetization pattern is small.

Further, as an example of the magnet roll using the bonded magnet as described above, the shaft 2 in the central portion is omitted,
In addition, there has been proposed one having a uniform diameter over the entire length (for example, Japanese Unexamined Patent Publication No. 62-81009, Japanese Utility Model Laid-Open No. 5-504).
69 publication). With this configuration,
It is said that the shaft 2 is not required, magnetic design can be easily performed, and sufficient magnetic force can be obtained even with a small diameter.

However, in the magnet roll having the above structure, the magnet roll is formed to have the same diameter over the entire length.
The size of the bearing is inevitably large, and there is the drawback that the size of the entire device is increased. Therefore, it is conceivable to reduce the diameter of the bearing portion by molding or processing to reduce the size of the entire device. In this case, the processing for reducing the diameter of the bearing portion is easy, but the wear resistance and strength of the bearing portion are insufficient, resulting in a problem of poor durability.

It has also been proposed to provide a support member with a cap-shaped shaft on both ends of the cylindrical magnet having the same diameter (see, for example, Japanese Utility Model Laid-Open No. 55508/1993). According to this proposal, the diameter of the bearing portion can be reduced, and the wear resistance can be improved. However, there are still problems with the concentricity and strength of the support metal fittings, there is also a question of cost reduction, and there is a need for further improvement in terms of practicality.

In order to solve the problem of strength of the above-mentioned bonded magnet, the present applicant forms an integral cylindrical body over the entire length with a ferrite-based sintered magnet material, and forms an intermediate body at both ends of this cylindrical body. Has been proposed to form a shaft portion having a diameter smaller than that of the shaft portion (Japanese Patent Application No. 5-137153).
issue).

According to the above proposal, it is possible to expect an effect that a magnet roll having high magnetic characteristics and a large degree of freedom of a magnetizing pattern can be relatively easily manufactured, but there are still some problems.

That is, since the cylindrical body made of the ferrite-based sintered magnet material is hard, it is necessary to depend on the grinding work to form the shaft portions at both ends, and the grinding allowance for forming the shaft portion is required. Since it is large, there is a problem that the grinding work takes time. Further, since the ferrite-based sintered magnet material is brittle, the strength of the shaft portion formed by grinding is insufficient, and undesired breakage, chipping, etc. may occur during handling in the magnetizing step and other working steps after grinding. There is a problem that accidents are likely to occur.

The present invention solves the problems existing in the prior art and the improved invention described above, and even if the diameter is small, the magnetic characteristics and strength can be secured, and the magnet roll can be manufactured at low cost, and the manufacturing method thereof. The purpose is to provide.

[0019]

In order to achieve the above object, first, in the first invention, a supporting shaft is fixed to a permanent magnet member integrally formed in a hollow cylindrical shape from a powder sintered magnet material. In the formed magnet roll, a shaft member made of a plastically deformable material and having a support shaft at one end and a press-fitting portion having a plurality of protrusions at the outer periphery of the other end are formed on at least one permanent magnet member. A technical means was adopted in which the hollow portion of one end portion is press-fitted and engaged via a press-fitting portion, and the shaft member is fixed to the permanent magnet member by plastic deformation of the protrusion.

In the above invention, the shaft member may be formed of an aluminum alloy, and the projection of the press-fitting portion may have a triangular screw shape (including not only the triangular screw but also a concentric groove having a triangular screw shape). In this case, the triangular screw-shaped peaks and valleys may be rounded.

Further, in the case where the protrusion of the press-fitting portion is formed in a triangular screw shape as described above, it is preferable to set the following dimensional relationship. d ₂ = di + (0.2 to 0.5 mm) dp = (d ₁ + d ₂ ) / 2≈di, where di is the inner diameter of the hollow portion at the end of the permanent magnet member d ₁ : the diameter of the valley of the triangular threaded protrusion d _2: mountain triangular screw thread shaped protrusion diameter dp: triangular in the case of a screw-shaped projections of the pitch diameter above, since d ₂ is insufficient fixing strength due to press-fitting of the shaft member is less than di +0.2 mm Not preferable. On the other hand, when d ₂ exceeds di +0.5 mm, the press-fitting margin becomes too large, which makes it difficult to press-fit and fix the shaft member to the permanent magnet member, and the plastic deformation amount of the press-fitting portion becomes large. This is inconvenient because the flash and other surplus materials will squeeze out.

If the axial length of the press-fitting portion of the shaft member is less than 5 mm, the axial length of the press-fitting portion is insufficient, and the strength of the shaft member against bending cannot be ensured, and so-called "tilt" occurs in the shaft member. This is not preferable because it tends to occur, and the identity of the axis with the permanent magnet member is impaired. On the other hand, if the axial length of the press-fitting portion exceeds 20 mm, the axial length of the press-fitting portion becomes excessive, which makes it difficult to press-fit and fix the shaft member to the permanent magnet member, which is inconvenient.

The pitch diameter dp of the triangular screw-shaped protrusions is
When the inner diameter di of the hollow portion is set to be substantially equal, the fixing strength of the shaft member can be secured, and the work of press-fitting the shaft member to the permanent magnet member can be easily performed.

Next, in the second aspect of the present invention, in the method of manufacturing a magnet roll, which is formed by fixing a support shaft to a permanent magnet member integrally formed into a hollow cylindrical shape by using a powder sintered magnet material, A shaft member made of a plastically deformable material whose outer periphery is machined, and a support shaft formed at one end and press-fitted portions having a plurality of protrusions formed at the outer periphery of the other end are formed on both ends of the permanent magnet member. A technical means was adopted in which the outer circumference of the support shaft of the shaft member is machined with the outer circumference of the permanent magnet member as a reference by press-fitting and fixing to the hollow portion of the shaft through the press fitting portion.

Further, in a third aspect of the present invention, in the method of manufacturing a magnet roll, wherein a supporting shaft is fixed to a permanent magnet member integrally formed into a hollow cylindrical shape by using a powder sintered magnet material, both ends of the permanent magnet member are provided. The hollow part of the part is used as a reference part for the outer peripheral processing, the outer periphery of the permanent magnet member is processed, and it is made of a plastically deformable material, and has a support shaft at one end and a plurality of protrusions at the outer periphery of the other end. A technical means is adopted in which the shaft members each having the press-fitting portion are press-fitted and fixed to the hollow portions at both ends of the permanent magnet member via the press-fitting portions.

[0026]

With the above structure, the permanent magnet member can be easily molded, and the fixing strength of the shaft member can be greatly improved. Further, the concentricity between the support shaft of the shaft member and the permanent magnet member is secured, and the fixing work becomes easy,
The manufacturing cost can be reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a cross-sectional structure of essential parts showing an embodiment of the present invention. In FIG. 1, the permanent magnet member 1 is made of a ferrite sintered magnet (YBM-3 made by Hitachi Metals), for example, outer diameter dm = 13.7 mm, inner diameter di = 4 mm, length Lm = 223 mm.
It is formed into a hollow cylindrical shape. In order to form such a hollow-cylindrical permanent magnet member 1, it is possible to form by hydrostatic molding or rubber pressing as described above, but it is also possible to form by extrusion molding means.

Next, the raw materials constituting the permanent magnet member will be described. First, ferrite particles (MO ・ nF) having a magnetoplumbite type crystal structure with a particle size of 0.7 to 1.5 μm.
e ₂ O ₃ : M = one or more of Ba, Sr, and Pb, n = 5
~ 6) and a mixed solution such as water and alcohol are thoroughly mixed to prepare a mud-like or ointment-like raw material. In this case, if the particle size of the ferrite particles is too small, the formability at the time of extrusion molding is lowered, while if the particle size is too large, the density of the sintered body is lowered and the magnetic properties are lowered, which is not preferable. Therefore, it is preferable to use particles having a particle size in the range of 0.7 to 1.5 μm.

If the amount of the mixed liquid added to the ferrite particles is too small, the viscosity of the raw material becomes large, the moldability at the time of extrusion molding is deteriorated, and the density of the molded body is locally varied, and at the time of sintering. In this case, cracks will be generated, which is not preferable. On the other hand, if the amount of the mixed solution added is too large, cracks occur when the molded body is dried, and high density during molding cannot be obtained, which is inconvenient. Therefore, the addition amount of the mixed solution is 1 with respect to the ferrite particles.
It is preferable to set it in the range of 0 to 30% by weight.

The ferrite particles contain methyl cellulose,
Moldability can be improved by adding an organic binder such as carboxymethyl cellulose. However, if the amount of the organic binder added is too large, cracks occur during extrusion molding, and these cracks develop during sintering, which is not preferable. Therefore, the amount of the above organic binder added to the ferrite particles is 2% by weight.
Below, it is preferably 0.5 to 1.0% by weight.

Further, the ferrite particles contain 0.1 to 3% by weight of B.
By adding an oxide such as ₂ O ₃ , CaO or SiO ₂ , the density of the sintered body can be improved and the magnetic characteristics can be improved.

The raw material prepared as described above is extrusion-molded by a known extrusion-molding means, cut into a predetermined length, and then the mixed solution is removed through a drying step and sintered at a predetermined temperature. Form a sintered body.

The sintered body formed as described above is then finished to a predetermined size after smoothing the outer peripheral surface by grinding as in the prior art. The sintered body for forming the permanent magnet member is a long cylindrical body having a large axial length dimension as compared with the diameter dimension, and the sintered body has a high hardness. Therefore, dimensional accuracy (frame etc.)
From this point of view, it is preferable that the outer peripheral surface is processed by centerless grinding. According to the above coreless grinding process, the outer diameter dimension tolerance is 2
It is possible to process with high accuracy of 0 to 50 μm, and a hollow cylindrical permanent magnet member with high straightness can be obtained. In particular, a sintered permanent magnet material having a large mechanical strength is most suitable for the shaft member press-fitting and fixing method of the present invention.

Next, in FIG. 1, 11 is a shaft member, which is a plastically deformable material, such as A3003, A5052, A
A support shaft 12 is formed at one end, a press-fitting portion 13 is formed at the other end, and a stopper portion 14 is formed at an intermediate portion, using an aluminum alloy such as 5056. The press-fitting part 13 is
For example, it is formed into an M4.5 metric thread, and its axial length Ls is set to 15 mm. On the other hand, the outer diameter ds of the support shaft 12 is determined in accordance with the specifications of the device to be incorporated, and is formed to be 6 mm, for example.

FIG. 2 is an enlarged explanatory view of an essential part showing the press-fitting portion 13 in FIG. 1. A plurality of protrusions 15 having a triangular shape in a cross-sectional shape in a plane including the axis are formed on the outer peripheral portion. It should be noted that d ₁ , d ₂ , and dp are the diameter of the valley, the diameter of the crests, and the pitch diameter of the triangular screw, respectively. In this case, dp is preferably formed as ((d ₁ + d ₂ ) / 2), and is preferably formed to be substantially equal to the inner diameter di of the hollow portion 1a at the end of the permanent magnet member 1 shown in FIG.

With the above structure, when the shaft member 11 is press-fitted into the hollow portion 1a through the press-fitting portion 13 as shown in FIG. 1, the shaft member 11 is firmly fixed to the end of the permanent magnet member 1. You can In this case, since the projection 15 shown in FIG. 2 is plastically deformed by the hollow portion 1a shown in FIG.
In addition to facilitating the press-fitting work of (1) and firmly adhering to the hollow portion 1a, the fixing strength can be improved. An adhesive may be used in combination with the press-fitting portion 13 and the hollow portion 1a.

Next, FIG. 3 is a vertical cross-sectional view showing an example of a press-fitting jig in the embodiment of the present invention, which is made of, for example, stainless steel in a hollow cylindrical shape. The support portion 1 is provided in the press-fitting jig 16.
7, 18 and 19 are provided respectively, but these support portions 17 to
The shape and size of 19 are formed so as to correspond to the shape and size of the support shaft 12, the stopper portion 14 and the permanent magnet member 1 shown in FIG.

FIG. 4 is an explanatory view showing a mode of press-fitting by the press-fitting jig 16 of FIG. In FIG. 4, first, the press-fitting jig 1
6, the shaft member 11 is inserted, and the support shaft 12 and the stopper portion 14 of the shaft member 11 are respectively attached to the support portion 1 in the press-fitting jig 16.
Position within 7,18. Next, if the permanent magnet member 1 is press-fitted in the arrow direction along the support portion 19 of the press-fitting jig 16,
The press-fitting portion 13 of the shaft member 11 is the hollow portion 1a of the permanent magnet member 1.
The shaft member 11 is press-fitted into the shaft member 11 and can be firmly fixed to the permanent magnet member 1 in the above-described manner.

The magnet roll that is the subject of the present invention is
Although it is required that the axis of the permanent magnet member 1 and the axis of the shaft member 11 be concentric, a manufacturing means for concentrating the two axes will be described below.

First, as a first means, the outer circumference of the permanent magnet member 1 shown in FIG. 1 is processed by, for example, centerless grinding, and then the shaft member 11 is press-fitted and fixed as shown in FIG. Next, based on the outer circumference of the permanent magnet member 1, the shaft member 1
If the outer periphery of the support shaft 12 of No. 1 is processed by grinding or turning, for example, the axis of the permanent magnet member 1 and the axis of the shaft member 11 can be formed concentrically.

As the second means, first, the hollow portions 1a at both ends of the permanent magnet member 1 shown in FIG. 1 are used as the reference portion of the rotation center. Then, a mandrel (not shown) is fitted into the reference portion, and the permanent magnet member 1 is supported by, for example, supporting both ends.
The outer periphery of is ground. Then remove the mandrel,
Shaft member 1 in which support shaft 12 and press-fitting portion 13 are concentrically formed
1 is press-fitted and fixed to the permanent magnet member 1 as shown in FIG.

In the above embodiment, the permanent magnet member 1
Although the description has been given of the example in which the magnet is formed of a ferrite-based sintered magnet material, it may be formed of a rare earth-based sintered magnet material. As the material forming the shaft member 11, a non-magnetic material or a magnetic material can be used as long as it is plastically deformable and has a predetermined mechanical strength, and a non-metallic material such as engineering plastic is also used. Can be used. Further, the press-fitting portion 13 formed on the shaft member 11 may be a screw other than a triangular screw, and the protrusion 15
Is not limited to a continuous helical shape such as a screw, but may be independently shaped in the axial direction and / or the circumferential direction. It is also possible to provide the press-fitting portion 13 with, for example, a slit extending in the axial direction so as to give some elasticity in the direction orthogonal to the axial line. Further, the shaft member 11 may be provided at one end of the permanent magnet member 1 and the outer periphery or hollow portion of the permanent magnet member 1 may be used as a sliding surface directly as a supporting means for the other end.

[0043]

EFFECTS OF THE INVENTION Since the present invention has the structure and operation as described above, the following effects can be obtained.

(1) Since the permanent magnet member is made of powder-sintered magnet material, magnetic characteristics and strength can be ensured even if it has a small diameter. (2) Since the press-fitting portion of the shaft member is press-fitted and fixed to the permanent magnet member by plastic deformation, the fixing strength can be improved.

(3) The axes of the shaft member and the permanent magnet member can be made concentric, and the characteristics required for the magnet roll can be improved. (4) Since the work of press-fitting and fixing the shaft member and the permanent magnet member is easy, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view of a cross-sectional configuration of essential parts showing an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part showing a press-fitting portion 13 in FIG.

FIG. 3 is a vertical sectional view showing an example of a press-fitting jig in an embodiment of the present invention.

FIG. 4 is an explanatory view showing a mode of press-fitting by the press-fitting jig 16 of FIG.

FIG. 5 is a partially omitted vertical sectional view showing an example of a conventional magnet roll.

FIG. 6 is a longitudinal sectional view of a main part showing another example of a conventional magnet roll.

[Explanation of symbols]

 1 Permanent magnet member 11 Shaft member 13 Press-fitting part 15 Protrusion

Claims (5)

[Claims] 1. A magnet roll formed by fixing a support shaft to a permanent magnet member integrally formed into a hollow cylindrical shape by using a powder sintered magnet material, which is made of a plastically deformable material and is supported at one end. A shaft member, each of which is formed with a press-fitting portion having a plurality of protrusions on the outer circumference of the other end of the shaft, is press-fitted into the hollow portion of at least one end of the permanent magnet member via the press-fitting portion, and A magnet roll characterized in that a shaft member is fixed to a permanent magnet member by plastic deformation of a protrusion. 2. The magnet roll according to claim 1, wherein the shaft member is made of an aluminum alloy, and the projection of the press-fitting portion has a triangular screw shape. 3. d ₂ = di + (0.2 to 0.5 mm) dp = (d ₁ + d ₂ ) / 2≈di, where di is the inner diameter of the hollow portion at the end of the permanent magnet member d ₁ : triangular screw-shaped The magnet roll according to claim 2, wherein the diameter of the valley of the protrusion is d ₂ : the diameter of the crest of the triangular screw-shaped protrusion dp: the pitch diameter of the triangular screw-shaped protrusion. 4. A method of manufacturing a magnet roll, comprising a permanent magnet member integrally formed of a powder-sintered magnet material in a hollow cylindrical shape and having a support shaft fixed to the permanent magnet member. A shaft member made of a possible material and having a supporting shaft at one end and press-fitting portions each having a plurality of protrusions on the outer periphery of the other end, respectively, and press-fitting portions at the hollow portions at both ends of the permanent magnet member. Fixed by press fitting through
A method of manufacturing a magnet roll, characterized in that the outer circumference of a support shaft of a shaft member is processed with reference to the outer circumference of a permanent magnet member. 5. A method for manufacturing a magnet roll, comprising a permanent magnet member integrally formed of a powder-sintered magnet material in a hollow cylindrical shape and having a supporting shaft fixed to the permanent magnet member. The outer periphery of the permanent magnet member was machined as a reference part for machining, and a press-fitting part made of a plastically deformable material was formed with a support shaft at one end and a plurality of protrusions at the outer periphery at the other end. A method for manufacturing a magnet roll, comprising press-fitting and fixing a shaft member into hollow portions at both ends of a permanent magnet member via press-fitting portions.