JP2001138351A - Method of molding cylindrical magnet rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a magnetic rubber ring having high magnetic force and reduced in the irregularity of magnetic force in a circumferential direction. SOLUTION: Magnetic powder-containing unvulcanized rubber is extruded into a string shape and inclined parts are formed on both end surfaces of the string shaped extrudate and both inclined end surfaces of the extrudate are bonded to form a rubber ring 1. This rubber ring 1 is injected in the groove part of a cavity in a compressed state by the projected part of an upper mold 3a to obtain a magnetic rubber ring having high magnetic force and reduced in the irregularity of magnetic force in a circumferential direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cylindrical magnet rubber having a high magnetic force and a small magnetic variation around the circumference.

[0002]

2. Description of the Related Art Conventionally, in producing a rubber ring having magnetism, an appropriate amount of magnetic powder is mixed with a rubber material, and then sheet-shaped rolls are used to form a flat unvulcanized rubber material. The vulcanized rubber fabric was cut to an appropriate width and length, joined together in a ring shape, and this unvulcanized ring fabric was supplied to a mold and molded. Due to the occurrence of variations, these days, unvulcanized rubber dough is punched into a ring to form a dough ring, which is supplied to a mold and compressed and formed to form a circumferential magnetic rubber ring. Are coming. In addition, with the expectation of improved workability and moldability, unvulcanized rubber dough containing magnetic powder is directly injected into the mold from the center and heated and molded to form a circular magnetic rubber ring. Molding methods have also been widely used. It is also possible to carry out a molding method in which a magnetic field is formed by energizing the coil, the unvulcanized rubber material containing the magnetic powder is molded by a mold in the magnetic field, and the magnetic powder is aligned in one direction.

[0003]

However, such a rubber material is kneaded, and roll sheeting is performed.
The molding method of stamping and forming from a plate-like material has a large defect that the directionality of the plate-like material by the roll sheeting appears as it is on the molded product, the magnetic force varies, and the circumference is not uniform. In addition, in the injection molding method in which unvulcanized rubber material is injected and molded into a mold, it is not possible to obtain satisfactory appearance and accuracy unless the rubber viscosity is reduced and injection is performed. Because a large amount of magnetic powder is mixed with the rubber material to obtain strong magnetism, the hardness of the dough is inevitably increased, so the workability is extremely poor, and it is difficult to say that it has reached a level that can be practically used. there were. In molding in a magnetic field, it is inevitable that the combined structure of the magnetic field generator and the mold is large and complicated, and the molding workability using this is extremely deteriorated, so that a burden is imposed on the manufacturing cost. It was a big factor to multiply.

In view of the above drawbacks, the present invention provides a method of forming a magnet rubber ring having a small variation by uniformly flowing a rubber material and magnetic powder in order to make the magnetic force characteristics of a cylindrical rubber ring uniform in the circumferential direction. It is intended to provide a way.

[0005]

The present invention will be described with reference to the accompanying drawings. This is a method for molding a magnet rubber A having a cylindrical shape as shown in FIG. A rubber material extruded in a string shape is prepared, and inclined portions are formed on both end surfaces obtained by cutting the rubber material, and the inclined portions on both end surfaces are joined to each other.
As shown in FIG. 5, a rubber ring 1 having substantially the same shape as the center diameter of the molded product is formed, and a groove 22a on which the rubber ring 1 is placed is provided at the entrance of a cavity 21a cut into the lower mold 2a. Both sides of the groove 22a are tapered so as to open outward, and are combined with an upper mold 3a having a projection 32a that matches the taper of the groove 22a as shown in FIG. It is characterized in that the rubber ring 1 is charged between 3a and 2a and is formed by compression and heating as shown in FIG.

As shown in FIG. 1, the diameter of the string of the rubber ring 1 is 3 to 1 of the thickness of the rubber portion of the cylindrical magnet rubber A.
It is characterized in that it is formed to have a thickness of 0 times.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the present invention extrudes unvulcanized rubber mixed with magnetic powder using an extruder, and cuts and joins it to an appropriate size to form an O-ring. At this time, a slant is formed on the joint surface and these are connected to form a ring-shaped rubber ring 1. The rubber ring 1 thus formed is divided into upper and lower molds 3.
a and the lower mold 2a are axially heated and compressed to form a cylindrical magnet rubber A. In the mold for forming the groove, a tapered groove 22a is formed at the entrance of the cavity 21a of the lower mold 2a, and the upper mold 3a having a convex portion 32a to be fitted with the groove 22a is combined. In molding, the rubber ring 1 is put into the groove 22a of the lower mold 2a, and the rubber ring 1 is compressed by the convex portion 32a of the upper mold 3a and pushed into the cavity 21a to be filled. The magnetic powder in the material is arranged in parallel in the axial direction of the cylinder, and flows with one direction. At this time, since the cord-shaped rubber ring 1 is compression-filled into the cylindrical portion, a high rubber pressure is ensured, and the flow is filled up to every corner of the cavity 21a, so that good moldability can be obtained. When the outer periphery of the cylindrical magnet rubber A formed by such a manufacturing method is magnetized, a magnet having a high magnetic force and a circumferentially small magnetic variation can be formed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the practice of the present invention, a rubber material produced by an extruder is arranged such that mixed magnetic powder (for example, ferrite) is aligned in the extrusion direction (the cross section is symmetrical), and the ferrite in the circumferential direction of the joint portion is joined. The uniformity of the arrangement is such that the closer the cut surface is to the direction of compression molding, that is, the surface perpendicular to the axial direction, the less the irregularity of the arrangement is, so it is important to form the cut surface at an angle and join it, A cut surface close to a tilt angle perpendicular to the compression direction is preferable.

Such magnetic powders include NBR, H-NB
R (hydrogenated NBR) and other polymers in a weight ratio of 70 to 98
% And mixed with rubber chemicals to form an unvulcanized rubber. This is extruded using an extruder. The diameter of the string of the rubber ring 1 to be formed is 3 to 10 times the thickness of the rubber portion of the cylindrical magnet rubber A. Is a guide. As a specific example, for a product having a rubber part thickness of 1 mm and a height of 8 mm, 4 to 6 m
The diameter of the string of m is a guide.

As the magnetic powder used here, ferrite powder which is inexpensive and can retain ferromagnetism is the most suitable, and is easy to handle in view of kneading workability or extrusion workability. Material.

In the formation of a ring-shaped joint from the rubber material to the rubber ring 1, the rubber material alone may be formed into an O-ring shape by itself, as shown in FIGS. 1, 2 and 3. As described above, when the metal core 4 is buried and arranged for the purpose of reinforcing the product, the rubber core 1 and the metal core 4 can be integrated by heating and pressing the metal core 4. In addition, this press-contact method not only facilitates the rounding, but also dramatically improves the workability from storage / transportation to loading into a mold.

[0012]

According to the present invention, the unvulcanized rubber mixed with the magnetic powder is extruded, and a slope is formed on the connecting surface to form a rubber ring 1, which is poured into a cylindrical gap from one direction. In this way, the magnetic powder is arranged in parallel, and the magnetic powder in the rubber material, that is, the ferrite is arranged in a uniform direction and arrangement enhances the magnetic force, and it is distributed uniformly without variation on the circumference . In setting the dimensions for the filling rate of the unvulcanized rubber, it is sufficient to adjust only the diameter of the string, which is extremely simple. In addition, since the cross-sectional shape of the unvulcanized rubber is a circular string shape, it is less affected by placement errors such as twisting and falling, and the processing and bonding of the bonding portion are simple and excellent in handling.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention before molding.

FIG. 2 is a sectional view showing a molding state of the present invention.

FIG. 3 is a sectional view showing a state where the mold is clamped from FIG. 2;

FIG. 4 is a perspective view showing a cylindrical magnet rubber.

[Explanation of symbols]

 A Cylindrical magnet rubber 1 Rubber ring 2a Lower mold 21a Cavity 22a Groove 3a Upper mold 32a Convex part 4 Core

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Claims (3)

[Claims] 1. A method of molding a cylindrical magnet rubber, comprising preparing a rubber material extruded in a string shape by mixing magnetic powder, making both cut end surfaces of the rubber material inclined portions, and inclining the both end surfaces. The rubber parts are joined to form a rubber ring having substantially the same shape as the center diameter of the molded product. At the entrance of the cavity cut into the lower mold, a groove part for mounting the rubber ring is provided, and both side parts of the groove part are provided. With a tapered shape that opens outward,
Forming a cylindrical magnet rubber, which is combined with an upper mold having a convex portion to be fitted to the tapered groove portion, and the rubber ring is put between the upper and lower molds and compressed and heated to form. Method. 2. The method according to claim 1, wherein the diameter of the rubber ring is 3 to 10 times the thickness of the rubber portion of the cylindrical magnet rubber. 3. A cylindrical ring according to claim 1, wherein said rubber ring for joining said rubber material is formed into a ring by adhering to a surface of a metal core embedded in a cylindrical magnet rubber. Method of molding magnet rubber.