JP2008258460A - Manufacturing method of annular resin magnet for magnetic encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an annular resin magnet for a magnetic encoder having a good yield and excellent magnetic characteristics. <P>SOLUTION: In this manufacturing method of the annular resin magnet for the magnetic encoder consisting of an annular ring shaped resin molded body, a resin raw material 12 containing an unoriented anisotropic magnetic powder and a molding die 11 equipped with an annular ring shaped cavity 11ba are prepared, the resin raw material is loaded into the cavity and compression hot molding and die clamping is carried out with the molding die to orient the magnetic powder in the resin raw material, then the molding die is cooled in that state, and the die is released to obtain the annular ring shaped resin molded body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an annular resin magnet for a magnetic encoder that is used for rotation detection and absolute position detection of automobile wheels and the like.

Conventionally, for example, as a magnetic encoder for detecting rotation of an automobile wheel, a slinger fixed to the rotation side of a wheel bearing portion is used as a core metal, and magnetic powder such as ferrite is used as a rubber or resin raw material on the sling-like portion of the slinger. And a molded body (magnet) formed by magnetizing and forming a number of N poles and S poles in the circumferential direction.
Patent Document 1 below discloses a method for manufacturing the magnetic encoder as described above, in which a magnet material containing magnetic powder and a thermoplastic resin as a binder of the magnetic powder is injection-molded in an annular shape, and then magnetized. A magnetic encoder using a plastic magnet manufactured by doing so is described.

Thus, when producing a magnetic encoder using a plastic magnet by injection molding, there is a problem in that a weld can be formed at a portion where the resin raw materials are joined in the process of loading the resin raw materials into an annular mold. It was. In order to solve this problem, the following manufacturing method has been adopted.
FIG. 6 is a diagram showing a conventional method for manufacturing an annular resin magnet for a magnetic encoder.
In the figure, G is a gate part for injecting a resin raw material, R is a runner part formed on the outer peripheral part of a part to be a product, 100 is a cored bar, and 200 is a resin molded body containing magnetic powder.
According to this, the resin raw material injected and loaded from the gate portion G is first loaded into the runner portion R, and then the resin raw material is loaded into the cavity of the portion that becomes the product. It can be assumed that there is no weld in the product.
JP 2006-313117 A

  However, in the above-described conventional manufacturing method, the material loaded in the parts other than the product, that is, the runner part R and the gate part G part is unnecessary as the material although it becomes an unnecessary part after molding. It was necessary to prepare. In addition, since it is practically difficult to reuse all unnecessary portions after molding, the yield of the annular resin magnet manufactured by this method is only about 30%, and this poor yield has been a problem. .

Furthermore, when producing an annular resin magnet by injection molding, if anisotropic ferrite is used as the magnetic powder, a magnetic field is applied from the outside to the resin raw material loaded in the cavity of the mold so that the ferrite is oriented. Thus, an annular resin magnet having a uniform magnetic force on the product can be produced. At this time, in order to obtain an annular resin magnet having strong magnetic properties, it is necessary to use a magnetic field forming ferrite having a thick crystal thickness, and the coercive force is higher than that of such a magnetic field orientation ferrite. The scale-like ferrite for mechanical orientation could not be used.
However, in recent years, plastic magnets have been actively developed, and there is a demand for the development of magnetic encoders made of plastic magnets having high coercive force and good magnetic properties that are not affected by the outside.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing an annular resin magnet for a magnetic encoder having a good yield and excellent magnetic characteristics.

According to a first aspect of the present invention, there is provided a method of manufacturing an annular resin magnet for a magnetic encoder, comprising: preparing a resin raw material containing unoriented anisotropic magnetic powder; and a mold having an annular cavity, The resin raw material is loaded, compression-heat-molded with the mold, and clamped to orient the magnetic powder in the resin raw material. Then, the mold is cooled in this state, demolded, and annular A resin molded body is obtained.
The manufacturing method of the annular resin magnet for a magnetic encoder according to the invention of claim 2 is characterized in that ferrite for machine orientation is used as the magnetic powder.

  According to a third aspect of the present invention, there is provided a method for producing an annular resin magnet for a magnetic encoder, comprising: preparing a resin raw material containing unoriented anisotropic magnetic powder; and a mold having an annular cavity, The magnetic powder in the resin raw material is charged with the resin raw material, compression-heat-molded with the molding die, and a magnetic field is applied in a direction perpendicular to the surface that becomes the magnetized surface when the resin molded body is formed. Then, the mold is cooled in this state, and after cooling, demagnetization or demagnetization is performed, and demolding is performed to obtain an annular resin molded body.

  According to a fourth aspect of the present invention, there is provided a method for producing an annular resin magnet for a magnetic encoder, wherein the cavity further includes a receiving portion for concentrically receiving an annular cored bar, and the resin raw material is loaded in advance in the cavity. In addition, by arranging the cored bar in the receiving portion, an annular resin molded body integrally fixed with the cored bar is obtained.

  And, as in the invention of claim 5, the resin raw material can be extruded and loaded in a string shape, and as in the invention of claim 6, the heating at the time of compression heating molding is performed by high frequency induction heating. Can do.

According to the method for manufacturing an annular resin magnet for a magnetic encoder according to the first aspect of the present invention, since an annular resin molded body can be obtained by compression heating molding, like a resin molded body formed by conventional injection molding No extra material is required to be loaded into the gate or runner. Therefore, it is possible to obtain an annular resin magnet with no waste of material and good yield.
Further, even when welds are generated when the resin raw material is loaded, the welds can be eliminated by compression of the upper and lower molds, and an annular resin magnet without welds can be obtained.
Furthermore, the anisotropic magnetic powder in the resin raw material can be oriented by clamping the mold at the time of compression heating molding, so that a magnetic field orientation process is not required. Therefore, the magnetic field orientation equipment is not required, and the equipment cost can be suppressed.

  According to the method of manufacturing the annular resin magnet for a magnetic encoder according to the invention of claim 2, since the ferrite for mechanical orientation can be used as the anisotropic magnetic powder, the magnetic orientation is not performed as described above. The ferrite can be oriented during compression molding. Therefore, it is possible to obtain an annular resin magnet having a strong magnetic force and a good magnetic property having the properties of a mechanical orientation ferrite having a high coercive force.

According to the method for manufacturing an annular resin magnet for a magnetic encoder according to the invention of claim 3, it is not necessary to use an extra material to be loaded in the gate portion or the runner portion as in the case of a conventional molded body by injection molding. Therefore, it is possible to obtain an annular resin magnet with no waste of material and good yield.
Further, even if welds are generated when the resin raw material is loaded, the welds can be erased by compression of the molding apparatus, and an annular resin magnet without welds can be obtained.

  According to the manufacturing method of the annular resin magnet for a magnetic encoder according to the invention of claim 4, the cavity further includes a receiving portion for receiving the annular core metal concentrically, so that it is integrally fixed with the core metal. A resin molded body can be obtained, and a resin molded body that is fixed and integrated with such a mandrel can be manufactured with high yield.

According to the method of manufacturing the annular resin magnet for a magnetic encoder according to the invention of claim 5, since the resin raw material is loaded by the method of extruding in a string shape, the resin raw material is not wasted and the manufacturing is easy. be able to.
According to the method of manufacturing an annular resin magnet for a magnetic encoder according to the invention of claim 6, since the heating at the time of compression heating molding is performed by high frequency induction heating, the heating speed is fast, so the heating molding process is short. Manufacturing efficiency can be increased.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an example of a bearing unit in which a magnetic encoder using an annular resin magnet obtained by the manufacturing method of the present invention is incorporated, and FIG. 2 shows a part of a molding apparatus used in the manufacturing method of the present invention. FIG. 3 is a schematic process diagram of the manufacturing method of the present invention, and FIGS. 4A, 4B and 4C are vertical cross-sectional views showing the molding procedure according to the manufacturing method of another embodiment of the present invention. FIG. 5 is a schematic process diagram of a manufacturing method according to another embodiment of the present invention.

  FIG. 1 shows an example of a structure in which a wheel of an automobile is supported by a rolling bearing unit 2 with respect to a shaft 1. A tire wheel (non-rotating wheel) is formed by a bolt 3 b on a hub wheel 3 a constituting an inner ring (rotation side member) 3. (Shown) is fixed. Reference numeral 3c denotes a spline hole formed in the hub wheel 3a. The drive shaft 1 is spline fitted into the spline hole 3c and is integrally fixed to the hub wheel 3a. Drive is transmitted to the tire wheel via the wheel 3a. 3d is an inner ring | wheel member, and the inner ring | wheel 3 is comprised with the said hub ring 3a.

  Reference numeral 4 denotes an outer ring (fixed side member), which is fixedly attached to a vehicle suspension system (not shown). Two rows of rolling elements (balls) 5 are interposed between the outer ring 4 and the inner ring 3 (hub 3a and inner ring member 3d) while being held by a retainer 5a. S and S ′ are seal rings for preventing leakage of lubricant (grease or the like) loaded in the rolling parts of the rolling elements 5... Or preventing intrusion of muddy water or dust from the outside. The outer ring 4 and the inner ring 3 are press-fitted. The seal ring S on the vehicle body side includes a ring-shaped cored bar 6 that is press-fitted into the inner periphery of the outer ring 4, and an elastic seal member (seal lip) 7 that is fixed to the cored bar 6 and made of an elastic material such as rubber. And a core metal (slinger) 8 fitted and fixed to the outer periphery of the inner ring member 3d is combined to form a pack seal type seal ring as shown in the figure.

The core metal (slinger) 8 includes a cylindrical portion 8a that is fitted and fixed to the outer periphery of the inner ring member 3d, and an outward flange portion (鍔) Shape portion) 8b.
The vehicle body side surface (outer surface) of the outward flange portion 8b of the core bar (slinger) 8 is made of an annular resin molded body obtained by kneading an anisotropic magnetic powder such as ferrite with a resin raw material. A magnetic encoder 9 that is magnetized so that the poles and the S poles are alternately arranged is integrally attached. On the vehicle body side (fixed side), a magnetic sensor 10 is fixed so that the detection surface faces the magnetic encoder 9, and the magnetic sensor 10 and the magnetic encoder 9 are used to determine the rotational speed (rotational speed) of the wheel. Detection is made. A method for manufacturing the annular resin magnet for the magnetic encoder 9 will be described in detail later.

  In the seal ring S assembled between the inner ring 3 and the outer ring 4 in this way, the slinger 8 rotates about the axis of the drive shaft 1 as the drive shaft 1 and the inner ring 3 rotate. The magnetic encoder 9 also rotates about the axis of the drive shaft 1, the magnetic sensor 10 detects the alternating magnetic change of the N pole and the S pole accompanying the rotation of the magnetic encoder 9, and counts the pulse signal due to this magnetic change. Thus, the rotational speed of the drive shaft 1, that is, the tire wheel (not shown) is calculated.

  The core bars 6 and 8 are formed by processing a cold rolled steel sheet such as SPCC into a shape as shown in the figure, and the seal member 7 includes NBR, H-NBR, ACM, AEM, Any rubber material selected from FKM or the like is used.

Next, an outline of a method for producing the annular resin magnet for a magnetic encoder according to the present invention will be described with reference to FIGS.
The molding apparatus 11 includes an upper mold 11a, a lower mold 11b, and a core 11c, and a burr groove 11aa is formed in the upper mold 11a. The lower mold 11b includes a cavity 11ba formed in a main shape of an annular resin molded body and a receiving portion 11bb that receives an annular core metal (slinger) 8 concentrically. The lower die 11b is moved up and down by a core 11c and a ram (not shown) together with the lower die 11b of the molding apparatus 11, and the lower die 11b becomes the movable side and the upper die 11a becomes the fixed side. According to the manufacturing method of the present invention, the annular resin magnet is molded by compression heating molding. As the heating means, high-frequency induction heating with a high heating rate, an embedded heater (hot plate), or the like is employed.

First, in order to fix the core metal (slinger) 8 to the resin molded body, it is placed in the receiving portion 11bb before loading the resin raw material (step 1). Then, the resin raw material 12 prepared by kneading a predetermined amount of anisotropic magnetic powder such as ferrite powder and appropriate additives in advance is loaded into the annular cavity 11ba (step 2). At this time, as shown in FIG. 2, if the resin material is extruded and loaded, the resin raw material is not wasted and manufacturing can be facilitated.
Then, the lower mold 11b is moved together with the core 11c in the direction D indicated by the white arrow in FIG. 2, and is compression-heat molded (200 to 300 ° C.) (step 3), and then clamped in the resin raw material 12 Orient the magnetic powder (step 4). At this time, the anisotropic magnetic powder kneaded and blended in the resin raw material 12 receives the action of clamping, and its easy magnetization axis is aligned along the clamping direction (white arrow direction D), In this state, the molding device 11 is cooled by a press station (not shown) of a cooling device (100 to 130 ° C.) (step 5), and the magnetic powder oriented in the resin raw material layer is fixed. Thereafter, the mold is removed and the burr is removed to obtain an annular resin molded body that is fixedly integrated with the core metal 8 (step 6). Then, if a magnetic field along the orientation direction of the resin molded body is applied by a known magnetizing device and magnetized in a pattern in which a large number of N poles and S poles repeat in the circumferential direction (step 7), the magnetic encoder 9 is completed (step 8).
Here, the magnetizing step by the magnetizing device is not limited to after demolding, and may be performed after orienting the magnetic powder. The resin raw material 12 is not limited to the method of extruding and loading the resin material 12 as described above, but a method of molding after injecting the resin raw material from several places by a pin gate and loading it into a preliminary shape as described later (FIG. 4). Reference), a pellet-shaped resin material may be loaded into the cavity 11ba. Further, an adhesive may be applied to the fixing surface between the core 8 and the annular resin molded body before molding, and the lower mold 11b and the core 11c may be an integrated mold. Needless to say.

As the anisotropic magnetic powder, ferrite powder, rare earth powder (NdFeB, SmFeN, etc.) and the like are employed. In particular, when the mold is clamped and compression-molded as described above, mechanical orientation ferrite can be used.
The resin material (binder) 12 of the cyclic resin magnet is a thermoplastic resin, and nylon 6, nylon 12, nylon 66, nylon 6T, nylon 9T, polyphenylene sulfide (PPS), or the like is employed. The resin molded body is kneaded with these resin raw materials (including additives, plasticizers and the like as necessary) and molded as a resin composition, but the magnetic powder is contained in the resin composition in an amount of 70 to 95% by weight. . Here, when the magnetic powder contained is less than 70% by weight, the magnetic strength is not sufficiently obtained, and when it exceeds 95% by weight, the binding force of the resin raw material 12 as a binder tends to be weakened.

According to the above, there is no need for extra material loaded in the gate part or the runner part as in the case of the conventional annular resin magnet manufactured by injection molding, so that the magnetic encoder 9 with no waste of material and good yield is obtained. be able to. According to this manufacturing method, the yield can be about 60%.
Further, even if a weld occurs when the resin raw material 12 is loaded, the weld can be eliminated by compressing the upper and lower molds 11a and 11b, and an annular resin magnet without a weld can be obtained. For example, as shown in FIG. 2, when the resin raw material 12 is extruded and loaded in a string shape, the joining portion when forming the annular shape becomes a weld, but such a weld disappears by clamping with the molding apparatus 11 later. Can be made.

Furthermore, the magnetic powder in the resin raw material 12 can be oriented by clamping the mold at the time of compression heating molding, so that a magnetic field orientation process is not required. Therefore, the magnetic field orientation equipment is not required, and the equipment cost can be suppressed.
In addition, in conventional manufacturing by injection molding, ferrite for machine orientation could not be used as magnetic powder. However, in the case of manufacturing by compression molding as described above, ferrite for mechanical orientation can be used, and a magnetic field can be used. Even without magnetic field orientation by a molding apparatus, the ferrite can be oriented during compression molding. Therefore, it is possible to obtain a ring-shaped resin magnet having good magnetic properties that has the properties of scale-like ferrite having a high magnetic force and coercive force and high mechanical orientation.

Next, an outline of a manufacturing method according to an embodiment different from the above will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the location similar to the above-mentioned example, and description of a common part is omitted.
The embodiment shown here is different from the above-described example in the loading method of the resin raw material 12 and the orientation method of the magnetic powder contained in the resin raw material.
In the figure, reference numeral 13 denotes a temporary mold provided with a pin gate 13a serving as an inlet for charging the resin raw material 12 into a preliminary shape, and reference numeral 14 denotes a preliminary molding table. The molding apparatus 11 itself is the same as the above example.

First, the core metal (slinger) 8 is placed on the preforming table 14, and the resin raw material 12 is loaded in a preliminary shape from the white arrow direction D1 through several pin gates 13a provided along the annular core metal 8. Then, a preform is formed (see step 1, FIG. 4 (a)). The resin raw material 12 is prepared by kneading a predetermined amount of anisotropic or isotropic magnetic powder such as ferrite powder and an appropriate additive in advance. When the resin material 12 is injected by the pin gate 13a, a weld 12a is generated on the surface of the resin material 12 as shown in FIG. Then, the preformed product in this state is placed in the cavity 11ba of the molding apparatus 11 so that the cored bar 8 is positioned in the receiving portion 11bb (step 2).
After the placement, the lower mold 11b is moved in the direction D indicated by white arrow in FIG. 4 (c), compression-molded (200 to 300 ° C.) (step 3), and a current is generated in the magnetic field generating coil (not shown). Is applied and heated (200 to 300 ° C.) while applying a magnetic field in a direction perpendicular to the surface that becomes a magnetized surface when the resin molded body is formed, and magnetic field molding is performed. At this time, the weld 12a existing on the surface of the resin raw material 12 can be extinguished by compression by the upper mold 11a. The anisotropic or isotropic magnetic powder kneaded and blended in the resin raw material 12 is subjected to the action of a magnetic field and aligned along the magnetic field direction. The magnetic powder is cooled (100 to 130 ° C.) (step 5) and the magnetic powder oriented in the resin raw material layer is fixed. Thereafter, demagnetization or demagnetization (step 6), demolding, and removal of burrs, an annular resin molded body fixed and integrated with the core metal 8 is obtained (step 7). Then, if a magnetic field along the orientation direction of the resin molded body is applied by a known magnetizing device and magnetized in a pattern in which a large number of N poles and S poles repeat in the circumferential direction (step 8), the magnetic encoder 9 is completed (step 9).
Here, the magnetizing step by the magnetizing device is not limited to after demolding, and may be performed after orienting the magnetic powder with the magnetic field orientation. The loading method of the resin raw material 12 is not limited to the above, and a method of extruding and loading in a string shape (see FIG. 2), or a method of loading a pellet-shaped resin raw material into the cavity 11ba. Further, an adhesive may be applied to the fixing surface between the core metal 8 and the annular resin molded body at the time of molding, and it goes without saying that the lower mold 11b and the core 11c may be an integrated mold. Yes.

  As the magnetic powder, ferrite powder for magnetic field orientation, rare earth powder (NdFeB, SmFeN, etc.) and the like are adopted, and as the resin raw material (binder) 12 of the cyclic resin magnet, the same ones as described above can be used.

According to the above, there is no need for extra material loaded in the gate part or the runner part as in the case of the conventional annular resin magnet manufactured by injection molding, so that the magnetic encoder 9 with no waste of material and good yield is obtained. be able to. According to this manufacturing method, the yield can be about 60%.
In addition, since the magnetic powder contained in the resin raw material 12 can be either anisotropic or isotropic, an annular resin magnet having no weld can be obtained while utilizing the respective characteristics.

In the embodiment described above, the annular resin molded body is integrated with the core metal (slinger) 8. However, it is also possible to magnetize the annular resin magnet and use it alone as the magnetic encoder 9. . Also, the shape of the magnetic encoder 9 is not limited to that shown in the figure, and it goes without saying that other shapes can be adopted depending on the portion to be applied. Further, FIG. 1 shows an example in which the magnetic encoder 9 is incorporated as a constituent member of the bearing whose inner ring 3 is on the rotating side, but the outer ring 4 is configured to be incorporated in a rotating side bearing or a rotating member other than the bearing. It is also possible to do.
The magnetic encoder 9 is formed so that a large number of N poles and S poles are alternately arranged in the circumferential direction. However, the magnetic encoder 9 is not limited to this. The present invention can also be applied to a method for manufacturing a circular resin magnet for a two-pole magnetic encoder in which the outer peripheral surface portion of the magnetized region and the remaining semicircular portion is an N-pole magnetized region.

It is a longitudinal cross-sectional view which shows the example of the bearing unit incorporating the magnetic encoder by the cyclic | annular resin magnet obtained by the manufacturing method of this invention. It is a longitudinal cross-sectional view which shows a part of shaping | molding apparatus used for the manufacturing method of this invention. It is a schematic process drawing of the manufacturing method of the present invention. (A) (b) (c) is a longitudinal cross-sectional view which shows the molding point by the manufacturing method of another embodiment of this invention. It is a schematic process drawing of the manufacturing method by another embodiment of the present invention. It is the figure which showed the manufacturing method of the conventional cyclic resin magnet for magnetic encoders.

Explanation of symbols

8 Core metal (Slinga)
9 Magnetic encoder 11 Molding device (molding die)
11ba cavity 11bb receiving part 12 resin raw material

Claims (6)

A method for producing an annular resin magnet for a magnetic encoder comprising an annular resin molded body,
A resin raw material containing unoriented anisotropic magnetic powder and a mold having an annular cavity are prepared, the resin raw material is loaded into the cavity, and the mold is compression-heat molded with the mold. An annular resin magnet for a magnetic encoder, characterized in that the magnetic powder in the resin raw material is oriented by tightening, the mold is then cooled in that state, and the annular resin molded body is obtained by demolding Method. In the manufacturing method of the annular resin magnet for magnetic encoders according to claim 1,
A method for manufacturing a magnetic encoder, wherein a magnetic orientation ferrite is used as the magnetic powder. A method for producing an annular resin magnet for a magnetic encoder comprising an annular resin molded body,
Preparing a resin raw material containing unoriented anisotropic magnetic powder and a mold having an annular cavity, loading the resin raw material in the cavity, and compression heating molding with the molding die, Orient the magnetic powder in the resin raw material by applying a magnetic field in a direction perpendicular to the surface that becomes the magnetized surface when it becomes the resin molded body, and then cool the mold in that state, after cooling, A method for producing an annular resin magnet for a magnetic encoder, comprising demagnetizing or demagnetizing and demolding to obtain an annular resin molded body. In the manufacturing method of the annular resin magnet for magnetic encoders according to any one of claims 1 to 3,
The cavity further includes a receiving portion that receives the annular core metal concentrically,
A magnetic encoder characterized in that, when the resin raw material is loaded into the cavity, the core metal is disposed in the receiving portion in advance, thereby obtaining an annular resin molded body integrally fixed with the core metal. Of manufacturing a circular resin magnet for use. In the manufacturing method of the cyclic resin magnet for magnetic encoders according to any one of claims 1 to 4,
A method for producing an annular resin magnet for a magnetic encoder, wherein the resin material is extruded and loaded into the cavity in a string shape. In the manufacturing method of the annular resin magnet for magnetic encoders according to any one of claims 1 to 5,
The method of manufacturing an annular resin magnet for a magnetic encoder, wherein the heating at the compression heating molding is performed by high frequency induction heating.

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