JP2008139161A - Magnetic encoder, rolling bearing, and magnetic field injection molding machine for multi-pole magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic encoder capable of appropriately detecting magnetic forces. <P>SOLUTION: The magnetic encoder 16 includes both a ring-like multi-pole magnet 23 in which magnetic poles are alternately arranged in its circumferential direction and a slinger 24 for housing the multi-pole magnet 23. The multi-pole magnet 23 includes both magnetic powder and a resin. The multi-pole magnet 23 is produced by a magnetic field injection molding machine for multipole magnets, which is provided with a metal mold part including metal molds constituting a cavity, which forms an external shape; an injection part for injecting a magnet material into the cavity; a coil for generating magnetic fields in axial directions in the metal mold part when the injection part injects the magnet material into the cavity; and a cooling part for cooling the coil, while generating magnetic fields in axial directions at the time of injection molding and cooling the coil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic encoder, a rolling bearing, and a magnetic field injection molding apparatus for a multipolar magnet, and more particularly, to manufacture a magnetic encoder provided in a rolling bearing that supports a rotating shaft, and a multipolar magnet included in such a magnetic encoder. The present invention relates to a magnetic field injection molding apparatus for multipolar magnets used in the field and a rolling bearing including such a magnetic encoder.

2. Description of the Related Art Conventionally, as a bearing used in an automobile ABS (Antilock Break System) apparatus, there is a rolling bearing with a seal provided with a magnetic encoder. Such a rolling bearing is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-221329 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2006-90995 (Patent Document 2). According to Patent Document 1, a rotation detection device that detects a rotation speed and a rotation direction includes a magnetic encoder and a sensor. The magnetic encoder includes a multipolar magnet having magnetic poles alternately formed in the circumferential direction, and a slinger that supports the magnet. The sensor detects alternating magnetic poles of a magnetic encoder that rotates with the rotating shaft. In this way, the rotation detection device detects the number of rotations and the like.
Japanese Patent Laying-Open No. 2005-221329 (FIG. 1) JP 2006-90995 A

  The multipolar magnet of the magnetic encoder described above contains magnetic powder, but it is preferable to use a plastic such as a thermoplastic resin as a binder for the magnetic powder from the viewpoint of productivity and the like. When the magnetic encoder is made of plastic, it is easy to mass-produce by molding by injection molding, which is effective in terms of productivity.

  A method for manufacturing a multipolar magnet will be briefly described. First, a magnet material in which magnetic powder and a thermoplastic resin are kneaded is prepared. And this magnet material is injection-molded by a disk gate system, and the external shape of a multipolar magnet is formed. In this case, a magnetic field is applied so that the magnetic powder contained in the multipolar magnet is oriented in the axial direction, and injection molding is performed while generating a magnetic field in the mold. Thereafter, the magnet is magnetized by a magnetizing yoke or the like to obtain a multipolar magnet.

  Here, when applying the magnetic field, generally, a coil is disposed outside the mold and the coil is energized. In this case, the coil generates heat by energizing the coil, but if injection molding is continuously performed, heat is accumulated in the coil and the coil is damaged by the heat. In addition, the electrical resistance of the coil increases due to the temperature rise of the coil. As a result, it becomes difficult for current to flow, and it becomes difficult to stabilize the magnetic field generated in the mold part.

  In such a coil, the magnetic field cannot be properly applied, the orientation of the magnetic powder contained in the multipolar magnet becomes insufficient, and the multipolar magnet is appropriately magnetized in the magnetization process after molding. I can't. In a magnetic encoder including such a multipolar magnet, it is difficult to properly detect the magnetic force by a sensor. Furthermore, a rolling bearing provided with such a magnetic encoder cannot appropriately detect the rotational speed or the like. In addition, if it manufactures with the space | interval of the shaping | molding by injection molding, the above-mentioned problem will be reduced. However, productivity will deteriorate.

  An object of the present invention is to provide a magnetic encoder capable of appropriately detecting a magnetic force.

  Another object of the present invention is to provide a rolling bearing capable of appropriately detecting the rotational speed and the like.

  Still another object of the present invention is to provide a magnetic field injection molding apparatus for multipolar magnets with good productivity.

  The magnetic encoder according to the present invention includes an annular multipolar magnet in which magnetic poles are alternately arranged in the circumferential direction, and a slinger that holds the multipolar magnet. The multipolar magnet includes magnetic powder and resin. A multi-pole magnet includes a mold part including a mold constituting a cavity forming an outer shape, an injection part for injecting a magnet material into the cavity, and a mold part when the magnet material is injected into the cavity by the injection part. A magnetic field injection molding device for a multipolar magnet including a coil that generates an axial magnetic field and a cooling unit that cools the coil is manufactured while generating a magnetic field in the axial direction and cooling the coil during injection molding. The coil is cooled to 80 ° C. or lower, more preferably 70 ° C. or lower. When the temperature of the coil exceeds 80 ° C., even if it is attempted to generate a magnetic field by energizing continuously, problems such as heat storage may occur and the coil may be damaged.

  Since the magnetic encoder having such a configuration is manufactured while cooling a coil that generates a magnetic field, the magnetic powder contained in the multipolar magnet can be highly oriented in the axial direction by a stable magnetic field. Such highly oriented multipolar magnets can be appropriately magnetized by a subsequent magnetizing step. Therefore, the magnetic encoder including such a multipole magnet can appropriately detect the magnetic force.

  Preferably, the resin is a thermoplastic resin. By doing so, magnetic field injection molding can be easily performed.

  More preferably, the magnetic powder is a ferrite-based magnetic powder. By carrying out like this, anticorrosion property can be improved.

  In another aspect of the present invention, the rolling bearing includes any one of the magnetic encoders described above. Since such a rolling bearing includes a magnetic encoder that can appropriately detect the magnetic force, the number of rotations and the like can be appropriately detected.

  In still another aspect of the present invention, a magnetic field injection molding apparatus for a multipolar magnet manufactures an annular multipolar magnet in which magnetic poles are alternately arranged in the circumferential direction. Here, the magnetic field injection molding apparatus for a multipolar magnet includes a mold part that includes a mold that forms a cavity that forms the outer shape of the multipolar magnet, and an injection part that injects a magnet material of the multipolar magnet into the cavity. When the magnet material is injected into the cavity by the injection unit, the coil unit includes a coil that generates an axial magnetic field, and a cooling unit that cools the coil.

  According to such a magnetic field injection molding apparatus for a multipolar magnet, it is possible to prevent damage to the coil due to heat storage when continuously manufacturing the multipolar magnet. If it does so, a magnetic field can always be stably generated in a metallic mold part. Therefore, productivity can be improved.

  Since the magnetic encoder having such a configuration is manufactured while cooling a coil that generates a magnetic field, the magnetic powder contained in the multipolar magnet can be highly oriented in the axial direction by a stable magnetic field. Such highly oriented multipolar magnets can be appropriately magnetized by a subsequent magnetizing step. Therefore, the magnetic encoder including such a multipole magnet can appropriately detect the magnetic force.

  Moreover, since such a rolling bearing is provided with the magnetic encoder which can detect a magnetic force appropriately, it can detect rotation speed etc. appropriately.

  Moreover, according to such a magnetic field injection molding apparatus for a multipolar magnet, it is possible to prevent damage to the coil due to heat storage when continuously manufacturing the multipolar magnet. If it does so, a magnetic field can always be stably generated in a metallic mold part. Therefore, productivity can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a part of a rolling bearing according to an embodiment of the present invention. With reference to FIG. 1, the rolling bearing 11 supports a rotating shaft (not shown). The rolling bearing 11 includes a ball 12 as a rolling element, an inner ring 13 disposed on the inner diameter side of the ball 12, an outer ring 14 disposed on the outer diameter side of the ball 12, a cage 15 that holds the ball 12, The magnetic encoder 16 for detecting the rotation speed of a rotating shaft, etc. and the seal | sticker 17 for sealing the inside of a bearing are included. The inner ring 13 is fixed to the rotating shaft and rotates together with the rotating shaft. On the other hand, the outer ring 14 is fixed to a housing (not shown). The ball 12 rolls on the raceway surfaces 18a and 18b provided on the inner ring 13 and the outer ring 14 when the rotary shaft rotates.

  The seal 17 includes a cored bar 31 having rigidity and a rubber part 32 having elasticity. The cored bar 31 is attached and fixed to the outer ring 14. The rubber part 32 is configured to cover a part of the cored bar 31. The rubber portion 32 is in contact with a slinger 24 described later at a plurality of locations with appropriate pressure. Specifically, a plurality of lip portions 28 a, 28 b, 28 c protruding to the inner diameter side of the seal 17 and the bearing outer side are in contact with the slinger 24. In this way, the inside 19 of the rolling bearing 11 is sealed. By doing so, it is possible to prevent leakage of the lubricating oil sealed in the interior 19 and prevent foreign matter from entering the interior 19 of the rolling bearing 11.

  A rotation detection device 21 that detects the number of rotations of the rotation shaft and the like includes a magnetic encoder 16 included in the rolling bearing 11 and a rotation sensor 22. The magnetic encoder 16 and the rotation sensor 22 are provided at positions facing each other. The rotation sensor 22 is fixed to the housing together with the outer ring 14 and the like, for example.

  Here, the configuration of the magnetic encoder 16 will be described. The magnetic encoder 16 includes a multipolar magnet 23 in which magnetic poles are alternately arranged in the circumferential direction, and a metal slinger 24 that holds the multipolar magnet 23. FIG. 2 is a conceptual diagram showing the configuration of the multipolar magnet 23. Referring to FIGS. 1 and 2, multipolar magnet 23 is annular and has a through hole at the center thereof. The multipolar magnet 23 is magnetized in a multipolar manner in the circumferential direction, and is configured such that N poles 27 a and S poles 27 b are alternately arranged on a PCD (Pitch Circle Diameter) 26.

  The slinger 24 includes a cylindrical portion 29a and a flange 29b extending from one end of the cylindrical portion 29a to the outer diameter side. The cross section of the slinger 24 is substantially L-shaped. The end 30 on the outer diameter side of the multipolar magnet 23 has a key shape. The multipolar magnet 23 is held by the slinger 24 so that the end portion 30 is hooked on the outer diameter portion 29c located at the outermost diameter of the flange 29b.

  The multipolar magnet 23 held by the slinger 24 rotates with the inner ring 13 as the rotation shaft rotates. At this time, the change in the magnetic force of the N pole 27 a and the S pole 27 b of the multipolar magnet 23 is read by the detection unit 25 of the rotation sensor 22 disposed on the outer side in the axial direction and facing the multipolar magnet 23. In this way, the rotation detection device 21 detects the number of rotations of the rotation shaft and the like.

  Here, the multipolar magnet 23 which comprises the magnetic encoder 16 is comprised from magnetic powder and the thermoplastic resin as a binder. With this configuration, the magnetic encoder 16 can be easily manufactured by magnetic field injection molding described later.

  The magnetic powder having magnetism is a barium-based or strontium-based ferrite powder, which may be an isotropic ferrite powder or an anisotropic ferrite powder. Since such ferrite powder is difficult to oxidize, the corrosion resistance of the magnetic encoder 16 can be improved. In addition, when the magnetic force is insufficient with only ferrite powder, rare earth magnetic powder such as samarium iron magnetic powder or neodymium iron magnetic powder may be mixed with ferrite powder.

  As the thermoplastic resin, polyamide 12, polyamide 612, polyamide 11, polyphenylene sulfide and the like are preferable. Such a thermoplastic resin is particularly effective in an environment with a lot of water such as salt water, muddy water, rain water and the like because of poor water absorption. Moreover, you may comprise so that the 1 or more compound selected from the group which consists of an above-described thermoplastic resin may be included.

  Here, a manufacturing method of the magnetic encoder 16 will be described. First, using a twin screw extruder or a kneader, the magnetic powder and the molten thermoplastic resin are kneaded, and the magnetic powder is appropriately dispersed in the thermoplastic resin. Thus, the magnet material of the multipolar magnet 23 is prepared. Next, magnetic field injection molding is performed using the magnet material so as to obtain the shape of the multipolar magnet 23 described above.

  FIG. 4 is a schematic diagram showing the magnetic field injection molding apparatus in this case. FIG. 5 is an enlarged cross-sectional view showing a main part of the magnetic field injection molding apparatus shown in FIG. FIG. 6 is an enlarged view of a portion indicated by VI in FIG. The configuration of the magnetic field injection molding apparatus will be described with reference to FIGS. 4, 5, and 6. The magnetic field injection molding apparatus 61 includes a mold part 62 that forms the outer shape of the multipolar magnet 23, an injection part 63 that injects a magnet material into the mold of the mold part 62, and an axial direction on the mold part 62. A coil 71 for generating a magnetic field. The mold part 62 and the injection part 63 are installed on the base part 64.

  The mold part 62 includes a fixed part 65, 66 fixed to the base part 64, a movable part 67 movable between the fixed parts 65, 66 in the direction of arrow A in FIG. Parts 65, 66 and a plurality of tie bars 68 attached to the movable part 67.

  The movable part 67 and the fixed part 66 are provided with a movable mold 69 and a fixed mold 70 that form the outer shape of the multipolar magnet 23, respectively. A coil 71 is arranged outside the movable side mold 69 and the fixed side mold 70. By energizing the coil 71, an axial magnetic field can be generated in the mold part 62.

  Here, a cooling pipe 78 for cooling the coil 71 is provided outside the coil 71. The cooling pipe 78 is attached so as to be in close contact with the outer diameter side of the coil 71. The cooling pipe 78 can flow in cold water from the outside and flow out the cold water to the outside, and can cool the coil 71 with water.

  Between the movable mold 69 and the fixed mold 70, a cavity 75 along the outer shape of the multipolar magnet 23 and a disk gate 76 that allows the flow of the magnet material into the cavity 75 are formed. . In the cavity 75, the slinger 24 included in the magnetic encoder 16 described above can be accommodated. The movable die 69 is composed of a plurality of divided dies 72a, 72b, 72c. The split molds 72a to 72c are respectively attached to the support portions 73 that support them. Similarly, the stationary mold 70 is composed of a plurality of divided molds 74a, 74b, and 74c.

  The injection unit 63 injects the magnet material from the nozzle 77 and fills the cavity 75 through the disk gate 76. When injecting the magnet material, the coil 71 is energized and applied to generate a magnetic field. In this case, by attaching the slinger 24 in the cavity 75, the multipolar magnet 23 integrated with the slinger 24 can be obtained.

  Here, since the coil 71 is water-cooled by the cooling pipe 78, the coil 71 does not store heat. Then, damage to the coil 71 due to heat storage can be prevented. Therefore, such a magnetic field injection molding apparatus 61 can continuously perform magnetic field injection molding, so that productivity can be improved. The coil 71 is desirably cooled to 80 ° C. or lower, more preferably 70 ° C. or lower. If the temperature of the coil 71 exceeds 80 ° C., problems such as heat storage may occur due to continuous energization and generation of a magnetic field, and the coil 71 may be damaged.

  Specifically, when the multipolar magnet 23 is manufactured by the magnetic field injection molding apparatus 61 using, for example, a magnet material in which a thermoplastic resin is PPS (polyphenylene sulfide), the mold temperature of the mold part 62 is set to 140 ° C. Need to be around. If it does so, the coil 71 will be damaged by heat storage. Therefore, as described above, the coil 71 is cooled by the cooling pipe 78 so that the temperature of the coil 71 becomes 80 ° C. or lower, so that the coil 71 can be prevented from being damaged.

  Moreover, since such a coil 71 is water-cooled, the temperature rise of the coil 71 can be prevented. If it does so, it will become difficult to flow an electric current with the increase in the electrical resistance in the coil 71, and the generated magnetic field can be stabilized. Then, the magnetic powder contained in the multipolar magnet can be highly oriented in the axial direction during the magnetic field injection molding. Such highly oriented multipolar magnets can be appropriately magnetized by a subsequent magnetizing step. Therefore, the magnetic encoder including such a multipole magnet can appropriately detect the magnetic force.

  After the magnet material is solidified in the cavity 75, demagnetization is performed. Thereafter, the multipole magnet 23 is magnetized by the magnetizing yoke to obtain the desired magnetic encoder 16.

  The magnetic encoder 16 including the multi-pole magnet 23 having such a configuration can be appropriately magnetized by a subsequent magnetization process because the magnetic powder is highly oriented. Therefore, the magnetic encoder 16 including such a multipole magnet 23 can appropriately detect the magnetic force. Moreover, the rolling bearing 11 provided with such a magnetic encoder 16 can detect a rotation speed etc. appropriately.

  Moreover, since such a multipolar magnet 23 contains the above-mentioned thermoplastic resin, there is little possibility of deterioration with respect to salt water, muddy water, rain water, a snow melting agent, etc. Therefore, the magnetic encoder 16 including such a multipole magnet 23 can prevent a decrease in magnetic characteristics.

  A rolling bearing including such a magnetic encoder is provided in a support structure for an automobile axle. FIG. 3 is a schematic sectional view showing an axle support structure. Referring to FIG. 3, axle support structure 41 includes a hub wheel 42 that rotates together with an axle (not shown), and a rolling bearing 51 that supports the axle. The flange 44 of the hub wheel 42 is fixed to a wheel (not shown) by a bolt 43. The rolling bearing 51 is a double row angular ball bearing, and includes balls 52 arranged in a double row, an inner ring 53, an outer ring 54, a retainer 55, a seal 56, and a magnetic encoder (not shown). .

  The inner ring 53 is fixed to the hub wheel 42 and rotates with the rotation of the axle. The outer ring 54 is fixed to a housing (not shown) arranged on the outer diameter side. The seal 56 includes a magnetic encoder including a multipolar magnet and a slinger, and the rotation sensor 57 can detect the rotation speed.

  Thus, the axle support structure 41 is configured. Such an axle support structure 41 has good sensitivity for sensing a multipolar magnet included in the magnetic encoder, and thus can appropriately detect the rotational speed and the like.

  In the above-described embodiment, heat storage of the coil is prevented by water cooling using the cooling pipe. However, the present invention is not limited to this, and heat storage of the coil portion may be prevented by air cooling using air blowing. Furthermore, you may decide to provide a heat insulating material etc. between a coil and a metal mold | die part.

  The slinger may have a substantially L-shaped cross section or a substantially Z-shaped cross section. Further, the cylindrical portion may not be continuous in the circumferential direction, or may be a tongue piece shape partially provided with a notch.

  Moreover, in said embodiment, although the case where a ball was used as a rolling element was demonstrated, it applies, also when using rollers, such as a cylindrical roller, a needle roller, and a rod roller, as a rolling element. The present invention is also applied to a rolling bearing that does not include a seal, and a rolling bearing that does not include an outer ring or an inner ring.

  The magnetic encoder described above is included in the rolling bearing. However, the magnetic encoder is not limited to this and may be included in the sliding bearing. Furthermore, the present invention is not limited to the rotating shaft and the like, and may be applied when detecting the rotational speed or the like of another rotating member, and may constitute a rotation detecting device that detects the rotational speed or the like of the rotating member together with the detection sensor. .

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The magnetic encoder and the rolling bearing according to the present invention are effectively used for a rolling bearing for an axle such as an automobile.

  The magnetic field injection molding apparatus for a multipolar magnet according to the present invention is effectively used when manufacturing a multipolar magnet included in a magnetic encoder.

It is sectional drawing which shows a part of rolling bearing which concerns on one Embodiment of this invention. It is a conceptual diagram which shows the structure of a multipolar magnet. It is a schematic sectional drawing which shows the axle shaft support structure containing the rolling bearing which concerns on one Embodiment of this invention. It is a schematic diagram which shows the magnetic field injection molding apparatus which forms a multipolar magnet. It is a schematic sectional drawing which shows the principal part of the magnetic field injection molding apparatus shown in FIG. It is an expanded sectional view of the part shown by VI in FIG.

Explanation of symbols

  11, 51 Rolling bearing, 12, 52 ball, 13, 53 Inner ring, 14, 54 Outer ring, 15, 55 Cage, 16 Magnetic encoder, 17, 56 Seal, 18a, 18b Track surface, 19 Inside, 21 Rotation detection device, 22, 57 Rotation sensor, 23 Multi-pole magnet, 24 Slinger, 25 Detector, 26 PCD, 27a N pole, 27b S pole, 28a, 28b, 28c Lip part, 29a, cylindrical part, 29b, 44 Flange, 29c Outer diameter Part, 30 end part, 31 cored bar, 32 rubber part, 41 axle support structure, 42 hub wheel, 43 bolt, 61 magnetic field injection molding device, 62 mold part, 63 injection part, 64 base part, 65, 66 fixing part , 67 Movable part, 68 Tie bar, 69 Movable side mold, 70 Fixed side mold, 71 Coil, 72a, 72b, 72c, 74a, 74b, 7 c mold blocks, 73 support, 75 cavity, 76 disk gate, 77 a nozzle, 78 a cooling tube.

Claims (5)

A magnetic encoder including an annular multipole magnet in which magnetic poles are alternately arranged in a circumferential direction, and a slinger that holds the multipole magnet,
The multipolar magnet includes magnetic powder and resin,
The multipolar magnet includes a mold part including a mold that forms a cavity forming an outer shape, an injection part that injects the magnet material into the cavity, and the magnet material is injected into the cavity by the injection part. In this case, a magnetic field injection molding device for a multipolar magnet, which includes a coil for generating an axial magnetic field in the mold part and a cooling part for cooling the coil, generates a magnetic field in the axial direction during injection molding. Magnetic encoder manufactured while cooling. The magnetic encoder according to claim 1, wherein the resin is a thermoplastic resin. The magnetic encoder according to claim 1, wherein the magnetic powder is a ferrite-based magnetic powder. A rolling bearing comprising the magnetic encoder according to claim 1. A magnetic field injection molding apparatus for a multipolar magnet for manufacturing an annular multipolar magnet in which magnetic poles are alternately arranged in a circumferential direction,
A mold part including a mold that forms a cavity forming the outer shape of the multipolar magnet;
An injection part for injecting the magnet material of the multipolar magnet into the cavity;
A coil for generating an axial magnetic field in the mold part when the magnet material is injected into the cavity by the injection part;
A magnetic field injection molding apparatus for a multipolar magnet, comprising: a cooling unit that cools the coil.

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