JP2010032303A - Wheel bearing device with rotation detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact wheel bearing device with a rotation detection device, which is capable of preventing wear, swelling, and cracking of a magnetic encoder, and enables structure reinforcement and use of the encoder under high and low temperature environments. <P>SOLUTION: The wheel bearing device includes rolling elements 5 provided between rolling surfaces 3, 4 of an outer member 1 and an inner member 2. Onto the outer peripheral face of the inner member 2, the magnetic encoder 21 having an inclined face 23b inclined with respect to the axial direction is fitted and mounted. An annular sensor holder 25 with a built-in magnetic sensor 24 is mounted on the outer member 1. The magnetic sensor 24 faces the inclined face 23b of the magnetic encoder 21 in parallel via a predetermined space. A sealing device 8 for sealing a space between the sensor holder 25 and the inner member 2 is provided at a position more outside the bearing than the magnetic encoder 21. As the magnetic encoder 21, a thermoplastic elastomer magnetic encoder is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wheel bearing device with a rotation detection device used in an automobile or the like equipped with an antilock brake system.

  In recent years, exports of automobile parts to BRICs countries where economic growth is remarkable are increasing. Among such automobile parts, in a wheel bearing device that rotatably supports a wheel with respect to a vehicle body, as a tire lock detection sensor of the anti-lock brake system (ABS), a magnetic encoder, and this magnetic encoder as a target In many cases, a rotation detector including a magnetic sensor for detecting the rotation of the wheel is incorporated, and the magnetic encoder is made of magnetic rubber.

  In the above-mentioned BRICs countries, an automobile is often driven on an unpaved rough road. Therefore, when a rotation detecting device is built in a wheel bearing device of the automobile, the magnetic encoder has high wear resistance. Things are required. For this reason, conventionally, measures have been taken such as to prevent wear by covering the surface of a magnetic rubber magnetic encoder manufactured by heat compression with a protective cover made of a non-magnetic material.

  However, if the surface of the magnetic encoder is covered with a protective cover made of a non-magnetic material, the gap between the surface of the magnetic encoder and the magnetic sensor arranged opposite to the surface becomes large. An encoder is required.

Therefore, as a means for solving such a problem, a wheel bearing device with a rotation detection device in which the magnetic encoder and the magnetic sensor are installed in the bearing in the axial direction is also proposed (for example, Patent Document 1). .
Japanese Patent Laying-Open No. 2005-300289

  However, when a rubber magnetic encoder is installed inside the bearing in this way, the grease, which is a lubricant, comes into contact with the magnetic encoder, and the magnetic encoder is placed in a high-temperature environment near the bearing heat generating part such as a rolling element. Therefore, there is a problem that the magnetic encoder easily swells, the magnetic signal is disturbed, and accurate rotation cannot be detected.

  Accordingly, the present inventors have developed, for example, in the wheel bearing device with a rotation detection device disclosed in Patent Document 1, a magnetic encoder that is a plastic magnetic encoder in which the magnet to be detected is a plastic magnet. (Japanese Patent Application No. 2008-027280).

  However, in this case as well, the plastic magnetic encoder is still placed in a high temperature environment near the bearing heat generating part such as a rolling element, and when the automobile is used in a very low temperature region, the plastic magnetic encoder is low in temperature. You will be exposed to the environment. For this reason, the difference in linear expansion coefficient between the plastic magnetic encoder and the metal shaft to which the plastic magnetic encoder is attached causes the plastic magnetic encoder to be easily damaged, causing a problem that the magnetic signal is disturbed, and also cannot accurately detect rotation. The problem remains.

  Further, in the configuration in which the plastic magnetic encoder and the magnetic sensor are arranged to face each other in the axial direction, the space in the axial direction of the wheel bearing device with the rotation detection device becomes large, which is an obstacle to downsizing.

  An object of the present invention is to provide a wheel bearing device with a rotation detection device that can prevent wear, swelling and damage of a magnetic encoder, and can be strengthened in structure, can be used even in a high-temperature environment, and can be made compact. It is to be.

In the wheel bearing device with a rotation detecting device of the present invention, a double row rolling surface is formed on the inner periphery and an outer member serving as a fixed member and a rolling surface facing each of the rolling surfaces are formed on the outer periphery. A wheel bearing device that includes an inner member that is a rotating side member and a double-row rolling element interposed between the opposing rolling surfaces, and that supports the wheel rotatably with respect to the vehicle body. A magnetic encoder that is fitted and attached to the outer peripheral surface near the end of the member and is inclined with respect to the axial direction so that the outer peripheral surface faces the end of the inner member; And an annular sensor holder that is attached to the outer member in a fitted state and has a built-in magnetic sensor that faces the inclined surface of the magnetic encoder in parallel through a gap, and a magnetic encoder. Between the sensor holder and the inner member at a bearing outer position. And the magnetic encoder is a thermoplastic elastomer magnetic encoder in which the magnet to be detected is a thermoplastic elastomer magnet in which magnetic powder is mixed with thermoplastic elastomer. And
According to this configuration, the detected surface of the magnetic encoder is an outwardly inclined surface, a sensor holder incorporating a magnetic sensor facing the inclined surface is attached to the outer member, and the sealing device is disposed at a position outside the bearing relative to the magnetic encoder. Since it is provided, it is possible to prevent the magnetic encoder from being worn by foreign matters from the outside.
In particular, since a thermoplastic elastomer magnetic encoder is used as the magnetic encoder, unlike the rubber magnetic encoder, swelling is avoided even if the magnet portion comes into contact with grease as a lubricant. In addition, the stress inside the magnetic encoder due to the difference in linear expansion coefficient in a high and low temperature environment is smaller than a plastic magnetic encoder and is not cracked if it is a thermoplastic elastomer. As a result, wear, swelling and damage of the magnetic encoder can be prevented and accurate rotation detection is possible.
In addition, since the magnetic encoder has an inclined surface to be detected, the cross-sectional outline can be made triangular and the structure can be strengthened. Since the detection surface of the magnetic encoder is an inclined surface, the magnetic encoder is disposed at the same axial position as the sensor holder. Therefore, the axial length of the wheel bearing device with the rotation detecting device can be shortened by the axial length of the magnetic encoder, and the device can be made compact.

In this invention, the thermoplastic elastomer magnetic encoder is a multipolar magnet in which the thermoplastic elastomer magnet has magnetic poles arranged in a circumferential direction. The multipolar magnet includes magnetic powder and a thermoplastic resin, and contains the magnetic powder. The melt viscosity of the thermoplastic resin may be 30 Pa · s or more and 1500 Pa · s or less.
When the melt viscosity is less than 30 Pa · s, the magnetic powder-containing thermoplastic elastomer, which is a material for the thermoplastic elastomer multipolar magnet, generates a large amount of burrs during injection molding, making it difficult to mold appropriately. If the melt viscosity of the thermoplastic elastomer is greater than 1500 Pa · s, it becomes difficult to knead the magnetic powder into the thermoplastic elastomer. In particular, when the proportion of the magnetic powder is increased, the kneading failure becomes remarkable. Thus, by setting the melt viscosity of the magnetic powder-containing thermoplastic elastomer to 30 Pa · s or more and 1500 Pa · s or less, a thermoplastic elastomer magnetic encoder with good productivity can be obtained. Further, the productivity improvement of the thermoplastic elastomer magnetic encoder also leads to the improvement of the productivity of the wheel bearing device with the rotation detection device.

In the present invention, the thermoplastic elastomer may contain one or more compounds selected from the group consisting of ester, urethane, vinyl chloride, and olefin.
Since these thermoplastic elastomers have a very small amount of swelling (less than 10%) even when they are immersed in grease used as a lubricant for bearings at a high temperature, they are materials for thermoplastic elastomer magnetic encoders incorporated in wheel bearing devices. As particularly effective.

  In the present invention, the magnetic powder may be a ferrite-based magnetic powder. Since ferrite magnetic powder is difficult to oxidize, the corrosion resistance of the thermoplastic elastomer magnetic encoder can be improved.

  In the present invention, the magnetic powder may be anisotropic ferrite magnetic powder.

  In this invention, the thermoplastic elastomer magnet of the thermoplastic elastomer magnetic encoder may be an injection molded product.

  When the thermoplastic elastomer magnet is an injection molded product, the thermoplastic elastomer magnet may be a magnetic field molded product in injection molding. That is, it may be formed by magnetic field molding in an injection mold during injection molding. By forming the magnetic field in this way, a thermoplastic elastomer magnetic encoder having a larger magnetic flux density can be obtained.

In the present invention, the thermoplastic elastomer magnetic encoder is a single annular thermoplastic elastomer magnet having an inner peripheral surface that is press-fitted and fixed to the outer peripheral surface of the inner member and an outer peripheral surface that is the inclined surface. May be.
Thus, if a thermoplastic elastomer magnetic encoder is constituted by a single thermoplastic elastomer magnet having no slinger, the cost of the thermoplastic elastomer magnetic encoder can be reduced.

  In the present invention, the thermoplastic elastomer magnetic encoder includes a cylindrical portion that is press-fitted and fixed to the outer peripheral surface of the inner member, and a slinger having an L-shaped cross section that includes a standing plate portion that rises from one end of the cylindrical portion. The slinger may be formed of a thermoplastic elastomer magnet having an outer peripheral surface integrally formed over the cylindrical portion and the standing plate portion of the slinger.

In this invention, the thermoplastic elastomer magnetic encoder having the slinger is an insert-molded product in which the thermoplastic elastomer magnet is integrally formed by injecting a magnetic powder-containing thermoplastic elastomer into a mold in which the slinger is disposed. Also good. Alternatively, a slinger and a thermoplastic elastomer magnet may be manufactured separately, and a thermoplastic elastomer magnetic encoder having the slinger integrated by bonding them together may be used.
As an adhesive at this time, an isocyanate, urethane, ester, vinyl chloride, rubber, or cyanoacrylate adhesive can be used. In particular, urethane type and cyanoacrylate type are preferable.

In the present invention, when the thermoplastic elastomer magnet is integrally formed with the slinger by the insert method in the injection molding of the thermoplastic elastomer magnetic encoder, a nonmagnetic material is preferable as the slinger material. By using a non-magnetic material as a material for the slinger, the magnetic powder distribution in the thermoplastic elastomer magnetic encoder is improved compared to the case where a magnetic material is used, so that the magnetic force can be increased.
In addition, when a slinger and a thermoplastic elastomer magnet are manufactured separately, and they are bonded and integrated to form a thermoplastic elastomer magnetic encoder having a slinger, a magnetic material is used as the slinger material. Compared with the case of using a nonmagnetic material, the magnetic force can be increased.

  The wheel bearing device with a rotation detecting device according to the present invention is fitted to and attached to the outer peripheral surface in the vicinity of the end of the inner member, and the axial direction is such that the outer peripheral surface faces the end of the inner member. A magnetic encoder having an inclined surface and a cored bar on the outer periphery are attached to the outer member in a fitted state, and a magnetic sensor is incorporated, and the magnetic sensor passes through a gap with respect to the inclined surface of the magnetic encoder. And an annular sensor holder facing in parallel, and a sealing device that seals a space between the sensor holder and the inner member at a position outside the bearing at a position outside the magnetic encoder, and the magnetic encoder is detected The thermoplastic magnet magnetic encoder, which is a thermoplastic elastomer magnet, is used to prevent wear / swell / damage of the magnetic encoder and to strengthen the structure. Can, and it is possible to compact the device.

  An embodiment of the present invention will be described with reference to FIGS. The wheel bearing device with a rotation detection device of this embodiment is a double row angular contact ball bearing type classified as a third generation type, and is an inner ring rotation type and a drive wheel support type. In this specification, the side closer to the outer side in the vehicle width direction of the vehicle when attached to the vehicle is referred to as the outboard side, and the side closer to the center of the vehicle is referred to as the inboard side.

  As shown in the sectional view of FIG. 1, the wheel bearing device in the wheel bearing device with the rotation detecting device includes an outer member 1 in which a double row rolling surface 3 is formed on the inner periphery, and each of these rolling surfaces. 3, an inner member 2 formed on the outer periphery with a rolling surface 4 facing the outer periphery 3, and a double row rolling element 5 interposed between the outer member 1 and the rolling surfaces 3, 4 of the inner member 2. The The rolling elements 5 are formed of balls and are held by the cage 6 for each row. The rolling surfaces 3 and 4 have a circular arc shape in cross section, and the rolling surfaces 3 and 4 are formed so that the contact angles are aligned with the back surface. The end of the bearing space between the outer member 1 and the inner member 2 is sealed by a sealing device 7.

The outer member 1 is a fixed side member, and has a flange 1a for mounting a vehicle body attached to a knuckle 60 in a suspension device (not shown) of the vehicle body on the outer periphery, and the whole is an integral part. . Bolt holes 14 for mounting the vehicle body are provided in the flange 1a at a plurality of locations in the circumferential direction, and knuckle bolts 61 inserted from the inboard side into the bolt insertion holes 60a of the knuckle 60 are screwed into the bolt holes 14 of the flange 1a. By doing so, the flange 1a is bolted to the knuckle 60.
The inner member 2 is a rotating side member, and includes a hub wheel 9 having a hub flange 9a for wheel mounting, and an inner ring 10 fitted to the outer periphery of the end portion on the inboard side of the shaft portion 9b of the hub wheel 9. And become. The hub wheel 9 and the inner ring 10 are formed with the rolling surfaces 4 of the respective rows. An inner ring fitting surface 12 having a small diameter with a step is provided on the outer periphery of the inboard side end of the hub wheel 9, and the inner ring 10 is fitted to the inner ring fitting surface 12. A through hole 11 is provided at the center of the hub wheel 9. The stem portion 63a of the outer ring 63 of the constant velocity joint 62 is inserted into the through-hole 11, and the inner member 2 is sandwiched between a step surface around the proximal end of the stem portion 63a and a nut 64 that is screwed to the distal end. Thus, the wheel bearing device and the constant velocity joint 62 are connected. The hub flange 9a is provided with press-fit holes 16 for hub bolts 15 at a plurality of locations in the circumferential direction. In the vicinity of the base portion of the hub flange 9a of the hub wheel 9, a cylindrical pilot portion 13 for guiding a brake rotor and a wheel (not shown) protrudes toward the outboard side. The pilot rotor 13 guides the hub flange 9 a so that the brake rotor and the wheel are overlapped with each other and fixed with the hub bolt 15.

  FIG. 2 is an enlarged cross-sectional view of part A in FIG. A thermoplastic elastomer magnetic encoder 21 is fitted and attached to the inboard side end of the outer peripheral surface of the inner member 2. An annular sensor holder 25 having a built-in magnetic sensor 24 for detecting the magnetic flux of the thermoplastic elastomer magnetic encoder 21 is attached to the inboard side end of the outer member 1. The thermoplastic elastomer magnetic encoder 21 and the magnetic sensor 24 constitute a rotation detection device 20 that detects the rotation of the inner member 2 integrated with the thermoplastic elastomer magnetic encoder 21, that is, the rotation of the wheel.

The thermoplastic elastomer magnetic encoder 21 has an inner peripheral surface 23a that is press-fitted and fixed to the outer peripheral surface of the inner member 2 (here, the outer peripheral surface of the inner ring 10), and the axial direction so that the inside of the bearing has a large diameter. Thus, a single annular thermoplastic elastomer multipolar magnet 23 having an inclined surface 23b that is an outer peripheral surface inclined outward is formed. The inclined surface 23b becomes a detected surface. The thermoplastic elastomer multipolar magnet 23 has a sealing device fitting projection 23c that fits on the outer diameter surface of a sealing plate 31 of the sealing device 8 described later at the outer end in the axial direction.
The sensor holder 25 is attached to the outer member 1 so that the magnetic sensor 24 faces the inclined surface 23b of the thermoplastic elastomer magnetic encoder 21 (thermoplastic elastomer multipolar magnet 23) in parallel with a predetermined gap. Mounted.

As shown in FIG. 3, the thermoplastic elastomer multipolar magnet 23 is an annular member magnetized in multiple poles so that the magnetic poles N and S are alternately arranged in the circumferential direction. It is an injection-molded article containing a plastic elastomer. The magnetic poles N and S are formed to have a predetermined pitch p in the pitch circle diameter PCD.
The thermoplastic elastomer contains one or more compounds selected from the group consisting of ester, urethane, vinyl chloride and olefin. For example, TPO (olefin-based thermoplastic elastomer), TPV (vinyl chloride-based thermoplastic elastomer), TPEE (polyester-based thermoplastic elastomer), or the like can be used as the thermoplastic elastomer.

The melt viscosity of the thermoplastic elastomer containing magnetic powder that is the material of the thermoplastic elastomer multipolar magnet 23 is preferably in the range of 30 to 1500 Pa · s. If this melt viscosity is less than 30 Pa · s, a large amount of burrs are generated during injection molding, making it difficult to mold appropriately. If the melt viscosity of the thermoplastic elastomer is greater than 1500 Pa · s, it becomes difficult to knead the magnetic powder into the thermoplastic elastomer. In particular, when the proportion of the magnetic powder is increased, the kneading failure becomes remarkable. Therefore, in this embodiment, the melt viscosity of the magnetic powder-containing thermoplastic elastomer is 30 Pa · s or more and 1500 Pa · s or less. Thereby, the thermoplastic elastomer magnetic encoder 21 with good productivity can be obtained. Moreover, it leads also to the productivity improvement of the wheel bearing apparatus with a rotation detection apparatus.
In this case, the melt viscosity of the thermoplastic elastomer is a capillograph (manufactured by Toyo Seiki Co., Ltd.), using a capillary with a diameter of 1 mmφ and a land length of 10 mm, a shear rate of 100 (l / s), and a melting point of the thermoplastic elastomer. The result measured at the temperature of +50 degreeC is shown.

In this case, as the thermoplastic elastomer, Hytrel 4767 (manufactured by Toray DuPont Co., Ltd.), which is an ester-based thermoplastic elastomer having a very small amount of swelling even when immersed in grease used as a lubricant for a bearing at a high temperature, is used. ), Ferrite powder (FA700 manufactured by Toda Kogyo Co., Ltd.) was added at a volume content of 50 vol% at 220 ° C., and kneaded with a kneader.
Such a thermoplastic elastomer is particularly effective as a material for the thermoplastic elastomer magnetic encoder 21 which has good oil resistance and is incorporated in a wheel bearing device.

  As the magnetic powder that is the material of the thermoplastic elastomer multipolar magnet 23, barium-based or strontium-based ferrite powder is used. In the case of a ferrite magnetic powder, it may be an isotropic ferrite magnetic powder or an anisotropic ferrite magnetic powder. Since such ferrite-based magnetic powder is difficult to oxidize, the corrosion resistance of the thermoplastic elastomer magnetic encoder 21 can be improved. In addition, when the magnetic force is insufficient with only ferrite magnetic powder, rare earth magnetic powder such as samarium iron magnetic powder or neodymium iron magnetic powder may be mixed with ferrite magnetic powder and used.

  The thermoplastic elastomer magnetic encoder 21 is manufactured by the following steps. First, the magnetic powder and the molten thermoplastic elastomer are kneaded using a twin screw extruder or a kneader, and the magnetic powder is appropriately dispersed in the thermoplastic elastomer. Then, injection molding etc. are performed so that it may become a shape of a multipolar magnet, and a desired molded object is obtained. The molded product thus obtained is magnetized into multiple poles using a magnetizing yoke to form a magnetic pole. At the time of the injection molding, it is preferable to form a magnetic field while applying a vertical magnetic field of 80000 Oe or more to the magnetic encoder magnetized surface and to orient the contained magnetic powder. By forming the magnetic field in this way, the thermoplastic elastomer magnetic encoder 21 having a larger magnetic flux density can be obtained.

  The annular sensor holder 25 includes an annular cored bar 26 and a resin sensor holder 27 that incorporates a magnetic sensor 24 and is coupled to the cored bar 26. The sensor holding body 27 protrudes from the inner bearing end in the axial direction to the inner peripheral surface, and is provided with a sensor embedded protrusion 27a. In the sensor embedded protrusion 27a, the corner between the tip surface and the bearing inner surface is an inclined surface parallel to the inclined surface 23b of the magnetic encoder 21, and the magnetic sensor 24 is built in along the inclined surface. Yes. The sensor embedding protrusion 27a may be annular or may be locally provided in a part of the circumferential direction. The core metal 26 includes an outer diameter cylindrical portion 26a that is press-fitted and attached to the outer peripheral surface of the outer member 1, a flange portion 26b that extends from the inboard side end of the outer diameter cylindrical portion 26a toward the inner diameter side, and the flange portion 26b. The inner diameter cylindrical portion 26c extends in the axial direction from the inner diameter side end of the inner diameter. The cored bar 26 is formed by pressing a corrosion resistant stainless steel plate or the like. Perforations 28 are formed at a plurality of locations in the circumferential direction of the inner diameter cylindrical portion 26c in the cored bar 26, and a resin sensor holding body 27 is integrally molded at a portion extending from the inner diameter cylindrical portion 26c to the flange portion 26b. In a state where the outer diameter cylindrical portion 26a of the metal core 26 is press-fitted into the outer peripheral surface of the outer member 1, and the flange portion 26b is brought into close contact with the inboard side end surface of the outer member 1, the sensor holder 25 is moved to the outer member. 1 is fixed to the inboard side end.

The space between the inner periphery of the sensor holder 25 and the outer periphery of the inner member 2 is sealed by the sealing device 8 installed at a position outside the bearing relative to the thermoplastic elastomer magnetic encoder 21. The sealing device 8 includes annular first and second seal plates 31 and 32 attached to the outer peripheral surface of the inner member 2 and the inner peripheral surface of the sensor holder 25, respectively.
The first seal plate 31 includes a cylindrical portion 31a that is press-fitted and attached to the outer peripheral surface of the inner member 2, and a cross-section L that includes a vertical plate portion 31b that extends from the inboard side end of the cylindrical portion 31a to the outer diameter side. It is formed in a letter shape. The first seal plate 31 is formed by pressing an austenitic stainless steel plate or a cold-rolled steel plate that has been rust-proofed.
The second seal plate 32 includes a cylindrical portion 32a that is press-fitted and attached to the inboard side of the inner peripheral surface of the sensor holder 25, and a standing plate portion 32b that extends from the outboard side end of the cylindrical portion 32a to the inner diameter side. The cross section is formed in an inverted L shape. The second seal plate 32 has an upright plate portion 32b positioned on the outboard side of the upright plate portion 31b of the first seal plate 31, and is axially aligned with the upright plate portion 31b of the first seal plate 31. It arrange | positions so that it may face. A seal member 33 having a side lip 33a, a grease lip 33b, and an intermediate lip 33c is vulcanized and bonded to the second seal plate 32. The seal member 33 is made of an elastic member such as rubber. The side lip 33 a is in sliding contact with the standing plate portion 31 b of the first seal plate 31, and the grease lip 33 b and the intermediate lip 33 c are in sliding contact with the cylindrical portion 31 a of the first seal plate 31. The tip of the upright plate portion 31b of the first seal plate 31 is opposed to the cylindrical portion 32a of the second seal plate 32 via a slight radial gap to constitute a labyrinth seal. The sealing device 8 seals the inboard side end in the bearing space between the outer member 1 and the inner member 2.

  According to the wheel bearing device with a rotation detection device having the above-described configuration, the thermoplastic elastomer magnetic encoder 21 integrated with the inner member 2 rotates as the wheel rotates. At this time, the magnetic sensor 24 facing the inclined surface 23b, which is the magnetized surface of the thermoplastic elastomer magnetic encoder 21 (thermoplastic elastomer multipolar magnet 23), in parallel with a predetermined gap is provided in the thermoplastic elastomer magnetic encoder 21. The change in magnetic force of the magnetic poles N and S is read. Thereby, the rotation detection apparatus 20 comprised with the thermoplastic elastomer magnetic encoder 21 and the magnetic sensor 24 can detect rotation of a wheel.

  Further, in this wheel bearing device with a rotation detection device, a sensor holder incorporating a magnetic sensor 24 constituting the rotation detection device 20 with a thermoplastic elastomer magnetic encoder 21 fitted and attached to the outer peripheral surface of the inner member 2. 25 is attached to the outer member 1 so that the magnetic sensor 24 faces the inclined surface 23b of the thermoplastic elastomer magnetic encoder 21 in parallel, and the sensor holder 25 and the inner side are positioned in the bearing outer position than the thermoplastic elastomer magnetic encoder 21. Since the sealing device 8 that seals the space between the members 2 is provided, it is possible to prevent the thermoplastic elastomer magnetic encoder 21 from being worn by foreign matters from the outside.

  In particular, since the thermoplastic elastomer magnetic encoder 21 (thermoplastic elastomer multipole magnet 23) is used as the magnetic encoder, unlike the rubber magnetic encoder, the magnetic encoder can be prevented from coming into contact with the lubricant grease and swelling. . Also, the stress inside the magnetic encoder due to the difference in linear expansion coefficient under a high and low temperature environment is smaller than a plastic magnetic encoder as long as it is a thermoplastic elastomer and does not crack. As a result, wear, swelling, and damage of the magnetic encoder can be prevented and accurate rotation detection can be performed.

  Moreover, in this wheel bearing device with a rotation detection device, the cross-sectional outline of the thermoplastic elastomer magnetic encoder 21 can be made triangular, so that the structure of the thermoplastic elastomer magnetic encoder 21 can be strengthened.

  Furthermore, in this embodiment, since the thermoplastic elastomer magnetic encoder 21 is disposed at the same axial position as the sensor holder 25, the wheel bearing device with a rotation detector is provided by the axial length of the thermoplastic elastomer magnetic encoder 21. The axial length can be shortened, and the apparatus can be made compact.

When polymer substances are roughly classified, they are divided into resin and elastomer as follows.
(1) Resin-Thermosetting resin: phenol resin, urea resin, etc.-Thermoplastic resin: PP (polypropylene), ABS resin (acrylonitrile butadiene styrene resin), PPS (polyphenylene sulfide), etc. (2) Elastomer-Synthesis Rubber, natural rubber: NBR (nitrile rubber), CR (chloroprene rubber), VMQ (silicon rubber), etc. ・ Thermoplastic elastomers: TPO (olefin), TPVC (vinyl chloride), TPEE (ester), etc. In order to show that a thermoplastic elastomer is superior as a material for a magnetic encoder, the data of its physical properties and the like compared to other materials (plastic, elastomer) will be described below.
Plastic (thermoplastic resin or thermosetting resin) ............ High hardness and low elastic deformation (within several percent).
Thermoplastic elastomer: A polymer material that behaves as a rubber elastic body at room temperature, but melts as the temperature rises. It has both rubber properties and plastic properties (elastic deformation of about 10%). For this reason, it has flexibility, is stretchable and is not easily broken.
Elastomer: A flexible (low hardness) elastic body with a large amount of elastic deformation (about several hundred percent). It is a general term for polymer substances (natural rubber, synthetic rubber, etc.) that have very large elasticity at room temperature, and has elongation.
FIG. 4 is a graph showing a comparison of stress-strain behavior of four materials, ie, a thermoplastic resin, polyurethane (thermoplastic elastomer), polyester (thermoplastic elastomer), and elastomer (rubber) as plastics. The graph shows the following.
Plastic: Harder than rubber, large stress during deformation, and small amount of elastic deformation. For this reason, it is easy to break.
Rubber: The elastic deformation is large and it extends sufficiently. Low elastic modulus (Young's modulus).
Thermosetting elastomer: Combines the strength of plastic and the flexibility of rubber. As long as it is used within the range of the strain amount W shown in FIG. 4, the behavior as an elastic body is shown.
Thus, in the case of a thermoplastic elastomer, since the elastic region is wider than that of plastic, it is more resistant to impact and is hard to crack.

FIG. 5 shows another embodiment of the present invention. In this embodiment, the thermoplastic elastomer magnetic encoder 21 formed of a single unit of the thermoplastic elastomer multipolar magnet 23 is replaced with an annular slinger 22 and a heat in the wheel bearing device with a rotation detection device of the embodiment of FIGS. This is a thermoplastic elastomer magnetic encoder 21A made of a composite of a plastic elastomer multipole magnet 23. As the thermoplastic elastomer in this case, Hytrel 4767 (manufactured by Toray DuPont Co., Ltd.), which is an ester-based thermoplastic elastomer, is used, and ferrite powder (FA700 manufactured by Toda Kogyo Co., Ltd.) at a volume content of 50 vol. It was added and kneaded with a kneader.
A thermoplastic elastomer magnetic encoder 21A molded with this material was incorporated into a bearing and examined for cracks after 800 cycles in a low temperature side -35 ° C and high temperature side 110 ° C heat cycle test (held at each temperature for 1 hour). Cracking did not occur and good high and low temperature characteristics were exhibited. This shows that it can be used even in a sufficiently high and low temperature environment.

  The slinger 22 is a cylindrical portion 22a that is press-fitted and fixed to the outer peripheral surface of the inner member 2 (here, the outer peripheral surface of the inner ring 10), and a standing plate portion that rises to the outer diameter side from the inner end of the bearing of the cylindrical portion 22a. It is a cored bar having an annular shape and an L-shaped cross section composed of 22b. The thermoplastic elastomer multipolar magnet 23 is molded separately from the slinger 22 and then bonded to the slinger 22 with a one-component cyanoacrylate adhesive (Toagosei Aron α201) to integrate the heat. A plastic elastomer magnetic encoder 21A is configured. The fact that the outer peripheral surface of the thermoplastic elastomer multipolar magnet 23 is the inclined surface portion 23b is the same as in the previous embodiment. The slinger 22 is made of a magnetic steel plate (SUS430). Thus, by using a magnetic material as the material of the slinger 22, the magnetic force of the thermoplastic elastomer magnetic encoder 21 </ b> A can be increased compared to the case of using a nonmagnetic material.

  The thermoplastic elastomer magnetic encoder 21A in this embodiment can also be manufactured by insert molding according to the following steps. First, the magnetic powder and the molten thermoplastic elastomer are kneaded using a twin screw extruder or a kneader, and the magnetic powder is appropriately dispersed in the thermoplastic elastomer. Thereafter, a thermoplastic elastomer containing magnetic powder is injected into the mold in which the slinger 22 is disposed, and the thermoplastic elastomer multipolar magnet 23 is integrally formed with the slinger 22 to obtain a desired thermoplastic elastomer magnetic encoder 21A. The insert molded product of the thermoplastic elastomer magnetic encoder 21A thus obtained is magnetized into multiple poles using a magnetizing yoke, thereby forming the magnetic poles of the thermoplastic elastomer multipolar magnet 23. Also in this case, at the time of the injection molding, it is preferable to form a magnetic field while applying a vertical magnetic field of 80000 Oe or more to the inclined surface 23b which is a magnetized surface, and to magnetically orient the contained magnetic powder. Other configurations are the same as those of the embodiment shown in FIGS. 1 to 3, and the description thereof is omitted here.

It is sectional drawing of the bearing apparatus for wheels with a rotation detection apparatus concerning one Embodiment of this invention. It is an expanded sectional view of the A section in FIG. It is explanatory drawing of the magnetic pole which looked at the thermoplastic elastomer magnetic encoder from the front. 3 is a graph showing the stress-strain behavior of an elastomer compared to other materials such as plastic. It is a partial expanded sectional view of the bearing device for wheels with a rotation detector concerning other embodiments of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Outer member 2 ... Inner member 3, 4 ... Rolling surface 5 ... Rolling body 8 ... Sealing device 20 ... Rotation detection device 21, 21A ... Thermoplastic elastomer magnetic encoder 22 ... Slinger 22a ... Cylindrical part 22b ... Standing plate Part 23 ... Thermoplastic elastomer multipolar magnet 23a ... Inner peripheral surface 23b ... Inclined surface 24 ... Magnetic sensor 25 ... Sensor holder

Claims (11)

An outer member that is a fixed side member with a double row rolling surface formed on the inner periphery, an inner member that is a rotating side member that has a rolling surface that faces each of the rolling surfaces on the outer periphery, and these facing members A wheel bearing device for supporting a wheel rotatably with respect to a vehicle body, comprising:
A magnetic encoder that is fitted and attached to the outer peripheral surface near the end of the inner member and is inclined with respect to the axial direction so that the outer peripheral surface faces the end of the inner member, and An annular sensor holder that is attached to the outer member in a fitted state with a cored bar having a built-in magnetic sensor and that faces the inclined surface of the magnetic encoder in parallel via a gap; and A sealing device that seals a space between the sensor holder and the inner member at a position outside the bearing at a position outside the magnetic encoder, and the magnet serving as the detected portion includes magnetic powder applied to the thermoplastic elastomer. A wheel bearing device with a rotation detecting device, characterized in that a thermoplastic elastomer magnetic encoder which is a mixed thermoplastic elastomer magnet is used.   2. The thermoplastic elastomer magnetic encoder according to claim 1, wherein the thermoplastic elastomer magnet is a multipolar magnet in which magnetic poles are arranged in a circumferential direction. The multipolar magnet includes magnetic powder and a thermoplastic resin, and the magnetic powder A bearing device for a wheel with a rotation detector, wherein the thermoplastic elastomer contains a melt viscosity of 30 Pa · s to 1500 Pa · s.   3. The wheel bearing device with a rotation detector according to claim 2, wherein the thermoplastic elastomer includes one or more compounds selected from the group consisting of ester, urethane, vinyl chloride and olefin.   4. The wheel bearing device with a rotation detecting device according to claim 2, wherein the magnetic powder is a ferrite-based magnetic powder.   5. The wheel bearing device with a rotation detecting device according to claim 4, wherein the magnetic powder is anisotropic ferrite magnetic powder.   The wheel bearing device with a rotation detecting device according to any one of claims 1 to 5, wherein the thermoplastic elastomer magnet of the thermoplastic elastomer magnetic encoder is an injection molded product.   7. The wheel bearing device with a rotation detecting device according to claim 6, wherein the thermoplastic elastomer magnet of the thermoplastic elastomer magnetic encoder is formed by magnetic field molding in injection molding.   8. The thermoplastic elastomer magnetic encoder according to claim 1, wherein the thermoplastic elastomer magnetic encoder has an inner peripheral surface that is press-fitted and fixed to an outer peripheral surface of the inner member and an outer peripheral surface that is the inclined surface. A wheel bearing device with a rotation detection device, which is a single piece of an annular thermoplastic elastomer magnet.   8. The thermoplastic elastomer magnetic encoder according to claim 1, wherein the thermoplastic elastomer magnetic encoder includes a cylindrical portion that is press-fitted and fixed to an outer peripheral surface of the inner member, and a standing plate portion that rises from one end portion of the cylindrical portion. For a wheel with a rotation detector comprising an annular slinger having an L-shaped cross section, and a thermoplastic elastomer magnet having an outer peripheral surface formed integrally with the cylindrical portion and the standing plate portion of the slinger and having an inclined surface Bearing device.   10. The rotation detection device according to claim 9, wherein the thermoplastic elastomer magnetic encoder is an insert-molded product in which the thermoplastic elastomer magnet is integrally molded by injecting a thermoplastic elastomer containing magnetic powder into a mold in which the slinger is disposed. Wheel bearing device.   11. The wheel bearing device with a rotation detecting device according to claim 9, wherein the slinger is made of a nonmagnetic material.

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