JP2007107911A - Bearing apparatus with magnetic encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing apparatus with a magnetic encoder capable of improving resistance to the occurrence of crevice corrosion in adverse environments by blocking the intrusion of salt water between a plastic magnet and a slinger while securing desired functions as a magnetic encoder for detecting the rotational speed of a rotator. <P>SOLUTION: A rolling bearing unit 2a for supporting axles comprises an outer ring 5a; a hub 7a and an inner ring 16a for rotating relatively to the outer ring 5a; a plurality of balls 17a rotation-freely arranged between the outer ring 5a and the hub 7a and the inner ring 16a; and the magnetic encoder 26 comprising both the slinger 25 mounted to the inner ring 16a and a magnetic-pole-forming ring 27 joined to the slinger 25 and containing a magnetic powder of 60-80 vol.% for detecting the rotational speed of both the hub 7a and the inner ring 16a. The slinger 25 has recession and protrusion parts 28 formed by blasting, and the magnetic-pole-forming ring 27 is adhered and joined only to the recession and protrusion parts 28. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic encoder-equipped bearing device including a magnetic encoder used for detecting the rotational speed of a rotating body.

  Conventionally, anti-skid to prevent car skid (a phenomenon in which the wheel slips in a substantially stopped state) or traction control to effectively transmit the driving force to the road surface (unnecessary idling of the driving wheel that is likely to occur at the time of start and acceleration) As a rotation speed detection device used for control, etc., there are an annular encoder in which N poles and S poles are alternately magnetized in the circumferential direction, and a sensor for detecting a change in the magnetic field in the vicinity of the encoder. It is also known that an encoder is provided alongside a sealing device for sealing a bearing that supports a wheel so that the encoder rotates together with the rotation of the wheel, and a magnetic field change synchronized with the rotation of the wheel is detected by a sensor. (For example, refer to Patent Document 1).

  As shown in FIG. 6, the rotational speed detector with seal described in Patent Document 1 is attached to a seal member 102 attached to the outer ring 100, a slinger 103 fitted to the inner ring 101, and an outer surface of the slinger 103. The multi-pole magnet 104 that generates a magnetic pulse and the sensor 105 that is disposed in the vicinity of the multi-pole magnet 104 and detects the magnetic pulse. In the bearing unit to which this rotational speed detector with a seal is attached, the sealing member 102 and the slinger 103 prevent foreign matters such as dust and water from entering the inside of the bearing, so that the lubricant filled in the bearing can be prevented. Prevents leakage outside the bearing. Further, the multipolar magnet 104 generates a number of magnetic pulses corresponding to the number of poles during one rotation of the inner ring 101, and detects the number of rotations of the inner ring 101 by detecting this magnetic pulse with the sensor 105. Yes.

Conventionally, as the multipolar magnet 104 used for the wheel bearing, magnetic rubber or plastic magnet obtained by mixing magnetic powder into an elastic material such as rubber or resin is used.
JP 2001-255337 A

  By the way, the magnetic encoder is required to further improve the detection accuracy, but in a multipolar magnet encoder using magnetic rubber, in order to further improve the sensing performance, the blending amount of the magnetic powder in the magnetic rubber is reduced. It is difficult to dramatically improve the performance of the magnetic encoder in the future.

  On the other hand, an encoder using a plastic magnet has an advantage that an anisotropic magnet indispensable for developing excellent magnetic properties can be obtained because injection molding (magnetic field molding) in a state where a magnetic field is applied is possible. . In other words, if a plastic magnet that can maximize its magnetic performance by controlling the orientation of the magnetic powder is used, it is considered that a magnetic encoder having better sensing performance than that of magnetic rubber can be produced.

  However, when using an adhesive as a method of fixing a plastic magnet to a slinger, if the magnetic encoder, which is an adhesive joint, is exposed to a harsh salt water environment for a long period of time, the adhesive will absorb moisture and the salt water will be blocked. The effect is reduced. As a result, it is assumed that crevice corrosion occurs between the multipolar magnet and the slinger, and in the worst case, the multipolar magnet is detached from the slinger.

  The present invention solves the above-mentioned problems, and its object is to prevent the intrusion of salt water between the plastic magnet and the slinger while ensuring a desired function as a magnetic encoder for detecting the rotational speed of the rotating body. An object of the present invention is to provide a bearing device with a magnetic encoder having improved resistance to crevice corrosion in an environment.

The above object of the present invention is achieved by the following configurations.
(1) stationary wheel,
A rotating wheel that rotates relative to the stationary wheel;
A plurality of rolling elements rotatably disposed between the stationary wheel and the rotating wheel;
A magnetic encoder for detecting the rotational speed of the rotating wheel, comprising a slinger attached to the rotating wheel, and a plastic magnet joined to the slinger and containing 60-80% by volume of magnetic powder;
A bearing device with a magnetic encoder comprising:
The slinger has a concavo-convex portion formed by blasting, and the plastic magnet is bonded and bonded only to the concavo-convex portion.
(2) The magnetic encoder bearing device according to (1), wherein the concavo-convex portion is formed only on the end surface in the axial direction of the slinger.
(3) The bearing unit with a magnetic encoder according to (1), wherein the uneven portion is formed on the entire surface of the slinger.

  According to the present invention, the slinger has a concavo-convex portion formed by blasting, and the plastic magnet is bonded and bonded only by the concavo-convex portion. Therefore, the bearing device with a magnetic encoder can be provided with an excellent unevenness and a very excellent adhesion durability under salt spray.

  FIG. 1 shows a case where the bearing device with a magnetic encoder of the present invention is applied to a wheel bearing rolling bearing unit 2a for supporting a non-driven wheel, which is supported by an independent suspension, as an embodiment of the present invention. Shows about. Note that the configuration and operation other than the features of the present invention are the same as those of a conventionally well-known structure. Therefore, the description will be simplified, and the features of the present invention will be mainly described below.

  The rolling bearing unit 2a includes an outer ring 5a that is a stationary wheel, a hub 7a and an inner ring 16a that are rotating together with a mounting flange 12 for fixing a wheel (not shown), an outer ring 5a, a hub 7a, and an inner ring. A plurality of balls 17a and 17a, which are a plurality of rolling elements arranged in a circumferential direction by an annular gap formed between the inner ring 16a and guided by a cage 18, are provided. A magnetic encoder 26 is provided on the inner ring 16a. It is fixed.

  The inner ring 16a that is externally fitted to the small-diameter step portion 15 formed at the inner end portion of the hub 7a is restrained by a caulking portion 23 that is formed by caulking the inner end portion of the hub 7a radially outward. By attaching, it is fixedly coupled to the hub 7a. In addition, the wheel can be coupled and fixed by a plurality of studs 8 to a mounting flange 12 formed at a portion protruding from the outer end portion of the outer ring 5a at the outer end portion of the hub 7a. On the other hand, the outer ring 5a can be coupled and fixed to a knuckle or the like (not shown) constituting a suspension device by a coupling flange 11 formed on the outer peripheral surface thereof.

  Further, seal rings 21a and 21b are provided between the inner peripheral surface of both ends of the outer ring 5a, the outer peripheral surface of the intermediate part of the hub 7a, and the outer peripheral surface of the inner end part of the inner ring 16a, respectively. The seal rings 21a and 21b block the annular space provided with the balls 17a and 17a from the outer space between the inner peripheral surface of the outer ring 5a and the outer peripheral surfaces of the hub 7a and the inner ring 16a.

  Each of the seal rings 21a and 21b is formed by bending a mild steel plate and reinforcing the elastic members 22a and 22b with core bars 24a and 24b having an L-shaped cross section and an annular shape as a whole. Each of such seal rings 21a and 21b has a metal core 24a and 24b fitted into both ends of the outer ring 5a by an interference fit, and the tip ends of the seal lips formed by the respective elastic members 22a and 22b are connected to the hub. The slinger 25 is externally fitted and fixed to the outer peripheral surface of the intermediate portion 7a or the outer peripheral surface of the inner end portion of the inner ring 16a.

  The magnetic encoder 26 includes a slinger 25 attached to the inner ring 16 a and a magnetic pole forming ring 27 fixed to the side surface of the slinger 25. As shown in FIG. 3, the magnetic pole forming ring 27 is a multipolar magnet, and N and S are alternately formed in the circumferential direction. A magnetic sensor (not shown) is arranged facing the magnetic pole forming ring 27.

  In the present invention, the magnetic pole forming ring 27 of the magnetic encoder 26 is composed of a multipolar plastic magnet composed of magnetic powder and a resin composition serving as a binder. The basic specifications of the magnetic encoder according to the present invention are as follows. The magnetic encoder of the present invention is basically a plastic magnet material that is formed by insert molding of a plastic magnet material using a slinger that has been baked in a semi-cured state in advance as a core, and then the adhesive is completely cured. And the slinger are integrally bonded and bonded at the same time as molding, and the obtained bonded assembly is manufactured by multipolar magnetization in the circumferential direction.

  In the magnetic encoder of the present invention, as a binder for the plastic magnet, in consideration of the possibility that the polyamide resin, specifically, calcium chloride used as a snow melting material may be taken together with water, the water absorption rate Polyamide 11 resin, polyamide 12 resin, polyamide 612 resin, or semi-aromatic polyamide resin obtained by partially copolymerizing terephthalic acid with adipic acid units, polyamide 6T / 6-6, polyamide 6T. / 6I, polyamide 6T / 6I / 6-6, polyamide 6T / M-5T, polyamide 9T and the like are used.

  In addition, the magnetic encoder according to the present invention is a binder for a plastic magnet, for example, in order to further ensure the reliability under a situation where a repeated thermal shock of −40 ° C. to 120 ° C. is applied. The resin composition is a polymer alloy of a polyamide resin exhibiting low water absorption and a soft component blended as an impact strength improver.

  Here, as a soft component blended in an amount of 5 to 50% by weight, preferably 10 to 35% by weight based on the total weight of the resin composition, the glass transition temperature is at least −40 ° C. or less in the molecular structure. It is a block copolymer containing a soft segment. The block copolymers that can be used in the present invention include polystyrene, polyolefin, vinyl chloride, polyester, polyurethane, polyamide, polydiolefin, and silicon. In consideration, polyester-based and polyamide-based ones are more preferable, and it is sufficient that the glass transition temperature of the soft segment in these block copolymers is -40 ° C or lower.

  Furthermore, the resin composition includes a heat stabilizer (heat-resistant processing stabilizer, antioxidant), a light stabilizer, an antistatic material, a plasticizer, an inorganic or organic flame retardant, and other reinforcing agents as necessary. Although it is added, especially in consideration of the use environment, the addition of a heat stabilizer is indispensable. As an amine-based antioxidant, 2,2,4-trimethyl-1,2 is preferably added. -Amine-ketone series represented by dihydroquinoline polymer, diallylamine series represented by p, p'-dicumyldiphenylamine, and p-phenylenediamine series represented by N, N'-diphenyl-p-phenylenediamine, Examples of phenolic antioxidants include monophenolic compounds represented by 2,6-di-tert-butyl-4-methylphenol, and 2,2′-methylenebis. There is a polyphenolic typified by 4-methyl -6-t-butylphenol). On the other hand, a hydroquinone type such as 2,5-di-t-butylhydroquinone can also be used. Furthermore, a peroxide decomposition type antioxidant (secondary antioxidant) may be used in combination with the antioxidant. As the secondary antioxidant, a sulfur secondary antioxidant such as 2-mercaptobenzimidazole or a phosphorus secondary antioxidant such as tris (nonylated phenyl) phosphite is used. In addition, the blending amount of the heat stabilizer is preferably about 0.1 to 3 wt% with respect to the resin, but depending on the type (additionally, it does not bloom or adversely affects the physical properties of the resin). May be.

  On the other hand, as magnetic powder contained in the magnetic encoder according to the present invention, ferrite such as strontium ferrite and barium ferrite, rare earth magnetic powder such as neodymium-iron-boron, samarium-cobalt, samarium-iron can be used, Furthermore, in order to improve the magnetic properties of ferrite, lanthanum and cobalt may be mixed. In the present invention, in order to sufficiently secure the magnetic characteristics of the magnetic pole forming ring, the content is set to 60 to 80% by volume. However, when the content of the magnetic powder is less than 60% by volume, the magnetic This is because the characteristics are inferior and it becomes difficult to multi-pole magnetize in the circumferential direction at a fine pitch. On the other hand, when it exceeds 80% by volume, the amount of the resin binder becomes too small and the strength of the whole magnet is low. At the same time, the molding becomes difficult and the practicality is lowered.

  That is, the present inventors have already found that a magnetic encoder 26 with good performance and durability can be obtained by using the above-mentioned materials and the basic specifications as described above. In order to further improve the resistance to crevice corrosion between the magnetic pole forming ring 27 and the slinger 25, which occurs when exposed to a long period of time underneath. As a result, the entire surface of the adhesive bonding surface of the slinger 25 with the magnetic pole forming ring 27 is subjected to concavo-convex processing by blasting using an abrasive, and in addition to the concavo-convex processing, the slinger that is difficult to blast. By adopting a magnetic encoder specification that prevents the outer diameter end face from being an adhesive joint with a plastic magnet, it is highly reliable that crevice corrosion between the magnetic pole forming ring 27 and the slinger 25 does not easily occur even in adverse environments. The present inventors have found that a magnetic encoder 26 can be obtained and completed the present invention.

  That is, the blasting process is performed on the outer end surface in the axial direction of the slinger 25, which is relatively easy to process, and the uneven portion 28 as shown in FIG. 4A is formed. And this uneven | corrugated | grooved part 28 is made into the structure which makes the magnetic pole formation ring 27 bite to the slinger 25 by injection molding by making an adhesive joint surface.

  Further, regarding the blasting of the slinger 25 with the abrasive according to the present invention, the method and the abrasive are not particularly limited, but in the processing, in order to minimize the deformation of the slinger 25 as the workpiece, It is preferable to process with relatively weak processing strength (low projection energy). For this reason, alumina (aluminum oxide) -based abrasives, that is, brown and white / green silicon carbide alumina are particularly suitable as the abrasive in the present invention. By the way, the particle size of the alumina-based abrasive mainly used as the abrasive is about 0.08 to 0.18 mm, and those within this range can also be suitably used in the present invention. The roughness of the processed surface obtained when using an alumina-based abrasive having a particle size of 0.06 to 0.3 mm is 0.8 to 1.5 μm in Ra, and the inventors have a slinger within this range. It has been confirmed by experiments that sufficient adhesion durability can be secured with respect to the adhesion surface roughness. For this reason, the particle size range of the alumina type abrasive | polishing material used suitably in this invention can be 0.06-0.3 mm.

  The magnetic encoder 26 according to the present invention is basically composed of an annular magnetic pole forming ring 27 made of a resin composition as a binder and magnetic powder, and a slinger 25. Hereinafter, a method for manufacturing the magnetic encoder 26 according to the present invention will be described.

  The magnetic encoder 26 according to the present invention is formed into a pellet by using a slinger 25 in which an adhesive joint surface 28 is formed into a concavo-convex shape by blasting and a thermosetting resin adhesive such as phenol resin or epoxy resin is baked. The magnetic pole forming ring 27 and the slinger 25 are integrally bonded and joined by insert molding of a plastic magnet material, and then multipolar magnetized in the circumferential direction.

  The thermosetting resin-based adhesive used in the present invention is a half of the degree that it is not washed away by a high-temperature and high-pressure molten plastic magnet material at the time of insert molding, for example, under curing conditions of 100 ° C. to 120 ° C. for several minutes to 30 minutes. It can be baked on the slinger 25 in a cured state, and is completely cured by heat from the molten plastic magnet at the time of insert molding, and further by subsequent secondary heating.

  Moreover, the pellet of the plastic magnet material of the present invention can be produced, for example, by the following method. A plastic magnet material obtained after kneading a resin composition comprising a polymer alloy of a polyamide resin and a soft component blended as an impact strength improver into magnetic powder with a biaxial extruder, kneader or Banbury mixer, etc. It is obtained by pelletizing by customary methods.

  Therefore, according to the magnetic encoder 26 of the present embodiment, the slinger 25 has the concavo-convex portion 28 formed by the blasting process, and the magnetic pole forming ring 27 is bonded and bonded only by the concavo-convex portion 28. As a result, it is possible to provide a magnetic encoder with extremely excellent adhesion durability under salt spray.

  Moreover, since the uneven | corrugated | grooved part 28 is formed only in the axial direction outer end surface at the slinger 25, a blasting process can be performed comparatively easily.

  In addition, since the magnetic powder in the plastic magnet obtained by the production method of the present invention is highly oriented in the thickness direction of the annular magnet, the magnetic characteristics of the encoder obtained by the magnetization are extremely good. It becomes. For this reason, depending on the content of the magnetic powder in the magnet, it is possible to improve the magnetic flux density, which was conventionally about 20 mT, to 26 mT or more. Therefore, when the gap between the magnetic encoder and the sensor is set to 1 mm as in the conventional case, what was conventionally multipolarly magnetized to 96 poles is multipolarly magnetized to 120 poles or more while maintaining the magnetic flux per pole. It is possible. At this time, the single pitch error can be ± 2% or less. In other words, according to the magnetic encoder of the present invention, when the air gap is the same as that of the prior art, the number of poles can be increased to improve the detection accuracy of the rotational speed of the wheel. In addition, when the plastic magnet according to the present invention has the same number of poles as the conventional one, the air gap can be made large, and the degree of freedom in arranging the sensor can be improved.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.

  For example, as shown in FIG. 5A, even if the slinger 25A has a shape having an inclined surface 29 on the outer diameter side of the axially outer end surface, the concavo-convex portion 28 is located outside the axial direction as in the above embodiment. Since it is formed on the end face, the blasting process can be performed relatively easily.

  Further, when the blasting process is performed on the outer diameter end surface of the slinger, it is necessary to perform the blasting process again from a direction different from the axial outer end surface, which increases the processing time and the processing cost. Therefore, as described above, it is preferable to perform the blasting process only on the outer end surface in the axial direction. However, when the magnetic pole forming ring 27 has a shape covering the outer diameter end surface 30, the slinger shown in FIG. As shown in FIG. 25B, the concavo-convex portion 28 by blasting may be formed on the outer diameter end surface 30 to form an adhesive bonding surface.

  Further, the blasting process of the slinger with the abrasive according to the present invention may be substantially only the adhesive joint surface with the plastic magnet, but the slinger 25C shown in FIG. As described above, the uneven portion 28 may be processed on the entire surface. However, in that case, the treatment must be performed to such an extent that the uneven structure formed by the blast treatment (also formed on the seal sliding surface) does not affect the sealing performance of the seal.

  EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

  The plastic magnet material constituting the magnetic encoder of the present invention can be manufactured by the following method, for example. First, additives such as a soft component, a heat stabilizer, and a plasticizer blended as an impact strength improver are added and kneaded into a polyamide resin by a twin screw extruder, a kneader, or a Banbury mixer. The kneading is performed at a temperature of 160 ° C. to 280 ° C. for 1 minute to 20 minutes. Thereafter, the resin composition is pelletized by a usual method. Furthermore, the pellets of the resin composition are put into the magnetic powder, kneaded for 1 to 20 minutes while being heated at a temperature of 160 to 280 ° C. using a twin screw extruder, and then extruded. Next, a molding material can be obtained by pelletizing the extruded magnetic powder-containing resin composition.

  Moreover, the manufacturing method of the magnetic encoder which concerns on this invention follows the procedure described below, for example. First, a thermosetting resin adhesive is applied to the entire surface of the adhesive bonding surface with the plastic magnet on a slinger that is subjected to concavo-convex processing that is indispensable for improving adhesive durability by blasting using an abrasive. After this is air-dried at room temperature, the adhesive is baked in a semi-cured state. The baked slinger is set in a mold, and this is used as a core for insert molding of a plastic magnet material. Next, the obtained molded body is magnetized in multiple poles using a yoke coil with a plastic magnet and slinger adhesive obtained by, for example, processing at 150 ° C. under heating conditions of about 2 hours (main curing of the adhesive). By doing so, the plastic magnet magnetic encoder of the present invention is obtained.

  Using the plastic magnets having the blending amounts shown in Table 1, magnetic encoders having the shapes according to the present invention were produced as Examples 1 and 2 in accordance with the manufacturing method described above. On the other hand, the magnetic encoder produced using the slinger by which the uneven | corrugated process by an abrasive material is not given to the outer diameter end surface with respect to Example 1, 2 was made into the comparative example.

(Salt spray test)
Table 1 shows the results of the salt spray test for Examples 1 and 2 and the comparative example. As a test, the degree of progress of adhesion peeling after being allowed to stand in a salt water atmosphere of 5% by weight and 35 ± 2 ° C. for 1500 hours was evaluated. In addition, the judgment criterion of the result is a pass (◯) when the adhesion peeling distance from the encoder end is less than 1 mm, and a failure (×) when the adhesion peeling distance is 1 mm or more. did. As is apparent from the result of the notation, in the embodiment of the present invention, the slinger-plastic magnet is formed by adopting a slinger shape in which the outer diameter end face, which is difficult to be blasted, is prevented from being an adhesive joint with the plastic magnet. As a result of suppressing the occurrence of crevice corrosion between the two, the salt water resistance is improved. On the other hand, in the case of the comparative example, when exposed to a harsh environment such as salt spray for a long time, the adhesive interface at the outer diameter end deteriorates water absorption in a relatively short time, and between the slinger and the plastic magnet. The occurrence of crevice corrosion is induced, and it can be seen that the peeling progressed.

It is sectional drawing which shows the rolling bearing unit of one Embodiment of this invention. It is sectional drawing which shows the sealing device provided with the magnetic encoder of this embodiment. It is a perspective view which shows the example by which the multipolar magnetization was carried out in the circumferential direction of the encoder magnet. (A) is sectional drawing which shows the slinger which performed the blast process of this embodiment, (b) is sectional drawing which shows the magnetic encoder after insert molding. It is sectional drawing which shows the modification of the magnetic encoder of this embodiment. It is sectional drawing which shows the conventional rolling bearing unit.

Explanation of symbols

2a Wheel support rolling bearing unit 5a Outer ring 7a Hub 8 Stud 11 Coupling flange 12 Mounting flange 15 Small diameter step portion 16a Inner ring 17a Ball 18 Cage 21a, 21b Seal ring 22a, 22b Elastic member 23 Caulking portion 24a, 24b Core metal 25, 25 'slinger 26, 26' magnetic encoder 27 magnetic pole forming ring (plastic magnet)
28 Concavity and convexity

Claims (3)

A stationary wheel,
A rotating wheel that rotates relative to the stationary wheel;
A plurality of rolling elements rotatably disposed between the stationary wheel and the rotating wheel;
A magnetic encoder for detecting the rotational speed of the rotating wheel, comprising a slinger attached to the rotating wheel, and a plastic magnet joined to the slinger and containing 60-80% by volume of magnetic powder;
A bearing device with a magnetic encoder comprising:
The said slinger has an uneven | corrugated | grooved part formed by a blast process, and the said plastic magnet is adhesively bonded only to the said uneven | corrugated | grooved part, The bearing apparatus with a magnetic encoder characterized by the above-mentioned.   2. The bearing device with a magnetic encoder according to claim 1, wherein the uneven portion is formed only on an end surface of the slinger in the axial direction.   The bearing device with a magnetic encoder according to claim 1, wherein the uneven portion is formed on the entire surface of the slinger.

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