JP4586475B2 - Magnetic encoder - Google Patents

Description

  The present invention relates to 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 rotational speed detection device used for control, etc., an annular magnetic encoder in which N poles and S poles are alternately magnetized in the circumferential direction, a sensor for detecting a change in the magnetic field in the vicinity of the magnetic encoder, The magnetic encoder is rotated together with the rotation of the wheel by arranging the magnetic encoder in the sealing device for sealing the bearing that supports the wheel, and the magnetic field change synchronized with the rotation of the wheel is detected by the sensor. Things are known.

Magnetic encoders used in the above wheel bearings are those in which magnetic rubber mixed with magnetic powder is vulcanized and bonded to slinger, or plastic magnets in which magnetic powder is mixed in plastic are bonded and bonded to slinger. Is used. Furthermore, there has been proposed one in which an annular plastic magnet and a slinger are bonded and bonded with a so-called elastic adhesive. (For example, refer to Patent Document 1.)
JP 2003-222150 A

  By the way, the greatest advantage of using a rubber magnet is that the generation of internal stress can be suppressed to some extent because of its low modulus, and the generated internal stress can be efficiently relaxed and absorbed by viscoelastic behavior. Therefore, a magnetic encoder using a rubber magnet does not generate excessive stress even when exposed to a severe temperature environment (for example, −40 ° C. to 120 ° C.), and is unlikely to cause a peeling problem.

  In recent years, magnetic encoders have been more compactly incorporated as a part of bearing seal devices, but in such a configuration, it is easier to assemble a larger air gap between the encoder and the sensor. Convenient from the aspect. For this reason, it is desired to enlarge the air gap. In this case, however, more powerful encoder capability is required to ensure a highly accurate rotation detection function. That is, the magnetic encoder is strongly required to further improve the magnetic flux density.

  In order to respond to such a demand for increased magnetic force, it is sufficient to increase the amount of magnetic powder mixed in, but in this case, the modulus of rubber magnets increases and at the same time the viscoelastic side is lost. Suppression and mitigation absorption capacity will be extremely reduced. In other words, when the amount of magnetic powder is increased, in a severe temperature environment, an excessive stress is generated based on the difference in thermal expansion coefficient between the rubber magnet and the slinger, and this is not relaxed (mechanical defect portion and As a result of concentrating on the adhesive interface layer (which is considered), the adhesion between the rubber magnet and the slinger was gradually reduced and could eventually peel off.

  On the other hand, when a plastic magnet is used, it is possible to mix a relatively large amount of magnetic powder into the rubber magnet. In this respect, it can be an encoder material having a magnetic property superior to that of the rubber magnet. It becomes a characteristic material. Furthermore, the plastic magnet can be easily injection molded (magnetic field molding) in a state where a magnetic field is applied, and an anisotropic magnet indispensable for developing excellent magnetic properties can be obtained.

  However, when a magnetic magnet is magnetized by bonding a plastic magnet to a slinger, the problem of peeling occurs in a severe temperature environment, like a rubber magnet with an increased amount of magnetic powder. Is expected. Even in the case of securing a highly reliable (non-peeling under severe temperature environment) and strong adhesion, it is assumed that the maximum stress is concentrated inside the plastic magnet. In this case, it is assumed that the plastic magnet breaks down due to stress. Furthermore, in order to solve such a problem, a method using an elastic adhesive such as the magnetic encoder described in Patent Document 1 can be considered, but there is a problem that the cost is increased and the productivity is deteriorated.

The present invention has been made in order to solve the above-described problems, and has the object of having high magnetic properties and high reliability that does not fall off the slinger or break itself even under a severe temperature environment. A magnetic encoder and a rolling bearing unit using the same are provided.

The above object of the present invention can be achieved by the following constitution.
(1) A magnetic encoder comprising: a fixing member that can be attached to a rotating body; and a substantially annular magnet portion that is attached to the fixing member and is multipolarly magnetized in the circumferential direction,
The magnet portion is made of a magnet material containing a polyamide resin composition and magnetic powder,
The magnetic powder is one selected from the group of strontium ferrite, barium ferrite, neodymium-iron-boron, samarium-cobalt, samarium-iron,
The content of the magnetic powder of the magnet material is 60 to 80% by volume,
The magnet part is integrally joined to the fixing member by insert molding the magnet material with the fixing member baked adhesive as a core,
The magnetic encoder has a thickness of 0.6 to 1.2 mm, and the fixing member has a thickness of 0.4 to 1.0 mm.
(2) The polyamide resin composition comprises at least a polyamide resin selected from the group consisting of polyamide 12, polyamide 11, and polyamide 612, and a polyamide system including a soft segment having a glass transition temperature of at least −40 ° C. or less in its molecular structure. The magnetic encoder according to (1), which is a resin composition comprising a polymer alloy with a block copolymer.
(3) The magnetic encoder according to (1), wherein the adhesive to be baked on the fixing member is a phenol resin adhesive.
(4) The magnetic encoder according to (1), wherein insert molding of the magnet material is performed using the fixing member obtained by baking the adhesive in a semi-cured state as a core.
(5) The magnetic encoder according to (4), wherein the adhesive is completely cured by secondary heating performed after the insert molding.
(6) The magnetic encoder according to (1), wherein the magnetic powder is strontium ferrite or barium ferrite, and lanthanum and cobalt are mixed therein.
(7) In a rolling bearing unit comprising a fixed wheel, a rotating wheel, and a plurality of rolling elements arranged to be freely rollable in the circumferential direction between the fixed wheel and the rotating wheel, (1) to (6) A rolling bearing unit, wherein any one of the magnetic encoders is fixed to the rotating wheel.

  The encoder of the present invention has a good magnetic property and is highly reliable without dropping from the slinger or self-destructing even under a severe temperature environment.

  Hereinafter, embodiments of the encoder and the rolling bearing unit of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows, as an example of an embodiment of the present invention, a case where the present invention is applied to a wheel support rolling bearing unit 2a for supporting a non-driving wheel supported by an independent suspension. 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 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. The hub 7a and the inner ring 16a constitute a rotating wheel. Further, the wheel is formed by a stud 8 planted at a predetermined interval in the circumferential direction on a mounting flange 12 formed at a portion protruding from the outer end portion of the outer ring 5a which is a fixed wheel at the outer end portion of the hub 7a. It can be connected and fixed freely. 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. These seal rings 21a and 21b block the 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.

  As shown in FIG. 2, the magnetic encoder 26 includes a slinger 25 that is a fixed member, and a magnetic pole forming ring 27 that is a magnet portion integrally joined 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. Then, a magnetic sensor 28 is disposed facing the magnetic pole forming ring 27 (see FIG. 1).

  Hereinafter, basic specifications of the magnetic encoder 26 according to the present invention will be described. The magnetic pole forming ring 27 of the magnetic encoder 26 is composed of a multipolar plastic magnet made of a magnet material containing magnetic powder and a resin composition serving as a binder thereof. Also, the magnetic encoder uses a slinger baked with phenol resin adhesive as the core, insert molding of the magnet material, and integrally bonding and joining the plastic magnet and slinger constituting the magnetic pole forming ring at the same time, The obtained adhesive is manufactured by multipolar magnetization in the circumferential direction. As a binder for the plastic magnet, polyamide 11 and polyamide 12 with low water absorption are taken into consideration that polyamide resin, specifically, calcium chloride used as a snow melting material may be taken together with water. Polyamide 612 is used. In addition, a chemical etching process is performed on the bonding surface of the slinger in order to make the adhesion between the plastic magnet and the slinger stronger.

  The inventors of the present invention have already found that a magnetic encoder having excellent performance and durability can be obtained if the basic specifications are as described above. However, as a result of earnest research, the reliability has been improved. The thicknesses of the plastic magnet and slinger in the magnetic encoder are each set within a preferable range. Further, a resin composition that is a binder of the plastic magnet has a glass transition temperature of at least −40 ° C. or less in the polyamide resin and its molecular structure. Highly reliable without causing problems such as cracks even under severe temperature conditions while satisfying the required functions as a magnetic encoder by using a polymer alloy with a polyamide block copolymer containing a soft segment. It has been found that a magnetic encoder can be obtained.

  First, as a result of investigating the relationship between the configuration of a magnetic encoder, its performance, and durability, the present inventors have determined the thickness of the plastic magnet formed on the slinger to ensure high performance and high reliability. It was concluded that (meaning maximum thickness: hereinafter simply referred to as thickness) should be 0.6 mm to 1.2 mm and the thickness of the slinger should be within the range of 0.4 mm to 1.0 mm. That is, according to the basic specifications of the magnetic encoder according to the present invention, the plastic magnet and the slinger are bonded and bonded very firmly by the phenol resin adhesive. For this reason, there is a possibility that the maximum concentration point of the stress generated based on the difference in the amount of thermal deformation between the plastic magnet and the slinger in a severe temperature environment exists slightly on the plastic magnet side from the adhesive layer. Here, when attention is paid to the deformation mechanism of the plastic magnet and slinger, it is presumed that as the thickness of the plastic magnet increases, the difference in deformation amount due to the environmental temperature change between the plastic magnet and the slinger increases. However, since the restraining effect of the phenolic resin adhesive layer decreases as the distance from the adhesive interface layer increases, the resin of the plastic magnet further away from the adhesive interface layer can be deformed more freely and largely (note that The resin component of the plastic magnet in the vicinity of the adhesive interface is strongly fixed to the phenolic resin adhesive layer, so that the deformation is interpreted to a certain extent). For the above reasons, as the thickness of the plastic magnet increases, the amount of deformation accompanying the environmental temperature change increases. As a result, the difference in the amount of deformation relative to the slinger increases. The possibility of occurring inside was considered sufficiently. For this reason, it was concluded that an increase in the thickness of the plastic magnet is not preferable in terms of durability.

  However, considering the performance aspect, the thickness of the plastic magnet cannot be made too thin. That is, if the thickness of the plastic magnet is too thin, the magnetic characteristics required (maximum energy product (BHmax) in the range of 1.3 to 15 MGOe, more preferably 1.8 to 12 MGOe) are extremely satisfied. It becomes difficult. The present inventors have found this through experiments, and in order to ensure high performance and high reliability in the magnetic encoder of the present invention specification, the thickness of the plastic magnet formed on the slinger is 0.6 mm to 1 mm. A conclusion was reached that it should be in the range of 2 mm. That is, when the thickness of the plastic magnet is less than 0.6 mm, it is not preferable because the magnetic characteristics do not satisfy the required performance. When the thickness is greater than 1.2 mm, the relative deformation amount with the slinger is not preferable as described above. This is not preferable because the difference becomes large and tends to be disadvantageous in terms of durability.

  Further, as will be described in detail below, the present inventor has found that there is an appropriate value for the slinger. As the material of the slinger of the magnetic encoder according to the present invention, ferritic stainless steel (SUS430 or the like), martensitic stainless steel (such as SUS430) having a certain level of corrosion resistance, which does not deteriorate the magnetic characteristics of the plastic magnet and is used from the usage environment. Magnetic stainless steel such as SUS410 is used, but the present inventor has the effect as a back yoke of a plastic magnet unless the thickness of the slinger made of such magnetic stainless steel is at least 0.4 mm or more. I found that I could not expect enough. That is, when the thickness of the slinger is less than 0.4 mm, not only the rigidity as the slinger is insufficient, but also the effect as the back yoke is insufficient, which is not preferable. On the other hand, when the thickness is larger than 1.0 mm, the molding processability is lowered, and the manufacturing cost tends to be disadvantageous. For the reasons described above, it has been concluded that the thickness of the slinger needs to be in the range of 0.4 mm to 1.0 mm.

  By the way, the magnetic encoder according to the present invention is sufficiently assumed to be used under a severe use environment, that is, an environment in which repeated thermal shock is applied. In the present invention, in order to further ensure reliability under a situation where repeated thermal shock is applied at −40 ° C. to 120 ° C., in the present invention, a resin composition that is a binder of a plastic magnet is used as a polyamide. A polymer alloy of a resin and a polyamide-based block copolymer including a soft segment having a glass transition temperature of at least −40 ° C. or less in the molecular structure thereof is used. The reason is as follows. First, considering the case where the temperature of a magnetic encoder of the present invention specification (however, the binder of the plastic magnet is an ordinary (unmodified) polyamide resin) is raised to 120 ° C., in this case, the thermal expansion of the plastic magnet and the slinger The stress caused by the difference is thought to be concentrated in the part that entered the plastic magnet side somewhat from the adhesion interface, but in this temperature range, the molecular chain in the amorphous of the polyamide resin that is the binder of the plastic magnet is Since it is in a rubber state, it has the ability to partially absorb and absorb stress. For this reason, the stress generated inside the plastic magnet is presumed to be relaxed to some extent by the molecular chain motion. On the other hand, considering the case where the temperature is lowered to −40 ° C., in this case, at 120 ° C. Unlike the glass transition temperature of the polyamide resin, the stress relaxation absorption effect due to molecular chain motion is hardly expected. From the above considerations, it was concluded that the possibility of cracking in the low temperature region would be very large. That is, in the magnetic encoder of the present invention specification, the inherent flexibility of the polyamide resin such as polyamide 12, polyamide 11, and polyamide 612 is not necessarily sufficient, and the reliability under severe temperature environment is further improved. Considered the most important to improve flexibility, especially at low temperatures (or low temperature impact resistance). Specifically, in the magnetic encoder of the present invention specification, the resin composition serving as the binder of the magnet material is made of polyamide resin of polyamide 12, polyamide 11, and polyamide 612, and the glass transition temperature in the molecular structure is at least −40 ° C. By using a resin composition mainly composed of a polymer alloy with a polyamide-based block copolymer containing a soft segment as described below, flexibility at a particularly low temperature could be secured.

  In addition, as a soft segment of the polyamide-type block copolymer based on this invention, a glass transition temperature should just be -40 degrees C or less, and it does not specifically limit by other properties. As candidates for the soft segment, polyester, polyether, polybutadiene, polyisoprene, polycarbonate, polycaprolactam, and the like can be considered, and there are many options. However, in view of the ease of availability from the market, the polyamide block copolymer according to the present invention is currently selected as a polyamide block copolymer having polyester or polyether in a soft segment. Would be optimal as. In particular, in view of hydrolysis resistance, the polyamide block copolymer containing the latter polyether segment can be considered more suitable. Specific examples of the polyether segment according to the present invention include polytetramethylene oxide, polypropylene oxide, polyethylene oxide, and copolymers thereof. In addition, the compounding quantity of the polyamide-type block copolymer demonstrated above is 5 to 50 weight% with respect to the total weight of a resin composition, Preferably it is 10 to 35 weight%. If it is less than 5% by weight, the absolute amount is too small to provide the desired low-temperature flexibility. On the other hand, if it exceeds 50% by weight, the heat resistance is particularly insufficient, and it is not suitable for use as a magnet material for a magnetic encoder.

The resin composition according to the present invention may be further improved in low temperature characteristics by adding a plasticizer. In particular, those having a freezing point of −40 ° C. or lower are suitable. Specifically, aliphatic esters such as di-2-ethylhexyl adipate, di-2-ethylhexyl sebacate, and di-2-ethylhexyl azelate, , 2,4-trimethyl-1,3-pentanediol monoisobutyrate, polyhydric alcohol esters such as 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, and tributyl phosphate, phosphorus Tri-2-ethylhexyl acid, tributoxyethyl phosphate, and the like can be particularly preferably used. Further, other plasticizers for polyamide may be used in combination with these plasticizers aimed at improving the low temperature characteristics. For example, benzenesulfonic acid alkylamides, toluenesulfonic acid alkydamides, and ethylhexyl hydroxybenzoate, or phenols or cresols and unsaturated aliphatic esters that exhibit a stable plasticizing effect without volatilization even at high temperatures. Specifically, a phenol resin composition obtained by reaction of phenol and methyl oleate or cresol and 2-ethylhexyl oleate may be added.
In addition, the compounding quantity of the plasticizer demonstrated above (when using multiple) is 1-20 weight% with respect to the total weight of a resin composition, Preferably it is 3-15 weight%. If it is less than 1% by weight, the absolute amount is too small to provide sufficient flexibility. On the other hand, when it exceeds 20% by weight, adverse effects such as a decrease in strength and heat resistance of the whole material become apparent, which is not preferable.

  Moreover, you may add suitably an antioxidant, a weather resistance improving material, an antistatic material, an inorganic or organic flame retardant, a reinforcing material, etc. to the resin composition concerning this invention as needed.

  On the other hand, as the 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. 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 is difficult to perform multipolar magnetization 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.

  A magnetic encoder according to the present invention comprises an annular resin comprising a polymer alloy of a polyamide resin and a polyamide block copolymer containing a soft segment having a glass transition temperature of at least −40 ° C. or less in the molecular structure thereof and a magnetic powder. Multi-pole magnets (thickness: 0.6 mm to 1.2 mm) and slinger (thickness: 0.4 mm to 1.0 mm). In the following, a method for manufacturing a magnetic encoder according to the present invention will be described in detail.

  The magnetic encoder according to the present invention includes a slinger baked with a phenol resin adhesive as a core, insert molding of a plastic magnet, and then completely curing the phenol resin adhesive by secondary heating. After the magnet material and slinger are integrally bonded and bonded, they are manufactured by multipolar magnetization in the circumferential direction.

  The phenol resin-based adhesive used in the present invention contains at least a resol type phenol resin and a bisphenol A type epoxy resin, for example, at 100 ° C. to 120 ° C. under curing conditions of about several minutes to 30 minutes, at a high temperature during insert molding. It can be baked on the slinger in a semi-cured state not to be washed away by the high pressure molten plastic magnet material, and further, the heat from the molten plastic magnet at the time of insert molding and further secondary heating (for example, 150 ° C., 2 hours) Degree).

Furthermore, as to the molding of the encoder part, the molding of the encoder part is a disk gate type injection in which the plastic magnet material melted from the inner diameter thick part simultaneously flows into the mold at a high pressure and is rapidly cooled and solidified in the mold. Molding is preferred. The molten resin spreads in a disk shape, and then flows into the mold corresponding to the inner diameter thick portion, so that the flake-like magnetic powder contained therein is oriented parallel to the surface. In particular, the portion between the inner diameter portion and the outer diameter portion detected by the rotation sensor in the vicinity of the inner diameter thick portion has higher orientation and is very close to the axial anisotropy oriented in the thickness direction. If a magnetic field is applied to the mold in the thickness direction during molding, the anisotropy becomes closer to perfection. Even when magnetic field molding is performed, if the gate is made of a pin gate other than a disk gate, for example, the resin viscosity gradually increases toward solidification, the orientation at the weld is completely anisotropic. It is difficult to cause cracks and the like in the wade where the magnetic properties are lowered and the mechanical strength is lowered.
The plastic magnet material pellets of the present invention can be produced, for example, by the following method. A resin composition comprising a polymer alloy of a polyamide resin and a polyamide block copolymer containing a soft resin segment having a glass transition temperature of −40 ° C. or less on a magnetic powder by a biaxial extruder, a kneader or a Banbury mixer. After kneading, the obtained plastic magnet material is obtained by pelletizing by a usual method.

  Therefore, according to the magnetic encoder of the present invention, the magnet thickness and slinger thickness of the plastic magnet encoder are determined within the range defined by the present invention, and the binder of the plastic magnet is excellent in high temperature characteristics and low temperature flexibility and has a wide range of temperatures. By using a resin composition that can exhibit stable performance at a high level in the region, it will peel off from the slinger and drop off even under operating conditions such as repeated vibration and severe changes in heat and heat, or the plastic magnet will self-destruct This makes it possible to manufacture a highly reliable magnetic encoder. 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 will be a thing. For this reason, depending on the content of the magnetic powder in the magnet, the magnetic flux density, which was conventionally about 20 mT, can be improved to 26 mT or more. Therefore, when the gap between the magnetic encoder and the sensor is set to 1 mm as in the prior art, an object that has been multipolarly magnetized to 96 poles is magnetized to more than 120 poles 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.

  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, a polyamide block copolymer containing a soft segment having a temperature of −40 ° C. or lower and an additive such as a plasticizer are added and kneaded into a polyamide resin by a biaxial extruder, a kneader, a Banbury mixer, or the like. The kneading is performed at a temperature of 160 ° C. to 280 ° C. for 1 minute to 20 minutes. At that time, 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 plastic magnet 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 phenol resin adhesive is applied onto a chemically etched slinger (thickness: 0.4 mm to 1.0 mm), left to stand for 20 to 60 minutes at room temperature, and then air-dried. For about 30 minutes. Set the slinger, which has been heat-treated and baked adhesive, in a mold so that the thickness of the plastic magnet after molding is in the range of 0.6 mm to 1.2 mm. Insert molding of the produced plastic magnet material according to the present invention is performed. After that, the obtained molded body is heated (secondary curing) at about 150 ° C. for about 2 hours, and a plastic magnet and slinger adhesive is magnetized in multiple poles using a yoke coil. A magnetic encoder can be obtained.

  Here, using the magnetic encoders of Examples and Comparative Examples having the blending amount of the plastic magnet, the thickness of the plastic magnet, and the thickness of the slinger as shown in Table 1, the magnetic property evaluation test, the heat A shock test was conducted. In addition, regarding the evaluation of the magnetic properties, those exceeding the required performance value determined by the present inventors are passed (O), and Comparative Example 2 has the required performance because the plastic magnet thickness is not appropriate (thin). Since it was not satisfied, it was judged that there was a problem in practical use. On the other hand, in Comparative Example 3, a tendency was observed that the magnetic characteristics gradually decreased after fabrication, so it was judged that there was a problem in practical use and failed. (X).

[Evaluation of thermal shock resistance]
For Examples 1 and 2 and Comparative Example 1 in which the magnetic characteristics satisfied the required performance, repeated heat shock tests were performed to evaluate the thermal shock resistance. Table 2 shows the results. The test conditions were 1000 cycles (120 ° C., 30 minutes) and (−40 ° C., 30 minutes) as one cycle. The appearance during the test was checked every 100 cycles.

  As is apparent from the results in Table 2, an example in which a plastic magnet with improved low-temperature flexibility is formed on a slinger made with an appropriate thickness so as to have the same appropriate thickness is used as a magnetic encoder. While ensuring a desired function, the generation of cracks under a severe temperature environment is completely prevented.

It is sectional drawing which shows the rolling bearing unit for wheel support which is an example of embodiment of this invention. It is sectional drawing which shows the sealing device provided with the magnetic encoder which is an example of embodiment of this invention. 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.

Explanation of symbols

2a Wheel bearing rolling bearing unit 5a Outer ring 7a Hub 8 Stud 10a, 10b Outer ring raceway 11 Coupling flange 12 Mounting flange 14, 14a, 14b Inner ring raceway 15 Small diameter step 16a Inner ring 17a Ball 18 Cage 21a Seal rings 22, 22a, 22b Elastic member 23 Caulking portion 24b Core metal 25 Slinger 26 Magnetic encoder magnetic pole forming ring 27 Magnetic pole forming ring

Claims (7)

A magnetic encoder comprising: a fixing member that can be attached to a rotating body; and a substantially annular magnet portion that is attached to the fixing member and is multipolarly magnetized in the circumferential direction,
The magnet portion is made of a magnet material containing a polyamide resin composition and magnetic powder,
The magnetic powder is one selected from the group of strontium ferrite, barium ferrite, neodymium-iron-boron, samarium-cobalt, samarium-iron,
The content of the magnetic powder of the magnet material is 60 to 80% by volume,
The magnet part is integrally joined to the fixing member by insert molding the magnet material with the fixing member baked adhesive as a core,
The magnetic encoder has a thickness of 0.6 to 1.2 mm, and the fixing member has a thickness of 0.4 to 1.0 mm. The polyamide resin composition is a polyamide block copolymer comprising at least a polyamide resin selected from the group consisting of polyamide 12, polyamide 11, and polyamide 612 and a soft segment having a glass transition temperature of at least −40 ° C. or less in the molecular structure. The magnetic encoder according to claim 1, wherein the magnetic encoder is a resin composition made of a polymer alloy with a coalescence. The magnetic encoder according to claim 1, wherein the adhesive to be baked on the fixing member is a phenol resin adhesive. 2. The magnetic encoder according to claim 1, wherein the magnet material is insert-molded using the fixing member baked in a semi-cured state as a core. 3. The magnetic encoder according to claim 4, wherein the adhesive is completely cured by secondary heating performed after the insert molding. The magnetic encoder according to claim 1, wherein the magnetic powder is strontium ferrite or barium ferrite, and lanthanum and cobalt are mixed therein. In a rolling bearing unit comprising a fixed wheel, a rotating wheel, and a plurality of rolling elements arranged to be freely rollable in the circumferential direction between the fixed wheel and the rotating wheel,
  A rolling bearing unit, wherein the magnetic encoder according to claim 1 is fixed to the rotating wheel.

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