JP2006214752A - Magnetic encoder and rolling bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable magnetic encoder and reliable rolling bearing unit that hardly cause a crack or the like, even in a structure that has improved bending flexibility and extension of the material itself in addition to the heat resistance and water resistance possessed by a plastic magnet material, and is integrally bonded to a magnet section by insert molding using a slinger as the core. <P>SOLUTION: The magnet section 27 of the magnetic encoder 26 contains magnetic powder and thermoplastic resin as a binder. The thermoplastic resin contains at least modified polyester resin, which is a block copolymer having one hard segment of polybutylene terephthalate and polybutylenenaphthalate rate and at least one soft segment of polyether component and polyester component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic encoder used for detecting the rotational speed of a rotating body and a rolling bearing unit including the magnetic encoder.

  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. 11, the rotational speed detection device with a seal described in Patent Document 1 is attached to the seal member 102 attached to the outer ring 101a, the slinger 103 fitted to the inner ring 101b, and the outer surface of the slinger 103. The encoder 104 is configured to generate a magnetic pulse, and the sensor 105 is disposed adjacent to the encoder 104 to detect 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. The encoder 104 generates the number of magnetic pulses corresponding to the number of poles during one rotation of the inner ring 101b, and detects the number of rotations of the inner ring 101b by detecting this magnetic pulse with the sensor 105.

Conventionally, the encoder 104 used for the wheel bearing is made of an elastic magnetic material obtained by mixing magnetic powder into an elastic material such as rubber or resin, and the flange portion 103a of the slinger 103 coated with an adhesive in the mold. It is joined by press molding. Generally, a nitrile rubber containing ferrite is used as a magnetic powder for an encoder, and the magnetic powder is mechanically oriented by being kneaded with a roll.
JP 2001-255337 A

  However, in recent years, in order to more accurately detect the rotational speed, the number of magnetic poles that are multipolar in the circumferential direction of the magnet portion of the magnetic encoder tends to increase. As a result, in conventional ferrite magnet rubber encoders using the mechanical orientation method, the magnetic flux density per pole is reduced, and it is necessary to keep the air gap with the magnetic sensor low in order to accurately detect the rotational speed. ing. In addition, this magnetic encoder is used in the undercarriage of automobiles as the performance of automobiles increases, so that it is exposed to a high temperature environment of about 120 ° C. or a low temperature environment of about −40 ° C., muddy water, snow melting agent, It is assumed that greases such as grease and oil adhere to the surface.

  In order to increase the air gap amount of the above problem, it is necessary to improve the magnetic characteristics. However, in order to achieve with a rubber magnet, it is common to use rare earths as magnetic powder. However, the rare earth magnetic powder is expensive and the oxidation resistance of the powder itself is lower than that of the ferrite system. Therefore, when used in the environment described above, there is a possibility that the magnetic properties will be greatly lowered due to oxidation degradation. Also, if ferrite magnetic powder is used and plastic is used as a binder, a larger amount can be filled than a rubber magnet, and magnetic properties can be improved by magnetic field injection molding. However, when ferrite is highly filled, the magnetic properties are improved, but the material becomes brittle and the elongation and deflection are reduced.

  For this reason, it has a structure in which a metal slinger is used as a core, mechanically joined by insert molding using a plastic magnet material highly filled with ferrite, and further chemically joined via an adhesive. In this case, if a high temperature environment / low temperature environment assumed in an automobile or the like is repeatedly applied, the deformation of the plastic magnet material cannot follow the deformation (dimensional change) of the slinger. As a result, in the worst case, a crack or the like may occur in the plastic magnet starting from a relatively weak part such as a mechanical joint, and the magnetic encoder may not function.

  The present invention has been made in view of such problems, and in addition to the heat resistance and water resistance of the plastic magnet material, the bending flexibility and the elongation of the material itself are improved, and the slinger is used as a core. An object of the present invention is to provide a highly reliable magnetic encoder and a rolling bearing unit that are less likely to be cracked even if the structure is integrally formed with a magnet portion by insert molding.

The above object of the present invention is achieved by the following configurations.
(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 fixing member is made of a magnet material,
The magnet part contains magnetic powder and a thermoplastic resin as a binder,
The thermoplastic resin contains at least a modified polyester resin which is a block copolymer having a hard segment of any one of polybutylene terephthalate and polybutylene naphthalate and a soft segment of at least one of a polyether component and a polyester component. A magnetic encoder characterized by that.
(2) A fixed bearing, a rotating wheel, a rolling bearing having a plurality of rolling elements arranged to be freely rollable in a circumferential direction in an annular gap formed between the fixed wheel and the rotating wheel, and the rotation A rolling bearing unit comprising: the magnetic encoder according to claim 1 fixed to a ring.

  According to the magnetic encoder of the present invention, since the magnet portion contains the modified polyester resin as the binder, the bending deflection amount is larger than that of a conventional magnet made of only a thermoplastic resin binder such as polyamide 12, and the resistance to resistance. Cracking is improved. As a result, even in a structure that is mechanically joined (and chemically joined with an adhesive) by insert molding with a slinger as the core, high and low temperature, high temperature ← → low temperature thermal shock that the undercarriage part of the automobile is exposed to When a stress such as the above is applied to the magnet portion, it is possible to effectively prevent the magnet portion from cracking, and the reliability can be greatly improved.

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

(First embodiment)
FIG. 1 shows a case where the present invention is applied to a hub unit bearing 2a for supporting a non-driving wheel supported by an independent suspension, as an example of an embodiment of the present invention. 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 hub unit bearing 2a includes an outer ring 5a that is a fixed ring, a hub 7a and an inner ring 16a that are rotating wheels (rotating bodies) that rotate integrally with a mounting flange 12 for fixing a wheel (not shown), an outer ring 5a, Balls 17a and 17a, which are a plurality of rolling elements arranged in a circumferential direction in an annular gap formed between the hub 7a and the inner ring 16, are provided. A magnetic encoder 26 is fixed to the inner ring 16. Yes.

  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. 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. Between the outer ring 5a, the hub 7a, and the inner ring 16a, a plurality of balls 17a and 17a guided by the cage 18 are arranged so as to be rotatable in the circumferential direction.

  Further, seal rings 21a and 21b, which are sealing devices, are provided between the inner peripheral surfaces of both ends of the outer ring 5a, the outer peripheral surface of the intermediate portion of the hub 7a, and the outer peripheral surface of the inner end of the inner ring 16a. These seal rings 21a and 21b block the annular gap provided with the balls 17a and 17a and the external 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 poles are alternately formed in the circumferential direction. Then, a magnetic sensor 28 is disposed facing the magnetic pole forming ring 27 (see FIG. 1).

  In the present invention, as the magnet material of the magnetic pole forming ring 27 of the magnetic encoder 26, an anisotropic magnet compound containing 86 to 92% by weight of anisotropic magnetic powder and using a thermoplastic resin as a binder is preferably used. be able to. As the magnetic powder, ferrite such as strontium ferrite is most suitable in consideration of environmental resistance such as oxidation stability, and lanthanum and cobalt are mixed to improve the magnetic properties of the ferrite. Also good. When the content of the magnetic powder is less than 86% by weight, the magnetic properties are inferior, and it becomes difficult to perform multipolar magnetization in the circumferential direction at a fine pitch, which is not preferable. On the other hand, when the content of the magnetic powder exceeds 92% by volume, the amount of the resin binder becomes too small, the strength of the whole magnet is lowered, and at the same time, molding becomes difficult and practicality is lowered. If a higher magnetic force is required, rare earth magnetic powder may be used. In this case, the rare earth magnetic powder can be used alone or in combination with ferrite magnetic powder.

  As a binder, in order to prevent cracks that occur in various environments such as temperature changes, a modified polyester resin that is a block copolymer having a polyester hard segment and at least one soft segment of a polyether component and a polyester component. In order to maintain the balance with the tensile strength, heat resistance, etc. as an essential constituent component, a composition in which a polyester resin is further mixed may be used. In the case of mixing a polyester resin, it is more preferable to form a hard segment of the modified polyester resin to be used in consideration of compatibility. Specific examples of the modified polyester resin include a modified polybutylene terephthalate resin having a polybutylene terephthalate represented by Chemical Formula 1 as a hard segment and a polyether component as a soft segment,

  A modified polybutylene terephthalate resin having a polybutylene terephthalate represented by Chemical Formula 2 as a hard segment and a polyester component as a soft segment,

  A modified polybutylene naphthalate resin having a polybutylene naphthalate represented by Chemical Formula 3 as a hard segment and a polyether component as a soft segment;

Etc. Among the above three specific examples, the modified polyester resin of Chemical Formula 2 or Chemical Formula 3 with high heat resistance is more preferable, and further has a naphthalene ring when ozone resistance, water resistance, and oil resistance are necessary for selection criteria. A modified polyester resin of Formula 3 is more preferred.

  As the modified polyester resin, those having a melting point of 150 to 233 ° C. and a flexural modulus of 50 to 1300 MPa can be suitably used. Considering heat resistance and prevention of cracking, it is more preferable that the melting point is in the range of 180 to 232 ° C. and the flexural modulus is in the range of 100 to 500 MPa. If a modified polyester resin having a melting point of less than 150 ° C. or a flexural modulus of less than 50 is used, the flexibility of the magnet material as a whole is improved, but heat resistance, tensile strength, etc. are assumed to decrease, which is not preferable. . On the other hand, when the flexural modulus exceeds 1300 MPa, the effect of improving the flexibility is low, and it is difficult to improve the amount of bending deflection to a level that is effective for preventing cracks.

The magnet material used in the present invention has a higher maximum energy product BHmax than that of a rubber-based ferrite magnet, specifically, a ferrite in the range of 13 to 19 (1.63 to 2.38) kJ / m ³ (MGOe). It retains high magnetic properties as a system magnet, and at the same time has an excellent bending property in which the bending deflection at 23 ° C. (t = 3.0 mm, ASTM D790; span distance 50 mm) falls within the range of 2 to 15 mm. It has high cracking properties.

  In order to achieve the above-described magnetic characteristics, bending amount, etc., the magnetic material of the present invention is composed of 88 to 92% by weight of anisotropic strontium ferrite and 1 to 12 of modified polyester resin. % By weight, polyester resin is 0 to 11% by weight. Also, at least one specific plasticizer selected from benzenesulfonic acid alkylamides, toluenesulfonic acid alkylamides, and hydroxybenzoic acid alkyl esters to achieve an amount of bending deflection and improve crack resistance. May be contained in an amount of about 0.1 to 4% by weight in the total weight. Specific examples of benzenesulfonic acid alkylamides include benzenesulfonic acid propylamide, benzenesulfonic acid butyramide, and benzenesulfonic acid 2-ethylhexylamide. Specific examples of toluenesulfonic acid alkylamides include N-ethyl-o- or N-ethyl-p-toluenesulfonic acid butyramide, N-ethyl-o- or N-ethyl-p-toluenesulfonic acid 2- Examples include ethylhexylamide. Specific examples of the hydroxybenzoic acid alkyl esters include ethylhexyl o- or p-hydroxybenzoate, hexyldecyl o- or p-hydroxybenzoate, o- or ethyldecyl hydroxybenzoate, o- or p- Mention may be made of octyl hydroxybenzoate, decyldodecyl o- or p-hydroxybenzoate, dodecyl o- or p-hydroxybenzoate, and the like. Among these, benzenesulfonic acid butyramide, ethyl hexyl p-hydroxybenzoate, and hexyldecyl p-hydroxybenzoate are particularly preferable from the viewpoint of compatibility with the resin, low bleed-out property, and heat resistance.

  Further, in addition to the above compounding materials, various additives such as a silane coupling agent and an antioxidant that improve the dispersibility of ferrite and the adhesion between the polyester compound and the like may be added. In particular, in order to prevent deterioration of the polyester-based elastomer due to heat, it is more preferable to add an antioxidant separately from the material originally added to the material. Antioxidants used include 2,4-bis [(octylthio) methyl] -o-cresol, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate ], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl tetrakis [3- (3,5-di-t-butyl) -4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, octadecyl-3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate, 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, , 3,5-trimethyl-2,4,6-tris (3,5-di -t- butyl-4-hydroxybenzyl) hindered phenol-based antioxidants such as benzene are preferred. The amount added is about 0.1 to 0.5% by weight in the total amount.

  As the material of the slinger 26, ferritic stainless steel (SUS430, etc.), martensitic stainless steel (SUS410, etc.), etc. that do not deteriorate the magnetic properties of the magnet material and have a certain level of corrosion resistance or more depending on the usage environment. Magnetic materials are most preferred. In order to improve the bondability with the magnet material, at least the magnet bonding surface of the stainless steel slinger surface is roughened by chemical etching, roughened by shot blasting, and gold is applied during slinger press molding. It is preferable that a concave surface treatment by mold convex portion transfer is performed. In addition, since the encoder used in the part used in combination with the resin sensor cap (without the combination with the seal) does not use so much corrosion resistance, the material of the slinger 26 is a cold rolled steel plate (SPCC) or the like in consideration of cost. But you can.

  In the magnetic encoder of the present embodiment, after the magnet part is molded separately, the magnet part may be bonded and bonded to the slinger 25, or an adhesive layer that is preliminarily baked in a semi-cured state is provided on the surface of the slinger 25. Alternatively, the plastic magnet material may be insert-molded into the material to be joined by heat from the molten resin, and further heated after the molding to be completely cured to give a stronger joint. Adhesives that can be used can be diluted with a solvent, and phenol resin adhesives and epoxy resin adhesives that progress in a two-step curing reaction are considered in consideration of heat resistance, chemical resistance, and handling properties. It is preferable.

  The phenol resin-based adhesive is preferably used as a rubber vulcanized adhesive, and the composition is not particularly limited, but a novolac-type phenol resin, a resol-type phenol resin, and a curing agent such as hexamethylenetetramine. Can be used in which methanol or methyl ethyl ketone is dissolved. Moreover, in order to improve adhesiveness, you may mix these with a novolak-type epoxy resin.

  As the epoxy resin adhesive, a one-pack type epoxy adhesive that can be diluted into a solvent is suitable as a stock solution. This one-pack type epoxy adhesive, after evaporating the solvent, becomes a semi-cured state on the slinger surface at an appropriate temperature and time so as not to be washed away by the high-temperature and high-pressure molten resin at the time of insert molding. The resin is completely cured by heat from the resin and secondary heating.

  The one-pack type epoxy adhesive used in the present embodiment is composed of at least an epoxy resin and a curing agent, and the curing agent hardly undergoes a curing reaction near room temperature, for example, becomes a semi-cured state at about 80 to 120 ° C. By applying high-temperature heat of ˜180 ° C., the thermosetting reaction proceeds completely. This adhesive was stressed by other epoxy compounds used as reactive diluents, curing accelerators that improve the thermal cure rate, inorganic fillers that have the effect of improving heat resistance and strain resistance, and stress Cross-linked rubber fine particles or the like that improve flexibility that sometimes deforms may be further added.

  As the epoxy resin, those having two or more epoxy groups in the molecule are preferable in that a crosslinked structure capable of exhibiting sufficient heat resistance can be formed. Also, 4 or less, and further 3 or less are preferable from the viewpoint that a low-viscosity resin composition can be obtained. If the number of epoxy groups contained in the molecule is too small, the heat resistance of the cured product tends to decrease and the strength tends to decrease. On the other hand, if the number of epoxy groups contained in the molecule is too large, the resin This is because the viscosity of the composition increases and the curing shrinkage tends to increase.

  The number average molecular weight of the epoxy resin is preferably 200 to 5500, particularly preferably 200 to 1000 from the viewpoint of balance of physical properties. If the number average molecular weight is too small, the strength of the cured product tends to decrease and the moisture resistance tends to decrease.On the other hand, if the number average molecular weight is too large, the viscosity of the resin composition increases and workability adjustment is possible. This is because there is a tendency that the use of a reactive diluent increases.

  Furthermore, the epoxy equivalent of the epoxy resin is preferably 100 to 2800, particularly 100 to 500 from the viewpoint that the blending amount of the curing agent is within an appropriate range. If the epoxy equivalent is too small, the amount of the curing agent will increase too much and the physical properties of the cured product will deteriorate. On the other hand, if the epoxy equivalent is too large, the amount of the curing agent will decrease and the epoxy resin will decrease. This is because the molecular weight of the resin itself tends to increase and the viscosity of the resin composition increases.

  Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, glycidylamine type epoxy resin, alicyclic epoxy resin, dicyclopentadiene. Type epoxy resin, phenol novolac type epoxy resin, polyester modified epoxy resin, copolymer with other polymers such as silicon modified epoxy resin, and the like. Among these, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, etc. have a relatively low viscosity and excellent heat resistance and moisture resistance of the cured product. Therefore, it is preferable.

  As the curing agent, an amine curing agent, a polyamide curing agent, an acid anhydride curing agent, a latent curing agent, or the like can be used.

  The amine-based curing agent is an amine compound and does not generate an ester bond by a curing reaction. Therefore, the amine-based curing agent is preferable because it has excellent moisture resistance as compared with the case where an acid anhydride-based curing agent is used. As the amine compound, any of an aliphatic amine, an alicyclic amine, and an aromatic amine may be used, but the aromatic amine is most preferable because the storage stability of the blend at room temperature is high and the cured product has high heat resistance. .

  As aromatic amines, 3,3′-diethyl-4,4′-diaminodiphenylmethane, 3,5-diethyl-2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 3,5 Examples thereof include a mixture of diethyl-2,6-toluenediamine and 3,5-diethyl-2,4-toluenediamine, and the like.

  The polyamide-based curing agent is also called a polyamidoamine, and is a compound having a plurality of active amino groups in the molecule and similarly having one or more amide groups. A polyamide-based curing agent synthesized from polyethylene polyamine is preferable because it produces an imidazirine ring by secondary heating and improves compatibility with the epoxy resin and mechanical properties. The polyamide curing agent may be an adduct type in which a small amount of epoxy resin has been reacted in advance, and by using the adduct type, the compatibility with the epoxy resin is excellent, and the curing drying property and water / chemical resistance are improved. preferable. By using this polyamide-based curing agent, a tough cured resin having a particularly high flexibility is obtained by crosslinking with the epoxy resin, and therefore, it is excellent in the thermal shock resistance required for the magnetic encoder of the present invention, and is suitable.

  Cured products cured with acid anhydride curing agents have high heat resistance and excellent mechanical and electrical properties at high temperatures, but tend to be somewhat brittle, but are curing accelerators such as tertiary amines. Can be improved by combining with. Examples of acid anhydride-based curing agents include phthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, methyleneendomethylenetetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, trimellitic anhydride, etc. Can do.

  The latent curing agent has excellent storage stability at room temperature in a mixed system with an epoxy resin, and cures rapidly under conditions of a certain temperature or more. As an actual form, a curing agent for an epoxy resin Neutral salts or complexes of acidic or basic compounds that can be activated when heated, those that harden in microcapsules and break down by pressure, crystalline, high melting point, compatible with epoxy resins at room temperature There are some materials that are not dissolved by heating.

  As the latent curing agent, 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin, eicosanedioic acid dihydrazide, adipic acid dihydrazide, dicyandiamide, 7,11-octadecadien-1 which is a high melting point compound , 18-dicarbohydrazide and the like. Among these, 7,11-octadecadien-1,18-dicarbohydrazide is used as a curing agent, and thus becomes a tough cured resin rich in flexibility by crosslinking with an epoxy resin. It is excellent in thermal shock resistance required for the magnetic encoder of the invention and is suitable.

  As the reactive diluent, t-butylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, or the like can be used. Flexibility can be imparted. However, these reactive diluents, when used in a large amount, reduce the moisture resistance and heat resistance of the cured product, and therefore, preferably 30% or less, more preferably 20%, based on the weight of the main epoxy resin. It is added in the following ratio.

The curing accelerator is preferably one that has sufficient storage stability without accelerating the curing reaction at room temperature and rapidly proceeds with the curing reaction when the temperature reaches 100 ° C. or higher. And compounds having one or more ester bonds produced by the reaction of 1-alkoxyethanol and carboxylic acid. This compound is for example represented by the general formula (I):
^{R 3 [COO-CH (OR} 2) -CH 3] n (I)
(In the formula, R ³ is an n-valent hydrocarbon group having 2 to 10 carbon atoms and optionally containing one or more of nitrogen atom, oxygen atom, etc., R ² is 1 to 6 carbon atoms, A monovalent hydrocarbon group which may contain one or more of a nitrogen atom, an oxygen atom and the like, and n is an integer of 1 to 6. A specific example is shown in Chemical Formula 4.

The compound represented by Formula 4 is a compound in which R ³ is a divalent phenyl group and R ² is a propyl group, R ³ is a trivalent phenyl group and R ² is a propyl group, and R ³ is a tetravalent compound. Examples thereof include a compound having a phenyl group and R ² being a propyl group. These may be used alone or in combination of two or more. Among these, the compound represented by Chemical Formula 4 is most preferable from the viewpoint of the balance between curing reactivity and storage stability.

  In addition to the compounds described above, imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, and 2-phenylimidazole may be used as the curing accelerator.

  Further, as a curing accelerator, a carboxylic acid such as adipic acid, which is a compound having active hydrogen that reacts with an epoxy group to cause a ring-opening reaction, may be used. By using adipic acid as a curing accelerator, it reacts with the epoxy group of the epoxy resin and the amino group of the curing agent, and the resulting cured product becomes flexible as the amount of adipic acid added increases. In order to express flexibility, the amount of adipic acid added is 10 to 40% by weight, more preferably 20 to 30% by weight, based on the total amount of the adhesive. When the addition amount is less than 10% by weight, sufficient flexibility is not exhibited. On the other hand, when the addition amount exceeds 40% by weight, the total amount of the epoxy resin in the adhesive is reduced correspondingly, and the adhesive force and mechanical strength are lowered. Since adipic acid is also a starting material for polyamide resin, when the binder of magnetic powder is a polyamide resin such as polyamide 12 or polyamide 6, it reacts with a monomer or oligomer component remaining in a trace amount in the binder material itself. The adhesive composition contains adipic acid, and stronger adhesion is possible.

  Further, as a curing accelerator, a tertiary amine such as dimethylbenzylamine, a quaternary ammonium salt such as tetrabutylammonium bromide, which acts as a catalyst for promoting a ring-opening reaction of an epoxy group, 3- (3 ′, 4′-dichlorophenyl) An alkyl urea such as -1,1-dimethylurea may be added.

  The OH groups generated by the ring-opening reaction, including the amines described above, form hydrogen bonds with the hydroxyl groups on the metal surface, which is the adherend, and also act on the amide bonds of nylon, which is the binder material. And can maintain a strong adhesive state.

  The inorganic filler can be used without particular limitation as long as it is conventionally used. Examples thereof include fused silica powder, quartz glass powder, crystalline glass powder, glass fiber, alumina powder, talc, aluminum powder, and titanium oxide.

  As the crosslinked rubber fine particles, those having a functional group capable of reacting with an epoxy group are preferred, and specifically, vulcanized acrylonitrile butadiene rubber having a carboxyl group in the molecular chain is most preferred. A finer particle diameter is preferable, and an ultrafine particle having an average particle diameter of about 30 to 200 nm is most preferable in order to exhibit dispersibility and stable flexibility.

  The one-component epoxy adhesive described above hardly undergoes a curing reaction at room temperature, for example, becomes semi-cured at about 80 to 120 ° C., and is completely cured by applying high-temperature heat at 120 to 180 ° C. The reaction proceeds. More preferably, the curing reaction proceeds at a temperature of 150 to 180 ° C. in a relatively short time, and the one that can be bonded by high-frequency heating at about 180 ° C. is most preferable.

  The cured product after the thermosetting of the phenol resin-based adhesive and the epoxy resin-based adhesive described above has a physical property of flexural modulus or Young's modulus of 0.02 to 5 GPa, more preferably 0.03 to 4 GPa. Yes, or hardness (durometer D scale; HDD) is preferably in the range of 40 to 90, more preferably 60 to 85. When the flexural modulus or Young's modulus is less than 0.02 GPa or the hardness (HDD) is less than 40, the adhesive itself is too soft and easily deforms due to vibrations during running of an automobile or the like, and thereby the magnet part moves easily. For this reason, the detection accuracy of the rotational speed may be lowered, which is not preferable. On the other hand, if the flexural modulus or Young's modulus exceeds 5 GPa or the hardness (HDD) exceeds 90, the adhesive itself is too hard and the thermal expansion / contraction difference between the magnet of the magnetic encoder and the fixing member (that is, both It is difficult to deform so as to absorb the difference in expansion / contraction amount due to the difference in linear expansion coefficient, and in the worst case, there is a possibility that a crack or the like may occur in the magnet. The one-pack type epoxy adhesive of the present invention is required to have thermal shock resistance when used in an automobile, and more preferably has flexibility (deforms when stressed) in a cured state.

  Hereinafter, an example of the manufacturing method of the magnetic encoder of the present invention using the above materials will be described. First, the surface of the slinger is roughened with chemical etching in the above-described step, and the surface is roughened as shown in the cross-sectional electron micrograph of FIG. Then, injection molding (insert molding) of a plastic magnet material using a slinger with a glue baked in a semi-cured state on the surface as a core is performed using a magnetic field injection molding machine 80.

  As shown in FIG. 5, the magnetic field injection molding machine 80 includes a mold clamping device 82 and an injection device 83 on a support base 81. The mold clamping device 82 includes a movable part 86 that is movable with respect to a housing 85 that is fixed to the support base 81 by a movable mechanism 84 such as a toggle mechanism, a fixed part 87 that is fixed to the support base 81, and a movable part 86. Are provided between the housing 85 and the fixed portion 87 and four tie bars 88. The movable part 86 and the fixed part 87 include a movable mold 89 and a fixed mold 90, respectively. In addition, coils 91 and 92 are disposed on the side surfaces of the movable portion 86 and the fixed portion 87, and are energized by the power supply device 93. The control device 94 is connected to the movable mechanism 84, the power supply device 91, and the injection device 83, and is configured to control them.

  As shown in FIG. 6A, the movable side mold 89 is composed of a plurality of movable side mold pieces 89a to 89c that are bolted to the contact plate 95, and the fixed side mold 90 is also a plurality of fixed sides. It consists of mold pieces 90a to 90c. A cavity 96 and a disk gate 97 are formed between the opposed surfaces of the movable mold 89 and the fixed mold 90. Thereby, the melted plastic magnet material injected from the nozzle 98 of the injection device 83 is filled into the cavity 96 from the sprue portion 99 through the disk gate 97. As shown in FIG. 6B, an annular space for accommodating the cylindrical fitting portion of the slinger 25 is formed between the movable side mold pieces 89a and 89b, and the fixed side mold located at the center. The mold piece 90a protrudes toward the movable mold 89 from the fixed mold piece 90b located on the outer diameter side, and the fixed mold piece 90a overlaps the accommodated slinger 25 in the radial direction. Located.

  In addition, when a plastic magnet material melted in the molds 89 and 90 attached to the magnetic field injection molding machine 80 is injected, a coil current is applied to the coils 91 and 92 at both ends of the molds 89 and 90 to generate them. The plastic magnet material is magnetized with a magnetic field in one direction (with the same polarity) to align the magnetic powder. After that, demagnetization that demagnetizes with a magnetic field in the opposite direction to the magnetization direction during cooling in the molds 89 and 90, and an initial coil current that is higher than the coil current at the time of magnetization, the polarity is alternately reversed and the amplitude gradually increases. The demagnetization is performed by at least one step of reversal demagnetization in which a plurality of pulse currents that become smaller are applied to the coils 91 and 92 at both ends of the mold to demagnetize. Next, after removing the gate portion, the adhesive is completely cured by heating at a constant temperature for a certain time in a thermostatic bath or the like. In some cases, it may be completely cured by heating at a high temperature for a short time, such as by high-frequency heating. Thereafter, it is further demagnetized to a magnetic flux density of 2 mT or less, more preferably 1 mT or less, using a known oil condenser type demagnetizer. In the subsequent process, multipole magnetization is performed by superimposing with a known magnetizing yoke to complete the manufacture of the magnet part. The number of poles of the magnet portion is about 70 to 130, preferably 90 to 120. If the number of poles is less than 70, the number of poles is too small and it is difficult to accurately detect the rotational speed. On the other hand, when the number of poles exceeds 130, each pitch becomes too small, and it is difficult to suppress a single pitch error, and practicality is low.

  As shown in FIG. 2, the magnet material also wraps around the outer peripheral portion of the flange portion of the slinger 25 and is mechanically joined.

  In addition, as described above, the encoder part is molded by a disk gate type injection molding (insert) 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, whereby the flake-like magnetic powder contained therein is oriented in 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 a side gate other than a disk gate, for example, the orientation at the weld is completely anisotropic in the process of gradually increasing the resin viscosity toward solidification. It is difficult to do so, which may cause cracks and the like due to long-term use of the weld portion where the magnetic properties are lowered and the mechanical strength is lowered. Therefore, in the present embodiment, insert molding by a disk gate is performed in a state where a slinger is used as a core and a magnetic field is applied in the thickness direction.

Therefore, according to the magnetic encoder of the present embodiment, the magnetic pole forming ring 27 as the magnet portion contains the magnetic powder and the thermoplastic resin as the binder, and the thermoplastic resins are at least polybutylene terephthalate and polybutylene. Since it contains a modified polyester resin which is a block copolymer having either one hard segment of phthalate and at least one soft segment of a polyether component and a polyester component, only conventional thermoplastic resins such as conventional polyamide 12 are included. Compared to a magnet made of the above binder, the bending amount is large, and the crack resistance is improved. As a result, even in a structure that is mechanically joined (and chemically joined with an adhesive) by insert molding with a slinger as the core, high and low temperature, high temperature ← → low temperature thermal shock that the undercarriage part of the automobile is exposed to When a stress such as the above is applied to the magnet portion, it is possible to effectively prevent the magnet portion from cracking, and the reliability can be greatly improved.
Further, by using such a binder, a desired bending deflection (thickness t = 3.0 mm, 23 ° C., ASTM D790; 2 to 15 mm at a span distance of 50 mm) and desired magnetic properties (maximum energy product BHmax) : 1.63 to 2.38 MGOe (13 to 19 kJ / m ³ )).

As a modification of the present embodiment, a hub unit bearing 30 shown in FIG. 7 has a cover member 32 attached to the inner peripheral surface of the outer ring 5a via a fixing jig 31, and the axial end portion of the hub unit bearing 30 is provided. It is comprised so that it may cover. Therefore, it is not necessary to provide the seal ring 21b between the end inner peripheral surface of the outer ring 5a and the end outer peripheral surface of the inner ring 16a, and the magnetic pole forming ring 27 of the magnetic encoder 26 is attached to the end outer peripheral surface of the inner ring 16a. It is attached to the fixing member 25 '. The magnetic pole forming ring 27 is disposed so as to face the sensor 28 attached to the cover member 32 in the radial direction, and the rotational speed of the inner ring 16 a is detected via the sensor 28.
(Second Embodiment)
Next, a magnetic encoder and a rolling bearing unit according to the second embodiment of the present invention will be described in detail.

  As shown in FIGS. 7 and 8, the rolling bearing unit 40 including the magnetic encoder according to the present embodiment includes an outer ring 41 that is a fixed ring, an inner ring 42 that is a rotating ring (rotating body), an outer ring 41, and an inner ring. A rolling bearing comprising a plurality of balls 43 which are a plurality of rolling elements which are arranged in an annular gap defined by 42 so as to be freely rollable and are held at equal intervals in the circumferential direction by a cage 44; A sealing device 45 disposed at the end, a magnetic encoder 46, and a sensor 47 are provided.

  The sealing device 45 includes a seal member 50 mounted on the inner peripheral surface of the outer ring 41, and a slinger 60 disposed on the bearing outer side than the seal member 50 and fixed to the outer peripheral surface of the inner ring 42. The sealing member 50 and the slinger 60 close the opening end of the annular gap to prevent foreign matters such as dust from entering the bearing and prevent the lubricant filled in the bearing from leaking. . The magnetic encoder 46 includes a slinger 60 and a magnet portion 65 attached to the slinger 60. The magnet portion 65 is fixed to the inner ring 42 with the slinger 60 as a fixing member.

  The seal member 50 is configured by reinforcing an elastic member 52 formed in an annular shape having a substantially L-shaped cross section with a core metal 51 formed in an annular shape having a substantially L-shaped cross section. It is installed. The distal end portion of the elastic member 52 is branched into a plurality of sliding contact portions, and each sliding contact portion is formed on the end surface facing the bearing inward of the flange portion 62 of the slinger 60 or the outer peripheral surface of the fitting portion 61. They are in sliding contact with each other around the circumference. Thereby, a high sealing force is obtained.

The slinger 60 is formed in an annular shape having an L-shaped cross section, and has a substantially cylindrical fitting portion 61 that is fitted on the outer peripheral surface of the inner ring 42, and a hook-like shape that is radially expanded from one end of the fitting portion 61. The flange portion 62 and a protruding portion 63 that protrudes outward in the axial direction from the flange portion 62 on the inner diameter side of the flange portion 62 by bending one end portion of the fitting portion 61. Further, the outer peripheral surface of the protruding portion 63 is provided with notch portions 64 formed at a plurality of locations in the circumferential direction. A magnet portion 65 that changes a nearby magnetic field (for example, magnetic flux density) in synchronization with the rotation of the inner ring 42 is joined to an end surface (hereinafter referred to as a joining surface) 62a of the flange portion 62 facing the outside of the bearing. ing. At the same time, the magnet portion 65 is also mechanically joined to the outer peripheral portions of the notch portion 64 and the flange portion 62.
The composition and molding method of the magnetic encoder 46 are the same as those in the first embodiment.

Therefore, according to the magnetic encoder of the present embodiment, in addition to the outer diameter portion of the flange portion 62 of the slinger 60, the melted magnet material includes a plurality of notch portions 64 provided in the circumferential direction of the protruding portion 63 provided on the inner diameter side. It also flows in and is mechanically joined. As a result, the contraction of the magnet material is received not only by the outer diameter portion of the flange portion 62 but also by the protruding portion 63 on the inner diameter side, thereby further reducing the frequency of occurrence of cracks in the magnet portion caused by thermal shock or the like. Can do.
Note that the magnetic encoder 46 of this embodiment can also be used by being incorporated in a hub unit bearing as shown in FIG.

(Third embodiment)
Next, a hub unit bearing for supporting a non-driven wheel, which is supported by an independent suspension, according to a third embodiment of the present invention will be described in detail. In addition, the same code | symbol is attached | subjected about a part equivalent to 1st Embodiment, and description is abbreviate | omitted or simplified.

  In the first embodiment, the magnetic encoder 26 and the sensor 28 face each other in the axial direction. However, in the hub unit bearing 70 of the present embodiment, as shown in FIG. Opposite the radial direction.

In the magnetic encoder 71 of the present embodiment, an annular slinger 73 as a fixing member is fitted and fixed to the outer peripheral surface of the inner end portion of the inner ring 16a, and the inner peripheral surface of the slinger 73 extending in the axial direction from the inner ring 16a A magnetic pole forming ring 74 that is a magnet portion is attached. Further, a cover member 75, which is a stationary member, is fixed to the outer peripheral surface of the outer ring 5a so as to cover the axial end of the hub unit bearing 70, and a sensor 72 is provided in an opening formed in the cover member 75. It is attached so as to face the magnetic pole forming ring 74 in the radial direction.
The composition and the molding method of the magnetic encoder 71 are the same as those in the first embodiment.

  Therefore, according to the magnetic encoder 71 of the present embodiment, the diameter of the detected surface can be increased with respect to the same space as compared with the magnetic encoder facing in the axial direction. Can be large and easy to manufacture.

In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.
In the present embodiment, the magnetic encoder is used with the magnet portion attached to a fixing member such as a slinger. However, the present invention can also be applied to a configuration in which the magnet portion is directly attached to a rotating body.
In the present embodiment, the hub unit bearing and the rolling bearing unit in which the magnetic encoder is incorporated have been described. However, the magnetic encoder of each embodiment can also be applied to a hub unit bearing, a rolling bearing unit, or a spindle device.

  Here, although an Example is given and this invention is demonstrated further, this invention is not restrict | limited at all by this. Hereinafter, a crack resistance comparison test was performed using the magnet materials shown in Examples 1 to 3 and Comparative Examples in Table 1. Table 1 shows the composition, physical properties, and thermal shock test results of the magnetic material.

  As a surface treatment for the slinger, a chemiblast treatment made by Nihon Parkerizing was performed. Specifically, irregularities were formed by chemically etching an iron oxalate film formed on the surface of a plate material made of SUS430 having a thickness of 0.6 mm. The arithmetic average height Ra of the irregularities was 0.2 to 0.3 μm, and the maximum height Rz was 1.8 to 3.1 μm.

  Then, a 30% solid content phenol resin adhesive (Metal Lock N-15 manufactured by Toyo Chemical Laboratories Co., Ltd.) mainly composed of a resol type phenol resin was further diluted three times with methyl ethyl ketone and applied to the slinger surface by dipping treatment. . Then, after drying at room temperature for 30 minutes, it was made into the semi-hardened state by leaving it to stand in 120 degreeC for 30 minutes.

  And after performing said surface treatment to the SUS430 slinger shown in FIG. 2, insert molding was performed with the disk gate from an inner peripheral part by making into a core the thing which baked said adhesive agent in the semi-hardened state. Immediately after molding, the gate was cut and further heated at 150 ° C. for 1 hour to completely cure the adhesive.

  After that, the thermal shock that repeats 30 minutes at 120 ° C and 30 minutes at -40 ° C with the encoder part (inner diameter 66mm, outer diameter 76mm, magnet part thickness 0.9mm) obtained by molding and integration with the slinger A test was conducted. Ten samples of each of Examples 1 to 3 and Comparative Example were put, and cracks generated in the magnet portion were observed every 50 cycles. As is clear from Table 1, it was found that the crack resistance was improved by increasing the amount of bending deflection of the material itself by containing the modified polyester resin as a binder.

It is sectional drawing which shows the rolling bearing unit of 1st Embodiment of this invention. It is sectional drawing which shows the sealing device provided with the magnetic encoder of 1st 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. It is a cross-sectional microscope picture which shows the surface of the slinger processed by chemical etching. It is a schematic diagram which shows a magnetic field injection molding machine. It is sectional drawing of the movable side metal mold | die and fixed side metal mold | die which form a cavity. It is sectional drawing which shows the rolling bearing unit which is a modification of 1st Embodiment of this invention. It is sectional drawing which shows the rolling bearing unit of 2nd Embodiment of this invention. It is sectional drawing which shows the sealing device provided with the magnetic encoder of 2nd Embodiment of this invention. It is sectional drawing which shows the sealing device provided with the magnetic encoder of 3rd Embodiment of this invention. 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 10a, 10b Outer ring raceway 11 Coupling flange 12 Mounting flanges 14a, 14b Inner ring raceway 15 Small diameter step 16a Inner ring 17a Ball 18 Cage 21a, 21b Seal ring 22a, 22b Elastic material 23 Caulking portion 24b Core metal 25 Slinger 26 Magnetic encoder 27 Magnetic forming ring

Claims (2)

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 fixing member is made of a magnet material,
The magnet part contains magnetic powder and a thermoplastic resin as a binder,
The thermoplastic resin contains at least a modified polyester resin which is a block copolymer having a hard segment of any one of polybutylene terephthalate and polybutylene naphthalate and a soft segment of at least one of a polyether component and a polyester component. A magnetic encoder characterized by that.   A fixed ring, a rotating wheel, a rolling bearing having a plurality of rolling elements arranged in a circumferential direction by an annular gap formed between the fixed wheel and the rotating wheel, and fixed to the rotating wheel A rolling bearing unit comprising: the magnetic encoder according to claim 1.