JP4910316B2 - Magnetic encoder and rolling bearing unit including the magnetic encoder - Google Patents

Description

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

  Conventionally, as a rotational speed detection device used for anti-skid for preventing skid of an automobile or for traction control for effectively transmitting driving force to the road surface, a magnetic encoder that generates pulses by magnetism, and this magnetic Many of them are composed of a sensor for detecting magnetic pulses of an encoder. In this rotation speed detection device, a seal device for sealing a bearing is generally provided with a magnetic encoder, and the sealing means and the rotation speed detection device are integrated to form a seal with the rotation speed detection device. (For example, see Patent Document 1).

  An example of a seal with a rotational speed detection device is shown in FIG. 13, but a seal member 102 attached to the outer ring 101a, a slinger 103 fitted to the inner ring 101b, and an outer surface of the slinger 103 are attached to generate magnetic pulses. The magnetic encoder 104 and the sensor 105 which is disposed in the vicinity of the magnetic encoder 104 and detects a 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, and the lubricant filled in the bearing Prevents leakage outside the bearing. Further, the magnetic encoder 104 generates the number of magnetic pulses corresponding to the number of poles while the inner ring 101b rotates once, and detects the number of rotations of the inner ring 101b by detecting this magnetic pulse with the sensor 105. .

  In the magnetic encoder 104, a magnet portion made of an elastic magnetic material obtained by mixing magnetic powder into an elastic material such as rubber or resin is press-molded on the flange portion 103a of the slinger 103 to which an adhesive is applied in a mold. Are joined together. Nitrile rubber containing ferrite is generally used as the elastic magnetic material, and the magnetic powder is mechanically oriented by kneading with a roll.

JP 2001-255337 A

  In recent years, the number of poles in the circumferential direction of the magnetic encoder 104 tends to be increased (multipolarization) in order to more accurately detect the rotation speed of the wheel. However, in the magnetic encoder 104 made of a ferrite-containing rubber magnet by the conventional mechanical orientation method, the magnetic flux density per pole becomes too small, and the gap between the sensor 105 and the magnetic encoder 104 is detected in order to detect the rotational speed with high accuracy. It is necessary to reduce (that is, the air gap). Further, since the magnetic encoder 104 is used in the undercarriage of automobiles as the performance of automobiles increases, 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, grease. It is assumed that fats and oils such as oil adhere to the surface.

  In order to increase the air gap amount as a countermeasure, it is necessary to improve the magnetic characteristics of the magnet portion. However, in addition to the fact that rare earth magnetic powders are generally expensive as magnetic materials having high magnetic characteristics, Since the chemical conversion property is also lower than that of ferrite magnetic powder, when used in the above environment, there is a possibility that the magnetic properties will be greatly lowered due to oxidative degradation. In addition, by using a plastic magnet made of ferrite magnetic powder and plastic, magnetic powder can be filled in a larger amount than rubber magnets, improving the magnetic properties, but the magnet part becomes brittle and elongation and deflection are reduced. To do. For this reason, when repeatedly exposed to a high temperature environment or a low temperature environment assumed in an automobile or the like, the deformation of the magnet portion cannot follow the deformation (dimensional change) of the slinger 103, and in the worst case, it starts from a weak portion of the joint portion. As a result, cracks or the like may occur in the magnet portion. In addition, when exposed to high temperatures, the oxidative degradation of the resin material that is the binder of the magnet portion proceeds, further reducing the elongation and deflection of the magnet portion. When repeatedly exposed to high and low temperature environments, the magnet portion Cracks are more likely to occur.

  In addition, automobiles have many opportunities to come into contact with water, including rain and muddy water, and magnetic encoders have many opportunities to come into contact with water. Therefore, although water resistance is also required for the magnetic encoder, water-absorbing resin may be used for the binder forming the magnet part, and the entire magnet part may swell.

  The present invention has been made in order to solve the above-mentioned problems, is excellent in water resistance, does not generate cracks even under severe use conditions such as rapid temperature changes, and has high magnetic properties, It is an object of the present invention to provide a highly reliable magnetic encoder that enables highly accurate rotation speed detection, and a high-performance and highly reliable rolling bearing unit that includes the magnetic encoder.

  In order to achieve the above object, the present inventors focused on a plastic magnet material that can contain a large amount of magnetic powder and have excellent magnetic properties, and as a result of various studies of binder materials for the purpose of improving water resistance and elasticity, The inventors have found that it is effective to use a binder containing a specific polyamide resin, an impact resistance improver, and a specific antioxidant, and have completed the present invention.

That is, the present invention provides the following magnetic encoder and rolling bearing unit.
(1) In a magnetic encoder including a magnet portion in which a magnetic material including a magnetic powder and a binder of the magnetic powder is formed in an annular shape,
The binder is a polyamide 12, a block copolymer having a polyamide 12 as a hard segment and at least one of a polyester component and a polyether component as a soft segment, and N, N′-diphenyl-p- Phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, N, N′-di-2-naphthyl-p-phenylenediamine, N, N′-bis (1-methylheptyl) -p-phenylenediamine N, N′-bis (1,4-dimethylpentyl) -p-phenylenediamine and N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, It contains a 0.5 to 2.0 mass% of aminic antioxidant binder total amount, and the modified polyamide Magnetic encoder, characterized in that 12 is 10 to 40 wt% relative to the total amount of the polyamide 12.
(2) The magnetic encoder according to (1), wherein the bending deflection amount of the magnetic material is 2 to 15 mm at a thickness = 3.0 mm, a span distance = 50 mm, and a temperature = 23 ° C.
(3) The above (1) or characterized in that the slinger and the magnet portion are joined by insert molding the magnet portion with a slinger provided with an adhesive in a semi-cured state in advance as a core. (2) The magnetic encoder according to (2).
(4) The magnetic encoder according to ( 3 ) above, which is obtained by secondary heating after the insert molding .
(5) The magnetic encoder according to ( 3 ) above, wherein the adhesive is a phenol resin adhesive or an epoxy resin adhesive .
(6) In a rolling bearing unit comprising a fixed ring, 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 any one of (1) to (5) is fixed to the rotating wheel .

  In the magnetic encoder of the present invention, the magnet part contains a large amount of magnetic powder and has excellent magnetic properties, and is excellent in fatigue resistance and heat resistance, and has a low water absorption rate, and an impact resistance improver. And specific antioxidants. Therefore, swelling due to water absorption is suppressed, and the amount of bending deflection increases, so even when exposed to high and low temperatures, and even when repeatedly exposed to high and low temperatures, the elastic characteristics are maintained well, and rotation is detected. High accuracy and high reliability. In addition, the rolling bearing unit including the magnetic encoder also has high performance and high reliability.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  The magnetic encoder of the present invention is formed by integrally joining a magnet portion in which a magnetic material containing magnetic powder and a specific binder described later is formed in an annular shape, and a slinger made of the magnetic material.

  As a material of the slinger, a magnetic material such as ferritic stainless steel (SUS430, etc.) and martensitic stainless steel (SUS410, etc.) that does not deteriorate the magnetic properties of the magnet material and has a certain level or more of corrosion resistance depending on the usage environment. Most preferred. In addition, in a bearing unit (refer to 3rd Embodiment) provided with a sensor cap, since corrosion resistance is not requested | required so much, a cold rolled steel plate (SPCC) etc. may be sufficient in consideration of cost.

  On the other hand, as the magnetic powder forming the magnetic material, ferrite magnetic powder such as strontium ferrite and barium ferrite, samarium-iron-nitrogen, samarium-cobalt, neodymium-iron-- Rare earth magnetic powders such as boron can be preferably used. These magnetic powders can be used alone or in combination of two or more. When the main usage environment is high temperature (for example, about 150 ° C.), rare earth magnetic powder is used when high magnetic characteristics (BHmax exceeds 2.0 MGOe) is required, and low magnetic characteristics (BHmax 1. In the case where 6 to 2.0 MGOe) may be used, a blend containing ferrite-based magnetic powder as a main component is preferable in consideration of cost. Moreover, although content of the magnetic body powder in a magnetic material changes with kinds of magnetic body powder, if it is the range of 70-92 mass%, there is no problem practically. However, since the molding of the magnet part is performed at a temperature equal to or higher than the melting point of the low water-absorbing polyamide resin as the binder, when using samarium-iron-nitrogen, demagnetization is expected at this molding temperature, so the content is It is preferable to increase the number.

  The magnetic powder preferably contains a silane coupling agent having an organic functional group such as an amino group or an epoxy group in the magnetic material in order to improve the dispersibility and the interaction with the binder.

In the binder, polyamide 12 is used as a resin component. Polyamide 12 is a low water-absorbing polyamide resin having a water absorption rate of 0.25% by mass when left in water at 23 ° C. for 24 hours.

Polyamide 12 has a melting point of 176 ° C. and also has heat resistance .

The polyamide 12 is preferably a powder product in consideration of the dispersibility when mixed with magnetic powder and pelletized with an extruder, the homogeneity of the material in the obtained magnet portion, and the like.

An impact resistance improver is blended in the binder. The impact resistance improver is an elastic material that has a function of reducing vibration and impact. In the present invention, the block co- polymer has polyamide 12 as a hard segment and at least one of a polyester component and a polyether component as a soft segment. A modified polyamide 12 which is a polymer is used.

The modified polyamide 12 Pas Uda products are preferred.

The addition amount of the modified polyamide 12 is against the total amount of the polyamide 12 1 0 to 40 wt%. If the addition amount is less than 10 % by mass, it is too small, and the effect of improving impact resistance is small, which is not preferable. When the addition amount exceeds 40 % by mass, the impact resistance is improved, but the amount of polyamide 12 is relatively reduced, the tensile strength and the like are lowered, and the practicality is lowered.

In order to prevent the polyamide 12 and the modified polyamide 12 from being deteriorated by heat, the binder includes N 2 , N′-diphenyl-p-phenylenediamine, N-isopropyl-N ′, in addition to those originally added to the material. -Phenyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylenediamine, N, N'-bis (1-methylheptyl) -p-phenylenediamine, N, N'-bis (1 , 4-Dimethylpentyl) -p-phenylenediamine and at least one amine-based antioxidant selected from N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine is added .

The addition amount of the amine-based antioxidant is 0.5 to 2.0% by mass with respect to the total amount of the binder. When the addition amount of the amine-based antioxidant is less than 0.5% by mass, the effect of improving the antioxidant is small, which is not preferable. In addition, when the amount of the amine-based antioxidant exceeds 2.0% by mass, the antioxidant effect does not change so much, and the amount of magnetic powder and binder decreases accordingly, so that the magnetic properties and mechanical strength are reduced. This is undesirable because it leads to a decrease in

  The magnetic material containing the binder falls within a range of 2 to 15 mm in bending deflection (t = 3.0 mm, ASTM D790; span distance 50 mm) at 23 ° C. By being excellent in flexibility, crack resistance becomes high, and even when repeatedly exposed to high and low temperatures, breakage such as cracks hardly occurs in the magnet portion.

  In manufacturing the magnetic encoder, first, the magnetic material is insert-molded using a slinger pre-baked with an adhesive as a core. At this time, it is preferable to use a disk gate type injection molding machine. The molten magnetic material 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. In addition, when a magnetic field is applied to the mold in the thickness direction during molding (magnetic field molding), the anisotropy becomes closer to perfection. On the other hand, when the side gate is used even if magnetic field shaping is performed, the orientation of the weld part is completely anisotropic in the process of gradually increasing the viscosity of the molten magnetic material toward solidification. It is difficult to cause a crack or the like to occur in the welded portion where the magnetic field characteristics are lowered and the mechanical strength is lowered due to long-term use.

  As the adhesive to be baked on the slinger, a phenol resin-based adhesive, an epoxy resin-based adhesive, or the like that can be diluted with a solvent and progresses a curing reaction close to two stages is preferable. These adhesives have the advantage of being excellent in heat resistance, chemical resistance, handling properties and the like.

  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 or 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 plastic magnet material at the time of insert molding. The cured magnetic material is completely cured by the heat from the molten magnetic material and the secondary heating.

  The one-pack type epoxy adhesive 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., and a high temperature of 120 to 180 ° C. The heat curing reaction proceeds completely by applying the heat. 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 from the viewpoint 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 be low and the strength tends to be weak, and if too large, the viscosity of the resin composition increases, and the curing shrinkage. Tends to occur.

  The number average molecular weight of the epoxy resin is preferably 200 to 5500, and more preferably 200 to 1000 from the viewpoint of the balance of physical properties. If the number average molecular weight is too small, the cured product tends to be weak and the moisture resistance tends to decrease.If the number average molecular weight is too large, the viscosity of the resin composition increases, which is reactive to adjust workability. Tendencies such as increased use of diluents tend to occur.

  Furthermore, an epoxy resin having an epoxy equivalent of 100 to 2800, particularly 100 to 500 is preferable 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 cured product will tend to have poor physical properties, and if it is too large, the amount of the curing agent will decrease and the molecular weight of the epoxy resin itself will decrease. A tendency to increase and the viscosity of the resin composition to increase tends to occur.

  Specific examples of such an epoxy resin include, for example, 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, and alicyclic epoxy. Examples thereof include a resin, a dicyclopentadiene type epoxy resin, a phenol novolac type epoxy resin, a polyester-modified epoxy resin, and a copolymer with another polymer such as a silicone-modified epoxy resin. 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 the heat resistance and moisture resistance of the cured product. It is preferable because it is excellent.

  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. . Specific examples of the aromatic amine include 3,3′-diethyl-4,4′-diaminodiphenylmethane, 3,5-diethyl-2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, Examples thereof include a mixture of 3,5-diethyl-2,6-toluenediamine and 3,5-diethyl-2,4-toluenediamine.

  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, it becomes a tough cured resin that is particularly flexible due to cross-linking with the epoxy resin, so that it becomes excellent in heat shock resistance required for the magnetic encoder of the present invention. It is.

  A cured product cured with an acid anhydride curing agent has high heat resistance and excellent mechanical and electrical properties at high temperatures, but tends to be somewhat brittle, but with a curing accelerator such as a tertiary amine It can be improved by combining. Specific examples of the acid anhydride curing agent include phthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, methyleneendomethylenetetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, trimellitic anhydride, etc. Can be mentioned.

  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, heated when heated, encapsulated with a curing agent in a microcapsule, destroyed by pressure, crystalline, high melting point, compatible with epoxy resins at room temperature There is a substance that does not have heat and dissolves by heating. Specific examples of the latent curing agent include 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin, eicosandioic acid dihydrazide, adipic acid dihydrazide, dicyandiamide, and 7,11-octadeca, which are high melting point compounds. Examples include diene-1,18-dicarbohydrazide. Among these, 7,11-octadecadien-1,18-dicarbohydrazide becomes a tough cured resin rich in flexibility by crosslinking with an epoxy resin, and thus is required for the magnetic encoder of the present invention. It is excellent in heat shock resistance, which is preferable.

  As the reactive diluent, t-butylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, or the like can be used. It is preferable. However, when these reactive diluents are used in a large amount, the moisture resistance and heat resistance of the cured product are lowered. Therefore, the amount is preferably 30% by mass or less, more preferably 20%, based on the main epoxy resin. Less than mass%.

The curing accelerator is preferably one that does not act as a curing accelerator at room temperature, has sufficient storage stability, and rapidly proceeds with a curing reaction when the temperature reaches 100 ° C. or higher. There are compounds having one or more ester bonds produced by the reaction of 1-alkoxyethanol and carboxylic acid. This compound is represented, for example, by the general formula (1):
R ² [COO—CH (OR ¹ ) —CH ₃ ] _n (1)
(In the formula, R ² has 2 to 10 carbon atoms and may contain one or more of nitrogen atom, oxygen atom and the like, n-valent hydrocarbon group, R ¹ has 1 to 6 carbon atoms, A monovalent hydrocarbon group which may contain one or more of nitrogen atom, oxygen atom and the like, and n is an integer of 1 to 6. Specific examples thereof include the following formula (A):

R ² is a divalent phenyl group and R ¹ is a propyl group, R ² is a trivalent phenyl group and R ¹ is a propyl group, R ² is a tetravalent phenyl group and R Examples thereof include compounds in which ¹ is a propyl group. These may be used alone or in combination of two or more. Of these, the compound represented by the formula (A) is most preferable from the viewpoint of the balance between curing reactivity and storage stability.

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

  Moreover, you may use carboxylic acids, such as adipic acid, as a compound which has an active hydrogen which reacts with an epoxy group and causes a ring-opening reaction as a hardening accelerator. By using adipic acid, 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 develop flexibility, the amount of adipic acid added is 10 to 40% by mass, more preferably 20 to 30% by mass, based on the total amount of the adhesive. When the addition amount is less than 10% by mass, sufficient flexibility is not exhibited. On the other hand, when the addition amount exceeds 40% by mass, the total amount of the epoxy resin in the adhesive is reduced, and the adhesive force and mechanical strength are lowered, which is not preferable.

  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) ) Alkyl urea such as 1,1-dimethylurea may be added.

  The OH group generated by this ring-opening reaction, including the amines described above, acts as a hydrogen bond with the hydroxyl group on the surface of the slinger, or acts on the amide bond of the low water-absorbing polyamide as the binder material, A strong adhesion state can be maintained.

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

  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 above one-component epoxy adhesive hardly undergoes a curing reaction at room temperature, for example, becomes a semi-cured state at about 80 to 120 ° C., and completes the thermosetting reaction by applying high-temperature heat of 120 to 180 ° C. It is a waste. 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 0.02-5 GPa, more preferably 0.03-4 GPa, Alternatively, the hardness (durometer D scale; HDD) falls within the range of 40 to 90, more preferably 60 to 85. If 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, etc. Becomes easy to move. As a result, the rotational speed detection accuracy may decrease, which is not preferable. On the other hand, when the flexural modulus or Young's modulus exceeds 5 GPa or the hardness (HDD) exceeds 90, the adhesive is too rigid to absorb the difference in linear expansion coefficient between the magnet portion and the slinger. It is difficult to deform, and in the worst case, a crack or the like is expected to occur in the magnet portion, which is not preferable. Further, the adhesive is required to have heat shock resistance on the premise of use in an automobile, and more preferably has flexibility (deforms when stress is applied) in a cured state.

  After the mold is filled with a magnetic material as described above, demagnetization is performed with a magnetic field in the direction opposite to the magnetization direction during cooling in the mold. Next, after removing the gate portion, the adhesive is completely cured, and further demagnetized to a magnetic flux density of 2 mT or less, more preferably 1 mT or less, using an oil capacitor type demagnetizer.

  Next, gate cutting is performed, and heating is performed at a constant temperature for a certain time in a thermostatic bath or the like in order to completely cure the adhesive. In some cases, heating can be performed at a high temperature for a short time, such as high-frequency heating.

  Thereafter, the magnetic encoder is obtained by superimposing the magnetized yoke and multipolarly magnetizing (see FIG. 3) in the circumferential direction. The number of poles 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.

  In the above description, the magnetic encoder is formed by insert molding the magnetic material using the slinger as a core. However, the slinger and the magnet are separately manufactured, and the slinger and the magnet are bonded with an adhesive. May be joined. In consideration of heat resistance and water resistance, the one-pack epoxy adhesive shown above is most suitable as the adhesive used in that case, but it is not necessary that the solvent can be diluted.

  In addition, when the magnetic encoder is used in an environment where the humidity is high in addition to the high temperature, it is preferable to form a moisture-proof coating on the exposed surface of the magnet part in order to prevent deterioration of the magnetic powder due to water absorption. This is particularly effective when rare earth magnetic powder is used. As the moisture-proof coating material, an amorphous fluororesin, a curable urethane resin, a curable acrylic resin, a curable epoxy resin, a polyparaxylene derivative, and the like are suitable, but the resin itself has a water repellency. A fluororesin and a polyparaxylene derivative are particularly preferable because they have a high effect of suppressing moisture penetration.

  Amorphous fluororesin is a polymer having a fluorine-containing aliphatic ether ring structure in the main chain, and specifically, a monomer comprising alkenyl vinyl ether such as perfluoro (allyl vinyl ether) or perfluoro (butenyl vinyl ether). Can be obtained by cyclopolymerization of these monomers or by copolymerizing these monomers with radically polymerizable monomers such as tetrafluoroethylene, chlorotrifluoroethylene, and perfluoro (methyl vinyl ether). The amorphous fluororesin preferably has a structure in which a functional group such as a carboxyl group is introduced at the end or the like in order to improve adhesion (adhesion) with the magnet portion. Further, since this amorphous fluororesin is dissolved in a perfluoro solvent such as perfluoro (2-butyltetrahydrofuran), about 1 to 10% by mass of the amorphous fluororesin is dissolved in the perfluoro solvent during film formation. What is necessary is just to immerse in the solution and dry. At this time, the film thickness of the coating depends on the concentration of the dipping solution, and the concentration is adjusted appropriately so as to obtain a desired film thickness. In order to maintain sufficient moisture resistance, the thickness of the coating is preferably 0.1 to 10 μm, and more preferably 0.3 to 2 μm. When the film thickness is less than 0.1 μm, it is difficult to stably form such a thin film, and it is difficult to ensure sufficient moisture resistance. On the other hand, if the thickness of the coating exceeds 10 μm, the moisture resistance does not change, and it is difficult to uniformly form such a thick coating, resulting in an increase in cost. In order to further improve the adhesion to the magnet portion, it is more effective to perform heat treatment at about 100 to 120 ° C. for about 0.5 to 2 hours after film formation, or to perform primer treatment in advance.

  The curable urethane resin, curable acrylic resin, and curable epoxy resin have functional groups that are cured by heat or ultraviolet rays in the structure. The film thickness is about the same as that of the amorphous fluororesin. Note that curable urethane resins, curable acrylic resins, and curable epoxy resins do not have water repellency and are not superior in their ability to block moisture. It is good also as a structure to interpose. Aluminum, chromium, nickel and the like are suitable as the kind of the metal vapor deposition film. The film thickness is preferably 0.008 to 0.1 μm, more preferably 0.01 to 0.05 μm. If the film thickness is less than 0.008 μm, it is difficult to stably form such a thin film, and it is difficult to ensure sufficient moisture resistance. On the other hand, if the thickness exceeds 0.1 μm, the moisture resistance is not changed, and an increase in cost and weight are assumed, which is not preferable. However, since it is difficult to obtain a sufficient film strength and adhesiveness by directly forming a metal vapor deposition film, it is preferable to interpose a curable urethane resin, a curable acrylic resin, or a curable epoxy resin as an underlayer.

  The polyparaxylylene derivative is represented by the following chemical formula (2), and is formed by chemical vapor deposition of a (2,2) -paracyclophane compound represented by the chemical formula (3).

In the chemical formulas (2) and (3), X ₁ and X ₂ are a hydrogen atom, a lower alkyl, or a halogen atom, which may be the same or different. In addition, specific examples of the polyparaxylene derivative represented by the chemical formula (2) include polyparaxylylene, polymonochloroparaxylylene, polydichloroparaxylylene, and the like. Assuming that the operating temperature of the magnetic encoder is higher, polymonochloroparaxylylene having a normal maximum operating temperature of about 120 ° C. and polydichloroparaxylylene having a temperature of about 150 ° C. are more suitable.

  In addition, the compound represented by the following general formula (4) obtained by fluorinating a part of hydrogen of the polyparaxylylene derivative represented by the chemical formula (2) has a very high usual use temperature of about 250 ° C., A preferred moisture barrier coating.

  The film thickness of this polyparaxylylene derivative is preferably 0.5 to 5 μm. If the film thickness is less than 0.5 μm, it is difficult to ensure sufficient moisture resistance, and the moisture resistance changes even if it exceeds 5 μm. This is not preferable because it increases the cost.

  Next, an embodiment of a rolling bearing unit including the magnetic encoder configured as described above will be described.

(First embodiment)
FIG. 1 is a cross-sectional view showing an example of a rolling bearing with a magnetic encoder assembled therein, and FIG. 2 is an enlarged view around the magnetic encoder. The illustrated rolling bearing 10 is rotatably disposed in an annular space defined by an outer ring 11 that is a fixed ring, an inner ring 12 that is a rotating ring (rotating body), and the outer ring 11 and the inner ring 12, and a cage. 14, which are a plurality of rolling elements that are held at equal intervals in the circumferential direction by a ball 14, a sealing device 15 disposed at the opening end of the annular gap, and a magnetic encoder for detecting the number of rotations of the inner ring 12. 20.

  The sealing device 15 includes a seal member 16 that is fixed to the inner peripheral surface of the outer ring 11, and a slinger 17 that is disposed outside the opening end portion of the seal member 16 and is fixed to the outer peripheral surface of the inner ring 12. . The sealing device 15 closes the opening end portion of the annular gap by sliding contact between the seal member 16 and the slinger 17 to prevent foreign matters such as dust from entering the inside of the bearing, and a lubricant filled in the bearing. Is prevented from leaking outside the bearing. The seal member 16 is configured by reinforcing a rubber seal 19 that is also formed in an annular shape that is substantially L-shaped in cross section with a cored bar 18 that is formed in an annular shape having an approximately L-shaped cross section. The portion is branched to form a plurality of seal lips 19 a, 19 b, 19 c, which are in sliding contact with the surface of the slinger 17.

  On the other hand, the magnetic encoder 20 includes a slinger 17 and a magnetic pole forming ring 21 that is attached to the outer surface (magnet bonding surface) of the slinger 17 and made of the magnetic material. The slinger 17 is fixed to the inner ring 12 as a fixing member.

  The slinger 17 is made of a thin plate such as ferritic stainless steel (such as SUS430) or martensitic stainless steel (such as SUS410), and includes a cylindrical portion 17a fitted to the inner ring 12 and a curved portion 17b at the axial end of the cylindrical portion 17a. And a flange-like flange portion 17c formed so as to spread outward in the radial direction. As shown in FIG. 3, the magnetic pole forming ring 21 is a multipolar magnet, and N and S poles are alternately formed in the circumferential direction. The number of poles of the magnetic pole forming ring 21 is about 70 to 130, preferably 90 to 120. A magnetic sensor (not shown) is disposed facing the magnetic pole forming ring 27.

  Further, as shown in FIG. 4, fine uneven portions 17 d are provided on the magnet bonding surface of the slinger 17. The fine concavo-convex portion 17d present on the magnet joint surface is transferred by pressing only the magnet joint surface against the fine concavo-convex provided on the mold surface when a thin plate of magnetic material is press-molded between dies. It is formed. Specifically, as shown in FIG. 5, the press molding machine 30 includes a base 32 having a columnar guide portion 31 having an outer diameter substantially the same as the inner diameter of the cylindrical portion 17 a of the slinger 17, and a base An annular surface precision roughing die 33 fitted on the guide portion 31 on the upper side 32 and movable in the vertical direction above the roughing die 33 and having an inner diameter substantially the same as the outer diameter of the cylindrical portion 17a. And an annular pressing die 34. On the surface of the roughing mold 33, fine irregularities 33a are provided. As a method of providing the fine irregularities 33a, chemical etching, electric discharge machining, rolling, or cutting knurling is suitable. Further, as a method of forming the unevenness 33a, roughening may be performed by shot blasting or the like.

  Then, the pressing die 34 is driven downward, and the magnetic material thin plate provided between the roughing die 33 and the pressing die 34 is press-molded, so that the outer peripheral surface of the guide portion 31 and the inside of the pressing die 34 are A cylindrical portion 17a is formed between the peripheral surface. At this time, a relatively high convex portion of the concave and convex portion 33a is actually preferentially pressed by pressing the thin magnet coupling surface forming the slinger 17 against the concave and convex portion 33a provided in the roughing mold 33, and smoothing Concave and convex portions 17d are formed in the portions that were.

  The depth of the concave portion of the uneven portion 17d is about 1 to 20 μm, more preferably about 2 to 10 μm. When the depth of the concave portion is less than 1 μm, the depth is too shallow to enter the concave portion to express the anchor effect of the adhesive, so that the bonding force is not improved so much and the practicality is low. When the depth of the concave portion exceeds 20 μm, it is necessary to further deepen the convex portion provided on the mold 33. Therefore, there is a possibility of affecting the smooth surface on the back side when transferring during press molding, which is not preferable. .

  In addition, the surface finish state of the smooth surface other than the magnet joint surface in the slinger 17 is not particularly limited. However, the BA2 (about Ra 0.06) and the BA5 (about Ra0.03) with Ra of 0.1 μm or less. BA finish such as No. An AP finished product such as 2B (about Ra 0.06) is preferable in consideration of the aggressiveness to the seal lips 19a, 19b, 19c that are in sliding contact.

  An adhesive is applied to the magnet joining surface of the slinger 17 configured in this way, but the adhesive enters the uneven portion 17d of the magnet joining surface, so that the magnet portion 21 and the slinger 17 are joined by the anchor effect. Strengthen power.

(Second Embodiment)
FIG. 6 is a partial cross-sectional view showing an application example of the independent suspension type suspension to the wheel support rolling bearing unit 100 for supporting the driven wheel.

  An inner ring 107 of the rolling bearing unit 100 is externally fitted to a small diameter step portion 106 formed at the inner end portion of the hub 103, and a caulking portion 109 formed by caulking and expanding the inner end portion of the hub 103 radially outwardly, It is fixedly coupled to the hub 103. The hub 103 and the inner ring 107 constitute a rotating wheel (rotating body) 102. In addition, the wheel is formed by a stud 105 implanted at a predetermined interval in the circumferential direction on a mounting flange 104 formed at a portion protruding from the outer end portion of the outer ring 101 which is a fixed wheel at the outer end portion of the hub 103. It can be connected and fixed freely. On the other hand, the outer ring 101 can be coupled and fixed to a knuckle or the like (not shown) constituting a suspension device by a coupling flange 111 formed on the outer peripheral surface thereof. Between the outer ring 101, the hub 103, and the inner ring 107, balls 112, which are a plurality of rolling elements guided by a cage 113, are arranged so as to be able to roll in the circumferential direction.

  Further, sealing devices 15 and 115 are provided between the inner peripheral surfaces of both ends of the outer ring 101, the outer peripheral surface of the intermediate portion of the hub 103, and the outer peripheral surface of the inner end portion of the inner ring 106, respectively. These sealing devices 15 and 115 block the space provided with the balls 112 from the outer space between the inner peripheral surface of the outer ring 101 and the outer peripheral surfaces of the hub 103 and the inner ring 107. And the magnetic pole formation ring 21 is attached to the outer surface of the slinger 17 which comprises this sealing device 15, and the magnetic encoder 20 is comprised similarly to the form of FIG. Note that a magnetic sensor 114 is disposed opposite to the outer side of the magnetic encoder 20 in the axial direction, and the rotational speed of the wheel can be detected by detecting a change in magnetic flux density.

(Third embodiment)
FIG. 7 is a partial cross-sectional view showing an application example to the wheel support rolling bearing unit 100 for supporting the driven wheel in the independent suspension, and FIG. 8 is an enlarged view around the magnetic encoder. In addition, the same code | symbol is attached | subjected to the same member as the wheel bearing rolling bearing unit 100 shown in FIG. 6, and description is abbreviate | omitted.

  The wheel support rolling bearing unit 100 shown in the figure has a configuration in which the sealing device 15 is removed from the wheel support rolling bearing unit 100 shown in FIG. The sensor cap 115 is a resin lid member that is mounted so as to cover the opening surrounded by the outer ring 101, and the sensor 114 is fixed to the sensor cap 115.

(Fourth embodiment)
FIG. 9 shows a configuration in which the magnetic encoder 20 and the sensor 114 face each other in the radial direction. In the magnetic encoder 20 of the present embodiment, an annular slinger 17 as a fixing member is fitted and fixed to the outer peripheral surface of the inner end portion of the inner ring 107, and the inner peripheral surface of the slinger 17 extending in the axial direction from the inner ring 107 is provided on the inner peripheral surface. A magnetic pole forming ring 21 that is a magnet portion is attached. A cover member 115, which is a stationary member, is fixed to the outer peripheral surface of the outer ring 101, and a sensor 114 is opposed to the magnetic pole forming ring 21 in the radial direction at an opening formed in the cover member 115. It is attached.

  According to such a configuration, 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 as described above. Therefore, when the number of pitches is the same, each pitch width is increased. It is easy to manufacture.

  In the illustrated example, the magnetic encoder 20 is disposed at the shaft end, but the magnetic encoder 20 may be disposed between the rows (between the two balls 112, 112). In the case of arranging between the rows, a material to be used is appropriately selected in consideration of heat resistance. Moreover, also when arrange | positioning to a shaft bridge, a use material is selected suitably in consideration of water resistance. Further, in the example shown in the figure, the sensor 114 is disposed inside the magnetic encoder 20, but may be disposed outside.

  The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like can be made as appropriate. For example, as shown in FIG. 10, the magnetic pole forming ring 21 can be a radial facing type magnetized in a V shape. In the V-shaped magnetic pole, the left and right inclinations (α, β) are not necessarily the same, and the boundary of the V-shaped magnetic pole is not limited to a straight line but may be a curved line or a wavy line. The magnetization method may be either single-pole magnetization in which magnetization is repeated for each pole or a plurality of poles, or multi-pole magnetization in which all the magnetic poles are magnetized at once.

  Further, the shape of the magnetic pole may be trapezoidal as shown in FIG. Furthermore, in the above-described fourth embodiment, a magnet portion magnetized in a trapezoidal shape as shown in FIG.

The present invention will be further clarified by giving test examples below.
(Test-1)
As shown in Table 3, a magnetic material and a binder were kneaded to prepare a magnetic material. In addition, an adhesive solution was prepared by diluting a 30% solid content phenol resin adhesive (Metal Lock N-15, manufactured by Toyo Chemical Laboratory) with methyl ethyl ketone three-fold with a novolac type phenol resin as a main component. In addition, a thin plate made of ferritic stainless steel (SUS430) having a thickness of 0.6 mm is formed into an annular shape having an inner diameter of 66 mm and an outer diameter of 76 mm, and the magnet joint surface is further roughened with Ra 0.8 (seal slide) by shot blasting. The moving surface was dipped in a slinger with a raw material roughness Ra 0.08), dried at room temperature for 30 minutes, and then left in a dryer at 120 ° C. for 30 minutes to baked the adhesive in a semi-cured state. .

  Then, the slinger obtained by baking the adhesive in a semi-cured state was used as a core, and the magnetic material was insert-molded (disc gate from the inner peripheral portion). Immediately after molding, the gate was cut and further heated at 150 ° C. for 1 hour to completely cure the adhesive to obtain a magnetic encoder having an inner diameter of 66 mm, an outer diameter of 76 mm, and a magnet part thickness of 0.9 mm.

  Put the 10 magnetic encoders into a thermal shock tester, apply a thermal load that holds 30 minutes at 120 ° C and 30 minutes at -40 ° C, and observe the magnet part every 50 cycles. The presence or absence of cracks was confirmed. The results are shown in Table 3.

From Table 3, the amount of bending deflection of the material itself is increased and the crack resistance is improved by using a binder in which the modified polyamide 12 and the amine-based antioxidant are blended with the polyamide 12 as in the example. It can be seen that the thermal shock resistance is significantly improved.

On the other hand, even if the polyamide 12 is used as in the comparative example, the modified polyamide 12 is not blended, the amine antioxidant is not blended, or an antioxidant other than the amine antioxidant (phenolic antioxidant) ) Is greatly inferior in thermal shock resistance.

It is sectional drawing which shows an example of a rolling bearing unit provided with a magnetic encoder. It is sectional drawing which shows the periphery of the magnetic encoder of FIG. It is a schematic diagram which shows an example of the magnet part by which the multipolar magnetization was carried out in the circumferential direction. It is a perspective view which shows the slinger after press molding. It is sectional drawing which shows the state by which a slinger is press-molded. It is sectional drawing which shows the other example of a rolling bearing unit provided with a magnetic encoder. It is sectional drawing which shows the further another example of a rolling bearing unit provided with a magnetic encoder. It is sectional drawing which shows the periphery of the magnetic encoder of FIG. It is principal part sectional drawing which shows the further another example of a rolling bearing unit provided with a magnetic encoder. It is a schematic diagram which shows the other example of the magnetic pole in a magnet part. It is a schematic diagram which shows the further another example of the magnetic pole in a magnet part. It is a schematic diagram which shows the other example of the magnetic pole in a magnet part. It is sectional drawing which shows a rolling bearing unit provided with the conventional magnetic encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rolling bearing unit 11 Outer ring 12 Inner ring 13 Ball 14 Cage 15 Sealing device 16 Seal member 17 Slinger 17d Uneven portion

Claims (6)

In a magnetic encoder comprising a magnet portion in which a magnetic material containing magnetic powder and a binder of the magnetic powder is formed in an annular shape,
The binder is a polyamide 12, a block copolymer having a polyamide 12 as a hard segment and at least one of a polyester component and a polyether component as a soft segment, and N, N′-diphenyl-p- Phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, N, N′-di-2-naphthyl-p-phenylenediamine, N, N′-bis (1-methylheptyl) -p-phenylenediamine N, N′-bis (1,4-dimethylpentyl) -p-phenylenediamine and N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, It contains a 0.5 to 2.0 mass% of aminic antioxidant binder total amount, and the modified polyamide Magnetic encoder, characterized in that 12 is 10 to 40 wt% relative to the total amount of the polyamide 12. 2. The magnetic encoder according to claim 1, wherein an amount of bending deflection of the magnetic material is 2 to 15 mm at a thickness = 3.0 mm, a span distance = 50 mm, and a temperature = 23 ° C. 3. 3. The magnet according to claim 1, wherein the slinger and the magnet portion are joined by insert molding the magnet portion with a slinger provided with an adhesive in a semi-cured state in advance as a core. Encoder. The magnetic encoder according to claim 3 , wherein the magnetic encoder is obtained by secondary heating after the insert molding . 4. The magnetic encoder according to claim 3, wherein the adhesive is a phenol resin adhesive or an epoxy resin adhesive . In a rolling bearing unit comprising a fixed wheel, a rotating wheel, and a plurality of rolling elements disposed so as 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 any one of claims 1 to 5 is fixed to the rotating wheel .

Images