JP4037406B2 - Magnetic encoder and bearing provided with the same - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder used in a rotation detecting device for a bearing portion that rotates relative to each other, and a bearing such as a wheel bearing provided with the magnetic encoder. The present invention relates to a magnetic encoder which is a component part of a bearing seal mounted on a detection device.

Conventionally, the following structure is often used as an anti-skid rotation detection device for preventing automobile skid. That is, the rotation detection device is composed of a toothed rotor and a sensing sensor, and in this case, the rotation detection device is generally arranged apart from the seal device for sealing the bearing, and constitutes an independent rotation detection device. Is.
Such a conventional example has a structure in which a toothed rotor fitted to a rotating shaft is detected by a rotation detection sensor attached to a knuckle, and a bearing used is provided independently on a side portion thereof. Protected against moisture or foreign material intrusion by a sealing device.

As another example, Patent Document 1 discloses a bearing seal having a rotation detection device for detecting wheel rotation for the purpose of reducing the mounting space of the rotation detection device and dramatically improving the sensing performance. A structure is shown in which an elastic member mixed with magnetic powder is circumferentially vulcanized and bonded in the radial direction of a slinger to be used, and magnetic poles are alternately arranged there.
Further, in Patent Document 2, for the purpose of reducing the dimension in the axial direction, improving the degree of sealing between the rotating member and the fixed member, and enabling easy attachment, the gap between the rotating member and the fixed member is disclosed. Is shown, and a rotating disk is attached to the rotating member, and a multi-polar coder is attached to the rotating disk. The coder used is made of an elastomer to which magnetic particles are added, and the side surface of the coder is a sealing means that is substantially flush with the side surface of the fixing member.

A coder made of plastic (plastomer) containing magnetic powder or magnetic particles is shaped by using a mold suitable for the product shape, as in conventional injection molding or compression molding. Or by forming a sheet by extrusion molding using a T-shaped die or sheet molding such as calendering, and then punching it into a product shape, and then bonding and fixing on a metal substrate with an adhesive You may make it. In this case, the metal substrate may be assembled in advance in the mold as in the case of insert molding, and then the molten resin may be poured and the bonding process may be simultaneously processed.
Japanese Patent No. 2816783 JP-A-6-281018 Publication Sho 63-115008 Publication Sho 63-300910

  However, among the above conventional examples, in the bearing seals shown in Patent Document 1 and Patent Document 2, an elastic member mixed with magnetic powder in the radial direction of the slinger used therein is vulcanized and bonded in a circumferential shape. In addition, if the coder is to be made into an elastomer with magnetic particles added as a coder built-in sealed structure with a multipolar coder attached, an elastomer or elastic member component that becomes a binder for holding magnetic powder or magnetic particles is required. Become. However, when an elastomer or elastic member component is used for the binder, a dispersion step is always required by kneading the magnetic powder or magnetic particles with the elastomer or elastic member before shaping into the coder shape. In this step, the binder component in the coder Since it is difficult to increase the relative content (volume fraction) of magnetic powder or magnetic particles, it is necessary to increase the thickness of the coder in order to obtain a magnetic force that is stably sensed by the magnetic sensor.

In addition, molding of elastic members and elastomeric coders containing magnetic powder and magnetic particles is performed by using a mold suitable for the product shape, such as injection molding and compression molding, and the vulcanization process is performed. When necessary, the vulcanization time required in the mold had to be maintained under pressure, requiring many steps in production.
In addition, elastic members and elastomeric coders containing magnetic powder and magnetic particles, for example, in bearing seals with a rotation detection device for detecting wheel rotation, reduce the mounting space for the rotation detection device and dramatically improve sensing performance. In order to improve the quality of the sensor, the sensor must be disposed at a position close to and opposite to the slinger used in the axial direction. However, in this case, if foreign particles such as sand particles enter the gap between the bearing seal surface on the rotating side and the surface of the sensing sensor on the fixed side while the vehicle is running, the elastic member and the elastomer coder surface will be worn. Severe damage was observed.

In the case of a coder made of plastic (plastomer) containing magnetic powder or magnetic particles, it is manufactured by conventional injection molding, compression molding, sheet molding such as extrusion molding using T-shaped dies or calendar molding, and insert molding. If it is going to do, the synthetic resin component used as a binder for hold | maintaining magnetic powder and a magnetic particle will be needed. However, when a synthetic resin component is used for a binder, a dispersion step by kneading magnetic powder, magnetic particles, plastomer, and an elastic member is always required before shaping into a coder shape, like an elastomer. Again, in this process, the relative content (volume fraction) of magnetic powder and magnetic particles with respect to the binder component in the coder is difficult to increase, so the thickness of the coder is used to obtain a magnetic force that is stably sensed by the magnetic sensor. It was necessary to increase the dimensions. In addition, pre-molding materials produced by kneading magnetic powder, magnetic particles, plastomers, and elastic members in this way by conventional manufacturing methods are injected (injected) into the mold or compressed (compressed) to be applied to the coder. When forming, or by shaping by insert molding, etc., the magnetic particle component contained in the material is a metal oxide, so it is hard and wear of molds and molding machines becomes a problem in mass production. The pre-molding material with a high content of magnetic particle components has a problem that the melt viscosity becomes high and the molding load increases, such as increasing the molding pressure and the mold clamping force.

  Even in the case of sheet molding such as extrusion molding and calendar molding using a T-shaped die, the magnetic particle component contained in the material is hard with metal oxide, so that for mass production, T-shaped die and calendar molding machine Roll wear became a problem.

An object of the present invention is to provide a magnetic encoder that can secure a magnetic force capable of performing stable sensing, can be downsized, is robust, has excellent wear resistance, and is excellent in productivity.
Another object of the present invention is to provide a magnetic encoder for detecting rotation, which can secure a magnetic force capable of stable sensing, can be downsized, is robust, has excellent wear resistance, and has excellent productivity. It is to provide a wheel bearing.

The magnetic encoder according to the present invention is a magnetic encoder including a multipolar magnet having magnetic poles alternately formed in a circumferential direction and a cored bar that supports the multipolar magnet. It is a sintered body of a porous body obtained by sintering a powder compact with metal pores, which is formed by pressure-molding a mixed powder with metal powder, and the multipolar magnet is bonded to the core metal with an adhesive. Adhesive fixing, the adhesive is a clear anticorrosion paint, and using this clear anticorrosion paint, the surface of the entire magnetic encoder having the multipolar magnet and the cored bar has a thickness of 0.5 μm or more The anticorrosive film is formed by baking . The multipolar magnet is, for example, an annular shape such as an annular shape or a disc shape. The core metal may be an annular shape such as an annular shape, or a disk shape.
According to this configuration, since the multipolar magnet is a sintered body obtained by sintering a mixed powder of magnetic powder and nonmagnetic metal powder, the following advantages can be obtained.
(1). Compared to conventional elastomers and plastomers, the magnetic powder ratio can be increased, so that the magnetic force per unit volume can be increased. Thereby, the detection sensitivity can be improved.
(2). Compared to a conventional sintered magnet that is sintered only with magnetic powder, it is difficult to break due to the presence of non-magnetic metal powder as a binder.
(3). Since the surface is harder than conventional elastomers, etc., it is excellent in wear resistance and hardly damaged.
(Four) . Productivity is superior to conventional elastomers.

  Further, since the multipolar magnet is bonded and fixed to the core metal with an adhesive, it can be easily fixed to the core metal even though it is a sintered multipolar magnet. For example, the adhesive may be a clear anticorrosive paint. Moreover, a rust preventive film may be applied to the multipolar magnet, and the multipolar magnet may be fixed to the core metal by the effect of the rust preventive film as an adhesive. In particular, when a rust preventive coating is applied with a clear anticorrosive paint, the effect as an adhesive can be obtained on the rust preventive coating.

A clear anticorrosive coating was formed on the surface of the multipolar magnet made of the sintered body using a clear anticorrosive coating, and the thickness of the anticorrosive coating was 0.5 μm or more . As the clear highly anticorrosive coating, a modified epoxy phenol curing coating can be used.
When provided with the anticorrosive coating film, therefore the corrosion resistance, as possible out to be used in easily generated under the environment of rust, such as, for example, such as a wheel bearing. The paint can also be expected to have an effect as an adhesive between the cored bar and the sintered body, and penetrates into the pores of the surface of the sintered porous body, and is suitably held on the surface by the anchor effect of the clear coating film component. Thus, good adhesion as a rust-proof coating can be maintained even after long-term use.
These green compacts (green bodies) desirably have 5 to 30 vol% pores. Preferably it is 12-22 vol%, More preferably, it is 14-19 vol%. When the porosity is less than 5 vol%, the green compact may be damaged due to springback caused by recovery of elastic deformation of the raw material powder when the molding pressure is released. Further, when there are more voids than 30 vol%, the mechanical strength of the sintered body becomes weak, so that even if it is attempted to be mechanically fixed on the core metal by caulking or press-fitting, it will be broken. In addition, the green compact may not be formed due to insufficient adhesion between the particles.

Moreover, you may use together the adhesion fixation to the metal core with the adhesive agent of the said multipolar magnet, and fixation to the metal core of the multipolar magnet by caulking of a metal core.
When both bonding and caulking are used together, the core bar has a cylindrical section, a vertical plate section extending from one end of the core bar to the outer diameter side, and a cross section of the other cylindrical section extending from the outer diameter edge of the vertical plate section. An inverted Z-shaped annular shape may be used, and the multipolar magnet may be fixed to the cored bar by caulking the other cylindrical portion.

In the magnetic encoder of the present invention, the magnetic powder may be ferrite powder. Ferrite powder is cheaper than other magnetic powders, and using this, a magnetic encoder can be manufactured at low cost. The ferrite powder may be a granular powder or a pulverized powder made of a wet anisotropic ferrite core. When the pulverized powder of this wet anisotropic ferrite core is used, the mixed powder with the nonmagnetic metal powder needs to be a green body molded in a magnetic field. Green body is green compact.
The magnetic powder may be a rare earth magnetic powder. For example, a samarium-based magnetic powder or a neodymium-based magnetic powder may be used. When these samarium magnetic powder and neodymium magnetic powder are used, a strong magnetic force can be obtained. As the samarium-based magnetic powder, samarium iron (SmFeN) -based magnetic powder is used, and as the neodymium-based magnetic powder, neodymium iron (NdFeB) -based magnetic powder is used. In addition, the magnetic powder may be manganese aluminum (MnAl) gas atomized powder.

  The nonmagnetic metal powder may be stainless steel powder or tin powder. When the magnetic powder is ferrite powder, stainless steel powder may be used as the nonmagnetic metal powder, or tin powder may be used. When the magnetic powder is samarium-based magnetic powder, stainless steel powder may be used as the nonmagnetic metal powder, or tin powder may be used. When the magnetic powder is neodymium-based magnetic powder, stainless steel powder may be used as the nonmagnetic metal powder, or tin powder may be used. Stainless steel powder is superior in rust resistance as compared to other nonmagnetic metal powders, and a sintered body using the powder is excellent in rust resistance.

  The mixed powder may contain two or more kinds of magnetic powders, or may contain two or more kinds of nonmagnetic metal powders. The mixed powder may contain two or more kinds of magnetic powders and may contain two or more kinds of nonmagnetic metal powders. When two or more kinds of magnetic powders or two or more kinds of metal powders are included, desired characteristics can be obtained by arbitrarily mixing a plurality of kinds of powders. For example, when the magnetic force is insufficient with ferrite powder alone, it can be manufactured at low cost while improving the magnetic force by mixing the ferrite powder with samarium magnetic powder or neodymium magnetic powder, which are rare earth magnetic materials, in the required amount. .

  The magnetic powder in which two or more types are mixed is a mixture of two or more of samarium iron (SmFeN) magnetic powder, neodymium iron (NdFeB) magnetic powder, and manganese aluminum (MnAl) gas atomized powder. May be. For example, the magnetic powder is a mixture of samarium iron (SmFeN) magnetic powder and neodymium iron (NdFeB) magnetic powder, a mixture of neodymium iron magnetic powder and manganese aluminum gas atomized powder, manganese aluminum gas atomized Either a mixture of powder and samarium iron-based magnetic powder, or a mixture of samarium iron-based magnetic powder, neodymium iron-based magnetic powder, and manganese aluminum gas atomized powder may be used. The magnetic powder may be a mixture of a ferrite powder and a samarium iron (SmFeN) magnetic powder or neodymium iron (NdFeB) magnetic powder, which is a rare earth magnetic material, in a necessary amount.

The magnetic powder and the nonmagnetic metal powder are mixed at a predetermined blending ratio using a powder mixer, and the mixed powder is pressure-molded in a mold at room temperature to obtain a green compact.
At this time, the sintered body made of the mixed magnetic powder mixed with the magnetic powder using the nonmagnetic metal powder as the binder is dispersed by the powder mixer while adjusting the composition ratio of the nonmagnetic metal powder and the magnetic powder. Since dry blending can be performed, the relative content (volume fraction) of the magnetic powder in the sintered body can be increased. For this reason, the magnetic force stably sensed by the magnetic sensor can be easily obtained.
Moreover, even in the production of sintered bodies that are multipolar magnets, the sintered powder molding method using dry blending of powders is vulcanized compared to conventional injection molding and compression molding for elastomers and elastic members. Since there are no processes and the molding load is small, the production process can be greatly simplified. Further, in the case of forming a green compact by sintering, problems such as wear of the mold do not occur as compared with injection molding or compression molding of an elastomer or an elastic member.
In addition, when mounting this sintered body as a multipolar magnet to a cored bar, the mounting to the cored bar can be done by a simple caulking process or a mechanical fixing method such as press-fitting. Reliability can be maintained even when exposed to harsh conditions in the environment.
A magnetic pole is alternately magnetized in the circumferential direction on the sintered body to obtain a multipolar magnet.

  The magnetic encoder having this configuration is used for rotation detection with a magnetic sensor facing a multipolar magnet. When this magnetic encoder is rotated, the passage of each magnetic pole of the multipolar magnet is detected by the magnetic sensor, and the rotation is detected in the form of pulses. Since the multi-pole magnet is made of a sintered body mixed with magnetic powder, as described above, it is possible to secure a magnetic force with which stable sensing can be obtained, to make the magnetic encoder compact and to have excellent wear resistance. In addition, when a multi-pole magnet is supported on a cored bar, the metal cored bar and the multi-pole magnet can be integrated by an assembly method such as caulking or press-fitting. It will be a thing.

A bearing with a magnetic encoder according to the present invention is a rolling bearing in which a rolling element is interposed between raceways facing an inner ring and an outer ring. A magnetic encoder is attached to a rotating side wheel of the inner ring and the outer ring. A magnetic encoder having any one of the above-described configurations of the present invention is used as the magnetic encoder, which is disposed inside the end surface of the fixed side wheel in the space between the inner ring and the outer ring.
According to this configuration, the magnetic encoder for detecting rotation can secure a magnetic force that enables stable sensing, can be downsized, and is robust, excellent in wear resistance, and excellent in productivity.

  The wheel bearing according to the present invention includes an outer member having a double-row raceway surface formed on the inner peripheral surface, an inner member having a raceway surface opposite to the raceway surface of the outer member formed on the outer peripheral surface, A wheel bearing having a double row rolling element interposed between the raceway surfaces and rotatably supporting the wheel with respect to the vehicle body, wherein the rotating side member of the inner member and the outer member is magnetized. An encoder is attached, and the magnetic encoder is disposed on the inner side of the end surface of the fixed member in the space between the inner member and the outer member, and the magnetic encoder having any one of the above configurations of the present invention is used as the magnetic encoder. It is used.

In general, wheel bearings are exposed to the road surface environment, and particles such as sand particles may be caught between the magnetic encoder and the magnetic sensor that faces the magnetic encoder. Protected like.
That is, the surface hardness of the sintered multipolar magnet made of magnetic powder and nonmagnetic metal powder is harder than that of a conventional elastic member or elastomer coder containing magnetic powder or magnetic particles. For this reason, in a wheel bearing having a magnetic encoder for detecting wheel rotation, particles such as sand particles get caught in the gap between the surface of the rotating multipolar magnet and the surface of the stationary magnetic sensor during vehicle running. Even if rare, it has a significant reduction effect on wear damage of multipolar magnets.

The magnetic encoder according to the present invention is a magnetic encoder including a multipolar magnet having magnetic poles alternately formed in a circumferential direction and a cored bar that supports the multipolar magnet. It is a sintered body of a porous body obtained by pressing a powder mixture with metal powder and sintered with a powder compact having pores inside, and the multipolar magnet is bonded to the core metal with an adhesive. Adhesive fixing, the adhesive is a clear anticorrosion paint, and using this clear anticorrosion paint, the surface of the entire magnetic encoder having the multipolar magnet and the cored bar has a thickness of 0.5 μm or more Since the anti-corrosion coating is formed by baking , it can secure a magnetic force that enables stable sensing, can be made compact, and is robust, excellent in wear resistance, and excellent in productivity.
The magnetic encoder bearing and wheel bearing according to the present invention are magnetic encoders for detecting rotation and can secure a magnetic force capable of stable sensing, can be made compact, and are robust, excellent in wear resistance, and productive. Also excellent.

  A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the magnetic encoder 10 includes a metal annular cored bar 11 and a multipolar magnet 14 provided on the surface of the cored bar 11 along the circumferential direction. The multipolar magnet 14 is a member that is magnetized in multiple poles in the circumferential direction and has magnetic poles N and S alternately formed, and is composed of a magnetic disk magnetized in multiple poles. The multipolar magnet 14 is a sintered body obtained by sintering a mixed powder of magnetic powder and nonmagnetic metal powder. The multipolar magnet 14 is bonded and fixed to the core metal 11. The magnetic poles N and S are formed to have a predetermined pitch p in the pitch circle diameter PCD (FIG. 2). The magnetic encoder 10 is attached to a rotating member (not shown), and is used for rotation detection with a magnetic sensor 15 facing a multipolar magnet 14 as shown in FIG. The rotation detection device 20 is configured with the sensor 15. This figure shows an application example in which the magnetic encoder 10 is a component of a seal device 5 for a bearing (not shown), and the magnetic encoder 10 is attached to a bearing ring on the rotation side of the bearing. The seal device 5 includes a magnetic encoder 10 and a fixed-side seal member 9. A specific configuration of the sealing device 5 will be described later.

  The magnetic powder mixed in the multipolar magnet 14 may be isotropic or anisotropic ferrite powder such as barium-based and strontium-based. These ferrite powders may be granular powders or pulverized powders composed of a wet anisotropic ferrite core. When the pulverized powder made of this wet anisotropic ferrite core is used as a magnetic powder, it is necessary to use a mixed powder with a nonmagnetic metal powder as an anisotropic green body formed in a magnetic field.

  The magnetic powder may be a rare earth magnetic material. For example, samarium iron (SmFeN) magnetic powder and neodymium iron (NdFeB) magnetic powder, which are rare earth magnetic materials, may be used alone. The magnetic powder may be manganese aluminum (MnAl) gas atomized powder.

The magnetic powder may be a mixture of two or more of samarium iron (SmFeN) magnetic powder, neodymium iron (NdFeB) magnetic powder, and manganese aluminum (MnAl) gas atomized powder. For example, the magnetic powder is a mixture of samarium iron (SmFeN) magnetic powder and neodymium iron (NdFeB) magnetic powder, a mixture of manganese aluminum gas atomized powder and samarium iron magnetic powder, and samarium iron. Any of a mixture of a system magnetic powder, a neodymium iron system magnetic powder, and a manganese aluminum gas atomized powder may be used.
Also, for example, when the magnetic force is insufficient with only the ferrite content, the required amount of samarium iron (SmFeN) magnetic powder or neodymium iron (NdFeB) magnetic powder, which is a rare earth magnetic material, is mixed with the ferrite powder to improve the magnetic force. It can also be manufactured at a low cost.

  Further, the nonmagnetic metal powder forming the multipolar magnet 14 may be any one of powders of tin, copper, aluminum, nickel, zinc, tungsten, manganese, etc., or nonmagnetic stainless steel metal powder alone (one type). These powders, mixed powders of two or more, or alloy powders of two or more can be used.

Both the magnetic powder and the nonmagnetic metal powder have an average particle diameter of 10 μm or more and 150 μm or less, preferably 20 μm or more and 130 μm or less. If the average particle size of one or both of these powders is smaller than 10 μm, even if you try to obtain a green compact by pressing it in a mold at room temperature to form a mixed powder, it will mix well in the mold Powder may not flow in, and a green compact with a predetermined shape cannot be formed. In addition, if the average particle size of one or both of these powders is larger than 150 μm, even if an attempt is made to obtain a green compact by pressing it in a mold at room temperature as a mixed powder, the green compact strength Therefore, it cannot be removed from the mold and cannot be molded.
The above-mentioned average particle size range of magnetic powder and non-magnetic metal powder are mixed at a predetermined blending ratio using a powder mixer, and the mixed powder is pressed in a mold at room temperature. Obtain powder.

In the blending in the mixed powder forming the multipolar magnet 14, the volume blending ratio of the non-magnetic metal powder that is not magnetic powder is preferably 1 vol% or more and 90 vol% or less, preferably 5 vol% or more and 85 vol% or less, and more desirably 10 vol% or more and 80 vol% or less are good.
When the volume content of the nonmagnetic metal powder that is not magnetic powder is less than 1 vol%, the nonmagnetic metal powder is small as a metal binder, so that the multipolar magnet 14 obtained after sintering is hard but brittle. For this reason, as will be described later, even if the sintered body to be the multipolar magnet 14 is mechanically fixed on the core metal 11 by caulking or press-fitting, it is cracked. Moreover, since there are too few metal binders, a green compact may not be shape | molded.
If the volume content of the nonmagnetic metal powder that is not magnetic powder is more than 90 vol%, the magnetic component is relatively small, so that the magnetization strength of the obtained multipolar magnet 14 cannot be increased after sintering, and the magnetic encoder 10 Therefore, it is not possible to secure the magnetic force for obtaining the desired stable sensing.

The linear expansion coefficient of the multipolar magnet 14 obtained after sintering is preferably 0.5 × 10 ⁻⁵ or more and 9.0 × 10 ⁻⁵ or less, but preferably 0.8 × 10 ⁻⁵ or more and 7 × 10 ⁻⁵ or less, more preferably 0.9 × 10 ⁻⁵ or more and 5 × 10 ⁻⁵ or less.
For example, in the case of stainless steel (JIS standard SUS430), the linear expansion coefficient of the metal material used as the material of the core metal 11 is 1.0 × 10 ⁻⁵ . When the linear expansion coefficient of the multipolar magnet 14 is larger than 0.5 × 10 ⁻⁵ or smaller than 9 × 10 ⁻⁵ , the difference in linear expansion coefficient from the metal material that is the material of the core metal 11 is large. The difference in dimensional change when used in a high and low temperature environment becomes large, and the multipolar magnet 14 and the core metal 11 may interfere with each other and the multipolar magnet 14 may be damaged. Further, it becomes impossible to secure the multipolar magnet 14 and the cored bar 11.

In forming the green compact, a lubricant such as zinc stearate may be added to improve the green compact moldability when the magnetic powder and the nonmagnetic metal powder are blended.
These green compacts (green bodies) desirably have 5 to 30 vol% pores. Preferably it is 12-22 vol%, More preferably, it is 14-19 vol%. When the porosity is less than 5 vol%, the green compact may be damaged due to springback caused by recovery of elastic deformation of the raw material powder when the molding pressure is released. In addition, when the number of pores is more than 30 vol%, the mechanical strength of the sintered body is weakened, and as described later, even if it is attempted to be mechanically fixed on the core metal 11 by caulking or press fitting, etc. End up. In addition, the green compact may not be formed due to insufficient adhesion between the particles.

Since magnetic powder and non-magnetic metal powder are expensive, it is preferable that the plate thickness is thin. In view of compression moldability and handling, the preferred plate thickness is 0.3 mm to 5 mm, more preferably 0.6 mm to 3 mm. When the plate thickness is less than 0.3 mm, it is difficult to fill the mold and it is difficult to obtain a green molded body. Moreover, since the obtained green molded object may also be damaged at the time of handling, it is not preferable. On the other hand, when the green molded body is thicker than 10 mm, the moldability and handling are improved, but it is disadvantageous in terms of cost. On the other hand, when the thickness is too thick, uneven density of the green molded body tends to occur, and deformation after firing tends to occur. From these points, the plate thickness is preferably 0.3 mm to 5 mm.
The obtained green molded body is heated and sintered in a furnace as shown in FIG. 4 to form a disk-shaped sintered body. The heating and sintering in the furnace may be performed in an electric furnace in the atmosphere, or may be performed in a pusher furnace or an inert furnace while flowing an inert gas in a vacuum furnace.

The sintered body forming the magnetic encoder 10 may be provided with a rust preventive coating 22 as shown in FIG. In other words, the rust preventive film 22 is an anticorrosive film. The rust-proof coating 22 can be a clear high anti-corrosion paint. This paint can also be expected to have an effect as an adhesive between the core metal 11 and the sintered body, and penetrates into the pores of the surface layer of the sintered porous body and is suitably held on the surface by the anchor effect of the clear coating film component. Even during long-term use, good adhesion can be maintained as a rust-proof coating layer.
Examples of clear anticorrosive paints include modified epoxy paints, modified epoxy phenol curable paints, epoxy melamine paints, and acrylic paints. Among these, a modified epoxy phenol curing type and epoxy melamine type clear coating are particularly suitable.
Also, apply the clear to vacuum or impregnation (dipping), spray (spray) coating, electrostatic coating, etc. on fat or washed sintered body, and adhere to the sintered body by natural or forced air drying. The solvent component in the clear is removed, and the clear layer is baked on the sintered body under a predetermined baking condition (temperature and time), so that the rust preventive coating 22 is applied to the surface of the multipolar magnet 14 as shown in FIG. May be formed. The rust preventive coating 22 may be formed on the entire surface of the magnetic encoder 10. When this magnetic encoder 10 is attached to, for example, a wheel bearing, the film thickness of the anticorrosion (corrosion) film formed as described above is not particularly limited as long as it can satisfy the corrosion resistance required for the wheel bearing. However, 0.5 μm or more is desirable.
When used as a wheel bearing, if sand particles or the like are caught in the gap between the magnetic sensor 15 and the surface of the magnetic encoder 10, the surface of the magnetic encoder 10 may be damaged. If the thickness of the coating is thinner than 0.5 μm, the scratches may reach the sintered body as the base material, and the generation of rust from there may not be prevented.

  The metal that is the material of the core metal 11 is preferably a magnetic material, particularly a metal that is a ferromagnetic material. For example, a steel plate that is magnetic and has rust prevention properties is used. As such a steel plate, a ferritic stainless steel plate (JIS standard SUS430 series or the like), a rust-proof rolled steel plate, or the like can be used.

The shape of the core metal 11 can be various annular shapes, but a shape capable of fixing the multipolar magnet 14 is preferable. In particular, a shape capable of performing mechanical fixing such as caulking and fitting fixing is preferable.
In the case of caulking and fixing, for example, as shown in FIG. 1B, the core metal 11 includes an inner diameter side cylindrical portion 11a serving as a fitting side, an upright plate portion 11b extending from one end to the outer diameter side, The cross section formed by the other cylindrical portion 11c of the radial edge has a generally inverted Z-shaped annular shape.
The cylindrical portion 11a, the upright plate portion 11b, and the other cylindrical portion 11c are integrally formed by pressing from a metal plate such as a steel plate. The standing plate portion 11b is formed flat, and a non-magnetized sintered body of the multipolar magnet 14 is built on the surface of the flat standing plate portion 11b, and the other cylindrical portion 11c of the outer peripheral edge is crimped. Thus, the multipolar magnet 14 is fixed in an overlapping state with the standing plate portion 11 b of the core metal 11. The other cylindrical portion 11c has a crimped portion at the front end side portion or substantially the whole in its cross section. Further, this caulking portion extends over the entire circumference of the core metal 11 and thus has an annular shape. The portion fixed by the other cylindrical portion 11 c that is the crimping portion of the multipolar magnet 14 is a recessed portion 14 a that is recessed from the surface to be detected of the multipolar magnet 14, and the crimping portion of the core metal 11. The other cylindrical portion 11c is configured not to protrude from the surface to be detected of the multipolar magnet 14. The recessed portion 14 a is formed as a stepped portion that is slightly retracted to the back side from the surface to be detected of the multipolar magnet 14. A portion of the outer peripheral edge of the multipolar magnet 14 on the back side with respect to the recessed portion 14a is a curved surface having a circular cross section, and a crimped portion of the other cylindrical portion 11c is formed along the curved surface portion. As shown in the sectional view of FIG. 5, the caulking and fixing may be performed by caulking and fixing the outer periphery of the multipolar magnet 14 over the entire circumference.

  The mixed magnetic powder sintered magnet disk provided along the circumferential direction on the metal core 11 that is a metal annular member as described above becomes a multipolar magnet 14 by being magnetized in multiple directions in the circumferential direction. The magnet 14 and the cored bar 11 constitute a magnetic encoder 10. In this case, the mixed magnetic powder sintered magnet disk (sintered body) mixed with magnetic powder using nonmagnetic metal powder as a binder is adjusted with a powder mixer while adjusting the composition ratio of the nonmagnetic metal powder and magnetic powder. By dispersing, a dry blend of powders can be obtained. Therefore, the relative content rate (volume fraction) of the magnetic powder in the sintered body can be increased. Therefore, the magnetic force stably sensed by the magnetic sensor 15 (FIG. 3) can be easily obtained, and it is not necessary to make the multipolar magnet 14 thick.

As described above with reference to FIG. 3, the magnetic encoder 10 having this configuration is used for rotation detection with the magnetic sensor 15 facing the multipolar magnet 14. When the magnetic encoder 10 is rotated, the magnetic sensor 15 detects the passage of the magnetic poles N and S magnetized in the multipole of the multipolar magnet 14, and the rotation is detected in the form of pulses. The pitch p (FIG. 2) of the magnetic poles N and S can be set finely. For example, it is possible to obtain an accuracy that the pitch p is 1.5 mm and the pitch difference is ± 3%, thereby enabling highly accurate rotation detection. The pitch mutual difference is a value indicating a difference in distance between the magnetic poles detected at a position away from the magnetic encoder 10 by a predetermined distance as a ratio to the target pitch. When the magnetic encoder 10 is applied to the bearing seal device 5 as shown in FIG. 3, the rotation of the bearing to which the magnetic encoder 10 is attached is detected.
Since the multi-pole magnet 14 is made of a sintered body (mixed magnetic powder sintered disk) mixed with magnetic powder, the magnetic pole can be thinned while securing a magnetic force to obtain stable sensing as shown below. 10 can be made compact, and it is excellent in wear resistance and productivity.

Furthermore, the surface hardness of the multipolar magnet 14 is harder than that of an elastic member or elastomer coder containing conventional magnetic powder or magnetic particles. For this reason, when applied to the rotation detection device 20 for detecting wheel rotation, particles such as sand particles bite into the gap between the surface of the rotation-side multipolar magnet 14 and the surface of the stationary-side magnetic sensor 15 during vehicle travel. Even if it is inserted, wear damage of the multipolar magnet 14 hardly occurs, and there is a significant reduction effect of wear as compared with a conventional elastic body.
The flatness of the surface of the mixed magnetic powder sintered magnet disk that becomes the multipolar magnet 14 provided along the circumferential direction on the metal core 11 that is a metal annular member is preferably 200 μm or less, and preferably 100 μm or less. . When the flatness of the disk surface is higher than 200 μm, the gap between the magnetic sensor 15 and the disk surface (air gap) changes during the rotation of the magnetic encoder 10, thereby degrading the sensing accuracy.
For the same reason, the surface runout of the mixed magnetic powder sintered magnet disk surface during rotation of the magnetic encoder 10 is preferably 200 μm or less, and preferably 100 μm or less.

  Next, an example of a wheel bearing that is a bearing with a magnetic encoder provided with the magnetic encoder 10 and an example of the seal device 5 will be described with reference to FIGS. As shown in FIG. 6, the wheel bearing includes an inner member 1 and an outer member 2, a plurality of rolling elements 3 accommodated between the inner and outer members 1 and 2, and the inner and outer members 1 and 2. Sealing devices 5 and 13 for sealing the end annular space. The sealing device 5 at one end is provided with a magnetic encoder 10. The inner member 1 and the outer member 2 have raceway surfaces 1a and 2a of the rolling element 3, and each raceway surface 1a and 2a is formed in a groove shape. The inner member 1 and the outer member 2 are an inner peripheral member and an outer peripheral member that are rotatable with respect to each other via the rolling elements 3, respectively. An assembly member in which the bearing inner ring and the bearing outer ring are combined with another component may be used. Further, the inner member 1 may be a shaft. The rolling element 3 consists of a ball or a roller, and a ball is used in this example.

  This wheel bearing is a double-row rolling bearing, more specifically, a double-row angular contact ball bearing, and the inner ring of the bearing is a pair of split type in which the raceway surfaces 1a and 1a of the respective rolling element rows are respectively formed. It consists of inner rings 18 and 19. The inner rings 18 and 19 are fitted to the outer periphery of the shaft portion of the hub ring 6 and constitute the inner member 1 together with the hub ring 6. The inner member 1 is integrated with the hub ring 6 and one inner ring 18 instead of the three-piece assembly part including the hub ring 6 and the pair of split inner rings 18 and 19 as described above. It is good also as what consists of two components comprised by the hub ring with a raceway surface and the other inner ring | wheel 19. FIG.

One end (for example, an outer ring) of the constant velocity universal joint 7 is connected to the hub wheel 6, and a wheel (not shown) is attached to the flange portion 6 a of the hub wheel 6 with a bolt 8. The other end (for example, inner ring) of the constant velocity universal joint 7 is connected to the drive shaft.
The outer member 2 includes a bearing outer ring, and is attached to a housing (not shown) including a knuckle or the like in the suspension device. The rolling elements 3 are held by a holder 4 for each row.

FIG. 7 shows an enlarged view of the sealing device 5 with a magnetic encoder. The sealing device 5 is the same as that shown in FIG. 3 and a part of the sealing device 5 has been described above, but the details will be described with reference to FIG. The sealing device 5 is attached to a rotating member of the inner member 1 and the outer member 2 with the magnetic encoder 10 or its core 11 serving as a slinger. In this example, since the member on the rotation side is the inner member 1, the magnetic encoder 10 is attached to the inner member 1.
The magnetic encoder 10 is disposed in the space between the outer member 2 and the inner member 1 on the inner side of the end surface 2k of the outer member 2 which is a fixed side member of the outer member 2 and the inner member 1. Has been. In this embodiment, the magnetic encoder 10 is entirely composed of the raceway surfaces 1a and 2a in the space between the inner member 1 and the outer member 2, and the end surfaces 1k and 2k of the inner member 1 and the outer member 2. Is housed in between.

  This sealing device 5 has annular sealing plates (11), 12 made of first and second metal plates attached to the inner member 1 and the outer member 2, respectively. The first seal plate (11) is the core metal 11 in the magnetic encoder 10 and will be described as the core metal 11 below. The magnetic encoder 10 is according to the first embodiment described above with reference to FIGS. 1 to 3, and redundant description thereof is omitted. The rotation detection device 20 for detecting the wheel rotation speed is configured by arranging the magnetic sensor 15 as shown in the figure so as to face the multipolar magnet 14 in the magnetic encoder 10.

The second seal plate 12 is a member constituting the seal member 9 (FIG. 3), and slides on the side lip 16a and the cylindrical portion 11a that are in sliding contact with the upright plate portion 11b of the core metal 11 that is the first seal plate. Radial lips 16b and 16c that are in contact with each other are integrally provided. The lips 16 a to 16 c are provided as a part of the elastic member 16 that is vulcanized and bonded to the second seal plate 12. The number of the lips 16a to 16c may be arbitrary, but in the example of FIG. 7, one side lip 16a and two radial lips 16c and 16b positioned inside and outside in the axial direction are provided. The second seal plate 12 is configured such that an elastic member 16 is held in a fitting portion with the outer member 2 that is a fixed side member. That is, the elastic member 16 has a tip cover portion 16d that covers from the inner diameter surface of the cylindrical portion 12a to the outer diameter of the tip portion, and this tip cover portion 16d is formed between the second seal plate 12 and the outer member 2. Intervenes in the fitting part.
The cylindrical portion 12a of the second seal plate 12 and the other cylinder portion 11c of the core metal 11 that is the first seal plate are opposed to each other with a slight radial gap, and the labyrinth seal 17 is configured by the gap.

According to the wheel bearing of this configuration, the rotation of the inner member 1 rotating together with the wheel is detected by the magnetic sensor 15 via the magnetic encoder 10 attached to the inner member 1, and the wheel rotation speed is detected. The
Since the magnetic encoder 10 is a constituent element of the sealing device 5, the rotation of the wheel can be detected without increasing the number of parts. The wheel bearing is generally exposed to a road surface environment, and particles such as sand particles may be caught between the magnetic encoder 10 and the magnetic sensor 15 facing the magnetic encoder 10 as described above. Since the ten multipolar magnets 14 are made of a sintered body and are hard, wear damage on the surface of the multipolar magnets 14 is greatly reduced as compared with a conventional elastic body. Further, the space at the bearing end portion of the wheel bearing 5 is a narrow space limited by the constant velocity joint 7 and the bearing support member (not shown) in the periphery, but the multipolar magnet 14 of the magnetic encoder 10 is the above-described space. Therefore, the rotation detector 20 can be easily arranged.
As for the seal between the inner and outer members 1 and 2, the first seal plate is used for sliding contact of the seal lips 16 a to 16 c provided on the second seal plate 12 and the cylindrical portion 12 a of the second seal plate 12. It is obtained with the labyrinth seal 17 configured by the other cylindrical portion 11c of a certain core metal 11 facing each other with a slight radial gap.

  The magnetic encoder 10 in each of the above embodiments has been described as a component of the bearing seal device 5. However, the magnetic encoder 10 of each of the embodiments is a component of the seal device 5. Not limited to this, it can be used alone for rotation detection. For example, the magnetic encoder 10 in the embodiment of FIG. 1 may be provided in the bearing separately from the seal device 5.

(A) is a fragmentary perspective view of the magnetic encoder concerning the 1st Embodiment of this invention, (B) is a fragmentary perspective view which shows the assembly process of the magnetic encoder. It is explanatory drawing of the magnetic pole which shows the same magnetic encoder from the front. It is a partial fracture front view showing a sealing device provided with the magnetic encoder and a magnetic sensor. It is process drawing which uses a green body as a sintered compact. It is a fragmentary perspective view of the magnetic encoder concerning this embodiment other than this invention. It is a sectional view of the whole wheel bearing provided with the magnetic encoder concerning a 1st embodiment. It is a fragmentary sectional view of the bearing for the wheels.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner member 2 ... Outer member 1k, 2k ... End surface 1A ... Inner member 2A ... Outer member 3 ... Rolling body 5 ... Sealing device 10 ... Magnetic encoder 11, 11A, 11B ... Core metal (1st seal | sticker) Board)
11a ... Cylindrical part 11b ... Standing plate part 11c ... Other cylinder part 12 ... Second seal plate 14 ... Multipolar magnet 15 ... Magnetic sensor 16a ... Side lip 16b, 16c ... Radial lip 20 ... Rotation detection device 22 ... Rust prevention coating

Claims (6)

In a magnetic encoder including a multipolar magnet having magnetic poles alternately formed in the circumferential direction and a core metal supporting the multipolar magnet, the multipolar magnet is a mixture of magnetic powder and nonmagnetic metal powder. A sintered body of a porous body obtained by sintering a green compact having pores formed therein, wherein the multipolar magnet is bonded and fixed to the core metal with an adhesive, and the adhesive Is a clear anticorrosive paint, and a rust preventive film with a film thickness of 0.5 μm or more is formed on the entire surface of the magnetic encoder having the above-mentioned multipolar magnet and cored bar by baking with this clear anticorrosive paint. Magnetic encoder.   2. The magnetic encoder according to claim 1, wherein a rust preventive coating is applied to the multipolar magnet, and the multipolar magnet is fixed to the core metal by an effect of the rust preventive coating as an adhesive.   3. The magnetic encoder according to claim 1, wherein the multipolar magnet is bonded and fixed to the core metal with an adhesive and is fixed by crimping the core metal.   4. The cross-section of the cored bar according to claim 3, wherein the core bar has a substantially inverted Z-shaped cross section including a cylindrical portion, a vertical plate portion extending from one end thereof toward an outer diameter side, and another cylindrical portion extending from an outer diameter edge of the vertical plate portion. A magnetic encoder having an annular shape, in which the multipolar magnet is fixed to a cored bar by caulking the other cylindrical portion.   In a rolling bearing in which a rolling element is interposed between raceways facing the inner ring and the outer ring, a magnetic encoder is attached to a rotating side wheel of the inner ring and the outer ring, and the magnetic encoder is fixed in a space between the inner ring and the outer ring. A bearing with a magnetic encoder, wherein the magnetic encoder according to any one of claims 1 to 4 is used as the magnetic encoder. An outer member having a double-row raceway surface formed on the inner circumferential surface, an inner member having a raceway surface facing the raceway surface of the outer member on the outer circumferential surface, and a composite member interposed between the two raceway surfaces. A wheel bearing comprising a rolling element in a row and rotatably supporting the wheel with respect to the vehicle body,
A magnetic encoder is attached to the rotation side member of the inner member and the outer member, and the magnetic encoder is disposed on the inner side of the end surface of the fixed member in the space between the inner member and the outer member, 5. A wheel bearing using the magnetic encoder according to claim 1 as a magnetic encoder.

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