JP2006189365A - Magnetic encoder and bearing for wheel equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic encoder superior in corrosion protection and productivity, having no problem regarding the occurrence of rust, even when it is used over a long period of time or in adverse environments, and capable of achieving low cost. <P>SOLUTION: The magnetic encoder 10 is provided with both a multi-pole magnet 14 in which magnetic poles are formed alternately in the circumferential direction and a core bar 11 for supporting the multi-pole magnet 14. The multi-pole magnet 14 is a sintered body, acquired by sintering a mixed powder of magnetic powder and nonmagnetic metal powder. The multi-pole magnet 14 is fixed to the core bar 11 by temporarily tightening the core bar 11. The multi-pole magnet 14 made of the sintered body is plated with a corrosion protecting coating 22. Various types of platings may be adopted as the plating, and zinc-iron alloy or zinc-nickel alloy platings are superior in corrosion protection. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder used for a rotation detecting device for a bearing portion that rotates relatively, and a wheel bearing provided with the same. The present invention relates to a magnetic encoder which is a component of a bearing seal to be mounted.

  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 is generally arranged so as to be separated from the seal device for sealing the bearing and constitute one independent rotation detection device. . Such a conventional example has a structure in which a toothed rotor fitted to a rotating shaft is sensed and detected by a rotation detection sensor attached to a knuckle, and a bearing used is provided independently on the side thereof. Protected against intrusion of moisture or foreign matter by the sealed 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, Is shown, and a rotary disk is attached to the rotary member, and a multi-polar coder is attached to the rotary disk. The coder used is made of an elastomer to which magnetic particles are added, and is a sealing means in which the side surface of the coder is substantially flush with the fixing member.

  A coder made of plastic (plastomer) containing magnetic powder or magnetic particles can be formed into a bowl using a mold suitable for the product shape, like conventional injection molding or compression molding. Or by forming the sheet by extrusion molding using a T-shaped die or sheet molding such as calendering, and making it into a product shape by punching, etc., and then adhesively fixing on a metal substrate with an adhesive or the like 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

However, each of the above magnetic encoders contains a magnetic powder in a multipolar magnet. On the other hand, when used for a bearing for an automobile, etc., it is placed in a harsh environment exposed to road surface salty mud water. Rust generation during long-term use becomes a problem. In particular, when the content of magnetic powder is increased for miniaturization, rust is likely to occur. Then, although it thought about carrying out the antirust process of the multi-pole magnet of a magnetic encoder, selection of an appropriate antirust material is difficult.
In addition, the elastomer or plastomer in which the multipolar magnet contains the magnetic powder as described above has various problems as described below. The thing made into the sintered compact which sintered the powder mixed with powder was proposed (Japanese Patent Application No. 2001-290300). When such a multipolar magnet is used, a rust prevention treatment according to the characteristics is required.

  Further, the present applicant has proposed a multipolar magnet having a clear anticorrosive coating of a clear anticorrosive coating (Japanese Patent Application No. 2003-012710). However, better corrosion resistance may be desired. In addition, in order to ensure the film thickness uniformity and flatness of the film formation surface, the process control width such as coating and baking during film formation is narrow, and the yield may be poor. Furthermore, in order to improve the corrosion resistance between the cored bar and the sintered body in the state where the sintered multi-pole magnet is crimped to the cored bar, it is possible to impregnate with a modified epoxy clear paint, Although it may be painted, it is expensive and not economical.

An object of the present invention is to provide a magnetic encoder that can secure a magnetic force with which stable sensing can be obtained, has excellent corrosion resistance, and does not have a problem of rust generation even in long-term use and use under severe environments.
Another object of the present invention is to provide a wheel bearing that can detect rotation with a compact configuration without increasing the number of parts, and is excellent in corrosion resistance and productivity of a magnetic encoder for detecting rotation, and can reduce costs. It is to be.

  The magnetic encoder of the present invention is a magnetic encoder comprising a multipolar magnet having magnetic poles alternately formed in the circumferential direction and a cored bar that supports the multipolar magnet. It is a sintered body obtained by sintering powder mixed with powder, and is characterized in that at least the surface of the sintered body is provided with an anticorrosion film by plating.

  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 mixing ratio of the magnetic powder is increased while ensuring the strength of the sintered body. Therefore, it is possible to secure a magnetic force that can provide stable sensing, and to achieve a compact size. When the blending ratio of magnetic powder is increased, rust is likely to occur. However, because the anti-corrosion film by plating is applied to the sintered multi-pole magnet, the surface of the sintered body is porous. Therefore, it is possible to form a good film and to have excellent corrosion resistance. That is, according to the plating, it is possible to form an anticorrosion film composed of a plating layer on a fine portion on the porous body. That is, for a multipolar magnet made of a sintered body, a plating made of an anticorrosion film component 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 anticorrosion film component. Even during long-term use, good adhesion can be maintained as an anticorrosive film. Further, even when the multipolar magnet is fixed to the core metal by caulking or the like, an anticorrosion film is formed on the contact surface between the core metal and the multipolar magnet or the edge thereof without any gaps. An anticorrosion film is formed on the cored bar without gaps. As a result, the corrosion resistance is improved, and the magnetic encoder is free from the problem of rust even when used for a long time or under severe conditions.

  The plating may be zinc-iron alloy plating. Zinc-iron alloy plating is zinc plating containing 0.3 to 0.6 wt% of iron, and by containing a small amount of iron, excessive corrosion protection of zinc is suppressed, so the time for sacrificial corrosion protection of zinc is reduced. By being suppressed, the corrosion resistance is improved. In zinc-iron alloy plating, chromate treatment can be produced without silver salt.

  The plating may be zinc-nickel alloy plating. Zinc-nickel alloy plating is zinc plating containing 5 to 10 wt% of nickel, and has less hydrogen embrittlement and superior heat and corrosion resistance compared to normal plating. Therefore, it is particularly effective in the case of a magnetic encoder used in a high temperature environment.

  The multipolar magnet may be fixed to the cored bar by caulking the cored bar. In that case, the surface treatment may be performed in the state of a sintered body cored bar integrated product. When the surface treatment is performed in the state of a sintered metal core integrated product, the number of processes is fewer than in the case where the surface treatment is performed individually, the productivity is excellent, and the cost can be reduced. In this case, since the anticorrosion film is formed by plating, the film can be formed on the fine portion as described above, and the anticorrosion film can be formed on the integrated product of the multipolar magnet and the core metal without any gap. Accordingly, the corrosion resistance is excellent. The term “clamping” as used in this specification refers to the entire process of clamping and fixing by applying plastic pressure and plastic deformation, and includes clamping by bending or staking.

  The magnetic powder may be a samarium-based magnetic powder or a neodymium-based magnetic powder. When these samarium magnetic powder and neodymium magnetic powder are used, a strong magnetic force can be obtained. As the samarium magnetic powder, samarium iron (SmFeN) magnetic powder is used, and as the neodymium magnetic powder, neodymium iron (NdFeB) magnetic powder is used. In addition, the magnetic powder may be manganese aluminum (MnAl) gas atomized powder.

  The nonmagnetic metal powder may be tin powder. When the magnetic powder is ferrite powder, samarium-based magnetic powder, or neodymium-based magnetic powder, tin powder may be used as the non-magnetic metal powder.

  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 only the ferrite powder, it is possible to manufacture the ferrite powder at a low cost while improving the magnetic force by mixing the samarium-based magnetic powder or the neodymium-based magnetic powder, which are rare earth-based magnetic materials, with a necessary amount.

The wheel bearing according to the present invention includes an outer member having a double row rolling surface on the inner periphery, an inner member having a double row rolling surface on the outer periphery facing the rolling surface, and an opposing rolling In a wheel bearing comprising a double row rolling element interposed between the surfaces, and rotatably supporting the wheel with respect to the vehicle body,
A magnetic encoder is fitted to the inboard side end of the rotation-side member of the outer member and the inner member, and this magnetic encoder is a magnetic encoder having any one of the above-described configurations of the present invention.
The wheel bearing is generally exposed to a road surface environment, and the magnetic encoder may be subjected to salt mud water. However, since the anticorrosion film by plating is applied to the entire sintered body or the sintered metal core constituting the magnetic encoder, it has excellent corrosion resistance and is highly effective in preventing the magnetic encoder from being rusted by salt mud water.
Further, particles such as sand particles may be caught between the magnetic encoder and the magnetic sensor facing the magnetic encoder. The following protection is provided against this biting. That is, the surface height of the sintered multipolar magnet made of magnetic powder and non-magnetic metal powder is harder than that of an elastic member or elastomer coder containing conventional 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 wheel bearing according to the present invention is such that a sealing member having a plurality of lips that are in sliding contact with the core bar of the magnetic encoder is fitted to a fixed member of the outer member and the inner member. Also good.
In the case of this configuration, a sealing device is constituted by the sealing member and the magnetic encoder, and the magnetic encoder is a component of the sealing device. Therefore, the rotation of the wheel can be detected with a more compact configuration without increasing the number of parts. Further, when the magnetic encoder is configured in the sealing device in this way, there is a problem of biting of sand particles or the like between the magnetic encoder and the magnetic sensor due to exposure to the above road surface environment. As described above, since the surface height of the multipolar magnet is hard, an effect of reducing wear damage can be obtained.

The magnetic encoder of the present invention is a magnetic encoder comprising a multipolar magnet having magnetic poles alternately formed in the circumferential direction and a cored bar that supports the multipolar magnet, wherein the multipolar magnet comprises magnetic powder and nonmagnetic metal. It is a sintered body made by sintering powder mixed with powder, and at least the surface of this sintered body is coated with an anti-corrosion film by plating, so it has excellent corrosion resistance, and rust is generated even in long-term use and harsh environments There will be no problems.
In particular, when the plating is zinc-iron alloy plating, the corrosion resistance can be further improved. Further, when the plating is zinc-nickel alloy plating, it has excellent heat and corrosion resistance.
Since the wheel bearing of the present invention includes the magnetic encoder of the present invention, rotation detection can be performed with a compact configuration, and the durability, corrosion resistance, and productivity of the magnetic encoder for rotation detection are excellent. The cost can be reduced. In particular, when the component of the sealing device is a magnetic encoder, the rotation of the wheel can be detected without increasing the number of parts.

  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 magnetic poles N and S are formed to have a predetermined pitch p in the pitch circle diameter PCD (FIG. 2). The multipolar magnet 14 is a sintered body obtained by sintering a green compact of powder mixed with magnetic powder and nonmagnetic metal powder. The multipolar magnet 14 is attached to the core metal 11 by crimping the core metal 11. Fix it. An anticorrosive film 22 is applied to the sintered core metal integrated product 21 in which the sintered body is fixed to the core metal 11 by surface treatment.

  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 18 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 18 includes the magnetic encoder 10 and a fixed-side seal member 9. A specific configuration of the sealing device 18 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. For example, when ferrite powder alone is insufficient in magnetic force, the ferrite powder can be mixed with the required amount of rare earth magnetic material samarium iron (SmFeN) magnetic powder or neodymium iron (NdFeB) magnetic powder to improve the magnetic force. It can also be manufactured at low cost.

  The non-magnetic metal powder forming the multipolar magnet 14 may be a powder of tin, copper, aluminum, nickel, zinc, tungsten, manganese, or a non-magnetic stainless steel metal powder alone (one type). Body, a mixed powder composed of two or more kinds, or an alloy powder composed of two or more kinds can be used.

  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 diameter edge is a substantially inverted Z-shaped annular shape. The cored bar 11 may have an L-shaped cross section, and in that case, the cored bar 11 in FIG. 1B has a shape in which the other cylindrical portion 11c is omitted. When the metal core 11 has an L-shaped cross section, for example, a claw portion or the like is provided on the upright plate portion 11b or the like and fixed by caulking.

  In the cored bar 11 of FIG. 1B, the cylindrical portion 11a, the standing plate portion 11b, and the other cylindrical portion 11c are integrally press-formed 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 on the standing plate portion 11 b of the core metal 11, and the sintered core metal integrated product 21 is obtained. In the other cylindrical portion 11c, a tip side portion or substantially the whole in the cross section serves as a caulking portion. Further, the caulking portion extends over the entire circumference of the core metal 11 and thus has an annular shape. In addition, the part fixed by the other cylindrical part 11c of the multipolar magnet 14 becomes the recessed part 14b dented rather than the surface used as the to-be-detected surface of the multipolar magnet 14, Thereby, the plastic deformation part 11ca becomes a multipolar magnet. 14 so as not to protrude from the surface to be detected.

  The caulking and fixing may be performed as shown in the sectional view and the front view in FIGS. In this example, the cored bar 11 has a cylindrical portion 11a on the inner diameter side, a standing plate portion 11b extending from one end thereof to the outer diameter side, and a cylindrical other cylindrical portion 11c on the outer diameter edge, as in the example of FIG. The cross section is generally an inverted Z-shaped ring. In addition, a plastic deformation portion 11ca that is plastically deformed in a protruding state toward the inner diameter side by staking or the like is provided at a plurality of circumferential positions in the other cylindrical portion 11c, and the multipolar magnet 14 is attached to the core metal 11 by the plastic deformation portion 11ca. Are fixed to the standing plate portion 11b. Also in this example, the portion fixed by the plastic deformation portion 11ca of the multipolar magnet 14 is a dent portion 14b that is recessed from the surface of the multipolar magnet 14 that becomes the detection surface, whereby the plastic deformation portion 11ca is The multipolar magnet 14 is configured not to protrude from the surface to be detected. The recessed portion 14b is formed as an inclined surface 14b that approaches the rear surface side from the front surface as it reaches the outer diameter side.

  In each example shown in FIG. 1 and FIG. 4, the cored bar 11 has a two-stage shape in which the standing plate portion b is shifted in the axial direction between the inner peripheral portion 11 ba and the outer peripheral portion 11 bb as shown in FIG. 6. It can also be made. In FIG. 6, although not shown, the multipolar magnet 14 is disposed on the protruding side surface of the other cylindrical portion 11 c in the standing plate portion 11 b as in the example of FIG. 1.

  Further, as shown in FIG. 7, in the metal core 11 having a substantially inverted Z-shaped cross section similar to the example of FIG. 1, tongue-like claw portions are provided at a plurality of circumferential positions on the edge of the other cylindrical portion 11c. The multipolar magnet 14 may be fixed to the metal core 11 by providing 11 cb and plastically deforming the tongue-like claw portion 11 cb toward the inner diameter side as shown by an arrow, that is, by crimping the tongue-shaped claw portion 11 cb so as to be bent. The multipolar magnet 14 is disposed on the protruding side surface of the other cylindrical portion 11c in the upright plate portion 11b as in the example of FIG. Also in this example, like the example of FIG. 6, the standing plate portion 11b has a two-stage shape. When the standing plate portion 11b has a two-stage shape, the side shape on the standing plate portion 11b side of the multipolar magnet 14 is a side shape along the two-step shape of the standing plate portion 11b as shown in FIG. It is also good.

  As in each of the above examples, the anticorrosive film 22 is applied by plating to the surface of the sintered core metal integrated product 21 formed by crimping and fixing the multipolar magnet 14 to the core metal 11. The anticorrosion film 22 by plating may be applied in a single state of the multipolar magnet 14 before being fixed to the core metal 11.

  The plating includes black chrome plating, black nickel plating (black nickel), nickel-iron plating, nickel-cobalt-tungsten plating, tin plating, zinc-iron alloy plating, copper-nickel plating, copper tin (bronze) Plating, iron-carbon alloy plating, Kanigen plating (electroless nickel plating), tin-nickel plating, tin-nickel-copper plating, tin-lead plating, tin-zinc alloy plating, lead plating, zinc-nickel alloy plating, etc. Can be mentioned. Of these, zinc-iron alloy plating and zinc-nickel alloy plating are particularly suitable.

Zinc-iron alloy plating is zinc plating containing 0.3 to 0.6 wt% of iron. By containing a small amount of iron, excessive corrosion protection of zinc is suppressed, so the time for sacrificial corrosion protection of zinc is reduced. By being suppressed, the corrosion resistance is improved. Zinc-iron alloy plating can be produced without silver salt by chromate treatment.
Zinc-nickel alloy plating is zinc plating containing 5 to 10 wt% of nickel, and has less hydrogen embrittlement and superior heat and corrosion resistance compared to normal plating. Therefore, it is particularly effective in the case of a magnetic encoder used in a high temperature environment.

  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 18 as shown in FIG. 3, the rotation of the bearing to which the magnetic encoder 10 is attached is detected.

Since the magnetic encoder 10 is provided with the anticorrosion film 22 by plating on the multipolar magnet 14 of the sintered body, a favorable film can be formed regardless of whether the surface of the sintered body is a porous body, It can be excellent in corrosion resistance. That is, according to the plating, it is possible to form an anticorrosion film on a fine portion on the porous body, which is impossible with the liquid coating. That is, for a multipolar magnet made of a sintered body, a plating made of an anticorrosive film component 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 anticorrosive film component. Even during long-term use, good adhesion can be maintained as an anticorrosive film. Further, even when the multipolar magnet 14 is fixed to the core metal 11 by caulking or the like, the anticorrosion film 22 is formed without any gap on the contact surface between the core metal 11 and the multipolar magnet 14 or the edge thereof. . As a result, the corrosion resistance is improved, and the magnetic encoder is free from the problem of rust even when used for a long time or under severe conditions. Therefore, it can be used in an environment where rust is likely to occur, such as a wheel bearing.
In particular, when the plating is zinc-iron alloy plating or zinc-nickel alloy plating, more excellent corrosion resistance can be obtained.

  In addition, since the multipolar magnet 14 is made of a sintered body mixed with magnetic powder, it can increase the blending ratio of the magnetic powder while ensuring the strength of the sintered body, and can secure a magnetic force that provides stable sensing. It is excellent in wear 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 multipolar magnet 14 on the rotating side and the surface of the magnetic sensor 15 on the fixed side while the vehicle is running. 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.

  Next, the test results of the corrosion resistance performance of the anticorrosion film 22 by plating will be described together with Tables 1 and 2. The test was conducted for each sample to be Examples 1 to 6 and Comparative Examples 1 and 2 according to the above embodiment. In the above sample, samarium iron (Sm—Fe—N) based magnetic powder was used as the magnetic powder constituting the sintered multipolar magnet 14, and Sn was used as the nonmagnetic metal powder serving as the binder. As shown in Tables 1 and 2, the blending ratio is 60 wt% for the magnetic powder and 40 wt% for the binder. With this blending ratio, a green body (unsintered green compact) of φ54 mm × φ66 mm × 1.5 mm was molded with a pressure press and fired in the air for 1 hour. The shapes of the sintered body (multipolar magnet 14) and the cored bar 11 of each sample are those shown in FIG. In each sample which becomes Examples 1-3, the anticorrosion film 22 by zinc-iron alloy plating was formed. In each sample which becomes Examples 4-6, the anticorrosion film 22 by zinc-nickel alloy plating was formed. In contrast, each sample of Comparative Examples 1 and 2 was subjected to cationic electrodeposition. The film thickness of the anticorrosion film 22 was set to the thickness shown in the table. The unit of film thickness is μm. Note that “None” in the film thickness in Comparative Example 1 refers to a thickness that is so thin that it does not appear in units of 0.1 μm even though cationic electrodeposition was performed.

The following tests were performed on each of these samples.
(1) About each sample, NaCl heated at 80 degreeC was immersed in 5% solution for 24 hours, and the corrosion resistance performance was compared. Corrosion resistance was evaluated for the surface of the sintered body and the inner surface of the sintered body. In Tables 1 and 2, the marks ◎, ○, Δ, and × are shown in the order of excellent corrosion resistance.
(2) In order to evaluate the adhesion between the sintered body (multipolar magnet 14) and the cored bar 11, an iron jig was inserted into the gap between the sintered body and the cored bar 11 and was forcibly separated. When the adhesion is good, it does not peel off at the interface between the sintered body (multipolar magnet 14) and the cored bar 11, and breaks inside the sintered body, so that the amount of the coating film fixed on the surface of the cored bar 11 is large. In Table 1, ◎, ○, △, × marks are also shown in descending order of adhesion amount.

As shown in Table 1, among Examples 1 to 3 subjected to zinc-iron alloy plating and Examples 4 to 6 subjected to zinc-nickel alloy plating, each Example 2 having a film thickness of 10 μm and 30 μm was used. , 3, 5 and 6 were the most excellent evaluations in the four-step evaluation, and the adhesion was also excellent in both the surface and the inner diameter surface of the sintered body. Also in Example 1 and Example 4 in which the film thickness was reduced to 1 μm, both the surface and the inner diameter surface of the sintered body were evaluated as being the second best evaluation from the top in the four-step evaluation, and the adhesion was also good. ○ was the second best.
On the other hand, among Comparative Examples 1 and 2 subjected to cation electrodeposition shown in Table 2, Comparative Example 2 having a film thickness of 0.1 μm has a corrosion resistance of both the surface and the inner diameter surface of the sintered body. And the second lowest evaluation from the bottom in the four-stage evaluation, and the adhesion was the second lowest from the bottom. Further, Comparative Example 1 in which the cation electrodeposition to such an extent that the film thickness can be regarded as “None” was evaluated as Δ being the second lowest from the bottom for the surface of the sintered body, and × for the inner surface of the sintered body. The lowest rating. The adhesion was also Δ, the second evaluation from the bottom.

  As can be seen from Tables 1 and 2, when the anticorrosion film 22 is applied as a surface treatment by zinc-iron alloy plating or zinc-nickel alloy plating, corrosion resistance superior to that obtained by cationic electrodeposition is obtained. It was confirmed that The film thickness difference between the example and the comparative example is due to the fact that it is difficult to increase the film thickness by cation electrodeposition and that it is relatively thick by plating.

Next, an example of a wheel bearing provided with the magnetic encoder 10 and an example of the seal device 18 will be described with reference to FIGS. As shown in FIG. 8, the wheel bearing 10 is of the third generation type, and faces the outer member 1 having double-row rolling surfaces 1a on the inner periphery, and these rolling surfaces 1a. An inner member 2 having a rolling surface 2a, a double row rolling element 3 interposed between the opposing rolling surfaces 1a and 2a, and seal members for sealing both ends of the annular space between the inner and outer members 2 and 1, respectively. 8 and 9.
This wheel bearing 10 is a double-row rolling bearing, more specifically, a double-row angular contact ball bearing, and its inner member 2 includes a hub ring 5 and an inner ring 6 fitted to the outer periphery of the shaft portion. The rolling surfaces 2 a and 2 a in each row are formed on the outer circumferences of the hub wheel 5 and the inner ring 6. The hub wheel 5 has a wheel mounting flange 5 a on the outer periphery thereof, and a wheel (not shown) is mounted to the flange 5 a with a bolt 7. The outer member 1 is attached to the knuckle in the suspension device of the vehicle body with respect to the outer peripheral flange 1b. The rolling element 3 is a ball and is held by a cage 4.

  FIG. 9 shows an enlarged view of the sealing device 18 with a magnetic encoder. The sealing device 18 is the same as that shown in FIG. 3, and a part of the sealing device 18 has been described above, but details will be described with reference to FIG. The sealing device 18 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 sealing device 18 includes annular seal plates (11) and 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. 9, 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 cylindrical portion 11c of the core metal 11 serving as 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 component of the sealing device 18, the rotation of the wheel can be detected without increasing the number of parts. The wheel bearings are generally exposed to the road surface environment, and the magnetic encoder 10 may be covered with salty mud water. However, the entire sintered core metal integrated product 21 constituting the magnetic encoder 10 is protected by plating. Since the coating 22 is applied, it is possible to reliably prevent the magnetic encoder 10 from being rusted by salt mud water. Further, particles such as sand particles may be caught between the magnetic encoder 10 and the magnetic sensor 15 facing the magnetic encoder 10, but as described above, the multipolar magnet 14 of the magnetic encoder 10 is made of a sintered body. Since it is hard, wear damage on the surface of the multipolar magnet 14 is greatly reduced as compared with a conventional elastic body.

  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 constituted by the other cylindrical portion 11c of a certain core metal 11 facing each other with a slight radial gap.

  FIG. 10 shows another embodiment of the wheel bearing. This wheel bearing is of the second generation type, and the inner member 1 includes a hub wheel 5A and double row inner rings 6A and 6B fitted to the outer periphery of the hub wheel 5A. The outer ring of the constant velocity joint 7 is connected to the hub ring 5A. Other configurations are the same as those of the wheel bearing shown in FIGS. Although not shown in the example of FIG. 8, the wheel bearing of FIG. 8 is also connected to the outer ring of the constant velocity joint.

The wheel bearings shown in FIGS. 8 and 9 and the wheel bearing shown in FIG. 10 both show the case where the core metal 11 of the magnetic encoder 10 has the shape shown in FIG. As the encoder 10, the examples shown in FIGS. 4 to 7 may be used.
Further, when the magnetic encoder 10 is used as a component of the bearing seal device 18, the multipolar magnet 14 may be provided inward with respect to the bearing, contrary to the above embodiments. That is, the multipolar magnet 14 may be provided on the inner surface of the bearing of the core metal 11. In that case, the cored bar 11 is preferably made of a non-magnetic material.
Further, in a wheel bearing in which the outer member is a rotating member, a magnetic encoder is attached to the outer member.

(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 a perspective view which shows the back surface of an example of the multipolar magnet in the magnetic encoder. It is a perspective view which shows the back surface of the other example of the multipolar magnet in the same magnetic encoder. It is a fragmentary perspective view which shows an example of the metal core in the magnetic encoder. It is a fragmentary perspective view which shows the other example of the metal core in the magnetic encoder. 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. It is sectional drawing which shows the other example of the wheel bearing provided with the magnetic encoder concerning 1st Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner member 2 ... Outer member 3 ... Rolling body 10 ... Magnetic encoder 11 ... Core metal (1st sealing board)
DESCRIPTION OF SYMBOLS 14 ... Multipolar magnet 15 ... Magnetic sensor 16a ... Side lip 16b, 16c ... Radial lip 85 ... Sealing device 20 ... Rotation detection device 21 ... Sintered metal core integrated product 22 ... Anticorrosion film

Claims (6)

  In a magnetic encoder comprising a multipole magnet having magnetic poles alternately formed in the circumferential direction and a cored bar that supports the multipole magnet, the multipole magnet burns a mixed powder of magnetic powder and nonmagnetic metal powder. A magnetic encoder, characterized in that it is a sintered body, and at least a surface of the sintered body is coated with an anticorrosion film by plating.   The magnetic encoder according to claim 1, wherein the plating is zinc-iron alloy plating.   The magnetic encoder according to claim 1, wherein the plating is zinc-nickel alloy plating.   4. The magnetic encoder according to claim 1, wherein the multipolar magnet is fixed to the core metal by caulking the core metal. An outer member having a double row rolling surface on the inner periphery, an inner member having a double row rolling surface facing the rolling surface on the outer periphery, and a double row interposed between the opposing rolling surfaces In a wheel bearing comprising a rolling element and rotatably supporting the wheel with respect to the vehicle body,
5. The magnetic encoder according to claim 1, wherein a magnetic encoder is fitted to an inboard side end of a rotation-side member of the outer member and the inner member, and the magnetic encoder is the magnetic encoder according to claim 1. Wheel bearing.   6. The wheel bearing according to claim 5, wherein a seal member having a plurality of lips that are in sliding contact with the core of the magnetic encoder is fitted to a fixed member of the outer member and the inner member.

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