JP4633480B2 - Magnetic encoder and wheel bearing provided with the same - Google Patents

Description

  The present invention relates to a magnetic encoder and a wheel bearing provided with the magnetic encoder, and is used, for example, in a rotation detection device that detects the number of rotations of a wheel in an antilock brake system of an automobile.

  There are roughly two types of this type of rotation detection device: a passive type that reads the movement of the uneven teeth provided on the rotor as the magnitude of the magnetic change, and the strength of the magnetism associated with the rotation of the magnetic encoder. An active type that reads changes with a magnetic sensor such as a Hall IC is used.

  In an active type rotation detection device, a magnetic encoder is usually provided on the rotation side member of the wheel bearing, and a magnetic sensor is provided on the fixed side member.

The magnetic encoder includes, for example, an annular multipolar magnet in which N poles and S poles are alternately magnetized in the circumferential direction, and a core bar for fixing the multipolar magnet to the rotation side member. As the multipolar magnet, one made of an elastomer to which magnetic powder is added is known (see, for example, Patent Document 1). Recently, there are multipolar magnets that are sintered after compression molding a mixture of magnetic powder and non-magnetic metal powder (see, for example, Patent Document 2).
JP-A-6-281018 JP 2004-37441 A

  A multipolar magnet made of the above sintered body is very preferable as a product because it has the advantages of excellent wear resistance and low processing cost compared to an elastomer type multipolar magnet. There is a problem that it is difficult to make the density of the sintered body uniform throughout.

  The mixture of magnetic powder and nonmagnetic metal powder is compressed into a predetermined shape and then sintered. Normally, powder with a melting point lower than that of magnetic powder is used for nonmagnetic metal powder. When heated to a temperature higher than the melting point of nonmagnetic metal powder, nonmagnetic metal powder melts and functions as a binder for magnetic powder particles. To do. However, depending on the combination of the two, for example, when the nonmagnetic metal powder used has poor wettability to the magnetic powder, the molten nonmagnetic metal is unlikely to remain on the surface of the magnetic powder particles, and the non-magnetic metal powder is not inside the sintered body. The magnetic metal may be unevenly distributed or may flow out to the surface of the sintered body in some cases. For this reason, the density of the sintered body becomes non-uniform, and the required mechanical strength may not be obtained.

  An object of the present invention is to make uniform the density of a multipolar magnet in this type of magnetic encoder, particularly a multipolar magnet made of a sintered body.

  In order to solve the above problems, a magnetic encoder according to the present invention includes a multipolar magnet formed by compressing and molding a mixed powder of a magnetic powder and a nonmagnetic metal powder. It consists of 20 to 90 wt% magnetic powder and 10 to 80 wt% nonmagnetic metal powder, and is sintered at a temperature lower than the melting point of the nonmagnetic metal powder.

  As described above, by sintering the mixed powder at a temperature lower than the melting point of the nonmagnetic metal powder, the nonmagnetic metal powder is softened without being melted and fixed to the magnetic powder. The non-magnetic metal powder fixed to the magnetic powder acts as a binder between the magnetic powders. Even if the non-magnetic metal powder is partially fluidized, its fluidity is low, so it remains on the surface of the magnetic powder particles. Therefore, a sintered body in which the magnetic powder and the nonmagnetic metal powder are uniformly distributed over the entire surface is obtained without the nonmagnetic metal powder being unevenly distributed in the sintered body or flowing to the surface side. It is done. In this configuration, the multipolar magnet is preferably composed of 20 to 90 wt% of magnetic powder and 10 to 90 wt% of non-magnetic metal powder, and 40 to 80 wt% of magnetic powder and 20 to 60 wt% of What consists of nonmagnetic metal powder is more preferable. Yes. This is because when the blending ratio of the non-magnetic metal powder is less than 10 wt%, the binder action of the magnetic powder is not sufficient, and when the blending ratio of the magnetic powder is less than 20 wt%, the magnetic force becomes insufficient and sensing by the magnetic sensor. This is because the function is degraded.

  The nonmagnetic metal powder preferably has a maximum particle size of 63 μm or less. Thus, by making the nonmagnetic metal powder fine, the nonmagnetic metal powder is uniformly dispersed around the magnetic powder. Therefore, the density of the sintered body can be made more uniform. Further, the apparent density of the powder is reduced by reducing the size of the powder. Therefore, the compression ratio (compression stroke) at the time of compression molding can be increased without changing the size and weight of the molded product. Thereby, the entanglement between nonmagnetic metal powders or magnetic powder can be improved (contact area can be increased), and the strength of the molded product can be increased.

  Considering the entanglement between the powders during compression molding, the nonmagnetic metal powder may be non-spherical, such as spongy, acicular, angular, dendritic, fibrous, flaky, irregular, or teardrop-shaped. It is preferable to use an eggplant. According to this, the entanglement between the powders can be improved, and the strength can be further improved. These non-spherical non-magnetic metal powders can be formed by, for example, a water atomizing method or an oil atomizing method.

  For example, samarium-based magnetic powder is preferably used as the magnetic powder constituting the sintered body, and tin or tin-zinc alloy is preferably used as the nonmagnetic metal powder. Moreover, when using a tin-zinc alloy, it is good to make the compounding ratio of tin and zinc into zinc 15-40 wt% with respect to tin 60-85 wt%. According to this, since the apparent density of mixed powder becomes smaller, the further strength improvement can be aimed at.

  The magnetic encoder provided with the multipolar magnet having the above-described configuration can be suitably used for a wheel bearing, for example.

  Thus, according to the present invention, the density of the multipole magnets in this type of magnetic encoder can be made uniform. Accordingly, it is possible to provide a magnetic encoder that can obtain a sintered body with higher strength, can be easily handled during manufacture and assembly, and is excellent in productivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the magnetic encoder 10 includes an 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 has a disk shape and is magnetized in multiple poles in the circumferential direction, whereby magnetic poles N and S are alternately formed. For example, as shown in FIG. 2, the magnetic poles N and S are formed to have a predetermined pitch p in the pitch circle diameter PCD.

  The multipolar magnet 14 is composed of magnetic powder and nonmagnetic metal powder. Examples of magnetic powders include isotropic or anisotropic ferrite powders such as barium and strontium, samarium iron (SmFeN) magnetic powder, neodymium iron (NdFeB) magnetic powder, and manganese aluminum (MnAl) gas atomized powder. Rare earth magnetic powders such as can be used. In this embodiment, samarium iron (SmFeN) magnetic powder exhibiting ferromagnetism is used among the above magnetic powders.

  As the non-magnetic metal powder, for example, metal powder such as tin, copper, aluminum, nickel, zinc, tungsten, manganese, a powder obtained by mixing two or more of these, or two or more alloy powders can be used. In this embodiment, tin powder having a relatively low melting point is used among the nonmagnetic metal powders.

  As the nonmagnetic metal powder, for example, those having a maximum particle size of 63 μm or less are preferably used. In this embodiment, tin powder having a maximum particle size of 45 μm is used.

  In addition, as the tin powder as the nonmagnetic metal powder, those having a non-spherical shape such as a spongy shape, a needle shape, a square shape, a dendritic shape, a fiber shape, a piece shape, an irregular shape, and a teardrop shape are preferably used. The tin powder having such a shape can be formed by, for example, a water atomization method. The water atomization method is a method in which a molten metal is naturally dropped from pores, and a high-pressure water jet is sprayed on the narrow stream to pulverize, and the cooling time is shorter than that of the gas atomization method. Therefore, the cooled and powdered tin powder has a relatively non-spherical shape. As an example, a micrograph of tin powder formed by the gas atomization method is shown in FIG. 11A, and a micrograph of tin powder formed by the water atomization method is shown in FIG. 11B. From these figures, it can be seen that the tin powder formed by the gas atomization method is relatively spherical, whereas the tin powder formed by the water atomization method has a relatively irregular shape. In addition, the powder which makes non-spherical shapes, such as the said irregular shape, can be obtained also by the oil atomizing method, for example.

  The blending ratio in the mixed powder forming the multipolar magnet 14 is preferably 10-80 wt% of non-magnetic metal powder with respect to 20-90 wt% of magnetic powder, and 40-80 wt% of magnetic powder. %, And those containing 20-60 wt% of nonmagnetic metal powder are more preferred. If the blending ratio of the non-magnetic metal powder is less than 10 wt%, the non-magnetic metal powder does not function sufficiently as a binder for the magnetic powder, so that the multipolar magnet 14 obtained after sintering is hard but brittle. Therefore, cracks may occur when the multipolar magnet 14 is fixed to the cored bar 11. On the other hand, if the blending ratio of the magnetic powder is less than 20 wt%, the magnetizing strength of the multipolar magnet 14 obtained after sintering cannot be increased, and the magnetic force sufficient to satisfy the stable sensing ability desired for the magnetic encoder 10. May not be secured.

  For example, a lubricant such as zinc stearate may be added to the mixed powder of the magnetic powder and the nonmagnetic metal powder (for example, 1 wt% or less) to improve the compression moldability of the mixed powder.

The mixed powder having the above configuration is compression-molded with a predetermined pressure, and for example, a disk-shaped compression-molded body 14 ′ shown in FIG. The pressing force at the time of compression molding is preferably 6.0 × 10 ³ kgf / cm ² or more. Moreover, it is desirable that the compression molded body 14 ′ after the compression molding has 5 to 30 vol% voids. The porosity is more preferably 12 to 22 vol%, and further preferably 14 to 19 vol%. This is because if the porosity is less than 5 vol%, the compression molded body 14 ′ may be damaged by the spring back generated when the molding pressure is removed. Moreover, when the porosity exceeds 30 vol%, the mechanical strength of the sintered body is insufficient, and there is a possibility of cracking when fixed to the core metal 11.

  Since magnetic powder and non-magnetic metal powder are expensive, it is desirable that the thickness of the compression molded body 14 ′ be as thin as possible. In consideration of compression moldability and handling properties (easiness of handling including conveyance to assembling to the core metal 11 etc.), the wall thickness is preferably 0.3 mm to 5 mm, and 0.6 mm to 3 mm. More preferably. When the wall thickness is less than 0.3 mm, it is difficult to fill the powder into the molding die and the compression molded body 14 ′ is difficult to mold. Further, the obtained compression molded body 14 ′ is not preferable because it may be damaged during handling. On the other hand, when the thickness of the compression molded body 14 ′ is thicker than 10 mm, the moldability and handling properties are improved, but on the other hand, the cost is increased. On the other hand, if it is too thick, the density of the compression-molded body 14 ′ tends to be non-uniform, and there is a risk of distorted deformation after sintering.

  A disk-shaped sintered body as shown in FIG. 1 is obtained by heat-sintering the compression molded body 14 ′ obtained as described above in a furnace. At this time, by setting the heating temperature in the furnace to a temperature lower than the melting point of the nonmagnetic metal powder, the nonmagnetic metal powder is softened without being melted and fixed to the magnetic powder. The non-magnetic metal powder fixed to the magnetic powder acts as a binder between adjacent magnetic powders. Further, even if the non-magnetic metal powder is partially fluidized, its fluidity is low and remains on the surface of the magnetic powder particles. As a result, a sintered body in which the magnetic powder and the nonmagnetic metal powder are uniformly distributed over the entire surface is obtained without the nonmagnetic metal powder being unevenly distributed in the sintered body or flowing out to the external surface. It is done. Therefore, a high-strength sintered body (multipolar magnet 14) can be obtained.

  When using samarium iron (SmFeN) magnetic powder as the magnetic powder and tin (Sn) powder as the nonmagnetic metal powder as in this embodiment, the temperature during sintering is less than the melting point of tin (232 ° C.). It is preferable to set the temperature to be, specifically, a range of 200 to 225 ° C. Within this temperature range, the non-magnetic metal powder functions sufficiently as a binder for the magnetic powder, and a high-strength sintered body can be obtained.

  In this embodiment, since the nonmagnetic metal powder (tin powder) having a maximum particle size of 63 μm or less is used, a mixed powder in which a small nonmagnetic metal powder is uniformly dispersed around the magnetic powder is obtained. can get. Therefore, a sintered body having a uniform density can be obtained by compression molding and sintering the mixed powder. Moreover, since the nonmagnetic metal powder of the said size has a small apparent density, a compression ratio becomes large when shape | molding the compression molding body of the same dimension and the same density. Thereby, the entanglement between the powders can be improved, and the strength of the sintered body can be further increased.

  In particular, in this embodiment, since the irregularly shaped tin powder (see FIG. 11B) is used as the nonmagnetic metal powder, a compression molded body in which the powders are intertwined very well is obtained. Thereby, the intensity | strength of a sintered compact can further be raised.

  In this way, by increasing the strength of the sintered body, the handleability of the sintered body is improved, and the conditions for crimping and fixing to the core metal 11 can be easily determined. Moreover, when fixing the magnetic encoder 10 assembled to the rotation side member mentioned later by press-fitting the core metal 11 to the rotation side member, the sintered body magnetized by deformation | transformation of the core metal 11 accompanying press injection ( The multipolar magnet 14) is difficult to break. Therefore, it is possible to increase the tightening allowance at the time of press-fitting. Further, the disk-shaped sintered body can be thinned, thereby reducing the material cost.

  In addition, the said effect | action can be acquired also when not only a tin powder but another nonmagnetic metal powder is used. A suitable example is a tin-zinc alloy. In this case, the mixing ratio of tin and zinc is preferably 15 to 40 wt% for zinc with respect to 60 to 85 wt% for tin. The sintering temperature is preferably set to a temperature lower than the melting point of the tin-zinc alloy powder (about 250 ° C. in the above blend ratio), specifically in the range of 170 to 190 ° C. If it is the tin-zinc alloy powder of the said mixture ratio, even if sintering temperature is about 170-190 degreeC, it will soften to the extent which functions as a binder of magnetic powder. Therefore, the strength of the sintered body can be improved, and by lowering the sintering temperature, it is possible to suppress the magnetic deterioration accompanying the temperature increase of the magnetic powder as much as possible. As an example, FIG. 12 shows a micrograph of the inside of the sintered body when the tin-zinc alloy powder is used.

  Moreover, since the apparent density of the tin alloy powder having the above configuration is smaller than that of tin powder of the same size, the compression ratio can be increased and the strength of the sintered body can be further increased. As the size of the alloy powder, those having a maximum particle size of 63 μm or less can be preferably used. Further, in order to improve the entanglement between the powders, it is preferable to use a tin-zinc alloy powder formed in a non-spherical shape by, for example, a water atomizing method or an oil atomizing method, as in the case of tin powder. .

  The sintered body can be fixed to the cored bar 11 by, for example, caulking, press-fitting, or adhering the cored bar 11, but in addition, after the sintered body (compression molded body 14 ′) is sintered. It can also be fixed to the metal core 11 using expansion. In this embodiment, a fixing method to the cored bar 11 using expansion after compression of the compression molded body 14 ′ will be described.

  For example, as shown in FIG. 3, the core metal 11 includes a cylindrical mounting portion 12 a that is fixed to a rotation-side member by press-fitting or the like, and extends from one end of the mounting portion 12 a to the outer diameter side. The abutting portion 12b abuts against the disk end surface of the magnet 14) and the fixing portion 13 which is disposed on the side opposite to the mounting portion 12a on the outer diameter end of the abutting portion 12b and clamps and fixes the multipolar magnet 14. The fixed portion 13 includes a clamping surface 13 a that clamps the outer peripheral portion 14 a of the multipolar magnet 14 on the inner periphery thereof. As shown in FIG. 1, the clamping surface 13a includes a diameter-enlarging surface 13b that expands from the outer diameter end of the abutting portion 12b toward the axially opposite mounting portion 12a side (right side in the drawing), and a diameter-enlarging surface 13b. The cylindrical surface 13c extends from the large diameter end to the right side in the axial direction, and the reduced diameter surface 13d decreases from the end of the cylindrical surface 13c toward the right side in the axial direction. In this embodiment, the enlarged diameter surface 13b and the reduced diameter surface 13d each have a tapered surface shape. Further, the outer peripheral surface 14 b of the multipolar magnet 14 having a disk shape has a surface shape that follows the holding surface 13 a of the fixed portion 13.

  The cored bar 11 provided with the attachment part 12a, the contact part 12b, and the fixing part 13 can be integrally formed by, for example, press working. In that case, the portion of the fixed portion 13 where the cylindrical surface 13c is formed on the inner periphery is press-molded longer than the predetermined axial length by the portion where the reduced diameter surface 13d is formed on the inner periphery, and further reduced. A portion corresponding to the radial surface 13d is plastically deformed and bent toward the inner diameter side, whereby a cylindrical surface 13c and a reduced diameter surface 13d having a predetermined axial width are formed. Of course, the metal core 11 having the above-described shape may be formed by only one press working by devising a press die. Or you may finish the metal core 11 in the said shape by other machinings, such as cutting.

  As a material constituting the metal core 11, a magnetic material, particularly a metal that becomes a ferromagnetic material is preferable. For example, a steel plate that is a magnetic material and has rust prevention properties is used. In this embodiment, for example, a ferritic stainless steel plate (JIS standard SUS430 system) is used.

  A multipolar magnet 14 (compression molded body 14 ′) before sintering is attached to the core metal 11 having the above-described configuration. Specifically, as shown in FIG. 3, the compression molded body 14 ′ is baked in a state where the end surface of the compression molded body 14 ′ is in contact with the contact portion 12 b of the core metal 11 (the position indicated by the alternate long and short dash line in the figure). Conclude. As in this embodiment, when a samarium iron (SmFeN) magnetic powder is used for the magnetic powder constituting the compression molded body 14 'and a tin powder is used for the nonmagnetic metal powder, the compression molded body after sintering is used. The volume of 14 'increases compared to the volume of the compression molded body 14' before sintering. That is, the compression molded body 14 'expands before and after sintering. As a result, the outer peripheral portion 14 a ′ of the compression molded body 14 ′ is clamped by the clamping surface 13 a of the fixed portion 13. In this embodiment, a portion of the outer peripheral surface 14b 'of the compression molded body 14' facing the cylindrical surface 13c is sandwiched in the radial direction by the cylindrical surface 13c of the fixing portion 13. Further, the diameter-enlarging surface 13b and the diameter-reducing surface 13d of the fixed portion 13 sandwich the portions of the outer peripheral surface 14b 'that face the diameter-enlarging surface 13b and the diameter-reducing surface 13d in the axial direction. In this manner, the compression molded body 14 ′ is clamped and fixed to the core metal 11.

  According to this fixing method, the load on the sintered body at the time of fixing can be adjusted with the dimensional accuracy of the cored bar 11 formed by, for example, press working or the like without fixing by caulking. Therefore, it is possible to perform high-precision fixing as compared to fixing by caulking, in which the caulking amount tends to vary. Further, according to the fixing method, since the compression molded body 14 ′ can be sintered and fixed to the cored bar 11 at the same time, the work process can be simplified and the cost can be reduced.

  In addition, the fixing | fixed part 13 of the metal core 11 can take not only said form but another form. For example, in FIG. 5, the sandwiching surface 13 a is composed of an enlarged diameter surface 13 b, a reduced diameter surface 13 d, and a cylindrical surface 13 c, and a folded portion toward the inner diameter side (the portion in which the reduced diameter surface 13 d is formed on the inner circumference) The case where two or more are provided at predetermined intervals in the circumferential direction is illustrated.

  Further, as another configuration example of the fixing portion 13, for example, a form shown in FIG. The figure illustrates the case where the clamping surface 13a on the inner periphery of the fixed portion 13 is configured only by the cylindrical surface 13c. In this case, the compression molded body 14 ′ is sandwiched in the radial direction by the cylindrical surface 13 c due to the expansion after sintering of the compression molded body 14 ′ brought into contact with the contact portion 12 b. On the other hand, since the compression molded body 14 ′ is not restrained in the axial direction, the compression molded body 14 ′ can expand with a certain degree of freedom in the direction opposite to the contact portion 12 b (right direction in the drawing). This avoids a situation in which the compression molded body 14 ′ receives an excessive load in the anti-expansion direction from the cylindrical surface 13 c due to excessive expansion in the radial direction, and reliably prevents the sintered body 11 from being damaged. It becomes possible to fix to.

  Further, as shown in FIG. 7, a part of the clamping surface 13a of the fixing portion 13 is protruded and deformed to the inner diameter side, and the protruding portion 13g and the compression molded body 14 ′ serving as a sintered body are engaged in the circumferential direction. By doing so, the compression molded body 14 ′ can be prevented from rotating. In this case, a recess (corresponding to 14c in FIG. 7) corresponding to the protruding portion 13g of the core metal 11 is formed in the compression molded body 14 'in advance, and this recess and the protrusion of the core metal 11 are set when the core metal 11 is set. By fitting the part 13g together, the compression molded body 14 'is fixed to the fixing part 13. In addition, although the illustration is abbreviate | omitted for a rust prevention process, the said sintered compact can also form a rust prevention film, for example. For this type of anticorrosive coating, for example, a clear high anticorrosive paint can be used.

  As described above, the disc-shaped sintered body fixed to the cored bar 11 that is a metal annular member becomes a multipolar magnet 14 by being magnetized in a multipolar manner in the circumferential direction. The multipolar magnet 14 and the cored bar 11 constitute the magnetic encoder 10 shown in FIG.

  The magnetic encoder 10 is attached to a rotation side member (not shown), and is used for rotation detection with a magnetic sensor 21 facing the multipolar magnet 14 as shown in FIG. The rotation detection device 22 is configured as described above. This figure shows a configuration example in the case where the magnetic encoder 10 is used as a component part of a seal device 5 of a bearing (not shown), and the magnetic encoder 10 is used by being incorporated in a rotation side member 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.

  When the magnetic encoder 10 is rotated, the magnetic sensor 21 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 (see FIG. 2) of the magnetic poles N and S can be set finely. For example, the accuracy that the pitch p is 1.5 mm and the pitch difference is ± 3% can be obtained. 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 position as a ratio to the target pitch. When the magnetic encoder 10 is used in the bearing sealing device 5 as shown in FIG. 4, the rotation of the bearing to which the magnetic encoder 10 is attached is detected.

  The flatness of the surface of the disk-shaped multipolar magnet 14 (here, the surface facing the magnetic sensor 21) is preferably 200 μm or less, and preferably 100 μm or less. When the flatness of the surface of the multipolar magnet 14 exceeds 200 μm, the gap (air gap) between the magnetic sensor 21 and the surface of the multipolar magnet 14 changes during the rotation of the magnetic encoder 10, thereby degrading the sensing accuracy. For the same reason, the surface runout of the surface of the multipolar magnet 14 during rotation of the magnetic encoder 10 is preferably 200 μm or less, and preferably 100 μm or less. In this embodiment, since the compression-molded body 14 ′ is expanded evenly after sintering, the flatness of the surface of the multipolar magnet 14 can be easily suppressed to the above range (200 μm or less). In this embodiment, in order to obtain stable and high sensing performance, regardless of the shape of the fixing portion 13 (FIGS. 1 and 3 to 7), the multipolar magnet 14 fixed to the core metal 11 is detected. The magnetic encoder 10 is configured so that the fixed portion 13 does not protrude from the surface to the magnetic sensor 21 side.

  Next, an example of a wheel bearing provided with the magnetic encoder 10 and a configuration example of the seal device 5 will be described with reference to FIGS. As shown in FIG. 8, 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 15 for sealing the end annular space.

  The seal device 5 on one end side (constant velocity universal joint 7 side) includes a magnetic encoder 10 as a component. The inner member 1 and the outer member 2 have raceway surfaces 1a and 2a of the rolling elements 3, and each raceway surface 1a and 2a is formed in a groove shape. The inner member 1 and the outer member 2 refer to an inner peripheral member and an outer peripheral member that can be relatively rotated via the rolling elements 3, respectively. Alternatively, it may be an assembly member in which a bearing outer ring and another member are combined. 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 19 and 20. These inner rings 19, 20 are fitted on the outer periphery of the shaft portion of the hub ring 6 and constitute the inner member 1 together with the hub ring 6. It should be noted that the inner member 1 is integrated with the hub wheel 6 and one inner ring 19 instead of the three-part assembly part including the hub wheel 6 and the pair of split inner rings 19 and 20 as described above. It is good also as what consists of two components comprised by the hub ring with a track surface, and the other inner ring | wheel 20.

  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 via 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. 9 is an enlarged cross-sectional view of the sealing device 5 integrally provided with the magnetic encoder 10. The sealing device 5 is the same as that shown in FIG. 4, and a part of the sealing device 5 has been described above. The details will be described with reference to FIG. In the sealing device 5, the magnetic encoder 10 or the cored bar 11 serves as a slinger, and is attached to the rotating member of the inner member 1 and the outer member 2. In this example, since the rotating member is the inner member 1, the magnetic encoder 10 is attached to the inner member 1 by means such as press fitting.

  The sealing device 5 includes annular seal plates (11) and (16) 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 the same as the above-described configuration based on FIGS. By disposing the magnetic sensor 21 so as to face the multipolar magnet 14 in the magnetic encoder 10, a rotation detection device 22 for detecting the wheel rotation speed is configured. Of course, the magnetic encoder 10 having a configuration based on FIGS. 5 to 7 can be incorporated and used.

  The second seal plate 16 is a member constituting the seal member 9 (see FIG. 4), and is in sliding contact with the side lip 17a and the mounting portion 12a that are in sliding contact with the contact portion 12b of the core metal 11 that is the first seal plate. Radial lips 17b and 17c are integrally provided. These seal lips 17 a to 17 c are provided as a part of the elastic member 17 vulcanized and bonded to the second seal plate 16. The number of the lips 17a to 17c may be arbitrary, but in the example of FIG. 9, one side lip 17a and two radial lips 17b and 17c (so-called triple lips) located inside and outside in the axial direction are provided. ing. The second seal plate 16 is obtained by holding an elastic member 17 in a fitting portion with the outer member 2 which is a fixed side member. That is, the elastic member 17 has a covering portion 17d that covers from the inner diameter surface of the cylindrical portion 16a to the outer diameter of the tip portion, and this covering portion 17d serves as a fitting portion between the second seal plate 16 and the outer member 2. Intervene. Further, the covering portion 17d provides a slight radial gap between the cylindrical portion 16a of the second seal plate 16 and the fixing portion 13 (the portion where the cylindrical surface 13c is formed in FIG. 9) of the core metal 11 forming the first seal plate. The labyrinth seal 18 is formed by the gap.

  According to the wheel bearing of this configuration, the rotation of the inner member 1 rotating with the wheel is detected by the magnetic sensor 21 via the magnetic encoder 10 attached to the inner member 1, and the wheel rotation speed is detected. . Since the magnetic encoder 10 is a constituent element of the sealing device 5, it can detect the rotation of the wheel without increasing the number of parts. The space of the bearing end portion in the wheel bearing is a narrow space limited by the constant velocity universal 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-mentioned. Since the thickness can be reduced by increasing the strength as described above, the rotation detector 22 can be easily arranged. As for the seal between the inner and outer members 1 and 2, sliding contact between the seal lips 17 a to 17 c provided on the second seal plate 16, and a core metal which is the first seal plate on the cylindrical portion 16 a of the second seal plate 16. And 11 labyrinth seals 18 formed by confronting each other through a slight radial gap.

  In the wheel bearing shown in FIG. 8 and FIG. 9, the case where the multipolar magnet 14 of the magnetic encoder 10 is provided outward (opposite the magnetic sensor 21 on the right side in the figure) with respect to the bearing has been described. On the contrary, it may be provided inward with respect to the bearing (on the left side in the drawing, opposite to the magnetic sensor 21). In that case, the cored bar 11 is preferably made of a non-magnetic material.

  The magnetic encoder 10 is not limited to the multipolar magnet 14 oriented in the axial direction, and may be provided in the radial direction, for example, as shown in FIG. In the figure, a flange 12c extending from one end to the outer diameter side is provided on an attachment portion 12a of a core bar 11 forming a slinger of the sealing device 5, and an outer diameter edge of the flange 12c is provided via a contact portion 12d. The case where the fixing | fixed part 13 which clamps and fixes the multipolar magnet 14 is provided is illustrated. In this case, the multipolar magnet 14 is formed in a cylindrical shape instead of a disk shape, and the sandwiching surface 13a ′ (expanded surface 13b ′, cylindrical surface 13c) with its inner peripheral surface in contact with the contact portion 12d. ', The diameter-reduced surface 13d'). The magnetic sensor 21 is disposed to face the multipolar magnet 14 in the radial direction.

  In addition, although the magnetic encoder 10 of the said embodiment was demonstrated as the case where all were the components of the seal device 5 of a bearing, the magnetic encoder 10 of these each embodiment is restricted to what is used as the component of the seal device 5. Instead, 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 although illustration is omitted.

  In order to verify the effectiveness of the present invention, a magnetic encoder (conventional example) including a sintered body formed by a conventional method and a magnetic encoder including a multipolar magnet (sintered body) formed by the method according to the present invention. The encoders (Examples 1 and 2) were each subjected to a press-fitting test into a bearing inner ring (inner member 1 in FIG. 8), and the two were compared.

Here, the material composition and molding (sintering) conditions of the sintered body of the comparative example are as shown below.
Magnetic powder: Samarium iron (SmFeN) magnetic powder Non-magnetic metal powder; Tin powder (maximum particle size 63 μm, apparent density: 2.27 g / cm ³ , molded by gas atomization method)
Mixing ratio: (magnetic powder: non-magnetic metal powder = 55 wt%: 45 wt%
Molding density: 6.4 g / cm ³
Sintering temperature: 220 ° C, 1 hr hold

The material composition and molding (sintering) conditions of the sintered body of Example 1 are as shown below.
Magnetic powder: Samarium iron (SmFeN) magnetic powder Non-magnetic metal powder; Tin powder (350 mesh under, apparent density: 2.14 g / cm ³ , molded by water atomization method)
Mixing ratio: Samarium iron (SmFeN) magnetic powder: tin powder = 70 wt%: 30
wt%
Molding density: 6.6 g / cm ³
Sintering temperature: 220 ° C, 1 hr hold

The material composition and molding (sintering) conditions of the sintered body of Example 2 are as shown below.
Magnetic powder: Samarium iron (SmFeN) magnetic powder Non-magnetic metal powder: Tin-zinc alloy powder (tin 75 wt%: zinc 25 wt%, maximum particle size 45 μm, apparent density: 1.76 g / cm ³ , molded by water atomization method) )
Mixing ratio: Samarium iron (SmFeN) magnetic powder: tin-zinc alloy powder = 60 wt%: 40 wt%
Molding density: 6.4 g / cm ³
Sintering temperature: 180 ° C., 1 hr holding In addition, 0.8 wt% of zinc stearate is added as a lubricant in both the comparative example and the examples (1, 2).

  FIG. 13 shows the result of the press-fitting test. From the figure, in the comparative example, when the press-fit tightening margin exceeds a certain value (130 μm), the probability of occurrence of cracking increases, whereas in Example 1 (2), regardless of the press-fit tightening margin value, It was found that it showed high resistance to cracking.

It is a fragmentary perspective view of the magnetic encoder which concerns on embodiment of this invention. It is a front view explaining the magnetic pole arrangement of a magnetic encoder. It is a fragmentary perspective view which shows an example of the method of carrying out the sintering fixation of the compression molding body to a metal core. It is sectional drawing which shows the sealing device provided with the magnetic encoder, and a magnetic sensor. It is a fragmentary perspective view which shows the other example of the method of carrying out the sintering fixation of the compression molding body to a metal core. It is a fragmentary perspective view which shows the other example of the method of carrying out the sintering fixation of the compression molding body to a metal core. It is a fragmentary perspective view which shows the other example of the method of carrying out the sintering fixation of the compression molding body to a metal core. It is sectional drawing which shows one structural example of the wheel bearing provided with the magnetic encoder. It is an expanded sectional view around the magnetic encoder of the wheel bearing. It is an expanded sectional view which shows the other structural example of the magnetic encoder in the wheel bearing. (A) is the microscope picture of the tin powder shape | molded by the gas atomization method, (b) is the microscope picture of the tin powder shape | molded by the water atomization method. It is a microscope picture inside a sintered compact at the time of using a tin-zinc alloy powder for nonmagnetic metal powder. It is a figure which shows the result of the press fit test to the bearing inner ring | wheel of a magnetic encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner member 2 Outer member 3 Rolling body 5 Sealing device 7 Constant velocity universal joint 10 Magnetic encoder 11 Core metal 12a Attachment part 12b Contact part 13 Fixing part 13a Holding surface 14 Multipolar magnet 14a Outer part 14 'Compression molding 17 Elastic members 17a, 17b, 17c Seal lip 18 Labyrinth seal 21 Magnetic sensor 22 Rotation detection device p Pitch

Claims (7)

In a magnetic encoder provided with a multipolar magnet formed by compressing and molding a mixed powder of magnetic powder and nonmagnetic metal powder,
The multipolar magnet is composed of 20 to 90 wt% of the magnetic powder and 10 to 80 wt% of the nonmagnetic metal powder, and is sintered at a temperature lower than the melting point of the nonmagnetic metal powder. Features magnetic encoder.   The magnetic encoder according to claim 1, wherein the nonmagnetic metal powder has a maximum particle size of 63 μm or less.   The nonmagnetic metal powder has a shape selected from spongy, acicular, angular, dendritic, fibrous, flaky, irregular, and teardrop-shaped. The magnetic encoder according to claim 1.   4. The magnetic encoder according to claim 3, wherein the nonmagnetic metal powder is formed by a water atomizing method or an oil atomizing method.   The magnetic encoder according to claim 1, wherein the magnetic powder is samarium iron-based magnetic powder.   The magnetic encoder according to claim 1, wherein the nonmagnetic metal powder is tin or a tin-zinc alloy.   The wheel bearing provided with the magnetic encoder in any one of Claims 1-6.

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