JP2014202684A - Magnetic encoder and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic encoder capable of strongly fixing a multipolar magnet and a core metal at a low cost without causing a fault in the multipolar magnet and maintaining high rotation detection accuracy for a long term.SOLUTION: A magnetic encoder includes a multipolar magnet 2 having magnetic poles alternately formed in a circumferential direction and provided in a core metal 1. The core metal 1 includes an inner diameter cylindrical part 4, a standing plate part 5 extended from one end of the inner diameter cylindrical part 4 to an outer diameter side and an outer diameter cylindrical part 6 extended in an axial direction from the outer diameter side edge of the standing plate part 5. A staking part 7 projected on the inner diameter side is provided in the outer diameter cylindrical part 6. The multipolar magnet 2 is integrally molded in an annular part 8 over the standing plate part 5 and the outer diameter cylindrical part 6 of the core metal 1 by insert-molding so that the staking part 7 is buried.

Description

  The present invention relates to a magnetic encoder that is mounted on a bearing and functions to detect a rotational speed, and a method for manufacturing the same.

  For example, the magnetic encoder is incorporated in a wheel bearing device of an automobile and is used as a rotation detection device that detects the number of rotations of a wheel in an antilock brake system (ABS). This type of rotation detection device is a passive type that reads the movement of the uneven teeth provided on the rotor as the magnitude of magnetism, and an active type that reads changes in magnetism with the rotation of the magnetic encoder with a magnetic sensor such as a Hall IC. It is roughly divided into Among these, the active type rotation detection device tends to be frequently used in recent years because it is inexpensive and excellent in detecting the rotation speed in a low speed region.

The active type rotation detection device includes, for example, a magnetic encoder provided on the rotation side member and a magnetic sensor provided on the fixed side member. The magnetic encoder includes an annular multipolar magnet that is magnetized in multiple directions in the circumferential direction, and a metal core fixed to the multipolar magnet. As the multipolar magnet, a so-called sintered magnet obtained by compacting and sintering a magnetic material containing magnetic powder and non-magnetic powder, or a so-called sintered magnet obtained by injection molding a magnetic material containing magnetic powder and rubber. A so-called plastic magnet obtained by injection molding of a magnet material containing a rubber magnet, magnetic powder and resin is known.
These multipolar magnets 50 are bonded (for example, see Patent Documents 1 and 2) as shown in FIG. 9, or caulked (see, for example, Patent Document 3) as shown in FIG. Then, it is fixed to the cored bar 51.

JP 2003-057070 A JP 2008-233110 A JP 2005-274436 A

Magnetic encoders incorporated in wheel bearing devices have a wide operating temperature range and are used in harsh environments. When multipolar magnets are bonded and fixed to a core metal, the fixing force decreases due to deterioration of the adhesive over time. Is a problem.
In Patent Document 1, it is proposed to increase the fixing strength of both of the surfaces of the cored bar by increasing the contact (bonding) area by roughening the bonding surface with the multipolar magnet. Cost increase due to surface treatment is inevitable.
Also, as in Patent Document 2, a method has been proposed in which a plastic magnet is baked on the surface of the core bar in a semi-cured state with an adhesive that undergoes a curing reaction during insert molding, but this also increases the cost due to the baking process. Unavoidable.

  On the other hand, when the multipolar magnet is caulked and fixed to the metal core as in Patent Document 3, deterioration with time of the fixing force as in the case where both are bonded and fixed is avoided. However, especially when using a multi-pole magnet made of sintered magnets, an excessive load is easily applied to the multi-pole magnet during caulking, so that special problems are required for caulking. Although rubber magnets and plastic magnets can effectively avoid problems such as caulking, they are generally easy to expand and contract. Therefore, when the inner peripheral surface and the outer peripheral surface of the multipolar magnet are caulked with a core metal as in Patent Document 3, when the multipolar magnet expands particularly in a high temperature environment, the amount of expansion is reduced. There is a risk that the rotation detection accuracy may be deteriorated due to deformation of the multipolar magnet or the like, because it cannot be escaped to both the peripheral surface and the outer peripheral surface.

  An object of the present invention is to provide a magnet that can fix a multipolar magnet and a core metal firmly and at low cost without causing problems in the multipolar magnet, and can maintain high rotation detection accuracy over a long period of time. It is to provide an encoder.

A magnetic encoder of the present invention is a magnetic encoder provided with a multipolar magnet having magnetic poles alternately formed in a circumferential direction on a core metal,
The core metal has an inner diameter cylindrical portion, a standing plate portion extending from one end of the inner diameter cylindrical portion to the outer diameter side, and an outer diameter cylindrical portion extending in the axial direction from the outer diameter side end of the standing plate portion, A staking portion that protrudes toward the inner diameter side is provided in this outer diameter cylindrical portion,
The multi-pole magnet is integrally formed by insert molding so that the staking portion is embedded in an annular portion of the core bar that extends between the standing plate portion and the outer diameter cylindrical portion.

  According to this configuration, the outer diameter cylindrical portion of the cored bar is provided with a staking portion that protrudes toward the inner diameter side in advance, and in the cored bar provided with this staking portion, an annular portion that spans the standing plate portion and the outer diameter cylindrical portion, The multipolar magnet was integrally formed by insert molding so that the staking portion was buried. Instead of staking after the multi-pole magnet is insert-molded into the core metal, the core metal is provided with a staking part for preventing the multi-pole magnet from coming off and preventing it from rotating. The pole magnet is integrated by insert molding so that the staking portion is buried.

(1) A multi-pole magnet can be reliably and easily fixed to a cored bar by staking process + insert molding. Insert molding alone is insufficient to fix the multipolar magnet, but insert molding is performed so that the staking portion provided in advance in the core metal is embedded, so that part of the multipolar magnet is constrained by the staking portion. The pole magnet can be easily prevented from coming off and prevented from rotating, and the multipolar magnet can be firmly fixed to the cored bar. Moreover, since it is a staking process, a manufacturing cost can be reduced rather than the case where the conventional roughening process and baking process are performed.
(2) The conventional one that is fixed only by caulking needs to be performed on both the inner peripheral surface and the outer peripheral surface of the multipolar magnet in order to ensure the fixing. I can't escape. In the present application, since the staking portion that protrudes to the inner diameter side is provided in the outer diameter cylindrical portion of the core metal together with the insert molding, the multipolar magnet only needs to restrain the outer peripheral surface, and the inner peripheral surface is not restrained. Even when the multipolar magnet expands in a high temperature environment, the expansion can be released to the inner diameter side of the multipolar magnet. Thereby, it can prevent that a multipolar magnet deform | transforms undesirably, and can suppress the fall of rotation detection accuracy.
(3) Since a multipolar magnet is insert-molded after a staking portion is provided in advance in the core metal, no residual stress is generated in the multipolar magnet, and excessive stress is applied to the multipolar magnet as in caulking. It is possible to prevent a problem that a load is applied.

  The multipolar magnet may be a plastic magnet in which magnetic powder and a thermoplastic resin are mixed. Plastic magnets that are highly filled with magnetic powder can reduce the coefficient of linear expansion, thus reducing the difference between the coefficient of linear expansion of plastic magnets and the coefficient of linear expansion of metal-based materials used for metal cores. Can do. A multipolar magnet expands in a high temperature environment and contracts in a low temperature environment. However, since the difference in the linear expansion coefficient between the multipolar magnet and the core metal can be reduced as described above, the amount of expansion between the multipolar magnet and the core metal and The difference in shrinkage can be reduced. Therefore, when the multipolar magnet is expanded at a high temperature, an excessive load is not applied to the multipolar magnet, and a problem can be prevented. In addition, the play of the multipolar magnet at the time of low temperature shrinkage is small.

The multipolar magnet may be mixed with magnetic powder, and the magnetic powder may contain at least strontium ferrite.
The multipolar magnet includes a mixture of magnetic powder and a thermoplastic resin, and the thermoplastic resin includes one or more compounds selected from the group consisting of polyamide 12, polyamide 612, polyamide 11, and polyphenylene sulfide. There may be. As the thermoplastic resin, a resin having low water absorption is desirable in order to suppress the deterioration of the magnetic properties of the multipolar magnet due to water absorption as much as possible. When the thermoplastic resin contains one or more compounds, water absorption can be reduced, and deterioration of the magnetic properties of the multipolar magnet can be suppressed as much as possible. Polyphenylene sulfide is more desirable because it has a smaller linear expansion coefficient than that of the other workpieces and can easily achieve a linear expansion coefficient equivalent to that of the core metal.

The multipolar magnet is a plastic magnet in which magnetic powder and a thermoplastic resin are mixed, and a difference between a linear expansion coefficient of the multipolar magnet and a linear expansion coefficient of the core metal is 2.0 × 10 ^−5. What adjusted the compounding quantity of the said magnetic substance powder and the said thermoplastic resin which comprise the said plastic magnet so that it may become the following may be sufficient. In this case, it is possible to use a plastic magnet having a higher magnetic force filled with magnetic powder than a conventional product, which can improve the surface magnetic flux density and further contribute to cost reduction.

The method of manufacturing a magnetic encoder of the present invention is a method of manufacturing a magnetic encoder in which a multi-pole magnet having magnetic poles alternately formed in a circumferential direction is provided on a core metal,
The core metal has an inner diameter cylindrical portion, a standing plate portion extending from one end of the inner diameter cylindrical portion to the outer diameter side, and an outer diameter cylindrical portion extending in the axial direction from the outer diameter side end of the standing plate portion, A staking process of providing a staking portion protruding on the inner diameter side of the outer diameter cylindrical portion;
After this staking process, insert molding in which the multipolar magnet is integrally formed by insert molding so that the staking portion is embedded in an annular portion of the cored bar extending over the standing plate portion and the outer diameter cylindrical portion. Process.

In the staking process, a staking portion that protrudes toward the inner diameter side is provided on the outer diameter cylindrical portion of the cored bar. After the staking process, in the insert molding process, a multipolar magnet is integrally formed by insert molding in an annular portion of the core bar extending over the upright plate portion and the outer diameter cylindrical portion.
Since the multi-pole magnet can be easily prevented from coming off and prevented from being rotated by the staking portion provided in advance on the cored bar, the manufacturing cost can be reduced as compared with the case where the conventional rough surface treatment or baking treatment is performed. Moreover, since the multipolar magnet is insert-molded in the core bar provided with the staking portion, it is possible to prevent a problem that an excessive load is applied to the multipolar magnet as in the caulking process.
Since the multipolar magnet is integrally formed by insert molding in the annular part of the core bar extending from the vertical plate part and the outer diameter cylindrical part, even if the multipolar magnet expands in a high temperature environment, the expansion part is used as the inner diameter of the multipolar magnet. It is possible to escape to the side. Thereby, it can prevent that a multipolar magnet deform | transforms undesirably, and can suppress the fall of rotation detection accuracy.

  A magnetic encoder according to the present invention is a magnetic encoder in which a multi-pole magnet having magnetic poles alternately formed in a circumferential direction is provided on a core metal, the core metal having an inner diameter cylindrical portion and one end of the inner diameter cylindrical portion. A standing plate portion extending from the outer diameter side of the standing plate portion to the outer diameter side, and an outer diameter cylindrical portion extending in the axial direction from the outer diameter side end of the standing plate portion. The multipolar magnet is integrally formed by insert molding so that the staking portion is embedded in an annular portion of the cored bar that extends between the standing plate portion and the outer diameter cylindrical portion. Without making it possible, the multipolar magnet and the cored bar can be firmly and inexpensively fixed, and high rotation detection accuracy can be maintained over a long period of time.

  A method for manufacturing a magnetic encoder according to the present invention is a method for manufacturing a magnetic encoder in which a multi-pole magnet having magnetic poles alternately formed in a circumferential direction is provided on a core metal, wherein the core metal includes an inner diameter cylindrical portion, It has a standing plate portion extending from one end of the inner diameter cylindrical portion to the outer diameter side, and an outer diameter cylindrical portion extending in the axial direction from the outer diameter side end of the standing plate portion, and projects to the inner diameter side from the outer diameter cylindrical portion. A staking process in which a staking part is provided, and after the staking process, the staking part is embedded in the annular portion of the cored bar that extends over the standing plate part and the outer diameter cylindrical part. Thus, it has an insert molding process in which it is integrally formed by insert molding, so that it is possible to fix the multipolar magnet and the core metal firmly and at low cost without causing problems in the multipolar magnet, and high rotation. Long-term detection accuracy Over and it can be maintained.

It is sectional drawing of the magnetic encoder which concerns on 1st Embodiment of this invention. It is sectional drawing of the metal core of the magnetic encoder. It is a front view of a concentric bar. It is an enlarged view of the principal part of FIG. It is a flowchart which shows the manufacturing method of the magnetic encoder schematically. It is explanatory drawing which shows schematically the insert molding process of the magnetic encoder. It is explanatory drawing which shows schematically the magnetization process of the magnetic encoder. It is sectional drawing of the principal part of the wheel bearing apparatus which uses the magnetic encoder. It is sectional drawing of the magnetic encoder of a prior art example. It is sectional drawing of the magnetic encoder of another prior art example.

A magnetic encoder according to a first embodiment of the present invention will be described with reference to FIGS. The following description also includes a description of a method for manufacturing the magnetic encoder.
As shown in FIG. 1, the magnetic encoder has an annular cored bar 1 and a multipolar magnet 2 provided on the cored bar 1. The multipolar magnet 2 has magnetic poles N and S formed alternately in the circumferential direction. This magnetic encoder is attached to a rotation-side member (not shown), and is used for rotation detection with the magnetic sensor 3 facing the multipolar magnet 2.

  FIG. 2 is a cross-sectional view of the cored bar 1 of the magnetic encoder. The metal core 1 is formed of a magnetic material, particularly a ferromagnetic metal steel plate, for example, a ferritic stainless steel plate (JIS standard SUS430), a cold rolled steel plate (JIS standard SPCC), or the like. The metal core 1 includes an inner diameter cylindrical portion 4 fitted to the rotation side member, a standing plate portion 5 extending from one end of the inner diameter cylindrical portion 4 to the outer diameter side, and an outer diameter side end of the standing plate portion 5. And an outer diameter cylindrical portion 6 extending in the axial direction. The inner diameter cylindrical portion 4 extends in the axial direction from the inner diameter side end of the standing plate portion 5, and the outer diameter cylindrical portion 6 extends from the outer diameter side end of the standing plate portion 5 in the other axial direction. The axial length of the outer diameter cylindrical portion 6 in this example is shorter than the axial length of the inner diameter cylindrical portion 4.

  FIG. 3 is a front view of the cored bar 1, and FIG. 4 is an enlarged view of a main part of FIG. As shown in FIGS. 3 and 4, staking portions 7 projecting toward the inner diameter side are provided at a plurality of locations in the circumferential direction of the outer diameter cylindrical portion 6. These staking portions 7 are provided at regular intervals in the circumferential direction. The staking portion 7 is provided to fix the multipolar magnet 2 (FIG. 1) to the core metal 1 and to prevent the multipolar magnet 2 (FIG. 1) from coming off from the core metal 1 and to prevent rotation. Each staking portion 7 is plastically deformed so that the tip end portion in the axial direction of the outer diameter cylindrical portion 6 protrudes toward the inner diameter side and becomes substantially V-shaped in a front view. By providing the staking portion 7 only at the axial end of the outer diameter cylindrical portion 6, the multipolar magnet 2 (FIG. 1) is firmly pressed against the cored bar 1 in the direction of arrow A in FIG. 2. As a result, as shown in FIG. 1, the multipolar magnet 2 can be prevented from undesirably coming off in the axial direction with respect to the core metal 1, and the multipolar magnet 2 can be prevented from rotating relative to the core metal 1. Can do.

  The multipolar magnet 2 is, for example, a plastic magnet in which magnetic powder and a thermoplastic resin are mixed. The multipolar magnet 2 is integrally formed by insert molding in an annular portion 8 extending over the upright plate portion 5 and the outer diameter cylindrical portion 6 in the core metal 1. Of the multipolar magnet 2 provided on the annular portion 8 of the cored bar 1, the surface 2 a facing the magnetic sensor 3 is connected to form the same plane as the axial tip of the outer diameter cylindrical portion 6. The multipolar magnet 2 is formed so that the axial thickness t1 is larger than that of the conventional multipolar magnet. The multipolar magnet 2 has a thick-walled portion 9 on the outer diameter side and a thin-walled portion 11 connected to the thick-walled portion 9 on the inner diameter side via an inclined stepped portion 10. The step portion 10 is formed in a cross-sectional shape that is inclined so as to approach the upright plate portion 5 toward the inner diameter side. The surface 2 a facing the magnetic sensor 3 in the multipolar magnet 2 is within a predetermined squareness tolerance and within a predetermined circumferential runout tolerance with respect to the fitting surface 4 a which is a reference surface of the inner diameter cylindrical portion 4. It is formed to fit in.

  As magnetic powder, for example, anisotropic or isotropic ferrite magnetic powder represented by strontium ferrite, barium ferrite, etc., neodymium-iron-boron, samarium-cobalt, samarium-iron-nitrogen, etc. Known magnetic powders such as rare earth magnetic powders can be used, and these are used alone or in combination. In the present embodiment, ferrite-based magnetic powder that exhibits superiority in terms of cost and weather resistance is mainly used.

  As the thermoplastic resin, in order to suppress the deterioration of the magnetic properties of the multipolar magnet due to water absorption as much as possible, those having low water absorption are desirable. For example, polyamide 11 (PA11), polyamide 12 (PA12), polyamide 612 (PA612), Those containing at least one compound selected from the group of polyphenylene sulfide (PPS) are used. Polyphenylene sulfide (PPS) is more desirable because it has a smaller linear expansion coefficient than the other workpieces and can easily achieve a linear expansion coefficient equivalent to that of the core metal.

The compounding quantity of the said magnetic substance powder and the said thermoplastic resin which comprises the said plastic magnet is adjusted as follows. The blending amount is adjusted so that the difference between the linear expansion coefficient of the multipolar magnet 2 and the linear expansion coefficient of the cored bar 1 is 2.0 × 10 ⁻⁵ or less. The difference between the blending amount and the linear expansion coefficient is derived from the test result of the thermal endurance test.

The cold endurance test will be described.
Ten magnetic encoder examples 1 to 6 according to the present embodiment and ten comparative examples 1 and 2 of a conventional magnetic encoder were prepared, and a thermal durability test was performed under the same test conditions. After carrying out this cooling endurance test for 500 cycles, the presence or absence of cracks in the plastic magnet was confirmed. If none of the 10 cracks in each example was cracked, it was judged that “◯”, that is, the durability of cold heat was acceptable.

From the test results, the blending amount of the magnetic powder of the plastic magnet and the thermoplastic resin is adjusted so that the difference between the linear expansion coefficient of the plastic magnet and the linear expansion coefficient of the core metal is 2.0 × 10 ⁻⁵ or less. In the example, there were no cracks.

  FIG. 5 is a flowchart schematically showing a method for manufacturing the magnetic encoder. This will be described with reference to FIG. The magnetic encoder manufacturing method according to this embodiment includes a staking process (step s1), an insert molding process (step s2), and a magnetization process (step s3). First, in the staking process, the aforementioned staking portions 7 are provided at a plurality of locations in the circumferential direction of the outer diameter cylindrical portion 6 of the core metal 1. The staking portion 7 may be provided at the same time as the outer diameter cylindrical portion 6 of the core 1 is provided, or the outer diameter cylindrical portion 6 may be provided after the staking portion 7 is provided.

Next, in the insert molding process, as shown in FIG. 6, the cored bar 1 provided with the staking part 7 is set in the cavity of the injection molding machine 12, and a multipolar magnet is formed on the annular part 8 of the cored bar 1. 2 is integrally formed by insert molding. The injection molding machine 12 has, for example, first and second molds 12a and 12b to be combined. The first mold 12a holds the cored bar 1 in a positioned state. An annular cavity for forming the multipolar magnet 2 is formed in a state where the first and second molds 12a and 12b are combined with each other. In the injection molding machine 12, a gate (not shown) for filling the cavity with the material of the multipolar magnet 2 is provided.
Magnetic field shaping is performed while applying magnetic field orientation simultaneously with the insert molding. The magnetic field orientation at this time is a single pole magnetized in the axial direction, but before taking out (after cooling in the mold), a demagnetizing process is performed by applying a reverse magnetic field. If the demagnetization is insufficient, the accuracy of the magnetic properties after magnetization is affected, so that a complete demagnetization process may be performed in a separate process if necessary.
After the magnetic field forming is performed while integrally forming the multipolar magnet 2 on the core metal 1, the first and second molds 12a and 12b are opened, and the multipolar magnet 2 and the core metal 1 are taken out.

  As a reference proposal example, as shown in FIG. 7, the magnetic field forming machine 13 may sequentially magnetize the multipolar magnet 2 at a desired circumferential pitch while rotating it around the axis L <b> 1. At this time, when anisotropic magnetic powder is used for the plastic magnet, surface magnetic flux density after magnetization can be improved by performing magnetic field shaping while applying magnetic field orientation. Note that a complete demagnetization process may be added before magnetization. In this case, the peak difference between the N pole and the S pole after magnetization can be reduced. Note that the magnetic pole pattern may be transferred at once by the magnetizing yoke.

The effect will be described.
(1) The multipolar magnet 2 can be reliably and easily fixed to the cored bar 1 by staking process + insert molding. Although the fixing of the multipolar magnet is insufficient only by the insert molding, a part of the multipolar magnet 2 is formed on the staking portion 7 by insert molding so that the staking portion 7 provided in advance on the core metal 1 is buried. The multipolar magnet 2 can be easily prevented from coming off and prevented from being rotated, and the multipolar magnet 2 can be firmly fixed to the cored bar 1. Moreover, since it is a staking process, a manufacturing cost can be reduced rather than the case where the conventional roughening process and baking process are performed.
(2) The conventional one that is fixed only by caulking needs to be performed on both the inner peripheral surface and the outer peripheral surface of the multipolar magnet in order to ensure the fixing. I can't escape. In the present application, since the staking portion 7 protruding to the inner diameter side is provided in the outer diameter cylindrical portion 6 of the core metal 1 together with the insert molding, the multipolar magnet 2 only needs to be constrained on the outer peripheral surface. Therefore, even when the multipolar magnet 2 expands in a high temperature environment, the expansion can be released to the inner diameter side of the multipolar magnet 2. Thereby, it can prevent that the multipolar magnet 2 deform | transforms undesirably, and can suppress the fall of rotation detection accuracy.
(3) Since the multipolar magnet 2 is insert-molded after the staking portion 7 is provided in advance on the cored bar 1, no residual stress is generated in the multipolar magnet 2 so that the multipolar magnet 2 can be multipolar as in caulking. A problem that an excessive load is applied to the magnet 2 can be prevented.

  The multipolar magnet 2 is a plastic magnet in which magnetic powder and a thermoplastic resin are mixed. Since the plastic magnet highly filled with magnetic powder can reduce the linear expansion coefficient, the difference between the linear expansion coefficient of the plastic magnet and the linear expansion coefficient of the metal material used for the core metal 1 is reduced. be able to. The multipolar magnet 2 expands in a high temperature environment and contracts in a low temperature environment. However, since the difference in coefficient of linear expansion between the multipolar magnet 2 and the core metal 1 can be reduced as described above, the multipolar magnet 2 and the core metal 1 can be reduced. The difference between the amount of expansion and the amount of contraction can be reduced. Therefore, when the multipolar magnet 2 is expanded at a high temperature, an excessive load is not applied to the multipolar magnet 2 and a problem can be prevented. Further, the play of the multipolar magnet 2 at the time of low temperature shrinkage is also slight.

The thermoplastic resin in the multipolar magnet 2 contains one or more compounds selected from the group consisting of polyamide 12, polyamide 612, polyamide 11 and polyphenylene sulfide, thereby reducing water absorption and magnetic properties of the multipolar magnet 2. Can be suppressed as much as possible.
The blending amount of the magnetic powder and the thermoplastic resin constituting the plastic magnet is adjusted so that the difference between the linear expansion coefficient of the plastic magnet and the linear expansion coefficient of the core metal 1 is 2.0 × 10 ⁻⁵ or less. Thus, it is possible to use a plastic magnet having a higher magnetic force filled with magnetic powder than in the conventional product, thereby improving the surface magnetic flux density and further contributing to cost reduction.

FIG. 8 is a cross-sectional view of a main part of a wheel bearing device using this magnetic encoder.
The wheel bearing device is interposed between an inner member 14 that is a rotation side member, an outer member 15 that is attached to a knuckle (not shown) in the vehicle, and the inner member 14 and the outer member 15. The rolling element 16 is provided. In this example, a ball is applied as the rolling element 16, but it is also possible to apply a roller. The core bar 1 of the magnetic encoder according to the embodiment is fitted in a press-fit state on the outer peripheral surface of the inboard member 14 on the inboard side that is closer to the center in the vehicle width direction.

  In this example, the protective cover 17 is press-fitted into the inner peripheral surface of the outer member 15 on the inboard side, and the inboard side opening of the outer member 15 is closed. The protective cover 17 can prevent leakage of grease enclosed in the bearing and prevent muddy water, foreign matter, and the like from entering the bearing from the outside. The protective cover 17 is made of, for example, a non-magnetic steel plate such as an austenitic stainless steel plate that does not affect the sensing performance of the magnetic sensor 3 facing the multipolar magnet 2 of the magnetic encoder. Instead of the protective cover 17, for example, a sealing device (not shown) is provided on the inner peripheral surface of the outer member 15 so that the lip is in sliding contact with the outer peripheral surface of the inner diameter cylindrical portion 4 and the inner surface of the upright plate portion 5. Also good.

When the magnetic encoder according to the embodiment is applied to the wheel bearing device, the multi-pole magnet 2 can be easily prevented from coming off and prevented from rotating by the staking portion 7 provided in advance on the core 1, so that it is manufactured more than the prior art. Cost can be reduced. Moreover, since the multipolar magnet 2 is insert-molded in the core metal 1 provided with the staking portion 7, it is possible to prevent a problem that an excessive load is applied to the multipolar magnet as in caulking.
Since the multipolar magnet 2 is integrally formed by insert molding in the annular portion 8 extending over the upright plate portion 5 and the outer diameter cylindrical portion 6 of the core metal 1, even when the multipolar magnet 2 expands in a high temperature environment, Can be released to the inner diameter side of the multipolar magnet 2. Thereby, it can prevent that the multipolar magnet 2 deform | transforms undesirably, and can suppress the fall of rotation detection accuracy.

DESCRIPTION OF SYMBOLS 1 ... Core metal 2 ... Multipolar magnet 4 ... Inner diameter cylindrical part 5 ... Standing plate part 6 ... Outer diameter cylindrical part 7 ... Staking part 8 ... Annular part

Claims (6)

A magnetic encoder provided with a multi-pole magnet having magnetic poles alternately formed in a circumferential direction on a mandrel,
The core metal has an inner diameter cylindrical portion, a standing plate portion extending from one end of the inner diameter cylindrical portion to the outer diameter side, and an outer diameter cylindrical portion extending in the axial direction from the outer diameter side end of the standing plate portion, A staking portion that protrudes toward the inner diameter side is provided in this outer diameter cylindrical portion,
A magnetic encoder, wherein the multipolar magnet is integrally formed by insert molding so that the staking portion is embedded in an annular portion of the cored bar that extends between the standing plate portion and the outer diameter cylindrical portion.   The magnetic encoder according to claim 1, wherein the multipolar magnet is a plastic magnet in which magnetic powder and a thermoplastic resin are mixed.   3. The magnetic encoder according to claim 1, wherein magnetic powder is mixed in the multipolar magnet, and the magnetic powder contains at least strontium ferrite.   4. The magnetic encoder according to claim 1, wherein the multipolar magnet includes a mixture of magnetic powder and a thermoplastic resin, and the thermoplastic resin includes polyamide 12, polyamide 612, and polyamide. 5. 11. A magnetic encoder comprising one or more compounds selected from the group consisting of polyphenylene sulfide. 5. The magnetic encoder according to claim 1, wherein the multipolar magnet is a plastic magnet in which magnetic powder and a thermoplastic resin are mixed, and the linear expansion coefficient of the multipolar magnet. The magnetic encoder which adjusted the compounding quantity of the said magnetic substance powder and the said thermoplastic resin which comprise the said plastic magnet so that the difference with the linear expansion coefficient of the said core metal may be 2.0 * 10 <^-5> or less. A method of manufacturing a magnetic encoder provided with a multi-pole magnet having magnetic poles alternately formed in a circumferential direction on a mandrel,
The core metal has an inner diameter cylindrical portion, a standing plate portion extending from one end of the inner diameter cylindrical portion to the outer diameter side, and an outer diameter cylindrical portion extending in the axial direction from the outer diameter side end of the standing plate portion, A staking process of providing a staking portion protruding on the inner diameter side of the outer diameter cylindrical portion;
After this staking process, insert molding in which the multipolar magnet is integrally formed by insert molding so that the staking portion is embedded in an annular portion of the cored bar extending over the standing plate portion and the outer diameter cylindrical portion. Process,
The manufacturing method of the magnetic encoder which has.

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