JP2005214874A - Encoder, and rolling bearing equipped with encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder capable of enhancing a magnetic characteristic to facilitate assembling to a sensor, and capable of detecting precisely the number of revolution of a rotor, and a rolling bearing equipped the encoder. <P>SOLUTION: This encoder 30 attached to the rolling bearing 10 provided with an outer ring 11, an inner ring 12, balls 13, that is a plurality of rolling elements, arranged freely rollingly in an annular clearance formed by the outer ring 11 and the inner ring 12, and held circumferential-directionally with an equal space by a cage 14, and a sealing device 15 arranged in an opening end part of the annular clearance has an annular ring shape formed of a magnetic material containing magnetic powder, and a thermoplastic resin as a binder for the magnetic powder, has a magnetic attraction part attracted circumferential-directionally to multiple poles, and is injection-molded radial-circularly from an inner circumferential part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an encoder used for detecting the rotational speed of a rotating body and a rolling bearing provided with the encoder.

Conventionally, anti-skid to prevent car skid (a phenomenon in which the wheel slips in a substantially stopped state) or traction control to effectively transmit the driving force to the road surface As a wheel rotation number detection device used for control, etc., an annular encoder in which N poles and S poles are alternately magnetized in the circumferential direction, a sensor for detecting a change in magnetic field in the vicinity of the encoder, And the encoder is provided in a sealing device for sealing the bearing that supports the wheel so that the encoder is rotated together with the rotation of the wheel, and a change in the magnetic field synchronized with the rotation of the wheel is detected by the sensor. What is to be detected is known. (For example, see Patent Document 1)
Japanese Patent Laid-Open No. 2001-255337 (pages 2 and 3, FIG. 2)

  As shown in FIG. 8, the wheel rotation speed detection device disclosed in Patent Document 1 is attached to the seal member 2 attached to the outer ring 1 a, the slinger 3 fitted to the inner ring 1 b, and the outer surface of the slinger 3. The encoder 4 is rotated together with the inner ring 1b, and the sensor 5 is disposed close to the encoder 4. The seal member 2 and the slinger 3 allow foreign matters such as dust to enter the bearing. The lubricant filled in the bearing is prevented from leaking outside the bearing. The encoder 4 is bonded to the outer surface of the slinger 3 to which an adhesive is applied. The encoder 4 generates the number of magnetic pulses corresponding to the number of poles during one rotation of the inner ring 1b, and detects the number of rotations of the inner ring 1b by detecting this magnetic pulse with the sensor 5. In general, a rubber magnet containing ferrite as magnetic powder is used for the encoder 4, and the ferrite is mechanically oriented by rolling a magnet material with a roll.

  However, in order to efficiently perform anti-skid and traction control, it is necessary to detect the rotational speed of the wheel with high accuracy. In the above-mentioned wheel rotational speed detection device, the encoder is further magnetized in multiple poles. This is realized by reducing the interval between magnetic pulses. However, since the magnetic flux per pole decreases and the magnetic pulse becomes weak, it is necessary to reduce the gap (air gap) between the encoder and the sensor, which may make it difficult to assemble the two. In addition, the magnetic properties such as the magnetic flux density of the encoder can be improved to prevent a decrease in magnetic flux per pole. However, in rubber magnets, magnetic powder that can be mixed into ferrite such as strontium ferrite and barium ferrite. In addition, it is difficult to improve the magnetic properties only by mechanically orienting the ferrite.

  The present invention has been made in view of the circumstances described above, and an encoder capable of facilitating assembly with a sensor by improving magnetic characteristics and detecting the number of rotations of a rotating body with high accuracy, and the encoder. It aims at providing the rolling bearing provided with.

  In order to achieve the above-described object, an encoder according to the present invention is characterized by the following (1) to (2).

(1) An encoder,
A magnet material containing magnetic powder and a thermoplastic resin as a binder of the magnetic powder is formed in an annular shape,
Having a magnetized portion magnetized in multiple poles in the circumferential direction;
It must be injection-molded from the inner periphery using the disk gate method.
(2) The encoder according to (1) above,
60-80 volume% of said magnetic powder is contained.

  The rolling bearing according to the present invention is characterized by the following (3).

(3) A rolling bearing comprising the encoder according to (1) or (2) above,
A fixed wheel, a rotating wheel, a plurality of rolling elements disposed in a circumferential direction by an annular gap formed between the fixed wheel and the rotating wheel, and a magnetic material fixed to the rotating wheel A slinger made of
The encoder is joined to the slinger.

  According to the encoder of the present invention, a magnet material containing magnetic powder and a thermoplastic resin as a binder of the magnetic powder is formed in an annular shape, and is injection-molded by a disk gate method from the inner periphery. Therefore, the magnet material is injection-molded in a radial shape, the degree of orientation of the magnetic powder contained in the encoder is high, and the magnetic properties are excellent. In the disk gate type injection molding, molten magnet material is injected at a high pressure from an injection port (gate) provided over the entire circumference in the inner circumferential portion of the annular space of the mold corresponding to the shape of the encoder. . Thereby, the molten magnet material is uniformly filled in the annular space in a radial shape, and the magnetic powder in the magnet material is oriented in the thickness direction of the encoder. Furthermore, since no weld is formed, an encoder having excellent magnetic properties and high mechanical strength can be formed. In addition, when a magnetic field is applied in the thickness direction during injection molding (that is, magnetic field orientation), the degree of orientation of the magnetic powder can be further increased. In addition, injection molding by a gate system other than the disk gate system (for example, a pin gate system, etc.) completely aligns the weld portion generated by collision of molten magnet materials even if magnetic field alignment is performed. In addition, it is not preferable because there is a possibility that a crack or the like may occur in the welded portion due to long-term use.

  Furthermore, in addition to ferrites such as strontium ferrite and barium ferrite, rare earth magnetic powders with excellent magnetic properties such as neodymium-iron-boron, samarium-cobalt, and samarium-iron can be used as the magnetic powder. Since it is possible to use a material mixed with rare earth elements such as lanthanum in order to improve the characteristics, the magnetic characteristics of the encoder can be further improved. In addition, when rare earth magnetic powder is used for the magnetic powder, the oxidation resistance is lower than that of ferrite, so in order to maintain stable magnetic properties over a long period of time, electric nickel plating, electroless nickel plating, A surface treatment layer such as an epoxy resin coating, a silicon resin coating, or a fluororesin coating may be provided on the encoder surface.

  In addition, a thermoplastic resin that enables injection molding is used as the binder, and specifically, polyamide 6, polyamide 12, polyamide 612, polyamide 11, or polyphenylene sulfide (PPS) can be used. Since calcium chloride used as a snow melting agent and water may be applied to the encoder together, polyamide 12, polyamide 612, polyamide 11 or polyphenylene sulfide having poor water absorption is preferable.

  Moreover, it is preferable that content of the magnetic powder of an encoder shall be 60-80 volume%. This is because when the magnetic powder content is less than 60% by volume, the magnetic properties are inferior and it is difficult to magnetize multiple poles at a narrow pitch, while the magnetic powder content is 80% by volume. If it exceeds, the binder amount is insufficient, the mechanical strength of the entire encoder is lowered, and molding becomes difficult. Note that the number of poles of the magnetized portion magnetized in the circumferential direction is about 70 to 130, preferably 90 to 120. This is because if the number of poles is less than 70, the number of poles is too small to accurately detect the number of rotations of the rotating body, while if the number of poles exceeds 130, the pitch is small. This is because it becomes too difficult to suppress the single pitch error and the practicality is low. As the magnetic characteristics of the encoder, a maximum energy product (BHmax) of 1.3 to 15 MGOe, more preferably 1.8 to 12 MGOe is achieved. If the maximum energy product is less than 1.3 MGOe, the magnetic properties are too low, so the sensor must be placed very close to the encoder, which is not much different from the conventional rubber magnets containing ferrite and can be expected to improve performance. Absent. In addition, when the maximum energy product exceeds 15 MGOe, it is not possible to achieve with a composition having an excessive magnetic property and an inexpensive ferrite as a main component, and a large amount of expensive rare earth magnetic powder such as neodymium-iron-boron is blended. It is necessary and has poor moldability and low practicality.

  Further, according to the rolling bearing according to the present invention, the encoder is joined to the slinger made of a magnetic material and rotated together with the rotating wheel, so that the magnetic characteristics of the encoder are not deteriorated. As a magnetic material, ferrite stainless steel (SUS430 etc.), martensitic stainless steel (SUS410 etc.) etc. which have corrosion resistance can be used conveniently.

  When a polyamide resin such as polyamide 6 or polyamide 12 is used as the binder for magnetic powder, a silane coupling agent having an epoxy group such as γ-glycidoxypropyltrimethoxysilane is used on the joint surface between the slinger and the encoder. By applying high-frequency heating after coating, silanol groups (Si-OH) produced by hydrolysis of methoxy groups contained in the silane coupling agent cause a dehydration condensation reaction with hydroxyl groups (OH) on the slinger surface. A new bond is formed and the epoxy group reacts with the amide bond of the binder to form a new bond. Accordingly, the encoder and the slinger are completely joined chemically, and it is possible to reliably prevent the encoder from falling off the slinger and to improve the reliability.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.

  1 is a sectional view of a rolling bearing assembled with an encoder according to a first embodiment of the present invention, FIG. 2 is a front view of the slinger shown in FIG. 1, and FIG. 3 is a view of the slinger shown in FIG. 1 is a cross-sectional view of the main part of the rolling bearing shown in FIG. 1 in the same plane as the cross section, FIG. 4 is a cross-sectional view of the main part of the rolling bearing shown in FIG. Is a schematic diagram showing a magnetizing pattern of a magnetized portion of the encoder shown in FIG. 1, FIG. 6 is a sectional view of a mold used for injection molding of the encoder shown in FIG. 1, and FIG. 7 is a second embodiment according to the present invention. It is sectional drawing of the hub unit assembled | attached with the encoder which is a form.

  As shown in FIGS. 1 to 4, the rolling bearing 10 assembled with the encoder according to the first embodiment of the present invention includes an outer ring 11 that is a fixed ring, an inner ring 12 that is a rotating ring, an outer ring 11, and an inner ring 12. The ball 13 is a plurality of rolling elements that are arranged to be freely rollable in the annular gap defined by the holder and held at equal intervals in the circumferential direction by the retainer 14, and the opening end of the annular gap. The sealing device 15 and an encoder 30 for detecting the rotational speed of the inner ring 12 are provided. The sealing device 15 includes a seal member 40 fixed to the inner peripheral surface of the outer ring 11, and a slinger 20 disposed on the outer side of the opening end than the seal member 40 and fixed to the outer peripheral surface of the inner ring 12. The sealing member 40 and the slinger 20 close the opening end of the annular gap to prevent foreign matters such as dust from entering the bearing, and the lubricant filled in the bearing leaks to the outside of the bearing. It is preventing. The encoder 30 is joined to the slinger 20 and rotates together with the inner ring 12.

  The slinger 20 is formed by forming a magnetic material in an annular shape having an L-shaped cross section, and includes a substantially cylindrical fitting portion 22 that is fitted on the outer peripheral surface of the inner ring 1b, and one end of the fitting portion 22 on the opening end side. And a substantially disc-shaped flange portion 21 extending in the radial direction. A plurality of engaging portions 23 that are notched in a concave shape are provided at equal intervals in the circumferential direction on the outer peripheral edge portion of the flange portion 21. An encoder 30 that changes a nearby magnetic field (for example, magnetic flux density) in synchronization with the rotation of the inner ring 12 is joined to the end face outside the opening end of the flange portion 21.

  The encoder 30 includes an annular magnetized portion 31 having a substantially rectangular cross section, a plurality of locking pieces that engage with the locking portion 23 of the slinger 20, and a connecting portion 32 that connects the plurality of locking pieces. Is provided. The encoder 30 is formed by injection molding of a magnetic material containing magnetic powder as appropriate within a range of 60 to 80% by volume and using a thermoplastic resin as a binder, and insert molding with the slinger 20 in the mold as a core. Has been. By adopting insert molding, the molten magnet material is filled into the locking portion 23 of the slinger 20 to form a locking piece, and adjacent to the inner end face of the opening end of the flange portion 21, the locking A connecting portion 32 is formed by filling an annular space in a mold provided so as to connect the pieces. The encoder 30 and the slinger 20 are mechanically joined to each other by engaging the engaging portion 23 and the engaging piece and sandwiching the flange portion 21 between the magnetized portion 31 and the connecting portion 32 of the encoder. Yes.

  As shown in FIG. 5, the magnetized portion 31 is magnetized with S poles and N poles alternately (that is, with multiple poles) at equal intervals in the circumferential direction. While the inner ring 12 rotates once, the magnetic flux density at one point near the encoder 30 periodically changes with the number of peaks corresponding to the number of poles of the magnetized portion 31. And the change of the said magnetic flux density is detected by the sensor not shown arrange | positioned facing the axial direction end surface of the encoder 30 which faces a bearing outward, and the rotation speed of the inner ring | wheel 12 is detected.

  As shown in FIG. 3 or 4, the seal member 40 reinforces a seal lip 42 formed in an annular shape having a substantially L-shaped cross section by a core metal 41 formed in an annular shape having a substantially L-shaped cross section. The inner ring 11 is fixed by being fitted inside the outer ring 11. The front end portion of the seal lip 42 is branched into a plurality of sliding contact portions, and the plurality of sliding contact portions are arranged on the inner side surface of the flange portion 21 of the slinger 20 or the outer peripheral surface of the fitting portion 22 on the entire circumference. They are in sliding contact with each other. Thereby, a high sealing force can be obtained.

  With reference to FIG. 6, the encoder 30 is molded using an injection molding machine having a movable mold 51, a core 52, a fixed mold 53, a sprue ejector pin 54a, and an ejector pin 54b. ing. The movable side mold plate 51 has a nozzle port 55 into which a molten magnet material is injected and connected to a nozzle of an injection molding machine. 56 penetrates to the lower surface. The sprue 56 is an inflow path of the magnet material from the nozzle of the injection molding machine to the runner 57, and is formed in a tapered shape having a larger diameter on the runner 57 side than the nozzle port 55. This makes it easy to remove the magnet material (molded body) solidified by the sprue 56. The runner 57 is a resin inflow path from the sprue 56 to the gate 58, and is a space defined by a substantially disk-shaped recess provided in the fixed side mold plate 53 and the lower side surface of the movable side mold plate 51. . In addition, a reverse-tapered sprue lock serving as a stopper with respect to the take-out direction of the molded body is provided at the center of the bottom surface of the runner 57, and the movable side mold 51 is removed when the movable side mold plate 51 is removed after injection molding. The plate 51 and the molded body can be separated smoothly. A sprue ejector pin 54 a is provided below the sprue lock, and the molded body is pushed up from below to separate the molded body from the fixed-side template 53.

  The gate 58 is an inlet through which the magnet material flows from the runner 57 into the cavity 59, and the cavity 59 is a space for shaping the shape of the encoder 30. The cavity 59 is a space defined by an annular recess corresponding to the shape of the encoder 30 provided in the core 52, the peripheral surface of the fixed-side mold plate 53, and the lower surface of the movable-side mold plate 51. . A plurality of ejector pins 54 b are provided in the circumferential direction on the bottom surface of the cavity 59, and after the injection molding, the encoder 30 is pushed up from below to separate the encoder 30 from the core 52. The gate 58 is an annular space that connects the outer peripheral portion of the runner 57 and the inner peripheral portion of the cavity 59 so as to allow the runner 57 and the cavity 59 to communicate with each other, and is a so-called disc gate. is there.

  In the above-described injection molding machine, the encoder 30 is such that the molten magnet material flows from the nozzle port 55 through the sprue 56 into the runner 57, is injected into the cavity 59 at a high pressure from the disk gate 58, and is rapidly cooled and solidified. It is molded by. The magnet material injected from the disk gate 58 at a high pressure spreads radially from the inner peripheral portion of the cavity 59 and is uniformly filled in the cavity 59, so that the melted magnet materials do not collide with each other, and the magnet Each flake-like (plate-like crystal) magnetic powder contained in the material aligns the normal direction of the surface (that is, the direction of easy magnetization) parallel to the thickness direction of the encoder 30 (in other words, the axial direction). Oriented. In particular, the vicinity of the inner peripheral portion scanned by the sensor (that is, the magnetized portion) has a high degree of orientation and exhibits magnetic characteristics very close to axial anisotropy. In addition, by performing injection molding in a state where a magnetic field is applied in the thickness direction, the magnetic powder in the magnet material can be more completely oriented.

  According to the rolling bearing 10 assembled with the encoder 30 described above, a magnetic material containing a thermoplastic resin as a binder and appropriately containing magnetic powder in a range of 60 to 80% by volume is formed in a circular shape from the inner periphery by a disk gate method. Since the encoder 30 is formed into an annular shape by injection molding, the degree of orientation of the magnetic powder contained in the encoder 30 can be increased, and the magnetic characteristics of the encoder 30 can be improved. As a result, the gap between the encoder 30 and the sensor can be increased, and the magnetized portion 31 of the encoder 30 can be magnetized in multiple poles, which facilitates assembly with the sensor and the inner ring 12. The rotational speed can be detected with high accuracy. In addition, the encoder 30 does not have a welded portion that is solidified by collision between molten magnet materials, has high mechanical strength, and is unlikely to crack. Furthermore, since the encoder 30 is insert-molded with the slinger 20 as a core, the encoder 30 and the slinger 20 can be mechanically joined, and the encoder 30 is reliably prevented from falling off the slinger 20 to improve reliability. Can be made.

  Next, a hub unit incorporating an encoder according to the second embodiment of the present invention will be described with reference to FIG. In addition, description of the component common to the above-mentioned rolling bearing 10 is simplified or abbreviate | omitted by attaching | subjecting the same code | symbol.

  The hub unit 102 rotatably supports a wheel (not shown) fixed to the mounting flange 112 of the hub 107. Two rows of outer ring raceways 110a and 110b that are parallel to each other are formed on the inner peripheral surface of the outer ring 105, and the outer ring raceways 110a and 110b are respectively provided on the outer peripheral surfaces of the hub 107 and the inner ring member 106 that are rotating bodies. Opposing inner ring raceways 114a and 114b are formed. In the gap between the outer ring raceway 110a and the inner ring raceway 114a, and the gap between the outer ring raceway 110b and the inner ring raceway 114b, rolling elements 117 held at equal intervals in the circumferential direction by the cage 118 are respectively arranged to be able to roll. ing. In the gap between the inner peripheral surface of the outer ring 105 and the inner ring member 106, a sealing device 15 is assembled at the opening end of the rolling element 117 opposite to the wheel side (that is, the vehicle side). An encoder 30 is joined to the slinger 20 of the sealing device 15. A sensor 109 is disposed opposite to the axial end face of the encoder 30 facing the outside of the bearing. The sensor 109 detects the change in magnetic flux density to detect the rotational speed of the wheel.

    The magnetic encoder of the present invention is not limited to the above-described embodiments, and appropriate modifications and improvements can be made.

  For example, a polyamide resin such as polyamide 6 or polyamide 12 is used for the binder, an epoxy silane coupling agent is applied to the joint surface of the flange portion 21 with the encoder 30, and the slinger 20 is held in the mold. After the insert molding, the encoder 30 and the slinger 20 may be joined by high-frequency heating instantaneously at 200 to 350 ° C. Thereby, the encoder 30 and the slinger 20 can be joined mechanically and chemically, and the encoder 30 can be reliably prevented from falling off the slinger 20 and the reliability can be improved.

  Further, the structure of the flange portion 21 of the slinger 20 is not limited to that shown in FIG. 2. For example, a plurality of through holes and engagement recesses may be provided at equal intervals in the circumferential direction on the circumference of the central portion in the radial direction. Good. In this case, the encoder 30 is insert-molded so that the melted magnetic material is filled in the through hole or the engaging recess, and mechanically joined to the slinger 20. Further, in order to improve the adhesion between the relatively hard resin-based encoder 30 and the flange portion 21, a film-like elastic member such as rubber may be interposed therebetween. In the hub unit 102, the encoder 30 may be disposed between two rows of inner ring raceways 114a and 114b parallel to each other, and may be fixed to the rotating body via an attachment member. In this case, the sensor 109 is disposed so as to face the outer peripheral surface of the encoder 30 and is held by the outer ring 105. Further, the slinger 20 and the mounting member may have a simple annular shape without a flange portion. The encoder 30 may be formed separately from the slinger 20 and the attachment member, and may be joined to the slinger 20 and the attachment member using an adhesive. Further, the encoder 30 may be fixed by being press-fitted into the slinger 20, the attachment member, or the rotating body, or the encoder 30 may be fixed by jointly using an adhesive and fixing by press-fitting.

Next, an encoder manufactured according to the present invention will be described. The encoders of the first to fourth embodiments are those which are magnetized in the circumferential direction after being injection-molded in an annular shape. In addition, the magnet material used for the encoder of the 1st-4th Example is shown below.
Magnet material for testing:
Toda Kogyo 12 nylon anisotropic plastic magnet compound containing strontium ferrite "FEROTOP TP-A27N" (Strontium ferrite content: 75% by volume)

  The encoder in the first embodiment is molded by a disk gate type injection molding machine, and is not magnetically oriented during molding.

  The encoder in the second embodiment is formed by a disk gate type injection molding machine, and is magnetically oriented together with the molding.

  The encoder in the third embodiment is molded by a four-point pin gate type injection molding machine, and is not magnetically oriented during molding.

  The encoder in the fourth embodiment is formed by a four-point pin gate type injection molding machine, and is magnetically oriented at the time of molding.

  Table 1 shows the results of measuring the magnetic characteristics (maximum energy product BHmax) of the encoders of the first to fourth embodiments using a BH tracer. Incidentally, the measured values of the third and fourth examples are obtained by measuring the magnetic characteristics in the weld portion.

  According to Table 1, it can be seen that the encoder injection-molded by the disk gate method has magnetic characteristics superior to those by injection molding by the four-point pin gate method regardless of the presence or absence of magnetic field orientation. That is, according to the disk gate method, the easy magnetization directions of the magnetic powders can be aligned to obtain a high degree of orientation, and thus excellent magnetic properties can be obtained. On the other hand, in the four-point pin gate method, the magnetic properties in the melted magnet material collide with each other in the weld portion and the easy magnetization direction becomes random (isotropic), so that the magnetic characteristics are remarkably lowered. Even when the magnetic field orientation is performed together with the injection molding by the four-point pin gate method, it is difficult to completely align the magnetic powder in the weld, and only the injection molding by the disk gate method without the magnetic field orientation. It can be seen that the encoder does not reach the magnetic characteristics of the encoder formed by the above method. The same result is obtained when a plastic magnet material containing rare earth magnetic powder such as SmFeN (samarium-iron-nitrogen) is used.

It is sectional drawing of the rolling bearing assembled | attached with the encoder which is 1st Embodiment which concerns on this invention. It is a front view of the slinger shown in FIG. It is principal part sectional drawing of the rolling bearing shown in FIG. 1 in the same plane as the III-III arrow cross section of the slinger shown in FIG. It is principal part sectional drawing of the rolling bearing shown in FIG. 1 in the same plane as the IV-IV arrow cross section of the slinger shown in FIG. It is a schematic diagram which shows the magnetization pattern of the magnetizing part of the encoder shown in FIG. It is sectional drawing of the metal mold | die used for the injection molding of the encoder shown in FIG. It is sectional drawing of the hub unit assembled | attached with the encoder which is 2nd Embodiment which concerns on this invention. It is sectional drawing of the conventional wheel rotation speed detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rolling bearing 11 Outer ring 12 Inner ring 13 Ball 14 Cage 15 Sealing device 20 Slinger 30 Encoder 31 Magnetized part

Claims (3)

An encoder,
A magnet material containing magnetic powder and a thermoplastic resin as a binder of the magnetic powder is formed in an annular shape,
Having a magnetized portion magnetized in multiple poles in the circumferential direction;
An encoder characterized by being injection-molded from the inner periphery by a disc gate method.   The encoder according to claim 1, comprising 60 to 80% by volume of the magnetic powder. A rolling bearing comprising the encoder according to claim 1 or 2,
A fixed wheel, a rotating wheel, a plurality of rolling elements disposed in a circumferential direction by an annular gap formed between the fixed wheel and the rotating wheel, and a magnetic material fixed to the rotating wheel A slinger made of
The rolling bearing, wherein the encoder is joined to the slinger.

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