JP2013087786A - Hub unit bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hub unit bearing capable of suppressing occurrence of eddy current losses while increasing positioning accuracy of an encoder cap to improve reliability of rotational speed detection, and reducing bearing torque.SOLUTION: In the bottom of an encoder cap 19, a proximate part 27 having a bottom surface close to a magnetic encoder 16 is disposed so as to set the sensing surface of the magnetic sensor 20 to be close to the magnetic encoder 16 so as to face each other. The bottom other than the proximate part 27 is located closer to a vehicle inner side direction from the sensor element 30 of the magnetic sensor 20.

Description

  The present invention relates to a hub unit bearing that rotatably supports a wheel of an automobile or the like and includes a magnetic encoder used to measure the rotational speed of the wheel.

  Conventionally, as a hub unit bearing having a magnetic encoder, an outer ring fixed to a knuckle of a vehicle body, a wheel mounting flange and a shaft portion, a hub shaft having the shaft portion inserted into the outer ring, and the wheel mounting flange, Is an inner ring element that is externally fitted to the portion of the shaft portion on the opposite side, a rolling element that is movably interposed between the outer ring, the shaft portion, and the outer ring and the inner ring element; and Some have a magnetic encoder attached to the outer periphery, and an encoder cap attached to the outer ring and covering the magnetic encoder.

  In such a hub unit bearing, a non-magnetic austenitic stainless steel plate is formed by pressing, and provided with an encoder cap that has a three-dimensional structure with irregularities on the disk-shaped portion, and a wheel mounting flange. The end of the outer ring on the opposite side is processed for positioning the encoder cap, and the eyebrow-shaped proximity part that is close to the magnetic encoder is provided in the disk-shaped part that faces the magnetic encoder. There is a hub unit bearing that can be sensed near the magnetic encoder by forming the magnetic sensor against the bottom of the proximity portion (see Patent Document 1).

JP 2010-106909 A

  However, in the hub unit bearing according to Patent Document 1, an eddy current is generated in the stainless steel cap, which is a conductor, due to the alternating magnetic flux of the magnetic encoder, and a force to brake the rotation of the inner ring acts, resulting in a heavy bearing torque. There is a problem. In particular, the proximity portion has an eyebrow shape, and the bottom portion close to the encoder is long in the circumferential direction, so that there is a problem that a larger braking force is generated by the eddy current.

  In view of such a problem, the present invention provides a hub unit bearing that suppresses the generation of eddy current loss and reduces the torque of the bearing while increasing the positioning accuracy of the encoder cap and improving the reliability of rotational speed detection. The purpose is to provide.

  In order to solve the above problems, in the present invention, a substantially cylindrical outer ring having a double row outer rolling surface on the inner periphery, and an outer ring inserted into the outer ring and provided on the outer periphery facing the outer rolling surface. A substantially cylindrical inner ring portion having double-row inner rolling surfaces, and a wheel provided at one end of the inner ring portion and extending radially outward of the inner ring portion on the outer side in the axial direction of the outer ring. A hub shaft provided with a mounting flange, a plurality of rolling elements interposed between the outer rolling surface and the inner rolling surface, and a thin plate made of a non-magnetic stainless steel, and fixed to the outer ring Of the magnetic sensor with a part of the bottom portion interposed therebetween, and an encoder cap that includes a cylindrical fixing portion, a bottom portion extending radially inward from the fixing portion and covering an end portion of the inner ring portion. An annular magnetic encoder fixed to the outer periphery of the inner ring portion so as to face the sensing surface; A hub unit bearing that is in contact with an end face of the outer ring or an increased diameter step formed on an inner peripheral portion of the outer ring, and the magnetic sensor of the bottom part The portion interposed between the sensing surface is a bottom portion of a protruding portion that protrudes toward the magnetic encoder so that the sensing surface is opposed to the magnetic encoder, and the bottom portion other than the protruding portion is the magnetic portion. Provided is a hub unit bearing which is disposed in a vehicle inner side direction from a sensor element of a sensor.

  Preferably, the bottom portion other than the protrusion is disposed such that a surface on the magnetic encoder side is separated from the magnetic encoder by 2 mm or more.

  Preferably, the protrusion has a circular planar shape.

  More preferably, the encoder cap is formed by pressing a resin film laminated steel plate.

  More preferably, a ferrite coating is provided on a surface of the bottom portion that faces the encoder other than the protrusions.

  According to the present invention, it is possible to provide a hub unit bearing that increases the positioning accuracy of the encoder cap and improves the reliability of rotational speed detection, suppresses the occurrence of eddy current loss, and reduces the bearing torque.

It is sectional drawing which shows the hub unit bearing which concerns on 1st Embodiment of this application. It is a top view which shows the encoder cap of the hub unit bearing which concerns on 1st Embodiment of this application. It is an expanded sectional view of the magnetic encoder periphery of the hub unit bearing according to the first embodiment of the present application. It is an expanded sectional view of a magnetic encoder periphery of a hub unit bearing according to a second embodiment of the present application. It is an expanded sectional view of a magnetic encoder periphery of a hub unit bearing according to a third embodiment of the present application.

(First embodiment)
A hub unit bearing according to a first embodiment of the present application will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a hub unit bearing according to the first embodiment. Since the upper and lower cross sections have substantially the same configuration, the lower side is omitted in FIG. 1 and only the upper half is shown.

  The hub unit bearing 1 according to the first embodiment is mainly interposed between the outer ring 2, the hub shaft 3 partially inserted into the outer ring 2, and the outer ring 2 and the hub shaft 3. A large number of balls 4 are formed.

  The outer ring 2 has a substantially cylindrical shape, and an annular first outer rolling surface 5 and second outer rolling surface 6 are formed on the inner peripheral portion from the left side (that is, the vehicle outer side) as viewed in FIG. A vehicle body mounting flange (not shown) for fixing the outer ring 2 to the vehicle body extends radially outward from the outer peripheral surface of the outer ring 2.

  The hub shaft 3 includes a hub wheel 7 provided on the left side in FIG. 1, a wheel mounting flange 8 extending radially outward from the hub wheel 7, and an outer ring on the right side (that is, the vehicle inner side) in FIG. 1. 2 has a shaft portion 9 inserted into the interior of 2 and an inner ring element 10 fitted on the shaft portion 9.

  Bolt holes 11 for inserting wheel mounting bolts are formed in the wheel mounting flange 8.

  The shaft portion 9 has a substantially cylindrical shape, is formed integrally with the wheel mounting flange 8 and the hub wheel 7, and has an annular shape facing the first outer rolling surface 5 on the left outer peripheral surface as viewed in FIG. 1. The first inner rolling surface 12 is formed. A diameter-reduced portion 13 for fitting the inner ring element 10 is provided on the right side of the shaft portion 9 in FIG. 1, and the shaft end of the shaft portion 9 is caulked by swing forging or riveting on the further right side. Thus, a caulking portion 14 that fixes the inner ring element 10 to the shaft portion 9 is formed.

  An annular second inner rolling surface 15 is formed on the outer peripheral surface of the inner ring element 10 so as to face the second outer rolling surface 6. The portion on the right side of FIG. 1 (that is, the vehicle inner side portion) with respect to the second inner rolling surface 15 is formed to be thicker than the left portion, and the magnetic encoder 16 is provided on the outer peripheral surface of the thick portion. It is fixed. The magnetic encoder 16 is an axial type that is axially opposed to the magnetic sensor 20 fixed inside the vehicle. The magnetic encoder 16 is filled with a magnetic powder such as ferrite powder in a rubber material or a thermoplastic resin material serving as a binder, and the cross section is L. After being vulcanized or injection-molded integrally with a ring-shaped cored bar 28, N poles and S poles are alternately magnetized in multi-poles at equal intervals in the circumferential direction. The inner ring element 10 is press-fitted to the outer peripheral surface.

  The ball 4 is formed by the first rolling path formed by the first outer rolling surface 5 and the first inner rolling surface 12, and the second outer rolling surface 6 and the second inner rolling surface 15. A number of the second rolling paths are interposed. The ball 4 is held by a cage 17 so as to be able to roll. In the first embodiment, a ball is used as the rolling element. However, the present invention is not limited to this, and a rolling element such as a tapered roller can also be used.

  A seal 18 is mounted between the portion of the outer ring 2 on the wheel mounting flange 8 side and the portion of the hub shaft 3 facing the portion. On the other hand, the gap between the outer ring 2 on the magnetic encoder 16 side and the hub shaft 3 is covered with an encoder cap 19 made of a non-magnetic austenitic stainless steel plate fitted in the outer ring 2.

  FIG. 2 is a plan view of the encoder cap 19 as viewed from the right side in FIG. The encoder cap 19 includes a cylindrical fixed portion 21 extending to the back side in FIG. 2, a ring portion 22 extending radially inward from an end of the fixed portion 21 on the front side in FIG. 2 (that is, the vehicle inner side), A first inclined portion 23 that extends from the inner end of the ring portion 22 toward the front side in FIG. 2 and extends radially inward, and a convex that extends radially inward from the inner end of the first inclined portion 23. Part 24, a second inclined part 25 that inclines inward from the inner end of the convex part 24 toward the back side in FIG. 2 (that is, toward the outside of the vehicle) and extends radially inward, and the inner side of the inclined part 25 And a recess 26 for covering. In this way, the disc-shaped portion of the encoder cap 19 is formed into a three-dimensional shape, thereby increasing the rigidity of the encoder cap 19 and preventing the occurrence of warping and wrinkles due to press working, thereby contributing to the improvement of dimensional accuracy. doing.

  The ring portion 22 is formed with a proximity portion 27 that protrudes toward the back side in FIG. As shown in FIG. 1, the proximity unit 27 allows the magnetic sensor 20 to sense in the vicinity of the magnetic encoder 16.

  In addition, the air gap between the proximity portion 27 of the encoder cap 19 and the magnetic encoder 16 is minimized in consideration of the relative inclination and movement of the bearing outer inner ring when a load is applied, component accuracy, and assembly accuracy. Thereby, the magnetic sensor 20 and the magnetic encoder 16 are made to face each other in the axial direction, and the rotational speed can be measured with high accuracy.

  By the way, when the encoder cap 19 and the magnetic encoder 16 are close to each other, an eddy current is generated in the stainless steel encoder cap as a conductor by the alternating magnetic flux of the magnetic encoder 16 accompanying the rotation of the hub shaft 3 according to Lenz's law. (Eddy current loss), the force for braking the rotation of the hub shaft 3 works according to the principle of Arago's disk, and the torque of the hub unit bearing 1 becomes heavy.

It is known that eddy current loss is calculated by the following equation.
P _e = k _e (tfB _m ) ² / ρ (1)
Here, P _e is the eddy current loss, t is the plate thickness, f is the frequency, B _m is the maximum magnetic flux density, [rho is the resistivity of the magnetic material, k _e represents the proportionality constant.

As is apparent from equation (1), the eddy current loss P _e, since increases in proportion to the square of the plate thickness t and frequency f and maximum magnetic flux density B _m, effectively if it is possible to reduce these Eddy current loss can be reduced. However, the thickness t of the encoder cap 19 can not be excessively thinned from the request of the strength, as the number of poles of the magnetic encoder 16 is often associated with the frequency f, also magnetism associated with the maximum magnetic flux density B _m The stronger the magnetic flux density of the encoder 16, the better the rotation sensor.

  On the other hand, there is no general formula for calculating the magnetic flux density at a distance from the surface of the magnetic encoder. However, if the magnetic material often used for the hub unit bearing is a ferrite powder magnetic encoder, the maximum magnetic flux at a position of 1 mm from the surface. The density is generally about 20 to 30 mT, and if it is 2 mm, the magnetic flux density decreases to about 5 to 7 mT, roughly in inverse proportion to the square of the distance. Further, as described above, since the eddy current loss increases in proportion to the square of the maximum magnetic flux density, the eddy current loss decreases in inverse proportion to the fourth power of the air gap between the magnetic encoder 16 and the encoder cap 19. .

Therefore, in order to reduce the eddy current loss while ensuring the strength of the encoder cap 19 and the performance as a rotation sensor, the encoder cap 19 is removed except for the portion necessary to bring the magnetic sensor 20 close to the magnetic encoder 16. possible placed away from the magnetic encoder 16, reducing the maximum magnetic flux density B _m in the encoder cap 19 can be said to be effective.

  Therefore, in the present embodiment, a circular proximity portion 27 that is slightly larger than the distal end portion of the magnetic sensor 20 in accordance with the shape of the distal end portion of the magnetic sensor 20 that is generally cylindrical, and other than the proximity portion 27. By disposing the ring portion 22 (hereinafter referred to as “separation portion 31”) in the vehicle inner side of the sensor element 30 of the magnetic sensor 20 described later, eddy current loss is suppressed, and an increase in bearing torque is minimized. ing.

  By the way, a semiconductor element (IC chip) such as a Hall element or a magnetoresistive element is used for the sensor element described above. For example, when the temperature of the Hall element increases, the Hall output voltage decreases, and the temperature of the magnetoresistive element increases. It has a temperature dependency that the resistance value decreases as it rises. The eddy current loss eventually becomes heat and raises the temperature of the magnetic sensor 20, leading to deterioration of the sensor signal (deterioration of accuracy), but the structure of the present application that suppresses eddy current loss suppresses the temperature rise of the magnetic sensor 20. It also has an effect in preventing deterioration of the sensor signal.

  In the present invention, the shape of the proximity portion 27 is not limited to a circle, and can be various shapes according to the shape of the magnetic sensor 20. In addition, since the influence on the eddy current loss is small if the portion of the ring portion 22 does not face the magnetic encoder 16, for example, the proximity portion 27 has an elliptical shape or an oval shape that is long in the radial direction of the ring portion 22. Thus, a gap is provided in the radial direction between the proximity portion 27 and the magnetic sensor 20 to absorb the inevitable displacement in the radial direction. That is, in order to reduce the eddy current loss, the size of the proximity portion 27 in the circumferential direction of the ring portion may be reduced as much as possible, so that the radial size can have a degree of freedom.

  However, since the positioning of the proximity portion 27 in the circumferential direction needs to be strictly regulated, the press-fitting phase when the encoder cap 19 is press-fitted into the outer ring 2 is controlled by a bolt hole (not shown) of the body mounting flange. It is necessary to strictly carry out by a method such as image processing as a standard. Further, a minute phase error can be absorbed by performing a magnetic sensor locking procedure such as bolting after the magnetic sensor 20 is inserted into the proximity portion 27.

  Next, a configuration near the encoder 16 will be described with reference to FIG. FIG. 3 is an enlarged sectional view of the vicinity of the magnetic encoder 16.

  As described above, the magnetic encoder 16 is an axial type that faces the magnetic sensor 20 in the axial direction, and is filled with a magnetic material such as ferrite powder in a rubber material or a thermoplastic resin material as a binder, and has an L-shaped cross section. After being vulcanized or injection-molded integrally with an annular cored bar 28, N poles and S poles are alternately magnetized in multiple poles at equal intervals in the circumferential direction, via the cored bar 28. The inner ring element 10 is fixed to the outer peripheral surface.

  The encoder cap 19 is supported by the outer ring 2 by fitting and fixing the fixing portion 21 to the inner peripheral surface of the end portion of the outer ring 2. For the positioning of the encoder cap 19 in the axial direction, an annular diameter-expanded step 29 is formed at an appropriate position on the inner periphery of the end of the outer ring 2 on the encoder cap 19 side. 29, the encoder cap 19 can be pushed in accurately until the entire tip of the fixed portion 21 comes into contact. Further, the positioning of the encoder cap 19 in the circumferential direction can be accurately performed by using the position of the proximity portion 27 as a reference.

  The cross section of the encoder cap 19 in FIG. 3 shows a cross section that passes through the center of the proximity portion 27. The proximity portion 27 is a portion that extends from the end of the fixed portion 21 on the right side of FIG. 3 (that is, the inside of the vehicle) to the inside of the bearing so as to approach the magnetic encoder 16 from the ring portion 22 that extends radially inward. . In FIG. 3, the magnetic sensor 20 is indicated by a two-dot chain line. By applying the magnetic sensor 20 to the bottom of the proximity portion 27, the magnetic sensor 20 is brought closer to the magnetic encoder 16 so that high-precision measurement can be performed at a high magnetic flux density.

  As described above, the separation portion 31 is disposed such that the surface on the magnetic encoder 16 side is farther from the magnetic encoder 16 than the sensor element 30 is.

  The crystal air gap (distance from the encoder surface (detected surface) to the sensor element) of the sensor element 30 is generally the distance from the magnetic encoder surface to the magnetic encoder side surface of the encoder cap (usually about 1 mm). The sum of the plate thickness of the cap (usually 0.5 to 0.8 mm) and the covering of the sensor detection surface (usually about 0.5 mm) is often about 2 mm.

As described above, the eddy current loss decreases in inverse proportion to the fourth power of the air gap between the magnetic encoder 16 and the encoder cap 19. Therefore, if the surface of the separation portion 31 on the magnetic encoder 16 side is arranged to be away from the magnetic encoder 16 to the same distance (2 mm) as the sensor element 30, the separation portion 31 is separated from the general case (1 mm). The eddy current loss generated in the part 31 can be reduced to 1/2 ⁴ (1/16). However, since the position of the sensor element 30 is regulated by an alternating magnetic field (for example, 1 mT) that can be detected by the sensor element 30, the separation portion 31 is moved away from the sensor element 30 from the magnetic encoder 16 as in the first embodiment. If arranged (for example, 3 to 4 mm), the eddy current loss generated in the separation portion 31 can be reduced to 1/3 ⁴ to 1/4 ⁴ (1/81 to 1/256), and can be lowered to a level that can be almost ignored.

  If the separation portion 31 cannot be disposed at a sufficient distance from the magnetic encoder 16 due to dimensional restrictions or the like, or if the eddy current loss should be further reduced after the separation, the separation portion A ferrite film may be provided on at least the side surface of 31 on the magnetic encoder 16 side. Since ferrite is not only a ferromagnetic material but also a nonconductor, it can absorb alternating magnetic flux and reduce eddy current loss.

  A PCD method (physical vapor deposition method) or a CVD method (chemical vapor deposition method) can be applied to the ferrite coating on the encoder cap 19. However, if these are applied, a ferrite film is formed up to the proximity portion 27, so that it is necessary to perform masking or to drop the ferrite film of the proximity portion 27 in post-processing. Therefore, it is preferable to form a ferrite film only on the surface facing the magnetic encoder 16 by an aerosol deposition method (a method of forming a ferrite film by shooting a ferrite ball).

  Similarly to the rubber for the magnetic encoder 16, the same effect can be obtained by vulcanizing and bonding a magnetic rubber containing a large amount of ferrite powder only to the surface facing the magnetic encoder 16.

(Second Embodiment)
Next, a hub unit bearing according to a second embodiment of the present application will be described with reference to FIG. FIG. 4 is a cross-sectional view of the periphery of the magnetic encoder 41 of the hub unit bearing 40 according to the second embodiment.

  The hub unit bearing 40 according to the second embodiment has the same basic configuration as the hub unit bearing 1 according to the first embodiment described above. However, in the second embodiment, the encoder cap 42 has a resin. By using the film laminated steel plate, the strength of the encoder cap 42 and the formability with a press are ensured, and the thickness of the metal plate as a conductor is reduced, thereby reducing eddy current loss.

  In addition, the resin film laminated steel sheet is formed by performing a chemical conversion treatment such as a phosphoric acid coating on the metal plate of the core part, improving the ride of the adhesive, and pasting the resin film on the both surfaces with an adhesive. It is sold under the brand.

  The second embodiment can be used in combination with the hub unit bearing described in the first embodiment.

(Third embodiment)
Next, a hub unit bearing according to a third embodiment of the present application will be described with reference to FIG. FIG. 5 is a cross-sectional view around the magnetic encoder 51 of the hub unit bearing 50 according to the third embodiment.

  The hub unit bearing 50 according to the third embodiment has the same basic configuration as the hub unit bearing 1 according to the first embodiment described above, but the fixing portion of the encoder cap 52 is fitted on the outer ring 54. It is different in that it is fixed.

  In order to obtain such a configuration, the encoder cap 52 according to the third embodiment has a diameter dimension that fits the fixing portion 53 to the outer peripheral surface of the outer ring 54, and the right side of the fixing portion 53 in FIG. The ring portion 55 extends radially inward from the end portion on the vehicle inner side. Further, the end face of the outer ring 54 on the encoder cap 52 side is extended to a position where it comes into contact with the surface of the ring part 55 on the outer ring 54 side.

  The axial positioning of the encoder cap 52 is easily and accurately performed by fitting the fixing portion 53 to the outer ring 54 and pushing the encoder cap 52 until the ring portion 55 comes into contact with the end face of the outer ring 54 on the encoder cap 52 side. be able to.

  By adopting such a configuration, it is possible to more effectively prevent foreign matter from entering between the outer ring 54 and the encoder cap 52.

  Note that eddy current loss can be prevented if the encoder cap is made of a non-magnetic and non-conductive resin cap, but the resin material is not as strong as an austenitic stainless steel plate, and the resin moldability (in the injection mold) In consideration of the fluidity of the molten resin, the plate thickness cannot be reduced. Therefore, the resin cap is not preferable because the crystal air gap increases as the plate thickness increases and the performance as a rotation sensor decreases.

  As described above, the present invention shields and protects the bearing internal space (the space where the rolling elements and rolling surfaces exist) and the magnetic encoder from the outside of the bearing, and suppresses the occurrence of eddy current loss. It is possible to provide a hub unit bearing provided with a protective cover that can reduce the bearing torque and prevent the deterioration of the sensor signal.

1, 40, 50 Hub unit bearings 2, 54 Outer ring 3 Hub shaft 4 Ball 5 First outer rolling surface 6 Second outer rolling surface 7 Hub wheel 8 Wheel mounting flange 9 Shaft portion 10 Inner ring element 11 Bolt hole portion 12 First inner rolling surface 13 Reduced diameter portion 14 Clamping portion 15 Second inner rolling surface 16, 41, 51 Magnetic encoder 17 Cage 18 Seals 19, 42, 52 Encoder cap 20 Magnetic sensor 21 Fixing portions 22, 55 Ring part 23 First inclined part 24 Convex part 25 Second inclined part 26 Concave part 27 Proximity part 28 Core metal 29 Expanded step part 30 Sensor element 31 Separate part

Claims (5)

A substantially cylindrical outer ring having a double row outer rolling surface on the inner periphery;
A substantially cylindrical inner ring portion provided with a double row of inner rolling surfaces provided on the outer periphery facing the outer rolling surface, and provided at one end of the inner ring portion, A hub shaft comprising a wheel mounting flange extending radially outward of the inner ring portion on the outer side in the axial direction of the outer ring;
A plurality of rolling elements interposed between the outer rolling surface and the inner rolling surface;
An encoder comprising a thin cylindrical plate made of non-magnetic stainless steel and fixed to the outer ring, and a bottom extending radially inward from the fixed part and covering the end of the inner ring part A cap,
An annular magnetic encoder fixed to the outer periphery of the inner ring portion so as to face the sensing surface of the magnetic sensor through a part of the bottom portion;
In the hub unit bearing, the encoder cap is abutted against an end face of the outer ring or an enlarged diameter step formed on the inner peripheral part of the outer ring.
The portion of the bottom that is interposed between the magnetic sensor and the sensing surface is a bottom of a protrusion that protrudes toward the magnetic encoder so that the sensing surface is close to and opposed to the magnetic encoder.
The hub unit bearing according to claim 1, wherein the bottom portion other than the projecting portion is arranged in a vehicle inner side direction from a sensor element of the magnetic sensor.   2. The hub unit bearing according to claim 1, wherein the bottom portion other than the protrusion is disposed such that a surface on the magnetic encoder side is separated by 2 mm or more from the magnetic encoder.   The hub unit bearing according to claim 1, wherein the protrusion has a circular planar shape.   The hub unit bearing according to any one of claims 1 to 3, wherein the encoder cap is formed by pressing a resin film laminated steel plate.   The hub unit bearing according to any one of claims 1 to 4, wherein a ferrite coating is provided on a surface of the bottom portion that faces the encoder other than the protruding portion.

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