JP3939022B2 - Annular speed sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotational speed sensor, and more particularly to a sensor that can detect the rotational speed of a vehicle wheel.
[0002]
[Prior art]
In various situations, it may be necessary to measure the relative rotational speed of machine parts. For example, a rotation sensor is used to measure the rotation speed of a main shaft of a jet engine or a spindle of a machine tool. Rotation sensors are also used in anti-lock brake devices (ABS), which are increasingly equipped in recent automobiles. ABS maintains the running stability and directionality of an automobile by preventing the wheels from locking when sudden braking is applied. The ABS always requires a wheel speed sensor that sends a signal representing the rotation of the wheel to the ABS controller. Most passenger cars have rotation sensors on all four wheels. Based on the signal from the rotation sensor, the ABS control unit determines whether the wheel is locked or is about to lock, and performs anti-lock control based on the determination. The wheel speed sensor is also used for input to a traction control device that prevents spinning of the driving wheel during acceleration.
[0003]
A wide variety of ABS wheel speed sensors are currently known. Among them, the most widespread is a sensor including a non-rotating part (stator) and a rotating part (rotor) provided close to the stator. The rotating part, also called “tone ring”, has a detected part that is detected by the non-rotating part during rotation. For example, ferromagnetic teeth formed on the gear, magnetic poles having opposite magnetism formed on the rotating part, and the like are used as the detected part. The non-rotating part detects the passage of the detected part formed in the rotating tone ring and outputs the detection result as a signal.
[0004]
Examples of the transducer include a variable reluctance type device, a Hall effect device, and a magnetostrictive device. Most transducers detect magnetic fields (changing magnetic fields). Variable reluctance transducers are called “passive” sensors because they generate voltage without receiving electricity from an external power source. On the other hand, “active” sensors, such as Hall effect devices, are activated by an externally applied AC voltage and generate an output in response to a magnetic field passing through the device.
[0005]
One problem with today's wheel speed sensors is that the strength of the magnetic field is likely to change due to changes in the size of the air gap between the rotor and the stator. There is a type of magnetic field sensor in which a tone ring rotates together with a wheel bearing. Usually, the magnetic pole of the tone ring (rotor) of this type of sensor or the detected portion made of a ferromagnetic material is formed so as to extend in the axial direction or the radial direction. The detection portion of the stator is provided to face the upper surface or the lower surface of the tone ring so as to detect the magnetic pole in the axial direction. In this case, since the tone ring rotates together with the wheel, the size of the gap between the tone ring and the stator tends to fluctuate due to vibration or the like. As the gap increases, the magnetic field strength and the output of the stator corresponding to the magnetic field strength decrease. The size of the gap varies randomly due to random factors. Variation in the size of the air gap adversely affects the measurement accuracy of the wheel speed sensor.
[0006]
Modern automobile parts are required to be compact, lightweight, easy to assemble and highly reliable. Traditional sensors are sufficient to meet these demands, but engineers are striving every day to develop sensors that are more compact, easier to manufacture and assemble, and lower cost. In addition, such a sensor needs to be provided with some means for preventing mud, dust, salt, water, and the like jumping from the road surface from entering the inside. In addition, since such a sensor is provided near the brake, it is exposed to wear powder and high temperature due to brake operation. Many recent wheel speed sensors are integrated into a wheel bearing device. This is because the sensor can be tested before the vehicle manufacturing process, the assembly of the vehicle is facilitated, and the reliability of the entire apparatus is increased.
[0007]
Therefore, a wheel speed sensor that can minimize fluctuations in the air gap between the rotor and the stator is desired. Such a sensor is also desired to be easy to manufacture and low in cost. Such a sensor preferably has a structure that can be firmly fixed to the bearing by press fitting or the like. It is also desirable to save as much mounting space as possible.
[0008]
SUMMARY OF THE INVENTION
The present invention provides an annular speed sensor that is particularly suitable as a vehicle wheel speed sensor that can maintain a high level of output even at relatively low wheel speeds. This wheel speed sensor is incorporated in the hub bearing device. The hub bearing device is provided with sealing means for protecting the speed sensor.
[0009]
One object of the present invention is to provide a wheel speed sensor that can minimize fluctuations in the air gap between the rotor and the stator.
[0010]
Another object of the present invention is to provide a wheel speed sensor that is easy to manufacture and low in manufacturing cost.
[0011]
Still another object of the present invention is to provide a wheel speed sensor having a structure that can be firmly fixed to a bearing by press fitting or the like.
[0012]
Yet another object of the present invention is to provide a wheel speed sensor that takes up less mounting space.
[0013]
To achieve these objectives, the present invention provides a multipolar tone ring having an axial magnetic pole and a radial magnetic pole, a first portion for detecting the axial magnetic pole while the tone ring is rotating, and a radius. A wheel speed sensor comprising a stator having a second portion for detecting a magnetic pole in a direction is provided. The sensor with this structure can minimize the fluctuation of the air gap between the rotor and the stator, so that the wheel speed can be accurately measured even when the wheel speed is relatively low. Even if the axial clearance fluctuates, it is unlikely that the radial clearance between the tone ring and the second portion of the stator will fluctuate at the same time, so even in such a case, accurate wheel speed can be measured. . In addition, even though some of the gaps between the magnetic poles of the tone ring and the plurality of first portions may fluctuate greatly, it is hardly considered that all of these gaps fluctuate at the same time. Therefore, even if a part of the gap largely fluctuates, the gap as a whole hardly changes substantially, and the wheel speed signal can be output with high accuracy.
[0014]
The first and second portions of the stator are teeth formed on the stator. The axial magnetic field is detected by teeth facing the axial face of the tone ring, and the radial magnetic field is detected by teeth facing the radial face of the tone ring. By adopting such a configuration, it is possible to minimize the influence of fluctuations in the air gap between the rotor and the stator on the sensitivity of the sensor, so that the measurement accuracy can be further improved.
[0015]
Further, since the stator of the present invention has an inner diameter portion or an outer diameter portion having a considerably larger surface area than the conventional stator, the sensor can be firmly fixed to the bearing or seal by press-fitting this portion into the bearing or seal. it can.
[0016]
In addition, if the teeth formed on the stator are arranged so that they are aligned with the magnetic poles of the tone ring in the circumferential direction, strict accuracy in the circumferential direction is not necessary. Can be lowered.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show a hub bearing device 10 having an annular speed sensor of the present invention. The hub bearing device 10 is normally attached to a driven wheel axle of an automobile, but can also be attached to a drive wheel axle or a rotating part other than an automobile part.
[0018]
The hub 12 includes a radial flange portion having a mounting surface to a wheel (not shown). The hub 12 has a cylindrical inner peripheral surface 14 and a pair of roller bearing raceway surfaces, that is, an inboard raceway surface 16 and an outboard raceway surface 18. Further, the hub 12 is formed with a large-diameter bore 20 for attaching a wheel rotation speed sensor to be described later.
[0019]
A bearing inner ring 22 is provided inside the hub 12, and the inner ring 22 and a plurality of balls 24 rolling on the inner ring constitute an inboard side bearing. The outboard bearing, not shown, is a conventional bearing provided with a plurality of balls that roll on the inner peripheral surface. The inner ring 22 has a cylindrical inner peripheral surface 26 as a mounting surface for a fixed spindle 28. When the wheel rotates, the hub 12 fixed to the wheel rotates relative to the inner ring 22 fixed to the spindle 28. The hub bearing device 10 of the present invention includes a sensor 30 that detects the rotational speed of a wheel. As already described, the output of the sensor 30 is used to control the ABS of the vehicle and the traction control device. The sensor 30 includes a rotor or tone ring 32 and a stator or annular transducer 34. The sensor 30 will be described with reference to FIGS. 3, 4, 5, 8, 9, and 10 in addition to FIGS.
[0020]
The tone ring 32 is a disk-shaped permanent magnet having a radial surface 36 and an axial inner peripheral surface 38. As shown in FIG. 2, the tone ring 32 is attached to a tone ring holder 39 press-fitted into the hub bore 20. However, the holder 39 may be omitted, and the tone ring 32 may be directly press-fitted into the bore 20 of the hub. The tone ring shown in FIGS. 4 and 9 has a plurality of regions extending radially from the center of rotation of the hub bearing device, and a magnetic pole opposite to the region adjacent to each region is formed. On the radial surface 36 and the axial surface 38, magnetic poles having opposite polarities are alternately formed in the circumferential direction. An axial magnetic field 40 passes through the radial surface 36 and a radial magnetic field 42 passes through the axial surface 38. FIG. 4 shows the magnetic field passing through the tone ring 32 when used in combination with the stator having first and second teeth offset in the circumferential direction shown in FIG. FIG. 9 shows the magnetic field passing through the tone ring 32 when used in combination with the stator having first and second radially aligned teeth shown in FIG. There are various tone ring materials. In this embodiment, an Fe-Cr-Co alloy is used.
[0021]
The annular transducer 34 has a case 44 that is composed of a radial side wall 46 and a pair of cylindrical axial walls 48, 50, with the inner ends open. The walls 48 and 50 are separated by an annular gap 52. A plurality of teeth 54 and 56 are formed at the side ends of the walls 48 and 50. In the embodiment of FIG. 3, the teeth 54 are provided so as to be radially displaced from the teeth 56, and in the embodiment of FIG. 8, each tooth 54 is aligned on the same radial line with respect to the teeth 56. . In FIG. 8, the bobbin 60 is omitted for easy understanding. As shown in FIGS. 1 and 3, the coil 52 is wound around the bobbin 60 in the gap 52. The number of teeth 54 and 56 is made equal to the number of magnetic poles alternately formed in the circumferential direction on the surface of the tone ring 32.
[0022]
As the tone ring 32 rotates (in the direction of the curved arrow A in FIGS. 3 and 8), the transducer teeth 54, 56 are magnetically coupled to the alternating magnetic poles formed in the tone ring, and the transducer case An alternating magnetic field is generated in 44. The arrows extending along the surfaces of the case 44 and the tone ring 32 in FIG. 3 represent the magnetic flux passing through the case 44 and the tone ring 32. As the tone ring 32 rotates relative to the transducer, an alternating magnetic field is generated in the transducer case 44, resulting in an electromagnetic force (voltage) in the coil winding 58. The magnetic poles 40, 42 and the teeth 54, 56 are provided such that the teeth 54 are magnetically coupled to the magnetic pole 40 and the teeth 56 are magnetically coupled to the magnetic pole 42. As shown in FIG. 3, the teeth 56 are opposed to the radial inner surface 38 of the tone ring 32 with the gap 55 interposed therebetween. The magnetic poles 40 and 42 are arranged so that when the tooth 54 is magnetically coupled to one of the N pole and the S pole, the tooth 56 is coupled to the other magnetic pole. The tone ring 32 of FIG. 5 is used in combination with a transducer in which the teeth 54 and 56 are arranged while being shifted in the circumferential direction. In this case, when the tooth 54 is magnetically coupled to the north pole formed on the radial surface of the tone ring, the tooth 56 provided by shifting one pitch in the circumferential direction from the tooth 54 is the radial surface. Are magnetically coupled to the S pole on the axial surface arranged by shifting one pitch from the N pole in the circumferential direction. On the other hand, the tone ring 32 shown in FIG. 10 is used in combination with a transducer having teeth 54 and 56 aligned radially. In this case, when the teeth 54 are magnetically coupled to the north pole formed on the radial surface, the teeth 56 arranged on the radial line with respect to the teeth 54 are arranged on the axial surface. Magnetically coupled to the south pole.
[0023]
Since the tone ring of the present invention has a radial magnetic field on the axial surface and an axial magnetic field on the radial surface, the teeth 54 and 56 formed on the stator are opposed to the opposite magnetic poles of the tone ring, respectively. It suffices if they are arranged. The teeth 54 and 56 may be formed by shifting in the circumferential direction, or may be aligned in the radial direction. For this reason, the teeth 54 and 56 can be formed separately, and the manufacturing cost of the stator can be reduced.
[0024]
The annular transducer 34 is press-fitted on the cylindrical outer peripheral surface of the inner ring 22 shown in FIG. The bearing ball 24 and the sensor 30 are protected by a seal 62. The seal 62 comprises a retaining ring 64 press fitted to the hub 12 and an elastic lip 66 that contacts the transducer case 44. The transducer is open on the inner end side, that is, on the side facing the ball 24, and the walls 46, 48, 50 protect the ball 24 of the bearing. Further, since the sensor 30 is attached at a position where it can be easily reached, it can be easily repaired or replaced.
[0025]
6 and 7 show a hub bearing device 10 'according to another embodiment. The hub bearing device 10 'includes a sensor 30' that detects the rotational speed of the wheel. The hub 12 'includes a radial flange portion 13' having a mounting surface to a wheel (not shown). The wheel is fixed to the flange portion by a plurality of bolts 92 attached to the flange 13 '. The hub 12 'is formed with a cylindrical inner peripheral surface 14' and a pair of roller bearing raceway surfaces, that is, an inboard side raceway surface 16 'and an outboard side raceway surface 18'. Further, the hub 12 'is formed with a large-diameter bore 20' for attaching a wheel rotation speed sensor.
[0026]
A bearing inner ring 94 is provided inside the hub 12 ′, and the inner ring 94 and a plurality of balls 24 ′ rolling on the inner ring constitute an inboard side bearing. When the wheel rotates, the inner ring 94 rotates with respect to the outer ring 96 fixed to a spindle (not shown). As shown in FIG. 7, the annular stator 98 of the sensor is fixed to the outer ring 96, and the tone ring 100 rotates together with the inner ring 94 fixed to the wheel.
[0027]
11 and 12 show an embodiment in which the tone ring 110 and the annular transducer 112 are provided on the same axis. The tone ring 110 is a ring-shaped member having a shaft 114 as a center. Annular transducer 112 is centered about axis 114 and is located radially inward of tone ring 110 and comprises annular wall 120 and walls 116 and 118 extending radially outward from annular wall 120. As in the other embodiments, the coil winding 124 wound around the bobbin 126 is accommodated in the gap 122 inside the annular transducer 112. The magnetic poles formed on the tone ring 110 and the teeth formed on the transducer may be provided on the same radial line or may be provided in a shifted manner.
[0028]
13 and 14, the tone ring 110 'and the annular transducer 112' are provided on the same axis. The tone ring 110 ′ is a ring-shaped member centered on the shaft 114 ′. Annular transducer 112 'is centered about axis 114' and is located radially outward of tone ring 110 'and comprises annular wall 120' and walls 116 ', 118' extending radially inward from annular wall 120 '. . Similar to the other embodiments, a coil winding 124 ′ wound around a bobbin 126 ′ is housed in an air gap 122 ′ inside the annular transducer 112 ′. The magnetic poles formed on the tone ring 110 ′ and the teeth formed on the transducer may be provided on the same radial line or may be shifted.
[0029]
The present invention is not limited to the above-described embodiments, and various modifications and improvements can be added to the above-described embodiments without departing from the scope of the claims.
[Brief description of the drawings]
1 is an exploded perspective view of a hub bearing device of the present invention. FIG. 2 is a partial longitudinal sectional view showing an assembled state of the hub bearing device of FIG. 1. FIG. 3 shows a first tooth and a second tooth of a stator in a circle. FIG. 4 shows a part of an annular sensor formed by shifting in the circumferential direction. FIG. 4 shows a part of a tone ring according to the present invention used in combination with a stator formed by shifting the first and second teeth in the circumferential direction. FIG. 5 is a diagram showing the radial magnetic poles of the tone ring of FIG. 4. FIG. 6 is a longitudinal sectional view of a hub bearing device of another embodiment of the present invention. FIG. 8 is a view showing a part of an annular sensor in which the first and second teeth of the stator are radially aligned. FIG. 9 is a tone ring of the present invention used in combination with the stator of FIG. FIG. 10 is a diagram showing the radial magnetic poles of the tone ring of FIG. 11 is a perspective view of an embodiment in which the tone ring is provided coaxially with the stator on the outer periphery of the stator. FIG. 12 is a cross-sectional view taken along line 12-12 of FIG. FIG. 14 is a cross-sectional view taken along the line 14-14 in FIG. 13;
30, 30 'wheel speed sensor 32, 100, 110, 110' tone ring (rotor)
34, 98, 112, 112 'transducer (stator)
44 Case 54, 56 Teeth of transducer

Claims (17)

The stator includes a multipolar tone ring having a magnetic pole formed on an axial surface and a magnetic pole formed on a radial surface, and a stator made of a ferromagnetic case that rotates relative to the tone ring. Has a first portion for detecting the magnetic pole formed on the axial surface and a second portion for detecting the magnetic pole formed on the radial surface, and the first portion of the stator is on the axial surface of the tone ring. Formed by opposing teeth, the second part of the stator is formed by teeth facing the radial surface of the tone ring and contains a conductive winding in the case of the stator, relative rotation of the tone ring and the stator An annular speed sensor that detects the relative rotational speed between the tone ring and the stator using an alternating voltage generated by the magnetic flux in the stator. When the teeth constituting the first part are magnetically coupled to a magnetic pole formed on one axial surface having magnetism, the teeth constituting the second part are opposite to each other. The sensor of claim 1 adapted to be magnetically coupled to a magnetic pole formed on a radial surface having   The case includes a radial wall, and an inner cylindrical wall and an outer cylindrical wall connected to the radial wall, and teeth forming the first portion are formed on the inner cylindrical wall. 2. The sensor according to claim 1, wherein teeth constituting the second portion are formed on the outer cylindrical wall.   The case includes a radial wall, and an inner cylindrical wall and an outer cylindrical wall connected to the radial wall, and teeth forming the second portion are formed on the inner cylindrical wall. 2. The sensor according to claim 1, wherein teeth constituting the first portion are formed on the outer cylindrical wall.   The tone ring is mounted coaxially with the stator on the inner peripheral side of the stator, the stator having a cylindrical outer wall and two radial side walls extending radially inward from the outer wall toward the tone ring. The sensor according to claim 1, wherein teeth forming the first portion and the second portion are formed on the two side walls, respectively.   The tone ring is mounted coaxially with the stator on the outer peripheral side of the stator, and the stator includes a cylindrical inner wall and two radial side walls extending radially outward from the inner wall toward the tone ring. 2. The sensor according to claim 1, wherein teeth forming the first portion and the second portion are formed on the two side walls, respectively.   It is incorporated in a bearing device comprising an outer ring, an inner ring inside the outer ring, and a plurality of rolling elements provided so that the inner and outer rings can relatively rotate between the inner and outer rings, and the tone ring is attached to one of the inner and outer rings. The sensor according to claim 1, wherein the sensor is fixed and the stator is fixed to the other of the inner and outer rings. An outer ring, an inner ring inside the outer ring, a plurality of rolling elements provided so that the inner and outer rings can relatively rotate between the inner and outer rings, a magnetic pole formed on the axial surface, and a magnetic pole formed on the radial surface a multipole tone ring fixed to one of said inner and outer rings with, and a stator fixed to the other of said inner and outer rings, the stator is magnetically opposite the shaft which is formed in the direction of the surface magnetic pole A case made of a ferromagnetic material formed with first teeth that are coupled to each other and second teeth that are magnetically coupled to the magnetic poles formed on the radial surface, and the tone ring includes the stator. Magnetic poles formed on the axial surface and the radial surface are opposed to the first and second teeth, and are made of the ferromagnetic material. A conductive winding is housed in the case. There when rotated relative to the stator, an alternating magnetic flux generated in the stator, a bearing apparatus alternating voltage representative of the speed of the relative rotation in the winding is adapted to generate the magnetic flux.   The bearing device according to claim 8 attached to a wheel.   The bearing device according to claim 9, wherein the inner ring is fixed to a spindle of a non-rotating vehicle, and the outer ring is fixed to the wheel.   The bearing device according to claim 10, wherein the tone ring is inserted into a cylindrical inner peripheral surface of an outer ring.   The bearing device according to claim 9, wherein the outer ring is fixed to a spindle of a non-rotating vehicle, and the inner ring is fixed to the wheel.   The bearing device according to claim 12, wherein the tone ring is inserted into a cylindrical outer peripheral surface of an inner ring.   The case includes a radial wall, and an inner cylindrical wall and an outer cylindrical wall connected to the radial wall, and the first tooth is formed on the inner cylindrical wall, and the second tooth Teeth are formed on the outer cylindrical wall, the first and second teeth extend toward the rolling element, and the tone ring is provided between the rolling element and the first tooth, The bearing device according to claim 8, wherein the second tooth is provided adjacent to the tone ring.   The bearing device according to claim 8, wherein a seal having a seal lip portion that contacts the stator is fixed to a bearing outer ring to which the tone ring is attached.   The bearing device according to claim 8, wherein a seal having a seal lip portion contacting the stator is fixed to a bearing inner ring to which the tone ring is attached.   The bearing device according to claim 8, further comprising a seal having a seal lip surrounding the rolling element and the tone ring.

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