JP2005315652A - Bearing device for wheel having built-in load sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing for wheel having a built-in load sensor in which the load sensor can be compactly installed on a vehicle and which can stably detect the load on the wheel. <P>SOLUTION: An outer member 1 in which a plurality of rows of roll surfaces 4 are formed on the inner circumferential surface and an inner member 2 in which roll surfaces 5 disposed opposite the roll surfaces 4 of the outer member 1 are formed are provided. A plurality of rows of rolling bodies 3 are interposed between the facing roll surfaces 4 and 5 so that the wheel is rotatably supported with respect to the vehicle body. The load sensor 9 for detecting the load on the bearing by detecting the magnetostriction variation is provided at the position on the outboard side with respect to the position of the plurality of rows of the rolling bodies, in the space sealed by sealing devices 7 and 8 on both sides between the outer member 1 and the inner member 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wheel bearing device having a built-in load sensor for detecting a load applied to a bearing portion of the wheel.

  2. Description of the Related Art Conventionally, there has been a wheel bearing device provided with a sensor for detecting the rotational speed of each wheel for safe driving of an automobile. In such a wheel bearing device, there has been proposed a device in which sensors such as a temperature sensor and a vibration sensor are installed so that other states useful for driving a car can be detected in addition to the rotational speed (for example, patents) References 1, 2). In the wheel bearing disclosed in Patent Document 1, a detected portion of a rotation sensor is provided between two rows of rolling surfaces of the outer peripheral surface of the inner member on the rotation side, and is opposed to the detected portion. The detection part of the rotation sensor which detects the rotation is provided on the outer member on the fixed side.

In the wheel bearing device disclosed in Patent Document 2, a coil and a piezoelectric element that constitute a detected portion of the torque sensor are provided between two rows of rolling surfaces of the outer peripheral surface of the inner member on the rotation side. In addition, the detection part of the torque sensor is provided on the outer member on the fixed side. The detection unit detects a magnetic field generated in the coil in accordance with the potential difference, although the piezoelectric element generates a potential difference due to the displacement caused by torsion of the inner ring.
JP 2002-340922 A JP 2003-207402 A

  Conventional measures to ensure driving safety of general automobiles are performed by detecting the rotational speed of the wheels of each part, but the rotational speed of the wheels is not sufficient, and it is further safer by using other sensor signals. It is required to be able to control the surface. Therefore, it is conceivable to control the posture from the load acting on each wheel during vehicle travel. For example, a large load is applied to the outer wheel in cornering, and the load applied to each wheel is not uniform. In addition, even when the load is uneven, the load applied to each wheel is uneven.

  For this reason, if the load applied to the wheel can be detected at any time, based on the detection result, the suspension and the like are controlled in advance, thereby controlling the posture during vehicle travel (preventing rolling during cornering, preventing the front wheel from sinking during braking, It is possible to prevent subsidence due to uneven load capacity. However, there is no appropriate installation location of a sensor that detects a load acting on the wheel, and it is difficult to realize posture control by load detection.

  In addition, when steer-by-wire is introduced in the future, and the system is such that the axle and the steering are not mechanically coupled, it is required to detect the axle direction load and transmit the road surface information to the handle held by the driver.

  Moreover, in the wheel bearing incorporating the torque sensor shown in Patent Document 2, the influence of spline coupling used for coupling with a constant velocity joint is not touched. In Patent Document 2, a sensor for detecting torque is arranged between two rows of rolling surfaces on the outer peripheral surface of the inner member, and a spline is provided on the inner peripheral surface of the inner member corresponding to the sensor position. It has a structure. The driving force from the engine is transmitted to the wheel bearing by the constant velocity joint, and spline coupling is generally used for coupling the constant velocity joint and the wheel bearing. If there is play in the spline connection, the torque output hysteresis will increase. In order to close the backlash, the spline on the constant velocity joint side is provided with an angle of several degrees. When the spline is fitted to the spline provided in the wheel bearing, the backlash can be reduced by this twisting. .

  However, in the case of torque transmission that matches the twisting direction of the spline, distortion in proportion to the torque is generated in the sensor part. However, in the case of torque transmission in the reverse direction, the twisting acts in the direction in which the torque is loosened. It is not transmitted accurately and the sensitivity is lowered and the linearity is lost. In spline coupling, the contact portion is indefinite, and in some cases, torque may be transmitted past the torque sensor.

  An object of the present invention is to provide a load sensor built-in wheel bearing capable of eliminating such a problem and installing a load sensor compactly in a vehicle and stably detecting a load applied to the wheel.

The wheel bearing device with a built-in load sensor according to the present invention has an outer member in which double-row rolling surfaces are formed on the inner peripheral surface, and an inner side in which a rolling surface that faces the rolling surface of the outer member is formed. For a wheel that includes a member, a double row rolling element interposed between both rolling surfaces, and a sealing device that seals both ends between the outer member and the inner member, and rotatably supports the wheel with respect to the vehicle body In the bearing device, it acts on the bearing by detecting the magnetostriction change in the outboard side position rather than the double row rolling element position in the space sealed by the sealing devices on both sides between the outer member and the inner member. A load sensor for detecting a load is provided.
According to this configuration, in the wheel bearing device, the load sensor is provided at the position on the outboard side of the double row rolling element position, so that the load sensor can be compactly installed in the vehicle. The position on the outboard side of the double row rolling element position is a place where the load in the rotational direction does not act directly or hardly occurs between the inner diameter surface of the inner member and the constant velocity joint outer ring. By installing the load sensor at this position, the torque transmitted from the engine to the wheel or the torque generated from the traveling direction load applied to the tire can be detected stably and accurately. Further, since the load sensor is disposed in a sealed space by the bearing sealing device, it is protected from intrusion of dust and salt mud water, and it becomes unnecessary to separately provide a sealing means dedicated to protecting the load sensor.

In the present invention, the load sensor includes a detected portion including a magnetostrictive portion provided on an inner member, and a detection portion provided on an outer member for detecting a magnetostriction change of the detected portion, A portion in which a rotational load acts between the inner diameter surface of the inner member and the constant velocity joint outer ring may not be generated in the axial range where the magnetostrictive portion exists.
As described above, when the detected portion is arranged at a position where a portion in which the rotational load acts between the inner diameter surface of the inner member and the constant velocity joint outer ring does not occur, disturbance is not easily generated, and torque from the constant velocity joint is not generated. It is accurately transmitted to the detected part. Therefore, the load applied to the wheel can be detected more accurately.

In the present invention, the load sensor includes a detected portion including a magnetostrictive portion provided on an inner member, and a detection portion provided on an outer member for detecting a magnetostriction change of the detected portion, In the case where a spline coupling portion that detachably couples the inner diameter surface of the inner member and the shaft portion of the constant velocity joint outer ring is provided, the spline coupling portion may be disposed on the inboard side with respect to the magnetostrictive portion.
In this configuration, since the spline coupling portion between the constant velocity joint and the inner member deviates from the axial position of the detected portion consisting of the magnetostriction portion, the disturbance factor of torque detection generated at the spline coupling portion is difficult to be transmitted, and the constant velocity joint Is transmitted to the detected part accurately. Therefore, the load applied to the wheel can be detected more accurately.

In the present invention, the magnetostrictive portion is made of an Fe-Al alloy, and a plurality of grooves in the direction of about 45 degrees with respect to the axis are formed in the circumferential direction on the surface of the magnetostrictive portion, and the detection portion is made of a coil, The load sensor may be a torque sensor that detects a load as a torque value.
If the groove in the direction of about 45 degrees is provided, a shear stress in the direction of about 45 degrees acts on the surface of the detected part. When the inclination directions of the two rows of grooves are opposite, different tensile and compressive stresses act in the direction along the two rows of grooves. Torque can be detected by detecting the stress change of the reverse characteristics with the coil of the detection unit and taking the differential amplification. Further, when the magnetostrictive portion is an Fe—Al alloy, excellent magnetostrictive characteristics can be obtained.

  In this invention, the inner member has an inner diameter hole that is spline-coupled with the shaft portion of the constant velocity joint outer ring, and the diameter of the inner board is larger than the inner diameter of the spline forming portion. good. In the case of this configuration, the stress acting on the magnetostrictive portion that is the detected portion of the load sensor is increased, and the sensor sensitivity can be increased.

In this invention, you may incorporate the axial direction load detection means which detects an axial load in the space between the inner member formed in the middle of two rolling surfaces, and an outer member.
When the axial load detection means is added in this way, it is possible to simultaneously detect the two-way loads of the traveling direction load and the axial load applied to the wheel from the torque value detected by the load sensor. Therefore, it can be applied to driving plan control of automobiles and road surface information transmission in a steer-by-wire system. Since the load sensor is arranged on the outboard side of the double row rolling elements, the load sensor and the axial load detection are performed by arranging the axial load detection means between the double row rolling elements. Both means can be efficiently arranged in the spare space. Since the detection of the axial load is not easily affected by the rotational load between the inner diameter surface of the inner member and the constant velocity joint outer ring, when both the load sensor and the axial load detection means are installed, the axial load It is preferable in terms of detection accuracy to arrange the detection means between the double row rolling elements.

  The axial load detecting means may be a magnetostrictive sensor including a magnetostrictive portion disposed on the inner member and a detection coil disposed on the outer member so as to face the magnetostrictive portion. According to the magnetostrictive sensor, the axial load can be detected from the stress acting on the inner member.

  In the axial load detecting means, the magnetostrictive portion may be made of an Fe-Al alloy, and the surface of the magnetostrictive portion may have a portion where a plurality of axial grooves are formed and a portion where the axial grooves are not formed. . Two detection coils facing the portions where the grooves are formed and portions where the grooves are not formed may be arranged on the outer member, and the detection coils on the side where the grooves are not formed may be used for temperature compensation. When a compression or tensile load is applied to the inner member, the detection coil facing the portion where the axial groove is formed is more sensitive. Further, temperature compensation can be performed by providing a detection coil in a portion where the axial groove is not formed. The temperature environment in which the wheel bearings are placed is wide from a cold region to a high temperature region. Therefore, by performing temperature compensation, the reliability of axial load detection can be improved.

  In the wheel bearing device with a built-in load sensor according to the present invention, the load sensor detects a magnetostriction change of the detected portion provided on the outer member and a detected portion including the magnetostrictive portion provided on the inner member. The inner member may be made of carbon steel, the magnetostrictive portion may be made of an Fe-Al alloy, and the inner member and the magnetostrictive portion may be welded together.

  The load sensor built-in wheel bearing device of the present invention, an outer member formed with a double row rolling surface, an inner member formed with a rolling surface opposite to the rolling surface of the outer member, In a wheel bearing device comprising a double row rolling element interposed between both rolling surfaces, and a sealing device for sealing both ends between the outer member and the inner member, and rotatably supporting the wheel with respect to the vehicle body In the space sealed by the sealing device on both sides between the outer member and the inner member, the load acting on the bearing is detected by detecting the magnetostriction change in the outboard side position rather than the double row rolling element position. Since the load sensor to be provided is provided, the load sensor can be installed in the vehicle in a compact manner, and the load applied to the wheel can be detected stably.

A first embodiment of the present invention will be described with reference to FIGS. The wheel bearing device with a built-in load sensor of this embodiment is an example applied to a wheel bearing for driving wheel support, which is a third generation inner ring rotating type. In this specification, the side closer to the outer side in the vehicle width direction of the vehicle when attached to the vehicle is referred to as the outboard side, and the side closer to the center of the vehicle is referred to as the inboard side. In FIG. 1A, the left side is the outboard side and the right side is the inboard side.
In FIG. 1A, this wheel bearing 18 has an outer member 1 having a double row rolling surface 4 on the inner periphery and an inner surface having rolling surfaces 5 respectively facing the rolling surfaces 4 on the outer periphery. A side member 2 and a double row rolling element 3 interposed between the double row rolling surfaces 4 and 5 are provided. This wheel bearing is a double-row angular contact ball bearing, each of the rolling surfaces 4 and 5 has an arcuate cross section, and each of the rolling surfaces 4 and 5 is formed so that the contact angle is back to back. Has been. The rolling elements 3 are formed of balls and are held by the cage 6 for each row.

  The outer member 1 is a member on the fixed side, and has a vehicle body mounting flange 1a for fixing to a knuckle (not shown) on the outer periphery as shown in FIG. It is said that. The vehicle body mounting flange 1a is fastened to a knuckle installed in a vehicle body (not shown) with a plurality of bolts (not shown) in the circumferential direction. The bolt insertion hole 12 of the vehicle body mounting flange 1a is threaded. The bolt passes through a through hole provided in the knuckle, and the male screw portion at the tip is screwed into the bolt insertion hole 12. Instead of using the bolt insertion hole 12 as a screw hole, the bolt insertion hole 12 may be simply a hole through which a bolt is inserted, and the bolt may be tightened with a nut (not shown).

  The inner member 2 is a member on the rotation side, and a hub wheel 2A having a wheel mounting flange 2a on the outer periphery, and a separate member fitted to the outer diameter surface of the end portion on the inboard side of the hub wheel 2A. It consists of an inner ring 2B. An outer ring 13a of a constant velocity joint 13 is connected to the hub wheel 2A. Each row of rolling surfaces 5 is formed on the hub wheel 2A and the inner ring 2B. A stem 14 formed integrally with the outer ring 13a of the constant velocity joint 13 is inserted into the hub wheel 2A, and a bolt 16 is screwed into a tap hole 14a provided in the center of the stem 14 through a washer 15. By doing so, the constant velocity joint outer ring 13a is connected to the hub wheel 2A. That is, the washer 15 is disposed so as to abut on a stepped surface 2e formed on the outboard side of the inner diameter surface of the hub wheel 2A, and the bolt 16 inserted through the washer 15 is inserted into the tap hole 14a of the stem 14. By screwing, the constant velocity joint outer ring 13a is pressed and connected to the hub wheel 2A on the outboard side.

  A spline groove 2b is formed on the inboard side of the inner diameter surface of the hub wheel 2A from the position corresponding to the wheel mounting flange 2a, and the spline groove 14b formed on the outer peripheral surface of the stem 14 in the spline groove 2b. Is splined. The inner ring 2B is clamped and fixed in the axial direction with respect to the hub wheel 2A by a crimping portion 2Aa provided at the inboard side end of the hub wheel 2A. The open end portions on the outboard side and the inboard side of the annular space formed between the inner and outer members 2 and 1 are sealed by contact-type seals 7 and 8 which are sealing devices, respectively. Further, an O-ring 17 is inserted between the joint surface 13aa of the constant velocity joint outer ring 13a with the hub wheel 2A and the width surface of the inner ring 2B opposite to the joint surface 13aa, whereby the spline grooves 2b, 14b. Prevents moisture and foreign matter from entering the joint.

  A load sensor 9 is disposed in the annular space on the outboard side of the double row rolling surfaces 4 and 5 of the wheel bearing 18. The load sensor 9 includes a detection unit 10 and a detection unit 11 that detects a change in magnetostriction of the detection unit 10. The detected portion 10 is sandwiched between the wheel mounting flange 2a and the rolling surface 5 closer to the wheel mounting flange 2a than the two rows of rolling surfaces 5 formed on the inner member 2. The detected portion 10 made of a magnetostrictive material is fixed to the outer diameter portion 2c of the hub wheel 2A.

  As the detected portion 10, a ring-shaped member made of a Fe—Al alloy that is a magnetostrictive material is used, and is welded or diffusion bonded to the outer diameter surface of the hub wheel 2 </ b> A. The hub wheel 2A to which the Fe—Al alloy is fixed as the detected portion 10 is subjected to a quenching process, and then the surface of the Fe—Al alloy is ground and then shot peened to increase the residual stress. May be. As shown in FIG. 2, a plurality of inclined grooves 10 a having an inclination angle of ± 45 degrees with respect to the axial direction are arranged in the circumferential direction on the surface layer of the detected part 10 in two rows. The groove depth of the inclined groove 10a is preferably about 0.1 mm to 0.5 mm.

  The detection unit 11 is fixed to the inner surface of the outer member 1 by press fitting or the like so as to face the detected portion 10 in the radial direction. As shown in an enlarged cross-sectional view in FIG. 1C, the detection unit 11 includes coil windings 11a and 11b and a yoke 11c, and the coil windings 11a and 11b are arranged in the inclined grooves 10a of each row of the detection unit 10. Each one of is facing each other. The coil windings 11a and 11b are incorporated in the yoke 11c while being wound around a bobbin 11d made of resin. The cable 19 is pulled out from the detection unit 11. As shown in a plan view in FIG. 1B, the cable 19 is aligned with the position of the U-shaped notch 20 provided at the end of the outer member 1 on the outboard side. The detection unit 11 can be easily attached to the outer member 1 without being obstructed by the cable 19 by press-fitting the detection unit 11 afterwards.

  In order to seal the U-shaped notch 20, after the cable 19 is inserted through an elastic member 21 (for example, a rubber material) that matches the shape of the U-shaped notch 20, the elastic member 21 becomes U-shaped. It is inserted into the letter-shaped notch 20. In order to further improve the sealing performance of the U-shaped notch 20, a method using an adhesive or heat fixing may be used. After this process, the metal ring 7a (FIG. 1B) of the seal 7 is press-fitted and fixed to the outer periphery of the outer member 1. Thereby, a part of the seal metal ring 7a overlaps with the U-shaped notch 20, and the waterproofness of the U-shaped notch 20 can be enhanced. In addition, the waterproof effect can be further enhanced by setting the elastic member 21 to have a thickness that protrudes from the outer diameter surface of the outer member 1. As another waterproof measure, an elastic member such as rubber may be interposed over the entire circumference at the contact portion between the metal ring 7a of the seal 7 and the outer member 1.

  The inner diameter portion 2d on the outboard side of the inner surface of the hub wheel 2A than the spline coupling portion is larger than the inner diameter of the spline groove 2b forming portion, so that the detected portion 10 is fixed to the hub wheel 2A. Rigidity is reduced within a range that does not affect strength. With this structure, the shear stress applied to the detected portion 10 made of a magnetostrictive material is increased, and the sensitivity of the load sensor 9 can be improved.

  The load sensor 9 functions as a torque sensor. Due to the torsional torque applied to the hub wheel 2A, a shear stress of 45 degrees acts on the surface of the detected portion 10 made of a magnetostrictive material, and different tensile and compressive stresses are applied in the direction along the two rows of inclined grooves 10a. The torque can be detected by capturing the change in stress as a change in magnetoresistance with the coil windings 11a and 11b of the detection unit 11 facing each other. FIG. 3 shows a detection circuit example of the detection unit 11. This detection circuit comprises a first series circuit 22 comprising a coil winding 11a and a resistor and a second series circuit section 23 comprising a coil winding 11b and a resistor connected in parallel. An AC voltage of several tens of kHz is applied from the transmitter 24 to the series circuit unit 22 of the first and second series circuit units 23 connected in parallel thereto.

  The divided voltage applied to the first coil winding 11 a is converted into a DC voltage by the rectifier 25 and the low-pass filter 26 and input to the first input terminal of the differential amplifier 27. The divided voltage applied to the second coil winding 11 b is also converted into a DC voltage by another rectifier 25 and a low-pass filter 26 and input to the second input terminal of the differential amplifier 27. The differential amplifier 27 amplifies and outputs the difference between these two inputs. This output is obtained by detecting the torque applied to the hub wheel 2A. If the torque value and the tire radius are known, the traveling direction load applied to the tire can be easily calculated.

  The electrical processing by the detection circuit may be performed on a circuit board (not shown) provided on the outer member 1 or may be performed by fixing the circuit board to a knuckle (not shown). Furthermore, this circuit board can be built in the ECU side of the automobile. The torque information processed by the detection circuit in this way can also be transmitted wirelessly to a receiving means on the vehicle body side by a transmitting means (not shown). In this case, it is also possible to wirelessly supply power to the circuit board on which the detection circuit is mounted.

  A torque transmission path in the wheel bearing device will be described with reference to FIG. The driving force from the engine is transmitted to the wheel mounting flange 2a through a joint portion between the spline groove 14b of the constant velocity joint stem 14 and the spline groove 2b on the inner diameter surface of the hub wheel 2A, and finally the tire is driven. . The joint between the constant velocity joint 13 and the wheel bearing 18 is generally a spline joint, and the spline joint portion extends to a position corresponding to the wheel mounting flange 2a in the inner diameter portion of the hub wheel 2A. It is a structure.

  On the other hand, in this embodiment, there is no spline coupling portion at the position corresponding to the detected portion 10 of the inner diameter portion of the hub wheel 2A, and the position of the spline coupling portion in the axial direction and the position of the wheel mounting flange 2a Therefore, the torsion is reliably transmitted to the detected portion 10 made of a magnetostrictive material with the transmission of the driving force of the engine. As a result, the load sensor 9 can obtain a torque detection output with little hysteresis and linearity. In order to close the gap of the spline joint, the spline may be given an angle of several degrees to eliminate the gap, but in this embodiment, the torque in the direction opposite to the twisting direction of the spline joint is transmitted. Even so, the linearity of the sensor output is ensured.

  Thus, in the wheel bearing device with a built-in load sensor of this embodiment, the position of the double row rolling elements 3 in the space sealed by the seals 7 and 8 on both sides between the outer member 1 and the inner member 2 is as follows. Since the load sensor 9 for detecting the load acting on the bearing by detecting the magnetostriction change is provided at the outboard side position, the load sensor can be installed compactly in the vehicle, and the load applied to the wheel can be detected stably. . In particular, the inner diameter of the inner member 2 is within an axial range where the detected portion 10 made of a magnetostrictive material constituting the load sensor 9 exists (an axial range corresponding to the large diameter portion 2d of the inner diameter surface of the hub wheel 2A). Since the portion (spline coupling portion) where the load in the rotational direction acts between the surface and the constant velocity joint outer ring 13a is not generated, the torque from the constant velocity joint 13 is accurately transmitted to the detected portion 10 and is transmitted to the wheel. Such a load can be detected more accurately.

  FIG. 4 shows another embodiment of the present invention. The bearing device for a wheel with a built-in load sensor of this embodiment is obtained by adding a locking mechanism for the bolt 16 in the first embodiment shown in FIGS. The bolt loosening prevention mechanism has a polygonal cylindrical portion 28a fitted to the bolt head portion 16a as shown in FIG. 4B showing a partially broken front view seen from the direction of arrow A in FIG. A washer 28 having an L-shaped cross section and an engagement pin 29 projecting from the step surface 2e of the hub wheel 2A in the axial direction. By engaging the engagement pin 29 with one of a plurality of U-shaped notches 28c formed on the periphery of the flange portion 28b of the washer 28, the bolt 16 is prevented from loosening. . The bolt head 16a can be prevented from being pulled out of the bolt head 16a by inserting the first split pin 30 in the radial direction across the cylindrical portion 28a of the washer 28 fitted to the bolt head 16a. It has been. Other configurations are the same as those in the first embodiment.

  FIG. 5 shows still another embodiment of the present invention. In the first embodiment shown in FIGS. 1 to 3, the wheel bearing device with a built-in load sensor according to this embodiment has a constant velocity joint 13 on the large-diameter portion 2 d on the outboard side of the inner diameter surface of the hub wheel 2 </ b> A. The tap 31 is formed in consideration of the case where the stem 14 is pulled out from the hub wheel 2A. Other configurations are the same as those in the first embodiment.

  6 and 7 show still another embodiment of the present invention. The wheel bearing device with a built-in load sensor of this embodiment is a double-row rolling device separately from the load sensor 9 provided at a position adjacent to the wheel mounting flange 2a in the first embodiment shown in FIGS. An axial load detecting means 39 for detecting an axial load is disposed in a space between the running surfaces 5 and 5. The axial load detecting means 39 is made of a magnetostrictive material and is provided on the outer diameter surface of the inner member 2, and the inner diameter surface of the outer member 1 facing the detected portion 40 in the radial direction. It is a magnetostriction sensor which consists of detection part 41 provided in. The detected portion 40 is fixed to the outer diameter surface of the hub wheel 2 </ b> A at an intermediate position sandwiched between two rows of rolling surfaces 5, 5 formed on the inner member 2. As the detected portion 40, a ring-shaped member made of Fe—Al alloy is used, and after being press-fitted into the outer diameter surface of the hub wheel 2A, welding or diffusion bonding is performed. Of the outer diameter surface of the hub wheel 2A, the range including the fixed portion of the Fe—Al alloy that is the detected portion 40 and the rolling surface 5 is subjected to quenching treatment, and then the surface of the Fe—Al alloy is ground. Then, the residual stress may be increased by shot peening the surface.

  On the surface layer of one side of the detected portion 40, a plurality of grooves 40a directed in the axial direction are formed in a row in the circumferential direction as shown in a partially broken side view in FIG. The surface layer on the other side of the detected portion 40 is a magnetostrictive surface portion 40b in which no groove is formed. The groove depth of the axial groove 40a is preferably about 0.1 mm to 0.5 mm. The detection unit 41 is composed of two coil windings 41a and 41b and a yoke 41c, and each one of the coil windings 41a and 41b is coiled so as to face the axial groove 40a and the magnetostrictive surface portion 40b. Windings 41a and 41b are arranged. The coil windings 41a and 41b are assembled in the yoke 41c after being wound around a resin bobbin 41d. A cable 49 is pulled out from the detection unit 41. The cable 49 is pulled out of the bearing from a radial through hole 36 provided in the outer member 1, and the through hole 36 is sealed with an elastic member 37 such as rubber. Stop and waterproof.

In the wheel bearing device with a built-in load sensor of this embodiment, when a load that compresses or pulls the hub wheel 2A in the axial direction is applied, a tensile force is applied to the detected portion 40 of the axial load detection means 39 provided on the hub wheel 2A. (Or compression force) works. At this time, although the magnetic resistance of the coil windings 41a and 41b of the detection unit 41 varies depending on the magnitude of the tension and compression force, the coil winding 41a facing the axial groove 40a of the detection unit 40 is more suitable. Sensitivity is better than another coil winding 41b. The coil winding 41b on the low sensitivity side functions for temperature compensation.
If the detection outputs of the coil windings 41a and 41b are processed by the same circuit as the detection circuit shown in FIG. 3, the axial load can be detected. If the outputs of the load sensor 9 and the axial load detection means 39 obtained here are taken in as information, it can be applied to driving plan control of an automobile and road surface information transmission in a steer-by-wire system.

  In each of the above-described embodiments, the case where an Fe—Al alloy is used as the magnetostrictive material of the detected portions 10 and 40 constituting the load sensors 9 and 39 is exemplified, but Al is diffused in the surface layer of the hub wheel 2A. And it is good also as a Fe-Al alloy. As a method for diffusing Al in the metal surface layer, heating the sealed container containing the hub wheel 2A and Al powder to about 900 ° C. is performed. The Al diffusion depth in this case can be changed depending on the processing method and time, but the Al diffusion depth is processed in the range of about several tens of μm to 100 μm. The Al diffusion treatment is performed by diffusing and distributing Al in an inclined manner so that the concentration gradually increases in the structural steel that is the base material of the hub wheel 2A. Thereby, the Fe-Al alloy of the magnetostriction diffusion layer having high magnetostriction characteristics can be obtained without reducing the mechanical strength of the hub wheel 2A.

  In order to distribute Al from the surface so as to have a gradient concentration, Al is diffused from the surface in a high temperature atmosphere. As a result, it is possible to form a layer in which the Al concentration gradually decreases while drawing a gentle concentration curve from the surface toward the center of the steel material that is the base material of the hub wheel 2A. This diffusion layer having a gradient concentration is formed in a uniform alloy layer without pores as in the case of overlay welding, and the occurrence of early cracks due to fatigue is greatly suppressed. Further, no cracking occurs during the heat treatment.

  In addition, if the magnetostrictive material is made of a bulk material of Fe-Al alloy, the workability is lowered because it is brittle. However, according to the above diffusion process, the Al diffusion process is performed after the machining of the hub wheel 2A. Therefore, it has the same workability as a normal steel material, and the productivity is remarkably improved. Therefore, the cost can be reduced. When Fe-Al clad steel is used, only the Fe-Al alloy layer from which the carbon steel portion as the base material is deleted may be fixed to the hub wheel 2A as the detected portions 10 and 40. In this case, since the weldability between the Fe-Al alloy and the hub wheel 2A made of carbon steel is good, it is advantageous.

(A) is sectional drawing of the bearing apparatus for load sensor built-in wheels concerning 1st Embodiment of this invention, (B) is a partial top view of the same bearing apparatus, (C) is an expansion of the C section in (A). FIG. It is a partially broken side view of the same bearing device. It is a schematic block diagram of the detection circuit of the load sensor in the same bearing device. (A) is sectional drawing of the bearing apparatus for load sensor built-in wheels concerning other embodiment of this invention, (B) is the partially broken front view seen from the arrow A side in (A). It is sectional drawing of the bearing apparatus for load sensor built-in wheels concerning further another embodiment of this invention. It is sectional drawing of the bearing apparatus for load sensor built-in wheels concerning further another embodiment of this invention. It is a partially broken side view of the same bearing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Outer member 2 ... Inner member 3 ... Rolling elements 4, 5 ... Rolling surface 7, 8 ... Seal (sealing device)
DESCRIPTION OF SYMBOLS 9 ... Load sensor 10 ... Detected part 10a ... Inclined groove 11a, 11b ... Coil winding 13 ... Constant velocity joint 13a ... Outer ring 39 ... Axial load detection means 40 ... Detected part (magnetostrictive part)
40a ... Axial groove 40b ... Magnetostrictive surface 41 ... Detector

Claims (9)

An outer member in which a double row rolling surface is formed on the inner periphery, an inner member in which a rolling surface opposite to the rolling surface of the outer member is formed on the outer periphery, and an intermediate between both rolling surfaces In the wheel bearing device that includes the double row rolling elements, and a sealing device that seals both ends between the outer member and the inner member, and rotatably supports the wheel with respect to the vehicle body,
A load acting on the bearing is detected by detecting a change in magnetostriction at a position on the outboard side of the double row rolling element position in the space sealed by the sealing device on both sides between the outer member and the inner member. A load sensor built-in wheel bearing device comprising a load sensor.   In Claim 1, the load sensor is configured by a detected portion including a magnetostrictive portion provided in an inner member and a detecting portion provided in an outer member and detecting a magnetostriction change of the detected portion. A load sensor built-in wheel bearing device in which a portion in which a rotational load acts between the inner diameter surface of the inner member and the constant velocity joint outer ring does not occur in the axial range where the magnetostrictive portion exists.   In Claim 1, the load sensor is configured by a detected portion including a magnetostrictive portion provided in an inner member and a detecting portion provided in an outer member and detecting a magnetostriction change of the detected portion. For a load sensor built-in wheel having a spline coupling part that separably couples the inner diameter surface of the inner member and the shaft part of the constant velocity joint outer ring, and arranging the spline coupling part on the inboard side of the magnetostrictive part Bearing device.   The magnetostrictive portion according to any one of claims 1 to 3, wherein the magnetostrictive portion is made of an Fe-Al alloy, and a plurality of grooves in a direction substantially 45 degrees with respect to the axis are formed side by side in the circumferential direction on the surface of the magnetostrictive portion. A load sensor built-in wheel bearing device, wherein the detection unit is a coil, and the load sensor detects a load as a torque value.   5. The inner member according to claim 1, wherein the inner member has an inner diameter hole that is spline-coupled to a shaft portion of the constant velocity joint outer ring. A wheel bearing device with a built-in load sensor having a larger diameter than the inner diameter of the formed portion.   6. An axial load detecting means for detecting an axial load is built in a space between an inner member and an outer member formed between two rolling surfaces in any one of claims 1 to 5. Load sensor built-in wheel bearing device.   7. A bearing device for a load sensor built-in wheel according to claim 6, wherein the axial load detecting means is a magnetostrictive sensor comprising a magnetostrictive portion disposed on the inner member and a detection coil disposed on the outer member so as to oppose the axial load detecting means. .   8. The magnetostrictive portion in the axial load detecting means according to claim 7 is made of an Fe—Al alloy, and there are a portion where a plurality of axial grooves are formed and a portion where the axial grooves are not formed on the surface of the magnetostrictive portion. For the wheel with a built-in load sensor, two detection coils respectively facing the part where the groove is formed and the part where the groove is not formed are arranged on the outer member, and the detection coil on the side where the groove is not formed is used for temperature compensation. Bearing device.   In Claim 1, the load sensor is configured by a detected portion including a magnetostrictive portion provided in an inner member and a detecting portion provided in an outer member and detecting a magnetostriction change of the detected portion. A load sensor built-in wheel bearing device in which the inner member is made of carbon steel, the magnetostrictive portion is made of an Fe-Al alloy, and the inner member and the magnetostrictive portion are welded.

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