JP2011252883A - Wheel bearing with sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wheel bearing with a compact configuration and good assemblability having a sensor that can accurately detect load on the bearing part of a wheel.SOLUTION: A wheel bearing consists of a rolling element 5 provided between double rows of a rotation surface 3 of an outer member 1 and double rows of a rotation surface 4 of an inner member 2 facing each other. A fixed-side member of the outer member 1 and the inner member 2 has, on its outer periphery, a vehicle attachment flange 1a that is attached to a knuckle. One or more load detection sensor units 20 are provided on the outer diameter surface of the fixed-side member. The sensor unit 20 consists of a distortion generating member with two or more contact fixing parts that are in contact and fixed to the fixed-side member, and one or more sensors that are attached to the distortion generating member and detect a distortion of the distortion generating member. An arithmetic processing circuit 31 composed of an arc circuit board and circuit elements mounted on the circuit board is attached on a side surface of the vehicle attachment flange 1a to perform arithmetic processing of output signals from the sensors.

Description

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

  As a technique for detecting a load applied to each wheel of an automobile, as shown in FIG. 17, a strain gauge 91 is attached to an outer ring 90 that is a fixed ring of a wheel bearing, and the load is detected by detecting the strain. A bearing has been proposed (for example, Patent Document 1). In addition, a calculation method for estimating a load applied to a wheel from output signals of a plurality of strain sensors provided on the wheel has been proposed (for example, Patent Document 2).

Special table 2003-530565 gazette Special table 2008-542735 gazette

When the load applied to the wheel is measured using a strain sensor as in the techniques disclosed in Patent Documents 1 and 2, the drift of the sensor due to the environmental temperature and the initial drift due to the strain associated with the attachment of the sensor unit become a problem.
The drift due to distortion caused by the mounting of this sensor unit can be eliminated by adjusting the offset with the strain sensor installed and converting the change from the position as a signal output, so that the distortion signal can be detected accurately. .

  As the load estimation means having the above-described sensor output signal offset function, for example, those shown in block diagrams in FIGS. The sensor unit 110 in this example includes a strain generating member attached to an outer ring that is a fixed ring of a wheel bearing, and a strain sensor fixed to the strain generating member.

  18 includes an amplification circuit 101, an offset adjustment circuit 102, a storage unit 103, various correction circuits 104, a signal output circuit 106, and a control circuit 107. The control circuit 107 controls the offset adjustment circuit 102, the storage means 103, the correction circuit 104, the signal output circuit 106, and the like, and outputs a sensor output signal subjected to preprocessing such as offset adjustment to about 12 to 16 bits. It digitizes with AD converter 108 (FIG. 20) with resolution | decomposability, Based on this digitized sensor output signal, the load concerning a wheel bearing is calculated and estimated by the load calculation function. The offset adjustment circuit 102 adjusts the initial offset of the sensor unit 110 and the offset due to fixing to the wheel bearing to a normal value, and can be adjusted by the control circuit 107 or by an external command. ing.

  FIG. 19 shows a specific connection configuration example of the sensor unit 110, the amplifier circuit 101, and the offset adjustment circuit 102. The offset adjustment circuit 102 is configured as an adder including an operational amplifier OP, resistors R3 and R4, variable resistors VR1 and VR2. In this case, the resistance values of the variable resistors VRI and VR2 are adjusted and fixed so that the sensor output becomes a specified value (zero point voltage) after the assembly of the sensor-equipped wheel bearing is completed.

However, even with the circuit configuration of the load estimation means shown in FIG. 18, in order to cover the degree of distortion associated with the mounting of the sensor unit 110 and the characteristic variation of the sensor element Rg (FIG. 19) itself, Since it is necessary to provide a width and an adjustment step is required, the manufacturing cost increases.
In addition, when a large offset fluctuation occurs during long-term operation, the amplification circuit 101 at the subsequent stage is saturated depending on the magnitude, and it becomes difficult to detect the load.

  Further, as shown in FIG. 20, when the number of strain sensors 111 mounted on the outer ring 120 of the bearing is increased, the preprocessing circuit including the amplification circuit 101 and the offset adjustment circuit 102 is also increased in the same manner as the number of elements. The size of the substrate becomes large, and it becomes difficult to mount on the bearing outer ring 120. For this reason, a pretreatment circuit is installed at a location away from the bearing and the sensor output signal is routed.However, in this case, the number of cables increases, and thick wiring from the suspension parts to the body side is required. It will be installed, causing workability and reliability to deteriorate. In addition, since a weak sensor output signal is extracted by a long wiring, there is a problem that the influence of noise is increased.

  Therefore, a configuration is conceivable in which the AD converter 108 shown in FIG. 20 is arranged on the outer ring 120 of the bearing as shown in FIGS. 21 and 22 to reduce the number of wires. However, in this case, it is necessary to provide the AD converter 108 for each sensor unit 110, resulting in an increase in cost. 21 and FIG. 22 show examples in which one AD converter 108 is shared by two sensor units 110 and one AD converter 108 is shared by four sensor units 110. However, the AD converter 108 is shown. It becomes a new problem how to fix concrete. For example, when the AD converter 108 is provided on the outer peripheral surface of the cylindrical portion of the outer ring 120, it is necessary to provide a pedestal similar to that for mounting the sensor unit on the outer peripheral surface of the outer ring 120. Since the left and right are asymmetric, sensor output signals of a plurality of strain sensors that are constituent elements of the sensor unit 110 are complicated. In the case of a configuration example in which a protective cover that covers the sensor unit 110 is provided on the outer periphery of the outer ring 120, it is conceivable to fix the AD converter 108 to the protective cover. However, in this case, since circuit wiring must be performed when the protective cover is attached, the assembly of the bearing is deteriorated.

  As described above, when the above-described AD converter or the like is added to the arithmetic processing circuit that processes the sensor output signal, a new problem arises as to how to install the arithmetic processing circuit.

  An object of the present invention is to provide a sensor-equipped wheel bearing that has a compact configuration, is easy to assemble such as an arithmetic processing circuit, and can accurately detect a load applied to a bearing portion of the wheel.

  The sensor-equipped wheel bearing according to the present invention includes an outer member having a double-row rolling surface formed on the inner periphery, an inner member having a rolling surface opposed to the rolling surface formed on the outer periphery, A plurality of rolling elements interposed between the opposing rolling surfaces of the member, and the fixed side member of the outer member and the inner member has a flange for mounting the vehicle body attached to the knuckle on the outer periphery, In a wheel bearing for rotatably supporting a wheel with respect to a vehicle body, one or more load detection sensor units are provided on an outer diameter surface of the fixed side member, and the sensor unit is fixed in contact with the fixed side member. A strain generating member having two or more contact fixing portions, and one or more sensors attached to the strain generating member to detect the strain of the strain generating member, on the side surface of the flange for mounting the vehicle body , Arc-shaped circuit board and this circuit board Wherein the formed of a mounted circuit elements mounted an arithmetic processing circuit for processing an output signal of the sensor. In this case, the fixed member is, for example, an outer member of the bearing.

When a load acts between the wheel bearing or the tire of the wheel and the road surface, the load is also applied to the stationary side member (for example, the outer member) of the wheel bearing to cause deformation. Since the strain generating member in the sensor unit is fixed in contact with the stationary member, the strain of the stationary member is transmitted to the strain generating member in an enlarged manner, and the strain is detected with high sensitivity and the load can be accurately estimated.
In particular, an arithmetic processing circuit, which comprises an arc-shaped circuit board and a circuit element mounted on the circuit board, is mounted on the side surface of the flange for mounting the vehicle on the fixed side member, and performs arithmetic processing on the sensor output signal of the sensor unit. Therefore, it is possible to attach an arithmetic processing circuit including an AD converter in a compact configuration without changing the shape of the peripheral surface of the cylindrical portion of the fixed side member, and the assembly property is good. The load applied to the bearing portion can be accurately detected.

  In this invention, the arithmetic processing circuit may include an AD converter that AD converts the output signal of the sensor.

  In this invention, the arithmetic processing circuit may include an offset adjustment circuit that adjusts the offset of the sensor to a normal value, and an amplification circuit that amplifies the output signal of the sensor. The arithmetic processing circuit performs offset adjustment as normalization processing.

  In this invention, the said arithmetic processing circuit may be provided with the load estimation means which estimates the load added to a wheel from the output signal of the said sensor.

In the present invention, the arithmetic processing circuit includes: a first load estimating unit that estimates a load acting on the wheel bearing using an average value of the output signal of the sensor; and an amplitude value of the output signal of the sensor, or its One of the second load estimating means for estimating the load acting on the wheel bearing using the amplitude value and the average value, and one of the first and second load estimating means according to the wheel rotation speed. Selection output means for switching and selecting the estimated load value may be provided.
In the case of this configuration, the detection processing time can be shortened by outputting the estimated load value of the first load estimating means obtained from the average value obtained without performing the time averaging process when the wheel is stationary or at a low speed. In addition, when the wheel is in the normal rotation state, the average value and the amplitude value of the sensor output signal can be calculated with high accuracy. Therefore, the estimated load value of the second load estimating means obtained from the amplitude value or the average value and the amplitude value. Is output, the error of the estimated load value is reduced, and the detection delay time is sufficiently shortened.
As a result, the load applied to the wheel can be accurately estimated, and the detected load signal can be output without delay. For this reason, the responsiveness and controllability of the vehicle control using the load signal are improved, and safety and running stability can be further improved.

  In this case, the sensor unit has three or more contact fixing portions and two sensors, and is between the adjacent first and second contact fixing portions and between the adjacent second and third contact fixing portions. The sensors are respectively mounted between them, and the interval between the contact fixing portions adjacent to each other or the circumferential direction of the fixed side member of the adjacent sensors is {1/2 + n (n: integer)} times the arrangement pitch of the rolling elements, The first and second load estimating means may use the sum of output signals of the two sensors as an average value.

  In the present invention, an annular protective cover may be attached to the peripheral surface of the fixed side member concentrically with the fixed side member, and the sensor unit and the arithmetic processing circuit may be covered with the protective cover. In this configuration, the sensor unit and the arithmetic processing circuit can be covered with a protective cover to prevent the sensor unit and the arithmetic processing circuit from being damaged due to the influence of the external environment, and the load acting on the wheel bearings and the tire ground contact surface for a long time. Can be detected accurately. For example, the sensor unit and the arithmetic processing circuit can be reliably protected from stepping stones, muddy water, salt water and the like from the outside.

In this invention, the signal cable for taking out the signal processed by the arithmetic processing circuit to the outside of the bearing is attached to the arithmetic processing circuit, and the signal cable is connected to the cylindrical portion of the protective cover on the outboard side of the body mounting flange. It is also possible to provide a hole portion through which the lead-out portion from the protective cover is pulled out and apply a rust-proof seal material to the portion from which the signal cable lead-out portion is pulled out from the hole portion.
In the case of this configuration, the sealing performance of the protective cover can be further improved, and the displacement of the signal cable in the circumferential direction can also be restricted.

In this invention, the signal cable for taking out the signal processed by the arithmetic processing circuit to the outside of the bearing is attached to the arithmetic processing circuit, and the signal cable is connected to the cylindrical portion of the protective cover on the outboard side of the body mounting flange. A hole portion through which the lead-out portion from the protective cover is drawn out may be provided, and a bush made of an elastic material may be attached to a portion from which the signal cable lead-out portion is drawn out from the hole portion.
Also in this configuration, the sealing performance of the protective cover can be further improved.

In this invention, the signal cable for taking out the signal processed by the arithmetic processing circuit to the outside of the bearing is attached to the arithmetic processing circuit, and the signal cable is connected to the cylindrical portion of the protective cover on the outboard side of the body mounting flange. It is possible to provide a hole through which the lead-out part from the protective cover is pulled out, apply a rust-proof seal material to the part from which the signal cable lead-out part is pulled out from the hole part, and attach a bush made of an elastic material. good.
In the case of this configuration, since the sealing material and the bush are used in an overlapping manner, the sealing performance of the protective cover can be further enhanced.

  In this invention, the protective cover may be formed by, for example, pressing a corrosion-resistant steel plate, or may be obtained by performing metal plating or coating on the pressed steel plate. good.

  In the present invention, a flexible substrate may be attached to the peripheral surface of the fixed side member concentrically with the fixed side member, and the arithmetic processing circuit may be integrally formed on the flexible substrate. In this case, the connection work of the flexible substrate to the arithmetic processing circuit can be omitted.

  In this invention, a flexible substrate may be attached to the peripheral surface of the fixed side member concentrically with the fixed side member, and the sensor unit may be attached to the flexible substrate. As described above, the sensor unit can be easily attached by attaching the sensor unit to the flexible substrate.

  In this invention, the base material of the flexible substrate may be polyimide. When the base material of the flexible substrate is polyimide, the flexible substrate can have sufficient flexibility and heat resistance.

In the present invention, the sensor unit is arranged at 90 degrees in the circumferential direction on the upper surface portion, the lower surface portion, the right surface portion, and the left surface portion of the outer diameter surface of the fixed side member that is in the vertical position and the horizontal position with respect to the tire ground contact surface. Four of them may be equally arranged with a phase difference.
By arranging the four sensor units in this way, it is possible to estimate the vertical load Fz acting on the wheel bearing, the load Fx serving as a driving force or a braking force, and the axial load Fy.

In the present invention, the front shape of the flange of the stationary member may be a shape that is line symmetric with respect to a line segment orthogonal to the bearing axis or a shape that is point symmetric with respect to the bearing axis.
In the case of this configuration, the shape of the fixed side member is simplified, and variations in temperature distribution and expansion / contraction amount due to the complexity of the shape of the fixed side member can be reduced. Thereby, the influence by the variation in the temperature distribution and the expansion / contraction amount in the fixed side member can be sufficiently reduced, and the strain amount due to the load can be detected by the sensor unit.

In this invention, you may give the surface treatment which has corrosion resistance or corrosion resistance to the surrounding surface in which the flange of the said stationary-side member is provided. The surface treatment in this case is, for example, metal plating, painting, or coating treatment.
In this way, when the peripheral surface on which the flange of the fixed side member is provided is subjected to corrosion resistance or anticorrosive surface treatment, the mounting portion of the sensor unit rises due to rust on the peripheral surface of the fixed side member, or the sensor unit receives it. Rust generation can be prevented, sensor malfunctions due to rust can be eliminated, and load detection can be performed accurately over a longer period.

The method of assembling the sensor-equipped wheel bearing according to the present invention is the method of assembling the sensor-equipped wheel bearing according to the present invention, wherein the stationary member is a single member or the rolling element is assembled to the stationary member. The sensor unit is attached to the peripheral surface of the fixed side member, and further, the bearing is assembled after the protective cover is attached to the peripheral surface of the fixed side member.
According to this assembling method, the sensor-equipped wheel bearing in which the sensor unit and the protective cover are attached to the stationary member can be easily assembled.

The sensor-equipped wheel bearing according to the present invention includes an outer member having a double-row rolling surface formed on the inner periphery, an inner member having a rolling surface opposed to the rolling surface formed on the outer periphery, A plurality of rolling elements interposed between the opposing rolling surfaces of the member, and the fixed side member of the outer member and the inner member has a flange for mounting the vehicle body attached to the knuckle on the outer periphery, In a wheel bearing for rotatably supporting a wheel with respect to a vehicle body, one or more load detection sensor units are provided on an outer diameter surface of the fixed side member, and the sensor unit is fixed in contact with the fixed side member. A strain generating member having two or more contact fixing portions, and one or more sensors attached to the strain generating member to detect the strain of the strain generating member, on the side surface of the flange for mounting the vehicle body , Arc-shaped circuit board and this circuit board Since the circuit is mounted with an arithmetic processing circuit that performs arithmetic processing on the output signal of the sensor, it has a compact configuration, good assembling of the arithmetic processing circuit, etc., and the load applied to the wheel bearing is accurate. Can be detected.
The method for assembling the sensor-equipped wheel bearing according to the present invention is an assembly method for assembling the sensor-equipped wheel bearing according to the present invention, wherein the stationary member is in a single state or the rolling element is assembled in the stationary member. Since the sensor unit is attached to the peripheral surface of the fixed side member and the protective cover is further attached to the peripheral surface of the fixed side member, the bearing is assembled. Therefore, the sensor unit and the protective cover are attached to the fixed side member. The sensor wheel bearing can be easily assembled.

It is sectional drawing of the bearing for wheels with a sensor concerning one Embodiment of this invention. It is sectional drawing of an example of the outward member of the wheel bearing with a sensor. It is the front view which looked at the outward member from the outboard side. It is an enlarged plan view of a sensor unit in the wheel bearing with sensor. It is a VV arrow sectional view in FIG. (A) is a development top view which fractures | ruptures and shows a part of example of a flexible substrate, (B) is VIb-VIb arrow sectional drawing of (A). (A) is a development top view which fractures | ruptures and shows a part of other example of a flexible substrate, (B) is the same sectional drawing. (A) is the expansion | deployment top view which fractures | ruptures and shows a part of other example of a flexible substrate, (B) is the same sectional drawing. It is explanatory drawing of the influence of a rolling-element position with respect to the output signal of a sensor unit. It is a block diagram which shows an example of the whole structure of the detection system in the bearing for wheels with the said sensor. It is a block diagram which shows the other example of the whole structure of the detection system in the bearing for wheels with a sensor. It is a block diagram of the circuit example of the calculating part which calculates the average value and amplitude value of a sensor output signal. It is a block diagram of the circuit part which estimates and outputs a load from an average value and an amplitude value. It is sectional drawing of an example of the outward member in the bearing for wheels with a sensor concerning other embodiment of this invention. It is sectional drawing of the other example of the outer member. It is sectional drawing of the bearing for wheels with a sensor concerning further another embodiment of this invention. It is a perspective view of a prior art example. It is a block diagram which shows the structural example of the detection system in a proposal example. It is a circuit block diagram which shows the specific example of the amplifier circuit and offset adjustment circuit in the detection system. It is a block diagram which shows the structure of a detection system when the number of sensors increases in a proposal example. It is sectional drawing which shows an example of the installation structure of the AD converter in a proposal example. It is sectional drawing which shows the other installation structural example of the AD converter in a proposal example.

  A first embodiment of the present invention will be described with reference to FIGS. This embodiment is a third generation inner ring rotating type and is applied to a wheel bearing for driving wheel support. 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.

  As shown in the sectional view of FIG. 1, the bearing for this sensor-equipped wheel bearing includes an outer member 1 in which a double row rolling surface 3 is formed on the inner periphery, and rolling facing each of these rolling surfaces 3. The inner member 2 has a surface 4 formed on the outer periphery, and the outer member 1 and the double row rolling elements 5 interposed between the rolling surfaces 3 and 4 of the inner member 2. This wheel bearing is a double-row angular ball bearing type, and the rolling elements 5 are made of balls and are held by a cage 6 for each row. The rolling surfaces 3 and 4 have an arc shape in cross section, and are formed so that the ball contact angle is aligned with the back surface. Both ends of the bearing space between the outer member 1 and the inner member 2 are sealed by a pair of seals 7 and 8, respectively.

The outer member 1 is a fixed side member, and has a vehicle body mounting flange 1a attached to a knuckle 16 in a suspension device (not shown) of the vehicle body on the outer periphery, and the whole is an integral part. The flange 1a is provided with screw holes 14 for attaching a knuckle at a plurality of locations in the circumferential direction, and knuckle bolts (not shown) inserted into the bolt insertion holes 17 of the knuckle 16 from the inboard side are screwed into the screw holes 14. Thus, the vehicle body mounting flange 1a is attached to the knuckle 16.
The inner member 2 is a rotating side member, and includes a hub wheel 9 having a hub flange 9a for wheel mounting, and an inner ring 10 fitted to the outer periphery of the end portion on the inboard side of the shaft portion 9b of the hub wheel 9. And become. The hub wheel 9 and the inner ring 10 are formed with the rolling surfaces 4 of the respective rows. An inner ring fitting surface 12 having a small diameter with a step is provided on the outer periphery of the inboard side end of the hub wheel 9, and the inner ring 10 is fitted to the inner ring fitting surface 12. A through hole 11 is provided at the center of the hub wheel 9. The hub flange 9a is provided with press-fitting holes 15 for hub bolts (not shown) at a plurality of locations in the circumferential direction. In the vicinity of the base portion of the hub flange 9a of the hub wheel 9, a cylindrical pilot portion 13 for guiding a wheel and a braking component (not shown) protrudes toward the outboard side.

  FIG. 2 shows a cross-sectional view of the outer member 1 in this wheel bearing, and FIG. 3 shows a front view of the outer member 1 viewed from the outboard side. 2 shows a cross-sectional view taken along arrow II-II in FIG. The vehicle body mounting flange 1a has a shape in which the front surface shape is symmetrical with respect to a line segment perpendicular to the bearing axis O (for example, a vertical line segment LV or a horizontal line segment LH in FIG. 3), or a bearing axis O The shape is point-symmetric with respect to. Specifically, in this example, the front shape is a circle that is line symmetric with respect to the vertical line segment LV.

  Four sensor units 20 are provided on the outer diameter surface of the outer member 1 that is a stationary member. Here, these sensor units 20 are arranged in the circumferential direction 90 on the upper surface portion, the lower surface portion, the right surface portion, and the left surface portion of the outer diameter surface of the outer member 1 that is in the vertical position and the front and rear position with respect to the tire ground contact surface. They are equally distributed with a phase difference of degrees.

  As shown in the enlarged plan view and the enlarged sectional view in FIGS. 4 and 5, these sensor units 20 are attached to the strain generating member 21 and detect the strain 2 of the strain generating member 21. The two strain sensors 22A and 22B. The strain generating member 21 is made of an elastically deformable metal such as a steel material and is made of a thin plate material of 2 mm or less, and has a planar shape with a strip shape having a uniform width over the entire length, and has notches 21b on both sides. The corner of the notch 21b has an arcuate cross section. The strain generating member 21 has three contact fixing portions 21 a that are contact-fixed to the outer diameter surface of the outer member 1 via the spacers 23. The three contact fixing portions 21 a are arranged in a line in the longitudinal direction of the strain generating member 21. That is, in FIG. 5, one strain sensor 22A is arranged between the contact fixing portion 21a at the left end and the contact fixing portion 21a at the center, and the other between the contact fixing portion 21a at the center and the contact fixing portion 21a at the right end. One strain sensor 22B is arranged. As shown in FIG. 4, the notches 21 b are formed at two positions corresponding to the placement portions of the strain sensors 22 </ b> A and 22 </ b> B on both sides of the strain generating member 21. Thereby, the strain sensors 22A and 22B detect the strain in the longitudinal direction around the notch 21b of the strain generating member 21. Note that the strain generating member 21 is plastically deformed even in a state in which an assumed maximum force is applied as an external force acting on the outer member 1 that is a fixed member or an acting force acting between the tire and the road surface. It is desirable not to do so. This is because when the plastic deformation occurs, the deformation of the outer member 1 is not transmitted to the sensor unit 20 and affects the measurement of strain. The assumed maximum force is, for example, the maximum force within a range in which the normal functioning of the wheel bearing is restored when the force is removed without the wheel bearing being damaged. .

  In the sensor unit 20, the three contact fixing portions 21a of the strain generating member 21 are at the same position in the axial direction of the outer member 1, and the contact fixing portions 21a are positioned away from each other in the circumferential direction. These contact fixing portions 21 a are respectively fixed to the outer diameter surface of the outer member 1 by bolts 24 through spacers 23. At this time, the flexible substrate 30 disposed on the upper surface of the sensor unit 20 is also fixed to the outer diameter surface of the outer member 1 together with the sensor unit 20. The flexible substrate 30 is a strip-shaped single substrate disposed in a ring shape concentrically with the outer member 1 along the outer diameter surface of the outer member 1. That is, the four sensor units 20 are attached to the back surface side of one flexible substrate 30 and are fixed to the outer diameter surface of the outer member 1 together with the flexible substrate 30. Since the flexible substrate 30 is arranged in a ring shape along the outer diameter surface of the outer member 1, the base material is preferably polyimide. When the base material of the flexible substrate 30 is polyimide, the flexible substrate 30 can have sufficient flexibility and heat resistance, and can be easily along the circumferential direction of the outer member 1.

  Each of the bolts 24 is inserted from a bolt insertion hole 30a of the flexible substrate 30 into a bolt insertion hole 25 provided in the contact fixing portion 21a of the strain generating member 21 in the radial direction and a bolt insertion hole 26 of the spacer 23. Then, the outer member 1 is screwed into the screw hole 27 provided in the outer peripheral portion. A washer 28 is interposed between the head of the bolt 24 and the distortion generating member 21. In this way, by fixing the contact fixing portion 21a to the outer diameter surface of the outer member 1 via the spacer 23, each portion having the cutout portion 21b in the strain generating member 21 which is a thin plate shape becomes the outer member 1. It becomes a state away from the outer diameter surface of this, and distortion deformation around the notch 21b becomes easy. As the axial position where the contact fixing portion 21a is disposed, an axial position that is the periphery of the rolling surface 3 of the outboard side row of the outer member 1 is selected here. Here, the periphery of the rolling surface 3 of the outboard side row is a range from the intermediate position of the rolling surface 3 of the inboard side row and the outboard side row to the formation portion of the rolling surface 3 of the outboard side row. It is. In order to stably fix the sensor unit 20 to the outer diameter surface of the outer member 1, a flat portion 1 b is formed at a location where the spacer 23 is contacted and fixed on the outer diameter surface of the outer member 1.

  As the strain sensors 22A and 22B, various sensors can be used. For example, the strain sensors 22A and 22B can be configured with a metal foil strain gauge. In that case, the distortion generating member 21 is usually fixed by adhesion. Further, the strain sensors 2222A and 22B can be formed on the strain generating member 21 with a thick film resistor.

  6A and 6B are a plan development view and a sectional view of an arrangement example of the sensor unit 20 on the flexible substrate 30. FIG. In this arrangement example, four sensor units 20 are directly mounted on the flexible substrate 30. The sensor unit 20 is attached to the back surface of the flexible substrate 30 (the surface facing the outer diameter surface of the outer member 1), and the wiring circuit 34 is printed as a circuit pattern on the back surface, front surface, or both front and back surfaces of the flexible substrate 30. . The sensor unit 20 is connected to the wiring circuit 34 by soldering or the like. In the sensor unit 20, the surface of the distortion generating member 21 opposite to the contact surface with the outer member 1 is a circuit printed surface, and this circuit printed surface faces the printed surface of the wiring circuit 34 of the flexible substrate 30. It attaches to the flexible substrate 30 so that it becomes. In this example, strip-shaped openings 30 b extending in the longitudinal direction of the flexible substrate 30 are formed in portions corresponding to both side portions of the sensor unit 20 in the sensor unit arrangement portion of the flexible substrate 30. Thereby, the contact surface of the sensor unit 20 with the outer member 1 becomes a flat surface without a circuit printing surface or a solder portion, and the sensor unit 20 can be attached to the outer member 1 in close contact.

FIGS. 7A and 7B are a plan development view and a sectional view of another arrangement example of the sensor unit 20 on the flexible substrate 30. FIG. Also in this arrangement example, all of the sensor units 20 are mounted on the flexible substrate 30. In this arrangement example, a rectangular opening 30 c is formed in the sensor unit arrangement portion of the flexible substrate 30 so that substantially the entire sensor unit 20 is exposed.
In this way, by forming the rectangular opening 30 c in which the entire sensor unit 20 is exposed in the arrangement portion of the sensor unit 30 in the flexible substrate 30, the deformation of the strain generating member 21 in the sensor unit 20 is caused by the flexible substrate 30. It can be surely prevented from being restricted, and the load detection accuracy can be improved accordingly. Other configurations are the same as those in the arrangement example shown in FIG.

  FIGS. 8A and 8B are a plan development view and a cross-sectional view of still another arrangement example of the sensor unit 20 on the flexible substrate 30. FIG. In this arrangement example, each sensor unit 20 is separated from the flexible substrate 30 except for a connection portion between the flexible substrate 30 and the wiring circuit 34. Other configurations are the same as those in the arrangement example shown in FIG.

  The strain sensors 22 </ b> A and 22 </ b> B of each sensor unit 20 are connected to the arithmetic processing circuit 31 (FIGS. 1 to 3) via the wiring circuit 34 of the flexible substrate 30. The arithmetic processing circuit 31 performs arithmetic processing on the output signals of the strain sensors 22A and 22B to obtain force (vertical load Fz, driving force and braking force) acting between the wheel bearing and the wheel and the road surface (tire contact surface). The load Fx and the axial load Fy) are estimated by an arc-shaped circuit board and circuit elements mounted on the circuit board. An example of the configuration of the arithmetic processing circuit 31 is shown in block diagrams in FIGS.

  The arc-shaped circuit board of the arithmetic processing circuit 31 is attached to the side surface of the outer member 1 facing the outboard side of the flange 1a for mounting the vehicle body as shown in FIG. In the configuration example shown in FIGS. 1 to 3, an arithmetic processing circuit 31 is disposed concentrically with the outer member 1 via a spacer 33 on a side surface facing the outboard side of the flange 1 a, and the flange 1 a is Fixed to the side. The circuit board of the arithmetic processing circuit 31 is provided with a plurality of bolt insertion holes 36 (FIG. 2), and the spacer 33 is disposed at each position aligned with the bolt insertion holes 36. Each bolt 35 is inserted from the bolt insertion hole 36 of the circuit board of the arithmetic processing circuit 31 into the bolt insertion hole 38 of the spacer 32 and screwed into the screw hole 39 provided in the vehicle body mounting flange 1a. The wiring circuit 34 (FIG. 6) of the flexible substrate 30 and the arithmetic processing circuit 31 are connected via a connection cable 40 (FIG. 3). Connected to the arithmetic processing circuit 31 is a signal cable 41 for extracting an output signal processed by this circuit to the outside of the bearing.

  In the above configuration example, the flexible substrate 30 is connected to the arithmetic processing circuit 31 via the connection cable 40, but the arithmetic processing circuit 31 may be integrally formed on the flexible substrate 30. In this case, the connection work of the flexible substrate 30 to the arithmetic processing circuit 31 can be omitted. Further, a waterproof connector may be used for connection between the flexible substrate 30 and the arithmetic processing circuit 31.

  In the configuration example of the arithmetic processing circuit 31 shown in FIG. 10, the strain sensor 22 of each sensor unit 20 is connected to the load estimating means 50 via the AD converter 49. That is, the output signal of the strain sensor 22 is directly AD converted by the AD converter 49, and the output signal of the strain sensor 22 subjected to the AD conversion is input to the load estimating means 50. In this case, an AD converter 49 having a resolution of at least 20 bits is used. The AD converter 49 is a small multi-channel input element, and constitutes a conversion unit 59 that combines sensor output signals from a plurality of sensor units 20 into digital data. The AD converter 49 is preferably a digital sigma converter because it has high accuracy and relatively high speed characteristics.

  The load estimator 50 generates force (vertical load Fz, driving force and braking force) acting on the wheel bearing and between the wheel and the road surface (tire contact surface) from the AD-converted output signal of the strain sensor 22 of the sensor unit 20. The load Fx and the axial load Fy) are estimated by, for example, a microcomputer. The load estimating means 50 composed of this microcomputer may be one in which various electronic components are mounted on one substrate or one chip. The load estimation unit 50 includes an offset adjustment circuit 51, a temperature correction circuit 52, a filter processing circuit 53 such as a low-pass filter, a load estimation calculation circuit 54, a control circuit 55, and the like. The offset adjustment circuit 51 adjusts the initial offset of the strain sensor 22 and the offset due to fixing to the wheel bearing to a normal value. Adjustment by the control circuit 55 or offset adjustment by an external command is performed. It is configured as possible. Since the cause of the offset is a variation in the strain sensor 22 or a strain when the sensor is fixed, it is desirable to attach the sensor unit 20 to the wheel bearing and adjust the offset when the assembly is completed.

  As described above, after the assembly of the sensor-equipped wheel bearing is completed, when the offset is adjusted by the offset adjustment circuit 51 so that the output signal of the strain sensor 22 becomes the specified value, the sensor-equipped wheel bearing is completed. Therefore, the sensor output signal quality can be ensured.

  In addition, the output signal of the strain sensor 22 includes a drift amount due to temperature characteristics of the strain sensor itself, temperature distortion of the outer member 1 that is a fixed member, and the like. The temperature correction circuit 52 is a circuit that corrects drift caused by the temperature of the output signal of the strain sensor 22 that has been offset adjusted. In order to correct the drift due to temperature, a temperature sensor 29 is provided in the strain generating member 21 of at least one sensor unit 20 as shown in FIG. 4, and an output signal of the temperature sensor 29 is digitized by an AD converter 49. And then input to the temperature correction circuit 52.

  In the load estimation calculation circuit 54, based on the digitized output signal of the strain sensor 22 subjected to the offset adjustment process, the temperature correction process, the filter process, and the like by the offset adjustment circuit 51, the temperature correction circuit 52, and the filter processing circuit 53. A load estimation calculation is performed. The load estimation calculation circuit 54 is a relationship setting in which the relationship between the vertical load Fz, the load Fx as a driving force or braking force, the axial load Fy, and the output signal of the strain sensor 22 is set by an arithmetic expression or a table. Means (not shown), and using the relation setting means from the output signal of the strain sensor 22, the acting force (vertical load Fz, load Fx serving as driving force or braking force, axial load Fy) is estimated. . The setting contents of the relationship setting means are obtained by a test or simulation in advance. The load data obtained by the load estimation calculation circuit 54 of the load estimating means 50 is output to an upper electric control unit (ECU) installed on the vehicle body side through an in-vehicle communication bus (for example, CAN bus). This communication path may be wireless, and may be configured such that a transmitter / receiver is installed on each of the bearing side and the vehicle body side to output load data and the like. In this case, it is possible to reduce the number of necessary cables by attaching the necessary cables such as power supply and operating the sensor and transmitting the obtained data wirelessly. Becomes easier. The electric control unit is, for example, a unit that controls the entire vehicle, and includes a microcomputer or the like. It is good also as what outputs with an analog voltage as needed.

  In the configuration example of the arithmetic processing circuit 31 shown in FIG. 11, the amplification circuit 56 that amplifies the output signal of each strain sensor 22 and the above-described offset adjustment circuit 51 are provided in the front stage of the load estimating unit 50 as a preprocessing circuit. It is done. The configuration of the conversion unit 59 that converts the sensor output signals from the plurality of sensor units 20 into one and converts it into digital data and the load estimation means 50 in the subsequent stage are the same as those in the configuration example of FIG.

  The load estimation calculation circuit 54 of the load estimation means 50 includes an average calculation unit 68 and an amplitude calculation unit 69 shown in FIG. The average calculation unit 68 includes an adder, calculates the sum of the output signals of the two strain sensors 22A and 22B of the sensor unit 20, and extracts the sum as an average value A. The amplitude calculation unit 69 includes a subtracter, calculates the difference between the output signals of the two strain sensors 22A and 22B, and extracts the difference value as the amplitude value B.

  In the load estimation calculation circuit 54, a force F (for example, a force acting on the wheel bearing or between the wheel and the road surface (tire contact surface) is calculated from the average value A and the amplitude value B calculated by the average calculation unit 68 and the amplitude calculation unit 69. Calculate and estimate the vertical load Fz). For the calculation and estimation, the load estimation calculation circuit 54 has two load estimation means 71 and 72 shown in FIG. The first load estimating means 71 uses the average value A to calculate / estimate the load F acting on the wheel bearing. The second load estimating means 72 calculates and estimates the load F acting on the wheel bearing using the average value A and the amplitude value B.

The relationship between the load F acting on the wheel bearing and the output signal S of the strain sensors 22A and 22B is as follows:
F = M1 × S (1)
The load F can be estimated from this relational expression (1). Here, M1 is a predetermined correction coefficient.
In the first load estimation means 71, the average value A is used as a variable obtained by removing the offset from the output signals of the strain sensors 22A and 22B, and this variable is multiplied by a predetermined correction coefficient M1, that is, F = M1 × A (2)
The load F is calculated and estimated from the above. In this way, the load estimation accuracy can be improved by using the variable excluding the offset.

In the second load estimating means 72, the average value A and the amplitude value B are used as variables, and these variables are multiplied by predetermined correction coefficients M2 and M3, that is, F = M2 × A + M3 × B. (3)
The load F is calculated and estimated from the above. Thus, load estimation accuracy can be further improved by using two types of variables.
The value of each correction coefficient in each of the above arithmetic expressions is set by obtaining in advance by a test or simulation. The calculations by the first load estimating means 71 and the second load estimating means 72 are performed in parallel. In equation (3), the average value B, which is a variable, may be omitted. That is, the second load estimating means 72 can also calculate and estimate the load F using only the amplitude value B as a variable.

  Since the sensor unit 20 is provided at an axial position around the rolling surface 3 of the outboard side row of the outer member 1 as shown in FIG. 1, the output signals a and b of the strain sensors 22A and 22B are shown in FIG. 9 is affected by the rolling element 5 passing through the vicinity of the installation portion of the sensor unit 20. That is, the influence of this rolling element 5 acts as an offset. Even when the bearing is stopped, the output signals a and b of the strain sensors 22A and 22B are affected by the position of the rolling element 5. That is, when the rolling element 5 passes the position closest to the strain sensors 22A and 22B in the sensor unit 20 (or when the rolling element 5 is at that position), the amplitude of the output signals a and b of the strain sensors 22A and 22B. Becomes a maximum value, and decreases as the rolling element 5 moves away from the position as shown in FIGS. 14A and 14B (or when the rolling element 5 is located away from the position). When the bearing rotates, the rolling elements 5 sequentially pass through the vicinity of the installation portion of the sensor unit 20 at a predetermined arrangement pitch P, so that the analog output signals a and b of the strain sensors 22A and 22B have an amplitude of the rolling elements 5. A waveform close to a sine wave that periodically changes as shown in FIG. Therefore, in the load estimation calculation circuit 54 in the calculation processing circuit 31, as the data for obtaining the load, the sum of the amplitudes of the output signals a and b of the two strain sensors 22A and 22B is set to the above-described average value A, and the amplitude difference is obtained. (Absolute value) | a−b | is the amplitude value B described above. Thus, the average value A is a value obtained by canceling the fluctuation component due to the passage of the rolling elements 5. The amplitude value B is a value that offsets the influence of temperature appearing in the output signals a and b of the two strain sensors 22A and 22B and the influence of slippage between the knuckle and flange surfaces. Therefore, by using the average value A and the amplitude value B, the load acting on the wheel bearing and the tire ground contact surface can be accurately detected.

  Here, the sensor unit 20 includes two contact fixing portions 21a positioned at both ends of the array among the three contact fixing portions 21a arranged in the circumferential direction of the outer diameter surface of the outer member 1 which is a fixed side member. The interval is set to be the same as the arrangement pitch P of the rolling elements 5. In this case, the circumferential interval between the two strain sensors 22A and 22B respectively disposed at the intermediate positions of the adjacent contact fixing portions 21a is approximately ½ of the arrangement pitch P of the rolling elements 5. . As a result, the output signals a and b of the two strain sensors 22A and 22B have a phase difference of about 180 degrees, and the average value A obtained as the sum is obtained by canceling the fluctuation component due to the passage of the rolling element 5. It becomes. Further, the amplitude value B obtained as the difference is a value obtained by offsetting the influence of temperature and the influence of slippage between the knuckle and the flange surface.

In FIG. 9, the interval between the contact fixing portions 21 a is set to be the same as the arrangement pitch P of the rolling elements 5, and each one strain sensor 22 </ b> A, 22 </ b> B is disposed at an intermediate position between the adjacent contact fixing portions 21 a. Thus, the circumferential interval between the two strain sensors 22A and 22B is set to be approximately ½ of the arrangement pitch P of the rolling elements 5. Alternatively, the circumferential interval between the two strain sensors 22A and 22B may be directly set to ½ of the arrangement pitch P of the rolling elements 5.
In this case, the circumferential interval between the two strain sensors 22A and 22B may be {1/2 + n (n: integer)} times the arrangement pitch P of the rolling elements 5, or a value approximated to these values. good. Also in this case, the average value A obtained as the sum of the output signals a and b of both strain sensors 22A and 22B is a value obtained by canceling the fluctuation component due to the passage of the rolling element 5, and the amplitude value B obtained as the difference is the temperature. It is a value that offsets the influence and the effect of slippage between the knuckle and flange surfaces.

As shown in FIG. 13, both load estimation means 71 and 72 of the load estimation calculation circuit 54 are connected to the selection output means 73 in the next stage. The selection output means 73 switches and selects one of the estimated load values of the first and second load estimation means 72 according to the wheel rotation speed and outputs it. Specifically, the selection output means 73 selects and outputs the estimated load value of the first load estimation means 71 when the wheel rotation speed is lower than a predetermined lower limit speed.
When the wheel rotates at a low speed, the processing time for detecting the amplitude of the sensor output signal becomes longer, and further, the amplitude cannot be detected when the wheel is stationary. Thus, in this way, when the wheel rotation speed is lower than the predetermined lower limit value, the detected load is obtained by selecting and outputting the estimated load value from the first load estimating means 71 using only the average value A. The signal can be output without delay.

  In this embodiment, a rolling element detection sensor 60 for detecting the position of the rolling element 5 is provided on the inner periphery of the outer member 1 as shown in FIG. The rotational speed of the wheel is obtained from the output signal of the rolling element detection sensor 60. The selection output means 73 may receive information on wheel rotation speed from the outside. In this case, as information on the wheel rotation speed from the outside, a rotation sensor signal such as an ABS sensor from the vehicle body side may be used to estimate the wheel rotation speed. Moreover, it is good also as a structure which the selection output means 73 receives a switching selection instruction | command from the high-order control apparatus connected to the in-vehicle communication bus | bath by the side of a vehicle body as an alternative to the wheel rotational speed information. Furthermore, as the wheel rotation speed information, the wheel rotation speed may be estimated by detecting the passing frequency of the rolling element 5 from the output signals a and b of the strain sensors 22A and 22B.

  In this embodiment, the upper surface portion, the lower surface portion, the right surface portion, and the left surface portion of the outer diameter surface of the outer member 1 that is the fixed side member, which are in the vertical position and the horizontal position with respect to the tire ground contact surface, Since the four sensor units 20 are equally arranged with a phase difference of 90 degrees in the direction, it is possible to estimate the vertical load Fz acting on the wheel bearing, the load Fx serving as a driving force and a braking force, and the axial load Fy. it can.

  When a load acts between the tire of the wheel and the road surface, the load is also applied to the outer member 1 that is a stationary member of the wheel bearing, causing deformation. Here, since the two or more contact fixing portions 21 a of the strain generating member 21 in the sensor unit 20 are contact fixed to the outer member 1, the strain of the outer member 1 is transmitted to the strain generating member 21 in an enlarged manner. The distortion is easily detected by the distortion sensor 22.

  In particular, the side surface of the vehicle body mounting flange 1a of the outer member 1 which is a fixed side member is composed of an arc-shaped circuit board and circuit elements mounted on the circuit board, and the strain sensors 220A and 22B of the sensor unit 20 are arranged. Since the arithmetic processing circuit 31 for arithmetic processing of the output signal is attached, the arithmetic processing circuit 31 including the AD converter 49 and the like with a compact configuration without changing the peripheral surface shape of the cylindrical portion of the outer member 1. Can be attached, the assembly is easy, and the load applied to the bearing portion of the wheel can be accurately detected.

  Further, in this embodiment, the front shape of the vehicle body mounting flange 1a in the outer member 1 which is a stationary member is symmetrical with respect to line segments LV and LH perpendicular to the bearing axis O as shown in FIG. Therefore, the shape of the outer member 1 is simplified, and the temperature distribution and the amount of expansion / contraction caused by the complicated shape of the outer member 1 are obtained. The variation of can be reduced. Thereby, the influence by the variation in the temperature distribution and expansion / contraction amount in the outer member 1 can be made sufficiently small, and the strain amount due to the load can be detected by the sensor unit.

  14 and 15 show another embodiment of the present invention. 1 to 13, the sensor-equipped wheel bearing is provided with an annular protective cover 80 concentrically with the outer member 1 on the outer peripheral surface of the outer member 1 which is a stationary member. Each sensor unit 20 and the arithmetic processing circuit 31 are covered with a cover 80. FIG. 14 shows one configuration example of the protective cover 80 attached to the outer member 1, and FIG. 15 shows another configuration example.

  In the configuration example of FIG. 14, the protective cover 80 has a cylindrical shape whose inner diameter increases toward the inboard side. Specifically, the inboard side half is the large diameter portion 80a and the outboard side half. The portion has a stepped cylindrical shape with a small diameter portion 80b. The inboard side end of the protective cover 80 is fitted to the outer diameter surface of the flange 1a for mounting the vehicle body, and the outboard side end of the protective cover 80 is fitted to the outer diameter surface of the outer board 1 of the outer member 1. Can be combined. As the material of the protective cover 80, a steel plate having a corrosion resistance such as stainless steel, which is formed by pressing, or a steel plate which is formed by pressing, is subjected to metal plating or coating.

  A lead-out portion 41 a to the vehicle body side of the signal cable 41 connected to the arithmetic processing circuit 31 is drawn out from one place of the protective cover 80. Specifically, the small diameter portion 80b which is the half of the outboard side of the protective cover 80, that is, the hole portion through which the signal cable lead portion 41a is drawn out to the cylindrical portion on the outboard side from the body mounting flange 1a of the outer member 1. 81 is provided, and a portion of the signal cable lead portion 41a that is pulled out from the hole 81 is coated with a rust-proof sealant 82 to seal the lead portion of the signal cable lead portion 41a. Thereby, the sealing performance of the protective cover 80 is enhanced, and the sensor unit 20 and the arithmetic processing circuit 31 covered with the protective cover 80 can be reliably protected from stepping stones, muddy water, salt water, and the like from the outside. Further, the displacement of the signal cable 41 in the circumferential direction can be restricted.

  In the configuration example of FIG. 15, a bush 83 made of an elastic material is fitted into the hole 81 of the protective cover 80, and the signal cable lead-out portion 41 a is drawn out from the hole of the bush 83. Here, a rubber bush is used as the bush 83. Also in this case, the sealing performance of the protective cover 80 is enhanced, and the sensor unit 20 and the arithmetic processing circuit 31 covered with the protective cover 80 can be reliably protected from stepping stones, muddy water, salt water, and the like from the outside.

  In the configuration example of FIG. 15, the bushing 83 is provided in the hole 81 of the protective cover 80, and the sealing material 82 used in the configuration example of FIG. 14 is provided in a portion where the signal cable lead portion 41 a is pulled out from the hole 81. May be applied. In this case, since the sealing material 82 and the bush 83 are used in an overlapping manner, the sealing performance of the protective cover 80 can be further enhanced.

  The assembly of the sensor-equipped wheel bearing of this embodiment is performed according to the following procedure. First, the sensor unit 20, the flexible substrate 30, and the arithmetic processing circuit 32 are attached to the outer member 1 in a state where the outer member 1 is a single body or the rolling member 5 is assembled to the outer member 1. Next, the protective cover 80 is inserted from the outboard side of the outer member 1, the inboard side end is fitted to the outer diameter surface of the flange 1 a of the outer member 1, and the outboard side end is fitted to the outer member. The sensor unit 20, the flexible substrate 30, and the arithmetic processing circuit 32 are covered with the protective cover 80 by being fitted to the outer diameter surface of the one outboard side cylindrical portion. After this, the entire bearing is assembled. By assembling in this procedure, the sensor-equipped wheel bearing in which the sensor unit 20, the flexible substrate 30, and the arithmetic processing circuit 32 attached to the outer member 1 are covered with the protective cover 80 can be easily assembled.

  FIG. 16 shows still another embodiment of the present invention. In this sensor wheel bearing, in the embodiment shown in FIGS. 1 to 13, 14, and 15, the outer diameter surface provided with the flange 1 a of the outer member 1 that is a fixed member is provided with corrosion resistance or anticorrosion. A surface treatment layer 84 having a property is formed. As shown in FIGS. 1 to 15, the sensor unit 20, the flexible substrate 30, the arithmetic processing circuit 31, and the protective cover 80 are attached to the outer diameter surface of the outer member 1 on which the surface treatment layer 84 is thus formed. Other configurations are the same as those in the embodiments of FIGS.

  Examples of the surface treatment layer 84 having corrosion resistance or corrosion resistance include a surface layer subjected to metal plating treatment, a surface layer subjected to coating treatment, and a surface layer subjected to coating treatment. As the metal plating treatment, treatments such as zinc plating, unichrome plating, chromate plating, nickel plating, chrome plating, electroless nickel plating, Kanigen plating, iron trioxide film (black dyeing), and radient can be applied. As the coating treatment and coating treatment, cationic electrodeposition coating, anion electrodeposition coating, fluorine electrodeposition coating, ceramic coating such as silicon nitride, and the like are applicable.

  Thus, in this embodiment, since the surface treatment layer 84 having corrosion resistance or corrosion resistance is formed on the outer diameter surface of the outer member 1, the sensor unit 20 is caused by rust on the outer diameter surface of the outer member 1. It is possible to prevent the mounting portion of the flexible substrate 30, the arithmetic processing circuit 31, the protective cover 80, etc. from rising, or the sensor unit 20, the flexible substrate 30, the arithmetic processing circuit 31 from generating rust, and a strain sensor caused by rust. Malfunctions such as 22A and 22B can be eliminated, and load detection can be performed accurately over a long period of time.

  In each of the above-described embodiments, the case where the outer member 1 is a fixed side member has been described, but the present invention can also be applied to a wheel bearing in which the inner member is a fixed side member. The sensor unit 20 is provided on the peripheral surface that is the inner periphery of the inner member.

  In these embodiments, the case where the present invention is applied to a third generation type wheel bearing has been described. However, the present invention is for a first generation or second generation type wheel in which the bearing portion and the hub are independent parts. The present invention can also be applied to a bearing or a fourth-generation type wheel bearing in which a part of the inner member is composed of an outer ring of a constant velocity joint. The sensor-equipped wheel bearing can also be applied to a wheel bearing for a driven wheel, and can also be applied to a tapered roller type wheel bearing of each generation type.

DESCRIPTION OF SYMBOLS 1 ... Outer member 1a ... Car body mounting flange 2 ... Inner member 3, 4 ... Rolling surface 5 ... Rolling body 20 ... Sensor unit 21 ... Strain generating member 21a ... Contact fixing | fixed part 22, 22A, 22B ... Strain sensor 30 ... flexible substrate 31 ... arithmetic processing circuit 41 ... signal cable 41a ... signal cable lead-out part 49 ... AD converter 51 ... offset adjustment circuit 54 ... load estimation calculation circuit 71 ... first load estimation means 72 ... second load estimation means 73 ... Selection output means 80 ... Protective cover 81 ... Hole 82 ... Sealing material 83 ... Bush 84 ... Surface treatment layer

Claims (22)

An outer member having a double row rolling surface formed on the inner periphery, an inner member having a rolling surface facing the rolling surface formed on the outer periphery, and interposed between the opposing rolling surfaces of both members The fixed side member of the outer member and the inner member has a flange for mounting the vehicle body attached to the knuckle on the outer periphery, and supports the wheel rotatably with respect to the vehicle body. Wheel bearing
One or more load detection sensor units are provided on the outer diameter surface of the fixed side member, the sensor unit having two or more contact fixing portions fixed in contact with the fixed side member, and It comprises one or more sensors attached to the strain generating member to detect the strain of the strain generating member, and an arc-shaped circuit board and a circuit mounted on the circuit board are mounted on the side surface of the flange for mounting the vehicle body. A sensor-equipped wheel bearing comprising an arithmetic processing circuit configured by an element and configured to perform arithmetic processing on an output signal of the sensor.   The sensor-equipped wheel bearing according to claim 1, wherein the fixed-side member is an outer member.   3. The sensor-equipped wheel bearing according to claim 1, wherein the arithmetic processing circuit includes an AD converter that AD converts an output signal of the sensor.   3. The sensor-equipped wheel bearing according to claim 1, wherein the arithmetic processing circuit includes an offset adjustment circuit that adjusts an offset of the sensor to a normal value and an amplification circuit that amplifies the output signal of the sensor.   5. The sensor-equipped wheel bearing according to claim 1, wherein the arithmetic processing circuit includes a load estimation unit that estimates a load applied to the wheel from an output signal of the sensor.   The calculation processing circuit according to claim 5, wherein the arithmetic processing circuit includes: first load estimation means for estimating a load acting on the wheel bearing using an average value of the output signal of the sensor; and an amplitude value of the output signal of the sensor, or One of the second load estimating means for estimating the load acting on the wheel bearing using the amplitude value and the average value, and the first and second load estimating means depending on the wheel rotation speed. A sensor-equipped wheel bearing comprising: a selection output means for switching and selecting the estimated load value of the output.   7. The sensor unit according to claim 6, wherein the sensor unit has three or more contact fixing portions and two sensors, and is adjacent between the first and second contact fixing portions adjacent to each other and between the adjacent second and third contact fixing portions. Each sensor is mounted between the adjacent contact fixing portions or the interval of the adjacent sensors in the circular direction of the fixed side member is {1/2 + n (n: integer)} times the arrangement pitch of the rolling elements. The first and second load estimating means use a sum of output signals of the two sensors as an average value.   8. The method according to claim 1, wherein an annular protective cover is attached to the peripheral surface of the fixed side member concentrically with the fixed side member, and the sensor unit and the arithmetic processing circuit are covered with the protective cover. Bearing for wheel with sensor.   In Claim 8, the signal cable which takes out the signal processed by this arithmetic processing circuit to the outside of a bearing is attached to the arithmetic processing circuit, and the cylindrical part on the outboard side of the body mounting flange in the protective cover, A sensor-equipped wheel bearing in which a hole through which a lead-out portion from a protective cover of a signal cable is drawn is provided, and a seal material subjected to rust prevention treatment is applied to a portion from which the signal cable lead-out portion is drawn out from the hole.   In Claim 8, the signal cable which takes out the signal processed by this arithmetic processing circuit to the outside of a bearing is attached to the arithmetic processing circuit, and the cylindrical part on the outboard side of the body mounting flange in the protective cover, A sensor-equipped wheel bearing in which a hole portion from which a lead portion is drawn out from a protective cover of a signal cable is provided, and a bush made of an elastic material is attached to a portion where the signal cable lead portion is drawn out from the hole portion.   9. The signal processing circuit according to claim 8, wherein a signal cable for taking out a signal processed by the arithmetic processing circuit to the outside of the bearing is attached to the arithmetic processing circuit, and the signal is connected to a cylindrical portion on the outboard side of the body mounting flange in the protective cover. Provided with a hole through which the lead-out part from the cable protective cover is drawn out, and applied a sealing material subjected to rust prevention treatment to the part from which the signal cable lead-out part is drawn out from the hole part, and attached a bush made of an elastic material Wheel bearing with sensor.   The sensor-equipped wheel bearing according to any one of claims 8 to 11, wherein the protective cover is formed by pressing a corrosion-resistant steel plate.   12. The sensor-equipped wheel bearing according to claim 8, wherein the protective cover is obtained by applying metal plating or coating to a steel plate formed by pressing.   14. The sensor-equipped wheel bearing according to claim 1, wherein a flexible board is attached to a peripheral surface of the fixed side member concentrically with the fixed side member, and the arithmetic processing circuit is integrally formed on the flexible board. .   14. The wheel bearing with sensor according to claim 1, wherein a flexible board is attached to the peripheral surface of the fixed side member concentrically with the fixed side member, and the sensor unit is attached to the flexible board.   16. The wheel bearing with sensor according to claim 14 or 15, wherein a base material of the flexible substrate is polyimide.   The sensor unit according to any one of claims 1 to 16, wherein the sensor unit is an upper surface portion, a lower surface portion, a right surface portion of an outer diameter surface of the fixed side member that is in a vertical position and a horizontal position with respect to a tire ground contact surface. And four wheel bearings with a sensor arranged equally on the left surface with a phase difference of 90 degrees in the circumferential direction.   18. The sensor-equipped wheel bearing according to any one of claims 1 to 17, wherein a front shape of the flange of the stationary member is symmetrical with respect to a line segment orthogonal to the bearing axis.   18. The sensor-equipped wheel bearing according to claim 1, wherein a front shape of the flange of the fixed-side member is a point-symmetric shape with respect to the bearing axis.   20. The sensor-equipped wheel bearing according to any one of claims 1 to 19, wherein a peripheral surface provided with a flange of the fixed side member is subjected to a surface treatment having corrosion resistance or corrosion resistance.   21. The wheel bearing with sensor according to claim 20, wherein the surface treatment is metal plating, painting, or coating treatment.   The method of assembling a sensor-equipped wheel bearing according to any one of claims 8 to 21, wherein the stationary member is a single member or the rolling member is assembled to the stationary member. A method of assembling a sensor-equipped wheel bearing, comprising: mounting the sensor unit on a peripheral surface of the fixed side member; and further mounting the protective cover on the peripheral surface of the fixed side member;

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