JP2010181154A - Sensor-equipped bearing for wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor-equipped bearing for a wheel capable of accurately estimating a load acting on the wheel and outputting a detected load signal without delay. <P>SOLUTION: A fixed side member of an outer member 1 and an inner member 2 of the bearing for a wheel includes at least one sensor unit 20. The sensor unit 20 includes a deforming member 21 having two or more contact and fixed sections 21a making contact with and fixed to the fixed side member; and one or more sensors 22 mounted on the deforming member 21 and detecting strain in the deforming member 21. The bearing for a wheel is also provided with a first load estimating means 31 for calculating/estimating the load acting on the bearing for a wheel from the average value of sensor output signals; a second load estimating means 32 for calculating/estimating the load from the average value and amplitude value of the sensor output signals; and a selection output means 33 for selectively switching to one of estimated load values of the load estimating means 31 and 32 according to the wheel rotating speed, and outputting it. <P>COPYRIGHT: (C)2010,JPO&INPIT

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, a wheel bearing has been proposed in which a strain gauge is attached to the outer ring of a wheel bearing and the load is detected from the distortion of the outer surface of the outer ring (for example, a patent) Reference 1).

Special table 2003-530565 gazette

  With the technique disclosed in Patent Document 1, when detecting a load acting on a wheel bearing, the amount of deformation of the fixed ring with respect to the load is small, so the amount of distortion is small, the detection sensitivity is low, and the load cannot be detected with high accuracy.

  In order to solve the above-mentioned problems, the present inventors have developed a sensor-equipped wheel bearing having the following configuration. The wheel bearing in this sensor-equipped wheel bearing includes an outer member having a double-row rolling surface formed on the inner periphery, and an inner member having a rolling surface opposite to the rolling surface formed on the outer periphery. And a double-row rolling element interposed between the opposing rolling surfaces of the two members, and supports the wheel rotatably with respect to the vehicle body. At least three or more sensor units are provided on the outer diameter surface of the stationary member of the outer member and the inner member. The sensor unit includes a strain generating member having two or more contact fixing portions fixed in contact with the outer diameter surface of the fixed side member, and detects the strain of the strain generating member attached to the strain generating member. It shall have one or more sensors. In this configuration, an average value (DC component) and an amplitude value (AC component) are calculated from the output signals of the sensors of the sensor units, and the load acting on the wheel bearing is estimated using both values.

  In the above configuration, the load is estimated based on the average value and the amplitude value of the output signal of the sensor using the sensor unit having the strain generating member that expands the strain, so that the load detection accuracy can be improved.

However, in order to obtain the average value and the amplitude value, the bearing needs to rotate and revolve, and there remains a problem that an error becomes large in a stationary state or an extremely low speed state.
In particular, the calculation using the amplitude value requires a signal of at least one cycle, and the amplitude estimation accuracy is inevitably further lowered during low-speed rotation, resulting in a large load estimation error.

  Therefore, a means for reducing the load detection error in a stationary or low speed state and capable of accurately estimating the load regardless of the traveling speed is required. Further, in order to obtain the average value, it is necessary to examine a signal change of time according to the rotation speed, and particularly, the required time becomes long when the rotation speed is low. Therefore, the time delay of the estimated load output that is output as the calculation result increases, and the control response of the vehicle using this signal decreases in the low-speed rotation state.

  An object of the present invention is to provide a sensor-equipped wheel bearing capable of accurately estimating a load applied to a wheel and outputting a detected load signal without delay.

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 wheel bearing comprising a double row rolling element interposed between opposing rolling surfaces of the member and rotatably supporting the wheel with respect to the vehicle body, wherein the fixed side member of the outer member and the inner member Further, a strain generating member having two or more contact fixing portions fixed in contact with the fixed side member, and one or more sensors attached to the strain generating member and detecting the strain of the strain generating member A sensor-equipped wheel bearing provided with a load detecting sensor unit, wherein a first load estimating means for calculating / estimating a load acting on the wheel bearing using an average value of output signals of the sensors; The amplitude value of the output signal of the sensor, or its amplitude value One of the second load estimating means for calculating and estimating the load acting on the wheel bearing using the average value, and the first and second load estimating means according to the wheel rotational speed. Selection output means for switching and selecting the estimated load value is provided.
When a load acts between the tire of the wheel and the road surface, the load is also applied to the fixed side member (for example, the outer member) of the wheel bearing, causing deformation. Here, since the two or more contact fixing portions of the strain generating member in the sensor unit are contact fixed to the outer member, the strain of the outer member is easily transmitted to the strain generating member by expanding the strain. Is detected with high sensitivity.
In particular, a first load estimating means for calculating and estimating a load acting on the wheel bearing using an average value of the sensor output signal of the sensor unit, an amplitude value of the sensor output signal, or the amplitude value and the average value And a second load estimating means for calculating / estimating the load acting on the wheel bearing, and selecting the load value to be estimated from either of these load estimating means according to the wheel rotational speed. Since the selective output means for outputting is provided, 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 in a low speed state is output. Thus, the detection processing time can be shortened. 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 also sufficiently reduced.
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 invention, the sensor unit has two sensors, and the first load estimating means calculates and estimates a load acting on the wheel bearing using an average value of output signals of the two sensors. The second load estimating means may calculate and estimate a load acting on the wheel bearing using an average value and an amplitude value of output signals of the two sensors.
In this case, for example, the average value of the output signals of the two sensors in the first load estimating means and the second load estimating means is obtained by adding the output signals of the two sensors, and The amplitude value in the second load estimation means may be calculated from a difference value between output signals of the two sensors.

  In the present invention, three or more of the sensor units are provided, and the first and second load estimating means are configured so that each of the first and second load estimation means includes a vertical direction and a radial direction of the wheel bearing from the output signals of the sensors of the three or more sensor units. It is also possible to calculate / estimate loads in three directions, each radial load acting in the front-rear direction and an axial load acting in the axial direction of the wheel bearing.

  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. In the case of this configuration, loads in a plurality of directions can be estimated. That is, the vertical load Fz and the axial load Fy can be estimated from the output signals of the two sensor units arranged on the upper surface and the lower surface on the outer diameter surface of the fixed member, and the right surface portion on the outer diameter surface of the fixed member. From the output signals of the two sensor units arranged on the left surface portion, the load Fx due to the driving force and braking force can be estimated.

  In the present invention, the sensor unit includes three or more contact fixing portions and two sensors, and 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 distance between the adjacent contact fixing portions or the adjacent sensors in the circumferential direction of the fixing member 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 the output signals of the two sensors as an average value, and calculate and use the amplitude value from the difference. In the case of this configuration, the output signals of the two sensors have a phase difference of about 180 degrees, and the average value is a value obtained by canceling the fluctuation component due to passing through the rolling elements. In addition, the amplitude value is stable because it is hardly affected by temperature, and the detection accuracy is improved because two signals are used. As a result, the average value of the output signals of the two sensors becomes a value obtained by canceling the fluctuation component due to passage through the rolling elements, and the amplitude value becomes more stable and accurate.

In the present invention, a temperature sensor may be attached to the sensor unit, and temperature correction means may be provided for correcting an average value of the sensor output signal based on a detection signal of the temperature sensor.
If the temperature of the wheel bearing changes due to heat generated by the rotation of the bearing or the surrounding environment, the sensor output signal of the sensor unit will fluctuate due to thermal expansion, etc., even if the load does not change. Remain. Therefore, by providing temperature correction means for correcting the average value of the sensor output signal in accordance with the temperature of the wheel bearing or its surrounding temperature, it is possible to reduce the detected load error due to temperature.

In this invention, when the wheel rotation speed is lower than the set lower limit speed, the selection output means may select and output the estimated load value of the first load estimation means. The lower limit speed may be an arbitrarily set speed, but is set to a low speed, for example, enough for a person to walk.
When the wheel is stationary or at low speed, it takes time for one cycle of the sensor output signal to calculate the amplitude value, and the time delay of output of the estimated load value becomes large, but the load value is calculated only from the average value. The detected load signal can be output without delay from the first load estimating means.

  In the present invention, the first and second load estimation means calculate and estimate the load in parallel, and the selection output means determines the estimated load of either one of the load estimation means according to the wheel rotation speed. A value may be selected and output.

In this invention, the said selection output means is good also as what receives the information of wheel rotational speed from the outside with respect to this sensor-equipped wheel bearing, and performs the said selection according to the said wheel rotational speed.

  In this invention, the selection output means estimates the wheel rotation speed by detecting the passing frequency of the rolling element from the output signal of the sensor, and performs the selection according to the wheel rotation speed from the estimated wheel rotation speed. It is good as a thing. In the case of this configuration, an extra sensor and wiring are unnecessary, and the configuration is simplified.

  In this invention, the said selection output means is good also as what estimates a wheel rotational speed from the rotation sensor signal supplied from the vehicle body side, and performs the said selection according to the said wheel rotational speed from the estimated wheel rotational speed.

  In the present invention, the selection output means may perform the selection in response to a switching selection command corresponding to a wheel rotational speed from a control device on the vehicle body side.

  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 wheel bearing comprising a double row rolling element interposed between opposing rolling surfaces of the member and rotatably supporting the wheel with respect to the vehicle body, wherein the fixed side member of the outer member and the inner member Further, a strain generating member having two or more contact fixing portions fixed in contact with the fixed side member, and one or more sensors attached to the strain generating member and detecting the strain of the strain generating member A sensor-equipped wheel bearing provided with a load detecting sensor unit, wherein a first load estimating means for calculating / estimating a load acting on the wheel bearing using an average value of output signals of the sensors; The amplitude value of the output signal of the sensor, or its amplitude value One of the second load estimating means for calculating and estimating the load acting on the wheel bearing using the average value, and the first and second load estimating means according to the wheel rotational speed. Since the selection output means for switching and selecting the estimated load value is provided, the load applied to the wheel can be accurately estimated, and the detected load signal can be output without delay.

It is a figure showing combining the sectional view of the wheel bearing with a sensor concerning one embodiment of this invention, and the block diagram of the conceptual composition of the detection system. It is the front view which looked at the outer member of the wheel bearing with a sensor from the outboard side. It is an enlarged plan view of a sensor unit in the wheel bearing with sensor. FIG. 4 is a cross-sectional view taken along arrow IV-IV in FIG. 3. It is sectional drawing which shows the other example of installation of a sensor unit. 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 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 the front view which looked at the outward member of the bearing for wheels with a sensor concerning other embodiments of this invention from the outboard side.

  An 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 front view of the outer member 1 of the wheel bearing as viewed from the outboard side. 1 shows a cross-sectional view taken along the line II in FIG. As shown in FIG. 2, the vehicle body mounting flange 1 a is a projecting piece 1 aa in which a circumferential portion provided with each screw hole 14 protrudes to the outer diameter side from the other portion.

  Two sensor units 20A and 20B are provided on the outer diameter surface of the outer member 1 which is a fixed member. Here, these sensor units 20 </ b> A and 20 </ b> B are respectively provided on the upper surface portion and the lower surface portion of the outer diameter surface of the outer member 1 that is positioned vertically with respect to the tire ground contact surface.

  These sensor units 20A and 20B, as shown in an enlarged plan view and an enlarged cross-sectional view in FIGS. 3 and 4, detect the strain of the strain generating member 21 attached to the strain generating member 21 and the strain generating member 21. And two or more (two in this case) strain sensors 22. 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. Further, the strain generating member 21 has two or more (here, three) contact fixing portions 21 a that are fixed to the outer diameter surface of the outer member 1 through spacers 23. The three contact fixing portions 21 a are arranged in a line in the longitudinal direction of the strain generating member 21. The two strain sensors 22 are affixed to the strain generating member 21 where the strain increases with respect to the load in each direction. Specifically, it arrange | positions between the contact fixing | fixed parts 21a adjacent on the outer surface side of the distortion generation member 21. FIG. That is, in FIG. 4, 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. 3, the notch portions 21 b are formed at two positions corresponding to the placement portions of the strain sensor 22 on both side portions of the strain generating member 21. Thereby, the strain sensor 22 detects the strain in the longitudinal direction around the notch 21 b 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 plastic deformation occurs, the deformation of the outer member 1 is not transmitted to the sensor units 20A and 20B and affects the measurement of strain.

  In the sensor unit 20, the three contact fixing portions 21a of the strain generating member 21 are located at the same position in the axial direction of the outer member 1, and the contact fixing portions 21a are located at positions separated from each other in the circumferential direction. These contact fixing portions 21a are fixed to the outer diameter surface of the outer member 1 by bolts 24 via spacers 23, respectively. Each bolt 24 is inserted into a bolt insertion hole 26 of the spacer 23 from a bolt insertion hole 25 penetrating in the radial direction provided in the contact fixing portion 21 a, and a screw hole 27 provided in the outer peripheral portion of the outer member 1. Screwed on. 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 units 20 </ b> A and 20 </ b> B 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.

  In addition, as shown in a cross-sectional view in FIG. 5, grooves 1 c are provided at the three intermediate portions where the three contact fixing portions 21 a of the strain generating member 21 are fixed on the outer diameter surface of the outer member 1. Thus, the spacer 23 may be omitted, and the portions where the notches 21b of the strain generating member 21 are located may be separated from the outer diameter surface of the outer member 1.

  Various strain sensors 22 can be used. For example, the strain sensor 22 can be composed of a metal foil strain gauge. In that case, the distortion generating member 21 is usually fixed by adhesion. The strain sensor 22 can also be formed on the strain generating member 21 with a thick film resistor.

  The two strain sensors 22A and 22B of the sensor unit 20A (20B) are connected to an average value calculation unit 28 and an amplitude value calculation unit 29. As shown in FIG. 7, the average value calculation unit 28 includes an adder, calculates the sum of the output signals of the two strain sensors 22A and 22B, and extracts the sum as an average value A. The amplitude value calculation unit 29 includes a subtractor, calculates a difference between the output signals of the two strain sensors 22A and 22B, extracts a fluctuation component, and obtains an amplitude value B by a processing circuit or a calculation process.

  The average value calculator 28 and the amplitude value calculator 29 are connected to the estimation means 30. The estimation means 30 uses a force F (for example, vertical) acting on the wheel bearing or between the wheel and the road surface (tire contact surface) from the average value A and the amplitude value B calculated from the sensor output signals of the sensor units 20A and 20B. It is a means for calculating / estimating the directional load Fz). The estimating means 30 includes a first load estimating means 31 for calculating and estimating a load F acting on the wheel bearing using the average value A of the output signals of the strain sensors 22A and 22B, and the strain sensors 22A and 22B. The second load estimation means 32 for calculating and estimating the load F acting on the wheel bearing using the average value A and the amplitude value B of the output signal.

In general, the relationship between the load vector F acting on the wheel bearing and the output signal vectors S of the plurality of strain sensors is such that if an offset is excluded within a linear range,
F = M1 × S (1)
The load F can be estimated from this relational expression (1). Here, M1 is a predetermined correction coefficient matrix.
The first load estimating means 31 uses a mean value vector A obtained by excluding offsets from mean value signals from a plurality of sensor units, 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 the second load estimating means 32, the average value vector A and the amplitude value vector B are used as input 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 31 and the second load estimating means 32 are performed in parallel. In equation (3), the average value A that is a variable may be omitted. That is, the second load estimating means 32 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 on the outboard side row of the outer member 1, the output signals a and b of the strain sensors 22A and 22B are sensors as shown in FIG. It is affected by the rolling elements 5 passing near the installation part of the unit 20. That is, the influence of this rolling element 5 acts as the above-described 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 output signals a and b of the strain sensors 22A and 22B are maximum. 6 and decreases as the rolling element 5 moves away from the position as shown in FIGS. 6A and 6B (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. Therefore, the amplitudes of the output signals a and b of the strain sensors 22A and 22B are arranged in the arrangement of the rolling elements 5. With the pitch P as a cycle, the waveform is close to a sine wave that periodically changes as shown by a solid line in FIG. In this embodiment, the sum of the output signals a and b of the two strain sensors 22A and 22B is set as the above-described average value A, and the amplitude is obtained from the difference (absolute value) in amplitude and set as the above-described amplitude value B. Thus, the average value A is a value obtained by canceling the fluctuation component due to the passage of the rolling elements 5. In addition, the amplitude value is stable because it is hardly affected by temperature, and the detection accuracy is improved because two signals are used. 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.

  In FIG. 6 showing the configuration example of FIG. 5 as the sensor unit 20, of 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 between the two contact fixing portions 21 a located at both ends 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. In addition, the difference is stable because it is hardly affected by temperature, and the detection accuracy is improved because two signals are used.

In FIG. 6, 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 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 from the difference is the temperature value. It is stable because it is not easily affected, and the detection accuracy is improved because two signals are used.

As shown in FIG. 8, the estimation means 30 is connected to the selection output means 33 at the next stage. The selection output means 33 switches and selects one of the estimated load values of the first and second load estimation means 31 and 32 in accordance with the wheel rotation speed and outputs it. Specifically, when the wheel rotation speed is lower than a predetermined lower limit speed, the selection output means 33 selects and outputs the estimated load value of the first load estimation means 31. The predetermined lower limit speed may be a value set arbitrarily. For example, the predetermined lower limit speed is a speed at which a person walks (4 km / h) or a speed slower than that.
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. Therefore, in this way, when the wheel rotational speed is lower than the predetermined lower limit speed, the load estimated value from the first load estimating means 31 using only the average value A is selected and output, and thus detected. The load signal can be output without delay.

  For example, wheel rotation speed information is input to the selection output means 33 from the outside, and the switching selection is performed based on this information. 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 33 receives a switching selection instruction | command from the high-order control apparatus connected to the vehicle interior side in-vehicle communication bus as an alternative to the information of a wheel rotational speed. 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 the embodiment of FIGS. 1 and 2, since the two sensor units 20A and 20B are arranged at the upper and lower positions of the outer diameter surface of the outer member 1 which is a fixed member, the vertical load acting on the wheel bearing Fz can be estimated with high accuracy. If the number of sensor units 20 to be arranged is increased, the load Fx and the axial load Fy that become driving force and braking force can be estimated.

Further, as shown in FIG. 7, a temperature sensor 34 may be attached to the sensor units 20A and 20B, and a temperature correction means 35 for correcting the average value A of the sensor output signal by a detection signal of the temperature sensor 34 may be provided.
If the temperature of the wheel bearing changes due to heat generated by the rotation of the bearing or the surrounding environment, the sensor output signals of the sensor units 20A and 20B fluctuate due to thermal expansion even if the load does not change. The effects of remain. Therefore, if the temperature correction means 35 for correcting the average value A of the sensor output signal according to the temperature of the wheel bearing or its surrounding temperature is provided, the detection load error due to the temperature can be reduced.

  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 </ b> A (20 </ b> B) are fixed in contact with the outer member 1, the strain of the outer member 1 expands to the strain generating member 21. The distortion is easily detected by the strain sensors 22A and 22B.

In particular, a first load estimating means 31 for calculating / estimating a load acting on the wheel bearing using the average value A obtained by the sum of the output signals of the strain sensors 22A, 22B of the sensor unit 20, and a sensor output signal Second load estimating means 32 for calculating / estimating a load acting on the wheel bearing using the amplitude value B and the average value A, and estimating either one of the load estimating means 31, 32. Since the selection output means 33 for switching and outputting the load value to be switched according to the wheel rotation speed is provided, it is obtained from the average value A obtained without performing the time averaging process when the wheel is stationary or in a low speed state. By outputting the estimated load value of the first load estimating means 31, the detection processing time can be shortened. Further, when the wheel is in the normal rotation state, the average value A and the amplitude value B of the sensor output signal can be calculated with high accuracy, and therefore the estimated load of the second load estimating means 32 obtained from the average value A and the amplitude value B. By outputting the value, the error of the estimated load value is reduced, and the detection delay time is sufficiently reduced.
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.

FIG. 9 shows 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 outer member 1 that is the fixed side member, which is the vertical position and the horizontal position with respect to the tire ground contact surface. The front view seen from the outboard side of other embodiments which arranged four sensor units 20A, 20B, 20C, and 20D equally with a phase difference of 90 degrees is shown. Other configurations other than the arrangement configuration of the sensor units 20A to 20D are the same as those in the previous embodiment.
By arranging the four sensor units 20A to 20D 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 and a braking force, and the axial load Fy.

In each of the above-described embodiments, the case where the outer member 1 is a fixed side member has been described. However, the present invention can also be applied to a wheel bearing in which the inner member is a fixed side member. In this case, 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 2 ... Inner member 3, 4 ... Rolling surface 5 ... Rolling body 20, 20A-20D ... Sensor unit 21 ... Strain generating member 21a ... Contact fixing | fixed part 22, 22A, 22B ... Strain sensor 31 ... 1st 1 load estimation means 32 ... second load estimation means 33 ... selection output means 34 ... temperature sensor

Claims (13)

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 A double row rolling element, and a wheel bearing for rotatably supporting the wheel with respect to the vehicle body,
A strain generating member having two or more contact fixing portions fixed to the fixed side member of the outer member and the inner member in contact with the fixed side member, and attached to the strain generating member. A sensor-equipped wheel bearing provided with a load detection sensor unit comprising one or more sensors for detecting strain of a strain generating member,
First load estimating means for calculating / estimating a load acting on a wheel bearing using an average value of the output signal of the sensor, an amplitude value of the output signal of the sensor, or an amplitude value thereof and the average value A second load estimating means for calculating / estimating a load acting on the wheel bearing, and switching the estimated load value of one of the first and second load estimating means according to the wheel rotational speed. A sensor-equipped wheel bearing comprising a selection output means for selecting and outputting.   2. The sensor unit according to claim 1, wherein the sensor unit includes two sensors, and the first load estimating means calculates and estimates a load acting on the wheel bearing using an average value of output signals of the two sensors. And the second load estimating means calculates and estimates a load acting on the wheel bearing using an average value and an amplitude value of output signals of the two sensors.   3. The sensor-attached device according to claim 2, wherein the average value of the output signals of the two sensors in the first load estimating means and the second load estimating means is obtained by adding the output signals of the two sensors. Wheel bearing.   4. The sensor unit according to claim 1, wherein three or more sensor units are provided, and the first and second load estimation means are both based on sensor output signals of the three or more sensor units. Sensor-equipped wheel bearing that calculates and estimates the load in three directions, each radial load acting in the radial direction of the wheel bearing and the axial load acting in the axial direction of the wheel bearing .   5. The sensor unit according to claim 1, 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.   6. The sensor unit according to claim 1, wherein the sensor unit includes three or more contact fixing portions and two sensors, and is adjacent between and adjacent to the first and second contact fixing portions. Each sensor is mounted between the second and third contact fixing portions, and the distance between the adjacent contact fixing portions or the adjacent sensors in the circumferential direction of the fixing member is {1/2 + n of the arrangement pitch of the rolling elements. (N: integer)} times, and the first and second load estimation means use the sum of output signals of the two sensors as an average value.   7. The sensor-equipped wheel according to claim 1, wherein a temperature sensor is attached to the sensor unit, and temperature correction means is provided to correct an average value of the sensor output signal based on a detection signal of the temperature sensor. bearing.   The selection output means selects and outputs the estimated load value of the first load estimation means when the wheel rotation speed is lower than a set lower limit speed. A bearing for wheels with sensors.   9. The method according to claim 1, wherein the first and second load estimating means calculate and estimate the load in parallel, and the selection output means determines the both loads according to a wheel rotational speed. A sensor-equipped wheel bearing that selects and outputs an estimated load value of any one of the estimating means.   10. The wheel bearing with sensor according to claim 1, wherein the selection output means receives the information on the wheel rotation speed from the outside and performs the selection according to the wheel rotation speed. 11.   11. The selection output means according to any one of claims 1 to 10, wherein the selection output means detects a passing frequency of a rolling element from an output signal of the sensor to estimate a wheel rotation speed, and the estimated wheel rotation speed determines the wheel rotation speed. The wheel bearing with a sensor which shall perform the said selection according to wheel rotational speed.   11. The selection output means according to claim 1, wherein the selection output means estimates a wheel rotation speed from a rotation sensor signal supplied from a vehicle body side, and determines the wheel rotation speed based on the estimated wheel rotation speed. A sensor-equipped wheel bearing that performs the above selection.   11. The sensor-equipped wheel according to any one of claims 1 to 10, wherein the selection output means receives the switching selection command corresponding to the wheel rotation speed from a control device on a vehicle body side and performs the selection. bearing.

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