JP2013024791A - Wheel bearing with sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wheel bearing with sensors capable of performing load estimation calculation processing and obtaining a correct estimated load value without using the signal of a rotation sensor and wheel rotation speed information from a vehicle.SOLUTION: Multiple sensor units are arranged in a fixed side member between the outer member and inner member of a wheel bearing. The wheel bearing with sensors includes: load estimation means 34 having a first calculation processing part 35 for calculating a load to actuate on the wheel bearing by using only the average value A of sensor output signals of the sensor units, and a second calculation processing part 36 for calculating the load by using the average value A and amplitude value B of the sensor output signals; rotation speed evaluation means 37 for obtaining an evaluation value V expressing the rotation speed of a wheel on the basis of the sensor output signal; and estimated load output means 38 for synthesizing the two calculation processing results on the basis of the evaluation value V and outputting an estimated load value. The estimated load output means 38 synthesizes the calculation processing results with the use of a ratio r corresponding to an elapsed time from when the evaluation value V crosses with a predetermined threshold Vth.

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 the 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 the wheel bearing and the load is detected from the distortion of the outer surface of the outer ring (for example, a patent) Reference 1). However, in the technique disclosed in Patent Document 1, when detecting the load acting on the wheel bearing, the amount of deformation of the fixed wheel 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.

  As a solution to this problem, a sensor-equipped wheel bearing having the following configuration has been proposed (Patent Document 2). The wheel bearing in the sensor-equipped wheel bearing of the same document includes an outer member in which a double row rolling surface is formed on the inner periphery, and an inner member in which the rolling surface opposite to the rolling surface is formed on the outer periphery. A member and a double row rolling element interposed between the opposing rolling surfaces of both members are provided, and the wheel is rotatably supported with respect to the vehicle body. One or more sensor units are provided on the outer diameter surface of the stationary member of the outer member and the inner member. Each sensor unit has 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, the first load estimating means for calculating / estimating the load acting on the wheel bearing only from the average value of the sensor output signal, and the second calculating / estimating from the average value and the amplitude value of the sensor output signal. Load estimation means, and a selection output means for selecting and outputting the estimated load value of either of these load estimation means according to the wheel rotational speed. A schematic configuration in this case is shown in a block diagram in FIG.

  In this configuration, a formula using only the average value A of the sensor output signal as a variable and a formula using the average value A and the amplitude value B of the sensor output signal as variables are prepared as load estimation calculation formulas. Is used to switch the load calculation process. That is, in the normal running state, the load estimation calculation is performed by an arithmetic expression using the average value A and the amplitude value B of the sensor output signal, and the load estimation calculation by the arithmetic expression using only the average value A is performed at a low speed or in a stop state. I do.

Special table 2003-530565 gazette JP 2010-181154 A

  However, in the configuration disclosed in Patent Document 2, when the amplitude B is obtained by calculation, it is necessary to use a sensor output signal within a certain period of time, which causes a time delay due to signal processing. Further, when the load estimation calculation using only the average value A and the load estimation calculation using the average value A and the amplitude value B are switched according to the wheel rotation speed, the delay time of the estimated load output also changes due to the switching. Therefore, it is observed as a detection error. In addition, there may be a difference between the calculation results of the two calculation formulas, and when the output is switched in this state, the estimated load output changes discontinuously. For the control system that executes various operations based on the detected estimated load value, the above-described discontinuous change in the estimated load output and a large detection error are not preferable.

  In order to prevent these problems, a rotation sensor is installed to detect the rotation speed of the wheel, or the rotation speed information of the wheel is obtained separately from the vehicle side, so that the calculation result by the two calculation formulas is obtained. Although it is possible to switch continuously according to the rotation speed, it cannot be handled in a situation where rotation speed information is not available.

  Apart from this, it is also conceivable to calculate an evaluation value according to the rotational speed from the sensor output signal without using information such as the rotation sensor and to switch the load calculation processing based on this evaluation value. In this method, an evaluation value according to the rotation speed can be obtained even in a situation where the rotation sensor signal cannot be used or in a situation where the rotation speed information cannot be acquired continuously and stably. However, although it is possible to determine whether or not the engine is in a low-speed rotation state with this evaluation value, it is not an evaluation value that is exactly proportional to the speed, so that it is difficult to apply to the process of continuously switching according to the speed.

  An object of the present invention is to provide a sensor-equipped wheel bearing that can perform load estimation calculation processing and obtain an accurate estimated load value without using a rotation sensor signal or wheel rotation speed information from a vehicle. Is to provide.

The sensor-equipped wheel bearing according to the present invention includes an outer member 1 in which double-row rolling surfaces are formed on the inner periphery, and an inner member 2 in which a rolling surface opposite to the rolling surface is formed on the outer periphery. And a double-row rolling element 5 interposed between the opposing rolling surfaces of the two members, and in a wheel bearing for rotatably supporting the wheel with respect to the vehicle body, the outer member 1 and the inner member 2 are A strain generating member 21 having three or more contact fixing portions 21a fixed to the fixed side member in contact with the fixed side member, and a strain of the strain generating member 21 attached to the strain generating member 21 A plurality of load detection sensor units 20A (20B) each including two or more sensors 22A and 22B for detecting the above are provided.
The first arithmetic processing unit 35 that calculates and estimates the load acting on the wheel bearing using only the average value A of the output signals of the sensors 22A and 22B, and the average value of the output signals of the sensors 22A and 22B A load estimation means 34 comprising a second arithmetic processing unit 36 for calculating and estimating a load acting on the wheel bearing using A and the amplitude value B, and the rotational speed of the wheel from the output signals of the sensors 22A and 22B. A rotational speed evaluation means 37 for obtaining an evaluation value V representing the output, and an estimated load that outputs an estimated load value by combining the calculation processing results of the two calculation processing units 35 and 36 in the load estimation means 34 based on the evaluation value V An output means 38 is provided, and the estimated load output means 38 synthesizes the calculation processing results at a ratio r corresponding to an elapsed time after the evaluation value V crosses a predetermined threshold value Vth.

According to this configuration, when a load is applied 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 1) of the wheel bearing to cause deformation. Here, since the three or more contact fixing portions 21a of the strain generating member 21 in the sensor unit 20A (20B) are fixed in contact with the outer member, the strain of the outer member 1 is expanded to the strain generating member 21. The distortion is easily transmitted, and the distortion is detected with high sensitivity by the sensors 22A and 22B.
In particular, the first arithmetic processing unit 35 that calculates and estimates the load acting on the wheel bearing using only the average value A of the output signals of the sensors 22A and 22B of the sensor unit 20A (20B), and the sensors 22A and 22B. Load estimation means 34 comprising a second arithmetic processing unit 36 for calculating / estimating the load acting on the wheel bearing using the amplitude value B of the output signal and the average value A, and the outputs of the sensors 22A, 22B A rotational speed evaluation means 37 for obtaining an evaluation value V representing the rotational speed of the wheel from the signal, and an estimated load by combining the arithmetic processing results of the two arithmetic processing sections 35 and 36 in the load estimation means 34 based on the evaluation value V Estimated load output means 38 for outputting a value is provided, and the estimated load output means 38 has the ratio r corresponding to the elapsed time after the evaluation value V crosses a predetermined threshold value Vth. Since to carry out the synthesis of calculation processing result, effects are obtained as listed below.
・ Since load estimation calculation processing can be performed without using a rotation sensor signal or wheel rotation speed information from the vehicle, there is no need to increase the number of signal wires, and the manufacturing cost of the load sensor can be reduced. The degree of freedom when mounted on can be increased.
-By switching between the load estimation calculation process in the normal rotation state and the load estimation calculation process at low speed, the load estimation error is suppressed, so that a more accurate estimated load value can be obtained.
-Even when the load estimation calculation process is switched according to the rotation speed, the load signal is not discontinuously changed by the method in which the composition ratio is continuously changed, and the use of the load signal for various vehicle controls becomes easy.
・ If sudden braking is activated while driving, the rotational speed may change suddenly and the vehicle may slip, but the estimated load value is output even if the wheel is stationary or at extremely low speed. Therefore, the signal can be used for vehicle control or the like without depending on the traveling state.

In the present invention, the average value A and the amplitude value B of the output signals of the sensors 22A and 22B used for the arithmetic processing in the load estimating means 34 may be the output signals of the sensors 22A and 22B within a certain time T. good. In this case, the value of the predetermined time T may be changed according to the evaluation value V obtained by the rotation speed evaluation means 37.
If the fixed time T is set to be longer when the rotational speed of the wheel is low, and the fixed time T is shortened when the rotational speed is increased, the calculation process using the amplitude value B in the load estimating means 34 is performed. While suppressing deterioration in accuracy in the low speed region, the response time of the arithmetic processing result can be shortened in the speed region where a faster response is required.

In the present invention, in the sensor unit 20A (20B), the sensors 22A and 22B are arranged between the adjacent first and second contact fixing portions 21a and between the adjacent second and third contact fixing portions 21a. The interval in the circumferential direction of the fixed side member of the adjacent contact fixing portion 21a or the adjacent sensors 22A and 22B is set to {1/2 + n (n: integer)} times the arrangement pitch of the rolling elements, The sum of the output signals of the two sensors 22A and 22B may be used as the average value A in one or both of the first and second arithmetic processing units 35 and 36 in the load estimating unit 34.
In the case of this configuration, the output signals of the two sensors 22A and 22B have a phase difference of about 180 degrees, and the average value A is a value obtained by canceling the fluctuation component due to passing through the rolling elements. The amplitude value B is a value that sufficiently offsets the influence of temperature and the influence of slippage between the knuckle and flange surfaces. As a result, the average value A of the output signals of the two sensors 22A and 22B becomes a value obtained by canceling the fluctuation component due to passing through the rolling elements, and the amplitude value B is more influenced by temperature and the effect of slippage between the knuckle and flange surfaces. It will be accurate and surely excluded.

  In the present invention, the composition ratio r used by the estimated load output means 38 may be determined by a linear function having the elapsed time after the evaluation value V crosses a predetermined threshold value Vth as a variable. .

  In the present invention, the composite ratio r used in the estimated load output means 38 is determined by a quadratic or higher function whose variable is the elapsed time after the evaluation value V crosses a predetermined threshold value Vth. It is also good.

  In the present invention, the change in the composite ratio r used by the estimated load output means 38 is the elapse of a preset transition time a out of the elapsed time since the evaluation value V crosses a predetermined threshold th. It is good to complete it.

  In this case, when the elapsed time from when the evaluation value V crosses the predetermined threshold value Vth until it crosses the threshold value Vth again does not reach the transition time a, the threshold value Vth is crossed again. It is also possible that the subsequent synthesis ratio r changes with the current synthesis ratio r as the initial value.

  In the present invention, the rotational speed evaluation means 37 may obtain a value obtained by selecting and summing the amplitude values B of the output signals of the sensors 22A and 22B as the evaluation value V.

  In this invention, the said rotational speed evaluation means 37 is good also as what calculates | requires the said evaluation value V from the frequency of the amplitude component by the revolution motion of the rolling element contained in the output signal of the said sensors 22A and 22B.

  In the present invention, three or more sensor units 20A (20B) are provided, and the load estimating means 34 determines the radial direction of the wheel bearing from the output signals of the sensors 22A and 22B of the three or more sensor units 20A (20B). It is also possible to calculate / estimate two radial loads Fx, Fz in the vertical direction and left / right direction acting on the wheel and one axial load Fy acting in the axial direction of the wheel bearing.

  In this invention, the sensor unit 20A (20B) is circumferentially arranged 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 of 90 degrees in the direction. By arranging the four sensor units 20A (20B) in this way, 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 can be estimated more accurately. Can do.

  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 three or more contact fixing portions fixed in contact with the fixed side member, and two or more sensors attached to the strain generating member and detecting the strain of the strain generating member A plurality of load detection sensor units, a first calculation processing unit that calculates and estimates a load acting on the wheel bearing using only the average value of the output signal of each sensor, and the output signal of each sensor Acting on wheel bearings using average and amplitude values A load estimation unit comprising a second calculation processing unit for calculating and estimating a load; a rotation speed evaluation unit for obtaining an evaluation value representing a rotation speed of a wheel from an output signal of each sensor; and the load estimation based on the evaluation value And an estimated load output means for outputting an estimated load value by combining the calculation processing results of the two calculation processing sections in the means, the estimated load output means after the evaluation value crosses a predetermined threshold value Since the calculation processing result is synthesized at a ratio according to the elapsed time, load estimation calculation processing can be performed without using a rotation sensor signal or wheel rotation speed information from the vehicle, An accurate estimated load value can be obtained.

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 arithmetic processing part which calculates the average value and amplitude value of a sensor output signal. It is a block diagram which shows the whole structure of a detection system. It is a figure which shows the relationship between evaluation value V and rotation speed area | region RA, RB. It is a figure which shows the example of calculation of the estimated load value Lout in an estimated load output means. (A) is a graph showing the relationship between the amplitude of the sensor output signal at the upper part of the outer diameter surface of the outer member and the direction of the axial load Fy, and (B) is the amplitude and axis of the sensor output signal at the lower part of the outer diameter surface. It is a graph which shows the relationship with a direction load. It is a graph which shows the relationship between the magnitude | size of axial load Fy, and the difference of the sensor output signal of an upper and lower sensor unit. 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. It is a block diagram which shows schematic structure of the load estimation means in a prior art example.

  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. In addition, the wheel bearing of FIG. 1 shows the II sectional view taken on the line 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 in the vertical position 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. Two or more (two in this case) 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 or more (three in this case) 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. The two strain sensors 22 </ b> A and 22 </ b> B 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 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 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 units 20A and 20B, the three contact fixing portions 21a of the strain generating member 21 are located at the same size in the axial direction of the outer member 1, and the contact fixing portions 21a are separated from each other in the circumferential direction. The contact fixing portions 21 a are respectively fixed to the outer diameter surface of the outer member 1 by bolts 24 through spacers 23. 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.

  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 22A and 22B can be formed on the strain generating member 21 with a thick film resistor.

  As shown in FIG. 1, the two strain sensors 22A and 22B of the sensor unit 20A (20B) are connected to a signal preprocessing means 31 having an average value calculation unit 32 and an amplitude value calculation unit 33. As shown in FIG. 7, the average value calculation unit 32 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 33 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. Note that, as the average value A, in addition to calculating the sum of the sensor output signals, the time average value of the sensor output signals may be taken out.

  The signal preprocessing means 31 is connected to a load estimation means 34. The load estimator 34 uses a force (for example, vertical) acting on a wheel bearing or between a wheel and a 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 load estimation means 34 includes a first arithmetic processing unit 35 that calculates and estimates a load LA acting on the wheel bearing using only the average value A of the output signals of the strain sensors 22A and 22B, and the strain sensor 22A. , 22B using a mean value A and an amplitude value B of the output signal, a second computation processing unit 36 that computes and estimates a load LB acting on the wheel bearing.

The relationship between the load L acting on the wheel bearing and the output signal S of the strain sensors 22A and 22B is as follows:
L = M1 × S (1)
From this relational expression (1), it is possible to estimate the load L acting between the wheel bearing and the wheel and the road surface (tire contact surface). Here, M1 is a predetermined correction coefficient.
The first arithmetic processing unit 35 uses the average value A as a variable obtained by removing the offset from the output signals of the strain sensors 22A and 22B, and multiplies the variable by a predetermined correction coefficient M1, that is, LA = M1 × A (2)
From the above, the load L is calculated and estimated. In this way, the load estimation accuracy can be improved by using the variable excluding the offset.
In this example, since two sensor units 20A and 20B are used, the average value A obtained from each sensor unit 20A (20B) is used in the calculation according to the equation (2). That is, when the average value obtained from the sensor unit 20A is AA and the average value obtained from the sensor unit 20B is AB, the equation (2) is LA = M1A × AA + M1B × AB (2 ′)
Represented as: However, M1A is a predetermined correction coefficient for multiplying the average value AA, and M1B is a predetermined correction coefficient for multiplying the average value AB.

In the second arithmetic processing unit 36, 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, LB = M2 × A + M3 × B. (3)
From the above, the load L is calculated and estimated. Thus, load estimation accuracy can be further improved by using two types of variables.
In this example, since two sensor units 20A and 20B are used, the average value obtained from the sensor unit 20A is AA, the amplitude value is BA, the average value obtained from the sensor unit 20B is AB, and the amplitude value is BB. Then, Expression (3) is expressed as LB = M2A × AA + M2B × AB + M3A × BA + M3B × BB (3 ′). However, M2A is a predetermined correction coefficient for multiplying the average value AA, M2B is a predetermined correction coefficient for multiplying the average value AB, M3A is a predetermined correction coefficient for multiplying the amplitude value BA, and M3B is a predetermined correction coefficient for multiplying the amplitude value BB Is the correction coefficient. The value of each correction coefficient in each of the above arithmetic expressions is set by obtaining in advance by a test or simulation. Calculations by the first calculation processing unit 35 and the second calculation processing unit 36 are performed in parallel.

  Since the sensor unit 20A (20B) is provided at an axial position around the rolling surface 3 of the outboard side row of the outer member 1, the output signals a and b of the strain sensors 22A and 22B are shown in FIG. Thus, it is influenced by the rolling element 5 that passes in the vicinity of the installation part of the sensor unit 20A (20B). 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 20A (20B) (or when the rolling element 5 is at that position), the output signals a and 22a of the strain sensors 22A and 22B b becomes the maximum value 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 20A (20B) at a predetermined arrangement pitch P, so that the output signals a and b of the strain sensors 22A and 22B are output from 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. Further, the output signals a and b of the strain sensors 22A and 22B are affected by temperature and hysteresis due to slippage between the knuckle 16 and the body mounting flange 1a (FIG. 1). In this embodiment, the sum 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 absolute value | a−b | is obtained from the difference between the output signals a and b, and is time-averaged. Or the value obtained by calculating the RMS value (root mean square value) from the difference between the output signals a and b is referred to as 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.

  In FIG. 6 showing the configuration example of FIG. 5 as the sensor unit 20A (20B), 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 fixing side member, The interval between the two contact fixing portions 21 a located at both ends of the array is set to be the same as the array 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. 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 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.

  The signal preprocessing means 31 is also connected to a rotational speed evaluation means 37 as shown in FIG. The rotational speed evaluation means 37 discriminates the rotational speed of the wheel by using the average value A and the amplitude value B obtained from the output signals a and b of the strain sensors 22A and 22B in the signal preprocessing means 31. This is means for obtaining an evaluation value V as an index.

  As shown in FIG. 8, the load estimating means 34 is connected to the estimated load output means 38 in the next stage. The estimated load output means 38 combines the calculation processing results LA and LB in the two calculation processing sections 35 and 36 of the load estimation means 34 and outputs the final estimated load value Lout. In this case, the two arithmetic processing results LA and LB are combined by a ratio r (t corresponding to an elapsed time t after the evaluation value V obtained by the rotational speed evaluation means 37 crosses a predetermined threshold value Vth. ) The threshold value Vth is read from the memory 39.

Next, the operation of the detection system in this sensor-equipped wheel bearing will be described.
First, in the signal preprocessing means 31, an average value A and an amplitude value B are obtained from the output signals S of the respective strain sensors 22A and 22B, and an evaluation value V for discriminating the rotational speed using them is used as the rotational speed evaluation means. 37. The rotational speed evaluation means 37 compares the calculated evaluation value V with a separately determined threshold value Vth, so that the current state is the rotational speed region RA using the first arithmetic processing result LA in the load inference means 34. Or the rotational speed region RB using the second calculation processing result LB is determined.

  Here, as the evaluation value V for discriminating the rotational speed, for example, a value obtained by selecting and summing the amplitude values B of the output signals of the respective strain sensors 22A and 22B input within a predetermined time is used. . In this case, the amplitude values B of all output signals may be summed, or the amplitude values B of some sensor output signals may be selected and summed. As another method, the fundamental speed component may be extracted from the output signals of the strain sensors 22A and 22B to estimate the rotation speed. This evaluation value V does not have to have a relationship that is exactly proportional to the rotational speed, and it is sufficient if it is possible to determine whether or not it exceeds a certain fixed speed in the low-speed rotational speed region necessary for determining the rotational speed. As a result, the accuracy required for the evaluation value V is low, so there is no need to provide a rotation sensor that outputs an accurate rotation speed or a means for inputting external sensor information, and the configuration is simple. Can be

  In the load estimating means 34, the sum A of the output signals of the two strain sensors 22A, 22B arranged at a position shifted by 1/2 of the average value A of the output signals of the strain sensors 22A, 22B (1/2 of the arrangement pitch P of the rolling elements 5). ) Using the first calculation processing unit 35 using only the second calculation using the average value A (the average value may be Sum or the time average value Av) and the amplitude value B. The calculation processing result LB in the processing unit 36 is calculated in parallel. Then, according to the evaluation value V for discriminating the rotation speed, which calculation processing result is used as the estimated load value Lout is selected and output. When the evaluation value V changes during traveling and exceeds the boundary between the rotational speed region RA and the rotational speed region RB, two calculation results weighted according to the time after passing are combined and output. That is, the arithmetic processing result LA and the arithmetic processing result LB are synthesized based on the ratio r (t), and the final estimated load value Lout is output. The region RA is a low-speed rotational speed region, the region RB is a normal rotational speed region, and FIG. 9 shows the relationship between the evaluation value V and the rotational speed regions RA and RB.

FIG. 10 shows a calculation example of the estimated load value Lout by the estimated load output means 38. For example, when the rotational speed enters the region RB from the region RA, the estimated load output means 38 calculates the composition as follows, where t is the time after the boundary passage.
Lout = (1−r (t)) × LA + r (t) × LB; (r (t) is a value of 0 to 1) (4)
Here, the ratio r (t) is obtained by, for example, using a linear function: r (t) = t / a (0 <t <a) (5)
Or using trigonometric functions, r (t) = sin (πt / 2a) ^ 2 (0 <t <a) (6)
And so on. When a function of second order or higher is used, the switching part can be connected smoothly. In any case, the function changes from 0 to 1 from t = 0 to t = a. As a result of this calculation, an estimated load value Lout obtained by combining the calculation processing result LA and the calculation processing result LB is output until the elapsed time t = a after passing the boundary, and thereafter, the calculation result of the rotation speed region RB is output. It will be. Of the elapsed time after passing the boundary, a preset time a (hereinafter referred to as transition time) is written in advance in the memory 39 in FIG. 8 together with the threshold value Vth. Further, the elapsed time t after passing the boundary is measured by a timer 40 provided in the rotational speed evaluation means 37.

Conversely, when the rotational speed enters the region RA from the region RB, the estimated load output means 38 calculates the composition as follows, with the time after passing the boundary as t.
Lout = (1-r (at)) * LA + r (at) * LB (7)
In addition, after the rotational speed enters the region RB from the region RA, when the time t does not reach a (t = t1) and returns to the region RB again,
t = a−t1
The calculation process is continued with the synthesis ratio r (t) at the initial value.

  In the calculation of the average value A and the amplitude value B used in the calculation processing of the load estimating means 34 in the signal preprocessing means 31, the magnitude of the processing target time T is changed according to the value of the evaluation value V. Also good. When the processing time T is set to be longer when the rotational speed of the wheel is low and the processing time T is shortened when the rotational speed is increased, the calculation processing using the amplitude value B in the load estimation unit 34 is performed. While suppressing deterioration in accuracy in the low speed region, the response time of the arithmetic processing result can be shortened in the speed region where a faster response is required. Even when the correlation between the evaluation value V and the rotation speed is low, it is possible to optimally select the processing target time T according to the rotation speed region by creating a map corresponding to the value of the evaluation value V. Become.

  In this embodiment, 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 Fz acting on the wheel bearing is accurately estimated. it can. If the number of sensor units 20A and 20B to be arranged is increased, the load Fx and the axial load Fy that become driving force and braking force can be estimated.

  The load estimation means 34 shown in FIG. 8 is provided with a Fy direction discriminating unit 41 that discriminates the direction of the axial load Fy when calculating the axial load Fy. As described above, during the rotation of the wheel bearing, the amplitude of the sensor output signals of the sensor units 20A and 20B has a periodic change close to a sine wave, but the amplitude value is an axial load (moment force). ) Varies with the magnitude of Fy. 11A shows the sensor output of the sensor unit 20A disposed on the upper surface portion of the outer diameter surface of the outer member 1, and FIG. 11B is disposed on the lower surface portion of the outer diameter surface of the outer member 1. The sensor output of the sensor unit 20B is shown. In these drawings, the horizontal axis represents the axial load Fy, the vertical axis represents the strain amount of the outer member 1, that is, the sensor output signal, and the maximum value and the minimum value represent the maximum value and the minimum value of the vibrating signal. From these figures, when the axial load Fy is in the + direction, the load of the individual rolling elements 5 becomes smaller on the upper surface portion of the outer member 1 (that is, the difference between the maximum value and the minimum value of the output signal is small). It can be seen that it becomes larger at the lower surface of the outer diameter surface of the outer member 1 (that is, the difference between the maximum value and the minimum value of the output signal increases). On the other hand, when the axial load Fy is in the negative direction, the load of the individual rolling elements 5 increases at the upper surface portion of the outer member 1 and the lower surface of the outer member 1. It turns out that it becomes small in a part. FIG. 12 is a graph showing the relationship between the difference between the amplitudes of the sensor output signals of the upper and lower sensor units 20A and 20B and the direction of the axial load Fy.

  Therefore, the Fy direction discriminating unit 41 obtains the above difference in the amplitudes of the sensor output signals of the sensor units 20A and 20B disposed on the outer diameter surface upper surface portion and the outer diameter surface lower surface portion of the outer member 1, and calculates these values. By comparing, the direction of the axial load Fy is determined. That is, the difference in the amplitude of the sensor output signal of the sensor unit 20A on the outer surface of the outer member 1 is small, and the difference in the amplitude of the sensor output signal of the sensor unit 20B on the lower surface of the outer member is large. At this time, the Fy direction determination unit 41 determines that the direction of the axial load Fy is the + direction. Conversely, the difference in the amplitude of the sensor output signal of the sensor unit 20 </ b> A on the upper surface of the outer diameter surface of the outer member 1 is large, and the difference in the amplitude of the sensor output signal of the sensor unit 20 </ b> B on the lower surface of the outer diameter surface of the outer member 1. Is small, the Fy direction determination unit 41 determines that the direction of the axial load Fy is the negative direction. Correspondingly, the load estimation means 34 reflects the determination result of the Fy direction determination unit 41 when the first and second calculation processing units 35 and 36 calculate the axial load Fy. Processing such as reversing the sign of the parameter of the calculation estimation formula is performed.

  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 three 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, the first arithmetic processing unit 35 that calculates and estimates the load acting on the wheel bearing using only the average value A of the output signals of the strain sensors 22A and 22B of the sensor unit 20A (20B), and the sensor output signal From the load estimation means 34 comprising a second calculation processing unit 36 for calculating / estimating the load acting on the wheel bearing using the amplitude value B and the average value A, and output signals from the strain sensors 22A and 22B. Rotational speed evaluation means 37 for obtaining an evaluation value V representing the rotational speed of the wheel, and based on the evaluation value V, the calculation processing results of the two calculation processing units 35 and 36 in the load estimation means 34 are combined to obtain an estimated load value. The estimated load output means 38 for outputting is provided, and the estimated load output means 38 performs the calculation process at a ratio r corresponding to an elapsed time after the evaluation value V crosses a predetermined threshold value Vth. Since to carry out the synthesis of the fruit, effects are obtained as listed below.
・ Since load estimation calculation processing can be performed without using a rotation sensor signal or wheel rotation speed information from the vehicle, there is no need to increase the number of signal wires, and the manufacturing cost of the load sensor can be reduced. The degree of freedom when mounted on can be increased.
-By switching between the load estimation calculation process in the normal rotation state and the load estimation calculation process at low speed, the load estimation error is suppressed, so that a more accurate estimated load can be obtained.
-Even when the load estimation calculation process is switched according to the rotation speed, the load signal is not discontinuously changed by the method in which the composition ratio is continuously changed, and the use of the load signal for various vehicle controls becomes easy.
・ If sudden braking is activated while driving, the rotational speed may change suddenly and the vehicle may slip, but the estimated load value is output even if the wheel is stationary or at extremely low speed. Therefore, the signal can be used for vehicle control or the like without depending on the traveling state.

FIG. 13 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 left and right positions 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 bodies 20A-20D ... Sensor unit 21 ... Strain generating member 21a ... Contact fixing | fixed part 22A, 22B ... Strain sensor 31 ... Signal pre-processing means 32 ... average value calculator 33 ... amplitude value calculator 34 ... load estimation means 35 ... first calculation processing section 36 ... second calculation processing section 37 ... rotational speed evaluation means 38 ... estimated load output means

Claims (12)

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 three 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 plurality of load detection sensor units including two or more sensors for detecting strain of the strain generating member are provided.
A first arithmetic processing unit that calculates and estimates a load acting on the wheel bearing using only the average value of the output signal of each sensor, and the wheel using the average value and the amplitude value of the output signal of each sensor. Load estimation means comprising a second calculation processing section for calculating / estimating the load acting on the bearing for the vehicle, rotation speed evaluation means for obtaining an evaluation value V representing the rotation speed of the wheel from the output signal of each sensor, and the evaluation And an estimated load output means for outputting an estimated load value by combining the calculation processing results of the two calculation processing units in the load estimation means based on the value V. The estimated load output means has the evaluation value V determined in advance. A sensor-equipped wheel bearing, wherein the arithmetic processing results are synthesized at a ratio r corresponding to an elapsed time after crossing the threshold value Vth.   The sensor-equipped wheel bearing according to claim 1, wherein an average value and an amplitude value of the output signals of the sensors used for the arithmetic processing in the load estimating means are calculated using the output signals of the sensors within a predetermined time T.   3. The sensor-equipped wheel bearing according to claim 2, wherein the value of the predetermined time T is changed according to an evaluation value V obtained by the rotation speed evaluation means.   4. The sensor unit according to claim 1, wherein in the sensor unit, each sensor is disposed between adjacent first and second contact fixing portions and between adjacent second and third contact fixing portions. In the circumferential direction of the fixing member of the adjacent contact fixing portion or adjacent sensor is set to {1/2 + n (n: integer)} times the arrangement pitch of the rolling elements, and the load estimating means A sensor-equipped wheel bearing in which one or both of the first and second arithmetic processing units uses the sum of output signals of the two sensors as an average value.   5. The composition ratio r used in the estimated load output means according to claim 1, wherein the composite ratio r is a primary variable having an elapsed time after the evaluation value V crosses a predetermined threshold value Vth as a variable. Wheel bearing with sensor determined by function.   5. The composition ratio r used in the estimated load output means according to claim 1, wherein the composite ratio r used is an elapsed time after the evaluation value V crosses a predetermined threshold value Vth. Wheel bearing with sensor determined by the following function.   In any one of Claims 1 thru | or 6, The change of the synthetic | combination ratio r used by the said estimated load output means is the elapsed time after the said evaluation value V crossed the predetermined threshold th, A wheel bearing with sensor that is completed after a preset transition time a.   8. If the elapsed time from when the evaluation value V crosses the predetermined threshold value Vth until it crosses the threshold value Vth again is less than the transition time a, the threshold value Vth is crossed again. A sensor-equipped wheel bearing in which the composite ratio r at that time is an initial value and the subsequent composite ratio r changes.   9. The sensor-equipped wheel according to claim 1, wherein the rotation speed evaluation unit obtains a value obtained by selecting and summing amplitude values of output signals of the sensors as the evaluation value V. 10. bearing.   9. The sensor according to claim 1, wherein the rotational speed evaluation means obtains the evaluation value V from a frequency of an amplitude component due to a revolution motion of a rolling element included in an output signal of the sensor. Wheel bearing.   11. The sensor unit according to claim 1, wherein three or more sensor units are provided, and the load estimation unit acts in a radial direction of a wheel bearing from an output signal of a sensor of the three or more sensor units. A sensor-equipped wheel bearing that calculates and estimates two radial loads Fx and Fz in the vertical and horizontal directions and one axial load Fy that acts in the axial direction of the wheel bearing.   The upper surface portion, the lower surface portion, the right surface portion of the outer diameter surface of the fixed side member which is the vertical position and the left and right position with respect to the tire ground contact surface according to any one of claims 1 to 11. And four wheel bearings with a sensor arranged equally on the left surface with a phase difference of 90 degrees in the circumferential direction.

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