JP2012058141A - Wheel bearing with sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wheel bearing with a sensor capable of obtaining continuous estimated loads in accordance with various input load states while reducing load estimation errors by correcting non-linear characteristics of the sensor.SOLUTION: A sensor unit is attached to a fixed side member out of an outer member and an inner member of the wheel bearing and a load estimation means 30 for estimating loads from a sensor output signal is arranged. The load estimation means 30 includes: a load estimation operation part 35 for operating loads by using an estimation operation formula; an evaluation value calculation part 32 for calculating an evaluation value Ei to be a parameter switching index of the estimation operation formula from a plurality of sensor output signals; and a parameter switching part 34 for switching parameters based on a result obtained by comparing the evaluation value Ei with a threshold Ci. The load estimation operation part 35 includes an operation correction part 35a for correcting an operation result by combining two load estimation results operated by the parameters in both evaluation value areas sandwiching the threshold Ci within a fixed evaluation value area including the threshold Ci.

Description

  The present invention relates to a sensor-equipped wheel bearing having a built-in load detection 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). 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. A sensor unit comprising two sensor units arranged on the outer diameter surface of the fixed side member of the outer member and the inner member at a position that forms a phase difference of 180 degrees in the circumferential direction of the fixed side member. At least one pair is provided. 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 a sensor.

  In this configuration, based on the difference between the sensor output signals of the two sensor units in the sensor unit pair, the radial load estimating means estimates the radial load acting in the radial direction of the wheel bearing. Further, based on the sum of the sensor output signals of the two sensor units in the sensor unit pair, the axial load acting means estimates the axial load acting in the axial direction of the wheel bearing. Then, the two sensor units of at least one pair of sensor units are arranged on the upper surface portion and the lower surface portion of the outer diameter surface of the fixed side member that is in the vertical position with respect to the tire ground contact surface. Based on the output signal amplitude of the sensor of the sensor unit pair, the axial load direction determining means determines the direction of the axial load. An outline of the load estimation process in this case is shown in a block diagram in FIG.

  When the contact fixing portion of the strain generating member in the sensor unit is disposed in the vicinity of the rolling surface of the fixed member in the wheel bearing, the sensor output signal is fluctuated close to a sine wave as shown in FIG. 23 as the wheel rotates. It can be seen. This is a change in distortion due to the passage of rolling elements. In the above configuration, the axial load is determined based on the difference between the amplitude values (vibration components accompanying the revolution motion of the rolling elements) in the sensor output signals of the two sensor units arranged above and below, and depending on whether the axial load is positive or negative, Since the load is calculated using load estimation parameters suitable for each, the load can be estimated with high sensitivity.

Special table 2003-530565 gazette JP 2010-43901 A

  However, in the case of the configuration of Patent Document 2, it is necessary to calculate the amplitude value of the sensor output signal in order to select the optimum load estimation parameter, and it is not possible to cope with the case where the amplitude value cannot be calculated. That is, in a state where the rotation is stationary or in a very low speed rotation state, there is no signal change due to the rolling element load, or there is only a very slow change. In this case, the magnitude of the amplitude cannot be obtained from the fluctuation of the sensor output signal.

  On the other hand, as a means for detecting the amplitude value of the sensor output signal due to the rolling element load even in a stationary state, in a region sufficient to observe the influence of the rolling element load (the circumferential length corresponding to the arrangement pitch of the rolling elements) There is also a means for directly measuring the strain distribution by arranging a plurality of sensors. However, in this case, the number of sensors increases, and the detection circuit becomes complicated, so that cost increases and reliability are new issues.

  Accordingly, the present inventors have developed a new load estimating means in the sensor-equipped wheel bearing having the configuration shown in the block diagram of FIG. Here, as will be described later, A represents an average value of two sensor outputs arranged close to a position where the rolling element signal has a phase difference of 180 °. In this configuration, as the load estimation calculation formula, there are prepared 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. The load calculation process is switched. 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. In the case of this configuration, rotation speed information is used to determine the rotation speed.

  According to the state of the detected sensor output signal and the state of the estimated load, such as the configuration of Patent Document 2 and the above configuration newly proposed by the present inventors, a plurality of load estimation parameters When the optimum load is selected and the estimated load is calculated, a detection result with a small error in which the nonlinear characteristics of the sensor are corrected can be obtained.

  However, in this case, when the load estimation parameter is selected according to a plurality of conditions, the estimated load value obtained as a result of the calculation may become discontinuous due to the parameter switching. Such a discontinuous change is not preferable for a control system in an automobile or the like that executes various operations based on the detected estimated load value.

  An object of the present invention is to provide a sensor-equipped wheel bearing capable of obtaining a continuous estimated load according to various input load states while correcting a nonlinear characteristic of the sensor to reduce a load estimation error. is there.

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 plurality of load detection sensor units 20 are provided on the fixed side member, and the sensor unit 20 has two or more contact fixing portions 21a fixed in contact with the fixed side member, and a strain generating member 21. One or more sensors 22, 22 A, and 22 B that are attached to the strain generating member 21 and detect the strain of the strain generating member 21 are included. From the output signals of the sensors 22, 22 A, and 22 B of the plurality of sensor units 20. Estimate the load applied to the wheel A sensor equipped wheel support bearing assembly having a load estimation means 30 that,
The load estimation means 30 includes a load estimation calculation unit 35 that calculates the load acting on the wheel bearing by fitting the output signal of the sensor 22 of each sensor unit 20 to a predetermined estimation calculation formula, and the plurality of sensors. An evaluation value calculation unit 32 that calculates one or more evaluation values Ei that serve as an index for switching the parameters of the estimation formula from the output signal of the sensor 22 of the unit 20, and a threshold value Ci that defines the evaluation value Ei And a parameter switching unit 34 for switching the parameter of the estimation calculation formula according to the comparison result, and the load estimation calculation unit 35 is within a defined region in which the evaluation value Ei includes the threshold value Ci. In some cases, the calculation result is supplemented by combining the two load estimation results calculated by the above-described estimation equation using the parameters in the evaluation value regions on both sides of the threshold value Ci. Characterized in that it is assumed that an arithmetic correction unit 35a for.

  According to this configuration, the load estimation means 30 having the load calculation unit 35 that calculates the load acting on the wheel bearing by applying the sensor output signal of each sensor unit 20 to a predetermined estimation calculation formula includes a plurality of sensor units. One or more evaluation values Ei serving as an index for switching the parameters of the estimation calculation formula are calculated by the evaluation value calculation unit 32 from the 20 sensor output signals, and the evaluation value Ei is determined by the parameter switching unit 34. Compared with the threshold value Ci, the parameter is switched according to the comparison result. Further, in the load calculation unit 35, when the evaluation value Ei is within a predetermined region sandwiching the threshold value Ci, the correction calculation unit 35a uses the parameters in the evaluation value regions on both sides sandwiching the threshold value Ci. The calculation result is corrected by combining the two load estimation results calculated by the estimation calculation formula. Therefore, it is possible to obtain a continuous estimated load according to various input load states while correcting the nonlinear characteristic of the sensor 22 to reduce the load estimation error.

  In the present invention, the evaluation value Ei calculated by the evaluation value calculation unit 32 may indicate a vehicle traveling speed. In the case of this configuration, it is possible to reliably estimate the load applied to the wheel by switching the parameter of the estimation calculation formula used in the load estimation calculation unit 35 to one corresponding to the rotation speed region of the wheel.

  Moreover, in this invention, the said evaluation value calculation part 32 is the output of the sensor 22 of the sensor unit 20 provided in the upper surface part and lower surface part of the outer diameter surface of the said fixed side member which becomes a vertical position with respect to a tire ground-contact surface. The difference between the amplitude values of the signals may be calculated as the evaluation value Ei. In the case of this configuration, it is possible to estimate the load with higher accuracy according to the vertical load.

  Further, the evaluation value calculation unit 32 is an amplitude value of an output signal of the sensor 22 of the sensor unit 20 provided on the left surface portion and the right surface portion of the outer diameter surface of the fixed side member that is located on the left and right positions with respect to the tire ground contact surface. May be calculated as the evaluation value Ei. In the case of this configuration, more accurate load estimation can be performed according to the load in the vehicle propulsion direction.

  Further, the evaluation value calculation unit 32 is provided with an evaluation value indicating a vehicle traveling speed, and a sensor unit 20 provided on the upper surface portion and the lower surface portion of the outer diameter surface of the fixed side member that is positioned vertically with respect to the tire ground contact surface. Of the sensor unit 20 provided on the left surface portion and the right surface portion of the outer diameter surface of the fixed-side member that is in the left-right position with respect to the tire ground contact surface. An evaluation value Ei may be calculated by combining any two or more evaluation values obtained as the difference between the amplitude values of the output signals of the sensor 22. In the case of this configuration, more accurate load estimation can be performed according to the load in each direction.

  In the present invention, the predetermined area including the threshold value Ci of the evaluation value Ei for which the calculation correction unit 35a of the load estimation calculation unit 35 corrects the calculation result is an area having a predetermined width m exceeding the threshold value Ci. Further, it may be a region combining a region having a predetermined width m reaching the threshold value Ci. By setting this area, stable correction can be performed by simple calculation.

  In this invention, the calculation correction unit 35a of the load estimation calculation unit 35 synthesizes the two load estimation results in a predetermined area including the threshold value Ci of the evaluation value Ei, A linear sum of the two load estimation results may be obtained. In the case of this configuration, more accurate load estimation can be performed with a simple calculation.

  In this invention, the calculation correction unit 35a of the load estimation calculation unit 35 synthesizes the two load estimation results in a predetermined area including the threshold value Ci of the evaluation value Ei, The two load estimation results may be combined using a quadratic or higher function. In this configuration, more accurate load estimation can be performed.

  In the present invention, three or more of the sensor units 20 are provided, and the load estimating means 30 operates in the vertical direction and the left and right directions acting in the radial direction of the wheel bearing from the output signals of the sensors 20 of the three or more sensor units 20. It is good also as what estimates the load of 3 directions of two radial loads of a direction, and one axial load which acts on an axial direction. With this configuration, the load in each direction can be estimated.

  In the present invention, the sensor unit 20 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 left and right positions with respect to the tire ground contact surface. Four of them may be equally arranged with a phase difference of. By arranging the four sensor units 20 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 with higher accuracy.

  In the present invention, the load estimating means 30 determines the direction of the axial load by using the difference between the amplitude values of the output signals of the sensors 22 of the two sensor units 20 arranged facing the vertical position. The parameter switching unit 34 includes a direction corresponding command unit 34a that switches parameters of the estimation calculation formula of the load estimation calculation unit 35 corresponding to the determination result of the direction determination unit 33. Also good. With this configuration, it is possible to perform load estimation with higher accuracy according to the direction of the axial load acting on the wheel bearing.

  In the present invention, the load estimation means 30 has a pre-processing unit 31 that calculates an average value and an amplitude value of the output signals of each sensor in each sensor unit within a predetermined time, and the estimation calculation of the load estimation calculation unit 35 The equation may calculate the load using only the average value, only the amplitude value, or both the average value and the amplitude value.

In the present invention, the sensor unit 20 has three or more contact fixing portions 21a and two sensors 22, and is adjacent between the first and second contact fixing portions 21a and between the adjacent second and third contact fixing portions 21a. The sensors 22 are respectively mounted between the contact fixing portions 21a, and the distance between the adjacent contact fixing portions 21a or the adjacent sensors 22 in the circumferential direction of the fixed side member is {1/2 + n of the arrangement pitch of the rolling elements 5. (N: integer)} times, and the load estimation means 30 may use the sum of the output signals of the two sensors 22 as an average value.
In the case of this configuration, the output signals of the two sensors 22 have a phase difference of about 180 degrees, and the average value is a value obtained by canceling the fluctuation component due to the rolling element passage. In addition, the amplitude value is an accurate value that more reliably eliminates the effects of temperature and the effects of slippage between the knuckle and flange surfaces.

  In the present invention, each sensor unit 22 may be provided with a temperature sensor 36 and the sensor output signal of the sensor unit 22 may be corrected based on the output signal of the temperature sensor 36. In the case of this configuration, the temperature drift of the sensor output signal of the sensor unit 22 can be corrected, and the load can be estimated with higher accuracy.

  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 A plurality of load detecting sensor units, and the sensor unit is provided with a strain generating member having two or more contact fixing parts fixed in contact with the fixed side member, and attached to the strain generating member. A sensor-equipped wheel bearing having one or more sensors for detecting strain of a strain generating member and provided with load estimation means for estimating a load applied to the wheel from the output signals of the sensors of the plurality of sensor units, The load estimating means includes A load calculation unit that calculates the load acting on the wheel bearing by fitting the output signal of the sensor of the sensor unit to a predetermined estimation calculation formula, and the parameters of the estimation calculation formula from the output signals of the sensors of the plurality of sensor units An evaluation value calculation unit that calculates one or more evaluation values that serve as an index of switching, and a parameter switching unit that compares the evaluation value with a predetermined threshold value and switches a parameter of the estimation arithmetic expression according to the comparison result And when the evaluation value is within a predetermined region including the threshold value, the load calculation unit uses the parameters in the evaluation value regions on both sides sandwiching the threshold value to Since the calculation correction unit corrects the calculation result by combining the two calculated load estimation results, the nonlinear characteristic of the sensor is corrected to reduce the load estimation error. , It is possible to obtain a continuous estimation load in response to various input load state.

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 outward member of the wheel bearing for wheels with the same 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 graph which shows the discontinuity of the estimation calculation formula at the time of switching the parameter of an estimation calculation formula. It is a graph which shows the discontinuity of the estimated load value at the time of switching the parameter of an estimation formula. It is a graph which shows an example of the relationship between the defined area | region containing the threshold value in an evaluation value, and the parameter of the estimation arithmetic expression correct | amended correspondingly. It is a graph which shows the relationship between the evaluation value in this example, and the correction coefficient which correct | amends a parameter. It is a graph which shows the time change of the load calculation result in this example. It is a graph which shows the other example of the relationship between the defined area | region containing the threshold value in an evaluation value, and the parameter of the estimation arithmetic expression correct | amended correspondingly. It is a graph which shows the relationship between the evaluation value in this example, and the correction coefficient which correct | amends a parameter. It is a block which shows an example of a structure of the pre-processing part in a load estimation 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, and (B) is the amplitude of the sensor output signal and the axis at the lower surface 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 an axial load, and the difference of the sensor output signal of an upper and lower sensor unit. It is a figure showing combining the sectional view of the wheel bearing with a sensor concerning other embodiments of this invention, and the block diagram of the conceptual composition of the detection system. It is the front view which looked at the outward member of the wheel bearing for wheels with the same sensor from the outboard side. It is an enlarged plan view of a sensor unit in the wheel bearing with sensor. FIG. 20 is a cross-sectional view taken along the line XX-XX in FIG. 19. It is sectional drawing which shows the other example of installation of a sensor unit. It is explanatory drawing which shows the flow of the load estimation process in a proposal example. It is a wave form chart of a sensor output signal in the example of the proposal. It is a block diagram which shows schematic structure of the load estimation means in another proposal 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. 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.

  Four sensor units 20 are provided on the outer diameter surface of the outer member 1 that is a stationary member. Here, these sensor units 20 are provided on the upper surface portion, the lower surface portion, the right surface portion, and the left surface portion of the outer diameter surface of the outer member 1 that is in the vertical position and the front-rear position with respect to the tire ground contact surface.

  These sensor units 20 are, as shown in an enlarged plan view and an enlarged cross-sectional view in FIGS. 3 and 4, a strain generating member 21 and 2 attached to the strain generating member 21 to detect strain of the strain generating member 21. The two strain sensors 22A and 22B. The strain generating member 21 is made of an elastically deformable metal such as a steel material and is made of a thin plate material of 2 mm or less, and has a planar shape with a strip shape having a uniform width over the entire length, and has notches 21b on both sides. The corner of the notch 21b has an arcuate cross section. The strain generating member 21 has three contact fixing portions 21 a that are contact-fixed to the outer diameter surface of the outer member 1 via the spacers 23. The three contact fixing portions 21 a are arranged in a line in the longitudinal direction of the strain generating member 21. 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 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 sensors 22A and 22B detect the strain in the longitudinal direction around the notch 21b of the strain generating member 21. Note that the strain generating member 21 is plastically deformed even in a state in which an assumed maximum force is applied as an external force acting on the outer member 1 that is a fixed member or an acting force acting between the tire and the road surface. It is desirable not to do so. This is because when the plastic deformation occurs, the deformation of the outer member 1 is not transmitted to the sensor unit 20 and affects the measurement of strain.

  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 unit 20 to the outer diameter surface of the outer member 1, a flat portion 1 b is formed at a location where the spacer 23 is contacted and fixed on the outer diameter surface of the outer member 1.

  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 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 strain sensors 22 </ b> A and 22 </ b> B of the sensor unit 20 are connected to load estimation means 30 that estimates the load applied to the wheel from the output signal. Here, an axial load Fy acting in the axial direction of the wheel, a vertical load Fz acting in the vertical direction, and a load Fx acting in the front-rear direction serving as a driving force and a braking force are estimated. The load estimation unit 30 includes a preprocessing unit 31, an evaluation value calculation unit 32, an Fy direction determination unit 33, a parameter switching unit 34, and a load estimation calculation unit 35.

  The preprocessing unit 31 calculates the average value A and the amplitude value B from the output signals of the two strain sensors 22A and 22B in the sensor unit 20. Specifically, as shown in FIG. 14, the preprocessing unit 31 includes an average value calculation unit 31a including an adder and an amplitude calculation unit 31b including a subtractor. The average calculation unit 31a includes two distortion sensors 22A and 22B. Is calculated and the sum is taken out as an average value. The amplitude calculator 31b 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.

  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. Even when the bearing is stopped, the output signals a and b of the strain sensors 22A and 22B are affected by the position of the rolling element 5. That is, when the rolling element 5 passes the position closest to the strain sensors 22A and 22B in the sensor unit 20 (or when the rolling element 5 is at that position), the amplitude of the output signals a and b of the strain sensors 22A and 22B. Becomes a maximum value, and decreases as the rolling element 5 moves away from the position as shown in FIGS. 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 addition, the amplitudes of 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, in the pre-processing unit 31, the sum of the amplitudes of the output signals a and b of the two strain sensors 22A and 22B in each sensor unit 20 is the above-described average value A, and the amplitude difference (absolute value) | a -B | is time-averaged to obtain 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, among the three contact fixing portions 21a arranged in the circumferential direction of the outer diameter surface of the outer member 1 which is a fixed side member, the interval between the two contact fixing portions 21a located at both ends of the array is changed. It is set to be the same as the arrangement pitch P of the moving bodies 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 pre-processing unit 31 outputs the output signals a and b of the two strain sensors 22A and 22B. The average value A obtained as the sum is obtained by canceling the fluctuation component due to the passage of the rolling element 5. 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 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.

  In the evaluation value calculation unit 32, for example, the amplitude value B of each sensor output signal calculated by the preprocessing unit 31 within a predetermined time is used as an index for switching parameters of the estimation calculation formula used in the load estimation calculation unit 35 to be described later. One or more evaluation values Ei are calculated. The subscript i in this case identifies a plurality of parameter switching conditions. For example, the sum of the amplitude values B may be calculated as an example of obtaining the evaluation value Ei indicating the vehicle traveling speed. In addition, as the evaluation value Ei, the amplitude value B obtained from the sensor output signal of the sensor unit 20 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. The difference may be calculated. Further, as the evaluation value Ei, the amplitude value B obtained from the sensor output signal of the sensor unit 20 provided on the left surface portion and the right surface portion of the outer diameter surface of the outer member 1 that is in the left-right position with respect to the tire ground contact surface. The difference may be calculated. Furthermore, a combination of two or more evaluation values selected from the plurality of evaluation values Ei described above may be calculated as the evaluation value.

  In the parameter switching unit 34, the evaluation value Ei is compared with a predetermined threshold value Ci, and the parameter of the estimation formula is switched according to the comparison result.

  The Fy direction discriminating unit 33 discriminates the direction of the axial load Fy as follows. As described above, during the rotation of the wheel bearing, the amplitude of the sensor output signal of the sensor unit 20 has a periodic change close to a sine wave, but the amplitude value is an axial load (moment force) Fy. Varies depending on the size of FIG. 15A shows the sensor output of the sensor unit 20 disposed on the upper surface portion of the outer diameter surface of the outer member 1, and FIG. 15B is disposed on the lower surface portion of the outer diameter surface of the outer member 1. The sensor output of the sensor unit 20 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 signal. From these figures, when the axial load Fy is in the + direction, the load of each rolling element 5 becomes small at the upper surface portion of the outer diameter surface of the outer member 1 (that is, the difference between the maximum value and the minimum value of the amplitude becomes small). It can be seen that the outer member 1 increases at the lower surface of the outer diameter surface (that is, the difference between the maximum value and the minimum value of the amplitude 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. 16 is a graph showing the relationship between the difference between the amplitudes of the sensor output signals of the upper and lower sensor units 20 and the direction of the axial load Fy.

  Therefore, the Fy direction discriminating unit 33 obtains the above difference in the amplitude of the sensor output signal of the sensor unit 20 disposed on the outer diameter surface upper surface portion and the outer diameter surface lower surface portion of the outer member 1, and compares these values. Thus, the direction of the axial load Fy is determined. That is, the difference between the maximum value and the minimum value of the sensor output signal on the upper surface portion of the outer diameter surface of the outer member 1 is small, and the maximum value and the minimum value of the sensor output signal of the sensor unit 20 on the lower surface portion of the outer diameter surface of the outer member. When the difference is large, the Fy direction determination unit 33 determines that the direction of the axial load Fy is the + direction. Conversely, the difference between the maximum value and the minimum value of the sensor output signal of the sensor unit 20 on the upper surface of the outer diameter surface of the outer member 1 is large, and the sensor output signal of the sensor unit 20 on the lower surface of the outer diameter surface of the outer member 1. When the difference between the maximum value and the minimum value is small, the Fy direction determination unit 33 determines that the direction of the axial load Fy is the negative direction. Correspondingly, the parameter switching unit 34 selects the parameter of the calculation estimation formula by reflecting the determination result of the Fy direction determination unit 33 when the load calculation unit 35 calculates the axial load Fy. The direction corresponding command part 34a which gives a command such as to the load calculation part 35 is provided.

  The load estimation calculation unit 35 calculates and estimates the loads Fz, Fx, Fy acting on the wheel bearing by fitting the sensor output signal of each sensor unit 20 to a predetermined estimation calculation formula. In this case, only the average value A obtained by the preprocessing unit 31 or only the amplitude value B may be used as a variable of the estimation formula, or both the average value A and the amplitude value B may be used. When the evaluation value Ei is in a predetermined region including the threshold value Ci, the load calculation unit 35 uses the parameters in the evaluation value regions on both sides including the threshold value Ci to calculate the estimated equation. A calculation correction unit 35a that corrects the calculation result by combining the two calculated load estimation results is provided.

  By the way, when the parameter switching unit 34 switches the parameter of the estimation calculation formula used in the load estimation calculation unit 35 according to a plurality of conditions, the estimated load value obtained from the calculation result is not changed by switching as shown in FIG. May be continuous. In FIG. 7, the horizontal axis represents the evaluation value Ei used for parameter switching, and the vertical axis represents the estimated load value calculated. In this state, the time-series load estimation result is as shown in FIG. 8, and a discontinuous portion is generated. In FIG. 8, the horizontal axis is the time axis, and the vertical axis is the estimated load value calculated.

In a control system that performs various operations based on an estimated load value, such as a control system in an automobile, it is not preferable that the estimated load value changes discontinuously as described above.
Therefore, as a measure for eliminating this discontinuity, the calculation correction unit 35a provided in the load estimation calculation unit 35 performs the following processing.
First, a boundary region [Ci-m, Ci + m] having a width of 2 × m is provided, for example, as shown in FIG. In this region, a process for calculating an estimated load in consideration of the discontinuity of the estimated load values on both sides of the evaluation value Ei across the threshold value Ci is performed.
For example, the parameter of the estimation formula in the left area of the threshold value Ci is M1, and the parameter of the estimation formula in the right area is M2. Assuming that the estimated load values calculated with the respective parameters are F (M1) and F (M2), the estimated estimation calculation formula F is generated by synthesizing both estimation calculation results in the region as shown in the following equation. .
F = αF (M1) + βF (M2) (1)
α + β = 1 (2)
Here, α and β satisfy the relationship of Expression (2), and indicate the ratio of the estimated load F (M1) and the ratio of the estimated load F (M2), respectively. For example, α and β may change linearly within the boundary region as shown in FIG. In this case, the estimated load value in the boundary region changes in a polygonal line as shown in FIG. Here, if the increment from the threshold value Ci is x, the relationship between α and β is as follows.
α / β = (mx) / (m + x) (3)
In addition, the ratio of the estimated loads F (M1) and F (M2) may be a combined ratio represented by a quadratic curve as shown in FIG. In this case, the estimated load value in the boundary region changes smoothly as shown in FIG. By such processing in the calculation correction unit 35a, the estimated load value calculated in the load calculation unit 35 has continuity as shown as a time-series change in FIG. As a result, there is no discontinuous portion in the estimated load value to be calculated while switching the parameters of the estimated calculation formula used in the load calculation unit 35 so as to be suitable for the running state of the vehicle. It becomes easy to adapt to the control system which improves and performs various operation based on the estimated load.

  The type of estimated load to be output is not limited to the above-described three-direction loads Fx, Fy, and Fz, but the parameters of the estimation calculation formulas F1 and F2 in the load estimation calculation unit 35 are added to obtain the steering moment. It can also be configured to calculate Mz and the moment MX around the X axis.

  Further, as shown in FIG. 3, a temperature sensor 36 may be attached to the sensor unit 20, and each sensor output signal may be corrected by a detection signal of the temperature sensor 36. FIG. 14 shows a configuration example in which the temperature correction means 37 corrects the average value A calculated as the sum of the output signals of the two sensors 22A and 22B in the preprocessing unit 31 using the detection signal of the temperature sensor 36. Yes. 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 20 fluctuates due to thermal expansion or the like even if the load does not change. Remains. Therefore, if each sensor output signal is corrected by the detection signal of the temperature sensor 36 as described above, a detection load error due to 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 three contact fixing portions 21a of the strain generating member 21 in the sensor unit 20 are fixed in contact with the outer member 1, the strain of the outer member 1 is easily transmitted to the strain generating member 21 in an enlarged manner. The distortion is detected with high sensitivity by the distortion sensors 22A and 22B, and the hysteresis generated in the output signal is also reduced.

  In particular, in the load estimation unit 30 having the load calculation unit 35 that calculates the load acting on the wheel bearing by fitting the sensor output signal of each sensor unit 20 to a predetermined estimation calculation formula, the sensors of the plurality of sensor units 20 are used. One or more evaluation values Ei that serve as an index for switching the parameter of the estimation formula are calculated by the evaluation value calculation unit 32 from the output signal, and the evaluation value Ei is determined by the parameter switching unit 34. And the parameter is switched according to the comparison result. Further, in the load calculation unit 35, when the evaluation value Ei is within a predetermined region sandwiching the threshold value Ci, the correction calculation unit 35a uses the parameters in the evaluation value regions on both sides sandwiching the threshold value Ci. The calculation result is corrected by combining the two load estimation results calculated by the estimation calculation formula. Therefore, it is possible to obtain continuous estimated loads according to various input load states while correcting the nonlinear characteristics of the strain sensors 22A and 22B to reduce the load estimation error.

  17 to 21 show another embodiment of the present invention. In this sensor-equipped wheel bearing, each sensor unit 20 is configured as follows in the embodiment shown in FIGS. In this case, as shown in the enlarged sectional view of FIG. 20, the sensor unit 20 includes a strain generating member 21 and one strain sensor 22 that is attached to the strain generating member 21 and detects the strain of the strain generating member 21. Become. The strain generating member 21 has two contact fixing portions 21 a that are fixed to the outer diameter surface of the outer member 1 through spacers 23 at both ends. In addition, as shown in a cross-sectional view in FIG. 15, grooves 1 c are provided at two intermediate portions where the two 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 portion where the notch 21 b of the strain generating member 21 is located may be separated from the outer diameter surface of the outer member 1.

  Since only one strain sensor 22 is attached to each sensor unit 20, the pre-processing unit 31 of the load estimating means 30 observes the output signal of one strain sensor 22 in each sensor unit 20 for a certain period of time. Then, an average value A and an amplitude value B of the sensor output signal are obtained. Other configurations are substantially the same as those in the previous embodiment.

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 ... Sensor unit 21 ... Strain generating member 21a ... Contact fixing | fixed part 22, 22A, 22B ... Strain sensor 30 ... Load estimation means 31 ... Pre-processing unit 32 ... evaluation value calculation unit 33 ... Fy direction determination unit 34 ... parameter switching unit 34a ... direction corresponding command unit 35 ... load estimation calculation unit 35a ... calculation correction unit 36 ... temperature sensor

Claims (14)

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 plurality of load detection sensor units are provided on the fixed side member of the outer member and the inner member, and the sensor unit has two or more contact fixing portions fixed in contact with the fixed side member. A load that has a strain generating member and one or more sensors that are attached to the strain generating member and detect strain of the strain generating member, and that estimates a load applied to the wheel from the output signals of the sensors of the plurality of sensor units A wheel bearing with a sensor provided with an estimation means,
The load estimation means includes a load estimation calculation unit that calculates a load acting on the wheel bearing by fitting an output signal of the sensor of each sensor unit to a predetermined estimation calculation formula, and sensors of the plurality of sensor units. An evaluation value calculation unit that calculates one or more evaluation values that serve as an index for switching parameters of the estimation formula from the output signal, and the evaluation value is compared with a predetermined threshold value, and the estimation is performed based on the comparison result. A parameter switching unit that switches a parameter of the calculation formula, and the load estimation calculation unit is configured to perform evaluation in both evaluation value regions sandwiching the threshold value when the evaluation value is within a predetermined region including the threshold value. A sensor having a calculation correction unit that corrects a calculation result by combining two load estimation results calculated by the estimation calculation formula using the parameters of Wheel bearing.   The sensor-equipped wheel bearing according to claim 1, wherein the evaluation value calculated by the evaluation value calculation unit indicates a vehicle traveling speed.   In Claim 1, The said evaluation value calculation part is an amplitude value of the output signal of the sensor of the sensor unit provided in the upper surface part and lower surface part of the outer diameter surface of the said fixed side member which becomes a vertical position with respect to a tire ground-contact surface The wheel bearing with a sensor which calculates the difference of as said evaluation value.   In Claim 1, The said evaluation value calculation part is an amplitude value of the output signal of the sensor of the sensor unit provided in the left surface part and right surface part of the outer diameter surface of the said fixed side member which becomes a right-and-left position with respect to a tire ground-contact surface. The wheel bearing with a sensor which calculates the difference of as said evaluation value.   2. The sensor unit according to claim 1, wherein the evaluation value calculation unit includes an evaluation value indicating a vehicle traveling speed, and an upper surface portion and a lower surface portion of an outer diameter surface of the stationary member that are vertically positioned with respect to a tire contact surface. Of the sensor unit provided on the left surface portion and the right surface portion of the outer diameter surface of the fixed-side member which is the left-right position with respect to the tire ground contact surface, and the evaluation value obtained as the difference in the amplitude value of the output signal of the sensor of A sensor-equipped wheel bearing that calculates, as an evaluation value, a composite of any two or more evaluation values obtained as a difference between amplitude values of output signals.   6. The defined region including the threshold value of the evaluation value with which the calculation correction unit of the load estimation calculation unit corrects a calculation result exceeds the threshold value according to claim 1. A wheel bearing with sensor, which is a region obtained by combining a region having a predetermined width and a region having a predetermined width reaching a threshold value.   7. The calculation correction unit of the load estimation calculation unit according to claim 1, wherein the calculation correction unit of the load estimation calculation unit synthesizes the two load estimation results in a predetermined region including the threshold value of the evaluation value. The correction of the calculation result is a wheel bearing with sensor for obtaining a linear sum of the two load estimation results.   7. The calculation correction unit of the load estimation calculation unit according to claim 1, wherein the calculation correction unit of the load estimation calculation unit synthesizes the two load estimation results in a predetermined region including the threshold value of the evaluation value. The correction of the calculation result is a sensor-equipped wheel bearing in which the two load estimation results are synthesized using a second-order or higher function.   In any 1 item | term of Claim 1 thru | or 8, The said sensor unit is provided 3 or more, The said load estimation means is the radial direction of the wheel bearing from the output signal of the sensor of the said 3 or more sensor unit. A sensor-equipped wheel bearing for estimating a load in three directions of two radial loads acting in an up-down direction and a left-right direction and one axial load acting in an axial direction.   The sensor unit according to any one of claims 1 to 9, 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.   In Claim 6, the said load estimation means has a direction discriminating part which discriminate | determines the direction of an axial load using the difference of the amplitude value of the output signal of the sensor of two sensor units arrange | positioned facing an up-down position. And the parameter switching unit includes a direction corresponding command unit that switches a parameter of an estimation calculation formula of the load estimation calculation unit corresponding to a determination result of the direction determination unit.   12. The load estimation unit according to claim 1, wherein the load estimation unit includes a preprocessing unit that calculates an average value and an amplitude value within a predetermined time of an output signal of each sensor in each sensor unit, The estimation formula of the load estimation calculation unit is a sensor-equipped wheel bearing that calculates the load using only the average value, only the amplitude value, or both the average value and the amplitude value.   13. The sensor unit according to claim 12, wherein the sensor unit has three or more contact fixing portions and two sensors, and is adjacent between the first and second contact fixing portions adjacent to each other and between the second and third contact fixing portions adjacent to each other. Each sensor is mounted between the adjacent fixed contact portions or the interval between the adjacent sensors in the circumferential direction of the fixed side member is {1/2 + n (n: integer)} times the arrangement pitch of the rolling elements. The load estimating means uses a sum of output signals of the two sensors as an average value.   14. The sensor-equipped wheel according to claim 1, wherein a temperature sensor is provided in each sensor unit, and the output signal of the sensor of the sensor unit is corrected based on the output signal of the temperature sensor. bearing.

Images