JP2012037471A - Bearing for wheel with sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing for a wheel with a sensor for achieving switching of a calculation method corresponding to a vehicle speed by simple configurations without installing any additional sensor or the like, and for improving estimating accuracy of a load to be imposed on a wheel, and for achieving compactification, simplification of configurations, and improvement in reliability.SOLUTION: This bearing for a wheel with a sensor includes: a sensor unit in a fixed side member between an external member and an internal member of the bearing for the wheel. Load estimation means 31 is provided for estimating a load from a sensor output signal of the sensor unit. The load estimation means 31 includes: a rotational speed area determination unit 32 for determining a rotational speed area of the wheel from the total sum of an amplitude value of each sensor output signal; a load estimation arithmetic unit 35 for calculating and estimating the load by applying each sensor output signal to an estimation arithmetic formula; and a parameter switching unit 34a for switching the parameter of the estimation arithmetic formula according to the determined rotational speed area.

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. 18 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. 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.

  However, since this configuration uses rotational speed information, it is necessary to provide a separate rotational sensor or receive rotational speed information from a host ECU or the like, which causes a new problem that the number of sensors and wiring increases.

  The object of the present invention is to provide a simple structure and switch the calculation method according to the vehicle speed without providing an additional sensor or the like, improve the estimation accuracy of the load applied to the wheel, It is intended to provide a sensor-equipped wheel bearing that can be reduced in size by reducing the installation space, and that can improve reliability by simplifying the configuration.

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 estimating means 30 calculates the sum of values indicating the amount of variation within a predetermined time of the output signal of each sensor 22 in each sensor unit 20, and the rotational speed of the wheel is determined using the calculated value as an evaluation value. The rotation speed region discriminating unit 32 for discriminating which one of the plurality of rotation speed regions is included, and the output signal of the sensor 22 of each sensor unit 20 is applied to a predetermined estimation calculation formula and acts on the wheel bearing. A load estimation calculation unit 34 that calculates a load, and a load condition determination unit that switches parameters in the estimation calculation formula used in the load estimation calculation unit 35 according to the rotation speed region determined by the rotation speed region determination unit 32 34. Specifically, the above “total sum of values indicating variation amount” is, for example, a sum of standard deviations of input data.

  According to this configuration, the load estimating means 30 calculates the sum of the values indicating the amount of variation in the sensor output signal of each sensor unit 20, and uses the calculated value as an evaluation value in the rotational speed region determination unit 32 to determine the rotational speed region of the wheel. Is determined. The load condition determination unit 34 switches the parameters of the estimation calculation formula used in the load estimation calculation unit 35 in accordance with the determined rotational speed region. Therefore, it is possible to reliably estimate the load applied to the wheel by switching from the sensor output signal of the sensor unit 20 to the arithmetic processing according to the wheel rotation speed region without detecting the wheel rotation speed. For this reason, without providing an additional sensor or the like, the calculation method can be switched according to the vehicle speed with a simple structure, and the estimation accuracy of the load applied to the wheel can be improved. Further, the installation space for sensors and wiring can be reduced and the size can be reduced, and the reliability can be improved by simplifying the configuration.

  In the present invention, the rotational speed region discriminating unit 32 compares the evaluation value with a predetermined threshold value, so that the wheel is in a predetermined normal rotational speed region or a low rotational speed region. It is good also as what discriminate | determines. Since the rotation speed region is two regions, the calculation method can be switched according to the vehicle speed with a simpler structure.

  In the present invention, the rotational speed region discriminating unit 32 compares the evaluation value with two or more predetermined threshold values, and the wheel is selected from among the three or more rotational speed regions that are determined. It is good also as what discriminate | determines whether it exists in this rotation speed area | region. By switching the parameters in the estimation calculation formula by dividing into three or more rotation speed regions, it is possible to estimate the load with better estimation accuracy.

  In the present invention, the load condition determination unit 34, when the rotation speed region determination unit 32 determines that the rotation speed region is the lowest low speed rotation region, the estimation calculation used by the load estimation calculation unit after a predetermined time has elapsed. The parameter of the expression may be switched to a predetermined parameter. In other words, the parameter of the estimation calculation formula is reset to the initial value after a lapse of a fixed time after it is determined that the rotation speed range is the lowest. This is particularly effective when the rotation speed region discriminating unit 32 performs processing according to the axial load. If the speed is almost stationary and low, the parameters may not be switched according to changes in the axial load, etc., but by resetting the parameters of the estimation formula to the initial values, the load estimation accuracy at low speed is improved. Can be made.

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

  In the present invention, the sensor unit is arranged at 90 degrees in the circumferential direction on the upper surface portion, the lower surface portion, the right surface portion, and the left surface portion of the outer diameter surface of the fixed side member that is in the vertical position and the horizontal position with respect to the tire ground contact surface. Four of them may be equally arranged with a phase difference. By arranging the four sensor units 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.

  When the four sensor units 20 are arranged in this way, the load estimation calculation unit 35 has a plurality of the estimation calculation formulas, and a direction corresponding command unit 35a for selecting the plurality of estimation calculation formulas according to a selection command. The load estimation means 30 includes a direction determination unit 33 that determines the direction of the axial load by using the difference in the amplitude value of the output signals of the sensors of the two sensor units 20 disposed opposite to the vertical position. The load condition determination unit 32 corresponds to the determination result of the direction determination unit 33 and the parameter switching unit 34a for switching the parameter of the estimation calculation formula used in the load estimation calculation unit 35. A direction corresponding command unit 24b that gives the selection command to the direction corresponding command unit 35a of the load estimation calculation unit 35 may be included. 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 this case, when the rotation speed region determined by the rotation speed region determination unit 32 is a low speed region, an equation using an average value is adopted as the estimation calculation formula in the load estimation calculation unit 35, and the rotation speed region is a normal one. In the case of the velocity region, it is desirable to employ an equation using an amplitude value or an equation using an average value and an amplitude value as an estimation arithmetic expression.

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, a temperature sensor may be provided in each sensor unit 22, 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 more accurately.

  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 The sum of the values indicating the amount of variation within a certain time of the output signal of each sensor in the unit is calculated, and the rotation speed of the wheel is included in any of a plurality of defined rotation speed areas using the calculated value as an evaluation value. A rotational speed region discriminating unit for determining whether or not, a load estimation calculating unit for calculating a load acting on a wheel bearing by applying an output signal of a sensor of each sensor unit to a predetermined estimation arithmetic expression, and the rotational speed region A load condition determination unit that switches parameters in the estimation calculation formula used in the load estimation calculation unit in accordance with the rotation speed region determined by the determination unit, and has a simple structure without providing an additional sensor or the like. Therefore, the calculation method can be switched according to the vehicle speed, the estimation accuracy of the load applied to the wheel can be improved, and the installation space for sensors and wiring can be reduced. Compact can of, also it is possible to improve the reliability by simplifying the configuration.

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 block diagram which shows the structure of a load estimation means. It is explanatory drawing of the arithmetic processing operation | movement in the 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. It is XIV-XIV arrow sectional drawing in FIG. It is sectional drawing which shows the other example of installation of a sensor unit. It is a block diagram which shows the structure of a load estimation means. 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 units 20 </ b> A and 20 </ b> B to the outer diameter surface of the outer member 1, a flat portion 1 b is formed at a location where the spacer 23 is contacted and fixed on the outer diameter surface of the outer member 1.

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

  Various strain sensors 22 can be used. For example, the strain 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. As shown in the block diagram of FIG. 7, the load estimation unit 30 includes a preprocessing unit 31, a rotation speed region determination unit 32, an Fy direction determination unit 33, a load calculation condition determination unit 34, and a load estimation calculation unit. 35.

Before describing the configuration of each part of the load estimating means 30, an overview of the overall operation will be described.
First, from the output signals of the sensors 22 installed at a plurality of positions on the outer member 1, the magnitudes of fluctuation components due to the rolling elements 5 passing along with the rotation are extracted by calculation.
In the above arithmetic processing, the standard deviation is obtained as the value σi indicating the variation of the sensor signal within a certain time (T). In addition to this, a mean square value or a variance value around the average value may be used, and these values can be used as numerical values indicating the amplitude of the fluctuation component by the rolling element 5 in the data within a predetermined time (T). .
The value of T is set in consideration of the response time required for the sensor 22.
The obtained variation value σi of each sensor signal is summed up for all sensor signals to obtain an evaluation value E.
E = Σσi
The sensors 22 are arranged on the top, bottom, left, and right of the outer member 1, and when the wheel rotates, the fluctuation component due to the rolling element 5 is superimposed on any sensor signal.
Therefore, by setting an appropriate threshold value Vth, the following determination can be made.
E> threshold value Vth: Amplitude calculation processing is possible in the rotation state → The normal running state calculation processing is executed. E <threshold value Vth: Amplitude calculation processing is almost impossible in a stationary state. → Calculation processing without using amplitude is executed.
In this method, it is not necessary to detect the rotational speed, and the load estimation calculation method can be switched only by the arithmetic processing from the signal state of the strain sensor 22.

Next, the detail of each part which comprises the load estimation means 30 is demonstrated.
The preprocessing unit 31 calculates the sum Sum of the output signals of the two strain sensors 22A and 22B in the sensor unit 20, and calculates the average value A and the amplitude value B of each sensor output signal at a preset time T. . As the amplitude value B, a variation value σi (σi is a standard deviation or a mean square value around the average value or a variance value), which is a value indicating the variation of the sensor output signal within the set time T, is obtained here. The magnitude of the time T determined for calculating the average value A and the amplitude value B of each sensor output signal in the preprocessing 31 is arbitrarily set appropriately by a designer or the like in consideration of the required response time. Is done.
A standard deviation is preferably used as the variation value σi.
If the rotation speed of the wheel is high and the fixed time (T) set for calculation is a time at which at least one cycle of the fluctuation of the sensor signal due to the passing of the rolling element can be observed, it can be obtained by calculation. The standard deviation is equivalent to the amplitude component due to the passage of the rolling elements. As a result, this value can be used as the amplitude value B for the load estimation calculation. On the other hand, when the rotational speed of the wheel is low, the fluctuation component of the sensor due to the passage of the rolling element within the time T is not observed, and the numerical value is not proportional to the amplitude value. In this case, the obtained standard deviation cannot be used as the amplitude value B. The standard deviation at this time is a small value compared with the case of the sufficient rotational speed.
The strain sensors installed at several locations of the bearing output different signals depending on the state of the applied load, so the amplitude component due to the passing of the rolling elements is not superimposed on all signals in the same way. The evaluation value E obtained by summing the signal variation values σi for all sensor signals shows a small value as the rotational speed decreases.

  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 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 output signals a and b of the two strain sensors 22A and 22B calculated by the preprocessing unit 31 described above. The sum Sum of the amplitudes of b is obtained by canceling the fluctuation component due to the passage of the rolling element 5.

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 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.

  The rotational speed region discriminating unit 32 discriminates the region of the rotational speed of the wheel using the total E = Σσi of the variation values σi of the sensor output signals calculated by the preprocessing unit 31 as an evaluation value. Here, the evaluation value E is compared with a predetermined threshold value Vth (which is arbitrarily set to an appropriate value), and the wheel is in a normal rotation speed region or a low rotation speed region. It is determined whether it is in. The determination output R of the rotation speed region determination unit 32 at this time is represented by a binary value (0: E <Vth, 1: E> Vth), and is used to determine whether the rotation speed is sufficient to obtain the amplitude value. It is said.

  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 9A 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. 9B 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 amplitude of the sensor output signal, and the maximum value and the minimum value represent the maximum value and the minimum value of the amplitude. 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. 10 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 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 amplitude 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. On the contrary, the difference between the maximum value and the minimum value of the sensor output signal of the sensor unit 20 on the outer surface of the outer member 1 is large, and the sensor of the sensor unit 20 on the lower surface of the outer member 1 is large. When the difference between the maximum value and the minimum value of the amplitude of the output signal is small, the Fy direction determination unit 33 determines that the direction of the axial load Fy is the negative direction.

The load estimation calculation unit 35 calculates and estimates the loads Fz, Fx, and Fy acting on the wheel bearing by applying the sensor output signal of each sensor unit 20 to a predetermined estimation calculation formula. Here, two types of estimation arithmetic expressions are used for the calculation. One type of estimation formula F1 is
F1 = M1 (c) × [Sum] (1)
The other one type of estimation formula F2 is
F2 = M2 (c) × [A] + M3 (c) × [B] (2)
It is said. M1 (c), M2 (c), and M3 (c) are parameters of the estimation calculation formula, and are different for each load Fz, Fx, and Fy to be calculated and estimated. That is, the estimation formula F1 is obtained by multiplying the sum value Sum calculated by the preprocessing unit 31 as a variable and the parameter M1 (c). Since the sum value Sum can be accurately calculated even when the wheel is in a low speed state, this estimation formula F1 is used for low speed use. The estimation calculation formula F2 uses the average value A and the amplitude value B calculated by the preprocessing unit 31 as variables, and multiplies them by parameters M2 (c) and (M3 (c), respectively. Since the amplitude value B can be accurately calculated in the normal rotation state of the wheel, the estimation calculation formula F2 is used for normal rotation.
The load estimation calculation unit 35 includes a direction corresponding command unit 35a that selects the plurality of estimation calculation formulas F1 and F2 by a selection command.

The load calculation condition determination unit 34 includes a parameter switching unit 34a and a direction corresponding command unit 34b. The parameter switching unit 34a determines each parameter M1 (c) of the estimation calculation formulas F1 and F2 in the load estimation calculation unit 35 according to the output R of the rotation speed region determination unit 32 and the output sign (Fy) of the Fy direction determination unit 33. , M2 (c) and M3 (c) have a function of generating a signal C for designating switching. Thereby, according to the output R of the rotation speed region discriminating unit 32 and the output sign (Fy) of the Fy direction determining unit 33, the parameters M1 (c), M2 ( c) and M3 (c) are switched to optimum values.
The direction corresponding command unit 34b outputs any one of the low-speed estimation calculation formula F1 and the normal rotation estimation calculation formula F2 in the load estimation calculation unit 35 according to the output R of the rotation speed region determination unit 32. It has a function of generating a signal FSW (0: for low speed (R = 0), 1: for normal rotation (R = 1)) for determining whether to use. The determination signal FSW is input as a selection command to the direction corresponding command unit 35 a of the load estimation calculation unit 35, whereby the load estimation calculation unit 35 is rotated according to the output R of the rotation speed region determination unit 32. The output of the estimation formula corresponding to is selected as the load value.

FIGS. 8A to 8E show examples of specific operations of the load estimating means 30 in accordance with the traveling state as waveform diagrams. In these waveform diagrams, the horizontal axis represents time t, and the vertical axis represents the wheel rotation speed v, the evaluation value E, the rotation speed region determination output R, the Fy direction determination output sign (Fy), and the parameter switching designation signal C. It shows, and it shows from a stationary state until it starts driving | running | working and it stops again. The state notation of the parameter switching designation signal C in the figure shows the following state.
C [1]: (R = 0, FSW = 0, sign (−)): The parameter for the state of Fy <0 is used in the low speed state.
C [2]: (R = 1, FSW = 1, sign (−): The parameters for the state of Fy <0 in the normal rotation state are used.
C [3]: (R = 1, FSW = 1, sign (+): The parameters for the state of Fy> 0 in the normal rotation state are used.
C [4]: (R = 0, FSW = 1, sign (+): Use parameters for the state of Fy> 0 in the low speed state.

That is, the following determination process is performed in the operation example of FIG.
When R = 1, it is determined that amplitude calculation processing is possible in the rotation state, and calculation processing in the normal running state is executed (parameters are switched according to the Fy direction, using the moving average value A and amplitude value B of each sensor output signal) Load estimation).
When R = 0, it is determined that the amplitude calculation process is almost impossible in the stationary state, and the calculation process for low speed using only the sum value Sum is executed without using the amplitude (the parameter is the sensor unit at the vertical position) 20) Since the Fy direction cannot be determined based on the amplitude difference of the 20 sensor output signals, a fixed value is used. Since the moving average value A and the amplitude value B of each sensor output signal cannot be used, the load is estimated using the sum value Sum).

  After R = 0 in FIG. 8, since there is not a sufficient rotational speed for obtaining the amplitude value, the output sign (Fy) of the Fy direction discriminating unit 33 cannot be updated, and the last value is Will be retained. However, as shown in part Q of the figure, the output sign (Fy) of the Fy direction determination unit 33 may be reset to the initial value after a certain time t1 has elapsed. That is, after the Fy direction determination becomes impossible, the previous direction determination value is maintained until a certain time t1, but thereafter, processing may be performed so as to return to a predetermined initial state. As a result, when the low speed state continues, the parameter always returns to the same parameter (C [1] in this example). Therefore, if it is set to return to a parameter having a high appearance probability under these conditions, it is possible to stabilize the load estimation accuracy at a low speed. The fixed time t1 is arbitrarily determined.

  In addition to the above-described determination conditions, the parameters of the estimation calculation expressions F1 and F2 may be switched more finely according to the detected magnitude of the axial load Fy. By finely dividing the conditions, the influence due to the nonlinearity of the sensor output signal can be reduced, and the load estimation accuracy can be further improved. Further, the output R of the rotation speed region determination unit 32 may be configured to be multivalued using a plurality of threshold values instead of the binary value of 0/1. The load estimation accuracy can be improved by further dividing the parameters at the time of low-speed rotation and performing calculation processing suitable for the running state.

  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. 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, the load estimating means 30 calculates the sum Σσi of the variation values σi of the sensor output signals of the respective sensor units 20, and uses the calculated value as an evaluation value E to determine the rotational speed region of the wheel by the rotational speed region determination unit 32. Then, the parameter switching unit 34a switches the parameter of the estimation calculation formula used in the load estimation calculation unit 35 in accordance with the determined rotation speed region, and the rotation speed determined in the estimation calculation formula of the load estimation calculation unit 35 is determined. Since the calculation result of the estimated calculation formula corresponding to the area is selected and output by the direction corresponding command unit 34b, the sensor output signal of the sensor unit 20 is switched to the calculation process corresponding to the rotation speed area of the wheel. The load applied to the wheel can be accurately estimated.

  Further, in the above arithmetic processing, since it is possible to determine the switching of the arithmetic method using only the evaluation value E obtained by obtaining the variation from all the sensor output signals and mechanically summing them, processing is easy and processing overhead occurs. do not do. In addition, since the determination of switching of the calculation method using the evaluation value E is performed using the threshold value Vth, it is possible to perform the divisional adjustment to the optimum rotation speed region by setting the threshold value Vth. Further, there is no need to install a sensor for detecting rotation or to input rotational speed information such as the rotational speed of a wheel from a host ECU or the like, and the configuration space can be reduced by reducing the installation space for sensors and wiring. Since the configuration is simplified, the reliability can be improved.

  11 to 16 show another embodiment of the present invention. In this sensor-equipped wheel bearing, in the embodiment shown in FIGS. 1 to 10, each sensor unit 20 is configured as follows. In this case, as shown in the enlarged sectional view of FIG. 14, 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 does not calculate the sum value Sum in the previous embodiment, and averages the output signals of the sensors. A value A and an amplitude value B (standard deviation σi (or variance) indicating variations in sensor output signal within time T) are obtained. The load estimation calculation unit 35 uses one type of estimation calculation formula F3. This estimation calculation formula F3 has the same format as the estimation calculation formula F2 for normal rotation in the previous embodiment. That is, the average value A and the amplitude value B are variables, and these are multiplied by the parameters M4 (c) and M5 (c). The load calculation condition determination unit 34 includes a parameter switching unit 34a, and the parameter M4 (c) of the estimation calculation formula F3 according to the output sign (Fy) of the Fy direction determination unit 33 and the output R of the rotation speed region determination unit 32. , M5 (c). Here, when the output R of the rotation speed region determination unit 32 indicates that it is a normal rotation region, the parameter switching unit 34a uses the parameter switching designation signal C as the parameter M4 (c), M5 (c) which is not zero. Generate a signal to switch to the value of. That is, at the time of normal rotation, the estimation calculation formula F3 is used as an estimation calculation formula that varies the average value A and the amplitude value B. On the other hand, when the output R of the rotational speed region determination unit 32 indicates that the rotational region is the low speed rotational region, the parameter switching unit 34a sets the parameter M5 (c) to zero and sets the parameter M4 (c) as the parameter switching designation signal C. A signal for switching to a predetermined value other than zero is generated. That is, since the amplitude value B cannot be calculated in the pre-processing unit 31 at low speed, the estimation calculation formula F3 is used as an estimation calculation expression using only the average value A as a variable. Output as a load value. That is, the parameter switching unit 34a in this embodiment also functions as the direction corresponding command unit 34b in the previous embodiment.
In this low speed calculation, only the average value A is used, so that a calculation error increases. Therefore, a signal indicating that the low speed calculation mode is set may be output separately. By switching the processing method in a control circuit or the like that uses the signal according to the state of the signal, it is possible to reduce the influence of the detection error.

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 ... rotational speed region determination unit 33 ... Fy direction determination unit 34 ... load calculation condition determination unit 34a ... parameter switching unit 34b ... direction corresponding command unit 35 ... load estimation calculation unit 35a ... calculation formula selection unit 36 ... temperature sensor

Claims (10)

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 estimating means calculates a total sum of values indicating a variation amount within a predetermined time of an output signal of each sensor in each sensor unit, and using the calculated value as an evaluation value, a rotation speed of a wheel is determined by a plurality of predetermined values. A rotational speed region discriminating unit that determines which of the rotational speed regions is included, and load estimation that calculates the load acting on the wheel bearing by applying the output signal of the sensor of each sensor unit to a predetermined estimation formula A sensor comprising: a calculation unit; and a load condition determination unit that switches a parameter in the estimation calculation formula used in the load estimation calculation unit according to the rotation speed region determined by the rotation speed region determination unit. Wheel bearing.   In Claim 1, the said rotational speed area | region discrimination | determination part compares the said evaluation value with one defined threshold value, and a wheel exists in the defined normal rotational speed area | region or a low-speed rotational speed area | region. Wheel bearing with sensor to determine if there is.   In Claim 1, the said rotational speed area | region discrimination | determination part compares the said evaluation value with two or more defined threshold values, and a wheel is any rotation among three or more defined rotational speed areas. A wheel bearing with sensor that determines whether it is in the speed range.   4. The load condition determination unit according to claim 1, wherein the load condition determination unit determines that the load is determined after a predetermined time has elapsed when the rotation speed region determination unit determines that the rotation speed region is the lowest low speed rotation region. A sensor-equipped wheel bearing that switches a parameter of an estimation formula used in an estimation calculation unit to a predetermined parameter.   5. The sensor unit according to claim 1, wherein three or more sensor units are provided, and the load estimating unit is configured to output the output signals of the sensors of the three or more sensor units in a radial direction of the wheel bearing. 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 5, 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.   7. The load estimation calculation unit according to claim 6, wherein the load estimation calculation unit includes a plurality of the estimation calculation formulas and a direction corresponding command unit that selects the plurality of estimation calculation formulas according to a selection command. A direction discriminating unit that discriminates the direction of the axial load by using a difference between amplitude values of sensor output signals of two sensor units disposed opposite to each other, and the load condition judging unit includes the load estimation unit A parameter switching unit that switches the parameters of the estimation formula used in the calculation unit, and a direction correspondence that gives the selection command to the direction corresponding command unit of the load estimation calculation unit corresponding to the determination result of the direction determination unit A sensor-equipped wheel bearing having a command portion.   8. 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 of an output signal of each sensor in each sensor unit within a predetermined time, 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.   9. The sensor unit according to claim 8, wherein the sensor unit has three or more contact fixing portions and two sensors, and is adjacent between the first and second contact fixing portions adjacent to each other and between the adjacent second and third contact fixing portions. Each sensor is mounted between the adjacent 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.   The sensor-equipped wheel according to any one of claims 11 to 9, wherein a temperature sensor is provided in each of the sensor units, and the output signal of the sensor of the sensor unit is corrected based on the output signal of the temperature sensor. bearing.

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