JP4487528B2 - Load measuring device for rolling bearing unit for wheel support - Google Patents

Description

  A load measuring device for a wheel bearing rolling bearing unit according to the present invention is a load (one or both of a radial load and an axial load) applied to a rolling bearing unit for supporting a wheel of a vehicle such as an automobile or a railway vehicle. Is used to ensure the running stability of the vehicle.

  For example, an automobile wheel is rotatably supported by a double row angular rolling bearing unit with respect to a suspension device. In order to ensure the running stability of automobiles, vehicle running stabilizers such as an antilock brake system (ABS), a traction control system (TCS), and a vehicle stability control system (VSC) are used. . In order to control such various vehicle running stabilizers, signals such as the rotational speed of the wheels and the acceleration in each direction applied to the vehicle body are required. In order to perform higher-level control, it may be preferable to know the magnitude of a load (one or both of a radial load and an axial load) applied to the rolling bearing unit via the wheel.

  In view of such circumstances, Patent Document 1 describes a rolling bearing unit with a load measuring device capable of measuring a radial load. The rolling bearing unit with a load measuring device of the first example of this conventional structure measures a radial load and is configured as shown in FIG. A hub 2 for coupling and fixing the wheel is supported on the inner diameter side of the outer ring 1 supported by the suspension device. The hub 2 includes a hub body 4 having a rotation-side flange 3 for fixing a wheel at an outer end thereof (an end on the outer side in the width direction when assembled to a vehicle), and an inner end of the hub body 4. And an inner ring 6 that is externally fitted to the end (on the widthwise center side in the assembled state in the vehicle) and held down by a nut 5. A plurality of rolling rings are provided between the double row outer ring raceways 7 and 7 formed on the inner peripheral surface of the outer ring 1 and the double row inner ring raceways 8 and 8 formed on the outer peripheral surface of the hub 2. The moving bodies 9a and 9b are arranged to freely rotate the hub 2 on the inner diameter side of the outer ring 1.

  A mounting hole 10 that diametrically penetrates the outer ring 1 is formed in a substantially vertical direction at an upper end portion of the outer ring 1 in a portion between the double row outer ring raceways 7 and 7 at an intermediate portion in the axial direction of the outer ring 1. Yes. In the mounting hole 10, a circular rod-shaped (round bar-shaped) displacement sensor 11, which is a load measuring sensor, is mounted. This displacement sensor 11 is a non-contact type, and the detection surface provided on the front end surface (lower end surface) is closely opposed to the outer peripheral surface of the sensor ring 12 fitted and fixed to the intermediate portion in the axial direction of the hub 2. When the distance between the detection surface and the outer peripheral surface of the sensor ring 12 changes, the displacement sensor 11 outputs a signal corresponding to the amount of change.

  In the case of the conventional rolling bearing unit with a load measuring device configured as described above, the load applied to the rolling bearing unit can be obtained based on the detection signal of the displacement sensor 11. That is, the outer ring 1 supported by the vehicle suspension device is pushed downward by the weight of the vehicle, whereas the hub 2 supporting and fixing the wheel tends to stop at the same position. For this reason, the greater the weight, the greater the deviation between the center of the outer ring 1 and the center of the hub 2 based on the elastic deformation of the outer ring 1, the hub 2, and the rolling elements 9a, 9b. The distance between the detection surface of the displacement sensor 11 and the outer peripheral surface of the sensor ring 12 provided at the upper end of the outer ring 1 becomes shorter as the weight increases. Therefore, if the detection signal of the displacement sensor 11 is sent to the controller, the radial load applied to the rolling bearing unit in which the displacement sensor 11 is incorporated can be obtained from a relational expression or a map obtained beforehand through experiments or the like. Based on the load applied to each rolling bearing unit thus obtained, the ABS is appropriately controlled and the driver is informed of the poor loading state.

  In the conventional structure shown in FIG. 8, the rotational speed of the hub 2 can be detected in addition to the load applied to the rolling bearing unit. For this purpose, the sensor rotor 13 is fitted and fixed to the inner end portion of the inner ring 6, and the rotational speed detection sensor 15 is supported by a cover 14 attached to the inner end opening of the outer ring 1. And the detection part of this sensor 15 for rotational speed detection is made to oppose the to-be-detected part of the said sensor rotor 13 via a measurement clearance gap.

  When the rolling bearing unit incorporating the rotational speed detection device as described above is used, the sensor rotor 13 rotates together with the hub 2 to which the wheel is fixed, and the detected portion of the sensor rotor 13 is connected to the rotational speed detection sensor 15. When traveling in the vicinity of the detection unit, the output of the rotational speed detection sensor 15 changes. The frequency at which the output of the rotational speed detection sensor 15 changes in this way is proportional to the rotational speed of the wheel. Therefore, if the output signal of the rotational speed detection sensor 15 is sent to a controller (not shown), ABS and TCS can be controlled appropriately.

  The rolling bearing unit with a load measuring device of the first example of the conventional structure as described above is for measuring the radial load applied to the rolling bearing unit, but the structure for measuring the axial load applied to the rolling bearing unit is also, It is described in Patent Document 2 and the like and has been conventionally known. FIG. 9 shows a rolling bearing unit with a load measuring device for measuring an axial load described in Patent Document 2. As shown in FIG. In the case of the second example of this conventional structure, the rotation side flange 3a for supporting the wheel is fixed on the outer peripheral surface of the outer end portion of the hub 2a. A fixed-side flange 17 is fixed to the outer peripheral surface of the outer ring 1a for supporting and fixing the outer ring 1a to a knuckle 16 constituting a suspension device. A plurality of rolling rings are respectively provided between the double row outer ring raceways 7 and 7 formed on the inner peripheral surface of the outer ring 1a and the double row inner ring raceways 8 and 8 formed on the outer peripheral surface of the hub 2a. By providing the moving bodies 9a and 9b so as to be able to roll, the hub 2a is rotatably supported on the inner diameter side of the outer ring 1a.

  Further, a load sensor 20 is attached to a part surrounding the screw hole 19 for screwing the bolt 18 for connecting the fixed side flange 17 to the knuckle 16 at a plurality of positions on the inner side surface of the fixed side flange 17. Has been established. Each load sensor 20 is sandwiched between the outer side surface of the knuckle 16 and the inner side surface of the fixed-side flange 17 in a state where the outer ring 1 a is supported and fixed to the knuckle 16.

  In the case of the load measuring device of the rolling bearing unit of the second example having such a conventional structure, when an axial load is applied between a wheel (not shown) and the knuckle 16, the outer surface of the knuckle 16 and the fixed side flange 17 The inner surface strongly presses the load sensors 20 from both sides in the axial direction. Therefore, the axial load applied between the wheel and the knuckle 16 can be obtained by summing up the measured values of the load sensors 20. Although not shown, Patent Document 3 describes a method of obtaining the revolution speed of the rolling element from the vibration frequency of a member corresponding to an outer ring having a reduced rigidity, and measuring the axial load applied to the rolling bearing. ing.

  In the case of the first example of the conventional structure shown in FIG. 8 described above, the load applied to the rolling bearing unit is measured by measuring the displacement in the radial direction between the outer ring 1 and the hub 2 by the displacement sensor 11. However, since the displacement amount in the radial direction is small, it is necessary to use a highly accurate displacement sensor 11 in order to obtain this load with high accuracy. Since high-precision non-contact sensors are expensive, it is inevitable that the cost of the entire rolling bearing unit with a load measuring device increases.

  In the case of the second example of the conventional structure shown in FIG. 9 described above, it is necessary to provide as many load sensors 20 as the number of bolts 18 for supporting and fixing the outer ring 1a to the knuckle 16. For this reason, coupled with the fact that the load sensor 20 itself is expensive, it is inevitable that the cost of the entire load measuring device of the rolling bearing unit is considerably increased. Further, the method described in Patent Document 3 requires that the rigidity of a part of the outer ring equivalent member be lowered, and it may be difficult to ensure the durability of the outer ring equivalent member.

  In view of such circumstances, the present inventors have previously described this rolling bearing unit based on the revolution speed of a pair of rolling elements (balls) constituting a rolling bearing unit which is a double row angular ball bearing. An invention relating to a load measuring device for a rolling bearing unit that measures a radial load or an axial load applied to the bearing is performed (Japanese Patent Application Nos. 2003-171715 and 172483). FIG. 10 shows a load measuring device for a rolling bearing unit according to the present invention. In the case of the structure according to the previous invention, the sensor unit 21 is inserted into the mounting hole 10a formed in the portion between the double-row outer ring raceways 7 and 7 at the axial intermediate portion of the outer ring 1 (outer ring equivalent member) A detecting portion 22 provided at the tip of the outer ring 1 protrudes from the inner peripheral surface of the outer ring 1. The detection unit 22 is provided with a pair of revolution speed detection sensors 23a and 23b and one rotation speed detection sensor 15a.

  And the detection part of each revolution speed detection sensor 23a, 23b of these is provided in each retainer 24a, 24b which hold | maintained each rolling element 9a, 9b arrange | positioned in a double row freely, The revolution speed detection The revolving speeds of the rolling elements 9a and 9b are made freely detectable by being close to and facing the encoders 25a and 25b. Further, the rotational speed of the hub 2 can be detected by making the detection part of the rotational speed detection sensor 15a close to and opposed to the rotational speed detection encoder 26 that is externally fitted and fixed to the intermediate part of the hub 2 that is an inner ring equivalent member. It is said. According to the load measuring device for a rolling bearing unit according to the prior invention having such a configuration, a load (a radial load and a load) applied between the outer ring 1 and the hub 2 regardless of fluctuations in the rotational speed of the hub 2. Axial load) is required.

That is, in the case of the load measuring device for a rolling bearing unit according to the above-described prior invention, an arithmetic unit (not shown) performs the outer ring 1 and the hub 2 based on the detection signals sent from the sensors 23a, 23b, 15a. One or both of a radial load and an axial load applied between the two are calculated. For example, when the radial load is obtained, the computing unit obtains the sum of the revolution speeds of the rolling elements 9a and 9b in each row detected by the revolution speed detection sensors 23a and 23b, and the sum and the rotation speed. The radial load is calculated based on the ratio to the rotational speed of the hub 2 detected by the detection sensor 15a. Further, the axial load is obtained by calculating the difference between the revolution speeds of the rolling elements 9a and 9b in each row detected by the revolution speed detection sensors 23a and 23b, and this difference and the rotational speed detection sensor 15a are detected. Calculation is based on the ratio to the rotational speed of the hub 2. This point will be described with reference to FIG. In the following description, it is assumed that the contact angles α _a and α _b of the rolling elements 9 a and 9 b in the respective rows are the same in a state where the axial load Fy is not applied.

FIG. 11 schematically shows the wheel bearing rolling bearing unit shown in FIG. 10 described above and shows the action state of the load. Preloads F ₀ and F ₀ are applied to the rolling elements 9 a and 9 b arranged in a double row between the double row inner ring raceways 8 and 8 and the double row outer ring raceways 7 and 7. Further, a radial load Fz is applied to the rolling bearing unit during use due to the weight of the vehicle body or the like. Further, an axial load Fy is applied due to centrifugal force applied during turning. These preloads F ₀ , F ₀ , radial load Fz, and axial load Fy all affect the contact angles α (α _a , α _b ) of the rolling elements 9a, 9b. Then, the contact angle alpha _a, the alpha _b is changed, these rolling elements 9a, the revolution speed n _c of 9b changes. The diameter of the pitch circle of each of these rolling elements 9a, 9b is D, the diameter of each of these rolling elements 9a, 9b is d, the rotational speed of the hub 2 provided with each of the inner ring raceways 8, 8 is n _i , When the rotational speed of the outer race 1 provided with the outer ring raceway 7, 7 and n _o, the revolution speed n _c is expressed by the following equation.
n _c = {1− (d · cos α / D) · (n _i / 2)} + {1+ (d · cos α / D) · (n _o / 2)}

As is evident from this equation, the rolling elements 9a, revolution speed n _c of 9b, these rolling elements 9a, the contact angle α (α _a, α _b) of 9b varies in response to changes in, the above-described Similarly, the contact angles α _a and α _b vary according to the radial load Fz and the axial load Fy. Thus the revolution speed n _c is changed according to these radial load Fz and the axial load Fy. In this example, the hub 2 is rotated, since the outer ring 1 is not rotated, specifically, with respect to the radial load Fz, the revolution speed n _c is slow enough to increase. Further, with respect to the axial load Fy, the revolution speed of the row that supports the axial load Fy is increased, and the revolution speed of the row that does not support the axial load Fy is decreased. Therefore, on the basis of the revolution speed n _c, it will be asked to the radial load Fz and the axial load Fy.

However, the contact angle α which leads to a change in the revolution speed n _c, as well as the radial load Fz and the axial load Fy changes while associated with each other, also vary according to the preload F _0, F _0. Also, the revolution speed n _c is changed in proportion to the rotational speed n _i of the hub 2. Therefore, these radial load Fz, the axial load Fy, the preload F _0, F _0, to be considered in conjunction all the rotational speed n _i of the hub 2, it is impossible to correctly determine the revolution speed n _c. Of these, the preloads F ₀ and F ₀ do not change according to the operating state, so it is easy to eliminate the influence by initial setting or the like. The radial load Fz with respect to this, the axial load Fy, the rotational speed n _i of the hub 2, since the constantly changing depending on the operating conditions, it is impossible to eliminate the influence by such initialization.

In the case of the prior invention in view of such circumstances, as described above, when the radial load Fz is obtained, the rolling elements 9a, 9b of the respective rows detected by the respective revolution speed detection sensors 23a, 23b are detected. By determining the sum of the revolution speeds, the influence of the axial load Fy is reduced. Further, when the axial load Fy is obtained, the influence of the radial load Fz is reduced by obtaining the difference between the revolution speeds of the rolling elements 9a and 9b in each row. Furthermore, in any case, possible to calculate the radial load Fz or the axial load Fy on the basis of the ratio of the above sum or difference, the rotational speed detecting sensor 15a is a rotational speed n _i of the hub 2 for detecting way, by eliminating the influence of the rotational speed n _i of the hub 2. However, the axial load Fy, when calculating on the basis of the rolling elements 9a, 9b ratio of the revolution speed of said each row, the rotational speed n _i of the hub 2 is not necessarily required.

In any case, the load measuring device of the rolling bearing unit according to the above such prior invention, in order to determine the load applied between the outer ring 1 and the hub 2, the hub 2 rotational speed n _i and the It is necessary to accurately grasp the relationship (gain characteristic and zero point) between the revolution speeds n _ca and n _cb of the rolling elements 9a and 9b in each row and the radial load Fz or the axial load Fy. In this regard, basically, before the rolling bearing unit is shipped from the factory, the rolling bearing unit is rotated in a no-load state (zero load state), and the zero point of the revolution speed, that is, the radial load Fz and the axial load Fy. The revolution speeds n _ca and n _cb of the rolling elements 9a and 9b in each row in the case where is zero are grasped.

The load gain, which is the relationship between the amount of change in the revolution speeds n _ca and _ncb of the rolling elements 9a and 9b in each row and the radial load Fz and axial load Fy, is also determined prior to shipping from the factory. Keep it. In this case, for example, in a state of being loaded with a known load to the rolling bearing unit by rotating the hub 2 the revolution speed n _ca, measured n _cb, these load and revolution speed n _ca, and n _cb The relationship (load gain) is grasped in advance. Alternatively, the initial values of the contact angles α _a , α _b are calculated from the revolution speeds n _ca , n _cb in a state where no load is applied, and from this initial value, Hertz widely known in the field of rolling bearing units Using theory or the like, the relationship between the amount of change in the revolution speeds n _ca and n _{cb and} the loads Fz and Fy applied to the rolling bearing unit (load gain: change characteristics of the revolution speed based on the load) is designed in advance. It prescribes. Furthermore, only rolling bearing units obtained by the above-described method in which the load gain and the zero point are within the preset range are selected and shipped.

Regardless of which method is used, if the rolling bearing unit is assembled as designed and the contact angles α _a and α _b with no load applied are still measured prior to shipment at the factory, the above revolution Based on the speeds n _ca and n _cb , the loads Fz and Fy are obtained with an accuracy required for control for ensuring the stability of the automobile. However, in the case of a rolling bearing unit for supporting a wheel of an automobile, the contact angles α _a and α _{b in a} state where no load is applied may change due to a decrease in preload associated with traveling over a long period of time. In addition, the wheel support rolling bearing unit used for driving wheels (FR vehicle, RR vehicle, rear wheel of MR vehicle, front wheel of FF vehicle, all wheels of 4WD vehicle) constitutes a hub which is a member corresponding to the inner ring. There is a structure in which the coupling and fixing of the hub body and the inner ring is completed only when the hub is coupled and fixed to the constant velocity joint. In the case of the wheel bearing rolling bearing unit having such a structure, the value of the preload applied to each rolling element is determined in a state where the hub is coupled and fixed to the constant velocity joint. The operation of coupling and fixing the hub to the constant velocity joint is performed not at the wheel bearing rolling bearing unit manufacturing plant but at the automobile assembly plant. Therefore, even if the gain characteristic and the zero point are grasped at the manufacturing factory of the wheel bearing rolling bearing unit, the gain characteristic and the zero point in a state where the wheel characteristic is actually assembled to the automobile may be different. In any case, if the gain characteristic and the zero point at that time are different from the gain characteristic and the zero point grasped at the initial stage, the load applied to the wheel support rolling bearing unit cannot be obtained accurately.

JP 2001-21577 A Japanese Patent Laid-Open No. 3-209016 Japanese Patent Publication No.62-3365

  In view of the circumstances as described above, the present invention accurately determines the load applied to the wheel-supporting rolling bearing unit even when the characteristics of the wheel-supporting rolling bearing unit change with long-term use. Invented to realize a load measuring apparatus.

Each of the load measuring devices for the wheel bearing rolling bearing unit of the present invention includes an outer ring equivalent member, an inner ring equivalent member, a plurality of balls , a pair of revolution speed detection encoders, and a pair of revolution speed detections. Sensor and an arithmetic unit.
Outer ring member of this has outer ring raceway of the double row angular type on the inner peripheral surface, it does not rotate during use.
The inner ring equivalent member is disposed concentrically with the outer ring equivalent member on the inner diameter side of the outer ring equivalent member, has a double-row angular inner ring raceway on the outer peripheral surface, and rotates during use .
Further, the respective balls is between these two inner ring raceway and the outer ring raceways, while applying a contact angle of the double-row angular type is and rear combination type in opposite directions between the two rows to each other, A plurality are provided for each row, and are provided in a state of being rotatably supported by a pair of cages that are independent from each other between the rows .
The both revolution speed detecting encoders are provided in a part of the two cages, and the characteristics are changed alternately and at equal intervals in the circumferential direction.
Further, the both revolution speed detection sensors are provided in a state in which the respective detection portions are opposed to the detected surfaces of the both revolution speed detection encoders, and the revolution speeds of the balls in both rows are set as described above. It detects as a rotational speed of both cages.

Further, in the case of the invention described in claims 1 and 2, the outer ring equivalent member is disposed on the detection surface of the rotation speed detecting encoder provided concentrically with the inner ring equivalent member on a part of the inner ring equivalent member. The rotational speed of the member corresponding to the inner ring can be detected by making the detection part of the rotational speed detection sensor supported by a part face each other.
In the case of the invention described in claim 1, the computing unit calculates a ratio between the sum of the revolution speed of the balls in one row and the revolution speed of the balls in the other row and the rotation speed of the inner ring equivalent member. Based on the above, a radial load applied between the outer ring equivalent member and the inner ring equivalent member is calculated.
Further, in the case of the invention described in claim 2, the computing unit calculates the difference between the revolution speed of the balls in one row and the revolution speed of the balls in the other row, and the rotation speed of the inner ring equivalent member. Based on the ratio, an axial load applied between the outer ring equivalent member and the inner ring equivalent member is calculated.
Further, in the case of the invention described in claim 3, the computing unit is configured such that the outer ring equivalent member and the inner ring are based on a ratio between the revolution speed of the balls in one row and the revolution speed of the balls in the other row. The axial load applied between the corresponding members is calculated.

Further, in the case of the invention described in claims 1 to 3, the computing unit is configured to load the load (in the case of the invention described in claim 1, a radial load, in the case of the invention described in claims 2 to 3). In addition to the function of calculating the axial load (hereinafter the same when simply referred to as “load”) , the lateral acceleration applied to the vehicle body equipped with the rolling bearing unit comprising the outer ring equivalent member, the inner ring equivalent member and the balls. And between the outer ring equivalent member and the inner ring equivalent member based on one or more state values selected from a plurality of state values that affect the load, including the yaw rate, travel speed, and steering angle By comparing the estimated load with the load calculated based on the detection signal, the gain characteristic and zero point when calculating the load based on the detection signal are compared. Self-learning And a function.

In the case of the invention described in any one of claims 1 to 3 , the load measuring device for the wheel supporting rolling bearing unit of the present invention configured as described above can be used in the rolling bearing unit by detecting the revolution speed of the ball. The load applied can be measured. That is, when the load on such rolling bearing unit of the ball bearing is loaded, the contact angle of the ball is changed, the revolution speed of the balls is changed. Therefore, if this revolution speed is detected, a load acting between the outer ring equivalent member and the inner ring equivalent member can be obtained.
Furthermore, in any case , the load measuring device for the wheel support rolling bearing unit of the present invention self-learns the gain characteristic and zero point when the calculator calculates the load. Even when is changed, the load applied to the wheel bearing rolling bearing unit can be accurately obtained.

Further, the load measuring device for a wheel supporting rolling bearing unit according to the present invention is a rolling bearing unit that supports a wheel on an independent suspension suspension generally used for passenger cars, and the contact angle directions differ from each other. By detecting the revolution speed of the balls in the pair of rows, the load (radial load and axial load) applied between the outer ring equivalent member and the inner ring equivalent member constituting the rolling bearing unit can be accurately obtained. That is, when a load is applied to a rolling bearing unit such as a double-row angular ball bearing, the contact angle of the balls in each row changes, and the revolution speed of the balls in both rows changes. Therefore, if this revolution speed is detected as the rotational speed of the cage, a load acting between the outer ring equivalent member and the inner ring equivalent member can be obtained.
Furthermore, in any case, the load measuring device for a wheel bearing rolling bearing unit of the present invention can apply loads (radial load and thrust load) applied to the rolling bearing unit regardless of fluctuations in the rotation speed of the inner ring equivalent member. Accurately required.

Preferably, when implementing the present invention, as described in claim 4, when at least one of the self-learned gain characteristic and the zero point is different from the gain characteristic or zero point stored in the computing unit, this is stored. The arithmetic unit has a function of correcting the gain characteristic or the zero point.
If comprised in this way, the load added to the wheel bearing rolling bearing unit will be calculated | required correctly immediately after starting next. That is, the corrected gain characteristic or zero point is stored in a memory such as an EEPROM built in the arithmetic unit, and when the vehicle is stopped (ignition OFF) and restarted (ignition ON), self-learning is performed before the vehicle stops. If the corrected gain characteristic or zero point is continuously used, the load applied to the rolling bearing unit can be accurately obtained based on the gain characteristic and zero point immediately after restart.

Preferably, as described in claim 5 , 1 to 1 selected from a plurality of state values affecting the load, including lateral acceleration applied to the vehicle body, yaw rate, traveling speed, and steering angle. Only when it is determined that the vehicle is in a stable state (a state where the vehicle is in control of the driver) based on the plurality of state values, one or more state values (a state value for determining a stable state) Is not necessarily the same).
When the vehicle is in a stable state, the load applied to the wheel-supporting rolling bearing unit is obtained based on previously known values. For example, when the vehicle is in a stopped state or a constant speed straight traveling state, the radial load is based on the vehicle weight, and the axial load is zero. In addition, even in the acceleration state, deceleration state, and turning state, when the vehicle is in a stable traveling state in which the grip of the wheel is not lost, the radial force applied to the wheel bearing rolling bearing unit is calculated from the previously known value and the state value. Load and axial load are required.
Therefore, if the load is estimated in a stable state, the gain characteristic or the zero point can be corrected accurately without particularly troublesome calculation processing.

Preferably, as described in claim 6 , the load is estimated based on one or more state values only when it is determined that the steering angle is not large based on one or more state values. If comprised in this way, the influence of the axial load which generate | occur | produces in the inside of a wheel support rolling bearing based on the difference in the steering angle of a right-and-left wheel will be suppressed, and the said gain characteristic or zero point correction | amendment can be performed correctly. The reason for this is as follows.
The vehicle steering device is configured by a link mechanism, and when the steering angle of the steering wheel becomes larger than a certain degree (the turning radius during turning is small), a difference in steering angle occurs between the left and right steering wheels. Such a difference between the left and right rudder angles may arise due to restrictions on the link mechanism, or it may be intentionally set for the purpose of optimizing the distribution of the load applied between the left and right wheels during turning. is there.

  In any case, when the steering angle becomes large, a difference (other than the difference necessary for the Ackerman turn) occurs between the left and right steering wheels. When such a difference in steering angle occurs between the left and right steered wheels, these steered wheels are pushed against each other or pulled together, generating a lateral internal force. This internal force is generated in the relationship of action and reaction between the two steered wheels, so it becomes zero if the load on the left and right steered wheels is added. An axial load is generated. Since this axial load is a load unrelated to the state quantity such as the lateral acceleration and yaw rate of the vehicle, the gain characteristic and the zero point are accurately corrected in a state where such an axial load is generated. I can't do that. Therefore, if the load is estimated when the steering angle is less than a preset value and the lateral internal force is not generated or is negligibly small even if it is generated, the gain characteristics and zero point correction can be corrected. Can be performed with high accuracy. In this case, the steering angle can be obtained directly from a steering angle sensor incorporated in the steering device, or can be estimated from a comparison between the vehicle speed and the yaw rate, or a comparison between the vehicle speed and the lateral acceleration. The magnitude of the rudder angle at which the gain characteristic and the zero point can be corrected is determined by design for each vehicle. In general, the turning radius of the vehicle (the radius of the trajectory of the steered wheels on the inside during turning) is 20 m. The value is as above. When the turning radius is about 5 to 10 m, an internal force that cannot be ignored is generated in the rolling bearing unit that supports the steered wheels even when the vehicle is traveling at a low speed. On the other hand, if the turning radius exceeds 20 m, this internal force is hardly generated.

  An embodiment of the present invention will be described with reference to FIGS. The feature of this embodiment is that, as in the structure of the prior invention shown in FIG. 10, the revolution speed of each rolling element 9a, 9b arranged in a double row, and consequently the load applied to the rolling bearing unit. In order to realize a load measuring device for a rolling bearing unit that is required accurately after long-term use or after assembly at an automobile assembly plant, the influence of aging or assembly errors of the rolling bearing unit is eliminated. There is in point to do. Since the configuration and operation of the other parts are the same as in the case of the prior invention described with reference to FIGS. 10 to 11, the illustration and description regarding the equivalent parts are omitted. The point of eliminating the influence of changes or assembly errors will be described.

  In the present embodiment, in order to eliminate the influence of the secular change or the assembly error, when self-learning the gain characteristic and the zero point when calculating the radial load Fz and the axial load Fy, first, one or more Based on the state value, it is determined whether or not the vehicle is in a stable traveling state (whether or not the steering angle is large as necessary). The one or more state values are selected from a plurality of types of state values that affect the load, including lateral acceleration applied to the vehicle body equipped with the rolling bearing unit, yaw rate, travel speed, and rudder angle. Whether or not the vehicle is in the stable running state is determined by a procedure as shown in one or both of FIGS. 1 and 2, for example.

同時に、車体に設置したヨーレートセンサの出力に基づいて、実際の旋回角速度を求める。そして、上記走行速度ｖと横加速度ｙ″と旋回半径ｒとから求めた旋回角速度ωと、上記ヨーレートの出力から求めた実際の旋回角速度とを比較し、これら両旋回角速度同士の差が予め設定しておいた閾値よりも小さければ、安定走行状態と判断する。 In the determination procedure shown in the flowchart of FIG. 1, the turning angular velocity ω during turning is calculated from the traveling speed v of the vehicle body, the lateral acceleration y ″, and the turning radius r using the following equation (1). presume.

At the same time, the actual turning angular velocity is obtained based on the output of the yaw rate sensor installed on the vehicle body. Then, the turning angular velocity ω obtained from the traveling speed v, the lateral acceleration y ″ and the turning radius r is compared with the actual turning angular velocity obtained from the output of the yaw rate, and the difference between these turning angular velocities is set in advance. If it is smaller than the predetermined threshold value, it is determined that the vehicle is in a stable running state.

  In the determination procedure shown in the flowchart of FIG. 2, the turning angular velocity ω during turning is estimated from the rudder angle obtained based on the output signal of the rudder angle sensor provided in a part of the steering device and the traveling speed v. To do. Then, the estimated turning angular velocity ω is compared with the actual turning angular velocity obtained based on the output of the yaw rate sensor installed on the vehicle body as in FIG. If the difference between the two turning angular velocities is smaller than a preset threshold, it is determined that the vehicle is in a stable running state.

  As described above, when the self-learning of the gain characteristic and the zero point is performed, the reason for determining whether or not the vehicle is in a stable state is that the vehicle is in an unstable state such as oversteer or understeer. This is because the radial load Fz and the axial load Fy applied to the rolling bearing unit cannot be accurately estimated. That is, the rolling bearing is based on one or more state values selected from a plurality of state values that affect the load, including the vehicle body lateral acceleration, the yaw rate, the traveling speed, and the rudder angle during traveling. The load applied to the unit (the load applied between the outer ring equivalent member and the inner ring equivalent member) is required (can be estimated) because there is no excessive slip at the contact portion between the wheel (tire) and the road surface (limit (The grip force is not exceeded). Accordingly, when self-learning the gain characteristic and the zero point, first, it is determined whether or not the vehicle is in a stable state by at least one (preferably both) procedure shown in FIGS.

  And only when it is in a stable state (when the steering angle is not large if necessary), a load estimated as described later, a pair of revolution speed detection sensors 23a and 23b, and a rotational speed detection sensor 15a. The load applied between the outer ring equivalent member (outer ring 1) and the inner ring equivalent member (hub 2) obtained based on the output of (see FIG. 10) is compared. Further, based on the outputs of the pair of revolution speed detection sensors 23a and 23b and the rotational speed detection sensor 15a, the gain characteristic of the equation in the software installed in the calculator is calculated so that the estimated load can be calculated. And self-learning zeros. When the learned gain characteristic and zero point differ from the value previously set in the equation in the software by exceeding a preset threshold value, at least one of the gain characteristic and zero point is corrected. To do. That is, the estimated load is replaced with a value that can be calculated for the gain characteristic and the zero point that differ beyond the threshold.

  The outer wheel equivalent member based on one or more state values selected from a plurality of state values affecting the load, including lateral acceleration applied to the vehicle body, yaw rate, travel speed, and rudder angle There are a plurality of methods for estimating the load applied to the inner ring equivalent member, and any of these methods can be used when the present invention is implemented. Hereinafter, one example will be described with reference to FIG.

While the vehicle 27 is turning in a steady circle (turning with a constant steering angle), a radial load Fz (right front wheel: Fz _(F-RH) acting on the front wheels 28, 28 and the rear wheels 29, 29, left front wheel: Fz _(F-LH), right rear wheel: Fz _(R-RH), a left rear wheel: Fz _(R-LH)), respectively represented by the following (2) to (5) below. The turning direction is counterclockwise (left turning), and the lateral acceleration in the right direction is positive (the right wheel is turning outside and the left wheel is turning inside).

In these formulas (2) to (5), M represents a vehicle body mass, and g represents a gravitational acceleration (9.8 m / s ² ). Further, y ″ is a lateral acceleration applied in the lateral direction of the vehicle body 30 when turning as described above. Further, L _F is a distance from the center of gravity of the vehicle body 30 to the center of the front wheel 28, and L _R is a center of gravity of the vehicle body 30. To the center of the rear wheel 29 (L _F + L _R = wheel base), T _r is the distance (tread) between the centers of the ground planes of the wheels 28 and 29 in the width direction of the vehicle 27, and H is the above vehicle body. The height of the center of gravity of 30 from the road surface 31 is shown.

Further, the total value of the axial loads acting on the front wheels 28 and 28 and the rear wheels 29 and 29 (total of the axial loads applied to the left and right wheels) is expressed by the following equations (6) and (7), respectively.

Next, the axial load Fy (cornering force) generated on the ground contact surface (the contact portion between the road surface 31 and the tire) is formulated by the centrifugal force applied to the vehicle body 30 during turning.
The relationship between the axial load Fy and radial load Fz applied to the wheels 28 and 29 and the side slip angle β of the wheels 28 and 29 is as shown in FIGS. As shown in FIG. 6, the ratio between the axial load Fy and the side slip angle β (Fy / β: cornering power K) is plotted on the vertical axis, and the radial load Fz is plotted on the horizontal axis. When expressed, it becomes a negative quadratic curve. The relationship between the two K and Fz is expressed by the following equation (8).

ここで、図６に破線で示した楕円部分に相当する、コーナリングパワーＫが最大となるラジアル荷重Ｆｚ_{_max}は、タイヤのロードインデックス（タイヤ横面に刻印されている、タイヤの最大負荷能力を表す指標値）で代用する。又、上記コーナリングパワーＫが最大になるのは、このコーナリングパワーＫを、上記アキシアル荷重Ｆｙで微分した場合にゼロとなる場合に於けるラジアル荷重Ｆｚであるから（極値の考え方）、次の（１０）式が成り立つ。

そして、この（１０）式にＦｚ＝Ｆｚ_{_max}を代入すると、次の（１１）式を得られる。

When the radial load Fz is zero (Fz = 0), the cornering power K is also zero (K = 0) (the frictional force that overcomes the centrifugal force does not occur on the contact surface), so the following equation (9) is derived. It is burned.

Here, corresponding to an elliptical portion indicated by a broken line in FIG. 6, the radial load Fz _{_max} cornering power K is maximized, the load index of the tire (marked on the tire lateral surface represents the maximum load capacity of the tire (Indicator value) is substituted. Further, the cornering power K is maximized because the radial load Fz is zero when the cornering power K is differentiated by the axial load Fy (the concept of extreme values). Equation (10) holds.

Then, by substituting Fz = _{Fz_max} into this equation (10), the following equation (11) is obtained.

又、一方で各車輪２８、２９に加わるアキシアル荷重Ｆｙ（コーナリングフォース）は、Ｋ×βで表されるから、上記（１２）式を使って、例えば両前輪２８、２８に就いて表すと、次の（１３）（１４）式の様になる。

Substituting this equation (11) into the equation (9) gives the following equation (12).

On the other hand, since the axial load Fy (cornering force) applied to the wheels 28 and 29 is expressed by K × β, the expression (12) is used to express the front wheels 28 and 28, for example. The following equations (13) and (14) are obtained.

この（１５）式と、前記（２）（３）式と、車体３０に設置した加速度センサの検出信号に基づいて求められる横加速度と、各車輪２８、２９のスリップ角（横滑り角）βとより、前記接地面で発生しているアキシアル荷重Ｆｙ｛（１３）（１４）両式に表したコーナリングフォース｝を算出できる。尚、上記各車輪２８、２９のスリップ角βの算出方法に就いては、後述する。 Substituting these equations (13) and (14) into the equation (6) yields the following equation (15).

This equation (15), the above-mentioned equations (2) and (3), the lateral acceleration obtained based on the detection signal of the acceleration sensor installed on the vehicle body 30, and the slip angle (side slip angle) β of each wheel 28, 29 Thus, the axial load Fy {cornering force expressed in both equations (13) and (14)} generated on the ground contact surface can be calculated. The method for calculating the slip angle β of the wheels 28 and 29 will be described later.

Similarly, for the rear wheels 29, 29, the axial load Fy (cornering force) and the gain characteristic A can be calculated by the following equations (16), (17), and (18). In addition, when the tire characteristics of the rear wheels 29 and 29 are different from those of the front wheels 28 and 28, another value is used for _{Fz_max} corresponding to the tire index.

  On the other hand, the slip angle β of the wheels 28 and 29 is calculated from the vehicle state quantity, and the tire slip angle of the wheels 28 and 29 is calculated from the slip angle of the vehicle body 30. This point will be described with reference to FIG. When the roll angle of the vehicle body 30 does not change as in the case of steady circle turning at a constant speed, the slip angle β of the wheels 28 and 29 is determined between the left and right wheels 28 and 28 (29 and 29). Ignoring the tread, it can be considered as a two-wheel model as shown in FIG. 7 in which an equivalent wheel exists in the center of the tread (vehicle center). FIG. 7 is an image diagram in a case where a steady circular turn is performed at an extremely low speed so that the tire does not slip. Under such conditions, when the slip angle β ′ of the vehicle body 30 is obtained using the acceleration in the front-rear direction (vehicle traveling direction) and the acceleration in the lateral direction, the following is considered.

The turning centrifugal acceleration corresponding to the vehicle body posture is output to the longitudinal acceleration sensor for detecting the longitudinal acceleration x ″ and the lateral acceleration sensor for detecting the lateral acceleration y ″. Then, when considering a constant circular turning at a constant speed without acceleration / deceleration operation, the vehicle body posture is determined from the ratio of acceleration detected by the both acceleration sensors {tangent value = tan (y ″ / x ″)}. Can be estimated. The slip angle β ′ of the vehicle body 30 is an angle formed by a vehicle speed vector and the center line of the vehicle body 30 and varies depending on the installation positions of the both acceleration sensors. Can do. In this case, the slip angle β ′ of the vehicle body 30 can be simply expressed by the following equation (19).

又、この（２０）式中のφ₂ は、次の（２１）式で表わされる。

一方、縦方向の速度ｖ_x と、ヨー角速度ω_Rzと、旋回半径Ｒとの関係は、次の（２２）式で表される。

この（２２）式を上記（２１）に代入し、更にこの（２１）式を上記（２０）式に代入すると、次の（２３）式を得られる。

尚、前車輪２８のスリップ角β_(F) 関しては、上述した後車輪２９のスリップ角β_(R) を求める方法に加え、舵角δを考慮して、次の（２４）式により求める。

この様に（２３）（２４）両式により求められる、前後両車輪２８、２９のスリップ角β_(F) 、β_(R) を、前記（１３）〜（１８）に代入すれば、各車輪２８、２９に加わるアキシアル荷重Ｆｙ（コーナリングフォース）を算出できる。 If the slip angle β ′ of the vehicle body 30 can be calculated by the equation (19), the slip angle β of the wheels 28 and 29 can be calculated from the geometric relationship between the vehicle body 30 and the wheels 28 and 29 as follows. expressed.
First, the slip angle β _(R) of the rear wheel 29 is expressed by the following equation (20).

Further, φ ₂ in the equation (20) is expressed by the following equation (21).

On the other hand, the relationship between the vertical velocity v _x , the yaw angular velocity ω _Rz, and the turning radius R is expressed by the following equation (22).

Substituting this equation (22) into the above equation (21) and further substituting this equation (21) into the above equation (20) yields the following equation (23).

The slip angle β _{(F) of} the front wheel 28 is obtained by the following equation (24) in consideration of the steering angle δ in addition to the method for obtaining the slip angle β _(R) of the rear wheel 29 described above. .

Obtained by this as (23) (24) both equations, the slip angle beta _(F) of the front and rear wheels 28, 29, beta a _(R), by substituting in (13) to (18), each wheel The axial load Fy (cornering force) applied to 28 and 29 can be calculated.

  Based on the axial load Fy thus determined, the arithmetic unit self-learns the gain characteristic and zero point when calculating the load based on the detection signals sent from the sensors 23a, 23b, 15a. When one or both of the self-learned gain characteristic and zero point differ from the gain characteristic or zero point used so far by exceeding a preset threshold value, the gain characteristic or zero point is changed. to correct. For this reason, even if the characteristics of the wheel support rolling bearing unit change from the initial or design state due to long-term use or due to assembly errors at the assembly plant, this wheel support rolling bearing unit The applied load can be obtained accurately. Even with a radial load, self-learning and correction of gain characteristics and zeros are performed in the same manner.

The flowchart which shows the 1st example of the procedure for determining whether the vehicle is in the stable state sufficient for performing load estimation. The flowchart which shows the 2nd example. The schematic diagram of a vehicle for demonstrating the conditions for performing load estimation. The diagram which shows the 1st example of the relationship between an axial load, radial load, and the side slip angle of each wheel. The diagram which shows the 2nd example. The diagram which shows one example of the relationship between cornering power and radial load. The schematic diagram shown in the state which looked at the vehicle from upper direction in order to demonstrate the state which calculates the slip angle of a wheel from a vehicle state quantity. Sectional drawing of the rolling bearing unit which incorporated the sensor for radial load measurement known conventionally. Sectional drawing of the rolling bearing unit which incorporated the sensor for axial load measurement conventionally known. Sectional drawing of the load measuring apparatus of the rolling bearing unit which concerns on a prior invention. The schematic diagram for demonstrating the reason for which the load added to a rolling bearing unit is calculated | required.

DESCRIPTION OF SYMBOLS 1, 1a Outer ring 2, 2a Hub 3, 3a Rotation side flange 4 Hub body 5 Nut 6 Inner ring 7 Outer ring raceway 8 Inner ring raceway 9a, 9b Rolling element 10, 10a Mounting hole 11 Displacement sensor 12 Sensor ring 13 Sensor rotor 14 Cover 15, 15a Rotational speed detection sensor 16 Knuckle 17 Fixed flange 18 Bolt 19 Screw hole 20 Load sensor 21 Sensor unit 22 Detector 23a, 23b Revolution speed detection sensor 24a, 24b Retainer 25a, 25b Revolution speed detection encoder 26 Rotational speed Encoder for detection 27 Vehicle 28 Front wheel (front wheel)
29 Rear wheel (rear wheel)
30 body 31 road surface

Claims (6)

Has outer ring raceway of the double row angular type on the inner peripheral surface, and the outer ring member which does not rotate during use, the inner diameter side of the outer ring member disposed in the outer ring member concentrically, double row angular type on the outer peripheral surface The inner ring equivalent member that rotates in use, and the double ring angular type that is a reverse combination type between the two rows and the two outer ring raceways and in the reverse direction between the two rows. In a state where a contact angle is given, a plurality of balls for each row, a ball provided in a state of being rotatably held by a pair of independent cages between the rows, and holding these both A pair of revolution speed detection encoders whose characteristics are alternately and equally spaced in the circumferential direction provided on a part of the detector, and the detection surfaces of the two revolution speed detection encoders. Provided in a state of facing the above A pair revolution speed detecting sensor for detecting each revolution speed of the row of balls as rotational speed of both retainers, and the outer ring member on the basis of a detection signal fed from the both revolution speed detecting sensor A calculator for calculating a load applied between the inner ring equivalent member and a detection surface of a rotation speed detecting encoder provided concentrically with the inner ring equivalent member on a part of the inner ring equivalent member. The rotation speed of the inner ring equivalent member can be detected by making the detection part of the rotation speed detection sensor supported by a part of the outer ring equivalent member facing, and the computing unit can rotate the revolution speed of the balls in one row. In addition to the function of calculating the radial load applied between the outer ring equivalent member and the inner ring equivalent member based on the ratio of the sum of the revolution speed of the balls in the other row and the rotation speed of the inner ring equivalent member. The Comprising a lateral acceleration applied to the rolling bearing unit consisting of these outer ring member and the inner ring member and the respective balls to the vehicle body mounted, the yaw rate, and vehicle speed, and a steering angle, a plurality of types that affect the radial load Based on one or more state values selected from state values, a function of estimating a radial load applied between the outer ring equivalent member and the inner ring equivalent member, and on the basis of the estimated radial load and the detection signal by comparing the calculated radial load, the load measuring device of the wheel supporting rolling bearing unit having a function of self-learning the gain characteristics and zeros when calculating the radial load on the basis of the detection signal. A double-row angular type outer ring raceway that has a double-row angular type outer ring raceway on its inner peripheral surface and is arranged concentrically with this outer ring-equivalent member on the inner diameter side of this outer ring-equivalent member, which does not rotate during use. The inner ring equivalent member that rotates in use, and the double ring angular type that is a reverse combination type between the two rows and the two outer ring raceways and in the reverse direction between the two rows. In a state where a contact angle is given, a plurality of balls for each row, a ball provided in a state of being rotatably held by a pair of independent cages between the rows, and holding these both A pair of revolution speed detection encoders whose characteristics are alternately and equally spaced in the circumferential direction provided on a part of the detector, and the detection surfaces of the two revolution speed detection encoders. Provided in a state of facing the above A pair of revolution speed detecting sensors for detecting the revolution speed of the balls in the row as the rotational speeds of the two cages, and the outer ring equivalent member based on a detection signal sent from the two revolution speed detection sensors. A calculator for calculating a load applied between the inner ring equivalent member and a detection surface of a rotation speed detecting encoder provided concentrically with the inner ring equivalent member on a part of the inner ring equivalent member. The rotation speed of the inner ring equivalent member can be detected by making the detection part of the rotation speed detection sensor supported by a part of the outer ring equivalent member facing, and the computing unit can rotate the revolution speed of the balls in one row. In addition to the function of calculating the axial load applied between the outer ring equivalent member and the inner ring equivalent member based on the ratio of the difference between the revolution speed of the ball in the other row and the rotational speed of the inner ring equivalent member. A plurality of types that affect the axial load, including lateral acceleration, yaw rate, traveling speed, and rudder angle applied to the vehicle body equipped with the rolling bearing unit composed of the outer ring equivalent member and the inner ring equivalent member and the balls. A function of estimating an axial load applied between the outer ring equivalent member and the inner ring equivalent member based on one or a plurality of state values selected from the state value, and based on the estimated axial load and the detection signal. A load measuring device for a wheel support rolling bearing unit having a function of self-learning a gain characteristic and a zero point when calculating the axial load based on the detection signal by comparing the calculated axial load. A double-row angular type outer ring raceway that has a double-row angular type outer ring raceway on its inner peripheral surface and is arranged concentrically with this outer ring-equivalent member on the inner diameter side of this outer ring-equivalent member, which does not rotate during use. The inner ring equivalent member that rotates in use, and the double ring angular type that is a reverse combination type between the two rows and the two outer ring raceways and in the reverse direction between the two rows. In a state where a contact angle is given, a plurality of balls for each row, a ball provided in a state of being rotatably held by a pair of independent cages between the rows, and holding these both A pair of revolution speed detection encoders whose characteristics are alternately and equally spaced in the circumferential direction provided on a part of the detector, and the detection surfaces of the two revolution speed detection encoders. Provided in a state of facing the above A pair of revolution speed detecting sensors for detecting the revolution speed of the balls in the row as the rotational speeds of the two cages, and the outer ring equivalent member based on a detection signal sent from the two revolution speed detection sensors. A calculator for calculating a load applied between the inner ring equivalent member and the calculator based on a ratio between a revolution speed of the balls in one row and a revolution speed of the balls in the other row. In addition to the function of calculating the axial load applied between the equivalent member and the inner ring equivalent member, the lateral acceleration applied to the vehicle body equipped with the rolling bearing unit composed of the outer ring equivalent member and the inner ring equivalent member and the balls, and The outer ring equivalent member and the inner ring equivalent portion based on one or more state values selected from a plurality of state values that affect the axial load, including the yaw rate, travel speed, and steering angle When calculating the axial load based on this detection signal by comparing the estimated axial load and the axial load calculated based on the above detection signal Load measuring device for a wheel bearing rolling bearing unit having a function of self-learning a gain characteristic and a zero point. At least one of the gain characteristic and zeros, which is self-learning, when the gain characteristic or zero point stored in the calculator different, the arithmetic unit has a function of correcting the stored gain characteristic or zero, according to claim 1 The load measuring device of the rolling bearing unit for wheel support described in any one of -3. Only if the vehicle based on one or a plurality of state values is determined to be in a stable state, estimates the radial load or axial load on the basis of one or a plurality of state values, any one of claims 1 to 4 A load measuring device for a rolling bearing unit for supporting a wheel according to claim 1 . The radial load or the axial load is estimated based on one or more state values only when it is determined that the rudder angle is not large based on one or more state values . The load measuring device of the rolling bearing unit for wheel support described in item 1 .

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