JP2011196888A - Load measuring apparatus for wheel of automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load measuring apparatus for a wheel which has a structure in which a sensor is arranged near the upper end portion of an encoder 4a, to suppress a degradation in measurement precision to minimum while suppressing a degradation in camber rigidity of a roller bearing unit 14a for supporting a wheel.SOLUTION: A contact angle α given to balls 3a and 3a of an outside row which bear axial load directed inward in axial direction, among such balls 3a and 3b, as given contact angles α and β, coupled back to back, being arranged in a plurality of rows, in the load measuring apparatus for a wheel, is set larger than a contact angle β given to balls 3b and 3b in an inside row which do not support the axial load (α>β).

Description

  The present invention relates to an improvement in a vehicle wheel load measuring device for measuring an axial load applied to a vehicle wheel (a grip force acting on a ground contact surface). Specifically, it is intended to realize a structure capable of minimizing deterioration in measurement accuracy even when the installation position of the sensor is limited.

  Friction force (axial load on the ground contact surface) acting on the contact surface (ground contact surface) between the wheel (tire) and the road surface in order to properly control the stability control device etc. to ensure the running stability of the automobile It is thought that knowing the grip power) is effective. This grip force is applied as a moment and an axial load between a stationary wheel and a rotating wheel constituting a rolling bearing unit (hub unit) for supporting the wheel. In addition, the stationary wheel and the rotating wheel are oscillated and displaced in the direction of inclining the central axes of each other based on the moment and the axial load, and are relatively displaced in the axial direction. Accordingly, the grip force can be obtained if the swing displacement and the axial relative displacement amount can be measured. The grip force is applied between the stationary wheel and the rotating wheel as the moment and the axial load, and the moment and the axial load have a correlation close to a proportional relationship. Therefore, if the force acting between the stationary wheel and the rotating wheel is measured as an axial load, for example, the grip force can be obtained.

  For such a purpose, as a rolling bearing unit with a load measuring device capable of measuring an axial load applied to the wheel supporting rolling bearing unit, for example, a structure described in Patent Document 1 is known. An example of the conventional structure described in Patent Document 1 will be described with reference to FIGS. A plurality of balls 3, each of which is a rolling element, is provided with a hub 2 that is a rotating wheel that rotates together with the wheel in a state where the wheel is supported and fixed at the time of use on the inner diameter side of the outer ring 1 that does not rotate even when used. 3 is rotatably supported. A preload is applied to each of the balls 3 and 3 together with contact angles opposite to each other (in combination with the back surface).

  A cylindrical encoder 4 is supported and fixed concentrically with the hub 2 at the inner end portion of the hub 2. A pair of sensors 6 a and 6 b are supported inside a bottomed cylindrical cover 5 that closes the inner end opening of the outer ring 1, and the detection portions of both the sensors 6 a and 6 b are connected to the encoder 4. The outer peripheral surface, which is the detection surface, is placed close to and opposed to the detection surface. Of these, the encoder 4 is made of a magnetic metal plate. In the front half of the outer peripheral surface of the encoder 4 (the inner half in the axial direction), which is the detection surface, the through holes 7 and 7 and the column portions 8 and 8 are alternately arranged at equal intervals in the circumferential direction. It is arranged. The boundaries between the through holes 7 and 7 and the pillars 8 and 8 are inclined at the same angle with respect to the axial direction of the encoder 4, and the inclined direction with respect to the axial direction is set to the intermediate portion in the axial direction of the encoder 4. The directions are opposite to each other. Accordingly, each of the through holes 7 and 7 and each of the column portions 8 and 8 has a "<" shape with the axially intermediate portion protruding most in the circumferential direction. And among the axially outer half part and the axially inner half part of the detected surface, the inclination directions of the boundaries are different from each other, the axially outer half part is defined as the first characteristic changing part 9, and the axially inner half part is formed. This portion is the second characteristic changing portion 10.

  Each of the pair of sensors 6a and 6b includes a permanent magnet and a magnetic sensing element constituting a detection unit. The two sensors 6a and 6b are supported and fixed inside the cover 5, with the detection part of one sensor 6a serving as the first characteristic changing part 9 and the detection part of the other sensor 6b serving as the second sensor. The characteristic changing portions 10 are respectively close to and opposed to each other. The positions where the detection parts of both the sensors 6 a and 6 b face both the characteristic change parts 9 and 10 are the same position in the circumferential direction of the encoder 4. Further, in the state where an axial load does not act between the outer ring 1 and the hub 2, the portion that protrudes most in the circumferential direction in the axial direction intermediate portion of each of the through holes 7 and 7 and the column portions 8 and 8 (boundary boundary). The position where each member is installed is regulated so that the portion in which the inclination direction changes) is just at the center position between the detection parts of the sensors 6a and 6b.

  In the case of the rolling bearing unit with a load measuring device configured as described above, when an axial load acts between the outer ring 1 and the hub 2 and the outer ring 1 and the hub 2 are relatively displaced in the axial direction, the two sensors The phase at which the output signals 6a and 6b change is shifted. That is, in the neutral state where an axial load is not applied between the outer ring 1 and the hub 2, the detection portions of the sensors 6a and 6b are shown on the solid lines A and B in FIG. It faces a portion that is shifted by the same amount in the axial direction from the most protruding portion. Therefore, the phases of the output signals of the sensors 6a and 6b coincide as shown in FIG.

  On the other hand, when a downward axial load is applied to the hub 2 to which the encoder 4 is fixed as shown in FIG. 9A, the detecting portions of the sensors 6a and 6b are shown in FIG. , Opposite to the portions where the deviations in the axial direction from the most protruding portion are different from each other. In this state, the phases of the output signals of the sensors 6a and 6b are shifted as shown in FIG. Further, when an upward axial load is applied to the hub 2 to which the encoder 4 is fixed as shown in FIG. 9A, the detecting portions of the sensors 6a and 6b are connected to the chain line hub shown in FIG. The deviation in the axial direction from the uppermost part, that is, the most protruding part, faces different parts in the opposite direction to the above case. In this state, the phases of the output signals of the sensors 6a and 6b are shifted as shown in FIG.

  As described above, in the case of a conventionally known structure as described in Patent Document 1, the phase of the output signals of both the sensors 6a and 6b is applied between the outer ring 1 and the hub 2. It shifts in the direction corresponding to the acting direction of the axial load (the direction of the relative displacement between the outer ring 1 and the hub 2 in the axial direction). Further, the degree of the phase shift of the output signals of the sensors 6a and 6b due to the axial load (relative displacement) increases as the axial load (relative displacement) increases. Therefore, the direction and magnitude of the relative displacement in the axial direction between the outer ring 1 and the hub 2 based on the presence or absence of the phase shift of the output signals of the sensors 6a and 6b and the direction and magnitude of the deviation, if any. In addition, the acting direction and magnitude of the axial load acting between the outer ring 1 and the hub 2 can be obtained. The relative displacement in the axial direction is based on the ratio of the phase difference between the output signals of the sensors 6a and 6b to the one period of the output signals of the sensors 6a and 6b (phase difference / 1 period = phase difference ratio). And the process which calculates a load is performed by the calculator which is not shown in figure. Therefore, the relationship between the phase difference ratio, the relative displacement in the axial direction, and the load, which has been examined in advance by theoretical calculation or experiment, is incorporated in this arithmetic unit by a calculation formula or a model such as a map.

  In Patent Document 1, as a structure for obtaining an axial load acting between a stationary raceway such as the outer ring 1 and a rotary raceway such as the hub 2, the output signal of a single sensor is described. A structure obtained from the duty ratio (high potential duration / 1 period) (for example, the structure described in FIG. 18 of Patent Document 1) or a structure obtained from the same pulse ratio (a period for 1 pulse / 2 periods for 2 pulses) , The structure described by FIG. 10 of Patent Document 1). The structure for obtaining the axial load based on the duty ratio and the pulse ratio is also an object of the present invention. However, the structure and the action for obtaining the axial load by each of these ratios are described in detail in Patent Document 1. In addition, as will be described later, the structure of the present invention is characterized in that, even when the sensor installation position is limited, in order to minimize the deterioration of measurement accuracy, the wheel support is related to the sensor installation position. The point is to devise the structure on the rolling bearing unit side. Therefore, illustration and description of the structure and operation for obtaining the axial load based on the duty ratio and pulse ratio are omitted.

  Regardless of which ratio is used to determine the axial load, in order to improve the measurement accuracy of this axial load, the relative displacement amount between the encoder and the sensor based on this axial load is increased {gain (= relative displacement It is necessary to increase the amount / axial load). On the other hand, not only a pure axial load is applied to the wheel-supporting rolling bearing unit based on the grip force, but also a force that is a combination of the axial load and a moment is applied when the vehicle is turning. For this reason, the relative displacement amount in the axial direction between the encoder and the sensor differs in the circumferential direction. Specifically, when the encoder is supported and fixed to the inner end portion in the axial direction of the rotation side raceway, it is largest at the lower end portion and smallest at the upper end portion. This point will be described with reference to FIGS. Regarding the structure of the wheel-supporting rolling bearing unit, “inside” in the axial direction means the center side in the width direction of the vehicle in the assembled state to the automobile, and the right side in FIGS. On the contrary, the left side of FIGS. 1, 2, 7, and 10, which is the outer side in the width direction of the vehicle, is referred to as “outside” in the axial direction. This is the same throughout the present specification and claims.

  As shown in FIG. 10, the axial load Fa based on the grip force is applied to the ground contact surface that is a contact portion between the tire 12 and the road surface 13 constituting the wheel 11. This ground contact surface exists at a position greatly deviating from the center O of the wheel bearing rolling bearing unit 14 in the radial direction. Accordingly, in addition to the axially inward axial load, the hub 2 constituting the wheel-supporting rolling bearing unit 14 passes through the center O in the traveling direction (front and back direction in FIG. 10) due to the axial load Fa. On the other hand, a moment Ma about a parallel virtual axis is applied. The hub 2 is displaced by a force obtained by combining the axial load Fa and the moment Ma with respect to the outer ring 1 supported and fixed to the knuckle 15 constituting the suspension device.

For example, assuming that the encoder (for example, the inner end edge) is present at the position indicated by the line segment a in FIG. 2 during steady operation (the axial load Fa is zero), the axial load Fa acts on the ground contact surface. I will explain the case. In this case, the position of the encoder swings and displaces from the position indicated by the line segment a to the position indicated by the line segment b, as exaggeratedly shown in FIG. Further, based on the pure axial component, as shown exaggeratedly in FIG. 2, it is displaced (translated) to the position indicated by the line segment c. The output signal of the sensor having the detection unit opposed to the detection surface of the encoder is a change of the line segment a → the line segment b, “L _ab ” in FIG. 2 and a change of the line segment b → the line segment c. _That is, it is changed by the amount synthesized with “L _bc ” in FIG.

As is apparent from FIG. 2, the displacement amount of the encoder is LB (“L _ab ” + “L _bc ”), which is the sum of both changes at the lower end portion, whereas these displacement amounts are at the upper end portion. It becomes L _U (“L _ab ” − “L _bc ”) which is the difference between the two changes. In other words, the amount of change at the upper end is smaller by {2 (L _bc )} than the amount of change at the lower end by twice the parallel movement. When this amount of change is obtained as a phase difference ratio (phase difference / one cycle) of both the sensors 6a and 6b, when these sensors 6a and 6b are installed at the lower end of the encoder, they act on the ground plane. The relationship between the axial load (grip force) and the phase difference ratio greatly changes as shown by the broken line a in FIG. On the other hand, when both the sensors 6a and 6b are installed at the upper end of the encoder, the degree to which the relationship between the grip force and the phase difference ratio changes is small as shown by the solid line b in FIG. turn into. As is clear from these facts, in order to increase the gain in order to improve the measurement accuracy of the axial load Fa, it is advantageous to make the sensor face the lower end of the detection surface. For example, Patent Documents 2 and 3 describe a structure in which a sensor is opposed to the lower end of the encoder by utilizing the fact that the amount of axial displacement of the encoder increases at the lower end of the encoder. .

  In this way, if the sensor is opposed to the lower end portion of the encoder, the gain can be increased to improve the measurement accuracy of the axial load Fa applied to the wheel. However, as is clear from FIG. 10, the position facing the lower end of the encoder is close to the road surface 13, and there is no shielding object between the road surface 13 and the installation environment is severe. For this reason, there are many opportunities to travel on rough roads, and when it is intended to prevent damage caused by jumping stones, it may be preferable to install the sensor in the upper half of the encoder. Further, depending on the structure of the suspension device, it may be considered that the sensor cannot be installed on the lower end side of the encoder due to the handling of a harness for taking out the output signal of the sensor. In these cases, it is necessary to install the sensor on the upper half side (for example, the upper end) of the encoder. Even in this case, it is necessary to secure the gain as much as possible in order to ensure the required measurement accuracy.

  If this gain is merely increased, the rigidity of the wheel bearing rolling bearing unit may be lowered. For example, in the structure shown in FIG. 7 described above, the preload applied to each ball 3, 3 is reduced, the pitch circle diameter of each ball 3, 3 is reduced, The pitch (span) between the rows is reduced, the radius of curvature (groove curvature) of the cross-sectional shape of the outer ring race and the inner ring race with respect to the diameter of each of the balls 3, 3 is increased, or each of the balls 3, 3 If the contact angle is reduced, the rigidity can be lowered. If this rigidity can be lowered, the relative displacement between the outer ring 1 and the hub 2 based on the axial load Fa (grip force) is increased, the gain is ensured, and the measurement accuracy of the axial load Fa is increased. It can be secured. However, if the rigidity of the rolling bearing unit for supporting the wheel is lowered, the camber rigidity of the wheel supported by the rolling bearing unit is also lowered, and the wheel tends to swing left and right, and the running stability tends to deteriorate. It is not preferable.

  In view of the circumstances as described above, the present invention has a structure in which a sensor is arranged in the upper half of an encoder, and can suppress deterioration in measurement accuracy while suppressing a decrease in camber rigidity of a wheel bearing rolling bearing unit. It was invented to realize the structure.

The vehicle wheel load measuring device of the present invention includes a wheel bearing rolling bearing unit, an encoder, a sensor, and a computing unit.
Among these, the wheel support rolling bearing unit includes an outer ring equivalent member having a double row outer ring raceway on the inner peripheral surface, an inner ring equivalent member having a double row inner ring raceway on the outer peripheral surface, both the outer ring raceways and both inner ring raceways. And rolling elements provided in such a manner that a plurality of rolling elements are provided for each row. Further, the pitch circle diameters of the rolling elements in both rows are larger than the span of the rolling elements in both rows. And one member of the outer ring equivalent member and the inner ring equivalent member is a stationary side race ring that is supported and fixed to a suspension device and does not rotate during use, and the other member is also in a state where the wheel is fixed. A rotating raceway that rotates with this wheel is used. Further, a preload is applied to each of the rolling elements together with a contact angle of a rear combination type.
The encoder is supported and fixed concentrically with the rotation-side raceway at the axially inner end portion of the rotation-side raceway, and any one of the inner and outer peripheral surfaces is a detected surface. .
Further, the sensor is supported by a non-rotating portion, and the detection unit is opposed to the detection surface of the encoder.
Further, the computing unit has a function of measuring an axial load acting between the stationary side raceway and the rotation side raceway, based on an axial displacement amount of the detection surface of the encoder.

In particular, in the vehicle wheel load measuring apparatus according to the present invention, the sensor faces the upper half of the detected surface (for example, ± 45 degrees centering on the upper end and a total range of 90 degrees). Yes. Then, among the rolling elements, the contact angle given to the rolling elements in the row on the side supporting the axial load inward in the axial direction is the same as the contact angle given to the rolling elements in the row on the side not supporting this axial load. (For example, about 8 to 15 degrees) is increased.
Specifically, when the contact angle value regarding the rolling bearing unit in which both rows have the same contact angle is a standard value, the contact angle applied to the rolling elements in the row supporting the axial load. Is made larger than this standard value (for example, about 4 to 8 degrees). On the other hand, the contact angle given to the rolling elements on the side where the axial load is not supported is made smaller than the standard value (for example, about 4 to 8 degrees).

When implementing the present invention as described above, specifically, as in the invention described in claim 2, the rotating side raceway is an inner ring equivalent member and the stationary side raceway is an outer ring equivalent member. Then, among the rolling elements, the contact angle given to the rolling elements in the axially outer row is made larger than the contact angle given to the rolling elements in the same axially inner row.
Alternatively, as in the invention described in claim 3, the rotating side raceway is an outer ring equivalent member, and the stationary side raceway is an inner ring equivalent member. Then, among the rolling elements, the contact angle given to the rolling elements in the axially inner row is made larger than the contact angle given to the rolling elements in the same axially outer row.

According to the vehicle wheel load measuring device of the present invention configured as described above, the sensor is arranged in the upper half of the encoder, the camber rigidity of the wheel supporting rolling bearing unit is reduced, and the radial load capacity is reduced. The deterioration of measurement accuracy can be minimized while suppressing the decrease.
First, it is possible to minimize the deterioration in measurement accuracy by increasing the contact angle applied to the rolling elements in the row that supports the axially inward axial load and increasing the axial rigidity of this row. . By increasing the axial rigidity, the amount of translation (the amount of displacement in the axial direction, L _bc ) described in FIG. 2 is reduced, and the amount of displacement based on the translation is reduced from the displacement of the encoder based on the moment. Can be reduced. As a result, the amount of displacement of the portion where the sensor detection unit is opposed to the upper half of the encoder is ensured, and the measurement accuracy compared to the case where the sensor detection unit is opposed to the lower end of the encoder. Deterioration can be minimized.

In addition, the reduction of the camber rigidity and the radial load capacity can be suppressed by appropriately regulating the contact angle of the rolling elements arranged in double rows and acting in the direction corresponding to the contact angle direction of both rows. This can be realized by securing the distance between the line and the center axis of the rolling bearing unit. The camber rigidity, that is, the moment rigidity of the wheel-supporting rolling bearing unit can be ensured by increasing the support interval. Moreover, it is divided into the outer side and the inner side with respect to the axial direction, the vertical positions are opposite to each other, and among the plurality of rolling elements that support the moment based on the axial load (grip force), it is located on the load side of this moment Since the contact angle of the rolling element is small, the rigidity against the moment of the rolling element is increased. For this reason, the camber rigidity can be ensured.
Further, the rolling elements in the row with the smaller contact angle have a large load capacity with respect to the radial load. As far as the radial load is concerned, the load capacity of the rolling elements in the row where the contact angle is increased in order to increase the axial rigidity is reduced, but the load capacity of the rolling elements in the row where the contact angle is smaller is improved. The load capacity related to the radial load as the entire support rolling bearing unit can be sufficiently secured.

Sectional drawing which each shows embodiment (A) of this invention, and conventional structure (B). The schematic diagram for demonstrating the condition where the attitude | position and position of an encoder change with the axial load added to a ground plane. The diagram which shows the influence which the magnitude | size of the contact angle of the rolling element of both rows which comprises a wheel support rolling bearing unit has on the relationship between the axial load added to a ground-contact surface, and a camber angle. Similarly, the diagram which shows the influence which acts on the relationship between the axial load added to a ground-contact plane, and the amount of displacement of an axial direction. Similarly, the diagram which shows the 1st example of the influence which acts on the relationship between the axial load added to a ground surface, and the phase difference regarding the output signal of a sensor. The diagram which shows the 2nd example. Sectional drawing which shows an example of the conventional structure of the load measuring apparatus for wheels of a motor vehicle. The figure which looked at a part of to-be-detected part of the encoder from radial direction. The schematic diagram for demonstrating the principle which measures a load based on the displacement of an encoder. The schematic sectional drawing of the rotation support part of a wheel for demonstrating the force added to the rolling bearing unit for wheel support at the time of turning driving | running | working. The diagram which shows the influence which the installation position of a sensor exerts on the relationship between the axial load added to a ground surface and the phase difference regarding the output signal of a sensor. Sectional drawing which shows two examples of the method for determining the suitability of the positional relationship of the hub which comprises the rolling bearing unit for wheel support, and the encoder supported and fixed to this hub.

  An example of an embodiment of the present invention will be described with reference to FIGS. The feature of this example is that the axial load inputted to the hub 2a constituting the wheel bearing rolling bearing unit 14a from the contact surface (see FIG. 10) which is the contact portion between the tire 12 and the road surface 13 on the wheel 11. Is configured to be able to be measured with sufficient accuracy by a sensor having a detection portion opposed to the upper end portion of the encoder 4a. The wheel support rolling bearing unit 14a is changed from a driven wheel to a driving wheel, a load measuring encoder 4a is provided in addition to a load measuring encoder 4a, and the encoder 4a is made of a permanent magnet. Except for the points described above, the configuration and operation of the other parts are basically the same as those of the conventional structure shown in FIGS. For this reason, the overlapping description is omitted or simplified, and the following description will focus on the features of this example and the parts different from the conventional structure.

  In the case of this example, the load measuring encoder 4a is supported and fixed to the inner end of the hub 2a in the axial direction. The encoder 4a is formed by combining a cored bar 16 made of a magnetic metal plate and an encoder body 17 made of a permanent magnet. Of these, the metal core 16 is a crank-shaped cross section in which a small-diameter cylindrical portion and a large-diameter cylindrical portion are continuous at a stepped portion, and is entirely annular. Such a metal core 16 has the small-diameter cylindrical portion fixed to the axially inner end of the hub 2a with an interference fit, and the encoder body 17 is wound around the entire circumference of the large-diameter cylindrical portion. It is fixed with attachment. The encoder body 17 has a cylindrical shape as a whole, and S poles and N poles are arranged on the outer circumferential surface alternately and at equal intervals in the circumferential direction, and the shape of the boundary between these S poles and N poles is It has a "<" shape. In the detected surface, one side in the width direction (axial direction) sandwiching the “<”-shaped bent portion is a first characteristic changing portion, and the other side in the width direction is a second characteristic changing portion. Such properties of the encoder body 17 made of permanent magnets are also described in Patent Document 1 (FIGS. 33 to 35 and the description thereof), and thus detailed illustration and description thereof will be omitted.

  Above the encoder body 17 as described above (on the outer diameter side of the upper end), a pair of sensors 6a and 6b for load measurement (see FIG. 7 described above) are connected to the first characteristic changing unit or the respective detecting units. The second characteristic changing portion is supported in a state of being opposed to the second characteristic changing portion. In the case of this example, both the sensors 6a and 6b are supported by a structural member (not shown) of a suspension device such as a knuckle that supports and fixes the outer ring 1a constituting the wheel bearing rolling bearing unit 14a. In the case of this example, since the encoder body 17 is made of a permanent magnet, the permanent magnets on both the sensors 6a and 6b side are unnecessary.

  The encoder 4b for detecting the rotational speed is supported and fixed to a portion near the inner end in the axial direction of the hub 2a. The encoder 4b for detecting the rotational speed includes a core metal 16a that is L-shaped in cross section with a magnetic metal plate and is formed in an annular shape as a whole, and an axially inner side surface of an annular portion that constitutes the core metal 16a over the entire circumference. It consists of an encoder body 17a made of permanent magnets and attached in a fixed manner. S poles and N poles are alternately arranged at equal intervals in the circumferential direction on the inner surface in the axial direction of the encoder main body 17a, which is a detection surface for detecting the rotational speed. The rotational speed detection sensor supports the structural member of the suspension device in a state where the detection portion faces the detection surface of the encoder body 17a. For this purpose, the sensors 6a and 6b and the sensor for detecting the rotational speed are embedded and supported in a single holder made of synthetic resin or the like to constitute a sensor unit. It supports with respect to the structural member. Since the structure and operation of the wheel rotation speed detection device using the rotation speed detection encoder 4b are well known and not related to the gist of the present invention, detailed description thereof will be omitted.

  A plurality of hubs 2a, which are rotating side race rings and inner ring equivalent members, are arranged in a double row on the inner diameter side of the outer ring 1a, which is a stationary side race ring and outer ring equivalent member, each of which is a rolling element. The balls 3a and 3b are rotatably supported. For this purpose, double-row angular outer ring raceways 18a and 18b are provided on the inner peripheral surface of the outer ring 1a, and double-row angular inner ring raceways 19a and 19b are provided on the outer peripheral surface of the hub 2a, respectively. A plurality of the balls 3a and 3b are provided between the inner ring raceways 19a and 19b and the outer ring raceways 18a and 18b, respectively, in a state where a contact angle and preload of a rear combination type are applied to both rows. It is provided so that it can roll freely.

  In particular, in the case of the structure of this example, as shown in FIG. 1A, the contact angle α of the balls 3a and 3a in the axially outer row is set as the contact angle α of the balls 3b and 3b in the axially inner row. It is larger than β (α> β). For example, as shown in FIG. 1B, the value of the contact angle γ in the structure of the wheel bearing rolling bearing unit 14b in which the contact angles γ of the balls 3a and 3b in both rows are the same ( The standard value) is about 40 degrees (40 ± 5 degrees). On the other hand, in the case of the structure of this example shown in FIG. 1A, the contact angle α of the balls 3a, 3a in the outer row is set to about 45 degrees (45 ± 5 degrees), and the inner row The contact angle β of the balls 3b and 3b is set to about 35 degrees (35 ± 5 degrees), and a difference of about 10 degrees is set between the contact angles α and β.

  When the wheel support rolling bearing unit 14a having the encoders 4a and 4b as described above and having the contact angles α and β of the two rows different from each other as described above is assembled to an automobile, the shaft of the outer ring 1a is used. The inner end portion in the direction is fitted into a support hole formed in a structural member of the suspension device such as the knuckle. And the fixed side flange 20 provided in the axial direction intermediate part of the outer peripheral surface of the said outer ring | wheel 1a is couple | bonded and fixed to the structural member of the said suspension apparatus with a several volt | bolt. Further, a spline shaft 23 fixed to the central portion of the axially outer end surface of the constant velocity joint outer ring 22 is inserted into the spline hole 21 provided in the central portion of the hub 2a from the axially inner side. As a result, the spline shaft 23 is spline-engaged with the spline hole 21, and the outer peripheral portion of the outer circumferential surface of the constant velocity joint outer ring 22 is brought into contact with the inner circumferential surface of the hub 2 a. Further, in this state, the holding bolt 24 is screwed to the tip of the spline shaft 23 and further tightened, whereby the hub 25 is interposed between the head 25 of the holding bolt 24 and the outer ring 22 for the constant velocity joint. 2a is clamped and fixed. In this state, the sensor unit is supported and fixed to the constituent members of the suspension device. Further, a rotation-side flange 26 provided on the outer peripheral surface of the hub 2a near the outer end in the axial direction is provided with a rotating member for braking such as a rotor (not shown) and a wheel 27 (see FIG. 10). ) And fixed.

  When a moment and an axial load are applied to the hub 2a based on the grip force acting on the ground contact surface of the wheel 11 based on the turning of the automobile or the like, as in the case of the conventional structure described above, The encoder 4a is displaced. The direction and magnitude of the displacement is determined by the direction and magnitude of the moment and the axial load, and the phase difference existing between the output signals of the sensors 6a and 6b changes according to the direction and magnitude. To do. Therefore, the grip force can be obtained in the same manner as shown in FIG.

  In the case of this example, the detection parts of the sensors 6a and 6b are opposed to the upper end part of the outer peripheral surface of the encoder 4a. For this reason, as described above, the displacement amount of the outer peripheral surface of the encoder 4a where the detection portions of the sensors 6a and 6b face each other is purely axial from the swing displacement component based on the moment. The value obtained by subtracting the translation component in the direction. In the case of this example, by regulating the contact angles α and β of the balls 3a and 3b as described above, the value of the parallel movement subtracted from the swing displacement is reduced, and the measurement accuracy of the grip force is reduced. Is ensured. Hereinafter, this point will be described with reference to FIG. 1B and FIG. 2 in addition to FIG.

  Assuming that the grip force is the same, the parallel movement component in the pure axial direction becomes smaller as the axial rigidity of the wheel bearing rolling bearing unit 14a with respect to the acting direction of the axial load accompanying the grip force becomes higher. In addition, there is a possibility that an axial load in both directions may be applied to the wheel supporting rolling bearing unit 14a depending on the turning direction of the automobile. Of these, the problem is that the wheel supporting rolling bearing unit 14a is It is an axial load applied when it becomes the outside in the turning direction. That is, when the automobile is turning, a large grip force is generated on the wheel supported by the wheel bearing rolling bearing unit on the outer side in the turning direction along with the movement of the center of gravity based on the centrifugal force. The grip force generated on the wheel supported by the unit (the negative region on the horizontal axis in FIGS. 3 to 6 and 11) is reduced. This tendency becomes more pronounced when making a sharp turn, which requires fine control of the stability control device and the like.

For the above reasons, among the axial loads applied when there is a high need to ensure the measurement accuracy of the grip force, the axial load that is highly necessary to ensure the measurement accuracy is the axial load inward in the axial direction (rightward in FIG. 1). It is. In the case of the inner ring rotating type wheel support rolling bearing unit 14a in which the hub 2a is an inner ring equivalent member, among the balls 3a and 3b arranged in the double row, the balls 3a and 3a in the outer row are arranged. The axial load inward in the axial direction is supported. In the case of this example, the contact angle α of the balls 3a and 3a in the outer row is large, the rigidity against the axial load inward in the axial direction is high, and the amount of parallel movement based on the axial load is small. That is, as shown in FIG. 1B, when the contact angle γ of the balls 3a and 3a in the outer row is about 40 degrees, the encoder 4a is connected to the line b in FIG. It is displaced by “L _bc ” from the position to the position of the line segment c. On the other hand, as shown in FIG. 1A, when the contact angle α of the balls 3a and 3a in the outer row is about 50 degrees, the encoder 4a is based on the axial load as shown in FIG. Only the _distance “L _bd ” is displaced from the position of the line segment b to the position of the line segment d. Therefore, as shown in FIG. 2, the displacement L _B of the encoder 4a based on the moment, the displacement amount "L _bd" based on translation is suppressed reduce the amount to be reduced. As a result, the amount of displacement of the portion of the upper half of the encoder 4a where the detection portions of the sensors 6a and 6b face each other is ensured, compared with the case where the detection portion of the sensor faces the lower end of the encoder 4a. The deterioration of the measurement accuracy related to the grip force can be minimized.

In this example, instead of increasing the contact angle α of the balls 3a, 3a in the outer row, the contact angle β of the balls 3b, 3b in the inner row is reduced, so that the camber rigidity is excessive. Can be prevented, and the radial load capacity can be secured. As is clear from the above description, it is not preferable that the camber rigidity is excessively large in order to measure the grip force. Referring to FIG. 2, the displacement amount “L _ab ” of the detected surface of the encoder accompanying the inclination due to the moment, represented by line segment a → line segment b, is expressed in the pure axial direction represented by line segment b → line segment c. It is necessary to be larger than the displacement amount “L _bc ” of the detected surface (“L _ab ”> “L _bc ”). If the camber stiffness is excessively increased compared to the axial stiffness, there is a possibility that “L _ab ” ≦ “L _bc ”, and the both sensors 6a, There is a possibility that the phase difference existing between the output signals 6b becomes zero or negative. In such a state, in order to support the measurement of the grip force, it is necessary to ensure the condition “L _ab ”> “L _bc ”.

As is widely known in the technical field of rolling bearings, the moment stiffness of a double row rolling bearing unit such as a wheel supporting rolling bearing unit (camber stiffness in the case of a wheel supporting rolling bearing unit) is the rolling element of both rows. The longer the support interval {D _A , D _B } in FIGS. 1A and 1B), which is the interval between the line of action that coincides with the direction of the contact angle and the center axis of the rolling bearing unit, is greater. Become. In the case of the back combination type structure, the support intervals D _A and D _B become longer when the contact angle is increased, and conversely, become shorter when the contact angle is decreased. In the case of this example, instead of increasing the contact angle α of the balls 3a, 3a in the outer row, the contact angle β of the balls 3b, 3b in the inner row is reduced, so even when the axial rigidity is increased. The support interval D _A can be made substantially the same as the support interval D _B in the conventional structure shown in FIG. 1B (D _A ≈D _B ). For this reason, the camber rigidity can be maintained at an appropriate size regardless of the improvement of the axial rigidity.

Also, as is widely known in the technical field of rolling bearings, the radial load capacity of the rolling bearing unit increases as the contact angle decreases and decreases as the contact angle increases. In the case of the structure of the present example, the balls 3b and 3b in the inner row having a small contact angle β have a large load capacity related to the radial load. In order to increase the axial rigidity, the load capacity related to the radial load of the outer rows of balls 3a, 3a with the increased contact angle α decreases, but the load capacity of the inner rows of balls 3b, 3b with a smaller contact angle β. Therefore, the load capacity related to the radial load as the whole wheel bearing rolling bearing unit 14a can be sufficiently secured.
For the above reason, according to the wheel load measuring apparatus for automobiles of the present example, the camber rigidity of the wheel supporting rolling bearing unit 14a has a structure in which the sensors 6a and 6b are arranged in the vicinity of the upper end portion of the encoder 4a. The deterioration of measurement accuracy can be minimized while suppressing the decrease and the decrease of the radial load capacity.

  When carrying out the present invention, the pitch circle diameter of the balls 3a, 3b in both rows is the span of the balls 3a, 3b in both rows (inter-pitch pitch, distance between the centers of the balls 3a, 3b in both rows). Bigger than that is necessary. When the span becomes larger than the pitch circle diameter, when the moment based on the grip force and the axial load are input from the portion off the center of the wheel supporting rolling bearing unit 14a, the outer ring 1a and the hub 2a Regarding the relative displacement (with respect to the moment applied in the direction in which the central axes of these members 1a and 2a are inclined), the effects of radial stiffness and axial stiffness are different (and reversed), and the present invention does not hold (contact angle It is necessary to reverse the size of the present invention). However, generally, in the case of a rolling bearing unit for supporting a wheel, the pitch circle diameter is sufficiently larger (for example, twice or more) than the span, so that the present invention is established unless the design is so special.

  The results of the computer simulation performed to confirm the effect of the present invention will be described with reference to FIGS. In this computer simulation, the embodiment of the present invention shown in FIG. 1A is compared with the case where the sensor is opposed to the upper end of the encoder 14a in the conventional structure shown in FIG. It has been confirmed that this structure can increase the displacement in the axial direction of the upper end of the encoder 14a, and hence the change in the phase difference ratio between the output signals of the pair of sensors 6a and 6b.

The conditions that affect the simulation results are as follows.
[Condition common to previous structure and embodiment structure]
Material of outer ring 1a: Carbon steel for machine structure (medium carbon steel)
Curvature radius of cross-sectional shape of outer ring raceways 18a and 18b: 6.5 mm
Hub 2 body material: Carbon steel for machine structure (medium carbon steel)
Material of the inner ring fitted on the inner end of the main body in the axial direction: High carbon chrome bearing steel Material of the balls 3a, 3b: High carbon chrome bearing steel Diameter of the balls 3a, 3b: 12mm
Number of balls 3a, 3b: 8 in each row, 16 in total Pitch circle diameter of balls 3a, 3b in both rows: 66mm
Span of balls 3a and 3b in both rows: 22mm
Preload of each ball 3a, 3b: 6.86kN (700kgf)
[Different conditions between the previous structure and the embodiment structure]
Contact angles α and γ of the balls 3a and 3a in the outer row
Contact angle γ of the conventional structure: 40 degrees Contact angle α of the embodiment structure: 45 degrees Contact angles β, γ of the balls 3b, 3b in the inner row
Contact angle γ of the conventional structure: 40 degrees Contact angle β of the embodiment structure: 35 degrees

  3 to 6 showing computer simulations performed under the above-described conditions, first, FIG. 3 shows the relationship between the axial load (grip force) acting on the ground plane and the camber angle. In FIG. 3, the solid line a indicates the case of the conventional structure shown in FIG. 1B, and the chain line b indicates the case of the embodiment structure shown in FIG. As is apparent from FIG. 3, the camber rigidity is almost the same between the embodiment structure and the conventional structure.

Next, FIG. 4 shows the relationship between the grip force and the amount of displacement in the pure axial direction. The solid line a indicates the conventional structure, and the chain line b indicates the embodiment structure. As apparent from FIG. 4, according to the embodiment structure, the amount of displacement in the pure axial direction can be kept low.
Next, FIG. 5 shows the relationship between the grip force and the phase difference ratio related to the output signals of the pair of sensors 6a and 6b facing the outer peripheral surface of the upper end of the encoder 4a. The solid line a indicates the conventional structure, and the chain line b indicates the embodiment structure. As is clear from FIG. 5, according to the structure of the embodiment, the change in the phase difference ratio can be increased.

  Further, FIG. 6 is a combination of the above-described FIG. 11 and FIG. 5 described above, and the structure of the present invention is associated with the movement of the sensors 6a and 6b from the lower end portion to the upper end portion of the encoder 4a. This shows a situation where a part of the deterioration of the phase difference ratio can be compensated. 6 corresponds to the broken line a in FIG. 11, the solid line a in FIG. 6 corresponds to the solid line b in FIG. 11 and the solid line a in FIG. 5, and the chain line b in FIG. 6 corresponds to the chain line b in FIG. As is apparent from FIG. 6, according to the structure of the present invention, even when the installation position of the sensors 6a and 6b is limited to the upper end of the encoder 4a, the deterioration in measurement accuracy is minimized. Can be suppressed. Further, as is clear from comparison between the solid line a (prior structure) and the chain line b (embodiment structure) in FIGS. 5 and 6, according to the present invention, the magnitude of the grip force and the phase difference ratio of a pair of sensors Is close to a straight line, and the grip force can be easily obtained from the phase difference ratio of these two sensors.

  The above description has been given in the case where the present invention is implemented with respect to a rolling bearing unit for supporting an inner ring type wheel. On the other hand, the present invention can also be implemented with respect to a wheel bearing rolling bearing unit of an outer ring rotating type that rotatably supports a hub around a non-rotating shaft. In the case of a rolling bearing unit for wheel support of the outer ring rotation type, the row of rolling elements that support the axial load is reversed inside and outside in the axial direction from that of the inner ring rotation type. , The inner row. In addition, the present invention can be implemented with respect to a structure in which tapered rollers are used instead of balls as rolling elements. Even when the rolling elements are tapered rollers, the pitch circle diameters of the tapered rollers in both rows must be larger than the span of the tapered rollers in both rows (the distance between the centers of the tapered rollers in both rows).

  Also, including the structure of the present invention, the load or force in the axial direction applied to the rolling bearing unit is obtained by a combination of an encoder and a sensor having a “V” -shaped or “V” -shaped characteristic changing portion on the peripheral surface. In the case of the structure, the relative positional relationship in the axial direction between the encoder and the sensor, specifically, the positional relationship in the axial direction between the center of the “V” -shaped or “V” -shaped characteristic changing portion and the sensor. Need to be strictly regulated. If the structure is such that the sensors 6a and 6b are directly supported and fixed via the cover 5 or the like to the outer ring 1 constituting the wheel supporting rolling bearing unit as in the structure described in FIG. It is relatively easy to regulate this. For example, using the technology described in Patent Document 4, the rolling bearing unit for supporting the wheel is shipped in an assembled state in which the positional relationship between the encoder and the sensor is appropriately assembled, Can be assembled to a suspension system.

  On the other hand, when a structure in which the sensor is supported and fixed to a part other than the wheel support rolling bearing unit, such as a knuckle, is used, a wheel support rolling bearing unit manufacturing factory assembles only an encoder. It is necessary to combine the encoder and a pair of sensors that are separately supported and fixed to the suspension device. In this way, in a state where the encoder assembled to the wheel bearing rolling bearing unit and the pair of sensors separately supported and fixed to the suspension device are combined, the positional relationship in the axial direction between these encoders and both sensors is not good. When appropriate, there is a possibility that so-called overtaking occurs in which the front and rear of the output signals of the two sensors are reversed with the axial displacement of the encoder. In order to prevent such overtaking from occurring, the phase difference ratio existing between the output signals of the two sensors in a steady state (a state where the axial load is zero) is set to 0.5 or a value close thereto. (For example, 0.4 to 0.6) is preferable. However, if the position of the encoder in the axial direction is not strictly regulated, the phase difference ratio can be set to a value close to 0.5 even if the installation positions of the two sensors with respect to the suspension device are strictly regulated. Disappear.

  In consideration of these matters, it is necessary to ensure the positioning accuracy of the encoder 4c with respect to the hub 2a, for example, by a technique as shown in FIGS. is there. In order to ensure this positioning accuracy, the balls 3a, 3b and the outer ring 1a exist between the hub 2a on which the encoder 4c is mounted and the suspension device on which the sensors 6a, 6b are mounted. The dimensional errors of 3a, 3b, and 1a may affect the positioning accuracy in the axial direction between the encoder 4c and the sensors 6a and 6b. In order to improve the positioning accuracy, it is necessary to eliminate the influence of the dimensional errors of the members 3a, 3b and 1a. For this purpose, after assembling the encoder 4c to the hub 2a, a technique for determining whether or not the axial position of the encoder 4c with respect to the hub 2a is appropriate is required.

  Among the inspection methods developed as such a technique, first, in the method shown in FIG. 12A, the holder 29 holding the sensors 6a and 6b and the distance sensor 28 is attached to the encoder 4c. The hub 2a is rotated and brought close to the wheel bearing rolling bearing unit, and the two sensors 6a and 6b are brought close to and opposed to the outer peripheral surface of the encoder 4c. Then, according to the measured value of the distance sensor 28 in a state where the phase difference ratio of the output signals of both the sensors 6a and 6b is 0.5, the axial inner surface of the fixed flange 20 and the both sensors 6a, It is determined whether or not the positional relationship in the axial direction with 6b is appropriate.

In the method shown in FIG. 12B, the holder 29a holding both the sensors 6a and 6b is rotated by the wheel support rolling bearing unit with the encoder 4c while the hub 2a is rotated. A part of the holder 29a is brought close to the axially inner side surface of the fixed flange 20, and both the sensors 6a and 6b are brought close to and opposed to the outer peripheral surface of the encoder 4c. Then, the deviation from 0.5 of the phase difference ratio of the output signals of both the sensors 6a and 6b is measured. The suitability of the positional relationship in the axial direction between the axial inner surface of the fixed flange 20 and the sensors 6a and 6b is determined based on the magnitude of the deviation.
Since the inner side surface in the axial direction of the fixed flange 20 is an abutting surface to a structural member of the suspension device such as the knuckle, the positional relationship in the axial direction between the inner side surface in the axial direction and the sensors 6a and 6b. If the propriety is determined, it can be determined whether the axial position of the encoder 4c with respect to the hub 2a is appropriate.

DESCRIPTION OF SYMBOLS 1, 1a Outer ring 2, 2a Hub 3, 3a, 3b Ball 4, 4a, 4b, 4c Encoder 5 Cover 6a, 6b Sensor 7 Through-hole 8 Column part 9 First characteristic change part 10 Second characteristic change part 11 Wheel DESCRIPTION OF SYMBOLS 12 Tire 13 Road surface 14, 14a, 14b Rolling bearing unit for wheel support 15 Knuckle 16, 16a Core metal 17, 17a Encoder main body 18a, 18b Outer ring track 19a, 19b Inner ring track 20 Fixed side flange 21 Spline hole 22 Outer ring for constant velocity joint 23 Spline shaft 24 Retaining bolt 25 Head 26 Rotating flange 27 Wheel 28 Distance sensor 29, 29a Holder

JP 2006-317420 A JP 2005-172077 A JP 2007-199040 A JP 2008-157790 A

Claims (3)

A wheel bearing rolling bearing unit, an encoder, a sensor, and a calculator are provided.
Among these, the wheel support rolling bearing unit includes an outer ring equivalent member having a double row outer ring raceway on the inner peripheral surface, an inner ring equivalent member having a double row inner ring raceway on the outer peripheral surface, both the outer ring raceways and both inner ring raceways. Between the two rolling elements, and a plurality of rolling elements provided in such a manner that the pitch circle diameters of the rolling elements in both the rows are larger than the span of the rolling elements in both rows, One of the outer ring equivalent member and the inner ring equivalent member is a stationary side race wheel that is supported and fixed to a suspension device and does not rotate during use, and the other member is also used with this wheel while the wheel is fixed. A preload is applied to each of the rolling elements together with a contact angle of the rear combination type as a rotating raceway that rotates,
The encoder is supported and fixed concentrically with the rotation-side raceway at the axially inner end of the rotation-side raceway, and has either one of the inner and outer peripheral surfaces as a detected surface,
The sensor is supported by a portion that does not rotate, and the detection unit faces the detection surface of the encoder,
The arithmetic unit has a function of measuring an axial load acting between the stationary-side raceway and the rotation-side raceway based on an axial displacement amount of the detection surface of the encoder. In the load measuring device,
The sensor faces the upper half of the detected surface,
Of each of the rolling elements, the contact angle applied to the rolling elements in the row on the side supporting the axial load inward in the axial direction is larger than the contact angle applied to the rolling elements in the same row not supporting the axial load. This is a load measuring device for automobile wheels.   The rotating side race ring is an inner ring equivalent member, the stationary side race ring is an outer ring equivalent member, and among each rolling element, the contact angle given to the rolling element in the axially outer row is also in the axially inner row. The vehicle wheel load measuring device according to claim 1, wherein the load measuring device is larger than a contact angle applied to the rolling element.   The rotating side race ring is an outer ring equivalent member, the stationary side race ring is an inner ring equivalent member, and among each rolling element, the contact angle given to the rolling element in the axially inner row is also in the axially outer row. The vehicle wheel load measuring device according to claim 1, wherein the load measuring device is larger than a contact angle applied to the rolling element.

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