JP5471854B2 - Physical quantity measuring device for rolling bearing units - Google Patents

Description

  The present invention relates to an improvement in a physical quantity measuring device for a rolling bearing unit which is used for rotatably supporting a vehicle wheel with respect to a suspension device and measuring a physical quantity such as an axial load acting on the wheel.

  Friction force acting on the contact surface (ground surface) between the wheel (tire) and the road surface (axial load on the ground surface, For the purpose of knowing (grip force), for example, various types of rolling bearing units with a load measuring device as described in Patent Document 1 are known. An example of such a rolling bearing unit with a load measuring device will be described with reference to FIGS. Hubs 2 that rotate together with the wheels while being supported and fixed to the inner ring side of the outer ring 1 that does not rotate even when used while being supported and fixed to a structural member of a suspension device such as a knuckle are rolling elements. A plurality of balls 3 and 3 are 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).

  Further, the inner end of the hub 2 in the axial direction (inner with respect to the axial direction means the center side in the width direction of the vehicle when assembled to the vehicle. In this specification, the cylindrical encoder 4 is supported and fixed concentrically with 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 parts 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 pillars 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 This portion is the second characteristic changing portion 10.

  Each of the sensors 6a and 6b is composed of a permanent magnet and a magnetic sensing element constituting a detection unit. These 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 units of both the sensors 6a and 6b face the characteristic changing units 9 and 10 are the same in the circumferential direction of the encoder 4 or are shifted by a known value. Further, in the state where an axial load is not applied between the outer ring 1 and the hub 2, a 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 where the inclination direction changes) is just at the center position between the detection portions of the sensors 6a and 6b.

  In the case of a 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 as solid lines A and B in FIG. It faces a portion that is shifted from the most protruding portion by the same amount in the axial direction. Accordingly, the phases of the output signals of the two sensors 6a and 6b coincide with each other 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 in FIG. 7A, the detecting portions of the sensors 6a and 6b are shown in FIG. , Opposite to the portions that are different from each other in the axial direction from the most protruding portion. In this state, the phases of the output signals of the sensors 6a and 6b are deviated as shown in FIG. Furthermore, when an upward axial load is applied to the hub 2 to which the encoder 4 is fixed as shown in FIG. 7A, the detecting portions of both 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, is opposed to 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 deviated 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 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 to which the phase of the output signals of the sensors 6a and 6b is shifted due to the axial load (relative displacement amount) increases as the axial load (relative displacement amount) increases. Accordingly, based on the presence or absence of the phase shift of the output signals of both the sensors 6a and 6b and the direction and magnitude of the shift, the direction of the relative displacement amount in the axial direction between the outer ring 1 and the hub 2 and The magnitude and the direction and magnitude of the axial load acting between the outer ring 1 and the hub 2 are determined. 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 one cycle of the output signals of the sensors 6a and 6b (phase difference / 1 cycle = phase difference ratio). The processing for calculating the amount and the load is performed by an arithmetic unit (not shown). For this reason, in this computing unit, the relationship between the phase difference ratio, the relative displacement amount in the axial direction, and the load, which has been examined in advance by theoretical calculation or experiment, is incorporated in a calculation formula, a map, or the like. .

  In addition, the structure which uses the thing made from the permanent magnet magnetized in the radial direction as an encoder is also shown, for example in FIGS. 32-34 of patent document 1, and the description of each figure in the specification of this patent document 1. It has been known for some time. In such an encoder made of a permanent magnet, the S pole and the N pole are alternately arranged at equal intervals in the circumferential direction on the outer peripheral surface which is a detected surface. The boundary between the S pole and the N pole adjacent to each other in the circumferential direction has a “<” shape with the middle portion in the axial direction protruding most in the circumferential direction. When such a permanent magnet encoder is used, a permanent magnet on the sensor side is not necessary.

  Regardless of the structure of the encoder that incorporates the encoder, the axial load is calculated using the physical quantity measuring device of the rolling bearing unit. In order to ensure the measurement accuracy of the axial load, the positioning accuracy in the axial direction between the encoder and the sensor is required. It is necessary to secure. For this reason, conventionally, it has been considered to secure the positioning accuracy by using, for example, a technique described in Patent Document 2. However, simply securing this positioning accuracy is not sufficient in terms of ensuring the measurement accuracy. This is because the dimensions of the holder 11 that embeds and supports the sensors 6a and 6b change with the environmental temperature. That is, in order to easily support and fix the two sensors 6a and 6b at appropriate positions, the sensor unit 12 is configured by embedding and supporting these sensors 6a and 6b in a predetermined position in the synthetic resin holder 11. The sensor unit 12 may be supported and fixed to a fixed part such as the cover 5.

  However, the linear expansion coefficient of the synthetic resin constituting the holder 11 is larger than the linear expansion coefficient of each member of the rolling bearing unit and the iron-based alloy constituting the cover 5. For this reason, the positional relationship between the detection portions of the sensors 6a and 6b and the detected surface of the encoder 4 shifts with changes in temperature. For example, in the case of the structure shown in FIG. 5, when the temperature rises, the sensors 6a and 6b are shifted to the left in the figure with respect to the encoder 4, and as a result, the measured value of the axial load is shifted. This point will be described with reference to FIGS.

  In the state where an axial load does not act between the outer ring 1 and the hub 2 at room temperature, as shown in FIG. 8A, just in the center between the detection parts of the pair of sensors 6a and 6b, Consider a case where there is a portion where the inclination direction of the boundary between different characteristic portions changes. When the environmental temperature rises from this state and the holder 11 is thermally expanded, as shown in FIGS. 8A to 8B, the detected surface of the encoder 4 is the same as the case where the axial load is changed. And the detectors of the pair of sensors 6a and 6b are relatively displaced in the axial direction (vertical direction in FIG. 8). When such relative displacement occurs, the phase difference existing between the output signals of the sensors 6a and 6b changes as shown by the solid line → broken line in FIG.

  Thus, when the phase difference changes with the thermal expansion or contraction, the zero point of the relationship established between the phase difference and the state quantity (the position in the state where the axial load is not applied). Deviation occurs in the value of the phase difference. For this reason, an error occurs in the measurement result of the state quantity corresponding to the deviation. The error caused by such a cause can be reduced or eliminated by correcting the zero point on the arithmetic unit side while measuring the temperature around the bearing portion or the like. However, an excessive change in the phase difference caused by the thermal expansion or contraction is not preferable from the viewpoint of ensuring measurement accuracy. Therefore, it is desired to realize a structure that can sufficiently suppress the amount of change in the phase difference that occurs with the thermal expansion or contraction. In particular, the synthetic resin that is the material of the holder 11 is compared to a metal such as an iron-based alloy or aluminum-based alloy that is a material of other components such as the outer ring 1, the hub 2, the balls 3, 3, and the cover 5. The linear expansion coefficient is large. For this reason, it is desired to realize a structure that can sufficiently suppress the amount of change in the phase difference caused by thermal expansion or contraction of the holder 11.

  Corresponding to such circumstances, Patent Document 3 describes a structure for suppressing the thermal expansion and contraction of the holder 11a from being associated with a load measurement error as shown in FIG. 10, for example. In the case of the second example of this conventional structure, the holder 11a is supported to the cover 5a via a fixing ring 13. The fixing ring 13 is an L-shaped cross section made of a metal plate and is formed in an annular shape as a whole. A stepped cylindrical portion 14 and an inward flange-shaped circle provided at the axially outer end of the cylindrical portion 14 are provided. Annulus 15 is provided. Of these, the annular portion 15 is molded into the axially central portion (the portion corresponding to the central position O between the detection portions of the pair of sensors 6a and 6b) of the radially outer end portion of the holder 11a. Yes. In this state, the inner end portion or the central portion (the portion having a larger diameter than the outer end portion) of the cylindrical portion 14 is fitted and fixed to the intermediate portion of the cover 5a by an interference fit. An encoder 4a made of a permanent magnet is fitted and fixed to the inner end of the hub 2 in the axial direction. The detectors of both the sensors 6a and 6b are opposed to the detected surface provided on the outer peripheral surface of the encoder 4a, with the width direction being one side and the other side.

  In the case of the second example of the conventional structure configured as described above, when the holder 11a is thermally expanded or contracted due to a temperature change during use, the sensors 6a and 6b are associated with each other in the axial direction. They are displaced in the opposite directions and with the same size with respect to the center position O as a reference. For example, when the holder 11a is thermally expanded, as shown in FIGS. 11A to 11B, both the sensors 6a and 6b are in the axial direction (the horizontal direction in FIG. 10 and the vertical direction in FIG. 11). Are displaced in the direction away from each other and by the same amount with respect to the central position O. As a result, for example, as indicated by a solid line → broken line in FIG. 12, the phases of the output signals of the sensors 6a and 6b change in the same direction and by the same magnitude. In the case of thermal contraction, the same result can be obtained only by changing the direction of change to the case of thermal expansion. Therefore, in the case of the second example of the conventional structure, even if the phase of the output signals of both the sensors 6a and 6b changes as the holder 11a thermally expands or contracts, both of the sensors 6a and 6b The phase difference existing between the output signals does not change. Therefore, the measurement accuracy of the axial load acting between the outer ring 1 and the hub 2 can be maintained well regardless of the temperature change during use.

  According to the structure of the second conventional example as described above, measurement of the axial load in which the thermal expansion and contraction of the synthetic resin holder 11a having a large linear expansion coefficient acts between the outer ring 1 and the hub 2 is performed. It can prevent the accuracy from deteriorating. However, in the structure shown in FIG. 10 as described above, the sensors 6a and 6b are supported and fixed to the outer ring 1 via the cover 5a. On the other hand, it is considered to adopt a structure in which the sensor is mounted on a part other than the component parts of the wheel bearing rolling bearing unit, such as a component part of a suspension device such as a knuckle. The structure of the conventional second example shown in FIG. 10 cannot be adopted. As described above, a structure according to the prior invention disclosed in Japanese Patent Application No. 2009-215463 will be described with reference to FIG. 13 as an example of a structure in which the sensor is mounted on a portion other than the components of the wheel bearing rolling bearing unit. .

  Also in the structure of this prior invention, the encoder 4b is supported and fixed to the inner end of the hub 2a in the axial direction. The encoder 4b 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 continuously increased by stepped portions, and has an annular shape as a whole. The encoder body 17 has a cylindrical shape as a whole in a state where the encoder body 17 is attached and fixed to the outer peripheral surface of the large-diameter cylindrical portion over the entire circumference. On the outer peripheral surface of the encoder body 17, S poles and N poles are alternately arranged at equal intervals in the circumferential direction, and the shape of the boundary between these S poles and N poles is set to “<”. It has a shape. In such an encoder 4b, the outer half in the axial direction of the small-diameter cylindrical portion constituting the cored bar 16 is externally fitted to the inner end in the axial direction of the hub 2a with an interference fit. It is supported and fixed concentrically with the hub 2a.

  A pair of sensors 6a and 6b is embedded and supported at the tip of a holder 11b made of synthetic resin or the like to constitute a sensor unit 18. In the assembled state to the vehicle body, the sensor unit 18 includes a first characteristic changing portion which is a detection portion of one of the sensors 6a and 6b, which is one end portion in the axial direction of the outer peripheral surface of the encoder body 17. In addition, the detection part of the other sensor 6b is brought close to and opposed to the second both characteristic change parts which are also the other half part in the axial direction. Further, another encoder 4c is supported and fixed to a portion near the inner end in the axial direction of the hub 2a. This another encoder 4c is fixed to the entire circumference of a cored bar 19 which is L-shaped in cross section with a magnetic metal plate and is configured as a whole in an annular shape, and on the inner side surface in the axial direction of the annular part constituting the cored bar 19. The encoder body 20 is made of a permanent magnet and has a ring shape. On the inner side surface of the encoder body 20 in the axial direction, S poles and N poles are alternately arranged at equal intervals in the circumferential direction. The shape of the boundary between the S pole and the N pole is a linear shape that matches the width direction (radial direction) of the inner side surface in the axial direction. Such an encoder 4c is supported and fixed concentrically with the hub 2a by externally fitting the cored bar 19 to the portion near the inner end in the axial direction of the hub 2a. And the detection part of another sensor 6c is made to oppose the axial direction inner surface of the said encoder 4c. The sensor 6c constitutes a sensor unit 18a while being embedded and held at the tip of the holder 11c. The structure shown in FIG. 13 is a structure for a drive wheel. The spline shaft 21 attached to the constant velocity joint is inserted into the hub 2a from the inner side in the axial direction, and the retaining bolt 22 is used to prevent it from coming off. ing.

  Although FIG. 13 does not describe a specific support structure for the sensor units 18 and 18a, in the actual case, it is directly or appropriately applied to the components of the suspension device such as the knuckle 23. It will be supported through the bracket. The sensor unit 18 for measuring the axial load acting between the outer ring 1a and the hub 2a (or the relative displacement in the axial direction between the outer ring 1a and the hub 2a) is shown in FIG. As in the case of the first example of the conventional structure shown, there arises a problem of measurement error due to thermal expansion and thermal contraction of the synthetic resin holder 11b. If the sensor unit 12 is supported and fixed to the outer ring 1 via the cover 5 as in the first example of the conventional structure, the structure of the conventional second example shown in FIG. 10 is applied. Thus, the measurement error can be suppressed, but the structure of the second example cannot be applied to the structure in which the sensor unit 18 is supported on the components of the suspension device as shown in FIG.

  In view of the circumstances as described above, the present invention is a structure in which a pair of sensors are embedded and supported in a holder, and the thermal expansion and contraction of the holder are measured based on the output signals of both sensors. It was invented to realize a structure capable of reducing the influence on accuracy.

The physical quantity measuring device for a rolling bearing unit according to the present invention includes a rolling bearing unit, an encoder, a pair of sensors, and a calculator.
Of these, the rolling bearing unit is a combination of an outer ring that is supported and fixed to the structural member of the suspension device and does not rotate during use, and a hub that rotates together with the wheel during use in a relatively rotatable manner via a plurality of rolling elements. Become.
The encoder is supported and fixed to the inner end of the hub in the axial direction. The characteristics of the detected surface, which is the outer peripheral surface concentric with the hub, are alternately changed with respect to the circumferential direction, and the boundaries between the different characteristic portions adjacent to each other in the circumferential direction coincide with the axial direction of the encoder. The detected surface is inclined with respect to the width direction. In addition, the direction in which each boundary is inclined with respect to the direction of the central axis is opposite to each other in the half portion and the other half portion of the detected surface.
In addition, the two sensors are opposed to each other by separating the detection part into one half part and the other half part of the detection surface while being held by a holder supported and fixed to the structural member of the suspension device. . And each output signal is changed corresponding to the characteristic change of the said to-be-detected surface accompanying rotation of the said encoder.
Further, the computing unit is based on the output signals of the two sensors, and at least one of a relative displacement amount between the outer ring and the hub and an axial load acting between the outer ring and the hub. Is calculated.

  In particular, in the physical quantity measuring device for a rolling bearing unit according to the present invention, the angle at which each of the boundaries is inclined with respect to the direction of the central axis of the encoder is defined as one half and the other half of the detected surface. Are the same as each other. In addition, with respect to the axial direction of the encoder, the mounting surface of the holder relating to the structural member of the suspension device and the central portion in the axial direction of the detection portions of the two sensors are located at the same position.

When the physical quantity measuring device for a rolling bearing unit according to the present invention is implemented, it is preferable that an axial load does not act between the outer ring and the hub as in the invention described in claim 2. In a state where the hub and the hub are in a neutral position in the axial direction, in addition to the mounting surface of the holder and the central portion in the axial direction of the detecting portions of the two sensors, the characteristic portions existing on the detected surface of the encoder The portions where the inclination direction of the boundary changes are also present at the same position in the axial direction.
Preferably, as in the invention described in claim 3, the direction of the straight line connecting the central positions of the detection portions of the two sensors is made to coincide with the direction of the central axis of the encoder.
Further, preferably, as in the invention described in claim 4, the rolling bearing unit is fixed to the structural member by fixing the stationary side flange provided on the outer peripheral surface to the structural member of the suspension device. It shall be supported. Then, by holding a shim plate having a predetermined thickness between the axial inner surface of the stationary flange and the axial outer surface of the suspension device component, the axial position of the encoder relative to this component is adjusted. To do.

According to the physical quantity measuring device for a rolling bearing unit of the present invention configured as described above, a pair of sensors are embedded and supported in a holder, and the thermal expansion and contraction of the holder are the output signals of both sensors. It is possible to reduce the influence of the physical quantity obtained based on the measurement accuracy.
That is, in the case of the physical quantity measuring device for a rolling bearing unit according to the present invention, the mounting surface of the holder relating to the structural member of the suspension device and the central portion in the axial direction of the detecting portions of both sensors are in the same position with respect to the axial direction. Exists. For this reason, as shown in FIG. 11, the detection portions of the two sensors are moved at the central position as shown in FIG. 11 in accordance with the thermal expansion and contraction of the holder. The holders are displaced by the same amount on the opposite side in the axial direction with reference to the mounting surface of the holder related to the structural member of the suspension device. Therefore, the phases of the output signals of the two sensors change in the same direction and by the same magnitude. For this reason, even if the phases of the output signals of the two sensors change as the holder thermally expands or contracts, the phase difference existing between the output signals of the two sensors does not change. Therefore, the measurement accuracy of the axial load acting between the outer ring and the hub (the amount of axial relative displacement between the outer ring and the hub) can be favorably maintained regardless of the temperature change during use.

Further, as in the invention described in claim 2, in the neutral state, if the portion where the inclination direction of the boundary between the characteristic portions existing on the detected surface of the encoder changes also exists at the same position, the neutral state Thus, the phase difference between the output signals of the two sensors can be made zero, and the calculation for measuring the axial load from the output signals of both the sensors can be easily performed.
Further, as in the invention described in claim 3, if the direction of the straight line connecting the center positions of the detection portions of the two sensors is made to coincide with the direction of the central axis of the encoder, the holder is caused to thermally expand and contract. It is also possible to prevent the positional relationship between the two sensors from deviating with respect to the circumferential direction. And it can also prevent that a measurement error arises regarding the said axial load based on the shift | offset | difference regarding this circumferential direction.
Further, as in the invention described in claim 4, this structure is obtained by sandwiching a shim plate having a predetermined thickness between the axial inner surface of the stationary flange and the axial outer surface of the structural member of the suspension device. By adjusting the axial position of the encoder with respect to the member, the axial position of the mounting surface of the holder and the axial center of the detection parts of the two sensors are matched regardless of the dimensional error of the structural members of the suspension device. Can be easily performed.

The principal part sectional view showing one example of an embodiment of the invention. The figure which took out the sensor unit and was seen from the lower part of FIG. The perspective view shown in the state which took out the sensor unit and the encoder and was seen from the upper left of FIG. The figure which took out a pair of sensor and encoder, and was seen from the upper part of FIG. Sectional drawing which shows the 1st example of a conventional structure. The figure which looked at a part of encoder from the radial direction. The schematic diagram for demonstrating the reason for which an axial load is calculated | required. In order to explain the reason why the phase difference between the output signals of a pair of sensors changes with the thermal expansion of the holder, both these sensors and the encoder are taken out, and the normal state (A) and the state when the temperature rises ( B) and a schematic diagram. The diagram which shows the state from which the phase difference between the output signals of a pair of sensors changes with the thermal expansion of a holder. The principal part sectional drawing which is the 2nd example of the conventional structure, and shows the structure considered in order to suppress the measurement error accompanying the thermal expansion and thermal contraction of a holder. The same figure as FIG. 8 for demonstrating the reason which can suppress a measurement error. The same figure as FIG. Sectional drawing which shows the structure which concerns on a prior invention.

1 to 4 show an example of an embodiment of the present invention. The physical quantity measuring device for a rolling bearing unit of this example includes a rolling bearing unit 24, an encoder 4b, a pair of sensors 6a and 6b, and a calculator (not shown).
Of these, the rolling bearing unit 24 includes an outer ring 1a, a hub 2a, and a plurality of balls 3, 3 each of which is a rolling element. Of these, the outer ring 1a is provided with a double row outer ring raceway on the inner peripheral surface and a stationary flange 25 on the outer peripheral surface. The stationary flange 25 is screwed onto a knuckle 23, which is a component of the suspension device. It is fixed and does not rotate during use. A shim plate 31 is sandwiched between the stationary flange 25 and the knuckle 23. And as this shim plate 31, by selecting and using one having an appropriate thickness, the axial position of the outer ring 1a relative to the knuckle 23, and further, the inner diameter side of the outer ring 1a, The axial positions of the hub 2a and the encoder 4b can be adjusted. The hub 2a is provided with a double-row inner ring raceway and a rotation side flange 26 on the outer peripheral surface, and rotates with a wheel coupled and fixed to the rotation side flange 26 in use. The balls 3 and 3 are rotatably provided between the outer ring raceways and the inner ring raceways, and rotatably support the hub 2a on the inner diameter side of the outer ring 1a. In the case of this example, the spline shaft 28 attached to the constant velocity joint is inserted into the spline hole 27 formed at the center of the hub 2a so that the hub 2a can be driven to rotate.

  The encoder 4b is made of a magnetic metal plate and has a combination of a crank-type cored bar 16 and a permanent magnet encoder body 17. The cored bar 16 is connected to the inner end of the hub 2a in the axial direction. It is supported and fixed concentrically with the hub 2a by externally fitting with an interference fit. On the outer peripheral surface of the encoder body 17, the S pole and the N pole are changed alternately at equal intervals in the circumferential direction. The boundary between the adjacent S poles and N poles is inclined with respect to the direction of the central axis of the encoder 4b (the width direction of the outer peripheral surface of the encoder body 17 that is the detected surface). In addition, the direction in which each boundary is inclined with respect to the direction of the central axis is opposite to each other in one half and the other half of the detected surface. Further, the angle at which each boundary is inclined with respect to the direction of the central axis is the same (for example, 45 degrees) in one half and the other half of the detected surface. In the illustrated example, the encoder 4b is protected by covering the periphery of the encoder 4b with a protective cover 32 made of a non-magnetic plate.

  The sensors 6a and 6b constitute a sensor unit 30 in a state of being embedded and held in a synthetic resin holder 29 supported and fixed to the knuckle 23. Then, in a state where the sensor unit 30 is supported and fixed to the knuckle 23, the detection portions of the sensors 6a and 6b are respectively connected to the detection surface (the encoder main body 17 of the encoder body 17) via the protective cover 32. The outer peripheral surface is divided into one half (the left half in FIGS. 1, 3 and 4) and the other half (the right half in FIGS. 1, 3 and 4) and face each other. The output signals of both the sensors 6a and 6b are changed in response to the change in the characteristics of the detected surface accompanying the rotation of the encoder 4b. In the case of this example, in order to improve the measurement accuracy of both the sensors 6a and 6b, a differential type in which a pair of Hall ICs are shifted in the rotation direction of the encoder 4b as the sensors 6a and 6b. Hall IC is used. The structure and operation of the differential Hall IC are described in Patent Documents 4 and 5, etc., and are generally commercially available, so detailed explanations are omitted. In the illustrated example, the differential Hall IC is used as both the sensors 6a and 6b, and the center position of the detection part of both the sensors 6a and 6b is the central part of the pair of Hall ICs. . In the case of this example, the direction of the straight line connecting the central positions of the detection parts of both the sensors 6a and 6b is made to coincide with the direction of the central axis of the encoder 4b. In other words, the sensors 6a and 6b are arranged in the direction of the central axis of the encoder 4b (without shifting in the circumferential direction).

  In order to support and fix the sensor unit 30 as described above to the knuckle 32, a mounting portion 33 is formed at an intermediate portion of the outer diameter side surface of the holder 29. When the sensor unit 30 is supported and fixed to the knuckle 23, the axially outer side surface of the mounting portion 33 and the axially inner side surface of the knuckle 23 are brought into contact with each other. With respect to the axial direction of the encoder 4b, the position of the outer surface in the axial direction of the mounting portion 33 and the central portion in the axial direction of the detection portions of the sensors 6a and 6b are in the same position. Such regulation is performed when the holder 29 including the mounting portion 33 is injection-molded while the sensors 6a and 6b are embedded and supported at predetermined positions of the holder 29. Therefore, in the state where the sensor unit 30 is supported and fixed to the knuckle 32 as described above, the mounting surface of the holder 29 with respect to the knuckle 23 and the detection of the sensors 6a and 6b with respect to the axial direction of the encoder 4b. The central part in the axial direction of the part exists at the same position (on the chain line α in FIGS. 1, 2 and 4).

  Furthermore, in the case of the physical quantity measuring device for the rolling bearing unit of the present example, by selecting the shim plate 31 having an appropriate thickness dimension, the S pole existing on the detected surface of the encoder 4b. The portion where the inclination direction of the boundary between the N pole and the N pole changes is also located on the chain line α in a neutral state. That is, in the neutral state, as shown in FIG. 4, the detecting portions of the sensors 6a and 6b are portions where the inclination direction changes, that is, the center position in the width direction of the detection surface of the encoder 4b (the chain line α From the position) on the opposite side in the axial direction by the same distance. Such adjustment can be easily performed regardless of the dimensional error of the knuckle 23 only by selecting and using the shim plate 31 having an appropriate thickness.

  The computing unit calculates the relative displacement between the outer ring 1a and the hub 2a and the distance between the outer ring 1a and the hub 2a based on the output signals of the pair of sensors 6a and 6b as described above. At least one of the axial loads acting on is calculated. As described above, for example, the principle of calculating the axial load based on the output signals of the sensors 6a and 6b is as described in FIG.

  In the case of the physical quantity measuring device of the rolling bearing unit of the present example configured as described above, the mounting surface of the synthetic resin holder 29 with respect to the knuckle 23, and the axial central portion of the detecting portions of the sensors 6a and 6b, Are present at the same position in the axial direction. Therefore, even when the holder 29 is thermally expanded or contracted, the phases of the output signals of the sensors 6a and 6b are not shifted due to the thermal expansion and contraction. That is, when the holder 29 expands and contracts with a change in temperature, the mounting surface becomes the starting point of expansion and contraction, and the sensors 6a and 6b are displaced by the same length on the opposite side in the axial direction. As a result, as in the case of the second example of the conventional structure shown in FIG. 10, the phase difference existing between the output signals of the sensors 6a and 6b changes as described in FIG. do not do. Therefore, the measurement accuracy of the axial load acting between the outer ring 1a and the hub 2a can be satisfactorily maintained regardless of the temperature change during use.

  In the case of this example, in the neutral state, the portion where the inclination direction of the boundary between the S pole and the N pole changes on the detected surface of the encoder 4b also exists at the same position. The phase difference between the output signals of the two sensors 6a and 6b in the state can be made zero. As a result, the calculation for measuring the axial load can be easily performed from the output signals of both the sensors 6a and 6b. That is, since it is not necessary to set a zero point in the equation for obtaining this axial load from the phase difference (zero point can be set to 0), the speed of calculation processing is increased, the axial load is quickly obtained, and the vehicle travels. It is possible to more appropriately take measures to ensure stability.

  Further, in the case of this example, the direction of the straight line connecting the center positions of the detection portions of the sensors 6a and 6b is made to coincide with the direction of the central axis of the encoder 4b. It is possible to prevent the positional relationship between the two sensors 6a and 6b from deviating with respect to the circumferential direction due to heat shrinkage. That is, when the installation positions of both the sensors 6a and 6b are shifted in the circumferential direction, the magnitude of the shift in the circumferential direction of both the sensors 6a and 6b is caused by the thermal expansion and contraction of the holder 29. The phase difference existing between the output signals of both the sensors 6a and 6b changes due to factors other than the axial load. In this example, by restricting the arrangement direction of the sensors 6a and 6b as described above, it is possible to prevent the phase difference from being changed due to factors other than the axial load, and a measurement error occurs with respect to the axial load. Prevent things.

  The present invention is particularly effective when applied to a rolling bearing unit for a drive wheel as shown in FIG. 1, in which the sensor unit is difficult to be attached to the outer ring for the convenience of assembling the spline shaft of the constant velocity joint to the hub. There is. However, the present invention is not limited to such a drive wheel, but can be implemented in a rolling bearing unit for a driven wheel.

DESCRIPTION OF SYMBOLS 1, 1a Outer ring 2, 2a Hub 3 Ball 4, 4a, 4b, 4c Encoder 5, 5a Cover 6a, 6b, 6c Sensor 7 Through-hole 8 Pillar part 9, 9a First characteristic change part 10, 10a Second characteristic Change part 11, 11a, 11b, 11c Holder 12, 12a Sensor unit 13 Fixing ring 14 Cylindrical part 15 Annulus part 16 Core metal 17 Encoder main body 18, 18a Sensor unit 19 Core metal 20 Encoder main body 21 Spline shaft 22 Retaining bolt 23 Knuckle 24 Rolling bearing unit 25 Static side flange 26 Rotation side flange 27 Spline hole 28 Spline shaft 29 Holder 30 Sensor unit 31 Shim plate 32 Protective cover 33 Mounting part

JP 2006-317420 A JP 2007-309683 A JP 2008-175546 A JP-A-8-220200 JP 2007-93467 A

Claims (4)

A rolling bearing unit, an encoder, a pair of sensors, and a calculator;
Of these, the rolling bearing unit is a combination of an outer ring that is supported and fixed to the structural member of the suspension device and does not rotate during use, and a hub that rotates together with the wheel during use in a relatively rotatable manner via a plurality of rolling elements. It consists of
The encoder is supported and fixed at the inner end in the axial direction of the hub, and alternately changes the characteristics of the detected surface, which is the outer peripheral surface concentric with the hub, with respect to the circumferential direction, and is adjacent to the circumferential direction. The boundary between different characteristic parts is inclined with respect to the width direction of the detected surface that coincides with the axial direction of the encoder, and each boundary is inclined with respect to the direction of the central axis. Are opposite to each other in one half and the other half of the detected surface,
The two sensors are arranged so as to face each other by separating the respective detection units into one half and the other half of the detected surface in a state of being held by a holder supported and fixed to the structural member of the suspension device, Each output signal is changed in response to a change in the characteristics of the detected surface as the encoder rotates,
The computing unit calculates at least one of a relative displacement amount between the outer ring and the hub and an axial load acting between the outer ring and the hub based on the output signals of the two sensors. In the physical quantity measuring device for rolling bearing units,
The angle at which each of the boundaries is inclined with respect to the direction of the central axis of the encoder is the same in one half and the other half of the detected surface, and with respect to the axial direction of the encoder, An apparatus for measuring a physical quantity of a rolling bearing unit, wherein a mounting surface of the holder with respect to a constituent member and an axially central portion of the detection portions of the two sensors are present at the same position.   An axial load does not act between the outer ring and the hub, and the outer ring and the hub are in a neutral position with respect to the axial direction, in addition to the mounting surface of the holder and the central part in the axial direction of the detection part of both sensors. The physical quantity measuring device for a rolling bearing unit according to claim 1, wherein portions where the inclination direction of the boundary between the characteristic portions existing on the detection surface of the encoder changes also exist at the same position with respect to the axial direction.   The physical quantity measuring device for a rolling bearing unit according to any one of claims 1 to 2, wherein a direction of a straight line connecting the center positions of the detection units of the pair of sensors coincides with a direction of a central axis of the encoder. .   The rolling bearing unit is supported by fixing the stationary side flange provided on the outer peripheral surface to the structural member of the suspension device by screwing, and the axially inner side surface of the stationary side flange The axial position of the encoder with respect to the constituent member is adjusted by sandwiching a shim plate having a predetermined thickness between the axially outer surface of the constituent member of the suspension device. The physical quantity measuring device of the rolling bearing unit described in item 1.

Images