Drive unit

Abstract

To calculate drive torque in a drive unit.SOLUTION: A drive unit 10 comprises: a drive shaft 20 including an outer race section 21 and a shaft 22; a wheel bearing device 30 including a hub shaft 31, an outer ring 32, and multiple balls 33; and a sensor device 40 for detecting the torsion angle of the drive shaft 20 and the hub shaft 31. The sensor device 40 comprises: a first sensor 41 and a second sensor 42 disposed in the outer ring 32; a first sensor rotor 43 that is disposed in the inside in the radial direction of the first sensor 41 and is a detection object of the first sensor 41; and a second sensor rotor 44 that is disposed in the inside in the radial direction of the second sensor 42 and is a detection object of the first sensor 41. The first sensor 41 is disposed in one side in the axial direction in comparison with the second sensor 42, the first sensor rotor 43 is provided on an outer peripheral surface 24 of the outer race section 21, and the second sensor rotor 44 is provided on an outer peripheral surface 36 of the inner ring 34.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a drive device. [Background technology]

[0002] BACKGROUND ART Conventionally, a configuration is known in which a drive device for driving tires or the like of an automobile is provided with a sensor capable of detecting displacement of a hub axle (see Patent Document 1).

[0003] The driving device (rotating device) disclosed in Patent Document 1 uses an acting force calculation device to determine the rotation angle and displacement amount of the sensor rotor based on the waveform signal output from the sensor, thereby making it possible to calculate the acting force acting on the tire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-175376 Summary of the Invention [Problem to be solved by the invention]

[0005] The drive device disclosed in Patent Document 1 can calculate the tire stress (Fy) acting in the pitch axis (Y axis) direction and the moment (Mz) acting around the yaw axis (Z axis) from the rotation angle and displacement of the sensor rotor calculated by the acting force calculation device. However, the drive device disclosed in Patent Document 1 cannot calculate the drive torque, which is the moment (My) acting around the pitch axis (Y axis). An object of the present disclosure is to enable calculation of drive torque in a drive device. [Means for solving the problem]

[0006] The drive device disclosed herein is a drive device comprising: a drive shaft including an outer race portion provided on one axial side and an axle portion extending from an end face on the other axial side of the outer race portion to the other axial side; a hub axle having an axle hole through which the axle portion is inserted and an inner ring provided on one axial side; an outer ring provided radially outward of the hub axle; and a wheel bearing device including: a plurality of balls provided between the hub axle and the outer ring; and a sensor unit that detects the rotation angles of the drive shaft and the hub axle, wherein the sensor unit comprises a first sensor and a second sensor that are provided on the outer ring, a first target that is provided radially inward of the first sensor and is the detection target of the first sensor, and a second target that is provided radially inward of the second sensor and is the detection target of the second sensor, the first sensor is located on one axial side compared to the second sensor, the first target is provided on the outer peripheral surface of the outer race portion, and the second target is provided on the outer peripheral surface of the inner ring.

[0007] According to the present disclosure, it is possible to calculate the driving torque in the driving device. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a first embodiment of a drive device according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view illustrating a sensor device in the drive device according to the first embodiment. [Figure 3] FIG. 3 is a schematic diagram of the first sensor and the first sensor rotor as viewed from one axial side. [Figure 4] FIG. 4 is a schematic diagram of the second sensor and the second sensor rotor as viewed from one axial side. [Figure 5] FIG. 5 is a cross-sectional view showing a sensor device using a housing member. [Figure 6] FIG. 6 is an explanatory diagram of waveform signals output from the first sensor and the second sensor. [Figure 7] FIG. 7 is a block diagram illustrating the processing device. [Figure 8] FIG. 8 is an explanatory diagram of an angle signal obtained by converting a waveform signal. [Figure 9] FIG. 9 is a cross-sectional view showing a second embodiment of the driving device of the present disclosure. [Figure 10] FIG. 10 is a cross-sectional view showing a sliding portion and a sensor device in a drive device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Details of the embodiment of the present disclosure> Hereinafter, details of embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0010] [Overall configuration of the drive unit] FIG. 1 is a cross-sectional view showing a first embodiment of a drive unit according to the present disclosure. FIG. 2 is a cross-sectional view showing a sensor device in the drive unit according to the first embodiment. FIG. 1 shows a drive unit 10 according to the first embodiment of a drive unit according to the present disclosure. The drive unit 10 shown in this embodiment is a tire drive unit for an automobile. As shown in FIG. 1, the drive unit 10 includes a drive shaft 20 and a wheel bearing device 30. In the following description, the drive unit 10 according to the first embodiment will also be referred to as a first drive unit 10A. Note that in the following description, when the term "drive unit 10" is simply used, the description will refer to a configuration common to the first drive unit 10A and drive units 10 according to other embodiments (second drive unit 10B, described later; see FIG. 9).

[0011] As shown in FIGS. 1 and 2, the drive shaft 20 includes an outer race portion 21 and a shaft portion 22. The wheel bearing device 30 includes a hub axle 31, a cylindrical outer ring 32 provided radially outward from a portion of the hub axle 31, and balls 33 serving as rolling elements. In the drive unit 10, the direction along the center line C of the outer ring 32 is referred to as the "axial direction." Here, "axial direction" also includes a direction parallel to the center line C. The direction perpendicular to the center line C is referred to as the "radial direction." In the drive unit 10 of this embodiment, the hub axle 31 rotates around the center line C. The direction of rotation around the center line C is referred to as the "circumferential direction." The direction along the center line C is referred to as the Y-axis (pitch axis) direction. The horizontal direction perpendicular to the center line C is referred to as the X-axis (roll axis) direction. The vertical direction perpendicular to the center line C is referred to as the Z-axis (yaw axis) direction. In FIGS. 1 and 2, a Cartesian coordinate system is defined by the X-axis, Y-axis, and Z-axis. When the drive unit 10 is fixed to the vehicle body and the steering angle is zero, the front-to-rear direction of the vehicle coincides with the direction along the X axis, the left-to-right direction coincides with the direction along the Y axis, and the up-to-down direction coincides with the direction along the Z axis.

[0012] [Drive shaft] The drive shaft 20 is provided coaxially with the hub axle 31. The outer race portion 21 constitutes part of the constant velocity joint and is provided on one axial side of the drive shaft 20. The outer race portion 21 has an end face 23 on the other axial side and an outer peripheral surface 24. The shank portion 22 is provided on the other axial side of the drive shaft 20. The shank portion 22 is provided extending from the end face 23 of the outer race portion 21 to the other axial side. The shank portion 22 has splines formed on its outer peripheral surface.

[0013] [Wheel bearing device] The hub axle 31 has an inner shaft 31a, a flange portion 31b provided on one axial side of the inner shaft 31a, and a shaft hole 31c formed coaxially in the inner shaft 31a. The flange portion 31b is provided to extend radially outward from the other axial side of the inner shaft 31a. The shaft hole 31c has splines formed on its inner circumferential surface. A wheel and brake rotor (not shown) are attached to the surface of the other axial side of the flange portion 31b of the hub axle 31. The hub axle 31 also has an inner ring 34 provided on one axial side of the inner shaft 31a.

[0014] The shaft portion 22 of the drive shaft 20 is inserted into the shaft hole 31c of the hub axle 31. The shaft portion 22 and the shaft hole 31c are spline-fitted to each other, so that the hub axle 31 and the drive shaft 20 rotate together around the center line C.

[0015] The outer ring 32 has a cylindrical outer ring body 32a and a fixing flange 32b extending radially outward from the outer ring body 32a. The outer ring 32 is attached to a knuckle (not shown), which is a vehicle body member, by the flange 32b, thereby fixing the drive unit 10 including the outer ring 32 to the vehicle body. In this embodiment, the outer ring 32 is the fixed body, and the hub axle 31 (inner ring 34) is the rotating body. The hub axle 31 (inner ring 34) rotates around a center line C relative to the outer ring 32.

[0016] The inner ring 34 is an annular member that fits over the other axial side of the inner shaft 31a and is fixed in a state where it is prevented from slipping out in the axial direction. The inner ring 34 has an end face 35 on one axial side and an outer peripheral surface 36. An outer raceway surface with which the balls 33 roll and make contact is formed on the inner peripheral side of the outer ring main body portion 32a, and inner raceway surfaces with which the balls 33 roll and make contact are formed on the outer peripheral sides of each of the inner shaft 31a and the inner ring 34. The balls 33 are arranged in two rows between the outer ring 32 and the hub axle 31. The multiple balls 33 in each row are held in place by a cage (not shown).

[0017] In the drive unit 10, when the shaft portion 22 of the drive shaft 20 is inserted into the shaft hole 31c of the hub axle 31, the end face 23 of the outer race portion 21 and the end face 35 of the inner ring 34 face each other. In the drive unit 10, the end face 23 and the end face 35 are formed from separate members and are capable of relative displacement in the circumferential direction. In the first drive unit 10, the end face 23 and the end face 35 are in direct contact with each other.

[0018] [Sensor device] FIG. 3 is a schematic diagram of the first sensor and the first sensor rotor as viewed from one axial side. FIG. 4 is a schematic diagram of the second sensor and the second sensor rotor as viewed from one axial side. As shown in FIGS. 1 and 2, the drive device 10 further includes a sensor device 40. The sensor device 40 includes a first sensor 41, a second sensor 42, a first sensor rotor (first target) 43, and a second sensor rotor (second target) 44. As shown in FIGS. 3 and 4, the first sensor rotor 43 and the second sensor rotor 44 are annular members. The first sensor rotor 43 is a detection target (first target) for the first sensor 41 and rotates integrally with the hub axle 31. The second sensor rotor 44 is a detection target (second target) for the second sensor 42 and rotates integrally with the hub axle 31. In this embodiment, the first sensor rotor 43 and the second sensor rotor 44 have a gear shape with multiple teeth spaced (equally spaced) along the circumferential direction. The teeth are the detection targets of the first sensor 41 and the second sensor 42. The first sensor rotor 43 and the second sensor rotor 44 are preferably made of a ferromagnetic material.

[0019] As shown in FIGS. 1 and 2 , the first sensor rotor 43 is disposed on one axial side of the outer race portion 21. The first sensor rotor 43 is attached to the outer peripheral surface 24 of the outer race portion 21, centered on the center line C. In this embodiment, the first sensor rotor 43 is fitted onto and fixed to the outer race portion 21. The second sensor rotor 44 is disposed on the other axial side of the inner ring 34. The second sensor rotor 44 is attached to the outer peripheral surface 36 of the inner ring 34, centered on the center line C. In this embodiment, the second sensor rotor 44 is fitted onto and fixed to the inner ring 34.

[0020] 1 to 4, in the drive device 10 of the present disclosure, the sensor device 40 includes a plurality of first sensors 41 and a plurality of second sensors 42. Specifically, the drive device 10 of the present disclosure includes four first sensors 41 and four second sensors 42.

[0021] The first sensor 41 is provided radially outward of the first sensor rotor 43 and detects the first sensor rotor 43 (the teeth, which are part of the first sensor rotor 43). In this embodiment, four first sensors 41 are provided at equal intervals along the circumferential direction. The second sensor 42 is provided radially outward of the second sensor rotor 44 and detects the second sensor rotor 44 (the teeth, which are part of the second sensor rotor 44). In this embodiment, four second sensors 42 are provided at equal intervals along the circumferential direction. The subscripts (A, B, C, D) of the reference symbols attached to the first sensors 41 and the second sensors 42 indicate their positions with respect to the center line C, and in FIGS. 3 and 4 , indicate the top, bottom, front, and rear positions with respect to the center line C. For example, the reference symbols of the sensors located at the top are "41A, 42A," the reference symbols of the sensors located at the bottom are "41B, 42B," the reference symbols of the sensors located at the front are "41C, 42C," and the reference symbols of the sensors located at the rear are "41D, 42D."

[0022] The configuration of the first sensor 41 is the same regardless of whether it is on the top, bottom, front, or back, so the suffixes (A, B, C, D) will be omitted in common descriptions of the first sensor 41. The first sensor 41A and the first sensor 41B are provided 180 degrees apart around the center line C. These upper and lower first sensors 41A and 41B form one sensor group. The first sensor 41C and the first sensor 41D are provided 180 degrees apart around the center line C. These front and rear first sensors 41C and 41D form another sensor group. The first sensor 41A and the first sensor 41C are provided 90 degrees apart around the center line C.

[0023] The configuration of the second sensor 42 is the same regardless of whether it is above, below, front, or back, and therefore the suffixes (A, B, C, D) will be omitted in common descriptions of the second sensor 42. The second sensor 42A and the second sensor 42B are provided 180 degrees apart around the center line C. The upper and lower second sensors 42A and 42B form one sensor group. The second sensor 42C and the second sensor 42D are provided 180 degrees apart around the center line C. The front and rear second sensors 42C and 42D form another sensor group. The second sensor 42A and the second sensor 42C are provided 90 degrees apart around the center line C.

[0024] In this embodiment, the first sensor 41 and the second sensor 42 are magnetic sensors that function as displacement sensors and rotation sensors using magnetoresistive elements. The first sensor 41 and the second sensor 42 have an A-phase magnetoresistive element and a B-phase magnetoresistive element. The first sensor 41 and the second sensor 42 detect magnetic field changes associated with circumferential movement of the sensor rotors 43 and 44, which the first sensor 41 and the second sensor 42 face, using the A-phase and B-phase magnetoresistive elements, respectively. In this embodiment, as described above, the sensor rotors 43 and 44 are gears, and the first sensor 41 and the second sensor 42 detect the outer periphery of each sensor rotor 43 and 44, where the gear teeth are provided. As the sensor rotors 43 and 44 rotate around the center line C, the magnetic field in the first sensor 41 and the second sensor 42 changes. Based on this magnetic field change, the first sensor 41 and the second sensor 42 output waveform signals of phases A and B, which are out of phase, as detection signals. In the drive unit 10 of the present disclosure, the sensor device 40 detects the rotation angle of the outer race portion 21 (drive shaft 20) using the first sensor 41 and the first sensor rotor 43, and detects the rotation angle of the inner ring 34 (hub axle 31) using the second sensor 42 and the second sensor rotor 44.

[0025] [Modification of the sensor device] FIG. 5 is a cross-sectional schematic diagram showing a sensor device using a housing member. As shown in FIG. 5, in the drive unit 10 of the present disclosure, the first sensor 41 and the second sensor 42 may be fixed to the outer ring 32 via a housing member 38. The housing member 38 shown in this embodiment is made of resin. Therefore, in the drive unit 10 of the present disclosure, the housing member 38 having a complex shape can be easily manufactured by an existing method such as injection molding. Note that in the drive unit 10 of the present disclosure, the housing member 38 may be made of metal.

[0026] The housing member 38 includes a substantially annular housing main body 38a, two annular grooves 38b, and a window portion 38c formed in the bottom of the annular groove 38b. When the housing member 38 is used, the first sensor 41 is disposed inside the annular groove 38b on one axial side, and the second sensor 42 is disposed inside the annular groove 38b on the other axial side. The first sensor 41 and the second sensor 42 detect the first sensor rotor 43 and the second sensor rotor 44 disposed radially inward through the window portion 38c that opens radially inward.

[0027] 1, the first sensor 41 and the second sensor 42 are directly fixed to the inner peripheral surface of the outer ring 32, which is extended to one side in the axial direction. In this case, the outer ring 32 needs to be modified in shape to be extended to one side in the axial direction in order to secure space for arranging the first sensor 41 and the second sensor 42. In this case, it becomes difficult to use a conventional outer ring.

[0028] 5, when a housing member 38 is used, the drive unit 10 can be configured using a conventional outer ring. When the housing member 38 is used, the first sensor 41 and the second sensor 42 can be installed in the housing member 38 first, and then the housing member 38 can be fixed to the outer ring 32, thereby installing the first sensor 41 and the second sensor 42 on the outer ring 32. Therefore, when the housing member 38 is used, the work of installing the first sensor 41 and the second sensor 42 on the outer ring 32 becomes easier.

[0029] [Sensor device output signal] FIG. 6 is an explanatory diagram of waveform signals output from the first sensor and the second sensor. The output signals of the first sensor 41 and the second sensor 42 will now be further described. As described above, each sensor rotor 43, 44 has a gear shape. Therefore, the first sensor 41 and the second sensor 42 repeatedly output waveform signals, with one cycle spanning from one tooth of each sensor rotor 43, 44 (via the recess) to the adjacent tooth in the circumferential direction. The number of teeth on each sensor rotor 43, 44 is defined as "N." When the hub axle 31 (inner ring 34) and the drive shaft 20, which are integral with each sensor rotor 43, 44, rotate once (360 degrees), each of the first sensors 41A-41D and each of the second sensors 42A-42D repeatedly outputs one cycle of waveform signals N times. That is, each of the first sensors 41A to 41D and each of the second sensors 42A to 42D outputs a periodic waveform signal for a plurality of periods while the hub axle 31 (inner ring 34) and the drive shaft 20 rotate once together with the sensor rotors 43, 44.

[0030] As shown in Fig. 6, each of the first sensors 41A-41D and each of the second sensors 42A-42D outputs a periodic waveform signal of two phases (A-phase and B-phase) having a phase difference, as described above. That is, as the sensor rotors 43, 44 opposed to each of the first sensors 41A-41D and each of the second sensors 42A-42D move, a SIN signal is output from the A-phase magnetic resistance element, and a COS signal is output from the B-phase magnetic resistance element. When the hub axle 31 (inner ring 34) and the drive shaft 20 rotate once (360 degrees), each of the first sensors 41A-41D and each of the second sensors 42A-42D outputs one cycle of the SIN signal N times and one cycle of the COS signal N times. The sensor device 40 outputs waveform signals including these SIN and COS signals to a processing device 50, which will be described later.

[0031] Although this embodiment illustrates the first sensor 41 and the second sensor 42 having two magnetic resistance elements arranged circumferentially, one for phase A and the other for phase B, the configuration of the first sensor 41 and the second sensor 42 employed in the drive device 10 of the present disclosure is not limited to this, and various sensors capable of detecting the rotational angles of the first sensor rotor 43 and the second sensor rotor 44 may be employed.

[0032] The first sensor rotor (first target) 43 and the second sensor rotor (second target) 44 may have a shape other than a gear shape. For example, they may be made of magnets with north and south poles alternately arranged along the circumferential direction. The north poles (south poles) are evenly distributed. In this case, each of the first sensors 41A-41D and each of the second sensors 42A-42D repeatedly outputs a waveform signal, with one cycle consisting of a north pole, a south pole, and a next north pole of each of the sensor rotors 43, 44. Each of the first sensors 41A-41D and each of the second sensors 42A-42D may output a two-phase periodic waveform signal having a phase difference as the sensor rotors 43, 44 rotate, and the form of each sensor may be changed. That is, each of the first sensors 41A-41D and each of the second sensors 42A-42D may be a Hall sensor instead of an MR sensor. Alternatively, the sensors may be optical sensors such as a transmission-type photoelectric sensor or a reflection-type photoelectric sensor. Accordingly, the configuration of each of the sensor rotors 43 and 44 is also changed.

[0033] [Processing device] FIG. 7 is a block diagram showing a processing device. As shown in FIG. 1, the drive unit 10 further includes a processing device 50. The processing device 50 has a processor and a storage device such as a memory in which a computer program is stored, and processes the waveform signal output from the sensor device 40 through processing executed by the processor in accordance with the computer program. As shown in FIG. 7, the processing device 50 includes, as functional units, a first torsion angle calculation unit 51, a second torsion angle calculation unit 52, a relative torsion angle calculation unit 53, a storage unit 54, and a drive torque calculation unit 55. The storage unit 54 stores the torsional stiffness K1 of the drive shaft 20 and the torsional stiffness K2 of the hub axle 31. The first sensors 41A to 41D are connected to the first torsion angle calculation unit 51, and the second sensors 42A to 42D are connected to the second torsion angle calculation unit 52.

[0034] The processing performed by the processing device 50 will now be described. Here, we will explain the case where a downward load acts on the hub axle 31 along the Z axis while the hub axle 31 and inner ring 34 (see FIGS. 1 and 2) are rotating at a constant speed (angular velocity). In this case, the hub axle 31 and the sensor rotors 43, 44 are slightly displaced downward along the Z axis relative to the outer ring 32. This displacement can be considered equivalent to the rotational movement of the outer peripheral surfaces of the sensor rotors 43, 44. In FIGS. 3 and 4, the rotation direction of the hub axle 31 and the sensor rotors 43, 44 is the direction of arrow R. On the side of the first sensor 41A and the second sensor 42A, the direction in which the hub axle 31 and the sensor rotors 43, 44 are displaced by the load is opposite to the rotation of the hub axle 31 (i.e., tangent to the rotation trajectory). As a result, compared to when no load is applied, the first sensor 41A and the second sensor 42A output waveform signals with a delayed phase for both the A and B phases, as shown in the upper explanatory diagram of FIG. 6. In other words, the first sensor 41A and the second sensor 42A detect the displacement of the respective sensor rotors 43, 44 as a delay angle. Note that in FIG. 6, the signals from the first sensor 41 and the second sensor 42 before the load is applied are indicated by solid lines, and the signals from the first sensor 41 and the second sensor 42 after the load is applied are indicated by dashed lines. In FIGS. 3 and 4, on the side of the first sensor 41B and the second sensor 42B, the direction in which the hub axle 31 and the respective sensor rotors 43, 44 are displaced by the load is forward (same direction) with respect to the rotation of the hub axle 31 (with respect to the tangent direction of the rotation trajectory). As a result, compared to when no load is applied, the first sensor 41B and the second sensor 42B output waveform signals with a delayed phase for both the A and B phases, as shown in the lower explanatory diagram of FIG. 6. That is, the first sensor 41B and the second sensor 42B detect the displacement of each sensor rotor 43, 44 as a lead angle. As described above, when the hub axle 31 is displaced in one radial direction (downward along the Z-axis in this embodiment) relative to the outer ring 32, the first sensor 41A and the second sensor 42A output a waveform signal with a delayed phase, and the first sensor 41B and the second sensor 42B output a waveform signal with an advanced phase.

[0035] Conversely, when the load direction is upward along the Z axis, the first sensor 41A and the second sensor 42A detect the displacement as a leading angle, and the first sensor 41B and the second sensor 42B detect the displacement as a lagging angle.

[0036] When a load is applied to the hub axle 31, a phase difference Q1 (see FIG. 6) occurs between the signals output from a pair of first sensors 41A and 41B, which are spaced 180 degrees apart around the center line C. This phase difference Q1 is obtained as a time difference between the waveforms. Therefore, in order to detect the (instantaneous) phase difference Q1 at a specific timing, an angle conversion process is performed on the waveform signals obtained from the first sensors 41A and 41B. Similarly, when a load is applied to the hub axle 31, a phase difference Q2 (see FIG. 6) occurs between the signals output from a pair of second sensors 42A and 42B, which are spaced 180 degrees apart around the center line C. This phase difference Q2 is obtained as a time difference between the waveforms. Therefore, in order to detect the (instantaneous) phase difference Q2 at a specific timing, an angle conversion process is performed on the waveform signals obtained from the second sensors 42A and 42B.

[0037] [Regarding the output signal of the processing device] FIG. 8 is an explanatory diagram of an angle signal obtained by converting a waveform signal. The angle conversion process performed by the processing device 50 will now be described. The waveform signals from the first sensor 41A and the first sensor 41B, and the waveform signals from the second sensor 42A and the second sensor 42B, are subjected to a predetermined arithmetic process (arc tangent calculation) to be converted into angle signals (electrical angle signals) having monotonicity for each period of the waveform signal, as shown in FIG. 8. The angle signals here are signals of electrical angles (unit: rad). The monotonicity means that the signal increases or decreases without any peaks or valleys along the way. In this embodiment, a monotonic triangular wave angle signal is obtained. The upper side of FIG. 8 is a graph of the angle signals from the first sensor 41A and the second sensor 42A, and the lower side of FIG. 8 is a graph of the angle signals from the first sensor 41B and the second sensor 42B. The angle (angle signal) shown on the vertical axis of each graph in Figure 8 is the rotation angle (electrical angle [rad]) of each sensor rotor 43, 44 at the detection target positions of the first sensor 41A and the second sensor 42A and the detection target positions of the first sensor 41B and the second sensor 42B, respectively.

[0038] 8, based on the angle signal (rotation angle) obtained by angle conversion processing of the waveform signal from the sensor device 40, a rotation angle (electrical angle) θ1A of the first sensor rotor 43 at the detection target position of the first sensor 41A is determined, and a rotation angle (electrical angle) θ1B of the first sensor rotor 43 at the detection target position of the first sensor 41B is determined, at a specific timing (specific time) t. Similarly, based on the angle signal (rotation angle) obtained by angle conversion processing of the waveform signal from the sensor device 40, a rotation angle (electrical angle) θ2A of the second sensor rotor 44 at the detection target position of the second sensor 42A is determined, and a rotation angle (electrical angle) θ2B of the second sensor rotor 44 at the detection target position of the second sensor 42B is determined, at a specific timing (specific time) t.

[0039] Then, the first torsion angle calculation unit 51 (see FIG. 7) calculates the difference in rotation angle (θ1AB=θ1A-θ1B) between the first sensor 41A side and the first sensor 41B side at the same timing (same time) t at the detection target position of the first sensor 41A and the detection target position of the first sensor 41B. In this embodiment, the electrical angles θ1A and θ1B are expressed in units of [rad], and the difference in electrical angle (θ1AB [rad]) is calculated as the difference in rotation angle. The value θ1AB calculated in this manner is then set as the first torsion angle θ1 of the drive shaft 20 (outer race portion 21) at the detection target position of the first sensor 41.

[0040] Similarly, the first torsion angle calculation unit 51 (see FIG. 7) may calculate the difference in rotation angle (θ1CD=θ1C-θ1D) between the first sensor 41C side and the first sensor 41D side at the same timing (same time) t at the detection target position of the first sensor 41C and the detection target position of the first sensor 41D. The value θ1CD calculated in this manner may then be used as the first torsion angle θ1 of the drive shaft 20 (outer race portion 21) at the detection target position of the first sensor 41. Furthermore, both the values ​​θ1AB and θ1CD may be calculated, and their average value may be used as the first torsion angle θ1 of the drive shaft 20 (outer race portion 21) at the detection target position of the first sensor 41. Alternatively, both the values ​​θ1AB and θ1CD may be calculated, and the larger value may be used as the first torsion angle θ1 of the drive shaft 20 (outer race portion 21) at the detection target position of the first sensor 41.

[0041] Furthermore, the second torsion angle calculation unit 52 (see FIG. 7) calculates the difference in rotation angle (θ2AB=θ2A-θ2B) between the second sensor 42A side and the second sensor 42B side at the same timing (same time) t at the detection target position of the second sensor 42A and the detection target position of the second sensor 42B. In this embodiment, the electrical angles θ2A and θ2B are expressed in units of [rad], and the difference in electrical angle (θ2AB [rad]) is obtained as the difference in rotation angle. The calculated θ2AB is then used as the second torsion angle θ2 of the inner ring 34 (hub axle 31) at the detection target position of the second sensor 42.

[0042] Similarly, the second torsion angle calculation unit 52 (see FIG. 7) may calculate the difference in rotation angle (θ2CD = θ2C - θ2D) between the second sensor 42C side and the second sensor 42D side at the same timing (same time) t at the detection target position of the second sensor 42C and the detection target position of the second sensor 42D. The value θ2CD calculated in this manner may then be used as the second torsion angle θ2 of the inner ring 34 (hub axle 31) at the detection target position of the second sensor 42. Furthermore, both the values ​​θ2AB and θ2CD may be calculated, and their average value may be used as the second torsion angle θ2 of the inner ring 34 (hub axle 31) at the detection target position of the second sensor 42. Alternatively, both the values ​​θ2AB and θ2CD may be calculated, and the larger value may be used as the second torsion angle θ2 of the inner ring 34 (hub axle 31) at the detection target position of the second sensor 42.

[0043] Due to unavoidable manufacturing errors, the hub axle 31 of the drive unit 10 whirls slightly relative to the outer ring 32. In this case, the whirling of the hub axle 31 appears as periodic fluctuations in the detection signals of the first sensors 41A-41D and the second sensors 42A-42D. This periodic fluctuation is an unwanted component in the waveform signals output from the first sensors 41A-41D and the second sensors 42A-42D. For this reason, it is preferable that the processing device 50 appropriately executes correction processing to reduce this unwanted component and obtain appropriate signal output.

[0044] The processing device 50 (see FIG. 7) executes the following calculations. As shown in FIG. 8, the processing device 50 calculates a first torsion angle θ1 using a first torsion angle calculation unit 51 based on the waveform signals output from each of the first sensors 41A to 41D. The processing device 50 calculates a second torsion angle θ2 using a second torsion angle calculation unit 52 based on the waveform signals output from each of the second sensors 42A to 42D. Next, the processing device 50 calculates a relative torsion angle θ12 using a relative torsion angle calculation unit 53 based on the first torsion angle θ1 and the second torsion angle θ2. The relative torsion angle θ12 is calculated using the following mathematical formula (1).

[0045] θ12=θ1-θ2 (1)

[0046] Next, the processing device 50 calculates the driving torque My based on the relative torsion angle θ12, the torsional rigidity K1 of the outer race portion 21 stored in the memory unit 54, and the torsional rigidity K2 of the hub axle 31 (inner ring 34). The driving torque My is a moment acting on the hub axle 31 about the pitch axis (Y-axis). The driving torque My is calculated using the following equations (2) and (3). The value K12 shown in equation (2) is the difference in torsional rigidity between the outer race portion 21 and the hub axle 31 (inner ring 34).

[0047] K12=K1-K2 (2) My=θ12 / K12 (3)

[0048] In the driving device 10 of the present disclosure, the processing device 50 can calculate the driving torque My in the above-described manner.

[0049] [About each variable] Here, the variables used in each of the above processes will be collectively explained. θ1: the torsion angle of the first sensor rotor 43 at the position facing the first sensor 41, and is expressed in electrical angle (rad). θ2: the torsion angle of the second sensor rotor 44 at the position facing the second sensor 42, expressed in electrical angle (rad). θ12: the difference in torsion angle between the opposing position of the first sensor 41 and the opposing position of the second sensor 42, and is expressed in electrical angle (rad). The electrical angle is a virtual angle in which one cycle of a periodic waveform is defined as 360 degrees (2π radians). My: Moment acting around the center line C of the hub axle 31, expressed in newtons [N]. K1: A constant, which is the torsional rigidity of the outer race portion 21 in the direction along the Z axis. The unit is Newton / millimeter [N / mm]. K2: A constant that represents the torsional rigidity of the hub axle 31 (inner ring 34) in the direction along the Z axis. The unit is Newtons per millimeter [N / mm].

[0050] In the drive unit 10 of the present disclosure, it is preferable that the processing device 50 calculates the displacement of the hub axle 31, the load applied to the hub axle 31, the tire stress acting in the direction of the pitch axis (Y axis), and the moment acting around the yaw axis (Z axis) using a known method (see Patent Document 1) based on the waveform signal (see Figure 6) output from the sensor device 40.

[0051] The drive device 10 of this embodiment has a pair of sensors (first sensor 41A and first sensor 41B, second sensor 42A and second sensor 42B) arranged at positions that are 180 degrees out of phase with each other in the circumferential direction, calculates a first torsion angle θ1 and a second torsion angle θ2 based on the difference between the rotation angles acquired by the pair of sensors, and calculates a relative torsion angle θ12 from the first torsion angle θ1 and the second torsion angle θ2. In this case, the relative torsion angle θ12 can be calculated with high accuracy, taking into account the load acting on the drive device 10. Note that the method for calculating the relative torsion angle θ12 in the drive device 10 of the present disclosure is not limited to this method. For example, the relative torsion angle θ12 may be the difference between the rotation angle of the first sensor rotor 43 detected by the first sensor 41A and the rotation angle of the second sensor rotor 44 detected by the second sensor 42A at the same time. In this case, for example, only one pair of first sensor 41A and second sensor 42A having the same circumferential phase is required, and there is no need to arrange a pair of sensors (first sensor 41A and first sensor 41B, second sensor 42A and second sensor 42B) at positions that are 180 degrees out of phase with each other in the circumferential direction, so the relative torsion angle θ12 can be calculated with a simple configuration. Note that in the drive device 10 of this embodiment, the first sensors 41 may be arranged as a pair at positions that are 180 degrees out of phase with each other in the circumferential direction of the outer ring 32, and the second sensors 42 may be arranged as a pair at positions that are 180 degrees out of phase with each other in a different phase from the first sensors 41 in the circumferential direction of the outer ring 32.

[0052] [Regarding the drive device according to the second embodiment] FIG. 9 is a cross-sectional schematic diagram showing a second embodiment of a drive unit according to the present disclosure. FIG. 10 is a cross-sectional schematic diagram showing a sliding portion and a sensor device in a drive unit according to the second embodiment. FIG. 9 shows a drive unit 10 according to the second embodiment of a drive unit according to the present disclosure. In the following description, the drive unit 10 according to the second embodiment will also be referred to as a second drive unit 10B. The second drive unit 10B differs from the first drive unit 10A in that it includes a sliding portion 37, but shares other configurations with the first drive unit 10A. In the following description, the configuration of the second drive unit 10B that differs from the first drive unit 10A will be described, and a description of the common configuration will be omitted.

[0053] As shown in FIGS. 9 and 10, the second drive unit 10B includes a sliding portion 37 disposed between an end face 23 on the other axial side of the outer race portion 21 and an end face 35 on one axial side of the inner ring 34. The sliding portion 37 shown in FIGS. 9 and 10 is configured by an annular member (a washer member) disposed between the end face 23 and the end face 35. Specifically, the sliding portion 37 is configured by a metal washer member whose surface is coated with resin. Note that in the second drive unit 10B, the sliding portion 37 may be configured by a washer member whose entire body is made of resin.

[0054] The sliding portion 37 of this embodiment serves to reduce the frictional force when the end face 23 and the end face 35 are displaced relative to each other in the circumferential direction, compared to the frictional force that occurs when the end face 23 and the end face 35 are in direct contact with each other.

[0055] When comparing the relative torsion angle θ12 when the same magnitude of driving torque My is applied to the first driving device 10A (see Figure 1) and the second driving device 10B, the second driving device 10B, which has a sliding portion 37, can achieve a larger relative torsion angle θ12.

[0056] In other words, in the case of the first driving unit 10A (see FIG. 1), the frictional force generated between the end face 23 and the end face 35 is greater than that of the second driving unit 10B, and therefore the driving torque My is calculated based on the minute relative torsion angle θ12. For this reason, the first driving unit 10A has a small resolution for the relative torsion angle θ12, which results in low calculation accuracy for the driving torque My.

[0057] On the other hand, the second drive unit 10B can increase the resolution of the relative torsion angle θ12 compared to the first drive unit 10A (see FIG. 1), thereby increasing the calculation accuracy of the drive torque My compared to the first drive unit 10A.

[0058] In the second drive unit 10B, the sliding portion 37 may be a portion where at least a portion of the end face 23 of the outer race portion 21 is coated with resin (in other words, a coating layer formed on the end face 23), or may be a portion where at least a portion of the end face 35 of the inner ring 34 is coated with resin (in other words, a coating layer formed on the end face 35).

[0059] If the sliding portion 37 is formed of a washer member, it is necessary to provide a gap equal to the thickness of the washer member between the end face 23 and the end face 35. On the other hand, if the sliding portion 37 is formed of a coating layer formed on the end face 23 and / or the end face 35, the distance between the end face 23 and the end face 35 can be set to "0." Therefore, if the sliding portion 37 is formed of a coating layer formed on the end face 23 and / or the end face 35, the axial dimension of the second drive unit 10B can be reduced compared to when the sliding portion 37 is formed of a washer member.

[0060] [Operations and Effects of the Present Embodiment] (1) The drive unit 10 of the above embodiment includes a drive shaft 20 including an outer race portion 21 provided on one axial side and a shaft portion 22 extending from an end face 23 on the other axial side of the outer race portion 21 to the other axial side, a hub axle 31 having a shaft hole 31c through which the shaft portion 22 is inserted and an inner ring provided on one axial side, an outer ring 32 provided radially outward of the hub axle 31, and a plurality of balls 33 provided between the hub axle 31 and the outer ring 32, and a sensor device 40 that detects the rotation angles of the drive shaft 20 and the hub axle 31. The sensor device 40 includes a first sensor 41 and a second sensor 42 arranged on the outer ring 32, a first sensor rotor (first target) 43 arranged radially inward of the first sensor 41 and serving as a detection target for the first sensor 41, and a second sensor rotor (second target) 44 arranged radially inward of the second sensor 42 and serving as a detection target for the second sensor 42. The first sensor 41 is disposed on one axial side of the second sensor 42. The first sensor rotor 43 is provided on the outer peripheral surface 24 of the outer race portion 21, and the second sensor rotor 44 is provided on the outer peripheral surface 36 of the inner ring 34.

[0061] The drive unit 10 configured as described above includes a first sensor 41 and a second sensor 42 arranged side by side in the axial direction, a first sensor rotor 43 provided on the outer peripheral surface 24 of the outer race portion 21, and a second sensor rotor 44 provided on the outer peripheral surface 36 of the inner ring 34. The outer race portion 21 and the inner ring 34 are formed of separate members and are capable of relative displacement in the circumferential direction. This allows the drive unit 10 to calculate the relative torsion angle between the outer race portion 21 and the hub axle 31 based on the rotational angle of the first sensor rotor 43 detected by the first sensor 41 and the rotational angle of the second sensor rotor 44 detected by the second sensor 42. Therefore, the drive unit 1 of the above embodiment makes it possible to calculate the drive torque My, which is a moment acting about the pitch axis, based on the waveform signals output by the first sensor 41 and the second sensor 42.

[0062] (2) In the second driving device 10B of the above embodiment, when the shaft portion 22 is inserted into the shaft hole 31c, the end face 23 on the other axial side of the outer race portion 21 faces the end face 35 on one axial side of the inner ring 34, and the second driving device 10B further includes a sliding portion 37 provided between the end face 23 of the outer race portion 21 and the end face 35 of the inner ring 34. With the second driving unit 10B configured as described above, the provision of the sliding portion 37 makes it possible to increase the relative torsion angle θ12 between the hub axle 31 and the outer race portion 21 during rotation of the drive shaft 20 compared to when these members are in direct contact with each other. Therefore, with the second driving unit 10B of the above embodiment, it is possible to improve the resolution for calculating the driving torque My, and thereby improve the calculation accuracy of the driving torque My.

[0063] (3) In the drive unit 10 of the above embodiment, the first sensors 41 are arranged in pairs at positions 180 degrees out of phase with each other in the circumferential direction of the outer ring 32, and the second sensors 42 are arranged in pairs at the same phase as the first sensors 41 in the circumferential direction of the outer ring 32. With the drive device 10 configured in this manner, the relative torsion angle θ12 between the outer race portion 21 and the hub axle 31 can be calculated based on the waveform signals output by the first sensor 41 and the second sensor 42, thereby allowing the drive torque My to be calculated.

[0064] (4) The drive unit 10 of the above embodiment further includes a housing member 38 provided on one axial side of the outer ring 32, and the first sensor 41 and the second sensor 42 are provided on the outer ring 32 via the housing member 38. The driving device 10 having such a configuration can easily install the first sensor 41 and the second sensor 42 on the outer ring 32. Furthermore, this configuration makes it possible to reuse an existing outer ring 32 in the driving device 10 of the present disclosure.

[0065] (5) The drive unit 10 of the above embodiment further includes a processing unit 50 that processes the waveform signals output from the first sensor 41 and the second sensor 42. The processing unit 50 calculates the first torsion angle θ1 of the hub axle 31 based on the waveform signal output from the first sensor 41, calculates the second torsion angle θ2 of the outer race portion 21 based on the waveform signal output from the second sensor 42, calculates the relative torsion angle θ12 between the inner ring 34 and the outer race portion 21 based on the first torsion angle θ1 and the second torsion angle θ2, and calculates the drive torque My acting around the axis of the hub axle 31 based on the relative torsion angle θ12. According to the driving device 10 configured as above, the processing device 50 can calculate the driving torque My based on the waveform signals output by the first sensor 41 and the second sensor 42.

[0066] (6) In the second driving device 10B of the above embodiment, the sliding portion 37 is made up of a member that can be separated from the outer race portion 21 and the inner ring . In the drive unit 10 configured as described above, the sliding portion 37 is a separate member that can be separated from the outer race portion 21 and the inner ring 34, so that when the sliding portion 37 wears, it can be replaced. In this case, by replacing the sliding portion 37, the drive unit 10 can be easily restored to a normal state.

[0067] (7) In the second driving device 10B of the above embodiment, the sliding portion 37 is formed by a coating layer formed on at least one of the outer race portion 21 and the inner ring . This configuration allows the axial dimension of the drive unit 10 to be reduced.

[0068] [Others] In the above embodiment, the case where the drive device 10 is a hub unit for an automobile has been described, but the drive device 10 may be other equipment. Also, in the above embodiment, the case where the first sensor rotor 43 and the second sensor rotor 44 are separate from the outer race portion 21 and the hub axle 31 (inner ring 34) has been described, but a portion of the outer race portion 21 and the hub axle 31 (inner ring 34) may be configured to function as the sensor rotor.

[0069] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configurations described in the claims. [Explanation of symbols]

[0070] 10: Drive unit 20: Drive shaft 21: Outer race 22: Shaft 23: Outer surface 24: End face 30: Wheel bearing device 31: Hub axle 31c: Shaft hole 32: Outer ring 33: Ball 34: Insider 35: End face 36: Outer surface 37: Sliding part 38: Housing material 40: Sensor device 41: First sensor 42: Second sensor 43: First sensor rotor (first target) 44: Second sensor rotor (second target) 50: Processing equipment

Claims

1. a drive shaft including an outer race portion provided on one axial side and a shaft portion extending from an end face on the other axial side of the outer race portion toward the other axial side; a wheel bearing device including a hub axle having an axle hole through which the axle portion is inserted and an inner ring provided on one axial side thereof, an outer ring provided radially outward of the hub axle, and a plurality of balls provided between the hub axle and the outer ring; a sensor unit that detects the rotation angles of the drive shaft and the hub axle; A drive device comprising: The sensor unit includes a first sensor and a second sensor disposed on the outer ring; a first target disposed radially inside the first sensor and serving as a detection target of the first sensor; a second target that is disposed radially inside the second sensor and is a detection target of the second sensor; the first sensor is disposed on one side in the axial direction relative to the second sensor, the first target is provided on an outer peripheral surface of the outer race portion, The second target is provided on the outer peripheral surface of the inner ring.

2. the end face on the other axial side of the outer race portion and the end face on the one axial side of the inner ring face each other, The drive unit according to claim 1 , further comprising a sliding portion provided between the end surface of the outer race portion and the end surface of the inner ring.

3. the first sensors are arranged in pairs at positions that are 180 degrees out of phase with each other in the circumferential direction of the outer ring, 3. The drive device according to claim 1, wherein the second sensors are arranged in pairs in the same phase as the first sensors in the circumferential direction of the outer ring.

4. a housing member provided on one axial side of the outer ring, 3. The drive device according to claim 1, wherein the first sensor and the second sensor are provided on the outer ring via the housing member.

5. a processing device for processing signals output from the first sensor and the second sensor; The processing device includes: calculating a first helix angle of the hub axle based on the signal output from the first sensor; calculating a second torsion angle of the outer race portion based on the signal output from the second sensor; calculating a relative helix angle between the inner ring and the outer race portion based on the first helix angle and the second helix angle; 3. The drive device according to claim 1, wherein a drive torque acting around the axis of the hub axle is calculated based on the relative torsion angle.

6. The drive unit according to claim 2 , wherein the sliding portion is formed of a member that can be separated from the outer race portion and the inner ring.

7. The drive unit according to claim 2 , wherein the sliding portion is formed by a coating layer formed on at least one of the outer race portion and the inner ring.

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