Vehicle steering system and torque value correction system

Abstract

To provide a steering system for a vehicle capable of suppressing a torque fluctuation caused by a displacement of shaft centers between an input shaft and a detection coil of a torque sensor and also to provide a torque value correction system.SOLUTION: A steering system for a vehicle includes: a torque sensor configured to detect a steering torque generated between an input shaft coupled to a steering wheel and an output shaft to which a torque generated at an electric motor is transmitted through a reduction gear, according to an electric signal generated by a relative rotation of the input shaft and the output shaft; and an ECU configured to execute a steering assist control according to the steering torque. The ECU calibrates the steering torque according to a torque correction value obtained when the input shaft and the output shaft are rotated in a same direction at a same speed.SELECTED DRAWING: Figure 20

Description

Technical Field

[0001] The present invention relates to a vehicle steering system and a torque value correction system.

Background Art

[0002] A torque sensor that detects the torque applied to a rotating body is attached to the rotating body of a steering device, and can detect the torque by detecting the angular displacement in the rotation direction of the rotating body when a rotational torque acts on the rotating body. For example, in the torque detection device described in Patent Document 1, an input shaft and an output shaft are connected via a torsion bar, and a plurality of ridges extending in the axial direction are formed on either the input shaft or the output shaft, and on the other, a plurality of windows are formed and a cylindrical member into which the input shaft enters is fixed inside. Further, a detection coil held by a yoke is arranged around the cylindrical member, and by detecting the output voltage of the detection coil, the relative angular displacement in the rotation direction between the input shaft and the output shaft is detected, and the torque transmitted to the input shaft can be detected.

[0003] The torque sensor described in Patent Document 1 reads, as an electrical signal, the amount of change in impedance that changes due to a change in the magnetic field generated in the detection coil when a rotational torque is input and the torsion bar is twisted, causing a relative angle change between the input shaft and the output shaft, and detects the torque acting between the input shaft and the output shaft.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional technology described above, misalignment of the axial axis between the input shaft and the torque sensor's detection coil can occur during the manufacturing of the torque sensor or when incorporating the torque sensor into a vehicle steering system. In such cases, the signal resulting from the misalignment between the input shaft and the torque sensor's detection coil affects the output value, thus there is room for improvement.

[0006] This disclosure has been made in view of the above-mentioned problems, and aims to provide a vehicle steering system and a torque value correction system that can suppress torque fluctuations caused by misalignment of the axis between the input shaft and the detection coil of the torque sensor. [Means for solving the problem]

[0007] To achieve the above objectives, a vehicle steering system according to one aspect of the present disclosure includes a torque sensor that detects steering torque generated between the input shaft and the output shaft based on an electrical signal generated by the relative rotation of the input shaft and the output shaft to which the steering wheel is connected, and a control device that performs steering assist control based on the steering torque, wherein the control device corrects the steering torque based on a torque correction value obtained when the input shaft and the output shaft are rotated in the same direction at the same speed.

[0008] According to the above configuration, steering assist control can be performed using a corrected steering torque in which torque fluctuations caused by misalignment of the axis between the input shaft of the steering shaft and the detection coil of the torque sensor are suppressed during actual vehicle operation.

[0009] A preferred embodiment of the control device for a vehicle steering system may include an angle sensor for detecting the absolute angle of the output shaft, and the control device may apply a torque correction value corresponding to the absolute angle detected by the angle sensor when correcting the steering torque.

[0010] A preferred embodiment of the control device for a vehicle steering system may include a position sensor that detects a reference for the rotational position of the input shaft or the output shaft, and the control device may, when correcting the steering torque, apply a torque correction value corresponding to an absolute angle calculated based on the rotation angle of the electric motor and the reference for the rotational position detected by the position sensor.

[0011] A preferred embodiment of the control device for a vehicle steering system includes an electric motor that applies torque to the steering shaft via a reduction gear, and a position sensor that detects a reference for the rotational position of the input shaft or the output shaft, wherein the control device may, when correcting the steering torque, apply a torque correction value corresponding to an absolute angle calculated based on steering angle information input from an external source and a reference for the rotational position detected by the position sensor.

[0012] To achieve the above objective, a torque value correction system according to one aspect of the present disclosure is a torque value correction system for a vehicle steering system comprising: a torque sensor that detects steering torque generated between the input shaft and the output shaft based on an electrical signal generated by the relative rotation of the input shaft and the output shaft to which a steering wheel is connected; and a control device that performs steering assist control based on the steering torque, wherein the system includes a processing device that rotates the input shaft and the output shaft in the same direction at the same speed and acquires a torque correction value to be applied when correcting the steering torque.

[0013] According to the above configuration, steering assist control can be performed using a corrected steering torque in which torque fluctuations caused by misalignment of the axis between the input shaft of the steering shaft and the detection coil of the torque sensor are suppressed during actual vehicle operation.

[0014] A preferred embodiment of the torque value correction system may be that the vehicle steering system has an angle sensor for detecting the absolute angle of the output shaft, and the processing device generates correction data for correcting the steering torque by relating the torque correction value detected by the torque sensor with the absolute angle detected by the angle sensor when the input shaft and the output shaft are rotated in the same direction at the same speed.

[0015] A preferred embodiment of the torque value correction system may be that the vehicle steering system includes an electric motor that applies torque to the steering shaft via a reduction gear, and a position sensor that detects a reference for the rotational position of the input shaft or the output shaft, and the processing device generates correction data for correcting the steering torque by relating the torque correction value detected by the torque sensor with an absolute angle calculated based on the rotation angle of the electric motor and the reference for the rotational position detected by the position sensor when the input shaft and the output shaft are rotated in the same direction at the same speed.

[0016] A preferred embodiment of the torque value correction system may include an external drive motor that rotates the input shaft and the output shaft in the same direction at the same speed, the vehicle steering system may include a position sensor that detects a reference for the rotational position of the input shaft or the output shaft, and the processing device may generate correction data for correcting the steering torque by relating the torque correction value detected by the torque sensor with the absolute angle calculated based on the rotation angle of the external drive motor and the reference for the rotational position detected by the position sensor when the external drive motor is driven.

[0017] As a desirable aspect of the torque value correction system, the torque sensor includes a sensor shaft portion provided on either the input shaft or the output shaft, and a sensor sleeve that is connected to the other of the input shaft and the output shaft and is disposed to cover the sensor shaft portion. The sensor shaft portion has a plurality of convex portions arranged at equal intervals along the circumferential direction on the radially outer side, and the sensor sleeve may be arranged such that a plurality of window holes penetrating in the thickness direction of the sensor sleeve are arranged side by side in the circumferential direction.

Effect of the Invention

[0018] The vehicle steering system and the torque value correction system according to the present disclosure have an effect of suppressing torque fluctuations caused by the misalignment of the axis between the input shaft and the detection coil of the torque sensor.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is a schematic diagram of a vehicle steering system according to Embodiment 1. [Figure 2] FIG. 2 is a longitudinal sectional view of a main part around the torque sensor shown in FIG. 1. [Figure 3] FIG. 3 is a perspective view showing the constituent members of the torque detection unit shown in FIG. 2. [Figure 4] FIG. 4 is a perspective view showing the constituent members of the torque detection unit. [Figure 5] FIG. 5 is a perspective view of the yoke shown in FIG. 4. [Figure 6] FIG. 6 is a sectional view taken along line A-A of FIG. 5. [[ID=3l]] [Figure 7] FIG. 7 is a plan view of a blank material used for manufacturing the yoke. [Figure 8] FIG. 8 is a sectional view taken along line B-B of FIG. 7. [Figure 9] FIG. 9 is an explanatory view showing a state where the sensor shaft portion rotates relative to the sensor sleeve. [Figure 10] FIG. 10 is an explanatory view showing a state where the sensor shaft portion rotates relative to the sensor sleeve. [Figure 11] FIG. 11 is a diagram showing an example of the relationship between the torque value obtained from the torque signal and the relative angular difference between the sensor shaft portion and the sensor sleeve. [Figure 12A] FIG. 12A is a cross-sectional view of the sensor sleeve and the sensor shaft portion. [Figure 12B] FIG. 12B is a cross-sectional view of the sensor sleeve and the sensor shaft portion. [Figure 13A] FIG. 13A is a cross-sectional view of the sensor sleeve and the sensor shaft portion. [Figure 13B] FIG. 13B is a cross-sectional view of the sensor sleeve and the sensor shaft portion. [Figure 14A] FIG. 14A is a conceptual diagram showing the torque components generated by the change in the distance between each convex portion of the sensor shaft portion and the detection coil in the examples shown in FIGS. 12A and 12B. [Figure 14B] FIG. 14B is a conceptual diagram showing the variation of the torque value calculated by the torque signal output from the torque sensor in the examples shown in FIGS. 12A and 12B. [Figure 15A] FIG. 15A is a conceptual diagram showing the torque components generated by the change in the distance between each convex portion of the sensor shaft portion and the detection coil in the examples shown in FIGS. 13A and 13B. [Figure 15B] FIG. 15B is a conceptual diagram showing the variation of the torque value calculated by the torque signal output from the torque sensor in the examples shown in FIGS. 13A and 13B. [Figure 16] FIG. 16 is a conceptual diagram showing the change in the torque value when the sensor shaft portion and the sensor sleeve rotate relative to each other as the input shaft rotates. [Figure 17] FIG. 17 is a block diagram showing a specific configuration example of the vehicle steering system and the torque value correction system according to Embodiment 1. [Figure 18] FIG. 18 is a diagram showing an example of the control block configuration of the processing device of the torque value correction system according to Embodiment 1. [Figure 19A] FIG. 19A is a conceptual diagram showing the torque correction value obtained at the time of obtaining the correction data. [Figure 19B] Figure 19B is a conceptual diagram showing the absolute angles obtained when acquiring correction data. [Figure 19C] Figure 19C is a conceptual diagram showing the correction data generated when correction data is acquired. [Figure 20] Figure 20 shows an example of the control block configuration of the ECU of a vehicle steering system according to Embodiment 1. [Figure 21] Figure 21 is a schematic diagram of a vehicle steering system according to Embodiment 2. [Figure 22] Figure 22 is a block diagram showing a specific configuration example of a vehicle steering system and torque value correction system according to Embodiment 2. [Figure 23] Figure 23 shows an example of the control block configuration of the processing unit for the torque value correction system according to Embodiment 2. [Figure 24A] Figure 24A is a conceptual diagram showing the torque correction values ​​obtained when correction data is acquired. [Figure 24B] Figure 24B is a conceptual diagram showing the electric motor angle signal acquired when correction data is obtained. [Figure 24C] Figure 24C is a conceptual diagram showing the position signals acquired when correction data is obtained. [Figure 24D] Figure 24D is a conceptual diagram showing the absolute angles obtained when acquiring correction data. [Figure 24E] Figure 24E is a conceptual diagram showing the correction data generated when correction data is acquired. [Figure 25] Figure 25 shows an example of the control block configuration of the ECU of a vehicle steering system according to Embodiment 2. [Figure 26A] Figure 26A is a conceptual diagram showing the electric motor angle signals acquired during actual vehicle operation. [Figure 26B] Figure 26B is a conceptual diagram showing the position signals acquired during actual vehicle operation. [Figure 26C]Figure 26C is a conceptual diagram showing the absolute angles obtained during actual vehicle operation. [Figure 27] Figure 27 is a schematic diagram of a vehicle steering system according to Embodiment 3. [Figure 28] Figure 28 is a block diagram showing a specific configuration example of a vehicle steering system and torque value correction system according to Embodiment 3. [Figure 29] Figure 29 shows an example of the control block configuration of the processing unit for the torque value correction system according to Embodiment 3. [Figure 30A] Figure 30A is a conceptual diagram showing the torque correction values ​​obtained when correction data is acquired. [Figure 30B] Figure 30B is a conceptual diagram showing the external drive motor angle signal acquired when correction data is obtained. [Figure 30C] Figure 30C is a conceptual diagram showing the position signals acquired when correction data is obtained. [Figure 30D] Figure 30D is a conceptual diagram showing the absolute angles obtained when acquiring correction data. [Figure 30E] Figure 30E is a conceptual diagram showing the correction data generated when correction data is acquired. [Figure 31] Figure 31 shows an example of the control block configuration of the ECU of a vehicle steering system according to Embodiment 3. [Figure 32A] Figure 32A is a conceptual diagram showing steering angle information acquired during actual vehicle operation. [Figure 32B] Figure 32B is a conceptual diagram showing the position signals acquired during actual vehicle operation. [Figure 32C] Figure 32C is a conceptual diagram showing the absolute angles obtained during actual vehicle operation. [Modes for carrying out the invention]

[0020] Hereinafter, embodiments for carrying out the invention (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments described below. Furthermore, the components in the embodiments described below include those that are easily conceivable by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the components disclosed in the embodiments described below can be combined as appropriate.

[0021] (Embodiment 1) Figure 1 is a schematic diagram of a vehicle steering system according to Embodiment 1. In the vehicle steering system 1 according to Embodiment 1 shown in Figure 1, the steering device 80 includes a steering wheel 81, a steering shaft 82, a steering force assist mechanism 83, a universal joint 84, an intermediate shaft 85, and a universal joint 86, all connected to a stub shaft 87, in the order in which the force applied by the operator is transmitted. In the steering device 80 according to this embodiment, the steering force assist mechanism 83 is located closer to the steering wheel 81 and is situated inside the vehicle cabin, separated from the outside.

[0022] The steering shaft 82 includes an input shaft 82a, an output shaft 82b, and a torsion bar 82c (see Figure 2). The torsion bar 82c is connected to both the input shaft 82a and the output shaft 82b, and the input shaft 82a and the output shaft 82b are connected via the torsion bar 82c. One end of the input shaft 82a is connected to the steering wheel 81, and the torsion bar 82c extends from the other end. The output shaft 82b has the torsion bar 82c extending from one end, and the other end is connected to a universal joint 84. Rotational torque is transmitted between the input shaft 82a and the output shaft 82b via the torsion bar 82c connected to both.

[0023] As shown in Figure 1, the intermediate shaft 85 connects the universal joint 84 and the universal joint 86. One end of the intermediate shaft 85 is connected to the universal joint 84, and the other end is connected to the universal joint 86. One end of the stub shaft 87 is connected to the universal joint 86, and the other end of the stub shaft 87 is connected to the steering gear 88. The universal joints 84 and 86 are, for example, cardan joints. The rotation of the steering shaft 82 is transmitted to the stub shaft 87 via the intermediate shaft 85. That is, the intermediate shaft 85 rotates in conjunction with the steering shaft 82.

[0024] As shown in Figure 1, the steering gear 88 includes a pinion gear 88a and a rack 88b. The pinion gear 88a is connected to a stub shaft 87. The rack 88b meshes with the pinion gear 88a. The steering gear 88 converts the rotational motion transmitted to the pinion gear 88a into linear motion using the rack 88b. The rack 88b is connected to a tie rod 89. The movement of the rack 88b changes the angle of the wheels.

[0025] As shown in Figure 1, the steering force assist mechanism 83 includes a reduction gear 91 and an electric motor 94. The reduction gear 91 is, for example, a worm gear reduction gear. The reduction gear 91 increases the torque generated by the electric motor 94 and transmits it to the output shaft 82b. In this way, the reduction gear 91 provides auxiliary steering torque to the output shaft 82b. The steering device 80 is a column-assist type electric power steering device. A column-assist type electric power steering device refers to a power steering device that applies assist torque generated by the electric motor 94 to the steering shaft 82 connected to the steering wheel 81.

[0026] In the vehicle steering system 1 according to Embodiment 1 shown in Figure 1, the steering device 80 includes an ECU (Electronic Control Unit) 90, a torque sensor 10, an angle sensor 11, and a vehicle speed sensor 95. The electric motor 94, torque sensor 10, angle sensor 11, and vehicle speed sensor 95 are electrically connected to the ECU 90. The torque sensor 10 detects the steering torque transmitted to the input shaft 82a and outputs it to the ECU 90. The angle sensor 11 detects the angle of the output shaft 82b and outputs it to the ECU 90. The vehicle speed sensor 95 detects the driving speed (vehicle speed) of the vehicle on which the steering device 80 is mounted. The vehicle speed sensor 95 is installed on the vehicle body and outputs the vehicle speed to the ECU 90 via CAN communication.

[0027] The ECU90 is a computer for controlling the steering of the vehicle. Specifically, the ECU90 controls the operation of the electric motor 94. The ECU90 acquires signals from the torque sensor 10, the angle sensor 11, and the vehicle speed sensor 95. When the ignition switch 98 is ON, the ECU90 is supplied with power from the power supply unit 99 (e.g., the vehicle's battery). The ECU90 calculates an auxiliary steering command value based on the steering torque and vehicle speed. The ECU90 adjusts the power value supplied to the electric motor 94 based on the auxiliary steering command value. The ECU90 acquires information on the induced voltage of the electric motor 94 or information output from a resolver or the like provided on the electric motor 94. By controlling the electric motor 94, the force required to operate the steering wheel 81 is reduced.

[0028] Figure 2 is a longitudinal cross-sectional view of the main part around the torque sensor 10 shown in Figure 1. The torque sensor 10 is located inside a housing 20 that covers the torque sensor 10. The housing 20 covers the connection portion between the input shaft 82a and the output shaft 82b, which are connected via a torsion bar 82c, and supports the input shaft 82a and the output shaft 82b. The housing 20 is divided into two parts in the axial direction of the input shaft 82a and the output shaft 82b that it supports, and has an input shaft side housing portion 20a, which is located on the input shaft 82a side, and an output shaft side housing portion 20b, which is located on the output shaft 82b side. The housing 20 is formed by combining the divided input shaft side housing portion 20a and the output shaft side housing portion 20b.

[0029] A bearing 21a is located inside the input shaft side housing portion 20a of the housing 20, and the input shaft 82a is rotatably supported by the bearing 21a. The input shaft 82a, supported by the input shaft side housing portion 20a, is supported in a manner that it protrudes from the input shaft side housing portion 20a toward the opposite side of the input shaft side housing portion 20b where the output shaft side housing portion 20b is located. Similarly, a bearing 21b is located inside the output shaft side housing portion 20b, and the output shaft 82b is rotatably supported by the bearing 21b. The output shaft 82b, supported by the output shaft side housing portion 20b, is supported in a manner that it protrudes from the output shaft side housing portion 20b toward the opposite side of the output shaft side housing portion 20a where the input shaft side housing portion 20a is located.

[0030] The input shaft 82a and output shaft 82b, supported by the input shaft side housing 20a and the output shaft side housing 20b, are connected via a torsion bar 82c disposed inside the input shaft 82a. The input shaft 82a, torsion bar 82c, and output shaft 82b are arranged coaxially, and the input shaft 82a and torsion bar 82c are connected by a pin connection, with the torsion bar 82c fitting into a hole formed inside the input shaft 82a. The torsion bar 82c and output shaft 82b are connected by a spline connection, with the torsion bar 82c fitting into a hole formed inside the output shaft 82b. The steering wheel 81 (see Figure 1) is attached to the end of the input shaft 82a opposite to the side where the output shaft 82b is located, that is, the end of the input shaft 82a that is exposed from the input shaft side housing 20a.

[0031] The reduction gear 91 is capable of transmitting the driving force generated by the electric motor 94 (see Figure 1) to the output shaft 82b within the housing 20. Specifically, the reduction gear 91 has a worm 93 and a worm wheel 92 that mesh with each other, and the worm 93 is attached to the output shaft of the electric motor 94. The worm wheel 92 is attached to the output shaft 82b coaxially and integrally with the output shaft 82b so as to be rotatable, and meshes with the worm 93 within the output shaft side housing portion 20b. The worm wheel 92 has a synthetic resin tooth portion 92b integrally fixed to a metal hub 92a. The driving force of the electric motor 94 is transmitted to the output shaft 82b via the worm 93 and worm wheel 92 that mesh within the output shaft side housing portion 20b, and by appropriately switching the rotation direction of the electric motor 94, steering assist torque is applied to the output shaft 82b in any rotation direction.

[0032] Next, the configuration of the torque detection unit 30, which constitutes the torque sensor 10 that detects torque between the input shaft 82a and the output shaft 82b, will be described. The torque detection unit 30 comprises a sensor shaft portion 31 provided on the input shaft 82a, a detection coil 40 arranged inside the input shaft side housing portion 20a, and a sensor sleeve 32 arranged between the sensor shaft portion 31 and the detection coil 40. The sensor shaft portion 31 is the part of the input shaft 82a that is located inside the sensor sleeve 32; in other words, the part of the input shaft 82a that is located inside the sensor sleeve 32 constitutes the sensor shaft portion 31 of the torque detection unit 30.

[0033] Figure 3 is a perspective view showing the components of the torque detection unit 30 shown in Figure 2. The sensor shaft portion 31 is made of a magnetic material, and as shown in Figure 3, a plurality of protrusions 31a projecting outward in the radial direction of the sensor shaft portion 31 are arranged in a line along the circumferential direction of the sensor shaft portion 31 on its surface. The plurality of protrusions 31a are formed extending in the axial direction of the sensor shaft portion 31 and are arranged at equal intervals along the circumferential direction. In addition, the portions between the circumferentially aligned protrusions 31a are grooves 31b. In other words, because the plurality of protrusions 31a extending in the axial direction of the sensor shaft portion 31 are arranged at equal intervals along the circumferential direction of the sensor shaft portion 31 on its surface, a plurality of grooves 31b extending in the axial direction of the sensor shaft portion 31 are formed at equal intervals along the circumferential direction of the sensor shaft portion 31. In this embodiment, the sensor shaft portion 31 has eight protrusions 31a, and consequently, eight grooves 31b are also arranged. In Figure 3, hatching is applied to one of the multiple protrusions 31a (protrusion 31aa) of the sensor shaft portion 31 in order to explain the operation of the torque detection unit 30 later.

[0034] The sensor sleeve 32 is formed in a cylindrical shape and is positioned inside the detection coil 40, covering the sensor shaft portion 31 of the input shaft 82a. The sensor sleeve 32 is made of a conductive and non-magnetic material, such as aluminum, and is positioned close to the sensor shaft portion 31 and coaxial with it. As shown in Figure 2, the portion of the sensor sleeve 32 that is formed in a cylindrical shape in the axial direction on the output shaft 82b side of the sensor sleeve 32 extends to the side where the output shaft 82b is located and is provided as a connecting portion 32a that connects to the output shaft 82b. The connecting portion 32a of the sensor sleeve 32 covers the end of the output shaft 82b on the input shaft 82a side from the radial outside of the output shaft 82b and connects to the output shaft 82b. In this way, the sensor sleeve 32 is attached to the output shaft 82b so as to be rotatable together with the output shaft 82b.

[0035] The detection coil 40 is formed in an annular shape by being wound around an annular coil bobbin 41. The coil bobbin 41 is formed in an annular shape with an inner diameter close to and larger than the outer diameter of the sensor sleeve 32. The detection coil 40 is provided as a pair of first detection coils 40a and second detection coils 40b of the same specifications, each wound individually around the coil bobbin 41. That is, the first detection coil 40a is wound around the first coil bobbin 41a, and the second detection coil 40b is wound around the second coil bobbin 41b. As a result, both the pair of first detection coils 40a and second detection coils 40b are formed in an annular shape.

[0036] The first detection coil 40a and the second detection coil 40b, which are wound around the first coil bobbin 41a and the second coil bobbin 41b, are spaced apart in the axial direction of the sensor sleeve 32, aligned in the axial direction, and arranged coaxially with the sensor sleeve 32 on the radially outer side of the sensor sleeve 32.

[0037] The detection coil 40, wound around the coil bobbin 41, is held in place by a yoke 42 that covers the detection coil 40. The yoke 42 is made of a magnetic material and has a first yoke 42a corresponding to the first detection coil 40a and a second yoke 42b corresponding to the second detection coil 40b. The first yoke 42a covers the first detection coil 40a wound around the first coil bobbin 41a and holds the first detection coil 40a together with the first coil bobbin 41a. The second yoke 42b covers the second detection coil 40b wound around the second coil bobbin 41b and holds the second detection coil 40b together with the second coil bobbin 41b.

[0038] As shown in Figure 2, the first yoke 42a and the second yoke 42b are positioned inside the input shaft side housing 20a and fixed to the input shaft side housing 20a. The output lines of the first detection coil 40a and the second detection coil 40b are connected to the board-side connector 47 of the circuit board 46, which is located inside the input shaft side housing 20a, via the coil-side connector 45. Alternatively, although not shown, the coil tips may be wrapped around the coil-side terminals pressed into the coil bobbin 41 and soldered in place before being inserted into the board through-hole and connected by soldering. Here, the electronic components responsible for the electrical circuit of the circuit board 46, including the board-side connector 47, are mounted by surface mounting using reflow soldering or lead soldering.

[0039] A cover yoke 43 is positioned between the first coil bobbin 41a and the second coil bobbin 41b. The cover yoke 43 is made of a magnetic material. As a result, the first detection coil 40a wound on the first coil bobbin 41a and the second detection coil 40b wound on the second coil bobbin 41b are surrounded on both sides in the axial direction and radially outward by the first yoke 42a and the second yoke 42b and the cover yoke 43, both made of magnetic material. Furthermore, a sensor shaft portion 31 made of a magnetic material is positioned radially inside the first detection coil 40a and the second detection coil 40b, with a sensor sleeve 32 made of a non-magnetic material in between.

[0040] The sensor sleeve 32, positioned inside the detection coil 40, has a plurality of window holes 33 that are arranged circumferentially around the sensor sleeve 32 and penetrate through the thickness direction of the plate forming the sensor sleeve 32. The plurality of window holes 33 are arranged circumferentially around the sensor sleeve 32. Each window hole 33 is formed in the shape of a rectangular hole. The window holes 33 include a first window hole 33a positioned inside the first detection coil 40a in the radial direction of the sensor sleeve 32, and a second window hole 33b that has the same shape as the first window hole 33a and is positioned inside the second detection coil 40b. That is, the window holes 33 include a first window hole 33a and a second window hole 33b that are positioned at different locations in the axial direction of the sensor sleeve 32.

[0041] The first window holes 33a and the second window holes 33b are arranged at equal intervals in the circumferential direction of the sensor sleeve 32, with the same number of first window holes 33a as the number of protrusions 31a arranged on the sensor shaft portion 31, and the same number of second window holes 33b as the number of protrusions 31a. Furthermore, the first window holes 33a and the second window holes 33b are arranged at different positions in the circumferential direction of the sensor sleeve 32. In other words, multiple first window holes 33a and second window holes 33b are arranged at positions in the circumferential direction of the sensor sleeve 32 that are at different phases. By arranging the window holes 33 on the sensor sleeve 32 in this way, the first window holes 33a are surrounded by the first detection coil 40a, and the second window holes 33b are surrounded by the second detection coil 40b.

[0042] Figure 4 is a perspective view showing the components of the torque detection unit 30. The coil bobbin 41 is a reel-shaped member made of a non-conductive material such as plastic, and is fixed coaxially to the input shaft side housing 20a with the input shaft 82a and output shaft 82b. The coil bobbin 41 has a pair of flange portions 41c, and the detection coil 40 is wound around the groove between the flange portions 41c.

[0043] In the torque detection unit 30 of this embodiment, two coil bobbins 41 of the same shape, each around which a detection coil 40 is wound, are used facing each other. Specifically, the coil bobbins 41 include a first coil bobbin 41a corresponding to the first detection coil 40a and a second coil bobbin 41b corresponding to the second detection coil 40b. The first detection coil 40a is wound around the first coil bobbin 41a, and the second detection coil 40b is wound around the second coil bobbin 41b.

[0044] Of the pair of flange portions 41c that each of the two coil bobbins 41 has, the side end of the flange portion 41c located on the side where the other coil bobbin 41 is located is provided with a terminal mounting portion 41g, which will be described later and constitute a coil-side connector 45 that can be connected to a substrate-side connector 47. Furthermore, on the side end of the flange portion 41c on the coil bobbin 41 where the terminal mounting portion 41g is provided, a restricting portion 41f is formed at a position symmetrical with respect to a perpendicular line passing through the center of the coil bobbin 41 when the terminal mounting portion 41g is located at the upper end of the coil bobbin 41.

[0045] When the torque detection unit 30 is assembled by arranging two coil bobbins 41 on the same axis with their flange portions 41c facing each other, the restricting portions 41f of both coil bobbins 41 come into contact and engage with each other. This allows the restricting portions 41f to determine the relative position of the two coil bobbins 41 in the circumferential direction and to restrict the relative rotation of the coil bobbins 41 in the circumferential direction. The number of restricting portions 41f can be appropriately selected, as long as there are two or more for a single coil bobbin 41.

[0046] The terminal mounting portion 41g is a member that protrudes radially outward from the flange portion 41c of the coil bobbin 41, and two coil-side terminals 41h for connection to the board-side connector 47 are press-fitted and fixed to the radially outer end face. The two coil-side terminals 41h that are placed on the board-side connector 47 are arranged parallel to each other and are fixed so as to protrude radially outward from the terminal mounting portion 41g of the coil bobbin 41. In this way, the terminal mounting portion 41g and coil-side terminals 41h provided on each of the two coil bobbins 41 constitute the coil-side connector 45.

[0047] The first yoke 42a and the second yoke 42b are identical in shape. Each of the first yoke 42a and the second yoke 42b has a wall portion 42c that fits onto the coil bobbin 41 from the outside in the radial direction, and a ring-shaped bottom portion 42f formed at the end facing outward in the axial direction when holding the coil bobbin 41. The wall portion 42c is formed in a substantially cylindrical shape, with an inner diameter approximately the same as the outer diameter of the coil bobbin 41. This allows the yoke 42 to hold the coil bobbin 41 with the coil bobbin 41 fitted inside the wall portion 42c. In other words, the substantially cylindrical wall portion 42c, by holding the coil bobbin 41 with the yoke 42, can cover the detection coil 40 wound around the coil bobbin 41 from the outside in the radial direction. Furthermore, the bottom portion 42f has an inner diameter approximately the same as the inner diameter of the coil bobbin 41, and when the coil bobbin 41 is held by the yoke 42, it can cover the detection coil 40 from the side in the axial direction of the detection coil 40 wound around the coil bobbin 41.

[0048] Figure 5 is a perspective view of the yoke 42 shown in Figure 4. Each of the yokes 42, the first yoke 42a and the second yoke 42b, has a recess 42d formed at the end opposite to the side of the wall portion 42c where the bottom portion 42f is located. The recess 42d is formed by the end of the wall portion 42c opposite to the side where the bottom portion 42f is located being recessed toward the side where the bottom portion 42f is located. Three such recesses 42d are arranged on the wall portion 42c, and the three recesses 42d are spaced apart from each other at predetermined angles in the circumferential direction of the yoke 42. The three recesses 42d formed on the wall portion 42c are positioned in the circumferential direction of the yoke 42 to correspond to the terminal mounting portion 41g and the two restricting portions 41f of the coil bobbin 41.

[0049] Furthermore, multiple fitting portions 42e are formed in the wall portion 42c of the yoke 42. The fitting portions 42e are formed by the end of the wall portion 42c opposite to the side where the bottom portion 42f is located recessing into the side where the bottom portion 42f is located to a depth shallower than the recess 42d. The fitting portions 42e are arranged in three locations on the wall portion 42c, similar to the recess 42d, and each of the three fitting portions 42e is positioned between adjacent recesses 42d in the circumferential direction of the yoke 42. In other words, the recesses 42d and fitting portions 42e arranged in the wall portion 42c of the yoke 42 are arranged alternately in the circumferential direction of the yoke 42.

[0050] Because the wall portion 42c of the yoke 42 has multiple recesses 42d and fitting portions 42e arranged therein, the height from the bottom portion 42f is formed to change periodically in the circumferential direction of the yoke 42.

[0051] The cover yoke 43 is a substantially ring-shaped member, and has three projections 43a arranged on its outer surface, spaced apart from each other at predetermined angles in the circumferential direction. The cover yoke 43 is press-fitted into the radially inner portion of the wall portions 42c of the first yoke 42a and the second yoke 42b, with the projections 43a fitted into the fitting portions 42e of the first yoke 42a and the fitting portions 42e of the second yoke 42b.

[0052] In other words, the press-fit depth when the cover yoke 43 is press-fitted into the first yoke 42a and the second yoke 42b is restricted by the projection 43a of the cover yoke 43 and the fitting portion 42e of the first yoke 42a and the second yoke 42b. Specifically, the axial depth of the fitting portion 42e formed on the first yoke 42a and the second yoke 42b is approximately half the thickness of the cover yoke 43, including manufacturing tolerances. In this embodiment, three projections 43a of the cover yoke 43 and three fitting portions 42e of the yoke 42 are provided, but the number of projections 43a and fitting portions 42e and the angle at which they are installed can be set as appropriate.

[0053] A board-side connector 47 is mounted on the circuit board 46. The board-side connector 47 has female terminals, and by connecting the coil-side connector 45 to the board-side connector 47 on the circuit board 46 in the thickness direction of the circuit board 46, an electrical connection is obtained between the torque detection unit 30 and the circuit board 46. Alternatively, the coil tip may be wrapped around the coil-side terminals, which are press-fitted into the coil bobbin 41, and soldered in place before being inserted into a through-hole on the board and connected by soldering.

[0054] Here, the yoke 42 will be described in more detail. Figure 6 is a cross-sectional view of AA in Figure 5. At the boundary between the bottom portion 42f and the wall portion 42c of the yoke 42, a groove portion 42g is provided where the thickness direction of the plate forming the yoke 42 is the depth direction. That is, the groove portion 42g is formed in a groove-like shape where the thickness direction of the plate forming the yoke 42 is the depth direction, and the direction along the bottom portion 42f and the wall portion 42c is the width direction, at the same position in the circumferential direction of the yoke 42.

[0055] In this context, the boundary between the bottom portion 42f and the wall portion 42c refers to the area that is bent between the bottom portion 42f and the wall portion 42c. In other words, the boundary between the bottom portion 42f and the wall portion 42c refers to the portion that is bent between the bottom portion 42f and the wall portion 42c when the blank material 42h (see Figure 7), which will be described later, is formed by bending.

[0056] The groove 42g is located in the portion where the outer peripheral end of the bottom 42f in the radial direction of the yoke 42 is connected to the end of the wall 42c on the side where the bottom 42f is located in the axial direction of the yoke 42. Specifically, the groove 42g is located in the portion where the surface of the bottom 42f on the side where the wall 42c is located in the thickness direction of the bottom 42f is connected to the surface of the wall 42c on the thickness direction of the bottom 42f; that is, it is located in the less angular portion of the corner formed by the bottom 42f and the wall 42c. The groove 42g, located at the boundary between the bottom 42f and the wall 42c of the yoke 42 in this way, is continuously arranged around the entire circumference of the yoke 42 in the circumferential direction.

[0057] Next, the manufacturing direction of the yoke 42 will be described. Figure 7 is a plan view of the blank material 42h used in the manufacture of the yoke 42. Both the first yoke 42a and the second yoke 42b of the yoke 42 are manufactured by bending a blank material 42h, which is a flat plate component. The blank material 42h is cut from a plate material before it is shaped into the blank material 42h, with a portion that will become the wall portion 42c and a portion that will become the bottom portion 42f.

[0058] Therefore, in the blank material 42h, the wall portion 42c is formed to be on the same plane as the bottom portion 42f, and the blank material 42h is a disc-shaped or annular member in which the portion that will become the bottom portion 42f is located radially outward from the portion that will become the bottom portion 42f, and the portion that will become the wall portion 42c is arranged around the entire circumference of the bottom portion 42f. The recess 42d and the fitting portion 42e formed in the wall portion 42c are formed at the blank material 42h stage.

[0059] Figure 8 is a cross-sectional view of BB in Figure 7. A groove 42g is positioned in the blank material 42h at the boundary between the bottom portion 42f and the wall portion 42c. The groove 42g is formed in a circular shape when viewed in plan from the blank material 42h, with the thickness direction of the flat blank material 42h being the depth direction of the groove. For example, as shown in Figure 8, the shape of the groove 42g when viewed in the direction of extension of the groove 42g is semicircular, with the width of the groove narrowing from the opening side to the bottom side of the groove.

[0060] The yoke 42 is formed into shape by press working on the blank material 42h formed in this manner. Specifically, the blank material 42h, which is made of a flat plate, is pressed by applying opposing forces in the thickness direction of the plate to the bottom portion 42f and the wall portion 42c, thereby bending the portion of the blank material 42h located outside the groove portion 42g in the thickness direction of the plate. In other words, the blank material 42h is bent at the position of the groove portion 42g. At this time, the groove portion 42g has a thinner plate thickness compared to the surrounding portion, so its rigidity is relatively low. For this reason, the blank material 42h is easier to bend with the groove portion 42g as a fulcrum, and it is possible to easily bend it at the position of the groove portion 42g.

[0061] When the blank material 42h is bent at the position of the groove 42g, the bent portion, that is, the portion of the blank material 42h located outside the groove 42g, is made into a cylindrical shape. This creates a shape in which a cylindrical wall portion 42c is arranged around the bottom portion 42f, forming the yoke 42. Both the first yoke 42a and the second yoke 42b are manufactured in this manner.

[0062] Next, the assembly of the torque detection unit 30 having the yoke 42 will be described. When assembling the torque detection unit 30, first, the detection coils 40 are wound onto the coil bobbins 41. When winding the first detection coil 40a onto the first coil bobbin 41a, the tip of the first detection coil 40a is wrapped around one of the coil-side terminals 41h and fixed with solder or TIG welding. After winding the first detection coil 40a onto the portion between the flange portions 41c of the first coil bobbin 41a, its end is wrapped around the other coil-side terminal 41h and fixed with solder or TIG welding. The same procedure is followed for the second detection coil 40b.

[0063] Next, the two coil bobbins 41 around which the detection coil 40 is wound are fitted inside the yoke 42. Then, these two coil bobbins 41 are positioned so that they face each other with the cover yoke 43 in between, and the first yoke 42a and the second yoke 42b are press-fitted into the cover yoke 43 from both sides in the axial direction.

[0064] The two coil bobbins 41 are press-fitted into the first yoke 42a and the second yoke 42b with the two coil bobbins 41 facing each other, so that the terminal mounting portion 41g of the first coil bobbin 41a and the terminal mounting portion 41g of the second coil bobbin 41b come together to form the coil-side connector 45. The torque detection unit 30 is mounted inside the input shaft-side housing portion 20a in this assembled state, and the coil-side connector 45 is connected to the board-side connector 47 of the circuit board 46. In this way, the torque sensor 10 is installed in the steering device 80.

[0065] The circuit board 46 is equipped with a torque calculation circuit (not shown) that constitutes the torque sensor 10. The torque calculation circuit detects the output voltages of the first detection coil 40a and the second detection coil 40b, and based on the difference in these output voltages, it detects the steering torque applied to the steering wheel 81 and transmitted to the input shaft 82a. In this way, the torque sensor 10 detects the relative displacement (rotational displacement) between the input shaft 82a and the output shaft 82b by corresponding it to the change in impedance of the two detection coils 40.

[0066] Next, the operation of the steering device 80 according to this embodiment will be described. When the steering wheel 81 is operated while driving a vehicle equipped with the steering device 80, the steering force applied to the steering wheel 81 is transmitted from the steering wheel 81 to the steering shaft 82.

[0067] The steering force transmitted to the steering shaft 82 is transmitted as steering torque from the steering shaft 82 to the intermediate shaft 85, and from the intermediate shaft 85 to the pinion gear 88a via the stub shaft 87. As a result, the steering gear 88, which has the pinion gear 88a, converts the rotational motion transmitted from the pinion gear 88a into linear motion of the rack 88b, and actsuates the tie rod 89.

[0068] Furthermore, the steering device 80 according to this embodiment has an electric motor 94 that generates auxiliary steering torque to assist the driver's steering. The electric motor 94 generates auxiliary steering torque based on the steering torque detected by the torque sensor 10 which is arranged along the steering shaft 82.

[0069] The torque sensor 10 detects the steering torque applied to the steering shaft 82 based on the angle of relative rotation when the input shaft 82a and output shaft 82b of the steering shaft 82 rotate relative to each other. That is, since the input shaft 82a and output shaft 82b are connected via a torsion bar 82c, when steering torque is applied to the steering shaft 82, the steering torque is transmitted between the input shaft 82a and output shaft 82b via the torsion bar 82c. At that time, the torsion bar 82c twists slightly, causing the input shaft 82a and output shaft 82b to rotate relative to each other.

[0070] The input shaft 82a has a sensor shaft portion 31 that constitutes the torque sensor 10, and the output shaft 82b is connected to a sensor sleeve 32 that also constitutes the torque sensor 10. Therefore, when the input shaft 82a and the output shaft 82b rotate relative to each other, the sensor shaft portion 31 and the sensor sleeve 32 also rotate relative to each other. The torque sensor 10 detects the steering torque by detecting the angle of relative rotation when the sensor shaft portion 31 and the sensor sleeve 32 rotate relative to each other.

[0071] In more detail, when detecting steering torque with the torque sensor 10, a magnetic field is generated in the detection coil 40, and when the sensor shaft 31 and the sensor sleeve 32 rotate relative to each other, the change in the impedance of the detection coil 40, which changes due to the change in the magnetic field generated in the detection coil 40, is read as an electrical signal to detect the steering torque.

[0072] The changes that occur when the sensor shaft portion 31 and the sensor sleeve 32 rotate relative to each other due to the relative rotation of the input shaft 82a and the output shaft 82b will be explained using Figures 9 and 10. Figures 9 and 10 are explanatory diagrams showing the state in which the sensor shaft portion 31 rotates relative to the sensor sleeve 32. Figures 9 and 10 are explanatory diagrams showing the state in which the sensor shaft portion 31 rotates relative to the sensor sleeve 32 in the direction of the arrows relative to Figure 3. The sensor shaft portion 31 has multiple protrusions 31a, and the sensor sleeve 32 has multiple window holes 33. When the sensor shaft portion 31 and the sensor sleeve 32 rotate relative to each other, the relative positions of the protrusions 31a of the sensor shaft portion 31 and the window holes 33 of the sensor sleeve 32 change.

[0073] Here, the yoke 42 and cover yoke 43, and the sensor shaft portion 31, which are arranged around the detection coil 40 that generates a magnetic field, are made of magnetic material, so magnetic flux can pass through them. On the other hand, the sensor sleeve 32 is made of a non-magnetic material, so magnetic flux does not easily pass through it, but since there is no non-magnetic material at the location of the window hole 33, magnetic flux can easily pass through it.

[0074] Therefore, at positions where a window hole 33 is located in the circumferential direction of the sensor shaft portion 31, the magnetic flux of the magnetic field generated by the detection coil 40 can pass through the window hole 33, resulting in a larger amount of magnetic flux in the magnetic path passing through the yoke 42, the cover yoke 43, and the protrusion 31a of the sensor shaft portion 31. In contrast, at positions where a window hole 33 is not located in the circumferential direction of the sensor shaft portion 31, the magnetic flux of the magnetic field generated by the detection coil 40 is more easily blocked by the sensor sleeve 32, resulting in a smaller amount of magnetic flux in the magnetic path passing through the yoke 42, the cover yoke 43, and the protrusion 31a of the sensor shaft portion 31.

[0075] Therefore, when the relative position between the protrusion 31a of the sensor shaft portion 31 and the window hole 33 of the sensor sleeve 32 changes, the ease with which the magnetic flux of the magnetic field generated by the detection coil 40 passes through changes, and thus the impedance of the detection coil 40 changes depending on the relative position between the protrusion 31a of the sensor shaft portion 31 and the window hole 33 of the sensor sleeve 32.

[0076] For example, if we focus on one of the multiple protrusions 31a arranged on the sensor shaft portion 31 shown in Figure 3, in the state shown in Figure 3, the protrusion 31aa is located at a different position in the circumferential direction from the window hole 33 of the sensor sleeve 32. Therefore, the magnetic flux of the magnetic field generated by the detection coil 40 has difficulty passing through the protrusion 31aa.

[0077] In contrast, when steering torque is input to the steering shaft 82, causing the torsion bar 82c to twist and the input shaft 82a to rotate relative to the output shaft 82b, the sensor shaft portion 31 also rotates relative to the sensor sleeve 32. As a result, the relative position of the protrusion 31a of the sensor shaft portion 31 and the window hole 33 of the sensor sleeve 32 changes. In this case, the ease with which the magnetic flux of the magnetic field generated by the detection coil 40 passes changes depending on the relative position of the protrusion 31a of the sensor shaft portion 31 and the window hole 33 of the sensor sleeve 32.

[0078] For example, suppose that the sensor shaft portion 31 shown in Figure 3 rotates relative to the sensor sleeve 32 in the direction indicated by the arrow in Figure 9, so that the circumferential position of the protrusion 31aa of the sensor shaft portion 31 becomes the same as one of the second window holes 33b, as shown in Figure 9. In this case, the magnetic flux of the magnetic field generated by the second detection coil 40b can easily pass through the second window hole 33b and then through the protrusion 31aa of the sensor shaft portion 31, so the amount of magnetic flux in the magnetic path passing through the protrusion 31aa tends to increase.

[0079] On the other hand, since the position of the protrusion 31aa in the circumferential direction is not the same as that of the first window hole 33a, the magnetic flux of the magnetic field generated by the first detection coil 40a has difficulty passing through the protrusion 31aa of the sensor shaft portion 31, and the amount of magnetic flux in the magnetic path passing through the protrusion 31aa tends to be small.

[0080] Furthermore, if the sensor shaft portion 31 shown in Figure 3 rotates relative to the sensor sleeve 32 in the direction indicated by the arrow in Figure 10, the circumferential position of the protrusion 31aa of the sensor shaft portion 31 becomes the same as the first window hole 33a, as shown in Figure 10. In this case, the magnetic flux of the magnetic field generated by the first detection coil 40a can easily pass through the first window hole 33a and then through the protrusion 31aa of the sensor shaft portion 31, so the amount of magnetic flux in the magnetic path passing through the protrusion 31aa tends to increase.

[0081] On the other hand, since the position of the protrusion 31aa in the circumferential direction is not the same as that of the second window hole 33b, the magnetic flux of the magnetic field generated by the second detection coil 40b has difficulty passing through the protrusion 31aa of the sensor shaft portion 31, and the amount of magnetic flux in the magnetic path passing through the protrusion 31aa tends to be small.

[0082] The magnetic flux of the magnetic field generated by the first detection coil 40a and the second detection coil 40b changes according to the relative rotation angle between the sensor shaft 31 and the sensor sleeve 32, and consequently, the impedance of each detection coil 40 changes. The torque sensor 10 outputs an electrical signal indicating the change in the impedance of the detection coil 40 as a torque signal from the circuit board 46 to the ECU 90.

[0083] The ECU 90 operates the electric motor 94 based on the torque signal transmitted from the torque sensor 10, generating auxiliary steering torque in the electric motor 94. In other words, the torque signal transmitted from the torque sensor 10 to the ECU 90 changes according to the relative rotation angle between the sensor shaft 31 and the sensor sleeve 32, and changes based on the steering torque acting between the input shaft 82a and the output shaft 82b of the steering shaft 82. For this reason, the ECU 90 uses the torque signal transmitted from the torque sensor 10 as information that changes according to the steering torque acting on the steering shaft 82, and adjusts the power value supplied to the electric motor 94 based on the torque signal transmitted from the torque sensor 10, thereby generating auxiliary steering torque in the electric motor 94.

[0084] Figure 11 is a diagram illustrating an example of the relationship between the torque value obtained from the torque signal and the relative angle difference between the sensor shaft and the sensor sleeve. Figure 11 shows an example where the torque value calculated from the torque signal increases as the relative angle difference between the sensor shaft 31 and the sensor sleeve 32 increases.

[0085] The ECU 90 acquires a steering torque signal from the torque sensor 10, a vehicle speed signal from the vehicle speed sensor 95, and operational information of the electric motor 94 from a rotation detection device provided on the electric motor 94. Based on this operational information, the steering torque, and the vehicle speed signal, the ECU 90 generates auxiliary steering torque in the electric motor 94. The auxiliary steering torque generated by the electric motor 94 is transmitted to the output shaft 82b of the steering shaft 82 via the reduction gear 91. As a result, the steering force applied by the driver to the steering wheel 81 is assisted by the auxiliary steering torque generated by the electric motor 94, and steering assist control is performed.

[0086] Furthermore, when steering torque is input from the steering wheel 81 to the steering shaft 82, if the steering shaft 82 does not receive any torque from the intermediate shaft 85 side that resists the steering torque, the input shaft 82a and output shaft 82b rotate together as a single unit, with the torsion bar 82c hardly twisting at all. In this case, the torque sensor 10 needs to output a signal indicating that the steering torque is 0. Hereinafter, the state in which the steering shaft 82 does not receive any torque from the intermediate shaft 85 side that resists the steering torque will also be referred to as the "no-load state" or "no-load condition".

[0087] In a torque sensor 10 with the configuration described above, a misalignment may occur between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4, which is composed of the detection coil 40, yoke 42, cover yoke 43, etc., during the manufacturing of the torque sensor 10 or when the torque sensor is incorporated into a vehicle steering system. In such cases, due to the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4, the difference between the output voltage of the first detection coil 40a and the output voltage of the second detection coil 40b is output as a torque signal, and the steering torque may not be zero even under no load.

[0088] Figures 12A, 12B, 13A, and 13B are cross-sectional views of the sensor sleeve and sensor shaft. Figures 12A and 12B show the cross-sectional structure when the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4 is approximately zero. Figures 13A and 13B show the cross-sectional structure when there is a misalignment of Δx between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4. Figures 12B and 13B show the state after a half-rotation (0 to π) relative to Figures 12A and 13A, respectively.

[0089] Figure 14A is a conceptual diagram showing the torque components generated by changes in the distance between each protrusion of the sensor shaft and the detection coil in the example shown in Figures 12A and 12B. Figure 14B is a conceptual diagram showing the fluctuation of the torque value calculated by the torque signal output from the torque sensor in the example shown in Figures 12A and 12B. The solid line in Figure 14A shows the torque components generated by changes in the distance between the protrusions 31aa of the sensor shaft 31 shown in Figures 12A and 12B and the detection coils 40a and 40b. The dashed line in Figure 14A shows the torque components generated by changes in the distance between the protrusions 31a of the sensor shaft 31 other than the protrusions 31aa shown in Figures 12A and 12B and the detection coils 40a and 40b.

[0090] Figure 15A is a conceptual diagram showing the torque components generated by changes in the distance between each protrusion of the sensor shaft and the detection coil in the example shown in Figures 13A and 13B. Figure 15B is a conceptual diagram showing the fluctuation of the torque value calculated by the torque signal output from the torque sensor in the example shown in Figures 13A and 13B. The solid line in Figure 15A shows the torque components generated by changes in the distance between the protrusions 31aa of the sensor shaft 31 shown in Figures 13A and 13B and the detection coils 40a and 40b. The dashed line in Figure 15A shows the torque components generated by changes in the distance between the protrusions 31a of the sensor shaft 31 other than the protrusions 31aa shown in Figures 13A and 13B and the detection coils 40a and 40b.

[0091] Figure 16 is a conceptual diagram showing the change in torque value when the sensor shaft and sensor sleeve rotate relative to each other as the input shaft rotates. The solid line in Figure 16 shows the change in torque value when there is a misalignment of Δx between the axis x of the input shaft 82a and the axis X of the yoke unit 4 (see Figures 13A and 13B), while the dashed line in Figure 16 shows the change in torque value when the misalignment between the axis x of the input shaft 82a and the axis X of the yoke unit 4 is approximately zero (see Figures 12A and 12B).

[0092] As shown in Figure 14A, when the misalignment between the axis x of the input shaft 82a and the axis X of the yoke unit 4 is approximately zero (Figures 12A and 12B), the torque component caused by the change in distance between each protrusion 31a of the sensor shaft portion 31 and the detection coils 40a and 40b becomes approximately zero. As a result, as shown in Figure 14B, the fluctuation of the torque value in the no-load state becomes approximately zero, and as shown by the dashed line in Figure 15C, the torque value fluctuation component due to the change in rotation angle when the sensor shaft portion 31 and the sensor sleeve 32 rotate relative to each other as the input shaft 82a rotates becomes approximately zero, and as shown by the dashed line in Figure 16, there is no fluctuation of the torque value due to the change in rotation angle.

[0093] On the other hand, as shown in Figure 15A, if there is a misalignment of Δx between the axis x of the input shaft 82a and the axis X of the yoke unit 4 (Figures 13A and 13B), a torque component is generated due to the change in distance between each protrusion 31a of the sensor shaft portion 31 and the detection coils 40a and 40b. As a result, as shown in Figure 15B, the torque value in the no-load state fluctuates according to the number of protrusions 31a of the sensor shaft portion 31. In the torque sensor 10 of this disclosure, since the sensor shaft portion 31 is provided with eight protrusions 31a, a fluctuation component with eight peaks is generated in one rotation (0 to 2π). When the sensor shaft portion 31 and the sensor sleeve 32 rotate relative to each other as the input shaft 82a rotates, this fluctuation component is superimposed on the torque value shown by the dashed line in Figure 16, and the torque value fluctuates with the change in the rotation angle, as shown by the solid line in Figure 16.

[0094] The following describes a vehicle steering system and a torque value correction system that suppress torque fluctuations caused by misalignment between the input shaft 82a of the steering shaft 82 and the yoke unit 4.

[0095] Figure 17 is a block diagram showing a specific configuration example of a vehicle steering system and torque value correction system according to Embodiment 1. The torque value correction system 100 according to Embodiment 1 acquires correction data to correct the torque value detected by the torque sensor 10 during actual vehicle operation, for example, before incorporating the vehicle steering system 1 according to Embodiment 1 into the vehicle.

[0096] The torque value correction system 100 comprises a processing unit 101 and an external drive motor 102. The processing unit 101 receives the torque signal Th output from the torque sensor 10 and the angle signal θh output from the angle sensor 11 via the ECU 90 of the vehicle steering system 1.

[0097] In the example shown in Figure 17, the external drive motor 102 is connected to the output shaft 82b of the steering shaft 82. The input shaft 82a of the steering shaft 82 is left unloaded (for example, the steering wheel 81 is not connected). This causes the sensor shaft 31 and the sensor sleeve 32 to rotate in the same direction at the same speed when the external drive motor 102 is driven. However, the external drive motor 102 may also be connected to the input shaft 82a of the steering shaft 82. In this case, the output shaft 82b of the steering shaft 82 is left unloaded (for example, the universal joint 84 is not connected). This causes the sensor shaft 31 and the sensor sleeve 32 to rotate in the same direction at the same speed when the external drive motor 102 is driven. Alternatively, the external drive motor 102 may be connected to both the input shaft 82a and the output shaft 82b of the steering shaft 82, driving both external drive motors 102 in the same direction at the same speed.

[0098] Figure 18 shows an example of the control block configuration of the processing unit of the torque value correction system according to Embodiment 1. The processing unit 101 of the torque value correction system 100 according to Embodiment 1 includes a correction data generation unit 103, a torque value calculation unit 104, and an absolute angle calculation unit 105. Each control block shown in Figure 18 is realized by a correction data acquisition program executed in the processing unit 101.

[0099] The torque value correction system 100 according to Embodiment 1 drives an external drive motor 102 to rotate the sensor shaft portion 31 and the sensor sleeve 32 in the same direction at the same speed once, and acquires correction data. Figure 19A is a conceptual diagram showing the torque correction value acquired when the correction data is acquired. Figure 19B is a conceptual diagram showing the absolute angle acquired when the correction data is acquired. Figure 19C is a conceptual diagram showing the correction data generated when the correction data is acquired.

[0100] Specifically, the torque value calculation unit 104 of the processing unit 101 calculates a torque correction value Th_nl based on the torque signal Th output from the torque sensor 10 when acquiring correction data (see Figure 19A). In addition, the absolute angle calculation unit 105 of the processing unit 101 calculates the absolute angle θ_abs based on the angle signal θh output from the angle sensor 11 when acquiring correction data (see Figure 19B). The torque correction value Th_nl calculated by the torque value calculation unit 104 of the processing unit 101 includes a fluctuating component caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4.

[0101] Then, the correction data generation unit 103 of the processing unit 101 associates the torque correction value Th_nl calculated by the torque value calculation unit 104 with the absolute angle θ_abs calculated by the absolute angle calculation unit 105 to generate correction data Cor_data (see Figure 19C).

[0102] Figure 20 shows an example of the control block configuration of the ECU of the vehicle steering system according to Embodiment 1. The ECU 90 of the vehicle steering system 1 according to Embodiment 1 includes a torque value correction unit 901, a torque value calculation unit 902, a storage unit 903, and an absolute angle calculation unit 904. Each control block shown in Figure 20 is realized by a torque value correction program executed in the ECU 90.

[0103] The correction data Cor_data acquired by the torque value correction system 100 during correction data acquisition is stored in the memory unit 903 of the ECU 90. The torque value correction system 100 is removed when the vehicle steering system 1 is installed in the vehicle.

[0104] The ECU 90 of the vehicle steering system according to Embodiment 1 applies correction data Cor_data obtained by the torque value correction system 100 to the torque value obtained during actual vehicle driving.

[0105] Specifically, the torque value correction unit 901 of the ECU 90 calculates the torque value Th_act based on the torque signal Th output from the torque sensor 10 during actual vehicle operation. In addition, the absolute angle calculation unit 904 of the ECU 90 calculates the absolute angle θ_abs calculated based on the angle signal θh output from the angle sensor 11 during actual vehicle operation.

[0106] Then, during actual vehicle operation, the torque value correction unit 901 of the ECU 90 reads the torque correction value Th_nl corresponding to the absolute angle θ_abs calculated by the absolute angle calculation unit 904 from the correction data Cor_data stored in the storage unit 903, subtracts it from the torque value Th_act calculated by the torque value calculation unit 902, and outputs the corrected torque value Th_cor (Th_cor = Th_act - Th_nl). This removes the fluctuation component caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4.

[0107] As a result, the ECU 90 can perform steering assist control using a corrected torque value Th_cor as the steering torque, which suppresses torque fluctuations caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4 during actual vehicle operation.

[0108] (Embodiment 2) In Embodiment 2, components and operations that differ from those in Embodiment 1 will be described in detail, and some descriptions that are the same as those in Embodiment 1 may be omitted.

[0109] Figure 21 is a schematic diagram of a vehicle steering system according to Embodiment 2. In the vehicle steering system 1a according to Embodiment 2, the steering device 80a includes a position sensor 12 instead of the angle sensor 11 in Embodiment 1. The position sensor 12 detects a reference position for the rotational position of the output shaft 82b and outputs it to the ECU 90. An index sensor is an example of the position sensor 12. However, the position sensor 12 may be, for example, a Hall element. The position sensor 12 may also be configured to detect a reference position for the rotational position of the input shaft 82a. The position sensor 12 detects a reference position for the rotational position of the input shaft 82a or the output shaft 82b. Torque is applied to the detection axis of the position sensor 12 (input shaft 82a or output shaft 82b) by the electric motor 94. That is, for example, in a configuration in which the electric motor 94 applies torque to the output shaft 82b, the position sensor 12 detects the rotational position (angle) of the output shaft 82b. The detection accuracy can be improved by detecting the rotational position (angle) of the shaft to which torque is applied by the electric motor 94.

[0110] Figure 22 is a block diagram showing a specific configuration example of a vehicle steering system and torque value correction system according to Embodiment 2. The torque value correction system 100a according to Embodiment 2 acquires correction data to correct the torque value detected by the torque sensor 10 during actual vehicle operation, for example, before incorporating the vehicle steering system 1a according to Embodiment 2 into the vehicle.

[0111] The torque value correction system 100a comprises a processing unit 101a and an external drive motor 102. The processing unit 101a receives the torque signal Th output from the torque sensor 10, the electric motor angle signal θm output from the rotation angle detection unit 94a of the electric motor 94, and the reference position signal P_ref output from the position sensor 12 via the ECU 90a of the vehicle steering system 1a.

[0112] Figure 23 shows an example of the control block configuration of the processing unit of the torque value correction system according to Embodiment 2. The processing unit 101a of the torque value correction system 100a according to Embodiment 2 includes a correction data generation unit 103, a torque value calculation unit 104, and an absolute angle calculation unit 105a. Each control block shown in Figure 23 is realized by a correction data acquisition program executed in the processing unit 101a.

[0113] The torque value correction system 100a according to Embodiment 2 drives an external drive motor 102 to rotate the sensor shaft portion 31 and the sensor sleeve 32 once in the same direction at the same speed, and acquires correction data. In this embodiment, instead of the angle signal θh output from the angle sensor 11, the absolute angle θ_abs is calculated using the electric motor angle signal θm output from the rotation angle detection unit 94a of the electric motor 94 and the reference position signal P_ref output from the position sensor 12.

[0114] Figure 24A is a conceptual diagram showing the torque correction value acquired when correction data is acquired. Figure 24B is a conceptual diagram showing the electric motor angle signal acquired when correction data is acquired. Figure 24C is a conceptual diagram showing the position signal acquired when correction data is acquired. Figure 24D is a conceptual diagram showing the absolute angle acquired when correction data is acquired. Figure 24E is a conceptual diagram showing the correction data generated when correction data is acquired.

[0115] Specifically, the torque value calculation unit 104 of the processing unit 101a calculates a torque correction value Th_nl based on the torque signal Th output from the torque sensor 10 when acquiring correction data (see Figure 24A). In addition, the absolute angle calculation unit 105a of the processing unit 101a calculates the absolute angle θ_abs based on the electric motor angle signal θm output from the rotation angle detection unit 94a of the electric motor 94 (see Figure 24B) and the reference position signal P_ref output from the position sensor 12 (see Figure 24C) when acquiring correction data (see Figure 24D). The torque correction value Th_nl calculated by the torque value calculation unit 104 of the processing unit 101a includes a fluctuating component caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4.

[0116] Then, the correction data generation unit 103 of the processing unit 101a associates the torque correction value Th_nl calculated by the torque value calculation unit 104 with the absolute angle θ_abs calculated by the absolute angle calculation unit 105a to generate correction data Cor_data (see Figure 24E).

[0117] Figure 25 shows an example of the control block configuration of the ECU of the vehicle steering system according to Embodiment 2. The ECU 90a of the vehicle steering system 1a according to Embodiment 2 includes a torque value correction unit 901, a torque value calculation unit 902, a storage unit 903, and an absolute angle calculation unit 904a. Each control block shown in Figure 25 is realized by a torque value correction program executed in the ECU 90a.

[0118] The correction data Cor_data acquired by the torque value correction system 100a during correction data acquisition is stored in the memory unit 903 of the ECU 90a. The torque value correction system 100a is removed when the vehicle steering system 1a is installed in the vehicle.

[0119] The ECU 90a of the vehicle steering system according to Embodiment 2 applies the correction data Cor_data obtained by the torque value correction system 100a to the torque value obtained during actual vehicle driving.

[0120] Specifically, the torque value correction unit 901 of the ECU 90a calculates the torque value Th_act based on the torque signal Th output from the torque sensor 10 during actual vehicle operation. Figure 26A is a conceptual diagram showing the electric motor angle signal acquired during actual vehicle operation. Figure 26B is a conceptual diagram showing the position signal acquired during actual vehicle operation. Figure 26C is a conceptual diagram showing the absolute angle acquired during actual vehicle operation.

[0121] The absolute angle calculation unit 904a of the ECU 90a calculates the absolute angle θ_abs during actual vehicle operation based on the electric motor angle signal θm (see Figure 26A) output from the rotation angle detection unit 94a of the electric motor 94 and the reference position signal P_ref (see Figure 26B) output from the position sensor 12 (see Figure 26C).

[0122] Then, during actual vehicle operation, the torque value correction unit 901 of the ECU 90a reads the torque correction value Th_nl corresponding to the absolute angle θ_abs calculated by the absolute angle calculation unit 904a from the correction data Cor_data stored in the storage unit 903, subtracts it from the torque value Th_act calculated by the torque value calculation unit 902, and outputs the corrected torque value Th_cor (Th_cor = Th_act - Th_nl). This removes the fluctuation component caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4.

[0123] As a result, the ECU90a can perform steering assist control using a corrected torque value Th_cor as the steering torque, which suppresses torque fluctuations caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4 during actual vehicle operation.

[0124] (Embodiment 3) Embodiment 3 will describe in detail components and operations that differ from those in Embodiments 1 and 2, and may omit descriptions that are the same as those in Embodiments 1 and 2.

[0125] Figure 27 is a schematic diagram of a vehicle steering system according to Embodiment 3. In the vehicle steering system 1b according to Embodiment 3, when the vehicle steering system 1b according to Embodiment 3 is installed in a vehicle, steering angle information is input to the ECU 90b from an external unit (not shown, e.g., steering angle detection unit) via CAN (Controller Area Network) 96. In Figure 27, a configuration in which the position sensor 12 detects the rotational position of the output shaft 82b is illustrated, but the position sensor 12 may also be configured to detect a reference position for the rotational position of the input shaft 82a, similar to Embodiment 2. The position sensor 12 detects a reference position for the rotational position of the input shaft 82a or the output shaft 82b. Torque is applied to the detection axis of the position sensor 12 (input shaft 82a or output shaft 82b) by the electric motor 94. That is, for example, in a configuration in which the electric motor 94 applies torque to the output shaft 82b, the position sensor 12 detects the rotational position (angle) of the output shaft 82b. The detection accuracy can be improved by detecting the rotational position (angle) of the shaft to which torque is applied by the electric motor 94.

[0126] Figure 28 is a block diagram showing a specific configuration example of a vehicle steering system and torque value correction system according to Embodiment 3. The torque value correction system 100b according to Embodiment 3 acquires correction data to correct the torque value detected by the torque sensor 10 during actual vehicle operation, for example, before incorporating the vehicle steering system 1b according to Embodiment 3 into the vehicle.

[0127] The torque value correction system 100b comprises a processing unit 101b and an external drive motor 102. The processing unit 101b receives the torque signal Th output from the torque sensor 10 and the reference position signal P_ref output from the position sensor 12 via the ECU 90b of the vehicle steering system 1b. The processing unit 101b also receives the external drive motor angle signal θm_ex output from the rotation angle detection unit 102a of the external drive motor 102.

[0128] Figure 29 shows an example of the control block configuration of the processing unit of the torque value correction system according to Embodiment 3. The processing unit 101b of the torque value correction system 100b according to Embodiment 3 includes a correction data generation unit 103, a torque value calculation unit 104, and an absolute angle calculation unit 105b. Each control block shown in Figure 29 is realized by a correction data acquisition program executed in the processing unit 101b.

[0129] The torque value correction system 100b according to Embodiment 3 drives an external drive motor 102 to rotate the sensor shaft portion 31 and the sensor sleeve 32 in the same direction at the same speed once, and acquires correction data. In this embodiment, steering angle information from an external unit (not shown) is not input when acquiring correction data. Therefore, in this embodiment, when acquiring correction data, the absolute angle θ_abs is calculated using the external drive motor angle signal θm_ex instead of steering angle information.

[0130] Figure 30A is a conceptual diagram showing the torque correction value acquired when correction data is acquired. Figure 30B is a conceptual diagram showing the external drive motor angle signal acquired when correction data is acquired. Figure 30C is a conceptual diagram showing the position signal acquired when correction data is acquired. Figure 30D is a conceptual diagram showing the absolute angle acquired when correction data is acquired. Figure 30E is a conceptual diagram showing the correction data generated when correction data is acquired.

[0131] Specifically, the torque value calculation unit 104 of the processing unit 101b calculates a torque correction value Th_nl based on the torque signal Th output from the torque sensor 10 when acquiring correction data (see Figure 30A). In addition, the absolute angle calculation unit 105b of the processing unit 101b calculates the absolute angle θ_abs based on the external drive motor angle signal θm_ex output from the rotation angle detection unit 102a of the external drive motor 102 (see Figure 30B) and the reference position signal P_ref output from the position sensor 12 (see Figure 30C) when acquiring correction data (see Figure 30D). The torque correction value Th_nl calculated by the torque value calculation unit 104 of the processing unit 101b includes a fluctuating component caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4.

[0132] Then, the correction data generation unit 103 of the processing unit 101b associates the torque correction value Th_nl calculated by the torque value calculation unit 104 with the absolute angle θ_abs calculated by the absolute angle calculation unit 105b to generate correction data Cor_data (see Figure 30E).

[0133] Figure 31 shows an example of the control block configuration of the ECU of the vehicle steering system according to Embodiment 3. The ECU 90b of the vehicle steering system 1b according to Embodiment 3 includes a torque value correction unit 901, a torque value calculation unit 902, a storage unit 903, and an absolute angle calculation unit 904b. Each control block shown in Figure 31 is realized by a torque value correction program executed in the ECU 90b.

[0134] The correction data Cor_data acquired by the torque value correction system 100b during correction data acquisition is stored in the memory unit 903 of the ECU 90b. The torque value correction system 100b is removed when the vehicle steering system 1b is installed in the vehicle.

[0135] The ECU 90b of the vehicle steering system according to Embodiment 3 applies the correction data Cor_data obtained by the torque value correction system 100b to the torque value obtained during actual vehicle driving.

[0136] Specifically, the torque value correction unit 901 of the ECU 90b calculates the torque value Th_act based on the torque signal Th output from the torque sensor 10 during actual vehicle operation. Figure 32A is a conceptual diagram showing steering angle information acquired during actual vehicle operation. Figure 32B is a conceptual diagram showing position signals acquired during actual vehicle operation. Figure 32C is a conceptual diagram showing absolute angles acquired during actual vehicle operation.

[0137] The absolute angle calculation unit 904b of the ECU90a calculates the absolute angle θ_abs (see Figure 32C) based on the steering angle information θh1 (see Figure 32A) input to the ECU90b from an external unit via CAN96 during actual vehicle operation, and the reference position signal P_ref (see Figure 32B) output from the position sensor 12.

[0138] Then, during actual vehicle operation, the torque value correction unit 901 of the ECU 90b reads the torque correction value Th_nl corresponding to the absolute angle θ_abs calculated by the absolute angle calculation unit 904b from the correction data Cor_data stored in the storage unit 903, subtracts it from the torque value Th_act calculated by the torque value calculation unit 902, and outputs the corrected torque value Th_cor (Th_cor = Th_act - Th_nl). This removes the fluctuation component caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4.

[0139] As a result, the ECU90b can perform steering assist control using a corrected torque value Th_cor as the steering torque, which suppresses torque fluctuations caused by the misalignment between the axis x of the input shaft 82a of the steering shaft 82 and the axis X of the yoke unit 4 during actual vehicle operation.

[0140] The figures used in the embodiments described above are conceptual diagrams for qualitative explanation of the present disclosure and are not limited thereto. Specifically, for example, in the embodiments described above, the torque sensor 30 is exemplified in which the sensor shaft portion 31 is provided on the input shaft 82a and the sensor sleeve 32 is connected to the output shaft 82b, but it may also be the case that the sensor shaft portion 31 is provided on the output shaft 82b and the sensor sleeve 32 is connected to the input shaft 82a. Furthermore, although the embodiments described above are examples of preferred implementations of the present disclosure, they are not limited thereto, and various modifications can be made without departing from the gist of the present disclosure. [Explanation of Symbols]

[0141] 1,1a,1b Vehicle steering system 4 Yoke Units 10 Torque Sensor 11 Angle sensor 12 Position Sensors 20 Housing 20a Input shaft side housing section 20b Output shaft side housing section 30 Torque detection unit 31 Sensor shaft section 31a Convex part 31b Groove 32 Sensor Sleeve 32a Connecting part 33 Window holes 33a First window opening 33b Second window opening 40 detection coils 40a First detection coil 40b Second detection coil 41 Coil Bobbin 42 York 42a First York 42b Second York 42c wall 42f bottom 42g groove 42h blank material 43 Cover yoke 45 Coil-side connector 46 Circuit boards 47. Circuit board side connector 80, 80a, 80b Steering system 81 Steering Wheel 82 Steering shaft 82a Input axis 82b Output shaft 82c Torsion Bar 83 Steering force assist mechanism 84 Universal Joint 85 Intermediate shaft 86 Universal Joint 87 Stub Shaft 88 Steering gear 88a Pinion Gear 88b rack 89 Tie Rod 90, 90a, 90b ECU 91 Reducer 92 Worm Wheel 93 Warm 94 Electric motor 94a Rotation angle detection unit 95 Vehicle speed sensor 98 Ignition Switch 99 Power supply 100, 100a, 100b Torque Value Correction System 101, 101a, 101b Processing Unit 102 External drive motor 102a Rotation angle detection unit 103 Correction Data Generation Unit 104 Torque value calculation unit 105, 105a, 105b Absolute angle calculation unit 901 Torque value correction unit 902 Torque Value Calculation Unit 903 Storage section 904, 904a, 904b Absolute Angle Calculation Unit

Claims

1. A torque sensor detects the steering torque generated between the input shaft and the output shaft based on an electrical signal generated by the relative rotation of the input shaft and the output shaft to which the steering wheel is connected, A control device that performs steering assist control based on the steering torque, It has, The control device is The steering torque is corrected based on the torque correction value obtained when the input shaft and the output shaft are rotated in the same direction at the same speed. Vehicle steering system.

2. It has an angle sensor that detects the absolute angle of the output shaft, The control device is When correcting the steering torque, a torque correction value corresponding to the absolute angle detected by the angle sensor is applied. The vehicle steering system according to claim 1.

3. An electric motor that applies torque to the steering shaft via a reduction gear, A position sensor for detecting a reference for the rotational position of the input shaft or the output shaft, It has, The control device is When correcting the steering torque, a torque correction value corresponding to the absolute angle calculated based on the rotation angle of the electric motor and the rotation position detected by the position sensor is applied. The vehicle steering system according to claim 1.

4. It has a position sensor that detects a reference for the rotational position of the input shaft or the output shaft, The control device is When correcting the steering torque, a torque correction value corresponding to the absolute angle calculated based on externally input rudder angle information and the rotational position detected by the position sensor is applied. The vehicle steering system according to claim 1.

5. A torque sensor detects the steering torque generated between the input shaft and the output shaft based on an electrical signal generated by the relative rotation of the input shaft and the output shaft to which the steering wheel is connected, A control device that performs steering assist control based on the steering torque, A torque value correction system for a vehicle steering system having, The device includes a processing unit that rotates the input shaft and the output shaft in the same direction at the same speed and acquires a torque correction value to be applied when correcting the steering torque. Torque value correction system.

6. The aforementioned vehicle steering system is It has an angle sensor that detects the absolute angle of the output shaft, The aforementioned processing apparatus is When the input shaft and the output shaft are rotated in the same direction at the same speed, the torque correction value detected by the torque sensor and the absolute angle detected by the angle sensor are associated to generate correction data for correcting the steering torque. The torque value correction system according to claim 5.

7. The aforementioned vehicle steering system is An electric motor that applies torque to the steering shaft via a reduction gear, A position sensor for detecting a reference for the rotational position of the input shaft or the output shaft, It has, The aforementioned processing apparatus is When the input shaft and the output shaft are rotated in the same direction at the same speed, the torque correction value detected by the torque sensor is associated with the absolute angle calculated based on the rotation angle of the electric motor and the rotation position detected by the position sensor, and correction data for correcting the steering torque is generated. The torque value correction system according to claim 5.

8. The system includes an external drive motor that rotates the input shaft and the output shaft in the same direction at the same speed. The aforementioned vehicle steering system is It has a position sensor that detects a reference for the rotational position of the input shaft or the output shaft, The aforementioned processing apparatus is When the external drive motor is driven, the torque correction value detected by the torque sensor is associated with the absolute angle calculated based on the rotation angle of the external drive motor and the rotation position detected by the position sensor, and correction data is generated to correct the steering torque. The torque value correction system according to claim 5.

9. The torque sensor is A sensor shaft portion provided on either the input shaft or the output shaft, A sensor sleeve is connected to the other of the input shaft and the output shaft, and is positioned to cover the sensor shaft portion. Equipped with, The sensor shaft portion has multiple protrusions arranged at equal intervals along the circumferential direction on its radially outward side. The sensor sleeve has a plurality of window holes that penetrate in the thickness direction of the sensor sleeve and are arranged in a circumferential direction. The torque value correction system according to claim 5.

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