Steering system and vehicle

Abstract

To provide a steering system and vehicle, capable of achieving high stability of a vehicle when an actuator of either of left or right wheel is under an abnormal state.SOLUTION: A steering system includes: a hub unit 1 with a steering function and a controller 29 which controls a steering actuator 5 of the hub unit 1 with a steering function. The steering actuator 5 includes a pair of actuators for independently steering left and right wheels. The controller 29 has a function of independently controlling steering of the left and right wheels and also has a function of acquiring tire angle information of the left and right wheels. The controller 29, when abnormality of an actuator 5 of either of the pair of actuators 5, 5 is detected, continuously controls the other actuator 5 based on the acquired tire angle information.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a steering system and a vehicle, and to a technique for improving fuel efficiency and stabilizing driving performance and improving redundancy by controlling the steering angles of left and right wheels to appropriate angles according to driving conditions. [Background technology]

[0002] In general automobiles and other vehicles, the steering wheel and steering device are mechanically connected, and both ends of the steering device are connected to the left and right wheels by tie rods. Therefore, the turning angle of the left and right wheels in response to the movement of the steering wheel is determined by the initial setting. There are two types of vehicle geometries known: (1) "parallel geometry," in which the turning angle of the left and right wheels is the same, and (2) "Ackermann geometry," in which the angle of the inside wheel is turned greater than the angle of the outside wheel in order to have a single turning center.

[0003] In Ackermann geometry, the steering angle difference between the left and right wheels is set so that each wheel turns around a common point in order to allow the vehicle to turn smoothly when cornering at low speeds where the centrifugal force acting on the vehicle can be ignored. However, in high speed cornering where centrifugal force cannot be ignored, it is desirable for the wheels to generate a cornering force in a direction that balances the centrifugal force, so parallel geometry is preferable to Ackermann geometry.

[0004] As mentioned above, the steering device of a typical vehicle is mechanically connected to the wheels, so that it can only have a single fixed steering geometry, and is often set to an intermediate geometry between the Ackermann geometry and the parallel geometry. However, in this case, the steering angle difference between the left and right wheels is insufficient at low speeds, resulting in an excessive steering angle of the outer wheel, and at high speeds, the steering angle of the inner wheel is excessive. If there is an unnecessary imbalance in the wheel lateral force distribution between the inner and outer wheels in this way, it can cause a deterioration in fuel efficiency and early tire wear due to an increase in running resistance, and also cause problems such as a loss of smooth cornering because the inner and outer wheels cannot be used efficiently.

[0005] In Patent Document 1, when a communication abnormality occurs between the first control means and the second control means, a means is provided for resetting the digital processor included in the second control means and cutting off the power supplied to the electric motor drive means for steering. Patent Document 2 proposes a means of avoiding abnormal vehicle behavior when an abnormality is detected in the toe angle sensor of one of the left and right rear wheels, by steering the rear wheel where the abnormality was detected to the limit of its steering range, and further steering the other rear wheel in the same phase as the rear wheel on the side with the abnormal toe angle sensor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3477889 [Patent Document 2] JP 2009-208718 A Summary of the Invention [Problem to be solved by the invention]

[0007] As in Patent Document 1, if the power supply to the actuator is cut off when an abnormality occurs, the actuator will stop regardless of the toe angles of the front and rear wheels, and depending on the toe angle conditions, such as extreme toe-in or extreme toe-out, the limit performance during cornering and straight-line stability may decrease, possibly causing the vehicle to become unstable.

[0008] As in Patent Document 2, if an abnormality occurs in the toe angle sensor of one of the rear wheels, and the other rear wheel is steered in the same phase as the rear wheel on the side where the abnormality occurs, the marginal performance during cornering will decrease if the steering wheel is steered in the opposite phase to the rear wheel at high speeds, which may cause the vehicle to become unstable.

[0009] An object of the present invention is to provide a steering system and a vehicle that can improve the stability of the vehicle when an abnormality occurs in an actuator for either the left or right wheel. [Means for solving the problem]

[0010] The steering system of the present invention is a steering system including a steering actuator 5 that rotates a wheel 9 around a steering axis A extending in a vertical direction, and a control device 29 that controls the steering actuator 5, The control device 29 has a function of independently controlling the steering of each of the left and right wheels 9 using a pair of steering actuators 5, 5, and also has a function of acquiring tire angle information of the left and right wheels. When the control device 29 detects an abnormality in either one of the pair of steering actuators 5, 5, it continues to control the other steering actuator 5 based on the acquired tire angle information. The "tire angle information" includes, for example, not only the steering angle, which is the tire angle of the wheel, acquired from a steering angle sensor or the like, but also position information equivalent to the tire angle, such as the motor angle and the linear position of the output rod.

[0011] According to this configuration, when the control device 29 detects an abnormality in the steering actuator 5 for either the left or right wheels, it continues to control the other steering actuator 5 based on the tire angle information of the left and right wheels. In this case, abnormality processing is performed taking into account the tire angle information of the left and right wheels, and the vehicle 10 is stopped at a toe angle that allows stable driving, thereby making it possible to improve the driving stability of the vehicle.

[0012] The vehicle is provided with a hub unit 1 with a steering function, the hub unit 1 having a hub unit body 2 with a hub bearing 15 that supports a wheel 9 for rotation, a unit support member 3 that is provided on a suspension frame component 6 (6R) of a suspension device 12 (12R) and supports the hub unit body 2 for rotation about a steering axis A extending in the vertical direction, and a steering actuator 5 that drives the hub unit body 2 to rotate about the steering axis A, Each steering actuator 5 may have a motor 26 and a linear motion mechanism 25 that converts the rotational output of the motor 26 into linear motion of an output rod 25a, and the hub unit body 2 in each wheel 9 may be rotated around the steering axis A as the output rod 25a moves back and forth.

[0013] When the control device 29 determines that the detected abnormality in the one steering actuator 5 is not a defined abnormality, the control device 29 may perform a retry operation to operate the one steering actuator 5 again. The "predetermined abnormality" is an abnormality in which the function of the steering actuator is lost, for example, a serious abnormality such as an abnormality in a motor angle sensor. In this case, since the steering system can continue to operate, the control device 29 can restore one of the steering actuators 5 to normal by causing the one of the steering actuators 5 to perform a retry operation.

[0014] The control device 29 may count the number of retry operations, and when the counted number of retries reaches a specified number, stop controlling the one steering actuator 5. The "prescribed number of times" is a number of times that is arbitrarily determined by design or the like, and is determined by obtaining an appropriate number of times, for example, by either or both of a test and a simulation. In this case, when the number of retries reaches a prescribed number, it is determined that the abnormal steering actuator 5 cannot be expected to recover, and control of this steering actuator 5 is stopped, thereby ensuring redundancy.

[0015] The control device 29 may stop control of the one steering actuator 5 when it determines that the detected abnormality in the one steering actuator 5 is a predetermined abnormality. The "predetermined abnormality" is an abnormality in which the function of the steering actuator is lost, for example, a serious abnormality such as an abnormality in a motor angle sensor. In this case, redundancy can be ensured by stopping the control of the one of the abnormal steering actuators 5 without delay.

[0016] The control device 29 may be provided in a plurality of units corresponding to the steering actuators 5, or may be a single control device capable of controlling all the steering actuators 5. When a plurality of control devices are provided corresponding to the steering actuators 5, one control device can continue the steering operation by acquiring tire angle information from the other control device. When a single control device capable of controlling all the steering actuators 5 is provided, it is possible to reduce the number of parts and manufacturing costs compared to a structure having a plurality of control devices.

[0017] The control device 29 may have a steering control section 30 that outputs a current command signal corresponding to a given steering angle command signal, and an actuator drive control section 31 that outputs a current corresponding to the current command signal input from the steering control section 30 to drive and control the steering actuator 5. With this configuration, the steering actuator 5 of the steering function-equipped hub unit 1 can be controlled with a simple configuration.

[0018] In the vehicle 10 of the present invention, either or both of the front wheels 9F and the rear wheels 9R are supported using the steering function equipped hub unit 1 in the steering system of any of the above configurations of the present invention. Therefore, the above-mentioned effects of the steering system of the present invention can be obtained. The front wheels 9F are generally considered to be steered wheels, and when the steering function equipped hub unit 1 is applied to the steered wheels, it is effective for adjusting the toe angle while traveling. In addition, the rear wheels 9R are generally considered to be non-steered wheels, but when applied to the non-steered wheels, it is possible to reduce the minimum turning radius during low-speed traveling by slightly steering the non-steered wheels. Effect of the Invention

[0019] When the steering system of the present invention detects an abnormality in the steering actuator for either the left or right wheel, it performs abnormality processing taking into account tire angle information of the left and right wheels, and stops the vehicle at a toe angle that allows stable driving, thereby improving the driving stability of the vehicle. [Brief description of the drawings]

[0020] [Figure 1] 1 is a vertical cross-sectional view showing a configuration of a steering function-equipped hub unit and its surroundings in a steering system according to a first embodiment of the present invention. FIG. [Diagram 2] 2 is a horizontal cross-sectional view of the steering function-equipped hub unit and a block diagram of a control system thereof. FIG. [Diagram 3] FIG. 2 is a perspective view showing the external appearance of the steering function-equipped hub unit. [Figure 4] FIG. 2 is a side view of the steering function-equipped hub unit. [Diagram 5] FIG. 2 is a plan view of the steering function-equipped hub unit. [Figure 6] 6 is a cross-sectional view taken along line VI-VI in FIG. 4. [Figure 7] FIG. 4 is a side view of the linear motion mechanism of the steering function-equipped hub unit. [Figure 8] FIG. 3 is a partially enlarged view showing a part of FIG. 2. [Figure 9] 4 is a flowchart showing the control of the steering system in stages. [Figure 10] FIG. 2 is a schematic plan view of an example of a vehicle equipped with the steering system. [Figure 11] FIG. 11 is a schematic plan view of another example of a vehicle equipped with any one of the steering systems. [Figure 12] FIG. 11 is a schematic plan view of another example of a vehicle equipped with any one of the steering systems. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [First embodiment] A steering system according to an embodiment of the present invention will be described with reference to FIGS. The steering system includes a hub unit with a steering function and a control device (to be described later) that controls a steering actuator of the hub unit with a steering function. The steering system is mounted on a vehicle.

[0022] <Outline of the structure of the hub unit with steering function> As shown in FIG. 1, this hub unit with steering function 1 includes a hub unit body 2, a unit support member 3, a rotation-permitting support part 4, and a steering actuator 5. The unit support member 3 is provided integrally with a knuckle 6, which is a suspension frame part. The steering actuator 5 is provided on the inboard side of this unit support member 3, and the hub unit body 2 is provided on the outboard side of the unit support member 3. With the hub unit with steering function 1 mounted on a vehicle, the outer side in the vehicle width direction is referred to as the outboard side, and the center side in the vehicle width direction is referred to as the inboard side. Note that the hub unit with steering function 1 may be simply referred to as the hub unit 1.

[0023] As shown in Fig. 2, the hub unit body 2 and the steering actuator 5 are connected by a joint portion 8. Usually, this joint portion 8 is fitted with a boot (not shown) for waterproofing and dustproofing.

[0024] As shown in Fig. 1, the hub unit body 2 is supported by a unit support member 3 at two upper and lower points via rotation-permitting support parts 4, 4 so as to be rotatable around a steering axis A extending in the vertical direction. The steering axis A is an axis different from the rotation axis O of the wheel 9, and is also different from the kingpin axis that performs the main steering. In a normal vehicle, the kingpin angle is set at 10 to 20 degrees for the purpose of improving the straight-line stability of the vehicle when traveling, but the hub unit 1 with steering function of this embodiment has a steering axis with an angle (axis) different from the kingpin angle. The wheel 9 includes a wheel 9a and a tire 9b.

[0025] <Installation location of steering function equipped hub unit 1> In this embodiment, the steering function equipped hub unit 1 is provided integrally with the knuckle 6 of the suspension device 12 as a mechanism for steering the left and right wheels individually a small angle (approximately ±5 degrees) in addition to the steering by the steering device 11 of the steering wheel, specifically the front wheels 9F of the vehicle 10 as shown in FIG. 10. However, in the steering function equipped hub unit 1 for the steering wheel, depending on the vehicle control requirements, the left and right wheels may each take a relatively large angle, for example 10° to 20°, instead of the small angle. The same applies to the steering function equipped hub unit 1 shown in FIG. 12 described later.

[0026] As shown in Fig. 10, the steering device 11 is attached to the vehicle body and is operated by the operation of a steering wheel 11a by the driver or by commands from an automatic driving device or a driving support device (not shown), and its advancing and retreating tie rod 14 is connected to a steering coupling portion 6d (described later) of the unit support member 3 in Fig. 2. The steering device 11 is of a rack and pinion type or the like, but any type of steering device may be used. The suspension device 12 in Fig. 10 applies, for example, a strut-type suspension mechanism in which a shock absorber is directly fixed to the knuckle 6, but a double wishbone suspension mechanism, a multi-link suspension mechanism, or other suspension mechanisms may also be applied.

[0027] <About hub unit body 2> As shown in FIG. 1, the hub unit body 2 includes a hub bearing 15 for supporting the wheel 9, an outer ring 16 which is a circular portion with a steering shaft, and an arm portion 17 (FIG. 3) which is a steering force receiving portion. As shown in Figure 6, hub bearing 15 has an inner ring 18, an outer ring 19, and rolling elements 20 such as balls interposed between the inner and outer rings 18, 19, and serves to connect components on the vehicle body side to the wheel 9 (Figure 1).

[0028] In the example of Fig. 1, this hub bearing 15 is an angular contact ball bearing in which the outer ring 19 is a fixed ring, the inner ring 18 is a rotating ring, and the rolling elements 20 are double-row. The inner ring 18 has a hub flange 18aa and a hub ring portion 18a that forms an outboard side raceway surface, and an inner ring portion 18b that forms an inboard side raceway surface. The wheel 9a of the wheel 9 is bolted to the hub flange 18aa in a state where it overlaps with the brake rotor 21a. The inner ring 18 rotates around the rotation axis O.

[0029] As shown in Fig. 6, outer ring (annular portion with steering shaft portions) 16 has annular portion 16a fitted to the outer peripheral surface of outer ring 19, and trunnion-shape steering shaft portions 16b, 16b provided so as to protrude upward and downward from the outer periphery of this annular portion 16a.

[0030] 2, the brake 21 has a brake rotor 21a and a brake caliper 21b. The brake caliper 21b is attached to upper and lower brake caliper attachment portions 22 (FIG. 4) that are integrally formed with the outer ring 19 and protrude like arms.

[0031] <About rotation-permitting support parts and unit support members> As shown in Fig. 6, each rotation-permitting support part 4 is made of a rolling bearing. In this example, a tapered roller bearing is used as the rolling bearing. The rolling bearing has an inner ring 4a fitted to the outer periphery of the steered shaft portion 16b, an outer ring 4b fitted to the unit support member 3, and multiple rolling elements 4c interposed between the inner and outer rings 4a and 4b.

[0032] The unit support member 3 has a unit support member main body 3A and a unit support member combination 3B. The generally ring-shaped unit support member combination 3B is detachably fixed to the outboard end of the unit support member main body 3A. Partial cylindrical fitting hole formation portions 3Ba are formed on the upper and lower portions of the inboard side surface of the unit support member combination 3B.

[0033] As shown in Figures 5 and 6, a partially cylindrical fitting hole forming portion 3Aa is formed in each of the upper and lower portions of the outboard end of the unit support member main body 3A. The unit support member combined body 3B is fixed to the outboard end of the unit support member main body 3A, and the fitting hole forming portions 3Aa, 3Ba of the upper and lower portions are combined with each other to form a fitting hole that continues around the entire circumference. An outer ring 4b is fitted into this fitting hole. In Figure 3, the unit support member 3 is represented by a dashed line.

[0034] As shown in FIG. 6, each steered shaft 16b is a hollow shaft, and a female thread is formed in the inner peripheral hole so as to extend radially, and a bolt 23 is provided to screw into the female thread. A disk-shaped pressing member 24 is interposed on the end face of the inner ring 4a, and a pressing force is applied to the end face of the inner ring 4a by the bolt 23 screwed into the female thread, thereby applying a preload to each rotation-allowing support part 4. In other words, an initial preload is set so that the preload does not disappear even when an external force such as the weight of the vehicle acts on the hub unit. This can increase the rigidity of each rotation-allowing support part 4. Note that the rolling bearing of the rotation-allowing support part 4 may be an angular ball bearing or a four-point contact ball bearing instead of a tapered roller bearing. In this case, the preload can be applied in the same manner as described above.

[0035] 1, the upper and lower steered shaft portions 16b, 16b are supported by the unit support member 3 via rotation-permitting support parts 4, 4, respectively, and each rotation-permitting support part 4 is located inside the wheel 9a of the wheel 9. In this example, each rotation-permitting support part 4 is disposed inside the wheel 9a near the middle of the wheel 9a in the width direction.

[0036] 2, the arm portion 17 is a point of action that applies auxiliary steering force to the outer ring 19 of the hub bearing 15, and protrudes integrally with a part of the outer circumference of the outer ring 16 or the outer ring 19. The arm portion 17 is rotatably connected to an output rod 25a that serves as a linear output portion of the steering actuator 5 via a joint portion 8. As a result, when the output rod 25a of the steering actuator 5 moves forward and backward (linear motion), the hub unit body 2 rotates about the steering axis A, that is, auxiliary steering is performed.

[0037] <Steering actuator 5> As shown in Fig. 2, the steering actuator 5 has a pair of steering actuators for independently steering each of the left and right wheels 9. The pair of left and right steering actuators have the same structure, and each actuator will be described below as the steering actuator 5. The steering actuator 5 includes a motor 26 as a rotational drive source that rotates the hub unit body 2 around the steering axis A, a reduction gear 27 that reduces the speed of the rotation of the motor 26, and a linear motion mechanism 25 that converts the forward and reverse rotational output of the reduction gear 27 into a reciprocating linear motion (linear motion) of an output rod 25a. The motor 26 is, for example, a permanent magnet type synchronous motor, but may be a DC motor or an induction motor.

[0038] <Reducer 27> The reducer 27 may be a wrap-around transmission mechanism such as a belt transmission mechanism or a gear train, and in the example of FIG. 2, a belt transmission mechanism is used. The reducer 27 has a drive pulley 27a, a driven pulley 27b, and a belt 27c. The drive pulley 27a is coupled to the rotor shaft 26b of the motor 26, and the driven pulley 27b is provided on the rotatable nut portion 35 of the linear motion mechanism 25. The driven pulley 27b is disposed parallel to the rotor shaft 26b. The driving force of the motor 26 is transmitted from the drive pulley 27a to the driven pulley 27b via the belt 27c. The drive pulley 27a, the driven pulley 27b, and the belt 27c constitute the wrap-around reducer 27.

[0039] <About Linear Motion Mechanism 25> As shown in Fig. 8, the linear motion mechanism 25 can use a feed screw mechanism of a sliding screw type such as a trapezoidal screw or a triangle screw, and in this example, a feed screw mechanism 33 using a sliding screw of a trapezoidal screw is used. Grease is sealed inside the sliding screw. This linear motion mechanism 25 has the feed screw mechanism 33, a rotation support bearing 28, a rotation prevention part 43, and an actuator case 34 that covers these components.

[0040] The feed screw mechanism 33 has a nut portion 35, the output rod 25a which is a screw shaft, and a sliding bearing 37. The output rod 25a is prevented from rotating relative to the unit support member 3 by a rotation prevention part 43. The nut portion 35 is provided with a driven pulley 27b at the axially intermediate portion of its outer periphery, and is rotatably supported on the unit support member 3 by rotation support bearings 28, 28 (FIG. 2) on both axial sides. A female thread portion 35a is provided on the inner periphery of the nut portion 35. A male thread portion 25aa which meshes with the female thread portion 35a of the nut portion 35 is provided on the outer periphery of the output rod 25a.

[0041] Slide bearings 37, 37 through which the output rod 25a slidably passes are provided on both axial ends of the nut portion 35. Each slide bearing 37 guides the axial movement of the output rod 25a and prevents a radial force from being applied to the output rod 25a when an external force from the tire side is input to the output rod 25a.

[0042] In this example, two tapered roller bearings are combined face-to-face via the driven pulley 27b as the rotation support bearing 28. The rotation support bearings 28, 28 (Fig. 2) may be arranged either back-to-back or face-to-face, but a face-to-face arrangement is preferable in terms of ease of assembly and preload adjustment using shims or the like. The rotation support bearing 28 may also be an angular ball bearing. In this case, too, the rotation support bearings 28, 28 (Fig. 2) may be arranged either back-to-back or face-to-face.

[0043] 7 and 8, the anti-rotation component 43 is a shaft-shaped member provided at the inboard end, which is the rear end, of the output rod 25a. The anti-rotation component 43 is fitted and fixed to the inboard end of the output rod 25a in a penetrating manner so as to extend, for example, in directions perpendicular to the up-down direction and the axial direction of the output rod 25a. Annular plain bearings 49a, 49b are fitted to both axial ends of the outer periphery of the anti-rotation component 43.

[0044] A flat surface (a so-called D-cut surface) 50 parallel to one end surface of the plain bearing 49b is formed on the inboard end of the output rod 25a, which faces one plain bearing 49b. One end surface of the plain bearing 49b abuts against the flat surface 50 of the output rod 25a, and a bolt 51 for pressing the other end surface of the plain bearing 49b is screwed into the anti-rotation part 43. This restricts the positions of the anti-rotation part 43, the bolt 51, and the plain bearings 49a and 49b (the positions in the vertical direction in FIG. 2) to desired positions with respect to the actuator case 34. The bolt 51 is provided with a measurement target Tg for a position sensor, which will be described later.

[0045] A guide groove 52 having a substantially rectangular parallelepiped shape and including guide surfaces 52a, 52b that respectively guide the outer circumferential surfaces of the plain bearings 49a, 49b is formed in the actuator case 34. In other words, the anti-rotation component 43 slidably contacts the guide surfaces 52a, 52b of the actuator case 34, which is a fixed part of the linear motion mechanism 25, via the plain bearings 49a, 49b. Thus, by sliding the anti-rotation component 43 along the guide groove 52 of the actuator case 34 via the plain bearings 49a, 49b, the output rod 25a can be reciprocated in the axial direction.

[0046] As shown in FIG. 2, the linear motion mechanism 25 includes a feed screw mechanism using a sliding screw of the trapezoidal screw, and therefore can enhance the effect of preventing reverse input from the tire 9b. The steering actuator 5 including the motor 26, the reducer 27, and the linear motion mechanism 25 is assembled as a subassembly and detachably attached to the case 6b with bolts or the like. The steering actuator 5 of this embodiment includes the motor 26, the reducer 27, and the linear motion mechanism 25, but the reducer may be omitted. In other words, a mechanism that transmits the driving force of the motor 26 directly to the linear motion mechanism 25 without the reducer is also possible. In addition, the linear motion mechanism 25 may be a mechanism that can convert rotational motion into linear motion, such as a ball screw or a rack and pinion mechanism, in addition to the trapezoidal screw shown in this embodiment.

[0047] In order to control the angle of the wheels 9 more accurately, it is necessary to know the rotation angle of the motor 26 and the position of the linear motion mechanism 25. Therefore, the steering function-equipped hub unit 1 is provided with the following position sensors and angle sensors.

[0048] <Position sensor> 8, the actuator case 34 is provided with a position sensor 44 that detects the position of the linear motion mechanism 25. The position sensor 44 can detect (monitor) the amount of axial movement of the output rod 25a and output it as a position sensor value. The position sensor 44 can be any of various types of sensors, such as magnetic, optical, and capacitance sensors, but in this embodiment, a magnetic sensor is used.

[0049] The position sensor 44 is fixed to a substrate 53 fixed inside the actuator case 34, and faces a path along which the position sensor measurement target Tg advances and retreats. When the output rod 25a is at a predetermined axial position (advance / retreat position), the position sensor 44 and the position sensor measurement target Tg face each other across a predetermined gap Gp. The predetermined axial position and the predetermined gap Gp are an axial position and a gap that are arbitrarily determined by design or the like, and are determined by, for example, determining an appropriate axial position and gap by either one or both of tests and simulations.

[0050] The anti-rotation part 43 is provided with a permanent magnet that serves as a measurement target Tg for the position sensor. Specifically, the permanent magnet is provided on the head of a bolt 51 that is screwed into the axial end of the anti-rotation part 43. The bolt 51 is made of a non-magnetic material such as resin or stainless steel. The position sensor 44 reads the change in the magnetic field of the permanent magnet that accompanies the advancement and retreat of the output rod 25a, and detects the advancement and retreat position of the output rod 25a. The bolt 51 may be omitted and a permanent magnet may be fixed directly to the anti-rotation part 43.

[0051] <Angle sensor> 6, an angle sensor 53 capable of detecting the amount of displacement, which is the rotation angle of the motor 26, and outputting an angle sensor value (tire angle information) is provided on the motor case of the motor 26. The angle sensor 53 has a detection target portion 53a fitted and fixed to the rotor shaft 26b, and a sensor portion 53b fixed to the motor case radially outward of the detection target portion 53a and detecting the detection target portion 53a. For example, a resolver is used as the angle sensor 53.

[0052] <Other mechanical configurations> 2, the case 6b is formed integrally with the unit support member main body 3A as a part of the unit support member 3. The case 6b is formed in a bottomed cylindrical shape, and is provided with a motor accommodating section that supports the motor 26 and a linear motion mechanism accommodating section that supports the linear motion mechanism 25. The motor accommodating section has a fitting hole that supports the motor 26 at a predetermined position in the case. The linear motion mechanism accommodating section has a fitting hole that supports the linear motion mechanism 25 at a predetermined position in the case, and a through hole that allows the output rod 25a to advance and retreat.

[0053] As shown in Fig. 3, the unit support member main body 3A has the case 6b, a shock absorber mounting portion 6c which serves as a mounting portion for a shock absorber, and a steering device coupling portion 6d which serves as a coupling portion for a steering device 11 (Fig. 2). The shock absorber mounting portion 6c and the steering device coupling portion 6d are also formed integrally with the unit support member main body 3A. The shock absorber mounting portion 6c is formed so as to protrude from the upper portion of the outer surface portion of the unit support member main body 3A. The steering device coupling portion 6d is formed so as to protrude from the side portion of the outer surface portion of the unit support member main body 3A.

[0054] <About the control system> As shown in Fig. 2, the control device 29 has a steering control section 30 and an actuator drive control section 31. The control device 29 has a function of independently controlling the steering of the left and right wheels. In this example, a pair of actuators 5 for the left and right wheels, that is, one control device 29 capable of controlling all the actuators 5, is applied. However, a plurality of control devices 29 may be provided corresponding to the respective actuators 5.

[0055] The steering control unit 30 outputs a current command signal according to an auxiliary steering angle command signal (command signal) given from the higher-level control unit 32. At this time, the steering control unit 30 performs feedback control using the position sensor output, which is information on the advance / retreat position of the output rod 25a, from the position sensor 44, so that the angle of the wheels 9 can be appropriately and accurately managed. The steering control unit 30 has a function of acquiring angle sensor values ​​(tire angle information) of the left and right wheels. Note that the steering control unit 30 may acquire position sensor values ​​(tire angle information) of the left and right actuators instead of the angle sensor values ​​of the left and right wheels. When the steering control unit 30 of the control device 29 detects an abnormality in one of the pair of steering actuators 5, 5, it continues to control the other actuator 5 based on the acquired angle sensor value or position sensor value.

[0056] The upper control unit 32 is a higher-level control means of the steering control unit 30, and as the upper control unit 32, for example, an electric control unit (Vehicle Control Unit, abbreviated as VCU) that controls the entire vehicle is applied. The actuator drive control unit 31 outputs a current corresponding to a current command signal input from the steering control unit 30 to drive and control the steering actuator 5. The actuator drive control unit 31 controls the power supplied to the coil of the motor 26. For example, the actuator drive control unit 31 configures a half-bridge circuit using a switch element (not shown) and performs PWM control to determine the motor application voltage according to the ON-OFF duty ratio of the switch element. This allows the wheel 9 to be minutely changed in angle in addition to the steering by the driver's steering wheel operation. Even when driving in a straight line, the amount of toe angle can be adjusted according to each situation. Note that the steering system may operate the steering actuators 5, 5 by commands from an automatic driving device or a driving support device (not shown) instead of the driver's steering wheel operation.

[0057] <Flowchart> Fig. 9 is a flow chart showing the steps of the control of this steering system. The explanation will be given with reference to Fig. 2 as well. When the steering control section 30 of the control device 29 determines that an abnormality has occurred in the steering actuator 5 for the left wheel (right wheel) as one of the actuators while the vehicle is traveling (step S1: Yes), it determines whether or not a predetermined abnormality (for example, a serious abnormality such as a motor angle sensor abnormality) has occurred (step S2). For example, when the angle sensor value falls outside a predetermined detection range with respect to the auxiliary steering angle command signal, the steering control section 30 determines that a serious abnormality has occurred.

[0058] When the steering control unit 30 determines that the detected abnormality of the steering actuator 5 for the left wheel (right wheel) is not a serious abnormality (step S2: No), the steering system can continue to operate, so that the steering control unit 30 performs a retry operation to operate the steering actuator 5 for the left wheel (right wheel) again (step S3) and counts the number of retries (step S4). If the counted number of retries N does not reach the specified number of retries Ar (step S5: No), the process returns to step S1.

[0059] When the counted number of retries N reaches a specified number Ar (step S5: Yes), the steering control unit 30 stops the control of the steering actuator 5 for the left wheel (right wheel) (step S6). When the steering control unit 30 determines in step S2 that the detected abnormality of the steering actuator 5 for the left wheel (right wheel) is a serious abnormality (step S2: Yes), the steering control unit 30 stops the control of the steering actuator 5 for the left wheel (right wheel) (step S6). After step S6, the steering control unit 30 determines whether the toe angle C of the vehicle based on the tire angle A of the left wheel and the tire angle B of the right wheel acquired from the angle sensor 53 or the position sensor 44 is within a safe driving range |X| or less (step S7). Whether the toe angle C is within a safe driving range |X| or less is determined by, for example, either one or both of a test and a simulation, taking into account the vehicle speed, the steering wheel angle, etc. The vehicle speed and the steering wheel angle are given, for example, from the upper control unit 32.

[0060] If the toe angle of the vehicle is not within the range for safe driving (step S7: No), the steering control unit 30 operates the other actuator, the steering actuator 5 for the right wheel (left wheel), until the toe angle of the vehicle is within the range for safe driving (step S8). Then, the process returns to step S7. If the toe angle of the vehicle is within the range for safe driving (step S7: Yes), the steering control unit 30 stops control of the steering actuator 5 for the right wheel (left wheel) (step S9). In this way, by stopping control when the toe angle of the vehicle is within the range for safe driving, it is possible to ensure stable vehicle driving even when an abnormality occurs in the steering actuator 5 for either the left or right wheel.

[0061] <Action and effect> According to the steering system described above, the hub unit body 2 including the hub bearing 15 supporting the wheel 9 shown in Fig. 1 can be freely rotated around the steering axis A by driving the steering actuator 5. This rotation is added to the steering by the driver's handlebar operation, that is, added to the rotation of the knuckle 6 around the kingpin shaft by the steering device 11 (Fig. 2), and is performed as auxiliary steering, and also allows independent steering of one wheel. By making the auxiliary steering angle of the left and right wheels 9, 9 different, the toe angle between the left and right wheels 9, 9 can be changed as desired.

[0062] Therefore, the hub unit 1 with steering function may be used for either steered wheels such as front wheels or non-steered wheels such as rear wheels. When used for steered wheels, it is installed on a member whose direction can be changed by the steering device 11, and becomes a mechanism that performs minute angle changes of the wheels 9 individually for the left and right wheels, or in conjunction with the left and right wheels, in addition to the steering by the driver's steering wheel operation. A small angle is sufficient for the angle of auxiliary steering to improve the maneuverability and driving stability of the vehicle, and it is sufficient even if the angle of auxiliary steering is within ±5 degrees. The angle of auxiliary steering is controlled by the steering actuator 5.

[0063] In addition, when turning, the steering angle difference between the left and right wheels can be changed according to the driving speed. For example, the steering geometry can be changed while driving, such as using parallel geometry when turning at high speeds and Ackermann geometry when turning at low speeds. In this way, the wheel angle can be changed freely while driving, improving the vehicle's maneuverability and enabling stable driving. By appropriately changing the steering angle of the left and right steering wheels when turning, the vehicle's turning radius can be reduced and its maneuverability can be improved. Furthermore, by adjusting the toe angle to suit each situation, even when driving in a straight line, it is possible to adjust the tires so that they are oriented straight in the direction of travel at low speeds, thereby reducing rolling resistance and preventing a deterioration in fuel efficiency, and at high speeds the tire angle is toe-in to ensure driving stability.

[0064] When the steering function equipped hub unit 1 is applied to the non-steered rear wheel 9R (Fig. 11), if the steering angle is set to the same phase as the front wheel 9F (Fig. 11) during cornering, the yaw that occurs during steering can be suppressed and the stability of the vehicle can be improved. By adjusting the toe angle independently for the left and right, driving stability can be ensured even during straight-line driving.

[0065] In order to control the behavior of the vehicle in this way, it is necessary to accurately control the steering angle of the wheels 9, and in the event of an abnormality, it is necessary to safely stop the control, taking into account the angles of the left and right wheels. In this embodiment, when an abnormality occurs in the steering actuator 5 for either the left or right wheels equipped on the vehicle, abnormality processing is performed taking into account the toe angle of the front wheels 9F, 9F (FIG. 10) and the vehicle is stopped at a toe angle at which it can travel stably. This makes it possible to improve the redundancy of the steering system.

[0066] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description is omitted. When only a part of the configuration is described, the other parts of the configuration are the same as the previously described embodiment unless otherwise specified. The same configuration has the same action and effect. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine embodiments together, provided that there is no particular problem with the combination.

[0067] <Application to non-steered wheels> The hub unit 1 with steering function may be used for non-steered wheels. For example, as shown in Fig. 11, in a front-wheel-steered vehicle, it may be set in a suspension frame part 6R that serves as a wheel bearing installation part of a suspension device 12R that supports a rear wheel 9R, and used for rear-wheel steering. In the hub unit 1 with steering function for non-steered wheels, depending on the requirements for vehicle control, the steering angle is not limited to the small steering angle described above, and a relatively large angle of, for example, 10° to 20° may be taken for each of the left and right wheels. Alternatively, as shown in FIG. 14, the steering function-equipped hub unit 1 may be used for each of the left and right front wheels 9F, 9F which are steered wheels, and the left and right rear wheels 9R, 9R which are non-steered wheels. It is also possible to apply the abnormality processing of this steering system to a vehicle that is equipped with a pair of steering actuators that rotate the left and right wheels around a steering axis extending in the vertical direction, and in which each steering actuator is controlled independently.

[0068] Although the embodiment of the present invention has been described above, the disclosed embodiment is illustrative in all respects and is not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0069] 1... hub unit with steering function, 2... hub unit main body, 3... unit support member, 5... steering actuator (actuator), 6... knuckle (suspension frame part), 6R... suspension frame part, 9... wheel, 9F... front wheel, 9R... rear wheel, 10... vehicle, 12, 12R... suspension device, 15... hub bearing, 25... linear motion mechanism, 25a... output rod, 26... motor, 29... control device, 30... steering control unit, 31... actuator drive control unit

Claims

1. A steering system comprising a steering actuator that rotationally drives a wheel around a steering axis extending in the vertical direction, and a control device that controls this steering actuator, wherein the control device has a function of independently controlling the steering of each wheel, which are the left and right wheels, by a pair of steering actuators, and also has a function of acquiring tire angle information of the left and right wheels, and when the control device detects an abnormality in one of the pair of steering actuators, based on the acquired tire angle information, it continuously controls the other steering actuator. A steering system.

2. In the steering system according to Claim 1, a hub unit body having a hub bearing that rotatably supports a wheel, a unit support member provided on a suspension device's undercarriage frame component that rotatably supports the hub unit body around a steering axis extending in the vertical direction, and a steering function hub unit having a steering actuator that rotationally drives the hub unit body around the steering axis are provided, each steering actuator has a motor and a linear motion mechanism that converts the rotational output of this motor into the linear motion of an output rod, and when the output rod moves forward and backward, the hub unit body in each wheel is rotationally driven around the steering axis respectively. A steering system.

3. In the steering system according to Claim 1 or Claim 2, when the control device determines that the detected abnormality in one of the steering actuators is not a defined abnormality, it performs a retry operation of operating the one steering actuator again. A steering system.

4. In the steering system according to Claim 3, the control device counts the number of retry operations, and when the counted number of retry operations reaches a specified number, it stops controlling the one steering actuator. A steering system.

5. In the steering system according to Claim 1 or Claim 2, when the control device determines that the detected abnormality in one of the steering actuators is a defined abnormality, it stops controlling the one steering actuator. A steering system.

6. In the steering system according to Claim 1 or Claim 2, the control device is a steering system that is provided in plurality corresponding to each steering actuator, or is one control device capable of controlling all the steering actuators.

7. ​ ​ ​ ​ ​ ​ ​ In the steering system according to claim 1 or claim 2, the control device includes a steering control unit that outputs a current command signal according to a given steering angle command signal, and an actuator drive control unit that outputs a current according to the current command signal input from the steering control unit and drives and controls the steering actuator. A steering system having the actuator drive control unit.

8. A vehicle in which one or both of the front wheels and the rear wheels are supported by using a hub unit with a steering function in the steering system according to claim 2.

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