Steering system and vehicle equipped with the same

Abstract

To provide a steering system which can improve fuel economy, and can improve traveling safety, and a vehicle having the same.SOLUTION: A steering system comprises a hub unit main body, a unit support member for supporting the hub unit main body so as to be turnable around a steering axial core, and a hub unit with a steering function having a steering actuator for rotationally driving the hub unit main body. The steering actuator has a motor and a linear motion mechanism, and the hub unit main body is rotationally driven. The steering system also comprises an actuator drive control part for drive-controlling the motor so that the motor of the steering actuator outputs a current corresponding to an inputted current command signal via a three-phase power line, and a relay circuit for short-circuiting at least two phases out of three phases of the power line, and the steering system operates the relay circuit when an abnormality of the motor of the steering actuator occurs.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a steering system and a vehicle equipped with the same, and relates to a technique for controlling wheels to an appropriate steering angle according to driving conditions.

Background Art

[0002] In a vehicle such as a general automobile, a steering wheel and a steering device (or a steering apparatus) are mechanically connected, and both ends of the steering device are connected to respective left and right wheels by tie rods. Therefore, the turning angles of the left and right wheels due to the movement of the steering wheel are determined by the initial settings. In vehicle geometry, there are known (1) "parallel geometry" in which the turning angles of the left and right wheels are the same, and (2) "Ackermann geometry" in which the turning angle of the inner turning wheel is made larger than the turning angle of the outer turning wheel in order to make the turning center of the vehicle a single point.

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

[0004] As described above, since the steering device of a general vehicle is mechanically connected to the wheels, generally only a fixed single steering geometry can be adopted, and it is often set to an intermediate geometry between Ackermann geometry and parallel geometry. However, in this case, in the low-speed range, the steering angle difference between the left and right wheels is insufficient and the steering angle of the outer wheel becomes excessive, and in the high-speed range, the steering angle of the inner wheel becomes excessive. If there is an unnecessary bias in the lateral force distribution of the inner and outer wheels in this way, it causes deterioration of fuel consumption due to deterioration of running resistance and early wear of the tires, and since the inner and outer wheels cannot be used efficiently, there is a problem that the smoothness of cornering is impaired.

[0005] Therefore, a technique has been proposed that changes the steering angle of the wheels according to the vehicle speed and turning G, and arbitrarily selects Ackermann geometry in the low-speed range and parallel geometry in the high-speed range, enabling both smooth turning performance at low speeds and cornering performance at high speeds without increasing the running resistance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Document 1, two motors are used to complexly control the toe angle and camber angle of the tires. In Patent Document 2, since the hub bearing is cantilever-supported with respect to the steering shaft, the rigidity is reduced, and there is a possibility that the steering geometry may change due to the occurrence of excessive running G. Further, when a speed reducer is provided on the steering shaft, the size including the motor becomes large. When the size of the motor or the like becomes large, it becomes difficult to arrange the whole inside the inner circumference of the wheel. Further, when a speed reducer with a large reduction ratio is provided, the responsiveness deteriorates.

[0008] As described above, the mechanism having the conventional steering function is intended to arbitrarily change the toe angle or camber angle of the wheels in a vehicle, so a plurality of motors and speed reduction mechanisms are required, resulting in a complicated configuration. Further, it becomes difficult to ensure rigidity, and in order to ensure rigidity, it is necessary to increase the size and it becomes heavy. Further, when the kingpin axis coincides with the steering axis of the mechanism having the steering function, the component parts are arranged behind the hub unit (inside the vehicle body), so the overall size becomes large and heavy.

[0009] In addition, in a moving vehicle, when the current of the motor for the steering actuator is cut off to stop the motor due to, for example, an abnormality of a sensor, an abnormality of a control device, or an abnormality of a motor among the system abnormalities of the hub unit with a steering function, the motor may rotate due to inertia, and the linear motion mechanism in the steering actuator may move to the stroke end of the trapezoidal screw and be damaged. In order to instantaneously stop the inertial rotation of the motor, for example, the switching element of the bridge circuit connected to the input side of the motor of the steering actuator needs to be turned on for all three phases of the Low side UVW (conductive state), turned off for all three phases of the High side UVW, and short-circuited in three phases to activate the brake. However, when the power supply fails during motor rotation (including system abnormalities), power for driving the switching element cannot be supplied, and this brake operation cannot be performed.

[0010] Accordingly, an object of the present invention is to provide a steering system capable of improving fuel efficiency and running stability by improving the above-described points, and a vehicle equipped with the same.

Means for Solving the Problems

[0011] The steering system of this invention includes a hub unit main body having a hub bearing that rotatably supports a wheel, a unit support member provided on a wheel-side frame component of a suspension device and rotatably supporting the hub unit main body around a steering axis extending in the vertical direction, and a hub unit with a steering function having a steering actuator that rotationally drives the hub unit main body around the steering axis. The steering actuator has a motor and a linear motion mechanism that converts the rotational output of this motor into a linear motion of an output rod. When the output rod moves forward and backward, the hub unit main body is rotationally driven around the steering axis. A steering system includes an actuator drive control unit that drives and controls the motor so that the motor of the steering actuator outputs a current corresponding to an input current command signal via three-phase power lines. It is provided with a relay circuit that short - circuits at least any two of the three phases of the power supply line. When an abnormality occurs in the motor of the steering actuator, the relay circuit is operated.

[0012] According to this configuration, the hub unit body is rotatably held around the swivel axis in the hub unit with the steering function. Also, when the output rod of the linear motion mechanism advances and retracts due to the rotation of the motor of the steering actuator arranged in the hub unit with the steering function, the hub unit body is rotationally driven around the swivel axis to perform steering. At this time, in order to control the behavior of the vehicle, it is necessary to accurately control the steering angle of the wheels, and in case of an abnormality, it is necessary to return the angle of the wheels to the initial state and stop the control. However, with the above configuration, it becomes possible to arbitrarily change the toe angle of the wheels attached to the hub unit with a simple structure. For example, according to the driving conditions of the vehicle, the angles of the left and right wheels can be independently and arbitrarily changed, so that the motion performance of the vehicle can be improved and it can run stably. Also, it is possible to improve the fuel efficiency by setting an appropriate wheel angle. Thus, it is possible to improve the fuel efficiency and the driving stability.

[0013] In addition, according to this configuration, in the three - phase power supply line used by the actuator drive control unit to drive - control the motor, when an abnormality occurs in the motor of the steering actuator due to an unexpected power supply defect or the like, depending on the type of the relay circuit, the relay circuit can be operated to short - circuit at least any two of the three phases of the power supply line (short - circuit brake). By adopting the short - circuit brake using the short - circuit of the relay circuit, when an abnormality occurs in the motor due to an unexpected power supply failure or the like, the overshoot due to the inertial rotation of the motor can be suppressed, and damage caused by operating beyond the movable range of the machine can be prevented.

[0014] A relay including a semiconductor element may be used for the relay circuit. Thereby, the on / off operation of the relay circuit can be performed at high speed. Further, the relay of the relay circuit may have one coil and two contacts. Thereby, a plurality of relays can be made into one component, and miniaturization can be achieved.

[0015] The actuator drive control unit has a plurality of switching elements, and drives and controls the motor of the steering actuator by the on / off operation of the plurality of switching elements. When power failure occurs during the occurrence of an abnormality in the motor of the steering actuator, the relay circuit may be operated. When power failure has not occurred, all of the Low sides of the plurality of switching elements may be turned on and all of the High sides may be turned off. Thereby, when it is other than power failure, all of the Low sides of the plurality of switching elements are turned on and all of the High sides are turned off, and when power failure occurs, a short-circuit brake is generated by the relay circuit, so that each short-circuit brake can be generated.

[0016] The control device includes a control device that controls the steering actuator of the hub unit with a steering function. The control device may include a steering control unit that outputs a current command signal corresponding to a given steering angle command signal, and the actuator drive control unit that outputs a current corresponding to the current command signal input from the steering control unit and drives and controls the steering actuator. According to this configuration, the steering actuator of the hub unit with a steering function can be controlled with a simple configuration.

[0017] The vehicle of the present invention is a vehicle equipped with the steering system of any of the above configurations of the present invention, and one or both of the front wheels and the rear wheels are supported using the hub unit with a steering function. Therefore, each of the effects described above for the steering system of the present invention can be obtained. Although the front wheels are generally used as steering wheels, when a hub unit with a steering function is applied to the steering wheels, it is effective for toe angle adjustment during running. Also, although the rear wheels are generally used as non-steering wheels, when applied to non-steering wheels, it is possible to reduce the minimum turning radius during low-speed running by slightly steering the non-steering wheels.

Advantages of the Invention

[0018] The steering system of the present invention includes a hub unit body having a hub bearing that rotatably supports a wheel, a unit support member provided on a suspension system's undercarriage frame component that rotatably supports the hub unit body around a steering axis extending in the vertical direction, and a hub unit with a steering function having a steering actuator that rotationally drives the hub unit body around the steering axis. The 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. By the advancement and retraction of the output rod, the hub unit body is rotationally driven around the steering axis. The steering system is such that an actuator drive control unit drives and controls the motor so that the motor of the steering actuator outputs a current corresponding to an input current command signal via three-phase power lines, and includes a relay circuit that short-circuits at least any two of the three phases of the power lines. When an abnormality occurs in the motor of the steering actuator, the relay circuit is operated. Thereby, it is possible to improve fuel efficiency and improve running stability.

[0019] The vehicle of the present invention is a vehicle equipped with the steering system of any of the above configurations of the present invention, and since one or both of the front wheels and the rear wheels are supported using the hub unit with a steering function, it is possible to improve fuel efficiency and improve running stability.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

DETAILED DESCRIPTION OF THE INVENTION

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

[0022] <Schematic Structure of the Hub Unit with Steering Function> As shown in Fig. 1, this hub unit 1 with a steering function includes a hub unit main body 2, a unit support member 3, and a steering actuator 5. The unit support member 3 is provided integrally with a knuckle 6 which is a wheelhouse frame component. The steering actuator 5 is provided on the inboard side of the unit support member 3, and the hub unit main body 2 is provided on the outboard side of the unit support member 3. When the hub unit 1 with a steering function is mounted on a vehicle, the outside in the vehicle width direction of the vehicle is referred to as the outboard side, and the center side in the vehicle width direction of the vehicle is referred to as the inboard side. Note that the hub unit 1 with a steering function may be simply referred to as the hub unit 1.

[0023] As shown in Figs. 2 and 3, the hub unit main body 2 and the steering actuator 5 are connected by a joint portion 8. Usually, a boot (not shown) is attached to this joint portion 8 for waterproof and dustproof purposes.

[0024] As shown in Fig. 1, the hub unit main body 2 is supported by the unit support member 3 via rotation allowance support parts 4, 4 at two locations in the up and down directions so as to be rotatable (rotary) around a steering axis A extending in the up and down direction. That is, the steering axis A exists on the hub unit main body 2 side and is an axis different from the rotation axis O of the wheel 9 and is also different from the kingpin axis that performs main steering. In a normal vehicle, the kingpin angle is set at 10 to 20 degrees for the purpose of improving the straight running stability of the vehicle running, but the hub unit 1 with a steering function of this embodiment has a steering axis at an angle (axis) different from the kingpin angle. The wheel 9 includes a wheel 9a and a tire 9b.

[0025] <Installation location of the hub unit 1 with a steering function> In this embodiment, the hub unit 1 with a steering function is provided integrally with the knuckle 6 of the suspension device 12 as a mechanism for individually steering the left and right wheels by a minute angle (about ±5 deg) in addition to the steering by the steering device 11 of the front wheels 9F of the vehicle 10 with respect to the steering wheel, specifically as shown in FIG. 7. However, in the hub unit 1 with a steering function of the steering wheel, depending on the requirements of vehicle control, not only the minute angle but also a relatively large angle such as 10° to 20° may be individually adopted for the left and right wheels. This also applies to the hub unit 1 with a steering function shown in FIGS. 8 and 9 described later.

[0026] As shown in FIG. 7, the steering device 11 is attached to the vehicle body and operates according to the operation of the driver's steering wheel 11a or commands from an automatic driving device or a driving support device (not shown), and the tie rod 14 that moves forward and backward is connected to the steering coupling portion 6d (described later) of the unit support member 3 in FIG. 2. The steering device 11 may be a rack and pinion type or the like, and any type of steering device may be used. Also, the position where the tie rod 14 is connected may be in front of the axle (front pull), behind the axle (rear pull), or any other position. The suspension device 12 applies, for example, a strut type suspension mechanism in which a shock absorber is directly fixed to the knuckle 6, but a double wishbone type suspension mechanism, a multi-link type suspension mechanism, or other suspension mechanisms may also be applied.

[0027] <Regarding the 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 an annular portion with a swivel shaft portion, and an arm portion 17 (FIG. 3) which is a steering force receiving portion. The hub bearing 15 in FIG. 1 has an inner ring 18, an outer ring 19, and rolling elements 20 such as balls interposed between these inner and outer rings 18 and 19, and serves to connect the member on the vehicle body side and the wheel 9.

[0028] In the illustrated example, this hub bearing 15 is an angular 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 arranged in two rows. The inner ring 18 has a hub flange 18aa shown in FIG. 6 and a hub ring portion 18a that forms the outboard raceway surface, and an inner ring portion 18b that forms the inboard raceway surface. As shown in FIG. 1, a 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, the outer ring (annular portion with swivel shaft portion) 16 has an annular portion 16a fitted to the outer peripheral surface of the outer ring 19, and trunnion shaft-shaped swivel shaft portions 16b, 16b provided so as to project vertically from the outer periphery of the annular portion 16a. Each of the swivel shaft portions 16b, which are the upper and lower mounting shaft portions, is provided coaxially with the swivel axis A.

[0030] As shown in FIG. 2, the brake 21 has a brake rotor 21a and a brake caliper 21b. The brake caliper 21b is attached to two upper and lower brake caliper attachment portions 22 (FIG. 4) formed so as to project integrally with the outer ring 19 in an arm shape.

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

[0032] The unit support member 3 has a unit support member main body 3A as shown in FIG. 3 and a unit support member coupling body 3B. A substantially ring-shaped unit support member coupling body 3B is detachably fixed to the outboard end of the unit support member main body 3A. Partial concave spherical fitting hole forming portions 3Ba as shown in FIG. 6 are formed in the upper and lower portions of the inboard side surface of the unit support member coupling body 3B.

[0033] As shown in FIGS. 5 and 6, partial concave spherical fitting hole forming portions 3Aa are respectively formed in the upper and lower portions of the outboard side end of the unit support member body 3A. A unit support member assembly 3B is fixed to the outboard side end of the unit support member body 3A. For each of the upper and lower portions, when the fitting hole forming portions 3Aa and 3Ba are combined with each other, a fitting hole continuous in the entire circumference is formed. An outer ring 4b is fitted into this fitting hole. In FIG. 3, the unit support member 3 is represented by a dashed line shaded pattern.

[0034] As shown in FIG. 6, each steering shaft portion 16b is a hollow shaft and is formed such that an internal thread portion extends in the radial direction within an inner peripheral hole. A bolt 23 that screws into this internal thread portion is provided. A disc-shaped pressing member 24 is interposed between the end surfaces of the inner ring 4a, and by applying a pressing force to the end surface of the inner ring 4a by tightening the bolt 23 that screws into the internal thread portion, preloads are respectively applied to the respective rotationally allowable support components 4. That is, an initial preload is set so that the preload does not escape even when an external force such as the weight of the vehicle acts on the hub unit. Thereby, the rigidity of each rotationally allowable support component 4 can be increased. Note that, depending on conditions such as the maximum load, the rolling bearing of the rotationally allowable support component 4 may be replaced with an angular ball bearing or a four-point contact ball bearing instead of a tapered roller bearing. Also in that case, preload can be applied in the same manner as described above.

[0035] As shown in FIG. 1, the upper and lower steering shaft portions 16b, 16b are respectively supported by the unit support member 3 via the rotationally allowable support components 4, 4, and each rotationally allowable support component 4 is located within the wheel 9a of the wheel 9. In this example, each rotationally allowable support component 4 is arranged near the middle in the width direction of the wheel 9a within the wheel 9a.

[0036] As shown in FIG. 2, the arm portion 17 is a portion that serves as a point of action for applying an auxiliary steering force to the outer ring 19 of the hub bearing 15, and integrally projects from a part of the outer periphery of the outer ring 16 or the outer ring 19. The arm portion 17 is rotatably connected to an output rod 25a, which is 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 main body 2 rotates (rotates) around the steering axis A, for example, is assisted in steering.

[0037] <the steering actuator 5> As shown in FIGS. 2 and 3, the steering actuator 5 includes a motor 26 as a rotational drive source for rotationally driving the hub unit main body 2 around the steering axis A (FIG. 1), a speed reducer 27 for reducing the rotation of the motor 26, and a linear motion mechanism 25 for converting the forward and reverse rotational outputs of the speed reducer 27 into a reciprocating linear motion (linear motion) of the output rod 25a. The motor 26 is, for example, a permanent magnet synchronous motor, but may be a DC motor or an induction motor.

[0038] <the speed reducer 27> For the speed reducer 27, a belt transmission mechanism such as a belt transmission mechanism or a gear train can be used. In the example of FIG. 2, a belt transmission mechanism is used. The speed reducer 27 includes 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 a rotatable nut portion 35 of the linear motion mechanism 25. The driven pulley 27b is arranged 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 a belt-type speed reducer 27.

[0039] <Regarding the linear motion mechanism 25> The linear motion mechanism 25 shown in Fig. 2 can use a sliding screw type feed screw mechanism such as a trapezoidal screw or a triangular screw. In this embodiment, a feed screw mechanism 33 using a trapezoidal screw sliding screw is used. Grease is enclosed inside the sliding screw. This linear motion mechanism 25 includes a feed screw mechanism 33, a rotary support bearing 28, a detent component 43, and an actuator case 34 that covers these components.

[0040] The feed screw mechanism 33 includes 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 with respect to the unit support member 3 by a detent component 43. The nut portion 35 is provided with a driven pulley 27b at an axial intermediate portion of its outer peripheral portion and is rotatably supported by the unit support member 3 by rotary support bearings 28, 28 on both axial sides. An internal thread portion (not shown) is provided on the inner periphery of this nut portion 35. An external thread portion (not shown) that meshes with the internal thread portion of the nut portion 35 is provided on the outer periphery of the output rod 25a.

[0041] Sliding bearings 37, 37 through which the output rod 25a slidably penetrates are provided at both axial ends of the nut portion 35. Each sliding 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, as the rotary support bearings 28, two cylindrical roller bearings are combined face to face via the driven pulley 27b. The arrangement of these rotary support bearings 28, 28 may be either back to back or face to face, but the face to face arrangement is preferred due to ease of assembly and preload adjustment using shims or the like. Note that the rotary support bearings 28 may be angular ball bearings. Also in this case, the arrangement of the rotary support bearings 28, 28 may be either back to back or face to face.

[0043] Also, as shown in FIG. 2, the rotation prevention component 43 is a shaft-shaped member provided at the inboard side end, which is the rear end of the output rod 25a. This rotation prevention component 43 is fitted and fixed to the output rod 25a in a penetrating manner at the inboard side end of the output rod 25a so as to extend, for example, in the vertical direction and in the direction orthogonal to the axial direction of the output rod 25a respectively. Annular slide bearings (not shown) are fitted to both axial ends of the outer periphery of the rotation prevention component 43.

[0044] Since the linear motion mechanism 25 includes a feed screw mechanism using the trapezoidal screw as a sliding screw, the effect of preventing reverse input from the tire 9b can be enhanced. The steering actuator 5 including the motor 26, the speed reducer 27, and the linear motion mechanism 25 is assembled as a subassembly and detachably attached to the case 6b by bolts or the like. The steering actuator 5 of the present embodiment includes the motor 26, the speed reducer 27, and the linear motion mechanism 25, but the speed reducer may be omitted. That is, a mechanism that directly transmits the driving force of the motor 26 to the linear motion mechanism 25 without passing through the speed reducer is also possible. In addition to the trapezoidal screw shown in the present embodiment, a mechanism capable of converting rotational motion into linear motion, such as a ball screw or a rack and pinion mechanism, can be used for the linear motion mechanism 25.

[0045] In order to more accurately control the angle of the wheel 9, it is required to grasp the rotation angle of the motor 26 and the position of the linear motion mechanism 25. Therefore, the hub unit 1 with a steering function is provided with the following position sensors and angle sensors.

[0046] <Position sensor> As shown in Fig. 2, a position sensor 44 for detecting the position of the linear motion mechanism 25 is provided in the actuator case 34. The position sensor 44 can detect (monitor) the amount of movement in the axial direction of the output rod 25a and output it as a position sensor value. As the position sensor 44, various sensors such as a magnetic sensor, an optical sensor, and a capacitance sensor can be used. In this embodiment, a magnetic sensor is used. The position sensor 44 is fixed to a substrate (not shown) fixed in the actuator case 34. Therefore, the position sensor 44 reads the change in the magnetic field of the permanent magnet accompanying the forward and backward movement of the output rod 25a and detects the forward and backward position of the output rod 25a. Note that the bolt may be omitted and the permanent magnet may be directly fixed to the anti-rotation part 43.

[0047] <Angle sensor> As shown in Fig. 2, an angle sensor 54 capable of detecting the rotation angle of the motor 26 and outputting two or more angle sensor values is provided in the motor case 26a of the motor 26. The angle sensor 54 is fixed to the motor case 26a via a substrate (not shown). A permanent magnet serving as a measurement target for the angle sensor that rotates integrally with the rotor shaft 26b is fixed to the inboard end of the rotor shaft 26b of the motor 26. The angle sensor 54 and the permanent magnet face each other with a predetermined axial gap therebetween. The angle sensor 54, which is a magnetic sensor, reads the change in the magnetic field of the permanent magnet accompanying the rotation of the rotor shaft 26b and detects the rotation angle of the motor 26. Note that the angle sensor 54 is not limited to the aforementioned axial gap type magnetic sensor, and a so-called radial gap type magnetic sensor can also be applied.

[0048] <Other mechanical configurations> As shown in Fig. 2, the case 6b is integrally formed 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 housing portion for supporting the motor 26 and a linear motion mechanism housing portion for supporting the linear motion mechanism 25. A fitting hole for supporting the motor 26 at a predetermined position within the case is formed in the motor housing portion. In the linear motion mechanism housing portion, a fitting hole for supporting the linear motion mechanism 25 at a predetermined position within the case, a through hole for allowing the forward and backward movement of the output rod 25a, and the like are formed.

[0049] As shown in Fig. 3, the unit support member main body 3A has the case 6b, a shock absorber attachment portion 6c that serves as an attachment portion for the shock absorber, and a steering device coupling portion 6d that serves as a coupling portion for the steering device 11 (Fig. 2). These shock absorber attachment portion 6c and steering device coupling portion 6d are also integrally formed with the unit support member main body 3A. The shock absorber attachment 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 surface portion of the outer surface portion of the unit support member main body 3A.

[0050] <Regarding the control system> As shown in FIG. 2, the aforementioned control device 29 that controls the steering actuator 5 of the hub unit 1 with a steering function includes a steering control unit 30 and an actuator drive control unit 31. The steering control unit 30 outputs a current command signal corresponding to an auxiliary steering angle command signal (steering angle command signal) given from the upper control unit 32. The upper control unit 32 is a control means superior to the steering control unit 30. As this 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 the current command signal input from the steering control unit 30 via, for example, the three-phase power supply lines described later, and drives and controls the steering actuator 5. That is, the actuator drive control unit 31 controls the power supplied to the coil of the motor 26. This actuator drive control unit 31 constitutes, for example, a bridge circuit (FIG. 10) using switching elements, and performs PWM control to determine the motor applied voltage based on the ON-OFF duty ratio of the switching elements. As a result, in addition to the steering by the driver's steering wheel operation, the angle of the wheel 9 can be slightly changed. Even during straight running, the amount of toe angle can be adjusted according to each situation. Therefore, improvement in motion performance and fuel efficiency can be achieved. Note that the steering system may operate the steering actuators 5, 5 according to commands from an automatic driving device or a driving support device (not shown) instead of the driver's steering wheel operation.

[0051] Fig. 10 shows an actuator drive control unit 31 that drives and controls the motor 26 of the steering actuator 5 by means of three-phase power supply lines PWa. Specifically, it is a wiring diagram showing the input side of the motor 26 of the present embodiment that uses a short-circuit brake in the power supply line PWa. An inverter circuit INV, which is a bridge circuit composed of six switching elements, is connected to the input side of the motor 26. The bridge circuit INV includes switching elements Q1, Q2, Q3 connected to the wire Hi on the + side (High side) and switching elements Q4, Q5, Q6 connected to the wire Lo on the - side (Low side) when viewed from the DC power supply E. Note that the switching elements Q1, Q4 are connected to the U-phase power supply line PWu, the switching elements Q2, Q5 are connected to the V-phase power supply line PWv, and the switching elements Q3, Q6 are connected to the W-phase power supply line PWw.

[0052] Also, between the U-phase and the V-phase on the input side of the motor 26 of the present embodiment, and between the V-phase and the W-phase, relays 1REL1 and 2REL2 of the b-contact type, each having coils Col1 and Col2 and opening contacts Cnt1 and Cnt2 when a coil applied voltage is applied, are respectively connected. Therefore, normally (when normal), since power is supplied from the power supply E to the coils Col1 and Col2 of the relays 1REL1 and 2REL2, the contacts Cnt1 and Cnt2 are in the off state. When an abnormality occurs in the motor, particularly when the power supply E fails, the power supply from the power supply to the coils Col1 and Col2 of the relays 1REL1 and 2REL2 is lost, so the contacts Cnt1 and Cnt2 become in the on state (contact closed state or conduction state), and the short-circuit brake occurs in the motor 26. Note that even when the power supply does not fail, by stopping the power supply from the power supply E, the contacts Cnt1 and Cnt2 can be brought into the on state, and the short-circuit brake can occur in the motor 26. The relays 1REL1 and 2REL2 constitute a relay circuit RELA. Note that the relays 1REL1 and 2REL2 may each be a relay including a semiconductor element. Also, the relays 1REL1 and 2REL2 may be composed of one component having one coil and two contacts. In the present embodiment, relays are provided between U-V and V-W, but relays may also be provided between V-W and W-U, and between W-U and U-V. Also, in the present embodiment, the operation of the relay circuit RELA means that the relays 1REL1 and 2REL2 each become in the on state at the contacts Cnt1 and Cnt2.

[0053] Figure 11 shows a flowchart until the short-circuit brake operation in the motor 26 including the operation of the relay circuit RELA of the present invention. During the running of the vehicle, it is determined whether the power supply is normal (S1). When the power supply is normal (Yes in S1), if a system abnormality such as a sensor abnormality, a control device abnormality, or a motor abnormality occurs (Yes in S2), all the high-side switching elements Q1 to Q3 are turned off, and all the low-side Q4 to Q6 are turned on (S3). As a result, the phases between the U-phase, V-phase, and W-phase are short-circuited (on the low side) (S6), and torque is applied to the motor in a direction that hinders the rotation of the motor 26 by the power generation action, and the short-circuit brake operates (S7). Note that all the high-side switching elements Q1 to Q3 may be turned on, and all the low-side Q4 to Q6 may be turned off, but a short circuit with all the low sides turned on is preferable from the viewpoint of electric shock and the like.

[0054] On the other hand, when the power supply fails due to a cause such as the above-mentioned system abnormality of the motor abnormality (power supply abnormality. No in S1), the power supply to the coils of the relays REL1 and REL2 connected between the U-V phase and the V-W phase on the motor input side is cut off (S4), and the contacts of the b-contact type relays REL1 and REL2 are turned on (S5). As a result, the three phases of UVW are short-circuited (S6), and torque is applied to the motor in a direction that hinders the rotation of the motor 26 by the power generation action, and the short-circuit brake operates (S7). Note that the relays REL1 and REL2 are turned off when the power supply is restored, and the three-phase short circuit of UVW is released. Also, when the high-side switching elements Q1 to Q3 are in the off state and the low-side Q4 to Q6 are in the on state, it is canceled by a reset signal at the time of system recovery, and the three-phase short circuit of UVW is released.

[0055] FIG. 12 shows the operation during power loss in this embodiment. When the tire angle is transitioning to the commanded position (command angle) (a), if the power supply fails due to a system abnormality such as the above motor abnormality at time Tb (b), when a current that generates an external force to promote the rotation of the motor in the stopping direction does not flow and the short-circuit brake of this embodiment is not applied, the motor rotates by inertia and greatly overshoots from the abnormal occurrence angle (b) to the angle of the waveform indicated by (c). On the other hand, when the short-circuit brake of this embodiment is applied, the contacts of the b-contact type relays 1REL1 and 2REL2 are turned on, resulting in a short circuit between the three phases of UVW, and torque is applied to the motor in a direction that hinders the rotation of the motor 26, and the motor stops electrically (short-circuit brake operation). As a result, it can stop at the angle of the waveform indicated by (d) from the abnormal occurrence angle (b).

[0056] In addition, even when the above system abnormality such as the motor abnormality occurs but the power supply does not fail, by turning off all the High-side switching elements Q1 to Q3 and turning on all the Low-side Q4 to Q6, the phases of the U-phase, V-phase, and W-phase are short-circuited (on the Low side), so the same effect as in FIG. 12 can be obtained. In this way, by performing the short-circuit brake operation that employs both the switching element and the relay during a system abnormality, it becomes possible to operate the short-circuit brake even during an unexpected power failure.

[0057] <Operational Effects> In the steering system of this embodiment, the hub unit 1 with a steering function includes a hub unit main body 2 having a hub bearing 15 that rotatably supports a wheel, a unit support member 3, and a steering actuator 5. The hub unit main body 2 is supported by the unit support member 3 via a rotation-permitting support component that is rotatable around the axis of the steering shaft extending in the vertical direction, and is rotated (rotated) around the axis of the steering shaft by the drive of the steering actuator 5. When this configuration is applied to the front wheels, the wheels are steered together with the knuckle and the unit support member 3 by the driver's steering wheel operation by the steering device, but a predetermined angle of steering, such as a slight angle, can be independently performed for each wheel around the axis A of the steering shaft in an additional form to this steering. Also, when this configuration is applied to the rear wheels, by the steering function, a slight angle of steering can be independently performed for each wheel in the same manner as the front wheels. When applied to the rear wheels, if the steering angle is set to the same phase as the front wheels, the yaw generated during steering can be suppressed, and the stability of the vehicle can be improved. Furthermore, by adjusting the toe angle independently for the left and right even during straight running, the running stability can be ensured.

[0058] As described above, by the steering actuator 5, the hub unit main body 2 can be freely rotated within a certain range around the axis A of the steering shaft, and for example, the toe angle of the wheel can be arbitrarily changed according to the running situation of the vehicle. Also, during turning running, the steering angle difference between the left and right wheels can be changed according to the running speed. For example, the steering geometry can be changed during running, such as parallel geometry during high-speed turning running and Ackermann geometry during low-speed turning running. Since the wheel angle can be freely changed during running in this way, the motion performance of the vehicle can be improved, and it becomes possible to run stably. Furthermore, by appropriately changing the steering angles of the left and right steering wheels, the turning radius of the vehicle during turning running can be reduced, and the small turning performance can be improved. Furthermore, even during straight running, by adjusting the amount of the toe angle according to each situation, at low speed, the tires can be directed straight to reduce resistance without deteriorating fuel consumption, and at high speed, the tire angle can be set to toe-in to ensure running stability, etc., and adjustment is possible.

[0059] Also, in the present embodiment, a short - circuit brake that turns all of the High - side or Low - side of the switching elements constituting the bridge circuit (inverter circuit) of the motor 26 of the steering actuator 5 on or off, and a short - circuit brake due to a relay short - circuit are adopted. By adopting the short - circuit brake of the present embodiment, when the hub unit 1 with a steering function stops the motor in the event of a system abnormality, in the case where the wheels operate beyond the movable range of the machine during the natural stop of the motor rotation, it becomes possible to prevent damage caused thereby.

[0060] <Regarding application to non - steering wheels> The hub unit 1 with a steering function may be used for non - steering wheels. For example, as shown in FIG. 8, in a vehicle with front - wheel steering, it may be set in the wheel - well frame part 6R which is the wheel bearing installation part of the suspension device 12R that supports the rear wheel 9R, and may be used for rear - wheel steering. In the hub unit 1 with a steering function for non - steering wheels, depending on the requirements of vehicle control, not only the aforementioned minute steering angles but also relatively large angles such as 10° - 20° etc. may be adopted individually for the left and right wheels. As shown in FIG. 9, the hub unit 1 with a steering function may be used for the left and right front wheels 9F, 9F which are steering wheels and the left and right rear wheels 9R, 9R which are non - steering wheels respectively.

[0061] As described above, the mode for implementing this invention based on the embodiment has been explained. However, the disclosed embodiment is illustrative in all respects and not restrictive. The scope of this invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of reference numerals

[0062] 1... Hub unit with steering function, 2... Hub unit body, 3... Unit support member, 5... Steering actuator, 6... Knuckle (suspension frame part), 9... Wheel, 9F... Front wheel, 9R... Rear wheel, 15... Hub bearing, 25... Linear motion mechanism, 25a... Output rod, 26... Motor, 29... Control device, 30... Steering control unit, 31... Actuator drive control unit, 32... Higher-level control unit, 44... Position sensor, 54... Angle sensor, INV... Bridge circuit (inverter circuit), PWa... Three-phase power line, Q1, Q2, Q3, Q4, Q5, Q6... Switching elements, REL1, REL2... Relays, RELA... Relay circuit

Claims

1. A hub unit body having a hub bearing for rotatably supporting a wheel, a unit support member provided on a wheel-side frame component of a suspension device and rotatably supporting the hub unit body about a turning axis extending in the vertical direction, and a steering actuator for rotationally driving the hub unit body about the turning axis. The steering actuator has a motor and a linear motion mechanism that converts the rotational output of the motor into the linear motion of an output rod. The hub unit body is rotationally driven about the turning axis by the forward and backward movement of the output rod. A steering system, An actuator drive control unit that drives and controls the motor of the steering actuator so that the motor outputs a current corresponding to an input current command signal via three-phase power supply lines. A relay circuit that short-circuits at least any two of the three phases of the power supply lines. A steering system that operates the relay circuit when an abnormality occurs in the motor of the steering actuator.

2. The steering system according to claim 1, wherein a relay including a semiconductor element is used in the relay circuit.

3. The steering system according to claim 1, wherein the relay of the relay circuit has one coil and two contacts.

4. In the steering system according to any one of claims 1 to 3, The actuator drive control unit has a plurality of switching elements, and drives and controls the motor of the steering actuator by the on / off operation of the plurality of switching elements. When a power failure occurs when an abnormality occurs in the motor of the steering actuator, the relay circuit is operated. When there is no power failure, all the Low sides of the plurality of switching elements are turned on and all the High sides are turned off.

5. In the steering system according to any one of claims 1 to 4, a control device for controlling the steering actuator of the hub unit with a steering function is provided. The control device has a steering control unit that outputs a current command signal corresponding to a given steering angle command signal, and the actuator drive control unit that outputs a current corresponding to the current command signal input from the steering control unit and drives and controls the steering actuator.

6. A vehicle equipped with the steering system according to any one of claims 1 to 5, wherein one or both of the front wheels and the rear wheels are supported by using the hub unit with a steering function.

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