JP2021146964A - Steering function-equipped hub unit and vehicle including the same - Google Patents

Abstract

To provide a steering function-equipped hub unit which has the steering function of steering a rear wheel, and which enables the improvement of running stability and so on; and to provide a vehicle including the same.SOLUTION: A steering function-equipped hub unit includes: a hub unit body which has a hub bearing 15 for supporting a rear wheel 9R; a unit support member 3 which is provided on a rear wheel suspension and rotatably supports the hub unit body around a turning shaft center extending in a vertical direction; and a steering actuator 5 which rotationally drives the hub unit body around the turning shaft center. An intersection point Pt of a turning axis and a road surface is arranged, as viewed from the upper side of a vehicle, behind the line of action of cornering force at a maximum rear wheel sideslip angle which does not cause the slip of the rear wheel 9R.SELECTED DRAWING: Figure 11

Description

The present invention relates to a hub unit with a steering function having a function of steering the left and right rear wheels and a vehicle equipped with the hub unit, the positional relationship between the intersection of the steering shaft of the hub unit with the steering function and the road surface and the tire contact point. It relates to a technology for improving running stability and safety by adjusting.

In Patent Document 1, in a torsion beam suspension, a bush having low rigidity is provided between the trailing arm and the beam and between the trailing arm and the wheel center behind the wheel center. As a result, when a lateral force is applied to the wheels, the turning outer ring is in a toe-in state, and running stability and steering stability are improved.

Patent Document 2 is a device in which a steering shaft is provided in a hub unit having a hub bearing that supports wheels, and is a grounding point of a kingpin shaft of a front wheel, a grounding point of the steering shaft of the device, and a grounding point of a tire. Is characterized in that they generally match.

Japanese Unexamined Patent Publication No. 2016-179757 Japanese Unexamined Patent Publication No. 2019-6226

Patent Document 1 employs a bush having low rigidity in order to bring the wheel into a toe-in state when a lateral force is applied, but the roll rigidity is low as compared with the conventional configuration in which the bush is not provided, and steering response and riding comfort are obtained. Get worse.

In the hub unit of Patent Document 2, there is a possibility that a minute error may occur in the detected value of the steering angle due to deformation of the member or the like when the vehicle is turning. However, if the hub unit is mounted on the front wheels and the grounding point of the kingpin shaft, the grounding point of the steering shaft of the hub unit, and the grounding point of the tire match, the error will be offset by the rotation around the kingpin shaft. , There is no risk of the behavior of the vehicle being disturbed.
On the other hand, when the hub unit as in Patent Document 2 is mounted on the rear wheels, the tires rotate only around the steering shaft of the hub unit, so that the error of the detected value has a large influence on the behavior of the vehicle.

Further, according to Patent Document 2, when the grounding point of the kingpin shaft, the grounding point of the steering shaft of the hub unit, and the grounding point of the tire do not match in the hub unit mounted on the front wheel, the rotation around the kingpin shaft and the hub unit When the rotation around the steering axis of the tire occurs at the same time, the tire slips in the lateral direction.
On the other hand, when the hub unit as in Patent Document 2 is mounted on the rear wheels, the tire rotates only around the steering shaft of the hub unit, so that the tire does not slip in the lateral direction. Therefore, there is no problem even if the structure does not match the grounding point of the steering shaft of the hub unit and the grounding point of the tire.

An object of the present invention is to provide a hub unit with a steering function for steering rear wheels, a hub unit with a steering function capable of improving running stability, and a vehicle equipped with the hub unit.

The hub unit with steering function of the present invention includes a hub unit body having a hub bearing that supports the rear wheels, and a hub unit body.
A unit support member provided on the rear wheel suspension that rotatably supports the hub unit body around the steering axis extending in the vertical direction.
A steering actuator that rotationally drives the hub unit body around the steering axis, and
A hub unit with a steering function that steers the rear wheels.
The intersection of the steering shaft and the road surface is arranged behind the line of action of the cornering force at the maximum rear wheel side slip angle at which the rear wheels do not slip.

According to this configuration, the intersection of the steering axis of the hub unit and the road surface is located behind the line of action of the cornering force at the maximum rear wheel side slip angle that does not cause the rear wheels to slip. NS. Therefore, when the cornering force acts on the rear wheels due to the turning of the vehicle, a moment of force is generated to steer the turning outer wheels in the toe-in direction and the turning inner wheels in the toe-out direction. At this time, the cornering force of the turning outer ring is larger than that of the turning inner ring, and the moment of force is larger. Therefore, it is possible to improve the passive running stability of a vehicle provided with a steering shaft on the rear wheels. The passive running stability is different from the running stability when the rear wheels are actively steered according to a control rule or the like, and is different from the running stability when the rear wheels are not intentionally steered, that is, depending on the rigidity of the suspension or the backlash. It refers to running stability when the tire angle changes.

The intersection of the steering shaft and the road surface may be outside the ground contact point of the rear wheels when viewed from above the vehicle.
According to this configuration, when braking the vehicle, a moment of force is generated by the braking force to steer both the left and right rear wheels in the toe-in direction. As a result, running stability can be maintained or improved even when the support rigidity of the rear wheels is small.

The steering shaft may be tilted in the front-rear direction of the vehicle. In this case, the positional relationship between the intersection of the steering shaft and the road surface and the tire contact point can be easily and surely adjusted.

The steering actuator may include a motor, a speed reducer that reduces the rotation of the motor, and a linear motion mechanism that converts the rotational output of the speed reducer into linear motion. In this way, the linear motion mechanism converts the rotational output of the speed reducer into a linear motion, so that the hub unit main body is rotationally driven around the center of the steering axis to be steered.

The linear motion mechanism may be a feed screw mechanism using a trapezoidal thread. In this case, the so-called self-locking function of the trapezoidal thread can enhance the effect of preventing reverse input from the tire.

The hub unit main body is supported by the unit support member via bearings at two upper and lower positions so as to be rotatable around the steering axis center, and the upper and lower bearings are located in the wheels of the rear wheels. May be good. In this case, the vehicle can be easily equipped with a hub unit with a steering function that has high rigidity and can be miniaturized. Therefore, since the existing vehicle can be easily equipped with the hub unit with the steering function, the versatility of the hub unit with the steering function can be enhanced.

The steering system of the present invention is a steering system including the hub unit with a steering function according to any one of the above and a control device for controlling a steering actuator of the hub unit with a steering function. , A steering control unit that outputs a current command signal corresponding to a given steering angle command signal, and an actuator that outputs a current corresponding to the current command signal input from the steering control unit to drive and control the steering actuator. It has a drive control unit.

According to this configuration, the steering control unit outputs a current command signal corresponding to a given steering angle command signal. The actuator drive control unit drives and controls the steering actuator by outputting a current corresponding to the current command signal input from the steering control unit. Therefore, the steering angle of the rear wheels can be arbitrarily changed in addition to the steering of the front wheels by the operation of the steering input unit of the driver.

The vehicle of the present invention is a vehicle in which the rear wheels are supported by using the hub unit with a steering function according to any one of the above, and the rear wheel suspension is a rigid axle suspension. According to this configuration, by providing the rigid axle suspension with the unit support member of the hub unit with steering function, the hub unit with steering function can be easily installed without major structural changes.

The hub unit with a steering function of the present invention is provided on a hub unit main body having a hub bearing for supporting the rear wheels and a rear wheel suspension, and the hub unit main body is rotatably supported around a steering axis extending in the vertical direction. A hub unit with a steering function for steering the rear wheels, comprising a unit support member for steering and a steering actuator for rotationally driving the hub unit main body around the steering shaft center, wherein the steering shaft and the road surface are used. The intersection with the vehicle is arranged behind the line of action of the cornering force at the maximum rear wheel side slip angle at which the rear wheels do not slip. Therefore, in the hub unit with a steering function that steers the rear wheels, it is possible to improve the running stability and the like.

The steering system of the present invention is a steering system including the hub unit with a steering function according to any one of the above and a control device for controlling a steering actuator of the hub unit with a steering function. , A steering control unit that outputs a current command signal corresponding to a given steering angle command signal, and an actuator that outputs a current corresponding to the current command signal input from the steering control unit to drive and control the steering actuator. It has a drive control unit. Therefore, in the hub unit with a steering function that steers the rear wheels, it is possible to improve the running stability and the like.

The vehicle of the present invention is a vehicle in which the rear wheels are supported by using the hub unit with a steering function according to any one of the above, and since the rear wheel suspension is a rigid axle suspension, the rear wheels are steered. In the hub unit with a steering function, it is possible to improve the running stability and the like.

It is a perspective view which shows the whole appearance when the hub unit with a steering function which concerns on 1st Embodiment of this invention is mounted on a vehicle. It is a horizontal cross-sectional view which shows the structure of the hub unit with a steering function and its periphery. It is a perspective view which shows the appearance of the hub unit with a steering function. It is a side view of the hub unit with a steering function. It is a top view of the hub unit with the steering function. FIG. 4 is a sectional view taken along line VI --VI of FIG. It is a side view when the hub unit with a steering function is mounted on a vehicle. It is a partial plan view when the hub unit with a steering function is mounted on a vehicle. It is a figure which shows the cornering force which acts when the vehicle turns. It is a figure explaining the positional relationship between the intersection of a steering shaft and a road surface, and the action line of a cornering force. It is a side view of the hub unit with a steering function which shows the positional relationship between the intersection of a steering shaft and a road surface, and a tire contact point. It is a side view of the hub unit with a steering function which shows the positional relationship between the intersection of a steering shaft and a road surface, and a tire contact point. It is a figure which shows the region of the intersection of a steering shaft and a road surface where a turning outer ring becomes toin at the time of turning. It is a figure which shows the region of the intersection of a steering shaft and a road surface where a turning outer ring becomes toin at the time of turning and braking. It is a schematic plan view of the vehicle provided with any of the hub units with a steering function.

[First Embodiment]
A hub unit with a steering function according to an embodiment of the present invention will be described with reference to FIGS. 1 to 15.
As shown in FIG. 15, the hub unit 1 with a steering function according to the embodiment has a function of independently steering the left and right rear wheels 9R and 9R, and the rear wheels 9R of the vehicle 10 with front wheel steering. Applies to 9R. The hub unit 1 with a steering function improves running stability and safety by adjusting the positional relationship between the intersection of the steering shaft and the road surface (hereinafter, "steering shaft grounding point") and the tire grounding point. To improve.

<Outline structure of hub unit with steering function>
As shown in FIG. 3, the hub unit 1 with a steering function includes a hub unit main body 2, a unit support member 3, a bearing 4 which is a rotation allowable support component, and a steering actuator 5. As shown in FIG. 15, the vehicle 10 equipped with the hub unit 1 with a steering function steers the left and right front wheels 9F and 9F by operating the steering wheel and the like, and also steers the left and right rear wheels 9R and 9R at a minute angle (about ± 5 deg). ) It can be steered independently. However, in the hub unit 1 with a steering function, depending on the demand of vehicle control, not only the minute angle but also a relatively large angle such as 10 ° to 20 ° may be taken individually for the left and right wheels.

As shown in FIG. 5, the hub unit main body 2 is provided on the outboard side of the unit support member 3. A steering actuator 5 is provided on the inboard side of the unit support member 3. With the hub unit 1 with steering function (FIG. 15) mounted on the vehicle, the outside of the vehicle in the vehicle width direction is referred to as the outboard side, and the center side of the vehicle in the vehicle width direction is referred to as the inboard side.

The hub unit main body 2 and the output rod 25a of the steering actuator 5 are connected by a joint portion 8. Normally, boots (not shown) are attached to the joint portion 8 for waterproof and dustproof purposes.
As shown in FIG. 6, the hub unit main body 2 is supported by the unit support member 3 via bearings 4 and 4 at two upper and lower positions so as to be rotatable around the steering axis A extending in the vertical direction. .. The steering axis A is an axis different from the rotation axis O of the rear wheel 9R. The rear wheel 9R includes a wheel 9a and a tire 9b.

<Installation location of unit support member 3>
As shown in FIG. 1, the unit support member 3 is fixed to the rigid axle suspension Rs, which is the rear wheel suspension in the vehicle 10. In this example, the torsion beam type suspension of the rigid axle suspension Rs is applied. As shown in FIGS. 7 and 8, the vehicle body mounting portion 35 in the torsion beam suspension is supported by the vehicle body. The unit support members 3 are fixed to the mounting portions 34 and 34 provided at both left and right ends of the beam 33 in the torsion beam type suspension, respectively. Although not shown, as a rear wheel suspension type, the unit support member 3 of the hub unit 1 with a steering function may be fixed to another suspension mechanism such as a multi-link suspension mechanism.

<About hub unit body 2>
As shown in FIG. 2, the hub unit main body 2 includes a hub bearing 15 that supports the rear wheels 9R, an outer ring 16, and an arm portion 17 that is a steering force receiving portion. The hub bearing 15 has an inner ring 18, an outer ring 19, and a rolling element 20 such as a ball interposed between the inner and outer rings 18 and 19, and serves to connect a member on the vehicle body side and the rear wheel 9R. ..

As shown in FIG. 6, in the illustrated example, the hub bearing 15 is an angular contact ball bearing in which the outer ring 19 is a fixed wheel, the inner ring 18 is a rotating wheel, and the rolling elements 20 are in a double row. The inner ring 18 has a hub ring portion 18a having a hub flange 18aa and forming a raceway surface on the outboard side, and an inner ring portion 18b forming a raceway surface on the inboard side. As shown in FIG. 2, the wheel 9a of the rear wheel 9R is bolted to the hub flange 18aa in a state of overlapping with the brake rotor 21a. The inner ring 18 rotates around the rotation axis O.

As shown in FIG. 6, the outer ring 16 has a ring portion 16a fitted to the outer peripheral surface of the outer ring 19 and a trunnion shaft-shaped mounting shaft portion provided so as to project vertically from the outer circumference of the ring portion 16a. It has 16b and 16b. Each mounting shaft portion 16b is provided coaxially with the steering shaft center A.
As shown in FIG. 2, the brake 21 has a brake rotor 21a and a brake caliper 21b. The brake caliper 21 is attached to the upper and lower brake caliper mounting portions 22 (FIG. 4) formed by integrally projecting from the outer ring 19 in an arm shape.

<Rotation allowable support parts and unit support members>
As shown in FIG. 6, a rolling bearing is applied to the bearing 4, which is each rotation allowable support component, and a tapered roller bearing is applied as the rolling bearing in this example. The bearing 4 has an inner ring fitted to the outer periphery of the mounting shaft portion 16b, an outer ring fitted to the unit support member 3, and a plurality of rolling elements interposed between the inner and outer rings. The upper and lower bearings 4 and 4 are provided so as to be located in the wheel 9a. Fitting holes are formed in the upper and lower portions of the unit support member 3, and the outer ring is fitted and fixed in each fitting hole. Each of the fitting holes is provided coaxially with the steering axis A.

Each mounting shaft portion 16b of the outer ring 16 is formed so that a female screw portion extends in the radial direction, and a bolt 23 screwed into the female screw portion is provided. A disk-shaped pressing member 24 is interposed on the end surface of the inner ring, and a pressing force is applied to the end surface of the inner ring by a bolt 23 screwed into the female thread portion to give a preload to each bearing 4. .. Thereby, the rigidity of each bearing 4 can be increased. Even if the weight of the vehicle acts on the hub unit 1, the initial preload is set so as not to come off. Therefore, the hub unit 1 with a steering function can secure the rigidity as a steering device. The bearing 4 is not limited to the tapered roller bearing, and an angular contact ball bearing can also be used depending on the usage conditions such as the maximum load. In that case as well, a preload can be applied in the same manner as described above.

As shown in FIG. 2, the arm portion 17 is a portion serving as an action point for applying an auxiliary steering force to the outer ring 19 of the hub bearing 15, and protrudes outward in the radial direction integrally with a part of the outer circumference of the outer ring 19. do. 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. By advancing and retreating the output rod 25a of the steering actuator 5, the hub bearing 15 is rotated around the steering axis A, that is, steered.

<Steering actuator 5>
The steering actuator 5 rotationally drives the hub unit main body 2 around the steering axis A. The steering actuator 5 includes a motor 26, a speed reducer 27 that reduces the rotation of the motor 26, and a linear motion mechanism 25 that converts the forward and reverse rotation outputs of the speed reducer 27 into a reciprocating linear operation of the 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.

As the speed reducer 27, a winding type transmission mechanism such as a belt transmission mechanism or a gear train or the like can be used, and the belt transmission mechanism is used in the example of FIG. The speed reducer 27 has a drive pulley 27a, a driven pulley 27b, and a belt 27c. A drive pulley 27a is coupled to the motor shaft of the motor 26, and a driven pulley 27b is provided in the linear motion mechanism 25. The driven pulley 27b is arranged parallel to the motor shaft. 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 form a winding type speed reducer 27.

As the linear motion mechanism 25, a feed screw mechanism such as a slide screw or a ball screw, a rack and pinion mechanism, or the like can be used. In this example, a feed screw mechanism using a slide screw of a trapezoidal thread Ts is used. Since the linear motion mechanism 25 includes a feed screw mechanism using the sliding screw of the trapezoidal thread Ts, the effect of preventing reverse input from the tire 9b can be enhanced. The steering actuator 5 provided with the motor 26, the speed reducer 27, and the linear motion mechanism 25 is assembled as a semi-assembly and is detachably attached to the case 6b with bolts or the like. A mechanism that directly transmits the driving force of the motor 26 to the linear motion mechanism 25 without going through a speed reducer is also possible.

<Other mechanical configurations>
As shown in FIG. 3, 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 accommodating portion for supporting the motor 26 and a linear motion mechanism accommodating portion for supporting the linear motion mechanism 25. The motor accommodating portion is formed with a fitting hole that supports the motor 26 at a predetermined position in the case. The linear motion mechanism accommodating portion is formed with a fitting hole that supports the linear motion mechanism 25 at a predetermined position in the case, a through hole that allows the output rod 25a to move forward and backward, and the like.

<Cornering force acting on the wheels when turning>
Generally, when the vehicle turns, the vehicle and the tires have a side slip angle, and the tires have a cornering force acting in a direction perpendicular to the traveling direction of each wheel. For example, the side slip angle and cornering force when the vehicle turns to the left are shown as shown in FIG. In FIG. 9, F and β are cornering force and side slip angle, respectively, and the subscripts FL, FR, RL, and RR indicate the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, respectively. The same applies to FIG. Since the cornering force is normally proportional to the lateral slip angle of the tire and the vertical load, the cornering force of the turning outer ring (the tire on the right side in FIG. 9) having a larger vertical load than that of the turning inner ring is larger.

<Most of the moment>
Especially when the rear wheels are generating cornering force and the steering shaft grounding point does not coincide with the tire grounding point located on the line of action of the cornering force, the cornering force causes a moment of force around the steering shaft. appear. The moment of this force causes the tire to be steered around the steering shaft by the amount of play and slight deformation of the hub unit with steering function, which is the product of the present invention.
The moment of force is proportional to the cornering force. Since the cornering force is proportional to the vertical load as described above, the turning outer ring is larger than the turning inner ring. Therefore, the moment of force is also larger in the turning outer ring, and the steering amount is also larger.

<Direction of moment>
For example, when the vehicle is turning to the left as shown in FIG. 9, that is, when the cornering force is acting to the left with respect to the direction of the wheels, the steering shaft is behind the action line Ls of the cornering force. When there is a grounding point Pt, a moment of force counterclockwise is generated on the wheel when viewed from above vertically as shown in FIG. 10A. On the contrary, when the steering shaft contact point Pt is located ahead of the cornering force action line Ls, a moment of clockwise force is generated on the wheel when viewed from vertically above as shown in FIG. 10 (b). In FIG. 10, M represents the moment of force generated in the tire.

11 and 12 show examples of the rear wheels viewed from the vehicle side in the vehicle width direction when the positional relationship between the tire contact point Pw and the steering shaft contact point Pt shown in FIG. 10 is applied. 11 (a) and 11 (b) are the left rear wheel and the right rear wheel when FIG. 10 (a) is applied, respectively. 12 (a) and 12 (b) are the left rear wheel and the right rear wheel when FIG. 10 (b) is applied, respectively. As shown in FIGS. 11 and 12, the steering shaft may be tilted forward of the vehicle to realize the positional relationship between the tire contact point Pw and the steering shaft contact point Pt in FIG. That is, in the example of FIG. 11, the positional relationship between the tire ground contact point Pw and the steering shaft ground contact point Pt represented by FIG. Can be realized. In the example of FIG. 12, by having an inclination β that inclines forward of the vehicle as the steering shaft goes downward, the positional relationship between the tire ground contact point Pw and the steering shaft grounding point Pt represented by FIG. It can be realized.

<Position of the steering shaft grounding point where the turning outer ring is toe-in when turning>
From the above, when the vehicle is turning to the left, the steering axis grounding point of the turning outer ring (right rear wheel) is behind the action line of the cornering force, that is, from the action line that does not include the action line. In the rear position, the turning outer wheel (right rear wheel) is slightly steered counterclockwise when viewed from above the vehicle according to the backlash and deformation of the member due to the moment of force. By steering the turning outer wheel in the toe-in direction, the running stability of the vehicle is improved.
Similarly, when the vehicle is turning to the right, when the turning shaft grounding point of the turning outer wheel (left rear wheel) is behind the action line of the cornering force, the turning outer ring steers in the toe-in direction. The running stability of the vehicle is improved.

Here, the lateral slip angles of the left and right rear wheels change depending on the traveling conditions such as the vehicle speed and the steering angles of the front wheels, and the direction of the cornering force also changes accordingly. In order to make the turning outer ring toe-in when turning regardless of the traveling situation, it is sufficient that the turning shaft contact point is behind the action line of the cornering force with reference to the cornering force at the maximum side slip angle. The maximum side slip angle is the maximum value in the so-called non-spin region of the vehicle, that is, the maximum rear wheel side slip angle that does not cause the rear wheels to slip, and varies depending on conditions such as tire material and road surface conditions, but is generally used. For passenger cars, rubber tires, and asphalt roads, the temperature is about 7 to 10 °.
Summarizing the above, the region of the steering shaft contact point where the turning outer ring becomes toin when the vehicle turns, regardless of the turning direction of the vehicle or the traveling condition, is represented by the shaded portion Ld in FIG.

<Toe-in during braking>
As shown in the shaded area Ld of FIG. 14, if the position of the steering shaft contact point is behind the action line Ls of the cornering force at the maximum side slip angle and outside the vehicle contact point Pw, The characteristic that the turning outer wheel is toe-in when the vehicle is turning is maintained, and further, when braking, the left rear wheel is steered clockwise and the right rear wheel is steered counterclockwise when viewed from above the vehicle. Therefore, the rear wheels become toe-in not only when turning but also when braking, further improving running stability.

<Effect>
According to the hub unit 1 with a steering function described above, the steering shaft contact point Pt of the hub unit 1 is more than the action line Ls of the cornering force at the maximum rear wheel side slip angle at which the rear wheels do not slip. It is placed behind when viewed from above. Therefore, when the cornering force acts on the rear wheels 9R due to the turning of the vehicle, a moment of force is generated to steer the turning outer wheels in the toe-in direction and the turning inner wheels in the toe-out direction. At this time, the cornering force of the turning outer ring is larger than that of the turning inner ring, and the moment of force is larger. Therefore, it is possible to improve the passive running stability of the vehicle provided with the steering shaft on the rear wheel 9R.

Further, the steering shaft grounding point Pt of the hub unit 1 is arranged outside the grounding point Pw of the rear wheels 9R when viewed from above the vehicle. In this case, when braking the vehicle, a moment of force is generated by the braking force to steer both the left and right rear wheels 9R and 9R in the toe-in direction. Thereby, even when the support rigidity of the rear wheel 9R is small, the running stability can be maintained or improved.

The hub unit main body 2 is supported by the unit support member 3 via bearings 4 and 4 at two upper and lower positions so as to be rotatable around the steering axis A, and the upper and lower bearings 4 and 4 are the wheels of the rear wheels 9R. It is located within 9a. Therefore, the vehicle can be easily equipped with the hub unit 1 with a steering function, which has high rigidity and can be miniaturized. Therefore, since the existing vehicle can be easily equipped with the hub unit 1 with a steering function, the versatility of the hub unit 1 with a steering function can be enhanced.

<About the steering system>
As shown in FIG. 3, the steering system includes a hub unit 1 with a steering function according to an embodiment and a control device 29 for controlling a steering actuator 5 of the hub unit 1 with a steering function. The control device 29 has a steering control unit 30 and an actuator drive control unit 31. As shown in FIG. 15, the driver operates the steering angle of the front wheels 9F with the steering wheel, but the upper control unit 32 takes into consideration the situation of the vehicle 10 and the like according to the operating angle of the steering input unit 11a which is the steering wheel. The calculated steering angle command signals for the left and right rear wheels 9R and 9R are output. The steering control unit 30 outputs a current command signal corresponding to the steering angle command signal given by the upper control unit 32.

The upper control unit 32 is a higher 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.
As shown in FIG. 3, the actuator drive control unit 31 outputs a current corresponding to the 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 electric power supplied to the coil of the motor 26. The actuator drive control unit 31 constitutes, for example, a half-bridge circuit using a switch element (not shown), and performs PWM control for determining the motor applied voltage according to the ON-OFF duty ratio of the switch element. As a result, the steering angle of the rear wheel 9R shown in FIG. 15 can be arbitrarily changed by changing the angle of the hub unit main body 2 with respect to the unit support member 3. Since the steering angle of the rear wheels 9R can be changed according to the traveling conditions of the vehicle 10, it is possible to improve the kinetic performance and fuel efficiency of the vehicle 10.

Instead of operating the steering wheel of the driver, the steering system may operate the steering actuators 5 and 5 by commands of an automatic driving device, a driving support device, etc. (not shown).

A plain bearing may be applied as each rotation allowable support component 4. As the slide bearing, a self-aligning spherical slide bearing capable of applying a radial load and an axial load in both directions can be applied. This spherical plain bearing has an inner ring fitted to the outer periphery of the steering shaft 16b and an outer ring fitted to the unit support member 3.

Although the embodiments for carrying out the present invention have been described above based on the embodiments, the embodiments disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

2 ... Hub unit body, 3 ... Unit support member, 4 ... Bearing, 5 ... Steering actuator, 9R ... Rear wheel, 9a ... Wheel, 15 ... Hub bearing, 25 ... Linear mechanism, 26 ... Motor, 27 ... Reducer , 29 ... Control device, 30 ... Steering control unit, 31 ... Actuator drive control unit, A ... Steering axis, Ls ... Action line, Pt ... Steering shaft grounding point (intersection of steering shaft and road surface), Pw ... Tire ground contact point (rear wheel ground contact point), Rs ... Rigid axle suspension (rear wheel suspension), Ts ... Trapezoidal screw

Claims (8)

A hub unit body with hub bearings that support the rear wheels,
A unit support member provided on the rear wheel suspension that rotatably supports the hub unit body around the steering axis extending in the vertical direction.
A steering actuator that rotationally drives the hub unit body around the steering axis, and
A hub unit with a steering function that steers the rear wheels.
A hub unit with a steering function in which the intersection of the steering shaft and the road surface is arranged behind the line of action of the cornering force at the maximum rear wheel side slip angle at which the rear wheels do not slip. The hub unit with a steering function according to claim 1, wherein the intersection of the steering shaft and the road surface is outside the ground contact point of the rear wheels when viewed from above the vehicle. The hub unit with a steering function according to claim 1 or 2, wherein the steering shaft is tilted in the front-rear direction of the vehicle. In the hub unit with a steering function according to any one of claims 1 to 3, the steering actuator travels straight through a motor, a speed reducer that reduces the rotation of the motor, and the rotation output of the speed reducer. A hub unit with a steering function that has a linear motion mechanism that converts it into motion. In the hub unit with a steering function according to claim 4, the linear motion mechanism is a hub unit with a steering function which is a feed screw mechanism using a trapezoidal thread. In the hub unit with a steering function according to any one of claims 1 to 5, the hub unit main body is provided with bearings at two upper and lower positions so as to be rotatable around the steering axis center. A hub unit with a steering function that is supported by a unit support member and whose upper and lower bearings are located inside the wheels of the rear wheels. A steering system including the hub unit with a steering function according to any one of claims 1 to 6 and a control device for controlling a steering actuator of the hub unit with a steering function. Is a steering control unit that outputs a current command signal corresponding to a given steering angle command signal, and outputs a current corresponding to the current command signal input from the steering control unit to drive and control the steering actuator. Steering system with actuator drive control unit. A vehicle in which the rear wheels are supported by using the hub unit with a steering function according to any one of claims 1 to 6, wherein the rear wheel suspension is a rigid axle suspension.

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