JP2022119413A - Hub unit with steering function, steering system, and vehicle - Google Patents

Abstract

To provide a hub unit with a steering function which achieves downsizing without deteriorating performance of a steering actuator and enables improvement of mountability on a vehicle and flexibility of peripheral design, and to provide a steering system and a vehicle.SOLUTION: A hub unit 1 with a steering function includes: a hub unit body 2; a unit support member 3; and a steering actuator 5 which rotationally drives the hub unit body 2 around a steering axis. The steering actuator 5 has: a motor 26; a speed reducer 27 which reduces a speed of rotation of the motor 26; and a linear motion mechanism 25 which converts rotation output of the speed reducer 27 into linear motion. The linear motion mechanism 25 has: a feeding screw mechanism 38 including a rotatable nut part 25c and a screw shaft 25A which may move forward or backward; and a rotation support part 28 which rotationally supports the nut part 25c. The speed reducer 27 is disposed at the outer side relative to the rotation support part 28 when viewed in a vehicle width direction.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a hub unit with a steering function, a steering system, and a vehicle, and more particularly to a technique for improving fuel efficiency, driving stability, and safety by controlling the steering angle of the left and right wheels appropriately according to the driving conditions. .

Since the steering system of a typical vehicle is mechanically connected to the wheels, it can generally only take on a single fixed steering geometry, which is intermediate between the Ackermann geometry and the parallel geometry. often set. However, in this case, the steering angle difference between the left and right wheels is insufficient in the low speed range, resulting in an excessive steering angle of the outer wheels, and an excessive steering angle of the inner wheels in the high speed range. Unnecessary imbalance in the wheel lateral force distribution between the inner and outer wheels causes deterioration of fuel efficiency and premature wear of tires due to worsening of running resistance. There is the issue of damage.

Therefore, techniques having an auxiliary steering function have been proposed (Patent Documents 1 and 2).
However, in Patent Document 1, since two motors are used, the increase in the number of motors not only raises the cost but also complicates the control.
In Patent Document 2, since the hub bearing is cantilevered with respect to the steering shaft, the rigidity is lowered, and there is a possibility that the steering geometry may change due to the generation of excessive traveling G.
In addition, when a speed reducer is provided on the steering shaft, the size including the motor becomes large. As the overall size increases, it becomes difficult to place the entire on the inner circumference of the wheel. Moreover, when a reduction gear with a large reduction ratio is provided, the responsiveness deteriorates.

Patent Document 3 shows an example in which a hub unit with a steering function is applied to front wheels of a vehicle in FIGS. 1 and 2 of Document 3. FIG. A steering actuator for rotating the hub bearing is mounted at a position adjacent to the inboard side surface of the hub bearing so as to extend inward in the vehicle width direction. A wheel house and a suspension system in a vehicle must be designed with a space secured to avoid interference with the steering actuator. The wheel house is the space in which the wheels are housed, and the suspension system includes suspension arms, springs, shock absorbers and stabilizers.

DE 102012206337 A1 JP 2014-61744 A JP 2019-59385 A

When the steering actuator is mounted at a position adjacent to the inboard side surface of the hub bearing so as to extend inward in the vehicle width direction, the following problems arise.
If the steering actuator protrudes greatly inward in the vehicle width direction of the vehicle, it may interfere with the wheel house or suspension system around the steering actuator. degree of freedom is greatly impaired. On the other hand, if the components of the steering actuator such as the motor are miniaturized, the steering force and response speed will decrease, making it difficult to achieve the original purpose of improving the stability of the running performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hub unit with a steering function, a steering system, and a vehicle, which are capable of reducing the size of the steering actuator without deteriorating its performance, and improving the mountability on the vehicle and the degree of freedom in peripheral design. That is.

A hub unit with a steering function according to the present invention comprises a hub unit body having a hub bearing for rotationally supporting a wheel; and a steering actuator for rotationally driving the hub unit main body around the turning axis,
The steering actuator is a hub unit with a steering function that includes a motor, a speed reducer that reduces rotation of the motor, and a linear motion mechanism that converts the rotational output of the speed reducer into linear motion,
The linear motion mechanism has a feed screw mechanism including a rotatable nut portion and a retractable screw shaft, and a rotation support portion that supports the rotation of the nut portion. It is arranged on the outside in the vehicle width direction of the vehicle.

According to this configuration, since the speed reducer is arranged outside in the vehicle width direction of the vehicle relative to the rotation support portion that rotationally supports the nut portion, the motor can be arranged further outside the vehicle in the vehicle width direction. As a result, it is possible to minimize the protrusion of the motor inward in the vehicle width direction without degrading the performance of the steering actuator including the motor. Therefore, it is possible to reduce the size of the steering actuator, and improve the mountability of the hub unit with steering function on the vehicle and the degree of freedom in peripheral design.

The speed reducer may be a parallel shaft type speed reducer having pulleys provided on the motor and the nut portion, respectively, and a belt stretched around these pulleys. In this case, the speed reducer having a gear train is superior in quietness and can also reduce operating resistance.

The speed reducer may be a parallel shaft type speed reducer including a gear train, and a driven gear in the gear train may be provided on the outer circumference of the nut portion. In this case, compared to a speed reducer having pulleys and belts, maintenance is superior and durability can be improved.

The linear motion mechanism may include the feed screw mechanism of a trapezoidal sliding screw type. In this case, the effect of preventing reverse input from the tires can be enhanced.

The linear motion mechanism may include an actuator case that is a cover that covers the feed screw mechanism and the rotation support. In this case, the actuator case can prevent foreign matter from entering the feed screw mechanism and the rotation support, and can retain lubricant in the feed screw mechanism and the rotation support.

The rotation support may be a pair of back-to-back tapered roller bearings. By arranging a pair of tapered roller bearings back-to-back in this way, the distance between the points of application is increased compared to the case of face-to-face alignment, and in addition to the rigidity against axial load, the rigidity against moment load can be improved. For example, when the steering angle increases, the load applied from the hub unit main body to the linear motion mechanism shifts obliquely with respect to the linear movement direction of the linear motion mechanism. Therefore, if the rigidity against moment load is high, it is advantageous in maintaining an accurate steering angle when an external force acts from the road surface.

The rotation support may be a pair of back-to-back angular contact ball bearings. In a small vehicle with a small steering load, the driving force of the steering actuator is relatively small, so a pair of angular contact ball bearings can be employed as the rotation support. By adopting a configuration in which the speed reducer is arranged outside in the vehicle width direction with respect to the rotation support portion that rotationally supports the nut portion according to the present invention, it is possible to suppress the motor from projecting inward in the vehicle width direction, thereby saving space. A hub unit with a steering function can be easily installed in a compact car. Also, by arranging the pair of angular contact ball bearings back to back, the distance between the points of application is increased, and in addition to the rigidity against axial load, the rigidity against moment load can be improved.

The rotation support portion may be a double-row tapered roller bearing. In this case, the space in the axial direction of the rotation support portion can be made more compact, and preload adjustment becomes possible through precision control of the bearing itself, so improvement in assembly efficiency can be expected.

The linear motion mechanism may include preload applying means for applying a preload to the rotation support portion. In this case, rattling of the linear motion mechanism can be reduced and rigidity against axial load can be ensured.

A steering system according to the present invention includes a hub unit with a steering function having any one of the above-described configurations of the present invention, and a control device for controlling a steering actuator of the hub unit with a steering function, the steering system comprising: The device includes a steering control section that outputs a current command signal corresponding to a given steering angle command signal, and a current corresponding to the current command signal input from the steering control section to drive and control the steering actuator. and an actuator drive control unit.

According to this configuration, the steering control section outputs a current command signal corresponding to the given steering angle command signal. The actuator drive control section outputs a current corresponding to the current command signal input from the steering control section to drive and control the steering actuator. Therefore, the wheel angle can be arbitrarily changed in addition to the steering by the steering wheel operation of the driver.

In the vehicle of the present invention, one or both of the front wheels and the rear wheels are supported using the hub unit with a steering function having any of the above configurations of the present invention. Therefore, the above-described effects of the hub unit with steering function of the present invention can be obtained. The front wheels are generally steered wheels, and if the hub unit with steering function of the present invention is applied to the steered wheels, it is effective in adjusting the toe angle during running. Rear wheels are generally non-steered wheels, but when applied to non-steered wheels, the minimum turning radius is reduced at low speeds and vehicle stability is improved at high speeds by slightly steering the non-steered wheels. can be achieved.

A hub unit with a steering function according to the present invention comprises a hub unit body having a hub bearing for rotationally supporting a wheel; and a steering actuator for rotationally driving the hub unit main body around the steering axis, the steering actuator comprising a motor, a speed reducer for reducing rotation of the motor, and a speed reducer for reducing rotation of the motor. A hub unit with a steering function and a linear motion mechanism for converting a rotational output of a speed reducer into linear motion, wherein the linear motion mechanism comprises a feed screw mechanism including a rotatable nut portion and a retractable screw shaft; and a rotation support portion that rotationally supports the nut portion, and the speed reducer is arranged outside the rotation support portion in the vehicle width direction of the vehicle. Therefore, it is possible to reduce the size of the steering actuator without degrading its performance, and to improve the mountability on the vehicle and the degree of freedom in peripheral design.

A steering system according to the present invention includes a hub unit with a steering function having any one of the above-described configurations of the present invention, and a control device for controlling a steering actuator of the hub unit with a steering function, the steering system comprising: The device includes a steering control section that outputs a current command signal corresponding to a given steering angle command signal, and a current corresponding to the current command signal input from the steering control section to drive and control the steering actuator. and an actuator drive control unit. Therefore, it is possible to reduce the size of the steering actuator without degrading its performance, and to improve the mountability on the vehicle and the degree of freedom in peripheral design.

In the vehicle of the present invention, one or both of the front wheels and the rear wheels are supported using the hub unit with a steering function having any of the above configurations of the present invention. Therefore, it is possible to reduce the size of the steering actuator without degrading its performance, and to improve the mountability on the vehicle and the degree of freedom in peripheral design.

1 is a perspective view showing the appearance of a hub unit with a steering function according to a first embodiment of the invention; FIG. FIG. 3 is a horizontal cross-sectional view showing the structure of the hub unit with steering function and its surroundings; It is a side view of the hub unit with a steering function. It is a top view of the same hub unit with a steering function. FIG. 4 is a cross-sectional view taken along line V-V of FIG. 3; FIG. 4 is an enlarged cross-sectional view showing in detail the internal structure of a steering actuator of the hub unit with a steering function; FIG. 5 is an enlarged cross-sectional view showing in detail the internal structure of a steering actuator of a hub unit with a steering function according to another embodiment of the present invention; FIG. 11 is a partially enlarged cross-sectional view showing in detail the internal structure of a steering actuator of a hub unit with a steering function according to still another embodiment of the present invention; FIG. 11 is a partially enlarged cross-sectional view showing in detail the internal structure of a steering actuator of a hub unit with a steering function according to still another embodiment of the present invention; 1 is a schematic plan view of a vehicle provided with a hub unit with steering function according to any one of the embodiments of the present invention; FIG. FIG. 4 is a schematic plan view of another example of a vehicle provided with a hub unit with steering function according to any one of the embodiments of the present invention; FIG. 5 is a schematic plan view of another example of a vehicle provided with a hub unit with steering function according to any one of the embodiments of the present invention; FIG. 10 is a horizontal cross-sectional view showing a configuration of a conventional hub unit with a steering function and its surroundings; FIG. 4 is an enlarged cross-sectional view showing in detail the internal structure of a steering actuator of the hub unit 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 6 and 10. FIG.
As shown in FIG. 1, the hub unit 1 with steering function includes a hub unit body 2, a unit support member 3, and a steering actuator 5. As shown in FIG. As shown in FIG. 10, in this embodiment, the hub unit 1 with a steering function has a function of independently steering the left and right rear wheels 9R, 9R supported by a torsion beam suspension system 12R. It is applied to the rear wheels 9R, 9R of the vehicle 10 with front wheel steering. The suspension system is not limited to a torsion beam type suspension, and other suspensions such as a multi-link type suspension can be applied.

The hub unit 1 with a steering function can steer the left and right front wheels 9F, 9F by operating the steering wheel 11a, etc., and can independently steer the left and right rear wheels 9R, 9R by a minute angle (approximately ±5 degrees). However, in the steering function-equipped hub unit 1, depending on vehicle control requirements, not only the small angle but also a relatively large angle such as 10° to 20° may be adopted for each of the left and right wheels.

As shown in FIGS. 1 and 10, unit support members 3 are attached to the left and right sides of the suspension device 12R. As shown in FIG. 2, the unit support member 3 is made of, for example, a plate-like member. A steering actuator 5 is provided on the inboard side of the unit support member 3 , and a hub unit main body 2 is provided on the outboard side of the unit support member 3 . When the hub unit 1 with steering function is mounted on the vehicle, the vehicle width direction outer side of the vehicle is called the outboard side, and the vehicle width direction central side of the vehicle is called the inboard side. Note that the hub unit 1 with a steering function may be simply referred to as the hub unit 1 in some cases.

The hub unit main body 2 and the steering actuator 5 are connected by a joint portion 8 . Normally, this joint portion 8 is attached with a boot (not shown) for waterproofing and dustproofing.

As shown in FIGS. 1 and 5, the hub unit main body 2 is provided with rotation support members at two upper and lower positions so as to be rotatable about a steering axis A extending vertically and perpendicular to the rotation axis O of the wheel. It is supported by the unit support member 3 via 4,4. As shown in FIG. 2, the wheel 9 includes a wheel 9a and a tire 9b.

<Regarding the hub unit body 2>
As shown in FIGS. 2 and 5, the hub unit main body 2 includes a hub bearing 15 that rotationally supports the wheel 9, upper and lower turning shafts 16b, 16b, and an arm portion 17 as a steering force receiving portion. . The hub bearing 15 has an inner ring 18, an outer ring 19, rolling elements 20 such as balls interposed between the inner and outer rings 18 and 19, and a retainer for holding the rolling elements 20. 9 and rotate the wheel 9 smoothly.

The 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 arranged in double rows. The inner ring 18 has a hub ring portion 18a having a hub flange 18aa and forming an outboard side raceway surface, and an inner ring portion 18b forming an inboard side raceway surface. A wheel 9a of the wheel 9 is bolted to the hub flange 18aa so as to overlap the brake rotor 21a. The inner ring 18 rotates around the rotation axis O.

The upper and lower steered shaft portions 16 b , 16 b are trunnion shaft-shaped and protrude vertically from the outer circumference of the outer ring 19 . In this example, the upper and lower turning shaft portions 16b, 16b are formed integrally with the outer ring 19. As shown in FIG. The above-mentioned "integrally formed" means that each steering shaft portion 16b and the outer ring 19 are not formed by combining a plurality of elements, but are made of a single material by, for example, forging or machining. It means molded as a part.
Alternatively, the steering shaft portions 16b, 16b may be trunnion shaft-shaped steerable shaft portions 16b, 16b provided with an annular portion fitted to the outer peripheral surface of the outer ring 19 and protruding vertically from the outer periphery of the annular portion.

As shown in FIGS. 2 and 3, the brake 21 has a brake rotor 21a and a brake caliper (not shown). The brake caliper is attached to two upper and lower brake caliper attachment portions 22 . The upper and lower brake caliper mounting portions 22 are provided so as to protrude in the form of arms from the inboard side end portion of the outer peripheral surface of the outer ring 19 . Therefore, the hub bearing 15 and the brake caliper mounting portion 22 are steered together.

<Rotating support member, etc.>
As shown in FIGS. 4 and 5, each rotation support member 4 is a rolling bearing, and 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 circumference of the steering shaft portion 16b, an outer ring 4b fitted to the holding member Bh, and a plurality of rolling elements 4c interposed between the inner and outer rings 4a and 4b.

The upper and lower steered shaft portions 16b, 16b are fitted into the pair of upper and lower rotation support members 4, 4 respectively fitted in the bearing fitting recesses 13, 13 of the upper and lower holding members Bh, Bh provided in the unit support member 3, respectively. It is supported by the unit support member 3 via the . Each holding member Bh has a substantially cylindrical holding member body portion Bb into which the outer peripheral surface of the outer ring 4b is fitted.
As shown in FIGS. 1 and 4, the upper and lower holding members Bh, Bh are provided with a pair of beams Bm, Bm for connecting the upper and lower holding member main bodies Bb, Bb to each other. Each beam Bm extends in the vertical direction, its longitudinal upper end is fastened with a bolt 33 to the threaded portion of the upper holding member body Bb, and its longitudinal lower end is bolted to the threaded portion of the lower holding member body Bb. 33. Thereby, the rigidity of the steered shaft portion 16b (FIG. 5) can be further increased.
As shown in FIGS. 4 and 5, each rotary support member 4 is located within a wheel 9a of wheels 9 (FIG. 2). In this example, each rotary support member 4 is arranged within the wheel 9a (FIG. 2) in the vicinity of the widthwise middle of the wheel 9a (FIG. 2).

Each steered shaft portion 16b is formed with a female thread extending along the steered axis A, and a bolt 23 screwed into the female thread is provided. The bolt 23 is a bolt 23 with a flange 23a, and can apply a pressing force to the end face of the inner ring 4a by screwing it into the internal thread portion while the flange 23a is in contact with the end face of the inner ring 4a. Thus, by applying a preload to each rotation support member 4, the rigidity of each rotation support member 4 can be increased. Even when the weight of the vehicle acts on the hub unit 1, the initial preload is set so as not to be lost.

The rotary support member 4 is not limited to a tapered roller bearing, and other types of bearings such as an angular contact ball bearing and a spherical slide bearing can be used depending on usage conditions such as maximum load. Also in that case, preload can be applied in the same manner as described above. A disc-shaped pressing member (not shown) is interposed between the head of the bolt without a flange and the end face of the inner ring 4a, and the bolt screwed into the female thread portion exerts a pressing force on the end face of the inner ring 4a. Preload may be applied to each rotation support member 4 by applying .

<Steering actuator 5>
As shown in FIG. 2, the steering actuator 5 has a function of rotationally driving the hub unit body 2 around the turning axis A. As shown in FIG. 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 rotational output of the speed reducer 27 into reciprocating 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.

<Reducer 27>
The speed reducer 27 can use a winding type transmission mechanism such as a belt transmission mechanism, a gear train, or the like, and the belt transmission mechanism is used in the examples of FIGS. 2 and 6 . The speed reducer 27 is a parallel shaft type speed reducer having a drive pulley 27a, a driven pulley 27b, and a belt 27c stretched over these pulleys 27a and 27b. A drive pulley 27a is coupled to the motor shaft of the motor 26, and a driven pulley 27b is provided to a nut portion (to be described later) 25c of the linear motion mechanism 25. As shown in FIG. The driven pulley 27b is arranged parallel to the motor shaft.

The speed reducer 27 is arranged outside in the vehicle width direction of the rotation support portion 28 described later. 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 winding-type speed reducer 27. As shown in FIG.

<Linear motion mechanism 25>
FIG. 6(a) is an enlarged cross-sectional view showing the details of the internal structure of the steering actuator 5, and FIG. 6(b) is a partially enlarged cross-sectional view of the VI(b) portion of FIG. 6(a).
As shown in FIGS. 6A and 6B, the linear motion mechanism 25 may be a feed screw mechanism such as a slide screw, or a rack and pinion mechanism. feed screw mechanism 38 is used. The linear motion mechanism 25 includes a feed screw mechanism 38, a rotation support portion 28, a rotation fixing member 43, a preload applying means 45, and an actuator case 46 which is a cover covering these components.

The feed screw mechanism 38 has a nut portion 25c to which a driven pulley 27b is fastened, a threaded shaft 25A threadedly arranged on the inner periphery of the nut portion 25c, and a sliding bearing 47. As shown in FIG. Grease, which is a lubricant, is sealed inside the slide screw. Since the nut portion 25c and the screw shaft 25A have the screw grooves and screw threads that constitute the trapezoidal screw 38a, the effect of preventing reverse input from the tire 9b (FIG. 2) can be enhanced. One end of the nut portion 25c in the axial direction is provided with the slide bearing 47 through which the output rod 25a of the screw shaft 25A slidably penetrates. The sliding bearing 47 guides the movement of the screw shaft 25A in the axial direction, and when an external force from the tire side is input to the screw shaft 25A, forces are applied to the sliding screw in the radial and moment directions. to prevent

A small-diameter portion, a large-diameter portion, a medium-diameter portion, and a male screw portion are formed in order from the outboard side to the inboard side on the outer periphery of the nut portion 25c. A large-diameter portion is connected to the small-diameter portion via a stepped portion, and a medium-diameter portion is connected to the inboard side of the large-diameter portion via a stepped portion. A space between the small-diameter portion of the nut portion 25c and the inner peripheral surface of the actuator case 46, which faces the small-diameter portion radially outward, prevents foreign matter, water, etc. from entering the actuator case 46 from the outside. An annular seal member 48 is provided.

The driven pulley 27b is fixed to the large diameter portion of the nut portion 25c by fitting, for example, and the rotation support portion 28 that rotationally supports the nut portion 25c is fitted and fixed to the intermediate diameter portion of the nut portion 25c. The rotation support portion 28 is arranged on the inboard side with respect to the speed reducer 27 including the driven pulley 27b. In other words, the speed reducer 27 is arranged outside the rotation support portion 28 in the vehicle width direction of the vehicle. As the rotation support portion 28, in this example, a pair of tapered roller bearings 28a, 28a are combined back to back. The inner peripheral surface of the driven pulley 27b may be fixed to the large diameter portion of the nut portion 25c via a key (not shown). A nut 49 is screwed onto the male threaded portion of the nut portion 25c.

Each tapered roller bearing 28a has an outer ring that is a fixed ring, an inner ring that is a rotating ring, a plurality of rolling elements interposed between the inner and outer rings, and a retainer that holds these rolling elements. Each of the inner rings is fitted and fixed to the middle diameter portion of the nut portion 25c, and a spacer 50 is arranged between the inner rings in the middle diameter portion. Each of the outer rings is fitted and fixed to the actuator case 46 . The preload applying means 45 includes a spacer 50 arranged between the inner rings and a nut 49 screwed onto the male screw portion, and applies preload to the rotation support portion 28 . Appropriate preload can be applied by adjusting the thickness of the spacer 50, that is, the axial dimension. The outboard-side end surface of the outboard-side inner ring is in contact with the stepped portion of the nut portion 25c, and the inboard-side end surface of the inboard-side inner ring is in contact with the nut 49, and the nut 49 is attached to the male thread portion. A preload is applied to the rotation support portion 28 by being tightened.

The rotation fixing member 43 is a shaft-like member that prevents rotation of the output rod 25 a with respect to the unit support member 3 . The rotation fixing member 43 is fitted and fixed to the output rod 25a so as to extend in a direction perpendicular to the axial direction of the output rod 25a at the inboard side end of the output rod 25a. For example, annular plain bearings 51 (see FIG. 8) are fitted to both ends in the axial direction of the outer periphery of the rotation fixing member 43 .

In the actuator case 46, there is formed a guide groove having a rectangular cross-section including a guide surface for guiding the outer peripheral surface of the sliding bearing along the axial direction of the screw shaft 25A. In other words, the rotation fixing member 43 slidably contacts the guide surface of the actuator case 46, which is the fixed portion of the linear motion mechanism 25, via the sliding bearing 51 (FIG. 8). Therefore, the output rod 25a can be reciprocated in the axial direction by sliding the rotary fixing member 43 along the rectangular cross-sectional guide groove of the actuator case 46 via the slide bearing 51 (see FIG. 8). .

The steering actuator 5 including the motor 26, the speed reducer 27 and the linear motion mechanism 25 is assembled as a sub-assembly and detachably attached to the unit support member 3 with bolts or the like. The unit support member 3 is formed with a fitting hole for supporting the linear motion mechanism 25 at a predetermined position in the case, a through hole ha for allowing the forward and backward movement of the output rod 25a, and the like.
Although the feed screw mechanism 38 using the sliding screw of the trapezoidal screw 38a is shown as the linear motion mechanism 25, it may be a linear motion mechanism using a ball screw (not shown).

<Sensors, etc.>
A position sensor 52 for detecting the position of the linear motion mechanism 25 is provided in the actuator case 46 in order to control the steering angle of the wheels more accurately. The position sensor 52 can detect the amount of axial movement of the output rod 25a and output it as a position sensor value. The position sensor 52 can use various sensors such as magnetic type, optical type, capacitance type, etc. In this embodiment, a magnetic sensor is used.

A position sensor 52 is fixed to a substrate 53 fixed in the actuator case 46 . A position sensor measurement target Tg (see FIG. 8) is provided at one axial end of the rotary fixing member 43 . A permanent magnet is applied as the measurement target for the position sensor. The position sensor 52 faces the path along which the position sensor measurement target advances and retreats. When the output rod 25a is at a predetermined axial position (advance/retreat position), the position sensor 52 and the position sensor measurement target Tg (see FIG. 8) are opposed to each other with a predetermined gap therebetween. The position sensor 52 reads a change in the magnetic field of the permanent magnet accompanying the advance and retreat of the output rod 25a, and detects the advance and retreat position of the output rod 25a. The determined gap is a gap that is arbitrarily determined by design or the like, and is determined, for example, by finding an appropriate gap through either one or both of tests and simulations.

<Effect>
According to the steering function-equipped hub unit 1 described above, the hub unit body 2 including the hub bearings 15 that support the wheels 9 can be freely rotated around the steering axis A by driving the steering actuator 5 . can. The hub unit main body 2 is rotated via the arm portion 17 connected to the output rod 25a by moving the output rod 25a of the steering actuator 5 forward and backward by driving the motor 26. As shown in FIG.

The steering actuator 5 allows the hub bearing 15 (FIG. 5) to be freely rotated around the steering axis A within a certain range. can be changed.
When the configuration of the hub unit 1 with steering function is applied to the front wheels, the wheels 9 are steered together with the knuckles 6 (FIG. 11) and the unit support member 3 by the driver's operation of the steering wheel 11a by the steering device 11 (FIG. 11). However, in addition to this steering, auxiliary steering of a slight angle around the steering axis A can be performed independently for each wheel. As for the angle of the auxiliary steering, a slight angle is sufficient to improve the motion performance of the vehicle and to improve the stability and safety of the vehicle. The angle of the auxiliary steering is controlled by the steering actuator 5 .

Also, during turning, the steering angle difference between the left and right wheels can be changed according to the running speed. For example, it is possible to change the steering geometry while driving, such as parallel geometry for high-speed cornering and Ackermann geometry for low-speed cornering. Since the wheel angle can be arbitrarily changed during running in this manner, the motion performance of the vehicle can be improved, and the vehicle can run stably and safely. Furthermore, by appropriately changing the steering angle of the left and right wheels, the turning radius of the vehicle during cornering can be reduced, and the tight turning performance can be improved.
Furthermore, even when driving in a straight line, by adjusting the toe angle according to each situation, it is possible to make adjustments such as ensuring driving stability at high speeds without degrading fuel consumption at low speeds.

When the configuration of the hub unit 1 with steering function is applied to the rear wheels, the hub unit as a whole does not steer, but the steering function allows each wheel to be steered independently by a slight angle in the same manner as the front wheels. By setting the steering angle of the rear wheels to the same phase as the front wheels, the yaw generated during steering can be suppressed and the stability of the vehicle can be enhanced. Furthermore, by adjusting the toe angle independently on the left and right sides even when driving in a straight line, it is possible to improve fuel efficiency and ensure driving stability.

A speed reducer 27 is arranged outside in the vehicle width direction of a rotation support portion 28 that rotationally supports the nut portion 25c. Therefore, compared to the conventional configuration (FIGS. 13 and 14) in which the driven pulley 27b is provided in the axially intermediate portion of the outer peripheral portion of the nut portion 25c and the rolling bearings 28b, 28b are provided on both sides in the axial direction of this driven pulley 27b. , the motor 26 can be arranged further outward in the vehicle width direction. As a result, the protrusion of the motor 26 inward in the vehicle width direction of the vehicle can be minimized without reducing the performance of the steering actuator 5 including the motor 26 . Therefore, it is possible to reduce the size of the steering actuator 5 and improve the mountability of the hub unit 1 with a steering function on a vehicle and the degree of freedom in peripheral design.

In the conventional configuration (FIGS. 13 and 14) in which the driven pulley 27b is arranged between a pair of rolling bearings 28b, 28b, the speed reducer is shifted inward in the vehicle width direction by one bearing width. For this reason, the motor protrudes inward in the vehicle width direction, and interference with the surroundings cannot be avoided. In addition, due to the convenience of assembling the rolling bearings, which are the rotation support parts, the pair of rolling bearings must be aligned face-to-face. As a result, the distance between the points of action cannot be increased, and an improvement in moment rigidity cannot be expected.

Since the speed reducer 27 is a parallel shaft type speed reducer having a drive pulley 27a, a driven pulley 27b, and a belt 27c, it is superior in quietness and lowers operating resistance than, for example, a speed reducer having a gear train. can be done.
The linear motion mechanism 25 can prevent foreign matter from entering the feed screw mechanism 38 and the rotation support portion 28 by the actuator case 46 , and can retain lubricant in the feed screw mechanism 38 and the rotation support portion 28 .

By adopting a pair of tapered roller bearings 28a, 28a that are aligned back to back as the rotation support portion 28, the distance between the points of application is increased compared to the case of the back-to-back alignment. can be improved. For example, when the steering angle increases, the load applied from the hub unit main body 2 to the linear motion mechanism 25 shifts obliquely with respect to the linear movement direction of the linear motion mechanism 25 . Therefore, if the rigidity against moment load is high, it is advantageous in maintaining an accurate steering angle when an external force acts from the road surface.

A driven pulley 27b is fastened to the nut portion 25c in which the trapezoidal thread 38a is formed. A pair of tapered roller bearings 28a, 28a having directional contact angles support rotation while receiving axial loads in both directions.
Since the linear motion mechanism 25 includes the preload applying means 45 that applies a preload to the rotation support portion 28, rattling of the linear motion mechanism 25 can be reduced and rigidity against an axial load can be ensured.

<About other embodiments>
In the following description, the same reference numerals are given to the parts corresponding to the items previously described in each embodiment, and redundant description is omitted. When only a portion of the configuration is described, the other portions of the configuration are the same as those previously described unless otherwise specified. The same configuration has the same effect. It is possible not only to combine the parts specifically described in each embodiment, but also to partially combine the embodiments if there is no problem with the combination.

[Second Embodiment: Reducer with Parallel-Axis Gear Train]
As shown in FIG. 7 , the speed reducer 27 may be a parallel shaft speed reducer including a gear train 57 . This speed reducer 27 comprises a gear train 57 having a drive gear 54 , a driven gear 55 and an idler gear 56 . The gear train 57 is selectable for grease lubrication or oil lubrication. Each gear of the drive gear 54, the driven gear 55 and the idler gear 56 is generically called "gear". As gears, for example, helical gears made of cast iron, cast steel, carbon steel for machine structural use, or the like are applied. Other materials that can be used for gears include, for example, resins such as polyamide, polyoxymethylene, and polycarbonate. It is also possible to use spur gears instead of the helical gears.

A drive gear 54 is coupled to the motor shaft of the motor 26 , and a driven gear 55 as an output gear is fitted and fixed to a large-diameter portion of the outer periphery of the nut portion 25 c of the linear motion mechanism 25 . The idler gear 56 is rotatably supported by a support shaft 58 supported by the actuator case 46 via rolling bearings 59 , 59 and meshes with the drive gear 54 and the driven gear 55 . The axis of the driven gear 55 is arranged parallel to the support shaft 58 and parallel to the motor shaft.

The driving force of the motor 26 is transmitted from the drive gear 54 to the driven gear 55 via the idler gear 56 . As each rolling bearing 59 that rotationally supports the idler gear 56, a deep groove ball bearing is applied in this example, but a rolling bearing such as a needle roller bearing or an angular ball bearing may be applied.

According to this configuration, the speed reducer 27 is a parallel shaft speed reducer including the gear train 57, and the driven gear 55 of the gear train 57 is provided on the outer circumference of the nut portion 25c. It is easier to maintain than a machine, and can improve durability. Other effects similar to those of the above-described embodiment are obtained.

[Third Embodiment: Single Row Angular Contact Ball Bearing Back-to-Back]
As shown in FIG. 8, the rotation support portion 28 of the linear motion mechanism 25 may be a pair of back-to-back angular ball bearings 28c, 28c. Otherwise, the configuration is the same as that of the first embodiment.
A pair of angular ball bearings 28c, 28c can be employed as the rotation support portion 28 in a small vehicle with a small steering load, since the driving force of the steering actuator is also relatively small. By adopting a configuration in which the speed reducer 27 is arranged outside in the vehicle width direction with respect to the rotation support portion 28 that rotationally supports the nut portion 25c, it is possible to prevent the motor from projecting inward in the vehicle width direction, thereby saving space. A hub unit with a steering function can be easily installed in a compact car. Also, by arranging the pair of angular ball bearings 28c, 28c back to back, the distance between the points of application is increased compared to the case of face to face alignment, and in addition to the rigidity against axial load, the rigidity against moment load can be improved. .

[Fourth Embodiment: Double Row Tapered Roller Bearing]
As shown in FIG. 9, the rotation support may be a double row tapered roller bearing 28A. In this case, the space in the axial direction of the rotation support portion 28A can be made more compact, and preload adjustment can be performed by precision control of the bearing itself, so improvement in assembly efficiency can be expected. Moreover, in this configuration, a proper preload can be applied by adjusting the width difference between the inner rings without arranging a spacer between the inner rings. The preload applying means 45 in this case is a nut 49 that is screwed onto the male threaded portion of the nut portion 25c. As in each embodiment, a spacer may be arranged between the inner rings and an appropriate preload may be applied by adjusting the axial dimension of this spacer.

In each embodiment, the linear motion mechanism 25 can be a trapezoidal screw 38a shown in this embodiment, a ball screw, a rack-and-pinion mechanism, or other mechanism capable of converting rotary motion into linear motion.
It is also possible to arrange a pair of tapered roller bearings 28a, 28a or angular ball bearings 28c, 28c face to face.

As shown in FIG. 11, in a front wheel steering vehicle, the hub unit 1 with a steering function may be mounted on the left and right front wheels 9F, which are steered wheels. In this case, the unit support member 3 ( FIG. 1 ) is provided integrally or separately with the knuckle (undercarriage frame component) 6 of the suspension system 12 . The steering axis A of the hub unit 1 with steering function is different from the kingpin axis for 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. It has a steering shaft of (axis).

Alternatively, as shown in FIG. 12, the hub unit 1 with steering function may be used for left and right front wheels 9F, 9F as steered wheels and left and right rear wheels 9R, 9R as non-steered wheels.

<About the steering system>
As shown in FIG. 1, this steering system includes a hub unit 1 with a steering function according to any one of the embodiments, and a control device 29 that controls the steering actuator 5 of the hub unit 1 with a steering function. The control device 29 has a steering control section 30 and an actuator drive control section 31 . The steering control section 30 outputs a current command signal according to the auxiliary steering angle command signal (steering angle command signal) given from the host control section 32 .

The host controller 32 is a host controller of the steering controller 30. As the host controller 32, for example, a vehicle control unit (VCU) for controlling the entire vehicle is applied. The actuator drive control section 31 drives and controls the steering actuator 5 by outputting a current corresponding to the current command signal input from the steering control section 30 . The actuator drive control section 31 controls power supplied to the coils of the motor 26 . The actuator drive control unit 31, for example, constitutes a half-bridge circuit using switch elements (not shown), and performs PWM control for determining the voltage applied to the motor according to the ON-OFF duty ratio of the switch elements. As a result, the angle of the wheels can be slightly changed in addition to the steering by the steering wheel operation of the driver. Even when driving in a straight line, the amount of toe angle can be adjusted according to each situation.

The steering system may operate the steering actuators 5, 5 according to a command from an automatic driving device or a driving support device (not shown) instead of the steering wheel operation by the driver.
As mentioned above, although the form for implementing this invention was demonstrated based on embodiment, embodiment disclosed this time is an illustration and is not restrictive at all points. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

DESCRIPTION OF SYMBOLS 1... Hub unit with a steering function, 2... Hub unit main body, 3... Unit support member, 6... Knuckle (undercarriage frame part), 9... Wheel, 9F... Front wheel, 9R... Rear wheel, 10... Vehicle, 12, 12R Suspension device 15 Hub bearing 25 Linear motion mechanism 25A Screw shaft 25c Nut 26 Motor 27 Reducer 27a Drive pulley 27b Driven pulley 27c Belt 28 Rotation support part 28A Double-row tapered roller bearing 28a Tapered roller bearing 28c Angular ball bearing 29 Control device 30 Steering control part 31 Actuator drive control part 38 Feed screw mechanism 38a Trapezoidal screw 45 Preload applying means 46 Actuator case 55 Driven gear 57 Gear train

Claims (11)

A hub unit body having a hub bearing that supports a wheel for rotation, a unit support member that is provided on an underbody frame component of a suspension system and supports the hub unit body rotatably around a steering shaft that extends in the vertical direction, and the hub A steering actuator for driving the unit main body to rotate about the turning axis,
The steering actuator is a hub unit with a steering function that includes a motor, a speed reducer that reduces rotation of the motor, and a linear motion mechanism that converts the rotational output of the speed reducer into linear motion,
The linear motion mechanism has a feed screw mechanism including a rotatable nut portion and a retractable screw shaft, and a rotation support portion that supports the rotation of the nut portion. A hub unit with a steering function located on the outside of the vehicle in the vehicle width direction. 2. The hub unit with steering function according to claim 1, wherein the speed reducer is a parallel shaft type speed reducer having pulleys provided on the motor and the nut portion, respectively, and a belt stretched around these pulleys. A hub unit with a steering function. 2. The hub unit with steering function according to claim 1, wherein the speed reducer is a parallel shaft type speed reducer including a gear train, and a driven gear in the gear train is provided on the outer circumference of the nut portion. hub unit. 4. A hub unit with a steering function according to claim 1, wherein said direct acting mechanism comprises said feed screw mechanism of trapezoidal sliding screw type. 5. The hub unit with steering function according to claim 1, wherein said linear motion mechanism comprises an actuator case which is a cover for covering said feed screw mechanism and said rotation support portion. unit. 6. The hub unit with steering function according to claim 1, wherein said rotation support portion is a pair of back-to-back tapered roller bearings. 6. The hub unit with steering function according to claim 1, wherein said rotation support portion is a pair of back-to-back angular contact ball bearings. 6. The hub unit with steering function according to claim 1, wherein said rotation support portion is a double-row tapered roller bearing. 9. The hub unit with steering function according to claim 6, wherein said linear motion mechanism comprises preload applying means for applying preload to said rotation support portion. A steering system comprising: the hub unit with steering function according to any one of claims 1 to 9; and a control device for controlling a steering actuator of the hub unit with steering function, wherein the control device is a steering control section that outputs a current command signal corresponding to a given steering angle command signal; and a current corresponding to the current command signal input from the steering control section to drive and control the steering actuator. a steering system having an actuator drive control; A vehicle in which one or both of front wheels and rear wheels are supported using the hub unit with a steering function according to any one of claims 1 to 9.

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