JP2020138691A - Hub unit with steering function and vehicle having the same - Google Patents

Abstract

To provide a hub unit with a steering function and a vehicle having the same, capable of achieving miniaturization of the whole hub unit and high strength and reliability of a connection part between a direct-acting mechanism and an arm part.SOLUTION: The hub unit with a steering function is structured so that a direct-acting mechanism 25 and an arm part 17 are connected through a joint part 8 and includes a first connection pin Pa provided on either of a front end part of the direct-acting mechanism 25 and the joint part 8 in parallel to a steering axial center and making a front end part of the direct-acting mechanism 25 and the joint part 8 rotatable each other and a second connection pin Pb provided on either of the joint part 8 and an arm part 17 in parallel to the steering axial center and making the joint part 8 and the arm part 17 rotatable each other. At the front end part of the direct-acting mechanism 25, the joint part 8, the first and second connection pins Pa, Pb and the arm part 17, wear prevention means Mb is provided.SELECTED DRAWING: Figure 10

Description

The present invention aims to improve fuel efficiency, stabilize driving performance, and improve safety by controlling the left and right wheels to appropriate steering angles according to the driving conditions with respect to a hub unit with a steering function and a vehicle equipped with the hub unit. Regarding technology.

In a vehicle such as a general automobile, the steering wheel and the steering device are mechanically connected, and both ends of the steering device are connected to the left and right wheels by tie rods. Therefore, the cutting angle of the left and right wheels due to the movement of the steering wheel is determined by the initial setting.
The geometry of the vehicle is (1) "parallel geometry" where the left and right wheels have the same cutting angle, and (2) the turning inner wheel wheel angle is cut larger than the turning outer wheel angle in order to have one turning center. Ackermann geometry is known.

Ackerman Geometry has a difference in steering angle between the left and right wheels so that each wheel turns around a common point in order to turn the vehicle smoothly when turning in a low speed range where the centrifugal force acting on the vehicle can be ignored. Is set. However, in high-speed turning where centrifugal force cannot be ignored, it is desirable that the wheels generate cornering force in a direction that balances with centrifugal force, so parallel geometry is preferable to Ackermann geometry.

As mentioned above, a typical vehicle steering device is mechanically connected to the wheels, so it can generally only take a single fixed steering geometry, somewhere between the Ackermann geometry and the parallel geometry. Often set to a typical geometry. However, in this case, the difference between the steering angles of the left and right wheels is insufficient in the low speed range, the steering angle of the outer wheels becomes excessive, and the steering angle of the inner wheels becomes excessive in the high speed range. If there is an unnecessary bias in the wheel lateral force distribution of the inner and outer wheels in this way, it causes deterioration of fuel efficiency due to deterioration of running resistance and premature wear of the tires, and the inner and outer wheels cannot be used efficiently, so that cornering smoothness is improved. There is a problem that it is damaged.

Therefore, the applicant has proposed a hub unit with an auxiliary steering function (Patent Document 4) that can perform auxiliary steering for each wheel according to the driving situation in addition to steering by operating the steering wheel of the driver. ..

Japanese Unexamined Patent Publication No. 2009-226972 German Patent Application Publication No. 1020122036337 Japanese Unexamined Patent Publication No. 2014-061744 JP-A-2019-006226

According to the proposals of Patent Documents 1 and 2, the steering geometry can be changed, but there are the following problems.
In Patent Document 1, the steering geometry is changed by relatively changing the positions of the knuckle arm and the joint, but a motor actuator that obtains a large force enough to change the geometry of the vehicle is provided in such a portion. Is very difficult due to space constraints. Further, the change in the wheel angle due to the change in the position of the knuckle arm and the joint is small, and in order to obtain a large effect, it is necessary to greatly change the position of the knuckle arm and the joint, that is, move it greatly.

In Patent Document 2, since two motors are used, not only the cost increases due to the increase in the number of motors, but also the control becomes complicated.
In Patent Document 3, since the hub bearing is cantilevered and supported with respect to the steering shaft, the rigidity is lowered, and the steering geometry may change due to the occurrence of excessive traveling G.
Further, when the reduction gear is provided on the steering shaft, the size including the motor becomes large. As the size of the motor or the like increases, it becomes difficult to arrange the entire motor on the inner peripheral portion of the wheel. Further, when a speed reducer having a large reduction ratio is provided, the responsiveness deteriorates.

As described above, the conventional mechanism provided with the auxiliary steering function is intended to arbitrarily change the toe angle or camber angle of the wheels in the vehicle, so that a plurality of motors and reduction mechanisms are required, which is a complicated configuration. It has become. In addition, it becomes difficult to secure the rigidity, and in order to secure the rigidity, it is necessary to increase the size and become heavy.
In addition, when the kingpin axis and the steering axis of the mechanism having the auxiliary steering function match, the overall size becomes large and heavy because the component parts are arranged behind the hub unit (on the vehicle body side). ..

Conventionally, in order to arbitrarily change the toe angle or camber angle of a wheel in a vehicle, a complicated configuration is required and the number of components is increased.
In order to accommodate a mechanism having an auxiliary steering function in a limited space in a wheel, miniaturization is required, and a structure in which the overall configuration is miniaturized (Patent Document 4) has been proposed.
In performing auxiliary steering in this structure, the hub bearing is steered around the steering axis by pushing and pulling the arm portion protruding from the hub bearing with the linear motion mechanism of the actuator. In this structure, the linear motion mechanism of the actuator moves linearly, whereas the arm portion rotates around the steering axis. Therefore, as the steering angle increases, the connection point of the arm portion moves linearly in the linear motion mechanism. It shifts from the top.

Therefore, in the hub unit with a steering function, the deviation between the linear motion and the locus of the rotary motion at the connection point between the linear motion mechanism of the actuator and the arm portion protruding from the hub bearing is absorbed, and the linear motion is smoothly converted into the rotary motion. There is a demand for a simple and inexpensive connection structure that can be converted.

In order to accommodate the mechanism having the steering function in the limited space in the wheel, it is necessary to reduce the overall configuration of the mechanism having the steering function, and there is a concern that the strength of each part may be insufficient. Further, the connecting portion between the linear motion mechanism and the arm portion, which directly receives a large impact force from the road surface, is easily affected, and ensuring strength and reliability is an issue.
Further, since the connecting portion always keeps fine operation, the lubricity is lowered, and there is a concern that premature wear or excessive temperature rise may occur, which may cause deterioration or abnormality of the function of the hub unit with steering function. ..

An object of the present invention is to provide a hub unit with a steering function capable of reducing the size of the entire hub unit and ensuring the strength and reliability of the connecting portion between the linear motion mechanism and the arm portion, and a vehicle provided with the hub unit. It is to be.

The hub unit with steering function of the present invention includes a hub unit body having a hub bearing that supports wheels, and a hub unit body.
A unit support member provided on the suspension frame component of the suspension device and rotatably supporting the hub unit body around the steering axis extending in the vertical direction.
A steering actuator for rotating the hub unit body around the center of the steering axis is provided.
The steering actuator has a motor and a linear motion mechanism that is connected to an arm portion provided on the hub unit main body and converts the rotational output of the motor into linear motion.
The linear motion mechanism and the arm portion are connected via a joint portion,
One of the tip portion and the joint portion of the linear motion mechanism is provided parallel to the steering axis, and the tip portion of the linear motion mechanism and the joint portion are axes parallel to the steering axis. The first connecting pin that can rotate around the center and
The joint portion and the arm portion are provided in parallel with the steering axis so that the joint portion and the arm portion can rotate around the axis parallel to the steering axis. With 2 connecting pins,
Wear prevention means are provided at the tip of the linear motion mechanism, the joint, the first and second connecting pins, and the arm.

According to this configuration, the linear motion mechanism of the steering actuator is steered by pushing and pulling the arm portion of the hub unit main body. At this time, the tip portion and the joint portion of the linear motion mechanism, and the joint portion and the arm portion can be rotated by the first and second connecting pins provided parallel to the steering axis, respectively, and the respective connecting portions. Are bendable to each other. By having two bending points, it is possible to absorb the deviation of the locus between the linear motion of the steering actuator and the rotational motion of the hub unit body. This makes it possible to smoothly convert the linear motion of the steering actuator into the rotary motion of the hub unit body. When the power transmission from the steering actuator to the steering becomes smooth, it becomes possible to reduce the power and size of the motor, reduce the load torque of the linear motion mechanism, and reduce the size of the entire hub unit, resulting in miniaturization, weight reduction, and energy saving of the entire hub unit. You can expect it.

By the way, when a tire or a wheel collides with an obstacle on the road surface such as riding on a curb during normal running of a vehicle, or when an excessively sharp turn occurs, a large impact force acts on the hub unit. In particular, when a lateral force acts on the ground contact surface of the tire with respect to the vehicle traveling direction, it is necessary for the connecting portion between the linear motion mechanism and the arm portion to support this force. Further, even during normal traveling, a turning force or a reaction force from the road surface is regularly and repeatedly input to the hub unit from various directions.
Then, if the power transmission from the steering actuator to the steering becomes smooth due to the above configuration, the entire hub unit can be miniaturized, but the surface pressure of the sliding contact portion such as the slide bearing portion increases due to the force acting on the hub unit. Therefore, it is important to ensure the impact resistance and fatigue strength of the sliding contact portion.

According to this configuration, since the tip portion of the linear motion mechanism, the joint portion, the first and second connecting pins, and the arm portion are provided with anti-wear means, they can withstand without preparing a complicated connecting structure. It is possible to improve the wear resistance and the fatigue strength. Further, as compared with a structure in which a rolling bearing or the like is used for the connecting portion between the linear motion mechanism and the arm portion, the size and weight of the entire hub unit can be reduced.

The wear prevention means may be a surface hardening treatment layer applied to at least a sliding contact portion of the tip portion of the linear motion mechanism, the joint portion, the first and second connecting pins, and the arm portion.
In this case, the surface hardness of the slip contact portion may be Hv550 or more and the core hardness may be Hv300 or less.

According to this configuration, at least the sliding contact portion of the tip portion, the joint portion, the first and second connecting pins and the arm portion of the linear motion mechanism has a surface hardness of Vickers hardness of Hv (Hv: Vickers hardness) of 550 or more. Therefore, it can withstand an impact load and improve wear resistance. Further, since the core hardness of the sliding contact portion is set to Hv300 or less, a high compressive residual stress exists on the surface layer of the sliding contact portion, and therefore, the fatigue strength can be improved. Further, since a sliding contact portion is adopted for the connecting portion between the linear motion mechanism and the arm portion, it is possible to reduce the size and weight of the entire hub unit as compared with the structure using a rolling bearing or the like. In this way, it is possible to reduce the size of the entire hub unit and secure the strength and reliability of the connecting portion between the linear motion mechanism and the arm portion.

The wear preventing means may include a grease reservoir for accumulating grease provided in a hole communicating with the sliding contact portion in the joint portion or the arm portion. In this case, since the grease held in the grease pool is supplied to the sliding contact portion, the durability of the connecting portion between the linear motion mechanism and the arm portion can be ensured. The grease pool is a space expanded to store grease.

The hole portion of the joint portion or the arm portion is formed in an elongated hole shape extending in a straight direction of the linear motion mechanism and in a direction orthogonal to the steering axis, respectively, and the portion having the elongated hole shape is the grease. It may be a puddle. In this case, the structure can be simplified and the cost can be reduced by using the elongated hole-shaped portion as a grease reservoir.

The gap between the joint portion or the hole portion of the arm portion may be allowed to occur in the locus of the linear motion and the rotational motion. In this case, the connecting pin can absorb the deviation of the locus of the straight motion and the rotary motion by moving in the hole portion having the elongated hole shape. Therefore, it is possible to realize a function of absorbing the deviation between the trajectories of the straight motion and the rotary motion with a simple structure and smoothly converting the linear motion into the rotary motion.

The steering system of the present invention is a steering system including a hub unit with a steering function having any of the above configurations of the present invention and a control device for controlling a steering actuator of the hub unit with a steering function. The control device drives the steering actuator by outputting a steering control unit 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 unit. It has an actuator drive control unit to control.

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 wheel angle can be arbitrarily changed in addition to the steering by the driver's steering wheel operation.

In the vehicle of the present invention, one or both of the front wheels and the rear wheels are supported by using the hub unit with a steering function having any of the above configurations of the present invention.
Therefore, the above-mentioned effects can be obtained for the hub unit with steering function of the present invention. The front wheels are generally regarded as steering wheels, but when the hub unit with a steering function of the present invention is applied to the steering wheels, it is effective for adjusting the toe angle during traveling. Further, the rear wheels are generally regarded as non-steering wheels, but when applied to non-steering wheels, the minimum turning radius at low speed can be reduced by slightly steering the non-steering wheels.

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 wheels and an undercarriage frame component of a suspension device, and rotates the hub unit main body around a steering axis extending in the vertical direction. A unit support member that freely supports the hub unit body and a steering actuator that rotates the hub unit body around the steering axis center are provided. The steering actuator includes a motor and an arm provided on the hub unit body. It has a linear motion mechanism that is connected to a portion and converts the rotational output of the motor into a linear motion, and the linear motion mechanism and the arm portion are connected via a joint portion, and the tip portion of the linear motion mechanism and the said A first joint portion is provided parallel to the steering axis so that the tip of the linear motion mechanism and the joint can rotate around an axis parallel to the steering axis. The connecting pin and either the joint portion or the arm portion are provided in parallel with the steering axis, and the joint portion and the arm portion rotate about an axis parallel to the steering axis. With a second connecting pin, which enables
Wear prevention means are provided at the tip of the linear motion mechanism, the joint, the first and second connecting pins, and the arm. Therefore, it is possible to reduce the size of the entire hub unit and secure the strength and reliability of the connecting portion between the linear motion mechanism and the arm portion.

The steering system of the present invention is a steering system including a hub unit with a steering function having any of the above configurations of the present invention and a control device for controlling a steering actuator of the hub unit with a steering function. The device drives and controls the steering actuator by outputting a steering control unit 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 unit. It has an actuator drive control unit. Therefore, it is possible to reduce the size of the entire hub unit and secure the strength and reliability of the connecting portion between the linear motion mechanism and the arm portion.

In the vehicle of the present invention, one or both of the front wheels and the rear wheels are supported by using the hub unit with a steering function having any of the above configurations of the present invention, so that the entire hub unit can be miniaturized and directly. The strength and reliability of the connecting portion between the moving mechanism and the arm portion can be ensured.

It is a vertical sectional view which shows the structure of the hub unit with a steering function which concerns on 1st Embodiment of this invention, and the periphery thereof. It is a horizontal 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 the 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. FIG. 5 is a sectional view taken along line VII-VII of FIG. It is an enlarged sectional view of the linear motion mechanism of the hub unit with a steering function. It is a partially enlarged view of the IX part of FIG. It is a partially enlarged view of the X part of FIG. 9 is a sectional view taken along line XI-XI of FIG. It is a schematic plan view of an example of a vehicle equipped with the hub unit with a steering function. It is a schematic plan view of another example of the vehicle provided with any of the hub units with steering functions. FIG. 3 is a schematic plan view of another example of a vehicle provided with any of the steering function hub units.

[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 12.
<Outline structure of hub unit with steering function>
As shown in FIG. 1, the hub unit 1 with a steering function includes a hub unit main body 2, a unit support member 3, a rotation allowable support component 4, and a steering actuator 5. A unit support member 3 is integrally provided with the knuckle 6, which is a suspension frame component. The actuator body 7 of the steering actuator 5 is provided on the inboard side of the unit support member 3, and the hub unit body 2 is provided on the outboard side of the unit support member 3. With the hub unit 1 with steering function 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 1 with a steering function may be simply referred to as a hub unit 1.

As shown in FIGS. 2 and 3, the hub unit main body 2 and the actuator main body 7 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. 1, the hub unit main body 2 is supported by the unit support member 3 via rotation allowable support parts 4 and 4 at two upper and lower positions so as to be rotatable around the steering axis A extending in the vertical direction. Has been done. The steering axis A is different from the rotation axis O of the wheel 9, and is also different from the kingpin axis that mainly performs steering. In a normal vehicle, the kingpin angle is set to 10 to 20 degrees for the purpose of improving the straight running stability of the vehicle, but the hub unit 1 with a steering function of this embodiment has an angle different from the kingpin angle. It has a (axis) steering shaft. The wheel 9 includes a wheel 9a and a tire 9b.

<Installation location of hub unit 1 with steering function>
In this embodiment, the hub unit 1 with a steering function is added to the steering of the steering wheels, specifically, the steering device 11 of the front wheels 9F of the vehicle 10, as shown in FIG. As a mechanism for steering (about ± 5 deg), it is integrally provided with the knuckle 6 of the suspension device 12.

As shown in FIGS. 2 and 12, the steering device 11 is attached to the vehicle body and is operated by the operation of the steering wheel 11a of the driver or a command of an automatic driving device or a driving support device (not shown), and the tie rods move forward and backward. 14 is connected to the steering coupling portion 6d (described later) of the unit support member 3. The steering device 11 is a rack and pinion type or the like, but any type of steering device may be used. For example, the suspension device 12 applies a strut type suspension mechanism that directly fixes the shock absorber to the knuckle 6, but a double wishbone type suspension mechanism, a multi-link type suspension mechanism, and other suspension mechanisms may be applied. ..

<About hub unit body 2>
As shown in FIG. 1, the hub unit main body 2 includes a hub bearing 15 for supporting the wheel 9, an outer ring 16, and an arm portion 17 (FIG. 3) which is a steering force receiving portion described later.
As shown in FIG. 6, 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, 19 and has a member on the vehicle body side and a wheel 9 (FIG. 6). It plays the role of connecting with 1).

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. 1, the 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 about the rotation axis O.

As shown in FIG. 6, the outer ring 16 has an annular portion 16a fitted to the outer peripheral surface of the outer ring 19 and a trunnion shaft-shaped steering shaft provided so as to project vertically from the outer circumference of the annular portion 16a. It has parts 16b and 16b. Each of the steering shaft portions 16b, which are the upper and lower mounting shaft portions, is provided coaxially with the steering axis A.

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 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, each rotation allowable support component 4 is composed of a rolling bearing. In this example, tapered roller bearings are applied as rolling bearings. The rolling bearing has an inner ring 4a fitted to the outer periphery of the steering 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 and 4b. ..

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

As shown in FIGS. 5 and 6, partial concave spherical fitting hole forming portions 3Aa are formed at the upper and lower portions of the outboard side ends of the unit support member main body 3A. The unit support member coupling 3B is fixed to the outboard side end of the unit support member main body 3A, and the fitting hole forming portions 3Aa and 3Ba are combined with each other at the upper and lower portions to form a fitting hole continuous on the entire circumference. It is formed. The outer ring 4b is fitted in this fitting hole. In FIG. 3, the unit support member 3 is represented by a alternate long and short dash line.

As shown in FIG. 6, each steering shaft portion 16b 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 4a, and a pressing force is applied to the end surface of the inner ring 4a by a bolt 23 screwed into the female screw portion to apply a preload to each rotation allowable support component 4. Giving. As a result, the rigidity of each rotation allowable support component 4 can be increased. As the rolling bearing of the rotation allowable support component 4, an angular contact ball bearing or a four-point contact ball bearing may be used instead of the tapered roller bearing. In that case as well, a preload can be applied in the same manner as described above.

As shown in FIG. 1, the upper and lower steering shaft portions 16b and 16b are supported by the unit support member 3 via the rotation allowable support parts 4 and 4, respectively, and each rotation allowable support component 4 is inside the wheel 9a of the wheel 9. Located in. In this example, each rotation allowable support component 4 is arranged in the wheel 9a near the middle in the width direction of the wheel 9a.

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 projects integrally with the outer ring 16 or a part of the outer circumference of the outer ring 19. .. The arm portion 17 is rotatably connected to the linear motion output portion 25a of the steering actuator 5 via the joint portion 8. As a result, the linear motion output unit 25a of the steering actuator 5 advances and retreats (straight motion), so that the hub unit main body 2 is rotated around the steering axis A, that is, auxiliary steering is performed.

<Steering actuator 5>
As shown in FIG. 3, the steering actuator 5 has an actuator body 7 that rotationally drives the hub unit body 2 around the steering axis A (FIG. 1).
As shown in FIG. 2, the actuator main body 7 includes a motor 26 as a rotation drive source for rotationally driving around the steering axis A, a speed reducer 27 for decelerating the rotation of the motor 26, and the forward and reverse of the speed reducer 27. It is provided with a linear motion mechanism 25 that converts the rotational output of the above into a reciprocating linear motion (that is, a reciprocating linear motion) of the linear motion output unit 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>
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 constitute a winding type speed reducer 27.

<About the linear motion mechanism 25>
As shown in FIGS. 2 and 8, the linear motion mechanism 25 can use a slide screw type feed screw mechanism such as a trapezoidal screw or a triangular screw. In this example, the feed screw mechanism using a trapezoidal screw slide screw is used. 33 is used. The linear motion mechanism 25 includes a feed screw mechanism 33, a rotary support bearing 28, a rotary fixing member 43 (FIG. 7), and an actuator case 34 which is a cover for covering these components.

The feed screw mechanism 33 has a nut portion 35 provided on the inner circumference of the driven pulley 27b, a screw shaft 36 arranged in a screwed state on the inner circumference of the nut portion 35, and a slide bearing 37. Grease is sealed inside the sliding screw. Since the nut portion 35 and the screw shaft 36 have thread grooves and threads forming the screw portion 38 of the trapezoidal screw, the effect of preventing reverse input from the tire can be enhanced. A slide bearing 37 through which the screw shaft 36 slidably penetrates is provided at one end of the nut portion 35 in the axial direction. The slide bearing 37 guides the axial movement of the screw shaft 36 and prevents a radial force from being applied to the screw portion 38 when an external force from the tire side is input to the screw shaft 36. ..

The rotary support bearing 28 rotationally supports the feed screw mechanism 33. As the rotary support bearing 28, in this example, two tapered roller bearings are combined in a front-to-face manner via a driven pulley 27b. The arrangement of these rotary support bearings 28, 28 may be either back-aligned or front-aligned, but the front-aligned arrangement is preferable in terms of ease of assembly and preload adjustment by shims and the like.

Each rotary support bearing 28 includes an outer ring 28a which is a fixed ring, an inner ring 28b which is a rotary ring, a plurality of rolling elements 28c interposed between the inner and outer rings 28b, 28a, and a cage 28d holding these rolling elements 28c. Has. Each inner ring 28b is fitted and fixed to the outer peripheral surface of the nut portion 35, and is regulated in the axial direction by the retaining rings 39 and 39. The outer ring 28a of the rotary support bearing 28 on the right side (outboard side) of FIG. 8 is fitted and fixed to the fitting hole 6bb in the case 6b, and the outer ring 28a of the rotary support bearing 28 on the left side (inboard side) of FIG. 8 is fitted and fixed. It is fitted and fixed to the inner peripheral surface of the actuator case 34 on the outboard side. With these rotary support bearings 28, 28, the driven pulley 27b and the nut portion 35 can rotate integrally. The rotary support bearing 28 may be an angular contact ball bearing. Also in this case, the rotation support bearings 28, 28 may be arranged in either the back surface alignment or the front surface alignment.

As shown in FIGS. 7 and 8, the rotary fixing member 43 detents the screw shaft 36. An output rod 40 is coaxially connected to the inboard side end, which is the rear end of the screw shaft 36. The output rod 40 has a bottomed substantially cylindrical screw shaft support member 40a that covers the inboard side end of the screw shaft 36. The screw shaft support member 40a is fixed to the actuator case 34 together with the screw shaft 36 by a plurality of (three in this example) axial rotation fixing members 43 extending in the radial direction. These rotary fixing members 43 extend radially and are arranged in a uniform circumference. For example, a pin or the like is applied as each rotation fixing member 43.

A slide bearing 46 is fitted on the outer circumference of each rotation fixing member 43. A guide groove 34a extending in the axial direction for guiding each slide bearing 46 is formed on the inner peripheral surface of the actuator case 34. Therefore, by sliding the rotary fixing member 43 along the guide groove 34a of the actuator case 34 via the slide bearing 46, the screw shaft 36 of the sliding screw can be reciprocated in the axial direction. Further, since the rotary fixing member 43 is slid via the slide bearing 46, wear of the sliding surface of the guide groove 34a is prevented. The slide bearing 46 may be made of a metal such as a copper alloy or a porous sintered alloy, or may be made of a resin such as a fluororesin.

<About the structure of the connecting part between the linear motion mechanism and the arm part>
As shown in FIGS. 8 and 9, the arm portion 17 is connected to the linear motion output portion 25a at the tip of the screw shaft 36 via the joint portion 8. The linear motion output unit 25a and the joint unit 8 can be rotated around the axis parallel to the steering axis A (FIG. 1) by the first connecting pin Pa. The joint portion 8 and the arm portion 17 can be rotated around the axis parallel to the steering axis A (FIG. 1) by the second connecting pin Pb. The first and second connecting pins Pa and Pb are parallel to the steering axis A (FIG. 1), respectively.

As shown in FIGS. 9 and 10, the joint portion 8 is coaxially connected to the cylindrical large diameter portion 8a and one end of the large diameter portion 8a in the axial direction, and is formed to have a smaller diameter than the large diameter portion 8a. It has a small diameter portion 8b, which is integrally molded. The large diameter portion 8a is formed with a fitting hole 8aa into which the tip end portion of the linear motion output portion 25a is fitted by a clearance fit from the other end in the axial direction of the large diameter portion 8a. A first connecting pin Pa is supported in parallel with the steering shaft in the through hole 8ab of the large diameter portion 8a. The joint portion between the large diameter portion 8a and the first connecting pin Pa constitutes the slide bearing B1. The portion Paa supported by the through hole 8ab on the outer peripheral surface of the through hole 8ab and the first connecting pin Pa corresponds to the sliding contact portion of the slide bearing B1.

The tip of the linear motion output portion 25a that fits into the fitting hole 8aa is connected to the first connecting pin Pa. The joint portion between the first connecting pin Pa and the tip end portion of the linear motion output portion 25a constitutes the slide bearing B2. A fitting hole h1 in which the outer peripheral surface of the first connecting pin Pa is fitted at the tip of the linear motion output portion 25a, and a portion supported by the fitting hole h1 on the outer peripheral surface of the first connecting pin Pa. The Pab corresponds to the sliding contact portion of the slide bearing B2. Retaining rings Tw for preventing the first connecting pin Pa from coming off are provided at both ends in the axial direction of the through hole 8ab of the large diameter portion 8a.

The arm portion 17 is formed with a through hole 17a into which the small diameter portion 8b of the joint portion 8 is fitted by gap fitting. Further, a second connecting pin Pb is supported in the through hole 17b of the arm portion 17 in parallel with the steering shaft. The joint portion between the arm portion 17 and the second connecting pin Pb constitutes the slide bearing B3. The portion Pba supported by the through hole 17b on the outer peripheral surface of the through hole 17b and the second connecting pin Pb corresponds to the sliding contact portion of the slide bearing B3.

A small diameter portion 8b that fits into the through hole 17a is connected to the second connecting pin Pb. The joint portion between the second connecting pin Pb and the small diameter portion 8b constitutes the slide bearing B4. The fitting hole h2 into which the outer peripheral surface of the second connecting pin Pb is fitted in the small diameter portion 8b, and the portion Pbb supported by the fitting hole h2 on the outer peripheral surface of the second connecting pin Pb are slipped. It corresponds to the sliding contact portion of the bearing B4. Retaining rings Tw for preventing the second connecting pin Pb from coming off are provided at both ends in the axial direction of the through hole 17b of the small diameter portion 8b. One or both of the first and second connecting pins Pa and Pb are clearance-fitted to the two members connected to each other, and the respective connecting portions are bendable (rotatable) to each other.

Therefore, the joint portion 8 is configured to be rotatable around the axial center parallel to the steering axis with respect to the linear motion output portion 25a within the clearance fitting range. The arm portion 17 is configured to be rotatable around the axis parallel to the steering axis with respect to the small diameter portion 8b within the clearance fitting range. Further, the fitting hole 8aa of the joint portion 8 and the through hole 17a of the arm portion 17 allow deviations that occur in the loci of the linear motion of the linear motion mechanism 25 (FIG. 2) and the rotational motion of the hub unit body 2 (FIG. 2). .. As a retaining ring for the connecting pins Pa and Pb, one of the first and second connecting pins Pa and Pb may be press-fitted to prevent the retaining ring Tw from coming off.

<About the force acting on the hub unit 1>
As shown in FIG. 2, when the tire 9b or the wheel 9a collides with an obstacle on the road surface, such as when the vehicle rides on a curb during normal running, or when an excessively sharp turn is made, a large impact force is applied to the hub unit 1. It works. In particular, when a lateral force (load F) acts on the ground contact surface of the tire 9b with respect to the vehicle traveling direction, it is necessary for the connecting portion between the linear motion mechanism 25 and the arm portion 17 to support this force. Further, even during normal traveling, a turning force or a reaction force from the road surface is regularly and repeatedly input to the hub unit 1 from various directions. Then, since the surface pressure of the above-mentioned sliding contact portion increases due to the force acting on the hub unit 1, it is important to secure the impact resistance and fatigue strength of the sliding contact portion.

<About surface hardening treatment, etc.>
Therefore, as shown in FIG. 10, wear prevention means Mb is provided on the tip portion of the linear motion output portion 25a, the joint portion 8, the first and second connecting pins Pa and Pb, and the arm portion 17. As the wear preventing means Mb, a surface hardening treatment layer Sf and a grease pool Gd described later are provided. The surface hardness of at least the sliding contact portion of the tip portion of the linear motion output portion 25a, the joint portion 8, the first and second connecting pins Pa and Pb, and the arm portion 17 is Hv (Hv: Vickers hardness) 550. The hardness of the core of the sliding contact portion was set to 230 or more and Hv300 or less. The tip portion of the linear motion output unit 25a refers to a portion of the linear motion output unit 25a that fits into the fitting hole 8aa.

Specifically, the tip portion of the linear motion output portion 25a, the joint portion 8, the first and second connecting pins Pa and Pb, and the arm portion 17 are each made of high carbon steel or hardened steel, and are surface-hardened, respectively. The surface hardening treatment layer Sf by the treatment is applied. By the surface hardening treatment, the surface hardness and the core hardness of the sliding contact portion are kept at desired Vickers hardness. As the surface hardening treatment, high frequency heat treatment, carburizing and quenching, gas soft nitriding, salt bath soft nitriding and the like can be adopted. When the high-frequency heat treatment is adopted, it is possible to apply surface hardening treatment only to the tip portion of the linear motion output portion 25a, the joint portion 8, the first and second connecting pins Pa and Pb, and the sliding contact portion of the arm portion 17. Is.

The depth of the cured layer of the surface-hardened layer Sf is appropriately set in consideration of the required impact resistance and fatigue strength according to the impact force acting on the hub unit 1 (FIG. 2) and the magnitude of the repeated load. Is desirable. In each component, the layer inside the surface hardening treatment layer Sf is referred to as the core portion, and the hardness in this core portion is referred to as the core portion hardness. For example, when verifying the core hardness of a connecting pin, the test piece after the surface hardening treatment is cut in a plane perpendicular to the axial direction, and the hardness of the core appearing on the cut surface is measured (for example, Vickers hardness test). Do. Similarly, for other parts, hardness measurement (for example, Vickers hardness test) is performed on the core portion appearing on the cut surface to verify the core hardness.

<About grease pool, etc.>
As shown in FIG. 11, in the large diameter portion 8a of the joint portion 8, the fitting hole 8aa into which the tip portion of the linear motion output portion 25a is fitted is a hole portion communicating with the sliding contact portion of the joint portion 8. The fitting hole 8aa is formed in an elongated hole shape extending in a straight direction of the linear motion mechanism 25 (FIG. 2) and in a direction orthogonal to the steering axis A (FIG. 1), and the portion having the elongated hole shape is formed. Grease pool Gd. Grease is stored in this grease pool Gd.

The upper and lower surfaces of the tip end portion of the linear motion output portion 25a are formed to have a so-called width across flats orthogonal to the axial direction of the first connecting pin Pa. Each portion of the fitting hole 8aa close to the upper and lower surfaces is formed substantially parallel to the width across flats, and suppresses the vertical movement of the joint portion 8 with respect to the tip end portion of the linear motion output portion 25a. By forming the fitting hole 8aa, which is the inner diameter portion of the joint portion 8, into the elongated hole shape as described above, the joint portion 8 is suppressed from moving in the vertical direction, and the shape also serves as a grease pool Gd. can do. As shown in FIG. 10, also in the arm portion 17, a grease reservoir Gd for accumulating grease is provided in the through hole (hole portion) 17a communicating with the sliding contact portion. By forming the through hole 17a into a long hole shape similar to that of the joint portion 8, the portion having the long hole shape can be a grease pool Gd.

As shown in FIG. 2, the actuator main body 7 including 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.
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 tubular shape, and is provided with a motor accommodating portion that supports the motor 26 and a linear motion mechanism accommodating portion that supports the linear motion mechanism 25. A fitting hole for supporting the motor 26 at a predetermined position in the case is formed in the motor accommodating portion. 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 linear motion output unit 25a to move forward and backward, and the like.

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

<Action effect>
According to the hub unit 1 with a steering function described above, the hub unit main body 2 including the hub bearing 15 that supports the wheels 9 can be freely rotated around the steering axis A by driving the actuator main body 7. .. This rotation is added to the steering by the driver's steering wheel operation, that is, is added to the rotation of the knuckle 6 around the kingpin axis by the steering device 11, and is performed as auxiliary steering, and one wheel can be independently steered. .. By making the auxiliary steering angles of the left and right wheels 9 and 9 different, the toe angle between the left and right wheels 9 and 9 can be arbitrarily changed.

Therefore, the hub unit 1 with a steering function may be used for either steering wheels such as front wheels or non-steering wheels such as rear wheels. When used for the steering wheel, by installing it on a member whose direction is changed by the steering device 11, the left and right wheels are individually or interlocked with the left and right wheels 9 in addition to steering by the driver's steering wheel operation. It becomes a mechanism to make a slight angle change of. Regarding the auxiliary steering angle, a slight angle is sufficient for improving the vehicle's kinetic performance and driving stability / safety, and even if the auxiliary steering angle is ± 5 degrees or less, it is sufficient. The angle of auxiliary steering is controlled by the steering actuator 5.

In addition, the difference in steering angle between the left and right wheels can be changed according to the traveling speed during turning. For example, the steering geometry can be changed during running, for example, the parallel geometry is used for turning in the high-speed range, and the Ackermann geometry is used for turning in the low-speed range. Since the wheel angle can be arbitrarily changed during traveling in this way, it is possible to improve the kinetic performance of the vehicle and to travel stably and safely. By appropriately changing the steering angles of the left and right steering wheels during turning, the turning radius of the vehicle can be reduced and the turning performance can be improved.
Furthermore, even during straight-line driving, by adjusting the amount of toe angle according to each situation, it is possible to make adjustments such as ensuring running stability at high speeds without lowering running resistance at low speeds and deteriorating fuel efficiency.

When the hub unit 1 with steering function is applied to the non-steering wheels which are the rear wheels 9R, if the steering angle is set to the same phase as the front wheels 9F during turning, the yaw generated during steering is suppressed and the stability of the vehicle is improved. be able to. By adjusting the toe angle independently on the left and right even when traveling straight, driving stability can be ensured.

The tip portion and joint portion 8 of the linear motion mechanism 25, and the joint portion 8 and arm portion 17 can be rotated by the first and second connecting pins Pa and Pb provided in parallel with the steering axis A, respectively. , Each connecting part is bendable to each other. By having the two bending points, it is possible to absorb the deviation of the locus between the linear motion of the steering actuator 5 and the rotational motion of the hub unit main body 2. As a result, the linear motion of the steering actuator 5 can be smoothly converted into the rotary motion of the hub unit main body 2. When the power transmission from the steering actuator 5 to the steering becomes smooth, the power saving and miniaturization of the motor 26, the load torque reduction and miniaturization of the linear motion mechanism 25 become possible, and the entire hub unit can be miniaturized and lightened. Energy saving can be expected.

Since the surface hardness of at least the sliding contact portion of the tip portion of the linear motion mechanism 25, the joint portion 8, the first and second connecting pins Pa and Pb, and the arm portion 17 is Hv550 or higher, it can withstand an impact load. Abrasion resistance can be improved. Further, since the core hardness of the sliding contact portion is set to Hv300 or less, a high compressive residual stress exists on the surface layer of the sliding contact portion, so that the fatigue strength can be improved. Further, since the sliding contact portion is adopted for the connecting portion between the linear motion mechanism 25 and the arm portion 17, it is possible to reduce the size and weight of the entire hub unit as compared with the structure using a rolling bearing or the like. In this way, it is possible to reduce the size of the entire hub unit and secure the strength and reliability of the connecting portion between the linear motion mechanism 25 and the arm portion 17.

Further, since the grease sump Gd for storing grease is provided in the holes communicating with the slip contact portion in the joint portion 8 and the arm portion 17, the grease held in the grease sump Gd is supplied to the slip contact portion. , The durability of the connecting portion between the linear motion mechanism 25 and the arm portion 17 can be ensured.

<About other embodiments>
In the following description, the same reference numerals will be given to the parts corresponding to the matters previously described in each embodiment, and duplicate description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described above unless otherwise specified. It has the same effect from the same configuration. In addition to the combination of the parts specifically described in each embodiment, it is also possible to partially combine the embodiments as long as the combination does not cause any trouble.

<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. 13, in a vehicle with front wheel steering, the suspension frame component 6R serving as a wheel bearing installation portion of the suspension device 12R supporting the rear wheel 9R may be set and used for rear wheel steering.
Others As shown in FIG. 14, the hub unit 1 with a steering function may be used for the left and right front wheels 9F and 9F which are steering wheels and the left and right rear wheels 9R and 9R which are non-steering wheels, respectively.

<About the steering system>
As shown in FIG. 3, this steering system includes a hub unit 1 with a steering function according to any one 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. The steering control unit 30 outputs a current command signal corresponding to the auxiliary steering angle command signal (steering angle command signal) given from 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. The actuator drive control unit 31 drives and controls the steering actuator 5 by outputting a current corresponding to the current command signal input from the steering control unit 30. 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 wheel can be slightly changed in angle in addition to steering by the driver's steering wheel operation. Even when traveling 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 and 5 by commands of an automatic driving device, a driving support device, etc. (not shown) instead of operating the steering wheel of the driver.
The lubricant for the sliding contact portion of the joint portion 8 and the arm portion 17 is not limited to grease, and may be a solid lubricant provided in the grease reservoir Gd or the like.
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 limiting. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 ... Hub unit with steering function, 2 ... Hub unit body, 3 ... Unit support member, 5 ... Steering actuator, 6 ... Knuckle (suspension frame parts), 8 ... Joint part, 9 ... Wheels, 9F ... Front wheels, 9R ... Rear wheel, 12, 12R ... Suspension device, 15 ... Hub bearing, 17 ... Arm part, 25 ... Linear mechanism, 26 ... Motor, 29 ... Control device, 30 ... Steering control unit, 31 ... Actuator drive control unit, Gd ... Grease pool, Mb ... Wear prevention means, Pa, Pb ... 1st and 2nd connecting pins

Claims (8)

A hub unit body with hub bearings that support the wheels,
A unit support member provided on the suspension frame component of the suspension device and rotatably supporting the hub unit body around the steering axis extending in the vertical direction.
A steering actuator for rotating the hub unit body around the center of the steering axis is provided.
The steering actuator has a motor and a linear motion mechanism that is connected to an arm portion provided on the hub unit main body and converts the rotational output of the motor into linear motion.
The linear motion mechanism and the arm portion are connected via a joint portion,
One of the tip portion and the joint portion of the linear motion mechanism is provided parallel to the steering axis, and the tip portion of the linear motion mechanism and the joint portion are axes parallel to the steering axis. The first connecting pin that can rotate around the center and
The joint portion and the arm portion are provided in parallel with the steering axis so that the joint portion and the arm portion can rotate around the axis parallel to the steering axis. With 2 connecting pins,
A hub unit with a steering function provided with wear prevention means at the tip of the linear motion mechanism, the joint, the first and second connecting pins, and the arm. In the hub unit with a steering function according to claim 1, the wear prevention means is applied to at least a sliding contact portion of the tip portion of the linear motion mechanism, the joint portion, the first and second connecting pins, and the arm portion. Hub unit with steering function, which is a surface hardening treatment layer that has been applied. The hub unit with a steering function according to claim 2, wherein the sliding contact portion has a surface hardness of Hv550 or more and a core hardness of Hv300 or less. In the hub unit with a steering function according to any one of claims 1 to 3, the wear prevention means is provided in a hole portion of the joint portion or the arm portion that communicates with the sliding contact portion. , Hub unit with steering function including grease pool to store grease. In the hub unit with a steering function according to claim 4, the hole portion of the joint portion or the arm portion has an elongated hole shape extending in a direction orthogonal to the linear motion mechanism and the steering axis. A hub unit with a steering function in which the formed portion having an elongated hole shape is used as the grease pool. The hub unit with a steering function according to claim 5, wherein the hole portion of the joint portion or the arm portion allows a deviation that occurs in the locus of the straight motion and the rotary motion. 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. A steering system with an actuator drive control unit. A vehicle in which one or both of the front wheels and the rear wheels are supported by using the hub unit with a steering function according to any one of claims 1 to 6.

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