Turning mechanism, steering system and vehicle

Abstract

To provide a turning mechanism that can accomplish a cost reduction.SOLUTION: A turning mechanism includes a steering-function-added hub unit and a follower-side hub unit. The steering-function-added hub unit includes: a first hub unit main body that includes a hub bearing which rotatably supports a wheel; a first unit support member which is provided at the underbody frame component of a suspension device, and which supports the first hub unit main body so as to be freely rotatable around a first turning axis; and a steering actuator that includes a motor which rotates and drives the first hub unit main body around the first turning axis. The follower-side hub unit includes: a second hub unit main body that includes a hub bearing which rotatably supports a wheel; and a second unit support member which is provided at the underbody frame component of the suspension device, and which supports the second hub unit main body so as to be freely rotatable around a second turning axis. The steering actuator and the second hub unit main body are coupled to each other via a linkage mechanism, and the second hub unit main body is rotated and driven around the second turning axis by the motor of the steering actuator.SELECTED DRAWING: Figure 6A

Description

[Technical Field]

[0001] The present invention relates to a steering mechanism including a hub unit with a steering function, and a steering system and a vehicle in which the steering mechanism is used. [Background technology]

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

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

[0004] As mentioned above, because the steering device of a typical vehicle is mechanically connected to the wheels, it is generally only capable of using a single fixed steering geometry, and is often set to a geometry somewhere between the Ackermann geometry and the parallel geometry. However, in this case, the difference in steering angle between the left and right wheels is insufficient at low speeds, resulting in an excessive steering angle for the outer wheel, and at high speeds, the steering angle for the inner wheel is excessive. If there is an unnecessary imbalance in the distribution of wheel lateral force between the inner and outer wheels, this can lead to increased running resistance, resulting in poor fuel economy and early tire wear, and the inefficient use of the inner and outer wheels can impair smooth cornering. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7037315 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, an electric actuator having an electric motor for each of the left and right wheels of the vehicle is used as the steering actuator, for a total of two. The electric actuator is made up of many parts such as a motor, a reducer, and a trapezoidal screw (ball screw), so the cost can become high if there are a large number of parts.

[0007] An object of the present invention is to provide a steering mechanism, a steering system, and a vehicle that can be reduced in cost. [Means for solving the problem]

[0008] The steering mechanism of the present invention, and the steering system and vehicle using this steering mechanism basically control the steering angles of left and right wheels to appropriate angles according to driving conditions using a steering actuator included in the steering mechanism, thereby improving fuel efficiency and enhancing driving stability and reliability. The steering mechanism, steering system, and vehicle of the present invention generally include a hub unit with a steering function having a steering actuator on one of the left and right wheels, and a driven hub unit (without a power mechanism such as an actuator or electric motor) on the other wheel, which is steered by the steering actuator via a link mechanism. This makes it possible to steer both left and right wheels with a single steering actuator, thereby reducing costs. Each hub unit is steered, for example, by a steering actuator about a steering axis different from the so-called kingpin axis. The steering mechanism and steering system of the present invention can be used, for example, to control the steering angle of front wheels in addition to the operation of the steering device, but are preferably used to control the steering angle of rear wheels.

[0009] The steering mechanism of the present invention comprises: a hub unit with a steering function, the hub unit including: a first hub unit body having a hub bearing that supports rotation of a wheel; a first unit support member that is provided on an underbody frame component of a suspension system and supports the first hub unit body rotatably about a first steering axis that extends in the vertical direction; and a steering actuator that includes a motor that rotationally drives the first hub unit body about the first steering axis; a driven-side hub unit including a second hub unit body having a hub bearing that supports the rotation of a wheel, and a second unit support member that is provided on an underbody frame component of a suspension system and supports the second hub unit body rotatably about a second steering axis that extends in the vertical direction; A steering mechanism including: The steering actuator and the second hub unit main body are connected by a link mechanism, The second hub unit body is rotationally driven about the second steering axis by the motor of the steering actuator via the link mechanism.

[0010] According to this configuration, in the steering mechanism, the steering function-equipped hub unit is equipped with the steering actuator including the motor that rotationally drives the first hub unit body about the first steering axis, and the driven-side hub unit has the second hub unit body, and the steering actuator and the second hub unit body are connected by the link mechanism, and the motor of the steering actuator drives the second hub unit body to rotationally drive about the second steering axis via the link mechanism. Therefore, it is possible to steer the left and right wheels with just one steering actuator or motor, enabling size and cost reductions.

[0011] The steering actuator may include a reducer that reduces the rotational speed of the motor and a linear motion mechanism that converts the rotational output of the reducer into linear motion. This allows the steering actuator to be an electromechanical conversion device capable of linear motion. Note that a trapezoidal screw may be used for the linear motion mechanism.

[0012] the first unit support member has a first bearing that supports the first hub unit body rotatably about the first steering axis, the second unit support member has a second bearing that supports the second hub unit body rotatably about the second steering axis, The first bearing and the second bearing may be located within the axial width of the tire wheel. This structure eliminates the need to place the steering function-equipped hub unit and the driven-side hub unit of the steering mechanism on the underside of the vehicle, where space is limited.

[0013] The steering system of the present invention is a steering system including a steering mechanism having any of the above configurations of the present invention and a control device that controls the steering actuator of the steering function-equipped hub unit, The control device has a steering control unit that outputs a current command signal in accordance with a given steering angle command signal, and an actuator drive control unit that outputs a current in accordance with the current command signal input from the steering control unit to drive and control the steering actuator.

[0014] According to this configuration, the steering control unit outputs a current command signal corresponding to the steering angle command signal provided thereto. The actuator drive control unit outputs a current corresponding to the current command signal input from the steering control unit to drive and control the steering actuator. Therefore, it is possible to provide a specific configuration that can arbitrarily change the wheel angle in addition to the steering performed by the driver operating the steering wheel.

[0015] In a vehicle of the present invention, the wheels are supported using a steering mechanism of any of the above configurations of the present invention, in which the suspension type is a rigid axle suspension. Therefore, in a vehicle equipped with such a suspension, the effects described above for the steering mechanism of the present invention are achieved. Front wheels are generally steered, and applying the steering mechanism of the present invention to the steered wheels is effective for adjusting the toe angle while driving. Rear wheels are generally non-steered, and applying the steering mechanism of the present invention to the non-steered wheels can reduce the minimum turning radius at low speeds and improve vehicle stability at high speeds by slightly steering the non-steered wheels. [Effects of the Invention]

[0016] The steering mechanism, steering system, and vehicle of the present invention can be made at low cost. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view showing the appearance of a steering function-equipped hub unit used in a steering mechanism according to one embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the steering function-equipped hub unit. [Figure 3] FIG. 2 is a horizontal cross-sectional view of the steering function-equipped hub unit. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5] FIG. 4 is a vertical cross-sectional view of a steering actuator of the steering function-equipped hub unit. [Figure 6A] 10 is a plan view showing a steering mechanism in which the steering function-equipped hub unit and a driven-side hub unit are connected by a link mechanism. FIG. [Figure 6B] FIG. 4 is a side view showing the connection of the link mechanism in detail. [Figure 7] FIG. 2 is a schematic plan view of a vehicle equipped with the steering mechanism. [Figure 8] FIG. 10 is a schematic plan view of another example of a vehicle equipped with the steering mechanism. [Figure 9] FIG. 10 is a schematic plan view of another example of a vehicle equipped with the steering mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0018] [First embodiment] A steering mechanism according to an embodiment of the present invention, a steering function-equipped hub unit included therein, and a steering system and a vehicle will be described with reference to FIGS. 1 to 9. Here, a driven-side hub unit 1' (described below) included in the steering mechanism HUS (FIG. 6A) and connected to the steering function-equipped hub unit 1 of FIG. 1 by a link mechanism LNK (described below) has the same structure, action, etc. as the steering function-equipped hub unit 1, except for the steering actuator 5 and related structures and their actions, etc. (described below). In other words, by replacing the configuration of "first..." in the steering function-equipped hub unit 1 with "second...", a person skilled in the art can conceive of each configuration, etc. of the driven-side hub unit 1', excluding the steering actuator 5 and related structures. Therefore, a description of the configuration, etc. included in the driven-side hub unit 1' will be omitted unless otherwise specified. Furthermore, the symbols for each component of the driven side hub unit 1' are the symbols for the corresponding components in the steering function hub unit 1 with an "'" added, similar to the relationship between the symbols for the steering function hub unit "1" and the symbols for the driven side hub unit "1'".

[0019] <Overall configuration of hub unit with steering function> FIG. 1 shows an overall external view of a steering function-equipped hub unit 1 when applied to a rear wheel. FIG. 2 is a view of the steering function-equipped hub unit 1 of FIG. 1 as seen from the front direction on the outside of the wheel. FIG. 3 is a view of FIG. 1 as seen from above perpendicular to the axle. FIG. 4 is a view showing a cross section taken along line IV-IV of FIG. 2. As shown in FIG. 1, this steering function-equipped hub unit 1 basically comprises a (first) hub unit body 2, a (first) unit support member 3, and a steering actuator 5. In this embodiment, the steering function-equipped hub unit 1 has the function of steering left and right rear wheels 9R, 9R supported by a torsion beam suspension 12R (or suspension system SUS) as shown in FIG. 7 in conjunction with each other, and is applied to the rear wheels 9R, 9R of a vehicle 10 with front wheel steering. The suspension system SUS is not limited to a torsion beam suspension, and other suspensions such as a strut suspension, a rigid axle suspension, or a multi-link suspension can be applied.

[0020] The steering function-equipped hub unit 1 is capable of steering the left and right front wheels 9F, 9F by operating the handlebars 11a, etc., and also steering the left and right rear wheels 9R, 9R in a linked left-right manner by a small angle (approximately ±5 degrees) (steering by the steering function-equipped hub unit 1 or the steering mechanism HUS is also called auxiliary steering). That is, the driver operates the steering angle of the wheels using the handlebars 11a, but in addition, the host control unit 32 of the vehicle as shown in FIG. 1 outputs steering angle command signals for the left and right wheels in accordance with the vehicle's situation to perform auxiliary steering. However, depending on the vehicle control requirements, the steering function-equipped hub unit 1 may individually adopt a relatively large angle, such as 10° to 20°, rather than the small angle. Here, for example, auxiliary steering by this steering mechanism or steering system can be used to control the steering angle of the front wheels in addition to a steering device having the handlebars 11a, as described below, but is preferably used to control the steering angle of the rear wheels.

[0021] More specifically, in this embodiment, the steering function-equipped hub unit 1 is comprised of a (first) hub unit body 2 having a hub bearing that supports the rotation of a wheel; a (first) unit support member 3 that is attached to an undercarriage frame component of a suspension system (for example, integrated with a knuckle) and supports the first hub unit body 2 rotatably about a first steering axis A; and a steering actuator 5 including a motor that drives the (first) hub unit body 2 to rotate about the first steering axis A (described below). Here, in this embodiment, as described below, the steering actuator 5 is fixed to the unit support member 3, and the hub unit body 2 and the output rod of the steering actuator 5 are connected by a joint. Although not shown in FIG. 1 etc., a boot is usually attached around this joint for waterproofing and dustproofing. Furthermore, a vehicle steering device that operates when the driver operates the steering wheel is attached to the vehicle body and connected to a vehicle steering device joint of the unit support member 3 by a tie rod.

[0022] <Unit support members, etc.> The unit support members 3 of FIG. 1 are attached to both the left and right sides of the suspension device 12R as shown in FIG. 7. The unit support members 3 are made of, for example, a flat plate-shaped member. A steering actuator 5 is provided on the inboard side of the unit support member 3, and the hub unit main body 2 is provided on the outboard side of the unit support member 3. When the hub unit 1 with steering function is mounted on a vehicle, the outside of the vehicle in the vehicle width direction is referred to as the outboard side, and the center of the vehicle in the vehicle width direction is referred to as the inboard side. Note that the hub unit 1 with steering function may also be simply referred to as the hub unit 1.

[0023] As shown in Figure 3, the hub unit body 2 and the steering actuator 5 are connected by a joint 8 such as a ball joint. Usually, a boot Bt is attached to this joint 8 for waterproofing and dustproofing.

[0024] <Hub unit body> As shown in FIGS. 1 and 4, the hub unit body 2 is supported by the unit support member 3 at two upper and lower locations via rotation support members 4, 4 so as to be rotatable about a (first) steering axis A that is perpendicular to the rotation axis O of the wheel (or tire wheel) 9 and extends in the vertical direction. As shown in FIGS. 2 and 4, the hub unit body 2 includes a hub bearing 15 that rotationally supports the wheel 9, upper and lower steering shaft portions 16b, 16b, and an arm portion 17 that serves as a steering force receiving portion. As shown in FIG. 4, the hub bearing 15 includes an inner ring 18, an outer ring 19, rolling elements 20 such as balls interposed between the inner and outer rings 18, 19, and a cage (not shown) that holds the rolling elements 20. The hub bearing 15 connects the wheel 9 to a member on the vehicle body side and allows the wheel 9 to rotate smoothly. Here, the first hub unit body 2 is supported by the first unit support member 3 via a first bearing, which is a rotation-permitting support component, so as to be rotatable about the first steering axis A that extends in the vertical direction. Additionally, the second hub unit body 2' is supported by the second unit support member 3' via a second bearing, which is a rotation-permitting support component, so as to be rotatable about a second steering axis A' extending in the vertical direction. As shown in FIG. 4, the first bearing and second bearing are positioned within the axial width of the tire wheel 9. Here, the axial direction refers to the direction of the rotation axis O of the tire wheel 9. This makes it possible to reduce the energy required for steering.

[0025] This hub bearing 15 is an angular contact ball bearing in which the outer ring 19 is a fixed ring, the inner ring 18 is a rotating ring, and the rolling elements 20 are double-row. The inner ring 18 has a hub flange 18aa and a hub ring portion 18a that forms the outboard side raceway, and an inner ring portion 18b that forms the inboard side raceway. The wheel 9 of the wheel is bolted to the hub flange 18aa in a state where it overlaps with the brake rotor. The inner ring 18 rotates around the rotation axis O.

[0026] The upper and lower steering shafts 16b, 16b shown in FIG. 4 are trunnion-shape shafts that protrude upward and downward from the outer periphery of the outer ring 19. In this example, the upper and lower steering shafts 16b, 16b are integrally formed with the outer ring 19. The phrase "integrally formed" means that the steering shafts 16b and the outer ring 19 are not formed by combining multiple elements but are formed as part of a single object from a single material by, for example, forging or machining. The steering shafts 16b, 16b may be trunnion-shape shafts that have an annular portion fitted to the outer peripheral surface of the outer ring 19 and protrude upward and downward from the outer periphery of this annular portion. The outer ring 19 may be an integrally molded product, but for convenience and ease of manufacturing, it may also be composed of the upper and lower steering shafts 16b, 16b and an outer ring portion OTR located on the inner diameter side thereof.

[0027] As shown in Figure 2, a brake 21, which is a braking device that brakes the wheels, has a brake rotor and a brake caliper. The brake caliper is attached to two brake caliper attachment parts 22, one at the top and one at the bottom. As shown in Figure 3, the two brake caliper attachment parts 22, one at the top and one at the bottom, are provided in arm-like shapes that protrude from the inboard end of the outer peripheral surface of the outer wheel 19. Therefore, the hub bearing 15 and the brake caliper attachment parts 22 are steered together.

[0028] <Rotational support members, etc.> 4, each of the rotation support members (rotation-allowing support parts) 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 fitted onto the outer periphery of the steered shaft portion 16b, an outer ring fitted onto the retaining member Bh, and multiple rolling elements interposed between the inner and outer rings.

[0029] The upper and lower steered shaft portions 16b, 16b are supported by the unit support member 3 via the pair of upper and lower rotation support members 4, 4 that fit into bearing fitting recesses 13, 13 of upper and lower holding members Bh, Bh provided on the unit support member 3. Each holding member Bh has a substantially cylindrical holding member main body portion Bb into which the outer peripheral surface of the outer ring fits.

[0030] As shown in Figures 1 and 4, the upper and lower holding members Bh, Bh are provided with a pair of beams Bm, Bm that connect the upper and lower holding member main bodies Bb, Bb to each other. Each beam Bm extends vertically, with its upper longitudinal end fastened to a threaded portion of the upper holding member main body Bb with a bolt 33 and its lower longitudinal end fastened to a threaded portion of the lower holding member main body Bb with a bolt 33. This can further increase the rigidity of the steered shaft 16b. As described above, each rotation support member 4 is located within the wheel 9 of the vehicle wheel. In this example, each rotation support member 4 is located within the wheel, near the center in the width direction of the wheel.

[0031] As shown in Figure 4, each steering shaft portion 16b is formed with an internal thread portion extending along the steering axis A, and a bolt 23 is provided that screws into this internal thread portion. The bolt 23 is a flanged bolt 23, and by screwing into the internal thread portion with the flange abutting against the end face of the inner ring of the rotation support member 4, a pressing force can be applied to the end face of the inner ring. This applies a preload to each rotation support member 4, thereby increasing the rigidity of each rotation support member 4. It is set so that the initial preload will not be released even when the weight of the vehicle acts on this hub unit 1.

[0032] The rotation support members 4 are not limited to tapered roller bearings, and other types of bearings such as angular contact ball bearings and spherical plain bearings can also be used depending on the maximum load and other operating conditions. In these cases, preload can be applied in the same manner as above. Alternatively, preload can be applied to each rotation support member 4 by interposing a disk-shaped pressing member (not shown) between the head of a flangeless bolt and the end face of the inner ring, and applying pressing force to the end face of the inner ring with the bolt screwed into the female thread.

[0033] <Steering actuator> The steering actuator 5 includes a rotational drive source that rotates the hub unit main body 2 around the steering axis A. As shown in Figure 5, the steering actuator 5 includes a motor 26 that is the rotational drive source, a 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 reducer 27 into reciprocating linear motion of an output rod 25a. The reducer 27 or the linear motion mechanism 25 is a rotational mechanism portion that is connected to the motor shaft 26a of the motor 26.

[0034] <Motor> The motor 26 is, for example, a permanent magnet synchronous motor, but may also be a DC motor or an induction motor. The motor 26 includes a motor case 34, a portion of a case base plate 35 facing the motor case 34, rolling bearings 36, 36, a motor shaft 26a, a rotor 26b, and a stator 26c. As shown in FIGS. 1 and 3, the motor case 34 is fixed to the inboard side of the unit support member 3 with a portion of the case base plate 35 fitted thereto. As shown in FIG. 5, the motor case 34 is formed in a cylindrical shape with a bottom, and the open end on the outboard side is closed by the case base plate 35. The open end of the motor case 34 and the mating surface of the case base plate 35 facing this open end are positioned relative to each other by pins 37 and fixed with bolts 39.

[0035] Rolling bearings 36, 36 are rotatably supported at a predetermined distance inside the motor case 34, and the motor shaft 26a is fitted and fixed to each inner ring of the rolling bearings 36, 36. Each rolling bearing 36 may be, for example, a deep groove ball bearing. A stator 26c is fixed inside the motor case 34. A rotor 26b is provided radially inward of the stator 26c with a predetermined radial gap therebetween, and the rotor 26b is fitted and fixed to the outer periphery of the motor shaft 26a. Here, the "radial direction" refers to a direction perpendicular to the rotational axis C1 of the motor shaft 26a, and the "radial inward direction" refers to a direction approaching the rotational axis C1. The case base 35 may be provided with an opening Ha (FIG. 1) that allows the motor shaft 26a shown in FIG. 5 to be directly and mechanically rotated. A cap Cp (FIG. 1) may be detachably provided in the opening Ha to prevent foreign matter from entering from the outside.

[0036] <Reducer> As shown in Fig. 5, the reducer 27 can be a wrap-type transmission mechanism such as a belt transmission mechanism or a gear train, and in the example of Fig. 5, a belt transmission mechanism is used. The reducer 27 is a parallel-shaft type reducer having a drive pulley 27a, a driven pulley 27b, and a belt 27c wound around these pulleys 27a and 27b. The drive pulley 27a is connected to the motor shaft 26a of the motor 26, and the driven pulley 27b is provided on a nut portion 25c (described later) of the linear motion mechanism 25. The driven pulley 27b is disposed parallel to the motor shaft 26a.

[0037] The reducer 27 is disposed on the outer side in the vehicle width direction of the vehicle than a rotation support portion 28, which will be described later. The driving force of the motor 26 is transmitted from the drive pulley 27a to the driven pulley 27b via a belt 27c. The drive pulley 27a, the driven pulley 27b, and the belt 27c constitute a wrap-type reducer 27. The steering actuator 5 of this embodiment is constituted by the motor 26, the reducer 27, and the linear motion mechanism 25, but the reducer 27 may be omitted in some cases.

[0038] <Linear motion mechanism> The linear motion mechanism 25 can use a feed screw mechanism such as a sliding screw, or a rack and pinion mechanism, and in this example, a trapezoidal sliding screw feed screw mechanism 38 is used. The linear motion mechanism 25 includes the feed screw mechanism 38, the rotation support portion 28, the rotation fixing member 43, a preload applying means 45, case segments 40 and 41 that cover these components, and a portion of the case base plate 35 that faces the case segment 40. A through hole Hb that allows the output rod 25a and the joint portion 8 to move back and forth is formed in the portion of the case base plate 35 that faces the case segment 40. The entire case base plate 35, the case segments 40 and 41, and the motor case 34 described above form the case of the steering actuator 5.

[0039] Case segments 40 and 41 are provided in sequence on the inboard side of case base plate 35. The outboard open end of case segment 40, located axially intermediate, is closed by case base plate 35. Here, the axial direction refers to the longitudinal center axis of output rod 25a. The outboard open end of case segment 40 and the mating surface of case base plate 35 facing this open end are positioned relative to each other by pin 37 and then secured together by bolts 39 (FIG. 1). The inboard open end 40a of case segment 40 and the open end 41a of case segment 41 facing this open end 40a are countersunk, and both case segments 40 and 41 are secured together by bolts 42.

[0040] The feed screw mechanism 38 includes a nut portion 25c to which a driven pulley 27b is fastened, a threaded shaft 25A threadedly disposed on the inner periphery of the nut portion 25c, and a plain bearing 47. Grease, a lubricant, is sealed inside the plain screw. The nut portion 25c and the threaded shaft 25A have a screw groove and threads that form the trapezoidal thread, which effectively prevents reverse input from the tire. Plain bearings 47, 47 are provided at both axial ends of the nut portion 25c, through which the output rod 25a of the threaded shaft 25A slidably passes. These plain bearings 47, 47 guide the axial movement of the threaded shaft 25A and prevent radial and moment forces from being applied to the plain screw when an external force from the tire is input to the threaded shaft 25A.

[0041] The outer periphery of the nut portion 25c is formed with a large diameter portion, a small diameter portion, and a male thread portion, successively from the outboard side to the inboard side. The small diameter portion is connected to the large diameter portion via a step portion. The driven pulley 27b is fixed to the large diameter portion of the nut portion 25c, for example, by fitting, and a rotation support portion 28 that supports the rotation of the nut portion 25c is fitted and fixed to the small diameter portion of the nut portion 25c. The rotation support portion 28 is disposed on the inboard side of the reducer 27, including the driven pulley 27b.

[0042] In this example, the rotation support portion 28 is a pair of tapered roller bearings 28a, 28a assembled 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 threaded onto the male thread portion of the nut portion 25c. Each tapered roller bearing 28a has an outer ring which is a fixed ring, an inner ring which is a rotating ring, multiple rolling elements interposed between the inner and outer rings, and a cage which holds these rolling elements. Each of the inner rings is fitted and fixed to the small diameter portion of the nut portion 25c, and a spacer 50 is arranged between the inner rings in the small diameter portion. Each of the outer rings is fitted and fixed to the case segment 40.

[0043] The preload applying means 45 includes a spacer 50 disposed between the inner rings and a nut 49 threaded onto the male thread portion, and applies a preload to the rotation support portion 28. An appropriate preload can be applied by adjusting the spacer width, which is the axial dimension of the spacer 50. The outboard end face of the outboard side inner ring abuts the stepped portion of the nut portion 25c, and the inboard end face of the inboard side inner ring abuts the nut 49, and the nut 49 is tightened to the male thread portion in this state, thereby applying a preload to the rotation support portion 28. This can increase the rigidity of the rotation support portion 28.

[0044] 3, the rotation fixing member 43 is a shaft-shaped member that prevents the output rod 25a from rotating relative to the unit support member 3. This rotation fixing member 43 is fitted and fixed to the inboard end of the output rod 25a in a penetrating manner so as to extend in a direction perpendicular to the axial direction of the output rod 25a. Annular plain bearings 51, 51, for example, are fitted into both axial ends of the outer periphery of the rotation fixing member 43.

[0045] A guide groove with a rectangular cross section is formed in case segment 41, and the guide groove includes a guide surface that guides the outer peripheral surfaces of plain bearings 51 along the axial direction of screw shaft 25A. In other words, rotation fixed member 43 slidably contacts the guide surface of case segment 41, which is a fixed part of linear motion mechanism 25, via plain bearings 51. By sliding rotation fixed member 43 along the rectangular cross section guide groove of case segment 41 via plain bearings 51, output rod 25a can be reciprocated in the axial direction.

[0046] The steering actuator 5, which includes the motor 26, reducer 27 (FIG. 5), and linear motion mechanism 25 shown in FIG. 1, is assembled as a sub-assembly and is detachably attached to the unit support member 3 with bolts 44 or the like. As shown in FIG. 3, the unit support member 3 is formed with a through-hole that allows the output rod 25a and the joint portion 8 to move back and forth. Note that although a feed screw mechanism 38 using a sliding screw of a trapezoidal screw is shown as the linear motion mechanism 25, a linear motion mechanism using a ball screw (not shown) may also be used.

[0047] <Sensors, etc.> In order to control the steering angle of the wheels more accurately, it is necessary to know, for example, the rotation angle of the motor 26 in FIG. 5 or the axial position of the screw shaft 25A of the linear motion mechanism 25. Therefore, the hub unit 1 is provided with one or both of the following position sensors and angle sensors (also called "rotation sensors"). As shown in FIG. 3, the position sensor 52 is provided, for example, in the case segment 41 and detects the axial position of the screw shaft 25A of the linear motion mechanism 25. The position sensor 52 is capable of detecting the amount of axial movement of the output rod 25a and outputting the result as a position sensor value. Various types of sensors can be used for the position sensor 52, such as magnetic, optical, and capacitance sensors, but in this embodiment, a magnetic sensor is used.

[0048] A position sensor 52 is fixed to a substrate 53 fixed within the case segment 41. A position sensor measurement target Tg is provided at one axial end of the rotating fixed member 43. A permanent magnet, for example, is used as the position sensor measurement target Tg. The position sensor 52 faces the path along which the position sensor measurement target Tg advances and retreats. When the output rod 25a is at a predetermined axial position (advance / retreat position), the position sensor 52 and the position sensor measurement target Tg face each other across a predetermined gap. The position sensor 52 reads changes in the magnetic field of the permanent magnet that accompany the advance / retreat of the output rod 25a, and detects the advance / retreat position of the output rod 25a. The predetermined gap is a gap that is arbitrarily determined by design or the like, and is determined by, for example, determining an appropriate gap through testing and / or simulation.

[0049] 5, the angle sensor Sa that detects the rotation angle of the motor 26 has, for example, a detection target portion Saa fixed to the inboard end of the motor shaft 26a, and a sensor portion Sab that is fixed to the motor case 34 across a predetermined axial gap from the detection target portion Saa and detects the detection target portion Saa. For example, a resolver is used as the angle sensor Sa.

[0050] As shown in FIG. 6A, the steering mechanism HUS of this embodiment includes the above-mentioned (e.g., left) steering function-equipped hub unit 1 and a (e.g., right) driven-side hub unit 1' that has the same structure, operation, etc. as the steering function-equipped hub unit 1 except for the steering actuator 5 and related structure. The steering actuator 5 and second hub unit body 2' are connected by a link mechanism LNK engaged with a ball joint 60, and the second hub unit body 2' is rotationally driven about the second steering axis A' via the link mechanism LNK by the motor 26 of the steering actuator 5. The ball joint 60 is disposed behind the output rod 25a of the steering actuator 5 (FIGS. 3 and 5). Specifically, the ball joint 60 of the output rod 25a is engaged with one end of the link mechanism LNK in FIG. 6B, and the arm portion 17' of the second hub unit body 2' is engaged with a ball joint 60' disposed at the other end of the link mechanism LNK. In this way, the hub units 1, 1' attached to the left and right are connected by the link mechanism LNK, so that the arm sections 17, 17' move in accordance with the linear forward and backward movement of the output rod 25a of the steering actuator 5, and the left and right rear wheel tires can be controlled at the same angle.

[0051] In more detail, a motor drive current is output to the motor 26 of the steering actuator 5, which changes (for example, slightly) the angle of the hub unit body 2 relative to the unit support member 3, and the hub unit with steering function for the right wheel (or left wheel) and the driven-side hub unit for the left wheel (or right wheel) are linked via a link mechanism to perform auxiliary steering on both wheels, thereby improving maneuverability and fuel economy. The link mechanism LNK is provided, for example, in a form that moves linearly along the longitudinal direction of the suspension device SUS and penetrates the suspension device SUS in the longitudinal direction. The link mechanism LNK may be shaped like a long, straight rod, or may be shaped like a rod with both ends bent in the same direction relative to the longitudinal direction.

[0052] <Action and effect> As explained above, by using the steering actuator 5 in only one of the hub units (hub unit 1 with steering function) for either the left or right wheel, and steering the other hub unit (driven-side hub unit 1') by the steering actuator 5 via the link mechanism LNK, the steering mechanism HUS can be configured simply and compactly, and it is possible to reduce the size and / or cost. In this regard, first, the hub unit 1 with steering function in FIG. 1 includes a first hub unit body 2 having a hub bearing 15 that supports the wheel for rotation, a first unit support member 3, and the steering actuator 5, and the first hub unit body 2 is supported by the first unit support member 3 via the first bearing, which is a rotation-permitting support part, so as to be rotatable about a first steering axis A that extends in the vertical direction. In other words, with the hub unit 1 with steering function, the hub unit body 2 including the hub bearing 15 that supports the wheel for rotation can be freely rotated about the steering axis A by driving the steering actuator 5.

[0053] Meanwhile, by driving the output rod of the steering actuator 5 to move back and forth by the motor 26, not only does it rotate the first hub unit body 2 engaged with the output rod, but it also rotates the second hub unit body 2' connected to the link mechanism LNK engaged with the output rod via the arm portion 17'. More specifically, in the above-mentioned steering mechanism HUS, the driven-side hub unit 1', which includes a second hub unit body having a hub bearing that rotationally supports the wheel and a second unit support member, is connected between the steering actuator 5 and the second hub unit body by the link mechanism LNK, so that the second hub unit body is rotationally driven about the second steering axis via the link mechanism LNK. The second hub unit body 2' is supported by the second unit support member 3' via a second bearing, which is a rotation-permitting support part, so as to be rotatable about the second steering axis A' extending in the vertical direction. By operating steering actuator 5, the first hub unit body having hub bearing 15 can be freely rotated within a certain range around first steering axis A, and the second hub unit body having hub bearing 15' can be freely rotated within a certain range around second steering axis A'. Therefore, for example, the toe angle of the wheels can be changed as desired depending on the driving conditions of the vehicle.

[0054] When the steering mechanism HUS including this steering function-equipped hub unit 1 and driven-side hub unit 1' is applied to the front wheels, as shown in Figure 8, the front wheels 9F are steered together with the knuckles 6 and the unit support member 3 of Figure 1 by the driver operating the steering wheel 11a through the steering device 11, but in addition to this steering, a steering operation (auxiliary steering) of a slight angle about the steering axis A can be performed in conjunction with the left and right wheels. Regarding the angle of the auxiliary steering, a small angle is sufficient to improve the vehicle's maneuverability and driving stability, and although an angle of ±5 degrees or less for the auxiliary steering possible angle is sufficient, it may also be around 10 to 20 degrees. The angle of the auxiliary steering is controlled by the steering actuator 5.

[0055] Furthermore, when cornering, the steering angle difference between the left and right wheels may be changed depending on the vehicle speed by providing a predetermined configuration to the steering mechanism HUS. For example, the steering geometry may be changed while the vehicle is traveling, such as using parallel geometry when cornering at high speeds and Ackermann geometry when cornering at low speeds. If the wheel angle can be freely changed while traveling in this way, the vehicle's maneuverability can be improved and the vehicle can travel more stably. Furthermore, by appropriately changing the steering angle of the left and right wheels, the vehicle's turning radius can be reduced during cornering, improving its maneuverability. Furthermore, if the toe angle can be adjusted to suit each situation during straight-line driving, adjustments can be made, such as pointing the tires straight at low speeds to reduce resistance and avoid a deterioration in fuel efficiency, and toeing the tires in at high speeds to ensure driving stability.

[0056] When the configuration of this hub unit 1 with steering function is applied to the rear wheels as shown in Figure 7, the hub unit as a whole does not steer, but the auxiliary steering function allows the left and right wheels to be steered slightly in the same way as the front wheels, in conjunction with each other. By making the steering angle of the rear wheels the same phase as the front wheels, the yaw that occurs during steering can be suppressed, improving vehicle stability. Furthermore, by adjusting the toe angle in conjunction with the left and right wheels even when driving in a straight line, it is possible to improve fuel efficiency and ensure driving stability. In order to control the vehicle behavior in this way, it is necessary to accurately control the wheel steering angle, and in the event of an abnormality, it is necessary to return the wheel steering angle to an angle that allows driving. However, in the event of a power failure or an abnormality in the electrical system such as the motor or sensor, the wheel angle cannot be returned to its original angle.

[0057] In this embodiment, it is conceivable that an abnormality in the electrical system of the steering actuator 5 may cause the hub unit 1 to stop at an angle that makes it difficult to drive. In such a case, the motor shaft 26a (Fig. 5) can be rotated directly from the outside, manually, through an opening Ha provided in the case of the steering actuator 5, without jacking up the wheels. This returns the toe angle, which is the angle of the hub unit 1, to an angle near 0 degrees that allows driving, ensuring the driving performance of the vehicle. This allows the vehicle to move under its own power to a safe location.

[0058] <Examples of vehicle installation of steering function hub units other than those listed above> As an example of installation other than that shown in FIG. 7, as described above using FIG. 8, in a front-wheel-steering vehicle, the driven-side hub unit 1' and steering-function hub unit 1 included in the steering mechanism HUS 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) of the steering-function hub unit 1 is provided integrally with or separately from the knuckle (suspension frame part) 6 of the suspension 12 (or suspension SUS). The steering axis A of the steering-function hub unit 1 and the steering axis A' of the driven-side hub unit 1' in FIG. 6A are different from the kingpin axes that perform the main steering. In a normal vehicle, the kingpin angle is set at 10 to 20 degrees to improve the straight-line stability of the vehicle, but the steering-function hub unit 1 of this embodiment has a steering axis at an angle (axis) different from the kingpin angle.

[0059] As shown in FIG. 9, the driven-side hub unit 1' and steering-capable hub unit 1 included in the steering mechanism HUS may be used for the left and right front wheels 9F, 9F, which are steered wheels, and the left and right rear wheels 9R, 9R, which are non-steered wheels, respectively. In this case, the unit support member 3 (FIG. 1) of the steering-capable hub unit 1 is provided integrally with or separately from the knuckles (suspension frame components) 6 of the suspension 12 and suspension 12R (suspension SUS). Even in this case, the steering axis A of the steering-capable hub unit 1 and the steering axis A' of the driven-side hub unit 1' in FIG. 6A are different from the kingpin axes that perform the main steering. In a normal vehicle, the kingpin angle is set at 10 to 20 degrees to improve the straight-line stability of the vehicle, but the steering-capable hub unit 1 of this embodiment has a steering axis at an angle (axis) different from the kingpin angle.

[0060] <About the steering system> 1, this steering system includes a steering mechanism HUS including a hub unit with steering function 1, and a control device 29 that controls the steering actuator 5 of this hub unit with steering function 1. 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 an auxiliary steering angle command signal (steering angle command signal) given from a higher-level control section 32.

[0061] The upper control unit 32 is a control means higher than the steering control unit 30, and an electric control unit (Vehicle Control Unit, abbreviated as VCU) that controls the entire vehicle may be used as the upper control unit 32. The actuator drive control unit 31 outputs a current corresponding to a current command signal input from the steering control unit 30 to drive and control the steering actuator 5. The actuator drive control unit 31 controls the power supplied to the coil of the motor 26. For example, the actuator drive control unit 31 forms a half-bridge circuit using switching elements (not shown) and performs PWM control to determine the voltage applied to the motor based on the ON-OFF duty ratio of the switching elements. This allows the wheel angle to be changed minutely in addition to the steering performed by the driver's steering operation. Even when driving in a straight line, the toe angle can be adjusted to suit each situation.

[0062] The steering system may operate the steering actuator in response to commands from an automatic driving device or a driving assistance device (not shown), instead of the driver operating the steering wheel. The hub unit with steering function of the present invention can be applied to both driving wheels and driven wheels. Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] REFERENCE SIGNS LIST 1...hub unit with steering function, 1'...driven-side hub unit, 2...first hub unit body, 2'...second hub unit body, 3...first unit support member, 3'...second unit support member, 5...steering actuator, 6...knuckle (suspension frame part), 9...wheel (tire wheel), 9F...front wheel, 9R...rear wheel, 10...vehicle, 12, 12R, SUS...suspension device, 15, 15'...hub bearing, 21...brake (braking device), 25...linear motion mechanism (rotation mechanism part), 26...motor, 26a...motor shaft, 27...reduction gear (rotation mechanism part), 29...control device, 30...steering control part, 31...actuator drive control part, A...first steering axis, A'...second steering axis, HUS...steering mechanism, LNK...link mechanism

Claims

1. a hub unit with a steering function, comprising: a first hub unit body having a hub bearing that supports a wheel for rotation; a first unit support member that is provided on an underbody frame component of a suspension system and supports the first hub unit body for rotation about a first steering axis that extends in the vertical direction; and a steering actuator that includes a motor that drives the first hub unit body to rotate about the first steering axis; a driven-side hub unit including a second hub unit body having a hub bearing that supports the rotation of a wheel, and a second unit support member that is provided on an underbody frame component of a suspension system and supports the second hub unit body rotatably about a second steering axis that extends in the vertical direction; A steering mechanism including: The steering actuator and the second hub unit main body are connected by a link mechanism, The second hub unit body is rotationally driven about the second steering axis by the motor of the steering actuator via the link mechanism. Steering mechanism.

2. 2. The steering mechanism according to claim 1, The steering actuator has a reducer that reduces the rotation speed of the motor, and a linear motion mechanism that converts the rotation output of the reducer into linear motion. Steering mechanism.

3. 3. The steering mechanism according to claim 2, A trapezoidal screw is used for the linear motion mechanism. Steering mechanism.

4. 2. The steering mechanism according to claim 1, the first unit support member has a first bearing that supports the first hub unit body rotatably about the first steering axis, the second unit support member has a second bearing that supports the second hub unit body rotatably about the second steering axis, The first bearing and the second bearing are located within a range of the axial width of the tire wheel. Steering mechanism.

5. A steering system comprising the steering mechanism according to any one of claims 1 to 4 and a control device that controls the steering actuator of the steering function-equipped hub unit, The control device is a steering system having a steering control unit that outputs a current command signal in accordance with a given steering angle command signal, and an actuator drive control unit that outputs a current in accordance with the current command signal input from the steering control unit to drive and control the steering actuator.

6. 5. A vehicle having wheels supported by the steering mechanism according to claim 1, wherein the suspension system is a rigid axle suspension.

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