Hub unit with steering function and vehicle

Abstract

To provide a hub unit with a steering function and a vehicle that are able to secure the traveling performance of the vehicle by returning the angle of the hub unit to a travelable angle when the hub unit stops at a difficult-to-travel angle due to an anomaly or the like in a steering actuator.SOLUTION: A hub unit 1 with a steering function includes: a hub unit body 2 having a hub bearing 15 that rotatably supports a wheel; a unit support member 3 that is provided in a chassis frame component of a suspension system and by which the hub unit main body 2 is rotatably supported about a turning axis A extending in a vertical direction; and a steering actuator 5 including a motor 26 that rotationally drives the hub unit body 2 about the turning axis A. A case of the steering actuator 5 is provided with an opening Ha through which a motor shaft of a motor 26 is directly rotatable.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hub unit with steering function and a vehicle, and to a technique for improving fuel efficiency and improving stability and reliability of driving performance by controlling the steering angles of left and right wheels to appropriate angles according to driving conditions. [Background technology]

[0002] In general automobiles and other vehicles, the steering wheel and 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 turning angle of the left and right wheels in response to the movement of the steering wheel is determined by the initial setting. There are two types of vehicle geometries 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 angle of the inside wheel is turned larger than the angle of the outside wheel in order to have a single turning center.

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

[0004] As mentioned above, the steering device of a typical vehicle is mechanically connected to the wheels, so that it can only have a single fixed steering geometry, and is often set to an intermediate geometry between the Ackermann geometry and the parallel geometry. However, in this case, the steering angle difference between the left and right wheels is insufficient at low speeds, resulting in an excessive steering angle of the outer wheel, and at high speeds, the steering angle of the inner wheel is excessive. If there is an unnecessary imbalance in the wheel lateral force distribution between the inner and outer wheels in this way, it can cause a deterioration in fuel efficiency and early tire wear due to an increase in running resistance, and also cause problems such as a loss of smooth cornering because the inner and outer wheels cannot be used efficiently. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3477889 Summary of the Invention [Problem to be solved by the invention]

[0006] The rear wheel steering device of Patent Document 1 is equipped with a means for cutting off the power supplied to the electric motor drive means for steering when an abnormality occurs. In this case, the actuator stops at the time when the abnormality occurs, regardless of the toe angles of the front and rear wheels. When the toe angle is such that it becomes difficult to drive the vehicle after the system is stopped, it is desirable to return the toe angle to near 0 degrees. However, because a trapezoidal screw is used in the actuator section to prevent reverse input from outside, the toe angle cannot be changed mechanically from outside.

[0007] An object of the present invention is to provide a hub unit with steering function and a vehicle that can return the angle of the hub unit to an angle at which driving is possible and ensure the driving performance of the vehicle when the hub unit stops at an angle at which driving is difficult due to an abnormality in the steering actuator, etc. [Means for solving the problem]

[0008] The hub unit with steering function of the present invention is a hub unit including a hub unit body having a hub bearing that supports a wheel for rotation, a unit support member that is provided on a suspension frame component for supporting the hub unit body for rotation about a steering axis extending in a vertical direction, and a steering actuator including a motor that drives the hub unit body to rotate about the steering axis, An opening is provided in a case of the steering actuator so that the motor shaft of the motor or a rotation mechanism connected to the motor shaft can be directly rotated.

[0009] According to this configuration, when the hub unit stops at an angle where driving is difficult due to an abnormality in the steering actuator, the motor shaft or the rotation mechanism connected to this motor shaft can be directly rotated from the outside through an opening provided in the case of the steering actuator. This makes it possible to return the toe angle, which is the angle of the hub unit, to an angle at which driving is possible, and ensure the driving performance of the vehicle. This makes it possible for the vehicle to move under its own power to a safe place.

[0010] The opening of the case may be provided on the outer diameter side of a braking device that brakes the wheel. The braking device is a disk brake, a drum brake, or the like. In this case, even when a tire is mounted on the hub unit, it is possible to easily rotate the motor shaft or the rotating mechanism from the outside through the opening of the case without interfering with the braking device or the like. Therefore, operability can be improved while ensuring the running performance of the vehicle.

[0011] The opening may be provided on the inboard side of the case. In this case, even when a tire is mounted on the hub unit, the motor shaft or the rotation mechanism can be easily rotated from the outside through the opening provided on the inboard side of the case without interfering with a braking device or the like.

[0012] The opening may be located at least on an extension of the motor shaft center in the case, in which case the motor shaft can be directly mechanically rotated from the outside through the opening of the case.

[0013] The motor shaft may have a slot at the end of its output shaft for rotating the motor shaft. In this case, the motor shaft can be directly rotated mechanically from the outside using a tool such as a flat-head screwdriver.

[0014] The steering actuator may have a reducer that reduces the rotation of the motor and a linear motion mechanism that converts the rotation output of the reducer into linear motion, and the rotation mechanism may be the reducer or the linear motion mechanism. In this way, the toe angle can be returned to an angle at which driving is possible by directly and mechanically rotating not only the motor shaft but also the reducer or the linear motion mechanism.

[0015] The steering system of the present invention is a steering system comprising a hub unit with a steering function of any of the above-mentioned configurations of the present invention, and a control device that controls the steering actuator of the hub unit with a steering function, wherein the control device has a steering control unit that outputs a current command signal corresponding to a given steering angle command signal, and an actuator drive control unit that outputs a current corresponding to the current command signal input from the steering control unit to drive and control the steering actuator.

[0016] According to this configuration, the steering control unit outputs a current command signal corresponding to the steering angle command signal provided. 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, the wheel angle can be arbitrarily changed in addition to the steering by the driver's steering wheel operation.

[0017] In the vehicle of the present invention, either or both of the front and rear wheels are supported using a steering hub unit of the present invention having any of the above configurations. Therefore, the effects described above for the steering hub unit of the present invention can be obtained. The front wheels are generally considered to be steered wheels, and when the steering hub unit of the present invention is applied to the steering wheels, it is effective for adjusting the toe angle while traveling. The rear wheels are generally considered to be non-steered wheels, and when applied to the non-steered wheels, slight steering of the non-steered wheels can reduce the minimum turning radius when traveling at low speeds and improve vehicle stability when traveling at high speeds. Effect of the Invention

[0018] In the hub unit with steering function of the present invention, an opening is provided in the case of the steering actuator that allows the motor shaft of the motor or the rotation mechanism connected to this motor shaft to be directly rotated. Therefore, if the hub unit stops at an angle that makes it difficult to drive due to an abnormality in the steering actuator, the angle of the hub unit can be returned to an angle at which driving is possible through the opening in the case, ensuring the driving performance of the vehicle. [Brief description of the drawings]

[0019] [Figure 1] 1 is a perspective view showing the appearance of a steering function-equipped hub unit according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a side view of the steering function-equipped hub unit. [Diagram 3] FIG. 4 is a horizontal 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. [Diagram 5] FIG. 4 is a vertical sectional view of a steering actuator of the steering function-equipped hub unit. [Figure 6A] FIG. 2 is a front view of a motor of the steering actuator. [Figure 6B] FIG. [Figure 7] FIG. 11 is a side view of a steering function-equipped hub unit according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a vertical cross-sectional view of a steering actuator of a steering function-equipped hub unit according to a third embodiment of the present invention. [Figure 9A] FIG. 11 is a vertical cross-sectional view of a steering actuator of a steering function-equipped hub unit according to a fourth embodiment of the present invention. [Figure 9B] FIG. 13 is a vertical cross-sectional view of a steering actuator of a steering function-equipped hub unit according to a fifth embodiment of the present invention. [Figure 10] 1 is a schematic plan view of a vehicle equipped with a steering function-equipped hub unit according to any one of the embodiments of the present invention. [Figure 11] FIG. 11 is a schematic plan view of another example of a vehicle equipped with a steering function-equipped hub unit according to any one of the embodiments of the present invention. [Figure 12] FIG. 11 is a schematic plan view of another example of a vehicle equipped with a steering function-equipped hub unit according to any one of the embodiments of the present invention. [Figure 13] FIG. 11 is a schematic plan view of another example of a vehicle equipped with a steering function-equipped hub unit according to any one of the embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [First embodiment] A steering function-equipped hub unit according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6B and 10. FIG. <Overall configuration of hub unit with steering function> As shown in Fig. 1, this hub unit with steering function 1 includes a hub unit main body 2, a unit support member 3, and a steering actuator 5. As shown in Fig. 10, in this embodiment, the hub unit with steering function 1 has a function of independently steering each of the left and right rear wheels 9R, 9R supported by a torsion beam suspension device 12R, and is applied to the rear wheels 9R, 9R of a vehicle 10 with front wheel steering. The suspension device is not limited to a torsion beam suspension, and other suspensions such as a multi-link suspension can be applied.

[0021] The steering function-equipped hub unit 1 can steer the left and right rear wheels 9R, 9R independently at a small angle (approximately ±5 degrees) in addition to steering the left and right front wheels 9F, 9F by operating the handlebars 11a, etc. However, in the steering function-equipped hub unit 1, depending on the vehicle control requirements, the left and right wheels may each take a relatively large angle, such as 10° to 20°, rather than the small angle.

[0022] <Unit support parts, etc.> As shown in Figures 1 and 10, a unit support member 3 is attached to each of the left and right sides of the suspension device 12R. The unit support member 3 is 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 a hub unit body 2 is provided on the outboard side of the unit support member 3. When the steering function-equipped hub unit 1 is mounted on a vehicle, the outer side in the vehicle width direction is referred to as the outboard side, and the center side in the vehicle width direction is referred to as the inboard side. Note that the steering function-equipped hub unit 1 may be simply referred to as the hub unit 1.

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

[0024] <Hub unit body> As shown in Figures 1 and 4, the hub unit body 2 is supported by the unit support member 3 via rotation support members 4, 4 at two upper and lower points so as to be freely rotatable around a steering axis A that is perpendicular to the rotation axis O of the wheel 9 and extends in the vertical direction. 2 and 4, the hub unit body 2 includes a hub bearing 15 that supports the rotation of the wheel 9, upper and lower steering shaft portions 16b, 16b, and an arm portion 17 that receives steering force. 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, and connects a member on the vehicle body side to the wheel 9, allowing the wheel 9 to rotate smoothly.

[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 surface, and an inner ring portion 18b that forms the inboard side raceway surface. The wheel of the wheel 9 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 shaft portions 16b, 16b are trunnion shaft-shaped and protrude upward and downward from the outer periphery of the outer ring 19. In this example, the upper and lower steering shaft portions 16b, 16b are formed integrally with the outer ring 19. The term "integrally formed" means that the steering shaft portions 16b and the outer ring 19 are not formed by combining a plurality of elements but are formed as part of a single object from a single material by, for example, forging or machining. Alternatively, the steering shaft portions 16b, 16b may be provided with a circular ring portion fitted to the outer peripheral surface of the outer ring 19, and may be trunnion-shape steering shaft portions 16b, 16b protruding upward and downward from the outer periphery of the circular ring portion.

[0027] As shown in Fig. 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 above and one below. As shown in Fig. 3, the two brake caliper attachment parts 22, one above and one below, are provided in an arm-like shape protruding from the inboard end of the outer peripheral surface of the outer wheel 19. Therefore, the hub bearing 15 and the brake caliper attachment part 22 steer together.

[0028] <Rotational support parts, etc.> 4, each rotation support member 4 is a rolling bearing, and in this example, a tapered roller bearing is used as the rolling bearing. The rolling bearing has an inner ring fitted to the outer periphery of the steered shaft portion 16b, an outer ring fitted to the retaining member Bh, and a plurality of 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 which respectively 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 circumferential surface of the outer ring is fitted.

[0030] As shown in Fig. 1 and Fig. 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 body parts Bb, Bb to each other. Each beam Bm extends in the vertical direction, with its upper end in the longitudinal direction fastened to the threaded part of the upper holding member main body part Bb by a bolt 33, and its lower end in the longitudinal direction fastened to the threaded part of the lower holding member main body part Bb by a bolt 33. This can further increase the rigidity of the steered shaft part 16b. Each rotation support member 4 is located within the wheel of the wheel 9. In this example, each rotation support member 4 is located within the wheel, near the middle in the width direction of the wheel.

[0031] As shown in Fig. 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 to screw into this internal thread portion. The bolt 23 is a flanged bolt 23, and can apply a pressing force to the end face of the inner ring by screwing into the internal thread portion with the flange abutting the end face of the inner ring of the rotation support member 4. 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 be used depending on the maximum load and other operating conditions. In this case, preload can be applied in the same manner as described above. Preload can also 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 body 2 around the steering axis A. As shown in Fig. 5, the steering actuator 5 includes a motor 26 that is a rotational drive source, a reduction gear 27 that reduces the speed of the rotation of the motor 26, and a linear motion mechanism 25 that converts the forward and reverse rotational output of the reduction gear 27 into a reciprocating linear motion of an output rod 25a. The reduction gear 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 type synchronous motor, but may be a DC motor or an induction motor. The motor 26 has 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 in a state where a portion of the case base plate 35 is fitted thereto. As shown in Fig. 5, the motor case 34 is formed in a bottomed cylindrical shape, and an 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 the open end are fixed to each other by a bolt 39 while being positioned relative to each other by a pin 37.

[0035] Inside the motor case 34, rolling bearings 36, 36 are rotatably supported at a predetermined interval, and the motor shaft 26a is fitted and fixed to each inner ring, which is the rotating ring of these rolling bearings 36, 36. For example, a deep groove ball bearing is used as each rolling bearing 36. Inside the motor case 34, a stator 26c is fixed. 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.

[0036] The case substrate 35 is provided with an opening Ha through which the motor shaft 26a can be directly rotated. Specifically, the opening Ha, which is a round hole, is located on at least an extension line of the motor axis C1 in the case substrate 35. The diameter of the opening Ha is formed to be approximately the same as the diameter of the output shaft tip of the motor shaft 26a. As shown in Figs. 6A and 6B, a slot Sp for rotating the motor shaft 26a is provided at the output shaft tip of the motor shaft 26a. This allows the motor shaft 26a to be directly and mechanically rotated from the outside through the opening Ha in Fig. 5 using a tool such as a flathead screwdriver. As shown in Fig. 1, the opening Ha of the case substrate 35 is provided with a cap Cp that prevents foreign matter from entering from the outside and is detachable. Normally, the cap Cp is attached to the opening Ha, and the cap Cp of the opening Ha is removed when the motor shaft 26a (Fig. 5) is directly and mechanically rotated.

[0037] <Reducer> As shown in Fig. 5, the reducer 27 may 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 the pulleys 27a and 27b. The drive pulley 27a is coupled 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.

[0038] The reduction gear 27 is disposed on the outer side in the vehicle width direction of the vehicle than a rotation support portion 28 described later. The driving force of the motor 26 is transmitted from the drive pulley 27a to the driven pulley 27b via a belt 27c. The drive pulley 27a, the driven pulley 27b, and the belt 27c constitute a wrap-around type reduction gear 27.

[0039] <Linear motion mechanism> The linear motion mechanism 25 may be a feed screw mechanism such as a sliding screw or a rack and pinion mechanism, and in this example, a feed screw mechanism 38 of a sliding screw type trapezoidal screw is used. The linear motion mechanism 25 includes the feed screw mechanism 38, the rotation support section 28, the rotation fixing member 43, the preload applying means 45, the case halves 40 and 41 which cover these components, and a portion of the case base plate 35 which faces the case halves 40. A through hole Hb which allows the output rod 25a and the joint section 8 to move forward and backward is formed in the portion of the case base plate 35 which faces the case halves 40. The entire case base plate 35, the case halves 40 and 41, and the motor case 34 described above form a case for the steering actuator 5.

[0040] Case sections 40, 41 are provided in sequence on the inboard side of case base plate 35. The outboard opening end of case section 40, located in the axial middle, is closed by case base plate 35. The outboard opening end of case section 40 and the mating surface of case base plate 35 facing this opening end are fixed together by bolts 39 (FIG. 1) while being positioned relative to each other by pins 37. Both case sections 40, 41 are fixed together by bolts 42 with an inboard opening end 40a of case section 40 and an opening end 41a of case section 41 facing opening end 40a being countersunk into each other.

[0041] The feed screw mechanism 38 has a nut portion 25c to which a driven pulley 27b is fastened, a screw shaft 25A arranged in a screw-engaged state on the inner periphery of the nut portion 25c, and a sliding bearing 47. Grease, which is a lubricant, is sealed inside the sliding screw. The nut portion 25c and the screw shaft 25A have a screw groove and a screw thread that constitute the trapezoidal screw, so that the effect of preventing reverse input from the tire of the wheel can be enhanced. Slide bearings 47, 47 through which the output rod 25a of the screw shaft 25A slidably penetrates are provided at both axial ends of the nut portion 25c. These slide bearings 47, 47 guide the axial movement of the screw shaft 25A and prevent radial and moment forces from being loaded on the sliding screw when an external force from the tire side is input to the screw shaft 25A.

[0042] The outer periphery of the nut portion 25c is formed with a large diameter portion, a small diameter portion, and a male thread portion in that order 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 by, for example, fitting, and a rotation support portion 28 that supports the nut portion 25c for rotation 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.

[0043] In this example, a pair of tapered roller bearings 28a, 28a are assembled back to back as the rotation support portion 28. The inner peripheral surface of the driven pulley 27b may be fixed to the large diameter portion of the nut portion 25c via a key (not shown). A nut 49 is screwed onto the male 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, a plurality of 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 disposed between the inner rings in the small diameter portion. Each of the outer rings is fitted and fixed to the case split body 40.

[0044] The preload applying means 45 includes a spacer 50 disposed between the inner rings and a nut 49 screwed onto the male thread portion, and applies a preload to the rotation support portion 28. An appropriate preload is applied by adjusting the spacer width, which is the axial dimension of the spacer 50. The outboard end face of the inner ring on the outboard side is brought into contact with the step portion of the nut portion 25c, and the inboard end face of the inner ring on the inboard side is brought into contact with the nut 49, which is then tightened to the male thread portion, thereby applying a preload to the rotation support portion 28. This can increase the rigidity of the rotation support portion 28.

[0045] 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. The 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.

[0046] A guide groove having a rectangular cross section and including a guide surface that guides the outer circumferential surfaces of the plain bearings 51, 51 along the axial direction of the screw shaft 25A is formed in the case segment 41. In other words, the rotation fixed member 43 is in slidable contact with the guide surface of the case segment 41, which is a fixed part of the linear motion mechanism 25, via the plain bearings 51, 51. By sliding the rotation fixed member 43 along the guide groove having a rectangular cross section of the case segment 41 via the plain bearings 51, 51, the output rod 25a can be reciprocated in the axial direction.

[0047] The steering actuator 5 including the motor 26, the reducer 27 (FIG. 5) and the linear motion mechanism 25 in FIG. 1 is assembled as a sub-assembly and is detachably attached to the unit support member 3 by means of 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 advance and retreat. Although the 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.

[0048] <Sensors, etc.> In order to control the steering angle of the wheels more accurately, for example, it is necessary to know 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 either or both of the following position sensors and angle sensors (also called "rotation sensors"). 3, the position sensor 52 is provided in, for example, the case segment 41, and detects the axial position of the screw shaft 25A of the linear motion mechanism 25. The position sensor 52 can detect the amount of axial movement of the output rod 25a and output it as a position sensor value. The position sensor 52 can be any of a variety of sensors, such as a magnetic type, an optical type, or a capacitance type, but in this embodiment, a magnetic sensor is used.

[0049] A position sensor 52 is fixed to a substrate 53 fixed in the case divided body 41. A position sensor measurement target Tg is provided at one axial end of the rotating fixed member 43. For example, a permanent magnet 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 / retract position), the position sensor 52 and the position sensor measurement target Tg face each other across a predetermined gap. The position sensor 52 reads the change in the magnetic field of the permanent magnet accompanying the advance / retraction of the output rod 25a, and detects the advance / retract 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 obtaining an appropriate gap by, for example, one or both of a test and a simulation.

[0050] 5, the angle sensor Sa for detecting the rotation angle of the motor 26 includes, for example, a detection target portion Saa fixed to the inboard end of the motor shaft 26a, and a sensor portion Sab fixed to the motor case 34 across a predetermined axial gap from the detection target portion Saa for detecting the detection target portion Saa. For example, a resolver is used as the angle sensor Sa.

[0051] <Action and effect> 1, the hub unit body 2, which includes the hub bearing 15 that supports the wheel, can be freely rotated about the steering axis A by driving the steering actuator 5. The hub unit body 2 is rotated via the arm portion 17 connected to the output rod by moving the output rod of the steering actuator 5 back and forth by driving the motor 26.

[0052] The steering actuator 5 allows the hub bearing 15 to rotate freely within a certain range around the steering axis A, allowing the toe angle of the wheels, for example, to be changed arbitrarily according to the running conditions of the vehicle. When the configuration of this hub unit with steering function 1 is applied to the front wheels, as shown in Fig. 11, the front wheels 9F are steered together with the knuckle 6 and the unit support member 3 in Fig. 1 by the driver operating the steering wheel 11a through the steering device 11, but in addition to this steering, auxiliary steering of a small angle about the steering axis A can be performed independently for each wheel. Regarding the angle of the auxiliary steering, a small angle is sufficient to improve the maneuverability and driving stability of the vehicle, and it is sufficient even if the auxiliary steering angle is within ±5 degrees. The angle of the auxiliary steering is controlled by the steering actuator 5.

[0053] In addition, when cornering, the steering angle difference between the left and right wheels can be changed according to the driving speed. For example, the steering geometry can be changed while driving, such as using parallel geometry when cornering at high speeds and Ackermann geometry when cornering at low speeds. In this way, the wheel angle can be changed freely while driving, improving the vehicle's maneuverability and enabling stable driving. Furthermore, by appropriately changing the steering angles of the left and right wheels, the turning radius of the vehicle during cornering can be reduced, improving maneuverability. Furthermore, by adjusting the toe angle to suit each situation, even when driving in a straight line, it is possible to adjust the vehicle without compromising fuel efficiency at low speeds, while ensuring driving stability at high speeds.

[0054] When this configuration of the hub unit 1 with steering function is applied to the rear wheels, the entire hub unit does not steer, but the steering function allows each wheel to be steered independently by a small angle, just like the front wheels. By making the steering angle of the rear wheels the same phase as the front wheels, the yaw that occurs when steering can be suppressed, improving the stability of the vehicle. Furthermore, by independently adjusting the toe angle on the left and right sides when driving in a straight line, it is possible to improve fuel efficiency and ensure driving stability. In order to control the behavior of the vehicle in this way, it is necessary to accurately control the steering angle of the wheels, and in the event of an abnormality, it is necessary to return the steering angle of the wheels to an angle at which the vehicle can be driven. 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 position.

[0055] In this embodiment, it is conceivable that the hub unit 1 may stop at an angle that makes it difficult to drive due to an abnormality in the electrical system of the steering actuator 5 for either the left or right wheel, or both. In such a case, the motor shaft 26a (FIG. 5) is rotated directly from the outside, for example manually, through an opening Ha provided in the case of the steering actuator 5, without jacking up the wheels, etc. This returns the toe angle, which is the angle of the hub unit 1, to an angle near 0 degrees at which driving is possible, and the driving performance of the vehicle can be ensured. This makes it possible for the vehicle to move under its own power to a safe place.

[0056] 5, the opening end of the motor case 34 and the mating surface of the case base plate 35 facing this opening end are positioned relative to each other by pins 37. This improves the positioning accuracy of the output shaft tip of the motor shaft 26a, which is rotatably supported by the motor case 34, and the opening Ha provided in the case base plate 35, and eliminates the need to make the opening Ha unnecessarily large.

[0057] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description is omitted. When only a part of the configuration is described, the other parts of the configuration are the same as the previously described embodiment unless otherwise specified. The same configuration has the same action and effect. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine embodiments together, provided that there is no particular problem with the combination.

[0058] [Second embodiment: the opening is on the outer diameter side of the braking device] 7, the opening Ha of the case may be provided on the outer diameter side of the brake rotor 21a of the brake 21. In this case, even when a tire is mounted on the hub unit, it becomes possible to easily rotate the motor shaft 26a from the outside through the opening Ha of the case without interfering with the brake 21. Therefore, operability can be improved while ensuring the driving performance of the vehicle.

[0059] [Third embodiment: opening on the inboard side of the case] 8, an opening Ha may be provided in the bottom surface on the inboard side of the motor case 34. The opening Ha, which is a round hole or the like, is provided in the bottom surface of the motor case 34 at least on an extension line of the motor axis C1. Since an angle sensor is provided on the inboard side of the motor case 34, an opening cannot generally be provided thereon.

[0060] However, as the angle sensor, a so-called radial gap type angle sensor is used, which has a ring-shaped detected part fixed to the outer circumferential surface on the inboard side of the motor shaft, and a sensor part that is fixed to the motor case 34 across a predetermined radial gap from the detected part and detects the detected part. By using such an angle sensor, it is possible to provide an opening Ha in the bottom surface on the inboard side of the motor case 34. In this case, even when a tire is mounted on the hub unit, it is possible to easily rotate the motor shaft from the outside through the opening Ha provided on the inboard side of the case without interfering with the braking device or the like.

[0061] [Fourth embodiment: Opening through which the reducer can be rotated] 9A, for example, at least a two-face width 27ba may be provided on a part of the driven pulley 27b of the reducer 27, and an opening Ha that allows the two-face width 27ba to be directly rotated by a tool such as a wrench may be provided in the case base plate 35 or the like. In this case, the opening Ha is a slit-like opening Ha that extends a predetermined length along the outer periphery of the case base plate 35 according to the swing angle of the tool, etc. In this way, the toe angle can be returned to an angle that allows travel by directly and mechanically rotating not only the motor shaft 26a but also the reducer 27.

[0062] [Fifth embodiment: Opening that can rotate the linear motion mechanism] 9B, for example, the outer periphery of the nut portion 25c of the linear motion mechanism 25 has at least a two-face width 25ca, and an opening Ha that allows this two-face width 25ca to be directly rotated by a tool such as a wrench may be provided in the case segment 41 or the like. In this case, the opening Ha is also a slit-like opening Ha that extends a predetermined length along the outer periphery of the case segment 41 depending on the swing angle of the tool, as in the above case. In this way, the toe angle can be returned to an angle that allows travel by directly and mechanically rotating not only the motor shaft 26a but also the linear motion mechanism 25.

[0063] The pair of tapered roller bearings 28a, 28a shown in Fig. 5 may be a pair of angular contact ball bearings. The pair of tapered roller bearings 28a, 28a or the pair of angular contact ball bearings may be arranged face to face. The motor shaft may be rotated using a power tool such as an impact driver.

[0064] <Other examples of vehicles with steering hub units> As shown in FIG. 11, in a front-wheel steering vehicle, the steering function equipped hub unit 1 may be mounted on the left and right front wheels 9F, which are the steered wheels. In this case, a unit support member 3 (FIG. 1) is provided integrally with or separately from a knuckle (suspension frame part) 6 of a suspension device 12. The steering axis center A (FIG. 1) of the steering function equipped hub unit 1 is different from the kingpin axis that performs the main steering. In a normal vehicle, the kingpin angle is set at 10 to 20 degrees for the purpose of improving the straight-line stability of the vehicle when traveling, but the steering function equipped hub unit 1 of this embodiment has a steering axis with an angle (axis) different from the kingpin angle.

[0065] As shown in FIG. 12, the steering function-equipped hub unit 1 may be used for each of 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.

[0066] As shown in Fig. 13, the left and right rear wheels 9R, 9R may be steered by one steering actuator 5. This steering actuator 5 is disposed near the center in the vehicle width direction of the vehicle body so that the actuator body extends in the left-right direction of the vehicle. Left and right output rods 25a, 25a are disposed so as to face outboard from the one actuator body. When the left and right rear wheels 9R, 9R are steered by one steering actuator 5, the number of parts can be reduced and the structure can be simplified compared to a configuration in which the left and right rear wheels are steered by two steering actuators. However, in this case, the steering angles of the left and right rear wheels 9R, 9R are controlled in the same phase.

[0067] <About the steering system> 1, this steering system includes a steering function-equipped hub unit 1 according to any one of the embodiments, and a control device 29 that controls the steering actuator 5 of this steering function-equipped hub unit 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) provided from a higher-level control section 32.

[0068] The upper control unit 32 is a higher-level 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 outputs a current according 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 configures a half-bridge circuit using a switching element (not shown), and performs PWM control to determine the motor application voltage according to the ON-OFF duty ratio of the switching element. This allows the wheel angle to be changed minutely in addition to the steering by the driver's steering wheel operation. Even when driving in a straight line, the amount of toe angle can be adjusted according to each situation.

[0069] The steering system may operate the steering actuator by commands from an automatic driving device or a driving support device (not shown) instead of the driver's steering wheel operation. The hub unit with steering function of the present invention can be applied to both driving wheels and driven wheels. Although the embodiment for carrying out the present invention has been described above, the embodiment disclosed herein is illustrative in all respects and is not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0070] 1...Hub unit with steering function, 2...Hub unit main body, 3...Unit support member, 5...Steering actuator, 6...Knuckle (suspension frame part), 9...Wheel, 9F...Front wheel, 9R...Rear wheel, 12R...Suspension device, 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 unit, 31...Actuator drive control unit, Ha...Opening, Sp...Slit

Claims

1. A hub unit with a steering function, comprising: a hub unit body having a hub bearing that supports a wheel for rotation; a unit support member that is provided on a suspension frame component and supports the hub unit body for rotation about a steering axis extending in a vertical direction; and a steering actuator including a motor that drives the hub unit body to rotate about the steering axis, A hub unit with a steering function, in which an opening is provided in a case of the steering actuator, through which a motor shaft of the motor or a rotation mechanism connected to the motor shaft can directly rotate.

2. 2. The steering function equipped hub unit according to claim 1, wherein the opening of the case is provided radially outwardly of a braking device that brakes the wheel.

3. 3. The steering function-equipped hub unit according to claim 1, wherein the opening is provided on an inboard side of the case.

4. 3. The steering function equipped hub unit according to claim 1, wherein the opening is located on at least an extension line of a motor shaft center in the case.

5. 5. The steering function-equipped hub unit according to claim 4, wherein a slot for rotating the motor shaft is provided at an output shaft tip of the motor shaft.

6. 3. A hub unit with steering function according to claim 1 or claim 2, wherein the steering actuator has a reducer that reduces the rotation of the motor, and a linear motion mechanism that converts the rotation output of the reducer into linear motion, and the rotation mechanism portion is the reducer or the linear motion mechanism.

7. 3. A steering system comprising a hub unit with a steering function according to claim 1 or 2, and a control device that controls a steering actuator of the hub unit with a steering function, wherein the control device has a steering control section that outputs a current command signal corresponding to a given steering angle command signal, and an actuator drive control section that outputs a current corresponding to the current command signal input from the steering control section to drive and control the steering actuator.

8. 3. A vehicle in which either or both of a front wheel and a rear wheel are supported by using the steering function-equipped hub unit according to claim 1 or 2.

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