In-wheel motor unit coupling structure

Abstract

An in-wheel motor unit coupling structure includes an in-wheel motor unit and a shock absorber. The in-wheel motor unit is disposed inside a wheel of a vehicle. The in-wheel motor unit is configured to support the wheel such that the wheel is rotatable. The in-wheel motor unit includes an electric motor that serves as a rotational driving source of the wheel. The shock absorber is coupled to the in-wheel motor unit. The shock absorber is a component of a vehicle suspension. A lower end portion of the shock absorber is fastened to a vehicle center side, in a vehicle width direction, of a motor part so as to be pressed against the motor part outward from the vehicle in the vehicle width direction. The motor part is a part in which the electric motor of the in-wheel motor unit is built.

Claims

1. An in-wheel motor unit coupling structure comprising: an in-wheel motor unit disposed inside a wheel of a vehicle, the in-wheel motor unit being configured to support the wheel such that the wheel is rotatable, the in-wheel motor unit including an electric motor that is a rotational driving source of the wheel; and a shock absorber coupled to the in-wheel motor unit, the shock absorber being a component of a vehicle suspension, a lower end portion of the shock absorber being fastened to a vehicle center side, in a vehicle width direction, of a motor part so as to be pressed against the motor part outward from the vehicle in the vehicle width direction, the motor part accommodating the electric motor of the in-wheel motor unit, wherein: the lower end portion of the shock absorber and the motor part are fastened to each other by a fastening member; the lower end portion of the shock absorber is configured to be pressed against the motor part by an elastic reaction force of the fastening member; the fastening member includes a bracket partially joined with the lower end portion of the shock absorber and extending toward the motor part; when an extended end portion of the bracket is fastened to the motor part, the lower end portion of the shock absorber is fastened to the motor part; and in a state where the lower end portion of the shock absorber is fastened to the motor part, the bracket is elastically deformed, and the lower end portion of the shock absorber is configured to be pressed against the motor part by a reaction force caused by an elastic deformation.

2. An in-wheel motor unit coupling structure comprising: an in-wheel motor unit disposed inside a wheel of a vehicle, the in-wheel motor unit being configured to support the wheel such that the wheel is rotatable, the in-wheel motor unit including an electric motor that is a rotational driving source of the wheel; and a shock absorber coupled to the in-wheel motor unit, the shock absorber being a component of a vehicle suspension, a lower end portion of the shock absorber being fastened to a vehicle center side, in a vehicle width direction, of a motor part so as to be pressed against the motor part outward from the vehicle in the vehicle width direction, the motor part accommodating the electric motor of the in-wheel motor unit, wherein: the motor part is placed so as to be offset in a vehicle front and rear direction with respect to a rotation axis of the wheel; and an amount of offset of an axis of the shock absorber in side view of the vehicle from the rotation axis of the wheel is less than or equal to ⅕ of an outside diameter of the wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Features, advantages, and technical and industrial significance of exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

(2) FIG. 1 is a side view of a vehicle suspension having an in-wheel motor unit coupling structure of an embodiment when viewed from a vehicle center side in a vehicle width direction;

(3) FIG. 2 is a front view of the vehicle suspension shown in FIG. 1 when viewed from a vehicle front side;

(4) FIG. 3 is a back view of the vehicle suspension shown in FIG. 1 when viewed from a vehicle rear side;

(5) FIG. 4 is a plan view of the vehicle suspension shown in FIG. 1 when viewed from above;

(6) FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 1 for illustrating a specific manner of fastening an in-wheel motor unit and a shock absorber to each other in the in-wheel motor unit coupling structure of the embodiment;

(7) FIG. 6 is a cross-sectional view taken along the line V-V in FIG. 1 for illustrating a specific manner of fastening an in-wheel motor unit and a shock absorber to each other in an in-wheel motor unit coupling structure of a modification; and

(8) FIG. 7A and FIG. 7B each are a schematic three-plan drawing for illustrating a specific manner of fastening an in-wheel motor unit and a shock absorber to each other in an in-wheel motor unit coupling structure of another modification.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) Hereinafter, an in-wheel motor unit coupling structure that is an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. The present disclosure may be implemented in various forms with various modifications or improvements based on the knowledge of persons skilled in the art, other than the following embodiment.

(10) Overall Configuration of Vehicle Suspension

(11) A suspension having the coupling structure of the embodiment and shown in FIG. 1 to FIG. 4 (hereinafter, which may be referred to as suspension of the embodiment) is a strut (MacPherson-type) suspension. The suspension is a suspension for a right front wheel that functions as a steer wheel in a vehicle. FIG. 1 is a side view of the suspension when viewed from a vehicle center side in a vehicle width direction (which may be referred to as vehicle side view). FIG. 2 is a front view of the suspension when viewed from a vehicle front side. FIG. 3 is a back view of the suspension when viewed from a vehicle rear side. FIG. 4 is a plan view of the suspension when viewed from above. Hereinafter, the overall configuration of the suspension of the embodiment will be described with reference to those drawings. In the following description, as shown in the drawings, a forward direction in a vehicle front and rear direction is referred to as vehicle front side, a rearward direction in the vehicle front and rear direction is referred to as vehicle rear side, a direction toward the center of the vehicle in the vehicle width direction is referred to as vehicle inner side, and a direction toward the outer side of the vehicle in the vehicle width direction is referred to as vehicle outer side.

(12) The suspension of the embodiment includes an in-wheel motor unit 12 disposed inside a wheel 10, more specifically, a rim 10a of the wheel 10. The unit 12 functions as a carrier that supports a tire-wheel assembly 14 such that the tire-wheel assembly 14 is rotatable around a wheel rotation axis WL by supporting the wheel 10 with an axle hub (hidden and not shown in the drawing) and that permits the up and down motion of the tire-wheel assembly 14 with respect to a vehicle body according to bounding or rebounding of the tire-wheel assembly 14 and the vehicle body. The tire-wheel assembly 14 is a component including the wheel 10 and a tire 16 fitted to the wheel 10.

(13) The unit 12 includes an electric motor, a bearing unit, and a speed reducer inside a housing 20. The electric motor serves as a rotational driving source of the wheel 10, that is, the tire-wheel assembly 14. The bearing unit supports the axle hub. The speed reducer reduces the speed of rotation of the electric motor and transmits the rotation to the axle hub. On the assumption that the electric motor and part of the housing 20 accommodating the electric motor make up a motor part 22 and the speed reducer and part of the housing 20 accommodating the speed reducer make up a speed reducer part 24, a motor axis ML that is the axis of the electric motor is shifted toward the vehicle rear side from the wheel rotation axis WL, and the motor part 22 is offset from the wheel rotation axis WL in the vehicle front and rear direction, more specifically, toward the vehicle rear side. The motor part 22 is also offset upward from the wheel rotation axis WL.

(14) The unit 12 is supported by A-shaped lower arm 32 via a ball joint 30 at its lower side. On the other hand, a shock absorber 40 is coupled to the unit 12 at the upper side of the unit 12. More specifically, the motor part 22 of the unit 12 and a lower end portion of the shock absorber 40 are fastened to each other. A coupling structure for coupling the unit 12 and the shock absorber 40 to each other is the coupling structure of the embodiment, and the details of the coupling structure will be described later.

(15) The shock absorber 40 includes an outer cylinder 40a and a piston rod. The outer cylinder 40a accommodates a piston. The piston rod extends upward from the outer cylinder 40a. An upper end portion of the shock absorber 40, that is, an upper end portion of the piston rod, is rotatably supported by an upper support 42 connected to a mount portion of the vehicle body. Therefore, the unit 12 is pivotable around a kingpin axis KL that is determined by the ball joint 30 and the upper support 42. When the axis of the shock absorber 40 is defined as absorber axis AL, the kingpin axis KL does not match the absorber axis AL.

(16) One end portion of a stabilizer bar (torsion bar) 46 is coupled to the outer cylinder 40a of the shock absorber 40 via a link rod 44. A spring lower seat 48 is connected to the outer cylinder 40a. A suspension coil spring 50 is disposed such that both ends are supported by the spring lower seat 48 and the upper support 42.

(17) A knuckle arm 60 is connected to the housing 20 of the unit 12 at the lower side of the vehicle front side. On the other hand, in the vehicle, a wheel steering rod (hidden and not shown in the drawing) having a rack is disposed so as to extend in the vehicle width direction. The wheel steering rod is coupled to a steering shaft and moves rightward or leftward by the rotation of a pinion shaft 62 having a pinion meshed with the rack, that is, the rotational operation of a steering wheel. One end of the wheel steering rod is coupled to the distal end of the knuckle arm 60 via the link rod 64. The vehicle includes the thus configured steering system. As a result of driver's steering operation, the unit 12 pivots around the kingpin axis KL, and the tire-wheel assembly 14 supported by the unit 12 is turned. With such a structure, the unit 12 functions as a steering knuckle. The vehicle includes a wheel steering actuator 68 that uses an electric motor 66 as a driving source in order to assist the wheel steering rod in moving rightward or leftward.

(18) The unit 12 supports a brake disc 70 together with the wheel 10 on the axle hub such that the brake disc 7 and the wheel 10 are rotatable. A brake caliper 72 made up of a brake pad and an actuator for pressing the brake pad against the brake disc 70 is also supported by the unit 12. Since the motor part 22 of the unit 12 is disposed inside the wheel 10 so as to be shifted toward the vehicle rear side, relatively large space is present inside the wheel 10. The brake caliper 72 is placed in this space inside the wheel 10 with sufficient room.

(19) Coupling Structure for Shock Absorber and In-Wheel Motor Unit

(20) The coupling structure of the present embodiment will be described also with reference to FIG. 5. The shock absorber 40 is fastened to the unit 12, more specifically, the unit 12 on the vehicle center side, in the vehicle width direction, of the motor part 22, by using a bracket 80 that is a fastening member. The bracket 80 is made by forming a plate material into a shape having substantially a U-shape in cross section. A portion 80a corresponding to the bottom of the U-shape (hereinafter, which may be referred to as proximal portion) is joined with the lower end portion of the shock absorber 40, more specifically, the lower end portion of the outer cylinder 40a, by welding. The bracket 80 has a pair of extended portions 80b, 80c extending from the proximal portion 80a toward the motor part 22 substantially parallel to each other. The extended portions 80b, 80c are respectively bent at their distal ends to provide flanges 80d, 80e as extended end portions. Two mounting holes 80f are perforated in the vehicle front-side flange 80d, and a single mounting hole 80f is perforated in the vehicle rear-side flange 80e.

(21) On the other hand, the housing 20 of the unit 12 includes a peripheral wall 20a and a lid 20b in the motor part 22. The lid 20b is connected by bolts so as to surround the vehicle inner side of the space surrounded by the peripheral wall 20a. The peripheral wall 20a has mounting bosses 20c each having an internal thread, in correspondence with the mounting holes 80f perforated in the flanges 80d, 80e of the bracket 80. The lid 20b has through-holes 20d in correspondence with the mounting holes 80f The bracket 80 is fastened to the motor part 22 by bolts 82. The bolts 82 serve as fasteners extending through the mounting holes 80f of the flanges 80d, 80e and the through-holes 20d of the lid 20b and screwed to the internal threads of the mounting bosses 20c.

(22) A mounting seat 20e is fixedly provided on the lid 20b. The groove 20f has a U-shape in cross section and extends in a direction parallel to the absorber axis AL. The outer cylinder 40a of the shock absorber 40 is just fitted to the groove 20f.

(23) In a state where the lower end portion of the shock absorber 40 is connected to the motor part 22 but the bolts 82 have not been tightened yet, a slight gap d is present between each of the flanges 80d, 80e and the surface of the lid 20b. When the bolts 82 are tightened into the mounting bosses 20c, the extended portions 80b, 80c are elastically stretched, with the result that the gap d disappears. In other words, the bracket 80 is elastically deformed, and the lower end portion of the shock absorber 40 is pressed against the motor part 22 of the unit 12, more specifically, the mounting seat 20e, toward the vehicle outer side in the vehicle width direction by a reaction force caused by the elastic deformation. In the pressed state, the positional variations of the shock absorber 40 in a direction perpendicular to the absorber axis AL, generally, the vehicle front and rear direction, are prohibited by the groove 20f of the mounting seat 20e.

(24) In the above-described suspension, as described above, the motor axis ML that is the axis of the electric motor is shifted from the wheel rotation axis WL toward the vehicle rear side, and the motor part 22 is offset from the wheel rotation axis WL in the vehicle front and rear direction, more specifically, toward the vehicle rear side. With the coupling structure of the embodiment, since the lower end portion of the shock absorber 40 is fastened to the vehicle center side of the motor part 22 in the vehicle width direction, space for disposing the brake caliper 72, and the like, that are other elements to be disposed inside the wheel 10, is less limited, so work, such as maintenance of the brake caliper 72, and the like, can be relatively easily performed.

(25) In the coupling structure of the embodiment, the lower end portion of the shock absorber 40 is fastened to the vehicle center side of the motor part 22 in the vehicle width direction, so the absorber axis AL can be brought close to the wheel rotation axis WL. Specifically, in a state where the tire-wheel assembly 14 is not turned, an offset amount 8 of the absorber axis AL from the wheel rotation axis WL in the vehicle side view is less than or equal to ⅕ of the outside diameter D of the wheel 10 (actually, almost not offset). As a result, a force that acts on the shock absorber 40 in a direction that intersects with the absorber axis AL (for example, a force that acts to bend the shock absorber 40) is relatively reduced.

(26) In addition, the rotation radius of the lower end portion of the shock absorber 40 around the kingpin axis KL at the time of turning the tire-wheel assembly 14 is relatively small, so space for avoiding interference with vehicle body-side components, or the like, may be relatively small.

(27) With the coupling structure of the embodiment, the lower end portion of the shock absorber 40 is fastened to the motor part 22 of the unit 12 so as to be pressed against the motor part 22. In other words, the lower end portion of the shock absorber 40 is fastened so as to be in close contact with the motor part 22 directly, that is, the mounting seat 20e that is a component of the motor part 22. For this reason, the shock absorber 40 and the unit 12 are firmly coupled. A force that acts on the shock absorber 40 is received not only via the bracket 80 but also by the unit 12 directly, so the stiffness of the coupling structure is sufficiently ensured, and reliability on the strength of the coupling structure is high.

(28) As a modification related to the mounting seat 20e, as shown in FIG. 6, instead of the U-shaped groove 20f, a mounting seat 20e′ having a V-shaped groove 20f in cross section may be provided. With such the groove 20f, in a state where the lower end portion of the shock absorber 40 is pressed against the mounting seat 20e, the positional variations of the shock absorber 40 in a direction perpendicular to the absorber axis AL, generally, in the vehicle front and rear direction, are prohibited.

(29) As schematically shown by the three-plan drawings in FIG. 7A and FIG. 7B, for example, a mounting seat 20e″ having substantially a triangular cross section and extending in a direction to make a grade separated crossing perpendicularly to the absorber axis AL may be provided one or two in the motor part 22.