WO2008128379A1

WO2008128379A1 - Independent suspension steering systems

Info

Publication number: WO2008128379A1
Application number: PCT/CN2007/001292
Authority: WO
Inventors: Yangsheng Xu; Huihuan Qian; Guoqing Xu; Chenggang Xia; Hong Tong; Tiande Mo; Zhiru Liu; Weimin Li; Zhancheng Wang; Ka Keung Caramon Lee; Bufu Huang; Weizhong Ye; Tin Lun Lam; Xinyu Wu; Zhi Zhong; Wing Kwong Chung
Original assignee: The Chinese University Of Hong Kong
Priority date: 2007-04-19
Filing date: 2007-04-19
Publication date: 2008-10-30
Also published as: CN101631711A; CN101631711B; WO2008128421A1; HK1137971A1

Abstract

Disclosed is an independent suspension steering system (100) for a vehicle, comprising: a rotational shaft (90); a wheel carrier (99); an upper control arm (50) and a lower control arm (60), one end of the upper control arm (50) and one end of the lower control arm (60) being connected to opposite ends of the rotational shaft (90), respectively, at a pair of first connections (20,20'), and another end of the upper control arm (50) and another end of the lower control arm (60) being connected to the wheel carrier (99); and an in wheel motor (40) mounted to the wheel carrier (99); wherein the pair of the first connections (20,20') defines a steering axis (101) around which the rotational shaft rotates to drive the upper control arm (50), the lower control arm (60), and the wheel carrier (99) to rotate as a whole. The independent suspension steering system (100) can realize a -90º-+90º large-steering-angle without needing any interference between the wheel and the control arms.

Description

INDEPENDENT SUSPENSION STEERING SYSTEMS

TECHNICAL FIELD OF THE INVENTION

[0001] This invention relates to a steering system, particularly to an independent suspension steering system used in an omni-directional vehicle with in-wheel motors.

BACKGROUND OF THE INVENTION

[0002] The steering angle of mass production commercial vehicles is usually between ±35°. Due to the limitation of the steering angle, it is not easy to park or turn a vehicle in a compact room.

[0003] US Patent No. 6,561,307 discloses a steer-by-wire steering system for an independent suspension as shown in Figure 1. An independent suspension steering system 10 includes a frame 12 to which an upper control arm 14 and a lower control arm 16 are connected at the first connections 18 and 18'. An intermediate suspension member 20 is connected to the upper control arm 14 and the lower control arm 16 at the second connections 22 and 22'. The member 20 moves upwards and downwards by means of the upper control arm 14 and the lower control arm 16 and is constrained from moving forward and aft. The member 20 supports a steer knuckle 24 at the third connections 26 and 26' that define a king pin axis A. The knuckle 24 includes a spindle 28 supporting a wheel 30. Rotation of the knuckle 24 about the king pin axis A to a desired steering angle will steer the vehicle. A motor 32 is mounted on the member 20 to rotate the knuckle 24 relative to the member 20. A controller 46 is connected to the motor 32 as well as the motors in the other three wheels (outer wheels 42). A steering sensor 50 is connected to the controller 46 to sense a steering signal corresponding to a desired steering angle from a steering device 48. The controller 46 receives the steering signal and generates a command signal corresponding to the received steering signal. The command signal is sent to the motors 32 to steer the wheel 30.

[0004] However, with the arrangement of the steering motor in the limited space between the upper control arm and the lower control arm, the unsprung mass becomes larger and the optimum solution can't be derived easily. Further, as we all know that the king pin i axis and the steering axis is same, it's not an easy way to a large-steering-angle solution up to +90° because the relationship between the control arms and the alignment parameters of wheel such as camber angle, castor angle, kingpin inclination angle and toe-in is necessary to be considered. In other words, due to the relative position between the wheel and the control arms, it's not an easy work to get a large-steering-angle solution up to +90° without the interference between the wheel and the control arms.

SUMMARY OF THE INVENTION

[0005] In view of the shortcoming of the conventional independent suspension steering system, the present invention provides an independent suspension steering system used in an omni-directional vehicle with in-wheel motors which realizes a -90° -+90° large-steering-angle without needing any interference between the wheel and the control arms so that a vehicle may be easily parked or turned in a compact room.

[0006] According to an aspect of the present invention, an independent suspension steering system for a vehicle is provided, which comprises rotational shaft; wheel carrier; n upper control arm and a lower control arm, one end of the upper control arm and one end of the lower control arm being connected to opposite ends of the rotational shaft, respectively, at a pair of first connections, and another end of the upper control arm and another end of the lower control arm being connected to the wheel carrier, respectively, at a pair of second connections; and an in wheel motor mounted to the wheel carrier, wherein an axis of the in wheel motor is fixed at a wheel to support the wheel; herein the pair of the first connections defines a steering axis around which the rotational shaft rotates to drive the upper control arm, the lower control arm, and the wheel carrier to rotate as a whole, so as to in turn drive the in-wheel motor to steer the wheel.

[0007] The independent suspension steering system as provided in the present invention can realize a -90° -+90° large-steering-angle without needing any interference between the wheel and the control arms. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The above and other advantages of the present invention will become more apparent by describing the preferred embodiments in detail with reference to the accompanying drawings, in which:

[0009] Fig. 1 schematically shows a known independent suspension steering system;

[0010] Fig. 2 schematically shows the mechanical outline of an independent suspension steering system according to the present invention;

[0011] Figs. 3A-3Q are the result drawings of a vehicle equipped with the independent suspension steering system as shown in Fig. 2; and

[0012] Figs 4A-4H show the different steering angles of the vehicle with the independent suspension steering system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0013] As shown in Fig. 2, it illustrates an independent suspension steering system 100 of the present invention used in an omni-directional vehicle with in- wheel motors. The independent suspension steering system 100 includes an wheel carrier 99 to which an upper control arm 50 and a lower control arm 60 are connected at a pair of the second connections 21 and 21', respectively. As shown in Fig. 2, the second connections 21 and 21' define a king pin axis 102 for defining a motion trace of a wheel. The opposite ends of the upper control arm 50 and the lower control arm 60 are connected with an upper end and a lower end of a rotational shaft 90, respectively, at a pair of the first connections 20 and 20'. The first connections 20 and 20' further define a steering axis 101. According to the present invention, the steering axis 101 and the king pin axis 102 is separated from each other, thus the length of control arms and the alignment parameters of the wheel can be considered independently.

[0014] Thus, the control arms and the wheel carrier can be turned as a whole. The rotational shaft 90 is able to rotate about the steering axis 101 but is constrained from being movable upwards and downwards in the direction along the vehicle body. The wheel carrier 99 is mounted to an axis of an in wheel motor 40, namely the stator of the in wheel motor 40 is mounted to the wheel carrier 99, to allow the rotation of the in wheel motor and prevent the in wheel motor 40 to move along the direction of its axis. The in wheel motor 40 is also mounted into a wheel 111 to support the wheel 111 in order to steer the wheel 111.

[0015] Referring to Fig. 2, a steering motor 11 is provided to be coupled to the rotational shaft 90 through a throttle valve. The throttle valve such as the worm gear box 10 but not limited driven by the steering motor 11 is connected to the rotational shaft 90 by a key, so that the output shaft of the gear box and the rotational shaft are concentric.

[0016] According to the present invention, in order to steer the wheel 111, the steering motor 11 is first activated to drive the shaft 90 to rotate about the steering axis 101 through the worm gear box 10. The rotation of the shaft 90 is transmitted to the wheel carrier 99 through the upper control arm 50 and the lower control arm 60 to drive the in wheel motor 40 via the wheel carrier so that the wheel 111 is steered at a desired steering angle. When turning, the in wheel motor 40, the wheel carrier 99 and the control arms 50 and 60 rotate as a whole In this way, there is no necessity to introduce any interference between the wheel and the control arms.

[0017] Unlike the prior art, the outer housing of the steering motor 11 is fixed on that of the throttle valve, and the outer housing of the throttle valve is mounted to the body frame 12. The steering motor 11 is mounted on a body frame 12, rather than in the limited space between the upper control arm and the lower control arm. With this arrangement, the unsprung mass may not be increased. Thus, omni directional turning may be easily realized.

[0018] The independent suspension steering system of the present invention allows the control arms 50 and 60, the in wheel motor 40 and the wheel carrier 99 to turn as a whole, so the vehicle employing this independent suspension steering system can easily achieve omni directional turning.

[0019] Referring back to Fig 2, one end of a damper 70, the upper end of the rotational shaft 90, the right end of the upper control arm 50 are connected at the connection 20, while the opposite end of the damper 70, the left end of the upper control arm 50 and the wheel carrier 99 are connected at the connection 21'. The rotational shaft and the body frame 12 of the vehicle body are mounted by bearings to allow rotation of rotational shaft 90 in the vehicle body. Further, similar as the prior art, a brake 31 is mounted to the out-frame 99. And a brake disk is mounted to the rotational part of the motor 40 by screws.

[0020] Fig. 2 schematically shows only one wheel 111. Those skilled in the art can understand the steering system 100 also includes an independent suspension steering system for the other wheels 222, 333, and 444 with the same steering mechanism as that of the wheel 111.

[0021] In general, to steer a vehicle, a controller is needed. Fig. 2 shows a controller 15 connected to the motor 11 of each of wheels 111, 222, 333 and 444. Similar to the prior art, a steering signal sensed by a sensor 16 from the steering device 17 is input into the controller 15. A command signal corresponding to the steering signal will be transferred to each of the motor 11 to steer each of wheels 111, 222, 333 and/or 444.

[0022] Due to the merit of steering of each wheel by its respective independent motor, all of the four wheels can be steered independently, but with constraint of Ackerman angle, i.e. the axis direction of all the four wheels should point to one point (i. e. the instantaneous center of rotation) on the 2-D plane that vehicle is on, to permit the vehicle for moving.

[0023] According to the above, the left front and the right rear wheels can have a steering range of -45 degrees to +90 degrees and the right front and the left rear wheels can have a steering range of -90 degrees to +45 degrees. The vehicle can take any point on the 2-dimensional motion plane as the instantaneous rotational center (ICR).

[0024] Figs. 3A-3Q exemplify 17 motion modes of an omni-directional vehicle equipped with the independent suspension steering system according to the present invention. The arrow on each wheel indicates the direction of the wheel. [0025] Figs. 3A-3D show four pure translations including directions of forward, lateral right, right forward and left forward, respectively. In these four motion modes, each of the wheels has an identical steering angle and an identical speed. It can be easily understood that the pure translations of backward, lateral left, left backward and right backward can be achieved by the reverse of the direction of each wheel.

[0026] In Figs. 3E-3F, a small-radius turning with ICRs to the left of the vehicle and a small-radius turning to the right of the vehicle are illustrated, respectively. The two rear wheels are steered towards the direction opposite to the two front wheels.

[0027] In Figs. 3G-3H, two rotations about the ICRs in the front of and at the rear of the vehicle are illustrated, respectively.

[0028] In Figs. 31, a zero-radius turning with the ICR in the vehicle body is illustrated.

[0029] In Figs. 3 J-3M, four rotations about the ICRs on each of the four wheels are illustrated, respectively.

[0030] In the last four Figs. 3N-3Q, four rotations about the ICR on the line segments between the front wheels, the rear wheels, the left wheels and the right wheels are illustrated, respectively.

[0031] Although only the counter-clockwise rotations about the ICRs are shown, it can be understood that clockwise motions are also admissible by reverting the speed of each wheel.

[0032] It can be understood that, with the configuration of the independent suspension steering system of the invention, the vehicle can rotate about any ICR on its motion plane. Moreover, it is also clear that, together with the mounted in- wheel motors, the vehicle is omni-directional as it is of the ability of all the motions as illustrated in Figs 3A-3Q. [0033] Figs 4A-4H show the different steering angles of the vehicle with the independent suspension steering system according to the present invention.

[0034] Figs. 4A-4B show the steering angle of -45 degree. According to the present embodiment, when receiving a steering command of turning -45 degree, the steering motor 11 is activated to startup the gearbox 10. The gearbox 10 drives the rotational shaft 90 to clockwise rotate about the steering axis 101. The shaft 90 in turn drive the upper control arms 50 and 60 as well as the wheel carrier 99. The wheel carrier 99 then drives the in wheel motor 40 to steer the left wheel 111 to turn 45 degree clockwisely. Figs. 4C-4D show, with the help of the independent suspension steering system of the present invention, the steering angle of the wheel 111 may be steered at 0 degree. It can also be seen from Figs. 4E-4F, the left wheel 111 may turn 90 degree clockwise, and the steering angle of the left wheel 111 is +45 degree seen from Figs. 4G-4H. The turning represented in Figs. 4C-4H is similar as those in Figs. 4A-4B. Their description is omitted.

[0035] The invention has been described in an illustrative manner, and it is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Claims

1. An independent suspension steering system for a vehicle, comprising: a rotational shaft; a wheel carrier; an upper control arm and a lower control arm, one end of the upper control arm and one end of the lower control arm being connected to opposite ends of the rotational shaft, respectively, at a pair of first connections, and another end of the upper control arm and another end of the lower control arm being connected to the wheel carrier, respectively, at a pair of second connections; and an in wheel motor mounted to the wheel carrier, wherein an axis of the in wheel motor is fixed at a wheel to support the wheel; wherein the pair of the first connections defines a steering axis around which the rotational shaft rotates to drive the upper control arm, the lower control arm, and the wheel carrier to rotate as a whole, so as to in turn drive the in-wheel motor to steer the wheel.

2. The system according to claim 1, further comprising a steering motor coupled to the rotational shaft through a throttle valve and configured to receive a steering command to rotate the rotational shaft.

3. The system according to claim 2, wherein the steering motor is mounted on a body frame and the body frame is configured to support the vehicle.

4. The system according to claim 1, further comprising a controller configured to electrically couple to the steering motor so as to send steering commands to the steering motor.