Abstract:
A wheel suspension assembly for a vehicle having wheels and a chassis, the vehicle suspension system comprising a suspension unit for at least one wheel, the suspension unit including a first pivot arm of which a wheel is mounted and a second pivot arm mounted on the chassis, a drive unit mounted to the chassis, and a transmission unit between the drive unit and the wheel, the transmission unit arranged to accommodate pivoting of the second pivot arm relative to the chassis during operation of the vehicle.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The invention relates to vehicle suspension systems in which a suspension for a vehicle wheel is associated with a drive unit.  
           [0003]    2. Description of Related Art  
           [0004]    Vehicles usually have a prime mover or power unit which drives two or more wheels of a vehicle. However, individual drive units for hydraulically or electrically driving the individual wheels have been used.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention provides an improved vehicle suspension system incorporating a drive unit. According to the invention, the vehicle suspension system comprises a suspension unit for at least one wheel, a drive unit for the wheel and transmission means between the drive unit and the wheel. The suspension unit is pivotally attached to the chassis, and pivotally receives the wheel. The transmission means accommodates pivoting of the suspension unit relative to the chassis during operation of the vehicle.  
           [0006]    In various exemplary embodiments, the drive unit is a motor arranged to drive the associated wheel and the transmission means includes a drive shaft, step down gearing, and a right angle gear box at the wheel.  
           [0007]    In other exemplary embodiments, there is a drive unit for each of a pair of wheels of the vehicle, and control means for controlling the driven wheels to obtain the desired drive characteristics of the vehicle, whereby the driven wheels may be driven at the same or different speeds according to predetermined driving parameters of the vehicle, for example, travelling in a straight line or travelling around bends.  
           [0008]    Other exemplary embodiments include two suspension units mounted on each end of a cross beam, which is mountable transversely on the vehicle chassis. In these embodiments, a drive motor for each drive wheel is mounted on the chassis in association with each suspension unit to drive the associated wheel. For a rear wheel drive vehicle, the cross beam may be mounted towards the rear of the vehicle and under the chassis.  
           [0009]    In other exemplary embodiments, the drive motor or motors of the vehicle are electric motors and the step down gearing is mounted adjacent the associated driven wheel. The motors may be mounted above the cross beam and at or above the lower level of the chassis, whereby the transmission from the motor has a downwardly extending drive shaft. Constant velocity joints may be provided towards each end of the drive shaft to accommodate movements of the wheel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    An exemplary embodiment of the invention is illustrated by the drawings, in which:  
         [0011]    [0011]FIG. 1 is a schematic view of an exemplary embodiment of a series hybrid electric vehicle on which the invention can be utilized;  
         [0012]    [0012]FIG. 2 is a plan view of a vehicle suspension system according to this invention;  
         [0013]    [0013]FIG. 3 is a side elevation of the system illustrated in FIG. 2;  
         [0014]    [0014]FIG. 4 is a further plan view of the system illustrated in FIGS. 2 and 3;  
         [0015]    [0015]FIG. 5 is a perspective view of a support bar and two of the vehicle suspension systems illustrated in FIGS.  2 - 4 , with the drive units omitted; and  
         [0016]    [0016]FIG. 6 is a plan view of the assembly of FIG. 5. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]    An exemplary embodiment of a suspension system  200  according to this invention is illustrated in FIGS.  2 - 6 . This invention has particular application to hybrid vehicles which have two power sources, one an electric power source powered by electric storage means, and the other a primary power source such as an internal combustion engine which is used to generate electric power upon depletion of the electric storage means. For example, suspension system  200  can be utilized on a hybrid electric vehicle, such as bus  100  in FIG. 1. The invention is, however, not limited to hybrid electric vehicles. The invention can be utilized on any wheeled vehicle.  
         [0018]    The bus  100  may be of generally conventional construction having a structural unit or chassis  120  on which is mounted the body of the bus  100 . Within the body is located the passenger space, including seating. The interior of the body of the bus  100  should have a generally flat floor, although the floor may have upward protrusions where the seating is located. Bus  100  includes four wheels  110 ,  112 ,  114 ,  116 , arranged as a front pair of wheels and a rear pair of wheels.  
         [0019]    In various exemplary embodiments, the bus  100  includes two rear wheels  114 ,  116  at opposite sides of the bus  100  and two front wheels  110  and  112 , also at opposite sides of the bus  100 . The two rear wheels  114 ,  116  may be driven by independent drive units, while the front wheels  110 ,  112  are not driven. Stated differently, there may be an individual drive unit for each rear wheel  114 ,  116 . Alternatively, in some embodiments, each wheel  110 ,  112 ,  114 ,  116  may have a separate drive unit, or only the front wheels  110 ,  112  may be driven, and have separate drive units. In bus  100 , the rear wheels  114 ,  116  are driven by separate drive units.  
         [0020]    Mounted to the underside of the rear of the chassis  120  of the bus  100  is a beam  10  which extends transversely to the direction of travel of the vehicle  100 . The beam  10  is fixed to the chassis  120  through vibration isolators  11  to reduce the transmission of vibrations in the beam  10  to the chassis  120 . The vibration isolators  11  are mounted on a pair of arms  12 , spaced from one another along the beam inwardly of the ends of the beam  10 . See FIGS. 5 and 6.  
         [0021]    Suspension system  200  includes support member  13 , pivot  14 , trailing arm suspension unit  15 , mounting  16 , mounting pad  17  and drive unit  30 . A support member  13  is rigidly attached to each end of the beam  10 . Each support member  13  rotatably receives and engages a pivot  14 . In this exemplary embodiment, pivot  14  extends parallel to and is spaced upwardly from the beam  10 . Trailing arm suspension unit  15  is fixedly attached to pivot  14 , such that trailing arm suspension unit  15  rotates with pivot  14 . In this exemplary embodiment, the suspension unit  15  is a trailing arm unit in the form of a triangular frame. One corner of the triangular frame is mounted to pivot  14 , such that the axis of rotation of pivot  14  is the axis of rotation of suspension unit  15 . Other shapes of trailing arm units can be equally utilized.  
         [0022]    A mounting  16  is attached at another corner of the suspension unit  15 . Mounting  16  is designed to receive a hub  24  of the wheels  114 ,  116 . The outwardly-extending mounting pad  17  is attached to the third corner of the suspension unit  15 . Mounting pad  17  is designed to interface with an air bag (not shown) for a resilient air suspension unit. The air bag is located between a part of the vehicle chassis  120  and the mounting pad  17 .  
         [0023]    In this exemplary embodiment, each trailing arm suspension unit  15  is associated with a drive unit  30 . Drive unit  30  includes electric drive motor  18  and a drive chain, as described below. The electric drive motor  18  is rigidly mounted on the vehicle chassis  120 . In various exemplary embodiments, the motor  18  is located in a housing (not shown) formed as a protrusion in the floor of the vehicle body which lies above the level of the chassis. The motors  18  are protected because the motors  18  are located in housings formed on the vehicle chassis  120 . The motors  18  may be liquid cooled and their location altered to further assist in utilizing this kind of motor.  
         [0024]    In this exemplary embodiment, the motor  18  drives the wheel through a drive train which includes a constant velocity joint  19 , a drive shaft  20 , a further constant velocity joint  21 , a spiral bevel gearbox  22  and a right angle gearbox  23 . Any other suitable drive train would be utilized. This drive train results in a reduction in the rotational speed from the motor  18  to the mounting  16 . The drive from the spiral bevel gearbox  22  is transmitted to the right angle gearbox  23  so that the drive axis is aligned with the rotational axis of the hub  24  and associated wheel. A planetary reduction gearing  25  is located between and interfaces with, the right-angle gearbox  23  and the wheel hub  24  to further reduce the drive ratio to the associated hub  24  and wheel  114 ,  116 .  
         [0025]    In practice, the motor  18  rotates at a high speed during driving of the wheel, for example 800 rpm, and a significant reduction is obtained through the gearing to impart a suitable speed of rotation to the wheel  114 ,  116 . For example, the planetary gears  25  may have a gear reduction of the order of 10:1, and may be in the form of two planetary gears in series. The spiral bevel gear  22  may have a reduction ratio in the order of 1.6:1. These reduction ratios are provided as examples only, and any suitable ratios may be utilized.  
         [0026]    The constant velocity joints  19  and  21  allow the distance between the (a) motor  18  and (b) the hub  24  and gearbox assembly  29  (spiral bevel gearbox  22  and right angle gearbox  23 ) to change according to the movement of the suspension unit  15 .  
         [0027]    As should be appreciated, in providing the drive assembly, the axis of the pivot  14  of the trailing suspension unit  15  is on one side and below the drive shaft  20 .  
         [0028]    Rotation of the trailing arm suspension unit  15  about the axis of pivot  14  is “controlled” by the resilient mounting provided by the pad  17  and the associated airbag abutting against a portion of the vehicle chassis  120 . This provides a damping force as to the rotation of the suspension unit  15 .  
         [0029]    Various structural arrangements can be used to provide additional support the unit  15 . An arm  31  may be provided having a rubber support  30  between the arm  31  and the chassis  120 . Alternatively, a steel cable (not shown) may extend between the arm  31  and the chassis  120 . A shock absorber  32  may also be provided between the arm  15  and the chassis  120 , attached by a bracket  33 . See FIG. 5. Any suitable structural support member or assemblies may be utilized.  
         [0030]    In this exemplary embodiment, each of the motors  18  is supplied electrical power from a common source in the form of electric storage means (not shown). To ensure that the motors  18  rotate at the appropriate speeds relative to one another, a control system  130  controls power to the motors  18 . In its simplest form, the control system  130  controls the motors  18  to rotate at the same speed so that the drive wheels  114 ,  116  each rotate at the same speed, which normally occurs when the vehicle  100  is travelling in a straight line. When the vehicle  100  is travelling around a bend, the wheels  114 ,  116  rotate at different speeds to accommodate for the lack of a differential between the wheels  114 ,  116 . Specifically, the wheel at the outer side of the bus  100  rotates at a faster speed than the wheel at the inner side. Thus, the rotational speeds of the respective motors  18  are determined by the control system  130  according to the turning radius of the bus  100  and other desired driving characteristics. In various exemplary embodiments, the wheel at the outer side of the bend is driven at greater torque than the wheel at the inner side to assist turning of the bus  100 . The control system  130  is arranged to monitor the parameters of the vehicle travel and to select the power to each motor  18 , including reverse drive.  
         [0031]    In addition, the electric drive to the wheels  114 ,  116  may be utilized to provide regenerative braking by which electrical power is generated during braking of the bus  100  to be fed back into the electric storage means and conserve energy, obtaining more efficient utilization of the available power.  
         [0032]    Specifically, in various exemplary embodiments, the wheel hub  24  is fitted with a disk  27  of a disk brake assembly for each wheel  114 ,  116  whereby the wheels  114 ,  116  are braked in the usual manner.  
         [0033]    The arrangement of the individual components of the suspension system  200  described herein permits the suspension system  200  to be assembled prior to being installed on the bus  100 , to ensure that the components are assembled in the desired relative orientation without misaligmnents and other problems, which may arise if the individual components are mounted directly to the vehicle chassis  120 . The preassembled construction is attached to the vehicle chassis  120 , at predetermined separate locations on the chassis  120 , to ensure that the components are in the right relationship to one another and to the bus  100 .  
         [0034]    It will be seen that the vehicle hubs  24  and wheels  114 ,  116 , are each mounted on the trailing arm suspension unit  15 , are independently suspended on the vehicle  100  and can move up and down independently about their pivots  14  to accommodate the road contours in the usual way, and under the restraint and damping action of the airbags. At the same time, the drive is transmitted to the wheels  114 ,  116  from the motors  18  through the drive transmission arrangement which permits the transmission of power to the hubs irrespective of the relative position of the wheels  114 ,  116 .  
         [0035]    While the invention has been described with reference to various exemplary embodiments thereof, it is to be understood that the invention is not limited to disclosed exemplary embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the disclosed invention are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.