Arrangements for Driving and Steering Of Motor Vehicles

Abstract

A transmission arrangement for an engine driven vehicle having two continuously variable transmissions serving to drive left and right hand vehicle wheels at separately variable drive ratios. Each transmission incorporates a variator of the type in which a net torque applied to the variator through its input and output is referred to a ratio control part, which may be formed as a control lever, whose position governs the transmission's drive ratio. The control parts of the variators are each operatively coupled to a driver's speed control, such that the speed control determines a mean position of the two control parts. However they are both also able to move relative to the mean position, under the influence of the torque they react. Additionally the control parts are coupled to each other such that any displacement of one control part from the mean position is accompanied by an opposite displacement of the other control part. In this way the transmissions are enabled to the relative speeds of the driven vehicle wheels automatically to reduce or even eliminate wheel slip, whilst still providing the driver with control over overall vehicle speed.

1 . A transmission arrangement for a motor vehicle, the arrangement comprising
 a speed control actuable by a driver of the vehicle;   a first continuously variable ratio device (“variator”) coupled between the engine and a right hand vehicle wheel and serving to determine a first drive ratio, at which the right hand vehicle wheel is driven by the engine; and   a second variator coupled between the engine and a left hand vehicle wheel and serving to determine a second drive ratio, at which the left hand vehicle wheel is driven from the engine, wherein   both variators are of the type in which a net torque applied to the variator is reacted through at least one movable ratio control part whose position governs the drive ratio,   the control parts of the first and second variators are each operatively coupled to the speed control, such that the speed control determines a mean position of the two control parts,   each of the control parts is able to move relative to the mean position under the influence of the torque which it reacts, and   the control parts are coupled to each other such that any displacement of one control part from the mean position is accompanied by an opposite displacement of the other control part, so that   through the speed control the driver has control over overall vehicle speed, but a difference between the first and second drive ratios is able to vary to accommodate differences in speed of the left and right driven vehicle wheels.   
     
     
         2 . A transmission arrangement as claimed in  claim 1 , further comprising a steering control which is actuable by the driver and which acts upon the first and second ratio control parts to influence their displacements from the mean position. 
     
     
         3 . A transmission arrangement as claimed in  claim 2 , wherein each of the ratio control parts is able to move, under the influence of the torque which it reacts, through a limited range on either side of a position determined by the steering and speed controls. 
     
     
         4 . A transmission arrangement as claimed in  claim 2 , wherein the steering control determines for each ratio control part a target displacement from the mean position, but the actual displacement of the ratio control part is able to vary through a limited range on either side of the target displacement under the influence of the torque reacted by the control part. 
     
     
         5 . A transmission arrangement as claimed in  claim 2 , wherein the steering control acts upon each ratio control part through a coupling arrangement incorporating a compliance, whereby the ratio control parts are each biased toward displacements from the mean position determined by the steering control, but are able to depart from these under the influence of the torques which they react. 
     
     
         6 . A transmission arrangement as claimed in  claim 5 , wherein the ratio control parts are coupled to each other through a lever pivoted about a fulcrum, the lever serving to ensure that any displacement of one ratio control part from the mean position is accompanied by an equal and opposite displacement of the other. 
     
     
         7 . A transmission arrangement as claimed in  claim 6 , wherein the position of the lever's fulcrum is movable by means of the speed control to determine the mean position. 
     
     
         8 . A transmission arrangement as claimed in  claim 7 , wherein the steering control acts upon the lever to influence its rotational position. 
     
     
         9 . A transmission arrangement as claimed in  claim 8 , wherein the steering control is coupled to the lever through a mechanism incorporating a compliance. 
     
     
         10 . A transmission arrangement as claimed in  claim 9 , wherein the steering control is operatively coupled to at least one steered vehicle wheel. 
     
     
         11 . A transmission arrangement as claimed in  claim 10 , wherein the driven vehicle wheel speeds are able to vary to accommodate a vehicle turn radius dictated by the steered vehicle wheel. 
     
     
         12 . A transmission arrangement as claimed in  claim 11 , wherein both variators are of toroidal-race rolling-traction type. 
     
     
         13 . A transmission as claimed in  claim 12 , wherein both variators comprise a pair of races mounted for rotation about a common axis and having facing shaped surfaces which together define a substantially toroidal cavity, and at least one roller running upon the said shaped surfaces of the races to transmit drive from one to the other. 
     
     
         14 . A transmission as claimed in  claim 13 , wherein the roller is provided with mountings which permit it to move circumferentially about the common axis. 
     
     
         15 . A transmission as claimed in  claim 14 , wherein the variator's ratio control part acts upon the roller to determine its circumferential position. 
     
     
         16 . A transmission as claimed in  claim 15 , wherein the variator's ratio control part is a ratio control lever coupled to the roller and mounted for rotation about a fulcrum. 
     
     
         17 . An arrangement for driving and steering a motor vehicle, the arrangement comprising: a user operable steeling control; at least one steered vehicle wheel movable by means of the steering control to steer the vehicle; a right hand transmission for transmitting rotary drive between a motor vehicle engine and a right hand driven vehicle wheel at a continuously variable drive ratio; and a left hand transmission for transmitting rotary drive between the motor vehicle engine and a left hand driven vehicle wheel at a continuously variable drive ratio, wherein both transmissions incorporate a respective ratio-varying device (“variator”) of the type in which variator reaction torque is referred to a ratio control part whose position governs the variator's drive ratio, the ratio control part of each variator is operatively coupled to the steering control, whereby a difference in speeds of the right and left hand driven vehicle wheels is urged to vary in sympathy with the position of the steered vehicle wheel(s), and the operative coupling of each ratio control part to the steering control incorporates a compliance or backlash, by virtue of which the ratio control part is permitted to move, under the influence of the reaction torque referred to it, as necessary to reduce any mismatch between the aforementioned difference in wheel speeds and the radius of vehicle turn dictated by the steered vehicle wheel(s). 
     
     
         18 . An arrangement as claimed in  claim 17  wherein the ratio control parts of the respective variators are additionally operatively coupled to each other such that a compliant change in the position of one ratio control part is accompanied by an opposite change in the position of the other. 
     
     
         19 . An arrangement as claimed in  claim 18  wherein the coupling is such that the said changes of ratio control part position are equal and opposite. 
     
     
         20 .- 23 . (canceled) 
     
     
         24 . An arrangement for driving a motor vehicle, the arrangement comprising: a user-operable speed control; a first continuously variable ratio device (“variator”) coupled between the engine and a right hand vehicle wheel and serving to control a first ratio, at which the right hand vehicle wheel is driven by the engine; a second variator coupled between the engine and a left hand vehicle wheel and serving to control a second ratio, at which the left hand vehicle wheel is driven from the engine, wherein both variators are of the type in which a net torque applied to the variator is reacted through at least one movable ratio control part whose position governs the drive ratio, and a control arrangement is coupled to the control parts and serves to set target values of the first and second ratios in dependence upon driver input, the variator ratios being able to deviate from their target values under the influence of the torques reacted by the control parts, and the control parts being coupled together such that an increase in one of the ratios is accompanied by a decrease in the other, such that a difference in speeds of the left and right hand wheels is able to vary whilst control over vehicle speed is maintained.