Internal combustion engine throttle control

An internal combustion engine throttle control comprising an accelerator pedal, a butterfly valve and linkage means connecting the accelerator pedal to the butterfly valve and including a first movable member coupled to the accelerator pedal, a second movable member coupled to the butterfly valve, first spring means connecting the first movable member to the second movable member whereby depression of the accelerator stresses said first spring means to tend to open the butterfly valve, mechanical limit means restricting relative motion of the ends of said first spring means as said first spring means is relaxed, second spring means acting to urge the butterfly valve towards a closed position, whereby lifting of the drivers foot from the accelerator pedal causes relaxing of said first spring means to the limit permitted by said limit means and movement of the butterfly valve to its closed position by said second spring means, a cam, cam follower means mounted on said second movable member and urged into engagement with said cam by the action of said first spring means so as to limit opening of the butterfly valve in accordance with the position of said cam, a servo-motor drivingly connected to said cam, and said cam being shaped to provide a desired non-linear relationship between butterfly valve opening and displacement of the cam by the servo-motor, and control means for the servo-motor operating to displace the cam to a position dependent on at least one vehicle operating parameter.