Systems for land vehicles

Claim 1

In a land vehicle having an internal combustion engine provided with an induction manifold, driving wheels, and a variable-ratio drive interconnecting the engine and driving wheels, an electronic system to control the change of ratio of said variable-ratio drive in dependence upon the forward speed of the vehicle and the torque of the engine, said system including; means to sense the forward speed of the vehicle and produce a d.c. signal, the level of which is variable in dependence upon said forward speed; first and second operational amplifiers, each arranged as a comparator and each having a sensing input, a reference input, and an output, said d.c. signal being applied to the sensing inputs of both operational amplifiers; a pressure transducer connected to the induction manifold to sense the depression therein; circuit means connected to and controlled by said transducer, said circuit means including third and fourth operational amplifiers each arranged as an adding circuit and providing, respectively, first and second d.c. reference outputs, the instantaneous level of the first d.c. reference output being always lower than that of the second d.c. reference output, and the level of each reference ouput being variable in dependence upon the induction manifold depression sensed by said transducer, the first and second reference outputs being applied, respectively, to the reference inputs of the first and second operational amplifiers; a first output circuit, including a first actuator operable to effect a change in ratio of said variableratio drive between first predetermined ratio and a second and lower predetermined ratio, connected to and controlled by the output of the first operational amplifier; and a second output circuit, including a second actuator operable to effect a change ratio between said second ratio and a third and lower predetermined ratio, the first operational amplifier being arranged to produce an output when the level of said first d.c. signal exceeds that of the first d.c. reference output and thereupon to energise said first actuator to effect a change from said first to said second ratio, and the second operational amplifier being arranged to produce an output when the level of the said d.c. signal exceeds that of the second d.c. reference output and thereupon to energise said second actuator to effect a change from said second to said third ratio.