Control system for a continuously variable transmission
Abstract:
Control system for a Continuously Variable Transmission with two pairs of conical sheaves each with an adjustable running radius, the sheave of each pair being coupled to a hydraulic actuator and the inlet port of each actuator being connected with the hydraulic actuator setting means, fed from the outlet port of a hydraulic displacement pump, connected to a supply of hydraulic medium and coupled to an electric motor which is controlled by a controller which controls the speed of the electric motor with a first control signal which is generated as a function of the actual transmission ratio of the transmission on one hand and of the desired speed of change of this transmission ratio on the other hand, all this in such a way that the speed of this first motor increases with an increase of the transmission ratio of the transmission on one hand and an increase of the speed of change of the ratio on the other hand, while the outlet port of the displacement pump is connected to the inlet of an electronically controllable pressure relief valve of which the set point is determined by a second control signal as a function of the set transmission ratio on one hand and the value of the actual torque transmitted through the transmission on the other hand, in such a way that de value of the resulting hydraulic pressure increases as the transmission ratio increases on one hand, and as the torque transmitted through the transmission increases on the other hand.
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