In this document, GM discusses using a hydraulic actuator to operate a clutch in automatic transmissions used in electric cars. A controller would vary the pressure of the fluid in the actuator, which in turn would move a piston that would open or close the clutch depending on what the controller determines is best in a given scenario.
This setup would be simpler than conventional automatic transmissions, something enabled by an electric motor’s need for fewer gearshifts, GM states in the patent filing. It would also avoid “instabilities at the electric motor” inherent in other types of clutch actuation, according to GM.
The patent, which was published earlier this month, explains that the new clutch would improve “efficiency and performance” of GM’s future electric models as it would give the driver “precise control over the clutch operation,” reports GM Authority.