Patent ID: 8852049

Claim:
A valve actuation method for an automatic transmission, the transmission comprising (a) a continuously variable ratio unit to transfer torque from a vehicle drive unit to a transmission output shaft and (b) a hydraulic circuit fluidly coupled to the variable ratio unit, the hydraulic circuit including (i) a first fluid chamber pressurizable to apply a first torque transmitting mechanism of the variable ratio unit, (ii) a second fluid chamber pressurizable to apply a second torque transferring mechanism of the variable ratio unit, (iii) a first shift valve fluidly coupled to the first fluid chamber to selectively direct fluid pressure to the first fluid chamber, the first shift valve including a first valve head and a first spring chamber axially spaced from the first valve head, (iv) a first electro-hydraulic actuator fluidly coupled to the first valve head of the first shift valve, (v) a second shift valve fluidly coupled to the second fluid chamber to selectively direct fluid pressure to the second fluid chamber, the second shift valve including a second valve head and a second spring chamber axially spaced from the second valve head, the first and second shift valves being in fluid communication with each other to connect one of the first and second fluid chambers to fluid pressure and disconnect the other of the first and second fluid chambers from fluid pressure in rapid succession, (vi) a second electro-hydraulic actuator fluidly coupled to the second valve head of the second shift valve, (vii) a first fluid passage that fluidly couples the first valve head of the first shift valve directly to the second spring chamber of the second shift valve, and (viii) a second fluid passage separate from the first fluid passage that fluidly couples the second valve head of the second shift valve directly to the first spring chamber of the first shift valve, wherein the first electro-hydraulic actuator is selectively coupled to the second spring chamber through the first valve head and the first fluid passage, and wherein the second electro-hydraulic actuator is selectively coupled to the first spring chamber through the second valve head and the second fluid passage, the method comprising detecting a change in torque direction, and stroking the first shift valve and destroking the second shift valve in rapid succession in response to the detected change in torque direction.