Pressure assisted park servo
AssigneeGM Global Technology Operations LLC
InventorsStephen W. Powell, Mark A. Vernacchia, Brian W. Whitmarsh, Ryan M. Jenness
Life of this patent
Estimating the term…
Abstract
A pressure assisted park servo assembly for an automatic transmission includes a servo or spool valve which receives pressurized hydraulic fluid from various sources including two solenoid valves and transmission ports. The servo valve controls two flows of pressurized hydraulic fluid to a servo assembly to place the transmission in or release it from park. The improved park servo assembly exhibits enhanced operating speed.
Claims14
A device for initiating in a transmission a park mode of operation and an out of park mode of operation, the device comprising:
- a housing that defines a cavity;
- a piston slidably disposed within the cavity and moveable between a first position and a second position, the piston having a first face and a second face;
- a first chamber defined by the housing and the first face of the piston;
- a second chamber defined by the housing and the second face of the piston;
- a first fluid port in communication with the first chamber;
- a second fluid port in communication with the second chamber;
- and
- a biasing member disposed within the housing and in contact with the piston,
- a valve in direct communication with the first fluid port and the second fluid port and operable to selectively provide a pressurized fluid to the first fluid port and the second fluid port, and
- wherein when a pressurized fluid enters the first chamber from the first fluid port the piston is moved to the first position to shift the transmission into the park mode of operation and the valve provides fluid communication between the second fluid port and a vent port in order to vent a fluid from the second chamber when the park mode of operation is selected, and
- wherein when a pressurized fluid enters the second chamber from the second fluid port the piston is moved to the second position to shift the transmission into the out of park mode of operation and the valve provides fluid communication between the first fluid port and the vent port in order to vent a fluid from the first chamber when the out of park mode of operation is selected.
A system for shifting a transmission into a first mode of operation and a second mode of operation, the system comprising:
- a servo assembly comprising:
- a housing that defines a cavity;
- a piston slidably disposed within the cavity and moveable between a first position and a second position, the piston having a first face and a second face;
- a first chamber defined by the housing and the first face of the piston;
- a second chamber defined by the housing and the second face of the piston;
- a first fluid port in communication with the first chamber;
- a second fluid port in communication with the second chamber;
- and
- a biasing member located within the housing and in contact with the piston;
- a valve assembly having a spool slidably disposed within a bore, the valve assembly having an inlet for receiving a pressurized fluid, a first outlet in communication with the first fluid port, a second outlet in communication with the second fluid port, and an exhaust port, wherein the valve assembly is operable to selectively provide the pressurized fluid from the inlet to the first outlet when the spool is in a first position and from the inlet to the second outlet when the spool is in a second position, and wherein the first outlet is in communication with the exhaust port when the spool is in the second position and the second outlet is in communication with the exhaust port when the spool is in the first position,
- wherein when the pressurized fluid is communicated to the first fluid port, the pressurized fluid enters the first chamber and the piston is moved to the first position to shift the transmission into the first mode of operation, and
- wherein when the pressurized fluid is communicated to the second fluid port, the pressurized fluid enters the second chamber and the piston is moved to the second position to shift the transmission into the second mode of operation.
Dependencies are inferred from the claim text.