Hydraulic control system for automatic power transmission having transmission throttle valve with failsafe means

In a hydraulic control system for an automatic power transmission of an automotive vehicle including an acceleration producing member movable between a released position and a fully accelerating position;

• means for producing a line pressure in response to a second pressure applied thereto;
• a transmission throttle valve;
• a mechanical linkage establishing operative connection between the acceleration producing member and said transmission throttle valve;
• first passageway communicating with said transmission throttle valve;
• second passageway communicating with said transmission throttle valve;
• said transmission throttle valve being operative, in the absence of a failure in said mechanical linkage, to pressurize said first passageway with a throttle pressure lower in magnitude than the line pressure and to exhaust said second passageway,
• said transmission throttle valve including means for, in response to the failure in said mechanical linkage, minimizing the throttle pressure within said first passageway and for pressurizing said second passageway;
• means for applying as said second pressure the throttle pressure within said first passageway to said line pressure producing means when the pressure within said second passageway is lower than the pressure within said first passageway, and for applying as said second pressure the line pressure within said second passageway to said line pressure producing means when the pressure within said second passageway is higher than the pressure within said first passageway.

In an automotive power transmission for an automotive vehicle including an acceleration producing member movable between a released position and a fully accelerating position wherein the power transmission includes a transmission mechanism having incorporated therein fluid operated frictional units to be selectively actuated to produce a plurality of gear ratios in the transmission mechanism, a hydraulic control system for the transmission mechanism, comprising:

• a pressure regulator valve for producing a line pressure;
• at least one shift valve through which the line pressure delivered from the pressure regulator valve is to be distributed selectively to said frictional units;
• a transmission throttle valve engaged by said acceleration producing member through a mechanical linkage,
• first passageway means providing communication between said throttle valve and said shift valve;
• and
• second passageway means for providing communication between the throttle valve and said pressure regulator valve;
• the transmission throttle valve being operative to develop in both of the first and second passageway means a throttle pressure continuously variable with the movement of said acceleration producing member between said released position and said fully accelerating position in the absence of a failure in said mechanical linkage and to discharge fluid pressure from the first passageway means and pass the line pressure to the second passageway means through the throttle valve in response to a failure brought about in the mechanical linkage,
• said throttle valve including a wall portion formed with a valve chamber which is open at at least one axial end thereof;
• a valve plunger axially movable in said valve chamber and partially projecting outwardly from the valve chamber through said open axial end for engagement with said mechanical linkage, the valve plunger being axially movable relative to said wall portion in response to the movement of said acceleration producing member between said released position and said fully accelerating position thereof;
• a valve spool axially movable within said valve chamber;
• and biasing means engaging said valve spool for urging the valve spool to move in one direction within the valve chamber, said valve plunger being moved in the other direction through the valve chamber in response to the movement of said acceleration producing member away from the released position toward the fully accelerating position thereof and engaging the valve spool for moving the valve spool in said other direction within the valve chamber against the force of said biasing means and thereby producing said throttle pressure continuously variable with the axial movement of the valve plunger through the valve chamber in the presence of said line pressure in the throttle valve,
• said throttle valve further including a throttle failsafe valve sleeve axially movable within said valve chamber and on said valve plunger toward and away from said valve spool and resilient biasing means urging the valve sleeve to axially move toward the valve spool independently of said valve plunger, the valve sleeve being movable within the valve chamber between a first axial position allowing throttle pressure to be developed in said first passageway means and a second axial position allowing the throttle pressure to be discharged from said first passageway means and the line pressure to be developed in said second passageway means, and resilient biasing means engaging the valve sleeve for urging the valve sleeve to move toward said first axial position thereof within said valve chamber, said mechanical linkage including resilient biasing means urging said valve plunger to axially move in said one direction, within said valve chamber, said valve plunger being in axially pressing engagement with the valve sleeve for holding the valve sleeve in second axial position thereof by the force of said biasing means of said mechanical linkage in the presence of a failure in the mechanical linkage.

In an automotive power transmission for an automotive vehicle including an acceleration producing member movable between a released position and a fully accelerating position wherein the power transmission includes a transmission mechanism having incorporated therein fluid operated frictional units to be selectively actuated to produce a plurality of gear ratios in the transmission mechanism, a hydraulic control system for the transmission mechanism, comprising:

• a pressure regulator valve through which the line pressure delivered from the pressure regulator valve is to be distributed selectively to said frictional units;
• a transmission throttle valve engaged by said acceleration producing member through a mechanical linkage;
• first passageway means providing communication between said throttle valve and said shift valve;
• second passageway means for providing communication between the throttle valve and said pressure regulator valve;
• and
• means disposed with said throttle valve for developing in both of the first and second passageway means a throttle pressure continuously variable with the movement of said acceleration producing member between said released position and said fully accelerating position in the absence of a failure in said mechanical linkage and for discharging fluid pressure from the first passageway means and passing the line pressure to the second passageway means through the throttle valve in response to a failure brought about in the mechanical linkage.

In an automotive power transmission having a hydraulic control system the combination comprising:

• an acceleration producing member movable between a released position and a fully acceleration position;
• fluid operated frictional units to be selectively actuated to produce a plurality of gear ratios in the transmission mechanism;
• a pressure regulator valve for producing a line pressure;
• at least one shift valve through which the line pressure delivered from the pressure regulator valve is to be distributed selectively to said frictional units;
• a mechanical linkage;
• first passageway means fluidly communicating with said shift valve;
• second passageway means fluidly communicating with said pressure regulator valve;
• and
• transmission throttle valve means which is operatively connected with said acceleration producing member through said mechanical linkage and which is fluidly communicated with said first and second passageway means for normally developing in both of said first and second passageway means a throttle pressure which is continuously variable with the degree of movement of said acceleration producing member between said released position and said fully accelerating position and for, upon the loss of said operative connection between said acceleration producing member and said transmission throttle valve, discharging the fluid pressure in said first passageway means and passing line pressure into said second passageway means.