Flow restrictor assembly in transmission clutch control system

In a vehicle having a power shift transmission engageable in a plurality of gear ratios with a clutch control system controlling a first clutch and at least a second clutch including a flow restrictor assembly, the flow restrictor assembly comprising:

• a manifold fluidly coupled to the clutch control system to conduct fluid from a fluid supply to the first and second clutches, with the manifold having a modulator bore and a piston bore each in fluid communication with the fluid supply and the clutch control system;
• a modulator spool reciprocally mounted in the modulator bore with the modulator spool having an axial, longitudinal unloading spool bore substantially throughout the modulator spool length and having a modulator tank orifice;
• a piston reciprocally mounted in the piston bore and operatively connected on one end, by a spring connector, to the modulator spool and biased by a piston spring on the other end;
• and
• an unloading spool reciprocally mounted in the unloading spool bore, thereby nested inside the modulator spool with the unloading spool selectively in fluid communication with the modulator spool through a modulator tank orifice and biased on one end by an unloading spool spring, with the unloading spool responsive to fluid pressure changes acting on the modulator spool, as the clutch control system operates, to control the length of time the modulator spool regulates the rate of flow of fluid to the clutch control system through the modulator tank orifice.

In a vehicle having a power shift transmission engageable in a plurality of gear ratios with a clutch control system controlling a first clutch and at least a second clutch including a flow restrictor assembly, the flow restrictor assembly comprising:

• a manifold fluidly coupled to the clutch control system to conduct fluid from a fluid supply to the first and second clutches, with the manifold having a modulator bore, an unloading spool bore, and a piston bore each in fluid communication with the fluid supply and the clutch control system;
• a modulator spool having a modulator tank orifice, reciprocally mounted in the modulator bore;
• a piston reciprocally mounted in the piston bore and operatively connected on one end, by a spring connector, to the modulator spool and biased by a piston spring on the other end;
• and
• an unloading spool reciprocally mounted in the unloading spool bore, with the unloading spool selectively in fluid communication with the modulator spool through the modulator tank orifice and biased on one end by an unloading spool spring, with the unloading spool responsive to fluid pressure changes acting on the modulator spool ,as the clutch control system operates, to control the length of time the modulator spool regulates the rate of flow of fluid to the clutch control system through the modulator tank orifice.

In a vehicle having a transmission engageable in a plurality of gear ratios by engaging and disengaging first and second fluid clutches with the fluid from a fluid supply, a clutch control system comprising:

• a first fluid control means for controlling the flow of the fluid to the first clutch;
• a second fluid control means for controlling the flow of the fluid to the second clutch, wherein the first and second fluid control means are not both engaged to permit the flow of fluid into their respective clutches during engagement of any gear ratio of the plurality of gear ratios;
• a means for conducting the flow of fluid from the fluid supply to the first and second fluid control means;
• a means for restricting the flow of the fluid from the fluid supply to the means for conducting the flow of fluid;
• and
• a means for generating a signal representative of the pressure of the fluid within the means for conducting the flow of fluid.