Vehicle drivetrain hydraulic coupling

A hydraulic coupling for use with a vehicle drivetrain within a housing thereof containing hydraulic fluid to rotatively couple a pair of rotary members about a rotational axis, the hydraulic coupling comprising:

• a casing of a hollow construction that is rotatable within the housing about the rotational axis and connected to one of the rotary members;
• a hydraulic pump located within the casing along the rotational axis and including an impeller rotatively connected to the other rotary member and having between five and seven external teeth;
• the hydraulic pump also including an internal ring gear mounted by the casing for rotation eccentrically with respect to the toothed impeller and including internal teeth of a number one more than the impeller teeth and in a meshing relationship therewith to provide a pumping action upon relative rotation between the casing and the toothed impeller;
• an inlet port through which hydraulic fluid is pumped into the casing by the hydraulic pump;
• an outlet port through which the pumped fluid flows;
• and a control valve including a bimetallic valve element movable between an open position spaced from the outlet port and a closed position that closes the outlet port when the pumped fluid reaches a predetermined pressure to rotatively couple the impeller with the internal ring gear and thereby also couple the pair of rotary members to each other, the valve element moving toward the outlet port upon heating as the hydraulic fluid is heated and moving away from the outlet port upon cooling as the hydraulic fluid is cooled such that the movement of the valve element to the closed position is compensated for viscosity change as the hydraulic fluid is heated and cooled.

A hydraulic coupling for use with a vehicle drivetrain within a housing thereof containing hydraulic fluid to rotatively couple a pair of rotary members about a rotational axis, the hydraulic coupling comprising:

• a casing of a hollow construction that is rotatable within the housing about the rotational axis and connected to one of the rotary members;
• a hydraulic pump located within the casing along the rotational axis and including an impeller rotatively connected to the other rotary member and having between five and seven external teeth;
• the hydraulic pump also including an internal ring gear mounted by the casing for rotation eccentrically with respect to the toothed impeller and including internal teeth of a number one more than the impeller teeth and in a meshing relationship therewith to provide a pumping action upon relative rotation between the casing and the toothed impeller;
• an inlet port through which hydraulic fluid is pumped into the casing by the hydraulic pump;
• the casing having a transfer port through which the fluid is pumped;
• a clutch that extends between the casing and the other rotary member;
• the clutch having an actuating piston that actuates the clutch and that has an outlet port through which the pumped fluid flows;
• and a control valve including a bimetallic valve element mounted on the actuating piston and movable between an open position spaced from the outlet port and a closed position that closes the outlet port when the pumped fluid reaches a predetermined pressure to rotatively couple the impeller with the internal ring gear and thereby also couple the pair of rotary members to each other, the valve element moving toward the outlet port upon heating as the hydraulic fluid is heated and moving away from the outlet port upon cooling as the hydraulic fluid is cooled such that the movement of the valve element to the closed position is compensated for viscosity change as the hydraulic fluid is heated and cooled.

A hydraulic coupling for use with a vehicle drivetrain within a housing thereof containing hydraulic fluid to rotatively couple a pair of rotary members about a rotational axis, the hydraulic coupling comprising:

• a casing of a hollow construction that is rotatable within the housing about the rotational axis and connected to one of the rotary members;
• a hydraulic pump located within the casing along the rotational axis and including an impeller rotatively connected to the other rotary member and having between five and seven external teeth;
• the hydraulic pump also including an internal ring gear mounted by the casing for rotation eccentrically with respect to the toothed impeller and including internal teeth of a number one more than the impeller teeth and in a meshing relationship therewith to provide a pumping action upon relative rotation between the casing and the toothed impeller;
• an inlet port through which hydraulic fluid is pumped into the casing by the hydraulic pump;
• the casing having a transfer port through which the fluid is pumped;
• a clutch that extends between the casing and the other rotary member;
• the clutch having an actuating piston that actuates the clutch and that has an outlet port through which the pumped fluid flows;
• the outlet port including a main passage and a bleed passage;
• the actuating piston having an elongated recess having one end spaced from the outlet port and having another end at which the outlet port is located;
• and a control valve including an elongated bimetallic valve element having one end mounted within the piston recess at the one end thereof and having another end that is movable between an open position spaced from the outlet port and a closed position that closes the main passage of the outlet port when the pumped fluid reaches a predetermined pressure to rotatively couple the pair of rotary members to each other, the bleed passage of the outlet port allowing a bleed fluid flow through the piston with the valve element closed, the valve element moving toward the outlet port upon heating as the hydraulic fluid is heated and moving away from the outlet port upon cooling as the hydraulic fluid is cooled such that the movement of the valve element to the closed position is compensated for viscosity changes as the hydraulic fluid is heated and cooled.