Hydraulically operated clutch

A power transmitting component comprising:

• a friction clutch having a plurality of first clutch plates and a plurality of second clutch plates that are interleaved with the first clutch plates;
• a reservoir configured to hold a hydraulic fluid;
• a hydraulic ram coupled to the friction clutch, the hydraulic ram having a chamber and a piston that is movable in the chamber between a first position which is retracted relative to the first and second clutch plates, and a second position in which the piston is extended toward the first and second clutch plates to a greater extent than when the piston is in the first position;
• a motor having an output shaft that is rotatable in a first rotational direction;
• a first pump driven by the output shaft and having a first port coupled in fluid communication to the reservoir, and a second port coupled in fluid communication to the chamber, the first pump having a first displacement and configured to provide hydraulic fluid of a first pressure and first flow rate from the second port when the output shaft rotates in the first rotational direction;
• a second pump driven by the output shaft and having third and fourth ports, the third port being coupled to the reservoir, the fourth port being coupled to the chamber, the second pump provides hydraulic fluid to the chamber when the output shaft rotates in the first rotational direction and a first pressure differential between the chamber and the fourth port is less than or equal to a first predetermined pressure differential, the second pump having a second displacement greater than the first displacement and configured to provide hydraulic fluid of a second pressure and a second flow rate from the fourth port when the output shaft rotates in the first rotational direction, the second pressure being less than the first pressure, and the second flow rate being greater than the first flow rate;
• and
• a first valve between the second pump and the hydraulic ram, the first valve moveable between an open position allowing fluid communication between the second pump and the chamber, and a closed position, fluidly isolating the second pump from the chamber, the first valve is moved from the open position to the closed position when the first pressure differential is greater than the first predetermined pressure differential;
• wherein the first and second pumps are simultaneously driven by the output shaft;
• and
• wherein the output shaft of the motor is rotatable in a second rotational direction opposite the first rotational direction, the first pump pumps hydraulic fluid from the chamber to the reservoir when the output shaft rotates in the second rotational direction, and the second pump circulates hydraulic fluid in a sub-circuit that is fluidly isolate from the hydraulic ram when the output shaft rotates in the second rotational direction and the first valve is in the closed position.

A power transmitting component comprising:

• a friction clutch having a plurality of first clutch plates and a plurality of second clutch plates that are interleaved with the first clutch plates;
• a reservoir configured to hold hydraulic fluid;
• a hydraulic ram having a chamber and a piston that is movable in the chamber between a first position, which is retracted relative to the first and second clutch plates, and a second position in which the piston is extended toward the first and second clutch plates to a greater extent than when the piston is in the first position;
• an isolation circuit coupled for selective fluid communication to the reservoir and the chamber;
• a motor having an output shaft that is driven by the motor in a first rotational direction;
• a first pump driven by the output shaft and having a first port coupled in fluid communication to the reservoir, and a second port coupled in fluid communication to the chamber, the first pump having a first displacement and configured to provide hydraulic fluid of a first pressure and first flow rate from the second port when the output shaft rotates in the first rotational direction;
• a second pump driven by the output shaft and having third and fourth ports coupled in fluid communication to the isolation circuit, the second pump having a second displacement and configured to provide hydraulic fluid of a second pressure and second flow rate from the fourth port when the output shaft rotates in the first rotational direction, the second flow rate being greater than the first flow rate, and the second pressure being less than the first pressure;
• and
• a first valve between the isolation circuit and the hydraulic ram, the first valve allowing fluid communication between the isolation circuit and the chamber when a first pressure differential between the chamber and the isolation circuit is less than or equal to a first predetermined pressure differential, and preventing fluid communication when the first pressure differential is greater than the first predetermined pressure differential;
• wherein the second pump circulates hydraulic fluid in a portion of the isolation circuit when the first pressure differential is greater than the first predetermined pressure differential.

A power transmitting component comprising:

• a friction clutch having a plurality of first clutch plates and a plurality of second clutch plates that are interleaved with the first clutch plates;
• a hydraulic ram coupled to the friction clutch, the hydraulic ram having a chamber and a piston that is movable in the chamber between a first position, which is retracted relative to the first and second clutch plates, and a second position in which the piston is extended toward the first and second clutch plates to a greater extent than when the piston is in the first position;
• a reservoir configured to hold a hydraulic fluid;
• an isolation circuit;
• a motor having an output shaft that is selectively rotatable in a first rotational direction and a second rotational direction that is opposite the first rotational direction;
• a high-pressure, low-displacement pump driven by the output shaft, a first input/output of the high-pressure, low-displacement pump being coupled in fluid communication to the reservoir, a second input/output of the high-pressure, low-displacement pump being coupled in fluid communication to the chamber;
• and
• a low-pressure, high-displacement pump driven by the output shaft and having a third input/output and a fourth input/output, the third and fourth input/outputs being coupled in fluid communication with the isolation circuit;
• wherein when the output shaft is driven in the first rotational direction and a pressure differential between hydraulic fluid output from the fourth input/output and hydraulic fluid in the chamber is less than or equal to a predetermined pressure differential, the isolation circuit permits fluid communication between the fourth input/output and the chamber and permits fluid communication between the reservoir and the third input/output;
• wherein when the output shaft is driven in the first rotational direction and the pressure differential between hydraulic fluid output from the fourth input/output and hydraulic fluid in the chamber is greater than the predetermined pressure differential, the isolation circuit inhibits fluid communication between the fourth input/output and the chamber, and permits fluid communication between the reservoir and the third input/output when a pressure of hydraulic fluid entering the third input/output is less than a second predetermined pressure;
• and
• wherein when the output shaft is driven in the second rotational direction, the low-pressure, high-displacement pump recirculates hydraulic fluid within a portion of the isolation circuit.