Clutch hydraulic control circuit with a pilot operated failure mode response valve

A method for hydraulically controlling a first clutch element along a first torque path of a transmission of a machine, the transmission including the first clutch element disposed on the first torque path from an input shaft to an output shaft;

• a second clutch element disposed on a second torque path from the input shaft to the output shaft, wherein the second clutch element is disposed on a portion of the second torque path that is different than the first torque path, a failure mode response (FMR) valve disposed between a first clutch valve and a first clutch actuator, the FMR valve having a normal position that permits hydraulic fluid received from the first clutch valve to flow to the first clutch actuator to engage the first clutch element when the first clutch valve is in an open position, and a failure position that obstructs the flow of the hydraulic fluid received from the first clutch valve to the first clutch actuator when the first clutch valve is in the open position, while simultaneously allowing flow from the first clutch actuator to a hydraulic fluid sump, wherein the transmission of torque along the first torque path is interrupted when the FMR valve is in the failure position, and a dual-purpose (DP) valve configured to:
• (a) permit, when in the open position, hydraulic fluid to flow:
• (i) to shift the second clutch element to an engaged position that permits transmission of torque along the second torque path at a second torque path gear ratio and (ii) to shift the FMR valve to the normal position and;
• (b) to obstruct, when in a closed position, the flow of hydraulic fluid:
• (i) to shift the second clutch element to the disengaged position that blocks transmission of torque along the second torque path and (ii) to shift the FMR valve to the failure position to disengage the first clutch element and block the transmission of torque on the first torque path,
• the method comprising:
• upon detecting a failed condition of the first clutch valve, activating, by a controller, shifting of the DP valve to the closed position to shift to or maintain the FMR valve in a failure position that disengages the first clutch element, the transmission of torque along the first torque path interrupted when the FMR valve is in the failure position, wherein the failed condition is when the first clutch valve is in the open position without a command from the controller.

A system for controlling a clutch element of a transmission of a machine, the transmission including an output shaft, a first torque path configured to provide a first torque path for transmission of torque from an input shaft to the output shaft, a first clutch element disposed on the first torque path and moveable between an engaged position and a disengaged position, the first clutch element configured to permit transmission of torque from the input shaft to the output shaft when in the engaged position and to block transmission of torque from the input shaft to the output shaft when in the disengaged position, wherein the first clutch element is the only clutch element disposed on the first torque path, a second torque path configured to provide a second torque path for transmission of torque from the input shaft to the output shaft, wherein a portion of the second torque path is different than the first torque path, and a second clutch element moveable between an engaged position and a disengaged position, the second clutch element disposed on the portion of the second torque path that is different than the first torque path, the second clutch element configured to permit the transmission of torque from the input shaft along the second torque path when in the engaged position and to block the transmission of torque from the input shaft on the second torque path when the second clutch element is in the disengaged position, the system comprising:

• a first clutch actuator configured to actuate shifting of the first clutch element between the engaged position and the disengaged position;
• a first clutch pressure control (CPC) valve having an open position and a closed position, the first CPC valve configured to permit when in the open position a flow of hydraulic fluid to the first clutch actuator through a first control pressure line to cause the first clutch actuator to shift the first clutch element to the engaged position;
• a failure mode response (FMR) valve in the first control pressure line between the first CPC valve and the first clutch actuator, the FMR valve having a normal position that permits hydraulic fluid received from the first CPC valve to flow to the first clutch actuator when the first CPC valve is in the open position, and a failure position that obstructs the flow of the hydraulic fluid received from the first CPC valve to the first clutch actuator when the first CPC valve is in the open position, while simultaneously allowing flow from the first clutch actuator to a hydraulic fluid sump, wherein the transmission of torque along the first torque path is interrupted when the FMR valve is in the failure position;
• a second clutch actuator configured to actuate shifting of the second clutch element between the engaged position and the disengaged position;
• a dual purpose (DP) valve having an open position and a closed position, the dual purpose valve configured to:
• (a) permit, when in the open position, hydraulic fluid to flow:
• (i) to the second clutch actuator through a second control pressure line to cause the second clutch actuator to shift the second clutch element to the engaged position and (ii) to the FMR valve through a pilot line to shift the FMR valve to the normal position and;
• (b) to obstruct, when in the closed position, the flow of hydraulic fluid:
• (i) to the second clutch actuator through the second control pressure line to cause the second clutch actuator to shift the second clutch element to the disengaged position and (ii) to the FMR valve through the pilot line to shift the FMR valve to the failure position, wherein transmission of torque from the input shaft to the output shaft is blocked along the first torque path when the dual purpose valve is in the closed position and transmission of torque from the input shaft through the second clutch element is blocked when the dual purpose valve is in the closed position;
• and
• a controller in communication with the first clutch valve and dual-purpose valve, the controller configured to:
• shift the first clutch valve to the open position to move the first clutch element to the engaged position, and shift the first clutch valve to the closed position to move the first clutch element to the disengaged position;
• and
• upon detecting a failed condition of the first clutch valve, shift the dual-purpose valve to the closed position, the first clutch valve being in the failed condition when the first clutch valve is in the open position without a command from the controller.