Active displacement control against temperature target

Abstract

A system includes a variable displacement pump (VDP) in fluid communication with an inlet line and with an outlet line. The VDP includes a variable displacement mechanism. A bypass valve (BPV) includes a BPV inlet in fluid communication with the outlet line, and a BPV outlet in fluid communication with a bypass line that feeds into the inlet line upstream of the VDP. An actuator is operatively connected to control the BPV to vary flow from the BPV inlet to the bypass line. An electromechanical actuator (EMA) is operatively connected to actuate the variable displacement mechanism. A temperature sensor is operatively connected to the outlet line to generate sensor output indicative of fluid temperature in the outlet line, wherein the temperature sensor is operatively connected to a controller for active control of the EMA and/or of the actuator based on temperature in the outlet line.

What is claimed is: 
     
         1 . A system comprising:
 a variable displacement pump (VDP) in fluid communication with an inlet line and with an outlet line, wherein the VDP includes a variable displacement mechanism configured to vary pressure to the outlet line;   a bypass valve (BPV) including a BPV inlet in fluid communication with the outlet line, and a BPV outlet in fluid communication with a bypass line that feeds into the inlet line upstream of the VDP;   an actuator operatively connected to control the BPV to vary flow from the BPV inlet to the bypass line;   an electromechanical actuator (EMA) operatively connected to actuate the variable displacement mechanism;   a controller operatively connected:
 to the EMA to control the variable displacement mechanism; and 
 to the actuator to control recirculation flow passed through the BPV based on requested flow from a downstream system supplied by the outlet line and based on a predetermined low threshold of flow through the VDP; and 
   a temperature sensor operatively connected to the outlet line to generate sensor output indicative of fluid temperature in the outlet line, wherein the temperature sensor is operatively connected to the controller for active control of the EMA and/or of the actuator based on temperature in the outlet line.   
     
     
         2 . The system as recited in  claim 1 , wherein the BPV includes no outlets other than the BPV outlet so all flow through the BPV is supplied to the BPV outlet. 
     
     
         3 . The system as recited in  claim 1 , wherein the controller is configured to:
 control the BPV to maintain a baseline flow through the BPV under a first condition wherein requested flow from the downstream system is above than the predetermined low threshold, and   control the BPV to increase the flow through the BPV above the baseline flow for a second flow condition wherein requested flow from the downstream system is at or below the predetermined low threshold.   
     
     
         4 . The system as recited in  claim 3 , further comprising a electrohydraulic servo valve (EHSV) connected in fluid communication with the BPV by a control line, wherein the EHSV is connected in fluid communication with both the inlet line and with the outlet line through respective connection lines, and wherein the EHSV is operatively connected to the controller for active control of the first EHSV to actuate the BPV. 
     
     
         5 . The system as recited in  claim 4 , wherein a first position sensor is operatively connected to the BPV to provide sensor output indicative of position of a valve member of the BPV, wherein the first position sensor is operatively connect the controller to provide feedback for controlling the BPV. 
     
     
         6 . The system as recited in  claim 1 , wherein a second position sensor is operatively connected to the variable displacement mechanism to provide sensor output indicative of position of the variable displacement mechanism. 
     
     
         7 . The system as recited in  claim 6 , wherein the second position sensor is operatively connect the controller to provide feedback for controlling the variable displacement mechanism. 
     
     
         8 . The system as recited in  claim 7 , wherein the controller is operatively connected to receive input indicative of flow demanded by the downstream system supplied by the outlet line. 
     
     
         9 . The system as recited in  claim 8 , wherein the controller is configured to control position of the valve member of the BPV to maintain bypass flow through the BPV in the second condition wherein the controller governs the bypass flow through the BPV according to
   BF=PF−DSFD
   
       wherein BF is flow through the BPV, PF is flow through the VDP, and DSFD is flow demanded by the downstream system supplied by the outlet line. 
     
     
         10 . A method comprising:
 receiving input indicative of flow demanded by a downstream system supplied from an outlet line of a variable displacement pump (VDP);   controlling a bypass valve (BPV) to recirculate flow from the outlet line to an input line of the VDP in the event of flow demanded by the downstream system dropping below a predetermined low threshold of flow through the VDP; and   controlling displacement of the VDP, wherein at least one of controlling the BPV and controlling displacement is based on fluid temperature in the output line.   
     
     
         11 . The method as recited in  claim 10 , further comprising controlling the BPV to recirculate flow from the outlet line to the inlet line at a constant base recirculation rate in the event of flow demanded by the downstream system being at or above the predetermined low threshold of flow through the VDP. 
     
     
         12 . The method as recited in  claim 11 , wherein the base recirculation rate is zero recirculation flow. 
     
     
         13 . The method as recited in  claim 10 , wherein controlling the BPV to recirculate flow includes governing the bypass flow through the BPV according to
   BF=PF−DSFD
   
       wherein BF is flow through the BPF, PF is flow through the VDP, and DSFD is flow demanded by the downstream system supplied by the outlet line. 
     
     
         14 . The method as recited in  claim 10 , further comprising receiving data from a sensor indicative of position of a valve member of the BPV, wherein controlling the BPV includes controlling the BPV based on position of the valve member. 
     
     
         15 . The method as recited in  claim 10 , further comprising receiving data from a sensor indicative of position of a variable displacement mechanism of the VDP, wherein controlling displacement includes controlling displacement of the VDP based on position of the variable displacement mechanism.