Hydraulic Power System for HVAC Compressor

Abstract

A modular HVAC unit may incorporate a hydraulically powered refrigerant compressor to more efficiently provide air conditioning to an operator cab of a work machine. The refrigerant compressor may be fluidly powered by a hydraulic fluid motor fluidly coupled to and driven by a variable displacement pump. An electronic controller may be configured to vary hydraulic pump flow rates to the motor via use of a proportioning control valve to maintain a desired evaporator performance temperature. The control valve may be configured to stop the HVAC unit whenever a backup system may be used, when a discharge is to be prevented, and/or when operator air-conditioning is not desired. The controller may monitor evaporator performance via a fin temperature sensor, and may send appropriate signals to the control valve for modulating hydraulic flows through the motor. The arrangement may provide a significant increase in the life and performance of the compressor.

What is claimed is: 
     
         1 . A fluid power system configured for supply operating power to, and control of, a refrigerant compressor in an HVAC unit adapted for air-conditioning a cab of a work machine, the fluid power system comprising:
 an electronic controller;   a fluid circuit including a fluid proportioning valve configured to receive signals from the electronic controller;   the fluid circuit including a variable displacement pump actuated by the electronic controller, and a fixed displacement motor driven by the variable displacement pump;   a refrigerant compressor rotatably coupled to the fixed displacement motor; and   a sensor configured to measure performance of an HVAC evaporator;   wherein the electronic controller is adapted to receive signals from the sensor to modulate the fluid proportioning valve to vary hydraulic motor speed and, in turn, the speed of the refrigerant compressor as a direct function of desired evaporator performance.   
     
     
         2 . The fluid power system of  claim 1 , wherein a fluid in the fluid circuit is a hydraulic fluid. 
     
     
         3 . The fluid power system of  claim 1 , wherein the sensor is a temperature sensor. 
     
     
         4 . The fluid power system of  claim 1 , wherein the motor and pump share a reservoir in an open loop circuit. 
     
     
         5 . The fluid power system of  claim 1 , wherein the HVAC unit is a modular unit. 
     
     
         6 . The fluid power system of  claim 1 , wherein the variable displacement pump includes a load sensing control aspect, whereby the pump is adapted to be automatically responsive to HVAC demand through sense of change in fluid circuit pressure. 
     
     
         7 . The fluid power system of  claim 1 , wherein the electronic controller is directly responsive to sensed change in refrigerant evaporator temperature, and commands changes in the fluid proportioning valve in response. 
     
     
         8 . An apparatus configured to power a refrigerant compressor of an HVAC unit adapted for air-conditioning a cab of a work machine, the apparatus comprising:
 an electronic controller;   a fluid proportioning valve configured to receive signals from the electronic controller;   a variable displacement pump adapted to be responsive to movements of the fluid proportioning valve, whereby the variable displacement pump is configured to be responsive to HVAC system demand;   a fixed displacement fluid motor fluidly driven by the pump, the motor being adapted for being rotatably coupled to a refrigerant compressor;   a fluid circuit configured to fluidly interconnect the pump, motor, and the fluid proportioning valve;   a sensor configured to measure performance of an HVAC evaporator; and   wherein the electronic controller is adapted to receive signals from the sensor for modulating the fluid proportioning valve to produce variation in motor speed and, in turn, the speed of the refrigerant compressor as a direct function of desired evaporator performance.   
     
     
         9 . The apparatus of  claim 8 , wherein a fluid in the fluid circuit is a hydraulic fluid. 
     
     
         10 . The apparatus of  claim 8 , wherein the sensor is a temperature sensor. 
     
     
         11 . The apparatus of  claim 8 , wherein the motor and pump share a common reservoir in an open loop circuit. 
     
     
         12 . The apparatus of  claim 8 , wherein the HVAC unit is a modular unit. 
     
     
         13 . The apparatus of  claim 8 , wherein the variable displacement pump includes a load sensing control aspect, whereby the pump is adapted to be automatically responsive to HVAC demand through sense of change in fluid circuit pressure. 
     
     
         14 . The apparatus of  claim 8 , wherein the electronic controller is directly responsive to sensed change in refrigerant evaporator temperature, and commands changes in the fluid proportioning valve in response. 
     
     
         15 . A control system for a hydraulically powered refrigerant compressor in an HVAC unit adapted for air-conditioning a cab of a work machine, the control system comprising:
 an electronic controller;   a fluid circuit including a fluid proportioning valve configured to receive signals from the electronic controller;   the fluid circuit including a variable displacement pump having an automated load sensing feature, and a fixed displacement motor driven by the variable displacement pump;   the fixed displacement motor being adapted to be coupled to a refrigerant compressor; and   a sensor configured to measure performance of an HVAC evaporator;   wherein the electronic controller is adapted to receive signals from the sensor to modulate the fluid proportioning valve to vary hydraulic motor speed and, in turn, the speed of the refrigerant compressor as a direct function of desired evaporator performance.   
     
     
         16 . The control system of  claim 15 , wherein a fluid in the fluid circuit is a hydraulic fluid. 
     
     
         17 . The control system of  claim 15 , wherein the sensor is a temperature sensor. 
     
     
         18 . The control system of  claim 15 , wherein the motor and pump share a common reservoir in an open loop circuit. 
     
     
         19 . The control system of  claim 15 , wherein the HVAC unit is a modular unit. 
     
     
         20 . The control system of  claim 15 , wherein the electronic controller is directly responsive to sensed change in refrigerant evaporator temperature, and commands changes in the fluid proportioning valve in response.