Hydraulic fan circuit having energy recovery

Abstract

A hydraulic fan circuit is disclosed. The hydraulic fan circuit may have a primary pump, a high-pressure passage fluidly connected to the primary pump, and a low-pressure passage fluidly connected to the primary pump. The hydraulic fan circuit may also have at least one accumulator in selective fluid communication with at least one of the high- and low-pressure passages, a motor, and a fan connected to the motor. The hydraulic fan circuit may further have a fan isolation valve fluidly connected to the high- and low-pressure passages. The fan isolation valve may be movable between a flow-passing position at which the motor is fluidly connected to the primary pump via the high- and low-pressure passages, and a flow-blocking position at which the motor is substantially isolated from the primary pump.

1 . A hydraulic fan circuit, comprising:
 a primary pump;   a high-pressure passage fluidly connected to the primary pump;   a low-pressure passage fluidly connected to the primary pump;   at least one accumulator in selective fluid communication with at least one of the high- and low-pressure passages;   a motor;   a fan connected to the motor; and   a fan isolation valve fluidly connected to the high- and low-pressure passages, the fan isolation valve being movable between a flow-passing position at which the motor is fluidly connected to the primary pump via the high- and low-pressure passages, and a flow-blocking position at which the motor is substantially isolated from the primary pump.   
     
     
         2 . The hydraulic fan circuit of  claim 1 , wherein the at least one accumulator includes:
 a high-pressure accumulator associated with the high-pressure passage; and   a low-pressure accumulator associated with the low-pressure passage.   
     
     
         3 . The hydraulic fan circuit of  claim 2 , further including a discharge valve in fluid communication with the high- and low-pressure accumulators, the discharge valve being configured to:
 selectively pass fluid from the primary pump to the high-pressure accumulator and from the high-pressure accumulator to the primary pump; and   selectively pass fluid from the motor to the low-pressure accumulator and from the low-pressure accumulator to the primary pump.   
     
     
         4 . The hydraulic fan circuit of  claim 1 , further including a discharge valve in fluid communication with the at least one accumulator and configured to selectively pass fluid from the primary pump to the at least one accumulator and from the at least one accumulator to the primary pump. 
     
     
         5 . The hydraulic fan circuit of  claim 4 , wherein the at least one accumulator is further configured to receive fluid from another hydraulic circuit. 
     
     
         6 . The hydraulic fan circuit of  claim 1 , wherein:
 the primary pump is a variable displacement pump;   the motor is a fixed displacement motor; and   the fan isolation valve is a two-position valve and moved to the flow-blocking position during discharge of the at least one accumulator.   
     
     
         7 . The hydraulic fan circuit of  claim 1 , wherein:
 the primary pump is a variable displacement pump;   the motor is a variable displacement motor; and   the fan isolation valve is movable to any position between the flow-passing and flow-blocking positions to adjust an amount of fluid allowed to pass from the at least one accumulator to the motor.   
     
     
         8 . The hydraulic fan circuit of  claim 7 , further including:
 a motor resolver in fluid communication with the high- and low-pressure passages; and   a motor displacement control valve in fluid communication with the motor resolver and the motor,   wherein the motor resolver and the motor displacement control valve are substantially isolated from the at least one accumulator and the primary pump when the fan isolation valve is in the flow-blocking position.   
     
     
         9 . The hydraulic fan circuit of  claim 1 , further including a makeup valve in fluid communication with the motor via the fan isolation valve when the fan isolation valve is in the flow-blocking position. 
     
     
         10 . The hydraulic fan circuit of  claim 1 , wherein the motor is allowed to free-spin when the fan isolation valve is in the flow-blocking position. 
     
     
         11 . The hydraulic fan circuit of  claim 10 , further including a flywheel connected to the fan to increase a free-spin duration of the fan. 
     
     
         12 . A hydraulic fan circuit, comprising:
 a primary pump;   a motor;   a fan connected to the motor;   a closed circuit fluidly connecting the primary pump to the motor;   a high-pressure accumulator in selective fluid communication with the closed circuit;   a low-pressure accumulator in fluid communication with the closed circuit;   an accumulator discharge valve in fluid communication with the high- and low-pressure accumulators;   a fan isolation valve fluidly connected to the closed circuit and to the motor; and   a controller in communication with the accumulator discharge valve and the fan isolation valve, the controller being configured to:
 regulate the accumulator discharge valve to:
 selectively pass fluid from the primary pump to the high-pressure accumulator and from the high-pressure accumulator to the primary pump; and 
 selectively pass fluid from the motor to the low-pressure accumulator and from the low-pressure accumulator to the primary pump; and 
 
 regulate the fan isolation valve to substantially isolate the motor from the primary pump during discharge of the high-pressure accumulator. 
   
     
     
         13 . The hydraulic fan circuit of  claim 12 , wherein the high-pressure accumulator is further configured to receive fluid from another hydraulic circuit. 
     
     
         14 . A method of recovering energy from a hydraulic fan circuit, comprising:
 pressurizing fluid with a pump;   directing the pressurized fluid to drive a fan motor;   accumulating excess pressurized fluid;   selectively discharging accumulated fluid to drive the pump; and   substantially isolating the fan motor from the pump during the discharging.   
     
     
         15 . The method of  claim 14 , wherein accumulating excess pressurized fluid includes accumulating excess pressurized fluid from the pump. 
     
     
         16 . The method of  claim 15 , wherein accumulating excess pressurized fluid also includes accumulating fluid from another circuit. 
     
     
         17 . The method of  claim 14 , further including allowing the fan motor to free spin during substantial isolation from the pump. 
     
     
         18 . The method of  claim 14 , further including providing makeup fluid to the fan motor during free spinning. 
     
     
         19 . The method of  claim 14 , further including adjusting pump displacement to absorb a desired torque during accumulator discharging. 
     
     
         20 . The method of  claim 14 , wherein accumulating includes accumulating high-pressure fluid from the pump for discharge to the pump, and accumulating low-pressure fluid from the fan motor for discharge to the pump.