Energy recovery system for off-highway vehicles with hydraulic transformer coupled to transmission power take-off

Abstract

An energy conserving hydraulic system for a mobile work machine includes a prime mover, a drivetrain, a baseline hydraulic system, a power-take-off, a transformer, a work implement, and an accumulator. The drivetrain may include an automated manual transmission (AMT) that is rotationally coupled to the prime mover and the power-take-off. The baseline hydraulic system is powered by the prime mover and includes a first hydraulic circuit. The transformer is hydraulically coupled to second and third hydraulic circuits. The work implement is actuated by an actuator that is adapted to be simultaneously hydraulically coupled to the first and the second hydraulic circuits. The power-take-off is adapted to exchange shaft power with the transmission. A clutch selectively rotationally couples the transmission and the power-take-off. The accumulator is hydraulically coupled to the second hydraulic circuit. The second hydraulic circuit is hydraulically coupled to a first rotating group of the hydraulic transformer, and a third hydraulic circuit is hydraulically coupled to a second rotating group of the hydraulic transformer.

What is claimed is: 
     
         1 . A hydraulic system for a mobile work machine comprising:
 a prime mover;   a drivetrain including a transmission, the transmission rotationally coupled to the prime mover;   a baseline hydraulic system powered by the prime mover, the baseline hydraulic system including a first hydraulic circuit;   a second hydraulic circuit including a hydraulic transformer; and   a work implement actuated by an actuator;   wherein the actuator is adapted to be simultaneously hydraulically coupled to the first hydraulic circuit and the second hydraulic circuit.   
     
     
         2 . The hydraulic system of  claim 1 , wherein the transmission is an automated manual transmission (AMT). 
     
     
         3 . The hydraulic system of  claim 1 , further comprising a power-take-off adapted to exchange shaft power with the transmission, wherein the hydraulic transformer is rotationally coupled to the power-take-off. 
     
     
         4 . The hydraulic system of  claim 3 , further comprising a clutch adapted to selectively rotationally couple the transmission and the power-take-off. 
     
     
         5 . The hydraulic system of  claim 1 , further comprising an accumulator hydraulically coupled to the second hydraulic circuit. 
     
     
         6 . The hydraulic system of  claim 5 , further comprising a third hydraulic circuit, wherein the second hydraulic circuit is hydraulically coupled to a first rotating group of the hydraulic transformer, and wherein the third hydraulic circuit is hydraulically coupled to a second rotating group of the hydraulic transformer. 
     
     
         7 . The hydraulic system of  claim 1 , further comprising:
 a directional control valve of the first hydraulic circuit adapted to selectively actuate the actuator, the directional control valve providing a first valve position feedback;   a mode valve of the second hydraulic circuit adapted to selectively actuate the actuator, the mode valve providing a second valve position feedback; and   a controller adapted to coordinate actuation of the actuator using the first valve position feedback and the second valve position feedback.   
     
     
         8 . A method of supplying hydraulic power to an actuator of a work machine, the method comprising:
 receiving an operator input signal from an operator input with an electronic control unit;   processing the operator input signal to determine a desired velocity and/or a desired force of the actuator;   receiving an actuator pressure signal of an actuator pressure with the electronic control unit;   calculating an actuator flow requirement and/or an actuator pressure requirement that satisfies the desired velocity and/or the desired force of the actuator, respectively;   allocating a first portion of the actuator flow requirement to a baseline hydraulic circuit;   allocating a second portion of the actuator flow requirement to a pump-motor of a hydraulic transformer; and   controlling a first valve position of a first proportional valve and a second valve position of a second proportional valve and thereby implementing flow sharing according to the allocating of the first portion and the second portion of the actuator flow requirement.   
     
     
         9 . The method of  claim 8 , wherein the calculating of the actuator flow requirement includes mapping the operator input signal to an output of a conventional work machine. 
     
     
         10 . The method of  claim 8 , further comprising:
 receiving an accumulator pressure signal with the electronic control unit; and   setting a swash plate angle based on the accumulator pressure signal.   
     
     
         11 . The method of  claim 8 , wherein the first portion of the actuator flow requirement is zero. 
     
     
         12 . The method of  claim 8 , wherein the second portion of the actuator flow requirement is zero. 
     
     
         13 . The method of  claim 8 , wherein the controlling of the first valve position includes measuring a spool position of the first proportional valve and feeding back the measured spool position in a feedback loop. 
     
     
         14 . A method of recovering energy from an actuator of a work machine, the method comprising:
 receiving an operator input signal from an operator input with an electronic control unit;   processing the operator input signal to determine a desired velocity of the actuator;   receiving an actuator pressure signal of an actuator pressure with the electronic control unit;   calculating an actuator flow requirement that satisfies the desired velocity of the actuator;   allocating a first portion of the actuator flow requirement to a baseline hydraulic circuit;   allocating a second portion of the actuator flow requirement to a pump-motor of a hydraulic transformer; and   controlling a first valve position of a first proportional valve and a second valve position of a second proportional valve and thereby implementing flow sharing according to the allocating of the first portion and the second portion of the actuator flow requirement.   
     
     
         15 . The method of  claim 14 , wherein the first portion of the actuator flow requirement is zero. 
     
     
         16 . The method of  claim 14 , wherein the second portion of the actuator flow requirement is zero. 
     
     
         17 . The method of  claim 14 , wherein the controlling of the first valve position includes measuring a spool position of the first proportional valve and feeding back the measured spool position in a feedback loop. 
     
     
         18 . A method of supplying hydraulic power to propel a work machine, the method comprising:
 receiving an operator input signal from an operator input with an electronic control unit;   processing the operator input signal to determine a desired velocity of the work machine;   receiving a first pump-motor pressure signal of a first pump-motor with the electronic control unit;   allocating a first portion of the power requirement to an internal combustion engine; and   allocating a second portion of power requirement to a hydraulic transformer.   
     
     
         19 . The method of  claim 18 , wherein the first portion of the power requirement is zero. 
     
     
         20 . The method of  claim 18 , wherein the second portion of the power requirement is zero.