Hydraulic Hybrid Boom System Hydraulic Transformer

Abstract

A hydraulic system includes a hydraulic actuator, an accumulator, an accumulator charge valve, and a hydraulic transformer fluidly connected between the accumulator charge valve and the accumulator. The hydraulic transformer includes a transformer motor mechanically coupled to a transformer pump. The accumulator charge valve is fluidly connected between the transformer motor and the hydraulic actuator. The transformer pump is sized to permit a maximum flow therethrough of no more than three-quarters of a flow permitted through the transformer motor.

I claim: 
     
         1 . A hydraulic system comprising:
 a hydraulic actuator;   an accumulator;   an accumulator charge valve; and   a hydraulic transformer unit fluidly connected between the accumulator charge valve and the accumulator, the hydraulic transformer unit including a transformer motor mechanically coupled to a transformer pump, the accumulator charge valve being fluidly connected between the transformer motor and the hydraulic actuator, the transformer pump being sized to permit a maximum flow therethrough of no more than three-quarters of a flow permitted through the transformer motor.   
     
     
         2 . The hydraulic system of  claim 1  wherein the transformer pump is sized to permit a maximum flow therethrough of no more than one-half of a flow permitted through the transformer motor, excess flow from the transformer motor that does not flow to the transformer pump being directed to a tank. 
     
     
         3 . The hydraulic system of  claim 1  further including a discharge valve fluidly connected to the accumulator to control flow out of the accumulator. 
     
     
         4 . The hydraulic system of  claim 3  wherein the discharge valve is selectively operable to supply stored fluid from the accumulator to cause fluid to be supplied to a hydraulic function. 
     
     
         5 . The hydraulic system of  claim 1  further including a pump configured to supply fluid to the hydraulic actuator, and a torque assistance motor drivingly connected to the pump and fluidly connected to the accumulator, the torque assistance motor being configured to receive stored fluid from the accumulator to drive the pump. 
     
     
         6 . The hydraulic system of  claim 5  further including a discharge valve fluidly connected between the accumulator and the torque assistance motor, the discharge valve being configured to supply stored fluid from the accumulator to the torque assistance motor. 
     
     
         7 . The hydraulic system of  claim 2  wherein the accumulator is sized to contain a maximum of sixty-four liters of hydraulic fluid. 
     
     
         8 . The hydraulic system of  claim 1  further including a controller connected to the charge valve, the controller being configured to receive a command to retract the hydraulic actuator, and in response to the command, open the charge valve. 
     
     
         9 . The hydraulic system of  claim 3 , further including a controller connected to the discharge valve, the controller being configured to receive a command to provide fluid to the hydraulic actuator, and in response to the command, open the discharge valve to discharge stored fluid from the accumulator. 
     
     
         10 . The hydraulic system of  claim 6 , further including a discharge valve fluidly connected between the accumulator and the torque assistance motor, the discharge valve being configured to supply the stored fluid from the accumulator to the torque assistance motor. 
     
     
         11 . The hydraulic system of  claim 5 , wherein:
 the hydraulic actuator is a hydraulic cylinder configured to move a boom that is movably connected to a body of a machine, the hydraulic cylinder being one of a plurality of hydraulic cylinders,   the pump is selectively configured to supply fluid to a plurality of first chambers of the plurality of hydraulic actuators in parallel and supply fluid to a plurality of second chambers of the plurality of hydraulic actuators in parallel;   in an overrunning load condition, the accumulator is configured to store fluid received from the plurality of first chambers; and   in a non-overrunning load condition, the torque assistance motor is configured to receive the stored fluid from the accumulator to drive the pump to supply fluid to the plurality of first chambers.   
     
     
         12 . A method of recovering and reusing energy with a hydraulic system, the method comprising:
 selectively actuating an accumulator charge valve to direct flow of hydraulic fluid from a hydraulic actuator to a transformer motor of a transformer unit;   pumping no more than three-quarters of the hydraulic fluid flowing through the transformer motor by way of a transformer pump mechanically coupled to the transformer motor to an accumulator;   selectively the accumulator charge valve to discontinue flow to the transformer motor; and   selectively opening a discharge valve to direct flow from the accumulator to cause hydraulic fluid to be supplied to a hydraulic function.   
     
     
         13 . The method of  claim 12  wherein pumping no more than three-quarters of the hydraulic fluid flowing through the transformer motor includes the transformer pump pumping no more than one-half of the flow through the transformer motor to the accumulator. 
     
     
         14 . The method of  claim 13  wherein the accumulator is sized to receive no more than sixty-four liters of hydraulic fluid. 
     
     
         15 . The method of  claim 13  wherein selectively opening the discharge valve includes directing flow to a torque assistance motor, and the torque assistance motor at least partially powering a pump to cause hydraulic fluid to be supplied to the hydraulic actuator. 
     
     
         16 . The method of  claim 12  further including sensing a pressure in the accumulator, and at least one of the following when pressure within the accumulator nears its maximum
 reducing flow through the transformer pump, 
 opening the discharge to permit flow to bypass the accumulator, or 
 relieving pressure by venting hydraulic fluid to a tank through a relief valve. 
 
     
     
         17 . The method of  claim 13  wherein selectively actuating the accumulator charge valve to direct flow from the hydraulic actuator includes selectively actuating the accumulator charge valve to direct flow from a plurality of head-end chambers of a plurality of hydraulic cylinders to the transformer motor, and the selectively opening the discharge valve includes selectively opening the discharge valve to direct flow to a torque assistance motor, and operating the torque assistance motor to assist in operation of a mechanically coupled hydraulic pump to supply fluid to a plurality of rod-end chambers of the plurality of hydraulic cylinders. 
     
     
         18 . A machine comprising:
 at least one hydraulic actuator;   a pump configured to supply hydraulic fluid to the hydraulic actuator;   a power source configured to supply power to drive the pump, the power source including a torque assistance motor mechanically coupled to the pump;   an accumulator;   an accumulator charge valve;   a hydraulic transformer unit fluidly connected between the accumulator charge valve and the accumulator, the hydraulic transformer unit including a transformer motor and a transformer pump, the accumulator charge valve being fluidly connected between the transformer motor and the hydraulic actuator, the transformer pump being mechanically coupled the transformer motor, the transformer pump being sized to permit a maximum flow therethrough of no more than three-quarters of a flow permitted through the transformer motor; and   a discharge valve fluidly connected between the accumulator and the torque assistance motor.   
     
     
         19 . The machine of  claim 18 , wherein the accumulator is sized to hold no more than 64 liters of hydraulic fluid. 
     
     
         20 . The machine of  claim 18 , wherein the transformer pump is sized to permit a maximum flow therethrough of no more than one-half of a flow permitted through the transformer motor, excess flow from the transformer motor that does not flow to the transformer pump being directed to a tank.