Hydraulic drive circuit with parallel architectured accumulator

Abstract

A hydraulic circuit architecture for use in a drive circuit having a hydraulic pump for driving a load is disclosed. The hydraulic circuit architecture includes a flow control valve for controlling a hydraulic fluid flow rate supplied from the hydraulic pump to the load. The hydraulic circuit architecture also includes a hydraulic fluid accumulator arranged in parallel with respect to the flow control valve. Hydraulic circuit architectures having multiple accumulators arranged in parallel with respect to the flow control valve are also disclosed.

1 . A hydraulic circuit architecture for use in a drive circuit having a hydraulic pump for driving a load, the hydraulic circuit architecture comprising:
 a flow control valve for controlling a hydraulic fluid flow rate supplied from the hydraulic pump to the load; and   a hydraulic fluid accumulator arranged in parallel with respect to the flow control valve.   
     
     
         2 . The hydraulic circuit architecture of  claim 1 , wherein the flow control valve is a proportional flow valve. 
     
     
         3 . The hydraulic circuit architecture of  claim 1 , further comprising a relief valve for controlling a hydraulic system pressure output by the pump. 
     
     
         4 . The hydraulic circuit architecture of  claim 3 , wherein the relief valve is a proportional relief valve. 
     
     
         5 . The hydraulic circuit architecture of  claim 1 , wherein the hydraulic pump is a fixed displacement pump. 
     
     
         6 . The hydraulic circuit architecture of  claim 5 , further comprising a constant speed electric motor for driving the fixed displacement pump. 
     
     
         7 . The hydraulic circuit architecture of  claim 1 , further comprising a work flow path that extends from the pump through the flow control valve to the load, wherein the hydraulic circuit architecture includes an accumulator subsystem in fluid communication with the work flow path, the accumulator subsystem including a charge line for charging the hydraulic fluid accumulator and a discharge line for discharging the hydraulic fluid accumulator, wherein the discharge line connects to the work flow path at a location downstream from the flow control valve, and wherein the charge line connects to the work flow path at a location upstream from the flow control valve. 
     
     
         8 . The hydraulic circuit architecture of  claim 7 , further comprising:
 a charge line valve for selectively opening and closing the charge line;   a charge line one-way check valve that allows hydraulic fluid to flow through the charge line from the work flow path to the accumulator and prevents hydraulic fluid from flowing through the charge line from the accumulator to the work flow path;   a discharge line valve for selectively opening and closing the discharge line; and   a discharge line one-way check valve that allows hydraulic fluid to flow through the discharge line from the accumulator to the workflow path and prevents hydraulic fluid from flowing through the discharge line from the work flow path to the accumulator.   
     
     
         9 . The hydraulic circuit architecture of  claim 8 , wherein the charge line valve and the discharge line valve each comprise a two position valve including an open position and a closed position. 
     
     
         10 . The hydraulic circuit architecture of  claim 8 , wherein the accumulator circuit includes an accumulator flow control valve for controlling a charge rate of the accumulator and for controlling a discharge rate of the accumulator. 
     
     
         11 . The hydraulic architecture of  claim 6 , further comprising:
 a relief valve for controlling a hydraulic system pressure provided to the flow control valve by the pump;   a first valve arrangement for enabling and disabling actuators corresponding to the load;   a second valve arrangement for controlling charging and discharging of the accumulator; and   an electronic controller for coordinating operation of flow control valve, the relief valve and the first and second valve arrangements such that the hydraulic accumulator is charged when a flow demand of the load is less than an output flow of the hydraulic pump and the hydraulic accumulator discharges when the flow demand of the load is greater than the output flow of the hydraulic pump.   
     
     
         12 . The hydraulic architecture of  claim 11 , wherein during discharge of the accumulator the hydraulic system pressure is less than the accumulator pressure. 
     
     
         13 . The hydraulic architecture of  claim 11 , wherein the actuators power components of a machine having a repeating work cycle, the work cycle including a pressure demand having a pressure profile that varies over a plurality of phases of the work cycle and a flow demand having a flow profile that varies over the plurality of phases of the work cycle. 
     
     
         14 . The hydraulic architecture of  claim 13 , wherein the machine comprises an injection molding machine and the actuators include a first hydraulic cylinder powering a clamp, and second hydraulic cylinder for axially moving an auger and a hydraulic motor for rotating the auger. 
     
     
         15 . The hydraulic architecture of  claim 1 , wherein the hydraulic fluid accumulator is a first hydraulic fluid accumulator, wherein a second hydraulic fluid accumulator is also arranged in parallel with respect to the flow control valve, and wherein the first and second hydraulic fluid accumulators have different accumulator operating pressure ranges. 
     
     
         16 . A method for driving a load with a drive circuit having a hydraulic pump, the drive circuit including a flow control valve for controlling a hydraulic fluid flow rate between the hydraulic pump and the load and a hydraulic fluid accumulator arranged in parallel with respect to the flow control valve, the load corresponding to actuators of a machine having a repeating work cycle, the work cycle including a pressure demand having a pressure profile that varies over a plurality of phases of the work cycle and a flow demand having a flow profile that varies over the plurality of phases of the work cycle, the method comprising:
 using flow from the hydraulic pump to drive the load and charge the accumulator when the flow demand of the load is less than an average system flow for the work cycle; and   using flow from the hydraulic pump and discharge flow from the accumulator to drive the load when the flow demand of the load is larger than the average system flow for the work cycle, wherein during discharge of the accumulator a hydraulic system pressure at an outlet of the hydraulic pump is controlled such that the hydraulic system pressure is less than a hydraulic pressure of the accumulator.   
     
     
         17 . The method of  claim 16 , wherein the hydraulic fluid accumulator is a first hydraulic fluid accumulator, wherein the drive circuit includes a second hydraulic fluid accumulator arranged in parallel with respect to the flow control valve, wherein the first hydraulic fluid accumulator has a higher accumulator operating pressure range than an accumulator operating pressure of the second hydraulic fluid accumulator, and wherein one of the first and second hydraulic fluid accumulators is selected to provide the discharge flow based on how closely the accumulator operating pressure matches a demand pressure of the load. 
     
     
         18 . A hydraulic drive system for powering a load, the hydraulic drive system comprising:
 a fixed displacement hydraulic pump;   a constant speed electric motor for driving the fixed displacement hydraulic pump;   a relief valve for controlling a system pressure of the fixed displacement hydraulic pump;   a flow control valve for controlling a hydraulic fluid flow rate supplied from the fixed displacement hydraulic pump to the load; and   a first hydraulic fluid accumulator arranged in parallel with respect to the flow control valve.   
     
     
         19 . The hydraulic drive system of  claim 18 , further comprising a second hydraulic fluid accumulator arranged in parallel with respect to the flow control valve. 
     
     
         20 . The hydraulic drive system of  claim 19 , each of the first and second hydraulic fluid accumulators includes an accumulator circuit including:
 a charge line positioned upstream from the flow control valve;   a discharge line positioned downstream from the flow control valve;   a charge line valve for selectively opening and closing the charge line; and   a discharge line valve for selectively opening and closing the discharge line.