Load-Sense Flow Control Valve for Independent Meter-In and Meter-Out
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Solution Overview
Problem
Conventional hydraulic systems using spool valves are limited in controlling both the speed and pressure of actuators simultaneously due to coupled meter-in and meter-out restrictions, leading to inefficiencies and increased costs from the need for separate pressure-reducing valves.
Innovation Solution
A flow control valve with load-sense signal generation is introduced, featuring a main spool and springs to independently control fluid flow to and from an actuator, eliminating the need for a separate pressure-reducing valve by internally generating the load-sense signal, allowing for two degrees of freedom in controlling actuator speed and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spool valve is used to control hydraulic fluid flow, then the valve can control actuator speed, but it cannot independently control both meter-in and meter-out flows due to coupled restriction sizes
Solution Approach 1:
The valve is segmented into two independent spools: a first spool for controlling meter-in flow and a second spool for controlling meter-out flow. This segmentation allows each spool to independently control one direction of fluid flow, resolving the coupling limitation of conventional single-spool valves and enabling separate adjustment of inlet and outlet restriction sizes.
Solution Approach 2:
The invention transitions from a single-degree-of-freedom control system to a two-degree-of-freedom system by adding an independent control dimension. Each spool operates independently with its own control mechanism, allowing simultaneous and independent adjustment of meter-in and meter-out flows, effectively adding a dimensional degree of freedom to the flow control system.
2Ease of operation
If a pressure reducing valve is added to provide pilot fluid signal, then the spool valve can be actuated, but the system cost increases
Solution Approach 1:
The valve combines multiple functions into a single integrated device: flow control for meter-in, flow control for meter-out, and internal generation of pilot fluid signals. By merging the pilot fluid generation function within the valve body itself, the system eliminates the need for separate pressure reducing valves, reducing component count and system cost while maintaining full actuation capability.
Solution Approach 2:
The valve is designed as a multi-functional device that simultaneously performs meter-in control, meter-out control, and pilot fluid signal generation. This universal design allows a single valve to replace what would traditionally require multiple separate components, simplifying the overall hydraulic system while maintaining comprehensive control functionality.
3Reliability
If outlet restriction is used to control flow for overrunning load, then the load can be controlled, but energy loss occurs in other operating conditions where the restriction is not needed
Solution Approach 1:
The valve employs dynamic control through two independent spools that can be adjusted based on operating conditions. The meter-in and meter-out restrictions are not fixed but can be independently varied, allowing the system to optimize flow control for different operational modes such as lifting, lowering, and holding, thereby minimizing energy loss while maintaining load control reliability.
Solution Approach 2:
The invention enables independent adjustment of restriction parameters for meter-in and meter-out flows. By changing the restriction size parameters independently for each direction, the system can adapt to different operating conditions (overrunning load, lifting, holding) and optimize energy efficiency by applying restrictions only when necessary rather than maintaining fixed restrictions that cause continuous energy loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances hydraulic system efficiency by enabling independent control of meter-in and meter-out flows, reducing energy losses and system costs by eliminating the need for external pilot fluid signals and pressure-reducing valves.
Implementation Method 1
at least one spring configured to apply a biasing force on the main spool
Implementation Method 2
a first fluid force applied by fluid from the first port
Implementation Method 3
a second fluid force applied by fluid in the spring chamber
Data Source
AI summary
An example valve includes a first port fluidly coupled to a source of fluid, a second port fluidly coupled to an actuator, a third port fluidly coupled to a reservoir, and a fourth port configured to export a load-sense (LS) fluid signal. The valve can operate in: a neutral state, wherein fluid is allowed to flow from the second port to the third port, while the first port and the fourth port are blocked; a first actuated state, wherein fluid flow is throttled from the second port to the third port, while the first port and the fourth port remain blocked; or a second actuated state, wherein fluid flow from the second port to the third port is blocked, while fluid flow is allowed from the first port to the second port and from the second port to the fourth port.