Hydraulic Pump and Meter-Out Valve Control for Lower Pressure Loss
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Solution Overview
Problem
Existing hydraulic systems for working vehicles face inefficiencies due to increased pressure upstream of proportional control valves, leading to reduced system efficiency and potential cavitation issues.
Innovation Solution
A hydraulic system configuration that includes a hydraulically actuated device, a hydraulic pump assembly with variable output, and a proportional control valve, where the hydraulic fluid exiting the actuated device flows through a restriction of the proportional control valve, allowing for independent control of fluid flow and pressure by varying the pump output and adjusting the restriction area of the proportional control valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the meter in area of the proportional control valve is reduced to control flow rate to the hydraulically-actuated device, then the flow rate is reduced, but the pressure upstream of the valve increases reducing system efficiency
Solution Approach 1:
Instead of controlling flow to the actuator by restricting inlet flow (traditional approach), the invention controls outlet flow from the actuator. This reverses the control direction, allowing flow rate adjustment without creating excessive upstream pressure, thereby maintaining system efficiency while achieving the desired flow control.
Solution Approach 2:
The invention changes the control parameter from inlet flow restriction to outlet flow restriction. By varying the meter out area rather than the meter in area, the system achieves flow control while avoiding the energy loss associated with upstream pressure buildup, thus changing the operational parameters to eliminate the contradiction.
2Speed
If the meter out area is decreased to reduce flow rate exiting the hydraulically-actuated device, then the flow rate is reduced and pressure is increased, but this can lead to cavitation when gravity complements the hydraulic force
Solution Approach 1:
The system incorporates feedback control by monitoring the flow rate and pressure conditions at the outlet of the hydraulically-actuated device. The proportional control valve adjusts the meter out area dynamically based on these conditions, ensuring that flow reduction does not create excessive pressure differentials that would cause cavitation, thus maintaining reliable operation.
Solution Approach 2:
The invention makes the meter out area dynamically adjustable through the proportional control valve, allowing real-time adaptation of the restriction level. This dynamic control enables the system to reduce flow rate when needed while simultaneously preventing cavitation by adjusting the restriction to maintain appropriate pressure conditions, resolving the contradiction between flow control and cavitation prevention.
3Productivity
If a single hydraulic pump supplies multiple hydraulically-actuated devices, then the pump output is shared based on meter in areas, but restricting meter in area to control flow sharing increases upstream pressure and reduces efficiency
Solution Approach 1:
Instead of controlling flow distribution to multiple actuators by restricting inlet flow at each actuator (traditional approach), the invention controls outlet flow from each actuator. This reversal allows each actuator to receive adequate flow from the shared pump without requiring restrictive meter in valves, thereby eliminating the upstream pressure buildup and associated energy losses while maintaining proper flow sharing.
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 configuration reduces hydraulic system losses by up to 50% compared to traditional independent metering systems, leading to improved efficiency, reduced pressure upstream of control valves, and enhanced control over fluid flow and pressure.
Implementation Method 1
the flow rate and pressure of hydraulic fluid expelled from a hydraulically-actuated device is often controlled by varying a 'meter out' area of a proportional control valve. For a given pump output and 'meter in' area, a smaller 'meter out' area results in a lower flow rate of hydraulic fluid from the hydraulically-actuated device than a larger 'meter out' area. In addition, the lower flow rate of hydraulic fluid associated with a smaller 'meter out' area results in an increase of pressure in a hydraulic fluid line connecting the hydraulically-actuated device to the proportional control valve.
Implementation Method 2
a hydraulic pump assembly for supplying a variable output of hydraulic fluid to the hydraulically actuated device
Data Source
AI summary
A hydraulic system for a working vehicle, the hydraulic system includes a hydraulically actuated device; a hydraulic pump assembly for supplying a variable output of hydraulic fluid to the hydraulically actuated device; and a proportional control valve, wherein the hydraulic system is arranged such that hydraulic fluid exiting the hydraulically actuated device flows through a restriction of the proportional control valve; and wherein the hydraulic system is configured to control a flow of hydraulic fluid supplied to the hydraulically actuated device by varying the output of hydraulic fluid from the hydraulic pump assembly, and to control a flow of hydraulic fluid exiting the hydraulically actuated device via adjusting a restriction area of the proportional control valve.