Dual Pressure Margin Priority Circuit for Higher Steering Pressure
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Solution Overview
Problem
Traditional hydraulic systems for tractors face limitations in steering force due to restricted hydraulic pressure, which is capped at less than 90% of the maximum pump outlet pressure to prevent blocking flow to low-priority functions, hindering the utilization of maximum pump pressure.
Innovation Solution
A dual pressure margin priority circuit is introduced, comprising a steering pressure compensation valve, priority valve, load sense cutoff valve, and load sense feed orifice, allowing the steering circuit to utilize higher pump pressure by dynamically controlling flow to steering and low-priority function inlets, ensuring maximum pump pressure is available without blocking low-priority functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single spool/single pressure margin priority valve with load sense relief feature is used to provide oil to the hydraulic steering circuit, then flow to low priority hydraulic functions is prevented from being blocked when steering pressure reaches relief setting, but the maximum pressure available at the steering valve inlet is reduced to less than 90% of the maximum pump outlet pressure
Solution Approach 1:
The patent divides the single priority valve into two separate priority valves with different relief settings. The first priority valve maintains flow to low-priority functions at lower pressures, while the second priority valve allows steering to access higher pressures up to the pump's maximum capability. This segmentation resolves the contradiction by allowing both flow continuity and maximum pressure availability.
Solution Approach 2:
The patent changes the pressure parameter by implementing two distinct relief pressure settings in the dual priority valve system. The first valve operates at a lower relief setting to protect low-priority functions, while the second valve operates at a higher relief setting to maximize steering pressure. This parameter differentiation enables both low-priority flow continuity and high steering pressure simultaneously.
2Force
If steering pressure is increased to maximize steering capacity, then steering force capability is improved, but flow to low priority hydraulic functions may be blocked
Solution Approach 1:
The dual priority valve system segments the pressure control into two stages: the first priority valve ensures flow availability to low-priority functions at normal operating pressures, while the second priority valve enables high steering force when needed by allowing pressure to rise to the pump's maximum capability without blocking low-priority flow paths.
Solution Approach 2:
The system dynamically adapts pressure allocation based on demand. When steering requires high force, the second priority valve allows pressure to increase to maximum levels. When steering demand is low, the first priority valve maintains pressure within ranges that ensure flow availability to low-priority functions. This dynamic response resolves the contradiction between maximum steering force and flow availability.
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 increases steering capacity by over 10% without modifying steering cylinders or valves, ensuring both steering and low-priority functions receive substantially all maximum pump pressure, enhancing operational efficiency.
Implementation Method 1
The load sense feed orifice has an inlet port hydraulically coupled to the outlet port of the steering pressure compensation valve to provide a steering valve dynamic load sense pressure
Implementation Method 2
The load sense cutoff valve can also include a bias spring, a second inlet port hydraulically coupled to a tank, and a load sense input hydraulically coupled to the steering valve dynamic load sense pressure at the first inlet port of the load sense cutoff valve
Implementation Method 3
A dual pressure margin priority circuit is disclosed that controls flow from a hydraulic pump to steering valve inlets and to low priority function inlets
Data Source
AI summary
A dual pressure margin priority circuit and method for controlling flow from a pump to steering valve and low priority inlets. A steering pressure valve controls flow from pump to steering valve inlets, and provides a steering valve load sense pressure. A priority valve controls flow from pump to low priority inlets. A load sense cutoff valve has a first inlet receiving the steering valve load sense pressure. The load sense cutoff valve controls flow through the priority valve based on steering valve load sense pressure at the first cutoff valve inlet. The cutoff valve can include a second inlet coupled to tank, and a load sense input coupled to the steering valve load sense pressure. The cutoff valve can be a pressure limiter valve. The priority and steering pressure valves can be 2-way proportional flow spool valves with bias springs, and contributing and opposing load sense inputs.