Mixed-Type Modular Directional Valve for LS Flow Sharing Saturation
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Solution Overview
Problem
Hydraulic systems face issues with energy inefficiency and responsiveness due to load-sensing and constant displacement pumps, where flow rates are not optimized for utilities with varying pressures, leading to excessive energy dissipation and unpleasant operator feedback in systems like excavators.
Innovation Solution
A modular directional valve with a combination of crossing and load-sensing elements, utilizing a constant displacement pump and a variable displacement pump, includes a summation element with a one-way valve and a two-way two-position piloted spool to automatically redirect flow rates and manage pressure, ensuring priority to functions under the constant displacement pump and optimizing flow distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a load-sensing variable displacement pump is used to supply flow rates independent of loads, then energy efficiency is improved, but the system becomes more reactive causing unpleasant operator feedback and excessive acceleration
Solution Approach 1:
The hydraulic system is divided into two separate circuits: a load-sensing circuit for excavation functions and a crossing circuit for travel functions. Each circuit has its own pump and control logic, allowing independent optimization of energy efficiency and operational smoothness for different machine functions
Solution Approach 2:
The system dynamically switches between load-sensing and crossing modes based on which circuit is active. The load-sensing pump varies displacement based on actual load requirements, while the crossing pump maintains constant displacement for smooth travel operation, adapting the control strategy to the specific function being performed
2Ease of operation
If a constant displacement pump is used to supply flow rates, then smoother operation is achieved, but energy dissipation increases due to excess flow rate being laminated to drain
Solution Approach 1:
The system segments hydraulic functions into two groups: those requiring smooth constant flow (travel) and those benefiting from load-adaptive flow (excavation). Each group is supplied by a dedicated pump type optimized for its specific requirements, eliminating the need to compromise between conflicting performance characteristics
Solution Approach 2:
Different pump types are assigned to different functional groups based on their specific requirements. The crossing circuit receives constant displacement pump output for smooth operation, while the load-sensing circuit receives variable displacement pump output for energy efficiency, allowing each local system to have optimal characteristics
3Productivity
If multiple utilities are operated simultaneously with an LS pump, then the pump sends only the total required flow rate, but excess pressure is dissipated by local compensators in utilities requiring low pressure
Solution Approach 1:
Utilities are segmented into high-pressure excavation functions and low-pressure travel functions, each supplied by dedicated pumps. This prevents the pressure mismatch that causes compensator dissipation, as each utility group receives pressure appropriate to its requirements without being forced to operate at unnecessarily high pressures
Solution Approach 2:
The summation element acts as an intermediary that combines the outputs of the two independent pump circuits. It allows each circuit to operate autonomously at its optimal pressure level while enabling simultaneous operation of multiple utilities without pressure conflicts or compensator dissipation
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 reduces energy dissipation by redirecting excess flow rates and managing pressure effectively, providing smoother operation and energy savings by ensuring only the required flow rate is used, while maintaining responsiveness and efficiency across multiple utility functions.
Implementation Method 1
a first one-way valve (8) allowing the flow rate to pass from the carry over (6) to the pressure load line (5)
Implementation Method 2
said summation element (3) comprising a two-way two-position piloted spool (4) which, through the LC of the crossing group of through type elements (E1, E2), connects or separates the delivery of the constant displacement pump (PA) from the tank (T)
Data Source
Figure 1
Figure 2
AI summary
A modular directional valve with two or more elements (E1, E2, E3, E4) in turn connectable to respective utilities (U) through the uses (A1, B1, A2... B4); of which one or more elements (E1 E2) are of the CA type while one or more elements are of LS flow sharing type (E3, E4). The valve designed to be connected to a first high pressure line P1 which connects the crossing elements to a constant displacement pump (PA) and a second high pressure line P2 which connects the LS flow sharing type elements to a variable displacement pump LS, the connection to a low pressure line, the connection to a load sensing signal line (LS2) with the variable displacement pump LS (PB). Said valve acting so that if the load sensing flow sharing elements (E3, E4) fed by the line (P2) designed for the connection with the pump (PB) are in saturation, it withdraws from the carry over (6) of the group of elements (E1, E2) of the crossing type the amount of flow rate equal to the difference between the flow rate required by the utilities (U) of the elements (E3, E4) and the maximum flow rate which can be supplied by the LS pump (PB); otherwise, it freely delivers the flow rate of the constant displacement pump to the low pressure line.