Dual Mode Hydraulic Circuit Control for Variable Displacement Pump
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Solution Overview
Problem
Existing open-centered hydraulic systems for vehicles face challenges in accurately controlling fluid flow when all control valves are in neutral position, leading to inconsistent command dead band and pressure issues at varying engine speeds and fluid temperatures, resulting in inadequate lubrication or wasted power.
Innovation Solution
A dual mode control system with a variable displacement pump and pressure sensors that adjust pump displacement based on fluid pressure measurements between valves, switching between operating and standby modes to maintain optimal pressure and flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If open-centered control valves are calibrated at high engine speeds with hot hydraulic fluid, then the system operates well under calibration conditions, but command dead band becomes inconsistent when operating at different conditions
Solution Approach 1:
The patent applies dynamics by making the pump displacement variable rather than fixed. The variable displacement pump automatically adjusts its displacement based on operating conditions (engine speed, fluid temperature, pressure demands), allowing the system to adapt dynamically to different operating scenarios rather than relying on static calibration. This resolves the contradiction by enabling the system to maintain consistent performance across varying conditions through real-time adjustment.
Solution Approach 2:
The patent changes the parameter of pump displacement from a fixed value to a variable parameter that can be adjusted based on operating conditions. By modifying this key parameter dynamically, the system can compensate for variations in engine speed and fluid temperature, maintaining consistent command dead band performance across different operating conditions rather than being constrained by fixed calibration.
2Reliability
If high pressure is maintained in open-centered systems at high engine speeds with low fluid temperature, then lubrication is adequate, but engine power is wasted
Solution Approach 1:
The variable displacement pump dynamically adjusts pump displacement based on actual system needs. When lubrication demand is low (high engine speed, low temperature), the pump reduces displacement to minimize energy consumption while still maintaining adequate pressure for lubrication. This dynamic adjustment eliminates the continuous high-pressure state that wastes engine power, resolving the contradiction between adequate lubrication and energy efficiency.
Solution Approach 2:
The patent changes the pressure parameter from a fixed high-pressure state to a variable pressure state that adjusts according to actual system demands. By modifying pump displacement, the system can maintain minimum necessary pressure for lubrication while avoiding excessive pressure that would waste engine power, thus resolving the energy loss contradiction.
3Loss of energy
If low pressure is maintained in open-centered systems at low engine speeds with high fluid temperature, then engine power is conserved, but lubrication becomes inadequate
Solution Approach 1:
The variable displacement pump dynamically responds to changing operating conditions. When engine speed is low and fluid temperature is high, the pump automatically increases displacement to maintain adequate pressure for proper lubrication, preventing the inadequate lubrication that would result from maintaining low pressure. This dynamic adjustment resolves the contradiction by ensuring lubrication adequacy while conserving energy through condition-based operation.
Solution Approach 2:
The patent adjusts the pressure parameter dynamically based on operating conditions. At low engine speeds with high fluid temperature, the system increases pump displacement to maintain necessary pressure for lubrication, rather than maintaining consistently low pressure. This parameter change ensures adequate lubrication while avoiding unnecessary energy consumption, resolving the contradiction between energy conservation and lubrication reliability.
Data Source
AI summary
A dual mode control system for a hydraulic circuit (200) having a variable displacement pump (216) includes at least two actuators, each controlled by a respective valve. The valves are connected in series with a pressure sensor (250) measuring a pressure of fluid between the first valve (224) and the second valve (234) and relaying a signal to the electronic controller (202). The electronic controller (202) operates in a first mode, varying the displacement of the pump (216) based on a command signal operating at least one of the valves, and operates in a standby mode, varying the displacement of the pump (216) based on the signal from the sensor, when both valves are in their respective neutral positions.