Hydraulic Drive System Tilting Angle Control for Construction Machines
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Solution Overview
Problem
In hydraulic drive systems of construction machines, rapid movement of the operating lever leads to energy loss of hydraulic oil due to inefficient control of pilot pressures, resulting in insufficient acceleration and deceleration torques.
Innovation Solution
A hydraulic drive system with a variable displacement bi-directional pump and a controller that adjusts the tilting angle of the pump based on turning signals to manage flow rates, reducing hydraulic oil outflow through relief valves and maintaining sufficient pressure for acceleration and deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the swash plate is directly moved by pilot pressures from the turning operation valve, then the response speed of the pump is improved, but a large amount of hydraulic oil flows out via the relief valve causing energy loss
Solution Approach 1:
The controller predicts the required flow rate based on the operation valve output and adjusts the swash plate tilting angle in advance. This preliminary action prevents excessive flow rate changes that would cause relief valve activation and energy loss, while still achieving rapid response through controlled prediction-based adjustment.
2Loss of energy
If the pilot pressures are controlled to prevent hydraulic oil from flowing out via the relief valve, then the energy loss is suppressed, but the pressure of the supply-side supply/discharge line decreases excessively resulting in insufficient acceleration
Solution Approach 1:
The controller continuously monitors the actual flow rate through the turning motor and compares it with the predicted flow rate. Based on this feedback, the controller dynamically adjusts the swash plate tilting angle to maintain optimal flow rate, preventing both excessive flow rate (which causes energy loss) and insufficient flow rate (which causes insufficient acceleration torque).
3Productivity
If the operating lever is moved fast, then the turning operation response is improved, but the hydraulic oil energy is lost due to relief valve activation
Solution Approach 1:
The controller predicts the required flow rate based on the operation valve output and adjusts the swash plate tilting angle in advance. This preliminary action prevents excessive flow rate changes that would cause relief valve activation and energy loss, while still achieving rapid response through controlled prediction-based adjustment.
4Speed
If the swash plate returns to center immediately during deceleration, then the turning operation response is improved, but a large amount of hydraulic oil flows out via the relief valve causing energy loss
Solution Approach 1:
The controller continuously monitors the actual flow rate through the turning motor and compares it with the predicted flow rate. Based on this feedback, the controller dynamically adjusts the swash plate tilting angle to maintain optimal flow rate, preventing both excessive flow rate (which causes energy loss) and insufficient flow rate (which causes insufficient acceleration torque).
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
The system effectively suppresses hydraulic oil energy loss during rapid lever movements, ensuring sufficient acceleration and deceleration while preventing vibration and maintaining stability.
Implementation Method 1
a variable displacement bi-directional pump connected to a turning motor by a pair of supply/discharge lines
Implementation Method 2
a regulator that changes a tilting angle of the bi-directional pump; a turning operation valve that receives a turning operation and outputs a turning signal
Data Source
AI summary
A bi-directional pump connected to a motor by a pair of supply/discharge lines; a regulator changes the bi-directional pump tilting angle; and a controller controls the regulator based on a turning signal outputted from a turning operation valve. At the turning acceleration, at which the signal increases, the controller calculates a motor flow rate passing through the motor and an instruction flow rate determined based on the turning signal. If the instruction flow rate is greater than a reference flow rate obtained by adding a predetermined value to the motor flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the reference flow rate. If the instruction flow rate is not greater than the reference flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the instruction flow rate.