Boom Lowering Hydraulic Control for Stable Meter-In Flow
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Solution Overview
Problem
Existing construction machines, such as hydraulic excavators, face issues with inconsistent meter-in flow rates to the boom cylinder during operations like bumping work, leading to mismatched motion speeds and reduced operability due to sudden fluctuations in boom cylinder pressures.
Innovation Solution
A construction machine equipped with a solenoid valve and a controller that adjust the communication area between hydraulic valves based on boom cylinder pressure and operation amount, limiting the meter-in flow rate through a solenoid valve's opening degree command values to match the required motion speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the meter-in flow rate is controlled based on bottom pressure of the boom cylinder, then energy loss is suppressed during boom lowering with suspended bucket, but the motion speed does not correspond with required speed during bumping work
Solution Approach 1:
The system uses feedback from sensors detecting boom cylinder pressure and bucket ground contact state to dynamically adjust the meter-in flow rate control strategy. The controller switches between different control modes based on real-time feedback, ensuring energy efficiency during suspended bucket operations while maintaining responsive motion control during bumping work.
Solution Approach 2:
The meter-in flow rate control is made dynamic by switching between two distinct control strategies based on operational conditions. When the bucket is suspended, flow rate is limited to suppress energy loss. When the bucket contacts the ground during bumping work, flow rate is increased to match required motion speed, creating a dynamic adaptation to operational needs.
2Speed
If the meter-in flow rate is increased for jack-up motion, then the boom can be lowered with bucket pressed against ground, but the motion speed becomes inconsistent during repeated boom raising and lowering operations
Solution Approach 1:
The system detects the ground contact state of the bucket through sensors and provides feedback to the controller. This feedback enables the controller to distinguish between sustained ground contact during bumping work and transient contact, allowing consistent motion speed control by maintaining the high flow rate mode only when genuinely needed for jack-up motion.
Solution Approach 2:
The system uses its own operational parameters (boom cylinder pressure, bucket position) to automatically determine the appropriate control mode without external intervention. The controller self-adjusts the meter-in flow rate based on detected conditions, ensuring consistent motion speed characteristics during repeated operations.
3Reliability
If the bottom pressure of the boom cylinder fluctuates sharply during bumping work, then the control system responds to pressure changes, but the meter-in flow rate selection becomes incorrect due to pressure fluctuation
Solution Approach 1:
The system uses feedback from multiple sensors (pressure sensors, position sensors) to cross-validate the operational state. By comparing multiple parameters simultaneously, the controller can distinguish between pressure fluctuations caused by normal operation and those indicating genuine changes in bucket ground contact state, maintaining control accuracy despite pressure variations.
Solution Approach 2:
The controller acts as an intermediary that processes and interprets sensor signals before making control decisions. It filters and analyzes the raw pressure fluctuation data in context with other operational parameters, preventing incorrect meter-in flow rate selection by mediating between the fluctuating pressure inputs and the control output.
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 solution ensures the boom motion corresponds to the required speed, reducing energy loss and improving operability by stabilizing the meter-in flow rate during various operations.
Implementation Method 1
control of the meter-in flow rate to the boom cylinder is executed by controlling the flow rate of supply of a pressurized fluid to the boom cylinder by a solenoid valve according to the bottom pressure of the boom cylinder
Implementation Method 2
a boom lowering pressure reducing valve that outputs a boom lowering pilot pressure that drives the first directional control valve and the second directional control valve in a boom lowering direction
Data Source
AI summary
A construction machine including a solenoid valve that reduces a boom lowering pilot pressure for a second directional control valve and a controller that controls the solenoid valve is provided. The controller computes a first opening degree command value in such a manner that a communication area between a boom lowering pressure reducing valve and a pressure receiving chamber of the second directional control valve decreases in association with a bottom pressure of a boom cylinder, computes a second opening degree command value in such a manner that the communication area increases in association with increase in a boom lowering operation amount, decides a minimum opening degree command value as an opening degree command value of the solenoid valve when an elapsed time after boom raising operation is shorter than a set time and decides a minimum selected value of the first and second opening degree command values as the opening degree command value of the solenoid valve when the elapsed time is equal to or longer than the set time, and outputs a command signal according to the decided opening degree command value to the solenoid valve.