Boom Pilot Pressure Control for Stable Excavator Lowering Speed
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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, leading to mismatched motion speeds and reduced operability during tasks like bumping and jack-up operations due to fluctuating bottom pressures, affecting the intended motion speed and efficiency.
Innovation Solution
A construction machine equipped with a solenoid valve controlled by a controller that adjusts the meter-in flow rate based on bottom pressure and operation amount, using a boom lowering and raising pressure reducing valves, and a pilot pump system to stabilize the flow rate, ensuring consistent motion speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the meter-in flow rate is controlled based on bottom pressure of the boom cylinder, then the flow rate can be adjusted for different work conditions (boom raising, boom lowering with suspended bucket, jack-up), but the flow rate becomes inconsistent during repeated boom operations (bumping work) due to sharp fluctuations in bottom pressure
Solution Approach 1:
A solenoid valve is introduced as an intermediary device between the bottom pressure sensor and the boom lowering pressure reducing valve. The solenoid valve receives electrical control signals from the controller and modulates the pilot pressure to the boom lowering pressure reducing valve, thereby stabilizing the meter-in flow rate during repeated boom operations while maintaining adaptability to different work conditions
Solution Approach 2:
The system implements feedback control by using the bottom pressure sensor to continuously monitor the bottom pressure of the boom cylinder and transmitting this information to the controller. The controller then adjusts the solenoid valve opening degree based on the feedback signal to maintain consistent meter-in flow rate during bumping work, while still responding appropriately to different operational states
2Speed
If the meter-in flow rate is increased for jack-up motion (when bucket is pressed against ground), then the boom motion speed increases, but the flow rate remains inappropriately high after switching from boom raising to boom lowering due to pressure fluctuation, causing motion speed mismatch
Solution Approach 1:
The controller predicts the upcoming boom lowering operation and提前 (in advance) adjusts the solenoid valve opening degree based on the operation amount sensor input. When the operator moves the operation lever toward the boom lowering position, the controller preemptively reduces the solenoid valve opening degree to prevent the meter-in flow rate from remaining inappropriately high, ensuring smooth transition and appropriate boom motion speed from the outset of the lowering operation
Solution Approach 2:
The system dynamically adjusts the solenoid valve opening degree in real-time based on the combination of bottom pressure feedback and operation lever position. This dynamic control allows the meter-in flow rate to adapt continuously to changing operational conditions, preventing motion speed mismatch during transitions between boom raising and lowering operations
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 flow rates during varying operational conditions.
Implementation Method 1
a solenoid valve that is disposed on a pilot hydraulic line that couples the boom lowering pressure reducing valve and a pressure receiving chamber of the second directional control valve and reduces the boom lowering pilot pressure for the second directional control valve
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 with use of the pilot fluid as a source pressure
Data Source
Figure 1~2
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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.