Boom-Down Flow Control Valve for Excavator Pressure Management
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Solution Overview
Problem
In construction machines like excavators, the boom-down operation experiences a slowdown and reduced fuel efficiency due to increased pressure in the boom cylinder's large chamber as a result of excessive hydraulic fluid return, which is not effectively managed by conventional control valves.
Innovation Solution
A flow control valve with a boom-down flow control mechanism that includes a boom spool with first and second spool notches, where hydraulic fluid from the large chamber returns to the tank only at a predetermined pressure via the boom booster poppet, and further allows direct return through the second spool notch after the initial boom-down section, facilitating regeneration flow to the small chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic fluid returns through the boom booster poppet via the first spool notch, then cavitation is prevented, but the pressure in the large chamber increases and boom-down speed decreases
Solution Approach 1:
The flow control valve divides the return path into two separate notches: the first spool notch for initial return flow through the boom booster poppet (preventing cavitation), and the second spool notch for direct return (increasing speed). This segmentation allows simultaneous achievement of both cavitation prevention and high-speed operation.
Solution Approach 2:
The system dynamically switches between two return paths based on operating conditions. During initial boom-down operation, hydraulic fluid returns through the first spool notch and boom booster poppet. When the spool moves beyond the initial section, the second spool notch opens to provide a direct return path, dynamically adapting to maintain optimal performance.
2Adaptability or versatility
If the stroke of the boom spool extends beyond the initial operation section, then the boom-down operation range increases, but the amount of returning hydraulic fluid increases causing pressure increase and fuel efficiency reduction
Solution Approach 1:
The return flow path is segmented into two stages: initial operation section using the first spool notch with boom booster poppet, and extended operation section using the second spool notch for direct return. This segmentation enables the system to handle extended operation ranges without excessive pressure buildup, maintaining fuel efficiency.
Solution Approach 2:
The system changes the flow path parameter based on spool position. When the spool extends beyond the initial section, the second spool notch provides a direct return path with lower resistance, changing the hydraulic parameters to maintain efficient operation over extended ranges.
3Device complexity
If a constant flow passage area is used in the boom booster poppet, then the structure is simple, but the returning hydraulic fluid amount increases causing pressure increase in the large chamber
Solution Approach 1:
Instead of using a single flow passage with variable area, the invention segments the return path into two constant-area passages (first and second spool notches). This maintains structural simplicity while enabling flexible flow control to prevent excessive pressure buildup in the large chamber.
Solution Approach 2:
The second spool notch acts as an intermediary direct return path that bypasses the boom booster poppet. This intermediary path provides an alternative route for hydraulic fluid, preventing pressure buildup without complicating the main boom control mechanism.
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 prevents abnormal pressure increases in the boom cylinder's large chamber, enhances boom-down speed, and improves fuel efficiency by managing hydraulic fluid flow effectively during extended boom-down operations.
Implementation Method 1
a boom booster poppet mounted on the boom valve block in a path for returning a part of the hydraulic fluid returning from the large chamber of the boom cylinder to the hydraulic tank through a first spool notch of the boom spool to be opened only at the predetermined pressure or higher during the boom-down operation
Implementation Method 2
a boom spool slidably coupled to the boom valve block and shifted to control hydraulic fluid supplied from the hydraulic pump to a boom cylinder in response to pilot signal pressure
Data Source
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AI summary
The present invention relates to a flow control valve for a construction machine, comprising: a boom valve block connected to a hydraulic pump; a boom spool coupled to the boom valve block so as to be slidably moved, and switched on by the supply of pilot signal pressure in order to carry out a boom-up or boom-down operation, thereby controlling the hydraulic oil supplied from the hydraulic pump to a boom cylinder; a boom-up flow control means for supplying the hydraulic oil from the hydraulic pump to the large chamber of the boom cylinder through the boom spool, when switching on the boom spool in order to carry out the boom-up operation; and a boom-down flow control means for returning a part of the hydraulic oil, which returns from the large chamber of the boom cylinder, to the hydraulic tank through the boom spool only at a predetermined pressure or higher, when the boom spool is switched on in order to carry out the boom-down operation, wherein the part of the hydraulic oil, which returns from the large chamber of the boom cylinder, is directly returned to the hydraulic tank through the boom spool, and the part of the hydraulic oil, which returns from the large chamber of the boom cylinder, is made to join, as regeneration flow, the small chamber side of the boom cylinder.