Boom Cylinder Flow-Rate Limiting for Hydraulic Pressure Relief
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Solution Overview
Problem
Construction machines with hydraulic attachments face inefficiencies due to increased rod-side pressure and decreased head-side pressure in boom cylinders during boom raising operations, leading to energy loss and reduced power supply to other hydraulic cylinders, impairing work efficiency.
Innovation Solution
A construction machine with a flow-rate-limiting section and anti-cavitation circuit that controls the supply of hydraulic fluid to the boom cylinder's head-side fluid chamber, limiting flow rate during boom raising operations when rod-side pressure exceeds head-side pressure, and replenishes the head-side chamber with fluid from a tank to prevent cavitation and maintain efficient power supply to other cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a boom raising operation is performed to relieve rod-side pressure during excavation work, then the rod-side pressure of the boom cylinder is reduced allowing excavation work to continue, but discharge fluid from the hydraulic pump is supplied to the head-side fluid chamber of the boom cylinder which requires no fluid, causing energy loss and reducing supply amount to other hydraulic cylinders
Solution Approach 1:
A flow rate limiting valve is introduced as an intermediary component in the head-side supply line of the boom cylinder. This valve mediates between the hydraulic pump and the boom cylinder by restricting the flow rate of discharge fluid supplied to the head-side fluid chamber during boom raising operations, thereby preventing energy loss while still allowing pressure relief
2Reliability
If discharge fluid is supplied to the head-side fluid chamber of the boom cylinder during boom raising operation, then the boom cylinder can bear the excavation reaction force, but the supply amount of discharge fluid to other hydraulic cylinders (arm cylinder, bucket cylinder) is reduced, decreasing their power and work efficiency
Solution Approach 1:
The flow rate limiting valve applies local quality control by restricting flow rate only in the head-side supply line of the boom cylinder during specific operations. Other hydraulic cylinders (arm cylinder, bucket cylinder) receive full supply from the hydraulic pump without restriction, maintaining their power levels while the boom cylinder receives controlled flow sufficient for pressure relief
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 ensures a sufficient flow rate to hydraulic cylinders, enhancing work efficiency by preventing pressure loss and cavitation, while maintaining power supply without incurring significant pressure loss or surplus rod-side pressure during boom operations.
Implementation Method 1
a flow-rate-limiting section which limits a supply flow rate from the hydraulic pump to a head-side fluid chamber of the boom cylinder
Implementation Method 2
an anti-cavitation circuit for replenishing the head-side fluid chamber of the boom cylinder with hydraulic fluid from the tank
Data Source
Figure 1
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AI summary
Provided is a construction machine in which a rod-side pressure in a boom cylinder can be relieved without difficulty. The construction machine includes: a hydraulic pump 14; a working attachment including a boom, a boom cylinder 6, and another fluid-supplied cylinder; first and second operation devices 10, 11 for the boom cylinder 6 and the fluid-supplied cylinder; first and second control valves 12, 13; a flow-rate-limiting section 16; and an anti-cavitation circuit 17. The fluid-supplied cylinder is, for instance, an arm cylinder 7 closer to a leading end than the boom cylinder 6, receiving supply of hydraulic fluid from the hydraulic pump 14, together with the boom cylinder 6. A reaction force upon work accompanying extension of the fluid-supplied cylinder increases the rod-side pressure of the boom cylinder 6 and reduces a head-side pressure. The flow-rate-limiting section 16 limits a supply flow rate to a head-side fluid chamber 6a of the boom cylinder 6 from the hydraulic pump 14 only during a boom raising operation in a situation where the rod-side pressure of the boom cylinder 6 is higher than the head-side pressure thereof. The anti-cavitation circuit 17 replenishes hydraulic fluid from a tank T to the head-side fluid chamber 6a.