Hydraulic Control Device for Excavator Boom and Arm Merging
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Solution Overview
Problem
In hydraulic excavators, the combined operation of boom lowering and arm pushing operations leads to power loss and decreased arm operation speed due to redundant oil flow to the boom cylinder, hindering energy efficiency.
Innovation Solution
A hydraulic control device with a merge switching valve that blocks hydraulic oil supply from the first hydraulic pump to the boom cylinder during combined operations, allowing oil to merge with the arm cylinder, and includes a replenishing circuit to prevent cavitation, enhancing energy efficiency by optimizing oil flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If oil from the first hydraulic pump is allowed to flow to the boom cylinder during combined operation, then the boom lowering operation is maintained, but redundant oil flow causes power loss and reduces arm cylinder flow rate
Solution Approach 1:
The merge switching valve dynamically switches between supply position and blocking position based on operational conditions. During combined operation (arm pushing + boom lowering), it blocks oil flow to the boom cylinder to prevent power loss, while during single boom lowering operation, it supplies oil to maintain operation. This dynamic switching resolves the contradiction by adapting the system state to operational requirements.
2Ease of operation
If oil from the first hydraulic pump is allowed to flow to the boom cylinder during combined operation, then the boom lowering operation is maintained, but the flow rate to the arm cylinder decreases, hindering arm operation speed acceleration
Solution Approach 1:
The merge switching valve dynamically controls oil flow distribution based on operational mode. During combined operation, it blocks the boom cylinder supply line to redirect all oil from the first hydraulic pump to the arm cylinder through the merging circuit, maximizing arm operation speed. During single boom lowering operation, it opens the supply line to maintain boom operation. This dynamic control resolves the contradiction between maintaining boom operation and maximizing arm speed.
3Productivity
If the flow rate of oil from the first hydraulic pump is increased to ensure sufficient flow to the arm cylinder during combined operation, then the arm pushing operation is accelerated, but the power consumption of the pump increases, reducing energy efficiency
Solution Approach 1:
The invention extracts the boom cylinder from the oil flow path during combined operation by using the merge switching valve to block its supply line. This extraction allows the first hydraulic pump to dedicate its full flow capacity to the arm cylinder without needing to increase overall pump power, thereby maintaining high arm operation speed while avoiding increased energy consumption. The merging circuit integrates this extracted flow with the second hydraulic pump's output.
4Loss of energy
If the merge switching valve blocks oil supply to the boom cylinder during combined operation, then energy efficiency is enhanced and arm operation speed is accelerated, but cavitation may occur in the boom cylinder
Solution Approach 1:
The replenishing circuit acts as an intermediary to prevent cavitation in the boom cylinder during combined operation. When the merge switching valve blocks oil supply from the first hydraulic pump, the replenishing circuit activates to supply necessary oil to the boom cylinder, preventing cavitation while allowing the main flow path to remain blocked for energy efficiency. This mediator resolves the contradiction between blocking flow for efficiency and maintaining flow for reliability.
Data Source
AI summary
A boom cylinder circuit is provided with a boom control valve for controlling supply and discharge of hydraulic oil to and from a boom cylinder, and a merge switching valve operable to be switched between a supply position at which hydraulic oil is suppliable from a first hydraulic pump to the boom control valve, and a blocking position at which a flow of hydraulic oil is blocked. A controller switches the merge switching valve to the blocking position when a combined operation of a boom lowering operation and an arm pushing operation is detected by pilot pressure sensors, and switches the merge switching valve to the supply position when only one of the boom lowering operation and the arm pushing operation is detected.