Hydraulic Relief Valve Air Bleed Circuit for Construction Machines
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Solution Overview
Problem
Existing hydraulic drive devices in construction machines fail to effectively discharge air buildup in relief valves, leading to inefficiencies and potential operational defects.
Innovation Solution
A construction machine with a relief valve system that utilizes an air bleed line and pressure difference to discharge air from the relief valve, incorporating an air bleed switching valve controlled by a controller to manage air bleed based on the hydraulic circuit's state, ensuring effective air removal regardless of the relief valve's orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a relief valve is disposed in a hydraulic circuit to limit pump discharge line pressure, then pressure control function is improved, but air buildup in the relief valve cannot be effectively discharged
Solution Approach 1:
The relief valve is divided into two functional parts: a main body that performs pressure limiting, and a separate air bleed mechanism with its own oil passage that enables air discharge. This segmentation allows each function to be optimized independently without interfering with the other.
Solution Approach 2:
An air bleed oil passage acts as an intermediary channel connected between the relief valve and hydraulic oil tank, providing a dedicated pathway for air to escape from the relief valve without affecting the main pressure control function.
2Reliability
If air bleed line is added to discharge air from relief valve, then air discharge capability is improved, but device complexity increases
Solution Approach 1:
The air bleed oil passage is integrated into the existing hydraulic circuit architecture, merging the air discharge function with the hydraulic oil flow path. The passage utilizes the existing hydraulic oil tank and circuit structure, avoiding the need for completely separate air discharge infrastructure.
Solution Approach 2:
The air bleed oil passage serves multiple functions: it enables air discharge from the relief valve, maintains hydraulic oil flow continuity, and integrates with the existing tank system. This multi-functionality reduces the need for additional dedicated components.
3Ease of operation
If air bleed switching valve is introduced to control air bleed, then air bleed control precision is improved, but device complexity increases
Solution Approach 1:
The air bleed switching valve dynamically changes the flow state of the air bleed oil passage based on operational requirements. It can switch between open and closed states, allowing the system to adaptively control air bleeding during different operational phases without requiring complex manual intervention.
Solution Approach 2:
The switching valve operates based on feedback from the hydraulic circuit state, enabling automatic control of air bleeding. The system monitors conditions such as pressure and flow to determine when air bleed is necessary, reducing the need for manual operation while maintaining precise control.
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 system effectively discharges air from the relief valve, reducing the risk of air buildup and enhancing operational freedom and reliability, while maintaining pressure control functions, even during automatic operations.
Implementation Method 1
an air bleed line that connects the relief valve and a portion downstream from the back pressure generation mechanism in the return line
Data Source
Figure 1
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AI summary
A construction machine (100) includes a relief valve (40) that opens to limit a pressure of a pump discharge line (91) that is a line between a main pump (22) and a direction switching valve (31), a back pressure generation mechanism (67) that is disposed on a return line (92) that is a line connected to a tank (21) and generates a back pressure in the return line (92), and an air bleed line (90) that connects the relief valve (40) and a portion (92b) downstream from the back pressure generation mechanism (67) in the return line (92).