Variable Relief Valve for Closed-Circuit Hydraulic System Boosting
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Solution Overview
Problem
The existing closed circuit hydraulic systems for construction machines require multiple relief valves to implement the boosting function, leading to increased complexity, parts, and cost, as well as energy loss due to pressure loss through main control valves in traditional systems.
Innovation Solution
A closed circuit hydraulic system that uses a single variable relief valve to control pressure, accompanied by a charge line, charge pump, pilot check valves, and accumulators to manage flow and pressure, allowing for bidirectional supply of working oil to actuators and reducing pressure in the opposite direction to increase thrust or torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple relief valves are used to implement the boosting function in closed circuit hydraulic systems, then the boosting function can be achieved, but the system complexity, number of parts, and cost increase
Solution Approach 1:
The patent combines multiple relief valve functions into a single variable relief valve that can dynamically adjust its set pressure. This single valve replaces what would traditionally require multiple fixed relief valves, thereby reducing part count and system complexity while maintaining the boosting function capability.
Solution Approach 2:
The patent employs a variable relief valve whose set pressure can be dynamically changed based on operational requirements. This dynamic adjustment capability allows the system to achieve boosting function without requiring multiple fixed relief valves set at different pressures, simplifying the overall system architecture.
2Ease of operation
If traditional hydraulic systems with main control valves are used, then flow direction control is achieved, but energy loss due to pressure loss occurs
Solution Approach 1:
The patent removes the main control valve from the hydraulic system architecture. Instead of using a main control valve to direct flow, the system uses individual 2-way proportional directional control valves at each actuator, eliminating the energy losses associated with flow passage through a central control valve.
Solution Approach 2:
The patent introduces a flow dividing valve as an intermediary device that distributes flow from the hydraulic pump to multiple actuators. This flow dividing valve operates with lower pressure loss compared to traditional main control valves, reducing overall energy loss while maintaining flow direction control capability.
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 configuration simplifies the hydraulic system, reduces parts and cost, and enhances the lifespan of components by implementing the boosting function with reduced maximum pressure and increased thrust or torque without increasing the opposite direction force.
Implementation Method 1
a variable relief valve selectively changing a normal mode to limit a pressure of the charge line to a predetermined pressure or less and a boost mode to limit the pressure of the charge line to a pressure lower than the pressure of the charge line in the normal mode
Implementation Method 2
a charge pump supplying a supplement flow to the charge line
Implementation Method 3
increase the pressure of the charge line to increase the thrust or torque of each actuator
Data Source
AI summary
The present disclosure relates to a closed circuit hydraulic system for a construction machine including a plurality of actuators and a plurality of hydraulic pumps selectively supplying working oil to the plurality of actuators bidirectionally and the closed circuit hydraulic system includes: a charge line selectively connected with a low-pressure side hydraulic line which returns to the hydraulic pump from the actuator among hydraulic lines connecting the hydraulic pumps and the actuators; a charge pump supplying a supplement flow to the charge line; and a variable relief valve selectively changing a normal mode to limit a pressure of the charge line to a predetermined pressure or less and a boost mode to limit the pressure of the charge line to a pressure lower than the pressure of the charge line in the normal mode.