Closed-Circuit Hydraulic Valve Control for Stuck-Open Faults
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Solution Overview
Problem
In hydraulic closed circuit systems, unintended operation of hydraulic actuators can occur due to failures in selector valves or control systems, leading to operational issues and inefficiencies, especially when multiple switching valves are opened simultaneously, causing hydraulic fluid to flow between actuators with different pressure levels, and in hydraulic open circuit systems, failure of control components results in uncontrolled directional valve states.
Innovation Solution
A construction machine is designed with multiple closed circuit pumps, hydraulic actuators, operation levers, switching valves, and a machine body controller, along with a first sensor to detect valve states and a compulsory valve closing device that ensures other switching valves connected to a faulty selector valve are closed, preventing unintended actuator connections and maintaining system control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple switching valves are opened simultaneously due to valve or controller failure, then hydraulic fluid flows between actuators with different pressure levels, but unintended operation of hydraulic actuators occurs
Solution Approach 1:
The controller monitors the opening/closing states of switching valves through sensors and compares actual states with commanded states. When a discrepancy is detected (indicating valve sticking), the controller activates the compulsory valve closing device to close other switching valves connected to the same pump, preventing unintended actuator operation while maintaining system functionality.
Solution Approach 2:
The compulsory valve closing device acts as an intermediary safety mechanism between the switching valves and hydraulic actuators. When valve sticking is detected, this device forcibly closes other switching valves to prevent hydraulic fluid from flowing between actuators with different pressure levels, thereby eliminating the unintended operation pathway.
2Reliability
If a compulsory valve closing device is added to prevent unintended actuator operation, then system safety is improved, but device complexity increases
Solution Approach 1:
The controller serves multiple functions: normal operation control of switching valves, monitoring of valve states through sensors, detection of valve sticking conditions, and activation of the compulsory valve closing device. By consolidating these functions in a single control unit, the system avoids adding separate dedicated safety hardware, thereby limiting the increase in device complexity.
Solution Approach 2:
The compulsory valve closing device is integrated with the existing switching valve structure and control system. The solenoid coils and valve bodies are combined in a way that shares common mounting structures, hydraulic lines, and control circuitry, reducing the overall complexity increase despite adding safety functionality.
Data Source
AI summary
A construction machine incorporates a hydraulic closed circuit system capable of suppressing, even where a selector valve is stuck in an open state by a failure of the selector valve or a control system therefor, unintended operation of a hydraulic actuator and continuing operation of a machine body. The construction machine includes first sensors that detect open-closed states of a plurality of switching valves, first compulsory valve closing devices that change over the plurality of switching valves to a closed position irrespective of open-close control by a machine body controller, and a valve device controller that controls, when it is detected based on the open-closed states of the plurality of selector values detected by the first sensors that one of the plurality of selector values is stuck in an open state, the first compulsory valve closing device such that other selector valve connected to one of the plurality of closed circuit pumps to which the one selector valve is connected is closed.