Hydraulic Closed-Circuit Valve Control for Stuck-Open Selector Failures
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Solution Overview
Problem
In hydraulic closed circuit systems for construction machines, unintended operation of hydraulic actuators can occur due to failures in selector valves or control systems, leading to operational issues and safety concerns, as check valves cannot be used to prevent bidirectional fluid flow, and existing solutions for hydraulic open circuit systems fail to control directional control valves effectively during controller failures.
Innovation Solution
A construction machine with multiple closed circuit pumps, hydraulic actuators, and switching valves, equipped with a machine body controller, first sensors to detect valve states, and a compulsory valve closing device that automatically closes other switching valves when one selector valve sticks open, preventing unintended actuator connections and ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching valves are used to connect hydraulic actuators to pumps in a closed circuit system, then operational flexibility and speed are improved, but unintended actuator operation occurs when valves stick open due to failure
Solution Approach 1:
The system applies preliminary anti-action by detecting valve open/closed states through sensors and preemptively closing other switching valves connected to the same pump when a valve is detected to be stuck open. This prevents unintended hydraulic fluid flow between actuators before it can cause harmful effects, while maintaining normal high-speed operation when valves function correctly.
2Reliability
If check valves are installed to prevent unintended fluid flow, then safety is improved, but the closed circuit system cannot function because check valves block bidirectional fluid flow required for actuator retraction
Solution Approach 1:
The system uses an intermediary control mechanism consisting of sensors that detect valve states and a controller that coordinates switching valve operations. This intermediary system prevents unintended fluid flow between actuators by closing other valves when one valve is stuck open, without blocking the necessary bidirectional flow through properly functioning valves, thus maintaining both safety and operational capability.
3Adaptability or versatility
If multiple switching valves are used for selective actuator connection, then operational versatility is improved, but system complexity increases making failure detection and control difficult
Solution Approach 1:
The system implements feedback by installing sensors on each switching valve to detect their open/closed states and providing this information to the controller. The controller uses this feedback to determine which valves are stuck open and automatically closes other valves connected to the same pump, enabling automatic failure response without increasing operational complexity for the user.
Data Source
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AI summary
[Subject] To provide a construction machine that incorporates a hydraulic closed circuit system capable of suppressing, even where a selector valve is sticked 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. [Solving Means] The construction machine includes first sensors (37d to 40d) that detect open-closed states of a plurality of switching valves (37 to 40), first compulsory valve closing devices (50, 51) that change over the plurality of switching valves to a closed position irrespective of open-close control by a machine body controller (11), and a valve device controller (33) 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 sticked 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 (35, 36) to which the one selector valve is connected is closed.