Steering Isolation Valve Pressure Diagnostics for Startup Fault Detection
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Solution Overview
Problem
Existing electro-hydraulic steering systems face challenges in detecting the functional state of isolation valves in real-time, particularly during machine startup, which can lead to undetected faults and reduced safety ratings.
Innovation Solution
A method utilizing an integrated diagnostic pressure signal and pressure sensor to detect the functional state of a piloted or direct-operated isolation valve, allowing for real-time fault detection and improved diagnostic coverage without relying on moving parts of the steering system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a proxy verification method using wheel movement is employed to detect isolation valve state, then the system can detect functional state of safety elements, but it requires undesirable conditions (wheel movement) during machine startup and normal operation
Solution Approach 1:
The patent extracts the diagnostic function from the mechanical wheel movement system and relocates it to the hydraulic isolation valve itself by adding a dedicated diagnostic port. This allows the isolation valve state to be detected independently without requiring wheel movement or involvement of other steering system components.
Solution Approach 2:
The patent introduces a diagnostic pressure signal as an intermediary element that mediates between the isolation valve state and the detection system. This pressure signal serves as a direct indicator of valve position and functionality, eliminating the need for proxy verification methods that rely on wheel movement.
2Reliability
If real-time fault detection is implemented using integrated diagnostic pressure signal, then the diagnostic coverage is improved, but the device complexity increases due to additional pressure sensor and diagnostic port
Solution Approach 1:
The patent merges the diagnostic function with the existing isolation valve by integrating a diagnostic port directly into the valve body. This combines the isolation function and diagnostic capability into a single component, avoiding the need for separate diagnostic hardware and reducing overall system complexity.
Solution Approach 2:
The isolation valve provides its own diagnostic capability through the integrated diagnostic port that directly exposes the pressure signal. The valve essentially diagnoses its own state by making its internal pressure information accessible, eliminating the need for external diagnostic systems.
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 approach enables real-time detection of isolation valve failures, enhancing the overall safety rating of the system by reducing undetected faults and improving the diagnostic coverage in accordance with ISO 13849 and IEC 61508 standards.
Implementation Method 1
A 7-way / 2-position isolation valve acts as a blocking valve for flow between the main-stage spool and the cylinder(s). An additional output pressure signal path (diagnostic signal) connects a dedicated diagnostic signal port to tank pressure when in the closed state (not actuated) and to reduced pilot pressure supply when in the open state (actuated).
Data Source
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AI summary
A system and method for detecting the functional state of a piloted or direct-operated isolation valve in a hydraulic circuit is presented. In some examples the hydraulic circuit is a steering circuit and the isolation valve provides selective isolation between a hydraulic actuator and one or more metering valves. In some examples, the isolation valve assembly is movable between a first position, in which fluid flow between the metering valve and the actuator is enabled, and a second position, in which fluid flow between the metering valve and the actuator is blocked. When the isolation valve assembly is moved to one of the first and second positions, an inlet port and a pressure sensing port of the isolation valve assembly are placed in fluid communication with each other. When the isolation valve assembly is moved to the other of the first or second position, a second inlet port and the pressure sensing port are placed in fluid communication.