Spool Valve Position Detection Without Added Sensors
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Solution Overview
Problem
The existing multiple direction switching valve systems fail to detect operation abnormalities, such as spool sticking, without increasing the number of parts, as they rely on additional position sensors to determine spool position and abnormality.
Innovation Solution
The spool valve device employs an electric actuator with a linear-motion conversion mechanism and an angle detector to calculate the spool position based on the angular position of the output shaft, allowing for the determination of operation abnormalities using the drive current and angular position, eliminating the need for additional position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a position sensor is provided at the spool to detect the position of the spool, then operation abnormality such as sticking can be determined, but the number of parts of the spool valve device increases
Solution Approach 1:
The angle detector, originally designed for controlling the electric motor's rotational position, is repurposed to also detect the spool's linear position. By establishing a correspondence relationship between the output shaft's angular position and the spool's linear position, the same sensor serves dual functions: motor control and spool position monitoring for abnormality detection.
Solution Approach 2:
A correspondence relationship (mapping function) is introduced as an intermediary to connect the angular position of the output shaft with the linear position of the spool. This mathematical relationship allows the angle detector's output to be converted into meaningful spool position information without requiring a separate position sensor on the spool.
2Device complexity
If the position of the spool is determined by thrust balance between electric motor and spring, then the system is simple, but malfunction such as sticking cannot be detected
Solution Approach 1:
The system implements feedback by continuously monitoring the correspondence between the angle detector's output and the expected spool position. When the spool is at a known position (detected by angle detector), the system expects a specific drive current. If the actual drive current deviates from the expected value, it indicates abnormality such as sticking, and the system can detect and report this condition.
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 enables the detection of operation abnormalities without increasing the number of parts, providing a more efficient and cost-effective solution for monitoring spool valve performance.
Implementation Method 1
an output shaft of an electric motor is coupled to a spool through a ball screw reduction gear. Therefore, when the output shaft of the electric motor is rotated, the spool moves in an axial direction thereof
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Provided is a spool valve device capable of detecting operation abnormality of a spool without increasing the number of parts. A spool valve device includes: a housing on which a plurality of channels are formed; a spool configured to move to change connection statuses of the plurality of channels; an electric actuator including an electric motor and a linear-motion conversion mechanism, the electric motor being configured to rotate an output shaft by torque corresponding to a drive current supplied to the electric motor, the linear-motion conversion mechanism being configured to convert rotational movement of the output shaft into straight movement and apply thrust corresponding to the torque to the spool to change the position of the spool; a biasing member configured to apply biasing force to the spool against the thrust of the electric actuator; an angle detector configured to detect an angular position of the output shaft of the electric motor; a driving portion configured to drive the electric motor by controlling flow of the drive current supplied to the electric motor based on a position command input to the driving portion and the angular position detected by the angle detector; and an abnormality determining portion configured to calculate the position of the spool based on the angular position detected by the angle detector and determine presence or absence of operation abnormality of the spool.