Asymmetric Piston Rotation Restriction for Accurate Stroke Detection
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Solution Overview
Problem
In hydraulic pressure control circuits, actuators with pistons and cylinders face challenges in accurately detecting piston position due to potential rotation, leading to inaccurate detection when the piston rotates, and existing solutions to prevent rotation increase manufacturing costs.
Innovation Solution
An actuator design with a cylinder, piston, and stroke sensor, featuring first and second restriction mechanisms to limit piston rotation, and a sensor positioned to maintain detection accuracy even when the piston rotates, by allowing more rotation on one side than the other and shifting the sensor's center to align with the detection member's center in the direction of greater rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a restriction mechanism is provided to prevent piston rotation, then detection accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies asymmetry by providing different restriction mechanisms for different rotation directions: a first restriction mechanism (edge portion) that allows larger rotation amounts and a second restriction mechanism (restriction protrusion) that allows smaller rotation amounts. This asymmetric design enables sufficient detection accuracy while using simpler, lower-cost restriction structures compared to requiring high-precision bidirectional restrictions.
Solution Approach 2:
The sensor center is preliminarily positioned at a location shifted from the member to be detected center in the direction of the larger rotation amount. This preliminary positioning compensates for potential rotation, ensuring that the sensor maintains accurate detection capability even when the piston rotates within the allowed range, thereby reducing the need for high-precision restriction mechanisms.
2Measurement precision
If the sensor is positioned at the center of the member to be detected, then detection accuracy is maximized, but rotation causes the member to move away from the sensor
Solution Approach 1:
The sensor center is preliminarily positioned at a location shifted from the member to be detected center in the direction of the larger rotation amount. This preliminary offset positioning ensures that even when the piston rotates within the allowed range, the member to be detected remains within the sensor's detection range, maintaining both accuracy and reliability.
Solution Approach 2:
The patent applies local quality by creating different functional zones: the sensor is positioned in a specific location that accounts for rotation, while the restriction mechanisms are positioned to control rotation in specific directions. This localized functional differentiation ensures detection reliability under rotation conditions.
Data Source
AI summary
An actuator having sufficiently high detection accuracy while having a simple configuration is provided. An actuator includes a cylinder (51), a piston (52) that moves inside the cylinder (51), a stroke sensor (53) that detects a position of the piston (52), an edge portion (51a1) that restricts rotation to one side, and a restriction protrusion (51b) that restricts rotation to the other side. The amount of rotation allowed by the edge portion (51a1) is larger than the amount of rotation allowed by the restriction protrusion (51b). A center of a sensor (53c) of the stroke sensor (53) is shifted to one side from a center of a member to be detected (53b) fixed to the piston (52).