Fluid Pressure Actuator Angular Position Detection
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Solution Overview
Problem
Existing fluid pressure actuators face challenges in accurately detecting the angular movement of a rod due to rotational deviations caused by gaps between the rod and guide flange, leading to potential mounting failures during semiconductor chip bonding.
Innovation Solution
Incorporating a fluid pressure actuator design with a first and second position detector, where the second scale is cylindrical with an axis of rotation aligned with the piston body, and a controller that performs precise positioning control in both sliding and rotation directions using axial and rotation direction sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the encoder is provided outside the cylinder to detect the angular movement of the guide flange, then the structure is simplified and easier to manufacture, but the detection precision of the rod's actual angular position deteriorates due to rotational deviation caused by the gap between the rod and guide flange
Solution Approach 1:
A magnetic coupling mechanism is introduced as an intermediary between the encoder (outside the cylinder) and the rod (inside the cylinder). The magnetic coupling transmits rotational motion through the fluid pressure bearing gap without physical contact, eliminating the need for direct mechanical coupling while ensuring accurate position detection. This resolves the contradiction by enabling precise detection without requiring the rod and guide flange to be tightly coupled.
Solution Approach 2:
The patent replaces direct mechanical coupling (which would require tight tolerances and complex manufacturing) with a magnetic field-based detection system. The encoder detects the position of a magnetic component attached to or coupled with the rod, allowing non-contact measurement of angular position. This substitution eliminates the trade-off between ease of manufacture and detection precision.
2Reliability
If a fluid pressure bearing portion with a polygonal shape is used to enable non-contact transmission of rotation, then the reliability of rotation transmission is improved, but the manufacturing precision required for the bearing portion increases
Solution Approach 1:
The patent employs fluid pressure bearings that use pressurized fluid (liquid or gas) to create a non-contact support system between the rod and guide flange. The fluid pressure generates a bearing film that eliminates mechanical contact, ensuring reliable rotation transmission without requiring high manufacturing precision for the bearing surfaces. This directly resolves the contradiction by using fluid mechanics to decouple reliability from manufacturing precision requirements.
Data Source
AI summary
A fluid pressure actuator including a fluid pressure cylinder having a first position detector and a second position detector, a piston body having a piston head and a rod, the piston head mounted on the rod and slidably accommodated in the fluid pressure cylinder, the rod including a first scale and a second scale, the first scale facing the first position detector and the first position detector configured to detect a position in a sliding direction of the piston body, the second scale facing the second position detector and the second position detector configured to detect a position of the rod in a rotation direction of the piston body, and a controller configured to perform a first positioning control of a position of the rod in the sliding direction and a second positioning control of the rod in the rotation direction may be provided.