Vacuum Pump Rotor Temperature Monitoring via Inductance
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Solution Overview
Problem
Turbo-molecular pumps face challenges in monitoring and controlling rotor temperature due to high tension stress on ferromagnetic bodies caused by centrifugal forces, which can lead to damage and creep deformation, especially since existing contactless temperature detection methods are not durable enough.
Innovation Solution
A vacuum pump design that incorporates a ferromagnetic body positioned near the rotational axis of the rotor with a Curie temperature matching the allowable temperature, using an inductance-type sensor to detect changes in magnetic permeability and control rotor speed or halt rotation when temperature limits are exceeded, thereby reducing stress and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring-shaped ferromagnetic body is installed around the rotor to detect temperature changes, then rotor temperature can be monitored contactlessly, but the ferromagnetic body is subjected to high tension stress from centrifugal force which may damage it
Solution Approach 1:
The ferromagnetic body is moved from a radial position (ring-shaped around the rotor) to an axial position (on the end face of the rotor). This dimensional change places the ferromagnetic body in a region with significantly lower centrifugal force, reducing tension stress while maintaining temperature monitoring capability through inductance detection
Solution Approach 2:
The invention uses the ferromagnetic body as a magnetic signature target that copies the temperature information of the rotor to which it is attached. The detecting portion detects temperature changes by measuring inductance variations caused by temperature-induced changes in the ferromagnetic body's magnetic permeability, rather than directly measuring the rotor itself
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 design effectively monitors and controls rotor temperature, preventing creep deformation and improving the durability of the ferromagnetic body by reducing tension stress and preventing overheating, while also reducing the number of parts and costs.
Implementation Method 1
uses the fact that the magnetic permeability of the ferromagnetic body greatly changes at the Curie temperature
Implementation Method 2
the magnetic permeability of the ferromagnetic body greatly changes at the Curie temperature
Implementation Method 3
The changes in magnetic permeability of the ferromagnetic body is detected by a coil as the temperature reaches the Curie temperature
Implementation Method 4
A detecting portion is provided in such a way as to oppose the ferromagnetic body and detects changes in magnetic permeability of the ferromagnetic body as the inductance changes
Implementation Method 5
Since the rotor of a turbo-molecular pump rapidly rotates, centrifugal force results in large tension stress
Data Source
AI summary
A vacuum pump configured to exhaust gas includes an inductance gap sensor positioned oppositely near an end face of a rotational axis of a rotational body including a rotor; a plurality of individually formed recesses disposed at the end face facing the gap sensor at respectively different angular positions; and at least one ferromagnetic body disposed in at least one of the recesses. The ferromagnetic body has a Curie temperature approximately equal to an allowable temperature of the rotor. The gap sensor senses inductance changes associated with changes in magnetic permeability of the ferromagnetic body to detect a temperature of the rotor. One of the recesses where the ferromagnetic body is not disposed is a rotational number sensor target. Thus, a rotational number of the rotor is detected based on a change in inductance when the rotational number sensor target passes opposite the inductance sensor.