Elevator Brake Proximity Sensor Mounting for Temperature Compensation
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Solution Overview
Problem
Temperature changes affect the position of switching points in inductive proximity sensors used in elevator machinery brakes, leading to design tolerance issues and inaccuracies due to thermal expansion and resistance changes, especially in applications with small target movement and significant temperature fluctuations.
Innovation Solution
A temperature change compensation device is introduced between the inductive proximity sensor and the frame or armature part, made of materials like polyphenylene sulfide doped with graphene, which expands oppositely to counteract switching point changes, maintaining sensor accuracy by adjusting the air gap and thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a proximity sensor is used to detect target position in an elevator brake, then the sensor can detect the presence or absence of the target, but temperature changes cause the switching point to move, reducing measurement precision
Solution Approach 1:
The patent applies thermal expansion by selecting mounting structure materials with specific thermal expansion coefficients that compensate for the sensor's switching point drift. The mounting structure expands or contracts with temperature changes in a way that counteracts the sensor's temperature-induced switching point movement, thereby maintaining measurement precision across varying temperatures.
Solution Approach 2:
The patent changes the physical parameters of the mounting structure, specifically the thermal expansion coefficient, to match or compensate for the sensor's temperature characteristics. By carefully selecting materials with appropriate thermal expansion properties, the system compensates for temperature-induced switching point shifts without requiring active control mechanisms.
2Ease of manufacture
If the proximity sensor is mounted directly to the frame or armature, then the mounting is simple, but thermal expansion causes additional switching point drift, worsening measurement precision
Solution Approach 1:
The patent introduces a mounting structure as an intermediary element between the proximity sensor and the frame/armature. This intermediate mounting structure is specifically designed with thermal compensation properties, acting as a mediator that isolates the sensor from direct thermal effects of the brake components while maintaining mechanical support.
3Manufacturing precision
If tight design tolerances are used for small target movement, then the brake control is precise, but temperature-induced switching point movement exceeds the tolerance, reducing reliability
Solution Approach 1:
The patent applies beforehand cushioning by pre-compensating for temperature effects through the mounting structure's thermal expansion properties. The mounting structure is designed to anticipate and counteract the sensor's switching point drift before it affects measurement accuracy, providing a buffer that maintains reliability even under temperature variations.
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
The solution effectively mitigates temperature-induced changes in switching points, ensuring accurate monitoring of the machinery brake's operational state by compensating for thermal expansion and resistance changes, thereby maintaining precise control and reducing design tolerance issues.
Implementation Method 1
the material of the temperature change compensation device is such that it expands to an opposite direction with respect to a change in a position of a switching point of the inductive proximity sensor in response to a temperature change
Implementation Method 2
An input current is provided to an oscillator that generates an alternating current to the coil, which, in turn, generates a magnetic field in front of the proximity sensor. Now, when a target made of conductive metal is brought in a zone defined by boundaries of the magnetic field, some of the energy is transferred into the target causing eddy currents flowing in the target surface.
Data Source
Figure 1~2
AI summary
The invention relates to a machinery brake of an elevator, wherein the machinery brake comprises: a frame part (120) comprising an electromagnet, an armature part (110), and wherein the machinery brake further comprising an inductive proximity sensor (122) indirectly mounted to a one of the following: the frame part (120), the armature part (110) and a target (124) mounted to another of the following: the frame part (120), armature part (110), wherein the machinery brake further comprises, for establishing the indirect mounting: a temperature change compensation device (150) mounted between the inductive proximity sensor (122) and the one of the following: the frame part (120), the armature part (110). Some aspects relates to a method for compensating a change in switching point of an inductive proximity sensor (122).