Expansion Valve Position Sensing Through a Heat-Conductive Can
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Solution Overview
Problem
Existing electric expansion valves in air conditioning systems of motor vehicles face challenges in accurately detecting the valve position due to temperature-related thermal expansions and air gaps that lead to measurement inaccuracies.
Innovation Solution
A sensor connected to a separating can via a heat-conductive layer, which minimizes temperature differences and maintains a constant distance, allowing for precise detection of the rotor and valve position, using a 3D Hall sensor for contactless distance measurement and temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sensor is separated from the rotor by a separating can, then the sensor is protected from the wet region, but temperature differences and air gaps cause measurement inaccuracies
Solution Approach 1:
A heat-conductive adhesive layer is introduced as an intermediary between the sensor and the separating can. This adhesive layer replaces the air gap with a material that conducts heat effectively, allowing thermal compensation while maintaining the protective separation. The adhesive layer enables temperature equalization between the sensor and the rotor environment, improving measurement precision without compromising sensor protection.
2Measurement precision
If the sensor is connected via a heat-conductive layer, then temperature compensation is achieved, but the device complexity increases
Solution Approach 1:
The heat-conductive adhesive layer serves multiple functions simultaneously: it provides thermal conduction for temperature compensation, mechanical bonding to secure the sensor, and maintains a constant distance between the sensor and separating can. By combining these functions into a single component, the device complexity is minimized while achieving temperature-independent detection.
3Measurement precision
If thermal expansion is compensated, then detection accuracy improves, but manufacturing complexity increases
Solution Approach 1:
The heat-conductive adhesive layer changes its thermal conduction parameter to equalize temperatures between the sensor and the rotor environment. By actively managing the thermal parameter (heat conduction), the system compensates for thermal expansion effects without requiring complex mechanical compensation mechanisms, thereby improving detection accuracy while keeping manufacturing relatively simple.
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
Enables precise, temperature-independent detection of the expansion valve's opening state, reducing measurement inaccuracies and allowing for cost-effective and space-efficient installation.
Implementation Method 1
the sensor is connected to the separating can via a heat-conductive adhesive layer. This heat-conductive layer brings it about that the sensor is not separated from the separating can by an air layer and is thereby insulated thermally from the separating can
Implementation Method 2
using a 3D Hall sensor for contactless distance measurement
Data Source
AI summary
An expansion valve for an air conditioning system of a motor vehicle may include a housing, a sensor, a stepping motor or a BLDC motor, a valve seat, and a valve body. The stepping motor or the BLDC motor may include a rotor and a stator surrounding the rotor. The rotor may include a permanent magnet body connected non-rotatably therewith. A separating can may be provided that surrounds the rotor and separates a wet region on a rotor side from a dry region on a stator side. The sensor may be connected with the separating can via an adhesive layer formed as a heat-conductive layer.