Optoelectric Sensor Mounting Structure for Thermal Stability
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Solution Overview
Problem
Optoelectric sensors with plastic housings suffer from measurement inaccuracies due to thermal expansion, which affects the relative position of light emitters and receivers, impacting measurement results.
Innovation Solution
The sensor design incorporates a monolithic sensor housing with a sleeve-shaped tube section and a carrier unit fixed by a common mounting point, decoupling thermal expansion from the light-emitting and receiving means, using materials with low thermal expansion coefficients like ceramic or metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plastic sensor housing is used, then manufacturing cost is reduced, but measurement precision deteriorates due to thermal expansion affecting the relative position of light emitters and receivers
Solution Approach 1:
The sensor housing is divided into two functionally distinct segments: an outer housing made of cost-effective plastic material and an inner carrier unit made of thermally stable material (metal or ceramic). This segmentation allows each part to fulfill its specific function - the outer housing provides cost-effective enclosure while the inner carrier unit maintains precise positioning of optical components despite temperature variations.
Solution Approach 2:
The carrier unit containing the light emitters and receivers is extracted as a separate component from the main plastic housing. This extracted carrier unit is made of material with low thermal expansion coefficient, isolating the sensitive optical components from the thermal effects of the plastic housing while maintaining the cost benefits of plastic construction.
2Measurement precision
If a metal sensor housing is used, then measurement precision is improved due to low thermal expansion, but manufacturing cost increases
Solution Approach 1:
Instead of making the entire housing from expensive metal, only the local region containing the optical components (the carrier unit) is made of metal or ceramic material with low thermal expansion. The remaining housing structure can be made of cheaper plastic, achieving thermal stability where needed while maintaining cost-effectiveness overall.
3Stability of the object's composition
If the sensor housing expands thermally, then the relative position of light emitters and receivers changes, but this cannot be avoided with plastic materials
Solution Approach 1:
The carrier unit acts as an intermediary between the plastic housing and the sensitive optical components. It provides a thermally stable mounting platform that mediates the thermal expansion of the plastic housing, preventing direct transmission of dimensional changes to the light emitters and receivers.
Solution Approach 2:
The design anticipates thermal expansion effects by providing a thermally stable carrier unit that cushions or compensates for the dimensional changes that will occur in the plastic housing during temperature variations, preventing these changes from affecting measurement accuracy.
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 maintains the relative position of light transmitters and receivers, ensuring accurate measurements by isolating thermal expansion effects, thus improving measurement precision.
Implementation Method 1
light transmitters (2) which are designed such that light signals can be emitted along a transmitting light path (SP) onto the detection area
Implementation Method 2
light receiving means (3) which are designed in such a way that light signals reflected from an object (100) in the detection area and propagating along a receiving light path (EP) can be detected
Implementation Method 3
the housing-side receptacle (7) is designed as a sleeve-shaped tube section (10) that completely penetrates the interior, and the carrier unit (9) comprises a circumferentially closed opening (11), with the tube section being located within this opening during operation
Data Source
Figure 1~2b
Figure 3~4b
AI summary
The present invention relates to an optoelectric sensor for detecting objects in a detection area, comprising light transmitters configured to emit light signals along a transmitting light path onto the detection area; light receivers configured to detect light signals reflected from an object in the detection area and propagating along a receiving light path; and a sensor housing comprising an interior space for receiving the light transmitters and the light receivers in a delivery state, wherein the sensor housing includes a receptacle for a fastening element to fix the optoelectric sensor to an external body in an operating state.According to the invention, the sensor in its delivered state comprises a carrier unit arranged in the interior for receiving and aligning the light transmitters and the light receivers, wherein the housing-side receptacle is designed as a sleeve-shaped tube section penetrating the interior completely, the carrier unit comprises a circumferentially closed opening, and in the operating state the tube section is arranged inside the opening in order to arrange the fastening element inside the opening and the tube section.