Measuring Device Membrane for Aqueous Urea Solution Freezing
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Solution Overview
Problem
Measuring devices for aqueous urea solutions in exhaust gas treatment face damage from freezing liquids expanding and exerting pressure on thin membranes, leading to measurement inaccuracies and short-term reliability due to the susceptibility of foam rubber compensators to chemical degradation and space constraints.
Innovation Solution
A measuring device with a membrane clamped between housing parts, featuring a trough-like design for support and a screw insert for secure installation, using a chemically resistant membrane that can deflect without material compression or stretching, allowing for flexible compensation of volume expansion and minimizing space usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measuring membrane is made thin to improve measurement sensitivity, then measurement accuracy is improved, but the membrane becomes susceptible to damage from freezing liquid expansion
Solution Approach 1:
The patent introduces a foam rubber compensating device that is pre-installed in the housing to absorb and compensate for the volume expansion of freezing liquid. This cushioning element is positioned beforehand to protect the thin measuring membrane from damage when freezing occurs, allowing the membrane to remain thin for high measurement accuracy while gaining protection against freezing-induced stress.
2Reliability
If foam rubber is used as a compensating device to counteract freezing expansion, then membrane protection is improved, but the device becomes susceptible to chemical degradation from aggressive urea solution
Solution Approach 1:
The patent separates the compensating function from the membrane structure by introducing a distinct foam rubber compensating device as a separate component. This extracted compensating element can be specifically designed and positioned to protect the membrane without requiring the membrane itself to have protective properties, allowing the membrane to remain thin and sensitive while the separate compensator handles the freezing expansion protection.
3Reliability
If foam rubber compensating device is used to relieve measuring surface stress, then membrane damage is prevented, but the device requires relatively large space in the housing
Solution Approach 1:
The patent employs a foam rubber compensating device that functions as a flexible volume-compensating element. The foam rubber's cellular structure allows it to expand and contract flexibly in response to freezing expansion, providing effective compensation while maintaining a compact form factor that minimizes space requirements within the housing.
4Measurement precision
If the measuring device is designed to be sensitive with thin membranes, then measurement quality is improved, but the device becomes vulnerable to tearing from overstressing during freezing
Solution Approach 1:
The patent introduces a foam rubber compensating device as an intermediary element between the thin measuring membrane and the freezing liquid. This mediator absorbs the mechanical stress from freezing expansion before it can reach the membrane, protecting the sensitive thin membrane from tearing while allowing the membrane to remain thin for high measurement quality.
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
Ensures long-lasting operation with high measurement accuracy and resistance to chemical damage, enabling precise control of nitrogen oxide reduction in exhaust gases while occupying less space.
Implementation Method 1
a membrane which is fixed in the housing at the edge and delimits an area free of this liquid with the housing on its side facing away from the measuring surface
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
1. Measuring device 2. A measuring device for determining an operating parameter, such as pressure or temperature, of a water-containing liquid, in particular an aqueous urea solution, which can be received in a measuring chamber (48) within a housing (8) which is also bounded by a measuring surface (2) of a measuring device (4) and an elastically deformable compensating device (26) which yields when the liquid freezes under its expansion pressure and thereby enlarges the measuring chamber (48), is characterized in that the compensating device has at least one membrane (26) which is fixed at the edge in the housing (8) and on its side facing away from the measuring surface (2) delimits a region (59) free of this liquid together with the housing (8).