Thermal Mass Flow Meter Weld Terminal
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Solution Overview
Problem
The thermal mass flow meter faces challenges in achieving stable spot welding of heating resistance wires to weld terminals due to differences in melting points and heat capacities, leading to issues like peeling and electrode adhesion, which decrease working efficiency.
Innovation Solution
Using Fe—Ni alloy wires and weld terminals with a melting point close to the heating resistance wire, and applying a coat layer on the weld terminals to prevent electrode welding while maintaining stable spot welding connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If weld terminals made of phosphor bronze are used for spot welding heating resistance wires, then ease of manufacture and electrical conductivity are improved, but welding stability deteriorates due to large melting point difference causing peeling
Solution Approach 1:
The weld terminal is constructed as a composite material structure with a phosphor bronze substrate providing ease of manufacture and electrical conductivity, and a nickel-plated surface layer providing welding stability by reducing melting point difference with the heating resistance wire. This composite structure resolves the contradiction by combining materials with complementary properties.
2Strength
If welding current is increased to improve welding strength, then connection strength is improved, but electrode adhesion worsens due to excessive heat causing working efficiency to decrease
Solution Approach 1:
The invention changes the material parameter of the weld terminal surface by applying nickel plating, which has a melting point closer to that of the Fe-Ni alloy heating resistance wire. This parameter change allows welding to be performed at lower currents, achieving sufficient connection strength without causing excessive heat that would lead to electrode adhesion, thus maintaining high working efficiency.
3Measurement precision
If Fe-Ni alloy wires are used for heating resistance wires, then measurement accuracy is improved, but welding stability worsens due to melting point difference with phosphor bronze weld terminals
Solution Approach 1:
The weld terminal uses a composite material structure where the phosphor bronze substrate maintains electrical conductivity and ease of manufacture, while the nickel-plated surface layer provides welding stability by matching the melting point characteristics of the Fe-Ni alloy heating resistance wire, enabling reliable spot welding while preserving 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
The solution ensures reliable electrical connections and improved reliability of the thermal mass flow meter by stabilizing spot welding and preventing electrode welding, thus enhancing the overall performance of the mass flow controller.
Implementation Method 1
A current is passed through the upstream heater element 3 and the downstream heater element 4, and a fluid flowing in the sensor tube 2 is thereby heated
Implementation Method 2
Since a fluid flows from the upstream toward the downstream and accordingly the heat applied to the fluid also move from the upstream toward the downstream, a temperature distribution of the sensor section 1 is changed
Implementation Method 3
a temperature distribution of the sensor section 1 is changed and electric resistances of the upstream heater element 3 and the downstream heater element 4 are changed. The changes of the electric resistances are measured, which can detect a mass flow of the fluid
Data Source
AI summary
A mass flow controller and mass flow meter are disclosed. The mass flow controller and mass flow meter include a sensor tube configured to transport a fluid, and an upstream heater element and a downstream heater element which are formed of heating resistance wires provided in an outer periphery of the sensor tube. At least one weld terminal is electrically connected to an end of one or more of the heating resistance wires by spot welding material. A temperature difference between the melting point of the weld terminal and a melting point of the heating resistance wires does not exceed 100 degrees Celsius, and one or more coat layer(s) is provided on a surface of the weld terminal.