Gas flow measuring apparatus

Abstract

To realize a gas flow rate measuring arrangement capable of suppressing the characteristic variation such as sensitivity, response by reducing stress transmission to a resister on a diaphragm without accompanying cost rise. The substrate around a diaphragm (10) is loaded with fixed resisters (3, 4) and a resistance thermometer bulb (5). These resisters are connected with exterior by terminals (12 ~ 24). To mitigate the stress transmission from a section the terminals (12 ~ 24) are arranged to the diaphragm (10), a groove (11) of U-shape is formed for length (Xd2) around the diaphragm (10). The groove (11) is formed of a horizontal groove 11a and two vertical grooves (11b, 11c). The region where the terminals (12 ~ 24) of the detection element 1 are formed and a region where the diaphragm (10) is formed are sectioned with the horizontal groove (11a) and the region where the terminals (12 ~ 24) are formed becomes a fixed part. The bottom of the fixed part is fixed to the substrate with adhesive bond and the actual stress to be transmitted to the region where the diaphragm (10) is formed is absorbed by the stress mitigating groove (11a).

Description

technical field [0001] The present invention relates to a flow meter for measuring the flow rate of gas, and more particularly to a gas flow measuring device suitable for detecting the flow rate of air sucked by an engine of a motor vehicle. Background technique [0002] As an example of a gas flow measuring device, a motor vehicle engine intake air flow meter is known: a motor vehicle engine intake air flow meter that detects a heating control current value of a heating resistor and converts it into an air flow rate; Alternatively, the engine intake air flowmeter of a motor vehicle detects the thermal influence on temperature sensing resistors arranged upstream and downstream of the heating resistor as a temperature difference signal, and captures it as a voltage of a bridge circuit. [0003] Here, when detecting the intake air flow rate to the engine of the motor vehicle, it is necessary to have stable characteristics even under the following conditions and environments. ...

AI Technical Summary

Problems solved by technology

In this miniaturization, in the technology described in Patent Document 1 above, when the detection element is already mounted on the substrate, stress due to the thermal expansion difference between the detection element part, the substrate, and the package (package) part may be generated or The residual deformation of the installation stress will affect the characteristics of the detection element

[0013] In addition, since the diaphragm on which the heater is mounted is a thin film, it is easy to cause deformation due to stress. The thin film forming the detection element uses a resistor made of polysilicon or platinum film, but these resistors have a resistance value that changes due to stress and strain. strain resistance effect

[0014] Therefore, if strain is applied to the resistor body, there is a possibility that a change in resistance may occur, resulting in a change in characteristics

Also, when a resin material or resin adhesive is used as the encapsulation material, stress changes due to creep may occur, and the characteristics may gradually change

[0015] Silicone adhesives have the problem of being prone to volume expansion due to deterioration due to gasoline or oil, and materials with reduced gasoline swelling properties are being developed, but they are costly and are used in large quantities for automobiles.

[0016] Moreover, it is difficult to control the application shape of the adhesive to a certain shape, and the stress is reduced and stabilized only by the limitation of the bonding position, which is also subject to great constraints in manufacturing

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