JPH02228524A - Hot wire type air flowmeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hot wire air flow meter, and particularly to a hot wire air flow meter for detecting the intake air flow rate of an internal combustion engine.

[Conventional technology]

Regarding the structure of an air flow meter in which a bypass air passage is provided in the main air passage, the patent application No. 59-186 has already been filed.
No. 370, however, the said patent does not particularly discuss the structure of the support member that supports the hot wire and the heat-sensitive resistor, and as a result, the insert fitting of the support member that supports the hot wire and the heat-sensitive resistor is deformed. There are drawbacks that can cause problems.

[Problem to be solved by the invention]

The above-mentioned prior art does not take into consideration the structure of the support member that supports the hot wire and the heat-sensitive resistor, and there is a problem in that the insert fitting of the support member that supports the hot wire and the heat-sensitive resistor is deformed.

An object of the present invention is to prevent deformation of an insert fitting of a support member that supports a heating wire and a heat-sensitive resistor. This provides a hot wire air flow meter with improved dimensional accuracy.

[Means to solve the problem]

In order to achieve the above object, the support member that supports the heat wire and the heat-sensitive resistor has a two-stage molded structure.

[Effect]

Deformation of the insert fitting can be countered by the structure of the support member that supports the hot wire and the heat-sensitive resistor. In other words, the structure should be such that molding pressure is not applied to the insert fitting of the support member that supports the hot wire and the heat-sensitive resistor. In this study, the support member that supports the hot wire and the heat-sensitive resistor is formed with a two-stage mold structure to suppress the molding pressure during molding, so that the insert fitting is not deformed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a structural diagram of a hot wire air flow meter for measuring air flow.

1 is a hot wire in which a platinum wire is wound around an alumina bobbin and one surface is coated with a glass material.

This hot wire 1 is welded to a metal fitting 7 inserted into a support member 8 that supports the hot wire 1 and the heat-sensitive resistor 2 of a base 4 made of a conductive member. Note that the temperature-correcting heat-sensitive resistor 2 for detecting the intake air flow rate also has the same structure as the heating wire 1. Further, the metal fitting 7 is connected to the drive circuit 1 via the aluminum wire 6.
2 is electrically connected. Further, the drive circuit 12 is fixed with adhesive to a shield case 13 made of a conductive material. This drive circuit 12 and the hot wire 1. The hot wire air flowmeter to which the heat-sensitive resistor 2 is welded has a main air passage 1.
A bypass air passage 15 is formed integrally in the main air passage 14, and a bottom opening 10 is installed in the bypass air passage 15 of the body 9, which is attached by a screw 11 on the downstream side of the main air passage 14. Further, the drive circuit 12 applies a current to the hot wire 1 to heat it to a constant temperature. Regarding this heating temperature, the difference between the heating wire 1 and the air temperature is kept constant regardless of the amount of intake air 5, and the air temperature is corrected by the heat-sensitive resistor 2. Therefore, when a high flow rate flows through the air passage, a high current is passed through the hot wire 1, and when a low flow rate flows, a low current is passed through the hot wire 1 to maintain a constant temperature.

There is a monotonically increasing relationship between the current flowing through the hot wire 1 and the air flow rate, and the flow rate is detected based on this relationship.

The present invention is to prevent deformation of the insert fitting 7 in this hot wire air flowmeter. Moreover, this is intended to improve reliability and improve one-dimensional tank efficiency.

That is, the support member 8 that supports the hot wire 1 and the heat-sensitive resistor 2
By having a two-stage mold structure, deformation of the insert fitting 7 can be prevented.

This also improves reliability and dimensional accuracy.

According to this embodiment, there is an effect of improving reliability and improving two-dimensional tank performance.

〔Effect of the invention〕

According to the present invention, since deformation can be prevented, reliability can be improved, and thereby dimensional accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hot wire air flowmeter according to an embodiment of the present invention. 1... Heat wire, 2... Heat sensitive resistor, 3... Molded case.

Claims (1)

[Claims] 1. In a hot wire type air flowmeter, a bypass passage is provided in the main air passage of the body, and a heat wire for detecting the amount of intake air and a heat sensitive resistor for detecting the air temperature are arranged in the bypass air passage. A hot wire air flowmeter characterized in that a support member that supports a resistor has a two-stage molded structure.