JP2000162010A - Heating resistance type air flow rate measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid dropping a sub-air passage in a main air passage by providing irregularities on a housing and the sub-air passage perpendicularly to the inserting direction. SOLUTION: A protrusion 32 provided at a sub-air passage 3 is fitted into a recess 14 provided at a circuit module 10 to mount the sub-air passage 3. If the wall of the protrusion 32 is thinned, the sub-air passage 3 can be easily pressure-fitted but may be easily drawn off. When the circuit module 10 has been inserted in a body 1, an elastic body 11 exists therebetween to function for clamping the sub-air passage barrel, thus resolving the dropping-off. Thus, while the conventional hermetic function of the elastic body is kept, the holding function of the sub-air passage can be enhanced, utilizing the nature of the elastic body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating resistor type air flow measuring device.

[0002]

2. Description of the Related Art As a known technique closest to the present invention, there is a heating resistor type air flow measuring device described in Japanese Patent Application Laid-Open No. 8-327423. As a feature of the heating resistor type air flow measuring device for an internal combustion engine, a sensor member is often provided in a sub air passage member 7 having a bend to reduce an error due to intake pulsation.

For this reason, the base member 1 including the support pins 5
0, the sensor members 4 and 5 are electrically connected, and then the sub air passage member 7 is attached to the base member 10 by bonding or the like.
The auxiliary air passage including the sensor unit is inserted into the insertion hole 19 provided in the main air passage component 1, and a part of the circuit module 18 is fixed to the outer wall of the main air passage using a screw or the like. .

In this structure, if the adhesive portion of the sub air passage member is peeled off, the sub air passage member may fall into the main air passage and be sucked into the engine. For this reason,
Japanese Patent Application Laid-Open No. 8-327423 has a structure in which a stopper member 11 is provided to prevent the auxiliary air passage from dropping off even if a part of the insertion hole 19 comes off.

[0005]

In the above-mentioned conventional method, ideally, it is better that the gap between the stopper member and the sub air passage member is small, but the stopper member surface and the sub air passage member surface contact each other. When fixing the circuit module to the outer wall of the main air passage component using screws or the like, there is a possibility of damaging the internal drive circuit board, so a certain gap is required in consideration of productivity. .

However, in this case, when the auxiliary air passage member comes off, not only the geometrical position of the auxiliary air passage and the sensor is displaced, but also the heating resistor type air flow measurement due to a change in ventilation resistance and the like in the auxiliary air passage. The output value of the device changes. The amount of this change is approximately proportional to the amount of the gap between the stopper member and the sub air passage member, and the function as the worst heating resistor type air flow measuring device cannot be achieved. For this reason, even if the auxiliary air passage member falls off, it is necessary to prevent the geometrical positions of the auxiliary air passage and the sensor from shifting.

[0007]

In order to solve the above-mentioned problems, the housing member and the sub air passage member of the heating resistor type air flow measuring device are provided with irregularities respectively in the direction perpendicular to the sub air passage insertion direction, The engagement of each prevents the auxiliary air passage member from dropping into the main air passage, and
By making use of the radial elastic force generated when an elastic body such as a ring is inserted into the insertion hole, it is possible to make it more difficult for the unevenness to come off by making it difficult for the irregularities to come off.

[0008]

FIG. 1 shows a heating resistor type air flow measuring device according to an embodiment of the present invention. The intake air flows through the body 1 that forms a part of the main air passage 2, and a part of the intake air passes through the sub air passage 3 and is supplied into the engine. A heating resistor 4 for detecting the air flow rate and a temperature-sensitive resistor 6 for detecting the intake air temperature are installed inside the sub air passage 3, and the heating resistor 4 and the temperature-sensitive resistor 6 are connected to the support pins 5. , And further electrically connected to a circuit board 8 via a lead wire 7.
The circuit board 8 is configured to use the electrical signals of the heating resistor 4 and the temperature-sensitive resistor 6 and output a signal related to the air flow rate based on the amount of heat released to the intake air.

The board circuit 8, the heating resistor 4, the temperature-sensitive resistor 6, the support pins 5 and the lead wires 7 are integrated together with a housing 9 for protecting the circuit board 8 by bonding and welding. Constitute. Further, the body 1
The sensing section and the sub air passage section of the circuit module 10 are inserted into the holes 12 provided in the circuit module 10.
When the intake air flows through the main air passage 2, a difference in intake air pressure occurs between the inside and the outside of the main air passage. Therefore, an elastic body 11 for preventing air leakage is provided between the circuit module 10 and the body 1. I have. Generally, an O-ring is used for the elastic body 11, and the cross-sectional inner diameter of the O-ring is provided to be larger than the dimension between members of the body 1 and the auxiliary air passage 3 in order to maintain airtightness. Therefore, the O-ring is elastically deformed and is interposed between the body 1 and the sub air passage 3.

Next, an embodiment will be described with reference to FIG.

This is an example in which a concave groove 14 in which a sub air passage 3 is provided in a circuit module and a convex portion 32 in which a sub air passage is provided are fitted by fitting. In this case, when the thickness of the convex portion 32 is reduced, the press-fitting of the sub air passage is facilitated, but there is a disadvantage that the sub air passage is easily removed. However, since the elastic body 11 is interposed when the circuit module is inserted into the body 1, the action of tightening the sub air passage cylindrical portion by the elastic force in the radial direction at the time of deformation works, and the above-mentioned drawback against falling off can be solved. That is, the present invention makes it possible to enhance the function of holding the auxiliary air passage by utilizing the properties of the elastic body while maintaining the airtight function of the conventional elastic body. FIG. 3 shows an embodiment in which the elastic body 11 is provided on the body 1 side.

[0012]

According to the present invention, an air flow measuring device with further improved safety can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an air flow measuring device showing an embodiment of the present invention.

FIG. 2 is a sectional view showing details of a sub air passage section of FIG. 1;

FIG. 3 is a sectional view showing details of a sub passage portion of the second embodiment of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body, 2 ... Main air passage, 3 ... Sub air passage, 4 ... Heating resistor, 5 ... Support pin, 6 ... Temperature sensitive resistor, 7 ... Lead wire, 8 ... Circuit board, 9 ... Housing, 10 ... Circuit module, 11: elastic body, 12: insertion hole, 14: concave groove, 3
1 ... seal surface, 32 ... convex type.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Chihiro Kobayashi 2520 Odaiba, Hitachinaka-shi, Ibaraki F-term in the Automotive Equipment Division of Hitachi, Ltd. (Reference) 2F035 AA02 EA03 EA04

Claims (1)

[Claims] An air flow meter used in an internal combustion engine and measuring an intake air flow rate, comprising a housing member having a connector connected to an interface with the outside, a sensor member for detecting a flow rate, and a sub air passage in which a sensor is provided. A module is formed by integrating members, drive circuit boards, and the like by bonding, welding, and the like, and at least the sensor member and the sub air passage member are inserted into insertion holes communicating with the main air passage provided on the outer wall of the main air passage constituent member. A ring-shaped elastic body such as an O-ring is disposed in the intake air passage, a part of the housing member is fixed to an outer wall of the main air passage constituting member using screws or the like, and an airtight leak of the insertion hole is prevented. In the heating resistor type air flow measuring device used, the housing member and the sub air passage member are provided with irregularities in a direction perpendicular to the sub air passage insertion direction, and further, Utilizing the elastic force when mounting the ring-shaped elastic body, heat resistor type air flow rate measuring apparatus characterized by fitting the irregularities.