JP2000314362A - Air flow amount measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent falling-out of an O-ring attached to a body of a stand-alone air flow amount measuring device, in which a circuit module is integrally formed with a main air passage. SOLUTION: Projections 11a are formed on the outer periphery of an O-ring 11 arranged between a body 1 and an air cleaner 20 of a heat resistor air flow amount measuring device. Width dimension of the projection is larger than the width of a groove of the body. By press-fitting the projections into the groove, holding can be attained by elastic force of the O-ring, while preventing falling-out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow measuring device used in an internal combustion engine for measuring an intake air flow.

[0002]

2. Description of the Related Art A body 1 forming a main air passage is fixed to an air cleaner 20 disposed upstream of a heating resistor type air flow measuring device for an internal combustion engine using screws or the like. When the intake air flows through the air passage 2, a difference in the intake air pressure is generated between the inside and the outside of the main air passage.
1 is provided. The elastic body 11 generally uses an O-ring and is held in a concave groove 13 provided in the body 1.

[0003]

When the heating resistor type air flow measuring device is mounted on a mating member such as an air cleaner, it is required that the O-ring does not fall out of the groove from the viewpoint of workability. For this reason, conventionally, a method has been used in which the inner diameter of the O-ring is made smaller than the inner diameter of the body groove so that the O-ring is held by a tension acting on the contact surface between the O-ring and the groove to prevent the O-ring from falling off.

[0004] However, the main part of the groove of the body is mainly formed by a mold, and by forming the body by the mold, a considerable amount of taper is generated on the side surface of the groove. When the groove side surface is angled, the O-ring held by the tensioning force follows the shape of the side surface and acts in a floating direction, so that the O-ring tends to come off easily.

For this reason, when the air flow measuring device is mounted on the air cleaner, the air flow measuring device may be installed without the O-ring mounted.

[0006]

In order to solve the above-mentioned problems, a convex protrusion is provided in the outer peripheral direction of an O-ring interposed between a body of a heating resistor type air flow measuring device and an air cleaner. Is provided larger than the groove width dimension of the body, and can be held by the elastic force of the O-ring by being press-fitted into the groove, thereby preventing falling off. Further, if the projection is made the same thickness as the O-ring, the surface pressure is partially increased during sealing, so that the thickness of the projection is made thinner than the depth of the groove as shown in FIG. It was decided to prevent the surface pressure from increasing.

[0007]

FIG. 1 shows a heating resistor type air flow measuring device according to an embodiment of the present invention. The intake air flows from the air cleaner 20 into the body 1 that forms a part of the main air passage 2, and a part of the 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 a circuit board 8 via a lead wire 7
Is electrically connected to The circuit board 8 is configured to use the electric 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 circuit board 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 to form a circuit module 10. Further, a mounting screw is passed through a hole provided in the body 1 so as to be fixed to the air cleaner 20.

When the intake air flows from the air cleaner 20 to the main air passage 2, a difference in the intake air pressure is generated between the inside of the main air passage and the outside thereof. An elastic body 11 is provided.
Generally, an O-ring is used as the elastic body 11, and hermetic leakage is prevented by using the elastic force of the O-ring.

FIG. 2 shows a conventional technique and an embodiment of the present invention.
This will be described with reference to FIGS.

FIG. 2 is a front view of the heating resistor type air flow measuring device as viewed from the air suction side. The O-ring 11 is inserted into a groove 13 provided in the body 1 and the O-ring 11 is provided for preventing falling off. The protrusion 11a is provided.

3 and 4 are detailed cross-sectional views of the O-ring portion shown in FIG. 2. FIG. 3 shows a cross-section of a conventional O-ring and a cross-sectional shape of a portion having no projection according to the present invention. FIG. 4 shows a cross-sectional shape of the O-ring projection of the present invention. As shown in FIG. 3, a conventional O-ring has a body
The groove 13 has a large cross-sectional area with respect to the O-ring 11 so that the deformation of the O-ring 11 when the O-ring 11 is fitted can be accommodated in the body groove 13. For this reason, in order to prevent the O-ring from dropping, as described above, the O-ring inner diameter is made smaller than the groove diameter so that the O-ring and the groove are held by the force acting on the contact surface 13a. In the case where the mold is removed at an angle, there is a disadvantage that the O-ring easily falls off from the groove.

On the other hand, the O-ring of the present invention has a partial cross section shown in FIG.
The protrusion 11a is provided and the width of the protrusion is made slightly larger than the width of the body groove, so that when the O-ring is attached, the protrusion is deformed and pressed into the groove. Can be held. This allows
It is possible to solve the problem of falling off, which is a drawback of the conventional technology, and it is possible to prevent the O-ring from being worn out.

[0013]

According to the present invention, it is possible to prevent the O-ring from being attached to the air flow measuring device.

[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 front view of an air flow measuring device showing one embodiment of the present invention.

FIG. 3 is a detailed sectional view of the O-ring of FIG. 2;

FIG. 4 is a detailed sectional view of the O-ring of FIG. 2;

[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 ... O-ring, 11a ... O-ring projection, 13 ...
O-ring groove, 13a: contact surface, 20: air cleaner.

Claims (2)

[Claims] 1. An air flow meter for use in an internal combustion engine for measuring an intake air flow rate, wherein a module member having at least an air flow rate detection unit, a control circuit, and the like integrated therein constitutes a part of a main air passage. The main air passage member is fixed to the air cleaner or the intake pipe component using screws or the like, and the airtight leak between the flat portion of the main air passage member and the flat portion of the air cleaner or the intake pipe component is fixed to the passage member. In an air flow measuring device provided with a ring-shaped elastic body for prevention and provided with a groove for holding the elastic body in the main air passage member, at least one or more portions are provided on a peripheral portion of the ring-shaped elastic body. An air flow measuring device, characterized by having an elastic body provided with a projection and fitted into the groove by press fitting. 2. The air flow measuring device according to claim 1, wherein the thickness of the projection provided on the elastic body is equal to or less than the depth of the groove provided in the main air passage.