JP2002318146A - Air flow rate measuring device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air flow rate measuring device which can reduce the number of assembling processes and secure sufficient air tightness between a sensor module 2 and a housing 9 by integrally forming the sensor module 2 at resin molding of the housing 9. SOLUTION: The sensor module 2 formed by a first resin 10 is integrally formed with the housing 9 and a second resin, and as a material for the first resin 10, one with a melting temperature lower than that of the second resin was chosen. A flange 10a (thin part) is formed continuously extending across the entire circumference of an outer circumference of the first resin 10. By this, a process of adhesive application to hardening is made unnecessary, and the number of assembling processes of the air flow rate measuring device 1 can be significantly reduced. And the first resin 10, especially the flange 10a is securely melted again and integrally welded with the second resin, and sufficient air tightness can be secured at this part.

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 for measuring an air flow flowing through an air flow path and a method for manufacturing the same.

[0002]

2. Description of the Related Art Heretofore, this type of air flow measuring device has been used, for example, as an air flow meter mounted on an internal combustion engine (hereinafter referred to as an internal combustion engine) to measure an intake air flow rate. The configuration of the air flow measuring device will be briefly described.

[0003] A flow rate measuring element which forms a central part of the air flow rate measuring function is connected to a terminal integrally formed of resin in advance so as to be electrically connected to form a sensor module.

The sensor module is bonded to a housing portion provided in a resin housing in a state where the flow rate measuring element is projected outside the housing, and a resin bypass channel is bonded to the housing. And then electrically connected by wire bonding, etc.
In order to protect the electronic components mounted on the circuit board from water droplets and dust and to improve the heat dissipation of the electronic components, a gel is filled in the housing so as to cover the circuit board, and a cover made of resin or the like is placed over the gel. Is attached to hermetically seal the storage section.

Here, the step of bonding and fixing the sensor module to the housing includes the step of applying an adhesive, the step of attaching and pressing the sensor module to the housing, and the step of curing the adhesive.

[0006]

SUMMARY OF THE INVENTION Adhesive application, and
In the adhesive curing step, a great number of man-hours are required.
Also, if the adhesive breaks for some reason in the adhesive application step, a partial gap may be created between the sensor module and the housing, resulting in poor airtightness between the two. For this reason, there is a possibility that the gel filled in the housing portion flows out through the gap or that moisture or foreign matter enters the housing portion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the number of assembling steps by integrally molding a sensor module during resin molding of a housing. An object of the present invention is to provide an air flow measuring device capable of ensuring sufficient airtightness between a module and a housing, and a method for manufacturing the same.

[0008]

In order to achieve the above object, the present invention employs the following technical means.

In the air flow measuring device according to the first aspect of the present invention, the sensor module is integrally formed with the housing and the second resin, and the melting temperature of the first resin is set to be lower than the melting temperature of the second resin. Was also set low. Thereby, the number of assembling steps of the air flow measuring device can be significantly reduced. Further, when the sensor module is integrally molded with the housing with the second resin, the first resin is re-melted and the second resin is melted.
By welding with the resin described above, the generation of a gap between the sensor module and the housing can be suppressed, and sufficient airtightness in this portion can be ensured.

In the air flow measuring device according to a second aspect of the present invention, a thin portion is formed on the outer periphery of the first resin of the sensor module so as to continuously project over the entire periphery. Accordingly, when the sensor module is integrally formed with the housing and the second resin, the first resin is surely re-melted and is welded to the second resin over the entire circumference, so that the distance between the sensor module and the housing is increased. Can be reliably prevented from occurring, and sufficient airtightness can be ensured in this portion.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking an example of an air flow measuring device mounted on an engine and used for measuring an intake air flow rate.

FIG. 1 is a sectional view showing a state in which an air flow measuring device 1 according to one embodiment of the present invention is mounted on an intake pipe of an engine. FIG. 2 is an external perspective view of the sensor module 2 of the air flow measuring device 1 according to one embodiment of the present invention. FIG. 3 is a partial sectional view taken along line III-III of FIG.

As shown in FIG. 1, an engine (not shown)
The air flow measuring device 1 is mounted in a mounting hole 101 formed at a predetermined position of the intake pipe 100 (air flow path) by a plug-in method. The air flow in the intake pipe 100 flows from the near side of the drawing of FIG. 1 to the far side of the drawing. An air cleaner (not shown) is disposed upstream of the intake pipe 100 (on the front side of FIG. 1). The air flow measuring device 1 is provided with an intake pipe 10 immediately after the air cleaner in order to prevent foreign matter from adhering to the inside thereof, particularly to a heating element 6 and a temperature sensing element 5 described later.
It is mounted in 0.

The air flow measuring device 1 includes a sensor module 2 forming a main function part of flow measurement, a circuit board 3 forming a control circuit for outputting a flow rate detection signal, Flow path 8 for introducing a part of the air flow to various elements for measuring the air flow rate, a housing 9 for accommodating the sensor module 2 and the circuit board 3 and holding and fixing the bypass flow path 8, and a circuit in the housing 9 And a cover 15 for holding the substrate 3 airtightly.

As shown in FIG. 2, the sensor module 2 has terminals 16 to 21 integrally formed of a first resin 10. The resin 10 has a mounting surface 10d to which the circuit board is adhered and fixed, a support portion 10b of the temperature-sensitive element 5 and the heating element 6 protruding on the opposite side of the mounting surface 10d, that is, on the side toward the inside of the intake pipe 100, It has a support portion 10c for the temperature measuring element 7. One end of each of the terminals 16 to 21 is exposed on a substantially same plane at a predetermined position on the mounting surface 10d to form an electrical connection contact. On the other hand, the other end of each of the terminals 16 to 21 is
0b or the inside of the support portion 10c and protrudes outside the support portion 10b or the support portion 10c. That is, the other ends of the terminals 16 to 19 protrude from the support portion 10b, and the heating elements 6 are connected to the terminals 16 and 17, respectively.
The temperature sensing elements 5 are respectively joined to 19. The terminals 20 and 21 protrude from the support 10c, and the air temperature detecting element 7 is joined thereto. In this embodiment, only the air temperature detecting element 7 is connected to the terminal 20 in advance.
After being joined to 21, it is integrally formed with the resin 10.
The temperature sensing element 5 is arranged as close as possible to the heating element 6 within a range that is not affected by the heat radiation of the heating element 6 in order to measure the temperature of the air touching the heating element 6. further,
In a completed state of the air flow measuring device 1, a bypass channel 8 is mounted around these two elements. As the air temperature measuring element 7, for example, a thermistor or the like is used.
It is arranged outside the bypass channel 8.

Here, as a material of the first resin forming the sensor module 2, a material whose melting temperature is lower than a melting temperature of a second resin forming the housing 9 described later is selected. Furthermore, the first of the sensor module 2
As shown in FIGS. 2 and 3, on the outer periphery of the resin 10
The direction substantially parallel to the mounting surface 10d (that is, the first resin 10
In a direction substantially perpendicular to the outer peripheral surface of the first resin 1 and the first resin 1
Flange 10a which is a thin portion continuous over the entire circumference of 0
Was formed. The flange 10a has a larger surface area per unit volume than other portions of the first resin 10, that is,
Large heat transfer area and high temperature rise rate. For this reason, when the sensor module is integrally molded with the housing with the second resin, the first resin 10, particularly the flange 10a, is reliably contacted with the molten second resin injected into the molding die. It is re-melted and welded integrally with the second resin over the entire circumference. Therefore, the sensor module 2 and the housing 9
It is possible to reliably suppress the generation of a gap at the joint portion with the first portion, and to secure sufficient airtightness at this portion.

The bypass channel 8 is formed by resin molding. After the sensor module 2 is integrally formed with the housing 9 with the second resin, the sensor module 2 is fixed to the housing 9 by adhesion or welding. The bypass channel 8 is an upstream channel 8b
And a downstream flow path (not shown). The bypass flow path 8 is attached to the housing 9 such that the heating element 6 and the temperature sensing element 5 project into the upstream flow path 8b. The air inlet 8a is provided on the upstream side of the upstream flow path 8b. When the air flow measuring device 1 is attached to the intake pipe 100, the air inlet 8a opens toward the upstream side in the intake pipe 100, and the intake pipe 100 A part of the airflow in the inside is introduced into the upstream flow path 8b. Intake pipe 100 during operation of engine (not shown)
Is the largest and stable near its center in a cross section perpendicular to the axial direction of the intake pipe 100. Further, the air flow velocity decreases from the center to the outer periphery and becomes unstable. Therefore, the air flow inlet 8a of the bypass flow passage 8 is set to open near the center of the intake pipe 100 in order to maintain the air flow measurement accuracy of the air flow measurement device 1 in a good condition.

A circuit board 3 for forming a control circuit for outputting a flow rate detection signal has a control circuit formed by mounting an electronic component 4 such as an IC on a board made of, for example, glass epoxy resin. After controlling the supply current and converting the current value to a voltage value, the current value is output to the outside as an air flow rate detection signal.

The housing 9 is formed integrally with the sensor module 2 using a second resin. During this molding, a connector 9b for electrically connecting the air flow measuring device 1 to the outside is also integrally molded, and a plurality of terminals 12 are insert-molded on the connector 9b. The circuit board 3 is bonded and fixed in the housing portion 9a of the housing 9, and the circuit board 3, the terminals 12 of the connector 9b, and the terminals 16 to 21 of the sensor module 2 are electrically connected by wire bonding 13. Have been. Further, the inside of the housing portion 9a of the housing 9 is filled with a gel 14 so as to completely cover the electronic components 4 and the wire bonding 13 on the circuit board 3. The gel 14 allows the electronic component 4 and the wire bonding 1
3 is protected from moisture and foreign matter. Further, since the gel 14 is a material having a large heat capacity, the housing 9 of the housing 9 that can effectively radiate heat generated by the heat-generating one of the electronic components 4 through the gel 14.
a is filled with the gel 14 and the housing 9 is covered with the cover 1.
5 is fixed by bonding or welding to secure the airtightness of the storage portion 9a.

The housing 9 has a fitting portion 9c fitted into the mounting hole 101 of the intake pipe 100. The O-ring 11 is mounted on the fitting portion 9c,
The airtightness of the department is maintained.

Next, a method of assembling the air flow measuring device 1 according to one embodiment of the present invention will be described.

First, terminals 16, 17, 18, 1
9 and the terminals 20 and 21 to which the air temperature detecting element 7 is joined are integrally molded with the first resin 10. Thereafter, the temperature-sensitive element 5 is connected to the terminals 16 and 17, and the heating element 6 is connected to the terminals 18 and 19. To form a sensor module 2 by fusing.

Next, the housing 9 is formed integrally with the sensor module 2 using the second resin. Here, when the sensor module 2 is mounted in the molding die of the housing 9, the support 10 b of the temperature-sensitive element 5 and the heating element 6 and the support 10 c of the air temperature measurement element 7 are connected to the housing 9.
In this case, the positional relationship between the sensor module 2 and the housing 9 can be accurately maintained at the time of the second resin injection. When the second resin is injected, the temperature of the flange 10a is higher than that of the other parts of the first resin 10, so that the flange 10a is surely remelted and integrated with the second resin over the entire circumference. Weld.

At this time, the connector 9b for connecting the circuit board 3 to the outside is also integrally molded, and the connector 9b
A plurality of terminals 12 are insert-molded at predetermined positions.

Next, the bypass passage 8 is fixed to the housing 9 by bonding or welding.

Next, the circuit board 3 on which the electronic components 4 are mounted
Is fixed to the storage portion 9a of the housing 9 integrally formed with the sensor module 2 by bonding.

Next, the circuit board 3, the temperature sensing element 5, the heating element 6, the air temperature detecting element 7, and the terminal 12 are electrically connected by wire bonding 13.

Next, the gel 1 is placed in the housing 9a of the housing 9.
Fill 4 At this time, the electronic component 4 and the wire bonding 13 on the circuit board 3 are completely covered.

Finally, the cover 15 is fixed to the storage portion 9a by bonding or welding, and the assembly of the air flow measuring device 1 is completed.

In the air flow measuring device 1 according to the embodiment of the present invention described above, the sensor module 2 is integrally formed with the housing 9 with the second resin, and the first resin for forming the sensor module 2 is formed. As the material of
Those whose melting temperature was lower than the melting temperature of the second resin forming the housing 9 were selected. Further, on the outer periphery of the first resin 10 of the sensor module 2, a thin portion protruding in a direction substantially parallel to the mounting surface 10 d for fixing the circuit board 3 and continuing over the entire periphery of the first resin 10. A certain flange 10a was formed. This eliminates the necessity of the step of applying and curing the adhesive in the bonding step of the sensor module 2 and the housing 9 by the conventional bonding, so that the man-hour for assembling the air flow measuring device 1 can be greatly reduced. Further, when the sensor module 2 is integrally molded with the housing 9 with the second resin, the first resin 10, particularly the flange 10a, comes into contact with the second resin injected into the molding die and reliably. It is remelted and welded integrally with the second resin. Therefore, generation of a gap at the joint between the sensor module 2 and the housing 9 is reliably suppressed, and sufficient airtightness at this portion can be ensured.

In the air flow measuring device 1 according to the embodiment of the present invention described above, the flange 10a
Is one, but may be two as shown in FIG. Further, it may be increased as needed.

Further, the shape of the flange 10a may be a shape as shown in FIG. Also in this case, the same effects as those of the air flow measuring device 1 according to the embodiment of the present invention can be obtained.

[Brief description of the drawings]

FIG. 1 shows an air flow measuring device 1 according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a state in which is attached to an intake pipe of an engine.

FIG. 2 is an air flow measuring device 1 according to an embodiment of the present invention.
FIG. 2 is an external perspective view of the sensor module 2 of FIG.

FIG. 3 is a partial sectional view taken along line III-III of FIG. 2;

FIG. 4 is a partial sectional view of another embodiment of the sensor module 2.

FIG. 5 is a partial cross-sectional view of another embodiment of the sensor module 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air flow measuring device 2 Sensor module 3 Circuit board 4 Electronic component 5 Temperature sensitive element (Flow measuring element) 6 Heat generating element (Flow measuring element) 7 Air temperature measuring element 8 Bypass flow path 8a Air inlet 8b Upstream flow path 9 Housing 9a Storage section 9b Connector 9c Fitting section 10 First resin 10a Flange (thin section) 10b Support section 10c Support section 11 O-ring 12 Terminal 13 Wire bonding 14 Gel 15 Cover 16-21 Terminal 100 Intake pipe 101 Mounting hole

Claims (2)

[Claims] 1. A flow rate measuring element disposed in an air flow path and measuring an air flow rate flowing through the air flow path, and a control circuit electrically connected to the flow rate measuring element and outputting a flow rate detection signal. A circuit board to be formed; a sensor module in which a conduction terminal is integrally molded with a first resin; and the flow rate measuring element is joined to the terminal; and a housing having a housing for housing and fixing the sensor module. An air flow measuring device comprising: a cover that hermetically covers the housing portion; wherein the sensor module is integrally formed with the housing and a second resin, and the melting temperature of the first resin is set to the second temperature. An air flow measuring device, wherein the temperature is set lower than the melting temperature of the resin. 2. The air flow measuring device according to claim 1, wherein a thin portion is formed on the outer periphery of the first resin forming the sensor module, the thin portion continuously projecting over the entire periphery. .