JP4196546B2 - Air flow measurement device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air flow measurement equipment for measuring the flow rate of air flowing through the air flow path.
[0002]
[Prior art]
Conventionally, this type of air flow rate measuring apparatus is used as an air flow meter that is mounted on an internal combustion engine (hereinafter, the internal combustion engine is referred to as an engine) and measures the intake air flow rate. The configuration of this air flow rate measuring device will be briefly described.
[0003]
A flow rate measuring element forming a central part of the air flow rate measuring function is joined so as to be electrically connected to a terminal previously molded integrally with a resin, and is formed into a sensor module.
[0004]
The sensor module is bonded to the housing provided in the resin housing in a state where the flow measuring element protrudes outside the housing, and further, the resin bypass flow path is bonded to the housing, and then the circuit board is bonded. Furthermore, 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 applied so as to cover the circuit board in the storage part. Filled, and a cover made of resin or the like is attached from above, and the storage part is hermetically sealed.
[0005]
Here, the adhesion fixing process of the sensor module to the housing includes an adhesive application process, a mounting / pressing process of the sensor module to the housing, and an adhesive curing process.
[0006]
[Problems to be solved by the invention]
In the adhesive application and the adhesive curing process, a great number of man-hours are required. In the adhesive application process, if the adhesive is interrupted for some reason, a partial gap may be generated between the sensor module and the housing, which may result in poor airtightness between the two. For this reason, there may be a problem that the gel filled in the accommodating portion flows out through the gap or moisture or a foreign substance enters the accommodating portion.
[0007]
The present invention has been made to solve the above-described problems. The object of the present invention is to reduce the number of assembling steps by integrally forming the sensor module during resin molding of the housing, and the sensor module and the housing. it is to provide an air flow measurement equipment can secure sufficient airtightness between.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention employs the following technical means.
[0009]
In the air flow rate measuring device according to claim 1 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 lower than the melting temperature of the second resin. did. Thereby, the assembly man-hour of an air flow measuring device can be reduced significantly. Further, when the sensor module is integrally formed with the housing and the second resin, the first resin is remelted and welded to the second resin, thereby preventing the gap between the sensor module and the housing. In this part, sufficient airtightness can be ensured.
[0010]
In the air flow rate measuring device according to the second aspect of the present invention, a thin portion that continuously protrudes over the entire circumference is formed on the outer circumference of the first resin of the sensor module. As a result, when the sensor module is integrally formed with the housing and the second resin, the first resin is surely remelted and is welded to the second resin over the entire circumference, whereby the sensor module and the housing are separated. It is possible to reliably suppress the generation of the gap and to secure sufficient airtightness in this portion.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, taking as an example an air flow rate measuring device mounted on an engine and used for measuring an intake air flow rate.
[0012]
FIG. 1 is a cross-sectional view showing a state in which an air flow rate measuring device 1 according to an embodiment of the present invention is attached to an intake pipe of an engine. FIG. 2 is an external perspective view of the sensor module 2 of the air flow rate measuring device 1 according to one embodiment of the present invention. 3 shows a partial cross-sectional view taken along line III-III in FIG.
[0013]
As shown in FIG. 1, an air flow rate measuring device 1 is attached by a plug-in method to an attachment hole 101 formed at a predetermined position of an intake pipe 100 (air flow path) of an engine (not shown). The air flow in the intake pipe 100 flows from the front side of the drawing in FIG. 1 to the back side of the drawing. An air cleaner (not shown) is disposed on the upstream side of the intake pipe 100 (the front side in FIG. 1). The air flow rate measuring device 1 is mounted in the intake pipe 100 immediately after the air cleaner in order to prevent foreign matter from adhering to the inside, particularly to a heating element 6 and a temperature sensitive element 5 described later.
[0014]
This air flow rate measuring device 1 includes a sensor module 2 forming a main function part of flow rate measurement, a circuit board 3 forming a control circuit for outputting a flow rate detection signal, and an air flow in the intake pipe protruding into the intake pipe 100. A bypass flow path 8 for introducing a part of the air flow rate to various elements for measuring the air flow rate, a housing 9 for holding and fixing the bypass flow path 8 while housing the sensor module 2 and the circuit board 3, and a circuit board 3 in the housing 9. It is comprised from the cover 15 hold | maintained airtight.
[0015]
As shown in FIG. 2, the sensor module 2 is obtained by integrally molding the terminals 16 to 21 with the first resin 10. The resin 10 includes a mounting surface 10d to which the circuit board is bonded and fixed, a supporting portion 10b of the temperature sensing element 5 and the heating element 6 protruding to the opposite side of the mounting surface 10d, that is, the side facing the inside of the intake pipe 100, and air. A support portion 10c for the temperature measuring element 7 is provided. One end of each terminal 16-21 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 terminal 16-21 protrudes outside the support part 10b or the support part 10c through the support part 10b or the support part 10c. That is, the other ends of the terminals 16 to 19 protrude from the support portion 10b, and the heating element 6 is joined to the terminals 16 and 17, and the temperature sensing element 5 is joined to the terminals 18 and 19, respectively. Moreover, the terminals 20 and 21 protrude from the support part 10c, and the air temperature detection element 7 is joined. In the present embodiment, only the air temperature detecting element 7 is joined to the terminals 20 and 21 in advance and then integrally molded with the resin 10. The temperature sensing element 5 is arranged as close as possible to the heating element 6 within a range 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 the completed state of the air flow rate measuring device 1, a bypass flow path 8 is mounted around these two elements. For example, a thermistor or the like is used as the air temperature measuring element 7 and is disposed outside the bypass flow path 8.
[0016]
Here, as the material of the first resin forming the sensor module 2, a material whose melting temperature is lower than the melting temperature of the second resin forming the housing 9 described later is selected. Further, on the outer periphery of the first resin 10 of the sensor module 2, as shown in FIGS. 2 and 3, a direction substantially parallel to the mounting surface 10d (that is, a direction substantially perpendicular to the outer peripheral surface of the first resin 10). The flange 10a, which is a thin-walled portion that protrudes in a continuous manner and is continuous over the entire circumference of the first resin 10, was formed. The flange 10a has a surface area per unit volume larger than that of the other portions of the first resin 10, that is, the heat transfer area is large and the temperature rise rate is large. Therefore, when the sensor module is integrally formed with the housing and the second resin, the first resin 10, particularly the flange 10 a is surely brought into contact with the molten second resin injected into the molding die. Remelted and welded integrally with the second resin over the entire circumference. Therefore, generation | occurrence | production of the clearance gap in the junction part of the sensor module 2 and the housing 9 can be suppressed reliably, and sufficient airtightness in this part can be ensured.
[0017]
The bypass channel 8 is formed by resin molding. The sensor module 2 is integrally formed with the housing 9 and the second resin, and then fixed to the housing 9 by adhesion or welding. The bypass channel 8 has an upstream channel 8b and a downstream channel (not shown), and the bypass channel is configured such that the heating element 6 and the temperature sensing element 5 protrude into the upstream channel 8b. 8 is attached to the housing 9. The air inlet 8a is provided on the upstream side of the upstream flow path 8b. When the air flow rate 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 air flow is introduced into the upstream flow path 8b. The axial air velocity in the intake pipe 100 during engine (not shown) operation is the largest and stable near the center in a cross section perpendicular to the axial direction of the intake pipe 100. Furthermore, the air flow rate becomes unstable as it decreases from the center toward the outer periphery. Therefore, in order to maintain good air flow measurement accuracy of the air flow measurement device 1, the air inlet 8 a of the bypass flow path 8 is set to open near the center of the intake pipe 100.
[0018]
A circuit board 3 that forms a control circuit that outputs a flow rate detection signal is formed with a control circuit by mounting an electronic component 4 such as an IC on a glass epoxy resin board, for example. While controlling, this electric current value is converted into a voltage value and then output to the outside as an air flow rate detection signal.
[0019]
The housing 9 is formed integrally with the sensor module 2 by the second resin. At the time of 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 in the connector 9b. The circuit board 3 is bonded and fixed in the housing portion 9 a of the housing 9, and the circuit board 3, the plurality of terminals 12 of the connector 9 b, and the terminals 16 to 21 of the sensor module 2 are electrically connected by wire bonding 13. Has been. Further, the accommodating portion 9a of the housing 9 is filled with the gel 14 so as to completely cover the electronic component 4 and the wire bonding 13 on the circuit board 3. The gel 14 protects the electronic component 4 and the wire bonding 13 from moisture and foreign matter. Furthermore, since the gel 14 is a material having a large heat capacity, the gel generated in the housing portion 9a of the housing 9 can effectively dissipate heat generated by the heat generating component in the electronic component 4 through the gel 14. After filling 14, a cover 15 is fixed to the housing 9 by adhesion or welding to ensure the airtightness of the storage portion 9 a.
[0020]
The housing 9 has a fitting portion 9c that fits into the mounting hole 101 of the intake pipe 100, and an O-ring 11 is attached to the fitting portion 9c to maintain the airtightness of the mounting hole 101 portion. ing.
[0021]
Next, an assembling method of the air flow rate measuring device 1 according to one embodiment of the present invention will be described.
[0022]
First, the terminals 16, 17, 18, 19 and the terminals 20, 21 to which the air temperature detecting element 7 are joined are integrally formed with the first resin 10, and then the temperature sensitive element 5 is connected to the terminals 16, 17. The heating element 6 is joined to the terminals 18 and 19 by fusing to form the sensor module 2.
[0023]
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 supporting portion 10 b of the temperature sensing element 5 and the heating element 6 and the supporting portion 10 c of the air temperature measuring element 7 are used as the molding die of the housing 9. By holding the mold, the positional relationship between the sensor module 2 and the housing 9 can be accurately maintained during the second resin injection. When the second resin is injected, the flange 10a has a higher rate of temperature rise than the other portions of the first resin 10, so it is surely remelted and integrated with the second resin over the entire circumference. Weld.
[0024]
At this time, a connector 9b for connecting the circuit board 3 to the outside is also integrally formed, and a plurality of terminals 12 are insert-molded at predetermined positions of the connector 9b.
[0025]
Next, the bypass passage 8 is fixed to the housing 9 by adhesion or welding.
[0026]
Next, the circuit board 3 on which the electronic component 4 is mounted is fixed to the housing portion 9a of the housing 9 formed integrally with the sensor module 2 by adhesion.
[0027]
Next, the circuit board 3, the temperature sensitive element 5, the heat generating element 6, the air temperature detecting element 7, and the terminal 12 are electrically connected by wire bonding 13.
[0028]
Next, the gel 14 is filled in the storage portion 9 a of the housing 9. At this time, the electronic component 4 and the wire bonding 13 on the circuit board 3 are completely covered.
[0029]
Finally, the cover 15 is fixed to the storage portion 9a by adhesion or welding, and the assembly of the air flow rate measuring device 1 is completed.
[0030]
In the air flow rate measuring apparatus 1 according to the embodiment of the present invention described above, the sensor module 2 is integrally formed with the housing 9 and the second resin, and the material of the first resin forming the sensor module 2 is as follows. The one whose melting temperature is lower than the melting temperature of the second resin forming the housing 9 was selected. Furthermore, the outer periphery of the first resin 10 of the sensor module 2 is a thin wall portion that protrudes in a direction substantially parallel to the mounting surface 10 d for fixing the circuit board 3 and continues over the entire periphery of the first resin 10. A certain flange 10a was formed. As a result, the steps of applying and curing the adhesive in the joining process of the sensor module 2 and the housing 9 by conventional bonding are not required, so that the number of assembling steps of the air flow rate measuring device 1 can be greatly reduced. Further, when the sensor module 2 is integrally formed with the housing 9 and the second resin, the first resin 10, particularly the flange 10a, comes into contact with the second resin injected into the molding die to ensure that Remelted and welded integrally with the second resin. Therefore, generation | occurrence | production of the clearance gap in the junction part of the sensor module 2 and the housing 9 can be suppressed reliably, and sufficient airtightness in this part can be ensured.
[0031]
In the air flow measuring device 1 according to the embodiment of the present invention described above, the number of the flanges 10a is one, but may be two as shown in FIG. Furthermore, you may increase as needed.
[0032]
Further, the shape of the flange 10a may be as shown in FIG. Also in this case, the same effect as the case of the air flow measuring device 1 according to the embodiment of the present invention described above can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a state in which an air flow rate measuring device 1 according to an embodiment of the present invention is attached to an intake pipe of an engine.
FIG. 2 is an external perspective view of a sensor module 2 of the air flow rate measuring device 1 according to one embodiment of the present invention.
3 is a partial cross-sectional view taken along line III-III in FIG. 2;
4 is a partial cross-sectional view of another embodiment of the sensor module 2. FIG.
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 sensing element (flow measuring element)
6 Heating element (flow rate measuring element)
7 Air temperature measuring element 8 Bypass flow path 8a Air inflow port 8b Upstream flow path 9 Housing 9a Storage portion 9b Connector 9c Fitting portion 10 First resin 10a Flange (thin wall portion)
10b support portion 10c support portion 11 O-ring 12 terminal 13 wire bonding 14 gel 15 cover 16-21 terminal 100 intake pipe 101 mounting hole

Claims (2)

A flow rate measuring element disposed in the air flow path for measuring the flow rate of air flowing through the air flow path;
A circuit board that forms a control circuit that is electrically connected to the flow rate measuring element and outputs a flow rate detection signal;
A sensor module formed by integrally molding a terminal for conduction with a first resin, and further joining the flow rate measuring element to the terminal;
A housing having a housing portion for housing and fixing the sensor module;
In an air flow rate measuring device comprising a cover that hermetically covers the storage portion,
An air flow rate measuring apparatus characterized in that the sensor module is integrally formed with the housing and a second resin, and the melting temperature of the first resin is set lower than the melting temperature of the second resin. 2. The air flow rate measuring device according to claim 1, wherein a thin portion that continuously protrudes over the entire circumference is formed on the outer circumference of the first resin forming the sensor module.

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