JPH0483122A - Air flow meter - Google Patents

Abstract

PURPOSE:To improve radio interference resistance and enhance a lower cost by directly mounting a circuit board on a base member consisting of a conductive material in a laminated state. CONSTITUTION:The hot wire and temperature detecting resistant elements 9, 10 of a flow rate detecting element are provided by a terminal wire 11 in the bypass passage 12b of a flow meter body 12 for the passage of a measuring air A. The back surface of a circuit board 4 is directly mounted on the bottom plate 1a of a metal base 1 of a shallow box conductive material having a side wall part 1b around, and the terminal wire 11 is held by its support shield member 14. The mounting member 3 of a through capacitor 2 is mounted so as to substitute one side of the side wall part 1b. Thus, by the board 4 easy to collect electromagnetic wave noise, a large electrostatic capacity is formed between its circuit pattern and the base 1, and effective bypass function is provided to attenuate the noise component. Further, the noise component is attenuated by the capacitor 2, and sufficient radio interference resistance can be obtained with a simple structure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for controlling the flow rate of intake air (referred to as intake air) of an internal combustion engine.
The present invention relates to an air flow meter that detects air flow using the temperature resistance characteristics of a heating wire, and particularly relates to a hot wire air flow meter that is suitable for automobile gasoline engines that use electronic fuel injection control.

[Prior Art] In automobile engines, such as gasoline engines, an air-fuel ratio control method based on intake flow rate measurement is widely used. Flow sensors are becoming widely used.

By the way, this hot wire type air flowmeter includes a circuit board on which a flow rate detection element and a measurement circuit are mounted, and thus easily picks up electromagnetic noise.

Therefore, as described in Japanese Patent Application Laid-open No. 58-6414, for example, the circuit board is housed in a shield case and the connection path with the outside is connected through a feed-through capacitor to improve the resistance to radio wave interference. Ta.

[Problem to be solved by the invention]

The above-mentioned conventional technology has a problem in that it does not take into account both the simplification of the structure and the good resistance to radio wave interference, and requires a strict shielding structure.

An object of the present invention is to provide an air flow meter that can easily obtain sufficient resistance to radio wave interference with a relatively simple shield configuration and can further reduce costs.

[Means to solve the problem]

In order to achieve the above object, the present invention mounts a circuit board directly on the inner surface of the bottom plate of a shallow box-shaped base member made of a conductive material having side walls at the periphery by laminating the back surface thereof, and also mounts a feedthrough capacitor. The members are installed on the side wall.

r effect] Since the circuit board is mounted in a stacked manner directly on the base member made of a conductive material, an effective bypass function is provided to the conductive pattern of the circuit board, and the induced noise component is attenuated. work. Since this attenuated noise component is further attenuated by the feedthrough capacitor, sufficient resistance to radio wave interference can be obtained with a simple shield configuration.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The air flow meter according to the present invention will be described in detail below with reference to illustrated embodiments.

Fig. 1 shows an example in which the present invention is applied to a hot-wire air flowmeter. In this figure, 12 is a flowmeter body formed of aluminum die-casting or the like, which serves as a passage for air A whose flow rate is to be measured. , the main air passage 12a and the bypass passage 1
2b is formed, and in this bypass passage 12b, a hot wire resistance element 9 and a temperature sensitive resistance element 1O, which serve as flow rate detection elements, are formed.
It is arranged by a terminal wire 11.

1 is a metal base similarly formed by aluminum die-casting or the like, and the terminal wire 11 is held by a supporting mold member 4 formed as a base material of the metal base I, and a hot wire resistance element is attached to a predetermined circuit pattern of the circuit board 4. 9 and the temperature-sensitive resistance element 1o.

The circuit board 4 is attached directly to the metal base 4 by a method such as gluing the back surface thereof.

Therefore, according to this embodiment, the flow rate detection element section and the detection circuit section are integrally constructed using the metal base 1 as a base material. The air flow meter is assembled simply by assembling it to the body 12.

The metal base l is formed into a shallow box-like shape, consisting of a bottom plate part 1a and a side wall part 1b that surrounds the circuit board 4 and has a rectangular planar shape. A mounting member 3 of the feedthrough capacitor 2 made of a metal material such as brass is attached to the bottom plate part ]a so as to replace one side of the part 1b.

Furthermore, a connector 7 for electrical connection with the outside is attached to the outside of the mounting member 3 of the metal base 1, and this connector 7 is made of a molded housing 7a and a metal connector terminal 7b. Become. The connector terminal 7b is connected from the center conductor of the feedthrough capacitor 2 to a predetermined terminal pad of the circuit board 4 via the lead wire 5.

A cover 8 is attached to the upper side of the side wall portion 1b of the metal base 1 by means not shown, and serves to protect the interior.

According to this embodiment, since the circuit board 4 is attached directly to the bottom plate portion 1a of the metal base 1 in a bonded state,
A considerably large capacitance is formed between the circuit pattern of the circuit board 4 and the metal base 1, and as a result,
In addition to sufficiently attenuating noise components, the metal base 1
The shielding function by the side wall portion 1b and the feedthrough capacitor 2
Since the noise removal function can be obtained, sufficient resistance to radio wave interference can be provided with a simple configuration.

Next, the present invention will be explained in more detail with reference to the embodiments shown in FIGS. 2 and 3.

In the embodiment shown in Fig. 1, the metal base 1 also serves as a case, and although this is still suitable for practical use, embodiments with even higher practicality are those shown in Figs. 2 and 3. As is clear from these figures, in this example,
A molded housing 7a constituting the connector 7 is configured as a cover that covers the entire surface of the metal base 1, and a portion thereof forms the connector 7.

Also in this embodiment, the metal base 1 has a bottom plate part 1a and a side wall part 1.
b, and the bottom plate part 1a is integrally formed with the side wall part 1b by die casting aluminum so as to have sufficient strength to hold the circuit board 4 and protect it from external stress. .

As is particularly clear from FIG. 2, there is a cutout part of the side wall 1b between the circuit board 4 and the connector 7, where the mounting member 3 of the feedthrough capacitor 2 is attached with the screw 15.
It is attached to the bottom plate mla.

As shown in the figure, this mounting member 3 is made of a metal plate, such as brass, which is bent into an L shape and can be soldered, and the feedthrough capacitor 2 is inserted into a predetermined hole formed therein. It is attached by soldering on the top.

According to this embodiment, since the molded housing 7a is provided, it is highly practical, and since the metal head 1 is made of aluminum die-casting, the side wall portion 1b can be easily formed, and high rigidity can be easily achieved. can give. In addition, since the feedthrough capacitor 2 only needs to be attached to the mounting member 3 made of a relatively small metal plate, it is possible to use the solder reflow method.
Easy to assemble. Furthermore, this mounting member 3 has a screw 15.
Since it is fixed to the metal base 1 by the metal base 1, the conductivity between them is maintained well, and the function of the feedthrough capacitor 2 is fully exhibited, so that the radio wave interference resistance can be sufficiently improved.

Next, FIG. 4 shows another embodiment of the present invention. In this embodiment, the mounting member 3 of the feedthrough capacitor 2 is formed vertically opposite to that in FIGS. 2 and 3. , it is attached to the upper end surface of the side wall portion 1b of the metal base l with screws 15a.

Therefore, according to this embodiment, in addition to the effects of the embodiments shown in FIGS. 2 and 3, the mounting member 3 can be screwed from the top surface, improving workability, and the side wall portion 1b. Since the mounting member 3 and the mounting member 3 are overlapped with each other, it can be expected that better shielding can be obtained.

FIG. 5 shows yet another embodiment of the present invention, in which folded portions 3a are formed at both ends of the mounting member 3 of the feedthrough capacitor 2, and these are formed at the end faces of the notch portions of the side wall portions 1b of the metal base 1. The mounting member 3 is elastically inserted into the groove 1c.
is attached to the side wall portion 1b. In this embodiment, a pin 16 is further driven into the folded portion 3a to provide even greater fixing strength.

Therefore, according to this embodiment, in addition to the effects of the embodiments already described, there is no need for screw tightening work to attach the mounting member 3, and there is no possibility of fixation failure due to loosening of the screws, resulting in cost reduction and reliability. It can be expected to improve sexual performance.

It goes without saying that this embodiment can be fully implemented without using the pin 16.

FIG. 6 shows another embodiment of the feedthrough capacitor mounting member 3, in which a small-diameter cylindrical portion 3a is formed at the bottom of the mounting member 3, and this is press-fitted into a hole formed in the bottom plate portion 1a of the metal base l. Accordingly, the mounting member 3 is fixed to the metal base l.

Further, the embodiment shown in FIG. 7 similarly uses a small-diameter cylindrical portion 3b, but in the embodiment shown in FIG. 6, an independent mounting member 3 is used for each feedthrough capacitor 2. In contrast, here, a plurality of feedthrough capacitors 2 are attached to the attachment member 3, and in this embodiment, the plate-like attachment member 3 and the small diameter cylindrical portion 3b are attached.
and are formed separately, and are integrated by press-fitting the mounting member 3 into a groove formed in the upper end surface of the small diameter cylindrical portion 3b.

Next, FIG. 8 shows still another embodiment of the present invention, in which the mounting member 3 of the feedthrough capacitor 2 is constructed integrally with the side wall part 1b of the metal base (2). represents.

This thin-walled portion 1d is formed in a portion of the side wall portion 1b between the circuit board 4 and the connector 7 (not shown in FIG. 8), and is penetrated into a hole formed there. Capacitor 2 is inserted and fixed. Note that this fixing method includes bonding with a conductive adhesive and fixing by press-fitting.

Therefore, according to this embodiment, the number of parts and installation man-hours can be reduced, and the feedthrough capacitor 2 is provided with almost perfect ground continuity, making it easy to achieve both low cost and excellent resistance to radio interference. can be achieved.

FIG. 9 is a characteristic diagram showing the electromagnetic interference resistance obtained by one embodiment of the present invention in comparison with the characteristics obtained by the conventional example.As is clear from this figure, according to the present invention ,
Excellent resistance to radio wave interference, which could not be expected with conventional techniques, can be easily obtained with good productivity.

[Effects of the Invention] According to the present invention, the detection circuit board is directly attached to the metal base that constitutes the detection circuit assembly of the air flow meter.

With the simple structure of mounting in a stacked state, the wave interference properties of #4 can be greatly improved, so an air flow meter with excellent characteristics can be easily provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the air flow meter according to the present invention, FIG. 2 is a plan view showing another embodiment, and FIG. 3 is a side sectional view of the embodiment shown in FIG. 4 is a perspective view showing still another embodiment of the present invention, FIG. 5 is a plan view showing still another embodiment of the present invention, and FIG. 6 is an embodiment of the feedthrough capacitor mounting member in the present invention. FIG. 7 is an explanatory diagram showing another embodiment of the mounting member, FIG. 8 is a perspective view showing an embodiment of the present invention in which the wall portion and the mounting member are integrated, and FIG. 9 is an explanatory diagram showing another embodiment of the mounting member. The figure is a characteristic diagram for explaining the present invention in detail. l...Metal base, la...Bottom plate part, 1b
... Side wall part, 2 ... Feedthrough capacitor, 3.
...Mounting member, 4...Circuit board, 5...
...Lead wire, 7...Connector, 7a...
Mold housing, 7b...Connector terminal, 8...Cover, 9...Hot wire resistance element, 10...Temperature sensitive resistance element, 11...・
・Terminal wire, 12...Flowmeter body. Fig. 2 Fig. 3 Fig. / Metal base la: A4 father) p tb: side wall t z, i & mounter 5 Original plate I pre 1 9. See, see, - (10 atmosphere, appearance and element) 12.

Claims (1)

[Claims] 1. An air flow meter configured by combining a unitized detection circuit assembly with a flowmeter main body, wherein the detection circuit assembly is made of a shallow box-shaped conductive material having side walls at the periphery. a circuit board whose back surface is attached directly to the inner surface of the bottom plate portion of the base member; a feedthrough capacitor mounting member forming a part of the side wall; A flow rate detection element is installed to protrude almost vertically to the outside through an opening formed in the section, and a connector for external connection, and the connection line between the circuit board and the connector is connected to the feedthrough capacitor. An air flow meter characterized in that the air flow meter is formed through a feedthrough capacitor provided on a mounting member. 2. The air flow meter according to claim 1, wherein the feedthrough capacitor mounting member is constituted by a thin-walled portion of the side wall formed integrally with the base member. 3. The air flow meter according to claim 1, wherein the feedthrough capacitor mounting member is formed of a conductive material separate from the base member. 4. In the invention of claim 3, the feedthrough capacitor mounting member is formed of a strip member having an L-shaped cross-sectional portion at both ends, and is screwed to the inner surface of the bottom plate portion of the base member by the L-shaped cross-sectional portion. An air flow meter characterized by: 5. In the invention according to claim 3, the feedthrough capacitor mounting member is formed of a strip member having an L-shaped cross-sectional portion at both ends, and is screwed to the upper surface of the side wall of the base member by the L-shaped cross-sectional portion. An air flow meter characterized by: 6. In the invention according to claim 3, the feedthrough capacitor mounting member is formed of an elastic band-like member having folded molded parts at both ends, and the folded parts are inserted into the notches formed in the side wall end surface of the base member. An air flow meter characterized in that the air flow meter is attached to the base member by being inserted into the base member. 7. The air flow meter according to claim 6, wherein a fixing pin is driven into the folded portion that is inserted into a notch formed in the end face of the side wall of the base member. 8. In the invention according to claim 3, the feedthrough capacitor mounting member is formed of a rectangular plate-like member having a small-diameter cylindrical portion for press-fitting and fixing at one side end, and the small-diameter cylindrical portion is connected to the bottom plate portion of the base member. An air flow meter characterized in that the feedthrough capacitor mounting member is attached to the base member by being press-fitted into an insertion hole formed on the inner surface. 9. The air flow meter according to claim 8, wherein the feedthrough capacitor mounting member is formed independently for each of the plurality of feedthrough capacitors. 10. The air flow meter according to claim 8, wherein the feedthrough capacitor mounting member is formed in common to two or more feedthrough capacitors.