JPH0515968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal air flow meter, and particularly to a thermal air flow meter suitable for detecting the intake air amount of an internal combustion engine.

[Prior Art] A conventional thermal air flowmeter has a structure in which an electronic device that controls a heating resistor and a support that supports the heating resistor are directly connected by a lead wire.
Note that this type of device is, for example, disclosed in Japanese Unexamined Patent Application Publication No. 1983-
There is a thermal air flow meter described in Publication No. 81159.

[Problem to be solved by the invention]

In a thermal air flow meter used in an internal combustion engine, the support for the heating resistor is disposed in the air passage, so it is required to have rigidity and heat resistance. On the other hand, in order to reduce the size and weight, the arrangement relationship between the control circuit of the heating resistor and its support is restricted.

However, in the above conventional technology, the support body supporting the heat generating resistor is directly connected to the control circuit of the heat generating resistor, so the arrangement position and structure of the drive circuit are limited depending on the installation position with the heat generating resistor. ,
There was a problem that it was not possible to sufficiently reduce the size and weight.

Furthermore, the interior of the engine room experiences large vibrations, and vibration resistance of about 10G is required when attached to the vehicle body, and about 30G when attached to the engine body, but this has not been sufficiently taken into account in the above-mentioned conventional technology.

An object of the present invention is to provide a thermal air flowmeter that is small, lightweight, vibration resistant, and highly reliable.

[Means to solve the problem]

The above object is a thermal air flow meter that is installed in an air passage and has a heat generating resistor that detects the air flow rate, and a drive circuit that controls the heat generation of the heat generating resistor and outputs a signal corresponding to the air flow rate. , a metal support supporting the heating resistor, a plate-shaped metal terminal electrically connected to the drive circuit, formed separately from the heating resistor and welded, and the terminal being inserted. and a metal base on which the drive circuit is arranged, and the support body and the terminal constitute a connection means for electrically connecting the heating resistor and the drive circuit. Further, the connecting means has a bent portion in which the projected position of the connecting portion between the terminal and the driving circuit and the connecting portion between the supporting body and the heat generating resistor is shifted from each other when projected onto a circuit forming surface of the driving circuit. This is achieved by

[Effect]

Since the metal support and the terminal are formed separately, the support can have sufficient rigidity, and the connection between the terminal and the drive circuit,
The heating resistor and the drive circuit are connected by a connection means consisting of a plate-shaped terminal having a bent part such that the projected position of the connection part between the support and the heating resistor on the circuit formation surface of the drive circuit is shifted. Because they are connected, electrical connection is easy, and since it is possible to provide an offset between the connection surface of the drive circuit and the heat generating resistor, it is not affected by the arrangement of the heat generating resistor and the drive circuit. The device can be made smaller.

〔Example〕

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a diagram schematically showing a heating resistor, in which the hot wire 1 of the heating resistor for sensing the amount of intake air and the cold wire 2 of the resistor for sensing the intake air temperature are both 0.5φ in diameter and long. It is a very small structure in which a platinum wire 102 is wound around an alumina bobbin 101 with a diameter of about 2 mm, both ends of which are welded to lead wires 103, and the surface is coated with a glass material 104. . As shown in FIG. 2, the hot wire 1 and the cold wire 2 having such a structure are connected to a bypass of a body 107, which has a main passage 105 through which most of the intake air passes and a bypass passage 106 through which a portion of the intake air flows. installed in the passageway 106.

By the way, the body 107 shown in FIG. 2 includes an air main passage 105, a bypass passage 106, and a mounting part 108 for a module 47 that constitutes a drive circuit part.
It is made of die-cast aluminum.

FIG. 3 is an exploded perspective view showing the overall configuration of the present invention;
Figure 4 is a cross-sectional view of the main part of module 47.
The figure shows the bottom part, and FIGS. 6 and 7 show the - and - cross sections of FIG. 4.

In these figures, a case 48 of a module 47 is molded from a thermoplastic resin with excellent heat resistance, such as glass fiber-reinforced unsaturated polyester resin.

A preferred embodiment of the present invention is shown below.

Metal pins 49 to 52 and each pin 49 to
Metal terminals 53-56 welded to 52
The power terminal 44, output terminal 45, ground terminal 46, pipe 57, and metallic collar 58 are integrally molded into the case 48 described above. The case 48 has a box shape with a thin bottom surface 95 of about 0.8 to 1 mm, has a groove 96 all around its outer circumferential wall, and has a connector 97 integrally formed therein. The pins 49 to 52 and the terminals 53 to 56 hold the hot wire 1 and the cold wire 2 disposed in the bypass passage 106, and electrically connect the hot wire 1 and the cold wire 2 to the hybrid IC that constitutes the drive circuit section of the module 47. It is connected to. Also, pipe 57
This ventilates the inside of the connector section inside the sealed case 48 to prevent the internal pressure of the case from increasing due to a temperature rise inside the case 48. case 48
After forming, the lead wires 103 of the hot wire 1 and the cold wire 2 are welded to the pins 49 to 52, respectively. The pins 49 to 52 on the bottom surface of the case 48 are arranged at the vertices of the rectangle. Further, the base 89 made of a metal plate has a hole 92 into which the terminals 53 to 56 formed integrally with the case 48 are inserted. Here, the terminals 53 to 56 are the drive circuit 6 of the terminals 53 to 56.
3 and the hot wire 1 of pins 49-52
and the drive circuit 6 of the connection part with the cold wire 2
It has a bent portion such that the projected position on the circuit forming surface of No. 3 is shifted.

By adopting such a configuration, the following effects can be achieved. Since the terminals 53 to 56 are plate-shaped, electrical connection with the drive circuit is easy. In addition, the terminal is connected to the drive circuit 63 at the connection part of the terminal with the drive circuit and the connection part of the pin with the hot wire 1 and the cold wire 2.
The terminal 53 is attached to the metal base 89 with a bent portion that shifts the projected position on the circuit forming surface of the terminal 53.
Since the hole 92 is provided for the insertion of the portion 56, the circuit configuration and installation position of the drive circuit 63 are not restricted by the hot wire 1 or the cold wire 2, and the entire thermal flowmeter can be made compact.

Further, pins 49 to 52 and a terminal 5 electrically connect the hot wire 1 and the drive circuit 63.
Since the terminals 3 to 56 are molded with synthetic resin and the terminal is plate-shaped, there is no possibility of poor contact between the pins and the terminal even if vibrations from the automobile are transmitted, and high vibration resistance can be ensured. Further, bent portions 59 provided in the terminals 53 to 56 and holes 60 to 62 provided in the case 48
It also has the effect of accurately holding insert fittings such as the terminal 53 in the mold during molding.

The hybrid IC 63 includes resistors such as the resistor 11 and conductor patterns 64 to 6 that constitute the drive circuit.
Semiconductor elements such as an operational amplifier chip 70, capacitors such as chip capacitors 42 and 43, and pads 70 to 83 for connecting the inside of the ceramic substrate 69 and external elements and external circuits are soldered to the ceramic substrate 69 on which 8 etc. are printed. ing.

The insulating plate 88 is thinner than the ceramic substrate 69,
It is made by depositing dungsten on a part 87 of a ceramic substrate 86 with a thickness of about 0.3 to 0.4 mm and then nickel plating it, and the power transistor chip 7 and pad 84 are soldered to this insulating plate 88.

A base 89 made of a metal plate has a wall 9 on its outer periphery.
0, a protrusion 91 on a part of the wall 90, a hole 92 on the bottom for receiving the terminals 53 to 56 integrally molded on the case 48, and a ceramic substrate 69;
It has a projection 93 for positioning the insulating plate 88 and a stepped portion 94 at one end, and a butt 85 is soldered to the stepped portion 94. This base 8
9, a ceramic substrate 69 and an insulating plate 88 are adhesively fixed in predetermined positions with a soft adhesive such as silicone rubber adhesive.

The base 89 described above is adhesively fixed to the bottom surface 95 of the case 48 at a predetermined position within the case 48 .

Between each terminal, that is, the pads 70 and 71 of the hybrid IC 63 are connected to the terminals 53 and 54 formed by connecting the hot wire 1, and the pads 72 and 73 are connected to the cold wires 2 placed on both sides of the terminals 53 and 54. (contrary to the embodiment, the terminals 55 and 56 of the cold wire 2 may be placed inside), and the pad 74 is connected to the pad 84 to which the connector of the power transistor 7 is connected.
, pad 75 connects to the base, pad 76 connects to the emitter, pad 77 connects to the power terminal 44, and pad 78 connects to the base.
is the output terminal 45, and the pad 79 is the ground terminal 46.
The pad 80 connected to the pad 79 by the conductor pattern is connected to the pad 85 on the base 89 and the pad 82.
are electrically connected to pads 81 and 83 by wire bonding with metal wires such as aluminum wires.

By connecting pads 80 and 85, base 89 is at ground potential.

Here, a power terminal 44, an output terminal 45, a ground terminal 46, and a hybrid terminal connected to these
Pads 77, 78, and 79 on IC 63 are arranged so that ground terminal 46 and pad 79 to which it is connected are between the other terminals.

Chip capacitors 42 and 43 for removing external surges and noise are connected to pads 77 and 7.
8 and 79 via a short conductor pattern.

The above-mentioned module sub-assembly is attached to the module attachment part 108 of the body 107 with a screw 97 with a sealing O-ring 96 in between, and the resistors 13, 15, 27 shown in FIG.
30 is function trimmed to adjust the output voltage versus air flow rate.

After adjusting the output voltage, a metal plate cover 98 is placed in contact with the wall 90 of the base 89 so as to cover the hybrid IC 63, the power transistor 7, and the terminals 53 to 56.
It is welded at the protrusion 91.

Vibrid is released from the small hole 99 provided in the cover 98.
In order to protect the IC 63 from moisture and the like, a soft resin 100 (generally gel-like) such as silicone rubber is filled into the case 48 and hardened to a height that does not block the end face of the ventilation pipe 57.

After that, the cap 10 made of the same material as the case 47 is
9 is adhered to the case 47 with its rib 110 fitted into the groove 96 of the case 47.

The electrical connection between the ground terminal 46 or the base 89, which is the ground of the drive circuit section, and the metal body 107 can be made as desired.

In the thermal flowmeter configured in this way,
Hot wire 1 and cold wire 2 that form part of the drive circuit (cold wire 2 is for detecting air temperature, and if the temperature inside the module and the air temperature are almost the same or when high accuracy is not required, the module The structure of this part was very complicated. It has a simple structure because the support for the electrical conductor that electrically connects the cold wire and the drive circuit is integrally formed with the synthetic resin case that houses the drive circuit.
It is small and lightweight, and has outstanding productivity.

In addition, since the case 48 has a box-shaped structure with a bottom surface 95, the resin 100 filled to maintain the drive circuit section's water resistance does not leak and has excellent water resistance.

Furthermore, since the pins 49 to 52 and the terminals 53, 56, which are a feature of the present invention, can be arranged relatively freely within the mold of the case 48, the configuration is less restricted by the arrangement of the hot wire 4 and the cold wire 2. Connection terminal 5 with the drive circuit section
There is an effect that numbers 3 to 56 can be arranged.

〔Effect of the invention〕

According to the present invention, the heating resistor can have sufficient rigidity and heat resistance, and the electrical connection between the support of the heating resistor and the drive circuit can be easily made, and the arrangement of the heating resistor and the driving circuit can be easily made. The device can be made smaller without being affected.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically showing a heating resistor, Fig. 2 is a longitudinal cross-sectional view of the main parts of the thermal air flow rate according to the present invention, Fig. 3 is an exploded perspective view of the module, and Fig. 4 is a diagram showing the main parts of the module. 5 is a bottom view thereof, FIG. 6 is a cross-sectional view taken from FIG. 4, and FIG. 7 is a cross-sectional view taken from FIG. 4. 1, 2... Heating resistor, 48... Case, 63
...Hybrid IC (drive circuit), 89...Metallic base.

Claims (1)

[Claims] 1. A heating resistor installed in the air passage to detect the air flow rate, and controlling the heat generation of the heating resistor,
In a thermal air flowmeter having a drive circuit that outputs a signal corresponding to the air flow rate, the metal support supports the heat generating resistor, and the metal support is electrically connected to the drive circuit. A plate-shaped metal terminal formed separately and welded, and a metal base having a hole into which the terminal is inserted and in which the drive circuit is disposed, and the heating resistor and the drive circuit are connected to each other. A connection means for electrical connection is constituted by the support body and the terminal, and the connection means includes a connection part between the terminal and the drive circuit, and a connection part between the support body and the heating resistor. A thermal air flow meter characterized by having a bent portion whose projected position on the circuit forming surface of the drive circuit is shifted.