JPH06109508A - Supporting structure for temperature-sensitive resistor, circuit housing therefor, and air flowmeter employing the same - Google Patents

Abstract

PURPOSE:To obtain a downsized supporting structure for temperature-sensitive resistor having a simple structure in which erroneous function of a circuit due to intrusion of noise is prevented. CONSTITUTION:Metal frames 21, 22 to be fixed with temperature-sensitive resistors 31, 32 are resin molded 4 and then fixed integrally with a board 1 thus constituting a temperature-sensitive support. The metal frames 21, 22 have a rectangular cross section at the parts to be fixed with the temperature- sensitive resistors. A metal of different type is applied to a part of the metal frame 21 to be connected with the circuit board and subjected to wire bonding. An earth electrode 11 is provided, while protruding through press molding, on the board 1 and connected with a circuit through more than one wire bonding 62 for every electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support structure of a temperature sensitive resistor suitable for detecting, for example, an intake air flow rate of an automobile engine and other air temperature, a housing of its circuit, and an air flow meter using these. .

[0002]

2. Description of the Related Art In automobile engines, there is an urgent need to reduce harmful exhaust emissions and improve fuel efficiency in order to protect the natural environment and save energy. In response to this, the mainstream is the adoption of an electronic control device that uses a microcomputer to perform high-precision control of fuel and ignition timing.
This electronic control unit requires many sensors and actuators for obtaining information from the engine, and miniaturization and weight reduction have become important issues as the number of electric components increases.

Further, the sensors and actuators determine the system accuracy of the electronic control unit, and not only the essential operation accuracy (for example, the detection accuracy of the sensor), but also the fact that malfunction does not occur due to noise or the like is a very important item. ing.

In view of the above background, as an air flow meter for the purpose of downsizing and improvement of noise resistance, for example, Japanese Patent Laid-Open No. 1-9
There is an example shown in Japanese Patent No. 7817.

[0005]

In this example, the mounting pins of the temperature-sensitive resistor (heat-generating resistor for measuring air flow rate, resistor for temperature compensation, etc.) used to detect the air flow rate are welded to the lead frame, Although the temperature sensitive resistor is connected to the drive circuit for measuring the air flow rate through the pin and the lead frame, the number of parts such as the pin and the lead frame is large, and the work process of connecting the pin and the lead frame by welding. Therefore, there is a point to be improved in workability.

Further, although a shield case and a feedthrough capacitor are used in the circuit module in order to prevent an electronic circuit due to noise, a complicated device is required for the electrical connection between the shield case and the substrate.

The present invention has been made in view of the above points, and an object thereof is to achieve a compact and lightweight air flow meter, temperature meter, etc., and prevent malfunction of a circuit due to intrusion of noise with a simple structure. Especially.

[0008]

SUMMARY OF THE INVENTION The present invention is basically provided as a support structure for a temperature sensitive resistor for electrical connection in order to reduce the size, weight, and mounting accuracy of parts. A metal frame is molded by resin molding on a substrate having protrusions, a part of the metal frame is projected by a molding resin, and a temperature-sensitive resistor is attached to the frame protrusion (the first one is proposed. As a means for solving problems).

Further, in order to improve the detection accuracy, it is proposed that the cross section of the temperature sensitive resistor mounting portion of the metal frame is rectangular, and the width dimension thereof and the plate thickness dimension of the frame are the same or substantially equal ( This is the second means for solving the problem).

Further, in order to improve the detection accuracy, the metal frame is molded by resin molding, a part of the metal frame projects from the molding resin, and the temperature sensitive resistor is mounted on the projecting portion. In the case where a plurality of temperature resistors are arranged in the respective corresponding metal frames with their positions shifted from each other, a step is formed on the surface of the molding resin on the protruding side of the metal frame, and one of the steps is formed. On the step surface, the metal frame of one temperature-sensitive resistor is projected as it is, and on the other step surface, a rib integral with the mold resin is attached, and the metal frame of the other temperature-sensitive resistor is attached through this rib. Proposed that the length of the metal frame from the step surface and the mold resin to the temperature sensitive resistor mounting portion is determined by projecting the step surface and the rib That (referred to as third means for solving problems).

Further, as a housing for accommodating the drive circuit of this type of temperature sensitive resistor, a housing coupled with a substrate on which the temperature sensitive resistor and the circuit board are mounted has a metal terminal for electrically connecting to the outside. However, one end of this metal terminal is exposed by only a part of the surface (this part becomes an electrical connection part with the circuit board) and is embedded in the resin, and this embedding is performed on the resin surface by metal. It is proposed that the terminal is in a valley bottom low position and the relationship between the lateral width W1 of the exposed surface portion and the lateral width W2 of the terminal is W1 <W2 (this is the fourth problem solving means).

Further, in an electronic circuit provided with a filter circuit for removing noise, it is proposed to use two or more wire bonding wires for grounding the filter circuit per terminal (this is referred to as a fifth problem solving means). To).

[0013]

The operation of the first means for solving the problem ... By having the projection for making an electrical connection, the ground terminal or the like of the circuit can be easily connected to the substrate by wire bonding or the like by using this projection. Further, by directly mounting the temperature sensitive resistor on the metal frame, it is possible to eliminate the conventional welding of the pin and the metal frame, and to reduce the number of parts. Also, a small metal frame can be realized by cold pressing.

Further, when this metal frame is resin-molded on an aluminum substrate processed by cold pressing, the cold-pressed material (aluminum substrate) can be thinner than the conventional mold-molded substrate and has a small forming shape. Since it can be easily performed, a small and lightweight support structure for the temperature sensitive resistor can be obtained. Furthermore, since the aluminum substrate is provided with the protruding electrode capable of wire bonding with the ground of the circuit substrate by cold press molding, it is possible to adopt a lightweight electrical connection structure.

Operation of the second means for solving the problem ... A case where a member (here, a metal frame) for supporting the temperature sensitive resistor is arranged together with the temperature sensitive resistor in the passage for measuring the air flow rate will be described.

The temperature sensitive resistor is used as, for example, a heat generating resistor for measuring an air flow rate and a temperature sensitive resistor for temperature compensation.
When a pair of support members for supporting each temperature-sensitive resistor are arranged in front of and behind the air flow, respectively, the air passage width of the temperature-sensitive resistor secured between the pair of support members in the front position and In view of detection accuracy, it is desirable that the air passage widths of the temperature-sensitive resistors secured between the pair of support members at the rear position are equal.

When the above-mentioned supporting member is formed of a metal frame, if a part of the metal frame is bent and arranged in a manner different from the rest of the metal frames for convenience of installation, the temperature-sensitive resistance of the metal frame is increased. The surface of the body attaching portion that receives air is the width surface or the plate thickness surface of the frame.

Even in such a situation, according to the means for solving the problem, the metal frame to which the temperature-sensitive resistor is directly attached has a rectangular cross-sectional shape, and the frame width dimension and the plate thickness dimension are the same or almost the same. By making them equal, the metal frames can be arranged so that the air passage widths of the temperature sensitive resistors between the metal frames are almost always equal, and the mounting limitation of the temperature sensitive resistors to the air flow is relaxed.

Operation of the third means for solving the problems ... A plurality of temperature sensitive resistors (for example, one is used as a heating resistor for measuring an air flow rate and the other is used as a resistor for temperature compensation) When mounting on the frame, the temperature compensating resistors are placed at different positions to avoid the thermal effect on the heating resistors side, but if the positions of the temperature sensitive resistors are shifted in this way, there is no consideration. In this case, the distance from the mold resin surface of the metal frame to the temperature sensitive resistor mounting position is significantly different for each temperature sensitive resistor. Therefore, there is a difference in the amount of heat transferred from the outside to the temperature-sensitive resistor via the mold resin, and thus the metal frame (for example, when the temperature-sensitive resistor is used as the intake air amount sensor of the engine, the heat of the engine). If there is a difference in the amount of heat transfer, these thermal noises cannot cancel each other, resulting in an error in the air flow measurement accuracy).

However, according to the means for solving the problem, a stepped surface is formed in accordance with each metal frame on the mold resin surface from which the metal frame is projected, and a rib provided on one side allows the metal frame to be sensed from the stepped surface and the rib. The length to the resistance thermometer can be adjusted in advance, so that the amount of external thermal noise received by the resistance thermometer can be made equal, and these thermal noises can be canceled out, so the measurement accuracy of the resistance thermometer can be improved. You can

Operation of the fourth means for solving the problems: When the housing of the temperature-sensitive resistor is molded with resin and the resin is molded by embedding a part of the metal terminal in the resin with its surface left, the conventional metal terminal is used. Due to the difference in thermal expansion between the resin and the resin, a resin shrinks after the housing is molded, so that a gap is created between the metal terminal and the mold resin, and the mounting strength of the terminal is significantly reduced.

However, as in the means for solving the problem, the metal terminal is located in a valley-shaped lower position with respect to the resin surface, and the relationship between the width W1 of the exposed surface of the metal terminal and the width W2 of the terminal is W1 <W2. Then, a force of contracting the resin corresponding to the width of W2-W1 in the direction of gripping the front surface and the back surface of the metal terminal acts, and as a result, the mounting strength of the metal terminal can be increased.

Operation of the fifth means for solving the problems ... When an electronic circuit used for measuring the air flow rate as described above is grounded through a filter circuit for removing noise, conventionally, a metal frame or the like is used as a ground terminal. , It was welded to the substrate. On the other hand, when wire bonding is used for the ground connection as in the means for solving the problem, the weight of the connecting member and the connecting work can be simplified. However, since wire bonding is a wire material, it has a higher impedance than the metal frame. However, the ground wire bonding of the noise removal filter circuit should be 2 per terminal.
If more than this number is used, the overall wire cross-sectional area can be increased, a low impedance can be achieved, a large-capacity ground can be obtained, and the protection effect against the intrusion of noise can be strengthened.

[0024]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a support structure (support) for a temperature sensitive resistor according to an embodiment of the present invention, FIG. 2 is its front view, and FIG. 3 is a side sectional view. 4, 5 and 6 are specific examples of the temperature sensitive resistor used in the above embodiment, FIG. 7 is a perspective view of the metal frame and the substrate before assembling, and FIGS. 8 and 9 are metal frames used in the above embodiment. And FIG. 10 and FIG. 11 are explanatory views showing a pasted state of the dissimilar metals, and a state before using the metal frame.

The present embodiment relates to a support structure provided with two temperature-sensitive resistors, for example, one for measuring the engine intake air flow rate.

1 to 3, 1 is a substrate made of aluminum, and the substrate 1 is press-molded as shown in FIG.
A hole 17 for inserting and setting a pair of metal frames 21 for supporting the temperature sensitive resistor and a pair of metal frames 22 similarly is provided near the center thereof. With the frames 21 and 22 set in the hole 17, the cylindrical resin 4 (see FIG.
(Shown in FIG. 3) is molded, and these metal frames are integrally connected to the substrate 1 through the resin 4 which is an insulator.

A part of the mold resin 4 is shown in FIGS.
As shown in FIG. 5, the step 16 provided around the molding hole 17 on the upper surface of the substrate 1 is molded on the substrate 1 in such a manner that the remaining columnar portion passes through the hole 17, and a part of the mold resin 4 is formed on the step 16. In this way, it is prevented from coming off.
The hole 17 and the step 16 are non-circular. This is to prevent the resin 4 from rotating when a gap is created between the molded resin 4 and the hole 17 due to contraction after molding.

On the substrate 1, in addition to the step portion 16 for molding, a step portion 15 and a step portion 14 are further press-formed around the step portion 16. Among these, the step portion 15 is for setting a mold at the time of molding the molding resin 4, and the step portion 14 is an adhesive groove for adhering a circuit board 6 (shown in FIG. 15) described later to the substrate 1. Becomes

On the upper surface of the mold resin 4, one surface 1 of the substrate 1 is formed.
Protrusion 41 that is at the same level as the height of 8 (circuit board mounting surface)
(See FIGS. 1 and 3) are integrally molded. This protrusion 41
Has a flat upper surface and serves as an adhesive surface of the circuit board together with the one surface 18 of the substrate. In particular, since the board 1 has a recess due to the provision of the step portions 14, 15 and 16, the adhesive surface for the circuit board is provided in the recessed portion. Play a role in ensuring. Further, a part 45 of the upper surface of the molding resin 4 for molding one end (circuit board connecting portion) 21a, 21b of the metal frames 21, 22 facilitates connection with a circuit board mounted on the board 1. Therefore, it is raised one step higher.

In addition to the above-mentioned elements, the substrate 1 is a substrate 1.
Has projections 11 and 12 provided by press working. Of these, the projection 12 is for positioning when fixing the circuit board, which will be described later, and the projection 11 is an electrode for wire bonding for connecting to the ground of the circuit board. is there. A frame-shaped protrusion 13 for fitting a housing 5 (shown in FIG. 13) described later is integrally formed on the upper surface of the substrate 1 with the substrate 1.

The metal frames 21 and 22 have a part (tip) protruding from the molding resin 4, a temperature sensitive resistor 31 is attached to the protruding portion of the metal frame 21, and a temperature sensitive resistor 32 is attached to the metal frame 22. It is attached by welding.
The metal frames 21 and 22 are electrically insulated by the mold resin 4 and fixed to the substrate 1 by the mold resin 4.

The temperature-sensitive resistors 31 and 32 have the same temperature-resistance characteristics. In this embodiment, the temperature-sensitive resistors 31 and 32 are used for the air flow meter. Is used as a heating resistor for so-called air flow rate measurement, while the heating current for maintaining a constant resistance value is controlled even if the temperature is increased or decreased. It is used as a temperature compensating resistor.

These temperature sensitive resistors 31 and 32 are, for example, as shown in FIG. 4, after a lead 301 is fixed to a ceramic bobbin 300 with an adhesive 302, a resistance wire 303 is formed.
After winding (for example, platinum wire) around the lead 301, the surface is covered with a coating agent (for example, glass, polyimide resin, etc.), or as shown in FIG. 5, a resistance film (for example, platinum, nickel, etc.) 305. 6 is formed on the surface of the ceramic bobbin and the resistance value is adjusted by performing spiral trimming, or as shown in FIG. 6, after forming the resistance film 305 on the ceramic rod 300, the cap 306 to which the lead 301 is welded is fitted. After the resistance value is adjusted by spiral trimming, the resistance surface is protected by the coating agent 304. These temperature sensitive resistors 31, 32 are
It is attached to the tips of the metal frames 21 and 22 by welding.

Before mounting the metal frames 21 and 22, the metal frames 21 and 22 are integrally connected by a connecting portion 23 as indicated by an imaginary line in FIG. This is for facilitating the mounting of the resin 4 on the mold at the time of molding, and the connecting portion 23 is separated after the molding. In addition, metal frames 21 and 2
As for No. 2, as shown in the development view of FIG. 10, one plate is punched by press working, and then bent and formed into a mode as shown in FIG.

Since the temperature sensitive resistor detects the flow of air (air temperature), the temperature sensitive resistors 31 and 3 are used.
When two pairs are used, it is desirable that they have the same characteristics. For that purpose, it is necessary to make the passage widths of the air flowing through the temperature sensitive resistors 31 and 32 installation portions equal, which is the case in the present embodiment. The following measures are taken.

That is, when the temperature sensitive resistors 31 and 32 are directly attached to the metal frames (plate materials) 21 and 22 instead of the pins, the temperature sensitive resistor attachment portion of the metal frame is as shown in FIG.
As shown in FIG. 1, the width W'is equal to the plate thickness W, and the cross section has a square shape (regular quadrangle). As a result, as shown in FIG. 7, the temperature-sensitive resistor mounting portion of the metal frame 21 of the metal frames 21 and 22 is bent so as to be positioned in front of the temperature-sensitive resistor mounting portion of the metal frame 22. Body 31,3
When mounting 2, the temperature sensitive resistor is attached to the metal frame 21 by the plate thickness surface of the metal frame, while the temperature sensitive resistor is attached to the metal frame 22 by the width surface of the metal frame. The interval between the metal frames 21 and 21 located at the front (the temperature-sensitive resistor air passage width) and the interval between the metal frames 22 and 22 located at the rear (the temperature-sensitive resistor air passage width) are the metal frames 21 and 22. Since the thickness W and the width W'of the temperature-sensitive resistor mounting portion of are made the same,
It is possible to make them equal and to improve the measurement accuracy.

As shown in FIG. 10, the metal frame 21,
It is possible to improve weldability by attaching R to the corner of the welded portion of the temperature-sensitive resistor 22.

As shown in FIG. 7, the metal frames 21,
Different metals are bonded to the P portion 2 (upper surface of the electrical connection portions 21a and 21b with the circuit board), and in this example, aluminum 24 is clad as shown in FIG. Further, FIG. 9 shows an example in which the bonding pad 25 is fixed with solder or a conductive adhesive 26. By providing such a dissimilar metal, electrical connection to the circuit board, for example, wire bonding is possible.

Next, the arrangement of the temperature sensitive resistors 31 and 32 and the shape consideration of the mold resin 4 related thereto will be described with reference to FIG.

The temperature sensitive resistors 31 and 32 are the metal frame 2
They are attached to the Nos. 1 and 22 with their positions displaced from each other. on the other hand,
A step 43 is formed on the protruding surface of the metal frames 21 and 22 in the molding resin 4, and one of the step surfaces of the step 43 has the metal frame 22 of the temperature-sensitive resistor 32 projected as it is and the other of the steps. A rib 42 integral with the mold resin 4 is attached to the step surface, and the metal frame 21 of the other temperature-sensitive resistor 31 projects through the rib 42, and the step surface 43 and the rib 42 cause the step surface 43 to pass.
Further, the length l of the metal frames 21, 22 from the rib 42 to the temperature sensitive resistor mounting portion is determined.

When the temperature sensitive resistor 31 is used as, for example, a heating resistor for measuring an air flow rate, and the other temperature sensitive resistor 32 is used as a resistor for temperature compensation, these temperature sensitive resistors are In order to avoid the thermal effect on the heating resistor side, the compensating ones are arranged with the positions shifted as described above, but if there is no consideration if the positions of the temperature sensitive resistors are shifted in this way. In addition, the distance 1 from the resin mold surface of the metal frame to the temperature sensitive resistor mounting position is significantly different for each temperature sensitive resistor. Therefore, heat transmitted from the outside to the temperature-sensitive resistors 31 and 32 through the mold resin 4 and further the metal frames 21 and 22 (for example, when the temperature-sensitive resistors are used as an intake air amount sensor of the engine, heat transfer). There is a difference in quantity. If there is a difference in the amount of heat transfer, these thermal noises cannot cancel each other out, resulting in an error in the air flow rate measurement accuracy.

For that purpose, it is necessary to adjust the distance l, and in the present embodiment, in order to adjust the distance l,
The stepped surface 43 corresponding to the positional deviation of the temperature sensitive resistors 21 and 22 is provided in the mold resin 4. When adjusting the distance 1 of the metal frame 21 on the temperature sensitive resistor 31 side and the distance 1 of the metal frame 22 on the temperature sensitive resistor 32 side, in addition to the amount of heat transfer from the mold resin 4 side, Frame 2
It is also necessary to consider the difference in the amount of heat radiation at the distance l'from the mounting position of the temperature sensitive resistor to the frame tip of the frame 1 and 22. This heat radiation amount is larger on the metal frame 21 side than that on the metal frame 22 because l'is longer, so the heat transfer distance 1 on the metal frame 21 side is made slightly shorter than on the metal frame 22 side in consideration of that amount. There is a need. A rib 42 is attached as the adjustment.

That is, by adjusting the length l from the step surface 43 and the rib 42 to the temperature sensitive resistors 31 and 32 of the metal frames 21 and 22 in advance, the amount of external thermal noise received by the temperature sensitive resistors. Can be made equal to each other and these thermal noises can be canceled out, so that the measurement accuracy of the temperature sensitive resistor can be improved.

FIG. 12 is a bottom view of the temperature-sensitive resistor support structure of the present invention. Two holes 19 for attaching the substrate 1 to another device are arranged on the diagonal line L, and the center C for arranging the temperature sensitive resistor at a fixed position is arranged on the straight line L. By doing so, when a bolt or the like is tightened in the mounting hole 19, a uniform fixing force is applied to the substrate 1 by only two holes, so that the substrate 1 and thus the temperature sensitive resistor portion can be stably fixed. You can According to the above-described embodiments, there is an effect that it is possible to realize a small-sized, light-weight, mechanically stable support structure for a temperature-sensitive resistor, which is a target of detection accuracy even if a plurality of temperature-sensitive resistors are set. Next, a description will be given of an embodiment of a housing that is combined with the support of the temperature-sensitive resistor. Figure 1
3A is a plan view of the housing 5 according to the embodiment of the present invention, FIG. 3B is a partial sectional view of the terminal portion, and FIG.
4 is a sectional view of the housing.

The housing 5 is formed integrally with a terminal case 5A containing a metal terminal 51 by resin, has a frame shape, and is connected and arranged on the above-described substrate 1 as shown in FIG. And its lower surface is the substrate 1
A groove 58 for fitting with the frame-shaped projection 13 is formed, and a groove 55 for connecting with the cover 7 (see FIG. 16) is formed on the opposite surface (upper surface) thereof. The groove 55 is located outside the side wall 57 of the housing 5 and is formed over the entire circumference of the housing 5. Further, the side wall 57 inside the groove 55 is made higher than the groove 55. By doing so, it is possible to prevent the adhesive from flowing into the inside of the housing 5 when the adhesive is applied to the groove 55 and the cover 7 is joined.

Each terminal 51 has two locations 51 at both ends.
The base materials of a and 51b are the same, but different surface treatments are applied. For example, one end 51 is subjected to a surface treatment with a metal material having elasticity and corrosion resistance (for example, gold plating or tin plating) so that the one end 51 is surely fitted and connected to an external plug, and the other end 52 is connected to a circuit board. Nickel plating is applied to enable wire bonding.

Three terminals 51 are used in this embodiment, and they are integrated by a connecting portion 53 before being molded into the housing 5. The connecting portion 53 is cut off after molding. Since one end 51b of the terminal 51 is subjected to ultrasonic aluminum wire bonding as described later, it is necessary to sufficiently fix the ultrasonic energy so that the ultrasonic energy can be efficiently transmitted to the terminal 52. The V-shaped groove mold 54 of FIG. 14 is provided for this purpose.

That is, when the V-shaped groove mold 54 of FIG. 14 is adopted, one end 51b of the terminal 51 is buried with resin by exposing only a part of the surface, and this embedding is such that one end 51b of the terminal is valley-bottomed with respect to the resin surface. At the low position, the width W1 of the exposed surface and the width W2 of the terminal
The relationship is W1 <W2.

By doing so, a force of contracting the resin corresponding to the width of W2-W1 in the direction (arrow direction) for pinching the front surface and the back surface of the terminal end 51b acts, and as a result, the mounting strength of the metal terminal is increased. It is possible to increase the number and solve the above problems.

Without the above consideration, if a part of the metal terminal is simply resin-molded with its surface left, the metal terminal and the molding resin will contract due to the resin contraction after the housing molding due to the difference in thermal expansion between the metal terminal and the resin. A gap is created between the terminal and the terminal and the mounting strength of the terminal is significantly reduced.

An embodiment of an air flow meter to which the above-mentioned temperature-sensitive resistor support structure and housing are applied will be described.

FIG. 15 is a plan view of the air flow meter of this embodiment,
16 is a sectional view thereof, FIG. 17 is a circuit diagram of an air flow meter, FIG. 18 is an embodiment of a noise prevention filter circuit used in the air flow meter, and FIG. 19 is another embodiment of the filter circuit. Further, FIG. 20 shows an embodiment of an air flow meter arranged in the air flow path.

As shown in FIG. 15, the substrate 1 described so far.
The housing 5 is connected to the projection 13 and the groove 58 by fitting and bonding, and the circuit board 6 is housed inside the housing 5.

On the surface of the circuit board 6, a transistor T,
A detection circuit including an IC (A), a resistor, a capacitor and the like and a filter circuit are mounted. Circuit board 6 is adhesive 64
It is fixed to the substrate 1.

One ends of the metal frames 21 and 22 are connected to the pads 61 on the circuit board 6 by aluminum wire bonding, and similarly, the terminals 52 of the housing 5 and the pads on the circuit board 6 are also connected by wire bonding.

The earth electrode portion 11 of the board 1 and the circuit board 6 are connected by two aluminum wire bondings 62. Here, the pad 61 of the circuit board 6 is not essential, and is not necessary if the conductor terminal is a material capable of aluminum wire bonding. Numeral 8 is a portion of the air flow meter which is accommodated in the passage through which the air to be detected flows, and the temperature sensitive resistors 31 and 3 are provided so that the seal member 81 can prevent air leakage.
2 is arranged in the air passage.

The operation of the air flow rate detector will be described with reference to FIG. Temperature-sensitive resistor 32, temperature-sensitive resistor 31 and resistance R
8 and resistors R1 and R7 form a bridge with a portion of the actuation amplifier A1 in IC (A). This bridge circuit is stable by the equation (1).

[0059]

RH = R1 (R8 + Rc) / R7 RH: Resistance value of the temperature sensitive resistor 32 Rc: Resistance value of the temperature sensitive resistor 31 Further, RH and Rc are each expressed by the equation (2).

[0060]

RH = RH0 (1 + αT) Rc = Rc0 (1 + βT) RH0: Resistance value at the reference temperature of RH Rc0: Resistance value at the reference temperature of Rc α, β: Temperature coefficient of each T: Temperature Therefore, temperature-sensitive resistance The body 32 is supplied with the heating current Ih at a value higher than the temperature sensitive resistor 31 by a constant temperature.

On the other hand, the heated resistor and the air flow rate are related by the equation 3 according to King's equation.

[0062]

## EQU3 ## Ih ² Rh = (A + B√q) (dTh) (3) A, B: Constants q: Air flow rate dTh: Temperature difference between the temperature sensing resistor 32 and air The current Ih becomes a function of the air flow rate, and this current is detected by the resistor R1 and the voltage is converted into a voltage signal suitable for output to the outside by the processing circuit DA, or converted into a current and a frequency, and the air flow rate signal O Is output.

Further, in FIG. 17, V _B is a power source (+), G
Is a power source (-), and OUT is connected to an external load via a wire harness.
Noise is applied by induction and static electricity and enters the circuit board side. The filter F prevents this invasion.

As shown in FIGS. 18 and 19, the filter F is a filter circuit composed of capacitors C1 and C2 and a ferrite bead B, or a circuit of a three-terminal capacitor C5 and a ferrite bead B. Furthermore, these grounds are connected to the substrate 1. When excessive noise is applied to the wire harness, it releases (inhales) free electrons of the aluminum of the substrate 1 and prevents noise current from flowing to the circuit board. Therefore, the connection impedance can be lowered, and the wire bonding 62 in this portion is
Book (or two or more).

FIG. 20 shows the air passage 8 of the above air flow meter.
Is shown in detail, a part q (q = Q / K) of the air Q flowing into the air passage 8 is introduced into the bypass passage in which the temperature sensitive resistor 31.32 is arranged, and the total air flow rate is increased. Is to detect. A screw 82 is passed through the mounting hole of the substrate 1 to fix the air flow meter of FIG. 15 to the wall of the air passage. If the passage 8 is made of metal, the noise resistance is further improved. By doing so, there is an effect that it is possible to provide a small-sized and lightweight air flow meter having an excellent effect of preventing noise.

The above-described temperature-sensitive support structure has been described by taking the air flow meter as an example, but the present invention is not limited to this and can be applied to various measuring instruments such as a temperature measuring meter.

[0067]

According to the present invention, a simple structure, small size,
It is possible to provide a lightweight temperature-sensitive resistor support structure and to realize an air flow meter with an excellent effect of preventing noise intrusion.
It can contribute to weight reduction and high precision (noise resistance).

[Brief description of drawings]

FIG. 1 is a plan view of a support structure for a temperature sensitive resistor according to an embodiment of the present invention.

FIG. 2 is a front view of the temperature-sensitive resistor support structure.

FIG. 3 is a side sectional view of the temperature-sensitive resistor support structure.

[Fig. 4] Structure diagram of temperature-sensitive resistor

FIG. 5: Structural diagram of temperature-sensitive resistor

FIG. 6 is a structural diagram of a temperature sensitive resistor.

FIG. 7 is an external view of a metal frame and a substrate used in the above embodiment.

FIG. 8 is an explanatory diagram showing an example of laminating the metal frame and the dissimilar metal.

FIG. 9 is an explanatory view showing an example of laminating the metal frame and a dissimilar metal.

FIG. 10 is an explanatory view showing a cross-sectional shape of a welded portion of the temperature sensitive resistor of the metal frame.

FIG. 11 is an explanatory diagram showing a state of the metal frame before being molded.

FIG. 12 is a bottom view of the temperature sensitive resistor support structure.

FIG. 13 is a plan view of a housing according to an embodiment of the present invention and a partial cross-sectional view of a terminal portion pressing shape.

FIG. 14 is a sectional view of the housing.

FIG. 15 is a plan view of an air flow meter according to an embodiment of the present invention.

FIG. 16 is a sectional view of the air flow meter.

FIG. 17 is a circuit diagram of the air flow meter.

FIG. 18 is a filter circuit diagram of the air flow meter.

FIG. 19 is a diagram showing another example of the filter circuit.

FIG. 20 is an explanatory diagram showing a state in which the air flow meter is provided in an air passage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 4 ... Mold resin, 5 ... Housing, 7 ... Cover, 11 ... Protrusion (projecting electrode), 16 ... Non-circular step, 18 ... One surface of circuit board (circuit board mounting surface), 19 ... For fixing board Holes 21, 22 ... Metal frame, 24 ... Dissimilar metals provided on the frame, 31, 32 ... Temperature sensitive resistor, 41 ... Mold protrusion, 42 ... Rib, 43 ... Mold step surface, 5
1 ... Metal terminal, 62 ... Aluminum wire bonding for ground, F ... Filter circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsukuni Tsutsui 2520 Takaba, Takata, Ibaraki Prefecture, Hitachi Ltd. Automotive Equipment Division (72) Inventor Minoru Takahashi 2520, Takata, Katsuta, Ibaraki Hitachi, Ltd. Factory Automotive Equipment Division

Claims (20)

[Claims] 1. A metal frame is molded by synthetic resin (hereinafter referred to as resin) molding on a substrate having protrusions provided for making electrical connection, and a part of the metal frame protrudes from the molding resin. A temperature-sensitive resistor support structure characterized in that a temperature-sensitive resistor is attached to the frame protrusion. 2. A metal frame for mounting a temperature-sensitive resistor on one side and connecting the other side to a circuit board; and a board on which the circuit board is mounted and having projecting electrodes, wherein the metal frame is insulated. A support structure for a temperature-sensitive resistor, wherein the support structure is provided on the substrate with protruding electrodes via the body. 3. The temperature sensitive resistor support structure according to claim 1 or 2, wherein a metal material different from the metal frame is provided for a part of the metal frame for electrical connection. 4. The protrusion according to claim 1, wherein a part of the mold (insulator) is provided with a protrusion having the same level as the height of the one surface of the substrate. Support structure for temperature-sensitive resistor characterized in that one surface of the substrate serves as an adhesive portion of the circuit board 5. The feeling according to claim 1, wherein the substrate is an aluminum plate, and a non-circular step for molding the metal frame is press-molded. Support structure for temperature resistance. 6. The board according to claim 1, wherein the board is fitted with a projecting electrode for connecting a ground of the circuit board and a housing mounted on the board. A support structure for a temperature-sensitive resistor, characterized in that the protrusions are formed by press molding. 7. The temperature-sensitive resistor mounting portion of the metal frame according to claim 1, wherein the temperature-sensitive resistor mounting portion has a rectangular cross-section, and the width dimension and the frame plate thickness dimension are the same or substantially equal to each other. A support structure for a temperature-sensitive resistor characterized by being provided. 8. The method according to claim 1, wherein holes for fixing the substrate are provided at two positions of the substrate, and these holes are aligned with the center of the mold portion. A structure for supporting a temperature-sensitive resistor, which is characterized in that it is arranged at. 9. The temperature-sensitive resistor according to claim 1, wherein a plurality of the temperature-sensitive resistors are attached to the respective corresponding metal frames with their positions displaced from each other, while A step is formed on the protruding surface of the metal frame in the molding resin, and the metal frame of one of the temperature sensitive resistors is projected as it is on one step surface of the step, and the above step is formed on the other step surface. A rib integral with the mold resin is provided, and the metal frame of the other temperature sensitive resistor projects through this rib, and the metal from the step surface and the rib to the temperature sensing resistor mounting portion is formed by these step surfaces and ribs. A support structure for a temperature-sensitive resistor, characterized in that the length of the frame is determined. 10. A metal frame is resin-molded, a part of the metal frame projects from the molding resin, and a temperature-sensitive resistor is attached to the frame protrusion, and a temperature-sensitive resistor mounting portion of the metal frame. The support structure for the temperature-sensitive resistor is characterized in that the sectional shape of the is rectangular and the width dimension thereof and the plate thickness dimension of the frame are the same or substantially equal to each other. 11. A metal frame is molded by resin molding, a part of the metal frame protrudes from the molding resin, and a temperature-sensitive resistor is attached to the protrusion, and a plurality of the temperature-sensitive resistors are provided. Are arranged on the individual metal frames corresponding to the above, while being displaced from each other, and on the other hand, a step is formed on the surface of the mold resin on the protruding side of the metal frame. The metal frame of the temperature-sensitive resistor is projected as it is, and a rib integral with the mold resin is attached to the other step surface, and the metal frame of the other temperature-sensitive resistor is projected through the rib, and these step differences are formed. A support structure for a temperature sensitive resistor, wherein the length of the metal frame from the stepped surface and the mold resin to the temperature sensitive resistor mounting portion is determined by the surface and the rib. 12. A housing, which is connected to a board on which a temperature sensitive resistor and a circuit board are mounted, has a metal terminal for electrically connecting to the outside, and one end of this metal terminal is a part of the surface (this A part of the surface is exposed to the electrical connection with the circuit board) and is buried in the resin, and the metal terminal is located at a valley bottom low position with respect to the resin surface, and the surface exposed part is The circuit housing is characterized in that the relationship between the lateral width W1 of the terminal and the lateral width W2 of the terminal is W1 <W2. 13. The housing for a circuit according to claim 12, wherein a portion of the metal terminal electrically connected to the outside and a portion exposed inside the housing are subjected to different surface treatments. 14. The method according to claim 12 or claim 13,
On the surface of the housing opposite to the substrate,
A circuit housing characterized in that a groove for coupling with a cover is provided over the entire circumference, and a height of a housing side wall located inside the groove is increased with respect to the groove. 15. A circuit board on which an electronic circuit is formed is fixed to the surface of the substrate of the support structure for a temperature sensitive resistor according to claim 1, and the metal frame and the circuit board are connected. The housing according to any one of claims 12 to 14 is fixed to the substrate, and a ground terminal of a filter circuit for noise removal mounted on the circuit board is connected to a grounding protrusion provided on the board. An air flow meter, wherein the circuit board and the metal terminal are connected, and the cover is mounted by fitting the peripheral edge of the cover into a groove provided in the housing. 16. The air flowmeter according to claim 15, wherein the dissimilar metal portion provided on the metal frame and the electrode provided on the circuit board are connected by aluminum wire bonding. 17. The method according to claim 15 or 16,
An air flow meter, wherein the circuit board and the terminal of the housing are connected by aluminum wire bonding. 18. The connection between the earth terminal of the circuit board and the earth projection of the board according to claim 15, wherein at least one earth terminal / earth projection is connected at least. An air flow meter characterized by performing bonding with two or more aluminum wires. 19. The measured air flow path of the air flow meter according to claim 15, wherein a bypass flow path is provided, and the temperature sensitive resistor is provided in the bypass flow path. An air flow meter, characterized in that the circuit module such as the circuit board, the board supporting the circuit board, the housing, and the cover is fixed through an attachment hole in a wall portion of the air flow path while being inserted. 20. An electronic circuit comprising a filter circuit for removing noise, wherein two or more wire bonding wires for grounding the filter circuit are used for each terminal.