JPH11118557A - Air flow rate-measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a count of parts and miniaturize an apparatus by setting a heat radiation member radiating heat generated from a circuit part, at the circuit part having a control circuit outputting an air flow rate detection signal and mounting the circuit part to an air suction pipe with the use of a mount part of the heat radiation member. SOLUTION: A control circuit 22 is held by a heat sink 23 of aluminum radiating heat generated by the control circuit, and electrically connected to a temperature-sensitive element 25 and a heat-generating element 26 via supporting members 25a, 26a. The control circuit 22 controls a current to be supplied to the heat-generating element 26 so as to make constant a difference of a temperature of the heat-generating element 26 obtained from a value of the current supplied to the heat-generating element 26 and an air temperature detected by the temperature-sensitive element 25. The control circuit outputs the current value. In this case, the heat sink 23 exerts both functions of radiating heat generated at the control circuit 22 and mounting an air flow rate- measuring apparatus to an air suction pipe. This structure reduces a count of parts and makes a mount part compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow measuring device for measuring an air flow flowing through an air flow path.

[0002]

2. Description of the Related Art Conventionally, as an air flow rate measuring device for measuring an air flow rate flowing through an air flow passage, Japanese Patent Laid-Open Publication No. Hei 8-3387.
No. 47 and Japanese Patent Application Laid-Open No. 8-21938 are known.

[0003]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. 8-33874
In the air flow measuring device disclosed in Japanese Patent Publication No. 7, the circuit portion is held by a metal case, and a mounting portion for fixing the air flow measuring device to the intake pipe is formed separately from the metal case. When the mounting portion is formed of resin as in this configuration, when the mounting portion is fastened and fixed to the intake pipe with bolts or the like, the resin near the mounting portion is deformed by the stress acting on the mounting portion,
The fixation to the intake pipe may become unstable. Further, the distortion of the mounting portion may be transmitted to the control circuit, and the control circuit may be disconnected. Further, when the mounting portion is formed by insert molding of metal, a metal member to be inserted is newly required, so that there is a problem that the number of parts increases and the manufacturing cost increases.

In the air flow measuring device disclosed in Japanese Patent Application Laid-Open No. 8-19838, a mounting portion is formed by insert molding a base member and a metal collar. In order to insert the metal collar, the base member needs to be spread to some extent, and the height of the mounting portion is increased. Therefore, there is a problem that the mounting work of the air flow measuring device in a narrow space becomes difficult because the mounting portion becomes large.

[0005] It is an object of the present invention to provide an air flow measuring device that reduces the number of parts and reduces the size of a mounting portion.

[0006]

According to the air flow measuring device of the first aspect of the present invention, the circuit section having the control circuit for outputting the detection signal of the air flow rate is made of a metal for radiating heat generated from the control circuit. The heat radiating member has a mounting portion for mounting the circuit portion to the intake pipe. Therefore,
Since one metal member has both functions of a heat radiating member and a mounting member, the number of components can be reduced and the mounting portion can be downsized.

According to the air flow measuring device of the second aspect of the present invention, since the mounting portion is exposed to the atmosphere, the heat generated from the control circuit is quickly released not only from around the control circuit but also from the mounting portion. Since the heat is dissipated inside, it is possible to suppress a rise in the temperature of the control circuit, and to prevent a malfunction of the control circuit. Furthermore, since the metal mounting portion is not distorted even when the mounting portion is fastened to the intake pipe with, for example, bolts, the distortion is transmitted to the control circuit, thereby preventing the disconnection.

According to the air flow measuring device according to the third aspect of the present invention, since the flow measuring element portion is accommodated in the bypass member having the bypass flow path, the flow rate can be reduced when the air flow measuring device is assembled to the intake pipe. This prevents the measurement element from coming into contact with the intake pipe. Therefore, it is possible to prevent the flow rate measuring element from being damaged during assembly. According to the air flow measuring device according to the fourth aspect of the present invention, since the bypass flow path is formed in a U-shape, the length of the bypass flow path is increased, and the pulsation generated in the air flow in the air flow path is reduced. Reduce on the road. Therefore, the air flow rate can be detected with high accuracy.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; (First Embodiment) FIGS. 3 and 4 show an example in which the air flow measuring device 10 shown in FIG. 2 according to the first embodiment of the present invention is attached to an intake pipe of an internal combustion engine.

The air flow measuring device 10 comprises a circuit module 20 and a bypass member 30. The bypass member 30 is inserted into a mounting hole 1 a provided in the intake pipe 1, and the circuit module 20 is fixed to the intake pipe 1 with bolts 29. ing. The circuit module 20 and the bypass member 30 are connected by bonding or welding. The circuit module 20 has a circuit section and a flow measurement element section. In addition, the circuit module 20
Has a thermistor 27 as an air temperature measuring element for measuring the air temperature in the air flow path 2. The circuit part includes a housing 21, a control circuit 22, a heat sink 23, a connector 24
And a cover 28, and the flow measurement element section has a temperature sensing element 25 and a heating element 26. A control circuit 22 that controls energization of the temperature sensing element 25 and the heating element 26 and outputs a flow rate detection signal is housed in a resin housing 21 of the circuit section.

The control circuit 22 is held by a heat radiating plate 23 made of aluminum as a heat radiating member for radiating heat generated from the control circuit 22. Electrically connected.
The heat radiating plate 23 may be formed of another metal material instead of aluminum. As shown in FIG. 1, the heat radiating plate 23 is formed of one part, and is insert-molded in the housing 21.
The heat radiating plate 23 has two mounting portions 23 a for mounting the circuit module 20 to the intake pipe 1. Mounting part 23a
The periphery of the through hole 23b is exposed from the resin portion. FIG.
As shown in FIG. 5, a bolt 29 for bolting the mounting portion 23a to the intake pipe 1 is in contact with an exposed portion of the mounting portion 23a.
Since the circuit module 20 and the bypass member 30 are combined and modularized, the air flow measuring device 10 is attached to the intake pipe 1 by attaching the circuit module 20 to the intake pipe 1.

That is, the heat radiating plate 23 is provided with a heat radiating member for radiating heat generated in the control circuit 22 and the air flow measuring device 10.
Is also used as a mounting member for mounting to the intake pipe 1, and the heat radiation function and the mounting function are realized by one component. On the side of the circuit module 20, a connector 24 for connecting a wire harness (not shown) is provided. Connector 2
The terminal buried in 4 is electrically connected to the control circuit 22.

The temperature sensing element 25 and the heating element 26 are installed in a flow path on the upstream side of a curved portion 34a of a bypass flow path 34 described later. Since the temperature sensing element 25 measures the temperature of the air that contacts the heating element 26, it is preferable to install the temperature sensing element 25 as close to the heating element 26 as possible without being affected by the heat radiation of the heating element 26. The bypass member 30 has an outer tube 31 and a venturi tube 32 formed integrally with the outer tube 31. The outer tube 31 and the venturi tube 32 are arranged parallel to the air flow. The venturi tube 32 is a circuit module 20 of the outer tube 31.
The partition wall 33 extends from the venturi tube 32 toward the circuit module 20. The partition 33 forms a U-shaped bypass passage 34 in the bypass member 30.

Next, the operation of the air flow measuring device 10 will be described. As shown in FIG.
The air that has flowed into the intake port 31a of the first
4 and a flow toward a Venturi flow path 32 a in the Venturi tube 32. The air that has flowed into the bypass flow path 34 joins with the air that has passed through the venturi flow path 32a on the downstream side of the venturi pipe 32, and
From the air flow path 2. On the downstream side of the Venturi tube 32, a negative pressure is generated because the flow velocity of the air increases. The air in the bypass passage 34 is sucked by the negative pressure, and the flow velocity of the air in the bypass passage 34 is increased.

The current supplied to the heating element 26 by the control circuit 22 so that the difference between the temperature of the heating element 26 calculated from the current value supplied to the heating element 26 and the air temperature detected by the temperature sensing element 25 becomes constant. The current value is output from the control circuit 22 as a flow rate detection signal. In the first embodiment, the bypass flow path 34 is formed in a U-shape, but the bypass flow path may be formed, for example, in a straight line. In the first embodiment, the bypass member 30 having the bypass flow path 34 is provided in the air flow path 2, and the flow rate measuring element is provided in the bypass flow path 34. A measurement element section may be provided.

In the air flow measuring device 10 of the first embodiment,
Although the thermistor 27 for detecting the air temperature in the air flow path 2 is provided, a configuration without the thermistor may be adopted. (Second Embodiment) FIG. 5 shows a second embodiment of the present invention. First
Components that are substantially the same as those in the embodiment are denoted by the same reference numerals.

The mounting portion 23a of the radiator plate 23 is not insert-molded in the housing 41 of the circuit module 40, and has a larger area exposed to the atmosphere as compared with the first embodiment. Therefore, since the heat generated in the control circuit 22 is radiated more quickly than in the first embodiment, it is possible to suppress an increase in the temperature of the control circuit 22 and prevent the control circuit 22 from malfunctioning.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
Shown in Components substantially the same as those in the first embodiment are denoted by the same reference numerals. The housing 51 of the circuit module 50 has two concave portions 51a formed in the peripheral wall surrounding the control circuit 22 on the straight line parallel to the intake air flow. The mounting portion 52a of the heat radiating plate 52 as the heat radiating member
Is provided at the formation position. Therefore, the plane area of the circuit module 50 can be reduced. In the above-described plurality of embodiments, the aluminum heat radiating plate that radiates the heat generated from the control circuit 22 is attached to the intake pipe by mounting the air flow measuring device. Part. Since the heat radiating plate realizes the heat radiating member and the mounting member as one component, there is no need to prepare a mounting member separately from the heat radiating plate. Therefore, the number of parts can be reduced, and a structure for separately forming and holding the mounting member in the housing of the circuit module is not required, so that the circuit module can be downsized.

Further, since the mounting portion is exposed to the atmosphere with a slight difference, the heat of the control circuit is radiated not only from the heat radiating plate close to the control circuit 22 but also from the mounting portion.
Therefore, since the heat generated in the control circuit 22 is quickly radiated, a rise in the temperature of the control circuit 22 can be suppressed, and malfunction of the control circuit 22 can be prevented. Further, since the bolt 29 comes into contact with the metal mounting portion and tightens the mounting portion to the intake pipe, no distortion occurs in the mounting portion during mounting.
Therefore, distortion is transmitted to the control circuit 22 and the control circuit 22
Disconnection can be prevented.

The present invention is not limited to an apparatus for measuring the air flow rate of an internal combustion engine, but can be used as an apparatus for measuring an air flow rate flowing through various air flow paths.

[Brief description of the drawings]

FIG. 1A is a plan view of an air flow measuring device according to a first embodiment of the present invention with a cover removed, and FIG.
FIG. 4 is a plan view showing a heat sink.

FIG. 2 is a partial cross-sectional view showing the air flow measuring device of the first embodiment.

FIG. 3 is a longitudinal sectional view showing a state where the flow measuring device of the first embodiment is attached to an intake pipe.

FIG. 4 is a view in the direction of arrows IV in FIG. 3;

FIG. 5 is a plan view of an air flow measuring device according to a second embodiment of the present invention with a cover removed.

FIG. 6 is a plan view of an air flow measuring device according to a third embodiment of the present invention with a cover removed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intake pipe 1a Mounting hole 2 Air flow path 10 Air flow measuring device 20 Circuit module 22 Control circuit (circuit part) 23 Heat radiating plate (heat radiating member, circuit part) 23a Mounting part 25 Temperature sensitive element 26 Heat generating element 27 Thermistor 30 Bypass member 32 Venturi pipe 33 Partition wall 34 Bypass flow path

Claims (4)

[Claims] 1. An air flow measurement device for measuring an air flow rate flowing through an air flow path, wherein the flow rate measurement element section disposed in the air flow path is electrically connected to the flow rate measurement element section. A circuit portion having a control circuit that outputs a flow rate detection signal, wherein the circuit portion has a metal heat radiating member that radiates heat generated from the control circuit, and the heat radiating member forms the air flow path. An air flow measuring device, comprising: a mounting portion for mounting the circuit portion on a suction pipe to be mounted. 2. The air flow measuring device according to claim 1, wherein the mounting portion is exposed to the atmosphere. 3. A bypass member provided in the air passage, the bypass member having a bypass passage into which a part of air flowing in the air passage flows. The air flow measuring device according to claim 1, wherein the flow measuring element is disposed in the air flow measuring device. 4. The air flow measuring device according to claim 1, wherein the bypass flow passage is formed in a U-shape.