JP2001124605A - Heating resistance element type air flow measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating resistance element type air flow measuring instrument reducing errors in detected inlet air temperature caused by a temperature change due to the self heating of a transistor mounted in an electronic circuit. SOLUTION: This instrument is structured so that the electronic circuit is directly exposed to the air in a main air channel, or else structured by providing a metallic plate with excellent thermal conduction between the electronic circuit and a housing, and exposing the metallic plate to the air in the air channel for beat dissipation by the air flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating resistor type air flow meter provided in a flow path, and more particularly to a heating resistor type air flow measurement device suitable for measuring an air flow rate of an internal combustion engine.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 11-14423 discloses a module in which an electronic circuit, a housing member for supporting and fixing a heating resistor and a temperature-sensitive resistor, and a sub-passage constituting member are mounted on a metal base member. The structure is such that the entire module of the heating resistor type air flow measuring device is disposed in the main air passage, and the entire module can be cooled by the airflow flowing through the main air passage.

[0003]

However, since the metal base member forming a part of the sub air passage also transfers heat to the inside of the sub air passage, the temperature sensing member detects the intake air temperature. The resistor detects a temperature higher than the actual intake air temperature due to the thermal influence caused by the self-heating of the transistor. As a result, more heating current is supplied to the heating resistor that maintains a constant temperature difference from the temperature-sensitive resistor, and an output signal having an air flow rate higher than the actual air flow rate is transmitted.
Therefore, the control unit supplies more fuel than the actual air flow rate, which affects the exhaust gas.

[0004]

As means for solving the above problems, a part of the electronic circuit board, which is transferred from the transistor, is directly cooled by the air flow in the main air passage, and excellent heat conduction is achieved. By transferring the heat to the metal plate and directly cooling it by the air flow in the main air passage by the radiating fins formed of the metal plate, more effective heat radiation becomes possible.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 6 taking a heating resistor type air flow measuring device as an example.

FIG. 1 is a heating resistor type air flow measuring device showing an embodiment of the present invention. FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. FIG. 6 is a diagram showing a drive circuit of the air flow measuring device of FIG.

First, the operation of the air flow measuring device will be described with reference to FIG. A bridge is formed by the heating resistor 4 arranged in the main air passage component 1 forming the main air passage 2, the temperature sensing resistor 5 for compensating the intake air temperature, and R 10 and R 11. The driving circuit thus configured. In this drive circuit, a heating current Ih is supplied to the heating resistor 4 to generate heat, and the temperature-sensitive resistor 5
The magnitude of the supply current Ih amplified by the transistor 16 is controlled so as to maintain a constant temperature. When the air flows, the amount of heat deprived from the heating resistor 4 increases, and the ratio changes according to the air flow speed, that is, the air flow speed.
The value of the current required for heating also changes. As a result, the magnitude of the current flowing through the heating resistor becomes a value corresponding to the air flow rate, and the air flow rate is measured. The output signal Vout indicating the detected air flow rate is converted into a voltage signal or a frequency or current value signal, and is output from the air flow rate measuring device to the control unit as a flow rate signal indicating the intake air.

A supporting pin 6 for holding the heating resistor 4 and the temperature-sensitive resistor 5 is a plastic surrounding the electronic circuit 8 for outputting a signal corresponding to the flow rate of air based on the amount of heat radiation from the heating resistor 4. It is formed integrally with the housing 9 of the member. The housing 9 is provided with a connector section 14 having a connector terminal 13 for electrically connecting the electronic circuit 8 to an external device. The electronic circuit 8 is provided with a transistor 16 for receiving power supply from an external device and amplifying the power. The sub-passage member 10 forms the sub-air passage 3 so as to surround the heating resistor 4, and
Is embedded in the housing 9 so as to be protected, and furthermore, the electronic circuit 8 and the heating resistor 4 are protected by the mold cover 11 to form an integrated module 7. The module 7 is inserted and fixed to the main air passage component 1 so that the sub air passage 3 is disposed in the main air passage 2.

The transistor 16 mounted on the electronic circuit 8
Generates heat by self-heating, and conducts heat to the entire electronic circuit to heat the electronic circuit 8. The heat transmitted to the electronic circuit 8 is further transmitted to the housing 9 and further transmitted from the housing 9 into the sub air passage, thereby changing the temperature of the intake air.

Here, as shown in FIGS. 2 and 3, the electronic circuit 8 directly under the transistor 16 is directly exposed to the main air passage 2, so that the heat generated by the heat generated by the transistor 16 is generated. By having a structure that can be directly cooled by airflow,
The heat resulting from the self-heating of the transistor 16 can be radiated, and the measurement error of the air flow measurement device due to the change in the intake air temperature can be reduced.

FIG. 4 is an enlarged view of a heating resistance type air flow measuring device according to another embodiment of the present invention.

FIG. 4 shows that a metal plate 19 having excellent heat conduction is arranged between the electronic circuit 8 and the housing 9.
Reference numeral 9 denotes a portion directly below the transistor 16 when connected to the electronic circuit 8, and has a structure in which it is folded in a projecting shape in the direction opposite to the electronic circuit side. Further, a through hole 18 is provided in the housing 9, and when the housing 9 is connected to the metal plate 19,
The heat radiation fin portion 20 is exposed to the main air passage side, and the heat conducted from the transistor 16 to the electronic circuit 8 is absorbed by the metal plate 19 and the heat is radiated by the airflow flowing through the main air passage 2. I have.

FIG. 5 shows an example in which the housing 9 shown in FIG.
The heat radiation fins 20 formed by folding back are exposed to the main air passage side.

[0014]

According to the present invention, the heat is transmitted by the self-heating of the transistor of the heating resistor type air flow measuring device.
Thermal effects can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an air flow measuring device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged detail view of a portion B in FIG. 2;

FIG. 4 is a diagram showing an air flow measuring device according to another embodiment of the present invention.

FIG. 5 is a diagram showing an application example of FIG. 4;

FIG. 6 is a drive circuit diagram of the air flow measuring device of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Main air path constituent member, 2 ... Main air path, 3 ... Sub air path, 4 ... Heating resistor, 5 ... Temperature sensitive resistor, 6 ... Support pin, 7 ... Module, 8 ... Electronic circuit, 9 ... Housing Member 10, sub-passage constituent member, 11 cover, 12 conductive lead, 13 connector terminal, 14 connector part, 15 mounting screw, 16 transistor, 17 air flow direction, 18 through hole , 19: metal plate, 20: radiating fin.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hitoshi Ishikawa 2477 Takaba, Hitachinaka City, Ibaraki Prefecture Inside Hitachi Car Engineering Co., Ltd. F-term in the Automotive Equipment Group of the Works (reference) 2F035 AA02 EA03 EA04 3G084 DA04 FA08

Claims (5)

[Claims] 1. An air flow measuring device used in an internal combustion engine for measuring a flow of intake air to an engine, wherein the air flow has a transistor for current amplification in an electronic circuit for outputting a signal corresponding to the amount of intake air. The air flow measuring device according to claim 1, wherein a substantially lower portion of the current amplification transistor is exposed at least through a circuit board into an intake air passage. 2. The air flow measurement device according to claim 1, wherein the air flow measurement device is a heating resistor type air flow measurement device that outputs a signal corresponding to an air flow based on a heat release amount from the heated resistor. 3. The electronic circuit board according to claim 2, wherein the electronic circuit board is provided in a case member made of resin, and the electronic circuit board is disposed so as to be substantially parallel to the air flow direction inside the intake passage. A heating resistor type air flow measuring device, characterized in that: 4. The electronic device according to claim 3, further comprising a metal plate having excellent heat conductivity between the case member and the electronic circuit,
The heating resistor-type air flow measurement device, wherein the metal plate is exposed in the main air passage as a radiation fin by being folded in a protruding shape immediately below the transistor mounted on the electronic circuit. 5. The heating resistor type air flow measuring device according to claim 4, wherein the metal plate is formed integrally with the case member.