JPH0229968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air flow rate measuring device for an internal combustion engine.

[Conventional technology]

A thermal flowmeter using a resistor is known as a method for measuring the amount of air in an internal combustion engine.

In general, thermal flowmeters are used as mass flow rate detection sensors with excellent high-speed response. However, when the resistor becomes contaminated with dust in the air, its heat dissipation characteristics change over time, making it difficult to maintain accuracy. Furthermore, in a high-speed response hot wire flowmeter that uses a single platinum wire as a resistor,
The disadvantage is that it does not have sufficient mechanical strength against air shock flows.

Therefore, an attempt has been made to solve the above-mentioned drawbacks by providing a thermal flowmeter in the branch pipe, as disclosed in Japanese Patent Application Laid-open No. 77731/1983.

[Problem that the invention seeks to solve]

However, in this method, the branch pipe, the resistor, the electronic circuit connected to the resistor, etc. are each constructed separately, and therefore, there is a drawback that a lot of time and man-hours are required to adapt the characteristics.

[Means for solving problems]

Features of the present invention include: (a) a main passage having a throttle valve and a throttle part formed upstream of the throttle valve; an outlet passage opening into the throttle part; and an inlet passage opening upstream of the throttle part; (b) When assembled to the main passage main wall, it connects to the inlet passage and the outlet passage and detours from the main passage to form a bypass forming passage, and the periphery is surrounded by the wall. A conductive path surrounded by the wall, a heating resistor and a temperature correction resistor disposed in the conductive path surrounded by the wall, and a substrate having a signal processing circuit for the resistor. An air flow measuring device for an internal combustion engine comprising a detection block.

[Effect]

According to this configuration, air branches off from the main passage, flows through the bypass forming passage, passes through the conduction passage of the detection block, and rejoins the main passage. At this time, the resistor is cooled by the air flowing through the conductive path, and the amount of air is determined from the degree of cooling.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. However, in each figure, similar or identical components are indicated using the same reference numerals.

FIG. 1 is a sectional view of an air flow measuring device for an internal combustion engine, which is mounted on the wall of a main passage main body and integrated with a detection block.

Reference numeral 12 denotes a main passage main wall forming a main passage 10 through which air taken into the internal combustion engine flows, and a mounting flange 1 to the intake manifold is provided at the downstream opening.
4 is provided, and an air cleaner mounting portion 16 is provided at the upstream opening. A constricted portion 18 with a streamlined cross section that swells inward is formed in the center of the wall of the main passage body. This constriction section 18 is provided to create an air pressure difference in the main passage 10. A butterfly type throttle valve 20 is attached downstream of this throttle section 18.

The vicinity of the constricted portion 18 of the main passage main wall 12 and the constricted portion 1
An outlet passage 26 and an inlet passage 24, which constitute a bypass forming path, are provided upstream of the passage 8.

Reference numeral 22 denotes a detection block attached to the outer periphery of the main passage body wall 12.

The detection block 22 is provided with a conduit passage 28 surrounded by a wall and communicating with an inlet passage 24 and an outlet passage 26 provided in the main passage body wall 12. Therefore, when the detection block 22 is assembled to the main passage body wall 12, the inlet passage 24, the outlet passage 26 and the conduit passage 28 complete a bypass forming passage.

Note that a flow regulating member 30 is provided between the inlet passage 24, the outlet passage 26, and the conduction passage 28.

A heating resistor 32 and a temperature compensation resistor 34 are supported and fixed inside the conductive path 28 by terminals 36, and the terminals 36 are inserted into terminal support insulators 38 that are integrally fixed to the wall surface of the detection block 22. Fixed.

A board 40 on which an electronic circuit (hybrid integrated circuit) is mounted is attached above the conductive path 28 provided in the detection block 22. The top of the detection block 22 is provided with a protective cover 42 that is attached after the electronic circuit is functionally trimmed. In addition,
Arrows in the figure indicate air flow.

FIG. 2 is a perspective view of the detection block 22 of FIG.

An inlet connection part 44 and an outlet connection part 46 to the conduit passage 28 are opened on the surface of the detection block 22 to be attached to the main passage body wall 12, and mounting flanges 48 are provided at both ends. The part indicated by the dotted line in the figure is a sensor section consisting of a heating resistor 32 and a temperature correction resistor 34 (see FIG. 1). A connector 52 is attached to the side surface of the detection block 22.

FIG. 3 is a three-dimensional perspective view of the sensor unit 50 in FIG. It passes through the installed interior and flows out through the outlet connection 46 into the outlet passage 26. The cross section of the inlet connection part 44 and the outlet connection part 46 is circular, but the cross section of the conduction path 28 has a uniform cross-sectional area,
Its cross-sectional shape is elliptical.

According to this embodiment, the heating resistor 32 and the temperature correction resistor 34 are installed not in the main path 10 but in the conduction path 28 which is a bypass forming path. Further, an electronic circuit consisting of a constant temperature drive circuit and a function signal output circuit for the heating resistor 32 is integrated with the heating resistor 32 and the temperature correction resistor 34, and is housed in the detection block 22 which also includes the conductive path. has been done. Immediately, a heating resistor 32, a resistor 34 for temperature correction of the fluid to be tested, and a substrate 4 on which a drive and signal output circuit are installed.
0 etc. are integrated.

Furthermore, the detection block 22 is connected to an electronic circuit board 40.
, the heating resistor 32 and the temperature correction resistor 34 , the lead-out portions of their electrodes, and the connector 52 of the electronic circuit.

〔Effect of the invention〕

As is clear from the above description, the present invention has the following effects.

(1) The flow rate and output signal characteristics can be measured and trimmed by the integrated unit composed of the detection block 22.

(2) Since the circuit section, detection section, and passage can be integrated into a module, it is possible to reduce the size and weight, increase mechanical strength, and use die-casting or molding technology to make additional machining possible with a small number of processes.

(3) Since the detection block 22 and the main passage main wall 12 are constructed so that they can be assembled separately, the main passage 1
0, the inlet passage 24 and the outlet passage 26 can be manufactured by die-casting, but the conduction passage 2 of the detection block 22
8 is required to be elliptical or rectangular depending on the shape of the hot wire resistor, so it is better to manufacture a separate detection block to improve accuracy.

(4) Since the conductive path 28 is surrounded by a wall and the resistor is housed within the wall, there is no problem of the resistor falling off when handling the detection block.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an air flow measuring device for an internal combustion engine which is an embodiment of the present invention, FIG. 2 is an enlarged perspective view of a detection block, and FIG. 3 is a three-dimensional perspective view of a sensor section. 12...Main passage main body wall, 14...Mounting flange, 16...Air cleaner mounting portion, 18...
Throttle portion, 20... Throttle valve, 22... Detection block, 24... Inlet passage, 26... Outlet passage, 28
... Conduction path, 30 ... Rectifying member, 32 ... Heat generating resistor, 34 ... Temperature correction resistor, 36 ... Terminal, 38 ... Terminal support insulator, 40 ... Substrate, 4
2...Protective cover, 44...Inlet connection part, 46...
...Outlet connection, 48...Mounting flange, 50...
Sensor section, 52...connector.

Claims (1)

[Scope of Claims] 1 (a) A main passage 10 having a throttle valve 20 and a throttle part 18 formed upstream of the throttle valve, an outlet passage 26 opening into the throttle part, and an outlet passage 26 opening upstream of the throttle part. (b) When assembled to the main passage main wall, the main passage body wall 12 has an inlet passage 24 connected to the inlet passage and the outlet passage, detouring from the main passage to form a bypass passage. , and a conductive path 28 surrounded by a wall,
A heating resistor 32 and a temperature correction resistor 34 are arranged in a conductive path surrounded by the wall.
and a substrate 4 having a signal processing circuit for the resistor.
An air flow measuring device for an internal combustion engine, comprising a detection block 22 that integrally includes a detection block 0 and a detection block 22. 2. The air flow measuring device for an internal combustion engine according to claim 1, wherein the cross-sectional shape of the conductive path is elliptical or rectangular.