JPH07128109A - Hot wire airflow meter integrated with throttle body - Google Patents

Abstract

PURPOSE:To eliminate a difference of an output flow rate of an airflow meter between those at the times of full closing and full opening of an idle speed control valve and to reduce a deflection of the output flow rate. CONSTITUTION:An outlet 8 of a first bypass passage 4 communicates with an inlet 12 of a second bypass passage 11 with a connector 15 formed of an L-shaped tube. A downstream end of the connector 15 is mounted at a throttle body 1, and an upstream end is approached to a downstream of the outlet 8 at an interval G. When opening degree of a throttle valve 3 is small and an idle speed control valve 13 is opened, an air flow flowing through the passage 11 increases an air flow of the passage 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot wire type air flow meter for detecting the flow rate of air supplied to an internal combustion engine, and more particularly to a hot wire type air flow meter integrated with a throttle body of a type integrally formed with a throttle body.

[0002]

2. Description of the Related Art A hot wire type air flow meter integrated with a throttle body is known in which a bypass passage serving as a flow rate measuring portion is formed across a main air passage (for example, an actual flat panel 2-).
No. 103145, Japanese Patent Laid-Open No. 3-25320).

In the throttle device disclosed in Japanese Patent Laid-Open No. 3-25320, a second bypass passage for bypassing the throttle valve is provided, and an engine idle speed is adjusted by adjusting an air flow rate bypassing the second bypass passage. It has an idle speed control valve to control the number.

A configuration diagram of this kind of throttle body integrated type hot wire type air flow meter is shown in FIGS. 3 (a) and 3 (b).
1 is a throttle body, 2 is a main air passage, 3 is a throttle valve, 4 is a first bypass passage formed across the main air passage 2 upstream of the throttle valve 3, and 5 and 6 are first bypass passages 4. The member 5 to be formed is integrally formed with the throttle body 1. The member 6 has a flat plate shape and is attached so as to abut against the lower surface of the member 5.

Reference numeral 7 is an inlet of a first bypass passage opened at the upstream end of the member 5, 8 is an outlet of the first bypass passage opened near the right end of the member 6 in the drawing, and 9 is an electronic circuit section for outputting a flow rate signal. Reference numeral 10 denotes a sensor portion including a stem protruding rightward in the drawing from the electronic circuit portion 9 and a heat wire attached to the tip of the stem. The heat wire senses the flow velocity of the air flowing through the first bypass passage 4. Detects the flow rate of air supplied to the internal combustion engine.

The output of the electronic circuit section 9 is an output signal of an air flow meter (hereinafter abbreviated as AFM). 1
1 is a second installed bypassing the throttle valve 3
The inlet 12 at the upstream end of the bypass passage opens to the main air passage 2 upstream of the throttle valve 3.

Reference numeral 13 is an idle speed control valve (hereinafter abbreviated as ISCV) for adjusting the flow rate of air flowing through the second bypass passage 11 to control the idle speed of the engine, which is driven by a control circuit (not shown). An actuator 14 is provided, and this actuator 1
The operation changes with 4 and the opening changes.

[0008]

In the prior art of FIG. 3,
The air that has flowed into the throttle body 1 splits and flows as shown by arrows A and B, and the portion of the arrow A flows from the inlet 7 into the first bypass passage 4 and is directly detected by the sensor unit 10.

The arrow C indicates the air flowing through the first bypass passage. When the opening degree of the throttle valve 3 is large, the air indicated by the arrows B and C is located downstream of the first bypass passage 4 and indicated by the arrow D.
And flow through the main air passage 2. And the second
Almost does not flow into the bypass passage 11.

When the throttle opening is small, the arrow B
The air of C and C flows through the second bypass passage 11 as shown by the black arrow in FIG. The inlet 12 of the second bypass passage 11 is connected to the outlet 8 of the first bypass passage 4.
Therefore, the ratio of the flow rate of the arrow A to the flow rate of the arrow B becomes small particularly in a region where the throttle opening is small.

As a result, there is a problem that the AFM output flow rate with respect to the actual air flow rate supplied to the internal combustion engine decreases and the AFM output flow rate deviation (error) with respect to the fully closed ISCV increases.

The polygonal line a in FIG. 2 shows the deviation when the throttle opening is small, and the polygonal line b shows the deviation when the throttle opening is large. As is apparent from this figure, in the conventional technique, the ratio of the air flowing through the first bypass passage 4 is small, so that a negative deviation occurs, and the deviation becomes particularly large in the region where the throttle opening is small. There was a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a heat wire type air flow meter integrated with a throttle body which can solve the above problems.

[0014]

In order to achieve the above object, a throttle body integrated hot-wire air flow meter according to claim 1 is formed across a throttle valve (3) upstream part of a main air passage (2). The first bypass passage (4), the sensor portion (10) arranged in the first bypass passage (4), and the second bypass passage (11) provided by bypassing the throttle valve (3). And an idle speed control valve (1) provided in the second bypass passage (11) for controlling the idle speed of the engine.
3), a hot-wire air flow meter, wherein the outlet (8) of the first bypass passage (4) and the inlet (12) of the second bypass passage (11) communicate with each other and the main air It is characterized in that it comprises a connecting part (15) having an opening (16) communicating with the passage (2).

According to a second aspect of the invention, in the first aspect of the invention, the connecting portion (15) is formed by an L-shaped pipe, and one end (downstream end) of the connecting portion (15) is the second bypass passage (1).
Throttle body (1) opening at the inlet (12) of 1)
And the other end (upstream end) of the first bypass passage (4) is close to the outlet (8) of the first bypass passage (4) and is opposed to the downstream thereof.

[0016]

The air that has flowed into the throttle body is divided into the first bypass passage (4) and the main air passage (2) and flows, and the flow of the first bypass passage is directly detected by the sensor section (10).
Detected in. When the opening degree of the throttle valve (3) is small, the air flowing through the second bypass passage (11) is particularly increased.

Therefore, the air flowing out from the outlet (8) of the first bypass passage (4) is sucked into the second bypass passage (11) via the connecting portion (15). Thus
The flow rate of air flowing through the first bypass passage (4) increases.

The air diverted to the main air passage (2) is
It is sucked into the second bypass passage (11) from the opening (16) of the connecting portion (15). The idle speed of the engine is controlled by the idle speed control valve (13).

[0019]

1 (a) and 1 (b) is an embodiment of the present invention, and since the reference numerals 1 to 14 are the same as those in the prior art shown in FIGS. .

In the illustrated embodiment, reference numeral 15 is a connecting portion formed of an L-shaped pipe, one end (downstream end) of which is attached to the throttle body 1 where the inlet 12 of the second bypass passage 11 is open, and the other. The end (upstream end) has the outlet 8 of the first bypass passage 4
Is arranged in the vicinity of the downstream side of the outlet 8.

Reference numeral 16 denotes an opening, which connects the connecting portion 15 to the main air passage. In the embodiment, the opening 16 is formed by making the upper end of the connecting portion 15 formed of an L-shaped pipe face the lower surface of the flat plate 6 with a gap G therebetween.

The air flowing into the throttle body 1 is divided as indicated by arrows A and B, the portion indicated by the arrow A flows through the first bypass passage 4, and the portion indicated by the arrow B flows through the main air passage 2. In the operating region where the opening degree of the throttle valve 3 is large, most of the air flowing out from the outlet 8 of the first bypass passage 4 exits from the opening 16 to the main air passage 2 and merges with the portion indicated by the arrow B to form the arrow D. Flow to.

When the ISCV 13 is closed, all the air discharged from the outlet 8 of the first bypass passage 4 is the opening 1.
6 and joins the main air passage 2. In the operating region where the opening degree of the throttle valve 3 is small, the ISCV is open, and the intake pipe negative pressure applied to the second bypass passage 11 affects the outlet 8 of the first bypass passage 4 via the connecting portion 15. This increases the flow rate of air in the first bypass passage 4.

The deviations of the AFM output flow rate when the ISCV is fully closed in the embodiment of the present invention are shown by polygonal lines C and D in FIG. The polygonal line C shows when the throttle opening is small, and the polygonal line D shows when the throttle opening is large. Especially, when the throttle opening is small, it is greatly improved over the polygonal line A of the prior art.

A gap G of 5 to 15 mm was suitable. In the embodiment shown in FIG. 1, the connecting portion 15 is composed of an L-shaped tube and the opening 16 is provided at the upstream end thereof.
The upper end of the V-shaped pipe may be attached to the lower surface of the flat plate 6 so that the downstream end of the pipe faces the inlet 12 of the second bypass passage 11 at a slight distance.

[0026]

Since the heat wire type air flow meter integrated with the throttle body of the present invention is configured as described above, the deviation of the AFM output flow rate between the ISCV fully closed state and the ISCV fully opened state can be reduced, and the actual air amount and AFM can be reduced. Not only does the output flow rate match well, but the first and second bypass passages are connected at the connecting portion to form a multi-crank type bypass passage, which also reduces the fluctuation in the output value of the air flow meter. Can be expected.

[Brief description of drawings]

FIG. 1A is a configuration diagram of an embodiment of the present invention, in which FIG.
(B) is a cross section.

FIG. 2 is a diagram showing an AFM output flow rate deviation when the ISCV is fully closed and when it is fully opened.

3A and 3B are configuration diagrams of a conventional technique, in which FIG. 3A is a vertical cross section and FIG. 3B is a horizontal cross section.

[Explanation of symbols]

1 Throttle body 2 Main air passage 3 Throttle valve 4 First bypass passage 8 Outlet 10 Sensor section 11 Second bypass passage 12 Inlet 13 Idle speed control valve (ISC)
V) 15 Connection 16 Opening G Gap

Claims (2)

[Claims] 1. A first bypass passage formed across an upstream portion of a throttle valve of a main air passage, a sensor portion arranged in the first bypass passage, and a second bypass passage provided by bypassing the throttle valve. A hot-wire air flow meter having a bypass passage and an idle speed control valve provided in the second bypass passage for controlling an idle speed of an engine, the outlet of the first bypass passage and the second bypass passage An air flow meter integrated with a throttle body, comprising a connecting portion having an opening communicating with the inlet of the main air passage. 2. The connecting portion is formed by an L-shaped pipe, one end of which is attached to a throttle body opening to the inlet of the second bypass passage, and the other end of which is close to the outlet of the first bypass passage. The heat wire type air flow meter integrated with a throttle body according to claim 1, wherein the heat wire type air flow meter is arranged downstream of the throttle body.