JPH0932702A - Fuel injection device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the fine graining of a fuel injected from an injection nozzle in an entire running area without an increase in an intake air amount. SOLUTION: The injection nozzle of an injector 15 for SPI arranged in a surge tank 3 is installed facingly to a throttle valve 5a and the extension of the spray angle θ of this injection nozzle is faced to the clearance 5b between the throttle valve 5a and a throttle main body 5. Further, the spout port 12a of an assist air passage 12 for bypassing the throttle valve 5a is opened near the injection nozzle and also an idle engine speed control valve 13 for adjusting the intake air amount at the idling time is interposed on this assist air passage 12. The injection fuel at the closing time of the throttle valve is mixed and fine-grained by an auxiliary intake air passing the assist air passage 12 adjusted by the idle engine speed control valve 13 and the intake air passing the throttle valve 5a and at the opening time of the throttle valve, fine graining is obtained by the collosion of the injection fuel with the intake air passing the throttle valve 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection system for an engine in which a single point injection (SPI) injector is arranged downstream of a throttle valve and an injection nozzle is directed toward the throttle valve.

[0002]

2. Description of the Related Art In general, an SPI injector is often disposed immediately above a throttle valve as disclosed in, for example, Japanese Patent Application Laid-Open No. 60-79162.
The fuel injected from the PI injector mixes with the high-speed air flow passing through the throttle valve to be atomized.
However, since a part of the injected fuel during idling collides with the throttle valve and is liquefied and flows into the downstream of the throttle valve as it is, it is difficult to sufficiently atomize all the injected fuel. In addition, a swirl flow is generated immediately below the throttle valve at the time of idling due to a high-speed air flow, and a part of the injected fuel is made into droplets in the central part of this swirl flow. It

As a countermeasure against this, for example, Japanese Patent Laid-Open No. 58-11 / 1983
In Japanese Patent No. 9966 or Japanese Patent Laid-Open No. 60-26165, an SPI injector is arranged downstream of a throttle valve and upstream of an intake manifold collecting section, and atomization of injected fuel (acceleration of atomization and vaporization) is performed. Therefore, a technique of supplying assist air to the vicinity of the injection nozzle has been proposed.

[0004]

In the above prior art, the throttle valve is opened because a part of the intake air is guided as assist air to the vicinity of the injection nozzle by utilizing the differential pressure between the upstream side and the downstream side of the throttle valve. Then, as the negative pressure downstream of the throttle valve decreases, it becomes difficult to supply the assist air sufficiently.

Therefore, the above-mentioned Japanese Unexamined Patent Publication No. 58-119966.
In the publication, a second assist air passage is provided in addition to the normal assist air passage in order to allow sufficient supply of assist air even when the throttle valve is opened. When the throttle valve is opened, the normal assist air passage is provided. Assist air is supplied from both the second and second assist air passages.

However, since the assist air supplied from the two systems of assist air passages only utilizes the differential pressure between the upstream and downstream sides of the throttle valve, when the throttle valve with a small differential pressure is opened, Even if the assist air is supplied from the two-system assist air passages, there is a limit to sufficiently atomize the fuel. Further, since the intake system is provided with two assist air passages, the structure is complicated and the manufacturing and assembling are complicated.

Moreover, when the throttle valve is opened,
When the second assist air passage is opened in addition to the normal assist air passage, the assist air supplied from the second assist air passage supplies air to each cylinder according to the throttle opening. The intake air is supplied in an amount larger than the intake air amount, and fuel corresponding to the intake air amount is injected from the injector, so that the engine output suddenly changes and the driver feels uncomfortable.

On the other hand, at the time of idling when the assist air is supplied only from the normal assist air passage, the amount of intake air exceeding the intake air amount required for idle rotation is supplied to each cylinder by the assist air. This leads to instability of idle rotation such as engine speed increase.

The present invention has been made in view of the above circumstances, and it is possible to sufficiently atomize the injected fuel without increasing the intake air amount not only during idling but also under normal operating conditions. It is therefore an object of the present invention to provide a fuel injection device for an engine that can achieve stable idle speed and good running stability performance.

[0010]

In order to achieve the above object, the present invention provides a fuel injection device for an engine in which an injection nozzle of a single-point injection injector is arranged downstream of a throttle valve. It is arranged at a position for injecting fuel toward it, and an inflow port of the assist air passage is opened upstream of the throttle valve, and the ejection port of this assist air passage bypasses the throttle valve and is located near the injection nozzle. It is characterized in that an idle speed control valve for adjusting the intake air amount during idling is provided in the assist air passage which is opened. Further, preferably, the injector for single-point injection is arranged in a surge tank connected to the collecting portion of the intake manifold, and the spray angle of the injection nozzle is made to face the gap between the throttle valve and the throttle body. It is characterized by

In the engine fuel injection system according to the present invention, the amount of intake air supplied to each cylinder at the time of idling with the throttle valve substantially closed is the amount of intake air passing through the gap between the throttle valve and the throttle body. Air volume,
It is determined by the sum of the auxiliary intake air amount supplied through the assist air passage that bypasses the throttle valve. Then, the auxiliary intake air amount is adjusted by the valve opening degree of the idle speed control valve provided in the assist air passage, and the idle speed is controlled to match the target speed. Auxiliary intake air passing through the assist air passage is supplied as assist air from a jet port of a single-point injection injector arranged downstream of the throttle valve, which is opened near the injection nozzle, and is mixed with fuel injected from the injection nozzle. To be done. Further, the fuel injected from the injection nozzle advances in a conical shape in the direction of the gap of the throttle valve arranged on the upstream side. As a result, during idling, atomization of the fuel injected from the injection nozzle is promoted by both the auxiliary intake air supplied as the assist air and the intake air flowing from the gap between the throttle valve and the throttle body. .

When the throttle valve is opened, the amount of intake air passing through the gap portion increases, and SP increases accordingly.
The amount of fuel injected from the injection nozzle of the I injector also increases, and the fuel injected from the injection nozzle of the SPI injector collides with the intake air passing through the gap,
It is actively atomized.

Further, at this time, by causing the spray angle of the injection nozzle to face the gap between the throttle valve and the throttle body, a part of the injected fuel collides with the high-speed air flow passing through the gap. More aggressively atomized

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Reference numeral 1 in FIG. 1 denotes an engine, which is a multi-cylinder engine such as a four-cylinder engine in this embodiment, in which intake ports 1a provided in each cylinder are collected through an intake manifold 2, and a surge tank is provided at this collecting portion. An intake pipe 4 is connected via 3. A throttle body 5 is provided in the middle of the intake pipe 4, and a throttle valve 5a is arranged in the throttle body 5. Further, an air cleaner 6 is attached to the air intake port of the intake pipe 4.

Further, in the exhaust port 1b of the engine 1,
An exhaust pipe 7 communicating with a muffler (not shown) is connected, a catalytic converter 8 is interposed in the middle thereof, and a 02 sensor 9 for detecting the air-fuel ratio from the oxygen concentration in the exhaust gas is arranged upstream of the catalytic converter 8. Has been done. Reference numeral 10 is a water temperature sensor for detecting the cooling water temperature, and 11 is an ignition plug.

Further, an SPI injector 15 which constitutes a fuel injection device is arranged in the surge tank 3.
The injection nozzle 15a of the SPI injector 15 is
It is installed directly below the throttle valve 5a, and its spray angle θ
Is extended so as to face the gap portion 5b formed between the throttle valve 5a and the throttle body 5 when the throttle valve is closed.

As shown in FIG. 2, a cover 16 is attached to the tip portion of the SPI injector 15 and a spray hole 16a is formed in the cover 16 in the fuel injection direction of the injection nozzle 15a. Incidentally, this spray hole 16a
The taper angle θ ′ is formed in a shape along the spray angle θ of the injection nozzle 15a or a taper angle slightly wider than the spray angle θ. Further, the injection nozzle 15a of the SPI injector 15 is provided on the side of the cover 16.
A jet port 12a of the assist air passage 12 for supplying assist air is opened in the vicinity. The assist air passage 12 bypasses the throttle valve 5a, and its inflow port 12b is opened upstream of the throttle valve 5a.

Further, in the assist air passage 12, the IS
A C (idle speed control) valve 13 is provided. The ISC valve 13 mainly controls the intake air amount during idling and controls so that the engine speed matches the target idle speed, and the valve opening degree is controlled by a control signal from an electronic control unit (not shown). It is variably set.

Reference numeral 14 is a pressure sensor provided in the surge tank 3, and detects the intake pipe pressure downstream of the throttle valve 5a.

Next, the operation of this embodiment having the above configuration will be described. The fuel injection amount injected from the injection nozzle 15a of the SPI injector 15 is calculated by an electronic control unit (not shown). In this embodiment, the intake air amount per cycle is estimated based on the intake pipe pressure downstream of the throttle valve 5a detected by the pressure sensor 14 and the engine speed, and based on this intake air amount and the engine speed. The so-called speed density (D-Jetronic) method for determining the basic fuel injection amount is adopted, and the fuel injection amount actually injected from the injection nozzle 15a of the SPI injector 15 is equal to the engine speed. The basic fuel injection amount set based on the intake pipe pressure is set based on various correction terms set based on the cooling water temperature detected by the water temperature sensor 10 and the air-fuel ratio detected by the O2 sensor 9. It is determined by correction using an air-fuel ratio feedback correction coefficient or the like.

At the time of idling, in an electronic control unit (not shown), the valve opening degree of the ISC valve 13 interposed in the assist air passage 12 bypassing the throttle valve 5a is variably set to adjust the amount of intake air supplied to each cylinder. , Feedback control is performed so that the engine speed matches the target speed.

On the other hand, the throttle valve 5a during idling
Is almost closed, the negative pressure downstream of the throttle valve 5a increases, and the intake air passing through the gap 5b between the throttle valve 5a and the throttle body 5 and the inlet 12b of the assist air passage 12 are closed. Auxiliary intake air flowing in from the jet nozzle 12a, which bypasses the throttle valve 5a and is jetted from the jet outlet 12a opening near the jet nozzle 15a of the SPI injector 15 is jetted as a high-speed air flow.

The fuel injected from the injection nozzle 15a is an auxiliary intake air which is ejected at a high speed from the ejection port 12b of the assist air passage 12 formed in the cover 16 attached to the tip of the SPI injector 15. Is atomized as assist air, and the spray holes 16 are opened in the cover 16 while being diffused into a conical shape with a spray angle θ.
After passing through a, it advances toward the gap 5b, a part of which collides with the high-speed air flow passing through the gap 5b, and the other fuel is sucked by the turbulent flow generated downstream of the throttle valve 5a. It is mixed with and is positively atomized. Then, the atomized mixed fuel is guided in the direction of the intake manifold 2 along the intake flow and distributed to each cylinder.

Since the injected fuel is atomized by both the intake air passing through the throttle valve 5a and the auxiliary intake air passing through the assist air passage 12, the fuel is vaporized and atomized even during the warm-up operation after the start. Is promoted, combustion efficiency is improved, and exhaust emission can be improved.

Furthermore, the amount of intake air supplied to each cylinder at the time of idling is determined by the IS provided in the assist air passage 12.
Since it is controlled by the C valve 13, the intake air in an amount exceeding the intake air amount required for idle rotation is not supplied to each cylinder, and stable idle rotation can be obtained.

On the other hand, when the throttle valve 5a is opened, the ISC valve 13 operates so as to close the assist air passage 12 and the supply amount of assist air is reduced. The amount of intake air passing through the gap 5b between the throttle valve 5a and the throttle body 5 gradually increases, and the fuel injected from the injection nozzle 15a of the SPI injector 15 collides with the intake air passing through the gap 5b. Then, they are positively mixed and atomized.

Accordingly, when the throttle valve 5a is opened, the fuel collides with the intake air amount passing through the gap 5b and atomizes the fuel, so that it is not necessary to supply assist air as in the conventional case. Intake air is supplied to each cylinder in an amount corresponding to the opening degree of the throttle valve 5a, and intake air in excess of the amount of air passing through the throttle is not supplied, and good running stability performance can be obtained. .

In this embodiment, the intake air amount is obtained by the so-called speed density (D-Jetronic) method, but the intake air amount is directly measured based on the intake air amount sensor arranged downstream of the air cleaner 6. Needless to say, the present invention can be applied to an engine that employs a so-called mass flow (L-Jetronic) method for calculation.

[0029]

As described above, according to the present invention,
A jet outlet of an assist air passage for supplying a part of intake air as assist air is opened in the vicinity of an injection nozzle of a single-point injection injector arranged downstream of the throttle valve, and the assist air passage is connected to the throttle valve. Bypassing, connecting to the inlet opening on the upstream side, and further, an idle speed control valve for adjusting the intake air amount during idling is provided in the assist air passage, so that assist air is supplied. Also in this case, the amount of intake air supplied to each cylinder does not increase, and a stable idle speed can be obtained.

Further, since the injection nozzle is arranged at a position for injecting fuel toward the throttle valve, the fuel injected from the injection nozzle is assist air ejected from the ejection port of the assist air passage, Since it is mixed with both the intake air passing through the throttle valve, the atomization of the fuel is more positively performed.

Further, since the assist air supplied during idling is adjusted by the valve opening degree of the idle speed control valve, the intake air amount supplied to each cylinder is also supplied during the assist air supply. A stable idle speed can be obtained without increasing. On the other hand, when the throttle valve opens, the idle speed control valve operates in the direction to close the assist air passage and the supply amount of assist air decreases, but the intake air passing through the throttle valve is opened by opening the throttle valve. Since the amount increases, the fuel injected from the injection nozzle collides with the intake air passing through the throttle valve and is mixed, and atomized more positively. Therefore, when the throttle valve is opened, the assist air is not required, and the intake air that is equal to or larger than the opening of the throttle valve is not supplied to each cylinder, and good running stability performance can be obtained.

Further, the single point injection injector is arranged in the surge tank connected to the collecting portion of the intake manifold, and the spray angle of the injection nozzle is directed to the gap between the throttle valve and the throttle body. The fuel injected from the injection nozzle collides with the high-speed airflow ejected from the gap portion to be more positively atomized, and during the cold operation after the start,
Combined with the assist air supplied from the assist air passage, fuel vaporization and atomization can be promoted, and combustion efficiency is improved,
Exhaust emissions can be improved.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an engine.

FIG. 2 is an enlarged view of part A of FIG.

[Explanation of symbols]

2 Intake manifold 3 Surge tank 5 Throttle body 5a Throttle valve 5b Gap 12 Assist air passage 12a Jet outlet 12b Inlet 13 Idle speed control valve 15 Single-point injection injector 15a Injection nozzle θ Spray angle

Claims (2)

[Claims] 1. A fuel injection device for an engine in which an injection nozzle of a single-point injection injector is arranged downstream of a throttle valve, wherein the injection nozzle is arranged at a position for injecting fuel toward the throttle valve, and The inlet of the assist air passage is opened upstream of the throttle valve, the jet outlet of the assist air passage is opened near the injection nozzle by bypassing the throttle valve, and the intake air is drawn into the assist air passage during idling. An engine fuel injection device, characterized in that an idle speed control valve for adjusting the amount of air is provided. 2. The single-point injection injector is arranged in a surge tank connected to the collecting portion of the intake manifold, and the spray angle of its injection nozzle is made to face the gap between the throttle valve and the throttle body. The fuel injection device for an engine according to claim 1, wherein: