JPH0932700A - Fuel injection device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To atomize injection fuel by assist air and to carry out stable idle rotation. SOLUTION: An injector 15 for SPI is arranged on a surge tank 3 on the downstream of a throttle valve 5a, and an jet out nozzle of an assist air passage 12 is opened in the neighbourhood of an injection nozzle of the injector 15 for SPI. An inflow port 12b of this assist air passage 12 is opened on the upstream of the throttle valve 5a, and an idle rotation number control valve 13 to control intake air capacity at the time of idling is interposed in the middle of the assist air passage 12. At the time of idling, the idle rotation number is controlled to match with the target rotation number by controlling intake air capacity passing through the assist air passage 12 by the idle rotation number control valve 13, and this intake air is used as assist air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an engine in which an injector for a single point injection (SPI) is disposed downstream of a 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 during idling due to a high-speed air flow, and a part of the injected fuel is turned into droplets at the center of this swirl flow, which also impedes atomization of the fuel. 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]

However, when the assist air for atomizing the injected fuel is supplied to the vicinity of the injection nozzle, the intake air in an amount exceeding the intake air amount necessary for idle rotation is supplied when idling. Since the fuel is supplied to the cylinders, the engine speed increases, and the idle speed becomes unstable.

On the other hand, if the supply of the assist air is stopped during idling, the fuel cannot be atomized and it becomes difficult to evenly distribute the fuel to each cylinder, resulting in instability of the idle speed. I will invite you.

The present invention has been made in view of the above circumstances, and it is possible to supply sufficient assist air for atomizing fuel injection in the vicinity of the injection nozzle without increasing the intake air amount during idling. It is an object of the present invention to provide a fuel injection device for an engine that can obtain stable idle rotation even when supplying assist air.

[0007]

To achieve the above object, the present invention is directed to an engine fuel injection system in which an injection nozzle of a single-point injection injector is arranged downstream of a throttle valve, and an assist air is provided upstream of the throttle valve. Idle rotation for opening the inlet of the passage, opening the jet outlet of the assist air passage near the injection nozzle by bypassing the throttle valve, and adjusting the intake air amount at idling in the assist air passage It is characterized in that a number control valve is provided. Further, preferably, the injector for single-point injection is arranged in a surge tank connected to the collecting portion of the intake manifold, and its injection nozzle is directed toward the collecting portion of the intake manifold.

In the fuel injection system for an engine according to the present invention, when the throttle valve is idling with the valve closed, the amount of intake air supplied to each cylinder is an idling rotation provided in the assist air passage bypassing the throttle valve. The idle speed is controlled so as to match the target speed by adjusting the valve opening of the number control valve. The intake air passing through the assist air passage is supplied as assist air from a jet opening of a single-point injection injector arranged downstream of the throttle valve and opened near the injection nozzle, and is mixed with fuel injected from the injection nozzle. The fuel is atomized. Further, at this time, the injector for single point injection is arranged in a surge tank connected to the collecting portion of the intake manifold, and its injection nozzle is directed toward the collecting portion of the intake manifold to inject the injected fuel into the intake air. By moving along the flow, fuel is quickly supplied to each cylinder.

[0009]

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 the present embodiment. Intake ports 1a provided in each cylinder are collected through an intake manifold 2, and a surge is provided in this collecting portion. An intake pipe 4 is connected through the tank 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 injector 15 for SPI 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 directed toward the collecting portion of the intake manifold 2.
In the case of a horizontally opposed engine, a V-type engine, or the like, in which the intake manifold 2 is assembled into the surge tank 3 for each of the left and right banks, the SPI injector 15 corresponds to the intake manifold assembly portion. A plurality of the same number are provided.

As shown in FIG. 2, a cover 16 is attached to the tip 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. Furthermore, this cover 16
A jet outlet 12a of the assist air passage 12 for supplying the assist air to the vicinity of the jet nozzle 15a of the SPI injector 15 is opened at the side portion of the. The assist air passage 12 bypasses the throttle valve 5a, and its inflow port 12b is opened upstream of the throttle valve 5a.

In the middle of the assist air passage 12,
An ISC (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 arranged 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, 1
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 basic fuel injection is performed based on the intake air amount and the engine speed. A so-called speed density (D-Jetronic) system for determining the amount is adopted, and the fuel injection amount actually injected from the injection nozzle 15a of the SPI injector 15 is based on the engine speed and the intake pipe pressure. The basic fuel injection amount set according to various correction terms set based on the cooling water temperature detected by the water temperature sensor 10 and the air-fuel ratio feedback correction coefficient set based on the air-fuel ratio detected by the O2 sensor 9 It is corrected and determined by.

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 intake air amount 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, so most of the intake air is supplied to each cylinder through the assist air passage 12. Since the negative pressure in the downstream of the throttle valve 5a is increased, the intake air passing through the assist air passage 12 is bored in the cover 16 attached to the tip of the SPI injector 15 so as to be in the vicinity of the injection nozzle 15a. A high-speed airflow is ejected from the opening ejection port 12a, and the ejection nozzle 15a is ejected.
Is supplied as assist air to the fuel injected from. As a result, the fuel injected from the injection nozzle 15a is atomized by the assist air and the cover 1
It is sprayed into the surge tank 3 through the spray hole 16a opening at 6.

The atomization of the fuel is carried out in order to promote the vaporization and atomization of the fuel, and is most necessary in the operating state where the vaporization rate and atomization rate of the fuel are low, for example, during warm-up operation after starting.
In the present embodiment, since most of the intake air amount is used as assist air when the throttle valve is closed, it is possible to atomize the fuel efficiently during warm-up operation after starting, and to improve combustion efficiency. Is improved and exhaust emission can be reduced. Further, since the intake air amount supplied to each cylinder at the time of idling is controlled by the ISC valve 13 provided in the assist air passage 12, it is necessary for the idle rotation even when the assist air is supplied. Stable idle rotation can be obtained without the amount of intake air exceeding the intake air amount being supplied to each cylinder.

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, but the intake air passing through the throttle valve 5a is reduced. The amount gradually increases, and the injection nozzle 15a of the SPI injector 15 is
Since the fuel injected from is moved along the air flow flowing in the direction of the intake manifold 2, during that time, the fuel is atomized and atomized fuel is supplied to each cylinder. As a result, the transient response performance during acceleration or the like is improved.

In the present embodiment, the intake air amount is obtained by the so-called speed density (D-Jetronic) method. It goes without saying that the present invention can be applied to an engine that employs a so-called mass flow (L-Jetronic) method that directly calculates.

[0021]

As described above, according to the present invention,
The injection nozzle of the injector for single-point injection is arranged downstream of the throttle valve, and the injection outlet of the assist air passage for supplying the assist air is opened in the vicinity of this injection nozzle. Bypass, connect to the inlet opening to the upstream side, and further, since the idle speed control valve that adjusts the intake air amount at idling is installed in the assist air passage, most of the intake air at idling is installed. Can be used as assist air, and atomization of fuel injected from the injection nozzle can be efficiently performed.
Further, at the time of idling, the intake air amount used as assist air is adjusted by the valve opening degree of the idle speed control valve. Therefore, even when assist air is being supplied, the intake air supplied to each cylinder is adjusted. Stable idle rotation can be obtained without increasing the amount of air.

Further, the injector for single-point injection is arranged in a surge tank connected to the collecting portion of the intake manifold, and its injection nozzle is directed toward the collecting portion of the intake manifold, so that it is injected from the injection nozzle. It is possible to move the fuel along the flow of the intake air, and during that time, the fuel is atomized and it is possible to supply the atomized fuel to each cylinder. Responsiveness is 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 5a Throttle valve 12 Assist air passage 12a Jet outlet 12b Inlet 13 Idle speed control valve 15 Single point injection injector 15a Injection nozzle

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 an inlet of an assist air passage is opened upstream of the throttle valve, and the injection of the assist air passage is performed. The engine is characterized in that the outlet is opened near the injection nozzle by bypassing the throttle valve, and an idle speed control valve for adjusting the intake air amount during idling is provided in the assist air passage. Fuel injection device. 2. The single-point injection injector is arranged in a surge tank connected to a collecting portion of the intake manifold, and its injection nozzle is directed toward the collecting portion of the intake manifold. Item 2. The engine fuel injection device according to item 1.