JPS6198920A - Suction device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To reduce uncombusted HC by installing a fuel injector so that the axis of fuel injection is directed toward the top wall part of the suction port near the center of combustion chamber, thereby expanding the fuel to a wider extent in the combustion chamber and suppressing eccentric existence of quench layers. CONSTITUTION:Each cylinder of an internal-combustion engine is equipped with two suction valves 11A, 11B and suction ports 12A, 12B associate therewith, and two exhaust valves 13A, 13B and exhaust ports 14A, 14B associate therewith. One of the suction ports 12A is furnished with an opening/closing valve 15, while the outer 12B with a fuel injector 16. The fuel injector 16 shall by so arranged that the axis of fuel injection is directed toward the top wall part of the suction port 12B near the center of combustion chamber 19. Here a major part of the fuel shall flow into the combustion chamber 19 from the periphery of the suction port 12B, i.e. from the side nearer the combustion chamber 19. This will allow the fuel to disperse to a wider extent in the combustion chamber 19.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a technology for improving the intake system of an internal combustion engine having two intake valves for each cylinder.

<Prior Art> An example of an intake system for this type of internal combustion engine is the one shown in Fig. 4 (Japanese Patent Application No. 58-225356).
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That is, one of the two intake valves 2A and 2B interposed with the two intake valves IA and IB of each cylinder, for example, the intake valve 2A, is provided with a butterfly type on-off valve 3, and the on-off valve 3 is operated at low engine speed. By closing the intake port 1-2B at the same time, the intake air flowing from only the other intake port 1-2B along the 4th peripheral wall of the combustion chamber is used to generate a large swirl in the combustion chamber, improving combustion performance at low speeds, and improving combustion performance at high speeds. At this time, the on-off valve 3 is opened to open the two intake ports 1-2A and 2B to reduce intake resistance, increase intake air filling efficiency, and improve output.

Further, since the on-off valve 3 is opened less frequently in the normal operating range, the fuel injector 5 is provided on the side of the intake valve 2A, which is always open, in order to obtain stable air-fuel ratio control responsiveness.

Note that two exhaust valves 6A, 6B and two exhaust ports 7A, 7B are also provided, and the ignition plug 8 is provided near the center of the combustion chamber 4.

<Problems to be Solved by the Invention> Incidentally, in such an intake system, the intake boat 2B is curved in an arc shape from the part where the fuel injector 5 is installed toward the intake valve IB, as shown in FIG. Since the fuel injection center axis of the injector 5 is set toward the inner circumferential side of the curved part of the intake boat IB,
This causes problems as described below.

That is, when the intake air flows through the curved part of the intake bow (IB), the intake pressure becomes large on the outer circumference side of the curved part and small on the inner circumference side due to centrifugal force. -2
The air flows through the center part of B from the inner circumferential side to the outer circumferential side, and the intake boat 2B
A secondary flow is formed along the wall from the outer circumferential side back to the inner circumferential side.

Therefore, the fuel injected from the fuel injector 5 and attached to the wall of the intake boat 2B forms a wall flow and moves slowly along with the intake air flow, but the area near the wall of the intake boat 2B dominates the secondary flow of intake air as described above. As a result, this secondary flow causes the intake bow) to
The fuel adhering to the top wall (top wall side) is also focused on the inner circumferential side. The fuel concentrated on the inner circumferential side in this way merges with the fuel directly attached to the inner circumferential side, and most of the fuel flows into the intake bow 1-2B.
HC flows into the combustion chamber 4 from the inner peripheral side of the combustion chamber 4, and the fuel is unevenly distributed at the end of the combustion chamber 4, forming a thick quench layer and being discharged unburned (hereinafter referred to as unburned HC). There was a problem of increasing

In particular, in the medium speed range of the engine where the on-off valve 3 switches from closed to open, the flow velocity of the intake valve 2B decreases, so the intake valve 2B
Since the fuel is not vaporized well in the combustion chamber 4 and approximately the same amount of air flows in parallel from the two intake valves 2A and 2B into the combustion chamber 4, swirl is not generated. The uneven distribution of HC is promoted, and the amount of unburned HC increases significantly.

In the case of an internal combustion engine with an exhaust turbo supercharger, the increase in non-fiHc becomes even more significant because the air-fuel ratio must be enriched in order to lower the exhaust gas temperature due to the heat resistance of the turbine rotor.

Furthermore, as a result of the formation of a thick quench layer, the adverse effect of a reduction in output due to uneven air-fuel mixture concentration distribution within the combustion chamber 4 cannot be ignored.

The present invention was made in view of the above-mentioned circumstances, and by changing the injection direction of the fuel injector, uneven distribution of the quench layer can be suppressed and unburned HC can be effectively reduced.
It is an object of the present invention to provide an intake system for an internal combustion engine that can prevent a decrease in output.

Means for Solving the Problems> For this reason, the present invention has a configuration in which the fuel injector is arranged with its fuel injection center axis directed toward the top wall portion of the intake boat near the center of the combustion chamber.

In this way, fuel is mainly supplied from the side of the intake boat near the center of the combustion chamber and diffused into the combustion chamber,
Uneven distribution of the thick quench layer is suppressed, unQgHC is reduced, and output decrease is also prevented.

<Example> Hereinafter, an example in which the present invention is applied to an internal combustion engine with an exhaust turbo supercharger will be described based on FIGS. 1 to 3.

A first engine is installed in each cylinder of an internal combustion engine equipped with an exhaust turbo supercharger (not shown). The second intake valve 11A, IIB, and the first intake valve 11A, IIB with these intake valves interposed therebetween. the second intake boats 12A, 12B and the first
．． The second exhaust valves 13A, 13B and the first exhaust valve with these valves interposed therein. Second exhaust boats 14A and 14B are provided, and the first intake valve 12A has an on-off valve 15, and the second intake boat 1
A fuel injector 16 is attached to each of the fuel injectors 2B.

The opening/closing valve 15 has its support shaft 15a connected to the output rod 18a of the diaphragm actuator 18 via a link mechanism.
When the supercharging pressure introduced into the pressure working chamber 18b of the actuator 18 exceeds the pressure near the intercept point where the engine rotational speed rapidly increases, the return spring 18
The output rod 18a extends against the biasing force c, thereby switching the on-off valve 15 from closed to open.

Here, as a configuration according to the present invention, the fuel injector 16 is arranged so that its fuel injection center axis faces the top wall portion of the intake boat 128 near the center of the combustion chamber 19. 20 is a spark plug.

In addition, intake valves 11Δ, 11B and exhaust valves 13A, 13
The operating characteristics of B are as shown in FIG.
The action of A increases the actual compression ratio and improves the intake air filling efficiency, and in the high speed range where the on-off valve 15 opens, supercharging is performed using inertia by the action of the intake valve 11B, which has a large delay in closing timing.
The aim is to improve output while suppressing knocking.

Next, the operation related to the configuration of the present invention will be explained.

The wall flow of fuel injected from the fuel injector 16 whose fuel injection axis direction is set as described above and adhering to the intake valve 12B is caused by the effect of the secondary flow on the intake valve 1.
2BAlthough there is a tendency toward the inner circumference of the curved part, most of the fuel is directed toward the outer circumference of the intake valve 1 because the injection center axis is directed toward the outer circumference.
It flows into the combustion chamber 19 from the outer peripheral side of 2B, that is, from the side closer to the center of the combustion chamber 19. Therefore, after the fuel flows into the combustion chamber 19, it is diffused over a wide range from the center of the combustion chamber 10 to the periphery, so the quench layer is spread thinly and vaporization is promoted, resulting in a significant reduction in the amount of unburned HC discharged. .

Further, the intensity of the air-fuel mixture formed in the combustion chamber 19 is also made uniform, resulting in good combustibility, and a decrease in output can be suppressed.

<Effects of the Invention> As explained above, according to the present invention, since most of the injected fuel flows into the combustion chamber from a portion close to the center of the combustion chamber,
Since it is diffused over a wide area in the combustion chamber and the quench layer is spread thin, the amount of unq4Hc emitted can be significantly reduced, the air-fuel mixture concentration distribution will be uniform, and a decrease in output can be prevented.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the vicinity of the combustion chamber of an intake system for an internal combustion engine according to an embodiment of the present invention, Fig. 2 is a sectional view taken along the line II in Fig. 1, and Fig. 3 is an embodiment of the same. FIG. 4 is a cross-sectional view showing the vicinity of the combustion chamber of the earlier application by the present applicant; FIG. 5 is a cross-sectional view taken along the line nn in FIG. Figure 6 is a perspective view for explaining the reason why the secondary flow occurs, and Figure 0 is a sectional view taken along the line mm in Figure (5). 11A...First intake valve 11B...Second intake valve 12A...First intake port) 12B...Second intake valve 15...Opening/closing valve 16...Fuel injector 19 ...combustion chamber

Claims (1)

[Claims] Each cylinder is equipped with two intake valves and two intake ports with these intake valves interposed therein, and one intake port of each cylinder is equipped with an on-off valve that opens and closes according to engine operating conditions, and the other An intake system for an internal combustion engine comprising a fuel injector that supplies fuel to an intake port, characterized in that the fuel injector is disposed with its fuel injection center axis facing a top wall portion of the intake port near the center of the combustion chamber. intake system for internal combustion engines.