JPH0635829B2 - Internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an internal combustion engine of a type in which alcohol fuel is directly injected into a combustion chamber and ignited by a spark plug.

[Prior Art] An internal combustion engine that uses alcohol having a low cetane number and high volatility as a fuel has been studied. However, when the alcohol fuel is directly applied to a fuel injection type internal combustion engine such as a diesel engine, it has been clarified that the following problems arise due to its high volatility.

[Problems to be Solved by the Invention] Since a large amount of fuel is supplied at high load, problems such as instability of combustion due to poor ignition do not occur, but at low load, the fuel supply amount is small but volatility is low. Therefore, the fuel is quickly dispersed and diluted in the entire combustion chamber, resulting in ignition failure and stable combustion cannot be obtained.

In order to stabilize the combustion in an internal combustion engine of a type in which fuel is supplied from a carburetor, a combustion chamber having a flat side wall portion, an arc-shaped corner portion and a bottom portion is formed in a cylinder head or a piston, and this combustion chamber is formed. There has been proposed an internal combustion engine in which one spark plug is provided at a predetermined position in a corner portion of the chamber, and a fuel injection nozzle having an injection port facing the spark plug is provided in a central portion of the combustion chamber (Japanese Patent Publication No. 51-4).
2246 publication). However, in such an internal combustion engine, since the fuel consumption rate is poor and alcohol fuel is not suitable because it is a carburetor type, and even if alcohol fuel is used, fuel is injected from one injection port in a low load range to 1
Since the flame is propagated from the ignition plug at some point, the combustion is still unstable, the combustion speed is slow, and the output is small.

The present invention has been made to solve the above-mentioned problems of the prior art, and it is possible to secure stable combustion not only at high loads but also at low loads, a high combustion speed, and high output. An object is to provide an internal combustion engine having an excellent fuel consumption rate.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention is such that combustion of alcohol fuel is flame propagation combustion, unlike diffusion fuel such as light oil. It was found that the flame propagated and the propagation speed became faster, and the combustion chamber was formed in an elliptical cross section. Further, a fuel injection nozzle having an ignition plug disposed at each corner of the combustion chamber and having an injection port facing each corner at the center of the combustion chamber and an injection port having a smaller diameter and facing away from the corner. Is provided.

[Operation] The fuel injected from the large-diameter injection port of the fuel injection nozzle collects at each corner of the combustion chamber and forms a high-concentration air-fuel mixture with good ignitability near each spark plug at the corner. Further, due to the small-diameter injection port, a low-concentration gas mixture having good explosive properties is formed in the central region of the combustion chamber. Due to the ignition by the ignition plug, the flame propagates quickly and evenly from both longitudinal end portions of the combustion chamber toward the central portion.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 is a cylinder of an alcohol fuel injection type internal combustion engine according to the present invention. A piston 2 is slidably fitted in the cylinder 1, and a cylinder head 3 is attached to the top of the cylinder 1. Has been.

A combustion chamber 4 is formed in the head portion of the piston 2 so as to face the cylinder head 3 and open. This combustion chamber 4
As shown in FIG. 2, is composed of two arc-shaped corner portions 5 and two planar side wall portions 6 connecting the both corner portions 5 and a bottom portion 7, and is formed in a plane or cross-section substantially elliptical shape. There is.

Further, the spark plugs 8 and the fuel injection nozzles 9 corresponding to the corner portions 5 of the combustion chamber 4 are attached to the cylinder head 3 in the following arrangement.
That is, the spark plugs 8 are arranged in the regions of the two corners 5 of the combustion chamber 4, and the injection nozzle 9 is arranged in the center (center of gravity) of the combustion chamber 4. In particular, the injection nozzle 9 has two nozzles 11 facing each corner portion 5 and nozzles 11 ′ having a diameter smaller than this and facing away from the corner portion 5, and the large diameter nozzles 11 reach the respective corner portions 5. A large amount of alcohol fuel is injected and a small amount is injected into the central region of the combustion chamber 4. Further, alcohol fuel is pressure-fed to the injection nozzle 9 according to the load.

Reference numeral 12 is an inlet manifold that communicates with the combustion chamber 4 through an inlet port 13 formed in the cylinder head 3, and an inlet valve 14 is provided at the opening of the inlet port 13.

Since the internal combustion engine according to the present invention is configured as described above, a large amount of alcohol fuel is injected from each large-diameter injection port 11 of the injection nozzle 9 to each corner portion 5 of the combustion chamber 4, and each small-diameter injection port is also injected. A small amount of alcohol fuel is injected from 11 'into the central region of the combustion chamber 4. At the corner portion 5, the air-fuel mixture is likely to collect, and even if the swirl is formed in the combustion chamber 4 by the known swirl forming means, it becomes a dead space of the swirl. It is formed. Further, a low-concentration air-fuel mixture is formed in the central region of the combustion chamber 4. Therefore, the spark plugs 8 simultaneously generate sparks at the optimum timing, so that the air-fuel mixture is ignited reliably, and the flames propagate from the corners 5 to the center along the longitudinal direction of the combustion chamber 4 by flame propagation combustion. Propagate quickly and evenly. Therefore, even when the fuel injection amount is small and the load is low, it is possible to reliably ignite highly volatile alcohol fuel to obtain stable combustion and increase the combustion speed, thereby increasing the output and fuel consumption. The rate can be improved.

The side wall chamber 6 of the combustion section 4 in the above embodiment may be rounded. Although the combustion chamber 4 is formed on the piston 2 side, the combustion chamber 4 may be formed on the cylinder head 3 side so as to face the piston 2.

[Effects of the Invention] In summary, according to the present invention, the following excellent effects are exhibited.

(1) Since a large amount of alcohol fuel is injected from each large-diameter injection port of the fuel injection nozzle located in the center of the combustion chamber to each corner of the combustion chamber, the air-fuel mixture enters each corner where the spark plug is located. It is easy to collect, and even if a swirl is generated, it is not affected, and it is possible to form a high-concentration air-fuel mixture that is easy to ignite in the vicinity of each spark plug. It is possible to ensure stable combustion of alcohol fuel even at times.

(2) The flame rapidly and evenly propagates from the spark plugs at each corner to the center along the longitudinal direction of the combustion chamber due to the flame propagation combustion of alcohol fuel, so efficient combustion with a high combustion speed can be obtained. The output can be increased and the fuel consumption can be improved.

[Brief description of drawings]

1 is a longitudinal sectional view showing an embodiment of an internal combustion engine according to the present invention, and FIG. 2 is a plan view of the piston shown in FIG. In the figure, 1 is a cylinder, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is a corner portion, 8 is a spark plug, 9
Is a fuel injection nozzle, and 11 and 11 'are injection holes.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area F02P 15/02

Claims (1)

[Claims] 1. A combustion chamber having a substantially elliptical cross section is formed, an ignition plug is provided at each corner of the combustion chamber, and an injection port facing each corner is provided at the center of the combustion chamber. An internal combustion engine comprising a fuel injection nozzle having a small diameter and an injection port facing away from the corner portion.