JPH02185666A - Suction device of four-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To improve atomization of fuel, enhance ignitability in particular during low speed operation, and prevent fuel concentration to a particular suction valve by furnishing a communication chamber for suction paths of three suction valves, and locating the central suction valve between an ignition plug and one fuel injection valve. CONSTITUTION:At the time of low-load and low speed operation, a control valve 44 is shut to introduce the suction gas from No.1 suction path 40a to a communication chamber 46, and the fuel injected thereinto intermittently has expansiveness to a certain degree and is diffused without colliding with the inner walls of the relatively wide communication chamber 46 for a long distance. This decreases fuel attached to the inner walls and promotes atomization of the fuel. Because this fuel is injected toward the central suction valve 20b, a rich mixture gas flows into a combustion chamber 16 from this central suction valve 20b. Supplying rich mixture gas to an ignition plug generates a combustion condition near stratified combustion, which improves ignitability and stabilizes combusting performance. During high-load and high speed operation, the control valve 44 is opened, and the suction gas comes into the communication chamber 46 from the No.1, No.2 suction paths 40a, 40b.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has three intake valves adjacent to each other for one cylinder, and fuel is injected from one fuel injection valve into the intake passage. This invention relates to an intake system for a four-stroke internal combustion engine.

BACKGROUND OF THE INVENTION There are four-stroke internal combustion engines that have three adjacent intake valves for one cylinder. In this type of engine, when one fuel injection valve is used for one cylinder and this injection valve injects fuel into the intake passage, the mounting position of the injection valve has a great effect on combustion. That is, if fuel is injected far from the intake valve, the fuel will adhere to the inner wall of the intake passage and form a wall flow, resulting in poor atomization of the fuel. Therefore, especially at low speeds when the amount of fuel injected is small, the ignition performance of the ignition plug deteriorates. Additionally, if fuel is injected too close to the intake valve, the fuel will be concentrated and supplied only to a specific intake valve, resulting in a situation where favorable combustion will not be achieved in response to changes in operating conditions such as rotational speed. There are problems that can arise.

(Object of the Invention) The present invention was made in view of the above circumstances, and is a four-stroke internal combustion engine having three adjacent intake valves.
When fuel is supplied to the intake passage using two fuel injection valves, the atomization of the fuel is good, the ignition performance is good especially at low speeds, and the fuel is prevented from concentrating only on a specific intake valve. It is an object of the present invention to provide an intake device for a four-stroke internal combustion engine that can improve combustion.

(Structure of the Invention) According to the present invention, this object is achieved in a four-stroke internal combustion engine that has three intake valves and a plurality of exhaust valves that are opened and closed by an overhead camshaft that crosses above the combustion chamber. an ignition plug with an ignition part facing the ignition plug; a communication chamber in which the intake passages communicating with each intake valve communicate with each other near the intake valve; and the communication chamber substantially along a plane perpendicular to the camshaft and including the cylinder centerline. A four-stroke internal combustion engine, comprising one fuel injection valve that injects fuel into a room, and a central intake valve among the intake valves is located between the spark plug and the fuel injection valve. This is achieved by an intake device.

(Operation) Fuel injected from the fuel injection valve is injected along the center line of the combustion injection valve, substantially along a plane that is perpendicular to the camshaft and includes the cylinder center line. The injected fuel moves toward the central intake valve within the communication chamber that communicates the intake passages near each intake valve, and during this time, the fuel diffuses into the air within the communication chamber.

Therefore, fuel is inhaled with almost no adhesion to the wall surface of the intake passage. Furthermore, at low speeds with a small amount of intake air, the intake flow rate is also slow, and a large amount of the fuel injected from the fuel injection valve is sucked into the central intake valve due to the influence of gravity. Since the ignition plug is located on the opposite side of the injection valve across the central intake valve, the rich air-fuel mixture entering from the central intake valve is guided to the ignition plug, improving combustion. Furthermore, during high-speed operation when the amount of intake air is large, the turbulent flow of intake air in the communication chamber causes the fuel to be widely diffused, and is no longer concentratedly supplied only to a specific intake valve.

(Embodiment) FIG. 1 is a partially sectional plan view of a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II--II, and FIG. 3 is a torque characteristic diagram. In Fig. 1.2, reference numeral 10 indicates a cylinder body, l2. 1 is a cylinder head, 14 is a piston, and a combustion chamber 16 is formed by these. The cylinder head 12 has two exhaust valves 18 (18a,
18b) and three mutually adjacent intake valves 20 (20
a, 20b, 20c) are provided. These wastes and
The intake valves 18.20 each have an overhead camshaft 22.24,
It is opened and closed by a known swing arm double overhead camshaft valve mechanism comprising swing arms 26 and 28. 30 is a cylinder head cover 32 which is an exhaust passage communicating with the exhaust valve 18, and in FIG.

36 is a surge tank, and 38 is an intake pipe that connects the surge tank 36 and the cylinder head 12 for each cylinder. Inside the intake pipe 38, there are a first intake passage 40a and a second intake passage 4.
0b is formed.

The first intake passage 40a and the second intake passage 40b have approximately the same diameter, and a valve shaft 42 passes through these passages 40a and 40b.
includes a butterfly-shaped control valve 44 that opens and closes the second intake passage 40b.
is installed. This control valve 44 is controlled to open and close in response to operating conditions, such as increases and decreases in operating load and engine speed.

The downstream side of the intake passage 40 is connected to a communication chamber 46 provided in the cylinder head 12, and this communication chamber 46 is connected to the three intake valves 2.
0 and communicates with these.

48 is an electromagnetic fuel injection valve. This injection valve 48 is the second
As shown in the figure, the distribution pipe 5 disposed at the upper part of the intake pipe 38
0 and the upper part of the communication chamber 46 of the cylinder head 12. As shown in FIG. 2, the injection port of the injection valve 48 is oriented to inject fuel substantially along a plane Z that is perpendicular to the camshafts 22 and 24 and includes the cylinder centerline α. Note that the central intake valve 20b is located between the injection valve 48 and the spark plug 34. Further, in this embodiment, the fuel injection ports of the injection valve 48 are connected to the two intake valves 20a on both sides,
A straight line X connecting the centers of the side end surfaces of the umbrella part of 20c and this straight line
and a straight line y that is parallel to and includes the center of the umbrella side end surface of the central intake valve 20b.

The injection valve 48 opens at a predetermined timing in response to an electric signal output by a controller (not shown), and intermittently injects fuel in the distribution pipe 50 pressurized to a predetermined pressure into the communication chamber 46. .

The operation of this first embodiment is as follows. During low load/low speed operation, the control valve 44 is closed and intake air is guided from the first intake passage 40a to the communication chamber 46. The fuel injected intermittently into the communication chamber 46 not only has a certain degree of spread, but also spreads over a long distance within the communication chamber 46, which is relatively wide, without hitting the inner wall. This reduces the amount of fuel adhering to the inner wall and promotes atomization of the fuel. Since this fuel is injected toward the central intake valve 20b, a rich air-fuel mixture flows into the combustion chamber 16 from the central intake valve 20b.
Since this rich air-fuel mixture is guided to the spark plug, a combustion state similar to stratified combustion is obtained, which improves ignition performance and stabilizes combustion.

During high-load/high-speed operation, the control valve 44 opens and the intake air flows into the first
, enters the communication chamber 46 from the second intake passages 40a, 40b.

In this embodiment, the intake passage 40 is connected to the central intake valve 2O.
Since the curvature becomes smaller near b and becomes larger near the intake valves 20a and 20c on both sides (Fig. 2), especially at high speeds, fuel is well guided to the outer intake valves 20a and 20c, resulting in premixed combustion. This results in a nearly homogeneous air-fuel mixture, which provides good fuel consumption.

In FIG. 3, the solid line A represents the torque characteristic when the control valve 44 is kept open, and shows that the torque decreases significantly due to the decrease in the intake inertia effect at medium and low speeds. The dashed line B in the figure is the torque characteristic when the control valve 44 is closed. These two characteristics A and B can be adjusted by opening and closing the control valve 44 in the medium speed range.
By combining these, it is possible to improve the torque characteristics.

FIG. 4 is a partially sectional plan view of the second embodiment. This embodiment is similar to the first intake passage 40a in the first embodiment.
is formed to have a smaller diameter than the second intake passage 40b.

According to this embodiment, the injection port of the injection valve 48 is offset toward the second intake passage 40b from the wall between the first and second intake passages 40a and 4°5. As a result, the control valve 44
When the second intake passage 40b opens, the intake air flowing into the communication chamber 46 from the second intake passage 40b hits the fuel injected from the injection valve 48 more effectively than in the first embodiment, and the atomization of the fuel is further promoted. Furthermore, since the second intake passage 40b has a small diameter, it is possible to increase the torque due to intake inertia from a lower speed than in the first embodiment. Furthermore, since the offset position of the first intake passage 40a with respect to the communication chamber 46 is larger than that in the first embodiment,
At low speeds when the control valve 44 is closed, the vortex generated in the communication chamber 46 becomes even stronger, and when the intake valve 20 is opened, this vortex generates an even stronger swirl (intake vortex) in the combustion chamber 16. Therefore, combustion at low speeds is stabilized, and the effect of smoothing low speed operation becomes even more pronounced.

FIG. 5 is a partially sectional plan view of the third embodiment, in which the first intake passage 40a is arranged in the center, while the second
The intake passage 40b is divided into two parts, each with a control valve 44.
．． 44.

According to this embodiment, the intake air passing through the first intake passage when the control valve 44 is closed at low load and low speed hits the fuel injected from the injection valve 48 well, and the atomization is particularly good at low load and low speed. 1. This is further improved compared to the second embodiment.

FIG. 6 is a partially sectional plan view of the fourth embodiment, which includes first, second, third intake passages 40a, 40b, 4
Control valves 44a and 44b having different opening and closing timings are disposed in second and third intake passages 40b and 40c sandwiching the first intake passage 40a.

According to this embodiment, as in the third embodiment (FIG. 5), not only the dewing at low speeds is promoted, but also the torque characteristics can be improved at the same time. That is, FIG. 7 is a torque characteristic diagram of this fourth embodiment, and the solid line A in this diagram indicates the control valves 44a, 44.
Characteristics when b is kept open, broken line B shows control valve 4 in the low speed range.
The characteristic when both control valves 4a and 44b are closed, and the chain line C is the characteristic when only the control valve 44b is opened in the medium speed range.

By opening and closing the control valves 44a and 44b at different operating speeds and combining these characteristics A, B, and C, it is possible to improve the torque in the medium speed range compared to the first to third embodiments.

FIG. 8 is a partially sectional plan view of the fifth embodiment, and this embodiment shows the first intake passage 4 in the fourth embodiment (FIG. 6).
0a and the second intake passage 40b are interchanged in position.

According to this embodiment, as in the fourth embodiment (FIG. 6), not only the torque in the medium speed range can be increased, but also the torque in the second
As in the embodiment (FIG. 4), the swirl is strengthened in the low speed range, so rotation during low speed operation becomes even smoother.

Note that in the second to fifth embodiments as well, the fuel injection valve 48 is
As in the embodiment, fuel is injected approximately along a plane perpendicular to the camshaft and including the cylinder centerline. Further, this injection direction is between the straight line X and the straight line y and is directed toward the central intake valve 20b.

In addition, in FIG. 4.5.6.8, the same parts as in FIG. 1 are given the same reference numerals, so the description thereof will not be repeated.

(Effects of the Invention) As described above, the present invention provides a communication chamber that communicates each intake passage with each other near each intake valve, and connects a fuel injection valve that injects fuel into this communication chamber so that the fuel injection valve is perpendicular to the camshaft and connected to the cylinder. Arranged so that fuel is injected approximately along a plane including the center line,
Since the central intake valve is located between this fuel injection valve and the ignition part of the spark plug facing the center of the combustion chamber, the injected fuel flows inside the communication chamber toward the central intake valve. During this time, the fuel diffuses into the air within the communication chamber. Therefore, the fuel hardly adheres to the wall surface of the intake passage, and atomization is improved. Furthermore, at low speeds with a small amount of intake air, the intake flow rate is also slow, and a large amount of the fuel injected from the fuel injection valve is sucked into the central intake valve due to the influence of gravity. For this reason, a rich air-fuel mixture is guided to the ignition part of the spark plug, resulting in good ignitability and good combustion.

4. Also, during high-speed operation where the amount of intake air is large, the turbulent flow of intake air in the communication chamber causes the fuel to be widely diffused and is no longer concentratedly supplied to a specific intake valve. Therefore, the distribution of fuel to each intake valve is improved, and combustion is stabilized.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional plan view of a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II--II, and FIG. 3 is a torque characteristic diagram. 4.5.6.8 is a partially sectional plan view of another embodiment, and FIG. 7 is a torque characteristic diagram of the embodiment of FIG. 6. 16... Combustion chamber, 20a, 20b, 20cm intake valve, 22.24... Camshaft, 40... Intake passage, 46
...Communication chamber, 48...Fuel injection valve, α...
・Cylinder center line, x, y...straight line, 2...plane. Patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Claims] 3 that is opened and closed by an overhead camshaft that crosses above the combustion chamber.
In a four-stroke internal combustion engine having a plurality of intake valves and a plurality of exhaust valves, an ignition plug with an ignition part facing the vicinity of the center of the combustion chamber, and an intake passage communicating with each of the intake valves are connected to each other near the intake valves. 1 for injecting fuel into the communication chamber substantially along a plane perpendicular to the camshaft and including the cylinder centerline;
An intake system for a four-stroke internal combustion engine, characterized in that a central intake valve among the intake valves is located between the ignition plug and the fuel injection valve.