JPH02161125A - Intake device for four-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To unify intake quantities flowing through intake valves and improve the output by providing three intake valves for each cylinder, providing a communicating chamber communicating intake passages connected to intake valves, and forming intake passages on both sides in a nearly linear shape. CONSTITUTION:Two exhaust valves 18 and three intake valves 20 (20a-20c) are arranged on a cylinder head 12 for each cylinder, they are opened or closed by two overhead cam shaft type valves system mechanisms, the first and second intake passages 40a and 40b are formed in an intake pipe 38 for each cylinder, the downstream side is connected to a communicating chamber 46 provided on the cylinder head 12, and the communicating chamber 46 is communicated to intake valves 20 via intake passages 47 (47a-47c). Three intake valves 20 and intake passages 47 are arranged perpendicularly to the cylinder train direction, and the intake passages 47a and 47c on both sides are formed in a nearly linear shape from the communicating chamber 46 to the intake valves 20a and 20c so th the cross section area are made nearly constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-cylinder engine having three intake valves for one cylinder.
This invention relates to an intake system for a cycle 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, an intake passage communicating with each intake valve may be communicated with a communication chamber, and intake air may be guided from the communication chamber to each intake valve. In this case, it is desirable that the intake air entering the communication chamber be appropriately distributed and guided to each intake valve depending on the operating state. For example, during high-speed operation, it is necessary that intake air be introduced to each intake valve to increase the amount of intake air.

(Object of the invention) The present invention was made in view of the above circumstances, and
This is a 4-cycle internal combustion engine with two intake valves, and when the intake air is guided from the communication chamber to each intake valve, the intake air flows smoothly into each intake valve, and especially during high-speed operation, each intake valve l
An object of the present invention is to provide an intake system for a four-stroke internal combustion engine that can increase the total intake flow rate by making the intake flow rate uniform.

(Structure of the Invention) According to the present invention, this object is achieved in a four-stroke internal combustion engine having three intake valves that are opened and closed by an overhead camshaft that crosses above the combustion chamber. The passages communicate with each other to a communication chamber, and each of the intake valves and the intake passage are disposed substantially symmetrically with respect to a plane that is orthogonal to the camshaft and includes the cylinder center line, and the intake valves on both sides are connected from the communication chamber to the intake valves on both sides. This is achieved by an intake system for a four-stroke internal combustion engine, which is characterized in that the intake passage leading to the engine is formed in a substantially straight shape.

If the intake passages from the communication chamber to the intake valves on both sides have a substantially constant cross-sectional area, the intake air will more easily flow into the intake passages on both sides. If the radius of curvature of the intake passage leading to the valve is made larger than the radius of curvature of the intake passage leading to the central intake valve, intake air will more easily flow into the intake passages on both sides using the flow velocity of intake air. The uniformity of the intake air flow rate guided to the valve can be further promoted.

(Operation) Intake air flowing into the communication chamber along a plane perpendicular to the camshaft and including the cylinder centerline is distributed to the intake passages of the three intake valves in the communication chamber. A large amount of this intake air tends to flow into the intake passage communicating with the central intake valve located on this plane. However, since the intake passages on both sides connect the communication chamber and the intake valve in a substantially straight line, intake air easily flows into the intake passages on both sides. Therefore, especially during high-speed operation where the intake air flow rate increases, intake air flows well into the intake passages on both sides.

Furthermore, if the cross-sectional areas of the intake passages on both sides are made substantially constant, the intake air flows into the intake passages even more smoothly. Furthermore, by making the radius of curvature of the intake passage leading to the intake valves on both sides as viewed from the camshaft direction larger than the radius of curvature of the intake passage leading to the central intake valve, the speed of the intake air is utilized to It is possible to make it easier for intake air to flow into the intake passage of
It is possible to further increase the amount of intake air flowing into this outer intake passage.

(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 is a cylinder body, 12 is a cylinder head, and 14 is a piston, and a combustion chamber 16 is formed by these. cylinder head I
2 has two exhaust valves 18 (18a, 1
8b) and three mutually adjacent intake valves 20 (20a
, 20b, 20c) are provided. These hangings/
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 is an exhaust passage communicating with the exhaust valve 18, and 34 in FIG. 1 is an ignition plug.

The ignition part of the ignition plug 34 faces near the center of the combustion chamber 16.

36 is a surge tank, and 38 is an intake pipe that connects the surge tank 36 and the cylinder rad 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 the valve shaft 4 passes through these passages 40a and 40b.
2 includes a butterfly-shaped control valve 4 that opens and closes the second intake passage 40b.
4 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 2, and this communication chamber 46 communicates with three intake valves 20 through intake passages 47a, 47b, and 47c, respectively. The three intake valves 20a described above
, b, and c are arranged symmetrically with respect to a plane Z (Fig. 1) that is perpendicular to the camshaft 22, 24 and includes the cylinder center line α (Fig. 2), and the intake passages 47a, 47c on both sides are It has a substantially linear shape from the communication chamber to the intake valves 20a, 20c, and its cross-sectional area is substantially constant. Furthermore, when these intake passages 47 are viewed from the direction of the camshafts 22 and 24 as shown in FIG. 2, the radius of curvature of the intake passages 47a and 47c on both sides is set to be larger than the radius of curvature of the central intake passage 47b. There is.

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. The injection port of the injection valve 48 is oriented to inject fuel substantially along a plane Z that is perpendicular to the camshaft 22.24 and includes the cylinder centerline α, as shown in FIG. 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
．． It enters the communication chamber 46 from the second intake passages 40a, 40b.

At this time, the intake passage 47 branches almost linearly from the communication chamber 46 to each intake valve 20, so that the intake air flows through each intake passage 47.
is distributed and flows smoothly. Here are the intake passages 47 on both sides.
a, 47c have a nearly constant cross-sectional area, and their radius of curvature is larger than that of the central intake passage 47b. 47b. Therefore, the intake air flows well into the intake passages 47a and 47c on both sides, making it possible to ensure a sufficient intake flow rate.

In this embodiment, since the central intake passage 47b has a larger curvature than the intake passages 47a and 47c on both sides (FIG. 2), especially at high speeds, both the intake air and the fuel flow through the outer intake valves 20.
The fuel is well guided to the fuels a and c, resulting in a homogeneous air-fuel mixture close to premixed combustion, which provides good fuel.

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 40b. As a result, the control valve 44
When the second intake passage 40b is opened, the intake air flowing into the communication chamber 46 from the second intake passage 40b hits the fuel injected from the injection valve 48 even more than in the first embodiment, and the atomization of the fuel is further promoted. 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, the offset position of the first intake passage 40a with respect to the communication chamber 46 is different from that in the first embodiment. Because it is larger compared to
At low speeds when the control valve 44 is closed, the vortex generated in the communication chamber 46 is even stronger, and when the intake valve 20 is open, this vortex generates an even stronger swirl (intake vortex) in the combustion chamber 16. This stabilizes combustion at low speeds, making the effect of smoother low-speed operation 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 shows the first, second, and third intake passages 4°a, 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, like the third embodiment (FIG. 5), not only atomization at low speeds is promoted, but also 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 and 44b.
The broken line B shows the characteristics when the control valve 44 is kept open in the low speed range.
The characteristic when both control valves a 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.

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

(Effects of the Invention) As described above, the present invention provides three intake valves and intake passages.
It is arranged almost symmetrically with respect to a plane that is perpendicular to the camshaft and includes the cylinder center line, and the intake passages on both sides are formed in an almost linear shape from the communication chamber that communicates each intake passage with each other. The air is smoothly distributed into three intake passages, allowing the intake air to be smoothly guided to each intake valve. Therefore, especially at high speeds, the amount of intake air flowing into the three intake valves can be equalized, increasing the overall amount of intake air and improving engine performance.

Further, by making the cross-sectional areas of the intake passages on both sides substantially constant, the flow of intake air into the intake passages on both sides becomes even smoother. Furthermore, by making the radius of curvature of the intake passages on both sides larger than the radius of curvature of the central intake passage, the inflow resistance of the outer intake passages becomes smaller, and the distribution of intake air to the intake passages on both sides becomes smoother.

[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-TI, 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, 20c -... Intake valve, 22.24
...Camshaft, 46...Communication chamber, 47...Intake passage, a...Cylinder center line, Z...Plane. Patent applicant Yamaha Motor Co., Ltd.

Claims (3)

[Claims] (1) In a four-stroke internal combustion engine having three intake valves that are opened and closed by an overhead camshaft that crosses above the combustion chamber, each intake passage connected to each intake valve is connected to a communication chamber, and each intake passage is connected to a communication chamber. The valves and the intake passages are arranged substantially symmetrically with respect to a plane that is perpendicular to the camshaft and includes the cylinder center line, so that the intake passages from the communication chamber to the intake valves on both sides are formed in a substantially linear shape. Intake system for a 4-stroke internal combustion engine. (2) The intake system for a four-stroke internal combustion engine according to claim 1, wherein the intake passages from the communication chamber to the intake valves on both sides have a substantially constant cross-sectional area. (3) The radius of curvature of the intake passage leading to the intake valves on both sides as viewed from the camshaft direction is made larger than the radius of curvature of the intake passage leading to the central intake valve. An intake system for a four-stroke internal combustion engine according to item 2.