JPH0433969B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a four-stroke internal combustion engine having three intake valves for one cylinder.

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, it is conceivable that the intake passages communicating with each intake valve are communicated with each other through a communication chamber, and intake air is 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 according to the operating conditions. 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.

However, since the intake air tends to flow along the inner wall surface of the communication chamber, the intake air flowing into the communication chamber tends to flow to the intake passages on both sides of the three intake passages, and is difficult to enter the central intake passage. As a result, the flow rate of intake air flowing into the three intake passages becomes non-uniform, causing a problem in that the total amount of intake air flowing through the three intake passages is limited, particularly during high-speed operation.

(Object of the Invention) The present invention has been made in view of the above circumstances, and is a four-cycle internal combustion engine having three intake valves. The purpose of the present invention is to provide an intake system for a four-stroke internal combustion engine that allows intake air to smoothly flow into the engine, and that can increase the total intake flow rate by equalizing the intake flow rate to each intake valve, especially during high-speed operation. It is something to do.

(Structure of the Invention) According to the present invention, the object is to provide each cylinder with three intake valves and a plurality of exhaust valves driven by a camshaft, and to connect these intake and exhaust valves to the camshaft through the vicinity of the center of the combustion chamber. The central intake valve is located on the outer side of the cylinder with respect to the straight line than the intake valves on both sides, and the three intake passages opened and closed by each intake valve are connected to the combustion chamber. In a four-stroke internal combustion engine, which is provided in the cylinder head almost symmetrically with respect to a plane passing near the center of the chamber and orthogonal to the camshaft, the three intake passages are communicated with a communication chamber provided on the side of the cylinder head, and The intake passages from the communication chamber to the intake valves on both sides are formed so as to smoothly expand from the communication chamber toward the intake valves, while the three intake passages are formed to pass through the center of the combustion chamber and approximately to the camshaft. It is formed so that it extends almost linearly from each intake valve when viewed from the direction of the cylinder centerline toward a point on a perpendicular plane, and has a substantially constant width when viewed from the direction of the cylinder centerline. This is achieved by an intake system for a four-stroke internal combustion engine characterized in that the partition wall is sufficiently short and its upstream edge is set back toward the central intake valve.

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. Furthermore, if the radius of curvature of the intake passages leading to the intake valves on both sides when viewed from the camshaft direction is made larger than the radius of curvature of the intake passages leading to the central intake valve, the intake air will flow into the intake passages on both sides using the flow velocity of the intake air. It becomes easier to flow in.
Therefore, the total amount of intake air flow guided to each intake valve further increases.

(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. This intake air tends to be guided by the inner wall surface of the communication chamber and flow into the intake passages on both sides, but the partition wall that forms the central intake passage is sufficiently short and its upstream edge is sufficiently close to the central intake valve. Because of this, the air flows smoothly from the communication chamber into this central intake passage. Therefore, the amount of intake air between each intake passage is equalized. In particular, since the widths of each intake passage viewed from the cylinder center axis direction are substantially the same, intake air flows smoothly into each intake passage, and the total amount of intake air inflow increases.

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,
By utilizing the speed of the intake air, it is possible to make it easier for the intake air to flow into the intake passages on both sides having a large radius of curvature, and it is possible to further increase the amount of intake air flowing into the outer intake passages.

(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 2, and FIG. 3 is a torque characteristic diagram. Number 10 in Figures 1 and 2
is the cylinder body, 12 is the cylinder head, 14
is a piston, and a combustion chamber 16 is formed by these pistons. The cylinder head 12 has two exhaust valves 18, 18a, 18b per cylinder and three mutually adjacent intake valves 20, 20a, 20b, 20.
c is provided. The exhaust valve 18 is located on one side of a straight line passing near the center of the combustion chamber and parallel to camshafts 22 and 24, which will be described later, and the intake valve 20 is located on the other side of this straight line. Here, the central intake valve 20b is located on the outer side of the cylinder with respect to this straight line than the intake valves 20a, 20c on both sides. In addition, these exhaust/intake valves 18,
20 is located symmetrically with respect to a plane (plane Z to be described later) that passes through the center of the combustion chamber and is orthogonal to the camshafts 22 and 24. These exhaust/intake valves 18, 20 are connected to overhead camshafts 22, 24 and swing arm 2, respectively.
It is opened and closed by a known swing arm type double overhead camshaft type valve mechanism consisting of 6, 28, etc. 3
0 is a cylinder head cover, 32 is an exhaust passage communicating with the exhaust valve 18, and 34 in FIG. 1 is a spark 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 head 12 for each cylinder. A first intake passage 40a and a second intake passage 40b are formed within the intake pipe 38.
The first intake passage 40a and the second intake passage 40b have approximately the same diameter, and a butterfly-shaped control valve 44 that opens and closes the second intake passage 40b is attached to a valve shaft 42 that passes through these passages 40a and 40b. It is being 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 connects the three intake valves 20 with intake passages 47a and 47a, respectively.
7b and 47c. The three intake valves 20a, b, c mentioned above are connected to the camshaft 2
2, 24 and the cylinder center line α (Fig. 2)
arranged symmetrically with respect to the plane z (Fig. 1) containing
The intake passages 47a, 47c on both sides have a substantially straight shape from the communication chamber to the intake valves 20a, 20c, and have a substantially constant cross-sectional area.

That is, each intake passage 47a, 47b, 47c
is a plane Z from each intake valve 20a, 20b, 20c
It extends almost linearly toward one point on the top, and has a constant width when viewed from the direction of the cylinder center line α.
Therefore, the partition wall between these intake passages 47 will necessarily be very short, and the upstream edge of this partition wall will be sufficiently close to the central intake valve 20b. As a result, the communication chamber 46 approaches the central intake valve 20b. Further, these intake passages 47 are connected to the camshaft 22,
In the state shown in FIG. 2 when viewed from the 24 direction, the radius of curvature of the intake passages 47a, 47c on both sides is set larger than the radius of curvature of the central intake passage 47b.

48 is an electromagnetic fuel injection valve. This injection valve 4
8 is located between a distribution pipe 50 disposed above the intake pipe 38 and the upper part of the communication chamber 46 of the cylinder head 12, as shown in FIG. As shown in FIG. 2, the injection port of this injection valve 48 is
4 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 port of the injection valve 48 is connected to a straight line x connecting the centers of the umbrella side end surfaces of the two intake valves 20a and 20c on both sides, and a line parallel to this straight line
It is oriented between the straight line y that includes the center of the umbrella side end surface of 0b.

The injection valve 48 opens at a predetermined timing in response to an electric signal output from a controller (not shown), and injects the fuel in the distribution pipe 50 pressurized to a predetermined pressure into the communication chamber 48.
Inject intermittently into 6.

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 within the relatively wide communication chamber 46 for a long distance 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 1 from the central intake valve 20b.
6. 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 intake air enters the communication chamber 46 from the first and second intake passages 40a, 40b. At this time, the intake passage 47 is connected to the communication chamber 4.
6 to each intake valve 20, and each of the branched intake passages 47a to 47c has approximately the same width in FIG. 1, the intake air is distributed to each intake passage 47 and flows smoothly. . Here are the intake passages 47 on both sides.
a, 47c have a substantially constant cross-sectional area, and their radius of curvature is larger than that of the central intake passage 47b, so the flow resistance of the intake air flowing into the intake passages 47a, 47c on both sides is greater than that of the central intake passage. 47b
flow path resistance. Therefore, not only the central intake passage 47b near the communication chamber 46,
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 47b and 47c on both sides (Fig. 2), both intake air and fuel are well guided to the outer intake valves 20a and 20c, especially at high speeds. This results in a homogeneous air-fuel mixture close to premixed combustion, resulting in 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. Chain B in the figure shows the torque characteristic when the control valve 44 is closed. By opening and closing the control valve 44 in the medium speed range, these two characteristics A and B can be combined to improve the torque characteristics.

FIG. 4 is a partially sectional plan view of the second embodiment. This embodiment is based on the first embodiment in the first embodiment.
The intake passage 40a 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 connected to the first and second intake passages 40a, 40.
It is deviated toward the second intake passage 40b from the wall between b. As a result, when the control valve 44 opens under high load and high speed, 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. Atomization 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 amount of deviation of the first intake passage 40a with respect to the communication chamber 46 is larger than that in the first embodiment, the vortex generated in the communication chamber 46 becomes even stronger at low speeds when the control valve 44 is closed, and the intake air When the valve 20 is opened, an even stronger swirl (suction vortex) is generated within the combustion chamber 16 due to this vortex. 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 intake passage 40b is divided into two.
Control valves 44, 44 are provided respectively.

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. It 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 40.
a, 40b, 40c, the first intake passage 40a
The second and third intake passages 40b and 40c sandwiching the
Control valves 44a and 44b whose opening and closing timings differ from each other are provided.

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. In this figure, the solid line A indicates the characteristic when the control valves 44a, 44b are kept open, and the broken line B indicates the characteristic when the control valves 44a, 44b are kept open in the low speed range.
The chain line C shows 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 is obtained by swapping the positions of the first intake passage 40a and the second intake passage 40b in the fourth embodiment (FIG. 6). It is.

According to this embodiment, as in the fourth embodiment (Fig. 6), not only can torque be increased in the medium speed range, but also swirl can be enhanced in the low speed range as in the second embodiment (Fig. 4). This makes rotation even smoother during low-speed operation.

In addition, in FIGS. 4, 5, 6, and 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 arranges the three intake valves and the intake passage almost symmetrically with respect to a plane perpendicular to the camshaft and including the cylinder centerline, and passes through the vicinity of the center of the combustion chamber. With respect to a straight line parallel to the camshaft, the central intake valve is located outside the cylinder from the intake valves on both sides, and each intake passage extends approximately straight from each intake valve toward a point on the plane of symmetry, and Since the width is made substantially constant when viewed from the direction of the cylinder centerline, the partition walls between the intake passages are sufficiently short, and the central intake valve is sufficiently close to the communication chamber. Therefore, intake air flows well into the central intake valve, and also flows well into the intake valves on both sides. That is, the intake air is smoothly distributed to the three intake passages, and the intake air can 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.

Furthermore, if the cross-sectional areas of the intake passages on both sides are made substantially constant, the intake air can flow into the intake passages on both sides even more smoothly. 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 drawings]

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 2, and FIG. 3 is a torque characteristic diagram. 4, 5, 6, and 8 are partially sectional plan views of other embodiments, 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, α...cylinder center line,
z...plane.

Claims (1)

[Claims] 1. Each cylinder is provided with three intake valves and a plurality of exhaust valves driven by a camshaft, and these intake and exhaust valves are connected to one side of a straight line passing near the center of the combustion chamber and parallel to the camshaft. and the other side, and the central intake valve is located further outside the cylinder with respect to the straight line than the intake valves on both sides, and the three intake passages opened and closed by each intake valve pass through the center of the combustion chamber. In a four-stroke internal combustion engine that is provided in the cylinder head almost symmetrically with respect to a plane perpendicular to the camshaft, the three intake passages are communicated with a communication chamber provided on the side of the cylinder head, and from this communication chamber both intake valves are connected. The three intake passages are formed so as to smoothly expand from the communication chamber toward the intake valve, while the three intake passages are formed toward a point on a plane that passes near the center of the combustion chamber and is approximately perpendicular to the camshaft. The pipe is formed so that it extends almost linearly from each intake valve when viewed from the direction of the cylinder centerline, and has a substantially constant width when viewed from the direction of the cylinder centerline, and the partition wall between each intake passage is sufficiently short and the upstream side thereof An intake system for a four-stroke internal combustion engine, characterized in that the edge is set back toward the central intake valve. 2. The intake system for a four-stroke internal combustion engine according to claim 1, wherein the intake passage from the communication chamber to the intake valves on both sides has a substantially constant cross-sectional area. 3. Claims 1 or 2, characterized in that the radius of curvature of the intake passage leading to the intake valves on both sides as viewed from the camshaft direction is 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.