JPH0230921A - Air intake device for multiple valve engine - Google Patents

Abstract

PURPOSE:To generate longitudinal swirls to improve combustibility by forming an intake port at a central portion in a more vertical direction in three intake ports provided at a single combustion chamber and also opening the intake valve at the central portion earlier. CONSTITUTION:An opening portion 6 at which the top end of an ignition plug 5 is formed at the central portion of a combustion chamber 4 formed in a cylinder block 1. Three intake ports 7a-7c and respective intake valve 8A-8C for opening and closing them are circularly arranged in half left side with centering round the opening portion 6 in the combustion chamber 4. In this case, the angle of the central portion intake port 7b inclining to the upper surface 20a of a piston 20 is formed to be close to a vertical direction more than that of the respective intake ports 7a, 7c of both the sides. In addition, the valve opening timing of the intake valve 8b of the central portion is set to be earlier than the valve opening timing of the respective intake valves 8A, 8C of both sides.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a multi-valve engine equipped with three intake valves.

(Prior art) Providing multiple intake valves and multiple exhaust valves in a 4-stroke engine can improve intake and exhaust efficiency, reduce the weight of each valve, and improve followability and allowable maximum during high-speed operation. The rotation speed can be increased. Therefore, as disclosed in Japanese Unexamined Patent Publication No. 60-216012, a five-valve engine has been proposed in which one combustion chamber is provided with three intake valves and two exhaust valves. In such a five-valve engine, three intake valves are arranged in parallel on the same cam shaft.
These cams open and close at the same timing.

However, although the provision of three intake valves increases the intake opening area and improves the intake air filling efficiency, it has not yet been possible to secure a sufficient improvement in engine output. The openings to the combustion chamber are arranged in an arc shape, and the openings to the combustion chamber are opened and closed.
When two intake valves are driven by the same camshaft,
Because the axis of the center intake valve is higher than the axes of the outer intake valves, the angle of inclination of the axis of the center intake valve with respect to the top surface of the piston is closer to the vertical direction than that of the outer intake valves ( As a result, the degree of curvature of the central intake port becomes greater than the other intake ports, which increases intake resistance and impedes improvement in output.

In addition, since the openings of the three intake ports to the combustion chamber are arranged in an arc shape along the outer periphery of the combustion chamber, the central intake port opens into the squish area of the combustion chamber. There is also the problem that the part directly below the intake valve that opens and closes the central intake port tends to become a knocking point during the compression stroke.

(Object of the Invention) Therefore, an object of the present invention is to provide an intake system that eliminates the drawbacks of the conventional multi-valve engine described above.

(Structure of the Invention) In the present invention, the central intake port is formed to stand up higher than the other intake ports among the three intake ports. The intake port is formed closer to the vertical direction than the intake port, and the opening timing of the intake valve that opens and closes the central intake port is earlier than the opening timing of the intake valves that open and close the outer intake ports, respectively. Features.

(Effects of the Invention) According to the present invention, the central intake port is formed to stand up higher than both outer intake ports, and the opening timing of the central intake valve is earlier than the opening timing of both outer intake valves. As a result, the air-fuel mixture flows in from the central intake port at high speed at the beginning of the intake stroke, thereby creating a strong vertical swirl within the combustion chamber, thereby achieving homogenization of the air-fuel mixture within the combustion chamber. Due to this vertical swirl, the air-fuel mixture reaches directly below the exhaust valve and is heated before reaching the vicinity of the ignition plug, which improves ignition performance and improves output. Further, by advancing the opening timing of the central intake valve, the fluidity of the air-fuel mixture directly below the central intake valve increases, which also has the effect of making knocking less likely to occur. Furthermore, since the intake resistance of the central intake port is reduced, the output can also be improved.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a DOHC type five-valve engine to which the present invention is applied, and FIG. 2 is a plan view of its combustion chamber. Note that FIG. 1 is a sectional view taken along line 1-1 in FIG. 2.

In FIGS. 1 and 2, 1 is a cylinder block equipped with a piston 20, and 2 is a cylinder head mounted on the upper part of the cylinder block. A combustion chamber 4 is formed in the cylinder head 2 at a portion corresponding to the cylinder 3 of the cylinder block 1, and an opening 6 is provided in the center of the combustion chamber 4 through which the tip of the spark plug 5 is exposed. The combustion chamber 4 has three intake bows 7a, 7 on the left half of the opening 6.
b, 7C are arranged in an arc shape and open, and each intake port 1a, 7b, 7c has an intake valve 8A that opens and closes them.
, 8B, and 8C are provided, respectively.

In addition, on the right half of the combustion chamber, there are two exhaust ports 9a,
9b is open, and exhaust valves 10A and IOB are respectively arranged there. Note that the hatched slope 15 in FIG. 2 is a squish area.

At the top of the cylinder head 2, there is a camshaft 11 with three cams arranged in parallel to drive the intake valves 8A to 8C, and a camshaft 12 with two cams arranged in parallel to drive the exhaust valves 10A and IOB. is pivoted.

Among the three intake ports 7a to 7, the center intake port 7b is the intake port on both outside sides? It is formed more erect than a and 7c. In other words, the central intake port 7b is formed such that its inclination angle with respect to the upper surface 20a of the piston 20 is closer to the vertical direction than the outer intake ports 7a and 7C, and )
? The degree of curvature of the intake ports a to 7c is approximately the same, so that the intake resistance of the intake ports 7a to 7c is approximately equal.

An intake manifold 13 is attached to the cylinder head 2, and within the intake manifold 13, three intake passages 142 to 14c are independently formed that extend on the extension line of the above-mentioned ventilation bows 7a to 7c. These intake passages 14a to 14C are surge tanks (not shown).
It is designed to be merged with

Figure 3 shows three intake valves 8A to 8C and two exhaust valves 1.
In the timing chart showing the opening/closing timing of 0A and IOB, the opening timing of the central intake valve 8B is the same as that of the intake valves 8 on both valve sides.
The valve opening timing is earlier than that of A and 8C.

With the above-described configuration, this embodiment can generate a strong vertical swirl within the combustion chamber 4, thereby improving combustibility.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view taken along the line 1-1 in FIG. 2 of an engine to which the present invention is applied, FIG. 2 is a plan view of a combustion chamber, and FIG. 3 is a timing chart showing valve opening/closing timing. 1-Cylinder block 2-Cylinder head 4...
・Combustion chamber a, 7 b, 7 c-1 ・Intake port A, 8B, 8
C - Intake valve a, 9b - Exhaust port OA, l0B - Exhaust valve 1.12... Camshaft 3 - Intake manifold 4a, 14b, 14cm - Intake passage O - Piston

Claims (1)

[Scope of Claims] In an intake system for a multi-valve engine in which three intake ports are provided for one combustion chamber, and each intake port is provided with an intake valve, the intake port located at the center of the three intake ports. The intake port is formed so that its inclination angle with respect to the top surface of the piston is closer to the vertical direction than the intake ports on both outer sides, and the opening timing of the intake valve that opens and closes the central intake port is adjusted to An intake system for a multi-valve engine characterized by opening timings earlier than the opening timings of intake valves that open and close respectively.