JPH04365906A - Four cycle engine - Google Patents

Abstract

PURPOSE:To form a combustion chamber in a compact size so as to increase a pressure ratio, in an engine provided with three cylinder valves and two exhaust valves per one cylinder. CONSTITUTION:Intake valves 5 are provided on one side of a combustion chamber 3, and exhaust valves 6 are also provided on the other side of the combustion chamber 3. The intake valves 5 on both side among the intake valves 5 are displaced from the intermediatary intake valve 5 toward the inside of combustion chamber 3. The combustion chamber 3 is formed in a nearly triangular shape by an inclining surface 5b on which both side intake valves 5 are provided an inclining surface 6b on which the exhaust valve 6 is provided, and a cylinder head bottom surface (d), and bevel parts 5c, 6c of both intake valves 5 and the intake valve 6 are arranged in nearly the center parts of respective inclining surfaces. The intermediatary intake valve 5 is faced to the combustion chamber 3, so that the bavel part center line 02 of the intermediatary intake valve 5 is positioned toward the cylinder side from the center line 01 of both side intake valves 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve device for a four-stroke engine.

0002

2. Description of the Related Art Conventionally, in order to improve output performance in a high-speed operating range of a four-cycle engine, the number of intake valves and exhaust valves per cylinder has been increased. In other words, by increasing the number of intake valves and exhaust valves, the total area occupied by the valves in the combustion chamber, that is, the valve area, increases, improving intake and exhaust efficiency, and each valve itself becomes smaller and lighter, which improves the engine performance. This is because the followability of the valve during high-speed operation is improved.

However, the area of the combustion chamber that each valve faces is limited, and there is a restriction that a plurality of valves must be provided within that area without interfering with each other.

[0004] Therefore, as described in British Patent No. 687,528, three intake valves are provided, and the intermediate valve is deviated to the outside of the cylinder from the valves on both sides in side view. Some combustion chambers have valves that do not interfere with each other.

[0005] Also, British Patent No. 296125 discloses a device with three intake valves.

[0006]

[Problems to be Solved by the Invention] However, when providing such a large number of valves, the problem is how to make the large number of valves face the combustion chamber. That is, it is difficult to increase the compression ratio with a structure in which the valves are arranged on one plane perpendicular to the cylinder axis, as described in British Patent No. 687,528.

Further, as described in the specification of British Patent No. 296125, valves are installed on the upper surface of the combustion chamber, which is formed into one curved surface centered on the camshaft, on the inside and outside of the combustion chamber. In structures arranged offset from each other,
In particular, since the valve deviated to the inside of the combustion chamber is separated upward from the cylinder, there is a problem that the combustion chamber becomes deep and it is difficult to increase the compression ratio.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to solve the problem in an engine having three intake valves and two exhaust valves per cylinder. The present invention aims to provide a four-stroke engine with a compact combustion chamber and a high compression ratio.

[0009]

[Means for Solving the Problems] In order to achieve the above object, a four-stroke engine according to the present invention has three intake valves facing one side of a combustion chamber and two exhaust valves facing the other side, and The intake valves on both sides of the valve are arranged to be offset toward the inside of the combustion chamber than the intake valve in the middle, and the combustion chamber of the cylinder head is divided into a slope on which the intake valves on both sides are placed and a slope on which the exhaust valve is placed. The lower surface of the cylinder head is formed into a substantially triangular shape when viewed in the camshaft direction, and the umbrella portions of the intake valves and exhaust valves on both sides are placed approximately in the center of each slope when viewed in the camshaft direction. The center of the umbrella is positioned closer to the cylinder than the intake valves on both sides, facing the combustion chamber.

0010

[Operation] Since this is a four-cycle engine configured as described above, three intake valves are placed on one side of the combustion chamber, and two exhaust valves are placed on the other side. Since the intake valves are arranged to be offset toward the inside of the combustion chamber than the intermediate intake valves, multiple valves can be provided within the combustion chamber without interfering with each other, and a wide valve area within the combustion chamber can be secured.

[0011] Furthermore, in order to have many valves, especially three intake valves that are offset from each other on the inside and outside of the combustion chamber, facing the combustion chamber, the combustion chamber of the cylinder head is formed into a slope on which the intake valves on both sides are arranged. The slope on which the exhaust valve is arranged and the lower surface of the cylinder head form a roughly triangular shape when viewed in the direction of the camshaft, and the umbrella portions of the intake and exhaust valves on both sides are placed approximately in the center of each slope when viewed in the direction of the camshaft. Therefore, not only the exhaust valve but also the intake valves on both sides, which are offset to the inside of the combustion chamber, can be arranged near the cylinder.

Furthermore, since the middle intake valve faces the combustion chamber so that the center of its umbrella part is located closer to the cylinder than the intake valves on both sides, the middle intake valve can also be placed closer to the cylinder. can.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described with reference to the accompanying drawings. The drawing shows one cylinder of a four-stroke engine.
In the figure, a is a cylinder, b is a cylinder head, 1 is an intake passage, and 2 is an exhaust passage.

Reference numeral 3 denotes a combustion chamber formed on the lower surface of the cylinder head b, into which an intake passage 1 and an exhaust passage 2 are opened. Reference numeral 4 denotes a screw hole for attaching a spark plug, which opens at the center of the upper surface of the combustion chamber 3.

Reference numeral 5 represents an intake valve that opens and closes the intake passage 1, and 6 represents an exhaust valve that opens and closes the exhaust passage 2. The lower ends of these intake valves 5 and exhaust valves 6 face the combustion chamber 3 and correspond to the opening ends of the intake passage 1 and the exhaust passage 2, respectively.
It is slidably supported on the wall.

Reference numerals 7 and 8 denote springs that bias the intake valve 5 and exhaust valve 6 in the valve-closing direction. Camshafts 9 and 10 drive the intake valve 5 and the exhaust valve 6, and are rotatably held between the cylinder head b and cam caps 11 and 12, respectively. 13 is the camshaft 9, 10
and a cover that covers the cam caps 11 and 12, and is connected to the upper end of the cylinder head b.

[0017]The four-stroke engine is provided with three intake valves 5 and two exhaust valves 6 per cylinder in order to improve its output performance. These intake and exhaust valves 5 and 6 are distributed on one side and the other side of a center line L4 passing through the center of the combustion chamber 3 and parallel to the camshafts 9 and 10. Note that, of course, the number of intake passages 1 and exhaust passages 2 is increased according to the number of valves 5 and 6.

The arrangement structure of the three intake valves 5 described above is such that the middle valve is provided to be deviated to the outside of the cylinder in side view from the valves on both sides, and the axis L1 of the cylinder a is
The cylinders face the combustion chamber 3 so that the central cylinder has a smaller inclination than the cylinders on both sides.

That is, the inclination angle of the intermediate intake valve 5 is α
1 and the inclination angle of the intake valves 5 on both sides is α2, then α1<α2. The three intake valves 5 are arranged such that their upper ends are close to each other in side view.
More specifically, they are arranged so as to be located on substantially the same straight line L3 parallel to the axis L2 of the camshaft 9.

Therefore, as shown in FIG. 2, in the combustion chamber 3 viewed from the side, the center line L4 that separates the intake side and the exhaust side of the intake valve 5 is such that the middle valve is deviated outward from the valves on both sides. This position prevents the valves 5 from interfering with each other.

Further, each of the intake valves 5 is connected to a camshaft 9, and a rocker arm 14 is used as the connection means. This rocker arm 14 has three arms 14a that engage with the upper end of each intake valve 5.
The tip of each intake valve 4a is in contact with the upper end of each intake valve 5 located on a straight line L3, and the base is coaxially supported on the wall surface of the cylinder head b by a single support shaft 18 so as to be able to freely swing up and down. , a cam 9 whose intermediate upper surface is provided on the cam shaft 9
It is engaged with a.

Therefore, the arm lengths of the rocker arms of each intake valve 5, that is, the length from the support shaft 18 to the upper end of each intake valve, and the length from the support shaft 18 to the engagement point of the cam 9a. , and the ratio thereof (rocker ratio) are approximately the same in each intake valve 5.

[0023] If the rocker arm 14 is structured to drive the three intake valves 5 by the rocker arm 14, which is formed by integrating the rear part of each arm 14a that contacts the upper end of each intake valve 5, as described above, the cam Only one cam 9a is required on the shaft 9, and the rocker ratios of each intake valve 5 can be matched to ensure synchronization of valve operations.

As a means for connecting the intake valves 5 to the camshaft 9, an independent rocker arm 15 may be used for each valve 5, as shown in FIGS. 5 and 6. In this case, each rocker arm 15 has its tip abutted against the upper end of each intake valve 5 located on a straight line L3, and the base end of each rocker arm 15 is attached to a bearing 1 extending substantially in the direction of the axis L1 of the cylinder a.
It is supported by 8'. In this case, each locker
The arms 15 can have substantially the same distance from the camshaft 9 to the upper end of each intake valve 5 and have the same shape. Moreover, the cams 9a of the camshaft 9 that engage with these rocker arms 15 can also have the same shape.

On the other hand, as the intake valve 5 is arranged as described above, the middle part of the intake passage 1 has a smaller inclination with respect to the axis L1 of the cylinder a than those on both sides, so that the combustion chamber 3 and the cylinder It will come within a.

[0026] With such a structure, as in the conventional case where there are two intake passages and their inclinations with respect to the axis of the cylinder are the same, the intake air flows from both intake passages in opposite directions. This solves the problem of the intake air colliding with the intake air on the way and stagnation, making it impossible to maintain a smooth flow of intake air.

That is, as shown in FIG. 7, in the cylinder a, the intake air flow S3 from the middle intake passage flows toward the point where the intake air flows S1 and S2 from the intake passages on both sides collide. Flows S1 and S2 are pushed down and collide with piston c, and thereafter the flow is maintained within cylinder a. As described above, the intake air flows S1, S
2. S3 does not stagnate midway, and the intake flow S1, S2,
The flow of S3 can be maintained smoothly.

On the other hand, two exhaust valves 6 are provided, and are arranged within the combustion chamber 3 on a straight line L5 parallel to the center line L4. Further, the exhaust valves 6 are set to have the same inclination angle α3 with respect to the axis L1 of the cylinder a, and their upper ends are connected to the camshaft 10 via rocker arms 16, respectively. Since there are two exhaust valves 6, they will not interfere with each other even if they are arranged in series within the combustion chamber 3.

The combustion chamber 3 formed in the cylinder head b includes a slope 5b on which the intake valves 5 are arranged on both sides, a slope 6b on which the exhaust valve 6 is arranged, and a lower surface d of the cylinder head.
The umbrella portions 5c and 6c of the intake valve 5 and the exhaust valve 6 on both sides are shaped like a triangle when viewed in the direction of the camshaft 9.
It is arranged approximately at the center of each slope 5b, 6b when viewed in the direction.

Further, the center O2 of the umbrella portion 5d of the middle intake valve 5 faces the combustion chamber 3 so as to be located lower toward the cylinder a than the center O1 of the umbrella portion 5c of the intake valves 5 on both sides.

[0031]

Effects of the Invention Since the present invention is constructed as described above, three intake valves are provided on one side of the combustion chamber, and two exhaust valves are provided on the other side, and the intake valves on both sides of the intake valves are Since the valves are located closer to the inside of the combustion chamber than the intermediate intake valves, multiple valves can be installed within the combustion chamber without interfering with each other, making it possible to secure a wide valve area within the combustion chamber. , can improve intake and exhaust efficiency.

[0032] Furthermore, in order to have many valves, especially three intake valves that are offset from each other on the inside and outside of the combustion chamber, facing the combustion chamber, the combustion chamber of the cylinder head is formed with a slope on which the intake valves on both sides are arranged. The slope on which the exhaust valve is arranged and the lower surface of the cylinder head form a roughly triangular shape when viewed in the direction of the camshaft, and the umbrella portions of the intake and exhaust valves on both sides are placed approximately in the center of each slope when viewed in the direction of the camshaft. Therefore, not only the exhaust valve but also the intake valves on both sides, which are deviated to the inside of the combustion chamber, can be arranged near the cylinder, making it possible to make the combustion chamber more compact and increase the compression ratio.

Furthermore, since the middle intake valve faces the combustion chamber so that the center of its umbrella part is located closer to the cylinder than the intake valves on both sides, the middle intake valve can also be placed closer to the cylinder. The combustion chamber becomes shallower and the compression ratio can be further increased.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a four-stroke engine according to the present invention.

FIG. 2 is a sectional view taken along the line E--I in FIG. 1.

FIG. 3 is a sectional view taken along Rollo in FIG. 2;

FIG. 4 is a cross-sectional view taken along the line in FIG. 3;

FIG. 5 is a longitudinal sectional view showing a modification of the rocker arm.

FIG. 6 is a cross-sectional view of FIG. 5;

FIG. 7 is a schematic diagram showing the flow of intake air within the cylinder.

[Explanation of symbols]

a Cylinder b Cylinder head d Cylinder head bottom surface O1 Center of umbrella part of both intake valves O2
Center of umbrella part of middle intake valve 3 Combustion chamber 5 Intake valve 5b Slope 5c with intake valves on both sides arranged
Intake valve umbrellas 5d on both sides Middle intake valve umbrella 6 Exhaust valve 6b Slope 6c with exhaust valves Exhaust valve umbrella 9 Camshaft 10 Camshaft

Claims (1)

[Claims] Claim 1: In a four-stroke engine that has three intake valves and two exhaust valves per cylinder, each of which is driven by a camshaft, the intake valve is located on one side of the combustion chamber, and the exhaust valve is located on the other side of the combustion chamber. The intake valves on both sides of the intake valves are arranged to be deviated toward the inside of the combustion chamber than the intermediate intake valve, and the combustion chamber of the cylinder head is formed with a slope on which the intake valves on both sides are arranged. The slope on which the exhaust valve is arranged and the lower surface of the cylinder head form a substantially triangular shape when viewed in the direction of the camshaft, and the umbrella portions of the intake and exhaust valves on both sides are placed approximately in the center of each slope when viewed in the direction of the camshaft. In addition, a four-cycle engine characterized in that the middle intake valve faces the combustion chamber so that the center of its umbrella part is located closer to the cylinder than the intake valves on both sides.