Internal combustion engine

Abstract

In an internal combustion engine includes an intake valve port that opens into a combustion chamber on one side of a plane containing the axis of a cylinder bore. An exhaust valve port opens into the combustion chamber on the other side of the plane. A spark plug has a tip end that fronts a substantially central portion of the combustion chamber. The spark plug is disposed between the intake valve and the exhaust valve. In order to restrain the blow-by of an unburned fuel-air mixture, and to suppress the bulging of the cylinder head to the intake system side, the operation axis of an intake valve is set to be substantially parallel to the axis of the cylinder bore. In addition, one side surface of a cylinder head is formed to be substantially parallel to the axis of the cylinder bore.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a side view of a motorcycle pertaining to a first embodiment of the present invention;

FIG. 2 is a vertical sectional side view of an essential part of an internal combustion engine;

FIG. 3 is an enlarged view of an essential part of FIG. 1;

FIG. 4 is a vertical sectional side view, corresponding to FIG. 2, of a second embodiment of the present invention;

FIG. 5 is a vertical sectional view, corresponding to FIG. 2, of a third embodiment of the present invention; and

FIG. 6 is a vertical sectional view, as viewed from the rear side, of an internal combustion engine mounted on an all-terrain vehicle, showing a fourth embodiment of the present invention.

Claims

1. An internal combustion engine, comprising: a piston slidably fitted in a cylinder bore;a combustion chamber formed between a cylinder block and a cylinder head, a top portion of said piston fronting said combustion chamber;an intake valve port that is opened and closed by an intake valve, said intake valve port being provided in said cylinder head to open into the combustion chamber on one side of a plane containing an axis of the cylinder bore;an exhaust valve port that is opened and closed by an exhaust valve, said exhaust valve port being provided in said cylinder head to open into the combustion chamber on the other side of said plane; anda spark plug having a tip end that fronts a substantially central portion of said combustion chamber, said spark plug being attached to said cylinder head and being disposed between said intake valve and said exhaust valve,wherein an operation axis of said intake valve is set to be substantially parallel to the axis of said cylinder bore.

2. The internal combustion engine according to claim 1, wherein a ceiling surface of said combustion chamber is provided, between said spark plug and said intake valve port, with a partition wall projecting toward said piston.

3. The internal combustion engine according to claim 2, wherein the tip end of said spark plug is disposed at substantially the same position as a projecting end of said partition wall.

4. The internal combustion engine according to claim 2, wherein the operation axis of said exhaust valve is so set as to skewly intersect said plane, and at least a part of said exhaust valve port is disposed above on the upper side relative to said partition wall.

5. The internal combustion engine according to claim 3, wherein the operation axis of said exhaust valve is so set as to skewly intersect said plane, and at least a part of said exhaust valve port is disposed above on the upper side relative to said partition wall.

6. The internal combustion engine according to claim 1, wherein one side surface of said cylinder head, in which an intake port opens contiguous with said intake valve port, is formed to be substantially parallel to the axis of said cylinder bore.

7. The internal combustion engine according to claim 2, wherein one side surface of said cylinder head, in which an intake port opens contiguous with said intake valve port, is formed to be substantially parallel to the axis of said cylinder bore.

8. The internal combustion engine according to claim 3, wherein one side surface of said cylinder head, in which an intake port opens contiguous with said intake valve port, is formed to be substantially parallel to the axis of said cylinder bore.

9. The internal combustion engine according to claim 4, wherein one side surface of said cylinder head, in which an intake port opens contiguous with said intake valve port, is formed to be substantially parallel to the axis of said cylinder bore.

10. The internal combustion engine according to claim 5, wherein one side surface of said cylinder head, in which an intake port opens contiguous with said intake valve port, is formed to be substantially parallel to the axis of said cylinder bore.

11. An internal combustion engine, comprising: a piston slidably fitted in a cylinder bore;a combustion chamber formed between a cylinder block and a cylinder head, a top portion of said piston fronting said combustion chamber, said cylinder head being provided with an intake valve port opening into said combustion chamber on one side of a plane containing an axis of said cylinder bore, and with an exhaust valve port opening into said combustion chamber on the other side of said plane;an intake valve disposed in said cylinder head to be able to open and close said intake valve port;a camshaft for driving said intake valve to open and close, said camshaft being disposed on an operation axis of said intake valve;an exhaust valve disposed in said cylinder head to be able to open and close said exhaust valve port;a rocker shaft fixedly disposed between said exhaust valve and said camshaft; anda rocker arm swung according to rotation of said camshaft to drive said exhaust valve to open and close, said rocker arm being swingably borne by said rocker shaft,wherein the operation axis of said intake valve is set substantially parallel to the axis of said cylinder bore.

12. The internal combustion engine according to claim 11, wherein one side surface of said cylinder head, in which an intake port opens contiguous with said intake valve port, is formed to be substantially parallel to the axis of said cylinder bore.

13. The internal combustion engine according to claim 11, wherein an intake system member connected to said intake port is disposed substantially along one side surface of said cylinder head.

14. The internal combustion engine according to claim 12, wherein an intake system member connected to said intake port is disposed substantially along one side surface of said cylinder head.

15. The internal combustion engine according to claim 11, wherein said intake valves are disposed respectively on the sides, close to each other, of a pair of said cylinder heads respectively constituting parts of a pair of banks disposed in a mutually V-shaped arrangement.

16. The internal combustion engine according to claim 12, wherein said intake valves are disposed respectively on the sides, close to each other, of a pair of said cylinder heads respectively constituting parts of a pair of banks disposed in a mutually V-shaped arrangement.

17. The internal combustion engine according to claim 13, wherein said intake valves are disposed respectively on the sides, close to each other, of a pair of said cylinder heads respectively constituting parts of a pair of banks disposed in a mutually V-shaped arrangement.

18. The internal combustion engine according to claim 14, wherein said intake valves are disposed respectively on the sides, close to each other, of a pair of said cylinder heads respectively constituting parts of a pair of banks disposed in a mutually V-shaped arrangement.