JPS59201923A - Four-cycle internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the efficiency of combustion of an engine in which an ignition plug, a single intake valve and a single exhaust valve are positioned in its cylinder head, by arranging the ignition plug and the valves in such a way that the axes of them extend in different radial directions. CONSTITUTION:If the invention is applied to a four-cycle and single cylinder engine of a motorcycle, intake and exhaust valves 20 and 21 are approximately symmetrically arranged laterally in the upper half section of the engine divided by a P-P line or a plane including the center axis of a cylinder and an ignition plug 22 is arranged in he lower half section thereof at approximately central part of the section. Additionally, the valve stems 23 and 24 of the valves 20 and 21 are inclined upwards and at such angles that they are opened in the lateral direction while the ignition plug 22 are arranged such that its longitudinal center axis is inclined downwards. The respective axes of the valves 23, 24 and the plug arranged to extend in the radial directions. The interior face of a combustion chamber 17 may be shaped in the approximately spherical form, hence improving combustion efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a four-stroke internal combustion engine with a combustion chamber facing a spark plug and a single intake valve and an exhaust valve, respectively.

In a four-stroke internal combustion engine, it is advantageous for the inner surface of the combustion chamber to have a smooth spherical shape, since the surface area is small, thereby reducing heat loss and improving combustion efficiency. However, if the axes of the intake and exhaust valves and the spark plugs are parallel to each other, corners are formed on the inner surface of the combustion chamber. In other words, when the valve axes of the intake and exhaust valves are parallel to each other, the valve seat surfaces of the valves are perpendicular to the valve axes, so the valve seat surfaces of the intake and exhaust valves are formed on the same plane. At least one large flat portion is formed on the inner surface of the combustion chamber, and therefore a corner is formed. Such corners cause an increase in the surface area of the combustion chamber and reduce heat loss.1. Furthermore, the corners act as resistance to swirl, resulting in a reduction in combustion efficiency.

The present invention was made based on these circumstances, and it is possible to easily make the inner surface of the combustion chamber into a smooth spherical shape.
The purpose of this invention is to provide a four-stroke internal combustion engine that can improve combustion efficiency.

The present invention is characterized in that the spark plug, intake valve, and exhaust valve facing the combustion chamber are arranged so that their respective axes extend in different radial directions.

An embodiment of the present invention will be described below based on the drawings.

The motorcycle shown in FIG. 1 has a four-stroke single-cylinder engine 2 suspended from a frame 1, and this engine 2 drives a rear wheel 4 through a shaft drive mechanism 3. Note 5
6 is a front wheel, 6 is a steering wheel, 7 is a windshield, 8 is a fuel tank, 9 is a seat, and IO is a backrest.

Details of the engine 2 are shown in FIG. 2 and below, where 11 is a crankcase, 12 is a cylinder, and 13 is a cylinder head. The cylinder 12 extends from the crankcase 11 in a forward-inclined posture, and the piston I4 fitted into the cylinder 12 slides substantially in the front-rear direction. The piston 14 is connected to a crankshaft 16 via a connecting rod I5, and the rotation of the crankshaft 16 is controlled by a clutch (not shown).
It is transmitted to the shaft drive mechanism 3 via the transmission.

A combustion chamber 17 is formed between the top surface of the piston 14 and the inner surface of the cylinder rad 13. This combustion chamber 17 communicates with an intake passage 18 and an exhaust passage 19. The intake passage 18 and the exhaust passage 19 sandwich the combustion chamber 17 and extend in the left-right direction of the vehicle body. The intake passage 18 communicates with a carburetor and an air cleaner (not shown), and the exhaust passage 19 communicates with an exhaust pipe and a muffler (not shown).

An intake port facing the combustion chamber 17 in the intake passage 18 is opened and closed by the intake pulp 20, and when this intake port is opened, air-fuel mixture flows into the combustion chamber 17 from the intake passage 18. Then, the air-fuel mixture in the combustion chamber 17 is ignited by the spark plug 22 and combusts. Further, the gas after combustion is released to the exhaust passage 19 when the exhaust pulp 21 opens the exhaust port. The intake pulp 20 and the exhaust pulp 21
Valve shafts 23 and 24fi: These pulps 20 and 21 are opened and closed by being pushed by rocker arms 15 and 26, which will be described later, respectively.

The intake pulp 20, exhaust pulp 21, and spark plug 22 are arranged with respect to the combustion chamber 17 as follows. That is, the pp line in FIG. 4 is a plane that includes the cylinder center axis, and the intake pulp 20 and the exhaust nozzle Q loop 21 are placed in the upper region divided by this plane PP so that they are approximately symmetrical left and right. It is placed in Also, the plane P-
In the lower region divided by P, a spark plug 22 is arranged approximately at the center. The intake valve 20 and the exhaust valve 21 are tilted so that their valve shafts 23 and 24 are respectively inclined upward and opened in the left-right direction as shown in FIG. Further, the central axis QQ of the spark plug 22 in the longitudinal direction of the plug is inclined downward. Therefore, each of these valve axes 2324 and the glove axes extend radially from each other.

As a result, the inner surface J of the combustion chamber 17 on the cylinder head 13 side
7a is formed into a substantially spherical surface.

In this embodiment, the top surface 14th of the piston 14 is also formed into a substantially spherical shape, so that the combustion chamber 17 is formed into a roughly grid-shaped space.

In the combustion chamber 17 having such a shape, the inner surfaces 17a and 14m of the combustion chamber 17 are spherical during the compression stroke, so that the air-fuel mixture is swirled smoothly, resulting in good flame propagation performance and improved combustion efficiency. do. Further, when the height of the inner surface 17a is the same, a spherical combustion chamber has a smaller surface area than an angular combustion chamber, resulting in less heat loss and improved output characteristics. Furthermore, even when the exhaust valve 21 is opened and exhaust gas is removed, since the inner surface of the combustion chamber 17 is spherical, the exhaust gas moves smoothly and the exhaust efficiency is improved.

Also, the combustion chamber 17 has a medium-height shape, and its axis Q-Q is aligned so that the ignition flag 22 faces the center of the combustion chamber 17.
Since the spark plug 22 is tilted, the protruding position of the electrode part of the spark plug 22 is at the center of the combustion chamber, where the amount of air-fuel mixture is large.
There is little risk of misfire due to residual burnt gas, and sufficient volume necessary for combustion is ensured in the swivel of the spark plug 22, allowing smooth and reliable combustion.

The rocker arms 25,26 for actuating the intake valve 20 and the exhaust pulp 21 are shown in FIGS. 5 et seq. That is, 27 is a rocker shaft, cylinder head 13,
It is pivotally supported between the head cover 28 and the head cover 28. The opening and the arms 25 and 26 are commonly attached to the rocker shaft 27. One rocker arm 25 is for suction pulp, and as shown in FIGS. 5 and 6, a push-up arm 25a and a push-down arm 25bf are provided at both ends in the axial direction.
It has a recess 29 in the center in the axial direction. The other rocker arm 26 is rotatably housed in the recess 29, and has a push-up arm 26a and a push-down arm 26bf at both ends. The rocker arms 25 and 26 are coaxially fitted and rotatably supported by the one rocker shaft 27, respectively. Note that 30.30 is a thrust washer.

Each push-up arm 25a+26a is pushed by a push rod 31.32, which is connected to a cam follower 33.34 as shown in FIG. Cam follower 33.
It is reciprocated by a camshaft 35 in the 3.4d crankcase 11, and this camshaft 35 is rotated by the crankshaft I6 through gears 36 and 37 at a reduced speed.

Each push-down arm 25b, 26b has an adjustment screw 38.
39 are screwed, and each valve shaft 23.
It is designed to press 24f. Note that 40 and 41 are covers for adjustment holes that are opened when adjusting the adjustment screws 38 and 39.

With such a configuration of the rocker arms 25 and 26, only one rocker shaft 27 is required, and the double-ended hook arm 25.
It can be assembled as a 26f unit, is small and lightweight, and the recess 29 serves as a lubricating oil reservoir to provide good lubrication.

As described above, according to the present invention, since the spark plug, intake pulp, and exhaust valve are arranged in directions in which their axes extend in different radial directions, the inner surface of the combustion chamber can be easily formed into a substantially spherical shape. be able to. Therefore, the movement of the air-fuel mixture in the combustion chamber is smooth, the flame propagation efficiency is improved, and since no extra corners are formed on the inner surface of the reed combustion chamber, the surface area can be reduced, and heat loss can be reduced. Combustion efficiency is improved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a side view of a motorcycle, FIG. 2 is a side view of the main part of the engine, and FIG. 4 is a sectional view taken along the line ■-■ in FIG. 2, FIG. 5 is an exploded perspective view of the rocker arm, FIG. 6 is a plan view of the rocker arm in its assembled state, and FIG. 7 is a cross-sectional view taken along the line ■-■ in FIG. 6, and FIG. 8 is a cross-sectional view taken along the line ■-■ in FIG. 2... 4-cycle single cylinder engine, 11... Crank case, 12... Cylinder, 13... Cylinder head, 14... Piston, 17... Combustion chamber, 18
...Intake passage, 19...Exhaust passage, 2o...Intake pulp, 21...Exhaust valve, 22...Spark plug, 2s, x 4-valve shaft, 17a ・BJ? Surface, 14a...spherical surface. Applicant's representative Patent attorney Takehiko Suzue 3 illustrations 4 illustrations 5 illustrations 7 3+6 illustration■: #7 illustration

Claims (1)

[Claims] The cylinder head is equipped with a single intake knob and exhaust knob, each facing the combustion chamber.
A four-cycle internal combustion engine, characterized in that the axis of the spark plug, the intake/rub axis, and the exhaust/rub axis are arranged in directions extending in different radial directions.