TECHNICAL FIELD

The present invention relates to spark ignition engines comprising a single chamber type combustion chamber.

BACKGROUND ART

Conventionally, in order to achieve the stable ignition performance even with the leaner air-fuel mixture, the spark ignition engine comprising the single chamber type combustion chamber comprises an ignition plug, which is provided in an auxiliary chamber without fuel supply (e.g. see JP-A-4-287826). In the spark ignition engine like this, as shown in FIGS. 15 and 16, a combustion chamber 25 is formed between a cylinder head 21 and the top of a piston 23 installed in a cylinder 22, and an ignition plug 27 is provided in the cylinder head 21 in such a way that ignition electrodes 27a are disposed over the combustion chamber 25. A cap 28 having a plurality of nozzle holes 28a is provided at the tip of the ignition plug 27 so as to cover the ignition electrodes 27a, and an auxiliary chamber 30 is thus formed in the cap 28, communicated with the combustion chamber 25 through the plurality of nozzle holes 28a. Therefore, when the air-fuel mixture flowed into the auxiliary chamber 30 from the cylinder 22 is spark-ignited with the ignition electrodes 27a of the ignition plug 27, the flame blown off out of the plurality of nozzle holes 28a becomes a flame jet. The flame jet makes the turbulence and is transmitted into the combustion chamber 25. As a result, the air-fuel mixture in the combustion chamber 25 is fully combusted. Hence, the turbulence generated by the flame jet makes the rapid combustion possible.

DISCLOSURE OF INVENTIONProblems to be Solved by the Invention

With respect to the conventional spark ignition engine, the auxiliary chamber is formed at the tip of the lower portion of the ignition plug, provided with the cap formed in the blind cylindrical shape. Thus, the diameter of the auxiliary chamber is limited by the diameter of the ignition plug. So, in order to secure the effective volume in the auxiliary chamber, the height thereof has to be higher. Therefore, the height of the auxiliary chamber becomes much longer than the width thereof, so that the length between the position of ignition by the ignition electrodes and the nozzle holes provided at the lower portion of the auxiliary chamber, and the residual gas is easy to remain around the position of ignition. As a result, the ignition in the auxiliary chamber or the flame expansion is prevented by the effect of the residual gas, so that the stable ignition and combustion performance with leaner air-fuel mixture is difficult to achieve.

The objective of the present invention is to provide a spark ignition engine capable of operating with a leaner air-fuel mixture to achieve stable ignition and combustion performance.

Means of Solving the Problems

The objective of the present invention is described above. The means of solving the problem are described below.

In accordance with the present invention, a spark ignition engine comprising a cylinder, a cylinder head, a piston, a sleeve formed in the blind cylindrical shape, an auxiliary chamber formed at the bottom part of the sleeve, an ignition plug fitted to the cylinder head through the sleeve, a set of ignition electrode of the ignition plug facing a single chamber type combustion chamber in the cylinder and one or more nozzle hole allowing the auxiliary chamber to communicate with the combustion chamber characterized in that the bottom of the sleeve is projected to the inside of the combustion chamber from an explosion surface of the cylinder head; and the ignition position by the ignition electrodes is set near the explosion surface.

Preferably, the auxiliary chamber is formed in the cylindrical shape and is surrounded by the sleeve and the ignition plug, and in that the ratio of the height of the auxiliary chamber to the diameter of the same is set within the range of 0.5 to 1.0.

Preferably, the position of ignition is set in the lower side than the residual gas that remains in the auxiliary chamber at ignition timing before the piston reaches top dead center.

Preferably, the ratio of the length between the inside upper surface of the auxiliary chamber and the position of ignition to the height of the auxiliary chamber is set within the range of 0.5 to 0.8.

Preferably, the ratio of the volume of the auxiliary chamber to that of the combustion chamber when the piston reaches top dead center is set within the range of 0.010 to 0.015.

Preferably, the nozzle holes are set as one or more pairs of the holes symmetrical relative to the position of ignition, and in that the angle that each of the pair of the holes makes in the gravity direction is set within the range of 80 to 100 degrees.

Preferably, the directions of the nozzle holes are set as the directions of the lines between the position of ignition and the centers of valve recesses provided in the outer periphery of the combustion chamber or the centers of the valve recesses adjacent to each other, and in that the tolerance angles that the directions of the nozzle holes and the directions of the lines make are set within the range of âˆ’10 to 10 degrees in the horizontal direction.

Effect of the Invention

The effects of the present invention are described below.

According to the present invention, the standard ignition plugs can be used for the spark ignition engine and cost reduction can be achieved. The flame jet can be generated by the flame blown into the combustion chamber out of the auxiliary chamber through the nozzle holes provided in the sleeve, so that the flame jet can generate the turbulence, which makes rapid combustion possible without the conventional auxiliary chamber type ignition plug. Moreover, the nozzle holes can be provided away from the explosion surface of the piston, so that the flame jet can prevent from being affected by the temperature of the explosion surface. Furthermore, the auxiliary chamber can be simply formed, so that the auxiliary chamber can be freely designed, the position of ignition can be freely disposed and, thus, the auxiliary chamber that is capable of preventing from being affected by the residual gas can be easily formed.

According to the present invention, the ratio of the height of the auxiliary chamber to the width of the same can be appropriately set, so that the spark ignition engine can be operated with the leaner air-fuel mixture than conventional.

According to the present invention, the position of ignition with the ignition plug can be disposed at an appropriate position to the auxiliary chamber, so that the auxiliary chamber can prevent the residual gas therein from affecting the ignition and combustion performance. Consequently, the stable ignition and combustion can be achieved even with the leaner air-fuel mixture, and thus the available operation range of the engine can be expanded to the lean side.

According to the present invention, the position of ignition with the ignition plug can be disposed at an appropriate position to the auxiliary chamber, so that the auxiliary chamber can prevent the residual gas therein from affecting the ignition and combustion performance. Consequently, the stable ignition and combustion can be achieved even with the leaner air-fuel mixture, and thus the available operation range of the engine can be expanded to the lean side.

According to the present invention, the ratio of the volume of the auxiliary chamber to the volume of the combustion chamber can be appropriately set, so that the stable combustion can be secured and thus the available operation range of the engine can be expanded to the lean side.

According to the present invention, the angles of the nozzle holes make can be appropriately set, so that the stable combustion can be secured as the flame jet is surely blown off out of the nozzle holes and thus the available operation range of the engine can be expanded to the lean side.

According to the present invention, the directions of the nozzle holes can be appropriately set, so that the stable combustion can be secured and thus the available operation range of the engine can be expanded to the lean side.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-section view of a combustion chamber, an ignition plug and a sleeve according to an embodiment of the present invention.

FIG. 2 is a cross-section view of the ignition plug and an auxiliary chamber formed in the sleeve.

FIG. 3 is a cross-section plan view of the sleeve.

FIG. 3(a) is a cross-section plan view of the sleeve in the case the directions of the nozzle holes are the same as the directions of the line O1.

FIG. 3(b) is a cross-section plan view of the sleeve in the case the directions of the nozzle holes are the same as the directions of the line O2.

FIG. 4 is a graph showing the relation between the ratio of the height to the width of the auxiliary chamber (i.e. L1/L2) and the density of the air-fuel mixture in misfire limit.

FIG. 5 is a graph showing the relation between the ratio of the height to the width of the auxiliary chamber (i.e. L1/L2) and the stability of combustion.

FIG. 6 is a cross-section view of the auxiliary chamber including the residual gas.

FIG. 7 is a graph showing the relation between the ratio of the length from the top of the auxiliary chamber to the position of ignition to the height of the auxiliary chamber (i.e. L3/L1) and the density of the air-fuel mixture in misfire limit.

FIG. 8 is a graph showing the relation between the ratio of the length from the top of the auxiliary chamber to the position of ignition to the height of the auxiliary chamber (i.e. L3/L1) and the stability of combustion.

FIG. 9 is a graph showing the relation between the ratio of the volume of the auxiliary chamber to that of the combustion chamber (i.e. V1/V2) and the density of the air-fuel mixture in misfire limit.

FIG. 10 is a graph showing the relation between the ratio of the volume of the auxiliary chamber to that of the combustion chamber (i.e. V1/V2) and the stability of combustion.

FIG. 11 is a graph showing the relation between the angles of the nozzle holes (i.e. the angle ) and the density of the air-fuel mixture in misfire limit.

FIG. 12 is a graph showing the relation between the angles of the nozzle holes (i.e. the angle ) and the stability of combustion.

FIG. 13 is a graph showing the relation between the direction of the nozzle holes (i.e. the angle ) and the density of the air-fuel mixture in misfire limit.

FIG. 14 is a graph showing the relation between the direction of the nozzle holes (i.e. the angle ) and the stability of combustion.

FIG. 15 is a cross-section view of the conventional combustion chamber comprising the auxiliary chamber type ignition plug.

FIG. 16 is an enlarged cross-section view of the conventional auxiliary chamber.

EXPLANATION OF NUMERALS

1 cylinder head
2 cylinder
5 combustion chamber
6 sleeve
7 ignition plug
7a ignition electrode (ground electrode)
7b ignition electrode (center electrode)
10 auxiliary chamber
12 position of ignition

THE BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the present invention will be described below.