JP2559119Y2 - 2 cycle engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a uniflow type two-stroke engine having an exhaust valve above the head, among two-stroke engines.

[0002]

2. Description of the Related Art Conventionally, in a uniflow type two-stroke engine provided with an exhaust valve above the head, for example, as described in Japanese Utility Model Laid-Open No. 55-116820, a cylinder bore is provided in the cylinder bore. The scavenging port is set in a tangential direction to the cylinder bore, and a swirl flow is given to the new intake air from the scavenging port into the cylinder bore, thereby facilitating scavenging in the cylinder bore and promoting combustion. Make up.

[0003]

However, in the conventional uniflow type two-stroke engine, the swirling flow in the cylinder bore does not occur when the exhaust valve opens, but the scavenging port opens due to the downward movement of the piston. This is generated when new intake air flows in from the scavenging port. In other words, the generation of the swirling flow in the cylinder bore exclusively depends on the new intake air flowing in from the tangential scavenging port. As a result, the swirl flow in the cylinder bore is weak, so that the scavenging and combustion promotion by the swirl flow are insufficiently achieved.

[0004] It is a technical object of the present invention to surely achieve scavenging and combustion promotion by a swirling flow.

[0005]

In order to achieve this technical object, the present invention provides a valve recess at a substantially central portion of the cylinder bore on the lower surface of a cylinder head fastened to the upper surface of a cylinder block having a cylinder bore. On the other hand, an exhaust port is provided in the cylinder head so as to open to the valve recess, an exhaust valve is provided in the opening of the exhaust port to the valve recess, and further, the cylinder block has an exhaust port in the cylinder bore. In a two-stroke engine in which a scavenging port that is opened and closed by reciprocation of a piston is provided to be inclined in a tangential direction with respect to a cylinder bore, to guide exhaust gas into the valve recess on an inner wall surface of the valve recess for the exhaust valve. At least one exhaust gas guide groove of the same type as the tangential direction of the scavenging port And the exhaust valve and the scavenging port are configured such that the exhaust valve is opened before the cleaning port is opened during the lowering process of the piston. " .

[0006]

In this configuration, the exhaust valve is opened before the scavenging port is opened during the lowering stroke of the piston, so that the exhaust gas in the cylinder bore blows out toward the exhaust port. In this case, since the exhaust gas guiding groove is provided on the inner wall surface of the valve recess with respect to the exhaust valve so as to be inclined in a tangential direction, the exhaust gas ejected toward the exhaust port at the moment when the exhaust valve is opened is the exhaust gas. Since the gas is ejected while being swirled by the guide action of the gas guiding groove, a swirling flow can be induced in the cylinder bore.

Next, when the scavenging port is opened, new intake air flows into the cylinder bore in the tangential direction via the scavenging port, so that a swirling flow can be given to the cylinder bore.

[0008]

As described above, according to the present invention, a swirl flow can be induced in the cylinder bore before introducing new intake air tangentially from the scavenging port into the cylinder bore. In other words, the swirl flow can be induced in the cylinder bore. Before the introduction of new intake air from the scavenging port, the swirl flow can be given in advance, and the swirl flow in the cylinder bore can be greatly improved as compared with the conventional case. This has the effect of reliably achieving promotion of combustion and promotion of combustion.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. In the figure, reference numeral 1 denotes a cylinder block in which a cylinder bore 3 with a built-in piston 2 is formed, and reference numeral 4 denotes
The cylinder head fastened to the upper surface of the cylinder block 1 with a gasket 5 interposed therebetween is shown.

On the lower surface of the cylinder head 4, a valve recess 6 is formed in a substantially central part of the cylinder bore 3, while an exhaust port 7 is opened in the cylinder head 4. An exhaust valve 8 is provided at an opening of the exhaust port 7 into the valve recess 6. Further, the cylinder block 1 is provided with a plurality of scavenging ports 9 which are opened in the middle of the lowering stroke of the piston 2 so as to open tangentially to the cylinder bore 3. In the middle of the stroke, first, the exhaust valve 8 is opened, and then each of the scavenging ports 9 is opened, so that new intake air is introduced into the cylinder bore 3.

The inner wall surface of the valve recess 6 with respect to the exhaust valve 8 is provided at a plurality of positions in the circumferential direction.
An exhaust gas guide groove 10 for guiding exhaust gas into the valve recess 6 is provided to be inclined in the same tangential direction as the tangential direction of each of the scavenging ports 9. In this configuration, when the exhaust valve 8 starts opening during the downward stroke of the piston 2, the exhaust gas in the cylinder bore 3 is ejected toward the exhaust port 7. In this case, a plurality of exhaust gas guiding grooves 10 are provided on the inner wall surface of the valve recess 6 with respect to the exhaust valve 8 so as to be inclined in the tangential direction. The exhaust gas that is ejected by the exhaust gas is ejected while being swirled by the guide action of the exhaust gas guide grooves 10 as shown by the arrow A in the figure, thereby inducing a swirling flow in the cylinder bore 3. Can be.

When each scavenging port 9 is opened following the opening of the exhaust valve 8, new intake air flows into the cylinder bore 3 in a tangential direction through each scavenging port 9. As shown by an arrow B in FIG.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a bottom view as viewed in the direction of line III-III in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Piston 3 Cylinder bore 4 Cylinder head 6 Valve recess 7 Exhaust port 8 Exhaust valve 9 Scavenging port 10 Exhaust gas guide groove

Claims (1)

(57) [Scope of request for utility model registration] 1. A cylinder block having a cylinder bore.
Of the lower surface of the cylinder head fastened to the upper surface
A valve recess is formed substantially at the center of the cylinder bore, and an exhaust port is provided in the cylinder head.
This exhaust port is provided so as to open to the valve recess.
An exhaust valve is provided at the opening to the valve recess, and the cylinder block is further provided with a piston in the cylinder bore.
In a two-cycle engine in which a scavenging port that is opened and closed by reciprocating motion is provided to be inclined in a tangential direction with respect to a cylinder bore, at least an inner wall surface of a valve recess with respect to the exhaust valve is provided for guiding exhaust gas into the valve recess. One exhaust gas guide groove is provided to be inclined in the same tangential direction as the tangential direction of the scavenging port, and the exhaust valve and the scavenging port
A cleaning port during the lowering process of the piston.
A two-stroke engine characterized in that the exhaust valve is opened before the valve opens .