JPH09158737A - Scavenging device of two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the scavenging efficiency by eliminating a non-scavenging region at the center of a cylinder. SOLUTION: A scavenging passage 6 is formed around an outer circumference of cylinders 1, 1 arranged in series in a scavenging chamber 2, a fresh air introducing port 7 to introduce the fresh air in the scavenging chamber 2 is opened in the tangential direction relative to the outer circumference of the cylinder 1, a scavenging port 4 in a circumferential wall 3 of the cylinder is inclined in the reverse direction to the scavenging flow direction in the scavenging chamber 2, and the scavenging flow in the direction to be determined by the direction of inclination of the scavenging port 4 from the scavenging chamber 2 in the stationary condition of the constant pressure in the initial stage of opening the scavenging port 4 is first formed in the cylinder 1. When the scavenging port 4 is opened in the middle or subsequent stage, the scavenging flow in the scavenging chamber 2 flows into the cylinder 1 to form the swirl flow in the cylinder 1 in the direction determined by the scavenging flow direction of the scavenging chamber 2, and the non-scavenging region at the central part of the cylinder 1 is eliminated by changing the scavenging flow direction in the cylinder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scavenger for a two-cycle engine, and more particularly to a uniflow scavenger (single-flow scavenging) scavenger for a multi-cylinder two-cycle engine.

[0002]

2. Description of the Related Art As a scavenging method for a two-cycle engine,
There is a uniflow scavenging method. The basic structure of the uniflow scavenging two-cycle engine is configured as shown in FIG. 2 (see Japanese Utility Model Laid-Open No. 63-15529). That is, the two-cycle diesel engine shown in FIG. 2 has a plurality of scavenging holes 2 at the intermediate height position of the cylinder peripheral wall 23.
4 is formed, and fresh air pressurized by the scavenging pump 38 is introduced into the cylinder 21 through the scavenging hole 24 as shown by an arrow, and the combustion gas is discharged from the exhaust valve 32 in the open state to the exhaust port 33. Is configured.

In such a two-cycle engine of the uniflow scavenging system in which gas flows in one direction in the cylinder 21 to perform scavenging, the one having a plurality of cylinders 21 is a cylinder in which a plurality of cylinders 21 are arranged in series. A water cooling jacket 35 is provided above the block 34 so as to surround each cylinder.
Is formed, and at the bottom thereof, as shown in FIG.
A single scavenging chamber 22 communicating with each other is formed around the cylinder, and fresh air is introduced into the cylinder 21 from the scavenging chamber 22 through a plurality of scavenging holes 24 formed in a cylinder liner 23 that forms a cylinder peripheral wall. It is configured to discharge the combustion gas from the exhaust port 33 provided in the head 36.
Each of the scavenging holes 24 is formed so as to form a swirl in the cylinder 21 and is inclined in the same direction in a tangential direction with respect to the radial axis of the cylinder 21 in an appropriate direction.

Further, if the flow of fresh air in the scavenging chamber 22 causes a reverse flow every time a plurality of cylinders 21 sequentially shifts to the scavenging process, the scavenging efficiency decreases, so that such a reverse flow is prevented from occurring conventionally. There has been proposed a device in which a fresh air introduction port for introducing fresh air is devised in the scavenging chamber 22 or a deflector is appropriately arranged.

In the example of FIG. 3 disclosed in Japanese Utility Model Laid-Open No. 63-15529, for example, fresh air inlets 25 and 26 are provided at one end on one side of the scavenging chamber 22 and the other end on the other side. A pair of scavenging passages 29, 30 are formed by projecting partition projections 27, 28 so that the fresh air introduced from the fresh air introduction ports 25, 26 flows only in one direction. The partition wall 31 is also provided between the cylinder liners 23, 23 so that the fresh air flowing through both scavenging passages 29, 30 does not mix and disturb the flow.
Is provided so that no backflow or the like occurs in the fresh air flow even if each cylinder 21 sequentially enters the scavenging process.

[0006]

By the way, in the configuration of FIG. 3, in order to improve the scavenging efficiency and the combustion efficiency due to the swirl, the scavenging holes 24 are provided in the scavenging passage 29 with respect to the radial axis of the cylinder 21. Although it is formed by inclining in the forward direction at an appropriate angle with respect to the flow direction of the scavenging air in 30, the scavenging air flow in the cylinder 21 is uniform along the inclination direction of the scavenging hole 24 from beginning to end. To be cylinder 2
It has been found that a non-scavenging region is formed in the central portion of No. 1 and as a result, the scavenging efficiency is reduced and output performance and the like are also reduced.

Further, since the fresh air introducing ports 25 and 26 are open toward the center of the cylinder liner 23 at the end portion, a relatively large amount of new air is introduced from the scavenging holes 24 facing the fresh air introducing ports 25 and 26. There is a problem that air flows in, which causes an uneven flow in the cylinder to reduce the scavenging efficiency, and it is also difficult to dispose the fresh air introduction ports 25 and 26 on both sides of the cylinder block in terms of arrangement configuration. There is also the problem that

In view of such conventional problems, the present invention can improve the scavenging efficiency by not forming a non-scavenging region in the central portion of the cylinder, and injecting fresh air evenly from each scavenging port. An object of the present invention is to provide a scavenging device for a two-cycle engine in which the arrangement of the air inlet is easy.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a plurality of cylinders are arranged in series to form a scavenging chamber consisting of a single chamber that surrounds each cylinder and communicates with each other. In a scavenging device of a two-cycle engine in which fresh air is introduced into a cylinder through a plurality of scavenging holes formed in a cylinder, a fresh air that forms a scavenging passage along the outer periphery of a cylinder row and introduces fresh air into a scavenging chamber The inlet is opened tangentially to the outer circumference of the cylinder, and the scavenging hole on the cylinder peripheral wall is formed so as to be inclined in the direction opposite to the scavenging flow direction in the scavenging chamber, so that the scavenging hole is initially constant at the initial opening. A scavenging air flow is formed in the cylinder from the scavenging chamber in the static pressure state, which is determined by the inclination direction of the scavenging hole, and then the scavenging hole opens tangentially to the outer circumference of the cylinder after the middle period. Mouth A strong unidirectional scavenging airflow is generated in the scavenging passage by the fresh air sent, and the scavenging airflow flows into the cylinder through the scavenging hole and a swirl flow in the direction determined by the scavenging flow direction in the scavenging passage is formed in the cylinder. The scavenging efficiency is improved by eliminating the non-scavenging region in the center of the cylinder by changing the direction of the scavenging air flow in the cylinder.

Further, since a scavenging airflow in one direction is formed in the scavenging passage formed along the outer circumference of the cylinder row, even if each cylinder sequentially shifts to the scavenging step, each scavenging port in the surroundings of each cylinder The fresh air flows in evenly, an optimum swirl is formed with the center of the cylinder and the center of the in-cylinder swirl aligned, and scavenging is performed in a state where the combustion exhaust gas and fresh air are less mixed to achieve the highest scavenging efficiency.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG.

In FIG. 1, reference numeral 10 is a cylinder block of a uniflow type scavenging multi-cylinder two-cycle engine, and two cylinders 1 are arranged in series above the cylinder block. A water cooling jacket (see FIG. 2) is formed in the upper part of the cylinder 1 so as to surround the peripheries thereof, and a scavenging chamber 2 composed of a single chamber is formed in the lower part of the cylinder 1 so as to surround the peripheries of the cylinders 1 and communicate with each other. ing. A cylinder liner 3 forming a peripheral wall of each cylinder 1 is fitted. The cylinder liner 3 has a plurality of scavenging holes 4 at appropriate intervals in the circumferential direction so that the inside of the cylinder 1 and the scavenging chamber 2 are communicated with each other.
Is formed, and fresh air is introduced from the scavenging chamber 2 into the cylinder 1 through the plurality of scavenging holes 4, and these scavenging holes 4 are tangential to the radial axis of the cylinder 1 in the same direction. It is formed so as to be inclined, and is configured to form a swirl in the cylinder 1.

Both cylinders 1, 1 are arranged close to each other,
Moreover, the peripheral wall 5 of the scavenging chamber 2 is formed in a gourd shape that is recessed between the cylinders 1 and 1 along the outer circumferences of the cylinders 1 and 1, so that the passage cross-sectional area changes along the circumference of the cylinders 1 and 1. Is formed, and the scavenging air flow is configured to flow substantially uniformly along the circumference of the cylinders 1, 1 row.

A fresh air inlet 7 for introducing fresh air into the scavenging chamber 2 is opened tangentially to the outer circumference of the cylinder 1 arranged at one end of the scavenging chamber 2. A scavenging pump 8 is connected to the fresh air introduction port 7, and the fresh air is supplied from the scavenging pump 8 so that the fresh air flows in the scavenging passage 6 substantially uniformly in one direction. A cylinder head equipped with an exhaust valve and a fuel injection valve is joined to the upper surface of the cylinder block 10.

The inclination of the scavenging hole 4 with respect to the axis line in the radial direction of the cylinder is inclined opposite to the flow direction of the scavenging air flow in the scavenging passage 6.

The operation will be described below. In a state where fresh air is pumped from the scavenging pump 8 to the scavenging passage 6 of the scavenging chamber 2 through the fresh air introducing port 7, the pistons are sequentially lowered in each cylinder 1. As a result, the scavenging hole 4 opens and the exhaust valve provided in the cylinder head opens, so that the combustion gas in the cylinder 1 is discharged from the exhaust port and fresh air flows into the cylinder 1 from the surrounding scavenging holes 4. Then, the scavenging of the cylinder 1 is performed.

At this time, in each cylinder 1, since the inside of the scavenging chamber 2 is in a stationary state at a constant pressure at the initial stage of opening the scavenging hole 4, the scavenging chamber 2 passes through the scavenging hole 4 in the inclination direction thereof. Along with the fresh air flowing into the cylinder 1, the cylinder 1
Inside, a scavenging air flow is formed in a direction determined by the inclination direction of the scavenging holes 4. After that, when the opening of the scavenging holes 4 is in the middle period or later, as the fresh air flow rate increases, the scavenging air flows to the outer periphery of the cylinders 1 and 1 row. A strong unidirectional scavenging airflow is generated in the scavenging passage 6 formed along
The scavenging air flows into the cylinder 1 through the scavenging holes 4 as it is, so that a swirl flow in a direction determined by the scavenging flow direction of the scavenging passage 6 is formed in the cylinder 1. Thus, the direction of the scavenging air flow in the cylinder 1 changes between the initial stage of the scavenging hole 4 and the middle stage and thereafter, so that the non-scavenging region in the central portion of the cylinder 1 is eliminated and the scavenging efficiency is improved.

Further, by introducing fresh air tangentially to the outer periphery of the cylinder 1 from the fresh air introduction port 7 to the scavenging passage 6, the scavenging passage formed along the outer periphery of the cylinder 1, 1 row. Since a unidirectional scavenging airflow is formed at 6, even if each cylinder 1 sequentially shifts to the scavenging process, fresh air uniformly flows into each cylinder 1 from each scavenging hole around the cylinder 1, and the center of the cylinder 1 and the inside of the cylinder 1 The optimum swirl with the same swirl center is formed, and the scavenging is performed in a state where the combustion exhaust gas and fresh air are less mixed to achieve the highest scavenging efficiency.
It is not necessary to provide it on both sides of the row, and the arrangement configuration is easy.

[0019]

According to the scavenging device for a two-cycle engine of the present invention, a scavenging passage is formed along the outer periphery of a cylinder row in which a plurality of cylinders are arranged in series as described above, and fresh air is introduced into the scavenging chamber. The scavenging air flow in the scavenging passage is made uniform by tangentially opening the fresh air inlet to the outer circumference of the cylinder, and the scavenging holes on the cylinder peripheral wall are aligned with the scavenging flow direction in the scavenging chamber. On the other hand, since it is formed by inclining in the opposite direction, in the initial stage of opening the scavenging hole, first, a scavenging air flow is formed in the cylinder from the static scavenging chamber at a constant pressure in the direction determined by the inclination direction of the scavenging hole, and thereafter. When the opening of the scavenging hole is in the middle period or later, a strong unidirectional scavenging airflow is generated in the scavenging passage, and a swirl flow in a direction determined by the scavenging airflow direction can be formed in the cylinder. Therefore, the direction of the scavenging airflow in the cylinder can be changed. Change the cylinder center It is possible to improve the scavenging efficiency can be eliminated care area. Further, since the scavenging airflow is made to uniformly flow in one direction in the scavenging passage, even if each cylinder sequentially shifts to the scavenging process, fresh air flows evenly from each scavenging port in each cylinder, It is possible to form an optimal swirl where the center of the cylinder and the center of the in-cylinder swirl coincide with each other, and it is possible to perform scavenging in a state where the combustion exhaust gas and fresh air are less mixed, achieving the highest scavenging efficiency. Since it is not necessary to provide them on both sides of the cylinder row, the arrangement configuration can be easily achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional plan view showing a configuration of a scavenging chamber in an embodiment of a scavenging device for a two-cycle engine of the present invention.

FIG. 2 is a vertical sectional front view of a scavenging device for a conventional two-cycle engine.

FIG. 3 is a cross-sectional plan view showing a configuration of a scavenging chamber in a scavenging device for a conventional two-cycle engine.

[Explanation of symbols]

 1 cylinder 2 scavenging chamber 3 cylinder liner (cylinder peripheral wall) 4 scavenging hole 6 scavenging passage 7 fresh air inlet

Claims (1)

[Claims] 1. A plurality of cylinders are arranged in series to form a scavenging chamber consisting of a single chamber that surrounds each cylinder and communicates with each other, and through the plurality of scavenging holes formed in the cylinder peripheral wall from the scavenging chamber. In a scavenging device for a two-cycle engine in which fresh air is introduced into a cylinder, a scavenging passage is formed along the outer circumference of the cylinder row and a fresh air inlet for introducing fresh air into the scavenging chamber is provided to the outer circumference of the cylinder. A scavenging device for a two-cycle engine, characterized in that the scavenging hole is formed in a tangential direction, and the scavenging hole in the cylinder peripheral wall is inclined in a direction opposite to the scavenging flow direction in the scavenging chamber.