JPH0868357A - Scavenging device for two-cycle engine - Google Patents

Abstract

PURPOSE: To reliably generate a swirl by the cylinders of a multicylinder two-cycle engine and to improve scavenging efficiency. CONSTITUTION: Fresh air is introduced in a cylinder 3 from a scavenging chamber 5 through a plurality of scavenging holes 8 formed in a cylinder liner 7. One side wall of the scavenging hole 8 consists of an outer wall surface inclined in the same direction as the direction of a tangential line based on an axis in a radial direction extending through the center of a pore and a swirl is reliably formed. In a part of the scavenging holes 8a where the direction of a scavenging flow is widely deviated from the inclination direction of a side wall, an in side wall is cut by a surface 18 extending approximately along a radial direction from the inner peripheral edge thereof to increase the effective opening area of the scavenging hole 8a. Further, in all the scavenging holes 8, the other wall may consist of a wall surface extending approximately along a radial direction or a wall surface inclined in a reverse direction.

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 scavenging (single-flow scavenging) scavenger for a multi-cylinder two-cycle engine.

[0002]

2. Description of the Related Art A uniflow scavenging method is one of the scavenging methods for a two-cycle engine. In this type of uniflow scavenging multi-cylinder two-cycle engine, a water cooling jacket is formed in the upper part of a cylinder block in which a plurality of cylinders are arranged in series so as to surround the circumference of each cylinder, and in the lower part thereof is shown in FIG. As described above, the scavenging chamber 22 is formed from a single chamber that surrounds each cylinder 21 and communicates with each other. Fresh air is introduced into the cylinder head, and combustion gas is discharged from an exhaust port provided in the cylinder head.

Each of the above-mentioned scavenging holes 24, as shown in detail in FIG. 7, in order to form a swirl in the cylinder 21,
Both side walls 24a are parallel wall surfaces formed by inclining in the same direction tangentially to the radial axis r passing through the scavenging hole center O by an appropriate angle θ °.

[0004]

However, the scavenging chamber 22
Has a limited volume, and the fresh air supplied to the scavenging chamber 22 passes through a relatively narrow passage having a complicated shape formed between the inner wall of the scavenging chamber 22 and the outer walls of the plurality of cylinder liners 23. Since fresh air flows into the scavenging holes 24 of each cylinder 21, the directions of the scavenging air flow in each scavenging hole 24 are all scavenging holes 2.
4 does not extend in the direction along the both side walls, and in the example of FIG.
As shown by the arrow, the direction of the scavenging air flow is largely deviated from the inclination direction of the side wall.

In this case, as shown in FIG.
There is a problem in that the effective opening width w in the direction of the scavenging air flow indicated by the white arrow becomes significantly smaller than the opening width W of the above, and the pump loss increases by that amount and the scavenging efficiency deteriorates.

Incidentally, JP-A-59-54730, JP-A-61-215419 and JP-A-63-1155.
Although Japanese Patent Publication No. 29 and the like disclose devices in which the shape of the scavenging holes is devised, those technical means are not for such problems, and the above problems cannot be solved.

In view of such conventional problems, the present invention is a two-cycle engine capable of forming a swirl in each cylinder and increasing the scavenging efficiency when scavenging a plurality of cylinders from a single scavenging chamber. The purpose of the present invention is to provide a scavenging device.

[0008]

According to a first aspect of 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 for a two-cycle engine in which fresh air is introduced into the cylinder through a plurality of scavenging holes formed in the cylinder peripheral wall, both side walls of the scavenging hole are tangential to the radial axis passing through the center of the scavenging hole. The scavenging holes are formed with parallel wall surfaces that are inclined in the same direction, and the direction of the scavenging air in the scavenging holes is largely deviated from the inclination direction of the side walls. It is characterized by being cut off at a surface along the direction.

A second aspect of the present invention is the scavenging device for a two-cycle engine, wherein one side wall of each scavenging hole is outwardly sloping in the same direction in a tangential direction with respect to a radial axis passing through the center of the scavenging hole. It is characterized in that the other side wall of each scavenging hole is formed from the inner peripheral edge of the scavenging hole in a substantially radial direction or a wall surface inclined in the opposite direction to the one side wall.

[0010]

According to the first invention of the present application, in a relatively large number of scavenging holes, fresh air flows into the cylinder from the scavenging chamber along the inclination direction of both side walls thereof, thereby forming a swirl in the cylinder. And, in some scavenging holes where the direction of the scavenging air flow in the scavenging hole is largely deviated from the inclination direction of the side wall, the side wall that blocks the fresh air from flowing into the cylinder and reduces the effective opening area, By cutting the surface along the substantially radial direction, the effective opening area is increased, the pump loss is reduced, and the scavenging efficiency is improved.

Further, according to the second aspect of the invention, for all the scavenging holes, one side wall is inclined along the swirl flow direction, and the other side wall is inclined substantially along the radial direction or in the opposite direction. Even if the flow direction of fresh air changes depending on the operating state, the maximum effective opening area can always be secured, pump loss can be reduced and scavenging efficiency can be improved in all operating states, and in many scavenging holes The fresh air flowing from the scavenging chamber into the cylinder flows along the inclination direction of the one side wall, so that the swirl can be reliably formed without hindering the swirl forming action.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.

In FIGS. 1 and 2, reference numeral 1 is a cylinder block of a uniflow type scavenging multi-cylinder two-cycle engine, and a plurality of (three in the figure) cylinders 3 are arranged in series in a cylinder arranging portion 2 above the cylinder block. It is installed in.
A water cooling jacket 4 is formed at an upper portion of the cylinder arranging portion 2 so as to surround each of the cylinders 3, and a scavenging chamber 5 that surrounds the periphery of each of the cylinders 3 and is composed of a single chamber communicating with each other is formed at a lower portion thereof. ing. Further, a scavenging gas introduction opening 6 communicating with the scavenging chamber 5 is formed on one side surface of the upper portion of the cylinder block 1 so as to project outward on one side. This scavenging introduction opening 6 is formed long in the arrangement direction of the cylinders 3 except for both ends of the cylinder block 1, and the height dimension in the vertical direction is also larger than that of the scavenging chamber 5, and functions as a surge tank. Is made to do.

A cylinder liner 7 forming a cylinder wall is fitted on the inner circumference of each cylinder 3 as shown by phantom lines in FIG. As shown in detail in FIG. 3, the cylinder liner 7 is provided with a plurality of scavenging ports 8 opening to the scavenging chamber 5 at positions corresponding to the upper part of the scavenging chamber 5 at appropriate intervals in the circumferential direction. Both side walls of the scavenging hole 8 in each of the cylinder liners 7 are parallel wall surfaces that are tangentially inclined in the same direction with respect to the radial axis r passing through the center O of the scavenging hole 8 as described in FIG. Although formed, the direction of the scavenging air flow in the scavenging holes 8 (indicated by an arrow in FIG. 3) is largely deviated from the inclination direction of the side wall of the scavenging holes 8
In a, as shown in detail in FIG. 4, one inwardly facing side wall 8b, which is an obstacle to the inflow of the scavenging airflow, is cut off from the inner peripheral edge thereof by a surface 18 extending substantially in the radial direction.

In FIG. 1, a piston 9 is fitted in the cylinder liner 7 so as to be vertically slidable. Further, a skirt portion 11 that constitutes the crank chamber 10 is formed in the lower portion of the cylinder block 1. A blow-by gas passage 12 penetrating from the crank chamber 10 toward the upper end surface of the cylinder block 1 is formed by vertically penetrating a position of the scavenging introduction opening 6 facing between the cylinder holes 3 and 3. Further, as shown by a phantom line in FIG. 2, a scavenging pump 13 is connected to the scavenging introduction opening 6 so as to supply a scavenging air flow. Although not shown, a cylinder head equipped with an exhaust valve and a fuel injection valve is joined to the upper surface of the cylinder block 1.

In the above structure, the piston 9 descends and the scavenging ports 8 and 8a are opened while the scavenging air is pumped from the scavenging pump 13 to the scavenging chamber 5 through the scavenging introduction opening 6 and the cylinder head is opened. By opening the exhaust valve provided in, the combustion gas is discharged from the exhaust port and the scavenging air flows into the cylinder 3 for scavenging.

At this time, in a relatively large number of scavenging holes 8, the scavenging chamber 5 and the cylinder 3 are arranged along the inclination direction of both side walls thereof.
A swirl is surely formed in each cylinder 3 by the fresh air flowing into the cylinder 3. At the same time, in a part of the scavenging holes 8a in which the direction of the scavenging air flow in the scavenging holes 8 is largely deviated from the inclination direction of the side walls, the side walls 8b which prevent fresh air from flowing into the cylinder 3 have a substantially radius. Face 1 along the direction
By cutting at 8, the effective opening area through which the scavenging air passes increases as indicated by W'in FIG. 4, so pump loss can be reduced and scavenging efficiency can be improved, so that in each cylinder 3 Swirl can be reliably formed and scavenging efficiency can be increased.

Further, since the scavenging chamber 5 and the scavenging introduction opening 6 function as a surge tank, it is possible to absorb the intake pulsation caused by the scavenging performed by shifting the timings between the cylinders 3 to obtain a smooth and uniform scavenging. It is performed stably.
Further, the scavenging gas flowing out to the crank chamber 10 is returned to the scavenging gas through the blow-by gas passage 12 and the cylinder head.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only different components will be described.

In the first embodiment described above, only the part of the scavenging holes 8a whose direction of the scavenging air flow is largely deviated from the inclination direction of the side walls of the scavenging holes 8 has its side wall 8b extending substantially radially.
Although the direction of the scavenging airflow in the scavenging chamber 6 is not always constant and changes depending on the engine operating state, the direction of the scavenging airflow is largely deviated from the inclination direction of the side wall of the scavenging hole 8. The scavenging holes 8a are not always constant. Therefore, in this embodiment, in each scavenging hole 8, one side wall 19 of the scavenging hole 8 is formed as an outwardly facing wall surface that is inclined in the same direction in the tangential direction with respect to the radial axis passing through the center of the scavenging hole, and the other side wall 20 thereof is formed. It is configured by a wall surface extending substantially in the radial direction from the inner peripheral edge or a wall surface inclined in the opposite direction to the one side wall 19.

According to this embodiment, one side wall 19 of all the scavenging holes 8 is inclined along the swirl flow direction, and the other side wall 20 is inclined substantially along the radial direction or in the opposite direction. Even if the flow direction of fresh air changes depending on the actual operating state, the maximum effective opening area can be always secured in all the scavenging holes 8, and pump loss is reduced to improve scavenging efficiency in all operating states. it can. Moreover, in many scavenging holes 8, the fresh air flowing from the scavenging chamber 6 into the cylinder 7 flows along the inclination direction of the one side wall 19 so that the swirl formation action is not hindered, and the swirl is surely performed. Can be formed.
When the other side wall 20 is inclined in the opposite direction with respect to the one side wall 19, the effective opening area increases and the swirl formation effect tends to be weaker than when the other side wall 20 is inclined in the substantially radial direction. It may be appropriately designed depending on operating conditions and the like.

[0022]

According to the scavenging device for a two-cycle engine of the first invention of the present application, as described above, in a relatively large number of scavenging holes, fresh air is introduced into the cylinder from the scavenging chamber along the inclination direction of both side walls thereof. The swirl can be surely formed in the cylinder due to the inflow of air, and the fresh air enters the cylinder in some of the scavenging holes in which the direction of the scavenging air in the scavenging hole is largely deviated from the inclination direction of the side wall. By blocking one side wall that blocks the inflow and reduces the effective opening area with a surface that extends in a substantially radial direction, the effective opening area can be increased to reduce pump loss and improve scavenging efficiency. it can.

According to the scavenging device for a two-cycle engine of the second invention, one side wall of all the scavenging holes is inclined along the flow direction of the swirl, and the other side wall is arranged substantially along the radial direction or one side wall. Is tilted in the opposite direction,
Even if the flow direction of fresh air changes depending on actual operating conditions, the maximum effective opening area can always be secured, pump loss can be reduced and scavenging efficiency can be improved in all operating conditions, and in many scavenging holes. The swirl can be surely formed without disturbing the swirl forming action by the fresh air flowing from the scavenging chamber into the cylinder along the inclination direction of the one side wall.

Therefore, according to the present invention, the swirl can be surely formed in each cylinder and the scavenging efficiency can be enhanced.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a cylinder block of a two-cycle engine according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional plan view taken along the line AA of FIG.

FIG. 3 is a cross-sectional plan view showing details of scavenging holes of each cylinder in the same embodiment.

FIG. 4 is an enlarged cross-sectional plan view of a scavenging hole of a main part of the embodiment.

FIG. 5 is a cross-sectional plan view showing details of the scavenging holes of each cylinder of the cylinder block of the two-cycle engine in the second embodiment of the present invention.

FIG. 6 is a cross-sectional plan view showing details of a scavenging hole of each cylinder in a conventional example.

FIG. 7 is an enlarged transverse plan view of a scavenging hole of a conventional example.

[Explanation of symbols]

 3 Cylinder 5 Scavenging chamber 7 Cylinder liner 8 Scavenging hole 8a Scavenging hole 18 Surface along substantially radial direction 19 Side wall 20 Other side wall

Claims (2)

[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, both side walls of the scavenging hole are formed by parallel wall surfaces inclined in the same direction in a tangential direction with respect to a radial axis passing through the center of the scavenging hole. However, in some scavenging holes in which the direction of the scavenging air flow in the scavenging hole is largely deviated from the inclination direction of the side wall, the side wall facing inward in the radial direction is cut off from the inner peripheral edge with a surface extending substantially in the radial direction. A two-cycle engine scavenger. 2. 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 scavenger for a two-cycle engine in which fresh air is introduced into a cylinder, an outward wall surface in which one side wall of each scavenging hole is inclined in the same direction in a tangential direction with respect to a radial axis passing through the center of the scavenging hole. And the other side wall of each scavenging hole is constituted by a wall surface extending from the inner peripheral edge thereof in a substantially radial direction or a wall surface inclined in the opposite direction to the one side wall.