JPH08218936A - Scavenging chamber structure of two-cycle engine - Google Patents

Abstract

PURPOSE: To secure capacity of a scavenging chamber sufficient to satisfy engine performance by penetrating cylinder head fixing bolts through the inside of recessed parts formed on an inside surface of the scavenging chamber. CONSTITUTION: Recessed parts 12 recessed in the vertical direction, that is, in the stroke direction of a piston from an inside surface of a scavenging chamber 4, are provided, and bolts 10 are penetrated here. Scavenging ports 3 are arranged aside to the upper side of the scavenging chamber 4, and by being constituted in this way, even if the scavenging ports 3 are bored in the diameter direction of cylinder liners 2, a scavenging inflow running toward upper parts of the cylinder liners 2 is obtained. When the scavenging ports 3 are opened aside to the lower side of the scavenging chamber 4, a downward scavenging inflow is obtained. Therefore, since the bolts themselves do not project to a space of the scavenging chamber, sufficient capacity of the scavenging chamber can be secured, and scavenging efficiency of an engine can be further enhanced without causing a turbulent flow in an air flow of the scavenging chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a scavenging chamber in a two-stroke engine, and is particularly used in the field of making the spatial shape of the scavenging chamber more advantageous.

[0002]

2. Description of the Related Art Before describing the prior art, a two-cycle engine to which the present invention is applied will be described with reference to FIG. 3, which is a uniflow type engine.
The cylinder liner 2 is inserted into the cylinder block 1,
A plurality of scavenging ports 3 are opened there. The scavenging chamber 4 formed in the cylinder block 1 is configured to surround the scavenging port 3. Cylinder head 5
Is fixed to the cylinder block 1 with bolts described later,
It has an exhaust port 6 and an exhaust valve 7. Reference numerals 8 and 9 are a piston and a connecting rod, respectively. Engines of this type are disclosed in Japanese Utility Model Laid-Open Nos. 63-15529 and 62-133945. The bolt 10 for fixing the cylinder head will be described with reference to FIG. 4 and FIG.
Since it is arranged in the vicinity of, the boss portion 11 is formed in a state of being raised in the space of the scavenging chamber 4, and the bolt 10 is passed through the boss portion 11.

[0003]

In the prior art as described above, since the boss portion 11 is raised in the scavenging space of the scavenging chamber 4, it becomes impossible to secure a required passage sectional area.
Therefore, when the bolt 10 is retracted in the diametrical direction of the cylinder in order to eliminate the raised portion, the pitches A and B (see FIG. 1) of the bolt 10 are increased as a result. Such an increase in pitch causes an increase in the outer dimensions of the cylinder head and the cylinder block, which is not preferable for downsizing the entire engine. Furthermore, the above-described pitch expansion is a factor that reduces the sealability between the cylinder head and the cylinder block and the joint rigidity, which is also not preferable. Furthermore, the important point is that the scavenging air in the scavenging chamber 4 behaves as smoothly as possible without being disturbed, and it is necessary to secure a sufficient scavenging chamber capacity to satisfy the engine performance. Nevertheless,
With this conventional technology, since the structure is as shown in the figure,
There is a problem that these important items cannot be realized.

[0004]

Means for Solving the Problem and Its Action The present invention was devised to solve the above-mentioned problems.
In a two-cycle engine having a scavenging chamber around a scavenging port, a bolt for fixing a cylinder head is characterized by passing through a recess formed on the inner surface of the scavenging chamber. , The raised boss part as mentioned above is abolished.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in FIGS. 1 and 2 will be described below. For members having the same functions as those shown in FIGS. 3 to 5, the same reference numerals are given in the drawings for detailed description. The description is omitted. FIG. 1 shows (1)-of FIG.
(1) It is a cross-sectional plan view shown in the form of a cross section, showing a scavenging chamber 4
A recess 12 is formed by denting it from the inner surface in the longitudinal direction, that is, along the stroke direction of the piston, and a bolt 10 is inserted therethrough. Reference numeral 13 is an air supply port that supplies air to the scavenging chamber 4, and is connected to a scavenging pump (not shown). In FIG. 2, the scavenging port 3 is a scavenging chamber 4
Of the scavenging port 3 in the diametrical direction of the cylinder liner 2 so that the scavenging gas inflow toward the upper side of the cylinder liner 2 can be obtained. Further, although not shown, if the scavenging port 3 is biased to the lower side of the scavenging chamber 4 and opened, a downward scavenging inflow can be obtained this time. The engine of the embodiment is water-cooled, and reference numeral 14 indicates a water jacket therefor. Further, reference numeral 15 indicates an inner surface of the scavenging chamber 4, and this inner surface is in the form of a cylindrical surface along the cylinder liner 2.

[0006]

According to the present invention, since the bolt for fixing the cylinder head is arranged in the recess formed on the inner surface of the scavenging chamber, the bolt itself can be projected into the space of the scavenging chamber. Therefore, it is possible to secure a sufficient capacity of the scavenging chamber, and to further improve the scavenging efficiency of the engine without causing turbulence in the air flow in the scavenging chamber. As shown in FIG. 4, the raised boss portion is eliminated and the bolts are arranged in the recesses. Therefore, it is possible to deal with the bolt positions, that is, the bolt pitch without enlarging. It is possible to avoid problems in terms of "property" and "coupling rigidity", and to make the entire engine compact.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view showing an embodiment of the present invention.

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

FIG. 3 is a vertical sectional side view of an engine to which the present invention is applied.

FIG. 4 is a partial transverse plan view of the prior art.

5 is a sectional view taken along line (5)-(5) of FIG.

[Explanation of symbols]

 3 Scavenging port 4 Scavenging chamber 10 Volt 12 Recess

Claims (1)

[Claims] 1. A two-cycle engine having a scavenging chamber around a scavenging port, wherein a cylinder head fixing bolt penetrates a recess formed in the inner surface of the scavenging chamber. Engine scavenging chamber structure.