JPH07109926A - Cylinder for two-cycle engine - Google Patents

Abstract

PURPOSE:To provide a cylinder for two-cycle engine, which is capable of reducing the capacity of a crank case, increasing the primary compression ratio of intake air, rectifying the flow of scavenging air so as to increase the scavenging efficiency, and thereby obtaining high output. CONSTITUTION:Block pieces 10 lined up nearly in parallel, are provided on the wall faces 11 of main scavenging passages 9 provided in a crank case 8, and the block pieces 10 are connected to the lower ends of the inner walls 12 of main scavenging passages 3 located on the right and the left of a cylinder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder for a two-cycle engine.

[0002]

2. Description of the Related Art A cylinder of a two-cycle engine has a scavenging passage and an exhaust hole integrally provided outside the cylinder hole.
It is formed by casting using cast iron or light alloy.

In the cylinder, as shown in FIG. 3, scavenging passages B are integrally provided on the left and right sides of the cylinder A, and the lower side is communicated with a scavenging passage D provided in a crankcase C. The lower side of the cylinder A has a cylindrical shape F around the cylinder hole E.
Then, the crankcase C is precisely fitted and tightened.

[0004]

In order to cut the lower side of the cylinder A into a cylindrical shape F, the lower part of the inner wall G of the scavenging passage B provided in the cylinder A is placed outside the outer peripheral surface of the cylindrical shape F. It cannot be expanded. Therefore, the cross-sectional area of the scavenging passage D portion provided in the crankcase C becomes large,
The scavenging passage D becomes wider. This increases the volume of the crankcase chamber and lowers the primary compression ratio of intake air.
Further, there is a problem that the flow of scavenging becomes slow and the scavenging efficiency decreases.

In view of the above point, the present invention provides a cylinder of a two-cycle engine which can reduce the volume of the crank chamber, increase the primary compression ratio of intake air, and rectify the flow of scavenging air to improve the scavenging efficiency and to increase the output. The purpose is to

[0006]

In order to achieve the above object, the cylinder of the two-cycle engine of the present invention is provided with a block piece aligned substantially parallel to the wall surface of the main scavenging passage provided in the crankcase. Is connected to the lower end of the inner wall of the main scavenging passage on the left and right of the cylinder.

[0007]

Since the block piece is connected to the lower end of the inner wall of the main scavenging passage on the left and right of the cylinder, the block piece can be prevented from being affected by the cylindrical processing portion on the lower side of the cylinder, and the main scavenging passage provided on the crankcase can be provided. Can be commensurate with the passage area of the main scavenging passage provided in the cylinder. For this reason,
The volume of the crank chamber can be reduced, and the primary compression ratio of intake air can be increased. Further, the flow of scavenging air can be rectified, and the scavenging efficiency is improved.

[0008]

Embodiments of the present invention will be described below with reference to FIGS. The cylinder 1 has a vertical cylinder hole 2, a main scavenging passage 3 on the left and right, a sub scavenging passage 4 on the rear side, and an exhaust hole 5 on the front side.
In addition, a water jacket 6 is provided around the water jacket to make it a water-cooled type. The cylinder 1 is machined into a cylinder 7 around the cylinder hole 2 on the lower side to form a crankcase 8
It is designed to fit precisely in. The crankcase 8 is provided with a main scavenging passage 9 communicating with the left and right main scavenging passages 3 of the cylinder 1, and the block piece 10 is connected to the main scavenging passage 9.
Are provided so as to be substantially parallel to the wall surface 11. Then, the block piece 10 is fitted and fitted to the lower end of the inner wall 12 of the main scavenging passage 3 of the cylinder 1, and is tightened and connected by using a bolt 13.

Since the block piece 10 is connected to the lower end of the inner wall 12 of the main scavenging passage 3 after processing the cylinder 7 on the lower side of the cylinder 1, the block piece 10 is stretched outside or on the lower side without being restricted by the surface of the cylinder 7. Can be issued. For this reason, the passage area of the main scavenging passage 9 provided in the crankcase 8 can be commensurate with the passage area of the main scavenging passage 3 of the cylinder 1.

[0010]

As described above, since the present invention is configured as described above, the block piece 10 is connected to the lower side of the inner wall 12 of the left and right main scavenging passages 3 of the cylinder 1, so that the crank The passage area of the main scavenging passage 9 of the case 8 can be made to match the passage area of the main scavenging passage of the upper cylinder 1. As a result, the volume of the crank chamber 14 of the crankcase 8 can be reduced, and the primary compression ratio of intake air can be increased. Further, the flow of scavenging air can be smoothly rectified, the scavenging efficiency is improved, and the engine output can be increased.

[Brief description of drawings]

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

FIG. 2 is a bottom view of a cylinder showing an embodiment of the present invention.

FIG. 3 is a vertical sectional view showing a conventional example.

[Explanation of symbols]

 1 Cylinder 3 Main Scavenging Passage 8 Crankcase 9 Main Scavenging Passage 10 Block Piece 11 Wall Surface 12 Inner Wall

Claims (1)

[Claims] 1. A block piece arranged substantially parallel to a wall surface of a main scavenging passage provided in a crankcase, and the block piece is connected to lower ends of inner walls of left and right main scavenging passages of a cylinder. A cylinder of a two-cycle engine.