JPS6238856A - Cylinder structure of two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent the anomaly and output reduction of an engine by forming a sealing surface at a part of a cylinder block body and forming an insertion part onto the sealing surface and fitting the cylinder edge pieces forming the skirt part into the insertion part. CONSTITUTION:A cylinder block 1 is constituted of a body 10 and a plurality of cylinder edge pieces 11. In this case, the sealing surface 10a of the body 10 which contacts with the sealing surface 4a of a crankcase 4 is formed flat. Further, an insertion part 10b is formed onto the cylinder 1c on the sealing surface 10a side. The cylinder edge pieces 11 are fitted into the insertion part 10b, projecting the skirt part 6. Further, each crankcase is fitted onto the outer peripheral surfaces 6a and 6b of the skirt part 6. Therefore, no gap is generated between the cylinder block 1 and the sealing surface of the crankcase. Therefore, mixing of outside air in the crank chamber and the effluence of the mixed gas can be prevented, and the prescribed purposes can be achieved.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cylinder structure for a two-stroke engine in which a plurality of cylinders are integrally molded. [Prior art] For example, the two-stroke engine shown in FIG.
To reduce weight, multiple cylinders are integrally molded. In FIG. 8, 1 is a cylinder block, 2 is a cylinder head, 8A and 8B are pistons, and 4 is a crankcase. As shown in FIG. 4, the cylinder block 1 and the crankcase 4 are separate bodies, and the sealing surface 1a of the cylinder block
, 1b and the sealing surfaces 4a, 4b of the crankcase 4 are in contact with each other with a gasket interposed therebetween, thereby making the inside of the cylinder IC and the crank chamber 5 airtight. Further, the skirt portion 6 of the cylinder block 1 is fitted onto the crankcase 4 to facilitate positioning of the cylinder block 1 and the crankcase 4. On the other hand, in a two-stroke engine, as shown in FIG. 8, as the piston 8A rises, the pressure in the crank chamber 6 decreases, and the air-fuel mixture flows into the crank chamber from an intake port (not shown). At the same time, the lowering of the piston 8B compresses the air-fuel mixture in the crank chamber 5, and the compressed air-fuel mixture passes through the scavenging passage 7 and flows out from the scavenging port 8 into the cylinder 1C. At this time, the combustion gas remaining in the cylinder IC is scavenged to the exhaust port 9.

[Problems to be solved by the invention]

However, in the above-mentioned prior art, the sealing surfaces 1a and lb of the cylinder block 1 and the outer peripheral surfaces 6a and 6b of the skirt portion 6 shown in FIG. The first process involves machining the seal surface 1b and the outer surface 6b with a lathe, and the corner seal surface (not shown) that cannot be machined with a lathe is machined with an end mill or the like. This is done in the eighth process. Therefore, a pole (slight step (not shown)) is generated on the sealing surfaces 1b and 1b by the first processing, the second processing, and the eighth processing. When assembling the case 4, this causes a gap to be created between the two seal surfaces 1m and 41 or between the seal surfaces 1b and 4b.And when the air-fuel mixture flows into the crank chamber 6, the crank chamber 6 Since the air-fuel mixture is in a negative pressure state, outside air flows in from the upper faN, thinning the air-fuel mixture and causing engine abnormality.On the other hand, when scavenging the air-fuel mixture in the crank chamber 5, is in a pressurized state, the air-fuel mixture escapes from the gap, resulting in insufficient pre-pressure in the crank chamber 6, which causes a decrease in engine output due to a decrease in filling amount. This was done in order to solve the problem, and the purpose is to provide a cylinder structure for a two-stroke engine that is free from the risk of engine abnormality or reduction in engine output. EMeans for solving the problem] In order to achieve the above object, the present invention first consists of a cylinder block consisting of a cylinder block main body and a plurality of cylinder end pieces.Furthermore, the sealing surface of the main body that contacts the crankcase is made flat. Furthermore, a feeding section is provided on the sealing surface, and the cylinder end piece forming the skirt section is fed into the feeding section. [Operation] According to the present invention, the cylinder block is inserted between the main body and the cylinder end Since it is constructed from one piece and the sealing surface that contacts the crankcase of the main body is made flat, the sealing surface can be machined to be smooth, so there is no risk of creating a gap between the sealing surface between the cylinder block and the crankcase. Furthermore, since a fitting portion is provided on the sealing surface and the cylinder end piece forming the skirt portion is fitted into the fitting portion, positioning of the cylinder block and the crankcase is easy.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a longitudinal section of a cylinder block 1 according to Jin's invention, and FIG. 2 shows a cylinder block main body 10 according to the invention. In these figures, Figures 8 and 4
Components that are the same as or corresponding to those in the conventional example shown in the drawings are given the same reference numerals, and detailed explanation thereof will be omitted. As shown in FIG. 1, the cylinder block 1 consists of the main body 10 and a plurality of cylinder end pieces 11, and in this embodiment, the number of cylinder end pieces 11 is two. As shown in FIG. 2, the main body 10 has a flat sealing surface 10m that comes into contact with the sealing surface 4a of the crankcase 4 shown in FIG. A feeding portion 10b is formed in the cylinder IC on the side of this sealing surface 10s1. As shown in FIG. 1, the cylinder end piece 11 is inserted into the insertion portion 10b with its skirt portion 6 protruding. The crankcase 4 shown in FIG. 4 is attached to the outer peripheral surfaces 6a and 6b of the skirt portion 6, respectively. In this way,
This facilitates positioning of the cylinder block 1 and crankcase 4. Next, the processing procedure for the cylinder IC having the above configuration will be explained. In FIG. 2, first, the reference surface 1d is smoothed. Next, with this reference surface 1d as a reference, the sealing surface is 10m.
Process to make it smooth. This processing. This may be done using a lathe or a milling machine. Thereafter, the inner surface of the cylinder 1C is rough-processed, and the fitting portion tab is further processed. In this way, the processed sealing surface 10a can be processed in -times, so that no level difference occurs. On the other hand, in the cylinder end pieces 11 shown in FIG. 1, the outer circumferential surfaces am and 6b of the skirt portion 6 and the fitting surfaces 11a and llb are processed individually. As shown in FIG.
0b to form an integrated cylinder block 1. Thereafter, the inner surface of the cylinder IC is finished, and finally the inner surface is subjected to surface treatment by plating or wire blast spraying. If the inner surface of the cylinder IC is finished after the cylinder IC is integrated as in the case of Jin, there will be no step on the divided surface 12 of the cylinder IC. This integrated cylinder block 1 is then transferred to the fourth cylinder block 1.
Although it is integrated with the crankcase 4 shown in the figure, since the sealing surface 10m is a flat surface as described above, there is no gap between it and the sealing surface 4a of the crankcase 4 shown in FIG. Therefore, if the pressure of the air-fuel mixture in the crank chamber fluctuates as the piston 8 moves, outside air may enter the crank chamber from outside, or the air-fuel mixture may flow out of the crank chamber from a source other than the insertion passage 7. There is no. Therefore, engine abnormalities and reductions in engine output can be effectively prevented. The piston ring 8a of the piston 8 is preferably set so as not to pass through the dividing surface 12 during engine operation. Further, it is preferable that the main body 10 and the cylinder end piece 11 be made of the same material from the viewpoint of performance, processing, aging, etc. [Effects of the Invention] As explained above, according to the present invention, the rail surface of the cylinder block body that comes into contact with the crankcase can be processed to be smooth, so there is no gap between the sealing surface between the cylinder block and the crankcase. It never occurs. Therefore, since the oil does not leak into the crank chamber, engine abnormalities and output reduction can be effectively prevented. Further, the positioning of the cylinder block and crankcase is easy as in the conventional case.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of an embodiment of the present invention, Fig. 2 is a longitudinal sectional view of the cylinder block main body, Fig. 8 is a longitudinal sectional view showing an example of a two-stroke engine, and Fig. 4 is a longitudinal sectional view of a conventional cylinder block. FIG. 3 is an exploded longitudinal cross-sectional view of the crankcase. l...Cylinder block, 10a...Seal surface, I
C...Cylinder, 4...Crankcase, 6...
Skirt part, lO... Cylinder block body, 11.
... Cylinder end piece.

Claims (1)

[Claims] (1) In a two-stroke engine cylinder structure in which multiple cylinders are integrally molded and each cylinder is equipped with a skirt portion that is fitted into the crankcase, a cylinder block body with multiple cylinders is flatly attached to one end of the cylinder block body. A cylinder structure for a two-cycle engine, characterized in that a sealing surface is formed, a fitting part is provided on the sealing surface, and a cylinder end piece forming the skirt part is fitted into the fitting part.