JPS63239341A - Cylinder sleeve for two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent a petal pattern from being formed when honing the inner surface of a cylinder sleeve, by tilting double side edges of the cylinder circumferential direction of a scavenging inlet to the cylinder longitudinal direction. CONSTITUTION:A cylinder sleeve 18 is attached to the inner surface of a cylinder 10. And, a crankshaft side end of this cylinder sleeve 18 is notched, and a scavenging inlet 26 is formed as opposed to a crankcase 20. Likewise, a scavenging outlet 28 to be opened to the inside of the cylinder 10 is formed in a spot little to the center of the cylinder sleeve 18. And the scavenging inlet 26 and the scavenging outlet 28 both are interconnected with each other through the scavenging passage 32 formed in a cylinder block 30. In this constitution, the scavenging inlet 26 is formed into an equilateral triangle having the apex situated at the top dead center side of a piston 12. That is to say, double side edges 38 of the circumferential direction of the cylinder 10 at the scavenging inlet 26 is tilted to the longitudinal direction of the cylinder 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cylinder sleeve for a two-stroke engine, and particularly to a cylinder sleeve that is formed by cutting out a scavenging inlet, a scavenging outlet, and an exhaust port. Regarding the shape of the notch.

[Conventional technology] For cylinder sleeves of 2-stroke engines.

As mentioned above! An air inlet, scavenging air outlet, and exhaust port are required, and these ports are formed by drilling or notching the wall of the cylinder sleeve, and the conventional shape of the cutout is generally rectangular.

The inner surface of the sleeve is honed as a finishing operation in the manufacturing process of such a cylinder sleeve, but the expansion pressure of the honing stone changes periodically at the notch,
Therefore, an uneven pattern, ie, a so-called petal pattern, is formed on the inner surface of the sleeve. This petal pattern reduces the accuracy of the sleeve diameter, which in turn causes a reduction in engine performance.

[Problems to be Solved by the Invention] In order to prevent such a petal pattern, it is possible to reduce the expansion pressure of the honing wheel, but this reduces the cutting efficiency and therefore increases the honing work time. There's a problem. It is also conceivable to make the notch smaller, but this has the problem of reducing engine performance.

The present invention was devised in view of the problems of the prior art, and its purpose is to improve the so-called petals of the honed surface on the inner surface of the sleeve without reducing honing efficiency or engine performance. To provide a cylinder sleeve for a two-stroke engine that can eliminate patterns.

[Means for Solving the Problems] The inventor noticed that the above-mentioned petal pattern was greatly influenced by the shape of the scavenging air inlet among the notches of the cylinder sleeve, and devised at least the shape of the scavenging air inlet. It has been subjected to

That is, in order to achieve the above object, the present invention provides a cylinder sleeve for a two-cycle engine in which a scavenging inlet facing the crank chamber, a scavenging outlet opening into the cylinder, and an exhaust port are perforated, at least in the cylinder of the scavenging inlet. Both edges in the circumferential direction are inclined with respect to the longitudinal direction of the cylinder.

[Function] With this configuration, during honing, when the honing stone moves in the circumferential direction on the inner surface of the cylinder sleeve with a predetermined expansion pressure, at least both side edges of the scavenging inlet are inclined with respect to the longitudinal direction of the cylinder. The rate of change in the contact area of the grindstone when the grindstone passes through the scavenging inlet is reduced, thereby preventing the formation of a so-called petal pattern.

[Example] The present invention will be explained below based on embodiments shown in the drawings.

First, FIG. 3 shows a cutaway front view of a two-cylinder two-stroke engine as an example to which the present invention is applied.

A piston 12 is arranged in each of the two cylinders IO of this engine, and each piston 12 is connected to a vertically placed crankshaft 16 via a conrod 14. Furthermore, a cylinder sleeve 18 is attached to the inner surface of each cylinder lO. A crank chamber 20 of the crankshaft 16 is connected to a carburetor 24 via an intake passage 22 for each cylinder.

A part of the end of the cylinder sleeve 18 on the side of the crankshaft 16 is cut out, thereby forming a scavenging air inlet 26 facing the crank chamber 20, and near the center of the cylinder sleeve 18, a scavenging air inlet 26 is opened into the cylinder lO. An outlet 28 is formed. The scavenging inlet 26 and the scavenging outlet 28 are communicated with each other through a scavenging passage 32 formed in the cylinder block 30.

Note that the reference numeral 34 is an exhaust passage, and the reference numeral 36 is a spark plug.

FIG. 1 shows an enlarged sectional view to make it easier to understand the shape of the scavenging inlet 26, and FIG. 2121 shows a developed view of the cylinder sleeve 18. In these figures,
The generally rectangular shape indicated by the two-dot chain line is the shape of a conventional scavenging inlet. In contrast, in this embodiment, the shape of the scavenging inlet 26 is a substantially equilateral triangle with the apex located on the top dead center side of the piston 12. In other words, the scavenging inlet 26 has a shape in which both side edges 38 in the cylinder circumferential direction are inclined with respect to the cylinder longitudinal direction.

Here, it is known that the width of the scavenging inlet 26, indicated by the symbol W, generally has a great influence on engine performance, #, horsepower, and torque. Therefore, in this embodiment as well, the width W of the scavenging inlet 26 is set at two points. The width W of the conventional scavenging inlet shown by the chain line is secured to be approximately the same as that of the conventional scavenging inlet, so there is no problem with engine performance. By making 26 into a substantially equilateral triangular shape, engine performance was slightly improved.

Further, the height of the scavenging inlet 26, that is, the length in the longitudinal direction of the cylinder, should be at least the same as that of the conventional one to ensure the opening area of the scavenging inlet 26.

In FIG. 2, reference numeral 40 indicates a second scavenging inlet, and 42 indicates a second scavenging outlet communicating with the second scavenging inlet 40. Regarding this @2 scavenging inlet 40,
Like the scavenging air inlet 26, its shape is a substantially equilateral triangle. Note that the scavenging outlet 28 and the second scavenging outlet 42 are located approximately at the center of the cylinder sleeve 18 and have a small opening area.
During honing, there is little effect on the petal pattern described above, so these outlets can remain in their conventional shape.
However, if the shape is substantially the same as that of the scavenging air inlet, the petal pattern can be more reliably prevented. Further, in FIG. 1.2, reference numeral 44 indicates an exhaust port, and if this exhaust port 44 is also shaped similarly to the scavenging inlet, petal patterns can be more reliably prevented during honing.

As described above, since the shape of the scavenging inlet 26 is such that both side edges 38 are inclined with respect to the longitudinal direction of the cylinder in the cylinder circumferential direction, when honing the inner surface of the cylinder sleeve 18, the honing stone moves in the circumferential direction. scavenging inlet 2
6, the rate of change in the contact [fI21] of the honing wheel becomes extremely small compared to the conventional case of a substantially rectangular shape, and therefore the change in expansion pressure of the honing wheel also becomes small, which causes The so-called petal pattern can be effectively prevented.

Note that the shape of the scavenging inlet is not limited to that of the first embodiment of the present invention described above, and can take various shapes, for example, as shown in FIG. 4.5.

That is, FIG. 4 shows a second embodiment of the present invention, and in this embodiment, the scavenging inlet 46 has a substantially trapezoidal shape. Furthermore, in the third embodiment of the present invention shown in FIG.
The scavenging inlet 48 has a smooth arc shape.

Note that the shape of the scavenging inlet may be various other shapes, but substantially the two edges 3 of the scavenging inlet in the circumferential direction of the cylinder.
8 is included in the present invention as long as it is inclined with respect to the longitudinal direction of the cylinder. In this case, the edge of the scavenging air inlet on the crankshaft side, that is, on the crank chamber side, has a great effect on engine performance, so it is desirable to make it as wide as possible, and the height of the scavenging air inlet in the longitudinal direction of the cylinder also depends on the engine. It is desirable to set it sufficiently high considering the effect on performance.

[Effects] As explained above, according to the present invention, there is an excellent effect that so-called petal pattern during honing can be effectively prevented without deteriorating engine performance or cutting efficiency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a cylinder sleeve of a two-stroke engine according to the present invention, FIG. 2 is a developed view of the cylinder sleeve in the same embodiment, and FIG. 3 is a two-stroke engine to which the present invention is applied. FIG. 4 is a cross-sectional view of main parts showing a second embodiment of the present invention,
Figure 5 shows the present invention! FIG. 7 is a cross-sectional view of main parts showing a third embodiment. 10...Cylinder 18...Cylinder sleeve 20...Crank chamber 26.40.46.48...Scavenging air inlet 28.42...
・Scavenging air outlet 38...Side edge 44...Exhaust port agent Yoshiyuki Inaba, patent attorney Figure 1 44: Outer edge Figure 2

Claims (1)

[Claims] (1) In a cylinder sleeve of a two-stroke engine that has a scavenging inlet facing the crank chamber, a scavenging outlet opening into the cylinder, and an exhaust port, at least both edges of the scavenging inlet in the circumferential direction of the cylinder are aligned in the longitudinal direction of the cylinder. A cylinder sleeve for a two-stroke engine that is tilted against the ground.