JPS5879621A - 2-cycle engine - Google Patents

Abstract

PURPOSE:To decrease flow resistance of a mixture in a scavenge passage of a 2-cycle engine, by both uniformly forming sectional area and decreasing a curvature of curved parts throughout a total length of the passage. CONSTITUTION:A fresh mixture, sucked into a crank case 23, is pressurized by the bottom part of a piston 17, rapidly lowered by explosion pressure, and this pressurized fresh mixture flows in through a scavenge passage 31, and is introduced into a cylinder 13 simultaneously with opening of scavenge holes 27. Sectional area of the scavenge passage 31 is almost equalized by protruding elements 59 of the crank case 23, and a curvature of curved parts of the scavenge passage 31 can be decreased and smoothed. In consequence, flow resistance of the mixture is reduced, and charging efficiency of the mixture into the cylinder 13 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a two-stroke engine whose cross section is approximately uniform and whose curved portions are smooth, and which can form a scavenging passage that can be cast with a lifeline.

Generally speaking, if the scavenging passage of a two-stroke engine has a uniform axis over its entire length and a smooth curved section, the flow side resistance of the air-fuel mixture will be smaller, and the filling efficiency of the air-fuel mixture into the cylinder will be improved. It is.

However, in order to obtain a smooth surface and to facilitate mass production, the cylinders of conventional two-stroke engines were made using a mold ##. For this reason, after casting, it was necessary to remove the mold forming the scavenging passage, and the scavenging passage had to have a draft angle that expanded toward its lower end, making it impossible to obtain a free cedar shape. . Therefore, in the scavenging passage, the lower Iyr 'tin 4111 is naturally larger than the upper cross section and narrows upward, and the scavenging passage has a draft slope.
II! The curvature of the part had become large. As a result of the above, conventional two-stroke engines have had to sacrifice some filling efficiency for casting reasons. On the other hand, as a means to eliminate such drawbacks, a two-stroke engine with a scavenging passage whose cross section is approximately uniform and whose wall surface has a small curvature, which does not require draft angle of the mold, is cast using shell casting. The core that forms the scavenging passage can only be used once,
Therefore, it has the drawback that it is expensive to produce and is not suitable for mass production.

In order to eliminate these drawbacks, this invention has developed a two-stroke engine that is approximately uniform in size, has small curvature of curved parts, and can form a scavenging passage with a high Wkm at low cost using a mold. It is to provide.

Hereinafter, an example of the present invention will be described based on the drawings.

In FIGS. 1 and 2, a two-stroke engine 11 has a cylinder 13, a cylinder head 15, a piston 17, a connecting rod 19, a crank 21, and a crank case 23. The cylinder 13 is made of a light alloy and is cast into a cylindrical shape, and a cylindrical cast iron sleeve 25 is cast-in or press-fitted into the inner surface of the cylinder 13 to form the interior of the cylinder 13.

In addition, inside cylinder 13, W! Rei s G goth sleeve 25
It is also possible to integrally cast the cylinder 13 with cast iron without using the cylinder 13. 2F is a scavenging hole, which is located inside the cylinder 13 consisting of the sleeve 25. It is perforated in the section. In the wall of the cylinder 13, there is a scavenging air outlet 29 which communicates with the interior of the cylinder 13 through an 11+1 hole 27 and whose diameter expands downward. 131 is provided. The reason why the scavenging passage 31 has a lower opening 29 that expands downward is that after the return passage 31 is integrally cast with the cylinder 13, it is necessary to create a draft angle to take out the gold. 33 is an element integrally cast on the outer periphery of the lower end of the cylinder 13, and is for contacting with an element 37 provided on the outer periphery of an opening 35 of the crank nurse 23, which will be described later. Further, on the outer peripheral surface of the cylinder 13, cooling fins 39 of a certain gPwI are provided for cooling the cylinder 13.
39. ... is integrally cast.Next, the cylinder head 15 has a concave inner surface, and the cylinder r
-13 upper end port 41f-11i! It is screwed onto the cylinder 13 via a gasket (not shown) to ensure this. Incidentally, like the cylinder 13, cooling fins 43, 43, . . . for cooling the cylinder head 15 are integrally cast into the cylinder head 15. Reference numeral 45 denotes a hole for mounting a spark plug 47, which is bored into the cylinder approximately at the center of the I door 15, and the spark plug 47 is removably screwed into the hole 45.

A piston 17 is slidably recessed by [11+1] inside the cylinder 13 in contact with the inner circumferential direction. This piston 1
7 is a 1ll for changing the vertical movement to 1q rotation interlocking with the crank 21 to be described later, with the piston pin 49 as the axis.
An irkIII connecting rod 19 is pivoted at its small end. Note that 51.51 is a notch, which is provided in the plate portion of the piston l).

The crankcase 23 connected to the lower 9111g is constructed by screwing together a right crankcase 53 and a left crankcase 55, and the upper surface has a diameter increasing upward. It has a skirt portion 5. What number is on the outer edge of the opening 35 at the tip of this skirt s57? is integrally cast, and this 4v3 is cylinder 1
3 and the crankcase 23 are screwed together, the cylinder 13
It is in contact with the row 33 of the lower gJmW. Reference numeral 59 is a protruding piece whose wall thickness becomes thinner toward the tip, and is integrally cast so as to protrude upward from the end of the opening [35 of the crankcase 23. This 59 piece crankcase 2
3 is screwed onto the cylinder 13, it is inserted into the scavenging air circuit 31 of the cylinder 13, and its outer hooked surface contacts the outer side of the scavenging passage 31.

This protrusion 59 is inserted into the downwardly expanding portion of the air passageway 31 to scavenge air! The area number of the passage 31 is approximately uniform from the bottom to the top, and the scavenging passage 3
The curvature of the curved portion 1 also becomes smaller and smoother. By integrally casting contact pieces (not shown) on both ends of the projecting piece 59, the thickness of which increases toward -E, the cross-sectional area and curvature of the scavenging passage 31 can be adjusted from three directions.

Next, inside the crank nurse 23 is a crank 21 consisting of a crank arm 61 pivotally connected to the connecting rod 19 via a crank pin (not shown) and a crank 163 placed in the center of the crank arm 61. It is accommodated. Also, 65 is a bearing for smoothing the same rotation of the crankshaft. In addition, 67 in the figure is the crankcase 23 and cylinder 13.
The bolt (not shown) for screwing on is the hole for pressing the bag.

= It is drilled in Sho.

Next, the operation of this invention will be explained.

The new mixture sucked into the crankcase 23 is pressurized at the bottom of the piston 17, which rapidly descends due to the explosion pressure. As soon as it opens, it rushes into the cylinder 13. In this case, in this invention, the l of the four scavenging passages 31 is
The ltl plane shaft can be substantially electrified by the protruding piece 59 of the crankcase 23, and the scavenging passage can be curved S S
Since the curvature of < can be made small and smooth, the resistance of the air-fuel mixture to 'i*A becomes small, and therefore the air-fuel mixture can be efficiently filled into the cylinder 13.

As described above, this invention has a cylinder provided with a scavenging passage in the wall, and an opening 8 provided on the upper surface of the crank nurse.
1) In the two-stroke engine, the scavenging bend has a diameter increasing toward the lower end opening, and the scavenging passage has a groove at the edge of the opening of the crankcase. Because this is a 2-cycle engine that is provided with a tapered protrusion that is inserted along the inner W11 [I, that is, the tapered protrusion is inserted into the scavenging passage along the inner W11 By adjusting the wall thickness of the protruding piece, it is possible to make the m commercial right of the scavenging passage approximately uniform over the entire area, and also to reduce the curvature of the scavenging passage. The flow resistance of the air-fuel mixture in the passage can be reduced, and the filling efficiency of the air-fuel mixture into the cylinder can be increased. Further, in this invention, since the diameter of the scavenging passage 1 increases toward the lower end opening, the mold forming this passage can be removed. Therefore, since a mold can be used during casting, the shell core and the raised mold can be used repeatedly, resulting in lower production costs and suitable for mass production. In addition, unlike a shell core, when a mold is used, the surface of the air passage is smooth, allowing the air-fuel mixture to escape smoothly. Furthermore, in the two-stroke engine according to the present invention, the shape of the scavenging passage can be freely changed by changing the wall thickness of the protrusion.

[Brief explanation of drawings]

No. 11 is a wITtT diagram of the present invention, and FIG. 2 is a large cross-section of @-I Nlb in No. 11. 11...2-cycle engine, 13...Cylinder, 23...Crankcase. 31...Scavenging passage, 35...Opening. 59... protrusion

Claims (1)

[Claims] l) In a two-stroke engine in which a cylinder with a scavenging passage in the wall is supported at the edge of an opening provided in the upper surface of the crankcase, the scavenging passage expands toward the lower end opening. A two-stroke engine with a diameter of 1.5 mm, and a tapered protrusion that is fitted into the scavenging passage along the inner wall thereof is provided on the edge of the mouth of the crankcase of the III ship.