JPS62243946A - Cylinder-piston assembly for two cycle engine - Google Patents

Abstract

PURPOSE:To eliminate the adaptive operation and to improve the affinity with the sliding face at the circumferential section of an exhaust port by providing a more abrasive surface pressure control member to a cylinder or a piston and bearing the pressure of the piston to the exhaust port side. CONSTITUTION:A cylinder 3 is constructed from a cylinder body 9 having a cylinder hole 3a and a pair of scavenge port covers 10 secured to the cylinder body 9 and forming the outside wall of a scavenge port 8. A pair of surface pressure control members 12 at the scavenge port 8 are held between the cylinder body 9 and the scavenge port cover 10. Said surface control member 12 is abraded more easily than the cylinder 3 or the piston 5 and arranged closely to an exhaust port 7 with a portion thereof projecting slightly into the cylinder hole 3a. Consequently, the pressure of the piston 5 to the exhaust port 7 side is born by said surface pressure control member and the excessive increase of the surface pressure at the circumferential section of the exhaust port 7 can be suppressed.

Description

[Detailed description of the invention] A0 Purpose of the invention! 1) Industrial Field of Application The present invention relates to an improvement in a cylinder-piston assembly for a two-stroke engine, in which a piston is fitted into a cylinder hole of a cylinder, and an exhaust port connected to an exhaust pipe is opened on the inner surface of the cylinder. .

(2) Conventional technology In such a two-stroke engine, the parts close to the exhaust port are heated by exhaust gas, so the piston is forced to move toward the exhaust port side before the sliding surfaces of the cylinder and piston have sufficiently adjusted. If a certain side pressure is applied, an oil film may break on the sliding surfaces of the cylinder and piston at the periphery of the exhaust port.

Therefore, conventionally, when operating such an engine immediately after manufacture, a so-called break-in period is performed in which high loads and high rotations are avoided as much as possible.

(3) Problems to be Solved by the Invention However, although the above-mentioned break-in operation is effective in prolonging the life of the engine, it is troublesome and is often neglected.

The present invention has been made in view of the above circumstances, and allows the sliding surfaces of the cylinder and piston to be well-familiarized at the periphery of the exhaust port without performing a break-in operation immediately after manufacture, thereby improving the life of the engine. It is an object of the present invention to provide the cylinder-piston assembly that can be used.

B1 Structure of the Invention Tll Means for Solving the Problems In order to achieve the above object, the present invention provides a surface pressure control member that is more likely to wear than both of the cylinder and the piston.
This is characterized in that it is provided so as to support the lateral pressure toward the exhaust port side of the piston with a higher surface pressure than other parts.

(2) Effect When the piston receives lateral pressure toward the exhaust port while the engine is operating, the lateral pressure is mainly supported by the surface pressure control member, so the surface pressure between the cylinder and piston at the periphery of the exhaust port becomes excessive. It is possible to prevent this from happening.

At this time, the surface pressure of the surface pressure control member is higher than that of other parts, but since this is more easily worn than the cylinder and piston, the cylinder and piston will not be damaged.

Since it takes a period of time for the surface pressure control member to wear out, the sliding surface of the piston and the peripheral edge of the exhaust port on the inner surface of the cylinder hole gradually become accustomed to each other during that period.

(3) Examples An embodiment of the present invention will be described below with reference to the drawings.

First, in FIGS. 1 and 2 showing the first embodiment of the present invention, E indicates a crank chamber compression type two-stroke engine, and the engine body L indicates the crank case 2) cylinder 3.
A piston 5 interlocked with a crankshaft (not shown) in a crankcase 2 is connected to a combustion chamber between the cylinder head 4 and a cylinder hole 3a of the cylinder 3. 6.

The cylinder 3 also has an exhaust port 7 whose one end is open to the inner surface of the cylinder 3 and whose other end is connected to an exhaust pipe (not shown), and an exhaust port 7 that is adjacent to both sides of the exhaust port 7 in the circumferential direction of the cylinder 3. A pair of scavenging ports 8.8 are provided which communicate the inside of the crankcase 2 with the cylinder hole 3a. The exhaust port 7 and the scavenging ports 8, 8 are configured to sequentially open into the combustion chamber 6 in the latter half of the downward stroke of the piston 5.
According to these sequential openings, from the combustion chamber 6 to the exhaust port 7
After the exhaust gas is discharged to, the air-fuel mixture from within the crankcase 2 is forced into the combustion chamber 6 through the scavenging port 8.8.

The cylinder 3 includes a cylinder body 9 having a cylinder hole 3a, and a bolt 1) attached to the cylinder body 9. 1) consists of a pair of scavenging port covers 10.10 that are removably fixed by... to form the outer wall of the scavenging port 8.8, and these cylinder body 9 and scavenging port cover 10.
．． A pair of surface pressure control members 12.12 are sandwiched between the scavenging ports 8.8 and 10. At this time, these surface pressure control members 12.12 are connected to the exhaust port 7 as shown in FIG.
The cylinder hole 3a is arranged as close as possible to the cylinder hole 3a, and a portion thereof slightly protrudes into the cylinder hole 3a.

The surface pressure control member 12 is molded from a material that wears more easily than the cylinder 3 and piston 5 and is less likely to cause metal contact. For example, when the cylinder 3 and piston 5 are made of A/alloy, the surface pressure control member 12 is made of epoxy resin containing AN powder.

Next, to explain the operation of this embodiment, the pair of surface pressure control members 12.12 are disposed close to the exhaust port 7 on both sides thereof, and a portion thereof slightly protrudes into the cylinder hole 3a. When the engine is operated under high load, when the piston 5 is strongly pressed against the exhaust port 7 due to large side pressure,
A pair of surface pressure control members 12, 12 cooperate to support the piston 5, and suppress excessive increase in surface pressure between the peripheral edge of the exhaust port 7 on the inner surface of the cylinder 3 and the piston 5. The distribution state of the surface pressure between the inner surface of the cylinder 3 and the piston 5 at this time is as shown in FIG. 4, and when compared with the conventional surface pressure distribution shown in FIG. The surface pressure is low,
Moreover, it can be seen that it is averaged.

If the surface pressure between the cylinder 3 and the piston 5 at the peripheral edge of the exhaust port 7 is controlled in this way, even if the peripheral edge of the exhaust port 7 is heated to a high temperature by exhaust gas, no oil film will run out between the edges. , the piston 5 can be slid smoothly.

On the other hand, the surface pressure between the surface pressure control member 12.12 and the piston 5 increases, but since the surface pressure control member 12.12 is molded from a material that wears more easily than the cylinder 3, the sliding surface of the piston 5 increases. It won't hurt you.

Therefore, even if the engine has just been manufactured, it can sufficiently withstand high-speed, high-load operation without particularly having to be run-in during storage.

As the operating period of the engine passes, the surface pressure control member gradually wears out, and as a result, the cylinder 3 and piston 5 gradually become accustomed to each other at the peripheral edge of the exhaust port 7, and the surface pressure control member 12°12 When the inner surface of the cylinder 3 is worn flush with the inner surface of the cylinder 3, the fitting is completed. Therefore, if this state is reached, the surface pressure control member 12
．． There is no problem even if 12 is removed from the cylinder 3, and by removing it, the scavenging resistance can be reduced.

5 and 7 show a second embodiment of the present invention,
The piston 5 is moved so that the pair of surface pressure control members 12 and 12 are opposed to the inner surface of the cylinder hole a on both sides of the exhaust port 7.
The structure is the same as that of the previous embodiment except for the fact that it is attached to the holder, and in the drawings, the same reference numerals are given to the parts corresponding to those of the previous embodiment.

To explain this in detail, the surface pressure control member 12.12 has a hollow recess 14 on the top of the pair of bottle bosses 13.13 of the piston 5.
, 14 and is removably fixed to the piston 5 with a screw 15, and a part of it is attached to the skirt portion 16 of the piston 5.
It is made to protrude slightly from the outer peripheral surface. This embodiment also provides the same effect as the previous embodiment.

C1 Effects of the Invention As described above, according to the present invention, a surface pressure control member, which is more likely to wear out than both of them, is provided on at least one of the cylinder and the piston, so that the side pressure on the exhaust port side of the piston is higher than that on the other parts. Because it is supported with pressure, the surface pressure control member prevents excessive surface pressure on the sliding surfaces of the cylinder and piston at the peripheral edge of the exhaust port even when the engine is operated at high loads and high speeds immediately after manufacture. In addition, as wear of the surface pressure control member progresses, the sliding surfaces can be better adapted to each other, and therefore, the life of the engine can be extended even when running-in is performed. .

[Brief explanation of drawings]

1 to 4 show a first embodiment of the present invention, in which FIG. 1 is a longitudinal cross-sectional side view of a two-stroke engine, FIG. 2 is a plan view of its cylinder/piston assembly, and FIG. Second
Fig. 4 is a surface pressure distribution diagram of the peripheral edge of the exhaust port in the cylinder/piston assembly of the present invention, and Figs. FIG. 5 is a partially vertical front view of the cylinder/piston assembly, FIG. 6 is a cross-sectional view of the piston taken along the line Vl--Vl in FIG. 5, and FIG. 6 is an enlarged view of part 2 in FIG. 6, and FIG. 8 is a surface pressure distribution diagram at the peripheral edge of the exhaust port in a conventional cylinder/piston assembly. E...2-stroke engine, l...engine body,
2...Crankcase, 3...Cylinder, 4...
Cylinder head, 5... Piston, 7... Exhaust port, 8... Scavenging port, 12... Surface pressure control member Figure 2 Figure 1 Figure 4 Figure 8 Figure 3 Figure 60 7 Figure 5

Claims (4)

[Claims] (1) In a cylinder-piston assembly for a two-stroke engine, in which a piston is slid into a cylinder hole of a cylinder, and an exhaust port connected to an exhaust pipe is opened on the inner surface of the cylinder, at least one of the cylinder and the piston is
A cylinder-piston assembly for a two-stroke engine, characterized in that a surface pressure control member, which is more prone to wear than both, is provided so that it supports the side pressure toward the exhaust port side of the piston with higher surface pressure than other parts. Three-dimensional. (2) In what is stated in claim (1),
A cylinder/piston assembly for a 2-stroke engine with a surface pressure control member installed in the cylinder. (3) In what is stated in claim (1),
A cylinder/piston assembly for a two-stroke engine with a surface pressure control member installed on the piston. (4) A cylinder/piston assembly for a two-stroke engine according to claim (1), (2), or (3), wherein the surface pressure control member is detachable.