JPH078543U - Two-cycle engine piston - Google Patents

Abstract

(57) [Summary] [Purpose] A scavenging airflow flows into the crankcase through the side relief formed in the pin hole of the piston for lubrication and stress relaxation, and blow-by gas increases or lubricating oil is blown off. This prevents the occurrence of poor lubrication, and relieves the excessive stress generated in the piston inner portion of the pin hole during engine operation. [Arrangement] A shell-shaped shell is formed on both sides with respect to a vertical centerline O passing through the axis of the pin hole 3, and in the axial direction of the pin hole 3 extending from the piston inner end of the pin hole 3 to a substantially middle portion. The side relief 8 is formed so that the scavenging air does not flow into the piston 1 through the side relief 8, and the side relief 8 is provided in a severe portion in terms of strength and lubrication.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a piston for a two-cycle engine.

[0002]

[Prior art]

 A two-cycle engine having a structure as shown in FIG. 3 is well known. In FIG. 3, 11 is a cylinder, 12 is a cylinder head, and 13 is a combustion chamber. Reference numeral 14 is a piston which moves up and down in the cylinder 11, and 15 is a piston pin for connecting the piston 14 and a connecting rod (not shown). On the circumferential surface of the cylinder 11, an exhaust port 16 is provided at an appropriate position in the circumferential direction immediately above the bottom dead center of the piston 14, and two pairs of exhaust ports 16 are provided on both sides of the direction connecting the exhaust port 16 and the center of the cylinder 11. Scavenging ports 17 and 18 are provided, and a booster port 19 is provided opposite to the exhaust port 16. These scavenging ports 17, 18 and booster port 19 communicate with a single scavenging inlet (not shown) on the side opposite to the exhaust port 16 and to a scavenging pump (not shown) via this scavenging inlet. It is connected.

As shown in FIG. 2, the piston 14 has a pair of boss portions 23 projectingly formed on the inner circumference of a piston body 22, and pin holes 24 are formed so as to penetrate these boss portions 23. . An annular groove 26 is formed at a position of the pin hole 24 at an appropriate distance from the outer periphery of the piston body 22, and a circlip 27 engaged with the annular groove 26 allows the piston pin 15 inserted and fitted in the pin hole 24 to come out. Is prevented.

Further, as shown in detail in FIG. 2B, the inner peripheral surface of the pin hole 24 is lubricated on both sides with respect to a vertical center line O passing through the axis of the pin hole 24. A pair of side reliefs 28 are recessed for stress relaxation. The side relief 28 has an arc-shaped cross section with a width of about 15 ° to 25 ° centered on a position of 20 ° to 30 ° above the horizontal center line passing through the axis of the pin hole 24, and has a pin hole. 24 is formed so as to penetrate in the axial direction.

By providing such a side relief 28 in the pin hole 24, the pin hole 24 and the piston pin 15 are smoothly lubricated by functioning as a lubricating oil reservoir, and at the same time, the piston pin 15 during engine operation is protected. By allowing the side relief 28 to deform, it is possible to relieve the excessive stress acting between the piston pin 15 and the pin hole 24.

[0006] In Japanese Utility Model Publication No. 61-21560, an oil groove is formed on the inner peripheral surface of the pin hole from the outer periphery of the piston main body so that lubricating oil can be efficiently sent to the peripheral surface of the pin hole. It is disclosed.

[0007]

[Problems to be solved by the device]

 By the way, if the opening area of the scavenging port 17 or 18 in FIG. 3 is increased in order to improve the scavenging efficiency of the two-cycle engine, the pin hole 24 of the piston pin 15 and the scavenging port 17 or 18 overlap when the piston 14 moves up and down. As a result, the scavenging air flows into the piston 14 through the side relief 28 and flows out to the crankcase side. As a result, the lubricating oil in the side relief 28 is blown off by the scavenging air flow, causing a shortage of the lubricating oil, which causes the seizure frequency of the piston pin 15 to increase, and the scavenging air flow into the crankcase causes an apparent blowby gas. And other problems occur.

According to the above publication, since the oil groove is not formed through the pin hole, such a problem does not occur, but when the engine is operated, the piston pin is deformed with its outer end as a fulcrum. As a result, there is a problem that particularly large stress is generated in the inner part of the piston of the pin hole, and there is a problem that the lubrication condition is severe.

In view of such conventional problems, the present invention causes the scavenging airflow to flow through the side relief into the crankcase, increasing blow-by gas, or causing the lubricating oil to be blown off to cause poor lubrication. It is an object of the present invention to provide a piston for a two-cycle engine that is free from the above and can relieve the excessive stress generated in the piston inner part of the pin hole during engine operation.

[0010]

[Means for Solving the Problems]

 The present invention relates to a two-cycle engine in which a pair of boss portions are formed on the inner circumference of the piston body so as to project, and pin holes are formed through these boss portions, and side reliefs are provided on the inner peripheral surface of the pin holes. In the piston, side reliefs are formed on both sides of the vertical center line that passes through the pin hole shaft center and extend in the pin hole shaft center direction from the piston inner end to almost the middle part. To do.

[0011]

[Action]

 According to the present invention, since the side relief is formed in the range from the piston inner end of the pin hole to the approximately middle portion in the axial direction, even if the piston pin and the outer peripheral end of the pin hole cross the scavenging port. The scavenging air does not flow into the piston through the side relief, so the lubricating oil is not blown off by the scavenging airflow, and the lack of lubricating oil does not cause poor lubrication. There is no increase in quantity. Furthermore, when the engine is operating, the piston pin is deformed with its outer end as a fulcrum, so excessive stress is generated especially in the piston inner part of the pin hole, which is a severe condition in terms of lubrication. Since it is formed, it is possible to reliably relieve excessive stress, improve the safety factor in terms of strength, and prevent seizure of the piston pin.

[0012]

【Example】

 An embodiment of the present invention will be described below with reference to FIG. The overall structure of the two-cycle engine to which the piston of this embodiment is applied is the same as that described with reference to FIG. 3 for the conventional example, and the description thereof will be omitted here. .

In the piston 1 shown in FIG. 1, a pair of boss portions 3 are formed so as to project from the inner periphery of a bottomed cylindrical piston body 2 with its bottom portion facing upward. A pin hole 4 is formed for insertion and fitting. An annular groove 6 is formed at an appropriate distance from the outer periphery of the piston body 2 of the pin hole 4, and a circlip (not shown) is engaged with the annular groove 6 to prevent the piston pin from coming out. It is configured.

As shown in FIG. 1B, the inner peripheral surface of the pin hole 4 is provided with lubrication and stress relaxation on both sides with respect to a vertical center line O passing through the axis of the pin hole 4. For this purpose, a pair of shell-shaped side reliefs 8 are recessed. The side relief 8 is formed in the axial direction of the pin hole 4 in the range from the piston inner end of the pin hole 4 to the substantially middle portion thereof, and the pin hole axial center is formed at the piston inner end in the circumferential direction of the pin hole 4. An angle range of 40 ° or more above the horizontal center line passing through, preferably 20 ° to 30 ° (A °) above the horizontal center line passing through the axis of the pin hole 4. Is formed in the range of 20 ° to 35 ° (B °) on both upper and lower sides of the center.

According to the above configuration, since the side relief 8 is formed in the range from the piston inner end of the pin hole 4 to the substantially middle portion in the axial direction, the piston pin and the outer peripheral end of the pin hole 4 are scavenging ports. The scavenging air flow does not flow into the piston 1 through the side relief 8 even if it crosses. Therefore, the lubricating oil held in the side relief 8 is blown off by the scavenging air flow, and the insufficient lubrication oil does not cause poor lubrication, and the apparent blow-by gas amount does not increase.

Further, when the engine is operating, the piston pin is deformed with its outer end as a fulcrum, so that particularly excessive stress is generated in the piston inner part of the pin hole 4, which causes severe lubrication conditions. Since the side relief 8 is formed over a wide angle range of 40 ° or more in the circumferential direction, it is possible to reliably relieve excessive stress, improve the strength safety factor and prevent seizure of the piston pin. .

[0017]

[Effect of device]

 According to the piston of the two-cycle engine of the present invention, since the side relief is formed in the range from the piston inner end of the pin hole to the substantially middle portion in the axial direction as described above, the scavenging air flow causes side relief. It does not flow into the piston through it, and therefore the lubricating oil is blown away by the scavenging air flow, and there is no possibility of poor lubrication due to insufficient lubricating oil, and the apparent blow-by gas amount increases. Even if the piston pin deforms with its outer end as a fulcrum when the engine is operating, a side relief is formed in the piston hole inside the pin hole, so excessive stress generated in this part is ensured. It is possible to alleviate, improve the safety factor in strength, and prevent seizure of the piston pin.

[Brief description of drawings]

FIG. 1 shows a piston of a two-cycle engine according to an embodiment of the present invention, (a) is a vertical sectional front view, and (b) is a view taken along the line I-I of (a).

FIG. 2 shows a piston of a two-cycle engine in a conventional example, (a) is a vertical sectional front view, (b) is II-II of (a).
FIG.

FIG. 3 shows a schematic configuration of a two-cycle engine, (a)
Is a vertical sectional front view, and (b) is a III-III arrow cross-sectional plan view of (a).

[Explanation of symbols]

 1 Piston 2 Piston body 3 Boss part 4 Pin hole 8 Side relief

Claims (1)

[Scope of utility model registration request] 1. A pair of bosses are formed on the inner circumference of the piston body so as to project, and pin holes are formed to penetrate these bosses.
In a 2-cycle engine piston with a side relief recessed on the inner peripheral surface of the pin hole, on both sides of the vertical center line passing through the pin hole axis, from the piston hole inner end to the pin hole axis direction. A piston for a two-cycle engine, which is characterized by forming a side relief that extends to almost the middle part.