JPH0622550U - 2-cycle engine - Google Patents

Abstract

(57) [Summary] [Purpose] The object is to provide a two-cycle engine having excellent internal cooling performance. [Structure] In a two-cycle engine configured to supply a fuel-air mixture from a crank chamber C to a combustion chamber B above a piston 2 through a scavenging passage 3, a base end side opening is provided in a crown portion 2B of the piston 2. A cooling passage 4 is formed in which 4a is formed to face the crank chamber C side and a front end side opening 4b is formed on the outer peripheral surface of the piston 2, and the cooling passage 4 is provided between the crank chamber C side and the combustion chamber B through the cooling passage 4. The scavenging passage 3 for supplying the air-fuel mixture is communicated.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a two-cycle engine having an excellent engine cooling property.

[0002]

[Prior art]

 A two-cycle engine, for example, a relatively small two-cycle engine used in a small planing boat, a motorcycle, or a general-purpose engine has a lead valve from the carburetor side (not shown) in the crank chamber C as shown in FIG. The intake air mixture is sucked through the intake valve 6 and is supplied to the combustion chamber B above the piston 2 from the scavenging passage 3'formed on the side of the cylinder 1 as shown by an arrow Y. ing. In general, the exhaust passage 5 is formed on the side of the cylinder 1 where the scavenging passage 3'is not formed, and as shown by an arrow Z, the exhaust passage 5 is exhausted through the exhaust passage 5 after combustion. (Combustion gas) is exhausted from the combustion chamber B to the outside of the engine.

[0003]

[Problems to be solved by the device]

 In a typical two-cycle engine of this type, the portion of the cylinder 1 where the scavenging passage 3'is formed is cooled by the air-fuel mixture having a low temperature, and the portion of the cylinder 1 where the exhaust passage 5 is formed is It is heated by the high temperature combustion gas (exhaust gas). Further, the upper surface of the crown portion 2B of the piston 2 is heated by combustion and becomes a considerably high temperature after being operated for a predetermined time.

As described above, the temperature distribution of the cylinder and the piston is considerably different depending on each part because a certain part of the cylinder and the piston is heated to a considerably high temperature and is partially cooled. Deformation due to thermal strain occurs in the cylinder and piston, which can cause seizure in high-performance engines.

As a countermeasure against the above phenomenon, there is a method of forming a large gap between the cylinder inner diameter and the piston outer diameter to prevent engine seizure. In such a case, however, a slap sound is generated due to the gap. Another inconvenience occurs.

Further, as another countermeasure, a through hole is formed in the side wall of the piston, and the air-fuel mixture is supplied from the vaporizer side to the crank chamber or from the crank chamber to the combustion chamber through the through hole, and the piston is There is a structure in which the crown part of the piston is cooled from the inner surface side, or in addition to this structure, a structure in which a cooling fin is additionally provided on the inner wall surface side of the crown part of the piston (Shokai Sho 60-194149, (Actual exploitation No. 57-33232, Japanese Patent Publication No. 41-16884).

However, even with this configuration, in the case of a high-performance engine, the current situation is that the temperature of each part of the piston and the cylinder cannot be made uniform.

The present invention has been made under such circumstances, and an object of the present invention is to provide a two-cycle engine having an excellent engine cooling property.

[0009]

[Means for Solving the Problems]

 A two-cycle engine according to the present invention is a two-cycle engine configured so that an air-fuel mixture is supplied from a crank chamber to a combustion chamber above a piston through a scavenging passage. A cooling passage having a side opening facing the crank chamber side and a tip side opening formed on the outer peripheral surface of the piston is provided, and the air-fuel mixture is supplied to the crank chamber side and the combustion chamber through this cooling passage. It is characterized in that it communicates with the scavenging passage.

[0010]

[Action]

 Therefore, according to the two-stroke engine of the present invention, in the scavenging stroke, the mixture having a low temperature flows from the crank chamber to the scavenging passage through the cooling passage formed in the crown portion of the piston. The temperature of the crown part, which had the highest temperature, became lower, and as a result, the temperature distribution of the piston became uniform, the deformation due to thermal strain was greatly reduced, and engine seizure can be effectively prevented. .

[0011]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view showing the structure of a water-cooled two-cycle engine according to an embodiment of the present invention, and FIG. 2 is a lateral sectional view taken along the line II of FIG.

In FIGS. 1 and 2, 1 is a cylinder, 2 is a piston, 3 is a scavenging passage formed on the side of the cylinder so as to communicate the cooling passage 4 with the combustion chamber B during the scavenging stroke, and 3'is a conventional one. Similarly, a scavenging passage for directly connecting the crank chamber C and the combustion chamber B, 4 is a cooling passage formed in the piston 2, 5 is an exhaust passage, 8 is a cylinder head, and B is formed in the cylinder 1 above the piston 2. The combustion chamber, C, is a crank chamber.

As shown in FIG. 1 or 2, the cooling passage 4 is formed in the crown portion 2B of the piston 2, and the cooling passage 4 faces the inner side of the lower side of the piston 2 toward the crank chamber C side. It has a base end side opening (base end side opening) 4a and a front end side opening (front end side opening) 4b penetrating the side wall 2A of the piston 2 and facing the inner wall surface 1A of the cylinder 1. The height position of the opening 4b in the piston 2 is the same as that of the scavenging passage 3 (in this embodiment, the scavenging passage located on the opposite side of the exhaust passage 5 with the piston 2 in between). It is formed at a position where it can communicate. In the case of the present embodiment, the cooling passage 4 is close to the upper surface of the piston 2 on the exhaust passage 5 side of the cylinder 1 and on the opposite side (scavenging passage 4 side) to the piston 2 as shown in FIG. Is formed obliquely (downward to the right in FIG. 1) so as to be slightly separated from the upper surface of the. Further, on the exhaust passage 5 side of the piston 2, a wall surface 4A serving as a partition wall with the crank chamber C of the cooling passage 4 is extended downward, and an opening 4a of the cooling passage 4 is formed from an inner wall surface of the crown portion 2B. It is formed in a fairly lowered position.

Then, in the cooling passage 4, as shown in FIG. 2, a flow straightening plate 4c which also functions as a strength reinforcing member is provided along the flow so as to improve the cooling property and the flow of the air-fuel mixture passing therethrough. It is included. In FIG. 1, reference numeral 6 is a reed valve (intake valve) provided in the crank chamber C for sucking the air-fuel mixture from a vaporizer (not shown). In FIGS. 1 and 2, reference numeral 7 is a water jacket provided in the cylinder 1 and the cylinder head 8.

However, the two-cycle engine according to the present embodiment configured as described above, when the engine is operating (scavenging stroke), receives the low-temperature air-fuel mixture sucked into the crank chamber C from the carburetor (not shown). As shown by an arrow X, the scavenging passage 3 is supplied from the opening 4a through the cooling passage 4 to the scavenging passage 3 and the scavenging passage 4 is supplied to the combustion chamber B of the engine. Further, the air-fuel mixture is also supplied to the combustion chamber B from the scavenging passage 3'which communicates directly with the crank chamber C as shown by an arrow Y.

The air-fuel mixture supplied as shown by the arrow X is effective in the portion close to the exhaust passage 5 of the piston 2 and the crown portion 2B where the temperature becomes highest due to combustion and the combustion gas shown in the arrow Z. Cool to. In this embodiment, the cooling passage 4 is formed close to the combustion chamber B side surface (crown portion surface) of the piston 2 in the crown portion 2B of the piston 2 near the exhaust passage 5 where the temperature is highest. Therefore, higher cooling can be obtained as compared with other portions, and the temperature distribution of the entire piston 2 is made uniform. Also, in the cylinder 1, the air-fuel mixture warmed in the cooling passage 4 as described above is supplied to the scavenging passage 3 portion farthest from the exhaust passage 5, and the crank is provided in the scavenging passage 3 ′ near the exhaust passage 5. Since the air-fuel mixture having a low temperature is directly supplied from the chamber C, the temperature distribution of the entire cylinder 1 is also made uniform. Further, when the flow straightening plate 4c is formed as in this embodiment, the strength of the crown portion 2B of the piston 2 can be increased to reduce the amount of strain, and the cooling area can be increased to improve the cooling performance. Furthermore, the air-fuel mixture flowing in the cooling passage 4 becomes a laminar flow, and the air-fuel mixture can flow in the cooling passage 4 extremely smoothly.

In another embodiment, as shown in FIG. 4 which is a cross-sectional view taken along the line II-II of FIG. 3, a cooling passage is provided on the side wall 2A of the piston 2 between the exhaust passage 5 and the scavenging passage 3 '. 4 is provided. In this case, an opening 4d for exposing the inner wall surface 1A of the cylinder 1 may be formed. As shown in FIG. 4, the opening 4d is formed at a position where the exhaust passage 5 is avoided in a plane, that is, between the exhaust passage 4 and the scavenging passage 3'in a plane.

When the cooling passage 4 is formed between the exhaust passage 5 and the scavenging passage 3 ′ as in this embodiment, the air-fuel mixture having a low temperature positively moves the piston side wall in contact with the exhaust passage 5 and the scavenging passage 3 ′. Can be cooled.

Further, since the piston side wall is provided with the opening 4d, the air-fuel mixture having a low temperature is brought into direct contact with the inner wall of the cylinder between the exhaust passage 5 and the scavenging passage 3'to cool it. The temperature distribution in the cylinder 1 can be made more uniform. Incidentally, in this embodiment, as shown in FIG. 3, the position of the opening 4a of the cooling passage 4 is formed at a slightly higher position (a position closer to the crown portion 2B) than that of the embodiment shown in FIG. It

[0021]

[Effect of device]

 According to the two-cycle engine according to the present invention, it is possible to effectively cool the high temperature parts of the piston and the cylinder by using the air-fuel mixture, and to make the temperature of each part uniform. The deformation of the piston and the cylinder due to the thermal strain can be reduced, and the engine seizure can be prevented.

Moreover, since it is not necessary to form a large gap between the cylinder outer diameter and the piston inner diameter, no slap noise is generated.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a configuration of a two-cycle engine according to an embodiment of the present invention.

FIG. 2 is a horizontal cross-sectional view taken along the line II of FIG.

FIG. 3 is a vertical cross-sectional view showing the configuration of a two-cycle engine according to another embodiment of FIG.

FIG. 4 is a transverse sectional view taken along the line II-II of FIG.

FIG. 5 is a vertical cross-sectional view showing the configuration of a conventional two-cycle engine.

[Explanation of symbols]

 2 ... Piston 2B ... Crown part 3 ... Scavenging passage 4 ... Cooling passage 4a ... Base end side opening 4b ... Tip side opening B ... Combustion chamber C ... Crank chamber

Claims (1)

[Scope of utility model registration request] 1. A two-cycle engine configured to supply an air-fuel mixture from a crank chamber to a combustion chamber above a piston through a scavenging passage, wherein a base end side opening is located in a crank chamber side in a crown portion of the piston. A cooling passage formed so as to face the piston and having a front end side opening formed in the outer peripheral surface of the piston was provided, and the crank chamber side and the scavenging passage for supplying the air-fuel mixture to the combustion chamber were communicated via this cooling passage. A two-cycle engine characterized by the following.