JPH0791982B2 - Connecting rod - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting rod for a two-stroke engine, and more particularly to its shape.

[0002]

2. Description of the Related Art In a two-cycle engine, conventionally, intake air introduced into a crank chamber is introduced into a cylinder through a space between a pair of crank webs as the piston moves upward (for example, Actual Kaihei 3-13042
(See Japanese Patent Publication No. 5). An example of this type of two-cycle engine is shown in FIG.

In FIG. 5, a pair of crank webs 20 is provided.
An introduction passage 23 that guides a part of the intake air A into the cylinder 26 is formed between them. The intake air A introduced into the crank chamber 15 is connected to the connecting rod 30A in the introduction passage 23.
It is introduced into the cylinder 26 through the outer periphery of the large end 31 of the and the periphery of the culm portion 33. According to this prior art, the surface P1 of the cross section of the culm portion 33 of the connecting rod 30A that abuts the intake air A is formed by a smooth curve so that the flow of the intake air A is not separated in the culm portion 33, thereby reducing the intake resistance. Is decreasing.

[0004]

By the way, in the intake air A flowing through the introduction passage 23 between the crank webs 20, the central portion of the crank shaft 17 in the axial direction D is closer to the crank web 2.
Faster than near 0 surface. However, in the above prior art,
Since the large end 31 of the connecting rod 30A has a convex shape in cross section, the intake resistance to the intake air A flowing through the center of the introduction passage 23 and having a high flow velocity is large. Therefore, there are cases where the output of the engine cannot be improved yet again.

The present invention has been made in view of the above problems of the prior art. By improving the shape of the connecting rod,
The purpose is to reduce the intake resistance in the crank chamber and improve the output of the two-cycle engine.

[0006]

In order to achieve the above object, the present invention relates to a connecting rod of a two-cycle engine in which intake air is introduced into a crank chamber, in the axial direction of the crank shaft at the large end attached to the crank shaft. A groove through which the intake air passes is formed in an arc shape along the outer periphery of the large end in the central portion.

[0007]

According to the present invention, since the arc-shaped groove is formed along the outer periphery of the large end at the central portion in the axial direction at the large end of the connecting rod, intake air having a high flow velocity passes through the groove, so that The passage area through which fast intake air passes increases. Therefore, the intake resistance is reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. In FIG. 2, the engine 10
Is a two-cycle engine, and an intake passage 16A in the carburetor 18 shown by a chain double-dashed line communicates with the inside of the crank chamber 15 via an intake passage 16B in the crankcase 19.

The crank shaft 17 has a disc-shaped crank web 20 and has an outer diameter close to the crank case 19. As shown in FIG. 3, the crank webs 20 are arranged on both sides of the connecting rod 30, and an intake passage 23 for the intake air A is formed between the crank webs 20 and 20. In this embodiment, the crank web 20
Of the crankshaft 17 protrudes toward the center of the crankshaft 17 in the axial direction D, and the introduction passage 23 is smaller than the width of the large end 31 of the connecting rod 30. An introduction passage 24 is also formed between the crankcase 19 and the crank web 20 in FIG. The intake air A introduced from the intake passage 16B is introduced into the cylinder 26 via the introduction passages 23 and 24.

Intake passage 16 in the crankcase 19
A reed valve 27 is provided at B. As shown in FIG. 3, the reed valve 27 has a valve body 28 whose valve opening direction is set to the axial direction D of the crankshaft 17.

The crank shaft 17 has a crank pin 21.
Is divided in the axial direction D, and therefore, the large end 31 of the connecting rod 30 is an integral type. Ota 31
Through the needle bearing 50 to the crank pin 21
Is attached to. The crankshaft 17 rotates in the direction of arrow R in FIG.

Next, the main part of the present invention will be described. In FIG. 1B, the connecting rod 30 includes a large end 31 and a small end 3 connected to the piston pin 40 (FIG. 2).
2 and the culm 33 extending from the large end 31 toward the small end 32 are integrally formed by forging. A groove 34, through which intake air passes, is formed in a central portion of the large end 31 in the axial direction D of the crankshaft 17 (FIG. 2) along a circumference of the large end 31 as shown by a broken line in FIG. It is formed in an arc shape. The width W of the groove 34 in FIG. 1B is set to be approximately the same as the width of the introduction passage 23, as shown in FIG. Further, the groove 34 and the introduction passage 23 have the same position in the axial direction D. The cross-sectional area and shape of the large end 31 of the connecting rod 30 are set based on the rigidity and strength required for the connecting rod 30.

In the above structure, in the intake stroke in which the large end 31 of FIG. 2 is at the position indicated by the arrow In, the intake air A hits the large end 31 of the connecting rod 30 and is introduced into the cylinder 26 from the crank chamber 15. Therefore, it is inevitable that the large end 31 of the connecting rod 30 hinders the flow of the intake air A.

Here, the flow velocity of the intake air A in the introduction passage 23 is higher in the central portion of the crank shaft 17 in the axial direction D than in the vicinity of the crank web 20 in FIG. In contrast,
At the large end 31 of the connecting rod 30, a groove 34 is formed along the outer periphery of the large end 31 at the center of the crankshaft 17 in the axial direction D as shown by the broken line in FIG. A portion of the intake air A having a high flow velocity is introduced into the crank chamber 15 through the groove 34. Therefore, since the passage area through which the intake air A having a high flow velocity passes increases, the intake resistance decreases as compared with the conventional case, and as a result, the output of the engine improves.

In particular, in the engine 10 in which the crank web 20 projects toward the introduction passage 23 side as in this embodiment, the groove 34 has a width W approximately the same as that of the introduction passage 23.
Since the flow of the intake air A is smooth by being provided in (FIG. 1B) and at the same axial position, the intake resistance is further reduced.

By the way, the needle bearing 50, which is a bearing of the connecting rod 30, receives the connecting rod 30 by the intake air A.
Is cooled via the large end 31 of the. Here, like the connecting rod 30, by providing the groove 34 in the large end 31, the surface area of the large end 31 on which the intake air A hits is increased, and the axial direction D of the large end 31 on which the needle bearing 50 is mounted is increased. Since the thickness of the central portion is thin, the cooling effect of the needle bearing 50 is enhanced.

In the first embodiment, a part of the crank web 20 is projected to the introduction passage 23 side, but it is not always necessary to do so, and the crank web 20 as in the second embodiment of FIG. The thickness may be set to be substantially uniform.
The other structure of the second embodiment is similar to that of the first embodiment, and the same portions or corresponding portions are designated by the same reference numerals and the description thereof will be omitted.

Further, in each of the above embodiments, the crank web 20 is provided on both sides of the connecting rod 30, but the present invention can be applied to the case where the crank web 20 is provided only on one side of the connecting rod 30. , Within the scope of this invention.

In each of the above embodiments, the connecting rod 30 is used.
The groove 34 is also provided at the base of the culm portion 33 at the large end 34 as shown in FIG. 1A, but it is not always necessary to provide the groove 34 almost all around. For example, Ota 3
It may be provided on the opposite side of the culm portion 33 in 1 along the outer circumference of the large end 31 by about 180 °.

[0020]

As described above, according to the present invention, the groove through which the intake air passes is formed in an arc shape along the outer periphery of the large end at the axially central portion of the crankshaft at the large end.
A portion of the intake air having a high flow velocity passes through the groove. Therefore, the intake resistance is reduced and the output of the two-cycle engine is improved. Further, since the groove is formed on the large end, the surface area of the large end that is cooled by the intake air is increased, so that the cooling effect of the bearing portion at the large end is increased through the large end.

[Brief description of drawings]

1A is a front view of a connecting rod showing a first embodiment of the present invention, and FIG. 1B is a longitudinal sectional view of the same.

FIG. 2 is a vertical sectional view of a two-cycle engine.

FIG. 3 is a main sectional view of the same.

FIG. 4 is a main sectional view of a two-stroke engine according to a second embodiment.

FIG. 5 is a main sectional view of a two-cycle engine according to a conventional example.

[Explanation of symbols]

15 ... Crank chamber, 17 ... Crank shaft, 30 ... Connecting rod, 31 ... Large end, 34 ... Groove, A ... Intake.

Claims (1)

[Claims] 1. In a connecting rod of a two-cycle engine in which intake air is introduced into a crank chamber, a groove through which intake air passes is formed in a central portion in the axial direction of the crank shaft at a large end attached to the crank shaft, the outer periphery of the large end. A connecting rod characterized by being formed in an arc shape along the line.