JPH066196Y2 - 2-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a two-cycle engine in which intake air is introduced into a crank chamber.

[Conventional technology]

In this type of two-cycle engine, generally, an intake passage to the crank chamber is provided in a state of being offset with respect to the axis of the crankshaft, and a passage for intake air is provided between the outer periphery of the crank web and the crankcase. (See, for example, Japanese Utility Model Publication No. 51-76204). Therefore, since the crank web is relatively small with respect to the volume of the crank chamber, the preload of the crank chamber cannot be sufficiently increased.

Therefore, conventionally, there has been known a two-cycle engine in which the outer diameter of the crank web is set to be approximately the same as the inner diameter of the crank case, and the intake air is guided between two crank webs arranged on both sides of the connecting rod as an introduction passage. ing. In this two-cycle engine, the preload of the crank chamber becomes relatively large.

[Problems to be solved by the device]

However, in this conventional technique, since the cross-sectional shape of the introduction passage between the crank webs is flat, the introduction passage having the flat shape and the cross-sectional shape of the intake passage toward the crank chamber are significantly different. Therefore, the flow of intake air collides with the outer circumference of the crank web. Therefore, the flow of intake air is not smooth, and intake resistance increases.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a two-cycle engine that can sufficiently increase the preload of the crank chamber and has a small intake resistance.

[Means for Solving the Problems]

In order to achieve the above object, the present invention firstly sets the opening direction of the reed valve provided in the intake passage to the axial direction of the crankshaft, and also the radial width of the crank web in the reed valve. Is set to be almost the same as the outer diameter of the crank web. The introduction passage side between the crank webs in the outer peripheral portion of the crank web is formed in a smooth curved shape and smoothly spreads in the axial direction of the crank shaft toward the intake passage,
The width of the introduction passage in the outer peripheral portion of the crank web is set to be substantially the same as the distance between the two valve bodies that are opened in the reed valve.

[Action]

According to this invention, since the radial width of the crank web in the reed valve is set to be substantially the same as the outer diameter of the crank web, the cross-sectional shape of the intake passage in the reed valve is relatively flat. Therefore, since the intake passage of the reed valve has a shape close to the cross-sectional shape of the introduction passage between the crank webs, it is possible to sufficiently guide the intake air to the narrow introduction passage without thinning the crank web. It is possible to prevent a decrease in preload.

Moreover, since the introduction passage between the crank webs smoothly expands in the axial direction of the crankshaft toward the intake passage, the width of the introduction passage in the outer peripheral portion of the crank web is increased by the opening of the reed valve. Since the distance between the two valve bodies is set to be approximately the same, intake air does not easily collide with the outer peripheral portion of the crank web even if the crank web is not made thin as a whole. The flow of intake air into the engine can be smoothed, and a decrease in the preload of the crank chamber can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, an engine 10 is, for example, a two-cylinder V-type two-cycle engine, and is mounted in the center of the body of an unillustrated motorcycle. Intake passage 16 to crank chamber 15
Is provided so as to extend obliquely downward and forward from above,
Therefore, the intake air A is introduced by downdraft. The axis C of the first and second cylinders 11 and 12 of the engine 10
1, C2 are set at positions farther than 90 ° from the axis C of the intake passage 16 about the crankshaft 17. The cylinders 11 and 12 are symmetrical with respect to the axis C of the intake passage 16.

The intake passage 16a in the carburetor 18 shown by the chain double-dashed line passes through the intake passage 16b in the crankcase 19 and the crank chamber 15
Are arranged in a straight line toward the above both intake passages.
16a and 16b extend toward the axis O of the crankshaft 17.

The crank shaft 17 has a disc-shaped crank web 20 and has an outer diameter close to the crank case 19 shown by a chain double-dashed line. The axial direction D of the crankshaft 17 shown in FIG. 2 is set in the width direction of the vehicle body.

The crank webs 20 are arranged on both sides of the connecting rod 22, and a first introduction passage 23 for the intake air A is formed between the crank webs 20, 20. The first introduction passage 23 has a flat cross-sectional shape in which the width in the axial direction D is set to be slightly wider than the culm portion 33 of the connecting rod 22.

As shown in FIG. 1, a second introduction passage 24 for the intake air A is also partially provided between the outer periphery of the crank web 20 and the crankcase 19. Therefore, the intake air A introduced from the intake passage 16 is introduced into the cylinder 26 via the first and second introduction passages 23 and 24.

The inlet of the carburetor 18 and the intake passage 16a therein
Is, as shown in FIG. 3, the crankshaft 17 (FIG. 1).
Has a substantially rectangular cross section that is long in the radial direction B.

The intake passage 16b in the crankcase 19 shown in FIG.
Crankshaft 17 as smooth as the first introduction passage 23 between
In the radial direction B. On the other hand, this intake passage 16b
As shown in FIG. 2, the shaft is smoothly narrowed in the axial direction D of the crankshaft 17 as it goes downstream. Therefore, the intake passage 16b in the crankcase 19 has a substantially rectangular cross section that is long in the radial direction B of the crankshaft 17 in FIG. 1 as it goes downstream, and is close to the cross sectional shape of the first introduction passage 23. It has a shape.

A reed valve 27 is provided in the intake passage 16b in the crankcase 19. The width W of the reed valve 27 in the radial direction B of the crank shaft 17 is set to be substantially the same as the outer diameter of the crank web 20. As shown in FIG. 2, in the reed valve 27, the valve opening direction of the valve body 28 is the crankshaft 17
Is set in the axial direction D.

The crank web 20 has a first outer peripheral portion 20a.
The introduction passage 23 side is formed in a smooth curved shape except for a connecting portion with the large end 29 of the connecting rod 22. Therefore,
The first introduction passage 23 extends smoothly toward the intake passage 16b in the crankcase 19.

The width D1 of the first introduction passage 23 at the outermost periphery of the crank web 20 is set to be substantially the same as the distance between the valve bodies 28 of the reed valve 27 that has been opened. The width D2 of the second introduction passage 24 is set to be substantially the same as the maximum width D1 of the first introduction passage 23.

The crankshaft 17 is located at the crankpin 30 in the axial direction D.
Is divided into, therefore, the large end 29 of the connecting rod 22.
Are integrated. The crankshaft 17 rotates in the direction of arrow R in FIG.

In the above-described configuration, the present invention sets the width W of the reed valve 27 in the radial direction B of the crankshaft 17 to the crank web 20.
The size of the intake passage is set to be about the same as the diameter of
The flow of the intake air A from the 16 to the first introduction passage 23 between the crank webs 20, 20 is smooth. Also, as shown in FIG.
Since the first introduction passage 23 spreads smoothly toward the intake passage 16, the flow of the intake air A from the intake passage 16 toward the first introduction passage 23 becomes smooth.

Particularly, in this embodiment, the width D1 of the first introduction passage 23 at the outermost circumference of the crank web 20 is set to the opened reed valve 27.
Since the distance between the valve bodies 28 is set to be almost the same, the flow of the intake air A becomes smoother.

Further, in this embodiment, the cross sectional shape of the intake passage 16a of the carburetor 18 shown in FIG. 3 is also long in the radial direction B of the crankshaft 17 shown in FIG.
The intake passage 16b in the crankcase 19 that communicates with the CW spreads smoothly toward the downstream side to the same extent as the first introduction passage 23 between the crank waves 20, 20, so that the flow of the intake air A becomes smoother. Become.

On the other hand, according to the present invention, as described above, the intake air A smoothly flows from the intake passage 16 to the first introduction passage 23 between the crank webs 20, 20, so that the diameter of the crank web 20 can be increased to increase the crank web. The second introduction passage 24 on the outer periphery of 20 can be made small. Therefore, the preload of the crank chamber 15 can be kept large.

Further, in this embodiment, since the axis lines C1 and C2 of the cylinders 11 and 12 are set at positions apart from the axis line C of the intake passage 16 to the crank chamber 15 by more than 90 °, the intake passage 16 is separated from the intake passage 16. The flow of intake air A toward the skirt portion 32 of the piston is
Both 11 and 12 do not turn much. Therefore, the flow of the intake air A becomes smooth.

In the above embodiment, the axis C of the intake passage 16 is arranged toward the axis O of the crankshaft 17, but the intake passage 16 is slightly offset to the second introduction passage 24 side for each cylinder 11, 12. May be provided.

Further, although the V-type engine has been described in the above embodiment, a 2-cycle engine other than the V-type engine may be used. Further, although the above embodiment has been described with respect to a two-cylinder engine, the present invention can be applied to an engine having one cylinder or three or more cylinders.

[Effect of device]

As described above, according to the present invention, the radial width of the crank web in the reed valve is set to be substantially the same as the outer diameter of the crank web, so that the cross-sectional shape of the intake passage in the reed valve is flat. Since it is close to the cross-sectional shape of the introduction passage between the webs, the resistance of the intake air due to the difference in the cross-sectional shape of both passages is reduced. Moreover, the introduction passage between the crank webs is smoothly expanded toward the intake passage, and therefore, the intake air smoothly flows from the intake passage to the introduction passage, so that the intake resistance is reduced. Further, since the intake air smoothly flows into the introduction passage between the crank webs as described above, the diameter and the wall thickness of the crank web can be set to be large, so that the preload of the crank chamber can be kept large.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a two-cycle engine showing an embodiment of the present invention, FIG. 2 is a main sectional view of the same, and FIG. 3 is II of FIG.
It is a sectional view taken along the line I-III. 10 ... 2-cycle engine, 15 ... Crank chamber, 16 ... Intake passage, 17 ... Crank shaft, 20 ... Crank web, 20a ... Crank web outer peripheral portion, 22 ... Connecting rod, 23 ... (first) introduction passage, 26 ... Cylinder , 27 ... Reed valve, 28 ... Valve body,
A ... intake air, D ... axial direction of crankshaft, D1 ... width of introduction passage, W ... width of reed valve.

Claims (1)

[Scope of utility model registration request] 1. A two-cycle engine in which crank webs are arranged on both sides of a connecting rod, and intake air is introduced into a cylinder from an intake passage of a reed valve via an introduction passage between the crank webs. The opening direction of the reed valve provided in the axial direction of the crankshaft is set, the radial width of the crank web in the reed valve is set to be substantially the same as the outer diameter of the crank web, and The introduction passage side of the outer peripheral portion of the crank web is formed in a smooth curved shape, and the introduction passage smoothly expands in the axial direction of the crank shaft toward the intake passage, whereby the outer peripheral portion of the crank web is formed. The width of the introduction passage in is set to be substantially the same as the distance between the two valve bodies that are opened in the reed valve. Two-cycle engine.