WO2012132658A1

WO2012132658A1 - Two-stroke engine

Info

Publication number: WO2012132658A1
Application number: PCT/JP2012/054304
Authority: WO
Inventors: 健治今福
Original assignee: 株式会社マキタ
Priority date: 2011-03-31
Filing date: 2012-02-22
Publication date: 2012-10-04

Abstract

Provided is a two-stroke engine capable of decreasing height in the vertical direction and reducing a blow-by by improving exhaust efficiency. This two-stroke engine comprises: a cylinder with a cylinder center axis extending in the horizontal or a nearly horizontal direction in a normal state of use, and with a columnar inner circumferential surface; a piston capable of reciprocating within the cylinder; and an exhaust channel portion provided in the cylinder. In the inner circumferential surface of the cylinder, an exhaust opening of the exhaust channel portion is formed, with most of the effective cross-sectional area of the exhaust opening being located at an upper-direction side position with respect to the center of the cylinder in a bore cross section in the normal state of use, the exhaust channel portion extending at an angle with respect to the radius direction in the bore cross section of the cylinder. In the inner circumferential surface of the cylinder, a cylinder-side scavenging opening of a scavenging channel portion is formed such that a scavenging flow scavenged via the cylinder-side scavenging opening is directed toward a lower-direction position with respect to the cylinder center axis in the bore cross section in the normal state of use.

Description

2-stroke engine

The present invention relates to a two-stroke engine.

The two-stroke engine can be easily reduced in size and weight because of its simple structure.
Therefore, it is often used for portable or small machines.
Here, the portable or small machine means, for example, a brush cutter, a coffee harvester, an olive harvester, a hedge trimmer, a chain saw, a blower, a management machine, a cultivator, a generator, a compressor, a pump, a work machine, a pocket bike, a motor. Leisure equipment such as paragliding.
These machines are required to be smaller, lighter, and have higher thermal efficiency and lower pollution than installation-type or large-scale machines.

Patent Document 1 discloses a technique in which an opening portion of an exhaust passage portion is formed at a horizontal position with respect to a center of a cylinder in a Schneure type two-stroke engine.

Patent Document 2 discloses a technique in which an opening portion of an exhaust passage portion is formed at a horizontal position with respect to a center of a cylinder in a schnuille type two-stroke engine.

Patent Document 3 discloses a technique in which an opening of an exhaust passage portion of a two-stroke engine in which a cylinder is arranged in a horizontal or nearly horizontal posture is formed at a horizontal position with respect to the center of the cylinder.

Patent Document 4 discloses a technique in which, in a two-stroke engine in which a cylinder is arranged in a horizontal or nearly horizontal posture, a large portion of the opening of the exhaust passage is formed in an upward direction from the center of the cylinder. Yes.

JP 59-134323 A JP 2000-34927 A JP 2000-310123 A JP-A 61-229923

In a hand-held or miniaturized engine, there is a demand to reduce the vertical height in a normal use state.
However, in the two-stroke engine in which the cylinders are formed in the vertical direction as in Patent Document 1 and Patent Document 2, it is difficult to reduce the height in the vertical direction because of the structure.
Therefore, as in Patent Document 3, the cylinder is arranged in a horizontal or nearly horizontal posture.
Further, as in Patent Document 4, in a Schneille type two-stroke engine, in a type in which the cylinder is arranged in a horizontal or nearly horizontal posture and the exhaust passage portion is extended in the vertical direction, the height of the exhaust passage portion in the vertical direction is increased. There is a problem that becomes high.
Furthermore, in the two-stroke engine, there is a problem that scavenging gas flows out through the exhaust passage without burning.

An object of the present invention is to provide a two-stroke engine capable of suppressing the height in the vertical direction and capable of reducing the blow-by by improving the exhaust efficiency.

A two-stroke engine according to a first aspect of the present invention includes a cylinder having a cylinder center axis extending in a horizontal or nearly horizontal direction in a normal use state, an inner peripheral surface having a cylindrical shape, a piston capable of reciprocating in the cylinder, An exhaust passage portion provided in the cylinder, and an exhaust opening portion of the exhaust passage portion is formed on an inner peripheral surface of the cylinder, and a large portion of an effective sectional area of the exhaust opening portion is a bore cross-section. The exhaust passage portion extends at an angle with respect to the radial direction in the bore cross section of the cylinder.

Preferably, the exhaust passage portion includes a first exhaust passage portion on the exhaust opening side, and a second exhaust passage portion connected to the first exhaust passage portion. The central axis of one exhaust passage portion extends in the radial direction in the bore cross section of the cylinder, and the central axis of the second exhaust passage portion extends at an angle with respect to the radial direction in the bore cross section of the cylinder. ing.

Preferably, the crankshaft is formed perpendicular to the central axis of the cylinder and in a horizontal direction in a normal use state.

Preferably, a cylinder-side scavenging opening of the scavenging passage is formed on the inner peripheral surface of the cylinder, and scavenging from the cylinder-side scavenging opening of the scavenging passage is within the inner peripheral surface of the cylinder. It is a Schnure type formed so as to be led to a position opposite to the portion where the exhaust opening is formed.

A two-stroke engine according to a second aspect of the present invention is a cylinder having a cylinder central axis extending in a horizontal or nearly horizontal direction in a normal use state, an inner peripheral surface having a cylindrical shape, a piston capable of reciprocating in the cylinder, A scavenging passage portion provided in the cylinder, and an exhaust passage portion provided in the cylinder, the exhaust passage portion being formed at an angle with respect to a radial direction in a bore section of the cylinder, A cylinder-side scavenging opening of the scavenging passage is formed on the inner peripheral surface of the cylinder, and the direction of the scavenging air scavenged from the cylinder-side scavenging opening is less than the central axis of the cylinder in the bore cross section. It is formed so as to face the lower direction position in a normal use state.

Preferably, the direction of the scavenging air scavenged from the cylinder-side scavenging opening is in the range of an angle of ± 60 ° with respect to the vertical under normal use condition with respect to the central axis of the cylinder 5 in the bore cross section. .

Preferably, a cylinder-side scavenging opening of the scavenging passage is formed on the inner peripheral surface of the cylinder, and scavenging from the cylinder-side scavenging opening of the scavenging passage is performed on the inner peripheral surface of the cylinder. Of these, it is a schnure type formed so as to be led to a position opposite to the portion where the exhaust opening is formed.

Preferably, an intake opening and a crank chamber side scavenging opening are formed in a crank chamber surrounded by the cylinder, the crankcase, and the piston, and the counterweight formed on the crankshaft is formed from the intake opening. It is formed so that the direction of the linear direction and the rotation direction of the counterweight coincide.

A two-stroke engine according to a third aspect of the present invention is a cylinder in which the center axis of a cylinder extends in a horizontal or nearly horizontal direction in a normal use state, an inner peripheral surface has a cylindrical shape, a piston capable of reciprocating in the cylinder, A scavenging passage portion provided in the cylinder; and an exhaust passage portion provided in the cylinder; a cylinder side scavenging opening of the scavenging passage portion is formed on an inner peripheral surface of the cylinder; A crankshaft that converts a reciprocating motion of the piston into a rotational motion via a connecting rod, and a crankcase that supports the crankshaft, and the crank chamber surrounded by the cylinder, the piston, and the crankcase A crank chamber side scavenging opening of the scavenging passage is formed, and most of the crank chamber side scavenging opening is in a normal use state. It arranged on the upper side than the central axis of the cylinder Te.

According to the present invention, it is possible to provide a two-stroke engine capable of suppressing the height in the vertical direction and capable of reducing the blow-by by improving the exhaust efficiency.

1 is a cross-sectional view of a two-stroke engine according to a first embodiment of the present invention. It is explanatory drawing in the cross section in II-II in FIG. It is explanatory drawing of A arrow in FIG. 1, and A arrow in FIG. It is explanatory drawing of 2nd Embodiment. It is explanatory drawing of 3rd Embodiment. It is explanatory drawing of 4th Embodiment. It is explanatory drawing of 5th Embodiment. It is explanatory drawing of 6th Embodiment. It is explanatory drawing of 7th Embodiment. It is explanatory drawing of 8th Embodiment. It is explanatory drawing of 9th Embodiment.

<First Embodiment>
FIG. 1 is a cross-sectional view of a two-stroke engine 1 according to a first embodiment of the present invention.

Hereinafter, the first embodiment of the present invention will be described in detail with reference to FIG.
As shown in FIG. 1, the two-stroke engine 1 includes a cylinder head 3, a cylinder 5, a crankcase 7, a piston 21, and a connecting rod 19.
The cylinder head 3 does not need to be separated from the cylinder 5 and may be formed integrally as shown in FIG.

A crank chamber 31 is formed by the cylinder 5, the crankcase 7 and the piston 21. That is, the crank chamber 31 is a space formed between the inner peripheral surface of the cylinder 5 and the piston 21 and the substantially cylindrical space on the crankcase 7 side, and the crankcase 7.
The volume of the internal space of the crank chamber 31 changes as the piston 21 slides.
A combustion chamber 29 is formed by the cylinder head 3, the cylinder 5 and the piston 21.

A crankshaft 9 is rotatably supported in the crank chamber 31.
The crankshaft 9 includes a crankpin 11, a crank journal 13, a counterweight 15, and a crank arm 17.
On the cylinder head 3 side of the connecting rod 19, the connecting rod 19 supports the crank pin 11 so as to be rotatable.
Further, on the side of the connecting rod 19 on the crank chamber 31 side, the connecting rod 19 supports the piston 21 so as to be swingable.
The piston 21 slides inside the cylinder 5.

The cylinder 5 is formed with an intake opening 23a.
An intake passage portion 23 through which an air-fuel mixture that has passed through an air cleaner (not shown) and a carburetor (not shown) flows into the crank chamber 31 is provided through the intake opening portion 23a.
The crank chamber 31 has a crank chamber-side scavenging opening 25a.
The scavenging gas is sent to the scavenging passage 25 through the crank chamber side scavenging opening 25a.
The scavenging of the scavenging passage 25 flows into the cylinder 5 (combustion chamber 29) through a cylinder-side scavenging opening 25b formed in the cylinder 5.
An exhaust opening 27 a is formed in the cylinder 5.
Exhaust gas is discharged into the exhaust passage 27 through the exhaust opening 27a.

The two-stroke engine assumed in the present embodiment is small for carrying and is not necessarily operated in a certain direction because of its portability.
However, for normal use, it is usually assumed that the most common work state. In other words, it is temporarily assumed that the top and bottom are used upside down, or that they are used with a large inclination, but when viewed comprehensively, they are designed for use in a certain state for many hours. . Even if the user temporarily uses the device in a different state, the user usually uses the device in the designed state.
Therefore, in the present embodiment, the state described in FIG. 1 and the like is that in the normal use state.
Here, the direction is defined.
In the normal use state, the upward direction in the vertical direction is referred to as the upper direction. Conversely, the ground side direction is defined as the lower direction.
In addition, a vertical direction is defined as a horizontal direction with respect to a vertical direction in a normal use state.

The central axis of the cylinder 5 is formed so as to be horizontal or nearly horizontal as shown in FIG. In FIG. 1, the center axis of the cylinder 5 is in a state inclined about + 30 ° from the horizontal direction.
In the present embodiment, the state close to the horizontal means a range up to about plus or minus 45 degrees with respect to the horizontal. This is because within this range, a two-stroke engine can be configured without increasing the height in the vertical direction.

The cylinder head 3 is provided with a spark plug 33 that penetrates the cylinder head 3 and exposes an ignition portion to the combustion chamber 29.
The ignition part of the spark plug 33 is also formed in the cylinder head 3 with an ignition space for this purpose.

An intake opening 23 a is formed in a portion of the cylinder 5 in the direction toward the crank chamber 31.
The intake passage portion 23 that forms the intake opening portion 23 a communicates from the cylinder head 3 side toward the crank chamber 31 side and toward the center axis side of the cylinder 5.
A crank chamber side scavenging opening 25a is formed at the center of the cylinder 5 or a portion in the upper direction.
The scavenging passage 25 forming the crank chamber side scavenging opening 25a is formed from the crank chamber 31 side toward the cylinder head 3 side.
Further, the rotation direction of the crankshaft 9 rotates counterclockwise in FIG. That is, the crankshaft 9 rotates in the direction in which the air-fuel mixture flowing in from the intake opening 23a enters.
In other words, when a straight line is drawn from the intake opening 23 a to the counterweight 15 of the crankshaft 9 in the state of FIG. 1, the direction of the straight line coincides with the rotational direction of the crankshaft 9.
Thus, the air-fuel mixture can flow more smoothly from the intake opening 23a to the crank chamber 31 by the rotation of the crankshaft 9 (particularly the counterweight 15).

The cylinder 5 is formed with a cylinder-side scavenging opening 25b and an exhaust opening 27a at a position in the direction of the crank chamber 31.
The cylinder side scavenging opening 25b is formed at a position closer to the crank chamber 31 than the exhaust opening 27a.
That is, the port timing is formed so that the exhaust opening 27a is opened first, and then the cylinder-side scavenging opening 25b is opened. Further, the scavenging passage 25 extends in the axial direction of the center axis of the cylinder 5 (from the position in the crank chamber 31 side direction to the position in the cylinder head 3 side direction). The scavenging passage 25 is opened to the cylinder 5 by the cylinder-side scavenging opening 25b.
The Schnule type two-stroke engine 1 having such a structure can increase the charging efficiency. The reason will be described below.

As described above, the scavenging passage 25 extends to the axial component of the central axis of the cylinder 5 and opens into the cylinder 5 through the cylinder-side scavenging opening 25b.
Therefore, the air-fuel mixture flowing in from the cylinder-side scavenging opening 25b has an angle component in the cylinder head 3 side direction (top dead center side).
As a result, when the piston 21 moves to the vicinity of the bottom dead center and the blockage of the cylinder-side scavenging opening 25b by the piston 21 is released, the air-fuel mixture becomes a side surface in a lower direction than the central axis of the cylinder 5, and Then, it flows into the side surface on the cylinder head 3 side so as to collide.
Then, the air-fuel mixture flows toward the exhaust opening 27a through the side surface on the lower side than the central axis of the cylinder 5 and the side surface on the cylinder head 3 side.
Then, the piston 21 moves before and after the leading portion of the air-fuel mixture flow reaches the exhaust opening 27a to close the cylinder-side scavenging opening 25b.
The air-fuel mixture efficiently sucked into the crank chamber 31 from the intake opening 23a is further pumped from the crank chamber 31 through the scavenging passage 25 to the combustion chamber 29 above the piston 21 from the cylinder-side scavenging opening 25b. Since the air-fuel mixture flows in the combustion chamber 29 in this way, the exhaust gas generated by the combustion cycle can be discharged more efficiently by the flow of the air-fuel mixture.
And since it becomes possible to discharge | emit exhaust efficiently in this way, it is possible to raise supply ratio, supply efficiency, and filling efficiency.

FIG. 2 is an explanatory view in a section taken along line II-II in FIG.

As shown in FIG. 2, the scavenging passage 25 is composed of two passages. A passage portion on the right side of the center axis of the cylinder 5 is the right scavenging passage portion 25R, and a passage portion on the left side of the center axis of the cylinder 5 is the left scavenging passage portion 25L.
The right scavenging passage portion 25R and the left scavenging passage portion 25L are formed so as to extend from the back side to the front side in FIG.
Note that the number of the scavenging passage portions 25 is not necessarily two as shown in FIG. 2, and may be more than that.
The opening part of the right scavenging passage 25R to the cylinder 5 is the right scavenging opening 25bR, and the opening part of the left scavenging passage 25L to the cylinder 5 is the left scavenging opening 25bL.
Moreover, the opening part to the cylinder 5 of the exhaust passage part 27 is the exhaust opening part 27a.

As shown in FIG. 2, the flow that has flowed out of the right scavenging opening 25bR and the left scavenging opening 25bL travels through the combustion chamber 29, and then collides with the side surface at a position below the central axis of the cylinder 5.
Furthermore, the flow from the right scavenging opening 25bR and the flow from the left scavenging opening 25bL collide with each other and flow toward the exhaust opening 27a as a mixed flow.

As shown in FIG. 2, a cross section in a direction perpendicular to the central axis of the cylinder 5 is called a bore cross section.
Further, in the bore cross section, the inner peripheral surface direction of the cylinder 5 is referred to as a circumferential direction. Further, in this bore cross section, the radiation direction from the intersection of the bore cross section and the central axis of the cylinder 5 is referred to as a radial direction.

As shown in FIG. 2, the exhaust opening 27 a opens at a position directly above the central axis of the cylinder 5 in the upper direction than the central axis of the cylinder 5.
A right scavenging opening 25bR and a left scavenging opening 25bL are formed at the right side position and the left side position of the exhaust opening 27a, respectively.
The right scavenging opening 25bR and the left scavenging opening 25bL are also opened at positions above the central axis of the cylinder 5 axis.

Here, from the scavenging passage 25, air-fuel mixture, liquid and particulate fuel components, oil, oil mist and the like flow into the combustion chamber 29 in the cylinder 5.
Most of the fuel component (liquid and particulate fuel, oil, oil mist, etc.) among them flows into the combustion chamber 29 on the air-fuel mixture flow as shown by the arrows in FIG.
However, a part of the fuel component having a large mass does not get on the flow of the air-fuel mixture, but flows along the wall surface of the cylinder 5 between the cylinder-side scavenging opening 25b and the exhaust opening 27a, or flows along the wall surface and directly. Exhausted from the exhaust passage portion 27 (hereinafter referred to as wall surface transmission and transmission of a large fuel component from the cylinder side scavenging opening 25b to the exhaust opening 27a along the wall surface or flowing along the wall surface. This is called a shortcut.)
That is, a part of the fuel component having a large mass is discharged from the exhaust passage portion 27 without being burned.
As described above, the generation of fuel components, oil, and oil mist that have entered the exhaust passage portion 27 without being burned lowers the air supply efficiency and lowers the charging efficiency.
Further, unburned fuel components, oil, and oil mist contaminate the exhaust of the 2-stroke engine 1 and deteriorate the environmental performance of the 2-stroke engine 1.
Therefore, the exhaust opening 27 a is formed at a position in the upward direction from the central axis of the cylinder 5.
If it does so, it can reduce that a fuel component with a large mass penetrate | invades into the exhaust passage part 27 by wall surface transmission and a shortcut.

The formation of the exhaust opening 27a at a position in the upper direction from the central axis of the cylinder 5 means that in the Schneure side two-stroke engine 1, most of the effective sectional area of the cylinder side scavenging opening 25b is in the bore cross section. The direction of the scavenging air disposed above the central axis of the cylinder 5 and scavenged from the cylinder-side scavenging opening 25b is the lower direction in the normal use state with respect to the central axis of the cylinder 5 in the bore cross section. In some cases, it is formed so as to face the position.

Alternatively, the direction of the scavenging air scavenged from the cylinder-side scavenging opening 25b is formed so as to face the lower direction position in the normal use state with respect to the center axis of the cylinder 5 in the bore cross section.
By adopting such a configuration, it is possible to suppress wall surface transmission and shortcut of a fuel component having a large mass.
Since the cylinder-side scavenging opening 25b is formed at such a position, the exhaust opening 27a is also formed at a position in the upward direction from the central axis of the cylinder 5 in the Schneure type two-stroke engine 1. become.

Furthermore, the direction of the scavenging air scavenged from the cylinder-side scavenging opening 25b is formed so as to be directed to the lower direction position in the normal use state with respect to the central axis of the cylinder 5 in the bore cross section.
More preferably, an angle range of ± 60 ° with respect to the vertical under normal use condition is more suitable than the central axis of the cylinder 5.
And by having comprised in this way, a fuel component with large mass (oil mist, the fuel which is not vaporized, etc.) can be sent out to the combustion chamber 29 side of the cylinder 5, and the burned gas can be scavenged efficiently. It becomes possible.
That is, the fuel component having a large mass is sent to the lower side of the center axis of the cylinder and then expelled the burned gas in the combustion chamber 29 while changing the direction. Easy to stop.
However, in the case of the above configuration, the fuel component having a large mass itself becomes a main scavenging air flow and performs a scavenging action, so that it is difficult to be discharged by shortcut to the exhaust opening 27a.
As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.

It is sufficient that the position of the exhaust opening 27 a is provided in the upper direction from the center axis of the cylinder 5.
That is, as shown in FIG. 2, the exhaust opening 27 a need not be formed only at a position directly above the central axis of the cylinder 5.
This is because the wall surface transmission and shortcut of the fuel component having a large mass can be prevented only by being provided above the central axis of the cylinder 5.
As a result, the exhaust opening 27a is not only located at the position directly above the center axis of the cylinder 5, but may be located at the right side position or the left side position as long as it is merely above the center axis of the cylinder 5. .
In other words, in other words, most of the effective sectional area of the exhaust opening 27a is formed at a position on the upper side in the normal use state with respect to the center of the cylinder 5 in the bore section. it can.
That is, if it is a part of the exhaust opening 27a, it is allowed to be formed at a position on the lower side in the normal use state with respect to the center of the cylinder 5 in the bore cross section.

The fact that most of the effective sectional area of the exhaust opening 27a is formed at a position on the upper direction side in the normal use state with respect to the center of the cylinder 5 in the bore cross section means that the Schneul type two-stroke engine 1 In this case, it is normal to cause the scavenging air to collide with the wall on the opposite side of the exhaust opening 27a.
Therefore, the right scavenging opening 25bR and the left scavenging opening 25bL are disposed on both sides of the exhaust opening 27a as shown in FIG.
Even if most of the effective sectional area of the exhaust opening 27a is formed at a position on the upper side side of the center of the cylinder 5 in the bore cross section, the right scavenging opening 25bR and the left scavenging opening 25bL are in the bore cross section. It is not necessarily formed at a position on the upper direction side of the center of the cylinder 5.
This is because the right scavenging opening 25bR and the left scavenging opening 25bL are arranged on both sides of the exhaust opening 27a.
Therefore, when the exhaust opening 27a is disposed at one horizontal position, the horizontal one-side cylinder-side scavenging opening 25b is positioned below the center of the cylinder 5 in the bore cross section. And it is because it will be formed in the position of the one side.

Further, as shown in FIG. 2, the exhaust passage portion 27 has a certain angle with respect to the radial direction in the bore cross section.
This is because if the exhaust passage portion 27 is formed with no angle with respect to the radial direction in the bore cross section, the height of the occupied space of the two-stroke engine 1 becomes high due to the exhaust passage portion 27.
Therefore, in order to reduce the occupied space of the two-stroke engine 1, it is preferable that the direction in which the exhaust passage portion 27 extends is the horizontal direction.
Even if the exhaust opening 27a is provided at a position directly above the central axis of the cylinder 5 as shown in FIG. 2, if the exhaust passage 27 is provided in a horizontal or nearly horizontal direction, the stroke is somewhat It is possible to reduce the height of the occupied space of the engine 1.
More preferably, the exhaust opening 27a is provided not at a position directly above the central axis of the cylinder 5 but at a right side position or a left side position. By providing the exhaust opening 27a at such a position and extending the exhaust passage 27 in a direction that is horizontal or nearly horizontal in the direction of the provided side, the height of the occupied space of the two-stroke engine 1 can be further suppressed. Because it becomes.

FIG. 3 is an explanatory view of the arrow A in FIG. 1 and the arrow A in FIG.

As shown in FIG. 3, the right scavenging opening 25bR and the left scavenging opening 25bL are located closer to the crank chamber 31 than the exhaust opening 27a.
Thus, since the exhaust opening 27a is located on the cylinder head 3 side, the exhaust passage 27 (exhaust opening 27a) first communicates with the combustion chamber 29 as the piston 21 moves toward the crank chamber 31. Will do.
As a result, the exhaust in the combustion chamber 29 is discharged out of the cylinder 5 from the portion of the exhaust opening 27a on the cylinder head 3 side.
While the piston 21 moves to the crank chamber 31 side, the exhaust gas is discharged from the combustion chamber 29 to some extent.
As a result, the right scavenging passage 25R (right scavenging opening 25bR) and the left scavenging passage 25L (left scavenging opening 25bL) communicate with the combustion chamber 29 in a state where the pressure in the combustion chamber 29 is reduced.
As a result, scavenging gas flows in with exhaust exhausted after the previous combustion cycle being exhausted, so exhaust can be exhausted more effectively. .

<Second Embodiment>
FIG. 4 is an explanatory diagram of the second embodiment.

As shown in FIG. 4, the exhaust passage portion 27 includes a first exhaust passage portion 127 provided on the cylinder 5 side (exhaust opening portion 27 a), and a second exhaust passage portion continuous with the first exhaust passage portion 127. And an exhaust passage portion 227.
The first exhaust passage portion central axis 127a of the first exhaust passage portion 127 is formed to coincide with or coincide with the radial direction in the bore cross section.
The second exhaust passage portion central axis 227a of the second exhaust passage portion 227 is formed to have a certain angle with the radial direction in the bore cross section.
As a result, the second exhaust passage portion center axis 227a is bent at a certain angle with respect to the first exhaust passage portion center axis 127a.
In addition, it is more preferable that the second exhaust passage portion center axis 227a extends in the horizontal or nearly horizontal direction.
This is because the height of the occupied space of the two-stroke engine 1 can be suppressed when extending in the horizontal or near-horizontal direction.
The reason why the height of the occupied space can be suppressed is that the exhaust passage portion 27 can be prevented from protruding upward.
Further, the reason why the height of the occupied space can be suppressed is that the exhaust cleaner can be prevented from protruding upward by setting the position of the exhaust cleaner connected to the exhaust passage portion 27 to the horizontal position. It is.

<Third Embodiment>
FIG. 5 is an explanatory diagram of the third embodiment.

As shown in FIG. 5, the second exhaust passage portion 227 may be formed to extend in the direction opposite to that in FIG.

<Fourth Embodiment>
FIG. 6 is an explanatory diagram of the fourth embodiment.

As shown in FIG. 6, the exhaust opening 27 a may be disposed at the right side position.

<Fifth Embodiment>
FIG. 7 is an explanatory diagram of the fifth embodiment.

As shown in FIG. 7, the exhaust opening 27a may be arranged at the left side position.

<Sixth Embodiment>
FIG. 8 is an explanatory diagram of the sixth embodiment.

As shown in FIG. 8, the extending direction of the second exhaust passage portion 227 may be formed on the side where the crankshaft 9 is formed.
Conversely, the direction in which the second exhaust passage portion 227 extends may be formed on the side opposite to the side on which the crankshaft 9 is formed.
This is because the height of the occupied space of the two-stroke engine 1 can be suppressed even in this way.

<Seventh Embodiment>
FIG. 9 is an explanatory diagram of the seventh embodiment.

The reason why the exhaust opening 27a is provided at a position in the upper direction of the center axis of the cylinder 5 in the bore cross section is to prevent the mass transmission of the fuel component from the scavenging passage 25 and the shortcut.
Therefore, in the seventh embodiment, the following method is used to further prevent wall surface transmission and shortcut of a fuel component having a larger mass.
A distance L1 between the cylinder side scavenging opening 25b (the left side scavenging opening 25bL in FIG. 9) and the exhaust opening 27a located at the upper side position in the bore cross section than the exhaust opening 27a.
A distance L2 between the cylinder side scavenging opening 25b (the right side scavenging opening 25bR in FIG. 9) and the exhaust opening 27a located at the lower side position in the bore cross section than the exhaust opening 27a.
By setting L1> L2, it becomes possible to further prevent wall surface transmission and shortcut of a fuel component having a larger mass.
That is, it is possible to suppress the wall surface transmission and the shortcut by forming the length of the portion where the wall surface transmission and the shortcut are more likely to occur.

<Eighth Embodiment>
FIG. 10 is an explanatory diagram of the eighth embodiment.

The two-stroke engine 1 described above is connected to a work tool 101, for example.
Here, in particular, the work tool 101 will be described on the assumption of a chainsaw, but it is of course not limited to this.
In the case of a chain saw, there is a demand to place the crank journal 13 which is the rotating shaft of the two-stroke engine 1 on the bar chain side of the chain saw as much as possible.
Therefore, as shown in FIG. 10, the cylinder 5 is formed so as to extend in the direction opposite to the bar chain (work tool 101) of the chainsaw.

Here, the reason why the cylinder 5 is formed so as to extend in the direction opposite to the chain saw (work tool 101) is to suppress the height of the space occupied by the two-stroke engine 1 and to effectively increase the bar chain portion. is there.
However, even if formed in this way, the exhaust passage portion 27 will extend upward if no action is taken. This makes it difficult to suppress the height of the occupied space of the two-stroke engine 1.
Further, if no measures are taken, the exhaust passage portion 27 is disposed in the upper direction position, and therefore an exhaust muffler comes to the user's face side or hand portion or to the hand portion, and the user's face side or hand portion. There is also a risk that the exhaust gas will be released to this part. In order to solve this problem, the intake passage portion 23 is disposed at a position above the center axis of the cylinder 5 and the scavenging passage portion 25 and the exhaust passage portion 27 are disposed at positions below the center axis of the cylinder 5 (that is, A method is generally employed in which only the intake passage portion 23, the scavenging passage portion 25, and the exhaust passage portion 27 are arranged upside down from FIG. However, since the rotation direction of the crankshaft 9 must be the same, even if this is done, the flow of the air-fuel mixture from the intake opening 23a to the crank chamber side scavenging opening 25a and the rotation direction of the counterweight 15 There is a problem that is reversed. This eliminates the effect that the counterweight 15 assists the flow of the air-fuel mixture and increases the intake amount, but rather hinders the flow of the air-fuel mixture to be sucked.

Therefore, in the present embodiment, the exhaust passage portion 27 is disposed at a position in the upper direction from the center axis of the cylinder 5.
Further, in the present embodiment, the intake passage portion 23 is arranged at a position in the lower direction than the center axis of the cylinder 5.
Because of this arrangement, it is possible to make the rotational direction of the counterweight 15 (crankshaft 9) coincide with the flow of the air-fuel mixture to be sucked.
As a result, the efficiency of the two-stroke engine 1 is further improved.
Furthermore, with such an arrangement, it is possible to avoid the problem of exhaust being emitted to the user's face or to the hand.
That is, as in the first to seventh embodiments, the exhaust passage portion 27 extends at an angle with respect to the radial direction in the bore cross section of the cylinder 5, so that the exhaust is on the face side of the user. Alternatively, it can be prevented from being released to the hand.

<Ninth Embodiment>
FIG. 11 is an explanatory diagram of the ninth embodiment.

As shown in FIG. 11, most of the crank chamber side scavenging opening 25a may be disposed above the central axis of the cylinder 5 in a normal use state.
In this case, since the scavenging passage portion 25 is formed so as to face downward from the center axis of the cylinder 5, the scavenging air flow scavenged from the cylinder-side scavenging opening 25b is the same as in the above embodiment. This is because the direction is directed to the lower side position in the normal use state with respect to the bore section in the bore cross section.
Further, because of such a configuration, the fuel component having a large mass in the crank chamber 31 is refined in the air-fuel mixture passing around the rotating counterweight 15 and then into the scavenging passage portion. It has the effect of suppressing wall surface transmission and shortcuts of fuel components with a large mass.

<Configuration and Effect of Embodiment>
The two-stroke engine of the present invention has a cylinder 5 whose central axis extends in a horizontal or nearly horizontal direction in a normal use state, a cylinder 5 whose inner peripheral surface has a cylindrical shape, and a piston 21 that can reciprocate in the cylinder 5, And an exhaust passage portion 27 provided in the cylinder 5.
Further, an exhaust opening 27a of the exhaust passage portion 27 is formed on the inner peripheral surface of the cylinder 5, and most of the effective sectional area of the exhaust opening 27a is more normal than the center axis of the cylinder 5 in the bore cross section. It is formed at a position on the upper direction side in the use state.
The exhaust passage portion 27 is formed with an angle with respect to the radial direction in the bore cross section of the cylinder 5.
A cylinder side scavenging opening 25 b of the scavenging passage 25 is formed on the inner peripheral surface of the cylinder 5.
Furthermore, the direction of the scavenging air scavenged from the cylinder-side scavenging opening 25b is formed so as to face the lower side position in the normal use state with respect to the center axis of the cylinder in the bore cross section.
The exhaust passage portion 27 extends at an angle with respect to the radial direction in the bore cross section of the cylinder 5.
Since it has such a structure, it becomes possible to suppress the height in the vertical direction.
Moreover, it becomes possible to suppress the wall surface transmission and shortcut of the fuel component having a large mass.
In addition, by adopting such a configuration, a scavenging flow is generated for the stagnant fuel component having a large mass, so that the fuel component having a large mass can be scavenged.
As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.

The exhaust passage portion 27 includes a first exhaust passage portion 127 on the exhaust opening portion 27a side, and a second exhaust passage portion 227 connected to the first exhaust passage portion 127.
The central axis of the first exhaust passage portion 127 extends in the radial direction in the bore section of the cylinder 5, and the central axis of the second exhaust passage portion 227 has an angle with respect to the radial direction in the bore section of the cylinder 5. It extends.
Since it has such a structure, it becomes possible to suppress the height in the vertical direction more easily.
Furthermore, since it has such a configuration, it is possible to prevent exhaust from being discharged to the user's face.

The crankshaft 9 is formed perpendicular to the central axis of the cylinder 5 and in the horizontal direction in a normal use state.
Since it has such a structure, it becomes possible to suppress the height of a perpendicular direction more reliably.

A cylinder-side scavenging opening 25 b of the scavenging passage 25 is formed on the inner peripheral surface of the cylinder 5.
And scavenging from the cylinder side scavenging opening 25b of the scavenging passage 25 is formed so as to be guided to a position on the opposite side of the inner peripheral surface of the cylinder 5 where the exhaust opening 27a is formed. It is a schneille type.
With such a configuration, it is possible to increase the effective compression ratio, the air supply ratio, and the charging efficiency.
Furthermore, having such a configuration makes it possible to suppress the height of the occupied space of the two-stroke engine 1 to a certain level while exhibiting the air-fuel mixture induction effect by the counterweight 15.

The work tool coupled to the crankshaft 9 is connected to the side opposite to the direction in which the cylinder 5 extends.
An intake opening and a crank chamber side scavenging opening 25a are formed on the inner surface of the crankcase where the crankshaft 9 is formed.
The linear direction from the intake opening 23a to the counterweight 15 formed on the crankshaft and the direction of rotation of the counterweight 15 are formed so as to coincide with each other.
With this configuration, it is possible to suppress the height of the occupied space of the two-stroke engine 1 to a certain level while exhibiting the air-fuel mixture induction effect by the counterweight 15.
Furthermore, since it has such a structure, it becomes possible to prevent exhaust from being emitted to the face side of the user or the hand.

The two-stroke engine of the present invention includes a cylinder in which the central axis of the cylinder 5 extends in a horizontal or nearly horizontal direction in a normal use state, an inner peripheral surface has a cylindrical shape, and a piston 21 capable of reciprocating in the cylinder 5; A scavenging passage portion 25 provided in the cylinder 5 and an exhaust passage portion 27 provided in the cylinder 5 are provided.
A cylinder-side scavenging opening 25 b of the scavenging passage 25 is formed on the inner peripheral surface of the cylinder 5.
Further, the piston 21 has a crankshaft 9 that converts the reciprocating motion of the piston 21 into a rotational motion via the connecting rod 19, and a crankcase 7 that supports the crankshaft 9.
Furthermore, a crank chamber side scavenging opening 25 a of the scavenging passage 25 is formed in the crank chamber 31 surrounded by the cylinder 5, the piston 21 and the crankcase 7.
And most of the crank chamber side scavenging opening 25a is arranged above the central axis of the cylinder 5 in a normal use state.
Since it has such a configuration, it becomes possible to suppress wall surface transmission and shortcut of a fuel component having a large mass.
In addition, by adopting such a configuration, a scavenging flow is generated for the stagnant fuel component having a large mass, so that the fuel component having a large mass can be scavenged.
As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
Further, because of such a configuration, the fuel component having a large mass in the crank chamber 31 is refined in the air-fuel mixture passing around the rotating counterweight 15 and then into the scavenging passage portion. It has the effect of suppressing wall surface transmission and shortcuts of fuel components with a large mass.

Further, the present invention is not limited to the above embodiment, and various changed structures, configurations, and controls may be performed.

<Definition etc.>
The normal use state in the present invention refers to this fixed state designed for use in a fixed state for a long time. Furthermore, the normal use state in the present invention refers to a state in which the user has been using for many hours.

The near-horizontal state in the present invention refers to a range up to about plus or minus 45 ° with respect to the horizontal. This is because within this range, a two-stroke engine can be configured without increasing the height in the vertical direction.
A cross section in a direction perpendicular to the central axis of the cylinder 5 is referred to as a bore cross section.
Further, in the bore cross section, the inner peripheral surface direction of the cylinder 5 is referred to as a circumferential direction. Further, in this bore cross section, the radiation direction from the intersection of the bore cross section and the central axis of the cylinder 5 is referred to as a radial direction.

DESCRIPTION OF SYMBOLS 1 2 stroke engine 5 Cylinder 9 Crankshaft 13 Crank journal 15 Counterweight 21 Piston 23 Intake passage part 23a Intake opening part 25 Scavenging passage part 25a Crank chamber side scavenging opening part 25b Cylinder side scavenging opening part 27 Exhaust passage part 27a Exhaust opening part 101 Work tool 127 First exhaust passage portion 227 Second exhaust passage portion

Claims

A cylinder having a cylinder central axis extending in a horizontal or nearly horizontal direction in a normal use state, and an inner peripheral surface having a cylindrical shape;
A piston capable of reciprocating in the cylinder;
An exhaust passage provided in the cylinder,
An exhaust opening of the exhaust passage is formed on the inner peripheral surface of the cylinder,
Most of the effective cross-sectional area of the exhaust opening is formed at a position on the upper direction side in a normal use state with respect to the central axis of the cylinder in the bore cross section,
The exhaust passage portion extends at an angle with respect to a radial direction in a bore section of the cylinder.
The exhaust passage portion is
A first exhaust passage on the exhaust opening side;
A second exhaust passage portion connected to the first exhaust passage portion,
A central axis of the first exhaust passage portion extends in a radial direction in a bore cross section of the cylinder,
The two-stroke engine according to claim 1, wherein a central axis of the second exhaust passage portion extends at an angle with respect to a radial direction in a bore section of the cylinder.
The two-stroke engine according to claim 1, wherein the crankshaft is formed perpendicular to the central axis of the cylinder and in a horizontal direction in a normal use state.
A cylinder side scavenging opening of the scavenging passage is formed on the inner peripheral surface of the cylinder,
A Schneule type is formed so that scavenging from the cylinder-side scavenging opening of the scavenging passage is guided to a position on the opposite side of the inner peripheral surface of the cylinder from the portion where the exhaust opening is formed. The two-stroke engine according to claim 1.
A cylinder in which the central axis of the cylinder extends in a horizontal or nearly horizontal direction in a normal use state, and the inner peripheral surface has a cylindrical shape;
A piston capable of reciprocating in the cylinder;
A scavenging passage provided in the cylinder;
An exhaust passage provided in the cylinder,
The exhaust passage portion is formed with an angle with respect to a radial direction in a bore cross section of the cylinder,
A cylinder-side scavenging opening of the scavenging passage is formed on the inner peripheral surface of the cylinder,
A two-stroke engine formed such that the direction of the scavenging air scavenged from the cylinder-side scavenging opening is directed to a lower direction position in a normal use state with respect to the central axis of the cylinder in the bore cross section.
The direction of the scavenging air scavenged from the cylinder-side scavenging opening is within an angle range of ± 60 ° with respect to the vertical bottom in the normal use state with respect to the center axis of the cylinder in the bore cross section. 2 stroke engine.
The exhaust passage portion is
A first exhaust passage on the exhaust opening side;
A second exhaust passage portion connected to the first exhaust passage portion,
A central axis of the first exhaust passage portion extends in a radial direction in a bore cross section of the cylinder,
The two-stroke engine according to claim 6, wherein a central axis of the second exhaust passage portion extends at an angle with respect to a radial direction in a bore section of the cylinder.
The two-stroke engine according to claim 5, wherein the crankshaft is formed perpendicular to the central axis of the cylinder and in a horizontal direction in a normal use state.
A cylinder-side scavenging opening of the scavenging passage is formed on the inner peripheral surface of the cylinder,
A Schneule type is formed so that scavenging from the cylinder-side scavenging opening of the scavenging passage is guided to a position on the opposite side of the inner peripheral surface of the cylinder from the portion where the exhaust opening is formed. The two-stroke engine according to claim 5.
In the crank chamber surrounded by the cylinder, the crankcase and the piston, an intake opening and a crank chamber side scavenging opening are formed,
9. The two-stroke engine according to claim 8, wherein a direction of a straight line from the intake opening to a counterweight formed on the crankshaft coincides with a direction of rotation of the counterweight.
A cylinder having a cylinder central axis extending in a horizontal or nearly horizontal direction in a normal use state, and an inner peripheral surface having a cylindrical shape;
A piston capable of reciprocating in the cylinder;
A scavenging passage provided in the cylinder;
An exhaust passage provided in the cylinder,
A cylinder-side scavenging opening of the scavenging passage is formed on the inner peripheral surface of the cylinder,
A crankshaft for converting the reciprocating motion of the piston into a rotational motion via a connecting rod;
A crankcase for supporting the crankshaft,
A crank chamber-side scavenging opening of the scavenging passage is formed in a crank chamber surrounded by the cylinder, the piston, and the crankcase.
A two-stroke engine in which most of the crank chamber side scavenging opening is disposed above the central axis of the cylinder in normal use.