JP2000034927A - 2-cycle internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an output without large structural change, effectively reduce harmful components in exhaust gas, effectively accelerate the atomization of fuel particles in mixture, and improve the exhaust gas cleaning performance and fuel consumption. SOLUTION: An inside horizontal scavenging angle α on the exhaust port 10 side formed by a scavenging flow blown out from first scavenging ports 9A, 9A and an outside horizontal scavenging angle β on the opposite side of the exhaust port 10 are both set to 116 deg.-124 deg. and an inside horizontal scavenging angle γin the exhaust port 10 formed by the scavenging flow blown out from the second scavenging ports 9B, 9B is set to 126 deg.-134 deg., and an outside horizontal scavenging angle δ on the opposite side of the exhaust port 10 is set to 146 deg.-154 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small displacement machine suitable for small work machines such as brush cutters and chainsaws.
The present invention relates to a small air-cooled two-cycle internal combustion engine of about 5 to 65 cc, and more particularly to a small air-cooled two-cycle internal combustion engine that reduces harmful components in exhaust gas without deteriorating output characteristics.

[0002]

2. Description of the Related Art Recently, due to growing environmental problems, a small air-cooled type 2 used for a portable working machine such as a brush cutter or a chain saw has been developed.
In a cycle gasoline engine, HC, CO, NOx, P
There is a strong demand for reducing and purifying M (fine particles of unburned components of oil) and the like. For example, an exhaust gas regulation bill in California, United States, so-called CA
According to the RB Tier II, from the year 2000, HC + NOx of 54 g / liter is used for an SI (spark ignition) two-cycle internal combustion engine having a displacement of 65 cc or less.
bhp-h or less, CO 400g / bhp-h or less, PM 1.5
g / bhp-h or less is required.

In order to cope with such exhaust gas regulations, the applicant of the present invention has made various proposals for a two-stroke internal combustion engine so far, and one of the proposals is disclosed in Japanese Patent Application Laid-Open No. 9-280057. In the publication disclosed in the official gazette, in a Schnüle scavenging type two-stroke internal combustion engine having an exhaust port and a scavenging port, attention is paid to opening / closing timing of the exhaust port and the scavenging port by a piston, and the opening / closing timing is set to be smaller than that of a conventional one. It was proposed to shorten it by looking at the crank angle. Specifically, the opening / closing timing of the exhaust port by the piston is set at 100 ° to 120 ° with respect to the bottom dead center when viewed from the crank angle, and the opening / closing timing by the piston of the scavenging port is viewed by the crank angle. It was set at 85 ° to 100 ° across the bottom dead center.

The opening / closing timing of the exhaust port and the scavenging port is set by lowering the upper end positions of the exhaust port and the scavenging port and shortening the distance between the upper end position of the exhaust port and the upper end position of the scavenging port. Is achieved by here,
In a conventional engine of the same type, the general opening and closing timing of the exhaust port and the scavenging port is usually 130 ° to 150 ° and 100 ° to 100 °, respectively, mainly in consideration of the main force characteristics.
Although they are set within the range of 110 °, they are set as described above, so that the exhaust port and the scavenging port are opened later in the descending stroke of the piston than in the conventional one, and the rising stroke of the piston is increased. Then, it is closed earlier than the conventional one.

[0005] For this reason, the explosion energy is sufficiently converted into a force for pushing the piston downward by the time the exhaust port starts to open, and the exhaust pressure at that time is reduced, so that the scavenging flow is not pushed back. As a result, the flow rate of the scavenging flow is increased, and scavenging is effectively performed. Since the scavenging is performed effectively, the amount of fresh air (air-fuel mixture) blown through the exhaust port is reduced, the HC component contained in the exhaust gas is reduced, and the output can be improved. In addition, since it is only necessary to change the shape and position of the scavenging port, there is no increase in cost.

[0006] On the other hand, in a general two-stroke internal combustion engine of the Schnüle scavenging type as described above, as shown in the above-mentioned publication (FIG. 3), a vertical cross section of the exhaust port (10) is divided into two parts ( F), a so-called two-stream scavenging system in which a pair of scavenging ports (9, 9) is provided symmetrically with respect to the scavenging flow of the air-fuel mixture blown out from the pair of scavenging ports (9, 9) is adopted. Is made to collide with a stationary cylinder inner wall (cylinder bore). In the related art, a so-called four-flow scavenging type in which two pairs of scavenging ports are additionally provided and provided. I have.

FIG. 8 shows a cross section of an example of a cylinder of a conventional four-flow scavenging two-cycle internal combustion engine. In the illustrated cylinder 2 ′, a pair of first scavenging ports 9A ′ and 9A ′ located on the side of the exhaust port 10 ′ are symmetrical with respect to a longitudinal section F ′ that divides the exhaust port 10 ′ into two. , A pair of second scavenging ports 9B ', 9 located on the opposite side of the exhaust port 10'.
B ′. And the first scavenging port 9
The inner horizontal scavenging angle α ′ on the exhaust port 10 ′ side formed by the scavenging air flow blown out from A ′ and 9 A ′ is set to around 100 ° (for example, 94 °), and the outer horizontal scavenging angle α ′ is opposite to the exhaust port 10 ′. The scavenging angle β ′ is set to around 120 °, and the inner horizontal scavenging angle γ ′ on the exhaust port 10 side formed by the scavenging flow blown out from the second scavenging ports 9B ′ and 9B ′ is set to around 120 °. In addition, the outer horizontal scavenging angle δ ′ on the side opposite to the exhaust port 10 ′ is set to around 150 °, and
The horizontal cross-sectional area Sa ′ of the first scavenging ports 9A ′ and 9B ′ is:
The horizontal cross-sectional area Sb of the second scavenging ports 9B ′, 9B ′ is smaller (Sa <Sb).

In such a conventional four-stroke scavenging two-stroke internal combustion engine, the scavenging air blown from the first scavenging ports 9A 'and 9A' collide with each other and the second scavenging ports 9B '. , 9B 'are also caused to collide with each other, so that a part of the scavenging flow is caused to collide with a stationary cylinder inner wall (cylinder bore) as in the above-described two-flow scavenging type. In comparison, the relative collision velocity between the scavenging flows doubles, the collision energy nearly quadruples, and the fuel particles in the air-fuel mixture that are not completely particulate until they are blown out from each scavenging port. Atomization is greatly promoted, and the ignitability and combustion efficiency of the air-fuel mixture are improved, resulting in improved exhaust gas purification performance and fuel economy.

[0009]

However, even in the two-cycle internal combustion engine proposed above, a part of the fresh air (air-fuel mixture) cannot escape from the exhaust port directly, albeit in a very small amount. Although the amount can be reduced to some extent, it is still not sufficient, and reduction of harmful components (especially HC components) in exhaust gas has not been said to be completely satisfactory. Further, even in the conventional four-flow scavenging two-stroke internal combustion engine as described above, the effect of accelerating the atomization of the fuel particles in the air-fuel mixture cannot be said to be sufficient, and further improvement is demanded.

The present invention has been made in view of the above problems, and its object is to increase the output without any major structural change and to effectively reduce the harmful components in the exhaust gas. Can be reduced, and
It is an object of the present invention to provide a two-stroke internal combustion engine capable of effectively promoting atomization of fuel particles in an air-fuel mixture and further improving exhaust gas purification performance and fuel efficiency.

[0011]

In order to achieve the above-mentioned object, a two-stroke internal combustion engine according to the present invention is basically provided with a schnüle scavenging system symmetrically with respect to a longitudinal section F dividing an exhaust port into two parts. A pair of first scavenging ports located on the exhaust port side and a pair of second scavenging ports located on the opposite side to the exhaust port are provided.

[0012] Both the inner horizontal scavenging angle on the exhaust port side and the outer horizontal scavenging angle on the opposite side to the exhaust port formed by the scavenging flow blown out from the first scavenging port are both 116 ° to 1 °.
24 °, and the inner horizontal scavenging angle on the side of the exhaust port formed by the scavenging flow blown out from the second scavenging port is 12 °.
6 ° to 134 °, the outer horizontal scavenging angle opposite to the exhaust port is 146 ° to 154 °, and the scavenging flows blown out from the first scavenging port collide with each other. The scavenging flows blown out from the second scavenging ports are also caused to collide with each other.

In a preferred aspect of the present invention, the horizontal cross-sectional area of the first scavenging port is made larger than the horizontal cross-sectional area of the second scavenging port. As described above, the two-stroke internal combustion engine of the present invention employs the four-way scavenging method having a pair of the first scavenging port and the second scavenging port. Compared to the case where the part of the scavenging flow collides with the stationary cylinder inner wall (cylinder bore) as in the formula, the relative collision speed between the scavenging flows doubles, and the collision energy becomes nearly four times. Therefore, atomization of fuel particles in the air-fuel mixture that is not completely particulate until blown out from the scavenging port is greatly promoted, and the ignitability and combustion efficiency of the air-fuel mixture are improved, and as a result, exhaust gas purification Improves performance and fuel economy.

In addition, the distance from the second scavenging port to the cylinder center line, that is, the distance until the scavenging flows (second scavenging flows) blown out from the second scavenging ports collide with each other is equal to the first scavenging flow. Since the distance between the scavenging flows (first scavenging flow) blown out from one scavenging port is shorter than the collision,
Also, the second scavenging flow has a shape in which the horizontal cross-sectional width is narrowed when viewed in the blowing direction, so that the speed is higher than the first scavenging flow. Therefore, the second scavenging flow collides earlier than the first scavenging flow, and the collision energy is larger than the first scavenging flow, so that atomization is more effectively promoted.

The horizontal cross-sectional area of the first scavenging port and the horizontal cross-sectional area of the second scavenging port are opposite to the conventional one shown in FIG. The horizontal cross-sectional area is larger than the horizontal cross-sectional area of the second scavenging port. Specifically, conventionally, the ratio of the horizontal cross-sectional area of the second scavenging port to the horizontal cross-sectional area of the first scavenging port is set to, for example, 0.6 to 1, but in the present invention, For example, it is set to 1.2: 1. By reversing the cross-sectional area ratio in this way, the collision occurs quickly and atomization is further promoted.
The gaseous second scavenging stream having a specific gravity is applied to the first scavenging stream whose total energy is larger than the second scavenging stream, in a direction farther (away) from the exhaust port, as if a large river flow is a small river flow. To raise the second scavenging flow, which has no other destination, along the cylinder bore.

[0016] Then, with the rising second scavenging flow, the first scavenging flow also rises more, so that the amount of air-fuel mixture flowing through the exhaust port is further reduced, and HC, which is an unburned component in the exhaust gas, is reduced. Ingredients are reduced more effectively. The combined scavenging flow of the first scavenging flow and the second scavenging flow respectively rises to the top of the cylinder bore after the collision and reverses to form a loop leading to discharge of the combustion exhaust gas from the exhaust port. Therefore, the filling efficiency is improved, the output is improved, and the HC component value contained in the exhaust gas per unit output is reduced.

In another preferred embodiment, the opening / closing timing of the exhaust port and the scavenging port by the piston is 100 ° to 1 ° across the bottom dead center when viewed from the crank angle.
20 ° and 85 ° to 100 ° are set. Thus, the exhaust port and the scavenging port (the first scavenging port and the second scavenging port) are opened later in the descending stroke of the piston than in the prior art, and are closed earlier in the ascending stroke of the piston.

Therefore, the explosion energy is sufficiently converted into a force for pushing the piston downward until the exhaust opening at which the exhaust port starts to open, and the exhaust pressure at that time becomes sufficiently small, so that the scavenging flow is pushed back. Without increasing the effective flow rate of the scavenging flow, scavenging is effectively performed, thereby also reducing the amount of fresh air (air-fuel mixture) blown out from the exhaust port and reducing the HC component contained in the exhaust gas. The power can be reduced and the output can be improved. In addition, since only the shapes and positions of the exhaust port and the scavenging port need to be changed, there is no increase in cost.

Further, in another preferred embodiment, the air-fuel mixture guided from the crank chamber to the first scavenging port and the second scavenging port through the first scavenging passage and the second scavenging passage is brought into contact with the skirt portion of the piston. To this end, a cutout opening is formed along the height direction below the first scavenging passage and the second scavenging passage, leaving a half wall having the same diameter as the cylinder bore and having a predetermined thickness above the first scavenging passage.

As described above, the provision of the half-wall and the notch opening in the first scavenging passage and the second scavenging passage allows the rigidity of the cylinder and the flow velocity of the scavenging flow to be improved. Through the air passage and the second scavenging passage,
Since the scavenging flow blown into the cylinder bore from the first scavenging port and the second scavenging port contacts the skirt portion of the piston and cools it, the heat of the piston ring and the piston pin is reduced. Moving and they are also cooled. For this reason, sticking of the piston ring and seizure of the piston are less likely to occur.

In another preferred embodiment, a reinforcing rib is provided on the outer periphery of the lower portion of the cylinder. In this case, the cylinder whose lower side is open tends to have a particularly low structural strength, but by providing the reinforcing ribs as described above, deformation of the cylinder is prevented, and roundness is maintained, Since the friction loss of the piston and the crankshaft is reduced, the output is improved.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a two-stroke internal combustion engine according to the present invention. In the figure, an engine 1 is a small air-cooled two-stroke gasoline engine of a Schnüle scavenging type incorporated as a power source of a portable work machine such as a brush cutter or a chain saw, and has a displacement of about 30 cc.

The engine 1 includes a cylinder 2 having a hemispherical combustion chamber 5 in which a spark plug 15 is disposed, and a crankcase 3 connected to a lower side thereof. In a manner known per se, the air-fuel mixture from a carburetor (not shown) is supplied to the crank chamber 13 below the piston 4 through an inlet 15 provided with a reed valve. Has become.

In addition to the cylinder shown in FIG.
As can be clearly understood from FIG. 4, the exhaust port 10 is provided, and the exhaust port 10 is positioned on the exhaust port 10 side symmetrically with respect to a longitudinal section F which divides the exhaust port 10 into a Schneule scavenging type. A pair of first scavenging ports 9A, 9A and a pair of second scavenging ports 9B, 9B located on the opposite side to the exhaust port 10 are provided. Further, the reciprocating motion of the piston 4 is converted into a rotational motion of a crankshaft 12 having a balance weight 14 via a connecting rod 11, and the shaft output thereof is used as power for the portable working machine. ing.

As shown in FIGS. 5 and 6 in addition to FIG. 1, the piston 4 has a portion of the top land 4A facing the exhaust port 10 from the center to the outer periphery. The upper side is inclined downward (inclined by a height h from the outer peripheral edge 4a of the top land 4A), is substantially rectangular in plan view, and has a peripheral edge length substantially equal to the width of the exhaust port 10. In addition, an inclined surface 24 whose depth L is approximately 1/3 of the diameter (2 · R) of the cylinder bore 2a is formed.

In addition, below the first scavenging ports 9A, 9A and the second scavenging ports 9B, 9B in the cylinder 2, the air-fuel mixture sucked into the crank chamber 13 is filled with the scavenging ports 9A, 9A. First scavenging passages 30A, 30A and second scavenging passages 30B, 30B for leading to 9A, 9B, 9B are provided, and through these first scavenging passages 30A, 30A and second scavenging passages 30B, 30B. The first scavenging passage is provided so that the air-fuel mixture guided to the first scavenging ports 9A, 9A and the second scavenging ports 9B, 9B directly contact the outer peripheral surface of the skirt portion 4B of the piston 4. 30A, 3
0A and the upper part of the second scavenging passages 30B, 30B, leaving half walls 31, 31, 32, 32 having the same diameter as the cylinder bore 2a and a thickness of, for example, about 2 mm and a height of about 10 mm. Elongated notch openings 33, 33, 34, 34 are formed along the height direction.

Further, an annular horizontal rib 41 is provided on the outer periphery of the lower portion of the cylinder 2 having an open lower surface, and a plurality of (four in the illustrated example) vertical ribs 42 are formed at predetermined angular intervals (FIG. The cooling fins 22 of the cylinder 2 are projected at the same height as the cooling fins 22 at 90 ° intervals in the illustrated example (see FIGS. 1 to 4). And the engine 1
In synchronization with the reciprocating motion of the piston 4 and the vertical movement thereof, in a well-known normal mode,
Each process of compression, combustion, suction, scavenging, expansion, and exhaust as a two-cycle internal combustion engine is performed.

Here, in this embodiment, as shown in FIG. 4, the scavenging flow (first scavenging flow) blown out from the first scavenging ports 9A, 9A is formed on the exhaust port 10 side. An inner horizontal scavenging angle α and an outer horizontal scavenging angle β opposite to the exhaust port 10 are both 120 °, and a scavenging flow (second scavenging flow) blown out from the second scavenging ports 9B, 9B. Is formed inside the horizontal scavenging angle γ on the exhaust port 10 side.
Is set to 130 °, the outer horizontal scavenging angle δ on the side opposite to the exhaust port 10 is set to 150 °, and the first scavenging flows blown out from the first scavenging ports 9A and 9A are separated from each other. Before colliding with the cylinder inner wall (the cylinder bore 2a), they are caused to collide with each other, and the second scavenging flows blown out from the second scavenging ports 9B, 9B also collide with the cylinder inner wall (the cylinder bore 2a). Before they hit each other.

The horizontal cross-sectional area Sa of the first scavenging ports 9A, 9A is equal to the horizontal cross-sectional area Sb of the second scavenging ports 9B, 9B.
It is larger (Sa> Sb). Specifically, conventionally, the ratio of the horizontal cross-sectional area Sb of the second scavenging ports 9B, 9B to the horizontal cross-sectional area Sa of the first scavenging ports 9A, 9A is set to, for example, 0.6: 1. However, in the present embodiment, for example, the ratio is set to 1.2: 1.

Further, the exhaust port 10 and the scavenging port 9
The opening / closing timing of the pistons 4 of A, 9A, 9B and 9B is determined by the crank angle, and the bottom dead center (BDC)
Are set to 110 ° and 94 °. The opening / closing timing of the exhaust port 10 and each of the scavenging ports 9A, 9A, 9B, 9B is set according to the setting of the exhaust port 10 and each of the scavenging ports 9A, 9A, 9B, 9B.
A, 9A, 9B, 9B lower the upper end position than the conventional general position, and the vertical distance between the upper end position of the exhaust port 10 and the upper end position of each of the scavenging ports 9A, 9A, 9B, 9B. Is made shorter than conventional general dimensions.

In the two-stroke internal combustion engine 1 of the present embodiment having such a configuration, a four-flow scavenging type having a pair of first scavenging ports 9A, 9A and second scavenging ports 9B, 9B is employed. Therefore, as compared with a case where a part of the scavenging flow is caused to collide with a stationary cylinder inner wall (cylinder bore) as in the above-described conventional general two-flow scavenging type, the relative scavenging flows are different from each other. The collision speed is doubled, the collision energy is nearly quadrupled, and the first and second scavenging ports 9A, 9
A, 9B, Atomization of fuel particles in the air-fuel mixture that is not completely particulate until blown out from 9B is greatly promoted, and the ignitability and combustion efficiency of the air-fuel mixture are improved, and as a result, It improves exhaust gas purification performance and fuel efficiency.

In addition, the second scavenging ports 9B, 9B
Is the distance from the first scavenging port to the cylinder center line C (FIG. 4), that is, the distance until the scavenging flows (second scavenging flows) blown from the second scavenging ports 9B, 9B collide with each other. 9A, since the scavenging flow (first scavenging flow) blown out from 9A is shorter than the distance before collision, and the horizontal cross-sectional width of the second scavenging flow is narrowed when viewed in the blowing direction. Due to the shape, the velocity is faster than the first scavenging flow. Therefore, the second scavenging flow collides earlier than the first scavenging flow, and the collision energy is larger than the first scavenging flow, so that atomization is more effectively promoted.

The horizontal cross-sectional area Sa of the first scavenging ports 9A, 9A and the horizontal cross-sectional area S of the second scavenging ports 9B, 9B.
b is opposite to the conventional one shown in FIG.
Since the horizontal cross-sectional area Sa of the first scavenging port is larger than the horizontal cross-sectional area Sb of the second scavenging port (the ratio is set to 1.2: 1), the collision occurs quickly. The gaseous second scavenging flow having a specific gravity is further promoted to be atomized, and the first scavenging flow having a larger total energy than the second scavenging flow is moved in a direction farther (away) from the exhaust port 10. Then, as if the flow of a large river pushes the flow of a small river, the second scavenging flow having no other place to go up is raised along the cylinder bore 2a.

Since the first scavenging flow also rises more with the rising second scavenging flow, the exhaust port 10
The amount of the air-fuel mixture blown directly from the exhaust gas is reduced, and the HC component, which is the unburned component in the exhaust gas, is more effectively reduced. The combined scavenging flow of the first scavenging flow and the second scavenging flow is the cylinder bore 2 after the collision.
a rises to the top of a and reverses to form a loop leading to discharge of the combustion exhaust gas from the exhaust port 10. for that reason,
The filling efficiency is improved and the output is improved, and the value of the HC component contained in the exhaust gas per unit output is significantly reduced.

The exhaust port 10 and the scavenging port 9
The opening and closing timings of the pistons 4 of A, 9A, 9B, and 9B are set at 110 ° and 94 ° with respect to the bottom dead center when viewed from the crank angle, respectively, so that the exhaust port 10 and the scavenging port (the The first scavenging ports 9A, 9A and the second scavenging ports 9B, 9B) are opened later during the descending stroke of the piston 4 than before, and closed earlier during the ascent stroke of the piston 4.

Therefore, the explosion energy is sufficiently converted into a force for pushing the piston 4 downward until the exhaust start time when the exhaust port 10 starts to open, and the exhaust pressure at that time is reduced, so that the scavenging flow is pushed back. Without this, the effective flow rate of the scavenging flow is increased, and scavenging is performed effectively, whereby the amount of fresh air (air-fuel mixture) blown through the exhaust port 10 is reduced, and the HC component contained in the exhaust gas is reduced. Can be further reduced, the output can be improved, and only the shapes and positions of the exhaust port and the scavenging port need to be changed, which does not lead to an increase in cost.

Further, the first scavenging passages 30A and 30A and the second scavenging passage 30
B, 30B, the mixture guided to the first scavenging ports 9A, 9A and the second scavenging ports 9B, 9B is brought into direct contact with the outer peripheral surface of the skirt portion 4B of the piston 4, The half-walls 31, 31, 3 having a predetermined thickness of the same diameter as the cylinder bore 2a are provided above the first scavenging passages 30A, 30A and the second scavenging passages 30B, 30B.
Since the notch openings 33, 33, 34, and 34 are formed in the lower part along the height direction except for the second and second scavenging flows, the rigidity of the cylinder 2 and the first and second scavenging flows Of the first scavenging passages 30A, 30A and the second scavenging passage 30A
B, 30B, from the first scavenging port 9A, 9A and the second scavenging port 9B, 9B, the first scavenging flow and the second scavenging flow blown into the cylinder bore 2a,
Since the piston 4 directly contacts the skirt portion 4B and cools it, the piston ring 16, the connecting rod small-end bearing 18 and the piston pin 17 (see FIG. 6)
Heat is transferred and they are also effectively cooled. For this reason, the sticking of the piston ring 16 and the piston 4
Is less likely to occur.

Further, the cylinder 2 having an open lower surface side tends to lack the structural strength of the lower part in particular. However, the annular lateral rib 41 is provided on the outer periphery of the lower part of the cylinder 2 and a plurality of cylinders are provided. Since the vertical ribs 42 are projected at predetermined angular intervals, the cylinder 2
Is effectively prevented, the roundness is maintained, and the friction loss of the piston 4, the crankshaft 12, etc. is reduced, so that the output is improved.

Further, at the portion of the top land 4A of the piston 4 facing the exhaust port 10,
It is inclined downward from the central portion to the outer peripheral side, is substantially rectangular in plan view, and the outer peripheral edge length 24B is the width 10 of the exhaust port 10.
B, and the depth 24L is formed to be approximately 1/3 of the diameter (2 · R) of the cylinder bore 2a, so that the inclined surface 24 is formed. The exhaust timing (exhaust start timing as seen from the crank angle) is advanced without changing the scavenging timing, that is, without increasing the amount of air-fuel mixture blow-through from the exhaust port 10, so that the output can be reduced. Increase.

In order to confirm the effects as described above, the engine 1 of the present embodiment (the present invention) and the first scavenging ports 9A ', 9A' as shown in FIG. The inner horizontal scavenging angle α ′ on the exhaust port 10 ′ side where the scavenging flow is formed is around 100 ° (for example, 94 °), and the outer horizontal scavenging angle β ′ on the opposite side to the exhaust port 10 ′ is 120 °.
°, and the inside horizontal scavenging angle γ 'on the exhaust port 10' side formed by the scavenging flow blown out from the second scavenging ports 9B 'and 9B' is set to around 120 °,
The outer horizontal scavenging angle δ ′ on the opposite side of the exhaust port 10 ′ is 15
0 °, and the first scavenging ports 9A 'and 9B'
Is the horizontal sectional area S ′ of the second scavenging port.
A conventional engine (comparative product) smaller than b '(Sa'<Sb') was prepared, and a comparative experiment was performed under the same conditions. FIG. 7 shows the experimental results.

Referring to FIG. 7, in the product of the present invention, the HC component in the exhaust gas is significantly reduced (about 57%) as compared with the comparative product.
% Reduction). As described above, one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above-described embodiment, and various designs may be made without departing from the spirit of the invention described in the claims. Can be changed.

[0042]

As will be understood from the above description, according to the two-stroke internal combustion engine of the present invention, it is possible to increase the output without major structural changes,
The harmful components in the exhaust gas can be effectively reduced, and the atomization of the fuel particles in the air-fuel mixture can be effectively promoted, so that the exhaust gas purification performance and the fuel efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a lateral center longitudinal section along a crankshaft showing an embodiment of a two-stroke internal combustion engine according to the present invention.

FIG. 2 is an enlarged laterally central longitudinal section along the crankshaft of the cylinder of the two-stroke internal combustion engine shown in FIG. 1;

FIG. 3 is an enlarged vertical cross-sectional view of the cylinder of the two-stroke internal combustion engine shown in FIG.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2;

FIG. 5 is a perspective view showing a piston of the two-stroke internal combustion engine shown in FIG. 1;

FIG. 6 is a partially enlarged longitudinal sectional view showing a part of an exhaust port and a piston of the two-stroke internal combustion engine shown in FIG. 1;

7 shows the H of the two-stroke internal combustion engine (product of the present invention) shown in FIG. 1 and the engine (comparative product) shown in FIG. 8;
7 is a graph showing the results of a comparative experiment on the effect of reducing the C component.

FIG. 8 is a horizontal sectional view showing an example of a conventional four-flow scavenging two-cycle internal combustion engine.

[Description of Signs] 1 Two-stroke internal combustion engine 2 Cylinder 2a Cylinder bore 4 Piston 4B Skirt 9A First scavenging port 9B Second scavenging port 10 Exhaust port 13 Crank chamber 30A First scavenging passage 30B Second scavenging passage 31, 32 Half wall 33, 34 Notch opening 41 Annular horizontal rib (reinforcement rib) 42 Vertical rib (reinforcement rib) α First inner horizontal scavenging angle β First outer horizontal scavenging angle γ Second inner horizontal scavenging angle δ Second outer horizontal scavenging Angle Sa Horizontal cross-sectional area of first scavenging port Sb Horizontal cross-sectional area of second scavenging port F Longitudinal cross section dividing exhaust port into two

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koujiro Mochizuka 1-7-2 Suehirocho, Ome-shi, Tokyo Co., Ltd. (72) Kentaro Matsuo 1-7-1-2 Suehirocho, Ome-shi, Tokyo Co., Ltd. Kyoritsu F-term (reference) 3G024 AA09 AA11 BA05 CA19 DA13 EA14 FA00

Claims (5)

[Claims] 1. A pair of first scavenging ports (9A, 9A, 10A) located on the side of the exhaust port (10), which are symmetrically arranged with respect to a longitudinal section F which divides the exhaust port (10) into two. 9
A) and a pair of second scavenging ports (9B, 9B) located on the opposite side of the exhaust port (10), in the two-stroke internal combustion engine (1) provided with the first scavenging port (9A). , 9A), the inner horizontal scavenging angle (α) on the exhaust port (10) side and the outer horizontal scavenging angle (β) on the opposite side to the exhaust port (10) formed by the scavenging flow blown out from the exhaust port (10A) are both 116 ° or more. 124 °, and an inner horizontal scavenging angle (γ) on the exhaust port (10) side formed by a scavenging flow blown out from the second scavenging ports (9B, 9B) is 126 ° to 134 °. With the exhaust port (1
0) the outer horizontal scavenging angle (δ) opposite to 146 ° to 15
4 °, the scavenging flows blown out from the first scavenging ports (9A, 9A) collide with each other, and the scavenging flows blown out from the second scavenging ports (9B, 9B). A two-stroke internal combustion engine, characterized in that the two engines are also collided with each other. 2. A horizontal cross-sectional area (Sa) of the first scavenging port (9A, 9A) is larger than a horizontal cross-sectional area (Sb) of the second scavenging port (9B, 9B). The two-stroke internal combustion engine according to claim 1, wherein: 3. The exhaust port (10) and the scavenging port (9).
A, 9A, 9B, 9B) is characterized in that the opening / closing timing by the piston (4) is set at 100 ° to 120 ° and 85 ° to 100 ° with respect to the bottom dead center when viewed from the crank angle. The two-stroke internal combustion engine according to claim 1 or 2, wherein: 4. A first scavenging passage (30A, 30A) and a second scavenging passage (30B, 30) from a crank chamber (13).
B), the first scavenging port (9A, 9A) and the air-fuel mixture guided to the second scavenging port (9B, 9B) are brought into contact with the skirt portion (4B) of the piston (4). Half walls (31, 31, 32, 32) having a predetermined thickness of the same diameter as the cylinder bore (2a) above the air passages (30A, 30A) and the second scavenging passages (30B, 30B).
, And a notch opening (3
The two-stroke internal combustion engine according to any one of claims 1 to 3, wherein (3, 33, 34, 34) is formed. 5. The cylinder according to claim 1, wherein a reinforcing rib is provided on an outer periphery of a lower portion of the cylinder having an open lower surface. Cycle internal combustion engine.