JP3021157B2 - 2 cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine in which a reed valve is attached to an intake port formed in a crankcase.

[0002]

2. Description of the Related Art The following two-stroke engine has been conventionally proposed. That is, the cylinder is screwed to the crankcase with left and right bolts when viewed from the front. In addition, an intake port is formed in the crankcase between the left and right bolts when viewed from the front, and a reed valve is attached to the intake port. During operation of the engine, the air-fuel mixture is sucked into the crankcase through the reed valve and the intake port, where it is once pre-compressed. Next, the pre-compressed air-fuel mixture is sent into the combustion chamber through the scavenging port and burned, whereby the engine outputs power.

[0003]

As one means for improving the charging efficiency, it is conceivable to increase the sectional area of the suction passage penetrating the reed valve body of the reed valve to reduce the suction resistance. Can be In this case, it is conceivable to increase the left-right width of the reed valve body.
Since the above-mentioned bolts for screwing the cylinder are located on the left and right sides of the reed valve main body, there is a limit in increasing the width dimension of the reed valve main body as described above. Further, when the cross-sectional area of the suction passage is simply increased, a part of the air-fuel mixture sucked into the crankcase through the suction passage flows into the scavenging port in a short-circuit manner.
The mixture is sent into the combustion chamber with insufficient mixing, and the ignition performance and the like may be reduced.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and when a cylinder is screwed to a crankcase with left and right bolts, a lead is provided so as not to interfere with these left and right bolts. The first is to improve the filling efficiency by rationally increasing the lateral width of the valve body, increasing the cross-sectional area of the suction passage, and thereby reducing the suction resistance of the air-fuel mixture in the suction passage. The purpose of. Also, the second problem is that the air-fuel mixture sucked into the crankcase through the reed valve is fed into the combustion chamber after being sufficiently mixed in the crankcase, thereby improving the ignition performance and the like. Aim.

[0005]

A feature of the present invention to achieve the above object is that a cylinder is screwed to a crankcase with left and right bolts when viewed from the front, and the same as above between the left and right bolts when viewed from the front. In a two-stroke engine in which an intake port is formed in a crankcase and a reed valve is attached to the intake port, when the axis of the cylinder is viewed vertically, the reed valve is constituted by an upper and lower reed valve, and an upper reed valve is provided. The width dimension of the upper reed valve main body constituting the lower reed valve is smaller than the width dimension of the lower reed valve main body constituting the lower reed valve. In the above case, the downstream end opening of the suction passage of the upper reed valve body is constituted by a plurality of openings arranged in a line in the left and right direction, and the downstream end opening of the suction passage of the lower reed valve body is formed in the left and right direction. It may be constituted by a plurality of openings in each row arranged in two rows above and below.

[0006]

[Operation] The operation of the above configuration is as follows. The cylinder 35 is bolted to the left and right bolts 3
5a, 35a, and the crankcase 2 between the left and right bolts 35a, 35a when viewed from the front.
0, an intake port 42 is formed, and a reed valve 48 is attached to the intake port 42. And the cylinder 3
5, the reed valve 48 is composed of upper and lower reed valves 58 and 59, and the left and right width dimension 1 of the upper reed valve main body 70 constituting the upper reed valve 58 is defined by the lower reed valve 59. Is smaller than the width dimension L of the lower reed valve main body 60.

For this reason, first, the left and right width dimension l of the upper reed valve main body 70 is reduced, so that the upper reed valve main body 70
Left and right sides of the cylinder 35
To prevent the bolt 35a from screwing with each other. Second, since the lower reed valve main body 60 is located below the upper reed valve main body 70 and does not interfere with the bolt 35a, the width dimension L of the lower reed valve main body 60 is reduced regardless of the bolt 35a. The cross-sectional area of the suction passage 62 of the lower reed valve main body 60 can be increased.
As a result, the cross-sectional areas of the suction passages 62 and 72 increase as a whole, and the air-fuel mixture 91 passing through the suction passages 62 and 72
Intake resistance can be reduced.

Third, as described above, the suction passages 62, 7
2, the amount of the air-fuel mixture 91 passing through these downstream end openings 62b, 72b per unit area is reduced by the whole cross-sectional area, so that the valve opening deformation of each of the valve bodies 64, 74 is reduced. Is small. Therefore, the responsiveness of the opening and closing operations of these valve bodies 64 and 74 to the negative pressure in the crankcase 20 is improved. Fourth, as described above, since the widths of the upper reed valve 58 and the lower reed valve 59 are different, the lower reed valve 5
9 can increase the sectional area of the suction passage 62.

Therefore, the air-fuel mixture 91 is supplied to the upper reed valve 58.
Therefore, the air-fuel mixture 91 passes through the lower reed valve 5 relatively far from the scavenging port 44.
9 through the suction passage 62.

Therefore, the mixture 91 sucked into the crankcase 20 through the reed valve 48 is prevented from flowing into the scavenging port 44 in a short-circuit manner.
1 is sufficiently mixed in the crankcase 20 and then sent to the combustion chamber 41 through the scavenging port 44.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 6 show a first embodiment. In FIG. 2, reference numeral 1 denotes a motorcycle as a vehicle. In the drawings, the arrow Fr indicates the front, and the left and right below refer to the direction toward the front. The above motorcycle 1
Has a head pipe 3 at its front end,
A pair of left and right main frames 4 extend rearward and downward from the head pipe 3. A rear arm bracket 5 extends downward from the rear end of each of the main frames 4.

A front fork 7 is supported on the head pipe 3 so as to be steerable. A front wheel 8 is supported at the lower end of the front fork 7, and a handle 9 is attached to the upper end. A rear arm 11 is pivotally supported on the rear arm bracket 5 by a pivot shaft 10 so as to be vertically swingable. A rear wheel 12 is supported on the swinging end of the rear arm 11, and a shock absorber 13 is provided between the rear end of the main frame 4 and the rear arm 11. In addition, a seat frame is provided that protrudes rearward and upward from the rear end of the main frame 4, and a seat 16 is mounted on the seat frame.

An engine 18 is provided below the main frame 4. The engine 18 is supported by the main frame 4 and the rear arm bracket 5 by the pivot shaft 10 and bolts 19. The engine 18 is a four-cylinder two-stroke engine, and has left and right lower cylinders 21 projecting forward and downward from the front lower surface of a crankcase 20. Left and right upper cylinders 22 project from the front upper surface side of the same crankcase 20 toward the front upper direction.
The intersection angle between 1 and the upper cylinder 22 is substantially 90 ° in side view.

A power transmission device 24 is connected to a rear portion of the crankcase 20. An output wheel 25 of the power transmission device 24 and an input wheel 26 attached to the rear wheel 12 are connected to each other.
And the transmission chain 27 is wound around. And
The power of the engine 18 is transmitted to the rear wheels 12 via the transmission chain 27 and the like, so that the motorcycle 1 can travel on a road surface 28. In addition, 30 is a fuel tank, 3
1 is an exhaust pipe.

In FIGS. 1, 3 and 4, a pair of upper and lower crankshafts 34 are supported in a crank chamber 33 in the crankcase 20. The lower cylinder 21 has a cylinder 35 projecting forward and downward from the front lower surface of the crankcase 20.
1 is screwed to the crankcase 20 with left and right bolts 35a, 35a when viewed from the front as shown in FIG. A protruding end of the cylinder 35 has a cylinder head 36.
Is attached. A piston 38 is slidably fitted in the cylinder 35 on its axis 37, and the piston 38 and the lower crankshaft 34 of the crankshaft 34 are connected by a connecting rod 39.

The cylinder 35, the cylinder head 36,
A space surrounded by the piston 38 and the combustion chamber 41 is a combustion chamber 41, and a spark plug 40 facing the combustion chamber 41 is attached to the cylinder head 36. An intake port 42 communicating with the crank chamber 33 is formed in the crankcase 20. The intake port 42 is provided between the left and right bolts 35a, 35a in a front view.
0 is formed. The cylinder 35 has a scavenging port 4 for communicating the crank chamber 33 with the combustion chamber 41.
4 are formed. On the other hand, an exhaust port 45 for communicating the combustion chamber 41 with the outside is formed.
5 is connected to the exhaust pipe 31. The above cylinder 3
A water jacket 46 is formed on the cylinder head 36 and the cylinder head 36.

The reed valve 48 and the throttle valve 4 are sequentially connected to the intake port 42 toward the upstream side of the intake air.
9, the reed valve 48 and the throttle valve 4
9 is disposed between the lower cylinder 21 and the upper cylinder 22.
The introduction of the traveling wind to the throttle valve 49 is performed by an air introduction pipe protruding forward of the head pipe 3.

2 to 4, the upper cylinder 22 has the same configuration as the lower cylinder 21 and has a cylinder 54 and the like. An intake port formed in the crankcase 20 corresponding to the cylinder 54 has a reed valve 48 and a throttle valve 49 provided corresponding to the lower cylinder 21.
Another reed valve 55 and throttle valve 56 having the same configuration as those described above are provided. These reed valve 55 and throttle valve 56 are provided adjacent to the reed valve 48 and the throttle valve 49 for the lower cylinder 21. Further, a piston of the upper cylinder 22 is connected to an upper crankshaft of the crankshaft 34 by a connecting rod. The two crankshafts 34 are linked to each other by a chain, and one of the crankshafts 34 is connected to the input shaft of the power transmission device 24.

In FIGS. 1, 3, 5 and 6, for convenience of explanation, as shown in FIG.
The description will be made in a state where the axis 37 of No. 5 is viewed vertically.

The reed valve 48 is paired up and down.
The lower reed valves 58 and 59 are configured. The lower reed valve 59 has a lower reed valve main body 60 having a substantially V-shaped box-shaped side cross section. The lower reed valve main body 60 is tapered toward the inside of the crank chamber 33, and an outward flange 61 is integrally formed at a base of the lower reed valve main body 60. A suction passage 62 extends through the inside of the lower reed valve main body 60. The upstream end opening 62 a of the suction passage 62 is open at the base end of the lower reed valve main body 60. The downstream end opening 62b of the suction passage 62 includes four openings formed in the upper and lower walls of the upper and lower reed valve main bodies 60, respectively. Indeed, they are arranged side by side. Upper and lower valve bodies 64 are provided so as to open and close the downstream end openings 62b respectively. One end of the upper valve body 64 is screwed to the upper wall of the base of the lower reed valve main body 60 by the first bolt 66. Have been. One end of the lower valve body 64 is connected to the second bolt 68 together with the stopper 67.
Thus, the upper and lower reed valve main bodies 60 are screwed to the lower surface wall of the base.

On the other hand, the upper reed valve 58 has an upper reed valve main body 70 whose side cross section has an arc-shaped box shape. The upper reed valve body 70 tapers toward the inside of the crank chamber 33, and an outward flange 71 is integrally formed at the base of the upper reed valve body 70. A suction passage 72 extends through the inside of the upper reed valve main body 70. The upstream end opening 72a of the suction passage 72 opens at the base end of the upper reed valve main body 70. Also, the downstream end opening 72b of the suction passage 72 is
Are formed in the upper surface wall of each of them, and each of the downstream end openings 72b has the same shape and size as each other, and is arranged side by side to the left and right. A valve 74 is provided to close and open the downstream end opening 72b so as to be openable and closable. One end of the valve 74 is screwed together with a stopper 75 to the upper wall of the base of the upper reed valve main body 70 by a third bolt 76.

Outward flange 71 of upper reed valve 58
The lower reed valve body 60 is fitted into the fitting hole 77 from the rear thereof, and the outward flanges 61 and 71 are overlapped with each other.
In this case, the first reed valve body 7 is
0 is fastened to the upper surface wall of the base of the lower reed valve main body 60 so that the upper and lower reed valves 5
8, 59 are firmly integrated. Further, a working hole 78 through which the first bolt 66 and a tool for screwing the first bolt 66 are inserted is formed in the upper surface wall of the base of the upper reed valve main body 70. It is closed by a valve body 74 attached to the main body 70.

In FIGS. 1, 3 and 4, the outward flanges 61 and 71 are connected to the first mounting bolt 79 and the second
With the mounting bolt 80, it is detachably screwed to the opening edge of the intake port 42. The second mounting bolt 80 is also used for screwing the reed valve 55 for the upper cylinder 22. A communication hole 81 is formed in the outward flange 61 of the lower reed valve 59 to communicate the inside of the throttle valve 49 with the inside of the upper reed valve body 70.

The throttle valve 49 has a throttle body 83 connected to the outward flanges 61 and 72. A throttle valve body 85 of a butterfly type is provided in an intake passage 84 in the throttle body 83. The throttle body 83 is detachably screwed to the crankcase 20 by the first mounting bolt 79 and the second mounting bolt 80. The throttle body 83 is also detachably screwed to the crankcase 20 side by a third mounting bolt 86. That is, the reed valve 48 and the throttle body 83 are removably fastened to the crankcase 20 side by the first mounting bolt 79, the second mounting bolt 80, and the third mounting bolt 86.

5 and 6, a gasket 87 is interposed between the outward flanges 61 and 71. If the gasket 87 is replaced with another gasket 87 having a different thickness, the relative position between the upper reed valve 58 and the lower reed valve 59 can be adjusted.

3 and 4, the upper wall of the throttle body 83 has a fuel injection valve 8 substantially at the center on the left and right sides.
8 is attached. When the piston 38 starts to rise from the bottom dead center (shown in FIG. 3) during operation of the engine 18, air 89 outside the engine 18 is sucked into the intake passage 84 in the throttle body 83, and this air 89
, The fuel 90 is injected by the fuel injection valve 88.

Further, the air 89 and the fuel 90, which are the intake air,
The mixture 91 is sucked into the crank chamber 33 through the suction passages 62 and 72 of the lower reed valve main body 60 and the upper reed valve main body 70. At this time, each of the valve bodies 64 and 74 is elastically opened and deformed by the negative pressure in the crank chamber 33 generated as the piston 38 rises, and automatically opens to allow the mixture 91 to pass. I do. The excessive opening of the valve bodies 64 and 74 means that these elastically deformed portions come into contact with the stoppers 67 and 75 and the arc-shaped convex stopper surfaces formed on the upper and lower surfaces of the intake port 42, Upper reed valve body 7
This is prevented by contacting the arc-shaped convex stopper surface 92 formed on the lower surface of the zero.

When the piston 38 rises, the air-fuel mixture 91 that has already been sent into the combustion chamber 41 is compressed by the piston 38. When the piston 38 is located near the top dead center, the air-fuel mixture 91 in the combustion chamber 41 is sufficiently compressed and ignited and burned by the ignition plug 40. Then, the piston 38 is pushed down. At this time, the valve bodies 64 and 74 are automatically closed by the pressure in the crank chamber 33 to prevent the backflow of the air-fuel mixture 91 sucked into the crank chamber 33 as described above. Then, the air-fuel mixture 91 is pre-compressed, and the pre-compressed air-fuel mixture 91 is sent to the combustion chamber 41 through the scavenging port 44. On the other hand, the combustion gas 93 generated in the combustion chamber 41 by the combustion is exhausted through the exhaust port 45. When the piston 38 rises again, the above operation is repeated, and power is output from the engine 18.

In FIG. 1, the width l of the upper reed valve main body 70 is made smaller than the width L of the lower reed valve main body 60. This prevents the left and right side portions of the upper reed valve main body 70 from interfering with the bolt 35a that screws the cylinder 35 to the crankcase 20. On the other hand, since the lower reed valve main body 60 is located below the upper reed valve main body 70 and does not interfere with the bolt 35a, the width L of the lower reed valve main body 60 is large regardless of the bolt 35a. The cross-sectional area of the suction passage 62 of the lower reed valve main body 60 is increased. As a result, the cross-sectional areas of the suction passages 62 and 72 are increased as a whole, and the intake resistance of the air-fuel mixture 91 passing through the suction passages 62 and 72 is reduced, thereby improving the charging efficiency.

Also, as described above, the suction passages 62, 72
Is increased as a whole, the amount of the air-fuel mixture 91 passing through these downstream end openings 62b, 72b per unit area is reduced, so that the valve opening deformation of each of the valve bodies 64, 74 is reduced. Small enough. Therefore, the responsiveness of the opening and closing operations of the valve bodies 64 and 74 to the negative pressure of the crank chamber 33 is improved, and the performance of the engine 18 is also improved in this respect. Further, as described above, the upper reed valve 58
In addition to the difference in width between the lower reed valve 59 and the lower reed valve 59, the downstream end openings 62b of the suction passages 62 in the upper reed valve 58 are formed in a line to the left and right. The downstream end openings 72b of the suction passages 72 at 59 are arranged in two rows in the vertical direction.

For this reason, the air-fuel mixture 91 passes through the suction passage 62 of the lower reed valve 59 more than the suction passage 72 of the upper reed valve 58, that is, the air-fuel mixture 91 is relatively lower than the scavenging port 44. Suction passage 62 of reed valve 59
And is sucked into the crank chamber 33.
Therefore, the mixture 91 sucked into the crank chamber 33 through the reed valve 48 is prevented from flowing into the scavenging port 44 in a short-circuit manner.
After being sufficiently mixed in the combustion chamber 41, the mixture is sent to the combustion chamber 41 through the scavenging port 44. As a result, ignition and combustion in the combustion chamber 41 are reliably performed, and the engine 1
8 is to be improved.

In a portion where the air 89 and the air-fuel mixture 91 flow separately into the lower reed valve main body 60 and the upper reed valve main body 70, a rectifying plate 94 for rectifying this flow is directed outward of the lower reed valve 59. It protrudes integrally with the flange 61. The current plate 94 prevents the air-fuel mixture 91 that is flowing into each of the intake passages 62 and 72 from causing boundary layer separation, thereby preventing the intake resistance from increasing. Further, by setting the fuel injection of the fuel injection valve 88 in a certain direction and selecting the shape and the projecting direction of the rectifying plate 94, a desired amount of fuel injection into each of the suction passages 62 and 72 of the reed valve 48 can be obtained. Can be distributed.

Each of the upstream end openings 62a and 72a has an elongated rectangular shape on the left and right sides, and has a rectangular shape elongated on the left and right as a whole. On the other hand, the intake passage 84 of the throttle body 83 has a pair of left and right passages 84a, 8a.
4a, each of the passages 84a has a circular shape. A partition wall 95 is interposed between the two passages 84a. As described above, the intake passage 84 is constituted by a pair of left and right passages 84a, 84a corresponding to the upstream end openings 62a, 72a of the reed valve 48 having a rectangular shape that is long on the left and right as a whole. In this way, the change in the cross section of the transition portion from the intake passage 84 of the throttle body 83 to each of the intake passages 62 and 72 of the reed valve 48 is reduced. Therefore, the mixture 9
1 smoothly flows from the intake passage 84 into the intake passages 62 and 72, thereby suppressing an increase in intake resistance.

The throttle valve body 85 is provided in each of the passages 84a with circular valve bodies 85a and 85a.
5a, these valve bodies 85a, 85a can be opened and closed individually. In the low-speed range of the engine 18, only one valve body 85a is opened and closed, and in the high-speed range, both the valve bodies 85a are simultaneously opened and closed. In this case, the two valve bodies 85a may be opened and closed integrally. The above-described configuration and operation are similar to those of the upper cylinder 22.
The same applies to the corresponding reed valve 55 and throttle valve 56. Further, the engine 18 may be constituted by a single lower cylinder 21 and an upper cylinder 22 each having a side surface intersection angle of 90 °.
1 and the upper cylinder 22 drive a single crankshaft 34.
Further, the downstream end openings 62b, 72b in the reed valve 48 are provided.
Is not limited to the above embodiment, and may be singular or plural.

FIGS. 7 to 11 show the second to fourth embodiments. In addition, about the structure and effect | action which each of these Examples and the said 1st Example have in common, a common code | symbol is attached | subjected to drawing and description is abbreviate | omitted, and a different part is demonstrated.

(Second Embodiment) FIGS. 7 and 8 show a second embodiment. According to this, the fuel injection valve 88 is connected to each passage 8.
4a, which are attached to the lower surface wall of the throttle body 83. Further, the center of the fuel 90 in the injection direction faces the inside of the lower reed valve main body 60. Since the opening area of the suction passage 62 of the lower reed valve main body 60 is large, the fuel 90 flows into the crank chamber 33 smoothly.

(Third Embodiment) FIGS. 9 and 10 show a third embodiment. According to this, the fuel injection valves 88 are provided for the respective passages 84a, and these are attached to the left and right side walls of the throttle body 83. The center of the fuel 90 in the injection direction is located at the lower reed valve main body 6.
The fuel 90 is substantially uniformly supplied to each of the suction passages 62 and 72, and is directed substantially toward the boundary between the inside of the cylinder 0 and the inside of the upper reed valve body 70.

(Fourth Embodiment) FIG. 11 shows a fourth embodiment. According to this, the fuel injection valve 88 is connected to each passage 84.
a, which are attached to the upper surface wall of the throttle body 83.

[0039]

According to the present invention, the cylinder is screwed to the crankcase with left and right bolts when viewed from the front, an intake port is formed in the crankcase between the left and right bolts when viewed from the front, and a lead is provided to the intake port. When the valve is installed, when the axis of the cylinder is viewed vertically, the reed valve is composed of an upper and lower reed valve, and the left and right width of the upper reed valve main body constituting the upper reed valve is the lower reed valve. First, since the left and right widths of the upper reed valve body are reduced, the left and right sides of the upper reed valve body are screwed to the crankcase with the cylinder. Interference with the bolts is prevented.

Second, since the lower reed valve body is located below the upper reed valve body and does not interfere with the bolt, the width of the lower reed valve body can be increased irrespective of the bolt. The cross-sectional area of the suction passage of the lower reed valve body can be increased. As a result, the cross-sectional area of the suction passage is increased as a whole, the intake resistance of the air-fuel mixture passing through the suction passage is reduced, and the charging efficiency is improved.

Third, as described above, since the cross-sectional area of the suction passage is increased as a whole, the amount of the air-fuel mixture passing through each downstream end opening per unit area is reduced. , The amount of valve opening deformation can be small. Therefore, the responsiveness of the opening and closing operations of each of these valve bodies to the negative pressure in the crankcase is improved, and in this respect, the performance of the engine is also improved.

Fourth, as described above, the cross-sectional area of the suction passage of the lower reed valve can be made larger than that of the upper reed valve by the difference in width between the upper reed valve and the lower reed valve. The air will pass more through the suction passage of the lower reed valve having a larger cross-sectional area than the suction passage of the upper reed valve,
That is, the air-fuel mixture is sucked into the crankcase through many suction passages of the lower reed valve relatively far from the scavenging port. Therefore, the mixture that is sucked into the crankcase through the reed valve is prevented from being short-circuited into the scavenging port, and the mixture is sufficiently mixed in the crankcase before the scavenging. It will be sent to the combustion chamber through the port. As a result, ignition and combustion in the combustion chamber are reliably performed, and the performance of the engine is improved.

In the above case, the downstream end opening of the suction passage of the upper reed valve body is constituted by a plurality of openings arranged in a line in the left and right direction, and the downstream end opening of the suction passage of the lower reed valve body is formed by the left and right. May be constituted by a plurality of openings in each row arranged in two rows in the upper and lower directions. By doing so, the above-mentioned fourth operation and effect become more remarkable.

[Brief description of the drawings]

FIG. 1 is a view of a first embodiment taken along line 1-1 of FIG. 3;

FIG. 2 is an overall side view of the motorcycle in the first embodiment.

FIG. 3 is a side cross-sectional view of the engine according to the first embodiment in a state where the axis of the lower cylinder is viewed vertically.

FIG. 4 is a view of the first embodiment taken along line 4-4 in FIG. 3;

FIG. 5 is a side elevational view of a reed valve according to the first embodiment.

FIG. 6 is a plan development view of the reed valve in the first embodiment.

FIG. 7 is a view corresponding to FIG. 3 in a second embodiment.

FIG. 8 is a diagram corresponding to a part of FIG. 4 in a second embodiment.

FIG. 9 is a view corresponding to FIG. 3 in a third embodiment.

FIG. 10 is a diagram corresponding to a part of FIG. 4 in a third embodiment.

FIG. 11 is a view corresponding to a part of FIG. 4 in a fourth embodiment.

[Explanation of symbols]

 Reference Signs List 18 engine 20 crankcase 33 crankcase 34 crankshaft 35 cylinder 35a bolt 42 intake port 44 scavenging port 48 reed valve 58 upper reed valve 59 lower reed valve 60 lower reed valve main body 62 suction passage 62a upstream end opening 62b downstream end opening 70 upper Reed valve body 72 Intake passage 72a Upstream end opening 72b Downstream end opening l Width L Width

Claims (2)

(57) [Claims] 1. A two-stroke cycle in which a cylinder is screwed to a crankcase with left and right bolts in a front view, an intake port is formed in the crankcase between the left and right bolts in a front view, and a reed valve is attached to the intake port. In the engine, when the axis of the cylinder is viewed vertically, the reed valve is composed of an upper and lower reed valve, and the left and right widths of an upper reed valve main body constituting the upper reed valve are lower reeds constituting the lower reed valve. A two-stroke engine that is smaller than the width of the valve body. 2. A downstream end opening of a suction passage of an upper reed valve main body is constituted by a plurality of openings arranged in a line to the left and right,
2. The lower reed valve body according to claim 1, wherein the downstream end opening of the suction passage is formed of a plurality of openings arranged in two rows in the vertical direction.
2. A two-stroke engine according to claim 1.