JP2873319B2 - Two-cycle internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-cycle internal combustion engine that circulates cooling water and cools it.

2. Description of the Related Art In a motorcycle, in order to lower the center of gravity, for example, a two-stroke internal combustion engine is tilted forward, a fuel tank is arranged in front of the internal combustion engine, and an intake passage and exhaust gas are provided on the same side of the engine body. There is one in which a passage is formed toward the rear of the vehicle body and includes an intake system and an exhaust system.

As a method for cooling the two-cycle internal combustion engine mounted in this manner, there is a water-cooled type. In this type, a water jacket is formed in the engine body, and cooling water is circulated from a radiator to the water jacket to cool the engine.

[Problems to be Solved by the Invention] By tilting the two-stroke internal combustion engine forward and forming the intake passage and the exhaust passage in the same direction on the same side surface of the engine body, the intake passage and the exhaust passage are close to each other. As a result, the temperature in the vicinity of the intake passage increases due to the influence of exhaust gas discharged from the exhaust passage. For this reason, the temperature of the air-fuel mixture supplied from the intake passage rises above a predetermined value, which affects the charging efficiency. Also, the spring constant of the reed valve changes due to the influence of heat, and the opening / closing accuracy decreases, or the durability increases. It may decrease.

The present invention has been made in view of such circumstances, and a branch cooling water flow path is provided separately from a cooling water flow path to improve the charging efficiency by efficiently cooling the intake system, and also to improve the reed valve by the influence of heat. It is an object of the present invention to provide a two-stroke internal combustion engine capable of preventing a change in a spring constant, improving opening / closing accuracy, improving durability of a reed valve, and blocking radiation heat from an exhaust passage side. And

[Means for Solving the Problems] In order to solve the problems and achieve the object, the present invention is configured as follows.

The invention according to claim 1 has “an intake passage and an exhaust passage extending from the same side surface of the engine body in substantially the same direction,
In the two-stroke internal combustion engine provided with a reed valve for guiding intake air to a crank chamber of the engine body in the intake passage, and circulating cooling water from a radiator to a water jacket of the engine body by a water pump for cooling, Cooling water, a cooling water passage circulating through a first water jacket formed around a cylinder of the engine body through a cooling water passage, and cooling water from the water pump through the branch cooling water passage. It is located between the intake passage and the exhaust passage, and is guided to a position on the upstream side in the direction of the flow of intake air of the second water jacket formed along the reed valve, and from the downstream side of the second water jacket. Merges into the first water jacket via a third water jacket formed around the exhaust passage 2-cycle internal combustion engine characterized by having a branch coolant passage. ].

According to the first aspect of the present invention, a branch cooling water flow path is provided separately from the cooling water flow path, and the direction of the flow of the intake air of the second water jacket formed directly along the reed valve from the branch cooling water flow path. To the upstream position, this second
From the downstream side of the water jacket through the third water jacket formed around the exhaust passage to the first water jacket of the cooling water flow path, so that the cold cooling water flows into the second water jacket of the intake system. It can be guided and cooled to improve the filling efficiency, prevent the spring constant of the reed valve from being changed by the influence of heat, improve the opening / closing accuracy, and improve the durability of the reed valve.

Further, since the second water jacket is located between the intake passage and the exhaust passage, radiant heat from the exhaust passage side is shut off, and the influence of the heat on the reed valve is reduced.

Embodiments of the Invention Hereinafter, an embodiment of a two-stroke internal combustion engine of the present invention will be described in detail with reference to the accompanying drawings.

1 is a side view of a motorcycle, FIG. 2 is a plan view of a two-cycle internal combustion engine, FIG. 3 is a left view of the two-cycle internal combustion engine, FIG. 4 is a right view of the two-cycle internal combustion engine, and FIG. Figure 2
FIG. 6 is a sectional view taken along line VI-VI of FIG. 5, FIG. 7 is a bottom view of the cylinder block, FIG. 8 is a sectional view taken along line VIII-VIII of FIG. 3, and FIG. 3 is a sectional view taken along line IX-IX, FIG. 10 is a sectional view taken along line XX in FIG. 3, and FIG. 11 is a rear view of the cover housing.

In the figure, reference numeral 1 denotes a motorcycle. A pair of left and right main frames 3 having a box-shaped cross section are connected to a head pipe 2 of the vehicle body so as to extend rearward. Down tubes 4 are respectively connected. The head pipe 2 is provided with a pair of front forks 6 on which a front wheel 5 is suspended, while the main frame 3 and the down tube 4 are mounted with a two-cycle internal combustion engine 7. The two-cycle internal combustion engine 7 is cooled by a water-cooling system. A radiator 8 for cooling the cooling water is attached to the down tube 4, and a fuel tank 9 is provided below the radiator 8.

At the center of the pair of left and right main frames 3, seat rails 10 are respectively provided toward the rear, and the pair of left and right seat rails 10 are respectively supported by the rear portions of the main frame 3 via the back stays 11. The seat 12 is placed on the seat rail 10. A bracket 13 is fixed to a rear portion of the main frame 3, and a rear arm 15 for suspending a rear wheel 14 is swingably provided on the bracket 13, and is swingable via a rear suspension 16.

A cowling 70 is provided so as to cover the sides of the radiator 8 from both sides of the pair of left and right main frames 3.

The two-stroke internal combustion engine 7 is mounted in a state of being tilted forward, thereby lowering the center of gravity of the two-stroke internal combustion engine 7, the head of the engine body is located forward of the down tube 4, and the fuel tank 9 is mounted in the two-stroke internal combustion engine. The center of gravity of the vehicle body is reduced by disposing the vehicle body in front of the engine 7.

An intake system 17 and an exhaust system 18 connected to the engine body are mounted toward the rear of the vehicle body. A carburetor 20 is connected to an intake pipe 19 of the intake system 17, and a connection pipe (not shown) is connected to the carburetor 20. The air cleaner 71 is connected via the. Exhaust system
As shown in FIG. 2, the exhaust pipe 22 is bent above the vaporizer 20 so as to avoid the vaporizer 20 and extends rearward along the seat rail 10, and a silencer 23 is connected to the rear end. Have been.

The crankshaft 24 of the two-cycle internal combustion engine 7 is provided on the crankcase 25 so as to be orthogonal to the traveling direction of the vehicle. A generator 26 is provided at one end of the crankshaft 24, and a reduction gear 27 is provided at the other end. The reduction gear 27 is provided with a reduction gear 29 engaged with the intermediate shaft 28. A friction multi-plate clutch 30 is provided on the intermediate shaft 28, and the friction multi-plate clutch 30 transmits power from the reduction gear 29 to the intermediate shaft 28.

The drive gear 31 fixed to the intermediate shaft 28 is a gear 33 of the main shaft 32.
The main shaft 32 is transmitted to a drive shaft 35 via a transmission mechanism 34, and the drive shaft 35 is provided with a drive sprocket 36.
36 transmits power to the rear wheel 14 via a chain 37.

A kick shaft 38 is pivotally supported on the crankcase 25,
The drive gear 39 of the kick shaft 38 is meshed with a driven gear 40 that rotates integrally with the reduction gear 29 of the intermediate shaft 28,
The two-cycle internal combustion engine 7 is started by forcibly rotating the crankshaft 24 via the reduction gear 29 and the reduction gear 27.

The cylinder block 41 is mounted on the crankcase 25 of the engine body.
A cylinder head 43 provided with an ignition plug 42 is mounted on an upper portion of the cylinder block 41, and a recess 8a is formed in a lower portion of the radiator 8 so as to avoid interference with the ignition plug 42. A piston 44 is provided on the cylinder block 41 so as to be able to reciprocate.
It is connected to the crankshaft 24 via 45 and converts the reciprocating motion into a rotary motion. A combustion chamber 46 is formed between the cylinder head 43 and the piston 44, and the combustion chamber 46 and a crank chamber 47 formed in the crankcase 25 have a scavenging passage 72 that communicates when the piston 44 descends. I have.

An intake passage 48 is formed on the upper side of the crankcase 25 toward the rear of the vehicle body. The carburetor 20 is connected to the intake passage 48 via an intake pipe 19, and a reed valve 49 is provided in the intake passage 48. The chamber 470 is opened and closed by pressure fluctuation.

An exhaust passage 50 is formed above the cylinder block 41 toward the rear of the vehicle body.
Is connected. Thus, the intake passage 48 and the exhaust passage
50 extends from the same side of the engine body toward the rear of the vehicle.

The exhaust passage 50 has an exhaust valve 52 formed in a substantially conical shape.
The exhaust valve 52 is rotated to change the exhaust timing and advances and retreats to the exhaust passage 50, and both ends are covered with covers 54 and 55. Exhaust valve 52
A notch 52a is formed in a part of the outer peripheral portion, and the notch 52 has a shape that matches the shape of the opening on the upper edge side of the exhaust passage 50. The outer peripheral portion 52b connected to the notch 52a is a combustion chamber.
The 46 side moves into and out of the exhaust passage 50 to raise and lower the upper edge of the opening of the exhaust passage 50 to adjust the opening timing of the exhaust passage 50.

A drive shaft 52c is provided on the shaft center of one end of the exhaust valve 52, and an operation lever 56 is provided on the drive shaft 52c. The operating lever 56 rotates the exhaust valve 52 to a predetermined position corresponding to the rotation speed of the two-cycle internal combustion engine by a centrifugal governor 73 as an exhaust timing control device, a rod (not shown), and the like.

The crankshaft is located below the crankcase 25 of the engine body.
A cooling water passage 74 is formed coaxially with the cooling water passage 24, and the cooling water passage 74 is formed via a communication passage 57 in a first water jacket 59 formed in the cylinder block 41 and a second water jacket 59 formed in the cylinder head 43. The cylinder block 41 and the cylinder head 43 are cooled by communicating with the first water jacket 61.

The crankcase 25 further includes an intake passage 48 and an exhaust passage.
A second water jacket 58 is also formed in a portion located between the second water jacket 50 and the portion 50 and cools the periphery of the intake passage 48. The second water jacket 58 communicates with a third water jacket 60 formed in the cylinder block 41, and the third water jacket 60 is formed around the exhaust passage 50. Cooling. A first water jacket 61 formed in the cylinder head 43 communicates with the third water jacket 60.

The two-stroke internal combustion engine 7 is mounted so as to be tilted forward, and an outlet 62 for cooling water is formed near the exhaust valve 52 at the uppermost position of the cylinder block 41, and is connected to the outlet 62. The cooling water is supplied to the radiator 8 by the pipe 63 thus set. As described above, the outlet portion 62 is provided at the uppermost position of the cylinder block 41, and air bubbles do not accumulate in the water jacket of the engine body. Further, a second water jacket 60 formed on the cylinder block 41 is formed.
Has a complicated shape due to the exhaust passage 50 and the exhaust valve 52, but since the outlet portion 62 is formed in the portion of the second water jacket 60, the cooling water stays in the second water jacket 60. And can be efficiently cooled.

Furthermore, since the outlet portion 62 is formed in the cylinder block 41 and connected to the radiator 8 by the pipe 63, when the cylinder head 43 is removed for maintenance of the two-cycle internal combustion engine 7, the pipe 63 does not hinder the workability. improves.

The cooling water is cooled by the radiator 8 and sent to a cover housing 65 provided on the crankcase 25 via a pipe 64.

The cover housing 65 is fastened and fixed to the side of the crankcase 25 with bolts 67 so as to cover a water pump 66 provided in the crankcase 25 shown in FIGS. Cooling water is introduced into the inlet passage 65a of the cover housing 65.
To the pump chamber 68 via The water pump 66 disposed in the pump chamber 68 is provided on the pump shaft 69,
69 is connected to the reduction gear 27 of the crankshaft 24 via gears 75 and 76, and rotates in conjunction with the crankshaft 24. By the operation of the water pump 66, the cooling water flows from the pump chamber 68 toward the crankshaft 24 formed in the crankcase 25 in a cooling water passage.
The cooling water is then sent to the first water jacket 59 via the communication passage 57.

Further, a branch passage 65b branching from the water pump 66 is formed in the cover housing 65, and the coolant flows from the branch passage 65b upstream of a second water jacket 58 formed between the intake passage 48 and the exhaust passage 50. Side. The cooling water from the radiator 8 is supplied to the second water jacket 58 by the driving of the
Since the air is directly fed from the air passage 68, the periphery of the intake passage 48 can be effectively cooled by the low-temperature cooling water cooled by the radiator 8, and the influence of heat from the exhaust passage 50 can be suppressed.

As described above, the cooling water sent from the cover housing 65 is supplied from the pump chamber 68 to the cooling water passage 74 via the communication passage 68a, and is further supplied to the cylinder block via the communication passage 57.
A cooling water passage which is supplied to the first water jacket 59 of the cylinder head 41 and circulates through the first water jacket 61 of the cylinder head 43 and joins the second water jacket 60 is formed.

The other is a second water jacket formed between the intake passage 48 and the exhaust passage 50 via the branch cooling water passage 65b.
A branch cooling water passage, which is supplied to the second water jacket 58 and is supplied from the second water jacket 58 to the third water jacket 60 of the cylinder block 41, is formed independently. And is sent to the radiator 8 from the outlet 62 via the pipe 63.

Although the cooling water from the radiator 8 is supplied to the water jackets 58 and 60 formed between the intake passage 48 and the exhaust passage 50 by the cover housing 65, the cooling water is not limited to this. The cooling water passage for feeding the cooling water may be formed in the crankcase 25 or the cylinder cylinder block 41 of the engine body. Further, the water jacket 59 and the water jacket 60 of the cylinder block 41 may be in communication. Further, the outlet for supplying the cooling water to the radiator 8 is not limited to one place, and the cylinder block 41
May be provided in communication with the water jacket 59 of the cylinder head 43, or may be provided in communication with the water jacket 61 of the cylinder head 43.

[Effects of the Invention] As described above, according to the first aspect of the present invention, a second cooling water flow path is provided separately from the cooling water flow path and formed along the reed valve directly from the branch cooling water flow path. The first water jacket of the cooling water flow path is guided from a downstream side of the second water jacket to a position upstream of the second water jacket through a third water jacket formed around the exhaust passage. The cooling water can be led to the second water jacket of the intake system for cooling, improving the charging efficiency, preventing the spring constant of the reed valve from changing due to heat, and improving the opening / closing accuracy. As a result, the durability of the reed valve is improved.

Further, since the second water jacket is located between the intake passage and the exhaust passage, radiant heat from the exhaust passage side can be cut off, and the effect of the heat on the reed valve can be reduced.

[Brief description of the drawings]

1 is a side view of a motorcycle, FIG. 2 is a plan view of a two-cycle internal combustion engine, FIG. 3 is a left view of the two-cycle internal combustion engine,
4 is a right view of the two-stroke internal combustion engine, FIG. 5 is a cross-sectional view of the two-stroke internal combustion engine, FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5, FIG. Fig. 8 shows the third
9 is a sectional view taken along line VIII-VIII of FIG. 9, FIG. 9 is a sectional view taken along line IX-IX of FIG. 3, FIG. 10 is a sectional view taken along line XX of FIG. 3, and FIG. In the figure, reference numeral 1 denotes a motorcycle, 7 denotes a two-cycle internal combustion engine, 8
Is a radiator, 25 is a crankcase, 14 is a cylinder block, 43 is a cylinder head, 47 is a crankcase, 58, 59, 6
0,61 is a water jacket, 65 is a cover housing, 65
a is an introduction passage, and 65b is a cooling water passage.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01P 3/12 F02B 25/16 F02B 33/30 B62M 7/02

Claims (1)

(57) [Claims] 1. An engine according to claim 1, further comprising an intake passage and an exhaust passage extending in substantially the same direction from the same side surface of the engine main body, wherein said intake passage includes a reed valve for guiding intake air to a crank chamber of said engine main body. In a two-stroke internal combustion engine in which cooling water is circulated through a water jacket of the engine body by a water pump to cool the engine, cooling water from the water pump is formed around a cylinder of the engine body through a cooling water passage. A cooling water flow path that circulates through the water jacket, and cooling water from the water pump.
It is located between the intake passage and the exhaust passage through the branch cooling water passage, and is guided to a position on the upstream side in the direction of the flow of intake air of the second water jacket formed along the reed valve. A two-stroke internal combustion engine, comprising: a branch cooling water flow path that joins the first water jacket from a downstream side of the second water jacket through a third water jacket formed around the exhaust passage.