JP2886944B2 - V-type two-stroke engine intake system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a V-type two-stroke engine in which a reed valve is mounted on a crankcase, and in particular, to a structure of an intake device of the engine.

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 63-302143 discloses an example of a two-stroke engine having a V-shaped cylinder arrangement.

In this engine, a crankcase containing a crankshaft is provided with a front cylinder extending forward and a rear cylinder extending upward, and a crank chamber connected to each cylinder is provided in the crankcase.

A plurality of intake ports connected to the crank chamber are opened on the front surface of the crankcase sandwiched between the front and rear cylinders. These intake ports are provided in a line in the axial direction of the crankshaft, and a carburetor is connected to each of these intake ports.In each intake port, only the flow of intake air from the carburetor to the crank chamber is provided. An acceptable reed valve is provided.

[Problems to be Solved by the Invention] However, in the case of this conventional configuration, the intake port is opened from the space between the front cylinder and the rear cylinder toward the center of the crankshaft. The reed valve gives directionality to the flow of intake air toward the crank chamber, so that intake air from the carburetor is sucked into the crank chamber in a direction away from the cylinder.

For this reason, the intake air sucked into the crank chamber has a problem that the flow direction is largely reversed or complicatedly bent in the crank chamber, and the intake resistance increases accordingly.

The present invention has been made in view of such circumstances, and the intake air sucked into the crank chamber smoothly flows toward the first and second cylinder portions, and more intake air is efficiently supplied to these two cylinder portions. It is possible to guide well and to equalize the suction conditions of the two cylinders. Further, when a plurality of fuel supply devices are arranged in a line between the first and second cylinders, the fuel It is an object of the present invention to provide an intake device for a V-type two-stroke engine that can reduce the bending of an intake pipe connecting a supply device and an intake port to reduce intake resistance.

Means for Solving the Problems In order to achieve the above object, the present invention provides a crankcase in which a first cylinder portion and a second cylinder portion are erected in a V-shape. Crank chambers are respectively formed inside the first and second cylinder sections, and each of the first and second cylinder sections has a crank chamber corresponding to the first cylinder section and a second crank section corresponding to the first cylinder section. A second crankshaft is accommodated, the first and second crankshafts are driven to rotate in opposite directions, and the first and second cylinders are connected to the first and second crankshafts. On the opposite side, a main shaft driven by power transmission from the first and second crankshafts is arranged, and a portion of the crankcase sandwiched between the first and second cylinder portions is A plurality of intake ports connected to the crank chamber are provided side by side in the axial direction of the first and second crankshafts. Each intake port is provided with a reed valve that allows only the flow of intake air toward the crank chamber. A fuel supply device is connected to the mouth via an intake pipe, and it is assumed that the fuel supply device is a V-type two-stroke engine provided in a line between the first and second cylinder portions.

The intake port is provided so as to be deviated to the side of the cylinder section where the first and second cylinder sections are connected to each other, and the reed valve located in the intake port passes through the center of the valve body. And a center line along the flow direction of the intake air is provided so as to be inclined in a direction in which the first and second cylinder parts are directed toward the first and second cylinder parts with respect to the first and second crankshafts in the crank chambers connected to each other. The rotation directions of the first and second crankshafts are determined so as to extend from the main shaft toward the first and second cylinder portions at mutually opposing portions of the crankshafts.

[Operation] According to this configuration, the reed valve that gives directionality to the flow of the intake air is inclined more in the direction toward the first and second cylinder portions than the first and second crankshafts, respectively. , The intake air taken into the crankcase is the first and second
Is guided to a position near the cylinder portion. For this reason, it is possible to minimize the inversion or bending of the intake air in the crank chamber as much as possible, and the intake air sucked into the crank chamber easily flows toward the first and second cylinder portions.

In addition, since the rotation directions of the first and second crankshafts in the crank chamber are defined, the intake air sucked into the crank chamber from between the first and second cylinder portions is inertial due to the rotation of the crankshaft. As a result, the crank chamber turns in a direction approaching the cylinder section. That is, since the intake air flows along the wall surface of the crank chamber by substantially the same distance before reaching the first and second cylinder portions, the flow direction of the intake air and the suction path length in the crank chamber are the first and second. It becomes equal for each cylinder, and the suction conditions of these two cylinders can be equalized.

In addition, since the intake port is biased toward the first and second cylinder portions, the reed valve can be made closer to the cylinder portion, and the length of the intake path in the crank chamber can be shortened.

At the same time, the shape of the intake pipe connecting the fuel supply device and the intake port can be made smooth with little bending, and the intake resistance can be reduced accordingly.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings applied to a motorcycle.

The motorcycle frame indicated by reference numeral 1 in FIG. 5 includes a steering head pipe 2 at a front end. A front wheel 4 is supported on the steering head pipe 2 via a front fork 3. A pair of left and right main pipes 5 extending obliquely downward and rearward is connected to the steering head pipe 2, and a water-cooled V-type two-stroke four-cylinder engine 6 according to the present invention is supported below the main pipes 5. Have been.

A first cylinder portion 8 extending obliquely downward and forward and a second cylinder portion 9 extending obliquely upward and forward are provided on a crankcase 7 of the engine 6. When the motorcycle is viewed from the side, the cylinder portions 8 and 9 are arranged substantially in a V shape toward the front.

In the crankcase 7, first and second two crankshafts 10, 11 are accommodated horizontally in the left-right direction. The crankshafts 10 and 11 are arranged vertically, and a first crankshaft 10 located below the crankshaft 10 corresponds to the first cylinder portion 8 and a second crankshaft 11 located above the same. Correspond to the second cylinder portion 9. As shown in FIG. 1, the crankcase 7 passes through the axis O ₁ , O ₂ of the crankshafts 10, 11 and is separated from the front case 7 a by a dividing line X ₁ -X ₁ extending in the vertical direction. It is divided into a rear case 7b and these front case 7a and rear case
7b, the crank chambers 12, 11 through which the crankshafts 10, 11 pass.
13 are formed.

The crank chambers 12 and 13 are provided separately from each other.

As shown in FIG. 1, first and second crankshafts 1
Interlocking gears 18a and 18b are mounted on 0 and 11, respectively. The interlocking gears 18a and 18b are always meshed, and the meshing causes the first and second crankshafts 10 and 11 to be rotationally driven in opposite directions in synchronization with each other. A drive gear 17 for taking out power is attached to one end of the first crankshaft 10.

The rear case 7b of the crankcase 7 also serves as a transmission case, and the main shaft 15 is supported inside the rear case 7b. The main shaft 15 is disposed behind the first and second crankshafts 10 and 11 in parallel with the crankshafts 10 and 11, and a driven gear 16 is attached to one end of the main shaft 15. The driven gear 16 meshes with a drive gear 17 of the first crankshaft 10, and the main shaft 15 is driven to rotate by the transmission of power from the first crankshaft 10 by this meshing.

Then, as shown by arrows in FIG.
The rotation directions of the crankshafts 10 and 11 are determined so as to be directed from the main shaft 15 to the first and second cylinder portions 8 and 9 at mutually opposing portions.

The first and second cylinder portions 8 and 9 include a cylinder block 21. Inside the cylinder block 21, a pair of left and right cylinders 20 are provided side by side. The cylinder block 12 is connected to the front case 7a, and extends forward and upward, respectively.A piston 22 housed in the cylinder 20 is connected to a crankshaft via a connecting rod 23.
It is linked to 10,11. An exhaust port 24 opening to the combustion chamber 20a and a scavenging port 25 are formed on the inner surface of the cylinder 20, and the exhaust port 24 and the scavenging port 25 are opened and closed by the piston 22. The exhaust ports 24 are respectively connected to the exhaust passage 26,
The exhaust passage 26 of the first cylinder portion 8 is opened at the lower surface of the cylinder block 21 extending forward, and the exhaust passage 26 of the second cylinder portion 9 is opened at the rear surface of the cylinder block 21 extending upward. ing. An exhaust pipe 27 extending rearward is connected to the open ends of the exhaust passages 26.

A plurality of scavenging ports 25 are provided so as to surround the cylinder 20, and these scavenging ports 25 are connected to a scavenging passage. The scavenging passage 28 extends in the axial direction of the cylinder 20, and its end on the side of the crankcase 7 is connected to the crank chambers 12, 13.
It is connected to.

On the other hand, the front case 7a of the crankcase 7 has an intake port 30 opening to the crank chamber 12 of the first cylinder portion 8,
The intake port 31 which opens to the crank chamber 13 of the cylinder section 9 is formed two by two. The intake ports 30 and 31 are opened on the front surface of the front case 7a sandwiched between the first and second cylinder portions 8 and 9. As shown in FIG. 3, the intake ports 30 and 31 are arranged along the axial direction of the crankshafts 10 and 11, and the opening shape is a vertically long rectangular shape.

The intake port 30 of the first cylinder section 8 and the intake port 31 of the second cylinder section 9 are alternately positioned on the front surface of the front case 7a. In addition to opening upward, the intake port 31 opens obliquely downward and forward from the front surface of the front case 7a. Then, the intake port 30 and 31, the center line Y ₁ passing between the cylinder portion 8, 9 facing each other in the V-shaped, provided at a position biased toward the cylinder portion 8, 9 side where the respective continuous I have.

For this reason, when the crankcase 7 is viewed from the front,
As shown in FIG. 3, the adjacent intake ports 30 and 31 are not aligned in a straight line but are shifted vertically.

A carburetor 34 as a fuel supply device is connected to the intake ports 30 and 31 via intake pipes 32 and 33 extending forward, respectively.
The carburetor 34 is housed in the space between the first and second cylinder portions 8,9. These carburetors 34 are arranged in a line in the left-right direction and are positioned at the same height with respect to the crankcase 7. For this reason, the intake pipe 32 connected to the intake port 30 of the first cylinder section 8 is bent downward as it goes to the front carburetor 34 side, whereas the intake pipe 32 is connected to the intake port 31 of the second cylinder section 9. The continuous intake pipe 33 is bent upward as it advances toward the front carburetor 34 side.

A reed valve 4 that allows only the flow of intake air from the carburetor 34 to the crank chambers 12 and 13 is provided in each of the intake ports 30 and 31.
0 is provided. The reed valve 40 has the same configuration as a conventionally known one, and includes a valve body 41 having an open side on the carburetor 34 side as shown in FIGS.
The valve body 41 has a flat box shape that matches the opening shape of the intake ports 30 and 31. The valve body 41 is disposed vertically with its long axis extending vertically, and the left and right sides of the valve body 41 are connected to the crank chamber 1.
As it proceeds to 2,13, it is inclined in a direction approaching each other.

For this reason, the tip 41a of the valve body 41 facing the crank chambers 12, 13 is tapered, and the tip 41a is connected to the crank arms 10a, 11a of the crankshafts 10, 11 in the crank chambers 12, 13. Close.

The left and right sides of the valve body 41 have crankcases 12 and 13
And a thin valve plate 4 that opens and closes the suction port 41 according to the pressure difference between the inside and outside of the crank chambers 12 and 13.
3, and a stopper 44 for regulating the maximum open position of the valve plate 43 are provided. The valve body 41 has intake ports 30, 3
A flange portion 45 is provided so as to be superimposed on the opening end face of the opening 1, and the flange portion 42 is provided together with the intake pipes 32 and 33 together with the intake port 3.
It is bolted to the opening edge of 0,31.

The valve body 41 of the reed valve 40 has a center line Z passing through the center of its long axis and extending along the flow direction of the intake air.
₁ is the crankshafts 10 and 11 of the crankcases 12 and 13
The _first and _second cylinder portions 8 and 9 are tilted in a direction in which the first and second cylinder portions 8 and 9 are directed from the axis centers O ₁ and O _{2 of} the first and second cylinders.

Further, in this embodiment, as is the valve body 41 shown in FIG. 3, it is offset in the lateral direction with respect to the bore center R ₁ of the cylinder 20. Therefore, the valve body 41 is provided inclined in the direction directed to the bore center R ₁ of the tip portion 41a.

According to such a configuration, the first cylinder portion 8 and the second cylinder portion
When the four intake ports 31, 31 are arranged in a line on the front surface of the front case 7a sandwiched by the cylinder section 9, the valve body 4 of the reed valve 40 installed in these intake ports 30, 31 is provided.
1, the center line Z ₁ passing through the center of the long axis and along the flow direction of the intake air is located between the first and second cylinder portions 8, 9 than the shaft centers O ₁ , O _{2 of the} crankshafts 10, 11. Of the crank chamber 1 through the reed valve 40.
The intake air sucked into 2, 13 is guided to a position near the cylinder 20 where the scavenging passage 28 opens.

For this reason, the flow of the intake air sucked into the crank chambers 12 and 13 can be suppressed from being greatly reversed or bent in the crank chambers 12 and 13 as much as possible. It becomes easy to flow in, and more intake air can be guided to the combustion chambers 20a of the first and second cylinder portions 8,9.

In addition, the first and second crankshafts 10 and 11 are rotated in opposite directions to each other, and their rotation directions are the same.
In the opposed portions 0 and 11, since they are defined so as to extend from the main shaft 15 in the direction of the first and second cylinder portions 8 and 9, the portion between the first and second cylinder portions 8 and 9 is provided. The intake air sucked into the crank chambers 12 and 13
Due to the inertia associated with the rotation of the cylinder 11, the interior of the crank chambers 12 and 13 is swung so as to approach the cylinder 20 as it is, and each cylinder 2
It reaches the scavenging passage 28 of 0.

For this reason, the intake path lengths from the intake ports 30 and 31 to the cylinder 20 in the crank chambers 12 and 13 are substantially equal, and the intake air supplied to the combustion chamber 20a of the first and second cylinder portions 8 and 9 is formed. The amount is also balanced, these two cylinder parts 8,
Nine inhalation conditions can be equalized.

In addition, each intake port 30, 31 is located on the front of the front case 7a,
The reed valve 40 can be made closer to the cylinder 20 because it is provided so as to be biased in a direction approaching the cylinder portions 8 and 9 that are connected to each other. For this reason, the intake paths in the crank chambers 12 and 13 can be made shorter, and the throttle response is improved.

At the same time, the intake port 30 of the first cylinder section 8 and the second
Since the intake ports 31 of the cylinder portions 9 are vertically displaced from each other, when the four carburetors 34 are arranged in a line in the space between the two cylinder portions 8 and 9, these carburetors 34 And the intake pipes 32, 33 connecting the intake ports 30, 31 can be formed into a smooth shape with little bending.

Therefore, the intake resistance can be suppressed to a small value in addition to the shortened intake path length, which contributes to an improvement in engine output.

The V-type two-stroke engine according to the present invention is not limited to a four-cylinder engine, but may be, for example, a two-cylinder engine or a three-cylinder engine.
Further, the present invention is not limited to motorcycles, and can be similarly applied to other vehicles such as small snowmobiles.

[Effects of the Invention] According to the present invention described in detail above, the flow of the intake air sucked into the crank chamber can be suppressed from being greatly reversed or bent in the crank chamber as much as possible. Can be guided to the cylinder.

In addition, the intake air sucked into the crank chamber from between the first and second cylinder portions turns through the inside of the crank chamber as it approaches the cylinder and reaches each cylinder as it is due to inertia accompanying rotation of the crankshaft. , The suction path lengths in the crank chamber become substantially equal. Therefore, the intake air amounts supplied to the first and second cylinder portions are also balanced, and the intake conditions of these two cylinder portions can be equalized.

In addition, the intake port of the crankcase is also biased in the direction of approaching the cylinder section, so that the reed valve can be closer to the cylinder, the intake path in the crank chamber is shorter, and the throttle response is good. Become.

At the same time, when a plurality of fuel supply devices are arranged in a line between the two cylinder portions, the intake pipe connecting these fuel supply devices and the intake port can be formed into a smooth shape with less bending, and In addition to shortening the intake path length, the intake resistance can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. FIG. 1 is a side view of a V-type two-stroke engine partially sectioned. FIG. 2 is a section taken along line II-II in FIG. Fig. 3, Fig. 3 is a front view of a crankcase, Fig. 4 is a front view of a V-type two-stroke engine, and Fig. 5 is a side view of a motorcycle. 7 ... Crankcase, 8 ... First cylinder part, 9 ...
... Second cylinder part, 10 ... First crankshaft, 11 ...
Second crankshaft, 12,13 ... Crank chamber, 15 ... Main shaft, 30,31 ... Inlet, 32,33 ... Intake pipe, 34 ... Fuel supply device (carburetor), 40 ... Lead Valve, 41 …… Valve body.

Claims (1)

(57) [Claims] 1. A crankcase having a first cylinder portion and a second cylinder portion standing upright in a V-shape, wherein the crankcase is internally connected to the first and second cylinder portions individually. A crank chamber is formed, and a first crankshaft corresponding to the first cylinder portion and a second crankshaft corresponding to the second cylinder portion are accommodated in the crank chambers. The first and second crankshafts are driven to rotate in opposite directions to each other, and the first and second crankshafts are arranged on opposite sides of the first and second cylinder portions.
A main shaft driven by power transmission from a crankshaft; and the first and second shafts in the crankcase.
A plurality of intake ports connected to the crank chamber are provided side by side in the axial direction of the first and second crankshafts in a portion sandwiched by the cylinder portions, and only the flow of intake air toward the crank chamber is allowed in each of the intake ports. V-type two-cycle fuel supply devices are connected to each intake port via intake pipes, and these fuel supply devices are arranged in a line between the first and second cylinder portions. In the engine, the intake port is provided so as to be deviated toward a cylinder portion connected to each of the first and second cylinder portions, and the reed valve located in the intake port has a center of the valve body. And the center line along the flow direction of the intake air is directed toward the first and second cylinder portions rather than the first and second crankshafts in the crank chambers connected to each other. With tilted provided, the first and second rotational direction of the crankshaft, in the mutual facing portions of the crank shaft, first from the spindle 1
And a second cylinder portion.