JPH03206318A - Two-cycle v-engine - Google Patents

Abstract

PURPOSE:To contrive shortening of length and its equality of an intake pipe, by extending the intake pipe of a front cylinder extended forward and the intake pipe of a rear cylinder extended upward almost radially with a crankshaft serving as the center and arranging these intake pipes adjacent their respective cylinders. CONSTITUTION:A 2-cycle V-engine 10 mounted on a motorcycle is formed by vertically providing a front cylinder 25, extended diagonally forward in a downward direction, and a rear cylinder 26, extended diagonally forward in a upward direction, in a front case 13 of a crankcase 11. An intake air port 35 opened to a crank chamber 16 of respective cylinders 25, 26 is formed in the crankcase 11, and intake pipes 37, 38 are connected to the intake air port 35. Here carburetors 40, 42, serving as a fuel supply means, are connected to point end parts of the intake pipes 37, 38 by extending the intake pipe 37 by the side of the front cylinder 25 linearly toward the front of the crankcase 11 and by extending the intake pipe 38 by the side of the rear cylinder 26 linearly toward the upper of the crankcase 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a V-type two-stroke engine in which an intake pipe is connected to a crankcase.

[Prior Art] Conventionally, for example, Japanese Patent Application Laid-open No. 198725/1983 discloses a V-type two-stroke engine mounted on a motorcycle. This engine has a front cylinder that extends forward on a crankcase that houses the crankshaft,
It has a rear cylinder extending upward, and a crank chamber connected to each cylinder is provided within the crankcase.

In this type of engine, a relatively large space can be secured on the transmission case connected to the rear of the crankcase, so an intake port that opens into the crank chamber of each cylinder is placed on the upper rear surface of the crankcase. are arranged in the axial direction, and an intake pipe connected to the carburetor is connected to these intake ports.

[Problem to be Solved by the Invention] However, in the case of this conventional configuration, although the front cylinder and the rear cylinder are arranged in a V shape toward the front of the crankcase, the intake air of these cylinders is Since the pipes are all arranged at the rear of the crankcase, the front cylinder and the rear cylinder have different positional relationships with the intake pipe.

As a result, there is a difference in the length of the intake path from the carburetor to the combustion chamber of the cylinder, resulting in an unbalanced output characteristic between the front and rear cylinders, which not only hinders the smooth rotation of the engine but also There is a problem that it also has a negative effect on performance.

Furthermore, especially on the front cylinder side, the fresh air sucked into the crank chamber traverses the crank chamber, so the intake path becomes longer, which increases intake resistance and reduces responsiveness to throttle operation. There is also a problem that it gets worse.

The present invention was made based on these circumstances, and
The objective is to provide a V-type two-stroke engine that can eliminate variations in output characteristics between cylinders, minimize the length of the intake pipe, and improve intake efficiency and responsiveness to throttle operation. shall be.

[Means for Solving the Problems] Therefore, in the present invention, a front cylinder that extends forward and a rear cylinder that extends upward are provided in the crankcase that accommodates the crankshaft, and these cylinders are separated from the axial direction of the crankshaft. In a V-type two-stroke engine, which is arranged in a V-shape when viewed from the outside and has a crank chamber connected to each cylinder in the crankcase, the front cylinder is placed on the front side of the crankcase located above the front cylinder. An intake pipe is provided that extends substantially linearly forward from the crank chamber, and an intake pipe that extends substantially linearly upward from the crank chamber of the rear cylinder is provided on the upper surface of the crankcase located on the rear side of the rear cylinder. It is characterized by providing fuel supply means in each intake pipe.

[Function] According to this configuration, the intake pipes of the front cylinder and the rear cylinder extend approximately radially around the crankshaft, so these intake pipes are located adjacent to each cylinder. . Therefore, the intake pipes can be arranged without difficulty, and the lengths of the intake pipes can be made equal.

At the same time, the positional relationship between each intake pipe and cylinder is the same, so the length of the intake pipes is the same, and the intake conditions for fresh air are the same for each cylinder, reducing variations in output characteristics between cylinders. can be resolved.

In addition, since the intake pipe extends linearly around the crankshaft, the length of the intake pipe can be kept as short as possible.
Intake resistance is reduced, intake efficiency can be increased, and responsiveness to throttle operation is also improved.

[Embodiment] A first embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

The first embodiment is applied to a motorcycle equipped with a V-type two-stroke engine, and the frame of the motorcycle, indicated by reference numeral 1 in FIG. 5, is provided with a steering head pipe 2 at its front end.

A front fork 3 is pivotally supported on the steering head pipe 2, and a front wheel 4 is supported at the lower end of the front fork 3.

A pair of left and right main pipes 5 extending rearward and diagonally downward are connected to the steering head pipe 2. The main pipe 5 has a basic cross-sectional shape of a vertically elongated rectangle, and a rear arm bracket 6 is connected to the rear end of the main pipe 5. A rear arm 7 extending rearward is pivotally supported on the rear arm bracket 6, and a rear wheel 8 is supported at the rear end of the rear arm 7.

Incidentally, below the main vibe 5, a water-cooled V-type two-stroke two-cylinder engine IO according to the present invention is arranged. This engine 10 is supported by a main pipe 5 and a rear arm bracket 6, and details of this engine 10 will be described below.

That is, in the crankcase l1 of the engine lO,
One crankshaft l2 is housed horizontally along the left-right direction. As shown in FIGS. 1 and 2, this crankcase 11 passes through the axis 01 of the crankshaft t2,
It is divided into a front case 13 and a rear case 14 with a dividing line X1-X1 extending in the vertical direction as a boundary, and both cases 13 and 14 are tightened and fixed with bolts 15. A crank chamber 16, through which the crankshaft 12 passes, is formed between the front case 13 and the rear case l4. The crank chamber i6 is divided into two chambers by a partition wall (not shown) that supports the journal portion 12a of the crankshaft 12, and these two crank chambers 16 are arranged side by side in the axial direction of the crankshaft 12.

The rear part of rear case l4 also serves as transmission case l7,
Inside this transmission case 17 is a main shaft 18 of a gear transmission.
and the output shaft 19 are supported. Main shaft l8 and output shaft l9
is provided parallel to the crankshaft l2, and its main axis l
8 is interlocked with the crankshaft 12 via a clutch (not shown). A drive sprocket 20 for extracting engine power is provided at the left end of the output shaft l9, and a chain 22 is stretched between the drive sprocket 20 and the driven sprocket 2l of the rear wheel 8.

Note that the reference numeral 23 in FIG. 1 indicates a balancer axis.

Further, a front cylinder 25 extending diagonally downward and a rear cylinder 26 extending diagonally upward and forward are provided in the front case l3. When the engine IO is viewed from the axial direction of the crankshaft 12, these cylinders 25 and 28 are
They are arranged in a V-shape toward the front, and in this example,
The angle θl of both cylinders 25 and 26 is set to 90°. The axes Y1 and Y2 of these cylinders 25 and 26 intersect the dividing lines X and -X1 of the crankcase 11 on the axis 01 of the crankshaft 12, and these axes Y1 and Y2 intersect with the dividing line X1-X1. intersection angle θ2,
θ3 is 45°.

The front case l3 has a mating surface 2 to which the cylinder blocks 27 and 28 of the front cylinder 25 and the rear cylinder 26 are connected.
9a and 29b are formed. These mating surfaces 29a, 2
9b is opened individually into the two crank chambers l6. For this reason, the mating surface 29a. The front cylinder 25 and rear cylinder 26 connected to 29b are offset in the axial direction of the crankshaft l2 with respect to the engine center line X2-X2, as shown in FIG.

The piston 30 in each cylinder 25.28 is coaxially connected to the crank pin 12b of the crankshaft l2 via a connecting rod 3l. A scavenging passage 32 and an exhaust passage 33 are formed in the cylinder block 25, 26 that houses the piston 30. The exhaust passage 33 of the front cylinder 25 is opened at the lower surface of the cylinder block 27, and the exhaust passage 33 of the rear cylinder 26 is opened at the front face of the cylinder block 28. is connected.

By the way, the crankcase U has a front cylinder 2.
An intake port 35 opens into the crank chamber 1B of the rear cylinder 26, and an intake port 36 opens into the crank chamber 16 of the rear cylinder 26. The intake port 35 of the front cylinder 25 is located at the front of the crankcase ti, and is opened forward above the base of the front cylinder 25.

On the other hand, the intake port 36 of the rear cylinder 26 is located on the upper surface of the crankcase 11.
It is opened upward at the rear side of the base of 6.

The opening end surface 3 of the intake port 35 on the front cylinder 25 side
5a is formed parallel to the dividing line X1-X1 of the crankcase {l, and the opening end surface 38a of the intake port 3B on the rear cylinder 26 side is formed perpendicular to the dividing line X1-Xl. Opening end surface 35a. 36
a have a positional relationship that is orthogonal to each other on the crankcase l1.

As shown in FIG. 3, such intake ports 35 and 36 are
The opening shape is an elongated rectangle in the left-right direction of the crankcase 11, and the opening end surfaces 35a. 36a, the intake pipes 37 and 38 are connected to bolts 3
It is connected via 9. An intake pipe 37 on the front cylinder 25 side extends linearly toward the front of the crankcase 11, and a side draft type carburetor 40 is installed at the front end of the intake pipe 37 as a fuel supply means. It is connected. This carburetor 40 is located between the crankcase 11 and the front wheel 4, and when the engine IO is viewed from the axial direction of the crankshaft 12, the carburetor 40 consists of a front cylinder 25 and a rear cylinder 26. It is housed in a sandwiched space 41 that is approximately V-shaped when viewed from the side.

The intake pipe 38 on the rear cylinder 26 side extends linearly upward from the crankcase 11, and a downward draft type carburetor 42 is connected to the upper end of this intake pipe 38. ing. The carburetor 42 is located behind the rear cylinder 26, and when the engine 1O is viewed from the axial direction of the crankshaft 12, the carburetor 42 is located in the space sandwiched between the rear cylinder 26 and the transmission case 17. 4
It is included in 3. The axes Z1 and z2 of each intake pipe 37.38 pass near the axis 01 of the crankshaft 12 in the crank chamber 1B, and from this, the intake pipes 37.38 are centered around the crankshaft 12. It extends radially.

Therefore, the intake pipe 35.36 of each cylinder 25.26
are provided adjacent to the cylinders 25.26, respectively, and the axes Y1, Y2 of the cylinders 25.28 and the axes Z1, Z2 of the intake pipes 37.38 are aligned with the engine 10 as shown in FIG. When viewed from the axial direction of the crankshaft 12, it has a substantially V-shape.

Further, a reed valve 45 is provided within the intake port 35.3Ii to allow only the flow of intake air from the carburetor 40.42 toward the crank chamber 16. The reed valve 45 has the same structure as a conventionally known one, and as shown in FIGS.
I have 6. Valve body 46 has intake port 35.3
The tip 46a of the valve body 46 faces the crank chamber l6.
is formed in a tapered shape.

On the tip side of the valve body 46, there is an inlet 47 that opens into the crank chamber 16, and a thin plate-like valve 48 that opens and closes the inlet 47 according to the pressure difference between the inside and outside of the crank chamber 16.
Stopper 49 that regulates the maximum opening position of this valve 48
is provided. The valve body 46 is formed with a flange portion 46b that overlaps the opening end surfaces 35a, 36a of the intake port 35.36, and the flange portion 46b is connected to the opening end surfaces 35a, 38a using the bolt 39. It is tightened.

Therefore, the reed valves 45 of the front and rear cylinders 25, 213 are arranged horizontally with the long sleeves of the flat valve bodies 46 aligned in the left-right direction.

Further, a tapered tip portion 46a of the valve body 46
is swung in a direction toward the piston 30 with respect to the axis 01 of the crankshaft 12. For this reason, the intake port 35.
The fresh air sucked into the crank chamber 16 from 36 flows smoothly toward the piston 30 along the inner surface of the crank chamber 16 and along the rotational direction of the crankshaft 12 shown by the arrow in FIGS. 1 and 2. As a result, the intake efficiency is increased accordingly.

In addition, in FIG. 5, the reference numeral 50 indicates a radiator, and the reference numeral 51 indicates a fuel tank.

According to such a configuration, the intake pipe 37 is provided on the front surface of the crankcase 11 and extends linearly forward from the crank chamber 16 of the front cylinder 25, and the intake pipe 37 is provided on the upper surface of the crank case 11, and the intake pipe 37 is provided on the front surface of the crankcase 11. Since the intake pipe 38 is provided that extends linearly upward from the engine 16, when the engine 10 is viewed from the axial direction of the crankshaft l2,
The two intake pipes 37 and 38 extend radially around the crankshaft l2.

For this purpose, each cylinder 25, 26 has an intake pipe 37.
38 are provided adjacent to each other, these intake pipes 37.3
8 can be arranged without difficulty, and the lengths of the intake pipes 37 and 38 can be made equal.

At the same time, the respective intake pipes 37, 38 and cylinders 25
．． Since the positional relationship with 28 is the same, the above-mentioned intake pipe 37
, :Ht, and the fresh air intake conditions are the same for each cylinder 25 and 26.

Therefore, variations in output characteristics and performance between the front cylinder 25 and the rear cylinder 26 can be eliminated.
The rotation of the engine 10 becomes smoother, and engine performance is improved.

Furthermore, since the intake pipes 37 and 38 extend linearly around the crankshaft 12, the lengths of these intake pipes 37 and 38 can also be kept as short as possible. Therefore, there is an advantage that the intake resistance is reduced, and accordingly more intake air can be drawn into the crank chamber 1B, and the responsiveness to throttle operation is also significantly improved.

Note that the present invention is not limited to the first embodiment described above, but a second embodiment of the present invention is shown in FIGS. 6 to 8. This second embodiment uses a fuel injection device in place of a carburetor, and the rest of the configuration is the same as the first embodiment, so the same components are given the same numbers and The explanation will be omitted.

That is, a fuel injection device 6l is connected to each of the two intake pipes 37 and 38 that extend radially around the crankshaft i2. The fuel injection device 61 includes a body main body 62, and an intake pipe 37.
An intake passage 63 connected to 38 and an operation chamber 64 are provided. Further, a throttle valve 65 is supported on the main body 62 to increase or decrease the opening area of the intake passage 63. The throttle valve 65 of this embodiment is a piston type that slides in a direction perpendicular to the intake passage 63, and when the throttle valve 65 is in the fully closed state shown in FIG. 46a and extends in the axial direction of the intake pipe 37.38
It is provided perpendicularly to 3.

An operating shaft 66 is pivotally supported in the operating chamber 64 so as to be rotatable in a direction around the axis. The operating shaft 66 extends in a direction perpendicular to the intake passage 63, and a pulley 67 that is connected to a throttle wire (not shown) is attached to one end of the operating shaft 66. The operating shaft 66 and the throttle valve 65 are connected via a link mechanism 68. This link mechanism 6
Reference numeral 8 is made up of a first link plate 69 that rotates together with the operating shaft 66 and a second link plate 70 that is connected to the throttle valve 65 and are rotatably connected to each other. The motion is converted into a linear motion and transmitted to the throttle valve 65.

A fuel injection valve 71 is attached to the main body 62 so as to be located on the opposite side of the operation chamber 64 across the intake passage 63 . The injection port 72 of the fuel injection valve 7l is open to the intake passage 63 and is arranged in an inclined position toward the intake pipe 37, 38 side. In the case of this embodiment, the injection port 72 is connected to the throttle valve. When 65 is in the fully closed position, it faces the venturi portion 65a at its tip.

Note that a suction port 73 that expands in a tapered shape is provided at the upstream end of the intake passage 63.

According to the second embodiment having such a configuration, the fuel injection device 6
1 does not require a large float chamber like a carburetor and the whole is compact, so even when connecting this fuel injection device 61 to the intake pipes 37 and 38 of each cylinder 25 and 26, it is possible to connect the fuel injection device 51 and Interference with cylinders 25 and 26 can be avoided.

Therefore, the intake pipes 37, 38 can be arranged without difficulty, and the intake pipes 37, 38 can be formed in a straight line with few bends, so that the intake resistance can be further suppressed.

Further, in the second embodiment, the injection port 7 of the fuel injection valve 7l
2 is provided at a position facing the pentulev 65a of the throttle valve 65, but the present invention is not limited to this. For example, as in the third embodiment of the present invention shown in FIG. They may be arranged side by side in the axial direction of the intake passage 63.

Further, in each of the embodiments described above, the reed valves of the rear cylinders are arranged horizontally along the left-right direction, but they may be arranged vertically along the up-down direction, for example.

Further, the V-type two-stroke engine according to the present invention is not limited to a two-cylinder engine, and may be, for example, a three-cylinder engine or a four-cylinder engine, and is of course not specified for use in motorcycles.

[Effects of the Invention] According to the present invention described in detail above, a plurality of intake pipes extend radially around the crankshaft, and the intake pipes are provided adjacent to each other for each cylinder. Therefore, the length of the intake pipe can be equalized.

At the same time, since the positional relationship between the intake pipe and the cylinder is the same, in addition to the above-mentioned length of the intake pipe being equal, the intake conditions for fresh air are the same for each cylinder, and the relationship between the front cylinder and the rear cylinder is the same. It is possible to eliminate variations in output characteristics and performance between the two.

Therefore, the engine not only rotates smoothly but also improves engine performance.

In addition, since the intake pipes extend linearly around the crankshaft, the length of these intake pipes can be kept as short as possible, which reduces intake resistance and allows more intake air to be drawn into the crank chamber. This has the advantage of improving responsiveness to throttle operation.

[Brief explanation of drawings]

1 to 5 show a first embodiment of the present invention.
The figure shows a partially sectional left side view of a V-type two-stroke engine.
Fig. 2 is a right side view with a partial cross section of a V-type two-stroke engine, Fig. 3 is a plan view showing the opening shape of the intake port, Fig. 4 is a view in the direction of the arrow in Fig. 5, Fig. 5 is a side view of the motorcycle, Figs. 6 to 8 show a second embodiment of the present invention, Fig. 6 is a partially sectional left side view of a V-type two-stroke engine, and Fig. 7 is a side view of the motorcycle. A right side view of the V-type two-stroke engine in cross section, a front view of the fuel injection device in Figure 8,
FIG. 9 is a left side view, partially in section, of a V-type two-stroke engine in a third embodiment of the present invention. 11... Crank case, 12... Crank shaft, 1
B...Crank chamber, 25...Front cylinder, 2B.
...Rear cylinder, 37.38...Intake pipe, 40,4
2.51...Fuel supply means (carburetor, fuel injection device)
.

Claims (1)

[Claims] A front cylinder extending forward and a rear cylinder extending upward are provided in the crankcase housing the crankshaft, and these cylinders are arranged in a V shape when viewed from the axial direction of the crankshaft. In a V-type two-stroke engine provided with a crank chamber connected to the cylinder, an intake pipe is provided on the front surface of the crankcase located above the front cylinder, and extends substantially straight forward from the crank chamber of the front cylinder, and V characterized in that an intake pipe extending substantially linearly upward from the crank chamber of the rear cylinder is provided on the upper surface of the crankcase located on the rear side of the rear cylinder, and each intake pipe is provided with a fuel supply means. Two-stroke engine.