JPS63302143A - Intake system for motorcycles equipped with V-type two-stroke engines - Google Patents

Abstract

PURPOSE:To aim at uniforming conditions of supply of mixture into engine cylinders, by forming the communicating part between intake-air passages and a crank chamber in a V-bank section formed between the engine cylinders, and by disposing reed valves for opening and closing the intake-air passages, in this communicating section. CONSTITUTION:In an engine 32 mounted on a motor-cycle, a plurality of engine cylinders 35 (35a, 35b) in a V-like shape so that the cylinders are distributed in front of and above a crank casing 34. A plurality of carburetors 36 are attached corresponding to these engine cylinders with the longitudinal attaching angles thereof being slightly different from each other. There are provided a plurality of intake-air passages 42 (42a, 42b) communicated with a crank chamber 38 which are sectioned in correspondence with the engine cylinders 35. The communicating section between the intake-air passages 42 and the crank chamber 38 are formed in a V-bank section A formed between the cylinders 35. Further, reed valves 43 (43a, 43b) for opening and closing the intake-air passages 42 are disposed in the communicating section 38a.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a V-type two-stroke engine, and particularly to a V-type two-stroke engine suitable for use in motorcycles.

"Prior Art" Conventionally, a so-called V-type two-stroke engine, in which a plurality of cylinders are divided into two positions and arranged in a V-shape, has been known as one form of two-stroke engine. For example, a structure shown in FIG. 1 is known.

This V type 2 cycle engine! In this example, a plurality of cylinders 2 are distributed and arranged in the front and upper portions of the crankcase 3, and the front cylinder is designated as 28 and the upper cylinder is designated as 2b). A crankshaft 6 to which a piston 4 fitted therein is rotatably connected via a connecting rod 5 is attached, and a crank chamber 7 is formed corresponding to each cylinder 2, and the crankcase 3, a plurality of intake passages 8 (only the upper cylinder is shown in the figure) are formed at a position rearward of the upper cylinder 2 (2b), which communicates with each of the crank chambers 7. , a reed valve 9 located in each intake passage 8 to open and close the intake passage 8 is attached to the crankcase 3, a carburetor IO is attached to the upstream side of the intake passage 8, and a cylinder 2 at the front part is attached.
(2a) is provided with an exhaust passage 11 directed downward, and the upper cylinder 2 (2b) is provided with an exhaust passage 11 directed downward toward the front.

Each of the exhaust passages 11 is connected to the crankcase 3.
It is connected to an exhaust pipe and an expansion chamber (both paths shown) extending rearward through the lower part of the engine.

"Problems to be Solved by the Invention" The present invention aims to solve the following problems in the above-mentioned conventional technology.

That is, in the case of the V-type two-stroke engine 1 having the above-mentioned configuration, the exhaust system is routed through the lower part of the crankcase 3 to the rear, but in the case of a two-stroke engine, there is a Since there is a large-diameter expansion chamber, and the distance between the expansion chamber and the cylinder 2 is preset according to engine characteristics, a large structure is disposed at the bottom of the crankcase 3. become.

This is particularly true when the V-type two-stroke engine l is applied to a motorcycle, since the distance between the engine and other components and the road surface is set in motorcycles, and as mentioned above, the crank If a large structure is installed at the bottom of the case 3, the mounting position of the engine and other components will be pushed upwards, which will have a large impact on the layout of the car body and reduce design freedom. This poses a problem in that it is easy to impose restrictions on the degree of use.

As the number of cylinders in the engine increases to three or four cylinders, the above-mentioned problems become more likely to occur due to the increase in the number of exhaust systems.

On the other hand, a technique capable of dealing with such problems has been proposed, for example, in Japanese Patent Laid-Open No. 60-56124.

As shown in FIG. 2, this technology involves raising the exhaust system 12 connected to each cylinder 11 upward from the front of the engine 13, and then passing it above the engine 13 to the vehicle body frame 14. It was routed along a route that led to the rear.

With such a configuration, it is possible to eliminate the large structure from below the engine 13 and solve the above-mentioned problems, but the following problems still remain to be solved. There is.

The problem is that when the exhaust systems 12 are routed as described above, these exhaust systems 12 come close to the intake system such as the carburetor 15 installed at the rear of the engine 13. The point is that it is assumed that there will be a thermal effect.

Furthermore, in a two-stroke engine, the air-fuel mixture is supplied to each cylinder 2 from the reed valve 9 through the inside of the crank chamber 7, but in any of the above-mentioned V-type two-stroke engines 1 (13), As is clear from FIG. 1, from the reed valve 9 to the front cylinder 2a (lla
) and the distance to the upper cylinder 2b (llb
), and due to this,
There is also a problem in that there is a difference in the conditions for supplying the air-fuel mixture to each cylinder 2 (11).

"Means for Solving the Problems" The purpose of the present invention is to provide a V-type two-stroke engine that can effectively solve the problems in the conventional technology described above, and in order to achieve that purpose, the present invention has been made. V related to the invention
In particular, a two-stroke engine has a plurality of cylinders arranged in a V-shape, a piston slidably fitted in each cylinder, and each piston connected via a connecting rod. L A single crankshaft, a crankcase in which each of the cylinders is integrally mounted and a crank chamber in which the crankshaft is rotatably mounted, and the crankcase is formed in communication with the crank chamber. In a V-type two-stroke engine equipped with an intake passage, a communication part between the intake passage and the crank chamber is formed in a V-bank part sandwiched between the cylinders, and
This communication portion is characterized by being provided with a reed valve that opens and closes the intake passage.

"Function" The V-type two-stroke engine according to the present invention has the above-described configuration, so that even when the exhaust system is routed from above the engine to the rear, the intake system is separated from the route of the exhaust system. In addition to suppressing the thermal influence from the exhaust system, the difference in distance between the reed valve and the distributed cylinders is minimized to equalize the conditions for supplying the air-fuel mixture to each cylinder.

"Embodiment" An embodiment of the present invention will be described below with reference to FIGS. 3 to 5.

In FIG. 3, the reference numeral 20 indicates a motorcycle to which this embodiment is applied. First, this motorcycle 20 will be explained as follows: a main frame 21;
Front fork 2 rotatably attached to the front end of 1
2, a steering handle 23 attached to the upper end of this front fork 22, and a front fork 2.
a front wheel 24 rotatably mounted on the lower end of the main frame 21; a rear fork 25 swingably mounted on the rear end of the main frame 21; The seat rail 28 is connected to the rear upper part of the main frame 21 via a bracket 27, and the seat rail 28 is attached to the front lower part of the main frame 21 in a state where it is divided into two parts, upper and lower. radiator 29 and
A fuel tank 30 attached to the upper front part of the main frame 21 and a seat 31 attached to the seat rail 28 are provided. A V-type two-stroke engine (hereinafter abbreviated as engine) 32 is attached. Further, in FIG. 3, the reference numeral 33 indicates a cowling, which is attached to cover the main frame 21 and the engine 32, and has a side portion facing the engine 32 that guides air into the inside of the cowling 33. An air introduction 033a is formed for this purpose.

As shown in FIGS. 3 and 4, the engine 32 according to the present embodiment includes a crankcase 34, and a V-V which is distributed in the front and upper portions of the crankcase 34.
A plurality of cylinders 35 are installed in a letter shape (hereinafter, the front cylinder will be referred to as 35a, and the upper cylinder will be referred to as 35b), and the installation angles are slightly different in the front and rear direction corresponding to each cylinder 35. A plurality of carburetors 36 (
The side corresponding to the front cylinder 35a is the carburetor 36a, the side corresponding to the upper cylinder 35b is the carburetor 36b), and each cylinder 35 (35a, 35b) has a third
Exhaust system 37 (37a, 37
b), and as shown in FIG.
The crank chamber 38 is formed in a partitioned state corresponding to the
and a piston 39 slidably fitted in each cylinder 35, and each piston 39 is connected via a connecting rod 40, and is rotatably mounted through each crank chamber 38. a single crankshaft 41 and a plurality of intake passages 4 provided in communication with the crank chamber 38.
2 (42a, 42b), and a communication portion 38a between the intake passage 42 and the crank chamber 38 is formed in the V-bank portion A sandwiched between the cylinders 35, and the communication portion 38a is provided with a communication portion 38a between the intake passage 42 and the crank chamber 38. Open/close valve 43
(43a, 43b) is provided in the internal shape.

Next, to explain these details, in this embodiment, the cylinders 35 are provided in a total of four, two each at the front and upper part of the crankcase 34 (one cylinder for each is shown in the figure). (The other cylinders 35 are provided in parallel at intervals in the length direction of the illustrated cylinder 35 and the crankshaft 41), and the front cylinder 35a has an exhaust passage 44 extending downward.
An exhaust passage 45 extending rearward is formed in the upper cylinder 35b.

On the other hand, the crank chamber 3
A scavenging boat 46 is formed which communicates with the air.

Therefore, each exhaust passage 44 and scavenging boat 46 formed in the front cylinder 35a and the upper cylinder 35
The exhaust passage 45 and the scavenging boat (not shown) formed in b are located at the center line of the V-bank portion A, that is, the two halves of the included angle formed by the front cylinder 35a and the upper cylinder 35b. They are arranged symmetrically with respect to the line.

As shown in FIG. 3, each exhaust system 37 (37a, 37b) has an expansion chamber 48 in the middle thereof.
49 is provided, and a silencer 50, 5 is further provided on the downstream side thereof.
1 are connected to each other, and an exhaust system 37a connected to the front cylinder 35a extends to the rear of the vehicle body via the lower part of the engine 32, and an exhaust system 37a connected to the upper cylinder 35b extends to the rear of the vehicle body. 37b extends almost straight from above the engine 32 toward the rear of the vehicle body.

The intake passage 42 is formed of a flexible material and has a substantially cylindrical shape, and is provided approximately at a bisector of the included angle between the front cylinder 35a and the upper cylinder 35b, and is located at a position approximately bisectoring the included angle between the front cylinder 35a and the upper cylinder 35b. They are arranged substantially parallel to each other at intervals in the length direction of the crankshaft 41 so as to correspond to the chamber 38 . Further, among the plurality of cylinders arranged in a V-shape, the intake passage includes an intake passage 42b communicating with the upper cylinder 35b and an intake passage 42a communicating with the front cylinder 35a. The intake passage 42b, which is offset in the direction and communicated with the upper cylinder, is arranged in a tilted state farther forward than the intake passage 42a, which communicates with the front cylinder.

Further, between the intake passage 42 and the communication section 38a, a base body 54 (54a, 54b) for supporting the reed valve is attached to a flange 52 on the periphery of the opening of the communication section 38a, which is formed integrally with the crankcase 34. It is fixed together with the intake passage by a bolt 52a. There are two types of base bodies, one of which is a flat base body 54a used for the front cylinder 35a, and the remaining base body 54a is wedge-shaped and used for the cylinder 35b. This is the base body 54b. By interposing the base bodies 54 (54a, 54b) with different shapes in this way, the intake passages 42 (42a, 42b) are formed as described above for each communication portion 38a having a common opening shape. It can be arranged with the central axis shifted in the front-back direction.

In this example, to shift the center axis of the intake passage 42, two types of base bodies 54 are used, a flat type and a wedge type, but only one type of base body 54 is used. However, if necessary, a wedge-shaped member may be interposed between the base body 54 and the crankcase 34 to cope with this problem.

The reed valve 43 (43a, 43b) is mounted on a base 54 (
54a and 54b), and is installed perpendicular to the upper inclined surface of the upper inclined surface.Similar to the carburetor 36 and the intake passage 42, one is for the front cylinder 35a and the other is for the upper cylinder 35b. They are arranged with the central axis slightly shifted in the front-back direction.

As shown in FIG. 5, the reed valve 43 has a valve seat 55 integrally formed with a base 54, and is attached to the valve seat 55 and elastically curved in the longitudinal direction of the crankshaft 41. and a plate-shaped valve body 56 that opens and closes the intake passage 42 by opening and closing the intake passage 42.

Here, the positional relationship of the scavenging boat 46 formed in the front cylinder 35a with respect to the reed valve 43a is almost the same as that of the scavenging boat (not shown) formed in the upper cylinder 35b with respect to the reed valve 43b. It is set as follows.

However, the engine 32 of this embodiment configured in this way
In addition to providing an intake passage 42 in the V-bank portion A between the front cylinder 35a and the upper cylinder 35b, a carburetor 36 is provided continuously upstream of this intake passage, that is, in front of the crankcase 34. Since the exhaust system 37b connected to the upper cylinder 35b is connected to the engine 32,
Even when the exhaust system 37b is routed from above toward the rear, it is possible to separate the exhaust system 37b from the intake system such as the intake passage 42 and the carburetor 36, thereby significantly suppressing the thermal influence on the intake system. becomes. In addition, in order to suppress the thermal influence from the exhaust system 37 on the intake system, it is necessary to
The exhaust system 37a connected to the carburetor 36 and the intake passage 4
However, even if this type of wiring is used, the number of exhaust pipes to be routed is small, half (for 4 cylinders) or one third (for 3 cylinders) of the total exhaust system, and other Attachment of components has less influence on position.

On the other hand, the installation of the reed valves 43 (43a, 43b), which are the entrances of the air-fuel mixture to the crank chamber 38, is limited by the position and the distance from the communication path to the scavenging boat 46 of each cylinder 35 (35a, 35b). Since the air-fuel mixture is sucked into the crank chamber 38, each cylinder 35 (35 m
The difference in time required to reach the scavenging boat 46 in b) is
Reduced as much as possible. Moreover, in this embodiment, each exhaust boat 44, 45 formed in each cylinder 35 (35a, 35b) is
Each cylinder 35 (35a', 3
5b), the above-mentioned air-fuel mixture supply path connects the front cylinder f15a and the upper cylinder 3.
5b, and therefore uniform air-fuel mixture is supplied to each cylinder 35 (35a, 35b).

Furthermore, since the reed valves 43 of each cylinder are arranged substantially linearly along the crankshaft 41, even if the angle of the V-bank portion formed by each cylinder 35 is relatively small, such as 112 degrees, the intake system can be arranged in the V bank portion.

Furthermore, in the embodiment described above, both the intake passages 42 are arranged such that the center axes of the intake passage 42b communicating with the upper cylinder 35b and the intake passage 42a communicating with the front cylinder 35a are shifted, and The passage 42b is the intake passage 4
Because it is placed tilted forward from 2a, the 5th
As shown by the arrow in the figure, the vaporizer 36 (36a, 36b)
from each crank chamber 38 to the scavenging boat 46 beyond that.
The air-fuel mixture flow path leading to the cylinders 35a and 35b
It is possible to avoid large bends in both flow paths associated with the engine, and as a result, intake resistance can be minimized, and a large amount of air-fuel mixture can be sent to the crank chamber 38 and further to the cylinders 35a and 35b. , the output of the engine can be improved.

It should be noted that the shapes and dimensions of each component shown in the above embodiments are merely examples, and can be variously changed based on the type and shape of the vehicle such as a motorcycle to which it is applied, or design requirements.

For example, the positional relationship of the cylinders 35 in the circumferential direction when attaching each cylinder 35 (35a, 35b) to the crankcase 34 is not limited to the example described above,
It can be set as appropriate.

Furthermore, the present invention is of course applicable even when the number of cylinders 35 is changed.

"Effects of the Invention" As explained above, the V-type two-stroke engine according to the present invention includes a plurality of cylinders arranged in a V-shape, and a piston slidably fitted in each of these cylinders. and,
A single crankshaft to which each of these pistons is connected via a connecting rod, and a crankcase in which each of the cylinders is integrally mounted and a crank chamber is formed in which the crankshaft is rotatably mounted. , 7 In a V-type two-stroke engine having an intake passage provided in communication with the crank chamber, a communication portion between the intake passage and the crank chamber is formed in a V-bank portion sandwiched between the cylinders, and This communication portion is characterized by being provided with a gate valve that opens and closes the intake passage, and provides the following excellent effects.

When the exhaust system connected to the cylinder is routed from above the engine to the rear, this exhaust system can be separated from the intake system, greatly reducing thermal effects on the intake system. It becomes possible to do so.

In addition, in order to suppress the thermal influence on the intake system, even if it becomes necessary to route the exhaust system from below the engine toward the rear, the number of exhaust systems to be routed should be half or one-third of the total exhaust system. Therefore, attachment of other structural members can be prevented from affecting the position. Therefore, restrictions on the degree of freedom in layout can be kept to a minimum.

Furthermore, the installation of the reed valve, which is the entrance of the mixture to the crank chamber, narrows the difference in position and distance from the exhaust boat, which is the entrance of the mixture to each cylinder, and allows the mixture to be distributed to each cylinder. The supply route of the engine can be made as uniform as possible, and therefore the power characteristics of the engine can be easily controlled.

In addition, among the plurality of cylinders arranged in a V-shape, the intake passage is divided into the intake passage leading to the cylinder arranged in the upper part and the intake passage leading to the cylinder arranged in the front part. The axis is shifted in the front-rear direction, and the intake passage leading to the cylinder located at the top is tilted forward compared to the intake passage leading to the cylinder located at the front. If configured as follows, the air-fuel mixture flow paths flowing from the intake passages to each crank chamber, both of the flow paths associated with both cylinders, will be bent with a relatively large radius of curvature, avoiding large bends. , the intake resistance can be made as small as possible, and the engine output can be improved.

[Brief explanation of drawings]

Fig. 1 is a partially sectional side view showing an example of a conventional V-type two-stroke engine; Fig. 2 is a side view schematically showing a motorcycle equipped with another conventional V-type two-stroke engine; 3 to 5 show an embodiment of the present invention, FIG. 3 is a side view schematically showing a motorcycle to which the embodiment is applied, FIG. 4 is a side view of main parts, and FIG. The figure is a partially sectional view similar to FIG. 4. 20...Motorcycle, 32...(V-type 2-cycle) engine,
34...Crankcase, 35...
・・・・・・Cylinder, 36・・・・・・Carburizer,
37...Exhaust system, 38...
...Crank chamber, 38a...Communication section, 4
0...Connecting rod, 41 Old...Crankshaft, 42...Intake passage, 43
...Old...Reed valve, 44/45...Exhaust passage,
46...Scavenging boat, A...V bank section.

Claims (2)

[Claims] (1) A plurality of cylinders arranged in a V-shape, a piston slidably fitted in each of these cylinders, and a single crank to which each of these pistons is connected via a connecting rod. The crank case includes a crankcase in which a shaft and each of the cylinders are integrally mounted, a crank chamber in which the crankshaft is rotatably mounted, and an intake passage provided in communication with the crank chamber. In a V-type two-stroke engine, a communication portion between the intake passage and the crank chamber is formed in a V bank portion sandwiched between the cylinders, and a reed valve for opening and closing the intake passage is provided in the communication portion. A V-type two-stroke engine with the following characteristics: (2) A plurality of the intake passages are provided corresponding to the cylinders, and among the plurality of cylinders, an intake passage communicates with the cylinder disposed at the top, and an intake passage communicates with the cylinder disposed at the front. The central axis of the cylinder is shifted in the front-rear direction, and the intake passage leading to the cylinder located at the top is tilted forward compared to the intake passage leading to the cylinder located at the front. 2. The V-type two-stroke engine according to claim 1, wherein the V-type two-stroke engine is provided with: