JPS6314181B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention belongs to the technical field of an air intake system for a 4-stroke, 2-cylinder, 180° crank engine, and its premise is to separate both intake ports of both combustion chambers of a 4-stroke, 2-cylinder, 180° crank engine. communicates with a common air cleaner through a container, purifies the air with the air cleaner,
This invention relates to a 4-cycle, 2-cylinder, 180° crank engine configured to divide the flow using a flow divider and supply the air to both combustion chambers from both intake ports.

Generally, in a 4-stroke engine, the intake valve is placed before the top dead center of the crankshaft in order to increase the intake air filling efficiency.
The valve is designed to open from around 40° to around 30° after bottom dead center.

However, in a four-stroke engine in which the crankshafts have a phase difference of 180 degrees from each other, as shown in FIG. 4, there is a portion R where the end of intake of the preceding cylinder and the beginning of intake of the succeeding cylinder largely overlap. This lapping causes a difference in the amount of intake air between the preceding and following cylinders, resulting in a problem of reduced output, vibration, and thermal distortion of the cylinder block.

As a technique for solving this problem, there is a technique shown in FIG. 5 (Japanese Patent Publication No. 10489/1989).

That is, when increasing the intake inertia and increasing the charging efficiency by forming the intake pipe long, in the wrap portion R, there is a delay in intake to the succeeding cylinder due to the strong intake inertia to the preceding cylinder. This occurs, and the amount of intake air in the following cylinders decreases.

Therefore, this technique uses a ventilator to suppress the amount of air taken into the preceding cylinder, thereby making it equal to the amount of air taken into the succeeding cylinder.

However, this structure has the following drawbacks.

b) The intake pipe extends outside the cylinder block for a long time, making the engine larger in size.

(b) Since the amount of intake air in the preceding cylinder and the amount of intake air in the following cylinder decrease, the output of the engine decreases.

The Bench-Yuri effect increases exponentially as the amount of air intake increases. For this reason, if the throttle amount of the ventilate is set to an appropriate value during high-speed operation, the ventilate effect will be insufficient during low-speed operation, and the amount of intake air in the preceding cylinder will be too large than the amount of intake air in the succeeding cylinder. Conversely, if the throttle amount of the ventilate is set to an appropriate value during low-speed operation, the ventilate effect will be excessive during high-speed operation, and the intake air amount of the preceding cylinder will become too small.

In either case, an unbalance in the amount of intake air occurs between both cylinders, making it impossible to solve the initial problem. The purpose of the present invention is to solve the initial problems, eliminate the above-mentioned conventional drawbacks A to C, and increase the output, suppress vibration, and prevent thermal distortion of the cylinder block while downsizing the entire engine. do.

In order to achieve the above object, the present invention has a basic structure that, contrary to the conventional example, shortens the intake passage in the flow divider to reduce intake resistance and increase filling efficiency. adopt.

In this case, there is a problem in that a large amount of intake air that has been sucked into the preceding cylinder at the wrap portion R is sucked out by the intake negative pressure of the following cylinder, reducing the filling efficiency of intake air into the preceding cylinder. be.

The present invention was proposed in order to solve this problem, and uses a buffer case as a flow divider, and makes the ventilation cross-sectional area of the buffer case on a plane perpendicular to the flow diversion direction larger than the passage cross-sectional area of each intake port. Each case outlet hole communicating with each intake port is opened in one side wall of the buffer case, and a case inlet hole is located approximately at the center of the other side wall opposite to the one side wall at a position approximately equidistant from each case outlet hole. The case inlet hole is connected to the air cleaner through the vaporizer, and both ends of the buffer case extend outward from each case outlet hole.

The present invention is configured and operates as described above, and thus has the following effects.

In other words, a buffer case is used as a flow divider, and this buffer case is simply formed so that its ventilation cross-sectional area is larger than the passage cross-sectional area of each intake port, so the buffer case does not protrude significantly outside the cylinder block. This allows the engine to be made smaller.

Moreover, the intake air drawn from the air cleaner is
The large ventilation cross-sectional area of the buffer case reduces intake resistance, improves charging efficiency, and increases engine output.

In addition, the intake air from the air cleaner is slowed down by the buffer case with a large ventilation cross-sectional area, suppressing the intake inertia. At the part where the end of the process and the beginning of the intake air on the trailing side overlap, the suction force on the trailing side is reduced by the buffer case and almost disappears, preventing the intake air from the cylinder on the leading side from being sucked out.

Furthermore, since both ends of the buffer case extend outside of each case outlet hole, intake air is stored at both ends of the buffer case, and this part of the intake air is also supplied to each intake port via the case outlet hole. can do. For this reason, fuel can be supplied to both cylinders in the above-mentioned lapped portions, etc., and there is no variation in the amount of fuel supplied to both cylinders.

This allows the intake air volume of both cylinders to be balanced with high charging efficiency from high-speed to low-speed engine operation, increasing engine output and improving acceleration performance, and greatly reducing engine vibration. can be reduced.

Moreover, each case outlet hole is opened in one side wall of the buffer case, and the case inlet hole is opened in the approximate center of the other side wall opposite to the one side wall at a position approximately equidistant from each case outlet hole, so that the buffer case The intake passages inside are short and have approximately the same distance. Therefore, when each cylinder takes in air independently, there is less intake resistance, the charging efficiency is increased, and there is no variation in the amount of fuel supplied.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a plan view of the main parts, and FIG. 2 shows an exploded perspective view of the main parts.

This engine 1 is a four-stroke, two-cylinder, 180° crank engine, and has an intake and exhaust block 4 attached to the front of a cylinder block 3 in which cylinders 2a and 2b are arranged side by side.

The intake/exhaust block 4 has one end of the exhaust port 5 open on the top surface 4a, and one end of the intake port 6 formed on the front surface 4b so as to approach each other as it gets closer to the front surface. The other end of 6 is opened into combustion chamber 7 .

A flow divider 8 is attached to the front surface 4b of the intake/exhaust block 4 where the intake port 6 opens. Box-shaped buffer case 1
0.

The ventilation cross-sectional area S of the buffer case 10 is formed to be larger than the ventilation cross-sectional area S' of the intake port 6, and a case outlet hole 1 is formed in the rear wall 10a of the buffer case 10 at a portion facing the intake ports 6.
1 and 11, and one case inlet hole 12 is provided in the front side wall 10b at a portion located between the case outlet holes 11 and 11.

The cover plates 9, 9 that cover both ends 10c, 10c of the buffer case 10 are positioned outward from the intake ports 6, 6 and the case outlet holes 11, 11, thereby increasing the volume of the buffer case 10.

A carburetor 13 is attached to a case inlet hole 12 formed in the front wall 10b of the buffer case 10, and an air cleaner 14 is attached to the front of the carburetor 13.

The operation of the flow divider 8 configured as described above will be explained next.

First, the intake air flowing from the air cleaner 14 to the buffer case 10 from the case inlet hole 12 via the carburetor 13 has a greatly reduced flow velocity due to the large ventilation cross-sectional area S of the buffer case 10, and the intake inertia is reduced. Most of it disappears. In addition, when the beginning of the intake stroke b of the succeeding cylinder (Fig. 4B) 2b overlaps near the end of the intake stroke a of the preceding cylinder (Fig. 4A) 2a, the intake negative pressure of the succeeding cylinder 2b is attenuated by the buffer case 10, and is prevented from acting on the intake port 6 on the leading side.

Note that the intake port 6 on the preceding cylinder 2a side has a larger ventilation cross-sectional area than the intake port 6 on the succeeding side.

Further, reference numeral 15 in the figure indicates a throttle valve provided in the carburetor 13, and this throttle valve 15
The throttle lever 16 that operates the throttle valve 16 is operated via a rod 18 by a governor lever 17 that is swung by a governor device (not shown), and has a structure for finely adjusting the opening amount of the governor lever 17 and the throttle valve 15. G is as shown in FIG.

That is, an adjustment swing lever 19 is provided near the tip of the governor lever 17 so as to be able to adjust and fix the swing, and a throttle lever 16 is provided at the tip of the adjustment swing lever 19.
The end of the rod 18 connected to the
The screw 20 fixing the adjustment swing lever 19 to the governor lever 17 is loosened, and the governor lever 17 and the adjustment swing lever 19 are made to swing relative to each other for adjustment.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention,
Figure 1 is a plan view of the main parts of a 4-stroke, two-cylinder, 180° crank engine, Figure 2 is an exploded perspective view of the main parts, Figure 3 is a front view of the governor lever, and Figure 4 is a process diagram of each cylinder. , FIG. 5 is a plan view showing a conventional example. 1...4-stroke 2-cylinder 180° crank engine,
6...Intake port, 7...Combustion chamber, 8...Flow divider, 10
...buffer case, 10a...one side wall (rear wall) of 10,
10b...10 other side wall (front wall), 10c...10
11... Case outlet hole, 12... Case inlet hole, 14... Air cleaner, S... Ventilation cross-sectional area of 10, 8, S'... Passage cross-sectional area of 6.

Claims (1)

[Claims] 1. Both intake ports 6, 6 of both combustion chambers 7 of a 4-stroke, 2-cylinder, 180° crank engine 1 are connected to a common air cleaner 14 via a flow divider 8, and the air is purified by the air cleaner 14. In an air supply system for a four-stroke, two-cylinder, 180° crank engine configured to divide the flow with a flow divider 8 and supply it from both intake ports 6, 6 to both combustion chambers 7, 7, a buffer case 10 is used as the flow divider 8. The ventilation cross-sectional area S of the buffer case 10 on a plane perpendicular to the flow dividing direction is made larger than the passage cross-sectional area S' of each intake port 6, and one side wall 10a of the buffer case 10 is connected to each intake port 6. Each case outlet hole 11 is opened, and a case inlet hole 12 is opened at approximately the center of the other side wall 10b opposite to the one side wall 10a at a position approximately equidistant from each case outlet hole 11, and the case inlet hole 12 is vaporized. An air supply system for a 4-stroke, 2-cylinder, 180° crank engine, which communicates with an air cleaner 14 through a container 13, and has both ends 10c and 10c of a buffer case 10 extending outward from each case outlet hole 11. . 2. The air supply device according to claim 1, in which both the intake ports 6 are formed in an inclined shape such that they approach each other closer to the buffer case 10.