JPS6027728A - Intake apparatus for two-cycle engine - Google Patents

Abstract

PURPOSE:To obtain a high output over the entire operational range of a two-cycle engine in which the valve opening and closing timing of a rotary valve is matched to the low-speed operation of the engine, by raising the charging efficiency by forming subsidiary intake ports on both sides of a main intake port, and providing check valves permitting only the flow of air-fuel mixture into subsidiary intake passages so that air-fuel mixture is drawn not only from the main intake port but also from the two subsidiary intake ports at the time of high- speed operation of the engine. CONSTITUTION:Subsidiary intake ports 9a, 9a are formed in a rotary valve 9 in the manner that they are communicated with a subsidiary intake passage 9 extending on both sides of a main intake passage 7, so that the two subsidiary intake ports 9a, 9a are communicated with each other. The subsidiary intake passage 9 is communicated with the main intake passage 7 via reed valves 10, 10. These reed valves 10 serve as check valves. That is, they permit the flow of air-fuel mixture from the side of the intake passage 7 to the side of the subsidiary intake passage 9 by causing elastic deformation but they do not permit the opposite flow of mixture. By employing such an intake apparatus, intake time and intake area corresponding to the sum of the area of the main intake port and the subsidiary intake ports can be obtained, so that the charging efficiency can be raised over the entire operational range of the engine from the low-speed operation to the high-speed operation of the same.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a two-stroke engine.

2. Description of the Related Art Some intake devices for two-stroke engines are designed to open and close an intake passage communicating with a crank chamber using a rotary valve that rotates in synchronization with the crankshaft.

However, with a rotary valve that rotates synchronously with the crankshaft, it is not possible to produce high output over the entire engine speed range from low to high speeds. , the internal pressure in the crank chamber changes from positive pressure to negative pressure earlier than bottom dead center due to suction by exhaust air and scavenging inertia, and this negative pressure is maintained until later than top dead center, so the rotary valve If the opening/closing timing is set to coincide with low speed rotation, the suction efficiency during high speed rotation will deteriorate and sufficient output will not be produced. Conversely, if the opening/closing timing of the rotary valve is set to coincide with high-speed rotation, the air-fuel mixture will be blown back during low-speed rotation, making it impossible to increase the output.

The purpose of the present invention is to provide an intake system for a two-stroke engine that can obtain high output over the entire rotation range from low speed to high speed, in view of the above-mentioned problems with the rotary valve type intake system. be.

To achieve the above object, the present invention opens and closes an intake hole that communicates an air-fuel mixture intake passage to a crank chamber with a rotary valve that rotates in synchronization with the crankshaft, and sets the opening and closing timing of the rotary valve to match low-speed rotation. In the cycle engine, auxiliary intake holes are provided on both front and rear sides of the intake hole in the rotating direction of the rotary valve, and the intake holes on both sides are connected to a common auxiliary intake passage that communicates with each other, and the auxiliary intake passage is connected to the intake passage. On the other hand, it is characterized by communication via a check valve that only allows the mixture to flow to the side of the auxiliary intake passage.

The present invention will be explained below with reference to embodiments shown in the drawings.

In the embodiment shown in FIGS. 1 to 4, 1 is a cylinder, 2 is a piston, and 3 is a crankshaft.

A scavenging hole 4 is provided on one side of the cylinder 1, an exhaust hole 5 is provided on the opposite side, and a crank chamber 6 is formed below.

An intake passage 7 is connected to the crank chamber 6, and the intake passage 7 introduces a mixture from a carburetor (not shown). Reference numeral 8 denotes a rotary valve having a substantially fan-shaped shape, such as a part of a disc cut out, which is fixed to the crankshaft 3 and integrally rotates in synchronization with the intake hole 7a, which communicates with the crank chamber 6 of the intake passage 7. It is designed to open and close. The opening/closing timing of this rotary valve 8 is set to match the low speed rotation of the engine.

The intake hole 7a has separate sub-intake holes 9a on both front and rear sides along the rotational direction of the rotary valve 8.

9a is provided. This intake hole on both sides9. a.

9 and a are in communication with each other by being connected to the sub-intake passages 9 extending on both the left and right sides. This sub-intake passage 9
further communicates with the main intake passage 7 via a reed valve 10.10.

The reed valve 10 functions as a check valve, and has a structure that allows the air-fuel mixture to flow from the intake passage 7 side to the auxiliary intake passage 9 side by elastically deforming as shown by the chain line, but does not allow the flow on the opposite side. It becomes.

Although two reed valves 10 are provided on the left and right sides in the above embodiment, only one reed valve 10 may be provided as in the embodiment shown in Fig. 5.6, or three as in the embodiment shown in Fig. 7.8. One or more may be provided. Moreover, two or more may be arranged in parallel on one surface.

When the above-mentioned two-stroke engine is operated at low speed, medium speed, and high speed, the relationship between the opening/closing timing of the rotary valve 8, the scavenging hole 4, and the exhaust hole 5 and the crank angle is as shown in FIGS. 10 to 13. Become.

Figure 10 shows the case of low-speed rotation, Figures 11 and 12 show the case of medium-speed rotation (Fig. 11 shows low-medium speed rotation, Fig. 12 shows high-medium speed rotation), and Fig. 13 shows the case of high-speed rotation. ing. The symbol EO written in the diagram corresponding to the crank angle is exhaust hole 5 open, SO is scavenge hole 4 open, RO is rotary valve 8 open, EC is exhaust hole 5 closed, SO is scavenge hole 4 closed, RC is rotation The timings of closing the valves 8 are respectively indicated, and the crank angle region indicated by A indicates the region where the gas pressure in the crank chamber 6 becomes negative pressure.

As mentioned above, in the above engine, the opening and closing timing of the rotary valve 8 is set to match the low speed rotation, so when the rotary valve 8 is opened, the crank chamber 6 is in a negative state as shown in FIG. The pressure starts to increase and changes to positive pressure when the rotary valve 8 closes. However, in the region from medium speed rotation to high speed rotation, as shown in FIGS. 11 to 13, the crank chamber 6 has already started to have a negative pressure in the crank angle region A1 before the rotary valve 8 opens, and the rotary valve 8 is Even after the valve is closed, negative pressure is maintained in the normal rank angle region A2.

In the above-described intake device, the sub-intake ports 9a are provided on both sides of the intake hole 7a along the rotational direction of the rotary valve 8, respectively.

9a, and is configured such that the air-fuel mixture can flow from the intake passage 7 into the auxiliary intake passage 9 communicating with the auxiliary intake ports 9a, 9a, so that the above-mentioned crank angle region A1. At A2, the air-fuel mixture is sucked into the crank chamber 6, improving the suction efficiency.

On the other hand, at low speed rotation, the above crank angle area A I,
The area corresponding to A2 is the area where the crank chamber 6 is under positive pressure, but this area A1. Sub-intake port 9a corresponding to A2
, 9a, the reed valve 10 having a check valve function prevents the backflow to the intake passage 7 side, so that blowing back of the air-fuel mixture does not occur.

Furthermore, the sub-intake passages 9 in which the intake holes 9a and 9a communicate with each other are not configured independently of each other as in the comparative example shown in FIG. The air-fuel mixture temporarily stored in the auxiliary intake passage 9 due to ventilation inertia at the moment when the auxiliary intake hole 9a is closed flows into the crank chamber 6 from the open air hole 9a on the opposite side when the open air hole 9a opens. This action is performed alternately through the common sub-intake passage 9 in the intake holes 9a, 9a on both sides. Therefore, the suction efficiency of the air-fuel mixture can be increased only by the supplementary bone.

When the intake conditions at the above-mentioned low-speed rotation, medium-speed rotation, and high-speed rotation are expressed as an intake time area, the result is as shown in FIG. 14.

In the figure, the area surrounded by the solid line M is the intake time area from the intake hole 7a, and the area surrounded by the broken line S is the sub-intake hole 9a,
This is the intake time area from 9a. Therefore, in the above-mentioned intake system, an intake time area equal to the sum of these two areas M and S is obtained, and therefore, the intake efficiency is extremely high over the entire rotation range from low speed to high speed of the engine, and high output can be obtained. .

As described above, the intake device of the present invention opens and closes the intake hole that connects the air-fuel mixture intake passage to the crank chamber using a rotary valve that rotates in synchronization with the crankshaft, and sets the opening and closing timing of the rotary valve to coincide with low-speed rotation. In the two-stroke engine, sub-intake holes are provided on both front and rear sides of the intake hole in the rotating direction of the rotary valve, and the intake holes on both sides are connected to a common sub-intake passage that communicates with each other, and the sub-intake passage is connected to the intake hole. Since the passage is communicated through a check valve that only allows the mixture to flow toward the sub-intake passage, during high-speed rotation, the mixture is sucked not only from the original intake hole but also from the sub-intake holes on both sides. Furthermore, since the sub-intake passage is used as an air reservoir and the temporarily stored air-fuel mixture is also charged, extremely high suction efficiency can be obtained and the output can be improved. Furthermore, even if the sub-intake hole is provided during low-speed rotation, the check valve prevents blowback, so the original high output during low-speed rotation is not hindered. Therefore, according to the intake system of the present invention, high output can be exerted over the entire rotation range of the engine from low speed to high speed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a two-stroke engine equipped with the intake system of the present invention, FIG. 2 is a view taken along the ■-■ arrow in FIG. 1, and FIG. 3 is a view taken along the mm--m arrow in FIG. Figure 4 shows tv-tv in Figure 3.
5 is a vertical sectional view of a main part of a device according to another embodiment, FIG. 6 is a view taken along the line VI-Vl in FIG. 5, and FIG. 7 is a main part of a device according to another embodiment. 8 is a cross-sectional view of a comparative example not according to the present invention, and FIG. 8 is a cross-sectional view corresponding to the nn arrow cross-section of FIG. 1. 10 to 13 are relationship diagrams showing the opening/closing timing of rotary valves, etc. in the device of the present invention, and FIG. 14 is a relationship diagram showing the intake time area in the same device. 1...Cylinder, 2...Piston, 3...Crankshaft,
6...Crank chamber, 7...Intake passage, 7a...Intake passage, 8...Rotary valve, 9...Sub-intake passage, 9a
... Sub-intake hole, 10... Reed valve (check valve). Agent: Patent Attorney Makoto Ogawa − Patent Attorney: Ken Noguchi Patent Attorney: Kazuhiko Saishita

Claims (1)

[Claims] In a two-stroke engine, an intake hole that communicates an air-fuel mixture intake passage with a crank chamber is opened and closed by a rotary valve that rotates in synchronization with the crankshaft, and the opening and closing timing of the rotary valve is set to coincide with low-speed rotation. Sub-intake holes are provided on both sides in the valve rotation direction, and the sub-intake holes are communicated with a common sub-intake passage that communicates with each other, and the sub-intake passage is connected to the intake passage to the sub-intake 1ffl road side. An intake system for a two-cycle engine, characterized in that the intake system is connected through a check valve that allows only a mixed air flow.