JPH0529767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the structure of an intake section of a two-stroke engine, and particularly to an improvement in the structure of an intake system including a reed valve.

(Prior art) In general, the intake passage of a two-stroke engine has a fifth reed valve for the purpose of preventing the intake air sent into the crank chamber from flowing back into the intake passage.
It is inserted in the position shown in the figure. The reed valve b is provided on one side with a thin plate-shaped reed c that opens and closes toward the crank chamber, and the reed c opens and closes in response to the pressure difference between the inside and outside of the crank chamber caused by the reciprocating movement of the piston d of the engine a. This allows the amount of intake air to be adjusted under various operating conditions. An example of this type of engine is the 50-year-old U.S.
There are crank chamber precompression type two-stroke engines as shown in Japanese Utility Model Application Publication No. 31306 and Japanese Utility Model Application Publication No. 52-1912.

(Problem to be Solved by the Invention) However, in the conventional reed valve as shown in the above-mentioned publication, the intake passage area is determined by the inner wall of the reed valve and remains unchanged.
It may not be possible to adjust the appropriate amount of intake air only by opening and closing the reed. In other words, when the throttle is fully opened when the engine is running at low speed, the negative pressure from the crank chamber is low, but the passage area is wide, so the flow rate of intake air slows down and the amount of lift of the reed valve decreases. There was a problem with the engine's response being poor.

In addition, as shown in Japanese Patent Application Laid-open No. 62-35019, when the engine is running at low speeds, intake air is guided through a reed valve to the crank chamber to prevent backflow of intake air, while at high engine speeds Sometimes, the intake air is guided to the crank chamber through a separate intake system without passing through the reed valve, allowing the intake air to be supplied without encountering resistance from the reed valve. Some models are designed to obtain a sufficient amount of intake air, but even with this configuration, when the throttle is fully opened at low engine speeds, the flow rate of intake air slows down and the amount of lift of the reed valve decreases. I have an issue that has arisen. Furthermore, in the configuration shown in this publication, when the engine is running at high speeds, intake air is supplied from the intake system that is not provided with a reed valve, so in this case, backflow of intake air may occur. There is a concern that if such intake air backflow occurs, engine performance will be significantly reduced.

The present invention has been made in view of this point, and it is an object of the present invention to prevent backflow of intake air in the entire rotation range of the engine, and to obtain the optimum amount of intake air according to the engine operating condition. With the goal.

(Means for Solving the Problems) In view of the above, the means of the present invention is such that the area of the flow passage on the upstream side of the valve body of the reed valve is changed in accordance with the engine speed. Specifically, the present invention is directed to the structure of the intake section of a two-stroke engine equipped with a reed valve having a valve body that is opened and closed by negative pressure caused by the reciprocating movement of a piston. The reed valve has a plurality of branch passages defined therein, and is rotated to the upstream side of the intake air flow of the valve body in at least one branch passage among the branch passages. A cylindrical rotary valve is provided in which a recess for adjusting the open area is formed in a part of the valve so that the open area can be adjusted. The rotational position of the rotary valve is adjusted in accordance with the engine speed, and the lower the engine speed, the smaller the open area of the branch path by the open area adjusting recess of the rotary valve. The configuration is such that the number detection means are connected.

(Operation) The operation of the present invention with the above configuration is to rotate the rotary valve by operating the engine rotation speed detection means according to the engine rotation speed. That is, when the engine speed is low, the open area of the branch path is reduced by the open area adjusting recess of the rotary valve, and conversely, when the engine speed is high, the open area of the branch path is reduced by the open area adjusting recess of the rotary valve. Enlarge. Therefore, the intake air always passes through the intake system equipped with the reed valve, so there is no possibility of intake air flowing backwards no matter what the engine operating condition is, and the intake air will not flow backwards depending on the engine speed. Since the intake passage area is changed by the engine, a sufficient flow velocity of the intake air can be ensured even when the engine is running at low speed, and the lift amount of the reed valve can be optimally obtained.

(Example) Next, an example of the present invention will be described with reference to the drawings. Further, the embodiment of the present invention has a technical concept of switching the passage area of the reed valve by opening and closing at least one of the plurality of branch passages provided inside the reed valve.

(First Example) This example will be explained with reference to FIGS. 1 to 3.

As shown in FIG. 1, the present invention includes a reed valve 1 provided with an intake inlet 1a and an intake outlet 1b, an intake passage 2 connected to the intake inlet 1a of the reed valve 1, and an intake passage 2 extending from the intake passage 2. established 2
It is constructed with a rotary valve 4 provided in one of the main branch paths 3a and 3b as a main part.

Intake outlet 1 provided in the above reed valve 1
A plurality of outflow windows 1c partitioned into a grid are formed in b, and each outflow window 1c is fixed with a thin plate-like lead 5, which is a valve body in the present invention and opens and closes toward the crank chamber. and the lead 5
Curved stopper 5 that regulates the maximum open position of
a (see FIG. 2) is screwed to the top of the reed valve 1.

Inside the reed valve 1, the intake passage 2 on the intake inlet port 1a side of the reed valve 1 is divided into two branch passages 3a and 3b, which are separated by two branch passages 3a and 3b. The partition wall 3c is extended and bonded to the lattice portion 1d of the outflow window 1c,
As shown in FIG. 1, a large-diameter branch path 3a and a small-diameter branch path 3b are formed.

Among the two branch passages 3a and 3b, a reed valve 1 is located in the middle of the small diameter branch passage 3b shown in FIG.
A substantially cylindrical rotary valve 4 is rotatably supported in the width direction. The rotary valve 4 is a second
As you can see from the figure, there is a branch road 3 with a small diameter approximately in the center.
A concave portion 4a for adjusting the open area conforming to the shape shown in FIG. The engine rotation speed detection means 6 is a first
As shown in the figure, the main parts include a well-known governor mechanism (not shown) connected to the engine crankshaft (not shown) and a rotary valve rotation mechanism 6a, and the rotary valve rotation mechanism 6a is connected to the governor mechanism. One end of a swinging lever 6e that swings about a shaft 6d is supported on the end of an actuating rod 6c that is urged upward by a spring 6b, and the other end of the swinging lever 6e is attached to a pin 6f. Therefore, it is locked to one side of the rotary valve 4. Further, the locking hole for the pin 6f provided in the swing lever 6e is an elongated hole 6g so that the pin 6f can move when the rotary valve 4 rotates.

Next, the operation of the present invention with the above configuration will be explained.

First, since the governor mechanism does not operate when the engine is running at low speed, the operating rod 6c is urged upward by the spring 6b, and the swing lever 6e is moved to a small diameter by the rotary valve 4 as shown in FIG. branch road 3b is closed. Therefore, the intake passage 2 of the reed valve 1 has only a large-diameter branch passage 3a, and the passage area becomes narrow.

On the other hand, when the engine rotates at high speed, the operating rod 6c is lowered by the governor mechanism against the biasing force of the spring 6b, the swinging lever 6e swings, and the rotary valve 4 is rotated, as shown in FIG. As shown, a recess 4a provided in the rotary valve 4 is opened to a small-diameter branch path 3b. Therefore, the intake passage 2 of the reed valve 1 has a small-diameter branch passage 3b in addition to a large-diameter branch passage 3a, and the passage area is expanded to the original width.

As mentioned above, by changing the passage area of the reed valve 1 depending on the engine speed, the required flow velocity for intake can always be obtained, and in particular,
When the throttle is fully opened from a low engine speed, the flow velocity does not slow down like in the conventional case, so the engine response is as good as ever. In addition, in this example, the intake air is always introduced into the crank chamber through the passage where the reed valve 1 is installed, so no matter what the engine speed is, there is no possibility that the intake air will flow backwards. Instead, it is possible to avoid deterioration in engine performance due to intake air backflow.

Although the above-mentioned embodiment provided two branch passages 3a and 3b, the present invention is not limited to this. Three branch passages are provided inside the rotary valve 1, and two branch passages are provided inside the rotary valve 1. It may also be configured to include a rotary valve. In addition, the rotational position of the rotary valve 4 is configured so that it can be switched not only to the position where the branch passage 3b is fully opened and fully closed, but also to a plurality of stages so that the optimum opening area can be set according to the engine speed. Good too. Furthermore, each branch road 3
A configuration in which a and 3b have the same diameter is also considered.

(Second example) Next, a second embodiment will be described using FIG. 4.

In this embodiment, differences from the first embodiment will be particularly described. In this embodiment, a partition wall 3c is provided in the longitudinal direction of the reed valve 1, two branch passages 3a and 3b are formed by the partition wall 3c, and a rotary valve is provided near the intake inlet port 1a of one of the branch passages 3a. 4, and the operation is the same as in the first embodiment.

(Effects of the Invention) As described above, according to the present invention, a plurality of branch passages are formed inside the reed valve, and a valve body in at least one of the branch passages is provided on the upstream side of the intake air circulation side of the valve body. , a cylindrical rotary valve having a recess for adjusting the open area is disposed in a part thereof so that the open area of the branch path can be adjusted by rotating; The rotating position of the rotary valve is adjusted according to the number of rotary valves, and the lower the engine speed, the smaller the open area of the branch path by the open area adjustment recess of the rotary valve is connected. Therefore, the intake air is always
Since the intake air passes through the reed valve, no matter what operating state the engine is in, the intake air will not flow backwards, and it is possible to avoid deterioration in engine performance due to the intake air backflow. In addition, since the intake passage area is changed according to the engine speed, a sufficient flow rate of the intake air can be ensured even at low engine speeds, and the lift amount of the reed valve can be optimally obtained. Therefore, the effect is achieved without causing any deterioration in the response of the engine.

[Brief explanation of drawings]

1 to 4 show embodiments of the present invention, FIG. 1 is a partially cutaway side view of a reed valve according to the first embodiment of the present invention, FIG. 2 is a front view of the same, and FIG. 1 is a sectional view taken along the - line in FIG. 1, FIG. 4 is a vertical sectional front view of a reed valve showing a second embodiment, and FIG. 5 is a vertical sectional view of the upper part of a two-stroke engine showing the mounting position of a conventional reed valve. . 1...Reed valve, 3a, 3b... Branch road,
4... Rotary valve, 4a... Recessed portion for adjusting open area, 6... Engine rotation speed detection means.

Claims (1)

[Claims] 1. A reed valve having a valve body that is opened and closed by negative pressure caused by reciprocating movement of a piston. 2.
In the structure of the intake part of a cycle engine, the reed valve has a plurality of branch passages defined therein, and at least one of the branch passages is divided into a plurality of branch passages.
On the upstream side of the intake air flow of the valve body in the two branch passages, there is a cylindrical rotary rotary member having a recess for adjusting the opening area in a part thereof so that the opening area of the branch passage can be adjusted by rotating the valve body. A valve is disposed in the rotary valve, and the rotational position of the rotary valve is adjusted according to the engine speed, and the lower the engine speed, the more the opening area adjusting recess of the rotary valve becomes smaller. A structure of an intake section of a two-cycle engine, characterized in that an engine rotation speed detection means is connected to reduce the open area. 2. The structure of the intake part of a two-cycle engine according to claim 1, wherein two branch passages are provided inside the reed valve, and one of the branch passages is equipped with a rotary valve. 3. The structure of the intake part of a two-cycle engine according to claim 1, wherein three branch passages are provided inside the reed valve, and two branch passages are provided with rotary valves.