JPH06108864A - Supercharging four-cycle engine - Google Patents

Abstract

PURPOSE:To reduce the weight and the size of a supercharging four-cycle engine by carrying out supercharging without providing a pressure chamber. CONSTITUTION:An intake route 22 for communicating between a carburetor 21 and am intake port 9 opened/closed by an intake valve 8, is provided, while a bypass route 23 for communicating between the carburetor 21 and a crank chamber 4 is provided, and a suction valve 24 for allowing mixture to be sucked only in the crank chamber 4, is provided on the connection part between the bypass route 23 and the crank chamber 4. A supercharging route 25 for communicating between the crank chamber 4 and the inside of a cylinder 2 is provided, and an outlet port 26 opened in the cylinder 2 of the supercharging route 25 is formed at a point where it is opened/closed by a piston 3, and where it is released when the piston 3 is lowered to the vicinity of a bottom dead center. A supercharging valve 27 opened when the piston 3 is lowered to the vicinity of the bottom dead point in the suction stroke, is provided in the middle of the supercharging route 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercharged four-cycle engine which supercharges an air-fuel mixture into a cylinder by utilizing a volume change in a crank chamber due to a reciprocating motion of a piston.

[0002]

2. Description of the Related Art Conventionally, a supercharged four-cycle engine utilizing the volume change in the crank chamber accompanying the reciprocating movement of a piston has been developed and put into practical use.
There is one disclosed in Japanese Patent No. 539. In this supercharged 4-cycle engine, air is sucked into the crank chamber by utilizing the volume change in the crank chamber due to the reciprocating motion of the piston, and further, this air is discharged from the crank chamber into the pressure chamber and the cylinder. The pressurized valve that opens and closes the inside is opened and closed at a predetermined timing to supercharge the pressurized air from the pressure chamber into the cylinder.

[0003]

However, the actual Kaihei 3-1.
In the supercharged four-cycle engine disclosed in Japanese Patent No. 19539, it is difficult to reduce the weight and size because a pressure chamber is required. Further, since a valve mechanism for opening and closing the pressurizing valve is required, the cost becomes high, and it is difficult to secure a space for mounting the pressurizing valve on the cylinder head in a small engine. Further, in order to improve the supercharging efficiency, it is desirable to open the pressurizing valve for a short time immediately after closing the intake valve, but it is difficult to design a high lift cam that opens for a short time.

[0004]

The invention according to claim 1 is
In a supercharged four-cycle engine that supercharges an air-fuel mixture into a cylinder by utilizing a change in volume in a crank chamber due to reciprocating movement of a piston, an intake passage that connects a carburetor and an intake port opened and closed by an intake valve A bypass passage that connects the carburetor and the crank chamber is provided, and a suction valve that allows only a mixture to be sucked into the crank chamber is provided at a connection portion between the bypass passage and the crank chamber. A supercharging passage that communicates between the crank chamber and the inside of the cylinder is provided, and when an outlet port of the supercharging passage that opens into the cylinder is opened and closed by the piston and when the piston descends to near the bottom dead center, A supercharging valve that is formed at the open position and opens when the piston descends near the bottom dead center in the suction stroke is provided on the way of the supercharging passage. It provided to.

According to a second aspect of the present invention, in the first aspect of the present invention, the supercharging valve is provided at a position in contact with either one of the intake cam that opens and closes the intake valve or the exhaust cam that opens and closes the exhaust valve.

[0006]

According to the first aspect of the invention, the air-fuel mixture produced by the carburetor is supplied into the cylinder through the intake passage, and is bypassed when the crank chamber is in a negative pressure state as the piston rises. It is sucked into the crank chamber through the passage. Then, when the piston descends to the vicinity of the bottom dead center in the intake stroke, the supercharging valve is opened and the outlet port is opened, so that the air-fuel mixture in the crank chamber is supplied into the cylinder through the supercharging passage. The outlet port is opened even when the piston is lowered to the bottom dead center in the expansion stroke, but because the supercharging valve is closed, supply of the air-fuel mixture from the crank chamber to the cylinder and combustion gas There is no backflow into the crank chamber.

According to the second aspect of the invention, the opening / closing control of the supercharging valve is performed by either the intake cam or the exhaust cam.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. First, FIG. 1 shows an overall structure of a supercharged four-cycle engine according to the present invention. A cylinder 2 is formed in an upper portion of a crankcase 1, and a piston 3 is reciprocally movable in the cylinder 2. It is stored. A crank chamber 4 is formed in the lower portion of the crank case 1, and a crank shaft 5 and a cam shaft 6 are rotatably provided in the crank chamber 4. Further, the cylinder 2
A cylinder head 7 is attached to an upper part of the cylinder head 7, and an intake port 9 opened and closed by an intake valve 8 and an exhaust port 11 opened and closed by an exhaust valve 10 are formed in the cylinder head 7. Here, the crankshaft 5 and the piston 3 are connected by a connecting rod 12, a piston pin 13 and a crankpin 14, and a crank gear 15 fixed to one end of the crankshaft 5 and one end of the camshaft 6 are connected to each other. It meshes with the fixed cam gear 16. The number of teeth of the crank gear 15 and the cam gear 16 is set to 1: 2.

An intake cam 17 and an exhaust cam 18 are fixed to the camshaft 6, and a slidable tappet 19 is brought into contact with the intake cam 17, and the tappet 19 is fixed.
The push rod 20 is in contact with one end of the push rod 20, and the other end of the push rod 20 is in contact with one end of a rocker arm (not shown) that drives the intake valve 8 to open and close. The exhaust cam 18 is also tappeted (not shown).
, And the other end of the push rod (not shown) whose one end is brought into contact with this tappet is brought into contact with one end of a rocker arm (not shown) that drives the exhaust valve 10 to open and close.

Next, there is provided a carburetor 21 which mixes liquid fuel mixed with lubricating oil and air to form an air-fuel mixture. The carburetor 21 and the intake port 9 are connected to the intake passage 2
It is connected by two. Further, a bypass passage 23 that connects the intake passage 22 and the crank chamber 4 is provided, and the air-fuel mixture is sucked into the crank chamber 4 at the connecting portion between the bypass passage 23 and the crank chamber 4. A suction valve 24 is provided to allow only that. Further, a supercharging passage 25 that connects the crank chamber 4 and the inside of the cylinder 2 is formed in the crankcase 1.

An outlet port 26 that opens into the cylinder 2 is formed at one end of the supercharging passage 25. The outlet port 26 extends from a position immediately before the bottom dead center of the piston 3 to a position immediately after it. It is formed at a position where it is opened when it descends, and is closed by the skirt portion 3a of the piston 3 when the piston 3 is positioned above it. further,
In the middle of the supercharging passage 25, the valve is opened when the piston 3 is lowered to the vicinity of the bottom dead center in the suction stroke, and is closed when the piston 3 is moved to the compression stroke and is raised to substantially the same position. A supercharging valve 27 is provided. Further, the supercharging valve 27 is provided slidably in a direction in which the supercharging valve 27 comes into contact with and separates from the exhaust cam 18.
A spring 28 is attached which biases 7 toward the exhaust cam 18. Further, the supercharging valve 27 has a communication hole 2 for communicating the supercharging passage 25 at a predetermined sliding position.
9 is formed. The relative angle θ between the axis of the tappet 19 and the axis of the supercharging valve 27 is set to 180 ° in the present embodiment, but the supercharging valve 27 can be changed by changing the relative angle θ. You can change the opening and closing time of. Further, although the supercharging valve 27 is brought into contact with the exhaust cam 18 in the present embodiment, it may be brought into contact with the intake cam 17 by setting the relative angle θ appropriately.

In such a structure, the operation of the intake, compression, explosion, and exhaust strokes of the supercharged four-cycle engine, the opening / closing timing of each valve 8, 10, 24, 27 and the outlet port 26, and the cylinder 2 The internal pressure and the internal pressure of the crank chamber 4 will be described with reference to the timing chart of FIG.

First, in the intake stroke, the intake valve 8
Is open and the exhaust valve 10 is closed.
Is lowered, and the air-fuel mixture created by the carburetor 21 is sucked into the intake passage 22.
And is supplied into the cylinder 2 through. On the other hand, an air-fuel mixture that has been sucked in during the previous compression stroke is present in the crank chamber 4, and this air-fuel mixture is compressed as the piston 3 descends. In this intake stroke, the intake valve 24
Is closed, so that the air-fuel mixture in the crank chamber 4 is prevented from flowing back to the intake passage 22 side through the bypass passage 23. Then, when the piston 3 descends near the bottom dead center, the exhaust cam 18 causes the supercharging valve 27 to move.
Is pressed and slides, and the communication hole 29 connects the supercharging passage 25. That is, the supercharging valve 27 opens. Further, when the piston 3 descends to the position immediately before the bottom dead center, the outlet port 26 closed by the skirt portion 3a of the piston 3 is opened, and the pressurized air-fuel mixture in the crank chamber 4 is supercharged by the supercharging passage 25. The gas is jetted into the cylinder 2 through the outlet port 26 to supercharge the air-fuel mixture.

In the compression stroke, the piston 3 rises with the intake valve 8 "closed" and the exhaust valve 10 "closed". When the crank chamber 4 has a negative pressure as the piston 3 moves upward, the intake valve 24 is opened and the air-fuel mixture is sucked into the crank chamber 4 through the bypass passage 23. Immediately after the piston 3 starts to rise, the outlet port 26 is closed by being closed by the skirt portion 3a, and the supercharging valve 27 is also closed after the skirt portion 3a is closed.

In the explosion stroke, the air-fuel mixture in the cylinder 2 explodes and the piston 3 descends with the intake valve 8 "closed" and the exhaust valve 10 "closed". When the piston 3 descends near the bottom dead center, the outlet port 26 is opened, but since the supercharging valve 27 is closed, the air-fuel mixture is jetted from the crank chamber 4 into the cylinder 2 or into the crank chamber 4. No backflow of the combustion gas of

In the exhaust stroke, the piston 3 rises with the intake valve 8 "closed" and the exhaust valve 10 "open", and the combustion gas in the cylinder 2 is discharged from the exhaust port 11 to the outside. The pressure in the crank chamber 4 decreases as the piston 3 rises, but since the air-fuel mixture sucked in the previous compression stroke exists in the crank chamber 4, mixing from the suction valve 24 into the crank chamber 4 occurs. Inhalation of Qi is rarely done.

Since the supercharged four-cycle engine does not require a pressurizing chamber for pressurizing the air-fuel mixture to be supercharged, it is possible to reduce the weight and size of the entire engine. Further, a dedicated valve operating mechanism for opening and closing the supercharging valve 27 in order to open and close the supercharging valve 27 by the exhaust cam 18 becomes unnecessary, and the mechanism for opening and closing the supercharging valve 27 becomes simple and the cost is reduced.

Further, since the air-fuel mixture is jetted from the crank chamber 4 into the cylinder 2 by opening and closing the outlet port 26 by the skirt portion 3a of the piston 3, a short-time open / close cam, which is difficult to design, becomes unnecessary and cost is reduced. Is reduced. Moreover, the discharge port 26 can be easily opened only for a short time, and the supercharging efficiency is improved.

Further, since the supercharging valve 27 is provided in the crankcase 1 which has a sufficient space, it is possible to easily provide the supercharging valve 27 even in a small engine, and therefore, the small size. A supercharged 4-cycle engine can be achieved.

Regarding the internal pressure of the cylinder 2 and the internal pressure of the crank chamber 4 shown in the timing chart of FIG. 2, the solid line shows the supercharged 4-cycle engine of this embodiment, and the broken line shows it. This is the case when the thing that does not supercharge.

In this embodiment, the bypass passage 2
Although the one end of 3 is connected to the intake passage 22 in the description, the one end of the bypass passage 23 may be directly connected to the carburetor 21.

[0022]

As described above, according to the invention described in claim 1, in the supercharged four-cycle engine which supercharges the air-fuel mixture into the cylinder by utilizing the volume change in the crank chamber due to the reciprocating movement of the piston, The intake passage that connects the intake port of the cylinder and the cylinder and the bypass passage that connects the carburetor and the crank chamber are provided, and only the air-fuel mixture is drawn into the crank chamber at the connection between the bypass passage and the crank chamber. Is provided with a suction valve, and a supercharging passage that connects the crank chamber and the inside of the cylinder is provided.The outlet port that opens in the cylinder of the supercharging passage is opened and closed by a piston, and this piston descends near the bottom dead center. Since it is formed in a position where it is opened when the piston is lowered to near the bottom dead center in the suction stroke, a supercharging valve is provided in the middle of the supercharging passage. Supercharging of the air-fuel mixture from the rank chamber into the cylinder can be performed from the crank chamber through the supercharging passage by opening / closing the outlet port and opening / closing the supercharging valve in accordance with the reciprocating movement of the piston. Since it is not necessary to provide a pressurizing chamber for pressurizing the supercharged air-fuel mixture, it is possible to reduce the weight and size of the engine as a whole and to add a complicated mechanism for opening and closing the pressurizing chamber and the cylinder. The present invention relates to the present invention even in a small engine in which the pressure valve drive mechanism is not required and the cost can be reduced, and moreover, the pressurizing valve provided in the cylinder head is not required, and therefore the pressurizing valve is not provided in the cylinder head. It has an effect that a supercharging system can be adopted.

As described above, the invention according to claim 2 provides the supercharging valve at the position where it abuts either one of the intake cam for opening and closing the intake valve and the exhaust cam for opening and closing the exhaust valve in the invention according to claim 1. Since it is provided, there is no need for a dedicated drive mechanism for opening and closing the supercharging valve, and there is an effect that the mechanism can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an embodiment of the present invention.

FIG. 2 is a timing chart.

[Explanation of symbols]

 2 cylinder 3 piston 4 crank chamber 8 intake valve 9 intake port 10 exhaust valve 11 exhaust cam 21 carburetor 22 intake passage 23 bypass passage 24 intake valve 25 supercharging passage 26 outlet port 27 supercharging valve

Claims (2)

[Claims] 1. A supercharged four-cycle engine which supercharges an air-fuel mixture into a cylinder by utilizing a volume change in a crank chamber due to a reciprocating movement of a piston, and a carburetor and an intake port opened and closed by an intake valve. An intake passage communicating with the carburetor and a bypass passage communicating with the crank chamber are provided to allow only a mixture to be sucked into the crank chamber at a connecting portion between the bypass passage and the crank chamber. An intake valve is provided, a supercharging passage that communicates between the crank chamber and the inside of the cylinder is provided, an outlet port of the supercharging passage that opens into the cylinder is opened and closed by the piston, and the piston is near the bottom dead center. A supercharging valve that is formed at a position that is opened when the piston descends to the position near the bottom dead center in the suction stroke. A supercharged 4-cycle engine characterized by being installed in the middle of the supercharge passage. 2. A supercharging valve is provided at a position in contact with either one of an intake cam that opens and closes an intake valve or an exhaust cam that opens and closes an exhaust valve.
The described supercharged 4-cycle engine.