JPH0474524B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a two-stroke engine, and particularly to a four-stroke engine.
The present invention relates to a two-cycle engine which, like a cycle engine, has an oil pan provided at the bottom of the crankcase so that a mixed oil supply system of fuel and lubricating oil or a separate lubrication system is not required.

[Prior art and problems to be solved by the invention] A two-stroke engine has one work stroke per rotation, has a larger output per unit cylinder volume than a four-stroke engine, and has no valve train. Therefore, it has the advantage of having fewer parts, being lightweight and inexpensive, and having no impact noise from the valve train and less risk of failure.

However, in a conventional two-stroke engine, when the intake port opens as the piston rises to near the top dead center, the air-fuel mixture is sucked into the crankcase below the piston, and the air-fuel mixture sucked into the crankcase is The scavenging port opens when the piston is pre-pressurized by the descending piston and reaches near the bottom dead center, and the pre-pressurized air-fuel mixture flows into the cylinder. In this way, conventional 2-cycle engines have a structure in which the air-fuel mixture flows into the crankcase, so unlike 4-stroke engines, an oil pan is provided to store lubricating oil in the crankcase, and the engine is heated by spray or forced lubrication. It is not possible to supply lubricating oil to each sliding and rotating part. Therefore, in order to supply lubricating oil to each sliding and rotating part of the engine,
A method is available: a mixture of fuel and lubricating oil in a predetermined ratio is supplied into the engine together with the fuel, or it is separated from the fuel and mixed with the air-fuel mixture midway through, for example in the intake pipe (separated lubrication). It is being Therefore, the lubricating oil is supplied into the cylinder combustion chamber together with the fuel (mixture) and burned, which consumes a large amount of lubricating oil, and the combustion of this lubricating oil tends to generate white smoke in the exhaust gas. The problem is that soot tends to accumulate in the air, exhaust, and scavenging ports.

However, as described in Japanese Utility Model Application Publication No. 55-78721 or Nikkei Mechanical No. 1985-2-25, pages 67 to 73, the conventional technology for two-stroke engines is to draw air-fuel mixture from the exhaust port. Although there are proposals to reduce the blow-through of fresh air (fresh air) and HC emissions, there are still no proposals to completely separate the fuel/air mixture from the lubricating oil and make the lubrication the same as in a 4-cycle engine. do not.

[Object of the Invention] The present invention has been made in view of these circumstances, and uses a lubrication method similar to that of a 4-stroke engine to reduce the consumption of lubricating oil while preventing white smoke in exhaust gas. The aim is to provide a two-stroke engine with

[Means and operations for solving the problem] In order to achieve the above object, the two-stroke engine according to the present invention includes a pulsating valve that opens and closes in the intake passage in front of the intake/scavenging ports by the pulsating pressure caused by sliding of the piston. At the same time, a volume chamber is provided that communicates with the intake passage, the intake/scavenge port, and the inside of the crankcase, and this volume chamber is displaced by pressure fluctuations due to volume fluctuations in the crankcase caused by sliding of the piston. The displacement member divides the air intake passage and the intake/scavenge chambers on the side of the intake/scavenge ports into an operating chamber communicating with the inside of the crankcase, and an oil pan for lubricating oil is provided in the lower part of the inside of the crankcase. ing.

In this configuration, the volume inside the crankcase contracts and expands due to the sliding of the piston, thereby displacing the displacement member of the volume chamber and expanding and contracting the working chamber.
Contracts and expands the intake and scavenging chambers. When the intake/scavenging chamber expands, the pulsating valve is opened to suck fresh air into the intake/scavenging chamber, and when the intake/scavenging chamber contracts, the pulsating valve is closed to prepress the intake fresh air and inhale/scavenge.
The scavenging air flows into the cylinder from the scavenging port. Therefore, the intake fresh air flows into the cylinder without entering the crankcase, and it becomes possible to provide an oil pan in the lower part of the crankcase.

[Example] Hereinafter, an example of the present invention will be specifically described with reference to the drawings.

1 to 3 relate to a first embodiment of the two-stroke engine of the present invention, FIG. 1 is a cross-sectional view, and FIG.
The figure is an explanatory cross-sectional view explaining the intake of fresh air when the intake/scavenging chamber expands (when the piston rises), and Figure 3 shows the preload of fresh air and the inside of the cylinder when the intake/scavenging chamber contracts (when the piston descends). It is an explanatory sectional view explaining the inflow to.

In these figures, 1 is a two-stroke engine, 2 is its cylinder, 3 is a crankcase, 4 is a cylinder head, 5 is a piston, 6 is a connecting rod, 7 is a crankshaft, 8 is a carburetor, 9 is an intake pipe, 10 is an exhaust port. or,
Reference numeral 11 denotes an intake/scavenge port formed in the cylinder 2, and this intake/scavenge port 11 serves as both an intake port and a scavenge port of the conventional type.
Its position is crankcase 3 when piston 5 rises.
It is formed in a position that does not communicate with the inside. Between the front of this intake/scavenge port 11 and the intake pipe 9,
A volume chamber 12 that also communicates with the inside of the crankcase 3 is formed. This volume chamber 12 includes a diaphragm 13 as a member that is displaced by pressure fluctuations within the crankcase 3 caused by sliding of the piston 5.
It is divided into an intake/scavenge chamber 14 on the side of the intake pipe 9 and the intake/scavenge port 11, and a working chamber 15 communicating with the inside of the crankcase 3. and,
As the volume within the crankcase 3 expands due to the rise of the piston 5, the pressure within the working chamber 15 decreases, causing the diaphragm 13 to be suctioned and displaced, thereby contracting the working chamber 15, while expanding the intake/scavenging chamber 14. , the pressure inside the air intake/scavenge chamber 14 is reduced. Further, as the volume inside the crankcase 3 contracts due to the lowering of the piston 5, the pressure inside the working chamber 15 increases and the diaphragm 1
3 to expand the working chamber 15, while contracting the air intake/scavenging chamber 14 and increasing the pressure within the air intake/scavenging chamber 14.

Further, an intake passage 16 is formed between the intake pipe 9 and the intake/scavenge port 11, and a reed valve 17 is provided as a pulsating valve that opens and closes depending on the pulsating pressure in the intake/scavenging chamber 14. has been done.

Furthermore, an oil pan 18 for lubricating oil is located at the bottom of the crankcase 3, similar to a 4-stroke engine.
is formed. In this embodiment, an oil scraper 19 is attached to the large end of the cooking rod 6, and is adapted to supply lubricating oil to each sliding part and rotating part by a droplet supply method.
A blow-by gas discharge passage in the crankcase 3 communicates with the atmosphere via an oil separator having a pressure valve. A slit 20 is formed in the communication portion between the inside of the crankcase 3 and the working chamber 15 to prevent the diaphragm 13 of the working chamber 15 from interfering with the crankshaft side, and to prevent the lubricating oil in the oil pan 18 from interfering with the crankshaft side. There is a large amount of working chamber 1
5 to prevent it from leaking into the interior.

In such a configuration, as shown in FIG. 2, the volume inside the crankcase 3 is expanded due to the rise of the piston 5, thereby reducing the pressure inside the working chamber 15, and the diaphragm 13 is sucked into the working chamber 15. The displacement expands the intake/scavenge chamber 14, and as a result, the pressure inside the intake/scavenge chamber 14 decreases, opening the reed valve 17 of the intake passage 16 and sucking fresh air into the intake/scavenge chamber 14. In addition, at this time, the intake/scavenging port 11
is closed by the raised piston 5. Next, as shown in FIG. 3, the volume inside the crankcase 3 is contracted by the descent of the piston 5, and the pressure inside the working chamber 15 increases, causing the diaphragm 1
3 is pushed and displaced to contract the intake/scavenge chamber 14,
At the same time, the reed valve 17 is moved to close. the result,
While prepressuring the sucked fresh air, the piston 5
When the piston falls to near the bottom dead center as shown in FIG. 3, the intake/scavenge port 11, which had been closed by the piston 5, opens and the pre-pressurized fresh air flows into the cylinder 2.

In this way, the fresh air taken in is pre-pressurized without flowing into the crankcase 3, and the cylinder 2
flow into the world. Therefore, fresh air is cut off from the inside of the crankcase 3, and an oil pan 18 can be formed in the lower part of the crankcase 3, similar to a four-cycle engine, so that a splash or forced lubrication system can be adopted. Therefore, the amount of lubricating oil consumed can be reduced and white smoke in the exhaust gas can be prevented.

4 to 6 relate to a second embodiment of the two-stroke engine of the present invention, and FIG. 4 is a sectional view thereof;
FIG. 5 is an explanatory cross-sectional view illustrating the intake of fresh air when the intake/scavenging chamber is expanded (when the piston is raised);
FIG. 6 is an explanatory cross-sectional view illustrating the preload of fresh air and its inflow into the cylinder when the intake/scavenging chamber is contracted (when the piston is lowered).

In this second embodiment, the volume chamber 12 is divided into an intake/scavenging chamber 14 and a working chamber 15, and a sliding member is used as a displacement member that is displaced by pressure fluctuations in the crankcase 3 caused by sliding of the piston 5. 21
It uses Therefore, in this embodiment, the lubricating oil inside the crankcase is prevented from blowing out toward the working chamber 15, and the lubricating oil inside the crankcase is
The sliding body 21 and the inner wall of the volume chamber 12 are processed to prevent the air from entering the scavenging chamber.

This second embodiment operates as shown in FIGS. 5 and 6 similarly to the first embodiment described above. That is, as the piston 5 rises, the volume inside the crankcase 3 is expanded and the pressure inside the working chamber 15 decreases, causing the sliding body 21 to be sucked down and the pressure inside the intake/scavenging chamber 14 being lowered to lead fresh air. Air is drawn into the intake/scavenging chamber 14 through the valve 17. On the other hand, piston 5
, the volume of the crankcase 3 contracts and the pressure inside the working chamber 15 rises, pushing the sliding body 21 upward and contracting the inside of the intake/scavenging chamber 14, which closes the reed valve 17 and sucks fresh air. Preload.
When the piston 5 descends to near the bottom dead center, the intake/scavenge port 11 is blocked by the piston 5.
opens and pre-pressurized fresh air flows into the cylinder 2.

[Effects of the Invention] As explained above, according to the present invention, an oil pallet is provided in the lower part of the crankcase in the same manner as in a 4-stroke engine, and a lubrication method similar to that of a 4-stroke engine can be adopted, and as a result, the consumption of lubricating oil can be reduced. This has the effect of reducing white smoke in the exhaust gas.

[Brief explanation of drawings]

1 to 3 relate to a first embodiment of the two-stroke engine of the present invention, FIG. 1 is a cross-sectional view, and FIG.
The figure is an explanatory cross-sectional view explaining the intake of fresh air when the intake/scavenging chamber expands (when the piston rises), and Figure 3 shows the preload of fresh air and the inside of the cylinder when the intake/scavenging chamber contracts (when the piston descends). 4 to 6 are explanatory cross-sectional views for explaining the inflow into the second embodiment of the present invention.
Regarding the second embodiment of the cycle engine, FIG. 4 is a sectional view thereof, FIG. 5 is an explanatory sectional view illustrating the intake of fresh air when the intake/scavenging chamber is expanded (when the piston is raised), and FIG. 6 is a sectional view thereof. FIG. 3 is an explanatory cross-sectional view illustrating the pre-pressure of fresh air and its inflow into the cylinder when the intake/scavenging chamber is contracted (when the piston is lowered). 2...Cylinder, 3...Crankcase, 11
...Intake, scavenging port, 12...Volume chamber, 13,
21...Displacement member, 14...Intake/scavenging chamber, 15
... Working chamber, 17... Pulsating valve, 18... Oil pan.

Claims (1)

[Claims] 1. A pulsating valve that opens and closes using pulsating pressure caused by sliding of the piston is installed in the intake passage in front of the intake/scavenging port, while a volume chamber is provided that communicates with the intake passage, the intake/scavenging port, and the inside of the crankcase. This volume chamber is communicated with the intake passage and the intake/scavenge chambers on the intake/scavenge port side and the inside of the crankcase by a displacement member that is displaced by pressure fluctuations caused by volume fluctuations in the crankcase caused by sliding of the piston. 1. A two-stroke engine, characterized in that the crankcase is divided into a working chamber and an oil pan for lubricating oil is provided in a lower part of the crankcase.