JPH0328564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transverse two-stroke internal combustion engine.

[Prior Art] Conventionally, outboard motors and the like have employed horizontal two-stroke internal combustion engines in which cylinders are arranged horizontally.

As such a two-stroke internal combustion engine, the one described in Japanese Utility Model Application Laid-Open No. 50-72827 has been proposed.

[Problems to be Solved by the Invention] However, the method described in Japanese Utility Model Application Publication No. 50-72827 has the following problems.

After the exhaust port 3 opens and the pressure inside the cylinder decreases, the discharge port 7 opens. As can be seen from the fact that a scavenging air flow is generated when the piston lowers a little further and the scavenging port opens, the residual pressure of the exhaust gas when the discharge port 7 opens is lower than the crank chamber pressure, and the oil in the oil sump 4' is It flows to the discharge port 7. At this time, the pressure difference between the oil reservoir 4' in the scavenging passage and the discharge port 7 is small, and the oil is efficiently transported into the cylinder.
It is not possible to sufficiently reduce the amount of oil remaining in the oil sump 4'.

Furthermore, even if the residual pressure of the exhaust gas is higher than the crank chamber pressure when the discharge port 7 opens, the exhaust port has already opened, so the differential pressure with the crank chamber is low, and the exhaust gas It is difficult to blow away the oil in the oil sump 4' in the scavenging passage due to the residual pressure. Therefore, the amount of oil remaining in the oil reservoir 4' cannot be sufficiently reduced.

As a result of the above, the oil remaining in the oil reservoir 4' is irregularly transported into the cylinder, resulting in unstable engine rotation in which the combustion state changes with each combustion cycle.

In addition, as a 2-cycle engine,
The engine disclosed in Japanese Patent No. 50416 is provided with an oil injection hole 37 that opens in the inner wall of the cylinder and communicates with the crank chamber via an oil pipe 39. This thing is
When the piston descends and the oil injection hole opens, high-pressure exhaust gas tries to enter the oil passage pipe 39, but the presence of the check valve 41 prevents the exhaust gas from entering. When the piston further descends and the exhaust hole 23 opens, the pressure inside the cylinder decreases, and the air-fuel mixture is compressed within the crank chamber 21.
The oil that collects at the bottom of the cylinder passes through the oil pipe 39 to the cylinder inner wall 3.
gushes out. However, in this case,
Simply drain the oil that accumulates at the bottom of the crank chamber 21 into the crank chamber 2.
It is ejected onto the cylinder inner wall 3 due to the rising internal pressure of 1,
This method merely aims to improve the lubricity between the piston and the inner wall of the cylinder, but cannot sufficiently reduce the amount of oil accumulated in the oil reservoir.

The present invention relates to a horizontally mounted two-stroke internal combustion engine.
The purpose is to reliably prevent unvaporized fuel and oil from accumulating in the reservoir and stabilize the combustion state.

[Means for Solving the Problems] The present invention provides a horizontal type 2 cylinder in which cylinders are arranged horizontally.
In a cycle internal combustion engine, an exhaust jet pipe that communicates from an upper end of an exhaust port in a cylinder to a region near top dead center opens into a scavenging passage located at least on the lower side of the cylinder.

[Function] In the present invention, when the piston descends and the cylinder side opening of the exhaust jet pipe 31 opens, high-pressure exhaust gas enters the exhaust jet pipe 31 and flows into the lower scavenging passage 26.
Blow out the oil that accumulates in the area.

Furthermore, in the present invention, when the piston descends and the exhaust port 25A opens, the air-fuel mixture flows from the crank chamber through the lower scavenging passage 26 into the cylinder. At this time, the oil that was just blown away is also carried into the cylinder. That is, the oil accumulated in the lower scavenging passage 26 is carried into the cylinder each time the piston descends, and a large amount does not accumulate. Therefore, even if the accumulated oil is irregularly carried into the cylinder, since the amount of accumulated oil is small, the amount of oil irregularly carried into the cylinder is also reduced accordingly.

Therefore, according to the present invention, unlike the prior art, there is no possibility of unstable engine rotation in which the combustion state changes with each combustion cycle.

[Embodiment] FIG. 1 is a sectional view showing a two-stroke internal combustion engine 11 for an outboard motor to which an embodiment of the present invention is applied, and FIG. 2 is a sectional view taken along the - line in FIG. 1.

This two-stroke internal combustion engine 11 uses low-quality fuel such as alcohol or kerosene, and is of a horizontal type mounted on the top of the outboard motor body, with cylinders 13 arranged horizontally inside a cylinder block 12. A cylinder head 14 and a crankcase 15 are integrated into the cylinder block 12. A crankshaft 16 is rotatably supported by the crankcase 15.
A piston 18 is connected to the piston 18 via a connecting rod 17.

A reed valve 20 is provided in the crank chamber 19 formed by the crank case 15 and the cylinder block 12.
A carburetor 22 is connected through an intake pipe 21 in which a carburetor 22 is built-in. The carburetor 22 is capable of generating a mixture of low quality fuel and air.

Further, a fuel chamber 23 can be formed in the cylinder 13, and the cylinder head 1 faces approximately the center of the combustion chamber 23.
A spark plug 24 is arranged at 4.

The cylinder block 12 includes an exhaust passage 25 that opens an exhaust port 25A to the cylinder 13, and a lower scavenging passage 26 that opens their outlet to the cylinder 13 slightly toward the bottom dead center of the exhaust port 25A; A scavenging passage 27 and an intermediate scavenging passage 28 are provided. The middle scavenging passage 28 is disposed at a position opposite to the piston center of the exhaust passage 25, and is disposed approximately in the middle of the cylinder 13 in the vertical direction. The lower scavenging passage 26 and the upper scavenging passage 27 are arranged symmetrically with respect to the connecting line connecting the exhaust passage 25 and the middle scavenging passage 28, and the lower scavenging passage 26 is arranged on the lower side in the vertical direction with respect to the cylinder 13. The upper scavenging passage 27 is arranged above the cylinder 13 in the vertical direction. Furthermore, the scavenging angles of the scavenging passages 26, 27, and 28 are each given a predetermined upward angle, thereby making it possible to perform single scavenging. Furthermore, the inlet of each scavenging passage 26, 27, 28 opens into the crank chamber 19, and each scavenging passage 26, 27, 28 opens into the crank chamber 19.
The intermediate portion from the inlet to the outlet of 28 is in a substantially horizontal state.

Here, cylinder block 12 and cylinder 13
A connecting pipe 2 of a predetermined diameter is provided at a location closer to the top dead center than the exhaust port 25A, that is, a location that opens at a time appropriately earlier than the exhaust timing of the exhaust port 25A.
9 are arranged. On the other hand, cylinder block 1
A connecting pipe 30 is disposed at a portion forming the lowest level of the lower scavenging passage 26 at the middle portion on the outlet side. The connecting pipe 29 and the connecting pipe 30 are communicated through an exhaust jet pipe 31. That is, the exhaust jet pipe 31 communicates with the top dead center side from the upper end of the exhaust port 25A in the cylinder 13, and opens into the lower scavenging passage 26 located on the lower side with respect to the cylinder 13.

Next, the operation of the above embodiment will be explained.

When the engine 11 remains idling or trolling for a long time, the air-fuel mixture supplied from the carburetor 22 to the crank chamber 19 comes into contact with the low-temperature crankcase 15 and crankshaft 16 and liquefies. The liquefied fuel and oil accumulate in the lower part of the crankcase 15 due to the action of gravity, and then flow in a liquid film flow into the lower scavenging passage 26 located at a low level position.

On the other hand, during the downward stroke of the piston 18, the combustion chamber 23
The high-temperature exhaust gas generated inside is ejected into the middle part of the lower scavenging passage 26 at an appropriately high pressure from the exhaust jet pipe 31, which opens at an appropriately earlier time than the exhaust port 25A.

Therefore, as described above, the lower scavenging passage 26
The fuel flowing in a liquid film state is vaporized by a jet of exhaust gas ejected from the exhaust jet pipe 31 during the downward stroke of the piston 18 . Also,
The oil is blown away and reduced to small particles.

Therefore, as the downward stroke of the piston 18 progresses and the exhaust port 25A opens, the inside of the cylinder reaches maximum negative pressure and each scavenging passage 26, 27, 28 opens, the precompressed mixture in the crank chamber 19 Air, fuel vaporized by exhaust gas in the lower scavenging passage 26, and atomized oil flow in the opposite direction of the exhaust port 25A, collide with each other, and reduce the mixture concentration in the cylinder. While being equalized, the gas rises along the inner peripheral surface of the cylinder, and at the same time, the burned gas remaining in the cylinder is pushed out from the exhaust port 25A to perform a scavenging action.

When the piston 18 begins its upward stroke, the scavenging passages 26, 27, and 28 are closed, and then the exhaust passage 25 is closed.
At the same time, intake of the air-fuel mixture from the carburetor 22 into the crank chamber 19 is started. Furthermore, as the piston 18 rises, the air-fuel mixture with a uniform concentration is gradually pushed up along the inner circumferential surface of the cylinder, and at the end of compression, from the squish area formed by the inner surface of the cylinder head 14 and the top surface of the piston 18,
The mixer flows toward the ignition plug 24 at high speed, and even when the engine 11 is operating at low speed, reliable ignition is achieved under the turbulent flow of the mixture with a uniform concentration. After that, combustion begins rapidly and the combustion chamber 23 The entire air-fuel mixture in the tank is quickly combusted.

According to the above embodiment, the fuel and large oil particles liquefied in the crankcase 15 are vaporized or reduced to small particles by the heat of the exhaust gas and the jet flow in the lower scavenging passage 26, and then flow into the cylinder 13. Even when idling and trolling conditions continue for a long time, the mixture concentration in the cylinder 13 can be made uniform, and even when low-speed operation conditions continue for a long time, ignition is performed reliably in every cycle. At the same time, combustion progresses quickly,
Since the rotation ends, it becomes possible to ensure a smooth rotation state.

In particular, according to the above embodiment, when using low-quality fuel such as alcohol or kerosene, it is possible to promote the vaporization of the fuel, stabilize the combustion state, and improve the startability and acceleration of the engine.

The fuel liquefied in the crank chamber 19 tends to flow mainly into the lower scavenging passage 26 due to the action of gravity, and flows into the upper scavenging passage 27 or the middle scavenging passage 28.
In the above embodiment, the exhaust jet pipe 31 is opened only in the lower scavenging passage 26 because it is difficult for the exhaust gas to flow into the lower scavenging passage 26. However, the exhaust jet pipe 31 may also be opened in the upper scavenging passage 27 or the middle scavenging passage 28 to vaporize the liquid film flow flowing into those scavenging passages.

Further, in the above embodiment, the lower scavenging passage 26
Since the middle part of is set in a horizontal state,
Although the exhaust jet pipe 31 is opened at the intermediate portion, if the exhaust passage is curved, it is preferable to open the exhaust jet pipe at the lowest part of the scavenging passage.

[Effects of the Invention] As described above, according to the present invention, in a horizontal two-stroke internal combustion engine, unvaporized fuel and oil can be reliably prevented from accumulating in the reservoir, and the combustion state can be stabilized.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a two-stroke outboard engine to which an embodiment of the present invention is applied, and FIG. 2 is a sectional view taken along the line - in FIG. 11...Internal combustion engine, 13...Cylinder, 25...Exhaust passage, 25A...Exhaust port, 26...Lower scavenging passage, 31...Exhaust jet pipe.

Claims (1)

[Claims] 1. In a horizontal two-stroke internal combustion engine in which the cylinders are arranged horizontally, an exhaust jet pipe that communicates from the upper end of the exhaust port in the cylinder to the top dead center side is connected to a scavenging passage located at least on the lower side with respect to the cylinder. A horizontally mounted two-stroke internal combustion engine characterized by an opening.