JPH0123650B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in the lubricity and cooling properties of a two-stroke engine with preloaded crank chamber.

In a two-stroke engine, if the mixture is made leaner to improve fuel efficiency, and if the amount of lubricant added is reduced to reduce lubricant consumption,
Lubrication of various parts of the engine deteriorates. In particular, it is difficult for the air-fuel mixture to flow on the back side of the top of the piston, so the lubricity at the small end of the connecting rod tends to deteriorate. Furthermore, when increasing output by rotating the engine at high speeds, the thermal load and mechanical load also increase, making the conditions for lubrication at the small end of the conrod even more demanding, resulting in reduced durability. occurs.

This invention was developed in view of the above circumstances, and is intended to improve the lubricity and cooling performance of the connecting rod small end in a crank chamber preload type two-stroke engine that has a scavenging passage located on the anti-thrust side of the piston's expansion stroke. It is an object of the present invention to provide a crank chamber preload type two-stroke engine that enables operation with a lean air-fuel mixture, reduces lubricating oil consumption, and further improves durability.

In order to achieve such an object, the present invention forms a window in the piston located on the anti-thrust side in the expansion stroke of the piston, and in the cylinder communicates the window with the scavenging passage in the scavenging stroke of the piston. An auxiliary scavenging passage is formed to allow a part of the scavenging air to flow while coming into contact with the small end of the connecting rod. The present invention will be described in detail below based on embodiments shown in the drawings.

Fig. 1 is a vertical side view of an embodiment in which the present invention is applied to a two-cylinder outboard engine, Fig. 2 is a cross-sectional view taken along the - line, and Fig. 3 is a cross-sectional view taken along the - line, a portion of which is omitted in Fig. 1. FIG. 4 is a sectional view taken along the - line in FIG. 3. In these figures, reference numeral 10 is a cylinder body, and 12 is a cylinder sleeve, which together form a cylinder. 14, 14 is a piston, 16 is a crankshaft, and this crankshaft 16 is a cylinder body 10.
and the crankcase 18 so as to be rotatable perpendicularly thereto. The crankshaft 16 and each piston 14, 14 are connected by connecting rods 20, 20, and each piston 14, 14 slides within the cylinder sleeve 12 with a phase difference of 180 degrees. 2
1 and 21 are piston pins. 22, 22 are carburetors, and these carburetors 22, 22 are respectively connected to crank chambers 26, 26 of the upper and lower cylinders via V-type reed valves 24 (FIG. 2). , 22 is sucked into the crank chambers 26, 26, and the mixture is drawn into the crankshaft 1.
6 rotates, the crank chambers 26, 26 are rotated periodically.
Preloaded inside. The lubricating oil is supplied into the crank chambers 26, 26 by an oil pump (not shown) driven by the crankshaft 16 in an amount corresponding to the rotational speed of the crankshaft 16 and the magnitude of the load. Therefore, this lubricating oil is in the crank chambers 26, 26.
It mixes with the air-fuel mixture inside the engine and is sent to various parts of the engine.
28 is a cylinder head, and 30, 30 are spark plugs.

The symmetry planes A, A passing through the cylinder center axes of the upper and lower cylinders (FIG. 3) are not perpendicular to the crankshaft 16 but are inclined. cylinder sleeve 1
2 and 12 are formed with exhaust ports 32 and 32 so that their centers are located on the planes of symmetry A and A, and the exhaust gas exiting each exhaust port is guided to exhaust passages 34 and 34 and discharged. be done. Note that the exhaust ports 32, 32 are located on the anti-thrust side of the pistons 14, 14, as shown in FIG. That is, in FIG. 2, the crankshaft 16 rotates clockwise, but during the expansion stroke of the piston 14, the explosive force of the combustion gas presses the piston 14, and at this time, the large end of the connecting rod 20 rotates as shown in FIG. The connecting rod 20 that acts on the piston 14 is located below the line connecting the center of the crankshaft 16 and the piston pin 21.
The reaction force is directed toward the upper right in Figure 2. Therefore, during the expansion stroke, the piston 14 is pushed toward the upper inner surface of the cylinder sleeve 12, that is, the thrust side 36 in the figure. The exhaust ports 32, 32 are formed on the opposite side of the thrust side 36, ie, on the anti-thrust side 38, which is the lower inner surface of the sleeve 12 in FIG.

40, 40 are sub-scavenging passages (Fig. 3),
The exhaust ports are formed so that their centers are located on the planes of symmetry A and A on the opposite side to the exhaust ports 32 and 32, and one opening thereof opens into the crank chambers 26 and 26, and the other opening opens into the cylinder sleeves 12 and 12. The opening serves as an auxiliary scavenging port 42 (only the one for the lower cylinder is shown in FIG. 1).

44, 44, 46, 46 are scavenging passages, and the pair of scavenging passages 44, 46 of each cylinder are formed symmetrically with respect to the symmetry plane A. Since the symmetry plane A is not perpendicular to the crankshaft 16 as described above (see FIG. 3), one scavenging passage 44 of each cylinder,
44 is located on the anti-thrust side 38. One end of each scavenging passage 44, 44, 46, 46 opens into the crank chamber 26, 26, and the other end opens into the cylinder sleeve 12, 12, which serves as a scavenging port 48, 48, 50, 50.

As shown in FIG. 2, a substantially annular groove 52 is formed in the crank chamber 26 in order to secure a movement space for the large end of the connecting rod 20. side 3
A notch 56 is formed in the cylinder sleeve 12 in correspondence with the notch 54 in the vicinity of the contact portion with the cylinder sleeve 6 in a substantially tangential direction. On the other hand, the piston 14 has these notches 54, 5 during the scavenging stroke.
A scavenging air introduction window 58 is formed which communicates with the scavenging air introduction window 6 .

The piston 14 also includes the piston pin 21.
A window 60 is formed near the rear surface of the top of the piston and located on the anti-thrust side 38, and the window 60 and the scavenging passage 44 are formed in the cylinder sleeve 12 and the cylinder body 10 during the scavenging stroke of the piston 14. A communicating auxiliary scavenging passage 62 is formed.

Next, the operation of this embodiment will be explained. In either the upper or lower cylinder, if the piston 14 is in the compression stroke, the inside of the crank chamber 26 becomes negative pressure, so the air-fuel mixture generated in the carburetor 22 is transferred to the reed valve 2.
4 into the crank chamber 26. At this time, an appropriate amount of lubricating oil corresponding to the rotational speed of the crankshaft 16 and the magnitude of the load is supplied from the oil pump into the crank chamber 26. This lubricating oil first lubricates the large end of the connecting rod 20, the bearing of the crankshaft 16, etc., and a part of it is led to the small end of the connecting rod 20, that is, near the piston pin 21; 14, the amount of lubricating oil supplied to the small end during this compression stroke is small.

During the expansion stroke of the piston 14, as the piston 14 moves toward the crank chamber 26, the internal pressure of the crank chamber 26 increases, and the reed valve 2
4 is closed. That is, the crank chamber 26 is preloaded. When the exhaust port 32 opens due to the movement of the piston 14, the burned gas in the combustion chamber is discharged through the exhaust passage 34. The piston 14 moves further to open the scavenging ports 48, 50 and the sub-scavenging port 42.
starts to open, the pre-pressurized air-fuel mixture in the crank chamber 26 flows through the scavenging passages 44, 46 and the sub-scavenging passage 4.
0 and flows into the combustion chamber. At this time, the air-fuel mixture flows into the combustion chamber from the scavenging ports 48, 50 at a steep angle along the top surface of the piston 14, and the air-fuel mixture exiting each scavenging port 48, 50 joins within the combustion chamber. Upper (cylinder head 28 direction)
Then, it hits the cylinder head 28 and is reversed.
Further, the air-fuel mixture from the sub-scavenging port 42 flows into the combustion chamber at a gentle angle along the inner surface of the cylinder sleeve 12, and merges with the air-fuel mixture from the respective scavenging ports 48, 50. These air mixture flows then push out the burned gas within the combustion chamber to the exhaust port 32.

On the other hand, due to the movement of the piston 14, the scavenging port 4
8, 50 and the sub-scavenging air port 42 open, the scavenging air introduction window 58 of the piston 14 opens into the notches 56, 54 on the cylinder sleeve 12 and crank chamber 26 side.
The window 60 of the piston 14 also communicates with the auxiliary scavenging passage 62. Therefore, the pre-pressurized air-fuel mixture in the crank chamber 26 flows through the notch 5.
4,58 The piston 14 passes through the scavenging air introduction window 58.
, particularly the small end of the connecting rod 20 and the back surface of the top of the piston 14, and further passes through a window 60 and an auxiliary scavenging passage 62 to join the air-fuel mixture flowing in the scavenging passage 44. Since the air-fuel mixture contains lubricating oil, when it hits the air-fuel mixture and the small end of the connecting rod 20, the lubricating oil adheres to the air-fuel mixture and the small end of the connecting rod 20, and the lubricating oil is sufficiently supplied to this small end. In addition, the low-temperature air-fuel mixture in the crank chamber 26 is exposed to this small end and piston 1.
4, the cooling performance of these is improved. In particular, since the notches 54, 56 and the scavenging air introduction window 58 are provided on the thrust side 36, and the window 60 and the auxiliary scavenging air passage 62 are provided on the anti-thrust side 38 (see FIG. 2), the crankshaft 16 is placed inside the crank chamber 26. The flow of the mixture generated by the rotation of
That is, the air-fuel mixture can be guided to the inner surface of the piston 14 by effectively utilizing the flow rotating in the same direction as the crankshaft 16.

In the above embodiment, the notch 5 is provided on the thrust side 36.
4, 56, and the scavenging air introduction window 58, it is possible to more effectively utilize the rotational flow of the air-fuel mixture in the crank chamber 26 to smoothly guide the air-fuel mixture to the back side of the piston 14. In the present invention, it is possible to obtain the desired effect without providing the notches 54, 56 and the scavenging air introduction window 58. Furthermore, if the window 60 on the anti-thrust side 38 of the piston 14 is formed as close to the top of the piston 14 as possible, the air-fuel mixture will more easily flow deeply into the piston 14, making the effects of the invention even greater. be able to. Furthermore, in the above embodiment, a separate refueling system is adopted in which the fuel and lubricating oil, which are stored separately, are mixed in the crank chamber 26, but it is also possible to adopt a mixed refueling system in which the two are mixed from the beginning. Of course.

As described above, in the present invention, the piston is provided with a window located on the anti-thrust side in the expansion stroke of the piston, and the cylinder is provided with an auxiliary scavenging passage that communicates the window with the scavenging passage in the scavenging stroke of the piston. During the scavenging stroke, the air-fuel mixture generated by the rotation of the crankshaft causes the air-fuel mixture to pass inside the piston, particularly between the small end of the connecting rod and the back side of the top of the piston, and into the window and auxiliary scavenging passage. flows. In other words, part of the scavenging air flows while coming into contact with the small end of the connecting rod. Therefore, lubricating oil is sufficiently supplied to the small end, and the cooling performance of the small end and the piston is improved. Therefore, even if the engine is operated with a lean air-fuel mixture or with a reduced amount of lubricant supplied, the lubricant is well supplied to this small end, so poor lubrication is unlikely to occur. In other words, it becomes possible to operate with a leaner air-fuel mixture and to further reduce lubricating oil consumption. Furthermore, since the cooling performance of the small end and the piston is improved, durability during continuous operation at high speed and high load can be increased.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the - line, FIG. 3 is a sectional view taken along the same line, and FIG. 4 is a sectional view taken along the line -
FIG. 14...Piston, 20...Conrod, 26
...Crank chamber, 38...Anti-thrust side, 44...
...Scavenging passage on the anti-thrust side, 60...Window, 62...
...Auxiliary scavenging passage.

Claims (1)

[Claims] 1. In a crank chamber preloaded two-stroke engine having a scavenging passage located on the anti-thrust side in the expansion stroke, the piston is formed with a window located on the anti-thrust side, and the cylinder is provided with the scavenging passage in the scavenging stroke of the piston. A crank chamber preload type 2 characterized in that an auxiliary scavenging passage is formed that communicates the window with the scavenging passage, and a part of the scavenging air flows while contacting the small end of the connecting rod.
cycle engine.