JPS6123371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an active thermal atmosphere combustion two-stroke internal combustion engine.

As a two-stroke internal combustion engine that can significantly reduce fuel consumption and harmful components in exhaust gas and achieve quiet operation, the cross-sectional area of the scavenging passage that connects the engine crank chamber and combustion chamber has been changed to the side closer to the crank chamber. Activated thermal atmosphere combustion 2 in which fresh air is allowed to flow into the combustion chamber at a low speed by narrowing the
A cycle internal combustion engine has already been proposed by the inventor. In this two-stroke internal combustion engine, an active thermal atmosphere is created in the combustion chamber by allowing fresh air to flow into the combustion chamber at a low speed, and this atmospheric condition is then maintained continuously during the compression stroke, so that at the end of the compression stroke, fresh air is introduced into the combustion chamber. is caused to ignite and burn.

An active thermal atmosphere refers to a state in which radicals are generated, as will be explained later.In order to create such an active thermal atmosphere, it is necessary to promote vaporization in the scavenging passage and suppress heat dissipation in the combustion chamber. It's having a big impact.

The purpose of the present invention is to promote the creation of an active thermal atmosphere.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIGS. 1 and 2, 1 is a crankcase, 2 is a cylinder block fixed on the crankcase 1, 3 is a cylinder head fixed on the cylinder block 2, and 4 is a substantially flat top. A piston having a surface and capable of reciprocating within a cylinder liner 5 fitted in the cylinder block 2; 6 a combustion chamber formed between the cylinder head 3 and the piston 4; 7 disposed at the apex of the combustion chamber 6; spark plug,
8 is a crank chamber formed in the crankcase 1, 9 is a balance weight, 10 is a connecting rod, 11
12 is an intake passage formed in the cylinder liner 5; 13 is a carburetor; 14 is a carburetor throttle valve; 15 is a pair of scavenging holes formed in the cylinder liner 5; 16 is a pair of scavenging holes formed in the cylinder liner 5. 17 is an exhaust pipe, and 18 is an exhaust passage. The embodiment shown in FIGS. 1 and 2 is a two-stroke internal combustion engine of the simulator type, and its effective compression ratio is 6.5.

As shown in FIGS. 2, 5, and 6, the crankcase 1 has three crankcase parts 1a,
It consists of 1b and 1c. cylinder block 2
A pair of vertical holes 40 are formed inside the cylinder liner 5 and extend vertically along the outer wall of the cylinder liner 5 and upwardly beyond the scavenging hole 15.
A pair of scavenging passages 20 having a smaller cross-sectional area than the vertical hole 40 and communicating with the vertical hole 40 are formed at the upper end. A partition wall 41 having a U-shaped cross section is inserted into the vertical hole 40 so that a gap 42 is formed between the partition wall 41 and the inner wall of the vertical hole 40, as shown in FIG. As shown in FIG. 2, an upwardly projecting rib 43 is formed on the upper end surface of the partition wall 41. As shown in FIG. The rib 43 is clamped between the cylinder liner 5 and the cylinder block 2, while the lower end of the partition wall 41 is fitted into the scavenging passage 20, thereby fixing the partition wall 41 within the cylinder block 2. In this way, there is a gap 4 inside the cylinder head 2 which acts as a heat insulator.
A scavenging passage 19 is formed in the partition wall 41 between the cylinder block 2 and the inner wall of the cylinder block 2. below,
The scavenging passages 19 and 20 are collectively referred to as a second scavenging passage.

FIG. 3 shows the inner wall surface of the crankcase portion 1c, and FIG. 4 shows the inner wall surface of the crankcase portion 1a. Referring to FIGS. 3 and 4, grooves 21a and 21b are formed on the inner wall surfaces of the crankcase portions 1a and 1c, and extend along the circular periphery thereof, and the insides of these grooves 21a and 21b have a width L. A shallow annular groove 22 is formed. Also, this annular groove 22
A groove 23 extending along the annular groove 22 is formed on the bottom surface of the annular groove 22 . The grooves 21a, 21b are connected to each other at their lower ends 24, and one end 25 of the groove 23 connects the lower ends of the grooves 21a and 21b via a hole 26 drilled in each crankcase part 1a, 1c. 24. On the other hand, the other end 27 of the groove 23 is connected to a short vertical groove 28 extending downward. As shown in FIG. 2, an annular plate 29 is fitted into the annular groove 22, and as shown in FIG.
When c are superimposed on each other, crankcase portion 1b causes crankcase portions 1a and 1c, respectively.
pressed on top. Accordingly, from FIGS. 2, 3, and 4, the crankcase parts 1a, 1b, 1
It can be seen that when the crank case 1 is formed by overlapping the grooves 21a, 21b, 23, and 28, the grooves 21a, 21b, 23, and 28 form passages. Furthermore, it can be seen from FIGS. 2 and 6 that the grooves 21a and 21b are deeper than the groove 23. Each crankcase part 1a, 1c
A groove 30 having approximately the same depth as the grooves 21a and 21b and forming the scavenging passage 20 is provided at the upper end of the inner wall surface of the groove 30.
is formed, and each groove 21 is formed at both ends of the bottom of this groove 30.
a and 21b are opened. As shown in FIGS. 1 and 2, a horizontal hole 31 is formed in the lower end of the crankcase portion 1b and is aligned with each vertical groove 28 formed in each crankcase portion 1a, 1c. 31 is connected to the inside of the crank chamber 8 through a vertical hole 32 bored on the bottom wall surface of the crank chamber 8. In this way, each scavenging passage 20 has a groove 21a,
21b, the hole 26, the grooves 23, 28, the horizontal hole 31, and the vertical hole 32. Below, grooves 21a, 21b, hole 26, groove 2
3, 28, horizontal hole 31, and vertical hole 32 to form the first
It is called a scavenging passage. Therefore, the crank chamber 8 is connected to the inside of the combustion chamber 6 via this first scavenging passage and the aforementioned second scavenging passage.

During engine operation, fresh air introduced into the crank chamber 8 from the intake hole 11 is compressed as the piston 4 descends, and then forced into the horizontal hole 31 through the vertical hole 32. This fresh air then passes through vertical groove 28 and groove 2.
3. It flows into the grooves 21a and 21b through the hole 26. As can be seen from FIGS. 1 and 6, the groove 23
Since the cross-sectional area of is extremely small, fresh air flows at high speed in the groove 23 and is then sent into the grooves 21a and 21b. In this way, the fresh air is given flow energy within the groove 23, so that the vaporization of the liquid fuel is promoted during this time. Next, fresh air flows into the grooves 21a, 2
1b, but the cross-sectional area of the grooves 21a and 21b is larger than the cross-sectional area of the groove 23, and the two grooves 2
Since the fresh air is divided into two parts and flows through 1a and 21b, the flow rate decreases. However, the flow rate of the fresh air flowing in the grooves 21a, 21b is fast, and the liquid fuel that could not be vaporized in the grooves 23 flows into the grooves 21a, 21b.
It is fully vaporized inside. After the vaporization of the liquid fuel is sufficiently promoted in this way, the fresh air in the first scavenging passage is sent into the second scavenging passage. At this time, the fresh air sent out from each groove 21a, 21b collides with each other in the scavenging passage 20, and since the cross-sectional area of the scavenging passage 20 is much larger than the cross-sectional area of the grooves 21a, 21b, each groove 21a, 21b The fresh air sent out is rapidly decelerated. This fresh air then rises at a low speed in the scavenging passages 20 and 19,
When the piston 4 opens the scavenging hole 15, it flows into the combustion chamber 6 at a low speed. As described above, the scavenging passage 19 has a heat insulating structure, and therefore, fresh air is maintained at a high temperature while flowing through the scavenging passage 19, and as a result, vaporization is further promoted. When the piston 4 opens the scavenging hole 15 and fresh air flows into the combustion chamber 6, the groove 23 is throttled due to its small cross-sectional area even if the pressure inside the crank chamber 8 is considerably higher than the pressure inside the combustion chamber 6. Due to this throttling effect, fresh air cannot be rapidly blown into the combustion chamber 6, and as a result, the inflow speed of the fresh air is low throughout the inflow period. Since the fresh air flows into the combustion chamber 6 at a low speed in this way, there is almost no flow of residual burnt gas within the combustion chamber 6, thus preventing the heat dissipation of the residual burnt gas, thereby preventing the residual burnt gas from dissipating. The residual burnt gas is kept at a high temperature. Particularly at the beginning of compression during partial load operation, a large amount of residual burnt gas is present in the combustion chamber 6. As described above, the residual burnt gas in the combustion chamber 6 is large in quantity and has a high temperature, so the fresh air sent into the combustion chamber 6 is heated and generates radicals, resulting in an active heat atmosphere ( An atmosphere in which radicals are generated is called an active thermal atmosphere. During the compression stroke, the gas flow in the combustion chamber 6 is very small, so there is little turbulence and thermal energy loss to the combustion chamber wall, so the gas in the combustion chamber 6 becomes increasingly hot as compression progresses, and as a result, the fresh air Generates more radicals. When radicals are being generated in this way, combustion called a pre-flame reaction has already started, and when the gas temperature in the combustion chamber 6 increases at the end of the compression stroke, a hot flame is generated and the ignition plug 7 is not activated. Self-ignites. Then, controlled gentle combustion is performed using the residual burnt gas, and when the piston 4 descends to open the exhaust hole 16, the burnt gas in the combustion chamber 6 is discharged into the exhaust passage 18.

Further, as described above, in order to ensure combustion in an active thermal atmosphere, it is preferable to suppress dissipation of heat to the cylinder wall as much as possible. For this purpose, the cylinder block 2, cylinder head 3 or piston 4 can also be constructed from ceramic, such as silicon nitride.

Note that in this specification, the term "thermal insulation structure" refers to a heat insulation structure for the scavenging passage as shown in FIG.

As described above, according to the present invention, by providing at least the scavenging passage with a heat-retaining structure, vaporization of the fuel is promoted, thereby making it possible to promote the creation of an active thermal atmosphere.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a two-stroke internal combustion engine according to the present invention, Fig. 2 is a side sectional view of Fig. 1, Fig. 3 is a view showing the inner wall surface of the crankcase portion 1c, and Fig. 4 is the crankcase portion. Fig. 5 is a plan view of the crankcase, Fig. 6 is a bottom view of the crankcase, and Fig. 7 is a view showing the inner wall surface of Fig. 2.
It is a sectional view taken along a line. 11... Intake hole, 15... Scavenging hole, 16... Exhaust hole, 19, 20... Scavenging passage, 41... Partition wall,
42...Void.

Claims (1)

[Claims] 1. A scavenging passage that communicates the engine crank chamber and the combustion chamber with a first scavenging passage that has a small cross-sectional area and is connected to the crank chamber, and a first scavenging passage that is connected to the first scavenging passage and has a larger cross-sectional area than the first scavenging passage. short second
Activated thermal atmosphere combustion 2 in which the second scavenging passage is connected to a scavenging hole opening into the combustion chamber, and the scavenging passage has a heat-retaining structure to promote vaporization of liquid fuel in fresh air. cycle internal combustion engine.