JPS6149494B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a two-stroke diesel engine.

As a two-stroke gasoline engine, the fuel consumption rate can be greatly improved, harmful components in exhaust gas can be greatly reduced, and even quieter operation can be achieved. By narrowing the area on the side closer to the crank chamber, fresh air flows into the combustion chamber at a low speed to create an active thermal atmosphere within the combustion chamber, and this atmospheric state is then maintained during the compression stroke until the end of the compression stroke. The present inventor has already proposed a two-cycle gasoline engine in which fresh air is ignited and burned without using a spark plug.

The present invention performs active thermal atmosphere combustion as described above in a two-stroke diesel engine, thereby greatly improving the fuel consumption rate and greatly reducing harmful components in exhaust gas, especially the generation of idle knock. Silent operation can be achieved by preventing
Our goal is to provide cycle diesel engines.

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

Figures 1 and 2 show the loop scavenging type 2 according to the present invention.
The case where it is applied to a cycle diesel engine is shown.
It goes without saying that the present invention can also be applied to other types of diesel engines, such as a uniflow two-stroke diesel engine equipped with an exhaust valve. 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 is a fuel injection valve arranged at the apex of the combustion chamber 6;
is the crank chamber formed in the crankcase 1,
9 is a balance weight, 10 is a connecting rod, 11 is a plurality of scavenging holes formed in the cylinder liner 5, 1
2 is a plurality of exhaust holes formed in the cylinder liner 5; 13 is an exhaust passage; 14 is an intake passage for introducing air or a fuel-air mixture into the crank chamber 8; and 15 is a passage from the intake passage 14 to the crank chamber 8. The reed valves 16, which can only flow inward, each represent an engine-driven fuel injection pump, which is connected to the fuel injection valve 7 via a fuel conduit 17. The compression ratio of the diesel engine shown in FIG. 1 is set to a low compression ratio of 12 to 14.
A scavenging passage 19 opening into the crank chamber 8 at an opening 18 is formed in the cylinder block 2 and crankcase 1, and this scavenging passage 19 is connected to the scavenging hole 11 via a branched scavenging passage branch 20. A scavenging control valve 21 is arranged in the scavenging passage 19 near the opening 18, and the valve shaft 2 of this scavenging control valve 21
The tip of an arm 23 fixed to 2 is connected to an accelerator pedal 25 via a wire 24. The relationship between the opening amount of the scavenging control valve 21 and the depression amount of the accelerator pedal 25 is shown by curve A in FIG. In addition, in FIG. 3, the vertical axis R represents the scavenging control valve 21.
The horizontal axis L indicates the opening amount of the accelerator pedal 2.
It shows the amount of depression of No. 5, that is, the load. It can be seen from FIG. 3 that the scavenging control valve 21 gradually opens until the load reaches about 40% of the full load, and when the load increases beyond that, it opens fully. As shown in FIG. 1, a fuel supply device 27 is provided within the intake passage 14 downstream of the air filter 26. In the embodiment shown in FIG. 1, this fuel supply device 27 is provided with a fuel injection nozzle 29 opening in a small bench lily 28 and a fuel passage 30 leading from this fuel injection nozzle 29 to a float chamber (not shown). It is comprised of a solenoid valve 31 that controls the supply of fuel. The solenoid of this electromagnetic valve 31 is the accelerator pedal 25
It is connected to a power source via a switch 32 that responds to the depression of the switch. In FIG. 4, the vertical axis S shows the on/off operation of the switch 32, and the horizontal axis L shows the amount of depression of the accelerator pedal 25, that is, the load. Fourth
As is clear from the figure, when the load is low (lower than _L0) , the switch 32 is turned off, and at this time the solenoid valve 31 opens the fuel passage 30 as shown in FIG. Therefore, at this time, fuel is supplied into the intake passage 14, and thus the fuel-air mixture is supplied to the reed valve 1.
5 into the crank chamber 8. Incidentally, not only light oil but also gasoline can be used as this fuel, and the amount of fuel supplied is set so that the air-fuel ratio is within the range of 15 to 20. On the other hand, when the engine load exceeds the load _L0 , the switch 32 is turned on and the fuel passage 30 is turned on.
is shut off by the solenoid valve 31, so that only air is supplied into the crank chamber 8 at this time. Note that fuel is constantly injected from the fuel injection valve 7 so that the fuel injection amount gradually increases as the load increases.
Further, the fuel injection timing of the fuel injection valve 7 is set to be gradually advanced as the load increases.

During low load operation when the scavenging control valve 21 is slightly open and fuel is being supplied into the intake passage 14 from the fuel supply device 27, the fuel-air mixture introduced into the crank chamber 8 via the reed valve 15. The air is compressed as the piston 4 descends, and then forced into the scavenging passage 19 through the opening 18. At this time, the fuel-air mixture flowing in the scavenging passage 19 is decelerated by the throttling action of the scavenging control valve 21, and then the fuel-air mixture flows from the scavenging hole 11 into the combustion chamber 6 via the scavenging passage branch 20. Inflow at low velocity. Further, when the combustion air mixture passes through the scavenging control valve 21, turbulence occurs in the fuel/air mixture; however, as shown in FIG.
By arranging the fuel-air mixture at a location remote from the opening 18, that is, in the vicinity of the opening 18, the turbulence of the fuel-air mixture is attenuated in the scavenging passage 19 before reaching the scavenging hole 11. As mentioned above, the fuel-air mixture flowing into the combustion chamber 6 has a low velocity and the turbulence is attenuated, so that when the fuel-air mixture flows into the combustion chamber 6, there is no residual burnt gas in the combustion chamber 6. Little gas flow occurs, thus preventing the dissipation of heat from the residual burnt gases, thereby keeping them at a high temperature. Moreover, the fuel-air mixture that has flowed into the combustion chamber 6 is surrounded by high-temperature residual burnt gas. Particularly at the beginning of compression during low-load operation, a large amount of residual burnt gas exists in the combustion chamber 6, and the fuel-air mixture is surrounded by a large amount of high-temperature residual burnt gas. The fuel at the contact interface with the residual burnt gas is thermally decomposed. As a result, a large amount of radicals such as OH・, CH・, C ₂・, H・, etc. are generated in the gas phase at the contact surface between the fuel-air mixture and the residual burnt gas, and thus they are released into the combustion chamber 6. An activated thermal atmosphere (an atmosphere in which a large amount of radicals are generated is referred to as an active thermal atmosphere) is formed. During the compression stroke, the gas flow in the combustion chamber 6 is very small, so there is little thermal energy loss to the combustion chamber wall, and therefore the gas in the combustion chamber 6 becomes increasingly hot as compression progresses, and as a result, more radicals are generated. do. Although a large amount of radicals are thus generated during the compression stroke, the gas temperature within the combustion chamber 6 is still not high enough to cause rapid combustion. Then, at the end of the compression stroke, when the gas temperature in the combustion chamber 6 becomes sufficiently high, self-ignition occurs and rapid combustion occurs. On the other hand, since the ambient temperature is maintained at a high temperature, the fuel injected from the fuel injection valve 7 at the end of the compression stroke immediately vaporizes and generates radicals, which generates a hot flame and self-ignites at the end of the compression stroke. do. Next, when the piston 4 descends and opens the exhaust hole 12, the burned gas in the combustion chamber 6 flows into the exhaust passage 13.
discharged inside.

On the other hand, during high-load operation when the scavenging control valve 21 is fully opened and the supply of fuel from the fuel supply device 27 is stopped, compression ignition is performed as in a conventional diesel engine.

As mentioned above, in order to promote the generation of radicals in the combustion chamber 6, it is necessary to prevent the heat dissipation of the residual burned gas in the combustion chamber 6. Gas turbulence and flow must be kept extremely small. Further causes of such turbulence and flow include the rapid ejection of exhaust gas from the exhaust hole 12 and exhaust pulsation interference.
In order to prevent these sudden jets of exhaust gas and interference with exhaust pulsation, it is preferable to dispose an exhaust control valve 34 in the exhaust passage 13, as shown by the broken line in FIG. The exhaust control valve 34 is connected to the accelerator pedal 25 via a link mechanism (not shown), and gradually opens as the load increases from low-load operation, as shown by the broken line B in FIG. The exhaust control valve 34 is fully opened before the exhaust gas is fully opened.

Generally speaking, the combustion process is considered as follows. That is, when the fuel is exposed to high temperatures, it thermally decomposes and becomes radicals. These radicals have intense activity, and the radicals react with each other to generate a hot flame, leading to combustion. Therefore, in order to cause combustion, it is necessary to generate a large amount of radicals, and if a large amount of radicals are generated too quickly, they will burn all at once, resulting in so-called diesel knock. However, if radicals are generated early in the compression stroke as in the case of low-load operation in the present invention, reactions between the radicals will have already started during the compression stroke, and therefore the fuel will not be injected in this state. When this happens, combustion starts sequentially starting from the fuel injected first. As a result, the rate of pressure rise is reduced, thereby preventing diesel knock from occurring.

As described above, according to the present invention, by generating a large amount of radicals during the compression stroke, generation of idle knock can be prevented, and quiet operation can thus be achieved.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a two-stroke diesel engine according to the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Fig. 3 shows changes in the opening degrees of the exhaust control valve and the scavenging control valve. The diagram shown in FIG. 4 is a diagram showing the operating state of the switch of FIG. 1. 5...Combustion chamber, 7...Fuel injection valve, 8...Crank chamber, 11...Scavenging hole, 12...Exhaust hole, 14
...Intake passage, 19...Scavenging passage, 21...Scavenging control valve, 27...Fuel supply device.

Claims (1)

[Claims] 1 A scavenging passage that communicates the engine combustion chamber and the crank chamber during the scavenging stroke, an intake passage for supplying air into the crank chamber, and a fuel injection valve for injecting fuel into the engine combustion chamber. In the equipped two-stroke diesel engine, a scavenging control valve that throttles the scavenging passage when the engine is running at low load and fully opens the scavenging passage when the engine is running at high load is placed in the scavenging passage near the crankcase. Fuel is supplied into the intake passage and a fuel-air mixture is supplied from the scavenging passage into the combustion chamber, and when the engine is operating under high load, the fuel supply to the intake passage is stopped and only air is supplied from the scavenging passage into the combustion chamber. A two-stroke diesel engine equipped with a fuel supply device that injects fuel from the fuel injection valve regardless of the engine load.