JP2000130180A - Six stroke diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce not only the discharge of NOx but also the discharge of soot. SOLUTION: In a six stroke diesel engine, one cycle is formed by six strokes such as a suction stroke, first compression stroke, first combustion stroke, second compression stroke, second combustion stroke and exhaust stroke. A first injection fuel out of the fuel injected by one cycle in the cylinder 11 of this engine is directly injected in the cylinder 11 from the latter term of the first compression stroke over the former term of the first combustion stroke and a second injection fuel is directly injected in the cylinder 11 from the initial term over the middle term of the second compression stroke and further it is constituted so that the first injection amount becomes same as the second injection amount or less than the second injection amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a six-stroke diesel engine in which one cycle is formed by six strokes of an intake stroke, a first compression stroke, a first combustion stroke, a second compression stroke, a second combustion stroke, and an exhaust stroke. It is about.

[0002]

2. Description of the Related Art Conventionally, in a 6-stroke diesel engine, as shown in FIGS. 4 and 5, first, in a suction stroke, a piston 2 descends with an intake valve 3 opened, and air is introduced into a cylinder 1 ( 4A, the piston 2 rises in the first compression stroke with the intake valve 3 closed, and the air is compressed (FIG. 4B). From the end of the first compression stroke to the early stage of the first combustion stroke (first expansion stroke), the first fuel is injected into the cylinder 1 from the fuel injection nozzle 8a (FIG. 5), and the piston 2 is moved above the first compression stroke. When reaching the vicinity of the dead center, the air-fuel mixture in the cylinder 1 self-ignites and burns, and the piston 2 descends (first combustion stroke (FIG. 4)
(C))). Next, in the second compression stroke, the piston 2 rises with the intake valve 3 and the exhaust valve 4 closed and the cylinder 1
The burned gas inside is compressed (FIG. 4D). From the end of the second compression stroke to the beginning of the second combustion stroke (second expansion stroke), the second fuel from the fuel injection nozzle 8a is supplied to the cylinder 1
When the piston 2 reaches near the top dead center of the second compression stroke, the air-fuel mixture in the cylinder 1 self-ignites and burns, and the piston 2 descends (second combustion stroke (FIG. 5)). (FIG. 4 (e))). Further, in the exhaust stroke, the piston 2 rises with the exhaust valve 4 opened, and the burned gas in the cylinder 1 is discharged (FIG. 4 (f)).

A paper entitled Performance prediction (analysis and model experiment using a phenomenological model) of a six-stroke diesel engine operating in this manner was presented at the 12th internal combustion engine symposium lecture (July 18-20, 1995). It has been announced. In this paper, when the fuel injected into the cylinder 1 in one cycle is 100% and the first and second fuel injection amounts are 40% and 60%, respectively, N
Ox emission is 1 / of the 4-stroke diesel engine
It is shown to be less than 10. This is because the burned gas generated by the first combustion of the 6-stroke diesel engine contains a large amount of gas that does not contribute to combustion.
It is considered that the second combustion temperature is kept low, and the emission of NOx can be reduced.

[0004]

However, the above conventional 6
In a stroke diesel engine, if the second fuel injection amount is larger than the first fuel injection amount as described above,
There is a problem of discharging a large amount of soot. This is because if a large amount of fuel is injected the second time, the fuel ignites before the fuel is sufficiently mixed with the burned gas in the cylinder, and incomplete combustion due to insufficient mixing with air and insufficient air volume. It is thought that it is. It is an object of the present invention to provide a six-stroke diesel engine that can reduce not only NOx emissions but also soot emissions.

[0005]

The invention according to claim 1 is
As shown in FIGS. 1 and 2, the intake stroke, the first compression stroke,
This is an improvement of a six-stroke diesel engine in which one cycle is formed by six strokes of a first combustion stroke, a second compression stroke, a second combustion stroke, and an exhaust stroke. Its characteristic configuration is 1
Of the fuel injected into the cylinder 11 in the cycle, the first injected fuel is directly injected into the cylinder 11 from the end of the first compression stroke to the first half of the first combustion stroke, and the second injected fuel is injected into the second compression stroke. Is injected directly into the cylinder 11 from the initial period to the middle period, so that the first injection amount is equal to or less than the second injection amount.

[0006] In the six-stroke diesel engine according to the first aspect of the present invention, the fuel injected the second time comes into contact with the high-temperature burned gas, so that it evaporates quickly. Further, since the fuel takes away the heat of the burned gas when the fuel is vaporized (vaporization latent heat), the burned gas is cooled and the compression work of the piston 12 can be reduced. Further, since the fuel is injected into the cylinder 11 early in the second compression stroke, the fuel is sufficiently mixed with the burned gas, and a uniform premixed gas can be formed.
Premixed compression ignition combustion with less Ox and soot is possible.

[0007] The invention according to claim 2 is the invention according to claim 1, and furthermore, as shown in FIGS. 1 and 2, the second injected fuel is supplied to the cylinder 11 from the beginning to the middle of the second compression stroke. It is characterized in that it is configured to be directly injected once or twice or more. In the six-stroke diesel engine according to the second aspect, the fuel to be injected for the second time is injected into the cylinder 11 at an early stage of the second compression stroke and once or twice or more, particularly twice. If the fuel is divided and injected, the fuel is more sufficiently mixed with the burned gas, and a more uniform premixed gas can be formed.
Premixed compression ignition combustion with less Ox and soot is possible.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein as shown in FIGS. 1 and 3, a fuel injection device 16 for injecting fuel into the cylinder 11 is of a common rail type. It is an injection device. In the six-stroke diesel engine according to the third aspect, the first and second fuel injection amounts and injection timings can be freely controlled to desired amounts and timings. In particular, the second fuel injection timing and the number of injections can be freely set.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIGS. 1 to 3, in the six-stroke diesel engine 10, an intake stroke, a first compression stroke, a first combustion stroke (first expansion stroke), a second compression stroke, and a second combustion stroke (second expansion stroke). And 1 in 6 exhaust strokes
A cycle is formed. This engine 10 has a cylinder 1
1, a piston 12 that moves up and down, an intake valve 13 that opens and closes an intake port 13a, an exhaust valve 14 that opens and closes an exhaust port 14a, and a fuel injection device 16 that injects fuel into the cylinder 11. The piston 12 is connected to a crankshaft (not shown) via a connecting rod 17. Although not shown, the intake port 13a is connected to an intake pipe via an intake manifold (FIG. 1).
a is connected to an exhaust pipe through an exhaust manifold (FIG. 1).
And FIG. 3).

The fuel injection device 16 is a common rail type fuel injection device. A unit injector 18 (FIGS. 1 and 3) is provided in each cylinder 11 and injects fuel into each cylinder 11; Room 19
It has a pressure feed pump 21 (FIG. 3) connected via (FIG. 3). As shown in detail in FIG.
The injection nozzle 18a of the injector 18 (FIG. 1)
An electromagnetic valve 18b for controlling the opening and closing of the pump is provided, and a pumping pump 21 is provided with a discharge amount control valve 21a for adjusting a supply amount of the fuel sucked up from the fuel tank 22 to the pressure accumulating chamber 19. The pressure accumulating chamber 19 is provided with a pressure sensor 19a for detecting the pressure of the fuel in the accumulating chamber 19.

A detection output of the pressure sensor 19a is connected to a control input of a controller 27 together with detection outputs of an engine load sensor 23, an engine rotation sensor 24, and a crank angle sensor 26. The control output of the controller 27 is connected to the solenoid valve 18b and the discharge amount control valve 21a, respectively. The fuel pumped by the pressure pump 21 is stored in the pressure accumulating chamber 19 at an extremely high pressure. Further, the controller 27 is configured to control the opening / closing timing and the opening time of the injection nozzle 18a (FIG. 1) of the unit injector 18 based on the detection output of the crank angle sensor 26. Reference numeral 28 in FIG. 3 denotes a muffler connected to the exhaust manifold 29 via an exhaust pipe 31.

A characteristic configuration of the present embodiment is that, among the fuel injected into the cylinder 11 in one cycle, the first injected fuel enters the cylinder 11 from the end of the first compression stroke to the first half of the first combustion stroke. Direct injection is performed, and the second injected fuel is supplied to the cylinder 11 from the beginning to the middle of the second compression stroke.
And the first injection amount is set to be equal to or less than the second injection amount. Further, the second injected fuel is configured to be directly injected into the cylinder 11 once or twice or more from the beginning to the middle of the second compression stroke.

Specifically, 30-50% of the fuel injected into the cylinder 11 in one cycle, preferably 40-45% of the fuel is supplied from the end of the first compression stroke to the first half of the first combustion stroke. Directly into the cylinder 11
The remaining 70 to 50% of the fuel, preferably 60 to 55%, is supplied to the cylinder 1 from the beginning to the middle of the second compression stroke.
It is configured to be directly injected once or twice or more (preferably 2 to 4 times) within one. The reason why the first fuel injection amount is set to 30 to 50% is that if the amount is less than 30%, the amount of burned gas is not sufficient, and if it exceeds 50%, soot is generated. Also, the second fuel injection amount is 7
The reason for setting it to 0 to 50% is that if it is less than 50%, there is a problem that the self-ignition timing of the premixed gas is too early.

The operation of the thus constructed 6-stroke diesel engine will be described. First, in the intake stroke, the piston 12 descends with the intake valve 13 opened, and air is introduced into the cylinder 13 from the intake port 13a (FIG. 1A). Next, in the first compression stroke, the intake valve 1
In a state where 3 is closed, the piston 12 rises to compress the air (FIG. 1B). From the end of the first compression stroke to the first
Early in the combustion stroke, that is, near the compression top dead center, the controller 27 operates the solenoid valve 18 of the unit injector 18.
b (FIG. 3) to directly inject the first fuel from the injection nozzle 18a into the cylinder 11 (FIG. 2). While the fuel is being injected, the air-fuel mixture in the cylinder 11 self-ignites, normal diesel combustion is performed, and the piston 12 descends (first combustion stroke (FIG. 1 (c))). NOx generated at this time is lower by the lower load, and soot generation is also suppressed.

Next, even if the first combustion stroke is completed, the exhaust valve 1
The process proceeds to the second compression stroke without opening the fourth compression stroke. That is, in the second compression stroke, the piston 12 rises in a state where the intake valve 13 and the exhaust valve 14 are closed, and the burned gas in the cylinder 11 is compressed (FIG. 1 (d)). The controller controls the solenoid valve 18b (FIG. 3) of the unit injector 18 from the initial period to the middle period to control the injection nozzle 18
A second fuel injection from a is directly injected into the cylinder 11 in three times (FIG. 2). This injected fuel comes into contact with the high-temperature burned gas, so it evaporates quickly. At the same time, when this fuel evaporates, the fuel takes away the heat of the burned gas (latent heat of vaporization). 12 can be reduced, and the fuel is injected into the cylinder 11 at an early stage of the second compression stroke and three times, so that the fuel is sufficiently mixed with the burned gas and uniform premixing is performed. You can build your mind. In this state, when the piston 12 reaches the vicinity of the compression top dead center of the second compression stroke, the premixed gas self-ignites and burns, and the piston 12 descends (second combustion stroke (FIG. 1)).
(E))). Further, in the exhaust stroke, the piston 12 rises with the exhaust valve opened, and the burned gas in the cylinder 11 is discharged (FIG. 1 (f)).

Since the premixed gas contains a large amount of gas that does not contribute to combustion, the combustion temperature in the cylinder 11 can be kept low, and the emission of NOx can be reduced. Further, air still remains in the burned gas generated in the cylinder 11 after the first combustion stroke, and the ratio of this air to the fuel injection amount is expressed by:
The first and second fuel injection amounts are 30 to 50 respectively.
% And within the range of 70-50%, 2
Ratio of theoretically complete combustion of the second combustion (stoichiometric: St
oichiometric) and the second self-ignition timing can be controlled near the top dead center of the second compression stroke, so that the second combustion can be improved. As a result, the soot remaining in the cylinder 11 in the first combustion is also re-oxidized in the second combustion, and the emission of soot can be reduced.

In the above embodiment, the second fuel is injected into the cylinder from the beginning to the middle of the second compression stroke.
The fuel was injected directly in two separate injections, but the second fuel did not reach the inner wall surface of the cylinder (it did not adhere to the inner wall surface), but was sufficiently mixed with the burned gas in the cylinder to obtain a uniform premixed gas. Can be formed by directly injecting the second fuel directly into the cylinder from the beginning to the middle of the second compression stroke, or
The injection may be performed directly or four times or more.

[0018]

As described above, according to the present invention, 1
Of the fuel injected into the cylinder of a 6-stroke diesel engine in a cycle, the first injected fuel is directly injected into the cylinder from the end of the first compression stroke to the first half of the first combustion stroke, and the second injected fuel is injected into the cylinder. 2 The injection is performed directly into the cylinder from the beginning to the middle of the compression stroke, and the first injection amount is set to be equal to or less than the second injection amount. Fuel comes into contact with the high-temperature burned gas and evaporates quickly.
Further, when the fuel is vaporized, the fuel deprives the burned gas of heat (vaporization latent heat), so that the burned gas is cooled and the compression work of the piston can be reduced. Further, since the fuel is injected into the cylinder at an early stage of the second compression stroke, the fuel is sufficiently mixed with the burned gas, and a uniform premixed gas can be formed. As a result, the second combustion can be improved, soot remaining in the cylinder in the first combustion is also reoxidized in the second combustion,
Soot emissions can be reduced. Further, since the premixed gas contains a large amount of gas that does not contribute to combustion, the combustion temperature in the cylinder can be kept low, and the emission of NOx can be reduced.

If the second injected fuel is configured to be directly injected into the cylinder once or twice or more from the beginning to the middle of the second compression stroke, particularly if the fuel is injected two or more times, In addition, the fuel is more sufficiently mixed with the burned gas, a more uniform premixed gas can be formed, and premixed compression ignition combustion with less NOx and soot can be performed. Further, if a common rail type fuel injection device is used as a fuel injection device for injecting fuel into the cylinder, the first and second fuel injection amounts and injection timings can be freely controlled to desired amounts and timings. In particular, the second fuel injection timing and the number of injections can be freely set.

[Brief description of the drawings]

FIG. 1 is a diagram showing the operation of a six-stroke diesel engine according to an embodiment of the present invention.

FIG. 2 is a timing chart showing fuel injection timing and valve opening / closing timing.

FIG. 3 is a cross-sectional configuration diagram of a common rail fuel injection device including an engine.

FIG. 4 is a diagram corresponding to FIG. 1 showing a conventional example.

FIG. 5 is a timing chart showing the fuel injection timing and the valve opening / closing timing.

[Explanation of symbols]

 Reference Signs List 10 engine 11 cylinder 12 piston 16 fuel injection device

Claims (3)

[Claims] 1. A six-stroke diesel engine in which one cycle is formed by six strokes of an intake stroke, a first compression stroke, a first combustion stroke, a second compression stroke, a second combustion stroke, and an exhaust stroke. (11) One of the fuels injected into
From the end of the first compression stroke, the first injected fuel
During the first half of the combustion stroke, it is directly injected into the cylinder (11), and the second injected fuel is directly injected into the cylinder (11) from the beginning to the middle of the second compression stroke, and the first injection amount is A six-stroke diesel engine, wherein the six-stroke diesel engine is configured to be equal to or less than the second injection amount. 2. The fuel injection system according to claim 1, wherein the second injected fuel is directly injected into the cylinder (11) one or more times from the beginning to the middle of the second compression stroke. Stroke diesel engine. 3. The six-stroke diesel engine according to claim 1, wherein the fuel injection device for injecting fuel into the cylinder is a common rail type fuel injection device.