Internal combustion engine, controller and method

Details Internal combustion engine, controller and method Internal combustion engine, controller and method

1999-07-07

2001-04-03

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Combustion chamber means having fuel injection only

Having a particular relationship between injection and...

C123S568210, C060S274000, C060S276000, C060S285000

Reexamination Certificate

active

06209515

ABSTRACT:

INCORPORATION BY REFERENCE
The disclosure of each of Japanese Patent Applications, No. HEI 10-233110 filed on Aug. 19, 1998, No. HEI 10-200651 filed on Jul. 15, 1998, No. HEI 10-278269 filed on Sep. 30, 1998, No. HEI 10-214300 filed on Jul. 29, 1998, No. HEI 10-205046 filed on Jul. 21, 1998, No. HEI 10-271615 filed on Sep. 25, 1998, No. HEI 10-234653 filed on Aug. 20, 1998, No. HEI 10-248644 filed on Sep. 2, 1998, No. HEI 10-299882 filed on Oct. 21, 1998, No. HEI 10-292186 filed on Oct. 14, 1998, No. HEI 10-298614 filed on Oct. 20, 1998, No. HEI 10-294034 filed on Oct. 15, 1998 and No. HEI 10-320927 filed on Nov. 11, 1998, including the specifications, drawings and abstracts, is incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an internal combustion engine having a combustion chamber into which inert gas is introduced so as to cause combustion.
2. Description of Related Art
Conventionally, in an internal combustion engine, for example, in a diesel engine, in order to restrict the generation of NOx, an engine exhaust passage and an engine intake passage are connected by exhaust gas recirculation (hereinafter, refer to EGR) so as to recirculate exhaust gas, that is, EGR gas into the engine intake passage via the EGR passage. In this case, since the EGR gas has a relatively high specific heat and accordingly can absorb a large amount of heat, the combustion temperature within the combustion chamber is lowered as an amount of the EGR gas is increased, that is, a rate of the EGR (EGR gas amount/(EGR gas amount+intake air amount)) is increased. When the combustion temperature is lowered, the generation amount of NOx is lowered, so that the greater the EGR rate is increased, the less the generation amount of NOx becomes.
As mentioned above, it has been conventionally known that the generation amount of NOx can be lowered when the EGR rate is increased. However, in the case where the EGR rate is increased, the generation amount of soot, that is, smoke suddenly starts increasing when the EGR rate is over a certain limit. With respect to this point, it has been conventionally considered that the smoke is unlimitedly increased when the EGR rate is increased further, so that it has been considered that the EGR rate at which the smoke suddenly starts increasing is the maximum allowable value of the EGR rate.
Accordingly, the EGR rate has been conventionally defined to stay within a range which is not over the maximum allowable limit. The maximum allowable limit of the EGR rate is significantly different in correspondence to a type of the engine and a fuel, however, is within a range between about 30% and 50%. Therefore, in the conventional diesel engine, the EGR rate is restricted to a range in which about 30% and 50% is the maximum.
As mentioned above, since it has been conventionally considered that the maximum allowable limit exists with respect to the EGR rate, the EGR rate has been defined within the range which does not exceed the maximum allowable limit and so that the generation amount of smoke becomes as little as possible. However, even when the EGR rate is defined so that the generation amount of NOx and smoke becomes as small as possible, a reduction of the generation amount of NOx and smoke has a limit. In fact, the generation of a considerable amount of NOx is inevitable.
SUMMARY OF THE INVENTION
In the process of researching combustion in the diesel engine, it has been found that when making the EGR rate greater than the maximum allowable limit, the smoke is suddenly increased as mentioned above. However, the generation amount of the smoke has a peak, and when further increasing the EGR rate over the value at which the peak occurs, smoke suddenly starts reducing at this time, so that when setting the EGR rate to a value equal to or more than 70% at a time of an idling operation or strongly cooling the EGR gas, the smoke becomes substantially 0, that is, the soot is hardly generated when setting the EGR rate to the value equal to or more than 55%. Further, it has been found that the generation amount of NOx becomes a significantly small amount at this time.
Thereafter, on the basis of this information, a consideration has been performed with respect to the reason why the soot is not generated. As a result, a new combustion system recently has been obtained that can simultaneously reduce the soot and NOx. The new combustion system will be described in detail below. In summary, it is based on a principle that the growth of a hydrocarbon is stopped in the middle of the process by which the hydrocarbon grows into soot.
That is, it has been ascertained as a result of many experiments and much research that the growth of the hydrocarbon stops in the middle of the process before becoming soot when the temperature of the fuel and the surrounding gas at a time of combustion within the combustion chamber is equal to or less than a certain temperature, and that the hydrocarbon grows into soot at a stroke when the temperature of the fuel and the surrounding gas reach a certain temperature. In this case, the temperature of the fuel and the surrounding gas is greatly influenced by an endothermic effect of the gas surrounding the fuel at a time when the fuel is burned, so that it is possible to control the temperature of the fuel and the surrounding gas by adjusting the heat absorption amount of the gas surrounding the fuel in correspondence to the generation amount at a time of the combustion of the fuel.
Accordingly, when restricting the temperature of the fuel and the surrounding gas at a time of combustion within the combustion chamber to the level equal to or less than the temperature at which the growth of the hydrocarbon stops, soot is not generated. Thus, it is possible to restrict the temperature of the fuel and the surrounding gas at a time of combustion within the combustion chamber to a level equal to or less than the temperature at which the growth of the hydrocarbon stops by adjusting the heat absorption amount of the gas surrounding the fuel. On the contrary, the hydrocarbon whose growth has been stopped before becoming soot can be easily purified by an after treatment using an oxidation catalyst or the like. This is a basic principle of the new combustion system.
In the new combustion system, the fuel injection timing at which stable combustion can be obtained is limited to a relatively narrow range of a crank angle. That is, when the fuel injection timing is quickened, the injected fuel is heated by the compressed high temperature gas for a long time, so that the temperature of the fuel and the surrounding gas becomes high at a time of combustion. As a result, since a hydrocarbon grows to soot, smoke is generated. On the contrary, when the fuel injection timing is delayed, the temperature of the injected fuel is not increased as much. Most of the fuel, thus, is not burned, leading to misfire.
In this new combustion system, there exists an optimum range of a crank angle at which a stable combustion can be obtained in a state where no smoke is generated and no misfire is generated with respect to the fuel injection timing. Accordingly, it is necessary to perform fuel injection at the optimum range of the crank angle in the new combustion system.
However, the optimum range of the crank angle at which the stable combustion can be obtained is changed in accordance with a value of a parameter for operating an engine which influences a temperature of a fuel and a surrounding gas at a time of burning within a combustion chamber, for example, an air fuel ratio, an EGR rate, a temperature of an intake gas flowing within the combustion chamber and the like.
For example, as the temperature of the intake gas flowing to the combustion chamber becomes higher, the temperature of the gas within the combustion chamber becomes higher, so that the temperature of the injected fuel is increased. In this case, in order to prevent smoke from being generated, it is necessary to shorten the heating time of th

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