US 2003/0196635 A1 · Combustion control apparatus of diesel engine

Abstract

In a combustion control apparatus of a direct-injection diesel engine, in which a fuel is injected at an early timing with an EGR ratio more than a first predetermined value at pre-mixed combustion area (H) where an engine load is relatively low so as to provide a pre-mixed combustion mode, while a diesel combustion mode is provided with the EGR ratio less than a second predetermined value at diffusion combustion area (D), when the operation of the engine 1 transfers from one of the pre-mixed combustion area (H) and the diffusion combustion area (D) to the other thereof, an opening of the an EGR valve 35 is changed and thereby a fuel injection mode is changed after an actual EGR ratio: EGR becomes a predetermined value: EGR1. When the EGR ratio: EGR is within a certain range (SB5→SB13→SB15), a follow-up injection (latter-injection) is executed (SB15, SB7) so that combustion thereby may begin at the timing when the main-combustion beginning at around TDC completes mostly. The latter-injection can make smoke produced by the main-injection burn again effectively. As a result, smoke concentration in the exhaust gas can be reduced greatly, and a transient deterioration of the exhaust gas condition at the transition between the operating areas (H), (D) and the like can be avoided.

Drawings

Drawings are temporarily unavailable. Open the PDF at USPTO

Drawings

Claims17

Dependent claims

A combustion control apparatus of a diesel engine, comprising a fuel injector projecting into a combustion chamber of a cylinder of an engine,

exhaust gas recirculation amount adjusting means for adjusting the amount of recirculated exhaust gas to the combustion chamber,
main-injection control means for controlling said fuel injector, so that the fuel injector injects the fuel at least during the intake stroke and/or the compression stroke of cylinder at a first engine operating condition to make a first combustion state where the rate of pre-mixed combustion is greater than that of diffusion combustion, while so that the fuel injector injects the fuel at least at around the top dead center of the compression stroke of cylinder at a second engine operating condition to make a second combustion state where the rate of diffusion combustion is greater than that of pre-mixed combustion, and
exhaust gas recirculation control means for controlling said exhaust gas recirculation amount adjusting means, in which an EGR value relating to the amount of recirculated exhaust gas at said first engine operating condition is larger than a first predetermined value, while the EGR value at said second engine operating condition is smaller than a second predetermined value which is smaller than said first predetermined value,
the combustion control apparatus comprising:
latter-injection control means for performing a latter-injection when the engine operating condition transfers from one of said first and second engine operating conditions to the other thereof, wherein the fuel is injected by said fuel injector within a predetermined range of the expansion stroke and/or the exhaust stroke of cylinder after the main-injection fuel injected into the combustion chamber by controlling said fuel injector by said main-injection control means begins to burn.

2 more elements

A combustion control apparatus of a diesel engine, comprising:

a fuel injector projecting into a combustion chamber of a cylinder of an engine;
an exhaust gas recirculation amount adjusting valve adjusting the amount of recirculated exhaust gas to said combustion chamber;
a sensor for sensing an engine speed;
a sensor for sensing the amount of intake air of engine;
a sensor for sensing the amount of accelerator operation;
and
a control unit for controlling said fuel injector and said exhaust gas recirculation amount adjusting valve at least according to signals from said sensors,
wherein said control unit comprises:
operating area determination section that determines at least according to the engine speed and the accelerator operation amount whether the engine operation is at a first engine operating area where the engine operation is relatively at low engine load and low engine speed or a second engine operating area where the engine operation is relatively at high engine load and/or high engine speed;
main-injection control section that controls said fuel injector, so that the fuel injector injects the fuel during the intake stroke and/or the compression stroke of cylinder at said first engine operating area, while so that the fuel injector injects the fuel at the timing which is delayed from the timing of the first operating area at said second engine operating area;
exhaust gas recirculation control section that controls said exhaust gas recirculation amount adjusting valve, in which an EGR value relating to the amount of recirculated exhaust gas at said first engine operating area is larger than a first predetermined value, while the EGR value at said second engine operating area is smaller than a second predetermined value which is smaller than said first predetermined value;
latter-injection control section that performs a latter-injection when the engine operation transfers from one of said first and second engine operating areas to the other thereof, wherein the latter-injection fuel is injected by said fuel injector after the main-injection fuel injected into the combustion chamber by controlling said fuel injector by said main-injection control section begins to burn and when a heat release rate by the combustion of the main-injection fuel becomes less than a predetermined value;
and
main-injection amount compensation section that reduces the amount of the main-injection fuel so as to offset an increase of engine torque by the latter-injection when said latter-injection control section performs the latter-injection.

11 more elements

Dependencies are inferred from the claim text.

Description19,575 words

Summary4,508 words

#The present invention relates to a combustion control apparatus of a direct-injection diesel engine, and in particular, belongs to a technical field relating to a transient control at a change of a combustion state of engine.

#In general, a direct-injection diesel engine injects a fuel into a combustion chamber with high pressure and high temperature at around the top dead center of the compression stroke of cylinder, so that the fuel is burned by its self-ignition. Here, the fuel injected into the combustion chamber proceeds being divided (atomized) into minute liquid drops by a collision with air having high density, and forms substantially a cone-shape fuel spray. The fuel evaporates from surfaces of the fuel drops and forms a fuel mixture by involving air surrounding around mainly a front end and a periphery of the fuel spray. Then, the fuel mixture is self-ignited when it becomes a certain condition with its appropriate concentration and temperature necessary for an ignition, and begins to burn (pre-mixed combustion). Then, it is considered that the portion beginning to burn becomes a core and diffusion combustion is performed involving surrounding fuel vapor and air.

#In such a normal combustion of the diesel engine (hereinafter, also referred to as diesel combustion, simply), the initial pre-mixed combustion may be followed by the diffusion combustion that burns most part of fuel. Here, nitrogen oxides (NOx) is produced at a portion, in which an air excessive ratio λ is nearly 1 in the fuel spray (fuel mixture) having un-homogeneous concentration, due to a rapid generation of heat, and also smoke is produced at a portion, in which a fuel concentration is too high, due to a lack of air. Conventionally, some measures to reduce NOx or smoke are took, such as recirculating part of an exhaust gas into an intake air (Exhaust Gas Recirculation, hereinafter, referred to as EGR, simply) and increasing injection pressure of fuel.

Brief description of the drawings23 figures

#FIG. 1 is an entire structure diagram of a combustion control apparatus of engine according to the first embodiment of the present invention.

#FIG. 2 is a diagram for showing an exemplified control map to change a combustion mode of engine.

#FIG. 3 is an explanatory diagram for showing schematically a state of injection operation by an injector.

Detailed description14,523 words

#Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

#Embodiment 1

#FIG. 1 shows an exemplified combustion control apparatus of diesel engines A according to an embodiment of the present invention. A reference numeral 1 denotes a diesel engine installed in a vehicle. The engine 1 comprises a plurality of cylinders 2, 2, . . . (only one cylinder is shown). A reciprocating piston 3 is inserted in each cylinder 2, and thereby a combustion chamber 4 is formed in each cylinder. An injector 5 (fuel injector) is provided at a ceiling of the combustion chamber 4, and a fuel with high pressure is injected directly into the combustion chamber 4 through injection ports formed at an end of the injector. Meanwhile, a base of the injector 5 at each cylinder 2 is coupled to a common fuel delivery pipe 6 (common rail) by respective branch pipes 6a, 6a, . . . (only one is shown). The common rail 6 is coupled to a high-pressure supply pump 9 by a fuel supply pipe 8 and accumulates the fuel from the supply pump 9 at a high pressure state so as to supply the fuel to the injectors 5, 5, . . . at any timing. A fuel pressure sensor 7 to sense its internal fuel pressure (common rail pressure) is provided.

Combustion control apparatus of diesel engine

Life of this patent

Combustion control apparatus of diesel engine

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims17

Description19,575 words

Drawings

Classification12 codes

Life of this patent

Description19,575 words