Internal-combustion engines – Charge forming device – Including cylinder pressure or temperature responsive means
Reexamination Certificate
2002-12-06
2004-04-20
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Including cylinder pressure or temperature responsive means
C123S299000, C123S447000, C701S105000
Reexamination Certificate
active
06722345
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Applications No. 2001-372257 filed on Dec. 6, 2001, No. 2002-27657 filed on Feb. 5, 2002 and No. 2002-296154 filed on Oct. 9, 2002 the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection system for an internal combustion engine. More in details, the invention relates to a fuel injection system for executing multi-injection including preceding injection and succeeding injection.
2. Description of Related Art
JP-2001-140689A discloses an accumulator fuel injection apparatus. According to an accumulator fuel injection apparatus, fuel is pressurized by a pump and pressurized fuel is accumulated in a common rail. High pressure fuel is distributed into a plurality of injectors from the common rail. The injector injects fuel into a combustion chamber. The accumulator fuel injection apparatus is referred to also as a common rail fuel injection apparatus.
In the case of accumulator fuel injection apparatus, a command injection amount (Q) is calculated by an engine revolution speed (NE) and an accelerator opening degree (ACCP), a command injection timing (T) is calculated by the engine revolution speed (NE) and the command injection amount (Q), electricity conducting time (command injection time: TQ) of an injector drive signal to the injector is calculated by fuel pressure (fuel pressure: Pc) in the common rail detected by a fuel pressure sensor and the command injection amount (Q), and a nozzle needle in the injector is opened by applying the injector drive signal in a pulse-like shape to an electromagnetic valve of the injector until finishing the command injection time (TQ) from the command injection timing (T) to thereby control the injection amount and the injection timing of fuel injected to supply from the injector into a respective cylinder of the engine.
Further, in order to deal with regulations of exhaust gas and noise in the accumulator fuel injection apparatus in recent years, specifically, with an object of reducing noise or vibration and promoting an exhaust gas performance of the engine by carrying out stable combustion from start of main injection, there is executed multi-injection (multi-injection) for carrying out small amounts of a plurality of times of preceding injection (pilot injection) before the main injection (main injection) which can constitute engine torque at a vicinity of top dead center. The multi-injection aims to restrain noise or vibration and promote the exhaust gas performance of the engine and the like in an injector of a specific cylinder of the engine by carrying out twice or more of multi-injection by opening the nozzle needle twice or more by driving the electromagnetic valve of the injector twice or more in the compression stroke and the expansion stroke of the engine (for example, once or more of pilot injection and main injection, or once or more of pre-injection and main injection, or pilot injection or pre-injection and main injection and after injection, or main injection and once or more of post-injection).
However, the injector mounted to the respective cylinder of the engine is constructed by a constitution in which by controlling back pressure of a command piston reciprocally moved in cooperation with the nozzle needle by opening and closing the electromagnetic valve, fuel pressure in a fuel storage provided at a surrounding of the nozzle needle, that is, fuel pressure operated in a direction of opening the nozzle needle overcomes urge force of a spring, etc. operated in a direction of closing the nozzle needle to thereby open the injector and therefore, after the elapse of predetermined injection delay time from starting electricity conduction to the electromagnetic valve of the injector, the nozzle needle is opened, further, after the elapse of predetermined injection finish delay time from finishing electricity conduction to the electromagnetic valve of the injector, the nozzle needle is closed.
Here, during the compression stroke of the engine, in carrying out multi-injection for carrying out once or more of small amounts of pre-injection or pilot injection prior to main injection by executing a plurality of times of electricity conduction to the electromagnetic valve of the injector, there poses a problem that by a change in the fuel pressure in the common rail which is brought about by pre-injection or pilot injection executed prior to main injection, the injection start delay time is shortened or prolonged to thereby bring about a variation in an injection amount relative to an aimed injection amount.
Hence, during the compression stroke of the engine, in executing multi-injection for carrying out once or more of small amounts of pre-injection or pilot injection prior to main injection by executing a plurality of times of electricity conduction to the electromagnetic valve of the injector, by inputting fuel pressure immediately before starting actual injection of preceding injection such as pre-injection or pilot injection and immediately before stating actual injection of succeeding injection such as main injection, injection time period of preceding injection and injection time period of succeeding injection are calculated. Or, as shown by a timing chart of
FIG. 7
, electricity conducting time of the injector drive signal for succeeding injection such as main injection executed after preceding injection such as pre-injection, that is, main injection time is calculated by adding an interval correction amount calculated by using a two-dimensional map of a non-injection interval between the pre-injection and the main injection (play interval) and fuel pressure in the common rail, to basic injection time calculated by a main injection amount (QM) which is set by the engine revolution speed and the command injection amount and the fuel pressure (Pc) in the common rail detected by a fuel pressure sensor.
However, there is a case in which depending on an engine operating condition or operating mode, an error between an actual main injection amount actually injected to supply into the cylinder of the engine and the aimed main injection amount (QM) is increased by only calculating the injection time period of preceding injection and the injection time period of succeeding injection by inputting fuel pressure immediately before starting actual injection of preceding injection such as pre-injection or pilot injection and immediately before starting actual injection of succeeding injection of main injection, further, adding the interval correction amount calculated by play interval and fuel pressure in the common rail during the basic injection time for main injection. As a result of intensive research on the cause, the applicant has found that the higher the combustion chamber pressure (pressure in cylinder) of the engine relative to standard combustion chamber pressure in a case in which preceding injection is not executed at a time point of starting actual injection of main injection, the larger the error between the actual main injection amount and the aimed main injection amount (QM) tends to increase.
According to the common rail fuel injection system, when fuel is injected, the injection amount of the injector is controlled by calculating from a characteristic map formed by calculating a relationship between the fuel injection amount and an injection time characteristic which is set in accordance with the engine operating condition previously by experiment and by outputting an injection command pulse to the injector.
Here, the characteristic map for calculating the fuel injection amount and the injection time characteristic is a map showing the relationship between the fuel injection amount and the injection time by assuming (predicting) fuel injection at predetermined angle at a vicinity of TDC of the engine. Further, although the injection time characteristic is influenced by combustion chamber pressure for injecting fuel and the common
Saeki Takayuki
Takashima Yoshimitsu
Denso Corporation
Nixon & Vanderhye P.C.
Solis Erick
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