JP2002180884A - Fuel injection method for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of problems caused by the injection of excessive fuel in an early period of fuel injection when an accelerator is stepped for re-accelerating during decelerating the engine in a common rail-type fuel injection system. SOLUTION: When the accelerator is stepped for re-accelerating during decelerating the engine, the target common rail pressure PS and the actual common rail pressure P at that time are compared, a correction value α in an injection starting period is determined on the basis of the deviation ΔP, and an actual injection starting period A is delayed by the mount of the correction value αto a target injection starting period AS to make the actual injection amount be approximately agreed with the target injection amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection method for an engine for injecting fuel stored in a common rail in a state of pressure from an injector into a combustion chamber, and more particularly to an accelerator pedal for accelerating the engine again during deceleration. The present invention relates to a fuel injection method for an engine, which prevents a problem caused by excessive injection of fuel due to a high actual common rail pressure with respect to a target common rail pressure in a case where the target common rail pressure is high.

[0002]

2. Description of the Related Art A common rail fuel injection system has been used as a system for increasing the injection pressure of an engine for fuel injection and optimally controlling injection conditions such as fuel injection timing and injection amount according to the operating state of the engine. Are known.

FIG. 7 is a block diagram showing an outline of a common rail fuel injection system. In the common rail fuel injection system, the fuel in the fuel tank 1 is pressurized by a fuel pump 2 which is, for example, a plunger type variable displacement high pressure pump. The fuel pump 2 is driven by an engine output. The fuel pump 2 boosts the fuel to a required predetermined pressure and supplies the fuel to a common rail 4 through a fuel pipe 3 to store the fuel in a pressure-accumulated state. The fuel pump 2 is provided with a flow control valve 5 for maintaining the fuel pressure in the common rail 4 at a predetermined pressure, and the fuel relieved from the fuel pump 2 is supplied to the fuel tank 1 by a return pipe 6.
Is returned to.

The fuel in the common rail 4 is supplied to a fuel supply pipe 7
Is supplied to a plurality of injectors 8 and injected into a combustion chamber of an engine (not shown). Of the fuel supplied from the fuel supply pipe 7 to the injector 8, the fuel not consumed for injection into the combustion chamber is returned to the fuel tank 1 through the return pipe 9.

The controller 10 which is an electronic control unit
Includes a cylinder discrimination signal 1 from an engine cylinder discrimination sensor.
1. A crank angle signal 12 from a crank angle sensor for detecting top dead center (TDC), an accelerator opening signal 13 from an accelerator opening sensor (engine load sensor) for detecting an accelerator pedal depression amount Acc, Signals from various sensors for detecting the operating state of the engine, such as an engine speed (Ne) signal 14 from the engine speed sensor, are input.

A pressure sensor 15 is provided on the common rail 4, and a pressure signal 16 in the common rail 4 detected by the pressure sensor 15 is input to the controller 10. Based on these signals, the controller 10 sends an injection command 18 to the solenoid valve 17 of the injector 8 so that the engine output becomes an optimum output in accordance with the operating state.
To control the fuel injection conditions, that is, the fuel injection timing (injection start timing and injection end timing) and the injection amount.

The fuel in the common rail 4 is consumed by the injector 8 injecting the fuel, and the pressure in the common rail 4 decreases. However, the controller 10 needs the pressure in the common rail 4 according to the operating state of the engine. The pressure control command 20 is sent to the solenoid valve 19 in the flow control valve 5 of the fuel pump 2 so that the fuel injection pressure is adjusted to control the discharge amount of the fuel pump 2, thereby controlling the pressure of the common rail 4.

In the conventional common rail fuel injection system, the fuel injection start timing and fuel injection end timing are calculated by a crank angle sensor by calculating a phase difference from a preset crank angle (for example, TDC), and a crank angle signal is output. 12
So that the fuel is injected at a predetermined time.
Is controlled by the controller 10 outputting a command pulse (injection command 18) for determining the drive current to the solenoid valve 17 of the first embodiment.

FIG. 8 is a diagram showing the accelerator opening when the accelerator is released from a predetermined accelerator opening state in which the accelerator is depressed, and then the accelerator is depressed again to accelerate. FIG. Target common rail pressure P _S (solid line) and actual common rail pressure P at each point of accelerator opening
FIG. 4 is a diagram showing a relationship with (broken line).

[0010]

As shown in FIG. 8, when the accelerator is released from a predetermined accelerator opening and decelerated,
As shown in FIG. 9, the target common rail pressure P _S is reduced at a predetermined reduction rate. At this time, since the actual common rail pressure P indicated by the broken line is reduced only by the leak from the injector 8, the reduction of the actual common rail pressure P with respect to the target common rail pressure P _S is delayed.

For this reason, if acceleration is performed again before the actual common rail pressure P does not decrease, the actual common rail pressure P is higher than the target common rail pressure P _S in the range W of FIG.

As described above, when the accelerator is depressed to accelerate again during deceleration of the engine, the following phenomenon occurs because the actual common rail pressure P is higher than the target common rail pressure P _S. That is, originally, FIG.
0 as indicated by a solid line, the fuel injection of the target injection amount Q _S so that the target injection waveform X between the target common rail pressure P target injection start timing based on the _S A _S and the target injection end timing B _S However, as described above, since the actual common rail pressure P is higher than the target common rail pressure P _S , the fuel is injected excessively by an increment Z at the initial stage of fuel injection. The actual injection amount increases as in the actual injection waveform Y 'shown by the dashed line.

[0013] As described above, the surplus fuel to the target injection amount Q _S in the fuel injection early is injected, and by increasing 'actual injection quantity Q as' actual injection waveform Y, explosive The combustion pressure rises due to excessive combustion, generating engine noise (crisp noise) and vibration, and there is a problem that uncomfortable feeling in drivability occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In a common rail fuel injection system, when an accelerator is depressed to accelerate again during deceleration of an engine, an initial fuel injection is performed. The present invention provides a fuel injection method for an engine in which a problem due to excessive fuel injection is prevented.

[0015]

According to the first aspect of the present invention,
When the accelerator is depressed to accelerate again while the engine is decelerating, the target common rail pressure at that time is compared with the actual common rail pressure, and a correction value of the injection start timing is obtained from the difference to determine the target injection start timing. The present invention relates to a fuel injection method for an engine, wherein an actual injection amount is made substantially equal to a target injection amount by setting an actual injection start timing delayed by a correction value.

According to a second aspect of the present invention, when the accelerator is depressed to accelerate again during deceleration of the engine, the target common rail pressure at that time is compared with the actual common rail pressure, and the injection amount is determined from the deviation. The present invention relates to a fuel injection method for an engine, wherein a throttle correction coefficient to be reduced is obtained, and the actual injection amount is made substantially coincident with the target injection amount by multiplying the throttle correction coefficient by the target injection amount.

According to a third aspect of the present invention, when the accelerator is depressed to accelerate again during deceleration of the engine, the target common rail pressure at that time is compared with the actual common rail pressure, and when a deviation occurs, A fuel injection method for an engine, wherein a part of the target injection amount is pilot-injected before the target injection waveform.

The present invention operates as follows.

According to the first aspect of the present invention, when the accelerator is depressed to accelerate again while the engine is decelerating, the initial injection rate increases and the amount of fuel injected before the explosion increases. By controlling the injection start timing to delay, the actual injection amount substantially matches the target injection amount, thereby preventing an increase in combustion pressure, reducing engine noise, and at the same time reducing discomfort in drivability during reacceleration. To eliminate.

According to the second aspect of the present invention, when the accelerator is depressed to accelerate again during deceleration of the engine, the throttle correction coefficient for reducing the injection amount from the deviation between the target common rail pressure and the actual common rail pressure is determined. Then, the actual injection amount is made substantially equal to the target injection amount by multiplying the throttle correction coefficient by the target injection amount, thereby preventing an increase in combustion pressure and reducing engine noise.

According to the third aspect of the present invention, when the accelerator is depressed to accelerate again during deceleration of the engine, the target common rail pressure at that time is compared with the actual common rail pressure, and a deviation occurs. The pilot injection of a part of the target injection amount before the target injection waveform suppresses explosive combustion, thereby preventing the increase in combustion pressure, reducing engine noise and drivingability at the time of re-acceleration. To eliminate discomfort.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. As for the common rail type fuel injection system applied to the engine fuel injection device shown in the embodiment, the one shown in FIG. 7 can be used, and therefore, detailed description is omitted in the description of the embodiment.

FIG. 1 shows a first embodiment of the present invention. When the controller 10 of FIG. 7 determines that the vehicle is decelerating, the injection timing of an injection command 18 output from the controller 10 to the injector 8 is shown. FIG. 3 is a control flow chart for controlling the control.

[0024] In Figure 1, when the accelerator is depressed in order to accelerate again during deceleration of the engine, the target injection starting timing A _S of the injection timing map in the injection command 18 is corrected by the correction circuit 21, resulting The injection timing is adjusted according to the actual injection start timing A.

The correction circuit 21 calculates the actual common rail pressure P
(+) And the target common rail pressure P _s (−) are subtracted by the subtractor 22 to obtain a pressure deviation ΔP. Then, the computing unit 23 obtains a correction value α based on a correction amount map in which the relationship between the pressure deviation ΔP and the correction amount is obtained in advance. At this time, when the pressure deviation ΔP is zero or smaller, the correction amount is zero. Then, the thus corrected value α determined, so as to obtain the actual injection start timing A by adding by the adder 24 as -α by signal inversion to the target injection start timing A _S. In the above, when the correction value α is used as it is without inverting the signal, a subtractor may be used instead of the adder 24.

According to the configuration shown in FIG. 1, when the accelerator is depressed to accelerate again during deceleration of the engine, the target injection start timing _AS is delayed by the correction value α as shown in FIG. The actual injection start timing A, and therefore, the actual injection waveform Y '
The injection amount decreases like the actual injection amount Q.

[0027] At this time, by delayed actual injection start timing A to the target injection start timing A _S is alpha, the increment Z and decrement Z 'is exactly the same size as the target injection waveform X as the diagram and correction amount map of the first arithmetic unit 23 is created by this, the actual injection quantity Q becomes substantially coincide with respect to the target injection amount Q _S.

Therefore, when the accelerator is depressed to accelerate again while the engine is decelerating, the actual common rail pressure P does not drop to the target common rail pressure P _S , and the pressure rises again while maintaining a high pressure. The effect of
The amount of fuel that the initial injection rate is injected until the explosion becomes higher had increased, it is possible to substantially match the target injection amount Q _S of the actual injection quantity Q by delaying the injection start timing, which As a result, it is possible to prevent an increase in combustion pressure, reduce engine noise, and at the same time, eliminate uncomfortable feeling in drivability during re-acceleration.

FIG. 3 shows a second embodiment of the present invention. When the controller 10 in FIG. 7 determines that the vehicle is decelerating, the fuel injection of the injection command 18 output from the controller 10 to the injector 8 is performed. FIG. 3 shows a control flow diagram for controlling the quantity.

[0030] In Figure 3, when the accelerator is depressed in order to accelerate again during deceleration of the engine, the target injection amount Q _S of the injection command 18 is corrected by the correction circuit 25, the resulting actual injection quantity Q The injection amount is adjusted.

The correction circuit 25 calculates the actual common rail pressure P
(+) And the target common rail pressure P _s (−) are subtracted by the subtractor 26 to obtain a pressure deviation ΔP. Then, the calculator 27 obtains an aperture correction coefficient K based on a correction amount map in which the relationship between the pressure deviation ΔP and the correction amount is obtained in advance. Then, the throttle correction coefficient K to 0-1 thus obtained, via the multiplier 28 to the target injection amount Q _S so as to obtain the actual injection quantity Q by multiplication.

According to the configuration shown in FIG. 3, when the accelerator is depressed to accelerate again during deceleration of the engine, control is performed so as to reduce the fuel injection amount. For example, as shown in FIG. 4, it decreases the amount of fuel injection by advancing than the target injection end timing B _S of the fuel injection end timing.

[0033] At this time, by adjusting the settings of the aperture correction coefficient K, so that the actual injection quantity Q by actual injection waveform Y ₁ indicated by a one-dot chain line is substantially equal to the target injection amount Q _S by the target ejection waveform X can be adjusted to, also adjusted to the actual injection quantity Q by actual injection waveform Y ₂ as shown by the broken line is reduced decrease Z 'only addition to the target injection amount Q _S by the target ejection waveform X be able to.

Accordingly, when the accelerator is depressed to accelerate again while the engine is decelerating, the actual common rail pressure P does not drop to the target common rail pressure P _S , and the pressure rises again while maintaining a high pressure. The effect of
The initial injection rate increased and the amount of fuel injected before the explosion increased, but by reducing the amount of fuel injected, it is possible to prevent an increase in combustion pressure and reduce engine noise. .

FIG. 5 shows a third embodiment of the present invention. When the controller 10 shown in FIG. 7 determines that the vehicle is decelerating, a pilot injection 18 output from the controller 10 to the injector 8 causes pilot injection. FIG. 4 shows a control flow chart for performing the control.

In FIG. 5, when the accelerator is depressed to accelerate again during deceleration of the engine, the actual common rail pressure P (+) and the target common rail pressure P
_S (−) is subtracted by the subtractor 29 to obtain a pressure deviation ΔP. The determination circuit 30 controls so that pilot injection is performed when the pressure deviation ΔP occurs, and is not performed when the pressure deviation ΔP does not occur.

According to the configuration of FIG. 5, as shown in FIG.
When the deviation ΔP of pressure occurs, by pilot injection 31 a portion of the target injection amount Q _S in the previous target injection waveform X,
Explosive combustion is suppressed, thereby preventing an increase in combustion pressure, reducing engine noise, and eliminating discomfort in drivability during reacceleration.

[0038]

According to the first aspect of the invention, when the accelerator is depressed to accelerate again while the engine is decelerating, the initial injection rate increases and the amount of fuel injected before the explosion increases. The problem of increase is controlled by delaying the injection start timing so that the actual injection amount substantially matches the target injection amount, thereby preventing an increase in combustion pressure,
This has the effect of reducing engine noise and at the same time eliminating discomfort in drivability during re-acceleration.

According to the second aspect of the present invention, when the accelerator is depressed to accelerate again during deceleration of the engine, the throttle correction for reducing the injection amount based on the deviation between the target common rail pressure and the actual common rail pressure. The actual injection amount is reduced so as to be substantially equal to or less than the target injection amount by multiplying the target correction amount by multiplying the throttle correction coefficient by the target correction amount, thereby preventing an increase in combustion pressure. ,
This has the effect of reducing engine noise.

According to the third aspect of the present invention, when the accelerator is depressed to accelerate again during deceleration of the engine, a deviation is generated by comparing the target common rail pressure at that time with the actual common rail pressure. At the time, a part of the target injection amount is pilot-injected before the target injection waveform to suppress explosive combustion, thereby preventing an increase in combustion pressure,
This has the effect of reducing engine noise and at the same time eliminating discomfort in drivability during re-acceleration.

[Brief description of the drawings]

FIG. 1 is a control flow chart showing a first embodiment of a fuel injection method for an engine according to the present invention.

FIG. 2 is a diagram showing the operation of FIG. 1;

FIG. 3 is a control flowchart showing a second embodiment of the engine fuel injection method of the present invention.

FIG. 4 is a diagram showing the operation of FIG. 3;

FIG. 5 is a control flow chart showing a third embodiment of the engine fuel injection method of the present invention.

FIG. 6 is a diagram showing the operation of FIG. 5;

FIG. 7 is a block diagram showing an outline of a common rail fuel injection system.

FIG. 8 is a diagram showing an accelerator opening when the accelerator is released from a predetermined accelerator opening state where the accelerator is depressed, and then the accelerator is depressed again to accelerate.

9 is a diagram showing a relationship between a target common rail pressure and an actual common rail pressure at each time point of the accelerator opening of FIG. 8;

FIG. 10 is a diagram showing a relationship between a target injection waveform and an actual injection waveform at the time of the target common rail pressure and the actual common rail pressure in FIG. 9;

[Explanation of symbols]

31 Pilot injection A Actual injection start timing A _S Target injection start timing K Throttle correction coefficient P Actual common rail pressure P _S Target common rail pressure Q Actual injection amount Q _S Target injection amount X Target injection waveform Y Actual injection waveform α Correction value

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideo Nagakura 3-1-1, Hinodai, Hino-shi, Tokyo Hino Motors Co., Ltd. (72) Koji Kondo 3-1-1, Hinodai, Hino-shi, Tokyo Hino Motors (72) Inventor Masayoshi Komiya 3-1-1, Hinodai, Hino-shi, Tokyo Fino term in Hino Motors Co., Ltd. (reference) 3G301 HA02 JA03 JA37 KA15 LB11 LC01 MA11 MA18 MA23 NA06 NA08 NC02 ND01 NE06 NE12 PB08A PE01A PE03A PE05A PF03A

Claims (3)

[Claims] When the accelerator is depressed to accelerate again during deceleration of the engine, the target common rail pressure at that time is compared with the actual common rail pressure, and a correction value of the injection start timing is obtained from the difference, A fuel injection method for an engine, wherein an actual injection amount is made substantially equal to a target injection amount by setting an actual injection start timing delayed by a correction value from a target injection start timing. 2. When the accelerator is depressed to accelerate again during deceleration of the engine, the target common rail pressure at that time is compared with the actual common rail pressure, and the throttle correction coefficient for reducing the injection amount based on the difference is calculated. A fuel injection method for an engine, wherein the actual injection amount is substantially equal to the target injection amount by multiplying the throttle correction coefficient by the target injection amount. 3. When the accelerator is depressed to accelerate again during deceleration of the engine, the target common rail pressure at that time is compared with the actual common rail pressure. Fuel injection method for an engine, wherein pilot injection is performed before a target injection waveform.