JPH0771289A - Fuel injection control device - Google Patents

Abstract

PURPOSE:To combine a dynamic injection characteristic with a static characteristic so as to improve a transient characteristic by deciding a fuel injection timing following a time corresponding to the surplus angle part between crank angle pulses, and applying predictive correction corresponding to a rotation fluctuating amount predictive amount to a surplus angle time at the time of acceleration and deceleration. CONSTITUTION:In an ECU 6 when a diesel engine 2 is operated, a target common rail pressure is calculated on the basis of operating condition of outputs of a rotational speed sensor 7 and an acceleration sensor 8 so as to realize fuel injection pressure having optimal engine combustion condition, and a variable discharging amount high pressure pump 5 is controlled according to the deviation between the target common rail pressure and detected pressure of a common rail pressure sensor 9. In this case, an instantaneous rotational speed in a cylinder pressure compressing stroke and an instantaneous rotational speed in a cylinder explosion stroke are calculated, and a rotational speed difference is found out as to obtain a rotational fluctuation amount predictive value. When the rotational fluctuation amount predictive value exceeds a prescribed value, a predictive correction coefficient according to the rotational fluctuation amount predictive value is multiplied by a surplus angle time interval. It is thus possible to enable predictive correction, and improve a torque shortage at the time of acceleration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention calculates fuel injection conditions such as a target fuel injection amount and a target fuel injection timing according to operating conditions, and injects high-pressure fuel stored in a pressure accumulator according to the fuel injection conditions. The present invention relates to a pressure accumulation type fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field, there is one described in Japanese Patent Laid-Open No. 59-82534. In the fuel injection amount control method for an internal combustion engine described in this, the variation in the fuel injection amount between the multiple cylinders is corrected for each cylinder based on the engine speed, and specifically, the variation in the fuel injection amount is the instantaneous rotation before and after the explosion. Deviations from the moving average of numbers have been detected and corrected. In the case of such a control method, when the vehicle is accelerated, or when a transient engine speed change such as clutch meet occurs, a deviation occurs in the correspondence between the average instantaneous speed and the instantaneous engine speed at the start of injection. Problems such as torque fluctuations and hunting have occurred due to injection timing deviation.

In order to avoid this problem, Japanese Patent Laid-Open No. 61-61
There is one disclosed in Japanese Patent Laid-Open No. 118545, and in this known technique, an angle control and a surplus angle (time) control are used as a solenoid valve control method, and the following attempts have been made to improve transient characteristics. FIG. 5 is a diagram illustrating conventional angle control and remainder angle control. As shown in the figure, an injection pulse is formed as follows with respect to the instantaneous engine speed (N) obtained by processing the NE pulse signal from the crank angle sensor by frequency-voltage conversion or the like. Here, the angle between NE pulses is 15 ° CA. Using the NE pulse number from the reference crank position, the target injection timing is TTFINI (°
CA: Crank Angle). Here, i is a measurement area of the crank angle sensor corresponding to the current cylinder, and i-1 is a suffix representing a measurement area of the crank angle corresponding to the previous cylinder. Of the target injection timings, the angle between NE pulses is 15 °
TANGi (° CA) for angle control that is an integer multiple of CA
Express. Furthermore, the surplus angle control is TREMi (° CA)
(<15 ° CA). Here, TREMi is obtained as TREMi = TTFINI-TANGi.

Further, the time interval of the NE pulse including the previous surplus angle is set to Tpi-1 (μsec) (interval of NE pulses 2 to 3 in FIG. 5). In this case, the margin angle time TTi obtained by converting the margin angle control amount into time is TTi = (TREMi /
15) × Tpi−1 (1) and the angle is converted into a time interval.

In calculating TTi, not Tpi, but Tpi-1
Is used because it is not in time to use Tpi of this time. In this way, the target injection timing is converted into time and set.

[0006]

However, the conventional angle control and surplus angle (time) control methods have the following problems. FIG. 6 shows N including the previous surplus angle during acceleration / deceleration.
It is a figure explaining the time interval of E pulse. As shown in the figure, the time interval of the NE pulse including the surplus angle at the constant speed is Tpi−1≈Tpi≈Tpi + 1≈Tpi + 2≈T.
pi + 3≈ ...

At the time of acceleration, the time interval of the NE pulse including the surplus angle is Tpi-1.apprxeq.Tpi.apprxeq.Tpi + 1> Tpi + 2.
> Tpi + 3> ... NE including extra angle when decelerating
The time interval of the pulse is Tpi−1≈Tpi≈Tpi + 1
<Tpi + 2 <Tpi + 3 <... At the time of acceleration, the residual angle time TTi in the above equation (1) is virtually obtained by using the time interval of the NE pulse of this time (or the previous time of steady state), and the static injection pulse (dotted line) )
Is more retarded than the dynamic injection pulse (solid line) obtained using the time interval of the previous NE pulse.

Similarly, when the deceleration is performed, the surplus angle time TTi in the equation (1) is statically obtained by virtually using the time interval of the NE pulse of this time (or the previous time of steady state). Inject pulse (dotted line) is more advanced than dynamic injector pulse (solid line) obtained by using the time interval of the previous NE pulse. In this way, the injection timing cannot follow the rapid rotation change that occurs during one injection,
There is a problem that torque is insufficient due to retardation during acceleration, HC and smoke are worsened, and detonation due to advancement occurs in the initial stage of deceleration.

Next, in addition to the above problems, the problems of the average instantaneous rotational speed and the rotational fluctuation amount during acceleration / deceleration will be described. FIG. 7 is a diagram for explaining the average instantaneous rotation speed and the rotation fluctuation amount.
As shown in the figure, the average instantaneous rotation speed N in each specific region of each crank sensor and the rotation speed fluctuation amount, which is the difference between this average instantaneous rotation speed N and the minimum instantaneous rotation speed, are quasi-statically averaged. When the instantaneous rotation speed changes, the rotation speed fluctuation amount is ΔN1, ΔN
2 and changes to ΔN3 and ΔN4 when the accelerator is added stepwise.

FIG. 8 is a diagram for explaining the relationship between the average rotation speed and the rotation fluctuation amount. As shown in the figure, when the quasi-static steady deceleration load is applied, as shown by the dotted line, ΔN1, ΔN2, etc. decrease as the average instantaneous rotational speed increases. This is because ΔN1 and ΔN2 are related to the generated torque. However, in the case of a decelerating load, the amount of rotational fluctuation becomes smaller with respect to the average instantaneous rotational speed with respect to a transient rotational change, and in the case of an accelerating load, the rotational fluctuation amount has a reverse sign. To do.

FIG. 9 is a diagram showing characteristics of static and dynamic injection timings at the same injection timing. As shown in the figure, when the average instantaneous rotational speed rapidly increases by ΔN, the torque is deficiently delayed by ΔT with respect to the (quasi) static injection timing characteristic, and torque shortage or smoke occurs. On the other hand, when the average instantaneous rotation speed suddenly drops, there is a problem that the angle is dynamically advanced and detonation occurs.

Therefore, in view of the above problems, it is an object of the present invention to provide a fuel injection control device capable of preventing torque shortage, smoke generation, and detonation during acceleration / deceleration.

[0013]

In order to solve the above problems, the present invention converts a surplus angle portion between crank angle pulses into time and determines a fuel injection control timing according to this time. In the first cylinder, a first memory for storing the instantaneous speed of the internal combustion engine in the previous cylinder compression stroke, a second memory for storing the instantaneous speed of the internal combustion engine in the current cylinder explosion stroke, and the cylinder for the current time A third memory that stores a difference between the instantaneous speed of the internal combustion engine in the explosion stroke and the instantaneous speed of the internal combustion engine in the previous cylinder compression stroke and stores the difference as a predicted value of the rotational fluctuation amount; The time of the surplus corner portion is corrected based on the variation predicted value.

[0014]

According to the fuel injection control device of the present invention, when the acceleration / deceleration is performed, the prediction correction corresponding to the predicted value of the rotation fluctuation amount is applied to the margin angle time. The characteristics can be matched with the static characteristics, and the injection control can be performed with good transient characteristics, which can prevent torque shortage during acceleration, reduction of smoke and HC emissions, and detonation during deceleration. Further, at the time of acceleration / deceleration, the rotational fluctuation rate with respect to the average instantaneous rotational speed can also be corrected, and the injection control can be performed with good transient characteristics.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a common rail fuel injection control device according to an embodiment of the present invention, which includes a variable discharge pump. A common rail fuel injection control device 1 shown in this figure includes a diesel engine 2 having 6 cylinders, an injector 3 for injecting fuel into each cylinder of the diesel engine 2, and a common rail 4 for accumulating high-pressure fuel supplied to the injector 3. , A variable discharge pump 5 for pumping high-pressure fuel to the common rail 4, and an electronic control unit (ECU) 6 for controlling these.

The ECU 6 controls the state of the diesel engine 2, for example, the detection value of the rotation speed sensor 7 and the accelerator sensor 8.
The target common rail pressure PFIN for realizing the fuel injection pressure that optimizes the combustion state of the diesel engine 2 is calculated by taking in the operating conditions such as the detection value of the above, and the detection value of the common rail pressure sensor 9 provided in the common rail 4 is calculated. Based on the actual common rail pressure PC based on the target common rail pressure PFI
Common rail pressure feedback control is performed to drive and control the variable discharge high pressure pump 5 so as to maintain N.

The variable discharge high-pressure pump 5 sucks the fuel stored in the fuel tank 10 through the low-pressure supply pump 11 in accordance with a control command from this ECU, pressurizes it to a high pressure inside itself, and pressurizes it. Supplying high pressure fuel 12
To the common rail 4 by pressure. Each injector 3
Is connected to a common rail 4 that stores high-pressure fuel by a pipe 13. Then, by opening and closing the control valve 14 arranged in each injector 3, the pressure is accumulated in the common rail 4 and the target common rail pressure PF.
The high pressure fuel that has become IN is injected into the fuel chamber of each cylinder of the diesel engine 2. The opening / closing operation of the control valve 14 of the injector 3 is executed based on an injector control command from the ECU 6. This injector control command is for adjusting the fuel injection amount and the fuel injection timing, and is calculated based on the detection values from the operating condition detecting means such as the rotation speed sensor 7 and the accelerator sensor 8, and the crank angle sensor 15 It is output from the ECU 6 at a predetermined timing based on the detection value of the cylinder discrimination sensor 16 or the like.
The control command for the variable discharge high pressure pump 5 is also output at a predetermined timing based on the detected values from the crank angle sensor 15 and the cam angle sensor mounted on the variable discharge high pressure pump 5.

Here, a method of calculating the fuel injection amount and the fuel injection timing for instructing the injector will be described. First, the fuel injection amount QFIN is the smaller injection amount of the injection amount QBASE obtained from the output rotation speed of the crankshaft rotation speed sensor 7 and the detection value of the accelerator sensor 8 and the injection quantity QFULL that is uniquely obtained from the crankshaft rotation speed. To be selected. Here, it is desirable to use the instantaneous rotational speed immediately before injection as the crankshaft rotational speed used for QBASE calculation. Then, the actual command to the injector includes the energization time T calculated from the fuel pressure PC and QFIN of the common rail 4.
QFIN is used.

FIG. 2 is a flow chart for explaining the calculation of the fuel injection timing according to the embodiment of the present invention. Next, the calculation of the fuel injection timing will be described. Since this part is a part according to the present invention, it will be described according to the flowchart of FIG. In step 101, the instantaneous engine speed N and the target injection amount QFIN are first input.

In step 102, the injection timing TTFI
Calculate N (° CA). Where TTFIN is N and QF
The two-dimensional map of IN is calculated as the angle from the reference crank position to the start of injection. In step 3, the angle TANGi (° CA), which is an integer multiple of the NE pulse, and the surplus angle TREM (° C, which is 15 ° CA in the present embodiment), which is an integral multiple of the NE pulse and the one tooth of the NE pulse is used in step 3.
Divide into A).

The following steps 104 to 110 are the application parts of the present invention. In steps 104 and 105, the previous cylinder compression stroke instantaneous rotational speed NEi-1 and the current cylinder compression stroke instantaneous rotational speed Nci are input, and each is input to the ECU.
6 in the first and second memories. Step 106
Then, the rotation fluctuation amount predicted value ΔN ′ (= NEi-1-Nc
i) is calculated as follows and stored in the third memory of the ECU 6.

FIG. 3 is a diagram for explaining the rotation fluctuation amount predicted value ΔN '. As shown in this figure, the two instantaneous rotational speeds NEi-1 and Nci of the previous cylinder explosion stroke and the current cylinder compression stroke are monitored, and when the steady state is changed to transient or load ON, the difference ΔN between the instantaneous rotational speeds. 'Is the rotation fluctuation prediction value,
ΔN ′ = NEi−1−Nci is calculated for acceleration.

This makes it possible to predict the instantaneous rotational speed fluctuation from the previous injection to one injection. Where NEi-1 and Nc
i is calculated from one tooth time of the NE pulse, and each NE pulse position is such that NEi-1≈Nci when the engine is in steady operation at a constant rotation speed, and its instantaneous rotation speed is It is desirable to detect a place close to the average instantaneous rotation speed.

In step 107, next, if the absolute value | ΔN '| In step 108, the prediction correction coefficient KDTA is stored in the fourth memory in the form of a map using ΔN ′ as a parameter, and the prediction correction coefficient KDTA corresponding to ΔN ′ is searched for in the map.

In step 9, if "not in a transient state (steady rotation)" in step 107, the prediction correction coefficient KDTA is set to 1. Here, the coefficient α for determining the transient state may be an amount that exceeds the rotation fluctuation amount when the engine is in steady rotation. In step 110, the remainder angle TREM (i) (° CA), the NE pulse time Tpi-1 (μsec) before one injection, the NE pulse 1 tooth angle (15 ° CA in this embodiment), and the prediction coefficient KDTA Convert angle to time TTi. Where step 1
The calculation formula of 10 is the conventional spare angle time interval conversion formula (1).
Is multiplied by the prediction correction coefficient KDTA.

In step 111, the injector is finally commanded to end the fuel injection timing control. According to this embodiment, the influence of the rotation fluctuation is taken into consideration in the prediction amount when the surplus angle is converted into time, so that the acceleration / deceleration or the load O
It is possible to eliminate the dynamic delay of the injection timing when the rotational speed changes transiently such as N and OFF, and prevent torque shortage during acceleration, deterioration of smoke, and detonation in the initial stage of deceleration.

Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, step 106 in FIG.
In the above, the rotational fluctuation amount predicted value ΔN ′ is obtained by the difference between the two instantaneous rotational speeds, but ΔN ′ may be obtained by the quotient of the two instantaneous rotational speeds (for example, NEi−1 / Nci). FIG. 4 is a diagram showing a prediction correction coefficient map. Although the determination of the transient state is performed in step 107 of FIG. 2, a dead zone may be provided as shown in the prediction correction coefficient map of FIG. 4 instead of the determination of the transient state.

Further, the prediction correction coefficient map of FIG.
Although it is a one-dimensional map of N ′, it may be a two-dimensional map of average instantaneous rotation speed N and ΔN in consideration of the influence of the instantaneous rotation speed.

[0029]

As described above, according to the present invention, the prediction correction corresponding to the rotation fluctuation amount prediction value is applied to the extra angle time during acceleration / deceleration, so that the prediction correction becomes possible and the dynamic injection is performed. The characteristics can be matched with the static characteristics, and the injection control can be performed with good transient characteristics, which can prevent torque shortage during acceleration, reduction of smoke and HC emissions, and detonation during deceleration. Furthermore, at the time of acceleration / deceleration, it is also possible to correct the rotational fluctuation rate for the average instantaneous rotational speed,
Injection control can be performed with good transient characteristics. In addition,
The invention is applicable to gasoline engines as well as diesel engines.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a common rail fuel injection control device according to an embodiment of the present invention, which includes a variable discharge high pressure pump.

FIG. 2 is a flowchart illustrating calculation of fuel injection timing according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a rotation fluctuation amount predicted value ΔN ′.

FIG. 4 is a graph showing a transient prediction correction coefficient map.

FIG. 5 is a diagram illustrating conventional angle control and remainder angle control.

FIG. 6 is a diagram illustrating a time interval of an NE pulse including a previous surplus angle during acceleration.

FIG. 7 is a diagram illustrating an average instantaneous rotation speed and a rotation fluctuation amount.

FIG. 8 is a diagram illustrating a relationship between an average rotation speed and a rotation fluctuation amount.

FIG. 9 is a diagram showing characteristics of static and dynamic injection timings at the same injection timing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Common rail fuel injection control device 2 ... Diesel engine 3 ... Injector 4 ... Common rail 5 ... Variable discharge high pressure pump 6 ... Electronic control unit (ECU) 7 ... Rotation speed sensor 8 ... Accelerator sensor 9 ... Common rail pressure sensor 10 ... Fuel Tank 11 ... Low-pressure supply pump 12 ... Supply pipe 13 ... Pipe 14 ... Control valve 15 ... Crank angle sensor 16 ... Cylinder discrimination sensor

Claims (5)

[Claims] 1. A fuel injection control device for converting a surplus angle portion between crank angle pulses into time, and determining a fuel injection control timing according to this time, storing an instantaneous rotational speed of an internal combustion engine in a previous cylinder compression stroke. And a second memory for storing the instantaneous speed of the internal combustion engine in the current cylinder explosion stroke, the instantaneous speed of the internal combustion engine in the current cylinder explosion stroke, and the previous cylinder compression stroke And a third memory that stores the difference from the instantaneous speed of the internal combustion engine as a predicted value of rotational fluctuation amount, and corrects the time of the surplus angle portion based on the predicted value of rotational fluctuation amount. A fuel injection control device. 2. The internal combustion engine in the cylinder explosion stroke of this time, instead of taking the difference between the instantaneous rpm of the internal combustion engine in the cylinder explosion stroke of this time and the instantaneous engine speed of the internal combustion engine in the previous cylinder compression stroke. The fuel injection control device according to claim 1, wherein a ratio between an instantaneous engine speed and an instantaneous engine speed of the internal combustion engine in the previous cylinder compression stroke is calculated. 3. The fuel injection control device according to claim 1, wherein the time of the surplus angle portion is corrected when the rotation fluctuation amount predicted value exceeds a predetermined value α. 4. A rotational fluctuation which is a difference between an average instantaneous engine speed of the internal combustion engine, an instantaneous engine speed of the internal combustion engine in the cylinder explosion stroke of the present time, and an instantaneous engine speed of the internal combustion engine in the previous cylinder compression stroke. The fuel injection control device according to claim 1, wherein the predicted amount of fuel and the amount of predicted fuel are stored in a map. 5. The instantaneous rotation speed of the internal combustion engine in the cylinder explosion stroke of this time and the instantaneous rotation speed of the internal combustion engine in the cylinder compression stroke of the previous time are set to substantially average instantaneous rotation speeds in a steady state. The fuel injection control device according to claim 1.