JP3864424B2 - Fuel injection control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a target fuel injection amount and target fuel injection timing of the fuel injection conditions calculated pressure fuel common rail fuel injection of an internal combustion engine that injects according to the above fuel injection condition example one担蓄the accumulator chamber in response to, for example, the operating conditions Relates to the device.
[0002]
[Prior art]
Conventionally, there is a technique described in Japanese Patent Application Laid-Open No. 59-82534 as a technology in such a field. In the fuel injection amount control method for an internal combustion engine described here, the variation in the fuel injection amount among the multiple cylinders is corrected for each cylinder based on the engine speed. Specifically, the variation in the fuel injection amount is the instantaneous rotation before and after the explosion. Deviations from the average number variation are detected and corrected. In the case of such a control method, there is a deviation in the correspondence relationship between the average instantaneous rotational speed and the instantaneous rotational speed of the engine at the start of injection when acceleration is performed or when a transient engine rotational change such as clutch meat occurs. Troubles such as torque fluctuation and hunting due to injection timing deviation have occurred.
[0003]
In order to avoid this problem, there is one described in Japanese Patent Application Laid-Open No. 61-118545, and this known technique uses angle control and remainder angle (time) control as electromagnetic valve control methods to improve transient characteristics. The following attempts have been made.
FIG. 5 is a diagram for explaining 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. The target injection timing is expressed as TTFINi (° CA: Crank Angle) using the number of NE pulses from the reference crank position. Here, i is a measurement area of the crank angle sensor corresponding to the current cylinder, and i-1 is a suffix indicating the measurement area of the crank angle corresponding to the previous cylinder. Of the target injection timing, an angle control amount that is an integral multiple of an angle of 15 ° CA between NE pulses is represented as TANGi (° CA). Further, the remainder angle control is expressed as TREMi (° CA) (<15 ° CA). Here, TREMi is
It is obtained as TREMi = TTFINi-TANGi.
[0004]
Further, the time interval of the NE pulse including the previous remainder angle is set to Tpi-1 (μsec) (the interval between the NE pulses 2 to 3 in FIG. 5). In this case, the remainder angle time TTi obtained by converting the remainder angle control amount into time is
TTi = (TREMi / 15) × Tpi−1 (1) and is converted from a corner to a time interval.
[0005]
The reason for using Tpi-1 instead of Tpi for the calculation of TTi is that the current Tpi is not used in time. In this way, the target injection timing is set after being converted into time.
[0006]
[Problems to be solved by the invention]
However, the conventional angle control and remainder angle (time) control methods have the following problems.
FIG. 6 is a diagram for explaining the time interval of the NE pulse including the previous remainder angle during acceleration / deceleration. As shown in this figure, the NE pulse time interval including the remainder angle at constant speed is
Tpi-1≈Tpi≈Tpi + 1≈Tpi + 2≈Tpi + 3≈.
[0007]
The time interval of the NE pulse including the remainder angle during acceleration is
Tpi-1≈Tpi≈Tpi + 1> Tpi + 2> Tpi + 3>...
During deceleration, the NE pulse time interval including the remainder angle is
Tpi-1≈Tpi≈Tpi + 1 <Tpi + 2 <Tpi + 3 <.
At the time of acceleration, the dynamic injection pulse (solid line) obtained by using the time interval of the previous NE pulse for the remainder angle time TTi in the above equation (1 ) is virtually the current (or steady time) It is retarded from the static injection pulse (dotted line) obtained using the time interval of the previous NE pulse.
[0008]
Similarly, at the time of deceleration, the dynamic injection pulse (solid line) obtained by using the time interval of the previous NE pulse for the remainder angle time TTi in the above equation (1 ) is virtually ( Alternatively, the angle is advanced from the static injection pulse (dotted line) obtained using the time interval of the previous NE pulse in the steady state.
In this way, the injection timing cannot follow the rapid rotational change that occurs during one injection, and torque is insufficient due to retard, acceleration of HC and smoke during acceleration, and detonation due to advance occurs at the beginning of deceleration. There's a problem.
[0009]
Next, in addition to the above problem, a problem between 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 rotational speed and the rotational fluctuation amount. As shown in this figure, the average instantaneous rotational speed N in a specific region of each crank angle sensor and the rotational speed fluctuation amount that is the difference between the average instantaneous rotational speed N and the minimum instantaneous rotational speed are averaged quasi-statically. It is assumed that when the instantaneous rotational speed changes, the rotational speed fluctuation amount changes to ΔN1 and ΔN2, and when the accelerator is applied stepwise, it changes to ΔN3 and ΔN4.
[0010]
FIG. 8 is a diagram for explaining the relationship between the average rotational speed and the rotational fluctuation amount. As shown in the figure, as indicated by the dotted line when a deceleration load is applied quasi-statically and constantly, ΔN1, ΔN2, etc. become smaller as the average instantaneous rotational speed increases. This is because ΔN1 and ΔN2 are related to the generated torque. However, with respect to the transient rotational change, the rotational fluctuation amount becomes smaller in the case of the deceleration load with respect to the average instantaneous rotational speed, and in the case of the acceleration load, the rotational fluctuation amount has the sign reversed. To do.
[0011]
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 suddenly increases by ΔN, the (quasi) static injection timing characteristic is dynamically retarded by ΔT, resulting in insufficient torque and smoke. On the other hand, when the average instantaneous rotational speed falls rapidly, there is a problem that the angle is dynamically advanced and detonation occurs.
[0012]
Accordingly, an object of the present invention is to provide a fuel injection control device that can prevent torque shortage, smoke generation, and detonation during acceleration / deceleration in view of the above problems.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention injects fuel accumulated in a common rail by an injector provided for each cylinder, and determines the fuel injection start timing from this injector as a remainder angle portion between crank angle pulses. In the common rail fuel injection control device that determines the fuel injection start time according to this time,
A first memory for storing an instantaneous rotational speed of the internal combustion engine at a predetermined pulse position during an explosion stroke at the time of previous fuel injection;
A second memory for storing the instantaneous rotational speed of the internal combustion engine at a predetermined pulse position during the compression stroke at the time of fuel injection;
The difference between the instantaneous rotational speed of the internal combustion engine during the compression stroke at the time of the fuel injection and the instantaneous rotational speed of the internal combustion engine during the explosion stroke at the time of the previous fuel injection is taken as a rotational fluctuation amount prediction value. A third memory for storing,
It said predetermined pulse positions, when the engine is steady operation at a constant rotational speed, the instantaneous Rotation number in the explosion stroke and the instantaneous rotational speed of in the compression stroke is set to be equal, Further, the instantaneous rotational speed during the explosion stroke and the instantaneous rotational speed during the compression stroke are set so as to detect a place close to the average instantaneous rotational speed when the engine is operating at a constant rotational speed. Then, the time of the remainder angle portion is corrected based on the predicted rotational fluctuation amount.
[0014]
[Action]
According to the fuel injection control device of the present invention, during the acceleration / deceleration, a prediction correction corresponding to the predicted rotation fluctuation amount is applied to the remainder angle time, thereby enabling the prediction correction and reducing the dynamic injection characteristics. Therefore, the injection control can be performed with a good transient characteristic, thereby preventing the torque shortage at the time of acceleration, the smoke, the reduction of HC emission amount, and the detonation at the time of 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]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram for explaining the 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 the figure includes a six-cylinder diesel engine 2, an injector 3 that injects fuel into each cylinder of the diesel engine 2, and a common rail 4 that accumulates high-pressure fuel supplied to the injector 3. A variable discharge pump 5 that pumps high-pressure fuel to the common rail 4 and an electronic control unit (ECU) 6 that controls them are provided.
[0016]
The ECU 6 takes in operating conditions such as the state of the diesel engine 2, for example, the detection value of the rotation speed sensor 7 and the detection value of the accelerator sensor 8, and realizes a fuel injection pressure that optimizes the combustion state of the diesel engine 2. Common rail pressure for driving and controlling the variable discharge high pressure pump 5 so as to maintain the actual common rail pressure PC at the target common rail pressure PFIN based on the detection value of the common rail pressure sensor 9 provided on the common rail 4. Perform feedback control.
[0017]
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 the ECU, pressurizes the fuel to a high pressure, and pressurizes the pressurized high-pressure pump 5. Fuel is pumped to the common rail 4 through the supply pipe 12.
Each injector 3 is connected to a common rail 4 accumulating high-pressure fuel by a pipe 13. Then, by opening and closing the control valve 14 disposed in each injector 3, the high pressure fuel accumulated in the common rail 4 to become the target common rail pressure PFIN is injected into the fuel chamber of each cylinder of the diesel engine 2. Is done. 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 detected value from the operating condition detecting means such as the rotational speed sensor 7 and the accelerator sensor 8, and the crank angle sensor 15 And output from the ECU 6 at a predetermined timing based on detection values of the cylinder discrimination sensor 16 and the like. A control command for the variable discharge high-pressure pump 5 is also output at a predetermined timing based on detection values from the crank angle sensor 15 and a cam angle sensor mounted on the variable discharge high-pressure pump 5.
[0018]
Here, a method for calculating the fuel injection amount and the fuel injection timing for instructing the injector will be described. First, the fuel injection amount QFIN is a small injection amount within the injection amount QBASE obtained from the output rotational speed of the crankshaft rotational speed sensor 7 and the detection value of the accelerator sensor 8 and the injection quantity QFULL uniquely obtained from the crankshaft rotational speed. Selected. Here, it is desirable to use the instantaneous rotational speed immediately before injection as the crankshaft rotational speed used for QBASE calculation. Then, an energization time TQFIN calculated from the fuel pressure PC of the common rail 4 and QFIN is used for an actual command to the injector.
[0019]
FIG. 2 is a flowchart for explaining calculation of the fuel injection timing according to the embodiment of the present invention. Next, calculation of the fuel injection timing will be described. Since this part is a part according to the present invention, description will be given according to the flowchart of FIG.
In step 101, first, an instantaneous engine speed N and a target injection amount QFIN are input.
[0020]
In step 102, the injection timing TTFIN (° CA) is calculated. Here, TTFIN is a two-dimensional map of N and QFIN and is calculated as an angle from the reference crank position to the start of injection.
In Step 103, then the integral multiple of NE pulses TTFIN as an angle control component angle TANGi (° CA) and NE pulse one tooth angle remainder angle of less than (15 ° CA in this embodiment) TREM (° CA) Divide into
[0021]
The next steps 104 to 110 are the application part of the present invention.
In steps 104 and 105, the previous cylinder explosion stroke instantaneous rotational speed NEi-1 and the current cylinder compression stroke instantaneous rotational speed Nci are input and stored in the first and second memories of the ECU 6, respectively.
In step 106, the predicted rotation fluctuation amount ΔN ′ (= NEi−1−Nci) is calculated as follows and stored in the third memory of the ECU 6.
[0022]
FIG. 3 is a diagram for explaining the rotational fluctuation amount predicted value ΔN ′. As shown in the 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 transient speed changes from the steady state or when the load is ON, the difference ΔN between the instantaneous rotational speeds. 'Is the predicted value of rotational fluctuation,
ΔN ′ = NEi−1−Nci
Is calculated.
[0023]
This makes it possible to predict the instantaneous rotational speed fluctuation between the previous injection and one injection. Here, NEi-1 and Nci are calculated from one tooth time of the NE pulse, but each NE pulse position is set to NEi-1≈Nci when the engine is operating at a constant speed. The It is also desirable to detect where the instantaneous rotational speed is close to the average instantaneous rotational speed.
[0024]
Next, in step 107, if the absolute value | ΔN '| of the rotation fluctuation amount predicted value ΔN ′ is a certain value or more (α or more in the flowchart), it is determined as a transient state.
In step 108, the prediction correction coefficient KDTA is stored in the fourth memory as a map using ΔN ′ as a parameter, and the prediction correction coefficient KDTA corresponding to ΔN ′ is searched for a map.
[0025]
In Step 9, when “not in a transient state (steady rotation)” in Step 107, 1 is set to the prediction correction coefficient KDTA. Here, the coefficient α for determining the transient state may be an amount that exceeds the rotational fluctuation amount when the engine is rotating at a steady state.
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 the present embodiment), and the prediction coefficient KDTA are used. Convert the corner to time TTi. Here, the calculation formula of step 110 is obtained by multiplying the conventional remainder angle time interval conversion formula (1) by the prediction correction coefficient KDTA.
[0026]
In step 111, a command is finally given to the injector, and the fuel injection timing control is terminated.
According to this embodiment, by considering the influence of the rotation fluctuation with the predicted amount at the time conversion of the remainder angle, the dynamic delay of the injection timing can be reduced at the time of transient rotation change such as acceleration / deceleration or load ON / OFF. This eliminates insufficient torque during acceleration, deterioration of smoke, and detonation at the beginning of deceleration.
[0027]
As mentioned above, although the Example of this invention was described, this invention is not limited to this. For example, in step 106 of FIG. 2, the predicted rotational fluctuation amount ΔN ′ is obtained as a difference between two instantaneous rotational speeds, but ΔN ′ is a quotient of the two instantaneous rotational speeds (for example, NEi−1 / Nci). You may ask for it.
FIG. 4 is a diagram showing a prediction correction coefficient map. Further, 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 transient state determination.
[0028]
Further, the prediction correction coefficient map of FIG. 4 is a one-dimensional map of ΔN ′, but may be a two-dimensional map of average instantaneous rotational speeds N and ΔN in consideration of the influence of the instantaneous rotational speed.
[0029]
【The invention's effect】
As described above, according to the present invention, during acceleration / deceleration, prediction correction corresponding to the predicted rotational fluctuation amount is performed in the extra angular time, so that prediction correction is possible, and dynamic injection characteristics are changed to static characteristics. Therefore, the injection control can be performed with a good transient characteristic, which can prevent insufficient torque during acceleration, smoke, reduction of 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. The present invention is applicable not only to diesel engines but also to gasoline engines.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a common rail fuel injection control apparatus 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 an embodiment of the present invention.
FIG. 3 is a diagram for explaining a predicted rotation fluctuation amount ΔN ′.
FIG. 4 is a graph showing a transient prediction correction coefficient map;
FIG. 5 is a diagram for explaining conventional angle control and remainder angle control;
FIG. 6 is a diagram for explaining a time interval of NE pulses including a previous remainder angle during acceleration.
FIG. 7 is a diagram for explaining an average instantaneous rotational speed and a rotational fluctuation amount.
FIG. 8 is a diagram for explaining a relationship between an average rotational speed and a rotational 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 type fuel injection control apparatus 2 ... Diesel engine 3 ... Injector 4 ... Common rail 5 ... Variable discharge high pressure pump 6 ... Electronic control unit (ECU)
7 ... Rotational 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 (4)

The fuel accumulated in the common rail is injected by the injector provided for each cylinder, the fuel injection start timing from this injector is converted into the time of the remainder angle between the crank angle pulses, and the fuel injection start timing is changed according to this time. In the common rail fuel injection control device to be determined,
A first memory for storing an instantaneous rotational speed of the internal combustion engine at a predetermined pulse position during an explosion stroke at the time of previous fuel injection;
A second memory for storing the instantaneous rotational speed of the internal combustion engine at a predetermined pulse position during the compression stroke at the time of fuel injection;
The difference between the instantaneous rotational speed of the internal combustion engine during the compression stroke at the time of the fuel injection and the instantaneous rotational speed of the internal combustion engine during the explosion stroke at the time of the previous fuel injection is taken as a rotational fluctuation amount prediction value. A third memory for storing,
It said predetermined pulse positions, when the engine is steady operation at a constant rotational speed, the instantaneous Rotation number in the explosion stroke and the instantaneous rotational speed of in the compression stroke is set to be equal, Further, the instantaneous rotational speed during the explosion stroke and the instantaneous rotational speed during the compression stroke are set so as to detect a place close to the average instantaneous rotational speed when the engine is operating at a constant rotational speed. A common rail fuel injection control device, wherein the time of the remainder angle portion is corrected based on the rotation fluctuation amount prediction value.   Instead of taking the difference between the instantaneous rotational speed of the internal combustion engine in the compression stroke at the time of the current fuel injection and the instantaneous rotational speed of the internal combustion engine in the explosion stroke at the time of the previous fuel injection, 2. The common rail fuel injection control device according to claim 1, wherein a ratio between an instantaneous rotational speed of the internal combustion engine and an instantaneous rotational speed of the internal combustion engine in an explosion stroke at the time of the previous fuel injection is taken.   2. The common rail fuel injection control device according to claim 1, wherein when the predicted rotational fluctuation amount exceeds a predetermined value [alpha], the moment of the remainder angle portion is corrected.   The amount of rotational fluctuation that is the difference between the average instantaneous rotational speed of the internal combustion engine and the instantaneous rotational speed of the internal combustion engine in the compression stroke at the time of the current fuel injection and the instantaneous rotational speed of the internal combustion engine in the explosion stroke at the time of the previous fuel injection 2. The common rail fuel injection control apparatus according to claim 1, wherein the predicted value is stored in a map.

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