JP2000257478A - Fuel injection control unit for high-pressure fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of fuel injection control by positively reflecting changes of fuel pressures inside a pressure accumulation pipe onto the fuel injection control. SOLUTION: Injectors 12 for injecting fuel into a combustion chamber of each cylinder #1 to #4 of an engine 10 are connected to a common rail 20 and receive high-pressure fuel from the common rail 20. A fuel pump 30 pressurizes fuel in a fuel tank 14 to a high pressure and pressure feeds it to the common rail 20. An electronic control unit(ECU) 60 computes fuel injection duration, based on a fuel pressure (rail pressure) in the common rail 20 and an engine- demand injection quantity. Furthermore, the ECU 60 estimates rail pressure changes from the detection time of the rail pressure to the starting time of a fuel injection, based on the compression transferred fuel quantity and a leaked fuel quantity which leaked from the common rail 20 through the injectors 12. Based on the rail pressure changes, the ECU 60 compensates for the fuel injection duration so that the actual fuel injection quantity agrees with the engine- demand injection quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control for a high-pressure fuel injection system in which fuel pressure-supplied from a fuel pump to a pressure accumulation pipe is injected and supplied to an internal combustion engine from a fuel injection valve connected to the pressure accumulation pipe. The present invention relates to an apparatus, and more particularly, to an embodiment of a control structure that is useful for improving control accuracy of fuel injection.

[0002]

2. Description of the Related Art In general, in an internal combustion engine having a pressure accumulation pipe such as a common rail, high pressure fuel is pumped from a fuel pump to a pressure accumulation pipe, and a fuel injection valve connected to the pressure accumulation pipe enters the engine combustion chamber. High-pressure fuel is injected. When controlling the fuel injection amount, first, the fuel pressure in the accumulator pipe is detected as the fuel injection pressure,
An engine required injection amount is calculated based on the engine operation state. Then, a command value for determining a valve opening period of the fuel injection valve is set based on the fuel pressure and the engine required injection amount, and the fuel injection valve is driven based on the command value. As a result, an amount of fuel equal to the engine required injection amount is injected from the fuel injection valve.

In the meantime, if the fuel pressure in the accumulator pipe rises, for example, due to the fuel pumping of the fuel pump between the time when the fuel pressure is detected as described above and the time when the fuel injection is started, Fuel injection is performed based on a higher fuel pressure than when the command value is set.
Therefore, the amount of fuel actually injected from the fuel injection valve becomes larger than the engine required injection amount, and if such a difference between the actual fuel injection amount and the engine required injection amount becomes excessive, problems such as deterioration of exhaust characteristics and the like occur. Will become apparent.

In order to suppress the deterioration of the accuracy of the fuel injection control, the period from the detection of the fuel pressure to the start of the fuel injection is set as short as possible, such as detecting the fuel pressure immediately before the start of the fuel injection. It is desirable. However, in practice, it is necessary to calculate a control command value for driving the fuel injection valve, such as the above command value, during this period.
Considering the calculation load and the like, there is naturally a limit in setting the period to be short.

Therefore, conventionally, for example, Japanese Unexamined Patent Application Publication No.
As described in Japanese Patent No. 15, during a transient operation of the engine, the difference between the previous detected value of the fuel pressure and the detected value two times before is added to the previously detected value, and the fuel injection is performed based on the added value and the required fuel injection amount. The period (command value) is set. That is,
A change in fuel pressure from the time of detection of the fuel pressure to the start of fuel injection is predicted based on the change history, and this predicted value is used instead of an actually measured value when setting the fuel injection period. ing. As a result, a proper fuel injection period can be set in anticipation of a change in fuel pressure from the detection of fuel pressure to the start of fuel injection, and the fuel injection amount can be accurately controlled even during transient engine operation. Will be able to

[0006]

However, in such a conventional fuel injection control, a fuel pressure change occurring after the fuel pressure is detected is predicted based on a fuel pressure change history. In, although the detected value of the fuel pressure hardly changes and is always substantially the same value,
If the fuel pressure changes greatly during the period between each detection time, it is no longer possible to predict this fuel pressure change, and it is naturally impossible to cope with this.

More specifically, as shown in FIG. 13, at each of the fuel pressure detection timings t1, t3 and t5, the fuel pressure is detected as a predetermined value PCR, but the fuel injection is started at timings t2, t4 and t6. If the fuel pressure rises to the predetermined value PCRINJ by the fuel pumping of the fuel pump by then, the conventional fuel injection control determines that there is no change in the fuel pressure. As a result, in spite of the fact that the fuel pressure has risen to the predetermined value PCRINJ at timings t2, t4 and t6 when the fuel injection is started,
The fuel injection period is set based on the detection values PCR at the respective detection timings t1, t3, and t5 without reflecting such an increase in the fuel pressure.

Accordingly, in such a case, in the conventional fuel injection control, the fuel injection period cannot be set as an appropriate value for matching the actual fuel injection amount with the engine required injection amount. A reduction in control accuracy has been unavoidable.

The present invention has been made in view of such a conventional situation, and has as its object to improve the control accuracy by reliably reflecting a change in fuel pressure in a pressure accumulating pipe in fuel injection control. It is an object of the present invention to provide a fuel injection control device for a high-pressure fuel injection system that can be used.

[0010]

The means for achieving the above object and the effects thereof will be described below. According to the first aspect of the present invention, a fuel injection valve for injecting fuel into the internal combustion engine is connected, and a fuel pressure in a pressure accumulation pipe to which fuel is supplied from a fuel pump is detected, and the detected fuel pressure and engine required injection are detected. In a fuel injection control device for a high-pressure fuel injection system that drives and controls the fuel injection valve based on a control command value set based on an amount, a variable element of the high-pressure fuel injection system that changes the fuel pressure in the pressure accumulation pipe Estimating means for estimating a change in the fuel pressure from the time of detection of the fuel pressure to the start of fuel injection based on the control command, and the control command to match the actual fuel injection amount of the fuel injection valve to the engine required injection amount. Correction means for correcting the value based on the estimated change in fuel pressure.

According to the above configuration, if the fuel pressure changes according to the variable element of the high-pressure fuel injection system from the time of detecting the fuel pressure to the time of starting the fuel injection, the detected value of the fuel pressure hardly changes. Even during steady operation, the change in fuel pressure can be reliably estimated based on the variable element. Therefore, by correcting the control command value of the fuel injection valve based on the change in fuel pressure, it is possible to prevent the actual fuel injection amount of the fuel injection valve from deviating from the required engine injection amount due to the change in fuel pressure. Can be. As a result, changes in the fuel pressure in the accumulator pipe, especially those that occur after the detection of the fuel pressure,
The fuel pressure change can be reliably reflected in the fuel injection control, and extremely accurate fuel injection control can be realized.

The control command value may include a valve opening period command value for determining the valve opening period of the fuel injection valve and an opening command value for determining the opening of the fuel injection valve. it can.

According to a second aspect of the present invention, in the fuel injection control device for a high-pressure fuel injection system according to the first aspect,
The estimating means estimates the fuel pressure change based on the fuel pumping amount from the detection of the fuel pressure to the start of fuel injection, with the fuel pumping amount of the fuel pump as the variable element.

[0014] According to the above configuration, in addition to the operation and effect of the invention described in the first aspect, the amount of increase in fuel pressure accompanying fuel pumping from the detection of fuel pressure to the start of fuel injection is reliably estimated. By correcting the control command value based on the increase amount, it is possible to suppress the actual fuel injection amount from becoming larger than the engine required injection amount. As a result, it is possible to avoid a problem such as deterioration of the exhaust characteristics, which is caused by an excessive amount of fuel that is not suitable for the engine operating state being supplied to the internal combustion engine.

According to a third aspect of the present invention, in the fuel injection control device for a high-pressure fuel injection system according to the first aspect, the estimating means sets a leak amount of fuel leaking from the pressure accumulation pipe as the variable element, The fuel pressure change is estimated based on the leak amount from the time of detecting the pressure to the time of starting the fuel injection.

According to the above configuration, in addition to the operation and effect of the invention described in claim 1, the amount of decrease in fuel pressure due to fuel leakage from the detection of fuel pressure to the start of fuel injection is reliably estimated. By correcting the control command value based on this reduction amount, it is possible to suppress the actual fuel injection amount from becoming smaller than the engine required injection amount. As a result, it is possible to avoid problems such as a decrease in engine output caused by a failure to supply a sufficient amount of fuel suitable for the engine operating state to the internal combustion engine.

Further, as a more specific structure for realizing such fuel injection control, as in the invention according to claim 4, the fuel of the high-pressure fuel injection system according to any one of claims 1 to 3 is provided. In the injection control device, the control command value is a valve opening period command value of the fuel injection valve, and the correction unit calculates a correction value of the valve opening period command value based on the fuel pressure change. And the valve opening period command value is corrected based on
In the fuel injection control device for a high-pressure fuel injection system according to any one of claims 1 to 3, the control command value is a valve opening period command value of the fuel injection valve, and the correction is performed. The means may correct the valve opening period command value by previously correcting the detected fuel pressure based on the fuel pressure change when setting the valve opening period command value. it can.

According to each of these configurations, in addition to the functions and effects of the invention described in any one of the first to third aspects, the valve is opened to an appropriate value for making the actual fuel injection amount coincide with the engine required injection amount. The period command value can be corrected, and the fuel injection period of the fuel injection valve can be set very accurately.

In particular, according to the configuration of the invention described in claim 5, in correcting the valve opening period command value to an appropriate value, it is only necessary to correct the detected fuel pressure in advance based on the fuel pressure change. In addition, since it is not necessary to separately calculate the correction value of the valve opening period command value, the control structure can be simplified.

According to a sixth aspect of the present invention, in the fuel injection control device for a high-pressure fuel injection system according to the fourth or fifth aspect, the estimating means includes a step of: The change in pressure is further estimated based on the fuel pumping amount during the fuel injection period, and the correction means changes the valve opening period command value so that the actual fuel injection amount matches the engine required injection amount during the fuel injection period. It is further corrected based on the change in the fuel pressure.

According to a seventh aspect of the present invention, in the fuel injection control device for a high-pressure fuel injection system according to the fourth or fifth aspect, the estimating means includes a fuel injection control device that supplies fuel from the pressure accumulating pipe during a fuel injection period. The change in the fuel pressure due to the leak is further estimated based on the leak amount during the same fuel injection period, and the correction means adjusts the valve opening period command value so that the actual fuel injection amount matches the engine required injection amount. Further correction is made based on the change in fuel pressure during the fuel injection period.

When fuel is pumped from the fuel pump during the fuel injection period, the fuel pressure in the accumulator pipe decreases gradually, and the fuel injection amount increases as compared with the case where such fuel pumping is not performed. Become like On the other hand, if fuel leaks from the pressure accumulating pipe during the fuel injection period, the fuel pressure in the pressure accumulating pipe decreases more rapidly, so that the fuel injection amount decreases as compared with the case where there is no such fuel leak.
Therefore, in order to further enhance the control accuracy of the fuel injection amount, in addition to the fuel pressure change from the time of detecting the fuel pressure to the start of the fuel injection, the influence of the fuel pumping and the fuel leak during the fuel injection period is controlled by the valve opening period command. It is desirable to take this into account when setting the value.

According to the structure of the invention described in claim 6,
In addition to the effects of the invention described in claim 4 or 5, in addition to the fact that the actual fuel injection amount becomes larger than the engine required injection amount due to the fuel pressure change accompanying the fuel pumping during the fuel injection period. At this point, it is possible to avoid the occurrence of troubles such as deterioration of exhaust characteristics caused by the supply of an excessive amount of fuel unsuitable for the engine operating state to the internal combustion engine.

According to the structure of the invention described in claim 7, in addition to the effect of the invention described in claim 4 or 5, in addition to the effect of the fuel pressure change accompanying the fuel leak during the fuel injection period. It is possible to suppress the actual fuel injection amount from becoming smaller than the engine required injection amount.In this regard, it is possible to prevent a sufficient amount of fuel suitable for the engine operating state from being supplied to the internal combustion engine, such as a decrease in engine output. This makes it possible to avoid the occurrence of inconvenience.

According to an eighth aspect of the present invention, in the fuel injection control device for a high-pressure fuel injection system according to the first aspect,
The high-pressure fuel injection system divides an amount of fuel equal to the engine required injection amount and injects the same from the fuel injection valve.The control command value includes a required fuel injection amount for each fuel injection and the detected fuel pressure. Is set for each fuel injection based on the fuel pressure, and the estimating means converts the change in the fuel pressure from the detection of the fuel pressure to the start of a specific fuel injection of each fuel injection into the variable element. The correction means controls the specific fuel injection based on the fuel pressure change so that the actual fuel injection amount in the specific fuel injection matches the required fuel injection amount in the specific fuel injection. It is said that the command value is corrected.

According to the above configuration, in the operation and effect of the first aspect of the invention, in particular, by correcting the control command value in the specific fuel injection based on the fuel pressure change,
It is possible to prevent the actual fuel injection amount in the specific fuel injection from deviating from the engine required injection amount due to the fuel pressure change. As a result, even in a high-pressure fuel injection system in which the required engine injection amount is divided into multiple injections, fuel injection control with extremely high accuracy can be realized.

According to a ninth aspect of the present invention, in the fuel injection control device for a high-pressure fuel injection system according to the eighth aspect,
The estimating means uses the fuel injection amount of the fuel injection valve as the variable element, and calculates the fuel pressure based on an integrated value of the fuel injection amount from the time of detecting the fuel pressure to the time of starting the specific fuel injection. It estimates the change.

According to the above configuration, in addition to the effects of the invention described in claim 8, the fuel pressure is reduced due to the fuel injection performed from the time of detecting the fuel pressure to the time of starting the specific fuel injection. By reliably estimating the amount and correcting the control command value for a specific fuel injection based on this decrease amount,
It can be suppressed that the actual fuel injection amount becomes smaller than the engine required injection amount. As a result, it is possible to avoid problems such as a decrease in engine output caused by a failure to supply a sufficient amount of fuel suitable for the engine operating state to the internal combustion engine.

According to the tenth aspect of the present invention, in the eighth aspect,
In the fuel injection control device for a high-pressure fuel injection system described in the above, the estimating means uses the fuel pumping amount of the fuel pump as the variable element, from the time of detecting the fuel pressure to the time of starting the specific fuel injection. It is assumed that the fuel pressure change is estimated based on the fuel pumping amount.

According to the above configuration, in addition to the operation and effect of the invention described in claim 8, the amount of increase in fuel pressure accompanying the fuel pumping from the time when the fuel pressure is detected to the time when a specific fuel injection is started is determined. By accurately estimating and correcting the control command value in the specific fuel injection based on the increase amount, it is possible to suppress the actual fuel injection amount from becoming larger than the engine required injection amount. As a result, it is possible to avoid a problem such as deterioration of the exhaust characteristics, which is caused by an excessive amount of fuel that is not suitable for the engine operating state being supplied to the internal combustion engine.

[0031] According to the eleventh aspect of the present invention, in the fuel injection control device for a high pressure fuel injection system according to the eighth aspect, the estimating means uses the amount of fuel leaking from the pressure accumulation pipe as the variable element, It is assumed that the fuel pressure change is estimated based on the leak amount from the detection of the fuel pressure to the start of the specific fuel injection.

According to the above construction, in addition to the function and effect of the invention described in claim 8, the amount of decrease in fuel pressure due to fuel leakage from the time of detection of fuel pressure to the time of starting specific fuel injection. Is reliably estimated, and the control command value in the specific fuel injection is corrected based on the decrease amount, so that the actual fuel injection amount can be suppressed from being smaller than the engine required injection amount. As a result, it is possible to avoid problems such as a decrease in engine output caused by a failure to supply a sufficient amount of fuel suitable for the engine operating state to the internal combustion engine.

Further, as a more specific configuration for realizing such fuel injection control, as in the twelfth aspect of the present invention, the fuel of the high pressure fuel injection system according to any one of the eighth to eleventh aspects is provided. In the injection control device, the control command value is a valve opening period command value of the fuel injection valve,
The correction means calculates a correction value of the valve opening period command value in the specific fuel injection based on the fuel pressure change, and corrects the valve opening period command value based on the correction value. According to a thirteenth aspect of the present invention, in the fuel injection control device for a high pressure fuel injection system according to any one of the eighth to eleventh aspects, the control command value is a valve opening period command value of the fuel injection valve. The correction means corrects the detected fuel pressure in advance based on the change in the fuel pressure when setting the valve opening period command value in the specific fuel injection, thereby obtaining the valve opening period command in the specific fuel injection. A configuration in which the value is corrected can be adopted.

According to each of these configurations, claims 8 to 11
In addition to the functions and effects of the invention described in any one of the above, the valve opening period command value in the specific fuel injection is set to an appropriate value in order to match the actual fuel injection amount in the specific fuel injection with the engine required injection amount. The fuel injection period of the fuel injection valve in the specific fuel injection can be set very accurately.

In particular, according to the configuration of the invention described in claim 13, in correcting the valve opening period command value in a specific fuel injection to an appropriate value, the detected fuel pressure is corrected in advance based on the fuel pressure change. It is not necessary to calculate the correction value of the valve opening period command value separately, so that the control structure can be simplified.

According to a fourteenth aspect of the present invention, in the fuel injection control device for a high-pressure fuel injection system according to the twelfth or thirteenth aspect, the estimating means is configured to control the fuel injection during the specific fuel injection period. A change in the fuel pressure accompanying the pumping of the fuel is further estimated based on the fuel pumping amount during the same injection period, and the correction unit matches the actual fuel injection amount with the required fuel injection amount in the specific fuel injection. For this purpose, the valve opening period command value in the specific fuel injection is further corrected based on the fuel pressure change during the injection period.

According to the above construction, in addition to the effects of the invention described in claim 12 or 13, the fuel pressure changes along with the fuel pumping during the fuel injection period in the specific fuel injection, and the fuel pressure changes. It is possible to prevent the actual fuel injection amount in the specific fuel injection from becoming larger than the required fuel injection amount in the specific fuel injection due to the change. It is possible to avoid a problem caused by an excessive amount of fuel that is not suitable for the operating state being supplied to the internal combustion engine.

According to the fifteenth aspect of the present invention, the first aspect is provided.
14. The fuel injection control device for a high-pressure fuel injection system according to item 2 or 13, wherein the estimating means detects a change in the fuel pressure caused by a fuel leak from the pressure accumulation pipe during an injection period of the specific fuel injection. Further, the correction unit estimates the valve opening period command value in the specific fuel injection so that the actual fuel injection amount matches the required fuel injection amount in the specific fuel injection. Further correction is made based on the change in fuel pressure during the period.

According to the above configuration, in addition to the effects of the invention described in claim 12 or 13, the fuel pressure changes with fuel leakage during the fuel injection period in specific fuel injection,
It is possible to prevent the actual fuel injection amount in the specific fuel injection from becoming smaller than the required fuel injection amount in the specific fuel injection due to the change in the fuel pressure. For example, it is possible to avoid a problem caused by a failure in supplying a sufficient amount of fuel suitable for the operating state of the engine to the internal combustion engine.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Hereinafter, a first embodiment in which the present invention is applied to a fuel injection control device for a four-cylinder direct injection diesel engine (hereinafter simply referred to as "engine"). Will be described.

FIG. 1 shows a schematic configuration of the engine 10 and its high-pressure fuel injection system. As shown in FIG. 1, the high-pressure fuel injection system includes injectors 12 provided for each of cylinders # 1 to # 4 of the engine 10, a common rail 20 to which the injectors 12 are connected, and a fuel tank 14. A fuel pump 30 for pressure-feeding the fuel to the common rail 20 and an electronic control unit (hereinafter abbreviated as “ECU”) 60 are provided.

The common rail 20 has a function of accumulating high-pressure fuel fed from the fuel pump 30 to a predetermined pressure. The common rail 20 uses the fuel pressure of the injector 12 based on the internal fuel pressure (hereinafter referred to as “rail pressure”). The injection pressure is determined. The common rail 20 has a relief valve 22.
The relief valve 22 is connected to the fuel tank 14 via a relief passage 21.
The relief valve 22 opens when the rail pressure becomes equal to or higher than a predetermined upper limit set pressure, and reduces the rail pressure.

The injector 12 is an electromagnetic valve driven by the ECU 60 to open and close, and injects fuel supplied from the common rail 20 into the combustion chambers (not shown) of the cylinders # 1 to # 4. Each injector 12 is also connected to the fuel tank 14 via a relief passage 21. Injector 1
Even when all the valves 2 are in the valve closed state, a part of the fuel supplied from the common rail 20 to each injector 12 is constantly leaking into the injector 12, and the fuel leaking in this manner is The fuel is returned to the fuel tank 14 through the passage 21.

The ECU 60 controls the fuel pumping of the fuel pump 30 and the fuel injection of the injector 12. The ECU 60 stores a memory 64 in which various control programs, function data, and the like are stored.
2 and the like.

Various sensors for detecting the operating state of the engine 10, the fuel state in the common rail 20, and the like are connected to the ECU 60, and detection signals are input from these sensors.

For example, a rotation speed sensor 65 is provided near a crankshaft (not shown) of the engine 10, and a cylinder discrimination sensor 66 is provided near a camshaft (not shown). The ECU 60 controls these sensors 65 and 6
The rotation speed of the crankshaft (engine rotation speed NE) and the rotation angle of the crankshaft (crank angle CA) are calculated based on the detection signal input from step S6.

An accelerator sensor 67 is provided in the vicinity of an accelerator pedal (not shown). The accelerator sensor 67 outputs a detection signal corresponding to the accelerator pedal depression amount (accelerator opening ACCP). . The common rail 20 is provided with a fuel pressure sensor 68, which outputs a detection signal corresponding to the rail pressure (actual fuel pressure PCR). Discharge port 38 of fuel pump 30
A fuel temperature sensor 69 is provided in the vicinity, and the fuel temperature sensor 69 outputs a detection signal corresponding to the temperature of the fuel (fuel temperature THF). The ECU 60 controls each of these sensors 67 to 6.
9, the accelerator opening ACCP, the actual fuel pressure PCR, and the fuel temperature THF are respectively detected.

The fuel pump 30 is provided with a drive shaft 4 driven by a crankshaft of the engine 10.
0, a feed pump 31 that operates based on the rotation of the drive shaft 40, and a pair of supply pumps (a first supply pump 50a and a second supply pump 50b) that are driven by an annular cam 42 formed on the drive shaft 40. Etc. are provided.

The feed pump 31 draws the fuel in the fuel tank 14 from the suction port 34 through the suction passage 24, and feeds the fuel to the first pump at a predetermined feed pressure.
Supply pump 50a and second supply pump 50
b. Of the fuel sucked from the suction port 34 in this manner, each of the supply pumps 50a, 50
Excess fuel not supplied to any one of b is returned to the fuel tank 14 from the relief port 36 through the relief passage 21.

Each of the first supply pump 50a and the second supply pump 50b is a so-called inner-cam type pump, and the fuel supplied from the feed pump 31 is further increased in pressure based on the reciprocating motion of a plunger (not shown). (For example, 25 to 180 MPa), and the pressurized fuel is fed from the discharge port 38 to the common rail 20 through the discharge passage 23. The fuel pumping operation is performed alternately and intermittently by the supply pumps 50a and 50b.

The fuel pump 30 has a first pump for adjusting the fuel pumping amount of each of these supply pumps 50a and 50b.
And a second adjustment valve 70b. Each of these adjustment valves 70a and 70b is composed of an electromagnetic valve, and is opened and closed by the ECU 60.

FIG. 2 shows each supply pump 50a, 50b.
4 is a timing chart showing the timing of fuel suction / feed and the change in rail pressure due to fuel leak and the like in FIG.

As shown in the figure, the fuel suction in the fuel pump 30 has a phase of 180 degrees with respect to the crank angle CA.
The operation is performed alternately by the supply pumps 50a and 50b in a state shifted by ° CA (CA: Crank Angle). Also,
Similarly, for fuel pumping in the fuel pump 30,
Each supply pump 50 with the phase shifted by 180 ° CA
a and 50b are performed alternately.

As shown in FIG. 5C, the first regulating valve 7
At 0a, the valve is opened during the suction stroke of the first supply pump 50a to start sucking fuel, while the valve is closed at a predetermined time (crank angle CA) to stop sucking the fuel. All of the fuel sucked in this way is pressurized in a pumping stroke following the suction stroke, and is pumped from the first supply pump 50a to the common rail 20. The fuel supply amount of the first supply pump 50a can be adjusted by changing the closing timing of the first regulating valve 70a.

For example, as shown by a dashed line in FIGS. 3C and 3D, the valve closing period (crank angle CA) of the first regulating valve 70a is delayed (retarded) to reduce the valve opening period. If it is increased, the fuel suction period of the first supply pump 50a becomes longer, and the fuel suction amount increases, so that the fuel pumping amount increases. Also, as described above, the first regulating valve 70
When the valve closing timing of a is retarded, the pumping start timing (crank angle CA) of the first supply pump 50a is advanced (advanced) by the crank angle CA equal to the retard amount, and the fuel pumping period is shortened. become longer.

On the other hand, as shown by the two-dot chain line in FIGS. 7C and 7D, when the valve closing period of the first regulating valve 70a is advanced to reduce the valve opening period, the first regulating valve 70a is opened. Supply pump 5
As a result, the fuel intake period is shortened, and the fuel intake amount is reduced. As a result, the fuel pumping amount is reduced. Further, as described above, when the valve closing timing of the first regulating valve 70a is advanced,
The pumping start timing of the first supply pump 50a is retarded by the crank angle CA equal to the advance amount, and the fuel pumping period is shortened.

Similarly, for the second supply pump 50b, the valve closing timing of the second regulating valve 70b (crank angle C
By retarding or advancing A), the amount of fuel pumped can be changed, and the second supply pump 50b has a crank angle CA equal to the retarding or advancing amount of the valve closing timing. Is advanced or retarded.

The fuel suction start timing and the fuel feeding end timing of each of the supply pumps 50a and 50b are always set to a fixed timing (crank angle CA), and the supply of the supply pumps 50a and 50b. The start timing can be obtained based on the closing timing of each of the regulating valves 70a and 70b. In addition, each supply pump 50a, 5
0b of the fuel pumping amount per unit crank angle CA (hereinafter, referred to as
The "fuel pumping speed KQPUMP" is equal, and is always constant regardless of the pumping start timing. Therefore, by multiplying the fuel pumping speed KQPUMP during the fuel pumping period of each of the supply pumps 50a and 50b, the total fuel pumping amount during the fuel pumping period can be obtained.

The ECU 60 sets a target rail pressure based on the engine operating state, and based on the difference between the target pressure and the actual fuel pressure PCR detected by the fuel pressure sensor 68, determines the rail pressure and the target pressure. Are controlled so that the values of the control valves 70a and 70b coincide with each other.

For example, when the actual fuel pressure PCR is lower than the target pressure, the closing timing of each of the control valves 70a and 70b is retarded to increase the fuel pumping amount, thereby increasing the rail pressure. . On the other hand, when the actual fuel pressure PCR is higher than the target pressure, the valve closing timing of each of the regulating valves 70a and 70b is advanced to reduce the fuel pumping amount.
The rail pressure is reduced by fuel injection while suppressing the rise of the rail pressure.

By performing such fuel pressure control, the rail pressure, that is, the fuel injection pressure is controlled to a pressure suitable for the operating state of the engine. Further, the ECU 60 calculates an engine required injection amount based on the engine operating state, and calculates a fuel injection period (valve opening period) based on the engine required injection amount and the rail pressure (actual fuel pressure PCR). The injector 12 is driven to open and close based on the fuel injection period.

Here, the rail pressure value at the time of calculating the fuel injection period, that is, the actual fuel pressure PCR detected by the fuel pressure sensor 68 does not always match the rail pressure value at the start of fuel injection. .

For example, as described above, the common rail 20
Since the fuel inside is constantly leaking to the fuel tank 14 through the injector 12, the rail pressure PCRINJ at the start of the fuel injection may be lower than the actual fuel pressure PCR due to such fuel leak as shown in FIG. . Alternatively, as shown in FIG. 3, when the fuel pumping period of the fuel pump 30 becomes longer and the fuel pumping is started before the fuel injection is started, the rail pressure PC at the start of the fuel injection is changed.
RINJ may be higher than the actual fuel pressure PCR by this fuel pumping.

In this embodiment, the actual fuel pressure PCR
A change in rail pressure from the time of detection to the start of fuel injection is estimated, and the change in rail pressure is reflected in the calculation of the fuel injection period.

Hereinafter, a control procedure related to such fuel injection will be described with reference to FIGS. FIG. 4 and FIG.
5 is a flowchart illustrating a procedure for calculating a fuel injection period.
The ECU 60 executes a series of processes shown in each of the flowcharts as an interrupt process for each predetermined crank angle (each 180 ° CA).

First, at step 100, the ECU 6
0 detects the actual fuel pressure PCR. The detection timing of the actual fuel pressure PCR, that is, the interruption timing of this routine is shown in FIGS.
As shown in FIG. 3, the timing at which the state of each supply pump 50a, 50b switches from the suction stroke to the pressure feeding stroke (the crank angle CA is, for example, CA0, CA1, CA2, CA shown in each drawing)
3 is reached).

In step 200, the accelerator operation amount ACC
Engine required injection amount Q based on P and engine speed NE, etc.
Calculate FIN. In step 300, a basic injection period TQFINB is calculated based on the engine required injection amount QFIN and the actual fuel pressure PCR. Engine required injection amount QFIN, actual fuel pressure PCR, and basic injection period TQFIN
The relationship with B is obtained in advance based on an experiment or the like, and EC is used as function data for calculating the basic injection period TQFINB.
It is stored in the memory 64 of U60.

FIG. 6 shows this function data as a function map. As shown in the figure, the basic injection period TQF
INB is calculated as a relatively long period as the engine required injection amount QFIN increases and the actual fuel pressure PCR decreases.

Next, at step 400, the ECU 6
0 calculates the pressure change amount DPCR. This pressure change amount DPCR is obtained when the actual fuel pressure PCR is detected (C in FIGS. 2 and 3).
A0 to CA3) to the time when fuel injection by the injector 12 is started (crank angle interval: FIG. 2A)
(See FIG. 3A) (hereinafter, this period is referred to as “rail pressure change estimation period APCR”). This is the amount of change in rail pressure due to fuel pumping and fuel leak.

FIG. 5 is a flowchart showing in detail the procedure for calculating the pressure change amount DPCR. In step 402 shown in FIG.
Calculate MP. This fuel pumping period APUMP (FIG. 3)
(A) is a period (crank angle interval) during which fuel pumping is performed during the rail pressure change estimation period APCR.

First, the ECU 60 determines that this fuel pumping period A
When calculating PUMP, each of the regulating valves 70a, 7 set in the suction stroke before the current fuel pumping is started.
Based on the valve closing timing of 0b, the pumping start timing of the fuel pump 30 is calculated. For example, when the current interrupt timing is the timing CA1 shown in FIG.
The pumping start timing is calculated based on the valve closing timing set in 1). Similarly, the interrupt timing is set to the timing CA.
When it is 2, the pumping start timing is calculated based on the valve closing timing set in the period (CA1 to CA2).

Next, the ECU 60 compares this pumping start time with a separately calculated fuel injection start time, and when the pumping start time is a timing that is more retarded than the fuel injection start time, that is, the fuel injection is started. If the fuel pumping is not performed before the fuel pumping is started, the fuel pumping period APUMP is calculated as “0”. On the other hand, when the pumping start timing is a timing that is more advanced than the fuel injection start timing, that is, when the fuel pumping is started before the fuel injection is started, the fuel injection start timing and the pumping start timing are compared. The period between the fuel pumping period AP
Calculated as UMP.

After calculating the fuel pumping period APUMP in this way, the ECU 60 calculates the fuel pumping amount QPUMP during the rail pressure change estimation period APCR in step 404 according to the following equation (1).

QPUMP = APUMP · KQPUMP (1) APUMP: fuel pumping period KQPUMP: fuel pumping speed Next, at step 406, the ECU 60 calculates a fuel leak period TLEAK. This fuel leak period TL
EAK is obtained by converting the rail pressure change estimation period APCR using the crank angle CA as a unit into time. EC
U60 calculates the fuel leak period TLEAK according to the following equation (2).

TLEAK = K · APCR / NE (2) APCR: Rail pressure change estimation period NE: Engine rotation speed K: Conversion constant In step 408, the fuel leak period TLEAK
Fuel leak amount QLEAK during rail pressure change estimation period APCR based on actual fuel pressure PCR and fuel temperature THF
Is calculated. The fuel leak amount QLEAK tends to increase as the fuel leak period TLEAK increases, as the actual fuel pressure PCR increases, and as the fuel temperature THF increases. The fuel leak period TLEAK and the actual fuel pressure PC
R and the relationship between the fuel temperature THF and the fuel leak amount QLEAK are obtained in advance by experiments or the like.
4 is stored as function data for calculating the fuel leak amount QLEAK.

Next, at step 410, the actual fuel pressure PCR
And the bulk modulus E of the fuel is calculated based on the fuel temperature THF. The bulk modulus E tends to increase as the actual fuel pressure PCR increases and as the fuel temperature THF decreases. Such actual fuel pressure PCR and fuel temperature TH
The relationship between F and the bulk modulus E is obtained in advance by an experiment or the like, and is stored in the memory 64 of the ECU 60 as function data for calculating the same bulk modulus E.

Thus, the fuel pumping amount QPUMP,
After calculating the fuel leak amount QLEAK and the bulk modulus of elasticity E, in step 412, the ECU 60 calculates the pressure change amount DPCR according to the following equation (3).

DPCR = E · (QPUMP−QLEK) / VCR (3) E: bulk modulus QPUMP: fuel pumping amount QLEAK: fuel leak amount VCR: volume of common rail 20 It is apparent from this arithmetic expression (3). Thus, the fuel pumping amount QP
When UMP is larger than the fuel leak amount QLEAK,
The pressure change amount DPCR is calculated as a positive value. Conversely, when the fuel leak amount QLEAK is larger than the fuel pumping amount QPUMP, the pressure change amount DPCR is calculated as a negative value.

After calculating the pressure change amount DPCR in this way, the ECU 60 shifts the processing to step 500 shown in FIG. 4, and calculates the sensitivity coefficient TQPCR based on the engine required injection amount QFIN and the actual fuel pressure PCR.

When the rail pressure changes during the rail pressure change estimation period APCR and becomes a pressure value different from the actual fuel pressure PCR, when each injector 12 is driven based on the basic injection period TQFINB, the actual fuel injection amount becomes It will be deviated from the engine required injection amount QFIN. Sensitivity coefficient TQPCR
Is a value obtained by converting a deviation amount of the fuel injection amount with respect to a unit change amount (for example, 1 MPa) when the rail pressure changes as described above into a deviation amount of the fuel injection period.

The relationship between the sensitivity coefficient TQPCR and the required engine injection amount QFIN and the actual fuel pressure PCR is determined in advance by an experiment or the like.
It is stored as function data for calculating QPCR. FIG. 7 shows this function data as a function map. As shown in the figure, the sensitivity coefficient TQPCR is
It is calculated as a relatively large value as the engine required injection amount QFIN increases and the actual fuel pressure PCR decreases.

Next, in step 600, the ECU 60 calculates the injection period correction value TQFINH by the following equation (4).
Calculated according to TQFINH = TQPCR · DPCR (4) TQPCR: Sensitivity coefficient DPCR: Pressure change amount The injection period correction value TQFINH is the actual fuel injection amount and the engine required injection amount Q due to the rail pressure change as described above.
Basic injection period TQFI to compensate for deviation from FIN
This is a value for correcting NB.

Then, in step 700, the ECU 60 calculates the final injection period TQF according to the following equation (5).
Calculate IN. TQFIN = TQ FINB−TQ FINH (5) TQ FINB: Basic injection period TQ FINH: Injection period correction value After calculating the final injection period TQ FIN in this way, ECU
60 ends this routine once.

The ECU 60 determines that the final injection period T
A drive signal for the injector 12 is generated based on QFIN, and the drive signal is output to the injector 12 when the crank angle CA coincides with the fuel injection start time. As a result, the injector 12 requests the engine required injection amount QFIN
Will be injected.

As described above, in the fuel injection control of this embodiment, the pressure change amount DPCR during the rail pressure change estimation period APCR is estimated based on the fuel pumping amount QPUMP and the fuel leak amount QLEAK, and The basic injection period TQFINB corrected by the injection period correction value TQFINH based on the DPCR is set as the final injection period TQFIN.

Therefore, if the rail pressure changes due to fuel pumping or fuel leakage during the rail pressure change estimation period APCR,
Even if the detected value of the rail pressure (actual fuel pressure PCR) does not substantially change during engine steady operation, the change (pressure change DPCR) can be accurately determined based on the fuel pumping amount QPUMP and the fuel leak amount QLEAK. Can be estimated.
Then, based on the pressure change amount DPCR, the final injection period TQFIN can be set extremely accurately as an appropriate value for suppressing the actual fuel injection amount from deviating from the engine required injection amount QFIN.

(1) As a result, according to the present embodiment, even if the rail pressure changes, particularly those that occur after the detection of the actual fuel pressure PCR, the rail pressure changes are surely reflected in the fuel injection control. Thus, highly accurate fuel injection control can be realized.

(2) In particular, when estimating the pressure change amount DPCR, the fuel pumping amount QPUMP and the fuel leak amount QL
Since the EAK is referred to, both the increase in the rail pressure due to the fuel pumping and the decrease in the rail pressure due to the fuel leak can be reflected in the estimation of the pressure change amount DPCR. Therefore, the actual fuel injection amount is reduced by the increase of the rail pressure to the engine required injection amount QFIN.
It is possible to prevent the actual fuel injection amount from becoming smaller than the engine required injection amount QFIN due to a decrease in the rail pressure.

As a result, problems such as deterioration of the exhaust characteristics and the like caused by the supply of an excessive amount of fuel unsuitable for the operating state of the engine to the engine 10, reduction of the engine output, etc.
It is possible to avoid problems caused by a failure in supplying a sufficient amount of fuel suitable for the engine operating state to the engine 10, respectively.

[Second Embodiment] Next, a second embodiment of the present invention will be described, focusing on differences from the first embodiment. The description of the same configuration as that of the first embodiment will be omitted.

In this embodiment, the final injection period TQFIN
Is different from that of the first embodiment. Hereinafter, the calculation procedure of the final injection period TQFIN will be described with reference to the flowchart shown in FIG. Note that, among the steps 100 to 710 shown in the same figure, the steps denoted by the same reference numerals as those in FIG. 4 described above perform the same processing, and thus the description of the processing content is omitted.

After executing the processes in steps 100 and 200, the ECU 60 calculates the pressure change amount DPCR in step 400. Then, in step 610, the pressure change amount DPCR is added and corrected to the actual fuel pressure PCR, and the correction value is set as a new actual fuel pressure PCR.

Next, the ECU 60 refers to the function data shown in FIG. 6 in step 710 in the same manner as in the processing in step 300 shown in FIG. 4 to obtain the updated actual fuel pressure PCR and the engine required injection amount QFIN. The final injection period TQFIN is calculated based on After calculating the final injection period TQFIN in this way, the ECU 60 once ends the processing of this routine.

As described above, in the present embodiment, the actual fuel injection amount is changed to the engine required injection amount QFI due to the change in the rail pressure.
In suppressing the deviation from N, the final injection period TQFI
It is only necessary to correct the actual fuel pressure PCR based on the pressure change amount DPCR before calculating N.

(3) Therefore, in addition to the functions and effects described in (1) and (2) in the first embodiment, there is no need to intentionally calculate the basic injection period TQFINB or the injection period correction value TQFINH. As shown in FIG. 7, there is no need to prepare in advance function data or the like for calculating the injection period correction value TQFINH, so that the control structure can be simplified.

[Third Embodiment] Next, a third embodiment of the present invention will be described, focusing on differences from the second embodiment. The description of the same configuration as that of the second embodiment is omitted.

In the present embodiment, the fuel injection control device according to the present invention is applied to an engine 10 capable of executing pilot injection. As is well known, in the pilot injection, a small amount of fuel is injected in advance (pilot injection) prior to the main injection, thereby suppressing a rapid increase in combustion pressure and reducing combustion noise. In the fuel injection control of the present embodiment described below, when the rail pressure decreases due to the pilot injection, the injection period during the main injection (main injection period TQMAIN) is corrected to an appropriate period based on the reduction amount of the rail pressure. I am trying to do it.

In this embodiment, the closing timing of each of the regulating valves 70a and 70b is set in advance so that the fuel pumping by the fuel pump 30 is always started after the end of the main injection (see FIG. 11). Therefore, no fuel pumping is performed during the period from the detection of the actual fuel pressure PCR to the end of the main injection, and the rail pressure does not change due to the fuel pumping.

Hereinafter, such a main injection period TQMAI
The procedure for calculating N will be described. FIG. 9 and FIG. 10 are flowcharts showing a procedure for calculating the main injection period TQMAIN and the pilot injection period TQPLT. FIG. 11 is a timing chart showing the timing of fuel suction / feed in each of the supply pumps 50a and 50b, the manner of change in rail pressure accompanying pilot injection, main injection, and the like.

The ECU 60 performs a series of processes shown in the flowcharts of FIGS.
This is executed as an interrupt process for each 0 ° CA). Note that the interrupt timing of this routine is the timing at which the state of each supply pump 50a, 50b switches from the suction stroke to the pressure feeding stroke (the crank angle CA is, for example, CA0 shown in FIG. 11) as in the processing routines shown in FIGS. , CA1, CA2, and CA3).

The ECU 60 executes Step 10 shown in FIG.
At 0 and 200, the actual fuel pressure PCR is detected, and further, the engine required injection amount QFIN is calculated based on the accelerator opening ACCP and the engine speed NE.

In step 320, a pilot injection amount QPLT is calculated based on the engine speed NE and the required engine injection amount QFIN. This pilot injection amount Q
PLT, engine speed NE and engine required injection quantity QFIN
Is determined in advance by experiments or the like so as to be an amount most suitable for the engine operating state in consideration of combustion noise, smoke concentration, etc., and is stored in the memory 64 as function data for calculating the pilot injection amount QPLT. Is stored in

Next, at step 330, the main injection amount QMAIN is calculated according to the following equation (6). QMAIN = QFIN-QPLT (6) QFIN: engine required injection amount QPLT: pilot injection amount Thus, pilot injection amount QPLT and main injection amount Q
After the MAIN is calculated, in step 450, the rail pressure change amount (pressure change amount DPCRP) during the period from the detection of the actual fuel pressure PCR to the start of pilot injection (rail pressure change estimation period APCRPLT: see FIG. 11).
LT) and a period from the time of the detection to the start of the main injection (rail pressure change estimation period APCRMAIN: FIG. 11).
Rail pressure change (pressure change DPCR)
MAIN).

FIG. 10 shows each of these pressure change amounts DPCRPL.
It is a flowchart which shows the calculation procedure of T and DPCRMAIN in detail. In step 452 shown in FIG.
The CU 60 calculates the above-described rail pressure change estimation period APCRPL.
T and APCRMAIN are respectively converted to time based on the engine speed NE, and the converted values are converted to actual fuel pressure PCR.
And TLEAKPLT, a fuel leak period from the time of detection to the start of pilot injection, and a fuel leak period TLEAKMAI from the time of detection to the start of main injection.
N is set.

Next, in step 454, the ECU 60 executes the fuel leak periods TLEAKPLT, TLEA in the same manner as in the processing of step 408 shown in FIG.
Based on KMAIN, actual fuel pressure PCR, and fuel temperature THF, a fuel leak amount (fuel leak amount QLEAKPLT) from the time of detecting the actual fuel pressure PCR to the start of pilot injection.
And a fuel leak amount (fuel leak amount QLEAKMAIN) from the time of detection to the start of main injection, respectively. Further, the ECU 60 calculates the bulk modulus E based on the actual fuel pressure PCR and the fuel temperature THF in step 456, similarly to the processing in step 410 shown in FIG.

Then, at step 458, the ECU
60 calculates the pressure change amounts DPCRPLT and DPCRMAIN according to the following arithmetic expressions (7) and (8), respectively. DPCRPLT = E · QLEKPLT / VCR (7) DPCRMAIN = E · (QPLT + QLEAKMAIN) / VCR (8) E: Bulk modulus QLEAKPLT, QLEAKMAIN: Fuel leak amount VCR: Volume of common rail 20 The above calculation As is apparent from equation (8), the actual fuel pressure P
Pressure change amount D from detection of CR to start of main injection
To calculate PCRMAIN, the fuel leak amount QLEAKM
In addition to AIN, the pilot injection amount QPLT is also reflected. This is because when the pilot injection is performed, the main injection is performed based on the rail pressure reduced by the pilot injection.

Thus, each pressure change amount DPCRPLT, D
After calculating the PCRMAIN, the ECU 60 executes the processing in FIG.
The process proceeds to step 620 shown in FIG. This step 620
Then, the rail pressure at the start of pilot injection (hereinafter,
PCRPLT)
The rail pressure at the start of the main injection (hereinafter referred to as “main injection fuel pressure”) PCRMAIN is calculated according to the following arithmetic expressions (9) and (10), respectively.

PCRPLT = PCR-DPCRPLT (9) PCRMAIN = PCR-DPCRMAIN (10) PCR: actual fuel pressure DPCRPLT, DPCRMAIN: pressure change amount It is clear from these arithmetic expressions (9) and (10). Like,
Both the pilot injection fuel pressure PCRPLT and the main injection fuel pressure PCRMAIN are obtained by correcting the actual fuel pressure PCR based on the pressure change amounts DPCRPLT and DPCRMAIN, respectively.

Next, in step 720, the fuel pressures PCRPLT, PCRMAIN and pilot injection amount QP are referred to by referring to the function data shown in FIG. 6 in the same manner as in step 710 shown in FIG.
Based on LT and main injection amount QMAIN, pilot injection period TQPLT and main injection period TQMAIN
Are calculated respectively. As a result, each of these injection periods TQ
PLT and TQMAIN are substantially the above fuel pressure PCRP
The correction is made based on LT and PCRMAIN.

Thus, each injection period TQPLT, TQMA
After each calculation of IN, the ECU 60 once ends the processing of this routine. As described above, in the present embodiment, the change in the rail pressure (the pressure change amount D) from the time when the actual fuel pressure PCR is detected to the time when the pilot injection or the main injection is started.
PCRPLT, DPCRMAIN) based on the pilot injection period TQPLT and the main injection period TQMAIN.
Is corrected.

(4) Therefore, due to such a change in the rail pressure, the actual fuel injection amount in the pilot injection or the main injection is reduced by the pilot injection amount QPLT or the main injection amount QMA.
Injection periods TQPLT and TQMAIN can be set extremely accurately as appropriate values for suppressing deviation from IN. Even when pilot injection is performed,
Extremely accurate fuel injection control can be realized.

(5) Also, the amount of decrease in rail pressure due to fuel leakage (pressure change amount DPCRPLT, DPCRMAI)
N), the actual fuel injection amount at the time of pilot injection or main injection is corrected by the pilot injection amount QPLT as the engine required injection amount by correcting each injection period TQPLT and TQMAIN based on the decrease amount. And the main injection amount QMAIN can be suppressed from being smaller than the main injection amount QMAIN. As a result, it is possible to avoid problems such as a decrease in engine output caused by a failure to supply a sufficient amount of fuel suitable for the engine operating state to the internal combustion engine.

(6) In particular, when estimating the pressure change amount DPCRMAIN from the detection of the actual fuel pressure PCR to the start of the main injection, not only such a fuel leak but also a decrease in the rail pressure due to the pilot injection is considered. Therefore, by executing the pilot injection, it is possible to prevent the rail pressure from decreasing and the actual fuel injection amount during the main injection from becoming smaller than the main injection amount QMAIN. Therefore, at this point, it is possible to more reliably avoid the occurrence of problems such as a decrease in engine output.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described, focusing on differences from the first embodiment. The description of the same configuration as that of the first embodiment will be omitted.

In this embodiment, in addition to the rail pressure change during the rail pressure change estimation period APCR, the rail pressure change due to fuel pumping and fuel leak during the fuel injection period is estimated, and the rail pressure change is estimated. Injection period TQF based on
By further correcting IN, the accuracy of the fuel injection control is further improved.

Hereinafter, a procedure for estimating the change in the rail pressure during the fuel injection period and a procedure for correcting the final injection period TQFIN based on the change in the rail pressure will be described. FIG.
6 is a flowchart showing a procedure for estimating a rail pressure change during the fuel injection period (hereinafter, referred to as “pressure change amount DPCRINJ”). Each process shown in this flowchart is a part of a series of processes shown in the flowchart of FIG. , Are executed subsequently to the processing of step 412.

First, in step 420 shown in the figure, the ECU 60 adds the actual fuel pressure PCR and the pressure change amount DPCR obtained through the processing in step 412, and based on the added value (PCR + DPCR) and the fuel temperature THF. Then, the bulk elastic coefficient E is calculated again so as to correspond to the value at the start of fuel injection.

Next, at step 422, a fuel leak amount QLEAKINJ during the fuel injection period is calculated based on the basic injection period TQFINB and the fuel temperature THF. Then, in step 424, it is determined whether or not the pumping start timing of the fuel pump 30 is on the more advanced side than the fuel injection start timing, that is, whether the fuel pump 30 is started before the fuel injection is started.
It is determined whether or not the fuel pumping is performed. Here, if it is determined that the fuel pumping is performed before the fuel injection is started, the fuel pumping is always performed during the fuel injection period. Therefore, in step 426, the ECU 60 sets the basic injection period TQFINB to the engine rotational speed. The crank angle CA is converted based on NE, and the converted value is set as a fuel pumping period APUMPINJ during the fuel injection period.

Next, at step 428, the fuel pumping amount Q during the fuel injection period is calculated according to the following equation (11).
Calculate PUMPINJ. QPUMPINJ = APUMPINJ · KQPUMP (11) APUMPINJ: fuel pumping period KQPUMP: fuel pumping speed On the other hand, if it is determined in step 424 that fuel pumping is not performed before fuel injection is started, the ECU 60 Shifts the processing to step 430, and sets the fuel injection end timing to the crank angle C based on the fuel injection start timing, the basic injection period TQFINB, and the engine speed NE.
Calculate using A as a unit.

In the following step 432, it is determined whether fuel pumping is started during the fuel injection period by comparing the fuel injection ending time with the fuel pump 30 pumping start time. Here, when it is determined that the fuel pumping is started during the fuel injection period, in step 434, the period (crank angle CA) from the pumping start timing to the fuel injection end timing is set to the fuel pumping period APUM during the fuel injection period.
Calculate as PINJ. Then, in step 436, the fuel pumping amount QPUMPINJ during the fuel injection period is calculated according to the above equation (11).

On the other hand, if it is determined in step 432 that the fuel pumping is not started during the fuel injection period, the fuel pumping period does not overlap with the fuel injection period.
In step 435, the ECU 60 sets the fuel pumping amount QPUMPINJ during the fuel injection period to “0”.

After executing any one of the above steps 428, 435, and 436, the ECU 60 calculates a pressure change amount DPCRINJ during the fuel injection period in step 440 according to the following equation (12).

DPCRINJ = E · (QPUMPINJ−QLEAKINJ) / VCR (12) E: Bulk modulus QPUMPINJ: Fuel pumping amount during fuel injection period QLEAKINJ: Fuel leakage amount during fuel injection period VCR: Common rail 20 In step 442, the ECU 60 calculates the pressure change amount DPCR during the rail pressure change estimation period APCR and the pressure change amount DP during the fuel injection period, which have already been calculated.
The average pressure change amount DPCRAVE is calculated according to the following arithmetic expression (13) based on the CRINJ.

DPCRAVE = DPCR + DPCRINJ / 2 (13) The average pressure change amount DPCRAVE is equal to the actual fuel pressure P.
The pressure change amount DPCR from the detection of CR to the start of fuel injection (that is, during the rail pressure change estimation period APCR) and the pressure change amount (DPCR +
DPCRINJ).

After calculating the average pressure change amount DPCRAVE in this way, the processing after step 500 shown in FIG. 4 is executed. At this time, in the process of step 600,
Pressure change amount D during rail pressure change estimation period APCR
Instead of the PCR, the injection period correction value TQFINH is calculated based on the average pressure change amount DPCRAVE. Accordingly, in the following step 700, the rail pressure change (pressure change amount DPC) during the rail pressure change estimation period APCR is performed.
R), the basic injection period T based on the rail pressure change (pressure change amount DPCRINJ) during the fuel injection period.
QFINB is corrected.

(7) Therefore, according to the present embodiment, the actual fuel injection amount is changed from the detection of the actual fuel pressure PCR to the start of fuel injection by the change in the rail pressure so that the engine required injection amount QFIN is obtained.
In addition to suppressing the deviation, it is also possible to suppress the deviation of the fuel injection amount due to the rail pressure change during the fuel injection period, and it is possible to realize more accurate fuel injection control. .

(8) In particular, when estimating the amount of change in rail pressure (pressure change DPCRINJ) during such a fuel injection period, the fuel pumping amount QPUMP and the fuel leak amount QL
Since the EAK is referred to, the increase in the rail pressure due to the fuel pumping and the decrease in the rail pressure due to the fuel leak both correspond to the pressure change amount DPCRIN.
J can be reflected. Therefore, the actual fuel injection amount becomes larger than the engine required injection amount QFIN due to the increase in the rail pressure, and the actual fuel injection amount becomes smaller than the engine required injection amount QFIN due to the decrease in the rail pressure. Can be suppressed. As a result, malfunctions caused by the supply of an excessive amount of fuel unsuitable for the engine operating state, such as deterioration of exhaust characteristics, to the engine 10 and a decrease in engine output, etc. It is possible to avoid each of the problems caused by the amount of fuel not being supplied to the engine 10.

[Other Embodiments] (a) In the first and second embodiments, the pressure change amount DPCR during the rail pressure change estimation period APCR is calculated using the fuel pumping amount QP
Although the estimation is performed based on both the UMP and the fuel leak amount QLEAK, the pressure change amount D is determined based on only the fuel pumping amount QPUMP or only the fuel leak amount QLEAK.
The PCR may be estimated.

(B) In the third embodiment, the actual fuel pressure PC
Pressure change amount DP from detection of R to start of main injection
Although CRMAIN is estimated based on the fuel leak amount QLEAKMAIN and the pilot injection amount QPLT, the pressure change amount DPCRMAIN may be estimated based only on the fuel leak amount QLEAKMAIN or only the pilot injection amount QPLT. .

(C) In the third embodiment, when the fuel pumping can be started before the main injection is started, when the actual fuel pressure PCR is detected and the main injection is started. The fuel pumping amount may be determined, and the pressure change amount DPCRMAIN may be estimated based on the fuel pumping amount, or in addition to the fuel pumping amount, based on the fuel leak amount QLEAKMAIN and the pilot injection amount QPLT.

(D) The third embodiment and the above (b),
In the embodiment shown in (c), each pressure change amount DPCRPL
T, DPCRMAIN, the actual fuel pressure PCR is corrected in advance, and the corrected value (the fuel pressure during pilot injection PC
RPLT, fuel injection period during pilot injection or main injection (pilot injection period TQPLT, main injection period TQ) based on main injection fuel pressure PCRMAIN.
MAIN) is calculated, but in the same manner as in the first embodiment, the correction values relating to the pilot injection period TQPLT and the main injection period TQMAIN are changed to the pressure change amounts D.
Calculated based on PCRPLT and DPCRMAIN, and based on the correction values, these fuel injection periods TQPLT,
TQMAIN may be corrected.

(E) The third embodiment and the above (b),
In the embodiments shown in (c) and (d), similarly to the fourth embodiment, a change in rail pressure due to fuel pumping or fuel leak during the pilot injection period or the main injection period is estimated, and the rail is changed. The pilot injection period TQPLT and the main injection period TQMAIN may be further corrected based on the pressure change.

(F) In the third embodiment, the pilot injection is performed only once before the main injection as an embodiment of the pilot injection. However, the pilot injection is executed a plurality of times before the main injection. May be performed. In such a case, for the second and subsequent pilot injections, a change in the rail pressure is estimated based on the total fuel injection amount of the pilot injection executed before that, and the pilot injection is performed based on the same rail pressure change. The fuel injection period at is corrected.

(G) In the fourth embodiment, the pressure change amount DPCRINJ during the fuel injection period is determined by the fuel pumping amount QPU
MPINJ and the fuel leak amount QLEAKINJ are estimated, but the fuel pumping amount QPUMPINJ
Alternatively, the pressure change amount DPCRINJ may be estimated based on only the fuel leak amount QLEAKINJ.

(H) In the first, second, and fourth embodiments, the fuel pumping speed of the fuel pump 30 is calculated assuming that the fuel pumping speed (KQPUMP) of the fuel pump 30 is constant. For example, even when the fuel pumping speed changes depending on the pumping start timing, the fuel pumping amount can be calculated by referring to a map or the like showing the fuel pumping speed corresponding to the pumping start timing.

(I) In each of the above embodiments, the case where the fuel injection amount is controlled based on the fuel injection period, that is, the valve opening period of the injector 12, has been described. However, the present invention is not limited to such a valve opening period. The fuel injection amount may be controlled on the basis of the opening degree of No. 12, and the opening degree command value may be corrected based on a change in the rail pressure.

(J) In each of the above embodiments, a diesel engine has been exemplified as an internal combustion engine to which the fuel injection control device of the present invention is applied. For example, a direct injection gasoline engine that directly injects fuel into a combustion chamber may be provided with the same device. Can also be applied.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a high-pressure fuel injection system of a diesel engine.

FIG. 2 is a timing chart showing a change mode of a rail pressure due to a fuel leak or the like;

FIG. 3 is a timing chart showing a change mode of a rail pressure accompanying fuel pressure feeding and the like.

FIG. 4 is a flowchart illustrating a calculation procedure of a fuel injection period according to the first embodiment.

FIG. 5 is a flowchart illustrating a procedure for calculating a pressure change amount according to the first embodiment.

FIG. 6 is a graph showing a relationship between a fuel pressure, a fuel injection amount, and a fuel injection period.

FIG. 7 is a graph showing a relationship between a fuel pressure, an engine required injection amount, and a sensitivity coefficient.

FIG. 8 is a flowchart illustrating a calculation procedure of a fuel injection period according to the first embodiment.

FIG. 9 is a flowchart illustrating a calculation procedure of a fuel injection period in a third embodiment.

FIG. 10 is a flowchart illustrating a procedure for calculating a pressure change amount according to the third embodiment.

FIG. 11 is a timing chart showing a change mode of a rail pressure accompanying a pilot injection, a main injection, and the like.

FIG. 12 is a flowchart illustrating a part of a procedure for calculating a pressure change amount according to the fourth embodiment;

FIG. 13 is a timing chart showing a variation of the fuel pressure in the pressure accumulation pipe.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Engine, 12 ... Injector, 14 ... Fuel tank, 20 ... Common rail, 21 ... Relief passage, 22 ...
Relief valve, 23: discharge passage, 24: suction passage, 3
0: fuel pump, 31: feed pump, 34: suction port, 36: relief port, 38: discharge port, 40
... drive shaft, 42 ... cam, 50a ... first supply pump, 50b ... second supply pump, 60 ... E
CU, 62 CPU, 64 memory, 65 rotational speed sensor, 66 cylinder discrimination sensor, 67 accelerator sensor, 6
8: fuel pressure sensor, 69: fuel temperature sensor, 70a: first regulating valve, 70b: second regulating valve.

Continued on the front page F term (reference) 3G301 HA02 JA00 LB06 MA14 MA18 NB02 ND01 PB01Z PB08A PB08Z PE01Z PE03Z PE05Z PF03Z

Claims (15)

[Claims] A fuel injection valve for injecting fuel into an internal combustion engine is connected, a fuel pressure in a pressure accumulating pipe to which fuel is supplied from a fuel pump is detected, and a fuel pressure is set based on the detected fuel pressure and an engine required injection amount. A fuel injection control device for a high-pressure fuel injection system that drives and controls the fuel injection valve based on a control command value that is performed, based on a variable element of the high-pressure fuel injection system that changes a fuel pressure in the pressure accumulation pipe. Estimating means for estimating the change in the fuel pressure from the time of detecting the fuel pressure to the time of starting the fuel injection; and estimating the control command value so that the actual fuel injection amount of the fuel injection valve matches the engine required injection amount. And a correcting means for correcting based on a change in the fuel pressure to be performed. 2. A fuel injection control device for a high-pressure fuel injection system according to claim 1, wherein said estimating means sets a fuel pumping amount of said fuel pump as said variable element and starts fuel injection from detection of said fuel pressure. The fuel pressure change is estimated on the basis of the fuel pumping amount up to the fuel injection control device. 3. The fuel injection control device for a high-pressure fuel injection system according to claim 1, wherein said estimating means sets a leak amount of fuel leaking from said pressure accumulation pipe as said variable element, and starts fuel injection from the time of detecting said fuel pressure. A fuel injection control device for a high-pressure fuel injection system, wherein the fuel pressure change is estimated based on the leak amount up to the start. 4. The fuel injection control device for a high-pressure fuel injection system according to claim 1, wherein the control command value is a valve opening period command value of the fuel injection valve, and the correction means is A fuel injection control device for a high-pressure fuel injection system, wherein a correction value of the valve opening period command value is calculated based on a fuel pressure change, and the valve opening period command value is corrected based on the correction value. 5. The fuel injection control device for a high-pressure fuel injection system according to claim 1, wherein the control command value is a valve opening period command value of the fuel injection valve, and the correction means is A fuel injection control device for a high-pressure fuel injection system, wherein the detected fuel pressure is corrected in advance based on the fuel pressure change when setting the valve opening period command value. . 6. The fuel injection control device for a high-pressure fuel injection system according to claim 4, wherein the estimating means detects a change in the fuel pressure accompanying the fuel pumping of the fuel pump during a fuel injection period. The correction means further estimates the valve opening period command value based on the fuel pressure change during the fuel injection period so that the actual fuel injection amount coincides with the engine required injection amount. And a fuel injection control device for a high-pressure fuel injection system. 7. The fuel injection control device for a high-pressure fuel injection system according to claim 4, wherein the estimating means detects a change in the fuel pressure due to a fuel leak from the pressure accumulation pipe during a fuel injection period. The correction means further estimates based on the leak amount during the fuel injection period, and the correction means changes the valve opening period command value so that the actual fuel injection amount matches the engine required injection amount during the fuel injection period. A fuel injection control device for a high-pressure fuel injection system, wherein the correction is further performed based on 8. The fuel injection control device for a high-pressure fuel injection system according to claim 1, wherein the high-pressure fuel injection system divides an amount of fuel equal to the engine required injection amount and injects the same from the fuel injection valve. The control command value is set separately for each fuel injection based on the required fuel injection amount and the detected fuel pressure in each fuel injection, and the estimating means sets the fuel injection amount for each fuel injection from the time of detecting the fuel pressure. Estimating the change in the fuel pressure until the start of the specific fuel injection based on the variable element, the correction means calculates the actual fuel injection amount in the specific fuel injection based on the fuel pressure change. A fuel injection control device for a high-pressure fuel injection system, wherein a control command value in the specific fuel injection is corrected so as to match a required fuel injection amount in the specific fuel injection. 9. A fuel injection control device for a high-pressure fuel injection system according to claim 8, wherein said estimating means sets a fuel injection amount of said fuel injection valve as said variable element, and sets said specific amount from said detection of said fuel pressure. A fuel injection control device for a high-pressure fuel injection system, wherein the fuel pressure change is estimated on the basis of an integrated value of the fuel injection amount until fuel injection is started. 10. A fuel injection control device for a high-pressure fuel injection system according to claim 8, wherein said estimating means uses a fuel pumping amount of said fuel pump as said variable element, and sets said specific fuel from the time of detecting said fuel pressure. A fuel injection control device for a high-pressure fuel injection system, wherein the fuel pressure change is estimated based on the fuel pumping amount until injection is started. 11. A fuel injection control device for a high-pressure fuel injection system according to claim 8, wherein said estimating means sets a leak amount of fuel leaking from said pressure accumulating pipe as said variable element, and specifies said leakage amount when said fuel pressure is detected. A fuel injection control device for a high-pressure fuel injection system, wherein the fuel pressure change is estimated based on the leak amount up to the time when the fuel injection is started. 12. The fuel injection control device for a high-pressure fuel injection system according to claim 8, wherein the control command value is a valve opening period command value of the fuel injection valve, and A fuel for a high-pressure fuel injection system, wherein a correction value of a valve opening period command value in the specific fuel injection is calculated based on a change in fuel pressure, and the valve opening period command value is corrected based on the correction value. Injection control device. 13. A fuel injection control device for a high-pressure fuel injection system according to claim 8, wherein said control command value is a valve opening period command value of said fuel injection valve, and said correcting means is When setting the valve opening period command value for a specific fuel injection, the detected fuel pressure is corrected in advance based on the change in the fuel pressure, thereby correcting the valve opening period command value for the specific fuel injection. A high-pressure fuel injection system. 14. A fuel injection control device for a high-pressure fuel injection system according to claim 12, wherein said estimating means is configured to control the fuel pressure accompanying the fuel pumping of the fuel pump during an injection period of the specific fuel injection. Is further estimated on the basis of the fuel pumping amount during the same injection period, and the correcting means adjusts the fuel injection amount in the specific fuel injection so that the actual fuel injection amount matches the required fuel injection amount in the specific fuel injection. A fuel injection control device for a high-pressure fuel injection system, wherein the valve period command value is further corrected based on a change in fuel pressure during the injection period. 15. A fuel injection control device for a high-pressure fuel injection system according to claim 12, wherein said estimating means includes a fuel leak associated with a fuel leak from said pressure accumulation pipe during an injection period of said specific fuel injection. The change in the pressure is further estimated based on the leak amount during the same injection period, and the correction means opens the fuel in the specific fuel injection so as to match the actual fuel injection with the required fuel injection in the specific fuel injection. A fuel injection control device for a high-pressure fuel injection system, wherein the valve period command value is further corrected based on a change in fuel pressure during the injection period.