JP3282581B2 - Fuel return amount calculation method, actual fuel injection amount calculation method, and fuel injection control method of common rail fuel injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common rail fuel injection device, and more particularly to a method of calculating a fuel return amount, a method of calculating an actual fuel injection amount, and a method of controlling fuel injection of a common rail fuel injection device.

[0002]

2. Description of the Related Art Fuel is supplied from a high-pressure fuel pump to a common common rail (accumulation chamber), and a fuel injection valve for each cylinder is connected to the common rail. 2. Description of the Related Art A so-called common rail type fuel injection device for performing injection is known.

In the common rail type fuel injection device, the injection rate of the fuel injector is controlled by the fuel pressure in the common rail, and the fuel injection amount is controlled by both the fuel pressure in the common rail and the valve opening (fuel injection) time of the fuel injector. Is done. An example of such an accumulator type fuel injection device is disclosed in, for example, Japanese Patent Application Laid-Open No. 64-73166. The device disclosed in this publication sets a target pressure of the fuel pressure in the common rail in accordance with the engine load and the number of revolutions, and controls the common pump so that the actual fuel pressure in the common rail detected by the pressure sensor becomes the target pressure. Control the amount of fuel pumped to the The device disclosed in the publication aims to accurately control the fuel injection amount and the fuel injection rate from each fuel injection valve by accurately controlling the common rail pressure to a target pressure.

[0004]

SUMMARY OF THE INVENTION The above-mentioned JP-A-64-73
In the device disclosed in Japanese Patent No. 166, the common rail pressure is accurately controlled to the target value, but the fuel injection amount from each fuel injection valve cannot be accurately controlled to the target fuel injection amount.
Even if each fuel injection valve is in a normal state, the fuel injection amount varies within a tolerance range. In addition, since the injection characteristics may change with the usage period of the fuel injection valve, the fuel injection valve used for a long time may have a large variation in the fuel injection amount with respect to the target fuel injection amount.

[0005] When the fuel injection amount of each fuel injection valve varies, there is a problem that the variation in the amount of fuel supplied to each cylinder causes a variation in the generated torque for each cylinder, or the deterioration of the exhaust characteristics. . In order to prevent this problem, for example, it is conceivable to accurately measure the variation in the fuel injection amount of each fuel injection valve in advance and correct the fuel injection amount command value according to the variation for each fuel injection valve. Can be However, in the method of measuring the variation of the fuel injection amount in advance, it is necessary to provide an identification device corresponding to the variation amount in the fuel injection valve itself and determine the variation amount from this identification device to correct the fuel injection amount command value. Therefore, there is a problem that the fuel injection control device becomes complicated and the cost for adding an identification device increases. In addition, even if the above-described identification device is provided, it becomes impossible to accurately control the fuel injection amount when the fuel injection amount variation of the fuel injection valve changes due to long-term use. .

Therefore, in order to accurately control the fuel injection amount of each fuel injection valve, it is necessary to accurately estimate the actual fuel injection amount of each fuel injection valve during operation. By the way, if the fuel flowing out of the common rail during engine operation is only from fuel injection from each fuel injection valve, the amount of fuel injection from each fuel injection valve should be measured by the change in common rail pressure before and after fuel injection. Can be calculated from the following equation.

Q = (V / K) × DPD × Kf Here, Q is a fuel injection amount, DPD is a pressure change (drop) amount before and after fuel injection from each fuel injection valve, and Kf is a viscosity determined by a fuel temperature. The correction coefficient, V is the common rail volume, and K is the bulk modulus of the fuel. However, actually, the fuel flowing out of the common rail during the operation of the engine is caused not only by fuel injection but also by leakage from sliding parts such as a fuel injection valve, or to cause the fuel injection valve to perform a fuel injection operation. There is a spilled fuel etc. required for In the present specification, a static leak, such as fuel flowing out of the common rail due to a leak from the sliding portion or the like irrespective of the fuel injection operation of the fuel injection valve, is referred to as a static leak. Fuel leaking from the common rail along with the fuel injection operation of each fuel injection valve, such as fuel required for performing the injection operation, is called dynamic leak. Fuel flowing out of the common rail due to the static leak and the dynamic leak is returned to the fuel tank from the common rail without being injected into the internal combustion engine. Therefore, in the following description, the amount of fuel returned to the fuel tank due to static leakage is referred to as a static return amount, and the amount of fuel returned to the fuel tank due to dynamic leakage is referred to as a dynamic return amount.

As described above, during the operation of the engine, in addition to the fuel amount flowing out of the common rail due to the fuel injection, the above-mentioned static return amount and the dynamic return amount of the fuel flow out of the common rail. For this reason, Q calculated by the above equation
Contains the amount of fuel equivalent to the static return amount and the dynamic return amount in addition to the actual fuel injection amount. Can not know.

One object of the present invention is to calculate the above-mentioned static return amount and dynamic return amount simply and accurately, thereby obtaining a return fuel amount which is the sum of the static return amount and the dynamic return amount. Is to provide a method capable of calculating It is another object of the present invention to provide a method capable of accurately calculating the actual fuel injection amount of each fuel injection valve using the return fuel amount calculated as described above.

Still another object of the present invention is to provide a fuel injection control method for correcting a variation in fuel injection amount from each fuel injector based on the actual fuel injection amount of each fuel injector calculated as described above. To provide.

[0011]

According to the first aspect of the present invention, a common rail for storing pressurized fuel, a fuel injection valve for injecting fuel in the common rail to the internal combustion engine at a predetermined timing, A method of calculating a fuel return amount of fuel flowing out of the common rail and returned to a fuel tank without being injected into an internal combustion engine in a common rail type fuel injection device having a fuel pump for supplying fuel in a tank to the common rail Measuring the change in common rail pressure when fuel is not injected from the fuel injection valve and when fuel is not supplied to the common rail from the fuel pump; andbased on the measured common rail pressure change. The fuel return amount from the common rail regardless of the presence or absence of the fuel injection operation of the fuel injector. Comprises calculating the static return amount is an amount of fuel to be refunded to the tank, the fuel return amount calculating method in a common rail fuel injection system is provided.

That is, in the first aspect of the present invention, the amount of fuel flowing out of the common rail is calculated based on the change in the common rail pressure when both the fuel injection and the fuel supply are not performed. Since no dynamic leak occurs when fuel injection is not performed, the fuel amount calculated as described above is the fuel amount flowing out due to the static leak that is constantly occurring regardless of the presence or absence of the fuel injection operation of the fuel injection valve, That is, it corresponds to the static return amount. Therefore, according to the first aspect of the present invention, the static return fuel amount is accurately calculated during the operation of the engine.

According to the second aspect of the present invention, further, the step of causing the fuel injection valve to perform an invalid injection operation that is a fuel injection operation that does not cause actual fuel injection, and the step of performing the invalid injection operation Measuring the common rail pressure change, the common rail pressure change when the invalid injection operation is performed, and the calculated static return amount. Calculating the dynamic return amount that is the amount of fuel returned from the common rail to the tank in accordance with (1), the fuel return amount calculation method for the common rail fuel injection device according to claim 1.

That is, according to the second aspect of the present invention, an invalid injection operation that does not actually cause fuel injection is performed. This invalid injection operation is performed, for example, by executing a short-time fuel injection operation that does not operate the valve element of the fuel injection valve. In this invalid injection operation, fuel corresponding to the dynamic return amount is required for the fuel injection operation. However, since fuel injection does not occur, the change in the common rail pressure during the invalid injection operation is the same as the dynamic return amount and the static return amount. It is caused only by the target return amount. Therefore, the dynamic return amount during the invalid injection operation is accurately calculated based on the common rail pressure change during the invalid injection operation and the static return amount calculated by the method of claim 1.

According to the third aspect of the present invention, a common rail for storing pressurized fuel, a fuel injection valve for injecting fuel in the common rail to the internal combustion engine at a predetermined timing,
A method for calculating an actual fuel injection amount of the fuel injection valve in a common rail type fuel injection device including a fuel pump for supplying fuel in a fuel tank to the common rail, wherein an actual fuel injection is performed on the fuel injection valve. Performing an invalid injection operation, which is a fuel injection operation that does not occur, and measuring a common rail pressure change when the invalid injection operation is performed, based on a common rail pressure change when the invalid injection operation is performed, Calculating a fuel return amount of the fuel flowing out of the common rail, which is returned to the fuel tank without being injected into the internal combustion engine, and performing an actual injection operation that is a fuel injection operation that causes an actual fuel injection to the fuel injection valve. And the fuel flowing out of the common rail based on the common rail pressure change when the actual injection operation is performed. Calculating the actual fuel injection amount in the actual injection operation of the fuel injection valve based on the outflow fuel amount and the fuel return amount. An amount calculation method is provided.

That is, according to the third aspect of the present invention, the amount of fuel returned from the common rail at the time of actual fuel injection is calculated from the change of the common rail pressure at the time of fuel injection, while calculating the fuel return amount by performing the invalid injection operation.
Since the amount of fuel flowing out of the common rail during actual fuel injection is the sum of the actual fuel injection amount and the fuel return amount,
The actual fuel injection amount is calculated by subtracting the fuel return amount from the fuel amount flowing out of the common rail at the time of actual fuel injection.

According to the fourth aspect of the present invention, the step of calculating the fuel return amount further comprises the step of: performing no fuel injection from the fuel injection valve and supplying fuel to the common rail from the fuel pump. Measuring the common rail pressure change when the fuel injection is not performed, and based on the measured common rail pressure change, the fuel returned from the common rail to the tank regardless of whether or not the fuel injection operation of the fuel injection valve is performed among the fuel return amount. Calculating a static return amount that is an amount, a common rail pressure change when the invalid injection operation is performed, and the calculated static return amount. Calculating a dynamic return amount, which is a fuel amount returned to the tank from the common rail along with the fuel injection operation; The actual fuel injection amount calculation method in a common rail fuel injection system according to claim 3 comprising the steps, the calculating the fuel return amount based on the said dynamic return amount and a static return amount is provided.

That is, in the invention of claim 4, in the invention of claim 3, the static return amount and the dynamic return amount at the time of invalid injection are calculated by using the same method as in claim 2, and these are used. The fuel return amount at the time of actual fuel injection is calculated. According to the fifth aspect of the present invention, a common rail for storing pressurized fuel, a fuel injection valve for injecting the fuel in the common rail to the internal combustion engine at a predetermined timing, and a fuel in a fuel tank are supplied to the common rail. A fuel pump that includes a fuel pump and a fuel pump that calculates a fuel return amount of fuel flowing out of the common rail and returned to a fuel tank without being injected into an internal combustion engine. A step of storing in advance a relationship between a dynamic return amount and a common rail pressure, which is a fuel amount returned from the common rail to the tank along with the fuel injection operation of the fuel injection valve, and a step of detecting the common rail pressure. , Based on the stored pressure from the detected pressure, a dynamic retardation during a fuel injection operation of the fuel injection valve. Calculating the amount,
And a method for calculating a fuel return amount in a common rail type fuel injection device.

That is, in the invention of claim 5, the relationship between the common rail pressure and the dynamic return amount is determined in advance by an experiment or the like, and is set, for example, in the form of an empirical formula. During the operation of the engine, the dynamic return amount is calculated based on the common rail pressure without performing the invalid injection operation by using the above empirical formula or the like. In the invalid injection operation, since the fuel injection operation is performed for a short time to the extent that actual fuel injection does not occur, the dynamic return amount varies depending on conditions, and the calculated value may be inaccurate. In the present invention, by calculating the dynamic return amount based on an empirical formula that is set in advance with high accuracy, it is possible to eliminate variations in the dynamic return amount due to measurement conditions.

According to the invention described in claim 6, further, a step of causing the fuel injection valve to perform an invalid injection operation, which is a fuel injection operation that does not cause actual fuel injection, and a step of performing the invalid injection operation. Measuring the common rail pressure change, calculating the invalid return dynamic return amount based on the common rail pressure change when the invalid injection operation is performed, and calculating the calculated invalid injection dynamic return. Correcting the dynamic return amount during the fuel injection operation of the fuel injection valve calculated using the common rail pressure and the stored relationship based on the amount. A method for calculating a fuel return amount in an apparatus is provided.

That is, in the invention of claim 6, in order to correct the dynamic return amount calculated based on the empirical formula, the dynamic return amount obtained by the invalid injection operation is used. When the fuel injection valve is used for a long time, the actual dynamic return amount also changes, so that the dynamic return amount based on the empirical formula may deviate from the actual value. According to the present invention, a change in the dynamic return amount over time is calculated based on the dynamic return amount at the time of invalid injection, and the dynamic return amount calculated based on the empirical formula is corrected.
This makes it possible to accurately calculate the current dynamic return amount even when the dynamic return amount changes over time.

According to the seventh aspect of the present invention, a common rail for storing pressurized fuel, a plurality of fuel injection valves for respectively injecting fuel in the common rail to the internal combustion engine at predetermined timings, A method for calculating an actual fuel injection amount of the fuel injection valve in a common rail fuel injection device including a fuel pump for supplying fuel to the common rail, regardless of whether or not each fuel injection valve performs a fuel injection operation. Calculating a static return amount, which is an amount of fuel returned to the fuel tank from the common rail;
Calculating, for each fuel injection valve, a dynamic return amount that is a fuel amount returned from the common rail to the fuel tank in accordance with the fuel injection operation of each fuel injection valve; Calculating a fuel return amount that is a fuel amount returned from the common rail to the fuel tank without being injected into the internal combustion engine during the fuel injection operation of each of the fuel injection valves, based on the dynamic return amount of the valve; Calculating, for each fuel injection valve, the amount of fuel flowing out of the common rail during the fuel injection operation of each fuel injection valve based on the common rail pressure change during the fuel injection operation of each fuel injection valve; Actual fuel injection at the time of fuel injection operation of each fuel injection valve based on the outflow fuel amount and the fuel return amount at each fuel injection valve Calculating respectively,
Calculating a deviation between a target fuel injection amount and an actual fuel injection amount of each of the fuel injection valves; and, based on the deviation, each actual fuel injection amount of each of the fuel injection valves is adjusted to match the target fuel injection amount. Correcting a fuel injection command value for the fuel injection valve.

That is, in the invention of claim 7, the actual fuel injection amount of each fuel injection valve is accurately calculated from the fuel return amount of the fuel injection valve during the fuel injection operation and the change in the common rail pressure during the fuel injection operation. Thereby, the injection amount variation of each fuel injection valve, that is, the deviation between the target fuel injection amount and the actual fuel injection amount is accurately calculated, and the fuel injection command value to each fuel injection valve is corrected so as to eliminate this deviation. By
The fuel injection amount from each fuel injection valve becomes equal to the target fuel injection amount.

According to the eighth aspect of the present invention, when the common rail pressure is in a plurality of predetermined pressure ranges,
The steps from the calculation of the static return amount of each fuel injection valve to the calculation of the deviation of the fuel injection amount are executed, and the average value of the deviation for each pressure region for each fuel injection valve is calculated. 8. The common rail type fuel injection system according to claim 7, wherein a fuel injection command value for each fuel injection valve is corrected based on an average deviation of the injection valves so that an actual fuel injection amount of each fuel injection valve matches a target fuel injection amount. , A fuel injection control method is provided.

That is, in the invention according to claim 8, a plurality of pressure regions with good calculation accuracy of the fuel return amount are set in advance,
The calculation of the actual fuel injection amount of each fuel injection valve and the calculation of the deviation from the target fuel injection amount are performed in these pressure regions.
Accordingly, the accuracy of calculating each deviation is improved, and the actual fuel injection amount is more accurately adjusted to the target fuel injection amount by correcting the fuel injection command value based on the average value of the deviation in each pressure region for each fuel injection valve. Can be matched.

According to the ninth aspect of the present invention, when the common rail pressure is in a plurality of predetermined pressure ranges,
The steps from the calculation of the static return amount of each fuel injection valve to the calculation of the deviation of the fuel injection amount are executed, and the calculated fuel injection deviation is stored as the deviation at the center pressure of each pressure region. By performing an interpolation calculation based on the difference between the two center pressures located on both sides of the common rail pressure during fuel injection, the actual fuel injection amount of each fuel injector with respect to the target fuel injection amount at the common rail pressure during fuel injection is calculated. A deviation is estimated, and a fuel injection command value for each fuel injection valve is corrected based on the estimated deviation of each fuel injection valve so that an actual fuel injection amount of each fuel injection valve matches a target fuel injection amount. 7. A method for controlling fuel injection in a common rail fuel injection device according to item 7.

That is, in the ninth aspect of the present invention,
A plurality of common rail pressure regions having high deviation calculation accuracy are set as in the case of the invention, and the fuel injection amount deviation of each fuel injection valve is calculated when the common rail pressure is within these regions. Then, the calculated deviation is used as the deviation at the center pressure of each pressure region, and the deviation at the common rail pressure at the time of fuel injection is calculated from the deviation at each center pressure by interpolation calculation. As a result, the fuel injection amount deviation of each fuel injection valve becomes a value that continuously changes in accordance with the common rail pressure, and the accuracy of calculating the fuel injection amount deviation is improved. For this reason, the actual fuel injection amount can be more accurately matched with the target fuel injection amount.

According to the tenth aspect of the present invention, when the common rail pressure is in a plurality of predetermined pressure ranges and the target fuel injection amount is in a predetermined injection amount range, the fuel injection valve of each fuel injection valve is controlled. A fuel injection control method for a common rail fuel injection device according to claim 8 or 9, wherein steps from calculation of a static return amount to calculation of a deviation of the fuel injection amount are performed.

That is, according to the tenth aspect of the present invention, a plurality of common rail pressure regions having high deviation calculation accuracy are set, and when the common rail pressure is within these regions, not only the fuel injection amount deviation is calculated but also the fuel injection amount deviation is calculated. The fuel injection amount deviation of each fuel injection valve is calculated only when the fuel injection amount from the injection valve is in the region where the deviation calculation accuracy is high. Therefore, the fuel injection amount deviation of each fuel injection valve can be calculated more accurately.

According to the eleventh aspect of the present invention, when the engine is idling, instead of correcting the fuel injection command value based on the fuel injection amount deviation, each fuel injection valve is controlled so as to suppress engine speed fluctuations. Correct the fuel injection command value,
A fuel injection control method for a common rail fuel injection device according to any one of claims 7 to 10 is provided.

That is, according to the eleventh aspect of the present invention, when the engine is in an idle state, the correction based on the engine speed fluctuation is not performed based on the fuel injection amount deviation of each fuel injection valve, but the fuel injection command value correction is performed. . As a result, the correction including the friction of each cylinder and the variation of the compression ratio at the time of low engine rotation is performed, and the fluctuation of the engine speed is reduced.

[0032]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment in a case where the present invention is applied to a common rail type fuel injection device for an automobile diesel engine. In FIG. 1, reference numeral 1 denotes a fuel injection valve for directly injecting fuel into each cylinder of an internal combustion engine 10 (a four-cylinder diesel engine in this embodiment), and reference numeral 3 denotes a common common rail to which each fuel injection valve 1 is connected. . The common rail 3 has a function of storing pressurized fuel supplied from a high-pressure fuel injection pump 5 described later and distributing the pressurized fuel to each fuel injection valve 1.

In FIG. 1, reference numeral 7 denotes a fuel tank for storing fuel (light oil in this embodiment) of the engine 10, reference numeral 9 denotes a low-pressure feed pump for supplying fuel to a high-pressure fuel pump, and reference numeral 9 denotes a low-pressure feed pump.
b indicates a fuel filter provided in a fuel supply pipe 13 for supplying fuel from the low-pressure fuel pump 9 to the high-pressure fuel pump 5. During operation of the engine, the fuel in the tank 7
After the pressure is increased to a constant pressure by the feed pump 9 and foreign matter, moisture and the like are removed by the fuel filter 9b, the fuel is supplied to the high-pressure fuel injection pump 5 through the fuel supply pipe 13. The fuel discharged from the high-pressure fuel injection pump 5 is supplied to the common rail 3 through the check valve 15 and the high-pressure pipe 17, and is injected from the common rail 3 into each cylinder of the internal combustion engine via each fuel injection valve 1. Is done.

In FIG. 1, reference numeral 19 denotes a return fuel pipe for returning the return fuel from each fuel injection valve 1 to the fuel tank 7. Return fuel from the fuel injection valve will be described later. In FIG. 1, reference numeral 20 denotes an engine control circuit (ECU) for controlling the engine. EC
U20 is a read only memory (ROM), a random access memory (RAM), a microprocessor (CP
U), a digital computer having a well-known configuration in which input / output ports are connected by a bidirectional bus, and further provided with a backup RAM capable of retaining stored contents even when the main switch is turned off. The ECU 20 controls the opening / closing operation of the suction valve 5a of the high-pressure fuel injection pump 5 to control the fuel oil pressure in the common rail 3 in accordance with the engine load, the number of revolutions, and the like, as described later. The fuel injection control is performed to adjust the injection rate of the fuel injection valve according to the engine load, the number of revolutions, and the like, and to control the valve opening time of the fuel injection valve 1 to control the amount of fuel injected into the cylinder.

In this embodiment, as described later, E
The CU 20 calculates the static return amount and the dynamic return amount of the fuel from each fuel injection valve based on the pressure fluctuation in the common rail, and calculates the fuel return amount and the common rail pressure at the time of fuel injection of each fuel injection valve. Based on the change, the actual fuel injection amount of each fuel injection valve is calculated, and control is performed so that the actual fuel injection amount matches the target fuel injection amount.

For the above control, a voltage signal corresponding to the fuel pressure and the fuel temperature in the common rail 3 from the fuel pressure sensor 31 and the fuel temperature sensor 33 provided in the common rail 3 is input to the input port of the ECU 20 from the AD. In addition to the signal input via the converter 34, a signal corresponding to the operation amount (depressed amount) of the accelerator pedal is also supplied from the accelerator opening sensor 35 provided on the engine accelerator pedal (not shown) to the AD converter 34. Have been entered through. Further, E
An input port of the CU 20 is provided with a reference generated when a crankshaft reaches a reference rotational position (for example, top dead center of the first cylinder) from a crank angle sensor 37 provided near the crankshaft (not shown) of the engine. Two signals, a rotation pulse signal, which are generated according to the pulse signal and the crank rotation angle (for example, every 30 degrees of the crank rotation angle) are input.

An output port of the ECU 20 is connected to the fuel injection valves 1 via a drive circuit 40 to control the operation of each of the fuel injection valves 1. Is connected to a solenoid actuator that controls the opening and closing of the suction valve 5a, and controls the discharge amount of the pump 5.

In this embodiment, the high-pressure fuel injection pump 5 is of the type of a piston pump having two cylinders. The piston in each cylinder of the pump 5 reciprocates in the cylinder by being pressed by a cam formed on a piston drive shaft in the pump. In addition, a suction valve that is opened and closed by a solenoid actuator is provided at a suction port of each cylinder. In the present embodiment, the piston drive shaft is driven by a crankshaft (not shown) of the engine 10,
It rotates at half the speed of the crankshaft in synchronization with the crankshaft. A cam having two lift portions is formed on a portion of the piston drive shaft of the pump 5 that engages with each piston.
The fuel is discharged in synchronization with the stroke of each cylinder. That is, in the present embodiment, since a four-cylinder diesel engine is used, the two cylinders of the pump 10 are respectively rotated twice while the crankshaft rotates 720 degrees in synchronization with the stroke of the engine cylinder (for example, The fuel is pumped to the common rail 3 (for each exhaust stroke of the cylinder).

The ECU 20 adjusts the closing timing of the suction valve 5a of each cylinder of the pump 5 to
The amount of fuel pumped to the common rail 3 is controlled by changing the effective stroke of the piston of the pump 5. In the present embodiment, the ECU 20 sets the target common rail fuel pressure based on the relationship previously stored in the ROM according to the engine load (accelerator opening) and the number of revolutions, and sets the fuel pressure sensor 3
The discharge amount of the pump 5 is controlled so that the common rail fuel pressure detected in 1 becomes the set target common rail fuel pressure. Further, the ECU 20 controls the valve opening time (fuel injection time) of the fuel injection valve 1 based on the relationship stored in the ROM in advance according to the engine load and the rotation speed.

That is, in this embodiment, the common rail 3
By changing the fuel pressure of the fuel injection valve 1 according to the engine operating conditions, the injection rate of the fuel injection valve 1 is adjusted according to the operating conditions,
By changing the fuel pressure and the fuel injection time, the fuel injection amount is adjusted according to the operating conditions. For this reason, in the common rail type fuel injection device as in the present embodiment, the fuel pressure in the common rail is in a very wide range (for example, about 10 MPa to 150 MPa in the present embodiment) depending on the operating conditions (load, rotation speed) of the engine. (In the range up to).

Next, the return fuel returned from the common rail 3 to the fuel tank 7 via the return fuel pipe 19 of the fuel injection valve 1 will be described. In the present embodiment, there are two types of fuel returning to the fuel tank 7 via the pipe 19: return fuel due to static leakage and return fuel due to dynamic leakage. The static leak is a leak from a clearance of a sliding portion of the fuel injection valve or the like, and always occurs regardless of the fuel injection operation of the fuel injection valve. The return fuel amount (static return amount) due to the static leak changes depending on the common rail pressure, the size of the sliding portion clearance, and the like.

The dynamic leak is return fuel generated by the fuel injection operation (valve opening operation) of the fuel injection valve 1. Since the fuel injection valve 1 of the present embodiment performs the valve opening operation of the fuel injection valve using the pressure of the fuel oil, a certain amount of the fuel oil determined from the fuel injection condition is returned to the fuel tank with the fuel injection operation. . More specifically, in the fuel injection valve of the present embodiment, when the valve is closed, the fuel pressure is applied to both the lower portion (injection hole side) and the upper portion of the valve body to balance the force applied to the valve body by the fuel pressure. The spring is pressing the valve body against the valve seat. On the other hand, at the time of fuel injection, the pressure acting on the upper portion of the valve is reduced by allowing the fuel oil on the upper portion of the valve to escape to the return pipe via the solenoid valve and the measuring orifice. Thus, the valve body is pushed up against the spring by the fuel oil pressure acting on the lower part of the valve body, and the injection hole is opened, so that fuel injection is performed. The return fuel amount (dynamic return amount) due to the dynamic leak changes according to the fuel injection time (valve opening time), common rail pressure (injection pressure), fuel temperature (fuel oil viscosity), and the like.

As described above, in this embodiment, in addition to the fuel injected from each fuel injection valve 1, fuel returning to the fuel tank 7 without being injected from the fuel injection valve to the internal combustion engine 10 flows out from the common rail 3. . Next, calculation of the amount of fuel flowing out of the common rail 3 will be described. In the present embodiment, the amount of fuel flowing out of the common rail 3 is calculated based on a change in the common rail 3 pressure detected by the fuel pressure sensor 31. FIG. 2 is a diagram schematically showing a change in pressure of the common rail 3 during fuel injection from the fuel injection valve. In FIG. 2, PD indicates a period during which fuel injection from any of the fuel injection valves is performed, and PU indicates a period during which fuel pumping from the fuel pump 5 to the common rail 3 is performed. As shown in FIG. 2, fuel pumping is performed every time fuel is injected from each fuel injection valve, and the fuel injection timing and the fuel pumping timing are set so as not to overlap.

Assuming that the common rail pressure immediately before the fuel injection period PD is PC1 and the common rail pressure after the end of the fuel injection period is PC2, the common rail pressure change (drop) DPD during the fuel injection period PD is DPD = PC1-PC2. . At this time, during the fuel injection period PD, the common rail 3
The amount of fuel Q _T flowing out of the fuel cell is expressed by the following equation. Q _T = (V / K) × DPD × Kf (1) V is the common rail volume (constant value), K is the bulk modulus of the fuel oil (constant value), and Kf is a relational expression predetermined by a viscosity correction coefficient. Calculated from the fuel oil temperature.

[0045] As described above, the fuel amount Q _T is the amount of fuel injected from the fuel injection valve, a fuel return amount QI _R is returned to the fuel tank without via the fuel injection valve is injected into the internal combustion engine Is the sum of Therefore, the actual fuel injection amount QI _INJ from the fuel injection valve is represented by _{QI INJ = Q T -QI R =} (V / K) × DPD × Kf-QI R ... (2).

Therefore, the fuel return amount Q_RExactly
The actual fuel injection quantity Q _iFrom the above equation
Can be issued. Fuel return QI_RIs static
Return amount Q_SRAnd dynamic return Q_DRExpressed as the sum of
(QI_R= Q_SR+ Q_DR). However, the amount of static return
Q_SRAnd dynamic return Q_DRIs common rail pressure or fuel injection
It changes according to the operating state such as aging of the firing valve. others
In order to calculate the actual fuel injection amount accurately,
Current static return Q_SRAnd dynamic return Q_DRAnd ask
Need to be Therefore, the present invention is described in the following embodiments.
Fuel return QI during operation_RAccurately calculated
Then, the actual fuel injection amount is obtained.

Hereinafter, an embodiment of a method for calculating the fuel return amount QI _R , the actual fuel injection amount, and controlling the fuel injection will be described. (1) First Embodiment In this embodiment, the static return amount _QSR is calculated from the common rail pressure change during operation. Accordingly, even when the static return amount Q _SR varies with time, always accurate calculation of the fuel return amount QI _R is possible.

In this embodiment, the static return amount Q _{SR is calculated} from the change in the common rail pressure measured in a state where the fuel injection is stopped, such as a fuel cut during deceleration running of the vehicle.
Is calculated. At the time of fuel cut, the fuel supply from the fuel pump 5 to the common rail 3 is also stopped along with the stop of the fuel injection. Therefore, the change in the common rail pressure measured during this period is a state in which the fuel injection and the fuel supply are not performed. The pressure changes.

In a state where fuel injection is not performed, fuel injection
There is no dynamic leak from the valve and no fuel
In this state, there is no change in rail pressure.
Common rail pressure change is common rail due to static leak
3 would only be caused by fuel escaping. Figure
3 is a state in which the fuel injection and the fuel supply are stopped.
Common rail pressure P _CRFIG. 4 is a diagram schematically showing a time change of
You. With both fuel injection and fuel supply stopped
The common rail pressure decreases over time due to static leakage
Down. In the present embodiment, both the fuel injection and the fuel supply
With the common rail pressure set to a predetermined pressure.
Force area (P₁≤P_CR≤P_Two) When there is a certain sun
Pulling timing (for example, crankshaft rotation angle 180 degrees
In each case, the output of the fuel pressure sensor 31 is A / D converted and read.
From the equation (1), the static return fuel amount Q_SRCalculate
I do.

Q _SRi = (V / K) × DPDS _i × Kf (3) where DPDS _i is the pressure sampling timing S
_i (see FIG. 3) at the previous sampling (S _i-1 )
From the common rail pressure change. Then, the static return amount Q _SR is an average value of the static return amounts Q _SRi at each sampling timing calculated as described above,
It is calculated by the following equation.

Q _SR = (1 / n) × _{i = 1Σi} ^{= n} Q _SRi (4) The pressure region P ₁ ≦ P for calculating the static return amount Q _SR
The defined _CR ≦ P _2, since the rate of change in static return amount Q _SR for the common rail pressure is changed by the common rail pressure P _CR 3, range rate of change of Q _SR is substantially uniform _{Is used} to calculate the _QSR . (2) Second Embodiment In this embodiment, a dynamic return is performed based on a change in common rail pressure when an invalid fuel injection operation of a fuel injection valve is performed in a state where both fuel injection and fuel supply are stopped. Calculate the amount.

As described above, the dynamic leak from the fuel injection valve causes the fuel oil that exerts pressure on the upper part of the valve body to operate the valve body of the fuel injection valve to escape to the return fuel pipe 19 through the orifice. It is caused by things. However, usually, a certain period of time is required from when the solenoid valve is opened to release the fuel oil above the valve body until the valve body actually moves, and the fuel oil is released from the upper part of the valve body for a short time. With only this, the valve body does not start moving, and no fuel injection from the fuel injection valve occurs. However, also in this case, oil is released from the upper part of the valve body through the orifice, that is, a dynamic leak occurs. Therefore, in the present embodiment, the electromagnetic valve in the fuel oil release passage from the upper part of the valve body is opened for a time (for example, about 1000 × 10 ⁻⁶ seconds) that is significantly shorter than the electromagnetic valve opening time (for example, about 1000 × 10 ⁻⁶ seconds) during the normal fuel injection operation. About 300 × 10 ^-6 seconds)
Only the dynamic leak occurs without actual fuel injection. Then, similarly to the first embodiment, the amount of fuel flowing out of the common rail is calculated from the change in the common rail pressure at this time.

FIG. 4 is a diagram for explaining a change in common rail pressure when the above-described ineffective fuel injection operation is performed when both fuel injection and fuel supply are stopped. In the present embodiment, the sampling of the common rail pressure is performed at the same sampling timing as in the first embodiment (for example, at every crankshaft rotation angle of 180 degrees). The invalid fuel injection operation of the fuel injection valve is performed once during each sampling timing.
In this case, the amount of fuel Q _Ri flowing out of the common rail between each sampling timing can be calculated from the above-described equation (1) using the common rail pressure change DPDD _i between each sampling timing. On the other hand, the amount of fuel flowing out of the common rail between each sampling timing is the sum Q _Ri of the dynamic return amount Q _DR generated by the invalid fuel injection operation and the static return amount Q _SR generated between the sampling timings. .

In this embodiment, a plurality of invalid fuel injection operations are performed for each fuel injection valve, and the pressure change D at that time is performed.
Calculates an average value Q _R of Q _Ri calculated from PDD _i, from this Q _R, by subtracting the static return amount Q _SR which has been determined by the method of the previously first embodiment, the invalid injection operation The dynamic return amount _QDR at the time of _execution is calculated.

[0055] That _{is, Q Ri = (V / K} ) × DPDD i × Kf ... (5) Q R = (1 / n) × i = 1 Σ i = n Q Ri ... (6) Q DR = Q R - Q _SR (7) Thereby, the dynamic return amount Q _DR at the time of invalid injection is calculated. (3) Third Embodiment In this embodiment, the static return amount Q _SR calculated using the method of the first embodiment and the invalid fuel injection operation calculated using the method of the second embodiment are described. The fuel return amount (hereinafter referred to as the injector return amount) during the period during which the actual fuel injection is performed (FIG. 2, period PD) is calculated using the dynamic return amount _QDR .

[0056] Injector return amount QI _R are the actual static return amount and a dynamic return amount during the fuel injection period, the first dynamic and static return amount Q _SR obtained in the second embodiment The return amount _QDR cannot be used as it is, and needs to be corrected according to conditions such as the actual fuel injection time during fuel injection and the common rail pressure. In the present embodiment, the actual static return amount QI _SR and the dynamic return amount QI _DR during the fuel injection period is calculated using the following equation, QI the injector return amount QI _{R R} = QI _SR
+ Calculated as QI _DR. QI _SR = Q _SR × (P _CR / ((P ₁ + P ₂ ) / 2)) × (NE ₁ / NE) × Kf ₂ (8) QI _DR = (Q _DR + C ₁ × (P _CR − (( in _{P 1 + P 2) / 2} ))) × (t / t 1) × C 2 × Kf 1 ... (9) QI R = QI SR + QI DR ... (10) (8) equation, (P _CR / (P ₁ + P ₂ ) / 2)) is the common rail pressure correction term, where P ₁ and P ₂ are the pressure range where _QSR was found (see FIG. 3), and _PCR is the common rail when actual fuel injection was performed. Pressure. Static return amount performs correction according to the ratio between the average value and the P _CR of P ₁ and P ₂ for sliding portion clearance is increased substantially in proportion to the common rail pressure if they are identical. Further, (NE ₁ / NE) is a rotation speed correction term, NE ₁ is the engine rotation speed when _QSR is obtained, and NE is the engine rotation speed at the time of actual fuel injection. As described above, in the present embodiment, _QSR is calculated as the amount of static leak that occurs while the crankshaft rotates by a fixed angle (for example, 180 degrees). Therefore, the higher the engine speed, the shorter this period (time), and the smaller the amount of static leakage. Therefore, in the present embodiment, in the rotational speed corrected by the ratio between the rotational speed NE ₁ and NE, to calculate a static return amount in the actual rotational speed NE at the time of fuel injection. Kf ₁ and Kf ₂ are viscosity correction coefficients determined by the fuel oil temperature, similarly to Kf in the first embodiment. Kf ₁ , Kf ₂ , and Kf are correction values for the viscosity coefficient of the reference fuel temperature (for example, 40 ° C.), and the temperature of the fuel actually injected is corrected by the Kf ₂ . Naturally, if the fuel temperature is high, the static return amount QI
_SR increases.

On the other hand, in equation (9), (C ₁ × (P _CR −
The term ((P ₁ + P ₂ ) / 2))) indicates a pressure correction term for the dynamic return amount. As described below, if the other conditions of the fuel injection time and the like are the same, the dynamic return amount is considered to increase substantially linearly in response to the approximately common rail pressure P _CR. Represent the coefficients C ₁ is the slope of this line pressure correction term is preset by an experiment or the like. (Q _DR + C ₁ × (P _CR −
_{((P 1 + P 2)} / 2))) , the common rail pressure is the Q _DR obtained by disabling the fuel injection when the _{((P 1 + P 2)} / 2), disabling the fuel injection in the current common rail pressure P _CR Is the value converted when Also, (t /
t ₁ ) represents the correction term of the fuel injection operation time, t represents the fuel injection time at the time of actual fuel injection, and t ₁ represents the time at the time of the invalid fuel injection operation for which _QDR was obtained. The longer the fuel injection operation time, that is, the longer the time for releasing the fuel oil from the upper part of the valve body, the larger the dynamic return amount becomes. Accordingly, in the present embodiment, the correction according to the fuel injection time is performed.

Actual fuel injection amount QI in actual fuel injection
_INJ is the common rail pressure change DPD before and after fuel injection
The fuel amount (the amount of fuel flowing out of the common rail during the fuel injection period) Q _T calculated from FIG.
And (8) and (9) using the QI _SR and QI _DR calculated by the equation, is calculated by the aforementioned equation (2). QI _INJ = Q _T -QI _R = (V / K) × DPD × Kf-QI _R (2) FIG. 5 is a flowchart illustrating the calculation operation of the actual fuel injection amount QI _INJ . This operation is performed by a routine executed by the ECU 20 at every constant crank rotation angle.

In FIG. 5, steps 501 and 505 show whether or not the common rail pressure change measurement condition for calculating the static return amount and the dynamic return amount is satisfied. That is, in step 501, it is determined whether or not both fuel injection and fuel supply are currently stopped (for example, during fuel cut operation).
5, the common rail pressure range is a predetermined range (P ₁ ≦
It is determined whether or not P _CR ≦ P ₂ ). Step 50
If both conditions 1 and 505 are satisfied, step 5
The calculation of the static return amount and the dynamic return amount from 07 to 525 is performed. If the condition is satisfied in step 501, the process proceeds to step 503 in which a flag FC described later is used.
The value of L is set to zero.

Steps 509 to 513 show the calculation of the static return amount, and steps 515 to 523 show the calculation of the return amount at the time of the invalid fuel injection of each cylinder.
That is, the pressure change DPDS _i in the common rail is calculated based on the output of the pressure sensor 31 in step 509, the above-mentioned (3) In step 511 a static return amount Q _SRi by formula is calculated.

In step 515, the cylinder number m (m = 1 to 4 in this embodiment) at the current fuel injection timing is determined. In step 517, the fuel injection valve of the determined cylinder (m-th cylinder) is determined. , An invalid fuel injection operation is performed. Then, the common rail pressure changes DPDD _mi under the invalid fuel injection operation of the m cylinders in step 519 are calculated, step 521 using DPDD _mi values Q _Rmi of Q _Ri of the m cylinders from the foregoing equation (5) Is calculated.
FL in steps 507, 513, and 523
This is a flag for alternately executing steps 09 to 513 and steps 515 to 523 (hereinafter, the subscript m means a value for the m-th cylinder).

After calculating Q _SRi and Q _{Rmi of} each cylinder as described above, when the fuel cut operation is completed and fuel injection is restarted, after step 501, steps 525 to 539 are performed.
Will be executed. Here, at the time of executing the first operation after restarting the fuel injection, step 527 is executed, and the above-mentioned (4) is used by using the Q _SRi calculated during the fuel cut operation.
The static return amount Q _SR is calculated from the equation, and the dynamic return amount Q _{DRm of} each cylinder is calculated from the above-described equations (6) and (7) using the calculated Q _SR and the Q _{Rmi of} each cylinder. Is done. The FCL in steps 503, 525, and 529 is performed only when the first operation is performed after the fuel cut operation.
27 is a flag for executing step 27.

After executing steps 527 and 529,
In step 531, the cylinder number m at the current fuel injection timing is determined. In step 533, a change in common rail pressure DPD _m before and after fuel injection of the determined cylinder is calculated based on the output of the fuel pressure sensor 31.
At 35, the amount Q _{Tm of} fuel flowing out of the common rail at the time of fuel injection of the m-th cylinder is calculated based on the equation (1). Further, in step 537, the common rail pressure at the fuel injection timing of the m-th cylinder, the engine speed, the fuel injection time, and the like are used to calculate step 527 according to equations (8) and (9).
The values of Q _SR and Q _DR calculated in are corrected, and the static return amount QI _SRm , the dynamic return amount QI _DRm , and these QI
_SRm, injector return amount QI _Rm of the m cylinders is calculated based on the QI _DRm.

[0064] Then, the actual fuel injection amount QI _INJM of the m-th cylinder at step 539 is calculated as QI _INJm = Q _Tm -QI _Rm. As described above, according to the present embodiment, the actual fuel injection amount of each fuel injector is accurately calculated by obtaining the static return amount and the dynamic return amount from the common rail during the operation of the engine. (4) Fourth Embodiment Next, a description will be given of a dynamic return amount calculation method different from that of the second embodiment.

In the second embodiment, the dynamic return amount is obtained by causing the fuel injection valve to perform an invalid injection operation in a state where both fuel injection and fuel supply are stopped during a fuel cut operation or the like. However, as described above, in the invalid injection operation, the fuel injection operation is performed for a very short time.
Depending on the fuel injection valve, the dynamic return amount at the time of the invalid injection operation may vary greatly and may not be stable. Therefore, in the present embodiment, the dynamic return amount at the time of fuel injection is calculated by an experimental formula set in advance without performing invalid injection.

That is, in the present embodiment, the relationship between the common rail pressure and the dynamic return amount is measured in advance by experiments or the like for the fuel injection valve, and the relationship between the dynamic return amount and the common rail pressure is determined based on the measurement result. Set the empirical formula to represent. Then, during the operation of the engine, the dynamic return amount from each fuel injection valve is calculated based on the common rail pressure at the time of fuel injection.

As described above, at the time of fuel injection, the dynamically leaked fuel is released from the upper portion of the fuel injection valve through the metering orifice (outlet orifice) to the fuel return pipe 19. Since the accuracy of the outlet orifice of the fuel injection valve is very strictly controlled, the dispersion of the dynamic leak among the fuel injection valves in the initial state is actually small. For this reason, even if the dynamic return amount at the time of actual fuel injection is calculated using an empirical formula based on the above measurement result, no large error occurs.

[0068] Figure 6 shows an example of the result by changing the common rail pressure P _CR was measured dynamic leak amount Q _DR of the fuel injection valve. FIG. 6 shows the measurement results in the case of fixing the fuel injection time to a predetermined time t _0. As shown in FIG.
The dynamic return amount _QDR is an intermediate pressure region other than the high pressure region or the low pressure region of the common rail pressure (P ₁ ≦ P _CR ≦ in FIG. 6).
In P ₂ ), it changes substantially linearly with respect to the common rail pressure. Note that the pressure region in which the dynamic return amount and the static return amount are calculated in the above-described embodiment is the pressure region (P ₁ ≦
P _CR ≦ P ₂ ).

In the present embodiment, the dynamic return amount during the actual fuel injection is calculated using the following empirical formula based on the above measurement results. QI _DR = (a + b × P _CR ) × (t / t ₀ ) × Kf ₁ (11) Here, the coefficient a in the above equation (11) is the pressure range (P ₁
Dynamic leakage amount of P _CR = 0 when the ≦ P _CR ≦ P ₂₎ dynamic leakage quantity QI _DR in approximated by a straight line (see FIG. 6), b is the slope of the straight line. Further, t is the fuel injection time at the time of actual fuel injection, and t ₀ is the fuel injection time (constant value) when the dynamic leak amount of FIG. 6 is measured. Kf ₁ is a correction coefficient determined by the fuel oil temperature.
Note that the coefficient C _{1 in the} equation (9) of the third embodiment described above.
Corresponds to the slope b of the straight line.

[0070] In the present embodiment, the measurement result based on the empirical formula ((11)) are set in advance, the dynamic return amount QI _DR using the empirical formula from the common rail pressure and temperature during engine operation By performing the calculation, it is possible to easily and accurately calculate the dynamic return amount. (5) Fifth Embodiment Next, another embodiment of the method of calculating the dynamic return amount will be described. In the fourth embodiment, the dynamic return amount is calculated by an empirical formula set in advance based on the measurement result. However, in practice, the dynamic return amount may change over time with the use of the fuel injection valve, and if the dynamic return amount is calculated based only on the empirical formula, it may deviate from the actual value. There is. Therefore, in the present embodiment, as in the second embodiment, when both the fuel injection and the fuel supply are not performed, the invalid injection operation of the fuel injection valve is performed to calculate the dynamic return amount. By using the dynamic return amount at the time of injection, the dynamic return amount at the time of actual fuel injection calculated by the above equation (11) is corrected.

That is, in the present embodiment, the dynamic return amount at the time of invalid injection is used only for correcting the secular change of the dynamic return amount. In the present embodiment, the following equation (12) is used as a dynamic return amount correction equation. QI _DR ′ = QI _DR × QI _DRF / QI _DR0 (12) where QI _DR ′ is the value after correction of the dynamic return amount, QI
_DR is the dynamic return amount calculated by empirical formula (11), QI
_DRF is a dynamic return amount at the time of invalid injection obtained by the method of the second embodiment during engine operation, and QI _DR0 is obtained by the method of the second embodiment at the start of use of the fuel injection valve (when the fuel injection valve is new). It is the initial value of the dynamic return amount at the time of invalid injection.

FIG. 7 is a flowchart for explaining the actual fuel injection amount calculation operation when the dynamic return amount calculation method of the present embodiment is used. This operation is similar to the operation of FIG.
The routine is executed by U20 at every constant crank rotation angle. In FIG. 7, Steps 701 to 735 are the same operations as Steps 501 to 535 in FIG. 5, and thus detailed description is omitted here.

In the present embodiment, at step 737, based on Q _SR and Q _DRm calculated at step 727, the static return amount QI of the m-th cylinder is obtained from the equations (8) and (9), respectively.
_SRm and a dynamic return amount _QIDRFm during invalid injection are calculated. Then, based on the step 739 empirical formula (11), the calculated dynamic return amount QI _DR from the current common rail pressure P _CR and fuel oil temperature, and QI _DRFM calculated in step 737 In step 741, advance ECU20 The correction based on the equation (12) is performed using the initial value QI _DR0 stored in the RAM of FIG. 7 to calculate the corrected dynamic return amount QI _DRm ′ of the m-th cylinder. Then, in step 743, the corrected dynamic return amount QI _DRm 'and step 73
Using the static return amount QI _SRm calculated in step 7, the outflow fuel amount Q _Tm at the time of fuel injection calculated in step 735 is the mth
The actual fuel injection amount QI _{INJm of the} cylinder is obtained.

According to this embodiment, an accurate actual fuel injection amount can be calculated irrespective of aging of the dynamic return amount and the static return amount. (6) Sixth Embodiment Next, another embodiment of the present invention will be described. In the third embodiment and the fifth embodiment described above, the actual fuel injection amount of each fuel injection valve is obtained by calculating the static return amount and the dynamic return amount. As mentioned earlier, the ECU
Numeral 20 controls the valve opening time of the fuel injection valve according to the operating conditions so that the fuel injection amount of each fuel injection valve matches the target fuel injection amount. However, the fuel injection characteristics of each fuel injection valve are not the same due to variations due to tolerances, aging, and the like, and the fuel injection amount varies slightly between the fuel injection valves.

Therefore, in the present embodiment, the deviation (variation) of the actual fuel injection amount of each fuel injection valve calculated from the above method from the target fuel injection amount is obtained, and the valve opening time command value of each fuel injection valve is calculated. By performing the correction, each fuel injection valve is controlled so that the actual fuel injection amount matches the target fuel injection amount.
FIG. 8 is a flowchart illustrating the fuel injection control operation of the present embodiment. This operation is performed by a routine executed by the ECU 20 at every constant crank rotation angle.

In step 801 in FIG. 8, FIG.
The actual fuel injection amount Q of each fuel injection valve calculated by the operation of
I _INJm is read. Here, m also represents the cylinder number, and in Step 801, the first cylinder (m = 1)
The actual fuel injection amounts of the fuel injection valves of the four cylinders (m = 4) are read. Step 803 shows the calculation of the deviation ΔQB _m (m = 1 to 4) of the actual fuel injection amount QI _INJm of each fuel injection valve from the target fuel injection amount QI _INJ0 .

[0077] At step 805, the plus the target fuel injection amount of pre-fuel injection valves deviation QB _m determined by the target fuel injection amount QI _INJm0 of the fuel injection valves, respectively, QI _INJm0 = QI _INJ0 - It is calculated as ΔQB _m . In the present embodiment, by correcting the target fuel injection amount (command value) for each fuel injection valve in advance by considering the fluctuation of the actual fuel injection amount of each fuel injection valve, the fluctuation of the fuel injection amount of each cylinder is reduced. It is possible to eliminate it. (7) Seventh Embodiment Next, another embodiment of the fuel injection control will be described.
In the above-described sixth embodiment, the static return amount and the dynamic return amount are calculated based on the common rail pressure change measured when the common rail is in a predetermined pressure region (P ₁ ≦ P _CR ≦ P ₂ ). I have. For this reason, when calculating the variation of the fuel injection amount of each fuel injection valve, when the common rail pressure is outside the above range, the static return amount and the dynamic return amount are calculated according to the above-mentioned equation (8). The need to correct the pressure using equation (9) has arisen.

On the other hand, in the present embodiment, a plurality of ranges of the common rail pressure are set, and when the common rail pressure is in each pressure range, the static return amount is calculated using the method of the first embodiment. I do. The dynamic return amount is calculated by the method of the second or fifth embodiment when the common rail pressure is in each pressure range, or is calculated by the method of the fourth embodiment.

Also, regarding the deviation (variation) between the actual fuel injection amount and the target fuel injection amount, when the common rail pressure is in each of the above pressure regions, the static return amount and the dynamic return amount obtained in each pressure region are obtained. It is calculated using the quantity and stored. In this case, the pressure region in which the actual fuel injection amount is calculated is the same as the pressure region in which the static return amount and the dynamic return amount are obtained, so that it is not necessary to correct the common rail pressure for each return amount.

For correcting the target fuel injection amount (command value) of each fuel injection valve, the average value of the variation calculated in each pressure region is used. That is, in the present embodiment, for example, a plurality (j) of pressure regions in which the respective return amounts are calculated are set as R1, R2, R3,..., Rj. Then, when the common rail pressure falls within these pressure ranges, the static return amount and the dynamic return amount are calculated and stored by the above-described method. Next, when the common rail pressure is in these pressure ranges and fuel injection is actually performed, each fuel injection valve is calculated using the static return amount and the dynamic return amount calculated in each region. Is calculated, and the deviation from the target fuel injection amount is calculated.

In this case, since the pressure region for calculating the actual fuel injection amount and the pressure region for calculating each return amount are the same as described above, the pressure correction for each return amount is not required, and the above-mentioned (8) Equation (9) and equation (9) are simplified as follows. Further, since the return amount in the pressure region is directly used without performing the pressure correction, the calculation accuracy of the actual fuel injection amount is improved.

QI _SR = Q _SR × (NE ₁ / NE) × Kf ₂ (8) QI _DR = Q _DR × (t / t ₁ ) × C ₂ × Kf ₁ (9) J deviations in each pressure range of the valve are calculated for each fuel injection valve. That is, the first cylinder fuel injection valve: ΔQB ₁₁ , ΔQB ₁₂ ... _, ΔQB _1j the second cylinder fuel injection valve: ΔQB ₂₁ , ΔQB ₂₂ ... _, ΔQB _2j the third cylinder fuel injection valve: ΔQB ₃₁ , ΔQB ₃₂ ... _, ΔQB _3j m-th cylinder fuel injection valve: ΔQB _m1 , ΔQB _m2 ... _, ΔQB _mj The variation (deviation) of the fuel injection amount of the fuel injection valve of each cylinder is calculated as the average value of the variation in each pressure region.

That is, first cylinder variation: ΔQB ₁ = (1 / j) × _{i =} 1Σi ^{= j} ΔQB _1i second cylinder variation: ΔQB ₂ = (1 / j) × _{i =} 1Σi ^{= j} ΔQB _2i Third cylinder variation: ΔQB ₃ = (1 / j) × _{i =} 1Σi ^{= j} ΔQB _3i mth cylinder variation: ΔQB _m = (1 / j) × _{i =} 1Σi ^{= j} ΔQB _mi The corrected target fuel injection amount for the cylinder is calculated as follows.

First cylinder: QI _INJ10 = QI _INJ0 -ΔQB ₁ Second cylinder: QI _INJ20 = QI _INJ0 -ΔQB _2nd cylinder: QI _INJ30 = QI _INJ0 -ΔQB _3rd cylinder: QI _INJm0 = QI _INJ0 -ΔQB _{m In} this embodiment, a plurality of common rail pressure areas are set,
The fuel injection amount variation of each fuel injection valve in each pressure region is calculated, and the average value of the variation in each pressure region is used as the fuel injection amount variation of each fuel injection valve, and the target fuel injection amount of each fuel injection valve is calculated. Is corrected, the accuracy of the correction is improved. Further, once the fuel injection amount variation of each fuel injection valve is calculated, it is not necessary to always perform the calculation, so that the calculation load on the ECU 20 is reduced. (8) Eighth Embodiment Next, another embodiment of the fuel injection control will be described.
In the above-described seventh embodiment, a plurality of pressure regions of the common rail are set, and the average value of the variation calculated for each region is used as the fuel injection amount variation of each fuel injector. In this case, a constant value is used as the fuel injection amount variation of each fuel injection valve regardless of the common rail pressure. However, in practice, the fuel injection amount variation of each fuel injection valve is an amount that continuously changes according to the common rail pressure. For this reason, when the method of the seventh embodiment is used, a difference may occur between the actual fuel injection amount variation and the calculated variation in some pressure regions.

On the other hand, in the present embodiment, the variation is calculated for each pressure region as in the seventh embodiment, but the average value is not used but the fuel calculated in each pressure region is used. the injection quantity variation and (if was pressure region, e.g. _{P 1i ≦ P CR ≦ P 2i} (P 1i + P 2i) / 2) the central pressure of the respective pressure zone is used as a fuel injection amount variation in. Then, at the common rail pressure intermediate between the center pressures, the variation in the fuel injection amount of each fuel injection valve is calculated by interpolation calculation based on the common rail pressure using the variation in the center pressure on both sides.

In the present embodiment, the fuel injection amount variation is obtained by the above interpolation calculation, so that the fuel injection amount variation of each fuel injection valve becomes a continuous value connecting the respective center pressures. The change becomes very close to the fuel injection amount variation. For this reason,
The accuracy of estimating the fuel injection amount variation of each fuel injection valve has been improved,
Accurate fuel injection amount correction becomes possible.

That is, the case of the m-th cylinder will be described as an example. In this embodiment, the m-th cylinder in each of the pressure regions R1, R2,.
Variation in the fuel injection amount of the fuel injection valve of the cylinder, ΔQB _m1 ,
ΔQB _m2 ... _, ΔQB _mj are calculated. Then, the common rail pressure during the actual fuel injection P _CR is, for example, a region Ri
Center pressure PC _i of region R and center pressure PC of region R (i + 1)
If _{(i + 1)} and was between by using the variation QB _mi and QB m _{(i + 1)} on both sides of the pressure region, the m in the current common rail pressure P _CR by the following interpolation calculation
It calculates the fuel injection quantity variation QB _m cylinder fuel injection valve. _{ΔQB m = (ΔQB m (i} + 1) -ΔQB mi) / (PC (i + 1) -PC i) × (P CR -P C i) + ΔQB mi ... (13) where, PC _{(i + 1 )} is the center pressure, PC _i the center pressure in the pressure region Ri of the low-pressure side of the pressure region R of the high-pressure side (i + 1). That is, in equation (13), the variation in the current common rail pressure is calculated by linearly interpolating the variation in the pressure regions on both sides based on the common rail pressure. As a result, variation close to actuality that continuously changes in accordance with the common rail pressure can be calculated without increasing the calculation load, and the injection amount can be corrected with high accuracy. (9) Ninth Embodiment In this embodiment, a plurality of pressure regions are set as in the seventh and eighth embodiments, and the fuel injection amount variation of each fuel injector is calculated for each pressure region. . However, in the present embodiment, the conditions for calculating the fuel injection amount variation are further limited, and when the common rail pressure is in the pressure region and the actual fuel injection amount during the fuel injection is within a predetermined range. The only difference is that the variation of the fuel injection amount is calculated. The reproducibility of the variation in the fuel injection amount of each fuel injection valve may be deteriorated depending on the fuel injection amount, and the accuracy of the variation calculation decreases. In the present embodiment, in order to prevent this, a fuel injection amount range with good reproducibility of the fuel injection amount variation is set in advance, and the common rail pressure is in a preset pressure range, and the fuel injection amount is reproducible. By calculating the fuel injection amount variation of each fuel injection valve only in the good range, the calculation accuracy of the variation can be further improved.

The variation used for correcting the target fuel injection amount of each fuel injection valve may be an average value of the variation of each pressure region as in the seventh embodiment, or may be the same as in the eighth embodiment. The variation in the pressure area on both sides may be a value linearly interpolated by the common rail pressure. (10) Tenth Embodiment In the present embodiment, in an operating state other than the idling operation of the engine, for example, the target fuel injection amount of each fuel injection valve is determined using one of the methods of the seventh to ninth embodiments. Make corrections,
At the time of engine idle operation, the target fuel injection amount is corrected by a method different from the above based on the engine speed fluctuation.

The method of the seventh to ninth embodiments aims at matching the fuel injection amount to each cylinder with the target fuel injection amount, and is effective in improving the exhaust characteristics. However, even when the fuel injection amount of each cylinder is completely matched,
Since the compression ratio and the friction are not the same in each cylinder, the output torques of the cylinders do not completely match. However, when the engine speed and the load are relatively high, the influence of the variation of the output torque among the cylinders is small, but the variation of the output torque among the cylinders causes an increase in the rotation speed and an increase in the vibration during the engine idle operation. In some cases, it is not always preferable to control the amount of fuel injection to each cylinder the same.

Therefore, in the present embodiment, at the time of the idling operation in which the variation of the output torque of each cylinder becomes a problem,
The fuel injection control of the seventh to ninth embodiments is not performed, and the fuel injection amount from each fuel injection valve is corrected so as to minimize the fluctuation in the rotation speed of each cylinder of the engine. The correction to minimize the rotation speed fluctuation is performed because the fluctuation of the generated torque of each cylinder and the fluctuation of the friction finally appear as the rotation speed fluctuation. This is because, by correcting the fuel injection amount, comprehensive correction including the influence of the variation of the compression ratio and the influence of the variation of the friction can be performed.

FIG. 9 shows the fuel injection control operation of this embodiment.
It is a flowchart explaining. In this operation,
Maximum crankshaft rotation speed ωb and compression stroke during the explosion stroke
The crankshaft rotation speed ωa at the top dead center (see FIG. 10)
Difference A) (A = ωb ^Two-Ωa^Two) For each cylinder
Calculated as rotation speed parameter, and immediately before the explosion stroke
By comparing with the rotation speed parameter of the
A fuel injection correction value ΔQB for the cylinder is calculated.

That is, in FIG.
Then, it is determined whether or not the engine is currently idling, and if it is not idling, the routine proceeds to step 921, where normal fuel injection control (for example, any of the seventh to ninth fuel injection controls) is executed. . If the idle operation is being performed in step 901, the fuel injection control based on the rotation speed fluctuation in step 903 and subsequent steps is executed. That is,
In step 903, the cylinder number m of the cylinder that is currently in the explosion stroke is determined. In step 905, the rotational speed ωa of this cylinder (m-th cylinder) is calculated from the crankshaft rotational speed calculated based on the output of the crank angle sensor 37. _m and ωb
_m is calculated. Then, in step 907 the rotational speed parameter A _m of the m cylinders, A _m = ωb _m ² -ωa
It is calculated as _m ^2.

[0093] Then, in step 909, the difference .DELTA.A _m between firing order just before the cylinder of the m cylinder rotational speed parameter is calculated by ((m-1) th and cylinder) A _m-1 and A _m
Is calculated. ΔA _m represents a difference in output torque between the (m−1) th cylinder and the mth cylinder, including a difference in cylinder generated torque and friction. In step 911, the absolute value of ΔA _m |
Based on ΔA _m |, the fuel injection amount correction amount ΔQB of the m-th cylinder
Is calculated. In the present embodiment, | Δ
The value of the correction amount ΔQB required to eliminate the output torque difference corresponding to A | and | ΔA |
Is stored in the ROM.

Next, in steps 913 to 917, Δ
A _m is the fuel injection amount correction amount of the m cylinders in the preceding the present operation performed in response to positive or negative QB m _(i-1) is increased or decreased corrected by the QB, the fuel injection amount correction amount of the m cylinders QB _m is calculated. Then, at step 919, the target fuel injection amount QI _INJm (command value) of the m-th cylinder is corrected by QB _m , and the corrected target fuel injection amount QI _{INJm0 of} the m-th cylinder is changed to QI _INJm0.
= QI _INJm + QB _m .

Thus, in the present embodiment, the fuel injection amount of each cylinder is corrected so as to suppress the rotation speed fluctuation during the engine idle operation, and the rotation speed fluctuation and vibration during idling are reduced. In the operation of FIG. 9, the rotational speed ωa of each cylinder,
ωb, and the rotational speed parameter A is calculated as A = ωb ²
−ωa ² , but approximately ωa or ωa
The same effect can be obtained by performing the same operation using any one of b as the rotation speed parameter. FIG.
Shows a fuel injection control operation flowchart when ωa is used as a rotation speed parameter. Each step in this flowchart is substantially the same as that in FIG.

[0096]

According to the first, second and fifth and sixth aspects of the invention, it is possible to accurately calculate the fuel return amount during the operation of the engine. According to the third and fourth aspects of the present invention, it is possible to accurately calculate the actual fuel injection amount of the fuel injection valve of each cylinder using the fuel return amount calculated as described above. To play.

According to the seventh to eleventh aspects of the present invention, it is possible to eliminate the variation in the amount of fuel injected from each fuel injection valve, suppress the variation in the torque generated in the cylinder, and improve the exhaust characteristics. It works.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an outline of a device configuration when the present invention is applied to an automobile diesel engine.

FIG. 2 is a diagram illustrating a change in common rail pressure during fuel injection.

FIG. 3 is a diagram illustrating a change in common rail pressure when calculating a static return amount.

FIG. 4 is a diagram illustrating a change in common rail pressure when a dynamic return amount is calculated.

FIG. 5 is a flowchart illustrating an embodiment of a method for calculating an actual fuel injection amount.

FIG. 6 is a graph showing a change in a dynamic return amount due to a common rail pressure.

FIG. 7 is a flowchart illustrating an embodiment of a method for calculating an actual fuel injection amount.

FIG. 8 is a flowchart illustrating an embodiment of a fuel injection control method.

FIG. 9 is a flowchart illustrating an embodiment of a fuel injection control method.

FIG. 10 is a diagram showing a rotation speed fluctuation at the time of engine idling.

FIG. 11 is a flowchart illustrating an embodiment of a fuel injection control method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 3 ... Common rail 5 ... Fuel pump 20 ... ECU 31 ... Fuel pressure sensor

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI G01M 15/00 G01M 15/00 Z (56) References JP-A-10-299557 (JP, A) JP-A-8-144824 ( JP, A) JP-A-9-273443 (JP, A) JP-A-10-246144 (JP, A) JP-A-11-30150 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) F02D 41/00 F02D 45/00

Claims (11)

(57) [Claims] 1. A common rail for storing pressurized fuel, a fuel injection valve for injecting fuel in the common rail to an internal combustion engine at a predetermined timing, and a fuel pump for supplying fuel in a fuel tank to the common rail. A method of calculating a fuel return amount of fuel flowing out of the common rail and returned to a fuel tank without being injected into an internal combustion engine in the common rail type fuel injection device, wherein fuel is injected from the fuel injection valve. Measuring a change in common rail pressure when no fuel is supplied to the common rail from the fuel pump; and, based on the measured change in common rail pressure, the fuel injection amount of the fuel injection valve in the fuel return amount. Static return, which is the amount of fuel returned to the tank from the common rail with or without movement Comprising the steps of: calculating a fuel return amount calculating method in a common rail fuel injection system. 2. A step of causing the fuel injection valve to perform an invalid injection operation, which is a fuel injection operation that does not cause actual fuel injection, and a step of measuring a change in common rail pressure when the invalid injection operation is performed. Based on the common rail pressure change when performing the invalid injection operation and the calculated static return amount, the fuel return amount is returned to the tank from the common rail along with the fuel injection operation of the fuel injection valve. Calculating the dynamic return amount that is the amount of fuel to be supplied to the common rail fuel injection device according to claim 1. 3. A common rail for storing pressurized fuel, a fuel injection valve for injecting fuel in the common rail into the internal combustion engine at a predetermined timing, and a fuel pump for supplying fuel in a fuel tank to the common rail. A method of calculating an actual fuel injection amount of the fuel injection valve in the common rail type fuel injection device, wherein the fuel injection valve performs an invalid injection operation that is a fuel injection operation that does not cause actual fuel injection, Measuring the common rail pressure change when the invalid injection operation is performed; and, based on the common rail pressure change when the invalid injection operation is performed, the fuel tank that is not injected into the internal combustion engine among the fuel flowing out of the common rail. Calculating a fuel return amount returned to the fuel injection valve; and a fuel injection operation for causing the fuel injection valve to perform actual fuel injection. Performing a certain actual injection operation; calculating a fuel amount flowing out of a common rail based on a change in common rail pressure when the actual injection operation is performed; based on the outflow fuel amount and the fuel return amount Calculating the actual fuel injection amount in the actual injection operation of the fuel injection valve by using a common rail type fuel injection device. 4. The step of calculating the fuel return amount further includes measuring a change in common rail pressure when fuel is not injected from the fuel injection valve and fuel is not supplied from the fuel pump to the common rail. Calculating the static return amount, which is the amount of fuel returned from the common rail to the tank regardless of whether the fuel injection operation of the fuel injection valve is performed, based on the measured common rail pressure change. Performing the inactive injection operation and the common rail pressure change when performing the invalid injection operation and the calculated static return amount. Calculating a dynamic return amount that is a fuel amount returned to the vehicle; Actual fuel injection amount calculation method in a common rail fuel injection system according to claim 3 including a step of calculating the fuel return amount based on the specific return amount. 5. A common rail for storing pressurized fuel, a fuel injector for injecting fuel in the common rail into the internal combustion engine at a predetermined timing, and a fuel pump for supplying fuel in a fuel tank to the common rail. A method of calculating a fuel return amount returned to a fuel tank without being injected into an internal combustion engine out of fuel flowing out of the common rail in the common rail type fuel injection device, wherein the fuel return amount of the fuel injection valve is included in the fuel return amount. A step of storing in advance a relationship between a dynamic return amount, which is a fuel amount returned from the common rail to the tank along with the fuel injection operation, and a common rail pressure; a step of detecting the pressure of the common rail; and A step for calculating a dynamic return amount during the fuel injection operation of the fuel injection valve based on the stored relationship. And a method for calculating a fuel return amount in a common rail fuel injection device, comprising: 6. A step of causing the fuel injection valve to perform an invalid injection operation that is a fuel injection operation that does not cause actual fuel injection, and a step of measuring a change in common rail pressure when the invalid injection operation is performed. Calculating a dynamic return amount during invalid injection based on a change in common rail pressure when the invalid injection operation is performed; based on the calculated dynamic return amount during invalid injection,
Correcting the dynamic return amount during the fuel injection operation of the fuel injection valve calculated using the common rail pressure and the stored relationship, the fuel return amount in the common rail fuel injection device according to claim 5. Calculation method. 7. A common rail for storing pressurized fuel, a plurality of fuel injectors for injecting fuel in the common rail into the internal combustion engine at predetermined timings, and a fuel pump for supplying fuel in a fuel tank to the common rail. A method of calculating an actual fuel injection amount of the fuel injection valve in a common rail type fuel injection device comprising: fuel returned from a common rail to a fuel tank regardless of whether or not each fuel injection valve performs a fuel injection operation. Calculating a static return amount, which is an amount, and calculating a dynamic return amount, which is a fuel amount returned from the common rail to the fuel tank with the fuel injection operation of each fuel injection valve, for each fuel injection valve. And, based on the static return amount and the dynamic return amount of each fuel injection valve, the fuel injection of each fuel injection valve. Calculating a fuel return amount, which is an amount of fuel returned from the common rail to the fuel tank without being injected into the internal combustion engine during operation; and each fuel based on a change in common rail pressure during the fuel injection operation of each of the fuel injection valves. Calculating the amount of fuel flowing out of the common rail during the fuel injection operation of each injector for each fuel injector; based on the amount of fuel flowing out of each fuel injector and the amount of fuel return in each fuel injector. Calculating the actual fuel injection amount of each of the fuel injection valves during the fuel injection operation; calculating a deviation between a target fuel injection amount and the actual fuel injection amount of each of the fuel injection valves; based on the deviation Correcting the fuel injection command value for each fuel injection valve so that the actual fuel injection amount of each fuel injection valve matches the target fuel injection amount; A fuel injection control method in a common rail fuel injection device including: 8. When the common rail pressure is in a plurality of pressure ranges set in advance, steps from calculation of the static return amount of each fuel injection valve to calculation of a deviation of the fuel injection amount are executed. The average value of the deviation for each pressure region is calculated for the injection valve, and each fuel injection is performed so that the actual fuel injection amount of each fuel injection valve matches the target fuel injection amount based on the calculated average deviation of each fuel injection valve. 8. The fuel injection control method according to claim 7, wherein the fuel injection command value for the valve is corrected. 9. When the common rail pressure is in a plurality of pressure ranges set in advance, steps from the calculation of the static return amount of each fuel injection valve to the calculation of the deviation of the fuel injection amount are executed and calculated. The fuel injection amount deviation is stored as a deviation at the center pressure of each pressure region, and at the time of fuel injection,
By performing an interpolation calculation based on the difference between the two central pressures located on both sides of the common rail pressure at the time of fuel injection, the actual fuel injection amount with respect to the target fuel injection amount of each fuel injection valve at the common rail pressure at the time of fuel injection is calculated. A deviation is estimated, and a fuel injection command value for each fuel injection valve is corrected based on the estimated deviation of each fuel injection valve so that an actual fuel injection amount of each fuel injection valve matches a target fuel injection amount. A fuel injection control method for the common rail fuel injection device according to claim 7. 10. When the common rail pressure is in a plurality of predetermined pressure ranges and the target fuel injection amount is in a predetermined injection amount range, the fuel return is calculated from the static return amount of each fuel injection valve. 10. The fuel injection control method for a common rail fuel injection system according to claim 8, wherein the steps up to the calculation of the deviation of the injection amount are executed. 11. When the engine is idling, instead of correcting the fuel injection command value based on the fuel injection amount deviation, the fuel injection command value for each fuel injection valve is corrected so as to suppress engine speed fluctuations. A fuel injection control method for a common rail fuel injection device according to any one of claims 7 to 10.