JP2014015893A - Control method of correction amount in fuel injection quantity correction and common rail fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize appropriate fuel injection quantity correction control according to dynamic viscosity change or environmental temperature change.SOLUTION: The common rail fuel injection control device with multistage injection capability, is made to use the correction factor of dynamic viscosity which suppresses deterioration of the fuel injection amount correction by the dynamic viscosity of the fuel when it calculates the correction amount of fuel injection quantity correction to control the correction amount in the fuel injection quantity correction executed to reduce the amount of injection quantity change due to the pulsation of fuel pressure which occurs between the previous fuel injection and the next fuel injection in an engine cycle. This common rail fuel injection control device can reduce and suppress the deterioration of the correction amount in the fuel injection quantity correction control due to dynamic viscosity change or environmental temperature change.

Description

  The present invention relates to fuel injection control of an internal combustion engine, and more particularly to the improvement of injection stability and reliability in multistage fuel injection control.

How to perform fuel injection control in an internal combustion engine is an important problem because it greatly affects the operation performance of the internal combustion engine, and various control methods have been proposed and put into practical use.
For example, various techniques related to so-called multistage injection control in which a plurality of fuel injections are performed during one engine cycle from the viewpoint of improving fuel efficiency and exhaust gas purification in a diesel engine have been proposed and put into practical use (for example, Patent Document 1). reference).
By the way, in such multi-stage injection control, it is known that when pilot injection is performed, pressure pulsation is generated in the injection pipe due to the reaction, and the injection amount in main injection is fluctuated. Therefore, multi-stage injection control is performed. In an internal combustion engine, in order to obtain an original main injection amount, a configuration in which injection amount correction is performed so as to compensate for fluctuations in the main injection amount due to pressure pulsation in the injection pipe is usually employed.

JP-T-2004-504528 (page 3-10, FIGS. 1 to 4)

However, the injection amount correction in the multistage injection control as described above is not always perfect.
That is, for example, in the case where the viscosity of the fuel used increases rapidly due to the environmental temperature, the pressure pulsation at the inlet of the fuel injection pipe is suppressed and is not as large as the pressure fluctuation assumed in the injection amount correction. Therefore, there is a problem that the effect of the original correction cannot be expected.
Also, the kinematic viscosity of the fuel varies depending on the type of fuel used, and the influence of the difference in kinematic viscosity in the injection amount correction cannot be ignored.

  Furthermore, in a low-temperature environment, the amount of fluctuation in the injection amount tends to be suppressed compared to the normal operating temperature range, while the correction amount in the injection amount correction is the normal operating temperature. Since the range is defined as a standard, it is not always possible to ensure a sufficiently appropriate correction amount in a low-temperature environment. Rather, the injection amount correction is more than necessary, and the injection amount after correction increases unnecessarily. There is also a problem that it ends up.

  The present invention has been made in view of the above circumstances, and with a simple configuration, the correction amount of the fuel injection amount correction is ensured to an appropriate size according to the change in kinematic viscosity and the environmental temperature, and is stable and reliable. The present invention provides a correction amount control method and a common rail fuel injection control device in fuel injection amount correction that can realize a highly fuel injection amount.

In order to achieve the object of the present invention, the correction amount control method in the fuel injection amount correction according to the present invention includes:
In a common rail fuel injection control device configured to be capable of multi-stage injection, in order to reduce a change in injection amount due to pulsation of fuel pressure that occurs between fuel injection that follows the end of preceding fuel injection in one engine cycle A fuel injection amount correction correction amount control method for controlling a correction amount in a fuel injection amount correction to be executed,
In the calculation process of the correction amount in the fuel injection amount correction, a kinematic viscosity correction coefficient that suppresses deterioration of the fuel injection amount correction due to kinematic viscosity is used.
In order to achieve the above object of the present invention, a common rail fuel injection control device according to the present invention comprises:
The control by the electronic control unit according to the operating state of the internal combustion engine enables the multi-stage injection to the internal combustion engine by the injector and the subsequent fuel injection after the end of the preceding fuel injection in one engine cycle A common rail fuel injection control device configured so that fuel injection amount correction control for reducing a change in injection amount due to pulsation of fuel pressure occurring in the electronic control unit can be executed by the electronic control unit,
The electronic control unit is configured such that a kinematic viscosity correction coefficient that suppresses deterioration of the fuel injection amount correction due to kinematic viscosity is used in the calculation of the correction amount in the fuel injection amount correction.

  According to the present invention, the kinematic viscosity correction coefficient for suppressing the change in the fuel injection correction amount accompanying the change in the kinematic viscosity is added to the existing fuel injection amount correction control, so that the hardware is not changed. Thus, with a simple configuration, appropriate fuel injection amount correction is ensured, and it is possible to obtain fuel injection with high stability and reliability.

It is a block diagram which shows the structural example of the common rail type | mold fuel injection control apparatus to which the correction amount control method in the fuel injection amount correction | amendment in embodiment of this invention is applied. In the microcomputer constituting the electronic control unit used in the common rail fuel injection control apparatus shown in FIG. 1, the first configuration example of the correction amount control method in the fuel injection amount correction according to the embodiment of the present invention is executed. It is a functional block diagram which shows the function required for this. A subroutine flow showing a processing procedure of the first configuration example of the correction control processing in the fuel injection amount correction of the embodiment of the present invention executed by the electronic control unit used in the common rail fuel injection control device shown in FIG. It is a chat. It is a subroutine flowchart which shows an example of the specific process sequence of the calculation process for the period in the flowchart shown in FIG. In the microcomputer constituting the electronic control unit used in the common rail fuel injection control device shown in FIG. 1, the second configuration example of the correction amount control method in the fuel injection amount correction according to the embodiment of the present invention is executed. It is a functional block diagram which shows the function required for this. It is a subroutine flowchart which shows an example of the concrete process sequence of the period calculation process in a 2nd structural example. The change characteristic of the fuel injection amount between the pre-injection and the post-injection when the correction amount control method in the fuel injection amount correction in the embodiment of the present invention is applied is shown as the change in the correction amount and the fuel injection amount before the correction. It is a characteristic diagram shown with a change characteristic. It is a characteristic diagram which shows the change characteristic of the fuel injection quantity between the pre-injection and the post-injection in the conventional common rail type fuel injection control apparatus with the change of the correction quantity and the change characteristic of the fuel injection quantity before the correction. It is a characteristic diagram which shows the example of a change characteristic of the injection quantity with respect to the change of the electricity supply time by the difference in the kind of fuel. It is a characteristic diagram which shows the example of the correlation of the temperature of fuel, and kinematic viscosity.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a configuration example of an internal combustion engine injection control device to which a correction amount control method in fuel injection amount correction according to an embodiment of the present invention is applied will be described with reference to FIG.
Specifically, the internal combustion engine injection control device shown in FIG. 1 is particularly configured as a common rail fuel injection control device.

The common rail fuel injection control device includes a high pressure pump device 50 that pumps high pressure fuel, a common rail 1 that stores the high pressure fuel pumped by the high pressure pump device 50, and a high pressure fuel supplied from the common rail 1 as a diesel engine. A plurality of injectors 2-1 to 2-n (hereinafter referred to as “engine”) for supplying fuel to three cylinders, and an electronic control unit (indicated as “ECU” in FIG. 1) 4 for executing fuel injection control processing and the like Is the main component.
Such a configuration itself is the same as the basic configuration of this type of fuel injection control apparatus that has been well known.

The high-pressure pump device 50 has a known and well-known configuration in which the supply pump 5, the metering valve 6, and the high-pressure pump 7 are configured as main components.
In this configuration, the fuel in the fuel tank 9 is pumped up by the supply pump 5 and supplied to the high-pressure pump 7 through the metering valve 6. As the metering valve 6, an electromagnetic proportional control valve is used, and the amount of energization is controlled by the electronic control unit 4, so that the flow rate of fuel supplied to the high-pressure pump 7, in other words, the discharge of the high-pressure pump 7. The amount is to be adjusted.
A return valve 8 is provided between the output side of the supply pump 5 and the fuel tank 9 so that surplus fuel on the output side of the supply pump 5 can be returned to the fuel tank 9. .
Further, the supply pump 5 may be provided separately from the high pressure pump device 50 on the upstream side of the high pressure pump device 50 or may be provided in the fuel tank 9.

The injectors 2-1 to 2-n are provided for each cylinder of the engine 3, are supplied with high-pressure fuel from the common rail 1, and perform fuel injection by injection control by the electronic control unit 4.
The injectors 2-1 to 2-n in the embodiment of the present invention are of a so-called solenoid valve type that has been used conventionally. The injectors 2-1 to 2-n are driven and controlled by the electronic control unit 4 so that high-pressure fuel can be injected into the cylinders of the engine 3.

The electronic control unit 4 includes, for example, a microcomputer 21 having a known and well-known configuration, a storage element (not shown) such as a RAM and a ROM, and injectors 2-1 to 2-n. A circuit (not shown) for energization drive and a circuit (not shown) for energization drive of the metering valve 6 and the like are configured as main components.
In addition to the detection signal of the pressure sensor 11 that detects the pressure of the common rail 1 (actual rail pressure), the electronic control unit 4 receives various signals such as engine speed, accelerator opening, engine coolant temperature, and fuel temperature. A detection signal is input for use in operation control of the engine 3 and fuel injection control.

  FIG. 2 is a functional block diagram illustrating the functions performed by the microcomputer 21 for executing the first configuration example of the correction amount control process in the fuel injection amount correction according to the embodiment of the present invention by using functional blocks. FIG. 3 is a subroutine flowchart showing the processing procedure of the first configuration example of the correction amount control in the fuel injection amount correction according to the embodiment of the present invention executed by the microcomputer 21. With reference to these drawings, a correction amount control processing procedure in the fuel injection amount correction according to the embodiment of the present invention will be described.

First, the conventional fuel injection amount correction as a premise will be described generally with reference to FIG.
The correction amount control method in the fuel injection amount correction according to the embodiment of the present invention is a so-called multistage injection control in which a plurality of fuel injections are performed during one engine cycle. The correction is performed in order to further adapt the correction amount according to the change in the environmental temperature.

On the other hand, FIG. 8 shows a fuel injection amount change characteristic example for explaining fuel injection amount correction in the conventional multistage injection control. Hereinafter, referring to FIG. 8, the fuel injection amount in the conventional multistage injection control is shown. The correction will be described.
In the figure, the horizontal axis represents the elapsed time (interval time Tdiff) from the end of the preceding injection to the start of the subsequent injection, and the vertical axis represents the deviation from the target injection amount of the subsequent injection in each interval. Each represents a quantity.
In the figure, a characteristic line represented by a two-dot chain line (characteristic line denoted by reference symbol A1) is a fuel injection amount correction in multistage injection control (hereinafter referred to as “multistage fuel injection amount correction” for convenience). When the post-injection is performed at a constant energization time in each interval after the preceding fuel injection is completed, there is a difference in the deviation amount from the target injection amount even though the energization time of the post-injection is constant However, the difference of the deviation | shift amount with the target injection quantity in each interval is plotted. Such a deviation from the target injection amount occurs because the fuel pressure in the injection pipes from the common rail 1 to the injectors 2-1 to 2-n pulsates due to the pre-injection, so that the injection of the post-injection starts. This is due to the difference in pressure.

Essentially, if the energization time is the same, the fuel injection amount in the post-injection should be constant.
However, in actuality, as described above, due to the pressure fluctuation at the start of the post-injection, there is a difference in the amount of deviation from the target injection amount in each interval (the two-dot chain line in FIG. 8). See characteristic line).

Therefore, the fuel injection amount correction in the multi-stage injection control is performed to correct the fuel injection amount so as to suppress the change in the fuel injection amount.
That is, in FIG. 8, a characteristic line represented by a dotted line (characteristic line denoted by reference symbol C1) is an example of a change characteristic of the correction amount ΔQ of the fuel injection amount correction in the multistage injection control. The fuel injection amount correction is performed so as to cancel the change in the fuel injection amount before correction indicated by the two-dot chain line in FIG. In FIG. 8, the vertical axis represents the change amount of the correction amount ΔQ with respect to the change characteristic line of the correction amount ΔQ.
A characteristic line represented by a solid line in FIG. 8 (characteristic line denoted by reference symbol B1) is obtained from the target injection amount of the post-injection in each interval after the fuel injection amount correction as described above is performed. This represents the amount of deviation, in other words, the amount of change in the fuel injection amount.

By the way, the fluctuation characteristic of the fuel injection amount after the end of the pre-injection as shown by the two-dot chain line in FIG. 8 changes depending on the environmental temperature, for example.
Therefore, the correction amount in the above-described fuel injection amount correction is determined in consideration of the change in the change characteristic of the fuel injection amount accompanying such a change in the environmental temperature to some extent. That is, for example, assuming a standard ambient temperature range, the change characteristic of the fuel injection amount change characteristic in that range is averaged, the standard fuel injection amount change characteristic is defined, and the fuel injection amount suitable for it Measures to determine the amount of correction are taken.

However, there is a problem that the correction amount of the fuel injection amount is not always appropriate particularly when the environmental temperature changes greatly or the kinematic viscosity of the fuel changes.
In the fuel injection control according to the embodiment of the present invention, in the fuel injection amount correction control as described above, an appropriate correction is realized even when the environmental temperature changes greatly or the kinematic viscosity changes. It is a thing.

  Here, when executing the correction amount control process in the fuel injection amount correction by the microcomputer 21, which will be described below, the microcomputer 21 uses the microcomputer 21 according to the operation status of the engine 3, that is, the engine speed and the accelerator opening as in the conventional case. It is assumed that fuel injection control, rail pressure control, and the like are performed based on the actual rail pressure and the like.

In the embodiment of the present invention, it is assumed that the electronic control unit 4 determines the kinematic viscosity of the fuel used by the conventional method.
Various methods for calculating and determining the value of the kinematic viscosity of fuel have been proposed and put to practical use.
As a specific method for calculating and determining the kinematic viscosity, for example, before cranking, the injectors 2-1 to 2-n are energized to open and close the internal electromagnetic valves, and the energization is interrupted from the time when the energization is interrupted. The time until the induced electromotive force generated later in the electromagnetic valve reaches a peak is measured, and the difference from the standard time is calculated. Based on the time difference, the kinematic viscosity classified in advance is the kinematic viscosity. There is a method to judge.

This method corresponds to the time when the peak of the induced electromotive force generated when the electromagnetic valve is de-energized, and the time when the electromagnetic valve is closed, and until the peak of the induced electromotive force after the de-energization occurs, that is, This is an application of the fact that the time until the valve is completely closed depends on the kinematic viscosity of the fuel.
Here, the standard time is the time from when the energization is cut off to the peak of the induced electromotive force, which is measured when the electromagnetic valve is driven as described above, when a preset fuel is used as the standard fuel. It is.

  In this method, for various fuels, the difference between the standard time and the time from when the energization is cut off to the peak of the induced electromotive force, which is measured when the electromagnetic valve is driven as described above, is acquired. It is stored in an appropriate storage area of the electronic control unit 4, and as described above, it is determined which of the various kinematic viscosities stored in advance corresponds to the kinematic viscosity. Is.

  In addition, an estimated value of the amount of fuel supplied to the common rail and an estimated value of pressure in a metering valve that adjusts the amount of fuel supplied to the common rail are obtained, and these estimated values and the inlet side of the common rail are obtained. A method for detecting the kinematic viscosity of a fuel based on the actually measured pressure is also known (for example, JP 2009-174383 A).

Thus, when the process is started by the microcomputer 21, first, calculation of the pre-injection amount Q1, the post-injection amount Q2, the interval Tdiff, and the rail pressure P is performed (see step S100 in FIG. 3).
Here, “pre-injection amount Q1” means the fuel injection amount in the preceding injection (pre-injection) among the injection amounts at the time of two injections that are temporally changed in one engine cycle. The amount Q2 ”is the fuel injection amount in the subsequent injection (post injection). For example, in the case of two-stage injection, the pre-injection amount is pilot injection, and the post-injection amount Q2 is main injection, but the present invention can also be applied to multi-stage injections of three or more stages. The two injections before and after the above are sufficient, and need not be limited to pilot injection and main injection.

Further, “interval Tdiff” is the time between the pre-injection and the post-injection, and the rail pressure P is the actual rail pressure.
The interval Tdiff is calculated by a predetermined arithmetic expression based on the operation information of the engine 3, that is, the engine speed, the accelerator opening, the actual rail pressure, and the like, as in the prior art.

Next, the microcomputer 21 performs phase calculation processing of the fuel injection correction amount (see step S200 in FIG. 3 and reference numeral 2-b1 in FIG. 2).
Here, the “phase amount” of the fuel injection correction amount is a change characteristic of the fuel injection amount after the end of the pre-injection when there is no fuel injection correction described with reference to FIG. In the characteristic line), the phase characteristic is for correcting the fluctuation of the fuel injection amount due to the change caused by the pressure fluctuation generated in the injectors 2-1 to 2-n.
In the embodiment of the present invention, based on the rail pressure P (actual rail pressure) and the pre-injection amount Q1, the phase is calculated by a predetermined phase calculation formula. The predetermined phase component calculation formula is determined based on simulations, test results, and the like.

Next, the microcomputer 21 calculates the fuel injection correction amount for the period (see step S300 in FIG. 3 and reference numeral 2-b4 in FIG. 2).
Here, the “cycle amount” of the fuel injection correction amount is to correct the influence of the change characteristic of the fuel injection amount on the cycle due to the change in the sound velocity in the injectors 2-1 to 2-n due to the pre-injection. (Details will be described later).
Next, base correction waveform calculation is performed by the microcomputer 21 (see step S400 in FIG. 3 and reference numeral 2-b5 in FIG. 2).
Here, the “base correction waveform” is a waveform representing a temporal change in the correction amount serving as a reference for determining the correction amount. More specifically, the waveform is represented by the interval Tdiff on the horizontal axis and the correction amount ΔQ on the vertical axis.

  Such a base correction waveform is calculated and calculated by using the previous phase and cycle multiplied values and the previous injection amount Q1 as parameters (see reference numerals 2-b5 and 2-b10 in FIG. 2). . That is, in calculating the base correction waveform, the deviation of the correction amount ΔQ caused by the rail pressure P, temperature, etc. is averaged for each pre-injection amount Q1. In the embodiment of the present invention, a microcomputer 21 generates a base correction waveform obtained in advance by simulation, test, or the like according to the actually used pre-injection amount Q1 with respect to the product of phase and period. The base correction waveform is selected according to the pre-injection amount Q1 that is actually used.

Next, the microcomputer 21 calculates an amplitude correction coefficient (see step S500 in FIG. 3 and reference numeral 2-b6 in FIG. 2).
Here, the “amplitude correction coefficient” is a coefficient for correcting the amplitude of the base correction waveform obtained in the previous step S400, and based on the rail pressure P and the post-injection amount Q2, a predetermined amplitude correction coefficient calculation formula. Is calculated. The predetermined amplitude correction coefficient calculation formula is determined based on simulations, test results, and the like.

Next, a temperature correction coefficient is calculated by the microcomputer 21 (see step S600 in FIG. 3 and reference numeral 2-b7 in FIG. 2).
This “temperature correction coefficient” is a predetermined temperature correction based on the rail pressure P and the estimated fuel temperature closest to the injectors 2-1 to 2-n (hereinafter referred to as “injector immediate fuel estimated temperature” for convenience). It is calculated by a coefficient arithmetic expression. Note that the predetermined temperature correction coefficient calculation formula is determined based on simulations, test results, and the like.

Further, the estimated fuel temperature closest to the injector is calculated by a predetermined estimated temperature calculation formula in the microcomputer 21 based on the engine coolant temperature and the fuel temperature (see reference numeral 2-b2 in FIG. 2). . In FIG. 2, “water temperature” means engine cooling water temperature, and “fuel temperature” means fuel temperature. Further, the predetermined estimated temperature calculation formula is determined based on simulations, test results, and the like.
The “temperature correction coefficient” in the embodiment of the present invention is for adjusting the amplitude of the correction amount ΔQ. When the environmental temperature is extremely low, that is, when the viscosity of the fuel is high, the correction sensitivity. On the other hand, the correction sensitivity is set to be higher as the ambient temperature approaches. Note that “high correction sensitivity” means that the value of the correction coefficient becomes large, and “low correction sensitivity” means that the value of the correction coefficient becomes small.

Next, it is determined whether or not the kinematic viscosity of the fuel has been acquired (ascertained) (see step S650 in FIG. 3). If it is determined that the kinematic viscosity has been acquired (in the case of YES), a step is performed. On the other hand, if it is determined that the kinematic viscosity has not yet been acquired (NO), the process proceeds to step S800.
Here, the kinematic viscosity of the fuel can be obtained and grasped based on various methods that have been proposed and put into practical use. In the embodiment of the present invention, as described above, the electronic control unit 4 It is assumed that the kinematic viscosity acquisition process by the conventional method is executed and the kinematic viscosity is appropriately acquired. In step S650, it is determined whether or not the kinematic viscosity is acquired by the process. It will be.

In step S700, a kinematic viscosity correction coefficient is calculated (see symbol 2-b8 in FIG. 2). That is, the kinematic viscosity correction coefficient is obtained based on the kinematic viscosity in order to compensate for the influence of the difference in fuel kinematic viscosity on the correction amount ΔQ.
Here, the difference in kinematic viscosity specifically causes the following effects.
That is, for example, FIG. 9 shows an example of change in fuel injection amount (vertical axis in FIG. 9) with respect to change in energization time for the injector (horizontal axis in FIG. 9) for three types of fuel. The fuel injection amount for the same energization time differs depending on the difference in kinematic viscosity. The fuel injection amount in FIG. 9 is the fuel injection amount per cylinder.

In the embodiment of the present invention, considering such points, the kinematic viscosity correction coefficient is obtained as described above.
More specifically, as a method for obtaining the kinematic viscosity correction coefficient based on the kinematic viscosity, for example, a map (not shown) configured so that kinematic viscosity correction coefficients for various kinematic viscosities can be read out using the kinematic viscosity as an input parameter. The kinematic viscosity correction coefficient is preferably calculated using
Such a map is preferably set in advance based on test results, simulation results, etc., and stored in an appropriate storage area of the electronic control unit 4 for use. Note that instead of the map, an arithmetic expression that is set based on a test result, a simulation result, or the like and that determines a kinematic viscosity correction coefficient using kinematic viscosity as an input parameter may be used.

  Further, FIG. 10 shows an example of change in kinematic viscosity (vertical axis in FIG. 10) accompanying change in fuel temperature (horizontal axis in FIG. 10) for four types of fuel. In the region where the fuel temperature exceeds normal temperature, the kinematic viscosity does not vary greatly due to the difference in the type of fuel. However, as the fuel temperature decreases, the kinematic viscosity gradually increases according to the difference in the type of fuel, and as the temperature falls below zero degrees Celsius, the difference in kinematic viscosity depending on the type of fuel tends to increase gradually.

  For this reason, the kinematic viscosity acquisition process separately executed in the electronic control unit 4 is performed by opening and closing the electromagnetic valves in the injectors 2-1 to 2-n before cranking in the conventional method described above. In the case of using the method of acquiring the viscosity, since the kinematic viscosity acquired in advance is at the fuel temperature before cranking, if used as it is in the calculation of the kinematic viscosity correction coefficient, the fuel temperature as described above. Considering that in some cases the kinematic viscosity correction coefficient is not appropriate due to the change in kinematic viscosity due to the kinetic viscosity, the dynamic viscosity corresponding to the fuel temperature when calculating the kinematic viscosity correction coefficient is described as follows. It is preferable to convert the viscosity into viscosity and use it for calculation of the kinematic viscosity correction coefficient.

  As a method of converting the kinematic viscosity before cranking into the kinematic viscosity at the time of calculating the kinematic viscosity correction coefficient, for example, first, for a plurality of fuels that may be used, the fuel temperature as shown in FIG. And kinematic viscosity change characteristics are acquired in advance and stored in a suitable storage area of the electronic control unit 4 as a so-called map or arithmetic expression. Then, from the kinematic viscosity obtained before cranking and the fuel temperature at that time, the kinematic viscosity obtained before cranking is correlated with the fuel temperature and kinematic viscosity stored in advance in the electronic control unit 4 as described above. Among the relationships, the change characteristic is specified, and the specified change characteristic is used to determine the kinematic viscosity corresponding to the fuel temperature when calculating the kinematic viscosity correction coefficient.

On the other hand, in step S800, the kinematic viscosity correction coefficient is set to “1” corresponding to the fact that the kinematic viscosity of the fuel is not acquired.
Finally, the final correction amount ΔQ of the fuel injection amount is calculated (see step S900 in FIG. 3).
That is, the correction amount ΔQ is obtained by multiplying the base correction waveform by the amplitude correction coefficient, the temperature correction coefficient, and the kinematic viscosity correction coefficient (reference numerals 2-b11 to 2- in FIG. 2). b13 and reference 2-b9).
After these series of processes are completed, the process once returns to the main routine (not shown), and after other necessary processes are executed, the series of processes shown in FIG. 3 is performed again.

FIG. 4 shows a more specific procedure of the period calculation processing in step 300 of FIG. 3 in a subroutine flowchart, and the contents thereof will be described below with reference to FIG.
When the process is started by the microcomputer 21, first, the engine coolant temperature is input to an appropriate storage area in the microcomputer 21 and temporarily stored (see step S302 in FIG. 4).
Next, similarly, the fuel temperature is input to an appropriate storage area in the microcomputer 21 and temporarily stored (see step S304 in FIG. 4).

Then, the microcomputer 21 calculates the injector nearest fuel estimated temperature based on the engine cooling water temperature and the fuel temperature input as described above by a predetermined nearest estimated temperature calculation formula (step S306 in FIG. 4 and 2 (see reference numeral 2-b2 in FIG. 2). The predetermined latest estimated temperature calculation formula is determined based on simulations, test results, and the like.
Next, the rail pressure P is input (see step S308 in FIG. 4).
Note that the rail pressure P can be input using the data acquired in the process of the previous step S100, and there is no need to input it again.

  Next, the sound speed ratio of the fuel is calculated by a predetermined fuel sound speed calculation formula based on the estimated fuel latest fuel temperature calculated in the previous step S306 and the rail pressure P obtained in step S308 (step in FIG. 4). The value is output as a period (see step S312 in FIG. 4 and reference numeral 2-b4 in FIG. 2). Note that the predetermined fuel sound velocity calculation formula is determined based on simulations, test results, and the like.

FIG. 7 shows a fuel injection amount change characteristic example for explaining fuel injection amount correction according to the embodiment of the present invention.
In the figure, the horizontal axis represents the elapsed time (interval) from the end of the preceding injection to the start of the subsequent injection, and the vertical axis represents the pulsation amount of the fuel injection amount, that is, the original amount. The amount of change from the fuel injection amount is shown.
In the figure, a characteristic line (characteristic line denoted by reference symbol A) represented by a two-dot chain line indicates an injector 2-1 after the preceding fuel injection operation is terminated when there is no multistage fuel injection amount correction. The example of the pulsation amount with respect to the time passage of the fuel injected from ˜2-n is shown.

In FIG. 7, a characteristic line represented by a dotted line (characteristic line to which reference character C is attached) represents a change characteristic of the correction amount ΔQ obtained as described above, and a characteristic line represented by a solid line (reference character B represents (Characteristic line attached) represents a change characteristic of the pulsation amount of the fuel injection amount when the multistage fuel injection amount correction having the characteristic shown by the dotted line is performed.
The change characteristic of the fuel injection amount shown in FIG. 7 (see the characteristic line labeled B) is the change characteristic of the fuel injection amount after the conventional multistage fuel injection amount correction shown in FIG. It can be confirmed that the fluctuation is sufficiently suppressed as compared with the characteristic line indicated by reference numeral B1 in FIG.

  In the embodiment of the present invention, in the process of calculating the correction amount ΔQ, the temperature correction coefficient is used as a multiplication coefficient in the process of calculating the correction amount ΔQ (reference numerals 2-b7 and 2-b12 in FIG. 2). This is coupled with the fact that when the environmental temperature changes from the normal temperature range to the low temperature range, the temperature correction coefficient is made small so that the correction amount ΔQ does not become larger than necessary unlike the conventional case. This is because the kinematic viscosity correction coefficient is used as the multiplication coefficient together with the temperature correction coefficient (see reference numerals 2-b8 and 2-b13 in FIG. 2).

Next, a second configuration example will be described with reference to FIGS.
FIG. 5 is a functional block diagram showing functions performed by the microcomputer 21 for executing the correction amount control process in the fuel injection amount correction of the second configuration example, and FIG. 6 is a block diagram showing the second configuration. It is a subroutine flowchart which shows the specific process sequence of the period calculation process in the fuel injection amount correction | amendment of an example.
In FIG. 5, the same functional blocks as those shown in FIG. 2 are given the same reference numerals, description thereof is omitted, and different points will be mainly described below. . Similarly, in FIG. 6, the same steps as the processing contents of the steps shown in FIG. 4 are denoted by the same reference numerals, detailed description thereof is omitted, and different points are mainly described below. It will be explained in

In the second configuration example, in particular, the influence of the kinematic viscosity of the fuel is added to the calculation of the sonic speed ratio in the period calculation process (see step S300 in FIG. 3).
First, since the entire processing procedure of the correction amount control in the second configuration example is basically the same as the procedure shown in FIG. 3, the description thereof will be omitted here.
In the second configuration example, the influence of the kinematic viscosity of the fuel is taken into account in the period calculation process as described below.

That is, when processing is started by the electronic control unit 4, first, the engine cooling water temperature is input (step S302 in FIG. 6), and the first configuration described above with reference to FIG. The same processing as in the example is executed.
In step S311a, a sound speed ratio correction coefficient is calculated (see reference numeral 2-b14 in FIG. 5).
In the embodiment of the present invention, based on the kinematic viscosity of the fuel and the actual rail pressure P, the sound speed ratio correction coefficient map (not shown) stored in an appropriate storage area of the electronic control unit 4 is used. A correction coefficient is determined.

  Here, the sound speed ratio correction coefficient map is a data map configured to be able to read out the sound speed ratio correction coefficient for various combinations of kinematic viscosity and actual rail pressure, using kinematic viscosity and actual rail pressure as input parameters. This is set based on the simulation result. Instead of the data map, it is also preferable to use an arithmetic expression set based on the test result or the simulation result so that the sound speed ratio correction coefficient can be calculated using the kinematic viscosity and the actual rail pressure as input parameters. .

  Further, as described in the first configuration example, the kinematic viscosity acquisition process, which is separately executed by the electronic control unit 4, energizes the injectors 2-1 to 2-n before cranking, In the case where the induced electromotive force generated when the valve is opened and closed is used, the kinematic viscosity acquired in advance is calculated using the same method as described in the first configuration example when calculating the sound speed ratio correction coefficient. It is preferable to convert the kinematic viscosity corresponding to the fuel temperature and use the converted kinematic viscosity for calculation of the sound speed ratio correction coefficient.

Next, the previously calculated sound speed ratio (see step S310 in FIG. 6) is corrected using the sound speed ratio correction coefficient obtained as described above (see step S311b in FIG. 6).
Specifically, the sound speed ratio is corrected by multiplying the sound speed ratio and the sound speed ratio correction coefficient (see reference numeral 2-b15 in FIG. 5). That is, the correction suppresses fluctuations in the sound speed ratio that accompany changes in kinematic viscosity.
The corrected sound speed ratio is output as a period (see step S312 in FIG. 6).

  As described above, by using the sound velocity ratio correction coefficient corresponding to the kinematic viscosity, the fluctuation of the correction amount ΔQ caused by the change in the kinematic viscosity is reduced and suppressed as compared with the first configuration example described above. It will be.

  The present invention can be applied to a common rail type fuel injection control device in which more stable fuel injection amount correction control is desired regardless of the type of fuel and the change in ambient temperature.

DESCRIPTION OF SYMBOLS 1 ... Common rail 2-1-2-n ... Fuel injection valve 3 ... Diesel engine 4 ... Electronic control unit 11 ... Pressure sensor 21 ... Microcomputer 50 ... High pressure pump apparatus

Claims (8)

In a common rail fuel injection control device configured to be capable of multi-stage injection, in order to reduce a change in injection amount due to pulsation of fuel pressure that occurs between fuel injection that follows the end of preceding fuel injection in one engine cycle A fuel injection amount correction correction amount control method for controlling a correction amount in a fuel injection amount correction to be executed,
A correction amount control method in fuel injection amount correction, wherein a kinematic viscosity correction coefficient that suppresses deterioration of the fuel injection amount correction due to kinematic viscosity is used in a calculation process of the correction amount in the fuel injection amount correction.   The kinematic viscosity correction coefficient is calculated by a predetermined kinematic viscosity correction coefficient arithmetic expression and is used in the correction amount calculation process in the fuel injection amount correction, and kinematic viscosity correction coefficients for various kinematic viscosities are determined in advance. The correction amount control method in the fuel injection amount correction according to claim 1, wherein the correction amount control method is obtained using a calculated arithmetic expression or a data map.   3. The fuel injection amount correction according to claim 2, wherein a sound speed ratio correction coefficient that suppresses fluctuations due to kinematic viscosity of the sound speed ratio calculated in the correction amount calculation process in the fuel injection amount correction is used. Correction amount control method. The sound speed ratio is used as a period for correcting the influence on the period of the change characteristic of the fuel injection amount due to the change in the sound speed change in the injector pipe due to the fuel injection in the calculation process of the correction amount in the fuel injection amount correction. And
The sound speed ratio correction coefficient is obtained by using a predetermined arithmetic expression or a sound speed ratio correction coefficient map, and is used for correcting the sound speed ratio,
The calculation formula and the sound speed ratio correction coefficient map are configured so that kinematic viscosity and rail pressure are input, and a sound speed ratio correction coefficient for these kinematic viscosity and rail pressure is obtained. The correction amount control method in the fuel injection amount correction according to claim 3. The control by the electronic control unit according to the operating state of the internal combustion engine enables the multi-stage injection to the internal combustion engine by the injector and the subsequent fuel injection after the end of the preceding fuel injection in one engine cycle A common rail fuel injection control device configured so that fuel injection amount correction control for reducing a change in injection amount due to pulsation of fuel pressure occurring in the electronic control unit can be executed by the electronic control unit,
The electronic control unit is configured to use a kinematic viscosity correction coefficient that suppresses deterioration of the fuel injection amount correction due to kinematic viscosity in calculation calculation of the correction amount in the fuel injection amount correction. Fuel injection control device. The kinematic viscosity correction coefficient is calculated by a predetermined kinematic viscosity correction coefficient arithmetic expression and is used in a correction amount calculation process in the fuel injection amount correction,
6. The common rail fuel injection according to claim 5, wherein the electronic control unit is configured to obtain a kinematic viscosity correction coefficient for various kinematic viscosities using a predetermined arithmetic expression or a data map. Control device. The electronic control unit is
The common rail type according to claim 6, wherein a sound speed ratio correction coefficient for suppressing fluctuation due to kinematic viscosity of the sound speed ratio calculated in the correction amount calculation process in the fuel injection amount correction is used. Fuel injection control device. The sound speed ratio is used as a period for correcting the influence on the period of the change characteristic of the fuel injection amount due to the change in the sound speed change in the injector pipe due to the fuel injection in the calculation process of the correction amount in the fuel injection amount correction. And
The electronic control unit is configured to obtain the sound speed ratio correction coefficient using a predetermined arithmetic expression or a sound speed ratio correction coefficient map and correct the sound speed ratio using the sound speed ratio correction coefficient. on the other hand,
The calculation formula and the sound speed ratio correction coefficient map are configured so that kinematic viscosity and rail pressure are input, and a sound speed ratio correction coefficient for these kinematic viscosity and rail pressure is obtained. The common rail fuel injection control device according to claim 7.

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