JP2011027034A - Injection control method and injection control device - Google Patents

Abstract

The present invention provides an injection control method and an injection control device for optimizing a pilot injection amount regardless of individual differences or aging of injectors.
Cylinder pressure of each cylinder # 1 to # 4 is measured, and a cylinder in which an increase width of the cylinder pressure measured at the compression top dead center with respect to the cylinder pressure measured at the time of pilot injection is higher than a target increase width The injector 2 decreases the pilot injection energization time, and the injector 2 of the cylinder whose in-cylinder pressure increase width is lower than the target increase width increases the pilot injection energization time.
[Selection] Figure 1

Description

  The present invention relates to an injection control method and an injection control device for optimizing a pilot injection amount regardless of individual differences or aging of injectors.

  Conventionally, by performing pilot injection that injects a small amount of fuel prior to main injection according to the operating state of the engine, engine performance such as combustion noise suppression, vibration suppression, NOx reduction, fuel consumption rate improvement, etc. Improvements are being made.

  As shown in FIG. 5, the energization pulse time (energization time to the injector) is calculated from the engine state for each of the number of injections in one combustion cycle. If the pilot injection and the main injection are performed twice in one combustion cycle, two energization pulses are energized in the injector in one combustion cycle.

  More specifically, when pilot injection is performed in an operating state of an engine having a relatively long ignition delay with only main injection, the ignition delay of main injection is shortened due to heat generation by pilot injection. As a result, the initial combustion due to the ignition delay is suppressed as compared with the case without pilot injection, and the combustion noise and vibration are suppressed. In addition, the fuel consumption rate is improved due to the effect of improving the ignition performance by shortening the ignition delay. Furthermore, NOx is reduced by the effect of internal EGR by the combustion product gas of pilot injection. Further, the main injection timing can be retarded, and NOx is reduced.

  On the other hand, when the pilot injection amount is increased more than necessary, the amount of soot discharged may increase, so the pilot injection amount and the pilot injection timing must be optimized according to the operating state.

JP 2006-83719 A JP 2007-23988 A

  If the characteristics (injection amount with respect to the energization time) of the injector, which is a fuel injection device, vary due to individual differences or change due to aging, the target optimum pilot injection amount cannot be secured. As a result, in the multi-cylinder engine, the pilot injection amount varies from cylinder to cylinder. If the pilot injection amount for each cylinder varies, the effect of improving the engine performance by the pilot injection cannot be sufficiently exhibited.

  For example, in a four-cylinder engine, when only one cylinder has a smaller pilot injection amount than the other cylinders, the ignition delay of main injection becomes longer only in that cylinder, the initial combustion becomes active, and combustion noise and vibration increase. . As a result, the engine rotational speed varies between cylinders, the smooth rotational feeling is impaired, and the performance of the engine as a whole is lowered. Further, since the ignition delay becomes longer, the fuel consumption rate deteriorates, leading to a deterioration of the fuel consumption rate of the engine as a whole.

  On the other hand, when only one cylinder has a larger pilot injection amount than the other cylinders, only that cylinder increases the soot discharge amount, and the soot discharge amount of the entire engine increases. In order to comply with exhaust gas regulations that are being strengthened globally, technology that minimizes the effects of such individual differences and aging of injectors is necessary.

  Accordingly, an object of the present invention is to provide an injection control method and an injection control device that solve the above-described problems and optimize the pilot injection amount regardless of individual differences or aging of injectors.

  In order to achieve the above object, an injection control method according to the present invention includes a plurality of cylinders each provided with an injector whose fuel injection amount is variable during energization time, and at least a main injection and a pilot injection preceding the main injection in one combustion cycle. In the engine injection control method, the cylinder pressure of each cylinder is measured, and the cylinder pressure increase range measured at the compression top dead center with respect to the cylinder pressure measured at the time of pilot injection is higher than the target increase range. This injector decreases the pilot injection energization time, and the injector of the cylinder whose in-cylinder pressure increase width is lower than the target increase width increases the pilot injection energization time.

  The in-cylinder pressure measurement for obtaining the in-cylinder pressure increase width may be performed when the state of the engine is stable for a predetermined time or more.

  The in-cylinder pressure measurement for obtaining the in-cylinder pressure increase width may be performed when the increase in the in-cylinder pressure due to the main injection is after the compression top dead center.

  Further, the injection control device of the present invention is a multi-injection that performs at least main injection and pilot injection prior to the main injection in one combustion cycle. In an engine injection control apparatus including a control unit, an in-cylinder pressure sensor that measures an in-cylinder pressure installed in each cylinder, and a compression top dead center measured with respect to the in-cylinder pressure measured at the time of pilot injection Injector time increase / decrease for cylinder injectors with higher in-cylinder pressure increase range than target increase range, and for cylinder injectors with in-cylinder pressure increase range lower than target increase range, increase pilot injection energization time Part.

  A cylinder for obtaining the in-cylinder pressure increase width when the rate of change in engine speed is equal to or less than a predetermined value and the rate of change in fuel injection amount is equal to or less than a predetermined value continues for a predetermined time or longer. You may provide the engine state determination part which permits internal pressure measurement.

  An energization time increase / decrease value map that is set in advance based on experiments and can refer to the increase / decrease value of the energization time corresponding to the difference between the in-cylinder pressure increase width and the target increase width may be provided.

  The present invention exhibits the following excellent effects.

  (1) The pilot injection amount can be optimized regardless of the individual difference of injectors or aging.

It is a block diagram of the injection control apparatus which shows one Embodiment of this invention. It is a graph which shows the time change of the energization current to the injector and the in-cylinder pressure in multi-injection for explaining that the amount of increase in the in-cylinder pressure is larger than the standard when the pilot injection amount is large. It is a flowchart which shows the procedure of the pilot injection energization time increase / decrease in the injection control apparatus of this invention. It is a flowchart which shows the setting procedure of the target raise range in the injection control apparatus of this invention. It is a graph which shows the time change of the energization current to the injector in multi injection, and cylinder pressure.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an injection control apparatus 1 according to the present invention includes an injector 2 that is installed in each of a plurality of cylinders # 1 to # 4 and has a variable fuel injection amount during an energization time, and at least a main in one combustion cycle. In-cylinder for measuring in-cylinder pressure installed in each cylinder # 1 to # 4 in an injection control device 1 of an engine 4 having a multi-injection control unit 3 that performs injection and pilot injection prior to the main injection The pressure sensor 5 and the injector 2 of the cylinder in which the increase range of the in-cylinder pressure measured at the time of compression top dead center with respect to the in-cylinder pressure measured at the time of pilot injection is higher than the target increase width reduce the pilot injection energization time. The injector 2 of the cylinder whose internal pressure increase width is lower than the target increase width has an energization time increasing / decreasing unit 6 that increases the pilot injection energization time, and the rate of change of the engine speed is less than a predetermined value. And when the state in which the rate of change of the fuel injection amount is a predetermined value or less continues for a predetermined time or longer, an engine state determination unit 7 that permits in-cylinder pressure measurement for obtaining the in-cylinder pressure increase width; An energization time increase / decrease value map 8 that is set in advance based on experiments and can refer to the increase / decrease value of the energization time corresponding to the difference between the in-cylinder pressure increase width and the target increase width, and the target increase width is referred to from the engine state. A possible target increase width base map 9, an intake air amount dependency correction map 10 for correcting a change in the in-cylinder pressure increase width depending on the intake air amount, and an in-cylinder pressure increase width depending on the intake air temperature. And an intake air temperature dependence correction map 11 for correcting the change.

  The multi-injection control unit 3, the energization time increase / decrease unit 6, the engine state determination unit 7, the energization time increase / decrease value map 8, the target increase width base map 9, the intake air amount dependency correction map 10, and the intake air temperature dependency correction map 11 It is provided in an ECU (electronic control unit or engine control unit) that is more used for engine control, or in a separate ECU.

  Members and sensors provided around the engine 4 are conventionally known. That is, the outlets of the cylinders # 1 to # 4 of the engine 4 communicate with the exhaust manifold 12. The exhaust manifold 12 is connected to the turbine 14 of the supercharger 13, and the turbine 14 has an exhaust pipe 15 to the atmosphere. Is connected. An intake pipe 16 from the atmosphere is connected to a compressor 18 of the supercharger 13 via an air cleaner 17. An air amount sensor 19 that measures the flow rate of intake air is disposed downstream of the air cleaner 17 of the intake pipe 16.

  A high-pressure air pipe 20 from the compressor 18 is connected to the intake manifold 21. An EGR pipe 24 including an EGR cooler 22 and an EGR valve 23 is connected to the exhaust manifold 12, and a downstream side of the EGR pipe 24 is connected to a high-pressure air pipe 20. A temperature sensor 25 that measures the temperature of the intake air is disposed upstream of the intake manifold 21 of the high-pressure air pipe 20.

  The injectors 2 of the cylinders # 1 to # 4 are supplied with fuel from the supply pump 26 via the common rail 27. The injectors 2 of the cylinders # 1 to # 4 receive a signal (energization pulse) from the ECU, and inject a desired injection amount by lifting the core valve for the pilot injection energization time or the main injection energization time. The injection amount is determined by the energization time of each injection and the common rail pressure. Here, the common rail pressure is assumed to be constant.

  Next, the operation of the injection control device 1 will be described.

  The present invention pays attention to an increase in in-cylinder pressure due to pilot injection as a method for optimizing the pilot injection amount of an injector having individual differences and aging. That is, because the in-cylinder pressure rises due to the burning of the fuel injected by the pilot, when the pilot injection amount is small in a certain cylinder, the increase in the in-cylinder pressure due to pilot injection in that cylinder is low, and when the pilot injection amount is large The increase in the cylinder pressure due to pilot injection of the cylinder is high. If the injection amount with respect to the energization time is deviated due to individual differences or aging of the injector, the pilot injection amount deviates from the original value, and the in-cylinder pressure increase width deviates from the original value. However, increasing the pilot injection amount of the cylinder when the in-cylinder pressure increase width is low increases the in-cylinder pressure increase width, and decreasing the pilot injection amount of the cylinder when the in-cylinder pressure increase width is high increases the in-cylinder pressure. Since the increase width becomes lower, the in-cylinder pressure increase width can be controlled to the target increase width by increasing or decreasing the pilot injection amount. That is, by increasing / decreasing the pilot injection energization time, it is possible to correct the increase / decrease of the injection amount due to individual differences of the injectors or aging.

  Specifically, as shown by a broken line and a solid line in FIG. 2, the in-cylinder pressure gradually increases during the compression process, and after the pilot injection, the fuel burns and the in-cylinder pressure increases. That is, an increase in the in-cylinder pressure due to the pilot injection is added to the increase in the in-cylinder pressure due to the compression process. As shown in the figure, the increase in the in-cylinder pressure resulting from the pilot injection is remarkable in the vicinity of the compression top dead center. Therefore, the increase range of the in-cylinder pressure measured at the time of compression top dead center with respect to the in-cylinder pressure measured at the time of pilot injection (moment of starting energization) can be considered as the increase range of the in-cylinder pressure due to pilot injection. . It is possible to determine whether the pilot injection amount is larger, smaller, or appropriate than the original value by comparing the amount of increase with a target amount of increase that is set in advance by experiments.

  Here, in the illustrated example, the change in the in-cylinder pressure in the solid line by the current injector 2 to be controlled is larger than the change in the in-cylinder pressure in the broken line by the proper injector 2. That is, the in-cylinder pressure increase due to pilot injection is higher than the target increase. Therefore, if the pilot injection energization time is shortened by the correction amount, the in-cylinder pressure increase width can be controlled to the target increase width. Actually, an energization time increase / decrease value map 8 that can refer to the increase / decrease value of the energization time (corresponding to the correction amount) corresponding to the difference between the in-cylinder pressure increase width and the target increase width based on the experiment conducted in advance. The increase / decrease value of the pilot injection energization time is determined with reference to the energization time increase / decrease value map 8 in advance.

  In this way, by increasing / decreasing the pilot injection energization time based on the increase in the in-cylinder pressure caused by the pilot injection for each cylinder, it is possible to correct the increase / decrease in the pilot injection amount due to individual differences of the injectors or secular change. This makes it possible to ensure the target optimum pilot injection amount without variation among cylinders. As a result, engine performance is improved such as combustion noise suppression, vibration suppression, NOx reduction, fuel consumption rate improvement, and soot emission suppression.

  When the main injection is performed before the compression top dead center, that is, at an advance angle, the increase in in-cylinder pressure due to the main injection (the white arrow in FIG. 2) may start at the compression top dead center. There is. Therefore, in-cylinder pressure measurement for determining the in-cylinder pressure increase due to pilot injection is performed only in an engine state where it is known that the increase in in-cylinder pressure due to main injection occurs after compression top dead center. I will decide. Specifically, the in-cylinder pressure may be measured in the engine state where the main injection is performed after the compression top dead center, that is, at a retarded angle. If the start of energization of the main injection is after the compression top dead center, there is a response time of the injector 2, so the main injection is surely after the compression top dead center.

  Next, a detailed procedure for increasing / decreasing the pilot injection energizing time in the injection control apparatus of the present invention will be described with reference to FIG.

  Step S1: The engine state determination unit 7 determines whether the engine coolant temperature is equal to or higher than a predetermined value Twx. If NO, repeat step S1, and if YES, proceed to step S2. This is because the increase / decrease of the pilot injection energization time by the energization time increase / decrease unit 6 after step S5 is permitted only when the engine is sufficiently warmed up.

  Step S2: The engine state determination unit 7 determines whether or not the rate of change of the engine rotation speed is equal to or less than a predetermined value NEx. If NO, the process returns to step S1, and if YES, the process proceeds to step S3. This is because the increase / decrease of the pilot injection energization time by the energization time increase / decrease unit 6 after step S5 is permitted only when the engine speed is substantially constant.

  Step S3: The engine state determination unit 7 determines whether the change rate of the fuel injection amount is equal to or less than a predetermined value Qx. If NO, the process returns to step S1, and if YES, the process proceeds to step S4. This is because the increase / decrease of the pilot injection energization time by the energization time increase / decrease unit 6 after step S5 is permitted only when the fuel injection amount is substantially constant.

  Step S4: The engine state determination unit 7 determines whether or not the stabilization time is equal to or longer than the predetermined time TSx. If NO, the process returns to step S1, and if YES, the process proceeds to step S5. This is because, in the determinations in steps S1 to S3, the engine coolant temperature is equal to or higher than the predetermined value Twx, the change rate of the engine speed is equal to or lower than the predetermined value NEx, and the change rate of the fuel injection amount is equal to the predetermined value Qx. This is because the increase / decrease of the pilot injection energization time by the energization time increase / decrease unit 6 after step S5 is permitted only when the engine state determined as follows continues for the predetermined time TSx or longer. Thus, the injection control device 1 of the present invention measures the in-cylinder pressure with high accuracy by measuring the in-cylinder pressure when the engine 4 is operating in a predetermined steady state.

  Step S5: The energization time increase / decrease unit 6 starts the in-cylinder pressure by the in-cylinder pressure sensor 5 of each cylinder, the intake air amount measurement by the air amount sensor 19, and the intake air temperature measurement by the temperature sensor 25.

  Step S6: The energization time increasing / decreasing unit 6 ends the measurement when the measured values from the sensors are collected. The in-cylinder pressure of each cylinder # 1 to # 4 is measured at the time of pilot injection and at the compression top dead center.

  Step S7: The energization time increasing / decreasing unit 6 calculates the in-cylinder pressure increase width by subtracting the in-cylinder pressure measured at the time of pilot injection from the in-cylinder pressure measured at the time of compression top dead center.

  Step S8: The energization time increase / decrease unit 6 calculates a deviation value (absolute value of the difference) between the in-cylinder pressure increase width and the target increase width.

  Step S9: The energization time increase / decrease unit 6 determines whether the deviation value is equal to or greater than a predetermined threshold. If NO, the process returns to step S1, and if YES, the process proceeds to step S10. This is because the increase / decrease of the pilot injection energization time is executed only when the difference between the in-cylinder pressure increase width and the target increase width is large.

  Step S10: The energization time increase / decrease unit 6 determines a correction value (increase / decrease value) of the pilot energization time with reference to the energization time increase / decrease value map 8.

  Step S11: The energization time increase / decrease unit 6 adds the correction amount to the pilot injection energization time before correction.

  Next, the procedure for setting the target increase width in the injection control apparatus 1 of the present invention will be described with reference to FIG.

  When the pilot injection amount is appropriate, the increase width of the in-cylinder pressure measured at the compression top dead center with respect to the in-cylinder pressure measured at the time of pilot injection is set as the target increase width. The target increase range varies depending on the engine state. Experiments have confirmed that the target increase range is uniquely determined on a graph having the engine speed and the commanded injection amount (total fuel injection amount in one combustion cycle), which are indicators of the engine state, in the vertical and horizontal axes. Therefore, the target increase width may be set in the target increase width base map 9 which is a two-dimensional map having the engine speed and the commanded injection amount as coordinates. Further, the target increase width varies depending on the intake air amount and the intake air temperature. Therefore, in order to determine the target increase range by measuring the intake air amount and intake air temperature and taking into account the effects of the measurement, the correction amount for the target increase range is a one-dimensional map that is determined by the intake air amount. The map 10 and the intake air temperature dependent correction map 11 which is a one-dimensional map in which the correction amount of the target increase width is determined by the intake air temperature are used.

As shown in FIG. 4, the basic target increase range is obtained by referring to the target increase range base map 9 with the engine speed and the commanded injection amount, and depends on the air amount with reference to the intake air amount dependency correction map 10. A change in the target increase width is corrected, and a change in the target increase width depending on the intake air temperature is corrected with reference to the intake air temperature dependency correction map 11. That is,
Target increase width = basic target increase width + correction amount by air amount + correction amount by temperature.

  In this embodiment, the pilot injection and the main injection are performed twice in one combustion cycle. However, if there is a state in which the injection other than the pilot injection is performed at a retarded angle, the injection is performed three times or more. Even in this case, the present invention can be applied.

DESCRIPTION OF SYMBOLS 1 Injection control apparatus 2 Injector 3 Multi-injection control part 4 Engine 5 In-cylinder pressure sensor 6 Energization time increase / decrease part 7 Engine state determination part 8 Energization time increase / decrease value map 9 Target rise width base map 10 Intake air amount dependence correction map 11 Intake air Temperature dependence correction map 12 Exhaust manifold 13 Supercharger 14 Turbine 15 Exhaust pipe 16 Intake pipe 17 Air cleaner 18 Compressor 19 Air quantity sensor 20 High pressure air pipe 21 Intake manifold 22 EGR cooler 23 EGR valve 24 EGR pipe 25 Temperature sensor 26 Supply pump 27 Common rail

Claims (6)

In an injection control method for an engine in which a plurality of cylinders are each provided with an injector whose fuel injection amount is variable during energization time, and at least a main injection and a pilot injection preceding the main injection are performed in one combustion cycle.
Measure the in-cylinder pressure of each cylinder,
An injector of a cylinder in which the increase in the in-cylinder pressure measured at the time of compression top dead center with respect to the in-cylinder pressure measured at the time of pilot injection is higher than the target increase width decreases the pilot injection energization time, and the in-cylinder pressure increase width is the target An injection control method characterized in that an injector of a cylinder lower than a rising width increases a pilot injection energization time.   2. The injection control method according to claim 1, wherein the in-cylinder pressure measurement for obtaining the in-cylinder pressure increase width is performed when the state of the engine is stable for a predetermined time or more.   The injection control method according to claim 1 or 2, wherein the in-cylinder pressure measurement for obtaining the in-cylinder pressure increase width is performed when the increase in the in-cylinder pressure by the main injection is after the compression top dead center. . Injection control of an engine provided with an injector with variable fuel injection amount installed in each of a plurality of cylinders and a multi-injection control unit that performs at least main injection and pilot injection prior to the main injection in one combustion cycle In the device
An in-cylinder pressure sensor for measuring the in-cylinder pressure installed in each cylinder;
An injector of a cylinder in which the increase in the in-cylinder pressure measured at the time of compression top dead center with respect to the in-cylinder pressure measured at the time of pilot injection is higher than the target increase width decreases the pilot injection energization time, and the in-cylinder pressure increase width is the target An injection control apparatus, wherein an injector for a cylinder lower than the ascending width includes an energization time increase / decrease unit that increases a pilot injection energization time.   A cylinder for obtaining the in-cylinder pressure increase width when the rate of change in engine speed is equal to or less than a predetermined value and the rate of change in fuel injection amount is equal to or less than a predetermined value continues for a predetermined time or longer. The injection control device according to claim 4, further comprising an engine state determination unit that permits internal pressure measurement.   5. An energization time increase / decrease value map that is set in advance based on an experiment and can refer to the increase / decrease value of the energization time corresponding to the difference between the in-cylinder pressure increase width and the target increase width. Or the injection control apparatus of 5.

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