JP2006016994A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of detecting a cetane number of a fuel being used during operation of the internal combustion engine.
The timing at which the in-cylinder pressure change rate dpdθ, which is the rate of change of the in-cylinder pressure with respect to the crank angle change, is detected as an actual ignition timing, and a delay from the fuel injection timing is detected as an ignition delay. The cetane number CET of the fuel in use is calculated according to the ignition delay. The cetane number learning value CETLRN is calculated by averaging the cetane number CET detected in a state where the engine speed NE, the engine water temperature TW, the intake air temperature TA, and the fuel temperature TF satisfy the learning condition. The fuel injection timing is controlled according to the cetane number learning value CETLRN.
[Selection] Figure 2

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to an apparatus that performs control in accordance with the combustion characteristics of the fuel being used.

  Patent Document 1 discloses an apparatus for analyzing combustion characteristics of fuel. The apparatus includes a constant volume combustion chamber, a pressurizing unit that pressurizes the combustion chamber, a heating unit that heats the combustion chamber, an injection unit that injects fuel into the combustion chamber, and the like. The combustion characteristics are analyzed based on the change characteristics of the pressure in the combustion chamber. By analyzing the combustion characteristics, for example, the cetane number of the fuel is obtained.

JP 2001-329905 A

  Since the combustion characteristic analysis device is for obtaining combustion characteristics using a combustion chamber having a constant volume different from that of an actual internal combustion engine, even when the analysis device is mounted on a vehicle, The cetane number of the fuel being used cannot be determined. Further, even if the analysis method used in the analysis apparatus is applied as it is, the cetane number of the fuel being used cannot be obtained during operation of the internal combustion engine.

  The present invention has been made paying attention to this point, and an object of the present invention is to provide a control device for an internal combustion engine that can detect the cetane number of the fuel being used during operation of the internal combustion engine.

  In order to achieve the above object, an invention according to claim 1 is a control device for an internal combustion engine provided with a fuel injection means (6) provided in a combustion chamber of the internal combustion engine (1) and injecting fuel into the combustion chamber. Based on the operation state detection means (3, 22 to 24) for detecting the operation state of the engine and the operation state detected by the operation state detection means, it is determined that the engine (1) is in a specific operation state. An ignition delay for detecting an ignition delay (TDFP, TDFM) of fuel injected into the combustion chamber when it is determined by the specific operation state determination means and the specific operation state determination means that the engine is in a specific operation state It has a detection means and a cetane number detection means for obtaining a cetane number (CETLRN) of the fuel used based on the detected ignition delay (TDFP, TDFM).

According to a second aspect of the present invention, there is provided a control apparatus for an internal combustion engine according to the first aspect, wherein the fuel injection timing control means controls the fuel injection timing based on the cetane number (CETLRN) detected by the cetane number detection means. Is further provided.
According to a third aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the amount of particulate matter contained in the exhaust gas based on the cetane number (CETLRN) detected by the cetane number detection means ( It further comprises particulate matter amount estimating means for estimating (PMC).

  According to the first aspect of the present invention, when it is determined that the engine is in the specific operation state, the ignition delay of the fuel injected into the combustion chamber is detected, and the engine is used based on the detected ignition delay. The cetane number of the fuel is required. Even during engine operation, the cetane number can be obtained based on the ignition delay of the fuel when in the specific operation state, so that an accurate cetane number can be obtained.

  According to the second aspect of the invention, since the fuel injection timing is controlled based on the detected cetane number, the fuel injection timing is suitable for the cetane number of the fuel in use, regardless of the fuel used. Therefore, it is possible to maintain good exhaust characteristics and improve startability at low temperatures.

  According to the third aspect of the present invention, since the amount of particulate matter contained in the exhaust is estimated based on the detected cetane number, the amount of particulate matter in the exhaust varies depending on the fuel used. However, accurate estimation is possible. Further, by using the estimated amount of particulate matter to calculate the amount of particulate matter deposited on the particulate matter filter provided in the exhaust system, an accurate amount of particulate matter is obtained, and the particulate matter filter Can be executed at an appropriate timing.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a fuel injection control device for an internal combustion engine according to an embodiment of the present invention. Each cylinder of a four-cylinder diesel engine (hereinafter referred to as “engine”) 1 is provided with an in-cylinder pressure sensor 2 that detects an in-cylinder pressure (combustion pressure). In the present embodiment, the in-cylinder pressure sensor 2 is configured integrally with a glow plug provided in each cylinder. A detection signal of the in-cylinder pressure sensor 2 is supplied to an electronic control unit (hereinafter referred to as “ECU”) 4. The detection signal of the in-cylinder pressure sensor 2 actually corresponds to a differential signal with respect to the crank angle (time) of the in-cylinder pressure PCYL, and the in-cylinder pressure PCYL is obtained by integrating the in-cylinder pressure sensor output. .

  The engine 1 is provided with a crank angle position sensor 3 that detects a rotation angle of a crankshaft (not shown). The crank angle position sensor 3 generates a pulse every crank angle, and the pulse signal is supplied to the ECU 4. The crank angle position sensor 3 further generates a cylinder identification pulse at a predetermined crank angle position of the specific cylinder and supplies it to the ECU 4.

  The ECU 4 includes an accelerator sensor 21 that detects an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, an engine water temperature sensor 22 that detects a cooling water temperature (hereinafter referred to as “engine water temperature”) TW of the engine 1, An intake air temperature sensor 23 that detects the intake air temperature TA and a fuel temperature sensor 24 that detects the temperature TF of the fuel supplied to the engine 1 are connected. The detection signals of these sensors are supplied to the ECU 4.

  The ECU 4 supplies a control signal for the fuel injection valve 6 provided in the combustion chamber of each cylinder of the engine 1 to the drive circuit 5. The drive circuit 5 is connected to the fuel injection valve 6, and supplies a drive signal corresponding to the control signal supplied from the ECU 4 to the fuel injection valve 6. Thus, at the fuel injection timing corresponding to the control signal output from the ECU 4, fuel is injected into the combustion chamber of each cylinder by the fuel injection amount corresponding to the control signal.

  The ECU 4 includes an amplifier 10, an A / D converter 11, a pulse generator 13, a CPU (Central Processing Unit) 14, a ROM (Read Only Memory) 15 that stores a program executed by the CPU 14, and a CPU 14. A RAM (Random Access Memory) 16 for storing calculation results and the like, and an input circuit 17 are provided. A detection signal of the in-cylinder pressure sensor 2 is input to the amplifier 10. The amplifier 10 amplifies an input signal. The signal amplified by the amplifier 10 is input to the A / D converter 11. The pulse signal output from the crank angle position sensor 3 is input to the pulse generator 13.

  The A / D converter 11 includes a buffer 12, converts the in-cylinder pressure sensor output input from the amplifier 10 into a digital value dpdθ, and stores it in the buffer 12. More specifically, the A / D converter 11 is supplied with a pulse signal PLS1 (hereinafter referred to as “1 degree pulse”) PLS1 having a crank angle of 1 degree from the pulse generator 13, and this 1 degree pulse PLS1. The in-cylinder pressure sensor output is sampled at a period of

  On the other hand, the pulse signal PLS6 with a crank angle of 6 degrees is supplied from the pulse generator 13 to the CPU 14, and the CPU 14 performs a process of reading the digital value stored in the buffer 12 with the period of the 6 degrees pulse PLS6. . That is, in this embodiment, the A / D conversion unit 11 does not issue an interrupt request to the CPU 14, but the CPU 14 performs a reading process at a cycle of the 6-degree pulse PLS6.

  The input circuit 17 converts detection signals from various sensors into digital values and supplies them to the CPU 14. The engine speed NE is calculated from the cycle of the 6-degree pulse PLS.

  FIG. 2 is a functional block diagram showing the configuration of the cetane number learning module realized by the processing executed by the CPU 14. The cetane number learning module includes a bandpass filter unit 31, a phase delay correction unit 32, an ignition timing detection unit 33, an ignition delay time calculation unit 34, a cetane number calculation unit 35, a learning condition determination unit 36, a cetane The price learning unit 37 is provided.

  A pressure change rate dpdθ output from the in-cylinder pressure sensor 2 is input to the band pass filter unit 31. A waveform W1 shown in FIG. 3 indicates an input waveform, and a waveform W2 indicates an output waveform. Since the phase delay occurs in the band pass filter unit 31, the phase delay correction unit 32 corrects this delay. The ignition timing detection unit 33 corresponds to the pilot injection, the crank angle position at which the pressure change rate dpdθ exhibits a peak value (hereinafter referred to as “pilot injection combustion crank angle”) CAPMAX, and the pressure change rate corresponding to the main injection. The crank angle position (hereinafter referred to as “main injection combustion crank angle”) CAMMAX at which dpdθ exhibits a peak value is detected. Specifically, as shown in FIG. 4C, the crank angle at which the pressure change rate dpdθ output from the phase delay correction unit 32 exceeds the pilot detection threshold DPP is detected as the pilot injection combustion crank angle CAPMAX. The crank angle at which the pressure change rate dpdθ exceeds the main detection threshold DPM is detected as the main injection combustion crank angle CAMMAX.

  The ignition delay time calculation unit 34 calculates the first ignition delay crank angle CADFP from the injection start crank angle CAIP (FIG. 4A) of the pilot injection to the pilot injection combustion crank angle CAPMAX, and the injection start crank of the main injection. A second ignition delay crank angle CADFM from the angle CAIM (FIG. 4B) to the main injection combustion crank angle CAMMAX is calculated. The ignition delay time calculation unit 34 further converts the first ignition delay crank angle CADFP and the second ignition delay crank angle CADFM into the first ignition delay time TDFP and the second ignition delay time TDFM, respectively, according to the engine speed NE. .

  The cetane number calculation unit 35 searches the CET table shown in FIG. 5 according to the first ignition delay time TDFP or the second ignition delay time TDFM, and calculates the cetane number CET of the fuel in use. The cetane number CET becomes smaller as the ignition delay time TDFP or TDFM becomes longer.

  The learning condition determination unit 36 determines whether or not the engine 1 is in the specific operation state, and determines that the learning condition is satisfied when the engine 1 is in the specific operation state. Specifically, the engine speed NE and the required torque TRQ are substantially constant (for example, 1500 rpm and 72 N / m, respectively), and the engine water temperature TW, the intake air temperature TA, and the fuel temperature TF are respectively set to a predetermined water temperature TW0 (for example, 80 To 90 ° C.), a predetermined intake air temperature TA0 (for example, 20 to 25 ° C.), and a predetermined fuel temperature TF0 (for example, 50 to 60 ° C.). The requested torque TRQ is calculated according to the accelerator pedal operation amount AP.

The cetane number learning unit 37 calculates the cetane number learned value CETLRN by applying the cetane number CET input when the learning condition is satisfied to the following equation (1).
CETLRN = α × CET + (1−α) × CETLRN (1)
Here, α is an annealing coefficient that is set to a value between 0 and 1, and CETLRN on the right side is a previously calculated value.

  When refueling is performed, the cetane number learning value CETLRN is initialized to the minimum value CET0 among the cetane numbers of fuels traded in the market, and the cetane number of the fuel in use is determined by subsequent learning. It converges to the indicated value. By initializing to the minimum value CET0, when used for the control of the fuel injection timing described below, it is possible to reliably ignite even the most difficult-to-ignite fuel when the engine is cold started.

  The cetane number learning value CETLRN described above is calculated using all the cylinder pressure sensor outputs of the four cylinders. Therefore, the cetane number CET detected for each cylinder and the cetane number CET with different detection timings are averaged by the above equation (1).

FIG. 6 is a functional block diagram showing a configuration of a start injection timing setting module for setting the main injection timing CAINJM at the start. The function of the start injection timing setting module is realized by arithmetic processing of the CPU 14.
The start injection timing setting module includes a basic start injection timing calculation unit 41, a start injection timing correction coefficient calculation unit 42, and a multiplication unit 43. The basic start injection timing calculation unit 41 calculates a basic start injection timing CAMM according to the engine speed NE and the engine water temperature TW. The basic start injection timing CAMM is set to be an optimal fuel injection timing for an average cetane number fuel in a corresponding engine operating state. The injection timing is indicated by an advance amount from top dead center.

The start injection timing correction coefficient calculator 42 calculates a start injection timing correction coefficient KCETS according to the cetane number learned value CETLRN. Specifically, the KCETS table shown in FIG. 8 is searched according to the cetane number learning value CETLRN, and the start injection timing correction coefficient KCETS is calculated. The KCETS table is set so that the correction coefficient KCETS decreases as the cetane number learning value CETLRN increases. Therefore, the fuel injection timing is retarded as the cetane number of the fuel in use increases. This is because the higher the cetane number, the better the ignitability. In FIG. 8, CETAV is the average cetane number of fuel that may be used.
The multiplying unit 43 calculates the start injection timing CAINJM by multiplying the basic start injection timing CAMM by the start injection timing correction coefficient KCETS.

  According to the start injection timing setting module shown in FIG. 6, the fuel injection timing at the start is corrected according to the cetane number learned value CETLRN, and the fuel is injected at the fuel injection timing suitable for the cetane number of the fuel in use. Therefore, it is possible to improve the startability particularly during the cold start.

FIG. 7 is a functional block diagram showing the configuration of a pilot injection timing setting module for setting the pilot fuel injection timing CAINJP during normal operation. The function of the pilot injection timing setting module is realized by arithmetic processing of the CPU 14.
The pilot injection timing setting module includes a basic pilot injection timing calculation unit 51, an injection timing correction coefficient calculation unit 52, and a multiplication unit 53. The basic pilot injection timing calculation unit 51 calculates a basic pilot injection timing CAPM according to the engine speed NE and the required torque TRQ. The required torque TRQ is calculated according to the accelerator pedal operation amount AP. The basic pilot injection timing CAPM is set to be an optimal pilot injection timing for an average cetane number fuel in a corresponding engine operating state.

  The injection timing correction coefficient calculator 52 calculates a pilot injection timing correction coefficient KCETP according to the cetane number learned value CETLRN. Specifically, the KCETP table (same as the KCETS table) shown in FIG. 8 is searched according to the cetane number learning value CETLRN, and the pilot injection timing correction coefficient KCETP is calculated.

  The multiplier 53 calculates the pilot injection timing CAINJP by multiplying the basic pilot injection timing CAPM by the pilot injection timing correction coefficient KCETP.

  According to the pilot injection timing setting module shown in FIG. 7, the pilot fuel injection timing CAINJP is corrected according to the cetane number learning value CETLRN, and the pilot injection is executed at the fuel injection timing suitable for the cetane number of the fuel in use. Therefore, the pilot injection timing CAINJP becomes suitable for the fuel in use, and in particular, the combustion noise suppression effect can be enhanced.

FIG. 9 is a functional block diagram showing the configuration of a PM deposition amount estimation module that calculates the particulate matter amount PMQTY deposited on the DPF 8 provided in the exhaust system. The function of the PM accumulation amount estimation module is realized by arithmetic processing of the CPU 14.
The PM accumulation amount estimation module includes a basic PM emission amount calculation unit 61, a PM correction coefficient calculation unit 62, a multiplication unit 63, and an integration unit 64. The basic PM emission amount calculation unit 61 calculates a basic PM emission amount PMM according to the engine speed NE and the required torque TRQ. The basic PM emission amount PMM is set to a PM emission amount per unit time of an average cetane number fuel in a corresponding engine operating state.

  The PM correction coefficient calculator 62 calculates a PM correction coefficient KPM according to the cetane number learning value CETLRN. Specifically, the KPM table shown in FIG. 10 is searched according to the cetane number learning value CETLRN, and the PM correction coefficient KPM is calculated. The KPM table is set so that the PM correction coefficient KPM increases as the cetane number learning value CETLRN increases. This is because the PM emission per unit time increases as the cetane number increases and the ignitability improves.

  The multiplier 63 calculates the corrected PM discharge amount PMC by multiplying the basic PM discharge amount PMM by the PM correction coefficient KPM. The integrating unit 64 calculates the accumulated particulate matter amount PMQTY by integrating the corrected PM discharge amount PMC.

  According to the PM accumulation amount estimation module shown in FIG. 9, the basic PM emission amount PMM is corrected according to the cetane number learning value CETLRN, and the correction is a PM emission amount per unit time corresponding to the cetane number of the fuel in use. The PM emission amount PMC is calculated, and the accumulated particulate matter amount PMQTY is calculated by integrating the corrected PM emission amount PMC. Therefore, the estimation accuracy of the amount of particulate matter PMQTY can be improved regardless of the fuel used. When the deposited particulate matter amount PMQTY reaches a predetermined amount PMTH, a regeneration process for burning the deposited particulate matter is performed. By improving the estimation accuracy of the accumulated particulate matter amount PMQTY, the regeneration process can be executed at an optimal time regardless of the fuel used. Since the regeneration process is usually performed by increasing the fuel supply amount, the fuel efficiency can be improved by optimizing the execution frequency of the regeneration process.

  In this embodiment, the fuel injection valve 6 corresponds to the fuel injection means, the in-cylinder pressure sensor 2 constitutes a part of the ignition delay detection means, the crank angle position sensor 3, the engine water temperature sensor 22, the intake air temperature sensor 23, and The fuel temperature sensor 24 constitutes an operation state detection unit. The crank angle position sensor 3 constitutes a part of the ignition delay detection means. The ECU 4 constitutes specific operating state determination means, part of ignition delay detection means, cetane number detection means, fuel injection timing control means, and particulate matter amount estimation means. Specifically, the bandpass filter unit 31, the phase delay correction unit 32, the ignition timing detection unit 33, and the ignition delay time calculation unit 34 shown in FIG. 2 correspond to a part of the ignition delay detection unit, and the learning condition determination unit 36 Corresponds to the specific operating state determination means, the cetane number calculation unit 35 and the cetane number learning unit 37 correspond to the cetane number detection means, the modules shown in FIGS. 6 and 7 correspond to the fuel injection timing control means, and FIG. The basic PM emission amount calculation unit 61, the PM correction coefficient calculation unit 62, and the multiplication unit 63 shown in FIG.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the in-cylinder pressures of all the cylinders are detected and the cetane number learning value CETLRN is calculated. However, the in-cylinder pressure sensor is provided only in one specific cylinder, and the in-cylinder pressure sensor The cetane number learning value CETLRN may be calculated based on the detected in-cylinder pressure.

  Further, the ignition delay times TDFP and TDFM change depending not only on the cetane number of the fuel but also on the deterioration of the fuel injection valve 6. Therefore, it is desirable to correct the ignition delay times TDFP and TDFM according to the travel distance of the vehicle or the integrated value of the operation time of the engine 1.

  In the above-described embodiment, an example of a four-cylinder diesel internal combustion engine has been described. However, the present invention is not limited to this, and a diesel internal combustion engine having a different number of cylinders or an outboard motor having a crankshaft in a vertical direction is used. The present invention can also be applied to control of a marine propulsion engine.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a block diagram which shows the structure of the module which calculates the cetane number learning value of the fuel in use. It is a figure which shows the output waveform of a cylinder pressure sensor, and the waveform after a filter process. It is a timing chart for demonstrating the measurement of an ignition delay crank angle (CADFP, CADFM). It is a figure which shows the table for calculating a cetane number (CET) from ignition delay time (TDFP, TDFM). It is a block diagram which shows the structure of the module which calculates the fuel-injection time at the time of engine starting. It is a block diagram which shows the structure of the module which calculates the pilot injection time at the time of normal driving | operation. It is a figure which shows the table for calculating a correction coefficient (KCETS, KCETP) according to a cetane number learning value (CETLRN). It is a block diagram which shows the structure of the module which calculates the amount of particulate matter (PMQTY) of a particulate matter filter. It is a figure which shows the table for calculating a correction coefficient (KPM) according to a cetane number learning value (CETLRN).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 In-cylinder pressure sensor 3 Crank angle position sensor (Operating state detection means, ignition delay detection means)
4 Electronic control unit (specific operating state determination means, ignition delay detection means, cetane number detection means, fuel injection timing control means, particulate matter amount estimation means)
6 Fuel injection valve (fuel injection means)
8 Particulate matter filter 22 Engine water temperature sensor (operating state detection means)
23 Intake air temperature sensor (operating state detection means)
24 Fuel temperature sensor (operating state detection means)

Claims (3)

In a control device for an internal combustion engine, provided in a combustion chamber of an internal combustion engine, comprising fuel injection means for injecting fuel into the combustion chamber,
Operating state detecting means for detecting the operating state of the engine;
Specific operation state determination means for determining that the engine is in a specific operation state based on the operation state detected by the operation state detection unit;
An ignition delay detection means for detecting an ignition delay of the fuel injected into the combustion chamber when the specific operation state determination means determines that the engine is in a specific operation state;
A control device for an internal combustion engine, comprising: a cetane number detection means for obtaining a cetane number of a fuel being used based on the detected ignition delay.   2. The control apparatus for an internal combustion engine according to claim 1, further comprising fuel injection timing control means for controlling fuel injection timing based on the cetane number detected by the cetane number detection means.   2. The internal combustion engine according to claim 1, further comprising particulate matter amount estimation means for estimating the amount of particulate matter contained in the exhaust based on the cetane number detected by the cetane number detection means. Control device.

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