JP2007077945A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine control device for accurately diagnosing the abnormality of the cetane number of fuel in use and the abnormality of an engine fuel supply system while distinguishing one from the other. <P>SOLUTION: When an engine operated condition is in a cetane number diagnosis region, the abnormality determination of the cetane number is performed in accordance with the maximum fluctuation crank angle CADPMAX where a pressure change rate dp/dθ of cylinder pressure is the maximum and a crank angle deviation DCA from its target value CADPMB (S12-S16). When there may be the abnormality of the cetane number, a crank angle deviation DCA is calculated in a fuel supply system diagnosis region and the abnormality diagnosis of a fuel supply system is executed in accordance with the calculated crank angle deviation DCA (S18-S20, S22), and the normality/abnormality determination of the cetane number is defined (S21, S22). The fuel supply system diagnosis region is set in an engine operation region different from the cetane number diagnosis region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a fuel supply system that supplies fuel for the internal combustion engine and a control device that has a function of diagnosing fuel abnormality.

  Patent Document 1 discloses a monitoring device that detects the temperature or pressure in a combustion chamber of a diesel engine and identifies a failure of a fuel metering device (fuel supply system) based on the detected temperature or pressure. According to this apparatus, when the detected temperature is significantly different from the target temperature, it is determined that a failure has occurred. Patent Document 1 does not describe the case of detecting the pressure in detail, but, similarly to the case of detecting the temperature, when the detected pressure is greatly different from the target pressure, it is determined as a failure. It has been suggested that

Japanese National Patent Publication No. 10-512345

  The monitoring device disclosed in Patent Document 1 focuses on the detected pressure itself, but detects the ignition timing of the fuel based on the rate of change of the pressure in the combustion chamber, and based on the detected ignition timing. It is conceivable to diagnose an abnormality in the fuel supply system. However, since the ignition timing of the fuel also changes depending on the cetane number of the fuel, it is necessary to perform an abnormality diagnosis in consideration of this point.

  The present invention has been made paying attention to this point, and provides an internal combustion engine control device that can accurately diagnose and distinguish between abnormalities in the cetane number of fuel in use and abnormalities in the fuel supply system of the engine. The purpose is to do.

  In order to achieve the above object, a first aspect of the present invention provides a control device for an internal combustion engine comprising a fuel supply means (6) for supplying fuel to the combustion chamber of the internal combustion engine (1). Pressure fluctuation detection means (2) for detecting (dp / dθ), maximum fluctuation crank angle calculation means for calculating a maximum fluctuation crank angle (CADPMAX) at which the detected pressure fluctuation value (dp / dθ) is maximum, Target value calculation means for calculating the target value (CADMB) of the maximum fluctuation crank angle (CADPMAX), engine operation state detection means for detecting the operation state of the engine, and the maximum fluctuation crank angle (CADPMAX, CADPMAX) Based on a deviation (DCA) from the target value (CADMB), an abnormality judgment for judging an abnormality of the cetane number of the fuel and an abnormality of the fuel supply means (6). The abnormality determining means determines an abnormality of the cetane number when the engine operating state is in a first region (cetane number diagnosis region), and the engine operating state is in the first region. When in a second region (fuel supply system value diagnosis region) different from the (cetane number diagnosis region), an abnormality of the fuel supply means (6) is determined.

  According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the first region (the cetane number diagnostic region) is a premixed combustion region.

  According to the first aspect of the present invention, the maximum fluctuation crank angle at which the detected pressure fluctuation value becomes the maximum is calculated, and the fuel cetane number abnormality is calculated based on the deviation between the maximum fluctuation crank angle and the target value. Then, abnormality of the fuel supply means is determined. When the engine operating state is in the first region, an abnormality of the cetane number is determined, and when the engine operating state is in a second region different from the first region, an abnormality of the fuel supply means is determined. . That is, since the first region for determining the cetane number abnormality and the second region for determining the abnormality of the fuel supply means are different engine operation regions, the cetane number abnormality and the fuel supply means abnormality are distinguished. Separately, it can be determined accurately.

  According to the second aspect of the present invention, the first region for determining the abnormality of the cetane number is the premixed combustion region. In the premixed combustion region, the ignition timing of the fuel changes relatively greatly depending on the cetane number, so the maximum variation crank angle also changes greatly. Therefore, it is possible to accurately determine the cetane number abnormality based on the deviation of the maximum variation crank angle from the target value.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter simply referred to as “engine”) 1 having four cylinders is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 6 is provided in each cylinder. The fuel injection valve 6 is connected to a high-pressure pump (both not shown) via a common rail. The fuel in a fuel tank (not shown) is boosted by a high-pressure pump, then sent to the fuel injection valve 6 through the common rail, and injected from the fuel injection valve 6 into the combustion chamber. A fuel supply system is constituted by the fuel injection valve 6, the common rail, the high-pressure pump, the fuel tank, and the fuel passage connecting them.

  Each cylinder of the 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 from the in-cylinder pressure sensor 2 is supplied to the 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 33 that detects an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, a cooling water temperature sensor 34 that detects a cooling water temperature TW of the engine 1, and an intake air temperature that detects an intake air temperature TA of the engine 1. The sensor 35 and an atmospheric pressure sensor (not shown) for detecting the atmospheric pressure PA are connected, and detection signals from 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, an input circuit 17, and an output circuit 18 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 conversion unit 11 includes a buffer 12, converts the in-cylinder pressure sensor output input from the amplifier 10 into a digital value (hereinafter referred to as “pressure change rate”) dp / dθ, and stores the converted value 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 ## EQU2 ## and converted into a digital value and stored in the buffer 12.

  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. Further, the required torque TRQ of the engine 1 is calculated according to the accelerator pedal operation amount AP.

  The ECU 4 controls the fuel injection valve 6 and diagnoses an abnormality in the cetane number of the fuel in use and an abnormality in the fuel supply system of the engine 1 according to the pressure change rate dp / dθ detected by the in-cylinder pressure sensor 2. I do.

FIG. 2 is a flowchart showing an abnormality diagnosis procedure executed by the CPU 14 of the ECU 4.
In step S11, it is determined whether or not a diagnosis execution condition is satisfied. The diagnosis execution condition is satisfied, for example, when the engine 1 has been warmed up and the engine speed NE, the intake air temperature TA, the coolant temperature TW, and the atmospheric pressure PA are in the normal range.

  If the answer to step S11 is affirmative (YES), it is determined whether or not the engine operating state is in a cetane number diagnosis region (step S12). Specifically, as shown in FIG. 4A, the first region R1 defined by the engine speed NE and the required torque TRQ is a cetane number diagnosis region, and in step S12, the engine speed NE and It is determined whether or not a coordinate point corresponding to the required torque TRQ is in this region. Here, the rotational speeds NE1 and NE2 shown in the figure are 1000 rpm and 3000 rpm, for example, and the required torques TRQ1 and TRQ2 are 15% and 75% of the full load, for example. The first region R1 is a premixed combustion region in which premixed combustion is performed such that the fuel is combusted after a delay time has elapsed since the time when the fuel was injected. In the premixed combustion region, the difference in the ignition timing due to the difference in the cetane number of the fuel becomes large, so that the abnormality determination of the cetane number based on the ignition timing can be performed accurately.

  If the answer to step S11 or S12 is negative (NO), the abnormality diagnosis is not executed. If the answer to step S12 is affirmative (YES), the crank angle deviation DCA is calculated by the procedure shown in FIG. 3 (step S13).

  In step S31 of FIG. 3, based on the time series data of the pressure change rate dp / dθ obtained from the output of the in-cylinder pressure sensor 2 of the cylinder in the expansion stroke, the crank angle at which the pressure change rate dp / dθ is maximized (hereinafter, “ CADPMAX (referred to as “maximum variation crank angle”). The maximum fluctuation crank angle CADPMAX substantially coincides with the actual ignition timing of fuel.

In step S32, the average value (smoothing value) CADMV of the maximum fluctuation crank angle CADPMAX is calculated by the following equation (1).
CADMV = A * CADPMAX + (1-A) * CADMV (1)
Here, A is an annealing coefficient set to a value between 0 and 1, and CADMAV on the right side is a previous calculated value of the average value.
Note that the average value CADDMA may be calculated as an average value of n maximum fluctuation crank angles CADPMAXi (i = 1 to n) by the following formula (1a).
CADMV = (CADPMAX1 + CADPMAX2 + ... + CADPMAXn) / n
(1a)

In step S33, a CADMB map (not shown) is searched according to the engine speed NE and the required torque TRQ, and a target value CADMB for the maximum fluctuation crank angle CADPMAX is calculated. In step S34, the target value CADMB and the average value CADDMA are applied to the following equation (2) to calculate the crank angle deviation DCA. The crank angle deviation DCA is a parameter indicating the delay angle of the actual ignition timing with respect to the target ignition timing.
DCA = CADMB-CADMV (2)

  FIG. 4B shows a waveform of the pressure change rate dp / dθ in the expansion stroke, and the crank angle at which the actual measurement value indicated by the solid line is the maximum is the maximum fluctuation crank angle CADPMAX. Moreover, the waveform shown with a broken line has shown the waveform corresponding to target value CADMB.

  Returning to FIG. 2, in step S14, it is determined whether or not the absolute value of the crank angle deviation DCA is equal to or greater than a first threshold value DCATH1 (for example, 3 degrees). When this answer is negative (NO), it is determined that the cetane number of the fuel in use is normal (step S15). On the other hand, when DCA ≧ DCATTH1, it is temporarily determined that there is a possibility that the cetane number of the fuel is abnormal (the cetane number is too low compared to the fuel that is normally used) (step S16).

  In step S17, it is determined whether or not the engine operating state is in the fuel supply system diagnosis region. The fuel supply system diagnosis region is the second region R2 shown in FIG. 4A, and the change in the ignition timing depending on the cetane number of the fuel is small in the second region R2. Therefore, the abnormality diagnosis of the fuel supply system can be performed without being affected by the cetane number. If the answer to step S17 is negative (NO), the process ends without executing diagnosis.

If the answer to step S17 is affirmative (YES), the crank angle deviation DCA is calculated again (step S18), and the calculated absolute value of the crank angle deviation DCA is greater than or equal to a second threshold value DCTH2 (eg, 3 to 5 degrees). It is determined whether or not there is (step S19). If the answer is affirmative (YES), it is determined that the fuel supply system is abnormal (step S20), and the cetane number of the fuel is determined to be normal (step S21).
When | DCA | <DCATH2 in step S19, it is determined that the fuel supply system is normal (step S22), and it is determined that the cetane number of the fuel is abnormal, that is, the provisional abnormality determination in step S17 is finalized (step S23). .

  As described above, in this embodiment, when the engine operating state is in the first region R1, an abnormality in the cetane number is determined, and the engine operating state is in the second region R2 different from the first region R1. An abnormality in the fuel supply system is determined. That is, as shown in FIG. 4 (a), the first region R1 for determining the cetane number abnormality is different from the second region R2 for determining the abnormality of the fuel supply system. And the abnormality in the fuel supply system can be distinguished accurately.

  Further, since the first region R1 is the premixed combustion region, the change in the maximum fluctuation crank angle CADPMAX due to the difference in cetane number becomes large, and the cetane number abnormality determination based on the crank angle deviation DCA can be accurately performed. it can.

  In this embodiment, the fuel injection valve 6, the common rail, the high pressure pump, the fuel passage, etc. constitute fuel supply means, the in-cylinder pressure sensor 2 constitutes pressure fluctuation detection means, and the crank angle position sensor 3 and the accelerator sensor 33 are The engine operation state detection means is configured, and the ECU 4 forms maximum fluctuation crank angle calculation means, target value calculation means, and abnormality determination means. Specifically, steps S31 and S32 in FIG. 3 correspond to the maximum fluctuation crank angle calculation means, step S33 corresponds to the target value calculation means, step S34 in FIG. 3, and steps S14 to S16, S19 in FIG. S23 corresponds to the abnormality determining means.

(Second Embodiment)
In the present embodiment, the final determination is made while correcting the fuel injection timing during the abnormality diagnosis. Except for the points described below, the second embodiment is the same as the first embodiment.

5 and 6 are flowcharts showing the procedure for abnormality diagnosis in the present embodiment.
Steps S41 to S46 are the same as the processes of steps S11 to S16 in FIG. In step S47, the fuel injection timing CAINJ is corrected according to the crank angle deviation DCA. Specifically, the first correction amount DCACR1 is calculated according to the crank angle deviation DCA, and the fuel injection timing CAINJ is advanced (when DCA> 0) or retarded (DCA <0) by the first correction amount DCACR1. 0). The first correction amount DCACR1 is set to be substantially proportional to the crank angle deviation DCA.

  In step S48, the crank angle deviation DCA is calculated again with the fuel injection timing CAINJ corrected. Next, it is determined whether or not the absolute value of the first correction amount DCACR1 calculated in step S47 is equal to or less than a correction amount threshold DCACTH (for example, 10 degrees) (step S49). If this answer is affirmative (YES), the process proceeds to step S51.

  In step S51, it is determined whether or not the absolute value of the crank angle deviation DCA is equal to or less than a first threshold value DCATH1. If the answer to step S47 is negative (NO), the process returns to step S47, the first correction amount DCACR1 is updated in a direction in which the absolute value increases, and the fuel injection timing CAINJ is corrected.

If the answer to step S49 is negative (NO) due to the increase in the absolute value of the first correction amount DCACR1, it is determined that the fuel supply system may be abnormal, and the fuel supply system temporary abnormality determination flag FFSUPF is set to “1”. (Step S50). Thereafter, the process proceeds to step S61.
If | DCA | ≦ DCATH1 in step S51, the process proceeds to step S61.

  Steps S61 to S63 in FIG. 6 are the same as steps S17 to S19 in FIG. If the answer to step S63 is negative (NO), that is, if | DCA | <DCATH2, the fuel supply system is determined to be normal (step S64). Next, it is determined whether or not the fuel supply system temporary abnormality determination flag FFSUPF is “1” (step S65). If the answer is affirmative (YES) and the fuel supply system temporary abnormality determination is made, Then, it is determined that the cetane number of the fuel in use is abnormal (step S66). On the other hand, when FFSUPF = 0, it is determined that the cetane number of the fuel is also normal (step S67).

  If | DCA | ≧ DCATTH2 in step S63, it is determined that the fuel supply system may be abnormal (step S68), and the fuel injection timing CAINJ is corrected (step S69). That is, the second correction amount DCACR2 is calculated according to the crank angle deviation DCA, and the fuel injection timing CAINJ is advanced (when DCA> 0) or retarded (DCA <0) by the second correction amount DCACR2. ) The second correction amount DCACR2 is set to be substantially proportional to the crank angle deviation DCA.

  In step S70, the crank angle deviation DCA is calculated again with the fuel injection timing CAINJ corrected. Next, it is determined whether or not the absolute value of the second correction amount DCACR2 calculated in step S69 is less than or equal to the correction amount threshold DCACTH (step S71). If this answer is affirmative (YES), the process proceeds to step S74.

  In step S74, it is determined whether or not the absolute value of the crank angle deviation DCA is equal to or smaller than a second threshold value DCATH2. If the answer to step S69 is negative (NO), the process returns to step S69, the second correction amount DCACR2 is updated in a direction in which the absolute value increases, and the fuel injection timing CAINJ is corrected.

  If the answer to step S71 is negative (NO) due to an increase in the absolute value of the second correction amount DCACR2, it is determined that the fuel supply system is abnormal (step S72), and the cetane number of the fuel in use is determined to be normal. (Step S73). At this time, the first correction amount DCACR1 is returned to “0”.

  On the other hand, if | DCA | ≦ DCATH2 is satisfied in step S74, it is determined that both the fuel supply system and the cetane number of the fuel in use are normal (steps S75 and S76). At this time, the first correction amount DCACR1 is returned to “0”.

  As described above, in the present embodiment, when the absolute value of the crank angle deviation DCA is greater than or equal to the threshold values DCATH1 and DCATH2, the fuel injection timing CAINJ is corrected, the correction amounts DCACR1 and DCACR2, and the corrected crank angle deviation DCA. Based on the above, an abnormality diagnosis is executed. Therefore, when the absolute value of the crank angle deviation DCA falls within the allowable range by a slight correction, it is determined that the fuel supply system and / or cetane number is normal, and the accuracy of abnormality determination can be improved.

  In the present embodiment, steps S44 to S46, S49 to S51, S63 to S68, and S71 to 76 in FIG. 5 correspond to the abnormality determining means.

  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 abnormality diagnosis is executed when the engine operating state changes according to the driver's intention and the state shifts to the cetane number diagnosis region or the fuel supply system diagnosis region. In such a vehicle, the automatic transmission may be controlled so that the engine operating state shifts to the cetane number diagnosis region or the fuel supply system diagnosis region.

  In the above-described embodiment, the cetane number diagnosis region and the fuel supply system diagnosis region are set according to the engine speed NE and the required torque TRQ. However, the cetane number diagnosis region and the fuel supply system diagnosis region are set in consideration of the air-fuel ratio factor of the air-fuel mixture in the combustion chamber. You may do it.

  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 flowchart which shows the procedure which performs the abnormality diagnosis of the cetane number of a fuel supply system and the fuel in use (1st Embodiment). It is a flowchart which shows the procedure which calculates a crank angle deviation (DCA). It is a figure which shows the output waveform of the driving | running | working area | region which performs abnormality diagnosis, and a cylinder pressure sensor. It is a flowchart which shows the procedure which performs the abnormality diagnosis of the cetane number of the fuel supply system and the fuel in use (2nd Embodiment). It is a flowchart which shows the procedure which performs the abnormality diagnosis of the cetane number of the fuel supply system and the fuel in use (2nd Embodiment).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 In-cylinder pressure sensor (pressure fluctuation detection means)
3 Crank angle position sensor (Engine operating state detection means)
4 Electronic control unit (maximum fluctuation crank angle calculation means, target value calculation means, abnormality determination means)
6 Fuel injection valve (fuel supply means)
33 Accelerator sensor

Claims (2)

In a control device for an internal combustion engine comprising fuel supply means for supplying fuel to a combustion chamber of the internal combustion engine,
Pressure fluctuation detecting means for detecting pressure fluctuation in the combustion chamber;
Maximum fluctuation crank angle calculating means for calculating a maximum fluctuation crank angle at which the detected pressure fluctuation value is maximum;
Target value calculating means for calculating a target value of the maximum variation crank angle;
Engine operating state detecting means for detecting the operating state of the engine;
An abnormality determining means for determining an abnormality of the cetane number of the fuel and an abnormality of the fuel supply means based on a deviation between the maximum fluctuation crank angle and the target value;
The abnormality determining means determines an abnormality of the cetane number when the engine operating state is in a first region, and when the engine operating state is in a second region different from the first region, A control device for an internal combustion engine, wherein abnormality of the fuel supply means is determined.   The control apparatus for an internal combustion engine according to claim 1, wherein the first region is a premixed combustion region.

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