JP2023145839A - Internal combustion engine control device - Google Patents

Abstract

To provide an internal combustion engine control device capable of more appropriately performing knock control even when an actual EGR rate sharply decreases.SOLUTION: An EGR clogging detection section 52 detects an EGR clogging index on the basis of a first EGR rate that is an EGR rate for control and a second EGR rate that is an actual EGR rate. The EGR clogging detection section 52 calculates limitation value relaxation amount on the basis of the EGR clogging index. A knock control section 51 calculates a knock timing delay amount limitation value on the basis of the limitation value relaxation amount.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to an internal combustion engine control device.

In a conventional multi-cylinder internal combustion engine diagnostic device, when an EGR (Exhaust Gas Recirculation) device is activated, a knock frequency is determined for each cylinder using a knock sensor, and a knock frequency ratio between the cylinders is calculated. Then, the difference between the knock frequency ratio of each cylinder and the initial knock frequency ratio is determined, and the EGR distribution deterioration state is diagnosed. Further, for a cylinder whose difference from the initial knock frequency ratio exceeds the first determination value, the ignition timing is corrected to the retarded side, and the fuel injection amount is corrected to the increased side (for example, Patent Document 1 reference).

Japanese Patent Application Publication No. 2010-156295

In the conventional multi-cylinder internal combustion engine as described above, for example, even though the EGR valve is operating normally, if the EGR passage suddenly becomes clogged with a large deposit, the actual EGR rate will suddenly decrease. In such a case, the corrected ignition timing is overadvanced with respect to the trace knock ignition timing, and the state of frequent knocking continues. As a result, the knock determination threshold value diverges, making it impossible to correctly detect the knock frequency.

The present disclosure has been made to solve the above-mentioned problems, and aims to provide an internal combustion engine control device that can perform knock control more appropriately even when the actual EGR rate suddenly decreases. shall be.

An internal combustion engine control device according to the present disclosure includes an electronic control device that controls ignition timing of an internal combustion engine based on a knock retard amount, and the electronic control device limits knock intensity and knock retard amount in the internal combustion engine. The electronic control device calculates the knock retard amount based on the knock retard amount limit value, and the electronic control device calculates the knock retard amount limit value when controlling the EGR valve provided in the EGR passage to perform exhaust gas recirculation. can be corrected to the retarded side.

According to the present disclosure, knock control can be performed more appropriately even when the actual EGR rate suddenly decreases.

1 is a schematic configuration diagram showing an internal combustion engine, an intake system, an exhaust system, an exhaust gas recirculation system, and an internal combustion engine control device according to a first embodiment. FIG. 2 is a block diagram showing main parts of FIG. 1. FIG. 3 is a block diagram showing main parts of the electronic control device of FIG. 2. FIG. 4 is a flowchart showing the operation of the EGR clogging detection section of FIG. 3. FIG. 5 is a graph showing temporal changes in the in-cylinder pressure knock index, knock signal, knock retard amount, and ignition timing when there is a sudden change from an EGR normal state to an EGR clogging state in the internal combustion engine control device of the first embodiment. 7 is a graph showing temporal changes in the in-cylinder pressure knock index, knock signal, knock retard amount, and ignition timing when there is a sudden change from an EGR normal state to an EGR clogging state in an internal combustion engine control device according to a comparative example. FIG. 2 is a configuration diagram showing a first example of a processing circuit that realizes each function of the electronic control device according to the first embodiment. FIG. 3 is a configuration diagram showing a second example of a processing circuit that implements each function of the electronic control device according to the first embodiment.

Hereinafter, embodiments will be described with reference to the drawings.
Embodiment 1.
FIG. 1 is a schematic configuration diagram showing an internal combustion engine, an intake system, an exhaust system, an exhaust gas recirculation system, and an internal combustion engine control device according to a first embodiment. The internal combustion engine 1 of the first embodiment is a gasoline engine mounted on a vehicle.

The internal combustion engine 1 includes a cylinder 2, a piston 3, a spark plug 4, an ignition coil 5, a variable intake valve mechanism 6, a variable exhaust valve mechanism 7, an injector 8, and a knock sensor 9.

The piston 3 is provided within the cylinder 2. The spark plug 4 is provided in the cylinder 2. Furthermore, the spark plug 4 ignites the air-fuel mixture within the cylinder 2 . The ignition coil 5 is connected to the ignition plug 4. Further, the ignition coil 5 generates a high voltage for the spark plug 4 to discharge.

The variable intake valve mechanism 6 has an intake valve. The intake valve opens and closes the intake port of the cylinder 2. Further, in the variable intake valve mechanism 6, the opening/closing timing of the intake valve can be controlled.

The variable exhaust valve mechanism 7 has an exhaust valve. The exhaust valve opens and closes the exhaust port of the cylinder 2. Further, in the variable exhaust valve mechanism 7, the opening/closing timing of the exhaust valve can be controlled.

The injector 8 is provided at the intake port of the cylinder 2. Further, the injector 8 injects fuel into the intake port. Note that the injector 8 may be arranged so as to be able to directly inject fuel into the cylinder 2.

The knock sensor 9 is provided in the cylinder 2. Further, the knock sensor 9 detects vibrations of the internal combustion engine 1.

Note that the knock sensor 9 may be, for example, a cylinder pressure sensor that detects pressure waves within the cylinder 2 as vibration data.

The intake system 21 includes an intake manifold 22, an air flow sensor 23, an electronically controlled throttle valve 24, a throttle opening sensor 25, a surge tank 26, an intake manifold pressure sensor 27, and an intake temperature sensor 28.

A downstream end of the intake manifold 22 is connected to an intake port of the cylinder 2. Air flow sensor 23 is provided in intake manifold 22. Furthermore, the air flow sensor 23 detects the intake air flow rate.

The electronically controlled throttle valve 24 is provided in the intake manifold 22 on the side closer to the internal combustion engine 1 than the air flow sensor 23 . The opening degree of the electronically controlled throttle valve 24 is electronically controlled to adjust the intake air flow rate. The throttle opening sensor 25 detects the opening of the electronically controlled throttle valve 24 .

The surge tank 26 is provided in the intake manifold 22 on the side closer to the internal combustion engine 1 than the electronically controlled throttle valve 24 . Further, the surge tank 26 equalizes the increase/decrease in the air flow rate. Intake manifold pressure sensor 27 detects the pressure within surge tank 26 .

The intake temperature sensor 28 is provided in the surge tank 26. Further, the intake temperature sensor 28 detects the intake manifold temperature, that is, the temperature of intake air.

Note that either the air flow sensor 23 or the intake manifold pressure sensor 27 may be omitted. For example, the intake air flow rate may be estimated based on the opening degree of the electronically controlled throttle valve 24.

Further, the intake air temperature sensor 28 may be omitted. In this case, for example, the temperature inside the surge tank 26 may be estimated based on the outside temperature detected by a temperature sensor built into the air flow sensor 23.

The exhaust system 31 includes an exhaust manifold 32, an oxygen sensor (not shown), and a catalyst (not shown). The upstream end of the exhaust manifold 32 is connected to the exhaust port of the cylinder 2. The oxygen sensor detects oxygen in exhaust gas. Catalysts purify exhaust gas.

The exhaust gas recirculation system 41 includes an EGR passage 42, an EGR valve 43, and an EGR valve opening sensor 44.

An upstream end of the EGR passage 42 is connected to the exhaust manifold 32. A downstream end of the EGR passage 42 is connected to the intake manifold 22 between the electronically controlled throttle valve 24 and the surge tank 26.

The EGR valve 43 is provided in the EGR passage 42. Further, the EGR valve 43 controls the amount of EGR. The EGR valve opening sensor 44 detects the opening of the EGR valve 43.

The internal combustion engine control device controls the internal combustion engine 1, the intake system 21, and the exhaust gas recirculation system 41. Further, the internal combustion engine control device includes an electronic control device 50.

FIG. 2 is a block diagram showing the main parts of FIG. 1. A vibration detection signal from the knock sensor 9 is input to the electronic control device 50 .

The electronic control device 50 also receives a flow rate detection signal from the air flow sensor 23, an opening detection signal from the throttle opening sensor 25, a pressure detection signal from the intake manifold pressure sensor 27, and a temperature detection signal from the intake air temperature sensor 28. A signal is also input.

Further, an opening detection signal from the EGR valve opening sensor 44 is also input to the electronic control device 50 .

Although omitted in FIG. 1, the atmospheric pressure sensor 11 detects atmospheric pressure. The atmospheric pressure detection signal from the atmospheric pressure sensor 11 is input to the electronic control device 50 .

Note that an atmospheric pressure sensor built into the electronic control device 50 may be used as the atmospheric pressure sensor 11. Further, the atmospheric pressure may be estimated by the electronic control device 50.

Further, in a system in which the EGR valve opening sensor 44 is not provided, such as a stepper motor type system, a control instruction value for the EGR valve 43 may be used instead of the opening of the EGR valve 43. .

Further, signals from various sensors 12 other than those described above are also input to the electronic control device 50. The various sensors 12 include an accelerator opening sensor, a crank angle sensor, and the like.

Further, signals from various controllers (not shown) are also input to the electronic control device 50. The various controllers include an automatic transmission controller, a brake controller, a traction controller, and the like.

The electronic control device 50 controls the ignition coil 5, the variable intake valve mechanism 6, the variable exhaust valve mechanism 7, the injector 8, the electronically controlled throttle valve 24, and the EGR valve 43. Further, the electronic control device 50 also controls various actuators 13 other than those described above.

The electronic control device 50 calculates a target throttle opening based on the accelerator opening, the operating state of the internal combustion engine 1, and the like. The electronic control device 50 then controls the electronically controlled throttle valve 24 based on the target throttle opening.

Further, the electronic control device 50 controls the variable intake valve mechanism 6, the variable exhaust valve mechanism 7, and the EGR valve 43 according to the operating state of the internal combustion engine 1. Then, the electronic control device 50 drives the injector 8 to achieve the target air-fuel ratio. Furthermore, the electronic control device 50 controls the energization of the ignition coil 5 so as to achieve the target ignition timing.

Furthermore, when knocking is detected by the method described below, the electronic control device 50 suppresses the occurrence of knocking by setting the target ignition timing to the retarded side. Furthermore, when no knock is detected, the electronic control device 50 returns the ignition timing to the advanced side. Further, the electronic control device 50 calculates instruction values for the various actuators 13.

Further, the electronic control device 50 calculates the sound velocity inside the exhaust manifold 32 based on the temperature inside the exhaust manifold 32. Further, the electronic control device 50 calculates the gas density inside the exhaust manifold 32 based on the temperature and pressure inside the exhaust manifold 32.

The temperature and pressure inside the exhaust manifold 32 may be detected by a temperature sensor and a pressure sensor provided in the exhaust manifold 32. Further, the temperature and pressure inside the exhaust manifold 32 may be calculated using a map centered on the engine rotation speed and the filling efficiency calculated from the intake air amount.

FIG. 3 is a block diagram showing main parts of the electronic control device 50 of FIG. 2. As shown in FIG. In FIG. 3, only the parts related to knock control and EGR clogging detection are shown.

The electronic control device 50 includes, as functional blocks, a knock control section 51 and an EGR clogging detection section 52 which is a limit value correction section.

The knock control section 51 includes an A/D conversion section 51a, a knock window setting section 51b, a vibration data extraction section 51c, a knock determination threshold calculation section 51d, a knock intensity calculation section 51e, and a knock retard amount calculation section 51f. There is.

The A/D converter 51a performs A/D conversion on the vibration detection signal from the knock sensor 9 at regular time intervals, for example, every 10 μs or 20 μs. Then, the A/D conversion section 51a sends the A/D converted signal to the knock window setting section 51b.

Based on the knock window, the knock window setting section 51b sends only the vibration data within the knock window period to the vibration data extraction section 51c, out of the vibration data included in the signal from the A/D conversion section 51a. The knock window period is set according to the operating conditions, for example, by using a table based on the engine speed.

Note that the order of the A/D conversion section 51a and the knock window setting section 51b may be changed to perform A/D conversion only within the knock window period.

The vibration data extraction unit 51c performs time-frequency analysis using digital signal processing. Examples of digital signal processing include STFT (Short-Time Fourier Transform) and DFT (Discrete Fourier Transform).

Vibration data extraction section 51c calculates spectral sequences of a plurality of natural frequencies by digital signal processing, calculates a peak value for each spectral sequence of natural frequencies, and outputs the peak value as a knock signal VP for each natural frequency. The knock signal VP from the vibration data extraction section 51c is input to the knock determination threshold calculation section 51d and the knock intensity calculation section 51e, respectively.

Note that the vibration level of the natural frequency may be extracted by using an IIR (Infinite Impulse Response) filter, FIR (Finite Impulse Response) filter, or the like as digital signal processing.

Further, the calculations by the vibration data extraction unit 51c may be performed while performing A/D conversion, or may be performed all at once by interrupt processing synchronized with the rotation of the internal combustion engine 1.

The knock determination threshold calculation unit 51d calculates the background level VBGL based on the knock signal VP. The background level VBGL is a smoothed value of the knock signal VP.

Further, the knock determination threshold calculation unit 51d calculates a knock determination threshold VTH by multiplying the background level VBGL by a gain, and sends the result to the knock intensity calculation unit 51e.

The background level VBGL is calculated by filtering the knock signal VP calculated for each cycle for each of the plurality of natural frequencies, as shown in equation (1) below. Note that K(n) is a filter coefficient, and n is the number of cycles.

VBGL(n)=K(n)×VBGL(n-1)+(1-K(n))×VP(n)...(1)

Two values K1 and K2 are used as the filter coefficient K(n). However, K1>K2.

Before formula (1), the knock signal VP(n) of the current cycle is compared with the knock judgment threshold VTH(n-1) of the previous cycle, and if VP(n)>VTH(n-1), , K(n)=K1. Furthermore, when VP(n)≦VTH(n-1), K(n)=K2. This prevents the background level VBGL from increasing unnecessarily due to the knock signal VP when a knock occurs.

Then, the knock determination threshold VTH is calculated using the following equation (2). Note that G _th is a threshold gain.

VTH(n)=VBGL(n)×G _th (n)...(2)

The threshold gain G _th (n) is set depending on the operating state, for example, by using a map centered on engine speed and charging efficiency.

The knock intensity calculation unit 51e compares the knock signal VP and the knock determination threshold value VTH for each natural frequency, and calculates the knock intensity VK' for each natural frequency using the following equation (3).

VK'(n)=max[{VP(n)-VTH(n)}÷VTH(n),0]...(3)

Then, the knock intensity calculation section 51e sends the total value of the knock intensity VK' for each natural frequency to the knock retard amount calculation section 51f as the knock intensity VK.

Note that the knock intensity VK may be, for example, the maximum value of the knock intensities VK' for each natural frequency, or the square root of the sum of squares of the knock intensity VK' for each natural frequency.

The knock retard amount calculation unit 51f first calculates the knock retard amount limit value θlim(n) using the following equation (4). Note that θlim_b is the basic knock retard amount limit value, and θlim_e(n) is the limit value relaxation amount.

θlim(n)=θlim_b+θlim_e(n)...(4)

The limit value relaxation amount θlim_e will be described later. Further, the basic knock retard amount limit value θlim_b is a value that is set in advance, but may be a value that is changed depending on the driving state, for example, by using a table based on the engine speed.

Next, the knock retard amount calculation unit 51f uses the knock intensity VK and the knock retard amount limit value θlim to calculate the knock retard according to the knock intensity according to the following formula (5) when the knock intensity VK>0. Calculate the angle θR.

θR(n)=max{θR(n-1)-VK(n),θlim(n)}...(5)

Furthermore, when the knock strength VK=0, the knock retard amount calculation unit 51f returns the knock retard amount θR to the advance side by a set amount.

Note that in order to suppress torque shock due to ignition retardation, a limit may be set on the amount of change ΔθR(n)=θR(n)−θR(n−1) in the amount of knock retardation.

In this way, the knock control unit 51 calculates the knock retard amount θR based on the knock intensity VK and the knock retard amount limit value θlim, and adjusts the ignition timing of the internal combustion engine 1 based on the knock retard amount θR. control. Further, the knock control unit 51 calculates the knock retard amount limit value θlim based on the limit value relaxation amount θlim_e. The knock retard amount limit value θlim is a value that limits the knock retard amount θR. The limit value relaxation amount θlim_e is an amount by which the knock retard amount limit value θlim is corrected to the retard side.

The knock control performed by the knock control unit 51 has been described above with respect to a processing method that realizes knock detection using frequency analysis results through digital signal processing and avoidance of knock by retarding the ignition timing.

Next, the EGR clogging detection section 52 will be explained. The EGR clogging detection section 52 includes a first EGR rate calculation section 52a, a second EGR rate calculation section 52b, a clogging index calculation section 52c, an EGR failure determination section 52d, and a retard amount limit value relaxation determination section 52e. .

Signals from a plurality of sensors are input to the first EGR rate calculation unit 52a and the second EGR rate calculation unit 52b, respectively. Thereby, the first EGR rate calculation unit 52a and the second EGR rate calculation unit 52b acquire the operating state value of the internal combustion engine 1 in the current cycle.

The plurality of sensors include an atmospheric pressure sensor 11, an air flow sensor 23, an intake manifold pressure sensor 27, an intake air temperature sensor 28, an EGR valve opening sensor 44, and the like.

In addition, the operating state values in this cycle include engine speed NE(n), intake air amount Qa(n), intake manifold temperature Tb(n), intake manifold pressure Pb(n), atmospheric pressure Pa(n), The exhaust pipe side pressure Pex(n), the exhaust pipe side temperature Tex(n), the exhaust pipe side gas density ρex(n), and the opening degree TPe(n) of the EGR valve 43 are included.

The exhaust pipe side pressure Pex(n) is the pressure inside the exhaust manifold 32. The exhaust pipe side temperature Tex(n) is the temperature inside the exhaust manifold 32. The exhaust pipe side gas density ρex(n) is the gas density inside the exhaust manifold 32.

The first EGR rate calculation unit 52a calculates a first EGR rate R1 used as a control EGR rate.

Specifically, the first EGR rate calculation unit 52a first calculates the first EGR amount M1 based on the opening area of the EGR valve 43 using the following equations (6) and (7).

In addition, Se(n) is the opening area of the EGR valve 43, κ is the specific heat ratio, R is the gas constant, Pex(n) is the exhaust pipe side pressure, Tex(n) is the exhaust pipe side temperature, and σe(n) is nothing. is the dimensional flow constant. Further, as the specific heat ratio κ, a value of 1.33, which is smaller than the value of air, 1.4, is used, for example. Further, Pb(n) is the intake manifold pressure.

The opening area Se(n) of the EGR valve 43 is calculated by using a table centered on the opening degree TPe(n) of the EGR valve 43. Further, the relationship between the opening area Se(n) and the opening degree TPe(n) of the EGR valve 43 obtained through learning in advance may be reflected in the table.

Then, the first EGR rate calculation unit 52a calculates the first EGR rate R1 by dividing the calculated first EGR amount M1 by the intake air amount Qa.

The second EGR rate calculation unit 52b calculates the second EGR rate R2. The second EGR rate R2 is used as a clogging determination EGR rate that corresponds to the actual EGR rate.

Specifically, the second EGR rate calculation unit 52b first calculates the cylinder flow rate Qall using the following equation 8 based on the volumetric efficiency correction coefficient Kv(n).

Note that Vc is the cylinder volume, and TIstr is the cycle for each stroke.

The volumetric efficiency correction coefficient Kv(n) is calculated by using a map centered on the engine speed NE and Pb÷Pa, which is the ratio of the atmospheric pressure Pa and the intake manifold pressure Pb.

Note that the volumetric efficiency correction coefficient Kv(n) changes depending on the valve timing, so two Kv maps are used: one that matches the target valve timing according to the operating conditions, and the other when the variable valve timing is not activated. is used.

Then, the second EGR rate calculation unit 52b calculates the second EGR amount M2 by subtracting the intake air amount Qa from the calculated cylinder flow rate Qall. Further, the second EGR rate calculation unit 52b divides the second EGR amount M2 by the intake air amount Qa to calculate the second EGR rate R2.

The clogging index calculation unit 52c calculates the EGR clogging index Ier based on the first EGR rate R1 and the second EGR rate R2. The EGR clogging index Ier is an index of the degree of clogging of the EGR passage 42. In this example, the clogging index calculation unit 52c calculates the EGR clogging index Ier by subtracting the second EGR rate R2 from the first EGR rate R1.

If the EGR clogging index Ier is a positive value, the EGR rate for clogging determination is lower than the EGR rate for control, and there is concern about the possibility of EGR clogging. If the EGR clogging index Ier has a negative value, the EGR rate for clogging determination is higher than the EGR rate for control, and there is concern about the possibility of excessive EGR.

A plurality of threshold values are set in the EGR failure determination section 52d. The plurality of threshold values include an open abnormality determination implementation threshold THR1_fs_h, an open abnormality determination threshold THIe_fs_h, a clogging abnormality determination implementation threshold THR1_fs_l, and a clogging abnormality determination threshold THIe_fs_l.

The EGR failure determination unit 52d performs EGR failure determination based on the first EGR rate R1, the EGR clogging index Ier, and a plurality of threshold values.

Specifically, the EGR failure determination unit 52d compares the first EGR rate R1 and the opening abnormality determination implementation threshold THR1_fs_h. Further, the EGR failure determination unit 52d compares the EGR clogging index Ier and the open abnormality determination threshold THIe_fs_h.

Then, the EGR failure determination unit 52d determines that an EGR opening abnormality has occurred when the following condition 1 is satisfied. The EGR opening abnormality is, for example, a state in which the EGR valve 43 is missing and the second EGR rate R2 is abnormally higher than the first EGR rate R1.

Condition 1: R1<THR1_fs_h and Ier<THIe_fs_h

Furthermore, if Condition 1 is not satisfied, the EGR failure determination unit 52d determines that an EGR opening abnormality has not occurred.

The EGR failure determination unit 52d compares the first EGR rate R1, which is the control EGR rate, with the opening abnormality determination execution threshold THR1_fs_h, and determines whether the control EGR rate is low, such as when the EGR valve 43 is close to fully closed, for example. Determine whether or not. Then, the EGR failure determination unit 52d compares the EGR clogging index Ier with the open abnormality determination threshold THIe_fs_h.

As a result, even if the opening degree of the EGR valve 43 is operating normally according to the indicated value, for example, the EGR valve 43 may be damaged and the EGR rate for clogging determination may become extremely high compared to the EGR rate for control. It is possible to detect the state in which That is, even if an abnormal state cannot be determined only by comparing the indicated value and the actual value of the opening degree of the EGR valve 43, it is possible to determine whether an EGR opening abnormality has occurred.

Note that a negative value is set as the open abnormality determination threshold THIe_fs_h. Further, the opening abnormality determination implementation threshold THR1_fs_h and the opening abnormality determination threshold THIe_fs_h may each be fixed values. Further, the opening abnormality determination implementation threshold THR1_fs_h and the opening abnormality determination threshold THIe_fs_h may be values that are respectively set using, for example, a map centered on the engine rotation speed and the charging efficiency.

When determining that an EGR open abnormality has occurred, the EGR failure determination unit 52d implements fail-safe control for the EGR open abnormal state, and resets the limit value relaxation amount θlim_e to a zero value. Fail-safe control for EGR opening abnormality is control that prevents the engine from stalling by controlling the electronically controlled throttle valve 24 to the open side, for example, in a low load range where combustion becomes particularly unstable due to EGR opening abnormality. It is.

Further, when determining that an EGR open abnormality has not occurred, the EGR failure determination unit 52d compares the first EGR rate R1 with a clogging abnormality determination implementation threshold THR1_fs_l. Further, the EGR failure determination unit 52d compares the EGR clogging index Ier and the clogging abnormality determination threshold THIe_fs_l.

Then, the EGR failure determination unit 52d determines that an EGR clogging abnormality has occurred when the following condition 2 is satisfied.

Condition 2: R1>THR1_fs_l and Ier>THIe_fs_l

Furthermore, if condition 2 is not satisfied, the EGR failure determination unit 52d determines that an EGR clogging abnormality has not occurred.

The EGR failure determination unit 52d compares the first EGR rate R1, which is the control EGR rate, with the clogging abnormality determination implementation threshold THR1_fs_l, and determines whether the control EGR rate is high, such as when the EGR valve 43 is near full open, for example. Determine whether or not. Then, the EGR failure determination unit 52d compares the EGR clogging index Ier with the clogging abnormality determination threshold THIe_fs_l.

As a result, even if the opening degree of the EGR valve 43 is operating normally according to the indicated value, for example, a large amount of deposits accumulates in the EGR valve 43 or the EGR passage 42, and the control EGR rate is judged to be clogged. It is possible to detect a state where the EGR rate is extremely low. That is, it can be determined whether an EGR clogging abnormality has occurred.

Note that a positive value is set as the clogging abnormality determination threshold THIe_fs_l. Furthermore, the clogging abnormality determination implementation threshold THR1_fs_l and the clogging abnormality determination threshold THIe_fs_l may be fixed values. Further, the clogging abnormality determination implementation threshold THR1_fs_l and the clogging abnormality determination threshold THIe_fs_l may be values that are respectively set using, for example, a map centered on the engine rotation speed and the charging efficiency.

When determining that an EGR clogging abnormality has occurred, the EGR failure determination unit 52d implements fail-safe control for the EGR clogging abnormality, and resets the limit value relaxation amount θlim_e to a zero value. In the fail-safe control for the EGR clogging abnormality, the EGR failure determination unit 52d sets the control EGR rate to zero, fully closes the EGR valve 43, and prohibits execution of EGR (exhaust gas recirculation).

Further, when the EGR failure determination unit 52d determines that an EGR clogging abnormality has not occurred, the retard amount limit value relaxation determination unit 52e determines the need for correction of the knock retard amount limit value θlim to the retard side. Determine whether or not.

Specifically, a clogging determination implementation threshold THR1_rtd and a clogging determination threshold THIe_rtd are set in the retard amount limit value relaxation determination unit 52e. The clogging determination implementation threshold THR1_rtd is set to a smaller value than the clogging abnormality determination implementation threshold THR1_fs_l. The clogging determination threshold THIe_rtd is set to a smaller value than the clogging abnormality determination threshold THIe_fs_l.

The retard amount limit value relaxation determination unit 52e compares the first EGR rate R1 and the clogging determination implementation threshold THR1_rtd. Then, when the following condition 3 is satisfied, the retard amount limit value relaxation determining unit 52e determines that it is necessary to correct the knock retard amount limit value θlim to the retard side. That is, when the first EGR rate R1 is higher than the clogging determination execution threshold THR1_rtd, the EGR clogging detection unit 52 calculates a limit value relaxation amount θlim_e that corrects the knock retard amount limit value θlim to the retard side.

Condition 3: R1>THR1_rtd

Further, if condition 3 is not satisfied, the retard amount limit value relaxation determination unit 52e determines that it is unnecessary to correct the knock retard amount limit value θlim to the retard side.

In this way, the retard amount limit value relaxation determination unit 52e compares the first EGR rate R1, which is the control EGR rate, and the clogging determination implementation threshold THR1_rtd. As a result, the EGR clogging abnormality has not occurred, but the control EGR rate is high to some extent, and depending on the difference between the control EGR rate and the clogging determination EGR rate, the range of the basic knock retard amount limit value θlim_b may vary. It is possible to determine whether there is a possibility that knock control cannot be performed appropriately based on the amount of knock retardation.

If the retard amount limit value relaxation determination unit 52e determines that the knock retard amount limit value θlim does not need to be corrected to the retard side, it resets the limit value relaxation amount θlim_e to a zero value.

When determining that the knock retard amount limit value θlim needs to be corrected to the retard side, the retard amount limit value relaxation determining unit 52e compares the EGR clogging index Ier and the clogging determination threshold THIe_rtd. , it is determined whether the following condition 4 is satisfied.

Condition 4: Ier>THIe_rtd

When condition 4 is satisfied, the EGR rate for clogging determination is lower to some extent than the EGR rate for control, and the difference between the two is large to some extent. The angle limit value θlim is corrected.

The correction based on setting A is a correction of the knock retard amount limit value θlim to the retard side according to the EGR clogging index Ier. In the correction based on setting A, the retard amount limit value relaxation determination unit 52e calculates the limit value relaxation amount θlim_e using a table centered on the EGR clogging index Ier.

Each table value in the table centered on the EGR clogging index Ier is set such that the higher the EGR clogging index Ier, the larger the limit value relaxation amount θlim_e. That is, when the EGR clogging index Ier is higher than the clogging determination threshold THIe_rtd, the EGR clogging index Ier increases the limit value relaxation amount θlim_e as the EGR clogging index Ier increases.

As a result, the limit value relaxation amount θlim_e according to the EGR clogging index Ier is applied, and even in a situation where knock control cannot be performed appropriately with the knock retard amount θR in the range of the basic knock retard amount limit value θlim_b, appropriate knock can be achieved. control can be implemented.

If condition 4 is not satisfied, the clogging determination EGR rate is not so low as compared to the control EGR rate, and the difference between the two is small. However, the retard amount limit value relaxation determination unit 52e corrects the knock retard amount limit value θlim according to setting B, taking into consideration the possibility of a calculation error between the first EGR rate R1 and the second EGR rate R2. The calculation error between the first EGR rate R1 and the second EGR rate R2 is caused by, for example, detection variations of each sensor.

In the correction based on setting B, the retard amount limit value relaxation determination unit 52e calculates the limit value relaxation amount θlim_e using a table centered on the first EGR rate R1.

Each table value in the table centered on the first EGR rate R1 is, for example, a positive number less than 1.0, for example 0.2, with respect to each table value in the table centered on the EGR clogging index Ier in setting A. is set to the value multiplied by . Thereby, even if there is a calculation error between the first EGR rate R1 and the second EGR rate R2, it is possible to correct the basic knock retard amount limit value θlim_b to some extent and perform appropriate knock control.

In this way, the EGR clogging detection unit 52 detects EGR clogging based on the first EGR rate R1, which is the control EGR rate for controlling the EGR valve 43, and the second EGR rate R2, which is the actual EGR rate. Calculate the index Ier. Further, the EGR clogging detection unit 52 calculates the limit value relaxation amount θlim_e based on the EGR clogging index Ier.

FIG. 4 is a flowchart showing the operation of the EGR clogging detection section 52 in FIG. 3. The EGR clogging detection unit 52 periodically executes the process shown in FIG. 4.

The EGR clogging detection unit 52 acquires a plurality of operating state values in step S101. Subsequently, the clogging detection unit 52 calculates the first EGR rate R1 in step S102, and calculates the second EGR rate R2 in step S103.

After this, the EGR clogging detection unit 52 calculates the EGR clogging index Ier in step S104. Then, in step S105, the EGR clogging detection unit 52 determines whether the above condition 1 is satisfied.

If condition 1 is satisfied, the EGR clogging detection unit 52 performs fail-safe control for EGR opening abnormality in step S106, and ends the current process.

If condition 1 is not satisfied, the EGR clogging detection unit 52 determines in step S107 whether condition 2 described above is satisfied.

If condition 2 is satisfied, the EGR clogging detection unit 52 performs fail-safe control for EGR clogging abnormality in step S108, and ends the current process.

If condition 2 is not satisfied, the EGR clogging detection unit 52 determines whether condition 3 above is satisfied in step S109.

If condition 3 is not satisfied, the EGR clogging detection unit 52 resets the limit value relaxation amount θlim_e to zero value in step S113, and ends the current process.

If condition 3 is satisfied, the EGR clogging detection unit 52 determines whether condition 4 described above is satisfied in step S110.

If condition 4 is satisfied, the EGR clogging detection unit 52 corrects the knock retard amount limit value θlim according to the above setting A in step S111, and ends the current process.

If condition 4 is not satisfied, the EGR clogging detection unit 52 corrects the knock retard amount limit value θlim according to the above setting B in step S112, and ends the current process.

Note that in the process of step S101, the intake air amount Qa may be calculated based on the opening area of the electronically controlled throttle valve 24, the atmospheric pressure Pa, and the intake manifold pressure Pb. Atmospheric pressure Pa corresponds to the upstream pressure of the electronically controlled throttle valve 24. The intake manifold pressure Pb corresponds to the downstream pressure of the electronically controlled throttle valve 24.

Furthermore, in the process of step S104, the EGR clogging index Ier is not limited to the difference between the first EGR rate R1 and the second EGR rate R2. For example, the EGR clogging index Ier may be calculated based on the ratio of the first EGR rate R1 and the second EGR rate R2.

Further, in the process of step S102 and the process of step S103, the EGR amount may be calculated instead of the EGR rate, and the processes after step S104 may be executed based on the EGR amount instead of the EGR rate.

Next, FIG. 5 shows changes over time in the cylinder pressure knock index, knock signal, knock retard amount, and ignition timing when there is a sudden change from a normal EGR state to a clogged EGR state in the internal combustion engine control device of the first embodiment. This is a graph showing.

Further, FIG. 6 is a graph showing temporal changes in the cylinder pressure knock index, knock signal, knock retard amount, and ignition timing when there is a sudden change from an EGR normal state to an EGR clogging state in an internal combustion engine control device according to a comparative example. It is. The internal combustion engine control device according to the comparative example differs from the internal combustion engine control device according to the first embodiment in that it does not include the EGR clogging detection section 52.

Further, the internal combustion engine control device according to the comparative example calculates the opening area of the EGR valve based on the intake air amount, the cylinder flow rate, the pressure before and after the EGR valve, and the like. Then, the internal combustion engine control device according to the comparative example learns the relationship between the calculated opening area of the EGR valve and the opening degree of the EGR valve, and determines the amount of EGR for control based on the learned relationship between the opening area and the opening degree. Estimate the control EGR rate.

In FIGS. 5 and 6, time T1 indicated by a two-dot chain line is the time when the EGR normal state suddenly changes to the EGR clogging state. Time T2 indicated by the two-dot chain line is the time when the knock retard amount is the same as the basic knock retard amount limit value.

The cylinder pressure knock index is an index indicating the knock occurrence status, and is calculated based on the pressure inside the cylinder 2. In the knock retard amount, a negative value is a value on the retard side. Further, in FIG. 5, a basic knock retard amount limit value corresponding to the knock retard amount limit value in FIG. 6 is added.

Trace knock ignition timing is ignition timing close to MBT (Minimum Spark Advance for Best Torque). MBT is the ignition timing at which the torque of the internal combustion engine 1 is maximum.

In FIGS. 5 and 6, before time T1, the EGR is in a normal state, the ignition timing is controlled to trace knock ignition timing, and the cylinder pressure knock index is at an appropriate level.

In FIG. 6, when the EGR normal state suddenly changes to the EGR clogging state at time T1, in the internal combustion engine control device according to the comparative example, since the above learning has not been completed, the ignition timing becomes excessive with respect to the trace knock ignition timing. It becomes a corner. Therefore, in the internal combustion engine control device according to the comparative example, as shown in FIG. 6, the level of the in-cylinder pressure knock index increases rapidly, resulting in a state where knocks occur frequently.

When knocking occurs frequently, the knocking signal exceeds the knocking determination threshold and the ignition timing is retarded. However, since the knock retard amount becomes the same as the knock retard amount limit value at time T2, after time T2, even if the knock signal exceeds the knock determination threshold, the knock retard amount is limited and the ignition timing is traced. The knock ignition timing is not retarded and the state of frequent knocking continues.

Since the knock signal continues to be high, the background level increases, and the knock determination threshold exceeds the knock signal at time T3. After time T3, the knock determination threshold exceeds the knock signal and no knock is detected, so the knock retard amount returns to the advanced side and the ignition timing also becomes more overadvanced. As a result, in the internal combustion engine control device according to the comparative example, the knock signal, the background level, and the knock determination threshold value further increase, that is, the knock determination threshold value diverges.

On the other hand, in the internal combustion engine control device of the first embodiment, as shown in FIG. 5, the knock retard amount limit value is further corrected to the retard side after time T1. Therefore, in the internal combustion engine control device of the first embodiment, the knock retard amount does not become the same as the knock retard amount limit value, and the ignition timing can be controlled to the trace knock ignition timing.

In such an internal combustion engine control device, the electronic control device 50 can correct the knock retard amount limit value θlim to the retard side when controlling the EGR valve 43 to perform EGR. Therefore, even if the actual EGR rate suddenly decreases, the knock retard amount limit value θlim can be corrected to the retard side, the ignition timing is controlled to the trace knock ignition timing, and knock control is performed more appropriately. be able to.

Furthermore, when the first EGR rate R1 is higher than the clogging determination execution threshold THR1_rtd, the EGR clogging detection unit 52 calculates a limit value relaxation amount θlim_e that corrects the knock retard amount limit value θlim to the retard side. Therefore, in an operating state where the first EGR rate R1 is low and the influence on the trace knock ignition timing is small, it is possible to suppress the knock retard amount limit value θlim from being unnecessarily corrected to the retard side.

Further, the EGR clogging detection unit 52 calculates the EGR clogging index Ier based on the first EGR rate R1, which is the control EGR rate, and the second EGR rate R2, which is the actual EGR rate. Further, the EGR clogging detection unit 52 calculates the limit value relaxation amount θlim_e based on the EGR clogging index Ier. Then, the knock control unit 51 calculates the knock retard amount limit value θlim based on the limit value relaxation amount θlim_e. Therefore, the ignition timing can be controlled to trace knock ignition timing, and knock control can be performed more appropriately.

Furthermore, the EGR clogging detection unit 52 increases the limit value relaxation amount θlim_e as the EGR clogging index Ier increases. Therefore, the limit value relaxation amount θlim_e according to the EGR clogging index Ier is applied, and even in a situation where knock control cannot be performed appropriately with the knock retard amount within the range of the basic knock retard amount limit value θlim_b, appropriate knock control can be performed. can be carried out.

In addition, when the EGR clogging index Ier is less than or equal to the clogging determination threshold THIe_rtd, a positive number less than 1.0 is set for the limit value relaxation amount θlim_e when the EGR clogging index Ier is higher than the clogging determination threshold THIe_rtd. The limit value relaxation amount θlim_e is calculated by multiplying the limit value relaxation amount θlim_e. Thereby, even if there is a calculation error between the first EGR rate R1 and the second EGR rate R2, it is possible to correct the basic knock retard amount limit value θlim_b to some extent and perform appropriate knock control.

Further, the EGR clogging detection unit 52 determines that an EGR opening abnormality has occurred when the first EGR rate R1 is lower than the opening abnormality determination implementation threshold THR1_fs_h and the clogging index Ier is lower than the opening abnormality determination threshold THIe_fs_h. It is determined that Therefore, even if the EGR valve 43 is operating normally according to the indicated value, an EGR open abnormality can be detected, and it is possible to detect that the EGR control will continue even when the EGR open abnormality has occurred. Can be suppressed.

Further, the EGR clogging detection unit 52 detects that when the first EGR rate R1 is higher than the clogging abnormality determination implementation threshold THR1_fs_l and the clogging index Ier is higher than the clogging abnormality determination threshold THIe_fs_l, an EGR clogging abnormality has occurred. It is determined that the Therefore, even if the opening degree of the EGR valve 43 is operating normally according to the indicated value, the EGR clogging abnormality can be detected, and the EGR control can be performed while the EGR clogging abnormality has occurred. It is possible to prevent it from continuing.

Note that the calculation of the second EGR rate R2 may be omitted. Then, the electronic control device 50 may change the amount by which the knock retard amount limit value is corrected to the retard side based on the first EGR rate R1. This also allows knock control to be performed more appropriately. Note that in this case, steps S103 to S108, S110, and S111 in FIG. 4 are omitted.

Further, each function of the electronic control device 50 of the first embodiment is realized by a processing circuit. FIG. 7 is a configuration diagram showing a first example of a processing circuit that implements each function of the electronic control device 50 of the first embodiment. The processing circuit 100 in the first example is dedicated hardware.

Further, the processing circuit 100 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Applicable. Further, each function of the electronic control device 50 may be realized by a separate processing circuit 100, or each function may be realized by the processing circuit 100 collectively.

Further, FIG. 8 is a configuration diagram showing a second example of a processing circuit that implements each function of the electronic control device 50 of the first embodiment. The processing circuit 200 of the second example includes a processor 201 and a memory 202.

In the processing circuit 200, each function of the electronic control device 50 is realized by software, firmware, or a combination of software and firmware. Software and firmware are written as programs and stored in memory 202. The processor 201 implements each function by reading and executing programs stored in the memory 202.

It can also be said that the program stored in the memory 202 causes the computer to execute the procedures or methods of each part described above. Here, the memory 202 includes, for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrical Non-volatile memory such as ically Erasable and Programmable Read Only Memory) It is a permanent or volatile semiconductor memory. Furthermore, magnetic disks, flexible disks, optical disks, compact disks, mini disks, DVDs, etc. also correspond to the memory 202.

Note that some of the functions of each part described above may be realized by dedicated hardware, and some may be realized by software or firmware.

In this way, the processing circuit can implement the functions of each section described above using hardware, software, firmware, or a combination thereof.

1 internal combustion engine, 42 EGR passage, 43 EGR valve, 50 electronic control device.

Claims (8)

Equipped with an electronic control device that controls the ignition timing of the internal combustion engine based on the knock retard amount,
The electronic control device calculates the knock retard amount based on the knock intensity in the internal combustion engine and a knock retard amount limit value that limits the knock retard amount,
The electronic control device is an internal combustion engine control device that can correct the knock retard amount limit value to the retard side when controlling an EGR valve provided in an EGR passage to perform exhaust gas recirculation. A clogging determination implementation threshold is set in the electronic control device,
The electronic control device corrects the knock retard amount limit value to the retard side when a first EGR rate that is a control EGR rate for controlling the EGR valve is higher than the clogging determination implementation threshold. The internal combustion engine control device according to claim 1. The internal combustion engine control device according to claim 2, wherein the electronic control device changes the amount by which the knock retard amount limit value is corrected to the retard side based on the first EGR rate. The electronic control device calculates an EGR clogging index that is an index of the degree of clogging of the EGR passage based on the first EGR rate and a second EGR rate that is an actual EGR rate, and calculates an EGR clogging index that is an index of the degree of clogging of the EGR passage. The internal combustion engine control device according to claim 2, wherein a limit value relaxation amount, which is an amount by which the knock retard amount limit value is corrected to the retard side, is calculated based on the above. The internal combustion engine control device according to claim 4, wherein the electronic control device increases the limit value relaxation amount as the EGR clogging index increases. A clogging determination threshold is set in the electronic control device,
When the EGR clogging index is less than or equal to the clogging determination threshold, the electronic control device determines that: 1. The internal combustion engine control device according to claim 5, wherein the limit value relaxation amount is calculated by multiplying by a positive number less than 0. An opening abnormality determination implementation threshold and an opening abnormality determination threshold are set in the electronic control device,
When the first EGR rate is lower than the opening abnormality determination implementation threshold and the clogging index is lower than the opening abnormality determination threshold, the electronic control device is configured to adjust the second EGR rate to the first EGR rate. The internal combustion engine control device according to any one of claims 4 to 6, wherein it is determined that an abnormally high EGR opening abnormality has occurred. A clogging abnormality determination implementation threshold and a clogging abnormality determination threshold are set in the electronic control device,
The electronic control device determines that an EGR clogging abnormality has occurred when the first EGR rate is higher than the clogging abnormality determination implementation threshold and the clogging index is higher than the clogging abnormality determination threshold. The internal combustion engine control device according to any one of claims 4 to 7, wherein the internal combustion engine control device makes a determination.