JP7596978B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine.

An exhaust passage of an internal combustion engine is provided with an exhaust purification section such as a filter to purify the exhaust. The filter collects particulate matter (PM). The filter can be regenerated by oxidizing and removing the PM. For example, a technology is known in which the supply of fuel to some cylinders of an internal combustion engine is stopped (fuel cut) to send more oxygen into the filter and remove PM (for example, Patent Document 1).

JP 2015-10470 A

To prevent knocking in an internal combustion engine, the ignition timing is sometimes retarded. However, since knocking is less likely to occur during fuel cut, the ignition timing is more likely to be advanced. If fuel supply is resumed after fuel cut, there is a risk that knocking will worsen due to the ignition timing being advanced. Therefore, the objective of this invention is to provide a control device for an internal combustion engine that can prevent knocking from worsening.

The above object can be achieved by a control device for an internal combustion engine comprising a fuel control unit that controls the supply of fuel to a plurality of cylinders of an internal combustion engine, a first ignition timing control unit that controls ignition timing in the plurality of cylinders by KCS (Knock control system) learning, and a second ignition timing control unit that performs knock correction of the ignition timing for each cylinder, wherein, when the fuel control unit stops the supply of fuel to at least one cylinder of the plurality of cylinders in order to regenerate an exhaust purification unit provided in an exhaust passage of the internal combustion engine, the first ignition timing control unit performs at least one of stopping the KCS learning and the second ignition timing control unit stops the knock correction for each cylinder, and when the fuel control unit stops the supply of fuel to the at least one cylinder, the first ignition timing control unit stops the KCS learning and the second ignition timing control unit stops the knock correction for each cylinder .

The first ignition timing control unit may perform the KCS learning to update the KCS learning value based on a KCS learning value and a feedback value, and when the fuel control unit stops the supply of fuel to the at least one cylinder, the first ignition timing control unit may stop updating the KCS learning value.

The first ignition timing control unit may obtain a feedback smoothed value by smoothing the feedback value and update the KCS learning value based on the feedback smoothed value, and when the fuel control unit stops the supply of fuel to the at least one cylinder, the first ignition timing control unit may set the feedback smoothed value to a predetermined value, and when the feedback smoothed value is the predetermined value, the first ignition timing control unit may stop updating the KCS learning value.

The second ignition timing control unit may perform knock correction for each cylinder by advancing the ignition timing of a cylinder among the plurality of cylinders that has a low frequency of knocking and retarding the ignition timing of a cylinder that has a high frequency of knocking, and when the fuel control unit stops the supply of fuel to at least one of the cylinders, the second ignition timing control unit may stop the knock correction for each cylinder.

It is possible to provide a control device for an internal combustion engine that can suppress the worsening of knocking.

FIG. 1 is a schematic diagram illustrating an engine system. 2(a) and 2(b) are schematic diagrams illustrating the ignition timing. FIG. 3 is a flowchart illustrating a process executed by the ECU. FIG. 4 is a diagram illustrating an example of a time chart.

The control device for an internal combustion engine according to this embodiment will now be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating an engine system 100. The engine system 100 has an internal combustion engine 10 and an ECU (Electronic Control Unit) 40.

The internal combustion engine 10 is, for example, a gasoline engine that uses gasoline as fuel, and is, for example, a four-cylinder engine having four cylinders 10a, 10b, 10c, and 10d. A spark plug 12a and a fuel injection valve 14a are provided in the cylinder 10a. A spark plug 12b and a fuel injection valve 14b are provided in the cylinder 10b. A spark plug 12c and a fuel injection valve 14c are provided in the cylinder 10c. A spark plug 12d and a fuel injection valve 14d are provided in the cylinder 10d. The knock sensor 26 is attached to the internal combustion engine 10 and is a sensor that detects vibrations of the internal combustion engine 10 and detects knocking of the internal combustion engine 10.

An intake passage 20 and an exhaust passage 30 are connected to the internal combustion engine 10. An air flow meter 22 and a throttle valve 24 are provided in the intake passage 20, in that order from the upstream side. The air flow meter 22 measures the flow rate of air. The throttle valve 24 adjusts the flow rate of air.

The intake passage 20 branches into four downstream of the throttle valve 24. The four branched passages are connected to the four cylinders 10a, 10b, 10c, and 10d of the internal combustion engine 10. The four branched intake passages 20 are provided with fuel injection valves 16a, 16b, 16c, and 16d. The four fuel injection valves 16a, 16b, 16c, and 16d are arranged corresponding to the four cylinders 10a, 10b, 10c, and 10d of the internal combustion engine 10, respectively.

The exhaust passage 30 has four branched passages. These four passages are connected to the four cylinders 10a, 10b, 10c, and 10d of the internal combustion engine 10, and merge into one passage downstream. In the exhaust passage 30, an air-fuel ratio sensor 36, a pressure sensor 32, an exhaust purification section 38, and a pressure sensor 34 are provided in this order from the upstream side. The air-fuel ratio sensor 36 detects the air-fuel ratio.

The exhaust purification unit 38 includes, for example, a GPF (Gasoline Particle Filter) and a catalyst. The GPF is, for example, a honeycomb-structured filter that collects PM in the exhaust. The catalyst is, for example, a three-way catalyst that is coated on the wall surface of the GPF and purifies CO, NOx, and other substances in the exhaust.

The pressure sensor 32 is provided upstream of the exhaust purification section 38 and detects the pressure in the exhaust passage 30 upstream of the exhaust purification section 38. The pressure sensor 34 is provided downstream of the exhaust purification section 38 and detects the pressure in the exhaust passage 30 downstream of the exhaust purification section 38. The internal combustion engine 10 may be provided with an EGR (Exhaust Gas Recirculation) device or the like.

The ECU 40 is a control device that includes a calculation device such as a CPU (Central Processing Unit), and storage devices such as a flash memory, a ROM (Read Only Memory), and a RAM (Random Access Memory), and performs various controls by executing programs stored in the storage devices.

The ECU 40 controls the opening of the throttle valve 24. The ECU 40 obtains the air flow rate from the air flow meter 22. The ECU 40 obtains the air-fuel ratio from the air-fuel ratio sensor 36. The ECU 40 obtains the pressure upstream of the exhaust purification unit 38 from the pressure sensor 32. The ECU 40 obtains the pressure downstream of the exhaust purification unit 38 from the pressure sensor 34. The ECU 40 calculates the difference between the pressure detected by the pressure sensor 32 and the pressure detected by the pressure sensor 34, i.e., the pressure difference between the upstream and downstream sides of the exhaust purification unit 38.

The ECU 40 obtains the signal output by the knock sensor 26 and detects knocking. For example, the ECU 40 obtains the frequency of knocking for each cylinder based on the combustion timing and knocking timing for each cylinder.

The ECU 40 functions as a fuel control unit that controls the supply of fuel from each of the fuel injection valves 14a to 14d and the supply of fuel from each of the fuel injection valves 16a to 16d. The ECU 40 can stop the injection of fuel to at least one of the four cylinders (fuel cut). For example, fuel cut is performed for cylinder 10a by stopping the supply of fuel from fuel injection valves 14a and 16a. Exhaust containing more oxygen is discharged from the cylinder during fuel cut compared to when fuel is supplied. By introducing more oxygen into the exhaust purification unit 38, PM is oxidized and removed.

The ECU 40 controls the on/off and ignition timing of each of the spark plugs 12a to 12d. The control of the ignition timing includes KCS (Knock control system) learning and cylinder-specific knock correction. The KCS learning is feedback control of the ignition timing of the spark plugs 12a, 12b, 12c, and 12d. For example, when knocking occurs, the ignition timing of the four spark plugs is retarded. When knocking stops, the ignition timing of the four spark plugs is advanced. The KCS learning controls the ignition timing of all four spark plugs. On the other hand, the cylinder-specific knock correction controls the ignition timing of the spark plugs of the four cylinders individually. The ECU 40 functions as a first ignition timing control unit that controls the ignition timing of all four cylinders 10a to 10d based on the KCS learning. The ECU 40 functions as a second ignition timing control unit that controls the ignition timing of each cylinder. Knocking can be suppressed by retarding the ignition timing.

Figures 2(a) and 2(b) are schematic diagrams illustrating ignition timing, and show an example of determining ignition timing through KCS learning. The upper side of the diagram is the advance side, and the lower side is the retard side. KCS learning uses a KCS learning value and a feedback value (F/B value). Figure 2(a) shows an example where the F/B value is F/B1. Figure 2(b) shows an example where the F/B value is F/B2.

Bkcs is the base ignition timing, which is determined, for example, by the operating range of the internal combustion engine 10 (such as the rotation speed and load), the timing and amount of fuel injection, and the amount of EGR. Rmax is the most retarded ignition timing, which is determined, for example, by the vehicle model. A0, A1 in FIG. 2(a), and A2 in FIG. 2(b) are KCS learning values. The KCS learning value changes as KCS learning is performed. In the examples of FIG. 2(a) and FIG. 2(b), the initial value of the KCS learning value is A0. In the example of FIG. 2(a), the KCS learning value is updated from A0 to A1, which is more retarded than A0. In the example of FIG. 2(b), the KCS learning value is updated from A0 to A2, which is more advanced than A0.

F/B0 is the limit of the advance side of the F/B value, for example 0° CA (Crank Angle). The F/B value can take on values ranging from F/B0 to Rmax. F/Bi is the initial value of the F/B value, a value that is more retarded than F/B0 and more advanced than Rmax, for example -3° CA.

F/B1 in Fig. 2A is an example of the F/B value. When F/B0 (0° CA) is used as a reference, F/B1 is more retarded than F/Bi. Akcs is the required ignition timing. The ECU 40 calculates the required ignition timing Akcs using the following equation.
Akcs=Bkcs-Rmax+A0-F/B1

The F/B value F/B2 in Fig. 2(b) is more advanced than the F/B1 and the initial value F/B0 in Fig. 2(a) The ECU 40 calculates the required ignition timing Akcs using the following equation.
Akcs=Bkcs-Rmax+A0-F/B2
The required ignition timing Akcs calculated using F/B2 is more advanced than Akcs in FIG.

KCS learning is performed for all four cylinders 10a, 10b, 10c, and 10d. In other words, the ignition timing for the four cylinders 10a, 10b, 10c, and 10d becomes the required ignition timing Akcs.

When knock sensor 26 detects knocking, ECU 40 retards the required ignition timing Akcs by setting the F/B value to a more retarded side than F/Bi, for example, F/B1 in FIG. 2(a). When knocking is not detected, ECU 40 advances the required ignition timing Akcs by setting the F/B value to a more advanced side than F/Bi, for example, F/B2 in FIG. 2(b).

The ECU 40 obtains the F/B smoothed value by smoothing the F/B value. When knocking occurs, the F/B value is retarded and the F/B smoothed value is also retarded. When knocking stops, the F/B value is advanced and the F/B smoothed value is also advanced. The ECU 40 determines whether or not to update the KCS learning value based on the F/B smoothed value.

In the example of FIG. 2(a), F/B1 is more retarded than F/Bi (-3° CA). If the F/B smoothing value obtained from F/B1 is more retarded than, for example, -4° CA, the ECU 40 retards the KCS learning value from A0 to, for example, A1. The ECU 40 retards the ignition timing using the updated KCS learning value A1.

In the example of FIG. 2(b), F/B2 is more advanced than F/Bi (-3° CA). If the F/B smoothing value obtained from F/B2 is more advanced than, for example, -2° CA, the ECU 40 advances the KCS learning value from A0 to, for example, A2. The ECU 40 advances the ignition timing using the updated KCS learning value A2.

In cylinder-specific knock correction, the ignition timing is controlled according to the frequency of knocking for each cylinder. The frequency of knocking is measured by the ECU 40. For example, if knocking is detected by the knock sensor 26 immediately after ignition in the cylinder 10a, it is assumed that knocking has occurred in the cylinder 10a, and the knocking frequency of the cylinder 10a is added. The ignition timing of the cylinder with a high frequency of knocking is retarded. The ignition timing of the cylinder with a low frequency of knocking is advanced. Table 1 shows an example of the frequency of knocking for each cylinder and the correction value for the cylinder-specific knock correction. The correction value is the amount of advance or retard of the ignition timing.

As shown in Table 1, the knocking frequency of cylinder 10a is n1 and the correction value is k1. The knocking frequency of cylinder 10b is n2 and the correction value is k2. The knocking frequency of cylinder 10c is n3 and the correction value is k3. The knocking frequency of cylinder 10d is n4 and the correction value is k4.

For example, if the knocking frequency n3 of cylinder 10c is a predetermined number of times or more higher than the knocking frequencies of the other cylinders, ECU 40 sets correction value k3 to a value that is more retarded than the other correction values. The predetermined number of times may be one time or more. By adding correction value k3 to the ignition timing Akcs obtained by KCS learning, it is possible to retard the ignition timing of cylinder 10c. When performing cylinder-specific knock correction in the example of FIG. 2A and retarding the ignition timing of cylinder 10c, the ignition timing is calculated, for example, by the following formula.
Akcs=Bkcs-Rmax+A0-F/B1+k3

For example, if the knocking frequency n4 of cylinder 10d is lower than the knocking frequency of the other cylinders, ECU 40 sets correction value k4 to a value that is more advanced than the other correction values. By adding correction value k4 to the ignition timing Akcs obtained by KCS learning, it is possible to advance the ignition timing of cylinder 10d. For example, if the knocking frequencies of two or more cylinders are equal, ECU 40 sets the correction values of the two or more cylinders to be equal. Knocking can be suppressed by the above-described KCS learning and cylinder-specific knock correction.

As shown in FIG. 1, an exhaust purification section 38 is provided in the exhaust passage 30. The filter of the exhaust purification section 38 collects PM. As more PM accumulates in the exhaust purification section 38, the differential pressure increases. For example, if the differential pressure exceeds a predetermined level, the ECU 40 cuts off fuel to regenerate the filter.

Knocking is less likely to occur in cylinders during fuel cut. If KCS learning and cylinder-specific knock correction are performed during fuel cut, the ignition timing may be advanced compared to before fuel cut. For example, if KCS learning is performed during fuel cut, knock judgment is not performed, so the F/B value is advanced and the F/B smoothing value is also advanced. When the KCS learning value is updated, the KCS learning value is advanced. The frequency of knocking does not increase in cylinders during fuel cut. For this reason, the correction value of the cylinder-specific knock correction shown in Table 1 is advanced.

Advancing the ignition timing during a fuel cut can cause knocking to worsen when fuel supply is restored after the fuel cut. If the fuel cut continues for, for example, more than a few minutes or more than 10 minutes, the amount of advance becomes larger, causing knocking to worsen. In this embodiment, the worsening of knocking when fuel supply is restored after a fuel cut is suppressed.

Figure 3 is a flowchart illustrating the process executed by the ECU 40. The ECU 40 determines whether knocking is occurring based on the signal input from the knock sensor 26 and other factors (step S10). If the determination is positive (Yes), the ECU 40 corrects the F/B value to the retard side (step S12). If the determination is negative (No), the ECU 40 corrects the F/B value to the advance side (step S14).

The ECU 40 determines whether or not fuel cut (F/C) is being performed in one cylinder (step S16). If the determination is negative, the ECU 40 smoothes the F/B value to calculate the F/B smoothed value (step S18). If the determination is positive, the ECU 40 initializes the F/B smoothed value to an initial value of -3° CA (step S20).

The ECU 40 determines whether the F/B smoothing value acquired in step S18 or S20 is less than -4° CA (on the retard side) or is greater than -2° CA (on the advance side) (step S22). If the determination is positive, the ECU 40 performs KCS learning and updates the KCS learning value (step S24). If the determination is negative, the ECU 40 stops KCS learning (step S26). By stopping KCS learning, the KCS learning value is not updated.

The ECU 40 determines whether or not fuel cut (F/C) is being performed in one cylinder (step S28). If the determination is negative, the ECU 40 performs individual cylinder knock correction (step S30). If the determination is positive, the ECU 40 stops individual cylinder knock correction (step S32). After step S30 or S32, the process ends.

Figure 4 is a diagram illustrating a time chart. From the top, the following are shown: 1-cylinder F/C flag, KCS learning flag, and individual cylinder knock correction flag. Before time t1 in Figure 4, the 1-cylinder F/C flag is off. The KCS learning flag and individual cylinder knock correction flag are on. For example, when the pressure difference between the upstream and downstream sides of the exhaust purification unit 38 is equal to or greater than a threshold value, the ECU 40 turns on the 1-cylinder F/C flag (time t1 in Figure 4) and performs F/C. In this case, the ECU 40 turns off the KCS learning flag and individual cylinder knock correction flag. KCS learning and individual cylinder knock correction are stopped (steps S26 and S32 in Figure 3).

According to this embodiment, the ECU 40 controls the ignition timing by KCS learning and cylinder-specific knock correction to suppress knocking. The ECU 40 also cuts fuel in one cylinder to regenerate the exhaust purification unit 38. During fuel cut, the ECU 40 stops KCS learning and cylinder-specific knock correction. By suppressing the advance of the ignition timing, it is possible to suppress the worsening of knocking.

As shown in FIG. 2(a) and FIG. 2(b), the ECU 40 performs KCS learning based on the KCS learning value and the F/B value. Since knocking is unlikely to occur in a cylinder during fuel cut, the F/B value is likely to be advanced. When KCS learning is performed, for example, as in the example of FIG. 2(b), the F/B value may become F/B2, and the KCS learning value may be advanced to A2 or the like. According to this embodiment, the advance of the KCS learning value is suppressed by stopping the update of the KCS learning value. During the fuel cut period, the KCS learning value maintains the value before the fuel cut, such as A0. Since the KCS learning value is not advanced, the advance of the ignition timing is suppressed. As a result, the worsening of knocking when returning from fuel cut is suppressed.

The ECU 40 corrects the ignition timing according to the frequency of knocking for each cylinder (cylinder-specific knock correction, Table 1). During fuel cut, the ECU 40 stops cylinder-specific knock correction. The correction value is prevented from advancing during fuel cut. For example, when fuel cut is performed on cylinder 10a, the correction value k1 for cylinder 10a is maintained at the value immediately before the fuel cut began. By preventing the correction value from advancing, the ignition timing is prevented from advancing. The worsening of knocking when returning from fuel cut is prevented.

During fuel cut, the ECU 40 may perform at least one of stopping KCS learning and stopping cylinder-specific knock correction. This can suppress the advance of the ignition timing and prevent the worsening of knocking. By performing both stopping KCS learning and cylinder-specific knock correction as shown in FIG. 3, it is possible to suppress the advance of the ignition timing and prevent the worsening of knocking more effectively.

Even during fuel cut, it is possible to retard and advance the F/B value (steps S12 and S14 in FIG. 3). By retarding the F/B, the ignition timing is retarded and knocking can be suppressed. If knocking is not detected, the F/B value is advanced. The F/B value is updated more quickly than the KCS learning value. By quickly updating the F/B value in response to knocking, the ignition timing is appropriately adjusted. Knocking can be suppressed and a decrease in output due to excessive retardation can also be suppressed.

The ECU 40 obtains the F/B smoothed value by smoothing the F/B value. When fuel cut is performed, the F/B smoothed value is set to a predetermined value (for example, -3° CA). If the F/B smoothed value is -3° CA, a negative determination is made in step S22, and the ECU 40 stops KCS learning and does not update the KCS learning value (step S26 in FIG. 3). This makes it possible to suppress the worsening of knocking.

During fuel cut, the F/B value may be advanced or retarded (steps S12 and S14 in FIG. 3). When the F/B smoothing value is calculated from the F/B value, the F/B smoothing value is also advanced or retarded. After recovery from fuel cut, if the KCS learning value is updated based on the F/B smoothing value, the KCS learning value will change significantly. For example, if the F/B smoothing value is advanced, the KCS learning value will be advanced after KCS learning begins. According to this embodiment, the F/B smoothing value during fuel cut is set to a predetermined value (e.g., -3° CA). After recovery from fuel cut, when KCS learning begins, the F/B smoothing value is, for example, -3° CA. It is possible to suppress erroneous learning of the KCS learning value. It is possible to suppress the advancement of the KCS learning value and suppress the worsening of knocking.

As shown in FIG. 1, the internal combustion engine 10 is provided with fuel injection valves 14a, 14b, 14c, and 14d for direct injection, and fuel injection valves 16a, 16b, 16c, and 16d for port injection. It is sufficient to provide either a fuel injection valve for direct injection or a fuel injection valve for port injection. The ECU 40 cuts fuel to one of the multiple cylinders, but may cut fuel to two or more cylinders. That is, the ECU 40 cuts fuel to at least one cylinder for filter regeneration. The number of cylinders in the internal combustion engine 10 may be four or less, or may be four or more. The number of fuel injection valves is changed according to the number of cylinders.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims.

REFERENCE SIGNS LIST 10 internal combustion engine 10a, 10b, 10c, 10d cylinder 12a, 12b, 12c, 12d spark plug 14a, 14b, 14c, 14d, 16a, 16b, 16c, 16d fuel injection valve 20 intake passage 22 air flow meter 24 throttle valve 30 exhaust passage 32, 34 pressure sensor 36 air-fuel ratio sensor 38 exhaust purification section 40 ECU
100 Engine System

Claims (4)

A fuel control unit that controls the supply of fuel to a plurality of cylinders of the internal combustion engine;
a first ignition timing control unit that controls ignition timing in the plurality of cylinders by learning a KCS (Knock control system);
A second ignition timing control unit that performs knock correction of the ignition timing for each cylinder,
When the fuel control unit stops the supply of fuel to at least one of the plurality of cylinders in order to regenerate an exhaust purification unit provided in an exhaust passage of the internal combustion engine, the first ignition timing control unit at least one of stopping the KCS learning and the second ignition timing control unit at least one of stopping the knock correction for each cylinder ,
a first ignition timing control unit that stops the KCS learning and a second ignition timing control unit that stops knock correction for each cylinder when the fuel control unit stops the supply of fuel to the at least one cylinder . the first ignition timing control unit performs the KCS learning to update the KCS learning value based on a KCS learning value and a feedback value;
2. The control device for an internal combustion engine according to claim 1 , wherein the first ignition timing control unit stops updating the KCS learning value when the fuel control unit stops the supply of fuel to the at least one cylinder. The first ignition timing control unit smoothes the feedback value to obtain a feedback smoothed value, and updates the KCS learning value based on the feedback smoothed value.
When the fuel control unit stops the supply of fuel to the at least one cylinder, the first ignition timing control unit sets the feedback smoothing value to a predetermined value,
3. The control device for an internal combustion engine according to claim 2 , wherein the first ignition timing control unit stops updating the KCS learning value when the feedback smoothing value is equal to the predetermined value. the second ignition timing control unit performs knock correction for each of the cylinders by advancing the ignition timing of a cylinder that has a low frequency of knocking among the plurality of cylinders and retarding the ignition timing of a cylinder that has a high frequency of knocking,
4. The control device for an internal combustion engine according to claim 1, wherein the second ignition timing control unit stops the knock correction for each of the cylinders when the fuel control unit stops the supply of fuel to the at least one cylinder .

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