Control device for internal combustion engine

Abstract

To provide an internal combustion engine control device capable of curbing aggravation of knocking.SOLUTION: An internal combustion engine control device comprises an air-fuel ratio control section which controls an air-fuel ratio of an internal combustion engine and an ignition timing control section which controls an ignition timing of the internal combustion engine through knock control system (KCS) learning. The ignition timing control section performs the KCS learning to update a KCS learning value on the basis of the KCS learning value and a feedback value and sets an upper limit on an advance angle side for the feedback value and stops updating of the KCS learning value when the air-fuel ratio control section makes an air-fuel ratio of the internal combustion engine leaner than a theoretical air-fuel ratio for regenerating an exhaust purification section arranged in an exhaust passage of the internal combustion engine.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] An exhaust passage of an internal combustion engine is provided with an exhaust purification section such as a filter to purify exhaust gas. The filter collects particulate matter (PM). The filter can be regenerated by removing PM through oxidation. For example, a technique is known in which the air-fuel ratio of the internal combustion engine is made lean to send more oxygen to the filter and remove PM (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-106687 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to suppress knocking in an internal combustion engine, the ignition timing may be retarded. On the other hand, when the air-fuel ratio becomes lean, the combustion pressure in the internal combustion engine decreases, making knocking less likely to occur. Therefore, the ignition timing is likely to be advanced during lean air-fuel ratio control. There is a risk that knocking will worsen after lean air-fuel ratio control ends. Therefore, an object of the present invention is to provide a control device for an internal combustion engine that can suppress the worsening of knocking. [Means for solving the problem]

[0005] The above object is to provide an internal combustion engine having an air-fuel ratio control unit that controls an air-fuel ratio of an internal combustion engine, and an ignition timing control unit that controls ignition timing of the internal combustion engine by KCS (Knock control system) learning, wherein the ignition timing control unit performs KCS learning to update the KCS learning value based on a KCS learning value and a feedback value, and when the air-fuel ratio control unit makes the air-fuel ratio of the internal combustion engine leaner than the stoichiometric air-fuel ratio in order to regenerate an exhaust purification unit provided in an exhaust passage of the internal combustion engine, the ignition timing control unit sets an upper limit on the advance side of the feedback value and stops updating the KCS learning value. The ignition timing control unit obtains a feedback smoothed value by smoothing the feedback value, and when the air-fuel ratio control unit sets the air-fuel ratio to lean, the ignition timing control unit sets the feedback smoothed value to a predetermined value and stops updating the KCS learning value, and when the air-fuel ratio returns from lean, the ignition timing control unit updates the KCS learning value using the feedback smoothed value set to the predetermined value. This can be achieved by a control device for the internal combustion engine.

[0006] The upper limit of the feedback value may be −3° CA (Crank Angle).

[0008] The internal combustion engine may have a plurality of cylinders, the ignition timing control unit may control the ignition timing in the plurality of cylinders by the KCS learning, the air-fuel ratio control unit may make the air-fuel ratios of the plurality of cylinders lean, and when the air-fuel ratio control unit makes the air-fuel ratios of the plurality of cylinders leaner than the stoichiometric air-fuel ratio, the ignition timing control unit may set an upper limit on the advance side of the feedback value and stop updating of the KCS learning values ​​for the plurality of cylinders. Effect of the Invention

[0009] It is possible to provide a control device for an internal combustion engine that is capable of suppressing the worsening of knocking. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an engine system. [Diagram 2] 2(a) and 2(b) are schematic diagrams illustrating the ignition timing. [Diagram 3] FIG. 3 is a flowchart illustrating a process executed by the ECU. [Figure 4] FIG. 4 is a diagram illustrating an example of a time chart. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The control device for an internal combustion engine according to the present 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.

[0012] The internal combustion engine 10 is, for example, a gasoline engine fueled by gasoline, 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 a sensor that detects vibrations and detects knocking of the internal combustion engine 10.

[0013] 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 this 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.

[0014] The intake passage 20 branches into four passages 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. Fuel injection valves 16a, 16b, 16c, and 16d are provided in the four branched intake passages 20. 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.

[0015] 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. An air-fuel ratio sensor 36, a pressure sensor 32, an exhaust purification unit 38, and a pressure sensor 34 are provided in the exhaust passage 30 in this order from the upstream side. The air-fuel ratio sensor 36 detects the air-fuel ratio.

[0016] The exhaust purification unit 38 includes, for example, a GPF (Gasoline Particle Filter) and a catalyst. The GPF is, for example, a honeycomb 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 the like in the exhaust.

[0017] 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.

[0018] 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.

[0019] The ECU 40 controls the opening degree of the throttle valve 24. The ECU 40 obtains the air flow rate from the air flow meter 22, the air-fuel ratio from the air-fuel ratio sensor 36, the pressure upstream of the exhaust purification section 38 from the pressure sensor 32, and the pressure downstream of the exhaust purification section 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 section 38.

[0020] The ECU 40 detects knocking by acquiring a signal output by the knock sensor 26. For example, the ECU 40 acquires the frequency of knocking for each cylinder based on the combustion timing and the knocking timing for each cylinder.

[0021] The ECU 40 controls the supply of fuel from each of the fuel injection valves 14a to 14d, and controls the supply of fuel from each of the fuel injection valves 16a to 16d. The ECU 40 functions as an air-fuel ratio control unit that controls the air-fuel ratio of the internal combustion engine 10 by adjusting the amount of fuel injection. The ECU 40 can make the air-fuel ratio leaner than the stoichiometric air-fuel ratio (lean control) by reducing the amount of fuel injection compared to the stoichiometric air-fuel ratio. By making the air-fuel ratio lean, exhaust gas containing more oxygen than when fuel is supplied is discharged. By allowing more oxygen to flow to the exhaust purification unit 38, PM is oxidized and removed.

[0022] 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 is performed based on KCS (Knock control system) learning. 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 ECU 40 functions as an ignition timing control unit that controls the ignition timing of all four cylinders 10a to 10d based on KCS learning. By controlling the ignition timing, knocking can be suppressed.

[0023] Figures 2(a) and 2(b) are schematic diagrams illustrating ignition timing, showing an example of ignition timing determination by KCS learning. The upper side in the figure 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) is an example where the F / B value is F / B1. Figure 2(b) is an example where the F / B value is F / B2.

[0024] Bkcs is the base ignition timing, which is determined, for example, by the operating range (rotation speed, load, etc.) of the internal combustion engine 10, the timing and amount of fuel injection, the amount of EGR, etc. Rmax is the most retarded ignition timing, which is determined, for example, by the vehicle type, etc. 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.

[0025] F / B0 is the limit of the F / B value on the advance side, 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.

[0026] 2(a) is an example of an F / B value, which 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

[0027] The F / B value F / B2 in Fig. 2(b) is more advanced than the F / B1 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. 2(a).

[0028] The KCS learning is performed for all four cylinders 10a, 10b, 10c, and 10d, i.e., the ignition timings of the four cylinders 10a, 10b, 10c, and 10d become the required ignition timings Akcs.

[0029] When the knock sensor 26 detects knocking, the ECU 40 retards the required ignition timing Akcs by setting the F / B value to a more retarded side than F / Bi, such as F / B1 in Fig. 2(a).When knocking is not detected, the ECU 40 advances the required ignition timing Akcs by setting the F / B value to a more advanced side than F / Bi, such as F / B2 in Fig. 2(b).

[0030] 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.

[0031] 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 A1. The ECU 40 retards the ignition timing using the updated KCS learning value A1.

[0032] 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 -2° CA, for example, the ECU 40 advances the KCS learning value from A0 to A2. The ECU 40 advances the ignition timing using the updated KCS learning value A2.

[0033] As shown in Fig. 1, an exhaust purification section 38 is provided in the exhaust passage 30. A filter in the exhaust purification section 38 collects PM. As the amount of PM that accumulates in the exhaust purification section 38 increases, the pressure difference increases. For example, when the pressure difference becomes equal to or exceeds a predetermined value, the ECU 40 regenerates the filter by making the air-fuel ratio leaner than the stoichiometric air-fuel ratio.

[0034] During lean control, the combustion pressure in the internal combustion engine 10 decreases, so knocking is unlikely to occur. When KCS learning is performed during lean control and the KCS learning value is updated, the KCS learning value is advanced. If the ignition timing is advanced during lean control, knocking may worsen when returning from lean control to fuel supply. If the lean control continues for, for example, several minutes or more, or 10 minutes or more, the advance amount becomes large, and knocking becomes even worse. In this embodiment, the worsening of knocking when returning from lean control is suppressed.

[0035] 3 is a flowchart illustrating a process executed by the ECU 40. The ECU 40 determines whether or not knocking is occurring based on a signal input from the knock sensor 26 and the like (step S10). If the determination is affirmative (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).

[0036] After step S14, the ECU 40 determines whether or not lean control is in progress (step S16). If the determination is affirmative, the ECU 40 sets an upper limit on the advance side for the F / B value (step S18). The upper limit is, for example, -3° CA. The F / B value is guarded at -3° CA and is more retarded than -3° CA.

[0037] After a negative determination in step S16, step S12, or step S18, the ECU 40 performs step S20. The ECU 40 determines whether or not lean control is in progress (step S20). If the determination is negative, the ECU 40 smoothes the F / B value to calculate an F / B smoothed value (step S22). If the determination is positive, the ECU 40 initializes the F / B smoothed value to an initial value of -3° CA (step S24).

[0038] The ECU 40 determines whether the F / B smoothed value acquired in step S22 or S24 is less than -4° CA (on the retard side) or whether the F / B smoothed value is greater than -2° CA (on the advance side) (step S26). If the determination is positive, the ECU 40 performs KCS learning (step S28). If the determination is negative, the ECU 40 stops KCS learning (step S30). The KCS learning value is not updated. After step S28 or S30, the process ends.

[0039] FIG. 4 is a diagram illustrating a time chart. From the top, the lean control flag and the KCS learning flag are shown. Before time t1 in FIG. 4, the lean control flag is off. The KCS learning flag is on. For example, when the pressure difference between the upstream side and the downstream side of the exhaust purification unit 38 is equal to or greater than a threshold value, the ECU 40 turns on the lean control flag (time t1 in FIG. 4) and makes the air-fuel ratio lean. In this case, the ECU 40 turns off the KCS learning flag. KCS learning is stopped (step S30 in FIG. 3).

[0040] According to this embodiment, the ECU 40 controls the ignition timing by KCS learning in order to suppress knocking. Furthermore, the ECU 40 makes the air-fuel ratio leaner than the theoretical air-fuel ratio in order to regenerate the exhaust purification unit 38. During lean control, the ECU 40 sets an upper limit on the advance side for the F / B value (step S18 in FIG. 3). The F / B value is guarded by the upper limit and becomes a value on the retard side of the upper limit. Furthermore, the ECU 40 stops KCS learning and does not update the KCS learning value (step S30).

[0041] By stopping the update of the KCS learning value during lean control, the KCS learning value maintains the value before lean control, such as A0. Because the KCS learning value is not advanced, the advance of the ignition timing is suppressed. This suppresses the worsening of knocking when returning from lean control.

[0042] Even during lean control, the F / B value may be advanced or retarded (steps S12 and S14 in FIG. 3). By setting an upper limit for the F / B value, the F / B value becomes more retarded than the upper limit. The upper limit for the F / B value is, for example, -3° CA. The F / B value is guarded by an upper limit, and becomes more retarded than -3° CA, for example, F / B1 in FIG. 2(a). This suppresses the advancement of the ignition timing. On the other hand, the retardation of the F / B value is permitted. This makes it possible to suppress worsening of knocking.

[0043] The upper limit of the F / B value is, for example, -3° CA and is equal to the initial value F / Bi. The upper limit may be a value other than -3° CA and may be different from the initial value F / Bi. The F / B value may be retarded, for example, by -0.5° CA or more, -1° CA or more, -2° CA or more, or -3° CA or more compared to the upper limit.

[0044] The ECU 40 obtains an F / B smoothed value by smoothing the F / B value. When performing lean control, 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 S26 of FIG. 3. The ECU 40 stops the KCS learning (step S30). This makes it possible to suppress the worsening of knocking.

[0045] During lean control, the F / B value may be advanced or retarded. When the F / B smoothed value is calculated from the F / B value, the F / B smoothed value is also advanced or retarded. After returning from lean control, if the KCS learning value is updated based on the F / B smoothed value, the KCS learning value will change significantly. For example, if the F / B smoothed value is advanced, the KCS learning value will be advanced after the start of KCS learning. According to this embodiment, the F / B smoothed value during lean control is set to a predetermined value (e.g., -3° CA). After returning from lean control, the F / B smoothed value is, for example, -3° CA at the start of KCS learning. It is possible to suppress erroneous learning of the KCS learning value. It is possible to suppress the advance of the KCS learning value and suppress the worsening of knocking.

[0046] The internal combustion engine 10 has four cylinders 10a, 10b, 10c, and 10d. The ECU 40 controls the ignition timing of all cylinders by KCS learning. The ECU 40 makes the air-fuel ratio in all cylinders leaner than the theoretical air-fuel ratio. By supplying exhaust gas containing a large amount of oxygen to the exhaust purification unit 38, PM can be oxidized and removed. During lean control, the ECU 40 stops KCS learning for all cylinders. By suppressing the advance of the ignition timing in the four cylinders, it is possible to suppress the worsening of knocking. 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.

[0047] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0048] 10 Internal combustion engine 10a, 10b, 10c, 10d cylinders 12a, 12b, 12c, 12d Spark plugs 14a, 14b, 14c, 14d, 16a, 16b, 16c, 16d Fuel injector 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

1. an air-fuel ratio control unit for controlling an air-fuel ratio of the internal combustion engine; an ignition timing control unit that controls the ignition timing of the internal combustion engine by learning a KCS (Knock control system), the ignition timing control unit performs the KCS learning to update the KCS learning value based on a KCS learning value and a feedback value, when the air-fuel ratio control unit makes the air-fuel ratio of the internal combustion engine leaner than a stoichiometric air-fuel ratio in order to regenerate an exhaust purification unit provided in an exhaust passage of the internal combustion engine, the ignition timing control unit sets an upper limit on the advance side of the feedback value and stops updating the KCS learning value; the ignition timing control unit obtains a feedback smoothed value by smoothing the feedback value, When the air-fuel ratio control unit sets the air-fuel ratio to be lean, the ignition timing control unit sets the feedback smoothing value to a predetermined value, and the ignition timing control unit stops updating the KCS learning value, A control device for an internal combustion engine, wherein, when the air-fuel ratio returns from lean, the ignition timing control unit updates the KCS learning value using the feedback smoothing value set to the predetermined value.

2. 2. The control device for an internal combustion engine according to claim 1, wherein the upper limit of the feedback value is −3° CA (Crank Angle).

3. The internal combustion engine has a plurality of cylinders, the ignition timing control unit controls ignition timing in the plurality of cylinders through the KCS learning, the air-fuel ratio control unit sets the air-fuel ratio of the plurality of cylinders to a lean value, 3. The control device for an internal combustion engine according to claim 1, wherein, when the air-fuel ratio control unit makes the air-fuel ratios of the plurality of cylinders leaner than the stoichiometric air-fuel ratio, the ignition timing control unit sets an upper limit on the advance side of the feedback value and stops updating the KCS learning values ​​for the plurality of cylinders.

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