Control device for internal combustion engine

Abstract

The present invention provides a control device for an internal combustion engine, the control device being capable of performing calibration with high accuracy regardless of a variation in a sensor element, even when a setting range of a target air excess rate is wider. As the value to which a voltage value VHG converges through feedback control becomes farther in one direction (for example, in a high voltage direction) from a value corresponding to the theoretical air fuel ratio, or as a target air excess rate λcmd is higher than a value corresponding to the theoretical air fuel ratio of the internal combustion engine, a control device (15) acquires, as a learning value of the voltage value VHG, the average value of the minimum value away in a direction opposite to the one direction (for example, in a low voltage direction) from the representative value (the average value of the minimum value) of the voltage value VHG before multiplication by a correction factor CF. Calibration of the voltage value VHG is performed on the basis of the acquired learning value.

Description

Control device for internal combustion engine

[0001] The present invention relates to a control device for an internal combustion engine that feedback controls the oxygen concentration in the exhaust gas of the internal combustion engine based on a signal value that changes in accordance with the oxygen concentration.

[0002] Conventionally, there has been known a control device for an internal combustion engine that includes an oxygen sensor having a detection unit that is provided so as to come into contact with the exhaust gas of an internal combustion engine that is equipped with a fuel injection valve and that detects the oxygen concentration in the exhaust gas, and that performs feedback control based on the detection value from the detection unit so that the excess air ratio λ becomes a predetermined target value (see, for example, Patent Document 1).

[0003] The device of Patent Document 1 includes a temperature detection unit that detects the temperature of a detection unit having predetermined temperature characteristics, and an excess air ratio calculation unit that calculates the exhaust excess air ratio λ using data obtained by linearizing the detection value with respect to the excess air ratio while compensating for the temperature characteristic, based on the detection value and the temperature of the detection unit.The oxygen sensor used is a titania-type oxygen sensor, which is a resistance-type oxygen sensor in which the resistance value of the detection unit changes depending on the oxygen concentration.

[0004] The excess ratio calculation unit has a data map that associates the temperature and detection value of the detection unit of the oxygen sensor with the excess air ratio λ of the exhaust, and uses this data map to obtain linearized converted data.When the detection value or the linearized converted data is equal to or less than a predetermined limit threshold, the linearized converted data is regarded as the excess air ratio λ of the exhaust.

[0005] However, if the resistance values ​​of the sensor element (detection unit) and the sensor heater vary due to manufacturing tolerances, etc., the excess air ratio obtained based on these resistance values ​​will also be inaccurate, which may cause problems in air-fuel ratio feedback control. Therefore, the excess air ratio calculation unit includes a calibration unit that checks the characteristics of the detection value that change in accordance with the above-mentioned variation in resistance values ​​and calibrates the above-mentioned data map based on the inspection results.

[0006] In this calibration section, the target air excess ratio is set close to stoichiometric, and the voltage peak value corresponding to the output of the detection section is obtained, and the data map is calibrated by comparing it with the peak value obtained in a similar manner for a standard sensor element.

[0007] Japanese Patent Application Laid-Open No. 2022-122785

[0008] However, since the calibration by this calibration unit is performed by comparing the peak value when feedback control is performed with the target air excess ratio set to near stoichiometric (1.00) with that of a standard sensor element, when the target air excess ratio is changed from near 1.00, highly accurate calibration cannot be performed, and a discrepancy occurs between the target value and the feedback value. In other words, the setting range of the target value in which variation can be calibrated with high accuracy is narrow.

[0009] In view of the problems with the prior art, an object of the present invention is to provide a control device for an internal combustion engine that can perform accurate calibration regardless of variations in sensor elements even when the target excess air ratio setting range is wider.

[0010] The control device for an internal combustion engine according to the first aspect of the present invention is a control device for an internal combustion engine that performs feedback control by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust gas of the internal combustion engine increases, so that the oxygen concentration converges to a predetermined target value, and acquires a value based on a representative value that represents the signal value as a learned value for the signal value, characterized in that the more the signal value converges by the feedback control to a value that is farther away in the one direction than a value corresponding to the theoretical air-fuel ratio of the internal combustion engine, the more the learned value that is acquired is a value that is farther away in the opposite direction from the representative value.

[0011] In this configuration, when detecting the feedback signal value during feedback control, deviations in the detected value for the oxygen concentration occur due to individual differences in the sensor element that detects the oxygen concentration. To eliminate these deviations, the detected value of the sensor element used for feedback control is calibrated so that the detected value of the sensor element used for feedback control matches the detected value when feedback control is performed using a reference sensor element.

[0012] However, the degree of deviation of the detected value varies due to individual differences in the sensor element, even when the target value of the feedback control is changed. Therefore, in the present invention, in order to suppress the variation of the degree of deviation due to the change of the target value, the more the signal value converges to a value that is farther away in one direction than the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine through feedback control, the more the learned value of the signal value is obtained that is farther away in the opposite direction from the representative value of the signal value.

[0013] This allows for the acquisition of learned values ​​for the signal values ​​in which the degree of deviation of the detected values ​​due to changes in the target value is suppressed, and the learned values ​​can be acquired for the reference sensor element and the sensor element to be calibrated, and more accurate calibration of the detected values ​​of the signal values ​​for the sensor element to be calibrated can be performed based on the learned values. Therefore, it is possible to provide a control device for an internal combustion engine that can perform accurate calibration regardless of variations in the sensor elements, even when the setting range of the target value is wider.

[0014] A control device for an internal combustion engine according to a second aspect of the present invention is a control device for an internal combustion engine that performs feedback control by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust gas of the internal combustion engine increases, so that the oxygen concentration converges to a predetermined target value, and that acquires a value based on a representative value that represents the signal value as a learned value for the signal value, and is characterized in that the larger the target value is than a value corresponding to the theoretical air-fuel ratio of the internal combustion engine, the more the learned value that is acquired is a value that deviates from the representative value in the direction opposite to the one direction.

[0015] In the second aspect of the invention, as in the first aspect, the degree of deviation of the detected value varies due to individual differences in the sensor element when the target value of feedback control is changed. Therefore, in order to suppress the variation in the degree of deviation due to the change in the target value, the second aspect of the invention acquires a value that deviates in the opposite direction from the representative value of the signal value as the target value is larger than the stoichiometric air-fuel ratio of the internal combustion engine.

[0016] Therefore, since a learned value of the signal value is obtained in which the degree of deviation of the detected value due to a change in the target value is suppressed, the learned values ​​are acquired for the reference sensor element and the sensor element to be calibrated, and the detected value of the signal value of the sensor element to be calibrated is calibrated based on the learned values, thereby enabling more accurate calibration. Therefore, it is possible to provide a control device for an internal combustion engine that can perform accurate calibration regardless of the variation of the sensor elements, even when the setting range of the target value is wider.

[0017] In the first and second aspects of the present invention, the signal value may be a voltage value corresponding to the oxygen concentration, the one direction may be a direction in which the signal value increases, the signal value may be a value that changes in the one direction as the air-fuel ratio of the internal combustion engine becomes leaner, and the representative value may be a value based on a peak value on the lean side of the oscillating signal value.

[0018] This makes it possible to provide a control device for an internal combustion engine that can perform accurate calibration regardless of variations in the sensor element, even when the element that detects the oxygen concentration is a titania-type oxygen sensor and the setting range of the target value is wider.

[0019] In this case, the representative value may be an average value of the lean-side peak values ​​within a predetermined period during the feedback control, which allows for more accurate calibration of the sensor element and improves the accuracy of the feedback control.

[0020] 1 is a schematic diagram showing the configuration of a main part of an internal combustion engine equipped with a control device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the main configuration of an ECU of the internal combustion engine of FIG. 1. FIG. 3 is an explanatory diagram for explaining a method for calibrating a voltage value VHG by a characteristic inspection unit and a calibration unit in the block diagram of FIG. 2. FIG. 4 is a graph showing a table stored in a memory unit in the block diagram of FIG. 2, which correlates a correction coefficient CF with a target air excess factor λcmd. FIG. 5A to FIG. 5C are explanatory diagrams for explaining a method for acquiring a learned value performed in an excess factor calculation unit in the block diagram of FIG. 2.

[0021] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 shows the configuration of the main parts of a four-stroke internal combustion engine equipped with an internal combustion engine control device according to an embodiment of the present invention. As shown in the figure, an engine body 1 of this internal combustion engine includes an intake pipe 2 provided in an intake port, and a throttle valve 3 provided in the intake pipe 2 for adjusting the amount of intake air supplied to the intake port from an air cleaner 4 in accordance with the opening degree of the throttle valve 3.

[0022] The throttle valve 3 is provided with a throttle sensor 5 that detects the opening degree of the throttle valve 3. A fuel injection valve 6 that injects fuel is provided near the intake port of the intake pipe 2. Fuel is pressure-fed to the fuel injection valve 6 from a fuel tank (not shown) by a fuel pump. The intake pipe 2 is provided with an intake pressure sensor 7 that detects the intake pressure in the intake pipe 2 and an intake air temperature sensor 8 that detects the temperature of the intake air in the intake pipe 2.

[0023] An exhaust pipe 10 connected to an exhaust port of the engine body 1 is provided in the exhaust pipe 10 with a catalyst 11 for reducing unburned components in the exhaust gas in the exhaust pipe 10 and an oxygen sensor 12 for detecting the oxygen concentration in the exhaust gas. An ignition plug 13 connected to an ignition device 14 is fixed to the engine body 1. An ECU (electronic control unit) 15 issues an ignition timing command to the ignition device 14, which causes a spark discharge to occur in the cylinder combustion chamber of the engine body 1.

[0024] Analog voltages indicating the detected values ​​of the throttle sensor 5, intake air pressure sensor 7, intake air temperature sensor 8, oxygen sensor 12, coolant temperature sensor 17, and atmospheric pressure sensor 20 are input to the ECU 15. The fuel injection valve 6 is also connected to the ECU 15.

[0025] The ECU 15 also receives a signal indicating the rotational angle position of the crankshaft 18 from a crank angle sensor 19. That is, the crank angle sensor 19 magnetically or optically detects a plurality of protrusions provided at predetermined angular intervals (for example, 15 degrees) on the outer periphery of a rotor 19a, which rotates in conjunction with the crankshaft 18, using a pickup 19b disposed near the outer periphery of the rotor 19a, and generates a pulse (crank signal) from the pickup 19b every time the crankshaft 18 rotates by the predetermined angle.

[0026] Specifically, the crank angle sensor 19 outputs a signal indicating a reference angle to the ECU 15 every time the piston 9 reaches top dead center or every time the crankshaft 18 rotates 360 degrees.

[0027] 2 shows the main components of the ECU 15. As shown in the figure, the oxygen sensor 12, which supplies the ECU 15 with a detection signal indicating the oxygen concentration in the exhaust gas, includes a sensor element 12a that is provided in contact with the exhaust gas from the internal combustion engine and serves as a detector for detecting the oxygen concentration in the exhaust gas, and a sensor heater 12b that is adjacent to the sensor element 12a and heats the sensor element 12a.

[0028] The sensor element 12a has a temperature characteristic in which the detection value changes depending on the temperature of the sensor element 12a. In this embodiment, a titania-type sensor element, which is a resistance-type oxygen sensor whose resistance value changes depending on the oxygen concentration, is used as the sensor element 12a.

[0029] The ECU 15 includes a heater controller 22 that controls the sensor heater 12b, a temperature calculation unit 23 that calculates a temperature value T that indicates the temperature of the sensor element 12a, and a voltage calculation unit 24 that converts the output signal of the sensor element 12a into a voltage value VHG that indicates the oxygen concentration in the exhaust gas.

[0030] The heater controller 22 controls the temperature of the sensor heater 12b by controlling the amount of current I supplied to the sensor heater 12b from a power supply (storage battery) (not shown) using pulse width modulation (PWM) control by the ECU 15. The temperature calculation unit 23 calculates the temperature value T by reading the resistance value of the sensor heater 12b with the ECU 15, for example.

[0031] The ECU 15 also includes a rotational speed calculation unit 27 that calculates the rotational speed NE and angular speed NETC of the internal combustion engine based on the detection results of the crank angle sensor 19, and an excess air ratio calculation unit 25 that calculates an excess air ratio λ based on the temperature value T from the temperature calculation unit 23, the voltage value VHG from the voltage calculation unit 24, and the angular speed NETC from the rotational speed calculation unit 27.

[0032] Furthermore, the ECU 15 includes a target value calculation unit 28 that calculates a target excess air ratio λcmd based on an estimated value of the amount of oxygen stored in the catalyst 11, etc.; a basic injection amount calculation unit 29 that calculates a basic injection amount BJ based on the rotational speed NE from the rotational speed calculation unit 27 and the pressure PM in the intake pipe 2 from the intake pressure sensor 7; a feedback coefficient calculation unit 30 that determines a feedback coefficient k for correcting the basic fuel injection amount BJ calculated by the basic injection amount calculation unit 29 so that the excess air ratio λ calculated by the excess ratio calculation unit 25 matches the target excess air ratio λcmd; and an injection amount calculation unit 31 that calculates the injection amount Ti based on the feedback coefficient k and the basic injection amount BJ and operates the fuel injection valve 6.

[0033] In the feedback coefficient calculation section 30, PID control is performed based on a comparison between the excess air ratio λ and the target excess air ratio λcmd, and a feedback coefficient k is calculated. Based on the injection amount Ti calculated by the injection amount calculation section 31 based on the feedback coefficient k and the basic injection amount BJ, the fuel injector 6 is opened for a time corresponding to this, and thus an amount of fuel corresponding to the feedback coefficient k of the PID control based on the comparison between the excess air ratio λ and the target excess air ratio λcmd is injected into the cylinder combustion chamber of the engine body 1.

[0034] However, if the resistance values ​​of the sensor element 12a (detection portion) and the sensor heater 12b (heater portion) vary due to manufacturing tolerances or the like, the excess air ratio obtained based on these resistance values ​​will also become inaccurate, which may cause problems with air-fuel ratio feedback control.

[0035] Therefore, the excess air ratio calculation unit 25 includes a characteristic inspection unit 32 that inspects the characteristics of the voltage value VHG (detected value) that changes in accordance with the variation in the resistance value, and a calibration unit 33 that calibrates the voltage value VHG for obtaining the excess air ratio based on the inspection results.

[0036] Fig. 3 shows a method for calibrating the voltage value VHG by the characteristic checking unit 32 and the calibration unit 33. The vertical axis in Fig. 3 is a scale showing the value of the voltage value VHG. Waveform 34 in Fig. 3 is an example of a standard waveform that schematically shows the change over time of the voltage value (detected value) VHG obtained in a predetermined short period of time while driving a vehicle equipped with a standard oxygen sensor having a standard resistance value in its internal combustion engine with the target excess air ratio λcmd set to 1.00.

[0037] Because the exhaust gas in the exhaust pipe and the oxygen concentration contained in the exhaust gas are pulsating, the standard waveform 34 oscillates around a voltage value VHG corresponding to an air excess ratio λ of 1.00, as shown in Figure 3. Therefore, the standard waveform 34 has alternating peaks 35 on the lean side and peaks 36 on the rich side that transition over time.

[0038] In this example, the average value (average value of maximum values) of the lean-side peak values, which are the voltage values ​​VHG at each peak 35 on the lean side of the standard waveform 34, over a predetermined time interval corresponds to an air excess factor λ of approximately λ1. Also, the average value (hereinafter referred to as the "average value of minimum values") of the rich-side peak values, which are the voltage values ​​VHG at each peak 36 on the rich side of the standard waveform 34, over the predetermined time interval corresponds to approximately the voltage value VHG when the air excess factor λ is λ2. However, the above-mentioned λ1 and λ2 satisfy the relationship λ1 > 1.00 > λ2.

[0039] 3 shows an example of the waveform of the voltage value VHG obtained in the same manner as the standard oxygen sensor, with the target air excess factor λcmd set to 1.00 for the oxygen sensor 12 whose voltage value VHG is to be calibrated. The characteristic inspection unit 32 compares the average value of the minimum values ​​for the standard waveform 34 with the average value of the minimum values ​​for the target waveform 37 whose voltage value VHG is to be calibrated.

[0040] Based on the result of this comparison, the calibration unit 33 calibrates the voltage value VHG from the oxygen sensor 12 to be calibrated so that the voltage value VHG of the average value of the minimum values ​​of the target waveform 37 matches the voltage value VHG of the average value of the minimum values ​​of the standard waveform 34.

[0041] Due to the characteristics of the titania-type oxygen sensor 12, the lean-side learned value does not change significantly regardless of individual differences between oxygen sensors 12. Therefore, here, the average of the minimum values ​​is taken as the representative value of the voltage value VHG, and calibration is performed so that this corresponds to the average of the minimum values ​​of the standard sensor.

[0042] 3, the average value of the minimum values ​​of the target waveform 37 is greater than the average value of the minimum values ​​corresponding to the air excess factor λ of λ2 in the standard waveform 34. Therefore, the voltage value VHG of the target waveform 37 is calibrated so that the average value of the minimum values ​​of the target waveform 37 corresponds to the average value of the minimum values ​​of the standard waveform 34 when the air excess factor λ is λ2.

[0043] That is, for the target waveform 35, the scale interval of the vertical axis indicating the value of the voltage value VHG in Fig. 3 is calibrated so as to be reduced from the value when the air excess factor λ is λ1 as the center. The scale interval is reduced so that the scale value of the average of the minimum values ​​for the target waveform 37 matches the scale value of the average of the minimum values ​​for the standard waveform 34 when the air excess factor λ is λ2.

[0044] This calibration (reducing the scale interval) causes the voltage value VHG of the target waveform 37 to match the voltage value VHG of the standard waveform 34, so that feedback control can be performed using the oxygen sensor 12 with the same accuracy as when a standard oxygen sensor is used.

[0045] On the other hand, there are cases where it is desired to change the target excess air ratio λcmd in feedback control to some extent from the value corresponding to the theoretical air-fuel ratio (=1.00) depending on the operating conditions of the internal combustion engine. In such cases, the calibration of the voltage value VHG by the characteristic checking unit 32 and the calibration unit 33 based on the inspection results cannot be applied as is.

[0046] The reason is that when feedback control is performed by changing the target excess air factor λcmd, the average value of the minimum value for the standard oxygen sensor also changes, causing a deviation in the voltage value VHG corresponding to the excess air factor λ of λ2. Note that even when the target excess air factor λcmd is changed, the average value of the maximum value on the lean side does not change significantly within the change range of λ1 to λ2, regardless of individual differences between oxygen sensors.

[0047] Therefore, in this embodiment, when the calibration described above with reference to FIG. 3 is performed also when the target air excess factor λcmd is changed, a learned value is acquired in which the deviation of the average value of the minimum value that occurs when the target air excess factor λcmd is changed is corrected as a prerequisite.

[0048] 4 is a graph showing a table in which the correction coefficient CF (vertical axis) by which the average of the minimum values ​​is multiplied to obtain such a learned value is associated with the target air excess ratio λcmd (horizontal axis). This table is stored in the storage unit 37 of the excess ratio calculation unit 25.

[0049] In order to obtain a learned value according to the target excess air ratio λcmd, the excess ratio calculation unit 25 obtains a correction coefficient CF corresponding to the set value of the target excess air ratio λcmd based on the table of FIG. 4, and multiplies the average value of the minimum values ​​of the voltage value VHG obtained using the standard oxygen sensor and the average value of the minimum values ​​obtained by the oxygen sensor 12 by the correction coefficient CF.

[0050] This multiplication corresponds to obtaining, as the learned value of the voltage value VHG, the average value of the minimum values ​​that are farther away in one direction (e.g., toward low voltage) from the representative value (average value of the minimum values) of the voltage value VHG before multiplication by the correction coefficient CF, the more the voltage value VHG converges to a value that is farther away in one direction (e.g., toward high voltage) from the value corresponding to the stoichiometric air-fuel ratio through feedback control, or the larger the target excess air ratio λcmd is than the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine.

[0051] The characteristic inspection unit 32 compares the two learned values ​​(average values ​​of the minimum values ​​after correction), and the calibration unit 33 calibrates (expands or reduces the scale value) the voltage value VHG of the oxygen sensor 12 based on the comparison result so that the learned value of the oxygen sensor 12 to be calibrated matches the learned value of the standard oxygen sensor (for example, the value corresponding to λ2 described above).

[0052] In this way, by appropriately acquiring a learned value (selecting the correction coefficient CF) in accordance with the target air excess factor λcmd, the deviation of the voltage value VHG (deviation from the average of the minimum values) caused by the target air excess factor λcmd being different from 1.00 is corrected, and based on the learned value obtained by this correction, the voltage VHG is appropriately calibrated even when the target air excess factor λcmd is different from 1.00, in the same way as shown in FIG. 3 for the case where the target air excess factor λcmd is 1.00.

[0053] 5A to 5C show an example of correction for the deviation of the average value of this minimum value. Fig. 5A shows the change over time of the voltage value VHG obtained by feedback control using a standard oxygen sensor or a calibrated oxygen sensor 12 when the target excess air ratio λcmd is a value corresponding to the stoichiometric air-fuel ratio, i.e., 1.00.

[0054] In this case, since the target excess air factor λcmd is 1.00, the corresponding correction coefficient CF (=1) is obtained from the table of FIG. 4, and the correction coefficient CF is multiplied by the average minimum value MMV for the standard oxygen sensor and the average minimum value MMV for the oxygen sensor 12 to be calibrated to obtain the respective learned values ​​RV, and calibration is performed based on these learned values ​​RV.

[0055] In this case, the correction coefficient CF is 1, so there is no change in the average value MMV of the two minimum values. Therefore, using the method described above with reference to Figure 3, the voltage value VHG of the oxygen sensor 12 is calibrated so that the learned value RV of the oxygen sensor 12 matches the learned value RV of the standard oxygen sensor when the target excess air factor λcmd is 1.00 (for example, the value corresponding to λ2 described above).

[0056] FIG. 5B shows the time variation of the voltage value VHG obtained by feedback control using a standard oxygen sensor or a calibrated oxygen sensor 12 when the set value of the target excess air ratio λcmd is a value corresponding to the stoichiometric air-fuel ratio, i.e., smaller than 1.00 (for example, λcmd2).

[0057] In this case, the average value MMV of the minimum values ​​of the obtained voltage value VHG will be smaller than the average value MMV of the minimum values ​​obtained when the target air excess factor λcmd is 1.00 (for example, the value corresponding to λ=λcmd2). In this case, a correction coefficient CF (CF>1) corresponding to a target air excess factor λcmd smaller than 1.00 (for example, λcmd2) is obtained from the table of FIG. 4, and multiplied by the average value MMV of the minimum values ​​of the standard oxygen sensor and the average value MMV of the minimum values ​​of the oxygen sensor 12 to be calibrated, thereby obtaining both learned values ​​RV.

[0058] In this case, because the correction coefficient CF by which the average value MMV of both minimum values ​​is multiplied is greater than 1, the average value MMV of both minimum values ​​is corrected in the direction in which it increases, as indicated by the arrow in Fig. 5B, to obtain the learned value RV. In other words, because the voltage value VHG has converged by feedback control to a value that is away in the lower voltage direction from the value corresponding to the stoichiometric air-fuel ratio, a value that is away in the higher voltage direction, that is, in the opposite direction from the average value MMV of the minimum values, which is a representative value of the voltage value VHG, is obtained as the learned value RV of the voltage value VHG.

[0059] The voltage value VHG of the oxygen sensor 12 is calibrated so that the learned value RV of the oxygen sensor 12 to be calibrated coincides with the learned value RV of the standard oxygen sensor thus obtained.

[0060] FIG. 5C shows the change over time in the voltage value VHG obtained by feedback control using a standard oxygen sensor or a calibrated oxygen sensor 12 when the set value of the target excess air ratio λcmd is greater than a value corresponding to the stoichiometric air-fuel ratio, i.e., 1.00 (for example, λcmd1).

[0061] In this case, the average value of the minimum values ​​of the obtained voltage value VHG will be a value (for example, a value corresponding to λ=1.00) greater than the average value of the minimum values ​​obtained when the target excess air factor λcmd is 1.00 (for example, a value corresponding to λ=λ2). In this case, a correction coefficient CF (CF<1) corresponding to a target excess air factor λcmd greater than 1.00 (for example, λcmd1) is obtained from the table of Fig. 4, and the correction coefficient CF is multiplied by the average minimum value MMV of the standard oxygen sensor and the average minimum value MMV of the oxygen sensor 12 to be calibrated, to obtain both learned values ​​RV.

[0062] In this case, because the correction coefficient CF multiplied by the average value MMV of both minimum values ​​is smaller than 1, the average value of the minimum values ​​is corrected to decrease as the learned value RV, as indicated by the arrow in Fig. 5C. In other words, because the voltage value VHG has converged to a value that is away in the high-voltage direction from the value corresponding to the stoichiometric air-fuel ratio through feedback control, a signal value that is away in the low-voltage direction, which is the opposite direction from the representative value of the voltage value VHG (average value MMV of the minimum values), is acquired as the learned value of the voltage value VHG.

[0063] In this way, both learned values ​​RV are obtained, and the voltage value VHG of the oxygen sensor 12 is calibrated so that the learned value RV of the oxygen sensor 12 to be calibrated matches the learned value RV of the standard oxygen sensor.

[0064] As described above, according to this embodiment, the more the voltage value VHG converges, through feedback control, to a value that is more distant in one direction from a value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine, or the larger the target air excess factor λcmd is from the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine, the more the learned value of the voltage value VHG is acquired that is more distant in the opposite direction from the representative value (average of the minimum values), making it possible to correct fluctuations in the degree of deviation of the voltage value VHG due to changes in the target air excess factor λcmd of the feedback control.This makes it possible to provide a control device for an internal combustion engine that can perform accurate calibration even when the setting range of the target air excess factor λcmd is wider, regardless of variations in the sensor element.

[0065] Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, instead of using the average value of the rich-side peak values ​​as the representative value of the voltage value VHG, the median or average value of the voltage value VHG may be used.

[0066] 1...engine body, 2...intake pipe, 3...throttle valve, 4...air cleaner, 5...throttle sensor, 6...fuel injection valve, 7...intake pressure sensor, 8...intake temperature sensor, 9...piston, 10...exhaust pipe, 11...catalyst, 12...oxygen sensor, 12a...sensor element, 12b...sensor heater, 13...spark plug, 14...ignition device, 15...ECU (electronic control unit), 17...cooling water temperature sensor, 18...crankshaft, 19...crank Rank angle sensor, 19a...rotor, 19b...pickup, 20...atmospheric pressure sensor, 22...heater controller, 23...temperature calculation unit, 24...voltage calculation unit, 25...excess rate calculation unit, 27...rotational speed calculation unit, 28...target value calculation unit, 29...basic injection amount calculation unit, 30...feedback coefficient calculation unit, 31...injection amount calculation unit, 32...characteristic inspection unit, 33...calibration unit, 34...standard waveform, 35, 36...peak, 37...memory unit.

Claims

1. A control device for an internal combustion engine that performs feedback control so that an oxygen concentration in exhaust gas of the internal combustion engine converges to a predetermined target value by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust gas of the internal combustion engine increases, and as a learning value regarding the signal value, acquires a value based on a representative value representing the signal value, the control device for an internal combustion engine, wherein when the signal value converges to a value further away from the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine in the one direction by the feedback control, as the learning value, a value further away from the representative value in the direction opposite to the one direction is acquired, the signal value is a voltage value corresponding to the oxygen concentration, the one direction is a direction in which the signal value increases, the signal value is a value that changes in the one direction as the air-fuel ratio of the internal combustion engine becomes leaner, the representative value is a value based on a lean-side peak value of the oscillating signal value, characterized by the control device for an internal combustion engine.

2. A control device for an internal combustion engine that performs feedback control so that an oxygen concentration in exhaust gas of the internal combustion engine converges to a predetermined target value by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust gas of the internal combustion engine increases, and as a learning value regarding the signal value, acquires a value based on a representative value representing the signal value, the control device for an internal combustion engine, wherein the larger the target value is than the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine, as the learning value, a value further away from the representative value in the direction opposite to the one direction is acquired, the signal value is a voltage value corresponding to the oxygen concentration, the one direction is a direction in which the signal value increases, the signal value is a value that changes in the one direction as the air-fuel ratio of the internal combustion engine becomes leaner, the representative value is a value based on a lean-side peak value of the oscillating signal value, characterized by the control device for an internal combustion engine.

3. (Deleted)

4. The representative value is an average value of the lean-side peak values within a predetermined period during the feedback control, characterized by the control device for an internal combustion engine according to claim 1 or 2.