Control device for internal combustion engines

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

Technical Field

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

Background Art

[0002] Conventionally, an oxygen sensor having a detection unit that is provided so as to be in contact with the exhaust of an internal combustion engine provided with a fuel injection valve and that detects the oxygen concentration in the exhaust is provided, and based on the detection value from the detection unit, the air excess ratio λ is Feedback control is known so as to reach a predetermined target value (see, for example, Patent Document 1).

[0003] In the device of Patent Document 1, a temperature detection unit that detects the temperature of a detection unit having a predetermined temperature characteristic, and based on the detection value and temperature of the detection unit, the detection value is compensated for the temperature characteristic and linearized with respect to the air excess ratio. An excess ratio calculation unit that calculates the air excess ratio λ of the exhaust using the converted data is provided. As the oxygen sensor, a titania-type oxygen sensor, which is a resistance-type oxygen sensor whose resistance value of the detection unit changes according to the oxygen concentration, is used.

[0004] The excess ratio calculation unit includes a data map that associates the temperature and detection value of the detection unit of the oxygen sensor with the air excess ratio λ of the exhaust. Using this data map, linearly converted data is obtained, and when the detection value or the linearly converted data is below a predetermined limit threshold value, the linearly converted data is regarded as the air excess 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 or the like, the air excess ratio obtained based on these resistance values will also be inaccurate, which may hinder the air-fuel ratio feedback control. Therefore, the excess ratio calculation unit includes a calibration unit that checks the characteristics of the detection value that changes according to the variation in the resistance value and calibrates the above-described data map based on the check result.

[0006] In this calibration unit, the target excess air ratio is set to near the stoichiometric value, and the voltage peak value corresponding to the output of the detection unit is obtained. The data map is then calibrated by comparing it with the peak value obtained in a similar manner for a standard sensor element. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-122785 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, this calibration unit performs calibration by comparing the peak value when feedback control is performed with the value of a standard sensor element, with the target air surplus ratio set to near stoichiometric (1.00). Therefore, if the target air surplus ratio is changed from near 1.00, high-precision calibration cannot be performed, and a difference occurs between the target value and the feedback value. In other words, the range in which a target value can be set for accurate variation calibration is narrow.

[0009] In view of the problems of the prior art, the 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 range of setting the target excess air ratio is wider. [Means for solving the problem]

[0010] The control device for an internal combustion engine according to the first invention is: Feedback control is performed by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust of an internal combustion engine increases, so that the oxygen concentration converges to a predetermined target value. A control device for an internal combustion engine that acquires a value based on a representative value that represents the signal value as a learned value for the aforementioned signal value, The characteristic feature is that when the signal value converges to a value that is further away in one direction from the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine by the feedback control, the learned value is obtained to be a value that is further away in the opposite direction from the representative value.

[0011] In this configuration, when performing feedback control, a discrepancy occurs in the detected value relative to the oxygen concentration due to individual differences in the sensor elements used to detect oxygen concentration. To eliminate this discrepancy, the detected value of the sensor element used for feedback control is calibrated so that it matches the detected value when feedback control is performed using a reference sensor element.

[0012] However, the degree of deviation in the detected value varies due to individual differences in the sensor elements, even when the target value of the 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 present invention acquires a value as the learned value of the signal value that is further away in the opposite direction from the representative value of the signal value, as the feedback control converges the signal value to a value that is further away in the direction of the stoichiometric air-fuel ratio of the internal combustion engine.

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

[0014] The control device for an internal combustion engine according to the second invention is: Feedback control is performed by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust of an internal combustion engine increases, so that the oxygen concentration converges to a predetermined target value. A control device for an internal combustion engine that acquires a value based on a representative value that represents the signal value as a learned value for the aforementioned signal value, The greater the target value is compared to the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine, the more the learned value is obtained that is further away from the representative value in the opposite direction to the one direction.

[0015] In this second invention, as in the first invention, the degree of deviation in the detected value fluctuates due to individual differences in the sensor elements when the target value of the feedback control is changed. Therefore, in the second invention, in order to suppress the fluctuation in the degree of deviation due to the change in the target value, the greater the target value is than the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine, the more the learned value of the signal value is obtained that is farther away from the representative value of the signal value in the opposite direction.

[0016] This allows for the acquisition of learned signal values ​​with reduced fluctuations in the degree of deviation of detected values ​​due to changes in the target value. By acquiring these learned values ​​in the reference sensor element and the sensor element to be calibrated, and then calibrating the detected signal values ​​in the sensor element to be calibrated based on these learned values, more accurate calibration can be performed. Therefore, it is possible to provide a control device for an internal combustion engine that can perform highly accurate calibration regardless of the variability of the sensor elements, even when the range of target value settings is wider.

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

[0018] According to this, in the case where the element for detecting the oxygen concentration is a titania type oxygen sensor, a control device for an internal combustion engine can be provided that can perform accurate calibration regardless of variations in the sensor element even when the setting range of the target value is wider.

[0019] In this case, the representative value may be the average value of the lean-side peak values within a predetermined period during the feedback control. According to this, calibration of the sensor element can be performed more accurately, and the accuracy of the feedback control can be improved.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic diagram showing the configuration of the main part of an internal combustion engine provided with a control device according to an embodiment of the present invention. [Figure 2] It is a block diagram showing the main configuration in the ECU of the internal combustion engine of FIG. 1. [Figure 3] It is an explanatory diagram for explaining a method of calibrating the voltage value VHG by the characteristic inspection unit and the calibration unit in the block diagram of FIG. 2. [Figure 4] It is a graph showing a table in which the correction coefficient CF is associated with the target air excess ratio λcmd and stored in the storage unit in the block diagram of FIG. 2. [[ID=z22]] [Figure 5] FIGS. 5A to 5C are explanatory diagrams for explaining a method of obtaining a learning value performed by the excess ratio calculation unit in the block diagram of FIG. 2.

Embodiments for Carrying Out the Invention

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

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

[0023] Inside the exhaust pipe 10 connected to the exhaust port of the engine body 1, a catalyst 11 is provided to reduce unburned components in the exhaust gas from the exhaust pipe 10, and an oxygen sensor 12 is provided to detect the oxygen concentration in the exhaust gas. A spark plug 13 connected to an ignition device 14 is fixed to the engine body 1. When the ECU (electronic control unit) 15 issues a command to the ignition device 14 regarding the ignition timing, a spark discharge occurs in the cylinder combustion chamber of the engine body 1.

[0024] The ECU15 receives analog voltages representing the detected values ​​from the throttle sensor 5, intake pressure sensor 7, intake air temperature sensor 8, oxygen sensor 12, coolant temperature sensor 17, and atmospheric pressure sensor 20, which detects atmospheric pressure. The fuel injector 6 is also connected to the ECU15.

[0025] The ECU 15 also receives a signal from the crank angle sensor 19 indicating the rotational angle position of the crankshaft 18. Specifically, the crank angle sensor 19 magnetically or optically detects multiple protrusions provided at predetermined angle intervals (for example, 15 degrees) on the outer circumference of the rotor 19a, which rotates in conjunction with the crankshaft 18, using a pickup 19b positioned near the outer circumference of the rotor 19a. The pickup 19b generates a pulse (crank signal) for each predetermined angle rotation of the crankshaft 18.

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

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

[0028] The sensor element 12a has a temperature characteristic in which the detected value changes according to the temperature of the sensor element 12a. In this embodiment, the sensor element 12a used is a titania-type sensor element, which is a resistive oxygen sensor whose resistance value changes according to the oxygen concentration.

[0029] The ECU15 includes a heater controller 22 that controls the sensor heater 12b, a temperature calculation unit 23 that calculates a temperature value T indicating 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 indicating the oxygen concentration in the exhaust gas.

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

[0031] Furthermore, the ECU 15 includes a rotational speed calculation unit 27 that calculates the rotational speed NE and angular velocity NETC of the internal combustion engine based on the detection results of the crank angle sensor 19, and an excess ratio calculation unit 25 that calculates the 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 velocity NETC from the rotational speed calculation unit 27.

[0032] Furthermore, the ECU 15 includes a target value calculation unit 28 that calculates a target air excess ratio λcmd based on an estimated value of the amount of stored oxygen in the catalyst 11, 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 finds a feedback coefficient k to correct the basic fuel injection amount BJ calculated by the basic injection amount calculation unit 29 in order to match the air excess ratio λ calculated by the excess ratio calculation unit 25 to the target air excess ratio λcmd, and an injection amount calculation unit 31 that calculates an injection amount Ti based on the feedback coefficient k and the basic injection amount BJ, and also operates the fuel injection valve 6.

[0033] In the feedback coefficient calculation unit 30, PID control is performed based on a comparison between the excess air ratio λ and the target excess air ratio λcmd to calculate the feedback coefficient k. Based on the injection amount Ti calculated by the injection amount calculation unit 31 based on the feedback coefficient k and the basic injection amount BJ, the fuel injection valve 6 is opened for a time corresponding to this, and 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] Incidentally, if the resistance values ​​of the sensor element 12a (detection part) and the sensor heater 12b (heater part) vary due to manufacturing tolerances, the excess air ratio obtained based on these resistance values ​​will also be inaccurate, which may interfere with air-fuel ratio feedback control.

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

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

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

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

[0039] Waveform 37 in Figure 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 ratio λcmd set to 1.00 for the oxygen sensor 12 to be calibrated for the voltage value VHG. The characteristic inspection unit 32 compares the average of the minimum values ​​for the standard waveform 34 with the average of the minimum values ​​for the target waveform 37 to which the voltage value VHG is calibrated.

[0040] Based on this comparison result, 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 of the minimum values ​​of the target waveform 37 matches the voltage value VHG of the average of the minimum values ​​of the standard waveform 34.

[0041] Furthermore, due to the characteristics of the titania-type oxygen sensor 12, the lean-side learned value does not change significantly regardless of individual differences in the oxygen sensor 12. Therefore, in this case, the average of the minimum values ​​is used as the representative value of the voltage value VHG, and calibration is performed so that this matches the average of the minimum values ​​in the standard sensor.

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

[0043] In other words, for the target waveform 35, the scale interval of the vertical axis showing the voltage value VHG in Figure 3 is calibrated so that it is narrowed around the value when the excess air ratio λ is λ1. The narrowing of the scale interval is performed 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 ​​when the excess air ratio λ is λ2 in the standard waveform 34.

[0044] This calibration (reduction of 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 using a standard oxygen sensor.

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

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

[0047] Therefore, in this embodiment, when performing the calibration described using Figure 3 above, even when the target excess air ratio λcmd is changed, a learned value is obtained that has been corrected for the deviation of the average value of the minimum value caused by changing the target excess air ratio λcmd.

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

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

[0050] This multiplication corresponds to obtaining the average of minimum values ​​that are further away in the opposite direction (e.g., in the direction of low voltage) than the representative value (average of minimum values) of the voltage value VHG before multiplying by the correction coefficient CF, as the learned value of the voltage value VHG, the more the voltage value VHG converges to a value that is further away in one direction (e.g., in the direction of high voltage) than the value corresponding to the stoichiometric air-fuel ratio due to feedback control, or the greater 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 learned values ​​(average of the corrected minimum values) of both, and the calibration unit 33 calibrates the voltage value VHG of the oxygen sensor 12 (expands or shrinks the scale value) based on this 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 as described above).

[0052] In this way, by appropriately acquiring learned values ​​(selecting the correction coefficient CF) according to the target air surplus ratio λcmd, the deviation in the voltage value VHG (deviation of the average value of the minimum) caused by the target air surplus ratio λcmd being far from 1.00 is corrected. Based on the learned values ​​obtained through this correction, appropriate calibration of the voltage VHG is performed even when the target air surplus ratio λcmd is far from 1.00, in the same manner as shown in Figure 3 for the case where the target air surplus ratio λcmd is 1.00.

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

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

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

[0056] Figure 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 air excess ratio λcmd is less than the value corresponding to the stoichiometric air-fuel ratio, i.e., 1.00 (for example, λcmd2).

[0057] In this case, the average value MMV of the minimum voltage value VHG obtained will be smaller than the average value MMV of the minimum value obtained when the target air excess ratio 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 ratio λcmd less than 1.00 (for example, λcmd2) is obtained from the table in Figure 4, and is multiplied by the average value MMV of the minimum value in the standard oxygen sensor and the average value MMV of the minimum value of the calibrated oxygen sensor 12 to obtain the learned value RV of both.

[0058] In this case, the correction coefficient CF, which is multiplied by the average value MMV of the minimum values ​​of both, is greater than 1. Therefore, as shown by the arrow in Figure 5B, the learned value RV is obtained by correcting it in the direction that increases the average value MMV of the minimum values ​​of both. That is, since the voltage value VHG is converged by feedback control to a value that is further away from the value corresponding to the stoichiometric air-fuel ratio in the direction of lower voltage, the learned value RV of the voltage value VHG is obtained to be further away from the average value MMV of the minimum values, which is the representative value of the voltage value VHG, in the direction of higher voltage, which is the opposite direction to the one in which the above occurred.

[0059] 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 obtained in this manner.

[0060] Figure 5C 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 air excess ratio λcmd is greater than the value corresponding to the stoichiometric air-fuel ratio, i.e., 1.00 (for example, λcmd1).

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

[0062] In this case, the correction coefficient CF, which is multiplied by the average of the minimum values ​​MMV, is less than 1. As shown by the arrow in Figure 5C, the average of the minimum values ​​is corrected to decrease, and this is used as the learned value RV. That is, because the voltage value VHG converges to a value that is further away from the value corresponding to the stoichiometric air-fuel ratio in the direction of higher voltage due to feedback control, the learned value of the voltage value VHG is a signal value that is further away from the representative value of the voltage value VHG (average of the minimum values ​​MMV) in the direction of lower voltage, which is the opposite direction to the one in which the above occurred.

[0063] In this way, the learned values ​​RV of both 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 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 to a value that is further away in one direction from the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine by feedback control, or the greater the target air-fuel ratio λcmd is than 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 obtained that is further away in the opposite direction from the representative value (average of the minimum values) than the representative value (average of the minimum values). This makes it possible to correct for fluctuations in the degree of deviation of the voltage value VHG due to changes in the target air-fuel ratio λcmd of the feedback control. As a result, it is possible to provide a control device for an internal combustion engine that can perform accurate calibration regardless of the variation in sensor elements, even when the setting range of the target air-fuel ratio λcmd is wider.

[0065] While embodiments of the present invention have been described above, the present invention is not limited thereto. For example, instead of using the average of the rich-side peak values ​​as a representative value of the voltage value VHG, the median or average value of the voltage value VHG may be used. [Explanation of symbols]

[0066] 1...Engine body, 2...Intake pipe, 3...Throttle valve, 4...Air cleaner, 5...Throttle sensor, 6...Fuel injector, 7...Intake pressure sensor, 8...Intake air temperature sensor, 9...Piston, 10...Exhaust pipe, 11...Catalytic converter, 12...Oxygen sensor, 12a...Sensor element, 12b...Sensor heater, 13...Spark plug, 14...Ignition system, 15...ECU (Electronic Control Unit), 17...Coolant temperature sensor, 18...Crankshaft, 19...C 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...Rotation 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...Cut, 37...Memory unit.

Claims

1. Feedback control is performed by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust of an internal combustion engine increases, so that the oxygen concentration converges to a predetermined target value. A control device for an internal combustion engine that acquires a value based on a representative value that represents the signal value as a learned value for the aforementioned signal value, The more the signal value converges in one direction to a value that is further away from the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine by the feedback control, the more the learned value is obtained that is further away in the opposite direction from the representative value. The aforementioned signal value is a voltage value corresponding to the oxygen concentration. The aforementioned one direction is the direction in which the signal value increases. The aforementioned signal value is a value that changes in one direction as the air-fuel ratio of the internal combustion engine becomes leaner. A control device for an internal combustion engine, characterized in that the representative value is a value based on the lean peak value of the oscillating signal value.

2. Feedback control is performed by feeding back a signal value that changes in one direction as the oxygen concentration in the exhaust of an internal combustion engine increases, so that the oxygen concentration converges to a predetermined target value. A control device for an internal combustion engine that acquires a value based on a representative value that represents the signal value as a learned value for the aforementioned signal value, The greater the target value is than the value corresponding to the stoichiometric air-fuel ratio of the internal combustion engine, the more the learned value will be a value that is further away from the representative value in the opposite direction to the one direction. The aforementioned signal value is a voltage value corresponding to the oxygen concentration. The aforementioned one direction is the direction in which the signal value increases. The aforementioned signal value is a value that changes in one direction as the air-fuel ratio of the internal combustion engine becomes leaner. A control device for an internal combustion engine, characterized in that the representative value is a value based on the lean peak value of the oscillating signal value.

3. (delete)

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

Images