WO2023181292A1 - Dispositif de commande de rapport air-carburant - Google Patents

Dispositif de commande de rapport air-carburant Download PDF

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Publication number
WO2023181292A1
WO2023181292A1 PCT/JP2022/014124 JP2022014124W WO2023181292A1 WO 2023181292 A1 WO2023181292 A1 WO 2023181292A1 JP 2022014124 W JP2022014124 W JP 2022014124W WO 2023181292 A1 WO2023181292 A1 WO 2023181292A1
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unit
value
control
temperature
section
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PCT/JP2022/014124
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English (en)
Japanese (ja)
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勝明 和知
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日立Astemo株式会社
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Priority to PCT/JP2022/014124 priority Critical patent/WO2023181292A1/fr
Publication of WO2023181292A1 publication Critical patent/WO2023181292A1/fr

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D45/00—Electrical control not provided for in groups F02D41/00 - F02D43/00

Definitions

  • the present invention relates to an air-fuel ratio control device that includes a resistance-type oxygen sensor that is provided in contact with the exhaust gas of an internal combustion engine that has exhaust pulsation.
  • Patent Document 1 it has been known to perform air-fuel ratio feedback control in the internal combustion process of an internal combustion engine based on the air-fuel ratio obtained from the output information of an oxygen sensor provided in contact with the exhaust gas of the internal combustion engine (for example, Patent Document 1 reference).
  • a resistance-type oxygen sensor that detects oxygen based on the internal resistance of a detection part is used as an oxygen sensor.
  • a first value indicating the oxygen content in the exhaust gas is determined based on the resistance of the detection section of the oxygen sensor.
  • a second value indicating the temperature of the oxygen sensor is determined based on the resistance of the heater portion of the oxygen sensor. The air-fuel ratio as a function of the first value and the second value is then determined as a third value.
  • the function for determining the third value includes a second value that affects the first value in real time, so even if the output characteristics change due to the temperature of the oxygen sensor, The air-fuel ratio is calculated based on the detected resistance value of the detection section of the oxygen sensor.
  • an object of the present invention is to appropriately compensate for the temperature characteristics of a resistance-type oxygen sensor, including the differences in characteristics between individual sensors, thereby achieving high robustness.
  • An object of the present invention is to provide an air-fuel ratio control device that can realize air-fuel ratio feedback control using a resistance-type oxygen sensor.
  • the air-fuel ratio control device of the present invention includes: An air-fuel ratio control device for an internal combustion engine, comprising a resistance-type oxygen sensor having a detection section provided in contact with exhaust gas of an internal combustion engine having exhaust pulsation, and a heater section adjacent to the detection section, a target value setting unit that sets a control target value related to an excess air ratio based on the operating state of the internal combustion engine; a detection unit temperature estimation unit that calculates the temperature of the detection unit based on the resistance value of the heater unit; a detected value reading unit that reads a resistance value of the detection unit to obtain a detection value of the detection unit; an excess rate calculation unit that calculates the excess air rate from the detected value and the temperature of the detection unit; A PD/PID that calculates a deviation between the excess air ratio and the control target value, and performs feedback control of the excess air ratio using the deviation and the derivative of the deviation, or the deviation, the integral of the deviation, and the derivative of the deviation as elements.
  • control unit a control unit; a PI control unit that performs feedback control of the excess air ratio using a deviation between the excess air ratio and the control target value and an integral of the deviation as elements; a control unit selection unit that selects which of the PI control unit or the PD/PID control unit to use for the feedback control; a characteristic checking unit that checks whether the detected value and the temperature of the detection unit correspond to each predetermined characteristic; a calibration unit that calibrates the detection unit temperature estimation unit and the detected value reading unit, respectively, based on the inspection;
  • the control section selection section is configured to be able to perform alternative selection of the PD/PID control section or the PI control section according to the detection value in the characteristic inspection section and the inspection result of the temperature of the detection section. It is characterized by being configured.
  • the characteristic checking section checks whether the detected value of the detecting section and the temperature of the detecting section correspond to each predetermined characteristic, and based on this, the detecting section temperature estimating section and the detected value reading section are connected to the calibration section.
  • the PD/PID control section or the PI control section is selected by the control section selection section according to the inspection result.
  • the reliability of the excess air ratio ⁇ calculated by the excess air ratio calculation unit is not guaranteed, so feedback from the PD/PID unit using this excess air ratio as a trigger is applied. Can not do it.
  • the characteristics of resistance-type oxygen sensors vary depending on the individual resistance-type oxygen sensors, and since there are large individual differences, the progress state of calibration also differs each time.
  • the characteristic inspection section checks whether the detection value of the detection section and the temperature of the detection section correspond to each predetermined characteristic, and based on this inspection, the control section selection section selects the PD/PID.
  • the control unit or the PI control unit is alternatively selected.
  • control section selection section grasps the progress of calibration for each resistance-type oxygen sensor, and determines that the calibration has progressed sufficiently to the extent that the control followability expected for PID or PD control can be achieved. If it is determined, the PD/PID control section can be selected to perform feedback control of the excess air ratio by PD/PID control. On the other hand, if it is determined that such a state does not exist, the PI control section can be selected to perform feedback control of the excess air ratio by PI control.
  • the calibration unit is configured to perform a lean air-fuel ratio range for determining whether the peak value of the wave height of the detected value due to exhaust pulsation of the internal combustion engine corresponds to which air-fuel ratio region of a rich region, a stoichiometric region, or a lean region.
  • the characteristic inspection unit may determine the progress state of the calibration by comparing the peak value with at least one of the lean-side threshold value and the rich-side threshold value.
  • the data map is calibrated based on the comparison between the data map and the peak value described above, and the progress state of the calibration is checked by comparing the peak value with at least one side of the lean side threshold or the rich side threshold. It will be judged. Therefore, by referring to the progress state of this calibration as the inspection result in the characteristic inspection section, the control section selection section can control the PD/PID control section or the PI control By appropriately selecting the air-fuel ratio feedback control, it is possible to ensure appropriate implementation of air-fuel ratio feedback control and suppress deterioration of emission performance.
  • a calibration reset unit configured to be able to issue an initialization command to initialize the correspondence in the data map
  • the control unit selection unit may be configured to select the PI control unit for a predetermined period after receiving a reset command from the calibration reset unit.
  • PI control when a reset command is received from the calibration reset section, feedback control by PI control is performed at least for a predetermined period, so that the characteristic inspection section performs an inspection during that time. , and is configured to appropriately determine the progress state of the calibration while steadily progressing recalibration by the calibration unit according to the result, and to appropriately select the PD/PID control unit or the PI control unit. can do. For example, if a failure is actually detected and confirmed in the detection part or heater part of an oxygen sensor, the repair work involves replacing the oxygen sensor body with a normal one and also issuing a reset command from the calibration reset part.
  • the calibration parameters stored in the air-fuel ratio control device are reset, but even if the characteristics of the replaced resistance-type oxygen sensor are large due to individual differences, the PI control section cannot be selected. Therefore, air-fuel ratio feedback control can be performed without any problem and deterioration of emission performance can be suppressed.
  • the on-board diagnostic section is configured to be able to diagnose abnormality or failure of the detection section or the heater section of the resistance-type oxygen sensor
  • the control section selection section is arranged in the on-board diagnostic section.
  • the sensor may be configured to select the PI control unit when it is determined that the detection unit or the heater unit of the resistance-type oxygen sensor is abnormal.
  • the detection section or heater section of the resistance type oxygen sensor is abnormal, even temporarily, it becomes difficult for the PD/PID control section to perform appropriate feedback control; however, in such a case, the PI control section Since this is selected, air-fuel ratio feedback control can be continued without any problem and deterioration of emission performance can be suppressed.
  • the calibration unit is configured to temporarily suspend control related to calibration when the on-board diagnosis unit determines that the detection unit or the heater unit of the resistance-type oxygen sensor is abnormal. may be done.
  • the control section selection section selects the control section of the calibration section.
  • the calibration control unit may be configured to restart control related to calibration and select the PI control unit in a predetermined period after the restart.
  • the PI control Since air-fuel ratio feedback is performed, the calibration section steadily progresses in calibrating the data map, and the progress of this calibration is appropriately determined, thereby determining the selection of the PD/PID control section or the PI control section. The deterioration of emission performance can be suppressed by making appropriate selections.
  • FIG. 1 is a schematic diagram schematically showing the configuration of main parts of an internal combustion engine including an air-fuel ratio control device according to an embodiment of the present invention.
  • 2 is a block diagram showing the main configuration of an ECU of the internal combustion engine of FIG. 1.
  • FIG. 3 is a flowchart showing an excess rate calculation process in which an excess air rate is calculated by an excess rate calculation unit in the ECU of FIG. 2.
  • FIG. 4 is a graph showing how the excess air ratio in the stoichiometric region is calculated in the process of FIG. 3.
  • 4 is a diagram showing a graph corresponding to a lookup table for calculating a lean side threshold value LREF and a rich side threshold value RREF, and a data map for calculating an excess air ratio in the process of FIG. 3.
  • FIG. 3 is a schematic diagram schematically showing the configuration of main parts of an internal combustion engine including an air-fuel ratio control device according to an embodiment of the present invention.
  • FIG. 3 is a flowchart showing an excess rate calculation
  • FIG. 4 is a graph schematically showing how the excess air ratio ⁇ calculated by the process of FIG. 3 changes;
  • FIG. 3 is a waveform diagram showing a voltage waveform representing a change in a voltage value output by a voltage calculation unit over time obtained while driving a vehicle equipped with an internal combustion engine.
  • 3 is a diagram showing an example of an inspection by a characteristic inspection section and calibration by a calibration section in the ECU of FIG. 2.
  • FIG. It is a figure which shows the other example of the inspection by the said characteristic inspection part and calibration by a calibration part.
  • It is a figure which shows another example of the inspection by the said characteristic inspection part and calibration by a calibration part.
  • It is a figure which shows yet another example of the inspection by the said characteristic inspection part and calibration by a calibration part.
  • 3 is a block diagram showing the configuration of a feedback coefficient calculating section in the ECU of FIG. 2.
  • FIG. 3 is a diagram showing an example of an alternative temperature Tsub obtained by an alternative temperature preparation section in the ECU of
  • FIG. 1 shows the configuration of the main parts of a four-stroke internal combustion engine equipped with an air-fuel ratio control device according to an embodiment of the present invention.
  • This air-fuel ratio control device has a function of performing air-fuel ratio feedback control based on the deviation between the excess air ratio obtained based on the oxygen concentration in the exhaust gas of the internal combustion engine and the target excess air ratio.
  • an engine body 1 of this internal combustion engine has an intake pipe 2 provided at an intake port, and an air cleaner 4 provided in the intake pipe 2 that controls the amount of intake air supplied to the intake port. and a throttle valve 3 that is adjusted according to the
  • 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 for injecting fuel is provided near the intake port of the intake pipe 2. Fuel is fed under pressure 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 temperature sensor 8 that detects the temperature of the intake air in the intake pipe 2.
  • an exhaust pipe 10 connected to an exhaust port of the engine body 1, a catalyst 11 for reducing unburned components in the exhaust gas from the exhaust pipe 10 and an oxygen sensor 12 for detecting the oxygen concentration in the exhaust gas are provided.
  • a spark plug 13 connected to an ignition device 14 is fixed to the engine body 1.
  • the ECU (electronic control unit) 15 issues an ignition timing command to the ignition device 14, spark discharge occurs within the cylinder combustion chamber of the engine body 1.
  • Analog voltages indicating respective detection values of the throttle sensor 5, intake pressure sensor 7, intake temperature sensor 8, oxygen sensor 12, cooling water temperature sensor 17, and atmospheric pressure sensor 20 that detects atmospheric pressure are input to the ECU 15. .
  • the above-mentioned fuel injection valve 6 is connected to the ECU 15.
  • a signal indicating the rotational angular position of the crankshaft 18 from the crank angle sensor 19 is further input to the ECU 15. That is, the crank angle sensor 19 includes a plurality of convex portions provided at predetermined angle intervals (for example, 15 degrees) on the outer circumference of the rotor 19a that rotates in conjunction with the crankshaft 18, and arranged near the outer circumference of the rotor 19a.
  • the pickup 19b detects it magnetically or optically, and the pickup 19b generates a pulse (crank signal) every time the crankshaft 18 rotates by a predetermined angle.
  • crank angle sensor 19 outputs a signal indicating the reference angle to the ECU 15 every time the piston 9 reaches the top dead center or every time the crankshaft 18 rotates 360 degrees.
  • FIG. 2 shows the main configuration of the ECU 15.
  • an oxygen sensor 12 that supplies a detection signal of the oxygen concentration in the exhaust gas to the ECU 15 is a detection unit that is provided in contact with the exhaust gas of an internal combustion engine that has exhaust pulsation and detects the oxygen concentration in the exhaust gas.
  • the sensor element 12a is provided with a sensor element 12a as a sensor element 12a, and a sensor heater 12b as a heater part that is adjacent to the sensor element 12a and heats the sensor element 12a.
  • the sensor element 12a has a resistance value that changes substantially stepwise when the exhaust gas of the internal combustion engine has an oxygen concentration near the stoichiometric value, and the detected value obtained from the resistance value is determined by the temperature of the sensor element 12a and the exhaust pulsation. It exhibits a pulse waveform with a peak value corresponding to the wave height.
  • a titania oxygen sensor which is a resistance type oxygen sensor whose resistance value changes depending on the oxygen concentration, is used.
  • the ECU 15 includes a heater controller 22 that controls the sensor heater 12b, a temperature calculation section 23 as a detection section temperature estimation section that calculates a temperature value T indicating the temperature of the sensor element 12a, and an output signal of the sensor element 12a, which is connected to the exhaust gas.
  • a voltage calculation unit 24 is provided as a detection value reading unit that converts into a voltage value VHG as a detection value indicating the oxygen concentration in the air.
  • the temperature of the sensor heater 12b is controlled by the heater controller 22 by performing pulse width modulation (PWM) control by the ECU 15 on the amount of current I supplied to the sensor heater 12b from an unillustrated power source (storage battery). Further, the temperature value T is calculated by the temperature calculation unit 23 by, for example, reading each value of the heater voltage and the current amount I applied to the sensor heater 12b with the ECU 15 to determine the resistance value of the sensor heater 12b, and calculating the resistance value of the sensor heater 12b. This is done by converting using table data or a calculation formula prepared in advance in the ECU 15 that indicates the correspondence between the heater resistance value and the temperature value T. The calculation results from the temperature calculation section 23 and the voltage calculation section 24 are supplied to an alternative value calculation section 26 of the excess rate calculation section 25, which will be described later.
  • PWM pulse width modulation
  • the ECU 15 also 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 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 a It includes an excess air ratio calculation section 25 that calculates an excess air ratio ⁇ based on the voltage value VHG and the angular velocity NETC from the rotational speed calculation section 27.
  • the ECU 15 includes a target value calculation unit 28 as a target value setting unit that calculates an excess air ratio ⁇ cmd as a control target value based on an estimated value of the amount of oxygen stored in the catalyst 11 and the operating state of the internal combustion engine, and a rotation speed
  • the basic injection amount calculation section 29 calculates the basic injection amount BJ based on the rotational speed NE from the calculation section 27 and the pressure PM in the intake pipe 2 from the intake pressure sensor 7, and the excess rate calculation section 25 calculates the basic injection amount BJ.
  • a feedback coefficient calculation section 30 that calculates a feedback coefficient k for correcting the basic fuel injection amount BJ calculated by the basic injection amount calculation section 29 in order to make the excess air ratio ⁇ match the target excess air ratio ⁇ cmd; It includes an injection amount calculation unit 31 that calculates the injection amount Ti based on the basic injection amount BJ and operates the fuel injection valve 6.
  • the calculation is performed based on the deviation P between the excess air ratio ⁇ and the target excess air ratio ⁇ cmd and the derivative D of the deviation, or the deviation P, the integral I of the deviation, and the derivative D of the deviation.
  • PD/PID control based on the excess air ratio ⁇ and the target excess air ratio ⁇ cmd, or PI control executed based on the deviation P between the excess air ratio ⁇ and the target excess air ratio ⁇ cmd and the integral I of the deviation is selectively performed and feedback is performed as described later.
  • a coefficient k is calculated. Based on the injection amount Ti calculated by the injection amount calculating section 31 based on the feedback coefficient k and the basic injection amount BJ, the fuel injection valve 6 is opened for a corresponding time. Thus, an amount of fuel is injected into the cylinder combustion chamber of the engine body 1 in an amount corresponding to the feedback coefficient k based on the comparison between the excess air ratio ⁇ and the target excess air ratio ⁇ cmd.
  • the excess ratio calculation unit 25 linearizes the voltage value VHG with respect to the excess air ratio while compensating for its temperature characteristics.
  • the excess air ratio ⁇ of the exhaust gas is calculated using the data LD obtained. However, as will be described later, this calculation is applied when the voltage value VHG is less than or equal to the lean side threshold value LREF, and when the voltage value VHG is larger than the lean side threshold value LREF, the excess air ratio ⁇ is determined by another method.
  • the excess rate calculation unit 25 includes a torque calculation unit 32 that calculates the torque value TQ of the internal combustion engine based on the crank angular speed NETC of the internal combustion engine, and a limit threshold setting unit 33 that sets a conversion limit threshold for the above-mentioned linearization conversion. , a storage unit 34 that stores data necessary for calculating an alternative value R for the excess air ratio ⁇ , a data map and a look-up table to be described later, and an alternative value calculation unit 26 that calculates the alternative value R.
  • the limit threshold value setting unit 33 sets a lean side threshold value LREF, which is a conversion limit threshold value on the lean side, and a rich side threshold value RREF, which is a conversion limit threshold value on the rich side, as conversion limit threshold values, with respect to the voltage value VHG from the voltage calculation unit 24.
  • LREF lean side threshold value
  • RREF rich side threshold value
  • T conversion limit threshold
  • FIG. 5 shows the first scale value G1 in the horizontal direction in FIG. 5 corresponding to the temperature value T calculated by the temperature calculation unit 23, and the voltage value VHG calculated by the voltage calculation unit A data map is posted that has a second scale value G2 in the vertical direction in FIG. Furthermore, examples of look-up tables corresponding to graphs 35 and 36 for determining the lean-side threshold LREF and the rich-side threshold RREF are shown superimposed on the data map.
  • the data map associates a plurality of excess air ratio values with a plurality of first scale values G1 for the temperature value T and a plurality of second scale values G2 for the voltage value VHG (detected value). This is what is shown.
  • the lookup table shows the correspondence between the rich side threshold value RREF and the lean side threshold value LREF for determining whether the voltage value VHG corresponds to a rich area, a stoichiometric area, or a lean air-fuel ratio area with the first scale value G1. It shows the relationship.
  • Graph 35 shows, for example, when the excess air ratio ⁇ as the boundary between the lean region and the stoichiometric region is 1.02, and the points on the data map whose coordinates are the voltage value VHG and temperature value T that have this value are plotted. This is a graph obtained by finding multiple points and connecting these multiple points by line interpolation. Further, the graph 36 shows, for example, that the excess air ratio ⁇ as the boundary between the stoichiometric region and the rich region is 0.98, and the voltage value VHG and temperature value T corresponding to this value are set as coordinates on the data map. This is a graph obtained by finding points and connecting each of these points by line interpolation.
  • the limit threshold setting unit 33 determines that the voltage value v0 derived from the coordinate t0 is in the lean region and the stoichiometric range. It can be set as the lean-side threshold LREF for the boundary with the region.
  • the voltage value v1 derived from the coordinate t0 is It can be set as a rich-side threshold RREF.
  • the storage unit 34 also stores, as data necessary for calculating the alternative value R, the execution time Ti1 of the fuel injection by the fuel injection valve 6, the torque value TQ1, the excess air ratio ⁇ b regarding the conversion limit threshold LREF is stored.
  • the excess rate calculation unit 25 calculates a substitute value R for the exhaust air in place of the excess air rate ⁇ as the linearized data LD. Regarded as excess rate ⁇ .
  • FIG. 3 shows an excess rate (lambda) calculation process in which the excess air rate ⁇ is calculated by the excess rate calculation unit 25. Note that the control by the ECU 15 including this excess rate calculation process is executed in synchronization with the stroke of the internal combustion engine based on a pulse signal from the crank angle sensor 19 indicating the rotational angular position of the crankshaft 18.
  • step S1 the torque calculation section 32 calculates the torque TQ (DCBCP) of the internal combustion engine based on the crank angular speed NETC from the rotational speed calculation section 27.
  • step S2 when the disconnection state of the sensor heater 12b is not detected when reading the resistance of the sensor heater 12b, in step S2, the limit threshold setting unit 33 Accordingly, the lean side threshold LREF and the rich side threshold RREF are respectively set using the first and second lookup tables (VHGLREF_N, VHGRREF_N) corresponding to the graphs 35 and 36 in FIG.
  • step S3 a voltage value VHG is acquired from the voltage calculation unit 24, and the voltage value VHG is corrected by a deviation VD obtained by a voltage difference confirmation unit 43, which will be described later, to obtain a control voltage value (detected value).
  • a voltage difference confirmation unit 43 which will be described later, to obtain a control voltage value (detected value).
  • step S4 the above-mentioned data map (FIG. 5) is scanned based on the temperature value T obtained in step S2 and the voltage value VHGcon obtained in step S3.
  • Data LD is obtained which has been linearized into excess air ratio ⁇ while being compensated.
  • step S5 it is determined whether the voltage value VHGcon acquired in step S3 is smaller than the rich-side threshold value RREF set in step S2. If it is determined that it is small, the flag F_DETECT is set to zero in the subsequent step S6, and the process proceeds to step S16, where the value of the data LD is set as the excess air ratio ⁇ value LAMBDA, and the excess ratio calculation process of FIG. 3 is ended. do.
  • step S7 the voltage value VHGcon acquired in step S3 is greater than the lean threshold LREF set in step S2. Determine whether or not.
  • step S7 when it is determined that the voltage value VHGcon is not large, in step S8, the voltage value lref of the lean side threshold LREF, the voltage value rref of the rich side threshold RREF, and the voltage value lref acquired in step S2 are determined.
  • the excess air ratio ⁇ is calculated as data LD obtained by linearizing the excess air ratio while compensating for the temperature characteristics of 12, and the process proceeds to step S9.
  • the excess air ratio ⁇ as the linearized data LD in step S8 is set in advance by numerically setting the excess air ratio ⁇ as the boundary between the predetermined stoichiometric region and the lean region.
  • a variable #LLMD (for example, 1.02) that can set If there is, it can be represented by a graph as shown in FIG. In this graph, the horizontal axis in the horizontal direction in FIG. 4 is the voltage value VHG, and the vertical axis in the vertical direction in FIG. 4 is the excess air ratio ⁇ . Therefore, for example, when the voltage value VHG is vhg1, the corresponding value ⁇ 1 of the excess air ratio ⁇ can be calculated using the following equation (2).
  • ⁇ 1 (((vhg1-rref) ⁇ (lref-rref)) ⁇ (#LLMD-#RLMD))+#RLMD (2)
  • step S9 the execution time Ti of the immediately preceding fuel injection by the fuel injection valve 6 and the torque TQ calculated in step S1 are respectively set as Ti1 and TQ1, and the excess air ratio ⁇ regarding the lean side threshold value LREF is stored as ⁇ b in the storage unit 34. .
  • the countdown timer value TIMER indicating the valid time of the memory is reset to its predetermined initial value #TMINT.
  • the flag F_DETECT is set to 1, and the process proceeds to step S16, where the value of the data LD acquired in step S8 is set as the excess air ratio ⁇ value LAMBDA, and the excess ratio calculation process of FIG. 3 is ended.
  • the value of the data LD acquired in step S8 is stored as ⁇ b.
  • the exponential moving average ⁇ a of the excess air ratio ⁇ (data LD) obtained by the following equation (3) is stored as ⁇ b.
  • ⁇ a LD ⁇ k1+ ⁇ ab ⁇ (1-k1) (3)
  • k1 is a moving average coefficient
  • ⁇ ab is a moving average value in the previous control cycle stored in the storage unit 34.
  • 0.34 is used as the moving average coefficient k1.
  • the storage unit 34 stores moving average values as the fuel injection execution time Ti1 and the torque value TQ1, respectively.
  • the exponential moving average TiFLT of the fuel injection execution time Ti is calculated using the following equation (4) and stored as Ti1
  • the exponential moving average TQFLT of the torque value TQ is calculated using the following equation (5) and stored as Ti1. is stored as.
  • TiFLT Ti ⁇ k2+TiFLTb ⁇ (1-k2)
  • TQFLT TQ ⁇ k3+TQFLTb ⁇ (1-k3) (5)
  • k2 and k3 are moving average coefficients
  • TiFLTb and TQFLTb are moving average values in the previous control cycle stored in the storage unit 34.
  • different values can be used as the moving average coefficients k1, k2, and k3.
  • step S7 if it is determined that the voltage value VHGcon acquired in step S3 is larger than the lean side threshold value LREF, in step S10, it is determined whether the above-mentioned countdown timer value TIMER has reached zero. judge. If TIMER has reached zero, the flag F_DETECT is reset to 0 (step S11).
  • step S14 it is determined whether the value of the data LD set in step S13 is larger than a predetermined upper limit value #LLMT. If the value of data LD set in step S13 is larger than upper limit value #LLMT, the value of data LD is set to upper limit value #LLMT (step S15). In this case, for example, 1.25 can be used as the upper limit value #LLMT.
  • step S12 the storage unit 34 does not store valid values regarding the excess air ratio ⁇ b, the fuel injection execution time Ti1, and the torque value TQ1 regarding the lean side threshold value LREF. Therefore, the alternative value R cannot be calculated. Also in this case, the value of data LD is set to the upper limit value #LLMT (step S15).
  • step S13 or step S15 The value of the data LD set in step S13 or step S15 is then set as the excess air ratio ⁇ value LAMBDA (step S16), thereby ending the excess ratio calculation process of FIG.
  • the ECU 15 converts the excess air rate ⁇ value LAMBDA calculated in the excess rate calculation process of FIG.
  • the amount of fuel injected by the fuel injection valve 6 is controlled via the feedback coefficient calculation unit 30 so as to match the rate ⁇ cmd.
  • FIG. 6 is a graph schematically showing how the excess air ratio ⁇ value LAMBDA calculated by the excess air ratio calculation process of FIG. 3 changes.
  • the horizontal axis of the graph is a numerical value indicating the passage of time, and the vertical axis is the excess air ratio ⁇ .
  • Graph 37 in FIG. 6 shows that the actual exhaust air excess rate gradually increases at a constant rate of change in the range from the left end side to near the center of the horizontal axis in the left-right direction in FIG.
  • the voltage value VHG read by the voltage calculation unit 24 of the ECU 15 is The figure shows a numerical change in the excess air ratio ⁇ value when the excess air ratio ⁇ value is calculated using data directly linearized with respect to the excess air ratio while compensating for temperature characteristics.
  • the graph 38 shows that when the actual excess air ratio of the exhaust gas is gradually increased or decreased at a constant rate of change from the left end to the right end of the horizontal axis, the voltage value VHG from the voltage calculation unit 24 is on the lean side.
  • the excess air ratio ⁇ value is calculated using the data map described above ( Figure 5) or the data obtained by directly linearizing the voltage value VHG using equation (2).
  • the voltage value VHG from the voltage calculation unit 24 exceeds the voltage value lref of the lean side range value LREF (corresponding to the value of excess air ratio ⁇ of 1.020), the voltage value VHG is linearized.
  • the graph shows the numerical change in the excess air ratio ⁇ value when the substitute value R obtained by the above-mentioned formula (1) is used as the excess air ratio ⁇ value in place of the above data.
  • the voltage value VHG from the voltage calculation unit 24 in response thereto is proportional (linear) to the actual excess air ratio ⁇ of the exhaust gas. ), so if the actual excess air ratio of the exhaust gas is 1.020 or less, graphs 37 and 38 both linearly follow the constant change in the actual excess air ratio of the exhaust gas. However, if the excess air ratio of the exhaust exceeds 1.020, the voltage value VHG, which exhibits nonlinearity under that situation, will rapidly change in the increasing direction.
  • the graph 37 showing the excess air ratio ⁇ value based on the linearized data similarly changes steeply and non-linearly in the increasing direction.
  • the excess ratio calculation unit 25 can interlock with the actual excess air ratio of exhaust gas over the entire range of the graph in FIG. It can be seen that the excess air ratio ⁇ value that changes proportionally can be supplied to the feedback coefficient calculation unit 30. This suppresses interruption of the calculation of the feedback coefficient k by the feedback coefficient calculation unit 30.
  • the excess rate calculation section 25 includes a characteristic inspection section 40 that inspects the characteristics of the voltage value VHG (detected value) that changes according to the variation in the resistance value, and a characteristic inspection section 40 that inspects the characteristics of the voltage value VHG (detected value) that changes according to the variation in the resistance value, and uses the above-mentioned data map and lookup based on the inspection results. and a calibration section 41 that calibrates the up-table.
  • the characteristic checking unit 40 includes a temperature difference checking unit 42 that checks the deviation amount TD of the temperature T of the sensor element 12a from the reference value and sets the temperature Tcon for control, and a temperature difference checking unit 42 that checks the deviation amount TD of the temperature T of the sensor element 12a from the reference value and sets the temperature Tcon for control, and It has a voltage difference confirmation unit 43 that confirms the deviation VD between the average value VHGSTD and the lean side threshold value LREF and sets the control voltage value (detected value) VHGcon, and the set control temperature Tcon and the control voltage
  • the output characteristic of the oxygen sensor 12 connected to the ECU 15 is checked according to the value (detection value) VHGcon.
  • control temperature Tcon is set to be the same as the engine temperature and intake air temperature at room temperature and before startup.
  • the temperature difference confirmation unit 42 substantially moves the lookup table corresponding to the data map and graphs 35 and 36 in parallel in the left-right direction (in the direction of the first scale value G1) in FIG. .
  • the voltage difference confirmation unit 43 determines the voltage value VHG obtained from the resistance value of the sensor element 12a.
  • the deviation VD between the average value VHGSTD and the lean side threshold value LREF within a predetermined period of time is obtained.
  • the wave height of the voltage value VHG becomes almost zero (state where the voltage value VHG does not move) and the standard resistance value decreases.
  • the voltage value VHGref that can be read from the sensor element 12a has the same value as the graphs 35 and 36 (the voltage value VHGref and the graphs 35 and 36 overlap). That is, when the control temperature Tcon is below a predetermined value, the standard voltage value VHGref becomes equal to graph 35 (lean side threshold value LREF), so this is the standard for setting the control voltage value (detected value) VHGcon.
  • the value can be determined by scanning the look-up table corresponding to graph 35 at the sufficiently low temperature Tcon.
  • the above average value VHGSTD can be obtained from the arithmetic average value of the voltage values VHG read many times in a period of 5 seconds, for example, thereby reducing the influence of quantization errors in reading the voltage values VHG.
  • control voltage value (detected value) VHGcon is corrected to be the same as the graph 35 (lean side threshold value LREF) when the control temperature Tcon is below a predetermined value.
  • the voltage difference confirmation unit 43 substantially translates the data map in the vertical direction (in the direction of the second scale value G2) in FIG. 5 .
  • the characteristic inspection unit 40 sets the target excess air ratio ⁇ cmd to near the stoichiometric value through the target value calculation unit 28, and obtains the peak value of the voltage value VHGcon. , it is checked whether this peak value corresponds to any of the air-fuel ratio regions.
  • the first and second lookup tables corresponding to the data map and graphs 35 and 36 are calibrated based on the results of the above inspection.
  • FIG. 7 shows a voltage obtained by the characteristic inspection unit 40 while driving a vehicle equipped with an oxygen sensor 12 having a standard resistance value in an internal combustion engine with the target excess air ratio ⁇ cmd set near the stoichiometric value.
  • a voltage waveform 44 representing the change over time of the value (detected value) VHGref is shown.
  • an air-fuel ratio waveform 45 indicating the waveform of an output signal from a wideband air-fuel ratio sensor temporarily installed for verification purposes.
  • the exhaust gas in the exhaust pipe and the oxygen concentration contained in the exhaust gas are pulsating, so as shown in FIG.
  • the voltage waveform 44 of the voltage value (detected value) VHGref and the air-fuel ratio waveform 45 of the attached air-fuel ratio sensor are observed as waveforms with wave heights that change oscillally over time, but especially when the air-fuel ratio During the illustrated period P in which the fuel ratio waveform 45 crosses the level where the excess air ratio ⁇ is 1.0, the resistance value of the sensor element 12a naturally changes steeply in a stepwise manner at the oxygen concentration near the stoichiometric range.
  • the wave height M of the voltage waveform 44 (the wave height value of the detected value) is observed as a waveform that oscillates significantly compared to the wave height of the air-fuel ratio waveform 45 during the same period P.
  • the first and second lookup tables corresponding to the graph 35 (lean side threshold LREF) and graph 36 (rich side threshold RREF) are created along the wave height transition of the voltage waveform 44 that oscillates greatly in this way. are set respectively.
  • the rich-side peak near the lower rich-side threshold RREF in FIG. 46 many of them are located approximately above the rich-side threshold RREF, while many of the lean-side peaks 47 near the upper lean-side threshold LREF in FIG. 7 are located approximately above the lean-side threshold LREF.
  • the voltage value of the oxygen sensor 12 actually connected to the ECU 15 is adjusted while performing feedback control of the air-fuel ratio so as to reproduce the state of the illustrated period P by setting the target excess air ratio ⁇ cmd near the stoichiometric value.
  • Detection value By measuring the wave height M expressed by VHGcon with the ECU 15 and checking whether the peak of the wave height M matches the lean side threshold LREF and the rich side threshold RREF, the standard It is possible to grasp and obtain how much the characteristic deviation of the voltage value VHGcon from the characteristic of the voltage value VHGref at a certain resistance value is.
  • the characteristic inspection unit 40 sets the target excess air ratio ⁇ cmd near the stoichiometric value and performs air-fuel ratio feedback control, while checking the wave height of the voltage value (detection value) VHGcon of the oxygen sensor 12 connected to the ECU 15. It is configured to acquire the peak value of the wave height M and check whether the peak value of the wave height M corresponds to a rich region, a stoichiometric region, or a lean region. Also, based on the inspection results, the calibration unit 41 performs affine transformation on the data map and the first and The second lookup table can be calibrated.
  • the calibration unit 41 enlarges or reduces the plurality of first scale values G1 and the plurality of second scale values G2 in a manner of so-called affine transformation, thereby adjusting the data map and the first and second lookup tables. It is provided with a first calibration magnification value C1 and a second calibration magnification value C2 for calibrating.
  • the calibration unit 41 calculates the lean side peak value 47v of the control voltage value VHGcon that changes over time and the graph 35 (lean side threshold value LREF). For example, when the lean side peak value 47v is in the lean region, when comparing the data map and the first lookup table corresponding to When the lean side peak value 47v is in the stoichiometric region, the first calibration magnification value C1 is decreased and the data map and the first lookup table are expanded to the left in FIG. 8B. Reduce towards.
  • the calibration unit 41 multiplies the first scale value G1 of the data map and the first lookup table by the increased or decreased first calibration magnification value C1, thereby converting the data map and the first look up in a manner of so-called affine transformation. Calibrate by substantially expanding or contracting the uptable. Note that 0 Kelvin (minus 273.15 degC; absolute zero) can be adopted as the expansion/contraction origin of the first scale value G1.
  • Tk degree Celsius temperature
  • the calibration unit 41 compares the rich-side peak value 46v of the control voltage value VHGcon that changes with the passage of time with the second look-up table corresponding to the graph 36 (rich-side threshold value RREF), For example, when the peak value 46v on the rich side is in the rich region, the second calibration magnification value C2 is increased to enlarge the data map and the second lookup table downward in FIG. When the peak value 46v is in the stoichiometric region, the second calibration magnification value C2 is decreased to reduce the data map and the second lookup table upward in FIG. 8C.
  • the calibration unit 41 multiplies the second scale value G2 of the data map and the second lookup table by the increased or decreased second calibration magnification value C2, thereby converting the data map and the second look up in the manner of so-called affine transformation. Calibrate by substantially expanding or contracting the uptable.
  • the value of the graph 35 (lean side threshold value LREF) when the above-mentioned control temperature Tcon is below a predetermined value can be adopted as the expansion/contraction origin of the second scale value G2.
  • the first calibration magnification value C1 or the second calibration magnification value C1 or The calibration unit 41 can be configured to include a transition process in which the second calibration magnification value C2 is gradually increased or decreased to gradually transition to the calibration complete state.
  • the on-board diagnosis in the ECU 15 definitively diagnoses that the signal line between the sensor heater 12b of the titania type oxygen sensor 12 and the temperature calculation unit 23 is disconnected or short-circuited, , the above transition process (increase or decrease) for the first calibration magnification value C1 is interrupted, and the first calibration magnification value C1 is reset to a default value (for example, a value such as #1.0 times).
  • a titania oxygen sensor which is an embodiment of a resistance-type oxygen sensor
  • the oxygen sensor 12a if the temperature of the sensor element 12a is too low or too high, the sensor element The resistance value of 12a is difficult to respond to the air-fuel ratio, resulting in a narrow dynamic range.
  • the temperature of the sensor element 12a is too low (for example, 280 degC or lower) or too high (for example, 870 degC or higher), as can be understood from FIG.
  • the resolution of the excess rate ⁇ is extremely reduced. This makes it difficult to control using the differential term of the deviation in PID or PD control, making it difficult to maintain the control followability expected of PID or PD control (including pseudo differential terms). There is a possibility that the accuracy of feedback control regarding the excess rate ⁇ may decrease.
  • the temperature of the sensor element 12a is too low (for example, 280 degC or lower) or too high (for example, 870 degC or higher), feedback control using PID or PD control including control using a differential term is performed. It is possible that there is no such thing.
  • the control temperature Tcon is lower than the second temperature or the third temperature
  • the PI control is selected and a step of switching to the PI control is performed.
  • the feedback coefficient calculation unit 30 calculates the deviation P between the excess air ratio ⁇ obtained according to the control temperature Tcon and the target excess air ratio ⁇ cmd, the differential D of the deviation P,
  • the PD/PID control unit 49 calculates the feedback coefficient k based on the deviation P, the integral I of the deviation, and the differential D of the deviation, and the excess air ratio ⁇ and the target excess air ratio calculated according to the control temperature Tcon.
  • a PI control unit 50 that calculates a feedback coefficient k based on a deviation P with respect to ⁇ cmd and an integral I of the deviation P, and which of the PI control unit 50 or the PD/PID control unit 49 is used to calculate the feedback coefficient k.
  • a control unit selection unit 51 selects the control temperature Tcon, and a plurality of temperature setting values regarding the control temperature Tcon are read from the storage unit 34, and based on the plurality of temperature setting values and the first calibration magnification value C1, the first calibration magnification value C1 is selected from the lowest one.
  • a temperature threshold setting section 52 that sets the first, second, third, and fourth temperatures t1, t2, t3, and t4, respectively, and a PI control section 50 or a PD/PID control section 49 according to the control temperature Tcon.
  • an activation determination unit 53 that determines whether or not to permit execution of the feedback control, and a deviation P between an excess air ratio ⁇ and a target excess air ratio ⁇ cmd determined according to an alternative temperature Tsub, which will be described later, and an integral I of the deviation.
  • a fault PI control unit 59 that calculates a feedback coefficient k based on the following.
  • the activation determination unit 53 allows execution of feedback control via the PI control unit 50 or the PD/PID control unit 49 when the control temperature Tcon is higher than the first temperature t1 and lower than the fourth temperature t4. do.
  • the control unit selection unit 51 selects the PD/PID control unit when the control temperature Tcon is higher than the second temperature t2 and lower than the third temperature t3. 49 is selected, and when the control temperature Tcon is lower than the second temperature t2 or higher than the third temperature t3, the PI control unit 50 is selected.
  • the feedback coefficient calculation unit 30 calculates the deviation P between the excess air ratio ⁇ and the target excess air ratio ⁇ cmd, and the deviation P of the deviation P. Calculate the feedback coefficient k based on the differentiation, or the deviation P, the integral of the deviation P, and the differentiation of the deviation P, and if the PI control unit 50 is selected, calculate the feedback coefficient k based on the deviation P, the integral of the deviation P, and the Based on this, a feedback coefficient k is calculated. Thereby, appropriate feedback control is performed depending on whether the control temperature Tcon is too low or too high.
  • the oxygen sensor 12 is used for a long period of time and the signal line from the sensor heater 12b is disconnected due to some external factor, the resistance value of the sensor heater 12b cannot be read accurately. This makes it difficult to accurately calculate the temperature value T of the sensor element 12a. In this case, if no measures are taken, air-fuel ratio control by the oxygen sensor 12, which is highly temperature dependent, cannot be continued.
  • an alternative temperature preparation unit 54 is used that prepares an alternative temperature Tsub to be used as an alternative to the control temperature Tcon when the resistance value of the sensor heater 12b cannot be read.
  • the alternative temperature preparation unit 54 sets a plurality of voltage values corresponding to a lean side peak value 47v of the wave height of the voltage value VHG of the sensor element 12a due to exhaust pulsation and a plurality of temperature values corresponding thereto as coordinates.
  • a third look-up table 55 and a fourth look-up table 56 whose coordinates are a plurality of voltage values corresponding to the rich-side peak value 46v of the wave height of the voltage value VHGcon and a plurality of temperature values corresponding thereto.
  • These third and fourth lookup tables 55 and 56 are stored in the storage unit 34.
  • the third lookup table 55 is set in a so-called inverse functional relationship with the lookup table corresponding to the graph 35 (lean side threshold LREF). That is, in this embodiment, the third lookup table 55 sets, for example, the excess air ratio ⁇ as the boundary between the lean region and the stoichiometric region to 1.02, and determines the voltage value VHG and temperature value T that will result in this value. It is expressed by a graph obtained by finding multiple points on the data map as coordinates and connecting these multiple points by line interpolation. The correspondence relationship with the second scale value G2 is shown.
  • the fourth lookup table 56 sets, for example, the excess air ratio ⁇ as the boundary between the stoichiometric region and the rich region to 0.98, and the voltage value VHG and temperature value that result in this value. It is expressed by a graph obtained by finding multiple points on the above data map with T as the coordinate and connecting these multiple points by line interpolation, and multiple temperature values are expressed with respect to the voltage value VHG (detected value). are shown in correspondence with the plurality of second scale values G2.
  • an alternative temperature preparation section 54 for example, if the lean side peak value 47v (see FIG. 7) of the wave height of the voltage value VHG of the sensor element 12a is 3.0 volts, as shown in FIG. , it can be seen from the third lookup table 55 that the corresponding alternative temperature value Tsub is 650 degC. That is, the alternative temperature preparation unit 54 can use the third lookup table to obtain the alternative temperature Tsub based on the lean side peak value 47v, and prepare this as the alternative temperature for the control temperature Tcon.
  • the alternative temperature value Tsub is 400 degC. That is, the alternative temperature preparation unit 54 can obtain the alternative temperature Tsub using the fourth lookup table and prepare this as the alternative temperature for the control temperature Tcon. In this way, even if the signal line from the sensor heater 12b is disconnected due to some external factor, the substitute temperature Tsub is determined as a substitute temperature for the control temperature Tcon, and the air-fuel ratio is determined by the oxygen sensor 12, which is highly temperature dependent. It becomes possible to continue control.
  • the alternative temperature preparation section 54 prepares the alternative temperature for the sensor element 12a at the peak of the wave height of the voltage value VHG of the sensor element 12a. This is done by checking the value.
  • the excess air ratio calculated from the alternative temperature Tsub and the voltage value VHG from the voltage calculation unit 24 ⁇ is a value that includes ambiguity in immediacy (real-time) and has a large detection delay. This means that the accuracy of PD/PID control based on the amount of change in deviation (differential term) with respect to the excess air ratio ⁇ may be significantly reduced.
  • PD/PID control is not performed, and limited control is performed only by PI control, which is a control method that does not include a differential term.
  • the alternative temperature preparation unit 54 is executed (step S2B).
  • the alternative temperature Tsub is determined from the lean side peak value 47v or the rich side peak value 46v as described above.
  • step S2B the limit threshold setting unit 33 is executed (step S2B).
  • the limit threshold value setting unit 33 sets a lean side threshold value LREF and a rich side threshold value RREF based on the alternative temperature value Tsub using the first and second lookup tables corresponding to the graphs 35 and 36 in FIG.
  • step S3B the voltage value VHG obtained from the voltage calculation section 24 is corrected by the deviation VD obtained from the voltage difference confirmation section 43, and a voltage value (detected value) VHGcon for control is set.
  • step S4B the above-mentioned data map (FIG. 5) is scanned based on the alternative temperature Tsub and the voltage value VHGcon obtained in step S3B, and data LD is obtained.
  • step S6 the flag F_DETECT is set to zero, and the process proceeds to step S16, where the value of the data LD is set as the excess air ratio ⁇ value LAMBDA. In this way, the excess rate calculation process shown in FIG. 3 in the event of a failure such as a disconnection of the sensor heater 12b is completed.
  • the activation determining unit 53 and the control unit selecting unit 51 detect that the signal line between the sensor heater 12b of the titania oxygen sensor 12 and the temperature calculating unit 23 is disconnected or short-circuited by the on-board diagnostic unit 62 in the ECU 15.
  • the alternative temperature Tsub is higher than the first temperature t1 and lower than the fourth temperature t4
  • the failure only allows execution of feedback control via the failure PI control unit 59. It has a time activation determining section.
  • the activation determination unit 53 and the control unit selection unit 51 permit PD/PID control when it is diagnosed that the signal line between the sensor heater 12b and the temperature calculation unit 23 is disconnected or short-circuited. It is configured not to.
  • the fault PI control unit 59 calculates the feedback coefficient k based on the deviation between the excess air ratio ⁇ obtained according to the alternative temperature Tsub and the target excess air ratio ⁇ cmd and the integral of the deviation, and thereby, Feedback control of the excess air ratio ⁇ can be performed by PI control. Therefore, even if it is diagnosed that the signal line between the sensor heater 12b and the temperature calculation unit 23 is disconnected or short-circuited, appropriate feedback control is continued.
  • control section selection section 51 selects the control voltage value (detected value) VHGcon in the characteristic inspection section 40 and the control
  • the PD/PID control unit 49 or the PI control unit 50 is configured to be selected depending on the inspection result of the operating temperature Tcon.
  • the calibration unit 41 sets the lean side threshold LREF and the rich side threshold RREF respectively to the first scale value G1 related to the control temperature Tcon and the first scale value G1 related to the control voltage value (detected value) VHGcon.
  • the first scale value G1 and the second scale value G2 regarding the correspondence in the data map are each calibrated based on the comparison between the data map respectively associated with the second scale value G2 and the peak values 46v and 47v. It is composed of
  • the calibration unit 41 adjusts the By gradually increasing or decreasing the calibration magnification value C1 or the second calibration magnification value C2, the calibration can be gradually progressed (learning) to a calibration completed state.
  • the characteristic inspection unit 40 compares the peak values 46v and 47v with at least one side of the rich side threshold RREF or the lean side threshold LREF to which the above-mentioned calibration is reflected, thereby checking the progress of the calibration by the calibration unit 41.
  • the control unit selection unit 51 calculates the difference between the peak value 46v and the rich side threshold RREF, or the peak value 46v and the lean side threshold LREF, and considers the difference as the progress state of the calibration by the calibration unit 41,
  • the progress state of this calibration can be used as the inspection result of the control voltage value VHGcon and the control temperature Tcon in the characteristic inspection section 40 to select the PD/PID control section 49 or the PI control section 50.
  • the control unit selection unit 51 determines the calibration progress state. It is possible to select the above-mentioned PD/PID control section 49 by assuming that the calibration is completed. Alternatively, if the difference between the peak value 46v and the rich side threshold RREF, or the difference between the peak value 46v and the lean side threshold LREF is larger than a predetermined threshold, the calibration progress state is the calibration incomplete state. In this case, the PI control unit 50 can be selected.
  • priority is given to determining whether or not to allow the execution of the feedback control by the above-mentioned activation determining section 53 and determining whether or not to permit the execution of the air-fuel ratio feedback control by the PI control section 50.
  • the PI control unit 50 and PD/PID control unit 49 are not selected, that is, feedback control is stopped.
  • control temperature Tcon is lower than the second temperature t2 or higher than the third temperature t3, and therefore execution of feedback control by the PI control unit 50 is selected, even if the peak value is 46V. Even if the rich side threshold RREF or the difference between the peak value 46v and the lean side threshold LREF is less than a predetermined threshold, the PD/PID control unit 49 is not allowed to perform control.
  • control temperature Tcon is higher than the second temperature t2 and lower than the third temperature t3, and the control temperature Tcon is such that execution of feedback control by the PD/PID control unit 49 can be selected. If the difference between the peak value 46v and the rich side threshold RREF or between the peak value 46v and the lean side threshold LREF is larger than a predetermined threshold and it is considered that the calibration is still incomplete, the PI control unit Execution of feedback control by 50 is selected.
  • the ECU 15 includes a calibration reset section 61 and the above-mentioned on-board diagnostic section 62, which output a trigger signal that causes the control section selection section 51 to make a selection based on the inspection result of the characteristic inspection section 40 (see FIG. 2). .
  • the calibration reset unit 61 is configured to be able to issue, to the control unit selection unit 51, an initialization command Rs that initializes the correspondence in the data map described above as the trigger signal.
  • the on-board diagnostic unit 62 is configured to be capable of diagnosing a failure such as a disconnection in the sensor element (detection unit) 12a or the sensor heater 12b (heater unit) of the titania oxygen sensor 12.
  • a failure such as a disconnection in the sensor element (detection unit) 12a or the sensor heater 12b (heater unit) of the titania oxygen sensor 12.
  • the on-board diagnostic unit 62 determines that there is an abnormality in the sensor element 12a or the sensor heater 12b
  • the on-board diagnostic unit 62 sends an abnormality signal As indicating this to the control unit selection unit 51 as the trigger signal. will be issued.
  • control unit selection unit 51 When the control unit selection unit 51 receives the initialization command Rs from the calibration reset unit 61, it preferentially selects the PI control unit 50 in a predetermined period thereafter.
  • This predetermined period is set to be a sufficient period required for the characteristics inspection section 40 to repeatedly perform inspections and for the calibration section 41 to determine the progress state of the above-mentioned calibration according to the results. Ru.
  • control unit selection unit 51 selects the PI control unit 50 when receiving the abnormality signal As from the on-board diagnosis unit 62.
  • the accurate temperature value Tcon of the sensor element 12a cannot be obtained, so the excess air ratio ⁇ obtained from the substitute value Tsub (see steps S2B to S43B, S6, and S16 in FIG. 3) )
  • the fault PI control unit 59 is selected as the PI control unit 50.
  • PI control by the failure PI control section 59 is selected until the abnormality signal As is released. Note that when the fault PI control section 59 performs PI control in response to the abnormal signal As, the above-mentioned calibration control by the calibration section 41 is interrupted (temporarily stopping calculation and updating of calibration values). ).
  • the control unit selection unit 51 selects the PI control unit 50 for a predetermined period after the cancellation.
  • This predetermined period is such that after the cancellation, the calibration unit 41 repeatedly performs the inspection by the characteristic inspection unit 40 as described above, and depending on the result, the calibration unit 41 indicates the progress status of the calibration described above. A period sufficient to allow a decision to be made will be set.
  • the temperature of the sensor element 12a of the oxygen sensor 12 when the temperature of the sensor element 12a of the oxygen sensor 12 is below the first temperature t1 which is too low or above the fourth temperature t4 which is too high, no feedback control is performed.
  • the control temperature when the control temperature is lower than the second temperature t2 or higher than the third temperature t3, feedback control is performed via the PI control unit 50, and the temperature of the sensor element 12a of the oxygen sensor 12 is lower than the second temperature t2.
  • feedback control is performed via the PD/PID control unit 49, so it is possible to substantially expand the operating temperature range of feedback control, improve availability, and improve exhaust purification performance. can.
  • the temperature corresponding to the peak value of the voltage value VHG from the voltage calculation unit 24 is determined, and the determined temperature is used for control in the excess rate calculation unit 25.
  • the prepared alternative temperature Tcon can be used. Since a failure PI control unit 59 is provided that calculates a feedback coefficient k based on the deviation P between the excess air ratio ⁇ obtained using Tsub and the target excess air ratio ⁇ cmd and the integral I of the deviation, it is possible to prevent a failure of the heater unit. Feedback control of the excess air ratio can be continued even at the same time.
  • control unit selection unit 51 selectively selects the PD/PID control unit 49 or the PI control unit 50 according to the inspection results of the detected value VHGcon, the control temperature Tcon, and the control temperature Tcon in the characteristic inspection unit 40. Since the oxygen sensor 12 is configured to be able to perform the following, it is possible to select an appropriate control according to the inspection result in accordance with differences in characteristics due to individual differences in the oxygen sensor 12. As a result, highly robust air-fuel ratio feedback control using the titania-type oxygen sensor 12 can be realized.
  • the data map is also calibrated based on the comparison between the data map and the peak value described above, and the progress of the calibration is determined by comparing the peak value with at least one of the lean threshold or the rich threshold. Therefore, the control unit selection unit 51 can appropriately select the PD/PID control unit 49 or the PI control unit 50 by referring to the progress state of this calibration as the inspection result in the characteristic inspection unit 40. can.
  • control unit selection unit 51 receives the initialization command Rs from the calibration reset unit 61, it selects the PI control unit for a predetermined period thereafter, so that the data is not stored in the predetermined period. While the map calibration is progressing, the progress state of the calibration can be appropriately determined, and the alternative selection of the PD/PID control unit 49 or the PI control unit 50 can be appropriately performed.
  • control unit selection unit 51 selects the PI control unit 50 when it is determined that the sensor element 12a or the sensor heater 12b of the oxygen sensor 12 is temporarily abnormal. It is possible to prevent inaccurate feedback control from being performed by the control unit 49.
  • control unit selection unit 51 selects a PI control unit in a predetermined period after the cancellation. 50 is selected, the calibration of the data map is progressing in the meantime, the progress state of this calibration is appropriately determined, and the alternative selection of the PD/PID control unit 49 or the PI control unit 50 is appropriately performed. I can do it.
  • the plurality of first scale values G1 of the data map and the first and second lookup tables, and the first, second, third, and fourth temperatures t1, t2, t3, t4 Although the calibration is performed by multiplying each of the values by the first calibration magnification value C1 (Equation (6a) and Equation (6b)), the present invention is not limited to this. For example, even with a configuration in which the temperature value is multiplied by the reciprocal of the first calibration magnification value C1, it is possible to substantially enlarge or reduce the data map and lookup table, and at this time, the data map and the lookup table can be substantially enlarged or reduced.
  • the pre-calibration values of the plurality of first scale values G1 or the plurality of first to fourth temperature setting values are Tk (degrees Celsius temperature), the first control scale values after calibration or the first and second temperature settings after calibration.
  • Tkcal is the third and fourth temperatures t1, t2, t3, and t4
  • Temp is the temperature value T from the temperature calculation unit 23 or the alternative temperature Tsub from the alternative temperature preparation unit 54, Tkcal and the control temperature
  • Tcon temperature in degrees Celsius
  • the reference value Tref for setting the temperature Tcon may be calculated from only one of them.
  • Characteristic inspection section 41... Calibration section, 42... Temperature difference confirmation section, 43...Voltage difference confirmation unit, 44...Voltage waveform, 45...Air-fuel ratio waveform, 46...Rich side peak, 47...Lean side peak, 46v, 47v...Peak value, 48...Feedback control unit, 49...PD ⁇ PID control unit, 50...PI control unit, 51...Control unit selection unit, 52...Temperature threshold setting unit, 53...Activity determination unit, 54...Alternative temperature preparation unit, 55...Third lookup table, 56...-Fourth Lookup table, 58... Graph, 59... PI control unit at the time of failure, 61... Calibration reset unit, 62... On-board diagnostic unit.

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  • Chemical & Material Sciences (AREA)
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  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

 Est fourni un dispositif de commande de rapport air-carburant qui peut réaliser une commande de rétroaction de rapport air-carburant avec un capteur d'oxygène résistif présentant une robustesse élevée. Ce dispositif de commande de rapport air-carburant comprend : une unité de commande de PD/PID (49) et une unité de commande de PI (50) qui réalise une commande de rétroaction d'un débit d'air excédentaire ; une unité de sélection d'unité de commande (51) qui sélectionne l'une des unités de commande ; une unité d'inspection de caractéristique qui inspecte si oui ou non une valeur de détection d'un capteur d'oxygène de dioxyde de titane et une température d'une unité de détection correspondent à des caractéristiques prescrites respectives ; et une unité d'étalonnage qui, sur la base de l'inspection, étalonne des première et seconde valeurs d'échelle (G1, G2) d'une carte de données pour déterminer le débit d'air excédentaire à partir de la valeur de détection et de la température. L'unité de sélection d'unité de commande (51) réalise la sélection alternative de l'unité de commande PD/PID ou de l'unité de commande de PI en fonction du résultat d'inspection.
PCT/JP2022/014124 2022-03-24 2022-03-24 Dispositif de commande de rapport air-carburant WO2023181292A1 (fr)

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PCT/JP2022/014124 WO2023181292A1 (fr) 2022-03-24 2022-03-24 Dispositif de commande de rapport air-carburant

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PCT/JP2022/014124 WO2023181292A1 (fr) 2022-03-24 2022-03-24 Dispositif de commande de rapport air-carburant

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07127502A (ja) * 1993-11-05 1995-05-16 Nippondenso Co Ltd 内燃機関の空燃比制御装置
JPH08338289A (ja) * 1995-06-09 1996-12-24 Honda Motor Co Ltd 空燃比制御装置
JPH09291843A (ja) * 1996-02-28 1997-11-11 Toyota Motor Corp 内燃機関の空燃比制御装置
US5826426A (en) * 1997-07-30 1998-10-27 Chrysler Corporation Oxygen sensor linearization system and method
JP2013142683A (ja) * 2012-01-13 2013-07-22 Ngk Spark Plug Co Ltd ガスセンサ処理装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07127502A (ja) * 1993-11-05 1995-05-16 Nippondenso Co Ltd 内燃機関の空燃比制御装置
JPH08338289A (ja) * 1995-06-09 1996-12-24 Honda Motor Co Ltd 空燃比制御装置
JPH09291843A (ja) * 1996-02-28 1997-11-11 Toyota Motor Corp 内燃機関の空燃比制御装置
US5826426A (en) * 1997-07-30 1998-10-27 Chrysler Corporation Oxygen sensor linearization system and method
JP2013142683A (ja) * 2012-01-13 2013-07-22 Ngk Spark Plug Co Ltd ガスセンサ処理装置

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