JP2013007347A - Oxygen sensor control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen sensor control apparatus capable of accurately calibrating the relationship between output characteristics of an oxygen sensor and oxygen concentration, through use of an output value from the oxygen sensor obtained when fuel supply to an internal combustion engine is stopped.SOLUTION: When an Air scavenging amount (total supply amount of atmosphere) becomes equal to or greater than a predetermined amount in each fuel cut of an internal combustion engine 100, a CPU 2 of an oxygen sensor control apparatus 10 obtains a peak value of an average output value Ipav and stores it in a RAM 4 while calculating the average output value Ipav averaged on the basis of a plurality of output corresponding values (concentration corresponding values) Ipr of the oxygen sensor 20, from which values deviating from a predetermined first range R1 have been excluded. Subsequently, the CPU 2 further averages peak values of the average output values Ipav obtained per a plurality of fuel cuts to thereby obtain a plural-average output value Ipavf. A correction coefficient for correcting the actual output value Ip of the oxygen sensor 20 is obtained on the basis of the plural-average output value and a preset reference output value.

Description

  The present invention relates to an oxygen sensor control device that calibrates the relationship between the oxygen concentration and the output characteristics of an oxygen sensor that detects the oxygen concentration of exhaust gas of an internal combustion engine, and detects the oxygen concentration of exhaust gas.

  2. Description of the Related Art Conventionally, an oxygen sensor is installed in an exhaust passage (exhaust pipe) of an internal combustion engine such as an automobile, and the air-fuel ratio is controlled by detecting the oxygen concentration in the exhaust gas. As such an oxygen sensor, for example, a sensor having a gas detection element provided with at least one cell in which a pair of electrodes are formed on oxygen ion conductive zirconia. However, there is a problem that the detection accuracy of the oxygen concentration differs due to variations in output characteristics of individual oxygen sensors and deterioration with time of the oxygen sensors. Therefore, there is known a technique for performing atmospheric correction to calibrate the relationship between the output value of the oxygen sensor and the oxygen concentration when it is estimated that the fuel supply to the internal combustion engine is stopped and the exhaust passage is almost in the atmospheric state. (For example, refer to Patent Document 1).

JP 2007-32466 A (paragraph 0040)

  However, in the atmospheric correction method described in Patent Document 1, the standard output value Vstd of the standard oxygen sensor in the atmosphere and the current output value of the oxygen sensor during the fuel cut in which the fuel supply is stopped (that is, 1 It is merely a calculation of a correction coefficient by comparing with two output values Vsen. Here, even during a fuel cut (during a fuel cut-off period), the output value of the oxygen sensor may pulsate with the operation of the internal combustion engine, or noise may be superimposed on the output value. Therefore, there is a problem that it is difficult to obtain an accurate correction coefficient by a method of calculating a correction coefficient by simply comparing one output value of an oxygen sensor during fuel cut with a reference output value.

  That is, the present invention calibrates the relationship between the oxygen sensor output characteristics and the oxygen concentration with high accuracy by using the output value from the oxygen sensor acquired when the fuel supply to the internal combustion engine is stopped. It is an object of the present invention to provide an oxygen sensor control device capable of performing the above.

  In order to solve the above-described problem, the oxygen sensor control device of the present invention provides an oxygen sensor actual output value attached to an exhaust pipe of an internal combustion engine and an oxygen output when a fuel cutoff is performed to stop the fuel supply of the internal combustion engine. An oxygen sensor control device for detecting an oxygen concentration of exhaust gas flowing through the exhaust pipe using the actual output value and the correction coefficient while obtaining a correction coefficient for calibrating the relationship with concentration, An average output value obtained by averaging the actual output values of the plurality of oxygen sensors acquired during the fuel cutoff period or the concentration corresponding value reflecting the oxygen concentration calculated using the actual output values is calculated. An average output value calculating means, a peak value storing means for storing a peak value of the average output value calculated by the average output value calculating means, and the fuel for two or more predetermined times of the fuel interruption Each time the peak value is stored A plurality of peak values stored in the step of further averaging a plurality of average output values to calculate a plurality of average output values; and, based on the plurality of average output values and a preset reference output value, the oxygen And correction coefficient calculation means for obtaining a new correction coefficient for correcting the actual output value of the sensor.

  In general, the output characteristics (output waveform) of the oxygen sensor when a fuel cutoff (so-called fuel cut) for stopping the fuel supply of the internal combustion engine is performed include an output waveform associated with the operation of the internal combustion engine at the time of the fuel cutoff. May pulsate, or noise may be included in the actual output value output from the oxygen sensor. Therefore, in the present invention, the actual output value of the oxygen sensor obtained during the period when the fuel cut is performed once, or a plurality of concentration-corresponding values reflecting the oxygen concentration calculated using the actual output value. The average output value is calculated based on the above, and the influence of pulsation and noise on the output waveform of the oxygen sensor is removed or reduced.

  In the present invention, the peak value of the average output value calculated by the average output value calculating means is stored. When the fuel cut-off starts, the influence of volatile gases such as hydrocarbons in the cylinders of the internal combustion engine may gradually appear in the exhaust pipe. When the oxygen concentration atmosphere gradually decreases, the actual output value or concentration corresponding value of the oxygen sensor also deviates from a value reflecting the oxygen concentration close to the atmosphere. Therefore, the average output value obtained in the second half of the fuel cut may be calculated as a value deviated from the value calculated in the oxygen concentration atmosphere close to the atmosphere. Therefore, in the present invention, the peak value of the average output value is obtained and the peak value is stored. As a result, even when the oxygen concentration atmosphere gradually decreases during fuel cut, the average output value calculated in the oxygen concentration atmosphere close to the atmosphere is stored (held) as a peak value. In the present invention, a plurality of average output values obtained by further averaging the peak values of a plurality of average output values obtained by a predetermined number of fuel interruptions are calculated, and new values are calculated based on the plurality of average output values and a preset reference output value. A correct correction coefficient is obtained. As a result, the multiple average output value is a value representative of the actual output value or the concentration corresponding value of the oxygen sensor calculated in the oxygen concentration atmosphere approaching the atmosphere. By using this multiple average output value, a highly accurate correction coefficient is obtained. Can finally be calculated.

  In the present invention, the “concentration-corresponding value reflecting the oxygen concentration calculated using the actual output value” means the current correction coefficient set in the oxygen sensor control device for each actual output value of the oxygen sensor. (If a new correction coefficient is found, the new correction coefficient) can be multiplied. Further, an amplified value obtained by amplifying the actual output value at a predetermined magnification, and a value obtained by multiplying the amplified value by the correction coefficient can be given.

  In the oxygen sensor control device of the present invention, the average output value calculation means calculates using the actual output values of the plurality of oxygen sensors or the actual output values acquired during one fuel cutoff period. An average output value that is averaged based on the remaining values excluding values that deviate from the predetermined first range among the concentration corresponding values that reflect the oxygen concentration to be calculated may be calculated.

  In this case, by calculating the average output value based on the remaining value excluding the value that deviates from the predetermined first range, the influence of the pulsation and noise of the output waveform of the oxygen sensor during the fuel cut-off period is obtained. It can be effectively removed or reduced, and a more stable correction coefficient can be obtained. The first range may be set to a range defined with the reference output value as a central value. By setting the first range to a range defined with the reference output value as the center value, it is possible to effectively remove or reduce the influence of the pulsation and noise of the output waveform of the oxygen sensor during the fuel cutoff period. It is.

  In the oxygen sensor control device of the present invention, the supply amount is acquired from a supply amount measuring unit that measures the supply amount of the atmosphere supplied from the internal combustion engine to the exhaust pipe, and the supply during the fuel cutoff period is obtained. A total supply amount calculating means for calculating a total supply amount that is a total amount of the amount, and the total supply amount calculated by the total supply amount calculation means in a single fuel cut-off period is equal to or greater than a predetermined amount set in advance A total supply amount determination means for determining whether or not the total supply amount is determined by the total supply amount determination means after the fuel cutoff is started. The average output value may be calculated based on the actual output values or the concentration-corresponding values of the plurality of oxygen sensors obtained at predetermined time intervals after the determination is made.

  In this case, the oxygen sensor is triggered by the fact that the total supply amount of the air supplied to the exhaust pipe has exceeded a predetermined amount from the start of the fuel cut (fuel cut per time). The average output value is calculated based on the actual output value or the density correspondence value. Therefore, the average output value can be calculated in a relatively stable state with no significant fluctuation in the output waveform of the oxygen sensor after the start of fuel cut-off, coupled with the effect of using the peak value of the average output value. Correction coefficients can be calculated.

  According to the present invention, it is possible to obtain a correction coefficient capable of accurately calibrating the relationship between the output characteristics of the oxygen sensor and the oxygen concentration, and as a result, the detection accuracy of the oxygen sensor can be satisfactorily maintained over a long period of time.

1 is a configuration diagram of an engine control system 1 including an oxygen sensor control device 10 according to an embodiment of the present invention. It is a figure which shows the method of calculating | requiring the correction coefficient Kp previously. A method of averaging a value Ipr obtained by multiplying a change in the total supply amount M1 of the atmosphere during the fuel cutoff period, a change in the output corresponding value Ipr of the mounted oxygen sensor 20 and the actual output value of the mounted oxygen sensor 20 by the correction coefficient Kp. FIG. It is a figure which shows the method of calculating the average output value Ipavf by further averaging the actual output value Ipav averaged by the method shown in FIG. FIG. 5 is a diagram illustrating a method for determining whether or not a plurality of average output values Ipavf calculated by averaging by the method illustrated in FIG. 4 has deviated from a range R3 that is a correction determination range. It is a figure which shows the flowchart which judges whether an atmospheric correction process is performed. It is a figure which shows the flowchart of the atmospheric correction process which calculates the correction coefficient Kq based on the value Ipr which multiplied the correction coefficient Kp to the actual output value of the mounting oxygen sensor 20, and updates it as a new correction coefficient Kp. It is a figure which shows the flowchart of the subroutine of the hold process of the peak value of Ipav. It is a graph which shows the state of the output Ip of an oxygen sensor, an engine speed, the quantity of all the hydrocarbons, and a 20-section moving average.

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings. These drawings are used for explaining the technical features that can be adopted by the present invention, and the configuration of the apparatus and the flowcharts of various processes described are not intended to be limited to the drawings. This is just an illustrative example.

  FIG. 1 is a configuration diagram of an engine control system 1 including an oxygen sensor control device 10. In the engine control system 1, an oxygen sensor 20 (hereinafter referred to as a mounted oxygen sensor 20) is attached to an exhaust pipe 120 of an internal combustion engine (engine) 100 of a vehicle, and a controller 22 is connected to the mounted oxygen sensor 20. . The oxygen sensor control device 10 is connected to the controller 22. The oxygen sensor control device 10 in this embodiment has a function of an engine control unit (ECU).

  The intake pipe 110 of the internal combustion engine 100 is provided with a throttle valve 102, and each cylinder of the internal combustion engine 100 is provided with an injector (fuel injection valve) 104 for supplying fuel into the cylinder. An exhaust gas purification catalyst 130 is attached to the downstream side of the exhaust pipe 120. Further, the internal combustion engine 100 is provided with various sensors such as a pressure sensor (not shown), a temperature sensor (not shown), and a crank angle sensor 108. An air flow meter 107 is installed in the intake pipe 110. The air flow meter 107 measures the amount of intake air. Since the sucked air is supplied to the exhaust pipe 120, the air flow meter 107 measures the amount of air supplied to the exhaust pipe 120 by measuring the amount of air sucked.

  Operating condition information (engine pressure, temperature, crank angle, engine speed, supply amount of air, etc.) from the various sensors and the air flow meter 107 is input to the oxygen sensor control device 10. Note that an arrow 125 in FIG. 1 simply represents a path through which engine pressure and temperature are input in the operating condition information. The oxygen sensor control device 10 controls the throttle valve 102 in accordance with the above operating condition information, the detected oxygen concentration value in the exhaust gas from the mounted oxygen sensor 20, the amount of depression of the accelerator pedal 106 by the driver, etc. The amount of air supplied to the engine 100 is controlled, and the amount of fuel injected from the injector 104 is controlled. Thereby, the oxygen sensor control apparatus 10 operates the internal combustion engine 100 at an appropriate air-fuel ratio.

  The ECU 10 includes a central processing unit (CPU) 2, a ROM 3, a RAM 4, an external interface circuit (I / F) 5, an external input device 7, an output device 9, a microcomputer, an EEPROM, and the like. This is a unit in which the nonvolatile memory 8 is mounted on a circuit board. Then, the ECU 10 (CPU 2) processes an input signal according to a program stored in advance in the ROM 3, outputs a control signal for the fuel injection amount by the injector 104 from the output device 9, and performs atmospheric correction processing described later.

  The mounted oxygen sensor 20 can be, for example, a so-called two-cell air-fuel ratio sensor using two cells in which a pair of electrodes are provided on an oxygen ion conductive solid electrolyte body. As a more specific configuration of the air-fuel ratio sensor, an oxygen pump cell and an oxygen concentration detection cell are stacked so that a hollow measurement chamber into which exhaust gas is introduced through a porous body is interposed, and these two cells are further stacked. A gas detection element in which a heater for heating the gas detection element to the activation temperature is stacked, and a housing for holding the gas detection element inside itself and mounting the gas detection element on the exhaust pipe 120 can be provided. . In the present invention, the oxygen sensor 20 attached to each actual internal combustion engine is referred to as a “mounting oxygen sensor” in order to distinguish it from a reference oxygen sensor described later.

  The mounted oxygen sensor 20 is connected to a known controller 22 which is a detection circuit including various resistors and a differential amplifier. The controller 22 supplies a pump current to the mounted oxygen sensor 20, converts the pump current into a voltage, and outputs it to the ECU 10 as an oxygen concentration detection signal. More specifically, the controller 22 controls the energization of the oxygen pump cell so that the output of the oxygen concentration detection cell becomes a constant value, and the oxygen pump cell pumps out oxygen in the measurement chamber to the outside, or the measurement chamber The pump current that flows through the oxygen pump cell at that time is converted into a voltage via a detection resistor and is output to the ECU 10.

  Next, the atmospheric correction method (correction coefficient calculation method) of the mounted oxygen sensor 20 will be described. Atmospheric correction is attached to the internal combustion engine 100 when a fuel cut (fuel cut, hereinafter referred to as “F / C” as appropriate) is performed to stop the fuel supply of the internal combustion engine (engine) 100 under specific operating conditions. This is a process of calculating a correction coefficient for calibrating the relationship between the output characteristic (actual output value) of the mounted oxygen sensor 20 and the oxygen concentration. The atmospheric correction is an ideal predetermined oxygen sensor, in other words, a standard oxygen sensor having an output characteristic at the center of manufacturing variation, and an oxygen sensor (hereinafter referred to as an oxygen sensor having the same configuration as the mounted oxygen sensor 20). , Referred to as “reference oxygen sensor”) and the output characteristic of the mounted oxygen sensor 20 attached to the internal combustion engine 100 is determined by obtaining a correction coefficient, and the obtained correction coefficient is Used to correct the actual output value of the mounted oxygen sensor 20 during operation of the internal combustion engine.

  Here, the value of the correction coefficient may be any value that eliminates the difference between the output characteristics of the reference oxygen sensor and the output characteristics of the mounted oxygen sensor 20, but for example, the following correction coefficient Kp can be used. In other words, in the present embodiment, the correction coefficient is previously stored in the nonvolatile memory 8 of the ECU 10 (when the reference oxygen sensor is exposed to a specific atmosphere with a known oxygen concentration) so that atmospheric correction can be performed when the internal combustion engine 100 is running. (Reference oxygen output value Ipso) / (output value Ipro when the actual oxygen sensor 20 is exposed to an atmosphere in which the oxygen concentration is substantially the same as the specific atmosphere) (a correction coefficient Kp) is stored. . Here, the “specific atmosphere with a known oxygen concentration” is, for example, the atmosphere (oxygen concentration of about 20.5%), but may be an oxygen atmosphere having a predetermined concentration different from the atmosphere. When the reference oxygen sensor is exposed to the “specific atmosphere with a known oxygen concentration”, the reference oxygen sensor may be attached to a predetermined measurement system and exposed to the atmosphere (for example, air).

  On the other hand, “the atmosphere in which the oxygen concentration is substantially the same as the specific atmosphere” that exposes the mounted oxygen sensor 20 means that the oxygen concentration is the same as the atmosphere that exposes the reference oxygen sensor, and the oxygen concentration that exposes the reference oxygen sensor. An atmosphere that deviates within a range of ± 5.0% (more preferably ± 1.0%) is allowed. When the mounted oxygen sensor 20 is exposed to the above “atmosphere having substantially the same oxygen concentration as the specific atmosphere”, it is attached to a predetermined measurement system in the same manner as the reference sensor and exposed to the atmosphere (for example, air). Alternatively, after being attached to the exhaust pipe 120 of the actual internal combustion engine 100, the gas that becomes the oxygen atmosphere is circulated in the exhaust pipe 120, so that the mounted oxygen sensor 20 is exposed to the atmosphere. Good.

  The correction coefficient Kp is updated as a new correction coefficient Kp when an atmospheric correction process is performed during traveling of the internal combustion engine 100 and a new correction coefficient Kq described later is obtained. In the present embodiment, Prior to shipment of the internal combustion engine 100, the initial correction coefficient Kp is stored in the nonvolatile memory 8 according to the following procedure. Specifically, a reference oxygen sensor is attached to a predetermined measurement system and exposed to the air atmosphere, and a reference oxygen output value Ipso is obtained as shown in FIG. Next, the mounted oxygen sensor 20 is attached to the exhaust pipe 120 of the internal combustion engine 100 before shipping (more specifically, at the time of shipping inspection), the internal combustion engine 100 is driven, and the fuel supply is stopped. The oxygen atmosphere of the gas flowing through the exhaust pipe is exposed to a state in which the atmosphere is substantially the same as, for example, the oxygen concentration in the atmosphere, by fully opening or maintaining the fuel supply stop state for a long time. The output value Ipro of the mounted oxygen sensor 20 obtained at this time is detected (see FIG. 2).

  Then, as shown in FIG. 2, (reference oxygen output value Ipso) / (output value Ipro of the mounted oxygen sensor 20), that is, the reference oxygen output value Ipso is the output value Ipro of the mounted oxygen sensor 20 in the same oxygen concentration atmosphere. The correction coefficient Kp is calculated by dividing and the correction coefficient Kp is stored in the nonvolatile memory 8. Thus, the correction coefficient Kp stored as the initial value in the nonvolatile memory 8 corrects the actual output value Ip of the mounted oxygen sensor 20 until the next correction coefficient update (correction coefficient overwrite) is performed. Is used as a correction coefficient.

  Next, an example of a change in the output corresponding value Ipr of the mounted oxygen sensor 20 during one fuel cutoff period will be described with reference to FIG. FIG. 3 shows the relationship between the time since the start of fuel cut-off and the total supply amount M1 of the atmosphere (the upper graph in the drawing), and the time since the start of fuel cut-off and the output corresponding value of the mounted oxygen sensor 20 This represents the relationship with Ipr (graph on the lower side of the drawing). The total air supply amount M1 is a value obtained by adding (integrating) the air supply amount to the exhaust pipe 120 measured by the air flow meter 107 during the fuel cut-off period. Every time after the fuel cut is started, the total atmospheric supply amount M1 increases. Since the atmosphere is supplied to the exhaust pipe 120, the exhaust gas remaining in the exhaust pipe 120 and the like before the start of fuel cutoff is replaced with the atmosphere.

  Since it takes time for the exhaust gas remaining in the exhaust pipe 120 and the like to be replaced with the atmosphere, it takes time for the oxygen concentration in the exhaust pipe 120 to approach the oxygen concentration in the atmosphere. FIG. 3 shows, as an example, a case where the oxygen concentration in the exhaust pipe 120 approaches the oxygen concentration in the atmosphere when the total supply amount M1 of the atmosphere reaches a predetermined amount M2 (g) (50 g as an example). Yes. The timing when the total supply amount M1 of the atmosphere reaches the predetermined amount M2 (g) is the start timing of the Ipr acquisition time shown in FIG. Therefore, the output corresponding value Ipr of the mounted oxygen sensor 20 gradually increases until the total supply amount M1 of the atmosphere reaches the predetermined amount M2 (g). Then, when the oxygen concentration in the exhaust pipe 120 approaches the oxygen concentration in the atmosphere, the value of the output corresponding value Ipr is substantially stabilized. However, even if the oxygen concentration in the exhaust pipe 120 approaches the oxygen concentration in the atmosphere, the piston movement of each cylinder of the internal combustion engine 100 is repeated, so that the output corresponding value Ipr pulsates. In the period from the start of F / C to the start of the Ipr acquisition time in FIG. 3, the output corresponding value Ipr gradually increases while pulsating, but the pulsation is not shown.

  Next, in the present embodiment, the fuel cutoff reference output value is used as a reference output value at the time of fuel cutoff in the target internal combustion engine 100 to which the mounted oxygen sensor 20 is attached, which is a comparison of the actual output value of the mounted oxygen sensor 20. Ipsf is stored in advance in the nonvolatile memory 8 (EEPROM) of the ECU 10. This fuel cutoff reference output value Ipsf is also stored in the nonvolatile memory 8 before shipment of the internal combustion engine 100. In this embodiment, after the correction coefficient Kp is calculated by the above-described procedure, the mounted oxygen sensor 20 is connected to the internal combustion engine. It is obtained by intentionally performing F / C while attached to 100 exhaust pipes 120. Specifically, at the time of shipment inspection of the internal combustion engine 100, the driving of the internal combustion engine 100 is started in a state where the mounted oxygen sensor 20 for which the correction coefficient Kp has been obtained as described above is attached to the exhaust pipe 120 of the internal combustion engine 100. . Then, the F / C under a specific operating condition is executed artificially or mechanically, and the time after the F / C exhausted from the cylinder is expected to reach the periphery of the mounted oxygen sensor 20 (for example, The correction coefficient Kp is set to the actual output value of the mounted oxygen sensor 20 obtained at predetermined time intervals after the F / C start and the total atmospheric supply amount M1 reaches a predetermined amount M2 (g) (50 g as an example). It is calculated by averaging a plurality of multiplied values. The fuel cutoff reference output value Ipsf obtained in this way is stored in the nonvolatile memory 8. The fuel cutoff reference output value Ipsf corresponds to the “reference output value” in the claims.

  In the internal combustion engine (engine) 100, the ECU 10 outputs an instruction for the fuel injection amount from the injector 104 to become zero in accordance with operating conditions such as the deceleration of the vehicle and the state of the intake air amount. It can be determined that F / C has been started by detecting the presence or absence of output. By the way, although there are various patterns in the operating conditions for starting F / C, specific conditions at the start of F / C executed at the time of shipping inspection of the internal combustion engine 100 to calculate the fuel cutoff reference output value Ipsf are described. If the operating conditions and the specific operating conditions at the start of F / C for executing the atmospheric correction process described later when the vehicle (internal combustion engine) 100 travels (driving) after shipment are not matched, the atmospheric correction process is performed under the same conditions. This cannot be performed, and the accuracy of atmospheric correction (in other words, the accuracy of calculation of an average output value Ipav, multiple average output values Ipavf, and a correction coefficient Kq described later) decreases. Accordingly, in the present embodiment, calculation of the average output value Ipav, the multiple average output value Ipavf, the fuel cutoff reference output value Ipsf, only for the fuel cutoff under a predetermined condition in which the operating conditions are determined, and A calculation process of a correction coefficient Kq, which will be described later, is executed.

  However, it is not indispensable to prepare the conditions for fuel cutoff, and the actual output value Ip of the mounted oxygen sensor 20 is acquired in each of a plurality of fuel cutoffs under different conditions, and the average output value Ipav and the multiple average output are obtained. The value Ipavf, the fuel cutoff reference output value Ipsf, the correction coefficient Kq, and the like may be calculated. In determining whether F / C is started under specific operating conditions during operation of the internal combustion engine 100, the engine speed immediately before F / C is started (F / C start is determined). At least one parameter representing the operating state of the internal combustion engine, such as the engine load and the intake air amount, is used, and the parameter satisfies a predetermined condition (that is, a predetermined condition set in advance to obtain the fuel cutoff reference output value Ipsf). When the condition is satisfied, it can be determined that the F / C is started under a predetermined condition in which the operation condition is determined in advance.

  Next, in a state in which the correction coefficient Kp and the fuel cutoff reference output value Ipsf are stored in the nonvolatile memory 8, the ECU 10 uses the average output value Ipav and the plurality of average output values Ipavf while the vehicle (internal combustion engine 100) is traveling. An outline of the atmospheric correction processing executed by the CPU 2 will be described based on the flowcharts shown in FIGS. FIG. 6 is a flowchart for determining whether or not to execute atmospheric correction processing. FIG. 7 shows atmospheric correction processing for calculating a correction coefficient Kq using the average output value Ipav and the multiple average output values Ipavf. These flowcharts correspond to the flowcharts to be executed. Both flowcharts start processing after the power supply of the ECU 10 is introduced, and are repeatedly executed at a predetermined cycle (for example, every 1 msec).

  First, with reference to FIG. 6, a process for determining whether or not to execute the atmospheric correction process will be described. The CPU 2 determines whether or not F / C is started during operation of the internal combustion engine 100 (S101). As described above, this determination is made based on whether or not an instruction that the fuel injection amount from the injector 104 is zero is output. When this instruction is issued, it is determined that F / C has started (S101: YES). Next, the CPU 2 determines whether or not the F / C is under a specific operating condition (S103). As described above, this determination is performed by using at least one parameter representing the operating state of the internal combustion engine, such as the engine speed, engine load, and intake air amount immediately before the start of F / C (determination of F / C start). It is determined whether the parameter satisfies a predetermined condition. When it is determined that the F / C is in a specific operating state (S103: YES), the CPU 2 sets the correction flag to “1” (S105). The correction flag is set to 0 when the ECU 100 is powered on. On the other hand, if it determines with S101: NO and S103: NO, this process will be complete | finished and CPU2 will perform the process (S101) from the beginning repeatedly. If it is determined in S101 that F / C has started (S101: YES), the total supply amount M1, which is the total amount of air supply to the exhaust pipe 120 during the fuel cut-off period, is “0”. Set to The total supply amount M1 is stored in the RAM 4. Next, the supply amount of the atmosphere is acquired from the air flow meter 107, and the integration of the total supply amount M1 is started.

  Next, the atmospheric correction process will be described with reference to the flowchart shown in FIG. First, in step S2, it is determined whether or not the correction flag is “1”. When the correction flag is “1” (S2: YES), the process proceeds to step S4. The correction flag is determined based on the flag set to “1” in step S105 of FIG. On the other hand, when the correction flag is not “1” (S2: NO), this process is terminated. S2: In the case of YES, the CPU 2 determines whether or not the F / C is continued (S4). When the F / C continues (S4: YES), the process proceeds to the determination process of S6.

  Next, in the determination process of S6, it is determined whether or not the air scavenging amount (total air supply amount M1) accumulated during one fuel cut-off period is equal to or greater than a predetermined amount M2 (for example, 50 g). (S6). The value of the predetermined amount M2 is stored in the nonvolatile memory 8. If the total supply amount M1 is not equal to or greater than the predetermined amount M2 (S6: NO), the process proceeds to S25, and the Ipavf acquisition process execution instruction has not been issued yet (S25: NO), and the process is terminated. Next, the determination of S6 is made repeatedly at a predetermined cycle (for example, every 1 msec).

  Here, as the F / C continuation time, waiting until the air scavenging amount (total supply amount M1 of the atmosphere) becomes equal to or greater than the predetermined amount M2 (50 g as an example) Because the combustion gas before / C remains in the exhaust pipe 120 and the like, and the combustion gas approaches or is replaced with fresh air (atmosphere), an air scavenging amount of a predetermined amount M2 is required, so the oxygen concentration in the exhaust pipe 120 is also atmospheric. There is a delay before the oxygen concentration approaches. Therefore, the actual output value (output waveform) of the mounted oxygen sensor 20 also gradually increases as the oxygen concentration in the exhaust pipe 120 increases after the start of F / C, and the output waveform when the exhaust pipe 120 approaches the atmosphere. Although it is affected by pulsation, the value is almost stable. Therefore, in step S6, after the F / C is started under specific operating conditions, has the F / C been continued until the air scavenging amount (M2) where the exhaust pipe 120 approaches the atmosphere or is assumed to be replaced? It is determined whether or not.

  Returning to FIG. 7, when the air scavenging amount (total supply amount M1) is equal to or greater than the predetermined amount M2 (50 g as an example) (S6: YES), the CPU 2 acquires the output corresponding value Ipr of the mounted oxygen sensor 20, Store in the RAM 4 (S8). Note that the output corresponding value Ipr is repeatedly acquired at predetermined time intervals (for example, every 1 msec) as long as F / C continues under a specific operating condition. The output corresponding value Ipr is a value obtained by multiplying the actual output value Ip output from the mounted oxygen sensor 20 by the current correction coefficient Kp stored in the nonvolatile memory 8. That is, the output corresponding value Ipr, which is a value obtained by multiplying the actual output value Ip by the current correction coefficient Kp, corresponds to the “concentration corresponding value reflecting the oxygen concentration calculated using the actual output value” in the claims. To do.

  Next, the CPU 2 determines whether or not the output corresponding value Ipr acquired in S8 is within the predetermined first range R1 (S10), and if the output corresponding value Ipr is within the predetermined first range R1. If so (S10: YES), the weighted average processing of the output corresponding value Ipr is performed (S12). On the other hand, when the output corresponding value Ipr is not within the range of the predetermined first range R1 (S10: NO), a discarding process for erasing the output corresponding value Ipr acquired in S8 and stored in the RAM 4 is performed (S14).

  Normally, even if the F / C is started under a predetermined condition in which the operating conditions are determined, each actual output value Ip (and thus the output corresponding value Ipr) in the mounted oxygen sensor 20 pulsates or its actual output value. There is a case where noise is accidentally included in Ip (and thus the output corresponding value Ipr). Therefore, in the present embodiment, the influence of pulsation and noise can be eliminated by calculating an average output value Ipav obtained by averaging the values of the plurality of output corresponding values Ipr acquired during the fuel cut-off period per time. The output state of the mounted oxygen sensor 20 is reduced and is stably obtained at one F / C. Specifically, as shown in FIG. 3, values obtained by multiplying individual actual output values Ip obtained during one fuel cut-off period by the current correction coefficient Kp (Ipr1-1, Ipr1-2... ) To obtain only the value within the predetermined first range (range) R1 (in other words, only the value of the output corresponding value Ipr determined as “YES” in S10) and calculate the average output value Ipav. And stored in the RAM 4 (S12). In the present embodiment, the range R1 shown in FIG. 3 includes a fuel cutoff reference output value Ipsf with a predetermined value of a fluctuation value of the fuel cutoff reference output value Ipsf (for example, the fuel cutoff reference output value Ipsf as a center value). 7.5% of the value plus or minus) is set as the upper and lower limits.

  As shown in FIG. 3, for example, two values Ipr1-1 among the output corresponding values Ipr1 obtained by multiplying the actual output value Ip of the mounted oxygen sensor 20 obtained during one fuel cutoff period by the correction coefficient Kp, The value of Ipr1-2 swings up and down (pulsates), but the effect of pulsation can be eliminated by taking the average of both. Further, the two output corresponding values Ipr1-6 and Ipr1-8 are estimated to be values including noise and values when the mounting oxygen sensor 20 is erroneously detected, both of which deviate from the range R1. Therefore, it is not used for calculating the average output value Ipav and is discarded (S14).

Next, in S12, a weighted average process of the output corresponding value Ipr (specifically, a weighted average process of 128 output corresponding values Ipr) is performed. A value obtained by performing weighted average processing on Ipr is a weighted average value Ipav corresponding to an average output value in step S22 described later.
Ipav = 1/128 × {latest Ipr−Ipav (n−1)} + Ipav (n−1) (Formula 1)
Ipav (n−1) in the above formula 1 corresponds to the weighted average value calculated in the immediately preceding process (immediately before). Since Ipav (n-1) does not exist immediately after the start of the atmospheric correction process, the weighted average value Ipav is obtained by substituting the output corresponding value Ipr obtained first into Ipav (n-1). . When the weighted average process (S12) of the output corresponding value Ipr is completed, the peak value (maximum value) of the weighted average value Ipav is held (S13). Specifically, the hold processing of the peak value of the weighted average value Ipav is performed according to a flowchart of a subroutine shown in FIG.

  As shown in FIG. 8, in the hold processing of the peak value of the weighted average value Ipav, first, the value of Ipav (n) calculated and obtained at this time in the weighted average processing in S12 is calculated in the previous weighted average processing in S12. It is determined whether or not the value is larger than the hold value stored in (S131). When the value of Ipav (n) acquired this time is larger than the hold value (S131: YES), Ipav (n) acquired this time is overwritten on the previous hold value stored in the RAM 4 (S132). ). The peak value hold is stored in the RAM 4 for each F / C. Further, the value of the weighted average value Ipav (n) obtained first after the start of F / C is stored as it is in the RAM 4 as a hold value, and is compared with the value of the weighted average value obtained next time. Next, the process returns to the flowchart of the atmospheric correction process shown in FIG. When the value of Ipav (n) acquired this time is equal to or smaller than the value of Ipav (n-1) of the hold value (S131: NO), the overwriting process is not performed and the flowchart of the atmospheric correction process shown in FIG. Return. In the flowchart of the atmospheric correction process shown in FIG. 7, if a negative determination is made in S6 (S6: NO), the process of discarding the Ipr in S14 (S14), and the process of S13 are completed, the process proceeds to S25. To do.

  On the other hand, if it is determined in S4 that the F / C is not continued (S4: NO), the correction flag is set from “1” to “0” (S16), and the process proceeds to S20. In S20, the air scavenging amount (total supply amount M1 in the atmosphere) accumulated in one fuel cutoff period is a predetermined amount M2 (as an example, 50 g) until the F / C under specific operating conditions is completed. It is determined whether or not the above has been reached (S20). When the total supply amount M1 is equal to or greater than the predetermined amount M2 (S20: YES), the CPU 2 determines the peak value of the weighted average value of the output corresponding value Ipr held in S13) as the peak value of Ipav that is the average output value. (S22). When the total supply amount M1 is not equal to or greater than the predetermined amount M2 (S20: NO), the CPU 2 calculates the weighted average value of the output corresponding value Ipr calculated in the weighted average processing (S12) of the output corresponding value Ipr. Then, it is discarded because it is not an average value based on a sufficient number of output corresponding values Ipr (S24).

  Next, when the process of S22 is completed, the CPU 2 instructs execution of an Ipavf acquisition process for obtaining a plurality of average output values Ipavf (S23). Then, after completing the process of S23 or S24, the CPU 2 proceeds to S25. In S25, it is determined whether or not there is an instruction to perform Ipavf acquisition processing in S23. If there is an instruction to perform Ipavf acquisition processing (S25: YES), the process proceeds to S26, and there is no instruction to perform Ipavf acquisition processing. If YES in step S25, the process ends. In S26, it is determined whether or not the peak value of the average output value Ipav used for calculating the correction coefficient Kq is within the predetermined second range R2, and if an affirmative determination is made in S26 (S26: YES), the process goes to S28. Transition.

  Here, even when the F / C is repeatedly performed under specific operating conditions, as shown in FIG. 4, the F / C is acquired in the process of S <b> 22 due to variations in the operating state of the internal combustion engine 100. In addition, the peak values (Ipav1, Ipav2,...) Of the individual weighted average values may vary. Therefore, if only the values within the predetermined second range (range) R2 are acquired from the peak values (Ipav1, Ipav2,...) Of the individual weighted average values and used for calculating the multiple average output value Ipavf. A stable multiple average output value Ipavf can be calculated. As the range R2, for example, a fluctuation value of a predetermined ratio of the fuel cutoff reference output value Ipsf (for example, a value of 2.0% of the fuel cutoff reference output value Ipsf with the fuel cutoff reference output value Ipsf as a central value) is added. , Minus values) can be set as the upper and lower limits. In this case, as shown in FIG. 4, for example, the peak values Ipav3 and Ipav4 of the two weighted average values are not used in the calculation of the multiple average output value Ipavf because they deviate from the range R2 (S26: NO).

  Note that the range R2 is applied to the peak value of the average output value Ipav that has already averaged the pulsations in the range R1, so that it is set within the range R1 and R2 <R1. By setting R2 <R1, the peak value of the average output value Ipav including an error can be eliminated to calculate the multiple average output value Ipavf, and the reliability of the calculated multiple average output value Ipavf is improved.

Next, if the determination in S26 is affirmative (S26: YES), further weighted average processing of each Ipav whose peak value is held in the RAM 4 in S13 (specifically, the weights of the peak values of the 16 weighted average values Ipav) Average processing) is performed (S28). The process is performed according to, for example, the following formula 2, and a value obtained by performing a weighted average process on this Ipav is acquired as a multiple average output value Ipavf (S28).
Ipavf = 1/16 × {the latest Ipav peak value−Ipavf (n−1)} + Ipavf (n−1) (Formula 2)
Ipavf (n−1) in the above formula 2 corresponds to the weighted average value calculated in the immediately preceding process (immediately before). Since Ipavf (n-1) does not exist immediately after the start of the air correction process, the first obtained Ipav peak value is substituted into Ipavf (n-1) to obtain the weighted average value Ipavf. .

  On the other hand, if the Ipav peak value is outside the range R2 (S26: NO), the process proceeds to S30, and the CPU 2 determines that the number of times that the Ipav peak value is outside the range R2 (S26: NO) is a predetermined number of times. Is judged (S30). The process of S30 corresponds to, for example, counting the number of objects (Ipav3, Ipav4) exceeding the range R2 in FIG. If the number of times that the peak value of Ipav falls outside the range R2 exceeds the predetermined number (S30: YES), it is considered that the abnormality in the output of the mounted oxygen sensor 20 has been frequently observed, and the CPU 2 replaces the sensor. An instruction is given (S32), and this process is terminated. The sensor replacement instruction can be executed by, for example, notifying the driver of the vehicle of an alarm or performing a display prompting replacement. On the other hand, when the number of times that the peak value of Ipav is out of the range R2 does not exceed the predetermined number (S30: NO), this process ends.

  Next, when the process of S28 is completed, the CPU 2 determines whether or not the multiple average output value Ipavf acquired in S28 is within a predetermined third range (range) (S36). Here, as the range R3, as shown in FIG. 5, a variation value of a predetermined ratio of the fuel cutoff reference output value Ipsf (for example, 1 of the fuel cutoff reference output value Ipsf with the fuel cutoff reference output value Ipsf as the center value). 0.0% of the value plus or minus) is set as the upper and lower limits. The range R3 is used to determine whether or not the correction coefficient Kq is updated in each F / C, so that it is set within the range R2 and R3 <R2.

When the multiple average output value Ipavf deviates from the predetermined third range even once (S36: NO), the process proceeds to S40, and a process of calculating a new correction coefficient Kq is executed (S40). In S40, as the calculation of the correction coefficient Kq, the fuel cutoff reference output value Ipsf stored in the nonvolatile memory 8 is changed to the latest plural average output value Ipavf (in other words, plural average output value Ipavf out of the range R3). It is calculated by dividing by the value divided by the current correction coefficient Kp.
Kq = fuel cutoff reference output value Ipsf / (latest multiple average output value Ipavf / current correction coefficient Kp)
Then, a process of updating (overwriting) the correction coefficient Kq calculated in the process of S40 in the nonvolatile memory 8 as a new correction coefficient Kp is executed (S42). As a result, the output corresponding value Ipr corrected by the new correction coefficient Kp is calculated from the actual output value Ip output from the subsequent mounted oxygen sensor 20, and the oxygen concentration in the exhaust gas is calculated based on the output corresponding value Ipr. Detection is performed.

  On the other hand, if “YES” is determined in the determination process of S36, this process ends. That is, the immediately preceding correction coefficient Kp is used without being updated.

  As described above, in the oxygen sensor control device 10 of the present embodiment, out of the plurality of output corresponding values Ipr of the mounted oxygen sensor 20 acquired during one fuel cut-off period, the oxygen sensor control device 10 deviates from the first range R1. An average output value Ipav is calculated based on the remaining values excluding the value, and a peak value of the average output value Ipav is obtained for each F / C, and a plurality of average output values Ipavf are calculated based on the respective peak values. Is calculated. Then, a new correction coefficient Kq is obtained by comparing the multiple average actual output value Ipavf and the fuel cutoff reference output value Ipsf, and the correction coefficient is updated. As shown in FIG. 9, when F / C is started and the engine speed (Eg speed) decreases, the volatile gas such as total hydrocarbons (THC) in the cylinder generated during F / C The concentration increases with the elapsed time of fuel cut. Then, the oxygen concentration in the atmosphere around the mounted oxygen sensor 20 gradually decreases, the Ip value that is the actual output value of the mounted oxygen sensor 20 decreases slightly but gradually decreases, and an error in ΔIp value (measurement error) ) Gets bigger. In FIG. 9, {(Ip value that is the actual output value of the mounted oxygen sensor 20−reference output value obtained when the oxygen concentration is equivalent to the atmosphere) / the reference output value} × 100 of 20 calculated values. The moving average value (20-section moving average value) is expressed as a ΔIp value (unit:%), and it can be seen that the error of this ΔIp value increases with the increase in the concentration of the volatile gas. Therefore, in the oxygen sensor control apparatus 10 of the present embodiment, by holding the peak value of the average output value Ipav obtained by averaging the output corresponding value Ipr, the total hydrocarbons (THC) generated in the cylinder during the F / C are held. ) Or the like (in FIG. 9, the peak value of the output average value Ipav is held when 11.5 seconds have elapsed since the start of F / C). Therefore, the relationship between the output characteristics of the oxygen sensor (the mounted oxygen sensor 20) and the oxygen concentration can be accurately calibrated, and the oxygen concentration can be continuously detected using a highly accurate correction coefficient. It can be maintained well over a long period of time.

  In the present embodiment, the CPU 2 that executes the process of S40 is an example of “correction coefficient calculation means”, and the CPU 2 that executes the processes of S10 and S12 is an example of “average output value calculation means”. . The CPU 2 that executes the processes of S26 and S28 is an example of “multiple average output value calculation means”, Ipav is an example of “average output value”, and Ipavf is an example of “multiple average output value”. . The RAM 4 that accumulates and stores the total supply amount M1 is an example of the “total supply amount calculation unit”, and the CPU 2 that executes the process of S6 is an example of the “total supply amount determination unit”. The RAM 4 is an example of the “peak value storage unit”. The process for obtaining the peak value of the average output value Ipav to be stored in the RAM 4 is executed in the process of S13 of the CPU 2 as described above.

  Needless to say, the present invention is not limited to the above embodiment, and various modifications are possible. For example, the mounted oxygen sensor 20 is not limited to the two-cell air-fuel ratio sensor, and a one-cell limit current-type air-fuel ratio sensor can be used. Moreover, in the said embodiment, although average output value Ipav and multiple average output value Ipavf were calculated | required as a weighted average value, you may make it use the value by not only a weighted average value but an arithmetic mean or a moving average.

  In the above-described embodiment, the target for determining whether or not it falls within the first range R1 is the output corresponding value Ipr obtained by multiplying the actual output value Ip of the mounted oxygen sensor 20 by the correction coefficient Kp. The numerical value range of the range R1 is appropriately changed, the first range R1 is compared with the actual output value Ip, and the correction coefficient is obtained by averaging the actual output value Ip excluding the value deviating from the first range R1. The average output value Ipav may be calculated by multiplying by Kp. Furthermore, in the above-described embodiment, the predetermined amount in steps S6 and S20 is a fixed value (M2). However, a variable value is set according to the numerical value of the engine speed immediately before the F / C is started under specific operating conditions. You may make it set as.

2 CPU
3 ROM
4 RAM
8 Nonvolatile memory 10 Oxygen sensor controller (ECU)
20 Mounted oxygen sensor (oxygen sensor)
100 Internal combustion engine Kp, Kq Correction coefficient Ipso reference oxygen output value Ipro Output value when oxygen sensor is exposed to an atmosphere in which the specific atmosphere and oxygen concentration are substantially the same Ipsf Fuel cutoff reference output value (reference output value)
Value obtained by multiplying the actual output value of the Ipr mounted oxygen sensor by the correction coefficient Kp (concentration corresponding value)
Ipav average output value Ipavf Multiple average output value R1 1st range R2 2nd range R3 3rd range M1 Total supply of air (air scavenging amount)
M2 predetermined amount

Claims (3)

When a fuel cut is performed to stop the fuel supply of the internal combustion engine, a correction coefficient for calibrating the relationship between the actual output value of the oxygen sensor attached to the exhaust pipe of the internal combustion engine and the oxygen concentration is obtained, while the actual output An oxygen sensor control device for detecting an oxygen concentration of exhaust gas flowing through the exhaust pipe using a value and the correction coefficient,
The average output averaged based on the actual output values of the plurality of oxygen sensors acquired during one fuel cut-off period or the concentration corresponding values reflecting the oxygen concentration calculated using the actual output values An average output value calculating means for calculating a value;
Peak value storage means for storing a peak value of the average output value calculated by the average output value calculation means;
A plurality of average outputs for calculating a plurality of average output values by averaging the plurality of peak values stored in the peak value storage means for each fuel cutoff for a predetermined number of times of fuel cutoff two or more times A value calculating means;
An oxygen sensor comprising: a correction coefficient calculating means for obtaining a new correction coefficient for correcting the actual output value of the oxygen sensor based on the plurality of average output values and a preset reference output value Control device.   The average output value calculating means is an actual output value of the plurality of oxygen sensors acquired during one fuel cutoff period or a concentration corresponding value reflecting an oxygen concentration calculated using the actual output value. 2. The oxygen sensor control device according to claim 1, wherein an average output value averaged based on a remaining value excluding a value deviating from a predetermined first range is calculated. The supply amount is acquired from a supply amount measuring unit that measures the supply amount of the air supplied from the internal combustion engine to the exhaust pipe, and a total supply amount that is a total amount of the supply amount during the fuel cutoff period is calculated. A total supply calculation means;
A total supply amount determination means for determining whether or not the total supply amount calculated by the total supply amount calculation means is greater than or equal to a predetermined amount set in advance in one fuel cutoff period;
The average output value calculating means has a plurality of times obtained at predetermined time intervals after the total supply amount determining means has determined that the total supply amount has become equal to or greater than the predetermined amount since the fuel cutoff was started. The oxygen sensor control device according to claim 1, wherein the average output value is calculated based on an actual output value of the oxygen sensor or the concentration corresponding value.

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