JP5770000B2 - Oxygen sensor control device - Google Patents

Description

  The present invention relates to an oxygen sensor control device that detects an oxygen concentration in exhaust gas using an oxygen sensor.

  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. 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, when it is estimated that the fuel supply to the internal combustion engine is stopped and the exhaust passage is almost in the atmosphere, a correction coefficient is calculated and the relationship between the output value of the oxygen sensor and the oxygen concentration is calibrated. A technique for performing atmospheric correction is known (see, for example, Patent Document 1 and Patent Document 2).

JP 2007-32466 A JP-A-4-103854

  However, even when the fuel supply to the internal combustion engine is stopped, in the internal combustion engine, the piston operation of intake, compression, expansion, and exhaust stroke is repeated in each cylinder. The pressure of the flowing atmosphere is fluctuating. Due to factors such as atmospheric pressure fluctuations, the output value of the oxygen sensor exhibits fluctuations (hereinafter referred to as “pulsation”) depending on the fluctuations in pressure and the like. For this reason, unless the influence of the pulsation on the output value of the oxygen sensor is taken into consideration, it is difficult to say that the correction coefficient can be calculated accurately using the output value of the oxygen sensor.

  An object of the present invention is to provide an oxygen sensor control device that accurately calculates a correction coefficient based on an output value of a pulsating oxygen sensor.

An oxygen sensor control device according to the present invention includes storage means for storing a correction coefficient for calibrating a relationship between an output value of an oxygen sensor attached to an exhaust pipe of an internal combustion engine and an oxygen concentration, and the storage means stores the correction coefficient. A crank angle sensor for detecting a crank angle of the internal combustion engine in an oxygen sensor control device for detecting an oxygen concentration of exhaust gas flowing through the exhaust pipe using the corrected correction coefficient and the output value of the oxygen sensor Output signal acquisition means for acquiring the output signal of the internal combustion engine, and during the fuel cutoff period during which the fuel cutoff for stopping the fuel supply of the internal combustion engine is performed, based on the output signal acquired by the output signal acquisition means Crank angle determining means for determining whether the crank angle is a predetermined angle set in advance, and the crank angle is determined by the crank angle determining means. Based on the output value acquisition means for acquiring the output value of the oxygen sensor and the output value acquired by the output value acquisition means during the fuel cutoff period when it is determined that the angle is constant, a new value is obtained. Correction coefficient calculation means for calculating a correction coefficient, storage control means for storing the correction coefficient calculated by the correction coefficient calculation means in the storage means, and the output value acquisition means acquired during the fuel cutoff period. Representative value determining means for determining a representative value that is a value representative of the output value during the fuel cutoff period based on the plurality of output values, and the correction coefficient calculating means Based on the representative value and the reference value determined by the representative value determining means so that a correction value obtained by multiplying the output value and the correction coefficient in FIG. A new correction coefficient is calculated, and each time the output value is acquired by the output value acquisition unit, the representative value determination unit sequentially calculates a value obtained by averaging the plurality of output values, and is sequentially calculated. The maximum value which is the largest value among the plurality of averaged values is determined as the representative value .

  In this case, the output value of the oxygen sensor is acquired when the crank angle determining means determines that the crank angle is a predetermined angle during the fuel cut-off period. Then, a new correction coefficient is calculated based on the acquired output value of the oxygen sensor. That is, the output value of the oxygen sensor is acquired at a constant crank angle, and the correction coefficient is calculated. The magnitude of the crank angle is linked to the operation state of the internal combustion engine (intake / compression / expansion / exhaust stroke of each cylinder). For this reason, the magnitude of the crank angle is linked to fluctuations in atmospheric pressure in the exhaust pipe provided with the oxygen sensor. In the present invention, since the output value of the oxygen sensor is acquired at a constant crank angle, the operating state of the internal combustion engine at the timing of acquiring the output value is substantially the same, and the atmospheric pressure in the exhaust pipe is also substantially the same. As a result, the variation width of the output value at a constant crank angle becomes a value smaller than the pulsation amplitude. For this reason, the influence which the pulsation of an output value has on calculation of a correction coefficient can be reduced. Therefore, the correction coefficient can be calculated with high accuracy even under the output value of the pulsating oxygen sensor. The new correction coefficient is calculated based on, for example, the acquired output value of the oxygen sensor and a reference value (for example, a value output by the sensor when the standard oxygen sensor is exposed to the air atmosphere). can do.

In addition , a representative value based on a plurality of output values is used, and a new correction coefficient is calculated. For this reason, it is possible to prevent the correction coefficient from being calculated based on one output value including accidental noise, to reduce the influence of variations in individual output values, and to calculate the correction coefficient with high accuracy. be able to. The representative value based on a plurality of output values can include, for example, a value obtained by averaging a plurality of output values and a maximum value of the averaged values. Examples of the averaging process include a weighted average, a moving average, and an arithmetic average of a plurality of output values.

  The oxygen sensor control device obtains the supply amount 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 calculates the total amount of the supply amount during the fuel cutoff period. Total supply amount calculation means for calculating a certain total supply amount, and whether or not the total supply amount calculated by the total supply amount calculation means in a single fuel cut-off period exceeds a predetermined amount set in advance. A total supply amount determination means for determining whether the total supply amount is determined to be equal to or greater than the predetermined amount by the total supply amount determination means. It may be determined whether or not the crank angle based on the output signal obtained by the above is the predetermined angle. When the total supply amount of the air exceeds a predetermined amount and when the crank angle becomes a predetermined angle, the output value of the oxygen sensor is acquired by the output value acquisition means. Then, a correction coefficient is calculated based on the acquired output value of the oxygen sensor. For example, if a predetermined amount is set to an amount in which the exhaust pipe has a substantially atmospheric atmosphere, the output value of the oxygen sensor can be reliably obtained in an environment having a substantially atmospheric atmosphere, and therefore the correction coefficient can be calculated with high accuracy.

  The oxygen sensor control device includes an elapsed time determination unit that determines whether or not an elapsed time from the start of the fuel cutoff has exceeded a predetermined time in a single fuel cutoff period. The crank angle determining means is acquired by the output signal acquiring means when the elapsed time determining means determines that the elapsed time from the start of fuel cutoff has passed the predetermined time. It may be determined whether the crank angle based on the output signal is the predetermined angle. The output value of the oxygen sensor is acquired by the output value acquisition means when a predetermined time has elapsed since the start of fuel cutoff and when the crank angle has reached a predetermined angle. Then, a correction coefficient is calculated based on the acquired output value of the oxygen sensor. For example, if the time required for the inside of the exhaust pipe to become a substantially atmospheric atmosphere after the start of fuel cutoff is set as a predetermined time, the output value of the oxygen sensor can be acquired in an environment that is in a substantially atmospheric atmosphere, so the accuracy is high. A correction coefficient can be calculated.

1 is a schematic diagram showing a physical configuration and an electrical configuration of an engine control system 1 including an oxygen sensor control device 10. FIG. It is a graph which shows an example of the change of the total supply amount M1 of air | atmosphere during a fuel cutoff period, and the change of the output value Ipb of the mounting oxygen sensor 20. FIG. It is a graph which shows an example of the change of the crank angle during a fuel cutoff period, and the change of the output value Ipb of the mounting oxygen sensor 20. It is a flowchart which shows a 1st main process. It is a flowchart which shows a 2nd main process.

  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. 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, and 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. The crank angle sensor 108 measures a rotation angle (hereinafter referred to as a crank angle) of a crankshaft 109 connected to the piston 103 of the internal combustion engine 100. In the present embodiment, a two-stroke engine in which the crankshaft 109 makes one rotation in one cycle of piston motion (intake / compression / expansion / exhaust stroke) will be described as an example. The CPU 2 can detect a crank angle between 0 degrees and 360 degrees (see FIG. 3) based on the output signal output by the crank angle sensor 108.

  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. 2 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 oxygen sensor control device 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, and an output device 9; This is a unit in which a nonvolatile memory 8 such as an EEPROM is mounted on a circuit board. The oxygen sensor control device 10 (CPU 2) processes an input signal according to a program stored in advance in the ROM 3, and outputs a control signal for the fuel injection amount by the injector 104 from the output device 9, or a first main process described later. Or do.

  The mounted oxygen sensor 20 is, for example, a so-called two-cell air-fuel ratio sensor that uses two cells in which a pair of electrodes are provided on an oxygen ion conductive solid electrolyte body. Specifically, the mounting oxygen sensor 20 includes a housing for holding the gas detection element on the inner side and mounting the gas detection element on the exhaust pipe 120. The gas detection element includes an oxygen pump cell and an oxygen concentration detection cell stacked so that a hollow measurement chamber into which exhaust gas is introduced through a porous body is interposed, and these two cells are brought to an active temperature. It is an element having a known configuration in which a heater for heating up to is stacked. The mounted oxygen sensor 20 attached to each actual internal combustion engine is referred to as a “mounted oxygen sensor” in the present embodiment in order to distinguish it from a reference oxygen sensor described later.

  The mounted oxygen sensor 20 is connected to a known controller 22 that 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 oxygen sensor control device 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. In this case, the oxygen pump cell operates to pump out oxygen in the measurement chamber to the outside or pump oxygen into the measurement chamber. At this time, a pump current flows through the oxygen pump cell. The controller 22 converts the pump current into a voltage via the detection resistor and outputs the voltage to the oxygen sensor control device 10. Since the pump current and the voltage output from the controller 22 have the same meaning in that they correspond to the oxygen concentration in the exhaust pipe 120, the oxygen sensor control device 10 is output from the controller 22. By detecting the voltage value, the pump current value is indirectly detected. Therefore, in the following description, the value of the pump current detected by the oxygen sensor control device 10 (CPU 2) is referred to as the “output value Ipb” of the mounted oxygen sensor 20. The fluctuation of the output value Ipb corresponds to the fluctuation of the oxygen concentration in the exhaust pipe 120.

  Next, the correction coefficient Kp will be described. The correction coefficient Kp is a coefficient for calibrating the relationship between the output value Ipb of the mounted oxygen sensor 20 attached to the internal combustion engine 100 and the oxygen concentration, and is stored in the nonvolatile memory 8. In the following description, an ideal oxygen sensor, in other words, a standard oxygen sensor having an output characteristic at the center of manufacturing variation, and an oxygen sensor having the same configuration as the mounted oxygen sensor 20, It is called “reference oxygen sensor”. The value of the current output when the reference oxygen sensor is exposed to the atmospheric atmosphere (oxygen concentration of about 20.5%) is referred to as a reference value Ipa. In the present embodiment, as an example, the reference value Ipa is “4 mA”. Suppose that

  The correction coefficient Kp is determined such that a value obtained by multiplying the output value Ipb of the mounted oxygen sensor 20 by the correction coefficient Kp (hereinafter referred to as “correction value Ipf”) approaches the output value of the reference oxygen sensor. For example, if the correction value Ipf when the mounting oxygen sensor 20 is exposed to the air atmosphere becomes the same as the reference value Ipa “4 mA”, the correction value Ipf based on the output value Ipb of the mounting oxygen sensor 20 and the reference oxygen sensor The output value is the same. In this way, by using the correction value Ipf, it is possible to reduce the influence of variations in characteristics (individual differences) and deterioration of the mounted oxygen sensor 20, and to detect the oxygen concentration with the same accuracy as the reference oxygen sensor. it can. For this reason, the fuel injection amount from the injector 104 can be controlled to an appropriate amount without depending on variations in characteristics or deterioration of the characteristics of the oxygen sensor. The correction coefficient Kp is stored in the nonvolatile memory 8. Further, in the present embodiment, the correction coefficient Kp is calculated (updated) based on the output value Ipb of the mounted oxygen sensor 20 during the atmosphere (fuel cut-off) in which the fuel supply to the internal combustion engine 100 is stopped. During the fuel cut-off period, fuel is not injected from the injector 104, so the atmosphere in the exhaust pipe 120 becomes an air atmosphere, and is corrected by comparing with the reference value Ipa, which is the output value in the air atmosphere of the reference oxygen sensor. This is because the coefficient Kp can be calculated. Details of the calculation of the correction coefficient Kp will be described later.

  Next, an example of a change in the output value Ipb of the mounted oxygen sensor 20 during one fuel cut-off period will be described with reference to FIG. FIG. 2 shows the relationship between the time since the start of fuel cutoff and the total supply amount M1 of the atmosphere (the graph on the upper side of the drawing), the time since the start of fuel cutoff, and the output value Ipb of the mounted oxygen sensor 20. (Graph on the lower side of the drawing). The total air supply amount M1 is a value obtained by adding 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. 2 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 in the atmosphere reaches a predetermined amount M2 (g). The time required for the total supply amount M1 of the atmosphere to reach the predetermined amount M2 (g) is time T2. Therefore, the output value Ipb of the mounted oxygen sensor 20 gradually increases during the time T2 required for the total supply amount M1 of the atmosphere to reach the predetermined amount M2 (g). When the oxygen concentration in the exhaust pipe 120 approaches the oxygen concentration in the atmosphere, the value of the output value Ipb 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 value Ipb pulsates. In the period of time T2 in FIG. 2, the output value Ipb actually increases gradually while pulsating, but the illustration of pulsation is omitted. In the following description, when a specific output value is described, it is represented by a code such as the output value 201, and when the output value is not specified, it is described as an output value Ipb. Also, the output values 201 to 209 indicated by “●” in FIG. 2 represent the output value Ipb when the crank angle is 180 degrees.

  Next, an example of the relationship between the change in the crank angle and the pulsation of the output value Ipb during the fuel cutoff period will be described with reference to FIG. In FIG. 3, the relationship between the time and the crank angle during the fuel cut-off period (upper graph in the drawing), and the relationship between the time during the fuel cut-off period and the output value Ipb of the mounted oxygen sensor 20 (lower graph in the drawing). Represents. The pulsation is generated depending on the pressure fluctuation in the exhaust pipe 120 due to the piston motion in each cylinder of the internal combustion engine 100. The piston motion of each cylinder corresponds to the crank angle, and one cycle of piston motion (intake, compression, expansion, exhaust stroke) is performed while the crank angle changes from 0 degrees to 360 degrees. That is, the magnitude of the crank angle is linked to the operating state of the internal combustion engine (intake, compression, expansion, exhaust stroke of each cylinder). For this reason, the magnitude of the crank angle is linked to the fluctuation of the atmospheric pressure in the exhaust pipe 120 and further linked to the pulsation of the output value Ipb of the mounted oxygen sensor 20. Therefore, as shown in FIG. 3, the values of the output values Ipb in the periods 31, 32, and 33 in which the crank angle changes from 0 degrees to 360 degrees show similar fluctuations in the respective periods. For this reason, output values 210 to 213 of the same crank angle “180 degrees” are close to each other.

  Next, the first main process executed by the CPU 2 of the oxygen sensor control apparatus 10 will be described with reference to FIG. The first main process is started when power is supplied to the oxygen sensor control device 10. By performing the first main process, the correction coefficient Kp is updated. In the following description, the variable N is a variable for counting the number of output values Ipb for calculating a weighted average value Ipc (described later). The maximum value Ipd is the maximum value of the weighted average value Ipc calculated during one fuel cut-off period. The representative value Ipe is a value representative of the output value Ipb of the mounted oxygen sensor 20 during one fuel cut-off period. Further, a step in the flowchart is abbreviated as “S”.

  In the first main process, first, it is determined whether or not a fuel cut is newly started (S1). In the internal combustion engine 100, the oxygen sensor control device 10 outputs an instruction that the fuel injection amount from the injector 104 becomes zero in accordance with operating conditions such as the deceleration of the vehicle and the state of the intake air amount. In S1, it is determined whether or not fuel cutoff has been started by detecting the presence or absence of the output of this instruction. When the fuel cut-off has not been started (S1: NO), the process returns to S1.

  When the fuel cut-off is started (S1: YES), the total supply amount M1, which is the total amount of air supplied to the exhaust pipe 120 during the fuel cut-off period, is set to “0” (S2). 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 total supply amount M1 is calculated (S3). Next, it is determined whether or not the total supply amount M1 calculated in S3 in a single fuel cut-off period is equal to or greater than a predetermined amount M2 (see FIG. 2) (S4). It is assumed that the value of the predetermined amount M2 is stored in the nonvolatile memory 8 (the same applies to the value of the predetermined angle described later). If the total supply amount M1 is not equal to or greater than the predetermined amount M2 (S4: NO), it is determined whether or not the fuel cut-off has ended (S5). When the fuel cut-off has not been completed (S5: NO), the process returns to S3. That is, the oxygen sensor control device 10 stands by until the total supply amount M1 during the fuel cut-off period is equal to or greater than the predetermined amount M2 or during which the fuel cut-off is completed.

  If the fuel cut is terminated before the total supply amount M1 becomes equal to or greater than the predetermined amount M2 (S5: YES), the process returns to S1. When the fuel cut continues and the total supply amount M1 becomes equal to or greater than the predetermined amount M2 (S4: YES), the maximum value Ipd is set to “0” and the representative value Ipe is set to “0” (S6). . Next, the variable N is set to “0” (S7). The maximum value Ipd, the representative value Ipe, and the variable N are stored in the RAM 4.

  Next, it is determined whether or not fuel cut-off has been completed (S8). If the fuel cut-off has not been completed (S8: NO), the output signal of the crank angle sensor 108 is acquired (S9). Next, a crank angle based on the output signal acquired in S9 is specified, and it is determined whether or not the crank angle is a predetermined angle (S10). In the present embodiment, it is assumed that the predetermined angle is “180 degrees”. If the crank angle is not “180 degrees” (S10: NO), the process returns to S8. That is, the acquisition of the output signal of the crank angle sensor 108 is repeated in S9 until the crank angle reaches a predetermined angle.

When the crank angle is “180 degrees” (S10: YES), the output value Ipb of the mounted oxygen sensor 20 is acquired (S11). Thereby, for example, an output value 201 (see FIG. 2) having a crank angle of “180 degrees” is acquired. Next, the output value Ipb of the mounted oxygen sensor 20 acquired in S11 is stored in the RAM 4 (S12). Next, the variable N is incremented and incremented by 1 (S13). Next, the following equation (1) is used to calculate the weighted average value Ipc of the output value Ipb (S14).
Ipc = 1/3 {Ipb-Ipc (N-1)} + Ipc (N-1) (1)

  “Ipc (N−1)” in the formula (1) is a weighted average value calculated immediately before. Note that immediately after the start of calculation of the weighted average value Ipc (when the variable N = 1) during the fuel cut-off period, there is no “Ipc (N−1)”, so the output value Ipb obtained when the variable N = 1. The weighted average value Ipc is calculated by substituting (output value 201 in the example of FIG. 2) into “Ipc (N−1)”.

  Next, the weighted average value Ipc calculated in S14 is stored in the RAM 4 (S15). Next, it is determined whether or not the variable N is “3” or more (S16). When the variable N is not “3” or more (S16: NO), the process returns to S8. On the other hand, when the variable N is “3” or more (S16: YES), it is determined whether or not the weighted average value Ipc newly calculated in S14 and newly stored in S15 is greater than the maximum value Ipd. (S17). When the weighted average value Ipc is larger than the maximum value Ipd (S17: YES), the weighted average value Ipc is substituted for the maximum value Ipd, and the maximum value Ipd is updated (S18). That is, so-called peak hold is performed. Next, the process returns to S8. If the weighted average value Ipc is not greater than the maximum value Ipd (S17: NO), the process returns to S8. That is, the maximum value Ipd is not updated.

  When S8 to S18 are repeated, for example, output values 201 to 209 (see FIG. 2) are sequentially acquired (S11), and a weighted average value Ipc is calculated (S14). If the calculated weighted average value Ipc is greater than the maximum value Ipd (S17: YES), the maximum value Ipd is updated (S18). Similar processing is performed for the subsequent output values.

  When the fuel cutoff is finished (S8: YES), the maximum value Ipd is set as the representative value Ipe (S19). Thus, the maximum value Ipd of the weighted average value Ipc of the output value Ipb in the fuel cutoff period is determined as the representative value Ipe. Next, it is determined whether or not the representative value Ipe is greater than “0” (S20). The case where the representative value Ipe becomes “0” is a case where the fuel cut-off is completed before S18 is performed (S8: YES). When the representative value Ipe is “0” (S20: NO), the process returns to S1 and waits for the next fuel cut.

  On the other hand, if it is determined in S20 that the representative value Ipe is greater than “0” (S20: YES), a new correction coefficient Kp is calculated (S21). In S21, a new correction coefficient Kp is calculated so that a correction value Ipf obtained by multiplying the output value Ipb and the correction coefficient Kp during the fuel cutoff period approaches a preset reference value Ipa (4 mA). In the present embodiment, a new correction coefficient Kp is calculated by dividing the reference value Ipa by the representative value Ipe in S21 (that is, “new correction coefficient Kp = reference value Ipa / representative value Ipe”). Perform the operation).

  Next, the correction coefficient Kp calculated in S21 is updated and stored in the nonvolatile memory 8 (S22). That is, the relationship between the output value Ipb of the mounted oxygen sensor 20 attached to the internal combustion engine 100 and the oxygen concentration is calibrated. Next, the process returns to S1. Since the correction coefficient Kp is newly calculated, the CPU 2 uses the latest correction coefficient Kp when the fuel is supplied to the internal combustion engine 100 (in the case other than the fuel cut-off period), and the oxygen concentration of the exhaust gas. Can be detected with high accuracy. For this reason, the internal combustion engine 100 can be operated at an appropriate air-fuel ratio.

  As described above, the first main process in the present embodiment is executed. In the present embodiment, even if the output value Ipb pulsates, as shown in FIG. 3, when the crank angle is “180 degrees”, the output values 210 to 213 acquired in S11 are close to each other. . In other words, the variation width of the output values 210 to 213 is smaller than the amplitude of the pulsation (the same applies to the output values 201 to 209 shown in FIG. 2). Since the correction coefficient Kp is calculated using the output value Ipb having a small variation width, the influence of the pulsation of the output value Ipb on the calculation of the correction coefficient Kp can be reduced. Therefore, the correction coefficient Kp can be calculated with high accuracy even under the pulsating output value Ipb of the mounted oxygen sensor 20.

  In the present embodiment, the representative value Ipe used for calculating the correction coefficient Kp is the maximum value Ipd of the plurality of weighted average values Ipc. The weighted average value Ipc is a weighted average value of the plurality of output values Ipb. That is, the correction coefficient Kp is calculated based on the representative value Ipe based on the plurality of output values Ipb and the reference value Ipa. Since the correction coefficient Kp is calculated based on the plurality of output values Ipb, it is possible to prevent the correction coefficient Kp from being calculated based on one output value Ipb including accidental noise, and to reduce the individual output values Ipb. The influence of variation can be reduced, and the correction coefficient Kp can be calculated with high accuracy.

  In the present embodiment, when the variable N is “3” or more (S16: YES), the maximum value Ipd is updated in S18. For this reason, when the variable N is 2 or less, the weighted average value Ipc calculated in S14 is not set to the maximum value Ipd and is not set to the representative value Ipe. That is, the weighted average value Ipc reflecting at least three output values Ipb is set as the representative value Ipe. For this reason, it is possible to reduce the influence of accidental noise, and to calculate the correction coefficient Kp with high accuracy.

  In the present embodiment, when the total supply amount M1 of the atmosphere becomes equal to or greater than the predetermined amount M2 (S4: YES), the output value Ipb of the mounted oxygen sensor 20 is acquired (S11). For this reason, since the output value Ipb of the mounted oxygen sensor 20 can be reliably obtained in an environment where the inside of the exhaust pipe 120 is in a substantially atmospheric atmosphere, the correction coefficient Kp can be calculated with high accuracy.

  In the present embodiment, the mounted oxygen sensor 20 corresponds to the “oxygen sensor” of the present invention, and the nonvolatile memory 8 corresponds to the “storage unit” of the present invention. The CPU 2 that performs the process of S9 in FIG. 4 corresponds to the “output signal acquisition unit” of the present invention, and the CPU 2 that performs the process of S10 corresponds to the “crank angle determination unit” of the present invention. The CPU 2 that performs the process of S11 corresponds to the “output value acquisition unit” of the present invention, and the CPU 2 that performs the process of S21 corresponds to the “correction coefficient calculation unit” of the present invention. The CPU 2 that performs the process of S22 corresponds to the “storage control unit” of the present invention, and the air flow meter 107 corresponds to the “supply amount measuring unit” of the present invention. The CPU 2 that performs the process of S3 corresponds to the “total supply amount calculation unit” of the present invention, and the CPU 2 that performs the process of S4 corresponds to the “total supply amount determination unit” of the present invention.

  In addition, this invention is not limited to said embodiment, A various change is possible. For example, the representative value Ipe is the maximum value Ipd of the weighted average value Ipc of the plurality of output values Ipb, but is not limited thereto. For example, a weighted average value newly calculated using a plurality of weighted average values Ipc may be used. Further, it may be the maximum value of the plurality of output values Ipb. Further, it may be one output value Ipb during the fuel cutoff period (for example, an output value Ipb indicating the maximum value during the fuel cutoff period). Further, the remaining three weighted average values excluding the maximum value and the minimum value among the five output values Ipb may be used. Further, it may be a correction value Ipf obtained by multiplying the output value Ipb during the fuel cutoff period and the correction coefficient Kp, or may be a weighted average value of the correction value Ipf during the fuel cutoff period. For example, when calculating the correction coefficient Kp based on the correction value Ipf, a new correction coefficient Kp is calculated by dividing the reference value Ipa by the value obtained by dividing the correction value Ipf by the current correction coefficient Kp. (That is, a new correction coefficient Kp = reference value Ipa / (correction value Ipf / current correction coefficient Kp) is calculated). Even when the representative value Ipe is set and the correction coefficient Kp is calculated as described above, since the output value Ipb is acquired at a constant crank angle, the correction coefficient Kp can be calculated with high accuracy.

  Moreover, although S6-S22 was performed and the correction coefficient Kp was updated for every fuel cut-off period, it is not limited to this. For example, the correction coefficient Kp may be updated at a rate of once every predetermined number of fuel cut-off periods set to two or more times.

  Further, the reference value Ipa is the value of the current output when the reference oxygen sensor is exposed to the atmospheric atmosphere (oxygen concentration of about 20.5%), but is not limited thereto. For example, the reference value Ipa may be a value that is arbitrarily set according to the design.

  The mounted oxygen sensor 20 is not limited to a two-cell air-fuel ratio sensor, and may be a one-cell oxygen sensor. The mounted oxygen sensor 20 may be a sensor having an oxygen concentration detection function (for example, a NOx sensor with an oxygen concentration detection function). Further, the averaging process for calculating all the weighted average values such as the weighted average value Ipc is not limited to the weighted average process, and for example, an average value obtained by performing an arithmetic average process or a moving average process is calculated. May be.

  Further, the first main process may be simplified by omitting the process using the variable N (for example, the processes of S7, S13, and S16). In this case, for example, when the output values are acquired sequentially (S11), the weighted average value may be calculated sequentially (S14), and the maximum value may be updated (S18). In this case, the variable N is used for “Ipc (N−1)” in Equation (1), but this “Ipc (N−1)” is the weighted average value calculated immediately before. Therefore, in S14, a new weighted average value may be calculated using the weighted average value calculated immediately before.

  Moreover, although the oxygen sensor control apparatus 10 had the function of ECU, it is not limited to this. For example, the correction coefficient Kp may be updated by being configured separately from the ECU and transmitting from the ECU that the fuel cut has been started or by transmitting the calculated correction coefficient Kp to the ECU.

  As shown in FIG. 3, the CPU 2 can measure a crank angle of 0 degrees to 360 degrees based on the output signal of the crank angle sensor 108, but is not limited to this. For example, an output signal is output from the crank angle sensor 108 at two crank angles of 180 degrees and 360 degrees in one cycle of piston motion of the internal combustion engine 100, and the CPU 2 outputs 180 degrees and 360 degrees. And may be measurable. In this case, when either crank angle is 180 degrees or 360 degrees, the output value Ipb of the mounted oxygen sensor 20 may be acquired to calculate the correction coefficient Kp. Further, for example, in the case of a 4-stroke engine or the like, since one cycle is constituted by two rotations of the crankshaft 109, the crank angle varies between 0 degrees and 720 degrees. Therefore, the CPU 2 can measure a crank angle of 0 to 720 degrees based on the output signal of the crank angle sensor 108, and obtains the output value Ipb at a constant crank angle between 0 and 720 degrees. May be.

  In the main process (see FIG. 4), when the total supply amount M1 of the atmosphere becomes equal to or larger than the predetermined amount M2 in one fuel cut-off period (S4: YES), the crank angle is a predetermined angle (180 degrees). It is determined whether or not the above has been reached (S10), and the output value Ipb has been acquired (S11). The time during which the exhaust pipe 120 is in the air atmosphere varies depending on the engine speed during the fuel cut-off period, but if the total supply amount M1 of the air is equal to or greater than the predetermined amount M2, the inside of the exhaust pipe 120 becomes the air atmosphere. . Therefore, it is desirable to start acquiring the output value Ipb based on the total supply amount M1 as in the present embodiment. However, it is not limited to this. For example, in a single fuel cut-off period, when a predetermined time T2 (see FIG. 2) has elapsed since the start of the fuel cut-off (that is, it is necessary for the exhaust pipe 120 to be in an air atmosphere). When the time T2 has elapsed), it may be determined whether or not the crank angle has become a predetermined angle (180 degrees), and the output value Ipb may be acquired. Hereinafter, this case will be described with reference to the second main process shown in FIG.

  The second main process shown in FIG. 5 is a modification of the first main process (see FIG. 4). More specifically, S2 to S4 of the first main process are deleted, and S31 to S34 are added. In the following description, the same processes as the first main process are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the second main process, first, as in the first main process, it is determined whether or not a fuel cutoff is newly started (S1). When the fuel cutoff is newly started (S1: YES), the time T1 is set to “0” (S31). Time T1 indicates an elapsed time since the start of fuel cut-off. Next, measurement of time T1 is started (S32). The CPU 2 measures time T1 using a clock signal of a vibrator (not shown). A separate timer may be provided, and the CPU 2 may be configured to measure the time T1 using the timer.

  Next, it is determined whether or not the time T1 is equal to or greater than the time T2 (S33). That is, it is determined whether or not the elapsed time from the start of fuel cut has exceeded a predetermined time T2 (see FIG. 2) set in advance. If the time T1 is not equal to or longer than the time T2 (S33: NO), it is determined whether or not the fuel cut-off has ended (S5). If the fuel cut-off has not been completed (S5: NO), the process returns to S33. When the fuel cut-off is completed (S5: YES), the process returns to S1. When the time T1 becomes equal to or longer than the time T2 (S33: YES), the measurement of the time T1 is ended (S34). Then, similarly to the first main process, S6 to S22 are executed, and the correction coefficient Kp is updated.

  In the present embodiment, a time T2 (see FIG. 2) necessary for the inside of the exhaust pipe 120 to become a substantially atmospheric atmosphere is set as a predetermined time. Then, when the time T1 after the start of the fuel cut has passed the time T2 (S33: YES), and when the crank angle becomes a predetermined angle (180 degrees) (S10: YES), the mounted oxygen sensor The output value Ipb of 20 is acquired (S11). Then, a new correction coefficient Kp is calculated (S21). As described above, since the output value Ipb of the mounted oxygen sensor 20 can be acquired in an environment where the time T2 has elapsed and the inside of the exhaust pipe 120 is in a substantially atmospheric atmosphere, the correction coefficient Kp can be calculated with high accuracy. In the present embodiment, the CPU 2 that performs the process of S33 corresponds to the “elapsed time determination means” of the present invention.

1 Engine control system 2 CPU
8 Nonvolatile memory 10 Oxygen sensor control device 20 Mounted oxygen sensor 100 Internal combustion engine 107 Air flow meter 108 Crank angle sensor 109 Crankshaft 120 Exhaust pipe Ipa Reference value Ipb Output value Ipe Typical value Kp Correction coefficient M1 Total supply amount M2 Predetermined amount

Claims (3)

Storage means for storing a correction coefficient for calibrating the relationship between the output value of the oxygen sensor attached to the exhaust pipe of the internal combustion engine and the oxygen concentration, and the correction coefficient stored in the storage means and the oxygen sensor In the oxygen sensor control device for detecting the oxygen concentration of the exhaust gas flowing through the exhaust pipe using the output value,
Output signal acquisition means for acquiring an output signal of a crank angle sensor for detecting a crank angle of the internal combustion engine;
The crank angle based on the output signal acquired by the output signal acquisition means is a predetermined angle set in advance during a fuel cutoff period, which is a period during which a fuel cutoff for stopping the fuel supply of the internal combustion engine is performed. Crank angle judging means for judging whether or not,
Output value acquisition means for acquiring the output value of the oxygen sensor when the crank angle determination means determines that the crank angle is the predetermined angle;
Correction coefficient calculation means for calculating a new correction coefficient based on the output value acquired by the output value acquisition means during the fuel cutoff period;
Storage control means for storing the correction coefficient calculated by the correction coefficient calculation means in the storage means ;
Representative value determining means for determining a representative value that is a value representative of the output value during the fuel cutoff period based on the plurality of output values acquired by the output value acquiring means during the fuel cutoff period;
With
The correction coefficient calculating means is configured to determine the representative value determined by the representative value determining means so that a correction value obtained by multiplying the output value and the correction coefficient during the fuel cutoff period approaches a preset reference value. And a new correction coefficient based on the reference value and
Each time the output value is acquired by the output value acquisition unit, the representative value determination unit sequentially calculates a value obtained by averaging a plurality of the output values, and sequentially performs the plurality of the averaged processings An oxygen sensor control device , wherein a maximum value which is the largest value among the values is determined as the representative value . 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 crank angle determination means determines the crank angle based on the output signal acquired by the output signal acquisition means when the total supply amount determination means determines that the total supply amount is equal to or greater than the predetermined amount. , the oxygen sensor control device according to claim 1, characterized in that determining whether the a predetermined angle. Elapsed time determination means for determining whether or not an elapsed time from the start of the fuel cutoff in a single fuel cutoff period has passed a predetermined time,
The crank angle determination means is configured to output the output acquired by the output signal acquisition means when the elapsed time determination means determines that the elapsed time from the start of fuel cutoff has passed the predetermined time. 3. The oxygen sensor control device according to claim 1, wherein whether or not the crank angle based on the signal is the predetermined angle is determined.

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