JP5565269B2 - Exhaust gas sensor signal processing device - Google Patents

Description

  The present invention relates to a signal processing device for an exhaust gas sensor.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2010-38794, an exhaust gas sensor signal processing apparatus that corrects the output of an exhaust gas sensor in accordance with the degree of influence of exhaust pulsation is known. An exhaust gas sensor signal processing device according to the above publication determines an influence degree of exhaust pulsation in an exhaust passage of an internal combustion engine, and an embodiment of sensor output smoothing calculation based on the determination result (specifically, calculation contents) And the execution and stop of smoothing calculation).

  Variations in exhaust pressure (exhaust pulsation) in the exhaust passage cause variations in the output value of an exhaust gas sensor (specifically, for example, an air-fuel ratio sensor). A technique for performing so-called “smoothing calculation” against the influence of such exhaust pulsation is known. The annealing calculation is an arithmetic process that averages time-series data so as to obtain a moving average process, and the output change can be smoothed in the time direction.

  While the annealing calculation can suppress the influence of exhaust pulsation, since the moving average process is performed, the response to an actual change in the gas atmosphere is lowered. In this regard, in the above publication, attention is paid to the fact that the influence of the pressure fluctuation in the exhaust passage on the exhaust gas sensor output is not constant, but changes depending on the gas atmosphere, the operating state of the internal combustion engine, and the like. In the above publication, the degree of influence due to pressure fluctuation in the exhaust passage is determined, and the mode of the smoothing calculation is changed based on the determination result. As a result, both reduction of sensor output fluctuation caused by pressure fluctuation of the gas atmosphere and securing of responsiveness of the sensor output are achieved.

JP 2010-38794 A JP 2004-150379 A

  In the above-mentioned publication relating to the above-mentioned prior art, the degree of influence of pressure fluctuation in the exhaust passage on the sensor output is (1) the gas atmosphere in the exhaust passage, (2) the rotational speed of the internal combustion engine, and (3) the inside of the exhaust passage. It is explained that it fluctuates according to each item of the pressure change rate. In the signal processing device for an exhaust gas sensor according to the above-described conventional technology, it is determined that the influence degree of pulsation is small, as described in paragraph 0017 of the publication, based on the matters (1) to (3) above. Sometimes, measures are taken not to perform the annealing calculation (or to reduce the annealing rate of the annealing calculation).

  However, in the above conventional technology, how much the exhaust pulsation actually affects the exhaust gas sensor output (contribution to exhaust gas sensor output fluctuation) and how much the contribution varies depending on the operating state of the internal combustion engine. It has not yet been possible to accurately add the matter of whether to do so to the correction contents of the sensor output. In this regard, there is still room for improvement from the viewpoint of accurately sensing exhaust gas while suppressing the influence of exhaust pulsation.

  The present invention has been made in order to solve the above-described problems. The exhaust gas sensor signal processing is capable of correcting the output value of the exhaust gas sensor in consideration of the influence of exhaust pulsation on the exhaust gas sensor output. An object is to provide an apparatus.

In order to achieve the above object, a first invention is a signal processing device for an exhaust gas sensor,
Output acquisition means for acquiring an output of an exhaust gas sensor provided in an exhaust passage of the internal combustion engine;
The exhaust gas sensor based on a pulsation influence value, which is a value representing the magnitude of the influence of the pulsation on the exhaust gas sensor, obtained based on the magnitude of the amplitude in the vibration waveform of the output of the exhaust gas sensor due to exhaust pulsation Correction means for correcting the output value of
Equipped with a,
The internal combustion engine has a plurality of cylinders,
Detection means for detecting variations in the air-fuel ratio among the plurality of cylinders based on the output of the exhaust gas sensor;
Correction content changing means for changing the correction amount or content of the correction means for the output value of the exhaust gas sensor based on whether or not the variation is detected by the detection means or the degree of the variation;
Further comprising wherein the Rukoto a.

The second invention is the first invention, wherein
The internal combustion engine has a plurality of cylinders,
The correction means includes
Cylinder output value acquisition means for acquiring a cylinder specific output value that is an output value of the exhaust gas sensor according to combustion of each of the plurality of cylinders in the vibration waveform of the output of the exhaust gas sensor;
A value obtained by averaging the deviation amount of the output value of each cylinder of the plurality of cylinders with respect to the center of the amplitude of the vibration waveform of the output of the exhaust gas sensor according to the number of cylinders of the internal combustion engine. An amplitude calculating means for calculating the amplitude;
Means for treating the value calculated as the amplitude by the amplitude calculating means as the pulsation influence value and correcting the output value of the exhaust gas sensor;
It is characterized by including.

The third invention is the first or second invention, wherein
The correction means includes
Amplitude acquisition means for determining the amplitude of the vibration waveform of the output of the exhaust gas sensor due to exhaust pulsation;
Learning means for updating the pulsation influence value or a correction amount when performing correction based on the pulsation influence value at a predetermined period based on the magnitude of the amplitude obtained by the amplitude acquisition means;
It is characterized by including.

Moreover, 4th invention is any one of 1st- 3rd invention,
The correction means includes
A first correction means for calculating a value obtained by smoothing an output change of the exhaust gas sensor in a time direction according to the pulsation influence value as a current output value after correction;
The value obtained by smoothing the output change of the exhaust gas sensor in the time direction so as to make the degree of smoothing according to the pulsation influence value smaller than the degree of smoothing by the first correcting means is Second correcting means for calculating the corrected output value;
Including
The correction content changing means includes
If the variation is relatively small based on whether or not the variation is detected by the detection unit, the output value of the exhaust gas sensor is corrected by the first correction unit when the variation is relatively small. Means for selectively executing the first correction means and the second correction means so that the output value of the exhaust gas sensor is corrected by the second correction means when the second correction means is relatively large. Features.

Moreover, 5th invention is based on any one of 1st- 4th invention,
The correction content changing means includes switching means for switching execution and stop of the correction of the correction means based on whether or not the variation is detected by the detection means or the degree of the variation.

Moreover, 6th invention in any one of 1-5 invention,
The detection means includes
First determination means for determining presence / absence of abnormality in air-fuel ratio variation among the plurality of cylinders based on the order of expression of the maximum value and / or minimum value in the vibration waveform of the exhaust gas sensor;
Based on a comparison between the maximum value or / and minimum value of the vibration waveform of the exhaust gas sensor and the magnitude of pulsation of the exhaust gas sensor determined by the pulsation influence value, variations in the air-fuel ratio among the plurality of cylinders Second determination means for determining presence or absence of abnormality;
Third determination means for determining whether there is an abnormality in air-fuel ratio variation among the plurality of cylinders based on whether an output value of the exhaust gas sensor is in accordance with a characteristic of a predetermined normal waveform;
Fourth determination means for determining presence / absence of an abnormality in air-fuel ratio variation among the plurality of cylinders based on variations in maximum and minimum values in the vibration waveform of the exhaust gas sensor;
Including at least one means.

According to the first aspect of the invention, the magnitude of the amplitude in the vibration waveform of the exhaust gas sensor output due to the exhaust pulsation is handled as the magnitude of the influence of the pulsation received by the exhaust gas sensor, thereby taking into account the degree of influence of the exhaust pulsation on the exhaust gas sensor output. In addition, the output value of the exhaust gas sensor can be corrected. Furthermore, in the multiple cylinder internal combustion engine, the degree of correction of the output value of the exhaust gas sensor can be changed according to the degree of variation in the air-fuel ratio between the cylinders. When the variation in the air-fuel ratio between cylinders (so-called imbalance) occurs, the output of the exhaust gas sensor differs from the normal state. According to the first invention, it is possible to prevent the detection accuracy of the exhaust gas sensor from deteriorating by making the same correction as in the normal state.

  According to the second invention, the exhaust gas sensor output value in the multi-cylinder internal combustion engine is taken into account in the multi-cylinder internal combustion engine by taking into account that the amplitude of the exhaust gas sensor output value changes due to the difference in air-fuel ratio among the cylinders in the multi-cylinder internal combustion engine. It is possible to accurately correct the influence of exhaust pulsation on the gas sensor.

  According to the third invention, since the pulsation influence value can be updated by the learning means in accordance with the state of the internal combustion engine, the degree of influence of the exhaust pulsation on the exhaust gas sensor output is considered in accordance with the current state of the internal combustion engine. can do.

According to the fourth aspect of the invention, when correcting the output value of the exhaust gas sensor, the correction of the relatively large degree and the relatively small value are performed in accordance with the degree of variation of the air-fuel ratio among the cylinders in the multiple cylinder internal combustion engine. The degree correction can be selectively executed.

According to the fifth aspect of the present invention, it is possible to switch between execution and stop of correction of the output value of the exhaust gas sensor in accordance with the degree of variation in the air-fuel ratio between the cylinders in the multi-cylinder internal combustion engine. Thereby, under the situation where the variation in the air-fuel ratio between the cylinders becomes a problem, the correction itself can be prohibited, and the detection accuracy by the exhaust gas sensor can be surely suppressed.

According to the sixth aspect of the invention, it is possible to accurately determine an abnormality in the air-fuel ratio variation between the cylinders using the output of the exhaust gas sensor.

1 is an overall configuration diagram for explaining an exhaust gas sensor signal processing device according to a first embodiment of the present invention and an internal combustion engine system to which the signal processing device is applied; FIG. It is a figure for demonstrating operation | movement of the signal processing apparatus of the exhaust gas sensor concerning Embodiment 1 of this invention. It is a figure for demonstrating operation | movement of the signal processing apparatus of the exhaust gas sensor concerning Embodiment 1 of this invention. It is a flowchart of the routine which ECU performs in Embodiment 1 of this invention. FIG. 10 is a diagram for explaining the operation of the signal processing device for the exhaust gas sensor according to the second embodiment. It is a flowchart of the routine which ECU performs in Embodiment 2 of this invention.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is an overall configuration diagram for explaining an exhaust gas sensor signal processing device according to a first embodiment of the present invention and an internal combustion engine system to which the signal processing device is applied. The exhaust gas sensor signal processing apparatus according to this embodiment is mounted on an internal combustion engine of a moving body such as a vehicle. The type of the vehicle or the like is not particularly limited, and the signal processing apparatus for the exhaust gas sensor according to the present embodiment may be applied to an internal combustion engine in an FFV (Flexible Fuel Vehicle) or a hybrid vehicle.

  In FIG. 1, an internal combustion engine (hereinafter, engine 10) is shown as indicated by reference numeral 10. In each cylinder of the engine 10, a combustion chamber 14 is formed by a piston 12, and the piston 12 is connected to a crankshaft 16 of the engine. The engine 10 also includes an intake passage 18 that sucks intake air into each cylinder, and an exhaust passage 20 through which exhaust gas is discharged from each cylinder. In FIG. 1, only one cylinder of the engine 10 is shown, but in this embodiment, the engine 10 has a plurality of cylinders.

  The intake passage 18 is provided with an electronically controlled throttle valve 22 that adjusts the intake air amount based on the accelerator opening and the like. On the other hand, the exhaust passage 20 is provided with a catalyst 24 for purifying the exhaust gas. Each cylinder has an intake port injection valve 26 for injecting fuel into the intake port, an ignition plug 30 for igniting an air-fuel mixture in the cylinder, and an intake valve 32 for opening and closing the intake port with respect to the cylinder. An exhaust valve 34 that opens and closes the exhaust port with respect to the inside of the cylinder is provided.

  Furthermore, the system according to the present embodiment includes a sensor system including a crank angle sensor 36, an air flow sensor 38, an air-fuel ratio sensor 40, and the like, and an ECU (Electronic Control Unit) 50 that controls the operating state of the engine 10. . First, the sensor system will be described. The crank angle sensor 36 outputs a signal synchronized with the rotation of the crankshaft 16, and the air flow sensor 38 detects the intake air amount. The air-fuel ratio sensor 40 is an exhaust gas sensor that detects the exhaust air-fuel ratio upstream of the catalyst 24. In the present embodiment, the air-fuel ratio sensor 40 is a limiting current type air-fuel ratio sensor including a diffusion layer having a predetermined thickness and having a predetermined porosity.

  In the sensor system, in addition to the sensors 36 to 44 described above, various sensors (for example, a water temperature sensor for detecting the cooling water temperature of the engine, an accelerator for detecting the accelerator opening degree) required for controlling the engine 10 and the vehicle on which the engine 10 is mounted. Opening sensors, etc.), and these sensors are connected to the input side of the ECU 50. Various actuators including a throttle valve 22, an injection valve 26, a spark plug 30, and the like are connected to the output side of the ECU 50.

  The ECU 50 detects the engine operation information by the sensor system and drives each actuator to execute the operation control. Specifically, the engine speed and the crank angle are detected based on the output of the crank angle sensor 36, and the intake air amount is calculated based on the output of the air flow sensor 38. Further, the engine load is calculated based on the intake air amount, the engine speed, and the like, and the fuel injection timing is determined based on the crank angle. Further, the fuel injection amount is calculated based on the intake air amount, the load, and the like. When the fuel injection timing comes, the injection valve 26 is driven, and the spark plug 30 is driven. By executing EFI (Electronic Fuel Injection) control in this way, the engine can be operated by burning the air-fuel mixture in the cylinder. Further, the ECU 50 executes air-fuel ratio feedback control for controlling the air-fuel ratio to the target air-fuel ratio based on the output of the air-fuel ratio sensor 40.

[Operation of Embodiment 1]
2 and 3 are diagrams for explaining the operation of the signal processing apparatus for the exhaust gas sensor according to the first embodiment of the present invention.

(Calculation of correction A / F after pulsation effect correction)
FIG. 2 is a diagram showing how the output of the air-fuel ratio sensor 40 oscillates with time as the crank angle CA increases within one cycle. It is assumed that the crank angle CA reaches one cycle at 720 °. In the present embodiment, the amplitude in the vibration waveform of the air-fuel ratio sensor 40 is considered as a pulsation influence value A as indicated by an arrow in FIG.
In the first embodiment, the influence of pulsation is corrected according to the pulsation under each operating condition. That is, the pulsation effect in the cycle becomes larger as the operating range of the internal combustion engine is lower and the higher the load. Therefore, the output value of the air-fuel ratio sensor 40 is corrected based on the rotational speed and the intake air amount (load) so as to eliminate the pulsation effect.

In the first embodiment, the ECU 50 calculates a correction A / F (n), which is an air-fuel ratio after pulsation effect correction based on the air-fuel ratio sensor 40, according to the following equation (1).
Correction A / F (n) = output (n−1) + (1 / A ′) × (output (n) −output (n−1)) (1)
The ECU 50 performs EFI control using the correction A / F (n).
Here, output (n) is an output value in n cycles, that is, the current cycle, and output (n−1) is an output value in n−1 cycles, that is, the previous cycle. In the above equation, A ′ is a value introduced to reflect the pulsation influence value A in the correction of the sensor output (hereinafter, “pulsation influence correction amount”). This A ′ is a numerical value given according to the operating conditions of the engine 10. For example, A ′ corresponds to the fact that the pulsation effect in the cycle becomes larger as the operating range of the internal combustion engine is lower and the load is higher. It can be prescribed. Then, the ECU 50 may detect the rotational speed and the load based on the outputs of the crank angle sensor 36 and the air flow sensor 38 and acquire A ′ according to the current operating conditions.

(Correction amount learning)
FIG. 4 is a diagram for explaining the learning operation of the pulsation effect correction amount in the signal processing apparatus for the exhaust gas sensor according to the first embodiment.
Strictly speaking, even if the air-fuel ratio sensors have the same specifications, the characteristics are not completely the same, and there is a slight deviation in the characteristics for each individual. For this reason, when actually applying to the engine 10, it is preferable to grasp and learn the pulsation effect for each individual. Therefore, in the first embodiment, the pulsation effect of each air-fuel ratio sensor 40 is grasped and learned under the operating condition where the pulsation is known. The significance of each air-fuel ratio sensor 40 here is to compare the individual air-fuel ratio sensors 40 when a plurality of air-fuel ratio sensors 40 are mounted on one internal combustion engine, or to one internal combustion engine. It includes the meaning of comparing each air-fuel ratio sensor 40 between different internal combustion engines when the air-fuel ratio sensor 40 is mounted.

  In the first embodiment, the influence of pulsation between individual sensors is grasped based on the sensor output under stable operating conditions represented by fuel cut (F / C). It should be noted that a desired pulsation change may be forcibly given by operating conditions such as idle operation, or by measures such as changing the exhaust valve timing, stopping the cylinder, or changing the compression ratio.

In the first embodiment, the ECU 50 calculates the pulsation influence value A according to the following equation (2).
A = Σ | (acquired value−average value) | / 2 m (2)
However, the characters and symbols written on the right side of the above expression have the following meanings.
m is a value indicating the number of cylinders per air-fuel ratio sensor 40.
The “acquired value” is the maximum value and the minimum value obtained by acquiring the maximum value and the minimum value of the output of the air-fuel ratio sensor 40 at every crank angle of 720 ° / m. Specifically, the black circle in FIG. 3 schematically shows the maximum value and the white circle shows the minimum value. The acquisition of the maximum value and the minimum value may be performed by the ECU 50 sampling the output of the air-fuel ratio sensor 40 at a predetermined cycle.
The “average value” is an average value of the output of the air-fuel ratio sensor 40 and corresponds to the midpoint of the vibration waveform of the air-fuel ratio sensor 40. In FIG. 3, the average value is schematically shown by a broken line that crosses the vibration waveform of the output of the air-fuel ratio sensor 40 at the center thereof.
A value obtained by dividing the deviation between the maximum value and the minimum value with respect to the average value by the number of cylinders × 2 according to the above formula is calculated as the pulsation effect value A.
Based on the pulsation influence value A thus obtained, the value of the pulsation influence correction amount A ′ is updated (for example, the current A ′ is overwritten with the latest A value after performing a predetermined calculation or as it is. Learning process).

[Specific Processing in First Embodiment]
Hereinafter, a specific process performed by the exhaust gas sensor signal processing apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a flowchart of a routine executed by ECU 50 in the first embodiment.

  In the routine shown in FIG. 4, first, the ECU 50 executes a process of starting the engine 10 and determining whether or not the air-fuel ratio sensor 40 is in a sensor active state (step S100). If the establishment of the conditions for this step is not recognized, the current routine is terminated.

  If the establishment of the condition in step S100 is confirmed, then the ECU 50 acquires the output of the air-fuel ratio sensor 40 (step S102). The exhaust pulsation is corrected with respect to the output acquired here. In the first embodiment, it is assumed that the ECU 50 performs a process of sampling and storing the output of the air-fuel ratio sensor 40 at a predetermined period while the engine 10 is operating.

Next, the ECU 50 executes a process for determining whether or not it is a learnable region (step S104). In this step, specifically, it is determined whether or not the engine 10 is operated under a predetermined operating condition in which pulsation is known. As the predetermined operation condition, for example, a stable operation condition represented by fuel cut (F / C) or idle operation is set.
Instead of this, the operating conditions of the engine 10 are forcibly changed to the desired pulsation by changing the operating conditions such as exhaust valve timing change, cylinder stop, compression ratio change, etc. May specify what kind of pulsation occurs). In this case, the processing content of step S104 is, for example, “determination process of whether or not the operation condition change can be added” → “process for executing the operation condition change when it is determined to be possible”. It may be changed.

  If the establishment of the condition of step S104 is confirmed, the ECU 50 next executes a process of calculating a pulsation effect correction amount (step S106). Specifically, the ECU 50 calculates the pulsation effect value A according to the above-described equation (2), and the pulsation effect correction amount A ′ for use in the equation (1) is updated based on the value of A.

  Next, the ECU 50 executes a correction amount learning determination process (step S108). In this step, it is determined whether the correction amount learning is completed.

  After completion of learning based on the correction amount learning determination in step S108, or after determination that the region is not a learnable region in step S104, the ECU 50 subsequently performs pulsation effect correction processing (step S110). In this step, the correction A / F (n) is calculated using the above-described equation (1).

  Subsequently, the ECU 50 executes EFI control using the correction output calculated in step S104, that is, the correction A / F (n) (step S112). Thereafter, the current routine ends.

  According to the above processing, by treating the magnitude of the amplitude in the vibration waveform of the air-fuel ratio sensor output due to the pulsation of the exhaust gas as the magnitude of the influence of the pulsation that the air-fuel ratio sensor 40 receives (pulsation influence value A), the air-fuel ratio sensor The output value of the air-fuel ratio sensor 40 can be corrected in consideration of the degree of influence of exhaust pulsation on the 40 output.

  Further, according to the above processing, an engine having a plurality of cylinders is taken into account by changing the amplitude of the output value of the air-fuel ratio sensor 40 from the difference in air-fuel ratio of each cylinder in the engine 10 having a plurality of cylinders. 10, the influence of the exhaust pulsation on the air-fuel ratio sensor 40 can be accurately corrected.

  Further, according to the above processing, the pulsation effect correction amount A ′ can be updated in accordance with the state of the engine 10 by the learning processing in step S106, so that the air-fuel ratio sensor 40 is adapted to the current state of the engine 10. The degree of influence of exhaust pulsation on the output (latest pulsation influence value A) can be taken into account.

In the first embodiment described above, the pulsation influence value A corresponds to the “pulsation influence value” in the first invention, and the ECU 50 executes the process of step S110 in the flowchart of FIG. The “correction means” in the first invention is realized.
Further, in the above-described first embodiment, the ECU 50 executes the arithmetic processing of the above-described formula (2) in step 106 in the flowchart of FIG. And “amplitude calculation means” are realized.
Further, in the first embodiment described above, the “amplitude acquisition means” and the “learning means” in the third aspect of the present invention are realized by the ECU 50 executing step 106 in the flowchart of FIG.

[Effects and background of the first embodiment]
Hereinafter, in order to explain the effect of the signal processing apparatus for the exhaust gas sensor according to the first embodiment, a technical explanation as the background will be given. As the background of the exhaust gas sensor signal processing apparatus according to the first embodiment, the following matters are mentioned.

・ To reduce emissions and improve OBD detectability, high response and high accuracy of A / F sensor output are required. However, if the actual air-fuel ratio in the cycle is to be detected with higher accuracy, the output deviation increases due to the pulsation effect.
・ Each exhaust gas sensor does not have the same effect due to pulsation, so variations occur and accuracy is low.
・ In order to understand the behavior in the cycle, there is a request to increase the porosity of the diffusion layer. On the other hand, the higher the porosity, the greater the influence of pulsation and the lower the sensing accuracy. There is also a problem that the output shifts due to a difference in gas diffusion rate.

-About sensor structure which improves detectability In order to improve imbalance detectability (improvement of in-cycle followability) with a limit current type A / F sensor, it is necessary to improve sensor response. Although measures to improve sensor response include measures such as cover improvement, “reducing diffusion resistance”, that is, increasing the porosity of the diffusion layer and shortening the diffusion distance are basically useful. However, this technique has the tradeoff of increasing the effects of pulsation. When the reduction of the diffusion resistance is pursued, the output accuracy of the sensor is lowered due to the accompanying increase in pulsation effect, so that the controllability of the exhaust gas is deteriorated and the emission may be deteriorated.
・ About cover improvement When trying to improve responsiveness by improving the cover, water resistance must be sacrificed and reliability cannot be ensured. Therefore, it is necessary to improve the response of the element itself by reducing the diffusion resistance.
As described above, there is a limit in pursuing the reduction of the diffusion resistance from the viewpoint of the pulsation effect, and there is a limit from the viewpoint of the water resistance performance depending on the cover improvement.

  In this regard, the exhaust gas sensor signal processing apparatus according to the first embodiment of the present invention acquires the pulsation effect in each sensor under a specific condition, corrects the air-fuel ratio sensor output based on the pulsation effect rate, and It is possible to improve the air-fuel ratio detectability at. Therefore, in the exhaust gas sensor signal processing apparatus according to the first embodiment, in light of the various technical backgrounds listed above, the pulsation of each environment of each exhaust gas sensor is performed using a technique other than reduction of diffusion resistance and cover improvement. An advantageous effect that the influence can be grasped and corrected can be exhibited.

[Modification of Embodiment 1]
In the first embodiment, the exhaust gas sensor signal processing apparatus according to the present invention is applied to the limit current type air-fuel ratio sensor 40. However, the present invention is not limited to this. The present invention may be applied to an air-fuel ratio sensor other than the limit current type, an oxygen sensor provided in the exhaust passage, and a gas sensor for detecting other specific exhaust gas concentration components such as NOx and HC.

In the first embodiment, the pulsation effect is corrected using Equation (1). In this mathematical expression (1), “the pulsation effect value is calculated based on the previous output value output (n−1) of the air / fuel ratio sensor 40 and the current output change output (n) −output (n−1) of the air / fuel ratio sensor 40. A value obtained by multiplying the value obtained by multiplying the pulsation effect correction amount A ′, which is a coefficient corresponding to A, is calculated as a correction A / F that is the current corrected output value. A value obtained by smoothing the output change of the air-fuel ratio sensor 40 in the time direction using the amount A ′ as a smoothing coefficient is calculated as the current corrected output value.
In the present invention, the specific mathematical formula executed when correcting the pulsation effect is not limited to the mathematical formula (1) in the first embodiment. Various publicly known mathematical formulas for smoothing the output change of the air-fuel ratio sensor or the like in the time direction can be used. That is, a coefficient (smoothing coefficient) that affects the degree of smoothing in the mathematical formula may be determined according to the pulsation influence value A. Then, a value obtained by smoothing the output change of the air-fuel ratio sensor or the like in the time direction according to the smoothing coefficient may be calculated as a correction A / F or the like.

  In the first embodiment, the pulsation effect correction amount A ′ is learned in steps S106 and S108 in the flowchart of FIG. However, the present invention is not limited to this, and learning may not be performed. In that case, based on the pulsation effect A, the characteristics of the pulsation effect correction amount A ′ according to the driving condition are stored in the ECU 50 as a map or a mathematical formula, and the pulsation effect correction amount A according to the driving condition of the engine 10 is stored. It is preferable to change '.

In the first embodiment, the pulsation effect correction amount A ′ is learned using the above mathematical formula (2). However, the present invention is not limited to this. Correction may be performed by following the following procedure.
As a first stage, the ECU 50 executes a process of calculating the magnitude of the amplitude in the vibration waveform of the output of the exhaust gas sensor due to exhaust pulsation.
As a second stage, the ECU 50 executes a process of updating the pulsation influence value A or the pulsation influence correction amount A ′ at a predetermined period based on the obtained amplitude.
With respect to the first stage, in Equation (2), the magnitude of the amplitude at the crank angle of 720 ° is obtained by obtaining the average deviation between the maximum value and the minimum value of the output of the air-fuel ratio sensor 40. However, the average for the crank angle of 720 ° does not necessarily have to be obtained (at least better), or conversely, the average amplitude over a crank angle wider than the crank angle of 720 ° may be obtained. Further, in Equation (2), the absolute value of the difference between the acquired value and the average value is taken so as to take a deviation with respect to both the maximum value and the minimum value, but this is not necessarily limited to this. Deviations may be taken for only the maximum value or only the minimum value (for example, when the vibration waveform is sufficiently symmetrical with respect to the average value (vibration center)).
Further, when obtaining the amplitude, the method is not necessarily limited to the method of obtaining the average deviation for the maximum value and the minimum value. For example, the amplitude may be calculated after specifying the vibration waveform as exemplified in FIG. 2 by fitting the vibration waveform using the output sampling value of the exhaust gas sensor or other waveform specifying methods.
For the second stage, depending on the amplitude value obtained using the various calculation methods, the pulsation effect correction amount A ′ of the first embodiment or the values of various smoothing coefficients described as the above-described modification examples are as follows: If there is a preparation that can be substituted as it is, the value itself can be used, and if it cannot be substituted as it is, it can be increased or decreased by using a predetermined conversion formula.

Embodiment 2. FIG.
The hardware configuration of the exhaust gas sensor signal processing apparatus and its peripheral system according to the second embodiment of the present invention is the same as that of the system according to the first embodiment shown in FIG. In order to avoid redundant description, the hardware configuration is not shown below.

[Operation of Embodiment 2]
FIGS. 5A and 5B are diagrams for explaining the operation of the signal processing apparatus for the exhaust gas sensor according to the second embodiment. FIG. 5A is a diagram illustrating an example of a sensor output waveform in a normal state. On the other hand, when an abnormal state relating to the air-fuel ratio such as an injection system failure occurs, the maximum value and the minimum value of the output of the air-fuel ratio sensor 40 do not appear alternately as shown in FIG. In such a case, if the same correction as in the normal state is performed, a deviation occurs in the actual air-fuel ratio. Therefore, in the second embodiment, abnormality determination (so-called imbalance determination) of the air-fuel ratio variation between cylinders is performed, and the correction method is changed at the time of abnormality.

(Abnormality judgment)
In the second embodiment, first, the cylinder air-fuel ratio variation abnormality determination is executed using at least one of the following determination methods (i) to (iv).
(I) A 1st determination method performs abnormality determination based on the order of expression of the maximum value and the minimum value for every 720 / m (°). As shown in FIG. 5A, when normal, the maximum value and the minimum value should appear alternately at a constant cycle determined by the operating condition (rotation speed). On the other hand, when the output waveform as shown in FIG. 5B appears, when sampling is performed at a constant cycle as in the normal state, the maximum value and the minimum value do not appear alternately, unlike in the normal state. . Therefore, in this method (i), when the order of expression of the maximum value and the minimum value is alternate, it is determined as normal, and when it is not, it is determined as abnormal.
(Ii) In the second determination method, the maximum value and the minimum value are more than the pulsation influence rate (the pulsation influence value A in the first embodiment) with respect to the average value (vibration center) of the vibration waveform. If it is determined to be abnormal.
(Iii) In the third determination method, the output value at the time when the maximum value (or a value on the lean side of the average value) should be taken is a value that is richer than the average value, or is originally the minimum value. If the output value at the time when it should be taken (or a value on the richer side than the average value) has a lean value from the average value, it is determined to be abnormal. The time points of the white circles of S1 and S2 shown in FIG. 5B are the time points when the value on the lower side of the paper surface should appear from the minimum value or at least the average value. However, contrary to such rules, S2 is located above the average value in the drawing. On the other hand, the time points indicated by black circles S3 and S4 shown in FIG. 5B are the time points when the value on the upper side of the paper should appear from the maximum value or the average value. However, contrary to such a rule, S3 and S4 are positioned below the paper surface from the average value. In this way, when it is contrary to the normal characteristics that should be followed, it is determined that the inter-cylinder air-fuel ratio variation is abnormal.
(iv) The fourth determination method determines that an abnormality has occurred when the variation between the maximum value and the minimum value is greater than a predetermined value. That is, as shown in FIG. 5A, at the normal time, the maximum value (black circle in the figure) and the minimum value (white circle in the figure) of the output should show a substantially constant value. If this variation becomes excessively large (so as to deviate from the predetermined range), it is determined that an abnormality has occurred.
As a result, it is possible to determine the air-fuel ratio variation abnormality between cylinders based on the vibration waveform of the output of the air-fuel ratio sensor 40.

(Change of correction method)
In the exhaust gas sensor signal processing apparatus according to the second embodiment, when an abnormality in the air-fuel ratio variation between cylinders is recognized as a result of the abnormality determination, instead of the expression (1) in the first embodiment, The output of the air-fuel ratio sensor 40 is corrected using Expression (3).
Correction A / F (n) = output (n−1) + (1 / 3A ′) × (output (n) −output (n−1)) (3)
The correction A / F calculated by this equation (3) is used for EFI control.
According to the calculation of the equation (3), the correction A / F can be calculated while reducing the contribution of the current change in the air-fuel ratio sensor output as compared with the case of the equation (1).

In particular, when the above (3) is compared with the expression (1) described in the first embodiment, in the expression (3), the second term on the right side (output (n) −output (n−1)) The coefficient is about 1/3 smaller than that of the equation (1). The reason why the value “1/3” is used is as follows.
The air-fuel ratio measurement in the limit current type air-fuel ratio sensor is basically performed based on the diffusion rate of oxygen (O ₂ ). On the other hand, the diffusion rate of hydrogen and oxygen is a ratio of hydrogen: oxygen = 3: 1, and hydrogen has a diffusion rate about three times larger. Therefore, in the second embodiment, in order to accurately eliminate the influence of the imbalance abnormality, the air-fuel ratio sensor is about three times as large as the output change based on the original oxygen due to the influence of hydrogen (H ₂ ) in the rich atmosphere. In view of the fact that an excessive output change is shown in FIG.

[Specific Processing of Embodiment 2]
Hereinafter, a specific process performed by the exhaust gas sensor signal processing apparatus according to the second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a flowchart of a routine executed by ECU 50 in the second embodiment.

  In the routine shown in FIG. 6, first, the ECU 50 executes the processes of steps S100, S102, and S104 as in the first embodiment. If the establishment of the condition in step S104 is confirmed, the processes in steps S106 and S108 are executed as in the first embodiment.

  If the conditions in step S104 are not satisfied, or if the process in step S108 is completed, the ECU 50 subsequently determines whether or not the engine is in an imbalance state (inter-cylinder air-fuel ratio variation abnormality state). Execute (Step S200). In this step, the ECU 50 executes a determination process according to at least one determination method (i) to (iv) described above, which is stored in advance. Here, as an example, it is assumed that the ECU 50 executes the determination process according to the determination method (i) described above.

  If it is determined in step S104 that the vehicle is in the imbalance state, the ECU 50 executes a process for correcting the imbalance pulsation effect (step S202). In this step, the correction A / F (n) is calculated using the above-described equation (3).

  Subsequently, the ECU 50 executes EFI control using the correction output calculated in step S202, that is, the correction A / F (n) (step S204). Thereafter, the current routine ends.

  On the other hand, when it is not recognized in step S200 that the vehicle is in the imbalanced state, ECU 50 executes steps S110 and S112, similarly to the routine of FIG. 4 in the first embodiment. Thereafter, the current routine ends.

  According to the above processing, the degree of correction of the output value of the air-fuel ratio sensor 40 can be changed in accordance with the degree of variation in the air-fuel ratio between the cylinders in the engine 10. When variation in the air-fuel ratio between cylinders (so-called imbalance state) occurs, the output of the air-fuel ratio sensor 40 differs from the normal state. In this regard, according to the above-described processing, it is possible to prevent the detection accuracy of the air-fuel ratio sensor 40 from being lowered by performing the same correction as that in the normal state.

  Further, according to the exhaust gas sensor signal processing apparatus according to the second embodiment, when correcting the output value of the air-fuel ratio sensor 40, according to the degree of variation in the air-fuel ratio among the plurality of cylinders in the engine 10, A relatively large degree of correction (correction according to Expression (1)) and a relatively small degree of correction (correction according to Expression (3)) can be selectively executed.

In the second embodiment described above, the ECU 50 executes the process of step S200 of the routine of FIG. 6 so that the “detection means” in the first invention is the same as step S110 of the routine of FIG. By selectively executing the processing of S202, the “correction content changing means” in the first aspect of the present invention is realized. In the second embodiment described above, the ECU 50 executes the correction process of S110 performed using the expression (1), so that the “first correction means” in the fourth invention is expressed by the expression (3). When the ECU 50 executes the correction process of S110 performed using (), the “second correction means” in the fourth aspect of the present invention is realized.

[Modification of Embodiment 2]
In the second embodiment, the abnormality determination of the air-fuel ratio variation between cylinders is performed using the determination methods (i) to (iv) described above. However, the present invention is not limited to this. Other known determination methods using sensors other than the air-fuel ratio sensor may be used.

  In the second embodiment, depending on the determination result of step S200, the process of step S110, which is a correction process according to equation (1), and the process of step S202, which is a correction process according to equation (3), are selectively performed. Executed. However, the present invention is not limited to this. In the cylinder engine 10, execution and stop of the correction of the output value of the air-fuel ratio sensor 40 may be switched according to the degree of variation in the air-fuel ratio between the cylinders. Thereby, under the situation where the variation in the air-fuel ratio between the cylinders becomes a problem, the correction itself can be prohibited and the detection accuracy by the air-fuel ratio sensor 40 can be surely suppressed.

  In the second embodiment, various modifications described in the column of modifications of the first embodiment may be used as appropriate. For example, in the first embodiment, it has been described that the specific calculation processing of correction is not limited to the equation (1). Similarly to this point, the second embodiment also replaces the equation (3) with various known types. A smoothing calculation method may be used. Further, different smoothing expressions may be used in steps S110 and S202.

10 Engine 12 Piston 14 Combustion chamber 16 Crankshaft 18 Intake passage 20 Exhaust passage 22 Throttle valve 24 Catalyst 26 Intake port injection valve 30 Spark plug 32 Intake valve 34 Exhaust valve 36 Crank angle sensor 38 Air flow sensor 40 Air fuel ratio sensor 50 ECU (Electronic Control Unit)

Claims (6)

Output acquisition means for acquiring an output of an exhaust gas sensor provided in an exhaust passage of the internal combustion engine;
The exhaust gas sensor based on a pulsation influence value, which is a value representing the magnitude of the influence of the pulsation on the exhaust gas sensor, obtained based on the magnitude of the amplitude in the vibration waveform of the output of the exhaust gas sensor due to exhaust pulsation Correction means for correcting the output value of
Equipped with a,
The internal combustion engine has a plurality of cylinders,
Detection means for detecting variations in the air-fuel ratio among the plurality of cylinders based on the output of the exhaust gas sensor;
Correction content changing means for changing the correction amount or content of the correction means for the output value of the exhaust gas sensor based on whether or not the variation is detected by the detection means or the degree of the variation;
Further comprising signal processing device of an exhaust gas sensor, wherein Rukoto a. The internal combustion engine has a plurality of cylinders,
The correction means includes
Cylinder output value acquisition means for acquiring a cylinder specific output value that is an output value of the exhaust gas sensor according to combustion of each of the plurality of cylinders in the vibration waveform of the output of the exhaust gas sensor;
A value obtained by averaging the deviation amount of the output value of each cylinder of the plurality of cylinders with respect to the center of the amplitude of the vibration waveform of the output of the exhaust gas sensor according to the number of cylinders of the internal combustion engine. An amplitude calculating means for calculating the amplitude;
Means for treating the value calculated as the amplitude by the amplitude calculating means as the pulsation influence value and correcting the output value of the exhaust gas sensor;
The exhaust gas sensor signal processing device according to claim 1, wherein The correction means includes
Amplitude acquisition means for determining the amplitude of the vibration waveform of the output of the exhaust gas sensor due to exhaust pulsation;
Learning means for updating the pulsation influence value or a correction amount when performing correction based on the pulsation influence value at a predetermined period based on the magnitude of the amplitude obtained by the amplitude acquisition means;
Signal processing device for an exhaust gas sensor according to claim 1 or 2, characterized in that it comprises a. Before Symbol correction means,
A first correction means for calculating a value obtained by smoothing an output change of the exhaust gas sensor in a time direction according to the pulsation influence value as a current output value after correction;
The value obtained by smoothing the output change of the exhaust gas sensor in the time direction so as to make the degree of smoothing according to the pulsation influence value smaller than the degree of smoothing by the first correcting means is Second correcting means for calculating the corrected output value;
Including
The correction content changing means includes
If the variation is relatively small based on whether or not the variation is detected by the detection unit, the output value of the exhaust gas sensor is corrected by the first correction unit when the variation is relatively small. Means for selectively executing the first correction means and the second correction means so that the output value of the exhaust gas sensor is corrected by the second correction means when the second correction means is relatively large. The signal processing apparatus for an exhaust gas sensor according to any one of claims 1 to 3 . Wherein the correction changing means, based on the degree of presence or the variation of the detection of the variation by the detection means, according to claim 1, characterized in that it comprises switching means for switching the execution and stop of the correction of the correcting means The signal processing apparatus of the exhaust gas sensor according to any one of? The detection means includes
First determination means for determining presence / absence of abnormality in air-fuel ratio variation among the plurality of cylinders based on the order of expression of the maximum value and / or minimum value in the vibration waveform of the exhaust gas sensor;
Based on a comparison between the maximum value or / and minimum value of the vibration waveform of the exhaust gas sensor and the magnitude of pulsation of the exhaust gas sensor determined by the pulsation influence value, variations in the air-fuel ratio among the plurality of cylinders Second determination means for determining presence or absence of abnormality;
Third determination means for determining whether there is an abnormality in air-fuel ratio variation among the plurality of cylinders based on whether an output value of the exhaust gas sensor is in accordance with a characteristic of a predetermined normal waveform;
Fourth determination means for determining presence / absence of an abnormality in air-fuel ratio variation among the plurality of cylinders based on variations in maximum and minimum values in the vibration waveform of the exhaust gas sensor;
Signal processing device for an exhaust gas sensor according to any one of claims 1 to 5, characterized in that it comprises at least one means among.

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