JP2007077849A - Correction device for suction air quantity detection means - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of determination of deterioration in an accurate air flow meter and correction process. <P>SOLUTION: In the correction device for a suction air quantity detection means including a throttle valve controlling quantity of air sucked in an internal combustion engine, a suction air quantity detection means detecting suction air quantity of the internal combustion engine, an air furl ratio sensor provided on an exhaust system of the internal combustion engine, a deterioration detection means detecting deterioration of suction air quantity detection means based on output of the air fuel ratio sensor when temperature relating to a throttle valve or a catalyst exceeds a predetermined value, a correction means correcting output of the suction air quantity detection means, a calculation means calculating a correction value of an output of the air fuel ratio sensor when fuel supply is shut off according to an operation condition of the internal combustion engine is included, a deterioration detection means detects deterioration of the suction air quantity detection means after output of the air fuel ratio sensor is corrected by the calculation means, and the correction means corrects output of the suction air quantity detection means based on a result of deterioration detection. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for correcting the output of intake air amount detection means of an internal combustion engine.

In the control of an internal combustion engine, if the detection accuracy of the air flow meter provided in the intake pipe deteriorates, the throttle valve is not fully air-fuel ratio feedback controlled and the catalyst temperature and MAT temperature estimated by the ECU (temperature of the catalyst holding mat) When the air temperature exceeds a predetermined temperature, the air-fuel ratio becomes lean. Using this phenomenon, for example, Patent Document 1 discloses a technique for correcting the output of the air flow meter when it is determined that the air is lean from the output of the air-fuel ratio sensor provided in the exhaust pipe.
JP-A-2-18551

  However, the conventional air flow meter correction method such as Patent Document 1 does not take into account the initial variation or deterioration of the air-fuel ratio sensor, which is a criterion for air flow meter deterioration determination and output correction. Since the output characteristics of the sensor change due to the initial variation or deterioration of the air-fuel ratio sensor, it also affects the deterioration determination and output correction processing of the air flow meter.

  An object of the present invention is to provide an apparatus capable of improving the above-described problems and performing highly accurate air flow meter deterioration determination and output correction processing.

  The present invention relates to a throttle valve for controlling the amount of air taken into the internal combustion engine, intake air amount detection means for detecting the intake air amount of the internal combustion engine, an air-fuel ratio sensor provided in the exhaust system of the internal combustion engine, and a throttle A deterioration detecting means for detecting deterioration of the intake air amount detecting means based on an output of the air-fuel ratio sensor when a temperature related to the valve or the catalyst exceeds a predetermined value, and a correcting means for correcting the output of the intake air amount detecting means. The correction apparatus for the intake air amount detection means having the following configuration is configured as follows. This apparatus has a calculation means for calculating a correction value of the output of the air-fuel ratio sensor when the fuel supply is shut off according to the operating state of the internal combustion engine. The deterioration detection means detects the deterioration of the intake air amount detection means after the calculation means corrects the output of the air-fuel ratio sensor. The correcting means corrects the output of the intake air amount detecting means based on the result of the deterioration detection.

  According to the present invention, since the correction of the intake air amount detection means is performed after the correction of the air-fuel ratio sensor, it is possible to avoid the influence due to variations in the air-fuel ratio sensor, characteristic changes due to deterioration of the air-fuel ratio sensor, etc. The accuracy of correction of the output of the intake air amount detection means is improved.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of an internal combustion engine (hereinafter referred to as “engine”) and a control device thereof according to an embodiment of the present invention.

  An electronic control unit (hereinafter referred to as “ECU”) 13 includes an input interface 13a that receives data sent from each part of the vehicle, a CPU 13b that performs calculations for controlling each part of the vehicle, and a read-only memory (ROM). And a memory 13c having a random access memory (RAM) for temporary storage, and an output interface 13d for sending a control signal to each part of the vehicle. The ROM of the memory 13c stores a program for controlling each part of the vehicle and various data.

  The program for the correction process of the air flow meter according to the present invention, and data and tables used when executing the program are stored in the ROM of the memory 13c. This ROM may be a rewritable ROM such as an EEPROM. The RAM is provided with a work area for calculation by the CPU 13b, and temporarily stores data sent from each part of the vehicle and control signals sent to each part of the vehicle.

  Various signals such as sensor output sent to the ECU 13 are transferred to the input interface 13a and subjected to analog-digital conversion. The CPU 13b processes the converted digital signal according to a program stored in the memory 13c to generate a control signal. The output interface 13d sends these control signals to each part of the vehicle.

  The engine 11 is an engine having, for example, four cylinders, and an intake pipe 15 is connected thereto.

  An air flow meter 16 is installed on the upstream side of the intake pipe 15 and outputs an electric signal indicating the amount of intake air to the ECU 13.

  A throttle valve 17 is installed downstream of the air flow meter 16. The throttle valve 17 is an electric throttle valve that adjusts the throttle opening by an actuator (not shown) such as a motor. Further, a throttle valve opening sensor (θTH) 19 is connected to the throttle valve 17, and an electric signal corresponding to the opening of the throttle valve 17 is output and supplied to the ECU 13.

  Between the engine 11 and the throttle valve 17, an injector 21 is provided for each cylinder. The injector 21 has its valve opening time controlled by a control signal from the ECU 13 corresponding to the operating state, and injects fuel at an optimal timing.

  The engine 11 is provided with a crank angle sensor 23. The crank angle sensor 23 outputs a CRK signal, which is a pulse signal, to the ECU 13 as the crankshaft rotates. The CRK signal is a pulse signal output at a predetermined crank angle (for example, 30 degrees). The ECU 13 calculates the rotational speed NE of the engine 11 according to the CRK signal.

  A water temperature sensor 25 is attached to the engine 11. The water temperature sensor 25 is attached to a cylinder peripheral wall (not shown) filled with cooling water in the cylinder block of the engine 11. The water temperature sensor 25 detects the temperature TW of the engine cooling water and sends the signal to the ECU 13.

  An exhaust pipe 27 is connected to the engine 11, and exhaust is performed via an exhaust gas purification device provided in the middle of the exhaust pipe 27. The LAF sensor 29 provided upstream of the exhaust gas purification device is a wide area air-fuel ratio sensor, detects the oxygen concentration in the exhaust gas, that is, the air-fuel ratio, in a range from lean to rich, and sends the signal to the ECU 13.

  Next, with reference to FIGS. 2 to 4, an outline of the deterioration detection and output correction processing of the air flow meter 16 using the LAF sensor 29 will be described.

  FIG. 2 is a diagram showing a change in characteristics when the air flow meter 16 is deteriorated. The horizontal axis of the graph indicates the air flow rate Q (g / s), and the vertical axis of the graph indicates the characteristic change amount dQ / Q (%) of the output of the air flow meter 16 with respect to the air flow rate Q.

  The characteristic change amount dQ / Q is a rate of change in output based on the output of a normal air flow meter. Therefore, the characteristic change amount dQ / Q of a normal air flow meter is zero and constant. When the output is lower than the normal output, the characteristic change amount dQ / Q becomes a negative value.

  As shown in FIG. 2, when the air flow meter 16 deteriorates, the output value of the air flow meter 16 decreases with respect to the air flow rate Q, and the degree increases as the air flow rate Q increases. That is, the larger the air flow rate, the less the deteriorated air flow meter is estimated than the actual air flow rate.

  During operation of the engine 11, by adjusting the fuel injection amount of the injector 21 based on the intake air amount calculated from the output value of the air flow meter 16 and the actual air-fuel ratio KACT calculated from the output of the LAF sensor 29. The air-fuel ratio is feedback controlled. When the air flow meter is deteriorated, the intake air amount is calculated to be smaller than the actual amount. Therefore, the fuel injection amount determined based on the intake air amount is smaller than the actually required amount. For this reason, when the air flow meter 16 is deteriorated, the actual air-fuel ratio becomes leaner than the set air-fuel ratio.

  FIG. 3 is a graph showing the transition of the ratio KACTAMAVE / KCMD between the average smoothed value KACTAMAVE of the actual air-fuel ratio KACT and the set air-fuel ratio KCMD accompanying the deterioration of the air flow meter 16.

Here, the smoothed value KACTAMAVE is a value obtained by averaging the actual air-fuel ratio KACT obtained from the output of the LAF sensor 29 over a predetermined time step (for example, 20 steps) and smoothing the average value by smoothing. It is. The annealing calculation is performed using, for example, a first-order low-pass filter represented by the following equation.
KACTAMAVE (k) = (1.0−CKACT) × KACTAMAVE (k-1) + CKACT × KACTAVE (k)
Here, KACTAMAVE (k) represents the current annealing value, and KACTAMAVE (k-1) represents the previous annealing value. KACTAVE (k) represents the current average value, and CKACT represents the coefficient. k represents a time step.

  The horizontal axis of the graph in FIG. 3 indicates the usage time of the air flow meter 16, and the degree of deterioration of the air flow meter 16 increases as time passes. The vertical axis of the graph indicates when the throttle is almost fully open, or when the catalyst temperature and MAT temperature (temperature of the catalyst holding mat) estimated by the ECU exceed the predetermined temperature (hereinafter referred to as “WOT (wide open KACTAMAVE / KCMD in “throttle” ”).

  In the current vehicle engine control, air-fuel ratio feedback control is executed in order to achieve a desired air-fuel ratio during normal operation of the engine. Even if the air flow meter 16 is deteriorated, the fuel injection amount is adjusted to be desired. The air-fuel ratio is realized. Since air-fuel ratio feedback control is not performed during WOT, KACTAMAVE / KCMD during WOT can represent the influence of deterioration of the air flow meter 16.

  As shown in FIG. 3, since the intake air amount can be accurately measured at the initial stage of using the air flow meter 16, the actual air-fuel ratio KACT is substantially equal to the set air-fuel ratio KCMD, and KACTAMAVE / KCMD is a value close to 1. As the air flow meter 16 is further deteriorated after the usage time, the actual air-fuel ratio KACT shifts to the lean side, and KACTAMAVE / KCMD decreases to 1 or less.

  Accordingly, in the WOT in which air-fuel ratio feedback control is not performed, the degree of deterioration of the air flow meter 16 can be determined by paying attention to the ratio KACTAMAVE / KCMD of the average air-fuel ratio KACTAMAVE and the set air-fuel ratio KCMD. Is possible. Then, when KACTAMAVE / KCMD falls below a predetermined threshold (time A in FIG. 3), it is determined that lean has occurred due to deterioration of the air flow meter 16, and the output of the air flow meter 16 is corrected. Execute.

  How much the output of the air flow meter 16 is corrected is determined according to the air flow rate (intake air amount). It can be set in advance using the characteristics shown in FIG. 2 or the like how much error is generated according to the flow rate when the air flow meter is deteriorated. FIG. 4 is a diagram illustrating the maximum value of the detection error of the air flow meter 16 with respect to the air flow rate. The horizontal axis of the graph indicates the output AFMCRK (v) of the air flow meter 16, and this value corresponds to the air flow rate. The vertical axis of the graph represents the maximum value DVGAIR (g / s) of the error in the air flow rate when the air flow meter is deteriorated.

  Referring to FIG. 4, first, the maximum value DVGAIR of the detection error is obtained from the output AFMCRK of the air flow meter 16. Subsequently, the correction amount DVGAIRAFM is obtained by multiplying DVGAIR by the correction coefficient KVG. The correction coefficient KVG is set based on the ratio KACTAMAVE / KCMD between the smoothed value of the actual air-fuel ratio and the set air-fuel ratio. This setting process will be described later with reference to FIG.

  Subsequently, an output correction process of the air flow meter 16 according to the present embodiment will be described with reference to FIGS. This process is executed by a software program stored in the ECU 13.

  FIG. 5 is a flowchart of a process for calculating the air flow rate by correcting the output of the air flow meter 16. This flowchart is performed at predetermined time intervals.

  In step S101, the maximum value DVGAIR of the error in the air flow rate is retrieved from the output AFMCRK of the air flow meter 16. When the air flow meter 16 is degraded, the output error of the air flow meter increases because the output of the air flow meter 16 decreases as the air flow rate increases. Therefore, for example, a maximum error map corresponding to the air flow rate as shown in FIG. 4 is created in advance, and the maximum output error value DVGAIR at the current air flow rate is searched.

  In step S103, the raising amount DVGAIRAFM is calculated. A value obtained by multiplying the maximum output error value DVGAIR by the correction coefficient KVG is defined as a raised amount DVGAIRAFM. The correction coefficient KVG is a value set according to KACTAMAVE / KCMD, and is updated every time it is determined that lean has occurred due to deterioration of the air flow meter. The update of KVG will be described later with reference to FIG.

  In step S105, the air flow rate VGAIR is retrieved from the output AFMCRK of the air flow meter 16. A conversion map between the output AFMCRK and the air flow rate VGAIR when the air flow meter 16 is normal is created in advance, and VGAIR is obtained using this map. Since the output of the air flow meter is decreasing when the air flow meter 16 is deteriorated, the required air flow rate VGAIR is smaller than the actual air flow rate.

  In step S107, the output-corrected air flow rate VGAIRF is calculated. The raised air amount DVGAIRAFM obtained in step S103 is added to the air flow rate VGAIR obtained in step S105 to obtain the air flow rate VGAIRF subjected to the output correction processing.

  FIG. 6 is a flowchart of a lean determination process due to deterioration of the air flow meter 16. This flowchart is performed at predetermined time intervals.

  In step S201, it is confirmed whether or not it is a detection region for determining deterioration of the air flow meter 16. In the present embodiment, the detection area is determined when the following conditions are satisfied. The first condition is the water temperature TW. In order to determine the deterioration of the air flow meter 16 in a state where the output KACT of the LAF sensor 29 is stable, the water temperature TW measured by the water temperature sensor 25 has a temperature higher than a predetermined value as a detection region. The second condition is the engine speed NE. In the low engine speed region, pulsation occurs in the intake air amount. In order to perform stable measurement while avoiding the pulsation region, the engine rotational speed NE measured by the crank angle sensor 23 is set to a detection region that is larger than a predetermined value. The third condition is that the engine operating state is WOT. As described above, in the current engine control, the air-fuel ratio feedback control is not performed during the WOT. Therefore, during the WOT, that is, when the throttle opening is substantially fully opened, or the catalyst temperature and the MAT temperature estimated by the ECU are the predetermined temperatures. The detection area is set when the value exceeds. If the current operating state is the predetermined detection region as described above, the process continues and proceeds to step S205. If it is outside the detection area, the current process is terminated.

  Subsequently, in step S205 to step S207, it is confirmed whether the correction process of the LAF sensor 29 is completed. In the present embodiment, since the correction process of the air flow meter 16 is performed based on the output of the LAF sensor 29, the detection accuracy of the LAF sensor 29 is required to improve the correction accuracy, and the output of the LAF sensor 29 is corrected in advance. It is desirable that is completed. The correction process of the LAF sensor 29 is performed by the ECU 13 in parallel with the correction process of the air flow meter 16.

  Here, an outline of the correction process of the LAF sensor 29 will be described with reference to FIGS.

  FIG. 7 is a graph showing the output characteristics of the LAF sensor. The horizontal axis of the graph represents the air-fuel ratio, where the positive direction is the lean side, the origin is the stoichiometric air-fuel ratio, and the negative direction is the rich side. The vertical axis of the graph represents the output of the LAF sensor. A straight line 71 represented by a dotted line indicates a characteristic of a normal LAF sensor. A straight line 73 represented by a solid line is a characteristic of the LAF sensor having an initial variation or aged deterioration. In the characteristic graph of FIG. 7, the output characteristic of the LAF sensor behaves so as to rotate around the origin (theoretical air-fuel ratio) with the initial variation and deterioration of the sensor.

  The correction process of the LAF sensor is performed by using the coefficient KVLFFC for correcting the inclination of the characteristic line 73 so that the characteristic line 73 of the LAF sensor 29 at the time of deterioration becomes the characteristic line 71 of the normal LAF sensor. Correct.

  First, the output of the LAF sensor 29 is measured while the operating state of the engine 11 is during fuel cut (hereinafter referred to as “F / C”). This is because the air-fuel ratio is clear and the value to be taken by the LAF sensor 29 is clear because the fuel is not contained in the exhaust during the fuel cut.

Subsequently, an average value VLAFFC for a predetermined time step of the LAF sensor output in F / C is calculated, and the average value VLAFFC is smoothed to calculate a smoothed value VLFFCR. The annealing calculation is performed using, for example, a first-order low-pass filter represented by the following equation.
VLFFCR (k) = (1.0−CVLAF) × VLFFCR (k-1) + CVLAF × VLAFFC (k)
Here, VLFFCR (k) represents the current annealing value, and VLFFCR (k-1) represents the previous annealing value. VLAFFC (k) represents the current average value, and CVLAF represents the coefficient. k represents a time step.

  Then, a correction coefficient KVLFFC is obtained based on the annealing value VLFFCR, and the inclination of the output of the LAF sensor 29 is corrected with this correction coefficient KVLFFC.

  FIG. 9 is a diagram showing the setting of the inclination correction coefficient KVLFFC based on the average value VLFFCR of the average value of the LAF sensor output during F / C. The horizontal axis of the graph represents the smoothed value VLFFCR, and the vertical axis of the graph represents the slope correction coefficient KVLFFC. The correction coefficient KVLFFC is set so that the output of the LAF sensor 29 during F / C becomes the output during normal F / C of the LAF sensor by the correction process.

  Returning to FIG. 6 again and continuing the description, in step S205, a difference DVLAFFC between the average value VLAFFC of the LAF sensor output during F / C and the smoothed value VLFFCR calculated from this average value VLAFFC is obtained.

  FIG. 8 is a graph showing the transition of the average value VLFFCR of the average value of the LAF sensor output during F / C. The horizontal axis of the graph represents elapsed time, and the vertical axis of the graph represents LAF sensor output. The straight line 81 represents the transition of the average value VLFFCR of the LAF sensor output during F / C, and the dotted line 82 represents the transition of the average value VLAFFC of the LAF sensor output during F / C. If there is a difference DVLAFFC, by repeating the correction process of the LAF sensor, the average value VLFFCR of the LAF sensor output in the F / C approaches the average value VLAFFC of the LAF sensor output in the F / C. DVLAFFC becomes smaller.

  In step S207, it is confirmed whether or not the difference DVLAFFC is larger than a predetermined threshold value. When it is smaller than the threshold value, it is determined that the correction of the output of the LAF sensor 29 has been completed or the LAF sensor 29 is functioning normally, and the process proceeds to step S209. When the value is larger than the threshold value, it is determined that the LAF sensor 29 has not sufficiently corrected the output, and the current process is terminated without performing the lean determination due to the deterioration of the air flow meter 16. As described above, in the present embodiment, while the correction process of the output of the LAF sensor 29 is being performed, the lean determination due to the deterioration of the air flow meter 16 is not performed, and after the output correction of the LAF sensor is completed, Go to step.

  In step S209, the ratio KACTAMAVE / KCMD between the average value KACTAMAVE of the average value of the actual air-fuel ratio calculated from the output of the LAF sensor 29 and the set air-fuel ratio KCMD is calculated.

  In step S211, it is determined whether KACTAMAVE / KCMD is smaller than a threshold value. If it is smaller than the threshold value, it is determined that the actual air-fuel ratio KACT exceeds the allowable range and is on the lean side, and the routine proceeds to step S213, where it is determined that the air flow meter 16 is lean due to deterioration. If it is larger than the threshold value, it is determined that the air flow meter 16 has not deteriorated enough to affect the air-fuel ratio, or the lean due to the deterioration of the air flow meter 16 has been corrected, and the current process is terminated. .

  FIG. 10 is a flowchart of processing for setting the correction coefficient KVG in the output correction processing of the air flow meter 16. This flowchart is carried out only once at the beginning of a driving cycle (Driving Cycle, hereinafter referred to as “D / C”) from ignition on to ignition off.

  In step S301, it is confirmed whether or not a lean determination has been made due to deterioration of the air flow meter 16 at the end of the previous D / C. If it is determined to be lean, the process continues and proceeds to step S303. If it is determined that there is no lean, this process ends.

  In step S303, the correction coefficient KVG is updated. The correction coefficient KVG is updated by, for example, selecting the current update width from a plurality of predetermined update widths according to the size of KACTAMAVE / KCMD, and adding the selected update width to the previous KVG. Alternatively, the correction coefficient KVG may be in a form in which a constant update width is added to the previous KVG. This process is executed only once during one D / C, and the updated correction coefficient KVG value is maintained in the same D / C after the correction coefficient KVG is updated. Keep doing.

  Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to such embodiments.

1 is a schematic diagram illustrating a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. It is a figure which shows the change of the characteristic when an airflow meter deteriorates. It is a figure which shows transition of ratio KACTAMAVE / KCMD of the actual air fuel ratio KACT and preset air fuel ratio KCMD accompanying deterioration of an air flow meter. It is the figure which illustrated the maximum value of the detection error of the air flow meter with respect to the air flow rate. It is a flowchart of the process which correct | amends the output of an air flow meter and calculates an air flow rate. It is a flowchart of the process which sets the correction coefficient KVG in the correction process of an airflow meter. It is a figure which shows the output characteristic of a LAF sensor. It is the figure which showed transition of the smoothing value VLFFCR of the average value of the LAF sensor output in F / C. It is the figure which showed the setting of the inclination correction coefficient KVLFFC based on the smoothing value VLFFCR of the average value of the LAF sensor output in F / C. It is a flowchart of the process which sets the correction coefficient KVG in the output correction process of an airflow meter.

Explanation of symbols

11 Engine 13 ECU
16 Air flow meter 17 Throttle valve 29 LAF sensor

Claims (1)

A throttle valve for controlling the amount of air taken into the internal combustion engine; intake air amount detection means for detecting the intake air amount of the internal combustion engine; an air-fuel ratio sensor provided in an exhaust system of the internal combustion engine; and the throttle valve Deterioration detection means for detecting deterioration of the intake air amount detection means based on the output of the air-fuel ratio sensor when the opening degree or the temperature related to the catalyst exceeds a predetermined value, and the output of the intake air amount detection means In a correction device for an intake air amount detection means having correction means,
Calculating means for calculating a correction value of the output of the air-fuel ratio sensor when fuel supply is interrupted according to the operating state of the internal combustion engine;
The deterioration detecting means performs deterioration detection of the intake air amount detecting means after the output of the air-fuel ratio sensor is corrected by the calculating means,
The correcting means corrects the output of the intake air amount detecting means based on the result of the deterioration detection;
A correction device for intake air amount detection means.

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