JP7559682B2 - Air flow meter deterioration calculation system - Google Patents

Description

The present invention relates to a system for calculating the deterioration level of an air flow meter.

Various devices have been proposed for diagnosing faults in air flow meters installed in the intake passages of internal combustion engines. For example, the device described in Patent Document 1 diagnoses faults in the air flow meter based on the difference between the detected value of the air flow meter and a learned value that learns the detected value.

JP 2000-274299 A

However, in the case of a hot wire airflow meter, as deterioration progresses due to the adhesion of foreign matter to the surface of the measuring part, the intake air volume value detected by the airflow meter becomes smaller than the actual intake air volume. The device described in the above Patent Document 1 is capable of diagnosing a malfunction of the airflow meter, but does not take into consideration the calculation of the degree of deterioration of the airflow meter described above.

The deterioration degree calculation system that solves the above problem calculates the deterioration degree of a hot-wire type air flow meter provided in an intake passage of an internal combustion engine. This deterioration degree calculation system includes an execution device. Then, when a value for correcting the fuel injection amount of a fuel injection valve provided in the internal combustion engine so that the air-fuel ratio of the mixture becomes a target air-fuel ratio is set as an air-fuel ratio correction value, a value for correcting the opening of the throttle valve provided in the intake passage of the internal combustion engine to compensate for changes in the intake air amount due to deposit adhesion to the throttle valve provided in the intake passage of the internal combustion engine is set as a throttle correction value, and a value for correcting the output torque of the internal combustion engine so that the engine speed of the internal combustion engine becomes a target idle speed is set as an idle correction value, the execution device executes an acquisition process for acquiring the air-fuel ratio correction value, the throttle correction value, and the idle correction value, a determination process for determining whether or not the calculation condition of the deterioration degree is satisfied based on the air-fuel ratio correction value, the throttle correction value, and the idle correction value, and a calculation process for calculating the deterioration degree based on the air-fuel ratio correction value when it is determined in the determination process that the calculation condition of the deterioration degree is satisfied.

As the deterioration of the hot-wire airflow meter progresses, the difference between the detection value of the airflow meter and the actual intake air volume becomes larger, and the value of the air-fuel ratio correction value increases. However, the value of the air-fuel ratio correction value changes not only due to the deterioration of the airflow meter, but also due to, for example, an error in the fuel injection amount. Here, as the deterioration of the hot-wire airflow meter progresses, not only the air-fuel ratio correction value but also the throttle correction value and the idle correction value change. Therefore, based on the air-fuel ratio correction value, the throttle correction value, and the idle correction value, it is possible to determine whether or not the change in the air-fuel ratio correction value is due to deterioration of the hot-wire airflow meter. Therefore, in this configuration, it is determined whether or not the deterioration degree calculation condition is met based on each of these values. Then, if it is determined that the deterioration degree calculation condition is met, the deterioration degree of the hot-wire airflow meter is calculated based on the air-fuel ratio correction value. Therefore, the deterioration degree of the hot-wire airflow meter can be appropriately calculated.

1 is a schematic diagram showing a configuration of an internal combustion engine according to an embodiment; 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment.

<Configuration of the internal combustion engine>
Hereinafter, a specific embodiment of the deterioration degree calculation system for an air flow meter will be described with reference to FIGS.

As shown in FIG. 1, an electric throttle valve 15 that changes the passage area is provided in the intake passage 11 of the internal combustion engine 10. By controlling the opening of this throttle valve 15, the intake air volume, which is the amount of air drawn in through the air cleaner 14, is adjusted. The air flowing through the intake passage 11 is mixed with fuel injected from a fuel injection valve 17, and the mixture is burned in the combustion chamber of the cylinder of the internal combustion engine 10.

The exhaust gas generated by the combustion of the mixture in the combustion chamber is discharged into the exhaust passage 13. The exhaust passage 13 is provided with a catalyst 21 that purifies the components in the exhaust gas. When combustion is performed near the theoretical air-fuel ratio, the catalyst 21 oxidizes HC and CO in the exhaust gas and reduces NOx in the exhaust gas to purify the exhaust gas. The catalyst 21 also has an oxygen storage function, storing oxygen in the exhaust gas when the air-fuel ratio of the exhaust gas passing through the catalyst 21 is leaner than the theoretical air-fuel ratio, and releasing the stored oxygen when the air-fuel ratio is richer than the theoretical air-fuel ratio.

The control device 100 performs various controls such as the amount of intake air and the amount of injected fuel for the internal combustion engine 10. The control device 100 includes a central processing unit (hereafter referred to as CPU) 110, a memory 120 in which control programs and data are stored, and the like. The control device 100 performs various controls by having the CPU 110 execute the programs stored in the memory 120. The CPU 110 and the memory 120 constitute an execution device.

The control device 100 refers to the output signal Scr of the crank angle sensor 30 and the intake air amount GA detected by the hot-wire airflow meter 31 in order to control the control amount of the internal combustion engine 10. The hot-wire airflow meter 31 may be a hot-wire type or a thin-film type airflow meter. The control device 100 also refers to the valve opening amount TA, which is the opening amount of the throttle valve 15, detected by the throttle sensor 32. The control device 100 also refers to the accelerator operation amount ACCP, which is the amount of depression of the accelerator pedal, detected by the accelerator sensor 33. The control device 100 also refers to the air-fuel ratio AF, which is detected by the air-fuel ratio sensor 34 provided upstream of the catalyst 21.

The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 30. The control device 100 also calculates the engine load factor KL based on the engine speed NE and the intake air amount GA. Here, the engine load factor KL represents the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 10 is operated steadily with the throttle valve 15 fully open at the current engine speed NE. The cylinder inflow air amount is the amount of intake air flowing into each cylinder during the intake stroke.

<Processing Executed by Control Device 100>
The control device 100 calculates the required torque T* of the internal combustion engine based on the accelerator operation amount ACCP and other factors, and calculates a required air amount GA*, which is the amount of intake air that can obtain the required torque T*. Then, it calculates a target opening degree TA* of the throttle valve 15 at which the required air amount GA* can be obtained. This target opening degree TA* is composed of the sum of a basic opening degree TAb calculated from the required air amount GA* and the engine rotation speed NE and other factors, and an opening degree correction amount obtained by multiplying the basic opening degree TAb by a throttle correction value TAH, which will be described later. Then, the control device 100 adjusts the opening degree of the throttle valve 15 so that it becomes the target opening degree TA*.

The control device 100 also determines the basic fuel injection amount Qb, which is the amount of fuel that will give the target air-fuel ratio for the actual intake air amount detected by the air flow meter 31. The control device 100 also calculates the air-fuel ratio correction value AFH based on the degree of deviation between the above-mentioned air-fuel ratio AF and the target air-fuel ratio AF*.

This air-fuel ratio correction value AFH is a value that corrects the fuel injection amount of the fuel injection valve 17 so that the air-fuel ratio of the mixture becomes the target air-fuel ratio AF*, and is an increase/decrease ratio that is multiplied by the basic fuel injection amount Qb. In this embodiment, the engine operating region is divided into multiple regions (e.g., m regions), and an air-fuel ratio correction value AFH[X] (X is 1 to m) is calculated for each of these regions.

Then, the control device 100 calculates the required injection amount Q, which is composed of the sum of the basic fuel injection amount Qb, the fuel correction amount obtained by multiplying the basic fuel injection amount Qb by the air-fuel ratio correction value AFH [X], and various other correction amounts.The control device 100 then adjusts the fuel injection amount of the fuel injection valve 17 so that the required injection amount Q is obtained.

The control device 100 also calculates the throttle correction value TAH. This throttle correction value TAH is a value that corrects the opening of the throttle valve 15 to compensate for changes in the amount of intake air caused by deposits adhering to the throttle valve 15, and is an increase/decrease ratio that is multiplied by the basic opening TAb. The throttle correction value TAH is calculated, for example, as follows:

That is, when the opening of the throttle valve 15 matches the target opening TA*, the difference ΔGA between the intake air amount GA detected by the air flow meter 31 and the required air amount GA* is calculated (ΔGA = GA* - GA). The throttle correction value TAH is calculated so that the larger the difference ΔGA, the larger the correction amount for opening the throttle valve 15. In this embodiment, the engine operating range is divided into multiple ranges (e.g., n ranges) when calculating the throttle correction value TAH, and a throttle correction value TAH[Y] (X is 1 to n) is calculated for each of these ranges.

In addition, when the operating state of the internal combustion engine 10 is an idle state, the control device 100 performs idle control so that the engine speed NE becomes a predetermined target idle speed NEId*. The required torque T* in this idle control is composed of the sum of the basic idle torque Tb calculated according to the target idle speed NEId*, the idle correction value IDH, and various other correction values. The idle correction value IDH is a torque value that corrects the output torque of the internal combustion engine 10 so that the engine speed becomes the target idle speed NEId*, and is calculated as follows. That is, the control device 100 calculates a speed difference ΔNE, which is the difference between the target idle speed NEId* and the actual engine speed NE (ΔNE = NEId* - NE). Then, when the speed difference ΔNE is a positive value and the actual engine speed NE is lower than the target idle speed NEId*, the value of the idle correction value IDH is calculated to be a positive value and the value is larger as the value of the speed difference ΔNE is larger. This causes the output torque of the internal combustion engine to increase, and the speed difference ΔNE becomes smaller.

On the other hand, when the speed difference ΔNE is a negative value and the actual engine speed NE is higher than the target idle speed NEId*, the smaller the speed difference ΔNE is (the larger the absolute value is), the smaller the idle correction value IDH is calculated to be (the larger the absolute value is). This causes the output torque of the internal combustion engine to decrease, and the speed difference ΔNE becomes smaller.

The control device 100 also executes a process for calculating the deterioration level R of the air flow meter 31 .
Fig. 2 shows a processing procedure for calculating the deterioration degree R. The processing shown in Fig. 2 is realized by the CPU 110 executing a program stored in the memory 120 at predetermined intervals. In the following, step numbers are represented by numbers preceded by the letter "S."

When this process is started, the CPU 110 executes an acquisition process for acquiring the maximum air-fuel ratio correction value AFHm, the maximum throttle correction value TAHm, and the idle correction value IDH (S100).
The maximum air-fuel ratio correction value AFHm is the maximum value of the air-fuel ratio correction values AFH[X] calculated for each region. The maximum throttle correction value TAHm is the maximum value of the throttle correction values TAH[Y] calculated for each region.

Next, the CPU 110 executes a determination process to determine whether or not the deterioration degree calculation condition is satisfied (S110). This deterioration degree calculation condition is determined to be satisfied when both the following condition (A) and condition (B) are satisfied.

(A) The difference between the maximum air-fuel ratio correction value AFHm and the maximum throttle correction value TAHm is within a preset value, and the maximum air-fuel ratio correction value AFHm and the maximum throttle correction value TAHm are approximately the same.

(B) The idle correction value IDH becomes smaller over time, or the idle correction value IDH reaches a predetermined lower limit value IDHLo.
When it is determined that the deterioration degree calculation condition is satisfied, the CPU 110 executes a calculation process to calculate a deterioration degree R of the air flow meter 31 based on the maximum air-fuel ratio correction value AFHm (S120). Here, the deterioration degree R is calculated based on the following equation (1).

R=AFHm/Em×100(%)…(1)
R: Deterioration degree AFHm: Maximum air-fuel ratio correction value Em: Maximum allowable value The maximum allowable value Em is the following value. That is, it is the maximum allowable error due to deterioration of the air flow meter 31 and is specified in advance. It should be noted that such a maximum error may be an error that requires cleaning of the measuring portion of the air flow meter 31 or replacement of the air flow meter 31. The value of the air-fuel ratio correction value AFHm is preset as the maximum allowable value Em. Therefore, when the air flow meter 31 is not deteriorated and the maximum air-fuel ratio correction value AFHm is "0", the deterioration calculated On the other hand, when the deterioration of the air flow meter 31 progresses and the value of the maximum air-fuel ratio correction value AFHm reaches the maximum allowable value Em, the calculated deterioration degree R becomes 100%.

When the process of S120 is completed or when a negative determination is made in the process of S110, the CPU 110 temporarily ends the series of processes shown in FIG.
<Action and Effects>
The operation and effects of this embodiment will be described.

When the airflow meter 31 deteriorates, the intake air volume GA (hereinafter referred to as the detected air volume) detected by the airflow meter 31 becomes smaller than the actual intake air volume (hereinafter referred to as the actual air volume). This deviation of the detected air volume from the actual air volume becomes larger as the deterioration of the airflow meter 31 progresses.

In this way, when the detected air volume becomes less than the actual air volume, or conversely, when the actual air volume becomes more than the detected air volume, the air-fuel ratio of the mixture adjusted through the air-fuel ratio feedback becomes leaner than the target air-fuel ratio AF*. Therefore, the air-fuel ratio correction value AFH changes in value in the direction of increasing the fuel injection amount, and the value increases as the deviation of the detected air volume from the actual air volume increases, that is, as the deterioration of the air flow meter 31 progresses.

In addition, when the detected air volume becomes smaller than the actual air volume, the difference ΔGA between the detected air volume and the required air volume GA* increases, and the value of the throttle correction value TAH changes so that the correction amount by which the throttle valve 15 is opened increases. In addition, the value of the throttle correction value TAH increases as the difference between the detected air volume and the actual air volume increases, that is, as the deterioration of the air flow meter 31 progresses. Here, if both the throttle correction value TAH and the air-fuel ratio correction value AFH change due to deterioration of the air flow meter 31, the throttle correction value TAH and the air-fuel ratio correction value AFH will be approximately the same value.

When the above-mentioned idle control is being performed, if the actual air volume is greater than the detected air volume due to deterioration of the airflow meter 31, the actual output torque of the internal combustion engine 10 becomes greater than the output torque required to maintain the target idle speed NEId*. Therefore, the actual engine speed NE becomes higher than the target idle speed NEId*, and the speed difference ΔNE becomes a negative value. When the speed difference ΔNE is a negative value, the value of the idle correction value IDH becomes a negative value. And, as the deterioration of the airflow meter 31 progresses, the difference between the actual air volume and the detected air volume becomes larger, so the speed difference ΔNE becomes a negative value and its absolute value becomes larger. Therefore, the value of the idle correction value IDH becomes smaller on the negative side as the deterioration of the airflow meter 31 progresses, and finally reaches the lower limit value IDHLo.

As the deterioration of the airflow meter 31 progresses in this way, not only the air-fuel ratio correction value AFH but also the throttle correction value TAH and the idle correction value IDH change. Therefore, based on the air-fuel ratio correction value AFH, the throttle correction value TAH, and the idle correction value IDH, it is possible to determine whether the change in the air-fuel ratio correction value AFH is due to deterioration of the airflow meter 31.

In this embodiment, it is determined whether the conditions for calculating the deterioration level R are met based on these values. More specifically, in S110 shown in FIG. 2, it is determined whether both of the above conditions (A) and (B) are met. If a positive determination is made in S110, that is, if it is determined that the conditions for calculating the deterioration level R are met, the process of S120 shown in FIG. 2 is executed, and the deterioration level R is calculated based on the air-fuel ratio correction value AFH. Therefore, the deterioration level R of the hot-wire air flow meter 31 can be properly calculated.

<Example of change>
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

- In the above condition (A), the maximum air-fuel ratio correction value AFHm is compared with the maximum throttle correction value TAHm, but other air-fuel ratio correction values AFH and throttle correction values TAH may also be compared. For example, the minimum value of the air-fuel ratio correction values AFH [X] calculated for each region may be compared with the minimum value of the throttle correction values TAH [Y] calculated for each region. Also, the average value of the air-fuel ratio correction values AFH [X] calculated for each region may be compared with the average value of the throttle correction values TAH [Y] calculated for each region.

- Although the air-fuel ratio correction value AFH and the throttle correction value TAH are calculated for each of multiple engine operating regions, the air-fuel ratio correction value AFH and the throttle correction value TAH may be calculated without dividing the engine operating region into multiple regions.

- The execution device is equipped with a CPU and memory, and is not limited to executing software processing. For example, it may be equipped with a dedicated hardware circuit (e.g., ASIC, etc.) that processes at least a part of the software processing executed in each of the above embodiments. That is, the execution device may have any of the following configurations (a) to (c). (a) It is equipped with a processing device that executes all of the above processing according to a program, and a program storage device such as a memory that stores the program. (b) It is equipped with a processing device and a program storage device that executes part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) It is equipped with a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software processing circuits and dedicated hardware circuits equipped with a processing device and a program storage device. That is, the above processing may be executed by a processing circuit equipped with at least one of one or more software processing circuits and one or more dedicated hardware circuits.

REFERENCE SIGNS LIST 10 internal combustion engine 11 intake passage 13 exhaust passage 14 air cleaner 15 throttle valve 17 fuel injection valve 21 catalyst 30 crank angle sensor 31 air flow meter 32 throttle sensor 33 accelerator sensor 34 air-fuel ratio sensor 100 control device 110 central processing unit (CPU)
120…Memory

Claims (1)

A deterioration degree calculation system for calculating a deterioration degree of a hot-wire air flow meter provided in an intake passage of an internal combustion engine, comprising:
An execution device is provided,
When a value for correcting a fuel injection amount of a fuel injection valve provided in the internal combustion engine so that the air-fuel ratio of the mixture becomes a target air-fuel ratio is defined as an air-fuel ratio correction value, a value for correcting an opening degree of a throttle valve provided in an intake passage of the internal combustion engine to compensate for a change in the intake air amount due to deposit adhesion to the throttle valve is defined as a throttle correction value, and a value for correcting an output torque of the internal combustion engine so that the engine speed of the internal combustion engine becomes a target idle speed is defined as an idle correction value,
The execution device is
an acquisition process for acquiring the air-fuel ratio correction value, the throttle correction value, and the idle correction value;
a determination process for determining whether or not a deterioration degree calculation condition is satisfied based on the air-fuel ratio correction value, the throttle correction value, and the idle correction value;
a calculation process for calculating the deterioration degree based on the air-fuel ratio correction value when it is determined in the determination process that the deterioration degree calculation condition is satisfied.

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