JP3267104B2 - Air-fuel ratio sensor deterioration determination control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio sensor deterioration judging control device for an internal combustion engine, and more particularly to an air-fuel ratio sensor deterioration judging accuracy which can prevent an increase in exhaust harmful component values. The present invention relates to an air-fuel ratio sensor deterioration determination control device for an internal combustion engine that can avoid erroneous determination, improve reliability, avoid unnecessary component replacement due to erroneous determination, and avoid an increase in cost.

[0002]

2. Description of the Related Art An internal combustion engine mounted on a vehicle is provided with an O2 sensor serving as an air-fuel ratio sensor in an exhaust passage, and a fuel injection amount is fed back so that the air-fuel ratio becomes a target value based on a signal output from the O2 sensor. Some control means are provided for control. As a result, in the internal combustion engine, the exhaust gas purification efficiency of the catalyst body is improved, and the exhaust emission harmful component value is reduced.

[0003] The function of the O2 sensor provided in the exhaust passage of the internal combustion engine does not cause a remarkable decrease in its function in an ordinary operating condition. But,
The O2 sensor deteriorates significantly when it supplies leaded gasoline to an internal combustion engine that uses unleaded gasoline as a fuel, or when exposed to high temperatures due to some unforeseen cause. Change.

As a result, when the fuel injection amount is controlled using the output of the O2 sensor, the fuel injection amount greatly changes from the target amount, causing an increase in the harmful component value of the exhaust gas. Will be discharged.

[0005] Therefore, some internal combustion engines are provided with an air-fuel ratio sensor deterioration judgment control device for judging the deterioration state of the O2 sensor.

An example of such an air-fuel ratio sensor deterioration determination control device is disclosed in Japanese Patent Application Laid-Open No. 2-169835. What is disclosed in this publication is to determine the deterioration state of the O2 sensor based on the increase / decrease cycle of the fuel supply amount under the operating condition in which the increase / decrease cycle of the fuel supply amount is stable during the feedback control of the air-fuel ratio by the O2 sensor, O2
When it is determined that the sensor has deteriorated, it is determined that the signal output from the O2 sensor has been inverted from the target air-fuel ratio to the lean side, and then the control for increasing the fuel supply amount is started after a predetermined time delay. is there.

[0007]

When the deterioration state of the O2 sensor is determined, if the accuracy of the determination is low, the O2
Although the function of the sensor is normal, the abnormality is notified, and there is a disadvantage that the confusion is unnecessarily caused and a problem that the reliability is lowered. Therefore,
The air-fuel ratio sensor deterioration determination control device requires high determination accuracy.

In a conventional air-fuel ratio sensor deterioration determination control device, as shown in FIG. 8, a cycle a of a signal output from an O2 sensor serving as an air-fuel ratio sensor, a rise response time b, and a fall response time c are measured. , Period a only, or
The deterioration state of the O2 sensor is determined based on only the rising response time b or only the falling response time c, or only the total time (b + c) of the rising response time b and the falling response time c.

However, when the determination is made based on the period a of the signal of the O2 sensor, as shown in FIGS.
Even if only the length becomes longer, there is a problem that the degree of deterioration for each exhaust gas component varies depending on the ratio between the rise response time b and the fall response time c. The same problem as described above also occurs when the determination is made based only on the rising response time b or the falling response time c of the O2 sensor, and only on the total time (b + c) of the rising response time b and the falling response time c.

For this reason, when the deterioration state is determined only by a part of the signal form of the O2 sensor, the degree of deterioration for each exhaust gas component changes, so that it is not possible to make an accurate determination, and the O2 sensor Function is normal, but an error is reported, which causes inconvenience unnecessarily, reduces reliability, and causes unnecessary component replacement due to erroneous determination, resulting in an increase in cost. Inconvenience.

[0011]

In order to solve the above-mentioned problems, the present invention provides an air-fuel ratio sensor in an exhaust passage of an internal combustion engine and a load sensor for detecting an engine load of the internal combustion engine. When the condition for determining the deterioration of the air-fuel ratio sensor is satisfied, the cycle of the signal output from the air-fuel ratio sensor, the rise response time, and the fall response time are measured, and the engine load is measured by the load sensor while these values are being measured. , The cycle, the rise response time, and the fall response time are corrected based on the engine load during measurement to obtain a correction cycle, a corrected rise response time, and a corrected fall response time. The average value, the average rise response time and the average fall response time are obtained by averaging the values of the times, respectively, and the average rise response time is averaged fall time. Control means for determining a deterioration comparison value of the air-fuel ratio sensor from a value obtained by dividing the air-fuel ratio sensor by a response time, and comparing the deterioration comparison value with a preset abnormality determination value to determine a deterioration state of the air-fuel ratio sensor. It is characterized by having.

[0012]

According to the configuration of the present invention, the air-fuel ratio sensor deterioration determination control device uses the control means to determine the cycle of the air-fuel ratio sensor, the rise response time, and the fall response time according to the engine load whose values are being measured. The average value, average rise response time, and average fall response time are obtained by averaging these corrected values at predetermined times as needed, and the average rise response time of each averaged value is divided by the average fall response time. By determining a deterioration comparison value of the air-fuel ratio sensor from the calculated value, and comparing the deterioration comparison value with a preset abnormality determination value to determine the deterioration state of the air-fuel ratio sensor,
The determination can be made in consideration of various aspects of the signal output from the air-fuel ratio sensor and the engine load, and the problem of changing the degree of deterioration for each exhaust gas component can be avoided and accurate determination can be performed. Can be.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 7 show an embodiment of the present invention. 7, 2 is an internal combustion engine, 4 is an intake passage, 6
Is an exhaust passage. The intake passage 4 of the internal combustion engine 2 is formed by an air cleaner 8, an air flow meter 10, a throttle body 12, and an intake manifold 14 which are sequentially connected from the upstream side. The intake passage 4 in the throttle body 12 is provided with an intake throttle valve 16. Intake passage 4
Is connected to a combustion chamber 18 of the internal combustion engine 2.

The exhaust passage 6 communicating with the combustion chamber 18 of the internal combustion engine 2 includes an exhaust manifold 20, an upstream exhaust pipe 22, a catalytic converter 24, and a downstream exhaust pipe 26 which are sequentially connected from the upstream. It is formed. A catalyst body 28 is provided in the exhaust passage 6 in the catalytic converter 24.

The internal combustion engine 2 is provided with a fuel injection valve 30 directed to the combustion chamber 18. The fuel injection valve 30
The fuel supply passage 34 communicates with the fuel tank 36 via the fuel distribution passage 32. The fuel in the fuel tank 36 is pumped by a fuel pump 38 and a fuel filter 40
Then, the dust is removed, and the dust is supplied to the fuel distribution passage 32 by the fuel supply passage 34 and distributed to the fuel injection valve 30.

The fuel distribution passage 32 is provided with a fuel pressure adjusting section 42 for adjusting the fuel pressure. The fuel pressure adjusting unit 42 adjusts the fuel pressure to a predetermined value by the intake pressure introduced from the pressure guiding passage 44 communicating with the intake passage 4, and returns excess fuel to the fuel tank 36 through the fuel return passage 46.

The fuel tank 36 is provided with the fuel vapor passage 4.
8, a two-way valve 50 and a canister 52 are provided in communication with the intake passage 4 of the throttle body 12 in the middle of the evaporative fuel passage 48. The throttle body 12 is provided with a bypass passage 54 that bypasses the intake throttle valve 16, and an idle air amount control valve 56 is provided in the middle of the bypass passage 54.

Reference numeral 58 denotes an air regulator, reference numeral 60 denotes a power steering switch, reference numeral 62 denotes a power steering air amount control valve, reference numeral 64 denotes a blow-by gas passage, and reference numeral 66 denotes a PCV valve.

The air flow meter 10 and the fuel injection valve 3
0, the idle air amount control valve 56 and the power steering air amount control valve 62 are provided by the air-fuel ratio sensor deterioration determination control device 6.
8 is connected to the control means 70. The control means 70 includes a crank angle sensor 72 for detecting the crank angle and the engine speed, a distributor 74 for distributing the ignition current, and an opening sensor 7 for detecting the opening of the intake throttle valve 16.
6 and a knock sensor 78 for detecting knock of the internal combustion engine 2
, A water temperature sensor 80 for detecting a cooling water temperature, and a vehicle speed sensor 82 for detecting a company rule. Reference numeral 84 is an ignition coil, and reference numeral 86 is an ignition power unit.

In the internal combustion engine 2, a first O2 sensor 88 and a second O2 sensor, which are air-fuel ratio sensors for detecting an oxygen concentration as an exhaust component value, are provided in the exhaust passages 6 upstream and downstream of the catalyst body 28, respectively. 90 are provided. These first
The O2 sensor 88 and the second O2 sensor 90 are provided with a heater and are connected to the control means 70.

The control means 70 performs feedback control of the operation of the fuel injection valve 30 based on the first signal and the second signal output from the first O 2 sensor 88 and the second O 2 sensor 90 so that the air-fuel ratio becomes a target value. Control the fuel injection amount.
Thereby, the exhaust gas purification efficiency by the catalyst body 28 is improved,
The emission harmful component value is reduced.

Reference numeral 92 indicates a dashpot, and reference numeral 9
4 is a thermo sensor, 96 is an alarm relay, 9 is
8 is a warning light, 100 is a diagnosis switch,
102 is a TS switch, 104 is a diagnosis lamp, 106 is a main switch, 108
Is a battery.

The air-fuel ratio sensor deterioration judging device 68 of the internal combustion engine 2 is controlled by the control means 70 to be a first oxygen-fuel ratio sensor provided in the exhaust passage 6 on the upstream side of the catalyst body 28.
The deterioration state of the sensor 88 is determined.

The air-fuel ratio sensor deterioration judging device 68 is provided with a first O 2 sensor 88 as an air-fuel ratio sensor in the exhaust passage 6 of the internal combustion engine 2, and detects an air flow as a load sensor for detecting the engine load of the internal combustion engine 2. A meter 10 is provided.

The control means 70 measures the period a, the rising response time b, and the falling response time c of the first signal output from the first O2 sensor 88 when the condition for determining the deterioration of the first O2 sensor 88 is satisfied. At the same time, while measuring these values, the air flow meter 10 detects the amount of air Ga, which is the engine load, by using the air flow meter 10. The period a, the rise response time b, and the fall response time c are used to determine the air load Ga, A correction cycle a0, a corrected rise response time b0, and a corrected fall response time c0 are obtained by correcting with the quantity Ga, and the values a0, b0, c0 of the predetermined times are averaged as needed, and the average cycle A and the average rise response time are obtained, respectively. B and the average fall response time C are obtained, and the average rise response time B of these values A, B, and C is calculated as the average fall response time C
The deterioration comparison value REK of the first O2 sensor 88 is obtained from the value (B / C) obtained by dividing by the formula (1), and the deterioration comparison value REK is compared with a predetermined abnormality determination value NG to determine the deterioration state of the first O2 sensor 88. I do.

When the value (B / C) obtained by dividing the average rise response time B by the average fall response time C is 1.0 or more, the control means 70 sets this value (B / C) to 1.0. Average period A in this case and average period A
(A × K) multiplied by the correlation value K1 based on the exhaust component value of
1) is added to the divided value (B / C) to obtain a deterioration comparison value REK, and a value (B / C) obtained by dividing the average rising response time B by the average falling response time C.
When C) is less than 1.0, this value (B / C) is 1.0
The value (A × K2) obtained by multiplying the average period A in the case of less than the correlation value K2 by the exhaust component value of the average period A from the divided value (B / C) is subtracted from the deterioration comparison value RE.
Find K.

The control means 70 calculates the degradation comparison value R
EK is compared with a preset minimum abnormality determination value NG1 and a maximum abnormality determination value NG2. If the deterioration comparison value REK is greater than the minimum abnormality determination value NG1 and less than the maximum abnormality determination value NG2, the first O2 sensor 88 is activated. If the deterioration comparison value REK is equal to or smaller than the minimum abnormality determination value NG1 and equal to or larger than the maximum abnormality determination value NG2, the first O2 sensor 88 is determined to be abnormal.

Next, the air-fuel ratio sensor deterioration determination control device 68
Will be described with reference to FIG.

When the control means 70 starts the internal combustion engine 2 and starts the judgment (step 200), the control means 70 reads a predetermined condition for judging deterioration (step 202), and the first O2 sensor 8
It is determined whether the deterioration determination condition of No. 8 is satisfied (step 2
04).

As the deterioration judgment condition, for example, the first O2
The feedback control is being performed by the sensor 86 and the predetermined time x has elapsed after the start of the feedback control, and the engine speed Ne is within a predetermined speed range (Nelow ≦ Ne ≦ N).
high), the engine load (air amount Ga) is within a predetermined range (Glow ≦ Ga ≦ Gahigh), and the engine negative change amount (for example, air amount change amount) △ GA is equal to or smaller than the determination value δGA (ΔGA ≦ δA), and that the internal combustion engine 2 has been completely warmed up.

In the above judgment (step 204), if any one of the conditions is not satisfied and the judgment is NO, the process returns to the reading of the deterioration judgment condition (step 202). In the judgment (step 204), all are satisfied and YES
In the case of (1), as shown in FIG. 2, the period a, the rising response time b, and the falling response time c of the first signal output from the first O2 sensor 88 are measured (step 206).

While measuring these values a, b, and c, the air flow meter 10 detects the air amount Ga as the engine load, and measures the air amount change ΔGa within a predetermined time (step 208).

When the deterioration judgment condition is not satisfied during the measurement, the measurement result up to that time is stored and the next deterioration judgment condition is satisfied (step 210).

It is determined whether N measurements have been completed (step 212). This determination (step 212) is N
In the case of O, the deterioration judgment condition is read (step 20).
Return to 2).

If the judgment (step 212) is YES, as shown in FIG. 3, the period a and the rising response time b
And the fall response time c are corrected by the air amount Ga to obtain a correction cycle a0, a corrected rise response time b0, and a corrected fall response time c0, and these N times a0, b0, c0 are averaged at any time. Then, an average period A, an average rise response time B, and an average fall response time C are obtained (step 214).

The period a, the rise response time b, and the fall response time c of the first O2 sensor 88 are substantially linear with respect to the engine load GA (air amount Ga in this embodiment) as shown in FIG. There is a great correlation. From this correlation,
Unless the values a, b, and c are corrected, the comparison determination value REK
Becomes large, and the judgment accuracy is reduced.

Therefore, the period a, the rise response time b, and the fall response time c are corrected as the engine load GA by, for example, the air amount Ga, and the correction period a ₀ , the corrected rise response time b _0, and the corrected fall response time are corrected. Find c ₀ . Note that this correction is performed by using the equations shown in FIG.
It is determined for each of bc.

The average period A, the average rise response time B, and the average fall response time C are calculated by the equations described in step 214 in FIG. Although only the equation of the average period A (AVEa ₀ ) is illustrated in step 214, the average rise response time B (AVE
b ₀ ) and the average fall response time C (AVEc ₀ ) are obtained by the same formula.

A deterioration comparison value REK of the first O2 sensor 88 is obtained from a value (B / C) obtained by dividing the obtained average rise response time B of the values A, B, and C by the average fall response time C. The deterioration state of the first O2 sensor 88 is determined by comparing the deterioration comparison value REK with a preset abnormality determination value NG (steps 216 to 22).
4).

First, the value (B / C) obtained by dividing the average rise response time B by the average fall response time C is 1.
It is determined whether it is 0 or more (step 216).

The value obtained by dividing the average rise response time B by the average fall response time C (B / C), and the value obtained by adding the average fall response time C to the average period A or the average rise response time B (B + C) And the exhaust gas component value have a relationship shown in FIGS. 4 and 5, where B / C ≧ 1.
In the case of 0, the CO value and the THC value are significantly deteriorated.
When B / C <1.0, the NOx value is significantly deteriorated.

Therefore, in the determination (step 216), when the value (B / C) obtained by dividing the average rise response time B by the average fall response time C is 1.0 or more, YE
In the case of S, the value (A × K1) obtained by multiplying the average period A when the value (B / C) is 1.0 or more by the correlation value K1 based on the exhaust component value of the average period A is calculated as The deterioration comparison value REK is obtained by adding to the divided value (B / C) (step 218).

On the other hand, in the judgment (step 216), the average rise response time B is divided by the average rise response time B by the average fall response time C (B
/ C) is less than 1.0 and NO, this value (B /
The value (A × K2) obtained by multiplying the average period A when C) is less than 1.0 by the correlation value K2 based on the exhaust component value of the average period A is subtracted from the divided value (B / C). To determine the deterioration comparison value REK (step 220).

The obtained deterioration comparison value REK is compared with a preset minimum abnormality determination value NG1 and a maximum abnormality determination value NG2 (step 222), and NG1 <REK <NG2.
Is determined (step 224).

In this determination (step 224), if the deterioration comparison value REK is greater than the minimum abnormality determination value NG1 and less than the maximum abnormality determination value NG2, that is, if YES, that is, NG
If 1 <REK <NG2, it is determined that the first O2 sensor 88 is normal, and the process ends (step 228).

In the above judgment (step 224), when the deterioration comparison value REK is one of the minimum abnormality judgment value NG1 or less and the maximum abnormality judgment value NG2 or more, that is, R
If EK ≦ NG1 or NG2 ≦ REK, the first O2
The sensor 88 is determined to be abnormal, a warning is issued by turning on the warning lamp 98, etc., and the user is notified (step 226), and the process ends (step 228).

As described above, when the condition for determining the deterioration of the first O2 sensor 88 is satisfied, the control means 70 sets the period a, the rising response time b, and the falling response time c of the first signal output from the first O2 sensor 88. While measuring these values, the air flow meter 10 detects the amount of air Ga, which is the engine load, while measuring these values, and determines the period a, the rising response time b, and the falling response time c by the engine that is measuring these values. The correction period a is corrected by the air amount Ga as a load.
0, a corrected rise response time b0, and a corrected fall response time c0, and these N times a0, b0, c
0 to obtain an average period A, an average rise response time B, and an average fall response time C, respectively.
A deterioration comparison value REK of the first O2 sensor 88 is obtained from a value (B / C) obtained by dividing the average rise response time B of B · C by the average fall response time C, and this deterioration comparison value R
EK is compared with a preset abnormality determination value NG to determine the first
The deterioration state of the O2 sensor 88 is determined.

When the value (B / C) obtained by dividing the average rise response time B by the average fall response time C is 1.0 or more, the control means 70 sets this value (B / C) to 1.0. Average period A in this case and average period A
(A × K) multiplied by the correlation value K1 based on the exhaust component value of
1) is added to the divided value (B / C) to obtain a deterioration comparison value REK, and a value (B / C) obtained by dividing the average rising response time B by the average falling response time C.
When C) is less than 1.0, this value (B / C) is 1.0
The value (A × K2) obtained by multiplying the average period A in the case of less than the correlation value K2 by the exhaust component value of the average period A from the divided value (B / C) is subtracted from the deterioration comparison value RE.
Find K.

The control means 70 calculates the deterioration comparison value R
EK is compared with a preset minimum abnormality determination value NG1 and a maximum abnormality determination value NG2. If the deterioration comparison value REK is greater than the minimum abnormality determination value NG1 and less than the maximum abnormality determination value NG2, the first O2 sensor 88 is activated. If the deterioration comparison value REK is equal to or smaller than the minimum abnormality determination value NG1 and equal to or larger than the maximum abnormality determination value NG2, the first O2 sensor 88 is determined to be abnormal.

As described above, the air-fuel ratio sensor deterioration determination control device 68 considers various aspects of the period a, the rise response time b, and the fall response time c of the signal of the first O 2 sensor 88 and takes into account the engine load. As a result, the problem that the degree of deterioration for each exhaust gas component changes can be avoided, and accurate determination can be made.

Therefore, the air-fuel ratio sensor deterioration determination control device can enhance the accuracy of the deterioration determination of the first O2 sensor 88, prevent the exhaust harmful component value from increasing, and avoid erroneous determination. Reliability can be improved, unnecessary component replacement due to erroneous determination can be avoided, and an increase in cost can be avoided.

[0052]

As described above, according to the present invention, the air-fuel ratio sensor deterioration determination control device takes into account various aspects of the period of the signal of the air-fuel ratio sensor, the rise response time, and the fall response time, as well as the engine. Since the determination is performed in consideration of the load, a problem in which the degree of deterioration of each exhaust gas component changes can be avoided, and accurate determination can be performed.

For this reason, this air-fuel ratio sensor deterioration determination control device can improve the accuracy of the deterioration determination of the air-fuel ratio sensor, can prevent an increase in the harmful component value of exhaust gas, can avoid erroneous determination, and can be reliable. Therefore, unnecessary parts replacement due to erroneous determination can be avoided, and an increase in cost can be avoided.

[Brief description of the drawings]

FIG. 1 is a flowchart of a determination performed by an air-fuel ratio sensor deterioration determination control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a signal of an O2 sensor.

FIG. 3 is a diagram showing a correlation between an engine load and a signal of an O2 sensor.

FIG. 4 is a diagram showing a correlation between an exhaust component value and a signal of an O2 sensor.

FIG. 5 is a diagram showing a correlation value based on an exhaust component value when a value obtained by dividing a rising response time by a falling response time is constant.

FIG. 6 is a diagram illustrating a relationship between a deterioration comparison value and an abnormality determination value.

FIG. 7 is a configuration diagram of an air-fuel ratio sensor deterioration determination control device.

FIG. 8 is a diagram showing a signal of an O2 sensor.

FIG. 9 is a diagram showing a correlation between an exhaust component value and a signal of an O2 sensor.

FIG. 10 is a diagram showing a correlation value based on an exhaust component value when a value obtained by dividing a rising response time by a falling response time is constant.

[Explanation of symbols]

 Reference Signs List 2 internal combustion engine 4 intake passage 6 exhaust passage 10 air flow sensor 30 fuel injection valve 68 air-fuel ratio sensor deterioration determination control device 70 control means 88 first O2 sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/14 310 F02B 77/08 G01M 15/00 F02D 45/00 314 F02D 45/00 358 G01M 15/00

Claims (2)

(57) [Claims] An air-fuel ratio sensor is provided in an exhaust passage of an internal combustion engine, a load sensor for detecting an engine load of the internal combustion engine is provided, and when a condition for determining deterioration of the air-fuel ratio sensor is satisfied, the air-fuel ratio sensor is provided. The cycle of the output signal, the rise response time, and the fall response time are measured, and while these values are being measured, an engine load is detected by the load sensor, and the cycle, the rise response time, and the fall response time are measured. Is corrected by the engine load being measured to obtain a correction cycle, a corrected rise response time, and a corrected fall response time, and these predetermined values are averaged at any time to obtain an average cycle, an average rise response time, and an average rise response, respectively. The fall response time is determined, and the average rise response time is averaged.
A control means for determining a deterioration comparison value of the air-fuel ratio sensor from a value obtained by dividing by the fall response time, and comparing the deterioration comparison value with a preset abnormality determination value to determine a deterioration state of the air-fuel ratio sensor. An air-fuel ratio sensor deterioration determination control device for an internal combustion engine, comprising: 2. When the value obtained by dividing the average rise response time by the average fall response time is equal to or greater than 1.0, the control means determines the average period and the average when the value is equal to or greater than 1.0. The value obtained by multiplying the value obtained by multiplying the correlation value by the exhaust component value of the cycle to the value obtained by the division is used to obtain a deterioration comparison value, and the value obtained by dividing the average rise response time by the average fall response time is less than 1.0. In this case, a value obtained by multiplying the average period when the value is less than 1.0 by a correlation value based on the exhaust component value of the average period is subtracted from the divided value to obtain a deterioration comparison value. The deterioration comparison value is compared with a preset minimum abnormality judgment value and a maximum abnormality judgment value. If the deterioration comparison value exceeds the minimum abnormality judgment value and is less than the maximum abnormality judgment value, the air-fuel ratio sensor is judged to be normal. And control means for determining that the air-fuel ratio sensor is abnormal when the deterioration comparison value is equal to or less than a minimum abnormality determination value and equal to or greater than a maximum abnormality determination value. Fuel ratio sensor deterioration determination control device.