JPH0828327A - Trouble existence judging method for internal combustion engine and abnormality detecting device - Google Patents

Abstract

PURPOSE:To speedily judge normality of an internal combustion engine, and reliably obtain a maximal value and a minimal value. CONSTITUTION:A catalytic converter 6 housing catalytic converter rhodium is arranged in an exhaust passage 5, and O2 sensors 7 and 8 are arranged in the exhaust passage 5 on the upstream side and the downstream side of the catalytic converter 6. A control circuit 11 has a CPU 12, a ROM 13, a RAM 14 or the like, and the RAM 14 encloses various counters and flags. When a trouble judgment is started, when an output value from the O2 sensor 8 is less than a second reference value, or when it exceeds a first reference value, the CPU 12 steps the count number, and hereafter, when the output value from the O2 sensor exceeds the first reference value, and when it is less than the second reference value, the CPU 12 steps the count number, respectively, and judges that the O2 sensor does not run into trouble when the count number reaches 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the presence / absence of a failure in an internal combustion engine, and more particularly to a method for determining the presence / absence of a sensor in an internal combustion engine for detecting the state of an engine and an abnormality detecting device for the internal combustion engine. .

[0002]

2. Description of the Related Art Conventionally, in internal combustion engines, diagnosis detection has been carried out, and when an abnormality is detected in one of several diagnosis detection items, a warning lamp is turned on. . According to legal regulations, if an abnormality is detected in one of several diagnostic detection items and the warning lamp is turned on, it is necessary to determine that all the points are normal in order to turn off the warning lamp. . Therefore, there is a demand to make a normal determination as soon as possible during normal operation.

One of several diagnostic detection items is the O ₂ sensor. In the O ₂ sensor,
In some cases, the maximum voltage value and the minimum voltage value of the O ₂ sensor waveform within the determination period determined to be normal or abnormal may be output. Reason for obtaining the maximum value, minimum value, Toka how close to the determination level (abnormal / normal) upon normal determination, i.e., like or not than being determined to be normal by the abnormality barely, deterioration of the O ₂ sensor This is to prepare the degree as an effective means for failure analysis in the market.

As a conventional method, after a certain amount of time (for example, 10 minutes) has passed, if there is no abnormality, it is determined to be normal, and the maximum value and the minimum value among them are taken.

[0005]

However, this method has a problem that it takes time to determine that the operation is normal even though the method is operating normally. Therefore, in order to determine the normality as soon as possible, it may be possible to determine when the level exceeds the predetermined level that can be determined to be normal.
There is a problem that the minimum value cannot be obtained. Also, the maximum value =
It can be considered that the maximum value and the minimum value = the minimum value, but as this method, (previous AD value)-(current AD value) = d, and when the sign of d is reversed, it is 1 bit due to noise or the like.
However, if there is a deviation, it may be judged as an extreme value.

Further, as shown in FIG. 13, when the maximum value and the minimum value are set as the maximum value and the minimum value in a predetermined time from the determination start time T1 to the determination end time T2, and the maximum value α is provided as the market analysis information, the maximum value α However, there is a risk that the ECU may be replaced by providing as the minimum value β1 a value whose minimum value is not determined at the end time T2 of the predetermined time. In FIG. 13, the true minimum value is β, and V1 and V2 indicate reference levels.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a failure presence / absence determining method and an abnormality detecting device for an internal combustion engine which can quickly determine normality. Another object of the present invention is to provide a failure presence / absence determining method and an abnormality detecting device for an internal combustion engine, which can reliably provide the maximum value and the minimum value as market analysis information.

[0008]

In order to achieve the above-mentioned object, the invention of claim 1 is provided for detecting the engine state of an internal combustion engine, and in a normal state, a plurality of reference values having a magnitude relationship are used. The maximum value that exceeds the first reference value of the larger one,
A method for determining the presence / absence of a failure in an internal combustion engine comprising a sensor that outputs an output waveform having a smaller minimum value that is smaller than a second reference value, when the output value from the sensor exceeds the first reference value, and The gist is that when the output value falls below the second reference value, the count number of the counting means is incremented, and when the count number reaches a predetermined number, it is determined that the sensor is not defective.

The invention according to claim 2 is provided for detecting the engine state of the internal combustion engine, and in the normal state, the maximum value exceeding the first reference value of the larger one of the plurality of reference values having a magnitude relationship is set. In a method for determining the presence / absence of a failure in an internal combustion engine that includes a sensor that outputs an output waveform having a smaller minimum value that is smaller than the second reference value, which is smaller than the second reference value, the output value from the sensor is the second reference when the failure determination starts. When it is below the value or when it exceeds the first reference value, the count value of the counting means is incremented, and thereafter, the output value from the sensor is the first value.
When it exceeds the reference value of, and when it falls below the second reference value, the count number of the counting means is incremented,
The gist is to determine that the sensor has not failed when the number of counts reaches a predetermined number.

The invention of claim 3 is the same as claim 1 or claim 2.
In the first counting means, the counting means counts when the output value from the sensor exceeds the first reference value;
And a second counter that counts when the output value from the sensor falls below the reference value of 1. When the count number of both counters reaches a predetermined number, it is determined that the sensor is not malfunctioning. .

The invention of claim 4 is the invention of claims 1 to 3.
In any one of the claims, the sensor is an air-fuel ratio sensor for detecting an air-fuel ratio arranged upstream and downstream of the catalytic converter arranged in the exhaust system of the internal combustion engine. Is the gist.

A fifth aspect of the present invention is provided to detect the engine state of the internal combustion engine. In a normal state, the maximum value exceeding the first reference value of the larger one of the plurality of reference values having a magnitude relationship is set as the maximum value. , A sensor that outputs an output waveform having a smaller minimum value that is smaller than the second reference value, storage means that stores the maximum value and the minimum value of the sensor that are output from time to time, and the first reference. When the output value from the sensor exceeds the value and when the output value falls below the second reference value, when counting means for incrementing the count number and when the count number by the counting means reaches a predetermined number The gist is an abnormality detection device for an internal combustion engine, comprising: a determination unit that determines that the sensor is not in failure.

According to the invention of claim 6, which is provided for detecting the engine state of the internal combustion engine, in the normal state, the maximum value exceeding the larger first reference value of the plurality of reference values having a magnitude relationship is set. , A sensor that outputs an output waveform having a smaller minimum value that is smaller than the second reference value, a storage unit that stores the maximum value and the minimum value of the sensor that are output at each time, and a failure determination start time When the output value from the sensor is lower than the second reference value or exceeds the first reference value, the count value is incremented, and thereafter the output value from the sensor is set to the first reference value. When the reference value is exceeded and when it is less than the second reference value, the counting means increments the count number respectively, and when the count number of the counting means reaches a predetermined number, the sensor is not defective. And a determination means for determining It is summarized in that an abnormality detection device combustion engine. .

The invention of claim 7 is claim 5 or claim 6.
In, the counting means counts the inversion of the flag when the output value from the sensor exceeds the first reference value, and the inversion of the flag when the output value from the sensor falls below the second reference value. And a second counter that counts the number of times, and the determination means is an abnormality detection device for an internal combustion engine that determines that the sensor has not failed when the count numbers of both counters reach a predetermined number. .

[0015]

According to the above construction, the invention of claim 1 is the first
When the output value from the sensor exceeds the reference value of, and when the output value is below the second reference value, the count number of the counting means is respectively incremented, and when the count number reaches a predetermined number, the sensor It is determined that is not broken.

According to a second aspect of the present invention, when the output value from the sensor is below the second reference value or exceeds the first reference value at the start of the failure determination, the counting means counts. When the output value from the sensor exceeds the first reference value and falls below the second reference value, the count number of the counting means is advanced,
When the number of counts reaches a predetermined number, it is determined that the sensor has not failed. According to the invention of claim 3, the first counter counts when the output value from the sensor exceeds the first reference value. When the output value from the sensor falls below the second reference value, the second counter counts. Then, when the number of counts of both counters reaches a predetermined number, it is determined that the sensor has not failed.

According to the fourth aspect of the invention, the presence / absence of a failure of the internal combustion engine is determined based on the output waveform of the air-fuel ratio sensor. In the invention of claim 5, the storage means stores the maximum value and the minimum value of the sensor which are output at each time. The counting means is first
When the output value from the sensor exceeds the reference value of, and when the output value falls below the second reference value, the counting is performed.
The determining means determines that the sensor is not in failure when the number counted by the counting means reaches a predetermined number.

According to the sixth aspect of the invention, the storage means stores the maximum value and the minimum value of the sensor which are output at that time. When the output value from the sensor is lower than the second reference value or exceeds the first reference value at the start of the failure determination, the counting means advances the count number, and thereafter, the sensor. When the output value from exceeds the first reference value and falls below the second reference value, the count number is incremented. The judging means judges that the sensor has not failed when the count number of the counting means reaches a predetermined number.

According to the invention of claim 7, the first counter counts the inversion of the flag when the output value from the sensor exceeds the first reference value. Further, the second counter counts the inversion of the flag when the output value from the sensor falls below the second reference value. The determination means determines that the sensor is not in failure when the count numbers of both counters reach a predetermined number.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIG.
~ It demonstrates based on FIG. FIG. 1 is a diagram showing the configuration of an embodiment according to the present invention. In FIG. 1, a throttle valve 3 that is opened / closed in conjunction with the operation of an accelerator pedal (not shown) is provided on the upstream side of the intake passage 2 of the engine body 1. Further, a fuel injection valve 4 for supplying pressurized fuel from the fuel supply system to the engine body 1 is provided on the downstream side of the intake passage 2. In the exhaust passage 5, a catalytic converter 6 that accommodates a three-way catalyst that simultaneously purifies three harmful components HC, CO, and NO _x in the exhaust gas is arranged. The exhaust passage 5 upstream and downstream of the catalytic converter 6, the upstream O ₂ sensor 7 and the downstream O ₂ of the air-fuel ratio sensor
Each sensor 8 is provided. Same O ₂ sensor 7,
8 outputs a voltage signal according to the oxygen component concentration in the exhaust gas. The air-fuel ratio is controlled according to this output value.

Further, the O ₂ sensors 7 and 8 are provided with heaters 9 and 10 for promoting activation of the O ₂ sensors 7 and 8. The heaters 9 and 10 are control circuits 1 described later.
The power is supplied in response to the power supply signal of 1 to generate heat. The warning lamp 19 receives an abnormality detection signal and displays a warning when an abnormality in the O ₂ sensors 7 and 8 is detected.

The control circuit 11 constituting the judging means is a CP
U12, ROM13, RAM14 as storage means and counting means, backup RAM15, reference clock generation circuit 16, A / D converter 17, and I / O port 1
8 is provided. Detection signals from the O ₂ sensors 7 and 8 are input to the control circuit 11, and the data is temporarily stored in the RAM 14. The RAM 14 incorporates various counters and flags described later. The ROM 13 stores the programs shown in FIGS.

Next, the operation of the abnormality detecting device of this embodiment will be described. In this embodiment, the detection of abnormality of the downstream O ₂ sensor 8 will be described. The failure diagnosis of the O ₂ sensor 8 is judged and displayed by the judgment routine of FIG. The determination routine performs processing at regular timing, for example, 40 ms. Therefore, it is determined at the timing of the determination routine whether it is the timing at which the determination can be made first, that is, whether the diagnosis execution condition is satisfied (step 210). As the diagnosis execution condition, whether the O ₂ sensor is activated by the heat generation operation of the heater 10 and the output voltage is stabilized (A / F feedback condition, etc.), or the erroneous determination is made. Whether the abnormality of the diagnosis of is detected.
When it is determined in step 210 that the diagnosis execution condition is not satisfied, this routine is ended.
When it is determined that the diagnosis execution condition is satisfied, the voltage AD (hereinafter referred to as OXAD) value of the O ₂ sensor 8 at that time is compared with the V2 level as the second reference value that can be determined to be a normal value (step 211). If it is equal to or higher than the V2 level, the process proceeds to step 216 described later. If it is smaller than the V2 level, it is next determined whether or not COX = 0 (step 212). In addition, whether or not COX = 0 is determined here is the first count after the diagnosis execution condition is satisfied,
OXAD <V regardless of the OXAD value before the execution condition is satisfied
This is because if the value is 2, it counts up by 1.

If C0X = 0 in step 212, step 213 is bypassed and step 214 is entered. If COX ≠ 0, an XOX flag (hereinafter referred to as XOX) = to see whether or not the OXAD value has crossed the V1 level (V1> V2) as the first reference value.
It is checked whether or not it is 0 (step 213). XOX =
If it is 1, XOX = 0 is set in step 214, and COX is set.
A counter (hereinafter referred to as COX) is incremented (step 215) and the process proceeds to step 216. If XOX = 0 in step 213, it means that the voltage has become smaller than the V1 level without exceeding the V2 level, and therefore COX is not incremented in step 216.
Move to. In step 216, the minimum OXAD value stored in the RAM 14 up to now (hereinafter referred to as OXMN) is compared, and if smaller, the current 0XAD value is stored in the RAM.
The OXMN is updated by storing it in 14 (step 217). On the contrary, if it is larger than the minimum value of the OXAD values so far, the OXMN is not updated and the process proceeds to step 218.

Next, the determination of the upper V1 level will be described. First, in step 218, the OXAD value at that time is compared with the V1 level as a reference level that can be determined to be a normal value, and if it is less than or equal to the V1 level, the process proceeds to step 223.
If it is higher than the V1 level, the process proceeds to step 219. Here, similarly to step 212, it is determined whether or not COX = 0. Whether or not COX = 0 is determined here because the first count of the COX counter after the diagnosis execution condition is satisfied is incremented by 1 if OXAD> V1 regardless of the OXAD value before the execution condition is satisfied. is there. Performing step 212 and step 219 twice,
This is because the OXAD value when the diagnosis execution condition is satisfied is unknown. COX = 0 in step 219
If so, bypass step 220 and go to step 22
In step 1, XOX = 1. And next step 2
22 OXAD regardless of the value before the execution condition is satisfied
When the level is> V1, the count is incremented by 1.

When COX ≠ 0, the OXAD value is V2.
In step 220, it is determined whether the level has been crossed.
If XOX = 1, it means that the V2 level has not been crossed since the previous XOX = 1 was set, and therefore the COX process is not performed and the process proceeds to step 223. Step 22
When XOX = 0 at 0, it means that the OXAD value exceeds the V1 level for the first time after crossing the V2 level, XOX = 1 (step 221), and COX is incremented (step 222). Then, in step 223, the maximum OXAD value stored in the RAM 14 up to now (hereinafter referred to as OXMX) is compared, and if the OXAD value at that time is larger than the maximum value, OXMX is updated (step 224). If it is less than the maximum value, the process proceeds to step 225.

Next, a routine for determining whether the operation is normal or abnormal will be described. First, in step 225, it is determined whether or not COX ≧ 4. If COX ≧ 4, it is determined to be normal in step 227, and the process proceeds to step 229. COX <4
In this case, in step 226, the abnormality detection condition for determining whether the abnormality is acceptable is checked. Abnormality detection conditions include, for example, the time during which the diagnosis execution condition is satisfied is far exceeded (the time required for COX ≧ 4 is far exceeded). Step 22
If the abnormality detection condition is satisfied in step 6, the process proceeds to step 228 and it is determined that there is an abnormality, and the warning lamp 1
9 is operated to display, and the process proceeds to step 229.

When the determination of abnormality or normal is completed in steps 227 and 228, the maximum value (OXMX) and the minimum value (OXMN) so far are stored in the backup RAM 15 (steps 229 and 230). If neither abnormal nor normal can be determined, the above steps are repeated.

The XOX flag and COX counter in the above description will be described with reference to FIG. 6 (b), (c),
6D shows the operating states of the XOX flag and the COX counter when the determination start time point differs from A, B, and C to the output voltage from the O ₂ sensor 8 shown in FIG. 6A. .

The XOX flag is set when the diagnosis execution condition is satisfied and OXAD> V1 level (step 210,
Steps 218 to 221) are set to 1, and when the diagnosis execution condition is satisfied and OXAD <V2 level (steps 210, 211 to 21).
4) is set to 0. The COX counter is initially XOX = 1,
When the condition that XOX = 0 is satisfied, counts 1 and then X
It counts up when the OX flag is inverted.

The reason for setting the XOX flag as described above is that by the time the OXAD value reaches OXAD <V2 level,
This is to check whether or not XAD> V1 level. Similarly, OXA until OXAD> V1 level
This is to check whether D <V2.

Further, the reason why the COX counter is set as described above is that the OXAD value at the start of judgment is unknown, and therefore the inversion of the XOX flag cannot be obtained at the first count, so XOX = 0, XOX. It is assumed that the condition of = 1 is satisfied.

After that, when XOX is inverted, the count-up is as shown in FIG.
This is because when the level is crossed, the operation is not normal and the count-up is not performed.

The reason why the normal judgment is made when COX ≧ 4 is as follows.
Although normal determination can already be made when COX ≧ 2, the maximum and minimum values can be surely obtained in FIGS. 5, 6 (a) and 6 (b),
As is clear from (c), when COX ≧ 3, the determination start B is good, but in the case of the determination start A, the minimum value cannot be taken, so in any case the determination is started. For good reason, COX ≧ 4.

When the judgment is made by this method, the maximum value and the minimum value are constantly updated by counting the peaks and valleys that make the maximum value and the minimum value. Can be surely obtained.

As shown in FIG. 7, when the V1 level is crossed and then the V2 level is not crossed and the V1 level is crossed again, the flag is not inverted and the count-up is not performed, so that the normal determination value = 4. There is no. Therefore, in the case of the characteristic that the amplitude does not cross the determination levels V1 and V2, it is not erroneously determined to be normal.

Next, a second embodiment will be described with reference to FIGS. 8 and 9. In this embodiment, only the difference from the first embodiment in the determination routine will be described, and the same steps as those in the first embodiment will be designated by the same step numbers and the description thereof will be omitted.

In this embodiment, in the flow chart of the first embodiment, steps 313 and 314 are performed instead of steps 213 and 214, and steps 320 and 321 are performed instead of steps 220 and 221. Done.

That is, step 21 as shown in FIG.
If C0X = 0 in step 2, step 313 is bypassed and step 314 is entered. If COX ≠ 0, it is checked whether or not the XOX flag (hereinafter referred to as XOX) = 1 to see whether the OXAD value has crossed the V1 level (V1> V2) (step 313). X
If OX = 0, XOX = 1 at step 314,
A COX counter (hereinafter referred to as COX) is incremented (step 215) and the process proceeds to step 216.
If XOX = 1 in step 313, V2
It means that it has become smaller than the V1 level without exceeding the level, so step 2 without incrementing COX.
Move to 16.

When COX = 0 in step 219, step 320 is bypassed and step 321 is executed.
At XOX = 0. And the next step 22
2 OXAD> regardless of the value before the execution condition was met
When the level is V1, the count is incremented by 1. Step 2
If COX ≠ 0 in 19, the OXAD value is V2.
In step 320, it is determined whether the level has been crossed.
If XOX = 0, it means that the V2 level has not been crossed since XOX = 0 was set before. Therefore, the COX process is not performed, and the process proceeds to step 223. Step 32
When XOX ≠ 0 at 0, it means that the OXAD value exceeds the V1 level only after crossing the V2 level, XOX = 0 (step 321), and COX is incremented (step 222).

Therefore, in the second embodiment, the relationship is the same as the setting and resetting of the XOX flag of the first embodiment, and the operation and effect thereof are the same as those of the first embodiment. Next, a third embodiment will be described with reference to FIGS.

In this embodiment, the RAM 14 as a counting means has a COXH counter as a first counter and a COXL counter as a second counter.

The failure diagnosis of the O ₂ sensor 8 in this embodiment is judged by the judgment routine of FIGS. 10 and 11 and displayed. Also in this embodiment, the determination routine performs processing at regular timing, for example, 40 ms. First, when this routine is entered, it is determined at the timing of the determination routine whether or not it is the timing at which the determination can be made first, that is, whether or not the diagnosis execution condition is satisfied (step 410). The diagnosis execution conditions are the same as those in the first embodiment.

When it is determined in step 410 that the diagnosis execution condition is not satisfied, this routine ends. When it is determined that the diagnosis execution condition is satisfied, the voltage AD of the O ₂ sensor 8 at that time (hereinafter, OXA
The value D is compared with the V2 level (step 41).
1). If it is equal to or higher than the V2 level, step 416 described later.
Move to

If it is smaller than the V2 level, then step 4
12, XFIRST flag (hereinafter, XFIRST
It is determined whether or not) = 1. In addition, here XFIR
Whether or not ST = 1 is determined is that the first count of the COXL counter after the diagnosis execution condition is satisfied is OXAD regardless of the OXAD value before the execution condition is satisfied.
This is because if V2, the count is incremented by 1. XFI
The RST is reset to 0 at the initial setting after the control circuit 11 of the internal combustion engine is started, and the step 433 described later is performed.
Is determined to be normal, or is determined to be abnormal in step 428, it is reset to 0.

In step 412, XFIRST ≠ 1
If so, bypass step 413 and step 43
XFIRST is set to 1 at 1, and X is set at step 414.
Set OX = 0. If XFIRST = 1, then OXA
In order to check whether the D value has crossed the V1 level (V1> V2), it is checked whether or not XOX = 0 (step 4).
13). If XOX = 1, then in step 414 XOX
= 0, COXL counter (hereinafter referred to as COXL)
Is incremented (step 415) and step 41
Go to 6. In step 413, XOX = 0
In the case of, it means that it has become smaller than the V1 level without exceeding the V2 level, and the process proceeds to step 416 without incrementing COXL. Steps 416-4
Since step 18 is the same as steps 216 to 218 of the first embodiment, its explanation is omitted.

Next, the determination of the upper V1 level will be described. First, in step 418, the OXAD value at that time and V1
The levels are compared. If the level is V1 level or less, step 42
If it is larger than V1 level, step 419 is executed.
Go to. Here, as in step 412, XFIRST is performed.
= 1 is determined. Whether or not XFIRST = 1 is determined here because the first count of the COXH counter after the diagnosis execution condition is satisfied is incremented by 1 if OXAD> V1 regardless of the OXAD value before the execution condition is satisfied. is there. In addition, the determination as to whether or not XFIRST = 1 is performed twice in step 412 and step 419 is performed when the diagnosis execution condition is satisfied.
This is because the XAD value is unknown. If XFIRST ≠ 1 in step 419, step 420 is bypassed, XFIRST is set to 1 in step 432, and the process proceeds to step 421. In step 421, XOX = 1 is set. Then, in the next step 422, if OXAD> V1 level, the count is incremented by 1 regardless of the value before the diagnosis execution condition is satisfied.

Further, in step 419, XFIRST
When = 1, it is determined in step 420 whether the OXAD value has crossed the V2 level. If XOX = 1 in step 420, V2 is set after the previous XOX = 1.
COX because it does not cross the level
No processing is performed, and the process proceeds to step 423. If XOX = 0 in step 420, the OXAD value is V2.
It means that V1 level was exceeded for the first time after crossing the level, and XOX = 1 (step 421), and COXH
The counter is incremented (step 422). Then, in step 423, it is compared with the maximum value (OXMX) of the OXAD values stored so far in the RAM 14, and if the OXAD value at that time is larger than the maximum value, OXMX is updated (step 424). If it is less than the maximum value, the process proceeds to step 425.

Next, the routine for determining whether the operation is normal or abnormal will be described. First, in step 425, it is determined whether or not COXL ≧ 2, and if COXL ≧ 2, it is determined in step 426 whether or not COXH ≧ 2. If COXH ≧ 2 in step 426, it is determined to be normal in step 433, and the process proceeds to step 429.

If COXL <2 in step 425, in step 427, the abnormality detection condition for determining whether or not the abnormality is acceptable is checked. Also, step 426
If COXH <2 in step (4), the abnormality detection condition for determining whether the abnormality is acceptable is checked in step 427. Abnormality detection conditions include, for example, the time during which the diagnosis execution condition is satisfied is far exceeded (the time required for COXL ≧ 2 and COXH ≧ 2 is far exceeded). Step 226
If the abnormality detection condition is satisfied in step 4, step 4
28, the warning lamp 19
Is displayed and the operation proceeds to step 429.

When the determination of abnormality or normal is completed in steps 427 and 428, the maximum value (OXMX) and the minimum value (OXMN) so far are stored in the backup RAM 15 (steps 429 and 430). If neither abnormal nor normal can be determined, the above steps are repeated.

XFIRST flag and COX in the above description
The L counter and the COXH counter will be described with reference to FIG. FIG. 12B shows the state of the XOX flag and the state of counting up the COXL counter and the COXH counter in the third embodiment. Also, FIG.
(A) shows the state of the XOX flag and the count-up state of the COX counter of the second embodiment.

The XOX flag is set when the diagnosis execution condition is satisfied and OXAD> V1 level (step 410,
Steps 418 to 421) are set to 1, and when the diagnosis execution condition is satisfied and OXAD <V2 level (step 410, steps 411 to 41)
4) is set to 0. The COXL counter first counts 1 when the condition of XOX = 0 is satisfied, and then counts up when the XOX flag is inverted from 1 to 0. Also, CO
The XH counter first counts 1 when the condition of XOX = 1 is satisfied, and then counts up when the XOX flag is inverted from 0 to 1.

The reason for setting the XOX flag as described above is that by the time the OXAD value reaches the level of OXAD <V2,
This is to check whether or not XAD> V1 level. Similarly, OXA until OXAD> V1 level
This is to check whether D <V2.

The reason why the COXL counter and the COXH counter are set as described above is that the OXA at the start of judgment is determined.
Since the D value is unknown and therefore the inversion of the XOX flag cannot be obtained at the first count, XOX = 0,
It is assumed that the condition of XOX = 1 is satisfied. The reason why the normal determination is made when COXL ≧ 2 and COXH ≧ 2 is that the maximum value and the minimum value are surely taken as in the first embodiment.

Therefore, even in the determination by the method of the third embodiment, the maximum value and the minimum value are constantly updated by counting the peaks and valleys that make the maximum value and the minimum value. Moreover, the maximum value and the minimum value can be surely obtained.

The present invention is not limited to the above embodiment, but may be carried out as follows. (1) Instead of the XFIRST flag of the third embodiment, steps 412 and 419 may be changed to steps of determining whether or not the total value of the COXL counter and the COXH counter is 0. In this case, step 431
And step 432 is omitted, and steps 412 and 41 are omitted.
When COXL + COXH = 0 in step 9, step 4
14 and 421 respectively. Also, step 41
If COXL + COXH ≠ 0 in 2 and 419, the process proceeds to steps 413 and 420, respectively.

(2) The setting and resetting of the XOX flag of the third embodiment may be reversed. That is, steps 420 and 421 are performed instead of steps 413 and 414 of the third embodiment, and steps 420 and 421 of the third embodiment are performed.
Instead of 421, steps 413 and 414 are performed.

(3) In the first embodiment described above, the normality judgment is made when COX ≧ 4, but it may be judged whether the predetermined number of times is 5 or more. However, as the predetermined number of times approaches 4, it becomes possible to determine the normality earlier.

(4) In the third embodiment, COXL ≧ 2,
When COXH ≧ 2, the normality was judged, but for example COXL
≧ 2, COXH ≧ 3 or COXL ≧ 3, COXH ≧ 2
It is also possible to determine whether or not the total number of COXL and COXH is normal as described above or with a count number of 5 or more. However, C
As the total number of times of OXL and COXH approaches 4, the normality determination can be made earlier.

(5) In each of the above-described embodiments, the counting is performed by adding, but it may be determined by subtracting whether or not the predetermined number of times is reached. Even in this case, since the maximum value and the minimum value are constantly updated beyond the peaks and troughs that make the maximum value and the minimum value, the normal determination can be performed quickly and the maximum value and the minimum value can be reliably obtained.

(6) In each of the above embodiments, at the start of the failure determination, if the output value from the sensor at that time is below V2 or exceeds V1, the count number of the counter is incremented. However, when the output value from the air-fuel ratio sensor exceeds V1 after the start of the failure determination, and V2
When it falls below, the count number of the counter may be incremented. In this case, the normality judgment is slightly delayed compared to the above-mentioned respective embodiments, but it is sufficient since it is sufficiently faster than the conventional one.

[0063]

As described above in detail, according to the present invention, the normal judgment of the sensor can be quickly performed, and the maximum value and the minimum value can be obtained.

In particular, the inventions of claims 2 and 6 count even when the failure judgment is started, so that the normality judgment of the sensor can be made earlier. Further, according to the invention of claim 4, it is possible to quickly determine whether the air-fuel ratio sensor is normal. Further, in the inventions of claims 5 to 7, it is possible to reliably provide the maximum value and the minimum value as the market analysis information.

[Brief description of drawings]

FIG. 1 is an electric block circuit diagram of an embodiment embodying the present invention.

FIG. 2 is a flowchart showing execution conditions of a determination process in the first embodiment.

FIG. 3 is a flowchart showing the execution condition of the determination process.

FIG. 4 is a flowchart for similarly obtaining a maximum value and a minimum value.

FIG. 5 is a waveform diagram showing characteristics of an O ₂ sensor, a flag, and a counter.

FIG. 6A is a waveform diagram showing the output voltage of the O ₂ sensor,
(B) is a flag at the start of determination A, a waveform diagram showing the characteristics of the counter, (c) is a flag at the start of determination B,
FIG. 5D is a waveform chart showing the characteristics of the counter, and FIG. 7D is a waveform chart showing the characteristics of the flag and the counter at the start C of determination.

[7] O ₂ sensor is a waveform diagram illustrating O ₂ sensor output voltage when not normal, flag, the characteristics of the counter.

FIG. 8 is a flowchart showing execution conditions of a determination process of the second embodiment.

FIG. 9 is a flowchart for similarly determining the determination process and the maximum / minimum values.

FIG. 10 is a flowchart showing execution conditions of determination processing according to the third embodiment.

FIG. 11 is a flowchart for similarly determining the determination process and the maximum / minimum values.

12 (a) and 12 (b) are waveform diagrams showing characteristics of an output voltage of an O ₂ sensor, a flag, and a counter, respectively.

FIG. 13 is an explanatory diagram in the case of taking a maximum value and a minimum value in the conventional example.

[Explanation of symbols]

1 ... Engine body, 5 ... Exhaust passage, 6 ... Catalytic converter, 7
... upstream O ₂ sensor, 8 ... downstream O ₂ sensor, 11 ... control circuit, 12 ... CPU, 13 ... ROM, 14 ... RAM,
15 ... Backup RAM, 19 ... Warning lamp.

Claims (7)

[Claims] 1. A normal maximum value, which is provided for detecting the engine state of an internal combustion engine, has a maximum value that exceeds a larger first reference value among a plurality of reference values having a magnitude relationship, and a smaller maximum value. A method for determining the presence / absence of a failure in an internal combustion engine that includes a sensor that outputs an output waveform having a minimum value that is less than the reference value of 2, when the output value from the sensor exceeds the first reference value, and the second reference value. A method for determining the presence / absence of a failure of an internal combustion engine, wherein when the output value falls below the value, the count number of the counting means is incremented, and when the count number reaches a predetermined number, it is determined that the sensor is not defective. 2. A maximum value which is provided for detecting the engine state of the internal combustion engine and which exceeds a first reference value of a larger one of a plurality of reference values having a magnitude relationship and a first value of a smaller one in a normal state. In the internal combustion engine failure presence / absence determination method including a sensor that outputs an output waveform having a minimum value that is less than the reference value of 2, the output value from the sensor is below the second reference value at the start of the failure determination. When, or when it exceeds the first reference value, the count number of the counting means is incremented, and thereafter, when the output value from the sensor exceeds the first reference value, and when the second reference value is set. A method for determining the presence or absence of a failure in an internal combustion engine, in which the count number of each of the counting means is stepped up when the count value falls below a predetermined number and when the count number reaches a predetermined number. 3. A first counter that counts when the output value from the sensor exceeds a first reference value,
2. A second counter which counts when the output value from the sensor falls below the second reference value, and when the count number of both counters reaches a predetermined number, it is determined that the sensor is not in failure. Alternatively, the internal combustion engine failure determination method according to claim 2. 4. The air-fuel ratio sensor for detecting an air-fuel ratio arranged upstream and downstream of a catalytic converter arranged in an exhaust system of an internal combustion engine. 13. A method for determining the presence or absence of a failure of an internal combustion engine according to any one of the above. 5. A normal value provided for detecting the engine state of an internal combustion engine, and in a normal state, a maximum value exceeding a larger first reference value among a plurality of reference values having a magnitude relation and a smaller maximum value. A sensor that outputs an output waveform having a minimum value that is less than the reference value of 2, storage means that stores the maximum value and the minimum value of the sensor that are output from time to time, and a first reference value from the sensor. When the output value exceeds, and when the output value falls below the second reference value, counting means for incrementing the count number respectively; and when the count number of the counting means reaches a predetermined number, the sensor fails. An abnormality detecting device for an internal combustion engine, comprising: a determining unit that determines that the abnormality has not occurred. 6. A normal maximum value, which is provided for detecting the engine state of an internal combustion engine, has a maximum value exceeding a larger first reference value and a smaller one of a plurality of reference values having a magnitude relationship. A sensor that outputs an output waveform having a minimum value that is less than the reference value of 2, a storage unit that stores the maximum value and the minimum value of the sensor that are output from time to time, and a sensor from the sensor at the start of failure determination. When the output value is below the second reference value or exceeds the first reference value, the count number is incremented, and thereafter, the output value from the sensor exceeds the first reference value. And counting means for incrementing the count number when the time count falls below the second reference value, and a determining means for determining that the sensor is not in failure when the count number of the count means reaches a predetermined number. Detection of internal combustion engine equipped with Output device. 7. The counting means counts the inversion of the flag when the output value from the sensor exceeds the first reference value, and when the output value from the sensor falls below the second reference value. 7. A second counter for counting the reversal of the flag of the above, wherein the judging means judges that the sensor is not broken when the count numbers of both counters reach a predetermined number respectively. Internal combustion engine abnormality detection device.