JPH09144593A - Diagnosis device of air-fuel ratio detecting body of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of engine operation, in the case where an engine is in an operating state or under operating conditions which are ununiform in fuel distribution in a cylinder at the time of judging the deteriorated degree of a detected body, by filtering the output signal of the detected body for removing the influence of an operation state where the air-fuel ratio of the engine is disturbed. SOLUTION: First the diagnosis of the air-fuel ratio is started 10. If a canister purging is in progress using a purging control valve 11, the output given from an air-fuel sensor is filtered 12. In this case, a digital filter used for the programming of a micro-computer in a control unit or a programmable IC filter installed in the input circuit of the control unit are used as the above filter. A low path or band path filters are effective. As the characteristics of the filter, the setting of cut off frequency on the side of high frequency wave is carried out to an extent where the step response speed of the output of an air ratio sensor can be preserved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for an air-fuel ratio detector such as an oxygen concentration sensor for an internal combustion engine or an air-fuel ratio sensor (hereinafter simply referred to as an air-fuel ratio sensor).

[0002]

2. Description of the Related Art As a conventional diagnostic device for an air-fuel ratio sensor of an engine, a device for detecting an output change speed of an air-fuel ratio detection sensor, or an inversion of air-fuel ratio feedback control of an engine utilizing the output of the air-fuel ratio sensor A device that detects the cycle, and a device that detects the response time of the output of the air-fuel ratio sensor when the air-fuel ratio is fixed to the rich or lean state and the fuel amount is changed stepwise, or the changing speed are known. Has been.

[0003]

The air-fuel ratio sensor sharply detects the influence of the turbulence of the air-fuel ratio near the stoichiometric air-fuel ratio because of its switching characteristics at the stoichiometric air-fuel ratio.
The output signal can be very noisy.
However, the diagnostic device of the conventional technology does not consider that an operating state in which the air-fuel ratio of the engine is disturbed, that is, a noise-like state occurs in the output signal of the air-fuel ratio sensor,
There was a problem that the risk of misdiagnosis was high.

For example, FIG. 1 illustrates the influence on the air-fuel ratio sensor by a canister purge, which is one of the operating states in which the air-fuel ratio of the engine is disturbed. In the detection of the air-fuel ratio sensor, in particular, many sensors have an output signal characteristic that switches at the theoretical air-fuel ratio, and when the response performance of the sensor is evaluated, the sensor output signal is digitally sampled by a control unit or the like. Stable detection of the output signal of is a prerequisite for ensuring accuracy. Under normal operating conditions, the output signal of the air-fuel ratio sensor is as shown in FIG.
As shown in (b), stable detection can be performed. But,
When the canister purge is performed, the air-fuel mixture containing an indefinite amount of fuel to be purged overlaps with the intake pulsation of the engine and disturbs the air-fuel ratio of the intake system, and the effect of the disturbed air-fuel ratio is after the combustion in the cylinder. In the exhaust, the air-fuel ratio sensor
It is detected as shown in (a). Therefore, there is a problem that the influence of the disturbed air-fuel ratio becomes a noise component and is detected as an output signal of the air-fuel ratio sensor, which causes a decrease in the accuracy of the air-fuel ratio sensor.

Alternatively, when a large amount of unburned gas (blow-by gas) accumulated in the crankcase of the engine is discharged to the intake pipe, the same cause may occur. The present invention has been made in view of such a problem, and its purpose is to diagnose the degree of performance deterioration of the air-fuel ratio sensor by eliminating the influence of the operating state in which the engine air-fuel ratio is disturbed, An object of the present invention is to provide a device that can be accurately executed while the engine is operating.

[0006]

[Means for Solving the Problems] To achieve the above object,
A diagnostic device for an air-fuel ratio detector of an engine according to the present invention determines the degree of deterioration of the detector by an output signal of the detector in an engine having an engine operating state detecting means including an exhaust oxygen concentration or an air-fuel ratio detector. And a means for filtering the output signal of the detector when the operating condition or operating condition is such that the fuel distribution of the cylinder is non-uniform when determining the degree of deterioration of the detector. It is characterized by that.

Further, the diagnostic device includes means for digitally filtering the output signal of the detection body, and changing the filter characteristic of the output filter of the detection body when determining the degree of deterioration of the detection body, It is characterized by comprising means for setting the characteristics of the filter of the output signal of the body so as to further attenuate the low frequency side component. Furthermore,
The diagnostic device is provided with means for prohibiting the determination of the degree of deterioration of the detection body when the degree of deterioration of the detection body is determined, when the operating state or operating condition is such that the cylinder fuel distribution becomes uneven. It is characterized by that.

Furthermore, when the operating range or period for determining the degree of deterioration of the detection body is entered during purging of the recovered fuel, the purge of the recovered fuel is performed during the period required for determining the degree of deterioration of the detection body. It is characterized by having means for interrupting. Further, the diagnostic device includes means for determining whether or not the degree of deterioration of the detection object is within a predetermined range, means for changing the sampling rate of the output signal of the detection object, and the sampling rate for the high frequency side. Means for digitally filtering the output signal of the detector, means for determining whether the degree of deterioration of the detector is within a predetermined range, and filter characteristics of the output signal filter of the detector. It is characterized in that it is provided with a means for changing and a means for setting the characteristics of the filter so as to further attenuate the components on the high frequency side.

Further, the diagnostic device is a diagnostic device for judging the degree of deterioration of the detection body in an engine equipped with a device for feedback controlling the air-fuel ratio by the output signal of the detection body, and the output signal of the detection body. Means for detecting the size of the inversion cycle in a predetermined range, means for interrupting or prohibiting the deterioration degree determination of the detection body according to the detection result of the inversion cycle detecting means, and the inversion cycle detecting means. And a means for determining whether or not the detection result is a predetermined value or more, and a means for detecting the magnitude of the correction coefficient of the feedback control, and a result of the means for detecting the magnitude of the correction coefficient. According to the above, the means for interrupting or prohibiting the determination of the degree of deterioration of the detection body, the determination means for determining whether or not the correction coefficient for the feedback control is within a predetermined range, and the connection of the determination means. It is characterized in that a means for interrupting or prohibiting the judgment of the degree of deterioration of the detector in accordance with the.

The engine air-fuel ratio detecting device diagnostic apparatus of the present invention constructed as described above detects the operating state and operating conditions that cause fluctuations in the output signal of the air-fuel ratio detecting device, and prohibits or interrupts the diagnosis. Means for performing, operating conditions that cause fluctuations, means for changing or prohibiting the control condition of operating conditions, means for performing corrections such as filtering to the output signal of the air-fuel ratio detector, filtering of the output signal of the air-fuel ratio detector By providing a means for changing the characteristic or a means for changing the sampling rate of the output signal of the air-fuel ratio detector, for example, in a driving state in which the air-fuel ratio of the engine is disturbed such as canister purge, the canister Elimination of noise in the output signal by stopping purging, elimination of noise in the output signal by filtering the output signal of the detection object, or discontinuation of diagnosis, etc. By making it possible to selectively execute control measures individually or in combination, the influence of operating conditions such as engine air-fuel ratio disturbance is eliminated, and the degree of performance deterioration of the air-fuel ratio sensor is diagnosed during engine operation. It can be executed accurately.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the entire configuration of the engine and the control device for the engine according to the present embodiment. The engine body 101 includes an intake passage 103 and an exhaust passage 111.
In the intake passage 103, an air cleaner 104 is provided, and an air flow sensor 105, a throttle actuator, a throttle sensor 106, and an idle speed control valve 107 are provided on the downstream side (engine body side). Further, a water temperature sensor 102 is attached to the engine body 101, and a rotation speed for generating and detecting a signal at a constant crank angle based on the rotation of a crank shaft (not shown) in the lower part of the engine body 101. Detection device and cylinder identification device (both not shown)
However, a camshaft (not shown) on the upper part of the engine body 101 is further provided with a phase sensor for generating a signal once every two rotations and a detecting device for the phase sensor (both not shown). The output signal of each sensor is input to the control unit 108, information such as crank angle, engine speed, intake air amount, etc. is measured and calculated, and ignition timing based on these parameters indicating the engine operating state,
The control amount such as the fuel injection amount is determined, and the spark plug 109,
Various output components such as the injector 110 and the idle speed control valve 107 are controlled to operate the engine.

Further, the exhaust passage 111 is provided with an air-fuel ratio sensor 112 and a catalytic converter 113, and the control unit 108 performs air-fuel ratio feedback control of the engine on the basis of an output signal of the air-fuel ratio sensor 112, and the exhaust gas is discharged from the engine. The efficiency of purification of exhaust harmful components is improved. A fuel pump 115 is provided in the fuel tank 114. The fuel pump 115 pressure-feeds the fuel to the injector 110 via the fuel pipe 116 and supplies the fuel to the cylinder 117 via the injector 110.
The surplus fuel is returned to the fuel tank 114 via a return pipe (not shown). During this time, the fuel receives heat from the engine 101 having a high temperature, so that the fuel tank 114
The temperature rises to some extent when returning to, and the generation of the evaporated fuel in the fuel tank 114 is promoted due to the influence of the increase in the fuel temperature. The evaporated fuel generated in the fuel tank 114 is captured by the canister 118, and the canister 1
Reference numeral 18 stores an adsorbent 119 (for example, <activated carbon) for adsorbing the evaporated fuel, and the evaporated fuel generated in the fuel tank 114 is released into the adsorbent 119 of the canister 118 via the introduction pipe 120. Adsorbed. The flow rate of the captured evaporated fuel is adjusted by the purge control valve 122 in the purge pipe 121 in the operating state in which a negative pressure is generated in the intake pipe (intake passage 103) on the downstream side of the throttle actuator 106, and the flow rate is adjusted downstream of the throttle actuator 106. To the side and burned in the cylinder 117.

FIG. 3 is a control flowchart for diagnosing the air-fuel ratio sensor 112, which is a basic example of the present embodiment. After starting diagnosis in step 10, step 11
If the canister is being purged, the process proceeds to step 12, where the output of the air-fuel ratio sensor 112 is filtered. The type of filter is, for example, a digital filter programmed by a microcomputer in the control unit, or a programmable IC installed in the input circuit of the control unit.
A low pass or band pass filter using a filter or the like is effective. As the filter characteristic, for example, the set of cutoff frequencies is that the high-frequency side is the air-fuel ratio sensor 112.
The step response speed of the output of is set to an extent that can be saved.

Further, when the low frequency side of the bandpass filter is set, the damping characteristic is such that the inversion frequency of the air-fuel ratio sensor can be stored at a minimum. Further, there is an advantage that the diagnostic logic of the response characteristic can be simplified by cutting the direct current component of the air-fuel ratio sensor due to the low frequency component attenuation by the band pass filter. By performing appropriate filtering on the output of the air-fuel ratio sensor according to the diagnostic purpose, the diagnostic accuracy can be significantly improved. Further, when the diagnosis is started and the canister is not purged, there is an advantage that the program load can be reduced by avoiding the filtering.

FIG. 4 is a control flow chart for explaining the characteristic changing means of the output filter of the air-fuel ratio sensor 112 during canister purging, in which the output of the air-fuel ratio sensor 112 is always filtered. If the diagnosis is started in step 13, the process proceeds to step 14. If it is determined in step 14 that the canister is being purged, the process proceeds to step 15 and the step 1
The characteristic of the filter is changed with 5. If it is determined in step 14 that the canister is not being purged, step 16
Proceed to and set other filter characteristics. The types of filters are
A digital filter by microcomputer programming in the control unit described in FIG. 3 and a low-pass or band-pass filter using a programmable IC filter installed in the input circuit of the control unit are effective. If the canister is being purged,
By switching the filter constant to set the filter characteristic so that the frequency on the high frequency side can be saved more,
Eliminates noise-like disturbances caused by canister purging. However, at the same time, the air-fuel ratio sensor 112 is set by setting the filter characteristic so that the frequency on the high frequency side can be stored.
However, it also has an adverse effect on the response characteristics of.

However, in the diagnosis of the air-fuel ratio sensor 112, in the research related to the present embodiment, it is more effective to judge the deterioration of the air-fuel ratio sensor 112 from the results of a plurality of times of diagnosis in order to ensure the diagnostic accuracy. The conclusion is that Therefore, the diagnostic accuracy is ensured by the comprehensive judgment of the diagnostic result of the air-fuel ratio sensor 112 during canister purging described in FIG. 4 and the diagnostic result when the canister is not purged, and the diagnostic is actively performed, so that Make sure that accurate diagnosis results are obtained early after the engine is started. This has the effect of always making a diagnosis even under the use conditions of a user who does not drive a long distance.

The filter constants may be given in advance as program data in a low-pass or band-pass digital filter in the control unit by microcomputer programming, and in a programmable IC filter installed in the input circuit of the control unit. If not, it may be calculated from a parameter indicating the operating state of the engine.

Unless the canister is being purged, highly accurate diagnosis can be performed without changing the characteristics of the filter. FIG. 5 is a flowchart illustrating a means for ensuring the diagnostic accuracy by prohibiting the diagnosis of the air-fuel ratio sensor 112. In step 17, it is determined whether or not the condition for diagnosis is satisfied. If the condition is satisfied, the process proceeds to step 18, and in step 18, it is determined whether or not the canister purge is being performed when the diagnosis of the air-fuel ratio sensor 112 is started. If the canister is being purged, the routine proceeds to step 19, and the diagnosis of the air-fuel ratio sensor 112 is prohibited. As a result, the diagnostic accuracy can be secured with a simple means and at a low cost without increasing the program load, the number of parts such as a special filter, and the number of matching man-hours for the diagnosis. In particular, in the future from the viewpoint of environmental problems, in the state of California in the United States, in the engine system compliant with the Lanlos Evapo regulation that requires a large amount of canister purging that is subject to legal regulation as a prelude,
It is considered to be an effective means.

If it is determined in step 18 that the canister is not being purged, the process proceeds to step 18 to immediately start diagnosis. FIG. 6 is a flowchart for explaining a means for ensuring the diagnostic accuracy of the air-fuel ratio sensor 112 by interrupting the canister purge. In step 21, it is determined whether or not the condition for diagnosis is satisfied. If the condition is satisfied, the process proceeds to step 22, and in step 22, it is determined whether or not the canister purge is being performed when the diagnosis of the air-fuel ratio sensor 112 is started. If the canister is being purged, the purging is interrupted in step 22, the process proceeds to step 24, and the diagnosis is started in step 24. As a result, similarly to the description of FIG. 5, without increasing the program load, the number of parts such as a special filter, and the man-hours required for diagnosis, it is possible to secure the diagnostic accuracy with a simple means and at a low cost. You can do it.
If it is determined in step 22 that the canister is not being purged, the process proceeds to step 24, and the diagnosis is started immediately.

FIG. 7 is a flow chart for explaining a means for ensuring the diagnostic accuracy of the air-fuel ratio sensor 112 by interrupting the air-fuel ratio sensor diagnosis. In step 25, it is determined whether or not the air-fuel ratio sensor 112 is being diagnosed. If so, the process proceeds to step 26. In step 26, it is determined whether the canister purge is started. If the canister purge is started, the process proceeds to step 27. The diagnosis of the air-fuel ratio sensor 112 is interrupted. As a result, similarly to the description of FIG. 5 and FIG. 6, without increasing the program load and the number of parts such as a special filter, and without increasing the adaptation man-hours for diagnosis,
Diagnostic accuracy can be secured with simple means and at low cost. FIG.
It is considered to be an effective means in the engine system that complies with the Lanlos Evapo regulation that requires a large amount of canister purging, which is the subject of legal regulation in the state of California in the United States from the viewpoint of environmental problems.
If it is determined in step 27 that the canister purge is not started, the diagnosis is started immediately.

Regarding the interruption of the diagnosis of the air-fuel ratio sensor 112, a means for discarding all the information from the start of this diagnosis,
There is a means to retain information until the diagnosis is interrupted. Either means can be used, but if the advantage of terminating the diagnosis described earlier with reference to FIG. 4 is obtained, a means for holding information up to the interruption of the diagnosis is used, and the interruption of the diagnosis is very much longer than a predetermined period. If it is long, it is better to discard all information from the start of diagnosis.

FIG. 8 is a flow chart for explaining a means for ensuring the accuracy of air-fuel ratio sensor diagnosis by prohibiting canister purge. During the air-fuel ratio sensor diagnosis, it is determined in step 28 whether the air-fuel ratio sensor 112 is under diagnosis. If it is under diagnosis, the process proceeds to step 29, and in step 29 it is determined whether the canister purge is started, and the canister purge is executed. If it is started, the canister purge is prohibited in step 30. Accordingly, similar to the description of FIGS. 5 to 7, without increasing the program load and the number of parts such as a special filter, and without increasing the man-hours required for diagnosis,
Diagnostic accuracy can be secured with simple means and at low cost. If the canister is not being purged, the diagnosis is started immediately.

Each of the control means in FIGS. 5 to 8 is selected in accordance with the characteristics of the target engine control device and the requirements of the specifications. Further, the diagnosis in the air-fuel ratio feedback closed loop state has been described so far, but each of the means checks the output response state of the air-fuel ratio sensor 112, including the stepwise diagnosis in the air-fuel ratio feedback open loop state. It is an effective means for the diagnosis method of.

FIG. 9 illustrates means for checking the output response state of the air-fuel ratio sensor 112 to ensure diagnostic accuracy. In the air-fuel ratio feedback closed loop state, unless the operating state changes abruptly or there is no air-fuel ratio disturbance such as canister purge, almost stable feedback cycle characteristics are shown. However, t ₁ shown in FIG. 9 indicates that the feedback cycle is long and there is a sudden change in the operating state or a disturbance of the air-fuel ratio such as a canister purge. In such a state, the air-fuel ratio is unstable, and the air-fuel ratio sensor 112
Even if the output of is not noise-like, it cannot be concluded that its output characteristics show true characteristics.

FIG. 10 is a flow chart for explaining a diagnostic accuracy ensuring means by checking the output response state of the air-fuel ratio sensor. As shown in FIG. 10, step 31
It is determined whether or not the diagnosis is being performed. If the diagnosis is being performed, the process proceeds to step 32, the output cycle of the air-fuel ratio sensor 112 is measured, and the process proceeds to step 33. In step 33, the output cycle or frequency of the air-fuel ratio sensor 112 is compared with a predetermined value (k _{1 in} FIG. 10) during diagnosis, and if the cycle is large (or the frequency is smaller than the predetermined value), step 3
Going to 4, the diagnosis is interrupted to ensure the accuracy of the diagnosis. If the output cycle is smaller than the predetermined value (or the frequency is larger than the predetermined value) in step 33, the diagnosis is continued. Regarding the interruption of the diagnosis of the air-fuel ratio sensor, as will be described with reference to FIG. 7, there is a means for discarding all the information from the start of the present diagnosis and a means for retaining the information until the interruption of the diagnosis.

FIG. 11 illustrates means for checking the air-fuel ratio feedback correction coefficient to ensure the accuracy of diagnosis. In the air-fuel ratio feedback closed loop state, the air-fuel ratio feedback correction coefficient α as shown in FIG. 11 has a sudden change in the operating state similar to the feedback cycle characteristic described in FIG. 9 or an air-fuel ratio disturbance such as canister purge. Is shown. Therefore, using the air-fuel ratio feedback correction coefficient α, the air-fuel ratio sensor 1
It is possible to determine the interruption of the diagnosis for ensuring the accuracy of the 12 diagnoses.

FIG. 12 is a flow chart for explaining how to secure the accuracy of diagnosis by checking the air-fuel ratio feedback correction coefficient. In step 35, it is determined whether or not the air-fuel ratio sensor 112 is under diagnosis, and if it is under diagnosis, the routine proceeds to step 36, and in step 36, whether the air-fuel ratio feedback correction coefficient α is within a range between a predetermined value PL and PH. Whether or not it is determined. If there is a sudden change in the operating state or an air-fuel ratio disturbance such as a canister purge, the effect appears in the air-fuel ratio feedback correction coefficient α as shown in FIG. When the air-fuel ratio feedback correction coefficient α is outside the range of the predetermined values PL and PH, the routine proceeds to step 37, where the diagnosis is interrupted and the air-fuel ratio sensor 112
Ensure the diagnostic accuracy of. Regarding the interruption of the diagnosis of the air-fuel ratio sensor 112, as will be described with reference to FIG. 7, there is a means for discarding all the information from the start of this diagnosis and a means for retaining the information until the interruption of the diagnosis. If the air-fuel ratio feedback correction coefficient α is within the range of the predetermined values PL and PH in step 36, the diagnosis is continued.

FIG. 13 illustrates means for changing the sampling rate of the air-fuel ratio sensor 112 as means for ensuring the diagnostic accuracy of the air-fuel ratio sensor 112. Normally, the output of the air-fuel ratio sensor 112 is sampled at a predetermined sampling rate.
If the output of is likely to deteriorate, the sampling rate is changed and diagnosis is performed. For example, assuming that the white dots shown in FIG. 13 have a normal sampling rate, if the output of the air-fuel ratio sensor 112 is likely to deteriorate, the cycle of the sampling rate is advanced and the black dots in FIG. 13 are also sampled to improve the diagnostic accuracy. Let

FIG. 14 shows the result of discrimination between the normal product and the deteriorated product of the air-fuel ratio sensor 112 based on the sampling rate. When the sampling rate is increased, the diagnostic accuracy can be improved, but the program load will be adversely affected. Therefore, it is necessary to consider the balance with the diagnostic accuracy. FIG. 15 illustrates means for changing the filter characteristic of the output of the air-fuel ratio sensor 112 as means for ensuring the diagnostic accuracy of the air-fuel ratio sensor 112. 3 and 4
Regarding the preservation of the high frequency side of the filter described in,
When the output of the air-fuel ratio sensor 112 is likely to be deteriorated, the diagnostic accuracy can be improved by setting the cutoff frequency, which is a filter characteristic, on the high frequency side for diagnosis, for example. However, since the output of the air-fuel ratio sensor 112 is in a more noisy state, it is necessary to carry out a diagnosis limiting condition such as a more limited operating state. In FIG. 15, the air-fuel ratio sensor 1 is set by setting the cutoff frequency to a higher frequency side.
Although the result of the discrimination state of the 12 normal products and the deteriorated product can be improved, it is shown that when the cutoff frequency set is on the high frequency side, the discrimination result sharply decreases due to the influence of the noise component.

Although some embodiments of the present invention have been described above in detail, the present invention is not limited to the above-mentioned embodiments, and does not depart from the spirit of the invention described in the claims. Therefore, various changes can be made in the design. For example, in the above-mentioned embodiment, the installation position of the air-fuel ratio sensor is located upstream of the catalyst device. However, even if the air-fuel ratio sensor is installed downstream of the catalyst device, the diagnostic device functions effectively. It is a thing. Further, in the above-mentioned embodiment, the canister purge is explained as the mode of the operating state, but the purge of blow-by gas,
Alternatively, the diagnostic device of the present invention can be applied to other sudden changes in operating conditions.

[0031]

As can be understood from the above description, the diagnostic device for an air-fuel ratio detector of an engine according to the present invention excludes a sudden change in the operating condition or an air-fuel ratio disturbance such as canister purge to improve the diagnostic accuracy. By improving, it becomes possible to more accurately diagnose the air-fuel ratio detector.

[Brief description of the drawings]

FIG. 1 shows a waveform of an output signal of an air-fuel ratio sensor,
(A) shows the influence state by the canister purge,
FIG. 6B is a diagram showing a stable state.

FIG. 2 is an overall configuration diagram of an engine including an engine according to an embodiment of the present invention and a control device for the engine.

FIG. 3 is a flowchart of air-fuel ratio sensor diagnosis during canister purging according to an embodiment of the present invention.

FIG. 4 is a flowchart showing a change in the characteristics of the output filter of the air-fuel ratio sensor during canister purging.

FIG. 5 is a flowchart showing the prohibition of diagnosis of the air-fuel ratio sensor.

FIG. 6 is a flowchart showing interruption of canister purge.

FIG. 7 is a flowchart showing interruption of air-fuel ratio sensor diagnosis.

FIG. 8 is a flowchart showing prohibition of canister purge.

FIG. 9 is a diagram showing changes in the cycle of the output waveform of the air-fuel ratio sensor.

FIG. 10 is a flow chart showing diagnosis cancellation by checking the output response state of the air-fuel ratio sensor.

FIG. 11 is a diagram showing a relationship between an output change of an air-fuel ratio sensor and an air-fuel ratio feedback correction coefficient.

FIG. 12 is a flowchart showing the diagnosis cancellation by the air-fuel ratio feedback correction coefficient check.

FIG. 13 is a diagram showing a change in the sampling rate of the air-fuel ratio sensor of the air-fuel ratio sensor.

FIG. 14 is a state diagram of distinguishing a normal air-fuel ratio sensor product from a deteriorated product based on a sampling rate.

FIG. 15 is a diagram showing changes in the characteristics of the output filter of the air-fuel ratio sensor.

[Explanation of symbols]

101 ... Engine body, 103 ... Intake passage, 105 ... Air flow sensor, 106 ... Throttle actuator and throttle sensor, 108 ... Control unit,
111 ... Exhaust path, 112 ... Air-fuel ratio sensor, 114 ... Fuel tank, 115 ... Fuel pump, 117 ... Cylinder, 1
18 ... Canister, 119 ... Adsorbent for adsorbing evaporated fuel, 121 ... Purge pipe, 122 ... Purge control valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akito Numata 2520 Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi Ltd. Automotive Equipment Division

Claims (18)

[Claims] 1. A diagnostic device for determining the degree of deterioration of a detection body based on an output signal of the detection body in an engine having an engine operating state detection means including an exhaust oxygen concentration or an air-fuel ratio detection body, the deterioration of the detection body. An engine diagnosing device comprising means for filtering an output signal of the detection body when the cylinder fuel distribution is in an operating state or an operating condition in which the fuel distribution is not uniform at the time of determining the degree. 2. The engine diagnostic device according to claim 1, further comprising means for changing a filter characteristic of an output filter of the detector. 3. The characteristic of the filter of the output signal of the detector is set to further attenuate the low frequency side component when the cylinder fuel distribution is in an operating state or an operating condition such that the fuel distribution is non-uniform. The engine diagnostic device according to claim 1 or 2, further comprising: 4. A fuel vapor recovery device for recovering fuel vaporized in a fuel tank, and a fuel recovery purge device for purging fuel captured by the fuel vapor recovery device into an intake passage or a blow-by gas discharge device. The engine diagnostic device according to any one of claims 1 to 3, wherein: 5. A diagnostic device for determining the degree of deterioration of a detection body based on an output signal of the detection body in an engine equipped with an engine operating state detection means including an exhaust oxygen concentration or an air-fuel ratio detection body, the deterioration of the detection body. An engine diagnostic, characterized in that it has means for prohibiting or interrupting the determination of the degree of deterioration of the detection body when the degree of determination is in an operating state or operating condition in which the cylinder fuel distribution becomes non-uniform. apparatus. 6. A diagnostic device for determining the degree of deterioration of a detection body based on an output signal of the detection body in an engine having an engine operating state detection means including an exhaust oxygen concentration or an air-fuel ratio detection body, the deterioration of the detection body. Deterioration degree of the detection body when the operation range or period for determining the deterioration degree of the detection body is entered in the operating state or the operating condition such that the cylinder fuel distribution becomes nonuniform at the time of determining the degree. The engine diagnostic device is provided with a means for interrupting or prohibiting the control for making the cylinder fuel distribution non-uniform during the period required for the determination. 7. An evaporative fuel recovery device for recovering fuel evaporated in a fuel tank, a recovered fuel purge device for purging fuel captured by the evaporative fuel recovery device into an intake passage, and an exhaust oxygen concentration or air-fuel ratio detector. In a diagnostic device for determining the degree of deterioration of the detection body based on the output signal of the detection body in an engine equipped with the detection body, when the degree of deterioration of the detection body is determined based on the output signal of the detection body, the detection body is detected during purging of recovered fuel. An engine control device comprising means for prohibiting determination of the degree of deterioration of the engine. 8. The device according to claim 4, further comprising means for interrupting the determination of the deterioration degree of the detection body when the purge of the recovered fuel is started during the determination of the deterioration degree of the detection body. The engine diagnostic device described. 9. An evaporated fuel recovery device for recovering fuel evaporated in a fuel tank, a recovered fuel purge device for purging the fuel captured by the evaporated fuel recovery device into an intake passage, and an exhaust oxygen concentration or air-fuel ratio detector. In a diagnostic device for determining the degree of deterioration of the detection body by an output signal of the detection body in an engine provided, in the case of entering an operating region or period for determining the degree of deterioration of the detection body during purging of recovered fuel, An engine diagnostic device comprising means for interrupting purging of the recovered fuel during a period required to determine the degree of deterioration of the detection body. 10. An evaporative fuel recovery apparatus for recovering fuel evaporated in a fuel tank, a recovered fuel purge apparatus for purging fuel captured by the evaporative fuel recovery apparatus into an intake passage, and an exhaust oxygen concentration or air-fuel ratio detector. In a diagnostic device for determining the degree of deterioration of the detection body by the output signal of the detection body in an engine provided, during the determination of the degree of deterioration of the detection body, when entering the purge operation region or period of the recovered fuel, An engine diagnostic device comprising means for prohibiting purging of the recovered fuel during a period required for determining the degree of deterioration of the detection body. 11. A diagnostic device for determining the degree of deterioration of a detection body according to an output signal of the detection body in an engine having an exhaust oxygen concentration or an air-fuel ratio detection body, wherein the degree of deterioration of the detection body is within a predetermined range. A diagnostic apparatus for an engine, comprising: a means for determining whether or not it is present, and a means for changing a sampling rate of an output signal of the detection body. 12. The engine diagnostic apparatus according to claim 11, further comprising means for setting the sampling rate to a high frequency side. 13. A diagnostic device for determining the degree of deterioration of a detection body based on the output signal of the detection body in an engine equipped with an exhaust oxygen concentration or an air-fuel ratio detection body, means for digitally filtering the output signal of the detection body, An engine diagnostic apparatus comprising: a unit that determines whether or not the degree of deterioration of the detector is within a predetermined range; and a unit that changes a filter characteristic of an output signal filter of the detector. 14. The engine diagnostic device according to claim 13, further comprising means for setting the characteristic of the filter so as to further attenuate the high frequency component. 15. A deterioration degree of the detection body is judged by an output signal of the detection body in an engine equipped with an exhaust oxygen concentration or an air-fuel ratio detection body and a device for feedback controlling the air-fuel ratio by the output signal of the detection body. In the diagnostic device, the means for detecting the magnitude of the inversion cycle in a predetermined range of the output signal of the detection body, and the determination of the degree of deterioration of the detection body depending on the detection result of the detection means of the inversion cycle, or An engine diagnostic apparatus comprising: a prohibition unit. 16. A means for determining whether or not the detection result of the inversion period detection means is a predetermined value or more, and a means for interrupting or prohibiting the determination of the degree of deterioration of the detection body according to the result of the determination means. The engine diagnostic device according to claim 15, further comprising: 17. A degree of deterioration of the detection body is determined by an output signal of the detection body in an engine equipped with an exhaust oxygen concentration or an air-fuel ratio detection body and a device for feedback controlling the air-fuel ratio by the output signal of the detection body. In the diagnostic device, means for detecting the magnitude of the correction coefficient of the feedback control, and means for interrupting or prohibiting the determination of the degree of deterioration of the detection object according to the result of the means for detecting the magnitude of the correction coefficient. An engine diagnostic device characterized by being provided. 18. A means for determining whether or not the correction coefficient of the feedback control is within a predetermined range, and a means for interrupting or prohibiting the determination of the degree of deterioration of the detection object according to the result of the determining means. 18. The engine diagnostic device according to claim 17, wherein: