JPH0933478A - Apparatus for diagnosing response of oxygen sensor in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a wrong diagnosis by an oxygen sensor, by detecting a parameter indicating an output response of the oxygen sensor, comparing the parameter with a parameter judgment value set based on an activity degree and a deterioration degree of a catalyst, and diagnosing a response deterioration of the sensor. SOLUTION: A control unit 12 detects an output inverse frequency of an oxygen sensor 17 as a parameter indicating an output response when a diagnosis permission condition is satisfied. Then, a parameter judgment value is set from a catalyst activity degree estimated from a catalyst temperature and a catalyst deterioration degree obtained by comparing output inverse frequencies of oxygen sensors 16, 17. The output inverse frequency of the sensor 17 is compared with the parameter judgment value. Only a response change of the sensor 17 is detected irrespective of a change of an air-fuel ratio change speed at the downstream side. In other words, when the output inverse frequency is smaller than the judgment value, it is detected as the response deterioration of the sensor 17. Accordingly, the output response of the sensor 17 is prevented from being diagnosed wrong.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a response diagnostic device for an oxygen sensor in an internal combustion engine, and more specifically, it shows the oxygen concentration in the exhaust gas which is provided on the downstream side of the catalyst and is closely related to the air-fuel ratio of the engine intake air-fuel mixture. The present invention relates to a technique for diagnosing a response deterioration of a detecting oxygen sensor.

[0002]

2. Description of the Related Art Conventionally, an oxygen sensor is provided on each of an upstream side and a downstream side of a catalyst provided in an exhaust passage for purifying exhaust gas, and engine intake mixing is performed based on the detection results of these two oxygen sensors. There is known an air-fuel ratio feedback control device that feedback-controls a fuel supply amount to an engine so that an air-fuel ratio of air approaches a target air-fuel ratio.

For example, in the air-fuel ratio feedback control device disclosed in Japanese Unexamined Patent Publication No. 4-72438, the rich / lean of the actual air-fuel ratio with respect to the target air-fuel ratio is judged based on the output of the upstream oxygen sensor, and the judgment result. While proportionally / integrally controlling the air-fuel ratio feedback correction coefficient for correcting the fuel supply amount based on the above, the operation amount (proportional amount) in the proportional control based on the rich lean detected by the oxygen sensor on the downstream side is controlled. By making the correction, the deviation of the air-fuel ratio control point based on the detection result of the upstream oxygen sensor is compensated.

[0004]

As described above, in the device for detecting the air-fuel ratio by the oxygen sensor and feedback-controlling the fuel supply amount, if the oxygen sensor is deteriorated, the control accuracy is deteriorated and the exhaust property is deteriorated. Therefore, it is necessary to diagnose deterioration of the oxygen sensor. However, the rate of change of the exhaust air-fuel ratio (oxygen concentration) on the downstream side of the catalyst changes under the influence of the catalyst, so when diagnosing the response deterioration of the oxygen sensor provided on the downstream side of the catalyst, the influence of the catalyst is affected. There was a risk that a misdiagnosis would occur.

For example, as shown in FIG. 5, when the catalyst is deteriorated (see FIG. 5B), it is not deteriorated (see FIG. 5A).
In comparison with the above, since the change speed of the exhaust air-fuel ratio on the downstream side of the catalyst becomes faster, there is a fear that the normal determination may be made despite the deterioration of the response of the downstream side oxygen sensor. That is, even if the response deterioration of the oxygen sensor occurs, the response speed B when the catalyst is deteriorated is larger than the response speed A of the oxygen sensor that shows a normal response when the catalyst is not deteriorated. The diagnosis cannot be made.

Similarly, when the activity of the catalyst is low, the rate of change of the exhaust air-fuel ratio on the downstream side of the catalyst becomes faster than that in the active state. Therefore, when the activity of the catalyst is low, the response of the downstream oxygen sensor deteriorates. Despite that, there was a fear that the judgment would be normal. The present invention has been made in view of the above problems, and an oxygen sensor response diagnostic device in an internal combustion engine that can avoid erroneous diagnosis of response degradation of a catalyst downstream side oxygen sensor that is influenced by the catalyst deterioration / active state. The purpose is to provide.

[0007]

Therefore, the invention according to claim 1 is constructed as shown in FIG. In FIG.
The oxygen sensor is a sensor that is provided on the downstream side of the catalyst installed in the engine exhaust passage and whose output value changes in response to the oxygen concentration in the exhaust gas. Further, the response parameter detecting means,
A parameter indicating the output response of the oxygen sensor downstream of the catalyst is detected.

On the other hand, the catalyst activity detecting means detects the activity of the catalyst, and the catalyst deterioration detecting means detects the deterioration of the catalyst. Then, the determination value setting means sets the determination value of the parameter based on the detected activity and deterioration of the catalyst. Here, the response diagnosing means compares the judgment value set by the judgment value setting means with the parameter detected by the response parameter detecting means to diagnose the response deterioration of the oxygen sensor.

According to this structure, in diagnosing the deterioration of the response of the oxygen sensor on the downstream side of the catalyst, the judgment value to be compared with the parameter indicating the output response of the oxygen sensor is set according to the degree of deterioration and the activity of the catalyst. Therefore, even if the change rate of the exhaust air-fuel ratio on the downstream side of the catalyst changes due to the degree of deterioration and the activity, it is possible to prevent the output response of the oxygen sensor from being erroneously diagnosed due to the change. That is, when the change in the exhaust air-fuel ratio on the downstream side of the catalyst becomes faster at the time of deterioration or inactivity, the exhaust air-fuel ratio becomes faster due to the influence of the catalyst by changing the judgment value correspondingly. The actual output response of the oxygen sensor can be diagnosed based on the change.

According to a second aspect of the present invention, there is provided air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio of the engine intake air-fuel mixture based on the output of the oxygen sensor provided on the upstream side of the catalyst, and the response parameter detection means. But,
The output fluctuation frequency of the oxygen sensor downstream of the catalyst under a predetermined operating condition during the air-fuel ratio feedback control by the air-fuel ratio feedback control means is detected as a parameter indicating the output response.

According to this structure, the response deterioration is diagnosed based on whether or not the output fluctuation frequency predicted by the air-fuel ratio feedback control under the predetermined operating conditions actually appears in the output of the oxygen sensor on the downstream side. . In the invention according to claim 3, the catalyst activity detecting means detects the catalyst temperature as a parameter indicating the catalyst activity.

According to this structure, the activity is detected based on whether or not the catalyst is at the activation temperature. In the invention according to claim 4, the catalyst activity detection means estimates the catalyst temperature from the engine operating condition.
According to this configuration, instead of directly detecting the catalyst temperature, the catalyst temperature is estimated based on, for example, the exhaust temperature estimated based on the engine load or the engine rotation speed, or the heat receiving amount of the catalyst estimated based on the exhaust flow rate. Can be detected indirectly.

According to a fifth aspect of the present invention, there is provided air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio of the engine intake air-fuel mixture based on the output of the oxygen sensor provided on the upstream side of the catalyst, and the catalyst deterioration degree detection is provided. The means is configured to detect the degree of deterioration of the catalyst based on the ratio of the output fluctuation frequency of the upstream oxygen sensor and the output fluctuation frequency of the downstream oxygen sensor during the air-fuel ratio feedback control by the air-fuel ratio feedback control means. .

According to this structure, in the non-deteriorated state of the catalyst, the oxygen storage effect of the catalyst causes a great delay in the change of the exhaust air-fuel ratio on the downstream side of the catalyst with respect to the change of the exhaust air-fuel ratio on the upstream side of the catalyst. The deterioration of the catalyst can be estimated when the change on the downstream side is close to the change on the upstream side.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In FIG. 2 showing an embodiment, the internal combustion engine 1 includes an air cleaner 2, an intake duct 3, and a throttle valve 4.
Air is taken in through the intake manifold 5. At the branch portion of the intake manifold 5, a fuel injection valve 6 is provided for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that is energized by a solenoid to open the valve, and deenergized to close the valve.
Is opened by energization by an injection pulse signal from the intake manifold 5 which is fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator.
Inject and supply.

A spark plug 7 is provided in each combustion chamber of the engine 1, and spark ignition is performed by the spark plug 7 to ignite and burn the air-fuel mixture. Exhaust gas is discharged from the engine 1 through the exhaust manifold 8, the exhaust duct 9, the exhaust purification three-way catalyst 10 and the muffler 11. The three-way catalyst 10 has the above-mentioned oxygen storage effect, oxidizes CO and HC in exhaust components, and reduces NOx,
It is a catalyst that converts to other harmless substances, and has the highest conversion efficiency when the engine intake air-fuel mixture is burned at the stoichiometric air-fuel ratio.

The control unit 12 includes a CPU and RO
A microcomputer including an M, a RAM, an A / D converter and an input / output interface is provided, and detection signals from various sensors are input to control the injection pulse width of the injection pulse signal. As the various sensors, a hot-wire type or flap type air flow meter 13 is provided in the intake duct 3 and outputs a voltage signal according to the intake air amount Q of the engine 1.

A crank angle sensor 14 is provided to output a reference angle signal REF for each predetermined piston position and a unit angle signal POS for each unit angle. Here, the engine rotation speed Ne can be calculated by measuring the generation cycle of the reference angle signal REF or the number of generations of the unit angle signal POS within a predetermined time. Further, a water temperature sensor 15 for detecting a cooling water temperature Tw of the water jacket of the engine 1 is provided.

Further, a first oxygen sensor 16 is provided at a collecting portion of the exhaust manifold 8 which is an upstream side of the three-way catalyst 10, and a downstream side of the three-way catalyst 10 is upstream of a muffler 11. Is provided with a second oxygen sensor 17. The first oxygen sensor 16 and the second oxygen sensor 17 are known oxygen concentration battery type sensors whose output value changes in response to the oxygen concentration in the exhaust gas, and the oxygen concentration in the exhaust gas at the theoretical air-fuel ratio. This is a rich lean sensor that can detect the rich lean of the exhaust air-fuel ratio with respect to the stoichiometric air-fuel ratio by utilizing the sudden change of the.

Here, the CPU of the microcomputer incorporated in the control unit 12 is operated by the first oxygen sensor 16 and the second oxygen sensor 16 as shown in the flow chart of FIG. 3 when a predetermined feedback control condition is satisfied. The air-fuel ratio feedback correction coefficient LMD is proportionally / integrally controlled so that the output of the oxygen sensor 17 approaches a value corresponding to the target air-fuel ratio (theoretical air-fuel ratio).

In this embodiment, the function as the air-fuel ratio feedback control means is provided by the control unit 12 as software, as shown in the flow chart of FIG. In the flowchart of FIG.
First, in step 1 (denoted as S1 in the figure. The same applies hereinafter), the output voltage of the first oxygen sensor 16 on the upstream side is read.

In the next step 2, the output voltage read in step 1 is compared with a predetermined value corresponding to the target air-fuel ratio (theoretical air-fuel ratio) to obtain the rich lean of the actual air-fuel ratio with respect to the target air-fuel ratio. Determine. When it is determined that the output voltage is larger than the predetermined value and the air-fuel ratio is rich, the routine proceeds to step 3, where it is determined whether or not this rich determination is the first time.

When it is the first time for rich determination, the routine proceeds to step 4, where the air-fuel ratio feedback correction coefficient L up to the previous time is set.
The air-fuel ratio feedback correction coefficient LMD is updated by performing proportional control for subtracting a proportional amount P _R set as described later from MD (initial value 1.0). On the other hand, when it is determined in step 3 that it is not the first time of rich determination, the process proceeds to step 5, and integral control for subtracting a predetermined integral amount I from the air-fuel ratio feedback correction coefficient LMD up to the previous time is performed to perform the air-fuel ratio feedback correction coefficient. Update LMD.

Air-fuel ratio feedback correction coefficient LMD
The reduction control of 1 corresponds to the reduction correction of the fuel injection amount Ti, so by repeating the integral control in step 5, the air-fuel ratio is reversed to lean. Then, when it is determined in step 2 that the air-fuel ratio has reversed to lean, the process proceeds to step 6 and it is determined whether or not it is the first lean determination.

If it is the first time of lean determination, the routine proceeds to step 7, where proportional control is performed to add a proportional amount P _L set as described later to the air-fuel ratio feedback correction coefficient LMD up to the previous time, The air-fuel ratio feedback correction coefficient LMD is updated. If it is not the first time the lean determination is made, the routine proceeds to step 8, where integration control for adding a predetermined integral amount I to the air-fuel ratio feedback correction coefficient LMD up to the previous time is performed, and the air-fuel ratio feedback correction coefficient LMD is performed.
To update.

On the other hand, in step 9, the second oxygen sensor is operated in the same manner as the proportional-integral control of the air-fuel ratio feedback correction coefficient LMD based on the output voltage of the first oxygen sensor 16 described above.
By the proportional-plus-integral control based on the output voltage of 17, the correction value PHOS (initial value = 0) for correcting the basic proportional components P _RB and P _LB , the air-fuel ratio detected by the second oxygen sensor 17 is the target air-fuel ratio (theoretical The air-fuel ratio) is controlled to approach.

In step 10, the correction value PHOS is subtracted from the basic proportional component P _RB, and the subtraction result is proportional component P _R (←
P _RB -PHOS), the correction value PHOS is added to the basic proportional amount P _LB , and the addition result is set to the proportional amount P _L (← P _LB + PHOS). The proportional component P _R is a proportional component used for the reduction control of the air-fuel ratio feedback correction coefficient LMD in the first rich determination as described above, and the proportional component P _L is empty in the first lean determination as described above. It is a proportional amount used for the increase control of the fuel ratio feedback correction coefficient LMD.
Is set to decrease when the second oxygen sensor 17 detects a rich condition, and therefore, when the second oxygen sensor 17 detects a rich condition, the control in the lean direction by the proportional amount P _R increases, and conversely, the proportional ratio increases. The control in the rich direction by the amount P _L is reduced, and the proportional control characteristic of the air-fuel ratio feedback correction coefficient LMD is changed in the direction in which the rich air-fuel ratio detected by the second oxygen sensor 17 approaches the target air-fuel ratio. .

Therefore, the detection result of the first oxygen sensor 16 is used.
Of the air-fuel ratio control point
The deviation is the correction value P set by using the second oxygen sensor 17.
Will be compensated by HOS. The second oxygen cell
The correction control using the detection result of the sensor 17 is performed by the proportional portion P above.
_R, P _LThe correction control is not limited to
To determine rich lean based on the output of sensor 16
Change the threshold level used for
Proportional control for rich / lean detection of sensor 16
The air-fuel ratio
It may be configured to change the feedback control characteristics.
No.

As described above, the air-fuel ratio feedback correction coefficient LMD set based on the output values of the first oxygen sensor 16 on the upstream side of the three-way catalyst 10 and the second oxygen sensor 17 on the downstream side is: It is used to calculate the fuel injection amount Ti in the next step 11. Specifically, based on the intake air amount Q and the engine rotation speed Ne, the basic fuel injection amount Tp (← K × Q
/ Ne: K is a constant), while various correction coefficients COEF based on operating conditions such as cooling water temperature Tw and voltage correction amount Ts according to battery voltage are calculated. Then, the basic fuel injection amount Tp is set to the air-fuel ratio feedback correction coefficient LMD, various correction coefficients COEF, and voltage correction amount Ts.
Etc., and the corrected fuel injection amount Ti (←
Tp × COEF × LMD + Ts).

The control unit 12 outputs an injection pulse signal having a pulse width corresponding to the most recently calculated fuel injection amount Ti to the fuel injection valve 6 at a predetermined injection timing so that the injection amount by the fuel injection valve 6 is determined. The air-fuel mixture is controlled to form an air-fuel mixture having a target air-fuel ratio (theoretical air-fuel ratio). by the way,
In this embodiment, the control unit 12 is shown in FIG.
As shown in the flowchart of FIG. 2, a diagnostic function for diagnosing the response deterioration of the second oxygen sensor 17 on the downstream side, that is, response parameter detecting means, catalyst activity detecting means, catalyst deterioration degree detecting means, judgment value setting means, response diagnosis Function as a means (Fig. 1
See) as software.

Steps in the flowchart of FIG.
At 21, it is determined whether or not a predetermined diagnosis permission condition is satisfied. The diagnosis permission condition is, for example, a steady operating condition during the air-fuel ratio feedback control, in which the basic fuel injection amount Tp and the engine rotation speed Ne representing the engine load are each within a predetermined range. It is preferable that the first and second oxygen sensors 16 and 17 are in an active state.

The active state of the oxygen sensors 16 and 17 can be determined based on whether or not the difference between the rich output and the lean output is a predetermined value or more. When the diagnosis permission condition is satisfied, the routine proceeds to step 22, and the output inversion frequency of the second oxygen sensor 17 on the downstream side is detected as a parameter indicating the output response. That is, when the response deterioration occurs in the oxygen sensor, as shown in FIG.
As shown in, since the response of the sensor output is delayed with respect to the change of the exhaust air-fuel ratio and the reversal frequency becomes smaller (the reversal period is extended), the engine load and the engine speed that cause the fluctuation of the reversal frequency are diagnosed. Characterize as a condition,
At this time, it is determined whether or not there is a decrease in the inversion frequency, which indicates deterioration in response, based on the inversion frequency actually detected.

In step 23, a judgment value to be compared with the output inversion frequency detected as the parameter indicating the output response is set according to the catalyst activity and the catalyst deterioration detected as described later. That is, when the catalyst is deteriorated or inactive, the rate of change of the exhaust air-fuel ratio on the downstream side of the catalyst becomes relatively fast, so even if there is a response delay in the second oxygen sensor 17 that detects this change in the exhaust air-fuel ratio, As the air-fuel ratio changes faster, the reversal frequency does not show a small value indicating the deterioration of the oxygen sensor, and the oxygen sensor with the response deterioration is erroneously diagnosed as normal. (See Figure 5).

Therefore, in step 23, the larger the catalyst deterioration degree and the lower the activity degree, the larger the judgment value (threshold value of frequency) (in other words, the faster the output response request is made). Therefore, it is possible to cope with the change in the changing speed of the exhaust air-fuel ratio on the downstream side of the catalyst due to the deterioration or inactivity of the catalyst. Therefore, by comparing the determination value with the output reversal frequency detected as the parameter indicating the output response, the change in the air-fuel ratio change speed on the downstream side of the catalyst due to the degree of deterioration or activity of the catalyst is not affected, and 2 Only the change in the response of the oxygen sensor 17 can be identified.

In step 24, the output inversion frequency detected in step 22 is compared with the judgment value set in step 23. When the output inversion frequency is smaller than the judgment value, the response deterioration of the second oxygen sensor 17 is deteriorated. Thus, it is determined that the output inversion frequency has decreased, and the routine proceeds to step 25, where it is determined whether the second oxygen sensor 17 has deteriorated response.

When it is determined that the response deterioration has occurred, it is advisable to warn the driver of the occurrence of the response deterioration or prohibit the use of the output of the second oxygen sensor 17 for the air-fuel ratio feedback control. The degree of catalyst deterioration and the degree of activity used for setting the determination value in step 23 can be detected as follows.

First, since the catalyst activity correlates with the catalyst temperature, the catalyst activity can be estimated by detecting the catalyst temperature. The catalyst temperature may be directly detected by a temperature sensor, but as shown in FIG. 6, for example, the basic fuel injection amount Tp is previously set.
A map that stores the catalyst temperature (catalyst inlet exhaust gas temperature) in the steady state is stored for each operating region divided into a plurality of (engine load) and engine rotation speed Ne, and the catalyst temperature of the corresponding operating region of the map is provided. The catalyst temperature may be estimated by performing a delay correction corresponding to the delay of the catalyst temperature change on the retrieved catalyst temperature.

Further, an operating region divided into a plurality of regions by the basic fuel injection amount Tp (engine load) and the engine rotation speed Ne is a region in which the catalyst temperature is raised above the activation temperature (a region in which the exhaust temperature is high). The catalyst temperature is divided into a region where the temperature is lower than the activation temperature (a region where the exhaust gas temperature is low), and the points are increased every predetermined time while the region where the temperature is raised corresponds to the region where the temperature falls. When it is present, the point may be lowered every predetermined time, and the point may be used as a parameter indicating the degree of activity.

Further, the exhaust flow rate passing through the catalyst is integrated,
The catalyst temperature may be estimated based on the integrated value. On the other hand, if the catalyst deteriorates, as described above, the rate of change of the exhaust air-fuel ratio on the downstream side of the catalyst becomes relatively fast, so during the air-fuel ratio feedback control, the output reversal frequency of the first oxygen sensor 16 on the upstream side becomes By comparing with the output reversal frequency of the second oxygen sensor 17 on the downstream side, it can be diagnosed that the exhaust air-fuel ratio change speed on the downstream side of the catalyst is increasing due to the deterioration of the catalyst.

Here, the oxygen sensor 17 responds to an increase in the rate of change of the exhaust air-fuel ratio on the downstream side of the catalyst due to catalyst deterioration.
The decrease in the output inversion frequency due to the deterioration of the response is relatively small, and the deterioration of the response of the oxygen sensor 17 does not cause the same output inversion ratio as that when the catalyst is not deteriorated, even though the catalyst is deteriorated. Therefore, even if the oxygen sensor 17 has a response deterioration, the catalyst deterioration can be diagnosed.

[0041]

As described above, according to the first aspect of the present invention, in diagnosing the deterioration of the response of the oxygen sensor on the downstream side of the catalyst, the judgment value to be compared with the parameter indicating the output response of the oxygen sensor, Since it is set according to the degree of deterioration and activity of the catalyst, even if the rate of change of the exhaust air-fuel ratio on the downstream side of the catalyst changes due to the degree of deterioration and activity, it is affected by this and the output response of the oxygen sensor is erroneously diagnosed. The effect is that it can be avoided.

According to the second aspect of the present invention, it is possible to diagnose the deterioration of the output response of the oxygen sensor based on the output response of the oxygen sensor on the downstream side of the catalyst with respect to the variation of the exhaust air-fuel ratio due to the air-fuel ratio feedback control. is there. According to the invention described in claim 3, there is an effect that the catalyst activity can be easily detected by detecting the catalyst temperature that correlates with the activity of the catalyst.

According to the fourth aspect of the present invention, instead of directly detecting the catalyst temperature, the catalyst temperature can be indirectly detected based on the engine operating conditions such as the engine load and the engine rotation speed. The effect is that the installation of the sensor can be omitted. According to the fifth aspect of the invention, the oxygen storage effect of the catalyst causes a decrease in the oxygen storage effect based on the characteristic that the change in the exhaust air-fuel ratio on the catalyst downstream side is greatly delayed with respect to the change in the exhaust air-fuel ratio on the catalyst upstream side. This has the effect of diagnosing the accompanying catalyst deterioration.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of the invention according to claim 1.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing an embodiment of air-fuel ratio feedback control.

FIG. 4 is a flowchart showing an embodiment of response deterioration diagnosis.

FIG. 5 is a diagram showing a correlation between catalyst deterioration and oxygen sensor response deterioration, where (a) shows a correlation when the catalyst is not deteriorated and (b) shows a correlation when the catalyst is deteriorated.

FIG. 6 is a diagram for explaining estimation control of catalyst temperature.

[Explanation of symbols]

 1 engine 6 fuel injection valve 10 three-way catalyst 12 control unit 13 air flow meter 14 crank angle sensor 16 first oxygen sensor 17 second oxygen sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01N 27/00 G01N 27/00 L 27/409 27/58 B

Claims (5)

[Claims] 1. A response diagnostic device for an oxygen sensor, which is provided on a downstream side of a catalyst interposed in an engine exhaust passage and whose output value changes in response to an oxygen concentration in exhaust gas. Response parameter detecting means for detecting a parameter indicating the output response of the oxygen sensor, catalyst activity detecting means for detecting the activity of the catalyst, catalyst deterioration detecting means for detecting the deterioration degree of the catalyst, and the detected A judgment value setting means for setting a judgment value of the parameter based on the activity and deterioration degree of the catalyst, a judgment value set by the judgment value setting means, and a parameter detected by the response parameter detecting means. In comparison, a response diagnostic device for an oxygen sensor in an internal combustion engine, comprising: a response diagnostic means for diagnosing the response deterioration of the oxygen sensor. 2. An air-fuel ratio feedback control means for feedback-controlling an air-fuel ratio of an engine intake air-fuel mixture based on an output of an oxygen sensor provided on the upstream side of the catalyst, wherein the response parameter detection means has the air-fuel ratio feedback. The oxygen sensor for an internal combustion engine according to claim 1, wherein an output fluctuation frequency of the oxygen sensor downstream of the catalyst under a predetermined operating condition during the air-fuel ratio feedback control by the control means is detected as a parameter indicating the output response. Response diagnostic device. 3. The response diagnostic device for an oxygen sensor in an internal combustion engine according to claim 1, wherein the catalyst activity detecting means detects the catalyst temperature as a parameter indicating the catalyst activity. 4. The response diagnostic device for an oxygen sensor in an internal combustion engine according to claim 3, wherein said catalyst activity detecting means estimates the catalyst temperature from engine operating conditions. 5. An air-fuel ratio feedback control means for feedback-controlling an air-fuel ratio of an engine intake air-fuel mixture based on an output of an oxygen sensor provided on the upstream side of the catalyst, wherein the catalyst deterioration degree detection means is the air-fuel ratio. The deterioration degree of the catalyst is detected based on a ratio between an output fluctuation frequency of the upstream oxygen sensor and an output fluctuation frequency of the downstream oxygen sensor during the air-fuel ratio feedback control by the feedback control means. 5. The response diagnostic device for an oxygen sensor in an internal combustion engine according to any one of 4 above.