JPH05106494A - Catalyst deterioration determination device - Google Patents

Abstract

PURPOSE:To provide a catalyst deterioration determination device which is rarely affected by the dispersion and deterioration of unitary performance of an O2 sensor. CONSTITUTION:Ordinarily, a first air fuel ratio control means M1 feed-back- controls an air fuel ratio based on the output of both an upstream side O2 sensor FS and a downstream side O2 sensor RS for a catalyst C. When an operation state determination means M3 identifies a specified engine operation state, an adjustment means switch means M4 switches from a first air fuel ratio adjustment means M1 to a second air fuel ratio adjustment means M2 and feed-back-controls the air fuel ratio based on only the output of the downstream side O2 sensor RS. At this time, a time measuring means M6 measures the length of time between the point of time when the amount of skip which causes the increase of the air fuel ratio occurs and the point of time when a reverse determination means M5 detects the reversal of the output of the downstream side O2 sensor RS and when the length of time becomes shorter than a specified value, a catalyst deterioration determination means M7 determines that the catalyst C is deteriorated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to determination of deterioration of a catalyst provided in an exhaust system of an engine to purify exhaust gas.

[0002]

2. Description of the Related Art As means for determining deterioration of a catalyst for purifying engine exhaust gas, O _{2 is provided} upstream and downstream of the catalyst.
The sensor is provided, while adjusting the supply air into the intake system in accordance with the output of the upstream O ₂ output and the downstream O ₂ sensor of the sensor, the output of the downstream O ₂ sensor from the inversion of the intake system supplying air It is publicly known to measure the time until the reversal (for example, Japanese Patent Laid-Open Nos. 2-30915 and 2-334).
08, JP-A-2-207159). As means for determining the deterioration of the catalyst, a method of comparing the outputs of the upstream O ₂ sensor and the downstream O ₂ sensor, for example, the output ratio method (see Japanese Patent Laid-Open No. 63-231252), the response ratio method (Japanese Laid-Open Patent Publication No. No. 3-57862), a phase difference time measuring method (see JP-A-2-310453), and the like have been proposed.

Further, the present applicant switched the fuel correction coefficient at a constant frequency, and generated O ₂ on the upstream side at that time.
Method of determining catalyst deterioration based on the area difference calculated from the output of the sensor and the output of the downstream O ₂ sensor (area difference method)
Have already been proposed by Japanese Patent Application No. 2-117890.

[0004]

However, in any of the above-mentioned conventional techniques, since the output of the upstream O ₂ sensor and the output of the downstream O ₂ sensor are compared, O ₂
An error occurs in the determination result due to the variation or deterioration of the single performance of the sensor. In particular, regarding the deterioration, the upstream O ₂ sensor is directly exposed to the exhaust gas having a higher temperature than the downstream O ₂ sensor, so that the deterioration tends to proceed in a short time. For this reason, the upstream O ₂ sensor and the downstream O ₂ sensor
_{2 The} degree of deterioration of the sensor is different, which causes an error in the judgment result.

Also in the area difference method proposed by the present applicant, if an error occurs due to deterioration of the O ₂ sensor and the center of the fuel correction coefficient for switching deviates from the theoretical air-fuel ratio, the output of the O ₂ sensor Change and the area difference fluctuates.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a catalyst deterioration determination device which can accurately determine the catalyst deterioration without being affected by the deterioration of the O ₂ sensor. And

[0007]

In order to achieve the above object, the inventions described in claims 1 to 4 are provided with the configurations shown in the claims correspondence diagrams of FIGS. 1 to 4, respectively.

That is, as shown in FIG. 1, in the exhaust gas purification system for an engine in which the catalyst is arranged in the exhaust system, the invention described in claim 1 is provided in the exhaust passage on the upstream side of the catalyst and The upstream O ₂ sensor for detecting the fuel ratio, the downstream O ₂ sensor provided in the exhaust passage downstream of the catalyst for detecting the air-fuel ratio of the engine, the output of the upstream O ₂ sensor and the downstream O ₂ sensor. First air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine according to the output, and the downstream side O
₂ Second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine according to the output of the sensor, operating state determining means for determining whether the engine is in a predetermined operating state, and when the engine is in the predetermined operating state , Adjusting means switching means for switching from the first air-fuel ratio adjusting means to the second air-fuel ratio adjusting means, and the downstream side O
₂ After switching the output of the sensor from the lean air-fuel ratio to the rich air-fuel ratio or from the rich air-fuel ratio to the lean air-fuel ratio to the inversion judgment means and the second air-fuel ratio adjusting means, The output of the downstream O ₂ sensor is rich with respect to the theoretical air-fuel ratio from the time when the second air-fuel ratio adjusting means generates the skip amount for changing the fuel correction coefficient from the rich side to the lean side with respect to the theoretical air-fuel ratio. It is characterized in that it is provided with a time measuring means for measuring a time from when the catalyst is turned to lean and a catalyst deterioration judging means for judging that the catalyst is deteriorated when the measured time is less than a predetermined time.

Further, as shown in FIG. 2, in the invention described in claim 2, in an engine exhaust purification system in which a catalyst is arranged in an exhaust system, the engine is provided in an exhaust passage on an upstream side of the catalyst and has an air-fuel ratio of the engine. An upstream O ₂ sensor for detecting
A downstream O ₂ sensor provided in the exhaust passage on the downstream side of the catalyst to detect the air-fuel ratio of the engine, and the air-fuel ratio of the engine is adjusted according to the output of the upstream O ₂ sensor and the output of the downstream O ₂ sensor. First air-fuel ratio adjusting means, second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine in accordance with the output of the downstream O ₂ sensor, and operating state for determining whether the engine is in a predetermined operating state The discriminating means, the adjusting means switching means for switching from the first air-fuel ratio adjusting means to the second air-fuel ratio adjusting means when the engine is in a predetermined operating state, and the output of the downstream O ₂ sensor with respect to the theoretical air-fuel ratio. From lean to rich,
Alternatively, after switching to the second air-fuel ratio adjusting means and the inversion determining means for determining that the air-fuel ratio has been changed from rich to lean, the second air-fuel ratio adjusting means changes the fuel correction coefficient to the theoretical air-fuel ratio. On the other hand, time measuring means for measuring the time from when the skip amount for changing from the lean side to the rich side is generated until the output of the downstream side O ₂ sensor changes from lean to rich with respect to the theoretical air-fuel ratio, And a catalyst deterioration determining unit that determines that the catalyst has deteriorated when the measured time is less than or equal to a predetermined time.

Further, as shown in FIG. 3, the invention described in claim 3 is an exhaust gas purification system for an engine in which a catalyst is arranged in an exhaust system, and is provided in an exhaust passage on the upstream side of the catalyst, and the air-fuel ratio of the engine is increased. An upstream O ₂ sensor for detecting
A downstream O ₂ sensor provided in the exhaust passage on the downstream side of the catalyst to detect the air-fuel ratio of the engine, and the air-fuel ratio of the engine is adjusted according to the output of the upstream O ₂ sensor and the output of the downstream O ₂ sensor. First air-fuel ratio adjusting means, second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine in accordance with the output of the downstream O ₂ sensor, and operating state for determining whether the engine is in a predetermined operating state The discriminating means, the adjusting means switching means for switching from the first air-fuel ratio adjusting means to the second air-fuel ratio adjusting means when the engine is in a predetermined operating state, and the output of the downstream O ₂ sensor with respect to the theoretical air-fuel ratio. From lean to rich,
Alternatively, after switching to the second air-fuel ratio adjusting means and the inversion determining means for determining that the air-fuel ratio has been changed from rich to lean, the second air-fuel ratio adjusting means changes the fuel correction coefficient to the theoretical air-fuel ratio. On the other hand, the first time for measuring the first time from when the skip amount for changing from the rich side to the lean side is generated until the output of the downstream O ₂ sensor is reversed from rich to lean with respect to the theoretical air-fuel ratio After switching to the time measuring means and the second air-fuel ratio adjusting means, the second air-fuel ratio adjusting means generated the skip amount for changing the fuel correction coefficient from the lean side to the rich side with respect to the theoretical air-fuel ratio. Second time measuring means for measuring a second time from the time when the output of the downstream O ₂ sensor changes from lean to rich with respect to the stoichiometric air-fuel ratio, and the measured first and second times. The time sum or average is at a specified time And a catalyst deterioration determining unit that determines that the catalyst has deteriorated when the time is not more than a certain period.

Further, as shown in FIG. 4, in addition to the configuration of the invention described in claim 3, the invention described in claim 4 is characterized in that the catalyst deterioration determining means is the second air-fuel ratio adjusting means. First measured in the air-fuel ratio feedback control by
Is calculated and the sum or average of the second time continuously measured after the first time and the first time is calculated, and when the calculated value is less than or equal to the predetermined time, it is determined that the catalyst has deteriorated.

The invention described in claims 5 to 8 is
In addition to the configurations of the invention described in claims 1 to 4, the catalyst is a good product when a predetermined time has elapsed after the second air-fuel ratio adjusting means generated the skip amount of the fuel correction coefficient. The present invention is characterized by including a catalyst normality determining means for making a determination and ending the catalyst degradation determination (see the claims correspondence diagrams of FIGS. 1 to 4).

[0013] In accordance with the invention according to claims 9 12, in accordance with the output of the output and the downstream O ₂ sensor at the upstream side O ₂ sensor in the invention described in claims 1 to 4 above In place of the first air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine, a first air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine according to the output of the upstream O ₂ sensor is provided. (Refer to the claims correspondence diagrams in FIGS. 1 to 4).

The invention according to claims 13 to 16
Is the configuration of the invention described in claims 1 to 4 above.
In addition to the above, the second air-fuel ratio adjusting means is arranged to scan the fuel correction coefficient.
The catalyst is good when a predetermined time has passed after the
It is determined that the product is genuine and the catalyst deterioration determination is completed.
An ordinary determination means is provided, and the above-mentioned claims 1 to 4 are further described.
Upstream O in the listed invention₂Sensor output and below
Flow side O₂Adjusts engine air-fuel ratio according to sensor output
In place of the first air-fuel ratio adjusting means, ₂Sensor
To adjust the air-fuel ratio of the engine according to the output of the first
The air-fuel ratio adjusting means of FIG.
(See claim correspondence diagram in 4).

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment corresponding to the invention described in claims 1 to 4 will be described below in detail with reference to the accompanying drawings.

FIG. 5 is an overall configuration diagram of a fuel supply control device to which the catalyst deterioration determination device of the present invention is applied. A throttle body 2 is provided in the middle of an intake pipe 1 of an engine E, and inside thereof. Is provided with a throttle valve 3. A throttle valve opening (θ _TH ) sensor 4 is connected to the throttle valve 3 and supplies an electric signal according to the opening θ _TH of the throttle valve 3 to the electronic control unit U.

The fuel injection valve 5 is provided for each cylinder between the engine E and the throttle valve 3 and slightly upstream of the intake valve 6, and each fuel injection valve 5 is connected to a fuel pump (not shown). , Is electrically connected to the electronic control unit U, and the valve opening time of fuel injection is controlled by a signal from the electronic control unit U.

On the other hand, an intake pipe absolute pressure (Pb) sensor 7 is provided immediately downstream of the throttle valve 3. The absolute pressure Pb detected by this absolute pressure sensor 7 is converted into an electric signal to be electronically controlled. Supplied to U. An intake air temperature (Ta) sensor 8 is attached downstream thereof, and the intake air temperature Ta detected by the intake air temperature sensor 8 is converted into an electric signal and supplied to the electronic control unit U.

The cooling water temperature (Tw) sensor 9 mounted on the main body of the engine E is composed of a thermistor or the like, and the cooling water temperature T
It detects w and supplies a corresponding electrical signal to the electronic control unit U. The engine speed (Ne) sensor 10 is mounted around a cam shaft or a crank shaft (not shown) of the engine E and outputs a pulse (hereinafter referred to as "TDC signal pulse") at a predetermined crank angle position of the crank shaft. , To the electronic control unit U. A vehicle speed (Vh) sensor 11 for detecting a vehicle speed is connected to the electronic control unit U, and an electric signal indicating the vehicle speed Vh is supplied.

At an upstream position of the catalyst C in the exhaust pipe 12, an upstream O ₂ sensor FS as an exhaust component concentration detector is provided.
Is installed, and a downstream side O
₂ sensor RS is mounted, an electric signal corresponding to the detected value by detecting the respective oxygen concentrations in the exhaust gas (FV _O2, R
V _O2 ) is supplied to the electronic control unit U. Also catalyst C
Is a catalyst temperature (T _CAT ) sensor 13 that detects the temperature.
Is mounted, and an electric signal corresponding to the detected catalyst temperature T _CAT is supplied to the electronic control unit U.

The electronic control unit U shapes the input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts the analog signal value into a digital signal value, and the like, the central processing unit. Circuit (hereinafter "C
15), and a ROM 1 in which various calculation programs and various reference values used for calculation in the CPU 15 are stored.
6, a RAM 17 in which the detected various engine parameter signals and calculation results are temporarily stored, an output circuit 18 for supplying a drive signal to the fuel injection valve 5, and the like.

Based on the above-mentioned various engine parameter signals, the CPU 15 determines various engine operating states of a feedback control region and a plurality of specific operating regions (hereinafter referred to as "open loop control region") in which feedback control is not performed, as described later. The TD is determined based on the following equation (1) according to the determined engine operating state.
Fuel injection time T of the fuel injection valve 5 synchronized with the C signal pulse
Calculate _OUT .

T _OUT = Ti × K _O2 × K _LS × K ₁ + K ₂ (1) where Ti is the basic fuel injection time of the fuel injection valve 5, the engine speed Ne and the absolute pressure in the intake pipe. It is determined according to Pb.

K _O2 is an O ₂ feedback correction coefficient (hereinafter, simply referred to as “correction coefficient”), which is obtained according to the oxygen concentration in the exhaust gas at the time of feedback control. It is set accordingly.

K _LS is set to a predetermined value less than 1.0 (for example, 0.95) when the engine E is in the lean region or the fuel cut region of the open loop control region, that is, the predetermined deceleration operation region. Is a leaning coefficient.

K ₁ and K ₂ are correction coefficients and correction variables calculated according to various engine parameter signals, respectively, and various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to the engine operating state are optimized. Such a predetermined value is determined.

The CPU 15 supplies a drive signal for opening the fuel injection valve 5 to the fuel injection valve 5 via the output circuit 18 based on the fuel injection time T _OUT obtained as described above.

6 and 7 determine whether the engine E is operating in the feedback control region or a plurality of open loop control regions, and set the correction coefficient K _O2 in accordance with the determined operating condition. The flowchart of a program is shown. This program is executed in synchronization with the generation of the TDC signal pulse.

First, at step 101, the flag n _O2
Is determined to be equal to the value 1. The flag n _O2 is used to determine whether the upstream O ₂ sensor FS and the downstream O ₂ sensor RS are in the activated state.
If the answer to 01 is (Yes), that is, both O ₂ sensors F
When it is determined that S and RS are in the activated state, it is determined in step 102 whether the cooling water temperature Tw is higher than the predetermined water temperature T _WO2 . The answer is (Yes), that is, Tw> T
_{When WO2} is established and the engine E has finished warming up, it is determined in step 103 whether the flag FLG _WOT is equal to the value 1. This flag FLG _WOT is set to a value of 1 when it is determined by the program (not shown) that the engine E is in the high load region in which the fuel supply amount should be increased.

When the answer to step 103 is (No), that is, when the engine E is not in the high load region, it is determined in step 104 whether the engine speed Ne is higher than a predetermined speed N _{HO P} on the high speed side. However, if the answer is (No), it is further determined in step 105 whether or not the engine speed Ne is higher than the predetermined speed N _LOP on the low speed side. When the answer is (Yes), that is, when N _LOP <Ne ≦ N _HOP is satisfied, the leaning coefficient K _LS is determined in step 106.
Is less than 1.0, that is, whether the engine E is in a predetermined deceleration operation range. When the answer to step 106 is (No), it is determined at step 107 whether or not the engine E is executing fuel cut. If the answer is (No), it is determined that the engine E is in the feedback control area, and step 10
At 8 it is determined whether the engine operating state is in a state in which the monitoring of the catalyst C is permitted. If the answer is (Yes), that is, if the monitoring is permitted, the correction coefficient K _O2 is controlled based on the output voltage RV _O2 of the downstream O ₂ sensor RS by the second air-fuel ratio adjusting means described later in step 109. At the same time, the deterioration of the catalyst C is monitored, and this program ends.

On the other hand, the answer to step 108 is (No),
That is, when the monitoring of the catalyst C is not permitted, it is determined in step 110 whether the previous monitoring is being performed. When the answer is (No), that is, when the monitoring is not continuously performed, the output FV _{O2 of} the upstream O ₂ sensor FS and the downstream O ₂ sensor RS by the first air-fuel ratio adjusting means described later in step 111, said correction coefficient based on the RV _O2 K _O2
The average value K _REF of the correction coefficient K _O2 is calculated, and this program is ended.

When the answer to step 105 is (No), that is, when Ne ≦ N _LOP is satisfied and the engine E is in the low speed region, the answer to step 106 is (Yes), that is, the engine E is in the predetermined deceleration operation region. Or if the answer to step 107 is (Yes), that is, if the engine E is executing fuel cut, the routine proceeds to step 112. In this step 112, it is judged whether or not the loop has continued for a predetermined time t _D , and when the answer is (No), the correction coefficient K _O2 is held at the value just before shifting to the loop in step 113. If the answer is (Yes), the correction coefficient K _O2 is set to a value of 1.0 in step 114, open loop control is performed, and this program ends. That is, when the engine E shifts from the feedback control region to the open loop control region due to any of the conditions of steps 105 to 107, the correction coefficient K
_O2 until the predetermined time t _D after the migration has elapsed while being held to a value that is calculated during the feedback control immediately before the transition, after the predetermined time t _D has elapsed is set to the value 1.0.

The answer to step 102 is (No), that is, when the engine E has not finished warming up, the answer to step 103 is (Yes), that is, when the engine E is in the high load region, or the step The answer of 104 is (Ye
s), that is, when the engine E is in the high rotation range,
In step 114, the open loop control is executed and this program is terminated.

The answer to step 101 is (No), that is, when it is determined that both O ₂ sensors FS and RS are inactive, and the answer to step 110 is (Yes), that is, the monitor is not activated for the first time. When the permission is granted, the routine proceeds to step 115, where it is judged if the engine E is in the idle region. This determination is performed, for example, by determining whether or not the engine speed Ne is equal to or lower than a predetermined speed and the throttle valve opening θ _TH is equal to or lower than a predetermined opening. When the answer to step 115 is (Yes), that is, when the engine E is in the idle region, the correction coefficient K _O2 is set to the average value K _REF0 for the idle region in step 116, open loop control is executed, and this program is executed. finish.

When the answer to step 115 is (No), that is, when the engine E is in an operating region other than the idle region (hereinafter referred to as "off idle region"), step 1
Proceeding to 17, the correction coefficient K _O2 is set to the average value K _REF1 for the off idle region.

8 and 9 show the correction coefficient K executed in step 111 of FIG. 6 during feedback control.
The flowchart of the calculation subroutine of _O2 is shown.

First, in step 201, it is judged whether or not the previous control was the open loop control, and the answer is (Ye
If s), it is determined in step 202 whether or not the value of the correction coefficient K _O2 was held by the execution of step 113 of FIG. 6 in the previous control. If the answer is (Yes),
In step 203, the value of the correction coefficient K _O2 is continuously held, and the integral control (I term control) in step 223 and later described later is performed. When the answer to step 202 is (No), that is, when the value of the correction coefficient K _O2 is not held in the previous control, it is determined in step 204 whether the engine E is in the idle region. When the answer is (Yes), that is, when the engine E is in the idle area, step 20
In step 5, the correction coefficient K _O2 is set to the average value K _REFO for the idle area.
, And the integral control from step 223 onward is performed.

When the answer to step 204 is (No), that is, when the engine E is in the off-idle region, the throttle valve opening θ _TH in the previous control is determined in step 206.
Is greater than the idle throttle valve opening θ _IDL . If the answer is (Yes), then step 2
At 07, the correction coefficient K _{O2 is set} to the average value K for the off idle region.
_It is set to _REF1 and the integral control from step 223 _onward is performed.

If the answer to step 206 is (No), that is, if θ _TH ≤ θ _IDL was satisfied in the previous control, then in step 208 the throttle valve opening θ
_It is determined whether _TH is larger than the idle throttle valve opening θ _IDL . The answer is (Yes), that is, the previous θ _TH ≤
When θ _TH > θ _IDL this time at θ _IDL , the correction coefficient K _O2 is set to the product C _R × K _REF1 of the average value K _REF1 for the off-idle region and the predetermined _enrichment value C _R at step 209. Then, the integral control from the step 223 onward is performed. Here, the enrichment predetermined value C _R is set to a value larger than 1.0.

When the answer to step 208 is (No), that is, when θ _TH ≤ θ _IDL is satisfied, the engine cooling water temperature Tw is set to a predetermined temperature T _WCL (for example, 70 °) in step 210.
C) Determine whether it is greater than or equal to. If the answer is (Yes), that is, Tw> T _WCL is satisfied, and therefore the engine cooling water temperature Tw is not in the low temperature range, the above step 205 is performed.
Proceed to.

If the answer to step 210 is (No), that is, Tw≤T _WCL is satisfied and therefore the engine cooling water temperature is in the low temperature range, the correction coefficient K is calculated in step 211.
_O2 is set to the product C _L × K _REF0 of the average value K _REF0 for the idle region and the leaning predetermined value C _L, and the step 2
Integral control of 23 or less is performed. Here, the leaning predetermined value C
_L is set to a value smaller than 1.0.

If the answer to step 201 is (No), that is, if the previous control was feedback control,
In step 212, it is determined whether or not the throttle valve opening θ _TH was larger than the idle throttle valve opening θ _IDL in the previous control. When the answer is (No), it is further determined in step 213 whether the throttle valve opening θ _TH this time is larger than the idle throttle valve opening θ _IDL . If the answer is (Yes), then step 20
Similarly to the case where the answer of 8 is (Yes), the process proceeds to the step 209, and the correction coefficient K _O2 is set to the average value K for the off idle region.
The product of _REF1 and a predetermined _enrichment value C _R is set to C _R × K _REF1 .

The answer to step 212 is (Yes), that is, when θ _TH > θ _IDL is satisfied in the previous control, or the answer to step 213 is (No), that is, θ this time.
_{When TH} ≤ θ _IDL is satisfied, it is determined in step 214 whether the output level of the upstream O ₂ sensor FS has been inverted. When the answer is (No), the correction terms ΔK _R and ΔK _L , which will be described later, are obtained in step 215, and the above-mentioned step 223 is executed.
The following integration control is performed.

The answer to step 214 is (Yes),
That is, when the output level of the upstream O ₂ sensor FS is reversed, proportional control (P term control) is performed. First step 2
In step 16, it is judged whether the output voltage FV _O2 of the upstream O ₂ sensor FS is lower than the above-mentioned reference voltage value V _REF . If the answer is (Yes), that is, FV _O2 <V _REF ,
In step 217, the correction term P _R is searched based on the output voltage RV _O2 of the downstream O ₂ sensor RS shown in FIG. 19, and in step 218 proportional control is performed to add the correction term P _R to the correction coefficient K _O2. .. On the other hand, the answer to step 216 is (N
when o), like searching correction term P _L based on the output voltage RV _O2 of the downstream O ₂ sensor RS shown in FIG. 19 at step 219, subtracted from the correction coefficient K _O2 said correction term P _L in step 220 Proportional control is performed.

When the output FV _O2 of the upstream O ₂ sensor FS reverses from rich to lean with respect to the theoretical air-fuel ratio, the correction term P _R increases the correction coefficient K _O2 in a stepwise manner to increase the air-fuel ratio. The output voltage RV _O2 of the downstream O ₂ sensor RS is referred to at that time, and the correction term P _R becomes smaller as the output voltage RV _O2 is biased to the rich side. , the output voltage RV _O2 reversed is set as the correction term P _R is increased enough that offset to the lean side. Also, the correction term P _L when the output FV _O2 of the upstream O ₂ sensor FS is inverted from lean to rich with respect to the theoretical air-fuel ratio, the correction coefficient K _O2 is decreased stepwise lean side air-fuel ratio intended for shifting to, where the output voltage RV _O2 of the downstream O ₂ sensor RS is referred to, the correction term P _L becomes larger as the output voltage RV _O2 are offset to the rich side, opposite Output voltage RV _O2
The correction term P _L is set to be smaller the closer to the lean side. In this way, the upstream O ₂ sensor F
Output FV _{O2 of} S and output voltage RF of the downstream O ₂ sensor RS
A fine proportional control of the correction coefficient K _O2 is performed based on both _O2 (see the normal F / B mode in FIGS. 17 and 18).

Next, in step 221, the above-mentioned step 21
The limit check of the correction coefficient K _O2 set in 8 or 220 is performed. That is, it is checked whether or not the correction coefficient K _O2 is within a predetermined range, and if it is not within the predetermined range, the correction coefficient K _O2 is held at the upper limit value or the lower limit value. Finally, in step 222, the average value K _REF of the correction coefficients K _O2 is calculated, and this program ends.

Next, the integral control after step 223 will be described. First, at step 223, it is judged whether or not the output voltage FV _O2 of the upstream O ₂ sensor FS is smaller than the reference voltage value V _REF , and the answer is (Yes), that is, FV _O2 <
When V _REF is established, the value 2 is added to the count number N _IL each time this step is executed in step 224, and the count number N _IL is set to the predetermined value N _{I in} step 225.
It is determined whether or not When the answer is (No), the correction coefficient K _O2 is held at the value immediately before it in step 226, and when the answer is (Yes), the correction term ΔK _R is added to the correction coefficient K _O2 in step 227. At the same time, in step 228, the count number N _IL is reset to 0, and each time N _IL reaches N _I , the correction coefficient K _O2 is set to a predetermined value ΔK.
Add _R.

Thus, the upstream side O₂Output of sensor FS
Voltage FV_O2Is the reference voltage value V_REFSmaller than you
That is, when the lean condition of the air-fuel ratio continues,
Number K _O2Is the count N_ILIs a predetermined value N_IEvery time
Predetermined value ΔK_RDirection to increase the air-fuel ratio
Controlled by. On the other hand, the answer to step 223 is (No)
 , Ie FV_O2≧ V_REFWhen is satisfied,
Every time this step is executed in step 229
Number N_IHAdd a value of 2 to and count the value in step 230
Number N_IHIs a predetermined value N_IIt is determined whether or not This answer
If is (No), execute step 226 to correct
Coefficient K_O2To the previous value, and when (Yes),
In step 231, the correction coefficient K_O2From the correction term ΔK_LTo
In addition to the subtraction, in step 232 the count number N
_IHIs reset to 0 and this count N_IHIs a predetermined value N_I
Correction coefficient K every time_O2To a predetermined value ΔK_LSubtract
It

[0049] Thus, the upstream O ₂ output voltage FV _O2 sensor FS is equal to or higher than the reference voltage value V _REF state, that is, when the rich state of the air-fuel ratio continues, the correction coefficient K
_O2 is decreased by a predetermined value ΔK _L each time the count number N _IH reaches a predetermined value N _I , and is controlled to lean the air-fuel ratio.

The correction terms ΔK _L and ΔK _R are determined in consideration of the output voltage RV _O2 of the downstream O ₂ sensor RS as shown in FIG. That is, the correction term [Delta] K _R is after the output FV _O2 of the upstream O ₂ sensor FS is inverted from rich to lean against the stoichiometric air-fuel ratio, a rich-side air-fuel ratio is increased stepwise the correction coefficient K _O2 The output voltage RV _O2 of the downstream O ₂ sensor RS is referred to at that time, and the correction term ΔK _R becomes smaller as the output voltage RV _{O2 deviates} to the rich side. the correction term enough output voltage RV _O2 conversely is offset to the lean side ΔK
_R is set to be large. Also, the correction term ΔK
_L is after the output FV _O2 of the upstream O ₂ sensor FS is inverted from lean to rich with respect to the stoichiometric air-fuel ratio, for the purpose of shifting the correction coefficient K _O2 stepwise decreasing the air-fuel ratio to the lean side However, at that time, the downstream O ₂ sensor RS
Of the output voltage RV _O2 is referred to, the correction term ΔK _L becomes larger as the output voltage RV _O2 is biased to the rich side, and conversely, the correction term is biased as the output voltage RV _O2 is biased to the lean side. is set so [Delta] K _L decreases. Thus, the output FV _O2 of the upstream O ₂ sensor FS and the downstream O ₂
Fine integration control of the correction coefficient K _O2 is performed by referring to both the output voltage RF _O2 of the sensor RS (see the normal F / B mode in FIGS. 17 and 18).

Next, a catalyst deterioration monitor will be described.

[0052] As described above, in the flowchart of FIG. 6, when the catalyst C of the monitor permission is not made in step 108, the output voltage of the output voltage FV _O2 and downstream O ₂ sensor RS of the upstream O ₂ sensor FS RV _O2 Based on the above, feedback control is performed by the first air-fuel ratio adjusting means (see the flowcharts of FIGS. 8 and 9). On the other hand, if the catalyst C is allowed to be monitored in step 108, the catalyst C monitoring mode is executed in step 109. The contents will be described in detail below with reference to the flowcharts of FIGS.

The deterioration of the catalyst C is monitored by the second air-fuel ratio adjusting means. At this time, the feedback control by the first air-fuel ratio adjusting means is performed by the output voltage FV _{O2 of the} upstream O ₂ sensor FS and the downstream. while was done based on both the output voltage RV _O2 side O ₂ sensor RS, the feedback control by the second air-fuel ratio adjusting means based on only the output voltage RV _O2 of the downstream O ₂ sensor RS Done. The time TL from the occurrence of the special P term P _LSP for skipping the correction coefficient K _O2 from the rich side to the lean side with respect to the stoichiometric air-fuel ratio until the inversion of rich → lean of the O ₂ concentration is confirmed. Is detected,
The time TR from the occurrence of the special P term P _RSP for skipping the correction coefficient K _O2 from the lean side to the rich side with respect to the stoichiometric air-fuel ratio to the confirmation of lean-> rich inversion of the O ₂ concentration is The deterioration of the catalyst C is determined based on the detected times TL and TR.

First, the schematic structure of the catalyst deterioration monitor will be described with reference to the flowchart of FIG. 10, and thereafter the subroutine of each step will be described in detail.

In FIG. 10, first, at step 301, it is judged if the precondition for detecting the deterioration of the catalyst is satisfied or not. If the answer is (No), then the step 30
2, n _TL (TL measurement count, that is, the time T
L is the total number of times measured, n _TR (the number of TR measurements, that is, the total number of times the time TR is measured), TL
_SUM (TL total value, that is, total time of TL measured multiple times) and TR _SUM (TR total value, that is, total time of TR measured multiple times) are set to zero. Then, at step 303, the above-mentioned normal feedback control is performed by the above-mentioned first air-fuel ratio adjusting means. If the preconditions are not met during the deterioration monitoring of the catalyst C,
K _REF is used as the initial value of the feedback control.

When the answer to step 301 is (Yes),
That is, when the precondition of the deterioration monitoring of the catalyst C is satisfied, it is determined in step 304 whether or not the TR measurement number n _TR is a predetermined value or more. If the answer to step 304 is (Yes), it is considered that the data for the deterioration determination of the catalyst C is prepared, the deterioration determination process B is executed in step 305, the monitoring is ended in step 306, and the normal feedback is performed. Return to control. Also in this case, K _REF is used as the initial value of the feedback control.

If the answer to step 304 is (No)
Has not prepared data for determining the deterioration of the catalyst C.
As a result, the following steps 307 to 313 are executed.
It That is, first, the monitor is permitted in step 307.
First Special P term P _LSP, P_RSPThere has occurred
Is determined. If the monitor has not started yet
The answer is (No), and in step 308 the monitor star
Processing is executed. On the other hand, the answer from step 307 is
(Yes) and already the first special P item P_LSP, P
_RSPIf it occurs, the downstream side O₂SE
Output voltage RV of sensor RS_O2Is reversed.
If the answer to step 309 is (Yes), step 310
At RV_O2Process at the time of inversion, that is, TL measurement number n_TLis there
I or TR measurement count n_TRIncrement, lean dire
Itima t_LD(RV_O2Special P term P after
_LSPMeasure the time until the
Delay timer t_RD(RV_O2Is reversed and then the special P
Term P_RSPStart measuring)
And special P term P_LSP, P_RSPThe occurrence of
It

On the other hand, when the answer to step 309 is (No), it is judged whether or not the output voltage RV _{O2 of the} downstream O ₂ sensor RS has been inverted even once after the monitoring is permitted in step 311. It The answer to step 311 is (N
In the case of o), that is, before the first inversion after the monitor is permitted, the inversion waiting process after the start is executed in step 312, while the answer in step 311 is (Yes), that is, if after undergoing one or more reverse the after start, RV _O2 inversion waiting process is performed in step 313. In these steps 312 and 313,
In either case, addition of the special I term I _LSP or reduction of the special I term I _RSP is performed on the correction coefficient K _O2 .
However, while the time TL and TR are measured in step 313, the measurement is not performed in step 312. This is because the duration of waiting for reversal after the start depends on the timing at which the monitor is permitted, and it is meaningless to measure the times TL and TR.

Next, steps 301, 308, 312, 313, 31 in the flowchart of FIG. 10 described above.
The subroutines 0 and 305 will be sequentially described in detail.

FIG. 11 shows a subroutine (pre-monitoring condition) of step 301 in the flow chart of FIG. 10. First, in step 401, the operating state of the engine E for starting monitoring is confirmed. That is, whether the output Ta of the intake air temperature sensor 8 is in the range of 60 ° C to 100 ° C,
Whether the output Tw of the cooling water temperature sensor 9 is in the range of 60 ° C. to 100 ° C., the output Ne of the engine speed sensor 10 is in the range of 2800 rpm to 3200 rpm, or the output Pb of the intake pipe absolute pressure sensor 7 is − 350mmHg ~
Whether it is in the range of −250 mmHg or the output Vh of the vehicle speed sensor 11 is in the range of 32 km / h to 80 km / h,
The output T _CAT of the catalyst temperature sensor 13 is 400 ° C to 800
It is checked whether it is in the range of ° C. Subsequently, at step 402, it is judged if the vehicle speed is constant, that is, if the fluctuation of the output Vh of the vehicle speed sensor 11 is 0.8 km / sec or less for a predetermined time (for example, 2 seconds). Next, at step 403, it is judged if the feedback control has been performed for a predetermined time (for example, 10 seconds) before the monitor is permitted. Further, in step 404, it is determined whether a predetermined time (for example, 2 seconds) has elapsed.

If all the answers in the above steps 401 to 404 are (Yes), the monitor is permitted in the step 405, and the process proceeds to the step 304 in the flowchart of FIG. 10, and any answer is (No). In this case, the monitor is not permitted in step 406, and the process proceeds to step 302 in the flowchart of FIG.

FIG. 12 is a flowchart of the flow chart of FIG.
Step 308 subroutine (monitor start processing)
First, in step 501, the downstream side O₂Sensor R
Output voltage RV of S_O2Is the reference voltage V_REFCompared to that
The answer is (Yes) and the output voltage RV_O2Is the reference voltage V_REFTo
If it is below, that is, downstream side O₂Inspection of sensor RS
Issued O₂If the concentration is lean, step
Correction coefficient K at 502_O2To the value immediately before the special P term P_RSP
Proportional control is performed to add the air-fuel ratio.
Increase in steps toward the side. On the other hand, the step 5
The answer of 01 is (No) and the output voltage RV_O2Is the reference voltage V
_REFWhen it is above, that is, the downstream side O ₂Sensor RS's
Detected O₂If the concentration is rich,
Correction coefficient K in step 503_O2From the value immediately before the special P term P
_LSPThe proportional control is performed by subtracting
Decrease to the lean side in steps.

FIG. 13 shows a subroutine (reversal waiting process after start) of step 312 in the flow chart of FIG. 10, and this flow is executed subsequently to the flow of FIG. 12 (monitor start process) described above. It is a thing. First, in step 601, the downstream O ₂ sensor RS
Compared output voltage RV _O2 is the reference voltage V _REF of, O ₂ the answer is the output voltage RV _O2 A (Yes) when below the reference voltage V _REF, i.e. it detects the downstream O ₂ sensor RS If the concentration is lean, step 6
In 02, integral control is performed in which the special I term I _RSP is added to the value immediately before the correction coefficient K _O2 , whereby the air-fuel ratio is gradually increased to the rich side. On the other hand, when the output voltage RV _O2 answer a (No) in step 601 is the reference voltage V _REF above, when that is detected O ₂ concentration of the downstream O ₂ sensor RS is rich state, step 60
At 3, the integral control is performed to subtract the special I term I _LSP from the value immediately before the correction coefficient K _O2 , whereby the air-fuel ratio is gradually reduced to the lean side.

FIG. 14 shows a subroutine (downstream O ₂ sensor inversion waiting process) of step 313 in the flow chart of FIG. 10, and this flow is based on the inversion of the output voltage RV _O2 of the downstream O ₂ sensor RS. It is what is executed. First, at step 701, it is judged if the rich delay timer t _RD is counting down or after the time is up. The rich delay timer t _RD is composed of a subtraction counter and outputs the output voltage R of the downstream O ₂ sensor RS.
The countdown is started at the moment when V _O2 is reversed from lean to rich with respect to the stoichiometric air-fuel ratio, and when a predetermined time elapses, the time is increased and the count value becomes zero. When the count value of the rich delay timer t _RD if the answer to the question of the step 701 (No) is not zero, that is, when the rich delay timer t _RD is in countdown, Special immediately prior value of the aforementioned correction coefficient K _O2 at step 702 Integral control is performed to add the I term I _RSP , thereby increasing the air-fuel ratio stepwise to the rich side.

On the other hand, if the answer to step 701 is (Yes),
If yes, in step 703 the previous rich delay
Imat_RDIs determined whether the count value is not zero, the answer is
When it is (Yes), that is, for the first time this time rich delay
Timer t_RDWhen the count value of is 0,
Start TL measurement at step 704 and step
Correction coefficient K at 705_O2To Special P term P_LSPSubtract
The air-fuel ratio is stepped to the lean side by performing proportional control.
Reduce. The answer to step 703 is (No).
The rich delay timer t_RDCount of
If the value is continuously zero, then step 706.
It is determined whether or not TL is being measured, and the answer is (Yes).
In this case, in step 707, the correction coefficient K_O2From specialist
Item I _LSPIntegral control for subtracting
Gradually decrease to the right side.

Then, at step 708, the lean delayer is
Imat_LDIs determined to have a count value of zero, and
If the answer is (No), that is, the lean delay time
Mat _LDIs counting down, step 7
Correction coefficient K at 09_O2Special I term I from the value immediately before_LSP
Integral control is performed to reduce the air-fuel ratio.
Gradually decrease to the right side.

On the other hand, if the answer in step 708 is (Yes), it is determined in step 710 whether the count value of the previous lean delay timer t _LD is zero, and if the answer is (Yes), that is, When the count value of the lean delay timer t _LD becomes zero for the first time this time, the TR measurement is started in step 711, and the proportional control for adding the special P term P _RSP to the correction coefficient K _O2 is performed in step 712 to perform the empty control. The fuel ratio is increased stepwise to the rich side. When the answer in step 710 is (No), that is, when the count value of the lean delay timer t _LD is continuously zero, it is further determined in step 713 whether TR is being measured, and the answer is ( If Yes, the correction coefficient K _{O2 is set} to the special I in step 714.
The air-fuel ratio is gradually increased to the rich side by performing integral control for adding the term I _RSP .

FIG. 15 shows a subroutine of step 310 of the flow chart of FIG. 10 (processing at the time of reversing the downstream O ₂ sensor). This flow is performed by the downstream O ₂ sensor R.
It is executed after S is inverted. First, step 8
In 01, it is determined whether or not the previous TL was being measured, and when the answer is (Yes), the TL measurement is stopped in step 802, and the TL measured this time is added to the TL total value TL _SUM in step 803. And TL measurement number n _Tl
Is incremented.

On the other hand, when the answer to step 801 is (No), that is, when the previous TL was not being measured, it is determined in step 804 whether or not the previous TR was being measured, and the answer is (Yes ), The TR measurement is stopped in step 805, and the TR measured this time is added to the TR total value TR _SUM in step 806.
The TR measurement number n _TR is incremented.

If n _TR is 1 in step 807 and n _Tl is 0 in step 808, TR _SUM is set to zero in step 809. This is T
This is because, in order to perform the measurement in the order of L → TR, if the TR is measured first, the TR is canceled.

[0071] Subsequently, the output voltage RV _O2 of the downstream O ₂ sensor RS is compared with the reference voltage V _REF in step 810,
Reference voltage V the answer is the output voltage RV _O2 A (Yes)
When it is below _REF , in step 811, the countdown of the lean delay timer t _LD is started, and
In step 812, integral control for subtracting the special I term I _LSP from the immediately preceding value of the correction coefficient K _O2 is performed, whereby the air-fuel ratio is gradually reduced to the lean side.

On the other hand, the answer to step 810 is (No).
Output voltage RV_O2Is the reference voltage V _REFIs above
In step 813, the rich delay timer t_RDThe cow
Start down and correct in step 814
Coefficient K_O2To the value immediately before the special I term I_RSPProduct of adding
Minute control is performed, which allows the air-fuel ratio to be stepped to the rich side.
To increase.

FIG. 16 shows a subroutine (deterioration determination process B) of step 305 in the flowchart of FIG. 10, and this flow is executed when the TR measurement number n _TR exceeds a predetermined number. First, step 901
The value obtained by dividing the total TL value by the number of TL measurements (TL _SUM /
n _Tl ) and TR total value divided by TR measurement number (TR
The average value of ( _SUM / n _TR ) is calculated to obtain the time T _CHK .

Then, at step S902, the time T
_It is determined whether or not _CHK is larger than a predetermined value, and when the answer is (Yes), it is determined that the O ₂ storage capacity of the catalyst C exceeds the standard, and the exhaust gas purification system is normal in step 903. To determine. On the other hand, when the answer to step S902 is (No), the O _{2 of} the catalyst C is
If storage capacity is below standard, step 9
In 04, it is determined that the exhaust gas purification system is abnormal.

The operation of the deterioration monitor of the catalyst C is shown in FIG.
Further description will be made with reference to the time chart of FIG.

At time (1) in FIG. 17, engine E
When the operating state of 1 satisfies the predetermined condition, the first air-fuel ratio adjusting means is switched to the second air-fuel ratio adjusting means, and the monitor mode of the catalyst C is entered. At this time, as shown in the figure, the output voltage RV _O2 of the downstream O ₂ sensor RS is equal to the reference voltage V _REF.
In the following (lean state), the fuel correction coefficient K _O2 increases stepwise by the special P term P _RSP , and subsequently, the special I term I in the region (2) and the region (4).
_The fuel correction coefficient K _O2 increases stepwise by the _RSP . In the middle of the time (3), the output voltage RV _O2 of the downstream O ₂ sensor RS is Invert from lean to rich with respect to the theoretical air-fuel ratio is rich delay timer t _RD is set to start counting down. Rich delay timer t _RD
When the time elapses at time (5), the fuel correction coefficient K _O2 decreases stepwise due to the special P term P _LSP , and subsequently the fuel is corrected by the special I term I _{LSP in} the regions (6) and (8). The correction coefficient K _O2 gradually decreases. Then, TL measurement is started at time (5) when the rich delay timer t _LD is up,
The TL is measured by measuring the output voltage RV at time (7).
It ends when _O2 reverses from rich to lean with respect to the stoichiometric air-fuel ratio. Similarly, TR lean delay timer t _LD starts measurement when the time is up at time (9), when the output voltage RV _O2 is inverted from lean to rich with respect to the theoretical air-fuel ratio at a time (11) Measurement ends. In the region (2), since the lean delay timer t _LD has not been operated before that, TR is not measured.

The time chart of FIG. 18 shows an example in which the monitor mode of the catalyst C is entered when the output voltage RV _O2 of the downstream O ₂ sensor RS is equal to or higher than the reference voltage V _REF (rich state). In this example, time T in region (2)
R is not measured, because the first measurement is preprogrammed to start at time TL (step 8 in the flowchart of FIG. 15).
07-step 809). For other points,
It is substantially the same as the time chart of FIG. 17 described above.

The time TL measured as described above is
From the moment when the fuel correction coefficient K _O2 is reduced stepwise by the special P term P _LSP to shift the air-fuel ratio to the lean side, the output voltage RV _{O2 of the} downstream O ₂ sensor RS is actually obtained.
Corresponds to the delay time from the rich to lean inversion with respect to the theoretical air-fuel ratio. Further, at the time TR, the fuel correction coefficient K _{O2 is set} to the special P in order to shift the air-fuel ratio to the rich side.
It corresponds to the delay time from the moment when the value is increased stepwise by the term P _RSP until the output voltage RV _O2 of the downstream O ₂ sensor RS actually changes from lean to rich with respect to the stoichiometric air-fuel ratio.

By the way, in the catalyst C, the air-fuel ratio is moved to the lean side.
Oxidizing gas (O ₂And NO_X)
There is an action to take in, and O₂And NO_XUptake of
Is completed, the downstream side O₂Output voltage RV of sensor RS_O2Is
It changes from rich to lean with respect to the theoretical air-fuel ratio. Also
The catalyst C returns to the exhaust gas when the air-fuel ratio shifts to the rich side.
The original gas (CO and HC) was taken in and already taken in
O₂And NO_XHas the effect of reacting with
And when HC uptake ends, downstream O₂Sensor RS's
Output voltage RV_O2Is lean to rich for stoichiometric ratio
Changes to. Therefore, the length of the time TL, TR is
O of catalyst C₂To be proportional to the amount of storage capacity
The catalyst C, which has deteriorated the length of the time TL, TR,
Nozawa O ₂Distinguish catalyst C with reduced storage capacity
Can be used as a parameter for

Further, time TL, that is, O ₂ in the exhaust gas
And the time until NO _x is completely taken up by the catalyst C, and the time TR, that is, the already taken in O ₂ and NO.
_{The time for X} to fully react with the next incorporated CO and HC is closely related. Therefore, the first measured time TL and the subsequently measured time TR are combined, and the catalyst C is calculated using the average value T _CHK of the TL and TR.
By measuring the O ₂ storage capacity of the catalyst, the deterioration of the catalyst C can be determined extremely accurately.

By the way, since the heat of the exhaust gas and various toxins contained in the exhaust gas are absorbed by the catalyst C, the influence of the exhaust gas on the downstream O ₂ sensor RS is smaller than that on the upstream O ₂ sensor FS. As a result, the output performance of the downstream O ₂ sensor RS is more stable than that of the upstream O ₂ sensor FS. In the second air-fuel ratio adjusting means for determining the deterioration of the catalyst C in the present invention, the output voltage RV of the downstream O ₂ sensor RS whose output performance is stable.
_Since only _O2 is used, the deterioration of the catalyst C can be judged extremely accurately.

It should be noted that instead of using the above-mentioned average value of TL and TR as the time for determining the deterioration of the catalyst C, TL and TR are used.
Only one of them may be adopted, or another combination of TL and TR (for example, the sum of TL and TR) can be adopted.

Next, a second embodiment corresponding to the invention described in claims 5 to 8 will be described.

The second embodiment is the same as the first embodiment shown in FIG.
In addition to the deterioration determination process B in step 305 of the flowchart of FIG. 3, the new deterioration determination process A is characterized, and the rest of the configuration is the same as that of the first embodiment.

That is, in the flowchart of FIG. 21, when the first special P term is generated in step 307, the deterioration determination process A is started in step 314 before the downstream O ₂ sensor RS is reversed in step 309, and the subsequent steps are executed. If the answer of 315 is (Yes) and normality is confirmed,
The process proceeds to step 306, and the monitoring ends. On the other hand, if the answer to step 315 is (No) and normality cannot be confirmed, the process proceeds to step 311.

FIG. 22 shows the subroutine of step 314 of FIG.
This is the first step in step 1001.
After the occurrence of the P term, the limit time t remains without the next inversion.
_STRGIs determined. When the limit here
Interval t_STRGAs time T compared with
The average value of (TL + TR) / 2 is used. And this
Mean value (TL + TR) / 2 is the limit time t_STRGLonger than
If not, O of catalyst C ₂When the storage capacity is large
Then, without executing the deterioration determination process B described above,
In step 1002, it is determined that the catalyst C is a good product. The limit
Time t_STRGFor the measurement of
It is described in the right column of the table.

The reason why it is possible to determine that the catalyst C is a good product in the deterioration determination process A is as follows. That is, the smaller the degree of deterioration of the catalyst C and the higher the O ₂ storage capacity, the longer the inversion period of the downstream O ₂ sensor RS when the feedback control is performed by the second air-fuel ratio adjusting means. Therefore, if the average value of the times TL and TR until the downstream O ₂ sensor RS reverses is greater than the limit time t _STRG, it can be determined that the catalyst C is a good product. Further, if the catalyst C is a good product and the inversion period is long,
It is known that drivability deteriorates and harmful substances in exhaust gas increase. Therefore, when the catalyst C is a non-defective product, the monitor mode is immediately stopped and the second air-fuel ratio adjusting means is switched to the first air-fuel ratio adjusting means, so that the inconvenience can be avoided.

This will be described with reference to the graph of FIG. 23. A limit time t _STRG that can prevent deterioration of drivability and increase of harmful substances in exhaust gas is set, and the average value (TL + TR) of the TL and TR is set. When / 2 exceeds the limit time t _STRG , it is determined that the catalyst C is a good product, and the monitor mode is stopped. From this graph, it is understood that a good product of the catalyst C can be accurately identified by using the limit time t _STRG .

Next, a third embodiment corresponding to the invention described in claims 9 to 12 will be described.

The third embodiment differs from the first embodiment in the structure of the first air-fuel ratio adjusting means, and the rest of the structure is the same as that of the first embodiment. That is, in the first embodiment has been performed a feedback control based on both the output voltage FV _O2 and downstream sensor O ₂ sensor RS output voltage RV _O2 of the first air-fuel ratio adjusting means upstream O ₂ sensor FS On the other hand, in the third embodiment, the first air-fuel ratio adjusting means is the upstream side O ₂
It is characterized in that performing feedback control based only on the output voltage FV _O2 sensor FS.

FIGS. 24 and 25 correspond to FIGS.
The correction terms ΔK _R and ΔK _L calculated in step 215 of FIG. 8 are determined in consideration of the output voltages FV _O2 and RV _O2 of the upstream and downstream O ₂ sensors FS and RS ( 20) (see step 215 of FIG. 24)
The correction terms ΔK _R ′ and ΔK _L ′ calculated by the above are determined only by the output voltage FV _O2 of the upstream O ₂ sensor FS. The correction terms P _R and P _L calculated in steps 217 and 219 of FIG. 9 are the upstream and downstream O ₂ sensors FS and RS.
Output voltage FV _O2 and RV _O2 are taken into consideration (Fig. 1
To 9 See) of the correction term is calculated in step 217 and 219 of FIG. 25 P _R ', P _L' upstream O ₂ sensor F
It is determined by only the output voltage FV _O2 of S.

As described above, the output voltage F of the upstream O ₂ sensor FS is fed back to the feedback of the first air-fuel ratio adjusting means.
By using only V _O2 , the configuration of the control system can be simplified.

Next, a fourth embodiment of the invention described in claims 13 to 16 will be described.

[0094] The fourth embodiment, a point of performing a new deterioration determination process A in addition to the deterioration determination process B, and the first air-fuel ratio adjusting means on the basis of only the output voltage FV _O2 of the upstream O ₂ sensor FS It is characterized in that feedback control is performed, and the rest of the configuration is the same as in the first embodiment described above. That is, the fourth embodiment is the same as the second embodiment and the third embodiment described above.
It corresponds to the combination of the features of the embodiments and has the respective operational effects.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various small design changes can be made without departing from the present invention described in the claims. It is possible to

[0096]

As described above, according to claim 1 or claim 2.
According to the described invention, the operation of the second air-fuel ratio adjusting means.
When performing catalyst deterioration determination with the catalyst deterioration determination means,
Flow side O ₂Downstream O without using sensor output₂Of the sensor
As the deterioration is judged using only the output, the upstream side
O₂Control air-fuel ratio due to sensor characteristics and deterioration
It is stable because it is not affected by the deviation from the fuel ratio.
Downstream side O₂Accurate catalyst deterioration based on sensor output
It becomes possible to make a judgment. Downstream O₂Of the sensor
O of the catalyst by the time measuring means using only the output₂Su
Because the storage capacity is measured in time, the upstream side O₂SE
Deterioration of catalyst without being affected by the output characteristics of the sensor
It can be performed.

According to the invention described in claim 3,
Since the catalyst deterioration determining means determines the catalyst deterioration based on the sum or average of the first time and the second time output by the first time measuring means and the second time measuring means, respectively, It is possible to accurately detect the O ₂ storage capacity of the catalyst and accurately determine the deterioration of the catalyst without being affected by the variation between the time measuring means and the second time measuring means.

According to the invention described in claim 4,
Since the catalyst deterioration determining means determines the deterioration of the catalyst based on the sum or average of the first time and the second time measured after that, the adsorption action of the oxidizing gas in the exhaust gas in the catalyst is determined. Further, it becomes possible to more accurately detect the O ₂ storage capacity of the catalyst based on the subsequent combined action of the adsorbed oxidizing gas and the reducing gas in the exhaust gas, and more accurately determine the deterioration of the catalyst.

According to the invention described in claims 5 to 8, in addition to the effects of the invention described in claims 1 to 4, the following effects are further achieved.

That is, since the second air-fuel ratio adjusting means is provided with the catalyst normality determining means for terminating the catalyst deterioration determination when a predetermined time has elapsed after the skip amount of the fuel correction coefficient is generated, The second air-fuel ratio adjusting means having a long fuel ratio inversion cycle is prevented from operating for an unnecessarily long time, and as a result, deterioration of drivability and increase of harmful substances in the exhaust gas are prevented.

According to the invention described in claims 9 to 12, in addition to the effects of the invention described in claims 1 to 4, the following effects are further achieved.

That is, since the first air-fuel ratio adjusting means does not use the output of the downstream O ₂ sensor but uses only the output of the upstream O ₂ sensor, the structure of the control system can be simplified. it can.

According to the invention described in claims 13 to 16, in addition to the effects of the invention described in claims 1 to 4, the following effects are further achieved.

That is, since the second air-fuel ratio adjusting means is provided with the catalyst normality determining means for ending the catalyst deterioration determination when a predetermined time has elapsed since the skip amount of the fuel correction coefficient was generated, The second air-fuel ratio adjusting means having a long fuel ratio inversion cycle is prevented from operating for an unnecessarily long time, and as a result, deterioration of drivability and increase of harmful substances in the exhaust gas are prevented. In addition, the first air-fuel ratio adjusting means does not use the output of the downstream side O ₂ sensor and
The configuration of the control system can be simplified by using only the outputs of the _two sensors.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram of claims 1, 5, 9 and 13;

FIG. 2 is a claim correspondence diagram of claims 2, 6, 10 and 14;

FIG. 3 is a claim correspondence diagram of claims 3, 7, 11, and 15;

FIG. 4 is a claim correspondence diagram of claims 4, 8, 12, and 16;

FIG. 5 is an overall configuration diagram of a fuel supply control device.

FIG. 6 is a first partial diagram of a flow chart of a program for setting a correction coefficient K _O2 .

FIG. 7 is a second partial diagram of a flow chart of a program for setting a correction coefficient K _O2 .

FIG. 8 is a first partial diagram of a flow chart of a program of first air-fuel ratio adjusting means.

FIG. 9 is a second partial diagram of a flowchart of a program of the first air-fuel ratio adjusting means.

FIG. 10 is a flowchart of a program of second air-fuel ratio adjusting means.

11 is a flowchart showing a subroutine of step 301 of FIG.

FIG. 12 is a flowchart showing a subroutine of step 308 of FIG.

13 is a flowchart showing a subroutine of step 312 of FIG.

FIG. 14 is a flowchart showing a subroutine of step 313 of FIG.

15 is a flowchart showing a subroutine of step 310 of FIG.

16 is a flowchart showing a subroutine of step 305 of FIG.

FIG. 17 is a time chart showing changes in the correction coefficient K _O2 .

FIG. 18 is a time chart showing changes in the correction coefficient K _O2 .

[19] term correction and the output voltage RV _{O2 R} R, a graph showing the relationship between the R _L

[20] Output voltage RV _O2 correction term [Delta] K _R, a graph showing the relationship between [Delta] K _L

FIG. 21 is a flowchart corresponding to FIG. 10 according to the second embodiment.

22 is a flowchart showing a subroutine of step 314 of FIG.

FIG. 23 is a graph showing the relationship between catalyst purification rate and measurement time T.

FIG. 24 is a flowchart corresponding to FIG. 8 according to the third embodiment.

FIG. 25 is a flowchart corresponding to FIG. 9 according to the third embodiment.

[Explanation of symbols]

M1 1st air-fuel ratio adjusting means M2 2nd air-fuel ratio adjusting means M3 Operating state judging means M4 Adjusting means switching means M5 Inversion judging means M6 Time measuring means M6 ₁ First time measuring means M6 ₂ Third time measuring means M7 catalyst deterioration determining means M8 catalyst normality determination unit FS upstream O ₂ sensor RS downstream O ₂ sensor FV _O2 upstream O ₂ sensor output voltage RV _O2 downstream O ₂ output voltage P _LSP special P term of the sensor (skip amount ) P _RSP Special P term (skip amount) TL 1st time TR 2nd time K _O2 Fuel correction coefficient C Catalyst E Engine

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Kenichi Maeda Kenichi Maeda 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Toshihiko Sato 1-1-4 Chuo, Wako-shi, Saitama Incorporated company Honda R & D Co., Ltd. (72) Inventor Eri Kuroda 1-4-1 Chuo, Wako City, Saitama Prefecture Incorporated Honda R & D Co., Ltd. (72) Inventor Masataka Chikamatsu 1-4-1 Wako, Saitama Prefecture Incorporated company Honda R & D Co., Ltd. (72) Inventor Toshihiro Terada 1-4-1 Chuo, Wako, Saitama Prefecture Incorporated Honda R & D Co., Ltd. (72) Inventor Kazuto Sawamura 1-4 Chuo, Wako, Saitama No. 1 Stock Company Honda Technical Research Institute

Claims (16)

[Claims] 1. An exhaust gas purification system for an engine (E) in which a catalyst (C) is arranged in an exhaust system, the upstream being provided in an exhaust passage upstream of the catalyst (C) and detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the output of the upstream O ₂ sensor (FS) (FV _O2) and the first air-fuel ratio adjustment of adjusting the air-fuel ratio of the engine (E) in accordance with the output of the downstream O ₂ sensor (RS) (RV _O2) Means (M
1), the output of the downstream O ₂ sensor (RS) and (second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to RV _O2) (M2), the engine (E) is a predetermined operating The operating state determination means (M3) for determining whether or not it is in the state, and the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in the predetermined operating state. and adjusting means switching means (M4) for switching on), inverted from lean to rich with respect to the output (RV _O2) is the stoichiometric air-fuel ratio of the downstream O ₂ sensor (RS) or from rich relative to the theoretical air-fuel ratio, the lean After switching to the reversal discrimination means (M5) for discriminating the fact and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. To the lean side to the lean side with respect to (P Time measuring means (M6) for measuring the time (TL) from the time when the _LSP ) is generated until the output (RV _O2 ) of the downstream O ₂ sensor (RS) changes from rich to lean with respect to the theoretical air-fuel ratio. ) And catalyst deterioration determination means (M7) for determining that the catalyst (C) has deteriorated when the measured time (TL) is less than or equal to a predetermined time.
An apparatus for determining deterioration of a catalyst, comprising: 2. An exhaust gas purification system for an engine (E) in which a catalyst (C) is arranged in an exhaust system, the upstream being provided in an exhaust passage upstream of the catalyst (C) and detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the output of the upstream O ₂ sensor (FS) (FV _O2) and the first air-fuel ratio adjustment of adjusting the air-fuel ratio of the engine (E) in accordance with the output of the downstream O ₂ sensor (RS) (RV _O2) Means (M
1), the output of the downstream O ₂ sensor (RS) and (second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to RV _O2) (M2), the engine (E) is a predetermined operating The operating state determination means (M3) for determining whether or not it is in the state, and the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in the predetermined operating state. and adjusting means switching means (M4) for switching on), inverted from lean to rich with respect to the output (RV _O2) is the stoichiometric air-fuel ratio of the downstream O ₂ sensor (RS) or from rich relative to the theoretical air-fuel ratio, the lean After switching to the reversal discrimination means (M5) for discriminating the fact and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. With respect to the lean side to the rich side, the skip amount (P Since that caused the _RSP), time measuring means for output of the downstream O ₂ sensor (RS) (RV _O2) measures the time (TR) from lean against the stoichiometric air-fuel ratio until the reversal to the rich (M6 ), And catalyst deterioration determination means (M7) for determining that the catalyst (C) has deteriorated when the measured time (TR) is less than or equal to a predetermined time.
An apparatus for determining deterioration of a catalyst, comprising: 3. An exhaust purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage on an upstream side of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the output of the upstream O ₂ sensor (FS) (FV _O2) and the first air-fuel ratio adjustment of adjusting the air-fuel ratio of the engine (E) in accordance with the output of the downstream O ₂ sensor (RS) (RV _O2) Means (M
1), the output of the downstream O ₂ sensor (RS) and (second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to RV _O2) (M2), the engine (E) is a predetermined operating The operating state determination means (M3) for determining whether or not it is in the state, and the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in the predetermined operating state. and adjusting means switching means (M4) for switching on), inverted from lean to rich with respect to the output (RV _O2) is the stoichiometric air-fuel ratio of the downstream O ₂ sensor (RS) or from rich relative to the theoretical air-fuel ratio, the lean After switching to the reversal discrimination means (M5) for discriminating the fact and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. The amount of skip (P to change from the rich side to the lean side with respect to Since that caused the _LSP), the output of the downstream O ₂ sensor (RS) (RV _O2) measures the first time from the rich with respect to the theoretical air-fuel ratio until inverted to lean (TL) 1 After switching to the time measuring means (M6 ₁ ) and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. skip amount for changing to the rich side (P _RSP) from the time which is generated from the lean side, the output of the downstream O ₂ sensor (RS) (RV _O2) is from lean against the stoichiometric air-fuel ratio until the reversal to the rich The second time measuring means (M6 ₂ ) for measuring the second time (TR) and the catalyst (when the sum or average of the measured first and second times (TL, TR) is less than or equal to a predetermined time And a catalyst deterioration determining means (M7) for determining that C) has deteriorated. Deterioration determination device of catalysts symptoms. 4. The first time (TL) measured by the catalyst deterioration determining means (M7) during the air-fuel ratio feedback control by the second air-fuel ratio adjusting means (M2) and the first time (TL).
Of the second time (TR) continuously measured after the time (TL), and it is determined that the catalyst (C) has deteriorated when the calculated value is less than or equal to a predetermined time. The catalyst deterioration determination device according to claim 3. 5. An exhaust gas purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage upstream of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the output of the upstream O ₂ sensor (FS) (FV _O2) and the first air-fuel ratio adjustment of adjusting the air-fuel ratio of the engine (E) in accordance with the output of the downstream O ₂ sensor (RS) (RV _O2) Means (M
1), the output of the downstream O ₂ sensor (RS) and (second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to RV _O2) (M2), the engine (E) is a predetermined operating The operating state determination means (M3) for determining whether or not it is in the state, and the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in the predetermined operating state. and adjusting means switching means (M4) for switching on), inverted from lean to rich with respect to the output (RV _O2) is the stoichiometric air-fuel ratio of the downstream O ₂ sensor (RS) or from rich relative to the theoretical air-fuel ratio, the lean After switching to the reversal discrimination means (M5) for discriminating the fact and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. To the lean side to the lean side with respect to (P Time measuring means (M6) for measuring the time (TL) from the time when the _LSP ) is generated until the output (RV _O2 ) of the downstream O ₂ sensor (RS) changes from rich to lean with respect to the theoretical air-fuel ratio. ), And the second air-fuel ratio adjusting means (M2) is operated by the fuel correction coefficient (K _O2 ).
The catalyst (C) is judged to be non-defective when a predetermined time has elapsed after the skip amount (P _LSP ) of
Catalyst normality determining means (M8) for terminating the deterioration determination and catalyst deterioration determining means (M6) for determining that the catalyst (C) has deteriorated when the time (TL) measured by the time measuring means (M6) is less than or equal to a predetermined time. M7), and a deterioration determination device for a catalyst. 6. An exhaust purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage upstream of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the output of the upstream O ₂ sensor (FS) (FV _O2) and the first air-fuel ratio adjustment of adjusting the air-fuel ratio of the engine (E) in accordance with the output of the downstream O ₂ sensor (RS) (RV _O2) Means (M
1), the output of the downstream O ₂ sensor (RS) and (second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to RV _O2) (M2), the engine (E) is a predetermined operating The operating state determination means (M3) for determining whether or not it is in the state, and the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in the predetermined operating state. and adjusting means switching means (M4) for switching on), inverted from lean to rich with respect to the output (RV _O2) is the stoichiometric air-fuel ratio of the downstream O ₂ sensor (RS) or from rich relative to the theoretical air-fuel ratio, the lean After switching to the reversal discrimination means (M5) for discriminating the fact and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. With respect to the lean side to the rich side, the skip amount (P Since that caused the _RSP), time measuring means for output of the downstream O ₂ sensor (RS) (RV _O2) measures the time (TR) from lean against the stoichiometric air-fuel ratio until the reversal to the rich (M6 ), And the second air-fuel ratio adjusting means (M2) is operated by the fuel correction coefficient (K _O2 ).
The catalyst (C) is determined to be non-defective when a predetermined time has elapsed after the skip amount (P _RSP ) of
Normality determining means (M8) for terminating the deterioration determination of the catalyst, and catalyst deterioration determining means (M8) for determining that the catalyst (C) has deteriorated when the time (TR) measured by the time measuring means (M6) is less than or equal to a predetermined time. M7), and a deterioration determination device for a catalyst. 7. An exhaust purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage upstream of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the output of the upstream O ₂ sensor (FS) (FV _O2) and the first air-fuel ratio adjustment of adjusting the air-fuel ratio of the engine (E) in accordance with the output of the downstream O ₂ sensor (RS) (RV _O2) Means (M
1), the output of the downstream O ₂ sensor (RS) and (second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to RV _O2) (M2), the engine (E) is a predetermined operating The operating state determination means (M3) for determining whether or not it is in the state, and the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in the predetermined operating state. and adjusting means switching means (M4) for switching on), inverted from lean to rich with respect to the output (RV _O2) is the stoichiometric air-fuel ratio of the downstream O ₂ sensor (RS) or from rich relative to the theoretical air-fuel ratio, the lean After switching to the reversal discrimination means (M5) for discriminating the fact and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. To the lean side to the lean side with respect to (P Since that caused the _LSP), the output of the downstream O ₂ sensor (RS) (RV _O2) measures the first time from the rich with respect to the theoretical air-fuel ratio until inverted to lean (TL) 1 After switching to the time measuring means (M6 ₁ ) and the second air-fuel ratio adjusting means (M2), the second air-fuel ratio adjusting means (M2) _{sets the} fuel correction coefficient (K _O2 ) to the theoretical air-fuel ratio. skip amount for changing to the rich side (P _RSP) from the time which is generated from the lean side, the output of the downstream O ₂ sensor (RS) (RV _O2) is from lean against the stoichiometric air-fuel ratio until the reversal to the rich The second time measuring means (M6 ₂ ) for measuring the second time (TR) and the second air-fuel ratio adjusting means (M2) function as a fuel correction coefficient (K _O2 ).
The catalyst normality determination means (M) that determines that the catalyst (C) is non-defective when a predetermined time has elapsed after the skip amount (P _LSP , P _RSP ) of
8) and the catalyst deterioration determining means for determining that the catalyst (C) has deteriorated when the sum or average of the first and second times (TL, TR) measured by the time measuring means (M6) is less than or equal to a predetermined time. (M7), and a deterioration determination device for a catalyst, comprising: 8. The first time (TL) measured by the catalyst deterioration determining means (M7) during the air-fuel ratio feedback control by the second air-fuel ratio adjusting means (M2) and the first time (TL).
Of the second time (TR) continuously measured after the time (TL), and it is determined that the catalyst (C) has deteriorated when the calculated value is less than or equal to a predetermined time. The catalyst deterioration determination device according to claim 7. 9. An exhaust purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system, wherein an upstream is provided in an exhaust passage upstream of the catalyst (C) and detects an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
And the output (FV _O2 ) of the upstream O ₂ sensor (FS) (F
The first to adjust the air-fuel ratio of the engine (E) according to V _O2 )
And air-fuel ratio adjusting means (M1) of the engine the second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the (E) (M2) in accordance with the output of the downstream O ₂ sensor (RS) (RV _O2), the engine When the engine (E) is in the predetermined operating state, the operating state determination means (M3) for determining whether or not (E) is in the predetermined operating state, and the first air-fuel ratio adjusting means (M1) to the second and adjusting means switching means for switching the air-fuel ratio adjusting means (M2) (M4), from lean to rich with respect to the output (RV _O2) is the stoichiometric air-fuel ratio of the downstream O ₂ sensor (RS), or the theoretical air-fuel ratio After switching to the second air-fuel ratio adjusting means (M2) and the inversion judging means (M5) for judging that the fuel has been reversed from rich to lean, the second air-fuel ratio adjusting means (M2) causes the fuel correction coefficient (K2) to change. It changes from the rich side to the lean side of the _O2) with respect to the theoretical air-fuel ratio Weight skip (P _LSP) from when caused to the output of the downstream O ₂ sensor (RS) (RV _O2) measures the time (TL) from the rich with respect to the theoretical air-fuel ratio until inverted to lean Time measurement means (M6) and catalyst deterioration determination means (M7) for determining that the catalyst (C) has deteriorated when the measured time (TL) is less than or equal to a predetermined time.
An apparatus for determining deterioration of a catalyst, comprising: 10. An exhaust gas purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage on an upstream side of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the upstream O ₂ sensor output (FS) and the first air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to (FV _O2) (M1), the downstream O ₂ sensor (RS) output engine second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the (E) (M2) in response to (RV _O2), the engine (E) operating state determination means for determining whether the predetermined operating condition (M3), adjusting means switching means (M4) for switching from the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in a predetermined operating state, and the output side O ₂ sensor (RS) and the inversion judging means (RV _O2) is determined from lean to rich with respect to the theoretical air-fuel ratio or that has been inverted from rich to lean against the stoichiometric air-fuel ratio, (M5), After switching to the second air-fuel ratio adjusting means (M2), Ratio adjusting means (M2) is a fuel correction coefficient (K _O2) skip amount varying from the lean side to the rich side with respect to the theoretical air-fuel ratio from the time that caused the (P _RSP), the downstream O ₂ sensor (RS) Measuring means (M6) for measuring the time (TR) until the output (RV _O2 ) of the air-fuel ratio changes from lean to rich with respect to the stoichiometric air-fuel ratio, and when the measured time (TR) is less than a predetermined time Catalyst deterioration determination means (M7) for determining that the catalyst (C) has deteriorated
An apparatus for determining deterioration of a catalyst, comprising: 11. An exhaust gas purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage upstream of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the upstream O ₂ sensor output (FS) and the first air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to (FV _O2) (M1), the downstream O ₂ sensor (RS) output engine second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the (E) (M2) in response to (RV _O2), the engine (E) operating state determination means for determining whether the predetermined operating condition (M3), adjusting means switching means (M4) for switching from the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in a predetermined operating state, and the output side O ₂ sensor (RS) and the inversion judging means (RV _O2) is determined from lean to rich with respect to the theoretical air-fuel ratio or that has been inverted from rich to lean against the stoichiometric air-fuel ratio, (M5), After switching to the second air-fuel ratio adjusting means (M2), Ratio adjusting means (M2) is a fuel correction coefficient (K _O2) skip amount varying from the rich side to the lean side with respect to the stoichiometric air-fuel ratio from the time that caused the (P _LSP), the downstream O ₂ sensor (RS) First time measuring means (M6 ₁ ) for measuring a first time (TL) until the output (RV _O2 ) of the fuel cell is reversed from rich to lean with respect to the theoretical air-fuel ratio, and second air-fuel ratio adjusting means After switching to (M2), the second air-fuel ratio adjusting means (M2) generates a skip amount ( _PRSP ) that changes the fuel correction coefficient ( _KO2 ) from the lean side to the rich side with respect to the theoretical air-fuel ratio. since the second time measuring means the output of the downstream O ₂ sensor (RS) (RV _O2) is for measuring a second time from lean against the stoichiometric air-fuel ratio until the reversal to the rich (TR) ( M6 ₂ ) and the measured first and second times (TL, TR) A catalyst deterioration determination device, comprising: a catalyst deterioration determination means (M7) for determining that the catalyst (C) has deteriorated when the sum or average of the above is less than a predetermined time. 12. The first time (TL) measured by the catalyst deterioration determining means (M7) during the air-fuel ratio feedback control by the second air-fuel ratio adjusting means (M2) and the first time (TL).
Of the second time (TR) continuously measured after the time (TL), and it is determined that the catalyst (C) has deteriorated when the calculated value is less than or equal to a predetermined time. The catalyst deterioration determination device according to claim 11. 13. An exhaust purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage upstream of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the upstream O ₂ sensor output (FS) and the first air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to (FV _O2) (M1), the downstream O ₂ sensor (RS) output engine second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the (E) (M2) in response to (RV _O2), the engine (E) operating state determination means for determining whether the predetermined operating condition (M3), adjusting means switching means (M4) for switching from the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in a predetermined operating state, and the output side O ₂ sensor (RS) and the inversion judging means (RV _O2) is determined from lean to rich with respect to the theoretical air-fuel ratio or that has been inverted from rich to lean against the stoichiometric air-fuel ratio, (M5), After switching to the second air-fuel ratio adjusting means (M2), Ratio adjusting means (M2) is a fuel correction coefficient (K _O2) skip amount varying from the rich side to the lean side with respect to the stoichiometric air-fuel ratio from the time that caused the (P _LSP), the downstream O ₂ sensor (RS) (M6) for measuring the time (TL) until the output (RV _O2 ) of RV _O2 changes from rich to lean with respect to the theoretical air-fuel ratio, and the second air-fuel ratio adjusting means (M2) is used for the fuel correction coefficient. (K _O2 )
The catalyst (C) is judged to be non-defective when a predetermined time has elapsed after the skip amount (P _LSP ) of
Catalyst normality determining means (M8) for terminating the deterioration determination and catalyst deterioration determining means (M6) for determining that the catalyst (C) has deteriorated when the time (TL) measured by the time measuring means (M6) is less than or equal to a predetermined time. M7), and a deterioration determination device for a catalyst. 14. An exhaust gas purification system for an engine (E), wherein a catalyst (C) is arranged in an exhaust system. An upstream provided in an exhaust passage upstream of the catalyst (C) for detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the upstream O ₂ sensor output (FS) and the first air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to (FV _O2) (M1), the downstream O ₂ sensor (RS) output engine second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the (E) (M2) in response to (RV _O2), the engine (E) operating state determination means for determining whether the predetermined operating condition (M3), adjusting means switching means (M4) for switching from the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in a predetermined operating state, and the output side O ₂ sensor (RS) and the inversion judging means (RV _O2) is determined from lean to rich with respect to the theoretical air-fuel ratio or that has been inverted from rich to lean against the stoichiometric air-fuel ratio, (M5), After switching to the second air-fuel ratio adjusting means (M2), Ratio adjusting means (M2) is a fuel correction coefficient (K _O2) skip amount varying from the lean side to the rich side with respect to the theoretical air-fuel ratio from the time that caused the (P _RSP), the downstream O ₂ sensor (RS) (M6) for measuring the time (TR) required for the output (RV _O2 ) of the engine to change from lean to rich with respect to the stoichiometric air-fuel ratio, and the second air-fuel ratio adjusting means (M2) (K _O2 )
The catalyst (C) is determined to be non-defective when a predetermined time has elapsed after the skip amount (P _RSP ) of
Normality determining means (M8) for terminating the deterioration determination of the catalyst, and catalyst deterioration determining means (M8) for determining that the catalyst (C) has deteriorated when the time (TR) measured by the time measuring means (M6) is less than or equal to a predetermined time. M7), and a deterioration determination device for a catalyst. 15. In an exhaust purification system of an engine (E), wherein a catalyst (C) is arranged in an exhaust system, an upstream provided in an exhaust passage on an upstream side of the catalyst (C) and detecting an air-fuel ratio of the engine (E). Side O ₂ sensor (FS)
And a downstream O ₂ sensor (RS) provided in the exhaust passage on the downstream side of the catalyst (C) for detecting the air-fuel ratio of the engine (E)
When the upstream O ₂ sensor output (FS) and the first air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine (E) according to (FV _O2) (M1), the downstream O ₂ sensor (RS) output engine second air-fuel ratio adjusting means for adjusting the air-fuel ratio of the (E) (M2) in response to (RV _O2), the engine (E) operating state determination means for determining whether the predetermined operating condition (M3), adjusting means switching means (M4) for switching from the first air-fuel ratio adjusting means (M1) to the second air-fuel ratio adjusting means (M2) when the engine (E) is in a predetermined operating state, and the output side O ₂ sensor (RS) and the inversion judging means (RV _O2) is determined from lean to rich with respect to the theoretical air-fuel ratio or that has been inverted from rich to lean against the stoichiometric air-fuel ratio, (M5), After switching to the second air-fuel ratio adjusting means (M2), Ratio adjusting means (M2) is a fuel correction coefficient (K _O2) skip amount varying from the rich side to the lean side with respect to the stoichiometric air-fuel ratio from the time that caused the (P _LSP), the downstream O ₂ sensor (RS) First time measuring means (M6 ₁ ) for measuring a first time (TL) until the output (RV _O2 ) of the fuel cell is reversed from rich to lean with respect to the theoretical air-fuel ratio, and second air-fuel ratio adjusting means After switching to (M2), the second air-fuel ratio adjusting means (M2) generates a skip amount ( _PRSP ) that changes the fuel correction coefficient ( _KO2 ) from the lean side to the rich side with respect to the theoretical air-fuel ratio. since the second time measuring means the output of the downstream O ₂ sensor (RS) (RV _O2) is for measuring a second time from lean against the stoichiometric air-fuel ratio until the reversal to the rich (TR) ( M6 ₂ ) and the second air-fuel ratio adjusting means (M2) K _O2 )
The catalyst normality determination means (M) that determines that the catalyst (C) is non-defective when a predetermined time has elapsed after the skip amount (P _LSP , P _RSP ) of
8) and the catalyst deterioration determining means for determining that the catalyst (C) has deteriorated when the sum or average of the first and second times (TL, TR) measured by the time measuring means (M6) is less than or equal to a predetermined time. (M7), and a deterioration determination device for a catalyst, comprising: 16. The first time (TL) measured by the catalyst deterioration determining means (M7) during the air-fuel ratio feedback control by the second air-fuel ratio adjusting means (M2) and the first time (TL).
Of the second time (TR) continuously measured after the time (TL), and it is determined that the catalyst (C) has deteriorated when the calculated value is less than or equal to a predetermined time. The catalyst deterioration determination device according to claim 15.