JPH08121148A - Absorbent self diagnosis device for internal combustion engine - Google Patents

Abstract

PURPOSE: To let fail-safe be materialized in all operations by diagnosing the degradation degree of absorbent based on the operated air-fuel ratio of the upstream side to the downstream side of absorbent in the internal combustion engine equipped with absorbent for unburnt gas in exhaust gas at an exhaust passage. CONSTITUTION: Exhaust temperature in the inside of absorbent 5 is detected by a temperature sensor 9, and an air-fuel ratio at the upstream side is detected by a front sensor 14 at the upstream side exhaust passage 2 of absorbent 5 for an usual air-fuel ratio feedback control by judging whether an air-fuel ratio is richer or leaner than its theoretical value in a form of ON/Off operations. An air-fuel ratio at the downstream side is detected by a rear oxygen sensor 15, and the temperature of engine cooling water and the revolution speed of an engine are detected by a water temperature sensor 10 and a revolution sensor 11 respectively. A control unit 12 diagnoses absorbent 5 by itself based on signals from these sensors. Respective proportions are obtained based on the period of lean time and the period of rich time, the ratio of both the proportions is compared with a judgment reference value, and it is judged by a resultant value large or small whether or not its absorbing action is normal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorbent self-diagnosis apparatus for an internal combustion engine, and more particularly, in an internal combustion engine having an adsorbent for adsorbing unburned gas in exhaust gas in an exhaust path The present invention relates to an adsorbent self-diagnosis device that diagnoses a failure or the like of the adsorbent based on a fuel ratio.

[0002]

2. Description of the Related Art In an internal combustion engine for a vehicle, in order to purify exhaust gas, HC (unburned gas) and CO in the exhaust gas are oxidized into H ₂ O and CO ₂ in the exhaust passage, while NO _X is converted into N ₂ . An exhaust gas purification catalyst called a three-way purification catalyst that reduces and purifies is installed. By the way, of the harmful components in the exhaust gas, H
The discharge amount of C is particularly susceptible to the exhaust temperature. In other words, even if a noble metal catalyst is used, it is generally 3
A catalyst temperature of 00 ° C or higher is required. For this reason, in the exhaust gas purification device having only the three-way catalyst, it is difficult to purify HC by the catalyst when the exhaust gas temperature is low, such as immediately after the engine is started cold.

Therefore, as an exhaust emission control device for vehicles,
As disclosed in Japanese Patent Application Laid-Open No. 55-101715, there has been proposed one in which an adsorbent for adsorbing HC is interposed in the exhaust passage on the upstream side of the exhaust purification catalyst. This one utilizes the fact that the adsorbent has the property of adsorbing HC at low temperatures and desorbing adsorbed HC at high temperatures.
At the low temperature before the exhaust purification catalyst is activated by interposing the adsorbent in the exhaust passage upstream of the exhaust purification catalyst, HC is adsorbed by the adsorbent and becomes high temperature and the exhaust purification catalyst is activated. After being converted, HC is desorbed and purified by an exhaust purification catalyst. As an adsorbent, for example, a monolith carrier coated with zeolite has been proposed because zeolite has excellent adsorbability.

[0004]

In the past, in an internal combustion engine equipped with an adsorbent, whether or not the capacity of the adsorbent has deteriorated was not monitored at all, and therefore the adsorbent failed. However, since the driver cannot detect the failure, there is a problem that the HC cannot be fully processed at low temperature.

Therefore, as an adsorbent self-diagnosis device for diagnosing the deterioration of the adsorbent, the applicant has provided an HC concentration detection sensor for detecting the HC concentration in exhaust gas on the upstream side and the downstream side of the adsorbent, and An adsorbent self-diagnosis device for performing deterioration diagnosis of the adsorbent by calculating the HC adsorbed amount of the adsorbent based on the output difference between the side HC concentration detection sensor and the downstream side HC concentration detection sensor and the intake air amount signal. It was previously proposed (see Japanese Patent Laid-Open No. 6-93829).

However, in this case, H which detects the HC concentration in the exhaust gas is provided upstream and downstream of the adsorbent.
Since the C concentration detection sensor is provided, the cost is increased. Further, since the adsorbent in the high temperature state after desorption of HC has a catalytic action, the applicant of the present application can diagnose the adsorption capacity of the adsorbent by judging whether the adsorbent has good catalytic performance. Paying attention to the fact that the air-fuel ratio of the exhaust gas on the downstream side of the material and the air-fuel ratio of the exhaust gas on the upstream side of the adsorbent differ depending on whether the adsorbent is performing a normal adsorption operation or not. It has been proposed that the adsorption capacity of the adsorbent is diagnosed based on the difference in the state of change between the upstream side air-fuel ratio and the downstream side air-fuel ratio in the high temperature state after HC desorption of the adsorbent ( See JP-A-6-66131).

However, in this case, the deterioration diagnosis of the adsorbent is possible only in the operating region where the catalytic action of the adsorbent is large, and it is difficult to perform the self-diagnosis of the adsorbent in all operating regions. . The present invention has been made in view of the above circumstances, at least the deterioration diagnosis of the adsorbent is performed based on the lean time of the exhaust air-fuel ratio on the downstream side of the adsorbent, and the deterioration of the adsorbent is determined in all operating regions. It is an object of the present invention to provide an adsorbent self-diagnosis device for an internal combustion engine, which is capable of performing accurate fail-safe.

[0008]

Therefore, as an invention according to claim 1, as shown in FIG. 1, in the engine exhaust passage,
In an internal combustion engine equipped with an adsorbent that has the function of adsorbing unburned gas in the exhaust at low temperatures and desorbing it at high temperatures, the downstream side air that detects the air-fuel ratio of the exhaust on the downstream side of the adsorbent in a predetermined operating state and ratio detecting means, for inverting the inverted downstream-side air-fuel ratio time the air-fuel ratio detected by the detecting means has become lean with respect to the target air-fuel ratio T _RL and lean-rich air-fuel ratio in the same direction Ratio to the elapsed time up to R _RL (=
T _RL / T _RL + T _RR ) for detecting downstream side air-fuel ratio time ratio, and based on the air-fuel ratio time ratio R _RL of the air-fuel ratio calculated by the downstream side air-fuel ratio time ratio calculating means A first deterioration diagnosis means for performing deterioration diagnosis is provided.

As the invention according to claim 2, FIG.
As shown in Fig. 4, in the engine exhaust passage, in an internal combustion engine in which an adsorbent having a function of adsorbing unburned gas in exhaust at low temperature and desorbing at high temperature is arranged, the air-fuel ratio of exhaust gas upstream of the adsorbent The upstream side air-fuel ratio detecting means for detecting, the downstream side air-fuel ratio detecting means for detecting the air-fuel ratio of the exhaust gas on the downstream side of the adsorbent, and the air-fuel ratio detected by the upstream side air-fuel ratio detecting means with respect to the target air-fuel ratio. Upstream of detecting the ratio R _FL (= T _FL / T _FL + T _FR ) between the time T _{FL during} which the air-fuel ratio is lean and the elapsed time from when the lean rich of the air-fuel ratio is reversed to when it is reversed in the same direction. identical to the side air-fuel ratio time ratio calculating means, the inverted lean-rich time T _RL and the air-fuel ratio has become lean with respect to the air-fuel ratio the target air-fuel ratio detected by the downstream side air-fuel ratio detecting means Ratio to the elapsed time until the direction is reversed R _RL
(= T _RL / T _RL + T _RR ) downstream air-fuel ratio time ratio calculation means, and upstream air-fuel ratio time ratio R _FL and downstream side of the air-fuel ratio calculated by the upstream air-fuel ratio time ratio calculation means A first ratio calculation means for calculating a ratio G _FR (= R _FL / R _RL ) of the air-fuel ratio calculated by the air-fuel ratio time ratio calculation means to the downstream side air-fuel ratio time ratio R _RL ; Second deterioration diagnosis means for performing deterioration diagnosis of the adsorbent based on the ratio G _FR of the upstream side air-fuel ratio time ratio R _FL and the downstream side air-fuel ratio time ratio R _RL calculated by the calculation means. It was configured.

As the invention according to claim 3, FIG.
As shown in FIG. 5, exhaust temperature detecting means for detecting the exhaust temperature Y inside the adsorbent is provided, and when the exhaust temperature Y detected by the exhaust temperature detecting means is equal to or lower than a predetermined temperature, the first deterioration diagnosing means or the first deterioration diagnosing means. The second deterioration diagnosis means may perform deterioration diagnosis of the adsorbent. In addition, claim 4
4, the engine load detection means for detecting the engine load (for example, the basic fuel injection amount Tp) is provided, and the second deterioration diagnosis means is detected by the engine load detection means. Deterioration diagnosis of the adsorbent may be performed when the load is less than or equal to a predetermined load.

As an invention according to claim 5, FIG.
As shown in FIG. 5, the diagnostic criterion J for diagnosing whether or not the adsorbent is deteriorated is determined based on the engine load (for example, the basic fuel injection amount Tp) detected by the engine load detecting means. May be. Further, as an invention according to claim 6, as shown in FIG. 5, an exhaust gas temperature detecting means for detecting an exhaust gas temperature Y inside the adsorbent is provided to diagnose whether or not the adsorbent is deteriorated. The diagnosis criterion J may be determined based on the engine load (for example, the basic fuel injection amount Tp) detected by the engine load detection means and the exhaust temperature Y detected by the exhaust temperature detection means.

Further, as an invention according to claim 7, FIG.
As shown in FIG. 3, an internal combustion engine is provided with an exhaust gas purification catalyst in the engine exhaust passage and an adsorbent having a function of adsorbing unburned gas in exhaust gas at low temperature and desorbing it at high temperature upstream of the exhaust gas purification catalyst. In the engine, upstream air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas upstream of the adsorbent, catalyst downstream-side air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas downstream of the exhaust purification catalyst, and upstream air-fuel ratio The ratio R of the time T _FL during which the air-fuel ratio detected by the fuel ratio detection means is lean with respect to the target air-fuel ratio and the elapsed time from when the lean rich of the air-fuel ratio is reversed to when it is reversed in the same direction. Time at which the air-fuel ratio detected by the upstream air-fuel ratio time ratio calculating means for detecting _FL (= T _FL / T _FL + T _FR ) and the catalyst downstream side air-fuel ratio detecting means is lean with respect to the target air-fuel ratio. Lean of T _SL and the air-fuel ratio
A catalyst downstream side air-fuel ratio time ratio calculating means for detecting a ratio R _SL (= T _SL / T _SL + T _SR ) with an elapsed time from when the rich is reversed to when it is reversed in the same direction, and an upstream air-fuel ratio time ratio The upstream side air-fuel ratio time ratio R of the air-fuel ratio calculated by the calculating means
The ratio G of _FL to the catalyst downstream side air-fuel ratio time ratio R _SL calculated by the catalyst downstream side air-fuel ratio time ratio calculating means
Second ratio calculating means for calculating _FS (= R _FL / R _SL ),
Ratio G _{FS of the} upstream side air-fuel ratio time ratio R _FL and the catalyst downstream side air-fuel ratio time ratio R _SL calculated by the second ratio calculating means
Exhaust purification catalyst deterioration diagnosis means for diagnosing the deterioration of the exhaust purification catalyst based on the above, and the upstream side air-fuel ratio time ratio R _FL and the catalyst downstream side air-fuel ratio time ratio R _SL calculated by the second ratio calculation means. Of the exhaust gas, the deterioration criterion of the adsorbent is diagnosed based on the ratio G _FS of the adsorbent, and a diagnosis criterion J for diagnosing whether the adsorbent is deteriorated is diagnosed by exhaust gas purification catalyst deterioration diagnosis means. And a third deterioration diagnosing means that is determined based on the degree of deterioration Z of the catalyst.

[0013]

First, in an internal combustion engine in which an adsorbent having a function of adsorbing unburned gas in exhaust gas at a low temperature and desorbing it at a high temperature is provided in an engine exhaust passage, the adsorbent is deteriorated and How the air-fuel ratio of the exhaust gas on the downstream side or the air-fuel ratio of the exhaust gas on the upstream side of the adsorbent changes will be described with reference to FIG. 7. In FIG. 7, various outputs when the adsorbent is normal are shown on the left side, and various outputs when the adsorbent is deteriorated are shown on the right side.

Here, it is assumed that the air-fuel ratio of the exhaust gas upstream of the adsorbent fluctuates around 14.6 as indicated by. Whether the adsorbent is normal or deteriorated, the air-fuel ratio of the exhaust gas on the upstream side of the adsorbent fluctuates around 14.6, so the waveform is the same in both normal and deteriorated conditions. . Also,
Shows the output of the oxygen sensor on the upstream side of the adsorbent, which also has the same waveform whether the adsorbent is normal or deteriorated as described above. Here, the time when the air-fuel ratio is leaner than stoichiometric when the adsorbent is normal is T _FLOK , the time when it is richer than stoichiometric is T _FROK, and the air-fuel ratio when the adsorbent is deteriorated is leaner than stoichiometric. Time to T
_Assuming that the time that is richer than _FLNG and stoichiometric is T _FRNG , the percentage of time that is leaner than stoichiometric when the adsorbent is normal or has deteriorated in the oxygen sensor on the upstream side of the adsorbent is calculated by the following formula. Can be expressed as

R _FLOK = T _FLOK / (T _FLOK + T _FROK ) R _FLNG = T _FLNG / (T _FLNG + T _FRNG ) By the way, even if the adsorbent is normal or deteriorated, it is omitted. It will be the same value. That is, R _FLOK ≈ R
It becomes _FLNG . Is the air-fuel ratio of the exhaust gas downstream of the adsorbent
It shows the case where it fluctuates around 14.6, but if the adsorbent is normal, HC is adsorbed on the adsorbent, so the air-fuel ratio becomes lean, and if the adsorbent is deteriorated, the air-fuel ratio Is not made lean. That is, the waveform is different under normal conditions and during deterioration.

The output of the oxygen sensor on the downstream side of the adsorbent is shown in FIG. Here, the time when the air-fuel ratio is leaner than stoichiometric when the adsorbent is normal is T _RLOK , the time when it is richer than stoichiometric is T _RROK, and the air-fuel ratio when the adsorbent is deteriorated is leaner than stoichiometric. a certain time T _RLNG, the rich time that is of stoichiometry and T _RRNG, the downstream oxygen sensor of the adsorbent, when the adsorbent is normal,
The time ratio that is leaner than each stoichiometry when deteriorated can be expressed by the following equation.

R _RLOK = T _RLOK / (T _RLOK + T _RROK ) R _RLNG = T _RLNG / (T _RLNG + T _RRNG ) Here, when the adsorbent is normal, the air-fuel ratio of the oxygen sensor on the downstream side is more than stoichiometric. The lean time T _RLOK becomes longer than the lean air-fuel ratio of the upstream oxygen sensor than the stoichiometric time T _FLOK (T _RLOK >> T _FLOK ), but if the adsorbent is deteriorated, The time T _{RLNG when} the air-fuel ratio of the oxygen sensor is leaner than stoichiometric does not become longer than the time T _FLNG when the air-fuel ratio of the upstream oxygen sensor is leaner than stoichiometric (T _{RLNG ≈T FLNG} ).

Therefore, when the adsorbent is normal, R _RLOK >>
R _FLOK , and if the adsorbent is deteriorated, R _RLNG
≈ R _FLNG . Next, the operation according to each claim will be described.
If the adsorbent is normal, the air-fuel ratio of the exhaust gas on the downstream side of the adsorbent becomes lean because the adsorbent adsorbs HC, and if the adsorbent is deteriorated, the air-fuel ratio becomes Does not lean. That is, when the adsorbent as described above is normal, when the next R _RLOK »R _FLOK, the adsorbent is deteriorated, the R _RLNG ≒ R _FLNG.

Here, by setting the predetermined operation condition as a load and a condition that the fluctuation is within a predetermined range and the fluctuation thereof is not more than a predetermined degree, the R detected by the upstream side air-fuel ratio detection means is detected.
Both _FLOK The R _FLNG is possible to a predetermined value, it is possible to be regarded as R _FLOK = R _FLNG have. Therefore, when the adsorbent is normal, R _RLOK >> R _RLNG , and when the adsorbent is deteriorated, R _RLOK = R _RLNG .

That is, according to the invention of claim 1,
In an internal combustion engine in which an adsorbent having a function of adsorbing unburned gas in exhaust gas at a low temperature and desorbing it at a high temperature is provided in the engine exhaust passage, in a predetermined operating condition, by the downstream side air-fuel ratio detecting means. The ratio R _RL (= T) between the time T _RL during which the detected air-fuel ratio is lean with respect to the target air-fuel ratio and the elapsed time from when the lean rich of the air-fuel ratio is reversed to when it is reversed in the same direction. It is possible to perform deterioration diagnosis of the adsorbent based on _RL / T _RL + T _RR ).

Therefore, the downstream side air-fuel ratio detecting means operates in a predetermined manner.
The air-fuel ratio of the exhaust gas downstream of the adsorbent in the state,
The downstream side air-fuel ratio time ratio calculation means has a ratio R_RL(= T_RL/ T_RL+
T_RR) Is detected, the first deterioration diagnosis means detects the time ratio R_RL
Based on the above, the deterioration diagnosis of the adsorbent is performed. In addition,
Thus, the air-fuel ratio of the exhaust gas downstream of the adsorbent is
If so, since the adsorbent has adsorbed HC, the air-fuel ratio is
If the adsorbent has deteriorated and the air-fuel ratio has
Does not lean. That is, the adsorbent is normal as described above.
If not, R_RLOK≫ R_FLOKAnd the adsorbent deteriorates
R if_RLNG≒ R _FLNGBecomes

Therefore, the ratio R_FL(= T_FL/ T_FL+
T_FR) And the ratio R_RL(= T_RL/ T_RL+ T _RR) Ratio G
_FR(= R_FL/ R_RL) Based on the diagnosis of deterioration of the adsorbent
It becomes possible to do. That is, according to the invention of claim 2,
As an operation, the upstream air-fuel ratio detection means is
The downstream air-fuel ratio detection means that detects the air-fuel ratio of the exhaust gas is adsorbent
Detects the air-fuel ratio of the exhaust gas on the downstream side of the
The calculation means is the ratio R_FL(= T_FL/ T_FL+ T_FR) Is detected and
The flow-side air-fuel ratio time ratio calculation means has a ratio R_RL(= T_RL/ T_RL+ T
_RR) Is detected. The first ratio calculation means is
Flow side air-fuel ratio time ratio R_FLAnd the downstream side air-fuel ratio time ratio R_RLWhen
Ratio G_FR(= R_FL/ R_RL) Is calculated and the second deterioration diagnosis is performed.
The means is the ratio G_FRDeterioration diagnosis of the adsorbent based on
U

Further, when the exhaust gas temperature becomes higher than the predetermined high temperature, the adsorbent does not exhibit the adsorbing action. That is, even if the adsorbent is normal when the exhaust temperature exceeds the predetermined high temperature, HC is not adsorbed on the adsorbent, so that the air-fuel ratio of the exhaust gas downstream of the adsorbent does not become lean. . Therefore, as an effect of the invention described in claim 3, only when the exhaust gas temperature Y detected by the exhaust gas temperature detecting means is equal to or lower than the predetermined temperature, the first deterioration diagnosing means or the second deterioration diagnosing means is operated. Deteriorate the adsorbent.

The engine load (for example, the basic fuel injection amount T
If p) is large, the ratio of adsorbing HC is small, and the diagnostic accuracy may be poor. Therefore, as an action of the invention described in claim 4, when the engine load detecting means for detecting the engine load (for example, the basic fuel injection amount Tp) is provided, and the engine load detected by the engine load detecting means is equal to or less than the predetermined load, Only by performing the deterioration diagnosis of the adsorbent, the accuracy of deterioration diagnosis is improved.

Further, the engine load (for example, intake air flow rate Qa
And the basic fuel injection amount Tp) are large, the ratio of adsorbing HC is small, and the diagnostic accuracy may be deteriorated. Therefore, as an operation of the invention described in claim 5, an engine load detecting means for detecting the engine load (for example, the intake air flow rate Qa and the basic fuel injection amount Tp) is provided to diagnose whether or not the adsorbent is deteriorated. The diagnostic criterion J when the engine load is detected is the engine load detected by the engine load detecting means (for example, the intake air flow rate Q).
a and the basic fuel injection amount Tp), the diagnosis criterion J increases as the engine load increases.
Is increased to compensate for the decrease in diagnostic accuracy due to the reduced ratio of adsorbing HC.

Further, as described in the operation according to the second aspect, when the exhaust temperature is high, the ratio of adsorbing HC becomes small, and the diagnostic accuracy may be deteriorated. Therefore, as an operation according to the invention described in claim 6, exhaust gas temperature detecting means for detecting the exhaust gas temperature Y inside the adsorbent is provided, and the diagnostic reference J is increased as the exhaust gas temperature Y becomes higher and the engine load becomes larger. , HC is absorbed to reduce the deterioration of diagnostic accuracy.

Further, as described above, the exhaust gas on the downstream side of the adsorbent
If the adsorbent is normal, the air-fuel ratio of
Therefore, the air-fuel ratio becomes lean and the adsorbent deteriorates.
If so, the air-fuel ratio is not made lean. Immediately
If the adsorbent is normal as described above, R_RLOK≫ R
_FLOKIf the adsorbent is deteriorated, R_RLNG≒
R _FLNGBecomes

The operation according to the invention of claim 7 is as follows.
In an internal combustion engine, an exhaust gas purification catalyst is provided in an engine exhaust passage, and an adsorbent having a function of adsorbing unburned gas in exhaust gas at low temperature and desorbing it at high temperature is arranged upstream of the exhaust gas purification catalyst. The air-fuel ratio detection means detects the air-fuel ratio of the exhaust gas upstream of the adsorbent, and the catalyst downstream side air-fuel ratio detection means detects the air-fuel ratio of the exhaust gas downstream of the exhaust purification catalyst. The upstream side air-fuel ratio time ratio calculation means detects the ratio R _FL (= T _FL / T _FL + T _FR ), and the catalyst downstream side air-fuel ratio time ratio calculation means calculates the ratio R _SL (= T
_SL / T _SL + T _SR ) is detected. Further, the second ratio calculation means calculates a ratio G _FS (= R _FL / R _SL ) between the upstream side air-fuel ratio time ratio R _FL and the catalyst downstream side air-fuel ratio time ratio R _SL, and exhaust purification catalyst deterioration diagnosis Means performs deterioration diagnosis of the exhaust purification catalyst based on the ratio G _FS . Further, the third deterioration diagnosing means performs the deterioration diagnosis of the adsorbent based on the ratio G _FS, and uses the exhaust purification catalyst as a diagnostic criterion J when diagnosing whether or not the adsorbent is deteriorated. Deterioration degree Z
Based on.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 8 showing the configuration of the first to third embodiments of the present invention.
In the exhaust gas passage 2 of the internal combustion engine 1, an exhaust gas purification catalyst (three-way catalyst) 3 is installed, and in the exhaust gas passage 3 upstream of the exhaust gas purification catalyst 3, an adsorbent 5 is installed. There is.

The adsorbent 5 is made of a material in which H-type or Y-type zeolite is ion-exchanged with Cu or Pt, and the zeolite and alumina are crushed and coated with 100 to 200 g per liter of cordierite. Is. And HC is a zeolite lattice (5Å diameter)
Is adsorbed inside. Further, this amount shows a larger characteristic as the temperature becomes lower. Zeolite has a high HC adsorption capacity at low temperatures, and acts as a catalyst at high temperatures (for example, 400 ° C. or higher) (see FIGS. 9 and 10).

Further, wherein the adsorbent 5, the temperature sensor 9 for detecting the exhaust temperature T _a of the 5 internal adsorbing material is mounted. Further, in the exhaust passage 2 on the upstream side of the adsorbent 5,
For normal air-fuel ratio feedback control, a front oxygen sensor 14 is provided as an upstream side air-fuel ratio detecting means for detecting the air-fuel ratio ON or OFF depending on whether the air-fuel ratio is richer or leaner than the theoretical air-fuel ratio. A rear oxygen sensor 15 is provided in the exhaust passage 2 between the main catalyst 3 and the downstream side air-fuel ratio detecting means for detecting the air-fuel ratio of the exhaust gas flowing in the exhaust passage downstream of the adsorbent 5.

In addition to the various sensors described above, a water temperature sensor 10 for detecting the engine cooling water temperature (water temperature) T _W and a rotation speed sensor 11 for detecting the engine rotation speed N are provided. Each detection signal from these sensors and a separate The calculated basic fuel injection amount Tp is output to the control unit 12 as an engine load detection signal. Then, the control unit 12 performs self-diagnosis of the adsorbent 5 according to the present invention based on these signals.

The self-diagnosis of the adsorbent 5 performed by the control unit 12 will be described below with reference to a flow chart. FIG. 11 shows a flowchart explaining the diagnosis contents of the first embodiment according to claim 1. In step (denoted as S in the drawing; the same applies hereinafter) 1, the coolant temperature T _W is detected by the coolant temperature sensor 10.

In step 2, the cooling water temperature T _W is 6
Judge whether it is 0 ° C or higher. And the cooling water temperature T _W is
When it is determined that the temperature is 60 ° C. or higher (T _W ≧ 60), the process proceeds to step 3 and subsequent steps to perform self-diagnosis. On the other hand, in step 2, the cooling water temperature T _W is lower than 60 ° C. (T _W <
If it is determined to be 60), the process directly returns without performing self-diagnosis.

In step 3, air-fuel ratio feedback control is performed based on the output of the front oxygen sensor 14. That is, as shown in FIG. 12, proportional / integral control of the air-fuel ratio feedback correction coefficient α is executed. First, in step 51, the voltage value VO ₂ output from the front oxygen sensor 14 according to the oxygen concentration in the exhaust gas is measured.

In the next step 52, the voltage value VO
₂ is compared with the slice level S / L corresponding to the theoretical air-fuel ratio which is the target air-fuel ratio, and the rich lean of the actual air-fuel ratio with respect to the target air-fuel ratio (theoretical air-fuel ratio) is determined. Then, the air-fuel ratio feedback correction coefficient α _n (initial value = 1.0) for correcting the basic fuel injection amount Tp is proportionally / integrally controlled based on the rich / lean determination (see FIG. 13).

That is, the voltage value VO ₂ is the slice level S /
When it is determined that the air-fuel ratio is larger than L and is rich with respect to the target, the routine proceeds to step 53, where a predetermined proportional amount P
Then, the correction coefficient α _n is reduced and corrected, and from then onward, the reduction and correction are repeated by a predetermined integral amount I until the lean state is inverted. On the other hand, when the voltage value VO ₂ is below the slice level S / L and it is judged that the air-fuel ratio is lean with respect to the target, the routine proceeds to step 54, where the correction coefficient α _n is increased and corrected by a predetermined proportional amount P. From then on, the increase correction by the predetermined integral amount I is repeated until the state is reversed to the rich state.

In the flow chart, α _n-1 indicates the previous value of the air-fuel ratio feedback correction coefficient α _n . The air-fuel ratio feedback correction coefficient α _n set by the proportional / integral control as described above is used for the calculation of the fuel injection amount Ti in step 55, and the basic fuel injection amount Tp is calculated by the air-fuel ratio feedback correction coefficient α _n . Based on the corrected value and the correction amount Ts for correcting the change in the effective opening time of the fuel injection valve due to the battery voltage, the fuel injection amount Ti ←
Set Tp × α _n + Ts.

Now, let us return to the description of the flowchart of FIG. 11 again. In step 4, the engine rotation speed N detected by the rotation speed sensor 11 and the separately calculated basic fuel injection amount T
Read p to detect the current operating conditions. Step 5
Then, it is determined whether or not the current operating condition is a predetermined steady operation based on the map determined by the engine speed N and the basic fuel injection amount Tp. Here, the predetermined steady operation means the engine speed N and the basic fuel injection amount T as a load.
It is a case where p is within a predetermined range and the fluctuation is within a predetermined degree.

If the current operating condition is a predetermined steady operation, the deterioration diagnosis of the adsorbent 5 is made based on the output of the rear oxygen sensor 15, and the process proceeds to step 6. In step 6, the time T _RL when the air-fuel ratio is leaner than stoichiometric and the time T _RR that is richer than stoichiometric are measured from the output waveform of the rear oxygen sensor 15. In step 7,
The lean ratio R _RL is obtained from the output waveform of the rear oxygen sensor 15.

R _RL = T _RL / T _RL + T _{RR In} step 8, the lean ratio R _RL is a comparison reference value R _RL0 which is a reference as to whether the adsorbent 5 is normal or deteriorated _.
Determine if it is greater than. Here, as mentioned above,
When the adsorbent is normal, the time T _RLOK when the air-fuel ratio of the rear oxygen sensor 15 is leaner than stoichiometry becomes longer than the time T _FLOK when the air-fuel ratio of the upstream oxygen sensor is leaner than stoichiometry (T _RLOK >> T _FLOK) is, when the adsorbent is deteriorated, the rear oxygen sensor 15 times the air-fuel ratio is lean of stoichiometry T _RLNG time air-fuel ratio of the upstream oxygen sensor is lean of stoichiometry of T _FLNG It does not become longer (T _RLNG ≈ T _FLNG ).

Here, in the first embodiment, the current operating condition is a predetermined steady operation, and both R _FLOK and R _FLNG detected by the front oxygen sensor 14 can be set to a predetermined value. _Therefore, it can be considered that R _FLOK = R _FLNG . Therefore, when the adsorbent is normal, R _RLOK >> R _RLNG , and when the adsorbent is deteriorated,
R _RLOK = R _RLNG .

Since the R _RLNG can be obtained in advance as a comparison reference value R _RL0 by an experiment or the like,
By comparing the lean ratio R _RL with the comparison reference value R _RL0 , it is possible to determine the deterioration of the adsorbent 5. Therefore, when it is judged in step 8 that R _RL > R _RL0 , it means that the adsorbent 5 has a sufficient function as an adsorbent, that is, the adsorbing action of the adsorbent 5 is normal. In this case, it is possible to judge that the adsorbent 5 has a normal adsorbing action.

On the other hand, when it is judged in step 8 that R _RL > R _RL0 is not satisfied (R _{RL ≤R RL0} ), the adsorbent 5
Since the catalytic action of is not normal, the process proceeds to step 10, and it is judged that the adsorption action of the adsorbent 5 is not normal, and step 11
To the adsorbent 5 by turning on the pilot lamp or the like.
Display the failure of. That is, the routine has the function of the first deterioration diagnosis means according to the first aspect.

Next, a second embodiment of the self-diagnosis according to claim 2 will be described with reference to the flow chart shown in FIG. 14. The steps having the same functions as those in the flow chart shown in FIG. The description is omitted.
After executing step 3, the process proceeds to step 21, and from the output waveform of the front oxygen sensor 14, the time T _FL when the air-fuel ratio is leaner than the stoichiometry and the time T _FR when the air-fuel ratio is richer than the stoichiometry.
Is measured to obtain the lean ratio R _FL .

R _FL = T _FL / T _FL + T _FR After executing step 7, proceed to step 22
Ratio G of R _FL obtained in 21 and R _RL obtained in step 7
_FR (= R _FL / R _RL ) is compared with the judgment reference value 0.5. Here, as described above, when the adsorbent is normal,
The time T _RLOK when the air-fuel ratio of the rear oxygen sensor 15 is leaner than stoichiometry becomes longer than the time T _FLOK when the air-fuel ratio of the upstream oxygen sensor is leaner than stoichiometry (T _RLOK >> T
_FLOK ), but when the adsorbent has deteriorated, the time T _RLNG when the air-fuel ratio of the rear oxygen sensor 15 is leaner than stoichiometric
_Does not become longer than the time T _FLNG when the air-fuel ratio of the upstream oxygen sensor is leaner than stoichiometry (T _{RLNG ≈T FLNG} ).

Therefore, in step 22, G _FR <0.5.
If it is determined that the adsorbent 5 has a sufficient function as an adsorbent, that is, it is possible to determine that the adsorbing action of the adsorbent 5 is normal. It proceeds to step 9 and determines that the adsorption action of the adsorbent 5 is normal. On the other hand, when it is determined in step 22 that G _FR <0.5 is not satisfied (G _FR ≧ 0.5), the catalytic action of the adsorbent 5 is not normal, so the process proceeds to step 10 and the adsorbent 5 is not normally adsorbed. If it is determined that the adsorbent 5 does not exist, the pilot lamp or the like is turned on to display a failure of the adsorbent 5.

That is, this routine has the function of the second deterioration diagnosing means described in claim 2. Next, claim 3
A third embodiment of the self-diagnosis according to the present invention will be described with reference to the flowchart shown in FIG. 15. However, steps having the same functions as those in the flowchart shown in FIG.

In the third embodiment, after executing step 3, the process proceeds to step 31 and the adsorbent 5 detected by the temperature sensor 9 is detected.
It reads the inside of the exhaust temperature T _a. At step 32, it is judged if the exhaust temperature T _a is higher than 500 ° C. here,
Since the adsorbent 5 does not exhibit an adsorbing action at high temperatures, the adsorbent 5 does not function when the exhaust gas temperature exceeds a predetermined high temperature.
Even if the condition is normal, HC is not adsorbed on the adsorbent 5, and thus the air-fuel ratio of the exhaust gas on the downstream side of the adsorbent 5 does not become lean.

Therefore, when it is judged that T _a > 500 ° C., the adsorption performance of the adsorbent 5 is lost and the self-diagnosis becomes impossible. Therefore, the process returns without performing the self-diagnosis. On the other hand, if it is determined in step 32 that T _a ≦ 500 ° C., the adsorbent 5 exhibits adsorbing performance, and therefore the process proceeds to step 21 to perform self-diagnosis.

That is, the routine has the function of the second deterioration diagnosing means described in claim 3. In addition, step
The functions of 32 and step 33 can also be applied to the flowchart shown in FIG. 11, and in this case, the function of the first deterioration diagnosis means according to claim 3 is achieved. Next, a fourth embodiment of the self-diagnosis according to claim 4 will be described.

First, the system configuration according to the fourth embodiment of the present invention will be described with reference to FIG. 16. The same components as those of the system configuration shown in FIG. Omit it. In this system configuration, an air flow meter 20 for newly measuring the intake air flow rate Qa as the load of the internal combustion engine is newly provided, and the measurement result is input to the control unit 12.

Next, a fourth embodiment of the self-diagnosis according to claim 4 will be described with reference to the flowchart shown in FIG. 17, except that step 41 and step 42 are different from the flowchart shown in FIG. Only the steps 41 and 42 will be described. In Step 41, the air flow meter
The intake air flow rate Qa as the load detected by 20 is read.

In step 42, the intake air flow rate Qa is 1 kg.
Judge whether it is larger than / min. Here, since the adsorbent 5 does not exhibit the adsorbing action at the time of high load, when the intake air flow rate Qa becomes large, even if the adsorbent 5 is normal, HC is not adsorbed on the adsorbent 5, Therefore, the air-fuel ratio of the exhaust gas on the downstream side of the adsorbent 5 does not become lean.

Therefore, when it is judged that Qa> 1 Kg / min, the adsorption performance of the adsorbent 5 is lost and self-diagnosis becomes impossible. Therefore, the flow returns without performing self-diagnosis. On the other hand, in step 42, Qa ≦ 1 Kg / m
If it is determined to be in, the adsorbent 5 exhibits adsorbing performance, so that the process proceeds to step 21 and self-diagnosis is performed.

That is, the routine is the same as that of claim 4.
The function of the deterioration diagnosing means 2 is achieved. Also, the above
In the second, third or fourth embodiment, in step 22
And G _FRWas compared with the judgment standard value of 0.5.
As shown in FIG. 18, the judgment reference value J is the exhaust temperature T_aAgainst
Accordingly, the exhaust temperature T_aSo that the higher the
You may

That is, when the exhaust temperature T _a is high, the rate of adsorbing HC on the adsorbent 5 is small, which may deteriorate the diagnostic accuracy. Therefore, the higher the exhaust temperature T _{a, the} more the judgment reference value J is set. By increasing the value, it is possible to compensate for the decrease in diagnostic accuracy due to the decrease in the ratio of adsorbing HC. Also, in the fourth embodiment, step 22
As shown in FIG. 19, the judgment reference value J with G _FR at
The intake air flow rate Qa may be increased as the intake air flow rate Qa increases.

That is, when the engine load is large, the adsorbent 5 has a small proportion of adsorbing HC, and there is a possibility that the diagnostic accuracy may deteriorate. Therefore, the diagnostic reference J for diagnosing whether or not the adsorbent 5 is deteriorated is increased as the intake air flow rate Qa is increased, and the ratio of adsorbing HC is decreased, resulting in a decrease in diagnostic accuracy. To make up for.

Next, a fifth embodiment of self-diagnosis according to claim 7 will be described. First, a system configuration according to the fifth embodiment of the present invention will be described with reference to FIG. 20, but the same components as those of the system configuration shown in FIG. In the fifth embodiment, an exhaust gas purification catalyst (three-way catalyst) 3 is provided in an exhaust gas passage 2 of an internal combustion engine 1, and an adsorbent 5 is provided in an exhaust gas passage 3 upstream of the exhaust gas purification catalyst 3. It is installed.

The rear oxygen sensor 15 is provided on the downstream side of the exhaust gas purification catalyst 3. Next, a fifth embodiment of self-diagnosis according to claim 7 will be described with reference to the flowchart shown in FIG. 21. Steps having the same functions as those in the flowchart shown in FIG. The description is omitted. In the fifth embodiment, after executing step 9 or step 11, the process proceeds to step 51.

In step 51, the frequency f _F of the output waveform of the front oxygen sensor 14 is obtained. In step 52, the frequency f _R of the output waveform of the rear oxygen sensor 15 is obtained. In step 53, the ratio f = f _F / f _R between the frequency f _F obtained in step 51 and the frequency f _R obtained in step 52 is compared with the judgment reference value 10. That is, when the air-fuel ratio feedback control is performed at the frequency of f _F , the three-way catalyst 3 acts more as a catalyst, so that the air-fuel ratio detected by the rear oxygen sensor 15 is equal to the reaction time on the catalyst. Changes slowly. Therefore, the inversion cycle of the output waveform of the rear oxygen sensor 15 becomes longer and the frequency f _R becomes smaller. Therefore, the ratio f becomes large.

Therefore, if it is judged in step 53 that f> 10, it means that the three-way catalyst 3 has a sufficient function as a catalyst, that is, the catalytic action of the three-way catalyst 3 is normal. It is possible to judge that the catalyst adsorbing action of the three-way catalyst 3 is normal. Further, when it is determined in step 9 that f> 10 is not satisfied (f ≦ 10), the catalyst storage function of the three-way catalyst 3 is not normal, and therefore the exhaust gas passes through the catalyst without being reacted, Therefore, the rate of change of the air-fuel ratio detected by the rear oxygen sensor 15 does not decrease, and the ratio f
Can be considered not to be big. Therefore, the routine proceeds to step 55, where it is judged that the catalytic action of the three-way catalyst 3 is not normal, and at the same time, the failure of the three-way catalyst 3 is indicated by turning on the pilot lamp or the like.

Next, a sixth embodiment of self-diagnosis according to claim 7 will be described with reference to the flow chart shown in FIG.
Note that the system configuration is the same as that of the fifth embodiment, so description will be omitted. Further, steps having the same functions as those in the flowchart shown in FIG. 21 are designated by the same step numbers, and description thereof will be omitted. In the sixth embodiment, step 7
After executing, proceed to step 61.

In step 61, the frequency f _F of the output waveform of the front oxygen sensor 14 is obtained. In step 62, the frequency f _R of the output waveform of the rear oxygen sensor 15 is obtained. In step 63, the ratio f = f _F / f _R between the frequency f _F obtained in step 61 and the frequency f _R obtained in step 62 is obtained,
Based on the ratio f, the deterioration determination level SL of the adsorbent 5 as shown in FIG. 23 is read.

Here, the deterioration determination level (SL) will be described. This is because the oxygen storage effect of the three-way catalyst 3 cancels the A / F shift effect of the adsorbent. Therefore, SL is determined corresponding to the O ₂ storage performance of the three-way catalyst 3, and the deterioration determination level SL is increased as f _F / f _R increases, that is, the O ₂ storage decreases.

In step 64, the ratio G _FR (= R _FL / R of the R _FL obtained in step 21 to the R _RL obtained in step 7)
_RL ) and the deterioration determination level SL are compared. And
If it is determined in step 64 that G _FR <SL,
This indicates that the adsorbent 5 has a sufficient function as an adsorbent, that is, it is possible to determine that the adsorbing action of the adsorbent 5 is normal. It is judged that the adsorption action of is normal.

On the other hand, when it is judged in step 22 that G _FR <SL is not satisfied (G _FR ≧ SL), the catalytic action of the adsorbent 5 is not normal, so the routine proceeds to step 10, where the adsorbent 5 is adsorbed. Is judged not to be normal, the process proceeds to step 11, and, for example, a pilot lamp or the like is turned on to display a failure of the adsorbent 5. That is, the routine has the function of the third deterioration diagnosing means described in claim 7.

As described above, according to the present invention, the front oxygen sensor 14 and the rear oxygen sensor 15 are arranged upstream and downstream of the adsorbent 5, and the adsorption performance is diagnosed from the lean ratio of the oxygen sensor output. With this configuration, it is possible to perform highly accurate self-diagnosis of the adsorbent 5 only with the front oxygen sensor 14 and the rear oxygen sensor 15, and it is possible to deal with a failure of the adsorbent 5 and the like, so that the driver can reliably fail. Will be detected, and it will be possible to avoid traveling while discharging harmful components.

Further, since it is not necessary to provide an HC concentration detection sensor for detecting the HC concentration in the exhaust gas on the upstream side and the downstream side of the adsorbent 5, there is no increase in cost. Also,
Since the operation of the present invention is not related to the catalytic action of the adsorbent, the self-diagnosis of the adsorbent can be performed in all the operating regions regardless of the operating region where the catalytic action of the adsorbent is large.

Further, even in the case where the three-way catalyst 3 is provided, it is possible to obtain an effect that both the three-way catalyst 3 and the adsorbent 5 can be diagnosed. Also, in the above,
The structure is shown in which the adsorbent is applied in series with the exhaust purification catalyst.By connecting the bypass passage in which the adsorbent is interposed in parallel to a part of the exhaust passage upstream of the exhaust purification catalyst. The main passage and the bypass passage are selectively opened and closed, and the bypass passage is opened at a low temperature before the exhaust purification catalyst is activated to adsorb HC to the adsorbent, and then the bypass passage is closed once. After the temperature rises to a high temperature, the exhaust purification catalyst is activated, and then the bypass passage is opened again so that the adsorbed HC is desorbed and purified by the exhaust purification catalyst. Since the desorption temperature is slightly lower than the activation temperature of the exhaust purification catalyst, it is superior in HC reduction performance to the structure connected in series. However, although the structure and control are more complicated and the cost is higher than that of the serial connection structure, the present invention is naturally applicable to the structure.

[0071]

As described above, according to the present invention, an internal combustion engine is provided with an adsorbent having a function of adsorbing unburned gas in exhaust gas at low temperature and desorbing it at high temperature in the engine exhaust passage. In the engine, upstream air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas upstream of the adsorbent, downstream air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas downstream of the adsorbent material, and upstream air-fuel ratio detection The upstream side for detecting the ratio between the time when the air-fuel ratio detected by the means is lean with respect to the target air-fuel ratio and the elapsed time from when the lean rich of the air-fuel ratio is reversed to when it is reversed in the same direction The time when the air-fuel ratio time ratio calculation means and the air-fuel ratio detected by the downstream side air-fuel ratio detection means are lean with respect to the target air-fuel ratio and the lean-rich of the air-fuel ratio is reversed and then reversed in the same direction Downstream to detect the ratio of elapsed time to Air-fuel ratio time ratio calculating means and upstream air-fuel ratio time ratio of the air-fuel ratio calculated by the upstream side air-fuel ratio time ratio calculating means and downstream air of the air-fuel ratio calculated by the downstream side air-fuel ratio time ratio calculating means A first ratio calculating means for calculating a ratio with a fuel ratio time ratio, and the adsorbent based on a ratio between the upstream side air-fuel ratio time ratio and the downstream side air-fuel ratio time ratio calculated by the first ratio calculating means. And a second deterioration diagnosing means for diagnosing deterioration of the adsorbent, which enables highly accurate self-diagnosis of the adsorbent with only the upstream air-fuel ratio detecting means and the downstream air-fuel ratio detecting means. It becomes possible to deal with a failure or the like, the driver can reliably detect the failure, and it is possible to avoid traveling while discharging harmful components.

Further, since it is not necessary to provide an HC concentration detecting sensor for detecting the HC concentration in the exhaust gas on the upstream side and the downstream side of the adsorbent, there is an effect that the cost does not increase. Further, since the operation of the present invention is not related to the catalytic action of the adsorbent, the self-diagnosis of the adsorbent can be performed in all the operating regions regardless of the operating region where the catalytic action of the adsorbent is large.

Further, the internal combustion engine is provided with an exhaust gas purification catalyst in the engine exhaust passage, and an adsorbent having a function of adsorbing unburned gas in the exhaust gas at low temperature and desorbing it at high temperature upstream of the exhaust gas purification catalyst. In the engine, instead of the second ratio calculating means, the air calculated by the upstream side air-fuel ratio time ratio calculating means by the upstream side air-fuel ratio time ratio of the air-fuel ratio and the catalyst downstream side air-fuel ratio time ratio calculating means. Second ratio calculating means for calculating a ratio of the fuel ratio to the catalyst downstream side air-fuel ratio time ratio;
Exhaust purification catalyst deterioration diagnosis means for performing deterioration diagnosis of the exhaust purification catalyst on the basis of the ratio of the upstream side air-fuel ratio time ratio calculated by the ratio calculation means of No. 2, and the second deterioration. Instead of the diagnosis means, the deterioration diagnosis of the adsorbent is performed based on the ratio between the upstream side air-fuel ratio time ratio calculated by the second ratio calculation means and the catalyst downstream side air-fuel ratio time ratio, and the adsorbent is also detected. And a third deterioration diagnosis means for deciding whether or not the exhaust purification catalyst is deteriorated based on the deterioration degree of the exhaust purification catalyst which is diagnosed by the exhaust purification catalyst deterioration diagnosis means. Therefore, it is possible to further diagnose both the exhaust purification catalyst and the adsorbent.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing the configuration and function of the invention according to claim 2;

FIG. 3 is a block diagram showing a configuration and a function of the invention according to claim 3;

FIG. 4 is a block diagram showing the configuration and function of the invention according to claims 4 and 5;

FIG. 5 is a block diagram showing the configuration and function of the invention according to claim 6;

FIG. 6 is a block diagram showing the configuration and function of the invention according to claim 7;

FIG. 7 is a time chart explaining the principle and operation of the present invention.

FIG. 8 is a system configuration diagram showing a configuration of first to third embodiments of the present invention.

FIG. 9 is a characteristic diagram showing a saturated adsorption amount of the adsorbent according to the above-mentioned embodiment per a predetermined amount of the adsorbent.

[FIG. 10] NO _X according to the temperature of the adsorbent in the same example
Characteristic diagram showing changes in conversion efficiency

FIG. 11 is a flowchart for explaining diagnosis contents in the first embodiment of the present invention.

FIG. 12 is a flowchart showing proportional / integral control of an air-fuel ratio feedback correction coefficient in the first embodiment.

FIG. 13 is a time chart showing the characteristics of feedback control in the first embodiment.

FIG. 14 is a flowchart for explaining diagnosis contents in the second embodiment of the present invention.

FIG. 15 is a flow chart for explaining diagnosis contents in the third embodiment of the present invention.

FIG. 16 is a system configuration diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 17 is a flow chart for explaining diagnosis contents in the fourth embodiment of the present invention.

FIG. 18 is a determination reference value J and exhaust temperature T in the same embodiment.
characteristic diagram showing the relationship between _a

FIG. 19 is a characteristic diagram showing the relationship between the judgment reference value J and the intake air flow rate Qa in the same embodiment.

FIG. 20 is a system configuration diagram showing the configurations of a fifth embodiment and a sixth embodiment of the present invention.

FIG. 21 is a flow chart for explaining diagnosis contents in the fifth embodiment of the present invention.

FIG. 22 is a flow chart for explaining diagnosis contents in the sixth embodiment of the present invention.

FIG. 23 is a characteristic diagram showing the relationship between the deterioration determination level SL and the frequency ratio f in the same example.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Exhaust Passage 3 Exhaust Purification Catalyst 5 Adsorbent 9 Temperature Sensor 11 Speed Sensor 12 Control Unit 14 Front Oxygen Sensor 15 Rear Oxygen Sensor 20 Air Flow Meter

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02D 41/14 310 F

Claims (7)

[Claims] 1. An internal combustion engine having an adsorbent having a function of adsorbing unburned gas in exhaust gas at a low temperature and desorbing it at a high temperature in an engine exhaust passage, in an engine exhaust passage at a downstream side of the adsorbent in a predetermined operating state. The downstream side air-fuel ratio detecting means for detecting the air-fuel ratio of the exhaust gas, and the time when the air-fuel ratio detected by the downstream side air-fuel ratio detecting means is lean with respect to the target air-fuel ratio and the lean rich of the air-fuel ratio is reversed. Based on the air-fuel ratio time ratio of the air-fuel ratio calculated by the downstream side air-fuel ratio time ratio calculation means for detecting the ratio with the elapsed time from An adsorbent self-diagnosis device for an internal combustion engine, comprising: a first deterioration diagnosing means for diagnosing the adsorbent deterioration. 2. An internal combustion engine having an adsorbent having a function of adsorbing unburned gas in exhaust at low temperature and desorbing it at high temperature in an engine exhaust passage, wherein the air-fuel ratio of exhaust gas upstream of the adsorbent is high. The upstream side air-fuel ratio detecting means, the downstream side air-fuel ratio detecting means that detects the air-fuel ratio of the exhaust gas downstream of the adsorbent, and the air-fuel ratio detected by the upstream side air-fuel ratio detecting means with respect to the target air-fuel ratio. Upstream air-fuel ratio time ratio calculating means for detecting the ratio of the time during which the air-fuel ratio is lean and the elapsed time from when the lean-rich of the air-fuel ratio is reversed to when it is reversed in the same direction, and downstream air-fuel ratio detection Downstream side that detects the ratio of the time when the air-fuel ratio detected by the means is lean to the target air-fuel ratio and the elapsed time from when the lean rich of the air-fuel ratio is reversed to when it is reversed in the same direction Air-fuel ratio time ratio calculation means and upstream air-fuel ratio A first ratio for calculating the ratio between the upstream side air-fuel ratio time ratio of the air-fuel ratio calculated by the inter-ratio calculation unit and the downstream side air-fuel ratio time ratio of the air-fuel ratio calculated by the downstream side air-fuel ratio time ratio calculation unit. Ratio calculation means, and second deterioration diagnosis means for performing deterioration diagnosis of the adsorbent based on the ratio of the upstream side air-fuel ratio time ratio calculated by the first ratio calculation means. An adsorbent self-diagnosis device for an internal combustion engine, comprising: 3. Exhaust temperature detecting means for detecting the exhaust temperature inside the adsorbent is provided, and when the exhaust temperature detected by the exhaust temperature detecting means is below a predetermined temperature, the first deterioration diagnosing means or the second deterioration diagnosing means. 3. The adsorbent self-diagnosis device for an internal combustion engine according to claim 1, wherein the deterioration diagnosis means performs deterioration diagnosis of the adsorbent. 4. An engine load detecting means for detecting an engine load is provided, and the second deterioration diagnosing means carries out a deterioration diagnosis of the adsorbent when the engine load detected by the engine load detecting means is a predetermined load or less. The adsorbent self-diagnosis device for an internal combustion engine according to claim 2, wherein 5. The diagnostic standard for diagnosing whether or not the adsorbent is deteriorated is determined based on the engine load detected by the engine load detecting means.
An adsorbent self-diagnosis device for an internal combustion engine according to claim 1. 6. An exhaust gas temperature detecting means for detecting an exhaust gas temperature inside the adsorbent is provided, and a diagnostic reference for diagnosing whether the adsorbent is deteriorated is an engine load detected by the engine load detecting means. The adsorbent self-diagnosis device for an internal combustion engine according to claim 4, wherein the determination is made based on the exhaust gas temperature detected by the exhaust gas temperature detecting means. 7. An internal combustion engine in which an exhaust gas purification catalyst is provided in an engine exhaust passage, and an adsorbent having a function of adsorbing unburned gas in exhaust gas at a low temperature and desorbing it at a high temperature is provided upstream of the exhaust gas purification catalyst. In the engine, upstream air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas upstream of the adsorbent, catalyst downstream side air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas downstream of the exhaust purification catalyst, and upstream air-fuel ratio The ratio of the time when the air-fuel ratio detected by the fuel ratio detection means is lean to the target air-fuel ratio and the elapsed time from when the lean rich of the air-fuel ratio is reversed to when it is reversed in the same direction is detected. The time when the air-fuel ratio detected by the upstream-side air-fuel ratio time ratio calculation means and the air-fuel ratio detected by the catalyst downstream-side air-fuel ratio detection means are lean with respect to the target air-fuel ratio and the same after the lean rich of the air-fuel ratio is reversed When elapses before reversing in the direction And a catalyst downstream side air-fuel ratio time ratio calculating means for detecting a ratio between the air-fuel ratio and an upstream side air-fuel ratio time ratio of the air-fuel ratio calculated by the upstream side air-fuel ratio time ratio calculating means. Second ratio calculating means for calculating a ratio of the air-fuel ratio to the catalyst downstream side air-fuel ratio time ratio calculated by: and the upstream side air-fuel ratio time ratio and catalyst downstream side calculated by the second ratio calculating means. Exhaust purification catalyst deterioration diagnosis means for performing deterioration diagnosis of the exhaust purification catalyst based on a ratio with an air-fuel ratio time ratio, and the upstream side air-fuel ratio time ratio and catalyst downstream side air-fuel ratio calculated by a second ratio calculation means. The exhaust purification is performed by exhaust purification catalyst deterioration diagnosing means as a diagnostic criterion for diagnosing deterioration of the adsorbent based on a ratio with a time ratio and for diagnosing whether the adsorbent is deteriorated. Based on the degree of catalyst deterioration Further comprising a third deterioration diagnosis means for determining Te adsorbent self-diagnosis system for an internal combustion engine characterized by.