JPH0666130A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent deterioration of conversion efficiency of a catalyst and grasp the abnormality of an adsorber when combustible gas is separated from the adsorber. CONSTITUTION:Abnormality occurrence at an adsorber 7 is judged when an engine cooling water temperature and an adsorber temperature are respectively judged to be a specified value or lower based on detection signals output from a water temperature sensor 14 and an adsorber temperature sensor 15, and when an air-fuel ratio on downstream is smaller than an air-fuel ratio on upstream by a specified value or more based on detection signals output from a downstream oxygen density sensor 10 and an upstream oxygen density sensor 9. An air-fuel ratio of an engine 1 is controlled based on detection signals from the downstream oxygen density sensor 10 at the introduction time of exhaust into the adsorber 7, and the air-fuel ratio at an inlet side of a catalyst 4 is properly controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to an exhaust gas purifying apparatus mainly for reducing unburned gas such as unburned HC at low engine temperature.

[0002]

2. Description of the Related Art Conventionally, as an exhaust gas purification device for an internal combustion engine,
It is widely known that a catalyst is arranged in the exhaust passage, and the chemical adsorption of the catalyst promotes the oxidation reaction of unburned gas in the exhaust to purify the exhaust. However, in such an exhaust gas purification device, when the exhaust gas temperature is low such as when the engine is started, the catalyst does not rise to the activation temperature and the exhaust gas purification action is significantly reduced, so the exhaust gas is sufficiently purified. I can't.

For this reason, in a specific operation region where the exhaust gas purification capability of the catalyst is insufficient, the unburned gas of the exhaust gas, for example, unburned HC is adsorbed by the adsorbent so that the exhaust gas is satisfactorily irrespective of the operating state. There has been proposed a technique for purifying it (see Japanese Patent Application Laid-Open No. 63-68713). In this technique, specifically, the exhaust passage on the upstream side of the catalyst is configured by the main passage and the bypass passage that are parallel to each other, and the adsorbent is arranged in the bypass passage. The exhaust flow from the engine is provided with a switching valve that switches between the bypass passage side and the main passage side according to the exhaust temperature.

In this technique, the desorption temperature of the adsorbent after the engine is started (the temperature at which desorption of adsorbed components is started)
In the region of less than, the unburned gas in the exhaust is adsorbed by the adsorbent by causing the exhaust to flow to the bypass passage side. After the temperature of the exhaust gas rises, the exhaust gas is caused to flow toward the main passage to prevent desorption of the adsorbent. Further, after the exhaust gas temperature rises to a temperature at which the purification action by the catalyst becomes active, the exhaust gas is sufficiently purified by the catalyst alone.
Also, after the catalyst is activated, exhaust gas is flown to the bypass passage side for a predetermined time to desorb the unburned gas from the adsorbent and the desorbed unburned gas is purified by the catalyst to regenerate the adsorbent. I am trying to do it.

[0005]

In an internal combustion engine equipped with such a conventional exhaust gas purification device, the following problems occur depending on the installation position of the oxygen concentration sensor as the air-fuel ratio sensor with respect to the adsorbent. To do. That is, when the oxygen concentration sensor is arranged in the exhaust passage on the upstream side of the adsorbent, the following problems occur.

When all the exhaust gas is flowed to the bypass passage side to desorb the unburned gas from the adsorbent, the air-fuel ratio is enriched by the desorbed unburned gas, but oxygen is introduced into the exhaust passage upstream of the adsorbent. Since the concentration sensor is provided, the air-fuel ratio at the catalyst inlet cannot be controlled correctly, the conversion efficiency of the catalyst deteriorates, and exhaust purification performance is hindered. On the other hand, when the oxygen concentration sensor is arranged in the exhaust passage on the downstream side of the adsorbent, the following problems occur.

Since the air-fuel ratio at the adsorbent inlet cannot be detected, it is not possible to grasp the abnormal state of the unburned gas adsorbed by the adsorbent and the desorbed state of the unburned gas adsorbed by the adsorbent. In view of the above conventional problems, the present invention aims to improve the exhaust purification performance by preventing the conversion efficiency of the catalyst from deteriorating when desorbing the unburned gas from the adsorbent. To do.

Another object of the present invention is to make it possible to grasp the abnormality of the adsorbed state of the unburned gas and the desorbed state of the unburned gas adsorbed by the adsorbent.

[0009]

Therefore, according to the present invention, as shown in FIG. 1, an exhaust gas purification catalyst and an adsorbent located upstream of the catalyst for adsorbing unburned gas are provided. And an upstream and downstream air-fuel ratio detecting means for detecting the air-fuel ratio of the exhaust gas in the exhaust passage in the exhaust passage on the upstream side of the adsorbent and the exhaust passage on the upstream side of the catalyst on the downstream side of the adsorbent, respectively. And an adsorbent for determining whether or not the adsorbent is abnormal based on at least the air-fuel ratio and the engine temperature in an engine operating state, and an engine temperature detecting means for detecting the engine temperature. And an abnormality determining means.

The adsorbent abnormality determining means determines that the adsorbent is abnormal when it is determined that the engine temperature is lower than or equal to a predetermined temperature and the downstream air-fuel ratio is smaller than the upstream air-fuel ratio by a predetermined value or more. It can be configured to determine that
Alternatively, an adsorbent temperature detecting means for detecting the temperature of the adsorbent is provided, and it is determined that the engine temperature and the adsorbent temperature are respectively below a predetermined temperature, and the downstream air-fuel ratio is smaller than the upstream air-fuel ratio by a predetermined value or more. When it is determined that the adsorbent is abnormal, it can be configured.

The exhaust passage on the upstream side of the catalyst is composed of a main exhaust passage and a bypass passage in which an adsorbent is interposed in parallel with each other, and the main exhaust passage and the bypass passage are arranged so as to selectively circulate exhaust gas. And a passage switching means for interrupting the inflow of exhaust gas to the bypass passage and flowing the exhaust gas to the main exhaust passage when the adsorbent abnormality determination means determines that the adsorbent is abnormal. Control means may be provided for controlling.

Based on the detection signal output from the downstream side air-fuel ratio detecting means when the exhaust air is introduced into the adsorbent or when the secondary air is being supplied to the exhaust passage on the upstream side of the adsorbent by the secondary air supply means. An air-fuel ratio control means for controlling the air-fuel ratio of the engine can be provided.

[0013]

In this configuration, for example, when it is determined that the engine temperature is lower than or equal to the predetermined temperature and the downstream air-fuel ratio is lower than the upstream air-fuel ratio by a predetermined value or more, or the engine temperature and the adsorption The adsorbent is determined to be abnormal when it is determined that the agent temperatures are lower than or equal to the predetermined temperatures and the downstream side air-fuel ratio is smaller than the upstream side air-fuel ratio by a predetermined value or more.

Particularly, when the exhaust air is introduced into the adsorbent or when the secondary air is being supplied to the exhaust passage on the upstream side of the adsorbent by the secondary air supply means, the detection signal output from the downstream air-fuel ratio detecting means. Since the air-fuel ratio of the engine is controlled based on the above, and the air-fuel ratio on the catalyst inlet side is appropriately controlled, the conversion efficiency in the catalyst can be improved and the exhaust purification performance can be improved.

Further, when it is determined that the adsorbent is abnormal, the inflow of exhaust gas into the bypass passage is blocked, and further deterioration of the adsorbent can be prevented, and the heat capacity of the bypass passage can be reduced to reduce the catalyst. The early activation of can be promoted.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In FIG. 2 showing the system configuration of an embodiment of the present invention, an exhaust gas purification catalyst 4 is provided in an exhaust passage 3 connected to an exhaust manifold 2 of an engine 1.

The exhaust passage 3 on the upstream side of the catalyst 4 is composed of a main exhaust passage 5 and a bypass passage 6 which are parallel to each other. In the bypass passage 6, unburned gas in the exhaust gas, for example, unburned HC etc. An adsorbent 7 for adsorbing is absorbed. Switching means is provided for switching the flow path so that the exhaust gas selectively flows through the main exhaust passage 5 and the bypass passage 6.

In the present embodiment, a switching valve 8 as switching means is provided at a branch portion of the bypass passage 6 extending from the main exhaust passage 5. The switching valve 8 can be controlled to have two valve openings, closed and open. When the switching valve 8 is closed, the main exhaust passage 5 is opened and the bypass passage 6 is closed so that the entire amount of exhaust gas flows into the main exhaust passage 5. When opened, the main exhaust passage 5 is closed and the bypass passage 6 is opened, and the entire amount of exhaust gas is allowed to flow into the bypass passage 6.

An upstream oxygen concentration sensor 9 as an upstream air-fuel ratio detecting means is provided in the exhaust passage 3 upstream of the switching valve 8, and a downstream air-fuel ratio is detected in the bypass passage 6 downstream of the adsorbent 7. A downstream oxygen concentration sensor 10 as a means is provided. On the other hand, the control unit 11 includes a rotation sensor 12 for detecting an engine speed, an air flow meter 13 as an intake air flow rate detecting means, a water temperature sensor 14 as an engine temperature detecting means for detecting an engine cooling water temperature, and an adsorption. The detection signals output from the adsorbent temperature sensor 15 as the adsorbent temperature detecting means for detecting the temperature of the agent, the upstream oxygen concentration sensor 9, and the downstream oxygen concentration sensor 10, respectively, are input. The control unit 13 executes various controls having the contents shown in the flowchart of FIG. 3 based on the detection signals output from these sensors.

In step 1 (abbreviated as S1 in the figure; the same applies hereinafter) in the flowchart, the N value described below is set to 0, and the M value described below is read from the backup memory (initial = 0), Two
Then, the actual adsorbent temperature TA is compared with the adsorbent heat resistant temperature ta, and if it is determined that TA <ta, the routine proceeds to step 3, where the switching valve 8 is controlled to the open state and the bypass passage 6 is opened. At the same time, the main exhaust passage 5 is closed so that the entire amount of exhaust gas flows to the bypass passage 6 and controlled (adsorption process or desorption process of the adsorbent 7), and the process proceeds to step 4. If it is determined that TA ≧ ta, the routine proceeds to step 5, where the switching valve 8 is controlled to the closed state, the bypass passage 6 is closed, and the main exhaust passage 5 is closed.
Is controlled so that the entire amount of exhaust gas flows into the main exhaust passage 5, and the routine proceeds to step 6.

In step 4, the actual engine cooling water temperature Tw is compared with the cryogenic temperature to, and if Tw <to is determined, the process proceeds to step 7, and if Tw ≧ to is determined, the step is performed. Go to 8. In step 7, the air-fuel ratio (A / F) is controlled by a function of the engine cooling water temperature Tw, the engine speed Ne and the intake air amount Qa (clamping the air-fuel ratio feedback control constant α = 1), and step 2
Return to.

That is, the fuel injection amount (Ti) is calculated based on the following equation.
Is calculated and the air-fuel ratio is controlled. Ti = basic injection amount (Tp) × variation correction coefficient (Co) + electric power correction amount (Ts) where Tp = K · Qa / Ne (K is a constant), Co = 1 +
Water temperature increase correction coefficient Ktw In step 8, it is determined whether or not the warm-up of the downstream oxygen concentration sensor 10 is completed. If the warm-up has not been completed, the process proceeds to step 7, and if the warm-up is completed, the process proceeds to step 9. The air-fuel ratio is controlled based on the signal output from the downstream oxygen concentration sensor 10, and the process proceeds to step 10.

That is, the fuel injection amount (Ti) is calculated based on the following equation.
Is calculated and the air-fuel ratio is controlled. Ti = basic injection amount (Tp) x various correction coefficients (Co) x air-fuel ratio feedback control constant (α) + power correction amount (T
s) In step 10, it is determined whether or not the warm-up of the upstream oxygen concentration sensor 9 is completed. If the warm-up has not been completed, the process returns to step 2, and if the warm-up is completed, the process proceeds to step 11.
The predetermined super air-fuel ratio rich number N is counted (N = N +
1) Go to step 12.

In step 12, the number N of times of rich air-fuel ratio is increased.
And set value A are compared, and if N ≠ A, step 13
Then, the air-fuel ratio (A / F = Y) is calculated from the signal output from the downstream oxygen concentration sensor 10, and the operation proceeds to step 14, where the air-fuel ratio (A / F = Y) is calculated from the signal output from the upstream oxygen concentration sensor 9. Calculate / F = X). At step 15, the air-fuel ratio Y calculated at step 13 and step 14
And the difference ΔX between X and Y is calculated (Y−X = ΔX), and step 16
And compare the calculated ΔX with the set value X1, and
If ≧ X1, it is determined that it is the adsorption process of the unburned gas by the adsorbent, and the count value of the predetermined super air-fuel ratio rich number N is reset to 0 in step 17. ΔX <X1
If so, the process proceeds to step 18, the calculated ΔX is compared with another set value −X2, and if ΔX ≧ −X2, it is determined that it is a desorption process of unburned gas by the adsorbent, and step 19 Then, the count value of the predetermined super air-fuel ratio rich number N is reset to zero. If ΔX <−X2, it is determined that the predetermined super air-fuel ratio is in a rich state (there is a possibility that the adsorbent is abnormal), and the process returns to step 2. It is to be noted that when it is determined that the predetermined super air-fuel ratio is in a rich state, the next control step 1
At 1, the predetermined number N of times the rich air-fuel ratio is rich is counted (N
= N + 1).

In this way, the determination of the predetermined super air-fuel ratio rich state is repeated, and in the determination of step 12,
When the super air-fuel ratio rich count N reaches the set value A (N =
A) In step 20, the number M of times the super air-fuel ratio rich number N has reached the set value A, that is, the history of a predetermined super air-fuel ratio rich state is counted (M = M + 1), and step 2
At 1, the M value is written in the backup memory.

In step 22, the number N of times of rich air-fuel ratio is increased.
Is compared with the set value B, and the number M of times the super air-fuel ratio rich number N has reached the set value A is the set value B.
When (M = B) is reached, it is determined that the adsorbent is abnormal, and the routine proceeds to step 23, where the red lamp for warning equipped on the automobile or the like is turned on. If M does not reach the set value B (M ≠
B), return to step 2.

Here, the count of the number N of times of the super air-fuel ratio rich and the count of the air-fuel ratio super-rich state in each operating state are integrated, but depending on the driving method of the driver, even if there is no abnormality, a predetermined value is determined. There is a possibility that the air-fuel ratio will become excessively rich. For example, when the adsorbent does not reach the desorption temperature, does not shift to the desorption stroke, and only the adsorption stroke is performed after a few short-distance operations, and then the high-speed operation is performed, the specified air-fuel ratio is exceeded. It may become rich.

However, according to the operation in the above flow chart, even when the above operation is performed, the super air-fuel ratio rich number N is counted, but the count value of N is cleared by stopping the engine. On the other hand, the number M of times the super air-fuel ratio rich number N reaches the set value A is stored in the backup memory as described above even after the engine is stopped, and the super air-fuel ratio rich number N reaches the set value A. The history of the predetermined air-fuel ratio super rich state is counted for each time, so that the true abnormality of the adsorbent 7 is determined based on the number M of times when the super air-fuel ratio rich number N reaches the set value A. Can be reliably determined.

On the other hand, the engine cooling water temperature Tw and the cryogenic temperature to are also compared in step 6 after step 5 in which the switching valve 8 is controlled to be closed so that the entire amount of exhaust gas flows to the main exhaust passage. , Tw <to, the process proceeds to step 7, and if Tw ≧ to, the process proceeds to step 24 to determine whether or not the warm-up of the upstream oxygen concentration sensor 9 is completed. If the warm-up has not been completed, the routine proceeds to step 7, and if the warm-up has been completed, the routine proceeds to step 25, the air-fuel ratio is controlled based on the signal output from the upstream oxygen concentration sensor 9, and the routine returns to step 2.

In the above flow chart, steps 11 to 23 correspond to the adsorbent abnormality determining means in claim 1 of the present invention. Further, step 9 corresponds to the air-fuel ratio control means in claim 5 of the present invention. According to such a configuration, as is clear from the control in steps 11 to 23, the adsorbent and engine cooling water temperatures are lower than the predetermined temperature, and as is clear from the step control, the output of the downstream oxygen concentration sensor is The number N of times when the super air-fuel ratio rich state is smaller than the output of the upstream oxygen concentration sensor by a predetermined value or more
When the number M of times when has reached the set value A reaches the set value B, it is possible to determine the abnormality of the adsorption / desorption state of the adsorbent.

Further, as is clear from the control in step 9, when the temperature of the adsorbent reaches the desorption temperature and the air-fuel ratio becomes rich, the catalyst 4 is detected by the oxygen concentration sensor 10 on the downstream side of the adsorbent. Since the air-fuel ratio on the inlet side is properly controlled,
The conversion efficiency in the catalyst 4 can be improved and the exhaust gas purification performance can be improved. Next, another embodiment of the present invention will be described.

The system configuration of this embodiment is the same as that of the embodiment shown in FIG. 2, and the control content is different from that of the embodiment shown in FIG. 2 as shown in the flowchart of FIG. That is, this flowchart is different from the flowchart of FIG. 3 in that steps 1 ′ and step 26 are added, and the control content of step 23 and the subsequent control are changed.

That is, in step 23, the red lamp is turned on, the fact that the red lamp is turned on is written in the memory, and the process proceeds to step 5. In step 5, the switching valve 8 is controlled to be closed, the bypass passage 6 is closed, and the main exhaust passage 5 is opened so that the entire amount of exhaust gas flows to the main exhaust passage. Therefore, when the adsorbent 7 is abnormal, Inflow of exhaust gas to the adsorbent 7 is blocked.

Further, step 1'before the control of reading N = 0, M value in step 1 and step 2 added after the air-fuel ratio control in step 7 and step 25.
At 6, it is determined whether or not the red lamp is lit. If the red lamps are not lit, return to step 2, and if they are lit (when the adsorbent is abnormal), step 5
Then, in order to prevent the exhaust gas from flowing into the adsorbent 7, the exhaust gas is prevented from flowing through the bypass passage 6.

In the above flowchart, step 5 corresponds to the control means in claim 4 of the present invention. According to this configuration, as is clear from the control in step 5, when the adsorbent 7 is abnormal, the adsorbent 7 is bypassed and the exhaust gas is allowed to flow into the main exhaust passage 5, thereby preventing the adsorbent 7 from further deterioration. At the same time, the heat capacity of the bypass passage 6 can be reduced to promote early activation of the catalyst 4.

Next, another embodiment of the present invention will be described. The system configuration of this embodiment is the same as that of the embodiment shown in FIG. 2, and the control content is different from that of the embodiment shown in FIG. 2 as shown in the flowchart of FIG. That is, after the control of reading N = 0 and M values in step 1, it is determined in step 1 ″ whether or not the red lamp is on. If the red lamp is not on, step 2
If it is turned on (when the adsorbent is abnormal), the process proceeds to step 5, the switching valve 8 is closed and the exhaust gas is not circulated in the bypass passage 6 to prevent the exhaust gas from flowing into the adsorbent 7. To do so.

In step 2, the adsorbent temperature TA is compared with the adsorbent heat resistant temperature ta, and if it is judged that TA <ta, the process proceeds to step 2 ', and if it is judged that TA≥ta, then step Go to 5. In step 2 ′, the number M of times the super air-fuel ratio rich number N reaches the set value A and the set value C
And the set value B are compared. That is, it is determined whether or not C ≦ M <B. When it is determined that C ≦ M <B,
Even if the adsorbent 7 is not determined to be abnormal, it can be determined that the adsorbent 7 is deteriorated or has an abnormal tendency.
Proceeding to ', the switching valve 8 is controlled to be half-opened, that is, the bypass passage 6 and the main exhaust passage 5 are each half-opened, and the exhaust is controlled to be distributed to the main exhaust passage 5 and the bypass passage 6,
Proceed to step 3 ″ to turn on the yellow lamp.

According to this structure, as is clear from the control in step 3 ', when the adsorbent 7 has a deterioration or an abnormal tendency, the amount of exhaust gas contacting the adsorbent 7 is reduced so that the engine is cold. Emission of the adsorbent 7 can be prevented, and the adsorbent 7
The flow rate of exhaust gas to the chamber is controlled, the degree of progress of deterioration of the adsorbent 7 can be minimized, and the yellow lamp can be turned on to call attention.

Although the switching valve 8 is controlled to be half-opened in the above embodiment, it does not necessarily have to be half-opened and may be controlled to an intermediate opening. The yellow lamp lighting control need not be added. Next, still another embodiment of the present invention will be described. In FIG. 6 showing the system configuration of this embodiment, the upstream side catalyst 2 is provided in the exhaust passage 3 connected to the exhaust manifold 2 of the engine 1.
0, the adsorbent 7, and the downstream catalyst 4 are sequentially provided from upstream to downstream.

A secondary air supply means 19 for introducing secondary air into the exhaust passage 3 between the upstream catalyst 20 and the upstream oxygen concentration sensor 9 is provided. The secondary air supply means 19 includes an air supply source such as the electric air pump 16, a secondary air supply pipe 17 connected to the electric air pump 16 and connected to the exhaust passage 3 for communication, and the secondary air supply pipe. The on-off valve 1 comprises an on-off valve 18 installed in
By the opening / closing control of 8, it is possible to control the supply / cutoff of the secondary air. The amount of secondary air supplied from the electric air pump 16 is a constant amount regardless of the rotation speed.

On the other hand, the control unit 11 includes a rotation sensor 12 for detecting the engine speed, an air flow meter 13 as an intake air flow rate detecting means, a water temperature sensor 14 for detecting the engine cooling water temperature, and the upstream oxygen. The detection signals output from the concentration sensor 9 and the downstream oxygen concentration sensor 10 are input, and the control unit 13 is based on the detection signals output from these sensors as shown in the flowchart of FIG. Various controls with various contents are executed.

In the flowchart, in step 31, the super air-fuel ratio rich number N is set to 0 and the number M of times the super air-fuel ratio rich number N reaches the set value A.
The value is read from the backup memory, and in step 32, the actual engine cooling water temperature Tw is compared with the cryogenic temperature to, and if it is determined that Tw <to, step 3 is performed.
3. If it is determined that Tw ≧ to, go to step 3,
Go to 4.

At step 33, it is judged whether or not a red lamp for notifying the abnormality of the adsorbent 7 described later is turned on,
If the light is on, the routine proceeds to step 35, where the on-off valve 18 of the secondary air supply means 19 is closed to shut off the supply of the secondary air, and the routine proceeds to step 36, where the engine cooling water temperature Tw and the engine speed Ne. The air-fuel ratio (A / F) is controlled by the function of the intake air amount Qa (clamping the air-fuel ratio feedback control constant α = 1), and the process returns to step 32. If it is not lit, the process proceeds to step 37. In this step 37, it is judged whether or not the warm-up of the upstream oxygen concentration sensor 9 has been completed. If the warm-up has not been completed, the routine proceeds to step 35,
Shut off the supply of secondary air. Step 38 at the end of warm-up
Next, it is determined whether or not the warming-up of the downstream oxygen concentration sensor 10 is completed. If the warming-up is not completed, the process proceeds to step 35 to shut off the supply of the secondary air. Upon completion of warming up, the process proceeds to step 39. At step 39, the number N of times of rich air-fuel ratio is counted (N = N + 1), and the routine proceeds to step 40.

At step 40, the number N of times of rich air-fuel ratio is increased.
And set value A are compared, and if N ≠ A, step 41
And if N = A, proceed to step 48. In step 41, the air-fuel ratio (A / F = Y) is calculated from the signal output from the downstream oxygen concentration sensor 10, and step 4
2, the air-fuel ratio (A / F = X) is calculated from the signal output from the upstream oxygen concentration sensor 9.

In step 43, the difference ΔX between the air-fuel ratios Y and X calculated in step 41 and step 42 is calculated (Y−
X = ΔX), the process proceeds to step 44, the calculated ΔX is compared with the set value X1, and if ΔX ≧ X1, the adsorbent 7
Is determined to be the adsorption process of the unburned gas, and the count value of the predetermined super air-fuel ratio rich number N is reset to 0 in step 45. If ΔX <X1, step 46
And compare the calculated ΔX with another set value −X2,
If ΔX ≧ −X2, it is determined that the unburned gas is desorbed by the adsorbent 7, and in step 47, the count value of the predetermined super air-fuel ratio rich number N is reset to zero. Δ
If X <-X2, it is determined that the predetermined super air-fuel ratio is in a rich state (the adsorbent may be abnormal), and step 35
Proceed to. It is to be noted that the predetermined super air-fuel ratio rich number N is counted (N = N + 1) in step 39 of the subsequent control based on the determination that the predetermined super air-fuel ratio is in the rich state.

In this way, the determination of the predetermined super air-fuel ratio rich state is repeated, and in the determination of step 40,
When the super air-fuel ratio rich count N reaches the set value A (N =
A) In step 48, the number M of times the super air-fuel ratio rich number N reaches the set value A, that is, the history of the predetermined super air-fuel ratio rich state is counted (M = M + 1). This M value is written in the backup memory.

In step 50, the number N of times of rich air-fuel ratio is increased.
Is compared with the set value B, and the number M of times the super air-fuel ratio rich number N has reached the set value A is the set value B.
When (M = B) is reached (M = B), it is determined that the adsorbent is abnormal, the process proceeds to step 51, the red lamp equipped on the automobile or the like is turned on, and the fact that the red lamp is turned on is written to the memory, and step 35 Then, the supply of secondary air is cut off. If M does not reach the set value B (M ≠ B), the red lamp is not turned on, the process proceeds to step 35, and the supply of the secondary air is cut off.

On the other hand, at step 34 after it is judged at step 32 that Tw ≧ to, the engine cooling water temperature Tw is reached.
And the secondary air cutoff temperature t ₁ are compared, and if it is determined that Tw ≦ t ₁ , the process proceeds to step 52, the opening / closing valve 18 of the secondary air supply means 19 is opened to introduce the secondary air, and the catalyst is Two
Aim for early activation of 0 and 4. If it is determined that Tw> t ₁ , the process proceeds to step 53 to shut off the secondary air.

In step 54, it is determined whether or not the warm-up of the upstream oxygen concentration sensor 9 has been completed. If the warm-up has not been completed, the routine proceeds to step 55, in which the engine cooling water temperature Tw, the engine speed Ne and the intake air are taken. The air-fuel ratio (A / F) is controlled by a function of the air amount Qa (air-fuel ratio feedback control constant α
= 1 is clamped), and the process returns to step 32. Step 54
If it is determined that the warm-up has ended, the process proceeds to step 56, this time it is determined whether or not the warm-up of the downstream side oxygen concentration sensor 10 has ended, and if the warm-up has not ended, the process proceeds to step 57,
The air-fuel ratio is controlled based on the signal output from the upstream oxygen concentration sensor 9, and the process returns to step 32.

In this case, the fuel injection amount (T
i) is calculated, but Ti = basic injection amount (Tp) × variation correction coefficient (Co) × air-fuel ratio feedback control constant (α) + power correction amount (T)
s) The secondary air introduction correction coefficient (K
O ₂ ) is added. That is, in this embodiment, since the secondary air is introduced into the portion that does not affect both oxygen concentration sensors 9, the air-fuel ratio for the catalyst 20 deviates from the target value when the secondary air is introduced. Specifically, when the secondary air is introduced, even if the oxygen concentration sensor 9 is feedback-controlled to the stoichiometric air-fuel ratio, it shows a lean tendency at the inlet of the catalyst 20.

As described above, since the secondary air is supplied by the electric air pump 16 in a constant amount regardless of rotation, the catalyst 2
The influence of the secondary air on the air-fuel ratio at the 0 inlet becomes smaller as the exhaust flow rate (that is, the intake air flow rate Qa) increases. Therefore, when introducing the secondary air during the air-fuel ratio control by the upstream oxygen concentration sensor 9, as shown in FIG.
The secondary air introduction correction coefficient (KO
₂ ), the secondary air introduction correction coefficient (KO ₂ ) is added to slightly shift the air-fuel ratio of the oxygen concentration sensor 9 to the rich side. When the secondary air is shut off, the secondary air introduction correction coefficient (KO ₂ ) is set to 0.

When it is determined in step 56 that the warm-up has ended, the routine proceeds to step 58, where the air-fuel ratio is controlled based on the signal output from the downstream oxygen concentration sensor 10, and the routine returns to step 32. In the above flowchart, step 58 corresponds to the air-fuel ratio control means in claim 6 of the present invention.

According to this structure, the engine cooling water temperature is lower than the predetermined temperature and the downstream oxygen concentration sensor 9
The output N of the super air-fuel ratio rich state is smaller than the output of the upstream side oxygen concentration sensor 10 by a predetermined value or more.
Since the number of times M has reached M, it is possible to determine an abnormality in the adsorption / desorption state of the adsorbent. Also, step 52
As is clear from the control of No. 2, since the secondary air is introduced from the upstream of the adsorbent 7 when the engine is cold, the catalysts 20, 4
Since the oxidizing action of the catalyst is activated and the temperature of the catalysts 20 and 4 can be quickly increased, the catalysts 20 and 4 can be activated early and the secondary air is introduced from the upstream of the adsorbent 7. In addition, since the oxygen concentration sensor 9 on the downstream side of the adsorbent 7 appropriately controls the air-fuel ratio on the inlet side of the catalyst 4, the conversion efficiency in the catalyst 4 can be improved, and exhaust emission reduction during cold can be achieved. be able to.

When the temperature of the cooling water is extremely low, the secondary air is shut off so that the catalysts 20 and 4 will not be cooled. Further, when it is determined that the engine has been warmed up, the secondary air is shut off, so that the temperature rise of the catalysts 20, 4 can be suppressed and the air-fuel ratio fluctuation can be prevented. Although the present invention has been described with reference to the specific embodiments as described above, the present invention is not limited to this, and the patents attached to the present invention by a person skilled in the art or the like. It should be noted that various changes and modifications can be made without departing from the scope of the claims.

[0055]

As described above, according to the present invention,
Since it is configured to determine whether or not the adsorbent is abnormal based on at least the air-fuel ratio and the engine temperature in the engine operating state, for example, the engine temperature is determined to be below a predetermined temperature, and the downstream air When it is determined that the fuel ratio is smaller than the upstream side air-fuel ratio by a predetermined value or more, or it is determined that the engine temperature and the adsorbent temperature are each lower than a predetermined temperature, and the downstream side air-fuel ratio is set to a predetermined value lower than the upstream side air-fuel ratio. By determining that the adsorbent is abnormal when it is determined to be smaller than the value, it is possible to easily grasp the abnormality of the adsorption / desorption state of the adsorbent.

In particular, when the exhaust gas is introduced into the adsorbent or when the secondary air is being supplied to the exhaust passage on the upstream side of the adsorbent, the air condition of the engine is detected based on the detection signal output from the downstream side air-fuel ratio detecting means. With the configuration in which the fuel ratio is controlled, the air-fuel ratio on the catalyst inlet side is appropriately controlled, the conversion efficiency of the catalyst can be improved, and the exhaust gas purification performance can be improved.
Further, the exhaust passage on the upstream side of the catalyst is constituted by a main exhaust passage and a bypass passage in which an adsorbent is interposed in parallel, and when the adsorbent abnormality is determined by the adsorbent abnormality determination means,
If the exhaust gas is blocked from flowing into the bypass passage and the exhaust gas is passed through the main exhaust passage, deterioration of the adsorbent can be prevented and the heat capacity of the bypass passage can be reduced.
It is possible to promote early activation of the catalyst.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exhaust gas purification device for an internal combustion engine according to the present invention.

FIG. 2 is a system diagram showing an embodiment of the same device.

FIG. 3 is a flowchart for explaining the operation of the above embodiment.

FIG. 4 is a flowchart for explaining the operation of another embodiment.

FIG. 5 is a flowchart for explaining the operation of still another embodiment.

FIG. 6 is a system diagram showing still another embodiment.

FIG. 7 is a flowchart for explaining the operation of another embodiment of the above.

FIG. 8 is a characteristic diagram of a secondary air introduction correction coefficient (KO ₂ ) according to the intake air flow rate Qa.

[Explanation of symbols]

 1 Engine 3 Exhaust Passage 4 Catalyst 7 Adsorbent 7 9 Upstream Oxygen Concentration Sensor 9 10 Downstream Oxygen Concentration Sensor 10 11 Control Unit 11 14 Water Temperature Sensor 15 Adsorbent Temperature Sensor 19 Secondary Air Supply Means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location F01N 3/24 N F02B 77/08 M 7541-3G F02D 41/14 310 A 8011-3G 41/22 305 Z 8011-3G

Claims (6)

[Claims] 1. An exhaust gas purification catalyst and an adsorbent located upstream of the catalyst for adsorbing unburned gas are provided in the exhaust passage, and the exhaust passage upstream of the adsorbent and the adsorbent downstream. On the upstream side of the catalyst, upstream and downstream air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas in the exhaust passage, and engine temperature detection means for detecting the engine temperature, the engine operating state detection Means, and an adsorbent abnormality determination means for determining whether or not the adsorbent is abnormal based on at least the air-fuel ratio and the engine temperature in an engine operating state, of an internal combustion engine characterized by including Exhaust purification device. 2. The adsorbent abnormality determination means, when it is determined that the engine temperature is equal to or lower than a predetermined temperature and the downstream air-fuel ratio is smaller than the upstream air-fuel ratio by a predetermined value or more,
The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the exhaust gas purification device is configured to determine that the adsorbent is abnormal. 3. An adsorbent temperature detecting means for detecting the temperature of the adsorbent is provided, and the adsorbent abnormality determining means determines that the engine temperature and the adsorbent temperature are lower than a predetermined temperature, respectively, and the downstream air-fuel ratio. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the adsorbent is determined to be abnormal when it is determined that is smaller than the upstream side air-fuel ratio by a predetermined value or more. 4. The exhaust passage on the upstream side of the catalyst is constituted by a main exhaust passage and a bypass passage in which an adsorbent is interposed in parallel with each other, and exhaust gas is selectively circulated through the main exhaust passage and the bypass passage. A passage switching means for switching the passage, and a passage switching means for interrupting the inflow of exhaust gas to the bypass passage and flowing the exhaust gas to the main exhaust passage when the adsorbent abnormality determination means determines that the adsorbent is abnormal. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3, further comprising control means for controlling the exhaust gas. 5. The air-fuel ratio control means for controlling the air-fuel ratio of the engine based on the detection signal output from the downstream side air-fuel ratio detection means when introducing the exhaust gas to the adsorbent. An exhaust emission control device for an internal combustion engine according to any one of claims. 6. A downstream air-fuel ratio when the secondary air is supplied to the exhaust passage on the upstream side of the adsorbent, and the secondary air is supplied to the exhaust passage on the upstream side of the adsorbent. An exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising: an air-fuel ratio control means for controlling an air-fuel ratio of the engine based on a detection signal output from the detection means. .