JPH11148344A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the HC adsorbed to a downstream catalyst of HC adsorbent from being desorbed and released to the atmosphere in the HC desorption treatment for the HC adsorbent. SOLUTION: Before starting HC desorption treatment for adsorbent 6 (judged in S2 and 3), HC adsorption quantity of an EHC (downstream catalyst of HC adsorbent) is estimated (S4) on the basis of the time required for adsorbing HC to adsorbent 6, while supplying air (oxygen) of quantity corresponding to the estimated value to the EHC 7 by means of an air pump 9 (judged in S6), the EHC 7 is preheated (S9 through S12). Through this operation, with the preheating of EHC 7, the HC desorbed from the EHC 7 with the preheating of the EHC 7 can be treated (oxidation removal) with the EHC 7 by the oxygen (supplied by the air pump 9) in the atmosphere. Therefore, such fear that the HC desorbed from the EHC 7 in the HC desorption treatment of adsorbent 6 in a conventional way is released to the atmosphere without being cleaned can be avoided.

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 preventing the emission of hydrocarbons (HC) contained in exhaust gas immediately after the start of the internal combustion engine into the atmosphere. The present invention relates to an exhaust gas purification device provided with an HC adsorbent.

[0002]

2. Description of the Related Art Catalysts carrying noble metals (platinum, rhodium, etc.) or other metals have been used for exhaust gas purification of automobiles. Such a catalyst purifies the exhaust gas by oxidizing or reducing HC, CO, NOx and the like, which are harmful components.

[0003] Of these, purification of HC with a catalyst is particularly affected by the temperature of exhaust gas.
Requires a temperature of 0 ° C. or higher. Immediately after the start of an internal combustion engine (hereinafter also referred to as an engine), the exhaust gas temperature is low,
Since the catalyst has not reached the activation temperature (350 to 400 ° C. or higher), the purification of HC cannot be performed satisfactorily. Further, there is a fear that the amount of HC emission during a cold state immediately after the start of the engine increases, and that the amount of HC released into the atmosphere generally increases when the exhaust gas temperature is low.

In order to solve such a concern, for example, as shown in FIG. 14A, the exhaust gas branches off from a main passage and merges again at a downstream side of a catalyst provided in an exhaust passage of the engine. An HC adsorbent and a heater-equipped catalyst downstream of the HC adsorbent are provided in the bypass passage, and a switching valve is provided at an exhaust gas upstream branch point of the bypass passage. An exhaust temperature sensor provided on the upstream side of the exhaust gas sensor and a device that controls the switching valve and the heater of the catalyst with a heater in accordance with the temperature of the exhaust gas detected by the exhaust temperature sensor have been proposed. See JP-A-6-66136).

In the above apparatus, during a period in which the temperature of the exhaust gas is low and the catalyst is not active, the exhaust gas is caused to flow to the HC adsorbent (hereinafter simply referred to as adsorbent) by the switching valve downstream of the catalyst to adsorb HC. This prevents release to the atmosphere. After the exhaust gas temperature rises and the catalyst is activated,
Exhaust gas is caused to flow into the main passage by the switching valve, while HC is desorbed from the adsorbent and purified by a downstream catalyst with heater (EHC).

[0006]

However, in general, since the catalyst also has the ability to adsorb HC, it is difficult to heat the EHC (catalyst with heater) provided downstream of the adsorbent as in the above-mentioned conventional apparatus. , H adsorbed on the EHC
C will be desorbed. For this reason, in the above-described conventional apparatus, H desorbed from the EHC due to heating of the EHC.
C may be released into the atmosphere together with the exhaust gas introduced to desorb HC from the adsorbent without being purified (see FIG. 14B).

[0007] The present invention has been made in view of such a conventional situation, and when the HC adsorbent is subjected to the HC desorption treatment, the HC is removed.
It is an object of the present invention to provide an exhaust gas purification device for an internal combustion engine that prevents HC adsorbed on a downstream catalyst of an adsorbent from being desorbed and released into the atmosphere.

[0008]

According to the first aspect of the present invention, as shown in FIG. 1, the exhaust passage is provided downstream of a main catalyst disposed in an exhaust passage of an engine. Branch at the branch point on the exhaust upstream side of
A bypass passage that merges again at a junction of the exhaust passage downstream of the exhaust gas, a bypass passage exhaust inflow control valve that is disposed at a branch point of the exhaust gas upstream and controls the flow of exhaust gas into the bypass passage, An exhaust gas purification apparatus for an internal combustion engine, comprising: an HC adsorbent interposed in a bypass passage; and an HC adsorbent downstream catalyst interposed in the bypass passage on the exhaust downstream side of the HC adsorbent. And the H
Before desorbing the HC adsorbed by the C adsorbent, before flowing at least a part of the exhaust gas into the bypass passage via the bypass passage exhaust inflow control valve, the HC adsorbent downstream through the heating means is heated. It comprises a catalyst adsorbing HC treatment means for heating the catalyst to desorb the HC adsorbed by the HC adsorbent downstream catalyst and purifying the desorbed HC by the HC adsorbent downstream catalyst. I did it.

With this configuration, when the catalyst disposed in the exhaust main passage is activated and at least a part of the exhaust gas flows into the bypass passage to perform the HC desorption process of the HC adsorbent, Before the HC desorbing process of the HC adsorbent is started (at least a part of the exhaust gas flows into the bypass passage), the HC adsorbent downstream catalyst is heated to adsorb the HC adsorbent downstream catalyst. While the HC is being desorbed, the desorbed HC is purified by the HC adsorbent downstream catalyst.

Therefore, with the start of the HC desorption process of the HC adsorbent, the temperature of the downstream catalyst of the HC adsorbent is raised and the HC is desorbed, and the HC desorbed from the downstream catalyst of the HC adsorber is transferred to the bypass passage. It is possible to avoid the fear that the exhaust gas is released into the atmosphere together with the exhaust gas that has flowed into the air. That is, according to the present invention, when the HC desorbing process of the HC adsorbent is started, HC is not adsorbed on the HC adsorbent downstream catalyst, so that the HC adsorbed by the HC adsorbent is not adsorbed. Even if at least a part of the exhaust gas flows into the bypass passage for desorption, HC is not desorbed from the HC adsorbent downstream catalyst, so that the HC desorption process of the HC adsorbent is completed from the start. In the meantime, HC
Release into the atmosphere can be minimized.

[0011] In the invention according to claim 2, an oxygen supply means for supplying oxygen to the HC adsorbent downstream catalyst is provided, and the HC adsorbent downstream catalyst is supplied by the catalyst adsorbing HC treatment means via the heating means. Is heated to desorb the HC adsorbed by the HC adsorbent downstream catalyst, and before or during purification of the desorbed HC by the HC adsorbent downstream catalyst, , An HC adsorbent downstream catalyst atmosphere control means for controlling the atmosphere of the HC adsorbent downstream catalyst to a predetermined oxygen concentration is provided.

With this configuration, before the HC desorbing process of the HC adsorbent is started (at least a part of the exhaust gas is caused to flow into the bypass passage), the HC adsorbent downstream catalyst is heated and the HC adsorbent is heated. When the desorbed HC is purified by the HC adsorbent downstream catalyst while the HC adsorbed by the adsorbent downstream catalyst is desorbed, the H in the HC adsorbent downstream catalyst is reduced.
Since the purifying action of C can be further improved, it is possible to further suppress the release of HC into the air from the start to the completion of the HC desorption process of the HC adsorbent. .

[0013] In the third aspect of the present invention, the HC adsorbent downstream catalyst atmosphere control means estimates the amount of HC adsorbed by the HC adsorbent downstream catalyst based on the estimation result of the catalyst HC adsorption amount estimation means. Thus, the oxygen supply means is configured to include a means for controlling an oxygen supply amount. With this configuration, the amount of HC adsorbed by the HC adsorbent downstream catalyst is estimated, and the oxygen supply amount of the oxygen supply means is controlled based on the estimation result.
Before the C desorption process is started, the HC adsorbent downstream catalyst is heated to desorb the HC adsorbed by the HC adsorbent downstream catalyst, and the desorbed HC is transferred to the HC adsorbent downstream. Since the desorption / purification action at the time of purifying with the catalyst can be further improved, HC is not released into the air from the start until the HC desorption process of the HC adsorbent is completed. Release can be further suppressed.

[0014] In the invention described in claim 4, the catalyst adsorbing HC treating means is configured to determine the amount of HC adsorbed by the HC adsorbent downstream catalyst based on the estimation result of the catalyst HC adsorbing amount estimating means. The apparatus is configured to include means for controlling the heating amount of the heating means. With this configuration, the amount of HC adsorbed by the HC adsorbent downstream catalyst is estimated, and the heating amount of the heating means is controlled based on the estimation result. Before the HC adsorbent downstream catalyst is heated to remove the HC adsorbed by the HC adsorbent downstream catalyst while purifying the desorbed HC with the HC adsorbent downstream catalyst. Since the desorption / purification action can be further improved, the release of HC into the atmosphere is further suppressed between the start and the completion of the HC desorption process of the HC adsorbent. It becomes possible.

[0015] In the invention described in claim 5, the catalyst HC
The adsorption amount estimating means is configured to estimate the amount of HC adsorbed by the HC adsorbent downstream catalyst based on the time when exhaust gas flows into the HC adsorbent and adsorbs HC in the exhaust gas. With such a configuration, the catalyst HC adsorption amount estimating means can be realized with a relatively simple configuration.

In the invention according to claim 6, the catalyst HC
The adsorption amount estimating means is configured to adsorb the HC adsorbent downstream catalyst based on a total exhaust flow rate flowing into the HC adsorbent during a period in which exhaust gas flows into the HC adsorbent and adsorbs HC in the exhaust gas. The estimated HC amount is estimated. With this configuration, the H value is determined based on the total exhaust flow rate introduced into the HC adsorbent during the period in which HC is adsorbed by the HC adsorbent.
Since the amount of HC adsorbed by the C adsorbent downstream catalyst is estimated, the HC adsorbent is estimated based on the time when the HC adsorbent adsorbs HC.
Since the estimation accuracy can be improved as compared with the invention according to the fourth aspect in which the amount of HC adsorbed on the downstream catalyst of the adsorbent is estimated, the HC performed before starting the HC desorption process of the HC adsorbent is started. The HC desorption process (or purification process) of the catalyst downstream of the adsorbent can be performed with high accuracy.
It is possible to further reduce the amount of HC released into the atmosphere until the adsorbent completes the desorption of HC.

According to a seventh aspect of the present invention, there is provided a bypass passage which branches once at a branch point on the exhaust upstream side of an exhaust passage of an engine and joins again at a junction of the exhaust passage on the downstream side of the exhaust gas; A bypass passage exhaust inflow valve means disposed at a branch point for controlling the flow of exhaust gas into the bypass passage; an HC adsorbent interposed in the bypass passage;
An exhaust gas purification device for an internal combustion engine, comprising: an exhaust gas downstream side of the HC adsorbent; and an HC adsorbent downstream catalyst interposed in the bypass passage, wherein the exhaust gas purification device is adsorbed by the HC adsorbent. In order to desorb HC, according to the elapsed time after flowing at least a part of the exhaust gas into the bypass passage via the bypass passage exhaust inflow control valve,
The exhaust gas flowing into the bypass passage is caused to flow to the upstream side of the main catalyst provided in the exhaust passage of the engine.

With this configuration, the desorption of HC from the downstream catalyst of the HC adsorbent is started by the heat of the exhaust gas flowing into the bypass passage, etc., in order to desorb HC adsorbed on the HC adsorbent. Even if it is performed, for a predetermined period of time, it is made to flow into the upstream side of the activated main catalyst, so that the HC desorbed from the HC adsorbent downstream catalyst (and the desorbed HC adsorbed by the HC adsorbent) Can be purified by the main catalyst.

That is, according to the present invention, the HC adsorbent H
With the start of the C desorption process, the temperature of the HC adsorbent downstream catalyst is raised and HC is desorbed, and the HC desorbed from the HC adsorbent downstream catalyst enters the atmosphere together with the exhaust gas flowing into the bypass passage. It is possible to avoid fear of being released. In the invention according to claim 8, as shown in FIG. 2, on the downstream side of the main catalyst interposed in the exhaust passage of the engine, the exhaust passage temporarily branches at a branch point on the exhaust upstream side of the exhaust passage. A bypass passage that rejoins at a junction downstream of the exhaust gas, a bypass passage exhaust inflow control valve that is disposed at a branch point upstream of the exhaust gas, and controls an inflow of exhaust gas into the bypass passage, An exhaust purification device for an internal combustion engine, comprising: an interposed HC adsorbent; and an HC adsorbent downstream catalyst interposed in the bypass passage on the exhaust downstream side of the HC adsorbent, A communication passage that branches from the bypass passage downstream of the HC adsorbent downstream catalyst and joins upstream of the main catalyst, and is disposed at a branch point of the bypass passage, and controls the flow of exhaust gas into the communication passage. control And at least a portion of the exhaust gas flows into the bypass passage via the bypass passage exhaust inflow control valve in order to desorb HC adsorbed on the HC adsorbent. Communication passage exhaust inflow control means for controlling the exhaust gas flowing into the bypass passage to flow to the upstream side of the main catalyst by the communication passage through the communication passage exhaust inflow control valve in accordance with the elapsed time; , Including.

With this configuration, for a predetermined period after the start of the HC desorbing process of the HC adsorbent, the communication path exhaust / inflow control means and the communication path exhaust / inflow control valve are used.
Exhaust gas (including HC adsorbent and HC desorbed from the HC adsorbent downstream catalyst) flowing into the bypass passage is not directly discharged to the atmosphere but is returned to the upstream side of the main catalyst by the communication passage. Therefore, even if HC is desorbed from the HC adsorbent downstream catalyst as the temperature of the HC adsorbent downstream catalyst rises during the HC desorption process of the HC adsorbent, it is oxidized and removed by the activated main catalyst ( Purification).

Therefore, unlike the conventional apparatus, the HC desorbed from the HC adsorbent downstream catalyst as the temperature of the HC adsorbent downstream catalyst rises during the HC desorbing treatment of the HC adsorbent is not purified, It is possible to avoid the fear that the adsorbent is discharged into the atmosphere together with the exhaust gas that has flowed into the bypass passage for the HC desorption treatment. That is, according to the present invention, with the start of the HC desorption process of the HC adsorbent,
It has been feared that the temperature of the adsorbent downstream catalyst is raised and HC is desorbed, and the HC desorbed from the HC adsorbent downstream catalyst is released into the atmosphere together with the exhaust gas flowing into the bypass passage. It is possible to avoid.

[0022]

According to the present invention, when HC is adsorbed on the HC adsorbent downstream catalyst, the HC adsorbent downstream catalyst is heated before the HC adsorbent is desorbed from the HC adsorbent.
While desorbing HC adsorbed by the C adsorbent downstream catalyst,
The desorbed HC is treated (purified) with the HC adsorbent downstream catalyst, or the H
The HC desorbed from the HC adsorbent or the HC downstream catalyst is flowed upstream of the main catalyst for a predetermined time from the start of the C desorption process, and the desorbed HC is processed (purified) by the main catalyst. Thus, the effect of minimizing the discharge of HC into the atmosphere until the completion of HC desorption of the HC adsorbent can be obtained.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described below with reference to the accompanying drawings. First, a system configuration according to the first embodiment of the present invention will be described with reference to FIG. An upstream catalyst 3 as a main catalyst is provided in a main passage (exhaust passage) 2 of exhaust gas of the engine 1.
And a downstream catalyst 4. On the downstream side of the downstream side catalyst 4, there is provided a bypass passage 5 which branches off from the main passage 2 of the exhaust gas and joins again.

The bypass passage 5 is provided with an electrically heated catalyst (hereinafter referred to as EHC) 7 and an HC adsorbent (adsorbent) 6 upstream of the exhaust gas. However, the heating means in the EHC 7 does not have to be an electric heating type such as an electric heating type heater, and may be a heating means using exhaust heat, a burner or the like. Further, the catalyst used for the EHC 7 may be a three-way catalyst or an oxidation catalyst. The catalyst included in the EHC 7 corresponds to the HC adsorbent downstream catalyst according to the present invention.

An air pump 9 for supplying air (oxygen) to the EHC 7 is connected to the bypass passage 5 on the upstream side of the exhaust of the adsorbent 6. The air pump 9
It corresponds to the oxygen supply means according to the present invention. Further, a bypass valve 8 is provided at a branch point of the main passage 2 ′ parallel to the bypass passage 5 and at a branch point of the bypass passage 5.
The state of the bypass valve 8 shown in FIG. 3 is closed. The bypass valve 8 corresponds to a bypass passage exhaust inflow control valve according to the present invention.

The control unit 10 controls the bypass valve 8, the air pump 9, the EHC 7 according to the activation state of the upstream catalyst 3 and the downstream catalyst 4 (main catalyst).
Of the heating means (electric heater etc.) can be controlled. By the way, the process of desorbing the HC adsorbed by the adsorbent 6 is achieved by opening the bypass valve 8 at a predetermined angle and flowing a part of the exhaust gas to the bypass passage 5 to warm the adsorbent 6.

Here, the control performed by the control unit 10 in the present embodiment will be described with reference to the flowchart shown in FIG. The flags FLGAP and FLGPH used in the following routine are set to IGN. It shall be cleared to 0 when it is ON (ignition ON).
As described below, the functions of the catalyst adsorbing HC treating means, the HC adsorbent downstream catalyst atmosphere controlling means, and the catalytic HC adsorbing amount estimating means according to the present invention are provided by the control unit 10 as software. is there.

First, in S1, it is determined whether or not the condition for the desorbing treatment of the adsorbent is satisfied. Here, it is determined whether the adsorbent 6 has been used during the actual operation, and if used, whether the HC desorption process (hereinafter, also simply referred to as desorption process) has been completed, and the like.
When desorption processing is required, it is determined whether or not the upstream catalyst 3 and the downstream catalyst 4 (main catalyst) interposed in the main passage 2 are activated based on, for example, the cooling water temperature of the engine. If active, the desorption processing conditions are satisfied.

If the conditions are not the desorption processing conditions, the routine is terminated. In the case of the desorption processing conditions, S2
In S2, it is determined whether or not a flag FLGAP indicating that the air pump 9 is being driven is 1, that is, whether or not the air pump 9 is currently being driven. F
If LGAP = 1, the process proceeds to S6 described below,
At 6, it is determined whether the driving time of the air pump 9 has reached a predetermined value.

On the other hand, if FLGAP = 0, the process proceeds to S3, in which whether the flag FLGPH indicating that the EHC 7 is being heated (preheated) is 1 or not, that is, whether the EHC 7 is currently being preheated. Is determined. When FLGPH = 1, the process proceeds to S12 described later, and in S12, it is determined whether the preheating time of the EHC 7 has reached a predetermined value.

If FLGPH = 0 in S3, the conditions for the desorption process of the adsorbent 6 are present, but the desorption process of the adsorbent 6 has not been started yet. Before desorbing the adsorbent 6, EHC (catalyst)
The desorption process of the HC adsorbed on 7 is performed. In S4,
The larger the amount of HC adsorbed on EHC7, the more this adsorbed H
Since the amount of air (oxygen) required for the treatment of C also increases, EH
An air pump driving signal, that is, a pump discharge flow rate is determined from the HC adsorption amount estimated value of C7, and driving of the air pump 9 is started so as to achieve the pump discharge flow rate. At this time, since the desorption process of the adsorbent 6 has not been started, the bypass valve 8 is closed.

The HC adsorption amount of the EHC 7 is determined based on the time CNTRTRAP during which exhaust gas is introduced (HC is adsorbed) into the adsorbent 6 determined by the routine shown in FIG.
It can be estimated by referring to the characteristic diagram shown in FIG. The air pump drive signal (pump discharge flow rate)
It can be determined based on the characteristic diagram shown in FIG.
In the present embodiment, the total air supply amount is controlled by changing the discharge amount while keeping the drive time of the air pump 9 constant. However, it is also possible to adopt a configuration in which the discharge time is changed and the track time is changed. .

The routine for calculating the time CNTRTRAP during which the exhaust gas is flown into the adsorbent 6 shown in FIG. 5 is a general counter, and therefore detailed description is omitted. Exhaust gas to 6 and HC
During the period in which the is adsorbed (during adsorption; determined in S21), the adsorption time counter CNTRTRAP is counted up (S2).
2).

In the next S5, the flag FLGAP = 1 is set, and the routine proceeds to S6. In S6, it is determined whether or not the air pump driving time has reached a predetermined value, that is, whether or not the supply of the necessary air amount for the HC desorption process (or the HC purification process) of the EHC 7 has been completed. If the predetermined time has not been reached, the routine is terminated as it is, and the driving of the air pump 9 is continued. When the predetermined time has been reached, the process proceeds to S7, in which the driving of the air pump 9 is stopped, and in S8, the air pump 9 is stopped.
FLGAP = 0 to indicate that is not being driven
And

In the next step S9, based on the routine shown in FIG. 5 and the HC adsorption amount of the EHC 7 obtained from FIG. 6, the heating (preheating) time of the EHC 7 is searched from the characteristic diagram shown in FIG. This is because EH during the preheat period
This is because the HC adsorbed on the C7 is desorbed, and the HC desorbed from the EHC 7 is oxidized by the oxygen in the air that has already been supplied. If the amount of HC adsorbed on the EHC 7 is large, the heating (preheating) time is correspondingly longer. become longer.

Next, at S10, the EHC 7 is energized to heat the EHC 7, and at S11 the flag FLGPH is set to 1 to indicate that the EHC 7 is being heated. Although the power supplied to the EHC 7 during preheating may be constant, the EHC temperature also increases in proportion to the preheating time, so the preheating time before reaching the catalyst deterioration temperature or the endurance temperature of the EHC (heater section, etc.). It is also possible to reduce the supply power and control the EHC temperature to be kept at a certain value.

In S12, it is determined whether or not the heating time of the EHC 7 has reached the predetermined time obtained in S9. If not, the routine is terminated as it is, and the EHC 7 is preheated, and is adsorbed by the EHC 7. The desorption process of the existing HC is continued. On the other hand, when the heating time has reached the predetermined time, the process proceeds to S13, and the desorption process of the HC adsorbed by the adsorbent 6 is performed as usual. That is, for example, when the bypass valve 8 is half-opened, a part of the exhaust gas flows into the bypass passage 5, and the HC desorbed from the adsorbent 6 is removed by E.
An operation of supplying an air amount (oxygen amount) necessary for oxidizing and removing with the HC 7 by the air pump 9 is performed. The HC desorption processing routine for the adsorbent 6 may be the same as the conventional one, and a detailed description thereof will be omitted.

As described above, according to the present embodiment, before the HC desorption process of the adsorbent 6 is started, the HC adsorbed on the EHC (catalyst) 7 disposed downstream of the adsorbent 6 is used. Is desorbed, so that the H of the adsorbent differs from that of the conventional apparatus.
HC desorbed from the EHC due to heating of the EHC (catalyst with a heater) at the time of the C desorption process is not purified but is released into the atmosphere together with the exhaust gas introduced for the HC desorption process of the adsorbent. The fear of being released can be avoided.

That is, in the present embodiment, the HC of the adsorbent 6
Before starting the desorption process, the amount of HC adsorbed on the EHC 7 is estimated based on the time during which HC is adsorbed on the adsorbent 6, and the amount of air (oxygen) corresponding to the estimated value is determined by the downstream catalyst (EH
C7) is supplied by the air pump 9 to perform preheating of the EHC 7, so that HC desorbed from the EHC 7 due to the preheating of the EHC 7 is treated (oxidized and removed) by oxygen in the atmosphere (oxygen supplied by the air pump 9). ), The HC desorbed from the EHC due to the heating of the EHC during the HC desorption process of the adsorbent is released to the atmosphere without purification as in the conventional device. Fear can be avoided.

That is, according to the present embodiment, the HC contained in the exhaust gas is adsorbed by the HC adsorbent immediately after the start of the internal combustion engine, so that the H to the atmosphere immediately after the start of the engine is obtained.
When the emission of C can be suppressed, and after that, the exhaust gas temperature rises and the main catalyst is activated, the main catalyst can oxidize and remove (purify) HC in the exhaust gas satisfactorily. HC is desorbed from the adsorbent while heating and activating the catalyst on the side through heating means,
The HC desorbed from the adsorbent is oxidized and removed by a catalyst on the downstream side of the HC adsorbent, whereby the emission of HC into the atmosphere can be suppressed. Further, the catalyst on the downstream side of the HC adsorbent (EHC)
Is heated through a heating means to activate it.
H desorbed from the catalyst (EHC) downstream of the C adsorbent
C can also be oxidized and removed (purified) satisfactorily, so that the amount of HC released into the air from the start to the completion of HC desorption of the HC adsorbent 6 can be extremely low.

In the first embodiment, the EHC7
Although the configuration has been described in which oxygen is supplied by the air pump 9 before heating is performed, the configuration may be such that oxygen is supplied by the air pump 9 at the same time as heating the EHC 7 or while heating the EHC 7. is there. That is, it is possible to provide a configuration in which oxygen is supplied to the EHC 7 according to a desorption request or a purification request (atmosphere of the EHC 7).

Next, a second embodiment of the present invention will be described. The system configuration in the second embodiment is shown in FIG.
Are the same as those of the first embodiment shown in FIG. The second embodiment is different from the first embodiment only in the method of obtaining the HC adsorption amount of EHC. In the second embodiment, the HC adsorption of EHC is performed using FIG. 6 in the first embodiment. Instead of adopting a method for obtaining the amount, the HC adsorption amount of EHC is obtained from the total exhaust gas amount during the period when the exhaust gas (HC) is adsorbed by the adsorbent.

Here, the routine for obtaining the total exhaust gas amount during the period when the exhaust gas (HC) is adsorbed by the adsorbent in the second embodiment will be described with reference to the flowchart of FIG. Product of engine speed (Ne) and suction negative pressure (Boost) {Ne * (Pa-Boost)}
Is proportional to the amount of intake air (Pa is atmospheric pressure).
It is determined whether or not the exhaust gas (HC) is being adsorbed on the adsorbent 6 at step S32. If the adsorbent 6 is being adsorbed, the product of the engine speed during suction of HC and the suction negative pressure is integrated at step S32. The total exhaust gas amount CNTRGAS is obtained.

Based on the total exhaust gas amount CNTRGAS during the period when the exhaust gas (HC) is adsorbed on the adsorbent 6 determined by this routine, the HC adsorption amount of EHC is determined from the characteristic diagram shown in FIG. Ask. in this way,
According to the second embodiment, the same operation and effect as those of the first embodiment can be obtained, and the total exhaust gas amount CNT during the period when the exhaust gas (HC) is adsorbed on the adsorbent 6 is obtained.
Since the HC adsorption amount of EHC is calculated based on RGAS, the HC adsorption amount of EHC 7 is calculated based on the time during which the exhaust gas (HC) is adsorbed on the adsorbent 6 as compared with the first embodiment. As a result, the estimation accuracy of the HC adsorption amount of the EHC 7 can be improved, so that the HC desorption process (or purification process) of the EHC 7 performed before the HC desorption process of the adsorbent 6 is started can be made highly accurate. Further, it is possible to further reduce the amount of HC released into the atmosphere from the start to the completion of the desorption of the HC adsorbent 6.

Next, a third embodiment of the present invention will be described. The system configuration according to the third embodiment is shown in FIG.
1, which is partially different from those of the first and second embodiments shown in FIG. 3, will be described. That is, in the third embodiment, as shown in FIG. 11, on the downstream side of the EHC 7 on the bypass passage 5, the fuel cell branches off from the bypass passage 5 and is downstream of the upstream catalyst 3 and downstream catalyst 4 of the main passage 2. A communication passage 11 communicating with the upstream side of the communication passage 11 is provided. A communication passage switching valve 12 driven by the control unit 10 is provided at a branch point between the bypass passage 5 and the communication passage 11. The communication path switching valve 12 closes the state shown in the figure. The communication path 11 corresponds to the communication path according to the present invention, and the communication path switching valve 12 corresponds to the communication path exhaust inflow control valve according to the present invention.

Here, the control performed by the control unit 10 in this embodiment, which functions as the communication passage exhaust gas inflow control means according to the present invention, will be described with reference to FIG.
This will be described according to the flowchart shown in FIG. The communication path switching valve 12 is an IGN. When it is ON (ignition ON), it is initialized to the closed state. First, in S41, it is determined whether or not the conditions for the desorption treatment of the adsorbent 6 are satisfied. This is the same as S1 in the flowchart of FIG. 3 in the first embodiment. If the conditions are not the desorption processing conditions, the routine ends. If the conditions for the desorption treatment are satisfied, in S42, preheating for raising the temperature of the EHC 7 to the activation temperature is started.

Next, in S43, it is determined whether or not the elapsed time from the start of the preheating has reached a predetermined value. If the predetermined time has not been reached, the routine is terminated and the preheating is continued. If the predetermined time has been reached, S
Go to 44. Note that the EHC supply power and the preheating time during preheating may be constant values, but may be changed in the same manner as described in the first embodiment.

In the next step S44, in order to perform the desorption process of the HC adsorbed on the adsorbent 6, the bypass valve 8 is opened at a predetermined angle to allow a part of the exhaust gas to flow toward the bypass passage 5 (adsorbent 6) to be adsorbed. While heating the agent 6, the air pump 9 is driven to supply processing air (oxygen) to the EHC 7. S
45, the EHC 7 was heated during preheating of the EHC 7
The communication path switching valve 12 is opened to allow the entire amount of HC desorbed from 7 to flow through the communication path 11 to the upstream side of the downstream catalyst 4 provided in the main path 2.

In the next step S46, it is determined whether or not a predetermined time determined by experiments or the like has elapsed since the communication path switching valve was opened, and if the predetermined time has not elapsed, the communication path switching valve 12 is turned off. The routine ends with the open state. If the predetermined time has elapsed, it is determined that all the HC desorbed from the EHC 7 has flowed upstream of the downstream catalyst 4 on the main passage, and the process proceeds to S47.

In S47, the communication path switching valve 12 is closed. Then, in S48, the desorbing process of the adsorbent 6 is performed until the termination of the desorbing process of the adsorbent 6 is determined, similarly to the normal desorption process of the adsorbent 6. As described above, according to the third embodiment, the HC desorption process of the adsorbent 6 and the EHC 7
For a predetermined period after the oxidation process (S44) is started,
The communication path switching valve 12 is opened (S45), and the exhaust gas (H desorbed from the EHC 7) flowing into the bypass path 5 is opened.
C) is returned to the upstream side of the downstream catalyst 4 on the main passage 2 without being released to the atmosphere as it is, so that the EHC 7 is heated during the HC desorption process of the adsorbent 6. Thus, the HC desorbed from the EHC 7 can be oxidized and removed (purified) by the activated downstream catalyst 4.

Therefore, as in the conventional apparatus, the HC of the adsorbent is
HC desorbed from the EHC due to the heating of the EHC (catalyst with heater) during the desorption process is released into the atmosphere together with the exhaust gas introduced for the desorption process of the adsorbent without being purified. It is possible to avoid fears of being done. That is, according to the third embodiment, the HC contained in the exhaust gas is adsorbed by the HC adsorbent immediately after the internal combustion engine is started, so that the H to the atmosphere immediately after the start is obtained.
When the emission of C can be suppressed, and after that, the exhaust gas temperature rises and the main catalyst is activated, the HC in the exhaust gas can be oxidized and removed (purified) by the main catalyst. And the exhaust gas flowing through the bypass passage is caused to flow to the upstream portion of the main catalyst for a predetermined period from the start of the HC desorption process of the HC adsorbent, so that the HC desorbed from the HC adsorbent and the EHC.
Can be satisfactorily oxidized and removed (purified) by the main catalyst, so that the amount of HC released into the air from the start to the completion of HC desorption of the HC adsorbent can be extremely reduced.

In the third embodiment, the downstream catalyst 4
Upstream of the upstream catalyst 3 and a bypass passage 5
Although the exhaust gas flowing into the catalyst is configured to be recirculated, it may be configured to recirculate the exhaust gas upstream of the upstream catalyst 3 depending on conditions (exhaust pressure) and the like. Further, in the third embodiment, EHC 7 is provided as the HC adsorbent downstream catalyst, and the configuration in which the preheating is performed by the electric heating means (heater or the like) has been described. When the temperature of the catalyst can be increased, or when the temperature of the HC adsorbent downstream catalyst can be increased by the exhaust radiation heat or the like, the preheating is performed by the electric heating means (heater or the like) (the electric heating means or S42 and S43 in the flowchart of FIG. 12).
Can be omitted.

That is, according to the invention of the third embodiment, for example, even if HC is desorbed from the HC adsorbent downstream catalyst by the heat of the exhaust gas flowing into the bypass passage 5, the downstream side already activated The HC (and H) desorbed from the downstream catalyst of the HC adsorbent by flowing into the upstream side of the catalyst (main catalyst) 4
The essence is to purify the HC desorbed from the C adsorbent 6 by the downstream catalyst 4.

Therefore, the invention according to the third embodiment can be configured as shown in FIG. That is, when the HC adsorbent 6 is desorbed, the bypass valve 8 is half-opened to allow a part of the exhaust gas to flow into the bypass passage 5, and accordingly, E
The HC desorbed from the HC 7 (and the HC desorbed from the HC adsorbent 6) may flow into the main catalyst 4 via the valve 13 and be purified by the main catalyst 4.

In each of the above embodiments, the upstream catalyst 3
In the case where the exhaust gas flow rate is small or the like, the configuration may include either the upstream catalyst 3 or the downstream catalyst 4. And
In each of the embodiments described above, the configuration in which the air pump 9 is provided has been described. However, for example, in the case where there is a sufficient amount of oxygen and the HC adsorbent can be desorbed or the HC can be desorbed and oxidized in the EHC 7, etc. And the air pump 9 can be omitted.

[Brief description of the drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of the invention described in claim 1 of the present invention.

FIG. 2 is a claim correspondence diagram showing a configuration of the invention described in claim 8 of the present invention.

FIG. 3 is a system configuration diagram according to the first embodiment of the present invention.

FIG. 4 is a control flowchart performed in the embodiment.

FIG. 5 is a flowchart for calculating an adsorption time of an HC adsorbent performed in the embodiment.

FIG. 6 is a view showing the relationship between the adsorbent adsorption time and the HC adsorption amount of EHC (HC adsorbent downstream catalyst) performed in the embodiment.

FIG. 7 is a diagram showing a relationship between an HC adsorption amount of an EHC (HC adsorbent downstream catalyst) and an air pump discharge amount.

FIG. 8 is a diagram showing the relationship between the HC adsorption amount of EHC (HC downstream catalyst) and the heating (preheating) time of EHC.

FIG. 9 is a flowchart for calculating a total exhaust gas amount (total exhaust flow rate) during an HC adsorption period performed in the second embodiment of the present invention.

FIG. 10 shows the total exhaust gas amount and EHC (H
Diagram showing the relationship between the amount of HC adsorbed by the C adsorbent downstream catalyst)

FIG. 11 is a system configuration diagram according to a third embodiment of the present invention.

FIG. 12 is a control flowchart performed in the embodiment.

FIG. 13 is a diagram showing another example of the system configuration in the embodiment.

FIG. 14A is a diagram illustrating a configuration of a conventional device. (B)
FIG. 3 is a diagram illustrating an adverse effect that may occur in a conventional device.

[Explanation of symbols]

Reference Signs List 1 engine (internal combustion engine) 2, 2 'exhaust passage (main passage) 3 upstream catalyst (main catalyst) 4 downstream catalyst (main catalyst) 5 bypass passage 6 HC adsorbent 7 EHC (catalyst provided with heating means; HC Adsorbent downstream catalyst) 8 bypass valve (bypass passage exhaust inflow control valve) 9 air pump (oxygen supply means) 10 control unit (microcomputer) 11 communication passage 12 communication passage switching valve (communication passage exhaust inflow control valve) 13 valve

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI F01N 3/20 F01N 3/20 G ZAB ZABK 3/32 ZAB 3/32 ZABB (72) Inventor Akira Tayama Kanagawa-ku, Kanagawa-ku, Kanagawa 2 Takaracho Nissan Motor Co., Ltd.

Claims (8)

[Claims] At a downstream side of a main catalyst interposed in an exhaust passage of an internal combustion engine, a branch is once made at a branch point on an exhaust upstream side of the exhaust passage, and then rejoined at a junction of the exhaust passage on a downstream side of exhaust gas. A bypass passage that is disposed at a branch point on the exhaust upstream side and controls an inflow of exhaust gas into the bypass passage; an HC adsorbent interposed in the bypass passage; An exhaust gas purification device for an internal combustion engine, comprising: an HC adsorbent downstream catalyst interposed in the bypass passage on the exhaust gas downstream side of the HC adsorbent, wherein the HC adsorbed by the HC adsorbent is provided. Before the at least a part of the exhaust gas flows into the bypass passage via the bypass passage exhaust inflow control valve, the HC adsorbent downstream catalyst is heated via a heating means to remove the H An internal combustion engine, comprising: a catalyst adsorbing HC treatment means for purifying the desorbed HC by the HC adsorbent downstream catalyst while desorbing the HC adsorbed by the adsorbent downstream catalyst. Exhaust gas purification device. 2. An HC supply means for supplying oxygen to the HC adsorbent downstream catalyst, and the HC adsorbent downstream catalyst is heated by the catalyst adsorbent HC treatment means via the heating means to thereby provide the HC adsorbent. While desorbing HC adsorbed by the adsorbent downstream catalyst, before purifying the desorbed HC by the HC adsorbent downstream catalyst,
Alternatively, in the meantime, the HC is supplied through the oxygen supply means.
HC for controlling the atmosphere of the catalyst downstream of the adsorbent to a predetermined oxygen concentration
2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, further comprising a catalyst atmosphere control means downstream of the adsorbent. 3. The HC adsorbent downstream catalyst atmosphere control means, based on the estimation result of the catalyst HC adsorption amount estimating means for estimating the amount of HC adsorbed by the HC adsorbent downstream catalyst,
3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, further comprising means for controlling an oxygen supply amount of said oxygen supply means. 4. The catalyst adsorbing HC treatment means estimates a HC amount adsorbed by the HC adsorbent downstream catalyst.
4. The internal combustion engine according to claim 1, further comprising a unit that controls a heating amount of the heating unit based on an estimation result of the adsorption amount estimation unit. 5. Exhaust gas purification device. 5. The catalyst HC adsorbing amount estimating means includes:
Based on the time when the exhaust gas flows into the adsorbent and the HC in the exhaust gas is adsorbed, the H adsorbed by the HC adsorbent downstream catalyst is adsorbed.
5. The C amount is estimated.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 6. The catalyst HC adsorption amount estimating means includes:
Based on the total exhaust flow rate that has flowed into the HC adsorbent during the period in which exhaust gas has flowed into the adsorbent and HC in the exhaust gas has been adsorbed,
The exhaust gas purifying apparatus for an internal combustion engine according to claim 3 or 4, wherein an amount of HC adsorbed by the HC adsorbent downstream catalyst is estimated. 7. A bypass passage, which once branches at a branch point on the exhaust upstream side of an exhaust passage of the internal combustion engine and joins again at a junction on the exhaust downstream side of the exhaust passage, and is disposed at the branch point on the exhaust upstream side. A bypass passage exhaust inflow control valve for controlling the flow of exhaust gas into the bypass passage; an HC adsorbent interposed in the bypass passage; and an interposition of the HC adsorbent downstream of the HC adsorbent in the bypass passage. An exhaust gas purification device for an internal combustion engine, comprising: an HC adsorbent downstream catalyst, wherein the HC adsorbent is desorbed from the HC adsorbent through the bypass passage exhaust inflow control valve. The exhaust gas flowing into the bypass passage flows to the upstream side of the main catalyst interposed in the exhaust passage of the internal combustion engine in accordance with an elapsed time after at least a part of the exhaust gas flows into the bypass passage. Exhaust purification system of an internal combustion engine, characterized in that there was Unishi. 8. A downstream side of a main catalyst interposed in an exhaust passage of an internal combustion engine, the branch once branches at a branch point on the exhaust upstream side of the exhaust passage, and rejoins at a junction on the exhaust downstream side of the exhaust passage. A bypass passage that is disposed at a branch point on the exhaust upstream side and controls an inflow of exhaust gas into the bypass passage; an HC adsorbent interposed in the bypass passage; An HC adsorbent downstream catalyst interposed in the bypass passage, on the exhaust gas downstream side of the HC adsorbent; and an HC purifier downstream of the HC adsorbent downstream catalyst. A communication passage that branches from the bypass passage and joins on the upstream side of the main catalyst; and a communication passage exhaust inflow control valve that is disposed at a branch point of the bypass passage and controls an inflow of exhaust gas into the communication passage. In order to desorb the HC adsorbed by the HC adsorbent, the communication passage according to an elapsed time after at least a part of the exhaust gas has flowed into the bypass passage via the bypass passage exhaust flow control valve. Through the exhaust inflow control valve,
An exhaust gas inflow control device for an internal combustion engine, comprising: a communication path exhaust inflow control means for controlling the exhaust gas flowing into the bypass passage to flow to an upstream side of the main catalyst by the communication path. .