JPH10252449A - Exhaust cleaning device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust cleaning device for an internal combustion engine for preventing discharge of hydrocarbon(HC) much contained in exhaust gas right after starting of the internal combustion engine into the atmosphere. SOLUTION: This device has a circulating passage 10 which is branched from downstream of a catalyst with a heater 7 on a bypass passage 5 and communicated with upstream of adsorbent 6 on the bypass passage 5 and circulating passage switch valves 9, 9a disposed at a branched point and a combined point of the circulating passage 10 and the bypass passage 5 and a circulating device arranged on the circulating passage 10 and a closed loop path is formed by the bypass passage 5 and the circulating passage 10 by the circulating passage switch valves 9, 9a when HC adsorbed to the adsorbent 6 is cleaned by the catalyst with the heater 7 of downstream and controlled to circulate by the circulating device until adsorbed HC is fully cleaned by the catalyst with heater 7 with new gas previously charged in the circulating passage 10.

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 a method for converting hydrocarbons (hereinafter referred to as 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 for an internal combustion engine provided with a device for preventing emission.

[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. this house,
In particular, the purification of HC with a catalyst is strongly affected by the exhaust gas temperature, and generally requires a temperature of 350 to 400 ° C. or higher. Immediately after the start of the engine, the exhaust gas temperature is low, and the catalyst has not reached the activation temperature (350 to 400 ° C. or higher). Furthermore, when the engine is cold, such as immediately after starting the engine, the amount of HC emission becomes very large. In general, when the exhaust gas temperature is low,
The amount of HC released into the atmosphere increases. In order to solve such a problem of the conventional exhaust gas purifying apparatus for an internal combustion engine, a bypass passage branched from a main passage of exhaust gas is provided on a downstream side of a catalyst provided in an exhaust passage of the engine; A switching valve provided at a branch point of the passage, an adsorbent provided in the bypass passage, a heater-equipped catalyst provided downstream of the adsorbent in the bypass passage, and an upstream end of the adsorbent And a control device configured to control the switching valve and the heater of the catalyst with a heater according to the temperature of the exhaust gas detected by the exhaust temperature sensor (Japanese Patent Laid-Open No. 6-66136). The technology described in Japanese Patent Application Publication No. H10-216, has been invented (see FIG. 8). In the above invention, 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 adsorbent by the switching valve downstream of the catalyst and the HC is adsorbed, thereby preventing the emission to the atmosphere. After the exhaust gas temperature rises and the catalyst is activated, the exhaust gas is caused to flow into the main passage by the switching valve, while the H 2 gas flows from the adsorbent.
C is desorbed and purified by a downstream catalyst with a heater.

[0003]

However, in such an exhaust gas purifying apparatus for an internal combustion engine, for example, generally, as shown in FIG. 9, the amount of desorbed adsorbent rapidly decreases as the temperature of the adsorbent rises. Due to the increasing characteristics, HC cannot be completely purified by the heater-equipped catalyst because the desorbed amount exceeds the purification capacity of the downstream heater-equipped catalyst when the adsorbent exceeds a certain temperature. There is a problem in that it may be released. To cope with this, a method of increasing the capacity of the catalyst with a heater can be considered, but the capacity is limited due to the problem of power consumption. The present invention has been made in view of such conventional problems, and includes a circulation passage that branches from a downstream side of the heater-equipped catalyst on a bypass passage and communicates with the adsorbent upstream on the bypass passage. A circulating passage switching valve provided at a junction of the passage and the bypass passage and a circulating device disposed on the circulating passage, and purifying HC adsorbed by the adsorbent by a downstream catalyst with a heater; In this case, a closed loop path is constituted by the bypass path and the circulation path by the circulation path switching valve, and the circulating device is operated until the adsorbed HC is completely purified by the catalyst with a heater by fresh air previously filled in the circulation path. An object of the present invention is to solve the above-mentioned problems by performing control so as to circulate the data.

[0004]

In order to solve the above-mentioned problems, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, a circulation branching from a downstream side of a catalyst with a heater on a bypass passage and communicating with an upstream side of an adsorbent on the bypass passage. A passage, a circulation passage switching valve provided at a junction and a junction of the circulation passage and the bypass passage, and a circulation device disposed on the circulation passage. When purifying by means of the circulation passage switching valve, the recirculation passage and the circulation passage constitute a closed loop, and the adsorbed HC
Is controlled by the circulation device until the exhaust gas is completely purified by the catalyst with a heater by fresh air previously filled in the circulation passage. That is, as shown in the claim correspondence diagram of FIG. 1, a circulation passage a branched from a bypass passage downstream of the catalyst with a heater downstream of the adsorbent and communicating with an upstream of the adsorbent similarly provided in the bypass passage; A circulation path switching valve b provided at the junction with the point, and a circulation device c disposed on the circulation path a
A purifying end determining means d configured to determine whether the HC adsorbed on the adsorbent has been completely purified by the catalyst with a heater, and the purifying when desorbing the HC adsorbed on the adsorbent. Until end determination means d determines that the process is completely completed, the circulation passage a and the bypass passage constitute a closed loop passage, and the circulation passage switching valve b and the circulation device c are controlled so as to circulate the desorbed HC. Circulation path control means e and H adsorbed on the adsorbent.
And a fresh air introduction device f for introducing fresh air into the circulation passage a after the C desorption process is completed. According to a second aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, wherein the purification completion determination means includes a process for desorbing HC adsorbed on an adsorbent. And a means for making a determination based on the elapsed time since the start of the process. According to a third aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, comprising:
The purification end determination means d is provided after a lapse of a predetermined time from the start of the desorption process of the HC adsorbed on the adsorbent of the oxygen sensor disposed in the closed loop formed by the circulation passage a and the bypass passage. It is characterized in that it is a means for making a judgment based on the output. According to a fourth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, comprising:
Is a circulation device c disposed on the circulation passage a.

[0005]

The operation of the invention will be described. When the HC adsorbed by the adsorbent is desorbed and purified by the heater-equipped catalyst disposed downstream of the adsorbent, the circulation passage control means e operates until the purification completion determination means d determines that the purification has been completed. Circulating passage switching valve b and circulating device c
Is controlled so that the desorbed gas that has passed through the heater-equipped catalyst is returned to the adsorbent upstream of the bypass passage by the circulation passage a and circulated. Thereafter, control for filling the circulation passage a with fresh air is performed by the fresh air introducing device f. Therefore, H
Even when HC cannot be completely purified by the heater-equipped catalyst, such as when the amount of C desorbed exceeds the purifying ability of the heater-equipped catalyst, until the purification end determination means d determines that the purification has been completed. The desorbed gas that has passed through the heater-equipped catalyst is circulated back to the adsorbent upstream of the bypass passage through the circulation passage a, and is repeatedly purified by the heater-equipped catalyst, whereby the release of adsorbed HC into the atmosphere is suppressed. . The operation of the second aspect will be described. When the catalyst disposed in the main passage of the exhaust gas is activated, the HC adsorbed by the adsorbent is desorbed and purified by the heater-equipped catalyst disposed downstream of the adsorbent, the purification end determination means d is deactivated. The circulation passage control means e circulates the circulation gas through the circulation passage switching valve b and the circulation device c until it is determined that the purification has been completed based on the elapsed time from the start of the separation treatment. Control is performed by the passage a so as to return and circulate the adsorbent upstream of the re-bypass passage. Thereafter, control for charging fresh air into the circulation passage a by the fresh air introducing device f is performed. The operation of the invention according to claim 3 will be described. When the catalyst disposed in the main passage of the exhaust gas is activated, the HC adsorbed by the adsorbent is desorbed and purified by the heater-equipped catalyst disposed downstream of the adsorbent, the purification end determination means d is deactivated. The circulation passage control is performed until it is determined that the purification is completed based on the output of the oxygen sensor disposed in the closed loop constituted by the circulation passage a and the bypass passage after a predetermined time has elapsed from the start of the separation process. By means e, the circulation path switching valve b and the circulation apparatus c are connected to the circulation path a by using the desorbed gas that has passed through the heater-equipped catalyst.
Thus, control is performed so as to return and circulate upstream of the adsorbent on the re-bypass passage. Thereafter, control for charging fresh air into the circulation passage a by the fresh air introducing device f is performed. The operation of the invention will be described. When the catalyst disposed in the main passage of the exhaust gas is activated, the HC adsorbed by the adsorbent is desorbed and purified by the heater-equipped catalyst disposed downstream of the adsorbent, the purification end determination means d performs the purification. Until it is determined that the process has ended, the circulation path control means e causes the circulation path switching valve b and the circulation apparatus c to circulate the desorbed gas passing through the heater-equipped catalyst back to the adsorbent upstream of the bypass path by the circulation path a. The control is performed as follows. Thereafter, control for charging fresh air into the circulation passage a by the circulation device c is performed.

[0006]

Hereinafter, the present invention will be described with reference to the drawings. Embodiment 1 First, the configuration will be described. FIG. 2 is a diagram showing a configuration of the first embodiment. In the main passage 3 for the exhaust gas of the engine 1, an upstream catalyst 2 and a downstream catalyst 4 are provided.
(Both are main catalysts). On the downstream side of the downstream catalyst 4, the main passage 3a of the exhaust gas is provided.
And a bypass passage 5 is provided in parallel. The bypass passage 5 has a catalyst 7 with a heater, and has an adsorbent 6 with a heater upstream thereof. The adsorbent 6 may not be equipped with a heater. In that case, when desorbing the adsorbed HC, the adsorbent 6 is opened slightly by opening a bypass passage switching valve 8 described later, and a small amount of exhaust gas is caused to flow through the bypass passage 5 to adsorb the HC. Warm agent 6. The catalyst supported on the heater-equipped catalyst 7 may be a three-way catalyst or an oxidation catalyst. Further, the bypass passage 5 is provided with a circulation passage 10 branched from the downstream of the heater-equipped catalyst 7 and also communicating with the adsorbent 6 upstream of the bypass passage 5. Circulation path switching valves 9 and 9a (hereinafter valves 9 and 9 respectively) are provided at a branch point and a junction of the bypass path 5 and the circulation path 10.
a) is attached. The valves 9, 9a are opened in the state shown in FIG. The circulation passage 10 is provided with a circulation pump 11 for circulating gas and an air pump 12 for filling the circulation passage 10 with fresh air. A bypass passage switching valve 8 (hereinafter, valve 8) is provided at a branch point between the main passage 3a and the bypass passage 5. The valve 8 closes the state shown in FIG. The control unit 13 controls the valve 8, the valve 9, 9a, the adsorbent 6 with a heater, the catalyst 7 with a heater, and the like according to the activation state of the main catalysts 2 and 4 and the purification state of the desorbed HC from the adsorbent 6.
The circulation pump 11 and the air pump 12 are driven.

Next, the control of the first embodiment will be described with reference to FIG.
This will be described according to the flow shown in FIG. First, as an initial state, at the time of IGNon, the valve 8 is opened, the valves 9 and 9a are closed, the counters TJK, TAP and the flag FTRAP,
TRAPEND is cleared to 0. In S1, it is determined whether the flag FTRAP = 1. The flag FTRAP indicates whether the adsorbent has been used in the current operation, and will be 1 when the adsorbent is used, as described later. If FTRAP is not 1, that is, if the adsorbent is not used in the current operation, the process proceeds to S3, and it is determined whether the main catalyst has been activated. This is determined based on, for example, whether the water temperature of the engine is higher than a predetermined value. If not active, S6
It is determined whether or not the adsorbent on the bypass passage 5 can be adsorbed. This can be done by monitoring the temperature of the adsorbent and determining that the adsorbent can be adsorbed when the temperature is equal to or lower than a predetermined value. If the adsorbent can be adsorbed, FTRAP is set to 1 to indicate that the adsorbent has been used in S7, the valve 8 is opened in S8, exhaust gas flows into the bypass passage 5, HC is adsorbed by the adsorbent, and the process is terminated. . If the adsorbent cannot be adsorbed, the valve 8 is closed in S5, and the process ends without flowing exhaust gas to the adsorbent. When the catalyst is activated in S3, the exhaust gas is purified by the main catalyst, so that in S4, the flag TRAPEND indicating that the use of the adsorbent in this operation has been completed is set to 1, and in S5, Close the valve 8 and terminate the process. In S1, if FTRAP = 1, that is, if the adsorbent is used in this operation, the process proceeds to S2, and it is determined whether TRAPEND = 1, that is, whether the use of the adsorbent has already been completed. TRAPEND =
If it is not 1, it is determined whether or not the condition for using the adsorbent is used after S3. If the use of the adsorbent has already been completed in S2, the process proceeds to S9, where the adsorbed HC is desorbed. At S9, the counter TJK after the start of the process of desorbing the HC adsorbed on the adsorbent has a predetermined value T indicating the end of purification.
Judge whether it is greater than JKEND. TJK> TJKE
If it is not ND, it is determined that the purification of the desorbed HC has not been completed yet, and in S10, the valves 9, 9a are opened, the circulation pump is turned on, the adsorbent heater is turned on, and the catalyst heater is turned on to circulate with the desorbed HC. The fresh air in the passage 10 is circulated in a closed loop passage formed by the bypass passage 5 and the circulation passage 10 and repeatedly purified by the heater-equipped catalyst 7, and TJK is counted up in S11 and the process is terminated. If TJK> TJKEND in S9, it is determined that the purification has been completed, the process proceeds to S12, and the process proceeds to S13 as the adsorbent heater off and the catalyst heater off.
In S13, the counter TAP after the start of the air purge in the circulation passage 10 has a predetermined value TAPE indicating the end of the purge.
It is determined whether it is larger than ND. If TAP> TAPEND is not satisfied, it is determined that the purge has not been completed,
In S14, the valve 9a is closed, the air pump 12 is turned on, fresh air supplied by the air pump 12 is sent by the circulation pump 11, and the inside of the circulation passage 10 is purged.
Is counted up and the processing ends. TAP> TA in S13
If it is PEND, it is determined that the purging has been completed and S1
Proceeding to 6, the valve 9 is closed, the air pump is turned off, and the circulation pump is turned off.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the first embodiment, when the amount of desorbed HC exceeds the purifying ability of the catalyst with heater 7 or the like, the HC is converted into the catalyst 7 with heater. Even if it is not possible to purify completely, the desorbed gas that has passed through the catalyst with heater 7 is returned to the upstream side of the adsorbent on the bypass passage 5 by the circulation passage 10 and circulated until the predetermined time elapses. By purifying with the catalyst 7, the adsorbed HC can be completely purified, and the emission of HC into the atmosphere is suppressed.

Second Embodiment The configuration of the second embodiment is the same as that of the first embodiment. Next, the operation will be described. The second embodiment is different from the first embodiment in the method of determining the completion of purification. The flow after S12 is different on the flow,
This is shown in FIG. First, as an initial state, IGNon
Sometimes valve 8 is open, valves 9 and 9a are closed, counter T
JK, TAP, TKAP and flags FTRAP, TR
APEND and FAP are cleared to 0. The elapsed time TJK from the start of purification in S9 is equal to a predetermined value TJKEND.
If it exceeds, the process proceeds to S21. In S21, it is determined whether or not the flag FAP = 1 indicating whether the air pump 12 has been driven to supply the additional air for purifying HC in the current operation. When the air pump 12 is driven to supply the additional air, it is determined in S22 whether the counter TKAP after starting the driving of the air pump 12 is larger than a predetermined value TKAPEND indicating that a predetermined amount of air supply has been completed. . If TKAP> TKAPEND is not satisfied, it is determined that the supply of the predetermined amount of air has not been completed yet, and S26
Then, the air pump 12 is turned on, FAP is set to 1 in S27, and TKAP is counted up in S28, and the processing is terminated. If TKAP> TKAPEND in S22, it is determined that the supply of the predetermined amount of air has been completed, and in S23, the air pump 12 is turned off and the process proceeds to S24. Also, S21
If FAP is not 1, that is, if air has not been added yet, the process proceeds to S24. The output of the O ₂ sensor provided in the closed loop path In S24, it is determined whether a leaner than a predetermined value. If the output of the O ₂ sensor is leaner than the predetermined value, the purification of HC has been completed, it is determined that the air (O ₂ ) is in a surplus state, and the process proceeds to S12, where the air purge in the circulation passage 10 is performed. I do. If the output of the O ₂ sensor is not leaner than the predetermined value, the HC remains without being purified, and the purification air (O ₂ )
Is determined to be insufficient, TKAP is cleared in S25, and air is newly added by the air pump 12 in S26.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the second embodiment, when the amount of desorbed HC exceeds the purifying ability of the catalyst with heater 7 or the like, the HC is converted into the catalyst 7 with heater. Therefore, even when the exhaust gas cannot be completely purified, the output of the O ₂ sensor provided in the closed loop after a predetermined time has elapsed since the start of the purification becomes leaner than a predetermined value, and the HC is completely purified. Until it is determined that the degassed gas has passed through the heater-equipped catalyst 7 while adding purification air, the desorbed gas is returned to the adsorbent upstream of the re-bypass passage 5 by the circulation passage 10 and circulated repeatedly. By purifying, it is possible to completely purify the adsorbed HC, and the emission of HC into the atmosphere is suppressed.

Third Embodiment FIG. 5 shows the configuration of the third embodiment. The basic configuration is the same as that of the first embodiment, except that the air pump 12 is not provided, and the valves 9, 9a
Is, for example, a rotary valve.
It has a structure that allows the two to communicate with each other. Positions a to c shown in FIG. 6 correspond to the rotary valves 9 and 9a in FIG.
It is an expansion of.

Next, the operation will be described. The third embodiment differs from the first embodiment in the method of air purging after the end of purification of desorbed HC. On the flow, S10, S14, S
16 are different, and become S30, S34, and S36, respectively. This is shown in FIGS. 7A and 7B. In S30, the valve 9 is set to the position c in FIG. 6, and the valve 9a is set to the position b to form a closed loop, and the circulation pump is turned on and the adsorbent heater o is turned on.
n, the catalyst heater is turned on. In S34, the valve 8
Is opened, the valve 9 is set to the position b, the valve 9a is set to the position c, and the circulation pump 11 sucks fresh air from an exhaust pipe to perform air purging in the circulation passage 10. S3
At 6, the valve 8 is closed, the valves 9 and 9a are at position a,
The circulation pump 11 is turned off, and the air purge ends. .

[0013]

According to the present invention, when the HC adsorbed by the adsorbent provided in the bypass passage branched from the main passage is desorbed and purified by the catalyst with a heater disposed downstream of the adsorbent, the desorption of HC is performed. Even when the amount of HC exceeds the purifying capacity of the heater-equipped catalyst, such as when HC cannot be completely purified by the heater-equipped catalyst, the amount of HC that has passed through the heater-equipped catalyst is maintained until it is determined that purification is completely completed. The separated gas is circulated back to the upstream of the adsorbent on the bypass passage by the circulation passage, and is repeatedly purified by the catalyst with a heater, so that the adsorbed HC can be completely purified, and the emission of HC into the atmosphere is suppressed. Is obtained.

[Brief description of the drawings]

FIG. 1 is a view corresponding to a claim showing an exhaust gas purifying apparatus for an internal combustion engine of the present invention.

FIG. 2 is a diagram showing a configuration of the present invention.

FIG. 3 is a flowchart according to the first embodiment.

FIG. 4 is a flowchart according to the second embodiment.

FIG. 5 is a configuration diagram of a third embodiment.

FIG. 6 is a diagram showing an open / close position of a valve according to a third embodiment.

FIG. 7 is a flowchart of (1) Embodiment 3. (2) It is a flowchart of Embodiment 3.

FIG. 8 is a diagram showing an exhaust gas purifying apparatus for an internal combustion engine according to a conventional example.

FIG. 9 is a diagram showing desorption characteristics of an adsorbent.

[Explanation of symbols]

 Reference Signs List a circulation passage b circulation passage switching valve c circulation device d purification completion determination means e circulation passage control means f fresh air introduction device 1 engine 2 upstream catalyst 3 main passage 3a main passage 4 downstream catalyst 5 bypass passage 6 adsorbent 7 heater With catalyst 8 bypass passage switching valve 9 circulation passage switching valve 9a circulation passage switching valve 10 circulation passage 11 circulation pump 12 air pump 13 control unit

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI F01N 3/34 B01D 53/34 120D (72) Inventor Akira Tayama 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (4)

[Claims] A bypass passage branched from a main passage of exhaust gas downstream of a catalyst provided in an exhaust passage of the engine; a bypass passage switching valve provided at a branch point of the bypass passage; An adsorbent provided in a bypass passage; a catalyst with a heater provided downstream of the adsorbent in the bypass passage; and a bypass switching valve and the heater in accordance with an activation state of a catalyst provided in the main passage. A control unit configured to control a heater of the catalyst with a fuel supply device. An exhaust gas purification device for an internal combustion engine, comprising: a control unit configured to control a heater of a catalyst with a fuel supply device; A circulation passage, a circulation passage switching valve provided at a junction of the circulation passage and the bypass passage, and a junction therewith; And a control unit configured to determine whether the hydrocarbon adsorbed on the adsorbent has been completely purified by the catalyst with a heater, and a process for desorbing the hydrocarbon adsorbed on the adsorbent. The control means configured to determine whether the hydrocarbons adsorbed on the adsorbent have been completely purified by the catalyst with a heater until the control means determines that the processing has been completely completed. Control means configured to control the circulation path switching valve and the circulation device so as to circulate the desorbed hydrocarbons, and into the circulation path after the desorption processing of the hydrocarbons adsorbed on the adsorbent is completed. An exhaust gas purification device for an internal combustion engine, comprising: a fresh air introduction device for introducing fresh air. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the control means configured to determine whether or not the hydrocarbon adsorbed on the adsorbent has been completely purified by the catalyst with a heater comprises: An exhaust gas purifying apparatus for an internal combustion engine, comprising means for performing a control for making a judgment based on an elapsed time from a start of a desorption process of the adsorbed hydrocarbon. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the control means configured to determine whether or not the hydrocarbon adsorbed on the adsorbent has been completely purified by the catalyst with a heater comprises: Means for performing a control for making a determination based on an output of an oxygen sensor disposed in a closed loop path constituted by the circulation path and the bypass path after a lapse of a predetermined time from the start of the desorption processing of the adsorbed hydrocarbons An exhaust gas purifying apparatus for an internal combustion engine, comprising: 4. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein fresh air is introduced into said circulation passage after the desorbing process of the hydrocarbon adsorbed on said adsorbent is completed. Is an exhaust purification device for an internal combustion engine, which is a circulation device disposed on the circulation passage.