JP3433461B2 - Exhaust gas purification device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus in which hydrocarbons contained in exhaust gas are adsorbed on an adsorption catalyst, and more particularly, to an exhaust gas purifying apparatus for starting an engine. The present invention relates to an exhaust gas purifying apparatus which is excellent in hydrocarbon purifying performance and has a simple apparatus configuration for post-treatment of adsorbed hydrocarbon. [0002] Exhaust gas purifying apparatuses for removing harmful substances contained in exhaust gas discharged from engines of automobiles and the like include hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides. A catalyst such as a three-way catalyst has been used to simultaneously reduce substances (NOx). However, the exhaust gas purifying action of the catalyst is not sufficiently exhibited until the catalyst reaches the activation temperature, so that harmful HC is discharged into the atmosphere at the time of cold start of the engine and the like. [0003] Therefore, HC contained in the exhaust gas at the time of cold start of the engine is adsorbed by an adsorbent provided downstream of the catalyst, and then the HC desorbed from the adsorbent is forcibly applied to the catalyst or the like. A structure for refluxing has been proposed.
For example, US Pat. No. 5,142,864 includes catalysts,
An exhaust gas treatment method using an adsorbent and a turbocharger is disclosed. In this method, in order to suppress the amount of HC emission from the exhaust gas at the time of cold start of the engine, the exhaust gas is discharged to the catalyst and the turbine side of the turbocharger before the exhaust gas is released to the atmosphere at the time of cold engine. The HC in the exhaust gas is adsorbed by the adsorbent through the adsorbent. Thereafter, when the temperature of the adsorbent rises, the exhaust gas bypasses the adsorbent and is exhausted to the atmosphere, while the HC desorbed from the adsorbent using a part of the exhaust gas is catalyzed through the compressor side of the turbocharger. The exhaust gas from the engine is merged on the upstream side of the engine, thereby purifying HC with a catalyst. [0004] Heimrich et al.
Paper published in February 1992, "Hydrocarbon Collection at Cold Start for Exhaust Emission Control" (SAE PAPER 9208)
47), the HC collected by the adsorbent provided in the exhaust system at the time of cold start of the engine, and then the HC desorbed from the adsorbent is
An apparatus is described in which a catalytic converter is forcibly refluxed to an upstream side of an oxidation catalyst provided downstream of a three-way catalyst to purify the catalyst. This paper also describes another device in which HC desorbed from the adsorbent is forcibly recirculated to the intake side of the engine and burned in the engine combustion chamber. [0005] However, in the above-mentioned conventional exhaust gas purifying apparatus for purifying HC desorbed from the adsorbent with a catalyst, the temperature of the adsorbent and the temperature of the catalyst are simply and preferably simultaneously controlled. This is not always easy, and the adsorbent may reach the HC desorption temperature before the catalyst reaches the activation temperature. In this case, the HC is desorbed from the adsorbent before the activation of the catalyst is completed, and the desorbed HC is removed.
Even if is refluxed to the catalyst, HC is discharged to the outside of the device without being purified by the catalyst. That is, the conventional device may not be able to perform required HC purification. Further, in the above-mentioned conventional apparatus, there is provided an HC recirculation means including, for example, a turbocharger or an air pump and a pipeline related thereto for recirculating the HC desorbed from the adsorbent to the catalyst or the engine intake side. Is indispensable, so that the apparatus configuration for the post-treatment of the adsorbed HC becomes complicated, and the apparatus cost increases. Therefore, the present invention is of a type in which hydrocarbons contained in exhaust gas at the time of cold start of an engine are adsorbed by an adsorption catalyst, and has excellent hydrocarbon purification performance at the time of engine start, and the hydrocarbon adsorbed by the adsorption catalyst. It is an object of the present invention to provide an exhaust gas purification device having a simple device configuration for post-treatment. SUMMARY OF THE INVENTION The exhaust gas purifying apparatus of the present invention is characterized in that a certain adsorbent, which has been considered to have a hydrocarbon adsorbing function, is an oxidation catalyst in a predetermined temperature range. It was created based on new knowledge recently obtained by the present inventors that it works, and is arranged in the middle of the main exhaust passage communicating with the exhaust side of the engine to purify exhaust gas from the engine. And a catalytic action for adsorbing hydrocarbons contained in exhaust gas and oxidizing the adsorbed hydrocarbons in a predetermined temperature range, which is disposed at least in the middle of a branch exhaust passage communicating with the main exhaust passage at the upstream end. Adsorbent having a sorbent (hereinafter referred to as adsorption catalyst)
Heating means for heating the adsorption catalyst, exhaust path selecting means for selectively preventing communication between the branch exhaust path and the main exhaust path at at least one end of the branch exhaust path, and detecting engine coolant temperature Temperature detection means for detecting the engine cooling water temperature at engine start
The predetermined time determined according to
Then, the branch exhaust passage and the main exhaust passage
Exhaust path so that operation to prevent communication with the road is not performed
Activate the selection means, and after the elapse of the predetermined time,
Control means for operating the exhaust path selecting means so that the communication blocking operation by the air path selecting means is performed . [0008] Preferably, the control means, after the exhaust path selection unit were communicating blocking operation, or, prior to the communication blocking operation, to initiate operation of the heating means, further, the start operation of the heating means It is desirable to stop the operation of the heating means when a second predetermined time has elapsed from the time. For details of the adsorption catalyst, see JP-A-3-22.
9638, JP-A-3-165816, JP-A-3-229620, JP-A-4-404
5, the catalysts described in JP-A-3-127628 can be used. [0010] [action] In such as during engine cold start of the engine temperature for example the engine coolant temperature level and the main catalyst temperature is low activation of the main catalyst is not completed, the temperature indicative of engine coolant <br/> temperature Under the control of the control means responsive to the output from the detection means, the exhaust path selection means operates such that the exhaust path selection means does not exert the exhaust communication blocking action. Sand <br/> KazuSatoshi, when the predetermined time determined in accordance with the detected engine value of the coolant temperature at the time of starting the engine is determined not yet been elapsed from the time of starting the engine, the control means, the exhaust passage communicating blocking The exhaust path selecting means is operated so that the operation is not performed. As a result, the exhaust gas from the engine flows into the branch exhaust passage from the main exhaust passage at the upstream end of the branch exhaust passage, and therefore, the hydrocarbons contained in the exhaust gas are adsorbed in the branch exhaust passage. Even if it is adsorbed by the catalyst and the activation of the main catalyst is not completed, it is not discharged out of the apparatus. Thereafter, when the engine temperature and the main catalyst temperature rise and the main catalyst is activated, the exhaust path selecting means is driven under the control of the control means, and the branch exhaust path at at least one end of the branch exhaust path is opened. And the communication with the main exhaust passage. That is, the control means, when determining from the time of starting the engine and a predetermined time has elapsed, driving the exhaust path selection means to communicate inhibitory action of the exhaust routing device is achieved. As a result, exhaust gas flows from the main exhaust passage into the branch exhaust passage at the upstream end of the branch exhaust passage, or exhaust gas flows out or flows into and out of the main exhaust passage from the branch exhaust passage at the downstream end of the branch exhaust passage. Therefore, the exhaust gas flows through the main exhaust passage without flowing further into the branch exhaust passage. As a result, even if the temperature of the exhaust gas subsequently increases, the temperature of the adsorption catalyst does not increase, and thus the desorption of the adsorbed hydrocarbon from the adsorption catalyst due to the increase in the temperature of the adsorption catalyst does not occur. Before or after communication between the two exhaust passages is blocked by the exhaust passage selecting means,
Preferably, under the control of the control means, the heating means starts operating to heat the adsorption catalyst. When the temperature of the adsorption catalyst falls within a predetermined temperature range, an oxidation catalytic action of the adsorption catalyst is exerted, whereby the adsorbed hydrocarbon is oxidized to harmless carbon dioxide, water and the like. That is, the hydrocarbon is purified by the adsorption catalyst, and the adsorption catalyst is regenerated so that the hydrocarbon can be adsorbed at the next cold start of the engine. As described above, since the adsorbed hydrocarbon is purified by the adsorbent catalyst, it is not necessary to reflux the desorbed hydrocarbon to the main catalyst or the like, and therefore, the configuration of the apparatus for post-treatment of the adsorbed hydrocarbon is simplified. Preferably, when the second predetermined time has elapsed from the start of the operation of the heating means, the operation of the heating means is stopped under the control of the control means. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust gas purifying apparatus according to an embodiment of the present invention will be described below with reference to FIG. An intake passage 12 and a main exhaust passage 13 are connected to combustion chambers (one of which is indicated by reference numeral 11 in FIG. 1) of each cylinder of the engine 10 mounted on the vehicle together with the exhaust gas purifying device. Room 11
The intake passage 12 or the main exhaust passage 13 is communicated or shut off by opening and closing the intake valve 14 or the exhaust valve 15. In the intake passage 12, for example, an air cleaner (not shown), a throttle valve 16, and a fuel injection valve (not shown) are provided in this order from the upstream side, and the main exhaust passage 13 is preferably provided as a main catalyst. An exhaust gas purifying catalytic converter 20 composed of a three-way catalyst and a muffler (not shown) are provided. Reference numeral 12 a indicates a surge tank provided in the intake passage 12 on the downstream side of the throttle valve 16. A branch exhaust passage 30 is provided downstream of the three-way catalyst 20 from the main exhaust passage 13.
The upstream end 31 and the downstream end 32 of the branch exhaust passage are connected to a first intermediate portion of the main exhaust passage 13 and a second intermediate portion downstream thereof.
Each is connected to the middle part. And the branch exhaust passage 30
On the way, the hydrocarbon (HC) is adsorbed and the adsorbed HC
An adsorption catalyst 40 for oxidizing the catalyst in a predetermined temperature range is provided. The adsorption catalyst 40 is, for example, a zeolite or a crystalline silicate or a similar adsorbent containing silicon, aluminum, oxygen, or the like as a component, or copper per 100 parts by weight of the porous crystal. Is formed into a predetermined shape and size, and has an adsorbing action of adsorbing HC and a self-oxidizing action of oxidizing the adsorbed HC with oxygen existing therearound in a predetermined temperature region. It is configured as follows. Referring again to FIG. 1, the branch exhaust passage 30
A three-way valve 51 for selectively permitting or preventing communication between the exhaust passages 13 and 30 is provided at a communication portion between the upstream end 31 and the main exhaust passage 13. This three-way valve 51 is
For example, the communication portion is formed of a plate-like member having substantially the same cross-sectional shape as the two exhaust passages 13 and 30 having the same cross-sectional shape and size in the communication portion, so that exhaust gas flow through the exhaust passage 13 or 30 can be shut off. I have. This three-way valve 51 is
A rotating shaft 52 rotatably supported by a wall of the exhaust passage at the joint of the exhaust passages 13 and 30 is integrally rotatably connected to the rotating shaft 52, and further, a negative pressure responsive valve via the rotating shaft 52 and a link mechanism 53. 54 is connected to the diaphragm 54a. A negative pressure responsive valve 54 is connected to a pressure chamber 54 communicating with the surge tank 12a (the intake passage 12) through a pipe 55.
b in the pressure chamber 54b.
A spring 54c that constantly biases the outside is provided. An opening / closing valve 56 for selectively allowing or preventing communication between the intake passage 12 and the pressure chamber 54b via the pipe 55 is provided in the middle of the pipe 55. For example, the on-off valve 56 is a valve body 56 for opening and closing the pipeline 55.
a, and a normally closed electromagnetic solenoid valve including a solenoid 56b for driving the valve body in the valve opening direction. Reference numeral 56c represents a filter. The above elements 51 to 56 are connected to the branch exhaust passage 3
Exhaust path selecting means 50 for selectively preventing communication between the branch exhaust path 30 and the main exhaust path 13 at the upstream end 31 of the exhaust path. That is, the conduit 55 is closed by the valve body 56a of the electromagnetic solenoid valve 56, and the negative pressure supply to the negative pressure responsive valve 54 is cut off. Therefore, the diaphragm 54a of the negative pressure responsive valve is urged outward by the spring 54c. In the normal operating state, the three-way valve 51 takes a first operating position (FIGS. 1 and 2) for preventing communication between the upstream end 31 of the branch exhaust passage 30 and the main exhaust passage 13, The exhaust gas is prevented from flowing into the branch exhaust passage 30. On the other hand, the solenoid valve 56 is opened, the pressure chamber 54b of the negative pressure responsive valve 54 communicates with the intake passage 12, and a negative pressure is introduced into the pressure chamber. Therefore, the diaphragm 54a resists the spring force of the spring 54c. Is moved inward, the three-way valve 51 is connected to the branch exhaust passage 30 and the main exhaust passage 13.
The exhaust gas flows into the branch exhaust passage 30 in a second operating position (FIG. 3) that allows communication with the exhaust gas. Further, a heater 60 for heating the adsorption catalyst 40 is disposed around the branch exhaust passage 30 at the position where the adsorption catalyst 40 is disposed. The heater 60 is connected to a battery 62 via a heater switch 61.
The heater switch 61 includes, for example, a normally open switch contact (not shown) and an electromagnetic relay (not shown) for closing the contact. A temperature sensor 70 for detecting the temperature of the engine cooling water and generating an output representing the temperature of the engine cooling water has its temperature detecting portion disposed in an engine cooling water passage formed in the cylinder peripheral wall of the engine 10. Thus, it is mounted on the engine 10. In FIG. 1, reference numeral 80 denotes a controller comprising a microprocessor, a memory, an input / output circuit and the like (not shown).
0, the electromagnetic solenoid valve 56 and the heater switch 61 are connected. The controller 80 includes the three-way catalyst 20,
The exhaust gas purifying apparatus is constituted by the adsorption catalyst 40, the exhaust path selecting means 50, the heater 60, the temperature sensor 70, and the like. Hereinafter, the operation of the exhaust gas purifying apparatus shown in FIG. 1 will be described. When an ignition key (not shown) is turned on to start the engine 10, the controller 80
Executes an exhaust path selection and adsorption catalyst heating routine shown in FIG. That is, the processor
Output of the temperature sensor 70 representing the temperature of the outgoing engine cooling water.
Reading (step S11), and then
FIG. 5 stored in the memory of the controller 80 and
Referring to the example map, the detected engine cooling water temperature
The corresponding predetermined time TSW is determined (step S12). So
Then, the processor uses a timer built in the controller 80.
(Not shown), a predetermined time T from the start of the engine.
It is determined whether or not the SW has elapsed (step S13).
If the determination result is negative, for example, c
To send out the control output at the low level to excite the solenoid.
(Step S14). As a result, a core (not shown) provided at the base end of the valve body 56a is electromagnetically attracted by the solenoid 56b, the valve body 56a moves backward, and the solenoid valve 56 opens. Accordingly, the negative pressure in the surge tank 12a is introduced into the pressure chamber 54b of the negative pressure responsive valve 54 through the pipe 55, and the diaphragm 54a of the valve 54 moves backward. With the movement of the diaphragm, the three-way valve 51 rotates integrally with the rotating shaft 52 connected to the diaphragm 54a via the link mechanism 53, and the three-way valve 51 is connected to the branch exhaust passage 30 at the upstream end 31 of the branch exhaust passage 30. 30 and main exhaust passage 13
To a second operating position (FIG. 3) that allows communication with As a result, the exhaust gas flows into the branch exhaust passage 30, and the HC contained in the exhaust gas after passing through the three-way catalyst 20 that has not been activated is transferred to the adsorption catalyst 40 provided in the branch exhaust passage 30. Adsorb. The exhaust gas from which HC has been removed is supplied to the downstream portion of the branch exhaust passage 30 and the branch exhaust passage 3.
A downstream portion of the main exhaust passage 30 communicating with the branch exhaust passage 30 at a second intermediate portion corresponding to the downstream end 32 of
It is released into the atmosphere via a muffler (not shown). As described above, when the three-way valve 51 is in the second operating position, the first intermediate portion of the main exhaust passage 13 corresponding to the upstream end 31 of the branch exhaust passage 30 and a portion downstream thereof. Can communicate only through the branch exhaust passage 30,
Direct communication between the intermediate portion and the downstream portion of the main exhaust passage 13 is shut off by the three-way valve 51. Therefore, the exhaust gas must pass through the adsorption catalyst 40 before being released to the atmosphere, and even when the activation of the three-way catalyst 20 has not been completed, the exhaust gas containing HC is released to the atmosphere. Is almost none. Thereafter, a predetermined time T SW from the start of the engine is set.
Is determined in step S13 , that is, when the completion of the warm-up of the engine 10 and the completion of the activation of the three-way catalyst 20 are determined, the processor sends, for example, a low-level control output to the solenoid 56b to turn off the solenoid. to energize (step S 15). As a result, the electromagnetic attraction force of the solenoid 56b disappears, the valve body 56a moves forward, and the solenoid valve 56 closes. Accordingly, the introduction of the negative pressure into the pressure chamber 54b of the negative pressure responsive valve 54 via the pipe 55 is interrupted, and the diaphragm 54a moves forward outward by the spring force of the spring 54c. With the movement of the diaphragm, the three-way valve 51 rotates via the link mechanism 53 and the rotary shaft 52, and the three-way valve 51 is connected between the branch exhaust passage 30 and the main exhaust passage 13 at the upstream end 31 of the branch exhaust passage 30. It reaches the first operating position (FIG. 2) which prevents communication. As a result, further inflow of exhaust gas into the branch exhaust passage 30 is prevented. Although the exhaust gas temperature rises with the completion of the warm-up of the engine 10, the adsorption catalyst 40 is not exposed to new high-temperature exhaust gas. Therefore, the HC once adsorbed on the adsorption catalyst 40 due to the increase in the temperature of the adsorption catalyst is adsorbed. There is no problem of desorbing from the catalyst and flowing out along with the flow of exhaust gas. On the other hand, the state in which the communication between the first intermediate portion of the main exhaust passage 13 corresponding to the upstream end 31 of the branch exhaust passage 30 and the downstream portion thereof is blocked by the three-way valve 51 is released. Therefore, the exhaust gas is released to the atmosphere via the main exhaust passage 13. In this case, since the activation of the three-way catalyst 20 has already been completed, harmful substances such as HC contained in the exhaust gas from the engine 10 are removed by the three-way catalyst 20, so that no particular inconvenience occurs. [0028] In step S 16 following the step S 15, the processor sends a control output of the high level, for example to an electromagnetic relay of the heater switch 61, to close the normally open switch contacts of the heater switch 61, the following in step S 17, it is preset and the controller 80
It is determined whether or not the second predetermined time ( predetermined adsorption catalyst heating time ) stored in the memory has elapsed since the start of the ON operation of the heater switch 61. For this reason, for example, when the heater switch 61 starts to be turned on, the processor sets a predetermined adsorption catalyst heating time in a timer (not shown) built in the controller 80 and starts the timer.
This timer is referred to each time the determination at 17 is made. And
If the determination result in the step S 17 is negative, the processor waits a predetermined time elapses. When the switch contact of the heater switch 61 is closed, electric power is supplied from the battery 62 to the heater 60 via the heater switch 61, and the heater 60 heats the adsorption catalyst 40. Thereafter, the temperature of the adsorption catalyst reaches a predetermined value, for example, about 120 ° C., and is therefore about 120 to about 2 ° C.
When the temperature falls within the predetermined temperature range of 00 ° C., the self-oxidizing effect of the adsorption catalyst 40 is exerted. That is, the HC adsorbed on the adsorption catalyst 40 is oxidized by the oxygen present around the HC to become harmless carbon dioxide, water and the like. [0030] Then, if it is determined in step S 17 with a predetermined adsorbing catalyst-heating time has elapsed, the processor causes the opening of the switch contact of the heater switch 61 sends a control output, for example, low level electromagnetic relay of the heater switch 61 (step S 18). As a result, the heating of the adsorption catalyst 40 by the heater 60 is stopped, and the exhaust path selection and adsorption catalyst heating routine of FIG. 4 ends. When the adsorbed HC is purified as described above, the adsorbent catalyst 40 is regenerated to a state where HC can be adsorbed at the next cold engine start. The exhaust gas purifying apparatus of the present invention is not limited to the above embodiment. For example, in the above embodiment,
A three-way valve 51 as a main element of the exhaust path selecting means 50 is disposed at the upstream end 31 of the branch exhaust passage 30 to selectively connect the branch exhaust passage with the main exhaust passage at the upstream end of the branch exhaust passage. However, in the exhaust gas purifying device configured such that both ends of the branch exhaust passage communicate with the main exhaust passage, the three-way valve 51 may be disposed at the downstream end 32 of the branch exhaust passage. Alternatively, it may be arranged at both the upstream end and the downstream end of the branch exhaust passage. The branch exhaust passage 30 may be configured to communicate with the main exhaust passage 13 only at its upstream end. The exhaust path selecting means 50 is not limited to the embodiment in which the three-way valve 51 composed of a plate-like opening / closing member, the negative pressure responsive valve 54, the electromagnetic solenoid valve 56 and the like are combined, and is mounted on a vehicle, for example. It can be constituted by a control valve driven by a pneumatic source or a hydraulic source. In the above embodiment, the heater 60 provided separately from the adsorption catalyst 40 is used as the heating means, but the adsorption catalyst 40 and the heating means may be provided integrally.
For example, a carrier obtained by coating an adsorbent constituting the adsorption catalyst 40 on a carrier for an electrically heated catalyst can be used. In the above embodiment, step S 1 in FIG.
5 , the adsorber catalyst 40 is heated by the heater 60 for a fixed predetermined adsorption catalyst heating time after the communication between the branch exhaust passage 30 and the main exhaust passage 13 is interrupted. May be variably set in accordance with the detected engine coolant temperature, or the heater 60 may be turned on and off so that the adsorption catalyst temperature is maintained within a predetermined temperature range. Further, it is not essential that the heating of the adsorption catalyst 40 be started at the same time as the communication between the branch exhaust passage and the main exhaust passage is interrupted. For example, the heating of the adsorption catalyst may be started before the communication with the exhaust passage is cut off. For example, the third predetermined time from when the engine is started to when the heater switch 61 is turned on is determined to be a value shorter than the predetermined time TSW and a value corresponding to the detected engine coolant temperature at the time of starting the engine. The heater switch 61 may be turned on for a second predetermined time (predetermined adsorption catalyst heating time) after determining the elapse of the predetermined time of No. 3. As described above, the exhaust gas purifying apparatus of the present invention comprises a main catalyst disposed in the middle of the main exhaust passage for purifying exhaust gas from the engine, and at least an upstream side catalyst. An adsorption catalyst for adsorbing hydrocarbons contained in the exhaust gas and oxidizing the adsorbed hydrocarbons in a predetermined temperature range, which is disposed in the middle of the branch exhaust passage communicating with the main exhaust passage at the end;
Heating means for heating the adsorption catalyst; exhaust path selecting means for selectively preventing communication between the branch exhaust passage and the main exhaust passage at at least one end of the branch exhaust passage; and detecting the engine coolant temperature. and temperature detection means, d
Depending on the value of the detected engine coolant temperature at engine startup
Until the predetermined time that has been determined has elapsed since the start of the engine,
The branch exhaust passage and the main exhaust passage by the exhaust passage selecting means
Exhaust path selection means so that the operation to prevent communication is not performed
Activate the stage, and after a predetermined time elapses,
Control means for operating the exhaust path selecting means so that the communication blocking operation by the selecting means is performed ,
It is excellent in hydrocarbon purification performance at the time of engine start, and has a simple apparatus configuration for post-processing of the hydrocarbon adsorbed on the adsorption catalyst, and can reduce the apparatus cost. Also, the exhaust path
Switching and, consequently, new hot exhaust gas
Of adsorbed hydrocarbons from the adsorbed catalyst by increasing the temperature of the adsorbed catalyst
Prevention of desorption can be performed at an appropriate timing to purify hydrocarbons
Perform more properly. Further, the operation of the heating means is started after the exhaust path selecting means performs the communication preventing operation or before the communication preventing operation is performed, and the second operation is started from the start of the operation of the heating means. According to the specific aspect of the present invention in which the operation of the heating means is stopped when the predetermined time has elapsed, the adsorption catalyst can be held in the predetermined temperature range where the oxidation of the adsorbed hydrocarbon in the adsorption catalyst is promoted. Thus, the efficiency of purifying hydrocarbons can be improved, and the deterioration of the adsorption catalyst due to an excessive rise in the temperature of the adsorption catalyst can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an exhaust gas purifying apparatus according to a first embodiment of the present invention together with peripheral elements. FIG. 2 is a partial view showing a state where communication between a branch exhaust passage and a main exhaust passage is interrupted by a three-way valve shown in FIG. 1; FIG. 3 is a partial view showing a state where a three-way valve is in an operating position for communicating a branch exhaust passage with a main exhaust passage. FIG. 4 is a flowchart showing an exhaust path selection and adsorption catalyst heating routine executed by a controller shown in FIG. 1; 5 is a graph illustrating a map used for determining a predetermined time TSW in an exhaust path selection and adsorption catalyst heating routine in FIG. 4 ;

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI F01N 3/20 ZAB B01D 53/36 ZAB // B01D 53/04 ZAB 103B (72) Inventor Daisuke Mibayashi Shibago, Minato-ku, Tokyo No. 33-8, Mitsubishi Motors Corporation (56) References JP-A-62-1191609 (JP, A) JP-A-4-31618 (JP, A) JP-A-1-91019 (JP, U) Hira 2-67020 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F01N 3/08-3/28 B01D 53/86 B01D 53/94 B01D 53/04

Claims (1)

(1) A main catalyst disposed in a main exhaust passage communicating with an exhaust side of an engine for purifying exhaust gas from the engine, and a main catalyst at least at an upstream end. An adsorbent having a catalytic action for adsorbing hydrocarbons contained in the exhaust gas and oxidizing the adsorbed hydrocarbons in a predetermined temperature range, which is disposed in the middle of a branch exhaust passage communicating with the exhaust passage; and Heating means for heating, exhaust path selecting means for selectively preventing communication between the branch exhaust path and the main exhaust path at at least one end of the branch exhaust path, and detecting an engine coolant temperature Temperature detection means and the detection engine at the time of engine start
The engine starts for a predetermined time determined according to the value of the cooling water temperature.
Until the time passes, the exhaust path selecting means
An action for preventing communication between the branch exhaust passage and the main exhaust passage.
Activate the exhaust path selection means so that no operation is performed.
After the predetermined time has elapsed, the exhaust path selection is performed.
Control means for operating the exhaust path selecting means so that the communication blocking operation by the selecting means is performed .