JP3396247B2 - Exhaust gas purification device - Google Patents

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 in which hydrocarbons contained in exhaust gas are adsorbed by an adsorption catalyst, and more particularly, it is excellent in hydrocarbon purifying performance at the time of engine starting, and further adsorbed carbonized. The present invention relates to an exhaust gas purification device having a simple device configuration for post-treatment of hydrogen.

[0002]

2. Description of the Related Art Exhaust gas purification devices for removing harmful substances contained in exhaust gas discharged from engines of automobiles include hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). A catalyst such as a three-way catalyst is used to simultaneously reduce). However, the exhaust gas purifying action of the catalyst is not sufficiently exerted until the catalyst reaches the activation temperature, so that harmful HC is exhausted to the atmosphere at the time of engine cold start.

Therefore, the HC contained in the exhaust gas at the time of engine cold start is adsorbed by the adsorbent provided on the downstream side of the catalyst, and thereafter the HC desorbed from the adsorbent is forcibly applied to the catalyst or the like. A structure designed for reflux has been proposed.
For example, US Pat. No. 5,142,864 discloses a catalyst,
An exhaust gas treatment method using an adsorbent and a turbocharger is disclosed. In this method, in order to suppress the HC emission amount from the exhaust gas at the time of engine cold start, the exhaust gas is allowed to pass through the catalyst and the turbine side of the turbocharger before the exhaust gas is released into the atmosphere during engine cold state. The HC in the exhaust gas is adsorbed by the adsorbent through the adsorbent. Then, when the adsorbent temperature rises, the exhaust gas is bypassed and the exhaust gas is discharged to the atmosphere, while the HC desorbed from the adsorbent by using a part of the exhaust gas is catalyzed via the compressor side of the turbocharger. The exhaust gas from the engine is merged on the upstream side of the engine to purify HC by a catalyst.

Heimrich et al.
Paper published in February 1992, "Hydrocarbon collection at cold start for exhaust emission control" (SAE PAPER 9208
In 47), the adsorbent provided in the exhaust system collects HC during cold start of the engine and then desorbs HC from the adsorbent.
In a catalytic converter, there is described an apparatus which is forcibly refluxed to the upstream side of an oxidation catalyst provided downstream of a three-way catalyst for purification. Further, this paper also describes another device in which the 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, it is not possible to simply and suitably simultaneously control the adsorbent temperature and the catalyst temperature. It is not always easy, and the adsorbent may reach the HC desorption temperature before the catalyst reaches the activation temperature. In this case, HC will be desorbed from the adsorbent before the activation of the catalyst is completed.
Even if the carbon is returned to the catalyst, HC is not purified by the catalyst and is discharged to the outside of the apparatus. That is, according to the conventional device, the required HC purification may not be performed.

Further, in the above conventional apparatus, an HC recirculation means including, for example, a turbocharger or an air pump and a pipe line related thereto is provided for recirculating the HC desorbed from the adsorbent to the catalyst or the engine intake side. Is essential, and therefore the device configuration for post-treatment of the adsorbed HC becomes complicated and the device cost increases. Therefore, the present invention is a type of adsorbing hydrocarbons contained in exhaust gas at the time of engine cold start to an adsorption catalyst, which is excellent in hydrocarbon purification performance, and is used for post-treatment of hydrocarbons adsorbed on the adsorption catalyst. It is an object of the present invention to provide an exhaust gas purification device having a simple device configuration.

[0007]

In the exhaust gas purifying apparatus of the present invention, some of the adsorbents which have hitherto been considered to have a hydrocarbon adsorbing action exert an oxidizing catalytic action in a predetermined temperature range. That is, the present invention was created based on new knowledge recently obtained by the present inventors, and is a main catalyst for purifying exhaust gas from an engine, which is arranged in the middle of a main exhaust passage communicating with the exhaust side of the engine. And a catalytic action for adsorbing hydrocarbons arranged in the middle of the branch exhaust passage communicating with the main exhaust passage at least at the upstream end and for oxidizing the adsorbed hydrocarbons in a predetermined temperature region lower than the activation temperature of the main catalyst. And the temperature of the adsorbent containing the adsorbent (hereinafter referred to as the adsorbent catalyst) falls within the predetermined temperature range.
As described above, there is provided a heating means for heating the adsorption catalyst, and an exhaust path selecting means for selectively blocking communication between the branch exhaust passage and the main exhaust passage at least at one end of the branch exhaust passage.

Preferably, the exhaust gas purifying device operates the temperature detecting means for generating an output indicating the temperature of the main catalyst or the exhaust gas temperature in the vicinity of the main catalyst and the heating means, and outputs the output of the temperature detecting means. And control means for actuating the exhaust path selecting means accordingly. Regarding the adsorption catalyst, the catalysts described in JP-A-3-229638, JP-A-3-165816, JP-A-3-229620, JP-A-4-4045, JP-A-3-127628 and the like can be used in detail.

This catalyst, expressed in a molar ratio of oxides in a dehydrated state, is (1 ± 0.6) R 2 O. [aM 2 O 3
.BAl2O3] .ySiO2 (wherein R is an alkali metal ion and / or hydrogen ion, M is a group selected from the group consisting of Group VIII metals, rare earth metals, titanium, vanadium, chromium, niobium, antimony and gallium The above metal is a crystalline silicate having the chemical formula of a ≧ 0, b ≧ 0, a + b = 1, y> 12) and having the X-ray diffraction pattern shown in Table 1, and copper is supported on the crystalline silicate. The present catalyst is used as a hydrocarbon adsorption catalyst by washcoating a cordierite honeycomb, for example.

[0010]

[Table 1] W: Weak [Irradiation and copper Kα rays] M: Intermediate [I0 is the strongest peak intensity, S: Strong I / I0 is the relative intensity] VS: Very strong

[0011]

[Operation] In order to prevent the exhaust passage selecting means from exerting the effect of blocking the exhaust passage communication at the time of engine cold start when the temperature of the main catalyst or the temperature of the exhaust gas near the main catalyst is low,
The exhaust path selecting means is activated. Preferably, the control means determines based on the output from the temperature detection means whether the main catalyst temperature or the exhaust gas temperature in the vicinity of the main catalyst has reached a predetermined value. For example, the main catalyst temperature is lower than the predetermined value. In this case, the control means actuates the exhaust path selecting means so that the exhaust passage communication blocking action is not exerted. 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, so that the hydrocarbons contained in the exhaust gas are adsorbed in the branch exhaust passage. It is adsorbed on the catalyst and is not discharged to the outside of the device.

Then, for example, when the temperature of the main catalyst rises,
Preferably, when the control means determines, for example, that the main catalyst temperature has reached a predetermined value based on the output of the temperature detection means, the exhaust path selection means is driven, preferably under the control of the control means, and the branch exhaust gas is driven. Communication between the branch exhaust passage and the main exhaust passage is prevented at at least one end of the passage. As a result, the exhaust gas flows from the main exhaust passage at the upstream end of the branch exhaust passage into the branch exhaust passage, or the 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. Both are blocked, so that the exhaust gas flows in the main exhaust passage without further flowing into the branch exhaust passage. As a result, even if the exhaust gas temperature rises thereafter, the adsorption catalyst temperature does not rise,
Therefore, desorption of adsorbed hydrocarbons from the adsorption catalyst does not occur due to the rise of the adsorption catalyst temperature.

Before or after the exhaust passage selecting means blocks the communication between the exhaust passages,
The heating means operates to heat the adsorption catalyst, preferably under the control of the control means. When the temperature of the adsorption catalyst falls within a predetermined temperature range, the adsorption catalyst acts as an oxidation catalyst, whereby the adsorbed hydrocarbon is oxidized and becomes harmless carbon dioxide, water and the like. That is, hydrocarbons are purified by the adsorption catalyst,
Further, the adsorbing catalyst is regenerated so that hydrocarbons can be adsorbed at the next engine cold start. Like this
Since the adsorbed hydrocarbon is purified by the adsorbent catalyst, it is not necessary to recirculate the desorbed hydrocarbon to the main catalyst or the like, and therefore, the device configuration for the post-treatment of the adsorbed hydrocarbon is simplified.

[0014]

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 a combustion chamber of each cylinder of an engine 10 mounted on a vehicle together with an exhaust gas purifying device (one of which is indicated by reference numeral 11 in FIG. 1), and combustion is performed. Room 11
The intake passage 12 and the main exhaust passage 13 are opened and closed by opening and closing the intake valve 14 or the exhaust valve 15. Then, 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 with a main catalyst. An exhaust gas purifying catalytic converter 20 including 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 on the downstream side of the three-way catalyst 20, branching from the main exhaust passage 13.
The upstream side end 31 and the downstream side end 32 of the branch exhaust passage are provided at a first intermediate portion of the main exhaust passage 13 and a second downstream side thereof.
It communicates with each middle part. The branch exhaust passage 30
Hydrocarbons (HC) are adsorbed and adsorbed HC
An adsorption catalyst 40 for oxidizing the carbon dioxide in a predetermined temperature range is provided.

The adsorption catalyst 40 is, for example, a zeolite (zeolite), a crystalline silicate, or the like, which is an adsorbent containing silicon, aluminum, oxygen, etc. as a constituent component, or copper based on 100 parts by weight of a porous crystal. Is contained in an amount of 1 part by weight or more and is molded into a predetermined shape and size, and exhibits an adsorbing action for adsorbing HC and an auto-oxidizing action for oxidizing adsorbed HC with oxygen existing around it in a predetermined temperature range. Is configured.

The hydrocarbon adsorption and desorption tests and the test results carried out using the present adsorption catalyst 40 will be described below. The test was carried out under the following conditions. <Catalyst amount> 1 l <Gas composition> C2H4 2,000ppm C3H6 2,000ppm (THC 10,000p
pm) O2 5% CO2 10% H2O 10% NO 10% N2 Residual <Adsorption temperature> 50 ° C <Desorption temperature> 150 ° C <GHSV> 30,000 / h Test using the test equipment shown in FIG. The amount of adsorbed hydrocarbons and the amount of desorption were detected using a hydrocarbon meter equipped with an FID. When the adsorption temperature is 50 ° C, the above gas composition is supplied for a predetermined time (30 minutes), and then the temperature of the adsorption catalyst is raised to 150 ° C (heating rate 20 ° C / mi).
n) Hold for a predetermined time (30 minutes). Temperature up to 150 ° C
When the temperature was raised to 1, the hydrocarbons were cut, other gases were supplied as they were, and the amount of desorbed hydrocarbons was monitored. The temperature change pattern of the catalyst is shown in FIG.
Table 2 shows the results of the adsorption amount and desorption amount of hydrocarbons when the adsorption temperature and the desorption temperature are alternately repeated under the above gas conditions to reach equilibrium.

[0018]

[Table 2] From the results of Table 2, by using this adsorption catalyst 40,
It can be seen that it adsorbs 35 g / l (catalyst) hydrocarbons at 50 ° C. Further, it has been found that when the temperature of the adsorption catalyst that adsorbed hydrocarbons is raised to 150 ° C. and kept, most of the adsorbed hydrocarbons are burned and removed, and the hydrocarbons are not desorbed as they are. It should be noted that this performance has stable adsorption and combustion behavior even after repeated execution.

Referring again to FIG. 1, the branch exhaust passage 30
A three-way valve 51 for selectively permitting or blocking the communication between the exhaust passages 13 and 30 is arranged in a communication portion between the upstream end 31 of the exhaust gas and the main exhaust passage 13. This three-way valve 51
For example, in the communicating portion, the exhaust passages 13 and 30 having the same cross-sectional shape and dimension are made of a plate-shaped member having substantially the same cross-sectional shape and dimension, and exhaust gas flow through the exhaust passage 13 or 30 can be blocked. There is. This three-way valve 51
A rotary shaft 52, which is rotatably supported by a wall of the exhaust passage, is rotatably connected to the rotary shaft 52 at the joint between the exhaust passages 13 and 30. Further, a negative pressure responsive valve is provided via the rotary shaft 52 and a link mechanism 53. 54 is connected to a diaphragm 54a.

The negative pressure responsive valve 54 is connected to the surge tank 12a (intake passage 12) via a pipe line 55 and is connected to the pressure chamber 54.
b, a diaphragm 54a is provided in the pressure chamber 54b.
A spring 54c for constantly urging the spring is arranged. An on-off valve 56 for selectively permitting or blocking the communication between the intake passage 12 and the pressure chamber 54b via the pipeline 55 is disposed in the middle of the pipeline 55. For example, the on-off valve 56 is a valve body 56 for opening and closing the conduit 55.
It is composed of a normally closed electromagnetic solenoid valve including a and a solenoid 56b for driving the valve body in the valve opening direction. Reference numeral 56c represents a filter.

The above-mentioned elements 51 to 56 correspond to the branch exhaust passage 3
The exhaust path selecting means 50 for selectively blocking the communication between the branch exhaust passage 30 and the main exhaust passage 13 at the upstream end 31 of 0 is configured. That is, the pipe 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 the first operating position (FIGS. 1 and 4) that blocks the 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 so that 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. When it moves backward inward, the three-way valve 51 causes the branch exhaust passage 30 and the main exhaust passage 13 to move.
The exhaust gas flows into the branch exhaust passage 30 in the second operating position (FIG. 5) that allows communication with the exhaust gas.

Further, a heater 60 for heating the adsorption catalyst 40 is arranged around the branch exhaust passage 30 at the location where the adsorption catalyst 40 is arranged. The heater 60 is connected to the battery 62 via the 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 switch contact. Further, a temperature sensor 70 for detecting the three-way catalyst temperature and generating an output representing the three-way catalyst temperature,
For example, the temperature detection unit is disposed so as to abut or be inserted into the three-way catalyst 20.

In FIG. 1, reference numeral 80 indicates a controller including a microprocessor, a memory, an input / output circuit, etc. (not shown).
0, the electromagnetic solenoid valve 56, and the heater switch 61 are connected. The controller 80 includes a three-way catalyst 20,
The adsorption catalyst 40, the exhaust path selecting means 50, the heater 60, the temperature sensor 70 and the like constitute an exhaust gas purifying device.

The operation of the exhaust gas purifying apparatus shown in FIG. 1 will be described below. When an ignition key (not shown) is turned on to start the engine 10, the controller 80
Executes the exhaust path selection and adsorption catalyst heating routine shown in FIG. That is, the processor reads the output of the temperature sensor 70 indicating the temperature of the three-way catalyst 20, and based on the output of the temperature sensor, the three-way catalyst temperature is a predetermined value, for example, the activation of the three-way catalyst 20 is completed about 350.
First, it is determined whether or not the temperature is above ° C (step S
1). When the engine is cold, for example, the three-way catalyst temperature is lower than the predetermined value, so the determination result in step S1 is negative. In this case, the processor sends a high-level control output to the solenoid 56b of the solenoid valve 56 to excite the solenoid (step S).
2).

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. Therefore, 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 inward. Along with the movement of the diaphragm, the three-way valve 51 rotates integrally with the rotary shaft 52 connected to the diaphragm 54a via the link mechanism 53, and the three-way valve 51 moves at the upstream end 31 of the branch exhaust passage 30 at the branch exhaust passage 30. 30 and main exhaust passage 13
It reaches a second operating position (FIG. 5) 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 unactivated three-way catalyst 20 is absorbed by the adsorption catalyst 40 provided in the branch exhaust passage 30. Adsorb. The exhaust gas from which the HC has been removed is supplied to the downstream side portion of the branch exhaust passage 30 and the branch exhaust passage 3
A downstream side 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 0;
It is released into the atmosphere via a muffler (not shown).

As described above, when the three-way valve 51 takes 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 the portion on the downstream side thereof. Can communicate only through the branch exhaust passage 30,
The three-way valve 51 blocks direct communication between the intermediate portion and the downstream portion of the main exhaust passage 13. Therefore, the exhaust gas must pass through the adsorption catalyst 40 before being released into the atmosphere, and the exhaust gas containing HC should be released into the atmosphere even when the activation of the three-way catalyst 20 is not yet completed. There is almost no.

As long as it is determined that the three-way catalyst temperature has not reached the predetermined value, the above steps S1 and S2 are repeatedly executed. Thereafter, when it is determined in step S1 that the three-way catalyst temperature has reached the predetermined value, the processor sends a low-level control output to the solenoid 56b to deactivate the solenoid (step S3). As a result, the electromagnetic attraction force of the solenoid 56b disappears, the valve body 56a moves forward, and the solenoid valve 56 closes. Therefore, the pipeline 55
The introduction of the negative pressure into the pressure chamber 54b of the negative pressure responsive valve 54 is cut off via the valve 5, and the spring force of the spring 54c causes the diaphragm 5 to move.
4a moves forward outward. 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 connects the branch exhaust passage 30 and the main exhaust passage 13 at the upstream end 31 of the branch exhaust passage 30. It takes a first operating position (FIGS. 1 and 4) that blocks communication.

As a result, the exhaust gas is prevented from further flowing into the branch exhaust passage 30. After that, the exhaust gas temperature rises as the three-way catalyst temperature rises.
Is not exposed to new high-temperature exhaust gas, so that due to the temperature rise of the adsorption catalyst, HC once adsorbed on the adsorption catalyst 40 is desorbed from the adsorption catalyst and flows out along with the flow of exhaust gas. Never.

On the other hand, the state in which the three-way valve 51 blocks 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 released. Therefore, the exhaust gas is discharged into the atmosphere through the main exhaust passage 13. In this case, the temperature of the three-way catalyst has already reached the predetermined value, and therefore the activation of the three-way catalyst 20 has already been completed, so that harmful substances such as HC contained in the exhaust gas from the engine 10 are removed by the three-way catalyst. It is eliminated by 20, so that no particular inconvenience occurs.

In step S4 following step S3, the processor sends, for example, a high-level control output to the electromagnetic relay of the heater switch 61 to close the normally open switch contact of the heater switch 61 to select the exhaust path and The adsorption catalyst heating routine ends. Then, 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.

After that, when the temperature of the adsorption catalyst reaches a predetermined value, for example, about 120 ° C. Therefore, when it enters the predetermined temperature range of about 120 to about 200 ° C., the auto-oxidation action of the adsorption catalyst 40 is performed. That is, the HC adsorbed by the adsorption catalyst 40
Are oxidized by the oxygen around them to become harmless carbon dioxide and water. When the adsorbed HC is purified as described above, the adsorbed catalyst 40 is regenerated to a state capable of adsorbing HC at the next engine cold start or the like.

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, which is a main element of the exhaust path selecting means 50, is arranged at the upstream end 31 of the branch exhaust passage 30 to selectively connect the branch exhaust passage and the main exhaust passage at the upstream end of the branch exhaust passage. However, in the exhaust gas purifying apparatus in which both ends of the branch exhaust passage communicate with the main exhaust passage, the three-way valve 51 may be arranged at the downstream end 32 of the branch exhaust passage. Alternatively, they 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, for example, a vehicle. It can be constituted by a control valve driven by an air pressure source or a hydraulic pressure source. Although the temperature sensor detects the three-way catalyst temperature in the embodiment, the exhaust gas temperature in the vicinity of the three-way catalyst, for example, immediately downstream of the three-way catalyst may be detected. Also, the controller 8 that responds to the temperature sensor output
It is not essential to automatically control the operation of the exhaust path selecting means 50 by 0, and the operation of the element 50 can be manually controlled by turning on the electromagnetic solenoid valve 56 via a manual switch.

In the above embodiment, the heater 60 provided separately from the adsorption catalyst 40 was used as the heating means.
0 and the heating means may be integrally provided. For example, a carrier for electric heating catalyst coated with an adsorbent that constitutes the adsorption catalyst 40 can be used. Further, in the above-described embodiment, the heater 60 is simply turned on after the communication between the branch exhaust passage 30 and the main exhaust passage 13 is blocked in step S3 of FIG. 6, but the adsorption catalyst temperature is maintained within the predetermined temperature range. As described above, the heater 60 can be on / off controlled.
Furthermore, it is not essential to start the heating of the adsorption catalyst 40 at the same time when the communication between the branch exhaust passage and the main exhaust passage is cut off.
The heating of the adsorption catalyst may be started before the communication of the exhaust passage is shut off at a timing such that the temperature of the adsorption catalyst does not reach such a degree that the desorption of the adsorbed HC proceeds. Further, it is not essential that the operation of the heater 60 be automatically controlled by the controller 80, and manual control is possible by manually operating the heater switch 61.

[0035]

As described above, the exhaust gas purifying apparatus of the present invention has the main catalyst disposed in the middle of the main exhaust passage for purifying exhaust gas from the engine and the main exhaust passage at least at the upstream end. A hydrocarbon is adsorbed in the middle of the communicating branch exhaust passage, and the adsorbed hydrocarbon activates the main catalyst.
The adsorption catalyst for oxidation in a predetermined temperature range lower than the oxidation temperature, and the temperature of the adsorption catalyst falls within the predetermined temperature range.
In addition, since it is provided with a heating means for heating the adsorption catalyst and an exhaust path selecting means for selectively blocking communication between the branch exhaust passage and the main exhaust passage at at least one end of the branch exhaust passage, the hydrocarbon purification performance is improved. The device configuration for the post-treatment of hydrocarbons adsorbed on the adsorption catalyst is simple, and the device cost can be reduced.

Further, according to the present invention, the exhaust route selecting means is operated by the control means responsive to the output of the temperature detecting means indicating the temperature of the main catalyst or the temperature of the exhaust gas near the main catalyst, and the heating means is operated under the control of the control means. According to the specific aspect of the above, both means can be operated at a suitable timing, and the hydrocarbon purification can be performed more appropriately.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an exhaust gas purifying apparatus according to an embodiment of the present invention together with peripheral elements.

FIG. 2 is a schematic diagram showing a test apparatus used for a hydrocarbon adsorption and desorption test on the adsorption catalyst shown in FIG.

FIG. 3 is a graph showing a temperature change pattern of a catalyst in a hydrocarbon adsorption / desorption test using the test apparatus shown in FIG.

FIG. 4 is a partial view showing a state in which the communication between the branch exhaust passage and the main exhaust passage is blocked by the three-way valve shown in FIG.

FIG. 5 is a partial view showing a state where the three-way valve is in an operating position where the branch exhaust passage and the main exhaust passage are in communication with each other.

FIG. 6 is a flowchart showing an exhaust path selection and adsorption catalyst heating routine executed by the controller shown in FIG.

[Explanation of symbols]

12 Intake passage 13 Main exhaust passage 20 three way catalyst 30 branch exhaust passage 31 upstream end of branch exhaust passage 32 Downstream end of branch exhaust passage 40 Adsorption catalyst 50 Exhaust route selection means 51 three-way valve 60 heater 70 Temperature sensor 80 controller

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F01N 3/24 B01D 53/36 ZAB // B01D 53/04 ZAB 103B (72) Inventor Yoshiro Danno 33, Shiba 5-chome, Minato-ku, Tokyo No. 8 Mitsubishi Motors Co., Ltd. (72) Inventor Daisuke Sanbayashi 5-3-33, Shiba, Minato-ku, Tokyo Mitsubishi Motors Co., Ltd. (72) Inventor Kozo Iida Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima 4-6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Research Institute (72) Inventor Aka Serizawa 1-1 1-1 Atsunoura-machi, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries Ltd. Nagasaki Shipyard (72) Inventor Keiko Kobayashi Chiyoda-ku, Tokyo Marunouchi 2-5-1 Mitsubishi Heavy Industries, Ltd. (56) Reference JP 62-191609 (JP, A) JP 4-311618 (JP, A) JP 4-284827 JP, A) JP flat 3-141816 (JP, A) JitsuHiraku flat 2-67020 (JP, U) JitsuHiraku flat 1-91019 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB name) F01N 3/20 B01D 53/86 B01D 53/94 F01N 3/24 B01D 53/04

Claims (2)

(57) [Claims] 1. A main catalyst arranged in the middle of a main exhaust passage communicating with the exhaust side of an engine for purifying exhaust gas from the engine, and a branch exhaust passage communicating with the main exhaust passage at least at an upstream end. wherein the hydrocarbons are allowed and adsorbed adsorbing hydrocarbons contained in disposed midway the exhaust gas
An adsorbent having a catalytic action for oxidizing at a low predetermined temperature range than the activation temperature of the main catalyst, the temperature of the adsorbent
A heating means for heating the adsorbent so as to enter the predetermined temperature region, and an exhaust path for selectively blocking communication between the branch exhaust passage and the main exhaust passage at least at one end of the branch exhaust passage. An exhaust gas purifying apparatus comprising: a selecting unit. 2. A temperature detecting means for generating an output indicating a temperature of a main catalyst or an exhaust gas temperature in the vicinity of the main catalyst, and the heating means, and at the same time, the exhaust path according to the output of the temperature detecting means. The exhaust gas purifying apparatus according to claim 1, further comprising control means for operating the selecting means.