JPH0771237A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the degradation of a CO oxidizing catalyst so as to effectively purify exhaust gas at the time of low temperature by cutting off the lead-in of high temperature exhaust gas to the CO oxidizing catalyst. CONSTITUTION:When the temperature of a monolithic catalyst 9 is less than the activation temperature, exhaust gas in purified by a catalyst cylinder 16, an HC adsorption base 18 and an NOx absorption base 20. At the time of the specified temperature, that is, when the monolithic catalyst 9 has the activation temperature or more, HC and NOx in the HC adsorption base 18 and NOx absorption base 20 are desorbed by the heat by the exhaust gas exhausted at this time, and led into an intake manifold 2 and purified by a catalytic converter 10. The exhaust gas is thereby purified regardless of the temperature. When the monolithic catalyst 9 has the activation temperature or more, a branch passage 14 is closed by a first control valve 26. The purifying ability of a CO oxidizing catalyst is thereby maintained without the degradation of the CO oxidizing catalyst 15 in the catalyst cylinder 16 so as to effectively purify the exhaust gas at the time of low temperature.

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 device for purifying exhaust gas discharged from an engine.

[0002]

2. Description of the Related Art In general, exhaust gas discharged from an engine is purified by a catalytic converter and released into the atmosphere. However, since the temperature is low immediately after the engine is started, the catalyst in the catalytic converter is in an inactive state, and exhaust gas is not sufficiently purified. Therefore, in Japanese Utility Model Laid-Open No. 2-67020, an HC trapper is provided downstream of the catalytic converter, and at low temperature, the exhaust gas passing through the catalytic converter is guided to the HC trapper to trap HC, and the catalyst is generated by the exhaust gas heat passing through the catalytic converter. When is activated, the HC adsorbed by the HC trapper is guided to the upstream side of the catalytic converter using the exhaust gas. The exhaust gas containing HC returned to the upstream side of the catalytic converter is purified by the catalytic converter together with the exhaust gas discharged from the engine. This makes it possible to purify exhaust gas at low temperatures.

[0003]

However, not only HC but also CO, NOx, and the like are included as harmful components contained in the exhaust gas. Therefore, it is conceivable to provide a catalyst cylinder containing a CO oxidation catalyst and a NOx absorption bed containing a NOx absorbent in the passage in which the HC trapper of the conventional art is provided. However, when the temperature is low, the exhaust gas that becomes hot enough to activate the catalyst in the catalytic converter, as in the above-mentioned conventional technique, absorbs HC or NOx adsorbed or absorbed by the NOx absorbent in the HC trapper or the NOx absorption bed. When desorbed, high temperature exhaust gas is introduced into the catalyst cylinder in the same passage and working at low temperature, which may cause deterioration of the CO oxidation catalyst in the catalyst cylinder.

Therefore, an object of the present invention is to prevent deterioration of the CO oxidation catalyst by cutting off the introduction of the high temperature exhaust gas into the CO oxidation catalyst, and to effectively purify the exhaust gas at low temperatures. .

[0005]

An exhaust gas purifying apparatus for an internal combustion engine according to the present invention uses a catalytic converter provided in an exhaust passage of the internal combustion engine, a branch passage provided downstream of the catalytic converter, and a catalyst temperature in the catalytic converter. A first control valve for controlling the opening of the branch passage with respect to the exhaust passage, a catalyst cylinder provided in the branch passage and containing a trapping means for absorbing or adsorbing HC or NOx and a CO oxidation catalyst, the trapping means and the catalyst barrel Is installed downstream of the catalyst converter and opens when the catalyst in the catalytic converter is below the activation temperature to communicate the branch passage with the outside air, and closes when the catalyst in the catalyst converter is above the activation temperature to shut off the branch passage from the outside air. A second control valve for
An exhaust gas purification device for an internal combustion engine, comprising: a control valve upstream, the capturing means, a downstream of a catalyst cylinder, and a communication passage that communicates with a catalytic converter upstream, wherein the catalyst when the catalyst in the catalytic converter is at an activation temperature or higher. It is characterized in that an exhaust gas cut-off means for cutting high-temperature exhaust gas into the cylinder is provided.

[0006]

According to the above means, when the catalyst in the catalytic converter is below the activation temperature, the branch passage for the exhaust passage is opened by the first control valve, and the exhaust gas not purified by the catalytic converter is discharged downstream of the catalytic converter. All are introduced into the branch passage. HC in the exhaust gas introduced into the branch passage
Alternatively, NOx is absorbed or adsorbed by the trapping means, and C
O is oxidized by the CO oxidation catalyst installed in the catalyst cylinder. Further, at this time, since the second control valve is opened and the branch passage is communicated with the outside air, the trapping means and the CO in the catalyst cylinder are
The exhaust gas purified by the oxidation catalyst is released into the atmosphere.

Exhaust gas is purified by the catalytic converter when the catalyst is activated by the heat of the exhaust gas passing through the catalytic converter and the temperature of the catalyst in the catalytic converter reaches the activation temperature or higher. At this time, the first control valve opens part of the branch passage and opens the exhaust passage. Therefore, a part of the exhaust gas flows to the branch passage downstream of the catalytic converter, and the other exhaust gas is discharged into the atmosphere from the exhaust passage. However, since the exhaust gas cutoff means is provided, the exhaust gas flowing into the branch passage is not introduced into the CO oxidation catalyst in the catalyst cylinder.
Since the exhaust gas has a temperature high enough to activate the catalyst, the exhaust gas flowing into the branch passage desorbs HC or NOx absorbed or adsorbed by the trapping means. Since the second control valve is closed and the branch passage is shut off from the outside air, the desorbed HC or NOx is discharged upstream of the second control valve between the trapping means, the downstream of the catalyst cylinder and the upstream of the catalytic converter. It is introduced upstream of the catalytic converter through a communication passage that communicates. Therefore, when the catalyst in the catalytic converter is below the activation temperature, the HC absorbed or adsorbed by the trapping means.
Alternatively, NOx is reintroduced into the catalytic converter that has reached the catalyst activation temperature to be purified, and is released into the atmosphere from the exhaust passage.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an exhaust purification system for an internal combustion engine in a first embodiment of the present invention. Reference numeral 2 is an intake manifold into which air or air-fuel mixture is introduced, 4 is an engine, and 6 is an exhaust manifold into which exhaust gas discharged from the engine 4 is introduced. The exhaust manifold 6 is connected to an exhaust pipe 7 downstream thereof, and exhaust gas is introduced into an exhaust passage 8 formed in the exhaust pipe 7.

The exhaust passage 8 is provided with a catalytic converter 10 containing a monolith catalyst 9 for purifying exhaust gas. The monolith catalyst 9 is composed of a carrier coated with alumina, and platinum, rhodium or the like supported thereon. Exhaust passage 8 downstream of catalytic converter 10
Is provided with a muffler 12 having a muffling function. A branch passage 14 branched from the exhaust passage 8 is connected to the exhaust passage 8 downstream of the muffler 12.

In the branch passage 14, a catalyst cylinder 16 in which a CO oxidation catalyst 15 for oxidizing CO in exhaust gas is installed, and an HC adsorption bed in which an HC adsorbent 17 as a trapping means for adsorbing HC in exhaust gas is installed. 18, a NOx absorption bed 20 in which a NOx absorbent 19 as a trapping means for absorbing NOx in exhaust gas is installed. A as the CO oxidation catalyst 15
u is used, the HC adsorbent 17 includes kanemite, activated carbon, zeolite and the like, and the NOx absorbent 19 includes FeO, BaO, CuBaO _{2 and the} like. Here, in order to desorb the absorbed NOx, it is preferable that the temperature is higher, and in this embodiment, the NOx absorption bed 20 is used.
Is in contact with the exhaust pipe 7.

Exhaust passage 8 immediately upstream of the catalytic converter 10.
A temperature sensor 22 for detecting the temperature of the exhaust gas flowing into the catalytic converter 10 is provided in the. A temperature sensor 2 is provided downstream of the muffler 12 and downstream of the NOx absorption bed 20.
A first control valve 26 and a second control valve 28 are provided as exhaust cutoff means for switching the flow of exhaust gas by a signal from an ECU (electronic control unit) 24 based on a signal from 2.

A first bypass passage 30 as a part of the branch passage is provided in the branch passage 14 downstream of the exhaust passage 8 and the catalyst cylinder 16 and upstream of the HC adsorption bed 18. On the branch passage 14 side of the first bypass passage 30, a third control valve 32 that switches the flow of exhaust gas based on a signal from the temperature sensor 22 by a signal from the ECU 24 is provided. A communication passage 34 is provided from the branch passage 14 downstream of the NOx absorption bed 20 and upstream of the second control valve 28 to the intake manifold 2.

The operation of the exhaust gas purifying apparatus for an internal combustion engine configured as above will be described. When the temperature detected by the temperature sensor 22 is lower than the activation temperature of the monolith catalyst 9 in the catalytic converter 10, the signal from the ECU 24 based on the signal from the temperature sensor 22 causes the first control valve 26 to rotate counterclockwise in the figure. The exhaust passage 8 is rotated and opened at the same time as the branch passage 14 branched from the exhaust passage 8 is opened. Further, the second control valve 28 causes the branch passage 14 to receive a signal from the ECU 24 based on the signal from the temperature sensor 22.
Is rotated so that it can communicate with the outside air. Further, the third control valve 32 connects the downstream side of the catalyst cylinder 16 and the upstream side of the HC adsorption bed 18, and at the same time, the first bypass passage 30 and the branch passage 1
4 is turned counterclockwise in the figure by a signal from the ECU 24 based on a signal from the temperature sensor 22 so as to shut off the signal from the temperature sensor 22.

The flow of exhaust gas when each control valve is in the above state will be described step by step. Since the monolith catalyst 9 in the catalytic converter 10 is below the activation temperature, the catalytic converter 10 does not purify the exhaust gas. Exhaust gas that has not been purified by the catalytic converter 10 is silenced through the muffler 12 and then introduced into the branch passage 14. Here, the exhaust gas is introduced into the branch passage 14 by utilizing the negative pressure in the intake manifold 2 by disposing the communication passage 34. Moreover, since the first bypass passage 30 and the branch passage 14 are blocked by the third control valve 32, the branch passage 14 does not pass through the catalyst cylinder 16.
There is no exhaust gas introduced into the. The exhaust gas introduced into the branch passage 14 first passes through the catalyst cylinder 16, and the CO oxidation catalyst 15 installed in the catalyst cylinder 16 oxidizes the CO in the exhaust gas. The exhaust gas from which CO has been removed next passes through the HC adsorption bed 18, and the HC in the exhaust gas is adsorbed by the HC adsorbent 17 installed in the HC adsorption bed 18. CO,
The exhaust gas from which the HC has been removed then passes through the NOx absorption bed 20, and the NOx absorbent 1 installed in the NOx absorption bed 20.
NOx in the exhaust gas is absorbed by 9. In the downstream of the NOx absorption bed 20, the second control valve 28 has the branch passage 1
Since it is rotated so that 4 can communicate with the outside air, C
The exhaust gas from which O, HC and NOx have been removed is released into the atmosphere.

Next, when the monolith catalyst 9 is activated by the heat of the exhaust gas passing through the catalytic converter 10, that is, the temperature detected by the temperature sensor 22 is the catalytic converter 10.
The time when the activation temperature of the monolith catalyst 9 in FIG. When the temperature detected by the temperature sensor 22 is equal to or higher than the activation temperature of the monolith catalyst 9 in the catalytic converter 10, the signal from the ECU 24 based on the signal from the temperature sensor 22 causes the first control valve 26 to rotate clockwise in the figure. By being moved, the branch passage 14 branched from the exhaust passage 8 is closed, and at the same time, the exhaust passage 8 is opened. Here, the first bypass passage 30 as a part of the branch passage remains open. Further, the second control valve 28 is rotated by the signal from the ECU 24 based on the signal from the temperature sensor 22 so as to block the branch passage 14 from the outside air. Furthermore, the third control valve 3
Reference numeral 2 indicates a clock in the figure by a signal from the ECU 24 based on a signal from the temperature sensor 22 so as to block the downstream of the catalyst cylinder 16 and the upstream of the HC adsorption bed 18 and connect the first bypass passage 30 and the branch passage 14 together. It is rotated around.

The flow of exhaust gas when each control valve is in the above state will be described step by step. Catalytic converter 1
In No. 0, the monolith catalyst 9 therein is already activated, so the exhaust gas discharged from the engine 4 passes through the catalytic converter 10 and is purified. The exhaust gas purified by the catalytic converter 10 is silenced via the muffler 12. Most of the exhaust gas is discharged to the atmosphere through the exhaust passage 8 as it is, but a part of the exhaust gas is
It is introduced into the branch passage 14 via the bypass passage 30. Here, the introduction of the exhaust gas into the branch passage 14 is performed by the communication passage 34.
By arranging, the negative pressure in the intake manifold 2 can be utilized. Since the first control valve 26 closes the branch passage 14 and the introduction of the exhaust gas from the first bypass passage 30 into the branch passage 14 is performed by using the negative pressure in the intake manifold 2 as described above. It is considered that there is almost no exhaust gas flowing from the first bypass passage 30 to the catalyst cylinder 16.

The exhaust gas introduced into the branch passage 14 from the first bypass passage 30 first passes through the HC adsorption bed 18. The HC adsorbed by the HC adsorbent 17 installed in the HC adsorption bed 18 is desorbed by the heat of the exhaust gas at a temperature higher than the activation temperature of the monolith catalyst 9. Detached H
The exhaust gas containing C then passes through the NOx absorption bed 20. The NOx absorbed by the NOx absorbent 19 installed in the NOx absorption bed 20 is desorbed by the heat of the exhaust gas at a temperature higher than the activation temperature of the monolith catalyst 9 and the heat of the exhaust pipe 7. In the downstream of the NOx absorption bed 20, the second
Since the control valve 28 is rotated so as to block the branch passage 14 from the outside air, the exhaust gas containing desorbed HC and NOx is introduced into the intake manifold 2 through the communication passage 34. The exhaust gas containing HC and NOx introduced into the intake manifold 2 is fed to the engine 4,
It is introduced into the exhaust passage 8 again through the exhaust manifold 6 and is purified by the catalytic converter 10 together with the exhaust gas discharged from the engine 4. Further, the HC adsorbing bed 18 and the NOx absorbing bed 20 recover their adsorbing ability and absorbing ability due to desorption of HC and NOx.

As described above, according to the exhaust emission control system for the internal combustion engine in the first embodiment of the present invention, the first control valve 26 closes the branch passage 14 when the monolith catalyst 9 is at the activation temperature or higher, and The exhaust gas is introduced from the bypass passage 30 to the branch passage 14 by the intake manifold 2 as described above.
Since the internal negative pressure is used, it is considered that there is almost no exhaust gas flowing from the first bypass passage 30 to the catalyst cylinder 16. Therefore, the CO oxidation catalyst 15 in the catalyst cylinder 16 does not deteriorate, the purification ability of the CO oxidation catalyst 15 is maintained, and the exhaust gas at low temperature can be effectively purified.

When the monolith catalyst 9 in the catalytic converter 10 is below the activation temperature, the catalyst cylinder 16 and the HC adsorption bed 1
8. The exhaust gas is purified by the NOx absorption bed 20 and then released into the atmosphere. Therefore, even if the monolith catalyst 9 in the catalytic converter 10 is not activated, most of the harmful substances in the exhaust gas released into the atmosphere are removed. When the monolith catalyst 9 in the catalytic converter 10 is at the activation temperature or higher, the heat of the exhaust gas discharged at that time desorbs HC and NOx in the HC adsorption bed 18 and the NOx absorption bed 20,
Since it is introduced into the intake manifold 2, the catalytic converter 10 together with the exhaust gas discharged from the engine 4
Is purified by. Therefore, HC and NOx when the monolith catalyst 9 in the catalytic converter 10 is not activated can be purified. In addition, the HC adsorption bed 18 and the NOx absorption bed 2
0 desorbs HC and NOx, and recovers its adsorption capacity and absorption capacity.

FIG. 2 is a block diagram of an exhaust purification system for an internal combustion engine showing a second embodiment of the present invention. Instead of the first bypass passage 30 in the first embodiment of the present invention, a second bypass passage 36 that bypasses the catalyst cylinder 16 in the branch passage 14 is provided. 38 is an exhaust gas inlet, and 40 is an exhaust gas outlet. Further, the exhaust gas inlet portion 38 serves as an exhaust gas shut-off means for switching the flow of exhaust gas by a signal from the ECU 24 based on a signal from the temperature sensor 22 instead of the third control valve 32 in the first embodiment of the present invention. A fourth control valve 42 is provided. The other structure is the same as that of the first embodiment.

Next, the operation of the second embodiment of the present invention will be described. When the temperature detected by the temperature sensor 22 is lower than the activation temperature of the monolith catalyst 9 in the catalytic converter 10, a signal from the ECU 24 based on a signal from the temperature sensor 22 causes the fourth control valve 42 to rotate counterclockwise in the figure. Being rotated,
At the same time when the branch passage 14 is opened, the second bypass passage 3 is opened.
6 is closed. The operation of the first control valve 26 and the second control valve 28 is the same as in the first embodiment.

The flow of exhaust gas when each control valve is in the above state will be described step by step. Catalytic converter 1
The exhaust gas that has not been purified by 0 is silenced through the muffler 12 and then introduced into the branch passage 14. Here, the exhaust gas is introduced into the branch passage 14 by utilizing the negative pressure in the intake manifold 2 by disposing the communication passage 34. The exhaust gas introduced into the branch passage 14 first passes through the catalyst cylinder 16, and the CO oxidation catalyst 15 installed in the catalyst cylinder 16 oxidizes the CO in the exhaust gas. The exhaust gas from which CO has been removed next passes through the HC adsorption bed 18, and the HC in the exhaust gas is adsorbed by the HC adsorbent 17 installed in the HC adsorption bed 18. CO, HC
The exhaust gas from which NO has been removed then passes through the NOx absorption bed 20, and the NOx absorbent 19 installed in the NOx absorption bed 20 absorbs NOx in the exhaust gas. NOx absorption bed 2
On the downstream side of 0, since the second control valve 28 is rotated so that the branch passage 14 can communicate with the outside air, CO,
The exhaust gas from which HC and NOx have been removed is released into the atmosphere.

Next, when the monolith catalyst 9 is activated by the heat of the exhaust gas passing through the catalytic converter 10, that is, the temperature detected by the temperature sensor 22 is the catalytic converter 10.
The time when the activation temperature of the monolith catalyst 9 in FIG. When the temperature detected by the temperature sensor 22 is equal to or higher than the activation temperature of the monolith catalyst 9 in the catalytic converter 10, the signal from the ECU 24 based on the signal from the temperature sensor 22 causes the first control valve 26 to rotate clockwise in the figure. Is moved,
A part of the branch passage 14 branched from the exhaust passage 8 is maintained in an open state. That is, the first control valve 26 is controlled to a position where both the exhaust passage 8 and the branch passage 14 are half opened. Further, the fourth control valve 42 is rotated clockwise in the figure by a signal from the ECU 24 based on the signal from the temperature sensor 22, the branch passage 14 to the catalyst cylinder 16 is blocked, and the second bypass passage is provided. 36 is opened. The operation of the second control valve 28 is the same as that of the first embodiment.

The flow of exhaust gas when each control valve is in the above state will be described step by step. Catalytic converter 1
In No. 0, since the monolith catalyst 9 inside thereof has already been activated, the exhaust gas that has passed through the catalytic converter 10 has been purified. The exhaust gas purified by the catalytic converter 10 is silenced via the muffler 12. Most of the exhaust gas is discharged to the atmosphere through the exhaust passage 8 as it is, but the first control valve 26 does not discharge the exhaust passage 8 nor the branch passage 14.
The exhaust gas is partly introduced into the branch passage 14 because it is controlled to a half-open position. Here, branch passage 1
The exhaust gas is introduced into the intake manifold 4 by utilizing the negative pressure in the intake manifold 2 by disposing the communication passage 34. Since the fourth control valve 42 blocks the flow of exhaust gas to the catalyst cylinder 16, the exhaust gas is not introduced into the catalyst cylinder 16. The exhaust gas introduced into the branch passage 14 is
It is entirely introduced into the second bypass passage 36 from the exhaust gas inlet 38, passes through the exhaust gas outlet 40, and passes through the HC adsorption bed 18. As described above, since the exhaust gas is introduced into the branch passage 14 by utilizing the negative pressure in the intake manifold 2, it is considered that there is almost no exhaust gas flowing from the exhaust gas outlet portion 40 toward the catalyst cylinder 16 side. .

HC adsorbent 1 installed in the HC adsorption bed 18
The HC adsorbed by 7 is desorbed by the exhaust gas at a temperature higher than the activation temperature of the monolith catalyst 9. The exhaust gas containing the desorbed HC then passes through the NOx absorption bed 20. NOx absorbent 1 installed in the NOx absorption bed 20
The NOx absorbed by 9 is desorbed by the exhaust gas at a temperature higher than the activation temperature of the monolith catalyst 9. NO
At the downstream of the x absorption bed 20, the second control valve 28 is rotated so as to block the branch passage 14 from the outside air, so that the exhaust gas containing desorbed HC and NOx is communicated with the communication passage 3
It is introduced into the intake manifold 2 via 4. HC and N introduced into the intake manifold 2
The exhaust gas containing Ox is introduced again into the exhaust passage 8 through the engine 4 and the exhaust manifold 6, and together with the exhaust gas discharged from the engine 4, the catalytic converter 1
Purified by 0. Further, the HC adsorbing bed 18 and the NOx absorbing bed 20 recover their adsorbing ability and absorbing ability due to desorption of HC and NOx.

As described above, according to the exhaust emission control system for the internal combustion engine in the second embodiment of the present invention, when the monolith catalyst 9 is at the activation temperature or higher, the first control valve 26 makes the branch passage 14 half open, but Since the control valve 36 blocks the flow of the exhaust gas to the catalyst cylinder 16, the exhaust gas is not introduced into the catalyst cylinder 16. As described above, since the exhaust gas is introduced into the branch passage 14 by utilizing the negative pressure in the intake manifold 2, it is considered that there is almost no exhaust gas flowing from the exhaust gas outlet portion 40 toward the catalyst cylinder 16 side. . Therefore, the CO oxidation catalyst 15 in the catalyst cylinder 16 does not deteriorate,
The purification ability of the CO oxidation catalyst 15 is maintained, and the exhaust gas at low temperature can be effectively purified.

Further, when the monolith catalyst 9 in the catalytic converter 10 is below the activation temperature, the catalyst cylinder 16 and the HC adsorption bed 1
8. The exhaust gas is purified by the NOx absorption bed 20 and then released into the atmosphere. Therefore, even if the monolith catalyst 9 in the catalytic converter 10 is not activated, most of the harmful substances in the exhaust gas released into the atmosphere are removed. When the monolith catalyst 9 in the catalytic converter 10 is at the activation temperature or higher, the heat of the exhaust gas discharged at that time desorbs HC and NOx in the HC adsorption bed 18 and the NOx absorption bed 20,
Since it is introduced into the intake manifold 2, the catalytic converter 10 together with the exhaust gas discharged from the engine 4
Is purified by. Therefore, HC and NOx when the monolith catalyst 9 in the catalytic converter 10 is not activated can be purified. In addition, the HC adsorption bed 18 and the NOx absorption bed 2
0 desorbs HC and NOx, and recovers its adsorption capacity and absorption capacity.

Although the temperature sensor 22 is provided upstream of the catalytic converter 10 in the above embodiments, it may be possible to provide it at the downstream of the catalytic converter 10. It is also conceivable to use the elapsed time after starting the engine 4 as a means for indirectly detecting the temperature of the catalytic converter 10. Further, if a flow rate control valve that controls the flow rate of the exhaust gas into the intake manifold 2 is provided in the communication passage 34, the air-fuel ratio can be controlled more finely. In addition, communication passage 3
4 may be provided between the branch passage 14 and the exhaust passage 8 upstream of the catalytic converter 10 (in that case, a pump for guiding the exhaust gas from the branch passage 14 to the upstream of the catalytic converter 10 is required), and the catalyst cylinder 16 is provided. , HC adsorption bed 18, NOx
The arrangement order of the absorption beds 20 is not limited to the embodiment of the present invention, and various modes can be considered.

[0029]

According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention, when the catalyst in the catalytic converter is at the activation temperature or higher, the high temperature exhaust gas is not introduced into the catalyst cylinder by the exhaust cut-off means, The CO oxidation catalyst does not deteriorate. Therefore, the purification ability of the CO oxidation catalyst is maintained, and the exhaust gas at low temperature can be effectively purified.

When the temperature of the catalyst in the catalytic converter is lower than the activation temperature, the exhaust gas is purified by the catalyst cylinder and the trapping means and then released into the atmosphere. Therefore, even if the catalyst in the catalytic converter is not activated, most of the harmful substances in the exhaust gas released into the atmosphere are removed. When the temperature of the catalyst in the catalytic converter is higher than the activation temperature, the heat of the exhaust gas discharged at that time desorbs HC and NOx trapped by the trapping means and introduces it upstream of the catalytic converter for purification by the catalytic converter. To be done. Therefore, when the catalyst in the catalytic converter is not activated, HC and N
Ox can also be purified. Further, the capturing means is HC, NOx
By desorbing, the adsorption capacity and absorption capacity are restored.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of an exhaust emission control device for an internal combustion engine according to a second embodiment of the present invention.

[Explanation of symbols]

 2 ... Intake manifold 4 ... Engine 6 ... Exhaust manifold 8 ... Exhaust passage 10 ... Catalytic converter 14 ... Branch passage 16 ... Catalyst cylinder 18 ... HC adsorption bed 20 ... .... NOx absorption bed 22 ... Temperature sensor 26 ... First control valve 28 ... Second control valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F01N 3/24 ZAB CEN F02M 25/07 ZAB Z

Claims (1)

[Claims] 1. A catalytic converter provided in an exhaust passage of an internal combustion engine, a branch passage provided downstream of the catalytic converter, and a first control valve for controlling an opening degree of the branch passage with respect to the exhaust passage according to a catalyst temperature in the catalytic converter. And a catalyst tube provided in the branch passage and containing a trapping means for absorbing or adsorbing HC or NOx and a CO oxidation catalyst, a catalyst tube provided downstream of the trapping means and the catalyst tube, and the catalyst in the catalytic converter is below the activation temperature. A second control valve that opens to communicate the branch passage with the outside air, and closes the catalyst in the catalytic converter to shut off the branch passage from the outside air when the catalyst in the catalytic converter is at an activation temperature or higher; An exhaust gas purification apparatus for an internal combustion engine, comprising: a trapping means, a downstream of the catalyst cylinder, and a communication passage that communicates with a catalytic converter upstream, the catalyst cylinder being used when the catalyst in the catalytic converter is at an activation temperature or higher. An exhaust gas purifying apparatus for an internal combustion engine, comprising: an exhaust gas cut-off means for cutting off high-temperature exhaust gas.