JP3125647B2 - Engine exhaust 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 engine exhaust gas purifying apparatus for purifying HC (hydrocarbon) contained in exhaust gas discharged from an engine.

[0002]

2. Description of the Related Art White smoke discharged when a diesel engine mounted on an automobile is cold contains a large amount of HC. In order to obtain good exhaust gas performance, it is necessary to purify this HC.

Therefore, it is conceivable to adsorb HC contained in exhaust gas using an HC adsorbent. However, simply adsorbing cannot maintain HC adsorption performance.

Therefore, recently, Japanese Patent Application Laid-Open No. 5-44446 discloses
There has been proposed an engine exhaust gas purification apparatus that regenerates and uses an HC adsorbent as disclosed in Japanese Unexamined Patent Publication (Kokai) Publication. In this engine exhaust purification device, as shown in FIG. 7, a bypass path c is provided upstream of an exhaust gas path b of an engine a, an HC adsorbent d is interposed in the bypass path c, and a downstream side of the exhaust gas path b is provided. The bypass e is provided with an on-off valve h at an inlet f and an outlet g of the bypass c, and a fresh air introduction passage i is provided at the outlet of the bypass c to communicate with the atmosphere via an air cleaner. Are connected to each other, and the inlet side of the bypass path c and the intake path j of the engine a are communicated via the introduction path k. In addition, m shows the on-off valve interposed in the introduction path k.

According to this exhaust gas purifying apparatus, when white smoke is discharged, for example, when the engine is cold, the on-off valve m is closed and each on-off valve h is opened toward the bypass as indicated by the solid line. As a result, the exhaust gas discharged from the engine a
As shown by the solid arrow in FIG. 7, the HC is adsorbed by the HC adsorbent d on the way so as to be introduced into the catalyst e via the bypass passage c.

[0006] Thereafter, when the engine is warmed to reduce the amount of HC, the on-off valve m is opened and each on-off valve h is closed on the bypass side as shown by the broken line, thereby obtaining the intake passage j.
At the intake negative pressure of, fresh air (atmosphere) is taken into the introduction path k from the fresh air introduction path i through the HC adsorbent d as shown by the dashed arrow in FIG.

At this time, the HC adsorbed on the HC adsorbent d is desorbed, returned to the intake side of the engine a, and burned again. As a result, the HC
The adsorbent d is regenerated.

[0008]

By the way, although the HC adsorbent is composed of an absorbing substance such as zeolite, it is known that the performance of the HC absorbent depends on the temperature. Specifically, the HC adsorbent has a property that when the temperature is low, it is easy to adsorb HC, and when the temperature rises, the action of desorbing the adsorbed HC becomes strong.

Therefore, in the conventional low-temperature atmosphere (fresh air),
With a structure that desorbs HC adsorbed on HC adsorbent d, HC
HC cannot be completely desorbed from the adsorbent d. Moreover,
The HC returned to the intake side of the engine a exhibits the behavior of being discharged again from the engine a without being combusted by the engine a, so that a sufficient purification effect cannot be expected.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine exhaust system capable of obtaining a sufficient HC purification effect by maximizing the regeneration capability of an HC adsorbent. It is to provide a purification device.

[0011]

According to a first aspect of the present invention, there is provided an HC adsorbent provided in a bypass passage branched from an exhaust gas passage of an engine, and the HC adsorbent is lifted. A heater for heating the fuel and an exhaust gas passage on the downstream side of the HC adsorbent.
Catalyst for reducing and purifying NOx , and upstream of the NOx reduction catalyst
Is provided in the exhaust gas passage on the side, and injects the reducing agent into the exhaust gas.
When the NOx reduction catalyst is inactive, HC contained in the exhaust gas is adsorbed by the HC adsorbent through the bypass passage when the NOx reduction catalyst is inactive. Desorb HC and NO
x reduction catalyst, and at the inlet of the NOx reduction catalyst.
The ratio of NOx to HC in the NOx reduction catalyst
From the reducing agent injection means so that the ratio is appropriate for the reduction of
It is to purify NOx with a NOx reduction catalyst by injecting a base agent .

[0012] In addition to the above objects, the invention described in claim 2 is intended to further purify blow-by gas.
The upstream side of the HC adsorbent of the exhaust gas passage according to claim 1,
It is connected to the blow-by gas passage of the engine.

[0013] In addition to the above objects, the present invention described in claim 3 is intended to effectively utilize the characteristics of the HC adsorbent to adsorb and desorb HC. A valve device for switching the flow of exhaust gas is provided at the entrance of the bypass passage described in 2.

[0014]

[0015]

According to a third aspect of the present invention, the operation of the valve device and the heater according to the third aspect is controlled by control means in order to further functionally operate the engine exhaust gas purifying apparatus according to the operating state of the engine. In accordance with the operation state of the engine, an adsorption mode in which the valve device is fully opened to the bypass passage side, a desorption mode in which the valve device is opened to a predetermined opening and the heater is operated, and a stop in which the valve device is fully closed to the bypass passage side. The control may be performed in the mode.

[0017] As embodiments of claims 3 and also to control of each mode is easily performed, the adsorption mode, the cooling water temperature of the engine is below a predetermined value, or when the exhaust temperature of the engine is lower than a predetermined value, Alternatively, it may be activated when the engine brake is activated.

[0018] embodiment of the third aspect, the same Ku desorption mode, a cooling water temperature of the engine is higher than a predetermined value, and the exhaust gas temperature of the engine may be operated when the predetermined value range.

[0019] embodiment of the third aspect, the same Ku hibernate mode, when the operating condition of the engine other than the adsorption mode and desorption mode, or engine may be operated at shutdown.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on a first embodiment shown in FIGS. FIG. 1 shows a schematic configuration of an engine exhaust gas purification device provided in an engine exhaust system. In FIG. 1, reference numeral 1 denotes a running diesel engine mounted on a vehicle such as a bus or a truck.

From the exhaust side of the cylinder head 1a of the diesel engine 1, an exhaust pipe 2 forming an exhaust gas passage is provided.
Is extending. On the upstream side of the exhaust pipe 2, there is formed a bypass passage 3 which branches off from the exhaust pipe 2 and merges again.

At the inlet 3a of the bypass passage 3, for example, a solenoid-operated on-off valve 4 (corresponding to a valve device) for opening and closing between the inlet 3a and the exhaust pipe 2 is provided. The flow of the discharged exhaust gas is switched so as to be guided to the bypass path 3 side or to the exhaust pipe 2a side.

An HC adsorbing device 5 is interposed in the bypass 3. The HC adsorbing device 5 includes, for example, a housing case 6 having an inlet and an outlet connected to the bypass path 3, and an HC adsorbent 7 made of an adsorbent such as zeolite provided to occupy most of the case 6. And

The HC adsorbent 7 can adsorb HC (hydrocarbon) contained in exhaust gas through the bypass 3. Further, a heater, for example, an electric heater 8 is provided on the inlet side in the housing case 6 near the HC adsorbent 7 so that the temperature of the HC adsorbent 7 can be increased by heating. is there.

Further to the exhaust pipe downstream portion of the bypass passage 3, NO _X reduction catalyst 9 reduces and purifies NO _X and HC as a reducing agent is interposed. On the other hand, 10 is a controller as control means.

The controller 10 includes, for example, a microcomputer and its peripheral devices. A water temperature sensor 11 for detecting a cooling water temperature of the diesel engine 1 and an exhaust gas temperature sensor 12 for detecting an exhaust gas temperature on an upstream side of the exhaust pipe 2 (upstream of the HC adsorbent 7) are connected to the controller 10. ing.

The controller 10 further includes an E / G (engine) speed sensor 13 for detecting the engine speed.
a, accelerator opening sensor 13b for detecting accelerator opening
(A sensor that detects the engine load) is connected.

As a result, the controller 10
Recognize the engine operation state where C emission is large,
Information necessary for recognizing whether the NO _X reduction catalyst 9 is in the inactive region or the active region is provided.

An on-off valve 4 and an electric heater 8 are connected to the controller 10. Then, by this controller 10, engine operating conditions, NO _X reduction catalyst 9
Based on the active state, the on-off valve 4, to operate the electric heater 8, HC emissions in large, and the HC adsorbent 7 when NO _X reduction catalyst 9 is in an inactive region (the following areas activation temperature) HC is adsorbed, and the HC adsorbed by the HC adsorbent 7 is desorbed when the NO _X reduction catalyst 9 is in an active region (an active temperature range in which NO _X is reduced and purified by addition of HC).
The function of the C adsorption device 5 is stopped.

That is, FIG.
, Three modes of an adsorption mode, a desorption mode, and a rest mode are set. Specifically, in the adsorption mode, the cooling water temperature is equal to or lower than a predetermined value, for example, the water temperature is 60 ° C.
(T ₁ ) or lower, or when the exhaust temperature is equal to or lower than a predetermined value, for example, when the exhaust temperature is equal to or lower than 150 ° C. (T ₂ ). Rotation speed rises)
This is performed by fully opening the on-off valve 4 to the bypass path side.

In the desorption mode, the cooling water temperature is higher than a predetermined value,
For example, when the water temperature is equal to or higher than 80 ° C. (T ₃ ) and the exhaust gas temperature is in a predetermined value range, for example, when the exhaust gas temperature is in the temperature range of 700 ° C. to 250 ° C., the on-off valve 4 is half-opened and the electric heater 8 is turned on. It is performed by turning on.

In the stop mode, when the engine is operating in modes other than the adsorption mode and the desorption mode, or when the engine is stopped (the accelerator opening is 0 and the engine speed is 0), the on-off valve 4 is fully closed to the bypass road side, This is performed by turning off the heater 8.

In this exhaust gas purifying apparatus, the desorbed H
When C content (HC to be added to the NO _X reduction catalyst 9) is insufficient, the system is provided to supplement the HC amount. To explain the system, reference numeral 14 denotes an HC sensor provided at an exhaust pipe portion on the inlet side of the NO _X reduction catalyst 9 for detecting the amount of HC (or HC concentration: corresponding to HC detecting means) at the catalyst inlet, and 15 denotes an HC sensor. Similarly, the NO _X amount at the catalyst inlet (or NO _X
Concentration: corresponds to the NO _X detection means) is NO _X sensor for detecting.

[0034] These HC sensor 14, NO _X sensor 15
, Which is connected to the controller 10, HC in the exhaust gas entering the NO _X reduction catalyst 9, are to provide a NO _X information to the controller 10.

A device for adding a reducing agent (with respect to the NO _x reduction catalyst 9) to the upstream side of the NO _x reduction catalyst 9, specifically, to the exhaust pipe portion upstream of each of the sensors 14 and 15, for example, Light oil injection device 1 that injects light oil into the pipe as a reducing agent
6 (corresponding to reducing agent injection means) is provided.

In the light oil injection device 16, for example, a light oil injection valve 17 is provided in an exhaust pipe portion 2a between the inlet 3a and the outlet 3b of the bypass passage 3, and the light oil injection valve 17 and a fuel tank 18 containing, for example, light oil are provided. Is connected by a circulation line 19 having a pump 19a interposed therebetween.

The light oil injection valve 17 is connected to the controller 10. The controller 10, upon desorption mode, NO ratio of the amount of NO _X and HC amount at the inlet of the NO _X reduction catalyst 9 reduction purification is performed efficiently at a predetermined constant rate of (NO _X reduction catalyst 9 _X: HC ratio), for example, NO _X
A function of controlling the injection operation of the light oil injection valve 17 is set so that the amount: HC amount = 1: 3, so that HC can be added to the NO _X reduction catalyst 9 without shortage.

With such an engine exhaust gas purifying apparatus,
HC purification can be performed by utilizing the capacity of the HC adsorbent 7. FIG. 3 shows a control functioning as an operation of the engine exhaust gas purifying apparatus.

Next, the operation of the engine exhaust gas purifying apparatus will be described with reference to the flowchart shown in FIG. The diesel engine 1 is started.

At this time, the controller 10 determines whether or not the engine has been operated as in step S1.
Proceed to 2.

By this step S2, the controller 10 sends the water temperature sensor 11 and the exhaust gas temperature sensor 12
The cooling water temperature and the exhaust gas temperature of the diesel engine 1 are read. In step S3, it is determined whether or not to enter the suction mode. Specifically, is the cooling water temperature <T ₁ (for example, 60 ° C.)
Alternatively, the determination is made based on whether the exhaust gas temperature is smaller than T ₂ (for example, 150 ° C.).

At this time, for example, the diesel engine 1
However, assuming that the temperature is in a cold state where white smoke is discharged, the cooling water temperature and the exhaust gas temperature are both equal to or lower than predetermined values. That is, the controller 10 determines that the amount of HC emission is large and the NO _X reduction catalyst 9 has not reached the active region, and
Reaches 4.

Then, as shown in FIG. 4, the controller 10 operates the on-off valve 4 to be fully opened with respect to the bypass path side. As a result, the exhaust gas containing a large amount of HC discharged from the diesel engine 1 passes through the bypass passage 3 and the HC adsorbent 7 as shown by the arrow in FIG.
Through O _X reduction catalyst 9 will be discharged to the atmosphere.

Here, since the HC adsorbent 7 is maintained at a low temperature in which it is easily adsorbed, it adsorbs HC contained in the exhaust gas. Next, the warm-up operation of the diesel engine proceeds, the cooling water temperature exceeds T ₁ (60 ° C.), and the exhaust gas temperature becomes T _2.
(150 ° C.).

Then, the process proceeds from step S3 to step S5. Here, assuming that the vehicle is running after the warm-up and the engine brake is used, the operation returns to the adsorption mode (step S4) again, and the emission of HC discharged from the diesel engine to the atmosphere due to the engine brake is suppressed.

On the other hand, if it is assumed that the vehicle is running without using the engine brake after the warm-up, the process proceeds from step S5 to step S6. In step S6, it is determined whether or not to enter the desorption mode. Specifically, cooling water temperature> T
₃ (eg, 80 ° C.) and T ₄ (eg, 700 ° C.)>
Exhaust gas temperature> T ₅ (e.g. 250 ° C.) or is determined by whether.

In normal traveling, both the water temperature and the exhaust gas temperature fall within the range defined by the above temperature values. That is, the controller 10 determines that the active region of the NO _X reduction catalyst 9 has been reached (the active temperature range in which NO _X is reduced and purified by the addition of HC), and the process proceeds to step S7.

Then, the controller 10 half-opens the on-off valve 4 and activates the electric heater 8 as shown in FIG. Thereby, the HC adsorbent 7 is quickly heated.

Here, the HC adsorbent 7 has a property that the action of releasing the adsorbed HC becomes stronger as the temperature rises. As a result, the previously adsorbed HC is efficiently desorbed from the HC adsorbent 7, rides on the exhaust gas flowing through the bypass 3, and is guided to the downstream side of the exhaust pipe 2.

Then, the HC is added to the NO _x reduction catalyst 9. Then, the NO _X reduction catalyst 9 uses this HC as a reducing agent to reduce and purify NO _X contained in the combined exhaust gas.

As a result, HC, NO contained in the exhaust gas
_X is broken down together into harmless components. At this time, the controller 10 determines the HC amount (or HC concentration) and the NO _X amount (or NO _X concentration) at the inlet of the NO _X reduction catalyst 9 from the HC sensor 14 and the NO _X sensor 15 as in the next step S8. I'm reading.

[0052] Further, in step S9 the following, the controller 10, HC amount to be added to the NO _X reduction catalyst 9 is determined whether or missing is an amount suitable for reducing and purifying. Specifically, NO _X amount (or NO _X concentration) 1
To, say the amount of HC (or HC concentration) at a ratio of 3, the amount of HC necessary for reduction and purification of the NO _X is, NO
_The determination is made based on whether or not the catalyst is introduced into the _X reduction catalyst 9.

If the amount of HC to be added is not insufficient, the process proceeds to step S10, and the desorption mode continues without operating the light oil injection valve 17. If it is determined that the amount of HC to be added is insufficient, the process proceeds to step S11, and the controller 10 turns on the light oil injection valve 17.

At this time, the pump 19 of the light oil injection device 16
In a, for example, the engine is driven to pump light oil from the fuel tank 18, so light oil is injected from the light oil injection valve 17 into the pipe on the upstream side of the sensor with the ON signal.

This injection of light oil is performed until the above condition is satisfied. As a result, the NO _X reduction catalyst 9
Under the C amount, reduction purification of NO _X is performed.

The desorption mode and the adsorption mode are as follows.
The switching is performed as appropriate in accordance with the driving state of the vehicle to suppress the emission of HC into the atmosphere. In cases other than the adsorption mode and the desorption mode, for example, when the exhaust gas temperature exceeds 700 ° C., the process proceeds to step S12, where the on-off valve 4 is fully closed to the bypass path side as shown in FIG.
Then, the light oil injection valve 17 is turned off to suspend the HC adsorbent device 5 (rest mode).

When the diesel engine 1 is stopped, the HC adsorber 5 is similarly stopped. In the case of an engine exhaust gas purifying apparatus that raises the temperature of the HC adsorbent 7 and desorbs the HC adsorbed on the HC adsorbent 7, it is possible to completely desorb HC from the HC adsorbent 7. .

[0058] Moreover, by directly utilizing the desorbed HC as a reducing agent, so NO _X reducing engine exhaust gas purifying apparatus to be processed by the catalyst 9, even includes a state in which white smoke is discharged, any engine operating condition However, emission of HC into the atmosphere is prevented.

Therefore, according to the engine exhaust gas purifying apparatus to which the present invention is applied, a sufficient HC purifying effect can be obtained by making the most of the regeneration capability of the HC adsorbent 7. When an on-off valve 4 is provided at the inlet 3a of the bypass passage 3, HC
Exhaust gas containing a large amount of water can be intensively led to the HC adsorbent 7, and the HC adsorbent 7 can be efficiently heated by the electric heater 8, so that the characteristics of the HC adsorbent 7 can be effectively utilized. The adsorption and desorption of the HC can be performed.

In addition, the controller 10 controls the adsorption mode (opening the on-off valve 4 fully to the bypass path side), the desorption mode (opens the on-off valve 4 to a predetermined opening and operates the electric heater 8), and the rest mode (opens the on-off valve 4). Is fully closed on the bypass road side), the engine exhaust purification device is functionally operated according to the operating state of the engine.

In particular, when each of the adsorption mode, the desorption mode, and the stop mode is defined mainly by the cooling water temperature of the diesel engine 1, the exhaust temperature of the diesel engine 1, and the like, the control of each mode becomes easy.

[0062] Also when insufficient desorbed HC is, providing a light oil diesel injector 16 added (reducing agent) (a reducing agent injection means), and effectively utilize the characteristics of the NO _X reduction catalyst 9 in the active region Can decompose HC.

In particular, when light oil is injected from the light oil injection device 16 so that the ratio between the NO _X amount and the HC amount becomes a predetermined constant ratio, the NO _X reduction catalyst 9 operates sufficiently. As defined, N using desorbed HC as a reducing agent
Reduction and purification of O _X is most effectively performed.

FIG. 6 shows a second embodiment of the present invention.
In the present embodiment, the exhaust pipe portion on the upstream side of the HC
A blow-by gas port 20 provided in an engine body 1b of the diesel engine 1, for example, a crankcase 1c.
(Blow-by gas passage)
Are connected to each other. Of course, although not shown, if the cylinder head 1a has a blow-by gas port, the upstream side of the exhaust pipe 2 may be connected to the port via a blow-by gas introduction pipe.

According to the present embodiment, not only the exhaust gas,
Blow-by gas (compression leak air from piston ring,
Combustion gas leaking from the piston rings into the combustion stroke, mist or the like is mixed gas of the lubricating oil) may also adsorb and desorption of HC by HC adsorbent 7, of the NO _X which was the HC by the NO _X reduction catalyst 9 reducing agent Purification can be performed using reduction purification.

However, in FIG. 6, the components other than the system for processing blow-by gas are the same as those of the first embodiment, and therefore, the same parts are denoted by the same reference numerals and description thereof is omitted. In both the first and second embodiments, light oil (reducing agent) is injected from a light oil injection device (reducing agent injection means) so that a predetermined NO _X : HC ratio is achieved, so that the shortage of HC is eliminated. But
The present invention is not limited to this. For example, a target HC amount for a certain NO _X amount (or NO _X concentration) is mapped using an engine speed and an engine load (accelerator opening degree),
According to this map, the controller may cause the light oil injection device to inject light oil when the HC is insufficient.
Also, an example in which the present invention is applied to a diesel engine has been described, but the present invention is not limited to this, and may be applied to other engines.

[0067]

According to the invention described in claim 1 as described in the foregoing, and take full advantage of the regenerative capacity of the HC adsorbent, it is possible to obtain a sufficient HC purification effect. Moreover,
The characteristics of the NOx reduction catalyst can be effectively used.
Furthermore, NOx reduction and purification using HC as a reducing agent
Can be performed most effectively.
Can be .

According to the invention described in claim 2, according to claim 1
In addition to the effects of the invention, the effect of purifying the blow-by gas can be achieved at the same time. According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the invention, the characteristics of the HC adsorbent are effectively utilized to adsorb HC,
This has the effect that desorption can be performed.

[0069]

[0070]

According to a third aspect of the present invention, the control means includes:
Move the valve device to the bypass side according to the operating condition of the engine.
When the suction mode is set to fully open and the valve device is opened to a predetermined opening,
Desorption mode that mainly operates the heater, bypasses the valve device
In the case of control in the stop mode in which the road side is fully closed,
, Depending on the operating conditions of the engine, functionally achieve the effect referred to can actuate the engine exhaust purifying device
Can be .

According to a third aspect of the present invention, the adsorption mode is set when the temperature of the engine coolant is equal to or lower than a predetermined value, or when the exhaust gas temperature of the engine is equal to or lower than a predetermined value, or when the engine brake is operated. The engine is activated when the engine coolant temperature is equal to or higher than a predetermined value and the exhaust gas temperature of the engine is within a predetermined value range, or when the engine is in an operation state other than the adsorption mode and the desorption mode or when the engine is stopped. In the case of operating, it is possible to obtain an effect that control of each of the adsorption mode, the desorption mode, and the pause mode can be easily performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an engine exhaust gas purification apparatus according to a first embodiment of the present invention.

FIG. 2 is a view for explaining settings of each of an adsorption mode, a desorption mode, and a stop mode of the engine exhaust gas purification apparatus.

[3] according to the engine operating condition of the engine exhaust gas purification apparatus, the HC adsorption by HC adsorbent, reduction purification by HC desorption, NO _X reduction catalyst and a reducing agent desorbed HC from the HC adsorbent 4 is a flowchart for explaining each step.

FIG. 4 is a view for explaining a state in an adsorption mode of the engine exhaust purification device.

FIG. 5 is a view for explaining a state in a desorption mode of the engine exhaust purification device.

FIG. 6 is a diagram illustrating an engine exhaust gas purification apparatus according to a second embodiment of the present invention.

FIG. 7 is a view for explaining a conventional engine exhaust gas purification apparatus for treating HC.

[Explanation of symbols]

1 ... diesel engine 2 ... exhaust pipe (exhaust passage) 3 ... bypass 4 ... off valve (valve unit) 5 ... HC adsorption device 7 ... HC adsorbent 8 ... electric heater 9 ... NO _X reducing catalyst 10 ... controller (control means 11) Water temperature sensor 12 ... Exhaust temperature sensor 13a ... E / G rotation speed sensor 13b ... Accelerator opening sensor (load sensor) 14 ... HC sensor 15 ... NO _X sensor 16 ... Light oil injection device (reducing agent injection means) 17 ... Light oil injection valve 20: blow-by gas port (blow-by gas passage) 21: blow-by gas introduction pipe.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI F01N 3/08 ZAB B01D 53/34 120D 3/28 301 53/36 101A 103B (72) Inventor Go Hashizume Shibago, Minato-ku, Tokyo No. 33-8, Mitsubishi Motors Corporation (72) Inventor Toshitaka Yokokawa 4-2-1-1, Shimomaruko, Ota-ku, Tokyo Mitsubishi Motors Engineering Co., Ltd. (56) References JP-A-6-33752 (JP) JP-A-7-19031 (JP, A) JP-A-5-44446 (JP, A) JP-A-4-303111 (JP, A) JP-A-6-81637 (JP, A) 2-94314 (JP, U) Shokai 58-165206 (JP, U) Shokai 2-94315 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 3/24 F01N 3/08 F01N 3/28 B01D 53/34 B01D 53/36

Claims (3)

(57) [Claims] 1. An HC adsorbent provided in a bypass passage branched from an exhaust gas passage of an engine, a heater for raising the temperature of the HC adsorbent, and an HC adsorber provided in an exhaust gas passage downstream of the HC adsorbent. A NOx reduction catalyst for reducing and purifying NOx with the use of a reducing agent as a reducing agent, and an exhaust gas upstream of the NOx reduction catalyst.
Reduction that is provided in the gas passage and injects a reducing agent into the exhaust gas
A material injection means, wherein at the time of deactivation of the NOx reduction catalyst, through the bypass passage, wherein the HC adsorbing the HC contained in the exhaust gas in the adsorber, at the time the activity of the NOx reduction catalyst, wherein in heating by the heater HC The HC is desorbed from the adsorbent and the NOx
Supply to the reduction catalyst and the inlet of the NOx reduction catalyst
The ratio of NOx to HC in the NOx reduction catalyst
Injection of the reducing agent so that the ratio becomes appropriate for the reduction of NOx
An exhaust gas purifying apparatus for an engine , wherein NOx is purified by the NOx reducing catalyst by injecting a reducing agent from an injection means . 2. The exhaust gas purifying apparatus according to claim 1, wherein an exhaust gas passage upstream of the HC adsorber is connected to a blow-by gas passage of the engine. 3. The engine exhaust gas purifying apparatus according to claim 1, wherein a valve device for switching a flow of exhaust gas is provided at an inlet of the bypass passage.