JP3552649B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to a nitrogen oxide (NO) contained in exhaust gas discharged from an internal combustion engine. _x The present invention relates to an exhaust gas purification device for an internal combustion engine that purifies the exhaust gas.
[0002]
[Prior art]
BACKGROUND ART In an internal combustion engine mounted on an automobile or the like, particularly an internal combustion engine driven by a mixture in an excessively oxidized state (a mixture having a lean air-fuel ratio) such as a diesel engine or a lean-burn gasoline engine, nitrogen oxides in exhaust gas ( NO _x Various techniques have been proposed to reduce the volume.
Nitrogen oxides in exhaust (NO _x As one of techniques for reducing the amount, for example, an exhaust gas recirculation device (EGR device: Exhaust Gas Recirculation device) that recirculates a part of exhaust gas flowing through an exhaust system of an internal combustion engine to an intake system is known. .
[0003]
This EGR device uses water (H ₂ O) and carbon dioxide (CO ₂ ) Is introduced into the combustion chamber of the internal combustion engine together with the air-fuel mixture, and the maximum combustion temperature of the air-fuel mixture is lowered by utilizing the non-combustibility and endothermic properties of the inert gas. Object (NO _x ) Is suppressed and the nitrogen oxides (NO _x ) The amount is reduced.
[0004]
In addition, nitrogen oxides (NO _x Other techniques for reducing the amount include selective reduction type NO. _x Catalyst and storage reduction type NO _x NO like catalyst _x A technique for arranging a catalyst in an exhaust system of an internal combustion engine is known. This is because the above-described EGR device uses nitrogen oxides (NO _x ) Itself, while the nitrogen oxides (NO _x ) Is purified before being released into the atmosphere.
[0005]
Selective reduction type NO _x The catalyst reacts with nitrogen oxides (NO _x ) Is a catalyst that reduces or decomposes).
This selective reduction type NO _x Nitrogen oxides (NO _x ) Requires an appropriate amount of a reducing agent. However, when the internal combustion engine is operated at a lean air-fuel ratio, the amount of hydrocarbons (HC) in the exhaust gas is extremely small. When operating at a lean air-fuel ratio, nitrogen oxides (NO _x ) Is purified by selective reduction type NO _x It is necessary to separately supply a reducing agent to the catalyst.
[0006]
Storage reduction type NO _x The catalyst is the storage reduction type NO. _x When the air-fuel ratio of the exhaust gas flowing into the catalyst is a lean air-fuel ratio, the nitrogen oxides (NO _x ) And the storage reduction type NO _x When the oxygen concentration of the exhaust gas flowing into the catalyst decreases and a reducing agent such as hydrocarbon (HC) or carbon monoxide (CO) is present, the stored nitrogen oxides (NO _x ) While releasing nitrogen (N ₂ ).
This storage reduction type NO _x Nitrogen oxide (NO _x If the internal combustion engine is operated at a lean air-fuel ratio for a long period of time, the NO _x NO of catalyst _x The storage capacity is saturated, and the nitrogen oxides (NO _x ) Will be released into the atmosphere without purification. Therefore, the storage reduction type NO _x Nitrogen oxides (NO _x )), The storage reduction type NO _x NO of catalyst _x Before the storage capacity is saturated, the storage reduction type NO _x It is necessary to make the air-fuel ratio of the exhaust flowing into the catalyst a rich air-fuel ratio to lower the oxygen concentration in the exhaust and increase the amount of the reducing agent contained in the exhaust.
[0007]
Then, nitrogen oxides (NO _x In order to efficiently reduce the amount, for example, an EGR device and a NO gas generator such as an “exhaust gas purification device for an internal combustion engine” described in JP-A-6-74022 are used. _x Techniques for combining with a catalyst have also been proposed.
[0008]
In the exhaust gas purifying apparatus for an internal combustion engine described in the above publication, a reducing agent addition device is attached to one branch pipe of an exhaust branch pipe (exhaust manifold) connected to the internal combustion engine, and an exhaust recirculation passage is provided to another branch pipe. (EGR pipe), or an exhaust inlet of an EGR pipe is provided in each branch pipe of an exhaust branch pipe (exhaust manifold), and a collecting portion of all the branch pipes (downstream from the exhaust inlet of the EGR pipe). ), The interference between the reducing agent adding device and the exhaust inlet of the EGR pipe is prevented, and the reducing agent added from the reducing agent adding device is prevented from entering the EGR pipe. Is what you do.
[0009]
[Problems to be solved by the invention]
However, in the exhaust gas purifying device disclosed in the above publication, the reducing agent adding device and the exhaust gas purifying catalyst are disposed separately, so that the particulate reducing agent injected from the reducing agent adding device is In the process of arriving at the purification catalyst, they mutually collide with and adsorb to each other, so that the particles of the reducing agent are likely to be coarsened, and the reducing agent may not be uniformly supplied to the entire exhaust purification catalyst.
[0010]
The present invention has been made in view of the above-described problems, and has been made in consideration of the problem that nitrogen oxides (NO _X NO) to reduce or decompose) _x In an exhaust gas purification device for an internal combustion engine equipped with a catalyst, the reducing agent added to the exhaust gas from the reducing agent adding device is prevented from flowing into the exhaust gas recirculation passage, and the reducing agent is reduced to NO. _x By providing a technology that can be evenly supplied to the entire catalyst, nitrogen oxides (NO _X The objective is to achieve efficient purification of
[0011]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
That is, the exhaust gas purifying apparatus for an internal combustion engine according to the present invention includes:
NO that is provided in an exhaust passage of an internal combustion engine and purifies nitrogen oxides in exhaust gas in the presence of a reducing agent _x A catalyst,
A reducing agent injection unit that is provided on a cylinder head of the internal combustion engine and injects a reducing agent toward an exhaust passage of the internal combustion engine;
NO _X A stirrer provided in the exhaust passage upstream of the catalyst to stir the reducing agent in the exhaust gas;
It is characterized by having.
[0012]
In the exhaust gas purification device configured as described above, the reducing agent injected from the reducing agent injection unit is NO _X It is stirred by a stirrer upstream of the catalyst. In this case, the reducing agent is atomized by stirring, and is uniformly mixed with the exhaust gas.
[0013]
As a result, NO _X A gas in which the reducing agent and the exhaust gas are homogeneously mixed flows into the catalyst, and the reducing agent and the exhaust gas are NO. _X It will be evenly distributed throughout the catalyst.
That is, the reducing agent injection means and NO _X When the catalyst is disposed at a position separated from the catalyst, the particulate reducing agent injected from the reducing agent injection means is NO _X In the process of arriving at the catalyst, they may be coarsened due to collision or adsorption with each other and unevenly distributed in exhaust gas. _X By providing a stirrer immediately upstream of the catalyst, the gas in which the exhaust gas and the reducing agent are homogeneously mixed is NO _X Will flow into the catalyst so that the reducing agent is NO _X The entire catalyst is supplied evenly.
[0014]
On the other hand, since the reducing agent injection means is exposed to high-temperature exhaust gas, appropriate cooling is necessary to improve the durability. However, in the exhaust gas purification apparatus according to the present invention, the reducing agent injection means includes a cylinder head of the internal combustion engine. Therefore, it is possible to cool using the engine cooling water circulating in the cylinder head, and the piping of the cooling water passage and the like are newly added as compared with the case where the reducing agent injection means is provided outside the internal combustion engine. Need not be added to
[0015]
In addition, as the above-mentioned stirrer, a centrifugal supercharged turbine can be exemplified. At this time, it is preferable that the injection of the reducing agent from the reducing agent injection means is performed when the supercharging pressure of the intake air by the centrifugal supercharger becomes equal to or higher than a predetermined pressure.
[0016]
This is because, in a centrifugal supercharger, a compressor driven by the rotational force of a turbine that is rotationally driven by exhaust performs supercharging of intake air, so that when the supercharging pressure of intake air is equal to or higher than a predetermined pressure, the compressor and the turbine are driven. This is because the rotation speed is sufficiently high, and the stirring of the reducing agent is performed well.
[0017]
Further, when the reducing agent is injected from the reducing agent injection means into the exhaust gas, the injection pressure of the reducing agent injection means needs to be higher than the pressure of the exhaust gas. For this reason, it is preferable to keep the differential pressure between the injection pressure of the reducing agent injection means and the exhaust pressure constant. On the other hand, the exhaust gas purification apparatus according to the present invention may be configured such that the reducing agent injection means includes a pressure regulating mechanism for adjusting the reducing agent injection pressure with respect to the pressure in the exhaust passage.
[0018]
Further, the reducing agent injection means is preferably arranged at a position closest to the stirrer in the cylinder head of the internal combustion engine. For example, an exhaust port at a position closest to the stirrer among a plurality of exhaust ports formed in the cylinder head You may make it arrange | position so that a reducing agent may be injected to a port.
In this case, the reducing agent injected from the reducing agent injection means does not easily stay in the exhaust port or the exhaust passage immediately downstream of the exhaust port, and easily reaches the stirrer.
[0019]
In the present invention, examples of the internal combustion engine include a direct-injection-type lean-burn gasoline engine and a diesel engine.
[0020]
In the present invention, NO _x As the catalyst, selective reduction type NO _x Catalyst or storage reduction type NO _x A catalyst can be exemplified.
[0021]
Selective reduction type NO _x The catalyst is the selective reduction type NO. _x When the exhaust gas flowing into the catalyst has an oxygen-excess atmosphere and a reducing agent is present, nitrogen oxides (NO _x ) Is a catalyst that reduces or decomposes).
Such selective reduction type NO _x As the catalyst, a catalyst in which a transition metal such as copper (Cu) is ion-exchanged and supported on zeolite, a catalyst in which a noble metal is supported in zeolite or alumina, a catalyst in which vanadium is supported on a carrier composed of titania and zeolite, And the like.
[0022]
Storage reduction type NO _x The catalyst is the storage reduction type NO. _x When the air-fuel ratio of the exhaust gas flowing into the catalyst is a lean air-fuel ratio, nitrogen oxides (NO _x ) And the storage reduction type NO _x When the oxygen concentration of the exhaust gas flowing into the catalyst decreases and the reducing agent is present, the stored nitrogen oxides (NO _x ) Is a catalyst that reduces and purifies while releasing).
Such storage reduction type NO _x As the catalyst, an alkali metal such as potassium (K), sodium (Na), lithium (Li) and cesium (Cs) and an alkali such as barium (Ba) and calcium (Ca) are formed on a support made of alumina. A catalyst in which at least one selected from earths, rare earths such as lanthanum (La) and yttrium (Y), and a noble metal such as platinum (Pt) can be exemplified.
[0023]
In the present invention, a reducing agent derived from ammonia can be used as the reducing agent, and examples of such a reducing agent include urea and ammonium carbamate.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described with reference to the drawings. Here, a case where the exhaust gas purification apparatus according to the present invention is applied to a diesel engine for driving a vehicle will be described as an example.
[0025]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification device according to the present invention is applied. The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cylinder diesel engine having four cylinders 2.
[0026]
The internal combustion engine 1 includes a fuel injection valve 3 for directly injecting fuel into a combustion chamber of each cylinder 2. Each fuel injection valve 3 communicates with a pressure accumulation chamber (common rail) 4 that accumulates fuel supplied from a fuel pump (not shown) to a predetermined pressure, so that the fuel accumulated in the common rail 4 is applied to each fuel injection valve 3. It has become. In this case, when the fuel injection valve 3 is opened, fuel is injected at the predetermined pressure.
[0027]
An intake branch pipe 5 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 5 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).
The intake branch pipe 5 is connected to an intake pipe 6, and the intake pipe 6 communicates with an air cleaner box 7. The intake pipe 6 downstream of the air cleaner box 7 is provided with an air flow meter 8 corresponding to the mass of intake air flowing through the intake pipe 6.
[0028]
The intake pipe 6 near the intake branch pipe 5 has an intake throttle valve 9 for adjusting the flow rate of intake air flowing through the intake pipe 6, an actuator 10 including a stepper motor and the like for driving the intake throttle valve 9 to open and close. Is provided.
[0029]
An intake pipe 6 located between the air flow meter 8 and the intake throttle valve 9 is provided with a compressor housing 11a of a centrifugal supercharger (turbocharger) 11 which operates using exhaust pressure as a driving source. An intercooler 12 is provided in the intake pipe 6 downstream of the compressor 11a to cool intake air which has been heated in the compressor housing 11a and has become high temperature.
[0030]
In the intake system configured as described above, the intake air that has flowed into the air cleaner box 7 is subjected to removal of dust and dirt from the intake by an air cleaner (not shown) in the air cleaner box 7, and then is passed through the intake pipe 6 through the compressor housing 6. 11a.
[0031]
The intake air flowing into the compressor housing 11a is compressed by rotation of a compressor wheel provided in the compressor housing 11a. The intake air which has been compressed in the compressor housing 11a and has become high temperature is cooled by the intercooler 12.
[0032]
The intake air cooled by the intercooler 12 reaches the intake branch pipe 5 with the flow rate adjusted by the intake throttle valve 9 as necessary. The intake air that has reached the intake branch pipe 5 is distributed to the combustion chamber of each cylinder 2 via each branch pipe, and is burned using the fuel injected from the fuel injection valve 3 of each cylinder 2 as an ignition source.
[0033]
On the other hand, an exhaust branch pipe 13 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 13 communicates with a combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust branch 13 and the intake branch 5 are communicated via an exhaust gas recirculation passage (EGR passage) 17 for recirculating a part of the exhaust flowing through the exhaust branch 13 to the intake branch 5. I have.
[0034]
An EGR valve 18 for adjusting the flow rate of exhaust gas flowing in the EGR passage 17 is provided in the EGR passage 17. When the EGR valve 18 is opened, a part of the exhaust gas flowing in the exhaust branch pipe 13 is guided to the intake branch pipe 5 through the EGR passage 17. The exhaust gas led to the intake branch pipe 5 is distributed to the combustion chamber of each cylinder 2 together with the intake air flowing from the upstream of the intake branch pipe 5, and the fuel injected from each fuel injection valve 3 is used as an ignition source for combustion. Is done.
[0035]
At that time, in the combustion chamber, the water (H) contained in the recirculated exhaust gas (EGR gas) ₂ O) and carbon dioxide (CO ₂ ) And the like, lower the combustion temperature and reduce nitrogen oxides (NO _X ) Is suppressed.
[0036]
Next, the exhaust branch pipe 13 is connected to a turbine housing 11 b of the centrifugal supercharger 11, and the turbine housing 11 b is connected to an exhaust pipe 14.
The exhaust pipe 14 is connected downstream to a muffler (not shown). In the middle of the exhaust pipe 14, two exhaust purification catalysts 15, 16 are arranged.
These exhaust gas purifying catalysts 15 and 16 are capable of removing nitrogen oxides (NO _x NO) can be purified _x Catalyst and such NO _x As the catalyst, the NO _x When the exhaust gas flowing into the catalyst is in an oxygen-excess atmosphere and a reducing agent is present, nitrogen oxides (NO _x NO) to reduce or decompose) _x Catalyst or the NO _x When the air-fuel ratio of the exhaust gas flowing into the catalyst is a lean air-fuel ratio, the nitrogen oxides (NO _x ) And the NO _x When the oxygen concentration of the exhaust gas flowing into the catalyst decreases and the reducing agent is present, the stored nitrogen oxides (NO _x NO) that reduces and purifies while releasing) _x A catalyst and the like can be exemplified. Here, zeolite / silica-based selective reduction type NO _x A description will be given using a catalyst as an example. In the following, the upstream side exhaust purification catalyst 15 is set to the upstream side selective reduction type NO. _X The catalyst 15 is referred to as a selective reduction type NO on the downstream side. _X The catalyst 16 is converted to a downstream selective reduction type NO. _X Called catalyst 16.
[0037]
The above-mentioned upstream and downstream selective reduction type NO _X The catalysts 15 and 16 serve as nitrogen oxides (NO _X ) Requires the presence of a reducing agent. Therefore, the exhaust gas purification apparatus according to the present embodiment includes the upstream side and the downstream side selective reduction type NO. _X A reducing agent supply mechanism for supplying a reducing agent to the catalysts 15 and 16 is also provided.
[0038]
The reducing agent supply mechanism is mounted on a cylinder head of the internal combustion engine 1 and injects a reducing agent into an exhaust passage in an exhaust branch pipe 13, and a reducing agent that stores liquid urea as a reducing agent A storage chamber 22, a reducing agent pump 23 that sucks and discharges the reducing agent stored in the reducing agent storage chamber 22, and a reducing agent supply that guides the reducing agent discharged from the reducing agent pump 23 to the reducing agent injection device 20. And a pipe 21.
[0039]
The reducing agent injection device 20 realizes a reducing agent injection unit according to the present invention. For example, as shown in FIG. 2, the injection hole has an exhaust port 101 of any one of the four cylinders 2. A reducing agent injection valve 200 attached to the cylinder head 100 so as to protrude therefrom.
[0040]
In the reducing agent injection valve 200, the injection hole of the reducing agent injection valve 200 is located downstream of the connection portion of the EGR passage 17 in the exhaust branch pipe 13 and is closest to the gathering portion of the four branch pipes in the exhaust branch pipe 13. It is preferable to be attached to the cylinder head 100 so as to protrude from the exhaust port 101 of the cylinder 2 and to face the collecting portion of the exhaust branch pipe 13.
This prevents the reducing agent injected from the reducing agent injection valve 200 from flowing into the EGR passage 17 and reaches the turbine housing 11b of the centrifugal supercharger without stagnation in the exhaust branch pipe 45. It is to make it.
In the example shown in FIG. 1, the first (# 1) cylinder 2 among the four cylinders 2 of the internal combustion engine 1 is located closest to the gathering portion of the exhaust branch pipe 13, so that the first (# 1) cylinder is used. When the reducing agent injection valve 200 is attached to the exhaust port 101 of the second cylinder 2, when the cylinder 2 other than the first (# 1) cylinder 2 is located closest to the gathering portion of the exhaust branch pipe 13, the cylinder 2 The reducing agent injection valve 200 is attached to the exhaust port 101.
[0041]
Further, the reducing agent injection valve 200 may be mounted so as to penetrate a water jacket 102 formed in the cylinder head 100 or to be mounted close to the water jacket 102. This is because the reducing agent injection valve 200 is exposed to relatively high temperature exhaust gas flowing through the exhaust port 101, and thus the reducing agent injection valve 200 is cooled using the cooling water flowing through the water jacket 102, thereby reducing the reducing agent injection valve 200. This is because the durability of the injection valve 200 can be improved.
[0042]
On the other hand, the reducing agent injection device 20 includes a pressure regulator 201 that adjusts the pressure of the reducing agent in the reducing agent supply pipe 21 (that is, the pressure of the reducing agent applied to the reducing agent injection valve 200). The pressure regulator 201 is in communication with the exhaust branch pipe 13 via an exhaust pressure introduction pipe 202, and the pressure difference between the exhaust pressure of the exhaust branch pipe 13 and the reducing agent pressure in the reducing agent supply pipe 21 is reduced. The reducing agent pressure is adjusted to be constant.
[0043]
According to the pressure regulator 201, the injection amount of the reducing agent injection valve 200 can be stabilized even when the exhaust pressure in the exhaust branch pipe 13 fluctuates due to a change in the operating state of the internal combustion engine 1 or the like.
[0044]
Here, returning to FIG. 1, the internal combustion engine 1 is composed of a digital computer, a ROM (Read Only Memory), a RAM (Random Access Memory), a CPU (Central Processor Unit), and an input, which are interconnected by a bidirectional bus. An engine control electronic control unit (ECU) 24 having a port, an output port, and the like is also provided.
[0045]
An input port of the ECU 24 has, in addition to the air flow meter 8 described above, an intake pressure sensor 19 attached to the intake branch pipe 5 and outputting an electric signal corresponding to the intake pressure (supercharging pressure) in the intake branch pipe 5. A crank position sensor 25 which is attached to the internal combustion engine 1 and outputs a pulse signal each time a crankshaft serving as an engine output shaft rotates a predetermined angle, and outputs an electric signal corresponding to an operation amount of an accelerator pedal (accelerator opening) (not shown). Various sensors such as an accelerator opening sensor 26 are connected via electric wiring.
[0046]
The fuel injection valve 3, the actuator 10, the EGR valve 18, the reducing agent injection device 20, and the like are connected to the output port of the ECU 24 via electric wiring.
The ECU 24 determines the operating state of the internal combustion engine 1 based on the output signals of the various sensors described above, executes basic control such as fuel injection control and EGR control based on the determined operating state, and performs injection of reducing agent. The control of the device 20 is executed.
[0047]
In the ROM of the ECU 24, the engine speed, the accelerator opening, and the NO discharged from the internal combustion engine 1 are stored. _X NO indicating relationship with quantity _X An emission map is stored. This NO _X The emission map is obtained experimentally in advance.
[0048]
The ECU 24 determines this NO _x Referring to the emission map, the NO corresponding to the engine speed and the accelerator opening _X Calculate emissions. The ECU 24 calculates the calculated NO _X The target supply amount of the reducing agent (opening time of the reducing agent injection valve 200) is calculated using the discharge amount as a parameter, and the reducing agent injection valve 200 is controlled based on the target supply amount.
[0049]
Hereinafter, the operation of the exhaust emission control device according to the present embodiment will be described.
The ECU 24 calculates the engine speed based on the time interval at which the crank position sensor 25 outputs the pulse signal, and inputs the output signal (accelerator opening) of the accelerator opening sensor 26.
[0050]
The ECU 24 _X Accessing the quantity emission map and determining the NO corresponding to the engine speed and the accelerator opening _X Calculate emissions, then NO _X The target supply amount of the reducing agent, that is, the opening time of the reducing agent injection valve 200 is calculated using the discharge amount as a parameter.
[0051]
On the other hand, the ECU 24 receives the output signal of the intake pressure sensor 19 and determines whether the supercharging pressure of the intake air by the centrifugal supercharger 11 is equal to or higher than a predetermined pressure.
When determining that the supercharging pressure is equal to or higher than the predetermined pressure, the ECU 24 applies a drive current to the reducing agent injection valve 200 to open the reducing agent injection valve 200. The ECU 24 continues to apply the drive current to the reducing agent injection valve 200 during the above-described valve opening time to inject the target supply amount of the reducing agent.
[0052]
When the reducing agent injection valve 200 is opened, the reducing agent supplied from the reducing agent pump 23 to the reducing agent injection valve 200 is injected into the exhaust branch pipe 13 at a pressure regulated by the pressure regulator 201.
[0053]
The reducing agent injected into the exhaust branch pipe 13 is guided to the turbine housing 11 b of the centrifugal supercharger 11 together with the exhaust discharged from the exhaust port of the internal combustion engine 1.
At that time, the reducing agent injection valve 200 is attached to an exhaust port located closest to the collecting portion of the exhaust branch pipe 13, in other words, an exhaust port located closest to the turbine housing 11b. Since the injection hole of the valve 200 is directed to the gathering portion of the exhaust branch pipe 13, almost all of the reducing agent injected from the reducing agent injection valve 200 is promptly stored in the exhaust branch pipe 13 without stagnation in the exhaust branch pipe 13. Will be reached.
[0054]
The reducing agent supplied from the reducing agent injection valve 200 to the turbine housing 11b is stirred by the turbine wheel rotating in the turbine housing 11b and mixed with the exhaust gas.
At that time, the supercharging pressure of the intake air by the centrifugal supercharger 11 is equal to or higher than a predetermined pressure, and the rotation speed of the turbine wheel is sufficiently high. Mix homogeneously.
[0055]
The exhaust gas and the reducing agent homogeneously mixed in the turbine housing 11b as described above are supplied to the upstream side selective reduction type NO located immediately downstream of the turbine housing 11b. _X The catalyst flows into the catalyst 15, and the upstream side selective reduction type NO _X It spreads evenly over the entire catalyst 15. As a result, the upstream side selective reduction type NO _X In the catalyst 15, nitrogen oxides (NO _X ) Is efficiently reduced or decomposed.
[0056]
As described above, the turbine housing 11b and the turbine wheel of the centrifugal supercharger 11 realize the stirrer according to the present invention.
Therefore, according to the present embodiment, the reducing agent injection valve 200 and the upstream selective reduction type NO _X When the catalyst 15 is disposed at a distance from the catalyst 15, the reducing agent injected from the reducing agent injection valve 200 becomes the upstream side selective reduction type NO. _X Even if the reducing agent particles are coarsened due to collision or adsorption with each other in the process of reaching the catalyst 15, the upstream side selective reduction type NO _X Since the reducing agent is stirred by the stirrer arranged immediately upstream of the catalyst 15, the upstream side selective reduction type NO _X A gas in which a reducing agent and exhaust gas are homogeneously mixed is supplied to the catalyst 15, and the reducing agent is mixed with an upstream-side selective reduction type NO. _X It is evenly supplied to the entire catalyst 15. As a result, the nitrogen oxides (NO _X ) Can be efficiently reduced and decomposed.
[0057]
Furthermore, according to the present embodiment, the reducing agent injection valve 200 and the upstream side selective reduction type NO _X Since the catalyst 15 can be arranged at a position remote from the catalyst 15, the reducing agent injection valve 200 is arranged on the cylinder head 100 of the internal combustion engine 1, and the cooling water flowing through the water jacket 101 of the cylinder head 100 is used. Accordingly, the reducing agent injection valve 200 can be cooled, and heat damage to the reducing agent injection valve 200 can be prevented without adding a new pipe of cooling water.
[0058]
【The invention's effect】
The exhaust gas purifying apparatus according to the present invention comprises a reducing agent injection unit and a NO. _X Between the catalyst, preferably NO _X A stirrer for stirring the reducing agent in the exhaust gas is disposed immediately upstream of the catalyst. _X Even when the catalyst is placed away from the catalyst, the gas in which the exhaust gas and the reducing agent are homogeneously mixed is NO _X It is possible to supply the catalyst.
[0059]
Therefore, according to the exhaust emission control device of the present invention, NO _X The reducing agent can be supplied uniformly over the entire catalyst, and the nitrogen oxides in the exhaust gas can be efficiently purified.
[0060]
Further, according to the exhaust gas purification device of the present invention, NO _X It is possible to dispose the reducing agent injection means on the cylinder head located at a position away from the catalyst, and to cool the reducing agent injection means using cooling water circulating in the cylinder head. It is also possible to improve the cooling of the reducing agent injection means and, consequently, the durability of the reducing agent injection means without adding any new components.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification device according to the present invention is applied;
FIG. 2 is a diagram showing a configuration of a reducing agent injection device.
[Explanation of symbols]
1 ... Internal combustion engine
11 ・ ・ ・ Centrifugal supercharger (turbocharger)
11a ・ ・ Compressor housing
11b Turbine housing
12 ・ ・ ・ Intercooler
13 ・ ・ ・ Exhaust branch pipe
14 ・ ・ ・ Exhaust pipe
15 ・ ・ ・ NO-side selective reduction type NO _X catalyst
16 ··· Downstream side selective reduction type NO _X catalyst
19 ... intake pressure sensor
20 ... reducing agent injection device
21 ... reducing agent supply pipe
22 ・ ・ ・ Reducing agent storage room
23 ・ ・ ・ Reducing agent pump
24 ... ECU
25 ... Crank position sensor
26 ・ ・ ・ Accelerator opening sensor
100 cylinder head
101 exhaust port
102 ・ Water jacket
200 ・ ・ Reducing agent injection valve
201 ・ ・ Pressure regulator
202 ・ ・ Exhaust pressure introduction pipe

Claims (3)

A NOx catalyst provided in an exhaust passage of the internal combustion engine and purifying nitrogen oxides in exhaust gas in the presence of a reducing agent;
A reducing agent injection unit that is provided on a cylinder head of the internal combustion engine and injects a reducing agent toward an exhaust passage of the internal combustion engine;
A stirrer provided in the exhaust passage upstream of the NOx catalyst, for stirring the reducing agent in the exhaust gas, comprising:
The stirrer is a centrifugal turbocharger turbine,
The exhaust gas purifying apparatus for an internal combustion engine, wherein the reducing agent injection unit executes the injection of the reducing agent on condition that a supercharging pressure of the intake air by the centrifugal supercharger is equal to or higher than a predetermined pressure . The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the reducing agent injection means includes a pressure regulating mechanism that adjusts a reducing agent injection pressure with respect to a pressure in an exhaust passage. 2. The exhaust system according to claim 1, wherein the reducing agent injection unit injects the reducing agent into an exhaust port closest to the stirrer among a plurality of exhaust ports formed in the cylinder head. 3. Purification device.

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