JP2002349236A - Exhaust emission control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce exhaust amounts of NOx and particulates contained in exhaust gas. SOLUTION: A NOx occluding reduction catalyst 24 is provided in an exhaust pipe 16 of an engine 11, and a liquid injecting nozzle 29 capable of injecting hydrocarbonic liquid toward the NOx occluding reduction catalyst is provided in the exhaust pipe in an exhaust gas upstream of the NOx occluding reduction catalyst. A hydrocarbonic liquid feeding means 36 feeds liquid to the liquid injecting nozzle via a liquid regulating valve 34, and a particulate filter 26 functioning as an oxidation catalyst is provided in the exhaust pipe in an exhaust gas downstream of the NOx occluding reduction catalyst. A bypass pipe 38 is connected to the exhaust pipe so as to bypass the NOx occluding reduction catalyst, and exhaust gas regulating valves 41 and 42 are switched so as to send the exhaust gas through either one of the NOx occluding reduction catalyst or the bypass pipe. A controller 44 respectively controls the liquid regulating valve and the exhaust gas regulating valves on the basis of a detection output of a temperature sensor 43 detecting exhaust gas temperature inside the exhaust pipe in the exhaust gas upstream of the NOx occluding reduction catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for reducing nitrogen oxides (hereinafter referred to as NOx) contained in exhaust gas of a diesel engine and collecting particulates contained in the exhaust gas.

[0002]

2. Description of the Related Art Conventionally, as this kind of exhaust gas purifying apparatus,
In the middle of the exhaust passage of the diesel engine, the oxidation catalyst, the particulate filter, and the NO
x catalyst, a particulate filter and NOx
There is disclosed an exhaust gas purifying apparatus for a diesel engine provided with a fuel addition nozzle for injecting light oil for reducing NOx in exhaust gas between the catalyst and a catalyst (Japanese Patent Application Laid-Open No. 2000-2000).
-199423). In the exhaust gas purifying apparatus for a diesel engine configured as described above, NO in the exhaust gas is oxidized by an oxidation catalyst into NO _2, and N ₂ having a high oxidizing function is obtained.
By reacting O ₂ with the particulates deposited on the particulate filter, the particulates deposited on the filter can be reduced. In addition, NO _{2 that} has passed through this filter without reacting with the particulates in the particulate filter becomes NO ₂ on the exhaust gas downstream side of the filter.
x catalyst, light oil injected from the fuel addition nozzle
It is reduced to ₂ or NO. As a result, the particulate filter can be continuously regenerated and the NO ₂ (NO
x) can be reduced.

[0003]

However, in the conventional exhaust gas purifying apparatus for a diesel engine disclosed in JP-A-2000-199423, light oil is injected from a fuel addition nozzle. The light oil (hydrocarbon) that was not removed may be discharged into the atmosphere in a vaporized state. An object of the present invention is to reduce the emission amount of NOx and particulates contained in exhaust gas with high efficiency, and discharge hydrocarbon-based liquid injected from a liquid injection nozzle to an exhaust pipe into the atmosphere in a vaporized state. It is an object of the present invention to provide an exhaust gas purifying apparatus for an engine, which can prevent the occurrence of the exhaust gas.

[0004]

The invention according to claim 1 is
As shown in FIG. 1, a NOx storage reduction catalyst 24 provided in an exhaust pipe 16 of the engine 11 and a NOx storage reduction catalyst 2
A liquid injection nozzle 29 provided in the exhaust pipe 16 upstream of the exhaust gas 4 to inject the hydrocarbon-based liquid 32 toward the NOx storage reduction catalyst 24, and supplies the liquid to the liquid injection nozzle 29 via a liquid regulating valve 34. Hydrocarbon-based liquid supply means 36, a particulate filter 26 provided in the exhaust pipe 16 downstream of the NOx storage reduction catalyst 24 on the exhaust gas side and carrying an active metal functioning as an oxidation catalyst,
A bypass pipe 38 connected to the exhaust pipe 16 on the exhaust gas upstream side of the Ox storage reduction catalyst 24 and the other end connected to the exhaust pipe 16 between the NOx storage reduction catalyst 24 and the particulate filter 26 to bypass the NOx storage reduction catalyst 24; The exhaust gas discharged from the engine 11 is converted into a NOx storage reduction catalyst 2
Exhaust gas adjusting valves 41 and 42 for adjusting the flow rates of the exhaust gas 4 and the bypass pipe 38, a temperature sensor 43 for detecting the temperature of the exhaust gas in the exhaust pipe 16 upstream of the NOx storage reduction catalyst 24, and detection of the temperature sensor 43. This is an exhaust gas purifying device for an engine including a controller 44 for controlling the liquid regulating valve 34 and the exhaust gas regulating valves 41 and 42 based on the output.

In the exhaust gas purifying apparatus for an engine according to the present invention, when the temperature sensor 43 detects an exhaust gas temperature lower than a predetermined value, the controller 44 controls the liquid regulating valve 34 based on the detection output of the temperature sensor 43. Off,
Exhaust gas control valves 41 and 42 so that the exhaust gas flows to the NOx storage reduction catalyst 24 and the exhaust gas does not flow to the bypass pipe 38.
To adjust. As a result, NOx in the exhaust gas is stored as nitrate in the catalyst 24, and HC in the exhaust gas is oxidized by the oxidizing action of the noble metal carried on the catalyst 24. When the temperature sensor 43 detects an exhaust gas temperature equal to or higher than a predetermined value, the controller 44, based on the detection output of the temperature sensor 43, causes most of the exhaust gas to flow to the bypass pipe 38 and some of the exhaust gas to the catalyst 24. Exhaust gas regulating valves 41, 42
At the same time, the liquid adjustment valve 34 is turned on for a predetermined time, and the liquid 32 is ejected from the liquid ejection nozzle 29. As a result, the concentration of hydrocarbons in the exhaust gas at the inlet of the catalyst 24 increases, so that the excess air ratio of the exhaust gas at the inlet of the catalyst 24 decreases, and that HC, CO, CO ₂ or H ₂ increases as a reducing agent. NOx occluded in the HC
Reacts with the like and becomes N ₂ , CO ₂ , H ₂ O and is released from the catalyst 24. Part of the light oil or HC generated by the injection of the liquid 32 passes through the catalyst 24 and is collected by the filter 26. Light oil or H trapped in this filter 26
When the liquid regulating valve 34 is turned on, most of the exhaust gas flows through the bypass pipe 38 and the exhaust gas with a high excess air ratio flows into the filter 26. Oxidized and burned by oxidizing action.

The invention according to claim 2 is the invention according to claim 1, wherein the exhaust pipe 1 between the NOx storage reduction catalyst 24 and the particulate filter 26, as shown in FIG.
Lambda sensor 4 for detecting excess air ratio of exhaust gas in 6
And / or a NOx sensor 46 for detecting the NOx concentration of the exhaust gas in the exhaust pipe 16 between the NOx storage reduction catalyst 24 and the particulate filter 26. The controller 44 includes a temperature sensor 43 and a lambda sensor. The liquid control valve 34 and the exhaust gas control valves 41 and 42 are respectively controlled based on each detection output from one or both of the NOx sensor 45 and the NOx sensor 46. In the exhaust gas purifying apparatus for an engine according to the second aspect, when the NOx sensor detects a NOx concentration equal to or more than a predetermined value, the controller 44 determines the Nx concentration.
The liquid regulating valve 34 is turned on based on the detection output of the Ox sensor 46, the liquid 32 is ejected from the liquid ejecting nozzle 29, and when the lambda sensor 45 detects an excess air ratio equal to or less than a predetermined value, the controller 44 detects the lambda sensor. The liquid regulating valve 34 is turned off based on the detection output of 45. Further, the exhaust gas control valves 41 and 42 are adjusted so that the exhaust gas flows through the bypass pipe 38 when the liquid control valve 34 is turned on. As described above, the output of the NOx sensor 46 allows the liquid regulating valve 3
4 is determined (NOx occlusion time by the catalyst 24), the time during which the liquid regulating valve 34 is on is determined by the detection output of the lambda sensor 45, and the detection outputs of the NOx sensor 46 and the lambda sensor 45 are further determined. Thus, the switching timing and switching time of the exhaust gas regulating valves 41 and 42 are determined.

A lambda sensor for detecting the excess air ratio of the exhaust gas in the exhaust pipe downstream of the particulate filter or NO for detecting the NOx concentration of the exhaust gas in the exhaust pipe downstream of the particulate filter.
The apparatus further includes one or both of the x sensor, and the controller controls the liquid regulating valve and the exhaust gas regulating valve based on respective detection outputs of the temperature sensor and one or both of the lambda sensor and the NOx sensor. You may comprise.

As shown in FIG. 4, the invention according to claim 4 is provided in the NOx storage reduction catalyst 24 provided in the exhaust pipe 16 of the engine 11 and in the exhaust pipe 16 upstream of the NOx storage reduction catalyst 24 in the exhaust gas. A liquid injection nozzle 29 capable of injecting the hydrocarbon liquid 32 toward the NOx storage reduction catalyst 24, a hydrocarbon liquid supply means 36 for supplying the liquid 32 to the liquid injection nozzle 29 via a liquid regulating valve 34, N
A particulate filter 26 provided on the exhaust pipe 16 on the exhaust gas downstream side of the Ox storage reduction catalyst 24 and carrying an active metal functioning as an oxidation catalyst; and an exhaust pipe 16 between the NOx storage reduction catalyst 24 and the particulate filter 26.
An air injection nozzle 71 provided in the air filter and capable of injecting air toward the particulate filter 26;
An air supply means 73 for supplying air to the exhaust gas through an air regulating valve 74; and a temperature sensor 43 for detecting the temperature of the exhaust gas in the exhaust pipe 16 on the exhaust gas upstream side of the NOx storage reduction catalyst 24.
And the liquid regulating valve 3 based on the detection output of the temperature sensor 43.
4 and an controller 44 for controlling the air regulating valve 74, respectively.

In the exhaust gas purifying apparatus for an engine according to the present invention, when the temperature sensor detects an exhaust gas temperature lower than a predetermined value, the controller adjusts the liquid regulating valve based on the detection output of the temperature sensor. Keep off. As a result, NOx in the exhaust gas is stored as nitrate in the catalyst 24, and HC in the exhaust gas is oxidized by the oxidizing action of the noble metal carried on the catalyst 24. When the temperature sensor 43 detects an exhaust gas temperature equal to or higher than a predetermined value, the controller 44 turns on the liquid regulating valve 34 for a predetermined time based on the detection output of the temperature sensor 43 and injects the liquid 32 from the liquid injection nozzle 29. Thereby, the catalyst 24
Since the concentration of hydrocarbons in the exhaust gas at the inlet increases, the catalyst 2
As the excess air ratio of exhaust gas at the 4 inlet decreases,
Since C, CO, CO ₂ or H ₂ increases as a reducing agent,
The NOx stored in the catalyst 24 reacts with the HC and the like to become N ₂ , CO ₂ , and H ₂ O, which are released from the catalyst 24.
Part of the light oil or HC generated by the injection of the liquid 32 passes through the catalyst 24 and is collected by the filter 26. The light oil or HC trapped in the filter 26 is exhausted by increasing the oxygen concentration by turning on the air control valve 74 and injecting air from the air injection nozzle 71 when the liquid control valve 34 is on. Flows into the filter 26, and is oxidized and burned by the oxidizing action of the active metal carried on the filter 26.

The invention according to claim 5 is the invention according to claim 4, wherein the exhaust pipe 1 between the NOx storage reduction catalyst 24 and the particulate filter 26, as shown in FIG.
Lambda sensor 4 for detecting excess air ratio of exhaust gas in 6
And / or a NOx sensor 46 for detecting the NOx concentration of the exhaust gas in the exhaust pipe 16 between the NOx storage reduction catalyst 24 and the particulate filter 26. The controller 44 includes a temperature sensor 43 and a lambda sensor. The liquid regulating valve 34 and the air regulating valve 74 are respectively controlled based on each detection output from one or both of the NOx sensor 45 and the NOx sensor 46. In the exhaust gas purifying apparatus for an engine according to the fifth aspect, the NOx sensor 46 detects that the NOx
When the concentration is detected, the controller 44 turns on the liquid regulating valve 34 based on the detection output of the NOx sensor 46 to inject the liquid 32 from the liquid ejecting nozzle 29, and the lambda sensor 45 detects the excess air ratio equal to or more than a predetermined value. Then, the controller 44 turns off the liquid regulating valve 34 based on the detection output of the lambda sensor 45. When the liquid adjustment valve 34 is on, the air adjustment valve 74 is turned on to inject air from the air injection nozzle 71. Thus, the interval at which the liquid regulating valve 34 is turned on (the NOx storage time by the catalyst 24) is determined by the detection output of the NOx sensor 46, and the time during which the liquid regulating valve 34 is turned on is determined by the detection output of the lambda sensor 45. Further, the ON timing and the ON time of the air regulating valve 74 are determined by the respective detection outputs of the NOx sensor 46 and the lambda sensor 45.

A lambda sensor for detecting the excess air ratio of exhaust gas in the exhaust pipe downstream of the particulate filter or NOx for detecting the NOx concentration of exhaust gas in the exhaust pipe downstream of the particulate filter.
The apparatus further includes one or both of the sensors, and the controller is configured to control the liquid regulating valve and the air regulating valve based on respective detection outputs of the temperature sensor and one or both of the lambda sensor and the NOx sensor. May be. Further, when the condition for opening the liquid regulating valve based on the detection output of the temperature sensor is satisfied, the controller is configured to open the liquid regulating valve for 0.01 to 30 seconds every 0.1 to 600 seconds. Is preferred. Further, when a condition for opening the liquid regulating valve based on each detection output of the temperature sensor and one or both of the lambda sensor and the NOx sensor is satisfied, the controller operates the liquid regulating valve for 0.1 to 600 seconds. Preferably, it is configured to open for 0.01 to 30 seconds each time.

The invention according to claim 9 is the invention according to claim 1 or 4, and further includes an engine 1 as shown in FIG.
Reference numeral 1 denotes an engine with a turbocharger.
A compressor 17a provided in the intake pipe 13 and capable of compressing and supplying air to the engine 11; and a compressor 17a provided in the exhaust pipe 16 and connected to the compressor 17a via a shaft and rotatable by the energy of exhaust gas flowing through the exhaust pipe 16. And a simple turbine 17b. In the exhaust gas purifying apparatus for an engine according to the ninth aspect, by supercharging the intake air with the turbocharger 17, it is possible to increase the oxygen concentration in the exhaust gas and reduce the amount of soot emission. Therefore, there is an advantage that the reaction speed of the NOx storage reduction catalyst 24 can be increased, the load of the soot combustion processing in the particulate filter 26 can be reduced, and the removal of hydrocarbons can be promoted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, an intake port of the diesel engine 11 is connected to an intake pipe 13 via an intake manifold 12, and an exhaust port is connected to an exhaust pipe 16 via an exhaust manifold 14. Intake pipe 1
3 is provided with a compressor 17a of the turbocharger 17 and an intercooler 18 for cooling the intake air compressed by the turbocharger 17, and an exhaust pipe 16 is provided with a turbine 17b of the turbocharger 17. Can be Although not shown, the rotor of the compressor 17a and the rotor of the turbine 17b are connected by a shaft. The compressor 17a is rotated by the energy of the exhaust gas discharged from the engine 11 via the turbine 17b and the shaft, and the rotation of the compressor 17a compresses the intake air in the intake pipe 13.

The exhaust manifold 14 and the intake pipe 13 are connected to each other by bypassing the engine 11 through an EGR passage 19. That is, the EGR passage 19 branches from the exhaust manifold 14 and joins the intake pipe 13 downstream of the intercooler 18. The EGR passage 19 has the E
Exhaust gas recirculated from the GR passage 19 to the intake pipe 13 (EG
An EGR valve 21 capable of adjusting the flow rate of R gas) is provided. Reference numeral 22 in FIG. 1 denotes an EGR cooler that cools exhaust gas (EGR gas) passing through the EGR passage 19. Further, an intake throttle valve 23 capable of adjusting the flow rate of intake air is provided in the intake pipe 13 upstream of the compressor 17a on the intake side. Further, a NOx storage reduction catalyst 24 and a particulate filter 26 are provided in the exhaust pipe 16 in order from the engine side (the exhaust gas upstream side). The NOx storage reduction catalyst 24 is accommodated in a cylindrical converter 27 in which the diameter of the exhaust pipe 16 is enlarged, and the particulate filter 26 is accommodated in a cylindrical collector 28 in which the diameter of the exhaust pipe 16 is enlarged.

The NOx storage reduction catalyst 24 stores NOx in the exhaust gas flowing into the exhaust pipe 16, and stores H 2 in the exhaust gas.
This catalyst is a catalyst that releases the stored NOx when C, CO, CO ₂ or H ₂ increases and oxygen decreases, and is subjected to a regeneration treatment. Although not shown, the catalyst 24 has a monolithic carrier (material: cordierite) in which a lattice-like (honeycomb-like) passage is formed in the flow direction of the exhaust gas, and is formed on the monolithic carrier and supports a noble metal and a NOx storage agent. And a coated layer. Noble metals include Pt, NO
x As an occluding agent, an alkali metal such as Li, Na, K, and Cs, an alkaline earth metal such as Mg, Ca, and Ba;
Rare earth metals such as La, Ce, Pr, Nd, Eu, Gd, and Dy (lanthanide-based metals other than Y). The NOx storage agent is supported at 2 to 20% by weight, preferably 5 to 10% by weight, based on the total weight of the catalyst 24. Alumina is used as the coating layer.

The particulate filter 26 is a catalyst-equipped honeycomb filter having a function as an oxidation catalyst, and as shown in FIG. 2, has a polygonal cross section partitioned by a porous partition wall 26a made of ceramics such as cordierite. Having. This filter 26 is composed of these partition walls 26a.
Thus, the inlet portions 26c and the outlet portions 26d of a large number of through holes 26b formed in parallel with each other are substantially alternately sealed. The partition 26a has
A platinum-zeolite catalyst or a platinum-ceria-zeolite catalyst is coated. The platinum-zeolite catalyst is formed by coating a slurry containing hydrogen ion-exchanged zeolite powder (H-ZSM-5) on a honeycomb support made of cordierite, and then supporting Pt. In addition, a platinum-ceria-zeolite catalyst is used on a honeycomb support made of cordierite to form a hydrogen ion-exchanged zeolite powder (H-ZS).
M-5) and a slurry containing ceria powder (CeO ₂ ), and then carrying Pt. Thereby, the oxidizing power of soot and hydrocarbon (HC) is given to the filter 26. In the filter 26, as shown by a solid arrow in FIG. 2, when the exhaust gas of the engine 11 introduced from the inlet side of the filter 26 passes through the porous partition wall 26a, fine particles contained in the exhaust gas are filtered. , And is discharged from the exit side.

On the other hand, a liquid injection nozzle 29 is provided toward the catalyst 24 at the exhaust pipe 16 on the exhaust gas upstream side of the NOx storage reduction catalyst 24, that is, at the inlet of the catalyst 24. One end of a liquid supply pipe 31 is connected to the liquid ejection nozzle 29, and the other end of the liquid supply pipe 31 is connected to a liquid tank 33 in which a hydrocarbon liquid 32 is stored. The liquid supply pipe 31
Is provided with a liquid adjustment valve 34 for adjusting the supply amount of the liquid 32 to the liquid ejection nozzle 29. The liquid supply pipe 31 between the liquid adjustment valve 34 and the liquid tank 33 is provided with the liquid 32 in the liquid tank 33. Pump 3 that can be supplied to liquid injection nozzle 29
6 are provided. The liquid regulating valve 34 is a first to third port 3
A three-way valve having a first port 34a
Is connected to the discharge port of the pump 36, the second port 34b is connected to the liquid ejecting nozzle 29, and the third port 34c
Is connected to the liquid tank 33 via the return pipe 37. The hydrocarbon liquid 32 is light oil. When the liquid regulating valve 34 is turned on, the first and second ports 34a and 34b communicate with each other. When the liquid regulating valve 34 is turned off, the first and third ports 34a and 34c are turned on.
Are configured to communicate with each other.

The exhaust pipe 16 has a NOx storage reduction catalyst 2
4 is connected. One end of the bypass pipe 38 is connected to the exhaust pipe 16 on the exhaust gas upstream side of the catalyst 24, and the other end is connected to the exhaust pipe 16 between the catalyst 24 and the filter 26. A first and a second exhaust gas control valve 41 for switching the exhaust gas discharged from the engine 11 to either the catalyst 24 or the bypass pipe 38 are provided in the bypass pipe 38 and the exhaust pipe 16 near one end of the bypass pipe 38. 42 are provided. The first exhaust gas control valve 41 is provided near one end of the bypass pipe 38 and is connected to the bypass pipe 3.
8, the second exhaust gas control valve 42 is provided in the exhaust pipe 16 between one end of the bypass pipe 38 and the catalyst 24, and is configured to adjust the opening of the exhaust pipe 16. In addition, even if a single exhaust gas control valve is provided at a connection portion of one end of the bypass pipe to the exhaust pipe, the flow rate of exhaust gas flowing to the NOx storage reduction catalyst and the bypass pipe can be adjusted by the exhaust gas control valve.

A temperature sensor 43 for detecting the temperature of exhaust gas in the exhaust pipe 16 is provided at the exhaust pipe 16 between the liquid injection nozzle 29 and the catalyst 24, that is, at the inlet of the catalyst 24. A rotation sensor 51 for detecting the rotation speed of the crankshaft is provided near the crankshaft of the engine 11, and a load sensor 52 for detecting the load of the engine is provided near the accelerator pedal or near the control lever of the fuel injection pump. . Each detection output of the temperature sensor 43, the rotation sensor 51, and the load sensor 52 is connected to a control input of a controller 44 composed of a microcomputer. Other control inputs of the controller 44 include the catalyst 24 and the filter 26.
The excess air ratio of the exhaust gas at the outlet of the catalyst 24 on the exhaust gas upstream side of the exhaust pipe 16 between the exhaust pipe 16 and the junction of the bypass pipe 38 with the exhaust pipe 16 (actual exhaust gas amount / theoretical combustion exhaust gas Lambda sensor 45 for detecting air volume)
And each detection output of the NOx sensor 46 for detecting the NOx concentration of the exhaust gas at the outlet of the catalyst 24. The control output of the controller 44 is the intake throttle valve 23, the liquid regulating valve 3
4. Pump 36, first and second exhaust gas control valves 41, 42
Connected to each other.

The controller 44 has a memory 47.
The memory 47 stores the exhaust gas temperature at the inlet of the catalyst 24, the rotation speed and load of the engine 11, the excess air ratio at the outlet of the catalyst 24, the opening degree of the intake throttle valve 23 according to the NOx concentration at the outlet of the catalyst 24, the liquid regulating valve 34. ON time and intervals thereof, the opening degrees of the first and second exhaust gas regulating valves 41 and 42, the pump 3
6 is stored in advance. Specifically, NOx
The interval at which the liquid regulating valve 34 is turned on (the NOx occlusion time by the catalyst 24) is determined by the detection output of the sensor 46, and the liquid regulating valve 34 is turned on by the respective detection outputs of the lambda sensor 45, the rotation sensor 51, and the load sensor 52. The switching time and switching time of the exhaust gas regulating valves 41 and 42 are determined by the detection outputs of the NOx sensor 46, the lambda sensor 45 rotation sensor 51, and the load sensor 52. In particular, as the engine rotation speed detected by the rotation sensor 51 increases and the engine load detected by the load sensor 52 increases,
The time for turning on the liquid regulating valve 34 is set longer as the engine rotation speed detected by the rotation sensor 51 is lower and the engine load detected by the load sensor 52 is lower. Preferably. This means that the first exhaust gas regulating valve 41 is fully opened and the second exhaust gas regulating valve 42 is slightly opened (opening degree: 1
-10%), a part of the exhaust gas flows toward the catalyst 24, and the flow velocity increases as the engine rotation speed detected by the rotation sensor increases and the engine load detected by the load sensor increases. This is because hydrocarbons injected from the fuel injection nozzle 29 reach the catalyst 24 quickly.

The operation of the exhaust gas purifying apparatus for the engine 11 configured as described above will be described. When the engine 11 is started, the temperature sensor 43 detects an exhaust gas temperature of less than 250 ° C.
The intake throttle valve 23 is opened at an opening of 100%, and the liquid regulating valve 3 is opened.
Turn off the EGR valve 21 and the first exhaust gas regulating valve 4
1 is closed, and the second exhaust gas regulating valve 42 is further opened at an opening of 100%. Accordingly, the exhaust gas discharged from the engine 11 passes through the exhaust pipe 16 and passes through the NOx storage reduction catalyst 24. At this time, NOx contained in the exhaust gas is stored in the catalyst 24. If, for example, Ba is used as the NOx storage agent carried on the coat layer of the catalyst 24, NOx discharged from the engine 11 will be converted to O ₂ in the exhaust gas by the catalyst 24.
Reacts with BaO and BaCO ₃ in the catalyst 24 to produce [Ba (NO ₃ ) ₂ ]. In this state, the catalyst 2
It is occluded at 4. The HC contained in the exhaust gas is the catalyst 24
Is oxidized by the oxidizing action of the noble metal (Pt) carried on the coat layer of the above.

While the temperature sensor 43 detects the exhaust gas temperature of 250 ° C. or more, the NOx sensor 46 detects the NOx concentration of 50 ppm or more, that is, the NOx concentration of the catalyst 24.
When the amount of occlusion approaches a saturation state, the controller 44 determines whether the temperature sensor 43, the rotation sensor 51, the load sensor 52, and the N
Based on each detection output of the Ox sensor 46, the EGR valve 21 is opened at an opening of 50%, and the intake throttle valve 23 is opened at an opening of 50%. At the same time, the first exhaust gas control valve 41 is opened at an opening of 100%, the second exhaust gas control valve 42 is throttled to an opening of 1 to 10%, most of the exhaust gas flows into the bypass pipe 38, and some of the exhaust gas is catalyzed. The liquid 32 is jetted from the liquid jet nozzle 29 by turning on the liquid regulating valve 34 while flowing the liquid 32.
Then, after the lapse of the ON time of the liquid regulating valve 34 determined by the detection outputs of the lambda sensor 45, the rotation sensor 51, and the load sensor 52, or when the lambda sensor 45
The liquid regulating valve 34 is turned off at an earlier time when the following excess air ratio is detected.

The interval for turning on the liquid regulating valve 34 is every 0.1 to 600 seconds, preferably every 10 to 30 seconds, and the time for turning on the liquid regulating valve 34 is 0.01 to 30 seconds, preferably 0.1 to 30 seconds. 10 seconds. That is, the light oil 32 is
As shown in (a), the liquid is ejected from the liquid ejecting nozzle 29. The interval at which the liquid regulating valve 34 is turned on is set to 0.
The reason for limiting to 1 to 600 seconds is that NOx
Time is too short to store NOx enough,
This is because if it exceeds 600 seconds, the catalyst 24 may not be able to occlude NOx and may emit NOx to the atmosphere. The reason why the time during which the liquid regulating valve 34 is turned on is limited to 0.01 to 30 seconds as described above is that if it is less than 0.01 second, the excess air ratio of the atmosphere on the surface of the catalyst 24 is 1.0 or less (so-called This is because a relatively large amount of unburned HC is discharged to the atmosphere when the temperature does not reach 30 seconds.

When the light oil 32 is injected from the liquid injection nozzle 29, the oxygen concentration in the exhaust gas at the inlet of the catalyst 24 decreases, that is, as shown in FIG. HC, CO,
Since CO ₂ or H ₂ increases as a reducing agent, NOx stored in the catalyst 24 is released from the catalyst 24 as follows. First, [Ba (NO ₃ ) ₂ ] stored in the catalyst 24.
Reacts with the reducing agent in the exhaust gas to reduce to NO ₂ or N ₂ , and then the catalyst 24 functions as a highly selective reduction catalyst, and the NO ₂ reacts with CO and HC in the exhaust gas to be harmless. N ₂ , CO ₂ , and H ₂ O are generated and discharged to the atmosphere. As a result, since the catalyst 24 is regenerated, NOx in the exhaust gas is occluded by the catalyst 24, and NOx in the exhaust gas at the outlet of the catalyst 24 decreases as shown in FIG.

The HC generated by the injection of the light oil 32
As described above, the catalyst 24 functions as a reducing agent in the catalyst 24, but not all HC functions as a reducing agent, and some HC pass through the catalyst 24. For this reason, as shown by the dashed line in FIG. 3D, although the HC concentration at the outlet of the catalyst 24 increases, the unburned HC is collected by the filter 26. The unburned HC collected by the filter 26 is
When the liquid regulating valve 34 is turned on, the exhaust gas with a high excess air ratio, that is, the lean exhaust gas flows into the filter 26 through the bypass pipe 38, so that the active metal carried on the filter 26 is oxidized by the oxidizing action.・ It is burned. As a result, the HC concentration at the outlet of the filter 26 is suppressed to a low level as shown by the solid line in FIG. 3D, so that the emission of particulates into the atmosphere can be suppressed.

FIG. 4 shows a second embodiment of the present invention.
4, the same reference numerals as those in FIG. 1 indicate the same parts. In this embodiment, the exhaust pipe 16 between the NOx storage reduction catalyst 24 and the particulate filter 26, that is, the filter 26
An air injection nozzle 71 is provided at the inlet, and the air injection nozzle 71 is configured to be able to inject air toward the filter 26. One end of an air supply pipe 72 is connected to the air injection nozzle 71, and the other end of the air supply pipe 72 is connected to an air tank 73 in which compressed air is stored. The air supply pipe 72 is provided with an air adjustment valve 74 for adjusting the amount of compressed air supplied to the air injection nozzle 71. When the air regulating valve 74 is turned on, the compressed air in the air tank 73 is supplied to the air injection nozzle 71. When the air adjustment valve 74 is turned off, the air injection nozzle 7 is turned off.
1 is configured so that the supply of the compressed air to 1 is stopped.
In this embodiment, the bypass pipe of the first embodiment is not provided. The control output of the controller 44 is connected to the intake throttle valve 23, the liquid regulating valve 34, the pump 36, and the air regulating valve 74, respectively. The memory 47 of the controller 44 stores the exhaust gas temperature at the inlet of the catalyst 24,
The opening degree of the intake throttle valve 23 according to the excess air ratio at the outlet and the NOx concentration at the outlet of the catalyst 24, the ON time and the interval of the liquid regulating valve 34 and the air regulating valve 74, and the presence or absence of the operation of the pump 36 are stored in advance. Is done. Except for the above, the configuration is the same as that of the first embodiment.

The operation of the exhaust gas purifying apparatus for the engine 11 configured as described above will be described. When the engine 11 is started, the temperature sensor 43 detects an exhaust gas temperature of less than 250 ° C., so that the controller 44 opens the intake throttle valve 23 at an opening of 100% based on the detection output of the temperature sensor 43 to adjust the liquid. The valve 34 and the air regulating valve 74 are turned off, and the EGR valve 21 is further closed. As a result, the engine 11
The exhaust gas discharged from the exhaust gas passes through the exhaust pipe 16 and passes through the NOx storage reduction catalyst 24. At this time, similarly to the first embodiment, NOx contained in the exhaust gas is occluded by the catalyst 24, and HC contained in the exhaust gas is oxidized by the oxidizing action of the noble metal (Pt) carried on the coat layer of the catalyst 24. You.

With the temperature sensor 43 detecting the exhaust gas temperature of 250 ° C. or higher, the NOx sensor 46 detects the NOx concentration of 50 ppm or higher, ie, the NOx concentration of the catalyst 24.
When the occlusion amount approaches the saturated state, the controller 44 opens the EGR valve 21 at an opening of 50% and opens the intake throttle valve 23 at an opening of 50% based on the detection outputs of the temperature sensor 43 and the NOx sensor 46. Open with At the same time, the liquid regulating valve 34
Turn on. And the lambda sensor 45 and the rotation sensor 51
And after the elapse of the ON time of the liquid regulating valve 34 determined by each detection output of the load sensor 52 or when the lambda sensor 45 detects an excess air ratio of 1.0 or less, whichever comes earlier. The valve 34 is turned off. As a result, the oxygen concentration in the exhaust gas at the catalyst 24 inlet decreases, that is, the HC concentration in the exhaust gas at the catalyst 24 inlet increases, and H
Since C, CO, CO ₂ or H ₂ increases as a reducing agent,
As in the first embodiment, the NO stored in the catalyst 24 is
x is released at the same time as being released from the catalyst.

HC generated by the injection of the light oil 32
As described above, the catalyst 24 functions as a reducing agent in the catalyst 24, but not all HC functions as a reducing agent, and some HC pass through the catalyst 24. For this reason, although the HC concentration at the outlet of the catalyst 24 increases, the unburned HC is collected by the filter 26. The unburned HC trapped in the filter 26 has a high excess air ratio, that is, lean exhaust gas flows into the filter 26 by turning on the air adjustment valve 74 only while the liquid adjustment valve 34 is on. Accordingly, the active metal carried on the filter 26 is oxidized and burned by the oxidizing action. As a result, the HC concentration at the outlet of the filter 26 can be kept low, so that the emission of particulates into the atmosphere can be suppressed.

[0030]

Next, examples of the present invention will be described in detail together with comparative examples. <Embodiment 1> As shown in FIG. 1, an NOx storage reduction catalyst 24 and a particulate filter 26 are provided in the exhaust pipe 16 of an 8000 cc turbocharged diesel engine 11 in order from the exhaust gas upstream side. Further, a liquid injection nozzle 29 capable of injecting light oil 32 is provided in the exhaust pipe 16 on the exhaust gas upstream side of the catalyst 24, a bypass pipe 38 that bypasses the catalyst 24 is provided in the exhaust pipe 16, and a second pipe is provided in the exhaust pipe 16 and the bypass pipe 38. First and second exhaust gas regulating valves 41 and 42 were provided, respectively. In the catalyst 24, the coat layer was made of alumina, the noble metal was made of platinum, and the NOx storage agent was made of Ba.
It is. The filter 26 is coated with a platinum-zeolite catalyst, that is, the filter is coated with a slurry containing hydrogen ion-exchanged zeolite powder (H-ZSM-5) and alumina powder (Al ₂ O ₃ ) on a honeycomb carrier made of cordierite. After that, Pt is supported.

<Embodiment 2> As shown in FIG.
Of the particulate filter 26
An air injection nozzle 71 capable of injecting air toward the filter 26 was provided at an inlet of the air filter. Except for the above, the configuration was the same as that of the first embodiment. <Comparative Example 1> A NOx storage reduction catalyst was added to an exhaust pipe of an 8000 cc naturally aspirated diesel engine (not shown).
And a particulate filter carrying platinum.
In addition, a liquid injection nozzle capable of injecting light oil was provided in an exhaust pipe on the exhaust gas upstream side.

<Comparative Test 1 and Evaluation> The emission amounts of NOx, particulates, and HC by the exhaust gas purifying devices of Examples 1, 2 and Comparative Example 1 were measured. The results are shown in FIGS. As is clear from FIG. 5, Comparative Example 1
In Example 1, NOx could be reduced only by 50% from the regulation value, whereas in Examples 1 and 2, it could be reduced by 60% from the regulation value. As is clear from FIG. 6, in Comparative Example 1, the particulate increased to 3.5 times the regulation value, whereas in Examples 1 and 2, the particulates could be reduced by 80% and 70% from the regulation value, respectively. As is clear from FIG. 7, in Comparative Example 1, HC increased 9 times the regulation value, whereas in Examples 1 and 2, the HC could be reduced by 80% and 70% from the regulation value, respectively.

[0033]

As described above, according to the present invention, the exhaust pipe of the engine is provided with the NOx storage reduction catalyst and the particulate filter with the oxidation catalyst in order from the exhaust gas upstream side.
A liquid injection nozzle capable of injecting a hydrocarbon-based liquid is provided at an inlet of the NOx storage reduction catalyst, and a hydrocarbon-based liquid supply unit supplies the liquid to the liquid injection nozzle through a liquid adjustment valve,
The exhaust gas regulating valve regulates the flow rate of the exhaust gas to the NOx storage reduction catalyst and the bypass pipe, and the controller controls the liquid regulating valve and the exhaust gas regulating valve based on the detection output of the temperature sensor that detects the exhaust gas temperature at the inlet of the NOx storage reduction catalyst. When the control is performed, when the temperature sensor detects an exhaust gas temperature lower than a predetermined value, NOx in the exhaust gas is occluded in the catalyst as a nitrate, and HC in the exhaust gas is oxidized. When the temperature sensor detects an exhaust gas temperature equal to or higher than a predetermined value, the controller adjusts the exhaust gas control valve so that most of the exhaust gas flows to the bypass pipe and some of the exhaust gas flows to the catalyst, and simultaneously, the liquid control valve is turned on for a predetermined time. Only to turn on and eject liquid from the liquid ejection nozzle. As a result, the oxygen concentration in the exhaust gas at the catalyst inlet decreases, and HC and the like increase as a reducing agent. Therefore, the NOx stored in the catalyst reacts with the HC and the like to become N _{2 and the} like and is released from the catalyst. Further, a part of the HC generated by the injection of the liquid passes through the catalyst and is collected by the filter. However, when the liquid regulating valve is turned on, exhaust gas with a high excess air ratio passes through the bypass pipe and passes through the filter. The captured HC is oxidized and burned by the oxidizing action of the active metal carried on the filter. As a result, the concentration of HC in the exhaust pipe on the downstream side of the exhaust gas from the filter can be kept low, so that the emission of particulates into the atmosphere can be suppressed.

The controller adjusts the liquid regulating valve and the exhaust gas based on the lambda sensor and / or the NOx sensor for detecting the excess air ratio or NOx concentration of the exhaust gas at the inlet of the particulate filter and the temperature sensor. If the control valves are individually controlled, the interval at which the liquid control valve is turned on (NOx storage time by the catalyst) is determined by the detection output of the NOx sensor, and the time during which the liquid control valve is turned on is determined by the detection output of the lambda sensor. , N
The timing and time for adjusting the exhaust gas control valve so that the exhaust gas passes through the bypass pipe are determined by the respective detection outputs of the Ox sensor and the lambda sensor. As a result, the optimal amount of liquid is injected at the optimal time, and the exhaust gas with a high excess air ratio is supplied to the filter in the optimal amount at the optimal time. Therefore, the emission amount of NOx and particulates contained in the exhaust gas is reduced. Can be reduced with high efficiency, and the liquid injected from the liquid injection nozzle to the exhaust pipe can be prevented from being discharged into the atmosphere in a vaporized state.

A NOx storage reduction catalyst and a particulate filter with an oxidation catalyst are provided in the exhaust pipe of the engine in order from the exhaust gas upstream side, and a liquid injection nozzle capable of injecting hydrocarbon liquid is provided at the inlet of the NOx storage reduction catalyst. The hydrocarbon-based liquid supply means supplies the liquid to the liquid injection nozzle through a liquid regulating valve, and an air injection nozzle capable of injecting air is provided at the inlet of the particulate filter. If the controller controls the liquid regulating valve and the air regulating valve based on the detection output of the temperature sensor that detects the temperature of the exhaust gas at the inlet of the NOx storage reduction catalyst by supplying air through the regulating valve, the temperature sensor is below a predetermined value. When the temperature of the exhaust gas is detected, NOx in the exhaust gas is stored in the catalyst as nitrate, and H
C is oxidized. When the temperature sensor detects an exhaust gas temperature equal to or higher than a predetermined value, the controller turns on the liquid regulating valve for a predetermined time and injects liquid from the liquid injection nozzle. This reduces the oxygen concentration in the exhaust gas at the catalyst inlet,
Increases as a reducing agent, so that the NO stored in the catalyst
x reacts with the HC or the like to become N ₂ or the like and is released from the catalyst. Further, although a part of HC generated by the injection of the liquid passes through the catalyst and is collected by the filter,
When the liquid control valve is turned on, the air control valve is turned on to inject air from the air injection nozzle, and exhaust gas having a high excess air ratio flows into the filter.
Is oxidized and burned by the oxidizing action of the active metal carried on the filter. As a result, the HC concentration in the exhaust pipe on the downstream side of the exhaust gas from the filter can be kept low, so that the emission of particulates into the atmosphere can be suppressed.

The controller controls the liquid regulating valve based on the lambda sensor and / or the NOx sensor for detecting the excess air ratio or the NOx concentration of the exhaust gas at the inlet of the particulate filter and the temperature sensor and the respective detection outputs. Then, the interval at which the liquid regulating valve is turned on is determined by the detection output of the NOx sensor, and the time during which the liquid regulating valve is turned on is determined by the detection output of the lambda sensor.
The timing and time for injecting air from the air injection nozzle by turning on the air adjustment valve by the detection outputs of the x sensor and the lambda sensor are determined. As a result, the optimal amount of liquid is injected at the optimal time, and the exhaust gas with a high excess air ratio is supplied to the filter in the optimal amount at the optimal time. Therefore, the emission amount of NOx and particulates contained in the exhaust gas is reduced. Can be reduced with high efficiency, and the liquid injected from the liquid injection nozzle to the exhaust pipe can be prevented from being discharged into the atmosphere in a vaporized state. Furthermore, if the engine is a turbocharged engine, by supercharging the intake air with the turbocharger, it becomes possible to increase the oxygen concentration in the exhaust gas and reduce the emission of soot, The effect of reducing NOx and particulates by the NOx storage reduction catalyst and the particulate filter can be enhanced.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a particulate filter of the device.

FIG. 3 shows the excess air ratio in exhaust gas when light oil is injected,
The figure which shows the change of NOx density | concentration and HC density | concentration.

FIG. 4 is a configuration diagram showing an exhaust gas purifying apparatus for an engine according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the amount of NOx emission by the exhaust gas purifying devices of Examples 1, 2 and Comparative Example 1, respectively.

FIG. 6 is a diagram showing the amounts of particulate emissions by the exhaust gas purifying apparatuses of Examples 1 and 2 and Comparative Example 1, respectively.

FIG. 7 is a diagram showing the amounts of HC emissions by the exhaust gas purifying devices of Examples 1 and 2 and Comparative Example 1, respectively.

[Explanation of symbols]

 Reference Signs List 11 diesel engine 13 intake pipe 16 exhaust pipe 17 turbocharger 17a compressor 17b turbine 24 NOx storage reduction catalyst 26 particulate filter 29 liquid injection nozzle 32 light oil (hydrocarbon liquid) 34 liquid regulating valve 36 pump (hydrocarbon liquid) Supply means) 38 Bypass pipe 41, 42 Exhaust gas control valve 43 Temperature sensor 44 Controller 45 Lambda sensor 46 NOx sensor 71 Air injection nozzle 73 Air tank (air supply means) 74 Air control valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/20 F01N 3/20 S 4G069 3/28 301D 3/28 301 3/30 B 3/30 C 3 / 36 J 3/36 B01D 46/44 // B01D 46/44 53/36 103B F term (reference) 3G090 AA03 AA06 BA02 CB04 CB07 DA10 DA12 DA18 DA20 EA02 EA05 EA06 3G091 AA10 AA11 AA18 AB02 AB06 AB09 AB13 CA02 CA12 CA13 CA18 CA23 CA24 CA26 CB07 EA01 EA03 EA17 EA33 EA34 FB01 FB09 GA06 GB02W GB03W GB06W GB17X HA09 HA15 HA22 HA36 HA37 HA42 HB05 HB06 HB07 4D019 AA01 BA05 BB06 BC07 CA01 4D048 AA06 AA02 BA03 BA02 DA02 BA02 DA02 BA02 DA02 JA32 MA44 MA51 MA54 QA01 QA03 QA19 QA23 QA30 SA08 TA06 UA25 4G069 AA03 AA08 BA01B BA07B BC13B BC75B CA03 CA07 CA08 CA13 CA15 CA18 EA19 FA03 ZA11B

Claims (9)

[Claims] An NOx storage reduction catalyst (24) provided in an exhaust pipe (16) of an engine (11), and an exhaust pipe upstream of exhaust gas from the NOx storage reduction catalyst (24).
A liquid injection nozzle (29) provided on the (16) and capable of injecting the hydrocarbon liquid (32) toward the NOx storage reduction catalyst (24); and a liquid regulating valve (34) provided on the liquid injection nozzle (29). A hydrocarbon-based liquid supply means (36) for supplying the liquid (32) via an exhaust pipe downstream of the NOx storage reduction catalyst (24).
(16) a particulate filter (26) carrying an active metal functioning as an oxidation catalyst; and one end connected to the exhaust pipe (16) on the exhaust gas upstream side of the NOx storage reduction catalyst (24). Is the NOx storage reduction catalyst (2
4) and the exhaust pipe (1) between the particulate filter (26).
A bypass pipe (38) connected to the NOx storage reduction catalyst (24) and bypassing the NOx storage reduction catalyst (24), and exhaust gas discharged from the engine (11) to the NOx storage reduction catalyst (24) and the bypass pipe (38). An exhaust gas regulating valve (41, 42) for adjusting the flow rate of each gas, and an exhaust pipe on the exhaust gas upstream side of the NOx storage reduction catalyst (24).
(16) a temperature sensor (43) for detecting the temperature of the exhaust gas, and the liquid regulating valve (34) and the exhaust gas regulating valve (41, 42) are respectively controlled based on the detection output of the temperature sensor (43). An exhaust gas purification device for an engine, comprising: a controller (44). 2. A lambda sensor (45) for detecting an excess air ratio of exhaust gas in an exhaust pipe (16) between a NOx storage reduction catalyst (24) and a particulate filter (26), or the NOx storage reduction catalyst (24). NOx for detecting the NOx concentration of the exhaust gas in the exhaust pipe (16) between the particulate filter (26) and the particulate filter (26).
The apparatus further includes one or both of the sensors (46), and the controller (44) includes a temperature sensor (43) and the lambda sensor (45).
Or a liquid regulating valve (34) and an exhaust gas regulating valve based on each detection output with one or both of the NOx sensor (46).
2. The method according to claim 1, wherein each of said first and second control means is controlled.
An exhaust gas purifying apparatus for an engine according to the above. 3. A lambda sensor for detecting an excess air ratio of exhaust gas in the exhaust pipe downstream of the particulate filter or NO for detecting a NOx concentration of exhaust gas in the exhaust pipe downstream of the particulate filter.
x sensor, and the controller further comprises a temperature sensor and the lambda sensor or the NOx sensor.
The exhaust gas purifying apparatus for an engine according to claim 1, wherein the liquid regulating valve and the exhaust gas regulating valve are respectively controlled based on each detection output from one or both of the sensors. 4. An NO provided in an exhaust pipe of an engine (11).
an x-storage reduction catalyst (24), and an exhaust pipe on the exhaust gas upstream side of the NOx storage-reduction catalyst (24)
A liquid injection nozzle (29) provided on the (16) and capable of injecting the hydrocarbon liquid (32) toward the NOx storage reduction catalyst (24); and a liquid regulating valve (34) provided on the liquid injection nozzle (29). A hydrocarbon-based liquid supply means (36) for supplying the liquid (32) via an exhaust pipe downstream of the NOx storage reduction catalyst (24).
(16) a particulate filter (26) carrying an active metal functioning as an oxidation catalyst; and an exhaust pipe (16) between the NOx storage reduction catalyst (24) and the particulate filter (26). An air injection nozzle (71) capable of injecting air toward the particulate filter (26), and an air supply means for supplying the air to the air injection nozzle (71) via an air regulating valve (74) ( 73), and an exhaust pipe on the exhaust gas upstream side of the NOx storage reduction catalyst (24).
(16) a temperature sensor (43) for detecting the temperature of the exhaust gas, and a controller for controlling the liquid regulating valve (34) and the air regulating valve (74) based on the detection output of the temperature sensor (43), respectively. 44) An exhaust gas purification device for an engine comprising: 5. A lambda sensor (45) for detecting an excess air ratio of exhaust gas in an exhaust pipe (16) between a NOx storage reduction catalyst (24) and a particulate filter (26), or the NOx storage reduction catalyst (24). NOx for detecting the NOx concentration of the exhaust gas in the exhaust pipe (16) between the particulate filter (26) and the particulate filter (26).
The apparatus further includes one or both of the sensors (46), and the controller (44) includes a temperature sensor (43) and the lambda sensor (45).
Alternatively, based on each detection output from one or both of the NOx sensor (46), the liquid regulating valve (34) and the air regulating valve (7
5. The exhaust gas purifying apparatus for an engine according to claim 4, wherein each of the steps (4) and (4) is controlled. 6. A lambda sensor for detecting an excess air ratio of exhaust gas in an exhaust pipe downstream of the particulate filter from the particulate filter, or a NO for detecting a NOx concentration of exhaust gas in an exhaust pipe downstream of the particulate filter to the particulate filter.
x sensor, and the controller further comprises a temperature sensor and the lambda sensor or the NOx sensor.
5. The exhaust gas purifying apparatus for an engine according to claim 4, wherein the liquid regulating valve and the air regulating valve are respectively controlled based on each detection output from one or both of the sensors. 7. When the condition for opening the liquid regulating valve (34) based on the detection output of the temperature sensor (43) is satisfied, the controller (44) sets the liquid regulating valve (34) to 0.1 to The exhaust gas purifying apparatus for an engine according to claim 1 or 4, wherein the apparatus is configured to open for 0.01 to 30 seconds every 600 seconds. 8. A condition for opening the liquid regulating valve (34) based on each detection output of the temperature sensor (43) and one or both of the lambda sensor (45) and the NOx sensor (46) is satisfied. 7. The system according to claim 2, wherein the controller (44) is configured to open the liquid regulating valve (34) for 0.1 to 30 seconds every 0.1 to 600 seconds when the controller is in operation. Exhaust gas purification equipment for engines. 9. The engine (11) is an engine with a turbocharger, wherein the turbocharger (17) is provided in an intake pipe (13) and can compress and supply air to the engine (11). Compressor (1
7a) and a turbine (17b) provided in an exhaust pipe (16), connected to the compressor (17a) via a shaft, and rotatable by energy of exhaust gas flowing through the exhaust pipe (16). Or an exhaust gas purifying apparatus for an engine according to 4.