JP2011122552A - Exhaust emission control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the emission of nitrous oxide released into the atmosphere in an exhaust emission control system of an internal combustion engine. <P>SOLUTION: The exhaust emission control system of an internal combustion engine is provided with a nitrogen oxide reducing device in the exhaust path of the internal combustion engine and an ammonia slip prevention catalyst at downstream of the nitrogen oxide reducing device, wherein there are provided an additive supplier for supplying an additive to the nitrogen oxide reducing device, an ammonia detection means for detecting the concentration of ammonia between the nitrogen oxide reducing device and the ammonia slip prevention catalyst, a nitrous oxide detection means for detecting the concentration of nitrous oxide downstream of the ammonia slip prevention catalyst, and an additive amount control means for controlling the amount of the additive supplied from the additive supplier to the nitrogen oxide reducing device according to the concentration of nitrous oxide detected by the nitrous oxide detection means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device for an internal combustion engine that can reduce nitrous oxide in the exhaust gas of the internal combustion engine.

An exhaust gas purification device for an internal combustion engine includes a urea SCR catalyst purification device equipped with a selective catalytic reduction (SCR) catalyst as an exhaust gas purification device for a diesel engine, and an exhaust gas purification device for gasoline and diesel engines. As an example, a NOx storage catalyst purification device including a NOx storage catalyst is known.
The exhaust gas purification device equipped with these urea SCR catalyst purification device, NOx occlusion catalyst purification device, etc., adds a reducing agent such as hydrocarbon (light oil), urea, etc. to the exhaust gas, thereby allowing selective catalytic reduction catalyst, NOx occlusion. NOx is reduced and removed using a nitrogen oxide reducing device such as a catalyst as a reducing atmosphere. (Patent Documents 1 to 3)

JP 2004-270565 A JP 2001-12231 A JP 2000-230414 A

By the way, a conventional exhaust gas purifying apparatus for an internal combustion engine generates nitrous oxide (hereinafter referred to as N ₂ ) which is a greenhouse gas when ammonia (hereinafter referred to as “NH ₃ ”) is generated in the process of purifying NOx. O) may be produced in large quantities. N ₂ O is a gas having a greenhouse effect that is 310 times that of CO ₂ , and the generation of N ₂ O promotes global warming, so that it is necessary to reduce emissions.
However, existing technologies have not taken sufficient measures to reduce N ₂ O.

.
An object of the present invention is to reduce the emission amount of nitrous oxide released into the atmosphere in an exhaust gas purification apparatus for an internal combustion engine.

  The present invention provides an exhaust gas purification apparatus for an internal combustion engine in which a nitrogen oxide reduction device is provided in an exhaust passage of the internal combustion engine, and an ammonia slip prevention catalyst is provided downstream of the nitrogen oxide reduction device. An additive supply device for supplying an additive to the reduction device, and an ammonia detection means for detecting an ammonia concentration between the nitrogen oxide reduction device and the ammonia slip prevention catalyst, the downstream side of the ammonia slip prevention catalyst Is provided with a nitrous oxide detecting means for detecting the nitrous oxide concentration, and is supplied from the additive supply device to the nitrogen oxide reducing device according to the nitrous oxide concentration detected by the nitrous oxide detecting means. An additive amount control means for controlling the amount of the additive is provided.

  The exhaust gas purifying device for an internal combustion engine of the present invention can control the amount of additive supplied to the nitrogen oxide reducing device according to the concentration of nitrous oxide, so that nitrous oxide released into the atmosphere Can be reduced.

It is a schematic block diagram of an exhaust gas purification apparatus. Example 1 It is a flowchart of an exhaust gas purification apparatus. Example 1 It is a flowchart of an exhaust gas purification apparatus. (Modification 1 of Example 1) It is a flowchart of an exhaust gas purification apparatus. (Modification 2 of Example 1) It is a schematic block diagram of an exhaust gas purification apparatus. (Example 2) It is a flowchart of an exhaust gas purification apparatus. (Example 2) It is a flowchart of an exhaust gas purification apparatus. (Modification 1 of Example 2) It is a flowchart of an exhaust gas purification apparatus. (Modification 2 of Example 2) It is a schematic block diagram of an exhaust gas purification apparatus. (Modification 3 of Example 2)

  Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show Embodiment 1 of the present invention. In FIG. 1, 1 is an internal combustion engine, 2 is a combustion chamber, 3 is an intake pipe, 4 is an intake manifold, 5 is an intake passage, 6 is an exhaust manifold, 7 is an exhaust pipe, and 8 is an exhaust passage. The internal combustion engine 1 includes a fuel supply device 9 that injects and supplies fuel to the combustion chamber 2. The fuel supply device 9 injects fuel into the combustion chamber 2 by the fuel injection valve 10. The internal combustion engine 1 communicates an intake passage 5 composed of an intake pipe 3 and an intake manifold 4 to the combustion chamber 2 and injects the air supplied to the combustion chamber 2 through the intake passage 5 into the combustion chamber 2 by the fuel injection valve 10. The fuel is mixed and burned, and the exhaust gas after combustion is discharged to the atmosphere through the exhaust passage 8 constituted by the exhaust manifold 6 and the exhaust pipe 7.
The exhaust gas purifying device 11 for purifying the exhaust gas of the internal combustion engine 1 is provided with a urea SCR purifying device 12 having a selective catalytic reduction (SCR) catalyst as a nitrogen oxide reducing device in the exhaust passage 8, and the urea SCR catalyst. An ammonia slip prevention catalyst 13 is provided in the exhaust passage 8 downstream of the purification device 12. The urea SCR purification device 12 is provided with an exhaust gas temperature sensor 14 for detecting the temperature of exhaust gas flowing into the selective catalytic reduction catalyst, and with a selective catalytic reduction catalyst temperature sensor 15 for detecting the temperature of the selective catalytic reduction catalyst. ing. The ammonia slip prevention catalyst 13 is provided with an ammonia slip prevention catalyst temperature sensor 16.
The exhaust gas purification device 11 includes a particulate filter 17 having an oxidation catalyst in the exhaust passage 8 upstream of the urea SCR catalyst purification device 12. The particulate filter 17 collects the particulate matter in the exhaust gas, and regenerates the collection function by oxidizing and oxidizing the collected particulate matter with an oxidation catalyst.
The exhaust gas purification device 11 includes a urea supply device 18 as an additive supply device for supplying an additive to the urea SCR catalyst purification device 12. The urea supply device 18 supplies the reducing agent urea to the exhaust passage 8 upstream of the urea SCR catalyst purification device 12 by the urea injection valve 19. Further, the exhaust gas purification device 11 includes a light oil supply device 20 as an additive supply device. The light oil supply device 20 supplies light oil of the reducing agent to the exhaust passage 8 upstream of the urea SCR catalyst purification device 12 by the light oil injection valve 21.
The exhaust gas purification device 11 includes ammonia detection means 22 for detecting the ammonia (NH ₃ ) concentration in the exhaust passage 8 between the urea SCR catalyst purification device 12 and the ammonia slip prevention catalyst 13, and downstream of the ammonia slip prevention catalyst 13. The exhaust passage 8 on the side is provided with nitrous oxide detection means 23 for detecting the nitrous oxide (N ₂ O) concentration. The nitrous oxide detection means 23 uses, for example, an IR (infrared absorption detection) method, and detects the concentration of nitrous oxide in the exhaust gas by measuring the absorbance at the infrared absorption wavelength peculiar to N ₂ O.

The fuel supply device 9, the exhaust gas temperature sensor 14, the selective catalytic reduction catalyst temperature sensor 15, the ammonia slip prevention catalyst temperature sensor 16, the urea supply device 18, the light oil supply device 20, and the ammonia detection means 22 The nitrous oxide detection means 23 is connected to the control means 24. The control means 24 is connected with an operating condition detecting means 25 for detecting the operating condition (engine speed, engine load, etc.) of the internal combustion engine 1.
The control unit 24 includes an injection amount control unit 26 that controls the injection amount of fuel supplied from the fuel injection valve 10 of the fuel supply device 9 to the combustion chamber 2, and urea injection of the urea supply device 18 to the urea SCR catalyst purification device 12. A urea amount control means 27 which is an additive amount control means for controlling the urea amount of the additive supplied from the valve 19, and an additive light oil supplied from the light oil injection valve 21 of the light oil supply device 20 to the urea SCR purification device 12. And a light oil amount control means 28 which is an additive amount control means for controlling the amount.
In the internal combustion engine 1, the fuel injection amount supplied from the fuel supply device 9 to the combustion chamber 2 is controlled by the injection amount control unit 26 in accordance with the operation state detected by the operation state detection unit 25.
The exhaust gas purification device 11 of the internal combustion engine 1 supplies the urea SCR catalyst purification device 12 from the urea supply device 18 according to the nitrous oxide concentration detected by the nitrous oxide detection means 23 by the urea amount control means 27. Control the amount of urea produced. Further, the exhaust gas purifying apparatus 11 determines that both the ammonia concentration detected by the ammonia detection means 22 and the nitrous oxide concentration detected by the nitrous oxide detection means 23 are equal to or higher than the set value. The urea amount control means 27 controls the urea supply device 18 to stop supplying urea. Further, when the temperature of the ammonia slip prevention catalyst 13 is equal to or lower than the set temperature, the exhaust gas purification device 11 does not perform urea amount control by the urea amount control means 27 according to the nitrous oxide concentration.

Next, the operation will be described.
The exhaust gas purification device 11 of the internal combustion engine 1 supplies fuel from the fuel supply device 9 to the combustion chamber 2 during operation of the internal combustion engine 1, and urea as a reducing agent from the urea supply device 18 upstream of the urea SCR catalyst purification device 12. Is supplied to the exhaust passage 8 on the side, and light oil as a reducing agent is supplied from the light oil supply device 19. The urea supplied to the exhaust passage 8 is hydrolyzed to generate ammonia. And the exhaust gas generated ammonia is introduced into the urea SCR catalytic purification device 12, and the NOx contained in the ammonia and exhaust gas reacts with selective catalytic reduction catalyst is reduced to N _2. Excess ammonia that has not been used in the reaction by the selective catalytic reduction catalyst is oxidized by the ammonia slip prevention catalyst 13 to generate N ₂ and water, thereby preventing discharge (ammonia slip).
The urea amount supplied from the urea supply device 18 is controlled according to the nitrous oxide N ₂ O concentration, as shown in FIG. When the program starts (A01), the exhaust gas purification device 11 takes in various signals such as a detection signal of the exhaust gas temperature sensor 14 (A02), and the nitrous oxide N ₂ O concentration is less than a set value K1 (for example, 10 ppm). It is determined whether (N ₂ O <K1) (A03).
When this determination (A03) is NO (a large amount of nitrous oxide is generated), urea injection is stopped and the light oil injection amount is controlled (A04). Thereafter, various signals are captured in a state where light oil is supplied (A05), and it is determined whether the nitrous oxide N ₂ O concentration is less than the set value K1 (N ₂ O <K1) (A06). When this determination (A06) is NO (the amount of nitrous oxide generated is large), the injection of light oil is stopped (A07), and the program is ended (A09).
On the other hand, when the determination (A03) is YES (the amount of generated nitrous oxide is small), and when the determination (A06) is YES (the amount of generated nitrous oxide is small), it depends on the concentration of nitrous oxide. The urea injection amount is controlled (A08), and the program is ended (A09).
As described above, the exhaust gas purifying device 11 of the internal combustion engine 1 stops or controls the supply of urea as an additive according to the nitrous oxide concentration detected by the nitrous oxide detecting means 23. Since the urea amount supplied from the urea supply device 18 to the SCR catalyst catalyst purification device 12 can be appropriately controlled, the emission amount of nitrous oxide released into the atmosphere can be reduced.

In the first embodiment, the amount of urea supplied to the urea SCR catalyst purification device 12 is controlled according to the nitrous oxide concentration. However, the urea SCR catalyst purification device is controlled according to the ammonia concentration and the nitrous oxide concentration. The amount of urea supplied to 12 can also be controlled. FIG. 3 shows a first modification of the exhaust gas purifying apparatus 11 according to the first embodiment.
In FIG. 3, when the program starts (B01), the exhaust gas purification device 11 takes in various signals such as a detection signal of the exhaust gas temperature sensor 14 (B02), and the ammonia NH ₃ concentration is a set value K2 (for example, 10 ppm). It is judged whether it is less than (NH ₃ <K2) (B03).
When this determination (B03) is NO (a large amount of ammonia is generated), it is determined whether the nitrous oxide N ₂ O concentration is less than a set value K1 (for example, 10 ppm) (N ₂ O <K1) (B04). ). If this determination (B04) is NO (a large amount of nitrous oxide is generated), urea injection is stopped (B05), and the program is ended (B07). In step (B05), the injection may be switched to light oil injection amount control instead of urea injection stop.
On the other hand, when the determination (B03) is YES (a small amount of ammonia is generated), and when the determination (B04) is YES (a small amount of nitrous oxide is generated), the urea concentration depends on the nitrous oxide concentration. The injection amount is controlled (B06), and the program is ended (B07).
As described above, the exhaust gas purifying device 11 of the internal combustion engine 1 is such that both the ammonia concentration detected by the ammonia detecting means 22 and the nitrous oxide concentration detected by the nitrous oxide detecting means 23 are equal to or higher than the set value. If this is the case, the urea amount control means 27 stops the urea supply by the urea supply device 18, whereby the amount of nitrous oxide released into the atmosphere can be reduced.

Moreover, in the above-described modified example 1, the supply of urea was stopped when both the ammonia concentration and the nitrous oxide concentration were equal to or higher than the set values. However, based on the temperature of the ammonia slip prevention catalyst 13, the urea SCR The amount of urea supplied to the catalyst purification device 12 can also be controlled. FIG. 4 shows a second modification of the exhaust gas purifying apparatus 11 according to the first embodiment.
In FIG. 4, when the program starts (C01), the exhaust gas purifying device 11 takes in various signals such as the detection signal of the exhaust gas temperature sensor 14 (C02), and the temperature TEMP1 of the ammonia slip prevention catalyst 13 becomes the set temperature T1 ( For example, it is determined whether the temperature exceeds 300 ° C. (TEMP1> T1) (C03).
When this determination (C03) is NO (the temperature of the ammonia slip prevention catalyst 13 is low), it is determined whether the ammonia NH ₃ concentration is less than a set value K2 (for example, 10 ppm) (NH ₃ <K2) (C04). ). When this determination (C04) is NO (a large amount of ammonia is generated), it is determined whether the nitrous oxide N ₂ O concentration is less than a set value K1 (for example, 10 ppm) (N ₂ O <K1) (C05 ). If this determination (C05) is NO (a large amount of nitrous oxide is generated), urea injection is stopped (C06) and the program is ended (C08).
On the other hand, when the determination (C03) is YES (the temperature of the ammonia slip prevention catalyst 13 is high), when the determination (C04) is YES (a small amount of ammonia is generated), and when the determination (C05) is YES ( If the amount of nitrous oxide generated is small), the urea injection amount is controlled according to the nitrous oxide concentration (C07), and the program is ended (C08).
As described above, the exhaust gas purifying device 11 of the internal combustion engine 1 does not generate nitrous oxide when the temperature of the ammonia slip prevention catalyst 13 exceeds the set temperature, and therefore controls the urea amount without stopping the supply of urea. If the temperature of the ammonia slip prevention catalyst 13 is equal to or lower than the set temperature, the urea supply is stopped and the urea amount control by the urea amount control means 27 according to the nitrous oxide concentration is not performed. It is not necessary to perform dedicated control according to the concentration, and appropriate control can be performed.

5 and 6 show a second embodiment of the present invention. In FIG. 5, 101 is an internal combustion engine, 102 is a combustion chamber, 103 is an intake pipe, 104 is an intake manifold, 105 is an intake passage, 106 is an exhaust manifold, 107 is an exhaust pipe, and 108 is an exhaust passage. The internal combustion engine 101 includes a fuel supply device 109 that injects and supplies fuel to the combustion chamber 102. The fuel supply device 109 injects fuel into the combustion chamber 102 by the fuel injection valve 110. The internal combustion engine 101 communicates an intake passage 105 including an intake pipe 103 and an intake manifold 104 to the combustion chamber 102, and injects air supplied to the combustion chamber 102 through the intake passage 105 into the combustion chamber 102 by a fuel injection valve 110. The fuel is mixed and burned, and the exhaust gas after combustion is discharged to the atmosphere through an exhaust passage 108 constituted by an exhaust manifold 106 and an exhaust pipe 107.
The exhaust gas purification device 111 for purifying the exhaust gas of the internal combustion engine 101 is provided with a NOx storage catalyst purification device 112 having a NOx storage catalyst as a nitrogen oxide reduction device in the exhaust passage 108, and the NOx storage catalyst purification device 112. In addition, an ammonia slip prevention catalyst 113 is provided in the exhaust passage 108 on the downstream side. The NOx storage catalyst purification device 112 is provided with an exhaust gas temperature sensor 114 that detects the temperature of exhaust gas flowing into the NOx storage catalyst, and is provided with a NOx storage catalyst temperature sensor 115 that detects the temperature of the NOx storage catalyst. The ammonia slip prevention catalyst 113 is provided with an ammonia slip prevention catalyst temperature sensor 116.
The exhaust gas purification device 111 includes a particulate filter 117 having an oxidation catalyst in the exhaust passage 108 upstream of the NOx storage catalyst purification device 112. The particulate filter 117 collects the particulate matter in the exhaust gas, and regenerates the collection function by oxidizing and oxidizing the collected particulate matter with an oxidation catalyst.
The exhaust gas purification device 111 includes a urea supply device 118 as an additive supply device that supplies an additive to the NOx storage catalyst purification device 112. The urea supply device 118 supplies urea, which is a reducing agent, to the exhaust passage 108 upstream of the NOx storage catalyst purification device 112 by the urea injection valve 119. Further, the exhaust gas purification device 111 includes a light oil supply device 120 as an additive supply device. The light oil supply device 120 supplies light oil of the reducing agent to the exhaust passage 108 upstream of the NOx storage catalyst purification device 112 by the light oil injection valve 121.
The exhaust gas purifying device 111 is provided with ammonia detecting means 122 for detecting the ammonia (NH ₃ ) concentration in the exhaust passage 108 between the NOx storage catalyst purifying device 112 and the ammonia slip preventing catalyst 113, and downstream of the ammonia slip preventing catalyst 113. the exhaust passage 108 on the side and a nitrous oxide detector 123 for detecting the nitrous oxide (N 2 _O) concentration. The nitrous oxide detection means 123 is, for example, an IR (infrared absorption detection) method, and detects the concentration of nitrous oxide in the exhaust gas by measuring the absorbance at the infrared absorption wavelength peculiar to N ₂ O.

The fuel supply device 109, the exhaust gas temperature sensor 114, the NOx occlusion catalyst temperature sensor 115, the ammonia slip prevention catalyst temperature sensor 116, the urea supply device 118, the light oil supply device 120, the ammonia detection means 122, The nitrogen oxide detection means 123 is connected to the control means 124. The control means 124 is connected with an operating condition detecting means 125 for detecting the operating condition (engine speed, engine load, etc.) of the internal combustion engine 101.
The control means 124 includes an injection amount control means 126 that controls the injection amount of fuel supplied from the fuel injection valve 110 of the fuel supply device 109 to the combustion chamber 102, and urea injection of the urea supply device 118 to the NOx storage catalyst purification device 112. The urea amount control means 127 which is an additive amount control means for controlling the urea amount of the additive supplied from the valve 119, and the additive supplied from the light oil injection valve 121 of the light oil supply device 120 to the NOx storage catalyst purification device 112. And a light oil amount control means 128 which is an additive amount control means for controlling the light oil amount.
In the internal combustion engine 101, the injection amount control unit 126 controls the fuel injection amount supplied from the fuel supply device 109 to the combustion chamber 102 in accordance with the operation state detected by the operation state detection unit 125.
The exhaust gas purifying device 111 of the internal combustion engine 101 has a fuel supplied from the fuel supply device 109 to the combustion chamber 102 according to the nitrous oxide concentration detected by the nitrous oxide detecting means 123 by the injection amount control means 126. The injection amount of the is controlled. Further, the exhaust gas purifying device 111 determines that both the ammonia concentration detected by the ammonia detecting means 122 and the nitrous oxide concentration detected by the nitrous oxide detecting means 123 are equal to or higher than the set value. Then, the fuel injection by the fuel supply device 109 is stopped by the injection amount control means 126. Further, the exhaust gas purification device 111 performs fuel injection amount control by the fuel injection control means 126 according to the nitrous oxide concentration when the temperature of the NOx storage catalyst of the NOx storage catalyst purification device 112 is equal to or lower than the set temperature. Absent.

Next, the operation will be described.
The exhaust gas purification device 111 of the internal combustion engine 101 supplies fuel from the fuel supply device 109 to the combustion chamber 102 during operation of the internal combustion engine 101, and urea as a reducing agent from the urea supply device 118 upstream of the NOx storage catalyst purification device 112. Is supplied to the exhaust passage 108 on the side, and light oil as a reducing agent is supplied from the light oil supply device 119. Ammonia produced from urea and exhaust gas are introduced into the NOx storage catalyst purification device 112, where ammonia and NOx contained in the exhaust gas react with each other and are reduced to N ₂ . Excess ammonia that has not been used in the reaction is oxidized by the ammonia slip prevention catalyst 113 to generate N ₂ and water, thereby preventing discharge (ammonia slip).
The fuel injection amount supplied from the fuel supply device 109 is controlled according to the nitrous oxide concentration, as shown in FIG. When the program starts (D01), the exhaust gas purification device 111 takes in various signals such as a detection signal of the exhaust gas temperature sensor 114 (D02), and the nitrous oxide N ₂ O concentration is less than a set value K1 (for example, 10 ppm). It is determined whether (N ₂ O <K1) (D03).
If this determination (D03) is NO (the amount of nitrous oxide generated is large), fuel injection is stopped (rich spike stop) (D04), and the program is ended (D06). If this determination (D03) is YES (the amount of nitrous oxide generated is small), the fuel injection amount is controlled (rich spike control) according to the nitrous oxide concentration (D05), and the program is ended (D06). ).
As described above, the exhaust gas purifying device 111 of the internal combustion engine 101 stops or controls the fuel injection according to the nitrous oxide concentration detected by the nitrous oxide detecting means 123, thereby supplying the fuel to the combustion chamber 102. Since the fuel injection amount supplied from the supply device 109 can be appropriately controlled, the emission amount of nitrous oxide released into the atmosphere can be reduced.

In the second embodiment, the fuel injection amount supplied from the fuel supply device 109 to the combustion chamber 102 is controlled according to the nitrous oxide concentration, but the combustion chamber is controlled according to the ammonia concentration and the nitrous oxide concentration. The fuel injection amount supplied to 102 can also be controlled. FIG. 7 shows a first modification of the exhaust gas purifying device 111 according to the second embodiment.
In FIG. 7, when the program starts (E01), the exhaust gas purification device 111 takes in various signals such as a detection signal of the exhaust gas temperature sensor 114 (E02), and the ammonia NH ₃ concentration is a set value K2 (for example, 10 ppm). It is judged whether it is less than (NH ₃ <K2) (E03).
When this determination (E03) is NO (a large amount of ammonia is generated), it is determined whether the nitrous oxide N ₂ O concentration is less than a set value K1 (for example, 10 ppm) (N ₂ O <K1) (E04). ). If this determination (E04) is NO (the amount of nitrous oxide generated is large), the fuel injection is stopped (rich spike stop) (E05), and the program is ended (E07).
On the other hand, when the determination (E03) is YES (the amount of generated ammonia is small) and when the determination (E04) is YES (the amount of generated nitrous oxide is small), fuel injection is performed according to the nitrous oxide concentration. The amount is controlled (rich spike control) (E06), and the program is ended (E07).
Thus, the exhaust gas purifying device 111 of the internal combustion engine 101 is such that both the ammonia concentration detected by the ammonia detection means 122 and the nitrous oxide concentration detected by the nitrous oxide detection means 123 are greater than or equal to the set value. If this is the case, the amount of nitrous oxide released into the atmosphere can be reduced by stopping fuel injection by the fuel supply device 109 by the injection amount control means 126.

Further, in the above-described modified example 1, the fuel injection is stopped when both the ammonia concentration and the nitrous oxide concentration are equal to or higher than the set values, but based on the temperature of the NOx storage catalyst purification device 112, the combustion chamber The fuel injection amount supplied to 102 can also be controlled. FIG. 8 shows a second modification of the exhaust gas purifying device 111 according to the second embodiment.
In FIG. 8, when the program starts (F01), the exhaust gas purification device 111 takes in various signals such as the detection signal of the exhaust gas temperature sensor 114 (F02), and the temperature TEMP2 of the NOx storage catalyst of the NOx storage catalyst purification device 112. Is over a set temperature T2 (for example, 400 ° C.) (TEMP2> T2) (F03).
This determination (F03) is in the case of NO (low temperature of the NOx storage catalytic purification device 112), ammonia NH ₃ concentration set value K2 (e.g., 10 ppm) to determine whether less than _(NH 3 <K2) ( F04). When this determination (F04) is NO (a large amount of ammonia is generated), it is determined whether the nitrous oxide N ₂ O concentration is less than a set value K1 (for example, 10 ppm) (N ₂ O <K1) (F05). ). If this determination (F05) is NO (the amount of nitrous oxide generated is large), the fuel injection is stopped (rich spike stop) (F06), and the program is ended (F08).
On the other hand, when the determination (F03) is YES (the temperature of the NOx storage catalyst purification device 112 is high), the determination (F04) is YES (a small amount of ammonia is generated), and the determination (F05) is YES. In the case of (the amount of nitrous oxide generated is small), the fuel injection amount is controlled (rich spike control) according to the nitrous oxide concentration (F07), and the program is ended (F08).
As described above, the exhaust gas purification device 111 of the internal combustion engine 101 is unlikely to generate nitrous oxide N ₂ O when the temperature of the NOx storage catalyst purification device 112 exceeds the set temperature. When the injection amount control is performed and the temperature of the NOx occlusion catalyst purification device 112 is equal to or lower than the set temperature, the fuel injection is stopped and the fuel injection amount control by the injection amount control means 126 according to the nitrous oxide concentration is not performed. Therefore, it is not necessary to perform dedicated control according to the nitrous oxide concentration, and appropriate control can be performed.

In the second embodiment, the ammonia slip prevention catalyst 113 is provided on the downstream side of the NOx storage catalyst purification device 112. However, as shown in FIG. 9, the exhaust gas purification device does not use the ammonia slip prevention catalyst. You can also. FIG. 9 shows a third modification of the exhaust gas purifying apparatus according to the second embodiment. 9, 201 is an internal combustion engine, 202 is a combustion chamber, 203 is an intake pipe, 204 is an intake manifold, 205 is an intake passage, 206 is an exhaust manifold, 207 is an exhaust pipe, and 208 is an exhaust passage. A fuel supply device 209 for injecting and supplying fuel to the combustion chamber 202 is provided, and a fuel injection valve 210 for injecting fuel into the combustion chamber 202 is provided.
The exhaust gas purification device 211 of the internal combustion engine 201 is provided with a NOx occlusion catalyst purification device 212 provided with an NOx occlusion catalyst as a nitrogen oxide reduction device in the exhaust passage 208. The NOx storage catalyst purification device 212 is provided with an exhaust gas temperature sensor 213 that detects the temperature of exhaust gas flowing into the NOx storage catalyst, and is provided with a NOx storage catalyst temperature sensor 214 that detects the temperature of the NOx storage catalyst.
The exhaust gas purifying device 211 includes a particulate filter 215 having an oxidation catalyst in the exhaust passage 208 upstream of the NOx storage catalyst purifying device 212. The particulate filter 215 collects the particulate matter in the exhaust gas and regenerates the collection function by oxidizing and oxidizing the collected particulate matter with an oxidation catalyst.
The exhaust gas purification device 211 includes a light oil supply device 216 as an additive supply device that supplies the additive to the NOx storage catalyst purification device 212. The light oil supply device 216 supplies light oil as a reducing agent to the exhaust passage 208 upstream of the particulate filter 215 by the light oil injection valve 217.
The exhaust gas purification device 211 includes ammonia detection means 218 that detects ammonia (NH ₃ ) concentration in the exhaust passage 208 upstream of the NOx storage catalyst purification device 212, and the exhaust passage 208 downstream of the NOx storage catalyst purification device 212. Is provided with nitrous oxide detection means 219 for detecting the nitrous oxide (N ₂ O) concentration. The nitrous oxide detection means 219 uses, for example, an IR (infrared absorption detection) method, and detects the concentration of nitrous oxide in the exhaust gas by measuring the absorbance of the infrared absorption wavelength peculiar to N ₂ O.

The fuel supply device 209, the exhaust gas temperature sensor 213, the NOx storage catalyst temperature sensor 214, the light oil supply device 216, the ammonia detection means 218, and the nitrous oxide detection means 219 are connected to the control means 220. Yes. The control means 220 is connected to the operating condition detection means 221 of the internal combustion engine 201. The control means 220 includes an injection amount control means 222 for controlling the injection amount of fuel supplied from the fuel injection valve 210 of the fuel supply device 209 to the combustion chamber 202, and a light oil injection of the light oil supply device 216 to the NOx storage catalyst purification device 212. And a light oil amount control means 223 which is an additive amount control means for controlling the amount of light oil of the additive supplied from the valve 217.
In the internal combustion engine 201, the fuel injection amount supplied from the fuel supply device 209 to the combustion chamber 202 is controlled by the injection amount control means 222 in accordance with the operating condition detected by the operating condition detecting means 221.
The exhaust gas purifying device 211 of the internal combustion engine 201 is a fuel supplied from the fuel supply device 209 to the combustion chamber 202 in accordance with the nitrous oxide concentration detected by the nitrous oxide detecting means 219 by the injection amount control means 222. The injection amount of the is controlled. Further, the exhaust gas purifying device 211 determines that both the ammonia concentration detected by the ammonia detecting means 218 and the nitrous oxide concentration detected by the nitrous oxide detecting means 219 are equal to or higher than the set value. Then, the fuel injection by the fuel injection device 209 is stopped by the injection amount control means 222. Further, when the temperature of the NOx storage catalyst of the NOx storage catalyst purification device 212 is equal to or lower than the set temperature, the exhaust gas purification device 211 performs fuel injection amount control by the fuel injection control means 222 according to the nitrous oxide concentration. Absent.

  The exhaust gas purification device 211 shown in FIG. 9 is a system that does not use an ammonia slip prevention catalyst on the downstream side of the NOx storage catalyst purification device 212. The ammonia detection means 218 is on the upstream side of the NOx storage catalyst purification device 212, and on the downstream side. Nitrous oxide detection means 219 is used. As a result, the exhaust gas purifying device 211 can detect the concentration more reliably by providing both the ammonia detecting means 218 and the nitrous oxide detecting means 219 even in the case of the NOx storage catalyst medium purifying device 212 alone. It is possible to reduce the amount of nitrous oxide released therein. Note that only one of the ammonia detection means 218 and the nitrous oxide detection means 219 may be used.

  The present invention is an exhaust gas purification device provided with a urea SCR catalyst purification device and a NOx occlusion catalyst purification device, and is not limited to a diesel engine, and can be diverted for lean burn or stoichiometric combustion of a gasoline engine. In addition, this exhaust gas purification can be used for exhaust gas treatment in boilers, incinerators, etc. other than the internal combustion engine.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Combustion chamber 5 Intake passage 8 Exhaust passage 9 Fuel supply device 10 Fuel injection valve 11 Exhaust gas purification device 12 Urea SCR purification device 13 Ammonia slip prevention catalyst 14 Exhaust gas temperature sensor 15 Ammonia slip prevention catalyst temperature sensor 18 Urea supply Device 19 Urea injection valve 20 Light oil supply device 21 Light oil injection valve 22 Ammonia detection means 23 Nitrous oxide detection means 24 Control means 25 Operating condition detection means 26 Injection amount control means 27 Urea amount control means 28 Light oil amount control means

Claims (4)

A nitrogen oxide reduction device is provided in the exhaust passage of the internal combustion engine,
In the exhaust gas purifying device for an internal combustion engine provided with an ammonia slip prevention catalyst downstream of the nitrogen oxide reducing device,
An additive supply device for supplying an additive to the nitrogen oxide reduction device;
Ammonia detection means for detecting the ammonia concentration between the nitrogen oxide reduction device and the ammonia slip prevention catalyst,
Nitrous oxide detection means for detecting the nitrous oxide concentration downstream of the ammonia slip prevention catalyst,
In accordance with the nitrous oxide concentration detected by the nitrous oxide detection means, the nitrogen oxide reduction device is provided with additive amount control means for controlling the amount of additive supplied from the additive supply device. An exhaust gas purification apparatus for an internal combustion engine characterized by the above. A nitrogen oxide reduction device is provided in the exhaust passage of the internal combustion engine,
In the exhaust gas purifying device for an internal combustion engine provided with an ammonia slip prevention catalyst downstream of the nitrogen oxide reducing device,
A fuel supply device for injecting and supplying fuel to the combustion chamber of the internal combustion engine;
Ammonia detection means for detecting the ammonia concentration between the nitrogen oxide reduction device and the ammonia slip prevention catalyst,
Nitrous oxide detection means for detecting the nitrous oxide concentration downstream of the ammonia slip prevention catalyst,
An internal combustion engine comprising: an injection amount control unit that controls an injection amount of fuel supplied from a fuel supply device to the combustion chamber according to a nitrous oxide concentration detected by the nitrous oxide detection unit. Engine exhaust gas purification device.   If both the ammonia concentration detected by the ammonia detection means and the nitrous oxide concentration detected by the nitrous oxide detection means are equal to or higher than a set value, the additive amount control means The exhaust gas purifying device for an internal combustion engine according to claim 1 or 2, wherein the fuel injection is stopped by the injection amount control means.   When the temperature of the ammonia slip prevention catalyst is equal to or lower than the set temperature, the additive amount control by the additive amount control means according to the nitrous oxide concentration is not performed, or the temperature of the nitrogen oxide reducing device is the set temperature. 3. The exhaust gas purifying device for an internal combustion engine according to claim 1, wherein the fuel injection amount control by the injection amount control means according to the nitrous oxide concentration is not performed in the following cases.

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