Exhaust gas purification device and method for diesel engine

• US 20030070425A1
• Filed: 10/11/2002
• Published: 04/17/2003
• Est. Priority Date: 10/12/2001
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kokusyo, Hajime, Kaneko, Hiroaki, Kamijo, Motohisa, Kitahara, Yasuhisa
• Granted Patent: US 6,792,751 B2
• Time in Patent Office: Days
• US Class Current: 60/295
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02D 2200/602 Pedal position
• CPC Class Codes: F02D 41/0275 the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/1446 the characteristics being exhaust temperatures
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02D 41/3809 Common rail control systems common rail apparatus F02M55/025, F02M63/0225
• CPC Class Codes: F02D 41/405 with post injections
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

In order to improve performance of NOx reduction, an additional fuel injection immediately after a main fuel injection is performed. By such additional fuel injection, hydrogen (H₂) is supplied to a NOx trap catalyst. And in order to prevent engine output torque from varying by the additional fuel injection, the main fuel injection is controlled by whether the additional fuel injection is performed.

Claims

1. An exhaust gas purification device for a diesel engine having an injector injecting fuel directly into a combustion chamber of the engine, comprising:

a NOx trap catalyst trapping nitrogen oxides (NOx) contained in exhaust gas when an air-fuel ratio of the exhaust gas is leaner than stoichiometric air-fuel ratio, and reducing NOx stored in the catalyst when the air-fuel ratio of the exhaust gas is richer than stoichiometric air-fuel ratio; and

a controller programmed to;

make a judgment as to whether the catalyst should be regenerated;

calculate instruction values regarding the main fuel injection, in accordance with engine operating conditions and the judgment;

calculate instruction values regarding additional fuel injection, when the judgment shows that the catalyst should be regenerated; and

control the injector according to the instruction values regarding the main and the additional fuel injection, in order to regenerate the catalyst.

2. An exhaust gas purification device as claimed in claim 1, wherein the instruction values regarding the additional fuel injection include a value indicating a timing of the additional fuel injection.

3. An exhaust gas purification device as claimed in claim 2, wherein the controller is further programmed to calculate the value indicating the additional fuel injection timing which is suitable for generating hydrogen (H₂).

4. An exhaust gas purification device as claimed in claim 3, wherein the H₂ is generated in a dehydrogenation reaction and a cracking reaction.

5. An exhaust gas purification device as claimed in claim 2, wherein the controller is further programmed to calculate the value indicating the additional fuel injection timing when temperature in the combustion chamber becomes higher than approximately 1600°

C.

6. An exhaust gas purification device as claimed in claim 2, wherein the controller is further programmed to calculate the value indicating the additional fuel injection timing within a bound of 30 degree in crank-angle from a timing of the main fuel injection.

7. An exhaust gas purification device as claimed in claim 1, wherein the controller is further programmed to:

calculate normal values regarding the main fuel injection based on the engine operating conditions; and

calculate the instruction values regarding the main fuel injection by making a correction to the normal values, when the judgment shows that the catalyst should be regenerated.

8. An exhaust gas purification device as claimed in claim 7, wherein the correction decreases engine torque to be generated by the main fuel injection.

9. An exhaust gas purification device as claimed in claim 8, wherein the normal values include a value indicating a timing of the main fuel injection, and the correction retards the main fuel injection timing.

10. An exhaust gas purification device as claimed in claim 8, wherein the normal values include a value indicating an amount of the main fuel injection, and the correction decreases the main fuel injection amount.

11. An exhaust gas purification device as claimed in claim 8, wherein the engine is operable with diffusion combustion or premixed combustion, and the normal values include a value indicating a timing of the main fuel injection and a value indicating an amount of the main fuel injection, and the correction which is made at timing of the diffusion combustion retards the main fuel injection timing, and the correction which is made at timing of the premixed combustion decreases the main fuel injection amount.

12. An exhaust gas purification device as claimed in claim 1, wherein the controller is further programmed to:

calculate normal values regarding the main fuel injection based on the engine operating conditions;

make a second judgment as to whether the catalyst is active;

calculate the instruction values regarding the main fuel injection by making a correction to the normal values, when the judgment shows that the catalyst should be regenerated and the second judgment shows that the catalyst is inactive; and

calculate the instruction values regarding the main fuel injection according to the normal values without the correction, when the judgment shows that the catalyst should be regenerated and the second judgment shows that the catalyst is active.

13. An exhaust gas purification device as claimed in claim 12, wherein the instruction values regarding additional fuel injection include a value indicating a timing of the additional fuel injection, and the controller is further programmed to:

calculate the instruction value regarding the additional fuel injection timing which is close to a timing of the main fuel injection, when the judgment shows that the catalyst should be regenerated and the second judgment shows that the catalyst is inactive; and

calculate the instruction value regarding the additional fuel injection timing which is far from the timing of the main fuel injection, when the judgment shows that the catalyst should be regenerated and the second judgment shows that the catalyst is active.

14. An exhaust gas purification device for a diesel engine having an injector injecting fuel directly into a combustion chamber of the engine, comprising:

a NOx trap catalyst trapping nitrogen oxides (NOx) contained in exhaust gas when an air-fuel ratio of the exhaust gas is leaner than stoichiometric air-fuel ratio, and reducing NOx stored in the catalyst when the air-fuel ratio of the exhaust gas is richer than stoichiometric air-fuel ratio;

means for making a judgment as to whether the catalyst should be regenerated;

means for calculating instruction values regarding the main fuel injection, in accordance with engine operating conditions and the judgment;

means for calculating instruction values regarding additional fuel injection, when the judgment shows that the catalyst should be regenerated; and

means for controlling the injector according to the instruction values regarding the main and the additional fuel injection, in order to regenerate the catalyst.

15. An exhaust gas purification method for a diesel engine having an injector injecting fuel directly into a combustion chamber of the engine, comprising:

providing a NOx trap catalyst trapping nitrogen oxides (NOx) contained in exhaust gas when an air-fuel ratio of the exhaust gas is leaner than stoichiometric air-fuel ratio, and reducing NOx stored in the catalyst when the air-fuel ratio of the exhaust gas is richer than stoichiometric air-fuel ratio; and

making a judgment as to whether the catalyst should be regenerated;

calculating instruction values regarding the main fuel injection, in accordance with engine operating conditions and the judgment;

calculating instruction values regarding additional fuel injection, when the judgment shows that the catalyst should be regenerated; and

controlling the injector according to the instruction values regarding the main and the additional fuel injection, in order to regenerate the catalyst.