Exhaust gas purification device of internal combustion engine

• US 20050262829A1
• Filed: 06/02/2005
• Published: 12/01/2005
• Est. Priority Date: 06/23/1998
• Status: Active Grant

• Current Assignee: Eiji Iwasaki, Kazuhiro Itoh, Shinya Hirota, Toshiaki Tanaka
• Original Assignee: Eiji Iwasaki, Kazuhiro Itoh, Shinya Hirota, Toshiaki Tanaka
• Inventors: Itoh, Kazuhiro, Hirota, Shinya, Tanaka, Toshiaki, Iwasaki, Eiji
• Granted Patent: US 7,272,924 B2
• Time in Patent Office: Days
• US Class Current: 60/278
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: B01D 53/90 Injecting reactants
• CPC Class Codes: B01D 53/9409 Nitrogen oxides
• CPC Class Codes: B01D 53/9431 Processes characterised by a specific device
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 13/011 having two or more purifying devices arranged in parallel
• CPC Class Codes: F01N 2250/12 absorption or adsorption, and catalytic conversion
• CPC Class Codes: F01N 2510/063 zeolites
• CPC Class Codes: F01N 2510/0682 having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
• CPC Class Codes: F01N 2560/06 the means being a temperature sensor
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 2570/18 Ammonia
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2610/146 Control thereof, e.g. control of injectors or injection valves
• CPC Class Codes: F01N 2900/08 said parameters being related to the engine
• CPC Class Codes: F01N 2900/1402 Exhaust gas composition
• CPC Class Codes: F01N 2900/1622 : Catalyst reducing agent absorption capacity or consumption amount
• CPC Class Codes: F01N 3/2053 : By-passing catalytic reactors, e.g. to prevent overheating
• CPC Class Codes: F01N 3/206 : Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents F01N3/2066 takes precedence
• CPC Class Codes: F01N 3/2066 : Selective catalytic reduction [SCR]
• CPC Class Codes: F01N 3/208 : Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: F02D 2200/0602 : Fuel pressure
• CPC Class Codes: F02D 2200/0802 : Temperature of the exhaust gas treatment apparatus
• CPC Class Codes: F02D 35/025 : by determining temperatures inside the cylinder, e.g. combustion temperatures
• CPC Class Codes: F02D 41/0055 : Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus
• CPC Class Codes: F02D 41/0235 : in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• CPC Class Codes: F02D 41/123 : the fuel injection being cut-off
• CPC Class Codes: F02D 41/1446 : the characteristics being exhaust temperatures
• CPC Class Codes: F02M 26/13 : Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
• CPC Class Codes: F02M 26/15 : in relation to engine exhaust purifying apparatus
• CPC Class Codes: Y02A 50/20 : Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 : Engine management systems

Abstract

A catalyst (22) suitable for reduction of the NO_x in an exhaust gas by ammonia in the presence of excess oxygen is arranged in the exhaust passage (18, 21) of an internal combustion engine. An aqueous urea solution is fed through a flow control valve (33) to the inside of the exhaust passage (21) upstream of the catalyst (22). When the temperature of the catalyst (22) is low, a large amount of the aqueous urea solution is fed to make the urea contained in the aqueous urea solution be stored in the catalyst (22). When the engine is accelerated and the temperature of the catalyst (22) rises, ammonia is released at a little at a time from the inside of the catalyst (22) and the NO_x in the exhaust gas is reduced by the released ammonia.

Claims

1. An exhaust gas purification device of an internal combustion engine arranging a catalyst suitable for reduction of NOx in exhaust gas by ammonia in the presence of excess oxygen in an engine exhaust passage, said device comprising:

feeding means for feeding a liquid containing an ammonia generating compound to the catalyst;

feed control means for controlling the amount of feed of the liquid, the catalyst storing inside it at least part of the ammonia generating compound contained in the liquid fed to the catalyst and having the function of causing the release of ammonia a little at a time from the ammonia generating compound stored in the catalyst along with the rise of temperature of the catalyst and reducing the NOx in the exhaust gas by the ammonia released;

decision means for deciding if the temperature of the catalyst is in an ammonia generating compound storage region which stores the ammonia generating compound contained in the liquid fed to the catalyst inside the catalyst and releases almost no ammonia from the stored ammonia generating compound, or if the temperature of the catalyst is in an ammonia release region which causes the ammonia to be released a little at a time from the stored ammonia generating compound;

an exhaust gas recirculation device for recirculating the exhaust gas in an intake passage;

wherein, when it is decided by the decision means that the temperature of the catalyst is in the ammonia generating compound storage region, said exhaust gas recirculation device stops a recirculation action of the exhaust gas and said feed control means controls the amount of feed of the liquid so that the amount of the ammonia generating compound in the liquid becomes more than the equivalent ratio=1 required for reducing the NOx in the exhaust gas.

2. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein said decision means decides that the temperature of the catalyst is in the ammonia generating compound storage region when a temperature representative of the temperature of the catalyst is lower than a predetermined temperature and that the temperature of the catalyst is in the ammonia release region when the temperature representative of the temperature of the catalyst is higher than the predetermined temperature.

3. An exhaust gas purification device of an internal combustion engine as set forth in claim 2, wherein the temperature representative of the temperature of the catalyst is the temperature of the exhaust gas flowing into the catalyst.

4. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein the decision means decides that the temperature of the catalyst is in the ammonia generating compound storage region at the time of engine startup.

5. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein the decision means decides that the temperature of the catalyst is in the ammonia generating compound storage region when a required load of the engine is lower than a predetermined load.

6. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein the decision means decides that the temperature of the catalyst is in the ammonia generating compound storage region at the time of engine deceleration.

7. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein the decision means decides that the temperature of the catalyst is in the ammonia release region at the time of acceleration of the engine.

8. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein said catalyst immediately produces ammonia from said liquid just when said liquid is fed to the catalyst when the temperature of the catalyst is higher than a predetermined temperature and said feed control means controls the amount of feed of the liquid so that the amount of the ammonia generating compound in the liquid becomes the equivalent ratio=1 required for reducing the NOx in the exhaust gas when the temperature of the catalyst is higher than the predetermined temperature.

9. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein said feed control means feeds the amount of the liquid necessary for reducing the NOx in the exhaust gas which cannot be reduced by the ammonia released from the ammonia generating compound.

10. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, wherein the liquid containing the ammonia generating compound is an aqueous urea solution.

11. An exhaust gas purification device of an internal combustion engine as set forth in claim 1, in which, when the temperature of one of a pair of the catalysts is in the ammonia generating compound storage region, the liquid is fed to said one of the catalysts to cause the ammonia generating compound contained in the liquid to be stored in said one of the catalysts, and the NOx in the exhaust gas is reduced in both catalysts by the ammonia released from the ammonia generating compound stored in said one of the catalysts when the temperature of said one of the catalysts becomes the ammonia release region.