# US 10,480,437 B2 · Exhaust purification system

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- Number: US 10,480,437 B2
- Document ID: US10480437B2
- Status: Granted
- Kind: B2
- Application number: 15/558,998
- Filed: 2016-03-16
- Published: 2018-08-30
- Granted: 2019-11-19
- Earliest claimed: 2015-03-18
- Assignees: Isuzu Motors Limited
- Applicants: Isuzu Motors Limited
- Inventors: Teruo Nakada; Takayuki Sakamoto; Daiji Nagaoka
- Web page: https://patentgrep.com/patent/US10480437B2

## CPC

- F02D 41/0275: {the exhaust gas treating apparatus being a NOx trap or adsorbent}
- B01D 53/94: by catalytic processes
- B01D 53/9422: {for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)}
- B01D 53/944: {Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts (three-way-catalysts [TWC] B01D53/9445)}
- B01D 53/9477: {with catalysts positioned on separate bricks, e.g. exhaust systems}
- B01D 53/9495: {Controlling the catalytic process}
- F01N 3/0814: {combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts}
- F01N 3/0842: {Nitrogen oxides}
- F01N 3/0871: {using means for controlling, e.g. purging, the absorbents or adsorbents}
- F01N 3/2006: {Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating (by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235)}
- F01N 3/2033: {using a fuel burner or introducing fuel into exhaust duct}
- F01N 3/206: {Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents}
- F01N 3/36: Arrangements for supply of additional fuel
- F01N 9/002: {of filter regeneration}
- F02D 41/0235: {in relation with the state of the exhaust gas treating apparatus (control of exhaust gas treating apparatus per se F01N)}
- F02D 41/04: Introducing corrections for particular operating conditions (F02D41/14 takes precedence)
- F02D 41/40: with means for controlling injection timing or duration
- F01N 2430/06: by varying fuel-air ratio, e.g. by enriching fuel-air mixture
- F01N 2430/085: at least a part of the injection taking place during expansion or exhaust stroke
- F01N 2550/03: of sorbing activity of adsorbents or absorbents
- F01N 2610/03: the substance being hydrocarbons, e.g. engine fuel
- F01N 2610/146: Control thereof, e.g. control of injectors or injection valves
- F01N 2900/0422: measuring the elapsed time
- F01N 2900/08: said parameters being related to the engine
- F01N 2900/1602: Temperature of exhaust gas apparatus
- F01N 2900/1614: NOx amount trapped in catalyst
- F01N 2900/1821: Injector parameters
- F02D 2200/0806: NOx storage amount, i.e. amount of NOx stored on NOx trap
- Y02T 10/12: Improving ICE efficiencies
- F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

An exhaust purification system is provided with a NOx-occlusion-reduction-type catalyst 32 that occludes NOx in exhaust when the exhaust is in a lean state and reduces and purifies the occluded NOx when the exhaust is in a rich state, and a NOx purge rich control unit 140 for reducing and purifying NOx occluded in the NOx-occlusion-reduction-type catalyst 32 by putting the exhaust into the rich state by repetitively performing fuel injection control of at least one of post injection and exhaust pipe injection at a predetermined interval.

## Claims

### Claim 1

An exhaust purification system comprising:
a NOx-occlusion-reduction-type catalyst that is provided in an exhaust passage of an internal combustion engine and occludes NOx in exhaust when the exhaust is in a lean state and reduces and purifies the occluded NOx when the exhaust is in a rich state;
an electronic control unit (ECU) for reducing and purifying NOx occluded in the NOx-occlusion-reduction-type catalyst by putting the exhaust into the rich state by repetitively performing fuel injection control of at least one of post injection and exhaust pipe injection at a predetermined interval; and
a processor which prohibits execution of NOx purge in a case where a fuel injection amount resulting from an accelerator operation is equal to or smaller than a lower limit threshold value,
wherein the processor does not prohibit the execution of the NOx purge during the execution of the NOx purge,
wherein the ECU is configured to determine a plurality of start conditions for starting NOx purge including:
a second start condition, that an estimated NOx occlusion amount value of the NOx-occlusion-reduction-type catalyst increases to a value equal to or greater than a predetermined occlusion amount threshold value,
a third start condition, that a NOx conversion efficiency of the NOx-occlusion-reduction-type catalyst is lowered to a value equal to or smaller than a predetermined conversion efficiency threshold value,
a seventh start condition, that a low-temperature state where the NOx-occlusion-reduction-type catalyst is at a temperature lower than a predetermined catalyst temperature threshold value continues during a predetermined time period, and
an identification flag is set for identifying based on which of the start conditions that the NOx purge is executed,
wherein the ECU is configured to determine a fourth prohibition condition where an in cylinder fuel injection amount is smaller than a predetermined lower limit injection amount threshold value, and
the ECU is further configured to identify the type of the NOx purge on the basis of the identification flag, and to not apply the fourth prohibition condition during the execution of the NOx purge in the cases of the second start condition, the third start condition, and the seventh start condition.

### Claim 2 (depends on 1)

The exhaust purification system according to claim 1,
wherein the ECU sets the interval of the fuel injection control such that a next fuel injection control is performed while a temperature of the NOx-occlusion-reduction-type catalyst is being increased due to a previous fuel injection control.

### Claim 3 (depends on 1)

The exhaust purification system according to claim 1,
wherein the ECU sets an interval between a first fuel injection control and a second fuel injection control to be longer than an interval between the second fuel injection control and a third fuel injection control.

### Claim 4 (depends on 1)

The exhaust purification system according to claim 1, wherein the ECU estimates a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst,
wherein the ECU performs the fuel injection control one time more than a number of times required so as to reduce and purify NOx of the NOx occlusion amount estimated by the ECU.