# US 10,309,328 B2 · Exhaust emission control system of engine

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- Number: US 10,309,328 B2
- Document ID: US10309328B2
- Status: Granted
- Kind: B2
- Application number: 15/644,438
- Filed: 2017-07-07
- Published: 2018-01-18
- Granted: 2019-06-04
- Earliest claimed: 2016-07-12
- Assignees: Mazda Motor Corporation
- Applicants: Mazda Motor Corporation
- Inventors: Takayuki Yamaguchi; Takashi Tanaka; Kota Matsue; Hiroshi Hayashibara; Yoshiaki Tomita; Kaoru Yamada; Masayuki Tetsuno; Daishi Ikeda; Kazunori Hirasawa; Masanobu Kanno
- Web page: https://patentgrep.com/patent/US10309328B2

## CPC

- F02D 41/0275: {the exhaust gas treating apparatus being a NOx trap or adsorbent}
- F01N 3/0814: {combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts}
- F01N 3/0842: {Nitrogen oxides}
- F01N 3/2066: {Selective catalytic reduction [SCR]}
- F01N 9/00: Electrical control of exhaust gas treating apparatus (monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00)
- F02D 41/0055: {Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus}
- F02D 41/10: for acceleration
- F02D 41/1454: {the characteristics being an oxygen content or concentration or the air-fuel ratio}
- F02D 41/1461: {of the exhaust gases emitted by the engine}
- F02D 41/405: {with post injections}
- F01N 2430/06: by varying fuel-air ratio, e.g. by enriching fuel-air mixture
- F01N 2560/026: for measuring or detecting NOx
- F01N 2570/14: Nitrogen oxides
- F01N 2610/02: the substance being ammonia or urea
- F01N 2900/0416: using the state of a sensor, e.g. of an exhaust gas sensor
- F01N 2900/08: said parameters being related to the engine
- F01N 2900/1614: NOx amount trapped in catalyst
- F02D 2200/0802: Temperature of the exhaust gas treatment apparatus
- F02D 2200/0806: NOx storage amount, i.e. amount of NOx stored on NOx trap
- F02D 2200/602: Pedal position
- F02D 2250/36: Control for minimising NOx emissions
- Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
- Y02T 10/12: Improving ICE efficiencies
- Y02T 10/40: Engine management systems
- 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)
- 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)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

An exhaust emission control system of an engine is provided, which includes a NOx catalyst disposed in an exhaust passage for storing NOx within exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NOx when the air-fuel ratio is approximately stoichiometric or rich. A processor executes a NOx reduction controlling module for performing, when the NOx stored amount exceeds a given amount, a NOx reduction control in which a fuel injector performs a post injection of fuel to continuously control the air-fuel ratio to a target ratio so that the stored NOx is reduced to be below a given amount, the target air-fuel ratio being a ratio at which the stored NOx is reducible, the post injection causing the injected fuel to combust inside a cylinder, the execution of the control permitted when an engine load is within a medium load range.

## Claims

### Claim 1

An exhaust emission control system of an engine, including a NOx catalyst disposed in an exhaust passage of the engine for storing NOx within exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NOx when the air-fuel ratio is approximately stoichiometric or rich, the system comprising:
a selective catalytic reduction (SCR) catalyst disposed in the exhaust passage for purifying NOx within the exhaust gas by causing a reaction with ammonia; and
a processor configured to execute:
a NOx reduction controlling module for performing, when a NOx stored amount in the NOx catalyst exceeds a given determination amount, a first NOx reduction control in which a fuel injector performs a post injection of fuel to continuously control the air-fuel ratio to a target air-fuel ratio so that the stored NOx is reduced and the NOx stored amount falls below a given amount, the target air-fuel ratio being a ratio at which the stored NOx is reducible, the post injection causing the injected fuel to combust inside a cylinder, the performance of the first NOx reduction control permitted when an engine load is within a predetermined medium load range equal to or higher than a first predetermined engine load but lower than a second predetermined engine load,
wherein the SCR catalyst purifies NOx within an engine operating range where the NOx reduction controlling module does not perform the post injection by the fuel injector to reduce the stored NOx.

### Claim 2 (depends on 1)

The system of claim 1, wherein the NOx reduction controlling module permits the performance of the first NOx reduction control when an engine speed is within a medium speed range.

### Claim 3 (depends on 2)

The system of claim 2, wherein when a temperature of the NOx catalyst is above a given value, the NOx reduction controlling module expands the medium speed range toward a higher speed side by raising a speed value defining a higher end of the medium speed range.

### Claim 4 (depends on 2)

The system of claim 2, wherein when the NOx stored amount is above a given value, the NOx reduction controlling module expands the medium speed range toward a higher speed side by raising a speed value defining a higher end of the medium speed range.

### Claim 5 (depends on 1)

The system of claim 1, wherein the NOx reduction controlling module suspends the first NOx reduction control when the engine load moves outside the medium load range, and resumes the first NOx reduction control when the engine load re-enters the medium load range so that a NOx stored amount falls below the given amount.

### Claim 6 (depends on 1)

The system of claim 1, wherein when a temperature of the NOx catalyst is above a given value, the NOx reduction controlling module expands the medium load range toward a higher load side by raising a load value defining a higher end of the medium load range.

### Claim 7 (depends on 1)

The system of claim 1, wherein when the NOx stored amount is above a given value, the NOx reduction controlling module expands the medium load range toward a higher load side by raising a load value defining a higher end of the medium load range.

### Claim 8 (depends on 1)

The system of claim 1, wherein when the NOx stored amount in the NOx catalyst is below the determination amount and the air-fuel ratio becomes rich due to acceleration of a vehicle, the NOx reduction controlling module also performs a second NOx reduction control in which the fuel injector performs the post injection to temporarily control the air-fuel ratio to the target air-fuel ratio so that the NOx stored in the NOx catalyst is reduced, the post injection causing the injected fuel to be discharged to the exhaust passage as unburned fuel without being combusted inside the cylinder, the performance of the second NOx reduction control permitted only when the engine load is within a high load range above a load defining a higher end of the medium load range.