Selective catalytic reduction system

• US 9,080,489 B2
• Filed: 05/16/2011
• Issued: 07/14/2015
• Est. Priority Date: 05/25/2010
• Status: Active Grant

• Current Assignee: Isuzu Motors Limited
• Original Assignee: Isuzu Motors Limited
• Inventors: Onodera, Takao, Hara, Shinji, Kamijyou, Tomoyuki
• Primary Examiner(s): Griffin, Walter D
• Assistant Examiner(s): PEREZ, JELITZA M
• Application Number:
  US13/699,491
• Publication Number:
  US 20130064718A1
• Time in Patent Office: 1,520 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2900/0416 using the state of a sensor, e.g. of an exhaust gas sensor
• CPC Class Codes: F01N 2900/1406 Exhaust gas pressure
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: 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
• CPC Class Codes: F02D 41/145 with determination means using an estimation
• CPC Class Codes: F02D 41/146 the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/1463 of the exhaust gases downstream of exhaust gas treatment apparatus
• CPC Class Codes: F02D 41/1465 with determination means using an estimation
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A Selective Catalytic Reduction (“SCR”) system that can detect a NO_x concentration accurately irrespective of an operation state of an engine is provided. The SCR system including: an SCR device; a dosing valve; a NO_x sensor; and an urea solution injection control unit.

Claims

1. An SCR system including:

an SCR (selective catalytic reduction) device provided in an exhaust pipe for an engine;

a dosing valve that injects urea solution on an upstream side of the SCR device;

a NO_x sensor provided in the exhaust pipe; and

a urea solution injection control unit that controls a urea solution injection quantity according to a NO_x concentration value detected by the NO_x sensor,

wherein the SCR system comprises;

a pressure estimation unit that estimates a NO_x sensor pressure that is a pressure inside the exhaust pipe at a position where the NO_x sensor is provided; and

a NO_x concentration detection value correction unit that corrects the NO_x concentration value detected by the NO_x sensor, according to the NO_x sensor pressure estimated by the pressure estimation unit.

2. The SCR system according to claim 1,

wherein the NO_x sensor is provided on the upstream side of the SCR device;

and

wherein the pressure estimation unit includes an exhaust gas flow estimation unit that estimates an exhaust gas flow by summing an intake air flow of the engine and a fuel flow calculated from an engine rotation speed and a fuel injection quantity,

an exhaust gas specific volume estimation unit that estimates an exhaust gas specific volume, based on an SCR entrance temperature that is an exhaust gas temperature at an entrance of the SCR device, and a barometric pressure,

an SCR differential pressure estimation unit that estimates a differential pressure between a pressure at the entrance of the SCR device and the barometric pressure, based on the exhaust gas flow estimated by the exhaust gas flow estimation unit, the exhaust gas specific volume estimated by the exhaust gas specific volume estimation unit, and the SCR entrance temperature, and

a NO_x sensor pressure estimation unit that estimates a NO_x sensor pressure by adding the barometric pressure to the differential pressure estimated by the SCR differential pressure estimation unit.