Method and system for controlling a nitrogen oxide (NOx) conversion efficiency monitor

摘要

A vehicle includes an engine, an exhaust system, a selective catalytic reduction (SCR) device, a first and a second NOx sensor configured to respectively measure an upstream and a downstream NOx level, and a controller or host machine. The controller, via the present method, calculates a NOx conversion efficiency rate of the SCR device using the NOx levels from the sensors. At the end of a key cycle when an accumulated amount of upstream NOx is less than a calibrated upstream NOx level, the controller determines if the NOx conversion efficiency rate is presently passing or failing. The accumulated upstream NOx is recorded in memory for use in calculating the NOx conversion efficiency rate during a subsequent key cycle only when the NOx conversion efficiency rate is presently passing at the end of the key cycle. A control system for the vehicle uses the controller and sensors as noted above.

主权项

1. A vehicle comprising:
an internal combustion engine; an exhaust system configured to condition an exhaust stream from the engine; a selective catalytic reduction (SCR) device that catalytically converts nitrogen oxide (NOx) gasses in the exhaust stream into water and nitrogen; a first NOx sensor configured to measure an upstream NOx level, wherein the upstream NOx level is a level of the NOx gasses upstream of the SCR device; a second NOx sensor configured to measure a downstream NOx level, wherein the downstream NOx level is a level of the NOx gasses downstream of the SCR device; and a controller configured to calculate a NOx conversion efficiency rate of the SCR device using the upstream NOx level and the downstream NOx level; wherein the controller is configured to determine, at the end of a key cycle and when an accumulated amount of upstream NOx is less than a calibrated upstream NOx level, whether the NOx conversion efficiency rate is presently passing or presently failing, and to record the accumulated amount of upstream NOx in memory, for use in calculating the NOx conversion efficiency rate during a subsequent key cycle, only when the NOx conversion efficiency rate is presently passing at the end of the key cycle.