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US 10,947,910 B2Granted
Method and system for catalyst feedback control
AssigneeFord Global Technologies, LLC
InventorsStephen Magner, Mario Santillo, Mrdjan Jankovic
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Abstract
Methods and systems are provided for catalyst control. In one example, a method may modulate a downstream catalyst by applying a square waveform to an outer feedback control loop. A fuel adjustment is performed in accordance with the square waveform to create an air-fuel ratio oscillation at an upstream catalyst brick and at a downstream catalyst brick.
Claims19
A method, comprising:
- during near steady exhaust air-fuel ratio conditions, adjusting a cylinder air-fuel ratio responsive to a first exhaust gas sensor upstream of a first and a second three-way catalyst, and a second exhaust gas sensor between the first and the second catalyst, including introducing modulation to a reference set-point compared with feedback from the second sensor, at a frequency slower than modulation generated from feedback from the first sensor.
A method, comprising:
- fueling an engine in accordance with a periodic signal that generates a larger than threshold air-fuel ratio modulation at each of a first, upstream exhaust catalyst brick and a second, downstream exhaust catalyst brick, parameters of the periodic signal adjusted responsive to exhaust mass flow and a temperature of the second catalyst brick, wherein the air-fuel ratio modulation includes lean and rich air-fuel ratio excursions relative to a reference set-point, and wherein the modulation dampens during passage through the first and second catalyst brick such that the air-fuel ratio is at the reference set-point downstream of the second catalyst brick.
A system, comprising:
- an engine with a plurality of cylinders;
- a mass air flow sensor coupled to an engine intake;
- cylinder fuel injectors;
- an exhaust passage with a first catalyst brick coupled upstream of a second catalyst brick;
- a first oxygen sensor coupled upstream of the first catalyst brick for sensing a feed gas air-fuel ratio;
- a second oxygen sensor coupled in between the first and second catalyst brick for sensing a mid-bed air-fuel ratio;
- and
- a controller with computer-readable instructions stored on non-transitory memory that when executed cause the controller to:
- responsive to upstream exhaust air-fuel ratio rate of change remaining below an upper positive threshold and above a lower negative threshold, command a square wave having control parameters, including amplitude and frequency, based on exhaust mass flow and catalyst temperature to generate an air-fuel ratio oscillation with a first offset about a reference set-point at the first catalyst brick and another air-fuel ratio oscillation with a second offset about the reference set-point, smaller than the first offset, at the second, downstream exhaust catalyst brick;
- and
- adjust engine fueling in accordance with the commanded square wave.
8 more elements
Dependencies are inferred from the claim text.