Method and system for resistive-type particulate matter sensors
AssigneeFord Global Technologies, LLC
InventorDavid Charles Weber
Life of this patent
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Abstract
Methods and systems are provided for reducing soot sensor electrode degradation in harsh chemical environment introduced as a result of desulfation of a lean NOx trap positioned upstream of the soot sensor. In one example, a method may include in response to the SOx load being higher than the threshold, prior to initiating desulfation of LNT, operating the soot sensor in a pre-desulfation mode where the negative electrode is connected to the positive electrode for a brief duration, while the positive electrode is disconnected from the positive electrode. However during desulfation, when H2S is released as a by-product, both the electrodes may be open, i.e. not connected to the positive electrode or ground, thereby reducing the possibility of sensor degradation.
Claims19
A method, comprising:
- selectively connecting and disconnecting a positive electrode of interdigitated comb electrodes of a sensor to and from a positive voltage;
- and
- selectively connecting a negative electrode of the interdigitated comb electrodes of the sensor to ground via a measuring resistor,
- wherein the sensor is a soot sensor coupled downstream of a lean NOx trap (LNT) in an exhaust system, and wherein the selectively connecting the positive electrode to the positive voltage is in response to any of the soot sensor being operated in a particulate matter detection mode and the LNT being operated in a regeneration mode.
A method, comprising:
- during a first condition, operating a first switch to electrically couple a positive electrode of a sensor to a positive voltage while operating a second switch to electrically couple a negative electrode of the sensor to ground via a measuring resistor;
- and
- during a second condition, operating the first switch to electrically decouple the positive electrode from the positive voltage while operating the second switch to electrically couple the negative electrode to the positive voltage,
- wherein the positive electrode and the negative electrode are interdigitated electrodes of an interdigitated comb soot sensor.
An engine exhaust system, comprising:
- an engine including an exhaust passage;
- a lean NOx trap (LNT);
- a diesel particulate filter (DPF);
- a soot sensor coupled downstream of each of the LNT and the DPF, the soot sensor including a first positive comb electrode interdigitated with a second negative comb electrode, the first positive electrode coupled to a positive voltage via a first switch, the second negative electrode coupled to ground via each of a measuring resistor and a second switch;
- and
- a controller with computer-readable instructions stored on non-transitory memory for:
- operating the exhaust system in a first mode with the first switch closed to electrically couple the first positive electrode to the positive voltage, and the second switch in a first position to electrically couple the second negative electrode to the ground via a measuring resistor;
- operating the exhaust system in a second mode with the first switch open to electrically decouple the first positive electrode from the positive voltage, and the second switch in a second position to electrically couple the second negative electrode to the positive voltage;
- and
- operating the exhaust system in a third mode with the first switch open to electrically decouple the first positive electrode from the positive voltage, and the second switch in a third position to electrically decouple the second negative electrode from both the positive voltage and the ground.
Dependencies are inferred from the claim text.