Air/fuel ratio controller for internal combustion engine
First Claim
1. An air/fuel ratio controller for an internal combustion engine, comprising:
- a upstream catalyst disposed upstream along an exhaust passage;
a hydrocarbon-adsorbent exhaust purification catalyst that is disposed downstream from said upstream catalyst and has the function of adsorbing hydrocarbons at low temperatures and releasing the adsorbed hydrocarbons as the temperature rises;
upstream air/fuel ratio detection means disposed upstream from said upstream catalyst, for detecting the exhaust air/fuel ratio of exhaust gas flowing into the upstream catalyst;
downstream air/fuel ratio detection means disposed downstream from the hydrocarbon-adsorbent exhaust purification catalyst, for detecting the exhaust air/fuel ratio of exhaust gas flowing out of the hydrocarbon-adsorbent exhaust purification catalyst;
middle air/fuel ratio detection means disposed downstream from said upstream catalyst and upstream from the hydrocarbon-adsorbent exhaust purification catalyst, for detecting the exhaust air/fuel ratio of exhaust gas flowing into the hydrocarbon-adsorbent exhaust purification catalyst;
air/fuel ratio main feedback control means for performing main feedback control such that the exhaust air/fuel ratio detected by the upstream air/fuel ratio detection means is kept at a specific main feedback target air/fuel ratio; and
air/fuel ratio sub-feedback control means for performing sub-feedback control such that the exhaust air/fuel ratio detected by the downstream air/fuel ratio detection means is kept at a specific sub-feedback target air/fuel ratio while the adsorbed hydrocarbons are being desorbed from the hydrocarbon-adsorbent exhaust purification catalyst, and for performing sub-feedback control such that the exhaust air/fuel ratio detected by the middle air/fuel ratio detection means is kept at a specific sub-feedback target air/fuel ratio after the adsorbed hydrocarbons have been desorbed from the hydrocarbon-adsorbent exhaust purification catalyst.
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Abstract
The air/fuel ratio (A/F) controller for an internal combustion engine having an upstream catalyst, a hydrocarbon-adsorbent exhaust purification (HAEP) catalyst that is disposed downstream from the upstream catalyst, an upstream A/F sensor disposed upstream from the upstream catalyst, a downstream A/F sensor disposed downstream from the HAEP catalyst, a middle A/F sensor disposed between the upstream catalyst and the HAEP catalyst, an A/F main feedback (F/B) control unit, and an A/F sub-F/B control unit. The A/F main F/B control unit performs main F/D control such that the exhaust A/F detected by the upstream A/F sensor is kept at a specific main F/B target A/F. The A/F sub-F/B control unit performs sub-F/B control such that the exhaust A/F detected by the downstream A/F sensor is kept at a specific sub-F/B target A/F during hydrocarbon desorption from the HAEP catalyst.
16 Citations
14 Claims
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1. An air/fuel ratio controller for an internal combustion engine, comprising:
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a upstream catalyst disposed upstream along an exhaust passage;
a hydrocarbon-adsorbent exhaust purification catalyst that is disposed downstream from said upstream catalyst and has the function of adsorbing hydrocarbons at low temperatures and releasing the adsorbed hydrocarbons as the temperature rises;
upstream air/fuel ratio detection means disposed upstream from said upstream catalyst, for detecting the exhaust air/fuel ratio of exhaust gas flowing into the upstream catalyst;
downstream air/fuel ratio detection means disposed downstream from the hydrocarbon-adsorbent exhaust purification catalyst, for detecting the exhaust air/fuel ratio of exhaust gas flowing out of the hydrocarbon-adsorbent exhaust purification catalyst;
middle air/fuel ratio detection means disposed downstream from said upstream catalyst and upstream from the hydrocarbon-adsorbent exhaust purification catalyst, for detecting the exhaust air/fuel ratio of exhaust gas flowing into the hydrocarbon-adsorbent exhaust purification catalyst;
air/fuel ratio main feedback control means for performing main feedback control such that the exhaust air/fuel ratio detected by the upstream air/fuel ratio detection means is kept at a specific main feedback target air/fuel ratio; and
air/fuel ratio sub-feedback control means for performing sub-feedback control such that the exhaust air/fuel ratio detected by the downstream air/fuel ratio detection means is kept at a specific sub-feedback target air/fuel ratio while the adsorbed hydrocarbons are being desorbed from the hydrocarbon-adsorbent exhaust purification catalyst, and for performing sub-feedback control such that the exhaust air/fuel ratio detected by the middle air/fuel ratio detection means is kept at a specific sub-feedback target air/fuel ratio after the adsorbed hydrocarbons have been desorbed from the hydrocarbon-adsorbent exhaust purification catalyst. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An air/fuel ratio controller for an internal combustion engine, comprising a upstream catalyst, and a hydrocarbon-adsorbent exhaust purification catalyst that is disposed downstream from said upstream catalyst and has the function of adsorbing hydrocarbons at low temperatures and releasing the adsorbed hydrocarbons as the temperature rises,
wherein an air/fuel ratio main feedback control is performed based on output of an air/fuel ratio sensor upstream from said upstream catalyst while hydrocarbons are being desorbed from the hydrocarbon-adsorbent exhaust purification catalyst, and an air/fuel ratio sub-feedback control, in which a target air/fuel ratio of the air/fuel ratio main feedback control is corrected, is performed such that an output of an air/fuel ratio sensor placed downstream from the hydrocarbon-adsorbent exhaust purification catalyst is kept at the target output, and after the desorption of hydrocarbons from the hydrocarbon-adsorbent exhaust purification catalyst, the air/fuel ratio sub-feedback control, in which the target air/fuel ratio of the air/fuel ratio main feedback control is corrected, is performed such that an output of an air/fuel ratio sensor placed between the upstream catalyst and the hydrocarbon-adsorbent exhaust purification catalyst is kept at the target output.
Specification