Exhaust purification system

An exhaust purification system comprising:

• a NOx catalyst provided in an exhaust passage of an internal combustion engine and configured to purify NOx in exhaust;
• an air flow sensor configured to acquire an air flow-rate of the internal combustion engine;
• and
• a controller,
• wherein the controller is operated to execute catalyst regeneration treatment of recovering a NOx purification capacity of the NOx catalyst by performing, in combination, air-based control of reducing the air flow-rate of the internal combustion engine to a predetermined target air flow-rate and injection-based control of increasing a fuel injection amount,
• wherein, in a case of executing the catalyst regeneration treatment, the controller starts with the air-based control so as to lower an air excess ratio from a value upon normal operation to a first target air excess ratio, and starts the injection-based control so as to lower the air excess ratio from the first target air excess ratio to a second target air excess ratio after the air flow-rate acquired by the air flow sensor is reduced to the predetermined target air flow-rate, and
• wherein after starting the injection-based control, the controller continues the injection-based control in a case where an increased amount of the air flow-rate acquired by the air flow sensor relative to the target air flow-rate is equal to or smaller than a predetermined threshold value, and forcibly ends the injection-based control in a case where the increased amount of the air flow-rate acquired by the air flow sensor relative to the target air flow-rate exceeds the predetermined threshold value.

An exhaust purification system comprising:

• a NOx catalyst provided in an exhaust passage of an internal combustion engine and configured to purify NOx in exhaust;
• an air flow sensor configured to acquire an air flow-rate of the internal combustion engine;
• and
• a controller,
• wherein the controller is operated to execute catalyst regeneration treatment of recovering a NOx purification capacity of the NOx catalyst by performing, in combination, air-based control of reducing the air flow-rate of the internal combustion engine to a predetermined target air flow-rate and injection-based control of increasing a fuel injection amount,
• wherein, in a case of executing the catalyst regeneration treatment, the controller starts with the air-based control and starts the injection-based control when the air flow-rate acquired by the air flow sensor is reduced to the predetermined target air flow-rate, and
• wherein after starting the injection-based control, the controller continues the injection-based control in a case where an increased amount of the air flow-rate acquired by the air flow sensor relative to the target air flow-rate is equal to or smaller than a predetermined threshold value, and forcibly ends the injection-based control in a case where the increased amount of the air flow-rate acquired by the air flow sensor relative to the target air flow-rate exceeds the predetermined threshold value.