Engine exhaust gas cleaning apparatus

An exhaust gas cleaning apparatus for an engine comprising:

• a fuel delivery device configured to deliver a fuel delivery quantity of fuel to the engine to produce an excess air ratio that is lean during normal operation of the engine;
• an exhaust gas cleaning device arranged in an exhaust system and configured to clean exhaust gas during a lean operation;
• and
• a control unit configured to control the fuel delivery device, the control unit including
• a regeneration timing determining section configured to determine a regeneration operation timing to regenerate the exhaust gas cleaning device;
• a regeneration control section configured to adjust the excess air ratio toward a rich target value to regenerate the exhaust gas cleaning device;
• a feedback control section configured to feedback-control the fuel delivery quantity such that the excess air ratio is substantially maintained at the rich target value during regeneration;
• and
• a feedback control restricting section configured to restrict the feedback control during regeneration until a difference between the rich target value and an actual excess air ratio is less than a prescribed value,
• the feedback control restricting section being configured to end restriction of the feedback control when the actual excess air ratio is determined to reach a stoichiometric air fuel ratio.

An exhaust gas cleaning apparatus for an engine comprising:

• a fuel delivery device configured to deliver a fuel delivery quantity of fuel engine to produce an excess air ratio that is lean during normal operation of the engine;
• an exhaust gas cleaning device arranged in an exhaust system and configured to clean exhaust gas during a lean operation;
• and
• a control unit configured to control the fuel delivery device, the control unit including
• a regeneration timing determining section configured to determine a regeneration operation timing to regenerate the exhaust gas cleaning device;
• a regeneration control section configured to adjust the excess air ratio toward a rich target value to regenerate the exhaust gas cleaning device;
• a feedback control section configured to feedback-control the fuel delivery quantity such that the excess air ratio is substantially maintained at the rich target value during regeneration;
• and
• a feedback control restricting section configured to restrict the feedback control during regeneration until a difference between the rich target value and an actual excess air ratio is less than a prescribed value,
• the feedback control restricting section being is configured to prohibit the feedback control in order restrict the feedback control during regeneration and to end restriction of the feedback control when the actual excess air ratio is determined to reach a stoichiometric air fuel ratio.

An exhaust gas cleaning apparatus for an engine comprising:

• a fuel delivery device configured to deliver a fuel delivery quantity of fuel to the engine to produce an excess air ratio that is lean during normal operation of the engine;
• an exhaust gas cleaning device arranged in an exhaust system and configured to clean exhaust gas during a lean operation;
• and
• a control unit configured to control the fuel delivery device, the control unit including
• a regeneration timing determining section configured to determine a regeneration operation timing to regenerate the exhaust gas cleaning device;
• a regeneration control section configured to adjust the excess air ratio toward a rich target value to regenerate the exhaust gas cleaning device;
• a feedback control section configured to feedback-control the fuel delivery quantity such that the excess air ratio is substantially maintained at the rich target value during regeneration;
• and
• a feedback control restricting section configured to restrict the feedback control during regeneration until a difference between the rich target value and an actual excess air ratio is less than a prescribed value,
• the feedback control restricting section being configured to lower the feedback control gain below a normal feedback control gain in order restrict the feedback control during regeneration and to end restriction of the feedback control when the actual excess air ratio is determined to reach a stoichiometric air fuel ratio.

An exhaust gas cleaning apparatus for an engine comprising:

• fuel delivery means for delivering a fuel delivery quantity of fuel to the engine to produce an excess air ratio that is lean during normal operation of the engine;
• exhaust gas cleaning means for cleaning exhaust emission particles contained in exhaust gas during a lean operation of the engine;
• regeneration timing determining means for determining a regeneration operation timing to regenerate the exhaust gas cleaning means;
• a regeneration control means for adjusting the excess air ratio toward a rich target value to regenerate the exhaust gas cleaning means by controlling an intake air throttle valve in an intake passage of the engine;
• feedback control means for feedback-controlling the fuel delivery quantity such that the excess air ratio is maintained at the rich target value during regeneration;
• and
• feedback control restricting means for restricting the feedback regeneration until a difference between the rich target value and an actual excess air ratio is less than a prescribed value;
• the regeneration control means further performing functions of reducing an opening degree of the intake air throttle valve to a prescribed opening degree before the difference between the rich target value and the actual excess air ratio is less than the prescribed value, and maintaining the fuel delivery quantity during regeneration before the difference between the rich target value and the actual excess air ratio is less than the prescribed value to a fuel delivery quantity being delivered before the regeneration starts.

A method of cleaning exhaust gas of an engine comprising:

• delivering a fuel delivery quantity of fuel and an intake air quantity to the engine to produce an excess air ratio that is lean during normal operation of the engine;
• cleaning exhaust emission particles contained in exhaust gas with cleaning device during a lean operation of the engine;
• determining a regeneration operation timing to regenerate the exhaust gas cleaning device;
• adjusting the excess air ratio toward a rich target value to regenerate the exhaust gas cleaning device by reducing an opening degree of an intake air throttle valve in an intake passage of the engine to a prescribed opening degree before a difference between the rich target value and an actual excess air ratio is less than a prescribed value, and maintaining the fuel delivery quantity during regeneration before the difference between the rich target value and the actual excess air ratio is less than the prescribed value to a fuel delivery quantity being delivered before the regeneration starts;
• feedback controlling the fuel delivery quantity such that the excess air ratio is maintained at the rich target value during regeneration;
• and
• selectively restricting the feedback-controlling of the fuel delivery quantity during regeneration until the difference between the rich target value and the actual excess air ratio is less than the prescribed value.