Exhaust gas purification system for internal combustion engine, internal combustion engine, and exhaust gas purification method for internal combustion engine

Abstract

An exhaust gas purification system for an internal combustion engine includes an oxidation catalyst device on an upstream side in an exhaust passage of an internal combustion engine and a lean NOx trap catalyst device on a downstream side, a controller which controls the exhaust gas purification system is configured to, when a temperature-rising control of an exhaust gas in a regeneration control is performed to recover a purification ability of the exhaust gas purification system, perform a control that changes a measurement position of a control temperature which is a control amount of a feedback control in the temperature-rising control, according to an excess air ratio or an oxygen concentration of the exhaust gas passing through the exhaust passage.

The invention claimed is: 
     
       1. An exhaust gas purification system for an internal combustion engine, which includes an oxidation catalyst device on an upstream side in an exhaust passage of an internal combustion engine and a lean NOx trap catalyst device on a downstream side, comprising:
 a controller which controls the exhaust gas purification system configured to, when a temperature-rising control of an exhaust gas in a regeneration control is performed to recover a purification ability of the exhaust gas purification system, perform a control that changes a measurement position of a control temperature which is a control amount of a feedback control in the temperature-rising control, according to an excess air ratio or an oxygen concentration of the exhaust gas passing through the exhaust passage. 
 
     
     
       2. The exhaust gas purification system for the internal combustion engine according to  claim 1 , the exhaust gas purification system comprising:
 a first temperature sensor which measures a first temperature relating to a temperature of the oxidation catalyst device; and 
 a second temperature sensor which measures a second temperature relating to a temperature of the lean NOx trap catalyst device, 
 wherein the controller is configured to, when the temperature-rising control of the exhaust gas in the regeneration control is performed to recover the purification ability of the exhaust gas purification system, perform a control such that the control temperature is set as the first temperature when the excess air ratio or the oxygen concentration of the exhaust gas passing through the exhaust passage is higher than an upper limit threshold set in advance, and the control temperature is set as the second temperature when the excess air ratio or the oxygen concentration of the exhaust gas passing through the exhaust passage is lower than a lower limit threshold set in advance. 
 
     
     
       3. The exhaust gas purification system for the internal combustion engine according to  claim 2 , wherein
 the controller is configured to, when the temperature-rising control of the exhaust gas in the regeneration control is performed to recover the purification ability of the exhaust gas purification system, perform a control such that a weight coefficient is set to be changed according to the excess air ratio or the oxygen concentration of the exhaust gas passing through the exhaust passage, and the control temperature is set to a weighted average value of the first temperature and the second temperature obtained using the weight coefficient, when the excess air ratio or the oxygen concentration of the exhaust gas passing through the exhaust passage is equal to or less than the upper limit threshold and equal to or more than the lower limit threshold. 
 
     
     
       4. An internal combustion engine comprising:
 the exhaust gas purification system for the internal combustion engine according to  claim 1 . 
 
     
     
       5. An exhaust gas purification method for an internal combustion engine having an exhaust gas purification system for the internal combustion engine, which includes an oxidation catalyst device on an upstream side and a lean NOx trap catalyst device on a downstream side in an exhaust passage of the internal combustion engine, the method comprising:
 changing, when a temperature-rising control of an exhaust gas in a regeneration control is performed to recover a purification ability of the exhaust gas purification system, a measurement position of a control temperature which is a control amount of a feedback control in the temperature-rising control, according to an excess air ratio or an oxygen concentration of the exhaust gas passing through the exhaust passage.