Control device for exhaust system

A control device for an exhaust system, the exhaust system comprising:

• a catalyst provided in an exhaust passage of an internal combustion engine and having sulfur components in exhaust gas adhered thereto, and releasing the adhered sulfur components by rich components in exhaust gas;
• and
• a gas sensor provided on a downstream side of the catalyst,
• wherein
• the gas sensor is configured as a limiting current sensor having a solid electrolyte, an exhaust side electrode provided on an exhaust side of the solid electrolyte, and a reference side electrode provided on a reference chamber side, and detects a specific gas component by causing a movement of oxygen ions in the solid electrolyte by applying a voltage to the exhaust side electrode and the reference side electrode;
• and
• the control device including:
• a determination unit that determines whether an operating state of the internal combustion engine is a sulfur release state in which the sulfur components are released from the catalyst;
• and,
• a reaction suppression unit that performs a reaction suppression processing to suppress the reaction between oxygen and the sulfur components at the exhaust side electrode of the gas sensor when the determination unit determines that the gas sensor is in the sulfur release state,
• the reaction suppression unit performs a process of lowering the temperature of the solid electrolyte below the active temperature as the reaction suppression processing.

A control device for an exhaust system, the exhaust system comprising:

• a catalyst provided in an exhaust passage of an internal combustion engine and having sulfur components in exhaust gas adhered thereto, and releasing the adhered sulfur components by rich components in exhaust gas;
• and
• a gas sensor provided on a downstream side of the catalyst,
• wherein
• the gas sensor is configured as a limiting current sensor having a solid electrolyte, an exhaust side electrode provided on an exhaust side of the solid electrolyte, and a reference side electrode provided on a reference chamber side, and detects a specific gas component by causing a movement of oxygen ions in the solid electrolyte by applying a voltage to the exhaust side electrode and the reference side electrode;
• and
• the control device including:
• a determination unit that determines whether an operating state of the internal combustion engine is a sulfur release state in which the sulfur components are released from the catalyst;
• and,
• a reaction suppression unit that performs a reaction suppression processing to suppress the reaction between oxygen and sulfur components at the exhaust side electrode of the gas sensor when the determination unit determines that the gas sensor is in the sulfur release state,
• the reaction suppression unit performs a process of stopping voltage application to the exhaust side electrode and reference side electrode or a process of stopping voltage application to cause movement of oxygen ions from the reference side electrode to the exhaust side electrode as the reaction suppression processing,
• the control device further including:
• a sulfur release control unit that releases sulfur components attached to the catalyst by making the exhaust passage rich with unburned fuel, wherein
• the sulfur release control unit performs either of a first release processing for releasing the sulfur component by making the exhaust passage in a weakly rich state and a second release processing for releasing the sulfur component by making the exhaust passage in a strongly rich state having a richer degree than that of the first release processing, and
• the reaction suppression unit performs the reaction suppression processing on the condition that the sulfur release state is obtained by performing the second release processing among the first release processing and the second release processing.