Atmosphere learning device for oxygen concentration sensor

Abstract

An atmosphere learning device performs atmosphere learning upon an output value from an oxygen concentration sensor based on the output value from the sensor when an exhaust passage is in an atmospheric state. The device includes a stop request determination device, an opening-closing valve control device, and a learning execution device. The stop request determination device is for determining whether an operation stop request of an engine has been made. The opening-closing valve control device is for controlling an opening-closing valve into a predetermined valve-opening state when it is determined by the determination device that the operation stop request has been made. The learning execution device is for executing the atmosphere learning after control of the opening-closing valve into the predetermined valve-opening state by the control device.

1 . An atmosphere learning device for an oxygen concentration sensor, wherein:
 the device is adapted for an internal combustion engine that includes:
 a combustion chamber; 
 an exhaust passage; 
 an opening-closing valve that is configured to regulate a state of one of intake of gas into the combustion chamber and exhaust of gas from the combustion chamber; and 
 the sensor that is provided for the exhaust passage to detect an oxygen concentration in exhaust gas; 
   the device is configured to perform atmosphere learning upon an output value from the sensor based on the output value from the sensor when the exhaust passage is in an atmospheric state; and   the atmosphere learning includes calibration of a relationship between the output value from the sensor and the oxygen concentration, the device comprising:   a stop request determination means for determining whether an operation stop request of the engine has been made;   an opening-closing valve control means for controlling the opening-closing valve into a predetermined valve-opening state when it is determined by the determination means that the operation stop request has been made; and   a learning execution means for executing the atmosphere learning after control of the opening-closing valve into the predetermined valve-opening state by the control means.   
     
     
         2 . The atmosphere learning device according to  claim 1 , wherein:
 the engine further includes an intake valve and an exhaust valve;   the opening-closing valve includes at least one of the intake valve and the exhaust valve; and   as the control of the opening-closing valve into the predetermined valve-opening state, the control means controls a valve-opening mode of the at least one of the intake valve and the exhaust valve such that a sum of valve opening amounts of the intake valve and the exhaust valve in a state in which the intake valve and the exhaust valve are opened at a same time after an operation stop of the engine reaches a predetermined amount for promotion of scavenging of the exhaust passage.   
     
     
         3 . The atmosphere learning device according to  claim 2 , wherein as the control of the opening-closing valve into the predetermined valve-opening state, the control means controls the sum of valve opening amounts into the predetermined amount for promotion of scavenging by adjusting an amount of valve overlap during which a valve-opening period of the intake valve and a valve-opening period of the exhaust valve overlap. 
     
     
         4 . The atmosphere learning device according to  claim 1 , further comprising:
 a scavenging state detecting means for detecting a scavenging state of the exhaust passage after a rotation stop of the engine; and   a time setting means for setting a required time before execution of the atmosphere learning after predetermined timing that follows the operation stop request, based on the scavenging state detected by the detecting means.   
     
     
         5 . The atmosphere learning device according to  claim 4 , wherein:
 the device is adapted for the engine which further includes an engine driven-type variable valve mechanism that is configured to variably control valve timing for at least one of an intake valve and an exhaust valve of the engine;   as the control of the opening-closing valve into the predetermined valve-opening state, the control means adjusts an amount of valve overlap, during which a valve-opening period of the intake valve and a valve-opening period of the exhaust valve overlap, through the variable valve mechanism;   the detecting means detects the amount of valve overlap at a time of the rotation stop of the engine as the scavenging state; and   the setting means sets the required time based on the amount of valve overlap detected by the detecting means.   
     
     
         6 . The atmosphere learning device according to  claim 1 , wherein:
 the engine further includes an intake passage;   the opening-closing valve is a throttle valve that is configured to regulate a passage sectional area of the intake passage; and   the control means puts the throttle valve into a fully open state when it is determined by the determination means that the operation stop request has been made.