| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent detection values of gas concentrations from getting abnormal when detecting an element resistance, and carry out an accurate gas concentration control by using a detected element resistance. <P>SOLUTION: An A/F signal proportional to an oxygen concentration is output upon a voltage application executed by a microcomputer 20 from an A/F sensor 30 for example, which is used as a gas concentration sensor for detecting a gas concentration in the exhaust gas from an internal combustion engine 10. When the element resistance is detected, a bias command signal Vr from the microcomputer 20 is converted by a D/A converter 21 to an analog signal Vb, and an output voltage Vc obtained by removing high-frequency components from the analog signal Vb through an LPF 22 is input to a bias control circuit 40. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal which has theretofore prevailed is held by an S/H (sample/hold) circuit 70 to thereby prevent the use of an error A/F signal. As a result, an accurate A/F control can be carried out by using the detected element resistance. <P>COPYRIGHT: (C)2007,JPO&INPIT |
