Air fuel ratio controller for engine

Abstract

Abstract PURPOSE:To control an air fuel ratio to a proper value by stopping an oxygen pump current and measuring the return time of an electromotive force, and comparing it with an initial return time. CONSTITUTION:An air fuel ratio sensor controls the electromotive force between a measurement electrode and a reference electrode or the potential difference between the electrodes to a specific value with the oxygen pump current. This is the same with control over the oxygen partial pressure in a diffusion resistance layer and the oxygen partial pressure on the reference electrode side to specific values. The oxygen pump current is stopped and then the electromotive force varies from the controlled value to a value corresponding to air fuel ratio in exhaust gas, i.e. almost 0V in a lean state or almost 1V in a rich state. Namely, various gaseous components in the exhaust gas are diffused naturally in the diffusion resistance layer and the air fuel ratio in the diffusion resistance layer becomes equal to the air fuel ratio in the exhaust gas. Therefore, the ratio of variation in the diffusion constant of the diffusion resistance layer is found from variation in the return time of the electromotive force. Then, when the variation rate of the diffusion constant is known, the output characteristics of the air fuel ratio sensor can be calibrated, so that accurate air fuel ratio control is performed.

Inventors

• 👤 Takayuki Itsuji
• 👤 貴之 井辻
• 👤 Sadayasu Ueno
• 👤 上野　定寧
• 👤 Norio Ichikawa
• 👤 市川　範男

Bibliographic Details