US 5,580,440 AGranted

Air fuel ratio sensory

AssigneeHitachi, Ltd.

InventorsSadayasu Ueno, Norio Hasegawa, Naoki Minami, Kanemasa Sato, Shiro Oouchi

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Abstract

A method and apparatus are disclosed for measuring atmospheric pressure in conjunction with an air-fuel ratio sensor of the type comprising a concentration cell with atmospheric air and exhaust electrodes on opposite sides of a solid-state electrolyte having oxygen ion conductivity. During an atmospheric pressure measuring cycle, oxygen ions are pumped from the atmospheric air electrode to the exhaust electrode, in a quantity which is either predetermined at a fixed value, or is sufficient to bring the cell to an equilibrium state. Atmospheric pressure is then calculated from measured emf of the cell, using an experimentally derived functional relationship. In a second embodiment, ions are pumped until a predetermined change of the concentration cell emf is achieved, and atmospheric pressure is determined based on the amount of time required to achieve such change. The atmospheric pressure measuring mode is operated on a time shared basis with the air-fuel ration detection mode.

Claims17

Dependent claims

Apparatus for measuring atmospheric pressure in conjunction with an air-fuel ratio sensor comprising:

a concentration cell having an atmospheric air side electrode and an exhaust gas side electrode arranged on opposite sides of a solid-state electrolyte having oxygen ion conductivity;
an exhaust gas diffusion rate control member covering said exhaust gas side electrode;
means for ionizing and pumping oxygen molecules between the atmospheric air side electrode and the exhaust gas side electrode;
means for controlling said pumping of ionized oxygen molecules to maintain an electromotive force to the concentration cell due to a ratio of oxygen partial pressure at said atmospheric air side electrode and said exhaust gas side electrode, at a set voltage level;
and
means for measuring pumping current due to said pumping of ionized oxygen molecules;
said apparatus comprising:
means for controlling said air-fuel ratio sensor to operate alternately in an air-fuel ratio detection mode and a separate atmospheric pressure measuring mode;
means operative during said atmospheric pressure measuring mode for controlling pumping of a quantity of ionized oxygen molecules from said atmospheric air side electrode to said exhaust gas side electrode, said quantity being one of:
a set quantity and a quantity which achieves equilibrium of said concentration cell;
means operative during said atmospheric pressure measuring mode for measuring electromotive force of said concentration cell following completion of pumping of said quantity of ionized oxygen molecules;
and
means for calculating atmospheric pressure as a function of the electromotive force of the concentration cell measured after completion of pumping of said quantity of ionized oxygen molecules, said function having been experimentally determined.

10 more elements

Apparatus for measuring atmospheric pressure in conjunction with an air-fuel ratio sensor comprising:

a concentration cell having an atmospheric air side electrode and an exhaust gas side electrode arranged on opposite sides of a solid-state electrolyte having oxygen ion conductivity;
an exhaust gas diffusion rate control member covering said exhaust gas side electrode;
means for ionizing and pumping oxygen molecules between the atmospheric air side electrode and the exhaust gas side electrode;
means for controlling said pumping of ionized oxygen molecules to maintain an electromotive force of the concentration cell due to a ratio of oxygen partial pressure at said atmospheric air side electrode and said exhaust gas side electrode, at a set voltage level;
and
means for measuring pumping current due to said pumping of ionized oxygen molecules;
said apparatus comprising:
means for controlling said air-fuel ratio sensor to operate alternately in an air-fuel ratio detection mode and a separate atmospheric pressure measuring mode;
means operative during said atmospheric pressure measuring mode for controlling pumping of ionized oxygen molecules from said atmospheric air side electrode to said exhaust gas side electrode until an electromotive force of the concentration cell changes by a set amount;
means for measuring a period of time t required for pumping of ionized oxygen molecules until said electromotive force of the concentration cell changes by a predetermined amount;
means for calculating atmospheric pressure as a function of said period of time t, according to an experimentally determined functional relationship.

8 more elements

Dependencies are inferred from the claim text.