Method and apparatus for obtaining a control variable for the closed-loop control of the fuel-air ratio in the operating mixture of internal combustion engines

Claim 1

A method for obtaining a control variable for a closed-loop control device for the closed-loop control of the fuel-air ratio of the operating mixture in internal combustion engines utilizing an exhaust gas threshold-current sensor exposed to the exhaust gas flow and a control device for adjusting the fuel-air ratio of the operating mixture, said sensor operating on the principle of oxygen ion conduction when exposed to voltage and having a body made of fixed electrolyte material which conducts oxygen ions and furnishes a control signal corresponding to the oxygen content in the exhaust gas, wherein the threshold current of the sensor, defined by the diffusion speed of the measured gas, is a standard for the oxygen content in the exhaust gas, the method comprising the steps of: generating a voltage difference signal which corresponds to the change in the air number λ of the operating mixture when there is a change in the operational state of the engine; generating a reference measurement voltage signal; adding the generated voltage difference signal and the generated reference measurement voltage signal; and applying the added generated voltage difference signal and the generated reference measurement voltage signal to the exhaust gas threshold-current sensor and measuring the resultant current through the exhaust gas threshold-current sensor, said resultant current serving as a standard for the percentage oxygen content in the closed-loop control circuit with the oxygen content which is to be maintained; whereby the closed-loop control device corrects the fuel-air ratio accordingly.

Claim 2

A method for obtaining a control variable for a closed-loop control device for the closed-loop control of the fuel-air ratio of the operating mixture in internal combustion engines utilizing an exhaust gas threshold-current sensor exposed to the exhaust gas flow and a control device for adjusting the fuel-air ratio of the operating mixture, said sensor operating on the principle of oxygen ion conduction when exposed to voltage and having a body made of fixed electrolyte material which conducts oxygen ions and furnishes a control signal corresponding to the oxygen content in the exhaust gas, wherein the threshold current of the sensor, defined by the diffusion speed of the measured gas, is a standard for the oxygen content in the exhaust gas, the method comprising the steps of: generating a voltage difference signal which corresponds to the change in the air number λ of the operating mixture when there is a change in the operational state of the engine; generating a reference measurement voltage signal; adding the generated voltage difference signal and the generated reference measurement voltage signal; and applying the added generated voltage difference signal and the generated reference measurement voltage signal to the exhaust gas threshold-current sensor and measuring the resultant current through the exhaust gas threshold-current sensor, said resultant current serving as a standard for the percentage oxygen content in the closed-loop control circuit with the oxygen content which is to be maintained; whereby the closed-loop control device corrects the fuel-air ratio accordingly.

Claim 3

An apparatus for obtaining a control variable for a closed-loop control device for the closed-loop control of the fuel-air ratio of the operating mixture in internal combustion engines, comprising: means for ascertaining the operational state of the engine; control means connected to the means for ascertaining the operational state of the engine for generating a voltage difference signal corresponding to the change in the air number λ resulting from the ascertained change in the operational state of the engine; an exhaust gas threshold-current sensor exposed to the flow of exhaust gas, said sensor having a fixed electrolyte body which conducts oxygen ions; means for adding the voltage difference signal to a reference measurement voltage signal and applying the added voltage signals to the exhaust gas threshold-current sensor; and current measuring means for measuring the resultant current through the exhaust gas threshold-current sensor as a result of applying the added voltage signals, whereby the resultant current serves as the control variable for the control device.

Claim 4

An apparatus for obtaining a control variable for a closed-loop control device for the closed-loop control of the fuel-air ratio of the operating mixture in internal combustion engines, comprising: means for ascertaining the operational state of the engine; control means connected to the means for ascertaining the operational state of the engine for generating a voltage difference signal corresponding to the change in the air number λ resulting from the ascertained change in the operational state of the engine; an exhaust gas threshold-current sensor exposed to the flow of exhaust gas, said sensor having a fixed electrolyte body which conducts oxygen ions; means for adding the voltage difference signal to a reference measurement voltage signal and applying the added voltage signals to the exhaust gas threshold-current sensor; and current measuring means for measuring the resultant current through the exhaust gas threshold-current sensor as a result of applying the added voltage signals, whereby the resultant current serves as the control variable for the control device.