US 3,946,198 A · Electrical control system for an exhaust gas sensor

Abstract

A system for controlling the application of heat energy to a ceramic exhaust gas sensor and for linearizing the output signal from the sensor is disclosed. The system compares, electrically, the resistance of a conductive heater winding against a fixed reference and permits a flow of electrical current through the heater whenever the comparison indicates that the temperature of the heater is below the desired level. By periodically establishing a flow of electrical energy through the heater and terminating that flow whenever the heater temperature reaches the desired level, the temperature of the heater may be held at the desired level with great accuracy. In order to periodically reestablish the flow of electrical energy through the heater, the system further provides an oscillator arranged to reestablish current flow through the heater a fixed time period following termination of current flow through the heater. The system also provides a linearizing amplifier connected to the sensor to provide an output signal which is linear with respect to changes in the air/fuel ratio of the mixture being combusted.

Claims9

Dependent claims

A system for controlling the application of heat by a platinum heater wire to a ceramic exhaust gas sensor to maintain a selected temperature at the sensor comprising in combination:

a source of electrical energy;
switching means having an on and an off state for applying electrical energy from said source to the heater wire;
amplifier means having input and output terminals, said output terminal connected to said switch means for controlling the state of said switch means;
first voltage divider circuit means connected to said switch means for establishing a reference voltage value;
first means for applying said reference voltage value to one of said input terminals;
second voltage divider circuit means, which includes the heater, electrically connected in parallel with the first voltage divider circuit means for establishing a heater voltage value;
second means for applying said heater voltage value to another of said input terminals;
timer circuit means connected to said switch means operative to cause said switch means to be switched to a selected one of said switch states from the other of its switch states a predetermined period of time after entering the other of its switch states;
and
said amplifier means operative to cause said switch means to enter the other switch state whenever the heater voltage value as compared with the reference voltage value, indicates a temperature in excess of the selected temperature.

7 more elements

A circuit for controlling the average electric power delivered to a heater winding comprising:

controllable switch means for establishing a power delivering circuit relationship between a source of electric power and the winding;
comparison means, including reference means, operative to compare an electrical parameter indicative of power delivery against a reference and to control said switch means to terminate the circuit relationship when power delivery reaches a preselected level;
and
oscillator means responsive to the termination of the power delivery to the winding operative to control said switch means to establish the circuit relationship between the source and the winding a fixed time interval following termination of the circuit relationship whereby the average power delivery to the winding may be controlled by controlling the duration of power delivery to the winding followed by periods of nondelivery.

1 more element

Dependencies are inferred from the claim text.

Electrical control system for an exhaust gas sensor

Life of this patent

Electrical control system for an exhaust gas sensor

Life of this patent

Abstract

Claims9