Exhaust gas sensor operating temperature detection system

• US 3,938,479 A
• Filed: 09/30/1974
• Issued: 02/17/1976
• Est. Priority Date: 09/30/1974
• Status: Expired due to Term

• Current Assignee: Siemens-Bendix Automotive Electronics LP
• Original Assignee: The Bendix Corporation (Honeywell International Inc.)
• Inventors: Oberstadt, Allan L.
• Primary Examiner(s): Goldstein, Herbert
• Assistant Examiner(s): Ciarlante, Anthony V.
• Application Number:
  US05/510,276
• Time in Patent Office: 505 Days
• Field of Search: 73/118, 73/117.3, 73/116, 60/276, 123/32 EA, 307/117
• US Class Current: 123/695
• CPC Class Codes: F02D 41/148 Using a plurality of comparators
• CPC Class Codes: F02D 41/1496 Measurement of the conductivity of a sensor F02D41/1455 takes precedence

Abstract

In a fuel management system having an exhaust gas sensor located in an exhaust gas system of an internal combustion engine for controlling the fuel air ratio of the fuel mixture to the internal combustion engine, a detection system for detecting when the operating temperature of the exhaust gas sensor is within its normal operating range. In the preferred embodiment, an oxygen gas sensor having a voltage output above a first threshold level in a rich fuel mixture and a voltage output below a second threshold level in a lean fuel mixture is used for controlling the fuel air mixture to the internal combustion engine. When the oxygen gas sensor is below its normal operating temperature, the internal impedance of the sensor is such that the voltage generated by the sensor through its amplifier is extremely high. The detection system compares a timed developed output of the sensor to a temperature reference voltage and supplies a signal to enable the control function of the sensor when operating within its normal temperature range.

Claims

1. In a fuel management system for an internal combustion engine having an exhaust gas sensor for supplying a control signal to the fuel management control, a detection system for detecting when the temperature of the sensor is at its operating temperature to provide an enabling signal to the fuel management control system, said system comprising:

an exhaust gas sensor operable at a high sensor temperature for generating a first voltage signal in response to the absence of a predetermined constituent gas in the exhaust gas and for generating a second voltage signal in response to the presence of the predetermined constituent gas in the exhaust gas, said sensor having an internal impedance varying inversely with the temperature of said sensor from a very high impedance at its low, nonoperable temperature to a very low impedance at its high operating temperature;

an exhaust gas sensor amplifier circuit means electrically connected to said sensor, the output signal of said circuit means normally having a first voltage level when said sensor'"'"'s internal impedance is very high corresponding to the low temperature of said sensor and said circuit means adapted to switch said output signal between said first voltage level and a second voltage level in response to said first and second voltage signals from said sensor;

storage means electrically responsive to said first voltage level from said circuit means for storing at a predetermined charging rate a voltage magnitude representing the temperature of said gas sensor;

storage discharge means electrically connected to said storage means and operable for discharging said storage means at a predetermined discharging rate, in response to said second voltage level from said circuit means;

temperature reference signal means for generating a threshold voltage level representing the normal operating temperature of said sensor; and

a comparator having one input electrically connected to said storage means and another input electrically connected to said temperature reference signal means, the output of said comparator being an enabling signal when the magnitude of the voltage level of said storage means is greater than said threshold voltage level.

2. In a fuel management system according to claim 1 wherein said exhaust gas sensor is a sensor for sensing the presence of oxygen in the exhaust gas of the internal combustion engine, said sensor at its operating temperature generating said first voltage signal in the absence of oxygen representing a rich fuel mixture and generating said second voltage signal in the presence of oxygen representing a lean fuel mixture.

3. In a fuel management system according to claim 2 wherein said operating temperature is greater than 600°

F and the threshold voltage level from said temperature reference signal means is intermediate said high and said low voltage level of said exhaust gas sensor amplifier circuit means.

4. In a fuel management system according to claim 1 wherein said storage means comprises:

a resistor electrically connected at one end to the output of said exhaust gas sensor amplifier circuit means and

a capacitor electrically connected between the other end of said resistor and a reference voltage level, said resistor for controlling the charging current to said capacitor thereby regulating the charging rate of said capacitor.

5. In a fuel management system according to claim 4 wherein said storage discharge means comprises:

a constant current source;

a transistor having its base lead electrically connected to said constant current source and its input circuit electrically connected to said storage means and its output circuit electrically connected in circuit to a reference voltage level;

said constant current source supplying sufficient base current to said transistor for controlling the discharge rate of said storage means through said input-output circuit of said transistor.

6. In a fuel management system according to claim 5 wherein said charging rate is substantially greater than said discharging rate.

7. In a fuel management system according to claim 3 wherein said internal impedance of said sensor at its low, nonoperable temperature is approximately 100 megohms and said internal impedance of said sensor at its operating temperature is approximately 1000 ohms.