Boots – shoes – and leggings
Patent
1991-04-22
1994-03-01
Teska, Kevin J.
Boots, shoes, and leggings
36457101, 36457105, 324600, G06F 1520, G01R 2700
Patent
active
052914178
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method and an arrangement for determining the internal resistance of a lambda probe with the aid of the output voltage values supplied by a lambda probe circuit. The invention furthermore relates to a method for the closed-loop heating control with the aid of the internal resistance determined.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,419,190 discloses a method according to which the internal resistance is measured with the aid of an alternating current passed through the probe. The alternating voltage component is separated from the direct voltage component of the probe and the internal resistance is determined from alternating current and alternating voltage. The frequency used is preferably about 5,000 Hz. From the difference between the measured internal resistance and a desired value of the internal resistance, a control deviation is formed with the aid of which heating of the probe is controlled. The disadvantage of this method for measuring the internal resistance is that a separate alternating current source and a separate alternating voltage evaluating circuit are required. An advantage is that no burden is placed on the probe voltage by the determination of the internal resistance, with the result that the internal resistance can be determined at very short time intervals.
U.S. Pat. No. 4,742,808 discloses a method for determining the internal resistance of a lambda probe, according to which the probe is periodically loaded by electrically connecting a load resistor. The internal resistance is calculated with the aid of the load resistor from the voltages measured in the loaded condition and in the unloaded condition. The value of the load resistor is compared to a threshold value to determine whether the probe is ready for operation. This method requires minimal circuit complexity since only the load resistor and a switch are required. A disadvantage is that the probe voltage recovers only relatively slowly after loading, with the result that the internal resistance cannot be measured by this method when the lambda probe is involved in control operations. In that case, the probe voltage must be measured approximately every 10 to 15 ms. However, after loading, the probe voltage only recovers in a time span of about 100 ms.
SUMMARY OF THE INVENTION
The invention has the object of providing a method for determining the internal resistance of a lambda probe which can be implemented with little circuit complexity and does not impair the normal measurement of the probe voltage. It is the further object of the invention to provide an arrangement for carrying out such a method. A further object is to indicate a method of using the determined internal resistance for the purpose of closed-loop heating control. The determined internal resistance is corrected taking into account a predetermined relationship with lean and rich lambda values. This teaching is based on the realization that, when the lambda values jump from rich to lean and vice versa, the internal resistance likewise changes abruptly even though the temperature of the probe does not change. The teaching can be used, inter alia, to ensure that the probe heating power is not altered abruptly when the internal resistance changes due to a jump in the lambda value instead of a change in temperature.
The method according to the invention for determining internal resistance is characterized in that a clocked direct-current counter voltage is applied to the lambda probe via a series resistor. The output voltage of the lambda probe circuit is measured with the counter voltage connected and disconnected and, taking into account known resistance values of the circuit, the internal resistance is calculated from the two voltage values measured. Compared to a conventional device, the only additional components required for this purpose by the arrangement according to the invention are a direct-current voltage source with a series resistor and a switch.
With the aid of the internal resistance measur
REFERENCES:
patent: 4419190 (1983-12-01), Dietz et al.
patent: 4471448 (1984-09-01), Williams
patent: 4523084 (1985-06-01), Tamura et al.
patent: 4742808 (1988-05-01), Blumel et al.
patent: 4930095 (1990-05-01), Yuchi et al.
patent: 5095453 (1992-03-01), Pierson et al.
patent: 5140535 (1992-08-01), Raff et al.
Homeyer Manfred
Raff Lothar
Schnaibel Eberhard
Westerdorf Michael
Ottesen Walter
Robert & Bosch GmbH
Teska Kevin J.
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