Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
1999-08-20
2001-10-23
Paschall, Mark (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S499000, C219S505000, C374S001000
Reexamination Certificate
active
06307187
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of operating a resistance heating element and a device for carrying out the method.
BACKGROUND INFORMATION
It is known that the actual temperature required for regulating a resistance heating element can be detected using a separate sensor. These sensor elements can be manufactured with a uniform quality. If the resistor of the resistance heating element is used for temperature detection, it exhibits a substantial spread compared with conventional temperature sensors. An object of the present invention is to provide the parameters required for operating the resistance heating element in a rational manner, allowing automation if required.
SUMMARY
In accordance with an example embodiment of the present invention, a method is provided for operating a resistance heating element. In a first step, a resistance R
h
of the resistance heating element is determined at a known base temperature. During a second step, a resistance setpoint value is determined as a function of resistance R
h
at the known base temperature and a known temperature coefficient. The resistance heating element is activated by approximately setting this resistance setpoint value. Despite the usually high spread of the values of R
h
, this resistance R
h
is accurately determined under known conditions. Thus the control parameters of the resistance heating element can be specifically adjusted to this resistance R
h
. The desired setpoint temperature can be attained because the resistance setpoint value is determined as a function of this widely fluctuating resistance R
h
. This adjustment can also be performed using software; therefore, the method according to the present invention can be easily automated, which contributes to the cost savings, in particular in the case of mass production. The measurement of resistance R
h
increases the accuracy of the temperature control.
In an advantageous embodiment, room temperature is used as the base temperature. Thus parameter adjustment is tailored to the known conditions in production. Because of the known temperature coefficient of resistor R
h
, resistor R
h
does not have to be heated.
Using a variable resistance, a signal processing unit determines the resistance R
h
at the known base temperature. A resistance setpoint that is determined as a function of resistance R
h
and the known temperature coefficient of resistor R
h
is set. Thus, the signal processing unit and the variable resistor contribute to setting parameters and to the subsequent operation of the resistance heating element. This saves the cost of separate adjustment devices.
According to an example embodiment, the resistance setpoint value is saved in a memory. The contents of the memory can be subsequently retrieved for control purposes.
One embodiment is distinguished by the fact that resistor R
h
is a part of a bridge circuit. Resistance R
h
can be easily determined, for example, by bridge balancing.
In another embodiment, the variable resistor is made up of individual resistors connected in parallel, which can be activated individually. Thus, an inexpensive and sufficiently accurate version is achieved.
The method and the device for carrying out the invention are used in a motor vehicle that is equipped with an air quality sensor. The wear on the air quality sensor is reduced by periodic heating.
REFERENCES:
patent: 4881057 (1989-11-01), Garcia et al.
patent: 38 02 051 (1988-08-01), None
patent: 0 492 670 (1992-07-01), None
patent: 0 743 516 (1996-11-01), None
patent: 2 191 292 (1987-12-01), None
Patent Abstract of Japan, vol. 96, No. 3, Mar. 29, 1996 & JP 07 306090 A (Murata Mfg Co. Ltd.), Nov. 21, 1995.
Ingrisch Kurt
Peter Cornelius
Riehl Guenther
Weigold Thomas
Kenyon & Kenyon
Paschall Mark
Robert & Bosch GmbH
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