Measuring and testing – Simulating operating condition – Marine
Patent
1991-03-20
1993-04-06
Myracle, Jerry W.
Measuring and testing
Simulating operating condition
Marine
7320417, F02M 6500
Patent
active
051993007
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to systems and methods for controlling activation of a circuit element when predetermined conditions exist. More specifically, the present invention relates to systems and methods for controlling activation of a circuit element in a special cycle when predetermined conditions exist to prevent contamination of the circuit element.
BACKGROUND OF THE INVENTION
In the past, there have been hot-wire, air-mass flowmeters described for use in motor vehicles. U.S. Pat. No. 4,373,383 discloses such a system. According to U.S. Pat. No. 4,373,383, a resistor in the form of a hot-wire, air-mass flowmeter is used for measuring purposes in a motor vehicle. The hot wire is burned free of dirt particles in a free-burning operation which takes place after every time an internal-combustion engine is shut off. This is accomplished by a predetermined unbalancing of a bridge circuit which contains the resistor in a bridge arm.
In principle, this recurrent free-burning brings about good results. In particular, the drift in characteristics caused by the contamination of the resistor (which is generally made of platinum wire) is eliminated after each shut-off operation of the internal-combustion engine. However, along with every free-burning operation, parts of the wire material of the resistor are also vaporized, so that after a large number of free-burning operations, there is a disadvantageous distortion of characteristics.
In the past, there have been other systems that are not hot wire systems that have the ability to prevent contamination of an element used in a measuring device. U.S. Pat. No. 4,125,093 discloses a flowmeter which is based on a semiconductor and can be installed in automotive fuel injection systems to measure air mass and fuel quantity. To prevent the sensor from being contaminated, U.S. Pat. No. 4,125,093 proposes covering the semiconductor sensor with a passivation layer of silicon nitride and possibly with gold plating.
Prior systems also have used integration and comparing steps in the context of free-burning operations. Japanese Patent Nos. 60 125 751 and 63 184 018 disclose methods of integrating or summing up the suctioned air mass and then comparing the integration or cumulative value with a limiting value for the free-burning operation. When the integration or cumulative value exceeds the limiting value, a free-burning operation is initiated.
SUMMARY OF THE INVENTION
According to the present invention, the actual degree of contamination is considered for controlling the temperature of a resister used in a measuring device. This makes it possible to drastically reduce the number of free-burning operations that take place, compared to the number that would take place if the operating method initiated a free-burning operation every time the internal-combustion engine is shut off without considering the degree of contamination of the resistor. The system and method of the present invention considerably reduce any distortion of characteristics of the resistor resulting from material vaporization, while still producing an adequate cleaning effect. Thus, the resistor that is temperature controlled by the system and method of the present invention has a considerably longer operational life and, at the same time, high measuring accuracy for the measuring device in which it is incorporated.
In the case of the system of the present invention, it is found that available conventional control instruments and internal-combustion engine components may provide direct or indirect measurements of the amount of contamination of the resistor. Air-mass measurements associated with a flowmeter provide a direct measurement method for determining contamination of the resistor, while the measurement of the fuel flow rate of the internal combustion engine is an indirect method for measuring resistor contamination because the fuel flow rate is proportion to the air-mass. That is, it is useful for the purposes of the present invention also to be able to use indirect m
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Gras Jurgen
Kienzle Wolfgang
Sauer Rudolf
Myracle Jerry W.
Robert & Bosch GmbH
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