Electrical transmission or interconnection systems – Anti-induction or coupling to other systems – Magnetic or electrostatic field control
Reexamination Certificate
1999-05-05
2001-08-14
Paladini, Albert W. (Department: 2836)
Electrical transmission or interconnection systems
Anti-induction or coupling to other systems
Magnetic or electrostatic field control
C073S204230, C102S202200, C333S012000, C361S818000
Reexamination Certificate
active
06274951
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates generally to an EMI energy absorber.
II. Description of the Prior Art
There are many electrical circuits, such as a hot wire air flow sensor for an internal combustion engine, which include components which exhibit antenna characteristics within predetermined frequency bands. For example, the posts for the hot and cold wire sensors of a hot wire air flow meter exhibit antenna characteristics typically in the frequency band of 500 MHz-1 GHz. Similarly, the pins on the electrical connector for the hot wire air flow sensor exhibit antenna characteristics in the frequency range of approximately 1-1.5 GHz while the wiring harness between the air flow sensor and its power supply typically exhibits antenna characteristics in the range of less than 100 MHz.
Electromagnetic interference (EMI) occurs from many different sources, such as radio frequency antennas, mobile telephones, radar, power lines and the like. Whenever the frequency of the EMI interacts with the resonant frequency of the components of the air flow meter which act as an antenna, the EMI is conducted to the various components of the air flow meter, such as the hot and cold wire sensors. Such EMI affects the overall output and current from the air flow sensor thus resulting in inaccurate readings from the air flow sensor. Such inaccurate readings, in turn, adversely affect the overall operation and emission output of the internal combustion engine associated with the air flow sensor.
SUMMARY OF THE PRESENT INVENTION
The present invention provides an energy absorber which overcomes the above-mentioned disadvantages of the previously known air flow sensors and other electronic circuits.
In brief, the present invention provides an energy absorber for use with an electrical circuit having at least one electrical element which exhibits antenna characteristics at a predetermined frequency range for the EMI. One such electrical circuit is an air flow sensor of the type used in internal combustion engines, although other types of electrical circuits are also adversely affected by EMI.
The absorber of the present invention comprises an electronic component which is electrically connected in series with the element exhibiting antenna characteristics. This component, furthermore, exhibits a resistance which varies as a function of frequency and is selected such that the component has a maximum resistance within the predetermined frequency range in which the element of the circuit exhibits antenna characteristics. As such, the component then absorbs the EMI and dissipates the EMI as heat.
In the preferred embodiment of the invention, the component exhibiting resistance which varies as a function of frequency comprises a ferrite bead although other components exhibiting a variable resistance as a function of frequency may alternatively be used. Furthermore, where at least two elements of the electrical circuit exhibit antenna-like characteristics, one component is electrically connected in series with each such element of the circuit. A capacitor is also preferably electrically connected between the two elements of the electrical circuit to stabilize the circuit and also conduct EMI in the predetermined frequency range for the EMI.
REFERENCES:
patent: 5226319 (1993-07-01), Suzuki
patent: 5490030 (1996-02-01), Taylor et al.
patent: 5654506 (1997-08-01), Yoneda et al.
patent: 5796323 (1998-08-01), Uchikoba et al.
patent: 5905226 (1999-05-01), Baginski
patent: 5969583 (1999-10-01), Hutchinson
Oho Shigeru
Saikalis George
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
Hitachi America Ltd.
Paladini Albert W.
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