Pressure transducer for monitoring a pneumatic tire
First Claim
1. A pressure transducer for use with a pneumatic tire monitoring system, the transducer comprising:
- a nonconductive resilient layer for responding to a change in pressure;
a piezo-resistive layer fixed to the resilient layer wherein the piezo-resistive layer consists essentially of between about 10% and about 20% activated N-type semiconductor material, between about 40% and about 60% of one of the group consisting of molybdenum disulfide, titanium, bismuth oxide, and between about 20% and about 50% of one of the group consisting of alkyd and silicone binder so as to produce a substantially constant resistance while under a substantially constant load.
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Accused Products
Abstract
A pressure transducer for use with a pneumatic tire monitoring system includes a non-conductor resilient layer and a piezo-resistive/variably conductive layer having a composition which provides substantially constant resistant while under a substantially constant load. In a preferred embodiment, the piezo-resistive/variably conductive layer includes N-type semiconductor material, molybdenum disulfide, titanium, bismuth oxide, and alkyd or silicone binder. The transducer also includes conductive elements which are attached to a nonconductive substraight and electrically insulated from each other. The piezo-resistive/conductive layer contacts at least two of the conductive elements with a surface area which is responsive to a change in pressure so as to produce a variable resistant/conductives between the conductive elements. In one embodiment, the piezo-resistive/conductive layer is hemispherically shaped and divided to produce two independent sensing transducers. The output of these transducers may be combined to improve the response linearity of the transducer. One embodiment utilizes a log/anti-log circuit and a differential amplifier to combine the output of the separate but integral transducers.
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Citations
21 Claims
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1. A pressure transducer for use with a pneumatic tire monitoring system, the transducer comprising:
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a nonconductive resilient layer for responding to a change in pressure; a piezo-resistive layer fixed to the resilient layer wherein the piezo-resistive layer consists essentially of between about 10% and about 20% activated N-type semiconductor material, between about 40% and about 60% of one of the group consisting of molybdenum disulfide, titanium, bismuth oxide, and between about 20% and about 50% of one of the group consisting of alkyd and silicone binder so as to produce a substantially constant resistance while under a substantially constant load. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A pressure transducer for use with a pneumatic tire monitoring system, the transducer comprising:
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a nonconductive resilient base having a substantially hemispherical portion; a variably conductive layer deposited on the substantially hemispherical portion wherein the conduction varies as a function of pressure exerted on the nonconductive base; a substantially flat nonconductive substrate; a plurality of conductive elements attached to the substrate, each of the plurality being electrically insulated from remaining conductive elements; wherein the conductive layer contacts at least two of the plurality of conductive elements with a surface area which is responsive to the pressure so as to produce a variable conductance between the at least two of the plurality of conductive elements indicative of the pressure. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A pressure transducer for use in a pneumatic tire monitoring system, the transducer comprising:
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a nonconductive resilient diaphragm having a conductive layer deposited thereon; a substantially flat nonconductive substrate; a plurality of conductive elements attached to the substrate, each of the plurality being electrically insulated from remaining conductive elements; a nonconductive spacer disposed between the diaphragm and the plurality of conductive elements, the spacer including an aperture allowing the conductive layer to contact at least two of the plurality of conductive elements with a surface area which increases with increasing pressure so as to produce a variable conductance between the at least two of the plurality of conductive elements. - View Dependent Claims (20, 21)
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Specification