Pneumatic detection apparatus for a tire which utilizes pressure-sensitive displacement of an internal magnet
First Claim
1. A pneumatic detection apparatus for a tire, comprising:
- pressure detecting means for detecting change in air pressure of a tire as change in magnetic flux;
signal outputting means for outputting signals which change in accordance with a amount of change of said magnetic flux;
amplitude compensating means for generating signals compensating for change in said signals from said signal outputting means due to tire rotating speed; and
discriminating means for discriminating pressure values of said air pressure as a plurality of values, in accordance with said signals from said amplitude compensating means.
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Accused Products
Abstract
A magnetic-flux change-generating device 2 causes amplitude modulation of alternating magnetic flux in accordance with displacement of a movable body, and an amplitude-compensating device (low-pass filter) 4 causes attenuation of amplitude of electromagnetic-induction voltage of a pickup coil 3 substantially proportionally to frequency. When frequency of the alternating magnetic flux (also termed "carrier frequency") fluctuates, the amplitude of the electromagnetic-induction voltage fluctuates in proportion to the frequency, but because the amplitude of the electromagnetic-induction voltage is caused to be attenuated at an attenuation rate which is substantially proportional to the frequency, displacement can be detected accurately by this amplitude change, irrespective of change in the frequency of the alternating magnetic flux (i.e., the carrier frequency of the electromagnetic-induction voltage).
16 Citations
14 Claims
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1. A pneumatic detection apparatus for a tire, comprising:
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pressure detecting means for detecting change in air pressure of a tire as change in magnetic flux; signal outputting means for outputting signals which change in accordance with a amount of change of said magnetic flux; amplitude compensating means for generating signals compensating for change in said signals from said signal outputting means due to tire rotating speed; and discriminating means for discriminating pressure values of said air pressure as a plurality of values, in accordance with said signals from said amplitude compensating means. - View Dependent Claims (2)
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3. A pneumatic detection apparatus for a tire, comprising:
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a sensor to output signals of which frequency and amplitude thereof change in accordance with change in tire air pressure and with tire rotating speed; amplitude compensating means for compensating for change in said signal amplitude due to tire rotating speed; and discriminating means for discriminating change in tire air pressure from said compensated signals. - View Dependent Claims (4, 5, 6, 7)
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8. A pneumatic detection apparatus for a tire, comprising:
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a pickup coil disposed on a vehicle; magnetic-flux change means installed in a tire to be displaced in accordance with tire air pressure and for causing an amount of magnetic flux, which is linked with said pickup coil, to change in accordance with the displacement; amplitude compensating means for attenuating amplitude of electromagnetic induction voltage of alternating current, which is generated at said pickup coil in accordance with the amount of said magnetic flux, at an attenuation rate substantially proportional to a rotating frequency of said tire; and discriminating means for discriminating said tire air pressure on a basis of amplitude of said electromagnetic induction voltage compensated by said amplitude compensating means. - View Dependent Claims (9, 10, 11)
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12. A pneumatic detection apparatus for a tire, comprising:
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a fixed magnet; a movable magnet facing said fixed magnet and of which an interval with said fixed magnet interposed therebetween changes in accordance with change in tire air pressure; a rotating magnet which is positioned between said fixed magnet and said moveable magnet and is supported freely rotatably, and which is rotated by displacement of said movable magnet, wherein said rotating magnet causes a pickup coil to generate an electromagnetic-induction signal having frequency corresponding to vehicle speed and amplitude corresponding to said vehicle speed and said displacement; amplitude compensating means for compensating change in amplitude of said electromagnetic-induction signal due to said vehicle speed; and discriminating means for discriminating said tire air pressure on a basis of amplitude of said electromagnetic-induction signal compensated by said amplitude compensating means. - View Dependent Claims (13, 14)
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Specification