Measuring and testing – Tire – tread or roadway – Tire inflation testing installation
Patent
1990-07-12
1991-10-08
Woodiel, Donald O.
Measuring and testing
Tire, tread or roadway
Tire inflation testing installation
340442, 374143, B60C 2304
Patent
active
050543156
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to the devices for monitoring tires. More particularly, it relates to the coding making possible the transmission of the value of several quantities measured by means of a single transmission channel between the wheel carrying the tire, moving in rotation, and the frame or support element, not moving in rotation.
Description of Related Art
Patent application WO87/00127 proposes a coding type making possible the transmission of the pressure of the tire and of its temperature. The measurements of the quantities observed (pressure, temperature) are coded in time intervals.
The operation of most electronic devices is liable to drift over time, by the aging of the components, by the effect of the temperature on the operation of the latter, or by other disturbing influences. Standard precautions for combating these drifts generally increase the cost, the space requirement, the consumption of the circuits. Now, in this application, these defects are incompatible.
SUMMARY OF THE INVENTION
The object of the invention is to be free of these drifts not by eliminating them or by limiting them but by sending image data of the drift in addition to researched data, which makes it possible, after the event, to remove the effect of the drifts on this data.
In another object, the invention proposes a coding which makes it possible to transmit the value of any number of quantities observed on a wheel.
According to the invention, the device for coding the value of n quantities measured on a tire, making possible the transmission of said values to the frame carrying said tire, is characterized in that it comprises
means making it possible to mark the start of the measuring cycle,
a generator delivering a cyclical signal in ramp form,
n means each sensitive to one of said quantities, each constantly delivering a signal as a function of the value of said quantity to which it is sensitive,
an element delivering a reference value corresponding to the end of the measuring cycle,
n+1 coincidence detectors receiving, at one of their two inputs, said signal in ramp form, and delivering a high signal when the signals at their two inputs are identical, and a low signal at any other time, said other input receiving
for the first coincidence detector, the output value of one of the means sensitive to said quantities,
for the last coincidence detector, said reference value
for the remaining n-1 coincidence detectors, the output value of a summation device working out the sum of the value of the input of the preceding coincidence detector and the output value of one of n means sensitive to said quantities.
The measuring cycle begins by the start of the ramp signal. If it is assumed that the observed quantities are equivalent to x.sub.i (i varying from 1 to n), thanks to the coincidence detectors, each value x.sub.i will be coded by a time period T.sub.i. The first coincidence detector will deliver a pulse to the end of time period T.sub.1 coding value x.sub.1 of the first quantity observed. By the use of a summation device, the second coincidence detector will deliver a pulse at the end of a time period T.sub.1 +T.sub.2 (counted from the start of the ramp), T.sub.2 coding value x.sub.2 of the second quantity observed, and so on up to T.sub.n coding x.sub.n. The reference value is selected so that the last detector delivers a pulse after a period T.sub.n+1 which is, in the most unfavorable case, always greater than T.sub.i. By the most unfavorable case, the case where all periods T.sub.i are the longest, taking into account the value of the observed quantities and the coding method, is meant. This last pulse also allows the start of a new measuring cycle, after a delay, if necessary.
Periods T.sub.i therefore are a function of values x.sub.i which it is desired to have, after decoding, aboard a vehicle. But they also are each a function of parasitic influences (aging, temperature, . . . ) because periods T.sub.i also depend on the slope of the ramp to which the various values are comp
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Patent Abstracts of Japan, vol. 8, No. 148 (M-308) (1585) Jul. 11, 1984, & P, A, 5945204, Mar. 14, 1984.
Compagnie Generale des Etablissements Michelin--Michelin & Cie
Woodiel Donald O.
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