Circuit arrangement for transmitting measurement values on vehic

Details Circuit arrangement for transmitting measurement values on vehic Circuit arrangement for transmitting measurement values on vehic

1988-06-09

1990-01-09

Woodiel, Donald O.

Measuring and testing

Tire, tread or roadway

Tire inflation testing installation

340448, 374143, B60C 2304, H03K 602, H05F 300, G08C 1512

Patent

active

048919730

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

The invention is based on a circuit arrangement for transmitting variable measurement values such as pressure and temperature on vehicle wheels according to the preamble of the main claim. Such a circuit arrangement is already known from DE-PS No. 30 29 563, in which energy is transmitted to a revolving repeater coil by a low-frequency chopper via a stationary repeater coil, a sensor circuit being connected to the revolving repeater coil. The measurement values of the sensors at the vehicle wheel are converted by means of a converter into signals having an analog frequency which amount to a multiple of the chopper frequency and reach the stationary evaluating circuit from the repeater coils via a high-pass filter. As long as a threshold value switch in the sensor circuit arrangement activates the measurement value converter, the stationary evaluating circuit interrupts the chopper. Accordingly, during the retransmission of the information signal via the converter coils, no energy is transmitted into the sensor circuit arrangement and, accordingly, the information signals arriving via the same channel are separated from the energy transmission.
A disadvantage in this known solution is that the measured values of the tire pressure and the tire temperature are not transmitted to the evaluating circuit separately from one another, but, rather, they are tied to one another already in the sensor circuit in such a way that a so-called temperature compensated tire pressure results as measurement value. Further, it is also disadvantageous that the frequency range for the signal transmission is relatively large if a fine grading of the measurement values to be transmitted is desirable. Moreover, the time for the measurement value transmission in the known solution is dependent upon the loading of a storage capacitor which was previously loaded by means of the switched on chopper. The transmission of the measurement values is accordingly delayed in an undesirable manner.
In the present solution, it is attempted to transmit the measurement values to the evaluating circuit quickly in the form of a pulse train in firmly predetermined time intervals in the operating pauses of a stationary square-wave generator for the energy supply of the sensor circuit arrangement in order to achieve in this manner a high information resolution and, consequently, a fine grading of the measurement values to be transmitted.


ADVANTAGES OF THE INVENTION

The circuit arrangement, according to the invention, with the characterizing features of the main claim has the advantage that measurement values at vehicle wheels can reach the evaluating circuit with high resolution as a digital pulse train with the low-frequency clock of the stationary square-wave generator for the energy supply of the sensor circuit arrangement, wherein the transmission time is fixed for every measurement value. Another advantage can be seen in that the voltage peak induced in the repeater coils when switching off the supply voltage in the clock of the square-wave generator does not fall in the time interval for the signal transmission and, accordingly, cannot effect a falsification of the measurement values to be transmitted. Moreover, these voltage peaks are used in an advantageous manner for triggering the transmission of the measurement values with a predetermined time delay and ensuring them over a predetermined time. Since the measurement values or measurement value changes are conveyed from the vehicle wheels in this manner in a rapid sequence, it is also possible to use them for regulating the tire pressure.
Advantageous developments and improvements of the characteristic features indicated in the main claim are made possible by means of the steps indicated in the subclaims. It is particularly advantageous that the timing circuit for transmitting measurement values, which is triggered by the timing element of the sensor circuit arrangement, which timing element responds to the voltage pulses, be a monostable multivibrator, wherein a coupling stage f

REFERENCES:
patent: 4467641 (1984-08-01), Abraham
patent: 4567459 (1986-01-01), Folger et al.
patent: 4749993 (1988-06-01), Szabo et al.

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