DE19702768C1 - Wireless transmission from moving parts - Google Patents

Abstract

The arrangement has a measurement transducer (M) and a measurement system containing an antenna (A2,A3) near the transducer, and at least one electronic assembly. At least one supply frequency is generated in the measurement system, which is radiated to the measurement transducer and received from the transducer. The transducer has at least one resonator coupled to at least one non-linear electronic component. The resonator is influenced by the value being measured. For mixing, or forming harmonics multiples of the supply frequency, the sums or differences of several supply frequencies are formed in the non-linear component. The frequencies formed in the transducer stimulate the resonator which transmits the measurement information to the receiver, at a measurement frequency lower then the supply frequencies.

Description

The invention relates to a device for wireless Transfer of at least one measured value from moving Sharing according to the preamble of claim 1.

A generic device is from DE 37 29 420 A1 known. For easy manufacture are with this Vorrich tion a reception coil and a transmission coil in the wheel rim merged into a common transmitting and receiving coil sums up. A switching device alternately connects one Frequency generator during a predetermined transmission period and / or the recipient during a given emp period of time with the transmitting and receiving coil.  

The determination of the pressure itself and the implementation in an electronic size is after State of the art unproblematic, suitable sensors mechanical or capacitive basis as well as integrated solutions based on semiconductors are well known.

The real problem with the vehicle is the data averaging and the power supply of the pressure sensor because the high and strongly fluctuating speed of the tire together with the Steering and chassis movements and heavy pollution wired transmission, e.g. B. via sliding contacts, as well optical or acoustic transmission is prohibited.

A possible solution to the problem was in patent application DE 196 21 354.1 proposed by the same inventor. According to this Registration is a difference signal from two in the transmitter Feed frequencies are formed and influenced by the measured value flowed filtering sent back to the measuring system.

Here, however, the problem arises that, due to the design of the receiver and the one that is difficult to reach Shielding from the feed signals in the input stage of the Receiver also mixed products are formed, the Can interfere with reception of the measurement signal and only with difficulty from this are separate.

The invention is based, which Generic device so that at high Reliability at least one measured value from the rotating Tire is determined and transferred.  

The object is achieved according to the invention by the device described in claim 1, the function of which is explained below using an exemplary embodiment ( drawing 1):
The device consists of a transducer located in the tire without its own power supply and a measurement system permanently installed in the vehicle, consisting of one or more antennas and one or more electronic modules, all of which are summarized below under the term control unit.

There is at least one high frequency in the control unit generator G1 for a carrier signal f1, preferably in the so-called Microwave frequency range around 2.4 GHz, which of at least a lower frequency signal (modulation frequency) f2, generated by the generator G2, preferably in the frequency range from 1 to 30 MHz, modulated becomes. Through this modulation, the necessary feed frequencies generated. The resulting signal is amplified and close of the tire radiated via an antenna A1.  

The modulation is preferably an amplitude or I / Q modulation. According to those applicable to such modulations Equations arise in the spectrum to the left and right of the Carrier frequency further sidebands, specifically z. B. at the Amplitude modulation at f1 + f2 and f1-f2. In case of use of several frequencies f2 results from their sum Sideband spectrum, this is also an example in the drawing depicted cautiously.

The modulation can abge by the electronic switch S1 are switched, the switch S1 is operated by a timer T1 periodically controlled.

There is a MG1 (transponder) transmitter in the tire, consisting of at least one antenna A2, a receiver with at least one diode D1, preferably as a Schottky or Detector diode, as well as a quartz resonator Q1 by the received modulation signal is excited. This quartz resonator (Quartz Q1) is now again with a modulator or Mixer diode D2, preferably a varactor diode for use the parametric gain. In addition, he is through the measured value is out of tune (pulled).

At time t1, the modulation by switch S1 turned off, and shortly thereafter, at a time t2, the receiver turns off E1 activated (EN enable input), t2 follows approx. 1 µs after t1.

If the modulation of the feed frequency is switched off at time t1, then the quartz Q1 will continue to oscillate for approx. 1 ms and due to the still existing carrier this feed frequency over the Modulate modulator diode D2. However, this only happens if the modulation frequency f2 already indicates the quartz Q1 had rain, d. H. if the modulation frequency f2 approximately ver mutated measured value. The receiver E1 now looks at his Antenna A4 a modulated signal from transmitter antenna A3, without the supply frequency (transmitted by antenna A1) is modulated and could cause interference, and can thus deduce the measured value from the modulation. At The absence of modulation or modulation that is too weak can result in more suspected measured values are sampled iteratively (e.g. by successive approximation or Newton iteration), with complete Failure to perform any modulation is due to a defect in the measured value donor, this can be signaled to the user.

Of course, others can be used instead of quartz long resonant resonators, e.g. B. SAW, piezo or Tuning fork resonators are used. Theoretically would also be one undamped resonant circuit is conceivable, but this will become practical the inevitable damping fail.

In addition, there is also the instead of the query using modulation Query in the baseband without modulator and demodulator in the measured value encoder (MG1) conceivable, but due to the generally available Frequencies rather a microwave frequency with modulation in question is coming.  

In this case, the accommodation of the first input amplifier and / or mixer stage in miniaturi Design in the antenna itself, a mixer can do this from the unmodulated transmission signal (direct Implementation in the baseband) or with another frequency high frequency (local oscillator signal) and by means of equals voltage decoupling also with supply voltage via a common antenna cable can be supplied. As an essential The advantage here is the frequency separation of transmission and receive signal and thus the possibility of use only a (coaxial) antenna cable for both signals and for the Power supply for preamplifier and mixer.

Such an arrangement together with Directional planar antennas, because this way directional transmission to and receiving from the transducer MG1 with separation of the two signal paths becomes possible.

With simultaneous modulation with multiple frequencies, either by backward Fourier transformation, pseudo-random noise and / or I / Q modulation occurs in any case Quartz Q1 or other resonators regardless of the measurement signal.

In addition, the resonant response signal z. B. by Digi Talization with A / D converter and further processing with Digital down converter and / or signal processor at the same time multiple frequencies can be queried. Because in the post-swing phase after t1 the frequency is unaffected by the excitation by the Is supply frequency modulation, so a precise determination of the measured value. One is advantageous here Combination of filtering and frequency measurement by determination the period or an application of the fast Fourier transformation. Also the evaluation of the resulting ones Phase information can be used in addition to the frequency information Determination of the maximum energy of the feed signal (for change tendency detection) may be advantageous for the next measurement.

The carrier frequency f1 should be by means of a stable oscillator be generated with low phase noise. Through PLL control the frequency f1 can be determined by means of a microcomputer command Interference and frequency assignments by other users, e.g. B. others Vehicles are deliberately evaded without the Contact with the transmitter is lost, as it is at the latter not too big changes from f1 only to the modulation arrives. The recipient must of course also do this be changed. This possibility of frequency change in Failure represents another significant advantage of the Invention.  

The generation of the modulation frequency (s) f2 is more sensible wise using a D / A converter through direct digital synthesis. Very pure frequencies can be achieved using a so-called phase accumulator with the following sine / cosine table generated will. Filtered pseudo-random phase jumps can be used the signal width in the spectrum at will also by means of Microcomputer command can be changed.

The times t1 and t2 are expediently specified by a processor-controlled timer, either by software or as a hardware timer. This is particularly advantageous Synchronization of both times and the restart for the purpose of renewed excitation with the tire rotation. This will the transducer MG1 excited at a time when it turns is particularly close to the antenna of the measuring system.

The entire control of the device is preferably carried out via a Microcomputer or signal processor, which also ver processing, conversion and evaluation of the measured values can. The microcomputer can also use a suitable grading Make suggestions for several resonators or transducers, an optimal timing behavior is started by starting a other resonators already during the measuring time after t2 or even t1 of the previous resonator on another excitation frequency reached.

For cost reasons, the integration of the Transmitter MG1 consisting of the (pressure) sensor together with the nonlinear electronic component and the resonance element a hybrid or integrated circuit.

A further reference quartz can also be located in the measuring transducer MG1 or another resonator can be accommodated, the regardless of the measured value always constant on one of the measured frequency independent further frequency reacts. Hereby can frequency shifts z. B. by the Doppler effect be calculated out again in the receiver. Further measuring frequencies f2 can e.g. B. for the transmission of further measured values such as tires temperature or structural stress (forces) used will.

Of course, by relay or electronic switching from multiple antennas on one electronics unit the same electronics Unit in the multiplex method for measuring at different Tires or also used on the spare wheel.

Of course, the invention is not based on the measurement of Tire pressure limited, but can generally be reliable Determination of measured values in the area of fast moving parts be applied.

Claims (10)

1. Device for wireless transmission of at least one measured value from moving parts, in particular a system for measuring the tire pressure in motor vehicles, consisting of

• - A transducer, especially pressure gauge in the fen, and
• - a measuring system which in turn has:
  • - at least one antenna near the sensor,
  • - a recipient and
  • at least one electronics module, at least one modulated supply frequency being generated in the measuring system and being radiated to and received by the transmitter,
  characterized in that
• - The transducer (MG1) has at least one resonating resonator (Q1) and the resonator (Q1) in its frequency or absorption characteristics is influenced by the value to be measured,
• - by receiving the modulated feed frequency in the transmitter (MG1), if the modulation frequency of the modulated feed frequency (indirect modulated excitation) matches the resonator frequency, the resonator (Q1) is excited to oscillate,
• after the excitation of the resonator (Q1), the modulation of the feed frequency is periodically switched off or changed so that no excitation of the resonator (Q1) takes place,
• - The resonator (Q1) thereafter oscillates, modulating these oscillations by the value to be measured and these modulated oscillations emitted by the transmitter (MG1), and
• - The existing receiver in the measuring system detects these modulated reverberations and uses them to derive the at least one measured value by frequency analysis and conversion.

2. Device according to claim 1,

• the modulated supply frequency is formed from an unmodulated supply frequency (carrier signal f1) which is modulated by a signal (f2),
  characterized,
• - That the signal (f2), with which the carrier signal (f1) is modulated, is low-frequency and the modulation thus carried out is an amplitude modulation, and
• - In the transmitter (MG1) this modulation by a non-linear component, in particular a detector diode, demodulated and used to excite the resonator (Q1).

3. Device according to one of claims 1 to 2, characterized, that the resonance of the resonator (Q1) with the after switching off the excitation remaining unmodu feed frequency in a non-linear building  part of the sensor (MG1), especially a Va reactor diode with parametric gain, mixed and as a measuring frequency by the transmitter (MG1) can be emitted. 4. Device according to one of claims 1 to 3, characterized, that a quartz crystal is used as the resonator (Q1) electrically by a capacitive or inductive Sensor or mechanically by stress or tempera door change is detuned (pulled). 5. Device according to one of claims 1 to 4, characterized, that after switching off the excitation of the resonator (Q1) the frequency analysis of the resonance of the Resona tors (Q1) through filtering and period measurement after the necessary demodulation is carried out and from this the at least one measured value by conversion voltage is derived. 6. Device according to one of claims 1 to 5, characterized, that after excitation of the resonator (Q1) the Transmitter (MG1) switching off the modulation of the Feed frequency allows further modulation the remaining unmodulated supply frequency finally done by the transmitter (MG1). 7. The device according to claim 3, characterized, that after excitation of the resonator (Q1) and shutdown modulation remaining unmodulated food  frequency for mixing in the receiver (E1) of the measuring system is used, the first stages preferably with the antenna (A4) form a structural unit. 8. Device according to one of claims 1 to 7, characterized, that directional illumination of the sensor (MG1) and reflection from this to the measuring system Use of directional, especially planar antennas follows. 9. Device according to one of claims 1 to 8, characterized, that the periodic switching on and off of the excitation of the resonator (Q1) of the transmitter (MG1) by ei NEN timer controlled, which with the wheel rotation is synchronized. 10. The device according to one of claims 1 to 9, characterized, that the radio described in the claims tions of the electronic components of the measuring system entirely or partially using a computer program (soft goods) can be realized.