DE102004001246A1 - Tire pressure monitoring device for automobile, has transponder with receiver resonant circuit that absorbs transmitted electromagnetic signal and decodes amplitude modulation caused by phase change of transmitted signal - Google Patents

Abstract

The device has a signal generating device that generates an electromagnetic signal (21) and modifies the phase of the signal. A wheel sensor measures variable state of a wheel, and a transmitter is utilized for the transmission of the signal. A transponder has a receiver resonant circuit that absorbs the transmitted signal to detect an amplitude modulation in the signal caused by the phase change of the transmitted signal. An independent claim is also included for a method for monitoring tire pressure.

Description

The The invention relates to a method and a device for tire pressure monitoring, especially in or for a vehicle.

Of the Air pressure of a tire is subject to various causes, for example, the ambient pressure of the tire, external temperature, etc., certain changes. In this regard, it was found that the pressure loss in the tire a major factor in road accidents represents. Because vehicle safety and reliability are key factors in the automotive industry, must be alone for safety reasons establish The tire pressure of motor vehicles are checked regularly. This will be very often failed. Among other things, modern motor vehicles have tire pressure monitoring devices for this reason on, which measure the tire pressure automatically, the at least one detect critical deviation from a setpoint of the and this Motor vehicle driver Show. A manual review will so dispensable.

A such device typically has at least one, a respective one Wheel associated with electronic wheel sensor. Such a wheel sensor takes the tire pressure of a respective assigned wheel and sends this information to an evaluation of the motor vehicle. As an electronic wheel sensor, any device can be understood the information is determined via possibly at the wheel occurring error conditions detected can be. additionally to the actual detection of a fault condition is in generic methods and facilities provided that also the wheel position of each Rä the determined becomes. The information of the wheel position is then together with a respective error state transmitted to a central evaluation. For the Determining the wheel positions, which are also common in the relevant literature is called a localization, are a variety of different Method known, but not to be detailed here.

In addition to the just mentioned data communication from the wheel sensors to a central evaluation device typically also exists a transmission electromagnetic signals from the central evaluation device to the wheel sensors. This is necessary because the wheel sensor typically does not have any own power supply has and only about the electromagnetic signals sent by the central evaluation device is energized. For this purpose, each wheel sensor points a receiver resonant circuit with a capacitor for recording and storing the transmitted Energy up. The stored energy supplies a particular provided in the wheel sensor integrated circuit. This integrated Circuit serves the purpose of providing information about the condition of a wheel, in particular its tire pressure, absorb, process and on a transmitter provided in the wheel sensor back to the central evaluation device to send.

In order to the receiver resonant circuit in the wheel sensor a sufficiently high voltage to supply the integrated To provide circuit, this must have the highest possible quality.

In addition to the transmission of energy is sent by the central evaluation device electromagnetic signal also for data communication between the used central evaluation and the wheel sensor. For data communication For example, the electromagnetic signal may be amplitude modulated become. Such a data communication provides the amplitude of the electromagnetic signal to change, so-called blanking intervals in the be sent transmitted electromagnetic signal. At these blanking intervals will the carrier signal the electromagnetic wave for a certain duration off or interrupted so that its Amplitude becomes zero. The coding then results, for example the duration of the blanking interval or from the time interval between two blanking intervals.

The problem, however, is that with a very high quality of the receiver resonant circuit said amplitude modulation in the transmitted signal in the received signal by the receiver is no longer sufficiently detectable. This is based on the two 4 and 5 explained.

4 shows in time representation a transmitted signal 21 and a received signal 22 , The transmitted signal 21 has a blanking interval 23 on. A blanking interval 23 denotes a portion of the transmitted signal 22 in which the vibration is absent or suppressed.

The blanking interval 23 is in the time range t1 <t <t2. In 4 Let it be assumed that the receiver has a high quality. A high quality goes along with a low attenuation of the receiver resonant circuit. However, this means that the received signal 22 in the time domain t1 <t <t2, ie in the range of the transmitter-side blanking interval 23 , a barely detectable reduction in the amplitude of the signal 22 having. In such a data transmission can thus a sender side the sent signal 21 Amplitude modu lation superimposed data information receiver side no longer or only incorrectly evaluated.

In case of 5 the receiver has a low quality and thus a high attenuation. Due to the high attenuation is achieved that the received signal 22 in the time domain t1 <t <t2 a successive reduction in the amplitude of the signal 22 shows. Only after the time t> t2 does the amplitude of the received signal go 22 back to its original value, as the signal sent 21 here again has its original amplitude. The reduction of the amplitude of the received signal 22 in the area of the blanking interval 23 can now be detected in the receiver, which makes a decoding of the transmitted information possible. The disadvantage here, however, that due to the high attenuation by the receiver resonant circuit, a comparatively low voltage is provided, which is often insufficient for the supply of the integrated circuit in the wheel sensor. In order to gain a high voltage, the transmitter would have to emit a higher-energy electromagnetic signal, which, however, is accompanied by a higher energy absorption on the transmitter side. This constellation is disadvantageous and should be avoided if possible. In addition, the maximum transmitted transmission energy is also limited by standards and statutory regulations.

Of the present invention is based on the object as possible good data communication with high reception voltage for a receiver resonant circuit a high-quality wheel sensor provide.

According to the invention this Task by a device having the features of the claim 1 and by a method having the features of the claim 2 solved.

• – Eine Vorrichtung zur Reifendrucküberwachung, insbesondere in oder für ein Fahrzeug, mit einer Signalerzeugungseinrichtung, die dazu ausgelegt, elektromagnetische Signale zur Energieversorgung mindestens eines Radsensors zu erzeugen, die zur Datenkommunikation die Phase der elektromagnetischen Signale verändert und die zumindest einen Sender zum Senden der elektromagnetischen, phasenveränderten Signale aufweist, mit zumindest einem Radsensor zum Messen zumindest einer Radzustandsgröße, der jeweils einen als Transponder ausgebildeten Empfänger zum Aufnehmen eines gesendeten, elektromagnetischen Signals aufweist, welcher einen Empfangsschwingkreis hoher Güte aufweist, der eine Auswerteeinrichtung aufweist, die dazu ausgelegt ist, die durch die Phasenveränderung des gesendeten Signals im Empfangsschwingkreis hervorgerufene Amplituden-Modulation zu dekodieren. (Patentanspruch 1)
• – Ein Verfahren zur Reifendrucküberwachung, mit den Schritten: (a) Bereitstellen elektromagnetischer Signale zur Energieversorgung mindestens eines Radsensors; (b) Verändern der Phase der elektromagnetischen Signale für eine vorgegebene Zeitdauer; (c) Senden der phasenveränderten Signale; (d) Bereitstellen eines Transponders mit einem Empfangsschwingkreis hoher Güte zum Aufnehmen eines gesendeten phasenveränderten Signals; (e) Auswerten der durch das gesendete phasenveränderte Signal im Empfangsschwingkreis hervorgerufenen Amplituden-Modulation. (Patentanspruch 2) Vorteilhafte Ausgestaltungen und Weiterbildungen der Erfindung sind den Unteransprüchen sowie der Beschreibung unter Bezugnahme auf die Zeichnung entnehmbar.

Accordingly, it is provided:

• A device for monitoring tire pressure, in particular in or for a vehicle, having a signal generating device, which is designed to generate electromagnetic signals for supplying power to at least one wheel sensor, which changes the phase of the electromagnetic signals for data communication and the at least one transmitter for transmitting the electromagnetic, phase-modulated signals, comprising at least one wheel sensor for measuring at least one wheel state variable, each having a trained as a transponder receiver for receiving a transmitted electromagnetic signal having a high-quality receiving resonant circuit having an evaluation device which is adapted to the by the Phase change of the transmitted signal in the receiving resonant circuit induced amplitude modulation to decode. (Claim 1)
• A tire pressure monitoring method comprising the steps of: (a) providing electromagnetic signals for powering at least one wheel sensor; (b) changing the phase of the electromagnetic signals for a predetermined period of time; (c) transmitting the phase changed signals; (d) providing a transponder having a high-quality receiving resonant circuit for receiving a transmitted phase-changed signal; (e) evaluating the amplitude modulation caused by the transmitted phase-changed signal in the receiving resonant circuit. (Claim 2) Advantageous embodiments and further developments of the invention are the dependent claims and the description with reference to the drawings.

The The idea underlying the present invention is that To equip a wheel sensor for tire pressure measurement with a transponder. To one as possible generate high receiving voltage, the receiving resonant circuit has the transponder a very high quality, for example, a quality of greater than 100, up. With such high grades is the recipient typically without further action no longer able to receive a blanking interval in the transmitted signal at the receiving end to recognize.

at Most receivers equipped with transponders - such as Example transponders for Immobilizer - is a high quality also not necessary, as these have a very low range too Have the transmitter and thus quite well provided with a low quality could be, to absorb the required energy. When using Transponders for Wheel sensors, in particular for transponders for wheel sensors for use in trucks, however, the distances are between Wheel sensor and transmitter of the electromagnetic wave much larger. Out For this reason, a respective receiving circuit of a transponder a very high quality of reception exhibit.

In the present invention, however, the vibration of the transmitted electromagnetic signal is attenuated quickly in the receiver despite high quality, to better detect an amplitude modulation in the transmitted signal. According to the invention, this is achieved by a region-wise phase modulation of the amplitude-modulated transmission signal reached. In this case, the phase of the transmission signal is shifted at a given time, in particular phase-shifted by 180 °. The phase shift causes in the transponder a forced attenuation, which is thus detectable even at high quality of the input resonant circuit.

Preferably indicates the phase-changed region at least five, in particular at least 10 oscillations.

In order to this damping with sufficient security in the receiver or by the transponder is detectable, are advantageously more than a vibration with a 180 ° phase shift present in the transmitted signal. Will a lower phase shift used, then a correspondingly higher number of vibrations for generating the forced damping to be provided.

In addition to the change The phase can then also provided a conventional blanking interval be directly adjacent to the area with the phase shift followed. Such a blanking interval can be realized by reducing the amplitude of the oscillation be. Preferably, the blanking interval but by turning off of the transmitted signal for a predetermined time is generated.

typically, the data communication takes place by transmission of encoded information, wherein the coding by varying the duration of the blanking interval and / or generated by a variation of the time interval between two blanking intervals becomes. additionally or alternatively, the coding may also be by varying the duration of the phase changed Area are generated.

In an embodiment of the invention are the coded information bitwise in the received signal, with between two magnitude changes the amplitude of the received signal in each case at least one data bit is provided, wherein the value of a respective data bit by the time interval between two changes in the amplitude in the received signal is determined, wherein a first duration of the change the amplitude of the received signal is a first logical value of Data bits and a second duration of the change of the received signal corresponds to a second logical value of the data bit. typically, is a change as lowering (damping) the amplitude of the received signal defined. typically, Further, the first logical value denotes a logic zero ("0") and the second logical value a logical one ("1").

The Invention will be described below with reference to the schematic figures The drawings specified embodiments explained in more detail. Show it attended:

1 a schematic representation of a motor vehicle with a plurality of wheel sensors;

2 a schematic representation of a transponder for a wheel sensor;

3 a temporal representation of a signal transmitted according to the inventive method and a received signal in the case of a high quality of the receiver resonant circuit;

4 a temporal representation of a transmitted and a received signal in the case of a high quality of the receiver resonant circuit;

5 a temporal representation of a transmitted and a received signal in the case of a low quality of the receiver resonant circuit.

In the figures of the drawing are the same or functionally identical elements and signals - if nothing another is indicated - with the same reference numerals have been provided.

1 shows a schematic representation of a vehicle, which in the present embodiment, four wheels 2 - 5 having. The trained as a motor vehicle, for example 1 has a tire pressure monitoring system, which is designed to characteristics of the wheels 2 - 5 display. Among other things, the tire pressure monitoring system has a device for determining the wheel positions of the various wheels 2 - 5 wherein the different wheel positions are labeled VL, VR, HL, HR.

Each of the wheels 2 - 5 is a wheel sensor 7 - 10 associated, for example, in a tire and / or in the region of the valve of the respective wheel 2 - 5 is arranged. The wheel sensors 7 - 10 contain each transmitting / receiving devices 11 - 14 to transmit, via respective transmitting antennas, those of the respective wheel units 7 - 10 to send provided data signals. The transmitting / receiving devices 11 - 14 each contain a transponder 11 - 14 , These data signals are typically high frequency, frequency and / or phase modulated data signals, the information about the state of the respective associated wheel 2 - 5 , in particular its tire pressure, and further information.

Furthermore, in 1 a central evaluation and control device 15 and a transmitting / receiving device connected thereto 16 intended. From the transponder 11 - 14 transmitted data signals are transmitted via an antenna of the transmitting and receiving device 16 received and the central evaluation and control device 15 fed. In the present example, four transmit / receive antennas 16A - 16D - one for each wheel 2 - 5 or its wheel sensor 7 - 10 - Provided, but only a single, central transmitting / receiving antenna could be provided. For evaluation and control includes the central evaluation and control device 15 a program-controlled device 17 , for example a microcontroller or a microprocessor.

In addition, electromagnetic signals D1 - D4 from the central evaluation and control device 15 over the antenna 16 to the different wheel sensors 7 - 10 or to their transponders 11 - 14 transfer. These electromagnetic signals D1-D4 are necessary to the various wheel sensors 7 - 10 to provide energy.

2 shows a schematic representation of a transponder 11 in a wheel sensor 7 - 10 is arranged. With a transponder 11 It is an electronic component which has a transmitting and receiving antenna to both transmit and receive data. For this purpose, a respective transponder 11 an input resonant circuit 18 . 19 on, which is an inductive element 18 and a capacitive element arranged parallel thereto 19 , for example a capacitor 19 , having. The structure and operation of such a transponder 11 is widely known, so that it is not discussed in detail below.

The capacitor 19 is in addition to the coil, the frequency-determining element of the resonant circuit. The energy is in a second capacitor 19A saved. In order to be able to absorb the highest possible energy, the input resonant circuit has 18 . 19 of the transponder 11 the highest possible quality, for example a quality of greater than 100.

In addition to the supply of energy, data communication also takes place from the central evaluation and control device 15 to the different wheel sensors 7 - 10 , For this purpose, the transmitted electromagnetic signals D1 - D4 also have an amplitude modulation, via which it is possible, a data communication from the central control and evaluation 15 to the transponders 11 - 14 to ensure. This also allows data on the respective transponders 11 - 14 transmit, for example, information about a serial number, etc.

Below is the inventive method for data communication between the central evaluation and control device 15 and wheel sensor 7 - 10 based on 3 described in more detail:
In 3 Let us assume that the central evaluation and control device 15 or its transceiver as transmitter and the respective transponder 11 - 14 acts as a recipient. The input resonant circuit 18 . 19 of the transponder 11 - 14 has a high quality. The signal sent by the transmitter points in 3 several blanking intervals 23 for data communication. A first blanking interval 23 is located in the time range t1 <t <t2. The duration Δt1 of this blanking interval 23 is defined as Δt1 = t2 - t1. Before this interval 23 is an area 24 (t0 <t <t1), at which the transmitted signal 21 has a phase shift. The duration Δt2 of the range 24 is defined as Δt2 = t1 - t0. In the present embodiment, the phase of the signal 21 is in the range 24 phase-shifted by 180 ° with respect to the regions t <t0 or t> t2. Due to this 180 ° phase shift, which is also referred to below as 180 ° phase jump, is in the range 24 a forced damping 25 of the received signal 22 rea lisiert. In the area of the blanking interval 23 , ie for t1 <t <t2, the amplitude of the received signal 22 not further dampened, however, the signal points 22 here a reduced amplitude compared to the ranges t <t0 and t> t2.

This results in a significantly reduced amplitude of the received signal 22 , which at least in the area of the blanking interval 23 from the receiver is also clearly visible, although the receiver resonant circuit 18 . 19 has a very high quality. From this damping 25 a subarea of the received signal 22 Thus, the information sent by the transmitter can be derived. This information can be, for example, the duration of the attenuation 25 are obtained, ie from the duration .DELTA.t1 + .DELTA.t2 = t2 - t0. Additionally or alternatively, it would also be conceivable for the information to be based on the time interval between two immediately consecutive attenuations 25 results, for example from the time period .DELTA.t3 = t3 - t2.

Although the present invention above based on a preferred embodiment It is not limited to this, but in many ways and modifiable.

Thus, the invention is not necessarily limited to a device for tire pressure monitoring in or for a motor vehicle, but can be applied to any applications for the tire pressure expand monitoring. In addition, the method according to the invention would of course also be applicable to data communication in other systems in which energy is simultaneously transmitted between a transmitter and a transponder for supplying the transponder and encoded data. In particular, the invention can, for example, in Sicherheitseinrichtun conditions in a motor vehicle, for example in an immobilizer, apply advantageous.

Also does not necessarily have a 180 ° phase jump to the realization a forced damping be provided in the received signal, but it can be here any phase change use. Also, not necessarily those areas, in which the transmitted signal has a phase change, one each blanking interval downstream. Rather, can on such a blanking interval too be waived. Depending on the quality and duration of the blanking interval can the transmitter rather either during the entire gap with the opposite phase or just for a set time.

Claims (13)

Device for tire pressure monitoring, in particular in or for a vehicle, with a signal generating device ( 15 - 17 ), - which are designed to generate electromagnetic signals (D1 - D4, 21 ) for supplying energy to at least one wheel sensor ( 7 - 10 ) to generate the data for the phase of the electromagnetic signals (D1 - D4, 21 ) and - the at least one transmitter ( 16 ) for transmitting the electromagnetic phase-changed signals (D1 - D4, 21 ), with at least one wheel sensor ( 7 - 10 ) for measuring at least one wheel state variable, - each one as a transponder ( 7 - 11 ) formed receiver for receiving a transmitted electromagnetic signal (D1 - D4, 21 ), which has a receiving resonant circuit ( 18 . 19 ) of high quality, - of an evaluation device ( 20 ), which is adapted to be detected by the phase change of the transmitted signal (D1 - D4, 21 ) in the receiving resonant circuit ( 18 . 19 ) induced amplitude modulation ( 25 ) to decode. A tire pressure monitoring method, in particular by means of a device according to claim 1, comprising the steps of: (a) providing electromagnetic signals (D1-D4, 21 ) for supplying energy to at least one wheel sensor ( 7 - 10 ); (b) changing the phase of the electromagnetic signals (D1-D4, 21 ) for a predetermined period of time (Δt2); (c) transmitting the phase-changed signals (D1-D4, 21 ); (d) providing a transponder ( 7 - 11 ) with a receiving resonant circuit ( 18 . 19 ) of high quality for receiving a transmitted phase-changed signal (D1-D4, 21 ); (e) evaluating the signal transmitted by the transmitted phase-changed signal (D1-D4, 21 ) in the receiving resonant circuit ( 18 . 19 ) Amplitude modulation ( 25 ). Device and method according to one of the preceding claims, characterized in that the receiving resonant circuit ( 18 . 19 ) has a quality of at least 100. Device or method according to one of the preceding Claims, characterized in that a change in the phase is a phase shift about ± 180 ° with respect to one not phase-shifted transmitted signal (D1-D4). Device or method according to one of the preceding claims, characterized in that the phase-changed region ( 24 ) has at least five, in particular at least 10 oscillations. Device according to one of the preceding claims, characterized in that the signal generating device ( 15 - 17 ) is adapted, in addition to the phase-changed region ( 24 ) in the transmitted signal (D1-D4, 21 ) also a blanking interval ( 23 ) in the transmitted signal (D1-D4, 21 ), which in particular directly adjoin the phase-changed region ( 24 ). Device or method according to claim 6, characterized in that the blanking interval ( 23 ) denotes a magnitude reduction of the amplitude of the transmitted signal (D1 - D4, 21), in particular an absolute reduction to approximately zero. Device or method according to one of claims 6 or 7, characterized in that the blanking interval ( 23 ) by switching off the transmitted signal (D1 - D4, 21 ) is generated for a predetermined time (Δt1). Device or method according to one of claims 6 to 8, characterized in that the data communication is carried out by transmission of coded information, wherein the coding by varying the duration (.DELTA.t1) of the blanking interval ( 23 ) and / or by a variation of the time interval (Δt3) between two blanking intervals ( 23 ) is produced. Device or method according to one of the preceding claims, characterized in that the data communication is carried out by transmission of encoded information, wherein the coding by varying the duration (Δt2) of the phase-changed region ( 24 ) is produced. Device or method according to one of the preceding claims, characterized in that the encoded information in the received signal ( 22 ) is present bitwise, whereby between two changes ( 25 ) the amplitude of the received signal ( 22 ) is provided in each case at least one data bit, wherein the value of a respective data bit by the time interval (.DELTA.t3) between two changes ( 25 ) of the amplitude in the received signal ( 22 ), wherein a first duration of the change of the amplitude of the received signal ( 22 ) a first logical value of the data bit and a second duration of the change of the received signal ( 22 ) corresponds to a second logical value of the data bit. Device or method according to claim 11, characterized in that a change ( 22 ) a reduction or a damping ( 25 ) the amplitude of the received signal ( 22 ) designated. Device or method according to one of claims 11 to 12, characterized in that the first logical value is a logical Zero and the second logical value denotes a logical one.