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EP1608519A1 - Device for transmitting signals by induction between a transponder circuit and an interrogation circuit - Google Patents

Device for transmitting signals by induction between a transponder circuit and an interrogation circuit

Info

Publication number
EP1608519A1
EP1608519A1 EP04716214A EP04716214A EP1608519A1 EP 1608519 A1 EP1608519 A1 EP 1608519A1 EP 04716214 A EP04716214 A EP 04716214A EP 04716214 A EP04716214 A EP 04716214A EP 1608519 A1 EP1608519 A1 EP 1608519A1
Authority
EP
European Patent Office
Prior art keywords
coil
circuit
transponder
transponder circuit
interrogation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04716214A
Other languages
German (de)
French (fr)
Inventor
Frank Bajahr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Smartrac Technology Germany GmbH
Original Assignee
Sokymat Automotive GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sokymat Automotive GmbH filed Critical Sokymat Automotive GmbH
Priority to EP04716214A priority Critical patent/EP1608519A1/en
Publication of EP1608519A1 publication Critical patent/EP1608519A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/70—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes
    • H04B5/77—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes for interrogation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
    • B60C23/041—Means for supplying power to the signal- transmitting means on the wheel
    • B60C23/0413—Wireless charging of active radio frequency circuits
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
    • B60C23/0422—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver characterised by the type of signal transmission means
    • B60C23/0425—Means comprising permanent magnets, e.g. Hall-effect or Reed-switches
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
    • B60C23/0422—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver characterised by the type of signal transmission means
    • B60C23/0427—Near field transmission with inductive or capacitive coupling means
    • B60C23/043—Near field transmission with inductive or capacitive coupling means using transformer type signal transducers, e.g. rotary transformers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
    • B60C23/0422—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver characterised by the type of signal transmission means
    • B60C23/0433—Radio signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/40—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by components specially adapted for near-field transmission
    • H04B5/48—Transceivers

Definitions

  • the invention relates to a device for transmitting signals by induction between a transponder circuit and an interrogation circuit.
  • the transponder circuit comprises a first coil
  • the interrogation circuit comprises a second coil.
  • the transponder circuit is placed on an object capable of turning around at least one axis of rotation passing through the object, while the interrogation circuit is placed on a structure, which can be fixed, to which the object is connected.
  • the rotating object can for example be a vehicle wheel, while the structure is for example the bodywork or the chassis of the vehicle.
  • the transponder circuit includes at least one sensor for measuring a physical parameter. It can be a pressure sensor for measuring the tire pressure of the vehicle, a temperature sensor, a force sensor, an accelerometer or another type of sensor. The measurements made by the sensor or sensors of the transponder circuit can be transmitted to the interrogation circuit in the inductive signals, for example by amplitude modulation.
  • the distance separating it from the interrogation circuit is not constant during the rotation of the object. Therefore, it is noted during the transmission of inductive signals between the interrogation circuit and the transponder circuit that a parasitic amplitude modulation of the signals occurs which can be a significant drawback. Thus, it may happen during demodulation operations in the receiving unit that the data received in the inductive signals do not completely correspond to the transmitted data. This disturbance on the transmitted data can also be dependent on the speed of rotation of the object. The higher the speed of rotation, the greater this disturbance can be.
  • FIG. 1 shows in a simplified manner the influence that the rotation of an object can have on the amplitude of the inductive signals picked up by the receiving unit.
  • Inductive signals are first transmitted by the transmitting unit at a determined carrier frequency and a determined amplitude.
  • the data modulated in the inductive signals are not represented in this figure for simplification.
  • the amplitude of the inductive signals picked up that is to say the amplitude of the voltage induced in the coil of the receiving unit, changes.
  • this variation in amplitude is illustrated by the envelope of the inductive signals picked up by the receiving unit.
  • This envelope is shown simply in sinusoidal shape corresponding to a constant speed of rotation of the object.
  • the shape of this envelope is not in reality sinusoidal, since the amplitude of the magnetic field created by the transmitting coil does not decrease linearly with the distance separating the transmitting coil from the receiving coil.
  • the transponder circuit transmits high frequency signals, it must in principle be provided with its own energy source, such as a battery. This can also be a disadvantage, because in this case the transponder circuit consumes energy even if the interrogation circuit does not interrogate it.
  • an object of the present invention consists in providing a device for transmitting inductive signals which comprises means suppressing unwanted amplitude modulation of the inductive signals during the rotation of the object relative to the structure in order to alleviate the drawbacks of the prior art cited above.
  • Another object of the present invention is to provide a device for transmitting inductive signals which is simple to produce while reducing manufacturing costs, and consumes little electrical energy.
  • the invention relates to a device for transmitting inductive signals cited above which is characterized in that a coupling coil, provided with at least one turn, is mounted on the structure or on the object of coaxially with the axis of rotation of the object, said coupling coil serving as an interface for inductive coupling between the first coil and the second coil.
  • the coupling coil makes it possible to serve as an interface between the interrogation circuit and the transponder circuit independently of the distance separating the first coil from the transponder circuit from the second coil from the interrogation circuit.
  • the coupling coil having at least one annular turn, be mounted on the structure or on the object coaxially with the axis of rotation of the object.
  • the first coil and the second coil can be considered as equidistant even with a rotation of the object.
  • the transponder circuit comprises a passive transponder. In this way, the transponder circuit is only supplied by the inductive signals produced by the interrogation circuit. As long as the interrogation circuit does not produce inductive signals, the transponder circuit therefore remains at rest without electrical supply.
  • the device for transmitting inductive signals is independent of manufacturing tolerances, in particular concerning the resonance frequency of resonant assemblies of each circuit.
  • the inductive signals are at low frequency, for example of the order of 125 kHz.
  • the transponder circuit comprises a resonant assembly constituted in particular by the inductance of the first coil and a capacitor mounted in parallel.
  • the values of the inductance and the capacitor are chosen so as to define a resonant frequency close to the frequency of the signals transmitted by the interrogation circuit. This makes it possible to have a maximum amplitude of the inductive signals picked up, and to facilitate the storage of energy for supplying the components of the transponder circuit.
  • the coupling coil is advantageously larger than the first coil of the transponder circuit and the second coil of the interrogation circuit.
  • This coupling coil may comprise only a single annular turn in the form of a closed loop.
  • the planes or axes of the turns of each coil are arranged parallel to each other.
  • the first coil, seen in the axial direction is located in the closed loop of the coupling coil.
  • the device for transmitting inductive signals is used for a vehicle.
  • the transponder circuit and the coupling coil are preferably placed on one of the wheels of the vehicle, and the interrogation circuit is placed on a fixed structure which is for example the chassis or the body of the vehicle.
  • the transponder circuit can also include at least one sensor for measuring a physical parameter. It may for example be a pressure sensor for measuring the pressure of a vehicle tire, a temperature sensor or a sensor for measuring the deformation of a tire.
  • the measurements made by the sensor (s) can be stored in the transponder circuit when it is supplied, or transferred by the inductive signals to the interrogation circuit.
  • the data is transmitted in the inductive signals preferably by amplitude modulation.
  • FIG. 2 schematically shows a front view A and a side view B partially in section of an embodiment of the device for transmitting inductive signals, according to the invention, mounted on a wheel and a chassis of a vehicle;
  • FIG. 3 schematically shows the various parts of the device for transmitting inductive signals according to the invention.
  • FIG. 4 shows graphs relating to the transmission of data by amplitude modulation of the inductive signals between the interrogation circuit and the transponder circuit of the device for transmitting inductive signals according to the invention.
  • the signal transmission device comprises a transponder circuit 1 preferably mounted on the tire 6 of a vehicle wheel 5, a magnetic coupling coil 2 of annular shape also mounted on the tire 6, and a circuit interrogation 3 mounted on a fixed structure of the vehicle, not shown, such as the chassis or the bodywork.
  • the coupling coil 2 comprises one or more turns forming at least one closed loop.
  • This coupling coil can be integrated into the structure of the tire 6 of the vehicle during its manufacture for example, or fixed on the outside or inside of the tire.
  • the shape of this coupling coil is circular.
  • This coupling coil is positioned on the tire 6 coaxially with an axis of rotation 9 which passes through the center of the rim 7 of the wheel of the vehicle 5.
  • a rotation of the wheel around its axis of rotation does not modify the position of this coupling coil, in particular with respect to the interrogation circuit.
  • this coupling coil 2 can also be mounted on the fixed structure coaxially with the axis of rotation 9 of the wheel.
  • the transponder circuit 1 comprises a first coil not shown in this figure.
  • the first coil can be produced for example on a flexible or rigid printed circuit board which carries the transponder integrated circuit.
  • This first coil can comprise turns arranged in the same plane in the form of a spiral or wound in helical form around a magnetic core.
  • the plane or the axis of the turns of this first coil is substantially parallel to the plane or the axis of the coupling coil 2 for better magnetic coupling between the two coils.
  • the first coil, seen in the axial direction of the coupling coil is for example inside the closed turn (s) of the coupling coil.
  • the transponder circuit 1 can be fixed on an outside side of the tire 6 as shown in FIG. 2, on an inside side of the tire, or on the rim 7.
  • the coupling coil it could be envisaged to integrate the circuit transponder in the mass of the tire 6 during its production.
  • the incorporation of the transponder circuit into the mass of the tire can pose certain manufacturing problems and does not allow said circuit to be changed in the event of a breakdown.
  • the interrogation circuit 3 comprises a second coil 4, shown with a magnetic core for concentrating the lines of force of the magnetic field in order to improve the quality factor Q of this coil.
  • the turns of this coil can be wound helically around the magnetic core.
  • the plane or the axis of the turns of this second coil is substantially parallel to the plane or the axis of the coupling coil 2.
  • this second coil 4 seen in the axial direction of the coil coupling 2 is located inside the closed coil (s) of the coupling coil.
  • the carrier frequency of said inductive signals is preferably of the order of 125 kHz, that is to say at low frequency.
  • the transponder circuit 1 As the transponder circuit 1 is mounted on the tire 6 of the wheel 5, it can comprise at least one sensor for measuring a physical parameter, such as the tire pressure, the temperature, the tire deformation, the speed of rotation . The measurements made by the sensor are transmitted by amplitude modulation in the inductive signals S2 to the interrogation circuit 3.
  • the transponder of the transponder circuit 1 is preferably a passive transponder without its own power source, the interrogation circuit 3 must always transmit inductive signals S1 to the transponder circuit 1.
  • the transponder circuit 1 can withdraw inductive signals received the electrical energy necessary for its operation.
  • the coupling coil has been chosen with a large diameter to ensure good magnetic coupling.
  • the number of turns of the first coil is preferably greater than the number of turns of the coupling coil, which may include only one closed turn.
  • This coupling coil is located on the periphery of the tire 6 of the wheel 5. The inductance value of this coupling coil depends on the surface described by the closed coil (s).
  • the mutual coupling inductance between the first coil and the coupling coil or between the second coil and the coupling coil depends on a coupling factor.
  • This coupling factor takes into account the radius of each coil, the orientation of the turns of each coil and the distance between each coil. As the calculation of these different parameters is well known in the field of magnetic coupling, it is only stated the essential elements to be taken into account for a good dimensioning of each coil.
  • FIG. 3 The various electronic components of the inductive signal transmission device are presented in a simplified manner in FIG. 3. It should be noted that the components of this figure, which correspond to those of FIG. 2, bear identical reference signs. It is shown in particular that the coupling coil 2 serves as a magnetic coupling interface between the first coil 10 and the second coil 4.
  • the interrogation circuit 3 is presented in schematic form. It can be powered electrically via the vehicle battery. It includes an alternating signal generator, presented as an alternating voltage source Vo, connected to a capacitor Co in series with a coil 4 of inductance value Lo. Normally, the alternating signal generator comprises an oscillator and a data modulator, which are connected to an antenna drive device, not shown in FIG. 3.
  • the oscillator produces signals at a determined frequency, for example 125 kHz , which corresponds to the carrier frequency of the inductive signals to be transmitted by the second coil 4, while the modulator makes it possible to connect or disconnect the oscillator in order to add digital data to the signals of the oscillator.
  • the amplitude modulated signals which exit from the drive device, represent a binary sequence of information S1 to be transmitted to the transponder circuit.
  • Each binary element of the sequence is defined over a determined period.
  • a binary element of the binary sequence is worth 1 when the amplitude of the signals is maximum, while a binary element of the binary sequence is worth 0 when the amplitude of the signals is close to 0 in at least a period of time in a period of determined time of the binary element.
  • This amplitude modulation by connection or disconnection of the oscillator is called an OOK (On-Off-Keying in English terminology) modulation.
  • the data to be transmitted relates for example to the command to activate the transponder circuit, the command to transmit data, a specific time delay or parameters to be stored in said transponder circuit.
  • a demodulator not shown, connected to the second coil 4 in order to demodulate data transmitted in the inductive signals S2 coming from the transponder circuit 1.
  • a microprocessor unit can receive the demodulated data by the receiver for processing this data.
  • the circuit called P4095 produced by EM Microelectronic-Marin SA in Switzerland, can be used as an interrogation circuit 3.
  • the transponder circuit 1 is also presented in schematic form. The elements of this circuit are only reported in a summary, because they are part of the general knowledge of a person skilled in the art in this technical field.
  • the transponder circuit notably includes a resonant assembly constituted by the first coil 10 of inductive value L1, a capacitor C1 mounted in parallel, and a resistor Rmod in series with a switch 11, which are connected to the first coil 10 and to the capacitor C1.
  • the resistor Rmod is connected in parallel to the first coil 10 and to the capacitor C1 when the switch 11 is closed.
  • the switch 11 is controlled by a logic part 12 of the transponder. By controlling the closing and opening of the switch, it is possible to amplify the inductive signals S2 for the transmission of data to the interrogation circuit.
  • the values of the inductance L1 and of the capacitor C1 are chosen so as to produce a maximum amplitude of oscillation during the reception of the inductive signals.
  • the resonant frequency of the resonant assembly is thus fixed as a function of the carrier frequency of the inductive signals received.
  • the transponder circuit 1 stores the electrical energy received in a specific capacitor, not shown, so as to supply electrical power to all the components of the transponder circuit.
  • timing clock signals of various operations performed in particular in the logic part 12 is also taken from the inductive signals picked up by the coil 10.
  • This logic part can comprise at least one memory for storing any type of data.
  • the transponder circuit 1 also comprises at least one sensor 13 for measuring a physical parameter.
  • the sensor may be a pressure sensor for measuring the pressure of the tire on which the transponder circuit is mounted, a temperature sensor, a sensor for measuring the deformation of the tire or a speed or acceleration sensor. A combination of several sensors can also be envisaged.
  • the sensor (s) 13 and the logic part 12 can be produced in the same semiconductor substrate, such as silicon.
  • the measurements made by the sensor (s) are memorized and processed in the logic part 12 in order to control the closing or opening of the switch 11 for the transmission of this data in the inductive signals S2.
  • the variation in amplitude of oscillation of the resonant assembly of the transponder circuit can be detected by the coil 4 of the interrogation circuit 3 using the magnetic coupling carried out by the coupling coil 2.
  • the transmission of the data or binary sequence is made by the transponder circuit without interrupting the oscillation of the resonant assembly.
  • the carrier frequency of the inductive signals S2 is therefore substantially the same as the carrier frequency of the inductive signals S
  • Each binary element of the sequence is defined over a determined period. A binary element of the binary sequence is worth 1 when the signal amplitude is maximum, while a binary element of the binary sequence is worth 0 when the signal amplitude is reduced by a certain value by paralleling the resistive load Rmod in the resonant assembly.
  • the circuit called P4150 produced by the company EM Microelectronic-Marin SA in Switzerland, can be used as transponder circuit 1.
  • the transponder of this circuit is passive and operates at low frequency, for example at 125 kHz.
  • Figure 4 shows on the upper graph of the inductive signals transmitted by the interrogation circuit and on the lower graph of the signals inductive transmitted by the transponder circuit.
  • the upper graph and the lower graph show the variation in amplitude Au and Au of the inductive signals at carrier frequency determined as a function of the data to be transmitted.
  • the data is transmitted according to a traditional binary sequence obtained by amplitude modulation.
  • a binary element of the binary sequence is worth 1 over a determined period Tj when the signal amplitude is maximum, while a binary element of the binary sequence is worth 0 when the signal amplitude is close to 0 for at least a period of time in the determined period of a binary element.
  • a binary element of the binary sequence is worth 1 over a determined period Tt when the signal amplitude is maximum, while a binary element of the binary sequence is 0 when the signal amplitude is reduced by some value.
  • the determined period Tt is less than the determined period Tj so as to distinguish the data transmitted from the data received.
  • the device can be applied in any field in which an object is rotatably mounted relative to a fixed structure. It can be partly mounted on a rotor of helicopter blades, in a steam turbine, on a carousel, or on any other rotor machine. It can be provided that the magnetic coupling coil has a polygonal shape while being positioned coaxially with respect to the axis of rotation of a rotating object, such as the vehicle wheel.
  • the interrogation circuit and the transponder circuit can each be provided with a transmission coil and a coil for receiving the inductive signals.
  • Frequency modulation can be used to transmit the data in the inductive signals to the instead of amplitude modulation.
  • the frequency of the inductive signals transmitted can be different in each circuit.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

The device for transmitting inductive signals comprises a transponder circuit (1) provided with at least one first coil, and an interrogation circuit (3) provided with at least one second coil (4). The transponder circuit is placed on an object (5) which can turn around at least one axis of rotation (9) passing via said object. The interrogation circuit is placed on a structure which can be fixed and to which the object is connected. A coupling coil (2), provided with at least one wrap describing a ring, is mounted on the structure or on the object in a coaxial manner with respect to the axis of rotation of the object. The coupling coil is used as an inductive coupling interface between the first coil and the second coil such that the transmission of inductive signals is substantially independent from the rotation of the object. The transponder circuit is of the passive variety and comprises at least one physical parameter measurement sensor. The device can be used in the automotive industry by placing the transponder circuit (1) and the coupling coil (2) on the wheel of a vehicle (5) and by placing the interrogation circuit (3) on the frame or body of said vehicle.

Description

DISPOSITI F DE TRANSMISSION DE SIG NAUX PAR I NDUCTION ARRANGEMENT FOR TRANSMITTING NATIONAL SIG BY I NDUCTION
ENTRE UN CIRCUIT TRANSPONDEUR ET UN CIRCUITBETWEEN A TRANSPONDER CIRCUIT AND A CIRCUIT
D' INTERROGATIONOF QUERY
L'invention concerne un dispositif de transmission de signaux par induction entre un circuit transpondeur et un circuit d'interrogation. Pour la transmission de signaux inductifs, le circuit transpondeur comprend une première bobine, et le circuit d'interrogation comprend une seconde bobine. Le circuit transpondeur est placé sur un objet susceptible de tourner autour d'au moins un axe de rotation passant par l'objet, alors que le circuit d'interrogation est placé sur une structure, qui peut être fixe, à laquelle l'objet est relié.The invention relates to a device for transmitting signals by induction between a transponder circuit and an interrogation circuit. For the transmission of inductive signals, the transponder circuit comprises a first coil, and the interrogation circuit comprises a second coil. The transponder circuit is placed on an object capable of turning around at least one axis of rotation passing through the object, while the interrogation circuit is placed on a structure, which can be fixed, to which the object is connected.
Dans une application automobile, l'objet tournant peut être par exemple une roue de véhicule, alors que la structure est par exemple la carrosserie ou le châssis du véhicule. Dans ce cas, il peut être envisagé que le circuit transpondeur comprenne au moins un capteur pour la mesure d'un paramètre physique. Il peut s'agir d'un capteur de pression pour la mesure de la pression des pneus du véhicule, d'un capteur de température, d'un capteur de force, d'un accéléromètre ou d'un autre type de capteur. Les mesures effectuées par le ou les capteurs du circuit transpondeur peuvent être transmises au circuit d'interrogation dans les signaux inductifs par exemple par modulation d'amplitude.In an automotive application, the rotating object can for example be a vehicle wheel, while the structure is for example the bodywork or the chassis of the vehicle. In this case, it can be envisaged that the transponder circuit includes at least one sensor for measuring a physical parameter. It can be a pressure sensor for measuring the tire pressure of the vehicle, a temperature sensor, a force sensor, an accelerometer or another type of sensor. The measurements made by the sensor or sensors of the transponder circuit can be transmitted to the interrogation circuit in the inductive signals, for example by amplitude modulation.
Comme le circuit transpondeur est placé sur l'objet tournant, la distance le séparant du circuit d'interrogation n'est pas constante lors de la rotation de l'objet. De ce fait, on constate lors de la transmission des signaux inductifs entre le circuit d'interrogation et le circuit transpondeur qu'une modulation d'amplitude parasite des signaux survient ce qui peut être un inconvénient important. Ainsi, il peut arriver lors d'opérations de démodulation dans l'unité réceptrice que les données reçues dans les signaux inductifs ne correspondent pas totalement aux données transmises. Cette perturbation sur les données transmises peut être dépendante aussi de la vitesse de rotation de l'objet. Plus la vitesse de rotation est élevée et plus cette perturbation peut être importante.As the transponder circuit is placed on the rotating object, the distance separating it from the interrogation circuit is not constant during the rotation of the object. Therefore, it is noted during the transmission of inductive signals between the interrogation circuit and the transponder circuit that a parasitic amplitude modulation of the signals occurs which can be a significant drawback. Thus, it may happen during demodulation operations in the receiving unit that the data received in the inductive signals do not completely correspond to the transmitted data. This disturbance on the transmitted data can also be dependent on the speed of rotation of the object. The higher the speed of rotation, the greater this disturbance can be.
A titre illustratif, la figure 1 montre de manière simplifiée l'influence que peut avoir la rotation d'un objet sur l'amplitude des signaux inductifs captés par l'unité réceptrice. Des signaux inductifs sont tout d'abord transmis par l'unité émettrice à une fréquence porteuse déterminée et une amplitude déterminée. Les données modulées dans les signaux inductifs ne sont par contre pas représentées dans cette figure par simplification. Comme la distance séparant l'unité réceptrice de l'unité émettrice varie lors de la rotation de l'objet, l'amplitude des signaux inductifs captés, c'est-à-dire l'amplitude de la tension induite dans la bobine de l'unité réceptrice, change.By way of illustration, FIG. 1 shows in a simplified manner the influence that the rotation of an object can have on the amplitude of the inductive signals picked up by the receiving unit. Inductive signals are first transmitted by the transmitting unit at a determined carrier frequency and a determined amplitude. The data modulated in the inductive signals, on the other hand, are not represented in this figure for simplification. As the distance between the receiving unit and the sending unit varies during the rotation of the object, the amplitude of the inductive signals picked up, that is to say the amplitude of the voltage induced in the coil of the receiving unit, changes.
Sur la figure 1 , cette variation d'amplitude est illustrée par l'enveloppe des signaux inductifs captés par l'unité réceptrice. Cette enveloppe est représentée simplement de forme sinusoïdale correspondant à une vitesse de rotation de l'objet constante. Toutefois, il est clair que la forme de cette enveloppe n'est pas en réalité sinusoïdale, car l'amplitude du champ magnétique créé par la bobine émettrice ne décroît pas linéairement avec la distance séparant la bobine émettrice de la bobine réceptrice. Dans certaines réalisations de dispositifs de transmission de signaux, il a également été proposé de transmettre des signaux haute fréquence entre le circuit transpondeur et le circuit d'interrogation. Ces signaux haute fréquence utilisés permettent de ne pas être trop dépendant de la rotation de l'objet sur lequel le circuit transpondeur est monté. Cependant en utilisant un tel dispositif qui produit des signaux haute fréquence (par exemple 2,45 GHz) dans une application automobile, il a été montré que l'eau peut avoir une influence négative sur la performance du dispositif. De plus, comme le circuit transpondeur transmet des signaux haute fréquence, il doit en principe être muni de sa propre source d'énergie, telle qu'une batterie. Ceci peut être également un inconvénient, car dans ce cas le circuit transpondeur consomme de l'énergie même si le circuit d'interrogation ne l'interroge pas.In FIG. 1, this variation in amplitude is illustrated by the envelope of the inductive signals picked up by the receiving unit. This envelope is shown simply in sinusoidal shape corresponding to a constant speed of rotation of the object. However, it is clear that the shape of this envelope is not in reality sinusoidal, since the amplitude of the magnetic field created by the transmitting coil does not decrease linearly with the distance separating the transmitting coil from the receiving coil. In certain embodiments of signal transmission devices, it has also been proposed to transmit high frequency signals between the transponder circuit and the interrogation circuit. These high frequency signals used make it possible not to be too dependent on the rotation of the object on which the transponder circuit is mounted. However, by using such a device which produces high frequency signals (for example 2.45 GHz) in an automotive application, it has been shown that water can have a negative influence on the performance of the device. In addition, since the transponder circuit transmits high frequency signals, it must in principle be provided with its own energy source, such as a battery. This can also be a disadvantage, because in this case the transponder circuit consumes energy even if the interrogation circuit does not interrogate it.
Ainsi, un but de la présente invention consiste à fournir un dispositif de transmission de signaux inductifs qui comprend des moyens supprimant une modulation d'amplitude parasite non désirée des signaux inductifs lors de la rotation de l'objet par rapport à la structure afin de pallier les inconvénients de l'art antérieur cité ci-devant.Thus, an object of the present invention consists in providing a device for transmitting inductive signals which comprises means suppressing unwanted amplitude modulation of the inductive signals during the rotation of the object relative to the structure in order to alleviate the drawbacks of the prior art cited above.
Un autre but de la présente invention consiste à fournir un dispositif de transmission de signaux inductifs qui soit simple à réaliser tout en réduisant les coûts de fabrication, et consomme peu d'énergie électrique. A cet effet, l'invention concerne un dispositif de transmission de signaux inductifs cité ci-devant qui se caractérise en ce qu'une bobine de couplage, munie d'au moins une spire, est montée sur la structure ou sur l'objet de manière coaxiale à l'axe de rotation de l'objet, ladite bobine de couplage servant d'interface de couplage inductif entre la première bobine et la seconde bobine. Un avantage du dispositif de transmission de signaux inductifs, selon l'invention, est qu'il n'est pas nécessaire de savoir, si l'objet tourne autour de son axe de rotation ou est au repos, car la transmission desdits signaux est sensiblement indépendante de la rotation de l'objet. La bobine de couplage permet de servir d'interface entre le circuit d'interrogation et le circuit transpondeur indépendamment de la distance séparant la première bobine du circuit transpondeur de la seconde bobine du circuit d'interrogation. Bien entendu, pour ne pas être influencé par la rotation de l'objet, il est nécessaire que la bobine de couplage, ayant au moins une spire annulaire, soit montée sur la structure ou sur l'objet de manière coaxiale à l'axe de rotation de l'objet. Ainsi grâce à cette bobine de couplage, la première bobine et la seconde bobine peuvent être considérées comme équidistantes même avec une rotation de l'objet. Dans un mode avantageux de réalisation du dispositif, le circuit transpondeur comprend un transpondeur passif. De cette manière, le circuit transpondeur n'est alimenté que par les signaux inductifs produits par le circuit d'interrogation. Tant que le circuit d'interrogation ne produit pas de signaux inductifs, le circuit transpondeur reste donc au repos sans alimentation électrique. De plus, le dispositif de transmission de signaux inductifs est indépendant des tolérances de fabrication notamment concernant la fréquence de résonance d'ensembles résonants de chaque circuit.Another object of the present invention is to provide a device for transmitting inductive signals which is simple to produce while reducing manufacturing costs, and consumes little electrical energy. To this end, the invention relates to a device for transmitting inductive signals cited above which is characterized in that a coupling coil, provided with at least one turn, is mounted on the structure or on the object of coaxially with the axis of rotation of the object, said coupling coil serving as an interface for inductive coupling between the first coil and the second coil. An advantage of the device for transmitting inductive signals, according to the invention, is that it is not necessary to know, whether the object rotates around its axis of rotation or is at rest, since the transmission of said signals is substantially independent of the rotation of the object. The coupling coil makes it possible to serve as an interface between the interrogation circuit and the transponder circuit independently of the distance separating the first coil from the transponder circuit from the second coil from the interrogation circuit. Of course, in order not to be influenced by the rotation of the object, it is necessary that the coupling coil, having at least one annular turn, be mounted on the structure or on the object coaxially with the axis of rotation of the object. Thus thanks to this coupling coil, the first coil and the second coil can be considered as equidistant even with a rotation of the object. In an advantageous embodiment of the device, the transponder circuit comprises a passive transponder. In this way, the transponder circuit is only supplied by the inductive signals produced by the interrogation circuit. As long as the interrogation circuit does not produce inductive signals, the transponder circuit therefore remains at rest without electrical supply. In addition, the device for transmitting inductive signals is independent of manufacturing tolerances, in particular concerning the resonance frequency of resonant assemblies of each circuit.
Comme les bobines sont proches l'une de l'autre, les signaux inductifs sont à basse fréquence par exemple de l'ordre de 125 kHz. De préférence, le circuit transpondeur comprend un ensemble résonant constitué notamment par l'inductance de la première bobine et un condensateur monté en parallèle. Les valeurs de l'inductance et du condensateur sont choisies de telle manière à définir une fréquence de résonance proche de la fréquence des signaux transmis par le circuit d'interrogation. Ceci permet d'avoir un maximum d'amplitude des signaux inductifs captés, et de faciliter le stockage d'énergie pour l'alimentation des composants du circuit transpondeur.As the coils are close to each other, the inductive signals are at low frequency, for example of the order of 125 kHz. Preferably, the transponder circuit comprises a resonant assembly constituted in particular by the inductance of the first coil and a capacitor mounted in parallel. The values of the inductance and the capacitor are chosen so as to define a resonant frequency close to the frequency of the signals transmitted by the interrogation circuit. This makes it possible to have a maximum amplitude of the inductive signals picked up, and to facilitate the storage of energy for supplying the components of the transponder circuit.
La bobine de couplage est avantageusement de plus grande dimension que la première bobine du circuit transpondeur et la seconde bobine du circuit d'interrogation. Cette bobine de couplage peut ne comprendre qu'une seule spire annulaire sous forme d'une boucle fermée. Les plans ou les axes des spires de chaque bobine sont disposés parallèlement les uns par rapport aux autres. De plus, la première bobine, vue dans la direction axiale se trouve dans la boucle fermée de la bobine de couplage.The coupling coil is advantageously larger than the first coil of the transponder circuit and the second coil of the interrogation circuit. This coupling coil may comprise only a single annular turn in the form of a closed loop. The planes or axes of the turns of each coil are arranged parallel to each other. In addition, the first coil, seen in the axial direction, is located in the closed loop of the coupling coil.
De manière avantageuse, le dispositif de transmission de signaux inductifs est utilisé pour un véhicule. Le circuit transpondeur et la bobine de couplage sont placés de préférence sur une des roues du véhicule, et le circuit d'interrogation est placé sur une structure fixe qui est par exemple le châssis ou la carrosserie du véhicule. Le circuit transpondeur peut également comprendre au moins un capteur pour mesurer un paramètre physique. Il peut s'agir par exemple d'un capteur de pression pour mesurer la pression d'un pneu du véhicule, d'un capteur de température ou d'un capteur pour la mesure de la déformation d'un pneu. Les mesures effectuées par le ou les capteurs peuvent être mémorisées dans le circuit transpondeur lorsqu'il est alimenté, ou transférées par les signaux inductifs au circuit d'interrogation. Les données sont transmises dans les signaux inductifs de préférence par modulation d'amplitude.Advantageously, the device for transmitting inductive signals is used for a vehicle. The transponder circuit and the coupling coil are preferably placed on one of the wheels of the vehicle, and the interrogation circuit is placed on a fixed structure which is for example the chassis or the body of the vehicle. The transponder circuit can also include at least one sensor for measuring a physical parameter. It may for example be a pressure sensor for measuring the pressure of a vehicle tire, a temperature sensor or a sensor for measuring the deformation of a tire. The measurements made by the sensor (s) can be stored in the transponder circuit when it is supplied, or transferred by the inductive signals to the interrogation circuit. The data is transmitted in the inductive signals preferably by amplitude modulation.
Les buts, avantages et caractéristiques du dispositif de transmission de signaux inductifs apparaîtront mieux dans la description suivante d'au moins une forme d'exécution illustrée par les dessins sur lesquels :The aims, advantages and characteristics of the device for transmitting inductive signals will appear better in the following description of at least one embodiment illustrated by the drawings in which:
- la figure 1 déjà citée montre de manière simplifiée l'influence de la rotation d'un objet, tel qu'une roue de véhicule, sur l'amplitude des signaux inductifs captés par la bobine d'une unité réceptrice d'un dispositif de transmission de signaux traditionnel;- Figure 1 already cited shows in a simplified way the influence of the rotation of an object, such as a vehicle wheel, on the amplitude of the inductive signals picked up by the coil of a receiver unit of a traditional signal transmission;
- la figure 2 montre schématiquement une vue de face A et une vue de côté B partiellement en coupe d'une forme d'exécution du dispositif de transmission de signaux inductifs, selon l'invention, monté sur une roue et un châssis d'un véhicule;- Figure 2 schematically shows a front view A and a side view B partially in section of an embodiment of the device for transmitting inductive signals, according to the invention, mounted on a wheel and a chassis of a vehicle;
- la figure 3 montre schématiquement les diverses parties du dispositif de transmission de signaux inductifs selon l'invention, etFIG. 3 schematically shows the various parts of the device for transmitting inductive signals according to the invention, and
- la figure 4 montre des graphiques relatifs à la transmission de données par modulation d'amplitude des signaux inductifs entre le circuit d'interrogation et le circuit transpondeur du dispositif de transmission de signaux inductifs selon l'invention.FIG. 4 shows graphs relating to the transmission of data by amplitude modulation of the inductive signals between the interrogation circuit and the transponder circuit of the device for transmitting inductive signals according to the invention.
On va décrire ci-après un mode préféré de réalisation du dispositif de transmission de signaux inductifs dans le domaine automobile. Il est à noter que dans la description suivante, tous les composants électroniques du dispositif de transmission de signaux inductifs, qui sont bien connus d'un homme du métier dans ce domaine technique, ne seront pas expliqués en détail.A preferred embodiment of the device for transmitting inductive signals will be described below in the automotive field. It should be noted that in the following description, all the electronic components of the device for transmitting inductive signals, which are well known to a person skilled in the art in this technical field, will not be explained in detail.
A la figure 2, le dispositif de transmission de signaux comprend un circuit transpondeur 1 monté de préférence sur le pneu 6 d'une roue 5 de véhicule, une bobine de couplage magnétique 2 de forme annulaire montée également sur le pneu 6, et un circuit d'interrogation 3 monté sur une structure fixe du véhicule, non représentée, telle que le châssis ou la carrosserie.In FIG. 2, the signal transmission device comprises a transponder circuit 1 preferably mounted on the tire 6 of a vehicle wheel 5, a magnetic coupling coil 2 of annular shape also mounted on the tire 6, and a circuit interrogation 3 mounted on a fixed structure of the vehicle, not shown, such as the chassis or the bodywork.
La bobine de couplage 2 comprend une ou plusieurs spires formant au moins une boucle fermée. Cette bobine de couplage peut être intégrée dans la structure du pneu 6 du véhicule lors de sa fabrication par exemple, ou fixée du côté extérieur ou intérieur du pneu. De préférence, la forme de cette bobine de couplage est circulaire. Cette bobine de couplage est positionnée sur le pneu 6 de manière coaxiale à un axe de rotation 9 qui passe au centre de la jante 7 de la roue du véhicule 5. Ainsi, une rotation de la roue autour de son axe de rotation ne modifie pas la position de cette bobine de couplage, notamment par rapport au circuit d'interrogation. Bien entendu, cette bobine de couplage 2 peut également être montée sur la structure fixe de manière coaxiale à l'axe de rotation 9 de la roue. Toutefois, cette construction est plus compliquée et peut causer certains problèmes de couplage magnétique, car la carrosserie ou le châssis du véhicule est généralement métallique. Le circuit transpondeur 1 comprend une première bobine non représentée sur cette figure. La première bobine peut être réalisée par exemple sur une plaque à circuit imprimé souple ou rigide qui porte le circuit intégré transpondeur. Cette première bobine peut comprendre des spires disposées dans un même plan sous forme d'une spirale ou enroulée sous forme hélicoïdale autour d'un noyau magnétique. De préférence la plan ou l'axe des spires de cette première bobine est sensiblement parallèle au plan ou à l'axe de la bobine de couplage 2 pour un meilleur couplage magnétique entre les deux bobines. La première bobine, vue dans la direction axiale de la bobine de couplage se trouve par exemple à l'intérieur de la ou des spires fermées de la bobine de couplage.The coupling coil 2 comprises one or more turns forming at least one closed loop. This coupling coil can be integrated into the structure of the tire 6 of the vehicle during its manufacture for example, or fixed on the outside or inside of the tire. Preferably, the shape of this coupling coil is circular. This coupling coil is positioned on the tire 6 coaxially with an axis of rotation 9 which passes through the center of the rim 7 of the wheel of the vehicle 5. Thus, a rotation of the wheel around its axis of rotation does not modify the position of this coupling coil, in particular with respect to the interrogation circuit. Of course, this coupling coil 2 can also be mounted on the fixed structure coaxially with the axis of rotation 9 of the wheel. However, this construction is more complicated and can cause certain problems of magnetic coupling, since the vehicle body or chassis is generally metallic. The transponder circuit 1 comprises a first coil not shown in this figure. The first coil can be produced for example on a flexible or rigid printed circuit board which carries the transponder integrated circuit. This first coil can comprise turns arranged in the same plane in the form of a spiral or wound in helical form around a magnetic core. Preferably the plane or the axis of the turns of this first coil is substantially parallel to the plane or the axis of the coupling coil 2 for better magnetic coupling between the two coils. The first coil, seen in the axial direction of the coupling coil is for example inside the closed turn (s) of the coupling coil.
Le circuit transpondeur 1 peut être fixé sur un côté extérieur du pneu 6 comme montré sur la figure 2, sur un côté intérieur du pneu, ou sur la jante 7. Comme pour la bobine de couplage, il pourrait être envisagé d'intégrer le circuit transpondeur dans la masse du pneu 6 lors de sa réalisation. Cependant, l'incorporation du circuit transpondeur dans la masse du pneu peut poser certains problèmes de fabrication et ne permet de changer ledit circuit en cas de panne. Le circuit d'interrogation 3 comprend une seconde bobine 4, montrée avec un noyau magnétique pour concentrer les lignes de force du champ magnétique afin d'améliorer le facteur de qualité Q de cette bobine. Les spires de cette bobine peuvent être enroulées de manière hélicoïdale autour du noyau magnétique. Comme pour la première bobine, le plan ou l'axe des spires de cette seconde bobine est sensiblement parallèle au plan ou à l'axe de la bobine de couplage 2. De préférence, cette seconde bobine 4 vue dans la direction axiale de la bobine de couplage 2 se trouve à l'intérieur de la ou des spires fermées de la bobine de couplage.The transponder circuit 1 can be fixed on an outside side of the tire 6 as shown in FIG. 2, on an inside side of the tire, or on the rim 7. As for the coupling coil, it could be envisaged to integrate the circuit transponder in the mass of the tire 6 during its production. However, the incorporation of the transponder circuit into the mass of the tire can pose certain manufacturing problems and does not allow said circuit to be changed in the event of a breakdown. The interrogation circuit 3 comprises a second coil 4, shown with a magnetic core for concentrating the lines of force of the magnetic field in order to improve the quality factor Q of this coil. The turns of this coil can be wound helically around the magnetic core. As for the first coil, the plane or the axis of the turns of this second coil is substantially parallel to the plane or the axis of the coupling coil 2. Preferably, this second coil 4 seen in the axial direction of the coil coupling 2 is located inside the closed coil (s) of the coupling coil.
Avec cette configuration des bobines énoncées ci-dessus, il est possible de transmettre des signaux inductifs S1 et S2 par couplage magnétique entre les deux circuits 1 et 3 de manière optimale. La fréquence porteuse desdits signaux inductifs est de préférence de l'ordre de 125 kHz, c'est-à-dire à basse fréquence. On comprend donc qu'avec la bobine de couplage positionnée de manière coaxiale à l'axe de rotation de la roue 5, la distance séparant le circuit transpondeur 1 du circuit d'interrogation 3 n'a plus d'importance. La distance rapprochée entre chaque bobine peut ainsi rester constante même si l'objet est en rotation autour de son axe de rotation. De ce fait, aucune modulation d'amplitude des signaux inductifs captés autre que la modulation nécessaire à la transmission des données entre les deux circuits n'apparaît dans l'unité réceptrice des signaux de l'un ou l'autre circuit 1 et 3.With this configuration of the coils stated above, it is possible to transmit inductive signals S1 and S2 by magnetic coupling between the two circuits 1 and 3 optimally. The carrier frequency of said inductive signals is preferably of the order of 125 kHz, that is to say at low frequency. We therefore understand that with the coupling coil positioned coaxially with the axis of rotation of the wheel 5, the distance separating the transponder circuit 1 from the interrogation circuit 3 no longer matters. The close distance between each coil can thus remain constant even if the object is rotating around its axis of rotation. As a result, no amplitude modulation of the inductive signals received other than the modulation necessary for the transmission of data between the two circuits appears in the signal receiving unit of one or the other circuit 1 and 3.
Comme le circuit transpondeur 1 est monté sur le pneu 6 de la roue 5, il peut comprendre au moins un capteur de mesure d'un paramètre physique, tel que la pression du pneu, la température, la déformation du pneu, la vitesse de rotation. Les mesures effectuées par le capteur sont transmises par modulation d'amplitude dans les signaux inductifs S2 à destination du circuit d'interrogation 3. Toutefois, comme le transpondeur du circuit transpondeur 1 est de préférence un transpondeur passif sans sa propre source d'alimentation, le circuit d'interrogation 3 doit toujours transmettre des signaux inductifs S1 à destination du circuit transpondeur 1. Ainsi, le circuit transpondeur 1 peut retirer des signaux inductifs reçus l'énergie électrique nécessaire à son fonctionnement.As the transponder circuit 1 is mounted on the tire 6 of the wheel 5, it can comprise at least one sensor for measuring a physical parameter, such as the tire pressure, the temperature, the tire deformation, the speed of rotation . The measurements made by the sensor are transmitted by amplitude modulation in the inductive signals S2 to the interrogation circuit 3. However, since the transponder of the transponder circuit 1 is preferably a passive transponder without its own power source, the interrogation circuit 3 must always transmit inductive signals S1 to the transponder circuit 1. Thus, the transponder circuit 1 can withdraw inductive signals received the electrical energy necessary for its operation.
Pour un bon couplage magnétique entre les bobines, il doit être tenu compte de la distance entre chacune de ces bobines, de l'orientation de l'axe des spires et de la surface de réception des signaux inductifs de chaque bobine. Comme la dimension de la bobine du circuit transpondeur est de petite dimension, la bobine de couplage a été choisie avec un diamètre de grande dimension pour assurer un bon couplage magnétique. Le nombre de spires de la première bobine est de préférence supérieur au nombre de spires de la bobine de couplage, qui peut ne comprendre qu'une seule spire fermée. Cette bobine de couplage est située en périphérie du pneu 6 de la roue 5. La valeur d'inductance de cette bobine de couplage dépend de la surface décrite par la ou les spires fermées. De plus, l'inductance mutuelle de couplage entre la première bobine et la bobine de couplage ou entre la seconde bobine et la bobine de couplage dépend d'un facteur de couplage. Ce facteur de couplage tient compte du rayon de chaque bobine, de l'orientation des spires de chaque bobine et de la distance séparant chaque bobine. Comme le calcul de ces différents paramètres est bien connu dans le domaine du couplage magnétique, il n'est énoncé que les éléments essentiels à tenir compte pour un bon dimensionnement de chaque bobine.For a good magnetic coupling between the coils, account must be taken of the distance between each of these coils, the orientation of the axis of the turns and the surface for receiving the inductive signals from each coil. As the size of the coil of the transponder circuit is small, the coupling coil has been chosen with a large diameter to ensure good magnetic coupling. The number of turns of the first coil is preferably greater than the number of turns of the coupling coil, which may include only one closed turn. This coupling coil is located on the periphery of the tire 6 of the wheel 5. The inductance value of this coupling coil depends on the surface described by the closed coil (s). In addition, the mutual coupling inductance between the first coil and the coupling coil or between the second coil and the coupling coil depends on a coupling factor. This coupling factor takes into account the radius of each coil, the orientation of the turns of each coil and the distance between each coil. As the calculation of these different parameters is well known in the field of magnetic coupling, it is only stated the essential elements to be taken into account for a good dimensioning of each coil.
Les différents composants électroniques du dispositif de transmission de signaux inductifs sont présentés de manière simplifiée à la figure 3. Il est à noter que les composants de cette figure, qui correspondent à ceux de la figure 2, portent des signes de référence identiques. Il est montré notamment que la bobine de couplage 2 sert d'interface de couplage magnétique entre la première bobine 10 et la seconde bobine 4.The various electronic components of the inductive signal transmission device are presented in a simplified manner in FIG. 3. It should be noted that the components of this figure, which correspond to those of FIG. 2, bear identical reference signs. It is shown in particular that the coupling coil 2 serves as a magnetic coupling interface between the first coil 10 and the second coil 4.
Le circuit d'interrogation 3 est présenté sous forme schématique. Il peut être alimenté électriquement par l'intermédiaire de la batterie du véhicule. Il comprend un générateur de signaux alternatifs, présenté comme une source de tension alternative Vo, connecté à un condensateur Co en série avec une bobine 4 de valeur d'inductance Lo. Normalement, le générateur de signaux alternatifs comprend un oscillateur et un modulateur de données, qui sont connectés à un dispositif d'entraînement d'antenne, non représenté sur la figure 3. L'oscillateur produit des signaux à une fréquence déterminée par exemple 125 kHz, qui correspond à la fréquence porteuse des signaux inductifs à transmettre par la seconde bobine 4, alors que le modulateur permet de connecter ou déconnecter l'oscillateur afin d'ajouter aux signaux de l'oscillateur des données numériques.The interrogation circuit 3 is presented in schematic form. It can be powered electrically via the vehicle battery. It includes an alternating signal generator, presented as an alternating voltage source Vo, connected to a capacitor Co in series with a coil 4 of inductance value Lo. Normally, the alternating signal generator comprises an oscillator and a data modulator, which are connected to an antenna drive device, not shown in FIG. 3. The oscillator produces signals at a determined frequency, for example 125 kHz , which corresponds to the carrier frequency of the inductive signals to be transmitted by the second coil 4, while the modulator makes it possible to connect or disconnect the oscillator in order to add digital data to the signals of the oscillator.
Les signaux modulés en amplitude, qui sortent du dispositif d'entraînement, représentent une séquence binaire d'information S1 à transmettre au circuit transpondeur. Chaque élément binaire de la séquence est défini sur une période déterminée. Un élément binaire de la séquence binaire vaut 1 quand l'amplitude des signaux est maximale, alors qu'un élément binaire de la séquence binaire vaut 0 quand l'amplitude des signaux est proche de 0 dans au moins un laps de temps dans une période de temps déterminée de l'élément binaire. Cette modulation en amplitude par connexion ou déconnexion de l'oscillateur est appelée une modulation OOK (On- Off-Keying en terminologie anglaise). Les données à transmettre concerne par exemple la commande de mise en fonction du circuit transpondeur, la commande de transmission de données, une temporisation spécifique ou des paramètres à mémoriser dans ledit circuit transpondeur.The amplitude modulated signals, which exit from the drive device, represent a binary sequence of information S1 to be transmitted to the transponder circuit. Each binary element of the sequence is defined over a determined period. A binary element of the binary sequence is worth 1 when the amplitude of the signals is maximum, while a binary element of the binary sequence is worth 0 when the amplitude of the signals is close to 0 in at least a period of time in a period of determined time of the binary element. This amplitude modulation by connection or disconnection of the oscillator is called an OOK (On-Off-Keying in English terminology) modulation. The data to be transmitted relates for example to the command to activate the transponder circuit, the command to transmit data, a specific time delay or parameters to be stored in said transponder circuit.
Dans le circuit d'interrogation 3, il est également prévu un démodulateur, non représenté, relié à la seconde bobine 4 afin de démoduler des données transmises dans les signaux inductifs S2 provenant du circuit transpondeur 1. Une unité à microprocesseur peut recevoir les données démodulées par le démodulateur pour le traitement de ces données.In the interrogation circuit 3, there is also provided a demodulator, not shown, connected to the second coil 4 in order to demodulate data transmitted in the inductive signals S2 coming from the transponder circuit 1. A microprocessor unit can receive the demodulated data by the receiver for processing this data.
Le circuit dénommé P4095, produit par la société EM Microelectronic-Marin SA en Suisse, peut être utilisé comme circuit d'interrogation 3.The circuit called P4095, produced by EM Microelectronic-Marin SA in Switzerland, can be used as an interrogation circuit 3.
Le circuit transpondeur 1 est présenté également sous forme schématique. Les éléments de ce circuit ne sont relatés que de manière sommaire, car ils font partie des connaissances générales d'un homme du métier dans ce domaine technique. Le circuit transpondeur comprend notamment un ensemble résonant constitué par la première bobine 10 de valeur inductive L1 , un condensateur C1 monté en parallèle, et une résistance Rmod en série avec un interrupteur 11 , qui sont connectés à la première bobine 10 et au condensateur C1. La résistance Rmod est connectée en parallèle à la première bobine 10 et au condensateur C1 lorsque l'interrupteur 11 est fermé. La commande de l'interrupteur 11 est réalisée par une partie logique 12 du transpondeur. En commandant la fermeture et l'ouverture de l'interrupteur il est possible de moduler en amplitude des signaux inductifs S2 pour la transmission de données au circuit d'interrogation.The transponder circuit 1 is also presented in schematic form. The elements of this circuit are only reported in a summary, because they are part of the general knowledge of a person skilled in the art in this technical field. The transponder circuit notably includes a resonant assembly constituted by the first coil 10 of inductive value L1, a capacitor C1 mounted in parallel, and a resistor Rmod in series with a switch 11, which are connected to the first coil 10 and to the capacitor C1. The resistor Rmod is connected in parallel to the first coil 10 and to the capacitor C1 when the switch 11 is closed. The switch 11 is controlled by a logic part 12 of the transponder. By controlling the closing and opening of the switch, it is possible to amplify the inductive signals S2 for the transmission of data to the interrogation circuit.
Les valeurs de l'inductance L1 et du condensateur C1 sont choisies de telle manière à produire une amplitude maximale d'oscillation lors de la réception des signaux inductifs. La fréquence de résonance de l'ensemble résonant est ainsi fixée en fonction de la fréquence porteuse des signaux inductifs reçus. Lors de la réception des signaux inductifs, le circuit transpondeur 1 stocke l'énergie électrique reçue dans un condensateur spécifique, non représenté, de manière à assurer l'alimentation électrique de tous les composants du circuit transpondeur. De plus, des signaux d'horloge de cadencement de diverses opérations effectuées notamment dans la partie logique 12 est également tirée des signaux inductifs captés par la bobine 10. Cette partie logique peut comprendre au moins une mémoire pour stocker tout type de données.The values of the inductance L1 and of the capacitor C1 are chosen so as to produce a maximum amplitude of oscillation during the reception of the inductive signals. The resonant frequency of the resonant assembly is thus fixed as a function of the carrier frequency of the inductive signals received. When receiving the inductive signals, the transponder circuit 1 stores the electrical energy received in a specific capacitor, not shown, so as to supply electrical power to all the components of the transponder circuit. In addition, timing clock signals of various operations performed in particular in the logic part 12 is also taken from the inductive signals picked up by the coil 10. This logic part can comprise at least one memory for storing any type of data.
Le circuit transpondeur 1 comprend encore au moins un capteur de mesure 13 d'un paramètre physique. Le capteur peut être un capteur de pression pour la mesure de la pression du pneu sur lequel le circuit transpondeur est monté, un capteur de température, un capteur pour la mesure de la déformation du pneu ou un capteur de vitesse ou d'accélération. Une combinaison de plusieurs capteurs peut être aussi envisagée. Le ou les capteurs 13 et la partie logique 12 peuvent être réalisés dans un même substrat semi-conducteur, tel que du silicium.The transponder circuit 1 also comprises at least one sensor 13 for measuring a physical parameter. The sensor may be a pressure sensor for measuring the pressure of the tire on which the transponder circuit is mounted, a temperature sensor, a sensor for measuring the deformation of the tire or a speed or acceleration sensor. A combination of several sensors can also be envisaged. The sensor (s) 13 and the logic part 12 can be produced in the same semiconductor substrate, such as silicon.
Lorsque le circuit transpondeur 1 est en état de fonctionnement, les mesures effectuées par le ou les capteurs sont mémorisées et traitées dans la partie logique 12 afin de commander la fermeture ou l'ouverture de l'interrupteur 11 pour la transmission de ces données dans les signaux inductifs S2. La variation d'amplitude d'oscillation de l'ensemble résonant du circuit transpondeur peut être détectée par la bobine 4 du circuit d'interrogation 3 à l'aide du couplage magnétique effectué par la bobine de couplage 2.When the transponder circuit 1 is in operating state, the measurements made by the sensor (s) are memorized and processed in the logic part 12 in order to control the closing or opening of the switch 11 for the transmission of this data in the inductive signals S2. The variation in amplitude of oscillation of the resonant assembly of the transponder circuit can be detected by the coil 4 of the interrogation circuit 3 using the magnetic coupling carried out by the coupling coil 2.
Il est à noter que la transmission des données ou séquence binaire est faite par le circuit transpondeur sans interrompre l'oscillation de l'ensemble résonant. La fréquence porteuse des signaux inductifs S2 est donc sensiblement la même que la fréquence porteuse de signaux inductifs S Chaque élément binaire de la séquence est défini sur une période déterminée. Un élément binaire de la séquence binaire vaut 1 quand l'amplitude des signaux est maximale, alors qu'un élément binaire de la séquence binaire vaut 0 quand l'amplitude des signaux est diminuée d'une certaine valeur par mise en parallèle de la charge résistive Rmod dans l'ensemble résonant.It should be noted that the transmission of the data or binary sequence is made by the transponder circuit without interrupting the oscillation of the resonant assembly. The carrier frequency of the inductive signals S2 is therefore substantially the same as the carrier frequency of the inductive signals S Each binary element of the sequence is defined over a determined period. A binary element of the binary sequence is worth 1 when the signal amplitude is maximum, while a binary element of the binary sequence is worth 0 when the signal amplitude is reduced by a certain value by paralleling the resistive load Rmod in the resonant assembly.
Le circuit dénommé P4150, produit par la société EM Microelectronic-Marin SA en Suisse, peut être utilisé comme circuit transpondeur 1. Le transpondeur de ce circuit est passif et fonctionne à basse fréquence, par exemple à 125 kHz.The circuit called P4150, produced by the company EM Microelectronic-Marin SA in Switzerland, can be used as transponder circuit 1. The transponder of this circuit is passive and operates at low frequency, for example at 125 kHz.
Pour représenter de manière simplifiée la forme dans le temps des signaux inductifs transmis entre le circuit d'interrogation et le circuit transpondeur, la figure 4 montre sur le graphe supérieur des signaux inductifs transmis par le circuit d'interrogation et sur le graphe inférieur des signaux inductifs transmis par le circuit transpondeur.To represent in a simplified way the form in time of the inductive signals transmitted between the interrogation circuit and the transponder circuit, Figure 4 shows on the upper graph of the inductive signals transmitted by the interrogation circuit and on the lower graph of the signals inductive transmitted by the transponder circuit.
Le graphe supérieur et le graphe inférieur montrent la variation d'amplitude Au et Au des signaux inductifs à fréquence porteuse déterminée en fonction de données à transmettre. Les données sont transmises selon une séquence binaire traditionnelle obtenue par modulation d'amplitude. Dans le graphe supérieur, un élément binaire de la séquence binaire vaut 1 sur une période déterminée Tj quand l'amplitude des signaux est maximale, alors qu'un élément binaire de la séquence binaire vaut 0 quand l'amplitude des signaux est proche de 0 pendant au moins un laps de temps dans la période déterminée d'un élément binaire. Dans le graphe inférieur, un élément binaire de la séquence binaire vaut 1 sur une période déterminée Tt quand l'amplitude des signaux est maximale, alors qu'un élément binaire de la séquence binaire vaut 0 quand l'amplitude des signaux est diminuée d'une certaine valeur. La période déterminée Tt est inférieure à la période déterminée Tj de manière à distinguer les données transmises des données reçues. A partir de la description qui vient d'être faite, de multiples variantes de réalisation du dispositif de transmission de signaux par induction peuvent être conçues par l'homme du métier sans sortir du cadre de l'invention défini par les revendications. Le dispositif peut être appliqué dans tout domaine dans lequel un objet est monté rotatif par rapport à une structure fixe. Il peut être monté en partie sur un rotor de pales d'hélicoptère, dans une turbine à vapeur, sur un carrousel, ou sur toute autre machine à rotor. Il peut être prévu que la bobine de couplage magnétique ait une forme polygonale tout en étant positionnée de manière coaxiale par rapport à l'axe de rotation d'un objet tournant, tel que la roue du véhicule. Le circuit d'interrogation et le circuit transpondeur peuvent être munis chacun d'une bobine d'émission et d'une bobine de réception des signaux inductifs. Il peut être utilisé une modulation en fréquence pour transmettre les données dans les signaux inductifs au lieu d'une modulation d'amplitude. De plus, la fréquence des signaux inductifs transmis peut être différente dans chaque circuit. The upper graph and the lower graph show the variation in amplitude Au and Au of the inductive signals at carrier frequency determined as a function of the data to be transmitted. The data is transmitted according to a traditional binary sequence obtained by amplitude modulation. In the upper graph, a binary element of the binary sequence is worth 1 over a determined period Tj when the signal amplitude is maximum, while a binary element of the binary sequence is worth 0 when the signal amplitude is close to 0 for at least a period of time in the determined period of a binary element. In the lower graph, a binary element of the binary sequence is worth 1 over a determined period Tt when the signal amplitude is maximum, while a binary element of the binary sequence is 0 when the signal amplitude is reduced by some value. The determined period Tt is less than the determined period Tj so as to distinguish the data transmitted from the data received. From the description which has just been made, multiple alternative embodiments of the device for transmitting signals by induction can be designed by a person skilled in the art without departing from the scope of the invention defined by the claims. The device can be applied in any field in which an object is rotatably mounted relative to a fixed structure. It can be partly mounted on a rotor of helicopter blades, in a steam turbine, on a carousel, or on any other rotor machine. It can be provided that the magnetic coupling coil has a polygonal shape while being positioned coaxially with respect to the axis of rotation of a rotating object, such as the vehicle wheel. The interrogation circuit and the transponder circuit can each be provided with a transmission coil and a coil for receiving the inductive signals. Frequency modulation can be used to transmit the data in the inductive signals to the instead of amplitude modulation. In addition, the frequency of the inductive signals transmitted can be different in each circuit.

Claims

REVENDICATIONS
1. Dispositif de transmission de signaux inductifs (S1 , S2), le dispositif comprenant un circuit transpondeur (1) ayant au moins une première bobine (10), ledit circuit transpondeur étant placé sur un objet (5) susceptible de tourner autour d'au moins un axe de rotation (9) passant par l'objet, et un circuit d'interrogation (3) ayant au moins une seconde bobine (4), ledit circuit d'interrogation étant placé sur une structure à laquelle l'objet est relié, caractérisé en ce qu'une bobine de couplage (2), munie d'au moins une spire en boucle fermée, est montée sur la structure ou sur l'objet de manière coaxiale à l'axe de rotation de l'objet, ladite bobine de couplage servant d'interface de couplage inductif entre la première bobine et la seconde bobine.1. Device for transmitting inductive signals (S1, S2), the device comprising a transponder circuit (1) having at least a first coil (10), said transponder circuit being placed on an object (5) capable of rotating around at least one axis of rotation (9) passing through the object, and an interrogation circuit (3) having at least a second coil (4), said interrogation circuit being placed on a structure to which the object is connected, characterized in that a coupling coil (2), provided with at least one closed loop turn, is mounted on the structure or on the object coaxially with the axis of rotation of the object, said coupling coil serving as an inductive coupling interface between the first coil and the second coil.
2. Dispositif selon la revendication 1 , caractérisé en ce que la dimension de la bobine de couplage annulaire (2) est plus grande que la dimension de la première bobine (10) du circuit transpondeur (1), et en ce que la première bobine vue dans la direction axiale de la bobine de couplage se trouve à l'intérieur de la boucle de la bobine de couplage.2. Device according to claim 1, characterized in that the dimension of the annular coupling coil (2) is larger than the dimension of the first coil (10) of the transponder circuit (1), and in that the first coil viewed in the axial direction of the coupling coil is inside the loop of the coupling coil.
3. Dispositif selon l'une des revendications précédentes, caractérisé en ce que le plan ou l'axe des spires de la première bobine (10) est disposé parallèle au plan ou à l'axe des spires de la seconde bobine (4), ainsi qu'au plan et à l'axe de la spire de la bobine de couplage (2). 3. Device according to one of the preceding claims, characterized in that the plane or the axis of the turns of the first coil (10) is arranged parallel to the plane or the axis of the turns of the second coil (4), as well as the plane and the axis of the coil of the coupling coil (2).
4. Dispositif selon l'une des revendications précédentes, l'objet tournant étant une roue de véhicule et la structure fixe étant une partie de la carrosserie ou du châssis dudit véhicule, caractérisé en ce que le transpondeur du circuit transpondeur (1) est passif, et en ce que le circuit d'interrogation (3) transmet des signaux inductifs (S1) à une fréquence de résonance déterminée pour que le circuit transpondeur retire des signaux inductifs reçus l'énergie électrique nécessaire à son fonctionnement.4. Device according to one of the preceding claims, the rotating object being a vehicle wheel and the fixed structure being a part of the bodywork or chassis of said vehicle, characterized in that the transponder of the transponder circuit (1) is passive , and in that the interrogation circuit (3) transmits inductive signals (S1) at a determined resonant frequency so that the transponder circuit withdraws from the inductive signals received the electrical energy necessary for its operation.
5. Dispositif selon la revendication 4, caractérisé en ce que des données sont transmises par les signaux inductifs (S1 , S2) par modulation d'amplitude du circuit d'interrogation au circuit transpondeur, et du circuit transpondeur au circuit d'interrogation, lesdits signaux inductifs à basse fréquence transmis entre les deux circuits ayant une fréquence porteuse identique.5. Device according to claim 4, characterized in that data are transmitted by the inductive signals (S1, S2) by amplitude modulation from the interrogation circuit to the transponder circuit, and from the transponder circuit to the interrogation circuit, said Inductive low frequency signals transmitted between the two circuits having an identical carrier frequency.
6. Dispositif selon l'une des revendications précédentes, caractérisé en ce que le circuit transpondeur comprend au moins un capteur (13) pour la mesure d'un paramètre physique, et en ce que le circuit transpondeur (1) transmet des signaux inductifs (S2) de données relatives aux mesures effectuées par ledit capteur. 6. Device according to one of the preceding claims, characterized in that the transponder circuit comprises at least one sensor (13) for measuring a physical parameter, and in that the transponder circuit (1) transmits inductive signals ( S2) of data relating to the measurements carried out by said sensor.
7. Dispositif selon la revendication 6, caractérisé en ce que le circuit transpondeur comprend un capteur de mesure de pression et/ou un capteur de mesure de température.7. Device according to claim 6, characterized in that the transponder circuit comprises a pressure measurement sensor and / or a temperature measurement sensor.
8. Dispositif selon l'une des revendications 6 et 7, caractérisé en ce que le circuit transpondeur comprend une partie logique (12) connectée à au moins un capteur de mesure et à un ensemble résonant, qui comprend, montés en parallèle, la première bobine (10), un condensateur (C1) et une charge résistive (Rmod) en série avec un commutateur (11), et en ce que la partie logique commande le commutateur de manière à moduler en amplitude les signaux inductifs à transmettre en fonction des mesures effectuées par le ou les capteurs.8. Device according to one of claims 6 and 7, characterized in that the transponder circuit comprises a logic part (12) connected to at least one measurement sensor and to a resonant assembly, which comprises, connected in parallel, the first coil (10), a capacitor (C1) and a resistive load (Rmod) in series with a switch (11), and in that the logic part controls the switch so as to amplitude-modulate the inductive signals to be transmitted according to the measurements made by the sensor (s).
9. Dispositif selon la revendication 8, caractérisé en ce que la partie logique (12) et le ou les capteurs (13) sont réalisés dans un même substrat semi-conducteur. 9. Device according to claim 8, characterized in that the logic part (12) and the sensor (s) (13) are produced in the same semiconductor substrate.
EP04716214A 2003-03-03 2004-03-02 Device for transmitting signals by induction between a transponder circuit and an interrogation circuit Withdrawn EP1608519A1 (en)

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EP03004618A EP1454769A1 (en) 2003-03-03 2003-03-03 Apparatus for inductively transmitting signals between a transponder circuit and an interrogating circuit
EP04716214A EP1608519A1 (en) 2003-03-03 2004-03-02 Device for transmitting signals by induction between a transponder circuit and an interrogation circuit
PCT/EP2004/002057 WO2004078495A1 (en) 2003-03-03 2004-03-02 Device for transmitting signals by induction between a transponder circuit and an interrogation circuit

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