FR2899538A1 - DATA TRANSMISSION DEVICE FOR VEHICLE SEAT - Google Patents

Abstract

The device according to the invention comprises a primary electric circuit (3) with a primary coil (4) fed by a switching circuit (5a) and magnetically coupled in the air with a secondary coil (9) provided in a secondary electric circuit ( 8) having at least one permanent secondary capacitor (10). The primary electrical circuit (3) is placed in the body (2) of a vehicle, while the secondary electrical circuit (8) is placed in a removable seat (1). The switching circuit (5a) generates a pulse voltage, which causes the oscillation of the secondary electrical circuit (8) itself returning to the primary coil (4) oscillations according to its natural frequency. A frequency measuring circuit (11, 12) makes it possible to measure the natural frequency of the secondary electric circuit (8), and to deduce from it the state of this circuit: presence or absence of the seat (1), switching of sensors ( 17, 19). An obstacle detection circuit (51, 52) detects the possible presence of an obstacle (50) electrically conductive, capable of distorting the detection of the state of the secondary electric circuit (8).

Description

The present invention relates to devices for

  transmission of data between a mobile and / or removable element and a vehicle body, for example between a removable vehicle seat and the body of the vehicle, in particular for transmitting to an on-board computer the status data of a mobile element and or removable and its associated members such as a seat belt fastener detector or a passenger presence detector for the control of airbags or simply for issuing an alert signal. Traditionally, in the fixed seats for vehicles, the state detection of the bodies associated with the seats has been achieved by permanent electrical connections between the electrical circuit in the vehicle seat and the electrical circuit of the vehicle body. In the case of removable seats for vehicles, there are provided disconnectable electrical connections between the electrical circuit in the removable seat and the electrical circuit of the vehicle body. But these disconnectable electrical connections present risks of connection failure or damage by pollution or by an unsuspecting or awkward user, risks which are particularly undesirable when it comes to controlling security elements such as a seat belt sensor or passenger presence detector for controlling airbags or other sensitive operating members. To overcome these drawbacks, it has already been imagined to transmit data between the removable seats of a vehicle and the body of the vehicle by means of a magnetic coupling between a primary electrical circuit in the body of the vehicle and a secondary electrical circuit in the removable seat, the primary electrical circuit having a primary coil magnetically coupled to a secondary coil of the secondary electrical circuit. Magnetic coupling replaces the disconnectable electrical connections, and eliminates the risk of disconnection.

  For example, the document FR 2 758 502 describes a data transmission via an electrical transformer whose primary is located in the primary electric circuit of the vehicle body and whose secondary is located in the removable seat. The transformer transmits, from the vehicle body to the vehicle seat, electrical energy in the form of alternating current for supplying active electrical circuits present in the removable seat, for example a motor belonging to the seat. For data transmission, an active electrical circuit present in the secondary electric circuit 4925FDEP.doc generates switching signals which are sent to the primary electrical circuit via the transformer. In the primary electrical circuit, detection means detect the received switching signals, and deduce the state of the secondary electrical circuit. Such a device is particularly complex, requiring to provide active electronic components both in the primary electrical circuit and in the secondary electrical circuit. On the other hand, the transmission of energy from the primary electrical circuit to the secondary electrical circuit requires the use of a strong magnetic coupling by continuous magnetic circuit formed by the assembly of a primary magnetic half-circuit in the vehicle body and a secondary magnetic half-circuit in the removable seat. The assembly of the magnetic circuit requires precise positioning of the seat in a specific area of the vehicle body, to avoid the interposition of an air gap between the magnetic half-circuits. Thus, this device is expensive and is sensitive to lateral movements of the seat vis-à-vis the vehicle body. More recently, in document US 2004/0008036 A1, it has been proposed to perform, by magnetic coupling between a primary electrical circuit of the vehicle body and a secondary electrical circuit of the removable seat, either the presence detection of the seat, or the checking the operating status of a firing device included in the seat. The magnetic coupling is also realized by a magnetic circuit between a primary coil and a secondary coil. For the presence detection of the seat, the voltage of a preloaded primary capacitor is applied to the primary coil, and the impedance in the primary circuit is evaluated by measuring the primary oscillation period of the circuit constituted by the primary capacitor. and the primary coil coupled to the secondary coil when the latter is present. To control the state of the firing device, an AC voltage at a predetermined frequency is applied to the primary coil to evaluate the impedance of the primary circuit by measuring the voltage on a series primary resistance. In both cases, the result of the impedance measurement is sensitive to the state of the magnetic coupling between the primary coil and the secondary coil, so that the device is also very sensitive to possible lateral displacements of the seat vis-à- screw of the vehicle body.

  Document GB 2 287 859 also discloses a device for detecting the presence of a child seat on a vehicle seat. A primary coil primary electrical circuit is provided in the vehicle seat, and a secondary secondary coil electrical circuit 4925FDEP.d is provided in the child seat. The secondary electrical circuit may comprise a transponder, or a simple resonant circuit constituted by the secondary coil and a permanent capacitor. In the primary electrical circuit, an AC voltage is applied to the primary coil, and the overall impedance seen from the primary electrical circuit is measured. The presence of the child seat and the resonant circuit it contains increases the impedance seen from the primary electrical circuit, and thus allows the detection of the child seat. As this is an overall impedance detection, this device also remains very sensitive to the lateral movements of the child seat on the vehicle seat. It is also sensitive to the accidental presence of an electrically conductive material between the primary and secondary coils. Also known from WO 2004/098943 A1 is a magnetic coupling device in the air between a primary coil primary circuit in the body of a vehicle and a secondary coil secondary circuit in a vehicle seat. The secondary circuit has variable components such as variable inductors or capacitors connectable by switches. A square voltage is injected into the primary circuit at a frequency Fo. The connectable capacitors are chosen so that the secondary circuit excited by the primary circuit resonates, according to the possible capacitor connections, at odd multiple resonance frequencies of the excitation frequency Fo. The detection of the resonance frequency returned in the primary circuit makes it possible to distinguish the connection of the capacitors. This device, based on the excitation of the harmonics of the frequency Fo, is very sensitive to the relative position of the seat and to the possible presence of a conductive obstacle of electricity. In addition, the detection thus performed is slow because it requires waiting for the stable establishment of the resonance in the secondary circuit to know for sure its frequency. In such devices which are sensitive to the presence of an electrically conductive material between the primary and secondary coils, there may be defects in the detection of the state in which the variable components of the secondary electrical circuit are located. headquarters. For example, the presence of a conductive material between the primary and secondary coils can change the resonant frequency of the secondary electrical circuit by changing the inductance of the secondary coil, so that the measurement of the resonant frequency will not give good information on the actual state of the variable components present in the secondary electrical circuit, which themselves inform the state of a body to be controlled. The detection device 4925FDEP.doc can then for example give the information that a seat belt is correctly attached, while this is not the case. On the other hand, the presence of an electrically conductive material between the primary and secondary coils may lead the device to indicate that there is no seat, while the seat is actually present. One can of course imagine other information errors. As regards information relating to safety devices such as seat belts and the control of airbags, these possible errors are naturally unacceptable, and it is understood that these known devices have so far not given rise to a problem. satisfactory commercial exploitation. The problem proposed by the present invention is to design a new data transmission structure by magnetic coupling between a movable and / or removable element of a vehicle and the body of the vehicle, which allows a reliable transmission of data, and in particular which ensures a correct interpretation of the received data avoiding any misinterpretation in the case of an accidental presence of an electrically conductive material between the primary and secondary coils. Such an electrically conductive material may for example be a piece of aluminum wrapping paper, a bottle or pot seal, or any other metal piece that could inadvertently slip between the movable member and / or removable and the body of the vehicle. Preferably, the structure according to the invention must be particularly inexpensive because of the absence of active electronic components in the mobile and / or removable element of the vehicle, and particularly insensitive to any variations or inaccuracies in the relative positioning of the vehicle. movable and / or removable element of the vehicle vis-à-vis the vehicle body. Another object of the invention is to design such a device that can be adapted for the reliable and rapid control of several organs present in the movable element and / or removable.

  To achieve these and other aims, the invention proposes a device for transmitting data between at least one movable and / or removable element of a vehicle and a vehicle body, comprising: a primary electrical circuit with a primary coil in the vehicle body, and a secondary secondary-coil electrical circuit in the movable and / or removable vehicle member, the primary and secondary coils being coupled to each other in the air, in the absence of magnetic coupling circuit, 4925FDEP.doc - in the secondary electrical circuit, at least one variable component which varies according to a test element, - in the primary electrical circuit, an electrical signal generator for generating electrical signals emitted in the primary electrical circuit, - in the primary electrical circuit, a state signal analyzer, which, during a state detection sequence, receives and analyzes the electrical signals. states of state which result in both the emitted electrical signals and the state of said at least one variable component in the primary electrical circuit, and which derives therefrom an output signal representative of the state of the organ to be tested, and further comprising obstacle detection means, for detecting the presence and / or absence of an electrically conductive material obstacle between the primary and secondary coils, and for producing an obstacle presence signal . The obstacle presence signal allows the user to know the presence of an obstacle that may affect the interpretation of the information given by the data transmission device. The user can then refrain from considering the information received, and proceed to the removal of the obstacle. The operation of the data transmission device can then resume without risk of error.

  In practice, the obstacle detection means according to the invention may comprise: a source of magnetic flux able to generate in the space between the primary and secondary coils, during an obstacle detection sequence, a alternating magnetic flux, - a detection coil arranged in or close to the space between the primary and secondary coils and capable of producing detection signals under the effect of the alternating magnetic flux passing through it; obstacle detection signals, capable of collecting the obstacle detection signals produced by the detection coil, and capable of producing an obstacle presence signal when the obstacle detection signals produced by the detection coil are affected by the presence of the electrically conductive material of the obstacle between the primary and secondary coils during the obstacle detection sequence. Preferably, the magnetic flux source may be constituted by the primary coil fed by the electric signal generator of the primary electrical circuit. Thus, the primary coil and the electrical signal generator of the primary electric circuit are given a dual function, ie a first function for generating the state signals which will subsequently make it possible to know the state of the variable components of the electrical circuit. secondary, and a second function for generating the obstacle detection signals. The cost of the device is thus reduced.

  To facilitate the detection of an obstacle, the magnetic flux source preferably produces an alternating magnetic flux at a frequency of between about 1 KHz and about 100 KHz, preferably of the order of about 10 KHz, during the detection sequence. 'obstacle. This frequency range is suitable for optimizing the generation and effect of eddy currents occurring in the electrically conductive material constituting the obstacle. Higher frequencies reduce the detection sensitivity of the device because the primary coil does not conduct enough current. Frequencies that are too low also cause any detection sensitivity to be lost, particularly in the presence of a steel obstacle, since the eddy currents are then too weak. According to a first embodiment, the detection coil may be the primary coil itself, and the obstacle detection signals are the current flowing through the primary coil and / or the voltage across the primary coil. An interest of such a solution is the small number of coils required, which can reduce the cost of production. Alternatively, the detection coil may be a coil separate from the primary coil, offset in the vehicle body relative to the primary coil in the direction of the secondary coil. The obstacle detection signals are then preferably the open-circuit voltage collected at the terminals of the detection coil. In an application well adapted to the usual motor vehicle technology, the electrical signal generator of the primary electrical circuit, used for an obstacle detection sequence, may comprise a switching circuit having an on state and a blocked state, suitable for periodically switching in series with the primary coil a DC voltage source such as the vehicle battery. Such a circuit is particularly simple and efficient, generating easily detectable large amplitude signals. Preferably, in order to further increase the sensitivity of the device, the detection signal analyzer performs the analysis of the voltage behavior of the detection coil during a detection sequence in the vicinity of the instant when the switching circuit passes from its state passing to its blocked state. In practice, a particularly simple structure of an obstacle detection signal analyzer comprises a comparator circuit adapted to compare the voltage of the detection coil with a predetermined threshold, and to produce a comparison signal when the voltage exceeds said predetermined threshold during the detection sequence. Said predetermined threshold is chosen less than the peak voltage produced on the detection coil in the absence of electrically conductive material between the primary and secondary coils. A processing circuit then produces an obstacle presence signal in the absence of a comparison signal during the obstacle detection sequence.

  During such an obstacle detection sequence, it may be advantageous to switch the electrical signal generator of the primary electrical circuit to its off state at the moment when the current flowing through the primary coil reaches a constant predetermined value. In this way, the signals obtained on the detection coil do not depend on operating conditions such as the temperature of the circuits, since switching is always done from the same value of electric current in the primary coil. The invention can in particular be applied to the control of the members implemented in a vehicle seat. Said movable and / or removable element is then a vehicle seat. An advantage of a separate detection coil obstacle detection circuit is the possibility of making obstacle detection for several seats of the same vehicle using a single common detection signal analyzer. 'obstacle. In this case, each seat can be associated with a respective detecting coil, and all the detection coils can be connected in series with the only common obstacle detection signal analyzer. This reduces the cost of production. In practice, the device of the invention will perform obstacle detection sequences separated by time intervals during which the device performs one or more state detection sequences. During a state detection sequence, the electrical signal generator of the primary electrical circuit preferably generates signals at a frequency of between about 1 Hz and about 100 Hz, that is to say a much lower frequency than the frequency used to detect obstacles. For the detection of state, the device can advantageously be such that: 4925FDEP.doc - the secondary electric circuit is an oscillating circuit, whose natural frequency depends on the state of said at least one variable component, - during a sequence of state detection, the electrical signal generator of the primary electrical circuit switches, on the primary coil, intermittently in an on state and a blocked state, a DC voltage source such as the battery of the vehicle, - the analyzer state signals during switching of the electrical signal generator to the off state, the frequency of the voltage oscillations across the primary coil generated by the oscillations of the secondary electrical circuit. An advantage of such a solution is the high speed of the detection: a first half-oscillation period is in principle sufficient to evaluate this frequency and to deduce the state of the components of the secondary electrical circuit. In that the magnetic coils are coupled to each other in the air in the absence of a mutual coupling magnetic circuit, the apparent inductance of the secondary coil in the secondary electric circuit is insensitive to a variation. possible magnetic coupling with the primary coil. As a result, the resonant frequency of the secondary electrical circuit is insensitive to any movement between the vehicle seat and the vehicle body. Since a detection or a control based on the measurement of this resonant frequency is carried out, the device according to the invention is generally insensitive to the variations or uncertainties of the positioning of the seat on the body of the vehicle. And in the absence of any active electronic component in the secondary electrical circuit, the invention allows a low cost and reliable realization, compatible with the requirements of the automotive industry. There is provided a permanent secondary capacitor permanently connected in the secondary electrical circuit across the secondary coil constituting a passive secondary oscillating circuit having its own permanent resonant frequency. The device thus defined allows at least to detect the presence or absence of the vehicle seat. The predetermined reference oscillation frequency enabling the presence control of the vehicle seat is then the permanent resonance frequency of the secondary electric circuit when the single permanent secondary capacitor is connected. The absence of oscillation makes it possible to deduce the absence of the vehicle seat. 4925FDEP.doc To control the state of a first member present in the removable seat of the vehicle, at least a first secondary capacitor connected to the terminals of the secondary coil is provided in the secondary electric circuit via a first secondary switch itself actuated by the first seat control member and modifying its connection in the secondary electrical circuit according to the state of said first body to be controlled. In this case, a predetermined reference oscillation frequency is the permanent resonant frequency of the secondary electric circuit in the absence of actuation of the first secondary switch, and a first predetermined oscillation frequency is the resonance frequency of the electrical circuit secondary when actuating the first secondary switch. Such a secondary electrical circuit oscillating structure and modification by varying capacity allows a good detection of variations while respecting a particularly low production cost.

  Preferably, in the presence of at least one organ to be checked in the seat, the frequency comparison electronic circuit is adapted to produce different specific signals each corresponding to the recognition of one of the predetermined oscillation frequencies. A seat control member may for example be the seat belt of said seat, or a passenger presence sensor on said seat. In an application well adapted to the usual technology of motor vehicles, the electrical signal generator may comprise a switching circuit having an on state and a blocked state, able to periodically switch in series with the primary coil a source of DC voltage such that the battery of the vehicle. In this case, the electronic frequency measuring circuit may advantageously perform the frequency measurement of the voltage oscillations at the terminals of the primary coil when the switching circuit goes from its on state to its off state. Switching to the off state is indeed the most favorable configuration to facilitate the detection and measurement of electrical oscillations in the primary electrical circuit: the primary coil undergoes a fast commutation which excites considerably the secondary electric circuit, and simultaneously the coil The primary is disconnected and is no longer influenced by the DC voltage source, which makes it easy to detect electrical oscillations in the form of AC voltage oscillations across the primary coil. The electronic frequency measuring circuit may then comprise a comparator circuit adapted to detect the zero crossings of the oscillatory voltage component at the terminals of the primary coil, and a counter circuit for measuring the time between successive detections of passage. zero provided by the comparator circuit. In this case, the comparator circuit and the counter circuit can be advantageously implemented in a microcontroller receiving, after conditioning by an amplifier circuit, the voltage across the primary coil.

  An improvement in reliability can still be obtained by providing means for detecting possible failures of the secondary electrical circuit. For this, according to an advantageous embodiment, the device is such that: - a control coil and a control capacitor are connected in parallel to the secondary coil, - the frequency comparison electronic circuit is adapted to produce a fault signal when measuring an oscillation frequency which differs from the resonant frequencies of the secondary electric circuit obtained in the presence of the secondary coil, the permanent secondary capacitor, the control coil and the control capacitor. In all embodiments, the coils may advantageously be constituted by simple conductive tracks provided on printed circuits. Better redundancy, to detect possible failures of the secondary electrical circuit, is obtained by providing that the secondary coil and the permanent secondary capacitor are arranged on a first face of the printed circuit, while the control coil and the control capacitor are arranged on the second opposite side of the printed circuit. Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, made with reference to the appended figures, among which: FIG. 1 is an electrical block diagram of a transmission device data according to a first embodiment of the present invention; FIG. 2 is a time diagram illustrating the waveforms of the voltage of the electrical signal generator, the voltage in the secondary electrical circuit and the voltage measured at the terminals of the primary coil during a detection sequence of state; Figure 3 is an electrical block diagram of a device according to a second embodiment of the invention; FIG. 4 is a schematic illustration of an electronic frequency measuring circuit and a frequency comparison electronic circuit according to an embodiment of the invention for state detection; - Figure 5 schematically illustrates, in section, an arrangement of the elements of the secondary electrical circuit on a printed circuit; FIG. 6 is a timing diagram illustrating the waveforms of the main electrical signals during an obstacle detection sequence on a separate detection coil, namely the control voltage of the electrical signal generator, the current in the primary coil, and the voltage collected across the coil of detection; FIG. 7 schematically illustrates an electronic circuit for analyzing obstacle detection signals in an embodiment of the invention adapted to detection on a separate detection coil according to FIG. 6; FIG. 8 schematically illustrates the application of obstacle detection to a plurality of vehicle seats with a plurality of separate detection coils and a single obstacle detection signal analyzing circuit; and FIG. 9 is a timing diagram illustrating the waveforms of the main electrical signals during an obstacle detection sequence on a detection coil constituted by the primary coil. In the embodiment illustrated in FIG. 1, the data transmission device according to the invention makes it possible to transmit state data between a removable vehicle seat 1, schematically illustrated in phantom, and a vehicle body 2 also schematically illustrated in phantom. First of all, the means of the device and their operation during a state detection sequence of the organs associated with the vehicle seat will be described.

  In the vehicle body 2, there is provided a primary electrical circuit 3 having a primary coil 4 and an electrical signal generator 5 connected to the primary coil 4 for applying to the primary coil 4 relatively low frequency electrical signals. Said electrical signals may be, for example, a voltage step, or a square voltage of given frequency FE. The electrical signal generator 5 as illustrated comprises a switching circuit 5a such as a transistor, able to periodically switch in series 4925FDEP.doc with the primary coil 4 a DC voltage source Vo such that the vehicle battery connected to the input terminals 6 and 7. The seat 1 contains a secondary electrical circuit 8, comprising a secondary coil 9 to which is permanently connected a permanent secondary capacitor 10. The secondary coil 9 and the secondary secondary capacitor 10 constitute a secondary electrical circuit passive type of oscillating type, having a permanent resonant frequency FSP given by the formula: FSP = 1 / 2rr.JLCo, L being the own inductance of the secondary coil 9, Co being the capacity of the permanent secondary capacitor 10.

  The frequency FE of the electrical signal generator 5 is deliberately chosen to be much smaller than the permanent resonance frequency FSP of the secondary electrical circuit 8. The primary electrical circuit 3 furthermore comprises a state signal analyzer, consisting for example of a circuit frequency measuring electronic circuit 11 and a frequency comparison electronic circuit 12. The frequency measuring electronic circuit 11 measures at the terminals of the primary coil 4 the frequency of the voltage oscillations resulting from the electrical oscillations of the secondary electrical circuit 8. The frequency comparison electronic circuit 12 receives the signals emitted by the electronic frequency measuring circuit 11, and is adapted to deduce, by comparison with predetermined frequencies, the presence and / or the state of the secondary electrical circuit 8. understand the principle operation of this device, one will refer now in Figure 2.

  This figure illustrates a timing diagram in which the curve 13 illustrates the waveform of the control voltage UE of the switching circuit 5a: at time t0, the switching circuit 5a connects the DC voltage source Vo to the terminals of the primary coil 4, and this voltage is kept constant until time t1. At time t1, the switching circuit 5a disconnects the DC voltage source Vo, and the disconnection is maintained until a time t2 at which the DC voltage source Vo is connected again. On the curve 14, the electrical oscillations of the secondary electrical circuit 8 are illustrated in the form of an oscillatory voltage V2 across the secondary coil 9 from the instant t1: this voltage is a damped sinusoid at the frequency resonance of the secondary electrical circuit 8, which starts at time t1 and gradually amortized. These electrical oscillations 14 of the secondary electrical circuit 4925 result from the magnetic coupling between the primary 4 and secondary 9 coils, which transmits to the secondary coil 9 an excitation pulse resulting from the sudden disconnection of the DC voltage source. at time t1 across the primary coil 4. By choosing a switching frequency of the switching circuit 5a substantially lower than the resonant frequency of the secondary electrical circuit 8, undisturbed and easily measurable damped sinusoidal electric oscillations 14 are generated. during the disconnection steps of the DC voltage source Vo.

  Curve 15 illustrates the electrical oscillations of the primary electrical circuit 3, in the form of a damped oscillatory voltage V, which appears at the terminals of the primary coil 4, and which has a waveform similar to electrical oscillations. of the secondary electrical circuit 8. These electrical oscillations 15 of the primary electrical circuit 3 result from the magnetic coupling between the primary 4 and secondary 9 coils, coupling which in turn returns to the primary coil 4 an oscillatory voltage at the resonant frequency of the electrical circuit 8. Thus, the voltage across the primary coil 4 has an oscillation frequency equal to the natural frequency of the secondary electrical circuit 8, which frequency can be measured for example by measuring the period T illustrated in Figure 2 The electronic frequency measuring circuit 11 measures this period T and deduces the corresponding frequency F = 1 / T. Then, the frequency comparison electronic circuit 12 compares this measurement F with predetermined frequencies, to deduce for example the presence or absence of the seat 1 and its secondary electrical circuit 8, or to deduce the value of the present capacity. in the secondary electrical circuit 8 if it is assumed that the inductance value of the secondary coil 9 is constant.

  In the embodiment of Figure 1, the secondary electrical circuit 8 further comprises a first secondary capacitor 16 connected to the terminals of the secondary coil 9 via a first secondary switch 17 itself actuated by a first member to control seat 1 and changing the connection of the first secondary capacitor 16 according to the state of said first member. For example, the first member may be a seat belt associated with the seat 1, the engagement actuates a first secondary switch 17 mechanical switching all or nothing. The secondary electrical circuit 8 of FIG. 1 further comprises a second secondary capacitor 18 connected to the terminals of the secondary coil 9 via a second secondary switch 19 which itself is actuated by a second member to be monitored. seat 1 and modifying itself the connection of the second secondary capacitor 18 according to the state of said second member. For example, the second member may be a presence sensor of a passenger on the seat 1 sensor that causes the switching of the second secondary switch 19. In some cases, the presence sensor may be a mechanical switch in all or nothing. However, the invention also makes it possible to use a passenger-sensing passenger-side passenger presence sensor, which is of a capacitive nature when it is not activated (passenger absent), and which is short-circuited when it is activated (passenger present). This embodiment has been illustrated in dotted lines, by the capacitor 17a across the switch 17. In operation, the first secondary capacitor 16 is found either connected directly to the secondary coil 9 (passenger present), or connected in series with the capacitor 17a and with the secondary coil 9 (passenger absent). The device according to the invention can also ensure the diagnosis of the passenger detection web when it is at rest (passenger absent).

  In all embodiments, the secondary switches modify the connection of the associated secondary capacitors, either by connecting them to the terminals of the secondary coil 9, or by disconnecting them, or by connecting them in series with a capacitive element. So that the device according to the invention can differentiate the respective states of the seat members 1 and their respective switches 17 and 19, and can also differentiate the state of presence or absence of the seat 1, the capacitances of the capacitors 10, 16 and 18 are chosen so that the resonance frequencies of the different connection states differ from each other. Thus, a reference resonant frequency equal to the resonant frequency of the secondary electrical circuit 8 formed of the secondary coil 9 and the only permanent secondary capacitor 10 is chosen. A first predetermined oscillation frequency equal to the resonance frequency is chosen. of the secondary electrical circuit 8 during the actuation of the first secondary switch 17, for example during the connection of the permanent secondary capacitor 10 and the first secondary capacitor 16. This first predetermined oscillation frequency must be different from a second frequency of predetermined oscillation equal to the resonant frequency of the secondary electric circuit 4925 when the second secondary switch 19 is actuated, for example when the permanent secondary capacitor 10 and the secondary secondary capacitor 18 are connected. In other words, the capacity of the second secondary capacitor 18 do it should be different from the capacity of the first secondary capacitor 16. Finally, there will be provided a third predetermined oscillation frequency equal to the resonant frequency of the secondary electric circuit 8 when the first secondary switch 17 and the second secondary switch are actuated. 19, for example during the connection of the permanent secondary capacitor 10 in parallel with the second secondary capacitor 18 and the first secondary capacitor 16. The frequency comparison electronic circuit will be adapted to produce different specific signals, each corresponding to the recognition of one of the predetermined oscillation frequencies.

  Preferably, a stabilizing resistor 20 is connected in parallel to the primary coil 4, so as to limit the reverse voltage caused by the primary coil 4 at time t1, and so as to obtain a clean and exploitable signal. In the embodiment diagrammatically illustrated in FIG. 4, the electronic frequency measuring circuit 11 comprises a comparator circuit 11a receiving on its inverting input the voltage signal at the terminals of the primary coil 4 and receiving on its non-inverting input a signal continuous equal to a reference voltage E, for example a zero voltage. The comparator circuit 11a produces at its output a switching voltage sent to a counter circuit 11b which measures the time flowing between successive switches at the output of the comparator circuit 11a, giving the value of the oscillation period at the terminals of the primary coil 4, and thus giving the value of the frequency of the oscillations. The output of the counter circuit 11b is sent to a microprocessor or microcontroller 12a associated with a memory 12b constituting the electronic frequency comparator circuit 12. In the memory 12b, the predetermined oscillation frequencies have been recorded, whether the microprocessor or microcontroller 12a will compare against the period it receives from the counter circuit 11b, to deduce a recognition signal of the state of the organs of the seat 1.

  The same microprocessor or microcontroller 12a can manage all the seats of the vehicle. The microcontroller or microprocessor 12a 4925FDEP.doc can also control the switching transistor constituting the switching circuit 5a. Referring now to Figure 3, which illustrates another embodiment of the data transmission device according to the invention.

  In this second embodiment, we find the essential elements of the embodiment of Figure 1, and these essential elements are identified by the same reference numerals, so they will not be described again. A first difference lies in the absence of the stabilizing resistor 20 at the terminals of the primary coil 4, illustrating that it is possible, in certain cases, to suppress this stabilization resistor when the frequency measuring circuits allow it. A second difference lies in the absence of a second secondary capacitor 18, the embodiment taking again only the permanent secondary capacitor 10 and the first secondary capacitor 16, for the control of a single organ and the presence control of the seat 1 A third difference is the presence of a control coil 9a and a control capacitor 10a connected in parallel with the first secondary coil 9. The two coils 9 and 9a can have the same inductance. This arrangement makes it possible to detect a possible failure of the secondary electrical circuit 8: in the event of a fault on one of the capacitors 10, 16 or 10a, or in the event of a break in a conductor of at least one of the coils 9 or 9a, the secondary electrical circuit 8 will have a resonance frequency different from the predetermined oscillation frequencies corresponding to the connection of the only permanent secondary capacitors 10 and control 10a or capacitors 10, 10a and 16. The frequency comparison electronic circuit 12 will be then adapted to produce a fault signal when measuring such an oscillation frequency which differs from the resonant frequencies of the secondary electric circuit 8 obtained in the presence of the secondary coil 9 and the control coil 9a with the secondary capacitor permanent 10 and the control capacitor 10a, or with the capacitors 10, 10a and 16. If the seat 1 is not present, there will be no signal in reception, that is to say no measured oscillation frequency of the primary coil 4, and therefore an error message will be sent. This embodiment of FIG. 3, comprising a control coil 9a, can also be used in the presence of a stabilizing resistor 20 and / or in the presence of a second secondary capacitor 18 and a second switch secondary 19. Preferably, as illustrated in Figure 5, the secondary electrical circuit 8 comprises components distributed on both sides of a printed circuit 100: the secondary coil 9 and the secondary secondary capacitor 10 are arranged on a first face 100a of the printed circuit 100, while the control coil 9a and the control capacitor 10a are disposed on the opposite second face 100b of the printed circuit 100. This ensures a real redundancy to detect possible defects of the secondary electrical circuit 8. On will now describe the means according to the invention, and their operation, for the detection of an obstacle. Referring again to the embodiments of Figures 1 and 3. The objective is then to detect an obstacle 50 of electrically conductive material, such as a sheet of an electrically conductive material, which would be engaged between the primary coil 4 and the secondary coil 9. For this, the invention provides a source of magnetic flux capable of generating in the space between the primary coil 4 and secondary 9 an alternating magnetic flux, a detection coil arranged in or in the immediate vicinity of the space between the primary 4 and secondary 9 coils, and an obstacle detection signal analyzer which collects and analyzes the obstacle presence signals present on the detection coil. In the embodiment illustrated in the figures, the magnetic flux source is constituted by the primary coil 4 itself, fed in a chopped manner by the electrical signal generator 5 of the primary electrical circuit. The detection coil 51 is a coil distinct from the primary coil 4, offset in the vehicle body 2 relative to the primary coil 4 in the direction of the secondary coil 9 to be in the space between the primary coil 4 and secondary 9, and near the obstacle 50 to be detected.

  An obstacle detection signal analyzer 52 connected to the terminals of the detection coil 51 receives the voltage across the detection coil 51 which is itself in open circuit. The obstacle detection signal analyzer 52 is able to produce an obstacle presence signal when the obstacle detection signals at the terminals of the detection coil 51, that is to say the voltage signals. are affected by the presence of the electrically conductive material obstacle 50 between the primary 4 and secondary 9 coils during the obstacle detection sequence. It should be noted that the 4925FDEP.doc obstacle detection signals are affected by the eddy currents that develop in the electrically conductive material of the obstacle 50. In operation during an obstacle detection sequence , the electrical signal generator 5, which comprises the switching circuit 5a such as a transistor, periodically switches in series with the primary coil 4 the DC voltage source Vo at a frequency FO higher than the frequency FE previously described for a sequence state detection. The timing diagram of FIG. 6 is now considered, which better explains the differences in operation between the obstacle detection sequence and the state detection sequence. The curve 53 illustrates the waveform of the control voltage UO of the switching circuit 5a during such an obstacle detection sequence: at time t3, the switching circuit 5a connects the direct voltage source Vo. at the terminals of the primary coil 4, and this voltage is kept constant until time t4. At time t4, the switching circuit 5a disconnects the voltage source Vo and the disconnection is maintained until a time t5 at which the DC voltage source Vo is connected again. Preferably, the instant t4 is the instant at which the current Il in the primary coil 4 reaches a predetermined constant value I, o.

  On the curve 54, the waveform of the current Il which circulates in the primary coil 4 is illustrated by the effect of the intermittent switching of the voltage source Vo. This waveform includes a relatively slow exponential rise 54a, and a fast exponential descent 54b. Curve 55 illustrates the waveform of the voltage UM that is recovered across the detection coil 51: at time t3, the voltage increases abruptly by following the voltage step of the voltage U0, then decreases rather slowly according to the curve 55a, to be reversed suddenly at time t4 as a negative pulse 55b of large amplitude, which then returns to the zero voltage in the form of an exponential curve 55c. It is this negative pulse 55b that is used for the detection of the obstacle. For this, the property is used according to which this negative pulse 55b has an amplitude which strongly depends on the presence or absence of an electrically conductive material in the vicinity of the detection coil 51 between the primary coil 4 and the secondary coil 9. This is done under the conditions in which the eddy currents developing in the obstacle 50 substantially affect the amplitude of the negative pulse 55b. 4925FDEP.doc The solid line curve of the negative pulse 55b schematically represents the pulse in the absence of the obstacle 50, while the dashed curve represents the pace of the negative pulse 55b in the presence of an obstacle 50 of electrically conductive material: it can be seen that, in the presence of an obstacle 50, the amplitude of the negative pulse 55b is greatly reduced, because of the eddy currents that develop in the conductive material of the electricity in the magnetic field generated by the primary coil 4. We will then compare the amplitude of the negative pulse 55b with a threshold UM0, and we can deduce that when the negative pulse 55b has a higher amplitude at the threshold voltage UM0, then there is no obstacle, whereas when the negative pulse 55b has an amplitude lower than the voltage UM0, then there is certainly an obstacle in electrically conductive material. FIG. 7, which schematically illustrates a possible structure for the obstacle detection signal analyzer 52 of FIG. 1. In this embodiment, the voltage at the terminals of the detection coil 51 is sent to a comparator. 56 which compares it to a voltage UM0, which then produces on its output 56a a pulse signal 56b when there is no obstacle 50, and which produces on its output 56a a signal 56c devoid of impulse when there is an obstacle 50. This signal is sent to a processing circuit 57 which will generate, at its output 57a, an output signal present when there is no pulse on the output 56a of the comparator 56 while a negative pulse 55b is present or that the control voltage UO returns to zero. Referring again to FIG. 1, it can be seen that the output signal of the obstacle detection signal analyzer 52 is sent to a decision circuit 58 which also receives the signals produced by the frequency comparator 12. The decision circuit 58 transmits on its output 58a the status data produced by the frequency comparison electronic circuit 12 as long as an obstacle presence signal is not produced by the obstacle detection signal analyzer. 52, and inhibits the transmission of status data from the frequency comparator 12 when the obstacle detection signal analyzer 52 produces an obstacle detection signal. In this way, the use of the erroneous state data possibly coming from the frequency comparator 12 is avoided in the event of the presence of an obstacle 50.

  The device according to the invention is controlled so as to perform obstacle detection sequences separated by time intervals during which the device performs one or more state detection sequences. For this purpose, the electrical signal generator 5 and the decision circuit 58 are controlled by a control circuit 60 in the following manner: during an obstacle detection sequence, the decision circuit 58 considers only the signals produced by the obstacle detection analyzer 52, and inhibits the signals produced by the frequency comparator 12, while the electrical signal generator 5 is driven at a relatively high frequency FO, of between approximately 1 KHz and 100 KHz about, preferably about 10 KHz; during a state detection sequence, the control circuit 60 drives the electric signal generator 5 at low FE frequency, between about 1 Hz and about 100 Hz, and it drives the decision circuit 58 so as to inhibit the signals from the obstacle detection signal analyzer 52, this time transmitting the signals produced by the frequency comparator 12 if the previously stored information indicates the absence of an obstacle 50. FIG. an obstacle detection embodiment for a plurality of seats. This figure shows three seats 61a, 61b and 61c, each associated with a respective detection coil 51a, 51b and 51c. Each seat is associated with a respective primary electric circuit 3a, 3b and 3c each having a respective primary coil 4a, 4b and 4c. The three detection coils 51a, 51b and 51c are connected in series with a single common analyzer of obstacle detection signals 52. The primary electrical circuits 3a, 3b and 3c are sequentially ordered one after the other, in order to detect sequence possible obstacles under the respective seats 61a, 61b and 61c. In the embodiment which has just been described with reference to FIG. 6 for the detection of an obstacle, the detection coil 51 is a coil distinct from the primary coil 4. Alternatively, the primary coil 4 can be used as means for generating obstacle detection signals, which avoids providing an additional separate detection coil. In this case, the obstacle detection signals consist of the voltage at the terminals of the primary coil 4 and / or the current flowing through the primary coil 4, after the switches of the electrical signal generator 5. As in the mode of In the preceding embodiment, the electrical signal generator 5 comprises a switching circuit 5a which periodically switches in series with the primary coil 4, the DC voltage source Vo at a frequency higher than the frequency FE used for the state detection sequence. The timing diagram of FIG. 9, which represents the waveform of the main electrical signals used for obstacle detection in this embodiment, is considered. The curve 53 again illustrates the waveform of the control voltage UO of the switching circuit 5a during such an obstacle detection sequence. We find the same shape as in Figure 6 above. The curve 54 illustrates the waveform of the current Il which flows in the primary coil 4 by the effect of the intermittent switching of the voltage source Vo. This waveform includes a relatively slow exponential rise 54a, and a fast exponential descent 54b. Note that the exponential rise 54a can take shapes 54a1 or 54a2 relatively different, corresponding to time constants that differ depending on the state of the secondary electrical circuit. It is thus possible to know the state of the secondary electrical circuit by analyzing the shape of the curve 54. For example, it is possible to locate the instants t6, t7 or t8 at which the curve 54 reaches a current II, of reference, each instant t6, t7 or t8 may correspond to a particular state of the secondary electrical circuit. The curve 66 illustrates the waveform of the voltage U1 across the primary coil 4 during such an obstacle detection sequence: at time t3, the voltage U1 becomes equal to vo, and is kept constant. (curve 66a) until time t4 to reverse suddenly at time t4 as a negative pulse which then returns to zero voltage by an exponential curve 66b. The exponential curve 66b has a shape that depends on the state of the secondary electrical circuit, which can assume a shape 66b1 or 66b2. On the other hand, the amplitude of the negative pulse may vary depending on the state of the secondary electrical circuit, as illustrated by the difference in amplitude DU. It is therefore possible to know the state of the secondary electric circuit by detecting the shape 66b1 or 66b2 or the amplitude variation DU, for example by locating the times t9, t10 or t11 at which the curve 66b reaches a determined voltage U, r.

  One can also combine the detection of the current Il according to the curve 54a and the voltage U, according to the curve 66b. The invention can find application in particular in the control of the organs of a removable vehicle seat, for example one of the following organs or a combination of several of them: - presence of a seat, - presence and / or weight of a passenger on the said seat, - condition of tension and / or fastening of a passenger's seat belt, 4925FDEP.doc - position of a headrest, - inclination of the backrest of a seat, - position of a seat. The present invention is not limited to the embodiments which have been explicitly described, but includes the various variants and generalizations thereof within the scope of the claims below.

4925FDEP.doc

Claims (2)

  1 - Device for transmitting data between at least one mobile and / or removable element (1) of a vehicle and a vehicle body (2), comprising: - a primary electric circuit (3) with a primary coil (4) in the vehicle body (2), and a secondary secondary circuit (8) with secondary coil (9) in the movable and / or removable vehicle element (1), the primary (4) and secondary (9) coils being coupled to one another in the air, in the absence of a mutual coupling magnetic circuit, - in the secondary electrical circuit (8), at least one variable component (16, 18) which varies according to a test member, - in the primary electrical circuit (3), an electrical signal generator (5) for generating electrical signals emitted in the primary electrical circuit (3), - in the primary electrical circuit (3), a test analyzer state signals (11, 12) which, during a state detection sequence, receives and analyzes the electronic signals in the primary electric circuit (3) both emitted electrical signals and the state of said at least one variable component (16, 18), and deriving therefrom an output signal representative of the state of the organ to be tested, characterized in that it further comprises obstacle detection means (51, 52) for detecting the presence and / or absence of an obstacle (50) of conducting material electricity between the primary (4) and secondary (9) coils, and to produce an obstacle presence signal. 2 - Device according to claim 1, characterized in that the obstacle detection means comprise: a source of magnetic flux (4, 5) able to generate in the space between the primary (4) and secondary (9) coils ), during an obstacle detection sequence, an alternating magnetic flux, - a detection coil (4, 51) disposed in or in close proximity to the space between the primary (4) and secondary (4) coils ( 9) and capable of producing detection signals under the effect of the alternating magnetic flux which passes through it, - an obstacle detection signal analyzer (52), able to collect the obstacle detection signals produced by the coil detection device (51), and capable of producing an obstacle presence signal when the obstacle detection signals produced by the detection coil (51) are affected by the presence of the electrically conductive material of the obstacle (50) between the primary coils (4) and seconda ire (9) during the obstacle detection sequence. 4925FDEP.doc3 ù Device according to claim 2, characterized in that the source of magnetic flux is constituted by the primary coil (4) fed in a chopped manner by the electrical signal generator (5) of the primary electrical circuit. 4 - Device according to claim 3, characterized in that the magnetic flux source (4, 5) produces an alternating magnetic flux at a frequency of between about 1 KHz and about 100 KHz, preferably of the order of about 10 KHz , during the obstacle detection sequence. 5 - Device according to any one of claims 2 to 4, characterized in that the detection coil is the primary coil (4), and the obstacle detection signals are the current (I,) traveling through the primary coil ( 4) and / or the voltage (U) at the terminals of the primary coil (4). 6 - Device according to any one of claims 2 to 4, characterized in that the detection coil (51) is a separate coil of the primary coil (4), and is offset in the vehicle body (2) in the direction of the secondary coil (9). 7 - Device according to claim 6, characterized in that the electrical signal generator (5) of the primary circuit (3) comprises a switching circuit (5a) having an on state and a blocked state, able to periodically switch in series with the primary coil (4), a DC voltage source (Vo) such as the vehicle battery. 8 - Device according to claim 7, characterized in that the detection signal analyzer (52) performs the analysis of the voltage behavior of the detection coil (51) during a detection sequence in the vicinity of the moment when the switching circuit (5a) switches from its on state to its off state. 9 ù Device according to one of claims 7 or 8, characterized in that the obstacle detection signal analyzer (52) comprises a comparator circuit (56) adapted to compare with a predetermined threshold (UMo) the voltage of the detection coil (51), and for producing a comparison signal when the voltage exceeds said predetermined threshold (UMo) during the detection sequence, said predetermined threshold (UMo) being chosen lower than the peak voltage produced on the detection coil (51) in the absence of electrically conductive material (50) between the primary (4) and secondary (9) coils. 10 ù Device according to one of claims 8 or 9, characterized in that the device performs obstacle detection sequences separated by time intervals during which the device performs one or more state detection sequences. 4925FDEP.doc11 - Device according to claim 10, characterized in that, during a state detection sequence, the electrical signal generator (5) of the primary electrical circuit (3) generates signals at a frequency of between about 1 Hz. and about 100 Hz. 12 - Device according to any one of claims 7 to 11, characterized in that, during an obstacle detection sequence, the electrical signal generator (5) of the primary electrical circuit (3) switches to its off state when the current flowing through the primary coil (4) reaches a constant predetermined value (Ilo). 13 û Device according to any one of claims 7 to 12, characterized in that the obstacle detection relative to several seats (61a, 61b, 61c) of the same vehicle is provided by associating with each seat (61a, 61b , 61c) a respective detecting coil (51a, 51b, 51c), and serially connecting all the detection coils (51a, 51b, 51c) with a single common obstacle detection signal analyzer (52). 14 - Device according to any one of claims 1 to 13, characterized in that: - the secondary electric circuit (8) is an oscillating circuit, whose natural frequency depends on the state of said at least one variable component (16, 18), - during a state detection sequence, the electrical signal generator (5) of the primary electrical circuit (3) switches, on the primary coil (4), intermittently into an on state and a state. blocked, a DC voltage source (Vo) such as the vehicle battery, - the state signal analyzer (11, 12) scans, when switching the electrical signal generator (5) to the blocked state , the frequency of the voltage oscillations at the terminals of the primary coil (4) themselves generated by the oscillations of the secondary electrical circuit (8). 15 - Device according to claim 14, characterized in that the secondary electric circuit (8) comprises: - a permanent secondary capacitor (10), permanently connected in the secondary electric circuit (8) to the terminals of the secondary coil (9) , constituting a passive secondary oscillating circuit having its own permanent resonance frequency, - at least a first secondary capacitor (16, 18) associated with a first secondary switch (17, 19) modifying its connection in the secondary electrical circuit (8) by function of the state of an organ to be controlled. 4925FDEP.doc16 - Device according to any one of claims 1 to 15, characterized in that the movable element and / or removable (1) is a vehicle seat. 17 - Device according to claim 16, characterized in that the organs to be tested may comprise one of the following organs, or a combination of several of them: - presence of a seat, - presence and / or weight of a passenger on said seat, - condition of tension and / or fastening of a seatbelt of a passenger, - position of a headrest, - inclination of the backrest of a seat, - position of a seat .