EP2146866A1

EP2146866A1 - Measuring system and measuring method for detecting at least one frequency-independent electrical variable

Info

Publication number: EP2146866A1
Application number: EP08750209A
Authority: EP
Inventors: Marcus Kandler
Original assignee: Takata Petri AG
Current assignee: Takata AG
Priority date: 2007-05-09
Filing date: 2008-05-08
Publication date: 2010-01-27
Also published as: JP5203452B2; JP2010528258A; CN101678780A; DE102007022463A1; US20100057304A1; CN101678780B; WO2008138870A1

Abstract

The invention relates to a measuring system comprising at least one first measuring means for detecting at least one frequency-independent electrical variable, an evaluation unit for detecting the temporal behavior of the frequency-independent electrical variable, the evaluation unit automatically generating a signal based on the detection of the evolution in time of the frequency-independent electrical signal, said signal being at least partially equivalent to a frequency-dependent signal. The invention also relates a measuring method. According to said method, at least one first measuring means detects at least one frequency-independent electrical variable and an evaluation unit detects the temporal behavior of the frequency-independent electrical variable, the evaluation unit automatically generating a signal based on the detection of the evolution in time of the frequency-independent electrical variable, said signal being at least partially equivalent to a frequency-dependent signal.

Description

Measuring system and measuring method for detecting at least one frequency-independent electrical variable

description

The invention relates to a measuring system and a measuring method, in particular for a motor vehicle.

Measuring methods are known from the prior art, which usually rely on the detection of frequency-dependent electrical quantities in order to detect different states. Thus, voltages, current intensities, charge quantities and capacities or other electrical or electromagnetic variables are regularly measured as a function of an applied frequency in order to be able to make statements about a change in state within a system to be monitored by means of their change or value relative to a reference value or by means of their course ,

Such measuring methods or measuring systems are usually also used in the field of seat occupancy detection in a motor vehicle. For example, US Pat. No. 6,563,231 B1 describes a vehicle occupant sensor whose electric field sensor has a plurality of first electrodes that can be accommodated in a vehicle seat and at least one second electrode. Via a measuring circuit connected to the first and the second electrode, according to an aspect of the invention, the level of a capacitance between a vehicle occupant on a motor vehicle seat and a ground of the circuit can be controlled. For this purpose, the measuring circuit generates a signal as a function of a property influencing the electric field of an object adjacent to the electric field sensor. This is not only intended to detect the seat occupancy of a motor vehicle seat but also to determine whether the vehicle occupant located on the motor vehicle is located within a risk area. If this is the case one is Shutting down the safety systems, in particular the airbag, necessary to minimize the risk of injury in the event of a crash.

In accordance with US 6,563,231 B1 and the associated family members e.g. Thus, US Pat. Nos. 7,180,306 B2, 6,825,765 B2, 6,598,900 B2, 6,577,023 B1, 6,563,231 B1, 6,520,535 B1, 6,517,106 B1, 6,445,294 B1, 6,392,542, 6,378,900 B1, 6,283,504 B1 and US Pat a seat occupancy detection for a motor vehicle seat as a function of a frequency-dependent variable described. The basis is always the influence of an electric field, which is applied to an electrode and by the application of a frequency-dependent electrical variable, e.g. an oscillating current is generated. An object to be detected affects the electric field, i. it changes e.g. the capacitance of the electrode relative to a ground or a reference potential. Thus, a frequency-dependent signal or a frequency-dependent variable is applied to the electrode and detected at the same time, so that its change can be assigned to a defined change of state within the electric field (for example a seat occupancy).

Likewise, US Pat. No. 6,609,055 B2 describes a vehicle occupant recognition system which decides on the occupancy situation of a vehicle seat and thus on the activation or deactivation of safety systems via logical links of a plurality of capacitances thus measured and weight values determined via weight sensors.

Fundamental to all these measuring methods or measuring systems is thus the generation of a frequency-dependent signal in order to determine based on which the seat occupancy or the type of seat occupancy and possibly also to be able to draw conclusions about the posture and stature of a vehicle occupant.

Such a measuring method or measuring system becomes problematic if, due to one or more modifications made within the system to be monitored, a previously unambiguous assignment of the generated signal to a defined state or a defined state change is no longer possible.

For example, the installation of a child seat according to the ISOFIX standard is such a modification for the already mentioned measuring methods or measuring systems for detecting a motor vehicle seat occupancy. Here, ISOFIX is a special form for the secure attachment of child seats or in general Child restraint systems in vehicles. About a standard connector of the child seat or the child restraint system is firmly connected to the body of the motor vehicle or the seat frame of the vehicle seat. In this way, on the one hand, the risk of incorrect operation is reduced and the protective effect is improved.

If now an ISOFIX compatible child seat is used, then this is electrically connected via its connection with the body or with the seat frame of the vehicle seat and thus possibly also grounded. However, the measuring principles mentioned measure, for example, even capacitances of an electrode relative to a ground or ground and distinguish a child seat arranged on the motor vehicle seat from a person by a smaller (capacitive) influencing of the electric field. Likewise, typically a reactive and a resistive component of an impedance between a sensor and a ground is measured, and then a distinction is made using real and imaginary part of the current, whether it is a person sitting on the vehicle seat or a child seat , However, an earthed or grounded ISOFIX child seat is indistinguishable from a human for the corresponding measurement system because it forms a ground shield that completely shields the sensing field, i.e., the frequency dependent quantity (e.g., a sine field). The signals generated by the measuring system for an ISOFIX child seat and a person are almost the same and no longer permit an error-free or unambiguous assignment of the generated signal to a specific type of seat occupancy.

The invention is therefore based on the problem of providing an improved measuring system and an improved measuring method, in particular for a motor vehicle.

This problem is solved by a measuring system having the features of claim 1 and a measuring method having the features of claim 15.

Thereafter, a measuring system is provided with at least one first measuring means for detecting at least one frequency-independent electrical variable, in particular a charge, with an evaluation unit for detecting the temporal behavior of the frequency-independent electrical variable (eg charge and discharge times of a capacitor), wherein the evaluation unit the temporal Course of the frequency-independent electrical variable converts into a signal, which in particular a connection state between two components (eg between a child seat and a seat of the motor vehicle) characterized, wherein that signal a frequency-dependent signal is at least partially equivalent. That is, statements about the behavior of frequency-dependent quantities can be made by means of the measuring system.

Therefore, it is also possible to make statements about the behavior of at least one frequency-dependent variable or even several frequency-dependent variables that were previously impossible due to a purely frequency-dependent measurement. For example, by detecting the time course of the frequency-independent variable and simultaneous detection of the frequency-dependent variable, the behavior of the frequency-dependent variable can be analyzed when the state of the measured or monitored system changes. For example, the reaction or the absence of a response of the frequency-dependent variable can thus be uniquely terminated and evaluated if a change in state has only been detected or determined by means of an equivalent signal of the frequency-independent variables.

In this connection, reference is again made, by way of example, to the child seats already mentioned, which can be fastened to a motor vehicle seat (for example rear seat) by means of snap fasteners, that is to say for example are provided with a so-called ISOFIX system and as a rule can not be distinguished from persons. As stated at the outset, this is due to the fact that such a child seat is electrically conductively connected to the grounded seat frame of the motor vehicle seat in a state fastened to a motor vehicle seat via the latching closure. Thus, a ground shield is formed by the child seat, which forms the sensing field, i. the frequency dependent quantity (e.g., a sine field) is completely shielded.

A particularly preferred embodiment of the invention makes it possible, in particular, to detect the occupancy of the seat by means of a child seat of the aforementioned type on the basis of a frequency-independent variable. Here, a signal based on the temporal behavior of a frequency independent quantity, e.g. an amperage or amount of charge at least partially equivalent to a signal of a frequency-dependent magnitude responsible for the activation and / or adjustment of safety-related vehicle systems.

In this case, in an especially preferred embodiment of the invention, an electrically conductive part of the latching closure (eg ISOFIX stirrup) which remains on the seat is used as the electrode. This electrode can take charge within a certain time and deliver it within a certain time (discharge). Drawer- or unloading time of the free, located on the seat part of the snap closure is used as a reference value. The child seat is thus in a not properly connected to the seat of the motor vehicle state.

If a first part of the latching closure located on the child seat (also electrically conductive) is then connected to a second part of the latching closure located on the seat, the capacity of the electrode increases and the charging or discharging time of that electrode changes accordingly. This change in the charging or discharging time relative to the reference value can be measured. Thus, with the measuring system according to the invention, e.g. be clearly differentiated, whether a child seat is attached to a seat of the motor vehicle as intended or not. In this case, the first part of the snap closure can of course be electrically connected to other parts of the child seat or possibly the entire child seat or frame of the child seat.

It is crucial that the latching closure has two electrically conductive parts or components - one part is located on the child seat, the other part on the seat of the motor vehicle - so that the closed latching closure (both parts or components are electrically connected to each other) has a higher capacity has, as taken on the vehicle seat part taken for themselves. Such a snap closure is provided for example by a known ISOFIX closure.

Further advantageous variants and details of the invention are also given in the dependent claims.

Accordingly, it is regarded as advantageous, regardless of the specific embodiment as a measuring system for determining or detecting a seat occupancy that the first measuring means comprises a capacitor and / or a coil.

In the present case, a measuring means is understood as meaning any electrical or electronic circuit arrangement or electrical or electronic component which is capable of detecting and / or storing an electrical variable or of an evaluation unit or e.g. to forward to a control unit.

Preferably, the current, voltage and / or charge is measured as the frequency-independent electrical quantity, e.g. their change from a reference value or their changes in their temporal behavior in a simple

Way to detect. Thus, an almost unique assignment of the Behavior of the frequency-independent electrical variable affecting changes or modification can be detected.

Therefore, it is also considered to be particularly advantageous if the time behavior of the frequency-independent variable detected by the evaluation unit is the behavior of a charging and / or a discharging process.

Based on the above-mentioned exemplary embodiment with an ISOFIX child seat, the at least one measuring device and the at least one evaluation unit are preferably arranged in a vehicle. Of course, the measuring system according to the invention is of course not limited to the mentioned embodiment but can also be used in connection with other vehicle systems or measuring systems.

However, based on the embodiment of the measuring system according to the invention with respect to an ISOFIX child seat described above, it is also generally considered advantageous that a first electrode of a capacitor is part of a first component, wherein a second electrode of a second component can be coupled to the first electrode is.

Furthermore, then from the dynamics of the charge and / or discharge of the capacitor, a signal on the mechanical connection state of the first component with the second component can be generated. This can be any form of component connection, ie a form, force or material connection. A signal characterizing the component connection would then, for example, be equivalent to a signal generated as a function of a frequency-dependent variable, which likewise characterizes a state of a component connection. However, it is also conceivable that the equivalent frequency-dependent signal generated by the measuring system or an electronic control device is interpreted as coincident, although it does not reflect the state of the component connection. For this purpose, the exemplary embodiment with an ISOFIX child seat could be mentioned as an example again, in which the detected connection of the two parts of the snap closure generates a signal which is advantageously completely equivalent to a frequency-dependent signal which "signals" to the measuring system that there is a child seat located on the vehicle seat. After all, a child seat not provided with the ISOFIX standard can also be detected with a frequency-dependent size. Accordingly, we prefer that at least one component, for example a child seat as a second component, is part of a snap closure, so that at least one signal of the evaluation unit can be used to detect a connection. Here, for example, the latching closure of the ISOFIX system is regarded as such a snap closure.

Therefore, it is advantageous if a coupling with at least one measuring means for detecting a frequency-dependent variable is possible in order to improve the integration and to combine advantages of the known systems with the measuring system according to the invention.

In this case, of course, a coupling with a passenger protection system, in particular an airbag system in a vehicle, leading the target, so as to minimize the risk of injury due to incorrect or insufficiently recognized seat occupancy states.

In view of the problem described at the outset, which results from grounding an ISOFIX child seat, it would of course also be possible to decouple the latching connection or the so-called ISOFIX bracket and thus avoid grounding. For this purpose, however, insulation with thicknesses in the cm - range would be necessary, which are thus neither economically nor constructively feasible feasible. Nevertheless, it is also preferred in the measuring system according to the invention and its use with a child seat when the child seat has (at least) a thin, so a few mm thick insulating layer.

One idea of the invention is, in particular, to combine the system according to the invention with a measuring system which generates a signal by means of a frequency-dependent variable, to which a specific or defined state or a corresponding state change can be assigned. By way of example, this is understood to mean a measuring system which, as already stated, determines the occupancy of a vehicle seat.

Accordingly, the method according to the invention provides for detecting at least one frequency-independent electrical quantity by means of at least one first measuring means, for detecting the temporal behavior of the frequency-independent electrical variable by means of an evaluation unit, the evaluation unit being based on the time profile of the frequency-independent electrical variable automatically generates a signal that is at least partially equivalent to a frequency-dependent signal.

In this way, the inventive method allows counteracting a frequency dependence of a measuring system by a signal is generated over a frequency-independent variable, which at least partially corresponds to a frequency-dependent signal. An inventively performed measurement method thus allows the

Recognition of a defined state or a defined state change within a monitored or measured system both on the basis of a frequency-dependent and a frequency-independent electrical variable.

Both when using the measuring system according to the invention and when using the measuring method according to the invention, a plurality of measuring means can be used or a plurality of electrical frequency-independent variables can be detected and evaluated. Thus, a logical link can also be provided within the evaluation unit, so that the signal generated by the evaluation unit is generated only when the time profiles of all or more of the frequency-independent electrical variables indicate a change of state within the measured (monitored) system. For example, an evaluation unit on a motor vehicle seat is intended to generate a signal only when a plurality of ISOFIX latching arms of a child seat are in engagement with ISOFIX latching hooks of the motor vehicle seat.

Further details and advantages of the invention will become apparent in the following description of exemplary embodiments with reference to the figures.

Show it:

1 is a perspective view of a motor vehicle seat with a snap closure for securing a child seat to the

Motor vehicle seat, in particular a rear bench;

FIG. 2 shows a schematic, sectional view of the motor vehicle seat of the type shown in FIG. 1, with a measuring system according to the invention; FIG.

Fig. 3 is a perspective view of a portion of a motor vehicle seat of the type shown in Figures 1 and 2, with a snap closure (ISOFIX) for attaching a child seat to the vehicle seat (the latching principle);

4 shows a schematic, partially sectioned view of the latching closure shown in FIG. 3;

5 is a block diagram of a measuring system for detecting the occupancy of a

Seat of a motor vehicle. Where "I" and "Q" are the in-phase reactive current components of the current sent to the sensor. These are used for classification in wet seats;

6 is another block diagram of a measuring system for detecting the

Assignment of a motor vehicle seat, in conjunction with a grounded motor vehicle seat;

7 shows a schematic, sectional view of a motor vehicle seat, with a seat occupant occupant;

8 shows a schematic representation of an arrangement for detecting the presence of a person on the basis of capacity measurements; and

9 is a block diagram of a measurement system for determining the occupancy of a motor vehicle seat (for example, a child seat).

1 shows a perspective rear view of a seat frame 4a of a motor vehicle seat 4 consisting of a seat part 401 and a backrest 402, which are articulated to each other in a known manner via a seat adjustment mechanism 10. In order to ensure that the backrest 402 relative to the seat part 401 can also be pivoted in the direction of the same in the upholstered state, said two parts of the motor vehicle seat 4 are spaced apart in a region 403 between the seat adjustment mechanism 10 connecting them laterally. At this area 403, which thus faces the rear side of a motor vehicle in the installed state, an ISOFIX latching clip 2 is provided on the seat part 401 or the seat frame 4. At the ISOFIX locking clip 2 are spaced apart from each other symmetrically to a seat longitudinal axis two ISOFIX locking hooks 1 attached or molded. These provide a connection to the seat frame 4a of the motor vehicle seat 4 or are part of the seat frame 4a.

In the sectional side view of Figure 2, the motor vehicle seat 4 of Figure 1 is shown with padding. The seat part 401 is provided with a cushion part 9 for providing a padded seat 90 and facing the seat part 401

Area of the backrest 402 is provided with a cushion part 8. In this

Sectional view is also a rigid rear wall 11 of the backrest 402 can be seen, which is provided on a side facing away from the seat surface 90 of the padded seat part 401 side of the backrest 402.

In the free area 403 between the backrest 402 and the seat part 401, a so-called Elo box 12, so a computer or evaluation unit, arranged, which is in operative connection with the ISOFIX bracket 2. Of course, it can also be used directly in conjunction with the ISOFIX locking hooks 1. All that matters is that the Elo box 12 is coupled to the ISOFIX components of the seat frame 4a so that it can detect an engagement of an ISOFIX locking arm with an ISOFIX locking hook 1. This means in this context that they have an applied Ladebzw. Entladevorgang respectively whose temporal course of the considered as an electrode ISOFIX latching clip 2 and the ISOFIX latching hook 1 can detect and evaluate.

With the Fig. 3 is a perspective view of the principle of operation of the ISOFIX child seat system illustrated. The motor vehicle seat 4 is here part of a rear seat of a motor vehicle and provides between the padded seat part 401 and the padded backrest 402 an opening 405, which is arranged next to a buckle receptacle 404 for inserting a lock tongue of a seat belt. Through this opening 405, an ISOFIX locking arm 301 of a child seat 3 is inserted, which is arranged on a child seat frame 3 a of the child seat 3. For this purpose, the ISOFIX latching arm 301 is located on a rear side of the child seat 3 facing the backrest 402 and extends substantially perpendicularly from it in the direction of the backrest 402.

As shown in the sectional side view of FIG. 4, the ISOFIX latching arm 301, after insertion into the opening 405, engages between the backrest 402 and the backrest 402

Seat part 401 in the ISOFIX latch hooks 1 of the ISOFIX latch 2 on the vehicle seat 4 on. In this way, the child seat 3 or the child seat frame 3 a firmly connected to the seat frame 4 a of the motor vehicle seat 4. To ensure a sufficiently stable connection, the ISOFIX locking arm 301 as well as the ISOFIX locking hook 1 are made of metal. Since so that the child seat frame 3a is electrically connected to the seat frame 1 a of the vehicle seat 1, both racks are at the same potential or at a grounded seat frame 4a and the child seat frame 3a is grounded. The measuring principles presented below with FIGS. 5-8 therefore no longer make it possible to distinguish between the child seat 3 connected to the seat frame 4 a and a person located on the motor vehicle seat 4 as a function of a frequency-dependent potential or capacitance measurement. A clear or error-free assignment of a signal that is generated by means of a frequency-dependent variable - based on a generated electric field - and causes the activation or deactivation of a safety system of a motor vehicle is no longer possible.

For this reason, it is provided according to the invention according to FIG. 4 that the ISOFIX latching clip 2 or only the ISOFIX latching hook 1 are used as the first electrode of a capacitor in the sense of a measuring device which is in the unconnected state, ie without connection to an ISOFIX child seat 3, are applied with a frequency-independent variable to determine a reference value. Thus, for example, e.g. the ISOFIX latching clip 2 or the ISOFIX latching hook 1 are repeatedly charged or discharged as the first electrode of a capacitor, and the time course of the charging or discharging process is determined as a reference. For this purpose, the ISOFIX latching hook 1 is coupled to an evaluation unit in the form of the Elo-box 12 via a contact 120 or a line element which determines and evaluates said time profile. Of course, the loading or unloading operation may of course be carried out continuously or only for a certain period of time, e.g. after opening the motor vehicle a predefined duration, and / or with a predetermined frequency.

If now the ISOFIX locking arm 301 of the child seat 3 is electrically connected to the ISOFIX locking hook 1, this forms a second electrode of the capacitor and the time course of the charging or discharging process is changed. The capacitance of the ISOFIX latching hook 1 considered as a capacitor, if necessary together with the ISOFIX latching clip 2, has increased and the charging and discharging behavior of the same has changed detectably. The Elo box 12 detects the resulting resulting change in the time course of the frequency-independent variable, for example, the charging or discharging, and generates a signal that leads, for example, to shutdown of the airbag system. In principle, therefore, the risk of injury to a child located in the child seat 3 should be reduced by an airbag deploying in the event of a crash. The corresponding signal of the Elo box 12 is equivalent to a signal that is generated by a frequency-dependent detection or measuring device for seat occupancy, for example, to determine the occupancy of the motor vehicle seat 4 with a child seat, which is not equipped with ISOFIX.

When detecting the time course of the charging or discharging process, it is also possible that the contacting 120 of the evaluation unit, corresponding to FIG. 4, the Elo box 12, not permanently connected to the ISOFIX latch hook 1 or the ISOFIX latch 2 is. Instead, as a result of the introduction of the ISOFIX latching arm 301 of the child seat 3, the contacting 120 may e.g. separated from the ISOFIX latch hook 1 and coupled directly to the ISOFIX latch arm 301. For this purpose, the contacting can e.g. be designed as a preloaded conductive spring or resiliently mounted. An inserted through the opening 405 end of the ISOFIX locking arm 301 could then change overcoming a spring force, the position of the contact 120, for example, move it in the direction of insertion of the ISOFIX locking arm 301. Along with this, the coupling of the contacting 120 with the ISOFIX locking hook 1 could be separated and at the same time an electrically conductive connection of the contacting 120 with the ISOFIX locking arm 301 realized. Accordingly, a change in the course over time, e.g. detect the charged via the contact 120 charging and discharging.

It is essential that the measuring systems shown in FIGS. 5-7 for determining the occupancy of a motor vehicle seat 4 are expanded on the basis of a frequency-dependent variable such that an occupancy with an ISOFIX child seat 3 can be clearly detected in order to be passive or active Safety systems, which mean a risk to an occupant to switch off or prevent their tripping. Thus, Fig. 5 shows a block diagram of a control system 21 with a power supply 14, which is ensured by a battery supply voltage V _Ba tteπe. Furthermore, the control system 21 has a connection to a harness 16 of the seat, eg for connection to a passive or active security system. The connection to the cable harness 16 is provided via a CAN bus 15, so a common in the automotive field communication system for connection to a control unit. The CAN-BUS 15 is coupled to a microprocessor 17, which in turn controls a sine wave generation 18 and a sampling current measurement 19 associated therewith.

With the Abstaststrom-measurement 19 is a detection unit 20 as a measuring means with a Sensierungs- or sensing element 5, e.g. an electrical sensor or heating mat, connected outside the control system 21. When the detection unit 20 is supplied with a sine signal, e.g. a 12 kHz harmonic sine signal, a current I and a charge Q can be measured, which the microprocessor 17 evaluates.

The sensing elements 5 or sensors, which may also be considered independent of the detection unit 20 as measuring means according to the invention are usually located below the seat 90 in the cushion part 9 of the seat part 401 and in the backrest 402. By feeding with an oscillating signal that generates Scanning element 5 an electric field. The sensing element 5 is advantageously designed as a capacitive sensor, so that a capacitance of a first electrode of the sensing element 5 with respect to a ground, present e.g. the reference potential of the seat frame 4a or a vehicle floor 7, can be measured. By an object or a person on the motor vehicle seat 4, the electric field and thus the measured capacitance are affected. From this influencing of the frequency-dependent variable, a seat occupancy or the type of seat occupancy can then be detected. Thus, the detected capacity is increased significantly by a vehicle occupant 6 located on the motor vehicle seat 4 in the normal case and the capacity is increased only slightly or scarcely by a child seat without ISOFIX system. An increase of this detected, frequency-dependent variable accordingly leads, for example, to a generation of a signal which activates the safety systems of the motor vehicle for the motor vehicle seat 4.

The wetness of a motor vehicle seat 4 or the upholstery parts 8 and 9, in which a sensing element 5 is located, can have a considerable influence on the capacitance of the sensing element 5 with respect to a reference potential or a ground. Thus, a conductive liquid on the sensing element 5 increases the detected capacitance. Therefore, for wet seating, in addition, the reactive and resistive component of the impedance between the sensing element 5 and a ground, ie grounding, is regularly measured and a distinction made for the type of seat occupancy in wet seats using real and imaginary part of the current. Thus, the I and Q values sensed by the microprocessor 17 in FIG. 5 are the in-phase and reactive current components of the supply current sent to the sensing element 5, which are used to classify seat occupancy in wet or wet seats.

An embodiment of a measuring system of the prior art for detecting the occupancy of a motor vehicle seat 4 shows the block diagram of Fig. 6. The detection is carried out in connection with a grounded motor vehicle seat 4 and housed therein in the seat part 401 heating mat as a scanning element 5 or detection unit.

It can be seen that the backrest 402 and the seat portion 401 are grounded through grounding leads 33 and 34, respectively, to produce a defined system. Furthermore, an electronic control unit 23 is here via an 8-pin connection with Vßatteπe. a ground 30, a first CAN bus 31, a second CAN bus 32, the grounding lines 33 and 34 of the motor vehicle seat 4, a first and second grounding line 35 and 36 connected to a heating device 27. The said eight connections or connection lines also lead to an electronic control unit 26 for the heating device 27 and have a branch to a cable harness connector 28. The harness connector 28 provides a connection to a connector 27 a of the heater 27. The heating device 27 then comprises the sensing element 5 designed as a sensor or heating mat and has a permanent connection 25 between the electronic control unit 23 and the heating mat. In this case, the permanent connection 25 is realized via a two-wire connection 24 to the electronic control unit 23.

By means of such an arrangement and interconnection of detection units or the sensing element 5, in particular, a capacitance C _og between a person occupying the motor vehicle seat 4 as intended, a vehicle occupant

6, and a vehicle floor 7 and the capacitance C _sg between the sensing element. 5 (Sensor) and the vehicle floor 7 and the capacitance C ₅₀ between the sensing element 5 (sensor) and the vehicle occupant 6 are detected and used to determine the occupancy of the vehicle seat 4.

Such an arrangement for the so-called capacitive detection of the presence of a person 6 is also shown in FIG. Herein, Kirchhoff's rules, which also apply in this context, are illustrated schematically. Thus, the presented measuring system with the capacitive sensing element 5 is subject to the law that the current of the generated electric field of the sensing element 5 must form part of a closed circuit. Thus, a sensor unit 38 is connected not only to a scanning electrode 37, which has the scanning element 5, but also capacitively via C _x i with the surrounding environment 39. Likewise, the person 6 to be detected capacitively via the scanning electrode 37 via Cχ ₂ likewise has a coupling with the surroundings 39 (Cχ ₃ ). In this way, an electrical circuit is formed in which the mass of the scanning electrode 37 and the sensing element 5 and the person to be detected 6 are interconnected.

This compelling condition is also taken into account with the circuit of Fig. 6, in which the motor vehicle seat 4 and its backrest 402 and its seat part 401 must be grounded for seat occupancy detection.

Accordingly, the operation of such a measuring system is impaired when the child seat frame 3a is connected to the seat frame 4a of the motor vehicle seat 4 via the ISOFIX system and the metal in the child seat 3 is also at the same potential as the rest of the motor vehicle seat 4. A distinction between persons 6 and ISOFIX system child seats 3 is made impossible, since values generated by the measuring system are the same (see Fig. 6-8) or in the same height of I and Q (see Fig. 5 ) are located.

A simple insulation is not enough to decouple the ISOFIX locking clip 2 from the rest of the mass, because it is not a "DC" resistor but an impedance.

According to the invention, therefore, an analog measuring method with a frequency-dependent measuring method, in particular one of those shown in FIGS. 5-7, connected to detect ISOFIX child seats 3 in this particular preferred embodiment and then disable passive or active safety systems that mean a risk to an occupant, or to prevent their triggering. Of course, this also allows the detection of child seats possible, which, although not ISOFIX standard, but also by means of the described frequency-dependent measurement methods or systems are not clearly distinguishable from a person due to comparable limitations.

Furthermore, it is considered advantageous if ISOFIX components of the motor vehicle seat 4, e.g. the ISOFIX latch 2, a simple (thin) insulation to a

To provide "DC isolation" with respect to the seat frame 4a. With others

In the words of the ISOFIX latching clip 2, which serves as the sensor electrode, has an insulation which, although it is operated under DC voltage, has sufficient separation from

ISOFIX locking bracket 2 and seat frame 4a would ensure, but the insulation is still clearly too small to provide in the illustrated case, a complete electromagnetic decoupling.

According to the measuring method according to the invention already described, a capacitor is provided in the present exemplary embodiment which is charged and discharged continuously. The loading and unloading time is used as reference. The ISOFIX locking clip 2 is used as an electrode. The charging of this electrode with its geometric properties takes a certain time like a capacitor. This time is used (after being subtracted from the reference time) to represent an "O" state, and if the area of the electrode is increased by connecting the child seat 3, that time also increases and it is recognized that the ISOFIX Child seat 3 was installed, resulting in a "1" state.

FIG. 9 shows a block diagram for determining the characteristic frequency-independent quantities of an electrode 7a (such as charging time and discharge time of the electrode 7a). The electrode 7a may be, for example, part of an (ISOFIX) snap fastener for the child seat 3, in particular the second part of the (ISOFIX) snap fastener provided on the motor vehicle seat 4, eg the ISOFIX snap-in clip 2 or the ISOFIX snap-in hook 1. Consequently, the circuit shown in FIG. 9 could also be part of the evaluation unit or the Elo box 12 of the preceding FIGS. 1-4. As a result of a start instruction 45 to a conventional electronic signal sequence controller 46 (so-called "burst controller"), a in single-slope switched capacitor or analog-to-digital converter 40 is driven. By means of this, the charging or discharging of the electrode 7a and a capacitance Cs defined as a function of the sensitivity is evaluated, which is connected via connecting lines 41 and 42 to the analog-to-digital converter 40. In this case, the electrode 7a has a capacitive ground Cx. Via a likewise applied to the connecting lines 41 and 42 charge amplifier 43, the time course of the charging or discharging process is forwarded to the analog-to-digital converter 40. This transmits on the one hand, a response 44 on the completion of the loading or unloading. On the other hand, it generates a signal 47, which reproduces the currently detected state of the electrode 7a, that is, for example, signals a "1" state in the case of an increased capacitance of the electrode 7a.

This signal 47 defines e.g. whether the child seat 3 is electrically connected via its ISOFIX locking arm 301 with the ISOFIX locking bracket 2, so that the loading or unloading time of the electrode 7a has changed, now the ISOFIX locking arm 301 and the ISOFIX locking hooks 1 and if necessary, the ISOFIX locking clip 2 includes. This change in the loading or unloading time can be detected by the ISOFIX child seat 3 to determine the occupancy of the motor vehicle seat 4.

Irrespective of what has been described so far, the application of the measuring method or measuring system according to the invention is also conceivable in other fields of application in which frequency-dependent measured values are determined in order to detect a specific state.

LIST OF REFERENCE NUMBERS

1 ISOFIX locking hook 1 a Seat frame

2 ISOFIX locking clips

3 child seat

3a child seat frame

4 motor vehicle seat 4a child seat frame

5 sensing element / sensor

6 inmates

7 Vehicle floor 7a Electrode 8 Upholstered backrest

9 upholstered seat

10 seat mechanism

1 1 rear wall

12 Elo-Box (computer / evaluation unit) 13 Vatatteπe

14 energy supply

15 CAN bus

16 seat harness

17 Microprocessor 18 Sine wave generation

19 Scanning current measurement

20 detection unit

21 control system

22 8-pin connection 23 Electronic control unit

24 two-wire connection

25 Permanent connection between electronic control unit and sensor mat

26 Electronic control unit for heating device

27 Heating device 27a Connecting piece (connection) of the heating device 28 Harness connection piece

29 Vatatteπe

30 mass

31 CAN bus 1

32 CAN bus 2

33 Grounding backrest

34 Grounding line seat part

35 first grounding line heating device

36 second grounding line heating device

Cso sensor-to-occupy capacity

C _o g inmate-to-earth capacity

Cs ₉ sensor-to-earth capacity

37 scanning electrode (detection unit)

38 sensor

39 Surrounding environment

40 single-slope switched capacitor ADC

41 connecting cable 1

42 connecting cable 2

43 charge amplifier

44 Feedback ("Done")

45 start instruction / signal ("start")

46 Signal Sequence Controller (Burst Controller)

47 status signal ("result")

90 seat

120 contacting

301 ISOFIX locking arm

401 seat part

402 backrest

403 Area between backrest and seat part

404 buckle mount

405 Opening for insertion of the ISOFIX locking arm on the vehicle seat

_{* * * * ** * * * *}

Claims

claims

1st measuring system with

a) at least one first measuring means for detecting at least one frequency-independent electrical variable;

b) an evaluation unit for detecting the temporal behavior of the frequency-independent electrical variable, wherein

c) the evaluation unit automatically generates a signal which is at least partially equivalent to a frequency-dependent signal from the detection of the time profile of the frequency-independent electrical variable.

2. Measuring system according to claim 1, characterized in that the first measuring means comprises a capacitor and / or a coil.

3. Measuring system according to claim 1 or 2, characterized in that the frequency-independent electrical variable is a current, a voltage and / or a charge.

4. Measuring system according to at least one of the preceding claims, characterized in that the temporal behavior of a charging and / or a discharge process is detected by the evaluation unit.

5. Measuring system according to at least one of the preceding claims, characterized in that the at least one measuring means and the at least one evaluation unit are arranged in a vehicle.

6. Measuring system according to at least one of the preceding claims, characterized in that a first electrode of a capacitor is part of a first component, wherein a second electrode of a second component can be coupled to the first electrode.

7. Measuring system according to claim 6, characterized in that from the dynamics of the charge and / or discharge of the capacitor, a signal on the mechanical connection state of the first component with the second component can be generated.

8. Measuring system according to claim 6 or 7, characterized in that the first electrode of the capacitor is coupled to a mounting bracket of an ISOFIX child seat and the second electrode of the capacitor is coupled to a child seat for the car.

9. Measuring system according to at least one of claims 6 to 8, characterized in that at least one component is part of a snap closure, so that at least one signal of the evaluation unit for detecting a connection can be used.

10. Measuring system according to at least one of the preceding claims, characterized by a coupling with at least one measuring means for detecting a frequency-dependent variable.

1 1. Measuring system according to at least one of the preceding claims, characterized by a coupling with a passenger protection system, in particular an airbag system in a vehicle.

12. Device for installation in a motor vehicle, characterized in that it can be coupled to a measuring system according to at least one of claims 1 to 1 1.

13. The apparatus according to claim 12, characterized in that it is designed as a child seat for a vehicle.

14. The apparatus according to claim 13, characterized in that the child seat has a thin insulating layer.

15. Measuring method in which

a) at least one first measuring means detects at least one frequency-independent electrical quantity;

b) an evaluation unit detects the temporal behavior of the frequency-independent electrical variable, wherein the evaluation unit automatically generates a signal which is at least partially equivalent to a frequency-dependent signal from the detection of the time profile of the frequency-independent electrical variable.

_{* * * * ** * * * *}