DE102004046190A1 - Motor vehicle seat occupancy detection device, has evaluator connected to detection unit to detect vehicle seat occupancy when change in predetermined resonance characteristics exceeds assigned threshold - Google Patents

Abstract

The device has a resonator (4), integrated in a vehicle seat (1), having predetermined resonance characteristics during unoccupied seat condition. A detection unit (7) connected with the resonator detects a change in the characteristics, due to occupants of the seat. An evaluator (8) connected with the unit (7) detects the seat occupancy when the change in the characteristics exceeds an assigned threshold. An independent claim is also included for a method of detecting seat occupancy in a motor vehicle.

Description

The The present invention relates to an apparatus and a method for detecting the seat occupancy of a seat, in particular for recognizing the Seat occupancy of a passenger seat arranged in a motor vehicle.

A Such a device and such a method can advantageously, although not exclusive, for controlling the operation or the opening a vehicle airbag be used so that the airbag actuator is only activated, when the corresponding assigned seat in the vehicle, for example the front passenger seat, occupied by an occupant.

It is becoming increasingly common Vehicles with so-called airbag restraints for both to equip the driver as well as the passenger. Because you accept can that the driver's seat of a vehicle is always occupied, if the vehicle is in motion, it is generally desirable that the Airbag operated on the driver's side If the vehicle is a negative acceleration above a certain threshold. Often the driver is alone in the vehicle, and consequently, an actuation of the airbag on the Passenger side not necessary. As an unnecessary operation of the airbag on the Passenger side increased Repair costs for reinstallation of the airbag entails it is a claim of i.a. Insurance company, with double airbag equipped vehicles with a device for deactivating the passenger-side airbag when the front-passenger seat is in an unoccupied condition located.

Of course there There are many different ways to determine if a vehicle seat is busy. For example, the vehicle can be equipped with a simple on-off switch be manually activated by the driver or passenger is. However, such a system is not preferred because the driver or Could forget passenger to activate the airbag actuator when occupying the seat. Accordingly a detection device is sought, which without human Intervention works.

Out US-A-3 863 209 is a vehicle seat with a load-responsive switch known, which is arranged in the seat cushion. When the seat occupied by a person of sufficient weight, will be the switch activated to activate the airbag sensor. A disadvantage with such a system is that the load-dependent switch do not differentiate between a living thing and a heavy object which can be on the seat.

It is also known, optical or ultrasonic based Transmitters and sensors for detecting the presence of one on the seat seated occupants, although such systems are relatively difficult to install. They require that components be different Locations are mounted inside the vehicle cabin. An example Such a system is disclosed for example in DE-A-4 023 109.

At the above approaches according to the state of However, technology has proved to be disadvantageous that they only with a great effort or under high Cost can be realized. Also, with some approaches the susceptibility and the efficiency such systems are not optimal.

One novel, currently developed by the applicant, not yet posted Seat occupancy detection system is the so-called HOBBIT system (= Human Observation by Beam Interference Technology). The HOBBIT system consists of a central base station and individual reflectors in the seat for detecting a respective seat occupancy. In the HOBBIT system becomes a diffraction, damping and / or reflection of high frequency signals (for example 2.45 GHz waves) usefully applied to the occupancy of the seat Recognize people. The HOBBIT system becomes a space for everyone seats to be monitored within a passenger compartment of a vehicle with the high-frequency, electromagnetic Wave field illuminated. For this, the base station transmits signals, which meet the reflectors on which they are modulated and in turn received by the base station.

Consequently The present invention is based on the object, a device and to provide a method which is simple and inexpensive a reliable one Ensure recognition of a seat occupancy of a seat.

According to the invention this Task device side by the device with the features of the patent claim 1 and procedurally by the method with the features of claim 10 solved.

The idea underlying the present invention is that at least one resonator integrated in the seat is provided with predetermined resonance characteristics in an unoccupied seated state of the seat, the at least one resonator having detection means for detecting a change in at least one of the predetermined resonance modes. Charakteris Tiken the at least one resonator is connected. Furthermore, an evaluation device connected to the at least one detection device is provided for evaluating the detected change in the at least one resonance characteristic of the at least one resonator, the evaluation device recognizing a seat occupancy of the seat when the assigned threshold value is exceeded by the changed at least one resonance characteristic.

Consequently shows the present invention over the known approaches according to the prior Technology has the advantage of being a simple, cost effective and above all trouble-free method is created for detecting a seat occupancy of a seat, which in addition to usual on Sitting objects, e.g. Jackets, briefcases, or the like relatively insensitive and without any wave radiation, for example radio radiation, is operable.

In the dependent claims find advantageous improvements and refinements of in the patent claim 1 device and in the claim 10 specified method.

According to one preferred development is as a measure of at least one to be controlled Resonant characteristic of the resonant frequency of at least one Resonator, the goodness or Vibration amplitude of the at least one resonator and / or the Coupling of the at least one resonator to one or more others Circuit elements used.

According to one Another preferred embodiment is the at least one resonator directly or indirectly as part of at least one oscillator, wherein whose oscillation frequency is measured and a change in its oscillation state is evaluated, with the at least one detection device connected. Advantageous is a predominantly areal trained condenser a component of the at least one resonator, wherein at least the capacitor is provided on a board or foil, which in the seat of the Seat is integrated. This is especially at frequencies in the MHz range advantageous. However, the at least one resonator can also Completely be provided on a slide, which in turn in the seat of the Seat is integrated. This is for example at higher frequency ranges advantageous.

According to one another preferred embodiment the at least one resonator has a resonant frequency at one Seat unoccupied seat state in the range of several MHz to several GHz. However, the present inventive concept is also on other frequency ranges applicable.

Preferably are several resonators at different positions of the seat, preferably at different positions in the seat surface of the Seat, arranged and with the at least one detection device connected. This allows a gross area Resolution, so that a reliable Seat occupancy detection ensured becomes.

Advantageous is a memory device for pre-storing predetermined, Thresholds associated with the respective resonant characteristics provided, which is connected to the evaluation device. In the storage device can for example, the resonance characteristics of at least a resonator in the unoccupied seating state pre-stored and for the plausibility check of the ongoing measurements are used.

According to one another preferred embodiment is the evaluation with at least one assigned to the seat Airbag module connected, wherein upon detection of a seat occupancy of the seat the functionality the at least one airbag assigned to the module by the evaluation device can be activated.

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

1 a schematic representation of a device for detecting the seat occupancy of a seat according to a preferred embodiment of the present invention; and

2 a circuit diagram of a resonator or oscillator for detecting a seat occupancy due to a changed resonance characteristic according to a preferred embodiment of the present invention.

In the same reference numerals designate the same or functionally identical Components, unless stated otherwise.

1 illustrates a simplified schematic representation of a device for detecting the seat occupancy of a seat 1 who is on the ground 2 a motor vehicle is mounted. Although the present invention is described below with reference to a motor vehicle seat, it will be apparent to one skilled in the art that the present inventive concept applies to all arrangements with a Seat occupancy can be applied.

As in 1 is apparent in the seat 1 preferably in the seat 3 at least one resonator 4 integrated. Preferably, in the seat 3 of the seat 1 several resonators 4 be accommodated in order to increase the sensitivity of the device accordingly and to obtain a plausibility check of the individual measurement results. However, the present invention concept is represented by a resonator 4 explained in more detail.

The resonator 4 is, for example, as in 2 represented as LC resonant circuit and as part of an oscillator 5 trained or connected to an oscillator circuit. The characteristic resonant frequency of the resonator 4 depends on its capacity, which in turn depends on the dielectric constant of the material, which is located in the immediate area of the resonator. If the seat is in the unoccupied seating state, a low dielectric constant exists to provide a small capacity. This implies that the oscillator circuit oscillates at a relatively high characteristic resonant frequency.

Vice versa lies when the seat 1 occupied by a passenger, has a higher dielectric constant because a clothed human body is an electrical insulator. Due to the high water content of the human body of about 80%, there is a high permittivity ε _r of about 60 to 80 and thus a higher dielectric constant than in the unoccupied sitting state. As a result, the oscillator circuit oscillates at a relatively lower frequency than in the unoccupied seating state.

Therefore, due to the presence of a human body on the seat 1 certain resonant characteristics of the resonator 4 measurably changed in comparison to an unoccupied seated state. For example, the change in the resonance characteristic is the changed resonant frequency of the resonator 4 , the changed oscillation amplitude of the resonator 4 and / or the changed coupling state of the resonator 4 with at least one further circuit element (not shown) measured with corresponding measuring devices and compared with the respective changes associated threshold values. This will be explained in more detail below.

At a seat occupancy of the seat 1 by an occupant, a change in the resonance characteristic can be made either directly by measuring the resonator 4 or indirectly detected by the resonator 4 is formed as part of one or more oscillators. The resonator determines 4 the oscillation frequency of the oscillator, which is for example measured and evaluated, as already explained above.

2 Figure 11 illustrates an exemplary circuit diagram of a circuit used to detect a seat occupancy of the seat 1 according to a preferred embodiment of the present invention is used. As in 2 can be seen, is the resonator 4 formed as an LC resonant circuit, which consists of an inductor L1 and a capacitive element C whose capacity is variable.

As in 2 is apparent, is the resonator 4 or the LC resonant circuit advantageously part of an oscillator 5 for example, in addition to the resonator 4 an amplifier for compensating for vibration loss and loss resistance and a feedback device 6 for generating an evaluable vibration change due to a body induced change in the positive feedback by a person in the seat 1 occupant. In the

2 shown circuit is purely exemplary to understand, which is only crucial that any resonance characteristic of the resonator 4 , For example, the resonant frequency, the amplitude or the coupling with a circuit element, due to a seat occupancy compared to an unoccupied seated state of the seat 1 changed and this change can be evaluated.

In order to obtain a large change in frequency in a compact and cost-effective structure, the resonant frequency of the resonator 4 in the unoccupied seating state, preferably in the range of a few MHz to a few GHz.

In the range of a few MHz, it is advantageous to use a resonator 4 as well known in the art LC oscillator circuit 5 to realize that a predominantly planar capacitor C as part of a resonant circuit or resonator 4 integrated on, for example, a circuit board or film. This board or foil is preferably in the seat 3 of the seat 1 at a suitable distance from the surface of the seat 3 built-in. The remaining components of the oscillator 5 can of that in the seat 3 of the seat 1 Built-in capacitor C spaced outside the seat 3 provided or also mounted on the film.

Now takes place by an occupant seat occupancy of the seat 1 , the effective Dielektrizi tätszahl and thus increases the capacitance of the resonant circuit capacitor C, whereby the resonant frequency of the resonant circuit C is reduced.

In the higher frequency range is advantageous, the entire resonator 4 as a component on a suitable carrier material, for example a film, a FF4 carrier, or the like, integrated, which in turn in the seat 3 of the seat 1 is installed. The change in the effective dielectric constant in the case of a seat occupancy of the seat 1 by an occupant causes a change in the guided wavelength of the line component, ie the entire resonator 4 , on the Resonatorbeeinflussung turn an evaluable frequency change.

Such a characteristic change can be achieved, for example, by means of a resonator 4 connected detection device 7 be captured, as in 1 is illustrated. The detection device 7 is preferably in turn with an evaluation device 8th , also out 1 can be seen, for transmitting the detected signals of the change of the measured resonance characteristic of the resonator 4 connected. The evaluation device 8th in turn, is advantageous with a memory device 9 data-connected, in which predetermined threshold values for the individual measured quantities of the resonant characteristics of the resonator 4 be stored in advance.

Thus measures at a seat occupancy of the seat 1 by an occupant the detection device 7 a change in a certain resonance characteristic of the resonator 4 , For example, a changed resonant frequency, a changed amplitude and / or a modified coupling with an additional circuit element, and transmits these measured change data to the evaluation device 8th , The evaluation device 8th compares the received change data with in the storage device 9 previously stored threshold values for the respective measured variable or resonance characteristic and detects, if appropriate, a seat occupancy of the seat 1 ,

As in 1 is further illustrated, is the evaluation 8th also with, for example, an airbag module 10 connected to in case of exceeding a predetermined in the memory device 9 stored threshold by the means of the detection device 7 detected change of a certain or more specific resonance characteristics, the functionality of the airbag module 10 or the associated airbag to activate. That is, there is a quasi-comparison of the measured parameters of the resonator 4 in the unoccupied sitting state with the newly acquired variation data of the resonator 4 with a change of certain resonance characteristics. Do these resonant characteristic changes have such magnitudes that those in the memory device 9 If the thresholds previously stored are exceeded or fallen below, the system recognizes a seat occupancy of the seat 1 by an occupant and accordingly activates the functionality of the airbag.

Looking at the oscillator 5 as a coupled selective amplifier, so an evaluable vibration change can alternatively be done by a body-induced change in positive feedback. For example, the co-coupling in the GHz range can be accomplished via a planar directional coupler realized on a foil. The change in the coupling factor of the directional coupler influences the oscillation of the oscillator. A measurement of the resonance frequency change by the detection device 7 can be advantageously carried out by means of a low-cost grid dipper, which is particularly advantageous in the case of a direct measurement of the resonator. In the case of an indirect measurement of the resonator 4 if the resonator 4 example, is part of an oscillator, a measurement, for example, a resonant frequency change of the resonator 4 preferably by means of a frequency discriminator, by counting pulses, or the like.

Consequently the present invention provides an apparatus and a method with which in a simple and inexpensive way a seat occupancy a seat can be detected. It is only necessary at least a resonator, which in case of occupancy by an occupant at least one of its measurable resonance characteristic quantities such changed that by means of a suitable detection and evaluation such a change recorded and evaluated accordingly. The resonator can be formed in different ways, so long by a changed Dielectric constant due the seat occupancy by an occupant ensures a change in a measurable resonance characteristic size is.

Even though the present invention with reference to preferred embodiments As described above, it is not limited thereto on diverse Modifiable way.

For example, the resonator 4 as a capacitor constructed of plates, an interdigitated coupling element having component, an LC resonant circuit, dipole antenna, capacitor-like structure, dipoles, or the like may be formed.

Claims (18)

Device for detecting the seat occupancy of a seat ( 1 ), in particular in a motor vehicle, comprising: at least one in the seat ( 1 ) integrated resonator ( 4 ) with predetermined resonance characteristics in an unoccupied seated state of the seat ( 1 ); at least one with the at least one resonator ( 4 ) associated detection device ( 7 ) for detecting a change of at least one of the predetermined resonance characteristics of the at least one resonator ( 4 ); and with one with the at least one detection device ( 7 ) associated evaluation device ( 8th ) for recognizing a seat occupancy of the seat ( 1 ) when an associated threshold value is exceeded by the changed at least one resonance characteristic. Device according to claim 1, characterized in that the resonant frequency of the at least one resonator ( 4 ), the quality or oscillation amplitude of the at least one resonator ( 4 ) and / or the coupling of the at least one resonator ( 4 ) to at least one other circuit element the at least one resonance characteristic of the at least one resonator ( 4 ). Device according to claim 1 or 2, characterized in that the at least one resonator ( 4 ) directly or indirectly as part of at least one oscillator ( 5 ), the vibration frequency of which is measured and a change in its vibration state is evaluated, with the at least one detection device ( 7 ) connected is. Device according to at least one of the preceding claims, characterized in that a predominantly planar capacitor (C) forms a part of the at least one resonator ( 4 ) is formed, wherein at least the capacitor (C) is provided on a board or foil which in the seat ( 3 ) of the seat ( 1 ) is integrated. Device according to at least one of claims 1 to 3, characterized in that the at least one resonator ( 4 ) is completely provided on a foil, which in the seat ( 3 ) of the seat ( 1 ) is integrated. Device according to at least one of the preceding claims, characterized in that the at least one resonator ( 4 ) a resonant frequency at an unoccupied seated state of the seat ( 1 ) in the range of several MHz to several GHz. Device according to at least one of the preceding claims, characterized in that a plurality of resonators ( 4 ) at different positions of the seat ( 1 ), preferably at different positions in the seat surface ( 3 ) of the seat ( 1 ) and arranged with the at least one detection device ( 7 ) are connected. Device according to at least one of the preceding claims, characterized in that a memory device ( 9 ) is provided for storing in advance predetermined threshold values assigned to the respective resonance characteristics, the memory device ( 9 ) with the evaluation device ( 8th ) connected is. Device according to at least one of the preceding claims, characterized in that the evaluation device ( 8th ) with at least one seat ( 1 ) associated airbag module ( 10 ) and upon detection of a seat occupancy of the seat ( 1 ) activates the functionality of the airbag associated with the airbag module. Method for detecting the seat occupancy of a seat ( 1 ), in particular in a motor vehicle, having the following method steps: providing at least one in the seat ( 1 ) integrated resonator ( 4 ) with predetermined resonance characteristics in an unoccupied seated state of the seat ( 1 ); Storing threshold values associated with the respective resonance characteristics in a memory device ( 9 ); Detecting a change in at least one of the predetermined resonance characteristics of the at least one resonator ( 4 ) by means of at least one with the at least one resonator ( 4 ) associated detection device ( 7 ); and recognizing a seat occupancy of the seat ( 1 ) when an associated threshold value is exceeded due to the changed at least one resonance characteristic by means of a with the at least one detection device ( 7 ) associated evaluation device ( 8th ). Method according to claim 10, characterized in that the resonant frequency of the at least one resonator ( 4 ), the quality or oscillation amplitude of the at least one resonator ( 4 ) and / or the coupling of the at least one resonator ( 4 ) to at least one other circuit element the at least one resonance characteristic of the at least one resonator ( 4 ). Method according to claim 10 or 11, characterized in that the at least one resonator ( 4 ) directly or indirectly as part of at least one oscillator ( 5 ), with its vibration frequency measured and a change in the sen vibration state is evaluated with the at least one detection device ( 7 ) is connected. Method according to one of claims 10 to 12, characterized in that a predominantly planar design capacitor (C) is a component of the at least one resonator ( 4 ), wherein at least the capacitor (C) is provided on a circuit board or foil which is in the seat ( 3 ) of the seat ( 1 ) is integrated. Method according to one of claims 10 to 13, characterized in that the at least one resonator ( 4 ) is completely provided on a foil, which in the seat ( 3 ) of the seat ( 1 ) is integrated. Method according to one of claims 10 to 14, characterized in that the at least one resonator is a resonant frequency in an unoccupied seated state of the seat ( 1 ) in the range of several MHz to several GHz. Method according to one of claims 10 to 15, characterized in that a plurality of resonators ( 4 ) at different positions of the seat ( 1 ), preferably at different positions in the seat surface ( 3 ) of the seat ( 1 ) and arranged with the at least one detection device ( 7 ) get connected. Method according to one of claims 10 to 16, characterized in that a memory device ( 9 ) is provided for storing in advance predetermined threshold values assigned to the respective resonance characteristics, the memory device ( 9 ) with the evaluation device ( 8th ) is connected. Method according to one of claims 10 to 17, characterized in that the evaluation device ( 8th ) with at least one seat ( 1 ) associated airbag module ( 10 ) and upon detection of a seat occupancy of the seat ( 1 ) activates the functionality of the airbag associated with the airbag module.