Sensor arrangement

BACKGROUND INFORMATION

[0001] The present invention relates to a sensor system, particularly for detecting mechanical forces which, for example, during a collision of a motor vehicle with an obstacle, lead to an intrusion or deformation of components on this motor vehicle.

[0002] Such sensor systems are used, for example, for so-called occupant-restraint systems in motor vehicles which, for instance, trigger airbags accidents to protect the vehicle occupants from the results of a collision. For triggering these occupant-restraint systems, for example, the acceleration in the passenger compartment or at peripheral regions of the motor vehicle is measured. In addition to the sensor or sensors in the passenger compartment, the peripheral sensors are, as a rule, preferably installed at the deformable areas of the vehicle. Thus, for example, for better and early recognition of lateral collisions, acceleration sensors are installed on the so-called B-pillar and/or C-pillar of the vehicle, or on the seat crossmembers below the front seat.

[0003] In comparable manner, for better recognition of head-on crashes, sensors which likewise usually measure the acceleration and convert the measured values into corresponding, electronically evaluable signals to better determine the severity of a crash are also built into the front crash crumple zone of the vehicle.

[0004] Particularly in the case of lateral collisions, the known acceleration sensors have the disadvantage that they permit rapid detection of a crash only if the sensor is directly struck. Thus, for example, when installed on the B-pillar, a fixed-pole crash into the door of the vehicle is recognized too late. Pressure sensors, known by themselves, also cause problems with respect to a separation of the triggering and non-triggering conditions when installed at these locations, since they should not respond, for instance, to heavy door slamming. In the case of a triggering of driver and front-seat passenger airbags, as well, these pressure sensors must not interpret the pressure rise in the passenger compartment as deformation of the door.

[0005] Furthermore, in the case of a collision, the velocity of the intrusion by the obstacle is also a decisive factor which determines the severity of the accident and the danger of injury for the occupants. In this context, the intrusion velocity is linked to the width of the obstacle and the location of the impact. For example, a post having a small surface intrudes very deeply and quickly, while a wide barrier which impacts on the vehicle with the same velocity intrudes more slowly and not as deeply. If the post strikes the middle of the door, it penetrates considerably more quickly than if it strikes on the B- pillar. The wider an obstacle is, the more slowly it will penetrate, and the softer the location of the impact, the deeper and more quickly it will penetrate.

SUMMARY OF THE INVENTION

[0006] A sensor system mentioned at the outset for detecting forces which lead to a deformation of mechanical components, e.g., on motor vehicles, is advantageously further developed according to the present invention in that, according to the characterizing part of the main claim, provision is made chiefly on the possibly deformed components for a number of contact elements which are arranged staggered one behind the other in a possible deformation direction.

[0007] Insulation layers, which are compressible by the deformation of the component, are advantageously disposed between the contact elements. The contact elements are electroconductively connected to an electronic evaluation circuit by which a contacting and/or de-contacting of adjacent contact elements, caused by the deformation, is then able to be detected and converted into control and/or regulating signals.

[0008] In the sensor system according to the present invention, it is particularly advantageous if one contact element represents a base element, and at least two contact elements are positioned in front of it at predefined distances. The distances, i.e. the geometric configuration, and the material for these two compressible insulation layers are in each case selected so that the intrusion velocity of the object causing the deformation is able to be derived from the moments of the contacting and or de-contacting of the contact elements situated one behind the other in the deformation direction.

[0009] In the present invention, the compressible insulation layer made, for example, of foamed plastic, between the contact elements has the function of correctly defining the geometrical spacings of the contact elements. Therefore, the compression properties of the material, in the same way as the temperature characteristic and the stiffness, is not critical. In constructing the sensor system, care must only be taken that the stiffness does not become so high over the course of the service life of the sensor system that compression of the sensor system is prevented. In most application cases, the deformation forces occurring are so considerable that an evaluable deformation is already ensured by them alone, even if the stiffness of the sensor system should vary.

[0010] The present invention permits the construction of a so-called intrusion sensor for a motor vehicle which, in response to an accident, detects in a simple manner the penetration of an obstacle into the components of the vehicle and, in so doing, allows determination of both the velocity of the intrusion and the width of the impacting object, as well as the location of the intrusion. The intrusion sensor itself is deformed by the penetration, and the deformation is utilized to bring the contact elements in contact with one another, it also being possible to utilize the deformation itself for determining the severity of the crash. Moreover, the intrusion sensor itself may be utilized as a structural element in such a way that the deformation characteristic of the vehicle may be influenced.

[0011] In addition to the lateral placement, such an intrusion sensor may also be used for detecting head-on collisions or rear collisions. For example, it is then mounted on the bumper between the bumper and the plastic cladding. In one such configuration, the sensor measures the relative velocity of the crash, and the width of the obstacle and the location of the impact may again be determined. For example, using this intrusion sensor, it is then possible to obtain information about the impacting obstacle, as well.

[0012] The signals generated by the contact elements are evaluated in a simple manner by connecting the contact elements, e.g., via an RC circuit, directly to a microprocessor of the electronic evaluation circuit, the microprocessor being able to directly measure the moments, e.g. T1 and T2, mentioned above. However, moments T1 and T2 may also be determined by charging a capacitor, and sent as coded information directly to an analyzing unit, e.g. an airbag control unit in a motor vehicle.

[0013] For the contact elements to come reliably in contact, the sensor system must also really be deformed. Misuse conditions such as hammer blows and striking the door will as a rule not deform the sensor to the extent that both contact elements are closed. The misuse problems, which are to some extent very serious for the known acceleration or pressure sensors, are substantially prevented by the present invention. If, for example, the sensor is structurally mounted near a reinforcement tube in the door of a motor vehicle, then the safety with respect to misuse conditions is again increased.

[0014] In the following, advantageous specific embodiments of the present invention are indicated having configurations of the contact elements and of the insulation layers, as well as of an RC circuit, designed for particular application cases.

[0015] In these specific embodiments, the compressible insulation layers are arranged in at least one partial area of the surface of the contact elements, and in the area remaining in each case, a contact is able to be produced with the adjacent contact element by compression of the insulation layer and/or by deformation of the respective contact element.

[0016] In a first specific embodiment, the insulation layers between the contact element situated at the top in the deformation direction and the middle contact element are disposed in at least one lateral partial area, and the insulation layers between the middle contact element in the deformation direction and the base element are arranged in two opposite lateral partial area.

[0017] The contact elements are provided geometrically here such that electrical contact is ensured in response to complete compression of the insulation layer; this may be additionally supported by suitable bars on the base element and, if desired, on the other contact elements, as well. The base contact element itself may also be formed geometrically so that it has an elevation in the middle. This elevation must be so high that it corresponds approximately to the thickness of the compressible material in the completely compressed state.

[0018] In another specific embodiment, the insulation layer between the contact element situated at the top in the deformation direction and the middle contact element is disposed in one lateral partial area, and the insulation layer between the middle contact element in the deformation direction and the base element is arranged in the same lateral partial area.

[0019] Thus, in this case, the actual contact surfaces are situated spatially next to the compressible areas. In this context, the base contact element is constructed such that it is stable enough so that the upper and the middle contact elements and the compressible material are pressed together for the contacting first, before the base element is bent. So that the sequence of the compression remains defined, it is advantageous to select a stiffness for the first insulation layer in the region between the upper and the middle contact elements which is less than that of the second insulation layer in the region between the middle contact element and the base element. This ensures that the upper and the middle contact elements are closed first before the second insulation layer is compressed at moment T2.

[0020] In a further specific embodiment, at least two contact elements are made of partial contact elements which, in the quiescent state, lie side by side, contacting. The compressible insulation layers are arranged in at least one partial area of the surface of the at least two contact elements, and in the area remaining in each case, a de-contacting, i.e. opening of the partial contact elements is able to be effected by compression of the insulation layer and/or by deformation of the respective contact element.

[0021] With this specific embodiment, an intrusion sensor may be implemented in that, due to the intrusion of an object and the resulting compression, the upper contact element is pressed, for example, by way of an electrically insulating spacer, onto a first closed contact of the middle contact element. In this context, the upper contact element is formed geometrically so that the contact of the middle contact element is opened. If the sensor system is further compressed, then the middle contact element and an electrically insulating spacer press on a lower contact element on the base element and open it. The intrusion velocity may then in turn be determined from the time interval of this opening.

[0022] For a particularly advantageous evaluation, the upper contact element and the base contact element may be made of a magnetic material, and the middle contact element may be a flat coil. In this case, a contacting of the contact elements leads to a change in the impedance between the upper and the middle and between the middle and the base contact element. The closing of the contact elements may also be detected by one or more Hall sensors. According to one advantageous further development, permanent magnets are provided in the upper contact element and in the base contact element. The contacting of the upper and middle contact elements and/or of the middle and the base contact elements is easily detectable by a contact of the Hall sensors with the permanent magnets.

[0023] In another specific embodiment, the contact elements may be formed by two planar-like fracture ceramics which in each case are separated by a compressible insulation layer. The fracture ceramics are provided here with an electroconductive path or layer whose interruption is detectable. In this case, an interruption in response to the intrusion of an object defines moment T of the impact. A fracture of the upper ceramic moment T1 of the impact, and the fracture of the lower ceramic moment T2. It is then possible to determine the intrusion velocity from the time difference between T1, and T2 and the thickness of the compressible insulation layer.

[0024] It is also advantageous if at least the upper and the middle contact elements are divided in a direction, preferably the longitudinal direction, into a plurality of contact regions, where in each case pairs of upper and middle contact elements are connected via separate lines to the evaluation circuit.

[0025] Information about the location of the deformation may also be obtained due to this division. Between the respective matching pairs, the intrusion velocity may now also be determined nearly independently for each partial area of the sensor system, and the width of the intruding object may be determined from the number of compressed subdivisions. Moreover, the location of the primary intrusion may also be determined from the time sequence of the closing of the respective contact pairs.

[0026] The already mentioned protective circuit in the connection of the contact elements may be implemented in a simple manner by a resistor network in which, for example, a parallel resistor situated in each case between the upper and the middle and the middle and the base contact element, as well as a series resistor leading from the middle contact element are applied. The series resistor is connected by a first line, and the joined connection terminals of the upper and the base contact elements are connected by a second line to the evaluation circuit.

[0027] If the contact elements are subdivided into a plurality of sub-regions, a resistor network may again be implemented, in which the contact elements are connected to the evaluation circuit via a resistor network, where in each of the divided contact regions, a parallel resistor is situated between the upper and the middle contact element. These parallel resistors are connected in series in the direction of the divided regions, and the outer connection terminals of this series circuit are run to the evaluation circuit. With this, it is also possible to reduce the number of lines via which the sensor system is connected to the evaluation circuit, without the evaluation capability suffering.

[0028] The surfaces of the contact areas of the contact elements may be treated in such a way that no erosion can take place and the closing of the contacts is also ensured over the entire service life of the sensor system. Since, when used in the motor vehicle, the sensor system is also able to be mounted in the door or on the bumper of the motor vehicle, the sensor system may also be enclosed in a simple manner by a waterproof casing which, however, must permit a deformation without hindrance. For example, this casing may be a thin rubber casing which hermetically seals the sensor, but permits compression and a pressure equalization in response to temperature fluctuations. For example, the entire sensor system may also be incorporated into a casing of thin, easily deformable metal, such as a thin aluminum casing.

[0029] These and other features of preferred further developments of the invention, in addition to being derived from the claims, are also derived from the specification and the drawings; the individual features, each by itself alone or combined in the form of sub-combinations, are able to be implemented in the specific embodiment of the invention and in other fields, and are able to represent embodiments which are advantageous as well as patentable by themselves, for which protection is claimed here.

BRIEF DESCRIPTION OF THE DRAWING

[0030] Exemplary embodiments of the sensor system according to the present invention are explained with reference to the drawing, in which:

[0031]
FIG. 1 shows a schematic representation of a first exemplary embodiment, in which the sensor system is mounted as an intrusion sensor in the door of a motor vehicle;

[0032]
FIG. 2 shows a second exemplary embodiment with a modification of the arrangement of contact elements and insulation layers in the intrusion sensor according to FIG. 1;

[0033]
FIG. 3 shows a third exemplary embodiment with a modification of the arrangement of contact elements and insulation layers in the intrusion sensor according to FIG. 1, in which the contact elements are opened by a deformation;

[0034]
FIG. 4 shows an intrusion sensor according to FIG. 1 having a resistor network as RC circuit;

[0035]
FIG. 5 shows a further exemplary embodiment of an intrusion sensor having regions of the contact elements that are distributed in the longitudinal direction and are connected via a resistor network; and

[0036]
FIG. 6 shows an intrusion sensor according to FIG. 5 having an expanded resistor network.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0037] An exemplary embodiment of a sensor system 1 according to FIG. 1 shows an upper electroconductive contact element 2, a middle electroconductive contact element 3 and a third electroconductive contact element 4 as base element. Situated between contact elements 2, 3 and 4 are compressible insulation layers 5, 6 and 7 made, for example, of foamed plastic, which spatially separate contact elements 2, 3 and 4 at a predefined distance, distance D between middle contact element 3 and base element 4 in particular being significant here for the evaluation of the sensor signals.

[0038] Sensor system 1 is installed, for example, in door trim 10 of a motor vehicle (not shown here), and is able to be deformed in a direction 11 during an accident. Contact elements 2, 3 and 4, possibly with bars 8 and 9, are provided in such a way that an electrical contact is ensured between these elements 2, 3 and 4 in response to complete compression of insulation layers 5, 6 and 7 because of a crash.

[0039] Sensor system 1 may be installed, for example, on the inside of the motor-vehicle door below the reinforcing tube; sensor system 1 may cover the entire length of the door, for example, from the front stop at the so-called A-pillar up to the door lock. If door trim 10 is now pressed in by an impact of an object, then upper contact element 3 is pressed onto middle contact element 4 and is contacted to it, so that moment T1, of the contacting may be detected via lines 12, 13 and 14 connected to these contact elements 2, 3 and 4. The obstacle then penetrates further and finally presses upper and middle contact elements 2 and 3 onto base element 4. The contact between middle contact element 3 and base element 4 is then closed at a moment T2.

[0040] Intrusion velocity Vi of the object may then be ascertained from the known distance D between middle contact element 3 and base element 4, and moments T1, and T2 according to the equation

V

i

=D/
(T2−T1) (1)

[0041] Typically, distance D is, let us say, 2 cm, with which at a velocity of 20 m/s (corresponding to 72 km/h) a time difference T2−T1 of 0.02/20 sec corresponding to 1 ms results. This time difference permits both a direct measurement by a microprocessor in the evaluation circuit, as well as a rapid triggering of actuators in the vehicle, such as, for example, an airbag.

[0042] In an exemplary embodiment according to FIG. 2, an intrusion sensor 20 is provided with contact elements 21, 22 and 23 which, in a modification with respect to FIG. 1, are in each case provided on one side with an insulation layer 24 and 25. Intrusion velocity Vi is determined here in the same manner as in the exemplary embodiment according to FIG. 1.

[0043]
FIG. 3 shows an exemplary embodiment of a sensor system 30 in which an upper contact element is implemented as pressure plate 31. A middle contact element 32 and a lower contact element 33 are also provided on a base plate 34. Contact elements 32 and 33 are made of partial contact elements which, in the quiescent state, lie side by side, contacting. Compressible insulation layers 35 and 36 are applied between contact elements 31 and 32 and between 33 and 34.

[0044] In this case, contact elements 32 and 33 open by compression of insulation layers 35 and 36 in response to a deformation of sensor element 30. Upon intrusion of an object and the resulting compression of insulation layers 35 and 36, upper pressure plate 31 presses on a first closed contact of middle contact plate 32. Pressure plate 31 is formed geometrically so that the contact of middle partial contact elements 32 is opened, for example, by way of an electrically insulating elevation 37. If the sensor system is further compressed, then middle contact element 32 and an electrically insulating elevation 38 press on lower contact element 33 and open the contact here. As mentioned above, intrusion velocity Vi may again be determined from the time interval of the opening.

[0045] As mentioned above, it is useful if contact elements 2, 3, 4; 21, 22, 23 or 31, 32, 33 are able to be connected via an RC circuit directly to the microprocessor of the evaluation circuit, the microprocessor being able to directly measure times T1, and T2. FIG. 4 shows an example for implementing a resistor network in conjunction with sensor system 1 described with reference to FIG. 1. Here, a resistor R1, is positioned in parallel with respect to contact elements 2 and 3, and a resistor R2 is arranged in parallel with respect to contact elements 3 and 3. From contact element 3, a series resistor R3 goes to connection terminal 14. Therefore, series resistor R3 is connected by a first line, and the joined connection terminals of resistors R1 and R2 of upper and base contact elements 2 and 3, respectively, are connected by a second line via connection terminal 15 to the evaluation circuit.

[0046] Thus, in this exemplary embodiment, the closing of both contacts can be determined using only two connections of the evaluation circuit to sensor system 1. If no impact exists at this intrusion sensor 1, and therefore exhibits no deformation, the total resistance is

R=R

3
+1/(1/R1+1/Rl). (2)

[0047] In the event of an impact, then initially the upper contact between contact elements 2 and 3 is closed. The total resistance is then

R=R

3

+R

2
. (3)

[0048] If sensor system 1 is further deformed and the lower contact closes, then the total resistance is

R=R1. (4)

[0049] If the total length of a sensor circuit 40 according to FIG. 5 is divided into a plurality of narrower regions 41, 42, 43 and 44, then it is also possible to obtain information about the location of a deformation. To that end, the upper and middle contact elements are in each case divided here into a plurality of regions, so that between respective matching pairs of upper and middle contact element and the lower base element, the intrusion velocity may now be determined nearly independently for each partial region 41, 42, 43 and 44 of sensor system 40.

[0050] The width of the intruding object may be determined from the number of compressed regions 41, 42, 43 or 44, and the location of the primary intrusion may be determined from the time sequence of the closing of the respective pairs of contact elements. The resistor network according to FIG. 5 usable here, in each of divided regions 41, 42, 43 and 44, contains a parallel resistor R11, R12; R21, R22; R31, R32 and R41, R42 in each case between the upper and the middle contact element and the middle and the base element. These parallel resistors are connected in series in the direction of the divided regions, and the outer connection terminals of this series circuit are connected to the evaluation circuit via connection terminals 45 and 46.

[0051]
FIG. 6 shows a modification of the resistor network according to FIG. 5, where the resistor pairs of parallel resistor R11, R12; R21, R22; R31, R32 and R41, R42 are run on one side in parallel via a series resistor R10, R20, R30 and R40, as well as a total series resistor R0 to connection terminal 46, and with the other side directly to connection terminal 45.

Sensor arrangement

Information

Publication Number

Date Filed

Date Published

Inventors

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Priority Claims (1)

PCT Information