WEIGHT-RESPONSIVE VEHICLE SEAT OCCUPANCY CLASSIFICATION SYSTEM

Abstract

A vehicle seat occupancy classification system having at least one weight-responsive sensor, including a supporting plate, a collecting plate, a hinge member mechanically connecting the supporting plate and the collecting plate, at least one elastic spring member, and a position sensor that is configured to determine a gap dimension between the supporting plate and the collecting plate. The occupancy seat classification system includes an evaluation unit that is configured to receive the output signal from the position sensor and to provide a seat occupant classification based on a level of the received output signal and at least a first pre-determined threshold value of the output signal.

Claims

1. A vehicle seat occupancy classification system, comprising at least one weight-responsive sensor, including a supporting plate that is fixable to a top surface of a seat pan and/or to a suspension of the seat pan, a collecting plate that in at least one operational state is arranged substantially parallel to the supporting plate and, with regard to a direction of mechanical load to be applied perpendicular to the supporting plate by a seat occupancy, between the supporting plate and a seat cushion of the vehicle seat, a hinge member having an axis of articulation that is arranged parallel to the supporting plate, wherein the supporting plate and the collecting plate are mechanically connected by the hinge member so as to enable a rotational movement of the collecting plate relative to the supporting plate and about the axis of articulation, at least one elastic spring member that is disposed, with respect to the direction of mechanical load, between the collecting plate and the supporting plate and is spaced from the axis of articulation, wherein the elastic spring force of the elastic spring member is provided to serve as a counteracting force for a mechanical load that is applied to the collecting plate in the direction of mechanical load, and a position sensor that is configured to determine a gap dimension between the supporting plate and the collecting plate in a specified distance to the axis of articulation , and to provide an output signal that is indicative of the determined gap dimension; and an evaluation unit that is configured to receive the output signal from the position sensor and to provide a seat occupancy classification based on a level of the received output signal and at least a first pre-determined threshold value of the output signal.

2. The vehicle seat occupancy classification system as claimed in claim 1, wherein the at least one weight-responsive sensor includes at least one elastic spring member that is spaced from the axis of articulation .

3. The vehicle seat occupancy classification system as claimed in claim 1, wherein the at least one weight-responsive sensor includes at least two elastic spring members that are spaced from each other and from the axis of articulation.

4. The vehicle seat occupancy classification system as claimed in claim 1, wherein upon applying a mechanical load in the direction of mechanical load to the collecting plate, the ratio of a maximum deflection of the at least one elastic spring member and a maximum deflection/deformation of the collecting plate in comparison to a mechanically unloaded shape of the collecting plate is larger than 3.0.

5. The vehicle seat occupancy classification system as claimed in claim 1, wherein the evaluation unit is configured to receive an input signal indicative of a status of activation of an automatic locking retractor of the vehicle, and wherein the classification is provided based both on a level of the received position sensor output signal and the indicated status of activation of the automatic locking retractor.

6. The vehicle seat occupancy classification system as claimed in claim 1, wherein the classification is provided based on the level of the received position sensor output signal and a second pre-determined threshold value of the position sensor output signal, if the indicated status of activation is negative, and wherein the classification is provided based on the level of the received position sensor output signal and a third pre-determined threshold value of the position sensor output signal, if the indicated status of activation is positive.

7. The vehicle seat occupancy classification system as claimed in claim 1, wherein a dimension of the collecting plate perpendicular to a seating direction is larger than 60 mm and less than 120 mm, and a dimension of the collecting plate parallel to the seating direction is larger than 80 mm and less than 150 mm.

8. A method for classifying an occupancy of a vehicle seat, the method comprising steps of: providing a vehicle seat occupancy classification system according to claim 1, installing the at least one weight-responsive sensor between a seat cushion and a seat pan of the vehicle seat, comparing the level of the position sensor output signal with a first pre-determined threshold value, and classifying the occupancy of the vehicle seat as a first class if the level of the position sensor output signal falls below the first pre-determined threshold value, and as a second class if the level of the position sensor output signal is equal to or larger than the first pre-determined threshold value.

9. The method for classifying an occupancy of a vehicle seat as claimed in claim 8, further comprising steps of providing an input signal to the evaluation unit that is indicative of the status of activation of an automatic locking retractor of the vehicle, if the status of activation is negative, classifying the occupancy of the vehicle seat as a first class if the level of the position sensor output signal falls below a second pre-determined threshold value and as a second class if the level of the position sensor output signal is equal to or larger than the second pre-determined threshold value, and if the status of activation is positive, classifying the occupancy of the vehicle seat as a first class if the level of the position sensor output signal falls below a third pre-determined threshold value and as a second class if the level of the position sensor output signal is equal to or larger than the third pre-determined threshold value.

10. A vehicle seat, comprising a seat structure supportable on the passenger cabin floor of a vehicle, a seat cushion, a seat pan and/or suspension of a seat pan having a top surface for receiving the seat cushion, a backrest, a vehicle seat occupancy classification system as claimed in claim 1, wherein the at least one weight-responsive sensor is arranged between the seat cushion and the seat pan and/or suspension of a seat pan.

11. The vehicle seat as claimed in claim 10, wherein at least one out of the seat cushion and the seat pan and/or suspension of a seat pan is furnished with a recess in a lower side of the seat cushion and the top surface of the seat pan and/or suspension of a seat pan, respectively, and the at least one weight-responsive sensor is fixable to the seat pan and is received in the recess.

12. A non-transitory digital memory unit comprising a software module having program code that is stored in the digital memory unit and that is executable by a processor unit of the vehicle seat occupancy classification system to carry out the method of claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0053] FIG. 1 schematically illustrates an embodiment of a vehicle seat occupant classification system;

[0054] FIG. 2 shows a schematic perspective view of the weight-responsive sensor pursuant to FIG. 1 to be installed in a vehicle seat; and

[0055] FIG. 3 shows a graphical representation of the classification by the vehicle seat occupant classification system in accordance with the invention, based on position sensor output signals and pre-determined threshold values for the mechanical load.

DETAILED DESCRIPTION

[0056] FIG. 1 schematically illustrates a partial view of a vehicle seat, in particular a passenger car seat, with an embodiment of a vehicle seat occupant classification system 10 in accordance with the invention. The vehicle seat comprises a seat structure (not shown) that is supportable on the passenger car cabin floor as is well known in the art. The vehicle seat further comprises a backrest (not shown) and a seat pan 12 that is mounted to the seat structure by a suspension 18. FIG. 1 is a view onto the vehicle seat from a position right behind the backrest.

[0057] The vehicle seat further includes a seat cushion (not shown) for comforting a seat occupant. The seat pan has a top surface for receiving the seat cushion. A back edge 16 of the seat pan is proximal to the backrest, and a front edge 14 of the seat pan, which is provided to support a lower thigh region of an adult seat occupant, is distal to the backrest. A seating direction 22 shall be defined pointing from the front edge 14 of the seat pan 12 in a direction that is perpendicular to the front edge 14 and horizontal to the cabin floor.

[0058] The vehicle seat is further equipped with a safety seat belt and an automatic locking retractor (both not shown) that allows to maintain high belt tension when installing a child seat.

[0059] The vehicle seat occupant classification system 10 includes a weight-responsive sensor 26 that is shown in FIG. 1 being installed in the vehicle seat. The weight-responsive sensor 26 includes a supporting plate 28 that is fixed in a substantially centered position to the top surface 20 of the seat pan 12 and to the seat pan suspension 18 by fixing members. As the person skilled in the art is aware of a plurality of suitable fixing members, no further specific details in this regard will be given herein.

[0060] The weight-responsive sensor 26 further includes a collecting plate 30 that in the ready-to-operate status shown in FIG. 1 is arranged parallel to the supporting plate 28 and in a mid-position with respect to a direction perpendicular to the seating direction 22 and parallel to the cabin floor. When the seat cushion is attached the vehicle seat, the collecting plate 30 is disposed, with regard to a direction 24 of mechanical load to be applied perpendicular to the collecting plate 30 by a seat occupant, between the supporting plate 28 and the seat cushion of the vehicle seat.

[0061] As can be seen best in FIG. 2, the supporting plate 28 and the collecting plate 30 are fixedly mounted to the two mutually movable sides of a hinge member 40. The hinge member 40 has an axis of articulation 42 that is arranged parallel to the supporting plate 28, disposed at a back side region of the supporting plate 28 that is proximal to the backrest and parallel to a rear edge of the supporting plate 28. In this way, the hinge member 40 enables a rotational movement of the collecting plate 30 relative to the supporting plate 28 about the axis of articulation 42.

[0062] The collecting plate 30 is of rectangular shape, with a shorter side of the rectangle fixedly mounted to the hinge member 18, and the opposite shorter edge of the rectangle, which is the front edge 34, being aligned with a front edge 32 of the supporting plate 28. The size of the rectangle is about 80 mm x 100 mm.

[0063] The weight-responsive sensor 26 comprises two elastic spring members 38, 38′ designed as metal springs that are disposed, with respect to the direction 24 of mechanical load, between the collecting plate 30 and the supporting plate 28, spaced from each other and spaced from the axis of articulation 42 by a distance d.sub.1. Each elastic spring member 38, 38′ is located in a corner region 36, 36′ of the front edge 34 of the collecting plate. The elastic spring members 38, 38′ are designed such that with no mechanical load L applied to the vehicle seat, the collecting plate 30 and the supporting plate 28 form a gap between the front edge 34 of the collecting plate 30 and the front edge 32 of the supporting plate 28.

[0064] In a ready-to-operate state, the weight-responsive sensor 26 is arranged, in the direction 24 of mechanical load, between the seat cushion and the seat pan 12 of the vehicle seat.

[0065] In case of a mechanical load L being applied to the vehicle seat in the direction 24 of mechanical load, the mechanical load L is transferred via the seat cushion to the collecting plate 30, which will be rotated about the axis of articulation 42, reducing the height of the gap until the mechanical load L is compensated by the counteracting force of the deflected spring members 38, 38′. In this way, the gap height is a measure for the mechanical load L applied to the weight-responsive sensor 26 by a seat occupant, and the applied mechanical load L can be determined by measuring the gap height between the supporting plate 28 and the collecting plate 30 in a specified distance d.sub.2 to the axis of articulation 42. A load vs. deflection characteristic of the combination of the two spring members 38, 38′ can readily be obtained in a calibration procedure.

[0066] To this end, the weight-responsive sensor 26 includes a position sensor 44 that is configured to determine the gap height between the supporting plate 28 and the collecting plate 30, and is arranged close to the front edge 32 of the supporting plate. In this embodiment, the function of the position sensor 44 is based on a capacitive operating principle, but any other position sensor may be employed that appears to be suitable to the person skilled in the art. The position sensor 44 is configured to provide an output signal 46 that is indicative of the determined gap height between the supporting plate 28 and collecting plate 30. Cabling to and from the position sensor 44 is omitted in FIG. 1 for clarity purposes.

[0067] Material and material thickness of the collecting plate 30 are selected such that in case of an applied mechanical load L in the direction 24 of mechanical load to the collecting plate 30, the ratio of a maximum deflection of each of the two elastic spring members 38, 38′ and a maximum deformation of the collecting plate 30 in comparison to a mechanically unloaded collecting plate 30 is larger than 25, so that the collecting plate 30 can be considered rigid compared to the elastic spring members 38, 38′.

[0068] Referring again to FIG. 1, the vehicle seat occupant classification system 10 further includes an evaluation unit 48 that is arranged in a remote position with regard to the vehicle seat. The evaluation unit 48 is configured to receive the output signal 46 from the position sensor 44 as a first input signal and to receive a signal 56 indicative of a status of activation of the automatic locking retractor of the vehicle seat as a second input signal.

[0069] The evaluation unit 48 is configured to provide a seat occupant classification based on a level of the received position sensor output signal 46, an indicated status of activation 56 and pre-determined threshold values tr.sub.1, tr.sub.2, tr.sub.3 of the position sensor output signal 46, as will be described in more detail in the following.

[0070] In the following, an embodiment of a method for classifying an occupancy of the vehicle seat is described. In preparation of operating the vehicle seat occupant classification system 10, it shall be understood that all involved units and devices are in ready-to-operate state and configured accordingly.

[0071] In order to be able to carry out the method, the evaluation unit 48 comprises a software module 54 (FIG. 1). The method steps to be conducted are converted into a program code of the software module 54, wherein the program code is implementable in a digital memory unit 50 of the evaluation unit 48 and is executable by a processor unit 52 of the evaluation unit 48.

[0072] In a first step of the method, the level of the position sensor output signal 46 is compared with a first pre-determined threshold value tr.sub.1 that is stored in the digital memory unit 50 of the evaluation unit 48. In a next step of the method, the evaluation unit 48 classifies the occupancy of the vehicle seat as a first class labeled “class 1” or “small child in a CRS” if the level of the position sensor output signal 46 falls below the first pre-determined threshold value tr.sub.1, and as a second class labeled “class 2” or “adult” if the level of the position sensor output signal 46 is equal to or larger than the first pre-determined threshold value tr.sub.1. In the upper part of FIG. 3, a graphical representation of the classification by the vehicle seat occupant classification system 10 according to this embodiment of the method is given.

[0073] In the first step of an alternative method for classifying an occupancy of the vehicle seat, the status of activation of the automatic locking retractor is checked by the evaluation unit 48. It is understood that the signal 56 indicative of the status of activation of the automatic locking retractor of the vehicle seat is provided to the evaluation unit 48.

[0074] In a next step of the method, the level of the position sensor output signal 46 is compared with a second pre-determined threshold value tr.sub.2 and a third predetermined threshold value tr.sub.3 that are stored in the digital memory unit 50 of the evaluation unit 48.

[0075] If the status of activation is negative, the evaluation unit 48 classifies the occupancy of the vehicle seat as a first class labeled “class 1” or “small child in a CRS” if the level of the position sensor output signal 46 falls below the second pre-determined threshold value tr.sub.2, and as a second class labeled “class 2” or “adult” if the level of the position sensor output signal 46 is equal to or larger than the second pre-determined threshold value tr.sub.2.

[0076] If the status of activation is positive, the evaluation unit 48 classifies the occupancy of the vehicle seat as a first class labeled “class 1” or “small child in a CRS” if the level of the position sensor output signal 46 falls below the third pre-determined threshold value tr.sub.3, and as a second class labeled “class 2” or “adult” if the level of the position sensor output signal 46 is equal to or larger than the third pre-determined threshold value tr.sub.3.

[0077] In the lower part of FIG. 3, a graphical representation of the classification by the vehicle seat occupant classification system 10 according to the alternative embodiment of the method is given.

[0078] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

[0079] Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.