Apparatus and method of producing a sensing substrate
An occupant or object sensing system in a vehicle includes electrical circuits for resistive and/or capacitive sensing and corresponding circuits shielding the sensing system from interference. A sensing circuit and a shielding circuit may be printed by screen printing with conductive ink on opposite sides of a non-conductive substrate. The substrate is a plastic film or other fabric that has an elastic memory structure that is resilient to stretching. The conductive inks used to print circuits onto the substrate have a similar resilience to stretching such that the substrate and the circuits thereon can be subject to deforming forces without breaking the printed circuits. The substrate may be covered with a carbon polymer layer to provide alternative conductive paths that enable fast recovery for conduction in the presence of any break in the printed conductive traces on the substrate.
1. A sensor for occupant monitoring in a vehicle, comprising:
a flexible substrate that is resilient to a deforming load thereon;
a plurality of conductive traces on the flexible substrate, said conductive traces configured for bending in response to the deforming load applied to the flexible substrate and the conductive traces; and
a resistive sensor circuit on a first side of said flexible substrate, the resistive sensor circuit comprising a respective set of the conductive traces, wherein said resistive sensor circuit has an electrical resistance that fluctuates according to a degree of deformation of the respective set of the conductive traces in response to the bending.
2. The sensor of claim 1 , wherein said plurality of conductive traces comprise conductive ink traces.
3. The sensor of claim 1 , wherein said plurality of conductive traces comprise screen printed conductive traces.
4. The sensor of claim 1 , wherein said plurality of conductive traces comprise silver polymer ink.
5. The sensor of claim 1 , wherein said substrate and said conductive traces have a mutual resilience configured to allow said substrate and said conductive traces to stretch and contract in conjunction with one another without breaking the conductive traces.
6. The sensor of claim 5 , wherein said substrate and said conductive traces comprise overlapping stretching parameters providing the mutual resilience.
7. The sensor of claim 6 , wherein said substrate and said conductive traces comprise a mutual resilience to withstand deforming forces that stretch a dimension of the sheet in any direction by an amount between 2 percent and 10 percent.
8. The sensor of claim 1 , wherein said substrate comprises a nonconductive substrate.
9. The sensor of claim 1 , wherein said substrate comprises a single layer of insulating material.
10. The sensor of claim 9 , further comprising respective circuit connections at a first end of at least one of said conductive traces and at an opposite end of said at least one of said conductive traces.
11. The sensor of claim 1 , further comprising a capacitive sensor circuit formed of a second set of said conductive traces on said first side of said flexible substrate.
12. The sensor of claim 1 , further comprising a capacitive shield circuit formed of a third set of said conductive traces on a second side of said substrate.
13. The sensor of claim 1 , further comprising a capacitive sensor circuit formed of a second set of said conductive traces on said first side of said flexible substrate and a capacitive shield circuit formed of a third set of said conductive traces on a second side of said substrate, wherein said resistive circuit, said capacitive circuit, and said capacitive shield circuit each comprise a plurality of layers.
14. The sensor of claim 13 , wherein said resistive circuit comprises a resistive circuit assembly comprising a highly conductive deposit layer of a first conductivity and a moderately conductive deposit layer of a second conductivity that is lower than the first conductivity.
15. The sensor of claim 13 , wherein said capacitive circuit comprises a multiple layer assembly formed alongside but without touching the resistive sensor assembly.
16. The sensor of claim 15 , wherein said capacitive circuit comprises a conductive patterned section and an overlay section.
17. The sensor of claim 16 , wherein said conductive patterned section comprises a highly conductive pattern having a respective conductivity and said overlay section comprises a moderate conductivity that is lower than the respective conductivity of the highly conductive pattern.
18. The sensor of claim 13 , wherein said capacitive shield circuit comprises a highly conductive trace having a respective trace layer of a respectively high conductivity and an overlay layer of a respectively moderate conductivity that is lower than the respectively high conductivity.
19. The sensor of claim 1 , wherein said flexible substrate comprises a non-conductive film.
20. The sensor of claim 19 , wherein said non-conductive film comprises at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide plastics (PI), a thermoplastic polyurethane, and combinations thereof.