WIM sensor with sensor package

• US 10,378,974 B2
• Filed: 07/24/2017
• Issued: 08/13/2019
• Est. Priority Date: 07/26/2016
• Status: Active Grant

• Current Assignee: Kistler Holding AG
• Original Assignee: Kistler Holding AG
• Inventors: Pfluger, Kim
• Primary Examiner(s): Gray, Francis C
• Application Number:
  US15/657,604
• Publication Number:
  US 20180031429A1
• Time in Patent Office: 750 Days
• CPC Class Codes: G01G 19/024 using electrical weight-sensitive devices
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G08G 1/02 using treadles built into the road pads or other sensitive devices responsive to passage of vehicles E01F11/00

Abstract

A WIM sensor for measuring wheel forces of vehicles on a road that pass over the sensor includes an elongated hollow profile along a longitudinal axis thereof. First and second inner pressing surfaces inside the profile are arranged connected in opposition on both sides by curved, pre-tensioned profile edges. Each of a plurality of piezoelectric measuring elements inside the profile has first and second force absorbing surfaces that face the first and said second pressing surface, respectively. Each of the measuring elements is disposed between two absorbing elements that exert a pretension thereon via the pressing surfaces. A long strip of insulating film provided with an electrically conductive layer on one of its sides electrically connects the first force absorbing surfaces of the measuring elements that are electrically insulated from the first pressing surface.

Claims

1. A WIM sensor for measuring wheel forces of vehicles that pass over the WIM sensor on a road, the WIM sensor comprising:

a hollow profile that is elongated along a longitudinal axis thereof, the hollow profile defining an interior space and defining a first inner pressing surface and a second inner pressing surface;

disposed within the interior space of the hollow profile are the first inner pressing surface and the second inner pressing surface, said inner pressing surfaces being arranged opposite of each other and connected to one another on both sides by curved, pre-tensioned profile edges that are defined by the hollow profile;

disposed within the interior space of the hollow profile are a plurality of piezoelectric measuring elements, each of the plurality of piezoelectric measuring elements defining a longitudinal axis and having a first force absorbing surface and a second force absorbing surface arranged along the respective longitudinal axis thereof, each said respective first and second force absorbing surface facing the respective first and said second pressing surface, wherein all first force absorbing surfaces of the measuring elements are electrically insulated from the first pressing surface of the hollow profile; and

an electrode connecting all first force absorbing surfaces of the measuring elements, the electrode formed as a long strip of insulating film having an electrically conductive layer on one of its sides, the electrode being disposed between the measuring elements and the first pressing surface and with the electrically conductive layer facing the measuring elements.

2. The WIM sensor according to claim 1, wherein the insulating film is a plastic film, preferably a polyimide film;

and the insulating film has a thickness of 0.02 mm to 0.2 mm, preferably of 0.05 mm.

3. The WIM sensor according to claim 2, wherein the insulating film has a thickness of 0.05 mm.

4. The WIM sensor according to claim 1, wherein a thickness tolerance of the insulating film over its entire length is no more than 10% and no more than 0.01 mm.

5. The WIM sensor according to claim 1, wherein the electrically conductive layer is adhered on the insulating film by at least one of the following:

(1) lamination;

(2) thermal evaporation;

(3) sputtering; and

(4) galvanizing.

6. The WIM sensor according to claim 5, wherein the electrically conductive layer has a thickness in the range of 0.005 mm to 0.05 mm.

7. The WIM sensor according to claim 6, wherein the electrically conductive layer has a thickness in the range of 0.009 mm to 0.036 mm.

8. The WIM sensor according to claim 5, wherein the electrically conductive layer has a thickness tolerance of no more than 10% and no more than 0.002 mm over its entire length.

9. The WIM sensor according to claim 1, wherein the electrically conductive layer is coated with a corrosion protection.

10. The WIM sensor according to claim 9, wherein the corrosion protection has a thickness of 0.0001 mm to 0.0005 mm.

11. The WIM sensor according to claim 1, wherein the insulating film includes on each side thereof an insulating edge portion disposed next to the electrically conductive layer.

12. The WIM sensor of claim 11, wherein each of the electrically insulating edge portions has a width of at least 0.5 mm;

and wherein the insulating film is wider than the width of the adjacent holding element.

13. The WIM sensor according to claim 11, wherein the electrically conductive layer has a uniform width that is at least as wide as the width of each of the plurality of measuring elements.

14. The WIM sensor according to claim 1, wherein the insulating film is disposed adjacent to the first pressing surface.

17. The WIM sensor according to claim 1, further comprising:

a first holding element and a second holding element disposed within the interior space of the hollow profile, the first and second holding elements being arranged opposite of each other, the first holding element being disposed between the first inner pressing surface of the hollow profile and the first force absorbing surface of a first one of the plurality of piezoelectric measuring elements, the second holding element being disposed between the second inner pressing surface of the hollow profile and the second force absorbing surface of the first one of the plurality of piezoelectric measuring elements, and wherein the first and second holding elements exert a pretension onto the first one of the plurality of piezoelectric measuring elements via the first and second pressing surfaces.

18. The WIM sensor according to claim 17, wherein at least one cage is arranged in the interior space, said cage serving as a mounting aid in which the plurality of measurement elements and the first and second holding elements are fixed, and wherein the cage has at least one insertion rail in which the insulating film is inserted.

15. A WIM sensor for measuring wheel forces of vehicles that pass over the WIM sensor on a road, the WIM sensor comprising:

a hollow profile that is elongated along a longitudinal axis thereof, the hollow profile defining an interior space;

disposed within the interior space of the hollow profile are a first inner pressing surface and a second inner pressing surface, said inner pressing surfaces being arranged opposite of each other and connected to one another on both sides by curved, pre-tensioned profile edges;

disposed within the interior space of the hollow profile are a plurality of piezoelectric measuring elements, each of the plurality of piezoelectric measuring elements defining a the longitudinal axis and having a first force absorbing surface and a second force absorbing surface arranged along the respective longitudinal axis thereof, each said respective first and second force absorbing surface facing the respective first and said second pressing surface, wherein all first force absorbing surfaces of the measuring elements are electrically insulated from the first pressing surface of the hollow profile;

an electrode connecting all first force absorbing surfaces of the measuring elements, the electrode formed as a long strip of insulating film having an electrically conductive layer on one of its sides, the electrode being disposed between the measuring elements and the first pressing surface and with the electrically conductive layer facing the measuring elements; and

wherein between the first one of the plurality of measuring elements and the second pressing surface is an additional insulating film comprising an electrically conductive layer that faces the first one of the plurality of measuring elements, and wherein the additional insulating film is identical in design to the insulating film.

16. The WIM sensor according to claim 15, wherein the additional insulating film is arranged symmetrically with respect to the insulating film with respect to the longitudinal axis.