Sensor element for detecting a physical measuring variable between bodies exposed to high tribological strain

• US 20040006258A1
• Filed: 04/25/2003
• Published: 01/08/2004
• Est. Priority Date: 09/08/2001
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Meyer, Klaus, Mueller, Ulrich, Nemzov, Julius
• Granted Patent: US 7,523,670 B2
• Time in Patent Office: Days
• US Class Current: 600/300
• CPC Class Codes: F16C 17/24 with devices affected by abnormal or undesired positions, e.g. for preventing overheating, for safety
• CPC Class Codes: F16C 19/52 with devices affected by abnormal or undesired conditions
• CPC Class Codes: G01L 5/0014 by using capacitive sensors
• CPC Class Codes: G01L 5/0085 Force sensors adapted for insertion between cooperating machine elements, e.g. for measuring the nip force between rollers

Abstract

The invention proposes sensor elements (5) for detecting a physical measurement variable such as a pressure, a temperature, a gap width, or a capacitance between two bodies (10, 20) that move in relation to each other during operation and experience high tribological stress. In certain areas between the surfaces of the bodies (10, 20) that move in relation to each other, in a surface region of at least one of the bodies (10), a sensitive layer (13, 30), in particular a sensor segment (13), is provided, which is separated from the body (10) by an insulation layer (12) and has a covering layer (14) in a first embodiment. In an alternative embodiment, a surface region of at least one of the two bodies (10) has a recess (23) in which the sensor surface (13) is disposed on the insulation layer (12). In a third embodiment, the sensor surface (13) has a length of 10 μm to 5 mm, a width of less than 5 μm, and a thickness of less than 200 nm.

Claims

1. A sensor element for detecting a physical measurement variable such as a pressure, a temperature, a capacitance, or a gap width between two bodies (10, 20) that move in relation to each other during operation and experience high tribological stress, wherein in certain areas between the surfaces of the bodies (10, 20) that move in relation to each other, in a surface region of at least one of the bodies (10), a sensitive layer (13, 30) is provided, which is separated from the body (10) by an insulation layer (12), characterized in that the sensitive layer (13, 30) is provided with a covering layer (14).

2. The sensor element according to claim 1, characterized in that in comparison to the sensitive layer (13, 30), the covering layer (14) is abrasion resistant and has a low electrical conductivity or is insulating.

3. The sensor element according to claim 1 or 2, characterized in that the covering layer (14) has a thickness of less than 500 nm, in particular less than 200 nm.

4. The sensor element according to one of the preceding claims, characterized in that the covering layer (14) contains or is at least essentially comprised of carbon, in particular a diamond-like carbon or an amorphous diamond-like carbon, or that it contains carbon, in particular a diamond-like carbon or an amorphous diamond-like carbon as well as oxygen and silicon.

5. The sensor element according to one of the preceding claims, characterized in that the sensitive layer (13, 30), which is particularly embodied in the form of a sensor segment (13), is comprised of a metal, in particular chromium, platinum, titanium, or a nickel-chromium or nickel-copper-manganese alloy and has an electrical resistance of 500Ω

to 3 kΩ

.

6. The sensor element according to one of the preceding claims, characterized in that the sensitive layer (13, 30) is connected to external electronic components as part of an electronic measurement bridge by means of contact surfaces (11), which are provided at two ends and are separated from the body (10) by means of the insulation layer (12), and possibly by means of additional strip conductors.

7. The sensor element according to one of the preceding claims, characterized in that the sensitive layer (13, 30) has a different thickness, in particular a significantly smaller thickness than the contact surfaces (11).

8. The sensor element according to one of the preceding claims, characterized in that the sensitive layer (13, 30), which is in particular embodied as a sensor segment (13), has a length of 10 μ

m to 5 mm, a width of 50 nm to 50 μ

m, in particular of 50 nm to 5 μ

m, and a thickness of less than 200 nm, in particular less than 10 nm.

9. The sensor element according to one of the preceding claims, characterized in that a bonding layer (33) is provided between the insulation layer (12) and the body (10) and/or between the sensitive layer (13, 30) and the covering layer (14).

10. The sensor element according to one of the preceding claims, characterized in that the bonding layer (33) between the insulation layer (12) and the body (10) has a thickness of 20 nm to 1 μ

m and/or the bonding layer (33) between the sensitive layer (13, 30) and the covering layer (14) has a thickness of 20 nm to 1 μ

m.

11. The sensor element according to one of the preceding claims, characterized in that the bonding layer (33) contains carbon, in particular a diamond-like carbon or an amorphous diamond-like carbon, and silicon, that the bonding layer (33) is comprised of a metal such as titanium or chromium, an alloy, or a semiconductor such as silicon, or that the bonding layer (33) has at least two component layers of different composition disposed one on top of the other.

12. The sensor element according to one of the preceding claims, characterized in that the insulation layer (12) has at least two component layers (31, 32), wherein one component layer (31) is a layer (31) with at least a low electrical conductivity in comparison to the sensitive layer (13, 30) and wherein a component layer (32) is a layer with a higher tribological stress capacity in comparison to the component layer (31) with the comparatively low electrical conductivity, or in that the insulation layer is a layer that is at least essentially comprised of carbon or contains carbon, oxygen, and silicon.

13. The sensor element according to claim 12, characterized in that the component layer with the higher tribological stress capacity is a layer (32) with a comparatively high electrical conductivity in comparison to the component layer (31) with the low electrical conductivity and has a high degree of hardness and/or a low coefficient of friction in comparison to it.

14. The sensor element according to one of the preceding claims, characterized in that the layer (32) with the higher tribological stress capacity is at least essentially comprised of carbon, in particular a diamond-like carbon or an amorphous diamond-like carbon, and that the layer (31) with the comparatively low electrical conductivity is comprised of carbon, in particular a diamond-like carbon or an amorphous diamond-like carbon, as well as oxygen and silicon.

15. The sensor element according to one of the preceding claims, characterized in that the insulation layer (12) has a number of recurring pairs of component layers stacked one on top of the other, wherein immediately underneath the sensitive layer (13, 30), first comes the layer (32) with the higher tribblogical stress capacity and underneath that, comes the layer (32) with at least a low electrical conductivity in comparison to the sensitive layer (13, 30), and wherein these two layers (31, 32) constitute the component layer pair.

16. The sensor element according to one of the preceding claims, characterized in that the influence of the physical measurement variable, in particular a changing pressure and/or a changing temperature, causes the sensitive layer (13, 30) to change in at least one measurable physical property, in particular its electrical resistance.

17. The sensor element according to one of the preceding claims, characterized in that the two bodies (10, 20) that move in relation to each other are separated from each other by a gap (21) that contains a lubricant (22).

18. A sensor element for detecting a physical measurement variable such as a pressure, a temperature, a gap width, or a capacitance between two bodies (10, 20) that move in relation to each other during operation and experience high tribological stress, particularly according to one of the preceding claims, wherein in certain areas between the surfaces of the bodies (10, 20) that move in relation to each other, in a surface region of at least one of the bodies (10), a sensitive layer (13, 30) is provided, which is separated from the body (10) by an insulation layer (12), characterized in that the sensitive layer (13, 30) has a length of 10 μ

m to 5 mm, a width of less than 5 μ

m, and a thickness of less than 200 nm.

19. A sensor element for detecting a physical measurement variable such as a pressure, a temperature, a gap width, or a capacitance between two bodies (10, 20) that move in relation to each other during operation and experience high tribological stress, particularly according to one of the preceding claims, wherein in certain areas between the surfaces of the bodies (10, 20) that move in relation to each other, in a surface region of at least one of the bodies (10), a sensitive layer (13, 30) is provided, which is separated from the body (10) by an insulation layer (12), characterized in that a surface region of at least one of the two bodies (10) has a recess (23) that contains the sensor surface (13) on the insulation layer (12).

20. The sensor element according to claim 19, characterized in that the upper edge of the sensitive layer (13, 30) or of the sensitive layer (13, 30) provided with a covering layer (14) is at least approximately flush with the surface of the body (10), protrudes above this surface by maximally 500 nm, in particular less than 100 nm, or is recessed below this surface by maximally 500 nm, in particular less than 100 nm.

21. The sensor element according to claim 19, characterized in that contact surfaces (11) are disposed in the recess (23) at two ends of the sensitive layer (13, 30), wherein the contact surfaces (11) and the sensitive layer (13, 30) are separated from the body (10) by means of the insulation layer (12), which is in particular only provided at the bottom of the recess (23).

22. The sensor element according to one of claims 19 to 21, characterized in that the recess (23) is produced in the insulation layer (12), wherein the sensitive layer (13, 30) is disposed in the recess (23), on the insulation layer (12).

23. The sensor element according to one of claims 19 to 22, characterized in that the insulation layer (12) has additional recesses, wherein the contact surfaces (11) are disposed on the insulation layer (12) in the vicinity of or inside the additional recesses, and are connected to the sensitive layer (13, 30).

24. The use of a sensor element according to one of the preceding claims to detect a contact pressure and/or a contact temperature and/or a gap width in the contact region between lubricated components that experience high tribological stress.