Method and apparatus for stabilizing parasitic error capacitance in oil quality sensors

• US 20040212375A1
• Filed: 04/28/2003
• Published: 10/28/2004
• Est. Priority Date: 04/28/2003
• Status: Active Grant

• Current Assignee: Detroit Diesel Corporation (Mercedes-Benz Group AG)
• Original Assignee: Detroit Diesel Corporation (Mercedes-Benz Group AG)
• Inventors: Marszalek, Gary A.
• Granted Patent: US 6,847,216 B2
• Time in Patent Office: Days
• US Class Current: 324/698
• CPC Class Codes: G01N 27/226 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

A sensor for detecting changes in the dielectric constant of a liquid is described. The sensor has two electrodes immersed in the liquid with dielectric surfaces substantially parallel with each other, and a ramp disposed on a support between the electrodes. The ramp intersects the surfaces at obtuse and acute angles respectively and provides a surface disposed at an angle relative to an electric field extending between the two electrodes, thereby reducing parasitic effects of the sensed dielectric content of the liquid. Slots in the electrode adjacent the lower end of the ramp reduce the strength of the field proximate to the ramp and thereby further reduce the parasitic effects.

Claims

1. A sensor adapted to be disposed in a flow of fluid for detecting changes in the dielectric constant of the liquid, the sensor comprising:

a first elongated electrode member having a metallic core and a first dielectric, fluid contacting surface;

a second elongated electrode member having a metallic portion and a second dielectric, fluid contacting surface;

a support supporting the electrodes and the fluid contacting surfaces in a spaced, substantially parallel disposition with the first and second dielectric, fluid contacting surfaces facing one another to accommodate the circulation of fluid through the space between the electrodes; and

a ramp disposed on the support between the dielectric surfaces of the electrodes;

the ramp intersecting the first and second contacting surfaces at obtuse and acute angles respectively and providing a surface angularly disposed relative to electric field coupling between the first and second electrode, thereby reducing parasitic effects of the sensed dielectric constant of the liquid.

2. The sensor of claim 1, wherein the acute and obtuse angles are about 45 degrees and 135 degrees respectively.

3. The sensor of claim 1 including at least one port disposed proximate to the ramp and allowing liquid flow therethrough.

4. The sensor of claim 3, wherein the port is disposed along a bottom of the ramp.

5. An oil condition sensor, comprising:

a housing having a cylindrical side wall with an inner surface defining a first electrode, the housing including at least one opening for accommodating a flow of oil therethrough, the first electrode having a metallic core and a first dielectric, fluid contacting inner surface;

a member concentrically disposed within the housing and having an outer surface defining a second electrode spaced from the inner surface, the second electrode having a metallic core and a second dielectric, fluid contacting outer surface;

the inner and outer dielectric, fluid contacting surfaces being substantially parallel in disposition;

a ramp disposed within the space between the inner and outer surfaces at obtuse and acute angles respectively, the ramp having a surface angularly disposed relative to electric field coupling between the first and second electrodes, thereby reducing parasitic effects of the sensed dielectric constant of the liquid.

6. The sensor of claim 5, wherein the acute and obtuse angles are about 45 degrees and 135 degrees respectively.

7. The sensor of claim 5 including at least one port disposed proximate to the ramp and allowing liquid flow therethrough.

8. The sensor of claim 7, wherein the port is disposed along a bottom of the ramp.

9. A method for sensing a variation in the dielectric constant of a liquid using a first elongated electrode member having a metallic core and a first dielectric, fluid contacting surface;

a second elongated electrode member having a metallic portion and a second dielectric, fluid contacting surface;

a support supporting the electrodes and the fluid contacting surfaces in a spaced, substantially parallel disposition with the first and second dielectric, fluid contacting surfaces facing one another to accommodate the circulation of fluid through the space between the electrodes;

said method comprising the steps of;

disposing a parasitic incline between the first and second dielectric, fluid contacting surfaces;

applying alternating current to the electrodes; and

generating an electric field between the electrodes, causing the strength of the electric field proximate to the parasitic incline to be relatively weaker than the strength in other regions between the electrodes, thereby reducing errors in the measurement of the dielectric constant of the liquid.

10. The method of claim 9 including the step of computing the dielectric constant.

11. The method of claim 9 including the step of reading an output.

12. The method of claim 9, wherein the parasitic incline is associated with a ramp disposed on the support between the dielectric surfaces of the electrodes;

the ramp intersecting the first and second contacting surfaces at obtuse and acute angles respectively and providing a surface angularly disposed relative to electric field coupling between the first and second electrode, thereby reducing parasitic effects of the sensed dielectric constant of the liquid.