Resistive oil quality sensor

• US 5,332,961 A
• Filed: 11/06/1986
• Issued: 07/26/1994
• Est. Priority Date: 11/06/1986
• Status: Expired due to Term

• Current Assignee: Virginia Tech Foundation, Inc. (Virginia Polytechnic Institute and State University)
• Original Assignee: Ford Motor Company
• Inventors: Hammerle, Robert H.
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): WILLIAMS, HOWARD L
• Application Number:
  US06/927,618
• Time in Patent Office: 2,819 Days
• Field of Search: 73/10, 73/54, 73/61 R, 73/64, 324/65 CR, 340/631, 340/634, 338/13, 338/14, 338/195, 338/229
• US Class Current: 324/700
• CPC Class Codes: G01N 17/00 Investigating resistance of materials to the weather, to corrosion, or to light
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

An on-board oil quality sensor for use in an internal combustion engine formed of a pair of resisitve elements mounted on a common substrate, wherein one of the resistive elements is exposed to the oil for corrosion as the oil contaminants increase and the other resistive element is protectively sealed from the oil contaminants. Both resistive elements are exposed to the oil temperature and are suitable for monitoring by a bridge type circuit to determine the level of corrosive contaminants in the oil.

Claims

1. A sensor for use in an internal combustion engine to measure the corrosive effects of lubricating oil, comprising:

a substrate having a thermally conductive and electrically insulative surface;

a first electrically resistive copper element mounted on said substrate surface, having a surface of said copper exposed;

a second electrically resistive element mounted on said substrate, having a thermal coefficient of resistance equal to that of said first resistive element; and

a protective coating of a material that is impervious and inert with respect to the corrosive effects of said lubricating oil, deposited over a portion of said substrate and said second electrically resistive element to seal said second element and prevent its corrosion by said oil;

said first and second resistive elements being immersed in oil of said internal combustion engine so that said first resistive element is exposed to said oil and the resistance value of said first resistive element increases due to corrosion as said oil deteriorates from usage;

said sensor further includes a four leg Wheatstone bridge, in which said first and second resistive elements are electrically connected to define first and second legs, for comparing the resistance values of said first and second resistive elements and outputting an electrical signal corresponding to the difference in said values; and

said Wheatstone bridge further includes third and fourth resistors electrically connected to define third and fourth legs of the bridge and physically remote from said first and second resistive elements, and one of said third and fourth resistors is adjustable so as to provide a balanced bridge when said oil is changed or said substrate, bearing said first and second resistive elements, is substituted with a new one.