Detection method for defect of sensor

• US 8,513,961 B2
• Filed: 01/18/2010
• Issued: 08/20/2013
• Est. Priority Date: 01/19/2009
• Status: Active Grant

• Current Assignee: Niterra Co., Ltd.
• Original Assignee: NGK Spark PLUG Company Limited
• Inventors: Fujita, Tomohisa, Kawai, Takeshi, Teramoto, Satoshi, Mori, Shigeki
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): NGUYEN, HOANG T
• Application Number:
  US12/688,956
• Publication Number:
  US 20100225339A1
• Time in Patent Office: 1,310 Days
• Field of Search: 73/233.1, 73/310.5, 204424-428, 204/431, 324/699
• US Class Current: 324/693
• CPC Class Codes: G01N 27/4067 Means for heating or controlling the temperature of the solid electrolyte
• CPC Class Codes: G01N 27/407 for investigating or analysing gases G01N27/411 takes precedence

Abstract

A defect detection method for a sensor in which a fixing member provides a seal between a sensor element and tubular metallic members, the method being capable of detecting breakage of a conductor caused by breakage of the element.

Claims

1. A defect detection method for a sensor comprising a sensor element which includes at least one cell having a solid electrolyte layer extending in an axial direction;

a tubular metallic member which surrounds the circumference of the sensor element; and

a fixing member which is in contact with an inner surface of the tubular metallic member and an outer surface of the sensor element and provides a seal therebetween, the cell including a pair of conductors which are formed on the solid electrolyte layer such that the conductors extend through a portion of the sensor element surrounded by the fixing member, the method comprising the steps of;

heating the tubular metallic member so as to produce a difference in dimension attributable to a difference in rate of thermal expansion between the tubular metallic member and the fixing member and a difference in rate of thermal expansion between the tubular metallic member and the sensor element; and

detecting breakage of a portion of the pair of conductors surrounded by the fixing member in a state where the difference in dimension is present.

2. The defect detection method for a sensor according to claim 1, wherein the heating is induction heating.

3. The defect detection method for a sensor according to claim 2, wherein the breakage of the pair of conductors is detected within a period which follows completion of the induction heating and in which the difference in dimension is present.

4. The defect detection method for a sensor according to any one of claims 1 to 3, wherein

the sensor element is configured such that a heater including a heat generation resistor and extending in the axial direction is laminated on the cell;

and

the solid electrolyte layer is heated with a supply of electricity to the heat generation resistor, and the breakage of the pair of conductors is detected in a state where the solid electrolyte layer is heated.

5. The defect detection method for a sensor according to any one of claims 1 to 3, wherein

the sensor element is configured such that a heater extending in the axial direction is laminated on the cell;

the heater includes a heat generation resistor extending through the portion of the sensor element surrounded by the fixing member; and

the tubular metallic member is heated so as to produce the difference in dimension, and breakage of the heat generation resistor is detected in a state where the difference in dimension is present.

6. The defect detection method for a sensor according to any one of claims 1 to 3, wherein the fixing member is a compact formed through compressively charging inorganic powder between the inner surface of the tubular metallic member and the outer surface of the sensor element.

7. The defect detection method for a sensor according to claim 4, wherein

the sensor element includes a heater laminated on the cell, said heater extending in the axial direction;

and having a heat generation resistor, said heat generation resistor being surrounded by the fixing member; and

the tubular metallic member is heated so as to produce the difference in dimension, and breakage of the heat generation resistor is detected in a state where the difference in dimension is present.

8. The defect detection method for a sensor according to claim 4, wherein the fixing member is a compact formed through compressively charging inorganic powder between the inner surface of the tubular metallic member and the outer surface of the sensor element.

9. The defect detection method for a sensor according to claim 5, wherein the fixing member is a compact formed through compressively charging inorganic powder between the inner surface of the tubular metallic member and the outer surface of the sensor element.