Ceramic heater, sensor element, and gas sensor

Patent metadata

Field	Value
Publication number	US-10712307-B2
Application number	US-201615238817-A
Country	US
Kind code	B2
Filing date	Aug 17, 2016
Priority date	Aug 21, 2015
Publication date	Jul 14, 2020
Grant date	Jul 14, 2020

Abstract

A heater 72 of a heater portion includes linear portions 78 and bend portions 77 . A resistance value per unit length of the bend portions 77 at least at a temperature within a temperature range of no less than 700° C. and no more than 900° C. is lower than a resistance value per unit length of the linear portions 78.

First claim

What is claimed is:

1. A ceramic heater including:
a heating element including a continuous heating path comprising a plurality of linear portions and a plurality of bend portions, and
a ceramic body surrounding the heating element,
the bend portions comprising at least one first side bend portion that is provided on a first end of the linear portions in a length direction of the linear portions and at least one second side bend portion that is provided on a second end of the linear portions in the length direction, the second end of the linear portions being opposite the first end of the linear portions each of the linear portions connecting one of the at least one first side bend portion at one end of a respective linear portion to one of the at least one second side bend portion at an opposite end of the respective linear portion, and each of the at least one first side bend portion and the at least one second side bend portion having a resistance value per unit length, at a temperature in a range of 700° C. to 900° C., that is lower than a resistance value per unit length of each of the plurality of linear portions, such that a unit resistance ratio R 1 /R 2 of unit resistance R 1 (μΩ/mm), being the resistance value per unit length of each of the at least one first side bend portion and the at least one second side bend portion, to unit resistance R 2 (μΩ/mm), being the resistance value per unit length of each of the plurality of linear portions, is no larger than 0.87 at the temperature in the range of 700° C. to 900° C.

2. The ceramic heater according to claim 1 ,
wherein the unit resistance value ratio R 1 /R 2 at the temperature in the range no larger than 0.80.

3. The ceramic heater according to claim 1 ,
wherein a sectional area of the bend portions that is perpendicular to the length direction is larger than a sectional area of the linear portions that is perpendicular to the length direction.

4. The ceramic heater according to claim 3 ,
wherein the heating element has a belt-like shape, and
a thickness of the bend portions is larger than or equal to a thickness of the linear portions.

5. The ceramic heater according to claim 3 ,
wherein a sectional area ratio S 2 /S 1 of a sectional area S 2 (mm 2 ) of the linear portions that is perpendicular to the length direction to a sectional area S 1 (mm 2 ) of the bend portions that is perpendicular to the length direction is no larger than 0.87.

6. The ceramic heater according to claim 5 ,
wherein the sectional area ratio S 2 /S 1 is no larger than 0.80.

7. The ceramic heater according to claim 1 ,
wherein a volume resistivity of the bend portions at the temperature in the range is lower than a volume resistivity of the linear portions.

8. The ceramic heater according to claim 7 ,
wherein a volume resistivity ratio ρl/ρ 2 that is a ratio of a volume resistivity ρ 1 (λΩ⋅cm) of the bend portions to a volume resistivity p 2 (λΩ⋅cm) the linear portions is no larger than 0.87 at the temperature in the range.

9. The ceramic heater according to claim 8 ,
wherein the volume resistivity ratio p 1 /p 2 at the temperature in the range is no larger than 0.80.

10. The ceramic heater according to claim 1 ,
wherein the ceramic body is a plate-like body having a longitudinal direction and a short-length direction,
the heating element includes, as the linear portions, four or more of the linear portions that are arranged along the short-length direction and whose length direction is along the longitudinal direction, and
the heating element includes, as the bend portions, plural first side bend portions that connect the linear portions adjoining in the short-length direction to each other on the first end in the longitudinal direction and the at least one second side bend portion that connects the linear portions adjoining in the short-length direction to each other on the second end in the longitudinal direction.

11. A sensor element including the ceramic heater according to claim 1 ,
wherein a concentration of a specific gas in a measurement-object gas is detected.

12. A gas sensor including the sensor element according to claim 11 .

Assignees

• Ngk Insulators Ltd

Inventors

• Watanabe Yusuke
• Murase Takao
• Yasui Masashi
• Sakaguchi Rui

Classifications

• G01N27/4067 Primary

  Means for heating or controlling the temperature of the solid electrolyte · CPC title

• H05B3/265

  the insulating base being an inorganic material, e.g. ceramic (H05B3/262 takes precedence) · CPC title

• H05B1/0247

  For chemical processes · CPC title