Ceramic heater, sensor element, and gas sensor

Patent metadata

Field	Value
Publication number	US-2020080959-A1
Application number	US-201916686812-A
Country	US
Kind code	A1
Filing date	Nov 18, 2019
Priority date	Aug 21, 2015
Publication date	Mar 12, 2020
Grant date	—

Abstract

A heater section includes a plate-like ceramic body (a first substrate layer 1, a second substrate layer 2, and a third substrate layer 3) having a longitudinal direction (front-rear direction) and a short-length direction (left-right direction), and a heater 72 disposed within the plate-like ceramic body and including a lead section 79 and a heating section 76 connected to the lead section 79. The heating section 76 includes a straight portion 78 extending along the longitudinal direction, and a lead side curved portion 77b connected to one of the ends of the straight portion 78 closer to the lead section 79. The lead side curved portion 77b has a lower resistance per unit length than the straight portion 78 at one or more temperatures in the range of 700° C. to 900° C.

First claim

What is claimed is:

1 . A ceramic heater comprising:
a plate-like ceramic body having a longitudinal direction and a short-length direction; and a heating element disposed within the plate-like ceramic body, the heating element including a lead section and a heating section connected to the lead section, wherein the heating section includes a straight portion whose length direction is along the longitudinal direction and at least one lead side curved portion connected to one of the ends of the straight portion closer to the lead section, and wherein the closest to the lead section of the at least one lead side curved portion has a lower resistance per unit length than the straight portion at one or more temperatures in the range of 700° C. to 900° C.

2 . A ceramic heater comprising:
a plate-like ceramic body having a longitudinal direction and a short-length direction; and a heating element disposed within the plate-like ceramic body, the heating element including a lead section having a positive lead and a heating section connected to the lead section, wherein the heating section includes a straight portion whose length direction is along the longitudinal direction and at least one lead side curved portion connected to one of the ends of the straight portion closer to the lead section, and wherein the closest to the positive lead of the at least one lead side curved portion has a lower resistance per unit length than the straight portion at one or more temperatures in a range of 700° C. to 900° C.

3 . The ceramic heater according to claim 1 ,
wherein the ratio R 1 /R 2 of unit resistance R 1 [μΩ/mm] being the resistance per unit length of the closest of the at least one lead side curved portion to unit resistance R 2 [μΩ/mm] being the resistance per unit length of the straight portion is 0.87 or less at one or more temperatures in the temperature range.

4 . The ceramic heater according to claim 3 ,
wherein the unit resistance ratio R 1 /R 2 is 0.80 or less at one or more temperatures in the temperature range.

5 . The ceramic heater according to claim 1 ,
wherein a cross section of the closest of the at least one lead side curved portion, taken in a direction perpendicular to a length direction thereof has a larger area than a cross section of the straight portion, taken in a direction perpendicular to a length direction thereof.

6 . The ceramic heater according to claim 5 ,
wherein the ratio S 2 /S 1 of the area S 2 [mm 2 ] of the cross section of the straight portion taken in the direction perpendicular to the length direction thereof to the area S 1 [mm 2 ] of the cross section of the closest of the at least one lead side curved portion taken in the direction perpendicular to the length direction thereof is 0.87 or less.

7 . The ceramic heater according to claim 6 ,
wherein the cross sectional area ratio S 2 /S 1 is 0.80 or less.

8 . The ceramic heater according to claim 1 ,
wherein the closest of the at least one lead side curved portion has a lower volume resistivity than the straight portion at one or more temperatures in the temperature range.

9 . The ceramic heater according to claim 8 ,
wherein the ratio ρ 1 /ρ 2 of the volume resistivity ρ 1 [μΩ·cm] of the closest of the at least one lead side curved portion to the volume resistivity ρ 2 [μΩ·cm] of the straight portion is 0.87 or less at one or more temperatures in the temperature range.

10 . The ceramic heater according to claim 9 ,
wherein the volume resistivity ratio ρ 1 /ρ 2 is 0.80 or less at one or more temperatures in the temperature range.

11 . The ceramic heater according to claim 1 ,
wherein the heating section includes four or more straight portions arranged along the short-length direction, and the at least one lead side curved portion connects a pair of the straight portions adjacent to each other in the short-length direction at one of the ends of each adjacent straight portion closer to the lead section, and wherein the heating section includes a plurality of non-lead side curved portions, each connecting a pair of the straight portions adjacent to each other in the short-length direction at one of the ends of each adjacent straight portion far from the lead section.

12 . A sensor element adapted to detect the concentration of a specific gas in a measurement-object gas, the sensor element comprising the ceramic heater according to claim 1 .

13 . A gas sensor comprising the sensor element according to claim 12 .

14 . The ceramic heater according to claim 2 ,
wherein the ratio R 1 /R 2 of unit resistance R 1 [μΩ/mm] being the resistance per unit length of the closest of the at least one lead side curved portion to unit resistance R 2 [μΩ/mm] being the resistance per unit length of the straight portion is 0.87 or less at one or more temperatures in the temperature range.

15 . The ceramic heater according to claim 14 ,
wherein the unit resistance ratio R 1 /R 2 is 0.80 or less at one or more temperatures in the temperature range.

16 . The ceramic heater according to claim 2 ,
wherein a cross section of the closest of the at least one lead side curved portion, taken in a direction perpendicular to a length direction thereof has a larger area than a cross section of the straight portion, taken in a direction perpendicular to a length direction thereof.

17 . The ceramic heater according to claim 2 ,
wherein the closest of the at least one lead side curved portion has a lower volume resistivity than the straight portion at one or more temperatures in the temperature range.

18 . The ceramic heater according to claim 2 ,
wherein the heating section includes four or more straight portions arranged along the short-length direction, and the at least one lead side curved portion connects a pair of the straight portions adjacent to each other in the short-length direction at one of the ends of each adjacent straight portion closer to the lead section, and wherein the heating section includes a plurality of non-lead side curved portions, each connecting a pair of the straight portions adjacent to each other in the short-length direction at one of the ends of each adjacent straight portion far from the lead section.

19 . A sensor element adapted to detect the concentration of a specific gas in a measurement-object gas, the sensor element comprising the ceramic heater according to claim 2 .

20 . A gas sensor comprising the sensor element according to claim 19 .

Assignees

• Ngk Insulators Ltd

Inventors

• Watanabe Yusuke
• Murase Takao
• Yasui Masashi

Classifications

• 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

• G01N27/4067 Primary

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

• H05B3/0014

  Devices wherein the heating current flows through particular resistances · CPC title