Gas sensor

Patent metadata

Field	Value
Publication number	US-10048097-B2
Application number	US-201514955369-A
Country	US
Kind code	B2
Filing date	Dec 1, 2015
Priority date	Dec 2, 2014
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

A gas sensor includes a sensor element that includes a gas inlet through which a measurement target gas is introduced into the sensor element and a protective cover that contains a substance having a capability of decomposing ammonia. The protective cover has a gas-contact surface area within a range of 450 mm2 to 1145 mm2, the gas-contact surface area being a sum of a surface area of a portion facing the inlet-side gas flow path and a surface area of a portion facing an in-element-chamber flow path of the sensor element chamber that is a shortest flow path for the measurement target gas from the element-chamber inlet to the gas inlet.

First claim

What is claimed is:

1. A gas sensor, comprising:
a sensor element that includes a gas inlet through which a measurement target gas is introduced into the sensor element, the sensor element being capable of detecting a predetermined gas concentration of the measurement target gas that has flowed into an inside of the sensor element through the gas inlet; and
a protective cover that contains a substance having a capability of decomposing ammonia, the protective cover defining a sensor element chamber and an inlet-side gas flow path, the sensor element chamber being a chamber in which a front end of the sensor element and the gas inlet are disposed, the inlet-side gas flow path including one or more element-chamber inlets serving as inlets to the sensor element chamber, the inlet-side gas flow path extending from an outside to the sensor element chamber,
wherein the protective cover has a gas-contact surface area S within a range of 450 mm 2 to 1145 mm 2 , the gas-contact surface area S being a sum of a surface area S 1 of a portion facing the inlet-side gas flow path and a surface area S 2 of a portion facing an in-element-chamber flow path in the sensor element chamber that is a shortest flow path for the measurement target gas from the element-chamber inlet to the gas inlet.

2. The gas sensor according to claim 1 ,
wherein the protective cover defines an outlet-side gas flow path extending to the outside from the sensor element chamber and including one or more element-chamber outlets serving as outlets from the sensor element chamber, and
wherein the protective cover has the one or more element-chamber inlets at a position spaced apart from the gas inlet a distance A 1 of −1.5 mm or more and the one or more element-chamber outlets at a position located away from the gas inlet in a direction toward a front end from a rear end of the sensor element, where the distance A 1 is a distance extending in a direction connecting a rear end and the front end of the sensor element and a direction from the front end to the rear end is regarded as a positive direction.

3. The gas sensor according to claim 1 ,
wherein the protective cover defines an outlet-side gas flow path extending to the outside from the sensor element chamber and including one or more element-chamber outlets serving as outlets from the sensor element chamber and the protective cover includes an inner protective cover and an outer protective cover disposed on an outer side of the inner protective cover,
wherein the inner protective cover defines the sensor element chamber, the one or more element-chamber inlets, and the one or more element-chamber outlets,
wherein the outer protective cover defines one or more outer inlets, which serve as inlets for the measurement target gas from the outside and constitute part of the inlet-side gas flow path, and one or more outer outlets, which serve as outlets for the measurement target gas to the outside and constitute part of the outlet-side gas flow path, and
wherein the outer protective cover and the inner protective cover define a first gas chamber and a second gas chamber, the first gas chamber being a space between the outer protective cover and the inner protective cover and constituting part of the inlet-side gas flow path, the first gas chamber being located between the one or more outer inlets and the one or more element-chamber inlets, the second gas chamber being a space between the outer protective cover and the inner protective cover and constituting part of the outlet-side gas flow path, the second gas chamber being located between the one or more outer outlets and the one or more element-chamber outlets and not directly communicating with the first gas chamber.

4. The gas sensor according to claim 3 ,
wherein an area ratio α falls within a range from 12 to 35, where the area ratio α=a cross-sectional area G 2 ×a cross-sectional area G 3 ×a cross-sectional area G 4 /a cross-sectional area G 1 , the cross-sectional area G 1 [mm 2 ] is a sum of cross-sectional areas of the one or more outer inlets taken perpendicularly to flow of the measurement target gas, the cross-sectional area G 2 [mm 2 ] is a sum of cross-sectional areas of the one or more element-chamber inlets taken perpendicularly to flow of the measurement target gas, the cross-sectional area G 3 [mm 2 ] is a sum of cross-sectional areas of the one or more element-chamber outlets taken perpendicularly to flow of the measurement target gas, and the cross-sectional area G 4 [mm 2 ] is a sum of cross-sectional areas of the one or more outer outlets taken perpendicularly to flow of the measurement target gas.

5. The gas sensor according to claim 1 ,
wherein the protective cover defines the one or more element-chamber inlets in such a manner that an element-side opening of each of the one or more element-chamber inlets, which is an opening located closer to the sensor element chamber, is open in a direction extending from a rear end to the front end of the sensor element.

6. The gas sensor according to claim 1 ,
wherein the protective cover is formed of a metal containing at least one of chromium and nickel as the substance having a capability of decomposing ammonia.

Assignees

• Ngk Insulators Ltd

Inventors

• Seimori Tomoya
• Murakami Mika
• Takeuchi Kengo

Classifications

• G01N33/0054

  Ammonia · CPC title

• G01N27/4077 Primary

  Means for protecting the electrolyte or the electrodes · CPC title

• G01D11/245 Primary

  Housings for sensors · CPC title

• Y02A50/246

  Cross-Sectional Technologies · mapped topic

• Y02A50/20

  Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters · CPC title