Gas sensor with increased heat resistance

Abstract

A gas sensor is disclosed including a sensor element, an element holder, an atmosphere-side insulator, an atmosphere-side cover, and a pressing member interposed between a shoulder portion of the atmosphere-side cover and a base end face of the atmosphere-side insulator. A heat-transfer restricting support member is associated with at least one of the shoulder portion of the atmosphere-side cover, the base end face of the atmosphere-side insulator and the pressing member to allow the pressing member to be held in contact with the shoulder portion of the atmosphere-side cover and the base end face of the atmosphere-side insulator in a minimum contact surface fore thereby restricting a heat transfer from a distal end of the gas sensor to a base end thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a gas sensor of a first embodiment according to the present invention.

FIG. 2 is a fragmentary enlarged cross sectional view of the gas sensor shown in FIG. 1 for illustrating a heat-transfer restricting support member associated with an atmosphere-side cover and a pressing member.

FIG. 3 is a cross sectional view taken on line A-A of FIG. 2.

FIG. 4 is a fragmentary enlarged cross sectional view showing a gas sensor of a second embodiment according to the present invention incorporating a pressing member acting as a heat-transfer restricting support member associated with the atmosphere-side cover and an atmosphere-side insulator.

FIG. 5A is a plan view showing the pressing member before spring portions are formed.

FIG. 5B is a plan view showing the pressing member after the spring portions are formed.

FIG. 6 a fragmentary enlarged cross sectional view showing a gas sensor of a third embodiment according to the present invention incorporating a heat-transfer restricting support member associated with an atmosphere-side insulator.

FIG. 7 is a cross sectional view taken on line B-B of FIG. 6.

FIG. 8 is a longitudinal sectional view of a gas sensor of a fourth embodiment according to the present invention.

FIG. 9 is a longitudinal sectional view of a gas sensor of the related art.

FIG. 10 is a longitudinal sectional view of another gas sensor of the related art.

Claims

1. A gas sensor comprising: a sensor element for detecting a concentration of specified gas in measuring gases;an element holder through which the sensor element extends and is retained with the element holder;an atmosphere-side insulator placed on a base end portion of the element holder so as to cover a base end portion of the sensor element;an atmosphere-side cover, placed on the base end portion of the element holder so as to cover the base end portion of the atmosphere-side insulator, which has a shoulder portion placed in face-to-face relation with a base end face of the atmosphere-side insulator;a pressing member interposed between the shoulder portion of the atmosphere-side cover and the base end face of the atmosphere-side insulator; anda heat-transfer restricting support member associated with at least one of the shoulder portion of the atmosphere-side cover, the base end face of the atmosphere-side insulator and the pressing member to allow the pressing member to be held in contact with the shoulder portion of the atmosphere-side cover and the base end face of the atmosphere-side insulator in a minimum contact surface.

2. The gas sensor according to claim 1, wherein: the heat-transfer restricting support member comprises a plurality of convexed ribs, formed on the shoulder portion of the atmosphere-side cover, which are held in abutting engagement with the pressing member.

3. The gas sensor according to claim 1, wherein: the heat-transfer restricting support member comprises the pressing member that includes an annular member having a plurality of spring portions, extending radially outward from an outer periphery of the annular member, which are interposed between the shoulder portion of the atmosphere-side cover and the base end face of the atmosphere-side insulator.

4. The gas sensor according to claim 1, wherein: the heat-transfer restricting support member comprises a plurality of convexed ribs, formed on the base end face of the atmosphere-side insulator, which are held in abutting engagement with the pressing member.

5. The gas sensor according to claim 1, wherein: the heat-transfer restricting support member comprises more than three convexed portions.

6. A gas sensor comprising: a sensor element for detecting a concentration of specified gas in measuring gases;an element holder including a housing adapted to be mounted on a gas flow passage and an element-side insulator, fixedly retained in the housing, for fixedly supporting the sensor element;an atmosphere-side insulator placed on a base end portion of the element holder so as to cover a base end portion of the sensor element;an atmosphere-side cover, placed on the base end portion of the element holder and fixedly supported with the housing so as to cover the base end portion of the atmosphere-side insulator, which has a shoulder portion radially extending inward from an outer periphery of the atmosphere-side cover in face-to-face relation with a base end face of the atmosphere-side insulator;a pressing member interposed between the shoulder portion of the atmosphere-side cover and the base end face of the atmosphere-side insulator; anda heat-transfer restricting support member including a plurality of convexed ribs, formed on the shoulder portion of the atmosphere-side cover, which are held in abutting engagement with the pressing member in a minimum contact surface.

7. A gas sensor comprising: a sensor element for detecting a concentration of specified gas in measuring gases;an element holder including a housing adapted to be mounted on a gas flow passage and an element-side insulator, fixedly retained in the housing, for fixedly supporting the sensor element;an atmosphere-side insulator placed on a base end portion of the element holder so as to cover a base end portion of the sensor element;an atmosphere-side cover, placed on the base end portion of the element holder and fixedly supported with the housing so as to cover the base end portion of the atmosphere-side insulator, which has a shoulder portion radially extending inward from an outer periphery of the atmosphere-side cover in face-to-face relation with a base end face of the atmosphere-side insulator;a heat-transfer restricting support member acting as a pressing member and including an annular member having a plurality of spring portions, extending radially outward from an outer periphery of the annular member, which are interposed between the shoulder portion of the atmosphere-side cover and the base end face of the atmosphere-side insulator.

8. A gas sensor comprising: a sensor element for detecting a concentration of specified gas in measuring gases;an element holder including a housing adapted to be mounted on a gas flow passage and an element-side insulator, fixedly retained in the housing, for fixedly supporting the sensor element;an atmosphere-side insulator placed on a base end portion of the element holder so as to cover a base end portion of the sensor element;an atmosphere-side cover, placed on the base end portion of the element holder and fixedly supported with the housing so as to cover the base end portion of the atmosphere-side insulator, which has a shoulder portion radially extending inward from an outer periphery of the atmosphere-side cover in face-to-face relation with a base end face of the atmosphere-side insulator;a pressing member interposed between the shoulder portion of the atmosphere-side cover and the base end face of the atmosphere-side insulator; anda heat-transfer restricting support member including a plurality of convexed ribs, formed on the base end face of the atmosphere-side insulator, which are held in abutting engagement with the pressing member in a minimum contact surface.

9. A gas sensor comprising: a sensor element for detecting a concentration of specified gas in measuring gases;an element holder including a housing adapted to be mounted on a gas flow passage and an element-side insulator, fixedly retained in the housing, for fixedly supporting the sensor element;an atmosphere-side insulator, placed on a base end portion of the element holder so as to cover a base end portion of the sensor element, which has an upper protrusion and an annular base end face formed around the upper protrusion;an atmosphere-side cover, placed on the base end portion of the element holder and fixedly supported with the housing so as to cover the base end portion of the atmosphere-side insulator, which has an annular shoulder portion radially extending inward from an outer periphery of the atmosphere-side cover in face-to-face relation with the annular base end face of the atmosphere-side insulator;a pressing member interposed between the annular shoulder portion of the atmosphere-side cover and the annular base end face of the atmosphere-side insulator; anda heat-transfer restricting support member including a plurality of convexed ribs, formed on the annular shoulder portion of the atmosphere-side cover, which are held in abutting engagement with the pressing member in a minimum contact surface.

10. A gas sensor comprising: a sensor element for detecting a concentration of specified gas in measuring gases;an element holder including a housing adapted to be mounted on a gas flow passage and an element-side insulator, fixedly retained in the housing, for fixedly supporting the sensor element;an atmosphere-side insulator, placed on a base end portion of the element holder so as to cover a base end portion of the sensor element, which has an upper protrusion and an annular base end face formed around the upper protrusion;an atmosphere-side cover, placed on the base end portion of the element holder and fixedly supported with the housing so as to cover the base end portion of the atmosphere-side insulator, which has an annular shoulder portion radially extending inward from an outer periphery of the atmosphere-side cover in face-to-face relation with the annular base end face of the atmosphere-side insulator;a heat-transfer restricting support member acting as a pressing member and including an annular member having a plurality of spring portions, extending radially outward from an outer periphery of the annular member, which are interposed between the annular shoulder portion of the atmosphere-side cover and the annular base end face of the atmosphere-side insulator.

11. A gas sensor comprising: a sensor element for detecting a concentration of specified gas in measuring gases;an element holder including a housing adapted to be mounted on a gas flow passage and an element-side insulator, fixedly retained in the housing, for fixedly supporting the sensor element;an atmosphere-side insulator, placed on a base end portion of the element holder so as to cover a base end portion of the sensor element, which has an upper protrusion and an annular base end face formed around the upper protrusion;an atmosphere-side cover, placed on the base end portion of the element holder and fixedly supported with the housing so as to cover the base end portion of the atmosphere-side insulator, which has an annular shoulder portion radially extending inward from an outer periphery of the atmosphere-side cover in face-to-face relation with the annular base end face of the atmosphere-side insulator;a pressing member interposed between the annular shoulder portion of the atmosphere-side cover and the annular base end face of the atmosphere-side insulator; anda heat-transfer restricting support member including a plurality of convexed ribs, formed on the annular base end face of the atmosphere-side insulator, which are held in abutting engagement with the pressing member in a minimum contact surface.