Gas sensor with improved heat resistance

Abstract

A gas sensor comprises an atmosphere-side cover, ventilation filter, and filter cover as well as a sensing element and housing. The atmosphere-side cover has i) a first section of a first diameter located on a tip-end side in a axial direction of the housing and fixed on an axially base end of the housing, ii) a second section of a second diameter smaller than the first diameter, the second section being located on an axially base-end side, iii) a stepped section formed between the first and second sections, and iv) a rib protruding outward from the second section and being formed between the stepped section and the second section. The ventilation filter is mounted on the second section and has an axially tip-end section being in contact with an axially base-end section of the rib. The filter cover fixes the ventilation filter between the second section and the filter cover.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross-sectional explanatory view of a gas sensor according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional explanatory view taken along line X-X in FIG. 1;

FIG. 3 is a cross-sectional explanatory view taken along line Y-Y in FIG. 2;

FIG. 4 is a cross-sectional explanatory view of the base-end section of a gas sensor according to a second embodiment of the present invention;

FIG. 5 is a cross-sectional explanatory view taken along line Z-Z in FIG. 4;

FIG. 6 is a cross-sectional explanatory view of the base-end section of a gas sensor according to a third embodiment of the present invention;

FIG. 7 is a cross-sectional explanatory view of the atmosphere-side cover in a direction perpendicular to the axis direction when the cross-sectional shape of the rib is changed in a fourth embodiment of the present invention;

FIG. 8 is a cross-sectional explanatory view of the atmosphere-side cover in the direction perpendicular to the axis direction when the cross-sectional shape of the rib is changed in the fourth embodiment;

FIG. 9 is a cross-sectional explanatory view of the atmosphere-side cover in the direction perpendicular to the axis direction when the cross-sectional shape of the rib is changed in the fourth embodiment;

FIG. 10 is a cross-sectional explanatory diagram of the base-end section of a gas sensor according to a fifth embodiment of the present invention;

FIG. 11 is a line graph showing the measurement results according to the fifth embodiment; and

FIG. 12 is a cross-sectional explanatory diagram of a gas sensor according to a conventional example.

Claims

1. A gas sensor comprising: a sensing element that detects a particular gas concentration within a gas to be measured;a housing into which the sensing element is inserted and held, the housing providing an axial direction and having a base end and a tip end both located along the axial direction;an atmosphere-side cover, formed into an approximately cylindrical shape, having i) a first section of a first diameter which is located on a tip-end side in the axial direction and which is fixed on the base end of the housing, ii) a second section of a second diameter smaller than the first diameter, the second section being located on a base-end side in the axial direction, iii) a stepped section formed between the first and second sections, and iv) a rib protruding outward from the second section, being formed between the stepped section and the second section and having a base-end section in the axial direction;a ventilation filter mounted on an outer periphery of the second section of the atmosphere-side cover, the ventilation filter having a tip-end section in the axial direction being in contact with the base-end section of the rib; anda filter cover that fixes the ventilation filter between the second section of the atmosphere-side cover and the filter cover.

2. The gas sensor according to claim 1, wherein a length of the rib in the axis direction is 3 to 10 mm.

3. The gas sensor according to claim 2, wherein the rib is composed of three to eight ribs.

4. The gas sensor according to claim 3, wherein the rib is formed by the second section having a rib-formation area and a rib-non-formation area in a circumferential direction perpendicular to the axial direction, wherein a length A in the circumferential direction of the rib-formation area and a length B in the circumferential direction of the rib-non-formation area between the ribs have a relationship of 0.15≦A/B≦1.

5. The gas sensor according to claim 4, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with the base-end section of the rib.

6. The gas sensor according to claim 4, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with an outer surface of the rib.

7. The gas sensor according to claim 4, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is spaced apart from the atmosphere-side cover.

8. The gas sensor according to claim 1, wherein the rib is composed of three to eight ribs.

9. The gas sensor according to claim 8, wherein the rib is formed by the second section having a rib-formation area and a rib-non-formation area in a circumferential direction perpendicular to the axial direction, wherein a length A in the circumferential direction of the rib-formation area and a length B in the circumferential direction of the rib-non-formation area between the ribs have a relationship of 0.15≦A/B≦1.

10. The gas sensor according to claim 9, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with the base-end section of the rib.

11. The gas sensor according to claim 9, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with an outer surface of the rib.

12. The gas sensor according to claim 9, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is spaced apart from the atmosphere-side cover.

13. The gas sensor according to claim 1, wherein the rib is formed by the second section having a rib-formation area and a rib-non-formation area in a circumferential direction perpendicular to the axial direction, wherein a length A in the circumferential direction of the rib-formation area and a length B in the circumferential direction of the rib-non-formation area between the ribs have a relationship of 0.15≦A/B≦1.

14. The gas sensor according to claim 13, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with the base-end section of the rib.

15. The gas sensor according to claim 13, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with an outer surface of the rib.

16. The gas sensor according to claim 13, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is spaced apart from the atmosphere-side cover.

17. The gas sensor according to claim 1, wherein the rib is formed by the second section having a rib-formation area and a rib-non-formation area in a circumferential direction perpendicular to the axial direction, wherein a length A in the circumferential direction of the rib-formation area and a length B in the circumferential direction of the rib-non-formation area between the ribs have a relationship of 0.15≦A/B≦1.

18. The gas sensor according to claim 1, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with the base-end section of the rib.

19. The gas sensor according to claim 1, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is in contact with an outer surface of the rib.

20. The gas sensor according to claim 1, wherein the filter cover has a tip-end section in the axial direction and is disposed so that the tip-end section thereof is spaced apart from the atmosphere-side cover.