Gas sensor

Abstract

To provide a gas sensor which prevents a ceramic housing in a state inclined from the axial direction from eating into a member disposed on the rear end side of the ceramic housing.SOLUTION: In a gas sensor according to one aspect of the present invention, a spacer having a Young's modulus of 80 GPa or more is disposed at least in a tip portion on the rear end side of the ceramic housing to which the terminal fitting is attached.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a gas sensor. [Background technology]

[0002] Conventionally, oxygen and NO in gases to be measured, such as automobile exhaust gas, x There are known gas sensors that detect the concentration of specific gases such as those described above. For example, Patent Document 1 listed below discloses a gas sensor that includes a cylindrical body in which a sensor element and a connector (ceramic housing) having a contact metal fitting that is electrically conductive with the sensor element are disposed, and an elastic body that seals the open end of the cylindrical body. In the gas sensor disclosed in Patent Document 1, an elastic body is disposed on the rear end side of the ceramic housing in the axial direction of the gas sensor (axial direction of the sensor element). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-196917 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have found that, in a conventional gas sensor as disclosed in Patent Document 1, when the ceramic housing is fixed inside the cylindrical body in a state inclined from the axial direction, the following problem occurs. That is, when the ceramic housing is fixed in a state inclined from the axial direction, an unintended stress (e.g., a stress in a direction other than a direction perpendicular to the axial direction) acts from the sensor element on the terminal metal fitting that is attached to the ceramic housing and connected to the sensor element. Therefore, the present inventors have found a problem that, when the ceramic housing is fixed in a state inclined from the axial direction in a gas sensor, the terminal metal fitting is more likely to break when an impact is applied to the gas sensor than when the ceramic housing is fixed parallel to the axial direction.

[0005] After further investigation, the present inventors have determined that the phenomenon in which the ceramic housing is fixed in a tilted state from the axial direction occurs, for example, in the following manner: In other words, in a conventional gas sensor, the elastic body that is disposed on the rear end side of the ceramic housing and seals the open end of the cylindrical body has a lower Young's modulus than the ceramic housing, i.e., is softer than the ceramic housing. Therefore, the present inventors have determined that the above-mentioned phenomenon occurs when, for example, during the manufacturing stage of the gas sensor, the ceramic housing bites into the elastic body that is softer than the ceramic housing in a tilted state from the axial direction.

[0006] As described above, the inventors of the present invention discovered a problem in that if the ceramic housing is tilted from the axial direction and bites into a member (e.g., an elastic body) arranged on the rear end side of the ceramic housing, the terminal fittings attached to the ceramic housing are prone to breakage.

[0007] In one aspect, the present invention has been made in consideration of the above circumstances, and its object is to provide a gas sensor that prevents the ceramic housing from biting into a member arranged on the rear end side of the ceramic housing when tilted from the axial direction. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention employs the following configuration.

[0009] A gas sensor according to a first aspect includes a sensor element extending in an axial direction, having a detection portion at a tip end and a connector electrode at a rear end end, a terminal fitting extending in the axial direction and having an element contact portion at a tip end for electrically connecting to the connector electrode, a ceramic housing accommodating the connector electrode and the element contact portion, a cylindrical body having an open end formed therein and having the sensor element, the terminal fitting, and the ceramic housing disposed therein, an elastic body disposed to seal the open end, and a spacer disposed between the ceramic housing and the elastic body in the axial direction, the spacer contacting the ceramic housing at a tip end face in the axial direction and contacting the elastic body at a rear end face in the axial direction, the Young's modulus of at least a tip portion including the tip end face being 80 GPa or more.

[0010] In the gas sensor having this configuration, the ceramic housing comes into contact with the tip portion of the spacer, which is disposed on the rear end side of the ceramic housing and has a Young's modulus of 80 GPa or more.

[0011] The inventors of the present invention have considered that by disposing the spacer between the ceramic housing and the elastic body, it is possible to prevent the ceramic housing from biting into the elastic body, and therefore, in the gas sensor, the spacer is disposed between the ceramic housing and the elastic body.

[0012] The present inventors further considered that in order to prevent the ceramic housing from biting into a member arranged on the rear end side of the ceramic housing, it is effective to make the tip end portion of the member arranged on the rear end side in the axial direction sufficiently hard. Here, as described above, in the gas sensor, the spacer is arranged between the ceramic housing and the elastic body. Therefore, the present inventors experimentally determined the hardness (softness) that the tip portion of the spacer should have in order to prevent the ceramic housing from biting into the spacer (particularly, the tip portion of the spacer). As a result, the present inventors confirmed that by setting the Young's modulus of the tip portion of the spacer to 80 GPa or more, the ceramic housing can be significantly prevented from biting into the spacer (particularly, the tip portion) compared to the case where the Young's modulus is less than 80 GPa.

[0013] In the gas sensor, the ceramic housing contacts the spacer disposed on the rear end side of the ceramic housing, particularly the end face on the tip side of the spacer, and the Young's modulus of the tip portion of the spacer including the end face on the tip side is 80 GPa or more, and the spacer has a sufficient hardness to remarkably prevent the ceramic housing from biting into the spacer (particularly the tip portion).

[0014] Therefore, in the gas sensor, a phenomenon does not occur in which "the ceramic housing bites into the spacer arranged on the rear end side of the ceramic housing while tilted from the axial direction, and this state becomes fixed."

[0015] Therefore, the gas sensor has the effect of preventing the ceramic housing from being jammed into a member (i.e., the spacer) arranged on the rear end side of the ceramic housing when tilted from the axial direction.

[0016] A gas sensor according to a second aspect may be the gas sensor according to the first aspect, wherein the Young's modulus of a rear end portion of the spacer, including the end face on the rear end side, is smaller than the Young's modulus of the front end portion of the spacer. In this configuration, in the gas sensor, the Young's modulus of the rear end portion of the spacer, including the end face on the rear end side, is smaller than the Young's modulus of the front end portion. That is, in the gas sensor, the rear end portion of the spacer is softer and more flexible than the front end portion of the spacer. In the gas sensor, the spacer is in contact with the elastic body at the end face on the rear end side in the axial direction.

[0017] Therefore, even if the end face (tip face) of the elastic body on the tip side in the axial direction is inclined with respect to the axial direction in the gas sensor, the inclination of the tip face of the elastic body can be absorbed by the rear end portion of the spacer. That is, in the gas sensor, the soft rear end portion of the spacer, which contacts the tip face of the elastic body, is deflected, so that the inclination of the tip face of the elastic body can be absorbed by the rear end portion of the spacer.

[0018] The spacer prevents the ceramic housing from tilting from the axial direction due to the tilt of the tip surface of the elastic body being transmitted to the ceramic housing via the spacer, by the rear end portion which is softer and more flexible than the tip portion. For example, if the tip surface of the elastic body is tilted from the axial direction, stress in a direction tilted from the axial direction is transmitted from the tip surface of the elastic body to the ceramic housing, and the ceramic housing may tilt from the axial direction due to such stress. The spacer prevents such a situation by the rear end portion which is softer and more flexible than the tip portion. That is, the spacer prevents the ceramic housing from tilting from the axial direction due to such stress by absorbing the stress from the tip surface of the elastic body in a direction tilted from the axial direction by the rear end portion. Moreover, the tip portion of the spacer has a sufficient hardness to significantly prevent the ceramic housing from biting into the spacer.

[0019] Therefore, the gas sensor has the effect of more effectively preventing the ceramic housing from getting caught in a member (i.e., the spacer) arranged on the rear end side of the ceramic housing when tilted from the axial direction.

[0020] A gas sensor according to a third aspect is the gas sensor according to the first or second aspect, wherein the contact area between the spacer and the ceramic housing is 3 mm 2 In the gas sensor, the contact area between the spacer and the ceramic housing may be 3 mm or more. 2 That's all.

[0021] The present inventors considered that it is effective to ensure a sufficient contact area (hereinafter referred to as "contact area A1") between the spacer and the ceramic housing in order to prevent the ceramic housing from being fixed in a state tilted from the axial direction. For example, when the contact area A1 is small, a force is more likely to act from the spacer to the ceramic housing in a direction tilted from the axial direction than when the contact area A1 is large, and as a result, the ceramic housing is more likely to be tilted from the axial direction. Also, when the contact area A1 is small, the contact between the spacer and the ceramic housing is less stable than when the contact area A1 is large, and as a result, the ceramic housing is more likely to be tilted from the axial direction, for example, when an impact is applied to the gas sensor. Therefore, the present inventors examined the range of the contact area A1 between the spacer and the ceramic housing that is effective in preventing the ceramic housing from being fixed in a state tilted from the axial direction. As a result, the present inventors considered that the contact area A1 should be set to 3 mm 2 By setting it to more than 3mm 2 It has been confirmed that this significantly prevents the ceramic housing from being fixed in a state tilted from the axial direction, as compared with the case where the height is less than 1 / 200 mm.

[0022] In the gas sensor, the contact area (contact area A1) between the spacer and the ceramic housing is 3 mm 2 Therefore, in the gas sensor, the contact area A1 between the spacer and the ceramic housing is set to 3 mm 2 This provides an effect of significantly preventing the ceramic housing from being fixed in a state tilted from the axial direction, as compared with the case where the angle is less than 100°.

[0023] Here, the gas sensor is manufactured, for example, through the following steps. That is, first, a contact member is prepared in which the ceramic housing to which the terminal metal fittings are attached, the spacer, and the elastic body are arranged in this order from the tip side in the axial direction (pre-assembly). At the time of pre-assembly, the "fixing metal fittings with pressure" and the "crimping ring" described below do not need to be attached to the outer periphery of the ceramic housing. After pre-assembly is completed, the rear end side of the sensor element is then inserted into the ceramic housing to which the terminal metal fittings are attached (particularly, into an insertion port provided on the tip side of the ceramic housing). Then, the sensor element and the ceramic housing (contact member) are integrated by crimping a crimping ring provided to fix the ceramic housing with the sensor element inserted from the outer periphery.

[0024] However, if the ceramic housing is tilted from the axial direction at the time of pre-assembly, the ceramic housing will be integrated with the sensor element in this tilted state, that is, the ceramic housing will become fixed in its tilted state from the axial direction.

[0025] Therefore, for example, by ensuring a sufficient contact area A1 between the spacer and the ceramic housing at the time of pre-assembly, it is possible to prevent the ceramic housing from being positioned in a state inclined from the axial direction in the above-mentioned contact member. 2 With the above, the gas sensor can prevent the occurrence of a situation in which "at the time of pre-assembly, the ceramic housing is positioned in a state inclined from the axial direction."

[0026] A gas sensor according to a fourth aspect is the gas sensor according to any one of the first to third aspects, wherein an area of ​​a portion of the tip end face of the elastic body that is in contact with the spacer is 25% or more of an entire area of ​​the tip end face of the elastic body. In this configuration, in the gas sensor, an area of ​​a portion of the tip end face of the elastic body that is in contact with the spacer is 25% or more of an entire area of ​​the tip end face of the elastic body.

[0027] The present inventors have considered that in order to prevent the ceramic housing from being fixed in a state tilted from the axial direction, it is effective to ensure a sufficient contact area between the spacer and the elastic body (hereinafter referred to as "contact area A2"). For example, when the contact area A2 is small, a force is more likely to act from the elastic body to the spacer in a direction tilted from the axial direction than when the contact area A2 is large, and as a result, the ceramic housing in contact with the spacer is also more likely to tilt from the axial direction. Also, when the contact area A2 is small, the contact between the elastic body and the spacer is less stable than when the contact area A2 is large, and the spacer (particularly, its end face) is more likely to tilt from the axial direction, for example, when an impact is applied to the gas sensor. And, when the spacer (particularly, its end face) tilts from the axial direction, the ceramic housing in contact with the spacer (particularly, its end face on the tip side) is also more likely to tilt from the axial direction. Therefore, the inventors of the present invention verified the range of the contact area A2 between the spacer and the elastic body that is effective in preventing the ceramic housing from being fixed in a state tilted from the axial direction. The inventors of the present invention confirmed that by setting the contact area A2 to 25% or more of the entire area of ​​the end face on the tip side of the elastic body, the ceramic housing can be significantly prevented from being fixed in a state tilted from the axial direction, compared to when the contact area A2 is less than 25%.

[0028] In the gas sensor, the area of ​​the portion of the end face of the tip side of the elastic body that is in contact with the spacer, i.e., the above-mentioned contact area A2, is 25% or more of the entire area of ​​the end face of the tip side of the elastic body.

[0029] Therefore, the gas sensor has the advantage of being able to significantly prevent the ceramic housing from being fixed in a state tilted from the axial direction, compared to a case in which the contact area A2 is less than 25% of the entire area of ​​the end face on the tip side of the elastic body.

[0030] Here, the gas sensor is manufactured, for example, through the following process. That is, the gas sensor is manufactured through a crimping process in which the elastic body arranged at the opening end of the cylindrical body and the cylindrical body are crimped in a reduced diameter state to fix the elastic body to the opening end and seal the opening end with the elastic body. In this crimping process, the elastic body may be deformed, and stress may act on the spacer in a direction inclined from the axial direction. For example, in the crimping process, the tip surface of the elastic body may be pushed out toward the tip side in the axial direction while being inclined from the axial direction, and stress may be applied to the spacer in a direction inclined from the axial direction. If the contact area A2 between the spacer and the elastic body is small at the time of the crimping process, the elastic body is soft and the spacer is not stable, and the elastic body may act on the spacer in a direction inclined from the axial direction, which may cause the spacer to be easily inclined from the axial direction. Furthermore, when the spacer (particularly the tip surface thereof) is tilted from the axial direction, there is a possibility that the ceramic housing in contact with the spacer may also be tilted from the axial direction.

[0031] Therefore, for example, by ensuring a sufficient contact area A2 between the spacer and the elastic body during the above-mentioned crimping process, the gas sensor can prevent the ceramic housing from tilting from the axial direction. Specifically, by setting the contact area A2 during the crimping process to 25% or more of the entire area of ​​the end face on the tip side of the elastic body, the gas sensor can prevent the ceramic housing from tilting from the axial direction during the crimping process.

[0032] A gas sensor according to a fifth aspect may be the gas sensor according to any one of the first to fourth aspects, wherein a distance from a position of a center of gravity of a portion of the spacer in contact with the ceramic housing at the end face on the tip side, which is a center of mass when a mass is virtually uniformly distributed on the portion of the end face on the tip side of the spacer in contact with the ceramic housing, to a straight line extending in the axial direction of the axis of the sensor element may be within 2 mm. In this configuration, in the gas sensor, a distance (hereinafter referred to as "distance L1") from a position of the center of gravity of the portion of the spacer in contact with the ceramic housing (hereinafter referred to as "center of gravity CG1") to a straight line extending in the axial direction of the axis is within 2 mm.

[0033] The present inventors considered that in order to prevent the ceramic housing from being fixed in a state tilted from the axial direction, it is effective to bring the spacer into contact with the ceramic housing on a straight line extending the axis in the axial direction (i.e., an extension of the axis). In particular, they considered that if the distance L1 from the center of gravity CG1 of the contact surface between the spacer and the ceramic housing to the extension of the axis can be sufficiently small, the ceramic housing can be effectively prevented from being fixed in a state tilted from the axial direction. Therefore, the present inventors examined the distance L1 from the center of gravity CG1 to the extension of the axis, which is effective in preventing the ceramic housing from being fixed in a state tilted from the axial direction. As a result, the present inventors confirmed that by setting the distance L1 from the center of gravity CG1 to the extension of the axis to within 2 mm, the ceramic housing can be significantly prevented from being fixed in a state tilted from the axial direction, compared to the case where the distance L1 is greater than 2 mm.

[0034] In the gas sensor, the distance from the position of the center of gravity (ie, center of gravity CG1) of the portion of the spacer in contact with the ceramic housing to an extension of the axis (ie, distance L1) is within 2 mm.

[0035] Therefore, the gas sensor has the effect of significantly preventing the ceramic housing from being fixed in a state tilted from the axial direction, compared to when the distance L1 from the center of gravity CG1 to the extension of the axis is greater than 2 mm.

[0036] The gas sensor is manufactured, for example, through the above-mentioned pre-assembly process. However, if the ceramic housing is tilted from the axial direction at the time of pre-assembly, the ceramic housing is integrated with the sensor element in such a tilted state, that is, the state in which the ceramic housing is tilted from the axial direction is fixed.

[0037] Therefore, for example, by contacting the spacer with the ceramic housing on the extension of the axis at the time of pre-assembly, it is possible to prevent the ceramic housing from being positioned at an angle from the axial direction in the contact member. Specifically, at the time of pre-assembly, the distance L1 from the center of gravity CG1 of the contact surface between the spacer and the ceramic housing to the extension of the axis is set to within 2 mm. This makes it possible to prevent the gas sensor from being positioned at an angle from the axial direction.

[0038] A gas sensor according to a sixth aspect may be the gas sensor according to any one of the first to fifth aspects, wherein a distance from a position of a center of gravity of a portion of the end face of the tip side of the elastic body in contact with the spacer, which is a center of mass when mass is virtually uniformly distributed on the portion of the end face of the tip side of the elastic body in contact with the spacer, to a straight line extending the axis of the sensor element in the axial direction, is within 2 mm. In this configuration, in the gas sensor, a distance (hereinafter referred to as "distance L2") from a position of the center of gravity of the portion of the elastic body in contact with the spacer (hereinafter referred to as "center of gravity CG2") to a straight line extending the axis in the axial direction is within 2 mm.

[0039] The present inventors considered that in order to prevent the ceramic housing from being fixed in a state tilted from the axial direction, it is effective to bring the elastic body and the spacer into contact on a straight line extending the axis in the axial direction (i.e., an extension of the axis). In particular, they considered that if the distance L2 from the center of gravity CG2 of the contact surface between the elastic body and the spacer to the extension of the axis can be sufficiently small, the ceramic housing can be effectively prevented from being fixed in a state tilted from the axial direction. Therefore, the present inventors examined the distance L2 from the center of gravity CG2 to the extension of the axis, which is effective in preventing the ceramic housing from being fixed in a state tilted from the axial direction. As a result, the present inventors confirmed that by setting the distance L2 from the center of gravity CG2 to the extension of the axis to within 2 mm, the ceramic housing can be significantly prevented from being fixed in a state tilted from the axial direction, compared to the case where the distance L2 is greater than 2 mm.

[0040] In the gas sensor, the distance from the position of the center of gravity (i.e., center of gravity CG2) of the part of the elastic body that is in contact with the spacer to a straight line extending in the axial direction of the axis (i.e., distance L2) is within 2 mm.

[0041] Therefore, the gas sensor has the effect of significantly preventing the ceramic housing from being fixed in a state tilted from the axial direction, compared to when the distance L2 from the center of gravity CG2 to the extension of the axis is greater than 2 mm.

[0042] The gas sensor is manufactured, for example, through the above-mentioned crimping process. However, if the elastic body is deformed during the crimping process and stress acts from the elastic body to the spacer in a direction inclined from the axial direction, the ceramic housing in contact with the spacer may also be inclined from the axial direction.

[0043] Therefore, for example, by contacting the elastic body with the spacer on the extension of the axis during the crimping process, the gas sensor can prevent the ceramic housing from tilting from the axial direction. Specifically, during the crimping process, the distance L2 from the center of gravity CG2 to the extension of the axis is set to within 2 mm. This makes it possible to prevent the gas sensor from being in a situation where the ceramic housing is positioned in a state where it is tilted from the axial direction during the crimping process.

[0044] A gas sensor according to a seventh aspect is the gas sensor according to any one of the first to sixth aspects, in which the material of the elastic body is fluororubber. In this configuration, the material of the elastic body in the gas sensor is fluororubber, which has excellent performance in various aspects such as resistance and strength, and is particularly excellent in heat resistance and oil resistance. Therefore, the gas sensor has an effect of ensuring the sealing property of the elastic body even in a high-temperature environment, for example, and maintaining and improving the detection accuracy of the gas concentration.

[0045] A gas sensor according to an eighth aspect is the gas sensor according to any one of the first to seventh aspects, wherein at least a portion of the spacer is made of ceramics. In this configuration, at least a portion of the spacer in the gas sensor is made of ceramics that has excellent heat resistance and generally has a higher melting point than resin. In the gas sensor, the spacer is disposed on the tip side in the axial direction relative to the elastic body. By making at least a portion of the spacer out of ceramics having excellent heat resistance, the gas sensor achieves the following effect. That is, the gas sensor achieves the effect of being able to prevent the occurrence of a situation in which at least a portion of the spacer is melted and damaged by heat generated from a heat source at the tip side of the gas sensor. Effect of the Invention

[0046] According to the present invention, it is possible to provide a gas sensor in which the ceramic housing is prevented from being bitten into a member arranged on the rear end side of the ceramic housing when the ceramic housing is tilted from the axial direction. [Brief description of the drawings]

[0047] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of a main configuration of a gas sensor according to an embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a main portion of the gas sensor shown in FIG. 1, showing the rear end side of the gas sensor. [Diagram 3] FIG. 3 is a schematic cross-sectional view illustrating an example of a main configuration of a gas sensor according to the first modification. [Figure 4] FIG. 4 is a schematic cross-sectional view illustrating an example of a main configuration of a gas sensor according to the second modification. [Diagram 5] FIG. 5 is a graph showing changes in temperature and acceleration in a durability performance comparison test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as "the present embodiment") will be described with reference to the drawings. However, the present embodiment described below is merely an example of the present invention in every respect. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention. In other words, in implementing the present invention, a specific configuration according to the embodiment may be appropriately adopted.

[0049] The present inventors have found that, in a conventional gas sensor in which an elastic body is disposed on the rear end side of the axial direction of the sensor element of a ceramic housing to which a contact metal is attached, the following problem occurs when the ceramic housing is fixed in a state inclined from the axial direction. That is, when the ceramic housing is fixed in a state inclined from the axial direction, an unintended stress (e.g., a stress in a direction other than a direction perpendicular to the axial direction) acts from the sensor element on the terminal metal attached to the ceramic housing. Therefore, the present inventors have found a problem that, in a gas sensor in which the ceramic housing is fixed in a state inclined from the axial direction, when an impact is applied to the gas sensor, the terminal metal is more likely to break than when the ceramic housing is fixed parallel to the axial direction.

[0050] After further investigation, the inventors have determined that the phenomenon in which the ceramic housing is fixed in a tilted state from the axial direction occurs, for example, in the following manner: That is, the inventors have determined that during the manufacturing stage of the gas sensor, the ceramic housing is in a tilted state from the axial direction and bites into an elastic body that is softer than the ceramic housing, causing the above-mentioned phenomenon.

[0051] Conventional gas sensors are manufactured, for example, through the following preliminary assembly process. That is, first, a ceramic housing with metal terminals attached and a contact member in which an elastic body is arranged in this order from the axial tip side are prepared (preliminary assembly process). Next, the rear end side of the sensor element is inserted into the contact member (particularly, an insertion port provided on the tip side of the ceramic housing). Then, the sensor element and the ceramic housing (contact member) are integrated by crimping a crimping ring provided to fix the ceramic housing with the sensor element inserted therein from the outer periphery.

[0052] In this embodiment, the end face of each member on the front end side in the axial direction (the axial direction of the sensor element) is also referred to as the "front end face." Similarly, the end face of each member on the rear end side in the axial direction is also referred to as the "rear end face."

[0053] In a conventional gas sensor manufactured through such a process, the ceramic housing may be inclined from the axial direction at the time of the pre-assembly process and may be embedded in an elastic body that is softer than the ceramic housing. In such a case, in the subsequent process of integrating the sensor element and the ceramic housing, the ceramic housing is fixed in the inclined state from the axial direction. In other words, the ceramic housing is integrated with the sensor element in the inclined state, and the ceramic housing is fixed in the inclined state from the axial direction.

[0054] Furthermore, the conventional gas sensor is manufactured, for example, through the above-mentioned preliminary assembly process as well as the following crimping process. That is, the conventional gas sensor is manufactured through the crimping process in which a cylindrical body in which a sensor element and a contact member integrated with the sensor element are disposed, and an elastic body disposed at an open end of the cylindrical body are crimped into a reduced diameter. In the crimping process, the elastic body is fixed to the open end of the cylindrical body, and the open end of the cylindrical body is sealed by the elastic body.

[0055] In this crimping process, the soft elastic body for sealing the open end of the cylindrical body may deform, causing the elastic body (particularly the end face on the tip side in the axial direction) to apply stress to the ceramic housing in a direction tilted from the axial direction. For example, in the crimping process, the tip face of the elastic body may be pushed out toward the tip side in the axial direction while tilted from the axial direction, causing stress to the ceramic housing in a direction tilted from the axial direction.

[0056] The present inventors have confirmed that, for example, during the manufacturing stage of the gas sensor (specifically, the above-mentioned pre-assembly process, crimping process, etc.), the ceramic housing may bite into the elastic body in a tilted state from the axial direction, and this state may become fixed.

[0057] Therefore, the present inventors have considered using a spacer to prevent "the ceramic housing from biting into an elastic body that is softer than the ceramic housing when tilted from the axial direction". That is, the present inventors thought that by disposing a spacer between the ceramic housing to which the terminal fittings are attached and the soft elastic body that seals the open end of the cylindrical body, it is possible to prevent the ceramic housing from biting into the elastic body when tilted from the axial direction. Furthermore, the present inventors thought that in order to prevent the ceramic housing from biting into the spacer disposed on the rear end side of the ceramic housing, it is effective to make the tip side portion of the spacer in the axial direction sufficiently hard.

[0058] The present inventors have experimentally determined the hardness (softness) that the tip portion of the spacer should have in order to prevent the ceramic housing from biting into the spacer (particularly the tip portion of the spacer) (for details of the experiment, see [Example] below). As a result, the present inventors have confirmed that by setting the Young's modulus of the tip portion of the spacer to 80 GPa or more, it is possible to significantly prevent the ceramic housing from biting into the spacer (particularly the tip portion) compared to when the Young's modulus is less than 80 GPa.

[0059] Therefore, a gas sensor according to one aspect of the present invention includes a spacer between a ceramic housing to which a terminal fitting is attached and a soft elastic body that seals the open end of the cylindrical body. In the gas sensor according to one aspect of the present invention, the ceramic housing contacts the spacer disposed on the rear end side of the ceramic housing, particularly the end face (tip face) on the tip side of the spacer. In the gas sensor according to one aspect of the present invention, the Young's modulus of the tip portion of the spacer including the tip face is 80 GPa or more, that is, the tip portion of the spacer has sufficient hardness to significantly prevent the ceramic housing from biting into the spacer (particularly its tip portion).

[0060] Therefore, in the gas sensor according to one aspect of the present invention, an event does not occur in which "the ceramic housing, in a state tilted from the axial direction, bites into a spacer arranged on the rear end side of the ceramic housing, and this state is fixed." Therefore, the gas sensor according to one aspect of the present invention has an effect of being able to prevent the ceramic housing from biting into a member (i.e., the spacer) arranged on the rear end side of the ceramic housing, in a state tilted from the axial direction. The gas sensor according to one aspect of the present invention can reduce the possibility of the terminal fittings breaking even if an impact is applied to the gas sensor by preventing "the ceramic housing, in a state tilted from the axial direction, biting into a member arranged on the rear end side of the ceramic housing." First, gas sensor 1 will be described below as a gas sensor according to one aspect of the present invention, with reference to Figs. 1 and 2.

[0061] [Configuration example] <Overview of gas sensors> Fig. 1 is a schematic cross-sectional view showing an example of the main configuration of a gas sensor 1 according to this embodiment. That is, Fig. 1 shows a schematic cross-sectional configuration of the gas sensor 1, which is parallel to and in contact with the longitudinal axis (axis line, a line along the left-right direction of the figure). The gas sensor 1 is an example of the "gas sensor" of the present invention, and is used to detect oxygen and NO in a measurement gas such as an automobile exhaust gas. xThe gas sensor 1 is capable of detecting the concentration of a specific gas (specific gas concentration) such as . As illustrated in FIG. 1, the gas sensor 1 has an axis, is configured to extend along the longitudinal direction (axial direction), and has a front end and a rear end as the respective longitudinal ends. One longitudinal end is the front end, and the other end is the rear end. In the example of FIG. 1, the gas sensor 1 is disposed so that the front end of the gas sensor 1 faces leftward, and the rear end of the gas sensor 1 faces rightward. That is, the left-right direction in FIG. 1 corresponds to the longitudinal direction (axial direction). In this embodiment, the gas sensor 1 includes a sensor element 10, a cylindrical body 20 (a metal shell 21, an outer cylinder 22, and a fixing bolt 23), a terminal metal fitting 30, a lead wire 40, an elastic body 50, a ceramic housing 60, a spacer 70, and a protective cover 80. In the gas sensor 1, the sensor element 10 is surrounded by a cylindrical body 20 and a protective cover 80, and the cylindrical body 20 and the protective cover 80 as a whole constitute a housing member (casing) that houses the sensor element 10. The sensor element 10 is disposed coaxially with the cylindrical body 20 and the protective cover 80, and the extending direction of the central axis of the sensor element 10 coincides with the axial direction of the gas sensor 1.

[0062] (sensor element) The sensor element 10 is an example of the "sensor element" of the present invention, and is configured to extend along the axial direction (the left-right direction in FIG. 1). The sensor element 10 illustrated in FIG. 1 is a thin, flat (long plate-like) element. The sensor element 10 has a detection section 11 at its tip end and a connector electrode (connector electrode 12) at its rear end. The connector electrode 12 of the sensor element 10 is illustrated in FIG. 2. The sensor element 10 illustrated in FIG. 1 is coated at its tip end with an outer porous layer, which serves as a protective layer that prevents, for example, moisture in the measured gas from adhering to the sensor element 10 and causing cracks in the element body of the sensor element 10.

[0063] In the gas sensor 1, the sensor element 10 is arranged so that its tip side faces the tip of the gas sensor 1. For example, in one embodiment of the sensor element 10, the measurement gas introduced into the sensor element 10 is reduced or decomposed inside the sensor element 10 to generate oxygen ions. In the gas sensor 1 including such a sensor element 10, the concentration of a specific gas, which is a detection target gas in the measurement gas, is determined based on the fact that the amount of oxygen ions flowing inside the sensor element 10 is proportional to the concentration of the specific gas.

[0064] In the example shown in FIG. 1, the tip side of the sensor element 10 is surrounded by a protective cover 80, and the rear end side protrudes into the outer tube 22, and the approximate center portion between the two is fixed inside the metal shell 21 by a ring part 90 in a manner that hermetically seals the area between both ends.

[0065] (Circumference parts) 1, the mounting part 90 includes a first ceramic supporter 91, a powder compact 92, and a second ceramic supporter 93. The first ceramic supporter 91 and the second ceramic supporter 93 are ceramic insulators. More specifically, a through hole (not shown) having a shape corresponding to the cross-sectional shape of the sensor element 10 is provided at the axial center position of the first ceramic supporter 91 and the second ceramic supporter 93, and the first ceramic supporter 91 and the second ceramic supporter 93 are mounted on the sensor element 10 by inserting the sensor element 10 into the through hole. The first ceramic supporter 91 is engaged with the tapered surface of the metallic shell 21 on the left side of the drawing.

[0066] On the other hand, the powder compact 92 is formed by molding ceramic powder such as talc. As with the first ceramic supporter 91 and the second ceramic supporter 93, the powder compact 92 is formed by inserting the sensor element 10 through the through-hole, and then the two molded bodies (not shown) that were mounted around the sensor element 10 are disposed inside the metal shell 21 in a state of being mounted around the sensor element 10, and then further compressed to be integrated. More specifically, the ceramic particles that form the powder compact 92 are surrounded by the first ceramic supporter 91, the second ceramic supporter 93, and the metal shell 21, and are densely filled in the space inside the metal shell 21 through which the sensor element 10 passes. By compressing and filling the powder compact 92, airtight sealing is realized between the front end side and the rear end side of the sensor element 10.

[0067] 1 shows an example in which the ring part 90 is composed of a first ceramic supporter 91, a powder compact 92, and a second ceramic supporter 93. However, in the gas sensor 1, it is not essential that the ring part 90 is composed of the first ceramic supporter 91, the powder compact 92, and the second ceramic supporter 93. The gas sensor 1 shown in FIG. 1 includes the ring part 90 that fixes the sensor element 10 inside the metallic shell 21 and hermetically seals the gap between the front end and rear end of the sensor element 10.

[0068] (Cylindrical body) The cylindrical body 20 is an example of the "cylindrical body" of the present invention. The cylindrical body 20 is, for example, a metallic tubular (e.g., cylindrical) member having an open end. The sensor element 10 is disposed inside the cylindrical body 20. In the example shown in Fig. 1, the cylindrical body 20 includes a cylindrical main metal fitting 21, a cylindrical outer cylinder 22, and a fixing bolt 23, each of which is a metallic member.

[0069] The metal shell 21 is a tubular (e.g., cylindrical) member made of metal. The sensor element 10 and a fixing ring part 90 ring-mounted around the sensor element 10 are housed inside the metal shell 21. In other words, the metal shell 21 is further ring-mounted around the ring part 90 ring-mounted around the sensor element 10. The metal shell 21 illustrated in Fig. 1 is configured to surround the sensor element 10 along the axial direction (longitudinal direction), and in particular, is configured to surround an area excluding a portion of each of the front end side and rear end side of the sensor element 10.

[0070] The outer cylinder 22 is a tubular (eg, cylindrical) member made of metal, and the outer cylinder 22 illustrated in FIG. 1 covers the rear end of the sensor element 10, the ceramic housing 60 (the terminal metal fittings 30), and the spacer 70.

[0071] An end (open end) on the tip side of the outer tube 22 is welded to an outer peripheral end on the rear end side of the metal shell 21. An elastic body 50 is disposed at the rear end side open end of the outer tube 22 so as to seal the open end. A reduced diameter portion 221 is formed at the rear end side of the outer tube 22, which crimps a part of the elastic body 50 from the periphery to seal the open end on the rear end side. The reduced diameter portion 221 crimps the outer tube 22 from the outside in a reduced diameter manner over its entire circumferential direction, thereby generating a reaction force in the elastic body 50 toward the radially outward direction, thereby sealing the outer tube 22.

[0072] Furthermore, the lead wire 40 is drawn out from the open end on the rear end side of the outer cylinder 22 sealed by the elastic body 50 through a through hole (not shown) formed inside the elastic body 50. Outside air (atmosphere) is introduced into the internal space of the outer cylinder 22 through a gap between the coating of the lead wire 40 and the metal wire (conductor) (in other words, inside the coating), and the internal space of the outer cylinder 22 becomes a reference gas (atmosphere) atmosphere. The rear end of the sensor element 10 is disposed within the internal space of the outer cylinder 22 filled with the reference gas.

[0073] The fixing bolt 23 is an annular member used when fixing the gas sensor 1 to a measurement position (mounting position), and is fixed coaxially with the metallic shell 21. The fixing bolt 23 has a threaded bolt portion and a holding portion that is held when the bolt portion is screwed. The bolt portion of the fixing bolt 23 is screwed into a nut provided at the mounting position of the gas sensor 1. For example, by screwing the bolt portion of the fixing bolt 23 into a nut (nut portion) provided in an exhaust pipe of an automobile, the gas sensor 1 is fixed to the exhaust pipe in a manner that the protective cover 80 side is exposed inside the exhaust pipe.

[0074] As described above, the cylindrical body 20 illustrated in Fig. 1 includes the metal shell 21, the outer tube 22, and the fixing bolt 23, and is configured as a cylindrical (e.g., cylindrical) member as a whole, particularly as a cylindrical member extending in the axial direction. That is, the cylindrical body 20 illustrated in Fig. 1 is a cylindrical member extending in the axial direction, including the cylindrical metal shell 21, the cylindrical outer tube 22 welded to the outer periphery end portion on the rear end side of the metal shell 21, and the fixing bolt 23 disposed on the outer periphery on the front end side of the metal shell 21. For example, the cylindrical body 20 and the gas sensor 1 (sensor element 10) are coaxial, and the cylindrical body 20 has a front end and a rear end as respective ends in the axial direction (longitudinal direction), and is disposed so that the front end of the cylindrical body 20 faces the front end of the gas sensor 1. The cylindrical body 20 accommodates the sensor element 10, a fixing ring part 90 ring-mounted on the sensor element 10, a ceramic housing 60 (terminal fittings 30), and a spacer 70, and the rear opening end is sealed by an elastic body 50. A reduced diameter section 221 for fixing the elastic body 50 for sealing the opening end of the cylindrical body 20 is formed on the rear end side of the cylindrical body 20 (outer tube 22), and the reduced diameter section 221 crimps a part of the elastic body 50 from the periphery.

[0075] In the gas sensor 1, it is not essential that the cylindrical body 20 includes the metallic shell 21, the outer cylinder 22, and the fixing bolt 23. The cylindrical body 20 does not have to include the fixing bolt 23, and the metallic shell 21 and the outer cylinder 22 may be an integrally formed member. In the gas sensor 1, the cylindrical body 20 may be any cylindrical member in which the sensor element 10 is disposed inside and in which an open end is formed.

[0076] (Terminal fittings) The terminal fitting 30 is an example of the "terminal fitting" of the present invention. The terminal fitting 30 is a metal member (contact member) extending in the axial direction. In the gas sensor 1, the sensor element 10 (particularly, its connector electrode 12) and the lead wire 40 are electrically connected via the terminal fitting 30. As will be described in detail in FIG. 2, the terminal fitting 30 has an element contact portion 31 at its front end that electrically connects with the connector electrode 12 of the sensor element 10, and also has a lead wire holding portion 32 at its rear end that crimps and holds the lead wire 40.

[0077] (ceramic housing) The ceramic housing 60 is an example of the "ceramic housing" of the present invention. The ceramic housing 60 is a ceramic member that houses the rear end side of the sensor element 10 (specifically, the connector electrode 12 provided on the rear end side of the sensor element 10) and the front end side of the terminal fitting 30 (specifically, the element contact portion 31 described in FIG. 2). That is, in the gas sensor 1 illustrated in FIG. 1, the sensor element 10 (particularly, the connector electrode 12) and the terminal fitting 30 (particularly, the element contact portion 31) are electrically connected within the ceramic housing 60.

[0078] For example, the rear end side of the sensor element 10 provided with the connector electrodes 12 is inserted into a ceramic housing 60 that accommodates the front end side (element contact portion 31) of the terminal fitting 30. In this inserted state, the connector electrodes 12 provided on the rear end side of the sensor element 10 and the front end side (element contact portion 31) of the terminal fitting 30 come into contact with each other. The front end side (element contact portion 31) of the terminal fitting 30 may be clamped and fixed between the rear end side of the sensor element 10 provided with the connector electrodes 12 and the ceramic housing 60, thereby electrically connecting the connector electrodes 12 of the sensor element 10 and the terminal fitting 30.

[0079] In the gas sensor 1, there is a gap between the ceramic housing 60 and the cylindrical body 20 (outer cylinder 22), that is, the ceramic housing 60 is not in contact with the cylindrical body 20. The ceramic housing 60 may be integrated with the sensor element 10 to fix its position inside the cylindrical body 20 without contacting the cylindrical body 20. As illustrated in FIG. 1, the sensor element 10 is fixed in its position inside the cylindrical body 20 by the ring part 90 and the cylindrical body 20 (particularly, the metal shell 21 and the outer cylinder 22). The ceramic housing 60 may be integrated with the sensor element 10, whose position inside the cylindrical body 20 is fixed by the ring part 90 and the cylindrical body 20, to fix its position inside the cylindrical body 20 without contacting the cylindrical body 20.

[0080] The ceramic housing 60 (more precisely, a contact member in which the ceramic housing 60, the spacer 70, and the elastic body 50 are arranged in this order from the axial tip side) may be integrated with the sensor element 10 as follows. That is, after the lead wire holding portion 32 of the terminal fitting 30 is connected to the tip of the lead wire 40 inserted through the elastic body 50 and the spacer 70, the ceramic housing 60 having an insertion opening at the axial tip side is assembled to the terminal fitting 30. More precisely, the ceramic housing 60 to which the fixing metal fitting having the pressure spring 61 (see FIG. 2) and the crimping ring 62 (see FIG. 2) are not yet assembled is assembled to the terminal fitting 30 to which the tip of the lead wire 40 is connected to the lead wire holding portion 32. Thereafter, the fixing metal fitting having the pressure spring 61 and the crimping ring 62 are assembled to the outer periphery of the ceramic housing 60 to prepare the contact member (pre-assembly). The pressure spring 61 is, for example, a leaf spring member having a trapezoidal cross section without an upper bottom portion, and generates an elastic force as a restoring force when an external force acts on the free end of the spring. When the sensor element 10 and the contact member described above are integrated, the crimping ring 62 is crimped with the sensor element 10 (particularly, the rear end portion) inserted into the insertion opening of the ceramic housing 60, that is, is contracted and deformed by the external force. This narrows the gap of the insertion opening of the ceramic housing 60, and the sensor element 10 and the ceramic housing 60 (contact member) are integrated. At this time, the element contact portion 31 of the terminal fitting 30 contacts the connector electrode 12 of the sensor element 10. Therefore, in the gas sensor 1, electrical conduction between the sensor element 10 and the outside is achieved through the lead wire 40 connected to the terminal fitting 30 and further through the contact member (terminal fitting 30) connected to the lead wire 40.

[0081] (Lead wire) The lead wire 40 is electrically connected to the connector electrode 12 of the sensor element 10 via the terminal fitting 30, and extends outward from the open end of the cylindrical body 20. Specifically, the lead wire 40 is electrically connected at its tip end to the rear end side of the terminal fitting 30 (specifically, the lead wire holding portion 32 described in FIG. 2), and the rear end side of the lead wire 40 extends outward from the open end of the cylindrical body 20. As described above, the gap between the lead wire 40 and the cylindrical body 20 (outer cylinder 22) is sealed by the elastic body 50.

[0082] For example, the lead wire 40 is inserted through a through hole (not shown) continuously provided in the elastic body 50 and the spacer 70. The tip end of the lead wire 40 is crimped and fixed to the rear end side (lead wire holding portion 32) of the terminal fitting 30, and the rear end of the lead wire 40 is connected to an external device (controller), a power source, etc. This allows the sensor element 10 (particularly the connector electrode 12 of the sensor element 10) to be electrically connected to the external device, the power source, etc. through the terminal fitting 30 and the lead wire 40. Note that FIG. 1 shows an example in which there are two terminal fittings 30 and two lead wires 40, but this is only for the sake of simplicity. In reality, the gas sensor 1 is provided with the number of terminal fittings 30 and the number of lead wires 40 required for the above-mentioned electrical connection.

[0083] (Elastic body) The elastic body 50 is an example of the "elastic body" of the present invention. The elastic body 50 is an elastic member, and is made of, for example, rubber. The elastic body 50 is arranged so as to seal the open end of the cylindrical body 20 (the open end on the rear end side in the example shown in FIG. 1), and the lead wire 40 is inserted into the elastic body 50. Specifically, a through hole extending in the axial direction is formed inside the elastic body 50, and for example, a plurality of through holes extending in the axial direction are formed. The lead wire 40 is accommodated (inserted) in the through hole formed inside the elastic body 50, and for example, each of the plurality of lead wires 40 is accommodated (inserted) in each of the plurality of through holes formed inside the elastic body 50.

[0084] The material of the elastic body 50 is, for example, fluororubber. Fluororubber has excellent properties in various aspects such as resistance and strength, and is particularly excellent in heat resistance and oil resistance. Therefore, by using the elastic body 50 made of fluororubber, the gas sensor 1 has an effect of ensuring the sealing property of the elastic body 50 even in a high-temperature environment, for example, and maintaining and improving the detection accuracy of the gas concentration. However, it is not essential for the gas sensor 1 that the material of the elastic body 50 is fluororubber, and the gas sensor 1 may use an appropriate material having elasticity as the material of the elastic body 50.

[0085] (Spacer) The spacer 70 is an example of the "spacer" of the present invention. The spacer 70 is disposed between the ceramic housing 60 and the elastic body 50 in the axial direction of the gas sensor 1 (sensor element 10), specifically, disposed on the rear end side of the ceramic housing 60 and on the front end side of the elastic body 50. The front end surface of the spacer 70 contacts the ceramic housing 60 (particularly, the rear end surface of the ceramic housing 60), and the rear end surface of the spacer 70 contacts the elastic body 50 (particularly, the front end surface of the elastic body 50). For example, the position of the spacer 70 in the inside of the cylindrical body 20 (outer cylinder 22) is fixed by the ceramic housing 60 and the elastic body 50. That is, the spacer 70 is sandwiched (interposed) between the ceramic housing 60 and the elastic body 50 in the inside of the cylindrical body 20. That is, the front end surface of the spacer 70 contacts the rear end surface of the ceramic housing 60, and as described above, the position of the ceramic housing 60 in the inside of the cylindrical body 20 is fixed by being integrated with the sensor element 10. In addition, the rear end surface of the spacer 70 contacts the front end surface of the elastic body 50, and as described above, the elastic body 50 is fixed to the open end of the cylindrical body 20 (the open end on the rear end side in the example shown in FIG. 1) by the reduced diameter portion 221. Therefore, the position of the spacer 70 inside the cylindrical body 20 (outer cylinder 22) is fixed by the ceramic housing 60 and the elastic body 50.

[0086] A lead wire 40 is inserted into the spacer 70 illustrated in Fig. 1. For example, in the example illustrated in Fig. 1, the lead wire 40 and the terminal fitting 30 (particularly, the rear end of the terminal fitting 30 electrically connected to the lead wire 40) are housed inside the spacer 70.

[0087] The spacer 70 is made of, for example, a heat-resistant material. By making the spacer 70 out of a heat-resistant material, it is possible to prevent the spacer 70, which is disposed on the tip side of the elastic body 50 in the axial direction, from being melted and damaged by heat generated from a heat source on the tip side of the gas sensor 1. For example, by interposing the spacer 70 between the elastic body 50 and the ceramic housing 60, it is possible to prevent the elastic body 50 from being excessively heated during use of the gas sensor 1. In other words, from the viewpoint of suppressing heat transfer to the elastic body 50, it is preferable that the thermal conductivity of the spacer 70 is low. However, while the spacer 70 suppresses the temperature rise of the elastic body 50, the spacer 70 becomes hot, so the spacer 70 itself needs to have sufficient heat resistance. Therefore, by making the spacer 70 out of a heat-resistant material, it is possible to prevent the spacer 70 itself from being melted and damaged by heat generated from the heat source while suppressing heat transfer from the heat source to the elastic body 50.

[0088] Specifically, in the gas sensor 1, the spacer 70 is made of ceramics. Ceramics have excellent heat resistance and generally have a higher melting point than resin. In the gas sensor 1, the spacer 70 is disposed on the tip side of the elastic body 50 in the axial direction. By making the spacer 70 out of ceramics having excellent heat resistance, the gas sensor 1 has the following effect. That is, the gas sensor 1 has the effect of preventing the spacer 70 from being melted and damaged by heat generated from a heat source at the tip side of the gas sensor 1. However, it is not essential for the gas sensor 1 that the spacer 70 be made of ceramics, and the gas sensor 1 may use a heat-resistant material as the material of the spacer 70 as appropriate.

[0089] The Young's modulus of at least the tip portion including the tip surface of the spacer 70 is 80 GPa or more. In the gas sensor 1, the Young's modulus of the entire spacer 70 is 80 GPa or more, that is, the Young's modulus of not only the tip portion but the entire spacer 70 is 80 GPa or more.

[0090] In the gas sensor 1, a spacer 70 is disposed between the ceramic housing 60 and the elastic body 50. In the gas sensor 1, the ceramic housing 60 (particularly, the rear end surface) is in contact not with the elastic body 50 but with the spacer 70 disposed on the rear end side of the ceramic housing 60, particularly with the tip surface of the spacer 70. Therefore, the gas sensor 1 can prevent the ceramic housing 60 from being wedged into the elastic body 50 in a state inclined from the axial direction.

[0091] Particularly, in the gas sensor 1, the ceramic housing 60 contacts the spacer 70 arranged on the rear end side of the ceramic housing 60, particularly the tip surface of the spacer 70. The Young's modulus of the tip portion of the spacer 70 including the tip surface is 80 GPa or more, that is, the tip portion of the spacer 70 has sufficient hardness to significantly prevent the ceramic housing 60 from biting into the spacer 70 (particularly the tip portion of the spacer 70).

[0092] Therefore, in the gas sensor 1, an event does not occur in which "the ceramic housing 60, in a state inclined from the axial direction, bites into the spacer 70 arranged on the rear end side of the ceramic housing 60, and this state becomes fixed." Therefore, the gas sensor 1 has an effect of being able to prevent the ceramic housing 60, in a state inclined from the axial direction, from biting into a member arranged on the rear end side of the ceramic housing 60 (i.e., the spacer 70). By preventing "the ceramic housing 60, in a state inclined from the axial direction, from biting into a member arranged on the rear end side of the ceramic housing 60," the gas sensor 1 can reduce the possibility of the terminal fitting 30 breaking even if an impact is applied to the gas sensor 1.

[0093] (Protective cover) The protective cover 80 is a substantially cylindrical exterior member that protects a predetermined range on the tip side of the sensor element 10, which is a portion that comes into direct contact with the gas to be measured during use. The protective cover 80 illustrated in FIG. 1 is configured to surround at least a portion of the tip side of the cylindrical body 20 (metal shell 21) along the axial direction (longitudinal direction) and extend beyond the tip of the sensor element 10. For example, the protective cover 80 is configured to surround the sensor element 10 and a portion of the tip side of the cylindrical body 20 around the axis. The protective cover 80 has a tip and a rear end as respective ends in the axial direction, and the tip of the protective cover 80 is disposed closer to the tip side of the gas sensor 1 than the tip of the sensor element 10.

[0094] The protective cover 80 is provided with a plurality of through holes (not shown) through which gas can pass. The measurement gas that flows into the protective cover 80 through the through holes is directly detected by the sensor element 10. The type, number, position, shape, etc. of the through holes provided in the protective cover 80 may be appropriately determined in consideration of the manner in which the measurement gas flows into the inside of the protective cover 80.

[0095] In the example shown in FIG. 1, the protective cover 80 includes a cylindrical inner cover 81 with a bottom that covers the tip of the sensor element 10, and a cylindrical outer cover 82 with a bottom that covers the inner cover 81. The inner cover 81 includes a first member 81B and a second member 81A, and is configured to cover at least a part of the periphery of the tip side of the sensor element 10 and the cylindrical body 20 (metal shell 21). The first member 81B is configured to extend along the axial direction from the outer wall of the tip of the cylindrical body 20, and after the diameter becomes smaller in a direction perpendicular to the axial direction around the tip of the cylindrical body 20, it is configured to further extend along the axial direction. The second member 81A is configured to cover a part of the periphery of the tip side of the first member 81B. The outer cover 82 is configured to cover the periphery of the inner cover 81.

[0096] A sensor element chamber is formed as a space surrounded by the inner cover 81, and the tip of the sensor element 10 is disposed within this sensor element chamber. Openings are appropriately provided in the first member 81B, the second member 81A, and the outer cover 82 of the inner cover 81, whereby the sensor element chamber is connected to the space outside the protective cover 80. However, the configuration and shape of the protective cover 80 are not limited to this example. The configuration and shape of the protective cover 80 may be appropriately determined depending on the embodiment.

[0097] The material of the protective cover 80 may be, for example, a metal material such as stainless steel (e.g., SUS). The protective cover 80 may be manufactured by appropriately shaping the metal material. The protective cover 80 may be omitted from the configuration of the gas sensor 1.

[0098] <Details of the rear end of the gas sensor> 2 is an enlarged cross-sectional view showing a schematic view of the main part of the gas sensor 1, specifically, an enlarged cross-sectional view showing the main part of the rear end side of the gas sensor 1. In FIG. 2, the left-right direction of the paper is the axial direction (longitudinal direction) of the gas sensor 1 (sensor element 10), the left side of the paper is the front end side, and the right side of the paper is the rear end side.

[0099] 2, the ceramic housing 60, the spacer 70, and the elastic body 50 are arranged in this order from the front end to the rear end at the rear end of the gas sensor 1. The rear end face of the ceramic housing 60 is in contact with the front end face of the spacer 70, and the rear end face of the spacer 70 is in contact with the front end face of the elastic body 50. As described above, in the gas sensor 1, the spacer 70 has an overall Young's modulus of 80 GPa or more. Therefore, in the gas sensor 1, the Young's modulus of the front portion of the spacer 70 is 80 GPa or more, that is, the ceramic housing 60 (particularly, the rear end face of the ceramic housing 60) is in contact with the spacer 70 (particularly, its front end face) whose Young's modulus is 80 GPa or more.

[0100] Here, the gas sensor 1 illustrated in Fig. 1 and Fig. 2 is manufactured, for example, through the following process. That is, first, a contact member is prepared in which the ceramic housing 60 to which the terminal fittings 30 are attached, the spacer 70, and the elastic body 50 are arranged in this order from the axial tip side (preliminary assembly). At the time of preliminarily assembling, the fixing metal fitting having the pressure spring 61 illustrated in Fig. 2 and the crimping ring 62 may not yet be assembled to the outer periphery of the ceramic housing 60. As described above, the pressure spring 61 is, for example, a leaf spring member, and the crimping ring 62 is contracted and deformed by an external force to integrate the sensor element 10 and the ceramic housing 60 (contact member). After the preliminarily assembling is completed, the rear end side of the sensor element 10 is then inserted into the ceramic housing 60 to which the terminal fittings 30 are attached (particularly, into the insertion opening provided on the tip side of the ceramic housing 60). Then, by crimping a crimping ring 62 provided for fixing the ceramic housing 60, into which the sensor element 10 is inserted, from the outer periphery, the sensor element 10 and the ceramic housing 60 (contact member) are integrated.

[0101] In addition to the above-mentioned pre-assembly process, the gas sensor 1 is manufactured through, for example, the following process: That is, the elastic body 50 arranged at the open end of the cylindrical body 20 (outer cylinder 22) is crimped to the cylindrical body 20 in a diameter-reduced shape to fix the elastic body 50 to the open end of the cylindrical body 20, and the gas sensor 1 is manufactured through a crimping process in which the open end is sealed with the elastic body 50.

[0102] (Contact between ceramic housing and spacer) 2, in the gas sensor 1, the contact area A1 between the spacer 70 (particularly, the front end surface of the spacer 70) and the ceramic housing 60 (particularly, the rear end surface of the ceramic housing 60) is adjusted to be sufficiently large. Specifically, in the gas sensor 1, the contact area A1 is 3 mm 2 However, in the gas sensor 1, the contact area A1 is set to 3 mm 2 It is not essential that the contact area A1 is 3 mm 2 It may be less than.

[0103] The present inventors considered that it is effective to ensure a sufficient contact area A1 between the spacer 70 and the ceramic housing 60 in order to prevent the ceramic housing 60 from being fixed in a state tilted from the axial direction. For example, when the contact area A1 is small, a force is more likely to act from the spacer 70 to the ceramic housing 60 in a direction tilted from the axial direction than when the contact area A1 is large, and as a result, it is considered that the ceramic housing 60 is more likely to be tilted from the axial direction. Also, when the contact area A1 is small, the contact between the spacer 70 and the ceramic housing 60 is less stable than when the contact area A1 is large, and as a result, it is considered that the ceramic housing 60 is more likely to be tilted from the axial direction, for example, when an impact is applied to the gas sensor 1. Therefore, the present inventors examined the range of the contact area A1 between the spacer 70 and the ceramic housing 60 that is effective in preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction. As a result, the present inventors considered that the contact area A1 is set to 3 mm 2 By setting it to more than 3mm 2 It was confirmed that this significantly prevented the ceramic housing 60 from being fixed in a state tilted from the axial direction, compared with the case where the angle was less than 100 mm.

[0104] In the gas sensor 1, the contact area A1 between the spacer 70 and the ceramic housing 60 is 3 mm 2 Therefore, in the gas sensor 1, the contact area A1 between the spacer 70 and the ceramic housing 60 is set to 3 mm 2 As compared with the case where the angle is less than 100°, this provides the effect of significantly preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction.

[0105] As described above, the gas sensor 1 is manufactured, for example, through a pre-assembly process. If the ceramic housing 60 is tilted from the axial direction at the time of pre-assembly, the ceramic housing 60 is integrated with the sensor element 10 in the tilted state, that is, the state in which the ceramic housing 60 is tilted from the axial direction is fixed.

[0106] Therefore, for example, by ensuring a sufficient contact area A1 between the spacer 70 and the ceramic housing 60 at the time of pre-assembly, it is possible to prevent the ceramic housing 60 from being positioned in a state inclined from the axial direction in the above-mentioned contact member. 2 As a result, the gas sensor 1 can prevent the ceramic housing 60 from being positioned in a state inclined from the axial direction during pre-assembly.

[0107] As illustrated in FIG. 2, in the gas sensor 1, the spacer 70 and the ceramic housing 60 are in contact with each other on a straight line (i.e., an extension of the axis) extending in the axial direction of the axis of the sensor element 10 (gas sensor 1). For example, in the gas sensor 1, a distance L1 from the position of the center of gravity CG1 of "a portion of the spacer 70 (particularly, its front end surface) in contact with the ceramic housing 60 (particularly, its rear end surface)" to an extension of the axis of the sensor element 10 is within 2 mm. The center of gravity CG1 is the center of mass when the mass is virtually uniformly distributed on the portion of the front end surface of the spacer 70 in contact with the ceramic housing 60 (particularly, the rear end surface of the ceramic housing 60). Note that in the gas sensor 1, it is not essential that the distance L1 is within 2 mm, and the distance L1 may be greater than 2 mm.

[0108] The present inventors considered that in order to prevent the ceramic housing 60 from being fixed in a state tilted from the axial direction, it is effective to bring the spacer 70 into contact with the ceramic housing 60 on the extension of the axis of the sensor element 10 (gas sensor 1). In particular, they considered that if the distance L1 from the center of gravity CG1 of the contact surface between the spacer 70 and the ceramic housing 60 to the extension of the axis can be made sufficiently small, the ceramic housing 60 can be effectively prevented from being fixed in a state tilted from the axial direction. Therefore, the present inventors examined the distance L1 from the center of gravity CG1 to the extension of the axis, which is effective in preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction. As a result, the present inventors confirmed that by setting the distance L1 from the center of gravity CG1 to the extension of the axis to within 2 mm, the ceramic housing 60 can be significantly prevented from being fixed in a state tilted from the axial direction, compared to the case where the distance L1 is greater than 2 mm.

[0109] In the gas sensor 1, a distance L1 from the position of the center of gravity CG1 of the portion of the spacer 70 that is in contact with the ceramic housing 60 to an extension of the axis of the sensor element 10 (gas sensor 1) is within 2 mm.

[0110] Therefore, the gas sensor 1 has the effect of significantly preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction, compared to when the distance L1 from the center of gravity CG1 to the extension of the axis is greater than 2 mm.

[0111] As described above, the gas sensor 1 is manufactured, for example, through a pre-assembly process. However, if the ceramic housing 60 is tilted from the axial direction at the time of pre-assembly, the ceramic housing 60 is integrated with the sensor element 10 in this tilted state, that is, the state in which the ceramic housing 60 is tilted from the axial direction is fixed.

[0112] Therefore, for example, by contacting the spacer 70 and the ceramic housing 60 on the extension of the axis at the time of pre-assembly, it is possible to prevent the ceramic housing 60 from being positioned at an angle from the axial direction in the contact member. Specifically, at the time of pre-assembly, the distance L1 from the center of gravity CG1 of the contact surface between the spacer 70 and the ceramic housing 60 to the extension of the axis is set to within 2 mm. This makes it possible to prevent the gas sensor 1 from being positioned at an angle from the axial direction.

[0113] In the gas sensor 1 illustrated in FIGS. 1 and 2, the front end surface of the spacer 70 and the rear end surface of the ceramic housing 60 are similar in area and shape, that is, they are substantially equal in area and shape.

[0114] By making the front end surface of the spacer 70 and the rear end surface of the ceramic housing 60 substantially equal (similar) in area and shape, the gas sensor 1 achieves the following effects. That is, when the front end surface of the spacer 70 and the rear end surface of the ceramic housing 60 are similar, it becomes easier to bring them into contact with each other on the extension of the axis of the sensor element 10, for example, during the manufacturing stage of the gas sensor 1, compared to when they are different. In particular, by making the front end surface of the spacer 70 and the rear end surface of the ceramic housing 60 similar, it becomes easier to reduce the distance L1 from the center of gravity CG1 of the contact portion between them to the extension of the axis of the sensor element 10 (for example, within 2 mm) during the manufacturing stage. Here, the front end surface of the spacer 70 and the rear end surface of the ceramic housing 60 being "similar" means, for example, that both are circular or elliptical and the difference in area between them is about 40% or less of the area of ​​at least one of them.

[0115] However, in the gas sensor 1, it is not essential that the front end surface of the spacer 70 be similar to the rear end surface of the ceramic housing 60, and for example, it is not essential that the front end surface of the spacer 70 and the rear end surface of the ceramic housing 60 be substantially equal in area and shape. In the gas sensor according to one aspect of the present invention, the front end surface of the spacer and the rear end surface of the ceramic housing may be similar to each other, or may be different from each other.

[0116] For example, in the gas sensor 1, the front end face of the spacer 70 may be smaller than the rear end face of the ceramic housing 60. Similarly, in the gas sensor 1, the front end face of the spacer 70 may be larger than the rear end face of the ceramic housing 60. By making the front end face of the spacer 70 larger than the rear end face of the ceramic housing 60, the gas sensor 1 achieves the following effect. That is, when the front end face of the spacer 70 is larger than the rear end face of the ceramic housing 60, it becomes easier to ensure a sufficient contact area A1 between the two during, for example, the manufacturing stage of the gas sensor 1, compared to when the front end face of the spacer 70 is smaller. Specifically, it is possible to make the contact area A1 3 mm 2 An example of a gas sensor according to one aspect of the present invention in which the tip surface of the spacer in contact with the ceramic housing (particularly the rear end surface) is made larger than the rear end surface of the ceramic housing will be described later with reference to FIG.

[0117] (Contact between the spacer and the elastic body) 2, in the gas sensor 1, the contact area A2 between the spacer 70 (particularly, the rear end surface of the spacer 70) and the elastic body 50 (particularly, the front end surface of the elastic body 50) is adjusted to be sufficiently large. Specifically, in the gas sensor 1, the contact area A2 is 25% or more of the entire area of ​​the front end surface of the elastic body 50. However, in the gas sensor 1, it is not essential that the contact area A2 is 25% or more of the entire area of ​​the front end surface of the elastic body 50, and the contact area A2 may be less than 25% of the entire area of ​​the front end surface of the elastic body 50.

[0118] The present inventors have considered that it is effective to ensure a sufficient contact area A2 between the spacer 70 and the elastic body 50 in order to prevent the ceramic housing 60 from being fixed in a state tilted from the axial direction. For example, when the contact area A2 is small, a force is more likely to act from the elastic body 50 to the spacer 70 in a direction tilted from the axial direction than when the contact area A2 is large, and as a result, it is considered that the ceramic housing 60 in contact with the spacer 70 is also more likely to tilt from the axial direction. Also, when the contact area A2 is small, the contact between the elastic body 50 and the spacer 70 is less stable than when the contact area A2 is large, and it is considered that the spacer 70 (particularly, its end face) is more likely to tilt from the axial direction, for example, when an impact is applied to the gas sensor 1. And, when the spacer 70 (particularly, its end face) tilts from the axial direction, it is considered that the ceramic housing 60 in contact with the spacer 70 (particularly, its end face on the tip side) is also more likely to tilt from the axial direction. Therefore, the present inventors have examined the range of the contact area A2 between the spacer 70 and the elastic body 50 that is effective in preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction. The present inventors have confirmed that by setting the contact area A2 to 25% or more of the entire area of ​​the tip face of the elastic body 50, the ceramic housing 60 can be significantly prevented from being fixed in a state tilted from the axial direction, compared to when the contact area A2 is less than 25%.

[0119] In the gas sensor 1, the area of ​​the portion of the tip face of the elastic body 50 that is in contact with the spacer 70, that is, the above-mentioned contact area A2, is 25% or more of the entire area of ​​the tip face of the elastic body 50.

[0120] Therefore, the gas sensor 1 has the effect of significantly preventing the ceramic housing 60 from being fixed in a tilted state from the axial direction, compared to a case in which the contact area A2 is less than 25% of the entire area of ​​the tip face of the elastic body 50.

[0121] Here, as described above, the gas sensor 1 is manufactured through, for example, a crimping process. In this crimping process, the elastic body 50 may be deformed, and stress may act on the spacer 70 in a direction inclined from the axial direction. For example, in the crimping process, the tip surface of the elastic body 50 may be pushed out toward the tip side in the axial direction while being inclined from the axial direction, and may apply stress to the spacer 70 in a direction inclined from the axial direction. If the contact area A2 between the spacer 70 and the elastic body 50 is small at the time of the crimping process, the elastic body 50 is soft and the spacer 70 is not stable. In addition, stress acts from the elastic body 50 on the spacer 70 in a direction inclined from the axial direction, so that the spacer 70 is likely to be inclined from the axial direction. In addition, when the spacer 70 (particularly, its tip surface) is inclined from the axial direction, the ceramic housing 60 in contact with the spacer 70 may also be inclined from the axial direction.

[0122] Therefore, for example, by ensuring a sufficient contact area A2 between the spacer 70 and the elastic body 50 during the above-mentioned crimping process, the gas sensor 1 can prevent the ceramic housing 60 from tilting from the axial direction. Specifically, by setting the contact area A2 during the crimping process to 25% or more of the entire area of ​​the tip surface of the elastic body 50, the gas sensor 1 can prevent the ceramic housing 60 from tilting from the axial direction during the crimping process.

[0123] As illustrated in FIG. 2, in the gas sensor 1, the elastic body 50 and the spacer 70 are in contact with each other on a straight line (i.e., an extension of the axis) extending in the axial direction of the axis of the sensor element 10 (gas sensor 1). In particular, in the gas sensor 1, a distance L2 from the position of the center of gravity CG2 of "the part of the elastic body 50 (particularly, its front end surface) in contact with the spacer 70 (particularly, its rear end surface)" to an extension of the axis of the sensor element 10 is within 2 mm. The center of gravity CG2 is the center of mass when the mass is virtually uniformly distributed on the part of the front end surface of the elastic body 50 in contact with the spacer 70 (particularly, the rear end surface of the spacer 70). Note that in the gas sensor 1, it is not essential that the distance L2 is within 2 mm, and the distance L2 may be greater than 2 mm.

[0124] The present inventors considered that in order to prevent the ceramic housing 60 from being fixed in a state tilted from the axial direction, it is effective to bring the elastic body 50 and the spacer 70 into contact with each other on the extension line of the axis of the sensor element 10 (gas sensor 1). In particular, they considered that if the distance L2 from the center of gravity CG2 of the contact surface between the elastic body 50 and the spacer 70 to the extension line of the axis can be made sufficiently small, the ceramic housing 60 can be effectively prevented from being fixed in a state tilted from the axial direction. Therefore, the present inventors examined the distance L2 from the center of gravity CG2 to the extension line of the axis, which is effective in preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction. As a result, the present inventors confirmed that by setting the distance L2 from the center of gravity CG2 to the extension line of the axis within 2 mm, the ceramic housing 60 can be significantly prevented from being fixed in a state tilted from the axial direction, compared to the case where the distance L2 is greater than 2 mm.

[0125] In the gas sensor 1, the distance L2 from the position of the center of gravity CG2 of the portion of the elastic body 50 that is in contact with the spacer 70 to the extension line of the axis of the sensor element 10 (gas sensor 1) is within 2 mm.

[0126] Therefore, the gas sensor 1 has the effect of significantly preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction, compared to when the distance L2 from the center of gravity CG2 to the extension of the axis is greater than 2 mm.

[0127] As described above, the gas sensor 1 is manufactured, for example, through the crimping process. However, if the elastic body 50 is deformed during the crimping process and stress acts from the elastic body 50 to the spacer 70 in a direction inclined from the axial direction, the ceramic housing 60 in contact with the spacer 70 may also be inclined from the axial direction.

[0128] Therefore, for example, by contacting the elastic body 50 and the spacer 70 on the extension of the axis during the crimping process, the gas sensor 1 can prevent the ceramic housing 60 from tilting from the axial direction. Specifically, during the crimping process, the distance L2 from the center of gravity CG2 to the extension of the axis is set to within 2 mm. This makes it possible to prevent the gas sensor 1 from being in a situation where the ceramic housing 60 is positioned in a state where it is tilted from the axial direction during the crimping process.

[0129] In the gas sensor 1 illustrated in FIGS. 1 and 2, the rear end face of the spacer 70 and the front end face of the elastic body 50 are similar in area and shape, that is, they are substantially equal in area and shape.

[0130] By making the rear end surface of the spacer 70 and the front end surface of the elastic body 50 substantially equal (similar) in area and shape, the gas sensor 1 achieves the following effects. That is, when the rear end surface of the spacer 70 and the front end surface of the elastic body 50 are similar, it becomes easier to bring them into contact with each other on the extension line of the axis of the sensor element 10, for example, during the manufacturing stage of the gas sensor 1, compared to when they are different. In particular, by making the rear end surface of the spacer 70 and the front end surface of the elastic body 50 similar, it becomes easier to reduce the distance L2 from the center of gravity CG2 of the contact portion between them to the extension line of the axis of the sensor element 10 (for example, within 2 mm) during the manufacturing stage. The rear end surface of the spacer 70 and the front end surface of the elastic body 50 being "similar" means, for example, that the difference in area between them is about 40% or less of the area of ​​at least one of the rear end surface of the spacer 70 and the front end surface of the elastic body 50.

[0131] However, in the gas sensor 1, it is not essential that the rear end surface of the spacer 70 be similar to the front end surface of the elastic body 50, and for example, it is not essential that the rear end surface of the spacer 70 and the front end surface of the elastic body 50 be substantially equal in area and shape. In the gas sensor according to one aspect of the present invention, the rear end surface of the spacer and the front end surface of the elastic body may be similar to each other, or may be different from each other.

[0132] For example, in the gas sensor 1, the rear end face of the spacer 70 may be larger than the front end face of the elastic body 50. By making the rear end face of the spacer 70 larger than the front end face of the elastic body 50, the gas sensor 1 achieves the following effect. That is, when the rear end face of the spacer 70 is larger than the front end face of the elastic body 50, it becomes easier to ensure a sufficient contact area A2 between the two, for example, during the manufacturing stage of the gas sensor 1, compared to when the rear end face is smaller. Specifically, when the rear end face of the spacer 70 is larger than the front end face of the elastic body 50, it becomes easier to ensure that the contact area A2 between the two is 25% or more of the total area of ​​the front end faces of the elastic body, compared to when the rear end face is smaller.

[0133] In the gas sensor 1, the rear end face of the spacer 70 may be smaller than the front end face of the elastic body 50. However, as described above, the contact area A2 between the spacer 70 and the elastic body 50 is preferably 25% or more of the entire area of ​​the front end face of the elastic body 50. In addition, it is preferable to make the distance L2 from the center of gravity CG2 of the contact surface between the elastic body 50 and the spacer 70 to the extension line of the axis sufficiently small, and specifically, it is preferable to make the distance L2 within 2 mm.

[0134] (Regarding the direction of the end faces of the ceramic housing, spacer, and elastic body) In the gas sensor 1, the ceramic housing 60 is disposed along the axial direction, that is, the ceramic housing 60 is disposed inside the cylindrical body 20 (outer cylinder 22) in a state of extending in the axial direction. In accordance with the ceramic housing 60 being disposed along the axial direction, for example, the rear end face of the ceramic housing 60 is perpendicular to the axial direction. Also, in the gas sensor 1, it is desirable that the tip face of the spacer 70 in contact with the rear end face of the ceramic housing 60 is also perpendicular to the axial direction.

[0135] Since the front end face of the spacer 70 as well as the rear end face of the ceramic housing 60 are perpendicular to the axial direction, the gas sensor 1 can more effectively prevent the ceramic housing 60 from tilting in the axial direction even when an impact is applied to the gas sensor 1.

[0136] Since the tip end face of the spacer 70 is perpendicular to the axial direction, it is preferable that the spacer 70 is disposed along the axial direction, and it is preferable that the rear end face of the spacer 70 in the gas sensor 1 is perpendicular to the axial direction. Similarly, it is preferable that the tip end face of the elastic body 50 in contact with the spacer 70 (particularly its rear end face) in the gas sensor 1 is also perpendicular to the axial direction. Since the tip end face of the elastic body 50 and the rear end face and tip end face of the spacer 70 are all perpendicular to the axial direction, the gas sensor 1 achieves the following effect. That is, the gas sensor 1 can extremely effectively prevent the ceramic housing 60 from being tilted from the axial direction even when, for example, an impact is applied to the gas sensor 1.

[0137] <Considerations regarding the spacer configuration> As described above, the gas sensor according to one aspect of the present invention solves the problem of conventional gas sensors, that is, "when the ceramic housing is tilted from the axial direction, it bites into an elastic body arranged on the rear end side of the ceramic housing," by using the following configuration. That is, the gas sensor according to one aspect of the present invention solves the problem of conventional gas sensors by arranging a spacer, particularly a spacer whose tip portion including a tip surface is sufficiently hard, on the rear end side of the ceramic housing. Specifically, the gas sensor according to one aspect of the present invention solves the problem of conventional gas sensors by arranging a spacer "whose tip portion has a Young's modulus of 80 GPa or more" on the rear end side of the ceramic housing.

[0138] Therefore, in the gas sensor according to one aspect of the present invention, the spacer disposed on the rear end side of the ceramic housing (i.e., in contact with the rear end face of the ceramic housing) only needs to have a Young's modulus of at least 80 GPa at the tip portion including the tip face. For example, in the gas sensor 1 described with reference to Figures 1 and 2, the spacer 70 disposed on the rear end side of the ceramic housing 60 (i.e., in contact with the rear end face of the ceramic housing 60) has an overall Young's modulus of 80 GPa or more.

[0139] However, for the gas sensor according to one aspect of the present invention, it is not essential that the Young's modulus of the "whole" spacer disposed on the rear end side of the ceramic housing is 80 GPa or more. As described above, in the gas sensor according to one aspect of the present invention, the spacer disposed on the rear end side of the ceramic housing only needs to have a Young's modulus of at least the tip portion including the tip surface of 80 GPa or more. For example, in the gas sensor according to one aspect of the present invention, the spacer disposed on the rear end side of the ceramic housing may have a hard tip side and a soft rear side. Hereinafter, a gas sensor according to one aspect of the present invention including a spacer "disposed on the rear end side of the ceramic housing, hard tip side and soft rear side" will be described with reference to FIG. 3.

[0140] FIG. 3 is a schematic cross-sectional view showing an example of a main configuration of a gas sensor 1A according to Modification 1. In FIG. 3, the up-down direction on the paper surface is the axial direction (longitudinal direction) of the gas sensor 1A, the lower side on the paper surface is the front end side, and the upper side on the paper surface is the rear end side. The gas sensor 1A includes a spacer 70A that is "disposed on the rear end side of the ceramic housing 60, and has a hard front end side and a soft rear end side." The gas sensor 1A shown in FIG. 3 is similar to the gas sensor 1 described with reference to FIGS. 1 and 2, except that the gas sensor 1A includes the spacer 70A instead of the spacer 70. Therefore, in the following description, detailed description of the configuration other than the "spacer 70A" will be omitted.

[0141] 3, in the gas sensor 1A, the spacer 70A includes a front end portion 71A and a rear end portion 72A. The spacer 70A is disposed inside the cylindrical body 20 (outer cylinder 22) such that the front end portion 71A is disposed on the front end side in the axial direction and the rear end portion 72A is disposed on the rear end side in the axial direction. The front end portion 71A and the rear end portion 72A have different hardness (softness), specifically, different Young's modulus from each other. That is, the Young's modulus of the front end portion 71A is 80 GPa or more, whereas the Young's modulus of the rear end portion 72A is less than 80 GPa.

[0142] 1 and 2 show an example of a gas sensor 1 in which a spacer 70 is one member. In contrast, in a gas sensor 1A shown in FIG. 3, a spacer 70A disposed on the rear end side of a ceramic housing 60 is composed of a plurality of components (components). In a gas sensor according to one aspect of the present invention, a spacer disposed on the rear end side of a ceramic housing may be composed of a plurality of components (components), and the Young's modulus of at least a front end portion may be 80 GPa or more. In a gas sensor according to one aspect of the present invention, a spacer has a spacer front end portion disposed on the front end side in an axial direction and a spacer rear end portion disposed on the rear end side, and the Young's moduli of both may be different from each other. In a gas sensor according to one aspect of the present invention, a spacer may have a multi-stage structure (for example, a two-stage structure) including the above-mentioned spacer front end portion and spacer rear end portion. For example, a spacer 70A shown in FIG. 3 has a two-stage structure having a front end portion 71A disposed on the front end side in an axial direction and a rear end portion 72A disposed on the rear end side. It is not essential that the spacer 70A has a two-stage configuration, and the spacer 70A may further include an intermediate portion between the front end portion 71A and the rear end portion 72A, that is, the spacer 70A may have a three or more stage configuration.

[0143] In the gas sensor 1A, the ceramic housing 60 is in contact with the spacer 70A disposed on the rear end side of the ceramic housing 60, specifically, with the front end surface of the spacer 70A (particularly, the front end surface 71A). The Young's modulus of the front end surface 71A of the spacer 70A, including the front end surface with which the ceramic housing 60 (particularly, the rear end surface of the ceramic housing 60) is in contact, is 80 GPa or more. By setting the Young's modulus of the front end surface 71A of the spacer 70A, including the front end surface with which the ceramic housing 60 is in contact, to 80 GPa or more, the gas sensor 1A achieves the following effect. That is, the gas sensor 1A achieves the effect that the ceramic housing 60 can be prevented from being cut into a member (i.e., the spacer 70A) disposed on the rear end side of the ceramic housing 60 in a state inclined from the axial direction.

[0144] As described above, the spacer 70A includes a tip portion 71A including a tip surface of the spacer 70A and a rear end portion 72A including a rear end surface of the spacer 70A. In the spacer 70A, the rear end portion 72A is softer than the tip portion 71A, and specifically, the Young's modulus of the rear end portion 72A is smaller than the Young's modulus of the tip portion 71A. That is, the Young's modulus of the tip portion 71A is 80 GPa or more, whereas the Young's modulus of the rear end portion 72A is less than 80 GPa.

[0145] That is, in the gas sensor 1A, the rear end portion 72A of the spacer 70A is softer and more flexible than the front end portion 71A of the spacer 70A. In the gas sensor 1A, the rear end surface of the spacer 70A is in contact with the elastic body 50 (particularly, the front end surface of the elastic body 50).

[0146] Therefore, in the gas sensor 1A, even if the tip surface of the elastic body 50 is inclined with respect to the axial direction, the inclination of the tip surface of the elastic body 50 can be absorbed by the rear end portion 72A of the spacer 70A. That is, in the gas sensor 1A, the soft rear end portion 72A of the spacer 70A, which contacts the tip surface of the elastic body 50, is deflected, so that the inclination of the tip surface of the elastic body 50 can be absorbed by the rear end portion 72A of the spacer 70A.

[0147] The spacer 70A prevents the ceramic housing 60 from tilting from the axial direction due to the tilt of the tip surface of the elastic body 50 being transmitted to the ceramic housing 60 via the spacer 70A, by the rear end portion 72A which is softer and more flexible than the tip portion 71A. For example, if the tip surface of the elastic body 50 is tilted from the axial direction, stress in the direction tilted from the axial direction is transmitted from the tip surface of the elastic body 50 to the ceramic housing 60, and the ceramic housing 60 may be tilted from the axial direction due to such stress. The spacer 70A prevents such a situation by the rear end portion 72A which is softer and more flexible than the tip portion 71A. In other words, the spacer 70A prevents the ceramic housing 60 from tilting from the axial direction due to such stress by absorbing the stress from the tip surface of the elastic body 50 in the direction tilted from the axial direction by the rear end portion 72A. Moreover, the tip portion 71A of the spacer 70A has a hardness sufficient to significantly prevent the ceramic housing 60 from biting into the spacer 70A.

[0148] Therefore, the gas sensor 1A has the advantage of being able to more effectively prevent the ceramic housing 60 from getting caught in a member (i.e., the spacer 70A) arranged on the rear end side of the ceramic housing 60 when tilted from the axial direction.

[0149] When the spacer 70A is used to suppress a rise in temperature of the elastic body 50 during use of the gas sensor 1A, the front end portion 71A and the rear end portion 72A may each be configured as follows. That is, as the material of the front end portion 71A arranged on the front end side in the axial direction, ceramics, which has a higher melting point than resin, is selected from the viewpoint of having better heat resistance than the rear end portion 72A. Preferably, ceramics with a thermal conductivity of 32 W / m·K or less, which is suitable from the viewpoint of heat resistance as well as heat insulation, are selected, and more preferably, alumina (thermal conductivity: 32 W / m·K) or steatite (thermal conductivity: 2 W / m·K) are selected. On the other hand, as the material of the rear end portion 72A in contact with the elastic body 50, resin is selected from the viewpoint of having low thermal conductivity rather than ceramics. Preferably, the resin used for the rear end portion 72A is PTFE (polytetrafluoroethylene, melting point 327°C) or PFA (perfluoroalkoxyalkane, melting point 310°C), both of which are fluororesins. These resins have low thermal conductivity and higher heat resistance than the rubber elastomer 50. For example, PTFE has a thermal conductivity of 0.2 W / m·K and a maximum continuous use temperature (the maximum temperature when used continuously at the maximum temperature) of 260°C.

[0150] That is, in the gas sensor 1A, at least a part of the spacer 70A is made of ceramics, for example, the tip portion 71A of the spacer 70A is made of ceramics. Ceramics have excellent heat resistance and generally have a higher melting point than resin. In the gas sensor 1A, the spacer 70A is disposed on the tip side in the axial direction than the elastic body 50, and in particular, the tip portion 71A of the spacer 70A is disposed on the tip side in the axial direction than the rear end portion 72A. By forming the tip portion 71A of the spacer 70A from ceramics having excellent heat resistance, the gas sensor 1A achieves the following effect. That is, the gas sensor 1A achieves the effect of being able to prevent the tip portion 71A of the spacer 70A from being melted and damaged by heat generated from a heat source at the tip side of the gas sensor 1A. However, for the gas sensor 1A, it is not essential that the tip portion 71A of the spacer 70A be made of ceramics. In the gas sensor 1A, a heat-resistant material may be used as the material for the tip portion 71A of the spacer 70A as appropriate.

[0151] In the gas sensor 1A, the contact area A1 (A) between the spacer 70A (particularly the tip portion 71A) and the ceramic housing 60 is 3 mm 2 The contact area A1 (A) between the spacer 70A (particularly, its tip surface) and the ceramic housing 60 (particularly, its rear end surface) is set to 3 mm 2 By configuring as described above, the gas sensor 1A has the following advantages, similar to the gas sensor 1. That is, the gas sensor 1A has a contact area A1 (A) between the spacer 70A and the ceramic housing 60 of 3 mm 2 As compared with the case where the angle is less than 100°, this provides the effect of significantly preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction.

[0152] In the gas sensor 1A, the area (contact area A2(A)) of the portion of the front end surface of the elastic body 50 that is in contact with the spacer 70A (particularly, the rear end portion 72A) is 25% or more of the entire area of ​​the front end surface of the elastic body 50, similar to the contact area A2 in the gas sensor 1. By making the contact area A2(A) between the elastic body 50 (particularly, its front end surface) and the spacer 70A (particularly, its rear end surface) 25% or more of the entire area of ​​the front end surface of the elastic body 50, the gas sensor 1A achieves the following effect similar to the gas sensor 1. That is, the gas sensor 1A achieves the effect that the ceramic housing 60 can be significantly prevented from being fixed in a state tilted from the axial direction, compared to a case in which the contact area A2(A) is less than 25% of the entire area of ​​the front end surface of the elastic body 50.

[0153] In the gas sensor 1A, the distance L1(A) from the position of the center of gravity CG1(A) of the portion of the spacer 70A in contact with the ceramic housing 60 to the extension of the axis of the sensor element 10 (gas sensor 1) is within 2 mm, similar to the distance L1 in the gas sensor 1. The center of gravity CG1(A) is the center of mass when the mass is virtually uniformly distributed on the portion of the tip surface of the spacer 70A (particularly, the tip portion 71A) in contact with the ceramic housing 60 (particularly, the rear end surface of the ceramic housing 60). By setting the distance L1(A) from the position of the center of gravity CG1(A) of the portion of the spacer 70A in contact with the ceramic housing 60 to the extension of the axis of the sensor element 10 within 2 mm, the gas sensor 1A exhibits the following effects, similar to the gas sensor 1. In other words, the gas sensor 1A has the effect of significantly preventing the ceramic housing 60 from being fixed in a tilted state from the axial direction, compared to when the distance L1(A) from the center of gravity CG1(A) to the extension of the axis of the sensor element 10 is greater than 2 mm.

[0154] In the gas sensor 1A, the distance L2(A) from the position of the center of gravity CG2(A) of the part of the elastic body 50 in contact with the spacer 70A to the extension of the axis of the sensor element 10 (gas sensor 1) is within 2 mm. The center of gravity CG2(A) is the center of mass when the mass is virtually uniformly distributed on the part of the front end surface of the elastic body 50 in contact with the spacer 70A (particularly, the rear end surface of the spacer 70A). By setting the distance L2(A) from the position of the center of gravity CG2(A) of the part of the elastic body 50 in contact with the spacer 70A to the extension of the axis of the sensor element 10 to within 2 mm, the gas sensor 1A has the following effect, similar to the gas sensor 1. That is, the gas sensor 1A has the effect of significantly preventing the ceramic housing 60 from being fixed in a tilted state from the axial direction, compared to a case in which the distance L2(A) from the center of gravity CG2(A) to the extension of the axis of the sensor element 10 is greater than 2 mm.

[0155] In the gas sensor 1A, the material of the elastic body 50 is fluororubber, similar to the elastic body 50 in the gas sensor 1. Therefore, similar to the gas sensor 1, the gas sensor 1A has an effect of ensuring the sealing performance of the elastic body 50 even in a high-temperature environment, for example, and maintaining and improving the detection accuracy of the gas concentration.

[0156] In the gas sensor 1A shown in FIG. 3, the front end surface of the spacer 70A (front end portion 71A) and the rear end surface of the ceramic housing 60 are similar in area and shape, that is, they are substantially equal in area and shape.

[0157] By making the front end surface of the spacer 70A and the rear end surface of the ceramic housing 60 substantially equal (similar) in area and shape, the gas sensor 1A has the following effects. That is, when the front end surface of the spacer 70A and the rear end surface of the ceramic housing 60 are similar, it becomes easier to bring them into contact with each other on the extension of the axis of the sensor element 10, for example, during the manufacturing stage of the gas sensor 1A, compared with when they are different. In particular, by making the front end surface of the spacer 70A and the rear end surface of the ceramic housing 60 similar, it becomes easier to reduce the distance L1 from the center of gravity CG1 of the contact portion between them to the extension of the axis of the sensor element 10 (for example, within 2 mm) during the manufacturing stage. Here, the front end surface of the spacer 70A and the rear end surface of the ceramic housing 60 being "similar" means, for example, that both are circular or elliptical and the difference in area between them is about 40% or less of the area of ​​at least one of them.

[0158] However, in the gas sensor 1A, it is not essential that the front end surface of the spacer 70A be similar to the rear end surface of the ceramic housing 60, and for example, it is not essential that the two be substantially equal in area and shape. In the gas sensor according to one aspect of the present invention, the front end surface of the spacer and the rear end surface of the ceramic housing may be similar to each other, or may be different from each other.

[0159] For example, in the gas sensor 1A, the leading end face of the spacer 70A may be smaller than the rear end face of the ceramic housing 60. Similarly, in the gas sensor 1A, the leading end face of the spacer 70A may be larger than the rear end face of the ceramic housing 60. By making the leading end face of the spacer 70A larger than the rear end face of the ceramic housing 60, the gas sensor 1A achieves the following effect. That is, when the leading end face of the spacer 70A is larger than the rear end face of the ceramic housing 60, it is easier to ensure a sufficient contact area A1(A) between the two, for example, during the manufacturing stage of the gas sensor 1A, compared to when it is smaller. Specifically, when the leading end face of the spacer 70A is larger than the rear end face of the ceramic housing 60, it is easier to ensure a contact area A1(A) of 3 mm during the manufacturing stage of the gas sensor 1A, compared to when it is smaller. 2 It becomes easy to do so.

[0160] In the gas sensor 1A shown in FIG. 3, the rear end surface of the spacer 70A and the front end surface of the elastic body 50 are similar in area and shape, that is, they are substantially equal in area and shape.

[0161] By making the rear end surface of the spacer 70A and the tip surface of the elastic body 50 substantially equal (similar) in area and shape, the gas sensor 1A achieves the following effects. That is, when the rear end surface of the spacer 70A and the tip surface of the elastic body 50 are similar, it becomes easier to bring them into contact with each other on the extension line of the axis of the sensor element 10, for example, during the manufacturing stage of the gas sensor 1A, compared to when they are different. In particular, by making the rear end surface of the spacer 70A and the tip surface of the elastic body 50 similar, it becomes easier to reduce the distance L2(A) from the center of gravity CG2(A) of the contact portion between them to the extension line of the axis of the sensor element 10 (for example, within 2 mm) during the manufacturing stage. The rear end surface of the spacer 70A and the tip surface of the elastic body 50 being "similar" means, for example, that the difference in area between them is about 40% or less of the area of ​​at least one of the rear end surface of the spacer 70A and the tip surface of the elastic body 50.

[0162] However, in the gas sensor 1A, it is not essential that the rear end surface of the spacer 70A be similar to the front end surface of the elastic body 50, and for example, it is not essential that the rear end surface of the spacer 70A and the front end surface of the elastic body 50 be substantially equal in area and shape. In the gas sensor according to one aspect of the present invention, the rear end surface of the spacer and the front end surface of the elastic body may be similar to each other, or may be different from each other.

[0163] For example, in the gas sensor 1A, the rear end face of the spacer 70A may be larger than the front end face of the elastic body 50. By making the rear end face of the spacer 70A larger than the front end face of the elastic body 50, the gas sensor 1A achieves the following effect. That is, when the rear end face of the spacer 70A is larger than the front end face of the elastic body 50, it becomes easier to ensure a sufficient contact area A2(A) between the two, for example, during the manufacturing stage of the gas sensor 1A, compared to when the rear end face is smaller. Specifically, when the rear end face of the spacer 70A is larger than the front end face of the elastic body 50, it becomes easier to make the contact area A2(A) between the two 25% or more of the total area of ​​the front end faces of the elastic body 50, compared to when the rear end face is smaller.

[0164] In the gas sensor 1A, the rear end surface of the spacer 70A may be smaller than the front end surface of the elastic body 50. However, as described above, the contact area A2(A) between the spacer 70A and the elastic body 50 is preferably 25% or more of the entire area of ​​the front end surface of the elastic body 50. In addition, it is preferable that the distance L2(A) from the center of gravity CG2(A) of the contact surface between the elastic body 50 and the spacer 70A to the extension line of the axis is sufficiently small, and specifically, it is preferable that the distance L2(A) is within 2 mm.

[0165] (Regarding the direction of the end faces of the ceramic housing, spacer, and elastic body) In the gas sensor 1A, the ceramic housing 60 is disposed along the axial direction, that is, the ceramic housing 60 is disposed inside the cylindrical body 20 (outer cylinder 22) in a state of extending in the axial direction. In accordance with the ceramic housing 60 being disposed along the axial direction, for example, the rear end surface of the ceramic housing 60 is perpendicular to the axial direction. In addition, in the gas sensor 1A, it is desirable that the tip surface of the spacer 70A (particularly the tip portion 71A) that contacts the rear end surface of the ceramic housing 60 is also perpendicular to the axial direction.

[0166] The gas sensor 1A has the following effect because the front end surface of the spacer 70A (particularly the front end portion 71A) as well as the rear end surface of the ceramic housing 60 are perpendicular to the axial direction: That is, the gas sensor 1A can more effectively prevent the ceramic housing 60 from tilting from the axial direction even when, for example, an impact is applied to the gas sensor 1A.

[0167] As described above, in the spacer 70A, the rear end portion 72A is softer than the front end portion 71A, that is, the rear end portion 72A is more flexible than the front end portion 71A. Therefore, even if the front end surface of the elastic body 50 is inclined from the direction perpendicular to the axial direction, the spacer 70A can absorb the inclination of the front end surface of the elastic body 50 by bending the rear end portion 72A, and can prevent the spacer 70A (particularly, its front end surface) from being inclined from the axial direction. The gas sensor 1A can prevent the ceramic housing 60 from being inclined from the axial direction by preventing the spacer 70A (particularly, its front end surface) from being inclined from the axial direction. Therefore, in the gas sensor 1A, the rear end surface of the spacer 70A (rear end portion 72A) does not have to be perpendicular to the axial direction. However, in the gas sensor 1A, the rear end surface of the spacer 70A may be perpendicular to the axial direction. Similarly, in the gas sensor 1A, the tip end surface of the elastic body 50 in contact with the spacer 70A (particularly, the rear end surface) may or may not be perpendicular to the axial direction.

[0168] <Considerations regarding the shape of the spacer> The gas sensors 1 and 1A described so far all have a spacer that is "arranged at the rear end side of the ceramic housing 60, has a hard tip side (specifically, a Young's modulus of 80 GPa or more), and has a tip surface similar to the rear end surface of the ceramic housing."

[0169] By making the front end surface of the spacer similar to the rear end surface of the ceramic housing, for example, by making the front end surface of the spacer and the rear end surface of the ceramic housing substantially equal in area and shape, the gas sensor according to one aspect of the present invention achieves the following effects. That is, when the front end surface of the spacer and the rear end surface of the ceramic housing are similar, it becomes easier to bring them into contact with each other on the extension of the axis of the sensor element (gas sensor), for example, during the manufacturing stage of the gas sensor, compared to when they are different. In particular, by making the front end surface of the spacer and the rear end surface of the ceramic housing substantially equal in area and shape, it becomes easier to reduce the "distance from the center of gravity of the contact portion between the two to the extension of the axis of the sensor element 10" during the manufacturing stage, etc. (for example, within 2 mm).

[0170] However, in the gas sensor according to one aspect of the present invention, it is not essential that the front end surface of the spacer and the rear end surface of the ceramic housing are similar, and for example, it is not essential that they are substantially equal in area and shape. In the gas sensor according to one aspect of the present invention, the front end surface of the spacer and the rear end surface of the ceramic housing may be similar, or may be different from each other. In the gas sensor according to one aspect of the present invention, the spacer disposed on the rear end side of the ceramic housing (i.e., in contact with the rear end surface of the ceramic housing) may have at least a front end portion including its front end surface of 80 GPa or more. In the gas sensor according to one aspect of the present invention, the shape of the spacer "disposed on the rear end side of the ceramic housing 60 and having a hard front end" is not particularly limited, and for example, the front end surface may be larger than the rear end surface of the ceramic housing. Hereinafter, an example of a gas sensor according to one aspect of the present invention, which includes a spacer "whose front end surface is larger than the rear end surface of the ceramic housing 60 and whose front end portion including the front end surface has a Young's modulus of 80 GPa or more", will be described with reference to FIG. 4.

[0171] FIG. 4 is a schematic cross-sectional view showing an example of a main configuration of a gas sensor 1B according to Modification 2. In FIG. 4, the left-right direction of the paper is the axial direction (longitudinal direction) of the gas sensor 1B, the left side of the paper is the front end side, and the right side of the paper is the rear end side. The gas sensor 1B includes a spacer 70B having a front end surface larger than the rear end surface of the ceramic housing 60 and a Young's modulus of a front end portion including the front end surface of 80 GPa or more. The gas sensor 1B shown in FIG. 4 is similar to the gas sensor 1 described with reference to FIGS. 1 and 2, except that the gas sensor 1B includes the spacer 70B instead of the spacer 70. Therefore, in the following description, detailed description of the configuration other than the spacer 70B will be omitted.

[0172] In the gas sensor 1B, the front end surface of the spacer 70B is larger than the rear end surface of the ceramic housing 60 that contacts the front end surface of the spacer 70B. In the gas sensor according to one aspect of the present invention, it is not essential that the front end surface of the spacer disposed on the rear end side of the ceramic housing be similar in area and shape to the rear end surface of the ceramic housing.

[0173] By making the leading end face of the spacer 70B larger than the rear end face of the ceramic housing 60, the gas sensor 1B achieves the following effect. That is, when the leading end face of the spacer 70B is larger than the rear end face of the ceramic housing 60, it becomes easier to ensure a sufficient contact area A1(B) between the two during, for example, the manufacturing stage of the gas sensor 1B, compared to when it is smaller. Specifically, when the leading end face of the spacer 70B is larger than the rear end face of the ceramic housing 60, it becomes easier to ensure a sufficient contact area A1(B) between the two during, for example, the manufacturing stage of the gas sensor 1B, compared to when it is smaller. 2 It becomes easy to do so.

[0174] In the gas sensor 1B, the ceramic housing 60 is in contact with the spacer 70B disposed on the rear end side of the ceramic housing 60, specifically, with the front end surface of the spacer 70B. The Young's modulus of the front end portion of the spacer 70B, including the front end surface with which the ceramic housing 60 (particularly, the rear end surface of the ceramic housing 60) is in contact, is 80 GPa or more. That is, in the gas sensor 1B, the Young's modulus of the entire spacer 70B is 80 GPa or more, that is, the Young's modulus of the entire spacer 70B, including the front end surface with which the ceramic housing 60 is in contact, is 80 GPa or more. By setting the Young's modulus of the entire spacer 70B, particularly the Young's modulus of the front end portion of the spacer 70B, including the front end surface with which the ceramic housing 60 is in contact, to 80 GPa or more, the gas sensor 1B achieves the following effect. That is, the gas sensor 1B achieves the effect of preventing the ceramic housing 60 from biting into a member (i.e., the spacer 70B) disposed on the rear end side of the ceramic housing 60 in a state inclined from the axial direction.

[0175] In the gas sensor 1B, the contact area A1(B) between the spacer 70B (particularly, the front end surface of the spacer 70B) and the ceramic housing 60 (particularly, the rear end surface of the ceramic housing 60) is 3 mm 2 The contact area A1(B) between the spacer 70B (particularly, its tip surface) and the ceramic housing 60 (particularly, its rear end surface) is set to 3 mm 2 By configuring as described above, the gas sensor 1B has the following effects similar to those of the gas sensor 1. That is, the gas sensor 1B has a contact area A1(B) between the spacer 70B and the ceramic housing 60 of 3 mm 2 As compared with the case where the angle is less than 100°, this provides the effect of significantly preventing the ceramic housing 60 from being fixed in a state tilted from the axial direction.

[0176] In the gas sensor 1B, the area (contact area A2(B)) of the portion of the front end surface of the elastic body 50 that is in contact with the spacer 70B (particularly, its rear end surface) is 25% or more of the entire area of ​​the front end surface of the elastic body 50, similar to the contact area A2 in the gas sensor 1. By making the contact area A2(B) between the elastic body 50 (particularly, its front end surface) and the spacer 70B (particularly, its rear end surface) 25% or more of the entire area of ​​the front end surface of the elastic body 50, the gas sensor 1B exhibits the following effect similar to the gas sensor 1. That is, compared to a case in which the contact area A2(B) is less than 25% of the entire area of ​​the front end surface of the elastic body 50, the gas sensor 1B exhibits the effect that the ceramic housing 60 can be significantly prevented from being fixed in a state tilted from the axial direction.

[0177] In the gas sensor 1B, the distance L1(B) from the position of the center of gravity CG1(B) of the portion of the spacer 70B in contact with the ceramic housing 60 to the extension of the axis of the sensor element 10 (gas sensor 1) is within 2 mm, similar to the distance L1 in the gas sensor 1. The center of gravity CG1(B) is the center of mass when the mass is virtually uniformly distributed on the portion of the front end surface of the spacer 70B in contact with the ceramic housing 60 (particularly the rear end surface of the ceramic housing 60). By setting the distance L1(B) from the position of the center of gravity CG1(B) of the portion of the spacer 70B in contact with the ceramic housing 60 to the extension of the axis of the sensor element 10 within 2 mm, the gas sensor 1B exhibits the following effects, similar to the gas sensor 1. In other words, the gas sensor 1B has the effect of significantly preventing the ceramic housing 60 from being fixed in a tilted state from the axial direction, compared to when the distance L1(B) from the center of gravity CG1(B) to the extension of the axis of the sensor element 10 is greater than 2 mm.

[0178] In the gas sensor 1B, the distance L2(B) from the position of the center of gravity CG2(B) of the part of the elastic body 50 in contact with the spacer 70B to the extension of the axis of the sensor element 10 (gas sensor 1) is within 2 mm. The center of gravity CG2(B) is the center of mass when the mass is virtually uniformly distributed on the part of the front end surface of the elastic body 50 in contact with the spacer 70B (particularly, the rear end surface of the spacer 70B). By setting the distance L2(B) from the position of the center of gravity CG2(B) of the part of the elastic body 50 in contact with the spacer 70B to the extension of the axis of the sensor element 10 to within 2 mm, the gas sensor 1B has the following effect, similar to the gas sensor 1. That is, the gas sensor 1B has the effect of significantly preventing the ceramic housing 60 from being fixed in a tilted state from the axial direction, compared to a case in which the distance L2(B) from the center of gravity CG2(B) to the extension of the axis of the sensor element 10 is greater than 2 mm.

[0179] In the gas sensor 1B, the material of the elastic body 50 is fluororubber, similar to the elastic body 50 in the gas sensor 1. Therefore, similar to the gas sensor 1, the gas sensor 1B has an effect of ensuring the sealing performance of the elastic body 50 even in a high-temperature environment, for example, and maintaining and improving the detection accuracy of the gas concentration.

[0180] In the gas sensor 1B, at least a part of the spacer 70B is made of ceramics. Specifically, the entire spacer 70B is made of ceramics. Ceramics have excellent heat resistance and generally have a higher melting point than resin. In the gas sensor 1B, the spacer 70B is disposed on the tip side of the elastic body 50 in the axial direction. By making the spacer 70B of ceramics having excellent heat resistance, the gas sensor 1B achieves the following effect. That is, the gas sensor 1B achieves the effect of preventing the spacer 70B from being melted and damaged by heat generated from a heat source at the tip side of the gas sensor 1B. However, it is not essential for the gas sensor 1B to make the spacer 70B of ceramics, and the gas sensor 1B may use a heat-resistant material as the material of the spacer 70B as appropriate.

[0181] In the gas sensor 1B shown in FIG. 4, the rear end surface of the spacer 70B and the front end surface of the elastic body 50 are similar in area and shape, that is, they are substantially equal in area and shape.

[0182] By making the rear end surface of the spacer 70B and the tip surface of the elastic body 50 substantially equal (similar) in area and shape, the gas sensor 1B achieves the following effects. That is, when the rear end surface of the spacer 70B and the tip surface of the elastic body 50 are similar, it becomes easier to bring them into contact with each other on the extension line of the axis of the sensor element 10, for example, during the manufacturing stage of the gas sensor 1B, compared to when they are different. In particular, by making the rear end surface of the spacer 70B and the tip surface of the elastic body 50 similar, it becomes easier to reduce the distance L2(B) from the center of gravity CG2(B) of the contact portion between them to the extension line of the axis of the sensor element 10 (for example, within 2 mm) during the manufacturing stage. The rear end surface of the spacer 70B and the tip surface of the elastic body 50 being "similar" means, for example, that the difference in area between them is about 40% or less of the area of ​​at least one of the rear end surface of the spacer 70B and the tip surface of the elastic body 50.

[0183] However, in the gas sensor 1B, it is not essential that the rear end surface of the spacer 70B be similar to the front end surface of the elastic body 50, and for example, it is not essential that the rear end surface of the spacer 70B and the front end surface of the elastic body 50 be substantially equal in area and shape. In the gas sensor according to one aspect of the present invention, the rear end surface of the spacer and the front end surface of the elastic body may be similar to each other, or may be different from each other.

[0184] For example, in the gas sensor 1B, the rear end face of the spacer 70B may be larger than the front end face of the elastic body 50. By making the rear end face of the spacer 70B larger than the front end face of the elastic body 50, the gas sensor 1B achieves the following effect. That is, when the rear end face of the spacer 70B is larger than the front end face of the elastic body 50, it becomes easier to ensure a sufficient contact area A2(B) between the two, for example, during the manufacturing stage of the gas sensor 1B, compared to when the rear end face is smaller. Specifically, when the rear end face of the spacer 70B is larger than the front end face of the elastic body 50, it becomes easier to make the contact area A2(B) between the two 25% or more of the total area of ​​the front end faces of the elastic body 50, compared to when the rear end face is smaller.

[0185] In the gas sensor 1B, the rear end surface of the spacer 70B may be smaller than the front end surface of the elastic body 50. However, as described above, the contact area A2(B) between the spacer 70B and the elastic body 50 is preferably 25% or more of the entire area of ​​the front end surface of the elastic body 50. In addition, it is preferable to make the distance L2(B) from the center of gravity CG2(B) of the contact surface between the elastic body 50 and the spacer 70B to the extension line of the axis sufficiently small, and specifically, it is preferable to set the distance L2(B) to 2 mm or less.

[0186] [Features] As described above, the gas sensor (1, 1A, 1B) according to one aspect of the present invention includes the sensor element 10, the terminal fitting 30, the ceramic housing 60, the cylindrical body 20, the elastic body 50, and the spacer (70, 70A, 70B). The sensor element 10 extends in the axial direction, has a detection portion 11 at the front end side, and has a connector electrode 12 at the rear end side. The terminal fitting 30 extends in the axial direction, has an element contact portion 31 at the front end side, and the element contact portion 31 is electrically connected to the connector electrode 12 of the sensor element 10. The ceramic housing 60 accommodates the connector electrode 12 of the sensor element 10 and the element contact portion 31 of the terminal fitting 30. The cylindrical body 20 is a cylindrical member in which the sensor element 10, the terminal fitting 30, and the ceramic housing 60 are disposed, and an open end is formed. The elastic body 50 is disposed so as to seal the open end (the open end on the rear end side) of the cylindrical body 20.

[0187] A spacer (70, 70A, 70B) according to one aspect of the present invention is disposed between a ceramic housing 60 and an elastic body 50 in the axial direction of a sensor element 10 (gas sensor (1, 1A, 1B)). The spacer contacts the ceramic housing 60 at its front end surface and contacts the elastic body 50 at its rear end surface. The spacer according to one aspect of the present invention has a Young's modulus of at least a front end portion including the front end surface of 80 GPa or more. For example, each of the spacers 70 and 70B has an overall Young's modulus of 80 GPa or more. The spacer 70A includes a front end portion 71A having a Young's modulus of 80 GPa or more and a rear end portion 72A having a Young's modulus less than 80 GPa.

[0188] The present inventors considered that by disposing spacers (70, 70A, 70B) between the ceramic housing 60 and the elastic body 50, it would be possible to prevent the ceramic housing 60 from biting into the elastic body 50. Therefore, in a gas sensor according to one aspect of the present invention, a spacer (70, 70A, 70B) is disposed between the ceramic housing 60 and the elastic body 50.

[0189] The present inventors further considered that in order to prevent the ceramic housing 60 from biting into a member arranged on the rear end side of the ceramic housing 60, it is effective to make the tip end portion of the member arranged on the rear end side in the axial direction sufficiently hard. Here, as described above, in the gas sensor according to one aspect of the present invention, the spacer (70, 70A, 70B) is arranged between the ceramic housing 60 and the elastic body 50. Therefore, the present inventors determined through experiments (Examples to be described later) the hardness (softness) that the tip portion of the spacer should have in order to prevent the ceramic housing 60 from biting into the spacer (70, 70A, 70B) (particularly, its tip portion). As a result, the present inventors confirmed that by setting the Young's modulus of the tip portion of the above-mentioned spacer to 80 GPa or more, it is possible to significantly prevent the ceramic housing 60 from biting into the spacer (particularly, its tip portion) compared to the case where the Young's modulus is less than 80 GPa.

[0190] In the gas sensor according to one aspect of the present invention, the ceramic housing 60 contacts the spacers (70, 70A, 70B) arranged on the rear end side of the ceramic housing 60, particularly the tip faces of the spacers (70, 70A, 70B). The Young's modulus of the tip portions including the tip faces of the spacers (70, 70A, 70B) is 80 GPa or more, and is sufficiently hard to significantly prevent the ceramic housing 60 from biting into the associated spacers (particularly their tip portions).

[0191] Therefore, in the gas sensor according to one aspect of the present invention, the following phenomenon does not occur: "the ceramic housing 60, in a tilted state from the axial direction, bites into the above-mentioned spacer arranged on the rear end side of the ceramic housing 60, and becomes fixed in this state."

[0192] Therefore, the gas sensor according to one aspect of the present invention can prevent the ceramic housing 60 from being jammed into a member (i.e., the spacer (70, 70A, 70B)) arranged on the rear end side of the ceramic housing 60 when tilted from the axial direction.

[0193] [Variations] Although the embodiments of the present invention have been described above, the above description of the embodiments is merely an example of the present invention in every respect. Various improvements and modifications may be made to the above embodiments. Regarding each component of the above embodiments, components may be omitted, replaced, or added as appropriate. In addition, the shape and dimensions of each component of the above embodiments may be changed as appropriate depending on the embodiment. For example, the following modifications are possible. In the following, the same reference numerals are used for components similar to those of the above embodiments, and the description of the same points as those of the above embodiments is omitted as appropriate. The following modifications can be combined as appropriate.

[0194] In a gas sensor according to an aspect of the present invention (for example, the gas sensor 1, 1A, 1B described above), the shape of the spacer (70, 70A, 70B) disposed between the elastic body (50) and the ceramic housing (60) is not particularly limited. The spacer may be, for example, cylindrical, truncated conical, or a combination of one or more cylinders and one or more truncated cones arranged in the axial direction. In addition, the length of at least a part of the spacer in a direction perpendicular to the axial direction (for example, the diameter in the direction perpendicular to the axial direction) may vary continuously or discontinuously along the axial direction. Furthermore, the spacer may have a front end surface and a rear end surface that are substantially the same shape, or the area of ​​the front end surface may be smaller than the area of ​​the rear end surface, or the area of ​​the front end surface may be larger than the area of ​​the rear end surface.

[0195] Furthermore, the leading end surface of the spacer may be the same as the rear end surface of the ceramic housing, for example, the leading end surface of the spacer and the rear end surface of the ceramic housing may be substantially equal in area and shape, or the leading end surface of the spacer and the rear end surface of the ceramic housing may be different from each other, that is, the two may differ from each other in at least one of area and shape.

[0196] Similarly, the rear end surface of the spacer may be the same as the front end surface of the elastic body, for example, the rear end surface of the spacer and the front end surface of the elastic body may be substantially equal in area and shape, or the rear end surface of the spacer and the front end surface of the elastic body may be different from each other, that is, they may differ from each other in at least one of area and shape.

[0197] [Example] In order to verify the effects of the present invention (particularly the durability of the terminal fittings), the present inventors fabricated gas sensors according to the following levels (Examples) 1 to 4 and performed a HALT test (Highly Accelerated limit Test). However, the present invention is not limited to the following levels (Examples). [Table 1]

[0198] The gas sensor of Level 1 is a conventional gas sensor as disclosed in the above-mentioned Patent Document 1 (JP 2014-196917 A), that is, a gas sensor in which no spacer is disposed between the ceramic housing and the elastic body. Specifically, in the gas sensor of Level 1, an elastic body is disposed on the rear end side of the ceramic housing in the axial direction of the gas sensor (axial direction of the sensor element), and in particular, the elastic body is in contact with the ceramic housing at the rear end of the ceramic housing.

[0199] The gas sensors of levels 2 to 4 are gas sensors having the configuration (members) illustrated in Fig. 1, that is, gas sensors in which a spacer is disposed between a ceramic housing and an elastic body. Specifically, in the gas sensors of levels 2 to 4, a spacer is disposed on the rear end side of the ceramic housing in the axial direction, and in particular, the spacer is in contact with the ceramic housing at the rear end of the ceramic housing. However, the gas sensors of levels 2 to 4 have different Young's moduli of the spacers in contact with the ceramic housing at the rear end of the ceramic housing.

[0200] That is, in the gas sensor of level 2, the Young's modulus of the spacer is 65 GPa, that is, the spacer in contact with the ceramic housing at the rear end of the ceramic housing has a Young's modulus of less than 80 GPa. In contrast, in the gas sensors of levels 3 and 4, the Young's modulus of the spacer is 80 GPa or more, that is, the spacer in contact with the ceramic housing at the rear end of the ceramic housing has a Young's modulus of 80 GPa or more. Specifically, in the gas sensor of level 3, the Young's modulus of the spacer is 80 GPa. Also, in the gas sensor of level 4, the Young's modulus of the spacer is 120 GPa.

[0201] The present inventors conducted the following HALT test (Highly Accelerated limit Test) to compare the durability performance of the terminal fittings mounted in the ceramic housing and connected to the sensor element for the gas sensors according to each of the levels 1 to 4. That is, the HALT test in which the temperature conditions and acceleration conditions were changed in the sequence shown in Fig. 5 was conducted for the gas sensors according to each of the levels 1 to 4 (multiple gas sensors according to each level).

[0202] Fig. 5 is a graph showing the changes (sequences) in temperature and acceleration conditions in HALT tests (durability performance comparison tests) conducted by the present inventors on gas sensors according to levels 1 to 4. In the graph shown in Fig. 5, the changes in temperature conditions are indicated by dotted lines, and the temperature conditions were changed in the range of "-90°C" to "190°C" as shown in Fig. 5. In addition, in the graph shown in Fig. 5, the changes in acceleration conditions are indicated by solid lines, and the acceleration conditions were changed in the range of "10Grms" to "70Grms" as shown in Fig. 5.

[0203] The HALT test was performed on a plurality of gas sensors according to each level, and the presence or absence of damage to the terminal fittings attached to the ceramic housing was confirmed after the HALT test (for example, at time = 200, in other words, at the time when the acceleration = 40 Grms). That is, the above-mentioned HALT test was performed on a plurality of gas sensors according to level 1, and the presence or absence of damage to the terminal fittings of each of the plurality of gas sensors was confirmed after the HALT test. Similarly, the above-mentioned HALT test was performed on a plurality of gas sensors according to levels 2 to 4, and the presence or absence of damage to the terminal fittings of each of the plurality of gas sensors was confirmed after the HALT test.

[0204] In Table 1, the evaluation of "◯ (very good)" indicates that there was no damage to the terminal metal fittings attached to the ceramic housing for all of the multiple gas sensors related to each level. The evaluation of "× (poor)" indicates that damage to the terminal metal fittings was confirmed for one or more of the multiple gas sensors related to each level.

[0205] In the above-mentioned HALT test, temperature and acceleration (vibration) stresses that exceed the actual use conditions of the gas sensors are applied to the gas sensors of each level. Therefore, even if the evaluation in Table 1 is "X (poor)", it should be noted that the evaluation of "X" does not mean that the gas sensor of the level evaluated as "X" is unsuitable for actual use.

[0206] The conventional gas sensor (a gas sensor in which no spacer is placed between the ceramic housing and the elastomer) was evaluated as "x (poor)" at level 1. The gas sensor (a gas sensor in which a spacer is placed between the ceramic housing and the elastomer, but the Young's modulus of the spacer is less than 80 GPa) was evaluated as "x (poor)."

[0207] In contrast, all of the gas sensors in levels 3 and 4 (gas sensors in which a spacer is disposed between the ceramic housing and the elastic body and the spacer has a Young's modulus of 80 GPa or more) were evaluated as "Good (very good)."

[0208] Therefore, the present inventors have confirmed the following facts through the above-described HALT tests and the test results (evaluations): Namely, the present inventors have confirmed that by disposing a spacer between the ceramic housing and the elastic body and setting the Young's modulus of the spacer to 80 GPa or more, it is possible to suppress the possibility of damage to the terminal fitting attached to the ceramic housing. [Explanation of symbols]

[0209] 1, 1A, 1B... gas sensor, 10... sensor element, 11... detection unit, 12...connector electrode, 20...cylindrical body, 30...terminal metal fitting, 31...element contact portion, 50: Elastic body; 60: Ceramic housing; 70, 70A, 70B: Spacer

Claims

1. a sensor element extending in an axial direction, having a detection portion at a front end side and a connector electrode at a rear end side; a terminal fitting extending in the axial direction and having an element contact portion at a tip end thereof for electrically connecting to the connector electrode; a ceramic housing that accommodates the connector electrodes and the element contact portions; a cylindrical body having an open end and in which the sensor element, the terminal metal fitting, and the ceramic housing are disposed; an elastic body arranged to seal the open end; a spacer disposed between the ceramic housing and the elastic body in the axial direction, a tip end surface of the ceramic housing in the axial direction contacts the ceramic housing; a rear end surface of the elastic body in the axial direction contacts the elastic body; At least the Young's modulus of the tip portion including the end face on the tip side is 80 GPa or more. A spacer; Equipped with Gas sensor.

2. In the spacer, a Young's modulus of a rear end portion including an end face on the rear end side is smaller than a Young's modulus of a tip portion.

2. The gas sensor according to claim 1.

3. The contact area between the spacer and the ceramic housing is 3 mm 2 That's all.

3. The gas sensor according to claim 1.

4. an area of ​​a portion of the end face of the elastic body on the tip side that is in contact with the spacer is 25% or more of an entire area of ​​the end face of the elastic body on the tip side; 3. The gas sensor according to claim 1.

5. a distance from the position of the center of gravity of the portion of the end face of the spacer on the tip side that is in contact with the ceramic housing, which is the center of mass when the mass is virtually uniformly distributed on the portion of the end face of the spacer on the tip side that is in contact with the ceramic housing, to a straight line extending in the axial direction of the axis of the sensor element, is within 2 mm; 3. The gas sensor according to claim 1.

6. a distance from a position of a center of gravity of a portion of the end face of the tip side of the elastic body in contact with the spacer, which is a center of mass when a mass is virtually uniformly distributed on the portion of the end face of the tip side of the elastic body in contact with the spacer, to a straight line extending in the axial direction of the axis of the sensor element, is within 2 mm; 3. The gas sensor according to claim 1.

7. The material of the elastic body is fluororubber.

3. The gas sensor according to claim 1.

8. At least a portion of the spacer is made of ceramics.

3. The gas sensor according to claim 1.

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