JP4465253B2 - Gas sensor and gas sensor unit - Google Patents

Description

  The present invention relates to a gas sensor having a gas detection element made of ceramic and a gas sensor unit.

Conventionally, various gas sensors having a gas detection element made of ceramic have been proposed. Examples of these gas sensors include those that are attached to an exhaust pipe of an internal combustion engine and detect the oxygen concentration in the exhaust gas.
Japanese Patent Laying-Open No. 2001-50928 (FIG. 1) Japanese Patent Publication No. 6-60883 (FIG. 1)

  By the way, in the gas sensor of patent document 1, the ceramic surrounding body which protrudes outside from an exhaust pipe was coat | covered with the metal cylinder. This is to prevent the ceramic enclosure from getting wet and damaged by thermal shock while the vehicle is running, and to protect the ceramic enclosure. However, in such a gas sensor, since the ceramic enclosure projecting to the outside is covered with a metal cylinder, the heat dissipation of the gas sensor is not good. For this reason, there is a possibility that the resin (rubber) parts constituting the gas sensor may deteriorate early due to exhaust heat.

  On the other hand, in the gas sensor of Patent Document 2, by dividing the metal cylinder and providing a gap therebetween, it is easy to dissipate heat through the ceramic enclosure exposed from the gap portion of the metal cylinder. It prevents the rubber grommets from deteriorating. However, since the ceramic enclosure is exposed from the gap between the metal cylinders, if the ceramic enclosure may get wet while the vehicle is running, the ceramic enclosure will crack or break due to thermal shock. There was a risk of doing so. Then, there is a possibility that an abnormality or the like occurs in the output of the gas sensor from the damaged portion, and as a result, a failure occurs.

  The present invention has been made in view of the current situation, and provides a gas sensor and a gas sensor unit that are less likely to cause an abnormality in the output of the gas sensor even when exposed to water from the outside and have good heat dissipation. Objective.

  The solution includes a gas detection element whose front end is exposed to the gas to be measured, a metal shell surrounding the periphery of the gas detection element, and a cylindrical shape made of an insulating ceramic, and surrounding the rear end side of the gas detection element. And a ceramic enclosure that is held by the metal shell in a form in which the rear end side of the metal shell is protruded from the rear end of the metal shell. In some cases, the gas sensor includes an enclosure exposed portion exposed to the outside on the rear end side from the rear end of the metal shell, and a glaze layer is formed at least on the enclosure exposed portion.

  The gas sensor of the present invention has a cylindrical shape made of ceramic and has a ceramic enclosure surrounding the periphery of the rear end side of the gas detection element. The ceramic enclosure is a metal shell when the gas sensor is used. An enclosure exposed portion exposed to the outside on the rear end side from the rear end is formed, and a glaze layer is formed at least on the enclosure exposed portion. For this reason, when the enclosure exposed portion of the ceramic enclosure gets wet during traveling of the vehicle, the glaze layer is first flooded. Then, the glaze layer alleviates the thermal shock, and the shock is not easily transmitted to the enclosure exposed portion. Furthermore, by forming the glaze layer on the envelope exposed portion, the outer peripheral surface of the envelope exposed portion can be smoothed, and the stress concentration of thermal shock can be suppressed. Thereby, the danger that a ceramic enclosure will be cracked or damaged can be reduced, and the risk that an abnormality or the like will occur in the output of the gas sensor or the like can be reduced.

  The enclosure exposed portion is not limited to a form in which the entire portion of the rear end side protruding from the rear end of the metal shell is exposed to the outside of the ceramic enclosure, but from the rear end of the metal shell of the ceramic enclosure. There is also a form in which a part of the protruding portion is exposed to the outside. As the latter form, for example, when covering the rear end portion of the ceramic enclosure with a resin cap to prevent water from entering the ceramic enclosure, the portion on the rear end side protruding from the rear end of the metal shell The form which exposes the part which is not closely_contact | adhered to the resin cap outside among these is mentioned.

  In addition, when the gas detection element is a gas sensor that is heated (exposed to high temperature) when used, the heat of the gas detection element and the metal shell is transferred to the ceramic enclosure and dissipated to the outside through the enclosure exposure part. Therefore, heat dissipation can be improved.

  Moreover, the glaze used for the glaze layer is also called an upper glaze, and is a glassy material applied to the surface of the ceramic enclosure in order to increase the mechanical strength of the ceramic enclosure. Specific examples include borosilicate glass and alkali borosilicate glass.

  Furthermore, the gas sensor may be a gas sensor in which the glaze layer has a surface roughness Ra of 0.4 μm or less.

  According to the gas sensor of the present invention, by setting the surface roughness Ra of the glaze layer to 0.4 μm or less, the surface of the glaze layer is further smoothed, and when a thermal shock is applied to the glaze layer, cracks, penetrations, etc. Can effectively reduce the risk of occurrence. In the present invention, the surface roughness Ra is the arithmetic average roughness Ra, and the value of the arithmetic average roughness Ra is defined in JIS: B0601 (1994) 3 “Definition of defined arithmetic average roughness and It is represented by “indication”.

  In order to effectively smooth the glaze layer, it is preferable that the surface roughness Ra of the envelope exposed portion (ceramic enclosure) as a base is 1.2 μm or less (preferably 1.0 μm), If the film thickness of the glaze layer is within a range of 15 μm to 100 μm with respect to such a base, the surface roughness Ra of the glaze layer can be formed to 0.4 μm or less. Furthermore, if it is in such a film thickness range, the assembling property with respect to the metal shell and the like becomes good.

  By the way, the ceramic enclosure is provided with a large diameter portion having a taper surface facing the rear end, and the rear end of the metal shell is caulked against the taper surface facing the rear end through the packing, so that the ceramic envelope is enclosed. The body may be held on the metal shell. At this time, cracks may occur in the ceramic enclosure due to the stress applied by the packing on the taper surface facing the rear end of the ceramic enclosure. Therefore, in the ceramic enclosure having such a large diameter part, the glaze layer is formed not only on the enclosure exposed part but also on the tapered surface facing the rear end, thereby increasing the strength of the ceramic enclosure and preventing the occurrence of cracks. can do.

  On the other hand, when the glaze layer is simply formed from the exposed portion of the enclosure to the taper surface facing the rear end, the boundary between the taper surface facing the rear end of the ceramic envelope and the outer surface extending to the rear end (hereinafter referred to as the boundary of the ceramic envelope) In other words, since the glaze at the time of molding tends to accumulate, a thicker glaze layer is easily formed than other portions. As a result, depending on the surface shape of the glaze layer, the stress due to the packing toward the ceramic enclosure is applied in the radial direction rather than the axial direction, and the ceramic enclosure is likely to crack. Therefore, in the present invention, the surface shape of the glaze layer at the boundary between the taper surface facing the rear end and the outer peripheral surface of the ceramic enclosure extending to the rear end side is provided with a recess having a radius of curvature of 1.5 mm or less. The metal shell is engaged through the packing. Thereby, the stress to the radial direction by the packing which goes to a ceramic enclosure can be reduced, and generation | occurrence | production of the crack of a ceramic enclosure can be suppressed. Note that if the radius of curvature exceeds 1.5 mm, the above-described effects cannot be sufficiently exhibited.

  Another solution is a gas detection element whose front end is exposed to the gas to be measured, a metal shell surrounding the periphery of the gas detection element, and a cylindrical shape made of an insulating ceramic, surrounding the periphery of the rear end of the gas detection element. From the gas detection element connected to the ceramic enclosure held by the metal shell in a form in which the rear end side of the metal metal body protrudes from the rear end of the metal metal fitting, and the inner electrode formed on the inner peripheral surface of the gas detection element A gas sensor having a terminal member that outputs an output signal of the gas sensor, a cylindrical cap terminal that is connected to the terminal member of the gas sensor and transmits the output signal to an external device, and the cap terminal and the ceramic enclosure A gas sensor unit that covers the rear end side and has an insulating part made of an insulating elastic body, wherein the ceramic enclosure includes the above A gas sensor unit having an envelope exposed portion exposed to the outside between the insulating portion of the sensor cap and the metal shell, wherein a glaze layer is formed at least on the envelope exposed portion It is.

  In general, since the insulating part of the gas sensor cap is made of resin (rubber) parts, when it comes in contact with the metal shell of the gas sensor, the heat of the gas detection element and the metal shell is directly transferred to the insulating part, and the insulating part is quickly There was a risk of deterioration. Therefore, in the gas sensor unit of the present invention, the ceramic enclosure between the insulating portion of the gas sensor cap and the metal shell is exposed to the outside. In other words, by providing a gap between the gas sensor metal shell and the gas sensor cap insulation, and making the gas sensor metal shell and the gas sensor cap insulation non-contact, the heat of the gas detection element and metal shell is reduced. Direct transmission to the insulation is suppressed.

  Furthermore, in the gas sensor unit of the present invention, the insulating portion of the gas sensor cap covers the rear end side of the ceramic enclosure, and the ceramic enclosure is externally disposed between the insulating portion of the gas sensor cap and the metal shell. An enclosure exposed portion that is exposed to is provided. For this reason, when the gas detection element is a gas sensor that is heated (exposed to a high temperature) when used, the heat of the gas detection element and the metal shell is transferred to the ceramic enclosure and is exposed to the outside through the enclosure exposure part. Since it is dissipated, heat dissipation can be improved.

  And according to the gas sensor of this invention, the glaze layer is formed in the enclosure exposure part. For this reason, when the enclosure exposed portion gets wet during traveling of the vehicle, the glaze layer is first wetted. Then, since the glaze layer relieves the thermal shock and it is difficult for the impact to be transmitted to the exposed part of the enclosure, it is possible to reduce the risk of the ceramic enclosure being cracked or broken. Accordingly, it is possible to reduce the risk of an abnormality or failure in the output of the gas sensor.

  Furthermore, according to the gas sensor of the present invention, the outer peripheral surface on the rear end side from the rear end of the metal shell in the ceramic enclosure forms a glaze layer, and the insulating portion is fitted into the ceramic enclosure in which this glaze layer is formed. I try to do it. For this reason, the inner peripheral surface of the gas sensor cap is fitted to the outer peripheral surface of the ceramic enclosure smoothed by the glaze layer, the adhesion between the gas sensor cap and the ceramic enclosure is improved, and improvement in waterproofness can be expected. .

  Further, the gas sensor unit may be a gas sensor unit in which the surface roughness Ra of the glaze layer is 0.4 μm or less.

  According to the gas sensor of the present invention, by setting the surface roughness Ra of the glaze layer to 0.4 μm or less, the surface of the glaze layer is further smoothed, and when a thermal shock is applied to the glaze layer, cracks, penetrations, etc. Can effectively reduce the risk of occurrence. In the present invention, the surface roughness Ra is the arithmetic average roughness Ra, and the value of the arithmetic average roughness Ra is defined in JIS: B0601 (1994) 3 “Definition of defined arithmetic average roughness and It is represented by “indication”.

  In order to effectively smooth the glaze layer, it is preferable that the surface roughness Ra of the envelope exposed portion (ceramic enclosure) as a base is 1.2 μm or less (preferably 1.0 μm), If the film thickness of the glaze layer is within a range of 15 μm to 100 μm with respect to such a base, the surface roughness Ra of the glaze layer can be formed to 0.4 μm or less. Furthermore, if it is in such a film thickness range, the assembling property with respect to the metal shell and the like will be good.

  By the way, the ceramic enclosure is provided with a large diameter portion having a taper surface facing the rear end, and the rear end of the metal shell is caulked against the taper surface facing the rear end through the packing, so that the ceramic envelope is enclosed. The body may be held on the metal shell. At this time, cracks may occur in the ceramic enclosure due to the stress applied by the packing on the taper surface facing the rear end of the ceramic enclosure. Therefore, in the ceramic enclosure having such a large diameter portion, the glaze layer is formed not only from the rear end of the metal shell in the ceramic enclosure but also to the outer peripheral surface of the rear end as well as the taper surface facing the rear end. The strength of the body is increased and the occurrence of cracks can be prevented.

  On the other hand, when the glaze layer is simply formed from the rear end side outer peripheral surface to the rear end tapered surface from the rear end of the metal shell in the ceramic enclosure, the ceramic envelope extends to the rear end tapered surface and the rear end side. At the boundary with the surface (hereinafter also referred to as the boundary of the ceramic enclosure), the glaze at the time of molding tends to accumulate, so that a thicker glaze layer is likely to be formed than other parts. As a result, depending on the surface shape of the glaze layer, the stress due to the packing toward the ceramic enclosure is applied in the radial direction rather than the axial direction, and the ceramic enclosure is likely to crack. Therefore, in the present invention, the surface shape of the glaze layer at the boundary between the taper surface facing the rear end and the outer peripheral surface of the ceramic enclosure extending to the rear end side is provided with a recess having a radius of curvature of 1.5 mm or less. The metal shell is engaged through the packing. Thereby, the stress to the radial direction by the packing which goes to a ceramic enclosure can be reduced, and generation | occurrence | production of the crack of a ceramic enclosure can be suppressed. Note that if the radius of curvature exceeds 1.5 mm, the above-described effects cannot be sufficiently exhibited.

Further, another solution is a gas detection element that extends in the axial direction and whose tip side is exposed to the gas to be measured, a metal shell that surrounds the periphery of the gas detection element, and a cylinder made of an insulating ceramic. A ceramic sensor that surrounds the periphery of the rear end side of the detection element and is held by the metal shell in a form in which the rear end side of the detection element protrudes from the rear end of the metal shell,
Production of a gas sensor in which a glaze material layer is formed on the outer peripheral surface of the ceramic enclosure by spraying the glaze material on the outer peripheral surface of the ceramic enclosure, and the glaze layer is formed by calcination of the glaze material layer Is the method.

  The gas sensor of the present invention has a ceramic envelope that surrounds the periphery of the rear end side of the gas detection element in a cylindrical shape made of ceramic, and sprays glaze on the outer peripheral surface of the ceramic envelope. The glaze material layer is formed on the outer peripheral surface of the ceramic enclosure. Thereby, the outer peripheral surface of the ceramic enclosure can be smoothed, and the concentration of thermal shock stress due to water can be suppressed in the enclosure exposed part exposed to the outside when the gas sensor is used. . Therefore, it is possible to reduce the risk that the ceramic enclosure will be cracked or broken, and to reduce the risk that the output of the gas sensor will become abnormal or break down.

  In addition, by spraying the glaze on the outer peripheral surface of the ceramic enclosure, and forming a glaze material layer on the outer peripheral surface of the ceramic enclosure, the surface shape of the glaze layer at the boundary of the ceramic enclosure has a radius of curvature. A recess that is 1.5 mm or less can be formed. Therefore, the stress in the radial direction of the packing toward the ceramic enclosure can be reduced, and the occurrence of cracks in the ceramic enclosure can be suppressed.

(Embodiment 1)
A first embodiment of the present invention will be described with reference to the drawings.
FIG. 1A is a cross-sectional view of the gas sensor 100 of the first embodiment, and FIG. 1B is a partially enlarged view of the gas sensor 100. The gas sensor 100 includes a gas detection element 120, an outer electrode 111, an inner electrode 112, a ceramic enclosure 130, a terminal member 150, and a casing 160.

  The casing 160 has a metal shell 161 and a protector 162. The metal shell 161 is made of SUS430 and is formed in a substantially cylindrical shape. The metal shell 161 includes an inner periphery receiving portion 161e for supporting a flange portion 120e of the gas detection element 120, which will be described later, and a tapered inner periphery receiving portion 161e whose diameter increases toward the rear end side. It is provided in a form that protrudes radially inward from the inner peripheral surface. Further, a screw part 161b for attaching the gas sensor 100 to the exhaust pipe 10 (see FIG. 3) is formed outside the metal shell 161, and a screw part 161b is provided on the rear end side of the screw part 161b. A hexagonal portion 161d is provided around the mounting tool for screwing into the exhaust pipe. The protector 162 is a metal, substantially cylindrical cylinder, and has a vent hole 162 b for introducing exhaust gas in the exhaust pipe 10 into the gas sensor 100.

The gas detection element 120 is made of a solid electrolyte having oxygen ion conductivity, and has a substantially cylindrical shape extending in the direction of the axis C with the front end 120b closed. On the outer periphery of the gas detection element 120, a flange portion 120e protruding outward in the radial direction is provided, and a metal is formed between the front end surface of the flange portion 120e and the surface of the inner periphery receiving portion 161e of the metal shell 161. The gas detection element 120 is disposed in the metal shell 161 with the made packing 142 interposed. As the solid electrolyte constituting the gas detection element 120, for example, ZrO2 in which Y2O3 or CaO is dissolved is representative, but other alkaline earth metal or rare earth metal oxides and ZrO2 are used. A solid solution may be used. Furthermore, HfO2 may be contained therein.
In the present embodiment, the front end 120b side of the gas detection element 120 in the axis C direction is described as the front end side, and the opposite side is described as the rear end side. The same applies to other forms.

  The outer electrode 111 is made of porous Pt or Pt alloy, and is provided so as to cover the outer surface 120 c of the tip 120 b of the gas detection element 120. The outer electrode 111 is provided up to the distal end surface of the flange portion 120e, and is electrically connected to the metal shell 161 via the packing 142. The inner electrode 112 is also formed by porous Pt or a Pt alloy, and is provided so as to cover the inner side surface 120d of the gas detection element 120.

  The ceramic enclosure 130 is made of an insulating ceramic (specifically, alumina) and has a substantially cylindrical shape. The ceramic enclosure 130 has a large-diameter portion 133 that protrudes radially outward on the front end side, and a small-diameter portion 134 that is located on the rear end side of the large-diameter portion 133. A rear end-facing tapered surface 135 facing the rear end side in the axis C direction is formed between the portion 134. In this embodiment, the small-diameter portion 134 is formed with a thickness of 1 to 1.4 mm. The large-diameter portion 133 of the ceramic enclosure 130 surrounds the periphery of the rear end side of the gas detection element 120, together with the ceramic powder 141 and the ring packing 143 formed from talc, and the gas detection element 120 and the metal shell 161. Is intervening between. A caulking ring 144 is disposed on the rear end side of the taper surface 135 facing the rear end, and the caulking portion 144c located at the steel end of the metal shell 161 is caulked inward, so that the caulking ring 144 surrounds the ceramic. The ceramic enclosure 130 is held by the metal shell 161 by being pressed toward the tapered surface 135 toward the rear end of the body 130.

  The ceramic envelope 130 is made of an insulating ceramic powder such as alumina in a predetermined ratio, and is molded by known press molding or extrusion molding to form a molded body that is the original shape of the ceramic envelope 130. . In some cases, the molded body may be cut in a cutting process. And the ceramic enclosure 130 is produced by baking this. Note that the surface roughness Ra of the ceramic enclosure 130 of the present embodiment is 0.8 μm.

  The ceramic enclosure 130 has an enclosure exposed portion 131 on the rear end side from the rear end of the metal shell 161. The enclosure exposed portion 131 is exposed to the outside when the gas sensor is used (see FIG. 3). Further, a glaze layer 132 is formed from the outer peripheral surface of the ceramic enclosure 130 to the rear end-facing tapered surface 135 to the rear end of the ceramic enclosure 130. This glaze layer 132 is, for example, SiO2: 77.5 wt%, Al2O3: 12.1 wt%, MgO: 3.4 wt%, K2O: 5.4 wt%, Na2O: 1.4 wt%, CaO: 0.1 wt%, The glaze which Fe2O3: 0.1wt% contains is used. And the surface roughness Ra of the glaze layer 132 is 0.4 μm. Moreover, the film thickness of the glaze layer 132 is 20 μm.

  Then, as shown in FIG. 1B, a recess 137 is formed at a boundary 136 between the taper surface 135 facing the rear end of the ceramic enclosure 130 and the outer peripheral surface of the ceramic enclosure 130 on the rear end side. In this embodiment, the curvature radius r of the surface shape of the recess is 1 mm. As described above, since the surface shape of the concave portion has a curvature radius of 1.5 mm or less, the radial stress due to the caulking packing 144 toward the ceramic enclosure 130 can be reduced, and cracks in the ceramic enclosure 130 can be reduced. Occurrence can be suppressed.

The glaze layer 132 is formed as follows.
First, a ceramic enclosure 130 having a predetermined shape is formed. And in this embodiment, the method of spraying the glaze slurry which melt | dissolved the said component in water or a solvent on the surface of the ceramic enclosure 130 from a spray nozzle is applied to the surface of the ceramic enclosure 130. FIG. By using this method, the glazed layer 132 after firing can smooth the outer peripheral surface of the ceramic enclosure, and when the gas sensor 100 is used, the enclosure exposed portion 131 exposed to the outside is covered with water. It is possible to suppress the concentration of stress due to thermal shock. Further, by using the above method, it is possible to prevent excess glaze from accumulating at the boundary 136 of the ceramic enclosure 130. As a result, the surface shape of the glaze layer 132 can be 1.5 mm or less (1 mm in this embodiment), and a recess 137 having a radius of curvature r can be formed. The diameter of the caulking packing 144 toward the ceramic enclosure 130 can be formed. Directional stress can be reduced. In addition to the above method, the ceramic enclosure 130 may be immersed in a water tank containing the glaze slurry, or the ceramic enclosure 130 while the ceramic enclosure 130 is in contact with the rotating body coated with the glaze slurry. Although there is a method of rotating the body 130 and the rotating body in the opposite directions, a better effect can be obtained by using the above method. Thereafter, the glaze layer 132 is formed by firing the ceramic enclosure 130.

  The terminal member 150 is made of, for example, Inconel 718 (English Inconel, trade name), has a substantially cylindrical shape, and includes an output terminal portion 151, an element-side terminal portion 153, and a connecting portion 152 that connects the two. Among these, the output-side terminal portion 151 has a substantially C-shaped cross section perpendicular to the axial direction, and the cap terminal 211 (see FIG. 2) of the cap terminal member 210 is inserted and connected to itself. In addition, it is configured to elastically expand its diameter. Furthermore, convex portions 151b projecting radially inward are formed at three locations in the circumferential direction on the rear end side.

  Further, in the output side terminal portion 151, at three locations in the circumferential direction corresponding to the convex portion 151b, there are an inner bent portion 151c punched out of the wall surface and bent radially inward, and an outer bent bent outward in the radial direction. A portion 151d is formed. Among these, the inner bent portion 151c is formed to be elastically bent radially outward when the cap terminal 211 (see FIG. 3) of the cap terminal member 210 is inserted and connected to the inner side of the output side terminal portion 151. Has been. Further, as shown in FIG. 1, the outer bent portion 151 d abuts on the front end surface of the stepped portion 130 b of the ceramic enclosure 130 and plays a role of preventing the output side terminal portion 151 from coming off.

  The element side terminal portion 153 has a cylindrical shape with a substantially C-shaped cross section orthogonal to the axial direction. As shown in FIG. 1, the element side terminal portion 153 is inserted into the gas detection element 120 while being elastically reduced in diameter, and is electrically connected to the inner electrode 112. Therefore, in the gas sensor 100, the element side terminal portion 153 is electrically connected while pressing the inner electrode 112 from the inner side toward the outer side in the radial direction.

Such a gas sensor 100 is manufactured as follows.
First, as shown in FIG. 1, a casing 160 in which a metal shell 161 and a protector 162 are integrated is prepared. Next, the gas detection element 120 provided with the outer electrode 111 and the inner electrode 112 is inserted into the casing 160 together with the packing 142. Next, a ring packing 143 is disposed on the rear end side of the flange 120e of the gas detection element 120, and a predetermined amount of ceramic powder 141 is filled in the gap between the metal shell 161 and the gas detection element 120. Next, the ceramic enclosure 130 is inserted so as to be interposed between the gas detection element 120 and the metal shell 161, and the tip surface is brought into contact with the ceramic powder 141. Next, the ceramic enclosure 130 is pressurized toward the front end side, and under the pressurized state, the rear end side of the metal shell 161 is swaged to form a swaged portion 161c, whereby the swaged portion of the metal shell 161 is formed. A caulking ring 144 is interposed between 161c and the ceramic enclosure 130, and the above components are fixed together.

Finally, the terminal member 150 is inserted inside the ceramic enclosure 130 and the gas detection element 120. Specifically, the element side terminal portion 153 is inserted into the gas detection element 120 while elastically reducing the diameter, and is electrically connected to the inner electrode 112. At the same time, the outer side bent portion 151 d is brought into contact with the front end surface of the stepped portion 130 b of the ceramic enclosure 130 while the output side terminal portion 151 is arranged inside the ceramic enclosure 130. Note that a gap is provided between the inner peripheral surface 130 c of the ceramic enclosure 130 and the outer peripheral surface 151 e of the output-side terminal portion 151.
In this way, the gas sensor 100 is completed.

  Next, FIG. 4 shows a state when the gas sensor unit 300 including the gas sensor 100 and the gas sensor cap 200 according to the first embodiment is used. This gas sensor unit 300 can be used, for example, to detect the oxygen concentration in the exhaust gas of an internal combustion engine.

First, the gas sensor cap 200 will be described with reference to the drawings. FIG. 2 is a partial cross-sectional view of the gas sensor cap 200. The gas sensor cap 200 includes a cap terminal member 210, an insulating portion 220 that covers the cap terminal member 210, and a lead wire 230.
The cap terminal member 210 is made of, for example, SUS310S, and includes a substantially cylindrical cap terminal 211 and a caulking portion 213 for caulking and connecting the lead wire 230. Among these, the cap terminal 211 has rigidity to expand the diameter of the output side terminal portion 151 without being deformed when inserted into the output side terminal portion 151 of the gas sensor 100 and connected thereto. The outer dimension of the cap terminal 211 is F.

One end of the lead wire 230 is crimped by a crimping portion 213 of the cap terminal member 210 and is electrically connected to the cap terminal 211. Therefore, an output signal from the gas detection element 120 of the gas sensor 100 can be transmitted to an external device (for example, an engine control unit (hereinafter also referred to as ECU)) through the lead wire 230.
The insulating part 220 is formed into a hollow shape using a fluorine-based rubber, and the insulating part 220 has a close contact part 221. Furthermore, the insulating part 220 is set to have a shorter axial length than the ceramic enclosure 130 of the gas sensor 100, and the gas sensor formed on the front side of the contact part 221 when the gas sensor cap 200 is assembled to the gas sensor 100. 100 enclosure exposed portions 131 are exposed to the outside.

  The gas sensor cap 200 is configured in such a manner that a cap terminal member 210 is disposed coaxially with the contact portion 221 in the insulating portion 220 and a lead wire 230 connected to the cap terminal member 210 extends from the insertion port 223 to the outside. ing.

  Next, the gas sensor unit 300 will be specifically described with reference to FIG. First, the gas sensor 100 is screwed into the exhaust pipe 10 such that the front end side including the protector 162 is located in the exhaust pipe 10 and the rear end side portion of the metal shell 161 is exposed to the outside. At this time, the outer electrode 111 electrically connected to the metallic shell 161 is grounded through the metallic shell 161. Next, the gas sensor cap 200 is attached to the gas sensor 100 such that the cap terminal 211 of the gas sensor cap 200 is inserted into the output side terminal portion 151 of the gas sensor 100.

At this time, since the inner diameter E of the output side terminal portion 151 is smaller than the outer diameter F of the cap terminal 211, the output side terminal portion 151 receives a force radially outward from the cap terminal 211 at the convex portion 151b. The output side terminal portion 151 is elastically expanded.
Therefore, the output side terminal portion 151 is electrically connected while pressing the cap terminal 211 radially inward. For this reason, the connection between the output-side terminal portion 151 and the cap terminal 211 is momentarily interrupted due to the influence of vibrations of the vehicle or the like, and the risk of generating noise or the like (the risk of a decrease in gas detection accuracy) can be reduced. .

  Furthermore, since the diameter of the output side terminal portion 151 is increased, the gap between the outer peripheral surface 151e of the output side terminal portion 151 and the inner peripheral surface 130c of the ceramic enclosure 130 becomes smaller than before insertion. Specifically, since the output-side terminal portion 151 in a state where the output-side terminal portion 151 is surrounded by the ceramic enclosure 130 is less likely to swing in the radial direction, fatigue in the connecting portion 152 of the terminal member 150 due to the influence of vibration. Destruction (cracking, breakage, etc.) can be suppressed.

  Further, the gas sensor cap 200 is attached to the gas sensor 100 so that the enclosure exposed portion 131 of the ceramic enclosure 130 is exposed. For this reason, when the gas detection element 120 is heated (exposed to a high temperature) when used, the heat of the gas detection element 120 and the metal shell 161 is transmitted to the ceramic enclosure 130, and the enclosure Since it is dissipated outside through the exposed part 131, heat dissipation can be made favorable.

  Further, a glaze layer 132 is formed on the enclosure exposed portion 131 (ceramic enclosure 130). For this reason, when the enclosure exposed portion 131 of the ceramic enclosure 130 gets wet during traveling of the vehicle, the glaze layer 132 relaxes and absorbs the thermal shock, and it is difficult for the impact to be transmitted to the enclosure exposed portion 131. It is possible to reduce the risk that the enclosure 130 is cracked or has a through hole. Therefore, it is possible to reduce the risk of an abnormality or failure in the output of the gas sensor 100 or the like.

Furthermore, the annular contact portion 221 made of rubber can be in close contact over the circumferential direction (360 degrees) of the outer peripheral surface 130d of the ceramic envelope 130 on which the glaze layer 132 is formed. Thereby, it is possible to prevent water from entering between the gas sensor 100 and the gas sensor cap 200 into the gas sensor unit 300.
In the gas sensor unit 300, since the insulating part 220 is formed of fluorine-based rubber, the heat resistance of the insulating part 220 is improved and the adhesiveness with the ceramic enclosure 130 is further improved.

  Further, in such a gas sensor unit 300, a reference gas (outside air) is taken into the insulating part 220 from the outside via the lead wire 230 of the gas sensor cap 200, and further, this reference gas is taken into the terminal member 150 (air passage T1). Can be taken into the gas detection element 120 (inside the cylinder).

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to the drawings.
4A is a cross-sectional view of the gas sensor 400 of the second embodiment, and FIG. 1B is a partially enlarged view of the gas sensor 100. FIG. The gas sensor 400 according to the second embodiment is different from the gas sensor 100 according to the first embodiment in the shape of the terminal member and the ceramic enclosure, and the other parts are the same.

The gas sensor 400 includes the same gas detection element 120, outer electrode 111, inner electrode 112, casing 160 as the gas sensor 100 of the first embodiment, and a ceramic enclosure 430 and a terminal member 450 that are different from the gas sensor 100 of the first embodiment.
Among these, the ceramic enclosure 430 is made of an insulating ceramic and has a substantially cylindrical shape, similar to the ceramic enclosure 130 of the first embodiment, but compared to the ceramic enclosure 130 of the first embodiment, The axial length is shortened. The glaze layer 132 is formed from the rear end-oriented taper surface 435 formed in the large diameter portion 433 to the rear end of the ceramic enclosure 430 in the outer peripheral surface of the ceramic enclosure 430 as in the first embodiment. .

  As shown in FIG. 4B, a recess 437 is formed at a boundary 436 between the taper surface 435 facing the rear end of the ceramic enclosure 430 and the outer peripheral surface of the ceramic enclosure 430 on the rear end side. In this embodiment, the curvature radius r of the surface shape of the recess is 1 mm. Thus, since the surface shape of the recess has a radius of curvature of 1.5 mm or less, the radial stress due to the caulking packing 144 toward the ceramic enclosure 430 can be reduced, and the occurrence of cracks in the ceramic enclosure 430 is generated. Can be suppressed.

As shown in FIG. 6, the terminal member 450 has a substantially cylindrical shape, and includes an output-side terminal portion 451, an element-side terminal portion 453, and a connecting portion 452 that connects the two.
Among these, the output side terminal portion 451 has a substantially C-shaped cross section orthogonal to the axial direction, and is inserted and connected to the inside of the cap terminal 511 (see FIG. 7) of the cap terminal member 510. It is configured to elastically reduce the diameter.

Furthermore, convex portions 451b protruding outward in the radial direction are formed at three locations in the circumferential direction of the central portion in the axial direction. The convex portion 451 b abuts on the rear end surface 430 f of the ceramic enclosure 430 and plays a role of preventing the output side terminal portion 451 from entering the ceramic enclosure 430. (See FIG. 4).
Further, an outer bent portion 451d that is punched and bent radially outward is formed on the distal end side of the output side terminal portion 451. The outer bent portion 451d abuts on the front end surface 430d of the step portion 430b of the ceramic enclosure 430 and plays a role in preventing the output side terminal portion 451 from coming off. (See FIG. 4).

  The element-side terminal portion 453 has a cylindrical shape having a substantially C-shaped cross section orthogonal to the axial direction. As shown in FIG. 5, it is inserted into the gas detection element 120 while being elastically reduced in diameter, and is electrically connected to the inner electrode 112. Therefore, in the gas sensor 400, the element side terminal portion 453 electrically connects the inner electrode 112 while pressing the inner electrode 112 from the inner side toward the outer side in the radial direction. For this reason, due to the influence of vibration or the like, the connection between the two is interrupted and the risk of generating noise can be reduced.

  Next, FIG. 6 shows a state when the gas sensor unit 600 including the gas sensor 400 and the gas sensor cap 500 according to the second embodiment is used. The gas sensor unit 600 can be used to detect the oxygen concentration in the exhaust gas of the internal combustion engine, for example, as in the first embodiment.

First, the gas sensor cap 500 will be described with reference to the drawings. FIG. 5 is a partial cross-sectional view of the gas sensor cap 500. The gas sensor cap 500 includes a cap terminal member 510, an insulating portion 520 that covers the cap terminal member 510, and a lead wire 230.
The cap terminal 510 includes a bottomed cylindrical cap terminal 511 having a substantially U-shaped cross section, and a crimping portion 513 for crimping and connecting the lead wire 230.

  Among these, the cap terminal 511 has rigidity to reduce the diameter of the output side terminal portion 451 without deforming itself when the output side terminal portion 451 of the gas sensor 400 is inserted and connected to the inside. Yes. Note that the cap terminal 511 has convex portions 511b protruding radially inward at three locations in the circumferential direction of the central portion in the axial direction. Here, the diameter H of the virtual circle in contact with the three convex portions 511b is defined as the inner diameter of the cap terminal 511 (see FIG. 5).

As in the first embodiment, one end of the lead wire 230 is crimped by a crimping portion 513 of the cap terminal member 510 and is electrically connected to the cap terminal 511. For this reason, output signals from the gas sensor 400 and the gas detection element 120 can be transmitted to an external device (for example, ECU) through the lead wire 230.
The insulating portion 520 is formed into a hollow shape using a fluorine-based rubber, and the insulating portion 520 has a close contact portion 521.

  Next, the gas sensor unit 300 will be specifically described. Specifically, the gas sensor 400 is attached to the exhaust pipe 10 as in the first embodiment. Next, the gas sensor cap 500 is attached to the gas sensor 400 such that the output-side terminal portion 451 of the gas sensor 400 is inserted inside the cap terminal 511 of the gas sensor cap 500.

At this time, since the outer diameter G of the output side terminal portion 451 is larger than the inner diameter H of the cap terminal 511, the output side terminal portion 451 receives a force radially inward from the convex portion 511b of the cap terminal 511, The output side terminal portion 451 is elastically reduced in diameter.
Therefore, the output-side terminal portion 451 is electrically connected while pressing the cap terminal 511 radially outward. For this reason, due to the influence of vibrations of the vehicle or the like, the risk that the connection between the output side terminal portion 451 and the cap terminal 511 instantly generates noise (risk of gas detection accuracy reduction) can be reduced.

  Further, the gas sensor cap 500 is attached to the gas sensor 400 so that the enclosure exposed portion 431 of the ceramic enclosure 430 is exposed between the close contact portion 521 of the gas sensor cap 500 and the metal shell 161. For this reason, when the gas sensor 400 is heated (exposed to high temperature) when it is used, (for example, when it is attached to an exhaust pipe of an internal combustion engine to detect the oxygen concentration in the exhaust gas). Since the heat of the gas detection element 120 and the metal shell 161 is transmitted to the ceramic enclosure 130 and dissipated to the outside through the enclosure exposed portion 431, the heat dissipation can be improved.

  Furthermore, the glaze layer 132 is formed in the enclosure exposed part 431 (ceramic enclosure 430). For this reason, when the enclosure exposed portion 431 of the ceramic enclosure 430 is wetted while the vehicle is traveling, the glaze layer 132 relaxes and absorbs the thermal shock, and the impact is not easily transmitted to the enclosure exposed portion 431. It is possible to reduce the risk that the enclosure 430 is cracked or has a through hole. Accordingly, it is possible to reduce the risk of an abnormality or failure in the output of the gas sensor 400.

  Furthermore, the annular contact portion 521 made of rubber can be in close contact over the circumferential direction (360 degrees) of the outer peripheral surface 130d of the ceramic envelope 430 where the glaze layer 132 is formed. Thereby, it is possible to prevent water from entering between the gas sensor 400 and the gas sensor cap 500 into the gas sensor unit 130.

  Also in such a gas sensor unit 600, similarly to the gas sensor unit 300 of the first embodiment, the reference gas (outside air) is taken into the insulating portion 520 from the outside through the lead wire 230 of the gas sensor cap 500, and further, this reference gas Can be taken into the inside (cylinder) of the gas detection element 120 through the terminal member 450 (air passage T2).

In order to confirm the effect of the present invention, the following experiment was conducted.
Various test products of the gas sensor 100 having the shape shown in FIG. 1 were prepared as follows. Note that alumina ceramic was used as the material of the ceramic enclosure 130. Further, the gas sensor 100 in which the glaze layer 132 is not formed on the outer surface of the ceramic enclosure 130, the gas sensor 100 in which the glaze layer 132 having a film thickness of 10 μm is formed on the outer surface of the ceramic enclosure 130, and the ceramic enclosure 130 Ten gas sensors 100 each having a glaze layer 132 having a thickness of 20 μm formed on the outer surface were prepared.

  First, the surface roughness Ra of the ceramic enclosure 130 of the gas sensor 100 was measured. The measuring method is based on JISB: 0601 shown above. When the glaze layer 132 is not formed on the surface of the ceramic enclosure 130, the surface roughness Ra of the ceramic enclosure 130 is 1 μm, and the glaze layer 132 having a thickness of 10 μm is formed on the surface of the ceramic enclosure 130. In this case, when the surface roughness Ra of the ceramic enclosure 130 is 0.5 μm and the glaze layer 132 having a film thickness of 20 μm is formed on the surface of the ceramic enclosure 130, the surface roughness Ra of the ceramic enclosure 130 is 0.15 μm. It became.

  Then, the screw part 161b of the gas sensor 100 is screwed into a screw part provided at the bottom of the water tank, and the ceramic enclosure 130 is disposed completely within the water tank. Then, while measuring the temperature of the hexagonal portion 161d of the gas sensor 100, a portion (for example, the protector 162 or the metal shell 161) protruding from the water tank of the gas sensor is heated using a burner. Thereafter, when the temperature of the hexagonal portion 161d reaches 400 ° C., water is poured so that the ceramic enclosure 130 is completely submerged in the water tank. Then, the ceramic enclosure 130 was submerged for 1 minute and then drained. This was defined as one cycle, and this was repeated 10 cycles, and it was visually confirmed whether or not the subsequent ceramic enclosure 130 was cracked.

The gas sensor 100 in which the glaze layer 132 was not formed on the surface of the ceramic enclosure 130 was cracked in all ten. In the gas sensor 100 in which the glaze layer 132 having a film thickness of 10 μm was formed on the surface of the ceramic enclosure 130, two out of ten gas sensors had cracks. In the gas sensor 100 in which the glaze layer 132 having a film thickness of 20 μm was formed on the surface of the ceramic enclosure 130, no cracks were generated in all 10 pieces.
Thus, by providing the glaze layer 132 on the ceramic enclosure 130, the ceramic enclosure 130 is less likely to crack. Furthermore, by setting the surface roughness Ra of the ceramic enclosure 130 to 0.15 μm, cracks and the like are less likely to occur in the ceramic enclosure 130.

In the above, the present invention has been described with reference to the first and second embodiments. However, the present invention is not limited to the above-described examples, and it can be applied as appropriate without departing from the scope of the present invention. Nor.
For example, in the gas sensors 100 and 400 of the first and second embodiments, the glaze layer 132 is provided on the rear end side from the rear end of the metal shell 161 of the ceramic enclosures 130 and 430, but is not limited thereto. For example, the glaze layer 132 may be provided only on the enclosure exposed portions 131 and 431.

1 is a partial cross-sectional view of a gas sensor 100 according to a first embodiment. 1 is a partial cross-sectional view of a gas sensor cap 200 according to a first embodiment. Explanatory drawing which shows a mode when the gas sensor unit 300 concerning Embodiment 1 is used. The fragmentary sectional view of the gas sensor 400 concerning Embodiment 2. FIG. The fragmentary sectional view of the gas sensor cap 500 concerning Embodiment 2. FIG. Explanatory drawing which shows a mode when the gas sensor unit 600 concerning Embodiment 2 is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,400 Gas sensor 112 Inner electrode 120 Gas detection element 130,430 Ceramic enclosure 131,431 Enclosure exposed part 132 Glaze layer 150,450 Terminal member 151,451 Output side terminal part 153,453 Element side terminal part 200,500 Gas sensor Cap 210, 510 Cap terminal member 211, 511 Cap terminal (external terminal)
220, 520 Insulating part 221, 521 Adhering part 230 Lead wire 300, 600 Gas sensor unit

Claims (12)

A gas detection element extending in the axial direction and having the tip side exposed to the gas to be measured;
A metal shell surrounding the gas detection element;
In a cylindrical shape made of an insulating ceramic, surrounding the periphery of the rear end side of the gas detection element, a ceramic enclosure that is held by the metal shell in a form in which the rear end side of the gas detection element protrudes from the rear end of the metal shell,
A gas sensor comprising:
The ceramic enclosure includes an enclosure exposed portion exposed to the outside on the rear end side from the rear end of the metal shell when the gas sensor is used.
A gas sensor, wherein a glaze layer is formed at least on the enclosure exposed portion. The gas sensor according to claim 1,
A gas sensor, wherein the glaze layer has a surface roughness Ra of 0.4 μm or less. The gas sensor according to claim 1 or 2,
The gas sensor according to claim 1, wherein the thickness of the glaze layer is 15 μm to 100 μm. The gas sensor according to any one of claims 1 to 3,
The ceramic enclosure has an outer diameter larger than the outer diameter of the enclosure exposed portion, and includes a large-diameter portion having a taper surface facing the rear end.
The gas sensor according to claim 1, wherein the glaze layer is formed from at least the enclosure exposed portion to the taper surface facing the rear end. The gas sensor according to claim 4, wherein
The glaze layer constitutes a recess having a radius of curvature of 1.5 mm or less at the boundary between the taper surface facing the rear end and the outer peripheral surface of the ceramic enclosure extending to the rear end side,
The gas sensor according to claim 1, wherein the concave portion is engaged with a metal shell through a packing. A gas detection element that extends in the axial direction and whose front end is exposed to the gas to be measured, a metal shell that surrounds the periphery of the gas detection element, and a cylinder made of insulating ceramic, surrounds the rear end of the gas detection element The gas detection element is connected to an inner electrode formed on the inner peripheral surface of the ceramic surrounding body and the gas detection element, which is surrounded and is held by the metal shell in a form in which the rear end side of the metal shell protrudes from the rear end of the metal shell A gas sensor having a terminal member for outputting an output signal from the outside,
A cylindrical cap terminal that is connected to the terminal member of the gas sensor and transmits the output signal to an external device, and an insulating elastic body that covers the cap terminal and the rear end side of the ceramic enclosure. A gas sensor cap having a portion;
A gas sensor unit comprising:
The ceramic enclosure has an enclosure exposed portion exposed to the outside between the insulating portion of the gas sensor cap and the metal shell,
A gas sensor unit, wherein a glaze layer is formed at least in the enclosure exposed portion. The gas sensor unit according to claim 6,
The gas sensor unit according to claim 1, wherein the glaze layer is formed on an outer peripheral surface on a rear end side with respect to a rear end of the metal shell in the ceramic enclosure. The gas sensor unit according to claim 6 or 7,
A gas sensor unit having the surface roughness Ra of 0.4 μm or less. In the gas sensor unit according to any one of claims 6 to 8,
The gas sensor unit, wherein the glaze layer has a thickness of 15 μm to 100 μm. In the gas sensor unit according to any one of claims 6 to 9,
The ceramic enclosure has an outer diameter larger than the outer diameter of the enclosure exposed portion, and includes a large-diameter portion having a taper surface facing the rear end.
The gas sensor unit, wherein the glaze layer is formed up to the taper surface facing the rear end. In the gas sensor unit according to claim 10,
The glaze layer constitutes a recess having a radius of curvature of 1.5 mm or less at the boundary between the taper surface facing the rear end and the outer peripheral surface of the ceramic enclosure extending to the rear end side,
The gas sensor unit according to claim 1, wherein the recess is engaged with a metal shell through a packing. A gas detection element extending in the axial direction and having the tip side exposed to the gas to be measured;
A metal shell surrounding the gas detection element;
In a cylindrical shape made of an insulating ceramic, surrounding the periphery of the rear end side of the gas detection element, a ceramic enclosure that is held by the metal shell in a form in which the rear end side of the gas detection element protrudes from the rear end of the metal shell,
A method of manufacturing a gas sensor comprising:
A glaze material layer is formed on the outer peripheral surface of the ceramic enclosure by spraying the glaze material on the outer peripheral surface of the ceramic enclosure,
A method for producing a gas sensor, wherein the glaze layer is formed by baking the glaze material layer.