JP2014081296A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor that prevents calking on the outer surface of a bent part from cracking or peeling a plated layer and prevents corrosion of the bent part, regarding a main body metal fitting including a main body part and the plated layer for covering the main body part.SOLUTION: The gas sensor includes a gas detection element 120, a main body metal fitting 160 having a bent part 161, and an outer cylinder 130 having a collar part 131. The collar part 131 of the outer cylinder 130 is disposed inside the main body metal fitting 160 in the radial direction, and is fixed in a state in which it is pressed to the tip side of the axial direction by the bent part 161 of the main body metal fitting 160. The main body metal fitting 160 includes a main body part 160b and a plated layer 160c covering the main body part 160b. The minimum value (minimum curvature radius) of curvature radius R of the outer surface 161f of the bent part 161 is 1.5 mm or more.

Description

  The present invention relates to a gas sensor.

  As a gas sensor, for example, a gas sensor that is attached to an exhaust pipe of an automobile or the like and detects a specific gas component contained in a gas to be measured such as exhaust gas is known. As a specific form of this gas sensor, for example, it has a form extending in the axial direction, a gas detection element whose tip side is exposed to the gas to be measured, and a cylindrical shape extending in the axial direction, and the gas detection element from its own tip. Some have a metal shell that surrounds the periphery of the gas detection element in a state where the front end portion is protruded, and an outer cylindrical body that has a cylindrical shape extending in the axial direction and is disposed on the rear end side of the metal shell ( For example, see Patent Document 1).

JP 2001-56312 A

  In the gas sensor of Patent Document 1, the metal shell has an annular bent portion formed by caulking so that the rear end portion thereof is bent radially inward. Further, the outer cylinder has an annular collar portion in which the tip portion of the outer cylinder is bent radially outward. And the collar part of an outer cylinder is arrange | positioned at the radial inside of a metal shell, and is fixed by the form pressed by the bending part of a metal shell to the front end side of an axial direction.

  By the way, a part of the metal shell (a part on the rear end side) is exposed to the outside when the gas sensor is used. Conventionally, the metal shell has been formed of stainless steel (SUS) in consideration of corrosion resistance. In contrast, the inventor of the present application has proposed that the metal shell is formed of a main body portion and a plating layer (a plating layer having higher corrosion resistance than the main body portion) covering the main body portion. The main body is preferably formed of an inexpensive material, for example, carbon steel. The main body is covered with a plating layer to prevent corrosion of the main body.

  However, as in the gas sensor of Patent Document 1, a bent portion is formed by caulking so that the rear end portion of the metallic shell is bent inward in the radial direction, and the bent portion of the outer cylinder body is axially moved by this bent portion. When it is configured to be pressed and fixed to the tip side, the following problems may occur. Specifically, when the bent portion is formed by caulking the rear end portion of the metal shell inward in the radial direction, a large tensile stress acts on the outer surface of the rear end portion (bent portion). Thus, there is a possibility that the plating layer may crack or peel on the outer surface of the bent portion. As a result, the main body portion of the bent portion is exposed to the outside, and the main body portion may corrode.

  The present invention has been made in view of such a situation, and for a metal shell composed of a main body portion and a plating layer covering the main body portion, cracking or peeling of the plating layer due to caulking on the outer surface of the bent portion is achieved. An object of the present invention is to provide a gas sensor which is prevented and corrosion of a bent portion is prevented.

  One aspect of the present invention has a form extending in the axial direction, a gas detection element whose tip side is exposed to the gas to be measured, a cylindrical shape extending in the axial direction, and a tip portion of the gas detection element from its tip. A metal shell that surrounds the periphery of the gas detection element in a protruding state, and has a ring-shaped bent portion that is formed by caulking so that its rear end is bent radially inward, An outer cylinder having a cylindrical shape extending in the axial direction and disposed on the rear end side of the metal shell, wherein the outer cylinder has an annular flange having a shape in which its tip end is bent radially outward. And the flange portion of the outer cylindrical body is disposed on the radially inner side of the metal shell, and is fixed in such a manner that it is pressed toward the distal end side in the axial direction by the bent portion of the metal shell. In the gas sensor, the metal shell is connected to the main body. Said plating layer covering the main body, made from a minimum radius of curvature of the outer surface of the bent portion, a gas sensor formed by a 1.5mm or more.

In the gas sensor described above, a metal shell made of a main body portion and a plating layer (a plating layer having higher corrosion resistance than the main body portion) covering the main body portion is used as the metal shell.
And in the above-mentioned gas sensor, the minimum curvature radius of the outer surface of a bending part is 1.5 mm or more. By increasing the minimum radius of curvature of the outer surface of the bent portion formed by caulking the metal shell to 1.5 mm or more, cracking and peeling of the plating layer due to caulking are prevented on the outer surface of the bent portion, and the main body portion is external. Can be prevented from being exposed. Thereby, corrosion of the main-body part of a bending part can be prevented.
In addition, as a plating layer, the nickel plating layer which carried out the chromate process can be mentioned, for example.

  Further, in the gas sensor, a filling member that is compressed and filled between an inner peripheral surface of the metal shell and an outer peripheral surface of the gas detection element, an inner side of the metal shell, and a rear side of the filling member. A pressing member that is positioned on the end side and that compresses the filling member by pressing the filling member toward the end in the axial direction, and the pressing member is positioned closer to the end in the axial direction than the bent portion of the metal shell. The bent portion is pressed together with the flange portion of the outer cylindrical body toward the distal end side in the axial direction, and the filling member is pressed toward the distal end side in the axial direction. A buckling portion that is located on the distal end side and is formed together with the bent portion by cold caulking, and has a cylindrical shape that swells only outward in the radial direction, and the buckling portion includes: A gas sensor that is separated from the pressing member may be used.

  In the gas sensor described above, the pressing member is pressed toward the distal end side in the axial direction together with the flange portion of the outer cylindrical body by the bent portion of the metal shell. Thereby, the filling member can be pressed toward the front end side in the axial direction by the pressing member, whereby the filling member can be filled without a gap between the inner peripheral surface of the metal shell and the outer peripheral surface of the gas detection element. it can. Thereby, the space between the inner peripheral surface of the metallic shell and the outer peripheral surface of the gas detection element can be hermetically sealed by the filling member.

  By the way, as described above, by increasing the radius of curvature of the bent portion, it is possible to prevent cracking and peeling of the plating layer due to caulking on the outer surface, and to prevent the main body portion from being exposed to the outside. However, as the radius of curvature of the bent portion increases, the force that presses the pressing member toward the distal end in the axial direction is weakened by the bent portion, and as a result, the airtightness of the filling member may be reduced.

  On the other hand, in the metal shell, the buckling portion is formed together with the bending portion by caulking at a position closer to the distal end than the bending portion, thereby increasing the force with which the pressing member is pressed toward the distal end side in the axial direction. As a result, the airtightness of the filling member can be improved. Specifically, since the axial distance between the bent portion and the pressing member is shortened by the amount of buckling of the metal shell, the force for pressing the pressing member toward the distal end side in the axial direction by the bent portion can be increased. . For example, the buckling portion can be formed together with the bent portion by heat-caching the metal shell.

  However, when the metal shell is heat-clamped, the buckled portion has a shape that bulges and buckles on both the radially outer side and the inner side of the metal shell. For this reason, in the case of a downsized gas sensor in which there is no gap between the inner peripheral surface of the metal shell and the pressing member (or there is only a very small gap), There is a possibility that the portion where the metal plate is formed interferes with the pressing member in an attempt to swell radially inward, and the metal shell cannot be sufficiently buckled. For this reason, the force which presses a pressing member to an axial direction front end side by a bending part is insufficient, and there exists a possibility that the airtightness by a filling member may fall.

  Therefore, in the above-described gas sensor, a buckling portion having a cylindrical shape that swells only outward in the radial direction is formed together with the bending portion by cold caulking instead of hot caulking. When the metal shell is buckled by cold caulking, it does not bulge radially inward but buckles in a form that bulges only radially outward. Thereby, the above-mentioned gas sensor becomes a gas sensor in which the buckling portion is separated from the pressing member. For this reason, even if the gas sensor is miniaturized with no gap (or only a very small gap) between the inner peripheral surface of the metal shell and the pressing member, the buckled portion formed by caulking is connected to the pressing member. The pressing member can be appropriately pressed toward the distal end side in the axial direction by the bent portion without interference.

  Furthermore, in any of the above gas sensors, the main body portion of the metal shell may be a gas sensor made of carbon steel.

By forming the main body of the metal shell from carbon steel, the cost becomes lower than when the metal shell is formed from stainless steel as in the prior art.
In addition, when the main-body part of a metal shell is formed with carbon steel, it is not preferable to form a bent part and a buckled part by heat caulking. This is because, in heat caulking, there is a possibility that the bent portion and the buckled portion cannot be appropriately formed, and iron constituting the carbon steel may be oxidized and become brittle. However, as described above, in the present application, since the bent portion and the buckled portion are formed by cold caulking of the metal shell, there is no possibility that the above-described problems occur.

  Further, in any one of the above gas sensors, the metal shell is located on a front end side of the gas sensor, a screw part for attaching the gas sensor to a member to be attached to which the gas sensor is attached, and a rear end of the screw part A tool engaging portion for engaging a tool for screwing the screw portion into the screw hole of the attached member, and a distal end side with respect to the bent portion. A buckling portion formed together with the bending portion, and having a cylindrical shape bulging radially outward, and the buckling portion is located on the rear end side of the tool engaging portion. The gas sensor is good.

  In the above-described gas sensor, a buckling portion having a cylindrical shape bulging radially outward is formed together with the bent portion by cold caulking of the metal shell. By the way, the buckled portion that has been buckled and deformed by cold caulking is originally thin in thickness so as to be appropriately buckled and deformed by cold caulking, and therefore has low rigidity. For this reason, when the buckling portion is positioned between the tool engaging portion and the screw portion in the axial direction, a tool (for example, a hexagon wrench) is engaged with the tool engaging portion, and the screw When the metal shell is tightened so that the portion is screwed into the screw hole of the attached member (for example, the exhaust pipe), tightening torque is applied to the buckled portion, and the buckled portion may be damaged (twisted). .

  On the other hand, in the above-described gas sensor, the buckling portion is located further on the rear end side than the tool engagement portion (for example, a hexagonal portion) located on the rear end side with respect to the screw portion. That is, with respect to the axial direction, the buckling portion is located on the side opposite to the screw portion with respect to the tool engaging portion (the buckling portion does not exist between the screw portion and the tool engaging portion). Thereby, when the tool is engaged with the tool engaging portion and the metal fitting is tightened so that the screw portion is screwed into the screw hole of the attached member, the tightening torque is not applied to the buckling portion, There is no risk of the buckling portion being damaged (twisted).

  Furthermore, in any one of the above gas sensors, the filling member filled between the inner circumferential surface of the metal shell and the outer circumferential surface of the gas detection element, and located on the rear end side of the filling member, A pressing member that presses and compresses the filling member toward the distal end side in the axial direction, and of the outer cylinder, the flange portion that is pressed toward the distal end side in the axial direction by the bent portion of the metal shell, It is preferable that the pressing member positioned on the distal end side of itself is a gas sensor that is pressed directly on the distal end side in the axial direction.

  In the gas sensor, the flange provided for fixing the outer cylindrical body is also used for pressing the pressing member toward the distal end side in the axial direction. Moreover, the pressing member is directly pressed toward the distal end side in the axial direction by the flange portion. For this reason, since a component can be reduced and a structure can be simplified compared with the case where the member which presses a press member separately is provided, it becomes low cost.

  By pressing the pressing member toward the distal end side in the axial direction by the flange portion of the outer cylindrical body, the filling member can be pressed toward the distal end side in the axial direction by the pressing member. And the outer peripheral surface of the gas detection element can be filled without a gap. Thereby, the space between the inner peripheral surface of the metallic shell and the outer peripheral surface of the gas detection element can be hermetically sealed by the filling member.

  Furthermore, in any one of the above gas sensors, an annular plate packing is interposed between the bent portion of the metal shell and the flange portion of the outer cylinder body, and the flange of the outer cylinder body The portion is pressed to the tip end in the axial direction through the plate packing pressed to the tip end in the axial direction by the bent portion of the metal shell, and the inner diameter of the plate packing is D1 and the outer diameter is D2. When the bent portion of the metal shell presses an annular portion having a width dimension of at least (D2-D1) / 2 in the plate packing toward the tip end in the axial direction, the outer cylindrical body passes through the annular portion. It is good to make it the gas sensor formed by pressing the said collar part to the said axial direction front end side.

  In the gas sensor described above, the bent portion of the metal shell is an annular portion having a width dimension of at least (D2-D1) / 2 in the plate packing (an annular portion having a width dimension of 50% or more of the width dimension of the plate packing). Is pressed to the front end side in the axial direction, and the collar portion of the outer cylindrical body is pressed to the front end side in the axial direction through the annular portion. Thereby, the flange of the outer cylinder can be firmly pressed and fixed by the bent portion of the metal shell, and the airtightness between the bent portion of the metal shell and the flange of the outer cylinder can be improved. it can.

  The width dimension of the plate packing and the annular portion refers to a dimension obtained by subtracting the inner diameter from the outer diameter. The width dimension of the plate packing having the inner diameter D1 and the outer diameter D2 is (D2-D1).

  Further, in the above gas sensor, the metal forming the plating layer constituting the outer surface of the metal shell, the metal constituting the outer surface of the plate packing, and the metal constituting the outer surface of the outer cylinder body are corroded. A gas sensor having the same potential is preferable.

  When the corrosion potential differs between the metal forming the outer surface of the metal shell, the metal forming the outer surface of the plate packing, and the metal forming the outer surface of the outer cylinder, the bent portion of the metal shell, the plate packing In addition, when water or an electrolytic solution (an aqueous solution in which an electrolyte is dissolved) adheres to the flange portion of the outer cylinder, a metal having a low corrosion potential may be dissolved (ionized). For example, if the metal forming the plating layer constituting the outer surface of the metal shell has a lower corrosion potential than the metal constituting the outer surface of the plate packing and the metal constituting the outer surface of the outer cylinder, the plating layer is dissolved. There is a risk that the internal body portion is exposed. Thereby, there exists a possibility that the bending part of a metal shell may corrode.

  On the other hand, in the gas sensor described above, the metal forming the plating layer that forms the outer surface of the metal shell, the metal that forms the outer surface of the packing, and the metal that forms the outer surface of the outer cylinder have the same corrosion potential. Therefore, there is no possibility of the occurrence of the above problems.

It is a longitudinal cross-sectional view of the gas sensor concerning embodiment. It is the B section enlarged view of FIG. It is a top view of board packing. It is sectional drawing of board packing. It is a figure explaining the cold crimping of a metal shell. It is a figure explaining the cold crimping of a metal shell. It is a partial expanded sectional view of the gas sensor concerning other forms. It is a partial expanded sectional view of the gas sensor concerning other forms.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a gas sensor 100 of the present embodiment. The gas sensor 100 includes a gas detection element 120, an outer electrode 111, an inner electrode 112, a metal shell 160, a first outer cylinder 130, and a protector 170.

  The metal shell 160 has a substantially cylindrical shape extending in the axial direction, and surrounds the periphery of the gas detection element 120 with the front end portion 120b of the gas detection element 120 protruding from its front end (lower end in FIG. 1). . The metal shell 160 includes a main body portion 160b made of carbon steel and a plating layer 160c (plating layer having higher corrosion resistance than carbon steel) covering the main body portion 160b (see FIG. 2). In the present embodiment, a nickel plating layer subjected to chromate treatment is used as the plating layer 160c.

  The metal shell 160 has a support surface 167 that supports a flange 120e of the gas detection element 120 and a rear end 171 of the protector 170, which will be described later. The support surface 167 is a tapered surface that increases in diameter toward the rear end side (upper side in FIG. 1).

  Furthermore, the metal shell 160 has a screw portion 165 for attaching the gas sensor 100 to a member to be attached (in this embodiment, an exhaust pipe) on the front end side thereof. Further, a tool engaging portion 166 (a hexagonal portion) that engages a tool for screwing the screw portion 165 into the screw hole of the attached member (exhaust pipe) at a position on the rear end side of the screw portion 165. )have. Furthermore, the metal shell 160 has an annular bent portion 161 formed by crimping so that its rear end portion 162 is bent inward in the radial direction.

  The gas detection element 120 is configured to extend in the axial direction (the direction along the axis AX, the vertical direction in FIG. 1), and the front end side (lower end side in FIG. 1) is a measurement gas (in this embodiment, exhaust gas). Be exposed. The gas detection element 120 is made of a solid electrolyte having oxygen ion conductivity, and has a substantially cylindrical shape with a closed end portion 120b. A flange portion 120e that protrudes outward in the radial direction is provided at the central portion in the axial direction of the gas detection element 120. The gas detection element 120 is disposed in the metal shell 160 with the metal packing 142 and the rear end portion 171 of the protector 170 sandwiched between the front end surface of the flange portion 120e and the support surface 167 of the metal shell 160. It is fixed.

As the solid electrolyte constituting the gas detection element 120, for example, ZrO _{2 in} which Y ₂ O ₃ or CaO is dissolved is representative, but oxidation of other alkaline earth metals or rare earth metals is typical. A solid solution of the product and ZrO ₂ may be used. Furthermore, HfO ₂ may be contained therein.
In the present embodiment, in the axial direction, the front end 120b side of the gas detection element 120 is the front end side, and the opposite side is the rear end side.

  The protector 170 is made of metal and has a substantially cylindrical shape. The protector 170 has a vent hole 170 b for introducing a gas to be measured (exhaust gas) into the gas sensor 100. The protector 170 is inserted into the metal shell 160 from the rear end side, and the tip end portion 172 having the vent hole 170b is exposed to the outside. The rear end portion 171 of the protector 170 is bent radially outward to form a hook shape, and is fixed between the flange portion 120e of the gas detection element 120 and the support surface 167 of the metal shell 160 together with the packing 142. ing.

  The first outer cylinder 130 has a cylindrical shape extending in the axial direction, and is disposed on the rear end side of the metal shell 160. This 1st outer cylinder 130 consists of the main-body part 130b which consists of carbon steel, and the plating layer 130c (plating layer with higher corrosion resistance than carbon steel) which coat | covers this main-body part 130b (refer FIG. 2). In this embodiment, similarly to the metal shell 160, a nickel plating layer subjected to chromate treatment is used as the plating layer 130c.

  Moreover, the 1st outer cylinder 130 has the cyclic | annular collar 131 of the form in which the front-end | tip part was bent to the radial direction outer side. The flange 131 is disposed on the radially inner side of the rear end 162 of the metal shell 160, and is fixed in such a manner that it is pressed toward the front end side in the axial direction (lower side in FIG. 1) by the bent portion 161 of the metal shell 160. Yes. Specifically, a plate packing 144 is interposed between the bent portion 161 of the metal shell 160 and the flange 131 of the first outer cylinder 130, and the flange 131 of the first outer cylinder 130 is It is pressed to the front end side in the axial direction through the plate packing 144 pressed to the front end side in the axial direction by the bent portion 161 of the metal fitting 160.

  As shown in FIGS. 3 and 4, the plate packing 144 has an annular shape in plan view and a flat plate shape in side view. When the inner diameter of the plate packing 144 is D1 and the outer diameter is D2, the width dimension of the plate packing 144 is represented by (D2-D1). The plate packing 144 includes a main body portion 144b made of carbon steel and a plating layer 144c (plating layer having higher corrosion resistance than carbon steel) covering the main body portion 144b (see FIG. 2). In the present embodiment, similarly to the metal shell 160, a nickel plating layer subjected to chromate treatment is used as the plating layer 144c.

The outer electrode 111 is a porous Pt or Pt alloy, and is provided so as to cover the entire outer surface of the tip 120b of the gas detection element 120. The outer electrode 111 is linearly provided from the rear end of the front end portion 120b of the gas detection element 120 to the front end surface of the flange portion 120e, and is electrically connected to the metal shell 160 through the packing 142 and the protector 170. The
The inner electrode 112 is also formed by porous Pt or a Pt alloy, and is provided so as to cover the inner surface of the gas detection element 120.

  A pressing member 140 made of an insulating ceramic (specifically, alumina) is disposed on the distal end side of the flange 131 of the first outer cylinder 130. The pressing member 140 has a cylindrical shape, is externally fitted to the gas detection element 120, and compresses a filling member 141, which will be described later, by pressing it toward the distal end side in the axial direction.

  The filling member 141 is made of talc powder and is filled between the inner peripheral surface 160 d of the metal shell 160 and the outer peripheral surface 120 c of the gas detection element 120. Specifically, the filling member 141 is located between the pressing member 140 and the flange 120e of the gas detection element 120 and the holding portion 168 of the metal shell 160, and the pressing member 140 and the flange are pressed by the pressing member 140. The space between the inner peripheral surface 160d of the metal shell 160 and the outer peripheral surface 120c of the gas detection element 120 is hermetically sealed by being compressed between 120e and the holding portion 168. The filling member 141 is not limited to talc powder, and may be, for example, boron nitride powder.

  More specifically, the pressing member 140 is pressed together with the flange 131 of the first outer cylindrical body 130 toward the distal end side in the axial direction by the bent portion 161 of the metal shell 160. As a result, the pressing member 140 can press the filling member 141 toward the front end side in the axial direction, whereby the filling member 141 made of talc powder can be attached to the inner peripheral surface 160d of the metal shell 160 and the outer peripheral surface of the gas detection element 120. It can be filled with no gap between 120c.

  In particular, in the present embodiment, the flange 131 that is pressed toward the front end side in the axial direction by the bent portion 161 of the metal shell 160 in the first outer cylinder 130 directly presses the pressing member 140 positioned on the front end side thereof. , It is pressing toward the front end side in the axial direction. That is, the flange 131 provided for fixing the first outer cylinder 130 is also used to press the pressing member 140 toward the distal end side in the axial direction. Moreover, the pressing member 140 is directly pressed toward the distal end side in the axial direction by the flange 131. For this reason, compared with the case where the member which presses the press member 140 separately is provided, since a component can be reduced and a structure can also be simplified, it becomes low cost.

  By pressing the pressing member 140 toward the front end in the axial direction by the flange 131 of the first outer cylinder 130, the filling member 141 can be pressed toward the front end in the axial direction by the pressing member 140. The filling member 141 can be filled without a gap between the inner peripheral surface 160d of the metal shell 160 and the outer peripheral surface 120c of the gas detection element 120. Thereby, the space between the inner peripheral surface 160 d of the metallic shell 160 and the outer peripheral surface 120 c of the gas detection element 120 can be hermetically sealed by the filling member 141.

  A second outer cylinder 135 is provided on the outer side in the radial direction of the first outer cylinder 130. The second outer cylindrical body 135 has a cylindrical shape extending in the axial direction, and is caulked and fixed to the first outer cylindrical body 130 with a cylindrical filter 138 sandwiched between the second outer cylindrical body 130 and the first outer cylindrical body 130. Has been. The filter 138 is formed of PTFE having air permeability and waterproofness.

A grommet 146 made of fluororubber is disposed on the radially inner side of the rear end portions of the first outer cylinder body 130 and the second outer cylinder body 135. A through hole 146b that penetrates the grommet 146 in the axial direction is formed at the center of the grommet 146.
Further, a separator 148 made of an insulating alumina ceramic is provided on the leading end side (lower side in FIG. 1) of the grommet 146. A through hole 148b is formed in the center of the separator 148 so as to penetrate the separator 148 in the axial direction.

  An output lead 151 connected to an external device is inserted into the through hole 146b of the grommet 146 and the through hole 148b of the separator 148. Furthermore, the output lead wire 151 is electrically connected to the output terminal member 153. The output terminal member 153 has a substantially cylindrical connection portion 153b that can be elastically expanded and contracted. The connection portion 153b is elastically pressed against the inner electrode 112 provided on the inner surface of the gas detection element 120. As a result, the output terminal member 153 is electrically connected to the inner electrode 112.

  By the way, in this embodiment, as mentioned above, the metal shell 160 comprising the main body 160b made of carbon steel and the plating layer 160c (chromium-treated nickel plating layer) covering the main body 160b is used as the metal shell 160. (See FIG. 2). Moreover, in the present embodiment, the bent portion 161 is formed by caulking the rear end portion 162 of the metallic shell 160 so as to be bent radially inward, and the bent portion 161 of the first outer cylindrical body 130 is formed by the bent portion 161. Is pressed and fixed to the front end side in the axial direction.

  Conventionally, when such a configuration is adopted, there is a possibility that the following problems may occur. Specifically, when the bent portion is formed by caulking the rear end portion of the metal shell inward in the radial direction, a large tensile stress acts on the outer surface of the rear end portion (bent portion). Thus, there is a possibility that the plating layer may crack or peel on the outer surface of the bent portion. Thereby, the main-body part of the bending part was exposed outside, and there existed a possibility that the carbon steel (iron which is a main component) which comprises a main-body part might corrode.

  On the other hand, in this embodiment, the minimum value (minimum curvature radius) of the curvature radius R on the outer surface 161f of the bent portion 161 is 1.5 mm or more. By increasing the minimum radius of curvature of the outer surface 161f of the bent portion 161 formed by caulking the metal shell 160 to 1.5 mm or more, cracking or peeling of the plating layer due to caulking is prevented on the outer surface 161f of the bent portion 161. The carbon steel constituting the main body 160b can be prevented from being exposed to the outside. Thereby, corrosion of the main-body part 160b can be prevented in the bending part 161. FIG.

  In this embodiment, the metal shell 160 is cold-swaged to form a buckled portion 163 having a cylindrical shape that bulges only radially outward along with the bent portion 161 (see FIG. 1). Here, the cold caulking of the metal shell of the present embodiment will be described in detail.

  As shown in FIG. 5, a metallic shell 160 having a cylindrical shape with a rear end 162 extending in the axial direction is prepared. Then, the gas detection element 120, the filling member 141, the pressing member 140, the flange 131 of the first outer cylindrical body 130, and the plate packing 144 are arranged inside the metal shell 160 from above the metal shell 160. The caulking die 10 is moved downward (in the axial direction front end side), and the metal shell 160 is cold caulked. As a result, as shown in FIG. 6, the rear end portion 162 of the metallic shell 160 is bent radially inward to form the bent portion 161, and the thin portion 163B that is thinner than the rear end portion 162 is buckled. Thus, the buckling portion 163 is formed.

  By the way, in the present embodiment, as described above, by increasing the radius of curvature R of the bent portion 161, the outer surface 161f is prevented from cracking or peeling of the plated layer 160c due to caulking, and the main body portion 160b is externally attached. To prevent exposure. However, as the radius of curvature R of the bent portion 161 increases, the force that presses the pressing member 140 toward the front end in the axial direction is weakened by the bent portion 161, and as a result, the airtightness by the filling member 141 may be reduced. is there.

  On the other hand, in the metal shell 160, the buckling portion 163 is formed together with the bending portion 161 by caulking at a position closer to the distal end side than the bending portion 161, so that the pressing member 140 is moved to the distal end side in the axial direction by the bending portion 161. As a result, the airtightness by the filling member 141 can be increased. Specifically, since the axial distance between the bent portion 161 and the pressing member 140 is shortened by the amount of buckling of the thin wall portion 163B of the metal shell 160, the pressing member 140 is moved to the distal end side in the axial direction by the bent portion 161. The pressing force can be increased.

  However, when the metal shell is caulked by heat caulking, the buckling portion bulges on both the radially outer side and the inner side of the metal shell and becomes a buckled shape. For this reason, in the case of a miniaturized gas sensor that has almost no gap between the inner peripheral surface of the metal shell and the pressing member as in this embodiment, if the metal shell is heat-clamped, the buckling portion There is a possibility that the portion to be formed will interfere with the pressing member in an attempt to swell radially inward, and the metal shell cannot be sufficiently buckled. For this reason, the force which presses a pressing member to an axial direction front end side by a bending part is insufficient, and there exists a possibility that the airtightness by a filling member may fall.

  For this reason, in the present embodiment, as described above, the buckling portion 163 having a cylindrical shape that swells only radially outward is formed together with the bending portion 161 by cold crimping instead of hot crimping. . When the thin part 163B of the metal shell 160 is buckled by cold caulking, as shown in FIG. 6, the thin part 163B does not bulge radially inward and buckles in a form that bulges only radially outward. . Thereby, the gas sensor 100 of this embodiment becomes a gas sensor in which the buckling portion 163 is separated from the pressing member 140 (see FIGS. 1 and 6). Therefore, in the gas sensor 100 of the present embodiment, the gap (radial distance) between the inner peripheral surface of the metal shell 160 and the pressing member 140 is equal to or less than the thickness of the thin portion 163B (buckling portion 163) of the metal shell 160. Although the gas sensor is miniaturized with almost no gap, the buckling portion 163 formed by caulking does not interfere with the pressing member 140, and the bending member 161 makes the pressing member 140 suitable for the front end in the axial direction. Can be pressed.

  In addition, in this embodiment, the bent portion 161 of the metal shell 160 has an annular portion 144d having a width dimension of at least (D2-D1) / 2 in the plate packing 144 (width of 50% or more of the width dimension of the plate packing). An annular portion 144d) having a dimension is pressed toward the distal end side in the axial direction, and the flange 131 of the first outer cylindrical body 130 is pressed toward the distal end side in the axial direction through the annular portion 144d (see FIG. 2). Accordingly, the flange 131 of the first outer cylinder 130 can be firmly pressed and fixed by the bent portion 161 of the metal shell 160, and the flange 161 of the metal shell 160 and the flange of the first outer cylinder 130 can be fixed. The airtightness between the parts 131 can be improved.

  In the present embodiment, the bent portion 161 of the metal shell 160 presses the entire width of the plate packing 144 toward the front end side in the axial direction (see FIG. 2). That is, the annular portion 144d coincides with the entire plate packing 144, and the annular portion 144d is a portion having a width dimension of (D2-D1) (a portion having a width dimension of 100% of the width dimension of the plate packing 144). ing.

Moreover, in this embodiment, as mentioned above, the main-body part 160b of the metal shell 160 is formed of carbon steel. By forming the main body 160b of the metal shell 160 from carbon steel, the cost becomes lower than when the metal shell is formed from stainless steel as in the prior art.
In addition, when the main-body part 160b of the metal shell 160 is formed of carbon steel, it is not preferable to form the bent part 161 and the buckled part 163 by heat caulking. This is because in the heat caulking, there is a possibility that the bent portion 161 and the buckled portion 163 cannot be appropriately formed, and iron constituting the carbon steel may be oxidized and become brittle. However, as described above, in the present embodiment, the buckling portion 163 is formed together with the bent portion 161 by the cold caulking of the metal shell 160, so that there is no possibility that the above-described problems occur.

  By the way, the buckling part 163 of the metal shell 160 is a part where the thin part 163B is buckled and deformed by cold caulking. The thin-walled portion 163B that becomes the buckled portion 163 has a low rigidity because it is thinned so as to be appropriately buckled and deformed by cold caulking. Therefore, when the buckling portion 163 is positioned between the tool engaging portion 166 and the screw portion 165 in the axial direction, a tool (for example, a hexagon wrench) is engaged with the tool engaging portion 166. When the metal shell 160 is tightened so that the screw portion 165 is screwed into the screw hole of the attached member (exhaust pipe), a tightening torque is applied to the buckling portion 163 and the buckling portion 163 is damaged ( There is a risk that it will break.

  On the other hand, in the gas sensor 100 of the present embodiment, the buckling portion 163 is located further on the rear end side than the tool engagement portion 166 (hexagonal portion) located on the rear end side with respect to the screw portion 165. ing. That is, in the axial direction, the buckling portion 163 is located on the opposite side of the screw portion 165 with respect to the tool engaging portion 166 (the buckling portion 163 is formed between the screw portion 165 and the tool engaging portion 166. Not in between). Thereby, when the tool is engaged with the tool engaging portion 166 and the metal shell 160 is tightened so that the screw portion 165 is screwed into the screw hole of the attached member, a tightening torque is applied to the buckling portion 163. There is no possibility that the buckling portion 163 is damaged (twisted).

  Further, when the corrosion potential of the metal constituting the outer surface of the metal shell, the metal constituting the outer surface of the plate packing, and the metal constituting the outer surface of the first outer cylinder are different from each other, There is a risk of malfunction. Specifically, when water or an electrolytic solution (an aqueous solution in which the electrolyte is dissolved) adheres to the bent portion of the metal shell, the plate packing, and the flange portion of the first outer cylinder, a metal having a low corrosion potential is dissolved ( There is a risk of ionization. For example, when the metal constituting the outer surface of the metal shell has a lower corrosion potential than the metal constituting the outer surface of the plate packing and the metal constituting the outer surface of the first outer cylinder, the metal constituting the outer surface of the metal shell There is a possibility that the (plating layer) dissolves and the internal main body (carbon steel) is exposed. Thereby, there exists a possibility that the bending part of a metal shell may corrode.

  On the other hand, in this embodiment, the outer surface of the metallic shell 160, the outer surface of the plate packing 144, and the outer surface of the first outer cylinder 130 are all constituted by a nickel-plated layer that has been chromated. As a result, the metal constituting the outer surface of the metal shell 160, the metal constituting the outer surface of the plate packing 144, and the metal constituting the outer surface of the first outer cylinder 130 have the same corrosion potential. For this reason, there is no possibility that the above problems will occur.

(Accelerated corrosion test)
Next, samples (samples 1 to 5) having different minimum values of radius of curvature R (minimum radius of curvature) on the outer surface of the bent portion of the metal shell were prepared. Specifically, bent portions having different minimum values of the radius of curvature R (minimum radius of curvature) on the outer surface were formed on the metal shell of each sample by cold caulking using caulking dies having different curvatures of the pressing surface.

In Sample 1, a bent portion with a minimum radius of curvature of the outer surface of 1.0 mm was formed by cold caulking of the metal shell. In sample 2, a bent portion having a minimum radius of curvature of the outer surface of 1.2 mm was formed. In Sample 3, a bent portion having a minimum radius of curvature of the outer surface of 1.5 mm was formed. In sample 4, a bent portion having a minimum radius of curvature of the outer surface of 1.7 mm was formed. In sample 5, a bent portion having a minimum radius of curvature of the outer surface of 1.9 mm was formed.
As in the embodiment, the metal shell of each sample includes a main body portion made of carbon steel and a plating layer (a nickel plating layer subjected to chromate treatment) covering the main body portion.

  These samples were then subjected to an accelerated corrosion test. Specifically, a salt spray test based on JIS H8502 was performed. Specifically, salt water was sprayed on the outer surface of the bent portion of each sample, and after 24 hours, it was confirmed whether red rust was generated on the outer surface of the bent portion. The results are shown in Table 1. By this test, in the sample in which red rust is generated, it can be determined that, due to cold caulking, a crack or the like of the plating layer occurs on the outer surface of the bent portion, and the main body portion is exposed. On the other hand, in the sample in which red rust did not occur, it can be determined that the crack of the plating layer does not occur on the outer surface of the bent portion, and the main body portion is not exposed.

As shown in Table 1, in samples 1 and 2 in which the minimum curvature radius of the outer surface was 1.0 mm and 1.2 mm, red rust occurred. Therefore, in Samples 1 and 2, it can be determined that, due to cold caulking, cracks or the like of the plating layer occurred on the outer surface of the bent portion, and the main body portion was exposed.
On the other hand, in samples 3 to 5 in which the minimum curvature radius of the outer surface was 1.5 mm, 1.7 mm, and 1.9 mm, red rust did not occur. Therefore, in Samples 3 to 5, it is possible to determine that the main body portion is not exposed because the plating layer does not crack on the outer surface of the bent portion due to cold caulking.

  From the above results, by setting the minimum curvature radius on the outer surface of the bent portion formed by caulking the metal shell to 1.5 mm or more, cracking and peeling of the plating layer due to caulking are prevented on the outer surface, and the main body portion Can be prevented from being exposed to the outside. Thereby, it can be said that corrosion (generation of rust) of a bending part can be prevented.

  In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

  For example, in the embodiment, the bent portion 161 of the metal shell 160 presses the entire width of the plate packing 144 toward the front end side in the axial direction (see FIG. 2). That is, the annular portion 144d pressed by the bent portion 161 coincides with the entire plate packing 144, and the annular portion 144d is a portion having a width dimension of (D2-D1) (100% of the width dimension of the plate packing 144). It was a part having dimensions).

However, as in the gas sensor 200 shown in FIG. 7, the bent portion 261 of the metal shell 260 has an annular portion 244d (with the width dimension of the plate packing) of the plate packing 144 having a width dimension of 3 (D2-D1) / 4. It is good also as a form which presses the cyclic | annular part 244d) which has a width dimension of 75% to the axial direction front end side.
Further, as in the gas sensor 300 shown in FIG. 8, the bent portion 361 of the metal shell 360 has an annular portion 344d (50 of the width dimension of the plate packing) having a width dimension of (D2-D1) / 2 in the plate packing 144. It is good also as a form which presses the cyclic | annular part 344d) which has a width dimension of% to an axial direction front end side.

  That is, the bent portion of the metal shell has an annular portion having an at least (D2-D1) / 2 width dimension (annular portion having a width dimension of 50% or more of the width dimension of the plate packing) of the plate packing. What is necessary is just to set it as the form which presses to a direction front end side, and presses the collar part of a 1st outer cylinder body to an axial direction front end side through this cyclic | annular part. In this way, the flange of the first outer cylinder can be firmly pressed and fixed by the bent portion of the metallic shell, and the bent portion of the metallic shell and the flange of the first outer cylindrical body can be fixed. The airtightness between can be increased.

100, 200, 300 Gas sensor 120 Gas detection element 120b Front end portion 120c Outer peripheral surface 130 First outer cylindrical body 131 ridge portion 140 Pressing member 141 Filling member 144 Plate packing 144d, 244d, 344d Annular portion 160, 260, 360 Metal shell 160b, 260b, 360b Body portion 160c, 260c, 360c Plating layer 160d Inner peripheral surface 161, 261, 361 Bending portion 161f Outer surface 162 Rear end portion 163 Buckling portion 165 Screw portion 166 Tool engaging portion

Claims (7)

A gas detection element having a shape extending in the axial direction, the tip side being exposed to the gas to be measured,
A metal shell that surrounds the periphery of the gas detection element with a cylindrical shape extending in the axial direction and projecting the front end of the gas detection element from the front end thereof. A metal shell having an annular bent portion formed by caulking to be bent inward;
An outer cylinder having a cylindrical shape extending in the axial direction and disposed on the rear end side of the metal shell, wherein the outer cylinder has an annular flange having a shape in which its tip end is bent radially outward. And comprising
In the gas sensor in which the flange portion of the outer cylindrical body is arranged in the radial direction of the metal shell, and is fixed in such a manner that it is pressed to the distal end side in the axial direction by the bent portion of the metal shell.
The metal shell is
The main body,
A plating layer covering the main body,
A gas sensor having a minimum radius of curvature of the outer surface of the bent portion of 1.5 mm or more. The gas sensor according to claim 1,
A filling member compressed and filled between the inner peripheral surface of the metal shell and the outer peripheral surface of the gas detection element;
A pressing member that is positioned on the inner side of the metal shell and on the rear end side with respect to the filling member, and compresses the filling member by pressing the filling member toward the front end side in the axial direction,
The pressing member is positioned closer to the distal end side in the axial direction than the bent portion of the metal shell, and is pressed toward the distal end side in the axial direction together with the flange portion of the outer cylindrical body by the bent portion. Is pressed toward the tip end side in the axial direction,
The metal shell is
A buckling portion that is located on the tip side of the bending portion and is formed together with the bending portion by cold caulking, and has a cylindrical shape that swells only radially outward,
The buckling portion is a gas sensor that is separated from the pressing member. The gas sensor according to claim 1 or 2, wherein
The main body of the metal shell is a gas sensor made of carbon steel. The gas sensor according to any one of claims 1 to 3,
The metallic shell is
A screw portion for attaching the gas sensor to a member to be attached, which is located on the tip side of the gas sensor,
A tool engaging portion that is located on the rear end side of the screw portion and engages a tool for screwing the screw portion into the screw hole of the attached member;
A buckling portion that is located on the tip side of the bending portion and is formed together with the bending portion by cold caulking, and has a cylindrical shape that swells only outward in the radial direction, and
The said buckling part is a gas sensor located in the back end side rather than the said tool engaging part. It is a gas sensor as described in any one of Claims 1-4, Comprising:
A filling member filled between the inner peripheral surface of the metal shell and the outer peripheral surface of the gas detection element;
A pressing member that is positioned on the rear end side with respect to the filling member and that compresses the filling member against the axial front end side,
Of the outer cylindrical body, the flange portion that is pressed toward the tip end in the axial direction by the bent portion of the metal shell directly presses the pressing member located on the tip end side thereof toward the tip end in the axial direction. A gas sensor. The gas sensor according to claim 1, wherein
An annular plate packing is interposed between the bent portion of the metal shell and the flange portion of the outer cylinder,
The flange portion of the outer cylindrical body is pressed toward the tip end in the axial direction through the plate packing pressed toward the tip end in the axial direction by the bent portion of the metal shell,
When the inner diameter of the plate packing is D1 and the outer diameter is D2,
The bent portion of the metal shell presses an annular part having a width dimension of at least (D2-D1) / 2 of the plate packing toward the distal end side in the axial direction, and passes through the annular part to A gas sensor formed by pressing a flange portion toward the tip end in the axial direction. The gas sensor according to claim 6,
A gas sensor in which a corrosion potential is equivalent to a metal constituting the outer surface of the metal shell, a metal constituting the outer surface of the plate packing, and a metal constituting the outer surface of the outer cylindrical body.

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