JP5524898B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor including a detection element for detecting the concentration of a specific gas contained in a detection target gas.

  2. Description of the Related Art A gas sensor is known that includes a detection element that is attached to an exhaust passage of an internal combustion engine such as an automobile engine and whose output changes according to the concentration of a specific gas (for example, NOx (nitrogen oxide) or oxygen) in the exhaust gas. . The detection element has a configuration including at least one cell in which a pair of electrodes is provided on a solid electrolyte body, and measures the concentration of the specific gas based on an output signal output from the cell according to the concentration of the specific gas.

  The detection element is held by being surrounded by a metal shell for attaching the gas sensor to the exhaust pipe in the radial direction. Further, the rear end portion side of the detection element protrudes rearward from the metal shell, and is surrounded by an outer cylinder attached to the rear end side of the metal shell. A plurality of electrodes for taking out the output are provided at the rear end of the detection element, and terminals provided on each of a plurality of lead wires that electrically connect the detection element and an external circuit. The bracket is connected. A separator made of an insulating ceramic is further disposed in the outer cylinder. The terminal fittings are housed inside the separator and are maintained in a non-contact state.

  Between the separator (terminal metal fitting holding member) and the outer cylinder, a cylindrical holding member (holding member support member) that holds the separator inside is disposed. The holding member is provided with a plurality of projecting pieces (spring pieces) projecting radially inward from a cylindrical peripheral wall portion (cylindrical plate wall portion) surrounding the outer surface of the separator. The projecting piece is formed in a plate shape by cutting out the peripheral wall portion into a rectangle that leaves one side (upper side) when viewed from the side and pushing the opposite side into the radial direction. The outer surface of the separator comes into contact with the tip of the projecting piece, and the separator is elastically supported by the projecting piece within the peripheral wall (see, for example, Patent Document 1).

JP 2007-285776 A

  However, since the protruding piece of the holding member is a rectangular plate shape as described above, the tip portion has a linear shape, and the outer surface of the cylindrical separator is in contact with one point of a straight line and a curved line, Hold the separator. For this reason, when the separator tries to move in the holding member due to vibration or the like accompanying the driving of the engine, stress concentrates on the contact point between the tip of some protruding pieces and the outer surface of the separator, There was a possibility that the projecting piece was rubbed and worn. As a result, a gap is provided between the separator and some of the projecting pieces, and the separator may move within the holding member. As a result, the reliability of the electrical connection between the electrode of the gas sensor element disposed in the separator and the terminal fitting may be reduced.

  The present invention has been made in order to solve the above-described problems, and improves the wear resistance of the protrusion of the holding member and improves the certainty of holding the separator by the holding member. It is an object of the present invention to provide a gas sensor that can maintain the reliability of electrical connection between the terminal and the metal fitting.

  According to an embodiment of the present invention, a detection element that extends in the axial direction and detects the concentration of a specific gas, a metal shell that surrounds and holds the periphery of the detection element in the radial direction, and a rear end side of the metal metal fitting And a plurality of terminal fittings that are formed in a cylindrical shape made of an insulating ceramic and are arranged in the outer cylinder to make electrical connection with the detection element. A separator to be housed, a cylindrical holding member that is disposed in a gap between the outer cylinder and the separator and holds the separator inside itself, and a cylindrical peripheral wall portion surrounding the outer surface of the separator; A plurality of first projecting pieces that project in a plate shape from the peripheral wall portion toward the inside in a radial direction, a tip end portion abuts on the outer surface of the separator, and elastically supports the separator in the peripheral wall portion. A holding member; In obtaining the gas sensor, when viewed in the axial direction from the rear end side, the tip portion of the first projecting piece is a gas sensor having an arc shape along the outer surface of the separator is provided.

  In the gas sensor of this embodiment, the tip of the first projecting piece has an arc shape along the outer surface of the separator. Therefore, when the first projecting piece contacts the outer surface of the separator, the contact range with the outer surface is set in the circumferential direction. Can be widely secured. For this reason, when the separator is about to move in the holding member due to vibration or the like accompanying the driving of the engine, the stress applied to the tip portion of some of the first projecting pieces is dispersed in the contact range, It is possible to suppress the wear of the first projecting piece occurring between the two.

  Furthermore, since the tip of the first projecting piece has an arc shape along the outer surface of the separator, the separator can be centered in the peripheral wall when the cylindrical separator is inserted and held in the holding fitting. As a result, the stress applied to the front end portions of the plurality of first projecting pieces is substantially uniform without stress being concentrated on the front end portions of some of the first projecting pieces, and the stress generated between the first projecting pieces and the outer surface of the separator. The wear of one protrusion can be suppressed for a long term.

  Therefore, the holding member can reliably hold the separator for a long period of time, and as a result, the reliability of the electrical connection between the electrode of the gas sensor element disposed in the separator and the terminal fitting can be maintained.

  In this embodiment, when the holding member is viewed from the rear end side along the axial direction, the radius of curvature of the arc shape formed by the tip of the first protrusion is the same as the radius of the outer surface of the separator. Or it may be larger. If the radius of curvature of the tip of the first protrusion is the same as or larger than the radius of the outer surface of the separator, contact with the outer surface of the separator when the separator is held This can be done in the arc part of the arc. That is, it is possible to ensure a wider contact range in the circumferential direction than in the case of contact with a single point between a conventional straight line and a curved line. Therefore, since the stress applied to the tip of the first protruding piece can be dispersed in holding the separator and the wear of the first protruding piece can be suppressed, the holding member can reliably hold the separator for a long period of time.

  In this embodiment, when the holding member is viewed from the rear end side along the axial direction, the arc-shaped curvature radius formed by the tip portion of the first protrusion is larger than the radius of the outer surface of the separator. It may be small. In the shape of the tip of the first protrusion, when the radius of curvature is smaller than the radius of the outer surface of the separator, contact with the outer surface of the separator when holding the separator is made at two points on both ends of the arc. Can be done. That is, it is possible to secure a larger number of contact portions in the circumferential direction than in the case of contact with a single point between a conventional straight line and a curved line. Therefore, since the stress applied to the tip of the first protruding piece can be dispersed in holding the separator and the wear of the first protruding piece can be suppressed, the holding member can reliably hold the separator for a long period of time.

  In the present embodiment, the holding member protrudes in a plate shape from the peripheral wall portion toward the inside at a position different from the first projecting piece in the axial direction, and a tip end portion projects from the outer surface of the separator. You may further have several 2nd protrusions which contact | abut and support the said separator elastically in the said surrounding wall part. In this case, the size of the first projecting piece in the width direction may be larger than the size of the second projecting piece in the width direction.

  Since the plate width of the first protruding piece is larger than the plate width of the second protruding piece, the first protruding piece has higher rigidity than the second protruding piece. Therefore, the separator can be reliably supported by the first projecting piece having high rigidity, and when the cylindrical separator is inserted and held in the holding metal fitting by the second projecting piece having low rigidity and spring property, the separator is You can divide roles to make them centripetal. As a result, when inserting and holding the separator in the holding metal fitting, both the centering of the separator and the support of the separator in the holding member are higher than those achieved by using only the first projecting piece. An effect can be obtained.

1 is a longitudinal sectional view of a gas sensor 1. FIG. FIG. 6 is a partial cross-sectional view seen from the side of the holding member 70. It is the figure which looked at the holding member 70 from upper direction. It is sectional drawing which looked at the holding member 70 in the arrow direction in the dashed-dotted line AA in FIG. FIG. 6 is a diagram for explaining a contact state between a projecting piece 72 of a holding member 70 and an outer surface 62 of a separator 60. FIG. 6 is a diagram for explaining a contact state between a projecting piece 172 of a holding member 170 and an outer surface 62 of a separator 60. 6 is a diagram for explaining a contact state between a protruding piece 272 of a holding member 270 and an outer surface 62 of a separator 60. FIG.

  Embodiments of a gas sensor embodying the present invention will be described below with reference to the drawings. First, the structure of the gas sensor 1 as an example will be described with reference to FIG. In FIG. 1, the axis O direction (indicated by a one-dot chain line) of the gas sensor 1 is shown as a vertical direction, and the front end portion 11 side of the detection element 10 held inside is the front end side of the gas sensor 1 and the rear end portion 12 side. The description will be made as the rear end side of the gas sensor 1.

  A gas sensor 1 illustrated in FIG. 1 is attached to an exhaust pipe (not shown) of an automobile. The gas sensor 1 is a so-called λ-type oxygen sensor that detects the presence or absence of oxygen in the exhaust gas when the tip portion 11 of the detection element 10 held inside is exposed to the exhaust gas flowing through the exhaust pipe. The gas sensor 1 includes a detection element 10, a metal shell 50, a separator 60, a holding member 70, and an outer cylinder 80.

  First, the detection element 10 will be described. The detection element 10 is a narrow and plate-shaped (strip-shaped) element extending in the direction of the axis O (in FIG. 1, the left-right direction on the paper surface is shown as the thickness direction, and the front-back direction on the paper surface is shown as the width direction). The detection element 10 is formed by laminating an element part 18 formed in a plate shape extending in the axis O direction and a heater 19 formed in a plate shape extending in the axis O direction.

  The element unit 18 includes a detection unit (not shown) in which a pair of porous electrodes are arranged on both surfaces of a plate-shaped solid electrolyte body so as to sandwich the solid electrolyte body. The solid electrolyte body is formed of zirconia in which yttria or calcia is solid-solved as a stabilizer, and the porous electrode is formed mainly of Pt. The detection electrode and the reference electrode are respectively connected to one of four electrode pads 13 (two of which are shown in FIG. 1) disposed on the outer surface of the rear end portion 12 of the detection element 10. .

  The heater 19 is formed by sandwiching a heating resistor pattern (not shown) mainly composed of Pt between insulating substrates mainly composed of alumina. Both ends of the heating resistor pattern are connected to one of the electrode pads 13, respectively. Further, the entire surface of the tip 11 of the detection element 10 including the surface of the detection electrode exposed to the exhaust gas is covered with the protective layer 9.

  Next, the metal shell 50 is a metallic cylindrical body having a screw portion 51 formed on the outer surface for fixing to the exhaust pipe, and has a cylindrical hole 59 penetrating in the direction of the axis O. A shelf 57 formed as an inwardly tapered surface protruding radially inward is provided on the tip side in the cylindrical hole 59. The metal shell 50 is configured to surround and hold the periphery of the detection element 10 inserted through the cylindrical hole 59 in the radial direction. Specifically, the front end portion 11 provided with the detection portion (not shown) of the element portion 18 protrudes from the front end side of the cylindrical hole 59 to the outside, and the rear end portion 12 provided with the electrode pad 13 is the cylindrical hole. The detection element 10 is fixed inside the metal shell 50 in a state of protruding from the rear end side of 59 to the outside.

  Inside the cylindrical hole 59 of the metal shell 50, the metal holder 55, the ceramic holder 56, the filling layers 53 and 58, and the sleeve 20 are arranged in this order so as to surround the circumference of the detection element 10 in the radial direction. It is laminated from the side toward the rear end side. The metal holder 55 is formed in a bottomed cylinder shape, and the edge portion of the bottom wall is disposed on the shelf 57 of the metal shell 50 and is positioned in the cylinder hole 59. A hole is provided in the bottom wall of the metal holder 55, and the detection element 10 is inserted through the hole. The ceramic holder 56 is formed in an annular shape, and is disposed on the bottom wall side in the metal holder 55 with the detection element 10 inserted through the ceramic holder 56. Further, a part of the filling layer 53 made of talc powder is filled in a compressed state on the opening side in the metal holder 55. The detection element 10 is fixed in the metal holder 55 by the filling layer 53 and airtightness between the inner surface of the metal holder 55 and the outer surface of the detection element 10 is ensured.

  The filling layer 58 is filled in a compressed state on the rear end side of the metal holder 55 in the cylindrical hole 59. Thereby, the detection element 10 is fixed in the metal shell 50, and airtightness between the inner surface of the cylindrical hole 59 and the outer surface of the detection element 10 is ensured. The sleeve 20 disposed on the rear end side of the filling layer 58 is a ceramic cylindrical body disposed so as to surround the circumference of the detection element 10 in the radial direction. A caulking ring 21 is disposed between the sleeve 20 and the rear end portion 54 of the metal shell 50. The rear end portion 54 of the metal shell 50 is crimped so as to press the sleeve 20 against the distal end side of the gas sensor 1 via the crimping ring 21. The filling layers 53 and 58 are compressed between the sleeve 20 and the ceramic holder 56 in the metal holder 55 locked to the shelf 57 by caulking.

  The sleeve 20 is provided with a pair of guide portions 23 projecting from the rear end of the cylindrical portion toward the rear end side along the axis O direction. Grooves that guide both ends of the detection element 10 in the width direction (front and back direction in FIG. 1) are inserted into the inner side surface of each guide portion 23 from the inner periphery of the hole of the cylindrical portion through which the detection element 10 is inserted. 25 is provided. In the state where the sleeve 20 is accommodated in the metal shell 50, the four electrode pads 13 provided on the rear end portion 12 of the detection element 10 are exposed to the outside from between the pair of guide portions 23.

  In addition, a bottomed cylindrical double protector (external protector 7 and internal protector 8) is attached to the outer periphery on the front end side of the metal shell 50 by welding or the like. The external protector 7 and the internal protector 8 are each formed from a metal (for example, stainless steel) having a plurality of holes, and covers and protects a detection unit (not shown) provided at the distal end portion 11 of the detection element 10.

  Next, the separator 60 is an alumina cylinder having a cylindrical shape. A first accommodating portion 61 that accommodates the rear end portion 12 of the detection element 10 together with the guide portion 23 of the sleeve 20 is formed on the distal end side in the axis O direction of the separator 60, and is open to the distal end surface of the separator 60. The 1st accommodating part 61 is connected to the 2nd accommodating part 65 divided into four in the rear end side of the axis line O direction, respectively. Each second accommodating portion 65 is opened at the rear end surface of the separator 60. In other words, the separator 60 penetrates in the direction of the axis O through the first housing portion 61 and the second housing portion 65. In addition, a flange portion 63 is formed on the rear end side of the separator 60 so as to protrude radially outward from the outer surface 62.

  The separator 60 accommodates four connection terminals 40 (two of which are shown in FIG. 1) for electrical connection with the electrode pads 13 of the detection element 10. The distal end portions of the connection terminals 40 are arranged so as not to contact each other in the first housing portion 61, and each contact with the electrode pad 13. The rear end portions of the connection terminals 40 are accommodated in the individual second accommodating portions 65, respectively, and the mutual insulation is ensured. Further, in the second accommodating portion 65, the rear end portion of each connection terminal 40 is pulled out from the gas sensor 1 and connected to the core wires of four lead wires 66 that are responsible for connection with an external device (not shown). ing.

  The outer surface 62 is surrounded and held by the cylindrical holding member 70, and the separator 60 is positioned in the outer cylinder 80 by fixing the holding member 70 to the outer cylinder 80. The holding member 70 is a metal member formed in a cylindrical shape, and includes a plurality of projecting pieces 72 and 73 projecting radially inward. The separator 60 is elastically supported by the projecting pieces 72 and 73 in the holding member 70. Details of the structure of the holding member 70 will be described later.

  The outer cylinder 80 is made of a metal and is formed in a cylindrical shape, and a front end portion is joined and fixed to the outer periphery of the rear end side (upper side in FIG. 1) of the metal shell 50 by laser welding or the like. The rear end portion of the outer cylinder 80 has a reduced outer diameter, and a fluoro rubber grommet 90 is fitted into the opening on the rear end side. The grommet 90 is fixed to the outer cylinder 80 by caulking the rear end portion of the outer cylinder 80 and closes the opening on the rear end side. In the grommet 90, four insertion holes 91 (two of which are shown in FIG. 1) for taking out the four lead wires 66 drawn out from the second accommodating portion 65 of the separator 60 to the outside are formed. Yes.

  The separator 60 has a rear end surface in contact with the front end surface of the grommet 90, and the flange portion 63 is in contact with the holding member 70. In this state, the outer periphery of the outer cylinder 80 is crimped, so that the holding member 70 is positioned and fixed in the outer cylinder 80. Therefore, the separator 60 is also elastically supported by the projecting pieces 72 and 73 in the holding member 70, and a portion from the flange portion 63 to the rear end surface is an opening 74 (see FIG. 2) on the rear end side of the holding member 70. It is sandwiched between the front end surfaces of the grommets 90 and is positioned and held in the outer cylinder 80.

  Next, the holding member 70 will be described with reference to FIGS. The holding member 70 shown in FIGS. 2 to 4 is in a state before the gas sensor 1 is assembled. For convenience, the axial direction of the holding member 70 is indicated by a one-dot chain line P in FIG. In FIG. 2, the front end side of the holding member 70 when assembled to the gas sensor 1 will be described as the lower side of the drawing, and the rear end side will be described as the upper side of the drawing. 3 and 4, the position where the outer surface 62 of the separator 60 is disposed when the holding member 70 is assembled to the gas sensor 1 is indicated by a two-dot chain line.

  The holding member 70 shown in FIG. 2 is a metal member formed in a cylindrical shape. The holding member 70 has a cylindrical peripheral wall portion 71 for surrounding the outer surface 62 (see FIG. 1) of the separator 60. The peripheral wall 71 is formed so that the outer diameter is slightly smaller than the inner diameter of the outer cylinder 80. The height of the peripheral wall 71 (length in the direction of the axis P) is substantially the same as the size of the portion (see FIG. 1) on the tip side in the direction of the axis O with respect to the flange 63 of the separator 60. As shown in FIG. 3, the opening 74 of the peripheral wall portion 71 on the rear end side when the holding member 70 is assembled to the gas sensor 1 is folded back inward in the radial direction. Further, the opening 75 on the distal end side of the peripheral wall portion 71 is widened outward so that the outer diameter of the peripheral wall portion 71 is slightly widened.

  As shown in FIG. 2, the holding member 70 has two types of projecting pieces 72 and 73 that project from the peripheral wall portion 71 toward the inside in the radial direction. As shown in FIGS. 2 and 3, the projecting piece 73 is configured so that the opening 74 on the rear end side of the peripheral wall portion 71 turned back inward in the radial direction protrudes in a plate shape at six locations in the circumferential direction. It is arrange | positioned inside the surrounding wall part 71 by folding back to the front end side. Further, the projecting piece 73 is bent radially inward from the approximate center in the projecting direction, and thus the projecting piece 73 projects inward in the radial direction. At this time, the distal end portion 77 on the distal end side of the projecting piece 73 is positioned radially inward from the position where the outer surface 62 of the separator 60 is disposed when the holding member 70 is assembled to the gas sensor 1. The protruding piece 73 is bent.

  Moreover, the front-end | tip part 77 of the protrusion 73 is formed in the circular arc shape by which the both ends of the board width direction protruded and the center part was scooped out in arc shape. In the present embodiment, the tip 77 has an arcuate radius of curvature R3 when the tip 77 is viewed along the thickness direction so as to be the same as the radius R1 in the circumferential direction of the outer surface 62 of the separator 60. Is formed. Further, both ends 79 of the tip 77 of the projecting piece 73 are rounded. The holding member 70 is manufactured by pressing an iron plate using a metal mold. However, the corner portion is rounded by chamfering, so that consumption of the metal mold can be suppressed.

  As shown in FIGS. 2 and 4, the projecting piece 72 protrudes in a plate shape from six locations in the circumferential direction toward the inside in the radial direction at the tip side of the peripheral wall portion 71. Specifically, when the peripheral wall portion 71 is viewed from the side, two cuts are formed along the direction of the axis P, and both ends on the leading end side of the cuts are connected and cut into a circular arc shape. Is pushed inward in the radial direction, and the projecting piece 72 is formed. At this time, the distal end portion 76 on the distal end side of the projecting piece 72 is positioned radially inward from the position where the outer surface 62 of the separator 60 is disposed when the holding member 70 is assembled to the gas sensor 1. The protrusion 72 is pushed in.

  Similarly to the above, the tip portion 76 of the projecting piece 72 is also formed in an arc shape in which both ends in the plate width direction protrude and the center portion is formed in an arc shape. In the present embodiment, similarly, the distal end portion 76 has an arcuate radius of curvature R2 when the distal end portion 76 is viewed along the thickness direction so as to have the same size as the radius R1 of the outer surface 62 of the separator 60. Is formed. Further, both ends 78 of the tip 76 of the projecting piece 72 are also rounded. In press working using a mold for producing the holding member 70, the projecting piece 72 is punch-pressed from the side on the peripheral wall portion 71, and the portion that becomes the projecting piece 72 is formed inside while forming the above-mentioned notch. It is formed by pushing. Since both ends 78 of the distal end portion 76 of the projecting piece 72 are rounded by chamfering, the consumption of the mold can be suppressed as described above.

  The protruding pieces 72 and 73 formed in this way are arranged such that the protruding piece 72 is closer to the distal end side in the axis P direction than the protruding piece 73. Further, the size B of the projecting piece 72 in the plate width direction is formed larger than the size C of the projecting piece 73 in the plate width direction. The protruding piece 72 and the protruding piece 73 have the same thickness, and the protruding piece 73 narrower than the protruding piece 72 is configured to have lower rigidity than the protruding piece 72.

  Further, as described above, the tip end portions 76 and 77 of the projecting pieces 72 and 73 of the holding member 70 have arc-shaped curvature radii R2 and R3 that are the same as the radius R1 of the outer surface 62 of the separator 60, respectively. ing. Therefore, as shown in FIG. 5, in the state where the separator 60 is held by the holding member 70, the distal end portion 76 of the projecting piece 72 extends with respect to the outer surface 62 of the separator 60 over the entire arc-shaped arc portion. Contact. Thereby, the range which each protrusion piece 72 contacts with the outer side surface 62 of the separator 60 can be ensured more widely in the circumferential direction than the case of the contact by the point of the conventional straight line and a curve. For this reason, in the holding of the separator 60, the stress applied to the tip 76 of the protruding piece 72 is dispersed. Therefore, even when the separator 60 receives vibration associated with driving of the engine to which the gas sensor 1 is attached and the separator 60 is about to move, between the tip 76 of the projecting piece 72 and the outer surface 62 of the separator 60. Therefore, the wear (wear) of the projecting piece 72 can be suppressed. The same applies to the protruding piece 73.

  In addition, since the tip portions 76 and 77 of the projecting pieces 72 and 73 are arc-shaped, when the separator 60 having the cylindrical outer surface 62 is inserted and held in the holding member 70, the outer surface 62 is the tip portion 76. , 77, and its own axis is aligned with the axis of the holding member 70. That is, since the plurality of projecting pieces 72 and 73 having the arcuate tip portions 76 and 77 protrude radially inward from the peripheral wall portion 71, the holding member 70 holds the separator 60 held inside the peripheral wall portion 71. Can be centripetal. As a result, the stress applied to the tip portions of the plurality of projecting pieces 72 becomes substantially uniform without stress being concentrated on the tip portions of the projecting pieces 72, and the wear of the projecting pieces 72 generated between the outer surfaces of the separators 60. Can be suppressed even in the long term.

  Therefore, the holding member 70 can reliably hold the separator 60 for a long period of time. As a result, the reliability of the electrical connection between the electrode pad 13 disposed in the separator 60 and the connection terminal 40 can be maintained.

  As described above, the protrusion 73 has higher rigidity than the protrusion 72. Therefore, the holding member 70 reliably supports the separator 60 by the protruding piece 72 having high rigidity, and when the separator 60 is inserted and held in the holding member 70 by the protruding piece 73 having low rigidity and springiness, You can divide roles to make them centripetal. Thereby, when the separator 60 is inserted into and held in the holding member 70, the centering of the separator 60 and the support of the separator 60 in the holding member 70 are achieved compared to the case where only the projecting piece 72 is achieved. Both higher effects can be obtained.

  Further, the projecting piece 72 is arranged on the tip side in the axis P direction from the projecting piece 73. Thereby, when the separator 60 is inserted and arranged from the rear end side of the holding member 70 by the projecting piece 73 arranged on the rear end side in the axis P direction, the separator 60 first comes into contact with the holding member 70 and is separated. When the most part of the separator 60 is inserted into the holding member 70, the separator 60 is securely held by the projecting piece 72 arranged on the tip end side in the axis P direction. .

  In addition, this invention is not limited to said embodiment, You may add a various change in the range which does not deviate from the summary of this invention. For example, the protrusions 72 and 73 of the holding member 70 do not have to be formed at the same position when viewed along the axis P. Further, the number of the projecting pieces 72 and the projecting pieces 73 is not limited to six, but may be three or more. Further, the protruding piece 73 may be formed by cutting out the peripheral wall portion 71 in the same manner as the protruding piece 72. Alternatively, the projecting piece 72 may be formed like the projecting piece 73 by projecting a part of the opening 75 on the distal end side of the holding member 70 and turning back inward in the radial direction. Alternatively, the configuration of the protrusion 73 may be omitted, and only the protrusion 72 may be formed. Further, the projecting pieces 72 and 73 do not have to be formed by cutting out the peripheral wall portion 71. For example, a plate piece having a tip formed in an arc shape may be joined to the peripheral wall portion 71.

  In the present embodiment, the radii of curvature R2 and R3 of the tip portions 76 and 77 of the projecting pieces 72 and 73 are the same as the radius R1 of the outer surface 62 of the separator 60. Not only this but the curvature radius R4 of the front-end | tip part 176 of the protrusion 172 which protrudes radially inside from the surrounding wall part 171 like the holding member 170 shown in FIG. 6, for example, is radius R1 of the outer side surface 62 of the separator 60. It may be smaller. In this case, the outer side surface 62 of the separator 60 is in contact with the end portions on the both sides in the plate width direction of the tip end portion 176 of the projecting piece 172 (parts surrounded by a dotted line D in the drawing). That is, since one protrusion piece 172 contacts the outer surface 62 of the separator 60 at two points, more contact portions can be secured in the circumferential direction than in the case of contact with a single point between a conventional straight line and a curved line. It is possible to disperse the stress applied to the front end portion 176. Therefore, the wear of the projecting piece 172 due to friction can be suppressed, and the holding of the separator 60 by the holding member 170 can be reliably maintained for a long time.

  Further, like the holding member 270 shown in FIG. 7, the radius of curvature R5 of the tip 276 of the projecting piece 272 protruding radially inward from the peripheral wall 271 is made larger than the radius R1 of the outer surface 62 of the separator 60. May be. In this case, the tip 276 of the projecting piece 272 that contacts the outer surface 62 of the separator 60 is in line contact in the vicinity of the center in the plate width direction (the part surrounded by the dotted line E in the figure) of the arc-shaped arc part. It will be in the state. That is, since the range of contact with the outer surface 62 of the separator 60 can be secured wider in the circumferential direction per one projecting piece 272 than in the case of contact with a single point between a conventional straight line and a curved line, the distal end portion 276 of the projecting piece 272 is secured. Can be dispersed. Therefore, the wear of the protruding piece 272 due to friction can be suppressed, and the holding of the separator 60 by the holding member 270 can be reliably maintained over a long period of time.

  Moreover, in the said embodiment, the gas sensor 1 which is a (lambda) type oxygen sensor was illustrated as one aspect | mode of the gas sensor which concerns on this invention. For example, a gas sensor using a holding member that houses a connection terminal for taking out the output of a detection element, such as an oxygen gas sensor, a full-range air-fuel ratio sensor, a NOx sensor, or an HC sensor, and holds the separator in an outer cylinder. The present invention may be applied.

  In the present invention, the connection terminal 40 corresponds to a “terminal fitting”. The protruding piece 72 and the protruding piece 73 correspond to a “first protruding piece” and a “second protruding piece”, respectively.

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Detection element 40 Connection terminal 50 Main metal fitting 60 Separator 62 Outer side surface 70 Holding member 71 Peripheral wall part 72,73,172,272 Projection piece 76,77,176,276 Tip part 80 Outer cylinder 90 Grommet

Claims (4)

A detection element that extends in the axial direction and detects the concentration of a specific gas;
A metal shell that surrounds and holds the periphery of the detection element in the radial direction;
A cylindrical outer cylinder attached to the rear end side of the metal shell,
A separator formed in a cylindrical shape made of an insulating ceramic, disposed in the outer cylinder, and containing a plurality of terminal fittings for electrical connection with the detection element inside itself;
A cylindrical holding member that is disposed in a gap between the outer cylinder and the separator and holds the separator inside thereof; a cylindrical peripheral wall portion that surrounds an outer surface of the separator; A holding member having a plurality of first projecting pieces that protrude in a plate shape toward the inside in a direction, a front end portion thereof abuts on the outer surface of the separator, and elastically supports the separator in the peripheral wall portion;
In a gas sensor comprising:
The gas sensor according to claim 1, wherein when viewed from the rear end side along the axial direction, the tip portion of the first projecting piece has an arc shape along the outer surface of the separator.   When the holding member is viewed from the rear end side along the axial direction, the arc-shaped curvature radius formed by the tip of the first projecting piece is equal to or larger than the radius of the outer surface of the separator. The gas sensor according to claim 1.   When the holding member is viewed from the rear end side along the axial direction, an arc-shaped radius of curvature formed by a tip portion of the first projecting piece is smaller than a radius of the outer surface of the separator. The gas sensor according to claim 1. The holding member protrudes in a plate shape from the peripheral wall portion toward the inside at a position different from the first projecting piece in the axial direction, and a tip portion abuts on the outer surface of the separator. A plurality of second projecting pieces that elastically support the inner wall in the peripheral wall portion,
4. The gas sensor according to claim 1, wherein a size of the first projecting piece in the width direction is larger than a size of the second projecting piece in the width direction. 5.

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