JP2012149960A - Gas sensor unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor unit with which connection completion between a gas sensor and a sensor cap is clearly learned by a click feeling, both of the gas sensor and the sensor cap are hard to be detached, and seal is certain.SOLUTION: A gas sensor unit 600 is constituted by including: a gas sensor 21 with a gas detection element 22, cylindrical casings 23, 25 which surround the surroundings of the gas detection element and have a recess 25e, and an output terminal 35; and a sensor cap having cylindrical cap bodies 752a, 752b having a side wall 752b and an internal space 752h, a through hole 752e provided at a position corresponding to the recess of the side wall, and an elastic member 757 which is arranged in the through hole, and engaged into the recess to fix the sensor cap 700 to the gas sensor; and assembling the sensor cap from the rear end side of the gas sensor. The gas sensor unit 600 includes a seal member 755 which seals between the outer surfaces of the casings and the inner surfaces of the cap bodies, and diameters Dof the outer surfaces of the casings are smaller than the minimum inner diameter Dof the elastic member.

Description

  The present invention relates to a gas sensor unit in which a gas sensor having a gas detection element and a sensor cap attached to the gas sensor and transmitting the output of the gas sensor to the outside are combined.

  Conventionally, various gas sensors having gas detection elements have been proposed. Examples of these gas sensors include those having a gas detection element made of a solid electrolyte having oxygen ion conductivity. The gas sensor is attached to an attachment object such as an exhaust pipe or an engine head of an internal combustion engine, and detects the concentration of a specific gas (for example, oxygen) in the exhaust gas with a pair of electrodes disposed on the front end side of the gas detection element. .

Generally, in such a gas sensor, the gas detection element outputs a voltage or a current corresponding to the detected gas concentration, and this output is taken out from a lead wire connected to the gas detection element.
Therefore, a gas sensor unit has been developed in which a sensor cap is detachably attached to the rear end of the gas sensor and the sensor output is taken out from the sensor cap (see Patent Document 1). In this gas sensor unit, a cylindrical terminal member is provided on the rear end side of the gas sensor, and a cylindrical cap terminal inserted into the terminal member is provided on the sensor cap side to electrically connect them.
In addition, a technique has been developed in which an external connector (second connector) for taking out the sensor output to the outside is attached to the sensor body by a substantially U-shaped elastically deformable presser pin (see Patent Document 2). In this technique, the presser pin is externally fitted to the connector (first connector) on the sensor body side, and when the external connector is inserted into the connector, the external connector is inserted while expanding the presser pin. The presser pin returns to the original position to a depth corresponding to the locking portion to lock the external connector.

JP 2009-63330 A JP 2002-340846 A

In the case of the gas sensor unit described in Patent Document 1 described above, when the sensor cap is repeatedly attached and detached, the cap terminal is repeatedly inserted into and extracted from the terminal member, so that the pullout strength may gradually decrease. Further, in the case of the gas sensor unit described in Patent Document 1, a cap terminal is provided with a reduced diameter portion, and a terminal member is provided with a cut-and-raised portion extending inwardly. A feeling is generated, and the completion of the insertion of the cap terminal can be known. However, the cap terminal also has a cylindrical edge portion outside the above-described insertion portion, and when the sensor cap is attached or detached, this edge portion rubs against the ceramic enclosure on the rear end side of the gas sensor to give a sense of resistance. Therefore, the click feeling may not be clearly obtained.
In the case of the sensor described in Patent Document 2, the protrusion at the tip of the external connector is pushed into a seal member disposed on the surface facing the rear end of the connector to seal between the external connector and the connector. In this case, when the external connector is inserted into the connector, the protrusion hits the holding pin and the protrusion is damaged, and the sealing performance between the seal member and the protrusion may be reduced. And when sealing performance falls, there exists a possibility that malfunctions, such as a short circuit, may generate | occur | produce in a sensor because water etc. penetrate | invade between an external connector and a connector and reach | attain a terminal.

  Therefore, the present invention provides a gas sensor unit in which a gas sensor and a sensor cap are combined. In the gas sensor unit, the completion of connection between the gas sensor and the sensor cap can be clearly recognized with a click feeling, and the gas sensor and the sensor cap are difficult to separate. The purpose is to provide a gas sensor unit that can securely seal with.

  In order to solve the above-described problems, a gas sensor unit of the present invention includes a gas detection element that extends in the axial direction and whose tip is exposed to the gas to be measured, surrounds the periphery of the gas detection element, and is radially disposed on its outer surface. A gas sensor comprising: a cylindrical casing having a concave portion recessed inward; and an output terminal disposed on a rear end side of the gas detection element to electrically extract a sensor output of the gas detection element; and the gas sensor A sensor cap to be assembled, having a side wall extending in the axial direction so as to straddle the recess, and a cylindrical cap body having an internal space for accommodating the output terminal, and corresponding to the recess among the side walls A through hole provided at a position to be engaged with, and an elasticity that is disposed in the through hole and that engages with the recess to fix the sensor cap to the gas sensor. And attaching the sensor cap from the rear end side of the gas sensor in a state where the elastic member is externally fitted from the outside of the through hole of the sensor cap. A gas sensor unit formed by engaging a member, comprising a sealing material that seals between an outer surface of the casing and an inner surface of the cap body while facing the internal space on the rear end side from the through hole, The diameter of the outer surface of the casing at a position in contact with the sealing material is smaller than the minimum inner diameter of the elastic member.

According to such a gas sensor unit, when the sensor cap is assembled from the rear end side of the gas sensor, when the elastic member is fitted into the concave portion of the casing through the through hole, the engaging member generates a sound or generates an impact. Therefore, it is possible to clearly recognize the completion of connection between the gas sensor and the sensor cap with a click feeling. In addition, since the sensor cap is fixed to the gas sensor in a state where a part of the elastic member is firmly fitted in the concave portion of the casing, the gas sensor and the sensor cap are not easily detached.
Further, the diameter of the outer surface of the casing at the position in contact with the sealing material is smaller than the minimum inner diameter of the elastic member, and the sealing material is located on the rear end side from the through-hole (that is, the position where a part of the elastic member protrudes toward the internal space). Has been placed. For this reason, when the gas sensor is assembled to the sensor cap, the elastic member does not come into contact with the outer surface of the casing having a diameter smaller than the minimum inner diameter of the elastic member, and the outer surface of the casing is prevented from being damaged. Since it is possible to prevent the sealing performance from being lowered, it is possible to suppress the entry of water or the like from the outside into the internal space, and to prevent the output terminal accommodated in the internal space from being short-circuited. Furthermore, since the inner diameter of the sealing material is smaller than the minimum inner diameter of the elastic member, a relatively small sealing material can be used, and the cost of an expensive sealing material such as an O-ring is reduced.

The sensor cap has a cap terminal that is electrically connected to the output terminal while facing the internal space, and the output terminal protrudes from the rear end of the casing while being biased toward the rear end, and is connected to the cap terminal. The cap terminal may be in contact with the pressed terminal.
According to such a gas sensor, the sensor-side output terminal pressed by the cap terminal is urged toward the cap terminal by a repulsive force, so that the sensor-side output terminal and the cap terminal are electrically and reliably connected to each other. Can improve the contact reliability.

The elastic member may include three or more reduced diameter portions that engage with the concave portion, and the through hole may be provided at a position corresponding to the reduced diameter portion.
According to such a gas sensor unit, since the gas sensor is supported by the sensor cap at three or more locations in the radial direction, the two are less likely to be displaced from each other in the radial direction after they are attached.

The outer diameter of the sensor cap around the through hole may be larger than the outer diameter of the elastic member.
According to such a gas sensor unit, the elastic member does not protrude outside the sensor cap, and it is possible to prevent the engaging member from being damaged or dropped due to an external impact.

  According to the present invention, in a gas sensor unit in which a gas sensor and a sensor cap are combined, the completion of connection between the gas sensor and the sensor cap can be clearly recognized with a click feeling, and the gas sensor and the sensor cap are difficult to come off. Can be reliably sealed.

It is sectional drawing which follows the axial direction of the gas sensor which the gas sensor unit concerning embodiment of this invention has. It is a perspective view of the gas detection element rear end vicinity before and after attaching a cover. It is sectional drawing which follows the axial direction of a sensor cap. It is a top view of an engaging member. It is a perspective view of a sensor cap. It is sectional drawing which follows the axial direction of the gas sensor unit formed by attaching a sensor cap to a gas sensor. It is a top view which shows the modification of an engaging member. It is a top view which shows another modification of an engaging member.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view along the axis O direction of a gas sensor 21 included in a gas sensor unit according to a first embodiment of the present invention. The gas sensor 21 is an oxygen sensor that measures the oxygen concentration in the exhaust gas. The gas sensor 21 does not have a heater, is attached to the engine head, and is used after being heated to the activation temperature by receiving heat from the exhaust gas.
The gas sensor 21 includes a gas detection element 22, a cover 23, a terminal member 24, a metal shell 25, an output terminal 35, an elastic body (coil spring) 38, and a protector 40. In the following description, in the direction along the axis O, the side to which the sensor cap is attached will be referred to as the rear end side, and the opposite side will be referred to as the front end side.

The gas detection element 22 is made of a solid electrolyte having oxygen ion conductivity, has a bottom having an opening 22h at the rear end while the front end portion 22a is closed, and has a cylindrical shape extending in the axis O direction. In addition, a flange-like protruding portion 22b is formed in the radially outer side in the center of the gas detection element 22 in the axis O direction, and the tip-facing surface of the protruding portion 22b has a taper shape with a diameter decreasing toward the tip. Yes.
An outer electrode 28 is formed on the outer peripheral surface of the distal end portion 22 a of the gas detection element 22. The outer electrode 28 is made of porous Pt or Pt alloy. The outer electrode 28 is provided up to the front end side surface of the protruding portion 22b, and is electrically connected to the inner peripheral receiving portion 25a of the metal shell 25 via the rear end edge of the protector 40 as will be described later. Therefore, the potential of the outer electrode 28 can be taken out from the metal shell 25. That is, the outer electrode 28 is in a state of being electrically grounded (grounded) with respect to the metal shell. On the other hand, an inner electrode 29 is also formed on the inner peripheral surface of the gas detection element 22. This inner electrode 29 is also made of Pt or a Pt alloy formed porous.
As the solid electrolyte constituting the gas detection element 22, for example, ZrO _{2 in} which Y ₂ O ₃ or CaO is dissolved is representative, but other alkaline earth metal or rare earth metal oxides can be used. A solid solution with ZrO ₂ may be used. Furthermore, HfO ₂ may be contained therein.

The metal shell 25 is made of metal (specifically, SUS430, S17C, S25C, etc.) and is formed in a cylindrical shape. The metal shell 25 includes an inner periphery receiving portion 25a for supporting the protruding portion 22b of the gas detection element 22 and has a tapered inner periphery receiving a diameter decreasing toward the tip side (downward in FIG. 1). The portion 25a is circumferentially provided so as to protrude radially inward from the inner peripheral surface.
Further, a screw portion 25b for attaching the gas sensor 21 to the exhaust pipe (attachment target body) is formed outside the metal shell 25, and on the rear end side (upward in FIG. 1) of the screw portion 25b. Is provided with a collar portion (hexagonal portion) 25c that engages an attachment tool for screwing the screw portion 25b into the exhaust pipe. The flange portion 25 c protrudes radially outward from the other outer surface of the metal shell 25. An annular gasket 27 for sealing when the gas sensor 21 is attached to the exhaust pipe is fitted to the tip-facing surface of the flange portion 25c.
Further, a concave portion 25e recessed radially inward for fixing a sensor cap 700 to be described later is provided continuously in the circumferential direction on the outer surface of the rear end of the metal shell 25 from the flange portion 25c.

Inside the metal shell 25, a rear end side of a cylindrical protector 40 that covers a front end portion 22 a of a gas detection element 22 described later is accommodated, and the front end side of the protector 40 protrudes from the front end of the metal shell 25. Further, the rear end edge 40f of the protector 40 is radially increased outwardly in a taper shape, and this tapered portion 40f is formed by the tip side surface of the protruding portion 22b of the gas detection element 22 and the inner peripheral receiving portion 25a of the metal shell 25. The protector 40 is fixed in the clamped state.
The protector 40 is a metal bottomed cylindrical body, and has a plurality of vent holes 40a on the tip (bottomed portion) side for introducing exhaust gas in the exhaust pipe into the gas sensor 21. And the front-end | tip part 22a of the gas detection element 22 protruded from the front-end | tip of the metal shell 25 is exposed to exhaust gas (measuring gas) through the vent hole 40a while being surrounded by the protector 40, and is specified in the measuring gas. Detect the gas concentration.

A cylindrical terminal member 24 having a substantially C-shaped cross section perpendicular to the axis O is inserted into the opening 22 h at the rear end of the gas detection element 22. In addition, a stop portion 24a formed in the shape of a petal that is orthogonal to the axis O and extends radially outward is provided at the rear end of the terminal member 24 (see FIG. 2). Then, the terminal member 24 is pushed in until the stopper 24 a contacts the rear end surface 22 e of the gas detection element 22, so that the terminal member 24 is fixed to the gas detection element 22 while being electrically connected to the inner electrode 29. . Since the terminal member 24 is formed in a cylindrical shape, a reference gas (outside air) taken into an internal space 752h (see FIGS. 3 and 5) of the sensor cap 700 described later is passed inside the gas detection element 22 (inner electrode). 29).
The terminal member 24 is made of, for example, Inconel (UK Inconel, trade name), and can be formed by integral molding by pressing using a single metal plate having a predetermined shape. For this reason, it is easy to form and low cost.

The cover 23 is made of an insulating ceramic (specifically, alumina or the like), and is formed in a cylindrical shape having a through hole 23h in its rear end surface 23b. The cover 23 is a ceramic powder 30 formed of talc in such a form that the front end portion 23a of the cover 23 surrounds the portion of the gas detection element 22 on the rear end side of the protrusion 22b. At the same time, it is held so as to be interposed between the gas detection element 22 and the metal shell 25.
In this embodiment, the cover 23 is located on the outermost radial side of the gas sensor 21 at a position on the rear end side of the metal shell 25, and the cover 23 and the metal shell 25 correspond to a “casing” in the claims. . Therefore, the outer diameter D ₂ of the cover 23 corresponds to the "diameter of the outer surface of the casing of the position in contact with the sealing member" in the claims. The cover 23 is in contact with a seal material (O-ring) 755 described later.

  An output terminal 35 is accommodated inside the cover 23. The output terminal 35 has a flange portion 35a having a diameter larger than that of the through hole 23h, a cylindrical protrusion 35b having a diameter smaller than that of the through hole 23h and extending to the rear end of the flange portion 35a, and a conductive member provided at the rear end of the protrusion 35b. And has a hemispherical contact portion 35e, and is formed in a hat shape as a whole. In the first embodiment, the output terminal 35 is formed by integral molding by pressing using a metal plate, and the whole has conductivity.

Here, in the output terminal 35, the flange 35 a is accommodated inside the cover 23 and covers the opening 22 h of the gas detection element 22, and the protrusion 35 b is arranged inside the through hole 23 h. A coil spring 38 that expands and contracts in the axial direction O is disposed between the stopper 24 a and the flange 35 a at the rear end of the gas detection element 22, and the output terminal 35 is moved toward the rear end by the elastic force of the coil spring 38. It is energized. With this elastic force, the output terminal 35 can advance and retract in the axial direction O. When the sensor cap 700 is not attached to the cover 23, the flange portion 35a is in contact with the front end facing surface of the rear end surface 23b, and the contact portion 35e is axial with respect to the rear end surface 23b (rear end facing surface) of the cover 23. It protrudes rear side protruding height h ₁ to O.

The coil spring 38 is in contact with the flange portion 35a and the stopper portion 24a, and electrical connection from the inner electrode 29 to the contact portion 35e is realized. Thereby, the output terminal 35 can electrically extract the sensor output of the gas detection element 22.
In the first embodiment, the entire cover 23 is made of an insulating material. However, the cover 23 and the output terminal 35 need only be insulated without being electrically connected. A portion (a peripheral edge of the through-hole 23h) that contacts with the cover 23 may be made of an insulating material, and the other portion of the cover 23 may be made of metal.

FIG. 2 is a perspective view of the vicinity of the rear end of the gas detection element 22 before the cover 23 is attached. Before and after the cover 23 is attached, the terminal member 24 is inserted into the opening 22h at the rear end of the gas detection element 22, and the stopper 24a at the rear end of the terminal member 24 contacts the rear end surface 22e at the rear end of the gas detection element 22. The terminal member 24 is inserted into the opening 22h (FIG. 2A).
Then, the cover 23 is attached by inserting the cover 23 inside the caulking portion 25d of the metal shell 25 and caulking as described later (FIG. 2B).
2A is the state before the cover 23 is inserted into the metal shell 25, the swaged portion 25d is not originally formed and the rear end of the metal shell 25 should be straight. However, for the sake of explanation, the caulking portion 25d will be described with reference to the figure after formation.

  Such a gas sensor 21 can be manufactured as follows. First, as shown in FIG. 1, the protector 40 is inserted into the metal shell 25 from the rear end side of the metal shell 25, and the tapered portion 40 f of the protector 40 is locked inside the metal shell 25. Next, when the gas detection element 22 provided with the outer electrode 28 and the inner electrode 29 is inserted into the protector 40, the front end side surface of the protrusion 22b of the gas detection element 21 is formed on the rear end facing surface of the taper portion 40f of the protector 40. (Tip facing surface) abuts. In this state, a predetermined amount of ceramic powder 30 is filled in the gap portion between the metal shell 25 and the gas detection element 22. Further, after inserting the terminal member 24 inside the gas detection element 22, the coil spring 38 is placed on the stopper 24 a, and the output terminal 35 is placed on the rear end of the coil spring 38. Next, the cover 23 is inserted so that the distal end portion 23a is interposed between the gas detection element 22 and the metal shell 25 and the protrusion 35b is positioned inside the through hole 23h, and contacts the ceramic powder 30. Let Next, the cover 23 is pressurized toward the distal end side, and the crimped portion 25d is crimped with a crimping ring 32 interposed between the crimped portion 25d of the metal shell 25 and the cover 23 under the pressurized state. . In this way, the component parts are fixed together.

Next, the sensor cap 700 will be described with reference to FIGS. FIG. 3 is a cross-sectional view taken along the axial direction O of the sensor cap 700, and FIG. 4 is a plan view of the engaging member 757. FIG. 5 is a perspective view of the sensor cap 700. The sensor cap 700 includes a cap terminal 751, an upper covering member 752a that covers and holds the cap terminal 751, a lower covering member 752b connected to the upper covering member 752a, a lead wire 753, a filter member 754, and a substantially C-shaped engagement. A joint member 757 and a lead wire seal portion 759 are provided, and a seal material (O-ring) 755 is separately disposed on the inner surface of the sensor cap 700.
The upper covering member 752a and the lower covering member 752b correspond to the “cap body” in the claims. In particular, a part of the lower covering member 752b corresponds to a “side wall” in the claims. The engaging member 757 corresponds to an “elastic member” in the claims.

  The cap terminal 751 (see FIGS. 3 and 5) is made of, for example, stainless steel (SUS310S or the like), has a substantially rectangular flat plate shape, and a lead wire 753 is fixed by crimping to its base end. The lead wire 753 has a coating material in addition to the core wire. An output signal from the inner electrode 29 of the gas detection element 22 of the gas sensor 21 can be transmitted to an external device (for example, an engine control unit (ECU)) through the lead wire 753.

The upper covering member 752a and the lower covering member 752b are made of resin, and each has a substantially cylindrical shape. The upper covering member 752a and the lower covering member 752b may be formed using rubber or ceramic in addition to resin.
The upper covering member 752 a has a rear end surface that is open at the front end side, and has an internal space 752 h that houses the cover 23. The inner surface of the tip edge of the upper covering member 752a is recessed in an annular shape, and an O-ring 755 is disposed here. In addition, one side surface of the distal end side of the upper covering member 752a protrudes in the radial direction to form a lead wire surrounding portion 753p. The lead wire surrounding portion 753p has an insertion hole 753h extending in the radial direction, and the insertion hole 753h communicates with the internal space 752h. Then, the cap terminal 751 with the lead wire 753 is inserted from the insertion hole 753h, and the cap terminal 751 is disposed so that the tip-facing surface of the cap terminal 751 faces the internal space 752h. At this time, the tip facing surface of the cap terminal 751 is in contact with the contact portion 35e of the output terminal 35 (see FIG. 6). Further, the lead wire seal portion 759 is disposed inside the insertion hole 753h to seal the insertion hole 753h.

On the other hand, a portion on the opposite side to the lead wire surrounding portion 753p protrudes in the radial direction to form a filter surrounding portion 754p. An insertion hole 754h extending in the radial direction is opened in the filter surrounding portion 754p, and the insertion hole 754h communicates with the internal space 752h through a small hole. And the filter member 754 is arrange | positioned so that the insertion hole 754h may be plugged up. The filter member 754 is made of PTFE having a continuous porous structure in which fine pores are continuous, and an annular protrusion (not shown) on the inner wall of the insertion hole 754 h is brought into close contact with the outer peripheral surface of the filter member 754 to hold the filter member 754. ing.
The filter member 754 does not transmit liquid (water) but transmits air and water vapor.

The lower covering member 752b has a cylindrical shape having a skirt portion 752f whose tip end is larger in diameter than the periphery, and an inner space 752h having the same diameter as the upper covering member 752a is formed inside the cylindrical portion. The hem 752f has engaging member mounting holes 752e opened in two slits in the radial direction in the form of slits, and the outer peripheral portion of the skirt 752f extends along the circumferential direction of the engaging member mounting hole 752e. Grooves are formed in. The engaging portion mounting hole 752e corresponds to a “through hole” in the claims.
Then, an approximately C-shaped and elastically deformable engaging member (wire spring) 757 shown in FIG. 4 is fitted into the outer peripheral groove of the skirt 752f. The engaging member 757 has an annular shape with a part opened, and further has a reduced diameter portion 757 s that is reduced in diameter at two positions facing each other in the radial direction, and an interval (diameter) D ₁ between the reduced diameter portions 757 s is It is smaller than the diameter of the internal space 752h. Accordingly, when the position of the reduced diameter portion 757s is aligned with the engagement member attachment hole 752e, the reduced diameter portion 757s protrudes from the engagement member attachment hole 752e toward the internal space 752h (see FIG. 5). The distance D ₁ corresponds to the "minimum inner diameter of the elastic member" in the claims. Further, the engaging member 757 is elastically deformed in the radial direction to expand and contract the diameter.

By overlapping the upper covering member 752a and the lower covering member 752b described above concentrically in the axial direction O, and locking the claw portion 752x of the lower covering member 752b to a side hole (not shown) of the upper covering member 752a, The upper covering member 752a and the lower covering member 752b are integrally connected to complete the sensor cap 700.
Here, the O-ring 755 is disposed on the rear end side with respect to the engagement member mounting hole 752e and faces the internal space 752h (see FIG. 5), and comes into contact with the outer surface of the cover 23 when the gas sensor 21 is accommodated. Sealing with the sensor cap 700 is performed (see FIG. 6). Therefore, the inner diameter D ₃ of the O-ring 755 is slightly smaller than the outer diameter D ₂ of the cover 23.

As shown in FIG. 6, when the cover 23 (see FIG. 2B) at the rear end of the gas sensor 21 is accommodated in the internal space 752h (see FIG. 5) of the sensor cap 700, the side surface of the metal shell 25 is engaged. The cover 23 is inserted into the sensor cap 700 while increasing the diameter of the reduced diameter portion 757 s by contacting the reduced diameter portion 757 s of the member 757. Then, positioning is performed in a state where the tip of the skirt 752 f of the sensor cap 700 is in contact with the rear end of the flange 25 c of the metal shell 25. At this time, the position in the axial direction O of the reduced diameter portion 757s matches the position of the recess 25e of the metal shell 25, reduced diameter portion 757s is fitted into the concave portion 25e reduced in diameter to the original distance D ₁ by an elastic force. Thereby, the sensor cap 700 is fixed to the gas sensor 21, and the gas sensor unit 600 is comprised. Further, when the sensor cap 700 is fixed to the gas sensor 21, the inner surface of the O-ring 755 is in close contact with the outer surface of the cover 23 and sealed.

Thus, the sensor cap 700 (inner space 752h of) and housing the gas sensor 21 rear end of the cover 23, but the reduced diameter portion 757s is fitted into the concave portion 25e reduced in diameter to the original spacing _{D 1} at a predetermined position At this time, since the engaging member 757 emits a sound or an impact is generated, the completion of connection between the gas sensor 21 and the sensor cap 700 can be clearly recognized with a click feeling.
Further, since the sensor cap 700 is fixed to the gas sensor 21 in a state where a part (the reduced diameter portion 757 s) of the engaging member 757 is firmly fitted in the recess 25 e of the metal shell 25, the gas sensor 21, the sensor cap 700, Is hard to come off.
Further, the outer diameter _{D 2} of the cover 23 is set to be smaller than the distance _{D 1} of the reduced diameter portion 757S, O-ring 755 engaging member mounting hole 752e (i.e., reduced diameter portion 757S inner space 752h side It is arranged on the rear end side from the position protruding to the rear. Therefore, when the housing cover 23 to the inner space 752h of the sensor cap 700, without reduced diameter portion 757s to the outer surface of the small diameter of the cover 23 abuts than the distance D _1, that scratched the outer surface of the cover 23 This can prevent the O-ring 755 and the cover 23 from being deteriorated in sealing performance. Further, since the inner diameter _{D 3} of the O-ring 755 is smaller in diameter than the distance _{D 1,} it is possible to use a relatively small O-ring 755, the cost of the O-ring 755 is lowered. The inner diameter D ₃ of the O-ring 755 is formed to be slightly smaller than the outer diameter D ₂ of the cover 23. Therefore, the O-ring 755 is always stretched when the sensor cap 700 and the gas sensor 21 are assembled, and is dimensioned to be in close contact with the outer surface of the cover 23.

On the other hand, when D ₂ ≧ D ₁ , when the cover 23 is accommodated in the internal space 752h of the sensor cap 700, the reduced diameter portion 757s comes into contact with the outer surface of the cover 23 and the outer surface of the cover 23 is easily damaged. The sealing performance between the O-ring 755 and the cover 23 is deteriorated.
Further, when the O-ring 755 is disposed on the tip side from the engagement member mounting hole 752e, the O-ring 755 is close to the metal shell 25 that is likely to become high temperature and is easily affected by heat. Furthermore, in order to prevent the outer surface of the gas sensor in contact with the O-ring 755 from being scratched, it is necessary to make the O-ring 755 a large O-ring 755 whose inner diameter D ₃ is larger than the distance D _1. Therefore, it leads to cost increase.

As shown in FIG. 3, in this embodiment, the outer diameter D ₅ of the sensor cap 700 (the skirt 752 f) around the engaging member mounting hole 752 e is larger than the outer diameter D ₄ of the engaging member 757. In this way, the engaging member 757 does not protrude outside the sensor cap 700, and the engaging member 757 can be prevented from being damaged or dropped due to an external impact.

Further, in this embodiment, in the state where the sensor cap 700 is secured to the gas sensor 21, axial O of the distance _{h 2} is the height _{h 1} is smaller than the projection of the rear end face 23b and the cap terminal 751 of the cover 23. Therefore, the contact portion 35e (the output terminal 35) is pressed against the forward-facing surface of the cap terminal 751, the rear end face 23b and the distance _{h 2} of the contact portion 35e is projected height _{h 1} from the tip side in the axial direction O (cover 23 Located at the height).
At this time, the coil spring 38 is compressed in the axial direction O, and the contact portion 35e is biased toward the cap terminal 751 by the repulsive force, so that the contact portion 35e and the cap terminal 751 are electrically and reliably connected, Contact reliability between the output terminal 35 and the cap terminal 751 can be improved. As described above, since the sensor cap 700 is fixed to the gas sensor 21 with a part (the reduced diameter portion 757 s) of the engaging member 757 firmly fitted in the recess 25 e of the metal shell 25, the coil spring The sensor cap 700 is not detached from the gas sensor 21 by the repulsive force of 38.

FIG. 7 shows a modification of the engaging member.
FIG. 7A shows an engagement member (wire spring) 857 that is substantially C-shaped and elastically deformable. The engaging member 857 has an annular shape with a part opened, and further includes three reduced diameter portions 857s reduced in diameter at three positions opposed in the radial direction. In the sensor cap (not shown), three engagement member attachment holes are provided at positions corresponding to the respective reduced diameter portions 857s, and the reduced diameter portions 857s protrude from the engagement member attachment holes to the internal space 752h side. It is supposed to be.
FIG. 7B shows an engagement member (wire spring) 957 that is substantially C-shaped and elastically deformable. The engaging member 957 has an annular shape with a part opened, and further has five reduced diameter portions 957s reduced in diameter at five positions opposed in the radial direction. In the sensor cap (not shown), five engagement member attachment holes are provided at positions corresponding to the respective reduced diameter portions 957s, and the reduced diameter portions 957s protrude from the engagement member attachment holes to the internal space 752h side. It is supposed to be.
The minimum inner diameter of each engagement member 857, 957 is the diameter of the maximum circle (broken line in FIG. 7) with which the tips of the respective reduced diameter portions 857s, 957s are in contact.

  As shown in FIG. 7, when the engagement member is provided with three or more reduced diameter portions, the gas sensor 21 is supported by the sensor cap 700 at three or more locations in the radial direction. Less shift from each other. On the other hand, if there are two reduced diameter portions, there may be a deviation in the direction perpendicular to the straight line connecting the reduced diameter portions in the radial direction.

  FIG. 8 shows another modification of the engaging member 1057. The engaging member 1057 is formed in a substantially octagonal plate shape from an elastically deformable resin, and has a substantially C-shape with one side cut out while the center is opened in an oval shape. A portion of the ellipse facing the short axis direction becomes a reduced diameter portion 1057s, and engages with the concave portion 25e of the metal shell.

  Needless to say, the present invention is not limited to the above embodiments, and various modifications are possible. For example, the shape of the engaging member can be made into a ring shape in which, for example, a U-shape, a C-shape, a U-shape, etc. are opened in accordance with the outer surface shape of the metal shell (the concave portion). Further, the sealing material is not limited to the O-ring.

21 Gas sensor 22 Gas detection element 23 Casing (cover)
25 Casing (metal shell)
25e Concave portion 35 Output terminal 600 Gas sensor unit 700 Sensor cap 751 Cap terminal 752a Cap body (upper covering member)
752b Cap body (lower covering member)
752b Side wall (part of lower covering member)
752e Through hole (engagement member mounting hole)
752h Internal space 755 Sealing material 757, 857, 957, 1057 Elastic member (engaging member)
757 s, 857 s, 957 s, 1057 s Reduced diameter portion of elastic member D ₁ Minimum inner diameter of elastic member D ₂ Diameter of outer surface of casing in contact with seal material D ₄ Outer diameter of elastic member D ₅ of sensor cap around through hole Outer diameter O Axial direction

Claims (4)

A gas detection element extending in the axial direction and having a tip exposed to the gas to be measured, a cylindrical casing surrounding the periphery of the gas detection element, and having a recess recessed radially inward on its outer surface; An output terminal arranged on the rear end side from the gas detection element to electrically extract the sensor output of the gas detection element;
A gas sensor comprising: a sensor cap assembled to the gas sensor,
A cylindrical cap body having a side wall extending in the axial direction so as to straddle the concave portion, and having an internal space for accommodating the output terminal;
A through-hole provided at a position corresponding to the recess in the side wall;
An elastic member that is disposed in the through hole and that engages with the concave portion and fixes the sensor cap to the gas sensor;
A gas sensor unit in which the elastic member is engaged with the concave portion by assembling the sensor cap from the rear end side of the gas sensor with the elastic member being fitted from the outside of the through hole of the sensor cap. And
A sealing material that seals between the outer surface of the casing and the inner surface of the cap body while facing the internal space on the rear end side from the through hole,
A gas sensor unit in which a diameter of an outer surface of the casing at a position in contact with the sealing material is smaller than a minimum inner diameter of the elastic member. The sensor cap has a cap terminal that is electrically connected to the output terminal while facing the internal space;
2. The gas sensor unit according to claim 1, wherein the output terminal protrudes from a rear end of the casing while being urged toward a rear end side, and is in contact with the cap terminal while being pressed by the cap terminal.   3. The gas sensor unit according to claim 1, wherein the elastic member has three or more reduced diameter portions that engage with the concave portion, and the through hole is provided at a position corresponding to the reduced diameter portion.   The gas sensor unit according to claim 1, wherein an outer diameter of the sensor cap around the through hole is larger than an outer diameter of the elastic member.

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