JP2019020223A - Gas sensor - Google Patents

Abstract

To provide a gas sensor reducing a spring-back in an axial line direction of a caulking portion and improving a sealing characteristic by improving a caulking force.SOLUTION: A gas sensor 100 includes: at least a cylindrical metal shell 20 having a caulking part 20a at a rear end side; a sensor element 3; and a ring-shaped other member 30 fixed to the caulking part. The other member is covered by the caulking part, and the caulking part is bent inside in a radial direction and pressures the other member to a center side along an axial line O of the metal shell, and a tip end 20f in a radial direction of the caulking part extends to the radial direction inner than the center of gravity G in a cross-section in the radial direction of the other member. Moreover, the caulking part contacts the other member at least at the side inner in the radial direction than the center of gravity G, and has at least a difference in height in the axial direction of an external surface 20ax, and is formed with a recessed portion or a projected portion 20u in the radial direction. The recessed portion or the projected portion is formed at least in a region R1 from the tip end in the radial direction of the caulking part to the center of gravity.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a gas sensor that detects the concentration of a gas to be detected.

  As a gas sensor for detecting the oxygen concentration in exhaust gas of an automobile or the like, there is known a gas sensor that inserts and holds a sensor element extending in the axial direction inside a cylindrical metal shell. This gas sensor is manufactured as follows. First, the sensor element is inserted inside the metallic shell, and the filling member and the cylindrical ceramic sleeve are arranged inside the rear end portion of the metallic shell. A caulking portion is provided on the rear end side of the metal shell, and the caulking portion is pressed and caulked by a caulking die toward the distal end side while being bent radially inward. As a result, the filling member is compressed to the distal end side through the metal ring and the ceramic sleeve pressed to the distal end side by the caulking portion, and the gap between the metal shell and the sensor element is sealed.

The caulking portion is formed by bending a cylindrical member (caulking element) extending in the axial direction inward in the radial direction by a caulking die. For this reason, when the caulking load is released, the caulking element is returned to the rear end side by the spring back, and accordingly, the load applied to the filling member via the metal ring and the ceramic sleeve is also slightly released in the axial direction. There is a risk that the gap between the metal shell and the sensor element will be insufficiently sealed. On the other hand, if the thickness of the caulking portion is excessively increased in order to reduce the spring back, bending work during caulking becomes difficult or the cost is increased.
For this reason, a technique has been developed in which irregularities that form reinforcing portions (ribs) are formed on the outer surface of the crimped portion to reduce the spring back (Patent Document 1).

JP 2014-222151 A

However, it has been found that even if the caulking portion is reinforced, depending on the length of the caulking portion applied to the metal ring, the load on the metal ring is not sufficient and the seal is insufficient.
Accordingly, an object of the present invention is to provide a gas sensor in which the spring back in the axial direction of the crimping portion is reduced and the sealing performance is improved by further improving the crimping force.

  In order to solve the above-described problems, a gas sensor according to the present invention includes a cylindrical metal shell having a crimped portion on its rear end, a sensor element that extends in the axial direction and is held in the metal shell, and the pressurizing member. In the gas sensor having at least a ring-shaped other member fixed to the tightening portion, the other member is covered with the crimping portion, and the crimping portion is bent radially inward to make the other member the main body. The metal member is pressed toward the central side along the axial direction of the metal fitting, and the distal end in the radial direction of the caulking part extends radially inward from the center of gravity in the radial cross section of the other member, and the caulking part Has at least an outer surface of the caulking portion that is in the radial inner side of the center of gravity and has a height difference in the axial direction and is formed with a concave portion or a convex portion extending in the radial direction. Convex is at least Characterized in that from the tip of the caulking portion is formed in a region up to the center of gravity.

According to this gas sensor, the distal end of the crimped portion in the radial direction extends radially inward from the center of gravity of the other member, and the crimped portion is in contact with the other member at least radially inward of the center of gravity. For this reason, a pressing force is applied to the other member on the inner side in the radial direction from the center of gravity, and a clockwise moment is exerted on the other member around the center of gravity. Is held at the proximal end. Therefore, the force from the inner peripheral portion on the tip side of the other member toward the tip side becomes dominant, and the caulking force can be further improved to improve the sealing performance.
In addition, since the concave portion or the convex portion formed on at least the outer surface of the crimped portion becomes a reinforcing portion (rib) and the strength of the crimped portion is increased, the crimped portion is returned to the rear end side by the spring back. It can suppress and can improve the caulking force of an axial direction. Furthermore, the concave portion or the convex portion is formed in at least a region from the radial tip of the crimped portion to the center of gravity. For this reason, the strength of the portion of the crimping portion that is in contact with the other member on the inner side in the radial direction from the center of gravity is reliably increased, and the above-described force is generated more strongly, thereby further improving the crimping force and improving the sealing performance. Can be made.

The tip of the caulking portion may extend radially inward from the other member.
According to this gas sensor, the caulking force to other members is further improved on the inner side in the radial direction from the center of gravity, and the above-described force is further increased to further improve the caulking force and improve the sealing performance. Can be made.

A second convex portion or a second concave portion that appears as a convex portion or a concave portion corresponding to each of the concave portion or the convex portion formed on the outer surface of the crimp portion is formed on the inner surface of the crimp portion. May be.
According to this gas sensor, the strength of the crimped portion is further increased.

  According to the present invention, it is possible to obtain a gas sensor that reduces the spring back of the caulking portion in the axial direction and further improves the caulking force to improve the sealing performance.

It is sectional drawing which cut | disconnected the gas sensor which concerns on embodiment of this invention by the surface which follows an axial direction. It is the elements on larger scale around the crimping part of FIG. It is a fragmentary perspective view of a caulking part periphery. It is sectional drawing of the thickness direction of the crimping part cut | disconnected by the surface perpendicular | vertical to the axis line O direction at the height of the AA line of FIG. In embodiment of this invention, it is a schematic diagram which shows the force which acts on a metal ring. It is a schematic diagram which shows the force which acts on a metal ring in case the front-end | tip of the radial direction of a crimping part is located in a radial direction outer side from the gravity center of a metal ring. It is the fragmentary sectional perspective view which looked at the crimping metal mold | die from the front end side. It is sectional drawing of the thickness direction which shows the modification of a crimping part.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a cross-sectional structure of a gas sensor 100 according to an embodiment of the present invention cut along a plane along the axis O direction. In this embodiment, the gas sensor 100 is an oxygen sensor that is inserted into an exhaust pipe of an automobile and has a tip exposed to the exhaust gas to detect the oxygen concentration in the exhaust gas. The sensor element 3 is a known oxygen sensor element that constitutes an oxygen concentration cell in which a pair of electrodes are laminated on an oxygen ion conductive solid electrolyte body and outputs a detection value corresponding to the amount of oxygen.
In addition, let the lower side of FIG. 1 be the front end side of the gas sensor 100, and let the upper side of FIG.

The gas sensor 100 is assembled so that a substantially cylindrical (hollow shaft-shaped) sensor element (oxygen sensor element in this example) 3 having a closed tip is inserted and held inside the cylindrical metal shell 20. The sensor element 3 includes a cylindrical solid electrolyte body that is tapered toward the tip, and inner and outer electrodes (not shown) formed on the inner and outer peripheral surfaces of the solid electrolyte body, respectively. Become. A round bar heater 15 is inserted into the hollow portion of the sensor element 3 so as to raise the temperature of the solid electrolyte body to the activation temperature.
A cylindrical outer tube 40 that holds a lead wire and a terminal (described later) provided on the rear end side of the sensor element 3 and covers the rear end portion of the sensor element 3 is joined to the rear end portion of the metal shell 20. ing. Further, an insulating cylindrical separator 121 is caulked and fixed inside the outer cylinder 40 on the rear end side of the sensor element 3. On the other hand, the detection part at the tip of the sensor element 3 is covered with a protector 7. Then, the male screw part 20d of the metal shell 20 of the gas sensor 100 manufactured in this way is attached to a screw hole such as an exhaust pipe, so that the detection part at the tip of the sensor element 3 is exposed in the exhaust pipe and the gas to be detected (exhaust gas) Gas). A polygonal flange portion 20c for engaging a hexagon wrench or the like is provided near the center of the metal shell 20, and a step between the flange portion 20c and the male screw portion 20d is attached to the exhaust pipe. A gasket 14 is inserted to prevent the gas from leaking when it is blown.

A flange portion 3 a is provided on the center side of the sensor element 3, and a step portion that is reduced in diameter is provided on the inner peripheral surface near the tip of the metal shell 20. In addition, a cylindrical ceramic holder 5 is disposed on the surface facing the rear end of the step portion via a washer 12. The sensor element 3 is inserted inside the metal shell 20 and the ceramic holder 5, and the flange portion 3 a of the sensor element 3 is in contact with the ceramic holder 5 through the washer 13 from the rear end side.
Further, a cylindrical talc powder 6 and a cylindrical ceramic sleeve 10 are arranged in the radial gap between the sensor element 3 and the metal shell 20 on the rear end side of the flange 3a. Then, the metal ring 30 is disposed on the rear end side of the ceramic sleeve 10 and the caulking portion 20a is formed by bending the rear end portion of the metal shell 20 inward, thereby pressing the ceramic sleeve 10 toward the front end side. As a result, the talc powder 6 is crushed and the ceramic sleeve 10 and the talc powder 6 are caulked and fixed, and the gap between the sensor element 3 and the metal shell 20 is sealed.
The metal ring 30 corresponds to “other member” in the claims.

The separator 121 disposed on the rear end side of the sensor element 3 is provided with insertion holes (four in this example), two of which are plate-like base portions of the inner terminal fitting 71 and the outer terminal fitting 91, respectively. 74 and 94 are inserted and fixed. Connector portions 75 and 95 are formed at the rear ends of the plate-like base portions 74 and 94, respectively, and lead wires 41 and 41 are crimped to the connector portions 75 and 95, respectively. Further, a heater lead wire 43 (only one is shown in FIG. 1) drawn from the heater 15 is inserted into two insertion holes (heater lead holes) (not shown) of the separator 121.
A cylindrical grommet 131 is caulked and fixed inside the outer cylinder 40 on the rear end side of the separator 121, and two lead wires 41 and two heater lead wires 43 are respectively inserted from the four insertion holes of the grommet 131. Has been pulled out.
A through hole 131 a is formed at the center of the grommet 131 and communicates with the internal space of the sensor element 3. A water-repellent ventilation filter 140 is interposed in the through-hole 131a of the grommet 131 so that the reference gas (atmosphere) is introduced into the internal space of the sensor element 3 without passing external water.

  On the other hand, a cylindrical protector 7 is fitted on the front end side of the metal shell 20, and the front end side of the sensor element 3 protruding from the metal shell 20 is covered with the protector 7. The protector 7 has a bottomed cylindrical shape having a plurality of holes (not shown) and is made of a metal (for example, stainless steel) outer protector 7b and an inner protector 7a that are double-attached by welding or the like. .

FIG. 2 shows a partially enlarged view around the caulking portion 20a of FIG. The caulking portion 20 a is bent radially inward to press the metal ring 30 toward the center side along the direction of the axis O of the metal shell 20. Further, the distal end 20 f in the radial direction of the caulking portion 20 a extends radially inward from the center of gravity G in the radial section of the metal ring 30.
Here, the “radial” tip 20f of the crimped portion 20a is the radially innermost portion of the crimped portion 20a and is not necessarily the same as the tip 20s of the crimped portion 20a itself.
The radial cross section of the metal ring 30 is a cross section cut along a plane from the center of the metal ring 30 toward the outer edge.

FIG. 3 shows a partial perspective view around the caulking portion 20a. The caulking portion 20a is formed in an annular shape, and the outer surface of the caulking portion 20a has unevenness 20u having a height difference in the direction of the axis O and extending in the radial direction over the entire circumference in the circumferential direction. It is formed in a region R1 beyond the center of gravity G from the radial tip 20f. In addition, the unevenness 20u has a wave shape in which concave portions and convex portions are alternately formed in the circumferential direction, and the curvatures of the concave portions and the convex portions are the same.
On the other hand, the caulking portion 20a is in contact with the metal ring 30 in a region R2 from the outer peripheral side of the metal ring 30 to beyond the center of gravity G and radially inward.

Thus, the radial tip 20f of the crimped portion 20a extends radially inward from the center of gravity G of the metal ring 30, and the crimped portion 20a is in contact with the metal ring 30 at least radially inward of the center of gravity G. Yes.
Therefore, as shown in FIG. 5, a pressing force P is applied to the metal ring 30 on the inner side in the radial direction from the center of gravity G, and a clockwise moment is applied to the metal ring 30 around the center of gravity G. The outer peripheral portion 20e on the rear end side of the ring 30 is held at the proximal end of the crimped portion 20a. Therefore, the force F1 from the inner peripheral portion on the tip side of the metal ring 30 toward the tip side becomes dominant, and the caulking force can be further improved to improve the sealing performance.

On the other hand, as shown in FIG. 6, when the radial tip 20wf of the caulking portion 20w is located at the same position on the radial inner side as the center of gravity G or radially outside the center of gravity G, the caulking portion 20w is located at the center of gravity. The metal ring 30 is not in contact with the inner side in the radial direction than G.
For this reason, a pressing force P toward the front end is applied to the metal ring 30 radially outside the center of gravity G, and a counterclockwise moment acts on the metal ring 30 around the center of gravity G. The caulking portion 20w is not interposed on the radially inner side of the center of gravity G. Accordingly, the force F2 directed from the inner peripheral portion on the rear end side of the metal ring 30 toward the rear end side becomes dominant, and the metal ring 30 floats and the caulking force is reduced.

Further, in the present invention, the unevenness 20u is formed on at least the outer surface 20ax of the crimped portion 20a, and the unevenness 20u becomes a reinforcing portion (rib) to increase the strength of the crimped portion 20a. It is possible to suppress the caulking portion 20a bent radially inward from returning to the rear end side by the spring back, and to improve the caulking force in the axis O direction. Therefore, it is possible to suppress the release of the load in the direction of the axis O of the talc powder 6 pressed to the tip side by the caulking portion 20a via the metal ring 30 and the ceramic sleeve 10, and the gap between the metal shell 20 and the sensor element 3 is suppressed. The seal will be secure.
Furthermore, the unevenness 20u is formed at least in a region R1 from the radial tip 20f of the crimped portion 20a to the center of gravity G. For this reason, the strength of the caulking portion 20a that is in contact with the metal ring 30 radially inward of the center of gravity G is reliably increased, and the force F1 is generated more strongly as shown in FIG. Can be further improved to improve the sealing performance.

  Conventionally, there is a method of intermittently crimping in the radial direction as in the so-called Happomaru caulking, but since the Happomaru caulking is not a method of caulking in the direction of the axis O, spring back in the direction of the axis O is suppressed. It is difficult to do.

Further, as shown in FIG. 4, which is a cross-sectional view taken along a plane perpendicular to the axis O direction at the height of the AA line in FIG. 3, in this example, the outer surface is viewed in the thickness direction of the crimped portion 20a. Concavities and convexities 20v complementary to the 20ax concavities and convexities 20u are formed on the inner surface 20ay.
That is, the unevenness 20v appears on the inner surface 20ay of the crimped portion 20a as a protrusion or recess corresponding to the recess or protrusion of the recess 20u. The unevenness 20v corresponds to the “second convex portion or the second concave portion” in the claims.

The gas sensor 100 according to the embodiment of the present invention can be manufactured as follows using, for example, the caulking die 200 of FIG.
FIG. 7 is a partial cross-sectional perspective view of the caulking die 200 for caulking the caulking portion 20a as viewed from the front end side. The caulking die 200 is formed in a substantially cylindrical shape having a center hole 200h, and the tip-facing surface 200a of the caulking die 200 has a flat surface on the radially outer side, and toward the rear end side on the radially inner side. The taper has a narrow and smooth taper shape, and the mold part unevenness 200u is formed on the taper surface. The mold part unevenness 200u has recesses and protrusions alternately formed in the circumferential direction.

First, the sensor element 3 is inserted into the metal shell 20, and the talc powder 6, the ceramic sleeve 10, and the metal ring 30 are sequentially disposed in the radial gap between the sensor element 3 and the metal shell 20.
Next, the sensor element 3 is inserted into the center hole 200h of the caulking die 200 and pressed toward the distal end side of the caulking die 200 to bend the caulking element portion that becomes the caulking portion 20a inward in the radial direction. While pressing toward the distal end side, the caulking portion 20a is formed. Since the above-mentioned mold part unevenness 200u is formed on the tip facing surface 200a, the unevenness 20u is embossed on the outer surface of the crimped part 20a by caulking.

It goes without saying that the present invention is not limited to the above-described embodiment, but extends to various modifications and equivalents included in the spirit and scope of the present invention.
The present invention can be applied to oxygen sensors such as a full-range air-fuel ratio sensor that measures the oxygen concentration in the exhaust gas of automobiles and various internal combustion engines and in the combustion gas of boilers and the like, but is not limited to these applications. . For example, the present invention can be applied to a gas sensor for detecting the concentration of NO _x gas or a gas sensor having a sensor element for measuring the concentration of a gas other than NO _x (for example, CO _x , H ₂ O, HC, etc.).
Further, the present invention can be applied to a plate-like sensor element without being limited to a cylindrical shape.

  Further, in the above embodiment, the radial tip 20f of the crimped portion 20a extends radially inward from the metal ring 30, but the tip 20f only needs to extend at least radially inward from the center of gravity G. However, in the former case, the caulking force applied to the metal ring 30 on the inner side in the radial direction from the center of gravity G can be further reliably improved, and the force F1 in FIG. 5 can be further increased to improve the sealing performance.

In addition, the concave and convex portions 20u and 20v do not necessarily have both concave and convex portions, and either the concave portion or the convex portion is formed on the outer surface 20ax or the inner surface 20ay of the crimped portion 20a. Good.
Moreover, although it is preferable that the unevenness | corrugation 20u is formed in the perimeter of the circumferential direction of the crimping part 20a, you may form in a part of circumferential direction. Also, as shown in FIG. 4, it is preferable that the inner surface 20y of the crimped portion 20a has a concave and convex portion 20v complementary to the concave and convex portion 20u because the strength of the crimped portion 20a is further increased. The unevenness 20v may not be formed on the inner surface 20y of the portion 20a. Examples of the method for forming the unevenness 20v on the inner surface 20y of the crimping portion 20a include adjusting the height difference of the mold portion unevenness 200u, the caulking load, or the thickness of the caulking portion 20a.
The shape of the unevenness 20u is not limited to the above. For example, as shown in FIG. 8, the corrugated shape 20u is formed only on the outer surface 20x of the crimped portion 20a, as shown in FIG. (FIG. 8 (b)), a shape with a narrow deep recess on the outer surface 20x of the crimped portion 20a, and a complementary protrusion on the inner surface 20y (FIG. 8 (c)), etc. You can also

3 sensor element 20 metal shell 20a caulking portion 20f radial end of caulking portion 20ax outer surface of caulking portion 20ay inner surface of caulking portion 30 other member (metal ring)
20u Concave portion or convex portion 20v Second concave portion or second convex portion 100 Gas sensor O Axis line G Center of gravity of radial cross section of other member R1 Area from the distal end of the caulking portion to the center of gravity

Claims (3)

A cylindrical metal shell having a crimping portion on its rear end side, a sensor element extending in the axial direction and held in the metal shell, and another ring-shaped member fixed to the crimping portion At least in the gas sensor
The other member is covered with the caulking portion,
The caulking portion is bent radially inward to press the other member toward the center side along the axial direction of the metal shell, and the distal end of the caulking portion in the radial direction is a diameter of the other member. Extending radially inward from the center of gravity in the cross section of the direction,
And the caulking part is in contact with the other member at least radially inward from the center of gravity,
A concave portion or a convex portion having a height difference in the axial direction and extending in the radial direction is formed on at least an outer surface of the crimp portion, and the concave portion or the convex portion is at least from the tip of the crimp portion to the center of gravity. A gas sensor formed in a region.   The gas sensor according to claim 1, wherein the tip of the caulking portion extends radially inward from the other member.   A second convex portion or a second concave portion that appears as a convex portion or a concave portion corresponding to each of the concave portion or the convex portion formed on the outer surface of the crimp portion is formed on the inner surface of the crimp portion. The gas sensor according to claim 1 or 2, wherein:

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