JP5514239B2 - In-vehicle sensor - Google Patents

Description

  The present invention relates to an in-vehicle sensor such as a gas sensor mounted on a vehicle.

Conventionally, a gas sensor (for example, a full-range air-fuel ratio sensor, an oxygen sensor, a NOx sensor, etc.) that is installed in an exhaust pipe of an internal combustion engine of a vehicle and detects a specific gas concentration in the exhaust gas, or an exhaust temperature that measures an exhaust gas temperature. In-vehicle sensors such as sensors are known. In these in-vehicle sensors, a lead wire conducting to the detection element is taken out from a metal casing and connected to a control device or the like installed at a location away from the sensor body. By the way, these in-vehicle sensors, especially in-vehicle sensors installed near the vehicle's undercarriage, such as exhaust pipes, are sprayed with water during spraying in the rain or washed with water, and dirt such as oil adheres to them. Therefore, there is a risk that water droplets or oil may enter the casing of the sensor and cause problems such as an electrical short circuit. Therefore, in such an in-vehicle sensor, as a structure for taking out the lead wire from the casing, a rubber grommet with the lead wire inserted is fitted into the opening on the base end side of the casing, and a liquid is provided between the lead wire and the casing. Close sealing may be performed. For example, Patent Document 1 discloses a gas sensor having such a sealing structure.
In addition, when a lead wire exposed to the outside of the grommet is protected or a plurality of lead wires are provided, a lead surrounding tube surrounding the lead wires may be provided in order to converge them.

JP 2004-245663 A

  However, in the conventional gas sensor, as in Patent Document 1, the lead wire near the grommet is not covered with the lead surrounding tube, and the grommet and the lead wire remain exposed to the outside. However, in this state, depending on how the water flow is applied when the car is washed using a high pressure washer, the water pressure resistance performance having the above-described sealing structure is not sufficient, but through the gap between the grommet and the lead wire, etc. There is a risk that water may enter the casing of the sensor.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an in-vehicle sensor that can appropriately prevent the intrusion of water into the sensor due to the splashing of rainwater or the water flow of a high-pressure car wash. To do.

  One aspect thereof is an in-vehicle sensor having a configuration extending in an axial direction along an axis, the detection element, one or a plurality of lead wires that are connected to the detection element and extend to the proximal end side in the axial direction, and It has a cylindrical shape extending in the axial direction, and is composed of a metal outer cylinder that accommodates the lead tip portion on the distal end side in the axial direction in the lead wire and a rubber-like elastic body, and the base of the outer cylinder It is arranged in the outer cylinder base end located on the end side, closes the outer cylinder base end, and consists of a grommet in which the lead wire passing through itself extends to the base end, and a resin tube, A lead enclosing tube that surrounds a portion of the lead wire that is closer to the base end than the grommet from the periphery, and the outer tube base end of the outer tube is reduced in diameter by caulking deformation. The grommet to be tightened A crimped portion that is compressed and held, and a proximal end large diameter portion that is positioned closer to the proximal end than the crimped portion and is larger in diameter than the crimped portion. A cover member that covers, from the inside, at least a portion from the caulking portion of the outer tube base end portion of the outer tube to the distal end side tube tip portion of the lead surrounding tube. It is a vehicle-mounted sensor provided with a cover member having a caulking portion abutting portion that bulges toward the caulking portion so as to be engageable with the base end diameter large portion of the outer cylinder base end portion.

  In this in-vehicle sensor, at least a portion from the crimped portion of the outer tube base end portion of the outer tube to the tube distal end portion of the lead surrounding tube is covered with the cover member. Thereby, a part of lead wire exposed from the grommet arrange | positioned in an outer cylinder base end part or the tube front-end | tip part of a lead surrounding tube is also covered by a cover member. For this reason, it can suppress that a grommet and a lead wire are exposed outside, and can prevent that water permeates into the inside of a sensor. The grommet may be arranged so that a part of the grommet protrudes to the base end side from the base end of the outer cylinder, or the entire grommet is located in the base end of the outer cylinder and the base end of the outer cylinder. You may arrange | position in the form which does not protrude from.

  Furthermore, the cover member has a caulking portion contact portion that bulges inward. The caulking portion abutting portion abuts on the caulking portion so as to be engageable with a large base end diameter portion of the outer cylinder base end portion. As a result, the cover member is unlikely to fall off from the base end portion of the outer cylinder to the base end side. In order to ensure that the cover member comes into contact with the caulking portion at the base end portion of the outer cylinder, the caulking portion abutting portion preferably has an annularly bulging shape toward the inside.

  Examples of the resin forming the cover member include fluororesins such as PTFE, PFA, and FEP, EPDM, and silicon resin. Examples of the lead surrounding tube made of resin include a fluororesin tube, a polyimide tube, and a silicon varnish glass tube using PTFE, PFA, FEP, and the like.

  Furthermore, the above-mentioned vehicle-mounted sensor, the vehicle-mounted sensor comprising a tightening member that surrounds and tightens a tightened portion including at least a part of the crimping portion contact portion on the inside of the cover member from the outside. Good.

In this in-vehicle sensor, the tightened portion of the cover member is tightened by the above-described tightening member. The to-be-clamped portion includes at least a part of the caulking portion abutting portion on the inner side, whereby the cover member can be reliably fixed to the outer cylinder base end portion.
Examples of the fastening member include a resin binding band and a metal clamp member.

  Furthermore, in the above-described on-vehicle sensor, the tightening member is made of metal, and an engagement portion provided at the other end portion of the engagement member provided at the one end portion thereof is engaged with an annular shape. It is good to set it as the vehicle-mounted sensor which is a clamp member formed by fastening the said to-be-clamped part.

  In this in-vehicle sensor, the above-described clamp member is used as the tightening member. For this reason, it is easy to attach and remove the cover member to the tightened portion, and the tightened portion can be securely tightened.

  Further, in the above-described gas sensor control device, the cover member includes an outer convex portion that is adjacent to the proximal end side and the distal end side of the tightened portion, and bulges outward. A sensor is recommended.

In this in-vehicle sensor, since the cover member has the above-described outer convex portion, the displacement of the tightening member toward the distal end side and the proximal end side is prevented, and the tightening member and the cover member are positioned at the outer cylinder proximal end. It can be appropriately prevented from coming off the part.
In addition, although an outside convex part is good also as a form provided in one or more places in the circumferential direction, it is preferable to set it as the form which bulges cyclically | annularly.

  Furthermore, in the above-described gas sensor control device, the cover member is positioned on the base end side with respect to the crimping portion contact portion, and bulges in an annular shape toward the inside, and is annularly formed on the lead surrounding tube. It is good to set it as the vehicle-mounted sensor which has the base end side contact part which contacts.

  In this in-vehicle sensor, the cover member has the above-described proximal end contact portion. By this proximal end side contact portion, a gap between the lead surrounding tube and the cover member can be eliminated. For this reason, it is possible to further suppress water from entering the sensor.

It is a side view of the whole area air-fuel ratio sensor concerning an embodiment. It is a longitudinal cross-sectional view of the full range air-fuel ratio sensor which concerns on embodiment. It is explanatory drawing which shows the structure of a base end part among the whole area | region air fuel ratio sensors which concern on embodiment. It is a half sectional view of a cover member used for the full range air-fuel ratio sensor concerning an embodiment. It is a perspective view of a clamp member used for a full range air-fuel ratio sensor concerning an embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show an all-range air-fuel ratio sensor 1 (hereinafter also referred to as an air-fuel ratio sensor 1 or simply a sensor 1) that is an in-vehicle sensor of the present embodiment. The air-fuel ratio sensor 1 is a kind of gas sensor, and is mounted on an exhaust pipe of an internal combustion engine of a vehicle to detect the concentration of oxygen in the exhaust gas in order to perform air-fuel ratio feedback control in the internal combustion engine of the vehicle. First, the outline of the air-fuel ratio sensor 1 will be described with reference to FIGS. 1 and 2.

  The air-fuel ratio sensor 1 extends in an axial direction HJ (vertical direction in the figure) along the axis AX, and as a part of its exterior, a cylindrical portion having a screw portion 41 for fixing to an exhaust pipe formed on the outer surface. A metal shell 40 is provided. A double bottomed cylindrical protector 50 having a plurality of vent holes 50C is fixed to the front end GS (lower side in the figure) of the metal shell 40 by laser welding. On the other hand, a cylindrical metal outer cylinder 30 is fixed to the base end side GK (upper in the drawing) of the metal shell 40 by laser welding. And the plate-shaped detection element 2 extended in the axial direction HJ is arrange | positioned inside the protector 50, the main metal fitting 40, and the outer cylinder 30. As shown in FIG.

  Of this detection element 2, the distal end portion 2 </ b> S protrudes from the metal shell 40 to the distal end side GS and is disposed inside the protector 50, and the distal end portion 2 </ b> S detects the oxygen concentration. It has become. In the air-fuel ratio sensor 1, the tip side GS with respect to the screw part 41 of the metal shell 40 is attached to an exhaust pipe (not shown) so as to be disposed in the pipe, and the concentration of oxygen in the exhaust gas is detected. To do. The detection element 2 has a configuration in which a detection unit that detects the concentration of oxygen and a heater unit that heats the detection unit are stacked. Three sensor electrode terminals 2a, 2b, and 2c that conduct to the detection unit are formed on one surface 2K1 of the base end side GK of the detection element 2, and two electrodes that conduct to the heater unit are formed on the other surface 2K2. Heater electrode terminals 2d and 2e are formed.

  On the other hand, the outer cylinder 30 disposed outside the exhaust pipe has an outer cylinder base end portion 31, a first large diameter portion 32, a reduced diameter portion 33, and a second diameter from the base end side GK toward the front end side GS. A large diameter portion 34 is provided. Among these, the outer cylinder base end portion 31 includes a base end side opening 30H that opens to the base end side GK of the outer cylinder 30 and is crimped toward the inner side in the radial direction HR. The diameter is reduced to a small diameter. The reduced diameter portion 33 is also reduced in diameter by caulking toward the inside in the radial direction HR.

  Further, the metal shell 40 has a shelf portion 42 protruding inward in the radial direction HR, and a cylindrical metal cup 43 is disposed so as to engage with the shelf portion 42. . Further, in the metal shell 40, in order from the front end side GS to the base end side GK, a cylindrical ceramic holder 44 made of alumina, a first powder filling layer 45 made of talc powder or glass powder, and the like talc powder A second powder filling layer 46 made of glass powder or the like, and a cylindrical ceramic sleeve 47 made of alumina are disposed. Among these, the ceramic holder 44 and the first powder filling layer 45 are located in the metal cup 43. Further, the ceramic holder 44 and the ceramic sleeve 47 are penetrated in a rectangular shape along the axis AX, and the detection element 2 is inserted therein. Further, a caulking ring 48 is disposed between the ceramic sleeve 47 and the base end portion 40 </ b> K of the metal shell 40.

  The base end portion 40 </ b> K of the metal shell 40 is bent and crimped inward in the radial direction HR, and presses the ceramic sleeve 47 via the crimping ring 48. Thereby, the powder of the 1st powder filling layer 45 and the 2nd powder filling layer 46 is compressed, the ceramic sleeve 47 is fixed in the metal shell 40, and the detection element 2 is supported.

  On the other hand, in the outer cylinder 30, a connection body 60 is disposed inside the first large diameter portion 32 to the second large diameter portion 34. The connection body 60 includes a ceramic separator 61, three sensor lead frames 62, 63, 64, and two heater lead frames 65, 66. The separator 61 accommodates the sensor lead frames 62, 63, 64 and the heater lead frames 65, 66 in a state where they are separated so that they do not contact each other.

  The connection body 60 is attached to the proximal end side GK of the detection element 2 while being separated from the ceramic sleeve 47 described above. Specifically, the base end side GK of the detection element 2 is inserted into the opening 61 </ b> C that opens to the front end side GS of the separator 61. The sensor lead frames 62, 63, 64 and the heater lead frames 65, 66 are formed by the three sensor electrode terminals 2 a, 2 b, 2 c and the two heaters formed on the base end side GK of the detection element 2. The electrode terminals 2d and 2e are in contact with each other and are electrically connected.

  The connecting body 60 is urged toward the proximal end GK so as to abut on a grommet 4 to be described later by a generally cylindrical urging metal member 70 disposed around the connection body 60. Is held in. The urging metal fitting 70 is crimped together with the reduced diameter portion 33 of the outer cylinder 30, and is fixed by crimping inside the reduced diameter portion 33.

  Further, among the outer cylinder 30, inside of the outer cylinder base end portion 31 in the radial direction HR, a total of five lead wires 3 including three for sensors and two for heaters are inserted through the insertion holes 4 c. Grommet 4 is provided. The grommet 4 is swaged together with the outer cylinder base end portion 31 and is held in the outer cylinder base end portion 31 in a form of compressing its own crimped portion 4a. The portion 31 (base end side opening 30H) is closed. The five lead wires 3 are crimped to the sensor lead frames 62, 63, 64 and the heater lead frames 65, 66, respectively, with the lead tip 3S on the tip side GS being inserted into the connecting body 60. It is fixed and electrically connected to these. Thereby, the lead wire 3 and the detection element 2 are electrically connected in the connection body 60. The lead wire 3 is taken out of the sensor 1 and connected to a control device (not shown) installed at a remote location.

Next, the configuration of the base end portion of the air-fuel ratio sensor 1 according to the present embodiment will be further described with reference to FIG. As described above, the outer cylinder base end portion 31 of the base end side GK of the outer cylinder 30 includes the base end side opening 30H. Then, a fluoro rubber grommet 4 for inserting the lead wire 3 is disposed in the outer cylinder base end portion 31, and the outer cylinder base end portion 31 is caulked together with the grommet 4 toward the inner side in the radial direction HR. ing. As a result, of the outer cylinder base end portion 31, the crimped portion 31 a that has been reduced in diameter by caulking deformation compresses and holds the tightened portion 4 a of the grommet 4, and the grommet 4 holds the outer cylinder base end portion. 31 (base end side opening 30H) is closed. Further, by compressing the grommet 4, the lead wire 3 is also in close contact with the insertion hole 4 c of the grommet 4, and the insertion hole 4 c is also sealed in a liquid-tight manner. Further, as a result of the caulking deformation of the outer cylinder base end portion 31, the base end side GK of the caulking portion 31a forms a base end large diameter portion 31b larger in diameter than the caulking portion 31a.
In the present embodiment, a part of the grommet 4 protrudes to the base end side GK from the outer cylinder base end part 31, but the entire grommet 4 is located inside the outer cylinder base end part 31 and It is good also as arrangement | positioning which does not protrude from the cylinder base end part 31. FIG.

  Further, the lead wire 3 is taken out from the grommet 4 to the outside of the base end side GK, and a portion of the lead wire 3 on the base end side GK from the grommet 4 is made of fluororesin from the outside in the radial direction HR. It is surrounded by the lead surrounding tube 5. Further, at least a portion from the crimped portion 31a of the outer tube base end portion 31 of the outer tube 30 to the tube distal end portion 5S of the distal side GS of the lead surrounding tube 5 (in this embodiment, the tube of the lead surrounding tube 5). A portion slightly proximal to the distal end side GK from the distal end portion 5S) is covered with a cylindrical cover member 10 made of a fluororesin from the outside in the radial direction HR. The cover member 10 also indirectly covers a part of the lead wire 3 exposed from the grommet 4 disposed in the outer cylinder base end portion 31 and the tube distal end portion 5S of the lead surrounding tube 5. FIG. 4 shows a half sectional view of the cover member 10.

  Further, the cover member 10 has a crimped portion contact portion 14 that bulges in an annular shape toward the radial direction HR inner RI at the distal end GS thereof. The caulking portion abutting portion 14 can be engaged with the base end diameter large portion 31b of the outer cylinder base end portion 31, and is in contact with the caulking portion 31a. Thereby, the cover member 10 is difficult to come out from the outer cylinder base end portion 31 to the base end side GK.

  In addition, a metal clamp member 20 that surrounds and tightens the tightened portion 11 of the cover member 10 from the outside in the radial direction HR is fitted. FIG. 5 shows a perspective view of the clamp member 20. The clamp member 20 has a form in which a metal plate material is rounded in the thickness direction of the clamp member 20, and the other end portion 22 (its own other end 22 ( An engagement portion 22k that is provided with a slit in the tongue shape provided on the inner side and protrudes obliquely is engaged to form an annular shape, and the tightened portion 11 of the cover member 10 is tightened. The clamp member 20 can be detached from the tightened portion 11 by releasing the engagement between the engaged portion 21h and the engaging portion 22k. The caulking part 11 includes at least a part of the caulking part abutting part 14 on the inner side, and the caulking part abutting part 14 is tightened to the outer cylinder base end part 31 by tightening the clamp member 20. It strongly contacts the tightening portion 31a. Thus, the cover member 10 can be reliably fixed to the outer cylinder base end portion 31 by the clamp member 20.

  In addition, the cover member 10 includes outer convex portions 12 and 13 that are adjacent to the proximal end side GK and the distal end side GS of the tightened portion 11 and bulge in an annular shape toward the radial direction HR outer RO. Have. The outer protrusions 12 and 13 prevent the clamp member 20 from being displaced in the distal end side GS and the proximal end side GK.

  Further, the cover member 10 is located on the proximal side GK with respect to the crimping portion abutting portion 14, bulges out in an annular shape toward the radial direction HR inner RI, and a proximal end that annularly contacts the lead surrounding tube 5. A side contact portion 15 is provided. The base end side contact portion 15 also eliminates a gap between the lead surrounding tube 5 and the cover member 10.

It should be noted that the lead enclosing tube 5 and the cover member 10 are inserted into the lead wire 3 before the lead wire 3 is inserted into the grommet 4 and fixed to the outer cylinder base end portion 31 by caulking. . Specifically, first, the lead wire 3 is inserted through the lead enclosing tube 5, and further, the cover member 10 is put on these radial direction HR outer ROs. Then, after the lead wire 3 is inserted into the grommet 4 and fixed to the sensor lead frames 62, 63, 64 and the heater lead frames 65, 66, the outer cylinder base end portion 31 is crimped together with the grommet 4. To do. Thereafter, the cover member 10 is moved to the proximal side so that the crimped portion contact portion 14 of the cover member 10 contacts the crimped portion 31a of the outer cylinder proximal end portion 31 and engages with the proximal end large diameter portion 31b. The cover member 10 is attached to the outer cylinder base end portion 31 by being pushed in from the GK toward the distal end side GS.
In addition, after the cover member 10 is attached to the outer cylinder base end portion 31, the clamp member 20 is arranged around the tightened portion 11 of the cover member 10, and is engaged with the engaged portion 21 h and the engaging portion. 22k is engaged. Thereby, the to-be-tightened part 11 of the cover member 10 is fastened, and the cover member 10 is fixed to the outer cylinder base end part 31.

  Thus, by covering the grommet 4 and the lead wire 3 with the cover member 10 and the lead surrounding tube 5, when the car is washed using a high-pressure washing machine, the gap between the grommet 4 and the lead wire 3, Water is prevented from entering the sensor 1 through the gap between the grommet 4 and the outer cylinder base end portion 31.

  As described above, in the air-fuel ratio sensor 1 of the present embodiment, at least the portion from the crimped portion 31a of the outer tube base end portion 31 of the outer tube 30 to the tube distal end portion 5S of the lead surrounding tube 5 is present. Covered with a cover member 10. As a result, the cover member 10 also covers a part of the lead wire 3 exposed from the grommet 4 disposed in the outer cylinder base end portion 31 and the tube distal end portion 5S of the lead surrounding tube 5. For this reason, it can suppress that the grommet 4 and the lead wire 3 are exposed outside, and can prevent water from entering the inside of the sensor 1.

  Furthermore, the cover member 10 has a crimped portion contact portion 14 that bulges in an annular shape toward the radial direction HR inside RI. The caulking portion abutting portion 14 abuts on the caulking portion 31 a so as to be engageable with the base end diameter large portion 31 b of the outer cylinder base end portion 31. Thereby, the cover member 10 is made difficult to come out from the outer cylinder base end part 31 to the base end side GK.

  Furthermore, in the air-fuel ratio sensor 1 of the present embodiment, the tightened portion 11 of the cover member 10 is tightened by the clamp member 20. Thereby, the cover member 10 can be reliably fixed to the outer cylinder base end part 31. Further, the clamp member 20 can surely perform the tightening of the to-be-tightened portion 11 and is easy to attach and remove.

  Furthermore, since the air-fuel ratio sensor 1 of the present embodiment has the outer convex portions 12 and 13, the displacement of the clamp member 20 to the distal end side GS and the proximal end side GK is prevented, and the clamp member 20 and the cover It is possible to appropriately prevent the member 10 from being detached from the outer cylinder base end portion 31.

  Further, in the air-fuel ratio sensor 1 of the present embodiment, the cover member 10 has a base end side contact portion 15, and the base end side contact portion 15 allows the lead enclosure tube 5 and the cover member 10 to be connected. The gap between them can be eliminated. For this reason, it is possible to further suppress water from entering the inside of the sensor 1.

In the above, the in-vehicle sensor of the present invention has been described according to the full-range air-fuel ratio sensor 1 of the present embodiment, but the present invention is not limited to the above-described embodiment, and is within a range not departing from the gist thereof. Needless to say, the present invention can be applied with appropriate changes.
For example, the “in-vehicle sensor” in the present invention is not limited to an all-range air-fuel ratio sensor that is a kind of gas sensor, and examples thereof include an oxygen sensor that detects oxygen concentration and a NOx sensor that detects nitrogen oxide (NOx) concentration. Another gas sensor or an exhaust temperature sensor for measuring the exhaust gas temperature may be used.
Moreover, in this embodiment, although the metal clamp member 20 was used as a fastening member, the material and shape can be changed suitably. Further, the material and shape of the lead surrounding tube 5 and the cover member 10 can be changed as appropriate.

1 Full-range air-fuel ratio sensor (air-fuel ratio sensor, sensor, vehicle-mounted sensor)
2 Detection element 3 Lead wire 3S Lead tip portion 4 Grommet 4a Clamped portion 5 Lead enclosing tube 5S Tube tip portion 10 Cover member 11 Clamped portion 12, 13 Outer convex portion 14 Clamped portion abutting portion 15 Base end side Contact part 20 Clamp member 21 One end part 21h Engaged part 22 Other end part 22k Engagement part 30 Outer cylinder 30H Base end side opening 31 Outer cylinder base end part 31a Clamping part 31b Base end large diameter part AX Axis line HJ Axis line Direction GK Base side GS Tip side

Claims (5)

An in-vehicle sensor having a form extending in an axial direction along an axis,
A sensing element;
One or a plurality of lead wires that conduct to the detection element and extend toward the proximal end in the axial direction;
A cylindrical shape extending in the axial direction, and a metal outer tube that accommodates a lead tip portion on the tip side in the axial direction among the lead wires; and
The lead wire, which is made of a rubber-like elastic body and is disposed in the outer cylinder base end portion located on the base end side of the outer cylinder, closes the outer cylinder base end portion, and the lead wire passing therethrough is the base A grommet extending to the end side,
Comprising a resin tube, and comprising a lead enclosing tube surrounding the proximal end portion of the lead wire from the periphery of the grommet,
The outer cylinder base end of the outer cylinder is
A caulking portion whose circumference is reduced by caulking deformation, compressing and holding the caulked portion of the grommet, and
It has a base end diameter large portion which is located on the base end side with respect to the caulking portion and is larger in diameter than the caulking portion,
A cover member that is cylindrical and made of resin, and covers at least a portion from the caulking portion of the outer tube base end portion of the outer tube to the distal end side tube tip portion of the lead surrounding tube from the periphery. There,
An in-vehicle sensor comprising a cover member that has a caulking portion abutting portion that bulges inward and abuts the caulking portion so as to be engageable with the base end diameter large portion of the outer cylinder base end portion. The in-vehicle sensor according to claim 1,
A vehicle-mounted sensor provided with a fastening member that surrounds and tightens a to-be-clamped portion including at least a part of the crimping portion contact portion on the inside of the cover member. The in-vehicle sensor according to claim 2,
The fastening member is
The clamp member is made of metal, and is engaged with an engaged portion provided at one end portion of the metal, and an engagement portion provided at the other end portion of the metal is engaged to form an annular shape, and the tightened portion is tightened. In-vehicle sensor. The in-vehicle sensor according to claim 2 or claim 3,
The cover member is
The in-vehicle sensor which has the outer side convex part which adjoins the said base end side and the said front end side of the said to-be-clamped part, respectively, and bulges outward. The vehicle-mounted sensor according to any one of claims 1 to 4,
The cover member is
An in-vehicle sensor having a base end side contact portion that is positioned on the base end side with respect to the crimping portion contact portion, bulges out in an annular shape toward the inside, and contacts the lead surrounding tube in a ring shape.

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