JP2008298558A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance reliability as electrode connections by preventing the damage of the soldering part of a lead wire with the electrode part of a heater. <P>SOLUTION: A gas sensor includes a cup-shaped sensor element 3 and the heater 4 for heating the sensor element 3 arranged in a hollow inner part of the sensor element 3. A stress absorbing region part which forms U-shaped curved part 23a and 24a is provided to lead wires 23 and 24 electrically connected to live wires 17 and 18 each for supplying power from the outside at one end and fixed to the electrode parts 4a and 4b of the heater 4 at the other end by soldering and electrically connecting the live wires 17 and 18 and the electrode parts 4a and 4b. The stress such as stretching acting on the lead wires 23 and 24 is absorbed by the U-shaped curved part 23a and 24a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas sensor, and is particularly suitable for an oxygen concentration sensor that is used in an exhaust gas purification apparatus and includes a cup-type sensor element and a heater for heating a sensor element that is disposed inside the sensor element.

  As described in Patent Document 1 below, the structure of the gas sensor includes a heater 1 for heating the sensor element in the hollow interior of the cup-type sensor element 2 (FIG. 1), and a lead for supplying power to the electrode portion of the heater 1. The line 103 is fixed by brazing (FIG. 2). The brazed lead wire 103 is formed with a bent portion having an angle as shown in the figure. The lead wire in which the bent portion is formed has a structure having high rigidity as a whole and is difficult to deform and absorb stress. The other end of the lead wire 103 is electrically caulked and connected to an energizing line that supplies electric power from the outside, and the caulking connection portion is a free end.

  Further, as shown in the drawing, the lead wire 103 has a structure in which a bent portion is formed in a brazed portion with the electrode portion of the heater 1 so as to protrude toward the base end side (direction in which the conducting wire is disposed). Yes.

Therefore, when assembling the lead wire 103 that is brazed and fixed to the electrode portion of the heater 1 and the conductive wire electrically connected to the lead wire 103, the lead wire 103 moves (direction along the drawing). ) And the bent portion are high in rigidity and difficult to absorb stress. Therefore, the brazed fixing portion of the lead wire 103 is pulled in a direction deviating from the electrode portion, and a large tensile stress acts on the brazed portion. There is a risk of defects such as cracks in the part. In addition, since the gas sensor is attached to the exhaust pipe of an automobile, the lead wire may move due to vibration, and the above-described problem may occur.
JP 2001-203063 A

  The present invention has been made in view of the above points. A stress acting on a lead wire, one end of which is connected to an energizing wire for supplying power and the other end is brazed and fixed to the electrode portion of the heater. By providing a stress-absorbing area that absorbs heat, it absorbs stress acting on the lead wire due to vibration or vibration, preventing damage to the brazed part between the lead wire and the electrode part of the heater. It is to improve the reliability.

The invention according to claim 1 includes a cup-type sensor element and a heater that is disposed inside the sensor element and that heats the sensor element, and one end of the sensor element is electrically connected to an energization line that supplies electric power from the outside. A gas sensor in which the other end is brazed and fixed to the electrode portion of the heater, and a lead wire for electrically connecting the energization wire and the electrode portion is disposed,
The lead wire is provided with a stress absorbing region portion that absorbs stress acting on the lead wire.

  According to the above configuration, stress acting on the lead wire due to assembly or vibration is absorbed by the stress absorption region portion to prevent damage to the brazed portion between the lead wire and the electrode portion of the heater, and as an electrode connection portion. Reliability can be improved.

  In the invention which concerns on Claim 2, let the said stress absorption area | region part be a curved part formed in curved shape.

  According to the above configuration, even when a tensile stress that causes the lead wire to be separated from the brazing portion of the electrode portion is applied to the lead wire, the bending portion is deformed, and the stress can be reliably absorbed by the bending portion.

  According to a third aspect of the present invention, the bending portion has a curved shape in which the lead wire protrudes from the electrode portion toward the distal end side at the brazing fixed position.

  According to the above configuration, even if a tensile stress that causes the lead wire to be separated from the brazed portion of the electrode portion acts on the lead wire, the bending portion protrudes toward the distal end side, so that the amount of stress absorption deformation is large. Since the stress that causes the lead wire to separate from the electrode portion hardly acts on the brazing fixing portion, the brazing fixing portion does not cause detachment damage.

  In the invention which concerns on Claim 4, the shape of the said curved part is made into U shape.

  According to the above configuration, by making the curved portion U-shaped, it is possible to obtain a larger amount of stress-absorbing deformation with respect to tensile stress that deviates from the brazed portion of the electrode portion, and absorbs stress at the U-shaped top portion. Accordingly, the stress that causes the lead wire to be separated from the electrode portion can be reliably absorbed in a U shape in the brazing fixing portion, and the detachment damage of the brazing fixing portion can be reliably prevented. In addition, since the lead wire can be made long by using the U shape, it is easy to secure a fixing allowance for the caulking connection portion between the lead wire and the conducting wire, and it is possible to achieve a caulking connection in a space-saving manner.

  Hereinafter, the gas sensor 1 of the present invention will be described with reference to FIG. In the description of the gas sensor 1 of the present invention, as shown in FIG. 1, the downward direction of the drawing is referred to as the distal end side of the gas sensor 1, and the upward direction is referred to as the proximal end side of the gas sensor 1. Further, the gas sensor 1 of the present invention is an example of an oxygen concentration sensor used in an exhaust gas purification device for an automobile.

  A housing 2 made of a heat-resistant metal such as stainless steel has a cylindrical shape, and a cup-type sensor element 3 having a proximal end opened and a distal end closed is disposed inside the hollow. The sensor element 3 is made of an oxygen ion conductive material such as zirconia.

  A heater 4 in which a ceramic material such as alumina is formed in a long axis is disposed in the hollow interior of the sensor element 3. An insulating powder 5 such as talc is filled between the hollow inner surface of the housing 2 and the outer peripheral surface of the sensor element 3, and an insulating powder molded body 6, a ring shape such as ceramic and glass is provided on the base end side. An insulating sealing member 7 is attached, and a ring-shaped metal cushioning member 8 made of an elastic member is attached to the base end side of the insulating sealing member 7. The sensor element 3 is fixed by caulking the base end portion 2 b on the base end side of the housing 2 through engagement with a metal-like buffer member 9. By the caulking and fixing, the insulating powder 5, the insulating powder molded body 6, and the ring-shaped insulating sealing member 7 separate and seal the front end side and the base end side on the outer peripheral surface of the sensor element 3, and the exhaust gas is basified from the front end side. Prevents distribution to the end side.

  A reference electrode fitting 10 is attached to the inner peripheral surface of the base end side of the sensor element 3 so as to be in close contact with the inner surface, and is electrically connected to the reference electrode layer 10a formed on the inner peripheral surface of the sensor element 3 on the front end side. The measurement electrode fitting 11 is gripped and attached to the outer peripheral surface of the proximal end side of the sensor element 3 and is electrically connected to the measurement electrode layer 11a formed on the outer peripheral surface of the distal end side of the sensor element 3. The electrode fittings 10 and 11 form a pair of electrodes, and the electrode fittings 10 and 11 have a pair of signal lines (not shown) for extracting an electromotive force signal generated between the electrode layers 10a and 11a in a direction orthogonal to the drawing. Has been placed.

  A cover inner cylinder 12 and a cover outer cylinder 13 that protect the sensor element 3 from exhaust gas and have a plurality of exhaust gas introduction holes 12a and 13a are caulked and fixed at the front end side of the housing 2 at the front end portion 2c.

  A cylindrical metal casing 14 is fixed to the base end side of the housing 2 by welding or the like, and a pair of sealing members 15 and 16 made of an insulating elastic material such as rubber are caulked to the base end side of the casing 14. A pair of conducting wires 17 and 18 that are fixed and supply power to the heater 4 in the axial direction of the sealing members 15 and 16 are passed. A pair of signal lines (not shown) that are electrically connected to the electrode fittings 10 and 11 are passed through the sealing members 15 and 16 in the axial direction.

  A plurality of lateral through holes 14 a are formed on the outer periphery of the base end side of the casing 14, and the through holes 14 a are mounted in the centers of the lateral holes 15 a formed in the sealing members 15 and 16 and the sealing members 15 and 16. A pair of ventilation holes 19a and 19b formed in the filter holding member 19 communicate with each other, and external gas (air) is introduced into the casing 14 through the through holes 14a, the lateral holes 15a, and the ventilation holes 19a and 19b. The gas (air) is introduced into the hollow interior of the sensor element 3 and touches the reference electrode layer 10a.

  The two vent holes 19a, 19b are formed so as to be shifted from each other within the range of the inner enlarged port 15b following the horizontal hole 15a with respect to the axis of the horizontal hole 15a. The sealing members 15, 16 and the filter holding member 19 One of the two vent holes 19a and 19b communicates with the lateral hole 15a even if there is a variation during assembly.

  A pair of heater electrode portions 4a and 4b are exposed on the outer peripheral surface of the proximal end side of the heater 4, and a heating element (not shown) is electrically connected between the electrode portions 4a and 4b and embedded in the heater 4. Then, electric power is applied between the electrode portions 4a and 4b, and the heating element generates heat to form a heater.

  An insulator 20 made of an insulating material is fixed to a substantially central portion of the casing 14 by a ring member 25. The central cylindrical hollow portion 20a has a proximal end side of the heater 4 in which the electrode portions 4a and 4b are disposed, and one end. Are electrically connected to energization wires 17 and 18 for supplying electric power from the outside by a pair of connection fittings 21 and 22, and the other ends are brazed and fixed to the electrode portions 4 a and 4 b of the heater 4. A pair of lead wires 23 and 24 that electrically connect the electrode portions 4a and 4b are disposed. The pair of connection fittings 21 and 22 are not fixed to the insulator 20 and can be displaced. The pair of lead wires 23 and 24 are connected to the connection fittings 21 and 22 at one end side (anti-brazing fixing portion side). ) Is the free end.

  The lead wires 23 and 24 are provided with the stress absorption region portion in the present invention, and specifically, curved curved portions 23a and 24a are formed. More specifically, the curved portions 23a and 24a are formed in a U shape.

  The lead wires 23 and 24 having U-shaped curved portions 23a and 24a are substantially on the outer peripheral surface of the heater 4 from the brazing fixing portion fixed to the electrode portions 4a and 4b of the heater 4 to the tip side as shown in the figure. A linear portion is formed by projecting along a straight line, curved in a semicircular shape at the tip, and formed into a straight portion substantially parallel to the outer peripheral surface of the folded heater 4 to be connected to the connection fittings 21 and 22. Yes. The lead wires 23 and 24 have curved portions 23a and 24a and have a thin U-shape as a whole.

  The gas sensor 1 having the above-described configuration is screwed and fixed to the exhaust pipe A by a mounting screw 2d provided on the housing 2 via a gasket 26.

  In the gas sensor 1 according to the present invention, a stress absorbing region is provided in the lead wires 23 and 24 that are brazed and fixed to the electrode portions 4a and 4b of the heater 4 and electrically connect the conducting wires 17 and 18 and the electrode portions 4a and 4b. Since the portions 23a and 24a are provided, the stress absorbing region portions 23a and 24a absorb the stress acting on the lead wires 23 and 24 due to vibration or the like so as to absorb the lead wires 23 and 24 and the electrode portion 4a of the heater. It is possible to prevent damage to the brazed portion with 4b and improve the reliability as the electrode connecting portion.

  Further, in the gas sensor 1 of the present invention, since the stress absorbing region portions 23a and 24a are specifically curved portions 23a and 24a, the lead wires 23 and 24 are connected to the lead wires 23 and 24 as electrode portions. Even if a tensile stress that deviates from 4a and 4b is applied, the bending portions 23a and 24a are deformed and the bending portions 23a and 24a can reliably absorb the stress.

  Furthermore, in the gas sensor 1 of the present invention, the bending portions 23a, 24a are curved in the direction in which the lead wires 23, 24 protrude from the electrode portions 4a, 4b to the distal end side at the brazing fixed position. Therefore, even if a tensile stress that causes the lead wires 23 and 24 to be separated from the brazing portions of the electrode portions 4a and 4b is applied to the lead wires 23 and 24, the lead wires 23 and 24 are applied to the brazing fixing portion. Since the stress that causes the electrode parts 4a and 4b to deviate from each other hardly acts, the brazing fixing part is not damaged.

  Further, in the gas sensor 1 of the present invention, the curved portions 23a, 24a are formed in a specific U shape, so that the line segment for absorbing stress becomes long, and the lead wires 23, 24 are connected to the electrode portions 4a, 4b. The amount of stress-absorbing deformation can be increased with respect to a tensile stress that is deviated from the brazing portion of the steel, and the stress is absorbed at the top of the U-shaped tip side. Accordingly, the stress that separates the lead wires 23 and 24 from the electrode portions 4a and 4b is reliably absorbed in the U-shape in the brazing fixing portion, and the detachment damage of the brazing fixing portion can be reliably prevented. Further, since the length of the lead wires 23 and 24 can be increased by making the curved portions 23a and 24a U-shaped, the caulking connection fittings 21 and 22 between the lead wires 23 and 24 and the conducting wires 71 and 18 are used. It is easy to secure the fixing allowance of the cable, and it is possible to enable caulking connection in a small space.

  In addition, since the gas sensor 1 of the present invention is applied to the oxygen concentration sensor of the exhaust gas purification apparatus, the exhaust gas purification function is ensured by the oxygen concentration sensor as the reliable gas sensor 1 of the electrode portions 4a and 4b which are electrode connection portions. Can be achieved.

  In addition, the shape of the stress absorption area | region parts 23a and 24a provided in the lead wires 23 and 24 mentioned above is a curved shape, Specifically, it is the curved parts 23a and 24a which protruded from the electrode parts 4a and 4b to the front end side, More specifically, the curved portions 23a and 24a are U-shaped. However, the stress absorption region portion in the present invention is not limited to the shape described above, and the curved portion may have various shapes such as a spiral shape and a wave shape. Any shape that absorbs the stress acting on the wire and functions so that the stress does not act on the lead wire and the brazed fixing portion of the electrode portion may be used. And it is important that the lead wire coming out of the brazing fixing portion of the electrode portion protrudes in the direction of the front end side of the heater.

  Furthermore, although the gas sensor according to the present invention is an application example of an oxygen concentration sensor used in an exhaust purification device, the present invention is not necessarily limited thereto, and the present invention may be another temperature sensor or the like.

It is a longitudinal cross-sectional view which shows one Embodiment of the gas sensor which becomes this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Housing 3 Cup-type sensor element 4 Heater 4a, 4b Electrode part 12, 13 Cover 14 Casing 15, 16 Sealing member 17, 18 Conductive wire 21, 22 Connection metal fitting 23, 24 Lead wire 23a, 24a Stress absorption area part U-shaped curved part

Claims (4)

A cup-type sensor element;
A heater disposed inside the hollow of the sensor element for heating the sensor element;
One end is electrically connected to a conducting wire for supplying electric power from the outside, the other end is brazed and fixed to the electrode portion of the heater, and a lead wire for electrically connecting the conducting wire and the electrode portion is disposed Gas sensor,
The gas sensor according to claim 1, wherein the lead wire is provided with a stress absorption region that absorbs stress acting on the lead wire.   The gas sensor according to claim 1, wherein the stress absorption region portion is a curved portion formed in a curved shape.   The gas sensor according to claim 2, wherein the curved portion has a curved shape in which the lead wire protrudes from the electrode portion toward the distal end side at the brazing fixing position. The gas sensor according to claim 2 or 3, wherein the curved portion is substantially U-shaped.