JP2015087383A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor having excellent current-carrying reliability of a heater.SOLUTION: Disclosed is a gas sensor which at least includes: a gas sensor element; a heater; a pair of conductive lines: and a pair of terminal metal fittings 1 which achieves connection between a pair of electrode pads and a pair of conductive lines provided on both sides on opposing flat surfaces of a heater. The terminal metal fitting 1 includes a flat plate like base part 10 extending in the axial direction, a bent part 11, an abutting part 12, and a crimp part 13. The abutting part 12 is formed in a spherical shape curved so as be projected toward the electrode pad side.

Description

  The present invention relates to a gas sensor for detecting the concentration of a specific gas component in a gas to be measured, and more particularly to a terminal fitting for connecting a heater and the outside for activating the gas sensor at an early stage.

  2. Description of the Related Art Conventionally, a gas sensor for detecting the concentration of a specific gas component such as oxygen contained in combustion exhaust has been provided in a combustion exhaust flow path of an internal combustion engine such as an automobile engine, and the air-fuel ratio is determined by the detected concentration of the specific gas component. Control and temperature control of exhaust treatment catalyst are performed.

  As such a gas sensor, an oxygen concentration detection element is provided in which a measurement electrode layer in contact with a gas to be measured and a reference electrode layer in contact with the atmosphere introduced as a reference gas are provided on the surface of an oxygen ion conductive solid electrolyte such as zirconia. An oxygen sensor that detects the potential difference between the two electrodes based on the difference between the oxygen concentration in the gas to be measured and the oxygen concentration in the reference gas to measure the oxygen concentration in the gas to be measured, An air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture introduced into the internal combustion engine from the concentration of the gas component, an ammonia sensor that detects the ammonia concentration in the gas to be measured using a hydrogen ion conductive solid electrolyte body, etc. are widely used It has been.

In Patent Document 1, a cup-shaped solid body having a cylindrical shape with a bottom, a reference gas chamber provided therein, an inner electrode on the inner surface facing the reference gas chamber, and an outer electrode provided on the outer surface in contact with the gas to be measured. A gas sensor having a sensor element made of an electrolyte body and having a heater inserted and arranged in the reference gas chamber by a heater holder is disclosed.
In such a gas sensor, conventionally, the connection between the heater and the energization line for connecting the external power source is made by connecting a pair of electrodes provided on the base end side of the heater by brazing, welding, etc. Then, the terminal member and the conductive wire are connected via a crimp terminal (see Patent Document 1, FIG. 2, etc.).

  On the other hand, in Patent Document 2, in a so-called stacked gas sensor in which two electrode pads are drawn out on both surfaces of the base end side of a sensor element formed in a flat plate shape, in order to achieve conduction with a signal line, A leaf spring-like terminal fitting is disclosed by providing a protrusion protruding to the sensor side (electrode side) at a contact point with the electrode (see, for example, FIG. 10 of Patent Document 2).

  When connecting the electrode pad of the so-called stacked heater as in Patent Document 1 and the conducting wire, the protrusion protruding toward the electrode pad side is elastically formed in the contact portion as in Patent Document 2. When the terminal metal fittings that are pressed and conductive are used, the pair of terminal metal parts press the electrode pads formed on both sides of the plate-shaped heater from both sides.

JP 2001-305098 A JP 2013-181769 A

At this time, due to the assembly error of the terminal fitting, the position where the projection of one terminal fitting presses the electrode pad provided on one side of the heater and the projection of the other terminal fitting is provided on the other side. If a deviation occurs in the cross-sectional direction perpendicular to the axial direction of the heater between the position where the electrode pad is pressed, a moment in the rotational direction acts around the longitudinal axis of the heater, and the heater tilts greatly. The angle with respect to the pressing direction of the electrode pad forming surface and the terminal fitting is increased.
For this reason, the contact load at the contact point becomes small, and when external vibration is applied, for example, there is a possibility that the instantaneous conduction is interrupted and the reliability of the gas sensor is lowered.

  Therefore, in view of such a situation, the present invention provides a flat heater extending in the axial direction, a pair of electrode pads provided on each of the opposing planes, and an elastic member that connects the pair of electrode pads and the pair of conductive wires. A gas sensor comprising a pair of terminal fittings, and a highly reliable gas sensor that can suppress a decrease in contact load and stabilize contact resistance even if a positional deviation occurs between a pair of opposing terminal fittings. The purpose is to provide.

  In the present invention, the gas sensor (GS) detects the concentration of a specific gas component in the gas to be measured, and at least the gas sensor element (4) generates heat when energized to activate the gas sensor element (4). A flat heater (3) provided in the axial direction of the gas sensor element (4), a pair of energizing wires (2) for connecting the heater (3) and the outside, and the heater (3) A pair of terminal fittings (1) made of an elastic member provided to connect the pair of electrode pads (31) provided on both sides of the opposing plane on the base end side of the pair and the pair of conductive wires (2); The terminal fitting (1) includes a flat base portion (10) extending in the axial direction, a bent portion (11) where the base portion (10) is folded back toward the base end, Provided at the tip of the bend (11) A contact portion (12) that is urged by the bent portion (11) and elastically contacts the electrode pad (31), and is provided on the base end side of the base portion (10), and is connected to the conductive wire (2). A crimping portion (13) connected to the core wire (20), and the contact portion (12) is formed in a spherical shape curved so as to be convex toward the electrode pad (31) side. It is characterized by that.

According to the present invention, the pair of contact portions opposed to each other with the heater (3) interposed therebetween, even when the positional deviation occurs in the cross-sectional direction due to the assembly accuracy of the pair of terminal fittings (1). In the straight line connecting the center point (O) of one of the cross-sectional curvature radii (R ₂ ) of (12) and the center point (O) of the other cross-sectional radius of curvature (R ₂ ), both contact portions are always provided. Since (12) contacts and generates a contact load (F) in a direction perpendicular to the electrode pad (31), a decrease in the contact load (F) can be suppressed.

The perspective view which shows the whole terminal metal fitting 1 outline | summary which is the principal part of the gas sensor in the 1st Embodiment of this invention. 1 is a longitudinal sectional view of the terminal fitting 1 of FIG. A cross-sectional view along the line BB in FIG. 1B in a state in which the pair of terminal fittings 1 is attached to the heater 3. As a comparative example, a perspective view showing an outline of a conventional terminal fitting 1Z in which a protrusion Pc is provided on the contact portion 12Z. Cross section showing the contact load reduction suppression effect of the present invention Cross-sectional view showing the problem of contact load reduction in the comparative example Characteristic diagram showing the relationship between the cross-sectional radius of curvature R ₂ to exhibit the effect of the present invention the amount of displacement δ Characteristic diagram showing the cross section radial extent R ₂ capable of exhibiting the effects of the present invention with respect to the thickness T ₃ of any of the heater 3 The longitudinal cross-sectional view which shows the outline | summary of the whole gas sensor GS in embodiment of this invention The perspective view which shows the modification 1a of the terminal metal fitting which is the principal part of this invention

The present invention relates to a gas sensor GS for detecting the concentration of a specific gas component in a gas to be measured, and a terminal fitting 1 for connecting a heater 3 and a conducting wire 2 used to activate the gas sensor GS at an early stage. The contact portion 12 is formed in a spherical shape that curves so as to protrude toward the electrode pad 31 provided on the surface of the opposing heater 3.
In the present invention, the detection target is not particularly limited, and the contact portion 12 of the terminal fitting 1 which is a main part of the present invention is formed in a predetermined shape, thereby improving the contact reliability of the contact. As long as not departing from the spirit of the invention, the configuration of the gas sensor element can be changed as appropriate.

The terminal fitting 1 will be described with reference to FIGS. 1A, 1B, and 1C.
The terminal fitting 1 is made of a metal material having excellent electrical conductivity and elasticity.
The terminal fitting 1 includes a base portion 10, a bent portion 11, a contact portion 12, a crimping portion 13, and a bent portion 14.

The base 10 is formed in a flat plate shape extending in the axial direction.
The bent portion 11 is formed by folding the distal end side of the base portion 10 toward the proximal end side.
The bent portion 11 urges the contact portion 12 provided on the distal end side thereof toward the electrode pad 31 provided on the surface of the heater 3.
The contact portion 12 elastically contacts the electrode pad 31 formed on the surface of the heater 3.
The crimping part 13 is provided on the proximal end side of the base part 10, connected to the core wire 20 of the conducting wire 2, and fixed by crimping.
The bending portion 14 is provided between the crimping portion 13 and the base portion 10, and when housed in the gas sensor GS, the bending portion 14 is appropriately curved and is displaced from a position where the terminal fitting 1 is held and a position where the conducting wire 2 is held. Buffer.

When the pair of terminal fittings 1 according to the present invention is assembled to the heater 3, the contact portion 12 of the terminal fitting 1 elastically holds the electrode pad 31 from both sides of the heater 3 with the heater 3 interposed therebetween, as shown in FIG. Thus, the terminal metal 1 and the electrode pad 31 are electrically connected.
The contact load F acts in the normal direction of the contact portion 12 on a straight line connecting the centers O of the cross-sectional curvature radii R ₂ of the respective contact portions 12, and the pair of terminal fittings 1 are located at the center position of the heater 3. Maximum when assembled.

Further, it sets in the abutment section 12, as in relation to the cross-sectional radius of curvature R ₂ which is perpendicular to the longitudinal section radius of curvature R ₁ and a longitudinal axis direction along the longitudinal axis of the heater 3, satisfy the relationship of Formula 1 Has been.
R ₂ > R ₁ Formula 1

Further, the difference ΔH (= H) between the free height H ₁ from the surface of the base 10 of the terminal fitting 1 to the contact portion 12 and the contact height H ₂ when contacting the electrode pad 31 of the heater 3. the ₁ -H _2), expressed as a relative displacement amount relative to the heater electrode portion thickness _{T 3 δ (= ΔH / T} 3), and the cross-sectional radius of curvature _{R 2} with respect to the heater electrode portion thickness _{T 3} It has been found that it is desirable to set the relationship of Equation 2 between the relative displacement δ and the relative radius r ₂ when expressed by the relative radius r ₂ (= R ₂ / T ₃ ).

Further, when the heater electrode portion thickness T ₃ the length leading to the surface of the electrode pad 31 formed on the other surface opposite from the surface of one electrode pad 31 formed on the surface of the heater 3, the heater electrode portion by forming such relationship of equation 3 is established between the thickness T ₃ and the transverse surface radius of curvature R _2, and the contact load F of the contact portion 12 with respect to the electrode pads 31 proved not to lower than 10% .
R ₂ ≧ 2 × T ₃ Formula 3

More specifically, the heater electrode portion thickness _{T 3,} 0.8 mm or more and 1.6mm or less, cross-sectional radius of curvature _{R 2} is 3.0mm or more, is set to be below 8.0 mm.

Here, a conventional terminal fitting 1Z shown as a comparative example with reference to FIG. 2 will be described.
In addition, about the common part of the terminal metal fitting 1Z and the terminal metal fitting 1 which concerns on this invention, since the same code | symbol was attached | subjected and the branch number of Z was attached | subjected to the different part, description about the same part is abbreviate | omitted, The difference will be mainly described.
In the comparative example, rather than a spherical curved drawing a relatively gentle curve, such as in the present invention, are projections P _C that protrudes toward the electrode pad side formed in the center of the contact portion 12Z, projection the radius of curvature R _Z parts Pc is a longitudinal sectional radius of curvature R ₁ of the contact portion 12 of the terminal fitting 1 of the present _invention, and, much smaller than any transverse section a radius of curvature R ₂ (e.g., R _Z = 0.3 to 0.7 mm).

Here, with reference to FIG. 3 and FIG. 4, the effect of this invention and the problem in a comparative example are demonstrated.
As shown in FIG. 3, when the pair of terminal fittings 1 are assembled, the center point O of one terminal fitting 1 and the center point O of the other terminal fitting 1 are X (mm) in the cross-sectional direction. even if the positional deviation occurs, then rotated by an angle θ tilt heater 3, and the center point O one cross-sectional radius of curvature R ₂ of the pair of contact portions 12 which face each other across the heater 3 and the other Since both contact portions 12 are always in contact with each other on the straight line connecting the center point O of the cross-sectional curvature radius R ₂ , the contact load F in the direction orthogonal to the electrode pad 31 is generated, so that the contact load F is reduced. Can be suppressed.
In this case, compared with the normal position of the center point O of the pair of terminal fittings 1 coincides with the center position of the heater 3, slightly abutment at the height of H ₂ abutting portion 12 when misalignment occurs Therefore, the displacement amount ΔH is slightly decreased, and the contact load F (equivalent to the spring constant K × displacement amount ΔH) is also decreased.
However, by setting the cross-sectional direction radius of curvature R ₂ within the scope of the present invention, even if a positional deviation amount X (mm) 1.5 times the heater electrode plate thickness T ₃ occurs in the cross-sectional direction, the contact point It has been found that the decrease in the load F can be suppressed within 10%.

On the other hand, in the comparative example shown in FIG. 4, when misaligned with the same amount of the pair of terminal fittings 1Z, since the radius of curvature R _Z of the projections P _C is small, the center point O _Z of both projections P _C rotation angle theta _Z to the direction of action of the straight line and the contact load F coincides connecting increases.
Therefore, depending on the width of the terminal fitting 1Z, before the line connecting the contact point load F acting direction and the center point O _Z coincide, the side surface of the heater 3 and the terminal fitting 1Z abuts, the rotation of the heater 3 Since it stops, the contact load F falls.
Moreover, the contact load F of the terminal fitting 1Z facing each other for deviates from a straight line connecting the center point O _Z, rotation moment that twisting the heater 3 is generated.
As a result, it has been found that in the conventional gas sensor, the stress remaining in the heater 3 and the thermal stress act in a superimposed manner during use, and the heater is likely to crack.

Here, with reference to FIG. 5A and FIG. 5B, the relative radius r ₂ and the relative displacement δ of the contact portion 12 of the terminal fitting 1 which is the main part of the gas sensor of the present invention, and the heater electrode portion plate thickness T ₃ , The result of investigating the relationship with the contact load F will be described.
Figure 5A is a cross-sectional direction of curvature radius R ₂ to change the displacement amount [Delta] H, determines that there is effective range does not decrease the contact force F is 10% or more, in which to determine the limit region. As a result, it was confirmed that there was an effect in the range satisfying the relationship of Formula 2.

Furthermore, as shown in Figure 5B, wherein 1, satisfy the relationship of Equation 3, the heater electrode portion thickness _{T 3} is 0.8mm or more, at 1.6mm or less, cross-sectional direction the radius _{R 2} is, 3.0 mm or more It was found that the effect of the present invention is exhibited when the thickness is 8.0 mm or less.
R ₂ > R ₁ Formula 1
By making the longitudinal section curvature radius R ₁ of the contact portion 12 smaller than the transverse section curvature radius R ₂ , even if there is a difference in the displacement amount ΔH of the contact portion 12, the spring arm up to the point of contact with the element Since the length is substantially constant and the change in the contact position is small, the contact load F can be stabilized.
As will be described later, since the middle of the heater 3 is held by the heater gripping portion 73 shown in FIG. 6, the linearity of the heater 3 is ensured and the contact displacement in the axial direction can be ignored.
R ₂ ≧ 2 × T ₃ Formula 3

An example of the gas sensor GS in the embodiment of the present invention will be described with reference to FIG.
The gas sensor GS of the present invention is not particularly limited in application, and can be applied to various applications by appropriately changing the configuration of the gas sensor element 4. For example, by devising the electrode shape and control method, the air-fuel ratio can be detected, NOx can be detected, or a solid electrolyte material having proton conductivity can be used for a gas sensor that performs ammonia detection or the like. it can.
In the following embodiments, a typical oxygen sensor will be described as an example of such a gas sensor.
The gas sensor GS detects the concentration of a specific gas component in the gas to be measured. The gas sensor GS includes at least the gas sensor element 4, the heater 3, the terminal fitting 1, and the conductive wire 2, and includes a configuration generally used for a gas sensor.

The conducting wire 2 is connected to a power supply (not shown) provided outside, and the core wire 20 covered with an insulating coating is caulked and fixed to the crimping portion 13 of the terminal fitting 1.
As described above, the terminal fitting 1 is made of an elastic member having conductivity and elasticity, and includes a base portion 10, a bending portion 11, a contact portion 12, a crimping portion 13, and a bending portion 14, and the contact portion 12 is an electrode. It is formed in a spherical shape that curves so as to be convex toward the pad 31.

The heater 3 is a so-called laminated heater, and a heating element 32 that generates heat when energized is embedded therein, and is covered with an insulator 30 made of a known insulating material such as alumina and formed in a flat plate shape. A pair of electrode pads 31 that are electrically connected to the heating element 32 are formed on opposing planes on the base end side.
The gas sensor element 4 is a so-called cup-type sensor element, in which a solid electrolyte material such as zirconia having conductivity with respect to oxygen ions is formed in a bottomed cylindrical shape, and a signal extraction unit 40, a diameter expansion unit 41, and a detection unit 42. A reference gas chamber 43 is used.

The detection unit 42 is formed on the solid electrolyte layer 420 and the inner peripheral surface thereof, is formed on the outer peripheral surface of the reference electrode layer 421 that is in contact with the atmosphere introduced into the reference gas chamber 43 as a reference gas, and is used as a gas to be measured. The measurement electrode layer 422 is in contact therewith.
The reference electrode layer 421 is connected to the plus terminal fitting 72+ on the base end side of the gas sensor element 1, and is connected to the plus signal line 70+ via a crimping portion 71+ provided on the base end side of the plus terminal fitting 72+.
A heater gripping portion 73 is provided on the front end side of the plus terminal fitting 72+, and the heater 3 is held in the gas sensor element 4.

The measurement electrode layer 422 is connected to the minus terminal fitting 72- on the base end side of the gas sensor element 4, and further through the crimping portion 71- provided on the base end side of the minus terminal fitting 72-. It is connected to the.
The pair of terminal fittings 1, the plus terminal fitting 72+, and the minus terminal fitting 72- are each insulated and separated by an insulator 80 formed of a known insulating material such as alumina.

The gas sensor element 4 is accommodated inside a housing 5 that is formed in a cylindrical shape using a known metal material such as stainless steel, iron, nickel, etc., and a diameter-expanded portion 41 is provided in a locking portion 51 provided inside the housing 5. It is locked.
Sealing composed of a powder filling portion 60 made of talc powder, a cylindrical insulator 61, and a metal seal 62 between the inner peripheral surface of the housing 5 and the outer peripheral surface of the gas sensor element 4 so as to cover the enlarged diameter portion 41. The member 6 is disposed, and the sealing member 6 is pressed in the axial direction by the caulking portion 53 to ensure the airtightness between the housing 5 and the gas sensor element 4.

The detection part 42 of the gas sensor element 4 is exposed at the front end side of the housing 5, and the detection part 42 is covered with a cover body 90 fixed to the front end of the housing 5.
The cover body 90 is provided with an opening 91 for introducing a gas to be measured.
In the present invention, the configuration of the cover body 90 is not limited, and a plurality of cover bodies may be arranged concentrically, and the position, size, shape, and the like of the opening 91 can be appropriately changed.

A screw portion 54 for fixing to the gas flow path to be measured is formed on the outer periphery on the front end side of the housing 5, and a hexagonal portion 55 for tightening the screw portion 54 is formed on the outer periphery on the base end side. A boss portion 52 is formed on the surface.
A stepped cylindrical casing 86 is fixed to the boss portion.
The casing 86 is made of a metal such as stainless steel and covers the base end side of the heater 3 and the gas sensor element 4, and includes a pair of terminal fittings 1, a plus terminal fitting 72+, a minus terminal fitting 72-, an insulator 80, and a pair of signal wires 70+. / 70-, the pair of conductive wires 2 are sealed and fixed.

The insulator 80 is accommodated in a cylindrical casing 86 and is elastically held by holding means 81.
A grommet 82 made of heat-resistant rubber or the like, a water repellent filter 83, and a vent hole 85 are provided on the base end side of the casing 86, and are caulked and fixed by a caulking portion 84 to prevent moisture from entering the sensor. Only the introduction of is allowed.

  In the gas sensor GS of the present invention, the terminal fitting 1 for conducting the heater 3 that heats and activates the gas sensor element 4 and the pair of conducting wires 2 has a contact portion that contacts the electrode pad 31 in a predetermined spherical shape. Since the contact load F is stabilized, problems such as momentary interruption can be suppressed and stable detection can be performed.

With reference to FIG. 7, the modification 1A of the terminal metal fitting which is the principal part of this invention is demonstrated.
The basic configuration is the same as that of the terminal fitting shown in FIG. 1, and the present modification is different in that a locking portion 15 is provided on both sides of the base portion 10A so as to project in a tongue shape.
By providing the locking portion 15, the fixing to the insulator 80 is facilitated, the positional displacement of the terminal fitting 1 </ b> A in the cross-sectional direction is suppressed, and the effect of the present invention that suppresses the decrease in the contact load F is further enhanced. be able to.
The locking portion 15 is not limited to the shape as shown in the figure, and can be appropriately changed according to the shape of the insulator 80 that fixes the terminal fitting 1A.
Also in this embodiment, the conduction reliability with the heater 3 can be improved by forming the cross-sectional curvature radius R ₂ and the longitudinal cross-section curvature radius R _{1 of the} contact portion 12 in the same ranges as described above. it can.

DESCRIPTION OF SYMBOLS 1 Terminal metal fitting 10 Base part 11 Bending part 12 Contact part 13 Crimping part 14 Deflection part 15 Locking part

Claims (5)

A gas sensor (GS) for detecting the concentration of a specific gas component in a gas to be measured,
at least,
A gas sensor element (4);
A plate-like heater (3) that generates heat when energized and is provided to activate the gas sensor element (4) and extends in the axial direction of the gas sensor element (4);
A pair of energization wires (2) for connecting the heater (3) to the outside;
A pair of terminals made of an elastic member provided to connect the pair of electrode pads (31) provided on both sides of the opposing plane on the base end side of the heater (3) and the pair of energization wires (2). Metal fitting (1),
In a gas sensor comprising:
The terminal fitting (1) is a flat base (10) extending in the axial direction;
A bent portion (11) obtained by folding the base portion (10) toward the base end side;
An abutting portion (12) provided at the tip of the bent portion (11), urged by the bent portion (11), and elastically abutted on the electrode pad (31);
A crimping portion (13) provided on the base end side of the base portion (10) and connected to the core wire (20) of the conductive wire (2),
The gas sensor is characterized in that the contact portion (12) is formed in a spherical shape that is curved so as to be convex toward the electrode pad (31) side. The contact portion (12)
In the relationship between the longitudinal section curvature radius (R ₁ ) along the longitudinal axis direction of the heater (3) and the transverse section curvature radius (R ₂ ) perpendicular to the longitudinal axis direction,
The gas sensor R ₂ > R _{1 according} to claim 1 that satisfies the relationship of Equation 1 Equation 1 The length from the surface of the electrode pad (31) formed on one surface of the heater (3) to the surface of the electrode pad (31) formed on the opposite surface is defined as the heater electrode portion plate thickness (T ₃ )
When the free height (H ₁ ) from the surface of the base (10) to the contact portion (12) of the terminal fitting (1) and the electrode pad (31) of the heater (1) are contacted The difference ΔH (= H ₁ −H ₂ ) from the contact height (H ₂ ) is expressed by a relative displacement amount δ (= ΔH / T ₃ ) based on the heater electrode plate thickness T ₃ .
When the radius of curvature of the cross section (R ₂ ) is expressed by a relative radius r ₂ (= R ₂ / T ₃ ) based on the heater electrode plate thickness T ₃ ,
In the relationship between the relative displacement (δ) and the relative radius (r ₂ ),
The gas sensor according to claim 2, satisfying the relationship of Formula 2.

In the relationship between the heater electrode portion plate thickness (T ₃ ) and the cross-sectional radius of curvature (R ₂ ),
The gas sensor R ₂ ≧ 2 × T _{3 (} Equation 3) according to claim 3 satisfying the relationship of Equation 3. 5. The heater electrode portion plate thickness (T ₃ ) is 0.8 mm or more and 1.6 mm or less, and the transverse section curvature radius (R ₂ ) is 3.0 mm or more and 8.0 mm or less. Gas sensor described in

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