JP6825919B2 - Temperature sensor - Google Patents

Description

The present invention relates to a temperature sensor in which a temperature sensitive element such as a thermistor element or a resistance temperature measuring resistor element is housed in a metal tube.

Conventionally, for example, as a temperature sensor for measuring the temperature of exhaust gas from an automobile, a temperature-sensitive element such as a thermistor element, a pair of electrode wires extending from the temperature-sensitive element, and a pair of electrode wires joined to each other in a metal tube. A temperature sensor containing a sheath member including a core wire of the above is known. The sheath member is a long member in which an insulating material is filled in the sheath tube and a core wire is inserted into the insulating material.

In this type of temperature sensor, the temperature sensitive element, the electrode wire, the core wire, and the like are fixed with cement so as not to be damaged by vibration or the like (see Patent Document 1).
Further, in a temperature sensor in which cement is filled from the tip side of the temperature sensitive element to the inner tip of the metal tube, the smaller the distance from the tip side of the temperature sensitive element to the inner tip of the metal tube, the more heat transferability. Is known to have good responsiveness.

Japanese Patent No. 3975023

However, the above-mentioned conventional techniques are not always sufficient, and further improvement is desired.
Specifically, the smaller the distance from the tip side of the temperature sensitive element to the tip inside the metal tube, the better the responsiveness, but there is a problem that the thermal shock resistance (robustness) is lowered.

For example, when a temperature sensor is used in an environment where the temperature changes significantly, when the length of the metal tube, electrode wire, or core wire changes significantly depending on the temperature, the thermal stress generated by the temperature sensor causes, for example, the electrode wire and the core wire. There is a risk of disconnection at the joints.

The present invention has been made in view of this background, and an object of the present invention is to provide a temperature sensor having excellent responsiveness and thermal shock resistance.

(1) The first aspect (temperature sensor) of the present invention includes a temperature sensitive element having a temperature sensitive portion whose electrical characteristics change depending on temperature, an electrode wire connected to the temperature sensitive portion, a sheath tube, and a sheath tube. A sheath member having an electrically insulating insulating material filled in a sheath tube and a core wire arranged through the insulating material and having a tip side connected to an electrode wire, and a sheath member having a tip side closed and inside. It includes a temperature-sensitive element and a metal tube in which at least the tip end side of the sheath member is housed.

Further, this metal tube has a small diameter portion on the tip side, a large diameter portion on the rear end side larger than the small diameter portion, and an intermediate portion connecting the small diameter portion and the large diameter portion, and also has a small diameter portion. A temperature sensitive element is arranged inside so that the tip of the temperature sensitive element is located on the tip side of the small diameter portion , and electricity is supplied in the metal tube at least from the temperature sensitive element to the tip side. It is filled with a filler that has insulating properties and is bonded to the temperature-sensitive element, and the temperature-sensitive element is fixed by this filler.

Moreover, in this temperature sensor, the inner diameter of the small diameter portion is smaller than the outer diameter of the sheath tube, and the distance (X) from the inner tip of the small diameter portion to the tip of the temperature sensing element is from the inner tip of the small diameter portion to the sheath. It is 19.5% or more of the distance (Y) to the tip of the pipe.

As described above, in the first aspect, the inner diameter of the small diameter portion is smaller than the outer diameter of the sheath tube, and the distance (X) from the inner tip of the small diameter portion to the tip of the temperature sensing element is the inside of the small diameter portion. Since the distance (Y) from the tip to the tip of the sheath tube is 19.5% or more, as is clear from the experimental examples described later, both high responsiveness and excellent thermal shock resistance can be achieved at the same time.

That is, when the diameter of the tip side of the metal tube is smaller than that of the rear end side, the responsiveness is superior as compared with the case where it is not. Moreover, when the ratio (X / Y) of the distance (X) to the distance (Y) is as large as 19.5% or more, even when the temperature change is transmitted from the tip side, thereby, from the tip side. The thermal stress applied to the temperature sensitive element (hence, the electrode wire and the core wire) is not so large as compared with the case where the ratio is not the above.

Therefore, disconnection and the like are unlikely to occur, and the heat and impact resistance is excellent. Therefore, it has a remarkable effect of being able to achieve both high responsiveness and excellent thermal shock resistance .

(2 ) In the second aspect of the present invention, at least one of the metal tube and the core wire is made of a nickel-based alloy.

In the second aspect, since at least one of the metal tube and the core wire is made of a nickel-based alloy having high strength against high temperature, the thermal shock resistance is further excellent.
<The configuration of the present invention will be described below>
-Examples of the temperature sensitive element include a resistance temperature detector such as a thermistor and a platinum resistor. Therefore, examples of the temperature sensitive element include a thermistor element and a resistance temperature measuring resistor element.

-Examples of the electrode wire include a wire rod obtained by adding a small amount of an alkaline earth metal element (for example, Sr) to Pt or Pt-Rh alloy, Pt-Ir alloy, Pt or Pt alloy.
-The sheath tube is a tubular member made of metal, and examples of the material thereof include stainless steel.

-As the material of the insulating material, for example, silica can be mentioned.
-As the core wire material (conductive material), for example, stainless steel or nickel-based alloy (for example, Inconel (registered trademark)) can be mentioned. The nickel-based alloy is an alloy containing nickel as a main component (the component having the highest content).

-A metal tube is a member made of a tubular metal simple substance or an alloy, and examples of the material thereof include stainless steel and nickel-based alloys (for example, Inconel (registered trademark)).
-As a material for the filler, for example, cement can be mentioned.

It is sectional drawing which shows the temperature sensor of 1st Embodiment by breaking in the axial direction. It is sectional drawing which shows the tip side of the temperature sensor by breaking in the axial direction along the plane perpendicular to the plane where the core wire is arranged, and is enlarged. It is explanatory drawing explaining the manufacturing process of a temperature sensor. It is sectional drawing which shows the temperature sensor of 2nd Embodiment by breaking in the axial direction. It is sectional drawing which shows the tip side of the temperature sensor by breaking in the axial direction along the plane perpendicular to the plane where the core wire is arranged, and is enlarged. It is a graph which shows the experimental result.

Hereinafter, embodiments of a temperature sensor to which the present invention has been applied will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Overall configuration of temperature sensor]
As shown in FIG. 1, the temperature sensor 1 of the first embodiment includes a resistor element 2 which is a temperature sensitive element and a sheath member 7 in which a pair of metal core wires 3 are insulated and held inside a sheath tube 5. , A tubular metal tube 9 whose tip side is closed and extends in the axis O direction (axial direction), a mounting member 11 that supports the metal tube 9, a nut member 17 having a hexagon nut portion 13 and a screw portion 15, and a mounting member. An outer cylinder 19 that fits inside the rear end side of 11 is provided.

The axis O direction is the longitudinal direction of the temperature sensor 1 (the direction in which the axis O extends), and corresponds to the vertical direction in FIG. Further, the front end side of the temperature sensor 1 is the lower side in FIG. 1, and the rear end side is the upper side in FIG. 1 (the same applies hereinafter).

The temperature sensor 1 is a sensor in which the resistor element 2 is housed inside the metal tube 9 on the tip end side in order to measure the temperature. Further, the temperature sensor 1 is mounted on a flow pipe such as an exhaust pipe of an internal combustion engine, and the tip end side of the temperature sensor 1 is arranged in the flow pipe through which the gas to be measured (exhaust gas) flows, so that the gas to be measured can be measured. Detect temperature.

Hereinafter, each configuration will be described in detail.
As shown enlarged in FIG. 2, the sheath member 7 includes a cylindrical metal (for example, stainless alloy) sheath tube 5, a pair of core wires 3 made of a conductive metal (for example, a stainless alloy), and a sheath tube. It is composed of an insulating material 23 (which is an insulating powder) such as silica that electrically insulates between the 5 and the two core wires 3 to hold the core wire 3.

The tip side of the pair of core wires 3 is connected to the pair of electrode wires 25 of the resistor element 2 by, for example, laser welding. Further, the rear end side is connected to a pair of crimping terminals 27 (see FIG. 1) by resistance welding, for example.

In addition to the stainless alloy (for example, SUS310S), a nickel-based alloy such as Incoloy (registered trademark) may be used as the core wire 3.
Returning to FIG. 1, the rear end side of the core wire 3 is connected to a lead wire 29 for connecting an external circuit (for example, an electronic control device (ECU) of a vehicle) via a crimping terminal 27.

The pair of core wires 3 and the pair of crimping terminals 27 are insulated from each other by an insulating tube 31, and the lead wire 29 penetrates the inside of the auxiliary ring 33 made of heat-resistant rubber by covering the lead wire with an insulating coating material. It is arranged in the state of doing.

The mounting member 11 has a cylindrical projecting portion 35 projecting outward in the radial direction, and a cylindrical rear end side sheath portion 37 extending from the projecting portion 35 to the rear end side. The rear end side sheath portion 37 has a cylindrical sleeve 39 extending toward the rear end side, and a metal tube 9 is joined to the sleeve 39. That is, the mounting member 11 surrounds the outer peripheral surface on the rear end side of the metal tube 9 and supports the metal tube 9.

The metal tube 9 is made of a corrosion-resistant metal such as a stainless alloy such as SUS310S, which is also a heat-resistant metal. A nickel-based alloy such as Incoloy (registered trademark) may be used. The metal tube 9 has a tubular shape extending in the axis O direction in which the tip end side of the tube is closed by deep drawing of a steel plate, and the rear end side of the tubular tube is open.

[1-2. Configuration of the tip side of the temperature sensor]
As shown in FIG. 2, the metal tube 9 has a small diameter portion 41 on the front end side having a small diameter (that is, an inner diameter and an outer diameter) and a large diameter portion 41 on the rear end side having a larger diameter than the small diameter portion 41. A diameter portion 43 and an intermediate portion 45 between the small diameter portion 41 and the large diameter portion 43 are provided.

Further, the inner diameter of the small diameter portion 41 (for example, φ2.0 mm) is smaller than the outer diameter of the sheath pipe 5 (for example, φ2.5 mm).
The small diameter portion 41 has a cylindrical shape with the tip side closed, the intermediate portion 45 has a truncated cone shape, and the large diameter portion 43 has a cylindrical shape, which are coaxial with the axis O.

Further, the resistor element 2 and the cement 47 are housed inside the metal tube 9, and the cement 47 is filled around the resistor element 2 to prevent the resistor element 2 from swinging. There is. The cement 47 is made of an insulating material containing alumina aggregate in amorphous silica.

In particular, in the present embodiment, the cement 47 is filled from the inner tip of the small diameter portion 41 so as to be in contact with the resistor element 2, and further exceeds the welded portion 26 between the electrode wire 25 and the core wire 3 to form a sheath member. It is filled up to the front of the sheath tube 5 and the insulating material 23 of No. 7 (that is, before the sheath end face 7a).

The distance (X) from the inner tip of the small diameter portion 41 to the tip of the resistor element 2 (specifically, the resistance detection unit 51) is the distance (Y) from the inner tip of the small diameter portion 41 to the tip of the sheath tube 5. ) Is 19.5% or more (preferably 50% or more).

For example, when the distance (X) is 1.1 mm and the distance (Y) is 9.8 mm, the ratio (X / Y) of X and Y is 11%.
The resistor element 2 described above has a resistance detection unit 51, which is a portion for detecting an electrical characteristic (that is, an electrical resistance value) that changes with temperature, and a pair of electrode wires 25 connected to the resistance detection unit 51. I have.

The resistance detection unit 51 includes a ceramic substrate 53, a metal resistor 55, a bonding layer 57, a ceramic coating layer 59, and an electrode pad 61.
The ceramic substrate 53 is a fired sheet made of alumina and obtained by firing a ceramic green sheet in advance.

The metal resistor 55 is a resistance temperature detector that is mainly composed of platinum (Pt) and whose electrical characteristics (that is, electrical resistance value) change according to temperature. The metal resistor 55 is formed on the surface of the ceramic substrate 53 in a predetermined pattern shape.

The ceramic coating layer 59 is a fired sheet made of alumina and obtained by firing a ceramic green sheet in advance. The ceramic coating layer 59 covers the tip end side of the metal resistor 55 on the surface of the metal resistor 55 opposite to the surface in contact with the ceramic substrate 53.

The bonding layer 59 is made of alumina. The bonding layer 59 is a paste containing alumina powder before bonding, and the fired ceramic substrate 53 and the ceramic coating layer 59 are bonded together with the above paste and then heat-treated to finally form the bonding layer 59. Become.

On the rear end side (right side of FIG. 2) of the metal resistor 55, the pair of electrode wires 25 are electrically connected to each other via the pair of electrode pads 61 formed wider than the conductor pattern coated by the ceramic coating layer 59. Is connected.

The pair of electrode pads 61 and the pair of electrode wires 25 are joined at a welding point 63 by welding such as resistance welding and laser welding.
The joint portion between the pair of electrode pads 61 and the pair of electrode wires 25 is covered with a covering member 65. The covering member 65 is made of a glass material mainly composed of aluminosilicate glass.

The pair of electrode wires 25 are arranged so as to extend from the rear end side of the metal resistor 55 toward the sheath member 7 side (rear end side).
The rear ends of the pair of electrode wires 25 and the tips of the pair of core wires 3 are joined by laser welding.

[1-3. How to manufacture a temperature sensor]
Next, a method of manufacturing the temperature sensor 1 will be described.
In order to manufacture the temperature sensor 1 of the first embodiment, parts such as a metal tube 9, a mounting member 11, and a resistor element 2 are prepared by a known method.

<Manufacturing process of sheath member>
The sheath member 7 is manufactured by the following method.
First, as in the conventional case, the insulating material 23 is arranged in the sheath tube 5, and the core wire 3 is arranged so as to penetrate the insulating material 23. Then, the sheath member 7 is manufactured by rolling the sheath pipe 5.

After that, the rear ends of the pair of electrode wires 25 of the resistor element 2 are placed in contact with the tips of the pair of core wires 3, respectively, and are joined by, for example, laser welding.
<Assembly process>
Since the manufacturing process after laser welding is the same as the conventional one, it will be briefly described.

For example, as shown in FIG. 1, the metal tube 9 is press-fitted into the mounting member 11 and the sleeve 39 is welded to integrate the metal tube 9 and the mounting member 11.
Subsequently, a tip component 71 (see FIG. 3) including a sheath member 7 to which the resistor element 2 is welded and a metal tube 9 to which the mounting member 11 is welded is assembled.

This work will be described with reference to FIG.
In manufacturing the tip component 71, first, the nozzle 73 is inserted into the tip portion of the metal tube 9 to which the mounting member 11 is welded, and the slurry-like (paste-like) cement 47 is injected. At this stage, the resistor element 2 and the like are not inserted into the metal tube 9.

Next, the sheath member 7 to which the resistor element 2 is welded is inserted into the metal tube 9 into which the cement 47 is injected. At this time, the inside of the small diameter portion 41 is filled with cement 47.
Then, with the sheath member 7 inserted inside the metal tube 9, the elongated hole is crimped by pressing the die 75 against the metal tube 9 from the outside in the radial direction while facing the mold 75. By this elongated hole crimping, the metal tube 9 and the sheath member 7 are completely positioned and fixed.

In this way, the tip component 71 is completed.
<Centrifugal defoaming treatment>
Then, a well-known centrifugal defoaming treatment is performed on the advanced component 71.

By this treatment, the solid component in the slurry-like cement 47 moves to the small diameter portion 41 side, so that the solid component of the cement 47 is sufficiently filled in the tip side of the metal tube 9. That is, the cement 47 is filled without a gap from the tip of the small diameter portion 41 to the front of the sheath end surface 7a. Further, moisture and air bubbles move to the large diameter portion 43 side.

Then, when the centrifugal defoaming treatment is completed, the tip component 71 is heat-treated to dry (harden) the cement 47.
In this way, the advanced component 71 after heat treatment is obtained.

Since the process of assembling the advanced component 71 and other components is the same as the conventional one, the description thereof will be omitted.
[1-4. effect]
In the temperature sensor 1 of the first embodiment, the metal tube 9 includes a small diameter portion 41 on the front end side, a large diameter portion 43 on the rear end side having a larger diameter than the small diameter portion 41, and a small diameter portion 41 and a large diameter portion 43. It has an intermediate portion 45 for connecting the above. Further, the resistor element 2 is arranged inside the small diameter portion 41. Further, the inside of the metal tube 9 is filled with a cement 47 having electrical insulation and joining to the resistor element 2 at least on the tip side from the resistor element 2, and the resistor element 2 is filled with the cement 47. Is fixed.

Moreover, in this temperature sensor 1, the inner diameter of the small diameter portion 41 is smaller than the outer diameter of the sheath tube 5, and the distance (X) from the inner tip of the small diameter portion 41 to the tip of the resistor element 2 is the small diameter portion 41. It is 19.5% or more of the distance (Y) from the inner tip of the sheath tube 5 to the tip of the sheath tube 5.

That is, in the temperature sensor 1 of the first embodiment, since the front end side is thinner than the rear end side, it has high responsiveness. Further, since the ratio (X / Y) of the distance (X) to the distance (Y) is set to an appropriate value of 19.5% or more (preferably 50% or more), it is clear from the experimental examples described later. As such, it has excellent thermal shock resistance (robustness).

Therefore, the temperature sensor 1 of the first embodiment has a remarkable effect of being able to achieve both high responsiveness and excellent thermal shock resistance.
When the metal tube 9 and the core wire 3 are made of, for example, Inconel (registered trademark), which is a nickel-based alloy, the heat impact resistance is further excellent.

Further, the shorter distance (Y) from the inner tip of the small diameter portion 41 to the tip of the sheath tube 5 is the resistor element 2 (hence, the electrode wire 25 and the core wire) which is a temperature sensitive element from the tip side. The thermal stress applied to 3) is large. Therefore, for example, the present invention is more effective when the distance (Y) is 15 mm or less.

[1-5. Correspondence with claims]
Here, the correspondence between the claims and the first embodiment will be described.
The temperature sensor 1, the resistor element 2, the core wire 3, the sheath tube 5, the sheath member 7, the metal tube 9, the insulating material 23, the electrode wire 25, the small diameter portion 41, the large diameter portion 43, and the intermediate portion 45 of the first embodiment. , Cement 47, resistance detection unit 51, respectively, of the present invention, temperature sensor, resistor element, core wire, sheath tube, sheath member, metal tube, insulating material, electrode wire, small diameter part, large diameter part, intermediate part, It corresponds to an example of a filler and a temperature sensitive part.

[2. Second Embodiment]
Next, the second embodiment will be described, but the description of the same configuration as that of the first embodiment will be omitted.

The type of the temperature sensitive element in the second embodiment is different from that in the first embodiment.
[2-1. Overall configuration of temperature sensor]
As shown in FIG. 4, the temperature sensor 81 of the second embodiment is a sheath in which a thermistor element 82, which is a temperature-sensitive element for measuring temperature, and a pair of metal core wires 83 are insulated and held inside a sheath tube 85. A member 87, a tubular metal tube 89 whose tip side is closed and extends in the axis O direction, a mounting member 91 that supports the metal tube 89, a nut member 97 having a hexagon nut portion 93 and a screw portion 95, and a mounting member 91. It is provided with an outer cylinder 99 or the like that is internally fitted on the rear end side.

Since the configuration is the same as that of the first embodiment except for the thermistor element 82, the description thereof will be omitted.
[2-2. Thermistor element]
As shown in FIG. 5, the thermistor element 82 shows the change in the electrical characteristics of the thermistor sintered body (temperature sensitive portion) 101 and the thermistor sintered body 101 whose electrical characteristics (electrical resistance value) change depending on the temperature. It is composed of a pair of electrode wires 103 for taking out.

The thermistor sintered body 101 is a hexagonal columnar ceramic sintered body, and is formed of, for example, a perovskite-type oxide having a base composition of (Sr, Y) (Al, Mn, Fe) O ₃ . The electrode wire 25 is made of, for example, platinum (Pt).

The pair of electrode wires 103 are arranged so as to extend from the rear end side of the thermistor sintered body 101 toward the sheath member 87 side (rear end side).
The rear ends of the pair of electrode wires 103 and the tips of the pair of core wires 83 are joined by laser welding.

In the second embodiment as well, the sheath tube 85 includes a small diameter portion 125, an intermediate portion 127, and a large diameter portion 129, as in the first embodiment.
The cement 131 is filled so as to reach the thermistor element 82 from the inner tip of the small diameter portion 125, and further fills beyond the welded portion 104 between the electrode wire 103 and the core wire 83 and before the sheath sheath end face 87a. ing.

The distance (X) from the inner tip of the small diameter portion 125 to the tip of the thermistor element 82 (specifically, the thermistor sintered body 101) is the distance (Y) from the inner tip of the small diameter portion 125 to the tip of the sheath tube 85. ) Is 19.5% or more (preferably 50% or more).

For example, when the distance (X) is 1.5 mm and the distance (Y) is 8.6 mm, the ratio (X / Y) of X and Y is 17%.
The configuration of the second embodiment described above produces the same effect as that of the first embodiment.

[3. Experimental example]
Next, an experimental example conducted for confirming the effect of the present invention will be described.
As a sample used in the experiment, for a temperature sensor having the same configuration as that of the first embodiment, five temperature sensors of four types of samples Nos. 1 to 4 were manufactured with different ratios of (X / Y). .. Sample No. 1 is a reference example, and Sample Nos. 2 to 4 are examples within the scope of the present invention.

The configuration other than this ratio is the same as that of the first embodiment. The material of the metal tube and the core wire is SUS310s.
Then, a heating cycle test in which the temperature of room temperature (25 ° C.) to 800 ° C. was periodically changed was carried out on the temperature sensor of each sample, and the number of cycles until disconnection (number of disconnection cycles) was investigated.

The result is shown in FIG. In FIG. 6, the horizontal axis shows the ratio of X / Y, and the vertical axis shows the ratio of the robustness of another sample to the heat impact resistance (robustness) of sample No.1. Note that this ratio is a numerical value obtained by normalizing the average value of the number of disconnection cycles of each sample by the number of disconnection cycles of sample No.1.

As is clear from FIG. 6, since the X / Y of Samples Nos. 2 to 4 of the present invention is 19.8% or more, the robustness is about 3 times that of Sample No. 1 of the comparative example. It is suitable because it is as large as the above. The number of disconnection cycles of sample No. 1 in the comparative example is 9232 cyc.

In particular, when X / Y is 50%, the robustness is very large, about 13 times, which is more suitable.
[4. Other embodiments]
It goes without saying that the present invention is not limited to the above-described embodiment, and can be implemented in various embodiments without departing from the present invention.

(1) For example, the temperature sensitive element, the insulating material, the filler, and the like are not limited to the above-described embodiments.
(2) Further, the ratio of the distance (X) to the distance (Y) is not limited to the above-described embodiment as long as it is within the scope of the present invention.

(3) Further, the method for manufacturing the temperature sensor is not limited to the above embodiment.
(4) Further, the object measured by the temperature sensor includes a fluid such as a gas or a liquid.

(5) It is also possible to appropriately combine the components of the above-described embodiments and the like.

1, 81 ... Temperature sensor 2 ... Resistor element 3, 83 ... Core wire 5, 85 ... Sheath tube 7, 87 ... Sheath member 9, 89 ... Metal tube 25, 103 ... Electrode line 41, 125 ... Small diameter part 43, 129 ... Large diameter part 45, 127 ... Intermediate part 47, 131 ... Cement 49 ... Thermistor sintered body 51 ... Resistance detector 82 ... Thermistor element

Claims (2)

A temperature-sensitive element having a temperature-sensitive portion whose electrical characteristics change depending on temperature and an electrode wire connected to the temperature-sensitive portion.
A sheath member having a sheath tube, an electrically insulating insulating material filled in the sheath tube, and a core wire arranged through the insulating material and having a tip side connected to the electrode wire, and the tip thereof. A metal tube in which the temperature sensitive element and at least the tip end side of the sheath member are housed while the side is closed.
With
The metal tube has a small diameter portion on the tip side, a large diameter portion on the rear end side having a larger diameter than the small diameter portion, and an intermediate portion connecting the small diameter portion and the large diameter portion, and said. The temperature sensitive element is arranged inside the small diameter portion so that the tip of the temperature sensitive element is located on the tip side of the small diameter portion .
In addition, the metal tube is filled with a filler having electrical insulation and joining to the temperature-sensitive element at least in a portion on the tip side from the temperature-sensitive element, and the temperature-sensitive element is filled with the filler. In the temperature sensor where
The inner diameter of the small diameter portion is smaller than the outer diameter of the sheath pipe.
The distance (X) from the inner tip of the small diameter portion to the tip of the temperature sensing element shall be 19.5% or more of the distance (Y) from the inner tip of the small diameter portion to the tip of the sheath tube. A temperature sensor characterized by. The temperature sensor according to claim 1 , wherein at least one of the metal tube and the core wire is made of a nickel-based alloy.