JP3706857B2 - Ceramic member for electrode and liquid level sensor - Google Patents

Description

【００５０】
この表１から明らかな様に、本発明の範囲内の試料Ｎo.２、３、５〜８は、電極用セラミック部材の第１端面の角部に切り欠きが設けてあり、かつその幅が１ｍｍ以上であり、しかも、第１端面と第２端面との間だけでなく、切り欠きにはんだが充填されているので、その接合部における蒸気の漏れが無い（又は少ない）ことが分かる。
【００５１】
それに対して、本発明の範囲外の試料No.１、４は、切り欠きがないか、又は切り欠きがあってもその幅が０．５ｍｍと短く、蒸気の漏れが発生するので、好ましくない。
（実施例２〜５）
次に、他の実施例について説明するが、前記実施例１と同様な箇所の説明は省略する。
【００５２】
尚、実施例２〜５の電極用セラミック部材は、前記実施例１とは、切り欠きの形状が異なっている。
図５（ｃ）に示す様に、本実施例２の電極用セラミック部材８５では、その切り欠き８７の形状（中心軸に沿った断面形状：以下同様）は、直線が途中で外側に突出するように折れ曲がっている。
【００５３】
尚、この場合に傾斜角θは、切り欠き８７の両端をつないだ線分の傾斜角である。
図５（ｄ）に示す様に、本実施例３の電極用セラミック部材８９では、その切り欠き９１は、外側に凸に湾曲した曲線の形状をしている。
【００５４】
図５（ｅ）に示す様に、本実施例４の電極用セラミック部材９３では、その切り欠き９５は、内側に凸に湾曲が連続した形状をしている。
図５（ｆ）に示す様に、本実施例５の電極用セラミック部材９７では、その切り欠き９９は、複数の階段が設けられた形状である。
【００５５】
尚、本発明は前記実施例になんら限定されるものではなく、本発明の要旨を逸脱しない範囲において種々の態様で実施しうることはいうまでもない。
【図面の簡単な説明】
【図１】 実施例１の液面センサを高圧ボイラに取り付けた状態を示す説明図である。
【図２】 実施例１の液面センサを一部破断して示す正面図である。
【図３】 実施例１の電極用セラミック部材を一部破断して示す正面図である。
【図４】 実施例１の液面センサの要部を一部破断し拡大して示す正面図である。
【図５】 実験例や他の実施例の電極用セラミック部材を破断して示す正面図である。
【図６】 従来技術を示す説明図である。
【符号の説明】
１…液面センサ
３…高圧ボイラ
７、８５、８９、９３、９７…電極用セラミック部材
９…中心電極
３１…第１端面
３３、８７、９１、９５、９９…切り欠き
６３…第２端面
４１…鍔部
６５…接合材（はんだ）
６６…接合部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ceramic member for an electrode and a liquid level sensor used when performing water level control in, for example, a boiler.
[0002]
[Prior art]
Conventionally, for example, a so-called liquid level sensor has been used to detect the height (liquid level) of liquid (water) accommodated in a boiler.
This liquid level sensor has a long bar shape, and a central electrode (electrode bar) through which a current flows when the tip is in contact with the liquid level is arranged at the center of the axis. Further, the center electrode is fitted into a cylindrical ceramic member in order to insulate the outer periphery of the center electrode (see Patent Document 1).
[0003]
In this type of liquid level sensor, as shown in FIG. 6, the flange portion 103 is formed so as to project annularly outwardly at the base end side of the outer periphery of the center electrode 101, that is, at a portion located outside the boiler. An end face 105 facing the ceramic member 107 of the flange 103 and an end face 109 on the base end side of the ceramic member 107 are joined by soldering or brazing.
[0004]
[Patent Document 1]
JP 2002-148097 A (2nd page, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, the inside of the boiler is usually high pressure (1 MPa or higher), high temperature (150 to 250 ° C.), and high alkali (pH = 11 or higher). ) Since the environment is harsh at a high temperature (200 to 250 ° C.), steam may leak from the joint portion 111 between the center electrode 101 and the ceramic member 107.
[0006]
When this steam leaks, there is a problem that the pressure in the boiler decreases and high alkaline water adheres around the outside of the boiler.
The present invention solves the above-mentioned problems, and an object thereof is to provide a ceramic member for an electrode and a liquid level sensor having high airtightness between a central electrode and a joint portion of the ceramic member.
[0007]
[Means for Solving the Problems and Effects of the Invention]
(1) The invention according to claim 1 is characterized in that a cylindrical electrode ceramic member (for example, a water level electrode ceramic member) and a central electrode fitted in the electrode ceramic member are connected to the base end of the electrode ceramic member. The first end surface on the side and the second end surface (that is, the end surface facing the first end surface) of the protruding portion (for example, the flange) projecting from the outer periphery of the center electrode are used for a liquid level sensor that is bonded by a bonding material. In the electrode ceramic member to be obtained, a notch for storing the bonding material having a width of 1 mm or more as viewed from the first end face side is provided along a corner on the inner peripheral side of the first end face. The gist is a ceramic member for electrodes.
[0008]
In the present invention, a notch (a joint material reservoir such as solder or brazing material) having a width of 1 mm or more is formed along the inner periphery of the first end surface of the electrode ceramic member on the base end side (the side opposite to the tip side in contact with the liquid surface). ) Is provided. That is, along the annular corner portion that is the inner peripheral end of the first end face, the corner portion is notched, and a notch that is annularly formed as a joint material reservoir is provided.
[0009]
As a result, the bonding material accumulates in the cutout portion and enters the inside of the space between the electrode ceramic member and the center electrode. For example, the tip side of the liquid level sensor disposed in the high pressure boiler (for example, a high pressure boiler or the like) Among the paths (leak paths) from the inside of the container) to the outside of the liquid level sensor through the joint portion between the first end face on the base end side of the electrode ceramic member and the second end face of the protruding portion of the center electrode, Since the length of the joint portion is increased, it is possible to prevent the vapor from leaking outside through the joint portion.
[0010]
That is, by providing the above-described notch in the electrode ceramic member, the path (from the inside of the sensor to the outside) in the joint portion can be lengthened, so that steam leakage can be effectively prevented.
(2) The invention according to claim 2 is a gist of the electrode ceramic member according to claim 1, wherein the first end surface of the electrode ceramic member and the surface of the notch are subjected to metallization. And
[0011]
The present invention shows the treatment on the first end face and the surface of the notch. That is, a bonding material such as a solder or a brazing material can be firmly bonded by subjecting the first end surface, which is the surface of the electrode ceramic member, or the surface of the notch to metallization processing (further, plating processing). This also effectively prevents vapor leakage.
[0012]
(3) The invention of claim 3 is characterized in that the notch is one or a plurality of C chamfers or R chamfers, or a combination of the C chamfers and R chamfers. The gist of the ceramic member for an electrode according to 2.
The present invention exemplifies the shape of the notch.
[0013]
That is, the notch is formed by one C chamfer (one with an inclination angle) or one R chamfer (one with radius R) along the inner periphery of the first end surface of the electrode ceramic member. be able to.
Further, the notch can be formed by a plurality of C chamfers (those whose inclination angle is bent in the middle) or a plurality of R chamfers (those whose radius R is changed in the middle).
[0014]
Furthermore, a notch can also be formed by combining one or more C chamfers and one or more R chamfers.
(4) The invention according to claim 4 is characterized in that the cutout is provided at an angle of 45 to 75 degrees from the first end face. Is the gist.
[0015]
The present invention exemplifies the shape of the notch.
Here, the angle from the first end surface (inclination angle θ) is, as illustrated in FIG. 5A, when the electrode ceramic member is broken along a plane along its central axis (that is, an axial section). ) Is an angle inclined inward from the first end face, and when this angle is 45 degrees or more, workability is easy, which is preferable. In addition, when the angle is 75 degrees or less, the bonding material is likely to be stably accumulated, and the path of the bonding portion described above can be set sufficiently long, so that it is possible to effectively prevent the leakage of steam, which is preferable.
[0016]
In addition, when the axial cross section of the notch is a curve, the average inclination of the curve (the inclination of the line connecting the left and right ends of the curve) may be in the range of the angle. In addition, when the notch axial cross section is compounded so that multiple straight lines and curves are connected, the average inclination of the combined line (the inclination of the line connecting the left and right ends of the line) is The angle may be in the range.
[0017]
(5) The fifth aspect of the present invention is the electrode ceramic member according to any one of the first to fourth aspects, wherein the notch is one or a plurality of (for example, vertical) steps. And
The present invention exemplifies the shape of the notch.
[0018]
Here, a notch is formed from one or a plurality of stepped steps.
(6) The invention according to claim 6 is characterized in that the notch is inwardly convex (indented inward) or outwardly convex in the corner portion. A gist of the ceramic member for electrodes according to the above.
[0019]
The present invention exemplifies the shape of the notch.
In addition, since the path | route in the said junction part becomes long when it is convex inward, it is suitable.
(7) The invention according to claim 7 is a liquid level sensor characterized in that the electrode ceramic member according to any one of claims 1 to 6 is provided on an outer periphery of the center electrode.
[0020]
Since the liquid level sensor of the present invention includes the above-described electrode ceramic member on the outer periphery (around the side surface) of the center electrode, it is excellent in insulation and airtightness.
(8) The invention according to claim 8 is characterized in that the bonding material is provided between the first end face of the electrode ceramic member and the second end face of the center electrode and in the notch. The liquid level sensor according to claim 7 is a gist.
[0021]
In the present invention, since the joining material is filled between the first end surface and the second end surface and the notch, the ceramic member for electrode and the center electrode are joined over a wide range (and thus over a long path). Yes. Therefore, the leakage of steam can be effectively prevented.
(9) The invention according to claim 9 is the liquid level sensor according to claim 7 or 8, characterized in that the liquid level sensor is for detecting a liquid level of a boiler.
[0022]
The present invention exemplifies an object (use) in which a liquid level sensor is used.
That is, by using the liquid level sensor described above, the liquid level can be accurately detected over a long period of time without leakage of water vapor even in a harsh environment such as in a high pressure boiler.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Below, the example (Example) of embodiment of the ceramic member for electrodes and liquid level sensor of this invention is demonstrated.
(Example)
The liquid level sensor provided with the electrode ceramic member of the present embodiment is used for detecting the liquid level (water level) in the high pressure boiler.
[0024]
a) First, the liquid level sensor of the present embodiment will be described.
As shown in FIG. 1, the liquid level sensor 1 of the present embodiment has a long rod shape and is disposed so as to penetrate a high-pressure boiler 3 made of metal (for example, stainless steel). The high pressure boiler 3 contains water 5 in a high temperature and high pressure state.
[0025]
The liquid level sensor 1 includes an electrode ceramic member 7 and a center electrode 9, and the outer periphery of the side surface of the center electrode 9 is covered with the electrode ceramic member 7 for insulation. The tip (downward in the figure) is set to be the position of the desired liquid level (water surface) to be notified.
[0026]
Further, the base end side (upper side of the figure) of the center electrode 9 of the liquid level sensor 1 and the outer wall 11 of the high-pressure boiler 3 are electrically connected by an electric circuit 13, and the electric circuit 13 includes an electric circuit. A measuring instrument (for example, an ammeter) 15 for measuring the current flowing through the power supply 13 and a power source 17 are arranged.
[0027]
b) Next, the structure of the liquid level sensor 1 will be described in more detail.
As shown in a partially broken view in FIG. 2, the liquid level sensor 1 mainly includes a long cylindrical ceramic electrode member 7, a rod-shaped center electrode 9 fitted into the electrode ceramic member 7, and It is comprised from the cylindrical metal shell 23 fixed to the outer periphery of the ceramic member 7 for electrodes.
[0028]
Of these, the electrode ceramic member 7 is a member made of a ceramic material having an alumina purity of 99.5% by weight or more, and a through hole 21 into which the center electrode 9 is inserted is formed at the center of the shaft. An annular convex part 25 is formed in a part. In particular, in this embodiment, as shown in FIG. 3, the first end face is formed on the base end side (upward in both figures) of the electrode ceramic member 7 along the inner peripheral corner of the first end face 31. A notch 33 (which is a bonding material reservoir described later) having a width of 1 mm or more is provided when viewed from the side 31.
[0029]
The notch 33 is curved and notched so as to be convex inward, and a metallized layer made of molybdenum-manganese is formed on the surfaces of the first end face 31 and the notch 33, although not shown. Furthermore, a plating layer made of nickel is formed on the surface thereof.
[0030]
A thread 35 is formed on the proximal end side of the inner peripheral surface of the through hole 21 of the electrode ceramic member 7.
Returning to FIG. 2, the center electrode 9 is made of a conductive material (for example, mild steel and SUS304), and both ends thereof protrude from the through holes 21 of the electrode ceramic member 7.
[0031]
A disc-shaped flange 41 is formed on the outer periphery on the proximal end side of the center electrode 9, and a screw portion 43 is provided on the proximal end side from the flange 41, The pair of hexagon nuts 49 and 51 are screwed together with the pair of washers 45 and 47 interposed therebetween. The screw portion 43 is connected to the electric circuit 13.
[0032]
Further, a screw portion 52 is provided on the outer periphery of the center electrode 9 on the tip side from the flange portion 41, and the screw portion 52 is screwed with the screw thread 35 of the electrode ceramic member 7.
On the other hand, a threaded portion 53 is also provided on the distal end side of the center electrode 9, and a removal preventing disk 55 is fitted into the threaded portion 53, and a long connection nut (hexagonal nut) 57 is screwed. . First and second screws 59 and 61 are attached to the connection nut 57 in parallel along the axial direction of the center electrode 9.
[0033]
In the present embodiment, as shown in FIG. 4, the second end surface 63 on the front end side in the plate thickness direction of the flange portion 41 of the center electrode 9, that is, the second end surface 63 facing the first end surface 31 of the electrode ceramic member 7. Is joined to the first end face 31 by an Sn-based solder 65 as a joining material. This solder 65 is also filled in the notch 33 of the electrode ceramic member 7 described above.
[0034]
That is, the electrode ceramic member 7 and the center electrode 9 are soldered and joined by the first end face 31 and the second end face 63 and are also soldered by the solder 65 filled in the notch 33. A joint portion 66 is formed.
Returning to FIG. 2, the metal shell 23 is a metal (for example, SUS304) cylindrical member. Between the metal shell 23 and the electrode ceramic member 7, a plate packing 71, wire packings 73 and 75, Filling powder 77 is disposed, and is fixed to the electrode ceramic member 7 by crimping the end 79 of the metal shell 23.
[0035]
The outer periphery of the metal shell 23 is provided with a hexagonal portion 81 formed in a hexagonal shape and a screw portion 83 having a screw thread formed on the tip side of the hexagonal portion 81. The liquid level sensor 1 is fixed to the high pressure boiler 3 by screwing into a screw hole (not shown) of the wall portion 11 of the boiler 3 and turning the hexagonal portion 81 with a spanner or the like.
[0036]
c) Next, the operation of the liquid level sensor 1 will be described.
In the liquid level sensor 1 of the present embodiment, a circuit through which a current flows is not formed until the water surface comes into contact with the tip end side of the center electrode 9, and therefore no current flows through the electric circuit 13 (and hence the ammeter 15).
[0037]
On the other hand, when the water surface rises and the tip of the center electrode 9 comes into contact with the water 5, a closed circuit "center electrode 9-water 5-high pressure boiler 3-electric circuit 13" is formed. Current flows through
Therefore, when this current (water level detection current) is detected by the ammeter 15, it can be determined that the water surface has reached the center electrode 9, while when it is not detected by the ammeter 15, the water surface is the center electrode 9. It can be determined that 9 has not been reached.
[0038]
And by using one or a plurality of liquid level sensors 1 (in this case, the center electrode 9 is installed so that the height of the central electrode 9 differs according to the height of the liquid level to be detected), the liquid level sensor 1 detects the level. The height of the water surface can be controlled based on the data on the height of the water surface. In addition, by connecting a conductive rod having a different length (for example, a bar made of SUS) to the tip of the center electrode 9 through a long connection nut 57, a desired water surface height is detected, Similarly, the height of the water surface can be controlled.
[0039]
d) Next, a method for manufacturing the liquid level sensor 1 will be described.
For example, a predetermined amount of an alumina material (average particle size 0.1 to 5 μm) was weighed, and wet strong pulverization was performed for 24 hours with an attritor using an organic solvent.
-Thereafter, drying was performed, paraffin was added, and pressure molding was performed by a rubber press at a pressure of 100 MPa or more.
[0040]
Next, this press-molded product was cut into the shape of the cylindrical electrode ceramic member 7 based on FIG.
-After degreasing, it baked for 4 hours by each baking conditions, for example, the temperature of 1500-1800 degreeC in air | atmosphere atmosphere.
[0041]
-Then, the metallization process and the plating process were performed to the surface of the end surface 31 and the notch 33 of the base end side of the said baked product, and the ceramic member 7 for electrodes was obtained.
Next, the center electrode 9 is inserted into the through-hole 21 of the electrode ceramic member 7, and a cut is made between the first end surface 31 of the electrode ceramic member 7 and the second end surface 63 of the flange portion 41 of the center electrode 9. The notch 33 was filled with solder 65 as a bonding material, and the screw thread 35 of the electrode ceramic member 7 and the screw portion 52 of the center electrode 9 were screwed together while soldering.
[0042]
Next, the metal shell 23 was fitted to the outer periphery of the electrode ceramic member 7 together with the packings 71 to 75 and the metal shell 23 was crimped and fixed to the electrode ceramic member 7.
After that, accessory level fittings such as hexagon nuts 49 and 51 were assembled to both ends of the center electrode 9 to complete the liquid level sensor 1.
[0043]
e) Next, the effect of the liquid level sensor 1 including the electrode ceramic member 7 of the present embodiment having the above-described configuration will be described.
The liquid level sensor 1 of this embodiment has a width of 1 mm or more as viewed from the first end surface 31 side along the inner peripheral side corner of the first end surface 31 on the base end side of the electrode ceramic member 7. A notch 33 is formed as a joining material reservoir.
[0044]
As a result, the solder 65 accumulates in the notch 33 and enters the inside of the space between the electrode ceramic member 7 and the center electrode 9, so that the tip side of the liquid level sensor 1 disposed in the high pressure boiler 3 (high pressure boiler) 3) to the outside of the liquid level sensor 1 through the joint portion 66 between the first end surface 31 on the proximal end side of the electrode ceramic member 7 and the second end surface 63 of the flange portion 42 of the center electrode 9. In the (leak path), since the length of the joint portion 66 is increased, it is possible to prevent the vapor from leaking to the outside through the joint portion 66. As a result, there is an advantage that the durability of the liquid level sensor 1 used in the high pressure boiler 3 is improved.
[0045]
In particular, in the present embodiment, the notch 33 is curved so as to be convex inward, so that the leak path is long, and from this point, steam leakage can be effectively prevented.
f) Next, experimental examples in which the effects of the present invention have been confirmed will be described.
[0046]
As shown in FIG. 5 and Table 1 below, the liquid level sensor (sample No. 2, 3, 5-8) of the present invention having notches (joint material pools) of various shapes, and cuts as comparative examples. Ten liquid level sensors having no notches (Sample No. 1) and ten liquid level sensors having a short notch width (Sample No. 4) were manufactured by the method described above.
[0047]
Specifically, as shown in FIG. 5A, in the cross section along the central axis of the electrode ceramic member, there is a notch that is linearly inclined inward from the first end surface at an inclination angle θ of 30 to 75 °. The liquid level sensor of sample Nos. 2 to 7 provided, or the liquid of sample No. 8 that was cut out in a step shape with a tilt angle of 90 ° (as shown in FIG. 5B). A surface sensor was manufactured.
[0048]
These liquid level sensors are attached to a high-pressure boiler, the pressure in the high-pressure boiler is set to 2 to 2.4 MPa, the temperature is 220 ° C., and the state of leakage of steam from the joint between the electrode ceramic member and the center electrode is determined. Examined. The results are also shown in Table 1 below.
In Table 1, “x” indicates that there are vapor leaks in all 10 samples, “Δ” indicates that when 10 samples are made, 5 to 9 have no leaks, "" Indicates that all 10 samples are free of vapor leakage.
[0049]
[Table 1]

[0050]
As is apparent from Table 1, Samples No. 2, 3, 5 to 8 within the scope of the present invention are provided with notches at the corners of the first end face of the electrode ceramic member and the width thereof is as follows. It is 1 mm or more, and not only between the first end surface and the second end surface, but also the notch is filled with solder, so it can be seen that there is no (or less) leakage of steam at the joint.
[0051]
On the other hand, Sample Nos. 1 and 4 outside the scope of the present invention are not preferable because they have no notches or have a notch, but the width is as short as 0.5 mm and steam leaks. .
(Examples 2 to 5)
Next, other embodiments will be described, but the description of the same portions as those of the first embodiment will be omitted.
[0052]
The electrode ceramic members of Examples 2 to 5 are different from Example 1 in the shape of the notches.
As shown in FIG. 5C, in the electrode ceramic member 85 of the second embodiment, the shape of the notch 87 (cross-sectional shape along the central axis: the same applies hereinafter) protrudes outward in the middle of the straight line. It is bent like so.
[0053]
In this case, the inclination angle θ is an inclination angle of a line segment connecting both ends of the notch 87.
As shown in FIG. 5D, in the electrode ceramic member 89 of the third embodiment, the notch 91 has a curved shape that curves outwardly.
[0054]
As shown in FIG. 5 (e), in the electrode ceramic member 93 of the fourth embodiment, the notch 95 has a shape in which the curve is continuously convex inward.
As shown in FIG. 5F, in the electrode ceramic member 97 of the fifth embodiment, the notch 99 has a shape provided with a plurality of steps.
[0055]
In addition, this invention is not limited to the said Example at all, and it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from the summary of this invention.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a state in which a liquid level sensor according to a first embodiment is attached to a high-pressure boiler.
FIG. 2 is a front view showing a partially broken liquid level sensor according to the first embodiment.
3 is a front view showing a partially broken electrode ceramic member of Example 1. FIG.
FIG. 4 is a front view illustrating a main part of the liquid level sensor according to the first embodiment, partially broken and enlarged.
FIG. 5 is a front view showing the electrode ceramic member in an experimental example and other examples in a cutaway manner.
FIG. 6 is an explanatory diagram showing a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid level sensor 3 ... High voltage | pressure boiler 7, 85, 89, 93, 97 ... Ceramic member 9 for electrodes ... Center electrode 31 ... 1st end surface 33, 87, 91, 95, 99 ... Notch 63 ... 2nd end surface 41 ... buttocks 65 ... bonding material (solder)
66. Joint part

Claims (9)

A cylindrical ceramic member for an electrode and a center electrode fitted into the electrode ceramic member, a first end surface on the base end side of the electrode ceramic member, and a projecting portion protruding from the outer periphery of the central electrode In the ceramic member for electrodes used for the liquid level sensor joined by the joining material at the second end face,
A ceramic member for an electrode, comprising a cutout for storing the bonding material having a width of 1 mm or more as viewed from the first end surface side along a corner on the inner peripheral side of the first end surface. 2. The electrode ceramic member according to claim 1, wherein the first end surface of the electrode ceramic member and the surface of the notch are subjected to metallization. 3. The ceramic member for an electrode according to claim 1, wherein the cutout is one or a plurality of cutouts by C chamfering or R chamfering, or a combination of the C chamfering and R chamfering. The electrode ceramic member according to any one of claims 1 to 3, wherein the notch is provided at an angle of 45 to 75 degrees from the first end face. 5. The electrode ceramic member according to claim 1, wherein the notch is one or a plurality of steps. The ceramic member for an electrode according to any one of claims 1 to 5, wherein the notch is inwardly convex or outwardly convex in the corner portion. A liquid level sensor comprising the electrode ceramic member according to any one of claims 1 to 6 on an outer periphery of the center electrode. 8. The liquid level sensor according to claim 7, wherein the bonding material is provided between the first end surface of the electrode ceramic member and the second end surface of the center electrode and in the notch. The liquid level sensor according to claim 7 or 8, wherein the liquid level sensor is used for detecting a liquid level of a boiler.

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