JP3117273B2 - Measuring instrument for pressure fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure fluid measuring instrument using a ceramic measuring tube for measuring physical quantities such as pressure, electric conductivity, flow rate and the like of a pressure fluid to be measured, and more particularly to an external apparatus which receives from a right and left pipe side. The present invention relates to a pressure fluid measuring instrument having improved sealing properties in addition to the structure of a ceramic measuring tube to which stress is not easily transmitted.

[0002]

2. Description of the Related Art Measuring tubes using ceramics of this kind are applied to flow meters and the like. Among these flow meters, the electromagnetic type is currently in the stage of widespread use. In the case of other types such as ultrasonic type, vortex type, and volume type, it is considered that they will gradually enter the stage of popularization.

In the case of a measuring instrument using a ceramic measuring tube, there are roughly two problems. One is the problem of breakage of the measuring tube and the weakness of the stress caused by the hair crack generated in the process of firing the ceramics, and the other is the problem of the sealing property of the electrode having the function of the measuring sensor. (1) Regarding the problem of the measurement tube Therefore, regarding the problem of the measurement tube, first, the processing steps of the ceramics that will be the measurement tube main body will be deeply mentioned, and an appropriate structure of the measurement tube will be found.

As shown in FIG. 18, a conventional measuring device for pressure fluid uses a ceramic measuring tube 1 having a thin portion 1a and a thick portion 1b, and a metal tube such as steel or aluminum is provided outside the measuring tube 1. An outer casing 2 is provided. The joint surface 3 between the measuring tube 1 and the outer casing 2 is joined by means such as brazing via a buffer layer or shrink fitting via an adhesive layer.

[0005] The measuring instrument as described above is sandwiched between the flanges 6a and 6b of the left and right plant pipes 5a and 5b via the packing 4, and is fixedly fastened by bolts 7, nuts 8 and spring washers 9.

[0006] Therefore, this measuring device is made based on the idea that the packing contact surface of the ceramic measuring tube 1 should be made only of ceramics. The reason is that, when considering the corrosion resistance of the measuring tube 1 to the liquid-contacting fluid, it is simpler not to mix other materials, since it is only necessary to check the corrosiveness of the ceramics alone, which is simple. Further, since the measuring tube 1 is sandwiched between the two flanges 6a and 6b via the packing 4 and then tightened by the bolts 7 and the nuts 8, the stress tightened by the bolts 7 and the nuts 8 is all the thickness of the measuring tube 1. The structure is such that the thin portion 1a is intensively added from the thin portion 1b.

As a result, when measuring medium or high pressure fluid, the flanges 6a, 6b of the plant piping 5a, 5b are measured.
Of the ceramic measuring tube 1 is buckled and the thinning portion 1a of the ceramic measuring tube 1 is greatly increased because the thickness of the plate becomes thicker, the mounting bolts 7 become thicker, and the number of the bolts increases. I do.

On the other hand, at the joint surface 3, the ceramic constituting the measuring tube 1 and the steel or aluminum constituting the outer casing 2 are joined, and this kind of steel or aluminum has a coefficient of thermal expansion which is almost one order of magnitude higher than that of the ceramic. Therefore, when the temperature of the pressure fluid to be measured changes suddenly, cracks may occur in the measuring tube 1. That is, thermal shock destruction occurs. At this time, the temperature difference of the thermal shock fracture was alumina (Al
_In the case of ₂ O ₃ ) ceramics, the temperature is about 65 to 100 ° C.

Then, there is a problem why such a measuring tube 1 needs to have the structure of the thin portion 1a. The reason is that, as shown in FIG. 19, the inner diameter ΦDo of the measuring pipe 1 is almost determined by the plant piping standard,
Since the position through which the bolt 7 passes is determined by the specifications of the flanges 6a and 6b attached to the a and 5b, the outer casing 2 is provided at least inside the bolt 7, and the outer casing 2 and the inner diameter ΦD
parts required for measurement between the measurement tube 1 subject to the constraint of o,
In particular, since it is necessary to insert an excitation coil and the like, the outside of the measuring tube 1 is made to have a thin structure, and the excitation coil and the like are inserted into the space 10 formed thereby.

Therefore, in order to create a space 10 for mounting an exciting coil and the like, unfired (green) ceramics are fired, and grinding is performed to eliminate any deviation in dimensions after firing. In addition, the residual stress and grinding defects of the ground ceramics cause the strengthening and weakening of the ceramics, and these factors greatly affect the strength of the ceramics. In particular, in the case of such a measurement tube 1, there is a high possibility that a hair crack is formed on the outer periphery of the thin portion due to the grinding process, and when swelling occurs in the thin portion 1 a by applying a fluid pressure in this state, the swelling occurs. There is a high possibility that the measuring tube 1 will be destroyed instantaneously.

There are two typical methods for producing unfired ceramics. One method is to produce a mixture of ceramic fine particles and a water-soluble binder by pressing with a press-type press. . Here, as the water-soluble binder, for example, an aqueous solution mainly containing vinyl alcohol, vinyl acetate, or the like is used . In another manufacturing method, a flexible green ceramic is made by adding a green ceramic fine powder and an oil-soluble binder and kneading them with a roll. Here, as the oil-soluble binder, for example, MEK mainly composed of resin such as polyvinyl butyral is used.
A solution such as (methyl ethyl ketone) is used. Therefore, the reason why the grinding process must be performed after firing the unfired ceramic will be described below from two production examples of the conventional ceramic measuring tube 1.

One of them is, for example, an actual measuring tube 1 using unfired ceramics to which a water-soluble binder is added.
An example will be described below. First, an unfired ceramic tube as shown in FIG. However, this unfired ceramic tube shrinks by firing. 16 to 2 in linear shrinkage
It shrinks by about 0% and body contraction rate by about 41 to 60%. The width of the shrinkage varies depending on the size of the ceramic particles, the type of the binder, the pretreatment conditions, the firing method, and the like. Therefore, by performing cutting processing in advance in anticipation of shrinkage during firing, FIG.
An unfired ceramic tube as shown in FIG. In this case, the unfired ceramic is soft like black ink and has good machinability, so that it can be processed in a short time even if cutting around the outer periphery is performed.

[0013] Thereafter, water and solvent in the binder are scattered by heat treatment at a low temperature, and further heat treatment at a medium temperature.
Management was separated construed binder component, and thereafter, fired at a high temperature. After sintering at this high temperature is completed, the material is gradually cooled, as shown in FIG.
A shrunk ceramic tube as shown in FIG. Thereafter, the surface of the ceramic tube is subjected to a grinding process as shown in FIG. 3 (c) to form the ceramic measuring tube 1. In this grinding process, a number of microscopic hair cracks are generated on the ground surface.

Therefore, such a ceramic measuring tube 1
When a fluid pressure (internal pressure) P is applied to the inside as shown in FIG. 3D, the thin portion 1a expands and instantaneously cracks. In addition, flanges 6a, 6
When the space between b is tightened with the bolts 7 and the nuts 8, a large stress is applied to the ceramics measuring tube 1 and cracks occur similarly.

An example of manufacturing another conventional measuring tube 1 will be described with reference to FIG. The manufacturing example of the ceramic measuring tube 1 gives rise to the idea that grinding must be performed after firing. That is, normally, when an unfired ceramic tube is fired, pores (pores) 11 are generated near the surface of the fired ceramics.
A ceramic measurement tube 1 indicated by a two-dot chain line is formed by shaving off a layer which is likely to cause cracks.

The pores 11 are likely to be generated when the solvent, volatile components, decomposition products and the like in the binder escape to the outside, or when fine particles are aggregated at a high temperature. Products with few pores have been made using a so-called HIP treatment method, which involves firing under high temperature and high pressure. However, even when the HIP processing is performed, the pores 11 still remain, so that the grinding is required as described above. (2) Regarding the problem of electrode sealing

Conventionally, there are the following two methods for attaching electrodes to the ceramic measuring tube 1. FIG. 22 (a)
As shown in FIG.
Insert the electrode 12 made of platinum rod to empty digits hole in the wall of a,
This is a method of sealing with the contraction force of the unfired ceramic tube 1a at the time of firing, and the other is an electric transmission method in which platinum powder is dispersed in unfired ceramic powder as shown in FIG.
This is a method of forming a cermet-type electrode to be fired after inserting the unfired cermet electrode 12 formed of a conductive member .

In the above electrode structure, the thermal expansion coefficients of alumina ceramics and platinum are almost the same, but the heat transfer coefficients are different from each other. Each temperature is different, and stress due to the temperature difference is generated on the sealing surface between the alumina ceramic and platinum, and cracks are generated. Many of these cracks also occur at the stage of cooling from firing. In addition, when an abrasive fluid flows through the ceramic measuring tube 1, alumina is strong, but platinum is soft and easily worn. Therefore, there is some concern about the long-term reliability of the seal and the mechanical and thermal shocks.

Therefore, if non-magnetic super-steel can be used instead of this soft electrode to perform integral firing, a product that meets the needs can be obtained. However, since the chemical and physical properties are different, mounting by tightening the integrated firing is difficult. Impossible.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure fluid measuring device using a ceramic measuring tube capable of maintaining a sufficient destruction prevention capability against internal pressure. Another object of the present invention is to provide a pressure fluid measuring instrument which has a structure in which external stress is not applied to the ceramic measuring tube and solves the conventional problems.

Still another object of the present invention is to provide a pressure fluid measuring instrument which can easily realize a ceramic measuring tube without grinding after firing of unfired ceramic.

[0022]

Means for Solving the Problems First, to solve the above problem, the invention according to claim 1 is a pressure fluid measuring instrument having a ceramic measuring tube obtained by firing an unfired ceramic body, When the ceramic measurement tube itself has a stress deformation region due to fluid pressure and a region where stress deformation due to fluid pressure can be ignored, the stress deformation region is a region that is not processed after the firing,
The region where the stress deformation is ignored is set as the workable region after the firing.

According to a second aspect of the present invention, in an unfired ceramic body having a thin portion and thick portions located at both ends of the thin portion, the thin portion is at least in a non-fired state. A predetermined shape having electrodes for measuring physical quantities such as pressure, electric conductivity, flow rate, etc. of the pressure fluid to be measured, which is fired after performing required processing and provided with a chamfered portion at an outer corner of the thick portion. Using a ceramic measuring tube
By compressing and interposing an elastic body in a space formed by the chamfered portion of the ceramic measuring tube and the outer casing or the chamfered portion of the ceramics measuring tube and the outer casing and the protector ring, the self-sealing mechanism and the stress received from the outside are applied. This is a pressure fluid measuring device with a structure that allows it to escape to the outer casing.

Further, according to a third aspect of the present invention, an elastic body is compressed and interposed in a space formed by the chamfered portion of the ceramic measuring tube and the outer case or the chamfered portion of the ceramic measuring tube, the outer case and the protector ring. In this case, the lining is interposed at least between the chamfered portion of the ceramic measuring tube and the elastic body.

[0025]

Therefore, in the invention corresponding to claim 1, by taking the above means, the stress deformation region due to the internal pressure of the measuring tube is set as a region which is not processed after firing, so that it can be microscopically processed by grinding. Hair cracks do not occur, and crack breakage due to expansion can be prevented even when a fluid pressure is applied during actual use.

Next, the invention corresponding to claim 2 has a structure in which an outer casing or a protector ring connected to this outer casing is floated on a chamfered portion of a ceramics measuring tube via an elastic body. The external stress escapes to the outer casing via the protector ring and does not apply to the ceramic measuring tube. In addition, the ceramic measurement tube performs the required processing only when the thin part is at least in the unfired state among the thin part and the thick part, so that microscopic hair cracks due to grinding may occur. And crack breakage due to expansion can be prevented even when a fluid pressure is applied during actual use.

Further, in the invention according to the third aspect, the corrosion resistance of the elastic body can be enhanced by interposing a lining between the chamfered portion of the ceramic measuring tube and the elastic body.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention,
The results of many years of research, experiments, and observations on the effectiveness of making ceramic measurement tubes without grinding after firing, which is an important feature of the present invention, by removing the idea of grinding after firing of unfired ceramics It will be explained first.

First, it has been described that pores are generated near the ceramic surface when unfired ceramic is fired. Therefore, in order to remove the pore-scattered layer as shown in FIG. 21, grinding is thoroughly performed up to the portion shown by the two-dot chain line. At this time, in the grinding process, microscopic hair cracks at the time of grinding are removed by performing fine-grained feather cloth processing, and thereafter, chemical polishing is performed to produce a poreless ceramic pipe. Here, the chemical polish is a method of applying a relatively low-melting glassy paint to the surface of a ceramic and then melting the ceramic surface by heating and melting. Then, after cooling, the glassy layer is dissolved and removed with an acid or alkali.

The surface of the poreless ceramic pipe is as if the candle was melted and solidified by the chemical polishing, and there is no possibility of creating a trigger for stress destruction. Therefore, a ceramic measuring pipe according to the present invention is to obtain a ceramic measuring pipe having substantially the same strength as the poreless ceramic pipe without performing grinding after firing.

First, a microscopic view of the surface layer of a ceramic pipe which is not ground after firing is in a state as shown in FIG. That is, in the pore dispersed layer, there are a pore 21a in a holed state, a pore 21b of a surface closed cell in which the hole is closed after the gaseous gas has escaped, and an internal independent pore 21c. On the other hand, the surface layer of the ceramic pipe has a very dense and hard structure. The pore 21a also has a strong structure around the pore sealed in the surface layer. Therefore, in such a state, there is no inferiority to the strength of the aforementioned poreless ceramics. The pressure fluid measuring instrument according to the present invention is used without any grinding after firing and in a state comparable to poreless ceramics.

However, if grinding is not performed after firing the unfired ceramics, it is necessary to take appropriate measures such as cutting at the unfired stage in consideration of shrinkage during firing. (1) One method is to selectively perform grinding after firing depending on the presence or absence of a stress deformation state due to fluid pressure (FIG. 2).

That is, the ceramic measuring tube is manufactured by firing the unfired ceramic pipe, but in actual use, the ceramic measuring tube 21 receives a fluid pressure and is subjected to stress deformation, and the stress deformation due to the fluid pressure can be ignored. When there is a region B, the region A is a region where grinding is not performed after firing, and the region B is a region where grinding is possible after firing. Generally, the central portion of the measuring tube is susceptible to the largest stress deformation.

Therefore, if the area A at the center of the measuring tube is formed into a thin portion at the stage of the unfired ceramic pipe, a space for accommodating the member 22 required for measurement can be secured, and grinding is performed after firing. Since there is no such structure, a structurally strong structure can be obtained. On the other hand, the area B where the stress deformation due to the fluid pressure can be neglected is the part corresponding to the end part, so that the part can be formed in a thick part so that the strength can be maintained and if grinding is performed after firing, Important dimensions required for sealing with plant piping can be reliably obtained.

(2) The other one will be described with reference to FIG. Generally, when firing an unfired ceramic tube,
When the tube is fired in the horizontal state, a collapse phenomenon of a (horizontal diameter)> b (vertical diameter) occurs as shown in FIG. Therefore, in order to eliminate this collapse phenomenon, at the time of firing, the unfired ceramic tube is fired in a vertically placed state as shown in FIG. Also, if the unsintered ceramic tube has uneven wall thickness 23 as shown in FIG. 3C at the unsintered stage, it is necessary to perform a grinding process after the sintering if the unsintered ceramic tube is fired as it is. Cutting is performed to remove the uneven wall thickness 23 in the circumferential direction as much as possible so that concentrated stress is not applied to the ceramics tube during actual use. FIG. 3D is a diagram showing that the uneven thickness 23 is removed by performing a cutting process in an unfired stage, and FIG. 4E is a diagram showing the ceramic measuring tube 21 contracted by firing.

[0036] Accordingly, by appropriately cutting the unfired ceramic pipes in the stage of unfired Thus, Runode has become sintering during the pores occurs though while the surface is very powerful organization, as described above High strength equivalent to that of poreless ceramics can be obtained.

By the way, the dense structure on the surface of the ceramic pipe having pores as described above is remarkably strong in tensile strength due to fluid pressure (internal pressure), but relatively weak in compressive and bending strength due to the thin wall of the pipe. Have. That is, there is a weak surface in the force in the fluid axis direction (thrust direction), that is, the stress when the ceramic pipe is clamped between the flanges of the plant piping.

Therefore, the present invention will be described with reference to FIG. 4 and FIG. 5 for a structure that is not affected as much as possible by an external force from the plant piping or a stress due to bolt tightening. 4 is a partially cutaway view showing the internal structure, and FIG. 5 is a schematic longitudinal sectional view of FIG.

In the figure, reference numeral 31 denotes a necessary processing only when the thin-walled portion of the unfired ceramic tube having the thin-walled portion 31a and the thick-walled portions 31b located at both ends of the thin-walled portion is at least in the unfired state. This is a ceramic measuring tube having a predetermined shape, which is fired after being performed, and provided with a chamfered portion 31c at an outer corner of the thick portion 31b. In addition, this chamfer 3
1c may have a linear tapered shape, a curved shape, or a shape combining a straight line and a curved line.

An outer casing 32 having an inverted concave cross section is disposed outside the ceramic measuring tube 31. At this time, for example, a rubber-like elastic body 33 is provided in a space defined by the chamfered portion 31c and the outer casing 32. Is interposed by compression. Accordingly, the outer casing 32 is formed by the rubber-like elastic body 33 so as to form the chamfered portion 31.
c, and thus floats from the measuring tube 31.
An outer casing 32 containing these ceramic measuring tubes 31
Protector rings 34, 34 each having an inner diameter smaller than the inner diameter of the end of the outer casing 32 are arranged on both sides of the outer casing 32. These protector rings 34, 34 are fixed to the outer casing 32 by mounting screws 35 from outside. At this time, since the rubber-like elastic body 33 is interposed in a space surrounded by the protector ring 34, the chamfered portion 31 c and the outer casing 32, the protector ring 34 is in a state of floating from the measurement tube 31.

That is, since the rubber-like elastic body 33 is in pressure contact with the chamfered portion 31c of the measuring tube 31, the outer casing 32 and the protector ring 34 as shown in FIG. Although set at the position of the solid line 37a, even if a large fluid pressure P is applied from the inside of the measuring tube 31, the chamfered portion 31 of the measuring tube 31 as shown by a dotted line 37b in the drawing is shown.
c and into the space between the outer casing 32,
Acts as a complete self-sealing mechanism. In addition, since only the rubber-like elastic body 33 is interposed in the space formed by the chamfered portion 31c of the measuring tube 31 and the outer casing 32 during assembly, leakage of the pressure fluid or the high-pressure fluid can be easily prevented. Furthermore, since the rubber-like elastic body 33 is interposed between the chamfered portions 31c at both ends of the measuring tube 31 and the outer casing 32 covers the same, the self-balancing centering function of the rubber-like elastic body 33 allows the automatic measurement tube to be mounted. Positioning is available
A measuring instrument can be made , and external force from the outer casing 32 can be isolated.

Further, it is installed so as to be sandwiched between the flanges 39a and 39b of the plant pipes 38a and 38b, and
When tightened and fixed with the mounting bolts 40 and the mounting nuts 41, the plant pipings 38a and 38 are tightened.
The structure is such that the external stress from b escapes to the outer casing 32 through the protector ring 34, and the ceramic measuring tube 3
1 can be solved.

42 is a wear-resistant lining, 43 is a packing, 45 is a capacitance type electrode for physical quantity measurement, and 46 is a V groove. The capacitance type electrode 45 is a thin film electrode 45 formed by spraying a metal on the outer surface of the ceramic measuring tube 31.
a and the electrode 45b are opposed to each other at a predetermined distance, and a physical quantity is determined from a change in capacitance between the electrodes 45a and 45b.
(Pressure, etc.) . In this electrode 45, 45c is an insulating electrode mounting material, 45d is a cap nut, 45e is a rubber elastic body, and 45f is a signal output line.

In the embodiment, the protector ring 3
4. The rubber-like elastic body 33 is directly interposed in the space surrounded by the chamfered portion 31c and the outer casing 32.
For example, as shown in FIG. 7A, the protector ring 34 is surrounded from between the chamfered portion 31c and the rubber-like elastic body 33.
Corrosion-resistant lining 46a or rubber-like elastic body 3
By providing the corrosion-resistant lining 46b so as to surround only 3, the protector ring 34 and the rubber-like elastic body 33 can be protected from corrosion prevention, and the corrosion resistance can be improved.

FIGS. 8 and 9 show another embodiment of the pressure fluid measuring device according to the present invention, which is provided outside the ceramic measuring tube 31. FIG.
Outer casings 32a and 32b are arranged so as to surround the end faces of the outer casings 32a and 32b.
Is fixed. Therefore, this structure has a chamfered portion 31c of the ceramic measuring tube 31 and each outer casing 32.
Since the rubber-like elastic body 33 is compressed and interposed between a and 32b,
As shown in FIG. 10, it is always set at the position of the solid line 37a in the figure, but when a large fluid pressure P is applied from inside the measuring tube 31, the chamfered portion 31c of the measuring tube 31 and the outer casing 32 as shown by the dotted line 37b in the figure. , So that a complete self-sealing mechanism is formed. Moreover,
The case where the outer casings 32a and 32b are attached to the measuring tube 31 is also very simple.

[0046] Incidentally, the measuring tube 31 has formed the inner surface taper 31d the thick portion 31b the inner surface of the measuring tube end and grinding as shown, which is an outer housing within bore .PHI.D ₀ of the measurement pipe 31 It is to prevent the disturbance of the fluid by eliminating the step between the inner diameter .PHI.D _1. However, when the inner surface of the thick portion 31b is ground, some hair cracks may occur,
Due to its thick wall, it has high resistance to fracture, but rather focuses on the effects of fluid turbulence, that is, safety design.

The pressure fluid measuring device employs a liquid contact type electrode structure as shown in the figure, for example, from the viewpoint of measuring electric conductivity. That is, the ceramic measuring tube 3
A funnel-shaped electrode mounting hole is formed in 1 and an electrode 51 is mounted in the electrode mounting hole. The electrode 51 has an electrode head having a substantially fan-shaped cross section, and a thread formed on the rear end side. The inclination angle of the side surface of the electrode head, that is, the packing contact surface, is formed to be steeper than the inclination angle of the funnel-shaped inclined surface of the electrode mounting hole with respect to the center axis of the electrode.

When the electrode is inserted into the funnel-shaped electrode mounting hole, a rubber elastic body, for example , a packing 5 made of rubber, Teflon or the like is used.
After the electrode 51 is inserted through the ceramic tube 1a, the receiving seat 52 holding the elastic member is inserted from the outside of the ceramic measuring tube 31. Finally, the bolt 51 is tightened to an appropriate position with a bolt and nut 53 so that the electrode 51 has a predetermined elasticity. Secure to give force.

The ceramic measuring tube 31 is composed of the thin portion 31a and the thick portion 31b as described above. For example, as shown in FIG. 11, at least one or more ceramic measuring tubes 31 are arranged in the circumferential direction of the thin portion 31a. By providing the ring-shaped thick portion 31e, it is possible to sufficiently cope with a stress change due to fluid pressure. FIG. 3D shows an example in which a thin thick portion 31a is provided with a dotted thick portion 31f. The measuring device may be provided with corrosion-resistant linings 46a and 46b as shown in FIG.

Next, the pressure fluid measuring device according to the present invention will be described in the case where it is applied to pressure measurement. The measuring instrument in this case measures the pressure using the capacitance type electrode 45 shown in FIGS. 4 and 5, and the principle of this measurement will be described.

The ceramic measuring tube 31 has a thin portion 31
a and a thick portion 31b, and the pressure is measured by utilizing the thin portion 31a which swells outward under fluid pressure. In general, ceramics
(Stress) and strain generated in ceramics by fluid pressure
As shown in FIG. 12, there is a characteristic having good linearity between the first and the second (elongation) . Therefore, as shown in FIGS. 4 and 5, one electrode 45a is formed on the outer periphery of the ceramic measuring tube 31 by thermal spraying or the like, and the other electrode 45b is insulated from the electrode 45a by a predetermined distance . Electrode removal
If the ceramic measurement tube 31 is changed from a predetermined thickness due to a fluid pressure, it can be detected as a change in capacitance if the ceramic measurement tube 31 is formed and disposed by spraying or the like on the attachment 45c .

Therefore, such a change in the capacitance is integrated a plurality of times by an integrating amplifier at predetermined intervals, and the obtained integrated outputs are averaged by an averaging circuit to obtain a signal corresponding to the pressure. or convert to, or integral voltage E ₁ of the integrating amplifier 60 as shown in FIGS. 13 to 15, ..., disk char the E _n in opposite polarity reference voltage E ₀ of the constant voltage generator 61
And di, E _1, ..., the width of the pulse corresponding to E _n (FIG. 14
b) and put it in the averaging circuit 63 for averaging.
You. The clock source 62 shown in FIG.
Used to determine TA, TB, etc. The averaging circuit
63 is for analog averaging and digital averaging
Either may be used. Analog averaging circuit is like a smoothing circuit
Circuit, and digital averaging is as shown in FIG.
Measurement pulse that is sufficiently faster than the pulse width.
To convert the pulse width to the number of pulses
Averaging (for example, moving average). This
After averaging in this manner , the arithmetic unit 64 converts the signal into a signal corresponding to the pressure. Then, the signal is converted into a signal in the range of, for example, 4 to 20 mA DC by the subsequent converter 65 and output.

Next, the electric conductivity measuring device will be described. This electric conductivity measuring device measures the electric conductivity by using the electrodes 51 as shown in FIGS. 8 and 9 and by using the circuit configuration as shown in FIG. That is, the pressure fluid measuring device 71 according to the present invention is inserted into one side of the bridge circuit 70, and a signal voltage of, for example, 4000 Hz is applied from the signal power supply 72 to the bridge circuit 70, and the bridge corresponding to the change in the electrical conductivity at this time is applied. The unbalanced output voltage of the circuit 70 is led to the conversion unit 73, where, for example, 4 to 20
Convert to a signal in the range of mADC and output. The reason why the signal power supply 72 outputs a high-frequency signal voltage is to prevent polarization between the electrodes. 74 is an impedance matching capacitor.

Further, when measuring the flow rate of the fluid, FIG.
As shown in FIG. 7, the thin portion 31a of the ceramic measuring tube 31
If the excitation coil 80 is installed in the space formed by
It can be applied to the original electromagnetic flowmeter. In the case of this electromagnetic flow meter, the capacitance type electrode of FIG.
Needless to say, any electrode structure of the liquid contact electrode may be used. Therefore, in the above embodiment, the pressure measuring device, the electric conductivity measuring device, and the flow meter are used, but the present invention can be similarly applied to the case of measuring other physical quantities. In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.

[0055]

As described above, according to the present invention, the following various effects can be obtained.

According to the first aspect of the present invention, the stress deformation region of the ceramics measuring tube due to the fluid pressure is processed only before firing and is not processed after firing, so that hair cracks do not occur and the fluid pressure is applied. Can also prevent crack breakage due to expansion.

According to the second aspect of the present invention, since the external stress of the plant piping or the like is released to the outer casing, it is possible to sufficiently cover the weakness of the ceramic measuring tube due to its thinness in the thrust axial direction.

Next, according to the third aspect of the present invention, the corrosion resistance of the elastic body can be improved by interposing the lining between the chamfered portion of the ceramic measuring tube and the elastic body that floats the outer casing.

Further, according to the invention of claim 4, since the uneven thickness of the unsintered ceramic body is removed in the unsintered stage, and the grinding process is not performed after the sintering, the concentrated stress is applied to the uneven thickness portion during actual use. And sufficient strength can be maintained without generating hair cracks.

[Brief description of the drawings]

FIG. 1 is a microscopic view of a surface layer of a ceramic measuring tube for explaining the reason why the ceramic measuring tube is not ground after firing.

FIG. 2 is a view for explaining a relationship between a stress deformation region of a ceramic measurement tube due to a fluid pressure, a stress deformation ignoring region, and a thickness of the measurement tube.

FIG. 3 is an explanatory diagram for finishing an unfired ceramic measuring tube without grinding after firing.

FIG. 4 is a view showing an internal structure of a partially cut-away view for explaining an embodiment of a pressure fluid measuring device according to the present invention.

FIG. 5 is a longitudinal sectional view schematically showing the pressure fluid measuring device of FIG. 4;

FIG. 6 is a diagram showing a deformed state of a rubber-like elastic body due to a fluid pressure.

[7] FIG subjected to corrosion lining in addition to corrosion only rubber-like elastic body and the protector ring or a rubber-like elastic body.

FIG. 8 is a view showing the internal structure of a partially cut-away view for explaining another embodiment of the pressure fluid measuring device according to the present invention.

FIG. 9 is a longitudinal sectional view schematically showing the pressure fluid measuring device of FIG. 8;

FIG. 10 is a diagram showing a deformed state of a rubber-like elastic body due to a fluid pressure.

FIG. 11 is a diagram in which a thick portion is formed in a circumferential direction of a thin portion of a ceramic measuring tube.

[12] The pressure of the ceramic measuring tube to the fluid pressure
FIG. 4 is a characteristic diagram showing (stress) / strain (elongation) .

FIG. 13 is an overall configuration diagram for measuring a fluid pressure.

FIG. 14 is a graph showing the integral value and the digital value of the integrating amplifier shown in FIG. 13;
State of discharge, discharge time and pulse
The figure explaining the relationship of width.

FIG. 15 shows a relationship for converting a pulse width into a pulse number.
FIG.

FIG. 16 is an overall configuration diagram of a measuring instrument for measuring electric conductivity.

FIG. 17 is a longitudinal sectional view schematically showing an electromagnetic flow meter for measuring the flow rate of a fluid.

FIG. 18 is a diagram showing a partially cut-away internal structure of a measuring device using a conventional ceramic measuring tube.

FIG. 19 is a view for explaining the reason for providing a thin portion in the ceramic measuring tube.

FIG. 20 is a diagram illustrating a process of manufacturing a conventional ceramics measuring tube and the influence of fluid pressure.

FIG. 21 is a diagram illustrating the reason for grinding a ceramic after firing.

FIG. 22 is an explanatory view for attaching electrodes to a conventional ceramics measuring tube.

[Explanation of symbols]

31: ceramic measuring tube, 31a: thin portion, 31b ...
Thick part, 31c: chamfered part, 31d: inner taper, 3
2, 32a, 32b ... outer casing, 33 ... rubber-like elastic body, 34
... protector ring, 42 ... wear-resistant lining, 45
... capacitance type electrodes, 46a, 46b ... corrosion resistant lining, 51 ... electrodes.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho 62-165517 (JP, U) Japanese Utility Model Sho 62-134030 (JP, U) Japanese Utility Model Sho 62-88918 (JP, U) Japanese Utility Model Sho 62- 75421 (JP, U) JP-A 62-49726 (JP, U) JP-B 3-4846 (JP, B2) JP-B 6-7317 (JP, Y2) JP-B 6-10257 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 15/14 G01L 19/00 G01N 27/08 G01R 27/22

Claims (4)

(57) [Claims] 1. A pressure fluid measuring device having a ceramic measuring tube made by firing an unfired ceramic body, wherein the ceramic measuring tube itself has a stress deformation region due to fluid pressure and a region where stress deformation due to fluid pressure can be ignored. Wherein the stress deformation region is a region that is not processed after the firing, and the stress deformation ignoring region is a workable region after the firing. vessel. 2. An unfired ceramic body having a thin portion and thick portions located at both ends of the thin portion, the thin portion is subjected to required processing only at least in an unfired state, and then fired. And a ceramic measuring tube of a predetermined shape provided with electrodes for measuring physical quantities such as pressure, electric conductivity, flow rate, etc. of the pressure fluid to be measured, which is provided with a chamfered portion at an outer corner of the thick portion. By compressing and interposing an elastic body in the space formed by the chamfered portion of the ceramic measuring tube and the outer casing or the chamfered portion of the ceramics measuring tube and the outer casing and the protector ring, the stress received from the self-sealing mechanism and the outside can be reduced. A pressure fluid measuring device characterized by having a structure that allows it to escape into a housing. 3. The pressure fluid measuring device according to claim 2, wherein the corrosion resistance is enhanced by interposing a lining between at least the chamfered portion of the ceramic measuring tube and the elastic body. 4. The measuring tube is characterized in that, in the unsintering step, the uneven thickness in the circumferential direction is removed by cutting the unsintered ceramic cylinder, and the measuring tube has a predetermined shape without performing the grinding after the sintering. The pressure fluid measuring device according to claim 2 or 3, wherein