JP2933856B2 - Level sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for filling a container such as a tank with an object such as liquid, powder, or granular material to determine whether or not the object has been filled to a predetermined height level. This is related to a level sensor that detects whether or not the level is high.

[0002]

2. Description of the Related Art Conventionally, as this type of level sensor,
A device described in JP-A-62-293127 as a filling surface adjusting device is known. This device elastically supports a vibrating rod having a piezoelectric element attached to one end of a strip-shaped metal vibrating piece by a support made of a metal thin film at two places where nodes of vibration in a primary vibration mode appear. Then, the two supports are attached to both ends of a cylindrical protective tube covering both nodes of the vibrating rod by welding, and the other end of the vibrating rod protruding from the protective tube is connected to a measurement probe of a material to be filled. The piezoelectric element and the mass body are attached to one end of a vibrating rod that is a part and protrudes from the opposite side of the protection tube. This mass body is provided to improve the detection accuracy of the filling object by shortening the cycle of vibration and increasing the amplitude of the measurement probe section.

[0003] In the above-mentioned apparatus, when the filling surface of the object to be filled, which rises with the filling operation of a storage container such as a tank, comes into contact with the measuring probe at the other end of the vibrating rod, the vibration of the vibrating rod is reduced. Is suppressed or stopped, thereby changing the output voltage from the piezoelectric element. Therefore, it is determined whether or not the object has been filled to a predetermined height level based on the magnitude of the output voltage.

[0004]

By the way, in the above-mentioned conventional apparatus, two portions of the vibrating rod, which are nodes of vibration, are respectively supported by supports, and the vibration acting on both supports is a phase of vibration. Are 180 ° different from each other, they cancel each other out if the amplitudes are the same, and become theoretically zero. Therefore, in order to make the amplitudes of both supports the same, a metal thin film formed of the same material and having the same diameter and thickness is used as both supports. However, if both supports are set to have the same size and small thickness, the supporting force for the vibrating rod is weak, so that it is difficult to stably support the vibrating rod for a long period of time, and reliability is reduced.
In addition, the support on the tip end side of the vibrating rod that is disposed so as to enter the storage container of the material to be filled is thin, and thus is easily damaged when the material to be filled hits. On the other hand, if both supports are set to a large thickness of the same size, the vibrating rod will also support nearby portions other than the nodes of vibration, and both supports will have a large resistance to the vibration of the vibrating rod and will vibrate. In order to attenuate the vibration, an attempt is made to obtain vibration of a predetermined amplitude, so that the power consumption of the piezoelectric element increases.

[0005] Since both supports are circular with the same diameter, during manufacture, one of the supports is fixed to the predetermined position of the vibrating rod by welding by inserting a vibrating rod through the slit-shaped mounting hole. Then, one end opening of the cylindrical protective tube into which the vibration rod is inserted is applied to this support and fixed by welding, and the other support is inserted through the slit-shaped mounting hole of the vibration rod. It is assembled in such a manner that it is applied to the other end opening of the protective tube and welded, and is fixed to the vibrating rod by welding. In the step of connecting the one support to the end face of the one end opening of the protection tube and connecting the same, the protection tube is welded to the vibrating rod while being concentrically held by a jig. Subsequently, while holding the protective tube concentrically with respect to the rod, the other support is applied to the end face of the other end opening of the protective tube and welded. As described above, since welding is performed while holding the protective tubes to both supports made of a metal thin film, assembly workability is poor.

Accordingly, the present invention provides a level at which a vibrating rod can be stably supported over a long period of time while suppressing the amount of vibration attenuation by two thin film supports, and can be assembled with good workability. It is intended to provide a sensor.

[0007]

In order to achieve the above object, a level sensor according to one aspect of the present invention has a base end and a free end which are free ends, and a front end of which is provided in a storage container for a material to be filled. A rod that is arranged to be advanced, a vibrator that applies vibration to the rod, and the rod that serves as a node of the vibration.
A support having a circular thin film shape to be supported at a location, and a cylindrical protection tube that covers between both nodes of the rod, and one of the support members is fitted to an inner surface of one end of the protection tube. The other support has an outer diameter larger than that of one of the supports, is fixed to the other end face of the protective tube, and is located near the tip of the rod. But
Thicker than other supports.

The above-mentioned level sensor is installed in a state where the tip of the rod is inserted into a storage container such as a tank filled with liquid or powder, and drives the vibrator to apply vibration to the rod. I do. When the filling material inside the container is filled up to the height level in contact with the tip of the vibrating rod, the vibration of the rod is suppressed by the filling material, and the electric signal of the vibrator changes. , It is detected that the object to be filled has been filled to a predetermined height level.

In this level sensor, both support members have different outer diameters. When assembling the sensor portion, first, a circular thin film-like support member is provided at each of two locations serving as nodes of rod vibration. Attach by fixing means such as welding. Next, when the protection tube is inserted from one of the support members having a small outer diameter and moved to a position covering between the two nodes of the rod, the other end surface of the protection tube is out of the other support member having a large outer diameter. The outer peripheral end surface of one of the supports is fitted to the peripheral edge portion and fits to the inner peripheral surface of one end portion of the protective tube. In this state, the protection tube and both supports are fixed by fixing means such as welding. In this manner, the two support members in the form of a circular thin film can be simultaneously positioned and fixed to the rod, and the fixing can be performed irrespective of the protection tube, so that welding for fixing can be performed easily and quickly. Moreover, since the cylindrical protective tube can be joined to both fixed supports, it is possible to eliminate the difficult work of welding the conventional protective tube while holding the protective tube concentrically with the rod.

[0010]

Further, since the support at the tip end of the rod, which is advanced into the storage container for the material to be filled, is thicker than the other support, it is possible to prevent troubles such as damage to the material being hit by the material. At the same time, the supporting force of the rod increases, and the rod can be stably supported for a long period of time, so that the reliability is improved. In addition, since only one of the supports is thick, the amount of vibration attenuation of the rod by both supports is not so large, and the power consumption of the vibrator does not increase.

In one embodiment of the present invention, the materials of both supports are different from each other. If only one of the supports located on the distal end side of the rod is formed of, for example, a thin metal film of stainless steel, the support does not easily rust even if it comes into contact with the material to be filled.
If the other support that does not contact the object to be filled is formed of an inexpensive metal thin film such as brass, high reliability can be obtained while suppressing the overall material cost of both supports.

[0013]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a level sensor according to an embodiment of the present invention, and FIG. 2 is a cut-away plan view of a main part thereof. In these figures, a cylindrical protective tube 7 is connected to a distal end portion of a casing 1 in which a main body case portion 2 and a mounting socket portion 3 are screw-connected to each other by fixing means such as welding. The first and second supports 4 in the form of circular thin films are provided at both ends, respectively.
9 is fixed by welding in a state where the opening of the protective tube 7 is airtightly closed. A rod 8 made of a flat band-shaped metal plate is inserted through a slit-shaped mounting hole (not shown) formed in the center of the support members 4 and 9, and is inserted through the protective tube 7. The rod 8 is welded to the two supports 4 and 9 at two places where nodes of vibration appear when the rod 8 is excited, and is supported by the two supports 4 and 9. Since both supports 4 and 9 are made of a thin metal film and have low rigidity, they support rod 8 elastically. The proximal end side (right end side in the figure) of the rod 8 enters the mounting socket portion 3, and the distal end side (left end side in the figure) protrudes from the protective tube 7. The details of the support structure of the rod 8 by the two supports 4 and 9 will be described later.

An additional weight body 10 is positioned by a positioning screw 11 and fixed by a fixing screw 12 at the center of the protection tube 7 of the rod 8, that is, between the two nodes. Further, a pair of piezoelectric elements (vibrators) 14A and 14B are attached to both sides of the rod 8 at a position closer to the base end than the first support 4. Power is supplied to the piezoelectric elements 14A and 14B from the drive circuit unit 17 via lead wires.

As shown in FIG. 3, the drive circuit section 17 converts the AC power of the commercial AC power supply 17a into DC power by the rectifier circuit 17b and supplies the DC power to one piezoelectric element 14A.
The piezoelectric element 14a converts supplied electric energy into mechanical energy and applies vibration to the rod 8. The mechanical energy due to the vibration of the rod 8 is equal to that of the other piezoelectric element 14B.
Is converted to electric energy. This piezoelectric element 14B
Is extracted only by the bandpass filter 17c of the drive circuit unit 17, and the output signal of the bandpass filter 17c is amplified by the amplifier circuit 17d, and then the rectifier circuit 17b
And is input to the relay output circuit 17e. The relay output circuit 17e turns on an indicator light (not shown) provided in the indicator light window lens 19 shown in FIG. 1 when a predetermined electric signal is input, and stores a storage container 20 such as a tank. A supply stop signal is output to a supply device (not shown) of the filling material 13 into the inside.

The drive circuit 17 and the piezoelectric elements 14A, 1
4B is connected to the rubber fastening plate 22 by screwing the rubber fastening screw 21 of FIG.
It is pressed and fixed to the inner surface of the mounting socket part 3 by a fixing rubber 24 which is sandwiched from both sides by a rubber tightening washer 23 and a rubber tightening plate 22 and bulges laterally. The part of the lead wire 18 pressed against the mounting socket part 3 by the fixing rubber 24 is the protective tube 3 shown in FIG.
1 and protected. Also, the casing 1
The female screw part 2a provided at the tip cylindrical part of the main body case part 2 is screwed into the male screw part 3a of the mounting socket part 3, and the front end part of the main body case part 2 is connected to the mounting socket part 3 via the gasket 27. The main body case portion 2 and the mounting socket portion 3 are hermetically connected to each other by being pressed against the flange portion 3b and further fixed by a lock nut 28 screwed into the male screw portion 3a. The rear end opening of the main body case portion 2 is closed by a case cover 30 with a packing 29 shown in FIG.

The level sensor having the above structure is mounted at a predetermined height on the side wall of the storage container 20 shown in FIG.
That is, a mounting hole 20a is formed at a position corresponding to the height position of the side wall of the storage container 20 at which the object 13 is to be filled, and the socket 32 having a female screw portion is fitted into the mounting hole 20a. It is fixed by welding. The level sensor is mounted on the mounting socket 3 of the casing 1.
Is screwed into the female thread of the socket 32, and the flange 3b of the mounting socket 3 is pressed against the end of the socket 32 with the gasket 33 interposed therebetween, so that the socket 3 is airtightly mounted. Have been.

FIG. 4 schematically shows a supporting component of the rod 8 in the level sensor. In the same figure, the broken line shows the vibration curve when the rod 8 is excited in the primary vibration mode. At this time, the two places where the nodes of the vibration appear are elastically displaceable by the two supports 4 and 9. So that the rod 8 is vibrated in the primary vibration mode. A sinusoidal vibration curve is formed between the nodes of the vibration of the rod 8, but the base end and the distal end of the rod 8 with respect to the supports 4 and 9 are free ends showing a linear vibration curve, and the distal end of the rod 8. (Left side) is advanced into the storage container 20 shown in FIG.

Also, as shown in FIG.
Are formed of a circular thin film, the thickness D of the second support 9 is formed larger than the thickness d of the first support 4, and the outer diameter R of the second support 9 is It is formed larger than the outer diameter r of the support 4. The second support 9 is welded to the protective tube 7 by abutting against a step formed by recessing the end face of the one end opening thereof, while the first support 4 is attached to the other end opening of the rod 8. The inner peripheral surface is fitted and welded. As a result, the protection tube 7 is formed to cover between the two nodes of the rod 8. Further, the first support 4 is formed of a brass thin film, and the second support 9 is formed of a stainless steel thin film. The protection tube 7 and the mounting socket portion 3 are welded and connected by fitting steps provided on end surfaces of each other.

Next, the operation of the level sensor will be briefly described. One of the piezoelectric elements 14A is supplied with DC power from the rectifier circuit 17b of the drive circuit unit 17, is applied with a vibrating force by a noise component included in the DC power, and is advanced into the storage container 20 in the rod 8. The vibrating tip portion vibrates in the horizontal direction as indicated by the arrow in FIG. As shown in FIG. 1, when the filling surface H of the object 13 in the storage container 20 is below the rod 8, the vibration component included in the other piezoelectric element 14B is extracted by the bandpass filter 17c in FIG. Then, after being amplified by the amplifier circuit 17d, it is superimposed on the DC power of the rectifier circuit 17b and input to the relay output circuit 17e. When the filling surface H of the filling object 13 in FIG. 1 rises to a height position in contact with the rod 8, the vibration of the rod 8 is suppressed or stopped by the filling object 13, and the output voltage of the piezoelectric element 14B in FIG. No vibration component is included. Therefore, the relay output circuit 17
Only the DC power from the rectifier circuit 17b is input to c. Accordingly, the relay output circuit 17e turns on the indicator lamp to notify the completion of the filling, and outputs a supply stop signal to the supply device of the filling material 13 in FIG. To stop the supply operation.

In the above-described level sensor, the second end supporting the distal end side of the rod 8 advanced into the storage container 20 is provided.
Since the thickness of the support 9 is larger than the thickness of the first support 4, the following effects can be obtained. That is, there is no possibility that a trouble such as damage to the second support 9 due to the contact of the object 13 with the filling material 13 may occur, and the supporting force of the rod 8 is increased by the second support having a large thickness. 8 can be stably supported over a long period of time, so that reliability is improved. In addition, the second support 9 of the two supports 4 and 9
However, since only the thickness of the piezoelectric element 14A is large, the attenuation of the vibration of the rod 8 due to the support of the supports 4 and 9 does not increase so much, and the power consumption of the piezoelectric element 14A does not increase.

Next, the assembly of the level sensor will be described with reference to FIG. First, the second with a large outer diameter
As shown in (a), the support 9 is positioned at a predetermined position on the distal end side of the rod 8 serving as a node of vibration by inserting the rod 8 into the mounting hole of the support 9 and then fixed to the rod 8 by welding. . Next, as shown in FIG.
Is attached to a predetermined portion of the rod 8 with a fixing screw 12, and then the first support 4 is inserted through the mounting hole of the first support 4 as shown in FIG.
Is fixed to the rod 8 by welding after positioning at a predetermined position on the base end side. As described above, unlike the conventional apparatus in which the circular thin film-shaped supports 4 and 9 are welded while holding the protective tube, the supports 4 and 9 can be fixed independently of the protective tube 7, so that the welding operation for fixing is easy and quick. Can be done. In addition, after both the supports 4 and 9 are positioned together, they can be simultaneously welded to the rod 8.

Subsequently, as shown by a two-dot chain line in (d), the protective tube 7 is inserted between the two nodes of the rod 8 by inserting the support 4 from the side of the first support 4 having a small outer diameter. When the outer peripheral end surface of the first support 4 is fitted to the inner peripheral surface of the opening on the base end side of the protective tube 7, the step on the end surface on the distal end side of the protective tube 7 Second support 9 having a large outer diameter
Is applied to the outer periphery. In this state, the protection tube 7 and the two supports 4 and 9 are fixed by welding. Here, the protection tube 7 is supported concentrically with respect to the rod 8 by fitting one end on the base end side to the inner peripheral surface of the first support 4 in a fixed state. Can be easily performed with simple holding, and the subsequent welding of the protective tube 7 to the first support 4 can be further easily performed. Therefore, it is possible to eliminate the difficult work of performing welding while holding the protection tube in an unstable state concentrically with the rod when assembling the conventional device.

Next, as shown in (e), after attaching the piezoelectric elements 14A and 14B to both surfaces of a predetermined portion of the rod 8, the mounting socket portion 3 of the casing 1 is brought into contact with the protective tube 7 by welding. Link. Piezoelectric elements 14A, 1
The 4B lead wire 18 is pulled out to the outside through the mounting socket portion 3, and the rubber tightening screw 21, which is inserted through the rubber tightening washer 23 and the fixing rubber 24 and temporarily fixed to the rubber tightening plate 22, is attached to the mounting socket portion 3. Is interposed between the plurality of lead wires 18 at the opening.

When the rubber tightening screw 21 is screwed into the rubber tightening plate 22, as shown in FIG.
3 and the rubber tightening plate 22 deform the fixing rubber 24 sandwiched from both sides so as to swell to the side.
8 is pressed against the inner surface of the mounting socket part 3 and fixed. After that, when the main body case portion 2 is connected to the mounting socket portion 3 by the above-described screw connection and fixed with the lock nut 28, the assembly is completed. As described above, the lead wire 18 can be easily fixed by the tightening operation of the rubber tightening screw 21 and the main body case portion 2 can be connected to the mounting socket portion 3 by screw connection. The bodies 4 and 9, the piezoelectric elements 14 </ b> A and 14 </ b> B, the additional mass body 10, and the protective tube 7 can be unitized as a sensor unit. By appropriately selecting and attaching the sensor units, various types of level sensors can be configured.

[0026]

As described above, according to one configuration of the present invention,
Since the outer diameters of the two supports for supporting the rod are different from each other, the two supports in the form of a circular thin film can be easily and quickly fixed to the rod by welding or other fixing means regardless of the protective tube. Difficult work in assembling can be eliminated.

Also , since the thicknesses of the two supports are different from each other, the support on the tip end side of the rod, which is advanced into the storage container for the material to be filled, is made thicker than the other support so that the material to be filled can be filled. In addition to preventing trouble such as damage to the support due to contact with an object, the rod can be stably supported for a long period of time, and reliability is improved. In addition, the attenuation of the rod vibration by the two supports is not so large, and the power consumption of the vibrator does not increase.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a level sensor according to an embodiment of the present invention.

FIG. 2 is a cut-away plan view of a main part of the above.

FIG. 3 is a block diagram of a driving circuit unit according to the embodiment.

FIG. 4 is a schematic view for explaining the operation of the rod according to the first embodiment.

FIGS. 5 (a) to 5 (f) are cross-sectional plan views sequentially showing manufacturing steps of the above.

[Explanation of symbols]

4 first support, 7 protection tube, 8 rod, 9 second support, 13 material to be filled, 14A, 14B piezoelectric element (vibrator), 20 storage container,

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein the proximal end and the distal end are free ends,
Is a rod that is arranged to advance into the storage container for the material to be filled.
And a vibrator for applying vibration to the rod, and a circular shape for supporting the rod at two points that serve as nodes of the vibration.
A thin-film support, and a cylindrical cover that covers between the nodes of the rod
A protective tube, and one of the supports is fitted on an inner surface of one end of the protective tube.
And the other support is one of the supports
The other end face of the protective tube, having an outer diameter larger than the body
And the support positioned near the tip of the rod is fixed to another support.
A level sensor that is thicker than the body.